GB2141803A

GB2141803A - Screwing device

Info

Publication number: GB2141803A
Application number: GB08413308A
Authority: GB
Inventors: Michel Lazarew
Original assignee: DECAUT ET BTR REUNIS SOC
Current assignee: DECAUT ET BTR REUNIS SOC
Priority date: 1983-05-26
Filing date: 1984-05-24
Publication date: 1985-01-03
Also published as: FR2546584A1; DE3419330A1; FR2546584B1; GB8413308D0

Abstract

Head 5 is of frusto-conical shape having a height between its ends 6 and 7 which is less than the diameter of the shank 2. Driving recess 8 is provided with six lobes 9 engagable by a complementary spanner 16. This form of screwing device is of reduced weight compared with screwing devices with conventional heads. <IMAGE>

Description

SPECIFICATION A screwing device of reduced weight in comparison with screwing devices for engagement by Allan Keys The invention relates to a screwing device, and particularly concerns a screwing device of relatively light weight in comparison with screwing devices currently in use such as, for example, known screw ing devices engageable by Allan Keys.

Known screwing devices, in particular metal screws, generally comprise a head, a shank fixed to the head and a portion of the shank provided with a screw thread. However, these devices have a mass which is not negligeable and when they are used in very large numbers to fix together many pieces of metal the article thus fabricated has a mass greatly exceeding the collective mass of the individual pieces. It is an important fact that in the aeronautics industry and in particular in the aerospace industry, it is desired to reduce the mass of the equipment with the aim of improving its performance.

An object of the invention is to provide a screwing device, in particular a metal screw, the weight of which is reduced in comparison with the known metal screws normally used.

According to the invention there is provided a screwing device comprising a head, a shank fixed to the head, and a shank portion provided with a screw thread, wherein the height of the head is less than the diameter of the shank, the head comprises a star-shaped recess, and externally the head has the shape of a truncated cone.

The combination of these features makes it possi ble to reduce the weight of the screwing device formed in accordance with the invention in compari son with screwing devices comprising a cylindrical or cheese-shaped head, with an hexagonal recess.

The star-shaped recess constitutes a kind of gearing and ensures better co-operation of the complementary tightening spanner with the recess.

The tightening spanner can engage immediately with the star-shaped recess with no need for the operator to make repeated attempts to mate the spanner with the recess.

For a device in accordance with the invention, a weight reduction of up to 30% can be attained in comparison with the weight of a known screw having a cylindrical or cheese-shaped head with an hexagonal recess and a shank of the same size as the device in accordance with the invention.

The angle which is subtended between a generat rix of the truncated-cone head and the axis of the head can have a value of between 15 and 30 approximately.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 is an elevation, partially in section, of a screwing device formed according to the invention; Figure 2 is an end-on view of the device in Figure 1; Figure 3 is an elevation, partially in section, of a known screwing device; Figure 3A is an end view of the known device in Figure 3; and Figure 4 is a perspective view on an enlarged scale of the screwing device in Figures 1 and 2 and a tightening spanner.

With reference to Figures 1, 2 and 4, the screwing device 1 comprises a shank with a shank portion 3 provided with a screw thread 4, and a head 5 fixed to the shank 2.

More specifically, the head 5 has a height H, that is the distance between its top end 6 and bottom 7, which is less than the diameter of the shank.

The head 5 has the shape of a truncated cone.

Thus, the head is a frustum of cone with a circular base, the axis of revolution of the head being the axis of revolution XX of the shank portion 3.

The head 5 also comprises a star-shaped recess 8.

This recess is preferably provided with six lobes 9, each being demarcated by two arcuate sides 10 and 11 which are both concave towards the recess and interconnected by an arcuate side portion 12 which is convex with respect to the recess.

Figure 3 and 3A show a known screwing device 12' as hitherto used provided with a cylindrical or cheese shaped head 13, a screwtheaded shank portion 14 and a shank 15. As can readily be seen, the head 13 has a height H' which is equal to the diameter D' of the shank. Moreover, the recess 8' is of hexagonal shape 19 engagable by a known Allan key.

The angle a subtended in Figure 1 between a generatrix 16 of the head 5 and the longitudinal axis XX of the head can have a value of between 15 and 30" approximately.

Figure 4 shows the screwing device 1 in relation to a spanner 16. The spanner 16 engages with the recess 8 through being provided with a complementary star-shaped cut-away portion 17 at its end 18.

The cut-away portion allows the spanner 16 readily to engage in the star-shaped recess 8. By reason of its shape the portion 17 does not readily wear.

The screwing device 1 can be 30% lighter than the screw 12 when made of the same material and having identical screw threaded shanks.

The screwing device is of a metal highly alloyed with refractory material, or titanium.

1. A screwing device comprising a head, a shank fixed to the head, and a shank portion provided with a screw thread, wherein the height of the head is less than the diameter of the shank, the head comprises a star-shaped recess, and externally the head has the shape of a truncated cone.

2. A screwing device according to the claim 1, in which the head is in the shape of a frustum of cone with a circular base and has an axis of revolution which is the longitudinal axis of the shank and an angle subtented by the generatrix of the frustum and the said axis has a value of between 15 and 30" approximately.

3. A screwing device according to claim 1 or claim 2, in which the recess comprises six lobes, each formed of two arcuate sides both concave

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A screwing device of reduced weight in comparison with screwing devices for engagement by Allan Keys The invention relates to a screwing device, and particularly concerns a screwing device of relatively light weight in comparison with screwing devices currently in use such as, for example, known screw ing devices engageable by Allan Keys. Known screwing devices, in particular metal screws, generally comprise a head, a shank fixed to the head and a portion of the shank provided with a screw thread. However, these devices have a mass which is not negligeable and when they are used in very large numbers to fix together many pieces of metal the article thus fabricated has a mass greatly exceeding the collective mass of the individual pieces. It is an important fact that in the aeronautics industry and in particular in the aerospace industry, it is desired to reduce the mass of the equipment with the aim of improving its performance. An object of the invention is to provide a screwing device, in particular a metal screw, the weight of which is reduced in comparison with the known metal screws normally used. According to the invention there is provided a screwing device comprising a head, a shank fixed to the head, and a shank portion provided with a screw thread, wherein the height of the head is less than the diameter of the shank, the head comprises a star-shaped recess, and externally the head has the shape of a truncated cone. The combination of these features makes it possi ble to reduce the weight of the screwing device formed in accordance with the invention in compari son with screwing devices comprising a cylindrical or cheese-shaped head, with an hexagonal recess. The star-shaped recess constitutes a kind of gearing and ensures better co-operation of the complementary tightening spanner with the recess. The tightening spanner can engage immediately with the star-shaped recess with no need for the operator to make repeated attempts to mate the spanner with the recess. For a device in accordance with the invention, a weight reduction of up to 30% can be attained in comparison with the weight of a known screw having a cylindrical or cheese-shaped head with an hexagonal recess and a shank of the same size as the device in accordance with the invention. The angle which is subtended between a generat rix of the truncated-cone head and the axis of the head can have a value of between 15 and 30 approximately. The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 is an elevation, partially in section, of a screwing device formed according to the invention; Figure 2 is an end-on view of the device in Figure 1; Figure 3 is an elevation, partially in section, of a known screwing device; Figure 3A is an end view of the known device in Figure 3; and Figure 4 is a perspective view on an enlarged scale of the screwing device in Figures 1 and 2 and a tightening spanner. With reference to Figures 1, 2 and 4, the screwing device 1 comprises a shank with a shank portion 3 provided with a screw thread 4, and a head 5 fixed to the shank 2. More specifically, the head 5 has a height H, that is the distance between its top end 6 and bottom 7, which is less than the diameter of the shank. The head 5 has the shape of a truncated cone. Thus, the head is a frustum of cone with a circular base, the axis of revolution of the head being the axis of revolution XX of the shank portion 3. The head 5 also comprises a star-shaped recess 8. This recess is preferably provided with six lobes 9, each being demarcated by two arcuate sides 10 and 11 which are both concave towards the recess and interconnected by an arcuate side portion 12 which is convex with respect to the recess. Figure 3 and 3A show a known screwing device 12' as hitherto used provided with a cylindrical or cheese shaped head 13, a screwtheaded shank portion 14 and a shank 15. As can readily be seen, the head 13 has a height H' which is equal to the diameter D' of the shank. Moreover, the recess 8' is of hexagonal shape 19 engagable by a known Allan key. The angle a subtended in Figure 1 between a generatrix 16 of the head 5 and the longitudinal axis XX of the head can have a value of between 15 and 30" approximately. Figure 4 shows the screwing device 1 in relation to a spanner 16. The spanner 16 engages with the recess 8 through being provided with a complementary star-shaped cut-away portion 17 at its end 18. The cut-away portion allows the spanner 16 readily to engage in the star-shaped recess 8. By reason of its shape the portion 17 does not readily wear. The screwing device 1 can be 30% lighter than the screw 12 when made of the same material and having identical screw threaded shanks. The screwing device is of a metal highly alloyed with refractory material, or titanium. CLAIMS

3. A screwing device according to claim 1 or claim 2, in which the recess comprises six lobes, each formed of two arcuate sides both concave towards the recess and interconnected by an arcuate side portion which is convex with respect to the recess.

4. A screwing device according to any one of claims 1 to 3, arranged to co-operate with a spanner having an extremity which is star-shaped to engage the recess.

5. A screwing device according to any one of claims 1 to 4, formed of metal alloyed with refractory material, or titanium.

6. A screwing device substantially as hereinbefore described with reference to Figures 1,2 and 4 of the accompanying drawings.