CLIP FOR SECURING ROTATING PARTS

Abstract: In order to clip independently rotatable parts (9, 10) that must be axially held relative to each other, but not be constrained from sliding axially together, each part (9, 10) has a bore and an internal annular groove (28) and the clip (22) has transverse flanges (23, 24) that spring out and enter the grooves (28) when the bores are aligned. The clip (22) has a gap so that the cross-section can be changed considerably by gripping holes (31) in the flanges with long-nosed pliars, or other gripping tool, that can enter the internal bores, address the clip (22) to the grooves (28), and release the clip (22) to enter the grooves (28). The tool is also used to remove the clip (22) for dissembling the parts. Thus the parts, eg mainshaft gears, that have to be slide each way to engage respective dogs, can be replaced individually - in contrast to existing gear-pairs which tend to be unseparable without destruction of the clip (22) (and usually of both gears).

Description: The present invention relates to an assembly comprising a clip adapted for securing at least two rotating coaxial gear wheels of the assembly axially together while allowing their relative rotations substantially freely. The pairs of gears held axially together may be those in heavy duty change speed gearboxes, especially those of the larger goods vehicles (HGV's). The invention involves adaptation of the gears, and of the clip, in the assembly. In some boxes, pairs of gears rotate independently of each other about a shaft, but radially supported by meshing gears, and having to move axially together as a pair for certain shifts. The invention is applicable where the gear-pairs slide against dog-clutches or the like fixed on a mainshaft in order to engage ratios, but not in those boxes where the clutches move axially and the gears stay axially stationary on the mainshaft. In the prior art, such sliding gear-pairs have been held axially together by each gear having extensions which telescope together, when respective grooves in the internal wall of the larger extension and the external wall of the smaller extension axially align and receive a circular spring clip. The clip axially holds the telescoped parts. This way of holding is operative and indeed forms the state of the art for this invention, but has drawbacks. It requires telescoping parts. The clip is hard to install in a new telescoped, eg telescoped gear, pair. The gear pair is often impossible to separate, for instance if one not both is worn or damaged and needs to be scrapped, and can only be separated by breaking the clip, at best with possible damage to the parts or gears. It would be desirable if the clip were removable, eg some time after installation. US-A-3 662 642 describes a resilient clip having many of the features of assembly of Claim 1, but aims to exert relative axial forces between clipped together telescoped pieces whose axial position appears not to be critical. Moreover these telescoped pieces of the reference are not required continuously to rotate relatively in closely but not quite abutting, held relationship as gears are, when in constant mesh. Thus, the clip has either non-radial flanges or non-radial tab portions thereof in the inventive assembly, which flanges or tabs have to be forced into oversized radial grooves. Only in this stressed state do the flanges or tabs of the reference become radial, in order to exert required axial stress. The problems to be solved by the present invention include axial stresses, too; indeed not only allowing said rotational freedom in the axially relatively located gears, but also holding them together against axial forces which are found to be inherent when one helical gear of a constantly meshed pair is driven with power and the other one is driven lightly, the pair being in individual constant mesh with different other gears, such holding together therefore requiring strength and yet requiring enough flexibility to give a manual ability to compress, locate and free the clip for removal or installation. It is relatively unusual in the gearbox art to arrange gear pairs slid in unison onto alternative dog-clutches; the stress problems are quite different than for the somewhat more usual axially fixed mainshaft gear-pairs, even though also floating, as typified by US-A-4 485 686. However Column 4 of the latter also brings out the importance of those not readily explicable axial stresses. According to the present invention there is provided Claim 1. The parts may be, but need not be, telescoped as the components in US-A-3 662 642 are, where any rotational relative motion could only be very brief and slow, or accidental and negligible. In embodiments, the following characteristics can be seen:- (A) There is provided a circumferentially resilient spring clip comprising a group of (typically two) parallel axially spaced part-annular flanges extending outwardly from an axially rigid web extending parallel to but not on the axis, which web joins the flanges together while allowing their cross-sectional resilient contraction due to a circumferential gap in the spring clip. The flanges each have a shaping or formation, at the two ends each side of the gap, to allow cooperation of a tool, by which the clip can be not only resiliently compressed in cross-section, effectively in diameter, but also introduced along the insides of tubular bodies. The web may be almost a complete tube or cylinder having said gap to allow said compression and contraction. (B) There is alternatively provided, for holding by the inventive clip, a gear group operative to be slidable axially as one, but to be rotatable independently of each other; wherein the gears each have a holding groove, both grooves being in internal walls thereof. The gears may be threaded over but need not be located radially by a mainshaft, eg twin countershafts may radially locate them in well-known manner. (C) Another aspect provides a gear pair required in operation to slide together as a pair about and along a shaft and carrying an external shaping to cooperate with the usual gear selector fork, the individual gears being also required to rotate independently of each other, in combination with a radially resiliently contractable holding clip with radially extensive flange portions for fitting in annular grooves in both gears to enable said requirements, wherein said annular groove in one gear is in an internal cylindrical wall, and said clip has a shaping to cooperate with a circumferentially compressing tool for installing the clip; the groove in the other said gear being also in an internal cylindrical wall thereof; the radially extensive portions of the clip being both outward radial extensions from a common web extending generally parallel to, but usually not on, a cylindrical axis; and the resilient circumferential and cross-sectional contraction, before an expansion towards normal cross-section being required on fitment of the clip. The invention enables removal of the clip by the tool which was almost impossible in the prior art. There conceivably may be more than two gears and respective flange portions. Further objects, features and advantages of the invention will appear from the following description of a forerunner embodiment, a later developed embodiment which is presently preferred, and of a prior art arrangement, given by way of example in conjunction with the drawings, in which:- Figure 1 is a radial section on the prior art gearbox, showing a clipped and axially secured gear pair; Figure 2 is a diametrical section on the forerunner gearbox, showing a clipped and axially secured gear pair in a manner from which the preferred embodiment was developed.; Figure 3 is an elevation, Figure 4 a plan view, and Figure 5 a perspective of a part of the above forerunner embodiment i.e. a resilient or spring clip; Figure 6 shows fragmentarily, diagrammatically and in elevation the grooved gears of an inventive assembly as held by the clip and presently preferred; Figure 7 is a plan view (ie, viewed along the cylindrical axis) and Figure 8 an elevation on an inventive assembly clip developed after experiments with the forerunner clip of Figures 3-5. Referring to Figure 1, a mainshaft 1 on the rotational axis 2 of the gearbox has splines 3 on which dog clutch members 4 and 5 are rotationally fixed. In effect the dog clutch members are axially fixed on the mainshaft too, but the splines 3 and springs 6 may allow a small measure of axial resilience. Dog clutch members 4 and 5 have external splines or teeth 7 to engage internal splines 8 on respective mainshaft gears 9 and 10 of a sliding pair in well known manner. The sliding pair have an external shaping, recess 11 to cooperate with the prong 12 of sliding means, conventionally a gear selector fork arranged by axially moving plunger 13 to slide axially, selectively to the right or left from the neutral position shown in Figure 1. Thus the gear pair 9/10 can be driven slidingly upon command by means not shown to move to the right whereupon gear 9 engages clutch 5 and hence is coupled to the mainshaft splines 3, or to move to the left whereupon gear 10 and splines 8 engage clutch 4 and hence becomes coupled to the mainshaft 3. In the condition illustrated, neither gear 9/10 is coupled. The coupling may be assisted by synchro-cone members 14 mated to the dog clutches and sliding along them dependent on what gear 9 or 10 is selected. The cone surfaces on the selected gear and its cone member 14 become aligned; the latter then makes contact with the chamfered teeth 8 on the relevant dog clutch 4 or 5, which in turn couples the selected gear 9 or 10 to take over the rotation of the mainshaft. Springs 6 provide resilience for these synchro-cone engagements. In many gearboxes, the clutches are slid to engage axially fixed gears, but the gear-pairs slide in this prior art example; and it is to such sliding gear-pair boxes that the invention relates. As further well-known background from this prior art, each of the gears 9,10 of the pair is in constant mesh with respective gears fixed to one or more countershafts each in constant mesh with an input gear. If gear 9 is clutched to mainshaft 3, one ratio is selected - likewise for gear 10 or other mainshaft gears and clutches such as 15, 16 and not further described here. One problem with gear pairs such as 9/10 is the installation of an axially retaining clip 17 by which the gear pair move axially as one in response to selector fork 12 being driven by plunger 13, but can rotate always at different speeds. The known spring clip 17 will typically resemble one of the two flanges of the novel clip, seen easily in Figure 4. It is thus an almost circular snap ring, a resilient ring sometimes known at least in the UK as a "Circlip" and having radial extent and a circumferential gap. The gap allows circumferential and radial contractions and expansions. Such clips are extremely common retaining means, in internally and externally grooved cylindrical walls. They are in general contracted to be presented to internal walls, and allowed to expand into the internal groove to assume slightly less than normal size. Or they may be expanded to be presented opposite external cylindrical grooves, thereafter being allowed to contract and enter into the external groove to assume slightly more than normal size. In the arrangement of gear-pair 9/10 there are two grooves 18, 19, to be entered, one external and one internal. Gears 9 and 10 telescope together, in that gear 9 has a female extension 20 with the internal groove 18 and gear 10 has a male extension 21 with the external groove 19. The clip 17 is inserted in both grooves 18, 19 and axially holds the gear pair. Drawbacks to this arrangement are (1) there must be telescoping parts; (2) the clip or snap ring must be both contracted and expanded from its normal radius, in order to be offered to each groove in turn for installation; (2) most important, the clip must be broken, if possible, before the gears can be separated. Gears do break as well as wear, and easy servicing, or easy replacements are highly desirable. Very often one gear 9 or 10 will fail before the other, and a necessity to replace only one of the pair would often be attractive and economical. Often, because of tolerances, it is difficult or impossible to break the clip, or possible only after damaging the telescoping parts. The snap ring may be 1.5 mm, and the groove 1.7 mm with a tolerance. So sometimes it will easily rupture, sometimes it is not possible. Another drawback (4) is that there is a limited total radial extent in which the two grooves can be accommodated, and if the mainshaft is to be made larger eg for heavier duty work, the total radial extent will diminish even more (unless at least the female gear 9 etc is redesigned of larger diameter). In further explanation of Drawback (2), the expansion back to normal size of the clip into the internal groove of the "larger" gear with the female extension and then its tapping into place in the groove are fairly straightforward. However, the clip must now be expanded, with a tool which allows the "smaller" gear to be inserted until its mating groove comes opposite. Then a special assembly tool has to be introduced, in order to expand the clip from normal, further into the internal groove, so that the smaller gear can also be introduced. The special tool is typically three fingers on expanding equilateral triangle points, the expansion being by a tapered screw. The smaller gear will have a chamfer at its entering portion, which will hold the clip expanded such that the special tool can be itself undone, ie contracted and removed. Then the smaller gear with the male extension is pushed fully home. This manoeuvre is cumbersome and tricky to perform. Referring to Figure 2, gears 9 and 10 are held together by a clip 22 which is an almost revolved U-shape. The "arms" 23, 24 of the U as seen in section (which are really annular flanges) engage in internal annular grooves in the gears 9, 10 and hold them together axially while permitting the independent rotations (needed to be accommodated as stated above by constant meshing of 9/10 with gears 25, 26 both fixed to the countershaft not shown). Clip 22 has an axially rigid cylindrical or tubular web 27 from which the annular flanges 23, 24 extend radially. The clip can be contracted to enter the gears 9, 10 and then be offered to the grooves 28 therein, thereafter the clip is allowed to relax and expand into the grooves. The axial retaining is now complete. Separation of the gear pair is easy, they are first slid off the mainshaft as a pair and the clip is easily accessible to a tool, for contraction and removal of the clip. There is no requirement to break the clip. Installation is the reverse, contract the clip with the tool or tools, position the gears as a pair, and offer the flanges 23 and 24 to the grooves 28 in the gears. Referring to Figures 3 and 4, the clip, being a forerunner of part of the inventive embodiment presently preferred is more clearly seen; web 27 axially locating flanges 23, 24 (and hence the grooves of the gears), possible apertures 29 if required for lightness, handling or oil circulation, and a gap 30 so that the spring clip can be compressed, or contracted in diameter and circumference. The contraction is necessary in order to introduce the clip through the internal bore of the gears in turn, until the flange is opposite a respective groove 28. Contraction to fit through the bore is enabled by introducing pliers into the bore, the ends of the pliers being shaped to engage small holes 31 in the ends of the flanges each side of gap 30, and to release the spring clip to expand into the groove. The pliers are also used to contract the clip again (the holes 31 being designed to remain accessible), when it is required to remove the clip, eg to service or replace one gear. Such holes and pliers are well known in general. It will be noted that the prior art arrangement of Figure 1 required not only contraction but also expansion by the pliers, to fit the clip in an external as well as an internal groove, whereas only contraction are required by the invention. The clip can be seen in perspective in Figure 5, with a portion about 15% of its circumferential extent being cut away from one free end. One hole 31 for the pliers can be seen. Figure 6 shows diagrammatically the assembled clip and gears with flanges 23, 24 installed in the two grooves 28, and axially stiff web 27 holding the gears together axially, but allowing their independent rotations. Referring again to Figure 2, the gears 9 and 10 may have parts which telescope together if desired for location, economy in axial length or strength and support, but such telescoping is no longer required in order to accommodate a clip arrangement as 17-19 in Figure 1. The above arrangement was primarily developed for the sliding gear pairs of the Twin Splitter transmission available from Eaton Corporation, USA and Eaton Limited and Eaton SA in Europe for medium and heavy duty goods vehicles. However sliding gear pairs required to be held as described are envisaged to be useful in much smaller, lighter environments as well as other heavy duty vehicular and other operations. In the Eaton Twin Splitter transmission mentioned above, the mainshaft floats between twin countershafts being thus supported thereby. There would rarely if never be risk of contact between the inventive clip and the (splined) exterior of the mainshaft. However, the invention is not concerned with the way the parts or the clip are radially supported or located, but merely with removably holding independently rotatable parts axially together. The compressive force required to be exerted through the pliers is found to be quite moderate, just enough to allow the gears to slide together (telescoping or not). Since the two grooves 28 of Figure 2 are not aligned as in Figure 1, there is more room to make them deeper in the inventive arrangement without prejudicial loss of strength. Eaton and Twin Splitter are both independent Trade marks of Eaton Corporation. The clip can be made from U-section strip carbon spring steel. After it has been heated to cherry-red temperature, it is bent while its form is maintained, around a mandrel. Drawbacks were found in the Figs. 3-5 clip. The holes in the flange were not readily accessible for handling once the flanges had expanded outwardly into the now possible deep grooves of the gear pairs. So easy removal, a main purpose of the invention, was not always possible. Moreover the flanges of the Figs. 3-5 clip had a tendency to distort out of their essential purely radial disposition during construction, even during annealling after bending and maintaining resilience. The former problem is met by the preferred placing of the shaping to receive the handling tool, in the web (near the discontinuity), rather than in one or both flanges. Such a placing is not possible in the arrangement of US-A-3 662 642. The latter problem is met by arranging breaks or discontinuities in the flanges at intervals around the near circumference of the clip. This is found to substantially eliminate the tendency to their unacceptable distortion out of the radial during bending or annealling. In contrast, the clip of US-A-3 662 642 teaches away from the preferred teachings of the following embodiment, in that circumferential flange breaks in the reference are introduced in order to be able to bend alternate flange portions out of the radial, for providing additional resilient securing capabilities in oversized grooves (contains relative rotations not being catered for in this reference). Nevertheless, the Figs. 3-5 embodiment was found to give some improvement in rotatably securing the gears 9,10 of Fig. 2. A modified and preferred spring clip also following the teachings of the invention is shown in the embodiment of Figures 7 and 8, having circumferential resilience, comprising an incompletely cylindrical web, at least two sets of outwardly radial projections therefrom, wherein the projections in each set resemble petals with spaces between them at which there is less or no projection from the web, said web comprising an incomplete cylinder in having a gap which allows a cross-sectional resilient contraction. Similar annular grooves in each gear, in an internal bore wall thereof, will receive the spring clip after an initial circumferential compression for its insertion within the bores of each gear, and its finally being allowed to expand into the two grooves as in the previous embodiment. The series of inventive spaces between the petal-like radial projections facilitate manufacture of the ring, as compared with the more continuous circular flanges of the parent Application. Referring to Figures 7 and 8, cylindrical web 41 has an interruption at 42. Web 41 has a relatively largish diameter, eg 74 mm compared with its width, eg 19 mm, but a short axis in comparison. At the two ends, axially speaking, of the web are similar set of radially extending flanges 43 and 44, somewhat resembling flower petals as drawn in plan, and separated by a series of gaps 45 and 46 respectively. There are two or more holes 47, two round holes are presently preferred, to assist in the compression prior to expansion required for assembly of the clip into grooved parts to be clipped. The previous embodiment featured a clip in which two or more flanges were circumferentially continuous over the distance between the ends of a circumferential gap analogous to that seen at 42 in Figure 7. Continuous flanges might present difficulties in manufacture and/or require more annealing, in order to assure the flanges being accurately radial and parallel and to avoid localized or more continuous distortions. Such distortions could prevent location in the grooves of the gears after being allowed to expand, or could inhibit the essential object of relative rotatability between the two gears. Accordingly, the inventive flanges 43 and 44 are made as respective series of, say, ten each with nine gaps 45, 46 thereby greatly reducing stresses. The radial extent of the 20 flanges, on the numerical example already given in part, is 20 mm, their thickness is 1.5 mm. The circumferential widths of the flanges could be about equal to those of gaps 45, 46. The two holes 47 may be 8 mm diameter and the web width about 16 mm, with a 100° angle separating the two 8 mm holes in the web. These are presently preferred dimensions, and obviously variable at will. Unlike the flanges or tabs of US-A-3 662 642 mentioned above, the entire group of flanges 43 or 44 are radial and perpendicular to the axis. The flexibility in this example is such that the clip must be compressible circumferentially to pass through bores of 87.5 mm diameter and then expandible to a free diameter of 94 mm. The clip is heat treated to Rc 58 file hardness, then a phosphate coat is produced before oil dipping. In order to grip the clip and compress it in cross-section while introducing it to the internal grooves, a shaping is provided, not shown, near the ends 48 of the web each side of the interruption. A tool similar to "Circlip" pliers would be used. In its compressed state, with the tool still attached, the clip would be, inserted into grooves in a pair of gears, then positioned and then released to clip the gears together. Thus there is shown in Figures 7 and 8 a detachable spring clip comprising a cylindrical web which is incomplete in that there is a gap, and at least two series of petal-like flange projections radially outwardly projecting from the web, the projections of each series lying on a planar circle and separated by gaps, such spring clip being circumferentially compressible (to form a smaller radius for entering a bore). The web could have further, intermediate sets of flanges at different axial positions, for holding more than two rotatable parts together, by grooves in the latter transverse to the cylindrical axis. The spring clip of Figures 7 and 8 could be used to clip an internal insert for receiving or transmitting a drive, to or from a toothed belt. For instance, the spring clip could be expanded outwards, and allowed to contract over and thus clip a piece of metal adapted to rotate. The piece of metal would be preferably of cross-section such that the cap was an odd multiple of half a pitch of the divided petal-like flanges 43, 44. The flanges could then obviously be driven by, or drive the toothed belt (not shown). The holes 47 could be used if required to bolt the insert to the clip.

Claims: An assembly of a resilient near-circular clip and two coaxial gears (9,10) requiring to be continuously relatively rotatable about, but not on, a mainshaft (1) whether under driving load or not, arranged so that each said gear is to constantly mesh with respective gears (25,26) fixed on plural axially fixed countershafts, which countershaft gears are also to supply all radial support for the mainshaft gears (9,10), while allowing them sufficient axial sliding freedom in that the two mainshaft gears are also required to be slid as a pair axially into fixed clutch engaging and disengaging positions, but to be held in accurate axial relationship relative to each other; the required holding means being a spring clip, which is circular except for a circumferential gap (30;42) said clip having flange portions (23,24; 43,44) to removably enter annular grooves (28,28) with rotational freedom in the two mainshaft gears, characterized in that in the assembled or disassembled conditions of the clip, the flange portions extend in their entirety radially outwardly from axially spaced circumferentially extending bases on a tubular web portion (22;41); the radial grooves of the gears are all internal grooves (28) in the bores of respective gears (9,10) of the pair; the clip further having, in known manner, a handling formation (31) towards the two ends of the clip defining the gap, to enable gripping and transport by a contracting tool to the receiving position, which is internal of not only one, but both said mainshaft gears. An assembly of a clip (22) and gears (9,10) according to Claim 1, characterized by one or more holes (29 47) in the web portion. An assembly according to claim 1 or 2, characterized by circumferential discontinuities (45, 46) in the flanges (43, 44) at circumferential points where the web (41) is continuous. An assembly according to Claim 3, wherein the discontinuities are gaps between flange portions (43). An assembly according to any preceding Claim, wherein the handling formation is the web portion, at each end. A circumferentially expandible clip having a web portion being an incomplete cylinder, a handling formation in the web portion at each end of the gap, and spaced flange portions to be installed in internal annular grooves in the parts to be clipped together and extending radially from each axial end of the web.

Inventors: COOPER, DAVID GREGORY
Applicants: EATON CORPORATION
Application year: 1987
Main classification: F16B21
IPC codes: F16B7, F16B3, F16B21, F16H57