USRE23466E - Loader machine - Google Patents

Description

March 4, 1952 E. M. M ELHINNEY ETAL LOADER MACHINE 3 Sheets-Sheet 1 Original Filed Dec. 13, 1946 IN V EN TOR. y; 1%

flow/ g 211 77. 97262712? Sic/F. i oc fi March 4, 1952 E. M. MOELHINNEY ET AL 23,466

LOADER MACHINE Original Filed Dec. 13, 1946 5 Shets-Sheet 2 March 4, 1952 M, McELl-NNEY ET AL Re. 23,466

LOADER MACHINE 3 Sheets-Sheet 3 Original Filed Dec. 13, 1946 Reissued Mar. 4, 1952 UNITED STATES FATENT OFFICE LOADER MACHINE Eric M. McElhinney, Bysart, and Theodore A. P-odhajshy, Traer, Iowa 7 8 Glaizns. 31. 214-141) This invention relates generally to loader machines and in particular to a loader attachment for a usual type farm tractor capable of handling manure, hay, dirt and the like.

An object of this invention is to provide I improved loader machine.

Another object of this invention is to provide a tractor loader attachment which affords visibility to the tractor operator is ca of elevating and positively holding a load -a carrying position closely adjacent to the end of the tractor, and then moving load upwardly and forwardly of the tractor to a dumping position.

A further object of this invention is to a loader attachment for a tractor having pivoted telescoping booms, in which the bcoms supported adjacent their load carrying ends at all elevated and extended positions thereof.

Another object of this invention is ts vide a loader attachment for a tractor in which. a pair of pivoted booms having a load carryim -iiit at their free ends, are supported at all elevated positions against movement sidewise or laterally of the tractor.

Still a further object of this invention is to provide a loader attachment for a tractor lch is of a construction such that the weight of the attachment and any load carried thereby is applied on the tractor frame intermediate the front and rear wheels therefor.

Another object of this inventi-on'is to provide a loader attachment for a tractor which is of a compact and rugged construction, eflicient in has a pair of forwardly extended lift members which are in a movable supporting engagement at their front ends with the telescoping members. The lift frame is pivoted by tractor operated means to raise and lower the lift members, and includes a pair of rearwardly extended levers or arms which are connected with the telescop1ng members through a lever system adapted to move the telescopin members in response to a pivotal movement of the. lift frame.

Another feature of this invention. is found in the provision of a tractor loader attachment having a pair of telescoping booms arranged at opposite sides of the tractor, and pivoted attheir ends on the tractor, in which a load carrying unit is mounted between the front ends ,of telescoping members supported on the forward ends of the booms. The booms are raised and lowered by means including a pivoted lift frame, pivotally supported at its rear end at a position above and forwardly from the pivots forthe boom and pivotally moved by tractor operated means. A pair of forwardly extended lift members on the pivoted frame movably engage and the telescoping members, which are moved in response to a pivotal movementof the lift frame by means incluing a pair of .rearwardly extended rock arms on. the lifting frame, a pair of upright levers pivoted at their lower ends the boom pivots, and links connected between the reel: arms and upright levers, and between the upright levers and the telescoping members. The rock arms and upright levers are relatively arranged so as to be in planes substantially normal to each other when the booms are in a substantially horizontal position so that the telescoping members are in contracted positions durin movement of the booms between horizontal and lowermost positions therefor.

A further feature of this invention is found in the provision of a tractor loader attachment. in which a pair of pivoted booms, with a load carrying unit between their front ends, are raised and lowered by a pivoted lift frame assembled relative to the booms and to a pair of .hydrauliccylinders arranged at opposite sides of the tractor such that a high elevation of the booms is accomplished with a minimum of movement for the lift pistons in the hydraulic cylinders.

Further objects, features and advantages of this invention will become apparent from the following description when taken in connection with the accompanying drawings, in which:

Fig. l is a side elevational view of thetractor loader attachment of this invention in assembly relation with a usual farm tractor, with certain parts being removed to more clearly showsuch assembly;

Fig. 2 is a plan view of the assembly shown in Fig. 1, with certain parts broken away for the purpose of clarity;

Fig. 3 is an enlarged sectional detail view. ,taken on the line 3-3 of Fig. 2;

Fig. 4 is a fragmentary perspective view of the scoop-latching mechanism Figs. 5 and 6 are enlarged sectional detail views as seen along the lines 5-5 and 6-6, respectively, in Fig. 1, with certain parts being broken away in Fig. 5;

Fig. 7 is an enlarged sectional detail view taken on the line 1-1 in Fig. 6;

Fig. 8 is an enlarged sectional detail view taken on the line 8-8 in Fig. 2; and

Fig. 9 is a fragmentary detail perspective view, with parts broken away, of a portion of a pivoted lifting frame which forms part of the loader attachment of this invention.

With reference to the drawings, the loader attachment of this invention is illustrated in Figs. 1 and 2 in assembly relation with a usual type farm tractor having a frame I0, steering wheels .II and traction wheels l3 mounted on a rear axle l4.

The attachment includes a pair of pivoted telescoping booms l6 having rear members H of a box shape in cross section and front members l8 of a channel construction adapted for telescopic assembly within the rear members |1 (Figs. 2 and 3). The telescoping members I8 ing pairs of rollers l9 rotatably supported in brackets 2| secured as by welding to the top and bottom walls or sections 22 and 23, respectively, f the rear members H.

The walls 22 and 23 are cut away, as indicated at 24, to receive the rollers |9 therethrough for riding engagement with the top and bottom sides of the front telescoping members I8.

The booms l6 are arranged at opposite sides of the tractor frame It] and are pivoted at their rear ends on the tractor rear axle l4 (Figs. 1 and 6) by the provision of a pair of transversely spaced lugs 26 projected rearwardly from the boom members [1 and adapted to receive therebetween a forwardly extended lug 21 mounted on the rear axle l4. Pivot bolts 28 inserted within aligned openings formed in the lugs 26 and 21 pivotally support the booms l6 for up and down pivotal movement.

The forward ends of the booms l6 are connected together by a transverse member 29 of a channel construction (Figs. 2 and 4) which is welded at its opposite ends to the telescoping members I8. Suitable brace members 3|! of a plate form are welded between the transverse channel member 29 and the telescoping members l8. Pivotally supported at 3| (Figs. 1 and 2) between the front ends of the telescoping members l8 and forwardly of the transverse connecting member 29 is a scoop or load carrying unit 32.

The booms l6 are raised and lowered by means including a lift frame, designated generally as 33 (Figs. 1 and 2) of a substantially inverted U-shape and transversely arranged in a straddling relation with the tractor frame Ill. The lift frame 33 is of a pipe construction and has a transverse pipe shaft 34 pivotally supported on the top of an upright transverse frame, indicated at 36, mounted on the tractor frame ID.

The upright frame 36 is located forwardly of the tractor rear axle I4 and includes a pair of upright side frame members 31 of a channel construction (Fig. which are mounted opposite each other on bracket members 38 welded on the tractor frame Ill. The side frame members 31 extend upwardly above the top level of the tractor engine hoodor cowl 39, and are connected across 4 their upper ends by a transverse channel member 4| which is faced upwardly. Brace members 42 are connected between the side frame members 31 and the top transverse frame member 4|.

The lower ends of the side frame members 31 terminate in rearwardly and downwardly extended projections 43 (Fig. l) for a purpose to be explained later. The upright frame 35 is supported against tipping movement by brace members 44 connected between the tractor frame In and the side frame members 31. r

The pipe shaft 34 of the lift frame 36, is rotatably supported within the upturned top transverse channel member 4| in bearings 46 (Fig. 5) located at opposite ends of the channel 4| and secured to the channel by U-clamps 41. The pipe shaft constitutes part of a transverse frame structure in the lift frame 36 which includes a second transverse pipe member 48 (Figs. 2 and 5) arranged forwardly of and in a spaced parallel relation with the pipe shaft 34. These two transverse pipe members 34 and 48 are connected together by braces 49 of a pipe construction.

Projected forwardly from opposite ends of the two transverse pipe members 34 and 48 are pipe members 5| and 52, respectively (Figs. 1 and 2), which are bent outwardly and then forwardly such that their front ends 53 and 54, respectively, are arranged side by side in a superposed parallel relation to provide for their being welded together. Brace members 56 are connected between the top pipe members 52 and the transverse pipe member 48. The brace members 56 in turn are connected together by a transverse pipe member 51a.

A pair of rods 55 (Figs. 1 and 8) are insertable to adjusted positions within the front ends of the pipe members 5| and 52 and are connected together at their forward ends by platemembers 51. Extended downwardly and forwardly from each plate member 51 is a pair of transversely spaced arms 58, of a flat bar construction, having rollers 59 rotatably supported between their lower ends. As best appears in Figs. 1 and 2, the front telescoping members l8 of the booms l6 extend between the arms 58 in supported positions on the rollers 59.

In order to adjust the rods 55 longitudinally of the pipe members 5| and 52, a circular opening 6| (Fig. 8) is formed between the adjacent sides of the pipe members 5| and 52 rearwardly from their front ends. The adjacent inner sides of the rods 55 are formed with a series of oppositely arranged axially spaced notches 62 of a semicircular shape corresponding in size to the opening 6|. When a pair of opposite notches 62 are positioned in alignment with the opening 6| a bolt 63 inserted therethrough holds the rods 55 in adjusted positions against axial movement relative to the pipe members 5| and 52.

On pivotal movement of the lift frame 33 the booms l6 are lowered and raised by virtue of their movable support on the rollers 59 at the front ends of the pipe members 5| and 52. It is seen, therefore, that each associated pair of pipe members 5| and 52 constitute a lift arm formed as part of the lift frame 33.

Pivotal movement of the lift frame 33 is accom plished by the provision of a pair of hydraulic cylinders 64 (Figs. 1, 2 and 5) arranged at opposite sides of the tractor frame and pivotally supported at their lower ends on a transverse shaft 66 supported at the lower or rear end of the extensions 43 of the upright side frame members 31. The cylinders 84 are maintained in a spaced relation outwardly from adjacent upright frame members 31 by collar or sleeve members 51 flowermost positions, the cylinders are substantially normal to the plane of the lift arms. Fluid I under pressure is supplied to the cylinders 64 from a usual type oil pump unit (not shown) carried v on the tractor and operated thereby.

The telescoping members I8 are extended and contracted in response to a pivotal movement of the lift frame 33 by the provision of means including a pair of longitudinally extended angle plate members ll (Figs. 1. and 9) which have their front ends connected between the upper ends of the pipe members 5| and 52 of the lift arms, and their rear ends 12 projected rearwardly from the lift frame 33.

The rear ends 12 t us constitute rocker arms on the pipe member 34. Inserted within the ends of the pipe member 34 (Fig. 5) are plugs 13 which have tapped holes in their outer ends to receive bolts 14 extended throu h the plates 1|. he pipe members 52 (Fig. 9) have lu s 16 on the rear sides of their top ends adapted to receive bolts which are insertable through the front ends of the plate arms I I.

A pair of upright le ers 11 (Figs. 2 and 6) have U-shaped lo er ends 18 pivoted on the boom pivot 1 bolts 28 and arranged in a straddling relation with the lugs 26. Forwardly and downwardly extended lin s 19 (Fig. l) have their front ends pivotally connected at 8! with the telescoping members l8 and their rear ends pi otally connected at 82 with t e upper ends of the upri ht levers H. Up ardly and for ardly extended lin"s 83 have their front ends pivotally connected at 84 with the free ends of the rock arms 12, and their rear ends 86 connected with the levers ll, intermediate their ends. by a lost motion means indicated generally as 81.

Since the construction and relative assembly of each lost motion means 81 with a corres onding upri ht lever 11 is the same, onl one of such assemblies will be referred to in the follo ing description. T e o t mot on means 81 inc udes a collar mem er 88 (Fi s. 6 and '7) hav n oppositelv arranged pi ots 89 supported in the lever 11 and in a brac"et member 9! secured to and spaced. laterallv from t e inner side of the lever H. Slidablv inserted throu h the collar member 88 is a tubu ar sleeve member 92 w ich is mounted about the threaded rear end 86 of the link 83.

A first adiusting nut 93 is threadable on the rear end 86 of the link 83 forwardly of the collar 88 and the sleeve 92. A coil spring 94 is mounted about the sleeve 92 and maintained in compression against the rear side of the collar 88 by a second ad ustin'r nut 96 threa'lable on t e rear end 85 of the l n" 83 rear ardlv of the sleeve 92. By relative adjustment of the nuts 93 and 98 the effective len th of the link 8'1! bet een the upright lever 11 and a roc arm 12 is varied, and the lost motion of the link 83 in a rearward direction relative to the upright lever 11 is adjusted.

In the operation of the loader machine of this invention, assume that the booms l6 are in their lo ermost positions as indicated in dotted lines at A in Fig. 1. At this position of the booms the pivoted connection 8| of the front ends of the links 19 are adjacent to the forward ends of the rear boom members [1, and the pivoted lift frame 33 is in a lowered position such that the lift arms, comprised of the members 5| and 52, are substantially normal to the hydraulic cylinders 64. On the application of fluid under pressure to the cylinders 54, to provide for an upward pivotal movement of the lift frame 33, the rollers 59 at the front ends of the lift arms are moved forwardly on the telescoping members IE to initially elevate the booms IE to their positions in a substantially horizontal plane, illustrated in full lines in Fig. 1.

During this initial upward movement of the booms I6 from their dotted line positions A to their horizontal full line positions, the upright levers H are pivotally moved rearwardly from their dotted line positions A to their full line positions also'illustrated in Fig. 1. This rearward pivotal movement of the levers 11 is accomplished by the downward pivotal movement of the roc: arms 72 from their dotted line positions AR to their full line positions, illustrated in Fig. 1. The lin 's 83, during this initial elevation of the booms I6, are maintained stationary by virtue of the action of the lost motion mechanism 81.

As a result the booms l8 are in contracted positions for their upward pivotal movement from the r dotted line positions A to their full line positions, so that the scoop 32 at a load carrying position, as defined by the horizontal position of t e booms i6, is ma ntained closely adia-cent to the forward end of the tractor. As best appears in Fig. l, a horizontal position of the booms 86 takes place when the rock arms 12 are in longitudinally aligned positions with the links 83, which aligned positions define the closest approach of the rear ends of the rock arms 72 to the upright levers H in the pivotal movement of the lift frame 33.

On a continued upward movement of the booms !6 from their full line positions to their dotted line positions, illustrated at C, the rock arms 12 move downwardly and forwardly in a pivotal path providing for a forward pivotal movement of the levers 11, which in turn act to move the links 19 in a forward direction. Due to the forward movement of the links 19 the telescoping members It! are extended forwardly from the boom rear members I! so that the booms are extended concurrently with their elevation from their full line positions to their dotted line positions C.

During this extension of the booms 16, the lift arms are pivotally moved forwardly and upwardly so that the movable support of the rollers 55 with the telescoping members l8 progresses in a direction forwardly of the booms Hi. In other words, the rollers 59 are in supporting positions relative to the telescoping members l8 such that the rollers 59 are maintained substantially at the same distance rearwardly of the scoop 32 for all elevated positions of the booms [6. A rigid support of the scoop 32 for all elevated positions thereof is thus accomplished, so as to eliminate what may be termed a freeswinging load at the front ends of the booms l5.

Further, since the supporting arms 58, for the rollers 59, are disposed at opposite sides of the telescoping members [8, the booms iii are maintained against swinging movement laterally of the tractor. Also, with the lift frame 33 pivoted on the upright frame 36 at a position intermediate the front wheels I I and rear wheels I3 of the tractor, and with the support of the hydraulic cylinders 64 rearwardly of the upright frame 36, the complete weight of the loader attachment, and the weight of the load carried in the scoop 32, is distributed over the tractor in a manner to substantially reduce any overloading of the small tires for the front wheels I I.

Because of the pivotal connection of the pistons 69, for the cylinder 64, with the lift arms at positions intermediate the ends of the lift arms, only a small movement of the pistons is required to pivotally move the lift frame 33 from its dotted line position LA to its dotted line position LC, illustrated in Fig. 1. As a result the pistons 69 are in full bearing support with the cylinders 64-for all elevated positions of the booms IS.

The latch mechanism for releasably holding the scoop 32 in a load carrying position includes a rock shaft liil (Fig. 4) rockably supported in bearings I02 and I53 mounted on the top of the transverse connecting member 29 and a telescoping member I8, respectively. An upright latch I03 mounted on the inner end of the rock shaft IOI has a slotted openin I34 adjacent to its free end which is adapted to receive in looking engagement a catch member IE6 extended rearwardly from the back wall I31 of the scoop 32.

The latch I03 is yieldably maintained in engagement with the catch I06 by a torsion spring I03 mounted on the rock shaft IilI, which has one end I09 engageable with the connecting member 29 and its opposite end III engageable with the rear side of the latch I03.

An upright rock arm I I2 mounted on the outer end of the rock shaft Isl, has its free end pivotally connected with the front end of a link II3, the rear end of which is pivoted to an upright pivoted lever H4 pivotally supported on a link member I9 (Figs. 1 and 2). A second link H6 is pivotally connected between the upright lever III and a pivoted handle I I1 carried on the link I9 adjacent to its rear end and at a position conveniently accessible to the tractor operator.

To dump the scoop 32, the handle H1 is pulled rearwardly whereby the latch I03 is moved rearwardly against the action of the sprin I08 out of an engaged position with the catch I06. The scoop 32 i returned by gravity to its load carrying position by virtue of its assembly on the I pivots 3| in a manner such that when empty its rear end overbalances the front end thereof.

From a consideration of the above description it is seen that the invention provides a loading machine which is of a simple and rugged construction, and capable of rigidly supporting a load at all elevated positions of the load.

The leader is adapted to initially lift a scoop to a load carrying position closely adjacent to the front end of the tractor, and then to move the load forwardly ahead of the tractor on a continued elevation of the load lifting arms. The attachment is relatively assembled with the tractor such that full visibility to the tractor operator and a complete maneuverability of the tractor is accomplished for all operating positions of the loader.

Although the invention has been describedwith respect to a preferred embodiment thereof, it is to be understood that it is not to be so limited since changes and modifications can be made therein which are within the full intended scope of this invention, as defined by the appended claims.

We claim:

1. A loading machine including a portable frame, a pair of pivoted telescoping booms arranged. at opposite sides of said portable frame having telescoping front members, first means pivotally supporting the rear ends of said booms on said portable frame, a load carrying unit mounted between the front ends of said telescoping members, a pair of forwardly extended lift members, second means pivotally supporting the rear ends of said lift members on said portable frame at a position spaced forwardly and above said first supporting means, means at the front ends of said lift members for movably supporting said booms, rearwardly extended rock arms mounted on said second supporting means for movement with said lift members, means for raising and lowering said lift members, means for moving said telescoping members in response to a pivotal movement of said lift members including upright levers on said first supporting means, first links connected between said upright I levers and the free ends of said rock arms, and

second links connected between said upright levers and said telescoping front members.

2. A loading machine including a portable frame, a pair of pivoted telescopin booms arranged at opposite sides of said frame having front telescoping members, means pivoting the rear ends of said booms on said frame, a load carrying unit mounted between the forward ends of said telescoping members, an upright transverse frame on said portable frame located forwardly of the rear ends of said booms, a pair of lift members pivotally supported at thei rear ends on said upright frame and having their front ends in a movable and supporting engagement with said telescoping members, rearwardly projected extensions on said lift members, means for pivotally moving said lift members to raise and lower said booms, means for moving said telescoping members in response to a pivotal movement of said lift members including a pair of upright levers pivoted on the pivot means for the rear ends of said booms, first link members movably connected between said upright levers and the rear ends of said extensions, and second link members movably connected between said upright levers and said telescoping members.

3. A loading machine including a portable frame, a pair of pivoted telescoping booms arranged at opposite sides of said frame having front telescoping members, means pivoting the rear ends of said booms on said portable frame, a load carrying unit mounted between the front ends of said telescoping members, an upright frame on said portable frame arranged forwardly of said pivot means, a lift frame rockably supported on said upright frame for up and down pivotal movement including a pair of forwardly extended lift arms having their front ends adapted to movably engage and support said telescoping members, means for rocking said lift frame to raise and lower said lift arms, means for moving said telescoping members in response to a pivotal movement of said lift frame including rearward extensions on said lift arms arranged so as to be inclined downwardly and rearwardly when said lift arms are in their lowermost positions, upright levers pivoted at their lower ends on said pivot means, first links pivotally connected with the rear ends of said extensions and with said levers intermediate the ends of said levers, and second links pivotally connected between said telescoping members and the upper ends of said upright levers.

4. A loading machine including a portable frame, a pair of pivoted telescoping booms arranged at opposite sides of said portable frame having front telescoping members, means pivoting the rear ends of said booms on said portable frame, a load carrying unit mounted between the front ends of said telescoping members, an upright transverse frame on said portable frame located forwardly of said pivot means, a pair of pivoted lift arms having their rear ends pivotally support on said upright frame and their frontends adapted to movably engage and sup-port said telescoping members, means for pivotally moving said lift arms to raise and lower said booms, means for moving said telescoping members in response to a pivotal movement of said lift arms including rearwardly projected extensions on said lift arms, a pair of upright levers having their lower ends pivoted on said pivot means, rod members connected between said telescoping members and the upper ends of said upright levers, and lost motion means connected between the rear ends of said extensions and said upright levers to provide for said extensions being substantially normal to said upright lever when said booms are in a substantially horizontal position,

5. A loading machine including a portable frame, a pair of pivoted telescoping booms arranged at opposite sides of said frame and pivotedat their rear ends on said frame said booms having front telescoping members, a load carrying unit mounted between the front ends of said telescoping members, an upright transverse frame carried on said portable frame, a pivoted lift frame pivotally supported on said upright frame and including a pair of forwardly extended lift arms, adjustable means supported on the front ends of said lift arms for movement longitudinally of said lift arms to adjusted positions, means on said adjustable means for movably engaging and supporting said telescoping members, means for swinging said lift frame to raise and lower said booms, means for moving said telescoping members in response to a swinging movement of said lift frame including rear extensions on said lift arms, upright levers having their lower ends pivoted on said portable frame adjacent to the rear ends of said booms, and link members movably connected with said upright levers and with said telescoping members and rear extensions.

6. A loading machine including a portable frame, a pair of pivoted telescoping booms arranged at opposite sides of said frame having front telescoping members, a load carrying unit mounted between the front ends of said telescoping members, means for pivoting the rear ends of said booms on said portable frame, an upright transverse frame on said portable frame, a pair of transversely spaced lift members pivoted intermediate their ends on said upright frame, means at the front ends of said lift members for movably engaging and supporting said telescoping members, means for swinging said lift members to raise and lower said booms, means for moving said telescoping members in response to a swinging movement of said lift members including upright levers pivoted at their lower ends adjacent to the pivot means for said booms, first links con- Cir nected between said upright levers and said telescoping members, and second links connected between said upright levers and the rear end portions of said lift members, with said rear end portions being adapted to be in longitudinal alignment with said second links when said booms are in substantially horizontal positions.

7. A loading machine including a portable frame, a pair of pivoted telescoping booms arranged at opposite sides of said portable frame having telescoping front members, first means pivotally supporting the rear ends of said booms on said portable frame, a load carrying unit mounted between the front ends of said telescoping members, a pair of forwardly extended lift members, second means pivotally supporting the rear ends of said lift members on said portable frame at a posit-ion spaced forwardly from said first supporting means, means at the front ends of said lift members for movably supporting said booms, rock arms mounted on said lift members for pivotal movement therewith, means for raising and lowering said lift members, means for moving said telescoping members in response to a pivotal movement of said lift members including upright levers pivoted on said portable frame at positions adjacent to said first supporting means, first links connected between said upright levers and the free ends of said rock arms, and second links connected between said upright levers and said telescoping front members.

8. A loading machine including a portable frame, a pair of pivoted telescoping booms arranged at opposite sides of said portable frame and pivotally supported at their rear end on said portable frame, said booms having front telescoping members, a pair of forwardly extended lift members pivotally supported at their rear ends on said portable frame for up and down movement, rock arms onsaid lift members for pivotal movement therewith, said lift members having their front ends in movable supporting engagement with said telescoping members, means for pivotally moving said lift members to raise and lower said booms, means for moving said telescoping members in response to an up and down movement of said lift members comprising first links pivoted at one of their ends to said front telescoping members, levers pivoted at one of their ends to said portable frame, means pivotally connecting together the other ends of said links and levers, and second links movably connected to said rock arms and to said levers.

ERIC M. MCELHINNEY. THEODORE A. PODHAJSKY.

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

UNITED STATES PATENTS Number Name Date 2,080,461 Cope May 18, 1937 2,126,791 Low Aug. 16, 1938 2,287,375 Ford, Jr. June 23, 1942 2,295,917 schwan Sept. 15, 1942 2,404,820 Wuertz et al July 30, 1946 2,454,461 Knapp Nov. 23, 1948 2,465,476 Pokorny et al Mar. 29, 1949

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