A CHAIN

Abstract: A chain comprises inner link assemblies (1) interconnected by rigid closed loop links (2). The loop link (2) is separable into two portions in a direction transverse to the longitudinal axis of the chain. Each portion engages with the other by means of a snap-fit or interference fit connection to enable rapid assembly or dismantling of the chain. One embodiment has a snap-fit connection with complementary engaging ramped surfaces.

Description: A CHAIN The present invention relates to a chain of the kind used in drive or transmission mechanisms or in lifting apparatus. Conventional roller and bush chains comprise a plurality of inner link assemblies that are interconnected by pairs of opposed outer link plates. Each inner link assembly comprises a pair of opposed inner link plates, each inner link plate having two apertures aligned with corresponding apertures in the opposed inner link plate. The inner and outer link plates are interconnected by pins that pass through aligned apertures in the plates. The pin is received in a bush that extends between opposed inner link plates, and is fixed in the aperture of the inner link plate. Such a chain can be relatively expensive to manufacture and assemble in view of the number of components. It is an object of the present invention to obviate or mitigate the aforesaid disadvantages by providing for a chain that is simpler and cheaper to manufacture and assemble. According to the present invention there is provided a chain comprising a plurality of first links each having at least two apertures, adjacent first links being interconnected by a second link which comprises a rigid closed loop that passes through at least one of said apertures, the loop being separable into two portions by relative movement of the portions in a direction transverse to the length of the chain. Preferably said first portion has ends that releasably engage with ends of said second portion. The ends may engage in a snap-fit or interference fit connection. The ends of the second link may each have ramped surfaces, the ramped surfaces of the first portion being complementary to those of the second portion. The second link may assembled by moving the first and second portions together in a direction transverse to the longitudinal direction of the chain so that the ramped surfaces engage. In one preferred embodiment there is provided a clearance between the second link and the inner link assembly to permit movement of the ends in a direction parallel to the longitudinal axis of the chain during engagement of the ramped surfaces. The ramped surfaces may each comprise two surfaces inclined in opposite directions. Alternatively, the ends of the first and second portions may be constrained against movement relative to the inner link assembly in a direction parallel to the longitudinal axis of the chain. In this case each ramped surface is divided into separate parts about a longitudinal axis of the second link so that during assembly of the link portions the ends are forced to move rotationally about the longitudinal axis relative to the inner link assembly. Preferably a first part of the ramped surface is concave and a second part is convex, the ramped surfaces of each second link portion being complementary such that during engagement the ends are caused to rotate about the longitudinal axis of the link. In a further alternative preferred embodiment said ends of the first portion of the second link engage with ends of the second portion in an interference fit connection. The connection may comprise a spigot and socket, a tongue and yoke connection, or a ball and socket joint. Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a plan view of a chain in accordance with the present invention; Figure 2 is a plan view of a link of the chain of figure 1 ; Figure 3 is a scrap enlarged part sectioned view of part of the link of figure 2; Figure 4 is a fragmented perspective view of a first alternative embodiment of the link shown separated; Figure 5 is a scrap view of the link of figure 4 shown connected; Figure 6 is a plan view of a second alternative embodiment of the link; and Figure 7 is a plan view of a third alternative embodiment of the link. Referring now to the drawings, figures 1 to 3 show part of a length of chain comprising two inner link assemblies 1 interconnected by a single closed loop link 2. The inner link assemblies 1 are constructed in the same way as those of a conventional roller bush chain. In particular, they comprise opposed inner link plates 3 bridged by a pair of bushes 4 (shown in dotted line) that are received in apertures 5 in each link plate 3. Each bush 4 supports a rotary roller 5a between the opposed inner link plates 3. In the embodiment of figures 1 to 3 the loop link 2 is constructed from an elongate metallic member of circular cross-section. The member is bent into an approximate rectangular loop configuration comprising two transverse parallel limbs 6 that each pass through a corresponding bush 4 ( with a small clearance) in adjacent inner link assemblies 1 and which are joined at each end by integral shorter limbs 7. The transverse parallel limbs 6 serve to replace the pins of a conventional bush roller chain. As can be seen from figures 2 and 3, each loop link 2 is separable into two portions 2a, 2b, the portions being joined by means of two snap-fit connections as indicated by reference numeral 8. Each snap-fit connection 8 comprises a pair of mating ramped tongues 9, one projecting from each end of the loop portions 2a, 2b. Complementary ramped surfaces 10 of the tongues 9 are defined in a plane that is approximately perpendicular to the longitudinal axis of the chain and each comprises a short incline 10a that meets with a longer reverse incline 1 Ob at an apex 11. The chain is assembled by threading the transverse parallel limbs 6 of the link portions 2a, 2b through the corresponding bushes 4 of adjacent inner link assemblies 1 , presenting the mating ramped tongues 9 to one another and pressing the portions 2a, 2b together in a direction transverse to the longitudinal axis of the chain until they engage in a snap-fit relationship. During assembly the short inclines 10a of the ramped surfaces 10 ride over each other until the apices 11 come into contact. Further movement in the same direction causes each longer reverse incline 10b to pass over the apex 11 of the other ramped surface 10 and engage with the opposed incline 10b in a snap-fit. The small clearance between each transverse parallel limb 6 and corresponding bush 4 allows limited relative movement of the limbs 6 in the direction of the longitudinal axis of the chain as the ramped surfaces 10 engage. In order to separate the two portions 2a, 2b of the loop link 2 significant force transverse to the chain is applied to the link portions 2a, 2b to release the snap-fit connections 8. Each snap-fit connection is shown at one end of the transverse limb 6 adjacent a shorter limb 7. In fact the connections 8 could be provided at any position along the transverse limbs 6 but the particular arrangement shown is preferable since it provides for an uninterrupted bearing surface between each bush 4 and transverse limb 6. An alternative snap-fit connection 108 is shown in figures 4 and 5 in which parts corresponding to those of figures 1 to 3 are indicated by the same reference numerals increased by 100 and are not further described except insofar as they differ from their counterparts in figures 1 to 3. Each tongue 109 has a mating surface 110 comprising a convex surface 120 and a vertically adjacent concave surface 121, the mating surface 110 being designed to mate with a complementary surface 110 of the other tongue 109 of the snap-fit connection 108. The division between the convex and concave surfaces 120, 121 coincides with the longitudinal axis of the elongate member that forms the loop link 102. When the two link portions 102a, 102b are fully engaged (see figure 5) the convex surface 120 of one tongue 109 is received by the concave surface 121 of the other tongue 109 and vice versa. When the tongues 109 are presented to each other for assembly of the loop link 102 and interconnection of the inner link assemblies, the transverse parallel limbs 106 are constrained against significant relative movement in the direction of the longitudinal axis of the chain by the bushes in which they are received. Accordingly the mating of the convex and concave surfaces 120,121 initially effects a rotational movement in the ends of the limbs 106 about the longitudinal axis of the elongate member. Further movement of the link portions 102a, 102b together ensures that the convex and concave portions are fully engaged and the ends twist back in a snap action. The snap-fit connections 108 are arranged such that the two ends of a given link portion 102a or 102b twist in opposite directions during assembly. A third embodiment of the loop link of the present invention shown in figure 6 has one end of each of the transverse limbs 206 in the form of a yoke 230 designed to receive a tongue 231 defined on the other end of the other limb 206. The tongue 231 is received by the yoke 230 in an interference fit. In a variation (not shown) of this embodiment the limbs are connected by a spigot and socket connection with an interference fit. Figure 7 shows a further alternative embodiment of the loop link which is split along the length of each transverse limb 306 into two portions 302a and 302b to provide elongate mating faces 340 extending along the length of the transverse limbs 306. Each end of the mating faces of one portion 302b has a nipple protrusion 341 that engages in a corresponding socket 342 formed in a mating face of the other portion 302a. It will be appreciated that numerous modifications to the above described design may be made without departing from the scope of the invention as defined in the appended claims. For example, any convenient form of snap-fit or interference fit connection may be used as an alternative to the exemplary embodiments described above. Such a connection may comprise one end of a limb having housed rotary ball bearings that are engageable in complementary sockets or recesses.

Claims: CLAIMS 1. A chain comprising a plurality of first links each having at least two apertures, adjacent first links being interconnected by a second link which comprises a rigid closed loop that passes through at least one of said apertures, the loop being separable into first and second portions by relative movement of the portions in a direction transverse to the length of the chain. 2. A chain according to claim 1, wherein said first portion has ends that releasably engage with ends of said second portion. 3. A chain according to claim 2, wherein said ends of the first portion of the second link engage with ends of the second portion in a snap-fit connection. 4. A chain according to claim 2 or 3, wherein said ends of the second link each have ramped surfaces, the ramped surfaces of the first portion being complementary to those of the second portion. 5. A chain according to claim 4, wherein the second link is assembled by moving the first and second portions together in a direction transverse to the longitudinal direction of the chain so that the ramped surfaces engage. 6. A chain according to claim 5, wherein there is a clearance between the second link and the inner link assembly to permit movement of the ends in a direction parallel to the longitudinal axis of the chain during engagement of the ramped surfaces. 7. A chain according to claim 4, 5 or 6, wherein the ramped surfaces each comprise two surfaces inclined in opposite directions. 8 A chain according to claim 5, wherein the ends of the first and second portions are constrained against movement relative to the inner link assembly in a direction parallel to the longitudinal axis of the chain. 9. A chain according to claim 8, wherein each ramped surface is divided into separate parts about a longitudinal axis of the second link. 10. A chain according to claim 9, wherein a first part of the ramped surface is concave and a second part is convex such that during engagement of the ramped surfaces of the first and second portions the ends are caused to rotate about the longitudinal axis of the link. 11. A chain according to claim 3, wherein the ends engage by means of a protrusion that engages in a corresponding socket. 12. A chain according to claim 1 or 2, wherein said ends of the first portion of the second link engage with ends of the second portion in an interference fit connection. 13. A chain according to claim 12, wherein the connection is a spigot and socket 14. A chain according to claim 12, wherein the connection is a tongue and yoke connection. 15. A chain according to claim 12, wherein the connection comprises a ball and socket joint. 16. A chain substantially as hereinbefore described with reference to figures 1 to 3, figures 4 to 5, figure 6 or figure 7 of the accompanying drawings .

Inventors: CHRISTMAS MICHAEL CHARLES, CHRISTMAS, MICHAEL, CHARLES
Applicants: CHRISTMAS MICHAEL CHARLES, RENOLD PLC, CHRISTMAS, MICHAEL, CHARLES
Application year: 1998
Main classification: F16G13
IPC codes: F16G13