This invention relates to fastening systems and is concerned with such fastening systems which include a fastening device for insertion into a member and adapted to become attached to the member when rotated with respect to the member by means of a tool.

Fastening systems of this type are well known. For example, it is known to provide such a fastening system wherein the fastening device is in the form of a rod carrying a fastening means in the form of a screw thread and including a nut or a slot defining driving faces whereby the device may be rotated about its longitudinal axis and wherein the tool is in the form of a spanner or screw driver appropriate to the nut or slot to rotate the device so that the screw thread engages in a corresponding thread provided on the member to which the device is to be attached.

A disadvantage of such conventional fastening systems is that it is readily apparent, from the appearance of the fastening device, how it may be unfastened and tools for rotating the fastening device are readily available. Thus, it is readily possible for unauthorised persons to remove the fastening device. Although it is known to provide tamper- resistant fastening devices which utilise a unique head shape for use with a correspondingly shaped tool, it is often possible for such fastening devices to be rotated using other commonly available tools and thus they are not as tamper-resistant as desired. It is one object of the present invention to provide a fastening system in which the aforementioned disadvantage is avoided.

It is also well known to use automatic production lines in, for example, the assembly of motor vehicles and the like. The fastening systems used in such assembly lines are frequently automated so that the

fastening device is automatically inserted into the member to which it is to be attached and then is automatically rotated by the tool so as to secure it to the member. In order to achieve this, the tool for rotating the fastening device needs to be appropriately oriented with respect to the driving faces on the fastening device so that it will engage with the device and rotate it. This increases expense and causes delay which is not acceptable when it is desired to increase the speed of the production line as much as possible. It is another object of the present invention to provide a fastening system wherein the problem of having to orient the fastening tool with respect to the drive faces of the fastening device does not arise. The fastening system of the present invention comprises a fastening device including a cylindrically shaped recess wherein the smooth cylindrical surface bounding the recess serves as the driving face for rotating the device with respect to the member to which it is to be attached and a tool for rotating the device having an effective diameter which can be varied so that it can be inserted into the recess of the fastening device when it is in its reduced diameter configuration and can then be caused to assume its increased diameter configuration wherein it wedges against the driving faces of the fastening device so as to transmit torque thereto.

According to an aspect of the present invention there is provided a wrench for engagement with a cylindrical recess in a fastening device so as to rotate the device, which wrench comprises:

(a) a shaft having a longitudinal axis and provided with a plurality of radially extending lobes,

(b) a plurality of rolling elements of circular section, and

(c) a retaining means for retaining said

elements adjacent to, and in rolling relationship with, the peripheral surface of the shaft, whereby rotation of the shaft about its axis causes said plurality of rolling elements to roll along the lobes and be displaced away from said longitudinal axis of the shaft to increase the effective diameter of the wrench and enable it to engage the cylindrical recess of the fastening device and transmit torque thereto.

Preferably the shaft includes at least 3 of said lobes in which case at least 3 of said rolling elements are present, the number of elements generally being equal to the number of lobes.

The wrench is for use with a fastening device including a recess bounded by a cylindrical surface and co-axial with the longitudinal axis of the device wherein the cylindrical surface serves as a driving face for rotating the device about its axis. In use of the wrench, it is inserted in the recess and rotated so as to apply a torque to the wrench about its longitudinal axis. As the wrench is turned, the rolling elements effectively roll along a path between the cylindrical surface of the fastening device and the surface of the lobes of the shaft so that they are displaced away from the longitudinal axis of the shaft and increase the effective diameter of the wrench. The path defined by the cylindrical surface and the surface of the lobes is convergent and hence the rolling elements become wedged between the shaft and the cylindrical surface. They thereby transmit the applied torque to the fastening device. This wedging action provides a driving force in either direction depending upon the direction of rotation of the wrench. As more torque is applied to the wrench, the rolling elements grip tighter against the cylindrical surface of the fastening device. The limit of torque which can be transmitted by the wrench to the fastening device is

governed mainly by the hardness and strength of the materials from which the wrench and the cylindrical surface are made.

Ordinarily, the rolling elements will tend to occupy a position between the apices of the lobes i.e. such that the wrench has a diameter which is less than its maximum effective diameter and thus the wrench can be inserted into the recess irrespective of the relative orientation of the recess and the wrench provided that the longitudinal axis of the recess and the longitudinal axis of the shaft are substantially co-linear. Thus, the wrench is particularly suitable for use in automated fastening systems in which case the wrench will be driven by means of a suitable motor. Further, a motor may be used to drive the wrench for non-automated applications. Alternatively, if desired, the wrench may be rotated by providing it with a suitable handle in the manner of a screw driver or by providing it with a lever lying in a generally radial plane with respect to the longitudinal axis of the wrench. When used manually the wrench can be used with one hand only in the manner of a screw driver or the like. However, there is no requirement to apply an end load as in the case of a conventional screw driver. According to another aspect of the present invention, there is provided a fastening device which includes a fastening means and which comprises a portion having a recess which is bounded by a cylindrical surface serving as a driving face for rotating the device about its longitudinal axis with respect to a member to secure the device to the member by the fastening means.

The fastening means may be a screw thread adapted to engage with a corresponding screw thread in the member. However, alternative fastening means may be present. For example, the fastening means may be in

the form of a projection adapted to engage under an abutment on the member in the manner of a bayonet fitting.

The recess may be a blind recess but is not necessarily so.

In a preferred embodiment, the fastening device includes a head portion in which the recess is located and a shank portion of reduced diameter. In this case, when the fastening means is a screw thread, the screw thread is preferably provided on the shank portion.

Preferably the head portion is of circular section so that it cannot be turned by means of an externally applied spanner. In this case, the head portion preferably includes a cylindrical outer surface. The head portion may, however, be of a countersunk configuration. Alternatively, and even more preferably, the head portion is part spherical so that it cannot be gripped externally by means of a pipe wrench or the like. In the case where the head portion is part spherical and is intended to remain proud of the member to which it is secured, it has the appearance of being a special rivet and it would not be apparent to an unauthorised person that it could be removed by rotation. Similarly in the case where the head portion includes an outer cylindrical surface or is of countersunk configuration so as to be completely enveloped by the member when the device is secured thereto, it is not possible to rotate the device by applying a tool to its external surface. Essentially, it is impossible to remove the fastening device using any tool other than a wrench as defined above.

The fastening system of the present invention is particularly useful for securing components together in the public utilities such as in telephone boxes and on road signs and also, for example, for securing wheels

to motor vehicles, all of which are frequent targets for tampering by unauthorised persons. It is also of benefit on production lines in the automotive, motorcycle, computer, business machines, and domestic electrical equipment industries. Cam covers and suspension components of vehicles can, for example, be secured by means of the invention.

In a particularly preferred embodiment, the rolling elements are positively located against the periphery of the shaft by means of a rotatable collar which may be in the form of a clip formed of, for example, spring-steel or of suitable plastics material. Alternatively, a sheath of plastics material or metal may be provided around the shaft and rolling elements to loosely retain the elements against the periphery of the shaft. This sheath need not be secured as such to the rolling elements which may effectively be anchored at their non-functional end by, for example, being embedded in a handle used to rotate the shaft. The rolling elements may be formed of spring steel wire in which case it is possible to reduce the size of the functional end of the wrench considerably so that it may be used with small fastening devices having a small driving recess. For a better understanding of the invention to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:-

Figure 1 is a view of a fastening device and a wrench in accordance with a first embodiment of the invention about to be engaged together,

Figure 2 illustrates, in diagrammatic form, the relative dispositions of the essential components of the wrench and fastening device of Figure 1 when engaged together but not transmitting torque,

Figure 3 corresponds to Figure 2 but shows the

relative dispositions of the components when torque is being transmitted,

Figure 4 is a perspective view of the functional end of a second embodiment of a wrench of the present invention,

Figure 5 is a section through the wrench of Figure 4 along lines V-V,

Figure 6 shows a perspective view of a rolling element of the wrench of Figure 4, Figure 7 shows a perspective view of a clip for mounting on the end of the wrench shown in Figure 4,

Figure 8 is a section through the wrench of Figure 4 along line IIX-IIX when the clip of Figure 7 is fitted, Figure 9 is a perspective view of a third embodiment of a wrench of the present invention,

Figure 10 is a section through a second embodiment of a fastening device in accordance with the invention, Figure 11 is a section through a third embodiment of a fastening device in accordance with the invention, and

Figure 12 is a section through a fourth embodiment of a fastening device in accordance with the invention. Referring now to Figures 1 to 3, the wrench comprises a shaft 1 having a longitudinal axis 6 and including a terminal portion 2 at its functional end. The portion 2 is provided with three equi-spaced radially extending lobes 3 defining cam surfaces. Three rolling elements 4 in the form of cylindrical rollers of circular section and formed of steel or the like are located along at least the terminal portion of the shaft 1 and are retained against the peripheral surface of the shaft 1 by means of a freely rotatable collar 5 formed of metal or plastics material and including recesses 5a to receive the rolling elements

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4. The recesses 5a are of part-oval section so as to allow the rolling elements to be radially displaced away from the surface of the shaft 1. Each recess ma include a resilient portion (not shown) arranged to bias the rolling element therein towards the shaft 1. Ordinarily, the rolling elements 4 will tend to adopt rest position wherein they are located mid-way betwee the apices of adjacent lobes 3. The shaft 1 may be rotated about axis 6 by means of, for example, a motorised chuck or handle or lever operably attached the other end of the shaft 1. Figure 1 also show a fastening device in accordance with the present invention. The device is generally cylindrical and includes a head portion 7 and a reduced shank portion which are co-axial with respect to longitudinal axis of the device. That face of the head portion 7 which is most remote from the shank portion 8 includes, in its end face, a cylindrical recess 10 bounded by a cylindrical surface 11 which serves as the driving f of the device. The longitudinal axis of the cylindrical recess 10 is co-axial with the longitudi axis 9. The reduced shank portion 8 includes a fastening means in the form of an external screw thread. The radius of the cylindrical recess 10 is less than the sum of the diameter of the cylindrical roll elements 4 and the distance from axis 6 to the apex the lobe 3 but is more than the sum of the diameter the rolling elements 4 and the distance between the longitudinal axis 6 and a point on the surface of th shaft 1 mid-way between the apices of adjacent lobes. Thus, when the rolling elements 4 are in their norma rest position with respect to the terminal portion o the shaft 1 (as described above) the effective diame of the wrench is a minimum and the end of the wrench can be readily inserted into the recess 10 merely by

aligning axes 6 and 9 and bringing the wrench and fastening device together. At this stage, the lobes 3, rolling elements 4 and head portion 7 have the relative disposition as shown in Figure 2. It can be seen from Figure 2 that each face of the lobed shaft defines, with the cylindrical surface 11, a path which converges at each end.

Once the wrench is rotated about axis 6 (in the direction shown in Figure 3), the rolling elements 4 are caused to rotate with respect to the terminal portion of the shaft 2 in the direction indicated by the arrow and hence move along the path towards the converging circumferential wall 11 and lobe surface. Thus, the rolling elements 4 roll over the surface of the lobes and become displaced away from axis 6 and increase the effective diameter of the wrench until they can roll no further because they engage the cylindrical surface 11. Because the rolling elements 4 are of circular section, irrespective of their rolling disposition with respect to the surface of the shaft and the cylindrical surface 11 of the fastening device, curvilinear portions of the rolling elements are always in contact with these surfaces. Continued rotation of the wrench about axis 6 results in transmission of the rotation of the wrench to the cylindrical surface 11 of the fastening device via the rolling elements 4 which tend to become wedged against the smooth cylindrical surface 11. Thus, the fastening device rotates in the same direction as the shaft as shown by the arrow in Figure 3. It will be appreciated that if the direction of rotation of the wrench is reversed, then the direction of rotation of the fastening device is similarly reversed.

In this way, a high torque can be transmitted from the wrench to the smooth cylindrical surface of the fastening device without slippage and without causing

-10- damage to that surface.

Referring now to Figures 4 to 8, there is shown another embodiment of the wrench of the present invention. This is particularly suitable for use with medium to large fastening devices.

Parts corresponding to parts of Figures 1 to 3 ar denoted by like reference numerals. Thus, the termina portion of the shaft 1 includes a first region 21 provided with radial lobes 3 and a second region 22 provided with lobes 3 which regions are separated by a cylindrical region 23 of circular cross-section. The first and second lobed regions 21 and 22 are disposed such that their respective lobes 3 are in registry. The terminal portion of the shaft is generally of a smaller diameter than the remainder of the shaft. Fro strength considerations, the various cross-sections of the terminal portion of the shaft are as large as possible. A clip 24 formed of spring steel is provide for mounting on circular sectioned region 23. The cli 24 as shown is closed and hence has to be slid onto th terminal portion from its free end. It may, however, be in the form of a split ring to facilitate assembly. The clip 24 includes three equally-spaced recesses 25 each having a dimension such that it can accommodate one of the circular sectioned rolling elements 4. As shown in Figure 6, the rolling elements 4 include a central portion of reduced diameter. The rolling elements 4 are located alongside, and adjacent to, th periphery of the shaft 1 (the rolling elements 4 havi been omitted from Figure 4 in the interest of clarity) and are retained against the periphery of the shaft 1 by the clip 24. The clip 24 is slid over the free en of the region 22 and onto region 23 where it is retained by the lobes 3 of regions 21 and 22 and engages with the reduced diameter portions of the rolling elements.

Referring now to Figure 9, there is shown a third embodiment of the wrench of the present invention. This is particularly suitable for use with small to medium sized fastening devices. Parts corresponding to parts of Figures 1 to 8 are denoted by like reference numerals. In this case, the rolling elements 4 are in the form of long spring steel wires. They are retained generally against the peripheral surface of the shaft 1 by means of a protective sheath 31 formed of suitable metal or plastics material. The rolling elements 4 are embedded, at their non-functional end, in a handle 32 at the end of the shaft 1. This handle may be formed of plastics material and be moulded integrally with the shaft 1. The protective sheath 31 is not essential but helps to protect the thin wire rolling elements 4 from damage.

The functional ends only of the rolling elements 4 protrude beyond the sheath. Since the rolling elements 4 are formed of thin wire, they have low torsional stiffness and thus the free ends of the rolling elements 4 can roll over the surface of the shaft 1 in the manner described above even though their other ends are secured against such rotation by being embedded in the handle 32 secured to the shaft 1. The inherent springiness in the rolling elements 4 rends to return the tips of the elements to their normal rest position where they are midway between the apices of adjacent lobes 3. If desired, a clip 24 as shown in Figure 7 or a collar 5 as shown in Figure 1 may be provided at the functional end if necessary. Also, if desired, the drive shaft 1 can be of a larger section at the non¬ functional end and taper gradually along its entire length to the functional end. In such a case, the rolling elements may not lie exactly parallel to the rotation axis 6 of the wrench (they may be inclined by 2 or 3 degrees to that axis). However, this is of

little consequence since, as the tips of the rolling elements are subjected to load, they will tend to be flattened against the shaft 1 at the lobed region. The advantage of this embodiment is that a much longer tool can be provided to enable remote fastening devices to be rotated.

Referring to Figure 10, there is shown a cross- section of another embodiment of a fastening device of the present invention inserted into a member. Parts corresponding to parts of Figures 1 to 9 are denoted by like reference numerals.

The fastening device shown in Figure 10 comprises a head portion 41 which is part-spherical and a reduced shank portion 8 which includes a fastening means in the form of an external screw thread 42. The head portion 41 includes a cylindrical recess 10 co-axial with the axis 9 of the device. The device is inserted through a hole 43 in a first member 44 and into a hole in a second member 45 provided with an internal thread 46 corresponding to thread 42. The device is rotated about its axis 9 by means of a wrench of the present invention as above described which is inserted into the recess 10 in the manner described above. Thus the device becomes attached to member 45 and fastens member 44 thereto. It can be seen that, when the device is fully engaged in the members as shown, it would not be immediately apparent, to an unauthorised person, that the device could be removed by rotation. Indeed, even if this were to be appreciated, the shape of the head portion 41 is such that it could not be rotated by, fox- example, a conventional pipe wrench but only by a wrench in accordance with the present invention.

Referring now to Figure 11, parts corresponding to parts of Figures 1 to 10 are denoted by like reference numerals.

There is shown the fastening device of Figure 1

inserted in a member 51. In this case, the fastening device is rotated, by means of a wrench in accordance with the invention, so that its external thread on reduced shank portion 8 engages with a corresponding screw thread in a bore provided in the member 51. The shape of the bore is such that the head portion 7 of the fastening device can enter into the bore and the free end face of the device is flush with the surface of the member 51. Again, it would not be apparent to unauthorised persons that the device could be removed by rotation and in any event, it could not be rotated in the absence of a wrench in accordance with the invention.

Referring now to Figure 12, parts corresponding to parts of Figures 1 to 11 are denoted by like reference numerals.

In this case, the head portion 61 of the fastening device is of countersunk configuration and the shape of the hole 43 in member 44 corresponds. Again, when the device is fully inserted into the members 44 and 45, it is not apparent that it could be removed by rotation. Moreover, it could not be rotated without the use of the wrench of the present invention.