US3727887A

US3727887A - Power hoist with load brake

Info

Publication number: US3727887A
Application number: US00222068A
Authority: US
Inventors: G Lytle; C Lytle
Original assignee: Eaton Corp
Current assignee: Yale Industrial Products Inc
Priority date: 1972-01-31
Filing date: 1972-01-31
Publication date: 1973-04-17
Anticipated expiration: 1990-04-17

Abstract

A power operated hoist having an overrunning clutch mounted on an extended end portion on the shaft of the hoist motor, and a simple brake that is constantly engaged between the clutch and a wall on the hoist frame so that the frame will accept directly the low amount of torque that is necessary to support a load on the load shaft of the hoist. Torque that is added by an operation of the motor will effect lowering of the load, while the heat that is generated by slip friction of the brake will be conducted away through a wall of the hoist frame. Lifting operation will be free from braking effect due to automatic release by the clutch. Speed reduction gears are connected to the opposed end of the motor shaft, being of rather simple design involving no brake parts.

Description

United States Patent 1 Lytle, deceased POWER HOIST WITH LOAD BRAKE Inventor: George F. Lytle, deceased, late of St.

Louis, M0. by Clara A. Lytle, executrix [56] References Cited UNITED STATES PATENTS 8/l962, Klimer ..254/187 7/1920 Libby ..254/168 FOREIGN PATENTS OR APPLICATIONS 657,252 5/1929 France ..254/168 184,105 6/1963 Sweden ..254/168 Primary Examiner-Harvey C. Hornsby Attorney-E. B. Brownson ABSTRACT A power operated hoist having an overrunning clutch mounted on an extended end portion on the shaft of the hoist motor, and a simple brake that is constantly engaged between the clutch and a wall on the hoist frame so that the frame will accept directly the low amount of torque that is necessary to support a load on the load shaft of the hoist. Torque that is added by an operation of the motor will effect lowering of the load, while the heat that is generated by slip friction of the brake will be conducted away through a wall of the hoist frame. Lifting operation will be free-from braking efi'ect due to automatic release by the clutch. Speed reduction gears are connected to the opposed end of the motor shaft, being of rather simple design involving no brake parts.

8 Claims, 3 Drawing Figures PATENTED APR 1 7197s SHEET 1 BF 2 POWER HOIST WITH LOAD BRAKE This invention relates to hoists and more particularly to a novel power operated hoist-that can be manufactured at relatively low cost.

It will be appreciated that many persons handle loads manually or by a hand operated hoist, simply because they find the price of a power operated hoist more than they ,wish to pay. Some power operated hoists actually have beendesigned to sell at low cost, but those hoists have not been fully satisfactory due to unreliable operation or other reasons. In other cases, where power operation is especially important, power hoists having a load capacity that is greater than necessary have been used when only relatively light loads are to be handled, but such over capacity is objectionable and naturally increases costs to a degree that is not permissible in an efficient operation. Thus, the market for power operated hoists has not been fully satisfied heretofore.

The novel concept of the present invention forms a very considerable contribution because it will enable the hoist industry to supply power operated hoists that are economical in price and in operation while offering extremely satisfactory service. The invention will be of particular value when building small hoists that are designed for relatively light loading conditions, but the invention is not so limited because it may be utilized to advantage when designing hoists of heavier load capacity.

The hoist of the invention will include a frame on which is a rotatable load shaft, a hoist motor, and speed reduction gearing through which the shaft of the hoist motor will rotate the load shaft. A load brake will berriounted to act between the motor shaft and a part of the hoist frame, applying to the frame a relatively low amount of torque that will enable the load shaft to support a load, and the brake will be equipped with brake surfaces that are constantly engaged and that move in slip friction relation incidental to an operation of the hoist motor to rotate the load shaft. Particularly, a surface of the load brake will be so arranged that heat that is developed by the slip friction will be conducted away through the hoist frame. 7

Thereby it will be possible to construct a power operated hoist that will very effectively offer automatic control of load lowering movement, while utilizing rather simple and direct speed reduction gearing whose design will involve no brake parts and requiring no electrical or other means for varying brake pressures. Moreover, the load brake need not be constructed to absorb high torque.

As a more particular feature, an overrunning clutch will be associated with the load brake, and will free the motor shaft from braking torque when the hoist motor rotates the load shaft in lifting direction. As a detailed part of this feature, the clutch and brake will form a rather simple unit that is mounted on an end portion of the hoist motor shaft.

I have thus outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception on which my disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of the invention. It is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart from the spirit and scope of the invention, in order to prevent the appropriation of the invention by those skilled in the art.

In the drawings:

FIG. '1 shows a perspective view of a hoist utilizing the present invention;

FIG. 2 shows a longitudinal section of the'hoist on a larger scale, substantially on the broken line 2-2 in FIG. 1, and

FIG. 3 shows a section on the line 3-3 in FIG. 2.

Referring now more particularly to FIG. 1 of the drawings, the hoist is indicated generally by the numeral 10, and includes a hoist frame 11 that is I equipped with means such as a hook 12 through which the hoist will be supported. As shown, the frame 11 is formed by sections that may be assembled by bolts, some of which are indicated at 13, as is rather usual in power operated hoists. The hoist 10 will lift a load through a chain 14 that is equipped with a load hook 15, while slack portions 16 of the chain extend downwardly from the hoist.

In the present invention, the hoist 10 is equipped with a reversible motor 17' shown in FIG. 2, having a field portion 18 mounted on frame 11 and an armature mounted on motor shaft 19. The motor 17 is one that can operate at relatively high speeds and preferably is a universal type equipped with holders 20 for brushes coacting with a commutator 21 on motor shaft 19. It is believed that it will be unnecessary to describe electrical features of the hoist in further detail because those features may be arranged by a person who is skilled in the art.

Referring again to FIG. 2, the shaft 19 of hoist motor 17 has

portions

22, 23 extending a considerable distance from opposed ends of the motor. The shaft portion 22 is mounted through a bearing 24 to rotate on a part of hoist frame 11, and the shaft portion 23 is mounted through a self-aligning bearing 25 on the motor end bell 26 secured to frame 11. A rather usual fan 27 may be mounted within end bell 26 on shaft portion 23 for circulating cooling air through suitable openings, not shown, in the end bell and frame.

The motor shaft portion 23 extends outwardly through a relatively large opening in an end wall 28 on hoist frame 11, and is equipped with an overrunning clutch 29. That clutch 29 includes a bushing 30 keyed or splined to rotate with shaft portion 23 while perhaps having a little end play, a series of rollers 31 best seen in FIG. 3, and a brake hub 32 formed with inner ramp pockets 33 for rollers 31'. Persons skilled in the art will recognize that rollers 31 will permit relatively free rotation in one direction between bushing 30 and hub 32 while coacting with pockets 33 to lock the busing to the hub when the bushing rotates in the opposed direction. In the present invention, it is important to realize that the direction of rotation in which the rollers 31 will lock is the load lowering direction of motor shaft 19.

In combination with clutch 29 is a load brake 134 comprising a brake disk 34 formed on the outer surface of hub 32. A coil spring 36 encircles hub 32 and presses disk 34 to hold the disk constantly in a frictional relation to the end wall 28 of the hoist frame, as by holding a surface of disk 34 against a surface on a circular block 35 of brake friction material that is secured by bonding or other suitable means to end wall 28. Brake block 35 thus forms a brake portion that is in direct heat conducting relation to end wall 28. The coil spring 36 is retained in position by a washer 37 that is held assembled on the motor shaft portion 23 by a snap ring 38. For reasons that will appear, the load brake 134 comprising disk 34, block 35 and spring 36 is so designed that the constantly engaged surfaces of disk 34 and block 35 will accept no more than a small amount of torque, and will rotate in slip friction relation when there is more than that small amount.

The pressure that the motor shaft 19 accepts in axial direction due to brake spring 36 may be taken up through spacers 40 and a Neoprene washer 41 assembled on shaft 19 between the fan 27 and the self-aligning bearing 25 on frame end wall 28. Similar spacers 42 and washer 43 may be utilized on shaft 19 between commutator 21 and bearing 24.

It will be seen that the brake 134 will oppose rotating movements motor shaft 19 at all times that the overrunning clutch 29 may be actuated by a tendency of that shaft to rotate in the load lowering direction. Also, the opposing effect of brake 134 will hole motor shaft 19 against rotation when its load lowering torque is quite small, and added torque will cause shaft 19 to rotate. Thus, the brake 134 will yield by slip friction that will continue while the hoist motor 17 operates in load lowering direction. Since motor 17 will operate at relatively high speeds the slip friction may generate large amounts of heat, but the brake block 35 is in a heat conducting relation that will facilitate dissipation of that heat. Brake 134 naturally will not oppose rotation of motor shaft 19 in load lifting direction, due to the action of clutch rollers 31. Coil spring 36 will be so arranged as to offer substantially no hindrance to the load lifting rotation, as by mounting the retaining washer 37 to rotate on the shaft portion 23 or, preferably, by interposing a thrust bearing 39 between spring 36 and the brake disk 34. A cover 39a may be mounted on frame 11 to enclose the brake and clutch parts.

The motor shaft portion 22, at the left end of shaft 19 as viewed in FIG. 2, is formed with gear teeth 44 that are connected through a series of speed reducing gears 45 to a gear 46 keyed to the load shaft 47. That series of gears 45 is designed to offer a relatively large speed ratio between motor shaft 19 and load shaft 47, as on the order of 280 or 300 to 1. Suitable shaft portions and hearings will mount the series of gears 45 on the hoist frame 11. Particular details of those gears and their mounting are not actually important to an understanding of the present invention, it being merely necessary to know here that the series of gears 45 will cause high torque of the load shaft 47 and much lower torque of motor shaft 19 to accompany one another.

The load shaft 47 is equipped with a sprocket 48 that engagesload chain 14, and naturally may be subjected to high torque due to a load on the'load hook 15. Merely by its capacity to apply a small amount of torque to the wall 28 of the hoist frame, the brake 134 will be fully effective to support any amount of load that is within the load capacity of the hoist. To effect lowering movement, when that is desired, an operation of hoist motor 17 in the appropriate direction will cause brake 134 to slip, lowering the load hook 15 under control by the motor 17. It will be observed that the motor 17 need apply no great amount of torque in order to do that, it merely being necessary that motor shaft 19 bring torque on the'brake 134 to an amount whichis somewhat greater than the small amount that brake 134 will accept.

By the present invention, it will be possible to build a power operated hoist that will offer very effective braking control while requiring no mechanism or controls of a kind that is needed in those hoists where braking pressures must vary between braking surfaces. Also, the present invention enables a direct gear reduction to be utilized without need for brake parts acting between the motor shaft and load shaft of the hoist. All of this is achieved through a brake that is mounted to act automatically in direct relation to a hoist motor shaft that operates at speeds considerably higher than the prior art generally has thought best, with effective dissipation of heat that is due to constantly engaged brake parts, and an overrunning clutch interposed to permit free running of the motor shaft in one direction. Moreover, the invention will offer extremely effective hoist braking control through a clutch and brake that have few parts and that are relatively simple. Thereby the hoist can be constructed at a low cost, and can be offered the market at a price that will be acceptable to persons who have no need to handle very heavy loads, but who wish to acquire a power operated hoist that will safely and efficiently handle loads whose weight is in a lower range. However, as has been indicated, the invention is not limited to hoists having a relatively small load capacity, because it also may be utilized to advantage when constructing high capacity hoists.

It is believed, therefore, that the very considerable value of the invention to the hoist industry will be understood, and that persons who are skilled in the art now will appreciate the contribution that the novel hoist of the invention makes over the prior art.

lclaim:

1. In a hoist having a frame on which is a rotatable load shaft, a hoist motor including a motor enclosure and a motor shaft, speed reduction gearing through which the motor shaft will rotate the load shaft, and a load brake mounted to act between the motor shaft and the hoist frame and through which the frame will accept from the motor shaft a relatively low amount of torque enabling the load shaft to support a load, the improvement that comprises a wall of the hoist frame ver- 1 tically and horizontally spaced around said hoist motor enclosure, a portion of said load brake in direct heat conducting relation to said spaced wall of the frame for dissipating heat through said frame and comprising a brake surface, a part of the load brake rotating with said end portion on the hoist motor shaft incidental to an operation of that shaft to rotate the load shaft, and means applying incessant pressure holding said part of the brake and said brake surface engaged so as to move constantly in slip friction relation during rotating motion of said brake part, the spaced hoist frame by its heat dissipation reducing deterioration of the hoist that may be due to large quantities of heat generated by the constant slip friction.

2. The construction set forth in claim 1 in which the hoist motor has an end wall past which its shaft extends, and said wall of the hoist frame being spaced a substantial distance relatively to said motor end wall whereby to reduce heat transfer between said wall of the hoist frame and the hoist motor.

3. The construction set forth in claim 2, including an overrunning clutch associated with said brake between said brake part and said end portion of the motor shaft and enabling said motor shaft to rotate substantially free from braking torque relatively to the hoist frame.

4. The construction set forth in claim 3 in which said end portion of the motor shaft rotates in position extending in outward directionthrough an opening in said wall of the hoist frame, and in which said overrunning clutch and brake part are mounted in position outwardly of said frame wall on said end portion of the motor shaft.

' 5. In a hoist having a frame on which is a rotatable load shaft, an enclosed hoist motor including a motor shaft that is reversible in operation for rotating the load shaft in load lifting and load lowering directions, and speed reduction gearing connecting the load shaft and motor shaft whereby high torque of the load shaft and a relatively low amount of motor shaft torque accompany one another, the improvement that comprises an end portion on said motor shaft extended beyond one end of the hoist motor, an overrunning clutch mounted on said extended portion on the motor shaft, including a part that is locked relatively to the motor shaft when the load shaft tends to rotate in lowering direction, and that is in release relation to the motor shaft when the motor rotates the load shaft in lifting direction, a wall of the hoist frame being vertically and horizontally spaced around said enclosed hoist motor, a load brake comprising a portion in direct heat conducting relation to said spaced wall of the frame for dissipating heat through said frame, a brake part mounted to rotate integrally with said part of the overrunning clutch and incessantly engaging said portion of the brake for applying to said frame the relatively low torque of the motor shaft, and said brake portion by its heat conducting relation to the spaced hoist frame reducing deterioration of the hoist that may be due to quantities of heat generated by slip friction between said brake portion and brake part while the hoist motor rotates its shaft to effect lowering of a load. v

6. The construction'set forth in claim 5 in which said overrunning clutch includes a driving member mounted to rotate integrally with said extended portion on the motor shaft for rotating said part of the clutch, and said brake part is mounted in position encircling said part ofthe clutch.

7. The construction set forth in claim 5 in which said transverse wall of the hoist frame has an opening encircling said extended portion on the motor shaft, said brake part being mounted in opposed relation to said through an end portion that is wall, and spring means applying substantially constant pressure in axial direction to said brake part to hold that part andsaid portion of the brake at all times engaged.

8. The construction set forth in claim 6 in which said motor shaft is connected to said reduction gearing opposed to its extende end portion, said transverse wall of the hoist frame is spaced a substantial distance in outward direction relatively to the hoist motor whereby to reduce heat transfer between said wall and motor, and said load brake and overrunning clutch being mounted in position outwardly of said wall on the extended portionon the motor shaft.

Claims

1. In a hoist having a frame on which is a rotatable load shaft, a hoist motor including a motor enclosure and a motor shaft, speed reduction gearing through which the motor shaft will rotate the load shaft, and a load brake mounted to act between the motor shaft and the hoist frame and through which the frame will accept from the motor shaft a relatively low amount of torque enabling the load shaft to support a load, the improvement that comprises a wall of the hoist frame vertically and horizontally spaced around said hoist motor enclosure, a portion of said load brake in direct heat conducting relation to said spaced wall of the frame for dissipating heat through said frame and comprising a brake surface, a part of the load brake rotating with said end portion on the hoist motor shaft incidental to an operation of that shaft to rotate the load shaft, and means applying incessant pressure holding said part of the brake and said brake surface engaged so as to move constantly in slip friction relation during rotating motion of said brake part, the spaced hoist frame by its heat dissipation reducing deterioration of the hoist that may be due to large quantities of heat generated by the constant slip friction.

4. The construction set forth in claim 3 in which said end portion of the motor shaft rotates in position extending in outward direction through an opening in said wall of the hoist frame, and in which said overrunning clutch and brake part are mounted in position outwardly of said frame wall on said end portion of the motor shaft.

5. In a hoist having a frame on which is a rotatable load shaft, an enclosed hoist motor including a motor shaft that is reversible in operation for rotating the load shaft in load liftinG and load lowering directions, and speed reduction gearing connecting the load shaft and motor shaft whereby high torque of the load shaft and a relatively low amount of motor shaft torque accompany one another, the improvement that comprises an end portion on said motor shaft extended beyond one end of the hoist motor, an overrunning clutch mounted on said extended portion on the motor shaft, including a part that is locked relatively to the motor shaft when the load shaft tends to rotate in lowering direction, and that is in release relation to the motor shaft when the motor rotates the load shaft in lifting direction, a wall of the hoist frame being vertically and horizontally spaced around said enclosed hoist motor, a load brake comprising a portion in direct heat conducting relation to said spaced wall of the frame for dissipating heat through said frame, a brake part mounted to rotate integrally with said part of the overrunning clutch and incessantly engaging said portion of the brake for applying to said frame the relatively low torque of the motor shaft, and said brake portion by its heat conducting relation to the spaced hoist frame reducing deterioration of the hoist that may be due to quantities of heat generated by slip friction between said brake portion and brake part while the hoist motor rotates its shaft to effect lowering of a load.

6. The construction set forth in claim 5 in which said overrunning clutch includes a driving member mounted to rotate integrally with said extended portion on the motor shaft for rotating said part of the clutch, and said brake part is mounted in position encircling said part of the clutch.

7. The construction set forth in claim 5 in which said transverse wall of the hoist frame has an opening encircling said extended portion on the motor shaft, said brake part being mounted in opposed relation to said wall, and spring means applying substantially constant pressure in axial direction to said brake part to hold that part and said portion of the brake at all times engaged.

8. The construction set forth in claim 6 in which said motor shaft is connected to said reduction gearing through an end portion that is opposed to its extended end portion, said transverse wall of the hoist frame is spaced a substantial distance in outward direction relatively to the hoist motor whereby to reduce heat transfer between said wall and motor, and said load brake and overrunning clutch being mounted in position outwardly of said wall on the extended portion on the motor shaft.