GB2307531A

GB2307531A - Method of locking rotation and tensioning coupling using such

Info

Publication number: GB2307531A
Application number: GB9702071A
Authority: GB
Inventors: Basil Ludkin
Original assignee: DRALLIM IND
Current assignee: DRALLIM IND
Priority date: 1996-02-07
Filing date: 1997-01-31
Publication date: 1997-05-28
Anticipated expiration: 2017-01-31
Also published as: GB9702071D0; GB2307531B

Abstract

Rotation of an inner body, e.g. a hollow cylinder 24, is allowed in one direction but prevented in the other, within an outer sleeve 23 by a spring 30 between them and cooperating with them. A tensioning coupling comprises two cylindrical bodies, each being provided with a respective connector and being arranged for linear movement with respect to each other. The first body comprises a threaded rod 22 and the outer sleeve 23 spaced apart therefrom, the second body comprising the hollow cylinder threadedly engaging the rod 22. The spring 30 engaging around the outer surface of the cylinder 24, has its ends 31 located in apertures 33 of the sleeve 23, one aperture retaining the end 31 fixed and the other being elongate to allow end movement. This allows for spring diameter to increase in one rotational direction to allow rotation of the cylinder 24 in the sleeve 23, e.g. for increasing tension in the coupling.

Description

TENSIONING COUPLING The present invention relates to a tensioning coupling, in particular a tensioning coupling of the type wherein the length of the coupling is adjusted by means of mutually rotating elements.

Often, when bulky articles are transported, they are held in place using chains or straps. To prevent movement, the chains or straps must be appropriately tensioned.

Typically, this is achieved using two shackles or similar connectors, one secured to a threaded shaft, the other to a threaded sleeve, the shaft being threaded into the sleeve.

Such tensioning couplings are effective and easy to use. However, they have a tendency to unwind or back off under vibration. This could result in particular problems when transporting hazardous cargo.

In its broadest sense, the present invention provides a method of locking rotation of a shaft within a sleeve, the method comprising providing a helical spring around the outer surface of the shaft, the spring being mounted co-operably between the shaft and sleeve such that rotation of the shaft within the sleeve is prevented in one direction, but allowed in the opposite direction.

A helical spring will ordinarily, of course, have two ends. Preferably, each end engages a respective engagement means in or on the sleeve. Preferably, the first engagement means is adapted to substantially prevent rotational movement of one end of the spring with respect to the sleeve, whilst the second engagement means is adapted to allow a degree of such rotational movement. Typically, the engagement means are in the form of apertures provided in the sleeve. Typically, the first aperture is of substantially the same dimensions as the cross-section of the end of the spring, whilst the second aperture is of a generally elongate shape.

In particular, the present invention also provides a tensioning coupling comprising two cylindrical bodies, each body being provided at one end thereof with a respective connector and being arranged for linear movement with respect to each other, wherein the first body comprises a threaded rod and a concentric outer sleeve spaced apart therefrom, and the second body comprises an internally-threaded hollow cylinder, the threaded rod being arranged to cooperate with the corresponding thread of the second body; wherein a helical spring is provided around the outer surface of the hollow cylinder, the spring being mounted co-operably between the hollow cylinder and the outer sleeve such that rotation of the cylinder within the sleeve is prevented in one direction, but allowed in the opposite direction.

As described above, a helical spring will ordinarily have two ends, and each end engages a respective engagement means in or on the outer sleeve. Preferably, the first engagement means is adapted to substantially prevent rotational movement of one end of the spring with respect to the sleeve, whilst the second engagement means is adapted to allow a degree of such rotational movement. Typically, the engagement means are in the form of apertures provided in the sleeve. Typically, the first aperture is of substantially the same dimensions as the cross-section of the end of the spring, whilst the second aperture is of a generally elongate shape.

Preferably, rotation of the cylinder within the sleeve is prevented by virtue of the spring reducing in diameter thereby engaging the hollow cylinder. Alternatively, the diameter of the spring is increased, thereby bearing upon the inner surface of the outer sleeve, to prevent rotation.

The above and other aspects of the present invention will now be described in further detail, by way of example only, with reference to the accompanying figures, in which: Figure 1 is a perspective side view, partly in section, of a tensioning coupling in accordance with the present invention; Figure 2 is a schematic part sectional view of the embodiment of Figure 1; Figure 3 shows a hollow cylinder of the embodiment of Figure 1, together with a helical spring; Figure 4 shows the hollow cylinder of Figure 3 mounted together with an outer sleeve; Figure 5 shows a cut-away view of a part of the embodiment of Figure 1; and Figures 6 and 7 illustrate respectively locked and unlocked configurations of the embodiment of Figure 1; and Figures 8 shows a slightly different embodiment of a tensioning coupling in accordance with the present invention.

Referring to Figures 1 and 2, an embodiment of a tensioning coupling 10 in accordance with the present invention has at one end thereof a first connector 11, as shown - a shackle, and at the other end thereof a second connector 12. As shown, typically second connector 12 will be of a conventional type for receiving and securing a chain 13 by means of a rotatable chain locking ring 51, the chain being attached to a further shackle 14. A half turn of the chain locking ring 51 secures the chain 13 in place. Typically, shackle 11 would be attached to a securing ring 15 or other suitable strongpoint and shackle 14 attached to the cargo or another link 16 in the lashing chain 13 (or vice versa, as appropriate). Figures 8 shows an alternative arrangement using a bowed shackle 61 secured with a drop-nosed pin 62.

Connector 11 forms a part of a first coupling body 20, and connector 12 correspondingly forms a part of a second coupling body 21. First coupling body 20 comprises a central threaded rod 22 (see Figure 2) and a concentric outer sleeve 23 spaced apart from threaded rod 22.

Second coupling body 21 includes an internally-threaded hollow cylinder 24 (see Figure 2) which is threaded onto rod 22 of the first coupling body and has an outer diameter less than the inner diameter of sleeve 23 to leave a space 26 therebetween.

Rotation of one coupling body 20, 21 with respect to the other adjusts the length of the coupling as a whole and thus, in use, the tension in the chain 13. Typically a handwheel 25 mounted upon cylinder 24 is provided to assist rotation of one body 20,21 with respect to the other.

We will now describe the mechanism for locking rotation of the two coupling body components with respect to each other. With particular reference to Figures 3 and 4, a helical spring 30 is provided around the hollow cylinder 24 of the second coupling body. Spring 30 is typically a 20 gauge ( lmm diameter) stainless steel wire and is wound to give a tight fit onto hollow cylinder 24 - an internal spring diameter (at rest) of about nine tenths of the outside diameter of cylinder 24 has been found to be particularly suitable. Spring 30 has two ends 31,32 bent outwardly to locate in corresponding apertures 33,34 in the outer sleeve 23. Aperture 33 is of such dimensions as to essentially prevent any rotation of the first end 31 of the spring 30 with respect to the outer sleeve 23.Aperture 34, however, is generally elongate to allow a certain degree of rotational movement of the second end 32 of the spring with respect to the outer sleeve 23.

As is more clearly shown in Figure 5, advantageously aperture 34 is enlarged and threaded to allow for insertion of a threaded bush 50 once end 32 of spring 30 has been located in aperture 34. This preferred embodiment aids in assembly of the apparatus.

With the spring wound in the direction shown in Figure 3 and viewed from the top and notionally keeping the outer sleeve 23 spatially fixed, rotation of the internallythreaded hollow cylinder 24 within outer sleeve 23 is possible clockwise but prevented in the anti-clockwise direction. In both cases, of course, the first end 31 is fixed relative to the outer sleeve. However, as soon as anti-clockwise rotation of cylinder 24 is attempted, the second end 32 of spring 30 moves towards (but avoids contacting) the (left-hand) edge 35 of elongate aperture 34. This closes the diameter of the spring 30 against the cylinder and friction between the spring and cylinder prevents rotation (Figure 6). In attempting clockwise rotation, end 32 of the spring 30 is free to move sufficiently to relax the frictional forces and thus allow rotation.

In the rest position, by virtue of the tight fit of the spring 30 against the cylinder 24, the natural spring-tension maintains a degree of grip against the cylinder such that the coupling cannot work lose of its own accord.

Furthermore, if the movable end 32 of the spring is manually pushed away from abutment with edge 35 of elongate aperture 34, the helix of the spring is opened up (Figure 7) thereby allowing rotation both clockwise and anti-clockwise.

With the screw-thread of the rod 22 and cylinder 24 and the helical spring wound in the same direction - as shown in Figure 3, clockwise as viewed from above - the locking mechanism serves to prevent loosening of the coupling unless the movable end 32 of the spring is purposefully moved to the 'unlocked' position. In other circumstances the reverse action may be preferred - positive action is required to tighten the coupling. Obviously, there are four combinations of thread and spring directions and the appropriate combination will be chosen depending upon the particular coupling operation required. A further advantage of the present arrangement is that as rotation in only one direction is allowed, any vibrations can actually result in self-tightening of the coupling.

As a further modification (not shown) of the arrangement described above, the locking mechanism may readily be adapted such that instead of gripping the hollow cylinder 24, the spring 30 expands to bear against the inner surface of the outer sleeve 23 in order to lock rotation.

In the preferred embodiment shown, an anti-backoff releasing sleeve 40 is provided engaging one end 32, of the spring. Simple rotation of the releasing sleeve 40 moves end 32 of the spring and thus releases the lock, avoiding the possibly fiddly operation with the end 32 of the spring alone.

A spring formed of a flat section wire may be preferred to a round section wire as a flat wire can be expected to result in less wear upon the surfaces of the cylinder 24 or outer sleeve 23.

Claims

1. A tensioning coupling comprising two cylindrical bodies, each body being provided at one end thereof with a respective connector and being arranged for linear movement with respect to each other, wherein the first body comprises a threaded rod and a concentric outer sleeve spaced apart therefrom, and the second body comprises an internally-threaded hollow cylinder, the threaded rod being arranged to cooperate with the corresponding thread of the second body; wherein a helical spring is provided around the outer surface of the hollow cylinder, the spring being mounted co-operably between the hollow cylinder and the outer sleeve such that rotation of the cylinder within the sleeve is prevented in one direction, but allowed in the opposite direction.

2. A tensioning coupling as claimed in Claim 1 wherein the helical spring has two ends each engaging a respective engagement means in or on the outer sleeve; wherein the first engagement means is adapted to substantially prevent rotational movement of one end of the spring with respect to the sleeve, whilst the second engagement means is adapted to allow a degree of such rotational movement.

3. A tensioning coupling as claimed in Claim 2 wherein the engagement means are in the form of apertures provided in the sleeve.

4. A tensioning coupling as claimed in any one of Claims 1 to 3 wherein rotation of the cylinder within the sleeve is prevented by virtue of the spring reducing in diameter thereby engaging the hollow cylinder.

5. A tensioning coupling substantially as herein described with reference to the accompanying drawings.

6. A method of locking rotation of a shaft within a sleeve, the method comprising providing a helical spring around the outer surface of the shaft, the spring being mounted co-operably between the shaft and sleeve such that rotation of the shaft within the sleeve is prevented in one direction, but allowed in the opposite direction.

7. A method as claimed in Claim 6 wherein the spring has two ends each engaging a respective engagement means in or on the outer sleeve; wherein the first engagement means is adapted to substantially prevent rotational movement of one end of the spring with respect to the sleeve, whilst the second engagement means is adapted to allow a degree of such rotational movement.

8. A method as claimed in Claim 7 wherein the engagement means are in the form of apertures provided in the sleeve.

9. A method as claimed in any one of Claims 6 to 8 wherein rotation of the shaft within the sleeve is prevented by virtue of the spring reducing in diameter thereby engaging the shaft.

10. A method of locking rotation of shaft within a sleeve substantially as herein described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. A tensioning coupling comprising two cylindrical bodies, each body being provided at one end thereof with a respective connector and being arranged for linear movement with respect to each other, wherein the first body comprises a threaded rod and a concentric outer sleeve spaced apart therefrom, and the second body comprises an internally-threaded hollow cylinder, the threaded rod being arranged to cooperate with the corresponding thread of the second body; wherein a helical spring is provided around the outer surface of the hollow cylinder, the spring being mounted co-operably between the hollow cylinder and the outer sleeve such that rotation of the cylinder within the sleeve is prevented in one direction, but allowed in the opposite direction.