4881 4885.output

* GB785288 (A)

Description: GB785288 (A) ? 1957-10-23

Air-heating apparatus particularly for motor vehicles

Description of GB785288 (A)

PATENT SPECIFICATION 785288 Date of application and filing Complete Specification: June 12, 1953. No 16324153. Application made in Germany on June 13, 1952. Application made in Germany on Oct 21, 1952. Application made in Germany on Oct 22, 1952. Complete Specification Published: Oct 23, 1957. Index at acceptance:-Classes 64 ( 1), L 2 A 1; and 75 ( 1), TA 2 A 1, TG( 11: 17: 19). International Classification: -F 23 d, f F 24 c. COMPLETE SPECIFICATION Air-Heating Apparatus particularly for Motor Vehicles We, WALTER EBERSPACHER and HELMUT EBERSPACHER, both of German Nationality, trading as J EBERSPACHER, of Eberspacherstrasse 24, Esslingen/Neckar, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - The invention relates to an air-heating apparatus which has its own source of heat, and which is particularly adapted for use in motor vehicles. According to the invention, an air-heating apparatus, particularly for motor vehicles, comprises a combustion chamber, a combustion air blower and a motor for driving the blower, all having a common longitudinal axis, and a pre-combustion chamber with an ignition plug and a fuel feed device, and means for maintaining the motor in operation after the fuel supply to the combustion chamber has been cut off, until the apparatus has cooled to a predetermined temperature. The means for maintaining the blower motor in operation after the fuel

supply has been cut off advantageously includes a thermal circuit-breaker which is in electrical connection with the ignition plug in the precombustion chamber and with the blower motor, and with the aid of which the ignition plug can be switched off when the heating flame has been lit and the blower motor maintained in operation until the apparatus has cooled to a predetermined temperature, after the fuel supply has been cut off Thus the apparatus may be cooled and cleansed of residual gases. In order to set the heating apparatus into operation, an electric main switch is provided which is so constructed that in the switchedon position current is supplied to a valve controlling the fuel flow, to the blower motor, to the ignition plug and to the thermal circuit-breaker When the main switch is in the lPrice 3 s 6 d l Ffce 4 S switched-off position, current is supplied only to the blower motor through the thermal circuit-breaker. The invention is diagrammatically illus 50 trated by way of example in the accompanying drawings, in which, Figure 1 is a longitudinal section of the heating apparatus, Figure 2 is a longitudinal section of the 55 combustion chamber and of the pre-combustion chamber of the heating apparatus, Figure 3 is a section through the pre-combustion chamber, Figure 4 is a cross -section of the fuel 60 supply means with the pre-combustion chamber and the combustion chamber, Figure 5 shows diagrammatically a stand pipe and a nozzle connection, and Figure 6 shows a nozzle connection with 65 fuel control means in longitudinal section. In the air-heating apparatus, a casing 1 surrounds an annular heat exchanger 2, a central cylindrical chamber 44, and a cylindrical combustion chamber 3, which all have 70 a common longitudinal axis A cylindrical whirler body 4 extends into the chamber 3. A fresh air blower 5 and a combustion air blower 6 are both mounted on a motor 7, on the same longitudinal axis as that of the 75 chamber 3, and are driven by the motor 7. The fresh air fed-in by the blower 5 flows through the interior of the heating apparatus casing 1, is heated by the heat exchanger 2 and the combustion gases in the central 80 chamber 44, and passes into the space to be heated through the opening 8 disposed at the end of the apparatus The combustion gases pass through the central chamber 44 and are discharged to atmosphere through apertures 85 45, heat exchanger 2 and an outlet pipe 9, which is mounted on the heat exchanger. Mounted on the apparatus casing and extending into the heat exchanger is a thermal switch 19, which is effective to maintain the 90 motor 7 in operation for a limited period of time after the heating has been switched off. 1, C-^'L Also mounted on the heating apparatus casing, approximately

at the level of the motor 7, is a float device, including a float 10, for regulating the flow of fuel A valve 11 having no operative relationship with the float 10, is provided and is controlled by an electromagnet which, when energised, opens the valve and permits the flow of fuel The float device 10 is supplied with fuel from a fuel tank (not shown) through a pipe 12 The fuel is then fed to the pre-combustion chamber 18 through a jet 15 which is adjustable to vary the fuel flow, pipe 16 and fuel feed pipe 17 If it is desired to increase the rate of flow of air through the heating apparatus, means are provided for proportionately increasing the flow of fuel These means comprise a compressed air line 13, connected to the casing 1 by a screw closure in such manner as to receive pressure from the blower fan 5 The pressure is transmitted through the line 13 to the fuel tank and thence through the pressure equalising line 14 to the float device so as to act upon the float 10 in such manner as to permit an increased flow of fuel to a pre-combustion chamber 18. In the partial illustration shown in Figure 2, several whirler vanes 20 are provided on the periphery of the whirler body 4 disposed in the combustion chamber 3 The whirler vanes 20 cause turbulence of the conveyed combustion air in the combustion chamber. The driving motor 7 and the blower fan 6 are surrounded by a casing 21 and a guide vane housing 22. A cowling 23 is disposed at the oppositely disposed opening of the combustion chamber Disposed between the blower fan 6 and the guide vane housing 22 are guide vanes 24 The pre-combustion chamber 18 is mounted laterally of the combustion chamber 3, and on the periphery thereof, and consists of a cylindrical or conical hollow body, into which the ignition plug 25 is fitted by screwing The element wires 26 of the ignition plug 25 are disposed approximately at the level of the whirler vanes 20, and approximately at the boundary between the pre combustion chamber and the combustion chamber. The fuel pipe 17 opens out into the hollow body 27 of the pre-combustion chamber 18 and is inclined at an angle of up to 60 ' to the axis of the pre-combustion chamber The fuel pipe 16 is connected to the fuel feed pipe 17 in known manner by means of a screw cap 28 A displacement wire 29 is provided within the fuel pipe 16 and extends as far as the screw cap leaving open a determined cross sectional area 30 for capillary effect. Instead of the device for the supply of readily volatile fuels hereinbefore described, according to the invention furthermore, provision is made for pumping fuel by means of an electric fuel pump and for passing it to the combustion chamber through a nozzle connection of special construction to the fuel feed pipe which is connected to the pre-com 70 bustion chamber The nozzle connection

consists of a stand pipe which is provided with an inlet nozzle, a supply nozzle, and an overflow nozzle The feed of the fuel to the stand pipe is effected through the inlet nozzle 75 and through the supply nozzle leading to the combustion chamber Both nozzles are so adjusted that a determined excess of fuel is always supplied to flow off through an overflow provided on the stand pipe 80 For rendering the fuel feed controllable, the supply nozzle is advantageously provided in the stand pipe so as to be displaceable so that the amount of fuel supplied to the combustion chamber may be varied as In the modifications illustrated in Figures 4 to 6, the nozzle connection 31 is connected to the fuel feed pipe 17 by means of a screw cap 32 and a packing 33 so as to be replaceable The direction of flow of the fuel 34 90 is illustrated by arrows in Figures 5 and 6. The inlet nipple 35 is screwed into the stand pipe 31 and is provided in its interior with an inlet nozzle 36, through which the fuel flows into the stand pipe A supply nozzle 95 37 is provided at the lower end of the stand pipe, and an overflow nipple 38 above the fuel level, for returning the fuel to the fuel tank The overflow nipple 38 is provided in its interior with an outlet nozzle 39 A venti 100 lating pipe 40 may be provided at the upper end of the nozzle connection 31. In the further constructional example illustrated in Figure 6, the supply nozzle 37 is provided so as to be displaceable in the 105 stand pipe by means of a piston rod 41 with a piston 42 and a circumferential sealing ring 43 The supply nozzle 37 is screwed into the head of the piston 42 and is in communication with the fuel 34 through a drilled 110 hole 44 At the upper end of the stand pipe the piston rod 41 extends into the nozzle connection, the internal space being sealed by the stuffing box screw nut 45 and the annular packing ring 46 The end 47 of the 115 piston rod projecting from the nozzle connection serves as means for connecting the piston to the control devices In this arrangement it is also possible, if desired, to provide the inlet nipple 35 at the position 35 ' indi 120 cated in dot and dashed lines in Figure 6 at the same level as the overflow pipe 38, or below the overflow pipe as shown at 3511.

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* GB785289 (A)

Description: GB785289 (A) ? 1957-10-23

Knitted fabric and method of and apparatus for the production thereof


PATENT SPECIFICATION 785289 _ i 2 Date of Application and filing Complete Specification June 23, 1953. No 17411153. Complete Specification Published Oct 23, 1957. Index at acceptance: -Class 74 ( 2), CIA( 5: 6), K 4 A( 2: 4: 12). International Classification: -D 04 b. COMPLETE SPECIFICATION Knitted Fabric and method of and Apparatus, for the Production thereof I, MAX NEBEL, of 160, Waldstrasse, Wiesbaden, Germany, a German Citizen, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a knitted fabric and to a method of and apparatus for production thereof. The invention relates more particularly to fine-gauge knitted fabrics made on a circular knitting machine with one needle row, and aims at providing a knitted fabric which will not ladded or run in use. The present invention also aims at providing a loop construction in which loosening of stitches cannot occur. To this end, referring to Fig 1 of the accompanying drawings, the present invention consists in a knitted fabric in which which each course consists of stitches of two yarns each stitch being knitted from a ground yarn (g) and an additional yarn (a, b), ground yarn being knitted with every course and wale, and the additional yarn (b) knitted with the ground yarn (g) in evry alternate wale (AW) of alternate courses (AC) ground yarn (g) being knitted in the intermediate wales (IW) of said alternate coures (AC) with a long loop (bh) of said additional yarn (b) which extends over two courses from a previous course in which said additional yarn (b) is knitted with ground yarn (g), ground yarn (g) being also knitted with the additional yarn (a) in every said intermediate wale (IW) of the

intermediate courses (IC), ground yarn (g) being knitted in the alternate wales (AW) of said intermediate courses (IC) with a long loop (ah) of said additional yarn (a) which extends over two courses from a previous course in which said additional yarn (a) is knitted with ground yarn (g). The invention also consists in a method of producing the fabric above described which comprises forming alternate courses by feeding a ground yarn to all the needles, feeding an additional yarn to alternate needles to knit in lPrice 3 s 6 d l alternate wales in one said alternate course normal stitches from said two yarns, forming the portions of said additional yarn between said alternate needles into long loops in the intermediate wales in said one alternate course, and knitting ground yarn in the said intermediate wales of said one alternate course with a said long loop formed during the knitting of the preceding alternate course, and forming intermediate courses in like manner but with the normal stitches in the intermediate wales and the stitches knitted from the long loops of additional yarn and ground yarn in the alternate wales. Such a knitted fabric may be produced, according to the invention, on a circular knitting machine which comprises two groups of needles and two groups of loop transfer members (hereinafter referred to as " transferring sinkers ") associated therewith, the needles and transferring sinkers of the first group being arranged in alternation with the needles and transferring sinkers of the second group, a pair of thread guides, one for feeding a ground yarn and one for feeding an additional yarn, the thread guide for the ground yarn being positioned in a lower horizontal plane than the thread guide for the additional yarn so that the ground yarn is fed beneath the transferring sinkers to all the needles and the additional yarn is fed to the needles of the second group and over the transferring sinkers associated with the needles of the first group, and a further pair of thread guides similarly arranged to feed ground yarn to all the needles and additional yarn to the needles of the first group and over the transferring sinkers associated with the second group of needles, the needles of one group and the transferring sinkers associated therewith being operable in such manner that after the additional yarn is fed over a said transferring sinker the latter is withdrawn out of the row of needles to hold the long loop formed thereover clear of the associated needle which knits ground yarn together with a long loop previously transferred to said needle from its associated transferring sinker, said associPice 25 p ated needle then receiving ground yarn and additional yarn from said second pair of thread guides to knit in the next course a normal stitch from said two yarns and thereafter the said transferring sinker is moved back into the row of needles to

transfer said long loop to the said needle to knit said long loop with the ground yarn fed by the ground yarn thread guide of the first pair in to a two thread stitch in the next but one course, the needles and transferring sinkers of the other group being operable in like manner. In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically the construction of knitted fabric according to the invention and the movement of the needles and the transferring sinkers to produce such fabric. Fig 1 illustrates the knitted fabric construction according to the invention; Fig 2 shows in rear view the manner of working of the needles and transferring sinkers on a circular knitting machine; Fig 3 is a corresponding plan view; Fig 4 is a section on the line 4-4 of Figs. 2 and 3, of an operating position of needles and transferring sinkers; and Fig 5 is a side view of the transferring sinkers. For the sake of clarity, Figs 2 and 3 show the sinker row and needle row of the circular knitting machine in a straight line. Referring to Fig 1, each course of the fabric according to the invention consists of stitches of two yams, each stitch being knitted from a ground yarn g and an additional yarn (ab) ground yarn g being knitted in every course and wale and the additional yarn b knitted with the ground yarn g in every alternate wale AW of alternate courses AC Ground yarn g is knitted in the intermediate wales 1 W of the alternate courses AC with a long loop bit of said additional yarn b which extends over two courses from a previous course in which the additional yarn b is knitted with ground yarn g The additional yarn (a) is also knitted withground yarn g in every intermediate wale 1 W of the intermediate course IC and ground yarn g is knitted in alternate wales AW of the intermediate courses IC with a long loop alt of the additional yarn (a) which extends over two courses from a previous course in which the additional yarn a is knitted with ground yarn g. In this way long side parts 10 a, l Ob of the stitches 10 formed from the long loops ah and bit respectively of the additional yarns pass over the sinker loops 6 and cross over themselves in the spaces between the needle stitches (see Fig 1). For producing such a knitted fabric a circular knitting machine is used which as shown in Figs 2 to 5 is provided with two groups of needles NI and N' and two groups of transferring sinkers Pl and P' associated therewith. The needles N' and transferring sinkers Pl of the first group are arranged in alternation with the needles N 2 and transferring sinkers P 2 of the second group Two pairs of thread guides 70 are provided,

one pair comprising thread guide 1 for additional yarn a (or b) and a thread guide 11 for ground yarn g, and the pair comprising thread guide 2 for additional yarn b (or a) and another thread guide 11 for second 75 ground yarn g The thread guides 11 of each pair are disposed in a lower horizontal plane than the thread guides 1 and 2 so that they are in such a position relatively to the lower edge of the transferring sinkers that the ground 80 yarn g is fed beneath the transferring sinkers to all the needles N' and N' The additional yarn a (or b) is fed by the thread guide 1 to the needles of N 2 of the second group and over the transferring sinkers P' of the first group 85 In a similar manner the additional yarn b (or a) is fed by the thread guide 2 to the needles N' of the first group and over the transferring sinkers P 2 of the second group. The needles and transferring sinkers are 90 operable in such manner that after additional yarn a (or b) is fed by thread guide 1 over a transferring sinker Pl the latter is withdrawn out of the needle row to hold the long loop 3 a formed thereover clear of the associated 95 needle N' Needle N' takes ground yarn g and knits together with a long loop loop 3 a, previously transferred to it from the associated transferring sinker P' as hereinafter described, stitch 4, 10 The needle N' then receives 100 ground yarn g and additional yarn b (or a) from the second pair of thread guides 11 and 2 to knit in the next course a normal stitch 4 from said two yarns The transferring sinker P' is thereafter moved back into the needle row 105 to transfer the long loop 3 a to the needle N' (see right hand end of Fig 3) to knit the long loop 3 a with the ground yarn g fed from thread guide 11 of the first pair into a two thread stitch 4/10 in the next but one course 110 The needles N 2 and transferring sinkers P 2 of the second group operate in a like manner to the above so that the needles N 2 knit normal two thread stitches 4 from the ground yarn g land additional yarn a (or b) fed from the first 115 ipair of thread guides 1 and 11 while the transferring sinkers P 2 receive additional yarn b (or a) from the thread guide 2. The fabric is produced in ithe following manner: 120 Considering first the pair of thread guides 1 and 11 at the right hand end of Figs 2 and 3, it will be seen that ground yarn g is fed to all the needles and additional yarn a (b) is fed only to needles N 2 (i e to alternate needles) so 125 that in the working direction R needles N 2 knit two thread stitches 4, 4 from yarns i and a As the yarn a is fed into the needles N 2 the transferring sinkers P' are -moved forward through the needle row so that the portions of 130 785,289 785,289 yarn a extending between two adjacent needles N pass over the transferring sinker P' between such needles to form a long loop 3 a thereover The transferring sinker Pl is then withdrawn out of the needle row as

shown in Figs 3 and 4 to hold the long loop 3 a formed thereon clear of the associated needle N' Needle N' takes ground yarn g and knits together with a long loop 3 a, previously transferred to it from the associated transferring sinker P', stitch 4, 10 The needle N' then receives ground yarn g and additional yarn b (a) from the next pair of thread guides 11 and 2 respectively to knit in the next course normal two thread stitches 4, 4 from said yarns g and b. The transferring sinkers P' with the long loops 3 a thereover remain in the withdrawn position at the second pair of thread guides 11, 2 and are not moved back into the needle row until shortly before again reaching thread guides 1 and 11 At this point shown at the right hand end of Fig 2 and 3, the transferring sinker P' is positioned through the needle row to permit the associated needle NI to move upwardly through the long loop 3 a so that on subsequent withdrawal of the transferring sinker Pl the long loop 3 a is transferred to the needle to lie on the opened latch as shown in Fig 4 In order to open the latch a short up and down movement is imparted to the needle. It will be seen that by placing the long loop 3 a over the opened latch of the needle ensures that this loop is separated from the previously formed stitch which still hangs on the shank of the needle below the opened latch This previously knitted stitch is knocked-over in the following downward movement of the needle whilst the newly taken yarn g and loop 3 a are held in the closed latch in readiness for knitting into stitches 4, 10 to form the next but one course. The above procedure is effected in the reverse order at the pair of thread guides 2 and 11 at which point ground yarn g is fed to all needles and additional yarn b (or a) is fed only to needles N' to knit two thread stitches 4,4 from these two yarns whilst the portions of yarn b extending between adjacent needles N' pass over the transferring sinker P' between them to form long loop 3 b thereover. In other respects the operation of the needles and transferring sinkers is as described above but with the long loops 3 b being transferred to the needles N 2 to be knitted with newly taken ground yarn g into sitches 4, 10 in the next but one course. In order still further to clarify the sequence of operations in the fabric shown in Fig 1, the courses marked 1 C are knitted from yarn fed from thread guides 1 and 11 whilst the courses marked AC are knitted from yarn fed from thread guides 2 and 11. In order that the long loops 3 a, 3 b, are still safely retained on the transferring sinkers when the free ends of the latter are drawn slightly out of the needle row, the free end p I of the transferirng sinker P' and P' is advantageously directed obliquely upwards (as shown in Fig. by free end Pb in dotted lines) 70 In order to permit the selective

operation of the two groups of needles and transferring sinkers, the butts of the two groups of needles and the butt of the two groups of transferring sinkers are respectively displaced along the 75 shanks of the needles and transferring sinkers in order to be operable by different sets of cams.


* GB785290 (A)

Description: GB785290 (A) ? 1957-10-23

Improvements in a process and apparatus for the production of iron granules


PATENT SPECIFICATION 785,290 Date of Application and filing Complete Specification July 20, 1953. No 20137153. Application made in Switzerland on Dec 6, 1952. Complete Specification Published Oct 23, 1957. Index at Acceptance: -Class 82 ( 2), D. International Classification: -C 22 f. COMPLETE SPECIFICATION Improvements in a Process and Apparatus for the Production of Iron Granules We, AKTIENGESELLSCHAFT DER VON MOOS'SCHEN EISENWERKE, of Lucerne (Switzerland), a company organised under the laws of the Swiss Confederation, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: -

The invention relates to a process and to apparatus for the production of iron granules for polishing castings and for descaling drawn and rolled products, such for example as section iron. Granules of iron and steel, are used with advantage instead of sand, for example quartz sand, for cleaning castings of cast steel, cast iron or non-ferrous materials, for mechanically descaling rolled products, and for cleaning the surfaces of articles which are to be subjected to a subsequent surface treatment, such as painting, z Inc plating or enamelling. According to the invention a method of producing iron granules comprises causing the iron to flow on to the apex and down the face of a conical member in such manner that several streams of molten metal impinge upon a high pressure annular spray of water whereby the metal is caused to disintegrate into particles the particles dropping into cooling water. The water pressure producing the spray must amount to at least 2 atmospheres gauge, but may conveniently amount to a multiple thereof This water pressure, and the velocity of the water resulting therefrom, determine decisively the size of the granules formed The higher the velocity of the water, the smaller are the granules formed By varying the water pressure or the velocity of the water and the mass flow of water per unit time depending on it, and by varying the quantity of iron to be poured on it per unit time, the granule size or the percentage of the various granule sizes in the mixture of granules formed can be influenced within very wide limits. In order that the invention may be clearly understood and readily carried into effect, two embodiments of apparatus for carrying out the process according to the invention are described by way of example with reference to the accompanying drawings, in which:Figure 1 is a lateral elevation of the first embodiment of apparatus according to the invention for the production of iron granules, and Figure 2 is a lateral elevation of the second embodiment of apparatus according to the invention for the production of iron granules. In the device for the production of iron granules according to Figure 1, the water basin is provided with an overflow 21 and a discharge pipe 22 Xn the middle of the water basin 20 is disposed a high-pressure spray nozzle 23, which is supplied with water under pressure through a high-pressure pipe 24, and the discharge openings of which lie in several rows one on top of the other on an annular conical face This high-pressure spray nozzle 23 produces a conical annular water spray mantle On the high-pressure spray nozzle 23 is mounted a support 25 which carries a conical jet distributor 26 of refractory material. The molten iron is poured out from the crucible 1 accurately on to the

apex of the jet distributor 26, and flows down over the distributor on all sides From the lower edge of the conical jet distributor 26 the iron flows on to the high velocity spray of the conical water mantle of the high pressure spray nozzle 23, and is granulated thereby. In the device for the production of iron granules according to Figure 2, in the middle of the water basin 30, which is provided with an overflow 31 and a drain pipe 32, is mounted a vertical tube 33 In the tube 33 is journalled a shaft 34, which is driven through a bevel gear 35, mounted on its lower end below the water basin 30, by a bevel gear 37 meshing therewith The gear 37 is mounted on the end of the shaft 36 and is driven by a motor (not shown in the drawing) On the upper end of the shaft 34 there is mounted coaxially to it a conical thrower disc 38 Above the water basin 30 there is fixedly mounted an annular L 2 785,290 high pressure spray nozzle 39 concentrically to the thrower disc 38, which is supplied with water by a high pressure pump (not shown in the figure) This high pressure spray nozzle 39 has a large number of downwardly directed water discharge openings and produces a water mantle formed by a plurality of high velocity sprays and surrounding the thrower disc 38. The molten iron is poured out from the crucible 1 accurately on to the apex of the rotating thrower disc 38, and is thrown off from its edge The iron droplets thrown off from the thrower disc 38 are intercepted by the water mantle of the high pressure spray, and are granulated by the high pressure spray. The process and the devices specifically described with reference to the accompanying drawings make it possible to regulate the sizes of granules of soft to medium hard iron produced, and thereby to attain an economical output of granules of the sizes required without any subsequent disintegration thereof The granules produced merely require grading according to size by sifting. Tests have proved that in this manner by selecting favourable conditions of water pressure and of the quantity of iron poured on to the water spray or sprays, and with the use of the best devices for carrying out the process, a yield of up to 80 % of granules of a size from 0.5 to 1 millimetre or of a size from 0 5 to 2 5 millimetre diameter can be attained.


* GB785291 (A)

Description: GB785291 (A) ? 1957-10-23

An improved process for moulding or casting profiled articles


COMPLETE SPECIFICATION. An Improved Process for Moulding or Casting Profiled Articles. We, POWER JETS (RESEARCH: AND DE VELOPMENT) LIMITED, a British Company, of 25 Green Street, London, W.1, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement Articles of a special but smoothly curved or twisted shape which are moreover required to be of accurately formed profile, and especially objects of aerofoil section, are commonly machined in a copying machine to a form which is a copy of a model serving as a master pattern. Turbine and dynamic compressor blades are machined to correct profile in this way. The making of the model, especially of an article which is of varying cross-section or twisted along its length, has hitherto been slow and costly. An object of the present invention is to enable a model to be made comparatively quickly. The invention consists in a method of moulding or casting a body having a curved or twisted surface which includes setting up in spaced relationship two or more correctly profiled templates, stretching a sheet of pliable material in contact with the profiled edges of the templates to form that surface in the mould and, while the sheet remains substantially in the stretched position thereby resulting, casting material against the sheet to form the body. The material may be plaster or other moulding material which is capable of consolidation substantially without damaging or distorting the sheet. Additional features of the invention are that the moulding material is introduced between adjacent templates and that after removal of the sheet an article. for example, a metal model is cast in contact with

said surface of the body. As will appear from what follows, the pliable material of the sheet may have in some cases a rubbery consistency but in other cases may conveniently be substantially nonelastic. In making a model of one half of a turbine blade--e.g. of the concave face-two end gauge plates and preferably one or more intermediate gauges are usually made of sheet metal with convex knife edges which will fit the concave surfaces of a correct model at chosen end and intermediate positions. According to previous practice a steel block is then worked until a concave surface thereon firstly fits the gauge plates in their assigned positions and subsequently presents a smoothly curved face extending between them. Both of these phases of working the block are laborious and costly. In comparison the present invention affords the possibility of eliminating the first phase and minimising the subsequent phase. The foregoing and other features of the invention will be readily understood from the following descriptions, with reference to Figures 1, 2 and 3 and Figures 4 and 5 respectively of the accompanying drawings, of two alternative methods for making in accordance with the invention, models corresponding to the convex and concave surfaces of a blade. Figure 1 shows an isometric view of the apparatus for use in carrying out the first method with the pliable sheet in position. Figure 2 shows a transverse section of the apparatus when adapted as a mould prior to casting the model and Figure 3 shows an isometric view of the cast model. The apparatus consists of a base plate 1 having at spaced points along its length a number of transverse slots 2. A number of templates 3 are entered one in each slot, each template having a base portion 4 of reduced width (see Figure 2) which is located laterally in the associated slot by set screws 5 entered into laterally extending screw holes coinciding with the slot and engaging opposite edges of the base portion 4. The upstanding portion of each template has parallel edges spaced inwardly from the sides of the base plate 1 and an intermediate convex knife edge having a profile complementary to the profile, at the corresponding position, of the concave surface of the blade which is to be copied from the model. The templates are conveniently aligned by reference to one of the parallel edges on each template. Two wooden shutters 6 bear on the respective parallel edges of the templates and the baseplate, being of such a thickness that their outer faces coincide with the sides of the baseplate. The upstanding edges of the shutters are co-extensive at each template with the abutting parallel edge of the template and are bevelled away from the templates. A sheet 7 of rubber or rubber substitute such as neoprene extends over the

outer face of one shutter, around the curved edges of the templates and over the outer face of the other shutter. Each longitudinal edge of the sheet 7 is gripped between two strips 8 which are riveted together through the sheets. At opposite ends of the strips forked yokes 9 are pivotably attached thereto, each yoke having a threaded extension 10 and a thumb screw 11 thereon bearing on a slotted extension 12 of the base plate. The sides of the baseplate 1 are provided with grooves 13 to accommodate the inner strip 8 and yokes 9, the heads of the set screws 5 being accommodated in recesses in the grooves. The lateral edges of the sheet are gripped between similar riveted strips 14 having in each case a single yoke 9 pivoted thereon with a corresponding threaded extension 10 and thumbscrews 11 bearing on a slotted projection 15 from the baseplate. By tightening the thumbs crews 11 the neoprene sheet 7 is tensioned in mutually perpendicular directions over the templates to simulate the concave face of the blade. The apparatus is then inverted and plaster is introduced between each successive pair of templates and into contact with the sheet 7 through holes 16 in the baseplate. When the plaster has set the sheet 7 and shutters 6 are removed. At this point a model may be cast by forming a mould box consisting as shown in Figure 2 of side walls 17 abutting on the parallel edges of the templates and end walls 18 abutting on the end templates and affording a cavity over the curved surface of the plaster in which the model is east. How- ever the model is preferably cast oversize to allow its curved surface to be cleaned up between the template stations. Accordingly a small amount of plaster, to a depth of only a few thousandths of an inch, is scraped away over the whole curved surface leaving the knife edges of the templates proud, before the model is cast and conveniently before the mould box walls 17 and 18 are fitted. The resulting casting, seen in Figure 3 will have, in its concave surface, reference lines 19 in the form of very shallow grooves. The surface can then be cleaned up by removal metal down to the level of the bottom of the grooves until the reference lines have almost disappeared. The casting is made in an alloy of comparatively low melting point and having no appreciable coefficient of expansion so that no allowance is made fop contraetion on cooling. Such an alloy is somewhat soft and may wear away or distort under repeated rubbing by the stylus of the copying machine. The model may be used once, or only a few times to make-by copying in the machine-one or more steel models to serve as master patterns. Alternatively the cast model may be chromium plated to form on its working surface a hard coating of considerably less thickness than one

thousandth of an inch. It has been found that such a coated model will long withstand the comparatively light pressure of the stylus of a hydraulically or electrically aetuated copying machine. For producing a model from a convex surface corresponding to the conves face of a blade, when the templates would have a concave profile, a method generally similar to that described above may be used but differing in that while the sheet is tautened over the templates an inflatable rubber or similar cushion is constrained against the sheet, the latter being constrained in turn against the templates when the cushion is inflated. Alternatively the sheet may be integrated in the cushion. Although it would seem impossible in either case to avoid some depression of the sheet between the templates this is not unacceptable since it results in an oversize model and therefore the error may be eliminated in the fiiiishing of the model. The alternative method illustrated by Figures 4 and 5 may be used for either convex or concave faces. In t,his method the apparatus, an exploded isometric view of which is shown in Figure 4, consists of a base plate 1 having as before a number of transverse slots 2 in which are inserted templates 3 held by set screws extending transversely into the slots. The templates each have a knife edge of concave profile (since the convex surface of a blade is to be simulated in the model) between two depending side portions 20 which latter enter the slots 2. One of the side portions 33 is notched at 21 to provide a reference face for the alignment of the templates. The upper corners of the templates are connected together by stays 23 which increase the rigidity of the structure. Opposed side walls 24 having slots 25 to receive the templates bear on the outer edges of the portions 20 of the templates and on the base plate 1, being clamped in position by suitable external elamps (not shoan). One side wall 24 has a groove 96 slightly deeper than the notch 21 in the templates so that the latter protrude slightly into the groove. Elsewhere the inner edges of the portions 20 of the templates are flush with the side walls. Before or after the side walls are fitted a length of pliable tape 27 just wide enough to cover the knife edges of the templates is drawn through the tunnel formed by the templates. One end of the tape is fastened by a temporary adhesive to the outer face of one end template; the tape is then tautened over the templates and its other end is fastened by a temporary adhesive to the outer face of the other end template, the ends of the tape being notched to accommodate the curvature of the tape. Alternatively a number of similar lengths of narrower tape may be arranged to overlap one another. The tape may be of substantially non-elastic material, for

example a linen backed tape, but must be resistent to sagging when wet. With the side walls 24 in position further lengths of tape are applied as gussets 28 along the junction between the tape 27 and walls 24, being secured to both by a temporary adhesive. Plaster is then introduced between the templates above and in contact with the tape and when the plaster has set the tape is removed. At this point, as in the previously described method, a very slight amount of plaster is preferably removed from the curved face between the templates. For this purpose the templates 3, stays 23 and plaster between them may be removed from the base plate and side walls. When the apparatus is subsequently reassembled, pairs of end plates 29 are attached to the end templates to enclose the tunnel formation of the templates. The end plates have runner and riser passages 30 by means of which metal is poured into the tunnel, and are split so as to be removable from the cast model. When the runner and riser are removed the cast model appears as shown in Figure 5, having reference lines 19 corresponding to the knife edges of the templates and other reference lines 31 corresponding to the notches 21 in the templates, both appearing as very shallow grooves. The model may be finished and plated in the same way as that produced by the method previously described but has the added advantage that a flat reference face may be obtained on the model from the grooves 31. Although the described methods of carry ing out the invention have been concerned in particular with the production of models for copying machines it will be apparent that a wider field of application exists. What we claim is I. The method of moulding or casting a body having a curved or twisted surface which includes setting up in spaced relationship two or inore correctly profiled templates and stretching a sheet of pliable material in contact with the profiled edges of the templates to form that surface in the mould and, while the sheet remains substantially in the stretched position thereby resulting, casting material against the sheet to form the body.


* GB785292 (A)

Description: GB785292 (A)

No title available


PATENT SPECIFIGMTION 783,292 Inventors: -NEVILL FRANCIS MARSH and DENIS SYDNEY PANISSET. 1 "" 15, 1 r _ q -1 -I" t, 51 ' O , 4 p if m p 4. 1 1,' ' ' 1 i i Dare of filing Complete Specification Nov 5, 1954. lpplicat ion Dale: Nov 5, 19; 3, No 555 53 C 7 i 1 plcle Seci ication Published: Oct 2 l, 195 i 7. Index at Acceptance:-Class 39 ( 3), H,1 D 1 L: 2 E 4 C 1. International Classification:-HO 5 b. COMPLETE SPECIFICATION. Improvements relating to Electrically Heated Cooking Appliances. We, SIMPLEX ELECTRIC COMPANY LIMITED, a British Company, of Broadwell, Oldbury, in the County of Worcester, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to electrically heated cooking appliances of the kind intended for use in cooking operations such as toasting or grilling involving the downward radiation of heat onto a substance to bei cooked, and comprising an electric heating element arranged and supported by the body or like supporting structure of the appliance in a horizontal or approximately horizontal plane, such body or structure affording space beneath the heating element for the accommodation of the substance to be cooked. The invention is applicable to appliances of this kind, whether these are in the form of separate grilling or toasting appliances or whether they constitute part of a cooking stove including other electrically heated cooking appliances Further, the invention is applicable to appliances of this kind whether they are intended or adapted to be used for cooking by downwardly directed radiant heat only, or whether they are arranged or constructed for alternative or additional use as heating units of the kind generally termed "hot plates," wherein heat is trans:35 mitted from the heating element to the underside of a cooking vessel supported above it by a combination of conduction,

convection and radiation. The inventioni is specifically concerned with electric heating appliances of the foreoing kind wherein the electric heating element is of the type in which the heated lPrice 3 s 641 l resistor is embedded in insulating material enclosed by an outer tubular sheath of metal, and has for its object to provide improved uniformity of heating of the area of the substance to be cooked Such appliances are hereinafter referred to as being of the kind specified. According to one aspect of the invention an electrically heated cooking appliance of the kind specified characterised in that the sheathed electric heating element is confined to a peripheral margin of a rectangular, or approximately rectangular, area by arranging the element in the form of a correspondingly shaped frame containing an outer run and an inner run of the element, the corner portions of the peripheral margin containing a greater length of the heating element per unit area than do the remaining side portions of peripheral margin, the electrical resistance of the heating element being substantially uniform along its length. According to a further aspect of the invention we provide an electrically heated cooking appliance of the kind specified, characterised in that the electric heating element is confined to a peripheral margin of a main rectangular area to be energised which is adapted to be so energised solely by an electric heating element, the corner portions of this margin, as defined by elemental rectangular areas having sides equal to the widths of the peripheral margins extending along respectively adjacent sides of the main rectangular area, containing a greater length of the heating element per unit area than do the remaining side portions of the peripheral margin, the electrical resistance of the heating element being substantially uniform along its length. The sheathed element may be bent into the form of a gapped or unclosed loop wherc _ 35 6 i 5 / _ 31) 1 1 1 p 785,292 it passes through a corner portion, while the parts of the element which extend along some or all side portions of the peripheral margin in which the element lies may be sub; stantially rectilinear, or of a curvature such as to provide a relatively smaller specific electrical loading of the side portions of the peripheral margin in comparison with the corner portions. 1 ( 1 Within the peripheral margin the sheathed electric heating element may be arranged so as to have a plurality of limbs or runs extending side-by-side along the side portions in laterally spaced relationship and 1., connected by respective looped portions disposed in the corner portions, thenlateral spacing of the limb or runs in the side portions being generally greater than the separation between

adjacent limbs of the same or 2 ( O different looped portions disposed in the corner portions. In a particularly convenient arrangement the looped portions in the corners may be so disposed that the spaced side limbs of 2, the loops lie on opposite sides of a diagonal of the main rectangular area with the gap or unclosed part of the loop situated inwardly, i e nearer to the centre of the main area than is the connecting part which :3 N unites the limbs of the loop. In any of the foregoing arrangements it is within the scope of the invention for the sheathed heating element to be in two or more separate lengths, such lengths being :35 connected individually to the supply with or without the interposition of a switching means enabling such lengths to be energised selectively or in different modes of connection to the supply (e g by series, or parallel 40) switching circuits). We, may however, employ a sheathed heating element formed in a single length, this being bent to provide at least two limbs along each of a pair of opposed side portions of the peripheral margin, which, through looped corner portions, are connected with U-shaped end portions, these U-shaped end portions having their closed ends disposed adjacent to each other at a 550 spacing to provide substantially uniform energisation of this side portion of the margin, the opposite parallel side portion heing that at which the ends of the singlelength element enter. 5., By adopting heating element dispositions as above described there is effective compensation for the inherently greater heat loss :it the corner portions as compared with the side portions In the preferred arrangement ji X wherein the heating element is confined to the peripheral margin there is, in addition, compensation for otherwise greater heating effect which would be attained in the central region of the surface of a substance undergoing cooking in comparison with that obtaining at the margins of this surface so that greater uniformity is attained. In some appliances the heating element may also be exposed at its upper side, to constitute a heated surface, upon which may 70 be supported a cooking vessel Whilst such a construction is advantageous in that it enables a common heating element to be utilised in different modes of cooking, (i e. grilling or toasting in respect of substances 75 disposed beneath it, and boiling, stewing, or even roasting in respect of substances disposed above it in suitable vessels, or containers), use simultaneously in the two modes may impair the uniformity of heating effect So produced upon the lower substance, due to local inequalities in the heat extraction rate from the upper side of the heating

element. A further object of the invention is to avoid or reduce this possible disadvantage 55 With this object in view an electrically heated cooking appliance in accordance with the invention as above described may have a heating element which serves both as the heating means for providing downwardly 90 directed radiant heat for grilling, toasting or the like cooking operations and itself presents a horizontal upwardly facing heating surface forming a hot plate on which a cooking vessel may be disposed to receive 95 the heat therefrom, the appliance being further characterised in that to reduce the conductive transmission of heat directly from the heating element to the vessel relatively to the heat transmitted thereto from 100 the element by convection or radiation the sheath has a greater vertical cross sectional dimension than horizontal cross sectional dimension, the topmost portion of the sheath being in the form of an upwardly projecting 105 rib or segment of an oval figure having its major axis vertical. Preferably the sheath is formed with two diametrically opposed ribs one of which projects upwardly to constitute the topmost por 110 tion of the sheath and the other of which projects downwardly. By disposing the sheathed element with its greater cross sectional dimension vertical and its smaller cross sectional dimension 115 horizontal the rigidity of the grid like structure afforded by the heating element when bent into the desired configuration and with respect to deflecting forces such as the weieht of a vessel supported thereon is in 120 creased, whereas the deformation of the metal of the sheath and displacement of the compacting insulating material usually provided in the sheath between the resistance wire and the inner surface of the sheath is 125 less severe at the locality at which maximum deformation or displacement occurs for examn le at the inner and outer boundaries of sharp bends, so that not only can the element he bent more readily into the 1:;) :1 735,2 u 2 required configuration but there is less risk that such bending will impair the mechanical and electrical properties of the element. Furthermore by making the topmost portion of the sheath in the form of an upwardly projecting rib or segment of an oval figure as above described, the underside of a vessel supported on such element Xill be resting on a portion of relatively sharp curvature which portion will be also furthest from the centre of cross section of the heating element so that any variations in contact pressure betwveen the underside of the vessel and the heating element are less likely to produce significant variations in temperature along the length of the elements, and the risk that the uniformity of downward radiation will be impaired when the appliance is in use both for toasting or grilling

and for supply2 k ing heat to a cooking vessel will be materially reduced. As a possible alternative means separate from the sheathed electric heating element itself may be provided for supporting the 2 base of a vessel in close proximity to the upper surface presented by the sheathed heating element without the vessel actually touching it so that conductive transmission of heat from the element to the vessel is 3:u 1 interrupted completely thereby avoiding differential local cooking of the clement by variations in contact area or pressure. The invention is illustrated in the accompanying drawings wherein::,.l Figure 1 is a plan view of one construction of electrically heated cooking appliance in accordance with the present invention; Figure 2 is a cross sectional view on the line 2-2 of Figure 1; pl Figure 3 is a cress sectional view on the line 3-3 of Figure 1. Figure 4 is a fragmentary view from the underside; and Figure 5 is a fragmentary view showing 4.5 the manner of supporting the heating element in the transverse members of the frame. In the construction illustrated the appliance which is of the kind specified may form part of an electrically heated cooking stove which may be of the kind including an oven of substantial size above which are disposed a plurality of cooking units including a combined hot plate and grilling ;) unit with which the present invention is specifically concerned The appliance may, however, be embodied in a smaller sized cooking stove intended usually to be used for grilling, toasting, or boiling and stewing 1.) only without the provision of a larger sized oven and in such a case the appliance may constitute the only unit of the stove or m-ay be associated with auxiliary hot plates if desired. 03.e In any of these possible applications of appliance this may comprise a supporting means for the electric heating element this supporting means preferably being in the form of a frame 10 of a'suitable heat resisting metal, for example chrom-iron alloy or 70 stainless steel. The frame may be formed of metal strip arranged with its major dimension vertically and may be o F rectangular figuration as viewed in plan the longer dimension and 75 shorter dimension of the frame conforming to accepted standards, namely 10 Q inches and S inches respectively. Intermediate its cnds the frame may inelude transverse reinforcing strips 11 extend SO in 2 parallel to its shorter sides, connected centrally by strips 12. Near the corners of the frame this may be provided with attachment lugs or brackets 13 having screw holes 14 or otherwise 85 adapted to permit the frame to be secured horizontally in the body of the

appliance above a grilling chamber 15 and flush or approximately flush with a hob-plate structure 16 affording a rectangular aperture for 90 the re-ception of the frame. One of the shorter sides of the frame may have secured thereto a supporting plate 17 for a terminal or connector unit having a housing IS serving to accommodate terminals 95 for the current to be supplied to the electric heating element of the appliance These terminals are connected to downwardly projecting contact pins 19 extending from the underside of the housing Heat insulation 100 between this housing and the supporting plate may be effected by inter-position of a strip of asbestos or similar material. The heating element itself is of the type wherein the resistance wire is enclosed in a 105 tubular metal sheath packed with insulating powder and preferably we employ a heating element of this type constructed as described and claimed in the Complete Specification of our prior British Letters Patent 110 No 592,124, wherein the cross sectional shape of the sheath is circular or approximately so with longitudinally extending ribs projecting from the outer surface at diam-trically opposed positions 115 The sheathed electric heating element may be formed in a single length and supported by the frame within the confines of a perinheral margin of the frame of a width of the order of + to i the corresponding dimen 120 sien of the frame itself. Conveniently, the element may be bent to form outer and inner runs conforming approximately to the shape of the frame and situated one inside the other in the same 125 plane, these runs being supported by the provision of slots 20 (Figure 5) formed in the transverse strips 11 and secured in position in these slots by deforming the outer parts 21 of the slots inwardly to grip the 1 20 so )O . 785,292 sides of the sheath where it passes through each slot. The inner run of the element may have r ectilinear limbs 22 extending parallel to 3 the longer sides of the frame these limbs being united at their ends with corner portions 23 of looped form These looped corner portions may be of U-shape as viewed in plane with their limbs extending approximately parallel to each other, and the axis of symmetry being disposed diagonally with respect to the main frame or approximately so, the unclosed or gapped part of the loop being situated inwardly. 13 If desired, the loops 23 may be made of more severe form, that is to say, the gap 24 or unacloscd part may be a narrow opening or neckh which widens out in the interior of the loop the latter then approximating to a partly closed circular or like convolution. If it is desired to position a still greater length of heating element within the confines of the corner portion, as defined by an elemental

rectangle having sides equal to the width of the peripheral margin, then the looped portion may include more than one complete convolution arranged in somewhat spiral form so that the whole length of the element in this portion may be disposed in the same horizontal plane, but ordinarily, as shown, a single U-shaned or unclosed loop will be found adequate. At the one end of the frame the ends of these looped corner portions 23 not united 3 a with the side limbs 22 of the inner run may be bent downwardly somewhat as at 25 and turned to enter the housing 18 at a position spaced below the frame, these downwardly turned connecting portions preferably including rods or other low resistance connecting elements rather than heating resistor elements so that these portions do not attain the same high temperature in use as a remaining length sheathed element. 43 At the opposite end of the frame the looped corner portions 23 of the inner run may be connected with substantial rectilinear limbs 26 of the outer run extending parallel to the adjacent end member of the frame by d O U-shaped end portions 27 which are situated one on either side of the longitudinal reinforcing strip 28. The outer run of the element includes rectilinear limbs 29 extending parallel to the longer sides of the frame and disposed between these and the corresponding rectilinear limbs 22 of the inner run The frame of the outer run has a further rectilinear limb extending parallel to the rear frame merm6 o ber and passing above the downwardly bent connecting portions of the inner run. All these rectilinear limbs 29 and 30 of the outer run are united with each other by corner portions 31 also of looped form but in which the degree of looping is not quite so severe as is the case for the looped portions of the inner run. For example, the looped portions of the outer run may be in the form of elbow sections having an included angle lying 7 i o betwezen 0 and 90 degrees for example, of the order of 80 degrees or thereabouts, this value being found to produce sufficient extra length in the corner portion to provide the additional heating required thereat in conm iparison with that required along the side portions of the peripheral margin. Instead of the limbs 22, 26, 29 and 30 being of strictly rectilinear form they could in appropriate cases be of somewhat curvate SC' form provided that the aggregate lengths of heating element in the side localities of the peripheral margin do not exceed the aggregate length of heating element in the corner location 83 In forming the configuration required for the heating element and particularly when utilising the heating clement constructed in the manner described and claimed in our aforementioned British Patent Specification 90 it is

preferred niot only for convenience in the actual bending operation but for other reasons as hereinafter particularly pointed out, to bend this element in a plane perpendicular to the diametral plane containing 91 the ribs 32 and 33. The principal reason for bending in this manner is so that one of the projecting ribs may lie uppermost and form the actual surface upon which the base of a cooking 100 vessel may rest. Contact between the base of such vessel and the sheathed heating element is thus confined to a line or relatively narrow zone such as will be afforded by the edge of the 103 rib 32, and consequently the proportion of heat transmitted to the vessel by conduction directly from the sheath will be reduced relatively to that transmitted by other means such as convection or radiation, in corm 110 parison with the ratio of he at transmitted by conduction to convection or reduction which obtains in the case of known hot plate structures formed by sheathed heating elements having a locally flattened upper face 113 It is almost inevitable owing to local distortions of the upper surface presented by the heating elements or owing to local distortions of the under-surface of the vessel, or owine to both these factors that some 120 parts of the under-surface of a vessel placed on the heating element will be pressed into contact therewith more strongly than other parts, whlich, in some cases may not actually touch the heating element at all 1 '2 If the heating element has a locally flattened upper surface there might, in consequence be significant local variations in the rate of heating extraction from the element to the vessel owing to extended area 130 l 785,292 of contact between these two parts With the above described construction, however, only a small proportion of the heat is transnitted by conduction and consequently even if there are variations in the contact pressure producing differential rates of conductive heat extraction at different localities these will not significantly affect the temperature of the sheath element at these localities, since most of the heat will be transmitted by convection or radiation at a rate which is not varied by the contact pressure. The result could be obtained by utilising a cross section of oval or elliptical form 1.5 arranged with its major axis vertical. The ribbed construction illustrated arranged with the ribs in the manner stated has an additional advantage of increasing the stiffness of the element as a whole in relation to lateral deflection in the vertical plane and therefore tends inherently to reduce the possibility or extent of distortion out of the true horizontal plane thereby reducing the differential contact pressures 2.5) at separated localities of the element. In order to increase the thermal efficiency of the appliance when in

use in only one of its possible modes we may provide a reflector plate 34. :3) Such plate may be formed of suitable metal such as aluminium and is preferably flanged as indicated at 35 or at its periphery and is provided with a handle 3 by means of which it can be placed either beneath the heating element as shown in full lines in Figure 3, or above the heating element as shown in chain lines in Figure 3. In the former position the plate is supported at its rearward end on pegs 37 projecting from plate 17 and at its forward end on collars 38 carried at the lower end of screws or studs 39 In the latter position, as seen in chain lines in Figure 3, it will be observed that the flange 35 of the plate is -15 received in a peripheral groove 36 and that the edges of the ffange rest on the bottom of this groove to maintain the main body of the plate out of contact with the heating element.


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