GB2115367A - An improved electric chain block or hoist - Google Patents

Abstract

In order to provide a chain block or hoist of economical design of which the overall size is reduced and which has side parts or members arranged substantially symmetrical with respect to the hook, an epicyclic reduction gear (7, 9, 10) is provided. A central input shaft (1) of the gear is rotatably supported in a cantilever manner by the associated bearings 3, 4 and gear (2), with which the chain (C) is coupled, and which forms a unitary body with the movable gear (7) of the reduction gear. A counterweight (19) is provided to determine a maximum load friction which can be applied. A self-braking electric motor for driving the input shaft (1) has a rotor comprising a series of conical packets surrounded by an air gap, and a brake is at least positioned within one of the motor winding heads. <IMAGE>

Description

SPECIFICATION An improved electric chain block or hoist This invention relates to an electric chain block or hoist of the kind comprising a self-braking electric motor operatively connected to an epicyclic reduction gear for driving a member engaging the chain and which is associated with a maximum load friction.

In the field of electric chain blocks or hoists, due to space and positioning considerations, it is often required to reduce floor space, and to provide a dimensional symmetry of the two side parts relative to a central supporting hook in order to avoid undue lateral overhang.

According to my invention, in an electric chain block orm hoist comprising a self-braking electric motor operatively connected to an epicyclic reduction gear for driving a member meshing with the chain and which is associated with a maximum load friction or clutch, the electric motor is operatively connected to the epicyclic reduction gear through a cantilevered portion of a shaft which is rotatably supported within the said member meshing with the chain.

This enables one to provide an electric chain block or hoist of particularly reduced size, economically and which for a given floor space, allows the diameter of the reduction gear planet wheels to be increased with the result that higher torques can be transmitted.

Preferably wheelwork meshing with the planet gears of the epicyclic reduction gear, are provided at one end of the cantilevered portion of the shaft means whilst the opposite end is provided with means for clutch coupling with respect to the axis of the electric motor.

In order that the present invention be more clearly understood, reference will be made to the accompanying drawings, inter alia, showing how the invention has been exemplarily realized.

In the drawings: Figure 1 is a longitudinal sectional view of the mechanics of the block or hoist; and Figure 2 is a longitudinal sectional view of the electrics of said block or hoist, i.e. the self-braking electric motor thereof.

In these Figures of the accompanying drawings, reference numeral 1 denotes a shaft, by means of which the self-braking electric motor, shown in Figure 2 is operatively coupled in end-to-end configuration to the epicyclic reduction gear of Figure 1, which in turn operates the gear 2 meshing with the chain C supporting the load through any known hook.

The shaft 1 is rotatably carried in the gear 2 by means of two ball bearings 3 and 4 arranged in the middle region of the shaft, whereby the latter has two cantilevered ends. One of these ends has a splined hole 5, accommodating therein the correspondingly splined projection 6 of shaft 25 of the electric drive motor. The other cantilevered projecting end of shaft 1 is machined to provide teeth 1A meshing with a pair of planet gears 10 at 1800 of the epicyclic reduction gear.

The gear 2 is integral with the movable planetary or crown wheel 7 of the reduction gear and rotates by bearing on a ball bearing 14 and on an annular surface 15 of a central portion 13 of a block or from which a hollow right portion 12 extends. The portion 12 is secured to the portion 13 by means of screws.

The panet gears 10 are rotatably mounted in a planet gear carrier mount 8 of anti-friction material. The left portion of the panet gears 8 is housed within the gear-movable crown wheel assembly 2, 7, and the right portion is housed within a fixed crown wheel 9 of the reduction gear. The fixed crown wheel 9 is pressed against a cutaway cylindrical collar of the right portion 12 of the block or hoist frame through a friction ring 16. The pressing action is exerted through a tie rod 17, and a nut 18 screwed onto the tie rod 17 and acting on a counterweight 19 through cup springs 18A. The counterweight 19 is machined to act as a counter-flange and pressed on the collar 11 through a friction ring 20, thus providing the desired safety of maximum load.

Obviously, each planet gear 10 comprises two sets of teeth of different diameters and numbers, of which one meshes with the movable crown wheel 7 and the other with the fixed crown wheel 9. The minor sets of teeth mesh with the teeth 1A of the shaft 1.

As shown, the structure of the two end portions for the reduction gear of the block or hoist according to the present invention (central cantilevered shaft 1 and counterweight 19 acting as counter-flange of the friction or clutch), and the use of the rational central members, such as the movable crown wheel 7, forming a unitary body with the gear, and the planet gear carrier mount 8 free of ball bearings, enables one to provide economically and rationally a reduction gear of highly reduced overall size.

In connection with overail size and cost, the cantilevered shaft 1, in addition to the evident advantages relating to the exclusion or omission of the second support in the fixed crown wheel 7, further provides the possibility of proportioning the assembly with planet gears of larger diameter and accordingly allows the consideration for such planet gears of a higher number of meshing teeth, with the favourable result of mechanically reducing the dimensions of the planet gears. In addition to a larger diameter of the planet gears, there would be correspondingly reduced angular speeds and thus an increased functional noiselessness of the assembly.

Then, because of the omission in the fixed crown wheel 9 of the housing for a second support for the driving shaft of the electric motor, the thickness of the crown wheel will be increased with added stiffness to the involved mechanical system.

Finally, the use of the counterweight 19 as the counter-flange of the safety friction of clutch, in addition to the advantages of omitting a normal blocking counter-flange, also provides the benefit that the heat developed by possible rubbing of the friction or clutch, on meeting a mass which is naturally very large, is easily taken by the involved assembly..

Continuing the description with reference to Figures ofthe accompanying drawings, reference numeral 21 represents three cylindrical sectors of the stator pack for the electric block or hoist operating motor, and reference numeral 22 represents the three corresponding sectors of the rotor, sectors which are originally cylindrical (on the outer side), but conical or tapered turned to provide an axial magnetic attraction when the motor is energized. Reference numeral 23 denotes a conical packing or gasket for a brake, the shoe 24 of which is fast with the axially movable shaft 25 of the motor. In a rest condition the shoe 24 is urged by spring 26 into engagement with the packing or gasket 23 to brake and block the motor shaft 25 against rotation.

Similarly, when the rotor is functioning, the shoe 24 is adapted to be urged away from the packing or gasket 23 by the magnetic attraction of the rotor, which attraction overcomes the pressure of the spring 26, releases the brake, and affords a regular functionality of the motor rotor. The conical friction packing or gasket 23 is mounted on a projection 23A of corresponding shape of the left frame of the motor. The rotor 22 is axially movable within bearings 28.

This self-braking motor corresponds structurally to a normal conical motor, and thus has a highly reduced floor space, particularly because the braking system is accommodated within the head 27 of the normal motor winding. However, it has the particu larfeatureofbeing implemented bythe use of a cylindrical magnetic lamination of standard shearing and die-cast rotors of normal production, and accordingly is highly economical and easy to manufacture.

The magnetic rotor pack is divide into sectors or packets, for example three as shown in Figure 2, to provide a reasonable average value of "air gap" (interspace between stator and rotor) by adopting a magnetic stator pack having a cylindrical inner face and a suitable taper.

In order to avoid magnetic attractions of opposite direction to useful direction, magnetic attraction relative to actions between the magnetic flux from the stator 21 and the rotor surface 29 forming the major base of the truncated cones of the rotor sectors, non-magnetic spacers 30 are provided in the rotor 22 to generate magnetic attractions of a direction consistent with the useful direction between the magnetic flux from the stator 21 and surfaces 32 of the involved rotor. Herein, these rotor spaces 21 simply comprise annular grooves.

Thus, by the solution according to the present invention, the driving section can be economically provided, of reduced floor space, and corresponding to the relevant part of the reduction gear.

The functionality of the assembly or unit is substantially immediate. Upon energization of the motor, the magnetic attraction of the stator causes a rightward displacement of the rotor 22, overcoming the pressure or force of the spring 26 and releasing the brake. The rotor 22 then accelerates and attains the provided r.p.m. The projection 6 of the rotor shaft 25 drives the central shaft 1 of the reduction gear, and by means of the planet gears 10 this drive is communicated to the movable crown wheel 7, that in turn rotating the gear 2, which drives the block or hoist operating chain. Upon shut-off the drive motor, the magnetic attraction of the stator 21 is cut-off, and the rotor 22 is urged by spring 26 in a leftward direction with the brake 23, 23A, 24 blocking and stopping the movement of the assembly or unit.

Claims (7)

1. An electric chain block or hoist, comprising a self-braking electric motor operatively connected to an epicyclic reduction gear for driving a member meshing with the chain and which is associated with a maximum load friction or clutch, in which the electric motor is operatively connected to the epicyclic reduction gear through a cantilevered portion of a shaft which is rotatably supported within the said member meshing with the chain.

2. A block or hoist according to Claim 1, in which the motor has a cylindrical stator with cylindrical sectors, and a conical rotor with conical sectors.

3. A block or hoist according to Claim 2, in which both the stator sectors and the rotor sectors are spaced apart fro each other.

4. A block or hoist according to Claim 1, in which the member is integrai with the movable crown wheel of the epicyclic reduction gear.

5. A block or hoist according to Claim 1, in which a planet gear carrier mount of the epicyclic reduction gear is made of anti-friction material provided with sliding coupling contacts.

6. A block or hoist according to Claim 1, in which the maximum load clutch comprises a counterweight acting as a counter-flange for the clutch.

7. A block or hoist substantially as described herein with reference to and as illustrated in the accompanying drawings.