US3021963A

US3021963A - Crane

Info

Publication number: US3021963A
Application number: US770670A
Authority: US
Inventors: Earl W Kasdorf; Richard T Fujioka
Original assignee: Manning Maxwell and Moore Inc
Current assignee: Manning Maxwell and Moore Inc
Priority date: 1958-10-30
Filing date: 1958-10-30
Publication date: 1962-02-20
Anticipated expiration: 1979-02-20

Description

Feb. 20, 1962 E. w. KASDORF EI'AL 3,021,963

CRANE Filed Oct. 30, 1958 5 Sheets-Sheet 1 hen-fans I far/ H4 lfaso f 9 Rickard 7.' Fujio/ra Feb. 20, 1962 E. w. KASDORF EI'AL 3,021,963

CRANE 5 Sheets-Sheet 2 Filed Oct. 30, 1958 ML Era-z: Ear/ W Kasdon" Richard 7. Fuji o/ra E hva . m. QM

Feb. 20, 1962 E. w. KASDORF ETAI.

CRANE 5 Sheets-Sheet 4 Filed Oct. 30, 1958 Eran-furs Ear/ fl4\/1asdorf' Ric/76rd 7. Fq/io/ra Feb. 20, 1962 E. w. KASDORF ETA]. 3,021,963

CRANE Filed Oct. 30, 1958 5 Sheets-Sheet 5 Earl 11 ffasa'orf' 35; 17 Ric/6am 7. Fajio/na United States Patent G 3,021,963 CRANE Earl W. Kasderf, Muskegon, and Richard T. Fujioka, Oxford, Mich, assignors to Manning, Maxwell 8: Moore, Inc., Muskegon, Mich, a corporation of New Jersey Filed Oct. 30, 1958, Ser. No. 770,670 Claims. (Cl. 212-428) The present invention relates to improved mechanisms for material handling and more particularly to the provision of an improved crane construction capable of rapidly lifting and handling loads without unwanted lateral swinging or swaying motions.

In many industries the need for a heavy duty crane which is capable of lifting and lowering a load and yet which does not have lateral sway has become prevalent. These qualifications are necessary both in locating the crane with respect to the load and with handling the load. The problems of unwanted lateral movement are increased with high speed operation. In a crane which is automatically operated and requires rapid operation, the problem of sway becomes accelerated. For example, where the crane is used in a device to rapidly move the partly assembled components from one assembly to another in short assembly cycle times, the load must be lifted, transferred and lowered within a short time, then the time limit leaves no time for control of the hook swing it an entirely automatic operation is desired. In industries such as automotive assembly, handling of munitions, and handling of radioactive materials, speed and safety of operation make the provision of a crane which is rigid against unwanted lateral movement of a great advantage over those which can swing freely.

Another requirement of cranes in numerous industries has been that the cranes take little head room, which is the distance from the top of the runway rail to the lowest overhead obstruction. The present invention contemplates the provision of a crane wherein a minimum amount of head room is required and wherein the crane has a high lift.

Accordingly, an object of the invention is to provide an improved crane which is well adapted to high speed automatic operation and which substantially eliminates unwanted lateral sway of the load.

A further object of the invention is to provide an improved crane capable of heavy duty use, which is capable of very fast movements in various directions.

Another object of the invention is to provide an improved crane which is collapsible vertically but which is rigid in a lateral direction.

Another object of the invention is to provide an improvide crane which requires a minimum head room and is capable of high lift.

A still further object of the invention is to provide an improved pantograph type of mechanism which is extremely well suited for-use in a crane having the above objectives.

A further object of the invention is to provide an over all crane assembly with improved mechanism for attaching and releasing a load.

Other objects and advantages will become more apparent with the disclosure of the preferred embodiments of the invention in connection with the description and showing thereof in the specification, claims, and drawings in which:

FIGURE 1 is a front elevational view of an overhead crane assembly embodying the principles of the present invention;

FIGURE 2 is an enlarged perspective view of a rack and pinion assembly in the form used in connection with a pantograph guide for the crane;

ice

FIGURE 3 is an elevational view showing details of the pantograph assembly;

FIGURE 4 is a plan view taken substantially along line IV-IV of FIGURE 3;

FIGURE 5 is a horizontal sectional view taken substantially along line V-V of FIGURE 3;

FIGURE 6 is a vertical sectional line illustrating the end of the pantograph assembly and taken substantially along line VI-VI of FIGURE 3;

FIGURE 7 is a vertical sectional view taken substantially along line VII--VII of FIGURE 3;

FIGURE 8 is a vertical sectional view taken substantially along line VIlIVIII of FIGURE 3;

FIGURE 9 is a vertical sectional view taken substantially along line IX-IX of FIGURE 5 with additional parts broken away for clarity;

FIGURE 10 is a vertical sectional view taken substantially along line XX of FIGURE 5; and,

FIGURE 11 is a vertical sectional view taken substantially along line XI-XI of FIGURE 5.

As shown in the drawings:

As particularly illustrated in FIGURE 1, and as also shown in FIGURES 3 and 6, the overhead crane mechanism includes a traveling bridge 12 which is adapted to be installed in an industrial building or the like and which is power driven for horizontal movement in a direction toward or away from the viewer. Movably mounted on the bridge 12 is a trolley 13 which moves laterally of the bridge and is power driven for this purpose. The bridge 12 and trolley 13 atlord horizontal movements to accurately position the mechanism with respect to an object to be lifted from a floor 15 and to be carried to a different location.

Suspended below the bridge 12 and trolley 13, and for purposes of attaching to a load, is a load attachment member shown in the form of a strongback 14. The strongback is provided with attaching means as will be described later in detail, especially in connection with FIGURES 5, and 7-1l. The strongback is provided with a rigid guide which prevents sway and lateral movement with respect to the bridge and trolley. The strongback is guided against these movements by a pantograph assembly 16. The pantograph is so constructed so as to prevent unwanted lateral movements of the strongback in either lateral direction and to prevent unwanted twisting movements thus holding the strongback steady and per rnitting rapid and immediate movements-of the bridge 12 and trolley 13 as soon as the load is lifted from the floor; This enables use of the crane for rapid movements such as are required when the load must be held for a limited time, such as when chemically treating an object. This also makes the crane well adapted for automatic operation where high speeds are essential.

Vertical movement of the strongback 14 is obtained by cables 17 and 18 which are connected to the strongback and are suspended from the trolley.

With respect to the supports and drives for the bridge 12 and trolley 13, as will be appreciated by those skilled in the art, Various satisfactory arrangements may be adopted. As shown in FIGURE 1, the bridge 12 is illustrated as supported on rollers 19 and 21 which roll on horizontal tracks 22 and 23. The tracks are supported on beams 24 and 26 which extend horizontally along a building at a location where the crane is to be used. The rollers 19 and 21 are restrained from upward movement by machined bars 24a and 26a, which are attached to the underside of the top flanges of beams 24 and 26. The relationship of the machined bars and the top of the rails results in a close clearance in which the rollers traverse.

Rollers

19a and 21a are attached to the bridge 12 for rotation about vertical axes and ride inside the beams on the side edges of the bars 24a and 26a to give stability in a horizontal direction. Horizontal movement of the bridge may be accomplished through various types of power drives. In the present embodiment, the bridge is driven by a hydraulic motor acting through gearing to turn a sprocket. The sprocket engages a chain which is securely anchored to each end of the crane runways. This mechanism is not shown in detail. The entire unit may be automatically operated or may be controlled by an operator located at 31. The building in which the crane is located is shown as having the floor 1S and having walls 29 and a ceiling 36. it is to be noted that a very small amount of head room 32 is required.

The trolley 13 is driven horizontally across the bridge 12 and is operated by cable 33. The cable is secured at its ends 33a and 33b to the trolley 13 and passes over a drive member 34 which may be a sheave or a sprocket depending upon whether the cable is in the form of a rope or chain. The drive sprocket 34 may be operated in various ways and may be arranged to be hydraulically driven for rapid movement, as will be appreciated by those skilled in the art. The cable 33 also passes over sheaves or sprockets 36, 37 and 38, each of which are mounted on the bridge 12 along with the drive sprocket 34.

As may be viewed in FIGURES 1, 3, 4 and 6, the trolley 13 is carried on the bridge 12 and is provided with wheels or rollers 42, 4-3, 44 and 46, which rol on rails 39 and 41 supported on brackets 39a and 41a on webs of the beam members 12a and 12b of the bridge. The rollers are also restrained from upward movement by horizontal bars 39b and 41b on the webs of the members 12a and 12b. The trolley is guided by rollers 46a and 4011 which roll along the inside of a plate 39a supporting the base of the track 39, and rollers 45a and 451; which roll along the inside of a plate 41a supporting the base of the track 41.

The pantograph is thus supported on a stable support. By the structure with which the pantograph is connected to the trolley 13 and is connected to the strongback 14, and the manner in which the pantograph itself is constructed, it supports a completely stable lateral guide for the strongback holding it in the exact position that it is located by the bridge and trolley and preventing sway or unwanted lateral movement as the strongback is moved into position for lifting a load or when the load is lifted and transported.

The force for raising or lowering the strongback 14 is applied directly to the strongback.

The cables 17 and 18 are operated simultaneously to maintain the strongback 14 horizontal. The cable 18 is connected at one end to an anchor 49 mounted on the bridge 12 and passes over a sheave 51 on the trolley 13, is looped downwardly over a sheave 48 on the strongback and passes up over a sheave 52 on the trolley. The cable 18 then runs along to be threaded over a sheave 53 on the bridge and is then connected to a cable actuating

mechanism including sheaves

54 and 56. A cable actuating mechanism is provided with a cylinder and piston, not shown, which is arranged to move the sheave 54, such as between the positions shown at 54 and shown at 54a. This will shorten or lengthen the cable 18 to raise or lower the strongback 14. Since the anchor 49 and the sheave 53 are both mounted on the bridge, horizontal movements of the trolley 13 will not affect the height of the strongback. The same is true with respect to the cable 17. This cable is connected to the anchor 49, passes over sheave 59 of the trolley and is looped down over a sheave 47 on the strongback. The cable then passes up over a sheave 58 on the trolley and passes over the bridge sheave 53 to connect to the

sheaves

54 and 56 which operate cable 17 simultaneously with the cable 18. Actually each cable 17 and 18 is a double cable or a double chain with the chain spaced to provide additional lateral support and with the spaced chains running over individual sprockets, such as shown at 47 in FIGURE 9. i

Since both cables 17 and 18 are connected to the anchor 49 which is secured to the bridge and are connected at their other end to the power expanded

sheaves

54 and 56 which are mounted on the bridge, movement of the trolley along the bridge will not alfect the height of the strongback 14 and will not alfect its horizontal position.

As illustrated in FIGURE 3, the strongback 14 is lifted and lowered by the cables 17 and 18 and is guided by the pantograph assembly 16 which is suspended from an overhead support shown in the form of the trolley 13. It is important for various operations that the strongback 14 be completely stable and have no lateral sway. This is achieved with the contruction of the pantograph as will be described. The pantograph has a plurality of crossed arms, and as illustrated in FIGURE 3, has individual arms as shown at 61, 62, 63, 64, 66, and 67. Each of the arms is pivotally connected at its mid-point and crossed

arms

61 and 62 are pivoted at 68,

arms

63 and 64 are pivotally connected at 69, and arms 66 and 67 are pivotally connected at 71. The arms are also pivotally connected at their ends with the pivotal connection for

arms

62 and 64 shown at 72,

arms

63 and 67 being pivotally connected at '74,

arms

61 and 63 pivotally connected at 73, and arms 64 and 66 pivotally connected at 76. The details of these pivotal connections are also illustrated in FIGURE 6.

Each of the pivotal connections between the arms are so constructed to prevent twist of the pivotal joint. To this end, the arms have a flat broad construction and each pivotal connection includes a pair of horizontally spaced bearing points which positively prevent twist of one arm of the pantograph with respect to the connected arm.

The

arms

61, 64, and 67 are fabricated of metal plates or the like and are of rectangular hollow construction. The other cross arms 62., 63, and 66, are each formed of side bars, such as illustrated at 63a and 63b for the arm 63, and such as illustrated at 66a and 66b for the arm 66, in FIGURE 6. The side bars 63a and 63b are located laterally outside of the fabricated arm 64 and the side bars 66a and 66b are located laterally outside of the fabricated arm 67. The bars 63a and 63b are joined by a plate 630 which is suitably attached thereto, such as by welding, at their upper ends and are joined by a similar plate 63d at their lower ends. Arms 66a and 66b are similarly joined by plates 66c and 66d. The plates form a gap at the center so that the

arms

64 and 67 may pass through them. A pivotal connection is then formed by

cross shafts

69 and 71.

At the ends of the arms, such as illustrated by pivotal joint 73,

bosses

63c and 63 are attached to the arm 63 and bosses 61a and 6112 are attached to the arm 61. Each of these bosses is arranged to pivotally receive a horizontal cross shaft 73a to complete the pivotal joint 73. Each of the joints in each of the arms, as described, are identical in construction and therefore all need not be described in detail. As will be appreciated by those skilled in the art, various departures fromthe exact showing of the pantograph illustrated, may be made to attain a rigid pantograph which will guide the strongback preventing lateral sway.

An important feature of the invention is the connection between the pantograph and the trolley 13, and between the pantograph and the strongback 14. At its upper end, the pantograph 16 is connected at one side by a pivotal connection to the arm 61. For this purpose, the trolley 13 has spaced side plates 13a and 13b and the pantograph arm 61 is connected to each of the side plates for a pivotal connection which. will be rigid in the lateral direction.

At the other side of the pantograph, the connection 79 permits the location of the connection to shift parallel to the trolley 13 as the pantograph extends or collapses and yet the connection prevents sway of the pantograph in a direction normal to the trolley and prevents twist of the pantograph with respect to the trolley. As is illustrated in FIGURES 3 and 4, this connection includes a pair of horizontal racks 83 and 84 which are fixedly mounted on the sides of the trolley 13. In non-twisting mesh with these racks are pinions 86 and 87, each nonrotatably secured at the ends of a shaft 88 which is rotatably mounted at the upper end of the arm 62. The pinions are held in mesh with the racks and horizontal movement of the upper end of the arm 62 is insured by sliding blocks 92, only one of which is shown. The blocks slide in

guides

93 and 94 which have elongated guide slots such as 93a. The pantograph 1 6 is connected to the strongback 14 in the same manner as it is connected to the overhead support trolley 13. 'The arm 66 is pivotally connected at its lower end at '78 to the strongback and at the other side a rack and pinion connection 81 is provided, which holds the strongback in non-twisting and non-shifting relationship to the pantograph. The connection 81 includes a pair of

horizontal racks

95 and 95a which are mounted on the strongback 14. A pair of

pinions

96 and 97 are in non-twisting mesh with the

racks

95 and 95a and are rigidly mounted on a cross shaft 98 which is rotatably supported at the lower end of the arm 67. Also secured to the arm 67 are sliding blocks 99 and 101. The blocks slide in

guide members

102 and 103 which have elongated slots 102a and 103a. The blocks and slots hold the pinions and racks in nontwisting meshing engagement and support the strongback from the arm 67. The rack and

pinion connections

79 and 81 at the top and bottom of the pantograph are of substantially the same construction and, therefore, the detailed drawing of FIGURES 2 and 5 which show the rack and pinion 81, need not be duplicated for the upper connection 79. As will be appreciated by those skilled in the art, various details of the arrangement may be changed to achieve a rack and pinion connection which is nontwisting and which connects the pantograph to the trolley and connects the pantograph to the strongback, the preferred form being illustrated in the drawings.

The strongback is provided with a mechanism for gripping a load so that the load may be picked up by the crane and transported. A load 104 is illustrated as being an elongated cylindrically shaped device, and may be a munition which requires accurate handling, and positive attachinent for purposes of safetly and purposes of treatment. The load 104 is provided with an attaching lug 108. When loads of a difierent length are lifted, they may be of a length to have lugs at 106 or 107, as shown in FIG- URE 5. The lug has laterally extending flanges or cars, such as illustrated at 108a and 1081) in FIGURE 7. For purposes of description, the end of the load Where the lug 108 is located, will be referred to as being the rear end. At the rear end of the strongback, spaced

rails

111 and 112 face inwardly and support a holding plate 109. Rail 111 is provided with

notches

111a, 111b, and 111c and rail 112 has opposed notches 112a, 112b, and 1120. The notches permit the strongback to be lowered over one of the attaching lugs 106, 107, or 108, depending on where the lug is located on the load and the lug will pass through one of the notches. The holding plate 109 has corresponding

notches

109a and 109!) which are aligned with

notches

111a and 112a when the holding plate 109 is in a position to receive or pick up a load. This position will have the plate 109 moved to the left of its position shown in FIGURE 5. In the position of FIGURE 5, the plate is in a holding position or a position where the lugs of the load are locked to the strongback. In the pick-up position of the plate, its notches 109d and 1092 will be aligned with notches 111b and 11% of the rails. The inner end of the holding plate 109, as shown in FIGURE 5, will expose the end notches 111a and 1120 of the rail.

The holding plate 109 slides in

grooves

114 and 116 on the inner sides of the

rails

111 and 112. This is illustrated in FIGURES 7 and 9. Bronze bearing inserts 117 and 118 are positioned at the base of the

grooves

114 and 116. The holding plate 109 has inclined ramp sur- 6 faces to engage lug 108 and raise the load when it is slid or driven to holding position.

The plate 109 is moved by hydraulic mechanism, and as illustrated in FIGURE 10, a lug 119 is connected to the plate 109 and is also connected to a piston rod 121. The piston rod is-connec'ted to a piston slidably mounted in a cylinder 122 which is secured on the strongback 14 and is provided with suitable fittings so that controlled hydraulic fluid will operate the piston rod. A lug 123 is attached to the holding plate 109 and a switch 124 is mounted on the strongback to be actuated by the lug when the plate is in holding position. Another switch, shown schematically at 125, is actuated by the lug 123 when the plate 109 is moved to open position. The two switches 123 and 125 are wired in an electrical safety circuit to prevent raising the strongback unless the holding plate 109 is fully latched or fully unlatched.

Another safety switch 127 is provided which is also connected in the safety circuit to prevent moving the plate 109 to latched position unless the strongback is in position on the load. The switch7127 also stops the lowering motion when tripped. These electrical circuits are not shown in detail, since various wiring expedients may be used to' obtain the circuitry above described, as will be fully appreciated and understood by those skilled in the art.

A bell crank 128 is pivotally supported at 129 and has a lower arm 131 with a pin 132 which is engaged by the ear 10611 of the lug 106, FIGURE 9. Only when the lug 106 is in properly locked position, will the bell crank 128 be pivoted to actuate the switch 127. Only when the switch is actuated will the circuit be operative. Again it must be understood that only one lug is provided on the load, and the lug will be positioned at 106,107 or 108, depending on the load length and the switch 127 will be arranged to have an operating pin, such as 132, at each location. i

A similar safety mechanism is provided at the front end of the strongback. As illustrated in FIGURE 11, an interlocking switch 133 has a switch operating plunger 134 which extends into a recess 136. A coil compression spring 137 urges the pin 134 into the recess 136 so that the pin will be moved upwardly to actuate the switch only when a lug 138 on the load is in the proper position. The switch 133 is connected so that the plate 139 can be moved to latched position only when the switch is actuated.

The holding mechanism for the front end of the load is illustrated in detail in FIGURES 5, 8 and 11. A single lug 138 is provided at the front end of the load and has laterally extending ears 138a and 138b, FIGURE 8.

A holding plate 139 is slidably mounted at the front end of the strongback 14, FIGURE 5. The holding plate 139 has a forked end extending rearwardly and defining a large receiving slot 141 which narrows to a smaller holding slot 142. The holding plate 139 is slidable in an opening 143 in the strongback and is shown in the locked position in FIGURE 5. For receiving the lug 138 of the load, the plate 139 is slid toward the front end of the strongback and the strongback is lowered over the load. The plate 139 is then slid inwardly toward the rear end of the strongback, and the sides of the holding slot 142 lock beneath the

ears

138a and 138!) of the lug 138, in the manner shown in FIGURE 8. The holding plate 139 slides in a guide member 144 mounted on the strongback. The base of the slot 144a has bearing

inserts

146 and 147 and the plate 139 has ramps which engage lug 138 and raise the load upwardly as the plate moves toward holding position.

The plate 139 is power operated and is connected to a piston rod 148 which is connected to a piston slidable within a cylinder 149. The cylinder is provided with suitable hydraulic fluid connections for controllably sliding the holding plate 139. This mechanism is illustrated in FIGURE 11. 1

In operation, as illustrated in FIGURES 1 and 3, the

bridge 12 and the trolley 13 are moved to position the strongback 14 over a load. The cables 17 and 18 then lower the strongback so that the lug 10-8 at the rear end of the load and the lug 138 will enter the slots in the strongback. The locking

plates

109 and 139 are then slid toward each other to locking position by their respective hydraulically operated

cylinders

122 and 149, FIGURES 10 and 11. The strongback is then raised by the cables 17 and 18. The pantograph 16 will extend and contract to guide the strongback and hold it in a laterally rigid position with respect to the trolley 13. One side of the pantograph is rigidly connected to the trolley and strongback by

pivotal connections

77 and 78 and the other side by the pinion and

rack connections

79 and 81. The pinion and

rack connections

79 and 81 permit change in the lateral dimensions of the pantograph 16 as it extends or contracts in a vertical direction and yet will positively hold the pantograph against twist or sway, thus holding the strong-back in a fixed non-swaying position.

Thus it will be seen that we have provided an improved overhead hoist mechanism which meets the objectives and advantages hereinbefore set forth. The hoist mechanism is especially well adapted to high speed operations such as are necessary with automatic mechanism. The lack of lateral sway is advantageous in rapid motions such as are necessary wherein the load must receive treatment of a limited time period, as where metal parts must be placed in a chemical bath or where the load must be moved from a position within a very limited time. The mechanism is also well adapted to uses where no unwanted lateral movements can be permitted, and where a maximum amount of lift and a minimum amount of head room are necessary.

We have, in the drawings and specification, presented a detailed disclosure of the preferred embodiments of our invention, and it is to be understood that we do not intend to limit the invention to the specific form disclosed, but intend to cover all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by our invention.

We claim as our invention:

1. An overhead hoisting crane comprising in combination, an overhead trolley, tracks supporting said trolley for movement therealong, power means for driving said trolley along said tracks, a laterally rigid pantograph supported from its upper end on the trolley, a rigid strongback connected to the lower end of the pantograph, means on the strongback for connecting to a load, power means connected to move the strongback while it is guided by the pantograph, means for pivotally connecting the strongback at a fixed pivot point to one arm at the end of the pantograph, means for connecting the strongbac-k to another arm at the end of the pantograph including a pinion and a rack in non-twisting engagement with means to hold said rack and pinion in engagement preventing twisting between the pantograph and strongback but permitting extension and compression of the pantograph, means for pivotally connecting one arm at the upper end of the pantograph at a fixed pivot point to the trolley, and means for connecting the trolley to another arm at the end of the pantograph including a pinion and a rack in non-twisting engagement with means to hold said rack and pinion in engagement preventing twisting between the pantograph and trolley but permitting extension and compression of the pantograph.

2. An overhead hoisting crane comprising in combination an overhead trolley, tracks supporting said trolley for movement therealong, power means for driving said trolley along said tracks, a laterally rigid pantograph supported from its upper end on the trolley, a rigid strongback connected to the lower end of the pantograph, power means connected to move the strongback while it is guided by the pantograph, pivotal connecting means for the ends of the arms of the pantograph connecting arms at each end to fixed pivot points on the trolley and strongback respectively and preventing twisting of the pantograph arms, and means for connecting other arms opposite said pivotally connected arms at the ends of the pantograph to the trolley and strongback respectively including a rack and a pinion in non-twisting meshing engagement and having means to maintain said meshing engagement.

3. A power transfer mechanism comprising a plurality of pivotally connected arms forming a rigid pantograph, means for supporting one end of the pantograph, a rigid strongback to be connected to a load to be guided by the pantograph and to be connected to the other end of the pantograph, means on the strongback for connecting to a load, power means connected to move the strongback while it is guided by the pantograph, means for pivotally connecting the strongback at a fixed pivot point to one arm at the end of the pantograph, and means for conmeeting the strongback to another arm at the end of the pantograph including a pinion and a rack in non-twisting engagement with means to hold said rack and pinion in engagement preventing twisting between the pantograph and strongback but permitting extension and retraction of the pantograph.

4. An overhead hoisting crane comprising in combination an overhead support, a rigid pantograph linkage de pending from and connected to said support, a rigid strongback connected at the lower end of the pantograph with one end pivotally connected to an arm at one side of the pantograph and the other and connected to an arm at the other side, power means for raising the strongback, and connecting means for said end of the strongback including a shaft carrying a pinion and a rack in non-twisting meshing engagement and secured between said strongback and the arm of the pantograph, including a member beside said rack on said strongback having a slot with upper and lower surfaces parallel to the rack, and including a sliding bearing block pivotally mounted on said shaft slidingly engaging said slot surfaces to hold the pinion and rack in meshing engagement.

5. An overhead hoisting crane comprising in combination an overhead trolley, tracks supporting said trolley for movement therealong, a power driven bridge carrying the trolley, power means for driving said trolley along said tracks, a laterally rigid pantograph supported from its upper end on the trolley, a rigid strongback connected to the lower end of the pantograph, power means for raising and lowering the strongback with respect to the trolley, means on the strongback for connecting to a load, means for pivotally connecting the strongback at a fixed pivot point to one arm at the end of the pantograph, means for connecting the strongback to another arm at the end of the pantograph including a pinion and a rack in non-twisting engagement with means to hold said rack and pinion in engagement preventing twisting between the pantograph and strongback but permitting extension and compression of the pantograph, means for pivotally connecting one arm at the upper end of the pantograph to a fixed pivot point on the trolley, and means for connecting the trolley to another arm at the end of the pantograph including a pinion and a rack in non-twisting engagement with means to hold said rack and pinion in engagement preventing twisting between the pantograph and trolley butpermitting extension and retraction of the pantograph.

6. An overhead hoisting crane comprising in combination a pantograph having a plurality of broad flat crossed arms with alternate arms being open to permit the other arm to cross at each location where the arms cross, pairs of pivotal connections joining the centers of the arms where they cross and joining the ends, with each pair of connections being horizontally spaced and coaxial to maintain the pantograph rigid, an overhead travelling trolley for supporting the pantograph, a strongback connected at the lower end of the pantograph for connecting to a load, a pairof pivotal connections between the end of an arm at the top of the pantograph and the trolley at a fixed pivotal location spaced and on a horizontal axis, a pair of spaced pivotal connections on a horizontal axis connecting the strongback at a fixed pivot point to the end of an arm at the base of the pantograph, a pair of racks and pinions in meshing engagement between the end of an arm opposite the pivotal connection t the top of the pantograph connecting the pantograph to the trolley with the pinions on a horizontal axis, means for holding the racks and pinions in mesh, a pair of racks and pinions in meshing engagement between the end of an arm opposite the pivotal connections at the base of the pantograph connecting the pantograph to the strongback with the pinions on a horizontal axis, and means for holding said racks and pinions for the strongback in mesh.

7. An overhead hoisting crane in accordance with claim 3 in which the means on the strongback for connecting to the load includes means on each end of the strongback defining an elongated receiving slot and an adjoining narrower holding slot whereby a flanged connecting member may be attached, and means for locking the flanged connecting member in the holding slots.

8. An overhead hoisting crane in accordance with claim 7 wherein each of said holding slots is provided with means responsive to the presence of a connecting member, and interlocking switches actuated by said means whereby the mechanism can be arranged to be operated only when a load is in safe position on the strongback.

9. A locking mechanism for use in an overhead hoisting crane on an overhead support and including a strongback for attaching to a load, and power means for raising and lowering said strongback to move the load, said locking mechanism comprising means on each end of the strongback defining an elongated receiving slot and an adjoining narrower holding slot whereby flanged connecting members may be attached, means for locking the flanged connecting members in the holding slots, locking members movable between a position for blocking the holding slots to lock a connecting member therein, and power releasing and locking means connected to said locking members and moving the locking members between a release position out of the slots and a locking position in the slots.

10. A locking mechanism for use in an overhead hoisting crane on an overhead support and including a strong back for attaching to a load, and power means for raising and lowering said strongback to move the load, said locking mechanism comprising means on each end of a strongback defining an elongated receiving slot and an adjoining narrower holding slot whereby flanged conneoting members may be attached, means for locking the flanged connecting members in the holding slots, locking members movable between a position for blocking the holding slots to lock a connecting member therein, power releasing and locking means connected to said locking members and moving the locking members between a release position out of the slots and a locking position in the slots, interlock means resiliently projecting into the holding slots, and interlocking switches actuated by said means whereby the mechanism can be arranged to be operated only when a load is in safe position on the strongback.

References Cited in the file of this patent UNITED STATES PATENTS 554,516 Huhle Feb. 11, 1896 1,405,301 De Vol Ian. 31, 1922 2,593,630 Thompson Apr. 22, 1952 2,861,700 James Nov. 25, 1958 FOREIGN PATENTS 125,312 Sweden June 28,1949