GB2323649A

GB2323649A - Nut slackening indicator

Info

Publication number: GB2323649A
Application number: GB9801219A
Authority: GB
Inventors: Grant Paul Cadman
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-03-25
Filing date: 1998-01-22
Publication date: 1998-09-30
Anticipated expiration: 2018-01-22
Also published as: GB2323649B; GB9706126D0; GB9801219D0

Abstract

A retaining collar 3 is secured to an end face of a nut 1 and defines an annular cavity co-axial with the threaded through bore 2 of the nut 1. A resiliently deformable ring 4 is retained within the cavity, also co-axial with the threaded through bore 2 in the nut 1, which exerts a greater frictional grip on a bolt or threaded stud than the threads of the threaded through bore 2 in the nut 1. The ring 4 carries a lug 9 which projects into a circumferentially extending slot 6 in the retaining collar 3 defining first and second circumferentially spaced end faces 7,8 and is rotatable in the annular cavity relative to the nut 1. When the nut 1 is rotated to the left the lug 9 is brought into abutment with the first end face 7 and when rotated to the right it is brought into abutment with the second end face 8.

Description

DESCRIPTION AN INDICATOR DEVICE The present invention relates to an indicator device for indicating slackening of a nut wound onto a bolt or threaded stud.

After any length of time a nut which has been tightened onto a bolt or threaded stud may begin to slacken off, particularly if it is subject to high levels of vibration. If this is not remedied the nut may slacken off to such an extent that a hazardous situation arises.

For certain applications it may be possible to use locking nuts which are much less prone to slackening off than ordinary nuts.

However, there are many applications where locking nuts are not suitable because the nut must be removed from time to time. By way of example one may consider the nuts securing the wheels of a vehicle to the vehicle axles.

Conventional nuts give no indication of slackening off and therefore the only way of checking if they have is to periodically retighten them.

It is an object of the present invention to provide an indicator device which can be used in combination with a nut to provide a visual indication of the nut slackening off.

It is another object of the present invention to provide a nut comprising an integral indicator device.

According to the present invention there is provided an indicator device for use in combination with a nut to show a slackening of the nut when wound onto a bolt or threaded stud, comprising a retaining collar adapted to be secured to an end face of the nut and defining an annular cavity co-axial with the threaded through bore of the nut and a ring retained within the cavity also co-axial with the threaded through bore in the nut which ring is adapted to exert a greater frictional grip on the bolt or threaded stud than the threads of the threaded through bore in the nut wherein the ring carries a lug which projects into a circumferentially extending slot in the retaining collar defining first and second circumferentially spaced end faces and is rotatable in the annular cavity relative to the main body such that when rotated to the left the lug is brought into abutment with the first end face and when rotated to the right it is brought into abutment with the second end face.

In one embodiment of the present invention the retaining collar is of L-shaped section and extends from an end face of the nut so as to define therewith the said annular cavity in which the indicator ring is received.

In another embodiment of the present invention the retaining collar comprises a C-shaped section which defines the annular cavity in which the indicator ring is received and a skirt which is adapted to fit over a nut to retain the retaining collar in place thereon.

The retaining collar is fitted in place onto the nut after the nut has been tightened onto a bolt or stud. This is achieved by pushing or tapping it over the bolt or stud and onto the nut. In order to ensure that the bolt or stud is securely gripped by the indicator ring, an additional grip ring may be provided between it and the bolt or stud. The grip ring protrudes from an annular slot or groove provided in the inside face of the indicator ring.

Preferably, the skirt defines an open-ended hexagonal cavity of the same dimensions as the nut on which the retaining collar is fitted.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic plan view of a nut comprising one embodiment of an indicator device in accordance with the present invention; Fig. 2 shows a section through the nut of Fig. 1 along lines A-A; Fig. 3 shows a section through the nut of Fig. 1 along lines B-B; and Fig. 4 shows a sectional view through another embodiment of an indicator device according to the present invention.

Referring to the drawings the nut comprises a steel body 1 of hexagonal section, having an axially extending threaded through bore 2 therein. A retaining collar 3 of L-shaped section extends from an end face of the steel body 1 and defines therewith an annular cavity co-axial with the through bore 2. Located in the cavity between the end face of the steel body 1 and the retaining collar 3 is a ring 4 of resiliently deformable material, for example, nylon. The ring 4 is also co-axial with the through bore 2 and has an internal diameter which is greater than the inner diameter of the threads 5 of the through bore 2 and less than the outer diameter thereof.

A section of the retaining collar 3 is cut away to define a circumferentially extending slot 6 the ends of which are defined by end faces 7 and 8 of the retaining collar 3.

The ring 4 is loosely retained within the cavity between the end face of the steel body 1 and the retaining collar 3 and as such it is capable of rotating relative thereto. However, this rotation is limited to the length of the slot 6 in the retaining collar 3 by a narrow lug 9 which projects from the ring 4 into the slot 6. As will become apparent hereinbelow when the ring 4 is rotated clockwise relative to the steel body 1 the lug 9 abuts against the end face 7 of the slot 6 and when it is rotated anti-clockwise the lug 9 abuts against the end face 8.

In use the nut is wound onto a bolt or threaded stud with the steel body to the inner end thereof. Turning the nut clockwise to tighten it eventually brings the ring 4 against the end of the bolt/stud.

Initially, further rotation of the nut causes the ring 4 to rotate anticlockwise relative to the steel body 1 as there is no turning force exerted upon it. However, as soon as the lug 9 abuts up against the end face 7 of the slot 6 the ring 4 is forced to rotate with the steel body 1 and is screwed onto the bolt/stud. As the ring 4 is wound onto the bolt/stud a thread is cut into it. However, because the ring 4 is comprised of a resiliently deformable material it grips the bolt/stud much more forcibly than the steel body 1 and exhibits considerably more resistance to turning forces applied to it than does the steel body 1.

When the nut has been tightened onto the bolt/stud to the required torque tightening stops. The nut now rests on the bolt/stud with the lug 9 in close abutment with the end face 7 of the slot 6.

If, over a period of time, the nut begins to slacken off this manifests itself in the following way. The steel body 1 turns anticlockwise on the bolt/stud at a faster rate than the ring 4 due to the greater frictional force exerted on the bolt/stud by the ring 4.

Consequently, the end face 8 of the slot 6 in the retaining collar 3 moves towards the lug 9. Further slackening off of the nut will cause the ring 4 to rotate at the same rate as the steel body 1 once the end face 8 abuts against the lug 9. However, the movement of the lug 9 from one end of the slot 6 to the other provides an immediate visual indication of the slackening off of the nut.

In order to emphasise any change of position of the lug 9 in the slot 6, that side of the ring 4 to the right of the lug 9 may have one colour and that to the left a different colour. In this way as the nut slackens off the colour viewed in the slot 6 will change.

In the embodiment of the present invention described hereinabove the ring 4 is described as being of a resiliently deformable material having no internal thread pre-cut in it. It will be appreciated that alternative forms of ring may be employed. The essential requirement of the ring is simply that it should exert a greater frictional grip on the threads of the bolt/stud than the steel body of the nut.

It will also be appreciated that the present invention can be applied to left hand threaded nuts as well as right hand threaded ones.

Referring now to Fig. 4 of the drawings there is shown an alternative embodiment of an indicator device in accordance with the present invention. Essentially, this embodiment of the invention is the same as the embodiment of Figs. 1 to 3. The difference is that the retaining collar takes the form of a cap which is fitted by either being pushed or tapped onto a nut. The upper part of the cap defines an annular cavity of C-shaped section between inner and outer skirt members 10 and 11, in which is received the indicator ring 12. The internal face of the inner skirt member 11 has an hexagonal finish which slides over the nut. Although not visible a slot is provided in the upper surface of the C-shaped section to accommodate the indicator lug 13 which serves to indicate slackening of a nut when tightened onto a bolt. In this regard the slot corresponds with the slot 6 and the lug 13 with lug 9 in the embodiment of Figs. 1 to 3.

The cap is held in place by the friction between the protruding threads of a bolt and the indicator ring 12. If required an additional grip ring 14 can be fitted, for added friction between the thread and the indicator ring 12. The indicator ring 12 is allowed to rotate within the cavity created between the inner and outer skirt members 10 and 11.

Claims

1. An indicator device for use in combination with a nut to show a slackening of the nut when wound onto a bolt or threaded stud, comprising a retaining collar adapted to be secured to an end face of the nut and defining an annular cavity co-axial with the threaded through bore of the nut and a ring retained within the cavity also coaxial with the threaded through bore in the nut which ring is adapted to exert a greater frictional grip on the bolt or threaded stud than the threads of the threaded through bore in the nut wherein the ring carries a lug which projects into a circumferentially extending slot in the retaining collar defining first and second circumferentially spaced end faces and is rotatable in the annular cavity relative to the nut such that when rotated to the left the lug is brought into abutment with the first end face and when rotated to the right it is brought into abutment with the second end face.

2. An indicator device according to claim 1, wherein the retaining collar is of L-shaped section and extends from an end face of the nut so as to define therewith the said annular cavity in which the indicator ring is received.

3. An indicator device according to claim 1, wherein the retaining collar comprises a C-shaped section which defines the annular cavity in which the indicator ring is received and a skirt which is adapted to fit over a nut to retain the retaining collar in place thereon.

4. An indicator device according to claim 3, wherein an additional grip ring is provided between the indicator ring and the bolt or stud in order to ensure that the bolt or stud is securely gripped by the indicator ring.

5. An indicator device according to claim 4, wherein the grip ring protrudes from an annular slot or groove provided in the inside face of the indicator ring.

6. An indicator device according to claim 3, 4 or 5, wherein the skirt defines an open-ended hexagonal cavity of the same dimensions as the nut on which the retaining collar is fitted.

7. An indicator device for use in combination with a nut, substantially as hereinbefore described with reference to the accompanying drawings.