GB2287447A

GB2287447A - Cable clamping device for a cable in tension

Info

Publication number: GB2287447A
Application number: GB9504305A
Authority: GB
Inventors: Walter Schroeder
Original assignee: MAN Gutehoffnungshutte GmbH
Current assignee: MAN Gutehoffnungshutte GmbH
Priority date: 1994-03-17
Filing date: 1995-03-03
Publication date: 1995-09-20
Anticipated expiration: 2015-03-03
Also published as: GB9504305D0; AU1366995A; AU694751B2; GB2287447B; DE4409191C1; ZA952064B

Description

2287447 CABLE CLAMPING DEVICE FOR A CABLE LOADED IN TENSION The present

invention relates to a cable clamping device for a cable loaded in tension.

Cable clamping devices are used for, inter alia, the detachable fastening of conveying cables to a conveying cage or the like in a shaft conveyor installation. Usually, gutter rings are used for this purpose, in which a wedge-shaped gutter ring core, around which the cable end is laid in a loop, i s mounted to be displaceable in a gutter ring housing narrowing in wedge shape and is clamped against the housing by the cable tension, for example as illustrated in Lueger, I'Lexikon der Technik", Volume 1, 1960, page 415, Figure 9. A cable gutter ring with circular gutter ring core, but which is not displaceable and has no clamping function, is known from DE 42 39 298 Al.

Gutter rings are expensive to manufacture, since the housing and the gutter ring core require precision production in order to ensure that the opening angle is maintained exactly. Production errors impair the security of the cable clamping. A further disadvantage consists in that the cable is clamped in self-locking manner in the gutter ring under tension loading, so that release of the cable clamping is possible only with very high expenditure of force, frequently with the use of hydraulic piston-cylinder units. Contamination and encrustation of the gutter ring, which can occur in dirty shafts, make the release process more difficult or even impossible.

A clamping device for the catching of a drill rod linkage, which can in theory also be used for the clamping of a stretched traction cable and which hasa pivotable clamping body and a counterbearing member cooperable with the body, is known from DE 41 04 896. Similar types of cable clamps for clamping cables on sailing boats are known as Curry clamps. However, these known clamping devices serve for the catching or brief holding of the linkage or cable and are not suitable in this form for a permanent, operationally reliable and highly loadable connection of a cable with a load, such as a conveying cage, carried by a cable.

The project of the invention is therefore to provide a cable clamping device which may ensure a reliable and highly loadable fixing of a cable, whilst at the same time being gentle on the cable, may be more easily detachable than gutter rings and may be simpler to manufacture while permitting large tolerances.

According to the present invention there is provided a cable clamping device for a cable loaded in tension, comprising a clamping body mounted to be pivotable about a pivot axis and having a circumferential surface or surface portion curved eccentrically with respect to the pivot axis and a counterbearing member co-operable with the body for clamping of the cable therebetween, the body and member being so arranged that the cable can extend around the circumferenti'al surface or surface portion for at least 90" between the point of first contact therewith and the region of clamping at the member and that tensioning of the cable causes pivotation of the body about the pivot axis in the sense of generating increased clamping pressure between the body and the member.

t c t Preferably, the clamping body is a round, eccentrically mounted clamping sheave. The angle of looping of the cable around the body is preferably at least 1800, for preference about 2700.

The direction of tension on the cable is preferably about parallel to the direction of the contact pressure against the counterbearing member.

The eccentricity of the clamping sheave is preferably one quarter and one half the radius of the sheave. The member may have a shape concavely rounded out concentrically with the sheave, and is, for preference, mounted to be pivotable. The body itself is preferably resiliently biassed, such as spring-loaded, inthe direction of pivotation reinforcing the pressure against the member.

The device may further comprise a housing with two side walls, between which the member and the body are arranged. The housing can be provided with attachment means for a load to be carried by the cable.

Due to the combination of a cable clamping with a looping angle of the cable borne in front thereof, a part of the cable tension is taken up through looping friction directly by the clamping body, so that only the remaining part of the tension force has to be taken up the actual clamping of the cable between the body and the member. The clamping device can therefore be loaded with - in which case absorption of the force takes place very high forces,, not only locally at the clamping location, but over the entire looping region of the cable, so that the cable is not overly stressed. By contrast to cable gutter rings, the cable looped T around the body can, apart from the region of the member, be exposed towards the side in the clamping device, so that the cable can easily be inspected at any time. In addition, no unventilated clamping zones are present, in which, for example, zones of corrosion can form. When the cable is not loaded, the clamping device is easily releasable, for example by tension at the cable free end.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic side elevation of a first cable clamping device embodying the invention; Fig. 2 is a schematic side elevation of a second cable clamping device embodying the invention; and Fig. 3 is a cross-section, to enlarged scale, along the line A-A of Fig. 2.

Referring now to the drawings in Fig. 1 there is shown a cable clamping device in which a fixedly located counterbearing member 2 is mounted at a housing 1, which in the simplest case can be a flat pl ate. A circular clamping sheave 3 is mounted eccentrically, so as to be rotatable about a bearing pin 4, at the housing or plate 1.

he eccentricity, i.e. the spacing between the axis of the bearing pin 4 and thle centre axis M of the sheave 3, is preferably between 1/4 and 1/2 the radius of the sheave. A cable S to be fastened is clamped between the circumference of the sheave and the counterbearing 2 and then so laid around the circumference of the C 0 clamping sheave 3 that a looping angle 4 of about 2700 is present between the first point of contact A of the cable 5 with the sheave 3 and the counterbearing 2. A tension force K acting on the cable 2 exerts a turning moment of the sheave 3 in such a manner that the clamping of the cable between the sheave and the counterbearing is reinforced. However, an appreciable part of the tension force K need not be taken up by the clamping force at the counterbearing, but is transmitted to the sheave through friction in the region of the cable looping angle. The formula is K = K' - ePcC according to Eytelwein applies, wherein K is the tension force of the cable, K' the clamping force at the counterbearing 2, p the coefficient of friction between the cable and the circumference of the clamping sheave 3 and or- the looping angle.

In the case of the embodiment illustrated in Figs. 2 and 3, the housing of the clamping device consists of two side plates 6 and 7 (only plate 6 is shown in Fig. 2), between which the counterbearing 2 is mounted to be pivotable on a strong rotary pin g. The clamping sheave 3 is mounted to be rotatable -between the side plates 6 and 7 on a further rotary pin 11, and in particular eccentrically of the centre axis M of the sheave 3. The cable 5 is laid around the sheave 3 in such a manner that its end S E is clamped between the sheave 3 and the counterbearing 2 and a looping angle of about 270 is present between the first point of contact A of the cable S on the sheave 3 and the centre of the counterbearing 2.

This has the additional advantage that the direction of tension of the cable S is at least approximately parallel to the direction of the clamping force exerted on the counterbearing by the sheave via cable end S P The end face 2a, which faces the clamping shave 3, of the counterbearing 2 is concavely rounded concentrically with the sheave, so that the clamping force can distribute itself substantially over the rotatability 1 the entire width of the counterbearing. Due to of the counterbearing 2 about the pin 9, the counterbearing can bear uniformly against the cable end S E over its entire width.

The clamping device according to Fig. 2 further comprises a receptacle 13a for attachment of a load, for example the conveying cage of a shaft conveyor, to be carried by the cable. This load receptacle 13 consists, in the illustrated embodiment, of a projection at at least one of the side plates 6 and 7 and an opening 13a, which is formed in the projection and through which, for example, a pin can be inserted for fastening thereto of the load to be suspended. The load receptacle is so arranged that it aligns itself with the axis of the tension-loaded cable S.

When the cable is loaded in tension, the friction of the cable at the clamping sheave 3 produces a turning moment at the sheave, which is directed counterclockwise in Fig. 2 and acts in the sense of an increased contact pressure between the sheave and the counterbearing. In order to achieve an initial clamping force, a I', biassing spring 15 can be provided, which produces a turning moment in the same direction independently of the tension force of the cabl e. To release the cable clamping whe the cable is relieved of tension, it is only necessary to exert a turning moment in opposite direction, i.e. clockwise in Fig. 2, on the clamping sheave 3. This can be effected, for example, through tension at the cable end S E As illustrated, the housing of the clamping device consists only of the two side plates 6 and 7, which are connected by the pins 9 and 11, but has no end side walls. Consequently, the cable laid around the clamping sheave is freely visible and is accessible from all sides with the exception of the portion clamped below the counterbearing 2. The cable is therefore able to be inspected all round and checked at any time, and it has full air access so that no corrosion zones can form. The manufacture of the clamping deivce is extremely simple. The side plates 6 and 7 need no machining apart from for the bores for the pins 9 and 11 and the bores 13a for the load pin. The clamping sheave 3 is a turned part and and therefore able to be manufactured cheaply and accurately. The entire clamping force, i.e. the maximum tension loading of the fastening device, is higher than for conventional gutter rings.

Changes in and refinements of the described embodiments are possible within the scope of the invention as defined in the appended cl aims. Thus, although a circular shape of the clamping body or sheave is preferred, it is not the only possible shape. The clamping body can also be oval or can have the shape of a semicircle or a sector with a circumferential surface curved eccentrically to the rotational axis 11 over only the angular region against which the cable lies. The looping angle of the cable around the body need not be 270', but can be smaller, for example 180' or 90'. Additional measures can be provided to increase operational reliability; for example, a locking of the clamping sheave 3 can be provided so that no undesired loosening of the cable clamping arises in the case of the cable being relieved of tension, i.e. if cable is slack.

In a further modification of the embodiment, the cable 5 can be laid with more than one loop around the cable sheave 3, for example with a looping angle of 540 or 720. In this case, the clamping sheave is to be constructed to be correspondingly thicker, so that at least two cable turns can find space one beside the other. However, the counterbearing 2 acts on only one of the cable turns, namely that with the cable free end. The appropriate constructional form of the clamping device will be apparent to the expert.

e 01 1 111 z

Claims

1. A cable clamping device for a cable loaded in tension, comprising a clamping body mounted to be pivotable about a pivot axis and having a circumferential surface or surface portion curved eccentrically with respect to the pivot axis and a counterbearing member co-operable with the body for clamping of the cable therebetween, the body and member being so arranged that the cable can extend around the circumferential surface or surface portion for at least 90 between the point of first contact therewith and the region of clamping at the member and that tensioning of the cable causes pivotation of the body about the pivot axis in -the sense of generating increased clamping pressure between the body and the member.

2. A device according to claim 1, wherein the clamping body is a circular cable sheave pivotably mounted eccentrically of its centre axis.

3. A device according to claim 1 or claim 2, wherein said angle is at least 180'.

4. A devi.ce -according to cl aim 3, wherein said angle is substantially 2700 - 10

5. A device according to any one of the preceding claims, wherein the direction of the tension loading on the cable is substantially parallel to the direction of contact pressure against the member.

6. A device according to claim 2 or any one of claims 3 to 5 when appended to claim 2, wherein the pivot axis of the sheave is spaced from the centre axis thereof by substantially one quarter to one half of the radius of the sheave.

7. A device according to claim 2 or any one of claims 3 to 5 when appended to claim 2, wherein the member has a concave surface portion concentric with the circumferential surface of the sheave.

8. A device according to any one of the preceding claims, wherein the member is mounted to be pivotable.

9. A device as according to any one of the preceding claims, wherein the body is resiliently biassed in said sense of pivotation thereof.

10. A device according to any one of the preceding claims, comprising a housing with two side walls, the body and member being arranged between the walls.

11. A device according to claim 10, wherein the housing is provided withmeans for attachment of a load to be carried by the cable.

01

12. A cable cl amping device substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawing.

13. A cable cl ampi ng device substantially as hereinbefore described with reference to Fig. 2 and 3 of the accompanying drawing.