# Patent

## Title
Chain hoist having a slip clutch

## Abstract

A chain hoist having an electric drive motor connected to a gearbox by a slip clutch, wherein the slip clutch comprises an enlarged outer surface area in the form of recesses disposed in the outer surface of the slip clutch for improving heat dissipation with the recesses being implemented circumferentially in the form of a thread pitch in the outer surface of the slip clutch.

## Background
CROSS REFERENCE TO RELATED APPLICATION
The present application claims the priority benefits of International Patent Application No. PCT/EP2010/066995, filed on Nov. 8, 2010, and also of German Patent Application No. DE 10 2009 053 613.2, filed on Nov. 17, 2009, which are hereby incorporated herein by reference in their entireties.
BACKGROUND OF THE INVENTION
The invention relates to a chain hoist having an electric drive motor which is connected to a gearbox by means of a slip clutch.
German patent DE 102 44 865 B4 already discloses a chain hoist having an electric drive motor which, by means of a gearbox connected downstream of the drive motor, drives a chain wheel for a chain for lifting and lowering a load. In order to avoid gearbox or drive motor overload e.g. when the chain is hooked onto the no-load side, a slip clutch is disposed between the drive motor and the gearbox. The slip clutch consists of a first annular clutch element and a second annular clutch element which are in engagement via a friction lining. The first clutch element is disposed concentrically on a driven-side end of a motor shaft of the drive motor and is connected in a rotationally fixed manner to the motor shaft. The second clutch element is disposed in a comparable manner on a first end of a gearbox input shaft of the gearbox. In order to be able to adjust the activation force of the slip clutch, the gearbox input shaft is disposed in an axially displaceable manner and the gearbox input shaft together with the second clutch element is pretensioned in the direction of the first clutch element by means of a spring element.
Furthermore, U.S. Pat. No. 3,396,557 A discloses a hammer drill which is driven by means of an electric motor. The electric motor is connected to receiver for a drilling tool by means of a gearbox. Disposed inside the gearbox is a slip clutch to be activated in the event of a pre-settable torque which acts upon the drilling tool. The slip clutch comprises a cylindrical housing which on its outer side comprises radially circumferential and outwardly directed fins. These fins should allow rapid dissipation of heat from the housing.
SUMMARY OF THE INVENTION
The object of the invention is to provide a chain hoist which comprises an improved slip clutch.
The object is achieved by a chain hoist in accordance with the present invention.
In accordance with an embodiment of the invention, in the case of a chain hoist having an electric drive motor which is connected to a gearbox by means of a slip clutch, wherein in order to improve the dissipation of heat the slip clutch has an enlarged outer surface in the form of recesses disposed in the outer surface of the slip clutch, the slip clutch thereof is improved by virtue of the fact that the recesses are formed circumferentially in the form of a thread pitch in the outer surface of the slip clutch. In this way, continuous slip tests which are required in accordance with applicable standards can be fulfilled. By virtue of the enlarged outer surface, adequate dissipation of heat can be achieved, without substantially increasing the installation size of the clutch. As a result, it is possible to achieve an increase in the size of the heat exchange surface using simple means. Improved dissipation of heat is also achieved by the conveying effect of the thread pitch.
In constructional terms, provision is made in a particular embodiment that the slip clutch consists of a sleeve-shaped first clutch element having a first annular clutch surface and of a sleeve-shaped second clutch element having a second annular clutch surface, and a friction lining is disposed between the first clutch surface and the second clutch surface.
As a further constructional detail, it is provided that the first clutch element consists of a sleeve-shaped first attachment part and of a sleeve-shaped first clutch disk part adjoining it, the second clutch element consists of a sleeve-shaped second attachment part and of a sleeve-shaped second clutch disk part adjoining it, and the outer surface for increasing the dissipation of heat is disposed in the region of the peripheral surface of the first clutch disk part. In this case, when the gearbox is blocked and the slip clutch effects a response the first clutch disk part continues to be rotated by the drive motor and gearbox oil thus continues to be conveyed from the thread-like recesses into the bore and further cooling is thus effected.
In this case, the second attachment part is advantageously inserted into the clutch element.
It is particularly space-saving that the slip clutch is disposed in bore of a housing of the gearbox.
In a particular constructional embodiment, the housing has a gearbox chamber disposed inside it which is connected to the bore and is filled with a gearbox oil.
In order to improve cooling and to convey the gearbox oil, a gap is disposed between the cylindrical outer surface of the slip clutch and the inner surface of the bore.
An exemplified embodiment of the invention is described with reference to the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a sectional view of a chain hoist in accordance with the invention, and
FIG. 2 shows an enlargement of a section of FIG. 1 from the region of a slip clutch of the chain hoist.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a sectional view of a chain hoist 1 in accordance with an embodiment of the invention. The chain hoist 1 is driven by an electric drive motor 2 which is attached by its driven-side end to a housing 3 of the chain hoist 1. A slip clutch 4, a gearbox 5 and a chain wheel 6 are accommodated in the housing 3. The drive motor 2 comprises a motor shaft 2a whose driven-side end is connected to the gearbox 5 by means of the slip clutch 4. The slip clutch 4 consists substantially of a first clutch element 4a and a second clutch element 4b which are in engagement with one another by means of a friction lining 4c (see FIG. 2). The first clutch element 4a is disposed concentrically with respect to the motor shaft 2a and in a rotationally fixed manner on its driven-side end. The second clutch element 4b is disposed concentrically with respect to a gearbox input shaft 5a and in a rotationally fixed manner on its first end. In this case, the motor shaft 2a and the gearbox input shaft 5a are disposed—as seen in the longitudinal direction thereof—one behind the other and concentrically with respect to each other. At the opposite second end, the gearbox input shaft 5a is mounted in an outer wall 3a of the housing 3. This second end is engaged by an electrically releasable brake 7 which is supported externally on the outer wall 3a. The brake 7 is disposed under a cover 8 which is attached to the outer side of the outer wall 3a. The cover 8 provides sufficient space to accommodate electrical and/or electronic components in a protected manner.
In order to be able to adjust the slip clutch 4 and to be able to pretension the second clutch element 4b in the direction of the first clutch element 4a, on the one hand the gearbox input shaft 5a is mounted so as to be displaceable in its axial direction and on the other hand is supported on the inner side of the outer wall 3a by means of a spring element 9. Furthermore, the gearbox input shaft 5a is formed as a pinion shaft having a first gear wheel 10a which meshes with a second gear wheel 10b of the gearbox 3. The two gear wheels 10a, 10b thus form the first gear stage.
In the illustrated embodiment the first gear wheel 10a of the gearbox input shaft 5a is formed with an oblique toothing arrangement such that during operation of the chain hoist 1 the axial force effected by the oblique toothing arrangement in the longitudinal direction of the gearbox input shaft 5a leads to an increase in the frictional force of the slip clutch 4 during the lifting operation. This makes it possible to effect an automatic change in the activation moment, without changing the setting of the activation moment of the slip clutch 4, during operation of the chain hoist 1 as opposed to when the chain hoist 1 is at a standstill. This is associated with the advantage that when the direction of the flow of force is reversed in the gearbox 5 by hooking the chain onto the no-load side the axial force of the toothing arrangement counteracts the pretensioning of the spring element 9 and the torque which activates the slip clutch 4 is reduced. This reduces the risk of damage to the chain hoist 1.
Furthermore, the gearbox 5 comprises a gearbox output shaft 5b which extends in parallel with the gearbox input shaft 5a and is mounted laterally thereto in an offset manner in the housing 3. On the driven-side, the chain wheel 6 is disposed on the gearbox output shaft 5b in a rotationally fixed manner and concentrically with respect thereto, wherein a chain 11 of the chain hoist 1 can be moved in the lifting and lowering direction by means of the chain wheel. The gearbox input shaft 5a and the gearbox output shaft 5b are disposed in a gearbox chamber 5c which is defined by the housing 3. The gearbox chamber 5c is typically filled with a gearbox oil.
The chain hoist 1 can be suspended at a desired location by means of an eyelet, not illustrated, which engages the housing 3 externally and at the top.
FIG. 2 illustrates an enlargement of a section of FIG. 1 from the region of the slip clutch 4 of the chain hoist 1. It is apparent that the slip clutch 4 is disposed in a bore 12 in an intermediate wall 3b of the housing 3. The bore 12 has a circular cross-section with an inner surface 12a and inner diameter i which is slightly larger than the outer diameter d of the slip clutch 4. The slip clutch 4 is substantially cylindrical with a stepped outer surface 4d. Between the inner surface 12a of the bore 12 and the outer surface 4d of the slip clutch 4 there is a gap s which extends around the slip clutch 4 and is approximately in the range of 1 mm to 5 mm. In this case, the bore 12 extends with its bore wall 12b starting from the intermediate wall 3b in the direction of the drive motor 2 and the bore wall 12b forms a type of projection on the intermediate wall 3b. 
The slip clutch 4 consists substantially of the first clutch element 4a and the second clutch element 4b. The first clutch element 4a attached to the motor shaft 2a is essentially in the shape of a sleeve which has a flange projection and can be divided into a first attachment part 4e and a flange-like first clutch disk part 4f. The attachment part 4e and the clutch disk part 4f differ substantially by virtue of their mutually different outer diameters a, b. The outer diameter a of the attachment part 4e changes suddenly into the outer diameter b of the clutch disk part 4f. As a consequence, the clutch disk part 4f has an annular bearing surface 4g formed thereon, against which lies the inner ring 13a of a ball bearing 13, by means of which the attachment part 4e and thus the motor shaft 2a inserted therein are supported on the inner surface 12a of the bore 12. Adjacent to the ball bearing 13 as seen in the direction of the drive motor 2, a sealing ring 14 is placed onto the attachment part 4e and is supported externally on the inner surface 12 of the bore 12 and therefore seals the attachment part 4e in the bore 12 and thus the gearbox chamber 5c. 
It is also apparent from FIG. 2 that the clutch disk part 4f of the clutch 4 comprises a circumferential peripheral surface 4h which is not formed in a planar manner but instead has recesses 15. The recesses 15 have the function of enlarging the peripheral surface 4h and thus improving the dissipation of heat from the clutch 4 into the gearbox oil. These recesses 15 are formed as circumferential thread pitches, wherein the mobility of the thread pitches is selected such that during the lifting operation of the chain hoist 1 gearbox oil is conveyed by the thread pitches into the bore 12. During the lowering operation, conveyance also takes place, since the thread pitches convey the gearbox oil out of the bore 12 and therefore fresh gearbox oil flows subsequently from the gearbox chamber 5c. Moreover, the clutch disk part 4f is over-dimensioned in relation to the required mechanical strength, in order to improve the absorption of the frictional heat of the clutch 4 on account of the mass present as a result. By reason of the improvement in cooling, the first clutch disk part 4f can be disposed completely in the bore 12.
It is also possible to vary the shape and pitch of the thread pitches. It is also feasible to use multi-pitch threads or grooves which are aligned in the longitudinal direction of the motor shaft, in order to create a type of bucket wheel effect.
In contrast to the first clutch element 4a, the requirements for sufficient cooling of the second clutch element 4b can be met more easily, since the second clutch element 4b is disposed at an end of the bore 12 facing the gearbox chamber 5c and therefore can deliver the frictional heat easily to the gearbox oil. The second clutch element 4b is basically of the same design as the first clutch element 4a, wherein the recesses 15 and the over-dimensioning are not required. Accordingly, the second clutch element 4b is in the shape of a sleeve which has a flange projection and can be divided into a second attachment part 4i and a flange-like second clutch disk part 4j. The second attachment part 4i and the second clutch disk part 4j differ substantially by virtue of their mutually different outer diameters e, f. The outer diameter e of the attachment part 4i changes suddenly into the outer diameter f of the clutch disk part 4j. This creates on the second clutch disk part 4j an annular second clutch surface 4l, to which the annular friction lining 4c is adhered. The friction lining 4c lies with its opposite friction surface against the first clutch surface 4k of the second clutch disk part 4j. The first annular clutch surface 4k is disposed in parallel with the bearing surface 4g of the first clutch disk part 4f and lies against the side of the first clutch disk part 4f opposite the bearing surface 4g. 
Furthermore, the second clutch disk part 4j comprises an annular surface 4m which is in parallel with and opposite to the second clutch surface 4l, is disposed at the end of the bore 12 and faces the gearbox chamber 5c. Accordingly, the second clutch element 4b can be cooled effectively via its annular surface 4m. 
FIG. 2 also shows that the second clutch element 4b is inserted with its second attachment part 4i into a clutch bore 16 in the interior of the first clutch disk part 4f and is mounted via a needle bearing 17. Accordingly, the outer diameter e of the second attachment part 4i is smaller than the inner diameter of the clutch bore 16. As a consequence, the friction lining 4c can come to lie against the first clutch surface 4k of the first clutch element 4a. 
LIST OF REFERENCE NUMERALS


    1 chain hoist
    2 drive motor
    2a motor shaft
    3 housing
    3a outer wall
    3b intermediate wall
    4 slip clutch
    4a first clutch element
    4b second clutch element
    4c friction lining
    4d outer surface
    4e first attachment part
    4f first clutch disk part
    4g bearing surface
    4h peripheral surface
    4i second attachment part
    4j second clutch disk part
    4k first clutch surface
    4l second clutch surface
    4m annular surface
    5 gearbox
    5a gearbox input shaft
    5b gearbox output shaft
    5c gearbox chamber
    6 chain wheel
    7 brake
    8 cover
    9 spring element
    10a first gear wheel
    10b second gear wheel
    11 chain
    12 bore
    12a inner surface of the bore 12
    13 ball bearing
    13a inner ring of the ball bearing 13
    14 sealing ring
    15 recesses
    16 clutch bore
    17 needle bearing
    a outer diameter of the first attachment part 4e 
    b outer diameter of the first clutch disk part 4f 
    d outer diameter of the clutch 4
    e outer diameter of the second attachment part 4i 
    f outer diameter of the second clutch disk part 4j 
    i inner diameter of the bore 12
    s gap

## Claims

1. Chain hoist having an electric drive motor which is connected to a gearbox by a slip clutch, wherein in order to improve the dissipation of heat the slip clutch has an enlarged outer surface in the form of recesses disposed in the outer surface of the slip clutch, wherein the recesses in the outer surface of the slip clutch are formed circumferentially in the form of a thread pitch.

2. Chain hoist as claimed in claim 1, wherein the slip clutch comprises a sleeve-shaped first clutch element having a first annular clutch surface and a sleeve-shaped second clutch element having a second annular clutch surface, and a friction lining is disposed between the first clutch surface and the second clutch surface.

3. Chain hoist as claimed in claim 2, wherein the first clutch element comprises a sleeve-shaped first attachment part and a sleeve-shaped first clutch disk part adjoining it, the second clutch element comprises a sleeve-shaped second attachment part and a sleeve-shaped second clutch disk part adjoining it, and in order to improve the dissipation of heat the outer surface is disposed in the region of the peripheral surface of the first clutch disk part.

4. Chain hoist as claimed in claim 2, wherein the slip clutch is disposed in a bore of a housing of the gearbox.

5. Chain hoist as claimed in claim 4, wherein the outer surface of the slip clutch is cylindrical and wherein a gap is disposed between the cylindrical outer surface of the slip clutch and an inner surface of the bore.

6. Chain hoist as claimed in claim 4, wherein the housing has a gearbox chamber disposed inside it which is connected to the bore and is filled with a gearbox oil.

7. Chain hoist as claimed in claim 6, wherein the outer surface of the slip clutch is cylindrical and wherein a gap is disposed between the cylindrical outer surface of the slip clutch and an inner surface of the bore.

8. Chain hoist as claimed in claim 3, wherein the second attachment part is inserted into the first clutch element.

9. Chain hoist as claimed in claim 8, wherein the slip clutch is disposed in a bore of a housing of the gearbox.

10. Chain hoist as claimed in claim 9, wherein the housing has a gearbox chamber disposed inside it which is connected to the bore and is filled with a gearbox oil.

11. Chain hoist as claimed in claim 10, wherein the outer surface of the slip clutch is cylindrical and wherein a gap is disposed between the cylindrical outer surface of the slip clutch and an inner surface of the bore.

12. Chain hoist as claimed in claim 9, wherein the outer surface of the slip clutch is cylindrical and wherein a gap is disposed between the cylindrical outer surface of the slip clutch and an inner surface of the bore.

13. Chain hoist as claimed in claim 3, wherein the slip clutch is disposed in a bore of a housing of the gearbox.

14. Chain hoist as claimed in claim 13, wherein the housing has a gearbox chamber disposed inside it which is connected to the bore and is filled with a gearbox oil.

15. Chain hoist as claimed in claim 13, wherein the outer surface of the slip clutch is cylindrical and wherein a gap is disposed between the cylindrical outer surface of the slip clutch and an inner surface of the bore.

16. Chain hoist as claimed in claim 14, wherein the outer surface of the slip clutch is cylindrical and wherein a gap is disposed between the cylindrical outer surface of the slip clutch and an inner surface of the bore.

17. Chain hoist as claimed in claim 1, wherein the slip clutch is disposed in a bore of a housing of the gearbox.

18. Chain hoist as claimed in claim 17, wherein the housing has a gearbox chamber disposed inside it which is connected to the bore and is filled with a gearbox oil.

19. Chain hoist as claimed in claim 17, wherein the outer surface of the slip clutch is cylindrical and wherein a gap is disposed between the cylindrical outer surface of the slip clutch and an inner surface of the bore.

20. Chain hoist as claimed in claim 18, wherein the outer surface of the slip clutch is cylindrical and wherein a gap is disposed between the cylindrical outer surface of the slip clutch and an inner surface of the bore.