GB2194827A

GB2194827A - Driving formations of screws

Info

Publication number: GB2194827A
Application number: GB08719327A
Authority: GB
Inventors: Leonard Albert Cooper
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-08-14
Filing date: 1987-08-14
Publication date: 1988-03-16
Also published as: GB8619770D0; GB8719327D0

Abstract

A security screw has a head with between three and six, preferably four, holes formed therein as driving formations. The head has no slot or slots, and is circular in cross-section, and can only be driven by a driver which has a head with projecting pins in a configuration corresponding to the holes in the screw head. The driver also has a collar of the same depth as the pins for fitting around the outer circular edge of the screw head. For additional security not all screws in an installation have the same screw head design, the configurations differing in the number, size, shape, and/or configuration of the holes, and requiring a corresponding set of driver head designs. <IMAGE>

Description

SPECIFICATION Screws The present invention relates to screws, and more specifically to security screws. The term "screw" here means a screw-threaded device, including a bolt.

An ordinary wood screw has a head which may have a simple slot so that the screw can be turned by means of a standard screwdriver, or may have a crossed slot which can also be turned by means of readily available screwdrivers with cross heads. Bolts may have similar heads, or may have hexagonal (or square) heads which may similarly be turned by standard and readily available spanners.

These screws can thus readily be undone by anyone with ordinary tools.

The object of the present invention is to provide a system which gives a substantially higher degree of security.

According to one aspect, the present invention provides a screw having a head with four or more holes formed therein. The head naturally has no slot or slots, and is circular (i.e.

not square or hexagonal). Such a screw cannot be turned by a conventional screwdriver or spanner, but only by a specially made driver having projecting pins of the appropriate size, shape, and configuration to match the holes in the screw head.

According to another aspect of the invention, there is provided a set of screw head designs each of which has a different configuration of holes therein, the configurations differing in the number, size, shape, and/or configuration of the holes, and a corresponding set of drive head designs, such that each driver head design will fit only the corresponding screw head design.

According to a further aspect of the invention, there is provided a driver having a head with a plurality of projecting pins and a collar, for driving a screw having a corresponding configuration of holes, with the collar of the driver head fitting aound the outer circular edge of the screw head.

Various screws and drivers in accordance with the invention will now be described, by way of example, with reference to the drawings, in which: Figures 1A to 1C show three screws, with their heads shown in section; Figure 2 is a common end view of these screws, showing the head pattern; Figure 3A is a section plane through a driver head for these screws; Figure 3B is the end view of the driver head; and Figure 4 shows a set of six mutually exclusive head patterns or configurations.

Referring to the drawings, Fig. 1A shows a wood screw with a round head 10 (shown in section) having four holes 11 therein instead of the usual slot or crossed slots. Fig. 2 shows the hole pattern as seen end-on. Fig.

1B shows a bolt having a circular head with the same hole pattern, and Fig. 1C shows a partially threaded bolt with a round countersunk head again having the same hole pattern.

Fig. 3A is a section plane through a driver head for these screws, and Fig. 3B is an end view of the driver head. The driver head comprises four pins 13 arranged to correspond with the pattern of holes of the screw head shown in Fig. 2. It is obvious that the screws of Figs. 1A to 1C cannot be turned by conventional tools (screwdrivers or spanners) but can be turned by a driver having the head shown in Figs. 3A and 38.

The driver head also includes a collar 12, which is as deep as the pins 13. This collar ensures that the driver head must be properly seated on the screw before the screw can be turned; thus it prevents the driver head from being engaged in an offset position with only two of the four pins 13 engaging the holes 11. The collar 12 also serves the further function of providing additional engagement of the driver with the screw head if the pattern of the pins and holes is generally offset to one side of the centre of the pattern.

There may be circumstances in which it is desired to provide additional security, so that not all screws in a given installation can be unscrewed by means of the same driver. To achieve this, it is necessary to provide a plurality of distinct patterns or configurations for the holes in the heads, such that each of the corresponding driver configurations will fit only its own head configuration.

Fig. 4 shows a set of six configurations A to F of four pins or holes which are mutually exclusive, in the sense that a driver for any one of the configurations will not fit a screw with any of the other configurations. The pins or holes may have different angular spacings around the centre of the screw head in different patterns, as with patterns A and F. They may have difference distances from the centre of the pattern, as with patterns B and E.

There may be a centre pin, as with patterns C and D. It is readily seen that a driver for any given one of these patterns will not fit a screw head of any other pattern. It will be noted that the provision of the collar on the driver head ensures that a driver of pattern A will not fit a screw of pattern B and vice versa.

It will be realized that different set of mutually exclusive patterns can be achieved by the use of pins of different sizes, or by the use of pins of different shapes, or by the use of different numbers of pins. For practical reasons, the number of pins cannot conveniently be less than three or more than five or six.

The combination of varying the angular positions of the pins, their radial positions, their shapes, and the number of pins means that a large number of mutually exclusive patterns can be generated.

Claims

1. A screw having a circular head with four or more holes formed therein.

2. A screw according to claim 1 wherein there are four holes at the vertexes of a square centred on the centre of the screw head.

3. A screw according to claim 1 wherein there are four holes at the vertexes of a square offset from the centre of the screw head.

4. A screw according to claim 1 wherein there are four holes at the vertexes of a diamond centred on the centre of the screw head.

5. A screw according to claim 1 wherein there are four holes at the vertexes of a trapezium surrounding the centre of the screw head.

6. A screw according to claim 1 wherein there are four holes one at the centre of the screw head and the other three symmetrically placed around the centre of the screw head.

7. A screw according to claim 1 wherein there are four holes one at the centre of the screw head and the other three symmetrically placed around the centre of the screw head.

8. For a screw according to any previous claim, a driver having a head with a plurality of projecting pins in a configuration corresponding to the holes in the screw head and having a collar of the same depth as the pins for fitting around the outer circular edge of the screw head.

9. A set of screws having a plurality of distinct head designs each of which has a different configuration of holes therein, the configurations differing in the number, size, and/or arrangement of the holes.

10. A set of screws having a plurality of distinct head designs each according to a different one of claims 2 to 7.

11. For a set of screws according to claim 9 or claim 10, a set of drivers each having a head with a plurality of projecting pins in a configuration corresponding to the holes in a different one of the patterns of screw head and having a collar of the same depth as the pins for fitting around the outer circular edge of the screw head.

12. A security screw substantially as herein described.

13. A driver for the security screw of claim 12, substantially as herein described.

14. A set of distinct security screws substantially as herein described.

15. A set of drivers for the set of security screws of claim 14, substantially as herein described.