GB2223288A

GB2223288A - Expansible screw fixing

Info

Publication number: GB2223288A
Application number: GB8823033A
Authority: GB
Inventors: Frederick Thomas Stephenson
Original assignee: Huntingdon Fastener Co Ltd
Current assignee: Huntingdon Fastener Co Ltd
Priority date: 1988-09-30
Filing date: 1988-09-30
Publication date: 1990-04-04
Anticipated expiration: 2008-09-30
Also published as: GB2223288B; GB8823033D0

Abstract

An expansible screw fixing comprising a sleeve (10) of plastics material and having at its inner end a cooperating plug (16) displaceable by an inserted screw (not shown) to expand the sleeve, the sleeve having an annular head (12) for abutting an item to be fixed and having a large area (20) sufficient to avoid distortion of the item under the applied compressive load, the head also having a recess (30) for receiving a lip (28) on the rim (26) of a cap (24) which will cover the screw head received in countersink (22). <IMAGE>

Description

Title Expansible Screw Fixing Field of the invention This invention relates to an expansible screw fixing, intended for fixing items to brickwork or blockwork and which is particularly suited to the fixing in position of timber or UPVC window frames, especially the latter.

Prior Art A known screw fixing especially suited to the fixing of UPVC window frames to brickwork comprises a screw extending through a radially expansible plastics sleeve and screwing into an axially displaceable plug engaging into the inner end of the sleeve. The device is intended to be used by drilling a hole through the UPVC frame and into the brickwork and inserting the fixing into the hole until a radially narrow peripheral lip on the outer end of the sleeve abuts against the face of the frame around the hole. The screw, which is of approximately the same length as the sleeve, is then tightened, drawing the plug deeper into the inner end of the sleeve to expand a longitudinally slotted portion of said sleeve into tight engagement with the wall of the hole in the brickwork.

Problems which can arise with the above-described known fixing include:a) covering any oversize opening of the drilled hole at the face of the frame. This can easily occur due to drill wander as ,the hole is being formed in the brickwork, which is a considerably harder material than UPVC; b) covering the screwhead itself. In the conventional fixing, the screwhead is provided with cross-slots for engagement by a power tool, and the known spigoted caps for locating into the junction of these cross-slots to cover the screwhead are liable to fit insecurely, especially if the cross-slots become damaged during the screw tightening action; and c) spreading the compressive load exerted by the screwhead on the UPVC frame, in order to avoid risk of distortion of the frame. This problem is aggravated if the drill hole in the frame is oversize.

An object of the present invention is to provide a screw fixing which avoids or minimises the above-described problems.

The invention According to one aspect of the invention, there is provided an expansible screw fixing comprising a sleeve of plastics material having at its inner end an axially displaceable plug and at its outer end a peripheral lip of larger than conventional diameter and for presenting an annular area of sufficient size to the item against which it is to abut that in use distortion of the item due to the compressive load applied thereto is substantially avoided. More especially, the diameter of the peripheral lip is at least 1 1/3 times the diameter of the main portion of the sleeve which in use extends into the drilled hole.

The sleeve is preferably also characterised by:a) a head on which said peripheral lip is provided, and a frusto-conical recess in said head, in use for receiving the head of the screw; b) a circular cap for fitting over said sleeve head, said cap having a peripheral rim carrying a radially inwardly directed rim; and c) a radially inward recess in the peripheral wall of the sleeve head into which the radially inwardly directed rim of the cap is a snap fit.

According to another aspect of the invention, there is provided a kit of parts comprising the combination of a radially expansible plastics sleeve, a plug at the inner end thereof, a headed screw for passing into and through the sleeve into screwthreaded engagement with the plug, and a cap for fitting over a head provided on the sleeve, in use to cover a screwhead received into said sleeve head without requiring engagement of the cap with the screwhead to retain the cap in position.

According to still another aspect of the invention, there is provided a softwood timber or UPVC widow frame in combination with a fixing kit which includes a radially expansible plastics sleeve, an axially displaceable plug at the inner end of the sleeve, and a head on the outer end of the sleeve, the head at the outer end of the sleeve including a flange or lip of sufficient diameter so to distribute the compressive load, when a screw is tightened through the sleeve into the plug at the inner end thereof, that inroad of the head into the timber or UPVC frame material is substantially avoided.

According to still another aspect of the invention, there is provided a method of fixing an item to brickwork (or blockwork) using an expansible screw fixing, according to which a hole is drilled through the said item into the brickwork, a radially expansible sleeve is inserted into the hole as far as permitted by a head on the sleeve which includes a radially outwardly directed flange, a screw extending through the sleeve is tightened into an axially displaceable plug at the inner end of the sleeve, the head of the screw being received into a recess in the sleeve head, and a cap for covering the screwhead is snap-fitted to the head of the sleeve.

Brief description of drawings In the accompanying drawings: Figure 1 is a longitudinal axial cross-section through a sleeve and cap forming part of an expansible screw fixing; Figures 2, 3 and 4 are axial cross-sections on the lines 2 - 2, 3 - 3 and 4 - 4 of Figure 1, respectively; and Figures 5A, 5B and 5C show a plug, also forming part of the fixing, in outer end view, longitudinal cross-section and inner end view, respectively.

Description of embodiment Referring to Figure 1 of the drawings, a preferred expansible screw fixing includes a plastics sleeve 10 having a head 12 at its outer end. The main portion of the sleeve between the head and its inner end is substantially cylindrical, but is formed with ribs, apertures and slots at various positions, as is substantially conventional in the art and is further illustrated in Figures 2 to 4.

A plastics plug 16, also of a substantially conventional kind as shown in Figures 5A, 5B and 5C, is locatable into the inner end 14 of the sleeve, which is appropriately internally tapered for the purpose.

When a screw (not shown), of approximately the same length as the sleeve, is entered through the sleeve screwthreadedly to engage into the plug located in the inner end of the sleeve, tightening of the screw causes the plug to be drawn into the sleeve to cause distortion and accompanying radial expansion of the longitudinally slotted region 18 of the sleeve. Assuming the fixing has been inserted into a hole drilled through a UPVC window frame into brickwork to which the frame is to be secured, radial expansion of the sleeve tightens the sleeve into binding engagement with the wall of the hole in the brickwork. At the same time, the frame becomes fixed in position as the screwhead tightens the head of the sleeve into engagement with said frame, pressing the latter tightly against the brickwork.

The present invention is more especially concerned with the region of the fixing at the head of the sleeve, where with conventional fixings various problems can arise in use, as hitherto described.

First, the head of the sleeve is made of greater diameter than the radially narrow peripheral lip with which conventional fixings are provided, more especially with a diameter at least 1 1/3 times the diameter of the main cylindrical portion of the sleeve. In the illustrated embodiment, the ratio of the diameters is approximately 1.4:1. The head thus possesses an annular undersurface 20 of substantial area for engagement with the face of the window frame, being a sufficient area to prevent the end biting into UPVC material and/or causing distortion thereof because the compressive load created when the screw is tightened is distributed over this increased area of engagement. The increased area of engagement is also important for the same reason if, for example due to inadvertent drill wander, the opening of the drilled hole in the frame is oversize. In this instance, however, the additional advantage arises that the head is of sufficient diameter entirely to cover the opening, even though it is oversize.

Second, even load distribution through the sleeve head is assisted by the formation of a frusto-conical recess 22 therein for receiving a screwhead with a matching underside.

Third, the increased thickness of the sleeve head in the axial direction, required to enable the above-described recess 22 to be provided therein, also enables a cap 24 to be fitted to said sleeve head, in order to cover the screwhead, without relying on unreliable engagement between the cap and the screwhead itself. For this purpose, the cap 24 has a peripheral lip 26 with a radially inwardly directed rim 28, which snap fits into a matching undercut recess 30 in the peripheral wall of the sleeve head 12. The fitting of the cap 24 in this way also assists in ensuring that an oversized opening of the drilled hole in the UPVC frame is completely covered.

Various modifications of the above-described and illustrated embodiment are possible within the scope of the invention hereinbefore defined.

Claims

1. An expansible screw fixing comprising a sleeve of plastics material having at its inner end an axially displaceable plug and at its outer end a peripheral lip of larger than conventional diameter and for presenting an annular area of sufficient size to the item against which it is to abut that in use distortion of the item due to the compressive load applied thereto is substantially woided.

2. A fixing according to claim 1, wherein the diameter of the peripheral lip is at least 1 1/3 times the diameter Or the main portion of the sieeve which in use extends into the drilled hole.

3. A fixing according to claim 1 or claim 2, wherein the sleeve is characterised by a head on which said peripheral lip is provided, and a frusto-conical recess in said head, in use for receiving the head of the screw.

4. A fixing according to claim 3, including a circular cap for fitting over said sleeve head, said cap having a peripheral rim carrying a radially inwardly directed lip.

5. A fixing according to clain- 4, wherein a ra101y inward recess is provided in the peripheral wall of the sleeve head, into which the radially inwardly directd i of the cap is a snap fit.

6. A kit of party comprising the combination or ; radially expansible plastics sleeve, a plug at tie inner end thereof, a headed screw for passing into and through the sleeve into screwthreaded engagement with the plug, and a cap for fitting over a head provided on the sleeve, in use to cover a screwhead received into said sleeve head without requiring engagement of the cap with the screwhead to retain the cap in position.

7. A kit according to claim 6, wherein the cap has a rim with an inwardly directed lip for engaging into a peripheral recess in a head provided on the sleeve.

8. A method of securing an item by use of an expansible screw fixing, substantially as hereinbefore described with reference to the accompanying drawings.

8. A softwood timber or UPVC window fram in corrbinati with a fixing kit which include a radial expansible plastics sleeve, an axially displaceable plug at the inn end of the sleeve, and a head on the outer end of the sieeve, the head at the outer end of the sleeve wnclud nb a flange or lip of sufficient diameter se to distribute the compressive load, when a screw is tightened through the sleeve into the plug at the inner end thereof, that inroad of the head into the timber or UPVC frame material is substantially avoided.

9. A combination as claimed in claim 8, wherein the sleeve is characterised by a head on which said peripheral lip is provided, and a frusto-conical recess in said head, in use for receiving the head of the screw.

10. A cowb as 0. o claimed in claim 9, includirì a circular cap for fitting over said sleeve head, said cap having a peripheral rim carrying a radially inwardly directed iip.

11. A combination as claimed in claim 10, including a radially inward recess in the peripheral wall of the sleeve head, into which the radially inwardly directed lip of the cap is a snap fit.

12. A method of securing an item to brickwork (or blockwork) using an expansible screw fixing, according to which a hole is drilled through the said item into the brickwork, a radially expansible sleeve is inserted into the hole as far as permitted by a head on the sleeve which includes a radially outwardly directed flange, a screw extending through the sleeve is tightened into an axially displaceable plug at the inner end of the sleeve, the head of the screw being received into a recess in th we head, and a cap for covering the screwhead is snap-fitte to the head of the sleeve.

13. An expansible screw fixing substantially as hereinbefore described with reference to the accompanying drawings.

14. A kit of parts substantially as hereinbefore described with reference to the accompanying drawings.

15. A method of securing by use of an expansible screw fixing, as claimed in claim 12 and substantially as hereinbefore described.

AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS 1. An expansible screw fixing comprising: a sleeve of plastics material having at its inner end an axially displaceable plug and at its outer end a peripheral lip of larger than conventional diameter, and for presenting an annular area of sufficient size to an item against which it is to abut so that in use distortion of the item due to the compressive load applied thereto is substantially avoided; wherein the sleeve has a head on which said peripheral lip is provided, and a frusto-conical recess in said head, in use for receiving a head of a screw; and a circular cap for fitting over said sleeve head, said cap having a peripheral rim carrying a radially inwardly directed lip.

2. A fixing according to claim 1, wherein the diameter of the peripheral lip is at least 1 1/3 times the diameter of the main portion of the sleeve which in use extends into a drilled hole for the fixing.

3. A fixing according to claim 1, wherein a radially inward recess is provided in the peripheral wall of the sleeve head, into which the radially inwardly directed lip of the cap is a snap fit.

4. A fixing according to any one of claims 1 to 3, and further comprising a headed screw for passing into and through the sleeve into screwthreaded engagement with the plug, and a cap for fitting over the head provided on the sleeve, whereby in use to cover the head of the screw received into said sleeve head without requiring engagement of the cap with the screwhead to retain the cap in position.

5. A fixing according to claim 4 in which the item to be abutted against is a softwood timber or UPVC window frame, whereby when the screw is tightened through the sleeve into the plug at the inner end thereof, the compressive load is so distributed that any inroad of the sleevehead into the timber or UPVC frame material is substantially avoided.

6. A method of securing an item te brickwork (or blockwork) using an expansible screw fixing according to any one of claims 1 to 5, in which a hole is drilled through the item into the brickwork, said sleeve inserted into the hole as far as permitted by the head on the sleeve which includes the radially outwardly directed peripheral lip, a screw extending through the sleeve is tightened into an axially displaceable plug at the inner end of the sleeve, the head of the screw being received in the recess in the sleeve head, and the cap for covering the screwhead is snap-fitted to the head of the sleeve.

7. An expansible screw fixing substantially as hereinbefore described with reference to the accompanying drawings.