INTER-LOCKING MECHANISM FOR TELESCOPIC MEMBERS

Abstract: An inter-locking mechanism for a tube assembly including an outer tubular member (1) and inner member (2), has a coiled torsion spring (5) which is interposed between the outer tubular member (1) and inner member (2) adjacent one end of the outer tubular member (1). One end (7) of the spring (5) is anchored with respect to the outer tubular member (1) and the other end (10) of spring (5) extends beyond the outer tubular member (1) and engages a cap (4) which is rotably mounted on the end of the outer tubular member (1), so that rotation of the cap (4) in one direction will apply a torsional load to the spring (5) which will unwind the coils of the spring (5) and rotation of the cap (4) in the other direction will tighten the coils of the spring (5). Axially opposed formations (12, 13) are provided on the outer tubular member (1) an cap (4), said formations (12, 13) being engageable to lock the cap (4) rotationally relative to the outer tubular member (1) in a plurality of angular relationships, the spring (5) applying a clamping load to the inner member (2) when the cap (4) and outer tubular member (1) are in at least one of said angular relationships. The opposed formations (12, 13) are resiliently urged axially into engagement in a manner which will permit limited relative axial movement, so that they may be disengaged to permit relative movement of the cap (4) and outer tubular member (1), so that the coils of spring (5) may be unwound to permit relative movement of the inner member (2) and outer tubular member (1) or tightened to clamp the inner member (2) and outer tubular member (1) in appropriate axial relationship.

Description: INTER-LOCKING MECHANISM FOR TELESCOPIC MEMBERS This invention relates to an improved inter-locking mechamism for use with telescopic assemblies. For the present purposes a telescopic assembly comprises an outer tubular member within which, in sliding relationship thereto, is provided an inner member which may be tubular or may be a solid cylindrical member such as a rod or shaft. Such telescopic assemblies find many uses, for example in props for clothes lines, extending fishing rods, tent poles, microphone stands, music stands, garden umbrellas as well as in the mining industry and in general engineering. In each of these applications there will generally be a need to provide means of varying the length of the telescopic assembly continuously, rather than in a stepwise manner; and to be able to clamp the members at any desired length so that the assembly is capable of resisting compressive and/or tensive forces. Hitherto, it has been proposed, for example as described in US Patent Specification number 3 856 253, to use in such telescopic assemblies an inter-locking mechanism having a coil spring which is located around an inner tube to apply clamping force thereto, one end of the spring being attached to the outer tube and the other end being located in a third member capable of rotation around the inner and outer tubes, so that upon rotation of said third member the coils of the spring will be unwound thereby increasing the diameter of the spring and relaxing the clamping force on the inner tube to enable that tube to move in telescopic relationship to the outer tube. The above arrangement is difficult to operate, as the outer tube must be held while the third member is rotated to unclamp the inner tube and the inner tube must then be adjusted axially while maintaining the angular relationship between the outer tube and third member. Furthermore, repeated unwinding of the coils of the spring will eventually result in permanent deformation of the spring so that it will relax on the inner tube and will no longer, in its naturally coiled condition, apply sufficient clamping force thereto to maintain the required axial relationship between the inner and outer tubes. The latter problem may be overcome, for example as described in UK Patent Specification number 2 171 444A, in which a spring loaded plunger is arranged to engage a hole in the outer tube to lock the third member with respect to the outer tube, when the spring is clampled on the inner tube. By this means, if the spring deforms during use so that it no longer naturally clamps the inner tube, the third member may be rotated to tighten the coils of th spring on the inner tube, until when the plunger engage the hole in the outer tube the spring will provid sufficient clamping load on the inner tube. Thi modification does not however do anything to ease operatio of the device. Furthermore, if the spring should stretc or the diameter of the inner tube become reduced due t wear, rotation of the third member to the point at whic the plunger engages the hole in the outer tube may not b sufficient to achieve the requisite clamping force. The plunger of the locking device disclosed in UK Paten Specification number 2 171 444A is spring loaded radiall through the third member and into engagement with the hol in the outer tube. This arrangement further complicate assembly of the device, as the hole in the outer tube must be made after assembly of the coil spring and third member on the telescoped tubes, in order to take account of tolerance variations in the diameters of the inner tube and the coil spring. According to one aspect of the present invention, an inter-locking mechanism for use with a telescopic assembly including an outer tubular member and an inner member comprises; a coiled torsion spring which is interposed between the outer tubular member and the inner member -4 - adjacent one end of the outer tubular member, one end of the spring being anchored with respect to the outer tubular member and the other end of the spring extending beyond the end of the outer tubular member; a cap being rotatedly mounted over the end of the outer tubular member and engaging said other end of the spring, so that rotation of the cap in one direction will apply a torsional load to the spring which will unwind the coils of the spring and rotation of the cap in the other direction will tighten the coils of the spring; characterised in that axially opposed formations are provided on the outer tubular member and cap, said formations being engageable to lock the cap rotationally relative to the outer tubular member in a plurality of angular relationships, the spring applying a clamping load to the inner member when the cap and outer tubular member are in at least one of said angular relationships; the opposed formations being resiliently urged axially into engagement in a manner which will permit a limited relative axial movement, so that they may be disengaged to permit relative movement of the cap and outer tubular member. Preferably, the formation on the outer tubular member and cap will also be engageable to lock the cap relative to the outer tubular member when the clamping load applied by the spring on the inner member has been relaxed sufficiently to -5 - permit axial adjustment of the inner member. With this arrangement, to unclamp the inner member, the axially opposed formations will be disengaged and the cap will be rotated from the first to the second position to unwind the spring. Formations may then be re-engaged in the second position so that the inner member may easily be adjusted axially. The formations can then be disengaged and the cap rotated back to the first position when the formations will be re-engaged. Preferably, the formations will also engage to lock the cap and outer tubular member in other angular relationships to permit further tightening of the spring to allow for stretching or wear. According to a preferred embodiment of the present invention a plurality of angularly spaced axial slots are provided in the circumferential edge of the cap and a pin is provided on the outer tubular member to engage the slots. The cap is mounted for limited axial movement with respect to the outer member so that the slots may be moved into and out of engagement with the pin, the axial resilience of the spring being used to resiliently- load the cap towards the pin, so that the pin engages in the slot. Alternatively, the formation on the cap may be in the form of a pawl formation which is resiliently urged into -6 - engagement with a ratchet teeth formation on the tubular member by separate spring means. Various embodiment of the invention are now described, by way of example only, with reference to the accompanying drawing in which:- Figure 1 is a part sectional view of a telescopic assembly with an interlocking mechanism in accordance with the present invention; Figure 2 is an elevation of the cap member of the mechanism illustrated in figure 1; Figure 3 is an elevation of the sleeve member of the mechanism illustrated in figure 1; Figure 4 is a part section view of an alternative mechamism formed in accordance with the present invention; and Figure 5 is a sectional view of the mechanism illustrated in figure 4, depicted at right angles to the view shown in figure 4. Referring to figures 1 to 3, a telescopic assembly comprises an inner member 2 (which may be a tube or solid shaft) mounted in telescopic relationship within an outer tube 1. A sleeve member 3 is secured about the end of the outer tube 1. A torsion coil spring 5 which is preferably made from flat section material, is interposed between the inner member 2 and outer tube 1. One end 7 of the spring 5 is turned outwardly and passes through the wall of the outer tube 1 and into engagement with a hole 9 in the sleeve member 3. The other end 10 of spring 5 extends beyond the end of outer tube 1, and is turned outwardly in like manner to the end 7. A cap 4 with a stepped axial bore engages over the telescoped inner member 2 and outer tube 1, a reduced diameter portion of the bore slidably engaging the inner member 2, while a larger diameter portion of the bore rotably engages the sleeve member 3 and an intermediate shoulder portion abuts the end of the outer tube 1. The end 10 of spring 5 engages in a hole 11 in the reduced diameter bore portion of cap 4. A plurality of angularly spaced radially extending pins 14 are located through the wall of the larger diameter portion of cap 4 and into engagement with a cylindrical ^groove 15 in the sleeve member 3. The groove 15 is wider than the thickness of the pins 14, so as to permit a limited degree of relative axial movement between cap 4 and sleeve member 244 -8 - 3 . A series of axial slots 12 are provided in the circumferential edge of the larger diameter end of cap 4 and a pin 13 is provided on the sleeve member 3, for engagement of the slots 12. The limited axial movement permitted by engagement of the pin 14 in groove 15 is sufficient to permit the pin 13 to be disengaged from the slots 12, while the axial resilience of spring 5 will urge the cap 4 towards the sleeve member 3 so that the pin 13 will engage in one of the slots 12. In the locked position, as illustrated in figure 1, the coils of spring 5 clamp tightly about the inner member 2 and pin 13 engages in one of the slots 12 to locate the cap 4 rotationally with respect to the sleeve member 3. For axial adjustment of the inner member 2 relative to the outer tube 1, the pin 13 is first disengaged from slot 12 by axial movement of the cap 4 away from the sleeve member 3, against the axial load applied by spring 5. The cap 4 may then be rotated to the right (as illustrated in figure 1) and such rotation will unwind the coils of spring 5 thereby increasing their diameter and relaxing the'clamping force on the inner member 2. When relaxation of the clamping force is sufficient to permit axial movement of the inner member 2, the pin 13 may be re-engaged in another of the slots 12, so that the required axial adjustment of the inner member 2 may be made. The clamping force on the inner member 2 may then be reapplied by disengaging pin 13 from the slot 12 engaged thereby and rotating the cap 4 to the left aided by the bias of spring 5, thus tightening the coils of the spring on the inner member 2. The pin 13 may then be re-engaged in one of the slots 12 when a sufficient clamping load has been applied to maintain the desired axial relationship between the inner member 2 and outer tube 1. The slots 12 are arranged so that the degree of tightening of the spring 5 may be varied to accommodate stretching of the spring 5 or variation in the diameter of the inner tube 2 as a result of wear or tolerance variations. The mechanism is assembled by first mounting the spring 5 within the sleeve member 3, so that end 7 engages in hole 9. The cap 4 is then rotatedly mounted on sleeve member 3 with the. end 10 of spring 5 engaged in hole 11. The cap 4 is then axially located with respect to sleeve member 3 by insertion of pins 14 so that they engage in groove 15. If it is desired to permit disassembly of the mechanism, the pins 14 may be in the form of grub screws. A longitudinal slit 8 is cut in the end of tube 1 to accommodate the end 7 of spring 5 so that the preassembled sleeve member 3, spring 5 and cap 4 may be pushed onto the end of outer tube 1 the sleeve member 3 being secured thereto in suitable manner, for example by an interference fit, adhesive, brazing, welding or journalling. The diameter of the spring 5 may then be increased by rotation of cap 4 to the right and the inner member 2 inserted. In the above mechanism the pin 13 may be engaged in a slot 12 to maintain the spring in the undamped condition, two hands may thus be used to effect axial adjustment of the inner member 2, this considerably eases operation of the device. Furthermore, engagement of the pin 13 in slots 12 permits locking of the device even if the effective diameter of the spring increases due to repeated unwinding of the coils. Various modifications may be made to the above embodiments, for example instead of locating peg 13 on the sleeve member 3 and slots 12 in the cap 4, a peg could be located on the skirt of the cap 4 and a circumferential ridge with slots 12 may be provided on the sleeve member 3. Alternatively, interengaging formations, for example in the form of ratchet teeth, could be provided on both the sleeve member 3 and cap 4. In a further embodiment, longitudinally extending slots may be provided in the upper edge of groove 15 to be engaged by one or more of the pins 14. While the sleeve member 3 of the above embodimen facilitates assembly of the mechanism and is extremel advantageous where the outer tube 1 has thin walls, it is not essential and, for example, the groove 15, pin 13 and hole 9 may be provided in the wall of the outer tube 1. In the alternative mechanism illustrated in figures 4 and 5, the peg 13 and slots 12 are replaced by a ratchet mechanism. In this embodiment, the sleeve member 3, spring 5 and cap 4 are mounted on the telescoped outer tube 1 and inner member 2 as described above. However the pins 14 which locate the cap 4 on sleeve member 3 engage in groove 15 the width of which is equal to the diameter of the pins 14, thereby preventing relative axial movement between the cap 4 and sleeve member 3. In place of the pin 13 and slots 12, a circumferential slot 16 is provided in the sleeve member 3, the lower edge of slot 16 defining a series of ratchet teeth 17. A pawl member 19 extends radially through the cap 4 and into the slot 16. The pawl member 19 is mounted for movement axially of the telescoped elements so that it may be moved into and out of engagement with the ratchet teeth 17. A compression spring 23 is located in a longitudinal closed bore 22 in the skirt of cap 4 and engages with the pawl member 19 to urge it into engagement with the ratchet teeth 17. A guide pin 25 is also located in bore 22, a reduced diameter portion 25 r thereof passing through a hole in pawl member 19 and extending coaxially of spring 23 and into engagement of the reduced diameter portion 24 of bore 22 and serving to retain the pawl member 19 in position. A button knob 20 is provided on the outer end of the pawl member 19, by which it may be pushed upwardly against spring 23, to disengage the pawl member 19 from the ratchet teeth 17. The above mechanism operates in similar manner to that illustrated in figures 1 to 3. Disengagement of the pawl member 19 permitting rotation of the cap 4 to the right to uncla p inner member 2. The inclined faces of the ratchet teeth 17, will permit the cap 14 to be rotated to the left without manually disengaging the pawl member 19 from the ratchet teeth 17. It is generally advantageous that engagement of the pawl member 19 with the ratchet teeth 17 will lock the mechanism in the undamped as well as the clamped condition and to this end, the spring 23 will preferably apply sufficient load to prevent rotation of the cap 4 under the torsional load applied by the partially unwound spring 5. However, in certain applications, for example where the outer tube is fixed structurally and does not need to be held while cap 4 is rotated to unwind the spring 5, so that this may be achieved using only one hand -13- and leaving one hand free to adjust the axial position of the inner member 2, then the ratchet mechanism may be arranged to permit rotation back to. the clamped position without disengaging the pawl member 19 from the ratchet teeth 17, under the torsional force applied by the partially unwound spring 5. The inter-locking mechanism illustrated in figures 4 and 5 may be assembled in similar manner to that illustrated in figures 1 to 3; the sleeve member 3, spring 5 and cap 4 first being pre-assembled complete with the ratchet mechanism, the sleeve 3 then being secured to the end of the outer tube 1 and the inner member 2 being inserted through the spring 5 after the internal diameter thereof has been increased by rotation of cap 4. The various components of the inter-locking mechanisms of the present invention may be made from suitable plastics materials, for example polyamides (nylon) or polypropylene, or metal. The pawl member 19 of the embodiment illustrated in figures 4 and 5 will however, preferably be made of metal or have a metal wear insert for engagement of the ratchet teeth 17.

Claims: CLAIMS 1. An inter-locking mechanism for use with a telescopic assembly including an outer tubular member (1) and an inner member (2) comprising; a coiled tension spring (5) which is interposed between the outer tubular member (1) and the inner member (2) adjacent one end of the outer tubular member (1), one end (7) of the spring (5) being anchored with respect to the outer tubular member (1) and the other end (10) of the spring (5) extending beyond the end of the outer tubular member (1); a cap (4) being rotatedly mounted over the end of the outer tubular member (1) and engaging said other end (10) of the spring (5), so that rotation of the cap (4) in one direction will apply a torsional load to the spring (5) which will unwind the coils of the spring and rotation of the cap (4) in the other direction will tighten the coils of the spring (5); characterised in that axially opposed formations (12, 13; 17, 19) are provided on the outer tubular member (1) and cap (4), said formations (12, 13; 17, 19) being engageable to lock the cap (4) rotationally relative to the outer tubular member (1) in a plurality of angular relationships, the spring (5) applying a clamping load to the inner member (2) when the cap (4) and outer tubular member (1) are in at least one of said angular relationships; the opposed formations (12, 13; 17, 19) being resiliently urged axially into engagement in a manner which will permi limited relative axial movement, so that they may b disengaged to permit relative movement of the cap (4) an outer tubular member (1). 2,. An inter-locking mechanism as claimed in claim characterised in that the formations (12, 13; 17, 19 engage to lock the cap (4) rotationally relative to th outer tubular member (1) in an angular relationship i which the clamping load applied to the inner member (2) b spring (5) is relaxed to permit relative axial movemen ' between the outer tubular member (1) and inner member (2). 3. An inter-locking mechanism as claimed in claim or 2 characterised in that the formations (12, 13; 17, 19) are capable of engagement to lock the cap (4) rotationall relative to the outer tubular member (1) in a plurality of angular relationships in which tightening of the spring (5) on the inner member (2) will vary to apply an appropriate clamping load to the inner member (2) despite variations in the dimensions of the inner member (2) and spring (5). 4. An inter-locking mechanism as claimed in any one of claims 1 to 3 characterised in that the cap (4) is mounted over the end of the outer tubular member (1) and located by means (14, 15) which will permit relative limited axial movement between the cap (4) and outer tubular member (1), the cap (4) being biased axially towards the outer tubular member (1) by axial resilience of the spring (5), so that the formations (12) on the cap (4) are biased into engagement with the formation (13) on the outer tubular member (1). 5. An inter-locking mechanism according to claim 4 characterised in that a plurality of angularly spaced axial slots (12) are provided in the circumferential edge of the cap (4) and these slots (12) engage a pin (13) provided on the outer tubular member (1). 6. An inter-locking mechanism according to any one of claims 1 to 3 characterised in that a series of ratchet teeth (17) are provided on the outer tubular member (1), a pawl member (19) being mounted for axial movement on the cap (4), spring means (23) being provided to urge the pawl member (19) into engagement with the ratchet teeth (17). 7. An inter-locking mechanism according to claim 6 characterised in that the ratchet teeth (17) are defined by an edge of a circumferentially extending slot (16), the pawl member (19) extending radially through the cap ' (4) and into the slot (16). 8. An inter-locking mechanism according to any one of claims 1 to 7 characterised in that the cap (4) is located axially on the outer tubular member (1) by means of series of angularly spaced pins (14), said pins (1 extending radially of the cap (4) and into engagement wi a circumferential groove (15). 9. An inter-locking mechanism according to claim when taken with claim 4 or 5, characterised in that th width of the groove (15) is greater than the thickness o the pins (14), so as to permit limited relative axia movement of the cap (4) relative to the outer tubula member (1) . 10. An inter-locking mechanism according to any one o claims 1 to 9 characterised in that a sleeve member (3) i attached to the end of the outer tubular member (1), sai sleeve member (3) providing location for the end (7) o spring (5) . 11. An inter-locking mechanism according to claim 1 when taken with claim 6 or 7 characterised in that th ratchet teeth (17) are defined by the sleeve member (3). 12. An inter-locking mechanism according to claim 1 or 11 when taken with claim 6 or 7 characterised in tha the sleeve member (3) defines the circumferential groov (15). 13. An inter-locking mechanism according to any one of claims 10 to 12 characterised in that an axially extending slot (8) is provided in the end of the outer tubular member (1) so that the sleeve member (3) with spring (5) assembled therein, may be pushed onto the end of the outer tubular member (1) with end (7) of spring (5) located through said axially extending slot (8), and the sleeve member (3) secured to the end of the outer tubular member (1) in suitable manner.

Inventors: MARCH BRIAN GEORGE, MARCH, BRIAN, GEORGE
Applicants: HUME CATHERINE GILLIES, MARCH BRIAN GEORGE, HUME, CATHERINE, GILLIES, MARCH, BRIAN, GEORGE
Application year: 1988
Main classification: F16B7
IPC codes: F16B7