AU691055B2

AU691055B2 - A locking mechanism

Info

Publication number: AU691055B2
Application number: AU40442/95A
Authority: AU
Inventors: Ronald Grierson Meade
Original assignee: Hills Ltd
Current assignee: Hills Ltd
Priority date: 1994-12-14
Filing date: 1995-12-14
Publication date: 1998-05-07
Anticipated expiration: 2015-12-14
Also published as: AU4044295A

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: HILLS INDUSTRIES LIMITED (ACN 007 573 417) Actual Inventor: RONALD GRIERSON MEADE 4* e Address for Service: MADDERNS, 1st Floor, 64 Hindmarsh Square, Adelaide, South Australia, Australia Invention title: A LOCKING MECHANISM

**S

Details of Associated Provisional Application No: PN 0064 dated 14th December 1994.

The following statement is a full description of this invention, including the best method of performing it known to us.

This invention relates to a locking mechanism, and although the invention will find many applications, it will be suited to use between telescoping members.

The invention is particularly suited to allowing two members which move relative to one another to lock in a particular position. In order for clarity, the invention will be described in respect of a pair of telescopic struts, but it should be realised that the scope of the invention will not be limited to this particular application.

Telescopic struts which extend and that are required to lock in a given position are extremely common. Examples of such struts include struts that are used to support various devices which are foldable or that extend from a retracted S position to an extended position.

*SeS An example is the clothes line described and illustrated in Australian Patent Specification No 553302. That specification describes a pivoting cantilever frame which has a rectangular frame for supporting a clothes line. When the frame is not being used, the frame may be lowered so it is against a S supporting surface such as a wall. When required for use, the frame is rotated about one edge so that it becomes substantially horizontal. In order to support the frame in this position, a strut extends between the frame and the support surface to hold the frame in a horizontal position.

Australian Patent Specification No 553302 describes a bracket assembly which automatically locks the frame in the substantially horizontal position. In use, the frame is rotated from a lowered position to the in-use position, and the bracket assembly automatically locks onto the strut thereby holding the frame in the required position. In order to lower the frame, it is necessary to manually disengage the bracket by means of pull cords and, in addition, raise the frame slightly so that the frame can then be lowered into the lowered position.

Although this arrangement works quite satisfactorily, there is a possibility that the bracket mechanism will accidentally release. This is both undesirable and unsafe. The accidental release may occur in windy conditions or quite accidentally through inadvertent lifting of the frame.

In addition, the above mechanism and other mechanisms which are used for locking telescopic members in place are generally considered to be of an unwieldy design. They are expensive to manufacture and generally not foolproof in their operation.

Accordingly, it is an object of this invention to produce a locking mechanism which is easy to operate and also is foolproof and safe in its operation. It is a further object Sof the invention to produce an arrangement which is simple to manufacture and of a generally pleasing design.

In its broadest form, the invention is a locking mechanism 20 for telescopic members which locks said members in an Sextended position comprising: a first member slidably located within a tubular second member; a follower attached to said first member that is 25 resiliently deflectable with respect to said first member; and track means, having at least one track, secured to said second member, said follower engaging a first said track as said first member is extended with res-')ct to said second member, said first track being arr~anged so as to deflect said follower with respect to said first member as said follower moves along said first track; said track means further comprising a locking recess spaced with respect to the distal end of said first track such that said follower is released into said locking recess as it leaves the end of said first track, said locking recess holding said follower and preventing collapse of said telescopic members, thereby locking said telescopic members in an extended position.

The invention may also comprise a locking mechanism as described above further comprising a mechanism for releasing the lock to allow said first and second members to telescopically collapse, said releasing mechanism comprising the following further components of said track means: an intermediate track which extends from said locking recess, said intermediate track being arranged to deflect said follower with respect to said first member as said follower moves along said intermediate track; and an exit track located at the distal end of said intermediate track such that said follower is urged into said exit track as it leaves the end of said intermediate track.

Preferably, there is provided a deflector member, located between the first track and the intermediate track, that prevents the follower engaging the locking recess and the 6 intermediate track, even though the first member continues to extend out of the second member. Preferably, the deflector member comprises a blind track into which the follower is directed, thus preventing further extension of the first member with respect to the second member.

The first and second members may comprise square tubular ,f steel with the track means comprising a sub-assembly which is "25 located in the end of the second tubular member. This subassembly may have a number of different track arrangements.

However, the tracks preferably comprise channels or recesses formed within a surface of the sub-assembly. Preferably, the follower is pivotably attached within the first member, and has track engaging surfaces which, in the case of the channel-type tracks, comprise a spigot of circular crosssection that locates within the channels.

Preferably, the operation of the locking mechanism enables the first member to be extended with respect to the second member so that it locks in an extended position. In this arrangement, the two members are locked together so that they resist compressive loading. Upon further extension of the two 4 members, the locking mechanism acts to release the follower from the locking recess to allow the first and second members to telescopically collapse under a compressive load.

In order for the invention to be fully understood, a preferred embodiment will now be described. However it should be realised that this embodiment is merely illustrative of the invention, and that the invention is not to be confined or restricted to the precise terms of this i0 embodiment.

This embodiment is illustrated in the accompanying representations in which:- Fig 1 shows a clothes line frame with a strut attached; Fig 2 shows both "exploded" and assembled views of the strut and locking mechanism; and Figs 3a to 3i show the operating sequence of the locking .o e ~mechanism as the first and second members are both extended 20 and retracted.

A seen in Fig 1, the invention is used on a rectangular frame that has clothes lines extending back and forth across the frame 10. The frame 10 is held in an elevated position, which is substantially horizontal, by a strut assembly 11 which comprises a first member 12 and a second tubular member 13. In operating the frame 10, it is lifted from its lowered position where it is substantially vertical to a substantially horizontal position whereupon the first and second members 12 and 13 lock so as to hold the frame 10 in its elevated position. In order to release the frame into its lowered position, the frame is lifted to release the locking mechanism between the first and second members 12 and 13, whereupon it can be dropped to its lowered position.

AS seen in Fig 2, the strut assembly 11 comprises a first member or strut rod 12, a track means assembly 14, a follower and a second tubular member or strut body 13. The track means assembly 14 comprises two halves 16 and 17 which have r slots or channels 18 formed within the wall 19 of each half 16 and 17. The halves 16 and 17 are designed to fit together so that they can be inserted in the end of the strut body 13, and there is provided recess 21 on the strut body 13 for engagement with latch means 20 on the track means assembly 14 such as to secure the track means assembly within the end of the strut body 13. There are provided flanges 22 on the end of each half 16 and 17 which abut against the end of the strut body 13 thereby securely restraining the assembly 14 in the end of the strut body 13 when the latch means 20 engages the recess 21.

The follower 15 is pivotably attached to the strut rod 12 by means of rivet 23 and apertures 24 in the strut rod 12 and apertures 25 in the follower 15. The follower 15 has a pair of spigots 26 which are formed by placing a metal rod through the end of the follower 15. The spigots 26 are designed to engage and move freely along the channels 18. The other end *o e ~of the follower comprises a spring means 27 which locates within the strut rod 12. The spring means 27 has a foot 28 at its end which engages a pair of inside walls of the strut rod 12 so that, as the follower 15 pivots about the rivet 23, the spring means 27 flexes to provide the necessary resilient movement of the follower The follower 15 is preferably manufactured from a plastic material, and the spring means 27 is an area of reduced coo• thickness which provides the required spring force. The spring means 27 is non load-bearing, as any compressive or tensile loads are transmitted via the rivet 23 and the portion of the follower 15 between apertures 25 and the pair of spigots 26.

Figs 3a to 3i show in cross-sectional view the strut rod 12, the strut body 13 and the track means assembly 14.

The first stage of operation is shown in Fig 3a where the strut rod 12 is extending from the strut body 13. Prior to the follower 15 entering the track assembly 14, the 6 longitudinal axis of the follower 15 is generally aligned with the longitudinal axis of the strut rod 12. The channels 18 comprise a first track 29 with an opening that is sufficiently wide to ensure that the spigots 26 engage the first track 29 as shown in Fig 3b.

The surface 30 is angled so that the follower 15 is deflected with respect to the strut rod 12 as shown in Fig 3c. The follower 15 is at its maximum deflection when it reaches the end of the first track 29 as shown in Fig 3c. As the follower leaves the end of the first track 29, the spring means 27 causes the follower 15 to move downwardly so that the spigots 26 abut against a deflector member 31. The deflector member 31 prevents the spigots 26 from immediately engaging the intermediate track 32 which would result in the spigots 26 S bypassing locking recess 33. If the strut rod 12 continues to be withdrawn from the strut body 13, then the spigots 26 will be directed by the deflector member 31 into a blind track 34 which comes to an end and therefore prevents any further 20 retraction of the strut rod 12.

When the spigots 26 are against the deflector 31 or in the blind track 34, the follower 15 is still in a deflected state so that, as the strut rod 12 moves back into the strut body 13, the spigots 26 are directed into the locking recess 33 as they leave the end of the deflector member 31, thus preventing any further inward movement of the strut rod 12.

In this position, the strut rod 12 is locked with respect to the strut body 13, provided that a compressive force is applied to the strut assembly 11. When the spigots 26 reach the end of the deflector 31, the follower 15 is once again in a neutral position such that its longitudinal axis is coincident with the longitudinal axis of the strut rod 12 (see Fig 3d). Therefore, with the spigots 26 located within the locking recess 33, as the strut rod 12 is again pulled out of the strut body 13, the spigots 26 are deflected downwardly into the intermediate track 32. This is illustrated in Fig 3e. The intermediate track 32 again ramps upwardly as shown in Fig 3e, so that the follower 15 is once 7

I

again deflected. When the spigots 26 leave the end of the intermediate track 32, the follower 15 once again drops downwardly as shown in Fig 3f, so that the spigots 26 are prevented from re-engaging the intermediate track 32. As shown in Fig 3f, the spigots 26 are once again in a second blind track 35 which limits the extent of retraction of the strut rod 12 with respect to the strut body 13. The end of the intermediate track 32 is above the centre line of the strut body 13 which means that, as the strut rod 12 is pushed inwardly, the spigots 26 are forced to engage the exit track 36 as illustrated in Figs 3g and 3h. Continued inward movement of the strut rod 12 with respect to the strut body 13 will force the follower 15 out of the end of the exit track 36 as shown in Fig 3i. Once in this position, the follower 15 resumes its central position which means that, when the strut rod 12 again moves out of the strut body 13, then the spigots 26 will engage the first track 29 rather than the end of the exit track 36.

20 As will be seen from the above description, one of the fundamental operating characteristics is the flexing of the go* end of the follower 15 and the spigots 26 either above or below the centre line of the strut body 13. This ensures that, when the spigots 26 reach the end of a given track, the e 25 spigots 26 will move away from the end thereby preventing reengagement of the previous track and thereby ensuring the correct sequence of operation. This ensures that the strut assembly 11, when being extended for the first time, gives both an audible and tactile response as to when it reaches the limit of its extension, whereupon it gives a further audible and tactile response once the follower 15 and spigots 26 enter the locking recess 33. Again, when the frame 10 is raised, a further audible and tactile response is provided when the strut rod 12 is at its maximum point of extension, and a further tactile and audible response is given once the follower 15 disengages the track assembly 14.

It will be clear from the above description that this invention provides a very unique means of providing a locking 8 and release mechanism, while at the same time producing a unit which is fail-safe, easy to operate, and pleasing in its design.

While the present invention has been described in terms of a preferred embodiment in order to facilitate better understanding of the invention, it should be appreciated that various modifications can be made without departing from the principles of the invention. Therefore, the invention should be understood to include all such modifications within its scope.

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Claims

2. A locking mechanism according to claim i, further comprising a mechanism for releasing the lock to allow said first and second members to telescopically collapse, said releasing mechanism comprising the following further components of said track means: an intermediate track which extends from said locking recess, said intermediate track being arranged to deflect said follower with respect to said first member as said follower moves along said intermediate track; and an exit track spaced from the distal end of said intermediate track such that said follower is released into said exit track as it leaves the end of said intermediate track, said exit track allowing said follower to disengage said track means, thereby allowing said telescopic members to collapse.
3. A locking mechanism according to claim 1 or 2, wherein said track means further comprises one or more deflector members arranged to ensure that said follower engages the appropriate track for each stage of the locking/releasing process, said deflector members comprising portions of said track means that are positioned so that when said follower is released after being deflected by either said first track or said intermediate track, it abuts against said deflector member which prevents it engaging the portion of track from wlhich it was released and ensures that it is directed into the appropriate portion of said track means.
4. A locking mechanism according to claim 2 or 3 further comprising a blind track at the end of said first and intermediate track into which said follower is directed, thus preventing further extension of said first member with respect to said second member.
5. A locking mechanism according to any one of claims 1 to 4, wherein said follower is pivotably attached to said first member and has a spring means attached to cause resilient deflection of said follower about said pivotable attachment. 9
6. A locking mechanism according to claim 5 wherein said spring means :20 comprises an extension of said follower that locates within said first member, said extension abutting against the inside surface of said first member and deflecting resiliently as said follower deflects. 4.
7. A locking mechanism according to any one of claims 1 to 5, wherein said *25 follower has a spigot that engages the track of said track means. "i 8. A locking mechanism according to any one of claims 1 to 6, wherein said first member comprises a square tube.
9. A locking mechanism according to any one of claims 1 to 7, wherein said second member comprises a square tube. t--W A locking mechanism according to claim 9 wherein said track means comprises a moulded polymeric component and wherein ir of track means are provided, each of the track means located respectively on adjacent inside walls of said square tube and facing one another.
11. A locking mechanism according to claim 10 wherein said follower comprises a further spigot so that there are a pair of spaced spigots that respectively engage said track means, said pair of spigots having a common central axis.
12. A locking mechanism for telescopic members which locks said members in an extended position and allows subsequent release into a collapsed position comprising: a first member slidably located within a tubular second member, a follower attached to said first member that is resiliently deflectable with respect to said first member and track means located at an end of said second member engaged by said follower, comprising a first track having a ramped surface that engages said follower and deflects it away from the centre of said second tube, a locking recess spaced with 2 respect of the distal end of said first track such that the follower is released and centralises with respect to said second tube to locate in said locking recess, an intermediate track extending from said locking recess having a ramped surface that engages said follower and deflects it away from the centre of said second tube, and exit track spaced with respect to the distal end of said first intermediate track such that the follower is released and centralises with respect to said second tube, a first deflector located adjacent the distal end of said first track against which said follower first abuts when it leaves said first track, said deflector preventing said follower from immediately engaging said locking recess, a blind track at the end of said first deflector to prevent said telescopic members from disengaging and a second deflector located directly beneath the distal end of said intermediate track against which said follower abuts to prevent it re-entering said intermediate track and ensuring that it re-enters said exit track, where said exit track allows said follower to disengage said track means thereby allowing said telescopic members to collapse.
13. A locking mechanism according to any one of claims 1 to 12 in combination with a pivotable cantilever frame for supporting one or more clothes lines, wherein said locking mechanism and said telescopi members are used to hold said frame in a raised position where said telescopic members are extended, and to release said frame to a storage position where said telescopic members are collapsed.
14. A locking mechanism according to any one of claims 1 to 8, substantially as herein described, and with reference to any one of the accompanying drawings. see* *Dated this 14th day of December 1995. HILLS INDUSTRIES LIMITED By its Patent Attorneys MADDERNS C i ABSTRACT This locking mechanism (11) for telescopic members (12, 13) serves to lock said members in an extended position. The locking mechanism (11) comprises: a first member (12) slidably located within a tubular second member (13); a follower (15) attached to said first member (12) so as to be resiliently deflectable with respect to said first member and track means having at least one track, secured to said second member said follower (15) engaging a first said track (29) as said first member (12) is extended with respect to said second member the first track (29) being arranged so as to deflect the follower (15) with respect to said first member (12) as the follower (15) moves along said first track (29); said track means (14) further comprising a locking recess (33) displaced with respect to the distal end of said first track (29) such that said follower (15) is urged into said locking recess (33) as it leaves the end of said first track (29). 00 O* 0* o