US3077964A

US3077964A - Boom control devices

Info

Publication number: US3077964A
Application number: US644675A
Authority: US
Inventors: Delbert J Kirk
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-03-07
Filing date: 1957-03-07
Publication date: 1963-02-19
Anticipated expiration: 1980-02-19

Description

Feb. 19, 1963 D. J. KIRK 3,077,964

BOOM CONTROL DEVICES Filed March 7. 1957 2 Sheets-Sheet 2 IN VENTOR Oe/b 0') J Kirk ATTORNEY 3,077,964 BOOM CQNTRGL DEVECES Delbert 1. Kirk, Beaconsfield Road, Willernie, Minn. Filed Mar. 7, 1957, Ser. No. 644,675 9 Claims. (Cl. 19212) This invention relates to an improvement in boom control devices for cranes and deals particularly with an apparatus useful in increasing the safety of operation of cranes of a certain type.

For many years cranes have been constructed having boom raising and lowering lines which function by winding or unwinding the line from a boom hoisting drum. Some cranes are constructed in such a manner that the rotation of the boom hoist drum is always power actuated so that the speed of raising and lowering the boom may be controlled only by variations in the driving speed of the apparatus. Other hoists have been produced in which the hoisting drum is power driven to raise the boom while the lowering of the boom is dependent upon brake control. In other words, the lowering of the boom is effected by the weight of the boom which tends to unwind the line from the drum and the speed of this lowering operation depends upon the operation of a manually controlled brake. Certain other cranes such as those produced by the Thew Shovel Company and known as Thew Lorain Cranes optionally incorporate a combination of both of these systems. In other words, the boom may be raised or lowered under power, or may be raised by power and lowered by manual brake operation. It is with this type of crane that the present invention is involved,

Hoists which are provided with a precision boom lowering device as well as with a manually operable brake actuated lowering device often employ a boom cable drum which is driven through an idler gear from a gear rotatably supported upon a constantly operating shaft. A clutch is provided for connecting the shaft with the gear and when this clutch is engaged the boom drum is rotated in a direction to wind the hoisting cable upon the drum. A brake is usually provided encircling the drum and controlling the operation of the gear on the constantly rotating shaft for normally holding this gear from rotation and accor ingly holding the hoisting drum rom rotation. This brake is usually wrapped about the brake drum forming a part of the clutch and is deadended at one end and spring loaded at the other end so that rotation of the clutch in a direction to hoist the boom can be effected Without releasing the brake. However, rotation of the gear and brake drum in the opposite direction tends to wrap the brake band tightly about the drum and hold the drum from rotation. Thus, the lowering of the boom may be accomplished by releasing the brake band upon the drum to permit a controlled lowering of the boom.

A pinion engages the gear attached to the boom cable drum and a ratchet clutch is mounted upon a second constantly rotating shaft which is normally the shaft on which the hoisting drums are located. This ratchet clutch is connected to the gear engaging the boom drum gear, by a suitable chain. Thus, rotation of the boom drum causes a corresponding motion of a part of the ratchet clutch. When the ratchet clutch is disengaged, operation of the boom drum merely causes free rotation of a portion of the clutch. However, when the clutch is engaged, rotation of the boom drum in a direction to lower the boom causes automatic engagement of the ratchets or pawls and as a result the boom cannot be lowered at a speed greater than the speed of the constantly operating shaft on which the ratchet clutch is mounted.

While this device functions very effectively for its intended purpose, certain difficulties are involved. If the boom is to be lowered under control of the hoist engine or motor the ratchet clutch must be engaged before each such lowering operation or this clutch may be continuously engaged. Obviously, in the interest of safety, this clutch should remain engaged at all times. However, the dogs or pawls Within the ratchet clutch constantly ride over the ratchet teeth or stops and provide a clattering sound which is extremely annoying to the operator, particularly as this clutch is usually located close to the head of the operator. Attempts have been made to silence this clutch by enclosing it in a silencing band but this band is not particularly effective. Accordingly, the operator often prefers to disengage the ratchet clutch at all times except when the boom is to be lowered and at this time engages the clutch for the lowering operation. This operation not only requires two additional movements on the part of the operator before and after the boom lowering operation but also greatly increases the hazard of operating the crane for if the operator fails to engage the ratchet clutch before pulling back the lever which releases the brake and permits the boom to drop, the boom will lower by gravity until the brake is again applied. When the ratchet clutch is engaged, the release of the brake will cause the boom to lower by gravity until the ratchet dogs of the ratchet clutch engage and from this point the ratchet clutch cannot operate at a speed greater than the speed of the shaft on which it is mounted. Thus, the brake lever can be fully released when the boom is lowered under power. Fully releasing the brake when the boom is not being lowered under power will cause the boom to drop at a terrific speed, creating the liability of accidents both to the equipment and to personnel.

This rather lengthy explanation is provided in order to give a better understanding of the reasons for producing the present invention.

ratchet clutch while the boom is being raised and lowered, and automatically releases this clutch during the 'remaining periods of operation. clutch is always engaged during the lifting and lowering of the boom but is always disengaged at other times so" that the noise caused by the ratchet dogs is eliminated during most of the operating time of the crane.

A feature of the present invention lies in the provision of a fluid actuated cylinder connected to the ratchet clutch operating arm and in the provision of a valve for con This valve is opengaged position. When the control lever for operating the boom drum in either direction is actuated, a valve is simultaneously actuated, controlling the flow of fluid to or' from the fluid actuated cylinder and moving the ratchet clutch operating arm into operating position.

These and other objects and novel features of the present invention will be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of the specification:

FIGURE 1 is a diagrammatic side elevational view of a portion of the drive mechanism of a crane showing the general arrangement of parts.

FIGURE 2 is a diagrammatic view of the added parts which form the automatic operator.

The present invention comprises a safety device which automatically engages the' As a result, the ratchet FIGURE 3 is a diagrammatic view of the ratchet clutch.

FIGURE 4 is a diagrammatic sectional View through the ratchet clutch showing the general arrangement of parts.

FIGURE 5 is a diagrammatic view of a safety pawl which must be released before the boom may be lowered.

FIGURE 6 is a view similar to FIGURE 5 showing the pawl in released position.

FIGURE 7 is a diagrammatic view of a crane of a type which may employ my mechanism.

In view of the fact that the crane construction is well known and is on the market, only portions of the mechanism which are important to the operation of the present device have been disclosed. Furthermore, in view of the complexity of the apparatus, the structure illustrated is for the most part shown diagrammatically in order to avoid complicating the drawing and description. In general, FIGURE 1 illustrates diagrammatically the floor of a crane cab A upon which the hoist mechanism is mounted. The floor is illustrated in general by the numeral 16 and it includes a pivotal support 11 for a boom hoist drum operating lever 12. An arcuate segment 13 is provided adjacent to the lever 12 and is provided with a central notch 14. The lever 12 supports a vertically slidable rod 15 which supports a lug or bolt 16 which is engageable in the notch 14. A push button 17 is provided at the top of the handle lever 12 and by depressing the button 17, the lug 16 may be disengaged from the notch 14 which normally holds the lever in a central neutral position. When the lug 16 is disengaged, the lever 12 may be either swung forwardly which acts to raise the boom or may be swung rearwardly which acts to release a brake and to permit the boom 9 to lower.

The motor or engine of the hoist or crane drive a drive gear 19 which meshes with a gear 20 mounted upon a transverse hoist shaft 21 and also engages a second gear 22 which is mounted upon a swing shaft 23. Hoisting drums such as 24 are mounted upon the hoist shaft 21 and are provided with suitable brakes and clutches by means of which they may be either engaged for rotation with the hoist shaft 21 or may operate independently thereof. The hoist shaft operates continually in a counter-clockwise direction as viewed in FIGURE 1. Swing drums 25 are mounted upon the swing shaft 23 and are also suitably controlled by clutches and may rotate in unison with the swing shaft 23 which operates continuously in a counter-clockwise direction as viewed inFIGURE 1. The rotation of the crane cab A about a. vertical axis is controlled by suitable mechanism actuated by the swing drums.

A boom hoist shaft 26 extends transversely of the cab and supports a boom drum 27 to which is attached a driving gear 29. An idler pinion 30 is mounted on a stub shaft 31 and engages the teeth of the gear 29. The idler pinion 36 also engages gear teeth of a gear 32 mounted upon the swing shaft 23 and which is engageable and disengageable therefrom by means of a clutch 33,v the detail of which is not disclosed. The clutch 33 is actuated'by a clutch shift lever 34 which is pivotally supported at 35 and extends through the cab floor 10. This clutch lever 34 is actuated through a transversely extending lever 36 which connects the shift lever 34 to a link 37 connected to the lower projecting end 39 of the control lever 12. Movement of the lever 12 in a forward direction transmits motion through the link 37 and the lever 36 to the clutch shifting lever 34 to engage this clutch. When engaged, the gear 32 rotates in unison with the swing shaft 23. Counter-clockwise movement of the gear 32 with the shaft 23 causes rotation of the idler gear 30 in a clockwise direction and this in turn rotates the gear 29 and the boom drum 27 in a counterclockwise direction. When moving in this direction, the cable or line 40 which is anchored to the drum 27 is wound upon the drum exerting a pulling force upon the line 40 and acting to raise the boom 5?. It will be understood that the line 49 passes through suitable sheaves such as 41 and extends to the boom through any of a series of line connections which usually involve a several part line in order to reduce the necessary pulling force to raise the boom.

A brake drum 42 is connected to the clutch 33 to rotate in unison therewith. A brake band 43 is dead ended at 44 and extends around the drum 42 in a clockwise direction as viewed in FIGURE 1. A pull rod 45 is connected to the end of the brake band 23, this rod 45 extending through a fixed support 46. A spring 47 is interposed between the fixed support 46 and a bearing plate 49 at the end of the rod which is adjustably held in place by nuts 56. The spring 47 applies a force to the brake band tending to hold it wrapped about the drum 42. When the brake drum 42 rotates in a counter-clockwise direction, the friction of the drum against the band 43 acts against the spring 4-7 and permits the drum to slip within the brake band without undue friction. However, rotation of the .drum 42 in a clockwise direction acts to wrap the band 43 tightly about the drum and to hold the drum 59m rotation unless the band is manually released.

' In order to release the brake band, an adjustable pro jection 51 is provided on the rod 45. A lever 52 is pivotally supported at 53 and includes a forked end 54 which engages the projection 51. The lever 52 is connected to the link 37 so that movement of the control lever 12 in a clockwise direction from center exerts a pull upon the link 37 swinging the lever 52 in a clockwise direction and urging the forked end 54 against the projection 51 to relieve the pull upon the brake band 43 and to permit this brake band to slip relative to the drum 42.

As is diagrammatically illustrated in FIGURES 5 and 6 of the drawings, the brake drum and clutch support a series of ratchet teeth 55 which are engaged by a pawl or dog 56 pivotally supported upon a transverse pivot 57 which may also serve as the anchor for the dead end of the brake band and may comprise the dead end point 44. An arm 5h is also pivotally supported upon the pivot 57 and includes a hook portion 6% which is engageable with a pin 61 projecting from the dog 56. The arm 59 is provided with a weighted end 62 which, in the position shown in FIGURE 5, holds the dog 56 against the ratchet teeth. When the arm 59 is swung in a clockwise direction as viewed in FIGURE 6, the weighted end 62 passes over the pivot 57 and the weight of the arm tends to disengage the pawl from the ratchet teeth 55 as shown in FIGURE 6.

The weighted arm 5h is in a position where it may be swung from one extreme position to the other by the foot of the operator. The purpose of the arm 59 is to provide a safety ratchet to prevent accidental lowering of the boom. When the arm 59 is in the position shown in FIGURE 5, the gear 32 attached to the clutch 33 and brake drum 42 cannot rotate in a clockwise direction and as this gear 32 is in constant mesh with the idler gear 30 which in turn is in mesh with the boom drum gear 29, the unwinding of the line 4% from this drum cannot take place when the ratchet .dog 56 is engaged.

An idler gear 63 is mounted upon a transverse stub shaft 64 and meshes with the gear 29 on the boom drum. The gear 63 is a combination gear and sprocket. The sprocket portion of the gear 63 is connected to the ratchet clutch 65 by means of a chain 66. Thus, the rotatable portion of the ratchet clutch rotates in unison with the boom drum during any movement thereof.

With reference now to FIGURE 4 of the drawings, the ratchet clutch is diagrammatically disclosed and is mounted upon the hoist shaft 21. A hub or sleeve 68 is mounted upon the end of the shaft 21 and is secured for rotation in unison therewith by a suitable key or spline 67. A flange 69 is provided at one end of the hub 68 to support a cylindrical flange 70 having ratchet teeth or ratchet pockets 71 in its inner surface. A bushing 72 encircles the hub 68 and rotatably supports a sleeve 73. The sleeve 73 is provided with a peripheral flange 74 which is toothed on its outer surface to provide sprocket teeth 75.

The sleeve 73 is also provided with a series of angularly spaced outwardly projecting ears 76. Ratchet arms 77 are mounted upon pivot pins 79 extending through the flange 74 and the ears 76. The ratchet arms are pinned to the pins 79 as indicated at 86.

A clutch sleeve 81 is mounted for axial slidable movement upon the sleeve 73 and includes camming surfaces 82 which engage cooperable surfaces 83 on the heads 54 of the pivot pins 79. When the sleeve 81 is moved to the left from the position illustrated in FIGURE 4, the camming surfaces 82 engage the heads 84 of the pivot pin 79 and swing the ratchet arms 77 into inoperative position.

As is indicated in FIGURE 3 of the drawings, the ratchet arms 77 include terminal rollers 85 which engage into the ratchet pockets or teeth 71. Springs 86 swing the roller bearing end of the arms 77 outwardly. Thus, when the clutch 65 is engaged, the rollers 35 are urged toward the pockets '71. When the sleeve 81 shown in FIGURE 4 is moved to the left in order to disengage the clutch, the various roller bearing ends of the arms 77 are swung inwardly by action of the pivot pins 79 so that the ratchet arms do not engage in the teeth and the inner portion of the clutch may rotate freely relatively to the outer portion thereof.

During operation of the hoist, the hoist shaft 21 opera-tes in a counter-clockwise direction and therefore carries the housing flange 70 in a clockwise direction. During this operation the rollers 85 successively roll over the teeth 71 and form a clattering noise which is very audible to the crane operator. The clutch may be engaged or disengaged by means of an operating lever 87 which is pivoted to the frame 89 of the crane by a vertical pivot 91). The lever 87 includes a loop portion 91 which encloses the sleeve 81. The sleeve 81 is provided with a peripheral groove 88 in its outer surface and pins 91 upon the loop portion 91 of the lever 87 engage in the groove 83. Thus, by pivotal movement of the lever 37 in a rearward direction as viewed in FIGURE 1, that is, away from the reader, the ratchet clutch is disengaged by the pivot pin 79. When this lever 87 is pulled outwardly toward the viewer in FIGURE 1, the ratchet clutch is engaged as the sleeve 81 is withdrawn from engagement with the heads of the pivot pins 79.

Thus, it will be seen that when the ratchet clutch 65 is engaged, the various ratchet arms continually pass over the ratchet teeth both while the hoist drum 27 is station ary and also when this hoist drum is being rotated in a direction to raise the boom through engagement of the clutch 33. However, in the event the boom is lowered, the weight of the boom acts through the cable line 41 to rotate the boom drum 27 in a clockwise direction. This action causes rotation of the gear and sprocket 63 in a counter-clockwise direction and causes corresponding counter-clockwise rotation of the clutch sleeve 73 of the ratchet clutch. Rotation of the ratchet sleeve 73 in a counter-clockwise direction at a speed greater than the speed of rotation of the shaft 21 causes the roller bearing ends 85 of the ratchet arm 77 to engage in the ratchet teeth or pockets 71 and as a result the boom is not permit-ted to drop faster than is allowed by the speed of rotation of the hoist drum shaft 21. Stated otherwise, the clutch housing 71} may rotate only as fast as the supporting shaft 21 and the engagement of the ratchet arms into the pockets 71 prevents rotation of the other portion of the clutch at a greater speed. As a result, the speed of lowering of the boom is definitely controlled.

It will be seen that when the ratchet clutch 65 is engaged, the boom will lower at a controlled speed as soon as the control lever 12 is moved rearwardly in order to relieve the pressure on the brake band 43, assuming that 6 the safety ratchet lock shown in FIGURES 5 and 6 is disengaged. However, when the clutch 65 is disengaged, the speed of lowering of the boom is controlled solely by the brake band 43.

In order to automatically operate the clutch 65, so that the clutch 65 is engaged only when the boom is being raised or lowered, I provide the arrangement diagrammatically illustrated in FIGURES 1 and 2. of the drawings. A cylinder 92 is provided pivotally attached at one end at 93 to a supporting bracket 94 which in turn is secured to a brace 95 forming a par-t of the frame of the crane by means of U-bolts 96 or other suitable means. The cylinder 92 includes a piston 97 mounted upon a piston rod 99 which is pivotally connected at 100 to a link 101 which extends through the operating lever 87 and which is secured in place by nuts 103 or other suitable means.

A spring 1114 is provided Within the cylinder 92 urging the piston 97 to the right as viewed in FIGURE 2 which tends to retract the piston rod 99 and to draw the operating lever 87 rearwardly as viewed in FIGURE 1 so as to disengage the clutch 65. The end of the cylinder 92 opposite the end through which the piston rod 99 extends may be vented as indicated at 105 so that the piston 97 may move to the right without compressing air in the end of the cylinder.

A valve 1% is mounted upon the operating lever 12 by means of a suitable bracket 1117 which is attached to the lever 12 by any suitable means such as U-bolts 109. In the diagrammatic view, the valve is shown forwardly of the operating lever but in actual practice it is usually located rearwardly of the lever due to restrictions of the operators cab. Furthermore, the size of the valve is exaggerated in order to better illustrate the construction.

The valve 1116 includes a valve cylinder which slidably supports a sleeve 111 having a flanged end 112 which limits the slidable movement of the sleeve into the body of the valve. A valve stem 113 extends through the sleeve 111 and is provided with a valve head 114 which is engageable against the end of the sleeve 111 to form a seal.

A passage 115 is provided at the base of the cylinder 1113 and this passage 115 is connected by a flexible conduit 116 to the interior of the cylinder 92 forwardly of the piston 97. A second passage 117 extends into the valve body at right angles to the cylindrical chamber 110, and this passage 117 is open to a point slightly above the lower end of the sleeve 111. When the head 114 of the valve stem engages the bottom of the sleeve 111, and lifts this sleeve, the passage into the interior of the valve is opened. Normally, the sleeve 111 closes this opening.

The passage 117 is connected to a flexible conduit 119 leading to a source of partial vacuum such as the manifold of the internal combustion engine driving the crane. A valve 12% is provided in the conduit 11!! so that the vacuum supply may be cut off in the event the operator desires to lower the boom under control of the brake only. In certain specific operations, the lowering of the boom by gravity is advantageous because of its speed.

A bracket 121 is connected to the outer surface of the valve 1116 and a lever 122 is pivotally supported on the bracket 121 by a pivot 123. The lever 122 is provided with a forked end 124 which straddles the upwardly projecting extremity 125 of the valve rod 113. A spring 126 encircles this projecting portion 125 of the valve rod and the spring extends between the forked end 124 of the lever and adjusting nuts 127.

The lever 122 is loosely pivoted at 129 to a clamp 130 which is secured by a set screw 131 or other suitable means to the operating rod 15 on the lever 12. Thus, when the rod 15 is pressed downwardly to disengage the lever 12 from its central position, the lever arm 122 is swung in a clockwise direction, compressing the spring 126 and raising the valve head 114 against the lower end of the sleeve 111, and then raising the sleeve 111 with the valve rod 113.

In normal position, the source of partial vacuum is cut off through the passage 117 by the sleeve 111. The valve head 114, which is of smaller diameter than the sleeve 111, is unseated below the lower end of the sleeve 111. The valve rod 113 is externally grooved or fits loosely within the sleeve 111, so that atmospheric air may enter the valve body through the sleeve 13.1 and about the valve head, replacing air withdrawn by the suction line 119 and equalizing air pressure on opposite sides of the piston 97. The piston 97 is accordingly normally held in retracted position by the spring 164. In this position, the ratchet clutch 65 is disengaged.

When the push button 17 is depressed, urging the operating rod downwardly to disengage the lug 16 from the notch 14 preparatory to raising or lowering the boom, the lever arm 122 is pivoted in a clockwise direction from the position illustrated. This action acts through the spring 126 to raise the valve stem 113 until the valve head 11-!- seats against the lower end of the sleeve 111. This action closes the vent passage about the stem 1E3. Further upward movement of the stem 113 moves the sleeve 111 upwardly, opening the passage 117 leading to the source of partial vacuum. Air is then withdrawn from the valve body, the conduit 116, and the portion of cylinder 92 to the left of the piston 97. The greater air pressure on the right of the piston 97 then moves the piston to the left, compressing the spring 104. Movement of the piston 97 acts through the rod 99 and link 101 to shift the clutch operating lever 87 into position to engage the clutch 65.

While the movement of several elements are involved, in actual practice the action takes place almost instantaneously. By the time the push button is fully depressed, the clutch lever is shifted. This is important, as it is essential that the clutch be engaged before the operating lever is swung into boo-m lowering position. The spring 104 is only strong enough to overcome the effect of friction, as instantaneous release of the clutch 65 is unessential. The suction lines are purposely large, so that quick action is obtained. During the time the operating lever is out of neutral position, the valve is held open to the suction supply by the engagement of the lug 16 with the segment 13.

In some instances a shallow notch may be formed in the segment 13 to hold the operating lever 12 in an extreme' position. The depth of this added notch, however, is insuihcient to permit the closing of the passage 117 by the sleeve 111.

When the operating lever 12 is returned to central position, the lug 16 engages the notch 14, swinging the lever 122 into normal position. The sleeve 111 slides downwardly to close the passage 117 to the partial vacuum source. The valve stem 113 then disengages the valve head 114- from its seat against the lower end of the sleeve 111, and air is drawn into the valve about the stem 113, flowing into the cylinder 92 to equalize pressure on opposite sides of the piston 97. The spring 104 then returns the piston 97 to normal position, disengaging clutch 65.

Thus, it will be seen that as long as the boom is being raised or lowered, the clutch 65 will be engaged. As soon as the operating lever 12 is returned to its central position, the clutch 65 will be disengaged. Thus, the objectional clatter caused by the ratchet clutch is eliminated.

While I have described the system as being operated by vacuum as a source of partial vacuum is usually accessible, it is obvious that air pressure or hydraulic pressure could be employed in a very similar manner. The main feature of the invention lies in the automatic control of the ratchet clutch when the operating handle 12 is moved.

In accordance with the patent statutes, I have described the principles of construction and operation of my boom control devices for cranes, and while I have endeavored to set forth the best embodiments thereof, I desire to have it understood that changes may be made within the scope of the following claims without departing from the spirit of my invention.

I claim:

1. A safety device for a crane having a boom, a drum rotatable in two directions, a power shaft, :1 pair of shafts driven by said power shaft, clutch engageable with one of said shafts to rotate said drum in one direction, brake means associated with said first clutch and releasable to permit rotation of said drum in the opposite direction, a second clutch engageable with the other of said shafts and connected to said drum to control rotation thereof in said opposite direction, a manually operable control lever connected to said first named clutch means and said brake means and movable from a neutral position into position to selectively control the operation thereof, an operating lever connected to said second clutch to 0pcrate the same, means releasably holding said control lever in neutral position and means operable upon release of said holding means for said control lever to engage said second clutch.

2. The structure of claim 1 and in which said last named means comprises a fluid actuated means.

3. The structure of claim 1 and in which said last named means comprises a fluid actuated means connected to said operating lever and a valve controlling the fluid supply thereto, said valve being actuated by release of said holding means for said control lever.

4. The structure of claim 1 and in which said last named means includes a vacuum cylinder connected to said operating lever to actuate the same and a valve acutated by release of said holding means for said control lever connected to said cylinder to control the flow of fluid therefrom.

5. A safety device for a crane having a boom, a drum rotatable in two directions, a power shaft, a pair of shafts driven by said power shaft, a first clutch means engage able with one of said shafts to rotate said drum in one direction, brake means associated with said clutch and releasable to permit rotation of said drum in the oppssite direction, a second clutch engageable with the other of said shafts and connected to said drum to control rotation thereof in said opposite direction, a manually operable control lever connected to said first named clutch means and said brake means and movable fro-m a neutral position into position to selectively control the operation thereof, an operating lever connected to said second clutch to operate the same, lever latching means on said control lever locking said control lever in neutral position, a valve connected to said lever latching means, a lluid line controlled by said valve, and a fluid actuated means connected to said fluid line and attached to said operating lever to move said operating lever and to engage said second clutch upon release of said lever latching means.

6. The structure of claim 5 and in which said fluid line is connected to a source of partial vacuum when said valve is opened.

7. The structure of claim 5 and including resilient means normally biasing said operating lever toward clutch disengaging position.

8. The structure of claim 5 including a source of partial vacuum connected to said fluid line when said valve is opened, an air inlet open to atmosphere into said valve when said valve is open, said valve closing said air inlet upon actuation of said lever latching means.

9. In a crane, a power-driven hoist shaft, a rotary cable drum adapted to be driven by said shaft, a brake to control the rotation of said drum, a clutch upon said hoist shaft operable to couple said hoist shaft and said drum, a lever hinged at one end to a stationary support on said crane, and secured to the clutch at a point removed from the hinged end thereof, spring means positioned between the lever and a stationary part of the crane and acting upon the lever to maintain the clutch in disengaged position, a cylinder mounted upon a stationary part oi the crane and including a piston-rod therein, said rod extending axially of the cylinder into contact with the lever at a right angle thereto, a fluid line leading to the cylinder to supply fluid under pressure to push the rod outwardly against said lever, a manual brake control, a normally closed valve in said fluid line, a valve control means mounted upon the manual brake control operable to open said valve to pass fluid through the fluid line to engage the clutch and to maintain the said valve open during the operation of the brake.

References Cited in the file of this patent UNITED STATES PATENTS 1,460,813 Harris July 3, 1923 1,579,903 Yungling Apr. 6, 1926 2,445,116 Huston July 13, 1948 2,501,198 Wagner et a1. Mar. 21, 1950 2,681,205 Bannister et a1. June 15, 1954 2,914,303 Holmes Nov. 24, 1959

Claims

1. A SAFETY DEVICE FOR A CRANE HAVING A BOOM, A DRUM ROTATABLE IN TWO DIRECTIONS, A POWER SHAFT, A PAIR OF SHAFTS DRIVEN BY SAID POWER SHAFT, CLUTCH ENGAGEABLE WITH ONE OF SAID SHAFTS TO ROTATE SAID DRUM IN ONE DIRECTION, BRAKE MEANS ASSOCIATED WITH SAID FIRST CLUTCH AND RELEASABLE TO PERMIT ROTATION OF SAID DRUM IN THE OPPOSITE DIRECTION, A SECOND CLUTCH ENGAGEABLE WITH THE OTHER OF SAID SHAFTS AND CONNECTED TO SAID DRUM TO CONTROL ROTATION THEREOF IN SAID OPPOSITE DIRECTION, A MANUALLY OPERABLE CONTROL LEVER CONNECTED TO SAID FIRST NAMED CLUTCH MEANS AND SAID BRAKE MEANS AND MOVABLE FROM A NEUTRAL POSITION INTO POSITION TO SELECTIVELY CONTROL THE OPERATION THEREOF, AN OPERATING LEVER CONNECTED TO SAID SECOND CLUTCH TO OPERATE THE SAME, MEANS RELEASABLY HOLDING SAID CONTROL LEVER IN NEUTRAL POSITION AND MEANS OPERABLE UPON RELEASE OF SAID HOLDING MEANS FOR SAID CONTROL LEVER TO ENGAGE SAID SECOND CLUTCH.