GB2248415A - Self-locking wrench - Google Patents

Abstract

A fastening system comprises a fastening device having a fastening means (42) and a wrench for rotating the device with respect to a member (45, 51) to cause the fastening means to become mechanically attached to the member. The fastening device includes a recess (10) bounded by a smooth cylindrical surface (11) and the wrench transmits a high torque without slippage to the smooth cylindrical surface. The wrench comprises a shaft (1) rotatable about its longitudinal axis (6) and having a portion includiing a plurality of lobes (3). A plurality of rolling elements (4) is located adjacent to the periphery of the shaft such that, when the shaft is rotated about its axis, the rolling elements roll along the lobes and increase the external diameter of the wrench. Thus, the rolling elements wedge between the surface of the lobes and the cylindrical surface and transmit torque from the shaft to the cylindrical surface.

Description

SELF-LOCKING CIRCULAR WRENCH This invention relates to a wrench for transmitting torque to cIrcular components.

There are circumstances in which it would be desirable to transmit a high torque to a smooth round component, without damage to the component. One such example is a fastener such as a screw with a totally smooth circular head. Any tool capable of tightening and untightening such a fastener would permit the use of an intrinsically highly tamper-resistant fixing.

Although there exists currently a range of tamper-resistant fastenings which utilise a unique head design with the co rrespcnding tool, they are very often able to be operated with a commonly available tool by wedging it in the head recess, thus recucing their actual level of tamper-resistanoe.

According to the present invention there is provIded a wrench with rolling elements which, when a torque is applied to the wrench, will roll between a smooth circular component and a lobed track on the wrench so as to wedge between the convergent surfaces, and hence to transmit the applied torqe to the circular component.

The wrench can be made in either of two versions, namely male or female, as explained later.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing hich:- KIgre shows in perspective, the female wrench about to be engaged on an external diameter.

Figure 2 shows in perspective, the wrench about to be engaged on an internal diameter.

Figure 3 illustrates the priniple of operation of the male wrench engaged in an internal diameter, not transmitting torque.

Figure 4 illustrates the principle of operation of the male wren engaged Ir. the internal diameter, transmitting torque.

The following description refers to the male wrench in Fig 2.

Reffering to the drawing the wrench comprises a shaft 1 having a lotted section 3 on which rolling elements 2 may roll, whilst belna held onto the lobed section 3 by a rotatable retaining sollar 4.

The wrench Is inserted into the internal diameter of the component 7 @female headed fastener] with the rolling elements @ in position mid-way between the lobes as in Fig 3. On turing the shaft 1 clockwise the rolling elements 2 rotate individually anticlockwise about themselves and roll between the lobed section 3 and the internal diameter 7, until they are wedged between the two surfaces as in Fig 4. At this stage any increase in torque applied to the shaft 1 will be transmitted by friction through the rolling elements to the internal diameter 7.

The torque may be transmitted equally in either direction due to the rotatIonally symmetric shape of the' lobed section 3.

The female wrench in Fig 1 works on the same principle except that the rolling elements 2 roll on an internally lobed bore 5, and transmit the torque to an external diameter 6. The rotatable retaining collar 4 is not visible in Fig 1 as it is situated inside the internally lobed bore 5.

Claims (2)

1 A wrench with self-locking rolling elements capable of transmitting a torque without slippage to a smooth circular internal diameter in either a clockwise or anticlockwise direction.

2 A wrench with self-locking rolling elements capable transmitting a torque without slippage to a smooth circular externs diameter in either a clockwise or anticlockwise direction.

A A wrench as claimed in Claim 1 or Claim 2 in which the rolling elements are retained by a rotatable collar.

- A wrench as claimed in Claim 1, Claim 2 or Claim 3 capable of transmitting torque to a smooth circular diameter.

- A wrench substantially as described herein with reference to Figures 1-4 of the accompanying drawing.