GB2336623A

GB2336623A - Locking assembly

Info

Publication number: GB2336623A
Application number: GB9808793A
Authority: GB
Inventors: Keith Denham
Original assignee: Avdel Textron Ltd; Textron Fastening Systems Ltd
Current assignee: Avdel UK Ltd
Priority date: 1998-04-24
Filing date: 1998-04-24
Publication date: 1999-10-27
Anticipated expiration: 2018-04-24
Also published as: GB9808793D0; GB2336623B

Abstract

A locking assembly for mutually locking together two members over a range of relative positions, e.g. for use as a clamp for securing the tube of a television set in its housing, which comprises: a first tubular member 22 and a second tubular member 26 which are relatively mutually adjustable along an adjustment direction to provide the range of relative positions, but which are not relatively mutually rotatable about the adjustment direction; each of the members 22, 26 having a bore, the bore 34 of the second member 26 being of larger diameter than the bore 11 of the first member 22; and a locking member in the form of a screw 38 having a first part 17 of a diameter such as to engage the bore 11 in the first member 22 but to be a clearance in the bore 34 of the second member 26, and a second part 19 of a diameter such as to engage the bore 34 of the second member 26; whereby the two members 22 can be mutually positioned in a selected relative position along the adjustment direction, and then locked together by inserting the first part 17 of the screw 38 through the bore 34 of the second member 26 and into engagement with the bore 11 of the first member 22 and screwing it thereinto until the second part 19 of the screw 38 engages with the bore 34 of the second member 26, so that the screw 38 locks the two members 22, 26 into the selected relative position.

Description

LOCKING ASS 2336623 This invention relates to a locking assembly, and more

particularly to a locking assembly for mutually locking together two members in a relative position which may vary over a range of relative positions. That is to say, the relative position of the two members may be selected from a range of relative positions before locking takes place, but after locking has taken place the two members are mutually locked in that selected relative position.

EP 302 026A and equivalent US 5054953, the contents of which are incorporated herein by reference, and to which the reader is referred for a fuller description of the background, describe such an assembly. As described therein, the locking assembly is applied to the task of locking the cathode-ray tube of a television set to its housing, which is the cabinet of the television set. The periphery of the screen face of the tube must be held in contact with the periphery of the corresponding aperture in the front of the housing. The side walls of the tube are provided with fixing lugs, but in practice there is a substantial tolerance in the position of each lug, at least in the direction away from the screen face. The lug has to be secured to an attachment point in the housing, but the relative position of the lug and the housing attachment point may fall anywhere within a range of relative positions, this range typically being a few millimetres.

In the assembly described in EP 302 026A, the first member is integral with the cabinet, the second member is initially adjustable in position with respect to the first to provide a selected relative position, and the second member is locked to the first member by means of a screw, the lug being secured to the second member by the head of the screw. The screw is first inserted into the second member and then progressively engages the first 1 j P.381 member and then the second member. It is essential that the screw engages the first member before it engages the second member, in order that the screw does not exert any axial force on the second member. Consequently, the design of the members is extremely complicated, and consequently their manufacture, even by plastic moulding, is difficult and expensive.

It is an object of the present invention to allow the design of the members to be simplified.

The present invention provides, in one of its aspects, a locking assembly for mutually locking together the two members over a range of relative positions, which locking assembly is as set out in claim 1 appended hereto.

Further features of the invention are set out in claims 1 to 10.

A specific embodiment of the invention, and a modification thereof, will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is an exploded longitudinal section of an embodiment of the assembly according to the present invention; Figure 2 is a similar section of the assembly of Figure 1 in the locked condition; Figure 3 is a cross-section of the assembly along section line III-III of Figure 2; and Figure 4 is a longitudinal section, similar to Figure 1, through a modified form of the second member.

The present example will also describe the assembly being used to secure a television set tube to its cabinet, in a similar manner to that in EP 302026A, and the general arrangement and relationship of the various elements is similar, and so far as is possible corresponding reference numerals will be used in the following description, for ease of comparison with the prior art.

2 P.381 Referring first to Figures 1, 2 and 3 of the accompanying drawings, the tube 10 of a television set must be secured to its cabinet 16 (which is of moulded plastics material) so that the periphery of the face of the tube abuts the surround 24 of the viewing aperture of the cabinet, as illustrated in Figure 2. Secured to the side walls of the tube are a number of fixing lugs such as 12, each generally T-shaped and comprising a base part 12b which is secured to the tube wall, and a part 12a projecting at right-angles therefrom and having an aperture 50. Because of the previously mentioned manufacturing tolerances, the distance H (Figure 2) between the cabinet surround 24 and the position of the part 12a of the lug may vary by a few millimetres, which variation must be accommodated by the locking assembly.

The first member of the locking assembly comprises an inner tubular part 22 and an outer tubular part 14. These are integral with the moulded plastics cabinet, and the outer tubular part 14 is reinforced and supported by three integrally moulded radial webs 18 which are spaced apart at 12011 (or, alternatively, two such ribs at 120 and 2401 apart.

The inner surface of the outer tubular part 14 has the cross-sectional shape of an irregular hexagon, and the outer surface of the inner tubular part 22 likewise has the cross-sectional shape of a similarly shaped irregular hexagon. This leaves between them an annular space which receives the second member 26. The inner part 22 has an axial height rather less than that of the outer part 14, and has an interior bore 11 of circular cross-section. The outer part 14 and webs 18 have a flat top surface 13 in a common plane.

The second member 26 of the locking assembly is also of moulded plastics material and is generally tubular in shape. Its outer surface has the cross- sectional shape of an irregular hexagon which is a sliding fit inside the outer part 14 of the first member and its inner surface defining a bore 34 through it has a uniform crosssectional shape of an 3 P.381 irregular hexagon which is a sliding fit outside the inner part 22 of the first member, as illustrated in Figure 3. At its upper end the second member 26 has a head 30 in the form of an outwardly projecting flange. From the periphery of the head flange project tabs 40, each of the tabs corresponding to one of the ribs 18. These tabs project radially outwardly and slightly downwards from the head flange 30, and are resilient, as will be described below.

The locking member is provided by a self-tap screw 38 having at one end an enlarged head 15. The shank of the screw comprises a first part 17 which is remote from the head 15 and has an external diameter such that it threadedly engages with the bore 11 of the first member, and a second part 19 nearer to the screw head 15 than is the fir st part 17 and of a larger external diameter such that it threadedly engages the hexagonal bore 34 of the second member. The axial pitch of the threads is the same along both parts of the screw.

The manner of use of the locking assembly will now be described.

The cabinet 16 is supported face down on a horizontal surface, so that the tubular parts 14 and 22 project vertically upwards as illustrated in Figure 1. The second member 26 is then inserted into the annular space between the parts 14 and 22 of the first member. The irregular hexagon configuration of the mutually engaging faces of the two members means that the second member can enter the first member in only one, predetermined, relative rotational position, which is the one in which the resilient tabs 40 on the head 30 of the second member 26 are aligned with the top surfaces 13 of the webs 18 respectively. Thus the resilient lugs rest on the tops of the webs 18 to resiliently support the second member in relation to the first member.

4 P.381 The television tube 10 is now lowered into the cabinet, so that the lug part 12a is aligned with the head 30 of the second part of the locking assembly. The tube is lowered until the periphery of its face abuts the cabinet surround 24, as illustrated in Figure 2. The lug 12a will have contacted the top of the head 30 of the second member, and will have pushed it down, against the resilient urging of the tabs 40, by a distance which depends upon the exact distance H of the lug 12a from the tube face. The preselected positional relationship of the second part 26 with respect to the first part 22 is thus determined.

A suitable resilient washer 48 is then placed on top of the lug 12a, and the locking screw 38 is inserted, point first, through the washer 48, through the aperture 50 in the lug, and into the bore 34 of the second member (the washer 48 may be pre- assembled with the screw 38). The leading first part 17 of the screw is a clearance in the bore 34 of the second member 26, and passes through it until its leading or point end meets the upper end of the inner part 22 of the first member. The screw 38 is now rotated by engaging a suitable tool with its head 15 so that its first part 17 progressively screws into the inner part 22 of the first member. This causes radial expansion of the inner part 22 of the first member, so that it frictionally engages the second member 26. Because of the relatively short length of the second part 19 of the screw, this second part 19 does not engage with the upper end of the second member 26 until after the first part 17 of the screw has engaged with the first member 22. Thus by this stage the axially downwards force on the screw is supported by the first member 22 and will not push the second member 26 downwards, to further deflect the resilient tabs 40 and separate the top face of the head 30 of the second member 26 from the lug 12a. As the insertion of the screw continues, the second member 26 is secured to the first member 22 against relative axial movement. When the screw head 15 is tightened against the washer 48 and lug 12a, the second part 26 P.381 is thereby secured to the first part 22, and the lug 12 and tube 10 are secured to the cabinet 16.

Figure 4 illustrates a modified form of second member 26, in which the bore 34 has a reduced diameter over the uppermost portion 21, having a length corresponding to the required minimum length of engagement of the second part 19 of the thread of the screw. However, the bore in the restricted portion 21 is of course large enough to allow entry of the first part 17 of the screw thread without interference.

The invention is not restricted to the details of the foregoing example. For instance, greater radial expansion of the part 22 could be achieved, if desired, by providing 10 it with one or more axial slots, and similarly with the second member 26.

6 i

Claims

P.381 A locking assembly for mutually locking together two members over a range of relative positions, which assembly comprises: a first member and a second member, which are relatively mutually adjustable along an adjustment direction to provide the range of relative positions, but which are not relatively mutually rotatable about the adjustment direction; each of the members having a bore, the bore of the second member being of larger diameter that the bore of the first member; and a locking member in the form of a screw having a first part of a diameter such as to engage the bore in the first member but to be a clearance in the bore of the second member, and a second part of a diameter such as to engage the bore of the second member; whereby the two members can be mutually positioned in a selected relative position along the adjustment direction, and then locked together by inserting the first part of the screw through the bore of the second member and into engagement with the bore of the first member and screwing it thereinto until the second part of the screw engages with the bore of the second member, so that the screw locks the two members into the selected relative position.

2. A locking assembly as claimed in claim 1, in which the first member and the second member are provided with mutually engaging faces, the engaging faces in each member being arranged in a form which in cross-section is a 9 1 P.381 simple non-re-entrant polygon, whereby the fir st and second members are restrained against relative rotation. A locking assembly as claimed in claim 1 or claim 2, in which the members are mutually engageable in only a preselected position of relative rotation about the adjustment direction.

4. A locking assembly as claimed in claim 2, in which the wall of the bore of the second member provides the aforesaid engaging faces of the second member.

5. A locking assembly as claimed in claim 2, in which exterior wall of the second member provides the aforesaid engaging faces of the second member.

6. A locking assembly as claimed in claim 4 and claim 5, in which the wall of the bore of the second member and the exterior of the second member both provide the aforesaid engaging faces of the second member.

7. A locking assembly as claimed in claim 2 and claim 3, in which the or at least one of the aforesaid polygons is non-regular, thereby to allow engagement of the second member with the first member in only one relative rotational alignment.

8. A locking assembly as claimed in any of the preceding claims, in which the bore of the second member is of uniform cross-sectional dimensions throughout its length.

9. A locking assembly as claimed in any of claims 1 to 7, in which the bore of the second member is of restricted cross-sectional dimensions adjacent that end into which the locking member is inserted.

9 P.381 10. A locking assembly, substantially as hereinbefore described with reference to and illustrated in Figures 1 to 3 of the accompanying drawings, with or without the modification substantially as hereinbefore described with reference to and illustrated in Figure 4 of the accompanying drawings.