AU2004200242B2

AU2004200242B2 - Spiral cam-lock system

Info

Publication number: AU2004200242B2
Application number: AU2004200242A
Authority: AU
Inventors: David George Cook
Original assignee: Supa Peg Australia Pty Ltd
Current assignee: Supa Peg Australia Pty Ltd
Priority date: 2004-01-23
Filing date: 2004-01-23
Publication date: 2011-03-03
Anticipated expiration: 2024-01-23
Also published as: AU2004200242A1

Description

1 SPIRAL CAM LOCK SYSTEM Technical Field This invention relates to a cam lock system and in particular to a cam lock system for use with extension poles to enable the length of extension poles to be fixed 5 at a desired length Background Art Most extension poles are fastened and held at the desired length by turning a screw or offset crank that compresses or forces out a ring on one pole that binds on the inside of the other pole telescopically engaged with the one pole to hold the poles at the 10 desired length. This method can only offer a small contact area which will often allow the poles to slip unless a large amount of twisting force is applied. This is often not possible for the elderly or females to apply. In addition because of the nature of screws they can become locked in place and can be very difficult to undo or become easily damaged and impossible to use. 15 It would be desirable if a system was available which overcome or alleviated the above disadvantages or which at least provided an alternative to the prior art. Summary of the Invention The present invention provides a cam lock assembly for locking inner and outer telescopically engaged poles in a desired extended position relative to each other, said 20 lock assembly comprising a first cam support member having a longitudinal axis adapted to be mounted to said inner pole to extend longitudinally thereof, said first cam support member having an outer cam surface extending spirally and continuously substantially 360 degrees around said longitudinal axis between a position of minimum radius to a position of maximum radius, and a generally annular cam member having an 25 outer surface adapted to be engaged with the inner surface of said outer pole and an inner spiral surface adapted to mate with said outer cam surface of said cam support member, said cam member having a longitudinally extending split defining opposite circumferentially spaced ends of said cam member, said inner spiral surface extending continuously between said opposite ends of said cam member and being 30 complementary to said outer cam surface of said cam support member, and wherein when said cam support member is rotated relative to said cam about said longitudinal axis, said spiral cam surfaces cooperate to cause radial expansion of said cam member to cause in use the outer surface of said cam member to bind with the inner surface of said outer poles to prevent longitudinally movement of said poles relative to each other.

2 Preferably a radial extending wall or step defines the first and second ends of the spiral cam surface, the first end of the cam surface being at the radially outermost portion of the wall or step and the second end of the cam surface being at the radially innermost end of the wall or step whereby the spiral cam surface extends 360 degrees 5 around the longitudinal axis of the cam support member. Preferably the cam member at its first end has a minimum radial thickness and at its second end has its maximum radial thickness. Preferably also the outer surface of the cam member has a least one longitudinally extending groove. Preferably the outer surface of the cam member has circumferentially spaced apart longitudinal extending 10 grooves. Preferably the cam support member includes a first and second spaced apart lands defining therebetween an annular groove for accepting the cam member. The respective lands delimit opposite axial edges of the outer spiral cam surface of the cam support member. 15 Preferably the cam support member includes a spigot adapted to be received in one end of the inner pole for connection thereto. Preferably the spigot includes a hole or holes into which portion of the inner pole may be deformed to connect the inner pole to the spigot. Preferably the outer pole includes an outer tubular pole of circular cross section 20 and the outer surface of the cam member is of substantially circular configuration. The present invention in a further aspect provides a telescopic pole assembly including a cam lock assembly as described above. Brief Description of the Drawings To assist in the understanding of the invention reference will now be made to the 25 accompanying diagrams which show one example of the invention and in which: Figure 1 is an exploded view of an extension pole provided with a cam lock assembly according to an embodiment of the invention; Fig. 2 is an exploded view of the cam lock assembly system; and Detailed Description of the Preferred Embodiment 30 Referring firstly to Fig. 1, there is illustrated in exploded view a spiral cam locking assembly 10 associated with a telescopic pole assembly 11 comprising a first inner pole 12 and a second outer pole 13 of a slightly greater outside diameter than the fixed pole 12 such that the movable outer pole 13 is telescopically engageable with the inner pole 12, both poles 12 and 13 being of a circular cross-section. The spiral cam 35 locking assembly 10 has an end member or spigot 14 which is of an external diameter 3 substantially the same as or slightly less than the internal diameter of the pole 12 such that the end member 14 can be received in an end of the fixed pole 12. The end member 14 also is provided with holes or recesses 15 on opposite sides. The end member 14 can be inserted into the end of the pole 13 and attached thereto by 5 depressing the wall of the pole 13 into the fixing point holes or recesses 15 such as by swaging. The cam locking assembly 10 also includes a first annular land 16 adjacent the end member 14 an a second annular land 17 spaced axially from the land 16 and being defined by a circular end member 18 of the locking assembly 10. The lands 16 and 17 10 have an outside diameter equal to that of the pole 12. An annular channel 19 is defined between the lands 16 and 17 with the inner wall 20 of the channel 19 defining a spiral cam surface. The wall 20 includes a radial step or shoulder 21 which extends longitudinally of the assembly 10 and which defines the opposite ends of the spiral cam which has a maximum radial dimension at the radially outermost part of the step or 15 shoulder 21 and a minimum radial dimension at the radially innermost part of the step or shoulder 21. The cm surface defined by the wall 20 thus extends spirally and continuously between the inner radial edge of the step or shoulder 21 and the outer radial edge of the step or shoulder 21. The spiral cam locking assembly 10 additionally includes a separate spiral cam 20 member or collar 22 which is of generally annular configuration and which has an axial width W slightly less than the width of the channel 19 such that the cam member 22 may be received freely therein. The cam member 22 is longitudinally split as at 23 has an outer part-circular surface 24 and an inner spiral surface 25 complementary to the spiral surface defined by the wall 20. The cam member 22 has a maximum radial 25 dimension at one end on one side of the split 23 and a minimum radial dimension at its opposite circumferential end on the opposite side of the split 23 and the cam surface 25 extends spirally and continuously between opposite circumferential ends of the cam member 22. The cam member 22 is additionally provided in the surface 24 with a pair of circumferentially spaced grooves 26. 30 The cam member 22 is positioned in the annular channel 19 to extend around the cam surface defined by the wall 20 in the orientation shown in Fig. 2 such that the maximum radial depth portion of the cam member 22 is located at the minimum radial thickness part of the wall 20 which is at the inner radial edge or bottom of the step 21. The minimum radial thickness part of the member 22 in this orientation is located at the 35 maximum radial dimension of the wall 20 at the radial outer edge or top of the step 21.

4 The cam assembly 10 in this position has minimum external radial dimensions to allow the cam assembly 10 to be inserted into the end of the movable pole 13. The pole 12 with attached cam lock assembly 10 can be then slid up and down the inside of the pole 13. 5 The movable pole 13 can be then adjusted to set the length of the pole assembly 11 at any desired length or position. The pole 12 is then twisted or rotated relative to the pole 13 causing the cam member 22 to grip on the inside of the pole 13. When this occurs the spiral cam surface defined by the wall 20 then forces the reverse spiral cam surface 25 on the cam member 22 outwardly to expand the cam member 22 10 and cause the full outside surface 24 of the cam member to 22 bind onto the inside of the pole 13. When using the cam lock assembly, very little twisting force is required to lock the extension pole into position and to release the pole when its use has been complete. 15 Because the cam has a very large flat surface area it is very unlikely that any damage could occur to the surface to cause failure of the device. 20 25 30 35

Claims

1. A cam lock assembly for locking inner and outer telescopically engaged poles in a desired extended position relative to each other, said lock assembly comprising a first 5 cam support member having a longitudinal axis adapted to be mounted to said inner pole to extend longitudinally thereof, said first cam support member having an outer cam surface extending spirally and continuously substantially 360 degrees around said longitudinal axis between a position of minimum radius to a position of maximum radius, and a generally annular cam member having an outer surface adapted to be engaged 10 with the inner surface of said outer pole and an inner spiral surface adapted to mate with said outer cam surface of said cam support member, said cam member having a longitudinally extending split defining opposite circumferentially spaced ends of said cam member, said inner spiral surface extending continuously between said opposite ends of said cam member and being complementary to said outer cam surface of said 15 cam support member, and wherein when said cam support member is rotated relative to said cam about said longitudinal axis, said spiral cam surfaces cooperate to cause radial expansion of said cam member to cause in use the outer surface of said cam member to bind with the inner surface of said outer poles to prevent longitudinally movement of said poles relative to each other. 20

2. A cam lock assembly as claimed in claim 1 wherein a radial extending wall or step defines the first and second ends of the spiral cam surface, the first end of the cam surface being at the radially outermost portion of the wall or step and the second end of the cam surface being at the radially innermost end of the wall or step whereby the 25 spiral cam surface extends 360 degrees around the longitudinal axis of the cam support member.

3. A cam lock assembly as claimed in claim 2 wherein said cam member at its first end has a minimum radial thickness and at its second end has its maximum radial 30 thickness.

4. A cam lock assembly as claimed in any one of claims 1 to 3 wherein the outer surface of the cam member has a least one longitudinally extending groove.

5. A cam lock assembly as claimed in claim 4 wherein the outer surface of the cam 35 member has circumferentially spaced apart longitudinal extending grooves. 6

6. A cam lock assembly as claimed in any one of the preceding claims wherein the cam support member includes a first and second spaced apart lands defining therebetween an annular groove for accepting the cam member, said lands delimiting 5 opposite axial edges of the outer spiral cam surface of the cam support member.

7. A cam lock assembly as claimed in any one of the preceding claims wherein the cam support member includes a spigot adapted to be received in one end of the inner pole for connection thereto. 10

8. A cam lock assembly as claimed in claim 7 wherein the spigot includes a hole or holes into which portion of the inner pole may be deformed to connect the inner pole to the spigot. 15

9. A cam lock assembly as claimed in any one of the preceding claims wherein the outer pole includes an outer tubular pole of circular cross section and wherein the outer surface of the cam member is of a substantially circular configuration.

10. A telescopic pole assembly including a cam lock assembly as defined in any one 20 of the preceding claims.

11. A cam lock assembly substantially as hereinbefore described with reference to the accompanying drawings. 25

12. A telescopic pole assembly substantially as hereinbefore described with reference to the accompanying drawings.