GB2236569A

GB2236569A - A security screw

Info

Publication number: GB2236569A
Application number: GB8922221A
Authority: GB
Inventors: Norman Cropper
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-10-03
Filing date: 1989-10-03
Publication date: 1991-04-10
Anticipated expiration: 2009-10-03
Also published as: GB2236569B; GB8922221D0

Abstract

A security screw (2) comprising a screw threaded shank (4) and a head (6), the head (6) having a slot (8) which is defined by a pair of parallel sides (10, 12) and which is for receiving a straight edged tip of a screwdriver, and a part of at least one of the parallel sides (10, 12) being an outwardly sloping portion (14, 16) over which the screwdriver will slip if the screwdriver is used to try and unscrew the security screw (2). The prongs of an unfastening tool (not shown) may be received in recesses (18, 20). <IMAGE>

Description

A SECURITY SCREW This invention relates to a security screw.

It is well known that a normal screw comprises a screw threaded shank and a head. The head has a slot which is defined by a pair of parallel sides and the slot extends across the entire width of the head and is able to receive a straight edged tip of a screwdriver. In order to give the screwdriver greater purchase in the screw head, it is known to replace the slot with a cross-shaped depression for receiving a correspondingly shaped tip of a screwdriver.

Irrespective of whether the slot is a single straight slot or a cross-shaped slot, the screw can usually be undone substantially as simply as the screw is- done up.

There is a need for a screw which either cannot be undone when it is screwed tight, or which requires a special shaped tool having a tip which needs to engage a part of the head other than the slot. It is an aim of the present invention to provide such a screw, the screw then being such that it can be used as a security screw.

Accordingly, this invention provides a security screw comprising a screw threaded shank and a head, the head having a slot which is defined by a pair of parallel sides and which is for receiving a straight edged tip of a screwdriver, and a part of at least one of the parallel sides being an outwardly sloping portion over which the screwdriver will slip if the screwdriver is used to try and undo the security screw.

Preferably, the security screw is one in which both of the parallel sides have a part which is the outwardly sloping portion.

Usually, the security screw with the pair of outwardly sloping portions is one in which the outwardly sloping portions extend from opposite ends of the slot and do not overlap by an extent sufficient to prevent the security screw from being tightened. Preferably, the outwardly sloping portions extend from opposite ends of the slot and do not overlap.

The or each outwardly sloping portion is preferably a chamferred portion. Generally, any shape may be employed for the outwardly sloping portion providing that the outwardly sloping portion does not give grip to a screwdriver when the screwdriver is being employed in an un-fastening mode of operation. Generally, any type of chamfer may be employed so that the outwardly sloping portion may have a bevelled edge or a planar inclined edge. The chamfer can be achieved by machining or otherwise cutting away the normally sharp edge of the slot. Alternatively, the outwardly sloping portion can be formed during manufacture of the screw so that there will be then no need to cut away part of the screw head to form the outwardly sloping portion.

If desired, the security screw may include aperture means for receiving a pronged tool to facilitate undoing of the security screw in cases where the outwardly sloping portion will prevent the screwdriver undoing the security screw. The pronged tool may simply have prongs for fitting in the aperture means, or the pronged tool may also have a straight edged portion for engaging in the slot.

The provision of the aperture means may be advantageous where the security screw is to be used for holding in place electrildevices such for example as electrical outlet sockets which are normally not required to be taken apart but which may on occasion need taking apart for repair.

Generally, the security screw of the present invention can be made in any desired and suitable materials. Thus, for example, typical materials are steel and brass. The screw may be a machine screw or a wood screw. The screw may have a flat head or a round head.

Generally, the security screw will be used to secure parts together where varying degrees of security are required. It is thus envisaged that the security screw may find use in homes where it is desired to prevent children from undoing various parts of equipment, especially electrical equipment. The security screw may also be used in public places where it is desired to prevent members of the public unscrewing fitments and causing damage and/or stealing the fitments. Thus, for example, mirrors and light fittings in public places may advantageously be held in position by the security screws of the present invention.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 is a plan view of a first security screw; Figure 2 is a side view of the security screw shown in Figure 1; Figure 3 is a plan view of a second security screw; and Figure 4 is a plan view of a third security screw.

Referring to Figures 1 and 2, there is shown a security screw 2 comprising a screw threaded shank 4 and a head 6. For simplicity of illustration, only part of the shank 4 has been shown and the screw threads have been omitted. It will be appreciated that the screw threads can be of various pitches and various types of threads. Further, all or part of the shank 4 can be threaded.

The head 6 has a slot 8 which is defined by a pair of parallel sides 10,12. The slot 8 is for receiving a straight edged tip of a screwdriver (not shown).

As can be seen from Figure 1, the side 10 has a part which is an outwardly sloping portion 14.

Similarly, the side 12 has a part which is an outwardly sloping portion 16. The outwardly sloping portions 14, 16 are such that the screwdriver will slip if the screwdriver is used to try and undo the security screw 2.

The security screw 2 can however be tightened because the remaining parts of the sides 10,12 are sharp-edged and the sides extend in a plane parallel to the longitudinal axis of the security screw 2 as can best be appreciated from Figure 2.

As can be seen from Figure 1, the outwardly sloping portions 14, 16 extend from opposite ends of the slot 8 and they do not overlap each other.

Referring now to Figure 3, there is shown a security screw 2 which is somewhat similar to the security screw 2 shown in Figures 1 and 2. Similar parts have been given the same reference numerals for ease of comparison and understanding, and their precise construction and operation will not again be given. In Figure 3, the head 6 is additionally provided with aperture means in the form of a pair of holes 18,20.

The holes 18, 20 are rectangular in plan. The holes 18,20 are for receiving prongs on a pronged tool. When the prongs are in the holes 18, 20, the pronged tool can be used to undo the security screw 2.

Referring now to Figure 4, there is shown another security screw which again has certain similarities to the security screw shown in Figures 1 and 2. Thus, similar parts have again been given the same reference numerals and their precise construction and operation will not again be given. In Figure 4, it will be seen that the outwardly sloping portions 14, 16 are triangular in plan. This compares with the outwardly sloping portions 14, 16 shown in Figures 1 and 3 which are rectangular in plan.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example, other types of outwardly sloping portions may be employed and the outwardly sloping portions 14, 16 may have an inclined planar edge 22 as shown in Figure 2 or they may have a curved edge.

Claims

1. A security screw comprising a screw threaded shank and a head, the head having a slot which is defined by a pair of parallel sides and which is for receiving a straight edged tip of a screwdriver, and a part of at least one of the parallel sides being an outwardly sloping portion over which the screwdriver will slip if the screwdriver is used to try and undo the security screw.

2. A security screw according to claim 1 in which both of the parallel sides have a part which is the outwardly sloping portion.

3. A security screw according to claim 2 in which the outwardly sloping portions extend from opposite ends of the slot and do not overlap by an extent sufficient to prevent the security screw from being tightened.

4. A security screw according to claim 2 in which the outwardly sloping portions extend from opposite ends of the slot and do not overlap.

5. A security screw according to any one of the preceding claims in which the or each outwardly sloping portion is a chamferred portion.

6. A security screw according to any one of the preceding claims and including aperture means for receiving a pronged tool to facilitate undoing of the security screw in cases where the outwardly sloping portion will prevent the screwdriver undoing the security screw.

7. A security screw according to any one of the preceding claims in which the head is a flat head or a round head.

8. A security screw substantially as herein described with reference to the accompanying drawings.