US3478678A - Pneumatic press - Google Patents

Description

NOV 18, 1969 R.-|=. LICKLITER T AL 3,478,678

PNEUMATIC PRESS 3 Sheets-Sheet 2 Filed July l5, 1968 SOLENOI D 7 u.. L 4; No L I 7.

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BY M 9L @QA/J ATTORNEYS.

Nov. 18, 1969 R. P. L lcKLlTr-:R ET AL 3,478,678

PNEUMATIC PRESS Filed July 15, 1968 3 Sheets-Sheet 5 9 342 ff"\ 4 I zal?. 4 2. wagt 68 \\l\ `1 69 .99), .942 77@ l \X i l 77 ,f77 .F3-n 70 67 96 70??" l: 97 62 BY v ,gm-fw ATTORNEYS'.

3,478,678 PNEUMATIC PRESS Robert P. Lickliter, 113 Buffalo St., and Earl Abbott, 81

Dudley Ave., both of Hamburg, N.Y. 14075, and John F. Reeves, Tonawanda, N.Y.; said Reeves assignor to said Lickliter and Abbott Continuation-in-part of application Ser. No. 604,955,

Dec. 27, 1966. This application July 15, 1968, Ser.

Int. Cl. B30b 15/16, 1/38 U.S. Cl. 100-49 10 Claims ABSTRACT OF THE DISCLOSURE An air actuated press having a fluid pressure tank directly mounted on a surface of a mounting plate opposite the surface to which a press cylinder for actuating a ram head is mounted. A control valve is mounted within the pressure tank for admitting air under pressure from the tank to the cylinder via an opening in the mounting plate. An exhaust valve mounted on the same surface of the mounting plate as the pressure tank but exteriorly of the latter is operable to exhaust pressure fluid from said cylinder to atmosphere via a second opening provided in the mounting plate.

CROSS-REFERENCE TO A RELATED APPLICATION This application is a continuation-in-part of application ser. No. 604,955 led Dec. 27, 1966 on a pneumatic press.

` BACKGROUND OF THE INVENTION This invention relates to an Iair actuated press and, more particularly, to a new and improved valving arrangement for rapidly admitting a large volume of air under pressure to an air powered cylinder for actuating said press and for rapidly exacuating such pressure fluid from said cylinder.

Conventional presses include a ram head mounted for vertical sliding movement on a plurality of vertical guideposts upstanding from a stationary bed, the ram head and stationary bed defining a die set area therebetween. Generally, an upper plate is secured to the upper ends of the guideposts to maintain the latter in vertical alignment thereby permitting free sliding movement of the ram plate. In certain instances, the ram head is fluid actuated by a piston and cylinder arrangement located above the upper plate with a piston rod extending therethrough to drive the ram head downwardly into the die set area, the ram head being mechanically returned by sprints or the like. inaccuracies in alignment and resulting reduction in eiliciency are introduced in these arrangement necessitating relatively high operating pressures and heavy return springs. Moreover, lagging and inconsistent ram head response to its actuating control signal occurs in these presses whereby press set-up time is increased yand Variations in work in the die set area introduced. An unacceptable noise level is also created due, in a large measure, to stopping the direction of the ram head at both ends of its stroke.

The teachings set forth in the labove-referred to copending application Se-r. No. 604,955 obviate the abovenoted deficiencies in the prior known conventional presses by providing a press having a piston and cylinder operable at low pressures and arranged between the upper United States Patent O plate and the ram head to directly drive the latter. Also ice the end of its downstroke to assist a spring means for completing the return of the ram plate.

Although the press described in said copending application Ser. No. 604,955 has served the purpose for which it was intended, it was found that commercially available 3-way valves have a limited capacity and the volume of pressure uid supplied thereby was insuicient for rapid operation with large diameter pistons. One solution to the problem is to provide a plurality of such 3-Way valves to control the volume of fluid necessary for satisfactory operation. However, shifting such 3-way valves between exhaust and operative positions results in a considerable blow by lor loss of pressure fluid to exhaust. This may be tolerable with a single small valve, but is excessive and costly with multiple valves which also require additional expensive flexible couplings, hoses, conduits and other hardware. Moreover, there are many more parts subject to breakdown with attendant press shutdown. It is readily apparent that eiciency and production can be seriously impaired.

SUMMARY OF THE INVENTION The apparatus -of the present invention, as hereinafter described, obviates the above disadvantages by providing an air pressure tank mounted directly on the surface of the upper or mounting plate opposite the surface to which the press cylinder is mounted, the tank containing a con trol valve for admitting pressure fluid to said press cylinder. The control valve means comprises a cylinder and a piston adapted to seal an opening in the mounting plate which communicates between the interior of the pressure tank and the Working chamber of the cylinder. A solenoid operated four-way valve acts 'as a pilot valve and is operative to direct pressure fluid into the control valve means for unseating the piston and admitting pressure fluid from the tank into the press cylinder via the mounting plate opening to drive the ram plate downwardly. An exhaust valve, mounted on the mounting plate surface opposite the press cylinder and exteriorly of the pressure tank, comprises a cylinder and piston adapted to seal a second opening in the mounting plate communicating with the press cylinder. When the four-way valve is shifted to exhaust position, the pressure fluid in the press cylinder unseats the piston of the exhaust valve and is exhausted to Iatmosphere through the second opening.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view, partially in section, of one form of air actuated press constructed in accordance with the principles of this invention;

FIG. 2 is `a horizontal, cross-sectional view thereof taken about on line 2 2 of FIG. l;

FIG. 3 is a longitudinal sectional view schematically illustrating a four-way pilot used With the present invention;

FIG. 4 is a vertical sectional view of the control valve of the present invention;

FIG. 5 is a vertical sectional view of the exhaust valve of the present invention; Iand FIG. 6 is a diagrammatic View illustrating the electrical control circuit for the air actuated press of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, there is shown a preferred embodiment of air actuated press constructed in accordance with the principles of the present invention and comprising -a stationary bed 10, a plurality of vertically extending guideposts 11 suitably xed at their lower ends to bed 10, a ram head plate 12 vertically slidable on guideposts 11 and defining a die set area 13 with bed 10, and an upper mounting plate 14 slidably adjustable on guideposts 11. Guideposts 11 extend upwardly from bed through suitable bores in ram plate 12 and mounting plate 14. A plurality of upstanding threaded posts 15 are threaded at their lower ends into bed 10 and extend upwardly through openings in ram plate 12 and mounting plate 14, the latter being secured to posts 15 adjacent their upper ends between nuts 16 to adjustably x the height of mounting plate 14 above bed 10.

Bed 10 and plates 12 and 14 lare preferably rectangular in plan form and can be formed of steel plating. Track members 18 and 19 are suitably secured on the undersurface of ram plate 12 and on the upper surface of bed plate 10, respectively, and are adapted to receive the upper and lower dies of the usual die set, not shown. However, it will be appreciated that the press of this invention is of general utility and is in no manner limited in use with die sets. The terms upper, lower, bottom, top, upwardly, downwardly, and the like, as used herein, are applied only for convenience of description with reference to the drawings and should not be taken as limiting the scope of this invention.

Ram plate 12 is suspended below mounting plate 14 by a ram plate return assembly comprising, in the illustrated form, eight rods 20 suitably fixed at their lower ends to ram plate 12 and passing upwardly through openings in mounting plate 14. The upper end of each rod 20 mounts a washer 21, a nut 22 and a lock nut 23, and a compression spring 24 encircles each rod 20 with its opposite ends bearing against washer 21 and the upper surface of mounting plate 14. Ram plate 12 is thus resiliently supported for reciprocating sliding movement on guideposts 11 by springs 24 -with downward movement thereof into die set area 13 being against the bias of springs 24 and limited by a plurality of stops 26 vertically adjustably mounted on rods 15 between ram plate 12 and bed plate 10. Stops 26 comprise sleeves 27 threaded on rods 15 and iixed in vertically adjusted position by jam nuts 28 engaging against their undersurfaces. The upper surface of each sleeve 27 has a resiliently deformable cushion 29 preferably formed of rubber, glued or other wise fixed thereon for limiting downward movement of ram plate 12 and providing a noiseless initial return thrust to ram plate 12 at the end of its downstroke.

A significant feature of the foregoing arrangement is that the shut height is easily adjusted by moving nuts 16 to adjust the height of mounting plate 14 which thereby `adjusts the height of ram plate 12 since the latter is suspended by the ram plate return assembly 20-24. Moreover, since stops 26 Iare adjustably mounted on rods 15 to vary the ram stroke, it will be seen that the stroke of ram plate 12 can be adjusted independently of shut height, and vice versa.

A pneumatically actuated piston and cylinder arrangement is disposed between mounting plate 14 and ram plate 12 to drive the latter downwardly into die set area 13. To this end, press cylinder 31 is suitably secured to the undersurface of mounting plate 14 inwardly of guideposts 11, posts 15 and rods 20 as by bolts 32 (FIGS. 1 and 2) and is provided with a suitable O-ring seal 33 sealing against mounting plate 14. A piston 34 is suitably secured to the upper surface of ram plate 12 in vertical registry with cylinder 31 as by bolts 35 and is formed of a heavy material providing considerable inertia to ram plate 12 during its downstroke. The upper edge of piston 34 has a pair of peripheral flanges 37 having a suitable O-ring seal 38 carried therebetween for sealing against the inner surface of press cylinder 31.

The upper surface of piston 34 is slightly cylindrically recessed as at 39 providing a narrow lip 40 about its periphery, recess 39 and lip 40 defining a working chamber 41 with mounting plate 14. It will `be appreciated that the diameter of piston 34 is very near the lateral dimension of rarn plate 12 providing a very large and substantial area on the upper surface of piston 34 against which air entering press cylinlder 31, as hereinafter described, can react whereby low pressure air can provide a considerable downward force. Also, the large lateral dimension of the piston and cylinder arrangement and the direct connection thereof to the ram and mounting plate, respectively, maintain ram plate 12 in accurate vertical slidable registry on guideposts 11 without undue friction therebeween.

A plurality of cylindrical cavities 42 are formed in the recessed surface of piston 34 for receiving resilient deformable cushions 43, preferably formed of rubber. Cushions 43 extend upwardly slightly beyond lip 40l to engage against the undersurface of upper plate 14 at the end of the piston upstroke whereby metaltometal contact between piston 34 and upper plate 14 is avoided and consequent noise therefrom eliminated.

In accordance with the instant invention a fluid pressure reservoir or tank 45, deiining a pressure chamber 46, has an open lower end secured directly onto the upper surface of mounting plate 14, as by means of bolts 47 extending through a ange therearound (FIG. 2), said pressure tank 45 being disposed interiorly of guideposts 11, posts 15, and rods 20. The upper end of pressure tank 45 is provided with a iiange 48 to which is attached a top cover plate 49 by means of a plurality of suitable bolts S0 and associated nuts 51 arranged in a circular array adjacent the periphery of cover plate 49. A suitable annular, resilient washer 52 can be interposed between flange 48 and cover plate 49. The wall of pressure tank 45 is provided with a suitable opening communicating with a suitable source of fluid under pressure, not shown, by means of a conduit 55 for supplying uid under pressure to pressure tank 45 at all times.

A control valve, generally designated 56, is contained within pressure tank 45 for controlling the admission of iiuid under pressure into press cylinder 31 by way of an opening 57 formed in mounting plate 14. Referring to FIG. 4, control valve 56 comprises a cylinder, generally indicated at 58, having an annular shell 59, an upper end wall 60, and a lower end wall 61. Cylinder 58 is suitably mounted on a plurality of circumferentially spaced riser blocks 62 supported on the upper surface of mounting plate 14. A plurality of bolts 64 extend downwardly through upper end wall 60, shell 59, lower end wall 61, and riser blocks 62 and have threaded portions 6:5 at their lower ends received in threaded bores 66 in mounting plate 14. As shown in FIG. 4, the inner surface of annular shell 59 is provided with grooves 68 adjacent both ends thereof for receiving suitable O-riug seals 69 for providing pressure sealing between the shell 59 and end walls 60 and 61, respectively. An annular recess 70 is formed in the lower end wall 61 and communicates with a radial passage 71 connected to a conduit 72 which extends through an opening in pressure tank 45 by means of suitable couplings and leads to a solenoid operated, spring returned, four-way pilot valve 54 (FIG. 3). Upper end wall 60 has an opening 73 connected to pilot valve 54 by means of conduit 74 which extends through pressure tank 45 through suitable coupling members.

A valve member, generally designated 76, is slidable between mounting plate 14 and the bottom surface of lower end wall 61 and is provided with an elongated stem 77 extending upwardly through an axial opening 78 in lower end wall 61 and terminating in an enlarged diameter stern portion 79 received in au axial opening 80 formed in the upper end wall 60. Suitable O-ring seals 81 and 82 are carried in peripheral grooves 83 and 84 of stem 77 and stern portion 79, respectively, for providing pressure sealing against openings 78 and 80, respectively. An annular shoulder 85 is formed by the transition between the stem 77 and the enlarged diameter stem portion 79.

An annular piston 87 is mounted about stem 77 and fixed in position against shoulder 85 by means of a retaining ring 88 encircled about stem 77. Suitable O-ring seals 89 and 90 carried in grooves 91 and 92 provide pressure sealing between annular ring 87 ,and stern 77 and the inner surface of shell 59, respectively. The lower surface of piston 87 is slightly cylindrically recessed as at 93 to form a chamber `94 with lower end wall 61 of cylinder 58.

Valve 76 comprises a circular retaining member 96 having an axial bore 97 and a cylindrical cavity 98 on its lower surface for accommodating an annular, resilient, deformable sealing element 99 formed of rubber or other suitable material. Sealing element 99 is provided with an axial bore 100 and has a lower surface engageable adjacent its periphery with the upper surface of mounting plate 14. A mounting member 101 is provided with a stem 102 and a reduced diameter stem portion 103 extending through the bores of sealing element 99 and retaining member 96, respectively. Member 96 and element 99 are interposed between a ange 104 of mounting member 101 and the lower flat abutment face 105 of stem 77. A bolt 106 threadably secures mounting member 101 to stem 77.

Referring to FIGS. 1 and 5, an exhaust valve, generally designated 110, has a cylinder 111 mounted on a plurality of circumferentially spaced riser blocks 112, which in turn are supported on the upper surface of mounting plate 14. Cylinder 111 is provided with an upper cover plate 113 and an annular resilient washer 114 interposed between said cover plate and the upper end of cylinder 111. A plurality of bolts 115 extend downwardly through cover plate 113, cylinder 111 and riser blocks 112, and have threaded lower end portions 116 secured in threaded bores 117 of mounting plate 14. Cover plate 113 has an opening 118 communicating with pilot valve 54 via a conduit 119. An opening 120 is provided n mounting plate 14 for connecting working chamber 41 of press cylinder 31 to atmosphere by means of the spaces between riser blocks 112.

An exhaust valve piston 122 is slidably mounted in cylinder 111 and is provided with a peripheral groove 123 for accommodating a suitable O-ring seal 124 for sealing the piston against the inner surface of cylinder 111. The upper surface of piston 122 is slightly cylindrical- 1y recessed as at 125 to form a chamber with the lower surface of cover plate 113 when the piston is disposed at its uppermost limit. A resilient sealing element 126, formed of rubber or other suitable material, is clamped between the lower surface of piston 122 and a flange 127 of a mounting member 128 and secured therebetween by a bolt 129 extending upwardly into threaded engagement with a threaded bore 130 formed in the bottom of piston 122.

Referring now to FIG. 3, pilot valve 54 comprises a housing 132 having a bore 133 therethrough for receiving a movable spool valve, generally designated 134, having a stem 135 and two annular enlargements or shoulders 136,` and 137 which fit snugly in bore 133. Spool valve 134 is actuated by a solenoid 139 against the bias of a spring 140 to serve as a pilot valve in initiating operation of the control valve 56 as hereinafter more fully explained.

control switch 142 is suitably mounted on mounting plate 14 and positioned to be engaged by a switch actuatingmember 143 carried by a threaded rod 144. Rod 144 is threaded at its lower end into a suitable opening in ram plate 12 and is fixed thereto by a jam nut 145. Rod 144 passes upwardly through an opening in mounting plate 14 and carries actuating member 143 above mounting plate 14 in vertically adjustable position between a pair of nuts 146 whereby member 143 can be adjusted to release actuator 147 and close switch 142 a preselected time interval prior to the end of the downstroke of piston 34.

FIG. 6 schematically illustrates an energizing circuit for shifting pilot valve 54 between positions providing pressure fluid to cylinder 31 and exhausting pressure uid from cylinder 31 to atmosphere. Power is provided from a suitable source, not shown, via conductors 150 and 151. Spring biased, normally open contacts 152 of a latching relay,generally designated 153, are closed by energization of v coil 154 via conductors 150, 155, normally closed contacts 156, 157 of a command switch, generally indicated 158, conductor 159, coil 154, and conductors 160 and 151. Command switch 158 may be conventional single pole double throw switch having a switch actuator 161 ,spring biased to a normally closed position With contact 1 57.

Command switch 158 is located in the path of movementof work passing through the die set area 13. The worl:` engages switch actuator 161 to close a circuit through contacts 156 and 162 and open the circuit through contacts 156 and 157 whereby coil 154 is de-energized. However, contacts 152 are maintained closed by a latch 163 ,operated by a latching coil 164, latch 163 latching contacts 152 closed immediately upon the closing thereof by way of coil 154. Closing of contacts 156 and 162 completes an energizing circuit to solenoid 139 by way of conductors 150 and 155, contacts 156 and 162, conductor 165, .contacts 152, conductor 166, solenoid 139, and conductors 167 and 151.

The'energization of solenoid 139 shifts the spool 134 of valve 54 into an operative position as shown in solid lines in FIG. 3 whereby pressure fluid in conduit 55 communicates with conduit 72 to direct pressure uid into passage 71, recess 70, and chamber 94 to raise piston 87 and lift the sealing element '99 of piston 76 away from mounting plate 14. Pressure uid in tank 45 is thereby admitted into working chamber 41 through opening 57 to drive piston 34 and ram plate 12 downwardly. Simultaneously, pressure fluid supplied via conduit 119 to exhaust valve 110 acts on the effective area of the upper surface of piston 122. Since this area is larger than the effective area of the underside of piston 122, a net force is produced which urges sealing element 126 against the upper surface of mounting plate 14, thus sealing olf the pressure fluid exhaust from press cylinder 31.

Near the end of the downstroke of piston 34, actuating arm 143 moves past roller actuator 147 to close normally open switch 142 and complete an energizing circuit for latching coil 164 via conductors 150, 170, switch 142, conductor 171, coil 164 and conductors 160 and 151 to release latch 163 and thereby allow contacts 152 to open. Opening of contacts 152 interrupts the energizing circuit for solenoid 139 and spool valve 134 thereupon is shifted by its return spring to the position illustrated in broken lines in FIG. 3. Thus, switch 142 is activated prior to piston 34 reaching the end of its downstroke to provide sufieient time for spool valve 134 to shift to an exhaust position thereby precluding piston return against fluid pressure remaining in cylinder 31.

With spool valve 134 in the exhaust position, pressure uid acting on the lower surface of piston 87 of control valve 56 and on the upper surface of piston 122 in exhaust valve 110 is vented to atmosphere via conduits 72 and 119, respectively, and bore 133. Piston 122 is raised by the fluid pressure acting on the lower surface of said piston permitting pressure fluid to escape from press cylinder 31 through opening 120 and the spaces between riser blocks 112. While fluid pressure on the lower surface of annular ring 87 is relieved, pressure Huid is applied to the upper surface of said ring by way of conduit 74 and opening 73, thereby driving ring 87 downwardly along with piston 76 to seat sealing element 99 on mounting plate 14. The pressure uid present in tank 45 acts on the upper surface of piston 76 to further assist in maintaining the piston in a downward closed position. It is a significant feature of this invention that the valving arrangement is fail-safe in that piston 76 is always urged downward to a closed position to preclude inadvertent or negligent lowering of ram plate 12 in the event of supply pressure failure.

As described above, pressure fiuid flow from tank 45 into cylinder 31 is interrupted and spring return assembly -24 and cushioned stops 26 act to return ram plate 12. Return of ram plate 12 re-engages arm 143 and actuator 147 to open switch 142 and command switch 158 is thereafter automatically reset upon removal of the work to reestablish the energizing circuit hereinbefore described through contacts 156 and 157 whereby contacts 152 are again closed and the ram plate is cocked ready for another downstroke. Pressure iiuid can thus be provided into cylinder 31 substantially instantaneously with actuation of command switch 158 whereby lag in ram plate response is substantially eliminated. It will be appreciated that switch 142 can be positioned to be engaged and closed by arm 143, instead of being closed by disengagement. In either case, arm 143 can overtravel relative to actuator 147 Without change to the switch.

As a result of this invention, an improved iiuid actuated press of a simple and rugged design is provided for rapidly actuating a ram head in an improved and more eicient manner. By directing mounting the fluid pressure tank on the surface of the mounting plate opposite the surface to which the press cylinder is mounted, pressure fiuid is readily accessible to the press cylinder for substantially instantaneous operation. Expensive and cumbersome piping couplings and hardware are eliminated.

Another advantage residing in the apparatus of this invention is that only a single control valve, mounted within the pressure tank, is utilized for controlling the large volume of pressure fluid required by the press cylinder for satisfactory rapid operation, thereby eliminating multiple control valves .and their associated piping and hardware. Furthermore, the attendant iiuid pressure loss through multiple valving arrangements is eliminated.

A further advantage in the pressure tank-control valve arrangement of this invention is that pressure in the tank constantly acts against the upper surface of the control valve piston to maintain it seated against the mounting plate to provide pressure sealing about the opening in the mounting plate, thus rendering the system fail-safe whereby the ram head remains in its upper position.

A three-way pilot valve 54 can be used instead of the four-way valve shown, by eliminating conduit 74 and relying upon gravity and the pressure iiuid in tank 46 acting on piston 76 to close the latter and hold it closed. However, a four-way valve arrangement as shown is preferred because it is doubly positive and fast acting.

It should be appreciated that, if desired, two iiuid pressure tanks, each having a control valve mounted therein, may be utilized for the selective application of high and low fluid pressures, respectively.

We claim:

1. An air actuated press comprising: a bed; ram plate means guided for movement relative to said bed; mounting plate means on the side of said ram plate means opposite said bed; a fluid cylinder directly mounted on one side of said mounting plate means; a piston movable in said cylinder directly mounted on the adjacent side of said ram plate means; a iiuid pressure tank directly mounted on the other side of said mounting plate means; a first passage through said mounting plate means between said pressure tank to said cylinder; and a control valve disposed within said pressure tank in controlling relation to said first passage.

2. An air actuated press as delined in claim 1 together with an exhaust valve mounted directly on said other side of said mounting plate exteriorly of said tank; and a second passage through said mounting plate means communicating with said cylinder; said exhaust valve controlling said second passage.

3. An air actuated press as defined in claim 2, together with means including pilot valve means having a tirst position for directing pressure fluid to said control valve for opening the latter to supply pressure liuid from said tank to said cylinder by way of said first passage.

4. An air actuated press as defined in claim 3, wherein said pilot valve means in said first position also directs pressure fluid to said exhaust valve for maintaining the latter closed relative to said second passage.

5. An air actuated press as defined in claim 4 wherein said pilot valve means has a second position effecting closing of said control valve relative to said first passage and opening of said exhaust valve to vent pressure liuid from said cylinder by way of said second passage.

6. An `air actuated press as defined in claim 5 including a switch means responsive to the presence of work for shifting said valve means to its first position.

7. An air actuated press as defined in claim 6 including means responsive to a predetermined downward movement of said ram plate for shifting said valve means to its second position to interrupt the supply of fluid pressure into said cylinder prior to the end of the downstroke of said ram plate.

8. An air actuated press as defined in claim 1 together with a plurality of guides extending upwardly from said bed, said ram plate means being slidable on said guides, a plurality of rods extending upwardly from said bed, means releasably clamping said upper plate means in adjusted position along said rods, resiliently deformable stops mounted on said rods for adjustment therealong to limit movement of said ram plate means, and return spring means suspending said ram plate means from said upper plate means.

9. An air actuated press as defined in claim 1 wherein said control valve has a piston engageable with said mounting plate means to close said first passage, and wherein uid pressure in said tank acts on said control valve piston to maintain a pressure seal between said piston and said mounting plate about said iirst passage.

10. An air actuated press as deiined in claim 1, together with means including valve means externally of said tank for opening said control valve whereby iluid pressure in said tank is admitted into said cylinder via said first passage.

References Cited UNITED STATES PATENTS 633,665 9/1899 Spaulding 100-266 XR 2,302,132 11/1942 MacMinin et a1. 10o- 269 XR 2,406,403 8/1946 Rogers 10o-266 XR 2,726,707 12/1955 Wellens et a1.

2,786,409 3/1957 Claire 10o-266 3,190,215 6/1965 Howard et a1. 10o-257 3,194,096 7/1965 Comet 83-588 XR FOREIGN PATENTS 489,776 1/1953 canada.

BILLY J. WILHITE, Primary Examiner U.S. C1. X.R.

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