US3043445A

US3043445A - Boom controlling device for power cranes

Info

Publication number: US3043445A
Application number: US84371A
Authority: US
Inventors: William C Holmes
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-01-23
Filing date: 1961-01-23
Publication date: 1962-07-10
Anticipated expiration: 1979-07-10

Description

July 10, 1962 w. c. HOLMES BOOM CONTROLLING DEVICE FOR POWER CRANES Filed Jan. 25, 1961 3 Sheets-Sheet l INVENTOR.

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July 10, 1962 w. c. HOLMES BOOM CONTROLLING DEVICE FOR POWER CRANES Filed Jan 23, 1961 5 Sheets-Sheet 2 hm m-I an um Q July 10., 1962 w, c, HOLMES 3,043,445

BOOM CONTROLLING DEVICE FOR POWER CRANES Filed Jan. 25, 1961 3 Sheets-Sheet 3 INVENTOR.

WILLIAM nite This application is a continuation in part of my copending patent application, Serial Number 697,696, filed November 20, 1957, and now abandoned, relating to a Boom Controlling Device for Power Cranes.

My invention pertains to means of controlling the lowering of a boom, particularly when the boom carries a heavy load. The invention is intended to be used on the type of power cranes in which it is possible to regulate the unwinding of the boom-operating cable from its drum by coupling the drum to the engine of the crane. Ordinarily the lowering of the boom is effected by means of a single lever which is operated manually and by means of which a satisfactory control of speed in the lowering of the-load may be attained.

When heavy loads are to be carried by the boom, and when the loads have to be lowered carefully to avoid damaging the load or injuring the workers in proximity of the place where the load is to be lowered, it was necessary to couple the drum to the engine of the crane and to control the speed of the lowering of the load by the speed of the engine. In order to do so, the operator of the crane had to actuate a special lever serving that particular purpose. As under the stress of work or because of a temporary diversion of his attention the operator was likely to forget to actuate said lever in order to regulate the speed of the lowering of the boom by said engine, I have devised means whereby the coupling of the engine to the cable drum will be efiected automatically, thus rendering the matter independent of the operators attention or lack thereof.

'1 shall now describe my improvement with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic presentation of a power crane of the kind in which my device is to be employed;

FIG. 2 is a side elevational view of the mechanism controlling the operation of the boom of the crane, the view including my device;

:FIG. 3 is a partly schematic front elevational view of a brake mechanism shown in combination with the cable drum and means to control its rotation;

are

FIG. 4 is a side elevational view of the brake wheel of the crane in combination with my device, as seen from line 4-4 of FIG. 2;

FIG. 5 shows the same view as FIG. 4 but discloses my device in a different operative position;

FIG. 6 is a top elevational View of elements seen from line 6-6 of FIG. 3;

FIG. 7 is a fragmentary perspective view of a clutchshifting fork used in the crane.

FIG. 8 is a perspective exploded view of the boom lowering control clutch.

FIG. 9 is a fragmentary vertical section of the boom elevating control clutch.

FIG. 10 is a fragmentary schematic diagram of the power transmission to the swing and hoist shafts.

Similar numerals refer to similar parts throughout the several views.

The principal elements of the power crane are shown in FIG. 1 in which the crawler-type traction gear is marked 11, and the boom is identified by numeral 12, while the cable by means of which the boom may be raised or lowered is marked 13. Numeral 14 identifies a bucket.

Prior to the description of my device, I will refer to the standard mechanism for raising and lowering the boom. As the mechanism is well known, minor details of its construction will be only alluded to or entirely omitted.

On reference to FIG. 2, it will be noted that boom 12 is pivotally mounted at its lower end, as shown at 15, Within a bracket 16 at the front portion of the turntable 17 which carries the mechanism for the operation of the crane as a whole. It is. at the upper end of the boom that said cable 13 is attached thereto. The cable passes over a pulley 18 at the upper end of a stationary beam 18A mounted on turntable 17 and is wound upon a drum 19 also mounted upon said turntable.

The rotation of the drum is controlled by means of a gear wheel 20 which is co-axially mounted with the drum on a shaft 21. The gear wheel is in mesh with an idler 22, and by means of said idler is in engagement with a pinion 82 mounted upon a shaft 80 known as a swing shaft. Mounted on the shaft and journaled thereon is a brake wheel 24, and encircling the wheel is a brake band which at one end is anchored to a stationary member 27 mounted upon the upper surface of the turntable.

The other end of the' brake band is connected to a horizontal rod 28. A spring 29 coiled about the rod and bearing at one end against a stationary member 29a keeps the band in a tight frictional engagement with the rim portion of the brake wheel 24. A ratchet wheel 30 secured to brake wheel 24, mounted upon the same shaft 80 which carries said brake wheel, is controlled by an oblong pawl 31 which is pivotally mounted in a bracket 32, as shown at 33. A weight 34a at one end of the pawl keeps it normally in engagement with said ratchet wheel.

The operative action of the swing shaft 80 which is driven by the engine of the crane is control-led by a connective clutch generally indicated at 34 to which -I shall presently return.

When the boom is to be lowered, it is first necessary to disengage the pawl 31 from the ratchet wheel 30 which rotates with the brake wheel 24. This may be done by kicking the weight upwardly. Next, it is necessary to loosen the brake band 25 on the brake wheel 24. This is eifected by means of a lever 35 which is one of the levers in front of the operator. The lever is mounted pivotally by means of a pin 36, in a bracket 37 upon the turntable 17. The lower end of the lever, below the said pin 36, is connected pivotally, as shown at 38, to one end of a horizontal link 39 which at its other end is pivotally connected to an L-shaped bell crank 40, as shown at 41 in FIG. 6. The bell crank is pivoted about a fulcrum pin 45.

Mounted upon the crank, at its mid-portion, as shown in FIG. 3, is a vertical member 42, best called a brakerelease lever, the lever being pivoted upon a pin 43 and including a short arm 44 extending above said pin and being in engagement with said rod 28. The arm serves to impart a longitudinal movement to the rod against the tension of said spring 29, and thus, to loosen the brake band 25, so that the brake wheel is free to rotate clockwise. The brake does not restrain the brake wheel against counterclockwise rotation.

Secured to the bell crank at the end, remote from the link 39, is the lower end of the stem 46 of a verticallydisposed fork 47. The stem is pivotally mounted, intermediate its ends, upon a pin 48 which projects horizontallyfrom a boss 49 which forms a part of member 32. The fork includes two tines 50, each of which terminates at its upper end with a U-shaped yoke 51. Fitting into each yoke is a pin 52 which projects radially from opposite sides of a band 53 clamped about said clutch 34.

In the cranes at present in use the boom may be lowered under its own gravity. This will take place when the brake band has been loosened and the pawl 31 has been disengaged from the ratchet wheel 30. For this purpose, the clutch lever 35 is to be shifted clockwise from its neutral position, FIG. 2.

In operation, to elevate the boom 12, lever 35, FIG. 2, is manually rotated counterclockwise to approximately the dotted line position 35. Link 39 moves to the right, and bellcrank 44 FIG. 6, rotates clockwise causing the lower end of stem 46 to move outwardly, FIG. 2. The fork 47 rotates clockwise about its pivot 48 causing the clutch control band 53 to move to the right of the position shown in FIG. 4. This engages the clutch assembly 34 with swing shaft 80 causing rotation of brake wheel 24 and the attached gear 32 in a counterclockwise direction. Gear 82 through idler gear 22 and gear wheel 20, FIG. 2, thus rotates drum 19 winding thereon the cable 13 to elevate the boom.

At the desired height lever 35 is returned to the neutral upright position shown. At this point the brake band 25 is effective to prevent unwinding of the boom control cable drum 19. Pawl 31-34a is an additional safety device for mechanically retaining brakewheel 25 against rotation in a clockwise direction.

If it is desired to lower the boom in the manner known as precision lowering, the cable drum is to be coupled, during its cable unwinding rotation, to the engine by means of what is known as a hoist shaft 81.

For this purpose, additional gear wheels are used. One, a sprocket wheel 54 is mounted, and journaled at one end of hoist shaft 81. This shaft is driven through intermediate means by the engine of the crane, as hereafter described. The other wheel, also a sprocket wheel 55, is journaled as hereafter described upon a shaft 56 and carries a gear wheel 57 for engagement with the gear wheel 20. A chain 58 serves to connect the sprocket wheels operatively to each other. A clutch generally indicated at 59, adapted to be operated manually upon the hoist shaft 81 of the engine by a handle 64 serves as a means of employing the power or drag of the engine to control, through said sprocket wheels and the gear wheel 20, the unwinding rotation of said hoist drum 19, also referred to as a cable drum. One end of handle 60 is pivotally mounted at 89 to stationary beam 18a, FIG. 2, for swinging movement in a horizontal plane.

When the operator intends to lower the boom 12 with a load, it is important that he shift the clutch 59 on the hoist shaft to its operative position before he pulls back the hoist lever 35, FIG. 2, or the boom, with the load, may suddenly drop down.

I wish to point out that all the above description pertains to a mechanism which is now in use and well known. The description was included herein for the understanding of the function of my very simple device which I shall now describe in detail.

The device includes a rail 61 disposed vertically and including, at its lower end, -a member 62 turned at right angle thereto. The member is provided with an eye for connection to the fulcrum pin 48 which supports the stem 46 of the fork 47. At the opposite or upper end, the rail is connected to a bar 63 slanting upwardly towards the handle 60 which serves to operate the hoist shaft clutch 59. The upper end of the bar 63 is provided with an eye for connection by means of a bolt 64 to said handle. A coiled spring 65 at one end secured to a clamp 66, upon a stationary member 67 of the crane, is connected at the other end to said member 63. The spring exerts a pull upon said member 63 and thereby, upon the handle 69, which handle holds the clutch 59 in a normally inoperative position, as hereafter described.

As shown in FIG. 2, the rail 61 includes a length disposed diametrically with respect to said clutch 34. Secured to the rail is a flat plate 68 which is disposed in a plane parallel to the face of the brakewheel 24, that is 4 at right angle to the swing shaft 8%) upon which the brake wheel is mounted.

Threaded through the plate 63 are two screws 69, each of them extending towards the fork 47, one of the screws bearing against the yoke 51 of the tine of the fork 47,

while the other screw bears similarly against the yoke of the other tine. Each screw 69 is provided with an adjusting nut 7 0, best shown in FIG. 7.

Thus, the rail 61, including its extension 63, is adapted to be actuated by the control lever 35 for clutch 34 on the swing shaft 80 of the crane, and by means of the handle 66 is also connected to the clutch 59 on hoist shaft 81 of said crane.

I shall now describe the operation of my device.

It will be assumed that the clutch 59 is in its normal inoperative position on the hoist shaft of the crane, while the clutch 34, of necessity, would be in its neutral central position upon the swing shaft 89 of the crane. The latter is the shaft which supports the brakewheel 24 and a pinion 82 in engagement with the gearwheel 22 in mesh with the gear wheel 20 rotating with the cable drum 19.

Now, if it is desired to lower the boom, the operator will disengage the pawl 31 from the ratchet wheel 30 by a swing of the weight 34a upwardly. At this point lever 35 is in neutral position and clutch 34 disengagedv The operator will pull the lever 35 towards himself in the direction of the arrow shown in FIG. 2. As the lever is so moved, the brake band 25 upon the brakewheel 24 is loosened in the manner already described, and the clutch operating stem 46 and connected fork 47 pivotally mounted on the fulcrum pin 48 is shifted to the position shown in FIG. 5.

As the fork, in response to the movement of lever 35, moves outwardly from its neutral position substantially as shown, FIG. 4, it also swings the rail 61 in the same direction as shown in FIG. 5. As a result, the extension 63 at the top of the rail 61 acts upon the handle 60, and by means of said handle shifts the clutch 59 to its operative position on the hoist shaft 81 of the crane. This serves to couple the engine of the crane to the cable drum 19 by means of the sprocket wheels 54 and and by means of the

gear wheels

57 and 20 which already have been described herein. Thus with the brakewheel released, unwinding of drum 19 and lowering of the boom is under the drag or control of the crane engine.

On reversal of the movement of the lever 35 to its neutral position, that is the position shown in FIG. 2, the rail 61 would be swung back under the pull of tension spring to the position shown in FIG. 4 when the handle 69, actuating the clutch 59 would shift said clutch to its inoperative position. Thus, the object of the device is to connect the swing shaft clutch operating lever, or break release lever 35, with the hoist shaft clutch 59 in such a manner that when for the purpose of lowering the boom the brake 25 is released, the clutch 59 on the hoist shaft 82 will be shifted automatically toits operative position. Furthermore when the clutch lever 35 is shifted back to its neutral position into operating position 35' for clutch 34, the other clutch 59 will be shifted automatically to its inoperative or normal position.

Swing Shaft Clutch 7 an enlarged scale in FIG. 9 and is substantially conventional in construction. The said swing shaft clutch 34 includes the cone element 83 slidably keyed as at 84 upon swing shaft 89 for rotation loosely within the laterally adjustable control band 53 in turn operated by the tiltable fork 47.

The control ring 53 includes one or more inwardly directed pins 85 which are loosely positioned within the annular groove in the exterior surface of the cone 83, as shown in FIG. 9. Accordingly tilting movementsof the link 46 and connected fork 4-7 will cause longitudinal shifting movements of the control ring 53, as indicated by the double headed arrow, FIG. 9.

Cone 83, FIG. 9, is in an inoperative position and at all times rotates with swingshaft 80 when swingshaft 80 is rotating. When the cone 83 is moved to the left, FIG. 9, under the control of the ring 53, it is adapted for operative frictional engagement with the undercut cone element 86, also forming a part of the clutch assembly 34. At the same time, axial pressure applied to the said cone element 86 by the cone 83, operatively engages the conventional clutch discs 87 for frictional operative engagement with the brakewheel 24 as at 88.

FIG. 9 is a schematic illustration of the general assembly of the clutch 34, above described in conjunction with swingshaft 80 and the brakewheel 24 journaled thereon, and provides a means of interlocking the brakewheel 24 with the swingshaft 80. Accordingly, when the cone element 83 of clutch 34 has been mechanically moved to the left, corresponding to a forward tilting movement of the control lever 35, FIG. 2, to the position shown at 35, the swingshaft 80, eifectively rotates brakewheel 24 and the gear 82 connected therewith for lifting the boom 12 in a manner above described in detail.

Accordingly the important factor in connection with the present inventionis that the control lever 35 which is employed for rendering the clutch assembly 34 operative for the purpose of elevating the boom 12, is also employed and tilted in the direction of the arrow shown in FIG. 2 for the double-fold purpose of releasing the brakeband on the brakewheel 24, and at the same tim actia vating the hoistshaft clutch 59.

The hoistshaft clutch 59 under the control of the illusstrative linkage above described, establishes a connection between the idle sprocket 54 on said hoistshaft and the said hoistshaft so that the lowering of the boom and the associated unwinding of the drum '19 is tied into the engine for the crane to thus provide a safety control for the lowering of the boom.

It is recognized that heretofore the operation of the hoistshaft clutch 59 was done manually and independently of the operation and application of the control lever for releasing the brake. The important factor in conjunction with the present invention is that the same movement of the lever 35 which releases the brake to permit lowering of the boom, simultaneously and automatically activates the clutch 59 on the hoistshaft 81 to control the lowering of the boom.

Hoist Shaft Clutch The hoistshaft clutch 59, heretofore referred to generally, is shown in detail by way of illustration, FIG. 8, which is an exploded perspective view of the hoistshaft clutch 59 and its association with the sprocket gear 55, illustrative of the method of control for unwinding of the cable drum 19. The present hoistshaft clutch 59 is illustrative of one form of clutch which will accomplish this result, it being contemplated that other forms of clutches could, of course, beernployed for the purpose of engaging the idle sprocket 54 with the power connected hoistshaft 81 for the control of the lowering of the boom 12 and the corresponding unwinding of the drum 19.

As above described and in normal operation, the clutch 59 is normally inoperative with the sprocket gear 54 loosely journaled upon the rotative hoistshaft 81. As above described, movement of the brake release lever 35 in the direction of the arrow shown in FIG. 2 and through the linkage, which includes the bellcrank 40, link-46 and the fork 47, and the rail 61, its extension 63 and the handle 60, the hoistshaft clutch 59 is rendered operative so as to be in driving engagement with the hoistshaft 81.

The assembly of the respective parts is shown in the exploded view, FIG. 8. Referring to FIG. 8, hoistshaft 81 has positioned thereover the central cylindrical hub 92 of the drum 90, which is keyed thereto as at 93, the said drum including upon its interior surface a series of spaced undercut grooves 91. Bearing 94 is slidably positioned over the hub 92 and is adapted to receive the elongated sleeve 95-96 over which is mounted and secured the idle sprocket gear 54.

The sleeve portion 96, projecting from the sprocket gear 54, is adapted to slidably receive thereover the one element 97 which forms a portion of the hoistshaft clutch 59, but which in the exploded view is shown spaced therefrom. Normally this cone in its operative position of the clutch assembly would be provisioned over the sleeve 96 and under the respective heads 102 of the pins 101, which extend through the transverse apertures #103 in the sprocket gear 54 and through the apertured supports 104 spaced on the opposite side thereof.

FIG. 8 also shows in the exploded view the pivotal arm 105 which is apertured at one end for pivotal mounting upon the pin 101, being secured thereto by the pin 1%, the said arm carrying at its opposite end the dog 107, which against the action of the assembly spring 108 is normally spaced radially inward from the undercut formation 91 on the interior surface of the control rum 90. Accordingly in the assembled relationship of the parts, the cone portion 97 of the clutch is positioned underneath the pins 101 and the flattened heads 102 so as to normally hold the said pins 101 in such position against the action of the respective spring 108 assembled on the said pins 101 that the said dogs 107 are spaced from and normally free of the interior control surface of the drum 90.

Accordingly, under normal circumstances with the drum 90 rotating in the direction indicated by the arrow under the control of the hoistshaft 81, the said drum is rotating free of the said dogs 107 and accordingly free of the sprocket gear 54.

In operation, however, when the handle is moved outwardly from .the position shown in FIG. 4 to the position shown in FIG. 5, there is effected a corresponding outward movement to the right, FIG. 8 of the control ring 99 for moving the cone clutch element 97 longitudinally outward, partially with respect to the pins 101- 102.

For this purpose, the cone element 97 has anannular grooved flange 98 thereon, which is received within the control ring 99 on the handle 60 and engaged thereby by the radial pin 100, which projects through the ring 99 and down into the grooved flange 98. By this construction, outward movement of the handle causes an outward movement of the cone element 97 with the result that the respective pins 101-102 are partially disengaged by the clutch cone 9'7 permitting the springs 108 to take over and to bias the dogs 107 into operative engagement with the formed grooved portions 91 in the interior surfaces of the drum 90.

Accordingly when the drum 19 begins to unwind, causing rotation of the sprocket 55 and corresponding rotation of the sprocket gear 54 there will be a tendency of the sprocket gear- 54 and the associated dogs 107 to override the rotation of the shaft 81. This results in effect a drive relation established between the dogs 107 and the drum so that unwinding movement of the drum 19 is restrained by the drag of the crane engine transmitted through the operating shaft 81 or hoistshaft 81.

Power Transmission Means carries the idler 115. Idler through the ring gear 116 is adapted to effect rotation of hoistshaft 81. .Idler 115 7 through the additional gear 117 is likewise adapted to effect rotation of the swingshaft 80. It is apparent from the increased size of the ring gear 116 with respect to the gear 117 that the said hoistshaft 81 will rotate considerably slower than swingshaft 80.

It Will be understood that the foregoing drawings illustrate merely a preferred embodiment of the present invention by way of illustration and that other embodiments are contemplated, within the scope of the claims hereinafter set forth.

The primary invention in the present application is particularly directed to the relationship between the brake and the drum which controls lowering of the boom, the release mechanism for the brake, the hoistshaft connected with the engine of the crane and a normally inoperative clutch on the hoistshaft associated with an idle gear means normally free of the said hoistshaft and wherein a suitable gear relationship or equivalent connection is established between the said idle gear means and the said drum together with a suitable linkage which interconnects the brake release lever and the said clutch on the said hoistshaft whereby when the brake is manually released the said clutch is simultaneously energized or activated for connecting the said idle gear .to the said hoistshaft for rotation in unison.

By this construction, on release of the brake to the drum, a safety mechanism is provided wherein lowering of the boom is tied into the engine of the crane and the drag thereon employed in effect placing an extra load against unwinding of the boom lowering drum so that the same may be safely lowered.

While in the present preferred embodiment, one form of linkage has been shown interconnecting the brake release lever and the clutch mechanism, it is contemplated that other forms of linkage may be employed for this purpose.

While in the preferred embodiment of the invention, there is shown a combination sprocket gear, sprocket chain and connected tooth gear relationship between the hoistshaft and the boom controlling drum, it is contemplated that any other equivalent gear means or other connecting means may be employed for this purpose. In other words, the primary invention in the present application is the tie-in between the brake release leverby a suitable linkage with a clutch mechanism on the hoistshaft by which the unwinding of the drum controlling lowering of the boom on the crane may be tied into the crane engine in an automatic type of operation.

Having described my invention, reference should now be had to the following claims.

I claim:

1. In a crane including a base, the improvement comprising a cable drum adapted to control lowering of a boom, a brake wheel, means interconnecting said brake wheel and drum for rotation in unison, a brake assembly retainingly engaging said brake wheel, a manual lever pivoted on said base connected to said brake assembly for releasing the same, a power driven hoistshaft, a normally inoperative clutch adjustably positioned over said hoistshaft, idle gear means on said hoistshaft responsive to said clutch, additional gear means connecting said idle gear means and said drum, and a linkage interconnecting said brake release lever and said clutch for simultaneous- 1y interconnecting said idle gear means with said hoistshaft upon release of said brake assembly.

2. In the improvement defined in claim 1, the means interconnecting said brake wheel and drum including a series of intermeshing gears.

3. In the improvement defined in claim 1, the means interconnecting said brake wheel and drum including a gear on said brake Wheel, a gear on said drum, and an idle gear journaled on said base interconnecting said brake Wheel and drum gears.

4. In the improvement defined in claim 1, said brake assembly including spring-biased means frictionally retaining said brake Wheel against rotation.

5. In the improvement defined in claim 1, said brake assembly including a spring-biased brake band surrounding and frictionally engaging said brake Wheel against rotation, a lever pivoted on said base and at one end engageable with said brake band for releasing the same, and linkage means interconnecting said brake release lever and said latter lever.

6. In the improvement defined in claim 1, said brake assembly including spring-biased means frictionally retaining said brake wheel against rotation, a lever pivoted upon said base and at one end engageable with said spring-biased means for releasing said brake assembly, and linkage means interconnecting said brake release lever and said latter lever.

7. In the improvement defined in claim 1, said idle gear means being a sprocket gear, said additional gear means including a gear on said drum, a second sprocket gear and a chain interconnected with said first sprocket gear, and a gear secured to said second sprocket gear for rotation therewith and in mesh with the gear on said drum.

8. In the improvement defined in claim 1, and spring means associated with said clutch normally maintaining the same inoperative relative to said hoistshaft.

9. In the improvement defined in claim 1, a stationary support on said base, said linkage including an operating handle pivotally mounted at one end upon said stationary support and intermediate its ends connected to said clutch.

10. In the improvement defined in claim 1, a stationary support on said base, said linkage including an operating handle pivotally mounted at one end upon said stationary support and intermediate its ends connected to said clutch, a second stationary support on said base, and a spring interconnecting said secondary support and said operating handle normally maintaining said clutch in inoperative position.

1'1. In the improvement defined in claim 1, a stationary support on said base, said linkage including an operating handle pivotally mounted at one end upon said stationary support and intermediate its ends connected to said clutch, a second stationary support on said base, and a spring interconnecting said secondary support and said operating handle normally maintaining said clutch in inoperative position, said linkage also including a rail pivotally mounted intermediate its ends upon said base, with one end connected to said handle at its other end, and lever means and a link interconnecting said brake release lever and the other end of said rail.

12. In the improvement defined in claim 1, the means interconnecting said brake wheel and drum including a series of interconnecting gears, a power driven swing shaft, said brake wheel journaled thereon, a clutch on said swing shaft normally in a neutral position and adapted on movement in one direction to interconnect said swing shaft and said brake wheel driving said drum to raise said boom, and an additional linkage interconnecting said first linkage and said swing shaft clutch whereby on movement in said one direction from a neutral positionof the brake release lever, said swing shaft clutch is adapted to raise the boom and on movement in the opposite direction from said neutral position said lever releases said brake wheel and simultaneously interconnects said hoistshaft clutch with said drum.

13. In a crane including a base, a power driven swing shaft, a first clutch upon one end thereof, the clutch being normally in neutral position, a fork in engagement with said clutch adapted to shift the clutch to operative position, the fork including a stem pivotally connected to said base at a point removed from said clutch, a power driven hoistshaft, a second clutch upon one end thereof, a stationary support on said base, an operating handle pivotally secured at one end to said stationary support and intermediate its ends secured radially to said second clutch, a rail at one end secured to thestem of the fork in a substantially parallel relation thereto connected at the other end to the above handle, the rail intermediate its length being connected to said fork, a second station ary support, spring means mounted on said second stationary support and adapted to exert a pull upon the handle to keep the second clutch in its inoperative position, and a manually operative lever movable in opposing directions from its neutral position and which on movement in one direction interconnects the first clutch with said swing shaft and on movement in the opposite direction from said neutral position shifts the second clutch to its operative position.

14. In a crane including a base, a power driven swing shaft, a first clutch upon one end thereof, the clutch being normally in neutral position, a fork in engagement with said clutch adapted to shift the clutch to operative position, the fork including a stem pivotally connected to said base at a point removed from said clutch, a power driven hoistshaft, a second clutch upon one end thereof, a stationary support on said base, an operating handle pivotally secured at one end to said stationary support and intermediate its ends secured radially to said second clutch, a movable rail at one end connected to said handle, spring means normally biasing the second clutch and connected handle maintaining said second clutch in inoperative position, a manually operative lever pivotally mounted on said base movable in opposing directions from a neutral position, and linkage means interconnecting said lever with said first clutch and with said rail, movement in one direction of said lever interconnecting said first clutch with said swing shaft, and movement of said lever in the opposite direction from said neutral position shifting the second clutch to its operative position.

References Cited in the file of this patent UNITED STATE; PATENTS 1,153,034 Crosby Sept. 7, 1915 1,469,579 Borden Oct. 2, 1923 1,470,321 Cooper Oct. 9, 1923 2,173,616 Towson Sept. 19, 1939 2,445,116 Huston July 13, 1948 2,501,198 Wagner et al. Mar. 21, 1950 2,694,280 Prosser Nov. 16, 1954 2,697,948 Holmes et al. Dec. 28, 1954