US2525402A - Hoist brake - Google Patents

Description

R. F. DEHN HOIST BRAKE Oct. 10, 1950 2' Sheets-Sheet 1 Filed Aug. 2. 1947 INVENTOR. /Pm/ /1 EH/v R. F. DEHN Oct. 10, 1950 HOIST BRAKEl 2 sheets-sheet 2 Filed Aug. 2, 1947 INVENTOR. 4/oy F EHN BY w, mm@

,4free/vf ya Patented ct. O, 1950 UNITED STATES vPATENT OFFICE HOIST BRAKE Roy F. Dehn, Cleveland, Ohio, assigner to The Cleveland Crane & Engineering Company, Wickliffe, Ohio, a corporation of Ohio Application August 2, 1947, Serial No. 765,734

13 Claims.

The present invention relates to hoists and,

more particularly, to motor-operated hoists of the type which sustain the load automatically at any point and regulate the speed when lowering.

Hoists of this character are used extensively on overhead traveling cranes and the like, and include a so-called load brake. Heretofore, considerable difculty has been experienced with the brake tending to chatter as it is applied to sustainv a, load. vThe matter of brake chatter isI not only very serious in the case of overhead traveling cranes but is also more difficult to eliminate than in other types of equipment because of the fact that the hoist is carried by a trolley movably supported on an inherently resilient bridge, which bridge is, in turn, movably supported on crane runways, all of which tends to make the brake vibrate and chatter.

The principal object of the invention is the provision of a no-vel and improved hoist of the character referred to especially adapted for use on 'overhead traveling cranes and which includes a so-called load brake that is simple in construction, reliable in operation, and free from chatter and vibration.

Another object of the invention is the provision of a novel and improved hoist of the character referred to which will sustain the load automatically at any point and regulate the speed when lowering and which comprises a so-called load brake constructed in such a manner that the load, -or at least the heavier loads for which the device is designed, are partly held by a resistance applied directly or indirectly to the driving member of the brake.

Another object of the invention is the pro-vision of a novel and improved, self-adjusting, aircooled load brake which will be free from chatter, will have a large braking area located at maximum distance from the center of rotation for any given over-all diameter of the device, and wherein the heat generating surfaces are located adjacent to the outside, thus facilitating rapid dissipation of the heat generated.

Another object of the invention is the provision of a new and improved hoist brake of the character referred to so constructed and arranged that its driving and driven connections and its supporting bearings may be positioned entirely toone side of the brake proper, leaving the other side readily accessible, thereby facilitating and reducing the cost of maintenance, etc.

'Ifhe invention resides in certain constructions and combinations and arrangements of parts and further objects and advantages thereof will be apparent to those skilled in the art to which the invention relates, from the following description of the preferred embodiment described with reference to the accompanying drawings in which similar reference characters designate correspending parts throughout the several views, and in which:

Fig. l is a plan elevational view of a hoist trolley of an overhead traveling crane embodying the present invention;

Fig. 2 is a side elevational view of Fig. 1;

Fig. 3 is a side elevational view, with portions thereof broken away, of a load brake employed with the hoist trolley shown in Figs. 1 and 2; and

Fig. 4 is a, sectional view taken approximately on line 4 4 of Fig. 3.

In view of the fact that the hoist of the present invention is particularly designed and adapted for use on overhead traveling cranes, it is herein shown as embodied in such a crane although the invention is equally adaptable for use in any other type of apparatus, such as elevators or the like, where heavy loads are to be raised, lowered, stopped, and suspended in an aerial position.

Referring to the drawings, the reference character A designates a crane trolley supported on a crane bridge B and movable therealong on suitable wheels III, one or more of which may be driven by a reversible, remotely controllable electric motor II. The bridge B comprises a pair oi horizontally spaced, parallel rails I2, I3 fixed to the upper surface of similarly spaced, parallel bridge members I4, I5 which are, in turn, supported for movement on suitable crane runways (not shown) fixed to the sidesof the building or structure on which the crane is located.:

The crane trolley A'has a frame including a base plate I6 on which is mounted a hoist or hoist mechanism including a hoist or load cable I1, both ends of which are connected to a rotatable cable drum I8 having a shaft I9 extending transversely of and suitably journaled -on the trolley A. The load cable |"1 is of conventional construction and is secured to the cable drum and to the trolley in the usual manner. The cable drum I8 is operatively connected to a reversible, remotely controllable, electric hoist motor 20 also mounted on the base plate I6 withV both sides of the housing thereof and has ori one end an electrically operated, friction brake 22 automatically engaged when the motor 20 iS esgalicia 3 not energized and disengaged when the motor 26 is energized for rotation in either direction. Because of the load brake to be described, the friction brake 22 need not be of a size sufficient to or have a holding force capable of sustaining a load of a size which the crane is capable of handling. Preferably it has suiicient holding force to actuate the load brake and/or support" a portion of the load as will appear.

The opposite end of the shaft 2| of the hoist motor 23 is connected by a coupling 23 to a shaft 24 provided with a pinion 25 continuously in mesh with a large gear 26. The gear 26 drives, through a load brake designated generally by the reference character C, a pinion 21 in turn in continuous mesh with a large gear 28 fixed to one end of the cable drum -shaft I9. The gears 25, 26, 21, 28 may be of conventional spur, helical, or herring-bone design and are enclosed in a suitable longitudinally extending housing adapted to retain lubricating oil for the gears, etc. reference character 30 and, as shown, forms a support forthe shafts I9 and 24 and the load brake C. The housing 30 is preferably formed in two halves, a lower half section 3| and an upper half section 32, each generally U or. channel shaped in cross section and arranged in opposed relationship with ,their vertical sides in spaced relationship to the sides of the gears. The lower half sectionV 3| is suitably fixed to the base |'6 of the crane trolley A, while the lower edges of the sides of the upper half section 32. aredetachably bolted to the. upper edges of the sides of the lower half section 3|. As shown, the upper and lower edges of the housing sections are disposed on a horizontal plane through the axes of the shafts I9, 24 and the load brakeC, and each edge preferably has one-half of the journal opening for the respective shafts formed therein whereby assembly is facilitated, as Will be apparent. l v

. Referring to Fig. 4, the pinion 21 and the gear 26 are each shown in slightly spaced relationship and rotatable about the same axis by means of concentrically arranged shafts. The pinion 21 is formed integral with an inner, short, transversely. extending shaft 34 and spaced from the right-hand end thereof, which end is journaled in a roller bearing 35 fixed in a Yjournal opening of a boss 36 formed on theright hand side of the housing 30. The vgear 26 is keyedY adjacent to the right end of a sleeve shaft 38 concentrically arranged about the portion of the shaft 34 to the left of the pinion gear 21. A snap ring 39 fitting in a groove in the outer surface of the shaft 38 to the rightof the gear 26 retains the gear 26 in assembled relationship with the shaft. TheY left hand side of the .housing 30 has an opening .formed in a boss 40 aligned with `the opening, in the boss 36 in which the sleeve shaft 38 lis rotatably journaled by a suitable roller 1'Jearing 4| Except for a small. rotative free playV between theshaft 34 and the sleeve shaft.

3.8, as will hereinafter be apparent, these shafts turn as a unit when a load-is being either raised or lowered and the roller bearings 35, 4|V in the aligned openings provide, Vin combination, spaced,

aligned, low-friction journals or supports for The housing is designated generally by thel closed by both shafts 34, 3B extending therethrough and a ring 44 positioned to the left of the boss 4D and concentric with the sleeve shaft 38. The ring 44 has a lubricant seal 45 on its inner edge.

In the construction shown, the bearings 35, 4| are preferably fixedly mounted against axial movement in their respective journal openings and the shaft 34 has adjacent to its right end an axially facing shoulder 46 which engages the left hand side of the inner race of the bearing 35, positioning the shaft 34 against movement to the right. The right hand end of the sleeve shaft 38 is in engagement with a radially extending shoulder to the left of the pinion gear 21, thus xedly positioning the sleeve shaft 38 against movement to the right relative to the shaft 34. The left hand side of the hub of the gear 26 keyed to the sleeve shaft 38 engages the right hand face of the inner race of the roller bearing 4| and together with a resilient ring 39 immediately to the right of the gear 26 and snapped into a suitable groove in the adjacent end of the sleeve shaft 38 positions the sleeve shaft 38 and the inner shaft 34 against movement to the left.

Both the inner shaft 34 and the sleeve shaft 38 extend outwardly to the left of the housing 3|) a substantial distance to support the load brake C entirely to one side of the housing 3|) whereby the load brake is clear of adjacent obstructions, thus facilitating air cooling of the brake and disassembly thereof for maintenance purposes.

The load brake C shown comprises a brake or clutch member 50, a driving member 5| formed integral with the left hand end of the sleeve shaft 38, and a driven member 52 keyed to the left hand end of the shaft 34. The member 58 comprises a disc-like web or flange 55 having a' central hub 56 with a transverse or axial openingY 51 therethrough counterbored a short distance at each end for the reception of the outer races of a pair of suitable bearings 53, the inner races of which surround and engage with the outer surface of the sleeve shaft 38 for rotatably supporting the member 58 thereon. As shown, vthe member is positioned on the sleeve shaft 38 just to the left or outwardly of the ring 44. The sleeve shaft 3B just to the left of the left hand bearing 58 is enlarged as at 59, forming an axially facing shoulder which positions the mem'- ber 50 against axial movement tothe left relative to the sleeve shaft 38. vThe member 50 is prevented from axial movement to the right by the ring 44.

The disc-like web has, adjacent its outer edge, a flange extending axially to the left forming a drum 54 generally cylindrical in shape and having an internal friction surface 60 and an outer concentric surface provided with a plurality of radial fins 6|, which fins serve to facilitate the radiation or other removal of heat from the load brake C as heat is generated when lowering a load.

The member 5D is held against rotation in a clockwise direction, as viewed in Fig.` 3, by a pivoted pawl 63 which cooperates with a plurality of ratchet teeth 64 having clockwise facing, substantially radial surfaces 65, which teeth1 as shown are arranged in circumferentially spaced relationship around the outer circumference of the web 55. The pawl 53 is fixed toa short, transverse shaft 66 having its axis parallel to the axis of the shafts 34, 38 and positioned.

amazing slightly yabove and ,to ,-the-r.right .of-' the' outer; upperzperiphery of the web 55. As shown, ithehousing 30: has horizontally aligned openings through which-the shaft -66 extends and is rotatably supported. A,.fsleevelike boss .68 concentric with the shaft -extends from thelefthand side -of the housing 30 andspaces the pawl 63 from the housing 38 to radially align .it with the ratchet teeth V64. The right hand end of the shaft |56 which, as shown, lextends slightly beyond @the .right hand :sideof the housing 30, has a washer 69 fitted gthereover, and a cotter .pin orithe .like 1U extending 'therethrough `for maintaining the shaft in assembled relationship and restricting its ,movement -to the left. In the embodiment shown, the pawl63 isgravityactuated into engagement withthe ratchet teeth 64; however, a spring or other means could be employed. Also, a stop restricting movement of the paw] -53 in a clockwise ydirection `could be employed.

The enlargement 5S of the sleeve shaft 38 has its left-end '.counterbored and a roller bearing fitted therein for journaling the leftend ofv the sleeve shaft 38 -on the inner shaft 34, which inner shaft extends beyond the left Iend of the sleeve-shaft 38 and tapers tothe left for engagement within a similarly tapered opening in the hub 1| ofthe drivenmember 52. A nut 12 and a washer 13 mounted on a threaded extension u of Athe inner shaft 34 beyond the tapered portion retain the driven member 52 Yin assembled relationship on the shaft 34. The right end of the hub 1| provides ashoulder-against which the inner race of the bearing 10 mayabut. Aswill be seen from Fig. 4, thedriven member maybe readily removed from the left endof the inner shaft .34, thus making it possible to disassemble and repair, if necessary, the load brake -in a simple and expedient manner and without disturbing the supporting roller bearings .35, 4|.

The driven -memberr52 includes a pair of oppositely and radially extending arms 14 which taper slightly in a radial direction. Each arm 14 has a yoke formed on its outer end by afmember V15 formed integralwith the arm and extendingfrom a general midpoint axially to the right a .short distance and -vthence terminating` in l an out- WardlyeXtending-arm l.16, the outer edge of which is `radially coextensive with the outer end of the arm V14'. The driven member 52 is located generally within the drum 54, with the outer ends of itsarms -14, l16 adjacent to but spaced slightly from the friction .surface 60.

Thebrake C also includes a pair of elongatedf shoe members 80 positioned internally and extending circumferentially of the drum 54. As shown, each shoe lmember 80 comprises A.a shoe member proper, generally T-shaped in cross section, including axially extending flanges 84 and a radially and inwardly extending web `85. VThe flanges84 have Va curvedouter surface of a radius generally the same as the radius of the friction surface on which is fixed a suitable friction material or lining 86, the outer surface of which is adapted to be urged into and outof engagement with thefriction .surface 68.

The counterclockwiseend of each shoe 80, `as viewed ,in Eig. 3, is vpivoted directly .to the outer end. of the yoke formed bythe pair. of arms `14, 18 adjacent thereto by a pin or shaft .81 extending through aligned openings in the Varms 14, A1S, and a boss 88 formed on the end of the shoe; thus, each shoe is pivoted relative tothe driven member 52 about an axis having a nxeddis- '6 tance with respect to the friction surface 160 and the axis of the inner shaft 34. driven member 52 is xedly connected to the pinion 21 which drives the cable drum to raise a load and controls the rotation of the cable drum in lowering a load. The load constantly urges the driven member 52 in a clockwise direction, as viewed in Fig. 3. The shoes are thus constantly urged in a clockwise direction, which direction is generally along or parallel to the friction surface 60.

The clockwise end of each shoe is constantly urged outwardly by a short, helical compression spring 89 bearing at one end against the adjacent end of one of the arms 14 on the driven member 52, that is, the end opposite to which the respective shoe is pivoted, and at the other end on the inner edge of the web 85. Pins 90 extend from the edge of the web into the end of the springs 89 and prevent the springs from being displaced from the positionsshown.

The driving member 5| is located within the shoe members 80 between the driven member 52 and the web 55 of the member 50 and comprises a pair of radially extending, oppositely disposed, radially tapering arms 9| which, in the embodiment shown, are integral with the enlargement 59 on the left hand end of the sleeve shaft 38. The length of the arms 9| is somewhat less than the length of the arms 14 of thedriven member' 52 and are connected to the clockwise ends of the shoe members 83 by pairs of thrust linkage members or connecting rods 92. One pair of the rods 92 is pivoted at one end to the web 85 of one of the shoe members 80 b-y a pin 93 and at the other end to one of the arms 9| of the driving member 5| by a second vpin 94, which pins are locked in position after assembly by means of suitable cotter pins or the like. The other pair of rods 92 is connected to the other shoe member and to the other arm 9| in a similar manner. As shown, the linkage members 92 extend from the clockwise ends of the shoes 8|) in a general clockwise but chordal direction whereby a longitudinal pull or push on the linkage members 92 tends to urge the clockwise ends of the shoe members 80, respectively, awayfrom or toward the friction surface 60. It will be appreciated that other means of pivotally supporting the linkage members 92 to the shoes 8B and/or the driving member 5| may be employed. Also, other forms of linkage members can be employed.

To assemble the Vbrake shown, the member 50, `the ring 45, the bearing 4|, and the gear 25 are slipped onto the right end of the sleeve shaft 38 in the order mentioned. The inner shaft 34 is inserted into the right end of the sleeve shaft 38 and the driven member 52 fixed on Vthe left-end thereof. The entire assembly then lowered onto the lower half section 3| of the housing 36 and thereafter the upper half section 32 of the housing is installed and clamped or bolted into position.

As previously stated, the load constantly urges the driven member 52 in a clockwise direction, the helical springs '89 .urge the shoes outwardly into engagement with the friction surface 6G] ofthe brake drum 54, and the .pawl 63 engages the ratchet teeth 64 such as to prevent rotation of the member .53 in a clockwise direction; thus, a frictionei braking force is set Vuptransferring at least a portion of the load on the driven member ,through vthe bra-king lmeinber 50 and the pawl |33 to the housing andthe trolley frame. When'the motor 22 .is ,nete-nerf As stated, the' g'iz'ed, the friction brake 22v is engaged', thus tending to prevent rotation of the' driving member I, and any tendency of the shoe members fto slip or move in a clockwise directionv is opposed by the driving member 5I, which simply acts to expand the lclockwise ends of the shoes' into rmer frictional engagement with the drum 54 whereby a greater braking effort is exerted and the load securely supported.

*When it is desired to raise a load, the motor 2Q is energized to drive the driving member 5! in'. a counterclockwise direction, the force of which driving movementis transferred to the shoe members through the thrust linkages 92, which force as will be seen from a study of Fig. S'tends to expand or move the shoes 8i) outwardly into more irm engagement with the drum 5d. Because of the ratchet and pawl arrangement, the member 5D is free to rotate in a counterclockwise direction, i. e., in a direction to enable a load to be raised. Should it be desired to lower a load, the motor 26 is energized to drive the driving member 5I in arclockwise direction, thus reducing or removing the force of the'thrust members 92 on the shoes 8B to decrease or release the frictional force 'between the shoe members 8i) and the friction surface 60. So long as the frictional forces are less than the load forces on the brake, the driven member 52 may rotate in a clockwise direction under the force or eifort of the load urging it in that direction. If at any time it is desired to stop the lowering of the load or to lower it more slowly than the motor 2U is being driven, the motor 2li is either stopped or slowed to the clesired speed. The driving member 5l thereupon urgesthe shoes 8i] outwardly into tighter frictional engagement with the member 50, either braking the speed of lowering to exactly coincide with the speed at which the motor 2Q is rotatingor stopping the load altogether if the motor 20 has itself been stopped. In the latter case, the friction brake 22 engages to restrict or resist movement of the driving member 5|. Normally an electric motor when stopped is unenergized and its rotor is yfree to be driven in either direction; therefore, ifit were not for the friction brake 22, the driving member 5l ycould not exert any substantial expanding effort on the brake shoes. If no load is on the crane, the driven member 52 may be driven to pay out cable l1 from the cable drum I8.

Preferably, the springs 89 are of such a size that the braking effort exerted by the brake, as a result of the action of the springs, will not sustain a heavy load, e. g., the normal load which the crane is designed to handle, and when heavy loads are to be sustained must be supplemented by braking effort resulting from expansion of the shoes due to the driving member 5| being in turn braked by the friction brake 22. Alternatively, the springs 89 could be eliminated or made of such a size and strength that the springs would expand the brake shoes with suicient force to either fully decelerate and suspend or merely suspend the load. In the event of increasing the size of the springs, the friction brake 22 could then for all intents and purposes be eliminated or only employed to increase the braking eiTort to decelerate faster a load being lowered. 'With springs of such strengtl the driving member 5l would then only serve as a remotely controllable means of releasing the brake to lower the load. If the helical springs B9 were eliminated entirely,

thebraking `actionwou1d result from the'res'ist-' ance ofthe driving member 5| to rotation: in a clockwise or lowering direction bythe friction 'in' the gears 26, 21, etc., and by the brake 22. `Alter#- natively, a self locking or semi-self locking Vdrive between the motor 20 and the gear'26 could'be employed in place of the friction brake 22, or other types of brakes could be employed.

It will be seen that the entire load brake is Supported outboard of the housing 30, that is, there are no supporting bearings to the left of the load brake C. By such a construction, the inner and outer shafts 34, 38 may each be formed in a single section or piece and the driven member 52pm`ay be readily assembled or disassembled, giving access to the brake shoes 80, etc., for adjustment;

repairs, or replacement of parts. v Also, the cooling fins 6I are clear of adjacent obstructions-toy enable a maximum circulation of air thereover and, accordingly, a maximum cooling action. Such is particularly desirable'in hoisting equip"- V ment of the type to which this invention refers wherein heavy loads must be rapidly deceleratedrA to a smooth stop and large amounts of heat are developed which must be rapidly dissipated intoV the surrounding air.

From the foregoing it will be seen thatthe ob-V jects of the invention have been accomplished and that there has been provided a hoist mechanisrn which is simple in structure and provides a degree of control not heretofore obtainable, while at the same time being safe and efficient.

Although in accordance with the provisions of the patent statutes this invention is described as embodied in concrete form and the principle thereof has been described together with the best mode in which it is now contemplated applying that principle, it will be understood that the ap-l paratus shown and described is merely illustra-l tive and that the invention is not limited thereto, since alterations and modiiications will readily suggest themselves to persons skilled in the art without departing from the true spirit of this invention or from the scope of the annexed claims.

Having thus described my invention, I claim:

1. In a brake of the character referred to, the combination of a frame, a driven member supported for movement in aV first and second direc# tion to respectively raise and lower a load and adapted to be continuously urged insaid second direction by said load, a member having a frictiony surface and supported for movement in said rst direction only, a friction member adapted to move toward and from said friction surface, said friction member being connected to said driven member so as to move therewith, and a driving member supported for movement in either direction and connected to said friction member at a point spaced from the connection between said friction member and said driven member so as to normally oppose movement of said friction member in said second direction and urge same into engagement with said friction surface whereby the weight of said load is frictionally transferred to said member. f y

2. In a brake of the character referred to, the

combination of a frame, a driven member sup! ported for movement in a rst and second direction to respectively raise and lower a loadand adapted to be continuously urged in said second direction by said load, a member having a fric'-4 tion surface and supported for movement in said rst direction only, a friction member connected to said driven member and having a frictionsurface in opposed relationship to said friction surface on' said member, said driven member urging said friction member in a direction generally along said friction surface, and a driving member supported: for movementl in either direction and adaptedto be moved tor respectively raise or lower said load, saidA driving member being connected to said friction member through a thrust linkage at a point spaced from the connection between said friction member and said driven member, whereby movement of said driving member in said first direction urging said friction member into frictional' engagement with said member to move same andfraise a load' and' movement of said driving member in said second direction reduces the force of said friction member against said member. allowing said driven member and said driving member to move in said' second direction to lower a load'l 3; In a brake ofi the character referred to, the combination of a frame, a driven member supported for movement in a first and second direction to respectively raise and lower a load and adapted to be continuously urged in said second direction by said load, a member having a friction surface and supported for movement in said i rst direction only, a friction member adapted to move toward and from saidV friction surface, a driving member supportedv for movement in either direction and adapted to beidriven in such direc tions to respectively raise and lower a load, said friction member being pivoted directly to said driven member, and a link pivoted to opposite ends to said friction member at a point spaced from the. connecton between said friction member and said driven member and to said driving member, the plane of saidlink member being normally an'gularly disposed relative to said friction surface adjacent to the point of its connection to saidv friction member whereby movement of said driving member in opposite directions urges said friction member toward and away from said friction surface.

4. In a brake of the character referred to, the combination ofv a frame, a driven load supporting member supported for movement in a first and second direction to respectively raise' and lower a load and adapted to be continuously urged in said second direction by said load, a driving member supported for movement in either direction, a member having a friction surface and being supported for movement in said rst direction only, a friction member movable towardv and fromV said friction surface, said friction member being pivotally connected adjacent' to one end'to said driven member, a linkage member pivotally connected to said friction member adjacent tothe opposite end thereof arid tosaid drivingmem-ber, and resilient means bearing adjacent said second mentioned end of said friction member normally urging said friction member into frictional engagement with said friction surface, movement of said driving member in said second direction acting againstv the force of said resilient means to urge said friction members out of friction engagement with said friction surfaces whereby to lower a load.

5. In a brake of the character referred to, a load supporting driven member supportedon said frame for rotation in opposite directions to respectively raise and lower a load and adapted to be continuously urged in one direction by said load, a member in the shape of a drum having a circumferentially extending internal friction surface and supported coaxially with said driven member for rotation in the direction to raise a l0 load only; a shoe having a curved friction surface adapted to be urged into engagement with said first mentionedl friction surface, a rotatable drivingy member'supported coaxiallywith said driven member for-'rotation in oppositev directions, said-shoe being'conn'ected tov said driven member for movement therewith, a link member connecting said shoe to said driving member'at a point spaced from thev connection between said friction member and said driven member for urging said' shoe ina direction: toward and from said rst mentioned` friction surface on said drum, andA spring means bearing between said driven member and'said second mentioned end of said shoe for urgingf'said shoe into fri-ctional engagement with said first mentionedv friction surface.

6. In a brake of the character referred to, the combination of a frame, a driven4 member and a driving member bothV supported for rotation in opposite directions about a common axis, a drum rotatable on an axis aligned with the axis of rotation of said members, a shoe adapted toengage said drum' and pivoted to said driven member, a link pivotally'connected rto said shoe at a point spaced from the connection of said driven member with said shoeV andy to'said driving member adapted to expand said shoe into engagement with said drum when said driving member is rotatecl to raise a load and to contract said shoe when said driving member is rotated to lower a load, saiddrum having means adapted to permit rotation of said drum only in a direction to raise said load,

7. In a brake of the charactery referred to, the

combination of a frame, a drive member adapted to be rotated in opposite directions and having a drive shaft, a driven member* adapted to be rotated in opposite directions and having a shaft concentrically arranged With said first-mentioned shaft, a drum member rotatable coaxially of said concentric shafts and having an internal'surface externally of said driving and driven members, a shoe adapted to engage said `internal surface on said drum member, said shoe being pivotally connectedV to said driven member, a thrust link connecting said shoe with said driven member at a point spaced from the connection of said driven 'member' with said shoe, said thrust link normally expanding said shoe into frictional engagement with said drum and operating to contract said shoe when said driving member is rotated in a direction to Alower a load, means permitting free rotation of said drum to raise a load and preventing rotation in the opposite direction.

8v. In a brake of thecharacter described, a pair of concentrically arranged shafts including a driving shaft and a driven shaftprojecting from'a support, Ya drum journaled lfor rotation on the axially extendingv portion of the outer of said shafts, means for preventingv rotation of said drum in onedirection, a shoe adapted to engage said drumg' a member fixed to said outer shaft and Vconnected to said shoe, said inner shaft extending axially beyond the end of said outer shaft, and a radially extending member detachably fixed on said last referred to portion of said inner shaft and pivotally connected to the opposite end of said shoe.

9. In an overheated hoist, a hoist motor adapted to be driven in opposite directions to raise and lower a load, a rotatable clutch member, a rotatable driving member mechanically connected with said hoist motor and adapted to be driven in opposite directions thereby, a rotatable driven membl adapted to be 'mechanically connected .to a load supporting member, a friction member interconnecting said driven and driving members, said driving member being connected with said friction member to urge same into frictional engagement with said clutch member when a load is being supported and to release said friction member from said clutch member when said motor is rotated in a direction to lower a load, means for preventing rotation of said clutch member Vin a direction to lower the load, and means restricting rotation of said driving member when said hoist motor is not energized.

10. In an overhead hoist, a hoist motor adapted to be driven in opposite directions to raise and lower a load, a rotatable clutch member, a rotatable driving member mechanically connected with said hoist motor and adapted to be driven in opposite directions thereby, a rotatable driven member adapted to be mechanically connected to a load supporting member, a friction member interconnecting said driven and driving members, said driving member being connected with said friction member to urge same into frictional engagement with said clutch member when a load is being supported and to release said friction member from said clutch member when said motor is rotated in a direction to lower a load, means Yfor preventing rotation of said clutch member in a direction to lower the load, and a friction brake engaged when said motor is deenergized and disengaged when said motor is energized restricting rotation of said driving member when said hoist motor is not energized.

11. In an overhead hoist, a hoist motor adapted to be driven in opposite directions to raise and lower a load, a rotatable clutch member, a rotatable driving member mechanically connected with said hoist motor and adapted to be driven in opposite directions thereby, a rotatable driven member adapted to be mechanically connected to a load supporting member, a friction member interconnecting said driven and driving members, 'said driving member being connected with said friction member to urge same into frictional engagement with said clutch member when a load vis being supported and to release said'frictional member from said clutch member when said motor is rotated in a direction to lower a load, means for preventing rotation of said clutch member in a direction to lower the load, means restricting movement of said driving member when said hoist motor is not energized and resilient means yieldingly urging said friction member into engagement with said clutch member.

- 12. In an overhead hoist, a hoist motor adapted l Yto be driven in opposite directions to raise and lowera load, a rotatable clutch member, a rotatable driving member mechanically connected with said hoist motor and adapted to be driven in opposite directions thereby, a rotatable driven member adapted to be mechanically connected to a load supporting member, a friction member interconnecting said driven and driving members, said driving member being yconnected with said friction member to urge same into frictional -engagement with said clutch member when a load ing said friction member into engagement with said clutch member, said resilient means urging said friction member into engagement with said clutch member with a force insufficient to support a normal load whereby a portion of the load is transferred to the driving member and said means restricting movement of said driving member for further increasing the frictional force.

13. In an overhead hoist, a hoist motor adapted to be driven in opposite directions to raise and lower a load, a rotatable clutch member, a rotatable driving member mechanically connected with said hoist motor and adapted to be driven in opposite directions thereby, a rotatable driven member adapted to be mechanically connected to a load supporting member, a friction member interconnecting said driven and driving menibers whereby movement of said hoist motor is transmitted to said load support member, said driving member being connected with said friction member to urge same into frictional engagement with said clutch member when a load is being supported and to move said friction member in a direction away from said clutch member when said motor is rotated in a direction to lower a load, means for preventing rotation of said clutch member in a direction to lower the load, and means restricting movement of said driving member when said hoist motor is not energized, said means including a friction brake engaged when said motor is unenergized and disengaged when said motor is energized for rotation Vin either direction, and resilient means normally urging said friction member into engagement with said clutch member with a force insufcient to support the load normally adapted to be supported whereby a portion of said load is transferred to said friction brake.

ROY F. DEI-IN. REFERENCES CITED `,The following references are of record in the file of this patent:

UNITED STATES PATENTS Ferguson Sept. 5, 1944

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