A device for locking a first component to a second

The present invention relates to locking devices and relates particularly but not exclusively, to devices for locking one component of a torque wrench to another.

A locking device currently in use is illustrated in figure 1. The device 10 has a cylindrical housing 12 with apertures in its surface 14 through which ball bearings 16 are able to protrude. A body 18 is slidably mounted within the housing and is biased by a compression spring 19. The body, slidably mounted within the housing, has two surface portions wherein one surface portion 20 is further from the axis of the cylindrical housing than another surface portion 22 and these two surface portions are connected by a cam surface 24.

When the device is not in use the spring remains at maximum extension and biases the slidable body such that the surface of the body furthest from the axis of the cylindrical housing is in contact with the ball bearings. In this position the ball bearings are forced into the apertures of the housing wherein they protrude through the surface of the housing. When an operator pushes the body, which is seen to extend beyond the housing in figure 1, the surface of the body closest to the axis of the cylindrical housing is moved beneath the ball bearings and so they are no longer forced into the apertures and can retract inside the housing.

The device can be locked to a component by sliding it into a cylindrical cavity in the component, the cavity also having an annular recess. When the device is mounted within the cavity, the protruding ball bearings engage its outer wall preventing the device from sliding completely into the cavity. When the operator presses the section of body extending beyond the housing, the ball bearings are released and move into the housing. The device is therefore able to fully slide Into the cavity. The operator then releases the button, allowing the ball bearings to protrude from the housing once again and into the annular recess within the cavity thereby impeding the slidable movement of the housing and locking the device to the component.

A major problem with this device of the prior art is that an operator Is required to press the button in order to lock the device. In some cases an operator may forget to press the button or may be unaware that this is necessary to lock the device. In other cases, when an operator has pressed the button, there may be some uncertainty as to whether the device has been locked successfully because the device provides no indication that it has been locked.

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.

According to the present invention, there is provided a device for locking a first component to a second component, the device comprising : - a housing having at least one aperture and adapted to be at least partially received in a cavity in a first component; at least one locking member adapted to move between a first position where at least one said locking member extends at least partially through at least one said aperture to lock the device to the first component and a second position releasing the device from the first component; a body slidably mounted within the housing and adapted to move at least one said locking member between said first and second positions; at least one pin for engaging a surface of the cavity in the first component; first biasing means having a first spring constant for biasing at least one said pin relative to the housing.

By providing a locking device having a pin that engages a surface of the cavity the advantage is provided that it is not necessary for an operator to press the button, that is part of the body, in order to ensure engagement of the locking device. As a result, it is unlikely that the components will be incorrectly engaged with each other and will remain correctly engaged during the operation of the tool. Furthermore, as the locking members lock into a recess in the cavity a clicking sound is produced. At this time the compression of the first

spring is released and the body extends slightly from the housing. This clicking noise indicates that the locking has occurred and the two components are correctly held together.

In a preferred embodiment the first biasing means comprises a spring mounted within the body, engaging a surface of the pin and a wall of the body.

In another preferred embodiment the device comprises second biasing means for biasing the body relative to the housing the second biasing means having a second spring constant less than the first spring constant.

In a further preferred embodiment the second biasing means comprises a spring adapted to engage abutment portions on an outer surface of the body and an inner surface of the housing.

The presence of a second spring provides the advantage that the force of impact on such abutment portions is reduced when the body moves to its maximum possible extension from within the housing as the device locks into an annular recess of a cavity.

In a preferred embodiment, the housing comprises a cylinder having at least one first aperture and at least one second aperture at respective opposing ends and adapted to have a second component fixably mounted to the housing adjacent one end .

In another preferred embodiment, the housing further comprises a plurality of third apertures for receiving the locking members .

In a further preferred embodiment, the locking members comprise ball bearings with diameters greater than the diameters of the third apertures.

In a preferred embodiment, the slidable body is substantially cylindrical and has three surface portions, a first surface portion at a first radial distance from an axis of the cylinder, a second surface portion at a second radial distance from the axis and a third surface portion connecting the first and second portions .

In a another preferred embodiment a pin is slidably mounted within the body, and has engaging means there on to retain the pin within the body.

By having engaging means on the pin that engages a lip at the aperture of the body that receives the pin, this provides the advantage of preventing the pin from separating from the device under the action of the first biasing means .

In a further preferred embodiment, a device for locking a first component to a second component substantially as herein before described with reference to Figures 3 to 5 of the accompanying

drawings .

Preferred embodiments of the invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings in which:-

Figure 1 is a cross sectional view of the locking device of the prior art; and

Figure 2 is a perspective view of the components of the device in Figure 1; and

Figure 3 is a cross sectional view of the locking device of the present invention; and

Figure 4 is a perspective view of the components of the device in Figure 3; and

Figure 5 is a series of cross sectional views of the locking device of Figure 3 at various stages of its operation.

With reference to figure 3, a locking device 100 has a substantially cylindrical housing 110 with a first and a second aperture 111 and 113 at either end. The housing 110 also has three third apertures 112 in its surface for receiving locking members in the form of ball bearings 114 adjacent the first aperture 111. Adjacent the second aperture 113 a first component

116 is fixably mounted using a split ring 117. A substantially cylindrical body 118 is slidably mounted within the housing 110. The body 118 has an aperture 119 at one end for receiving a pin 120. The pin is slidably mounted within the body and has an abutment portion 122 at the end of the pin within the cavity which engages a lip 124 at the aperture 119. The abutment portion 122 and lip 124 limit the extent of the slidable movement of the pin with the body. The body 118 and pin 120 are both substantially cylindrical and have a coincident axis 125.

A first spring 126 biases the pin 120 by engaging an end wall 127 of the body 118 within which it is mounted and an engaging surface 129 of the pin 120. A second spring 128 biases the body 118 with respect to the housing 110 by engaging a first abutment portion 130 on the outer surface of the body and a second abutment portion 132 on the inner surface of the housing. The body 118, slidably mounted within the housing 110 and biased by both first and second springs 126 and 128, has two surface portions with a first portion 134 closer to the axis 125 of the cylindrical housing than a second portion 136. Both first and second portions are connected by a cam surface 138. The locking device 100 is mounted to a second component 140 having a cavity 142 which has an inner surface 144 and an annular recess 146.

The operation of the locking device 100, shown in figure 3, will now be described. The second component 140 to which the locking device is to be mounted has a cylindrical cavity 142 with a flat

end surface 144 and must have an annular recess 146 or some other recess or apertures into which the locking members are received. As the locking device is mounted into the cavity in the second component 140, pin 120 engages the end surface 144 of the cavity, as illustrated in figure 5a.

The ball bearings 114 initially engage the lower surface portion 134 of body 118 and do not protrude their respective receiving apertures 112. This allows slidable movement between the cavity 142 and housing 110.

As the locking device is further moved into the cavity, illustrated in figure 5b, the pin 120 pushes against the first spring 126 which engages the engaging surface 129 of the pin 120. The pin causes slight movement of the body 118 through engagement of the first spring 126 which further engages the wall 127 of the slidable body opposite the aperture which receives the pin. In this situation the body moves relative to the housing in a direction away from the cavity and this motion is opposed by the second spring 128. The second spring provides a force to oppose the sliding motion of the body with respect to the housing in a direction away from the cavity by engaging abutment portions 130 and 132 on the outer surface of the slidable body and the inner surface of the housing respectively.

In figure 3b it is illustrated that as the housing is moved into the cavity the cam surface 138 becomes engaged with the ball

bearings . However the ball bearings 114 are prevented from outward movement by the wall of the cavity. When the locking device 100 has been moved into the cylindrical cavity sufficiently far that the apertures 112 and ball bearings 114 are in alignment with the annular recess 146, the component of force perpendicular to the axis 125 exerted by the cam surface 138 on the ball bearings is released. This results in the movement of the ball bearings which slide up the cam surface 138 into the annular recess 146 and the body 118 moves within the housing, away from the cavity under the action of the first spring .

When the ball bearings 114 are able to move into the annular recess the slidable body 118 is able to move under the force of the first spring 126 against that of the second spring 128 such that the outer surface portion 136 of the body engages the ball bearings and retains the ball bearings in the annular recess. In this situation the housing and hence the component 116 which is fixably mounted to the housing, is locked with respect to the component 140. This situation is illustrated in figure 5c.

An indication that the device has been successfully locked is provided by the sound created when the slidable body 118 of the device reaches maximum extension from within the housing. At the same time the abutment portions on the outer surface of the body and the inner surface of the housing come to their closest proximity separated by the second spring at its maximum

compression.

The spring constant of the first spring 126 is higher than that of the second 128 and therefore the slidable body 118 cannot move back towards the recess unless engaged by an operator. The situation when the slidable body protruding the housing of a locked device is engaged by an operator is illustrated in figure 5d. The body is slidably moved in the direction of the cavity against the force of the first spring 126. As a result the lower surface portion of the body slides beneath the ball bearings, and the ball bearings 114 can retract from the annular recess 146 so that they no longer protrude from the housing 110 of the locking device. This allows unimpeded slidable movement between the housing 110 and cavity 142 and the locking device 100 can be removed from the cavity and the previously locked components separated .

The engagement of an abutment portion of the pin 122 with a lip 124 at the aperture of the body limits the extent of the slidable motion of the pin and prevents it from being removed from the device by the first spring when the device is not mounted in a cavity.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of

-lithe invention as defined by the appended claims. For example, the recess, housing, body and pin could have cross sections that are not circular as illustrated, but have a square cross section. Also, the device could be made to function without a second biasing means. However the device would be difficult to lock from an upside down position. In such a situation the body would move to its position of maximum extension from within the housing under the force of gravity and cause the locking members to protrude the device which would subsequently not be able to slide into a cavity.