A cylindrical assembly having interconnectable parts

Abstract: An assembly has two interfitting generally cylindrical components (1,2) having sufficient clearance between their mating surfaces to permit relative rotation. At least one retractable locking projection (5) is provided on one of said surfaces and biased into a projecting position in which it interlocks with the other of said surfaces. Locking formations on said other surface include at least one corresponding labyrinth (7) of barriers to circumferential and axial movement through which labryrinth(s) said projection(s) may be manoeuvred by a known sequence of axial and rotational relative movements of said components for disengagement thereof. The arrangement of the projection(s) and the locking formations is such that said axial disengaging movement cannot cause retraction of the projection(s) but axial movement in the reverse direction results in temporary deflection of the projection(s) into the retracted position by the locking formations thereby permitting re-engagement of the components to be accomplished by relative axial movement alone.

Description: This invention relates to an assembly of two interfitting generally cylindrical components intended for use, for example, as a litter bin. It is well known for litter bins to be of hollow, generally cylindrical construction with a cylindrical base adapted to be anchored to the ground and a cylindrical body, with one or more openings for litter at the top thereof, arranged to fit into or over the base. The upper and lower parts of the litter bin are interlocked in the engaged position in order to prevent unauthorised removal of the upper part of the bin. It is nevertheless desirable that the upper part of the bin be easily removable from the base by service personnel in order to permit access to an internal liner containing the litter. It is an object of the present invention to provide an assembly of two interfitting generally cylindrical components, particularly but not exclusively for use in a litter bin, which can be engaged and disengaged in a simple and convenient manner without resort to a key operated locking system. US-A-3824815 describes locking apparatus designed to prevent unauthorised unlocking movement between two cylindrical members. A first member has a labyrinth relief formation defined on its cylindrical surface and the second member has a locking pawl designed to engage with the labyrinth. Unlocking of the members requires a known combination of rotational and axial movement between the members so as to release the pair from the labyrinth. According to the present invention there is provided an assembly comprising two interfitting generally cylindrical components having sufficient clearance between their mating surfaces to permit relative rotation, at least one retractable locking projection provided on one of said surfaces and biased into a projecting position in which it interlocks with the other of said surfaces, and locking formations on said other surface including at least one corresponding labyrinth of barriers to circumferential and axial movement through which labyrinth(s) said projection(s) may be manoeuvred by a known sequence of axial and rotational relative movements of said components for disengagement thereof, the arrangement of the projection(s) and the locking formations being such that said axial disengaging movement cannot cause retraction of the projection(s) but axial movement in the reverse direction results in temporary deflection of the projection(s) into the retracted position by the locking formations thereby permitting re-engagement of the components to be accomplished by relative axial movement alone, characterised in that the or each projection has a contact surface inclined in the direction of engagement movement of the locking formations so as to enable the locking formations to exert a progressively increasing deflection force on the projection(s) during engagement, the or each projection having a free end for engagement with the mating surface and being mounted with axial spacing from said free end, the or each projection having mounting means at the end opposite said free end and a hinge intermediate its ends, the hinge interconnecting relatively moveable portions of the projection(s), and having interlocking formations that serve to limit the extent of the projecting position of the projection(s). The or each projection is preferably integrally moulded in plastics material. Adjacent ends of said portions preferably have interlocking formations to resist reverse deflection of the projection. The labyrinth preferably includes a circumferential barrier which is only avoidable by axial movement in the direction of re-engagement. The assembly preferably includes a plurality of projections and corresponding labyrinths are unevenly spaced circumferentially so as to provide a limited number (less than said plurality) of start points for disengagement of said components. In accordance with a further aspect of the invention there is provided a litter bin comprising a hollow body made from an assembly as claimed in any one of the preceding claims, the cylinder axis of said components being arranged vertically and one of said components providing a base into or over which the other component fits. The invention will now be further described by way of example only, with reference to the accompanying drawings, in which:- Fig. 1 is a side view of one embodiment of litter bin in accordance with the invention; Fig. 2 is a corresponding view of the same litter bin with the base (indicated in dotted line) removed; Fig. 3 is a side view to an enlarged scale of the lower end of the upper part of the bin of Fig. 2; Fig. 4 is an underneath plan view of the upper part of the litter bin body shown in Figs. 1 and 2; Fig. 5 is a plan view from above of the base of the litter bin body with inserts showing locking projections to an enlarged scale; Fig. 6 shows part of the litter bin in longitudinal section to show the method of interlocking of the body components, details of the locking projection being shown to an enlarged scale and designated Figs. 6a, b and c, and Figs. 7 and 8 are diagrams showing the engaged condition of the body components and the manner of disengagement thereof respectively. Referring now to the drawings, Fig. 1 shows a litter bin of generally cylindrical shape with an enlarged base portion 1 and an upper body portion 2. The upper body portion 2 includes a top 3 with two openings 4 at opposite sides thereof. The body portions 1, 2 are of hollow construction and receive a removable litter container (not shown) with an open top immediately below the level of the openings 4. In order to empty the litter container, the upper body portion 2 is removed from the base 1 in the manner described below. The upper and lower portions 1, 2 of the litter bin are rotationally moulded in synthetic plastics material and the base portion 1 is of double skin construction for added strength as shown in Fig. 6. The lower end 2a of the upper body portion 2 fits into the base portion 1 as seen in Figs. 2 and 6. The interengaging parts of the base and body portions 1 and 2 are of generally cylindrical shape and the mating surfaces have sufficient clearance to admit of easy relative rotation of the base and body portions 1, 2. A locking system for interlocking the base and body portions 1, 2 of the litter bin comprises four equally spaced projections 5 mounted on the inner wall of the base portion 1 and corresponding locking formations in the form of labyrinths 7 on the outer surface of the lower end of the body portion 2. Each projection 5 comprises an integrally moulded body of synthetic plastics material having an upper portion 5a fixedly secured to the inner wall of the base 1 by fasteners (not shown) extending on lines 5b, 5c through openings in the upper portion 5a of the projection 5. The projection 5 also has a lower portion 5d connected to the upper portion 5a by a thin, flexible web 5e providing a hinge enabling resilient retraction of the lower portion 5d in the clockwise direction as seen in Figs. 6 and 6c. The lower portion 5d of the projection 5 has a contact surface inclined in the direction of engagement movement of the lower end 2a of the upper body portion 2. Adjacent ends of the upper and lower portions 5a, 5b of the projection 5 are configured as tapered jaws 5f, 5g which are engageable as shown in Fig. 6b to prevent deflection of the portion 5d in the anticlockwise direction indicated by the arrow. The lower end of the body portion 2 is shown in side view in Fig. 3 and is moulded with integral locking formations comprising a circumferential shoulder 8 providing a barrier to axial movement of the projections 5 save at four equally spaced entry gates 9 giving access to the respective labyrinths 7. Each labyrinth 7 includes a part-circumferential shoulder 10 providing a further barrier to axial movement of the projections 5 and axially extending abutment surfaces 11, 12 providing barriers to circumferential movement of the projection 5 in opposite directions in its respective labyrinth 7. Adjacent its abutment surface 12 each labyrinth 7 has an exit gate 13 (see also Fig. 4) and adjacent the gate 13 each shoulder 10 has a step 14 providing a further partial barrier to circumferential movement of the respective projection 5. In order to open the litter bin for the purpose of removing and emptying the litter container therein the upper body portion 2 of the bin may be rotated clockwise or anticlockwise to bring the entry gates 9 into alignment with the projections 5. This may be done either by aligning discrete marks (not shown) on the base portion 1 and upper body portion 2 or by rotating the upper body portion 2 in either direction whilst simultaneously applying a lifting force until engagement of the projections 5 in the gates 9 is felt. A straight upward lift of the upper body portion 2 then allows the projections 5 to pass through the entry gates 9 into the respective labyrinths 7 where they abut the shoulders 10 to prevent further lifting movement. The upper body portion 2 can then be rotated almost a quarter of a turn anticlockwise until the projections 5 encounter the axially extending abutment surfaces 11. Alternatively, in order to separate the body portions, a small clockwise rotation is possible until the steps 14 adjacent the exit gates 13 are encountered by the projections 5. In order to pass the partial barriers to circumferential movement provided by the steps 14 the upper body portion 2 must be lowered slightly back into engagement with the base portion 1 and then rotated clockwise until the axial abutment surfaces 12 are contacted by the projections 5. In this position each projection 5 is aligned with a respect exit gate 13 and the upper body portion may be lifted free. Figs. 7 and 8 show the grooves in which the projections 5 locate. The cross-hatched groove 15 shown in Fig. 7 is engaged by the projections 5 in the fully inserted position of the upper body portion 2 in the base portion 1 (see inset). As indicated by the double-headed circular arrow in the inset of Fig. 7 the upper body portion is capable of rotation through 360° in either direction relative to the base portion 1. In Fig. 8, the locating grooves in the labyrinths 7 are additionally shown cross-hatched and the arrows 16 show possible exit paths for the projections 5. The inset of Fig. 8 shows the upper body portion 2 being lifted clear of the base portion 1 with the exit path of the projections indicated by the line with arrow heads at the bottom of the inset. After the litter bin has been opened in the manner described, and the litter container has been removed, emptied and replaced, the upper body portion 2 may be re-inserted in the base 1 by simply lowering it into the base 1 in any orientation thereof. The projections 5 temporarily deflect into their retracted positions under the influence of the protruding shoulder portions at the lower end 2a of the upper body portion 2. As the shoulder 8 passes the free ends of the projections 5 the projections 5 snap back into their fully projecting positions in engagement with the peripheral groove 15. It will be appreciated that numerous modifications may be made without departing from the scope of the invention as defined in the attached claims. The number of projections 5 and corresponding labyrinths 7 may be increased or reduced. In the embodiment described above, the projections 5 and labyrinth 7 are evenly spaced thus permitting four equiangularly spaced start positions for the separation movement (i.e. each of the projections 5 can enter any of the labyrinths 7 through the respective entry gate 9). In an alternative design the projections 5 and labyrinths 7 are unevenly spaced or sized so as to permit only one or possibly two such start positions. The projections 5 may be fabricated in metal, e.g. spring steel. The litter bin may be made of alternative materials, e.g. metal, and in a variety of different shapes provided that the interengaging components are of generally cylindrical form to permit relative rotation of the two parts of the litter bin. A simpler or more complex labyrinth structure may be provided although the described design affords a reasonable compromise between complexity deterring unauthorised removal of the upper portion of the litter bin and simplicity permitting easy removal by authorised personnel. The arrangement may be reversed with the locking formations provided on the base and the retractable projections mounted on the removable body portion. In this case the projections will be inclined upwardly from their mountings in order to ride over the locking formations during the insertion movement.

Claims: An assembly comprising two interfitting generally cylindrical components (1, 2) having sufficient clearance between their mating surfaces to permit relative rotation, at least one retractable locking projection (5) provided on one of said surfaces and biased into a projecting position in which it interlocks with the other of said surfaces, and locking formations (8) on said other surface including at least one corresponding labyrinth (7) of barriers to circumferential and axial movement through which labyrinth(s) (7) said projection(s) (5) may be manoeuvred by a known sequence of axial and rotational relative movements of said components for disengagement thereof, the arrangement of the projection(s) and the locking formations (8) being such that said axial disengaging movement cannot cause retraction of the projection(s) (5) but axial movement in the reverse direction results in temporary deflection of the projection(s) (5) into the retracted position by the locking formations (8) thereby permitting re-engagement of the components to be accomplished by relative axial movement alone, characterised in that the or each projection (5) has a contact surface inclined in the direction of engagement movement of the locking formations (8) so as to enable the locking formations to exert a progressively increasing deflection force on the projection(s) (5) during engagement, the or each projection (5) having a free end for engagement with the mating surface and being mounted with axial spacing from said free end, the or each projection (5) having mounting means (5b, c) at the end opposite said free end and a hinge (5e) intermediate its ends, the hinge (5e) interconnecting relatively moveable portions (5a, 5d) of the projection(s) (5), and having interlocking formations (5f, 5g) that serve to limit the extent of the projecting position of the projection(s) (5). An assembly as claimed in claim 1, wherein the or each projection is integrally moulded in plastics material. An assembly according to claim 2, wherein the interlocking formations (5f, 5g) of the projection(s) (5) limit the relative lateral movement of the adjacent ends. An assembly as claimed in any one of the preceding claims, wherein a plurality of projections (5) and corresponding labyrinths (7) are unevenly spaced circumferentially so as to provide a limited number (less than said plurality) of start points for disengagement of said components. An assembly as claimed in any one of the preceding claims, wherein the hinge 5e or each projection (5) is axially and radially offset from an engaging end of the projection such that separating movement of the components causes limited reverse deflection of the projection into close engagement with the cooperating locking formation (8). An assembly as claimed in any one of the preceding claims, wherein the or each projection (5) is mounted on a strengthened part of the respective surface to prevent distortion of said surface if separation of the components is attempted by force. A litter bin comprising a hollow body made from an assembly as claimed in any one of the preceding claims, the cylinder axis of said components being arranged vertically and one of said components providing a base into or over which the other component fits.

Inventors: DIXON ROBERT, GILL STEPHEN JOHN, DIXON, ROBERT, GILL, STEPHEN JOHN
Applicants: GLASDON LTD, GLASDON GROUP LIMITED
Application year: 1995
Main classification: B65F1
IPC codes: F16B7, B65F1