US2710738A

US2710738A - Electric hoist

Info

Publication number: US2710738A
Application number: US339557A
Authority: US
Inventors: Frank H Wittberger
Original assignee: Harnischfeger Corp
Current assignee: Harnischfeger Corp
Priority date: 1953-03-02
Filing date: 1953-03-02
Publication date: 1955-06-14
Anticipated expiration: 1972-06-14

Description

F. H. WITTBERGER 2,710,738

ELECTRIC HOIST 2 Sheets-Sheet 1 June 14, 1955 Filed March 2, 1953 INVENTOR. Zno'JL/K W Q 2 MIT hm NIT June 1955 F. H. WlTTB ERGER ELECTRIC HOIST 2 Sheets-Sheet 2 Filed March 2, 1955 ELECTRIC HOIST Frank H. Wittberger, West Allis, Wis, assignor to llarnischfeger Corporation, Milwaukee, Wis, a corporation of Wisconsin Application March 2, 1953, Serial No. 339,557

7 Claims. (Cl. 254186) This invention relates to electric hoists for winding in and paying out a line or cable and it more specifically resides in a hoist having a cable winding drum and a motor joined with a shaft extending into the drum to drive a gear reduction train housed within the drum, the drum being mounted for rotation upon spaced bearings carried in a frame having a part which extends through one of the bearings and provides means for resisting the reaction of the gear reduction train, the gear reduction train sometimes comprising an epicyclic planetary unit of high driving ratio with irreversible properties so that a mechanical load brake may be dispensed with, the motor being sometimes provided with means causing its rotor to move axially to release a motor brake.

It is desirable that an electric hoist. be compact, simple and rugged. To this end it is important that the space within the winding drum be utilized, to house parts which would otherwise add to the dimensions of the apparatus. It is also desirable that the rather large ratio of driving reduction which is required be accomplished with as few parts as possible. It is furthermore desirable that means be included which will reliably prevent an unintended descent of the load or descent of the load at a rate more rapid than intended and to do so without resort to so-called friction load brakes which are subject to alteration in adjustment due to wear and temperature changes.

It is an object of this invention to provide a hoist for winding in and paying out a cable or line of rugged construction requiring less maintenance.

It is another object of this invention to provide a hoist with a gear reduction drive for the winding drum housed within the drum to permit a compact arrangement having minimum overall dimensions.

It is another object of this invention to provide a gear reduction drive for a hoist that affords the advantages of the foregoing objects in which only two sets of gear teeth are in mesh and in which an exceptionally large number of teeth of each set are engaged so that Wear is minimized.

It is another object of this invention to provide a hoist with a winding drum in which a drive motor is mounted on one side and a brake is mounted on the opposite side and in which an axial thrust delivered by the motor is transmitted through the drum to the brake to release the same.

It is still another object of this invention to provide a hoist in which unintended descent of a load or a descent at a rate faster than that desired is prevented by an irreversible reduction gear train in which a large number of gear teeth are continuously in engagement to provide an exceptionally high factor of safety.

These and other objects and advantages of this invention will appear in the description to follow. In the description reference is made to the accompanying drawings in which there is shown by way of illustration and not of limitation one specific form in which this invention may be embodied.

In the drawings:

Fig. 1 is a side view in elevation and in section of an electric hoist in which this invention is embodied,

* atent Patented June 14, 1955 Fig. 2 is a view in cross section of the hoist shown in Fig. I viewed through the plane 2-2, and

Fig. 3 is a view in cross section of the hoist shown in Fig. 1 Viewed through the plane 33.

Referring now to the drawings, more particularly Fig. 1, numeral 1 designates a main hoist frame comprising a centrally disposed drum hanger 2, generally cylindrical, and open beneath to permit a cable to extend downwardly from Within the hanger 2. A bracket 3 integral with the upper portion of the drum hanger Z rises upwardly and provides means for attachment to an overhead support. Bolted to the left hand side of the drum hanger 2, as a part of the main frame 1, is a motor bracket 4 that forms a support for a motor frame 5 of an electric motor 6. The motor bracket 4 includes a bell housing 7 that extends inwardly to seal one end of the motor 6 and to support a drum mounting hub 8 having a central opening.

Bolted to the right hand side of the drum hanger 2, as a part of the main frame 1, is a brake bracket 9 having a shroud plate It? extending inwardly and terminating in a second hub 11 in the form of a truncated cone open at the center. Non-rotatably secured within the hub 11 by means of a key is the shank 13 of an internal reaction gear 12. Gear 12 acts as an orbit gear for an epicyclic planetary system to be described.

A bearing 14 fitted within the hub 8 of the motor bracket 4, and a bearing 15 seated upon the shank 13 of the gear 12, provide means mounting a cable winding drum lo for rotation. The drum in is formed in two parts comprising the winding drum 1! having a hub at its right hand end supported by the ball bearing. 15 and an internal drum gear 18 keyed to the inner face of the drum l7 having a hub 19 supported within the bearing 14;. The internal drum gear 18 has a slightly larger pitch diameter than gear 12 and like the reaction gear 12 forms a part of a planetary system to be described.

The frame 5 of the motor 6 has a bell housing 20 at the outer end in which is mounted a roller bearing 21 held in place by a retaining ring 22. A motor drive shaft 23 with a bushing 24 carried on its left hand end is supported by and is free to rotate and to move axially within the roller bearing 21. The shaft 23 after a reduction in diameter extends to the right from the frame 5 and passes through the cable winding drum 16. From the drum 16 the shaft 23 continues through the hub 11 and the reaction gear 12 to the right hand side of the shroud plate ill.

The larger left hand end of shaft 23 serves as a mounting for a motor rotor 25 secured thereto. The construction of rotor 25 differs from that usually employed in that a series of circumferential slots 26 are cut in its outer periphery. The stator 27 of the motor 6 also includes a series of circumferentially disposed slots 28 that extend across the pole faces. As shown in Fig. 1, the rotor 25 is disposed in a standstill position which occurs when the motor 6 is not energized and in this standstill position the slots 26 are slightly to the left of and out of alignment with the stator slots 28. Upon energization of the stator 27 the magnetic attraction between the stator 27 and rotor 25 urges the rotor 25 axially to the right toward a position of alignment between the slots 26 and the slots 28. The motor 6 thus, while exerting torque, also exerts an axial thrust upon energization of the field 27 that is imparted to the drive shaft 23.

Splined to the central portion of the shaft 23 is an eccentric quill 29. The left hand end of quill 29 abuts a set of shims 30 that bear in turn upon a bushing 31, disposed in contact with the shoulder 32 formed by the increased diameter of the shaft 23. The eccentric quill 29 is supported in a pair of roller bearings 34 and 33, mounted respectively in the drum gear 18 and the reaction gear 12. The output shaft 23 is thus supported by the roller bearings 21, 33 and 34 each of which is constructed to permit axial shift of the shaft 23 together with the eccentric quill 29.

Mounted for rotation upon the quill 29, eccentrically disposed with respect to the shaft 23, is a compound planetary pinion 35, carried on roller bearings 36. The pinion 35 is cut with two

distinct planet pinions

38 and 39 of slightly different pitch diameters, coordinated with the diameters of

gears

12 and 18 so that planet pinion 38 is disposed in mesh with the reaction gear 12 which is fixed with respect to the frame 1, and planet pinion 39 is disposed in mesh with the drum gear 18. Mounted on either side of and retaining the planetary pinion 35 in position is a pair of counterweights 40 and 41 secured by pins 37 to the eccentric quill 29. The counterweights 40 and 41 are positioned to counterbalance rotational forces of the parts that gyrate about the shaft 23 which would otherwise be dynamically unbalanced. Placing the weights 40, 41 on both sides of the pinion 35 also reduces unwanted radial thrusts imparted to the supporting bearings.

The throw of eccentric 29 is approximately one-half the difference in the pitch diameters of pinion 38 and gear 12 on the one hand or one half the difference in pitch diameters of pinion 39 and gear 18. Upon rotation of the eccentric member 29 drum 16 will advance or retreat, depending upon the direction of rotation of member 29, an angular distance dependent upon the reduction ratio of the epicyclic gear train. This reduction ratio is approximately equal to the product of the ratios of the number of teeth in gear 38 divided by the difference in number of teeth between

gears

12 and 38 and the number of teeth in gear 18 divided by the difference in number of teeth between

gears

18 and 39. In a typical case gear 12 may have fifty-eight teeth, pinion 38, fifty-two teeth, gear 18, sixty-four teeth and pinion 39, fifty-eight teeth. In this case the ratios are 52:6 and 64:6 and the product of these ratios gives a reduction of approximately 92.4 to l.

The epicyclic gear train thus provided, has a very large driving ratio of reduction, comprises but two gears and one compound pinion, and as appears in Figs. 2 and 3, a large number of teeth are at all times in contact. The transmission is moreover self-locking since its efiiciency is determined largely by tooth friction and the efiiciency quotient is less than the reverse driving ratio.

Carried upon the right hand end of the shaft 23 with a splined connection is an elongated collar 42 which abuts the right hand end of the eccentric quill 29 to act as a continuation thereof for the transmission of axial thrust exerted by the motor 6. The collar 42 is formed to provide a toothed spider 43 that engages the toothed central opening in a brake disc 44 to cause the latter to turn with shaft 23. Axial forces exerted by the motor 6 are not however transmitted through the coupling between the spider 43 and disc 44. Brake elements associated with the disc 44 for frictional engagement therewith comprise the shroud plate 10 and a movable brake plate 45 to the right of the disc 44. Plate 45 is free to move axially but is restrained from rotation by pin 46 seated in the shroud plate 10. Brake plate 45 is open at its center and is threaded to receive a tubular collar 47 that is slidingly mounted on a stationary boss 48 at its right hand end. The collar 47 has an internal shoulder 49 disposed toward its left hand end that bears against a thrust bearing 50 mounted upon the end of the motor shaft 23 and abutting the collar 42. A brake spring 51 encircles the collar 47 to urge the brake plate 45 against the brake disc 44 which in turn is urged against the shroud plate 10. The internal shoulder 49 of the collar 47 is urged against the thrust bearing 50 by reason of the action of the brake spring 51 thus acting to move the shaft 23 when the motor 6 is not energized axially to the left of its running position. A housing plate 52 that supports the boss 48 and acts as a stationary reaction for the spring 51 closes the end of the brake bracket 9 to enclose the brake members.

The opposite side of the plate 52 may serve as a mounting for electrical switches and controlling apparatus for the hoist which may be enclosed by a cover 53.

The lower side of the brake bracket 9 is open at 54 to admit av pendant control cord not shown but intended to be attached to a switch lever designated by reference numeral 55. To secure the hoist cable to the drum 16 the dead end is fitted with an end fitting received within the cable socket 56.

To adjust for the desired length of the axial stroke of the shaft 23 the collar 47 which is threaded to the brake plate 45 is turned to a position that forms a gap between the collar 47 and the housing plate 52 that is equivalent to the stroke desired. This adjustment is made with the braking elements in braking position tightly sandwiching the brake disc 44 between the shroud 16 and the piate 45. The shims 30 between the bushing 31 and left hand end of the eccentric quill 29 are employed to provide an adjustment for the axial offset between the slots 26 in the armature 25 and the slots 28 in the field member 27. It has been found desirable to adjust the collar 47 and employ such thickness of shims 3% to ensure an axial stroke of about onethird the offset between the slots 26 and 28. When so adjusted upon energization of the motor 6 the axial thrust at ing from the attractive force acting to move the at; are 25 toward alignment of the slots 26 with the slots will be adequate to release the brake.

Release of the brake members 10, 44 and 45 is immediately followed by rotation of the drive shaft 23 which acts to rotate the cable drum 16 through the planetary gear train within the drum 16. The motor 6 may be driven to either pay out or wind in hoisting cable.

Because of the high ratio of reduction in the eccentric planetary and the inherent friction of such a driving system the gearing is irreversible and the load will not travel faster in either raising or lowering directions than the inherent limiting speed of the motor 6. The gear is also self locking and the need for a load brake is therefore eliminated.

I claim:

1. In an electric hoist the combination comprising a frame providing spaced bearing supports; a hollow cable winding drum mounted on spaced bearings supported by said spaced bearing supports; a motor mounted on said frame on one side of said drum having an axially displaceable rotor with an output shaft extending through each of said hearings to the side of said drum opposite said motor; said rotor and shaft having a running position assumed upon energization of said motor and a standstill position axially displaced from said running position; torque increasing reduction gearing housed Within said hollow drum having input means in driven relation to said motor output shaft, output means in driving relation to said drum, and reaction means sustaining the increased torque thereof; means secured to said frame and extending through one of said bearings secured to said reaction means to maintain the same stationary; a brake disposed to the side of said drum opposite that of said thrust motor cooperatively engaged with said output shaft and having a pair of axially separable brake members movable to disengaged position upon movement of said rotor and shaft to said running position; and bias means urging said brake members into engagement to retard shaft rotation and urging said rotor and shaft axially to said standstill position when said motor is deenergized, brake releasing thrust being delivered by said motor upon energization thereof through said shaft to disengage said brake members and to move said rotor and shaft to running position.

2. In an electric hoist the combination comprising a mounting frame providing spaced bearing supports; a hollow cable winding drum rotatably mounted on spaced bearings supported by said bearing supports; a motor mounted on said frame on one side of said drum having an output shaft extending through said bearings emerging from the side of said drum opposite said motor; a brake disposed to the side of said drum opposite said motor cooperatively engaged with said shaft for release upon energization of said motor, an eccentric member mounted on said shaft within said drum, a pinion gear mounted on said eccentric member and rotatable with respect thereto having two sets of teeth to form a pair of planets, a ring gear forming an extension of said frame extending through one of said bearings for said drum to within said drum disposed in mesh with one of said planets, and a second ring gear fixed to an interior wall of said drum in mesh with the second of said planets to rotatably drive said drum in response to motion of said pinion gear.

3. In an electric hoist the combination comprising a central drum assembly including a rotatable hollow cable receiving drum having a centrally disposed bearing support at one end, a reaction gear member with a central opening having a shank extending through and borne by a bearing in said bearing support and a reaction end within said drum, a quill with one end extending within the central opening of said reaction gear member rotationally supported thereby, reduction gearing within said drum with a gear member in mesh with said reaction gear member and having an input supported by said quill and an output, a drum gear secured within said drum for rotation therewith in driven relation to the output of said reduction gearing and having a centrally disposed hub at the end of said drum opposite said bearing support, and a bearing housed within said hub supporting the end of said quill opposite the end received in said reaction gear member; a motor disposed at one side of said drum assembly having a frame member supporting said motor and supporting the hub of said drum gear for rotation, said motor having an axially displaceable output shaft with an axially displaceable armature mounted thereon, said shaft having an end extending through and slidable with respect to said quill for rotation thereof; a brake housing disposed at the side of said drum assembly opposite said motor having a brake frame member rigidly secured to the shank of said reaction gear member and the frame of said motor; and brake elements within said brake housing operable between brake engaged and brake released positions in rc sponse to axial movement of said motor output shaft.

4. In an electric hoist the combination comprising a rotatable hollow cable receiving drum having a centrally disposed bearing support at one end; a reaction member with a central opening having a shank extending through and borne by a bearing in said bearing support and a reaction end within said drum; a quill having an eccentric and with one end extending within the central opening of said reaction member rotationally supported thereby; a drum gear member fitted within the end of said drum opposite said bearing support for rotation with said drum and having a centrally disposed hub; a bearing housed within said hub supporting the end of said quill opposite the end received in said reaction gear member; reduction gearing within said drum having a pinion mounted on the eccentric of said quill free to rotate with respect thereto and to be gyrated in response to rotation thereof having two sets of teeth to form a pair of planets, a fixed ring gear forming a part of said reaction member in mesh with one of said planets, and a second ring gear in mesh with the other of said planets supported by said drum gear member; a motor disposed at one side of said drum having a frame member supporting said motor and supporting the hub of said drum gear for rotation, said motor having an axially displaceable output shaft with an axially displaceable armature mounted thereon, said shaft having an end extending through and slidable with respect to said quill for rotation thereof and extending through the central opening in said reaction member; a brake housing disposed at the side of said drum opposite said motor having a brake frame member rigidly secured to the shank of said reaction member and the frame of said motor; and brake elements within said brake housing operable between brake engaged and brake released positions in response to axial movement of said motor output shaft.

5. An electric hoist in accordance with claim 4 having counterweights attached to said quill at both sides of said pinion to counterbalance rotational forces of said pinion and eccentric member.

6. In an electric hoist the combination comprising a rotatable hollow cable receiving drum having a centrally disposed bearing support at one end, a reaction gear member with a central opening having a shank extending through and borne by a bearing in said bearing support and a reaction end within said drum, a drum gear fitted within the end of said drum opposite said bearing support for rotation therewith and having a centrally disposed hub, a motor disposed at one side of said drum having a frame member supporting said motor and supporting the hub of said drum gear for rotation, said motor having an axially displaceable output shaft with an axially displaceable armature mounted thereon and having an end extending through said drum and extending within the central opening of said reaction gear member, said output shaft being rotatably borne by a bearing in said hub of said drum gear and a bearing in the shank of said reaction gear member, reduction gearing within said drum having agear member in mesh with said reaction gear member with an input driven by said output shaft and an output in driving relation to said drum gear, a brake housing disposed at the side of said drum opposite s'aid'motor having a brake frame member rigidly secured to the shank of said reaction gear member and the frame of said motor, and brake elements within said brake housing operable between brake engaged and brake released positions in response to axial movement of said output shaft.

7. An electric hoist in accordance with claim 6 in which said reduction gearing includes an eccentric Within said drum mounted on and rotatable with said output shaft, a pinion mounted upon said eccentric free to rotate with respect thereto and to be gyrated in response to rotation of said output shaft having two sets of teeth to form a pair of planets, one of said planets being in mesh with a fixed ring gear forming a part of said reaction gear member, and the other of said planets being in mesh with a ring gear forming a part of said drum gear.

References Cited in the file of this patent UNITED STATES PATENTS 1,384,839 Krohn July 19, 1921 1,771,281 Wilsing July 22, 1930 2,239,839 Benson Apr. 29, 1941 2,354,387 Lawler July 25, 1944