US2679938A - Loading crane - Google Patents

Description

June 1, 1954 c. H. WILLOWS 5 2,679,938

LOADING CRANE Filed July 14, 1950 3 Sheets-Sheet l INVENTOR. CL VDE k/ALLOWJ.

(-YTTOlE/VE 76 June 1, 1954 c. H. WILLOWS 2,679,938

LOADING CRANE Filed July 14, 1950 3 Sheets-Sheet 2 '62 as; in 57 59 63 u gi l INVENTOR. CLYDE H. WILLOWS 110 rams s.

June 1, 1954 c. H. WILLOWS I 2,679,938

LOADING CRANE Filed July 14, 1950 3 Sheets-Sheet 3 INVENTOR. CL YDE H. WILL 0W6.

ATTORNEYS- Patented June 1, 1954 LOADING CRANE Clyde H. Willows, Lakewood, Ohio, assignor to Cecil C. Peck Company, Cleveland, Ohio, a corporation of Ohio Application July 14, 1950, Serial No. 173,800

10 Claims. 1

This invention relates as indicated to a novel and improved crane and, more particularly, to a traveling lifting and loading device particularly suited for the loading of heavy objects within trucks, vans, trailers, box cars and the like having roofs or covers normally interfering with loading operations wherein the load is suspended from overhead supporting means.

Various types of monorail conveyors are well known in the art and are frequently employed to transport articles from place to place Within a manufacturing plant and also to and from the usual loading and unloading docks. It is customary to deposit the articles thus transported to a loading dock for shipment and then to manhandle the same into the waiting truck trailer, box car, or the like. The disadvantages of this procedure are obvious but have been considered largely unavoidable. It is frequently possible to deliver the articles to the loading dock for shipment much more rapidly than they can be stacked within the waiting vehicles so that congestion and inefficient handling results. The manual labor involved is of the most strenuous sort and the risk of injury both to the workers and to the articles being handled is considerable.

It is accordingly a primary object of my invention to provide a vehicle loading crane having an overhead support adapted to deposit a load where desired Within a covered vehicle and similarly to remove the same therefrom, regardless of variation in height of such cover.

A further object is to provide a crane of the .type indicated also adapted to be suspended from an overhead monorail for travel therealong.

Still another object is to provide such crane mounted for a degree of later swinging movement whereby loads may be raised and lowered from positions to either side of the path of travel of such crane along its overhead monorail support.

A further object is to provide control means for such crane whereby a single operator positioned adjacent the load to be transported may control both the travel of the crane and the, raising and lowering of the load.

Other objects of my invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

Fig. 1 is a perspective view of my new crane shown in the act of depositing a load within a covered truck trailer, 2. portion of the latter being broken away better to illustrate this operation;

Fig. 2 is a side elevational view of one preferred embodiment of the crane of my invention;

Fig. 3 is a vertical sectional view taken along the line 33 on Fig, 2;

Fig. 4 is an enlarged vertical sectional View taken along the line 44 on Fig. 2;

Fig. 5 is a top plan view of a preferred form of overhead supporting means for my new crane;

Fig. 6 is a wiring diagram of control means for operation of such crane;

Fig. 7 is a fragmentary side elevational view of the end of the crane boom modified for employment with a fork lift device;

Fig. 8 is an enlarged fragmentary elevational view of locking means for locking the boom in position parallel to the central monorail support;

Fig. 9 is a detail sectional View taken along the line 99 on Fig. 8; and

Fig. 10 is a reduced diagrammatic plan view of a track system for such crane at a multiple loading dock or the like.

Referring now more particularly to said drawing and especially Figs. 1-5 thereof, the embodiment of my invention there illustrated comprises a recurved hairpin boom including an upper horizontal arm l, a rigid, vertical elbow portion 2, and a relatively elongated, generally horizontal lower arm 3 adapted to be held rigid with such upper arm portion. As best illustrated in Figs. 3 and 4, such boom may be desirably of welded box frame construction comprising upper and lower plates 4 and 5 respectively joined by side plates or web portions 6 and l. The dimensions of such side plates will ordinarily be increased in the region of elbow 2, as illustrated, to ensure sufiicient strength and rigidity in this region of maximum strain, but the underside of upper arm I will ordinarily be generally parallel to the upper side of lower arm or boom 3 when such lower arm is in horizontal position. A window 8 is shown provided in such elbow portion 2 for a purpose to be explained below.

This crane is adapted to be suspended from an overhead central monorail 9 which is paralleled by two adjacent thrust rails It and H to either side thereof, the whole being suspended in the usual manner from overhead supports such as beams l2 and [3 or the like. Suspended from the center master rail 9 is a generally triangular carriage comprising a transverse member i4 and two legs or struts l5 and I6 joined at one end and at their other ends respectively connected with the extreme outer ends of transverse member 14. A curved I-beam trackway i? is supported by such carriage adjacent transverse member i l, having the point of joining [8 of such struts i5 and 16 as its center of curvature, such center being directly beneath master rail 9 and also being the point of attachment of upper boom arm i to such carriage by means of swivel 99, whereby the crane boom may be pivoted about a vertical axis. As best shown in Figs. 2 and 3, such swivel mount 19, connected to carriage strut members it and I6, is also provided with two pair of suspension rollers 29 adapted to travel along the lower flanges of master rail 9. Such swivel and rollers are designed to support the entire weight of the crane and any load carried thereby. Such swivel l9 may desirably be located approximately midway of the length of upper arm i, such upper arm in turn extending about the length of lower boom arm 3. Wherever two pair of rohers are employed in association, they should also be provided with swivel mounts to facilitate travel around curves.

The forward end of arm I is also provided with a swivel 2i carrying rollers 22 adapted to rest upon and travel along the lower flange of I-beam arcuate trackway I1. The hairpin boom is thus steadied and supported when swung from side to side about its main pivot or swivel 59, the degree of such swinging movement being limited by engagement of rollers 22 with the carriage side strut members and I5 (see diagrammatic Fig. 5). Brace rollers 23 and 24 are carried by the extreme outer ends of transverse member is and are adapted to bear upwardly against the undersides of the respective thrust rails l9 and il. Accordingly, when the crane boom is swung to one side as shown in Fig. 5, for example, tipping of the supporting carriage frame is prevented.

One or more monorail tractors such as 25 and 26 of standard design may be suspended from the lower flange of master rail 9 and connected to the forward nd of the boom supporting cari riage which is likewise suspended from the lower flange of such monorail by means of rollers 27. It will thus be seen that the boom supporting carriage is suspended from the master rail both in the region of swivel ill by rollers and at the forward end of such carriage by rollers 21. Such spaced points of suspension together with the provision of the laterally spaced brace rollers 23 and 24 adapted to engage the undersides of thrust rails I0 and H respectively aiford a maximum degree of support and stability. Tractors 25 and 26 are mounted to drive the crane supporting carriage in either direction along such overhead trackway.

Work lifting means is provided, normally at the extreme forward end of lower boom arm 3. As illustrated in Figs. 1-5 inclusive, such means may comprise a conventional Yale & Towne chain hoist 23 suspended in window 8 and including the usual electric motor driven reel or winch and chain storage pocket P from which the chain is paid out and into which it may be withdrawn by operation of such winch. The chain 29 may be brought down beneath a sprocket 38 within elbow portion 2 of the boom and then conducted over a series of supporting sprockets 3! to the forward end of boom arm 3 where it is secured at 32 to the underside of downwardly inclined guard end 33 of such boom. A hook 34 is shown suspended by block 35 in a loop 35 of such chain 29. Since ordinarily it will only be necessary to lift a load a relatively short distance to raise the same from the floor and to clear minor obstacles, there is ordinarily no need to provide hoisting means adapted to accommodate a great deal of chain or cable.

Now referring more especially to Fig. 7 of the drawing, an alternative lifting means is there illustrated in side elevation, comprising a standard fork lift 31 mounted on the end of boom arm 3 and adapted to be reciprocated up and down in the usual manner by means of fluid pressure piston-cylinder assembly 38. Such fork and its supporting means 39 will desirably be mounted for pivotal adjustment about a horizontal axis 40 transverse of such boom, being tilted into desired adjusted position by means of small fluid pressure piston-cylinder assembly M. A pump 42 driven by an electric motor 43 may be conveniently attached to the underside of boom arm 3 adjacent such fork lift to supply fluid pressure to piston-cylinder assembly 38. Likewise, a reservoir (not shown) of hydraulic fluid may conveniently be contained within such boom arm together with the usual conduits (likewise not shown). It will, of course, be understood that a variety of lifting means may be provided for the purpose of elevating a load relative to boom arm 3 in addition to the typical examples illustrated and described. In fact, since, as indicated, it is ordinarily only necessary to elevate a load a short distance from the floor, a manual chain hoist may be secured to the end of the boom for such purpose. Ordinarily, however, powered lifting means will be preferred.

When the crane is traveling along its trackway, down an aisle within a plant, for example, it is important that the boom be maintained parallel to the master rail 3 from which it is sus pended and that it shall not slew from side to side about its swivel 19. Accordingly, as best shown in Figs. 1, 8 and 9, a lock means is provided on upper boom arm i adapted to be engaged with appropriate retaining means on arcuate trackway I1 directly below master rail 9. In the form illustrated in Figs. 8 and 9, two spaced lugs -44 and 45 are welded to the lower flange 45 of track member 1! closely adjacent the vertical web portion thereof. A latch member t] is horizontally pivotally mounted at 48 in a frame 49 on upper boom arm i. A solenoid armature 59 is pivotally connected to such latch by means of link members 5| whereby such latch may be raised to disengage the same from between looking lugs 44 and 45 by energization of solenoid coil 52. It will thus be seen that when the boom is brought into parallel alignment with master rail 9 it will be locked in such position, preventing swinging of the same relative to its supporting carriage. When the operator desires to pick up a load adjacent an aisle along which the crane is travelling, for example, he will stop the crane, disengage the look by energizing solenoid 52 and then manually swing the boom to the side desired. After raising the load from the floor, the boom will again be swung into position parallel to master rail 9 and locked in such position for continued travel.

Referring now to Fig. 6 of the drawing, there is there illustrated a typical wiring diagram for control and operation of the crane shown in Fig. 2, for example. Power to energize the various tractor and hoist motors is taken from the usual monorail trolley wires 53 by the usual collectors 54. The reversible tractor motors 55 (only one being shown in this diagram, it being understood that any desired number of tractors may be employed) may be energized in the usual manner as by pressing forward push button 56 or reverse push button 57. Similarly, reversible hoist motor 58 may be energized to take in chain 29 by pressing button 59 and to pay out such chain by pressing button 60. A normally closed hoist limit switch 81 may desirably be provided (see also Fig. 2) which will automatically be opened by operation of control lever 62 when block 35 has been elevated to its uppermost position, thereby de-energizing hoist motor 58. The latch solenoid 52 is controlled by push button 82, the operator holding the push button in to complete the circuit to energize such solenoid when he wishes to disengage the latch 41. As shown in Fig. 2, such push button controls will desirably be located adjacent the end of lower boom arm 3 and preferably on the underside thereof, a guard 63 being provided to prevent possible damage thereto.

Unfortunately, as a practical matter, the height of covered vans and box cars varies considerably whereas the overhead trackway, once installed, is fixed at a definite elevation. To be commercially acceptable, the loading means must be adapted to enter all such covered vehicles in common use. Merely to employ a longer elbow portion 2 with lower boom arm 3 extending fixedly, rigidly therefrom is not a solution to this problem since it then becomes impossible to utilize the extra space in the upper portion of the higher vans. Neither has it been found satisfactory to mount the entire hairpin boom for raising and lowering relative to such trackway since this obviously will necessitate elaborate mechanism for such purpose if the desired structural rigidity is to be maintained. The lower boom arm should also, of course, be adapted for insertion of sub-- stantially its entire length within the vehicle.

To solve this difiiculty in a practicable manner, I secure lower boom arm 3 to the downward- 1y extending portion 2 by means of a horizontal pivot $4 permitting up and down swinging adjustment of such boom arm 3 in the vertical plane including upper boom member I. Such upper and lower boom members are respectively provided with rearward extensions 65 and 66 with a screw jack interposed therebetween. Such jack comprises a screw 6'! one end of which is threadedly engaged in a socket 68 in upper extension 65 and the other end of which is rotatably engaged in a swivel socket in sliding mount 69 in lower extension 86 permitting the same to accommodate itself to varying degrees of inclination. A transverse hole Ill through such screw permits insertion of a turning rod or handle. A large lock nut H serves to lock such jack in adjusted position. Since the outer end of boom arm 3 will ordinarily be maintained at a single selected elevation during loading of any particular car or van, jack 5'] will require only occasional adjustment. Furthermore, since arm 3 is much longer than its rearward extension 66, a relatively slight adjustment of jack 6? is correspondingly magnified at the extreme end of boom arm 3. Obviously, various equivalent adjustably extensible means may be employed instead of such screw jack, including a fluid pressure actuated pistoncylinder assembly. for example, pivotally interconnecting extensions 65 and 66.

Referring now more particularly to Figs. 1 and 10 of the drawing, the operation of my new crane may be explained as follows. Assuming that a heavy crated load is to be transported from the work floor of a plant to a waiting van or truck trailer, for example, the operator will first press either the forward button 56 or the reverse button 5! to energize the tractor motor or motors to cause the crane to travel to a point where the end of lower boom arm 3 is adjacent the load. The operator then stops the tractor motor and presses push button 62' to disengage latch 5? and permit him to swing the boom until hook at is above the load. He then presses hoist motor control button 6|] to lower block 35 and hook until such hook can be engaged to the load. Push button 59 is now pressed to reverse hoist motor to raise the load the necessary distance from the floor to ensure that all minor obstacles such as sills and the like will be cleared. When the boom has been swung back into parallel with master rail 9 and latched in such position (locking lugs 44 may be provided with beveled edges as shown in Fig. 9 to cam latch M upwardly, thereby causing the latter automatically to enter into latching position between such lugs when the boom is swung), the operator will now press forward push button 56 to cause the tractors to move the crane toward the loading dock, it being understood that the crane supporting carriage will be mounted on the trackway with the forward end of lower boom arm 3 directed toward such dock. Due to the convenient positioning of the control buttons, the operator may walk alongside the crane closely adjacent the load, with such crane and load under immediate control at all times. He is thus enabled to avoid obstacles and pass the load through openings where there is but small clearance with the greatest of ease. The trackway will extend out over the loading dock and somewhat beyond, as shown in Fig. 1, so that lower boom arm 3 may enter and reach to the forward end of a van or trailer parked therebeneath. The operator will enter the van with the load, stopping the tractor motor when such load has reached the desired position. If necessary, he may disengage the latch and swing the boom slightly to one side or the other in order to position the load exactly as desired. He will then press button as to cause the hoist to lower the load to the trailer floor whereupon hook 34 may be disengaged and the crane now backed away.

While lower boom 3 may be swung upwardly about its pivot fi l after a load has been raised by the hoisting means, it is obviously ordinarily preferable to make such adjustment in advance. When boom 3 is in horizontal position, it will be designed to enter the lowest roofed vehicles it is desired to load. Consequently, all normal adjustments thereof will be to raise the end of such boom rather than to lower the same below a horizontal position. This means that there will never be any problem of the boom encountering the roof of the vehicle after it has been partially inserted within the latter.

As diagrammatically illustrated in Fig. 10, the trackway comprising the parallel rails 9, l0, and ii may terminate in a separate segment ll mounted for lateral travel along transverse rails 72 and 13. When my new crane has been conducted onto such segment (in alignment with the main track rails), such segment and crane may then be shifted laterally along loading dock 14 as required to load any selected vehicle. Furthermore, when it is desired to deposit a load within the ends of a box car, for example, the end of the boom may first be inserted through the doorway and the track segment then shifted somewhat laterally so that the boom end may swing into the end of the car. Such track segment may be carried by the usual overhead traveling crane. It will be appreciated that arcuate trackway Il may comprise any desired part of a circle, even a full 360, if desired, in order to permit the requisite swinging movement of the boom for any particular installation.

By employing the crane of my invention it is possible to load heavy packaged materials, for example, in covered vehicles with ease where previously considerable man-power was required. With heavy items necessitating the use of a crane it was formerly customary to load the same on flat-cars or open trailers, exposed to the Weather. Certain articles such as rolls of carpet, long bundles of bar stock, etc., can be loaded into box cars without difiiculty whereas lift-trucks and the usual cranes have proven unequal to the job. By providing for upward swinging adjustment of the lower boom member I am enabled to take full advantage of the height of the vehicle both to load large objects and to stack articles therein. Instead of mounting my rane on a monorail system such crane may be mounted directly on the carriage of a two-way traveling overhead crane in the same manner in which it is mounted on the monorail carriage, and may then be employed to load box cars as described above.

Other modes of applying the principle or" the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A traveling loading crane comprising an upper horizontal boom member, a member extending downwardly from said boom member adjacent one end thereof and rigid therewith, a lower boom member generally parallel to said upper boom member and pivotally connected adjacent one end to said downwardly extending member for up and down swinging movement in a plane including said upper boom member, adjustable brace means interconnecting said two boom members adjacent such pivot adapted to regulate the inclination of said lower boom member relative to said upper boom member, and work lifting means on the extended end of said lower boom member adapted to lift such work relative to such lower boom end.

2, A traveling loading crane comprising a carriage, an upper horizontal boom member suspended from said carriage for swinging movement about a rigid vertical axis, a member extending downwardly from said boom member adjacent but spaced from one end thereof and rigid therewith, a relatively short extension of said boom member projecting therebeyond, a lower boom member generally parallel to said upper boom member and pivotally connected adjacent one end to said downwardly extending member for limited up and down swinging movement in a plane including said upper boom member, said lower boom member also having a relatively short extension projecting in the opposite direction beyond such pivot below and parallel to said short extension or said upper boom member, jack means interposed between said extensions and operative to rock said lower boom member about such pivot adjustably vertically to position the extreme loadlifting end of said lower boom member, and load lifting means on the end of said lower boom member adapted to elevate such load relative to said lower boom member.

3. In a loading crane adapted to be suspended from an overhead trackway, a carriage adapted to travel along such trackway, an upper horizontal boom member suspended from said carriage for swinging movement about a rigid vertical axis, an arcuate trackway on said carriage having such axis for a center, boom-supporting means on said boom and engaging said arcuate trackway for travel therealong when said boom is swung about such axis, a member extending downwardly from said boom adjacent but spaced from one end thereof and rigid therewith, a relatively short extension of said boom projecting therebeyond, a lower boom member generally parallel to said upper boo-m member and pivotally connected adjacent one end to said downwardly extending member for limited up and down swinging movement in a plane including said upper boom member, said lower boom member also having a relatively short extension projecting in the opposite direction beyond such pivot below and parallel to said short extension of said upper boom member, jack means interposed between said extensions and operative to rock said boom member about such pivot vertically ad- J'ustably to position the extreme load-lifting end of said lower boom, hoisting means on the end 01 said lower boom, drive means for said hoistin, means at least partially enclosed within such boom structure operative to raise and lower said hoisting means relative to said lower boom, and manual control means for said drive means on said lower boom.

4. In a loading crane adapted to be suspended. from an overhead trackway, a carriage adapted to travel along such trackway, tractor means operative to drive said carriage along such tract: way, an upper horizontal boom member sus-- pended from said carriage for swinging movement about a rigid vertical axis, an arcuate trackway on said carriage having such axis as a center, boom-suspending means on said boom and engaging said arcuate trackway for travel there" along when said boom is swung about such axis, a member extending downwardly from said boom adjacent but spaced from one end thereof and rigid therewith, a relatively short extension of said boom projecting therebeyond, a lower boom member generally parallel to said upper boo-m member and pivotally connected adjacent one end to said downwardly extending member for limited up and down swinging movement in a plane including said upper boom member, said lower boom member also having a relatively short extension projecting in the opposite direction beyond such pivot below and parallel to said short extension of said upper boom member, jack means interposed between said extensions and operative to rock said boom member about such pivot vertically adjustably to position the extreme loadlifting end of said lower boom, hoisting means on the end of said lower boom, drive means for said hoisting means at least partially enclosed within such boom structure operative to raise and lower said hoisting means relative to said lower boom, and manual control means for said tractor means and said hoist drive means on said lower boom.

5. A traveling loading crane comprising a carriage adapted to travel along an overhead trackway, a generally C-shaped boom structure suspended from said carriage by means of a rigid vertical pivot on the upper generally horizontally extending portion of said structure intermediate the ends thereof, the lower generally horizontally extending portion of said structure being pivotally connected to the remainder of said structure for up and down swinging adjustment relative thereto, means extending from said upper boom portion to said lower boom portion without obstructing the space between said upper and lower boom portions to hold said lower boom portion in selected adjusted inclination relative to said upper boom portion, and lifting means on the free end of said lower boom portion operative to elevate a load relative thereto.

6. A traveling loading crane comprising a carriage adapted to travel along an overhead trackway, a generally horizontally disposed elongated upper boom member mounted on the underside of said carriage intermediate the ends of said boom for swinging movement about a rigid vertical axis, a lower boom member pivotally connected to and downwardly spaced from said upper boom member adjacent one end for up and down swinging movement, whereby the other end of said lower boom may be adjustably positioned at a desired elevation, lateral brace means on said carriage adapted to engage an overhead abutment and thereby brace said carriage when said boom members are swung laterally of such trackway, supporting means on said carriage adapted to engage and support an end of said upper boom in all lateral swinging positions of the latter, and lifting means on the extended end of said lower boom operative to lift a load relative thereto.

7. A loading crane comprising a generally C-shaped boom structure, traveling overhead supporting means for said boom structure suspending the latter by means of a rigid vertical pivot on the upper generally horizontal portion of said structure, the lower generally horizontally extending portion of said structure being pivotally connected to the remainder of said structure for up and down swinging adjustment relative thereto, means extending from said upper portion to said lower portion without obstructing the space within such to hold said lower boom portion in selected adjusted position, supporting means on said upper boom portion spaced from such vertical pivot and adapted to support said boom structure to prevent bending action on such vertical pivot under load, and lifting means on the free end of said lower boom operative to lift a load relative thereto.

8. In a loading crane adapted to be suspended from an overhead traclrway, a carriage adapted to travel along such trackway, an upper horizontal boom member suspended from said carriage for swinging movement about a rigid vertical axis, an arcuate trackway on said carriage having such axis as a center, boom supporting means on said boom member and engaging said arcuate trackway for travel therealong when said boom member is swung above such axis, a member extending downwardly from said boom member adjacent one end thereof and rigid there-with, a lower boom member generally parallel to said upper boom member and p-ivotally connected adjacent one end to said downwardly extending member for up and down swinging movement in a plane including said upper boom member, adjustable brace means interconnecting said two boom members adjacent such pivot adapted to regulate the inclination of said lower boom member relative to said upper boom member, and work lifting means on the extended end of said lower boom member adapted to lift such work relative to such lower boom end.

9. A traveling loading crane comprising a carriage adapted to travel along an overhead trackway, a generally c-shaped boom structure having upper and lower boom portions which extend generally horizontally beneath said carriage, support means extending downwardly from said carriage and engaging the generally horizontal upper :portion of said boom structure at longitudinally spaced apart points there-along, said support means mounting said boom structure for swinging movement about a vertical axis, the generally horizontal lower portion of said boom structure being pivotally connected for vertical swinging adjustment relative to said upper boom portion, means extending between such upper and lower portions operative to hold said lower boom portion in selected adjusted position, and load engaging means on said lower boom portion.

10. A traveling loading crane comprising a carriage, a horizontal upper boom member suspended from said carriage for swinging movement about a vertical axis, boom-supporting means extending from said carriage to said upper boom member at a point spaced from said axis operative to prevent bending action of said upper boom member under load, a member extending downwardly from said upper boo-m member adjacent one end thereof, a lower boom member generally parallel to said upper boom member and pivotally connected to such downwardly extending member for up and down swinging movement, adjustable brace means interconnecting such boom members adjacent such pivot adapted to regulate the inclination of said lower boom member relative to said upper boom member, and work engaging means on the extended end of said lower boom member.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 428,301 Forter May 20, 1890 437,819 Morgan Oct. '7, 1890 744,316 Eitle Nov. 17, 1903 854,837 Paige May 28, 1907 1,521,266 Andrews Dec. 30, 1924 1,546,364 Bennington July 21, 1925 1,720,240 Saborsky July 9, 1929 1,783,021 Leach Nov. 25, 1930 2,322,636 Kidder June 22, 1943 2,546,362 Graham Mar. 27, 1951 FOREIGN PATENTS Number Country Date 256,568 Germany Feb. 15, 1913

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