GB2234797A

GB2234797A - Fixings

Info

Publication number: GB2234797A
Application number: GB8917541A
Authority: GB
Inventors: John Clifton
Original assignee: CENTRAL MOULDING SERVICES Ltd
Current assignee: CENTRAL MOULDING SERVICES Ltd
Priority date: 1989-08-01
Filing date: 1989-08-01
Publication date: 1991-02-13
Anticipated expiration: 2009-08-01
Also published as: GB2234797B; GB8917541D0

Abstract

An electrical light bulb fixing (21) is anchorable to a support and comprises a plug (25) for inserting into a hole in the support, a bolt (23) having a screwthreaded shank (29) engageable with a screwthread (28) in the plug, and a collar (24) coaxial of the shank (29). The plug (25) has deformable claws (27) that engage the collar (24) as the bolt (23) is screwed into the plug (25) to hold the collar (24) rotationally fast with the plug (25) and the collar (24) is moved axially into the plug causing ft to distort and anchor itself within the support. The collar (24) is rotatable about the bolt member (23) through a one-way ratchet mechanism allowing the bolt member to screw into the plug but preventing unscrewing.

Description

A FIXING This invention relates to a fixing and in particular, but not exclusively, to a fixing for securing an electrical fitting to a support and more particularly to a fixing for securing an electrical light bulb holder to a lamp base.

A typical prior art light bulb holder is illustrated in Fig. 1. The bulb holder 10 is mounted on a screw threaded spiyot 11 which passes through a hole 12 in lap base 13. The light bulb holder 10 is held to the base 13 by a pair of nuts 14 and 15 which clamp against a portion of the base 13 surrounding the hole 12 to secure the holder 10 to the base 13.

This prior art light bulb holder has a major disadvantage in that the nut located within the lamp base is difficult to access.

The present invention provides a fixing which can be anchored within a hole in a support from one side only.

Accordingly there is provided a fixing anchorable to a a support, and which comprises a plug for inserting into a hole in the support and which has a screwthreaded bore therein, a bolt member having a shank with a screwthread portion which is engageable with the screwthread in the plug, and a collar located coaxially on the shank and which is rotational relative to the shank, the collar being axially moveable towards the plug as the bolt member is screwed into the plug, said plug having deformable portions that are engageable with the collar as the bolt member is screwed into the plug so that the collar is held rotationally fast with the plug and is moved axially into the plug causing the plug to distort and thereby anchor the plug to the support.

The bolt member has at its end away from the plug a portion thereof adapted to receive a body for securing the body to the bolt member. Preferably the end portion is screwthreaded for receiving an electrical bulb holder.

Preferably the collar is rotational relative to the bolt member for one direction of rotation only allowing the bolt member to be screwed into the plug even when the collar is rotationally fast with the plug, but preventing the bolt member from being unscrewed due to the engagement between collar and the plug.

This is a safety precaution which prevents the bolt member from being unscrewed from the support e.g. a lamp base.

Also according to the invention there is provided a fixing for securing an electrical fitting to a cable and which comprises a bolt member having a coaxial bore through which an elctrical cable can pass, one end of the bolt member being attachable to a support, and the other end of the bolt member being adapted to receive an electrical fitting, the bolt member having integral fingers projecting in an axial direction only for gripping the cable, and a collar which fits coaxially on the bolt member to hold the fingers with their free ends in a gripping position.

Further there is provided a method of securing a fixing to a support , said fixing comprising a plug for inserting into a hole in the support and which has a screwthreaded bore therein, a bolt member having a shank with a screwthread portion which is engageable with the screwthread in the plug, and a collar located coaxially on the shank and which is rotational relative to the shank , the collar being axially moveable towards the plug , said plug having deformable portions that are engageable with the collar as the bolt member is screwed into the plug, wherein the plug is inserted into hole and the bolt member is screwed into the plug moving the collar into engagement with the plug thereby causing the plug to distort and engage the support.

The invention will be described by way of example and with reference to the accompanying drawings in which: Fig 2 is a longitudinal cross-section through a fixing according to one aspect of the invention Fig 3 is a view of a bolt member as is used in the fixing of Fig 2 Fig 4 is a view of a collar as is used in the fixing of Fig 2 Fig 5 is a plug as is used in the fixing o Fig 2 Fig 6 is a view of the bolt member taken on the line VI-VI of Fig 3 showing the Pawl mechanism on the bolt member Fig 7 is a view of the collar taken on the line VII-VII of Fig 4 showing the ratchet teeth on the collar, and Figs 8A & 8B are a schematic drawings showing the fixing attached to a support and with a light bulb holder in-situ.

Now with reference to Figs 2 - 7, there is described a fixing for securing a light bulb holder to a lamp base.

However it is considered that the fixing could be used to secure other components especially electrical fittings to any type of support.

The fixing 21 is shown in an assembled condition in Fig 2 and comprises three components, a bolt member 23 (Fig 3), a collar 24 (Fig 4) and a plug 25 (Fig 5).

The plug 25 in use will be inserted into a hole H in a lamp base B (see Fig 8) and comprises a cylindrical body 26 having an annular array of four equiangularly spaced axially extending flexible claws 27 projecting from one end of the body. The body 26 has a screwthreaded through bore 28 therein which is adapted to receive a like screwthreaded shank 29 of the bolt member 23. The plug is preferably formed as a plastic moulding and is preferably produced from nylon, polypropylene or acetal materials.

The bolt member 23 has cylindrical elongate body 30 with a coaxial through bore 31 and having at one axial end portion a first screwthreaded portion 32, and at its other axial end portion the shank 29. The two axial end portions being separated by a radially projecting annular flange 33. The first screwthreaded portion 32 in use provides a mounting point for some other body in this case a light bulb holder L (see Fig 8). Other well known mounting points such as bayonnette fittings could be used instead of the screwthread. The shank 29 has a pawl mechanism 34 adjacent the flange 33, a cable gripping device 35, and a screw threaded end portion 36 which in use engages with the screw threaded portion 28 of the plug 25. The pawl mechanism 34 is best seen in Fig 6 and comprises a pair of diametrically opposed flexible pawls 37 which extend tangentially from the bolt member body 30.The pawls 37 are sufficiently resilient to flex to allow rotation in one direction but not in the other.

The cable gripping device 35 comprises two diametrically opposed pairs of axially extending fingers 38 which are formed in the bolt member body 30 with their free ends adjacent the pawl mechanism 34. Opposed pairs of fingers have been found to provide a better grip on the external surface of a cable than single fingers. The radially outer surface of the fingers 38 is formed as a ramp that will stand proud of the bolt member body 30 so that the free ends of the fingers can be caused to move radially inwardly to grip an electrical cable passing through the bore 31. The bolt member 23 is preferably a plastics moulding formed from nylon, acetal or polypropylene.

The collar 24 has a "top hat" longitudinal section and fits coaxially around the shank 29 with its larger diameter portion 43 co-operating with the pawl mechanism 34 and its smaller diameter portion 45 with the fingers 38. The collar 24 has a stepped through bore therein, with a smaller diameter smooth bore 42 which is not engagable with the screw threaded portion 36 of the shank but which is engageable with the radially outer ramp surfaces on the fingers 38 to push the free ends of the fingers 38 radially inwardly to grip a cable.The end portion of the collar 24 which fits adjacent the flange 33 on the bolt member 23 has a larger diameter bore 40 which can pass over the pawl mechanism 34 and has an annular array of ratchet teeth 41 on its radially inner surface (best seen in Fig 7) which co-operates with the pawls 37 to allow rotation of the bolt member 23 relative to the collar 24 in one direction of rotation but not in the other direction. The radially outer surface of the collar has four equiangularly spaced flat ramp surfaces 44 which co-operate with the claws 27 on the plug so that as the collar is moved axially into the claws 27, the ramp surfaces 44 distort the free ends of the claws to grip the inner surface of the hole into which the fixing is anchored. The collar is again preferably a moulding formed from nylon, polystyrene, ABS or acetal resin.

In use, the collar 24 is pushed over the shank 29 so that the ratchet teeth 41 engage with the two pawls 37 on the bolt member body 30, and the larger diameter portion 43 of the collar is pushed into abutment with the flange 33 on the bolt member 23. The plug 26 is screwed onto the screwthreaded portion 36 of the shank 29 so that the claws 27 just engage with the flats 44 on the collar 24.

The assembled fixing is then taken and the plug 25 is pushed into the hole H in which it is to be anchored.

The plug 24 should be a push fit without any undue play and could have flexible ribs on its external surface to take up clearances.

The bolt member 23 is then screwed into the plug 25. The collar 24 is held stationary relative to the plug 25 and the bolt member 23 is allowed to rotate relative to the collar 24 by the pawl and ratchet teeth device 34/41 because the pawls 37 deflect allowing the ratchet teeth 41 to ride over. As the bolt member 23 is screwed into the plug 25, the collar 24 is moved axially into the plug 25 and the flats 44 on the collar futher engage with the claws 27 pushing them radially outwards to compress against the sides of the hole 11.When the bolt member 23 is fully screwed into the plug 25 the fixing is then fully anchored ( see Fig 8A If used with a thin walled support S as in Fig 8B , the plug is inserted beyond the hole H and as the bolt is screwed into the plug the collar causes the claws 27 to slay and engage against the back surface of the support S so that the support is clamped between the collar 24 and the claws 27. Using this method an electrical fitting can be secured to a thin walled lamp base, plaster board ,facia boarding or what have you.

Because the collar 24 is held rotationally fast in the plug 25 by the claws 27, and the one-way pawl and ratchet mechanism 34/41 now locks up and prevents rotation in the reverse direction, the fixing cannot be removed from its anchorage. This is particularly important for preventing tampering with electrical connections. The lamp holder L can then be screwed onto the screw threaded portion 32.

Alternatively, if desired ,the lamp holder 'L' could be assembled to the screwthreaded portion 32 with an electrical cable 'C' passing through the bore 31 in the bolt member body 30, before the fixing is anchored to its support. When the collar 24 is pushed into place on the shank 29 the cable is then held in position by the free ends of the fingers 38 digging into the outer layer of the cable. The process then continues as before.

Since the cable is locked relative to the lamp holder 'L' this also helps prevent the electrical connection in the lamp holder being opened for tampering.

If it is desired to release the fixing from its support, a means will be provided for disengaging the pawls 37 from their ratchet teeth.

Alternatively the claws 27 if accessible can be disengaged from the flats 44 on the collar but this may result in destruction of the plug which may be replaced when the fixing is re-used.

Claims

1. A fixing anchorable to a support, and which comprises a plug for inserting into a hole in the support and which has a screwthreaded bore therein, a bolt member having a shank with a screwthread portion which is engageable with the screwthread in the plug, and a collar located coaxially on the shank and which is rotational relative to the shank , the collar being axially moveable towards the plug as the bolt member is screwed into the plug, said plug having deformable portions that are engageable with the collar as the bolt member is screwed into the plug so that the collar is held rotationally fast with the plug and is moved axially into the plug causing the plug to distort and thereby anchor the plug to the support.

2. A fixing as claimed in claim 1, wherein the collar is rotational relative to the bolt member for one direction of rotation only allowing the bolt member to be screwed into the plug even when the collar is rotationally fast with the plug, but preventing the bolt member from being unscrewed due to the engagement between collar and the plug.

3. A fixing as claimed in claim 2 wherein the engagement between the collar and bolt member is a pawl and ratchet mechanism operating therebetween to allow relative rotation in one direction but preventing said relative rotation in the other direction.

4. A fixing as claimed in claim 3 wherein the ratchet teeth are formed on an annular surface on the collar, and the pawl mechanism is a pair of diametrically opposed flexible pawls formed on the bolt member body.

5. A fixing as claimed in any one of claims 1 to 4 wherein the plug has equiangularly spaced axially extending claws thereon that engage with co-operating surfaces on the collar to hold the collar rotationally fast with the plug, and the claws are deformed by said co-operating surfaces as the bolt member is screwed into the plug to secure the plug into its support.

6. A fixing as claimed in any one of claism 1 to 5 wherein the bolt member is hollow having a longitudinal through bore therein for receiving an elongate body, and the bolt member body has fingers which are displaced by the collar to grip the elongate body.

7. A fixing as claimed in any one of claims 1 to 6 and which is utilised for securing an electrical fitting to a support.

8. A fixing as claimed in claim 7 when dependent upon claim 6, wherein there are two pairs of diametrically opposed fingers with their free ends projecting away from the plug, and the ends of the fingers grip onto an electrical cable passing through the bolt member body to secure the electrical cable relative to the fitting.

9. A fixing as claimed in any of claims 1 to 8 wherein the end of the bolt member away from the plug has a portion adapted for attachment of a body to the bolt.

10. A fixing as claimed in claim 9 wherein said end portion is a screwthreaded portion is adapted to receive an electrical light bulb holder.

11. A fixing for securing an electrical fitting to a cable and which comprises bolt member having a coaxial bore through which an electrical cable can pass, one end of bolt member being screwable to a support, and the other end of the bolt member being adapted to receive an electrical fitting, the bolt member having integral fingers projecting in an axial direction only for gripping the cable, and a collar which fits coaxially on the bolt member to hold the fingers into their gripping position.

12. A fixing for securing an electrical light bulb holder to a support and which is substantially as described herein and with reference to the accompanying drawings.

13. A method of securing a fixing to a support , said fixing comprising a plug for inserting into a hole in the support and which has a screwthreaded bore therein, a bolt member having a shank with a screwthread portion which is engageable with the screwthread in the plug, and a collar located coaxially on the shank and which is rotational relative to the shank , the collar being axially moveable towards the plug , said plug having deformable portions that are engageable with the collar as the bolt member is screwed into the plug, wherein the plug is inserted into hole and the bolt member is screwed into the plug moving the collar into engagement with the plug thereby causing the plug to distort and engage the support.

14. A method as claimed in Claim 13 for use with a thin walled support , wherein the plug is inserted beyond the hole and the plug has claws thereon which are caused by the collar to splay to grip against the back surface of the thin walled support.