US2085815A - Hoist - Google Patents

Description

G. W. M COLLUM' HOIS'T Filed March 16, 1956 July 6, 1937.

@a wmiwzzum Patented July 6, 1937 UNITED STATES PATENT OFFICE HOIST George W; McColluin, Downers Grove, Ill. Application March 16, 1936, Serial No. 69,131

Claims. (01154-170) The present invention relates generally to hoists, chain blocks and similar apparatus, and is particularly concerned with the provision of new and improved means associated with the raising and lowering mechanism for automatically retaining the load in a given position.

Heretofore, various forms of screw hoists and gear hoists have been provided for the purpose of raising and lowering, or moving, loads and the like and each type has its advantages and. disadvantages. Gear hoists, using spur gears or similar mechanism, have as a rule been somewhat more efiicient than hoists operating on the worm Wheel and screw principle, commonly called screw hoists. Usually hoists of the latter type have an eficiency of around 35 percent, while the efli-- ciency of gear hoists have as a rule been substantially greater. However, gear hoists are usually considerably heavier than screw hoists and, in addition, have required special ratchet and similar mechanism to prevent the load from running backwardly. Screw hoists, on the other hand, usually operate without ratchets andthe like to hold the load securely'in position, due

, principally to the low efi'lciency of the worm and worm wheel in the first place and the considerable amount of friction which serves to prevent the worm wheel from driving the worm backwardly.

With these and other factors in mind, the principal object of the present invention is the provision of a screw or worm hoist of high emciency and light weight, and in which special means of simple and sturdy construction has been provided for automatically preventing the load from running backwardly unless the driving means is actually operated in that direction. More specifically, another object of the present invention is the provision of new and improved brake mechanism associated with a simple hoist of the screw or worm type in which the end thrust of the worm, arising by virtue of the reaction of the load thereon, is utilized for automatically controlling a brake or lock which se curely holds the load in any position to which it may be moved.

A further object of the present invention is the provision of a hoist of the screw type having a worm shaft which is axially shiftable in one direction under the reaction of the load and in the other direction under the reaction of driving means, with a simple form of brake mecha'- nism actuated by the axial movements of the worm shaft for holding the load in'any given position but which is adapted to be released whenv load chains.

ever the load is tion or the othe 7 s I I These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawing illustrating such embodiment. l V

In the drawing: a

Figure 1 is a vertical section taken substantially midway through a hoist embodying the principles of my invention; and V .Figure 2 is a fragmentary perspective, taken at an enlarged scale, illustrating the cam'mechanism carried by the worm shaft and driving shaft for the purpose of shifting the worm shaft to'release the brake mechanism when the driving means is operated.

Referring now more particularlyto Figure 1,

the reference numeral 10 indicates in its entirety associated lifting mechanism, as well as the load carried by the latter.

A worm wheel shaft is journaled for rotation in the central portion of the casing l0. and at its outer ends, which project exteriorly of the casing, carriestwo load sheaves 2| of; more or less conventional construction, there being one at each side of the casing, and usually each supports a load chain 22 trained thereover and have inga load receiving portion 22a extending downwardly to which the load to be raised is connected in any suitable manner, usually by a bottom book (not shown) or the like supported by the two Usually, the other end of each of the load chains 22 is connectedto the casing ID,- as by having one link disposed overone of the casing bolts l2. v

A worm wheel 30, usually of bronze or the like, is disposed within the casing I0 and-fixedly 56 cured to the worm wheel shaft 20 by any suitable manner, such as a key 3| or the like. Meshing with the teeth of the worm wheel is a worm 34 formed on a tubular wormshaft 35 of special construction, usually of steel, the worm teeth, being preferably,- but not necessarily,;formed as a girder or the like and, in turn, serves tosupport the casing land the to be driven, either in onefdirec set screw, key or the like.

integrally with the tubular worm shaft 35. The tubular worm shaft is journaled for rotation in the lower portion of the casing ID, as by being mounted over a driving shaft38 which has a reduced end 39 disposed in a bearing opening formed in the casing Hi. The reduced end 39 provides a shouldered portion 40 which is arranged to be disposed in thrust engagement with a boss 4| formed on the associated wall portions of the casing It]. The other end of the driving shaft 38 extends exteriorly of the casing and also exteriorly of the end 35a of the tubular worm shaft 35, which also extends exteriorly of the casing through a suitable bearing opening in the wall of the casing l0 opposite the portion 4| thereof.

Adjacent the end of the driving shaft 38 having the reduced portion 39 is provided a plurality, usually three, lugs 53 which have ends serving as oppositely angled cam surfaces 5| and 52, and these cam surfaces cooperate with companion cam surfaces 53 and 54 formed in notches 55 cut in the associated end of the tubular worm shaft 35. As best shown in Figure l, the lugs 50 are each more narrow than the circumferential dimension of the worm shaft notches 55 so that the driving shaft 38 is capable of limited rotation in either direction, relative to the tubular worm shaft 35, from the position shown in Figure 1 before engaging the ends of the notches 55. However, such relative rotation of one shaft with respect to the other serves to shift the tubular worm shaft 35 axially, due to the inclination of the cooperating cam surfaces 5|, 53 or 52, 54, depending upon in which direction the relative rotation between the shafts occurs.

The outer extended end 35a of the tubular worm shaft 35 carries a brake plate 60 suitably keyed, as at 6|, or otherwise fixedly secured to the worm shaft, and the brake plate 30 carries a friction member 62 suitably riveted or otherwise secured thereto. A stationary brake plate 65 is fastened, as by screws 61 or any other suitable means, to the casing II] in nonrotatable relation. Since the member 60 is fixed to the worm shaft 35 and the member 66 is fixed to the casing, when these brake parts are forced into engagement with one another, rotation of the worm shaft 35 is prevented.

Any suitable means may be provided for actuating the drive shaft 33 such as, for example, an electric motor or other source of power, but for purposes of simplicity I have shown a hand wheel 1|} as mounted on the outermost end of the driving shaft 38. The circumferential portion of the hand wheel 10 is suitably formed to receive a hand chain H which may be pulled by the operator so as to rotate the wheel Ill in one direction or the other. The wheel 10 is securely fixed to the driving shaft 38 by any suitable means, such as a While for purposes of simplicity I have shown a hand wheel associated with the driving shaft 38, itis to be understood that the wheel 10 represents any form of driving means for actuating the shaft 38. It is to be noted that there is a space 12 between the hand wheel 10 and the outer end of the tubular work shaft 35 and the associated rotatable brake member 60. This is for the purpose of accommodating the axial movement of the tubular worm shaft 35 referred to above.

In operation, when a load is supported on the portions 22a of the load chains 22, the weight of the load tends to rotate the worm wheel 30 in the direction of the arrow shown in Figure 1. This exerts a thrust on the worm shaft 35, tending rotate the latter.

to shift the same axially toward the right as viewed in Figure 1, and causes the lugs 50 to bottom in the notches 55, and in turn permits the brake plate 68 to be forced up against the stationary brake plate 66 fixed to the casing Hi. There is sufficient clearance between the lugs 50 and the bottoms of the notches 55 that the reaction of the load carried on the chains 22 is effective to hold the cooperating brake plates in frictional engagement with suiiicient force to prevent the lowering of the load. According to the principles of the present invention, the teeth on the worm and worm wheel are cut so as to secure a greater efliciency than has heretofore been possible so that, if it were not for suitable braking means, the load reacting through the Worm wheel 3|] and against the worm 34, would However, the reaction of the load in shifting the tubular worm shaft 35 to the right, as viewed in Figure 1, and causing the cooperating brake parts to be brought into engagement, effectively serves to lock the load in any position.

When it is desired, for example, to raise the load, the hand wheel 13 is actuated in the proper direction. Remembering that the driving shaft 38 is rotatable relative to the tubular worm shaft 35, the first angular movement of the shaft 38 brings thecooperating cam surfaces on the lugs 5|] and the notched end of the worm shaft 35 into engagement so that as the hand wheel 10 is turned in the desired direction, the first effect is to shift the tubular worm shaft 35 in a direction against the reaction of the supported load and opposite to the direction in which the reaction of the load tends to shift the tubular worm shaft 35. Axial movement of the shaft 35in said opposite direction, that is, to the left as viewed in Figure 1, thus serves to release the cooperating brake members 6|! and 66 so that at this time continued rotation .of the shaft 38 will then rotate the worm 34 and shift the load, either upwardly or downwardly, depending upon in which direction the hand wheel H1 is turned. In this connection it is to be observed that the lugs 50 and notches 55 have surfaces inclined in both directions, so that, regardless as to the direction in which the shaft 38 is rotated, the first angular movements thereof cause the tubular worm shaft 35 to be moved axially so as to release the brake means. Therer after, continued rotation of the driving shaft 38 in that direction rotates the lifting worm wheel 30 and the load connected therewith. As is obvious, in lowering the load, for example, the hand wheel I0 is first turned in that direction, and this shifts the worm shaft 35 and releases the brake means. Thereafter, it is then merely necessary to keep the hand wheel 10 and driving shaft 38 ahead of the rotation of the worm shaft 35. The lowering of the load may, of course, be terminated at any time by stopping the hand wheel 1|], whereupon the reaction of the load supported on the chains22 will become immediately effective to shift the tubular worm shaft 35 to the right so as to bring the cooperating brake parts into engagement to thereby prevent further lowering of the load, the only angular movement of any of the associated parts in thus locking the load being that sufficient to bring the lugs 55 from one end of the slots 55 to the intermediate portion thereof.

It is to be noted that by virtue of the construction described above, I am enabled to make use of an efficient form of screw and worm mechanism of the reversible type and that it is not necessary to rely upon friction between these parts for holding the load in any given position. Thus, the efficiency of a construction embodying the principles of the present invention may be practically doubled as compared with previous forms of screw hoists. It is also to be observed that the locking mechanism is engaged with a force that is proportional to the load reaction, and hence in no instance is the braking force greater than necessary to hold the load in position. Mention was made above of the fact that the hand wheel represents any form of driving means for the shaft 38. In many constructions, a power operation, rather than hand operation, is preferred. In this connection, certain features of the present invention are especially advantageous. For example, considering that the hand wheel 79 is replaced by an electric motor, whenever the power is shut off, the brake mechanism 60, 66 not only serves to bring the load to rest but, in addition, serves also to snub the motor and thus prevents any momentum in the latter from carrying the load downwardly or upward farther than is desired. In many hoists of prior construction employing motor drives, some form of brake mechanism was found necessary to be applied to the motor shaft, but according to the principles of the present invention, such brake mechanism is no longer necessary.

While I have shown and described above the preferred construction in which the principles of the present invention have been embodied, it is to be understood that my invention is not to be limited to the particular details shown and described above, but that, in fact, widely different means may be employed in the practice of the broader aspects of my invention.

What I claim, therefore, and desire to secure by Letters Patent is:

l. A hoist comprising a frame, a worm wheel shaft journaled for rotation on said frame, a load moving worm wheel on said shaft, a worm meshing with said worm wheel, a stationary brake member carried by said frame, and a cooperating brake member carried by said worm and actuated into braking engagement with said stationary brake member by the end thrust of said worm under the reaction of a load connected with said worm wheel for holding the worm against rotation.

2. A hoist comprising a frame, a worm wheel.

load moving worm wheel on said shaft, a worm meshing with said worm wheel, a stationary brake member carried by said frame, a cooperating brake member carried by said worm and actuated into braking engagement with said stationary brake member by the end thrust of said worm under the reaction of a load connected with said worm wheel for holding the worm against rotation, driving means for said worm, and means actuated by said driving means for counteracting the end thrust of said arm to release said brake means.

3. A hoist comprising a frame, a worm wheel shaft journaled for rotation on said frame, a load moving worm wheel on said shaft, a worm meshing with said worm wheel, a stationary brake member carried by said frame, a cooperating brake member carried by said worm and actuated into braking engagement with said stationary brake member by the end thrust of said worm under the reaction of a load connected with said worm wheel for holding the worm against actuated by said driving means in each direction of rotation thereof for counteracting the end thrust of said worm torelease said brake means.

4. A hoistcomprising means serving as a frame, a load supporting worm wheel journaled thereon, a driving shaft journale'din said frame, a tubular worm'shaft mounted for axial movement 'on said' driving shaft and including-a worm meshing wfith s'aid worm wheelfcooperating brake parts carried bysaid casingfandjsaid tubular worm shaft, cooperating camelements carried by said driving shaft and said tubular worm shaft providing for the axial movement of said worm shaft on said driving shaft under the reaction of a load connected with said wormwheel for bringing said brake parts into engagement to lock the load in position, and means for driving said drive shaft, the reaction of said driving means operating through said cooperating cam elements for shifting said tubular worm shaft against said load reactance so as to release said brake parts and to permit said worm shaft and worm wheel to be rotated bysaid driving means.

5. A hoist comprising means serving as a frame,-

a load supporting worm wheel journaled thereon, a driving shaft journaled in said frame, a tubular worm shaft mounted for axial movement on said driving shaft and including a worm meshing with said worm wheel, cooperating brake parts carrotation/driving means for said Worm, and means the reaction of the load connected with said wheel serving to shift said tubular worm shaft in a direction to engage said brake parts, whereby said load is locked in position, means for driving said drive shaft, and cooperating cam elements on said driving andworm shafts and operable when said drive shaft is rotated in either direction relative to the worm, shaft for first shifting the latter against the reaction of the load for releasing said brake parts and then rotating said worm shaft toshift said load.

6. A hoist comprising means serving as a casing,.a worm and worm shaft of the reversible type journaled for rotation thereon, said worm shaft being shiftable axially and extending to a point exteriorly of the casing at one end, a stationary brake member carried by said casing means, an axially movable brake member fixed to the outer end of said axially shiftable worm shaft, the reaction of a load connected with said worm wheel tending to shift said worm shaft axially and to bring said brake plates into braking engagement to hold the load in position, and driving means for driving said worm shaft including means reacting against said casing for axially shifting said worm shaft to release said brake plates and permit said worm shaft to be rotated by said driving means.

'7. A hoist comprising a load moving worm wheel, a worm meshing with said worm wheel and shiftable endwise by a load on the worm wheel, brake means applied by the endwise shifting movement imparted to the worm by a load on the worm Wheel for holding the load against lowering movement by the weight thereof, means for turning the worm to move the load, and cooperating cam elements actuated by said worm turning means in each direction of turning movement thereof for shifting the worm endwise to release said brake means.

8. A hoist comprising a load moving worm wheel, a worm meshing with said worm wheel, means for turning the worm to move the load, brake means applied by the end thrust imparted to the worm by a load on the worm wheel for preventing retrograde movement of'the load, and cooperating cam elements actuated by said worm turning means in each direction for releasing said brake means. v

9. In combination, a shaft, a tubular member surrounding said shaft, a wormon said tubular member, a worm wheelmeshing with said worm,- a stationary brake member, and a cooperating brake member movable into and out of engagee ment with said stationary brake member by endwise movement of said tubular member.

M s iashaft for shifting said tubular member endwise 10 to release said brake means.

G. W. MCCOLLUM.

Images