AU2013205194B2 - A lock for a telescopic leg - Google Patents

Abstract

A lock (11) for a telescopic leg assembly (12) wherein the leg assembly has an outer tube (14) and an inner tube (13) slidably received within an open end of the outer tube(14), a locator hole (16) in the outer tube (14) and spaced pin receiving apertures (15) in the inner tube (13); wherein the lock (11) includes; a sleeve (17) having an insert end (7) and a base end (9) , wherein the insert end (7) is adapted to fit into the open end of the outer tube (14) such that when fitted the sleeve (17) is interposed between the outer tube (14) and the inner tube (13), such that the inner tube (13) can slidably move within the sleeve (17) whilst the sleeve (17) remains substantially stationary with respect to the outer tube (14); a lock member (22) connected to the sleeve base, the lock member having a locking pin (25) biased towards a lock position in which, in use, the locking pin (25) engages a locator hole (16) in the outer tube and an aligned pin receiving aperture (15) in the inner tube (13), thereby locking the inner and outer tubes against relative slidable movement; and the lock member (22) is manually operable against the bias to move from the lock position to a free position in which the inner tube (13) is free to move within the outer tube (14). Figure 3 6 -25

Description

A LOCK FOR A TELESCOPIC LEG FIELD OF THE INVENTION The present invention relates to a lock for a telescopic leg. In particular, the 5 present invention relates to a lock for a telescopic table leg and a table leg having the lock mounted thereon. BACKGROUND OF THE INVENTION The present invention will be described with particular reference to a lock and 10 telescopic leg assembly for use with an item of furniture such as a table. However, it will be appreciated that the lock and adjustable leg assembly may be used for any suitable application such as a ladders, ironing boards, work platforms and also for supports for temporary constructions such as marquees, tents, annexes and the like. A particularly suitable application is for legs for school 15 desks where it is highly desirable to be able to adjust the height of the desk for use with children of different ages and/or sizes. Adjustable telescopic legs are well known in the furniture industry. Such legs have an inner leg member slidably mounted within an outer leg member. The outer leg 20 has a series of spaced holes and the inner leg has a spring loaded pin biased towards an extended locked position. In use, an operator depresses the pin and moves the inner leg until the pin pops up into the next hole. In practice, it can sometimes be difficult to depress the pin far enough to cleanly disengage the pin form the outer leg. Further, there is a risk of catching and injuring a person's 25 fingers during operation. Still further, manipulation of the pin may be difficult for some users. Numerous alternative extendible leg mechanisms have been proposed to address the art identified problems with the spring operated pins. Whilst many of these 30 offer functional alternatives, the mechanisms are often over complicated and/or expensive to produce. In the field of mass produced articles such as furniture, cost is an important consideration and the cost for adopting many of these earlier designs is prohibitive. 1 It is therefore an object of the present invention to provide an alternative lock for a telescopic leg and a leg assembly having the lock mounted thereon. 5 SUMMARY OF THE INVENTION According to a first broad form of the invention there is provided a lock for a telescopic leg assembly wherein the leg assembly has an outer tube and an inner tube slidably received within an open end of the outer tube, a locator hole in the outer tube and spaced pin receiving apertures in the inner tube; 10 wherein the lock includes; a sleeve having an insert end and a base end, wherein the insert end is adapted to be inserted into the open end of the outer tube such that when inserted, the sleeve is interposed between the outer tube and the inner tube, such that the inner tube can slidably move within the sleeve whilst the sleeve remains 15 substantially stationary with respect to the outer tube; a lock member connected to the sleeve base end, the lock member having a locking pin biased towards a lock position in which, in use, the locking pin engages the locator hole in the outer tube and an aligned pin receiving aperture in the inner tube, thereby locking the inner and outer tubes against relative slidable 20 movement; and the lock member is manually operable against the bias to move from the lock position to a free position in which the inner tube is free to move within the outer tube. The lock of the present invention is for a telescopic leg with inner and outer tubes. 25 The lock has a sleeve for insertion into the outer tube. The outer surface of the sleeve is preferably dimensioned so as to provide an interference fit with the inner surface of the outer tube. Typically, the sleeve is formed from a hard thermoplastics material that has some degree of resilience that allows the sleeve to be deformed slightly when being fitted into the outer tube. Suitable materials 30 include polyolefins such as polyethylene or polypropylene and acylonitrile butadiene styrene (ABS). Persons of skill in the art would be familiar with suitable materials. 2 The sleeve has an insert end for inserting into the outer tube and a base end. Preferably the base end of the sleeve has a stop that may prevent the sleeve from being fully inserted into the outer tube. The stop is suitably a projection extending from the base that abuts the lower edge of the outer tube. The projection may 5 extend partially or fully about the sleeve. Suitably, the projection is in the form of a flange, rim, lip or collar. Suitably the projection is dimensioned such that in use it will sit flush against the outer surface of the outer tube. The sleeve's inner dimensions are thus that when interposed between the inner 10 and outer tubes, slidable movement of the inner tube relative to the sleeve and outer tube is permitted. It will be appreciated that some degree of frictional engagement between the sleeve and inner tube may be tolerated or even preferred. Preferably, there is a snug fit between the sleeve and the inner tube. This snug fit assists in preventing lateral movement or wobbling of the inner tube 15 within the outer tube. Prior art legs of the type discussed above having spring loaded pins have a necessary degree of tolerance between the inner and outer tubes. This degree of tolerance may allow relative lateral movement of the legs that can cause wobbling. 20 The lock has a lock member connected to the base of the sleeve that is manually operable to move from a lock position to a free position. Any suitable means of connection is appropriate. The sleeve base may have a lock member mount which in one form may be a tongue or tab extending from the sleeve base. Typically, the lock and tongue or tab are injection moulded in one piece. 25 The lock member may formed separately from the base of the sleeve or integrally connected in that it is formed in one piece. The lock member is biased towards the lock position in which the locking pin 30 engages the locater hole of the outer tube and an aligned pin receiving aperture of the inner leg a so as to resist relative movement of the inner and outer tubes. The bias may be created by any suitable means. One form of bias may be a spring such as a torsion spring which is well known in the lock arts. Alternatively, the lock member may be formed from a resilient material such that the lock member is 3 inherently biased towards the locking position. Suitable materials may be a resiliently deformable plastics or metal material such as those used in the manufacture of spring clips. 5 The lock member is manually operable against the bias to a free position. In the free position the locking pin is disengaged from the pin receiving aperture of the inner tube and locater hole of the outer tube so as to allow relative movement of the inner and outer tubes. The lock member may be manually operated by any suitable means. In one embodiment the lock member is a lever pivotally mounted 10 to the base of the sleeve. In this case, the lock pin is positioned to one side of the pivot point and the finger engaging portion is positioned on the other side of the pivot point such that the finger engaging portion can be pushed by a user's finger or thumb so as to disengage the locking pin. 15 Alternatively, the finger engaging portion may be located at any place along the lock member and is adapted for movement away from the leg so as to disengage the locking pin. In this arrangement it will be appreciated that inadvertent bumping or other contact is unlikely to move the lock member into the free position. In this embodiment, the lock member is suitably provided with a recess or the like for 20 receiving the end of a person's finger . According to a further broad form of the invention there is provided a telescopic leg assembly having an outer tube, an inner tube slidably received within a first end of the outer tube, the outer tube having a locator hole and the inner tube 25 having spaced pin receiving apertures and a lock for locking the inner and outer tubes relative to each other wherein the lock includes; a sleeve having an insert end and a base end, wherein the insert end is adapted to be inserted into the open end of the outer tube such that when inserted the sleeve is interposed between the outer tube and the inner tube, such that the 30 inner tube can slidably move within the sleeve whilst the sleeve remains substantially stationary with respect to the outer tube; a lock member connected to the sleeve base, the lock member having a locking pin biased towards a lock position in which, in use, the locking pin engages a locator hole in the outer tube and an aligned pin receiving aperture in the inner 4 tube, thereby locking the inner and outer tubes against relative slidable movement; and the lock member is manually operable against the bias to move from the lock position to a free position in which the inner tube is free to move within the outer tube. 5 The pin receiving apertures may be indents or may extend completely through the inner tube. The leg may be of any suitable cross section. Where the cross section is irregular 10 such as square or rectangular, rotational movement of the sleeve relative to the outer and inner tubes is prevented. This is important for the purposes of maintaining alignment of the locator hole, locking pin and pin receiving apertures. In the case of a round sleeve and inner and outer tubes, some rotational movement of these parts may occur when adjusting the legs. In this case, the 15 inner leg and sleeve may be provided with a recess or projection that engages a corresponding projection or recess on the other of the sleeve or inner leg. In a further form of the invention, a telescopic leg may be provided with opposing locks such that there are locking pins operative on both sides of the leg. Such an 20 arrangement may be used for load bearing applications where extra strength is desirable and/or extra security against inadvertent disengagement. Examples of such applications are for trestles, ladders and scaffolding. BRIEF DESCRIPTION OF THE DRAWINGS 25 Figure 1 is a perspective view of a telescopic leg assembly having a preferred lock of the present invention mounted thereto; Figure 2 is a side elevation of the view of figure 1; 30 Figure 2a shows an alternative design for the lever as shown in figure 2; Figure 3 is an exploded view of the leg and lock of figure 1; 5 Figure 4 is a perspective view of the lever portion of the preferred lock as shown in figure 1; Figure 5 is a side view of the lever shown in figure 4; 5 Figure 6 is a front elevation view of the lever as shown in figure 4; Figure 7 is a cross section of the lever as shown in figure 4; 10 Figure 7(a) is a cross section of an alternative lever; Figure 8 is a cross section of a telescopic leg of round cross section for use with the preferred lock of the present invention; 15 Figure 9 shows an exploded view of a further preferred telescopic leg assembly of the present invention; Figures 10 and 10A show the lock shown in Figure 9 in the locked and open positions respectively; 20 Figure 11 shows perspective, plan, side and end elevation views of the lever of the assembly as shown in Figure 9; Figure 12 shows a bottom perspective view of a further preferred lock of the 25 present invention; Figure 13 shows a top perspective view of the lock shown in Figure 12; Figure 14 shows a side view of the lock shown in Figure 12; 30 Figure 15 shows a plan view of the lock shown in Figure 12; Figure 13 is a perspective view of a lock assembly with the lock as shown in Figure 12; 6 Figure 16 is a perspective view of a leg assembly including the lock shown in Figure 12; 5 Figure 17 is a front view of the lock assembly as shown in Figure 16; Figure 18 is a cross section of the assembly as shown in figure 16 and Figure 19 is a side view of the assembly as shown in Figure 16. 10 DETAILED DESCRIPTION OF THE FIGURES Figure 1 shows a perspective view of a preferred lock 11 of the present invention and telescopic leg assembly 12. Figures 2 and 2a show side view of the view shown in figure 1, with 2a showing an alternative shape of the lever portion that 15 will be discussed further below. The leg assembly 12 typically supports a table top. The nature of the object to be supported forms no part of the invention and need not be illustrated nor described. The leg assembly 12 has a square cross section with an inner square tube 13 slidably received within an outer square tube 14. The inner tube 13 has a series of spaced pin receiving holes 15. The outer 20 tube has a single locator hole 16. The lock 11 has an open ended sleeve 17 of square cross section that is interposed between the lower end of the outer 14 tube and inner tube 13. The sleeve 17 has an upper insert end 7 and a base end 9. The base end 9 has a lip 25 18 that extends below the lower edge of the outer tube 14. The lip 18 is dimensioned such that it is flush with the outer tube 14 and prevents the sleeve 17 from being drawn into the outer tube as will be discussed in further detail below. The lip 18 supports a tongue 19 that extends downwards from the sleeve 17 over the inner tube 13. 30 The sleeve 17 is dimensioned such that when assembled the locator hole 16 is just above the end of the sleeve 17. In some applications where additional strength or the like is desired, the sleeve 17 can extend above the locator hole 16, in which case the sleeve 17 will have a correspondingly aligned locator hole. 7 The base 9 of the sleeve 17 has a depending tongue 19 with opposed ears 20 which receive a pivot pin 21. This may be more easily seen with reference to Figure 3. A lever 22 is pivotally mounted to the sleeve 17 by pivot pin 21. The 5 lever 22 has a two part construction. The lever 22 has a plastics body 24 with a metal spine 23 running the length of the body for strength. The spine 23 has a metal locking pin 25 extending from one end of the lever 22. The other end 28 of the lever 22 has a finger engaging end portion 26. As shown in figure 1 the locking pin 25 pin can lock the inner 13 and outer tubes 14 together by extending 10 through the locator hole 16 into one of the pin receiving holes 15. The lever 22 can pivot between the locked position in which the holes are engaged and a free position as shown in Figures 1 and 2. The lever 22 is biased towards the locked position by torsion spring 8. 15 Figures 4 to 7 show further details of the lever 22. Figure 7 is a cross section which shows how the metal spine 23 runs along the length of the lever 22 providing reinforcement thereto. Figure 7a shows an alternative lever 40 whereby the locking pin 25 has a 20 recessed portion 35. When in the locked position, the recessed portion 35 receives the edge of the pin receiving aperture 15 of the inner tube 13. This guards against inadvertent unlocking. The pin 25 can only be withdrawn by applying an upwards force to the outer tube 14 so as to disengage the recessed portion 35 prior to actuating the lever 22. 25 In order to assemble the telescoping leg assembly 12, the sleeve 17 of the lock 11 is inserted into the lower part of the outer tube 14. The sleeve 17 is made of a hard thermoplastics material such as polyethylene. The sleeve 17 is partially resilient such that some force is required to insert the sleeve 17 into the end of the 30 tube such that it may be held in place by frictional or interference forces. No further means of fixation is required. It may be appreciated that this offers significant advantages in ease of assembly and therefore costs. The presence of lip 18 prevents the sleeve 17 from being inserted too far. The upper end inner tube 13 is then inserted into the sleeve 17. The inner dimensions of the sleeve 17 8 are dimensioned to allow for a snug fit between the sleeve 17 and the outer face of the inner tube 13. The sleeve 17 thereby assists in holding the inner tube 13 firmly in place with respect to the outer tube 14. This may be compared to conventional spring operated pin telescopic legs where there is a degree of 5 tolerance between the inner and outer legs which may result in a degree of movement and possible unsteadiness or wobbliness of the legs. When the leg forms part of a structure such as a table, in order to adjust the length of the leg a user normally bends over so as to actuate the lock. A user 10 would typically engage the finger engaging portion 24 with their thumb. It may be seen by reference to the figures that the position of the pivot point 21 on the lever 22 is close to the finger engaging portion 26 which means that the area of the lever 22 to which a force must be applied to pivot the lever 22 against the bias is relatively small. This reduces the risk of any inadvertent bumping or knocking of 15 the lever that may cause the lever to inadvertently move to the free position. Figure 2 (a) shows an alternate design for the finger engaging portion 24 in which the finger engaging portion 24 is concave and presents an upwardly facing section. The curved section is dimension to comfortably receive a user's finger or 20 thumb. In order to move the lever 22 in this case, a downward force as shown in the direction of arrow A must be applied to release the lock 11. This further reduces the likelihood of inadvertently releasing the lock as the likelihood of a downward force being applied is generally less likely than a horizontal force being applied. Still further, a downward motion is easier for an operator to carry out, 25 particularly when the operator is bent over. When an operator has actuated the lock 11 to the free position, the operator then moves the inner tube 13 relative to the outer tube 14 in or out as desired to lengthen or shorten the leg. During such manipulation, the lock 11 may be 30 released such that the pin 25 relocates within the locator hole 16. When the locator hole 16 aligns with the next pin receiving aperture 15, the locking pin 25 will be returned home by the bias into the aperture thereby locking the tubes 13, 14 into position. 9 When manipulating the inner leg 13, a function of the lip 18 may be appreciated. Should the fit between the sleeve 17 and the inner tube 13 be too snug, there is a risk that when moving the inner tube 13 into the outer tube 14, the sleeve 17 may be drawn into the outer tube 14. This is resisted by the presence of the lip 18. 5 Conversely, should movement of the inner tube 13 out of the outer tube 14 attempt to draw the sleeve 17 out of the outer tube 14, this may simply be prevented by gripping the lip 18 whilst pulling on the inner tube 13. Figure 8 shows a cross section of a furniture leg having a circular cross section for 10 use with the lock of the invention. The inner tube 13 has a longitudinally extending locating recess 27. The sleeve 17 has a rib 28 corresponding to the recess 27. As shown in Figure 8, the recess 27 receives rib 28. This prevents rotation of the sleeve 17 with respect to the inner tube 13 such that the position of the sleeve 17 and associated pin are maintained in a correct orientation with 15 respect to the locator hole in the outer tube. Figure 9 shows an alternative embodiment of the present invention. The lock 11 is essentially the same as that shown in Figure 1 and the same reference numerals have been used to describe the same features. The lever 30 is 20 constructed differently from the lever 22 shown in figure 1. The lever 30 does not have a metal spine and metal locking pin but is instead formed as a single piece of glass filled nylon. Figure 10 and 10A shows the lever 30 in the closed and release position respectively. 25 Figure 11 shows a perspective, plan, side and end view of lever 30. The finger engaging end 31 present a concave surface to a user's finger that enables the lever to be depressed using a downwards force as described above. The lever 30 also has a textured finger gripping surface to facilitate ease of use. 30 Figures 12 to 15 show an alternative lock 50 of the present invention. The same reference numerals will be used to describe those same features as shown in the embodiment as described with reference to Figure 1. 10 The lock 50 has a sleeve 17 and a flange 52 that extends fully around the base of sleeve. The flange is sufficiently wide so as to allow it to be grasped by a user's hand when moving the respective tubes. The locking member is in the form of a curved leg 54 that has a base end 56 and a free end 58. The base end 56 is 5 resiliently connected to the flange 52 through a V shaped section 60. The V shaped section 60 is resilient so as to bias the leg 54 towards the sleeve 17. The free end 58 of leg 54 has a locking pin 25. The locking pin 25 has a recess 35, similar to that as described above with reference to Figure 7a. 10 The leg 54 extends from the base 56 outwardly away from the sleeve 17 and then back towards the sleeve 17 so as to define an outwardly curved portion 62. At the return point 64 of the curved portion 62, the leg 54 has a straight portion 66 that terminates at the free end 58. At the return point 64, there is an inwardly facing 15 tab 68, the purpose of which will be discussed below. The free end 58 is shaped to define a curved recess 70 for receiving a user's finger so as to allow a user to easily pull the free end away from the outer tube.. 20 Figures 16 to 19 show the lock 50 forming part of a leg 12. The shape of the leg 54 can clearly be seen in Figure 19. The inwardly facing tab 68 abuts the outer face of the outer tube 14. This provides structural support to the leg short it be inadvertently bumped or knocked. It also spaces the straight portion 66, from the outer tube 14 such that it is substantially parallel to the outer tube. As the locking 25 pin 25 is substantially at 902 to the straight portion 66 by maintaining the straight portion 66 parallel to the outer tube 14, the locking pin 25 is positioned within the locating hole 16 and pin receiving aperture 15 at substantially 90 to the respective tube walls. This may be seen in Figure 18. 30 Figure 18 also shows how the recess 35 receives the upper edge of the pin receiving aperture 15. The weight of the tubes and object support thereby provides a downwards force which keeps the recess 35 in this position and protects against inadvertent unlocking. In order to unlock the leg 54, a user lifts the outer tube so as to take the weight from it and move the outer tube 14 so as 11 to move the lock upwards a small amount so as to disengage the recessed portion 35. The leg 54 may then be moved to a free position. It will be appreciated that the lock and telescopic leg assembly of the present 5 invention provides a simple and cost effective alternative to current telescopic furniture legs. As the sleeve can be injection moulded of a hard but resilient plastics material, it offers advantages in assembly in that no additional means of fixation such as bolts or screws are required. It also functions to cushion the inner tube or leg against lateral movement relative to the outer leg. This can avoid 10 "wobbling" of the leg and subsequent table wobble. Further as the main means of mounting the lock to the leg i.e. the sleeve, is internal the lock has the aesthetic advantages of a substantially internal mechanism without the disadvantages of a complex internal construction. 15 It will be appreciated that various changes and modifications may be made to the invention as described and claimed herein without departing from the spirit and scope thereof. 12

Claims (18)

1. A lock for a telescopic leg assembly wherein the leg assembly has an outer 5 tube and an inner tube slidably received within an open end of the outer tube, a locator hole in the outer tube and spaced pin receiving apertures in the inner tube; wherein the lock includes; a sleeve having an insert end and a base end, wherein the insert end is 10 adapted to fit into the open end of the outer tube such that when fitted the sleeve is interposed between the outer tube and the inner tube, such that the inner tube can slidably move within the sleeve whilst the sleeve remains substantially stationary with respect to the outer tube; a lock member connected to the sleeve base, the lock member having a 15 locking pin biased towards a lock position in which, in use, the locking pin engages a locator hole in the outer tube and an aligned pin receiving aperture in the inner tube, thereby locking the inner and outer tubes against relative slidable movement; and the lock member is manually operable against the bias to move from the lock position to a free position in which the inner tube is free to move 20 within the outer tube.

2. The lock of claim 1, wherein the outer surface of the sleeve is dimensioned such that in use there is an interference fit between the sleeve and the inner surface of the outer tube. 25

3. The lock of claim 1 or claim 2, wherein the sleeve is formed from a resilient thermoplastics material allows the sleeve to be deformed slightly when being inserted into the outer tube. 30

4. The lock of any one of the preceding claims, wherein the base end of the sleeve has a stop that resists the sleeve from being fully inserted into the outer tube. 13

5. The lock of claim 4, wherein the stop is a projection that extends substantially fully around the base end of the sleeve.

6. The lock of claim 5, wherein, when the sleeve is inserted into the outer 5 tube, the outer surface of the projection is flush with the outer wall of the outer tube.

7. The lock of any one of the preceding claims, wherein in use, there is a snug fit between the sleeve and the inner tube. 10

8. The lock of any one of the preceding claims, including a lock member mount extending from the base end of the sleeve.

9. The lock of claim 8, wherein the lock member is a lever pivotally mounted 15 to the lock member mount about a pivot point.

10. The lock of claim 9, wherein the lock pin is to one side of the pivot point and a finger engaging portion is on the other side of the pivot point such that the finger engaging portion can be pushed towards the outer tube as to disengage the 20 locking pin.

11. The lock of claim 9 or claim 10, wherein a spring associated with the pivot point provides the bias towards the lock position. 25

12. The lock of any one of claims 1 to 7, wherein the lock member is a leg member that is moulded from a resilient material as a single piece with the sleeve so as to have a base connected to the base end of the sleeve and a free end, the locking pin is towards the free end and the resilience of the material biases the locking pin towards the lock position. 30

13. The lock of claim 12, wherein the lock member has a finger engaging portion towards the free end for receiving an end of a user's finger so that the locking member can be pulled away from the lock position to the free position. 14

14. The lock of any one of the preceding claims, wherein the locking pin has a recess for receiving an upper edge of the pin receiving aperture when the locking pin is in the lock position. 5

15. A lock for a telescopic leg assembly, substantially as hereinbefore described with reference to the Figures.

16. A telescopic leg assembly having an outer tube, an inner tube slidably received within a first end of the outer tube, the outer tube having a locator hole 10 and the inner tube having spaced pin receiving apertures and a lock for locking the inner and outer tubes relative to each other wherein the lock includes; a sleeve having an insert end and a base, wherein the insert end is adapted to fit into the open end of the outer tube such that when fitted the sleeve is interposed between the outer tube and the inner tube, such that the inner tube 15 can slidably move within the sleeve whilst the sleeve remains substantially stationary with respect to the outer tube; a lock member connected to the sleeve base, the lock member having a locking pin biased towards a lock position in which, in use, the locking pin engages a locator hole in the outer tube and an aligned pin receiving aperture in the inner 20 tube, thereby locking the inner and outer tubes against relative slidable movement; and the lock member is manually operable against the bias to move from the lock position to a free position in which the inner tube is free to move within the outer tube. 25

17. A telescopic leg assembly substantially as hereinbefore described with reference to the Figures.

18. An item of furniture that includes at least one telescopic leg assembly of claim 16 or claim 17. 30 15