US2610048A - Kerf-cutting machine - Google Patents

Description

Sept. 9, 1952 F. A. LINDGREN 2,610,048

KERF-CUTTING MACHINE Filed NOV. 9, 1946 4 Sheets-Sheet l $1 v) Q I MNTOR Fanfd ind gml/ Jrromvfy Sept. 9, 1952 F. A. LINDGREN KERF-CUTTING MACHINE 4 Sheets-Sheet 2 Filed Nov. 9, 1946 J 3 m m a 9 M E $0 P m J a T a 4 w J m-. m a m M w u. m f m m m I 1% 74W 9w w Maw 1T? 3 kw a P 9, 1952 F. A. LINDGREN 2,610,048

KERF-CUTTING MACHINE Filed Nov. 9, 1946 4 Sheets-Sheet 3 JQVENTOQ Em i am [gm/z fli qq Sept- 9, 1952 F. A. LINDGREN 2,610,048

KERF-CUTTING MACHINE Filed Nov. 9, 1946 4 Sheets-Sheet 4 fliiomey Patented Sept. 9, 1952 D OFFICE ane-comma MA'omNE' Frank-Ar Lindgrcn, La Grange; Illa, a'ssignor to Goodman Manufacturing Company, Chicago; Ill., a corporationzof Illinois Application November 9, 194 Serial No. roasts Thisinventio'n relatesto improvements'i'n kerfcutting machines of theroomand; pillar type. The.principalobjects ofm'; invention are'to provide -a novel form of wheel niountedselfpropelled kerf cutting machine of the room? and pillar type arranged with ajview' towards'utmost compactness, simplicity andefilciency in operation,;jand' so constructed that the wheels and their supporting connections with. themac'hine may, support and propel the kerf-cutting machine abouttli'e'minefrom one working place" to the other, and? mayzlow'er the kerf cuttin machine into engagementwiththeground and raise said wheels above-the ground, to permit cutting by slidable movement of" the machine along the grouncton itskbottorn in the manner usual with machines of this type.

These 'andlother, objects of my invention will appear from time to time as the followingspecificationa proceeds and with reference to'the accompanyingv drawings wherein:

Figure 1 is a top plan view of a kerf-cutting machine constructednin accordance with'n my invention, with certain parts; broken away" and'certainlothervparts-shown in horizontal section;

Figure=2sis aiviewl-inside elevation:offlthelkerfcutting machine shown-in Figural;

Figure BLisan enlarged lfragmentaryv'transverse sectional View taken substantially. along line 1-3 of Figural;

Figure .4 is an enlarged fragmentary view in side-elevation of the kerfr -cutting machine shown inF'igure 1,. with certain parts thereof broken away-and. certainiother parts shown in substantially longitudinal section order to illustrate certain my details of the drive to the rubber-tired driving wheels;

' Figuret is an enlarged fragmentary transverse sectional view taken substantially along linen-5 of Figure 1; and a Figure 6 is: an enlarged detail. horizontal sectionallview taken through" the-drive to therubbier-tired wheelsa-nd showingz-certain other details of therdiiferentia-l driveto the driving-wheels. In: the; embodiment of-my invention illustrated in thew drawings; a kerf-icutting :machine of: a

well known; form of:roomand pillar ty-peisshown astincludinglraszmainrframe l having a motor: I l

'securedito and projecting forwlardlyironi it's for.- W8,Idfehd-Z Aifiexiblefeedingimeans may be ipr'oivided at opposite sidesof saiclfmain. frameirearrwardlyofsaid motor; which may comprisea pair of w; iI1r:li1'l'gdrums1 2-; l2 adapted to have flexible cables 13; l3 wound thereonandflarranged] to be anchored at their free end at suitable points 6 Claims; (CI. 262-281) adjacent the working face; for feeding the kerfcutting machine-into and across the Working face. i

A cutter bar 15 havinga cutter chain l6 guided for movement thereabout projects f-orwardly from themotor I I and may be mountedon the underside' of said motor (see Figures 1- and 5-). Said cutterbar and cutter chain mayextendbeneath saidmotorandmeiy be driven from the rear end thereofso as'to propel the cuttings cut beneath saidmotor and. main frame and discharge them from the rear end of said motor.

The machine j is supported for" transportation about the'mine' on' two driving wheels ll, llhaving-rubbertires l8; Ill-mounted thereon and disposed at oppositesidesof the motor I I adjacent the'forward end" of them-achine, and" on two inwardly toed; closely spaced steeringwheels [9, I9 having rubber tires 20, mounted thereon anddisposedrearwardlyv of the main frame! l0. Saiddriving wheels'a're recessed withinthe lateral boundaries of the: machine to' maintain the lateral dimensions of the machine and to facilitate the sumpingand cutting operations of the machine, especially in closeposting. V Said drive wheels, as'herein shown,. are mounted in the spaces usually occupied by thestarter and" resistance for the motor, said starter and resistance'beinginstead mounted on thetop fithemachine as'indicated generally by, reference character [4 in Fi'geuresI-1and2.

Thesteefingwheels I9; ware} each journaled on a dead axle 21. Said axles project in oppo site directions from a turning frame 22 and are inclined towards the ground so as to toe said wheels inwardly towards each other at the proper angle (see Figure 3); Said turning frame is journaled adjacent its upper end in a lower depending central. cylindrical portion. of a. support -frame= 23 on; a -taper roller bearing 24. A vertical shaft 25 issplinedinthe lowerendof said turning frame and; projects; upwardly therefrom. Said shaft is journaledadjacentits upper end on a=taper roller-bearing 26 mounted in: theupper end of said cylindrical portion ofsaidsupport frame: A wormrgear 2 7 is keyed" on the; upper end Of said :verticaL shaft and is meshed With-a wormu2 8 ona transverseshaft29." A steering wheel! on the upperend of a vertic-alsh'af-tSi is'z-providedwtoturn said? worm and: worm gear and? said wheels, fon steering the 'ma'chine', and is"? operatively connected therewith: by' means of a pair of meshing bevel gears 32, 32, one of which is o'n th'e vertical shaft 3 l and theotherpfw-hich IS? on the outer end of" the transverse shaft" 29;

The support frame 23 has two laterally spaced arms 33, 33 which project from it upper end towards the rear end of the kerf-cutting machine in an angularly downwardly direction. Said arms are pivotally connected to the rear end of said kerf-cutting machine on a transverse shaft 34 mounted adjacent its opposite ends in bosses 35, 35, projecting rearwardly from the rear end of the main frame and disposed beneath the top of said main frame. A cylinder 36 having an ear 31 projecting from its head end, is pivotally connected to a top cover 38 for said main frame by means of a pivotal pin 39. Said pivotal pin extends through said ear 31 and through two laterally spaced upright ears 40, 40 projecting upwardly from said top cover 38 and extending along opposite sides of saidear 31. A piston rod 4| extending from a piston (not shown) movable within said cylinder is extenslble from said cylinder. Said piston rod is pivotally connected to a connecting ear 42 extending from the support frame 23 towards the main frame l0 and disposed between the arm 33, 33.

When fluid under pressure is admitted into the head end of the cylinder 36, the piston rod 4| will be extended from the piston rod end of said cylinder to depress the support frame 23 about the axis of the transverse shaft 34 and engage the steering wheels l9, l9 with the ground. Further extension of said piston rod from said cylinder will elevate the rear end of the main frame Ii! above the ground, to permit saidsteering wheels to support the rear end of said main frame above the ground, so said wheels may steer the machine while it is traveling about the mine, as shown in Figure 2. Itshould here be understood that the rear end of the machine is supported above the ground during transportation, and that the wheels I9, l9 are also supported above the ground during the cutting operation by holding fluid pressure in either the head or piston rod ends of said cylinder 36.

Each front drive wheel 11 is mounted on a dead axle 45 projecting outwardly from a gear housing 46. Each of said gear housings is pivotally mounted adjacent its forward end to a side wall 48 of the casing for the motor II, and is guided for vertical movement about its axis of pivotal connection to said motor by means of an arcuate gibbed retaining guide 43, secured to the side of said motor and slidably engaging the outer side of an arcuate flange 44 which extends rearwardly from said gear housing. The driving connection to each drive wheel [1 and the support therefor are substantially the same for each side of the machine, so said support and driving connection for one side of the machine only need herein be described in detail.

The dead axle 45 is mounted in and projects from an annuarboss 41 which projects outwardly from an inner wall of said gear housing. A cover 49 serves to close the outer side of said housing. Said gear housing besides forming a vertically movable support for said front drive wheel, also forms a housing for a sprocket 50, a chain meshing with and driving said sprocket, and a drive sprocket 52 for driving said chain (see Figures- 1 and 4) Said sprocket 59 is herein shown as being secured to an outwardly extending substantially bell-shaped sleeve or hub 53, which is coaxial with and is journaled on the dead axle 45 on anti-friction bearings 54, 54. Said bellshaped sleeve 53 forms a mounting for the drive wheel I1.

The drive sprocket 52 has an integrally formed sleeve, 55 projecting outwardly therefrom, which 46 is also provided with an inwardly extending annular bearing portion 65 coaxial with the shaft 56, which is journaled in an annular recess 65 of said motor, which encircles the annular shaft support 59. A retaining flange 61 projects forwardly from the forward end of said gear housing and is engaged by a gib 68, detachably secured to an arcuate rib 69, projecting forwardly and outwardly from the forward end of the casing for the motor H, for retaining said gear housing within said annular recess, during vertical movement thereof about the axis of the sprocket 59, for raising the wheel 11 above the ground or for engaging said wheel with the ground and elevating the forward end of the kerf-cutting machine above the ground.

A spur gear 10 is splined on the outer end of the sleeve 55. Said spur gear is journaled on its hub on an anti-friction bearing 1| mounted on the shaft 56. The spur gear 10 is meshed with an idler gear 15 journaled on a transverse shaft 16, mounted in the gear housing 63 at one of its ends and in the cover 61 for said housing at its opposite end. A pinion 11 keyed on the outer end of a transverse shaft 19 meshes with and drives said idler gear. The transverse shaft 19 is journaled just inwardly of the pinion 11 in an inner wall of the gear housing 63 and projects inwardly therefrom within a housing for a differential 8!.

The drive from the motor I l to the differential 8| includes a pinion B2 keyed 0n the forward end of a shaft 83 of the motor H (see Figure 5). Said pinion meshes with and drives an intermediate gear 84 disposed thereabove, which meshes with and drives a spur gear 85 mounted on a longitudinal shaft 86. Said longitudinal shaft is journaled on opposite sides of the spur gear 85 in anti-friction bearings 81, 81, one of which is mounted in an end wall 88 of the housing-80 and the other of which is mounted in a cover 89 for the gear train just described. A bevel pinion 9D is keyed on the inner end of the longitudinal shaft 86 and meshes with and drives a bevel gear 91 mounted coaxially of the transverse shaft 19 and journaled on the hub of a cage 93- for said differential, on a ball bearing 94. said cage has a hub 95 which is journaled in one end wall of the housing 80' and is mounted for free'rotation with respect to the left-hand drive shaft 19. A sleeve 96 projects from the opposite end of said cage and is freely mounted on the opposite drive shaft 19. Said sleeve has the bearing 94 mounted thereon and has the hub of a bevel gear 9| extending therealong within a housing 91 of a friction-disk clutch 98. Said clutch housing is keyed on said sleeve and said clutch may be of any well known'form of friction disk type, so needinot herein be shown or described in detail; Said clutch is engaged by means of a forked lever 99 pivotally mounted in the differential housing 89 on'a vertical pivotal pin I00. .The free ends of the furcations of said lever have bearing engagement with opposite sides of a thrust bearing IBI, for moving said thrust bearing and clutch housing along saidsleeve to engage the clutch.

A1 hand 3 lover I 03; is: keyed; to the. outer: endccof said shaft outside of the housingBIl for: operating: said clutch to. selectivelydrive the differentiallcagei93 fronrthe bevel gear'SI. I

The cage 93 f the differential: has two diiferential pinions IIl I, I104 journaled on a shaft I05, which is mounted at its ends in opposite sides of said cage," Said pinions'mesh with bevelgears I06;=I06 splined on the inner ends of the: transverse shafts I9; T9 for differentially driving said shafts in awell known manner.

The meansfor' vertically moving each gear housing" 46- about the axis of the drive sprocket 52 and raising-or lowering the drive wheels I1, l'l with respect to the ground,and for elevating the kerf-cutting machineabove the ground, includes a fluid cylinder III-I. Said cylinder has a bifurcated ear: I09 projecting from the head end thereof, the furcations of whichextend along opposite sides of an-ear I'I-I extending upwardly from the top of the casing of themotor -I I, and which are'pivotally connected to said ear by means of a pivotal pin II2. A piston rod 3- extending from apiston (notshown), movable with said cylinder, is pivotally. connected at itsouterend to-a' rocking arm H4, by'means of apivotal pm I I5; Said rocking arm is mounted on andsecured to a transverse shaft II6 which is pivotally mounted intermediateits ends'on a bearing support II'I projecting upwardly from the'top, of'the casing for the motor II. A rockingarm H9 is mounted on the outer end of I said shaft and projectsangularly upwardly therefror'nin arear warddirection, and has a link I20 pivotally connected to its outer endona pivotal pin I2 I. Said link depends from the freej'end'ofsaid rocking arm and is connected at its lower end; to an ear I22 projecting upwardly from the rear end ofithe gear housing 46, bymeansof a pivotal pin I23.

When fluid under pressure is admitted to the head" ends of the cylinders I01, I01 and the cylinder 36, the piston rods H3, H3 and M will be extended from the piston rod ends of said cylinders to pivot the frame 23 and gear housings 46, 46 downwardly in a counterclockwise direction, to engage the wheels I7, I! and I9, I9 with the ground and bodily lift'the kerf-cutting, ma.- chine above the ground, for transportation onsaid driving and steering, wheels and toy hold said kerfcutting machine in said elevated position byv holding fluid pressure in said cylinders.

When fluid under pressure is released from the head ends of the cylinders I01, I01 and 36, the gear housings 46, 46 and support frame 23 will pivot upwardly in a clockwise direction about the axis of the shaft 34v and the axes of the sprockets 52; 52 until the kerf-cutting machine engages the ground. The admission of fluid under pressure to ,the piston rod ends of said cylinders will then raise said driving wheels. I1, I! and I9, I9 above the ground, to permit the cutting of a kerf along a mine bottom by slidable movement of the ma chine along itsbottom,effected by the feed drums I2, I2 and flexible cables 13, I3 in the well known manner. a l

A, suitable fluid pressure system may be provided to admit fluid under pressure to or to release pressure from the head and piston rodends of the cylinders 36 and I01, I01 and to hold pressure therein, to elevate or lower the kerf-cutting machine with respect to the ground and to raise the wheels I1, I! and I9, I9 out of engagement with the ground, and to hold said wheelsout of engagement with the ground or hold the kerfcutting machine in an elevated position above the ground: V Said: system. may be sovarrangedil aseto' admit-fluid under pressureto-the rear cylinder 36 independently=of *the. frontucylinders ,IBI- I01, to tilt thekerf-cutting machine about: one end or-the other, and is no part-'ofmy presentim vention 'so'will not herein be shown or described .in detailz, I

While I have herein shown and described one formin which my invention may be embodied'it willbe' understood that the construction thereof and the arrangement of thevarious parts may be altered without departing from the-spirit and scope thereof. Furthermore, I do not wish to be construed as limiting my inventionto the specific embodiment illustrated; excepting as it may be limited in theappended claims.

Iclaim asmy invention: I

1: Ina' room and pillar kerf-cutting machine; a mainframe, a motor mounted at the forward end of; said main frame; a cutter chain carrying cutter bar projecting forwardly of said motor, feeding mechanism disposed rearwardly of said motor; and means for elevating said machine above the mine floor andsupporting itfortrans" portation and forlowering said machine to rest upon the ground including rear steering, wheel means, and front drive wheels, said rear steering wheel means including a steering wheel support ing framehaving mine fioor engaging supporting wheels mounted thereon and bodily turnable about an upright axis for steering said machine, a transverse pivotal connection between the for ward end of saidframe andthe rear end of said main frame, and extensiblemeans mountedon top of; said main'fframe and connected between said main frame and" said: supporting frame for movingsaid frame about said transverse {axis r holdingsaid'frame in fixed relation with re,- sp'ectlto said main frame, to elevate. or lower the rear end ofysaidmain frame with respect to the mine'floor' and hold, the rear end of said main frame; in fixed relationwith respect to theinine floor, a' separate wheeli supporting frame trans,- versely'pivoted adjacent one of, its endsto each side of 'said motor, saidframes having said front drive wheels journaled therein, and disposed within theglateral limits of.the machine, drive connections fromsaid motor tosaid front drive wheels, and extensible means connected between said motor and saidwheel supportingframes for pivotally, moving said frames about said transfverse axes or for holding said frames in fixed relation with respectto saidmotor to elevate. or lower theforwardend of saidv machine with respect to the minefloor. andtochold the forward end. of said, machine in. fixed relation with respect to theminefloor.

2; Ina room and pillar kerf-cuttingmachine. amain frame, a motor mounted at the forward end, of said. main frame, a cutter chain carrying cutter bar projecting forwardly of said motor, feeding mechanism disposed rearwardly of saidmotor, and meansfor elevating said machineabove' the ground and supporting it for transportation and for lowering said machine torest; upon themine floor including rear steeringwheelmeans and front drive wheels, said rear steering wheel means including a steering wheelsupportingframe having ground engaging supporting wheels mounted thereon for bodilyturning movement about an upright axis, for steering said machine; a transverse pivotal connection between the forward end of said frame andtherear end of 'said' main frame, a fluid pressure cylinder having-a piston rod extensible main frame, to elevate or lower the rear end of saidmain frame with respect to the mine floor, a separate wheel supporting frame transversely pivoted adjacent one of its ends to each side of said motor, said frameslhaving said front drive wheels journaled therein and disposed, within the lateral limits of the machine, drive connections from said motor to; said front drive wheels, and a separate fluid pressure cylinder having a piston rod extensible therefrom connected between said motor and each of said supporting frames for pivotally moving said frames, or for holding said frames in fixed relation with respect to each other, to elevate or lower the forward end of said machine with respect to the mine floor and to hold the forward end of said machine in fixed relation with respect to the mine floor. 7

3L In a room and pillar kerf-cutting machine, a main frame, a motor mounted at the forward end of said main frame, a cutter chain carrying cutter bar projecting forwardly of said motor, feeding mechanism disposed rearwardly of said motor, and means for elevating said machine above the mine fioor and supporting it for transportation about the mine and for lowering said machine to rest upon the mine floor including rear steering wheel means and front drive wheels, said rear steering wheel means including a steering wheel supporting frame having floor engaging wheels mounted thereon for bodily turning movement about an upright axis, for steering said machine, a transverse pivotal connection between the forward end of said frame and the rear end of said main frame, a fluid pressure cylinder having a piston rod extensible therefrom mounted on top of said main frame and connected between said main frame and said supporting frame at points spaced from the pivotal axis thereof for moving said support frame about said transverse axis or for holding said frame in fixed relation with respect to said main frame, to elevate or lower the rear end of said main frame with respect to the mine fioor, a separate supporting frame extending along each side of said motor, each of said frames having pivotal connection with said motor adjacent one of its ends and being guided for vertical slidable movement with respect to said motor adjacent its opposite end and having one of said front drive wheels journaled thereon for movement therewith, drive connections from said motor to said front drive wheels including gearing co-axial with the axis of pivotal movement of said frame, and a separate fluid pressure cylinder having a piston rod extensible therefrom, connected between said motor and each of said supporting frames, for pivotally moving said frames or for holding said frames in fixed relation with respect to said motor, to elevate or lower the forward end of said machine or to hold it in fixed relation with respest to the mine fioor. Y

4. In a room and pillar kerfcutting machine, a main frame, a motor mounted at the forward end of said main frame, a cutter chain carrying cutter bar projecting forwardly of said motor, feeding mechanism disposed rearwardly of said motor, and means for elevating said kerf-cutting machine above the mine floor and supportingv it; for transportation. about, the mineand for lowering said machine to rest uponthe ground including rear. steering wheel means and front drive wheels, said rear steering wheel means including a, steering wheel sup orting frame having floor engaging wheels mounted therein for, bodily turning movement about an upright axis; for steering said machine, a transverse pivotal connection betweenthe forward end of said frame and the rear end of said main frame, a fluid pressure cylinder having a piston rod extensible therefrom mounted on top of said main frame and connected between said main frame and said supporting frame at points spaced from the pivotal axis thereof for moving said supporting frame about said transverse axis or for holding said frame in fixed relation with respect to said main frame, to elevate or lower the rear end of said machine withrespect to the mine floor, a supporting frame extending along each side of said motor, each of said frames having pivotal connection with said motor adjacent one of its ends and being guided for verticalslidable movement with respect to said motor adjacent its opposite end and having one .of said front drive wheels journaled thereon for movement therewith, a fluid pressure cylinder having a piston rod extensible therefrom connected between the casing for said motor and each of said. supporting frames, for vpivo tally moving said frames or for holding said frames in fixed relation with respect to said motor, to elevate or lower the forward end of said machine or, hold it in fixed relation with respect to the 'mine fioor, and drive connections from the forward end of said motor to said front drive wheels including differential gearing, a gear at each side of said motor and journaled'coaxial with the pivotal axes of said frames, drive connections from said differential gearing to said gears, and drive connections from said gears to said wheels.

5. In a room and pillar kerf-cutting machine, a main frame, a motor mounted at the forward endof said main frame, a cutter chain carrying cutter bar projecting forwardly of said motor, feeding mechanism disposed rearwardly of said motor, and means for elevating said kerf-cutting machine above the mine floor and supporting it for transportation about the mine and for lowering said machine to rest upon the mine floor including rear steering wheel means and front drive wheels, said rear steering wheel means including a steering wheel supporting frame having floor engaging wheels mounted therein for bodily turning movement about an upright axis for steering said machine, a transverse pivotal connection betweenrthe forward end of said frame and the rear end of said main frame, a fiuid pressure cylinder having a piston rod extensible therefrom mounted on top of said main frame and connected between said main frame and said supporting frame at points spaced from the pivotal axis thereof for moving said supporting frame about said transverse axis or for holding said frame in fixed relation with respect to said main frame, to elevate or lower the rear end of said machine with respect to the mine floor, a separate supporting frame extending along each side of said motor, each of said frames having pivotal connection with said motor adjacent one of its ends and being guided for vertical slidable movement with respect to said motor adjacent its opposite end and having one of said front drive'wheels journaled thereon for movement therewith, a separate fluid pressure cylinder having a piston rod extensible therefrom connected between the casing for said motor and each of said supporting frames, for pivotally moving said frames or for holding said frames in fixed relation with respect to said motor, to elevate or lower the forward end of said machine or hold it in fixed relation with respect to the mine floor, and drive connections from the forward end of said motor to said front drive wheels including differential gearing, a gear at each side of said motor and journaled coaxial with the pivotal axes of said frames, drive connections from said differential gearing to said gears, and drive connections from said gears to said wheels, including chain and sprocket drives carried by said frames and extending therealong.

6. In a room and pillar kerf-cutting machine, a main frame, a motor mounted at the forward end of said main frame, a cutter chain carrying cutter bar projecting forwardly of said motor, feeding mechanism disposed rearwardly of said motor, and means for elevating said machine above the mine floor and supporting it for transportation about the mine and for lowering said machine to rest upon the mine floor including rear steering wheel means and front drive wheels, said rear steering wheel means including a steering wheel supporting frame having floor engaging wheels mounted thereon for bodily turning movement about an upright axis, for steering said machine, a transverse pivotal connection between the forward end of said frame and the rear end of said main frame, a fluid pressure cylinder having a piston rod extensible therefrom mounted on top of said main frame and connected between said main frame and said supporting frame at points spaced from the pivotal axis thereof for moving said supporting frame about said transverse axis or for holding said frame in fixed relation with. respect to said main frame, to elevate or lower the rear end of said machine with respect to the mine fioor, a separate supporting frame extending along each side of said motor, each of said frames having pivotal connection with said motor adjacent one of its ends and being guided for vertical slidable movement with respect to said motor adjacent its opposite end and having one of said front drive wheels journaled thereon for movement therewith, drive connections from said motor to said front drive wheels including gearing coaxial with the axes of pivotal movement of said frames, a separate fluid pressure cylinder for each of said wheel supporting frames, pivotal mountings for said cylinders on the top of said motor, a piston rod extensible from each of said cylinders, a separate rocking arm for each of said frames mounted on the top of said motor adjacent opposite sides thereof and rocked by an associated piston rod, and a link connecting each of said rocking arms with an associated wheel supporting frame for pivotally moving said frames or holding said frames in fixed relation with respect to said motor, to elevate or lower the forward end of said machine with respect to the mine floor or to hold it in an elevated position for transportation about the mine.

FRANK A. LINDGREN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,253,626 Joy Aug. 26, 1941 2,282,749 Russell May 12, 1942 2,384,083 Doberstein Sept. 4, 1945

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