US2664788A - Stereotype finishing machine - Google Patents

Description

Jan. 5, 1954 C. V. KNELL STEREOTYPEI FINISHING MACHINE ll Sheets-Sheet 1 Filed NOV. 16, 1945 INVENTOR. C. VEHNE KNELL Jan. 5, 1954 c. v. KNELL 2,664,788

STEREOTYPE FINISHING MACHINE Filed Nov. 16, 1945 ll Sheets-Sheet 2 JNVE/VTOR VERNE KNELL 14770 five y Jan. 5, 1954 c. v. KNELL STEREQTYPE FINISHING MACHINE Filed Nov. 16, 1945 ll Sheets-Sheet 3 ATTORNEY Jan. 5, 1954 c, v, KNELL 2,664,788

STEREOTYPE FINISHING MACHINE Filed NOV. 16, 1945 ll Sheets-Sheet 4 INVENTOR c. mm: KNELL HTTORNFY Jan. 5, 1954 c. v. KNELL 2,654,788

STEREOTYPE FINISHING MACHINE Filed Nov. 16, 1945 11 Sheets-Sheet 5 Jan. 5, 1954 c. v. KNELL 2,654,788

, STEREOTYPE FINISHING MACHINE Filed Nov. 16, 1345 11 Sheets-Sheet e IN V EN TOR.

C VERNE KNELL 147T JIFNEY Jan. 5, 1954 c. v. KNELL STEREOTYPE FINISHING MACE'IINE 11 Sheets-Sheet 7 Filed Nov. 16, 1945 *L J-.J INVENTOR c VERNE KNELL ATTORNEY Jan. 5, 1954 c. v. KNELL 2,664,783

STEREOTYPE FINISHING MACHINE Filed Nov. 16, 1945 ll Sheets-Sheet 8 INVENTOR.

C. VERNE KNELL WQWAM Wink/v y Jan. 5, 1954 c. v. KNELL STEREOTYPE FINISHING MACHINE 11 Sheets-Sheet 10 Filed NOV. 16, 1945 INVENTOR. u. wanna mm.

Al Q ATToRNE STEREOTYPE FINISHING MACHINE Filed NOV. 16, 1945 ll Sheets-Sheet 11 INVENTOR. C. VERNE KNELL ATTTRN Y Patented Jan. 5, 1954 UNITED STATE ATENT OFFICE STEREOTYPE FINISHING MACHINE Application November 16, 1945, Serial No. 629,122

6 Claims.

1 The present invention relates to a novel and improved plate finishing machine and more particularly to an improved machine for accurately finishing the interior of semi-cylindrical stereotypes such as are conventionally used for newspaper presses.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

The accompanying drawings, deferred to herein and constituting a part hereof, illustrate one embodiment of the invention, and together with the description, serve to explain the principles of the invention.

Of the drawings:

Figure 1 is a side elevation, with certain parts broken away and other parts shown in section, of a typical and illustrative embodiment of the present invention;

Figure 2 is an end elevation of the plate finishing machine shown in Figure 1;

Figure 3 is a detail view of the upper portion of Figure 2 with certain parts omitted;

Figure 4 is a section along the broken line i-fi of Figure 3;

Figure 5 is a View showing two positions of the plate as it is moved into the supporting arch for finishing;

Figure 6 is an end view of the rotary boring and slot milling means forming a part of the preferred form of the present invention;

Figure '7 is a side elevation, with certain parts being shown in section and a rotary boring means and slot milling means forming part of the preferred embodiment of the present invention;

Figure 8 is an end elevation of the tool head shown in Figure 7;

Figure 9 is a section along the line 99 of Figure 8;

Figure 10 is a detailed view, partly in section and with other parts broken away of the means for controlling the slot milling means of Figure 6 Figure 11 is a top elevation of the milling cutter;

Figure 12 is a vertical section of the milling cutter housing and drive;

Figure 13 is a sectional view taken on the line l3- l3 of Figure 12;

Figure 14 is a sectional view taken on the line I l|4 of Figure 15;

Figure 15 is a sectional view of a finished stereotype as produced by the finishing machine of the present invention, taken on the line 15-45 of Figure 14;

Figure 16 is a fragmentary sectional view showing the section it-i 6 of Figure 17;

Figure 17 is a developed view of the interior surface of the plate prior to the plate being worked on by the finishing machine; and

Figure 18 is a sectional view taken on the line i8l8 of Figure 1'7 and showing the stereotype plate as it is received by the plate finishing machine.

The present invention has for its object the provision of a novel and improved stereotype plate finishing mechanism for accurately finishing the interior of a conventional semi-cylindrical stereotype without damaging its outer, or printing, surface. A further object is the provision of such a stereotype finishing machine in which the plate is accurately and firmly seated in a rigid form while the interior is surfaced and is automatically removed from the rigid form after the plate has been finished. The invention further provides a stereotype finishing machine which will accurately finish stereotypes which have been intene tionally cast with a slightly smaller diameter than the diameter of the plate cylinder onto which they are to be mounted for printing, thereby providing a plate which more accurately fits the plate cylinder. Still another object is the provision of a novel and improved stereotype finishing machine for automatically forming recesses or cavities in the interior of the plates to adapt the stereotypes to be secured by tension to the plate cylinders.

In accordance with the present invention, the stereotype plate finishing machine includes an arch or hollow, generally semi-cylindrical form, of a diameter and length corresponding to the external dimensions of the stereotype after it has been mounted on the plate cylinder for printing, and means are provided below the arch or form for supporting the plate by engagement with its straight edges, with the axis of the stereotype parallel to the axis of the arch, and for moving one or both of the plate edge supporting means upwardly while moving one or both of them towards and then away from the other, thereby compressing the plate diametrally as it is raised into contact with the arch to seat it firmly therein, the-movement of the supporting means away from each other being accomplished at the end of the seating operation whereby scarring of the plate on the arch is avoided and the plate supporting members are removed from the path of the finishing tool which will accurately surface the interior of the plate. A further feature of the seating movement is that one side edge is seated first and contact of the plate with the arch flows up from this side edge and down to the other edge. The arch preferably has open ends whereby the plate may be positioned therein and removed therefrom by axial movement.

The plate seating means preferably comprises a lever means operated by rotatable earns which have a common actuating means, the lever means being provided at each side of the arch and including vertically slidable blocks on which the levers are pivotally mounted so that the levers may be horizontally swung as they and the blocks are vertically moved. One of the levers is preferably resiliently connected to its plate supporting means whereby the final seating of the plate is accomplished by a yielding action to accommodate 1-311101 dimensional variations in the plate.

Means are provided for finishing the interior of the plate and preferably comprise an axially movable cutter head or boring tool which is moved through the arch by means of a power driven screw. eanrcontrolled milling cutters also provided for cutting the plat hoot: recesses in the interior of the plate adjacent to its straight edges, as the interior of the plate is surfaced. These recesses are preferably spaced apart axially of the plate and are accurately located with respect to the plate hooks on the plate cylinder.

The finished plate is preferably removed from the arch or form in the same direction as it was inserted and a support or saddle is provided just behind the axially movable cutter head so that, on release of the plate from the arch, the plate is lowered onto the support and is moved out of the arch as the cutter head is screw returned to its original position.

The boring head described and illustrated herein is claimed in the co-pcnding application, Serial No. 629, 23, filed November 16, 1945, of Curtis S. Crafts and Christopher Verne Knoll, now Patent 254,617.

Referring now in detail to the accompanying drawings which illustrate a typical, illustrative and preferred embodiment of the present invention, there is provided an arch 2t or supporting member having a semicylindrical interior face of a diameter and length corresponding to the desired printing surface of the stereotype plat and of sufficient strength so that it does not yield appreciably as the plate is firmly pressed into it and interiorly surfaced. Arch 2% comprises a heavily ribbed member which is bolted to'the up per portions of the main frame 22, and is preferably located substantially midway between the longitudinal ends of the main frame, thereby providing a plate receiving portion at one end of the frame, and a plate delivering portion at the other end of the frame onto which the finished plate is delivered. In actual practice, said arch generally has a diameter of from sixteen to twenty inches and an length of from fifteen to twenty inches, the interior surface of the arch corresponding accurately to the printing surface of the stereotypes to be finished therein.

At the receiving end A of the plate finishing machine, at the left as shown in Figure l are provided a pair of spaced plate edge receiving surfaces 25 which may receive and support the two straight, diametrally opposed edges of the stereotype 23 to be interiorly finished, axially alined with the longitudinal axis of the machine.

Means are provided at the plate finishing portion B of the machine, intermediate its longitudinal ends for supporting the plate, which supports as, 26 are normally alined axially and laterally with the surfaces 2 3 and the plate may be slid from one to the other while the supports 25, 26 are in their normal or lowest position. Plate receiving surfaces 24 are fixed to the frame of the machine while surfaces 25, 28 are for compound vertical and horizontal movement thereon independently of each other as more fully hereinafter described,

Plate supporting surfaces 2 3, 25 and 26 ar preferably all in a single horizontal plane parallel to the diametral edges of the semi-cylindrical interior surface of the arch 29, so that the arch is uniformly spaced from the upper surface of the plate 23 at both sides thereof.

The supports 25, 25 are carried on plate rails El, 28 slidable in lateral channels 23 formed in blocks 33, Si which are slidable in vertical guideways 32 mounted on the main frame Plate rails 2'5, 28 have depending portions with finished surfaces 33 engaging fiats formed on the main frame 22. A threaded tie rod 3t ties block St to block 35 similarly slidable in guideway whereby the distance between blocks 3i and may be varied to accommodate stereoplates 23 of varying diameters. Block till is resiliently and adjustably connected to block it slidable in guideway 32 by means of threaded plunger 3] extending through both blocks and surrounded by coil spring 3?; located in a stepped bore in blocl; and bearing upward against the latter and downward against nuts threaded on plunger El.

Four earns 39 each comprise two cam tracks ill, The tracks to, seen in front elevation in Figure 3, act through rollers t2 iournalled in blocks 35, 35, to raise the blocks upon revolution of the cams 555 from the illustrated pc ..i. Links d3 journalled in blocks 31?, 3i carry lulcrum journals id of levers 35. Cam rollers 4G in tracks all shown in broken lines in Figure 3, upon the above-mentioned revolution of cams 3t, oscillate with a horizontal directional component, the oscillation being transmitted over levers 35 to plate rails N, 28 to which the levers are pivotally connected at ll, causing lateral travel of rails ill, 28 in channels 29.

For simultaneously and equally operating the cams 39, a pair usually being provided at each end of the plate 23, the cams are mounted on shafts 5t which are parallel and suitably journalled above the arch 26 and inter-geared. embodied, each shaft 543 has a gear El meshing with a mitre gear 52 on transverse shaft journalled in the frame and provided with an operating lever 5d releasably coupled to the shaft 53 by means of set screw 55, so that a manual movement of the lever 5 can znove earns from their lowermost position to their uppermost position.

The two cams 39 connected to blocks 3! and 35 are designed to raise these blocks slightly ahead of blocks 30, 35, so that as the blocks 3!, 35, carrying support 25 with them, reach the upper limit of their travel, blocks 39, 36 and support 25 have not yet reached thei upper limit, all as clearly shown in Figures 3 and 5. These figures also show that the supports 25, 2B, actuated by the abovedescribed mechanism, have a compound motion which is upward and inward without tipping,

which is effective to compress plate 23 diametrally as it seats in arch 20 and thereby prevent any wiping action between plate and arch which would, damage the printing surface of the plate. Subsequent to the full line position illustrated in 5 Figure 5, support 25 is retracted laterally outward somewhat, which is effective to increase and equalize the uiametrally outward seating pressure of the right edge of the plate in the arch. contemporaneously with the lateral retraction of support 25, support 26 completes its upward travel and is laterally retracted. Completion of the upward travel of support 26 causes leftwardly successive peripheral portions of plate 23 to seat in the arch, the contact progressing upward from the right side of Figure 5 to the top of the arch and hence downward to the left edge which rests on support 26. It is notable that support 25 is positively actuated in its movement, while support 26 is resiliently actuated in its movement by mechanism which is similar to the actuating mechanism of support except for the addition of spring 38, which is effective through support 2t to press plate 23 upward and cause the latter to exert circumferentially transmitted pressure 25 against the positively actuated support 25. The right edge of plate 23 may be finished in register with its printing surface for color work or the like, and the above seating and clamping mechanism permits the entire plate to be seated in register with the registered right edge, so that the finishing of the interior and the forming therein or plate hook recesses for tension lockup of the plate on the printing cylinder may be done with unprecedented exactness of register. 5

While the plate is firmly secured in its position seated in the arch 20 it may be interiorly finished to conform accurately to the cylindrical surface of the plate cylinder of the printing press on which it will eventually be secured and printed. For this purpose, means axially movable of the plate are provided for boring or otherwise finish ing the interior cylindrical surface of the plate, and due to the firm support of the plate this finishing may be much more accurate than usual; thereby resulting in a printing plate which will produce impressions of higher quality than usual.

To carry out this interior finishing of the plates, means are preferably provided for accurately boring the interior of the plate, such means moving axially of the plate as the boring tool is rapidly revolved.

Figures 16 to 18 show various views of the plate as it is placed on the finishing machine, while Figures 14 and 15 show schematic views of the plate, as finished.

The finished plate shown in Figures 14 and 15 comprises a semi-cylindrical member having a printing surface BI and an interior sur-. face 62 to be seated on and closely conform to 60 the outer surface of a plate cylinder and when so seated to provide a printing member of a predetermined size and having an accurate cylindrical surface so that the impression thereof will be of high quality. 5

Plate 60 is provided with internal recesses 63 between ribs 64, to lighten the plate, these ribs and recesses being shown more in detail in the developed view, Figure 17. Plate 60 is also formed with straight edges 65 of less thickness than the main body of the plate. Recesses 63 are formed over the entire inner surface, except at the edges, although shown only over a portion of the surface in Figure 17.

Figures 14 and 15 show the plate as it is finished by the machine illustrated (except that the ribbing is omitted for clarity). The interior surface of the plate 60 has been surfaced so that all of the ribs lie in a uniform cylindrical surface and the inner surface is formed with two parallel series of slots 66 closely adjacent the straight edges 65 each slot having a flat side 61 inclined towards the straight edge, the other longitudinal side 68 of the slot being particylindrical and terminating in rounded ends 69.

The means for interiorly finishing the stereotype comprise an axially movable rotary surfacing means, preferably a boring tool or cutter for surfacing the plate and axially movable controlled milling means for forming the longitudinal series of spaced slots, both means acting on the same axial movement of the finishing means. The finishing means also include means for radially pressing the plate against the arch immediately in advance and to the rear of the cutter means to insure accurate finishing of the plate. While many different forms of such means may be employed, I preferably provide the means illustrated and the frame 22 formed with slideways 10 parallel to each other and horizontally spaced running the greater part of the length of the machine on which the cutter means are mounted for movement axially of the plate 23. The cutter or boring means are carried by a slidable frame 12 having guides 13 which cooperate with the slideways l0.

Slidable frame l2 carries a heavy shaft 15 journalled therein and at one end is provided with a boring head 76 driven thereby and having a plurality of boring bitsp'll extending radially therefrom and adjustable to bore the plate accurately to the proper diameter, the shaft 15 being accurately held in alinement with the axis of the arch 20. For accurately holding the plate during the finishing and to exert pressure in addition to that exerted by the supporting means 25, 26, axially in advance and just behind the boring tool, the frame i2 is formed with two substantially semi-cylindrical plates 80, 80A respectively, somewhat smaller than the interior of the plat 23, one at either side of the boring head 16, each plate carrying a plurality of partispherical rollers 8|, spaced to contact with axially extending ribs 64 on the stereotype, each of said rollers being yieldably mounted by heavy springs 82 engaging pillow blocks 82A for radial movement relative to shaft 15 so that any irregularity in the surface of the plate 23 is smoothed out while the plate is finished. Plate 80A is formed integral with frame 12 and carries concentrically anti-friction bearing 15A of shaft I5, while plate 80 is removably mounted on frame 12 as by cap screws 80B.

The boring head is preferably driven at a high speed so that a fine finish is obtained on the interior of the plate. For this purpose, motor 9B is mounted at one side of frame 22 and drives longitudinal shaft 9i by belt 92 and suitable pulleys. Means are provided for driving shaft 75 from shaft 9i, regardless of the axial position of boring head '56. Shaft 9! is formed to receive and drive slidably keyed or splined pulley 93 which is slidable on shaft 9i and is moved axially by bracket 94 depending from frame 12 and movable therewith. Pulley 93 by belt 95' drives pulley 95 on shaft 96 which carries pinion 91, journalled in frame l2, and meshing with gear 98 fast to shaft 75 and enclosed in housing 99.

Frame 72 is axially movable and may be moaces-res tor driven. Motor its mounted on frame 22 is belted to pulley i 31 carriedby screw shaft 102' journalled in the frame 22' and in cooperating threaded engagement with a threaded sleeve ill-4" on frame l2 sothat rotation of shaft Hi2 axially moves the frame 'ii and its boring head" 16' and pressure rollers 8i. Motor till! is reversible and may drive the frame E2 in either axial direc non.

Limit switches Hi and iilii are provided in themotor circuit to'prevent excessive axial movement of th boring head.

The ll'l 1g cutters for milling the plate hook receiving slots in thein-terior surface of the plate ES-may be drivenfrom the same motor 513 as the boringtoo-l. Gear drives pini-ons I98 onparallel shafts its which are mounted for rotation in and axial movement with frame 12. At its other end each shaft has abevel gear H-ll meshing with a bevel gear ill on the milling cutter shaft i 2 which is driven thereby to drive the milling cutters tit; while shaft H2 may oseiL late about s it We as the milling cutters H3- and charnfei milling cutters Hat-A the same shaft and just below them are moved into and out of cutting contact with the plate surface as the slots are formed.

Shaft H2 is mounted by bearings HA in a housing H5 which has sleeve-like ends llt con centric with shaft H32 and is mounted for oscillation by means of bearings iii, H3 seated" frame l2, while shaft see is rotatably mounted within one of the sleeves Ht by bearings liS Thus milling cutters till may be rapidly rotated from motor 9i and may also be moved'revolubl y about shaft 25%. In the full line posiirion'of Figure 6, the milling cutters it}? are rotating idly while in the dotted line position they are in cutting engagement with the plate 23: to form the slots therein.

Tocontrol the length of the slots 86 formed in the plate 23', means are provided for rocking each of the mil ng cutters H3 towardsa-nd from "is plate asthe cutters are moved axially of the plate. The cutters H 3 are mounted for rocking motion'by means of the sleeves H5, while the housing l is is provided with a depending armiEG pivotally connected to a slide 1 2-! carrying a cam follower which is guided and controlled by stationary cam i24 fast to frame Follower. 5:22. is a. roller mounted on a slide 525' which is connected to clevis #725- by screw rod Fill, clevis :25 lacing: pivoted to i528 by pivot pin Figure 1:0 shows the cam i'Edhaving: a; slot forming track its and a return track 53!" adapted to control. follower roller E22 and thereby the rocking of the milling cutter its. In its cutting the cutter frame i2 moves forward (downwards of the sheet in Fig. follower IE2 is moved laterally to form, for example, four slots 85 of the required depth and at the desired longitudinal points along the axial length of the plate 23. On reaching the end of the plate, follower i2" displaces switch 132 and enters the end of the cam track, switch E32 being then spring restored to the position shown. On reverse axial movement of the cutting and boring means, follower :22 travels in return track i3l until follower reaches star switch E33 which is rotated as the follower 522 enters the common cam track we, switch i533 being held against retrograde movement by means of the detent spring 36, so that follower 122 always enters track iz'ifi rather than the return track 1 5f.

The pitch of lead screw [02' and the cut and speed of cutter, bits H are so related that on one pass" of the boring tool the interior of the plate is accurately finished, and simultaneously al'l'of the plate hook recesses 66 are formed in the plate; Thereafterthe boring tool and milling cutters may be idly withdrawn in the opposite axial direction.

'When' the int rior of the plate has been fully finished, lever al may be returned to its original position dropping the plate to the lowermost position shown'in Figure 5 so that it is free to be removed from the archand the finishing machine. Means are preferably provided for automatically removing the plate from the arch on thereturn' movement of the cutters, thereby making use of the otherwise idle axial movement thereof; Tothis end,'framc'l'2- carries an arcuate saddle Hi6, preferably mounted on the gear housing at and shaped to fit the interior of the finished plate and at such a height that it, rather than the supporting ledges 2'5, 26 will support the plate as the cams return the ledges to their normal inoperative position. The finished plate is thus deposited" on the arcuate saddleid-i and when the axially movable frame 12 isreturned to its original position the plate is carried with it to its unloading position C.

Suitable conventional switches are provided for:

Starting, stopping and reversing motor I98 driving the lead screw to cause the forward and reversetravel of the axially movable frame 1-2;

Starting and stopping the motor 99 for the boring and milling cutters.

Energizing signal devices such as signal lights for indicating that the plate is securely held for finishing, has been finished and that the finishing operation has been completed and the machine is ready toreceive another plate;

By properly drivingthe various parts of themachine it is possible to finishstereotype platesat a ratewell in excess or twoplates per minute, depending onthe skill of the operator.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but" departures may be made therefrom within the scope of the accompany ng claims without departing from the principles of the invention and without sacrificing" its chief advantages. 7

What is cliamed is:

i.- In a stereotype plate finishing machine comprising a substantially semi-cylindricalform to receive a plate, substantially vertical guideways mounted on said machine. adjacent. said form, blocks. slidable; in: said guidewaya. said blocks. being; formed; with: channels, said. channels extending laterally of said. form, plate. rails slidable' in: said channels, said plate rails being. capacitated to support. the straight. edges of a platein operativerelationship to said formglevers mounted on said blocks and connected to said plate rails, and cam means connected to said blocks and to said levers and; effective to liftsaid plate rails-whilemoving them first inwardly then outwardly-'- diameti'a-lly of said form.

2'. A stereotype plate finishing machine: as defined inclaim 1- whichincludes milling means movable intocutting engagement with said plate for cutting axiallwspaced tension lock-uppockets therein adjacent and parallel to the straight edges of the plate whensaidplate is supported in operative relationship to said form.

3 In amachine for finishing printing plates,

the combination comprising a concave generally semi-cylindrical form for receiving a plate, means providing a pair of generally vertical guideways adjacent said form on opposite sides thereof, a pair of blocks respectively slidable in said guideways, said blocks having respective generally horizontal guideways thereon, a pair of supporting members for supporting the p posite straight edges of the plate, said members being slidably engaged with said horizontal guideways respectively, a pair of generally vertical levers respectively pivoted on said blocks and having their lower ends connected to said supporting members, and a pair of cam means connected to said blocks and said levers for elevating said blocks and said supporting members while moving the latter horizontally along said horizontal guide ways first inwardly and then outwardly to clamp the plate against said form, one of said cam means being positively connected and the other yieldably connected to said blocks respectively.

4. A machine for finishing printing plates as defined in claim 3 which includes milling means movable into cutting engagement with said plate for cutting axially-spaced tension lock-up pockets therein adjacent and parallel to the straight edges of the plate when said plate is clamped against said form.

5. In a machine for finishing printing plates, the combination comprising a concave generally semi-cylindrical form for receiving a plate, means providing a pair of generally vertical guideways adjacent said form on opposite sides thereof, a pair of blocks respectively slidable in said guideways, said blocks having respective generally horizontal guideways thereon, a pair of supporting members for supporting the opposite straight edges of the plate, said members being slidable engaged with said horizontal guideways respectively, and means connected to said blocks and said supporting members for elevating said blocks and said supporting members while moving the latter horizonally along said horizontal guideways first inwardly and then outwardly to clamp the plate against said form.

6. A machine for finishing printing plates as defined in claim 3 which includes milling means movable into cutting engagement with said plate for cutting axially-spaced tension lock-up pockets therein adjacent and parallel to the straight edges of the plate when said plate is clamped against said form.

CHRISTOPHER VERNE KNELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,134,798 Wood Apr. 6, 1915 1,230,034 Rollings June 12, 1917 1,238,973 Wood Sept. 4, 1917 1,346,601 Hopkins July 13, 1920 1,539,567 Hopkins May 26, 1925 1,616,256 Ericson Feb. 1, 1927 2,055,349 Harless Sept. 22, 1936 2,168,548 Wood Aug. 8, 1939 2,187,444 Behrens Jan. 16, 1940 2,305,338 Barber Dec. 15, 1942 2,421,556 Fulmer June 3, 1947 2,424,524 Weiner July 23, 1947 2,425,580 Tornberg et al. Aug. 12, 1947 2,531,647 Roesen et al Nov. 28, 1950 2,537,604 Ricards et al. Jan. 9, 1951

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