GB2099096A

GB2099096A - Screwthreaded inserts

Info

Publication number: GB2099096A
Application number: GB8112979A
Authority: GB
Original assignee: PSM Fasteners Ltd
Current assignee: PSM Fasteners Ltd
Priority date: 1981-04-28
Filing date: 1981-04-28
Publication date: 1982-12-01
Also published as: GB2099096B; DE3215547C2; IT8220850A0; IT8220850A1; FR2504616B3; IT1198365B; DE3215547A1; FR2504616A1

Abstract

An internally threaded insert for installation in a preformed bore has a series of vanes 16, 17, 18 whose diameters increase from the leading to the trailing end of the insert, so that each vane embeds further into the bore wall than the previous one during installation. The individual vanes are shaped to facilitate installation and resist pull-out. The head 12 is formed with toothed formations to resist torque loading when installed in place. A diametral slot is provided in the leading end to facilitate automatic feeding, and is so dimensioned that the insert body does not collapse radially. <IMAGE>

Description

SPECIFICATION Screwthreaded inserts This invention relates to an insert for installation in a preformed bore in a workpiece in order to provide a screwthreaded anchorage pilot.

The invention is particularly concerned with an insert which is intended to be installed as an interference fit and is provided with the formations for resisting axial pull-out and torque loading.

The object of the present invention is to provide a screwthreaded insert of the type referred to which is economic to manufacture and which, especially when installed in thermoplastics workpieces, does not unduly stress the material of the workpiece.

According to the present invention we provide an insert for installation in a preformed bore in a workpiece so as to provide a screwthreaded anchorage point, said insert comprising a body having at its trailing end an enlarged head provided with formations for resisting torque and between the head and its leading end a plurality of periphery extending vanes spaced from one snother and from said head, each such vane comprising a leading flank which, in a radially outwards direction, is inclined away from the leading end of the insert and a trailing flank which extends substantially perpendicularly to the main axis of the insert or is inclined in the same sense as the leading flank, the diameters of the said vanes increasing in a direction away from the leading end of the insert.

This configuration is especially suitable for installation as an interference fit in plastics material as the leading flanks of the vanes facilitate pushing in of the insert while the trailing flanks afford considerable resistance to pull-out loads due to the tendency for the plastics material to restore to its original shape and thereby occupy the region immediately behind the trailing flank of each vane. Moreover the vane configuration allows the vane to deflect elastically to some extent at its extremity thereby facilitating installation further -- and increase resistance to pull-out (particularly in harder materials which may not restore to their original shape).

When the insert is installed as an interference fit by a pressing-in operation, there will be a tendency for the successive vanes to shear away part of the bore wall. Such shearing may therefore render the subsequent vanes less effective in resisting pull-out. To overcome this, as mentioned above, the diameters of the successive vanes increase progressively from the leading towards the trailing end of the insert so that each successive vane tends to embed further into the wall of the workpiece bore.

Preferably the angle of inclination of the leading flank is between 450 and 600 relative to said main axis. An angle of this order coupled with the provision of spacings between the head and adjacent vanes avoids undue stressing of the workpiece and hence the risk of rejection through the generation of fractures during the installation procedure.

To facilitate automatic feeding from a bowl feeder for example and correct orientation of the insert, it is conveniently formed with a diametral slot across its leading end, which slot is so dimensioned and arranged that the insert body in this region has no significant tendency to collapse radially (due to the presence of the slot) when inserted into thermoplastic materials in contrast with known forms of slotted inserts in which the slot is provided to allow such radial collapse to take place and thereby add insertion of the inserts into hard materials. Such inserts are not inserted as an interference fit but rely on their radial collapsibility to enable them to be inserted into a bore. Subsequent insertion of a threaded fastener into the insert then serves to expand the insert thereby causing peripheral formations thereon to embed into the material.

To promote further understanding of the present invention, one example will now be described with reference to the accompanying drawing, the sole of which is a side view of an insert in accordance with the invention.

As shown, the insert comprises a generally cylindrical tubular body 10 having an internal screwthread. At its trailing end the body 10 has a radially enlarged head 12 provided with axial teeth which resist torque loading when the insert is installed in the workpiece. At its leading end there is a pilot portion 14 which may be of the same diameter as the insert body which, in turn, is slightly less than the diameter of the bore in which it is to be installed. The pilot portion 14 serves to locate the insert in the mouth of the bore prior to pressing-in.

Around its periphery, the insert body is formed with one or more vanes 1 6, 1 7 and 18 whose outside diameters increase progressively so that the leading vane 1 6 is of the smallest diameter and the trailing vane 18 is of the largest diameter.

The diameter of the vane 18 immediately adjacent the head portion 12 may be the same as the head diameter or slightly smaller. Each vane has an inclined leading flank 20 and a trailing flank 21 which extends substantially perpendicularly to the insert axis.

A diametrical slot 22 extends across the leading end of the insert but, as mentioned previously this slot is intended to aid feeding and orientation of the insert and is so arranged and dimensioned that the insert does not have any significant tendency to collapse radially when installed as an intereference fit in thermoplastic materials.

1. An insert for installation in a preformed bore in a workpiece so as to provide a screwthreaded anchorage point, said insert comprising a body having at its trailing end an enlarged head provided with formations for resisting torque and between the head and its leading end a plurality of peripherally extending vanes spaced from one another and from said head, each such vane

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Screwthreaded inserts This invention relates to an insert for installation in a preformed bore in a workpiece in order to provide a screwthreaded anchorage pilot. The invention is particularly concerned with an insert which is intended to be installed as an interference fit and is provided with the formations for resisting axial pull-out and torque loading. The object of the present invention is to provide a screwthreaded insert of the type referred to which is economic to manufacture and which, especially when installed in thermoplastics workpieces, does not unduly stress the material of the workpiece. According to the present invention we provide an insert for installation in a preformed bore in a workpiece so as to provide a screwthreaded anchorage point, said insert comprising a body having at its trailing end an enlarged head provided with formations for resisting torque and between the head and its leading end a plurality of periphery extending vanes spaced from one snother and from said head, each such vane comprising a leading flank which, in a radially outwards direction, is inclined away from the leading end of the insert and a trailing flank which extends substantially perpendicularly to the main axis of the insert or is inclined in the same sense as the leading flank, the diameters of the said vanes increasing in a direction away from the leading end of the insert. This configuration is especially suitable for installation as an interference fit in plastics material as the leading flanks of the vanes facilitate pushing in of the insert while the trailing flanks afford considerable resistance to pull-out loads due to the tendency for the plastics material to restore to its original shape and thereby occupy the region immediately behind the trailing flank of each vane. Moreover the vane configuration allows the vane to deflect elastically to some extent at its extremity thereby facilitating installation further -- and increase resistance to pull-out (particularly in harder materials which may not restore to their original shape). When the insert is installed as an interference fit by a pressing-in operation, there will be a tendency for the successive vanes to shear away part of the bore wall. Such shearing may therefore render the subsequent vanes less effective in resisting pull-out. To overcome this, as mentioned above, the diameters of the successive vanes increase progressively from the leading towards the trailing end of the insert so that each successive vane tends to embed further into the wall of the workpiece bore. Preferably the angle of inclination of the leading flank is between 450 and 600 relative to said main axis. An angle of this order coupled with the provision of spacings between the head and adjacent vanes avoids undue stressing of the workpiece and hence the risk of rejection through the generation of fractures during the installation procedure. To facilitate automatic feeding from a bowl feeder for example and correct orientation of the insert, it is conveniently formed with a diametral slot across its leading end, which slot is so dimensioned and arranged that the insert body in this region has no significant tendency to collapse radially (due to the presence of the slot) when inserted into thermoplastic materials in contrast with known forms of slotted inserts in which the slot is provided to allow such radial collapse to take place and thereby add insertion of the inserts into hard materials. Such inserts are not inserted as an interference fit but rely on their radial collapsibility to enable them to be inserted into a bore. Subsequent insertion of a threaded fastener into the insert then serves to expand the insert thereby causing peripheral formations thereon to embed into the material. To promote further understanding of the present invention, one example will now be described with reference to the accompanying drawing, the sole of which is a side view of an insert in accordance with the invention. As shown, the insert comprises a generally cylindrical tubular body 10 having an internal screwthread. At its trailing end the body 10 has a radially enlarged head 12 provided with axial teeth which resist torque loading when the insert is installed in the workpiece. At its leading end there is a pilot portion 14 which may be of the same diameter as the insert body which, in turn, is slightly less than the diameter of the bore in which it is to be installed. The pilot portion 14 serves to locate the insert in the mouth of the bore prior to pressing-in. Around its periphery, the insert body is formed with one or more vanes 1 6, 1 7 and 18 whose outside diameters increase progressively so that the leading vane 1 6 is of the smallest diameter and the trailing vane 18 is of the largest diameter. The diameter of the vane 18 immediately adjacent the head portion 12 may be the same as the head diameter or slightly smaller. Each vane has an inclined leading flank 20 and a trailing flank 21 which extends substantially perpendicularly to the insert axis. A diametrical slot 22 extends across the leading end of the insert but, as mentioned previously this slot is intended to aid feeding and orientation of the insert and is so arranged and dimensioned that the insert does not have any significant tendency to collapse radially when installed as an intereference fit in thermoplastic materials. CLAIMS

1. An insert for installation in a preformed bore in a workpiece so as to provide a screwthreaded anchorage point, said insert comprising a body having at its trailing end an enlarged head provided with formations for resisting torque and between the head and its leading end a plurality of peripherally extending vanes spaced from one another and from said head, each such vane comprising a leading flank which, in a radially outwards direction, is inclined away from the leading end of the insert and a trailing flank which extends substantially perpendicularly to the main axis of the insert or is inclined in the same sense as the leading flank, the diameters of the said vanes increasing in a direction away from the leading end of the insert.

2. An insert as claimed in Claim 1 in which the angle of inclination of the leading flank is between 450 and 600 relative to said main axis.

3. An insert as claimed in Claim 1 or 2 which is formed with a diametrical slot across its leading end, which slot is so dimensioned and arranged that the insert body in this region has no significant tendency to collapse radially (due to the presence of the slot) when inserted into thermoplastic materials.

4. An insert as claimed in any one of claims 1 to 3 in which the head is formed with axial teeth.

5. An insert as claimed in Claim 4 in which the outside diameter of said teeth is greater than the diameter of the vane immediately adjacent thereto.

6. An insert as claimed in Claim 3 including a pilot portion, said slot being formed in the pilot portion without interrupting the vane nearest the leading end of the insert.

7. An insert substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.