GB2343406A

GB2343406A - Tensioner for a coil spring

Info

Publication number: GB2343406A
Application number: GB9925585A
Authority: GB
Inventors: Horst Klann
Original assignee: Klann Tools Ltd
Current assignee: Klann Tools Ltd
Priority date: 1998-11-05
Filing date: 1999-10-28
Publication date: 2000-05-10
Anticipated expiration: 2019-10-28
Also published as: GB2343406B; FR2785561B1; GB9925585D0; DE29819740U1; FR2785561A1

Abstract

A spring tensioner 1, is composed of an upper gripper member 2 and a lower gripper member 3 designed to co-operate with a pre-tensioned spring coil 12 fitted between an upper and a lower spring plate of a suspension strut of a motor vehicle shock absorber. The upper gripper member 2 forms a closed ring of L-shaped cross-section fitted to the upper end of a guide tube 8. The lower gripper member 3 is slidably displaceable along the guide tube 8 and has an open loop form with an L-shaped cross-section. The upper gripper member 2 is placed on the upper spring plate 16 which holds the upper end of the coil spring 12 and the lower gripper member 3 is fitted partly around one of the coils of the spring 12. The lower gripper member 3 can then be displaced along the guide tube 8 to vary the tension in the coil spring. To compensate for the axial spacing between a planar support surface 30, 30' of the upper gripper member 2 and the thread-like annular surface 29 of the spring plate 16 one or more individual block-like support members 35, 36, 37 are interposed therebetween.

Description

Spring tensioner for tensioning a coil spring The invention relates to a spring tensioner for tensioning a coil spring. More particularly, the invention relates to a spring tensioner for use with a coil spring used in a vehicle suspension or shock absorber.

A spring tensioner usable to tension a coil spring supported under pre-tension against an upper spring plate of a motor vehicle shock absorber is known from EP 0 349 776 B1. This spring tensioner is composed of gripper members guided coaxially with respect to one another on a hollow guide tube and displaceable relative to one another in the axial direction of the guide tube. An adjustment member in the form of a threaded spindle in the guide effects such relative displacement. One of the gripper members is in the form of a circular ring adapted to receive an annular surface of the upper spring plate which extends in the form of a screw thread. The other gripper member is of fork-like form and engages with one of the coils of the spring from the outside. The first or upper gripper member is attached by means of a cylindrical holding member so that it is seated securely on one end of the guide tube, the gripper member being exchangeably connected by way of a coupling part to the holding member. The second or lower gripper member is exchangeably connected by way of a second coupling part to a second holding member and is likewise exchangeable. The second holding member, together with the second gripper member, is displaceable by the adjusting member axially along the guide tube to tension the coil spring.

The first gripper member is in the form of a closed ring having a L-shaped profile, which on the upper side can be fitted to the support ring of the spring plate of the vehicle shock absorber.

The inner support surface of the ring, on which the spring plate comes to bear during the tensioning operation, may comprise several centering steps, so that spring plates or adaptors or insert rings of different size can be received by the same gripper member.

The second gripper member is constructed to be approximately fork-shaped and in cross-section likewise has an essentially Lshaped profile. The two fork legs of this gripper member form an approximately horse-shoe-shaped ring member, which is open on the side lying opposite the coupling member and whereof the bearing surface has an approximately helical shape. The two gripper members are arranged on the guide tube so that their central connection axis extends parallel to the longitudinal central axis of the guide tube. Thus, a coil spring clamped between the gripper members is aligned with its longitudinal central axis likewise parallel to the guide tube. In order to carry out a tensioning operation, first of all the second gripper member is brought into engagement with one of the coils of the spring in the lower region of the coil spring, whereas the first gripper member is laid simultaneously or previously on the upper spring plate. On actuating the threaded spindle, the lower, second gripper member is moved along the guide tube towards the first gripper member, so that their spacing is reduced and the coil spring is shortened and thus tensioned.

For tensioning coil springs with a coarse pitch, the known spring tensioner with its gripper members can above all be used only conditionally. In shock absorbers, which comprise such coil springs of coarse pitch, this spring pitch continues approximately to the end turns of the coil spring, so that the flange-like support ring of the upper spring plate made from deep-drawn sheet metal, in many cases has a relatively high pitch. Therefore, centered tensioning of the coil spring is at least made more difficult, since the plane annular surface of the known gripper member can slide away on the spring plate during the tensioning operation. This may also lead to the spring plate tilting on the piston rod of the shock absorber, because the gripper member cannot be placed in one plane on the spring plate, which extends exactly at right angles to the axis of the shock absorber.

In order to avoid these drawbacks and risks and to make the tensioning of coil springs with a coarse pitch of the spring turns in connection with the spring plate more reliable, in a likewise known spring tensioner of the aforementioned general type disclosed in DE 298 01 172.7 U1 it is provided that the first gripper member comprises at least one support surface adapted to the helical shape of the support ring of the upper spring plate, so that at the time of tensioning, the upper spring plate bears at least over a supporting angle of at least approximately 180 , flat in the gripper member and the second gripper member is adapted to the pitch of the pre-tensioned spring.

Due to the one-piece design of the gripper member with the support surface, an economical manufacture of the gripper member can indeed be achieved, however, in this case the gripper member must be fastened in a quite different radial direction to the spring or the spring plate, which under certain circumstances may lead to problems.

Due to the provision of separate insert rings, which can be fitted into the first gripper member and provided on the pressure side with support surfaces, which are designed for the various thread pitches of the different support rings of spring plates, however this drawback is also obviated. Consequently an adaptation to different shapes of differently constructed spring plates can be carried out in a simple manner by exchanging insert rings with correspondingly differently adapted shapes.

Although, in this connection, a gripper member with a plurality of bearing surfaces of different diameter and with different surface shapes has also become known, these known gripper members or insert rings can also only be produced with relatively high costs and used respectively to match a certain spring plate.

Accordingly, it is an object of the invention to provide an improved form of spring tensioner. Another object of the invention is to construct the first gripper member of a spring tensioner of the aforementioned general type, suitable for tensioning coil springs with a coarse pitch, so that maximum reliability and universal use are guaranteed also with means able to be produced simply and economically.

According to the invention there is provided a spring tensioner for tensioning a coil spring, which is received under pretension between an upper and a lower spring plate of a suspension strut of motor vehicles, said spring tensioner comprising a first and a second gripper member, which are guided coaxially with respect to each other by means of a guide tube of the spring tensioner and are displaceable relative to each other by means of an adjusting member in the axial direction of the guide tube, whereby for acting axially on the front annular surface of a flange-like support ring of the upper spring plate, extending in the manner of a thread corresponding to the end section of the coil spring, the first gripper member has a support surface constructed at least approximately in the shape of a circular ring and the second gripper member is constructed approximately in the shape of a fork and can be applied radially from the outside to one of the coils of the spring coil, wherein one support member is provided or several support members are provided for the sectional bridging of the axial distance existing at the beginning or a tensioning operation between the support surface of the first gripper member and the annular surface of the spring plate and varying in the peripheral direction between a minimum and a maximum, the or each support member extending over a short section of the annular surface.

Preferably several support members are used and these support members, which in their simplest construction may have the shape of small, approximately parallelepipedal blocks, are themselves then able to be produced essentially more economically, if for each spring plate existing in practice, a particular set of for example two or three pieces is provided. Furthermore, these support members have the advantage of a considerable saving in weight.

Although the use of the support members according to the invention is also possible in conjunction with gripper members, which comprise a support surface wound in a helical manner, their use together with a plane support surface involves lower costs, because gripper members with plane support surfaces as the matching support members can be produced more simply. A plane support surface is understood to mean one which lies in a plane at right angles to the axis of the gripper member.

A further saving of costs can be achieved if the support members are fastened to the support surface for exchanging and/or displacement in the peripheral direction. The possibility of staggering the support members provides the additional advantage that in total fewer different support members are required.

The support members may consist of metal or a synthetic material resistant to compression. The support members may each have a first bearing surface adapted to the shape of the support surface and a second bearing surface lying opposite the latter, which surface is adapted to the thread-like pitch of the annular surface. This contributes to increasing the reliability, in that punctiform or linear pressure transmissions are avoided.

The support members may have centering lugs lying radially on the outside, which project axially beyond the second bearing surfaces and surround the peripheral edge of the support ring of the spring plate. Thus the support members may also carry out the task of centering the gripper member on the spring plate.

Whereas it is basically possible to fasten the support members directly to the support surface of a gripper member, it is preferred to fasten the members onto the support surface of a separate insert ring accommodated in the receiving part of the first gripper member. This arrangement is of particular advantage in so far that the possibility exists of rotating the gripper member with the entire spring tensioner with respect to the insert ring provided with the support members, which insert ring must adopt a certain angular position on the spring plate so that the spring tensioner can be applied for any radial direction to the spring to be tensioned or to the spring plate.

Means is preferably provided in order to prevent a rotation of an insert ring in the receiving part, which would otherwise jeopardise the handling reliability.

Whereas, in the known spring tensioner of the aforementioned general type, the gripper member to be applied to the spring plate consists of a closed ring having a L-shaped profile, whereof the cylindrical ring wall encloses the support ring of the spring plate, the support members according to the invention can also be used in conjunction with a gripper member, which has an open ring shape, especially if the support members are attached to a separate insert ring inserted in the open ring body of the gripper member.

The other optional features of the invention defined in Claims 6 to 10 serve for advantageous handling or reliability connected therewith, in which case the means provided can be produced very simply and economically.

The invention may be understood more readily, and various other aspects and features of the invention may become apparent, from consideration of the following description.

Embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of a spring tensioner constructed in accordance with the invention; Figure 2 is a perspective view of a first gripper member of the spring tensioner as seen from below; Figure 2a is a view corresponding to Figure 2 and showing a modified form of the first gripper member; Figure 2b is a view corresponding to Figure 2 and showing another form of the first gripper member; Figure 3 is a perspective view of an insert ring of the spring tensioner as seen from below ; Figure 3a is a perspective view of one of the support members of the insert ring shown in Figure 3, the view being taken on an enlarged scale; Figure 4 is a perspective view of a spring plate of a motor vehicle as seen from below; Figure 5 is a sectional view depicting the gripper member of Figure 2 mounted jointly with the insert ring of Figure 2 on the spring plate of Figure 4; Figure 6 is an elongated sectional view of the insert ring with two support members mounted on the support ring of the spring plate; Figure 7 is a perspective view of a modified form of the insert ring as seen from below; Figure 8 is a sectional view depicting the gripper member of Figure 2 mounted together with the insert ring of Figure 7 on the spring plate of Figure 4; Figure 8a is an enlarged detailed section A from Figure 8.

Figure 9 is a perspective view of a further form of insert ring as seen from below; Figure 9a is a perspective view of one of the support members of the insert ring shown in Figure 9 the view being taken on an enlarged scale; Figure 10 is a sectional view depicting the gripper member of Figure 2 mounted jointly with the insert ring of Figure 9 on the spring plate of Figure 4; Figure 10a is an enlarged detailed section B from Figure 10; Figure 11 is a sectional view depicting a gripper member with a fastened-on support member mounted directly on the spring plate of Figure 4 and Figure lla shows an enlarged detailed section C from Figure 11.

Figure 1 depicts a spring tensioner 1 constructed in accordance with. the invention. As shown, the tensioner has a first gripper member 2 and a second gripper member 3. The first gripper member 2 comprises a receiving part 4 constructed in the form of a circular ring. As can be seen from Figures 2 and 5, the ring is provided with a substantially L-shaped cross-section. This gripper member 2 is connected in a form-locking manner by way of a coupling part 5 to a holding member 6 of the spring tensioner 1. The coupling part 5 is located at the upper end 7 of a guide tube 8 of the spring tensioner 1 in a close-fitting manner.

The second gripper member 3 is provided with a receiving fork 9, which is likewise in form-locking engagement by way of a coupling part 10 with a second holding member 11 of the spring tensioner 1. The second holding member 11 is axially displaceable and is non-rotatably mounted on the guide tube 8 of the spring tensioner 1. The holding members 6 and 11 are aligned so that the receiving part 4 and the receiving fork 11 of the two gripper members 2 and 3 lie coaxially opposite each other, so that a coil spring 12 to be tensioned, as illustrated in Figure 1, is received with its longitudinal axis 13 extending parallel to the axis 14 of the guide tube 8 between the gripper members 2 and 3. Provided for the longitudinal displacement of the second holding member 11 on the guide tube 8, with the entrainment of the second gripper member 3, is an adjusting spindle, which is mounted to rotate coaxially within the guide tube 8. The spindle is not visible in the drawing but the spindle can be driven in a rotary manner by way of a hexagonal head 15 located axially outside the guide tube 8.

In Figure 1, the annular receiving part 4 of the first gripper member 2 is placed on a spring plate 16 of a suspension strut (not shown in the drawing), which serves to receive or to support the upper end of the coil spring 12 in the suspension strut. In Figure 4, this spring plate 16 is shown as an individual part. For fastening to the bodywork of a motor vehicle, the spring plate 16 comprises four mounting bores 17, which as a rule are approximately uniformly distributed in the peripheral direction in an end wall 18 of the spring plate 16 in the form of a circular ring. The end wall 18 of the spring plate 16 in the form of a circular ring surrounds a recessed mounting plate 19, which is provided with a through-hole 20 in its centre. The through-hole 20 of the mounting plate 19 serves to receive the piston rod (not shown in the drawing) of a shock absorber of the suspension strut and can be screwed securely to this piston rod.

In such a suspension strut, the lowermost spring coil 21 in the drawing is received by a second, lower spring plate (not shown) of the suspension strut. In the assembled state of the suspension strut, the coil spring 12 is received between the upper spring plate 16 and the lower spring plate of the suspension strut under pre-tension, so that in this pretensioned state, the coil spring 12 has a shorter length than in the relaxed state.

For tensioning the coil spring 12, the receiving fork 9 of the second gripper member 3 is brought into engagement with one of the spring coils 22, as is shown for example in Figure 1. In this case, the receiving fork 9 with its bearing surface 23 has a pitch which corresponds approximately to the pitch of the spring coil 22 in the case of the pre-tensioned installation length of the coil spring 12.

Due to this adaptation of the pitch of the receiving fork 9, the spring coil 22 is guided reliably on the one hand during a tensioning operation of the coil spring 12 as well as during a relaxing operation, until the removal of the spring tensioner 1.

On account of this adaptation of pitch with respect to the longitudinal central axis 13 of the coil spring 12, low eccentric tensioning forces occur solely to a small extent, which could produce high tipping or tilting torques.

As can also be seen from Figure 4, in the peripheral region axially above its end wall 18, the spring plate 16 possesses a peripheral, approximately cylindrically constructed annular wall 24. Located on the upper terminal edge of the wall 24 is a support ring 25 directed radially outwards and extending approximately at right angles to the longitudinal central axis 13. In its design, this support ring 25 is adapted to the pitch or shape of the uppermost spring coil 26 of the coil spring 12; accordingly, in the peripheral direction, it has a thread-like shape with a stepped shoulder 27.

The uppermost spring coil 26 is applied to the front annular surface 29 of the support ring 25 so that the end of the spring 28 lies directly in front of the shoulder 27. Due to this shouldered construction of the support ring 25, its annular surface 29 likewise has a pitch, which is adapted at least approximately to the pitch of the uppermost spring coil 26.

As already mentioned, the receiving part 4 has an annular construction and is provided with a plane, annular support surface 30, which is a component of a flanged ring 32, which is surrounded by a cylindrical annular wall 31 extending on the outside.

Also, the insert ring 45 (Figure 3) able to be inserted in this receiving part 4, comprises a plane support surface 30', i. e. a surface lying in a plane extending at right angles to its axis.

This is a component of a flanged ring 33 resting on the support surface 30 of the receiving part 4, which is surrounded by a stepped annular wall 34.

Because the support surfaces 30 or 30'lie in a plane extending essentially at right angles to the longitudinal axis 13 and on the other hand the support ring 25 with its annular surface 29 extends in the manner of a thread, different distances, for example al and a2 result between the support surface 30 and the annular surface 29 of the spring plate 16, at different points of the periphery, which distances are to be bridged at least in sections, if at the time of tensioning of the spring 12, a desired, axial force distribution, which is uniform in the peripheral direction, from the receiving part 4 to the spring plate 16 is to be achieved, in order to prevent tilting of the spring plate on the piston rod of the suspension strut.

To clarify the shape of the support ring 25 and its annular surface 29, Figure 6 shows the support ring 25 in elongated illustration with an insert ring 45 able to be fitted from below into the receiving part 4, which is shown in Figure 3 as an individual part.

For the sectional bridging of the spacing, for example al, a2 existing at the beginning of a tensioning operation between the plane support surfaces 30,30'of the receiving part 4 or of the insert ring 45 on one side and the annular surface 29 of the spring plate 16, varying in the peripheral direction between a minimum and a maximum, in the embodiments illustrated in the drawings according to Figures 3,7 and 9, respectively two or three support members 35 and 36,37 are provided. These support members 35,36 and 37 consist of metal or synthetic bodies, which each comprise a first bearing surface 38 adapted to the shape of the support surface 30 and a second bearing surface 39 located opposite the former, which is adapted to the thread-like pitch of the annular surface 29 of the support ring 25 of the spring plate 16. The support members 35,36 and 37 have substantially an approximately cuboid-shaped design or the design of small blocks, which extend in the peripheral direction respectively solely over a short section of the annular surface 29. They are respectively releasably fastened by means of screws 40 in an exchangeable manner or displaceable in the peripheral direction, either directly on the support surface 30 of the receiving part 4 or on the support surface 30'of a separate insert ring 45,46 or 47. To receive the screws 40, these support surfaces 30 or 30'are respectively provided with a suitable number of axial bores 50, which respectively facilitate the most favourable peripheral position of the support members. In order to prevent the support members 35, 36,37 from rotating on the support surface 30 or 30'about the screw axis, these members 35,36,37 are designed and arranged so that they bear respectively by one side against the annular wall 31 or 41 of the receiving part 4 or of the insert ring 45.

With respect to the direct attachment of the support members 35, 36,37 to the annular support surface 30 of the receiving part 4, the use of an insert ring 45 or 46 or 47 has the advantage that this insert ring 45,46,47 is able to rotate with the support members 35,36,37 attached thereto, in the receiving part 4. This means that the spring tensioner 1 can be applied from any radial direction to the spring or the suspension strut to be tensioned, whilst the insert ring 45,46,47 with its support members 35,36 and 37 rests in a quite specific angular position on the support ring 25 of the spring plate 16.

Indeed, due to the displaceability of the support members 35, 36,37, the possibility is also provided of dealing with their arrangement on the support surface 30 so that the spring tensioner 1 can be pressed in a spatially favourable position against the spring to be tensioned. However, due to this, the random attachment possibility is not guaranteed.

As shown in Figure 2a, the receiving part 4 may also be constructed as an open ring.

When using insert rings 45,46 or 47, it is important that precautions are taken which prevent a rotation of the insert ring 45,46 or 47, respectively, used, in the receiving part 4, during the tensioning and relaxing operation of the coil spring 12. As a result of the pitch of the support ring 25 of the spring plate 16 bearing against the inclined bearing surfaces 39 of the support members 35,36,37 of the insert ring 45,46 or 47, the spring plate 16 is also subject to a torque, due to which the spring 12 attempts to relax. A torsional resistance preventing rotation must oppose this torque. This torsional resistance can be produced in different ways. For example it is possible to use the existing bores 50, in order to screw the insert ring 45,46 or 47 to the receiving part 4 or to fix these corresponds by insertion bolts one against the other. Another possibility consists of the provision of friction surfaces, for example in the form of rubber rings between the surfaces of the insert ring 45,46 or 47 and of the receiving part 4, lying one on the other, or in the form of conical surfaces, which produce an increased resistance to friction. Figures 10 and 10a show an embodiment with an inserted rubber ring 49.

Figure 2b shows another embodiment of a receiving part 4 with a coupling part 5 formed integrally therewith, in which the annular wall 31 is provided with three segment-like cut-outs 42, 43,44, in which respectively one bearing edge 51,52,53 is located. In this case it is important that these bearing edges 51,52 and 53 lie in a common plane surface, in order that the receiving part 4 with these bearing edges 51,52,53 can be supported on an essentially triangular spring plate provided with a plane upper side so that the remaining segment-like wall portions 54,55 and 56 may serve as centering and fixing aids.

As can be seen from Figure 3a, the support members 35,36 inserted in the insert ring 45 are respectively provided with a stepped shoulder 60, which is adapted to the inner shoulder 61 of the annular wall 34, so that the shoulder can be accommodated.

Whereas the bearing surface 38 extends at right angles to the outer sides of the essentially cylindrical body, the other bearing surface 39, extending obliquely, is adapted to the pitch shape of the annular surface 29 of the support ring 25.

The fact that the insert ring 45 is only provided with two support members 35 and 36, is because the annular surface 29 of the support ring 25 of the spring plate 16 as a rule bears at one point directly against the support surface 30'or the shoulder 61, when the two support members 35 and 36 are located at an angular distance of approximately 120 from this point and bear against the annular surface 29 of the support ring 25.

Whether two, three or more support members are used, is in practice decided in situ and indeed essentially depending on how the annular surface 29 of the respective spring plate 16 extends and whether it has a coarse or fine pitch.

Both in the sectional illustration of Figure 5 as well as in the elongated sectional illustration of Figure 6, in each case only two support members 35 and 36 are provided, Figure 5 showing only the support member 36.

Whereas, when using the insert ring 45, its outer annular wall 34 can be used for centering the support ring 25 of the spring plate, in Figures 7 and 8 an insert ring 46 is provided, which instead of an outer annular wall 34, has an inner annular wall 34'. This annular wall 34'may, as shown in Figure 8, engage in a centering manner in the annular wall 24 of the spring plate 16, when the receiving part 4 with the inserted insert ring 46 is applied for tensioning a spring 12. The support members 35, 36 and 37 screwed to the plane of flanged ring 33 are in this case not provided with a shoulder 60.

Figures 9,10 and 10a show an insert ring 47, which has neither an outer nor an inner annular wall. In this case in order to also have a centering possibility, the three support members 35, 36 and 37 screwed to the flat, plane annular member, with the appropriate angular spacings, are respectively provided with centering lugs 58 lying radially on the outside, which are capable of enclosing the support ring 25 of the spring plate 16 received, in a centering manner on the periphery.

Furthermore, in this embodiment, located in the receiving part 4 between the insert ring 47 and the flanged ring 32 is a flat ring 49 acting as a means of resisting rotation and consisting of a material which has high compressive strength with high surface friction, which may for example consist of rubber.

Figures 11 and lla show one application of the support members 35,36,37 in which the latter are screwed directly to the support surface 30 of the receiving part 4. In this case also it is appropriate to use the support members 35,36 and 37 with centering lugs 58, in order to achieve a centering effect between the receiving part 4 and the support ring 25 of a spring plate 16, if the annular wall 31 has an excessively large inner diameter.

In order to be able to use the spring tensioner 1 in the highest number of vehicle types with different spring plates, without great conversion work, it is appropriate to have available several insert rings 45,46 or 47 with the appropriate and suitably arranged support members 35,36 and 37, so that they need solely be exchanged.

Claims

Claims 1. A spring tensioner for tensioning a coil spring, which is received under pre-tension between an upper and a lower spring plate of a suspension strut of motor vehicles, said spring tensioner comprising a first and a second gripper member, which are guided coaxially with respect to each other by means of a guide tube of the spring tensioner and are displaceable relative to each other by means of an adjusting member in the axial direction of the guide tube, whereby for acting axially on the front annular surface of a flange-like support ring of the upper spring plate, extending in the manner of a thread corresponding to the end section of the coil spring, the first gripper member has a support surface constructed at least approximately in the shape of a circular ring and the second gripper member is constructed approximately in the shape of a fork and can be applied radially from the outside to one of the coils of the spring coil, wherein one support member (35) is provided or several support members (35,36,37) are provided for the sectional bridging of the axial distance al, a2 existing at the beginning of a tensioning operation between the support surface (30,30') of the first gripper member (2) and the annular surface (29) of the spring plate (16) and varying in the peripheral direction between a minimum and a maximum, the or each support member extending over a short section of the annular surface (29).
2. A spring tensioner according to Claim 1, wherein several members (35,36,37) are provided and these are fastened relative to the support surface (30,30') so that they are exchangeable and/or displaceable in the peripheral direction.
3. A spring tensioner according to Claim 1 or 2, wherein several support members (35,36,37) are provided in the form of metal or synthetic members, which respectively comprise a first bearing surface (38) adapted to the shape of the support surface (30,30') and a second bearing surface (39) lying opposite the latter, which surface (39) is adapted to the thead-like pitch of the annular surface (29).
4. A spring tensioner according to any one of Claims 1 to 3, wherein several support members (35,36,37) are provided and the support members have centering lugs (58) lying radially on the outside, which each project axially beyond the second bearing surfaces (39) and surround the peripheral edge of the support ring (29) of the spring plate (16) during use.
5. A spring tensioner according to any one of Claims 1 to 4, wherein several support members (35,36,37) are provided which are fastened to the support surface (30') of a separate insert ring (45,46,47), which can be accommodated in the receiving part (4) of the first gripper member (2).
6. A spring tensioner according to Claim 5, wherein the insert ring (45) has an L-shaped cross-sectional profile with an outer annular wall (34), which surrounds the support members (35,36) and which at the time of the tensioning operation also surrounds the support ring (25) of the spring plate (16) in a centering manner, at least in sections.
7. A spring tensioner according to Claim 5, wherein the insert ring (46) is provided with an inner annular wall (34').
8. A spring tensioner according to any one of Claims 5 to 7, wherein the insert ring (45,46,47) is prevented from rotating in the receiving part (4).
9. A spring tensioner according to any one of Claims 1 to 8, wherein the receiving part (4) of the first gripper member and/or the insert ring is/are respectively provided with several fastening devices (50), offset with respect Lo each other in the peripheral direction, for accommodating one or more support members (35,36,37).
10. A spring tensioner according to any one of Claims 1 to 9, wherein the annular wall (31) of the receiving part (4) of the first gripper member (2) is interrupted by several segment-like cut-outs (42,43,44), in which bearing edges (51,52,53) are located, which lie in a common plane at right angles to the axis of the annular wall.
11. A spring tensioner substantially as described with reference to, and as illustrated in, any one or more of the Figures of the accompanying drawings.