GB1596268A - Clamps - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO CLAMPS (71) We, RACAL ANTENNAS LIMITED, a British Company, of Western Road, Bracknell, Berkshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to clamps.

According to the invention, there is provided a clamp, comprising first and second clamp arms having respective concave surfaces facing towards each other and pivotally attached to each other at one end, a one-piece rod extending between the other ends of the clamp arms, the rod defining a ring at one of its ends in which ring is rotatably mounted a disc which is attached to the first arm to be rotatable relative to an axis eccentric of the disc, the opposite end of the rod extending through a hole in the second arm and supporting a compression spring which bears against the surround of the hole, and a handle attached to the disc so as to be movable to rotate the disc about its eccentric axis and thereby draw the rod towards the first arm and thereby tend to compress the said spring and to draw the second arm towards the first arm.

A clamp embodying the invention and incorporated in a telescopic mast will now be described with reference to the accompanying diagrammatic drawings in which: Figure 1 is a diagrammatic view of part of the mast showing the clamp mounted thereon; Figure 2 is a plan view of a clamp; and Figure 3 is an end view of the clamp, looking in the direction of the arrow III of Figure 2.

As shown in Figure 1, the mast comprises a plurality of telescopically slideable sections of which two, referenced 5 and 6, respectively, are shown in the Figure - but of course in practice there could be several more. In one example of the mast, it is used for supporting a radio antenna and its fully extended height may be of the order of 12 metres.

The mast section 5 shown in Figure 1 is the base section which is in use positioned on the ground or on some other suitable support, such as a vehicle and the mast is held in an upright position by means of guy lines or, for example, a support attached to a higher point on the vehicle.

The bottom of the base of the section 5 is provided with a ball and socket joint to enable the mast to be mounted on, for example, a base plate or on a vehicle mounting bracket.

In use, the mast is erected by sliding each mast section upwardly, that is, out of the next lower one, until further movement is prevented by abutments (not shown) within the section. Each mast section, having been slid out in this way, is then clamped in that position by means of a clamp 44 which is mounted on the next lower mast section (section 5 in this example).

In practice, the innermost mast section (that is, the mast section which, in the extended mast, is the uppermost section) is slid out first, clamped by means of the clamp 44 on the next lower mast section, the latter is then slid out and clamped, and so on for the remaining sections.

The internal construction of the mast sections, which controls the manner in which they are allowed to slide relative to each other, is fully disclosed and claimed in our co-pending United Kingdom Patent Application No. 50640/76 (Serial No. 1 596267) from which this Application is divided.

The clamp 44 will now be described with reference to Figures 2 and 3.

As shown in Figure 2, the clamp assembly comprises two clamp arms 60 and 62, each having an approximately semi-cylindrical internal surface approximately matching the curvature and size of the outside of the mast section which passes through it.

The arm 62 is fixed by two pins 64 to a flange 40 around the upper end of the mast section 5 (see Fig. 1). The pins extend through the arm 62 and one of them pivotally supports the arm 60.

At its other end, the arm 62 has a recess 66 terminating in a through bore 68.

The corresponding end of the arm 60 is bifurcated to provide upper and lower wings 70, 72 (Fig. 3), and a connecting rod 74 extends from the recess 66 into the space between these wings 70 and 72. The rod 74 has at one end a washer 76 of larger diameter than the bore 68, which is slidable on a stem 78 whose outermost end is threaded to receive a nut 80. One or more disc springs 82 are clamped between the washer 76 and a washer 84 abutting the nut 80.

At its other end, the rod 74 is shaped to provide a closed ring 86 in which is freely rotatably mounted a circular disc 88. The latter has a through hole through which extends pin 90 which is located in sockets in the wings 70 and 72.

A locking handle 94 is rigidly secured to the nylon disc 88 by means of a pin 96.

When the locking handle 94 is moved in the direction of the arrow A, it will rotate the disc 88 within the ring 86 and about the axis of the pin 90. Since the latter is eccentric to the centre of the disc 88, the effect will be to draw the arms 60 and 62 together (the washer 76 abutting on the base of the recess 66 in the arm 62), and the inside curved surfaces of the arms 60 and 62 will frictionally clamp against the outside of the mast section sliding within them.

This mast section will therefore be clamped to the next lower mast section -- that is, the mast section on which the arms 60 and 62 are pivoted.

The clamping force reaches a maximum when the locking arm 94 is in the position shown in Figure 2 and further slight movement in the direction of the arrow A causes the pin 96 to go "over-centre", thus holding the clamp assembly in the locked position.

The frictional force depends on the rate of the disc springs 82 and the extent to which they are compressed, and this can be accurately adjusted by means of the nut 80.

WHAT WE CLAIM IS: 1. A clamp, comprising first and second clamp arms having respective concave surfaces facing towards each other and pivotally attached to each other at one end, a one-piece rod extending between the other ends of the clamp arms, the rod defining a ring at one of its ends in which ring is rotatably mounted a disc which is attached to the first arm to be rotatable relative to an axis eccentric of the disc, the opposite end of the rod extending through a hole in the second arm and supporting a compression spring which bears against the surround of the hole, and a handle attached to the disc so as to be movable to rotate the disc about its eccentric axis and thereby draw the rod towards the first arm and thereby tend to compress the said spring and to draw the second arm towards the first arm.

2. A clamp according to claim 1, in which the compression spring means comprises a disc-type spring.

3. A clamp according to claim 1 or 2, in which each concave surface is straight in the direction orthogonal to the plane in which it is concave.

4. A clamp, substantially as described with reference to Figures 2 and 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. bifurcated to provide upper and lower wings 70, 72 (Fig. 3), and a connecting rod 74 extends from the recess 66 into the space between these wings 70 and 72. The rod 74 has at one end a washer 76 of larger diameter than the bore 68, which is slidable on a stem 78 whose outermost end is threaded to receive a nut 80. One or more disc springs 82 are clamped between the washer 76 and a washer 84 abutting the nut 80. At its other end, the rod 74 is shaped to provide a closed ring 86 in which is freely rotatably mounted a circular disc 88. The latter has a through hole through which extends pin 90 which is located in sockets in the wings 70 and 72. A locking handle 94 is rigidly secured to the nylon disc 88 by means of a pin 96. When the locking handle 94 is moved in the direction of the arrow A, it will rotate the disc 88 within the ring 86 and about the axis of the pin 90. Since the latter is eccentric to the centre of the disc 88, the effect will be to draw the arms 60 and 62 together (the washer 76 abutting on the base of the recess 66 in the arm 62), and the inside curved surfaces of the arms 60 and 62 will frictionally clamp against the outside of the mast section sliding within them. This mast section will therefore be clamped to the next lower mast section -- that is, the mast section on which the arms 60 and 62 are pivoted. The clamping force reaches a maximum when the locking arm 94 is in the position shown in Figure 2 and further slight movement in the direction of the arrow A causes the pin 96 to go "over-centre", thus holding the clamp assembly in the locked position. The frictional force depends on the rate of the disc springs 82 and the extent to which they are compressed, and this can be accurately adjusted by means of the nut 80. WHAT WE CLAIM IS:

1. A clamp, comprising first and second clamp arms having respective concave surfaces facing towards each other and pivotally attached to each other at one end, a one-piece rod extending between the other ends of the clamp arms, the rod defining a ring at one of its ends in which ring is rotatably mounted a disc which is attached to the first arm to be rotatable relative to an axis eccentric of the disc, the opposite end of the rod extending through a hole in the second arm and supporting a compression spring which bears against the surround of the hole, and a handle attached to the disc so as to be movable to rotate the disc about its eccentric axis and thereby draw the rod towards the first arm and thereby tend to compress the said spring and to draw the second arm towards the first arm.

2. A clamp according to claim 1, in which the compression spring means comprises a disc-type spring.

3. A clamp according to claim 1 or 2, in which each concave surface is straight in the direction orthogonal to the plane in which it is concave.

4. A clamp, substantially as described with reference to Figures 2 and 3 of the accompanying drawings.