US3883119A

US3883119A - Hoist

Info

Publication number: US3883119A
Application number: US287368A
Authority: US
Inventors: Gunnar Christer Hansson
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1971-09-09
Filing date: 1972-09-08
Publication date: 1975-05-13
Anticipated expiration: 1992-05-13

Abstract

An overhead hoist has a disc brake operated by a cam mechanism having axial cam elements. The cam mechanism and the brake form a one-way clutch which automatically prevents a suspended load from falling. The cam mechanism is not, as in prior art hoists, utilized to moderate the braked torque by exerting on the brake an operating force in proportion to the actual load, but a spring is adapted to yield and provide for a constant braked torque so that the hoist cannot be overloaded.

Description

United States Patent [191 Hansson HOIST [75] Inventor: Gunnar Christer Hansson,

Stockholm, Sweden [73] Assignee: Atlas Copco Aktiebolag, Nacka,

Sweden [22] Filed: Sept. 8, 1972 [21] Appl. No.: 287,368

[56] References Cited UNITED STATES PATENTS 710,759 10/1902 Coleman et a1 188/829 1,347,785 7/1920 Libby 188/166 X 1,561,722 11/1925 Jimerson 1 254/168 X 2,566,036 8/1951 Shaff 188/166 2,991,976 7/1961 Carroll 254/168 3,034,619 5/1962 Glasgow et a1. 192/7 1 May 13,1975

3,062,344 11/1962 Kachinskas 254/168 X 3,285,377 1l/l966 Rasmussen... 188/134 X 3,367,456 2/1968 Bohnhoff 192/7 X 3,572,482 3/1971 Kalpas et a1. 254/187 R X FOREIGN PATENTS OR APPLICATlONS 1,012,444 7/1957 Germany 254/168 Primary Examiner-Evon C. Blunk Assistant Examiner-James L. Rowland Attorney, Agent, or Firm-Flynn & Frishauf [57] ABSTRACT 22 Claims, 16 Drawing Figures PATENIED RAY I 31975 SHEET 10F 4 SHEET 2 OF 4 luilurld PATENTED MAY 1 3% 3.883.119

SHEET 3 OF 4 2o 74 a2 a0 34 47 66 68 70 HOIST This invention relates to a hoist comprising a housing with a reversible motor which through a power transmission in the housing is arranged to rotate a drum carrying a flexible line having a fastening means from which a load can be suspended, a frictional brake means for locking the drum, and a mechanism responsive to a tendency of load driven turning of the drum to force the brake means into a braking position when the motor is stopped.

In prior hoists of this kind, a cam mechanism is adapted to apply to the brake an operating force that is proportional to the torque load to which the cam mechanism is subjected. This torque load originates from the weight of the work load and from the dynamic forces that may arise. If, for instance, a heavy but allowed work load is rapidly run down and then the brake is engaged by means of the cam mechanism, the cam mechanism will be subjected to a high torque and, ac-

cordingly, it will apply a very high operatingforce to the brake, which will further increase the torque in the cam mechanism. As a result, the braking force will be extreme and the entire hoist as well as the work load will be subjected to extreme and hazardous stresses.

If the braking force is limited to, for instance, twice the weight of the heaviest load allowed to be handled,

the hoist can be made lighter in weight, i.e., less expensive and easier to handle, and yet it will be'safer than prior art hoists.

It is therefore an object of the invention to provide for a limitation of the braking force in hoists of the kind referred to. An ancillary object is to provide in such a hoist a brake operated by a cam mechanism that does not transmit the braked torque.

The invention is further described with reference to the accompanying drawings in which:

FIG. 1 is a side view, partly in section, of a hoisting device in accordance with the invention.

FIG. 2 is a transverse section along line 22 in FIG.

FIG. 3 is a fragmentary section along line 3-3 in FIG. 4.

FIG, 4 is an enlarged section along line 4-4 in FIG. 1.

' FIG. 5 is a section along line 5-5 in FIG. 4.

FIG. 6 is a fragmentary section along line 6-6 in FIG. 5.

FIG. 7 is a section along line 7-7 in FIG. 5.

FIGS. 8a and 8b are fragmentary sections along line 8-8 in FIG. 4 and they show two alternative operating positions of the elements included in the sections.

FIG. 9 is a partly fragmentary exploded view of the details in FIG. 4 in a reduced scale.

FIG. 10 is a fragmentary section along line 10-10 in FIG. I and it illustrates schematically a control valve for the embodiment of the invention shown in FIGS. 1-10 as well as for a modified embodiment shown in FIGS. 11-13 and it illustrates schematically an additional control valve for the embodiment illustrated in FIGS. 11-13. The latter figures show a section corresponding to FIG. 4 with the various elements shown in three different operating positions.

FIG. 14 and 15 are sections corresponding to FIGS. 8a and 8b but showing a modified form of the elements illustrated.

The hoisting device shown in FIGS. 1-10 comprises a housing in which a reversible motor 21 rotates a drum 24 via a power transmission. The power transmission comprises a central shaft 22 and a conventional planet gear unit 23 driven by the shaft. The drum 24 carries a flexible line in the form of a chain 25 which extends out of the housing and has a fastening means or hook 26 from which a load can be suspended. In its turn, the housing 20 is suspendable in, for instance, a

nonillustrated trolley by means of an upper hook 27.

The motor 21 can be a pneumatic one or an electric one. Suitably it is a sliding vane motor 21 as illustrated to which compressed air is supplied through a hose 28 and a supply passage 29 in which a control valve 30 is arranged. The control valve is also connected to the exhaust of the motor. As shown in FIG. 10, the control valve 30 is preferably a four-port, three-way valve which, in its neutral middle position, closes the supply passage 29, and, in its end positions, results in a rotation of the motor 21 in the load-raising and loadlowering directions, clockwise and counter-clockwise, respectively, as seen from the right in FIG. 1. The control valve 30 is controlled by means of a lever 31 engaging the valve and swingably mounted in the housing 20 by means of a ball joing 32. The lever 31 is actuated by means of a cam 33 affixed on a control shaft 34 which extends longitudinally in the housing 20 and is turnably mounted in the housing.

A yoke 36 is affixed on the control shaft 34 and provided with an opening 37 through which the chain 25 can run freely. Two control ropes 39, 40 are suspended at the ends of the yoke 36 and they carry a control handle 41. When the handle 41 is actuated to pull the rope 39, the control shaft 34 and its cam 33 will turn counter-clockwise, FIG. 10. This turning results in a clockwise turning of the lever 31 so that the control valve 30 is moved to its right'end position and the motor 21 will start rotating in the load-raising direction. If the loadcarrying hook 26 would be run too high, it contacts the yoke 36 around the hole 37 and positively turns the yoke back so that the control valve 30 is moved to its neutral position or to its reverse position for loadlowering.

Referring to FIGS. 4, 8 and 9, the hoisting device is provided with a locking device in the housing 20 for retaining the load hook 26 with the load in a reached elevation when the motor is stopped. The locking device is inserted between the housing 20 and the central shaft 22 and comprises a brake disc 43 which has an oblong hole 44 and is axially movably carried by a key end 45 of the shaft 22 so as to rotate conjointly therwith. The locking device further comprises a brake shoe carrier 46 which means of brake shoes 47 cooperates with the brake disc 43 and with a cam mechanism between the carrier 46 and the housing. The cam mechanism is arranged to form together with the brake shoe carried 46 an automatic one-way friction clutch for the shaft 22.

The brake shoe carrier 46 is provided with a spherically incurved middle portion with a central hole 48 by means of which the brake shoe carrier 46 is axially slidably guided on an adjusting screw 50. The brake shoe carrier 46 has two opposite parallel side walls provided with recesses 51 receiving a parallelepipedic inner cross member 52. The adjusting screw carries freely turnably an outer cross member 53 near its outer end which projects out of the housing 20. The adjusting screw 50 has central threaded portion 54 which is screwed into a shield-formed plate 55 swingably attached to the housing 20. The outer cross member 53 carried guide pins 56 which project into holes 57 in the plate 55 so as to hold the cross member 53 nonturnable relative to the plate 55. The plate 55 is provided with parallel sides walls provided with recesses 58 which are directed towards the inner cross member 52 to receive the latter and to limit the angular movability thereof. The

cross members

52, 53 are provided with opposite directed bowl-formed

recesses

59, 60, FIG. 8a, on each side of the rotation axis of the central shaft 22, and the ends of two thrust rods 61 project into the

recesses

59, 60. The thrust rods extend freely through openings 62 in the plate 55 and they are obligue to the rotation axis of the central shaft 22. A weak leaf spring 63 acts between the threaded portion 54 of the adjusting screw 50 and the brake shoe carrier 46, and it straddles the inner cross member 52 with a play thereto. By this arrangement, a weak spring force is applied to the brake shoe carrier 46 to bias it into a slipping engagement with the brake disc 43, which is the released position between the brake disc 43 and the brake shoe carrier 46.

The spring force of the spring 63 holds the brake disc 43 in a slipping engagement with brake shoes 66 on another brake shoe carrier 64 which is limitedly angularly movable to but axially fixedly mounted in the housing 20 on a ball bearing 65. The angular movability is defined by a dog 67 on the brake shoe carrier 64. The dog projects with a tangential play in an opening 68 in a stop band 70 screwed to the housing 20, FIGS. 3, 9.

At its upper end, the plate 55 has a bore 71 by means of which it is suspended on a screw 72 fastened to the housing, so as to be swingable in the longitudinal direction of the central shaft 22. A screw spring 73 abuts the head of the screw 72 and forces the plate 55 against the housing 20. Between the lower swingable end of the plate 55 and the housing, there is a screw spring 74 which tends to force this end of the plate towards the head of a guide screw 75 which passes a hole 69 in the plate 55 and is affixed to the housing 20. The control shaft 34 passes through another hole 76 in the plate 55 and it is turnably mounted in the housing. These holes 69, 76 prevent turning of the plate 55. A cam block 80 is attached to the control shaft 34 to conjointly turn therewith and it is disposed between a shoulder 78 in the housing 20 and the plate 55, FIGS. 57. The spring 74 forces the plate against the cam block 80 and in bores 81 in the cam block there are two pairs of cam balls 82 that abut on the shoulder 78 and project out of the opposite surface of the cam block 80 so that the plate 55 will abut on the cam balls 82. In the neutral position of the control shaft 34, FIG. 5, the projecting cam balls 82 are at the base of a pair of cams 83 on the plate 55. When the control shaft 34 is turned counterclockwise in FIGS. 2 and 5 in order to move the control valve 30 to its position for load-raising, the cam block 80 turns conjointly so that its cam balls 82 move away from the cams 83. When the control shaft 34 is turned clockwise in load-lowering direction, the cam balls 82 roll up along the cams 83 and thereby they force, against the action of the spring 74, the plate 55 to swing towards the adjacent end wall of the housing taking the outer cross member 53 with it so that the thrust rods 61 will be too short to force the inner cross member and the shoe carrier 46 against the brake disc 43.

Assume that a source of compressed air is connected to the hose 28, that the load hook 26 is lowered and hooked on a load without carrying the load, and that the details of the hoisting device are in the position shown in FIGSv 1-7 and 8a while the control valve 30 is in neutral position, FIG. 10. When the load is to be raised, the yoke 36 is turned counter-clockwise in FIGS. 2 and 5 so that by means of the lever 31 the control shaft 34 and its cam 33 moves the control valve to the right in FIG. 10. The air motor 21 now starts rotating clockwise as seen from the right in FIG. 1 and through the central shaft 22 and the planet gear unit 23 it rotates the drum 24 clockwise in FIG. 2 so that the load is raised. The brake disc 43 rotates clockwise too but the brake shoe carrier 46 is in its released position in which it is loaded to the right only by the weak leaf spring 63 and the brake disc 43 slips between the

shoes

47, 66 of the

brake shoe carriers

46, 64 without preventing the raising of the load. Whenthe yoke 36 is moved back to its initial position, the control valve moves back to its neutral position and now the load tends to turn the drum 24 counter-clockwise. This tendency of turning is transmitted through the planet gear unit 23 to the central shaft 22 and from there to the brake disc 43 which, due to the spring load from the weak spring 63, transmit to the brake shoe carrier 46 a control friction torque which tends to turn the latter in the same direction. The inner cross member 52 is disposed in the recesses 51 of the brake shoe carrier 46 so as to turn conjointly therewith and it moves freely within the recesses 58 in the plate 55. The outer cross member 53 has a fixed position because of the guide pins 56 extending through the plate 55. As the brake shoe carrier 46 and the inner cross member 52 turn as a result of the control torque as much as the recesses 58 in the plate 55 permit, the thrust rods 61, FIG. 8a, are forced to turn almost into alignment and thereby they increase their extension in the direction of the shaft 22 so that they are braced between the bottoms of the bowl recesses 59, forcing the inner cross member 52 heavily against the brake shoe carrier 46, FIG. 8b. As a result, the brake shoe carrier 46 is forced against the brake disc 43 and moves the latter against the axially supported brake shoe carrier 64. During the turning of the thrust rods 61, the outer cross member 53 is forced against the head of the adjusting screw 50 which by means of its threads 54 forces the plate 55 to swing to the left in FIG. 1, compressing the spring 74. The thrust rods 61 will reach their position of FIG. 8b and maintain the brake disc 43 arrested by means of a friction torque that results from the axial force that clamps the brake disc 43 between the

brake shoe carriers

46, 64. The limited turnability of the brake shoe carrier 64 will permit the

entire brake

43, 46, to turn as a rigid unit until the thrust rods 61 reach their end positions in FIG. 8b. The axial force applied to the brake by the thrust rods is limited and defined by the spring 74 so that the torque transmitting elements can never be overloaded. The spring 74 should preferably give way to the axial force created by the thrust rods 61 as a result of a static load 1, 5 3 times the weight of the heaviest load allowed. At a tendency of momentarily overloading due to dynamic forces, the brake will therefore slip giving its constant maximum braking torque until the load is arrested. This means that the tension in the chain 25 can never exceed the predetermined value (determined by the spring 74) which thus can be about twice the weight of the allowed limit load.

For lowering a load, the yoke 36 is to be turned clockwise so that, by means of the cam 33 and the lever 31, the control shaft 34 moves the control valve 30 to its position for counter-clockwise rotation of the air motor 21 and drum 24. This clockwise turning of the control shaft 34 results in the cam balls 82 of the cam block rolling up along the cams 83 of the plate 55 so that the plate 55 is swung and the thrust rods 61 inactivated as previously described. The central shaft 22 will thus rotate freely in the load-lowering direction.

As the yoke 36 is moved back to its initial neutral position, the control valve 30 takes up its neutral position and the cama balls 82 leave the cams 83 so that the plate 55 returns under the influence of the spring 74. The cam mechanism formed by the

cross members

52,53 and the thrust rods 61 is therefore moved towards the brake shoe carrier 46 and the brake shoes 47 thereof contact the brake disc 43 under the influence of the weak leaf spring 63. The tendency of the load to turn the brake disc 43 counter-clockwise is therefore sensed by the brake shoe carrier 46 and a torque is applied to the thrust rods 61 and

cross members

52, 53 so .thatthe brake shoes 47 of the brake shoe carrier 46 are forced against the brake disc 43 after a slight turning of the latter by the influence of the load. The oneway friction clutch formed by the brake disc 43, the brake shoe carrier 46, the

cross members

52, 53 and the thrust rods 61 locks therefore immediately and automatically in response to a tendency of turning due to the weight of the load, but it permits rotation of the central shaft 22 in the load-raising clockwise direction. Motor driven rotation in load-lowering direction is automatically permitted by means of the earns 82, 83. The brake shoe carrier 64 is intended to increase the braking action against the disc 43 but it can be omitted and the brake disc 43 be axially fixed on the key end45.

In FIGS. 14 and a further improvement is shown. The cross member 52 does not stop against a fixed stop on the plate 55 as shown in FIG. 8b, but it contacts spring-loaded stop'members 84 that yield as shown in FIG. 15 and permit the thrust rods 61 to pass their position of alignment. In this design, the dog 67 should have a spring loaded stop as well or the brake shoe carrier 64 should be omitted or freely rotatable. As the thrust rods 61 move to their position in FIG. 15, the spring 74 will be compressed and limit the axial force in the brake but then it will extend again and the springs 84a of the stop members 84 will take over the control of the brake operating force. The springs 84a can for instance be pre-loaded to yield at a braked torque only 10-50 percent greater and preferably about percent greater than the torque created statically by the heaviest load allowed to be handled. Thus, as long as there is any slipping in the brake, the brake torque will have a constant value, and, when the brake does not slip, the braked torque will always be smaller. The braked torque determined by the springs 84a can be smaller than the torque determined by the spring 74 since variations in the friction constant do not influence the predetermined brake torque. The tangential play between the dog 67 and the recesses 68

permitsthe brake

46, 43, 64 toturn as a unit when the brake is actuated until the thrust rods 61 reachthe position shown in FIG. 15. In FIGS. 11-13 is shown a modified locking device in which the cam mechanism of the locking device is inserted between the central shaft 22 and the brake disc 43 instead of between the housing 20 and the brake disc. The brake disc 43 is carried by a hub 85 which is axially slidable and limitedly turnable ontheen d of the central shaft22..A weak screw spring 86 biases the hub and the disc 43 axially against an outer abutment ring 87. The central shaft 22 carries a through cross rod 88 which projects with its ends into diametrically opposite recesses in the hub 85. These recesses are formed by an axial cam 89 and two end stops 90 and they limit the turnability of the hub 85on the shaft'22.

A brake shoe carrier 92 has brake shoes or linings 93 and it cooperates with a brake disc 43. The brake shoe carrier 92 is axially displacably supported in the housing 20 and unturnable by means of dogs 94, FIG. 13, which project into longitudinal guide grooves 95 in the housing 20. The brake shoe carrier 92 is centered in the housing 20 by means of a central stub shaft 96 which projects slidable into a bushing 97. An adjusting screw 98 is screwed into the outer end of the bushing 97 to abut the stub shaft 96. At its inner end, the bushing 97 has a radial flange 99 and between this flange and a partition 101 fixed in the housing 20, there is a pile of Belleville-springs 100. The bushing 97 is sealing but slidably guided in the partition 101 and a disc 102 is screwed onto its outer end. The pile of springs biases the bushing 97, the adjusting screw 98 and the pivot 96 inwardly in the housing 20. The spring load is taken up by the disc 102 which forces the central portion of a membrane 103 against the partition 101. Thus, if the brake shoe carrier 92 is forced to the left in FIG. 11 it will be resiliently supported by means of its stub shaft 96. The outer edge of the membrane 103 is clamped between the housing 20 and the partition 101. A chamber 104 between the partition 101 and the membrane 103 is connected to a conduit 105 for compressed air. Through this conduit, the chamber 104 can be pressurized so that the membrane 103 and the disc 102 act as a servo-piston for forcing the bushing 97 out- I wardly against the action of the pile of springs 100 in order to move the brake shoe carrier 92 into an inactive position in which the

cams

88, 89 cannot exert an axial force on the brake.

The compressed air conduit 105 has a leak opening 107 and it is connected as shown in FIG. 10 to a control valve 106 mechanically connected to the control valve 30. The control valve 106 is suitably a three-position, two port valve connected to the supply passage 29 of v the hoist. The control shaft 34 has in this embodiment no cam block 80 and itis supported in the housing 20 by a simple bearing 108, FIG. 12.

When the control valve 30 is in its position for motor driven rotation of the central shaft 22 in the loadraising direction (clockwise as seen from the right in FIG 11) and when the control valve 30 is in its neutral position, the control valve 106 will take up closed position as can be seen from FIG. 10, so that the chamber 104 is vented through the conduit 105 and the leak opening 107. When the central shaft 22 is rotated in load-raising direction, its cross rod 88 contacts the end shoulder 90 of the hub 85 and forces the brake disc 43 to rotate, FIG. 11. By means of the weak spring 86, the brake disc 43 is held in slipping engagement with the brake shoes of the brake shoe carrier 92 so that the brake disc 43 is subjected to a small control torque also when it is released. As soon as the control valve 30 is moved to its neutral position, the load tends to turn the central shaft 22 counter-clockwise as seen from the right in FIG. l2.'The end of the cross rod 88 will now engagewith the axial cam 89 of the hub 85 which is subjected to the retarding control torque, and the disc 43 is forced to the left in FIG. 12 to a firm braking engagement with the shoes 93 of the brake shoe carrier 92. The brake shoe carrier 92, the pivot 96, the adjusting screw 98 and the bushing 97 yield until the cross rod 88 reaches its end position as shown in FIG. 12 because of a compression of the pile of spring discs 100. If the control valve 30 is again moved to its load-raising position, the

cams

88, 89 and the

brake

92, 43 acting as a one-way clutch immediately take up the positions shown in FIG. 11. When the control valve 30 is instead moved to its load lowering position," the conduit 105 and the chamber 104 are pressurized, the membrane l03 and the disc 102 compress the pile of springs 100 via the bushing 97, the adjusting screw 98 is moved back. so that the brake shoe carrier 92 is released for movement to the left in FIG. 13 out of reach of the brake disc 43. Now, the brake shoe carrier 92 and the brake disc 93. take up inactive position and the rotation is load-lowering direction of the central shaft 22 is permitted. As soon as the control valve 30 is returned to its neutral position or to its position for raising the load, the element of the locking device aremoved back to their position shown in FIGS. 12 and 11, respectively, to provide for an automatic one-way clutch action.

The wear of the brake shoes can be compensated for by an axial adjustment of the adjusting screw 98 from the outside in the same way as the adjusting screw 50 can be adjusted in the previously described embodiment.

The invention is not limited to the embodiments described but can be varied within the scope of the accompanying claims.

What I claim is:

l. A hoist comprising:

a housing with a reversible motor therein;

a drum in said housing and carrying a flexible line having a fastening means from which a load can be suspended;

a power transmission train in the housing and coupled to said motor to rotate said drum;

a friction brake means for selectively locking said drum;

a mechanism responsive to a tendency of load driven turning of said drum to force said brake means into a braking position when said motor is stopped so as to form an automatic one-way clutch together with said brake means;

an elastically yieldable means associated with at least one of said mechanism and said brake means'for limiting the operating force applied to said brake means by said mechanism whereby to limit the braking force and permit a slipping in said one-wayclutch when the tension in the flexible line exceeds a predetermined value; and

means separate from the power transmission train to selectively release said brake means so as to permit the drum to rotate in the load-lowering direction. I

2. A hoist as defined in claim 1 in which said elastically yieldable means is coupled to said cam mechanism.

3. A hoist as defined in claim 1 in which said elastically yieldable means is coupled to said brake means.

a friction brake means for selectively locking said drum;

a cam mechanism responsive to a tendency of load driven turning of said drum to force said brakes means into a braking position when said motor is stopped so as to form an automatic one-way clutch together with said brake means;

an elastically yieldable means associated with at least one of said cam mechanism and said brake means for limiting the operating force applied to said brake means by said cam mechanism whereby to limit the braking force and permit a slipping in said one way clutch when the tension in the flexible line exceeds a predetermined value; and

manually controlled means to release said brake means so as to permit said drum to rotate freely in the load-lowering direction;

said cam mechanism having a mechanical angular stop and being adapted to overcome said elastically yieldable means and reach its angular stop in response to the tension applied to the flexible line by a normal workload.

5. A hoist as defined in claim 4 in which said elastically yieldable means is coupled to said cam mechanism.

6. A hoist as defined in claim 5 in which said cam mechanism is adapted to pass a point of maximum axial extension, at which point said elastically yieldable means has given away, before said first friction members reaches its angular stop, said angular stop being defined by a stop means elastically yieldable in a tangential direction.

7. A hoist as defined in claim 6 means includes a pre-loaded spring.

8. A hoist as defined in claim 4 in which said elastically yieldable means is coupled to said brake means.

9. A hoist as defined in claim 4 wherein said means to relase said brake means comprises a manually controlled means.

j 10. A hoist comprising:

a housing, I

a reversible motor (21) carried in said housing,

a drive wheel (24) carrying a flexible line having a fastening means from which a load can be suspended,

a power .transmission train in the housing and coupled to said motor (21) to rotate said drive wheel a shaft (22) operatively coupled to said drive wheel a disc brake having a first friction member (43) mounted to co-rotate with said shaft (22) and a second friction member (46) limitedly turnable relative to said housing between a first angular stop means and a second angular stop means,

a spring means (63) to bias said first and second friction members axially together to provide for a fricin which said stop tional control torque therebetween for turning said is rotated in the opposite direction due to the drive wheel rotating in the hoisting direction, an axial cam mechanism (52, 61, 53) coupled between said housing and said second friction member (46) to create and apply an axial force to said second friction member to create a braking torque between said first and second friction members when said second friction member turns toward said first stop means. an elastically yieldable means (74) associated with at least one of said cam mechanism and said first friction member to permit an axial yielding movement thereof when said cam mechanism applied said axial force to said second friction member whereby to permit said second friction member to reach and take angular support against said first stop means, and a manually controlled means (80, 82) to selectively deactivate said disc brake and to permit said drive wheel (24) to rotate in the load lowering direction. 11. A hoist as defined in claim 10 wherein said cam mechanism comprises toggle rods.

12. A hoist as defined in claim 11 wherein said cam mechanism further comprises a supporting member (53) for said toggle rods, said supporting member being non-rotatably but axially movably mounted to said housing and forced against an axial stop by said elastically yieldable means (74) which comprises a preloaded spring (74).

13. A hoist as defined in claim 12 wherein said preloaded spring (74) is a compression spring that is operatively coupled between said supporting member (53) and said housing, and said manually controlled means (80, 82) is arranged to selectively and forcedly compress said spring (74).

14. A hoist as defined in claim 10 wherein said elastically yieldable means (74) is coupled between said mechanism and said housing.

15. A hoist as defined in claim 14 wherein said manually controlled means (80, 82) is arranged to selectively force said elastically yieldable means (74) to yield independently of said cam mechanism (52, 61, 53).

16. A hoist as defined in claim 10 in which said shaft is coupled directly to the output shaft of the motor to rotate conjointly therewith, said shaft being connected to said drive wheel through said power transmission train.

17. A hoist as defined in claim 10 wherein ssaid disc brake further comprises a third friction member (64), and said first friction member ot said disc brake is a disc (43) that is axially movably mounted on said shaft to axially abut against said third friction member which is disposed on the side of the disc (43) remote from said second friction member (46) when the latter is forced against the disc (43) by said cam mechanism (52, 61, 53), said third friction member (64) being axially supported by the housing and limitedly turnable relative to the housing between angular end positions in which it is angularly supported by the housing.

18. A hoist as defined in claim 17 wherein said third friction member is a disc (64) through which said shaft extends.

19. A hoist as defined in claim 10 in which said cam mechanism is adapted to pass a point of maximum axial extension, at which point said elastically yieldable means has given away, before said first friction member reaches said first step means, said first stop means being defined by a stop means elastically yieldable in a tangential direction.

20. A hoist as defined in claim 10 in which said first stop means includes a pre-loaded spring.

21. A hoist as defined in claim 10 in which said elastically yieldable means is coupled to said cam mechanism.

22. A hoist as defined in claim 10 in which said elastically yieldable means is coupled to said break means.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORREQTEGN Patent No, 3,883,119 Dated May 13, 1975 v fl Gunnar Christer HANSSON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Foreign Application Priority Data September 9, 1971 Sweden .ll4ll/7l- Column 8, line 17, before "release" insert selec tively.

Column 9, line 13, change "applied" to applies.

fiigned and Scaled this sixteenth D 3y 0f September 1975 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uj'Parents and Trademarks

Claims

1. A hoist comprising: a housing with a reversible motor therein; a drum in said housing and carrying a flexible line having a fastening means from which a load can be suspended; a power transmission train in the housing and coupled to said motor to rotate said drum; a friction brake means for selectively locking said drum; a mechanism responsive to a tendency of load driven turning of said drum to force said brake means into a braking position when said motor is stopped so as to form an automatic one-way clutch together with said brake means; an elastically yieldable means associated with at least one of said mechanism and said brake means for limiting the operating force applied to said brake means by said mechanism whereby to limit the braking force and permit a slipping in said one-way clutch when the tension in the flexible line exceeds a predetermined value; and means separate from the power transmission train to selectively release said brake means so as to permit the drum to rotate in the load-lowering direction.

4. A hoist comprising: a housing with a reversible motor therein; a drum in said housing and carrying a flexible line having a fastening means from which a load can be suspended; a power transmission train in the housing and coupled to said motor to rotate said drum; a friction brake means for selectively locking said drum; a cam mechanism responsive to a tendency of load driven turning of said drum to force said brakes means into a braking position when said motor is stopped so as to form an automatic one-way clutch together with said brake means; an elastically yieldable means associated with at least one of said cam mechanism and said brake means for limiting the operating force applied to said brake means by said cam mechanism whereby to limit the braking force and permit a slipping in said one way clutch when the tension in the flexible line exceeds a predetermined value; and manually controlled means to release said brake means so as to permit said drum to rotate freely in the load-lowering direction; said cam mechanism having a mechanical angular stop and being adapted to overcome said elastically yieldable means and reach its angular stop in response to the tension applied to the flexible line by a normal workload.

7. A hoist as defined in claim 6 in which said stop means includes a pre-loaded spring.

10. A hoist comprising: a housing, a reversible motor (21) carried in said housing, a drive wheel (24) carrying a flexible line having a fastening means from whiCh a load can be suspended, a power transmission train in the housing and coupled to said motor (21) to rotate said drive wheel (24), a shaft (22) operatively coupled to said drive wheel (24), a disc brake having a first friction member (43) mounted to co-rotate with said shaft (22) and a second friction member (46) limitedly turnable relative to said housing between a first angular stop means and a second angular stop means, a spring means (63) to bias said first and second friction members axially together to provide for a frictional control torque therebetween for turning said second friction member (46) against said first stop means when said first friction member (43) is rotated in one direction due to the drive wheel (24) rotating in the load lowering direction and for turning said second friction member against said second stop means when said second friction member is rotated in the opposite direction due to the drive wheel rotating in the hoisting direction, an axial cam mechanism (52, 61, 53) coupled between said housing and said second friction member (46) to create and apply an axial force to said second friction member to create a braking torque between said first and second friction members when said second friction member turns toward said first stop means, an elastically yieldable means (74) associated with at least one of said cam mechanism and said first friction member to permit an axial yielding movement thereof when said cam mechanism applied said axial force to said second friction member whereby to permit said second friction member to reach and take angular support against said first stop means, and a manually controlled means (80, 82) to selectively deactivate said disc brake and to permit said drive wheel (24) to rotate in the load lowering direction.

11. A hoist as defined in claim 10 wherein said cam mechanism comprises toggle rods.

12. A hoist as defined in claim 11 wherein said cam mechanism further comprises a supporting member (53) for said toggle rods, said supporting member being non-rotatably but axially movably mounted to said housing and forced against an axial stop by said elastically yieldable means (74) which comprises a pre-loaded spring (74).

13. A hoist as defined in claim 12 wherein said pre-loaded spring (74) is a compression spring that is operatively coupled between said supporting member (53) and said housing, and said manually controlled means (80, 82) is arranged to selectively and forcedly compress said spring (74).