WO1996023161A1

WO1996023161A1 - Improvements in and relating to supports

Info

Publication number: WO1996023161A1
Application number: PCT/GB1996/000185
Authority: WO
Inventors: Ellis Fitzroy Petersen Whitcomb
Original assignee: The Designaware Trading Limited
Priority date: 1995-01-28
Filing date: 1996-01-26
Publication date: 1996-08-01
Also published as: GB9501706D0

Abstract

A support, such as a monopod for a camera, comprises a telescopic member (6) having an inner portion (8) slidably movable within an outer portion (9). Retaining means (18) locks the portions at any selected relative position between the fully collapsed and fully extended conditions of the support, but is prevented by jam prevention means (62) from locking the portions at the fully extended position. The release of the retaining means requires the slight extension of the telescopic member, and the jam prevention means, therefore, prevents the retaining means from jamming the telescopic member in its fully extended condition. A preferred form of retaining means comprises a sleeve (26) which has apertures for accommodating ball bearings (e.g. 34) which are urged against the outer portion (8) by camming members to lock the outer and inner portions in a selected position. The sleeve (26) has a circlip which partially occludes the apertures to retain the ball bearings therein. The sleeve and ball bearings can thus be formed as an initially separate subassembly.

Description

Title: Improvements in and relating to Supports

Field of the invention

This invention relates to a support which comprises a telescopic member. Examples of such supports include supports for optical devices, such as video cameras and like, microphone and music stands and collapsible tent poles.

Background to the invention

A telescopic support can include a retaining mechanism operable to contain inner and outer portions of the support at a selected relative position, so as to retain the support at a selected effective length. One example of such a mechanism comprises a pair of opposed frusto cones which are carried on the inner portion of the member, and which act on a number of ball bearings. The mechanism is activated by moving the frusto cones towards each other, causing the bearings to be urged against the outer portion. The force with which the bearings are so urged dictates the resistance offered by the retaining means to be collapsed or extension of the telescopic member.

This sort of mechanism when activated, can be so arranged that the application of an external force to the telescopic member tending to extend or collapse the latter, will cause one of the frusto cones, depending on direction of said force, to urge its associated ball bearings against the outer portion with an increased force.

Thus, the retaining means can use the weight of, for example, a piece of equipment supported by the support to help to resist the collapse of the telescopic member. However, in order to release the retaining mechanism, the telescopic member then has to be extended slightly so that the force exerted by the upper frusto cone on the associated ball bearings to be reduced to a sufficient extent to enable the telescopic member to be collapsed.

This can give rise to problems if the telescopic member cannot be readily further extended.

Summary of the invention

According to a first aspect of the invention, there is provided a support comprising a telescopic member having inner and outer portions telescopically movable relative to each other within a range of allowable movement which has first and second limits, the support having retaining means which is operable to retain the portions at a selected relative position lying in said range, and which comprises a camming member, attached to one of said portions, operable to urge the locking member against the other of said portions to prevent movement of the portions towards the first limit, but requiring relative movement of the portions towards the second limit in order to release the locking member, wherein the support includes jam prevention means operable to prevent the retaining means from locking the portions at said second limit.

The invention thus prevents the retaining means from jamming the portions at the relative position at the second limit of the range of allowable movement, from which position the retaining means could not otherwise be released since the portions could not move beyond said second limit.

Preferably, the camming member is attached to the inner portion and the locking member engages the outer portion.

The retaining means preferably comprises a further locking member and a further camming member which is operable to urge the further locking member against the outer portion so as to prevent relative movement of the portions towards the second of said limits, and the jam prevention means preferably is operable to cause the further locking member to be so urged as the second limit is approached.

The jam prevention means may act directly on the further locking member, but preferably the locking member and further locking member are accommodated in a floating sleeve, into which the camming member and further camming member project, which sleeve is so connected to said inner portion as to be movable relative to the camming member. In this case, the jam prevention means preferably, acts on the further locking member via the sleeve.

Preferably, the second said limit corresponds to a fully extended condition of the telescopic member, and the first limit corresponds to the fully collapsed condition thereof.

The jam prevention means may act on the sleeve by directly engaging the latter, but preferably acts on the sleeve through a spring which in turn acts between the sleeve and the inner portion.

Preferably, the jam prevention means comprises a cap having a shoulder which abuts one end of the spring and a peripheral wall which extends from the shoulder away from the sleeve, wherein the wall engages a stop at an end of the outer portion as the relative position of the portions approaches said second limit.

By acting on the sleeve through a spring, the jam prevention means can reduce the likelihood of damage to the retaining means resulting from rapid extension of the telescopic member.

The further camming member is preferably arranged to urge the further locking member against the outer portion with a force which increases with the application of the force tending to collapse the telescopic member, and the support includes further jam prevention means operable to move the locking member relative to the camming member when the relative position of the portions approaches the first limit, so as to prevent the retaining means from jamming the telescopic member in its fully collapsed condition.

Conveniently, the further jam prevention means also comprises a cap which acts on the sleeve through a spring.

Preferably, the action of the jam prevention means, and further jam prevention means on the retaining means defines said second and first limits respectively.

Preferably, the locking member and further locking member each comprise one of a respective group of a plurality locking members and further locking members the members of each group being substantially equi-angularly spaced around the sleeve, the groups being axially spaced from each other. Preferably each locking member comprises a ball bearing.

According to a second aspect of the invention there is provided a support comprising a telescopic member having inner and outer portions and retaining means for retaining the portions in a selected position, the retaining means comprising a sleeve having apertures for accommodating a plurality of ball bearings and two camming members which extend into the sleeve through opposite ends thereof, and are operable to urge the ball bearings against the outer portion, thereby to retain the portions in said selected position, wherein the sleeve includes a circlip which partially occludes the apertures so as to retain the ball bearings therein.

The use of a circlip to retain the ball bearings in the sleeve facilitates the construction of the retaining means.

Preferably, the radial inner side of each aperture is of a smaller diameter than that of the ball bearing accommodated therein.

With this feature, the sleeve does not have to be mounted on the rest of the device before the ball bearings can be accommodated therein, enabling the sleeve and ball bearings to constitute an initially separate sub-assembly which is then mounted in position on the support.

Brief description of the drawings

The invention will now be described, by way of example only, with reference to the accompanying drawings which show a telescopic member which is extendible from a fully collapsed to a fully extended condition, and in which:

Figures 1 to 3 are sectional side elevations of the member at various position close to its fully collapsed condition;

Figures 4 to 6 show the lower and middle part of the telescopic member at various positions close to or at its fully extended condition;

Figure 7 is a sectional side view of a retaining mechanism for retaining the telescopic parts of the telescopic member at a selected relative position;

Figure 8 is a cross section taken along the line VIII - VIII of Figure 7;

Figure 9 is a sectional side view of one of the components shown in Figure 8; and

Figure 10 is an exploded perspective view of some of the components shown in Figures 7, 8 and 9 which constitute a sub- assembly for the retaining mechanism. Detailed description

The telescopic member shown in the drawings functions as a monopod support for a stills or video camera and includes at its bottom a foot 2 for standing on the ground, and at its top a part spherical head 4 for receiving a camera (not shown), which is rested on the head. The camera includes a recess, which is either integrally formed with the camera or is part of a separate attachment, into which the head 4 extends. An example of this arrangement of head and camera is shown in published PCT Patent Application WO95/01531.

The support comprises a telescopic member 6 having an inner tube 8 slidably mounted within an outer tube 9.

The head 4 is connected to the inner tube 8 via a collar 12 which includes a pair of opposed buttons 14 and 16 by which a user can operate a retaining mechanism 18 to lock the telescopic member 6 at a selected effective length.

With reference to Figure 7, the retaining mechanism comprises an upper camming member 20 which is firmly attached to the bottom of the tube 8 by being a close frictional fit therein. The lower end of the member 20 includes a frusto conical surface 22 and a central passage through which a rod 24 extends. The rod 24 is of a slightly smaller diameter than the passage in the member 20, which can therefore slide along the rod 24. The rod 24 also extends through a sleeve 26 and into a passage in a lower camming member 28, which is firmly secured to the bottom of the rod 24.

The sleeve 26 has two groups of three axially aligned, equi- angularly spaced apertures 30 and 32, which each accommodates a respective one of six ball bearings, such as the bearing 34.

As can be seen from Figure 8, the radial inner end of each aperture includes an annular rim, as a result of which the inner end of each aperture is of a smaller diameter than that of the ball bearings. The radial outer end of each aperture is of a diameter corresponding to that of the ball bearings, but is partially occluded by a circlip 38 which is located in an annular channel 40 in the centre of the sleeve, and which includes side portions 42 and 44 which partially extend over the outer ends of the apertures.

This type of sleeve is particularly advantageous because the sleeve and ball bearings can be formed as a separate sub- assembly before being placed in a position shown in Figure 7. The sub-assembly is formed by inserting the ball bearings into the apertures through the radial outer openings the rims in the apertures preventing the balls falling straight through the apertures. The circlip 38 is then placed on the body of the sleeve so that each ball bearing is then retained in its respective aperture.

The sub-assembly can then be placed over the rod 24 before the camming member 28 is secured in position. As can be seen from Figure 7, the camming members 22 and 28 extend into opposite ends of the sleeve 26, which is biassed into a neutral position between the camming members 28 and 22 by means of compression springs 46 and 48.

The spring 46 acts between a shoulder 50 at the bottom of the sleeve 26 and an annular radial shoulder of a cap 52 which, in turn, rests against an annular shoulder 54 at the bottom of the member 28.

The cap 52 has a cylindrical wall 56 extending down from the outer periphery of the annular shoulder of the cap 52. The spring 48 acts between a shoulder 60 at the top of the sleeve 26 and a cap 62 similar to the cap 52 the cylindrical wall of the cap 62 extends upwardly from the shoulder against which the spring 48 acts, and into the space between the tubes 8 and 9. Since the rod 24 is attached to the camming member 28, but can slide through the camming member 22, axial movement of the rod 24 moves the camming member 28 towards or away from the camming member 22. Movement of the camming member 28 towards the camming member 22 will result in the spring 46 undergoing greater compression than the spring 48 and therefore urging the sleeve 26 upwards towards the camming member 22. Thus, as the camming members move together, the frusto conical surface of each engages the ball bearings in its respective group of apertures 30 and 32, urging them against the outer tube 9.

As can be seen from Figures 1 to 3, the rod 24 extends through the tube 8 along its entire length, and into a cavity 64 in the collar 12 where the rod 24 terminates in a head 66. The head 66 abuts an elastomeric member 70 of which the buttons 14 and 16 (which extend through apertures in the collar 12) form an integral part. The cavity 64 also contains a compression spring (not shown) which is stronger than either of the springs 46 and 48, and which acts between the bottom of the cavity 64 and the underside of the head 66 to urge the rod 24 in an upward direction.

The member 70 has a central portion which is circularly cylindrical, which when no pressure is being applied to the buttons 14 and 16, but which deforms into an ellipsoidal sectional shape when buttons 14 and 16 are squeezed together.

The collar 12 also includes an annular downward facing external shoulder 68 which faces an annular shoulder 69 at the top of a cylindrical insert 70 in the top of the tube 9 the insert 70, like the wall of the cap 62, extends into the space between the tubes 8 and 9.

An elastomeric cylinder 72 is mounted on the inner portion 3 immediately under the shoulder 68.

When the telescopic member 6 is not in or near its fully extended and its fully collapsed conditions, and no external pressure is being exerted on the buttons 14 and 16, the force exerted by the spring in the cavity 64, 66 urges the latter up onto the member 70, the head 66 becoming partially embedded in the member. With the rod 24 in this position, the force exerted on the rod 24 by that spring overcomes the forces exerted by the springs 46 and 48 so that the lower camming member 28 is urged towards the upper caroming member 20.

As a result, the frusto conical surfaces 22 and 21 urge their respective groups of ball bearings against the inner surface of the outer tube 9. The engagement of the balls with the inner surface of the outer tube 9 prevents the inner tube 8 from axially sliding within the tube 9.

If an external force, for example the weight of the camera is applied to the tube 8, this will tend to urge the portion downwards, which, in turn, causes the camming member 20 to exert a greater outward force against the top group of ball bearings, which thus provide increased resistance to movement of the tube 8. Similarly, if an attempt is made to draw the tube 8 further out of the tube 9, the camming member 28 exerts an increased outward force on the lower group of ball bearings, which accordingly provide increased resistance to upward movement of the tube 8.

When the tube 3 is to be released, the user squeezes the buttons 14 and 16, causing the cylinder of the member 70 to distort into an ellipsoidal sectioned cylinder. This correspondingly pushes the head 66 down against the action of the spring in the cavity 63 and thus also causes the bottom of the rod 24 to be lowered. As a result, the springs 46 and 48 urge the members 20 and 28 away from each other, whilst maintaining the sleeve 26 in a position in between the members 20 and 28, so that the groups of balls are no longer urged against the tube 9. The tubes 8 and 9 can then move relative to each other so that effective length of the member 6 can be altered. It will be appreciated that the retaining means travels through the tube 9 with the lower end of the tube 8.

The member 6 can then be locked in its new effective length simply by releasing the buttons 14 and 16.

However, as the retaining mechanism approaches the foot 2 at the bottom of the tube 9, the wall 56 of the cap 52 engages the top of the foot 2 (as shown in Figure 2) regardless of whether or not the buttons 14 and 16 are being squeezed. Further downward movement of the tube 8 causes the camming member 28 to begin to slide down through the cap 52, which consequently increases the compressive force on the spring 46.

The spring 46, in turn, urges the sleeve 26 to stay at the same level as the rod 24 continues to descend until the camming member 20 urges its respective group of balls against the tube 9 with sufficient force to prevent further downward movement of the tube 8.

This relative movement of the sleeve 26 and rod 24 also moves the ball bearings in the group of apertures 30 away from the camming member 28, so that those ball bearings are not jammed against the tube 9 when the tube 8 is subsequently raised.

As can be seen from Figures 1 and 2, the cylinder 72 begins to be compressed just before the member 6 reaches its fully collapsed condition. The resilience of the member 72 helps the user subsequently to begin to extend the member 6. The cylinder 72 also helps the user to lock the tubes 8 and 9 at a relative position close to the fully collapsed condition of the member 6. It does this by preventing the cap 52 from reaching the foot 2, and thus preventing operation of the retaining mechanism, unless the member 6 is collapsed at considerable speed or with considerable force. As the member 6 approaches its fully extended condition, the cap 62 engages the bottom of the insert 70, causing the member 20 to begin to slide through the cap 62, and the compression of the spring 48 to increase. This lowers the sleeve 26 onto the camming member 28 until the ball bearings in the group of apertures 30 is forced by the member 28 against the tube 9. This movement of the sleeve also moves the ball bearings in the apertures 32 away from the camming member 22 so that those ball bearings are not jammed by the camming member 22 when the user subsequently tries to lower the tube 8.

The fully extended condition of the member 6 is shown in Figure 6, in which further upward movement of the tube is prevented by the ball bearings in the apertures 30 being urged against the tube 9.

Claims

1. A support comprising a telescopic member having inner and outer portions telescopically movable relative to each other within a range of allowable movement which has first and second limits, the support having retaining means which is operable to retain the portions at a selected relative position lying in said range, the retaining means having a locked condition, in which relative movement of the portions towards said first limit is prevented and a released condition in which said movement is allowed, relative movement of the portions towards the second limit being required to release the retaining means, wherein the support includes jam prevention means for preventing the retaining means from achieving said locked condition when the portions are at said second limit, thereby to prevent the retaining means from jamming the portions at said second limit.

2. A support according to Claim 1, in which the retaining means comprises a camming member, attached to one of said portions, the camming member being operable to urge a locking member against the other of said portions in such a way that the force with which the camming member so urges the locking member increases when either portion is urged towards a position closer to said first limit, the jam prevention means being operable to prevent the locking member from being so urged when the portions are at said second limit.

3. A support according to Claim 2, in which the retaining means includes a further locking member for preventing relative movement of the portions towards the second limit, the jam prevention means being operable to act on the further locking member so as to define said second limit.

4. A support according to Claim 2 or Claim 3, in which the camming member is attached to the inner portion and the locking member engages the outer portion.

5. A support according to Claim 4, in which the locking member is accommodated in a floating sleeve, into which the camming member projects, the sleeve being connected to said inner portion as to be movable relative to the camming member.

6. A support according to Claim 5, in which the further locking member is also accommodated in the sleeve, and in which the retaining means comprises a further camming member which extends into the sleeve through the opposite end to that through which the camming member extends, the further camming member being operable to act on the further locking member.

7. A support according to Claim 6, in which the jam prevention means is operable to act on the further locking member via the sleeve.

8. A support according to Claim 7, in which the jam prevention means acts on the sleeve through a spring which in turn acts between the sleeve and the inner portion.

9. A support according to any of the preceding claims, in which the second said limit corresponds to a fully extended condition of the telescopic member, and the first limit corresponds to the fully collapsed condition thereof.

10. A support according to Claim 8, in which the jam prevention means comprises a cap having a shoulder which abuts one end of the spring and a peripheral wall which extends from the shoulder away from the sleeve, wherein the wall engages a stop at an end of the outer portion as the relative position of the portions approaches said second limit.

11. A support according to Claim 6, in which the further camming member is arranged to urge the further locking member against the outer portion with a force which increases with the application to either portion of a force tending to move either portion towards the second limit, and the support includes further jam prevention means operable to move the locking member relative to the camming member when the relative position of the portions approaches the first limit, so as to prevent the retaining means from jamming the portions at said first limit.

12. A support according to Claim 11, in which the further jam prevention means also comprises a cap which acts on the sleeve through a spring.

13. A support according to Claim 6, in which the locking member and further locking member each comprises one of a respective group of a plurality, such locking members and such further locking members the members of each group being substantially equi-angularly spaced around the sleeve, the groups being axially spaced from each other.

14. A support according to Claim 6 or 13 in which each locking member comprises a respective ball bearing retained in a respective aperture, and in which the apertures are partially occluded by a circlip so as to retain the ball bearings therein.

15. A support comprising a telescoping member having inner and outer portions and retaining means for retaining the portions in a selected position, the retaining means comprising a sleeve having apertures for accommodating a plurality of ball bearings and two camming members which extend into the sleeve through opposite ends thereof, and which are operable to urge the ball bearings against the outer portion, thereby to retain the portions in said selected position, wherein the sleeve includes a circlip which partially occludes the apertures so as to retain the ball bearings therein.

16. A support according to Claim 15, in which the radial inner side of each aperture is of a smaller diameter than that of the ball bearing accommodated therein.

17. A support substantially as described herein with reference to, and as illustrated in the accompanying drawings.