WO1988001576A1

WO1988001576A1 - Suspension apparatus

Info

Publication number: WO1988001576A1
Application number: PCT/AU1987/000302
Authority: WO
Inventors: Ian Gordon Sutherland
Original assignee: Ian Gordon Sutherland
Priority date: 1986-09-05
Filing date: 1987-09-04
Publication date: 1988-03-10

Abstract

A suspension apparatus (10), for a vehicle, which comprises an arm member (26) arranged to be connected at a first location thereof to said vehicle, such that said arm member (26) is pivotable relative to said vehicle about a first axis (30) and a second axis (31), said arm member (26) being arranged to be connected at a second location to a link means (36).

Description

TITLE SUSPENSION APPARATUS DESCRIPTION The present invention relates to a suspension apparatus. FIELD OF THE INVENTION

The suspension apparatus of the present invention is particularly applicable to vehicles e.g. motor vehicles. It is suitable for semi-trailing arm and semi-trailing suspensions. SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention there is provided a suspension apparatus for a vehicle comprising an arm member arranged to be connected at a first location thereof to said vehicle such, that said arm member is pivotable relative to said vehicle about a first axis and a second axis, said arm member being arranged to be connected at a second location thereof to a link means connectable to said vehicle.

Preferably, the first and second axes are substantially at right angles to one another.

The present invention is particularly suitable for semi-trailing arm and semi-leading arm suspensions.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1(a) is a perspective view of a first embodiment of a suspension apparatus in accordance with the present invention;

Figure 1(b) is a representation of the axis orientation, relative to Figure 1(a), used in Figures 9(a), 9(b) and 9(c); Figure 2 is a perspective view of a second embodiment of a suspension apparatus in accordance with the present invention;

Figure 3(a) is a perspective view of a third embodiment of the present invention employing an additional link to control the castor angle change, particularaly in an undriven wheel;

Figure 3(b) is an end view of the upright shown in the embodiment of Figure 3(a); Figure 3(c) is a side view of the upright and sub axle shown in the embodiment of Figure 3(a);

Figure 3(d) is a plan view of the upright, steering arm and stub axle shown in Figure 3(a);

Figure 3(e) is a view of the end of the semi-trailing arm that is connected to the upright;

Figure 4 is a plan view of an alternative embodiment for controlling the castor angle change in an undriven wheel;

Figure 5 is an embodiment showing the use of a longitudinal link; Figures 6 and 7 show two different orientations of the joint that may be used to connect the semi-trailing arm to the vehicle;

Figure 8 is a perspective view of a fourth embodiment similar to the third embodiment but in which the axes of the joint connecting the semi-trailing arm to the motor vehicle are orientated differently;

Figure 9(a) is a geometric diagram of a rear end elevation view of the suspension apparatus used in connection with a mathematical analysis of the present invention; Figure 9(b) is a geometric diagram of a plan view of the suspension apparatus used in connection with the mathematical analysis;

Figure 9(c) is a geometric diagram of a side elevation view of the suspension apparatus used in connection with the mathematical analysis.

DESCRIPTION OF THE INVENTION In Figure 1(a) the suspension apparatus 10 is shown in connection with a driven wheel of a motor vehicle. Only one wheel is shown in Figure 1(a) for clarity, but it is to be understood that the other wheel on the same axle is also provided with a suspension apparatus 10. A similar situation exists with the embodiments shown in Figures 2, 3(a), 4, 5 and 8 of the accompanying drawings. The differential 12, a wheel 14 and a part of the frame assembly 19 of the motor vehicle are shown in Figure 1. A quarter shaft 16 is connected at one of its ends to an end of a short drive shaft 18 obscured in Figure 1(a). Such connection is by way of a joint 20 allowing relative movement in three dimensions. ( The drive shaft 18 and joint 20 can be seen in Figure 4.) The other end of the quarter shaft 16 is connected to the differential 12 by way of joint 22.

The joint 22 is of a similar type to the joint 20. The joints 20 and 22 may be universal joints.

The other end of the short drive shaft 18 is connected to the hub 23 of a wheel 14.

The quarter shaft 16 is able to vary in length. This may be achieved by incorporating sliding splines in the quarter shaft 16. Alternatively, constant velocity joints, or similar, may be used.

A semi-trailing arm 26 is connected at one end thereof to a part of the frame assembly 19 of the motor vehicle, by way of a joint 28.

The semi-trailing arm 26 has an offset portion through which the short drive shaft 18 passes.

Lateral movement of the semi-trailing arm 26 is controlled by way of a transverse link or arm 36, in the form of an elongate member, disposed in a manner substantially transverse to a longitudinal axis of the vehicle. The transverse link 36 is required since the quarter shaft 16 is able to vary in length. The transverse link 36 is connected to the offset portion of the semi-trailing arm 26 by a ball joint 38, or similar joint, obscured in Figure 1(a) but visible in Figure 3(a).

The other end of the transverse link 36 is connected to the frame assembly of the motor vehicle by another ball joint (not shown), or similar joint. The link 36 may alternatively be mounted behind the axle line in a similar manner.

The transverse link 36 is of a length such that the toe in, on bump and droop is substantially controlled. In most cases, it is likely that the optimum length of the transverse link 36 will cross the longitudinal centre line 40 of the vehicle. This will necessitate the respective transverse links 36, extending from the wheels of a pair of wheels mounted on the same axle, to be mounted one behind the other. In this way, the transverse links 36 will have slightly different lengths so as to achieve the same angle change in their respective semi-trailing arms 26 to control toe in.

The semi-trailing arm 26 may be suspended from the motor vehicle by a coil spring and a shock absorber 42. However, any suitable damped resilient means may be used in place of the shock absorber 42.

Figure 2 shows another embodiment of the suspension apparatus in accordance with the present invention. The same parts have been indicated with the same reference numerals in Figures 1(a) and 2.

In Figure 2, a solid quarter shaft 44 is used as the transverse link. The solid quarter shaft 44 is disposed in a manner substantially transverse to a longitudinal axis of the vehicle. Lateral force on the semi-trailing arm 26 is then transferred via the solid quarter shaft 44 and the differential 12 to the body of the motor vehicle. The remainder of the apparatus shown in Figure 2 is similar to that shown in Figure 1(a). Due to the reduced length of the transverse link (the transverse link being the solid quarter shaft 44) used in the apparatus of Figure 2, some degree of toe out in bump and droop may be induced. In Figure 3 (a) there is shown an embodiment of the suspension apparatus of the present invention for a front undriven wheel of a motor vehicle, whilst Figures 3(b) to 3(e) show details of various components in the embodiment of Figure 3(a). In Figure 3(a), one end of a semi-trailing arm 26 is connected to the motor vehicle by way of joint 28. The other end of the semi-trailing arm 26 is connected to an upright 47 via shaft bearings 48. A steering arm 49 is connected to the upright 47. The stub axle 51 is connected to the upright 47 by way of a king pin 46.

The shaft bearings 48 in the semi-trailing arm 26 permit relative rotation of the semi-trailing arm 26 with respect to the upright 47. A transverse link 36 is also provided, as described with reference to Figure 1(a).

A steering link or track rod (not shown) would also be provided in the usual way. An additional link 50 is provided substantially parallel to the semi-trailing arm 26. One end of the additional link 50 is connected to the upright 47 by way of a ball joint 52, or similar joint. The other end of the additional link 50 is connected to the motor vehicle by way of another ball joint 53, or similar joint. The provision of the additional link 50 controls the change in castor angle so that it is kept small.

In Figure 4 there is shown an alternative embodiment of the suspension apparatus of the present invention for an undriven wheel of a motor vehicle to control the castor angle.

In the embodiment shown in Figure 4 a solid quarter shaft 54, capable of moving in only a substantially vetical plane, is used as the transverse link. The solid quarter shaft 54 is disposed substantially transverse to a longitudinal axis of the motor vehicle.

The joint 56 is of a form which permits the solid quarter shaft 54 to move in only a substantially vertical plane. Such plane is shown edge-on by the broken line 60. The solid quarter shaft 54 is connected to the vehicle by the joint 56. The wheel 14 may pivot by way of king pin 46. In Figure 5 there is shown another embodiment of the suspension apparatus according to the present invention. In Figure 5, the semi-trailing arm 26 is positioned at substantially 45° to a longitudinal axis of the motor vehicle.

Under such circumstances, the longitudinal link 82 may be employed rather than a transverse link as shown in the previous embodiments. The longitudinal link 82 is disposed substantially parallel to a longitudinal axis of the motor vehicle.

The longitudinal link 82 would still act to resist lateral movement of the semi-trailing arm 26 in a similar manner to the transverse links of the previous embodiments. Further, a transverse link and a longitudinal link may be used simultaneously if they may be positioned such that may move in unison.

The joints 20 (obscured) and 22 are of a similar type to those shown in Figures 1(a) and 2. The joint that is used to connect the semi-trailing arm 26 to the motor vehicle in the present invention, is of a type which permits relative movement between the semi-trailing arm 26 and the motor vehicle about a first axis and a second axis. Preferably, the first and second axes are substantially at right angles to one another, i.e. substantially orthogonal.

Rotation about the third orthogonal axis is not possible.

Figures 6 and 7 show a form of the joint 28 that may be used to connect the semi-trailing arm 26 to the motor vehicle to allow for relative movement therebetween about two axes.

The joint 28 has a "U"-shaped bracket 62 which is attachable to the motor vehicle. A pin 64 is rotatably mounted in the bracket 62. The pin 64 has a first rotation axis 30. The pin 64 allows the semi-trailing arm 26 to pivot about the first axis 30.

The joint 28 further has a "U"-shaped bracket 68 which is attachable to the semi-trailing arm 26. A pin 66 is rotatably mounted in the bracket 68. The pin 66 has a second rotation axis 31. The pin 66 allows the semi-trailing arm 26 to pivot about the second axis 31. The pin 64 has an aperture through which the pin 66 passes. Alternatively, the pin 66 may be provided with an aperture through which the pin 64 passes.

The joint 28 may be mounted to the motor vehicle such that the first axis 30 is positioned in any desired orientation. The orientation will determine the orientation of the axis 31. In Figure 6, the joint 28 is shown with the first axis 30 being positioned substantially parallel to the horizontal whilst in Figure 7, the joint 28 is shown with the first axis 30 being positioned substantially at right angles to the horizontal. Further illustrations of the orientation of the first axis 30 and the second axis 31 are shown in Figures 1(a), 2 and 8.

In Figures 1(a) and 2, the joint 28 is mounted to the motor vehicle with the first axis 30 at substantially 45° to the horizontal and the second axis 31 at substantially 45° to the vertical.

The horizontal line 34 shown in Figure 1, 2, 4, 5 and 8 represents a vertical plane that passes through the centres of the two wheels connected on the same axle. This plane contains the effective axle line which coincides with the line 34.

The point of intersection of one of the axes 30, 31 with the above plane determines the instant arm length of the suspension apparatus Figure 8 shows a suspension apparatus in accordance with the present invention with the first axis 30 at substantially 45° to the horizontal and the second axis 31 at substantially 45° to the vertical, but wherein the axes 30 and 31 are rotated away from the horizontal and vertical, respectively, in the opposite direction to that shown in Figures 1(a) and 2.

The joint 28 shown in Figure 6 has the effect of giving a slight increase in a camber change in bump and droop as compared with a standard semi-trailing arm suspension due to the shortening of the instant arm length.

The joint 28 shown in Figure 7 tends to reduce the camber change due to the increase in the instant arm length, since the semi-trailing arm 26 is pulled in by the transverse link. The joint that connects the semi-trailing arm 26 to the vehicle may be attached to the vehicle frame or sub-frame. The resilient suspension of the semi-trailing arm 26 to the vehicle may be effected by any suitable damped resilient means, e.g., a coil spring and shock absorber 42, as previously described

In the embodiments shown in Figures 1 and 2, one end of such a damped resilient means may be attached to the semi-trailing arm 26 near the short drive shaft 18 whilst the other end is attached to the vehicle.

The semi-trailing arm suspension of the present invention may be applied to front or rear, driven or undriven, suspensions. The present invention allows a wide range of movement of the vehicle wheel in a series of vertical planes, with the rate of camber change dependant upon the instant arm length selected by the designer. As the instant arm length remains essentially constant, the roll centre and the camber change in bump and droop and roll also remain essentially constant when compared with most applications of double wishbone or strut type independent suspension systems. This allows a larger suspension travel without adverse camber change of the wheels. The roll centre is determined by the intersection of lines projected from the contact point between the wheel and the road surface at the wheel centre to the inboard mount of the transverse link of the same side to the vehicle. As the vehicle wheel moves in a substantially vertical (and not a forward) curve, it is possible to build-in anti-dive and anti-squat. This can be done by raising or lowering the position of the mounting joint that connects the semi-trailing arm 26 to the vehicle, above or below the effective axle line of the two wheels of a pair of wheels, such that the first axis line of the above mounting joint still intersects the effective axle line of the wheels. An approximation of the optimum mounting position of the joint 28 and the optimum length of the transverse link may be determined using a combination of mathematical calculation and geometric construction. However, empirical results would also be relevant in such a determination. The following mathematical analysis, given by way of example, is concerned with the analysis of a designed suspension to allow balancing and refinement at the actual design stage. Some variations wilϊ be generally required at the design stage to fulfil the design criteria. The following analysis uses approximations and should not be considered as a rigorous mathematical analysis. It may, however, provide useful approximations The analysis comprises a series of equations for determining design parameters in any given application of the present invention.

The two major approximations made are firstly, that the intersection of two curves, required for the analysis, is made approximate and secondly, that no allowance is made for the reducing toe change effect of the link in movement, i.e. if the semi-trailing arm, for example, were horizontal at rest, as it moves round in bump to 90° i.e. vertical to the approaching vertical, the link changes camber more than toe .

Reference is made to Figures 9(a), 9(b) and 9(c), which are geometric diagrams, in the mathematical analysis. DATA REQUIRED (Input values based on the measurements of the motor vehicle for which the suspension apparatus is being specifically designed)

1. TRACK WIDTH VW

2. AXLE CENTRE HEIGHT AW 3. INSTANT CENTRE HEIGHT BV

4. ARM MOUNT HEIGHT EL

5. HORIZONTAL DISTANCE ARM MOUNT TO AXLE CENTRE LINE. EK

6. HORIZONTAL DISTANCE OPPOSITE TRACK TO ARM MOUNT VL

7. VERTICAL HEIGHT OUTER END OF LINK QR

8. VERTICAL HEIGHT INNER END OF LINK GS

9. HORIZONTAL LENGTH BACK INNER END OF

LINK TO AXLE PG 10. HORIZONTAL DISTANCE INNER END OF

LINK TO OPPOSITE TRACK VS

11. HORIZONTAL DISTANCE OUTER END OF

LINK TO OPPOSITE TRACK VR

12. HEIGHT OF PUMP AND DROOP AA CONDITIONS

1. Inner end of transverse link behind axle centre line by at least the distance back that wheel centre moves. 2. Instant centre at opposite track - a small modification of the mathematics is necessary if the instant centre is not at opposite track.

3. Inner end of link should be close to AA above outer end.

CALCULATIONS FOR BUMP

Horizontal length of effective trail: WF (DW FIG. 9(a)

VERTICAL HEIGHT OF EFFECTIVE TRAIL: DF (Fig. 9(c)

ACTUAL LENGTH OF EFFECTIVE TRAIL ARM: AD (Fig 9(c) = ZX

ZX = √ [(WF)² + (DF - AW)²] VERTICAL HEIGHT OF AXLE CENTRE PLUS BUMP (AA) TO POINT D (Fig 9(c)

ZF= (DF-AW-AA) DISTANCE BACK AXLE CENTRE MOVES IN BUMP: ZB (Fig 9(c)

ZB = √[(ZX)² - (ZF)²] - WF EFFECTIVE LENGTH INSTANT ARM: BA (Fig 9(a) BA = √[(VW)² + (AW - BV)²]

AXLE CENTRE POINT A MOVES IN AS FOR CONVENTIONAL SEMI-TRAIL ARM ZA (Fig 9(a)

ZA = VW - √[(BA)² - (AW-BV+AA)²] ANGLE OF TOE OUT AS PER CONVENTIONAL SEMI TRAIL:ZE (Fig 9(b)

VERTICAL HEIGHT OF OUTER END OF LINK TRANSFERRED TO INSTANT ARM (VERTICAL) (Fig 9(b) (TO GROUND) (POINT Q Fig 9(a) = XZ XZ = +BV

THIS VERTICAL HEIGHT ON BUMP OF AA AT WHEEL CENTRE (Fig 1B) TO GROUND AT POINT Q TRANSFERRED TO INSTANT ARM = ZO ZO = +BV

MOVES UP ON BUMP AS BEFORE = ZP ZP = ZO-XZ LENGTH OF INSTANT ARM FROM POINT B TO TRANSFERRED POINT Q (Fig 9(a): BQ

BQ = √[(VR)² - (XZ-BV)²] OUTER END OF LINK MOVES IN FOR BUMP ZP AT TRANSFERRED POINT Q: XG (Fig 9(a)

XG = VR - √[(BQ)² - (ZO-BV)²] LENGTH OF LINK IN VERTICAL PLANE (GQ) (Fig 9(a): ZQ

ZQ = √[(GS-QR)² + (VR-VS)²] END OF LINK MOVES OUT FOR BUMP ZP IN VERTICAL PLANE FIG 9(a) = ZR

ZR = √[(ZQ)² - (GS-QR-ZP)²] - (VR-VS) LENGTH OF LINK IN HORIZONTAL PLANE ZU AT BUMP ZP =ZU

ZU √[(PG)² = (VR-VS+ZR)²] DISTANCE END OF LINK MOVES BACK (Fig 9(b) =ZS

ZS =

END OF LINK MOVES OUT ZT (Fig 9(b) FOR MOVE BACK ZS = ZT (TOTAL MOVE OUT)

ZT = √[(ZV)² - (PG - ZS)²] - (VR - VS) ANGLE OF SUSPENSION ARM IN HORIZONTAL PLANE AT BUMP, CONVENTIONAL SEMI-TRAIL (Fig 9(b) = XA XA =

LINK MOVES ARM FROM ABOVE ANGLE TO ANGLE XB (Fig 9(b)

XB = ATAN

LINK INDUCED ANGLE CHANGE = XC

XC = (XB-XA) TOTAL ANGLE CHANGE OF ARM = TOE IN TOE OUT CHANGE AT WHEEL = DIFFERENCE BETWEEN TOE CHANGE DUE TO CONVENTIONAL SEMI TRAIL AND EFFECT OF THE LINK = ZZ.

ZZ = ZE - XC FOR DROOP (CERTAIN CALCULATED QUANTITIES FROM BUMP USED). VERTICAL HEIGHT OF WHEEL CENTRE POINT A TO HEIGHT OF EFFECTIVE TRAIL PIVOT POINT = YF (Fig 9(c) YF = (DF-AW+AA)

POINT A MOVES FORWARD IN DROOP (Fig 9(c) = YB

YB = WF - √ [(ZX)² - (YF)²] POINT A MOVES OUT ON DROOP YA (Fig 1A) = YA YA = √ [(BA) ² - (AW-BV-AA)²] -VW TOE IN AS PER NORMAL SEMI-TRAIL SUSPENSION = YE (Fig 9(b)

YE = ATAN

VERTICAL MOVEMENT OF POINT "Q" TRANSFERRED TO EFFECTIVE SWING ARM (DOWN) (Fig 9(a) = YO GIVES HEIGHT TO GROUND. YO = +BV

VERTICAL MOVEMENT OF TRANSFERRED POINT Q = YP (Fig 9(a)

YP = XZ - YO POINT Q TRANSFERRED MOVES OUT IN DROOP: XI (Fig 9(a)

XI = √[(BQ)² - (YO-BV)²] - VR POINT Q MOVES FORWARD IN DROOP :YS (Fig 9(b)

YS =

POINT Q MOVES IN, IN VERTICAL PLANE - LINK ACTION FOR DROOP, YP = YR (Fig 9(a)

YR = (VR-VS) - √ [(ZQ)² - (GS-QR+YP)] NEW LENGTH OF LINK IN HORIZONTAL PLANE AT DROOP :YP YU = √ [(PG)² + (VR-VS-YR)²]

POINT Q MOVES IN WITH HORIZONTAL PLANE MOVEMENT FORWARD OF YS = YT (Fig 9 (b)

YT= (VR-VS) - √[(YU)² - (PG+YS)²] = TOTAL MOVE IN OF LINK ANGLE OF SUSPENSION ARM DUE TO NORMAL TRAIL ACTION = XK (Fig 9(b)

XK = ATAN

ANGLE CHANGE DUE TO LINK = XL (Fig 9(b)

XL+ ATAN

RESULTANT ANGLE CHANGE = XM (Fig 9 (b)

XM = (XK-XL) TOE CHANGE AT WHEEL = XN

XN = XM - YE ( - = TOE IN) TRACK CHANGE

LENGTH OF "BW" (INSTANT CENTRE TO OPPOSITE TRACK) (Fig 9(a)

BW = √[(VW)² + (VB)²] NOTE: FOR BUMP IF AA > BV CARE MUST BE TAKEN UNLESS BV=O WHEN CHANGE XO= √[(VW)² - (AA)²] TRACK CHANGE DUE TO EFFECTIVE SWING ARM IN BUMP ONE SIDE: XO (Fig 9(a)

XO = VW - √[(BW)² - (BV - AA)²] TOTAL CHANGE = 2 x XO = XQ TRACK CHANGE DUE TO EFFECTIVE SWING ARM IN DROOP ONE

XP = √[(BW)² - (BV+AA)²] -VW TOTAL CHANGE = 2 x XP = XR TOTAL TRACK CHANGE BUMP = XS

XS = XQ + (2 x ZT) TOTAL TRACK CHANGE DROOP = XT

XT = YR - 2x (XT) ROLL CENTRE HEIGHT

NOTE: ROLL CENTRE HEIGHT MUST REMAIN BELOW CGH AT DOUBLE DROOP. ROLL CENTRE HEIGHT = XV (Fig 9(a)

XV =

CAMBER CHANGE ANGLE "BWV" = RA (Fig 9(a) RA = ATAN

ANGLE IN BUMP "BVW" - RB (Fig 9(a)

RB = ATAN

ANGLE IN DROOP "BWV" = RE (Fig 9(a)

RC = ATAN

CAMBER CHANGE FOR BUMP = RD (Fig 9(a)

RD = RA-RB CAMBER CHANGE FOR DROOP = RE (Fig 9(a)

RE = RC-RA

As stated previously, the preceding mathematical analysis provides an approximation of the different design parameters for further refinement at an actual design stage.

The mathematical analysis may be supplemented by computer modelling and similar aids.

Modifications and variations such as would be apparent to a skilled addressee are deemed within the scope of the present invention.

Claims

1. A suspension apparatus for a vehicle characterised in that it comprises an arm member arranged to be connected at a first location thereof to said vehicle such that said arm member is pivotable relative to said vehicle about a first axis and a second axis, said arm member being arranged to be connected at a second location thereof to a link means connectable to said vehicle.

2. A suspension apparatus as defined in any one of the preceding claims, characterised in that said link means comprises a solid quarter shaft means positionable in a substantially transverse orientation with respect to the longitudinal axis of said vehicle.

3. A suspension apparatus as defined in claim 1, characterised in that a quarter shaft of variable length connects said arm member to said vehicle and said link means comprises an elongate member positionable in a substantially transverse orientation with respect to a longitudinal axis of said vehicle.

4. A suspension apparatus as defined in any one of claims 1 or 3, characterised in that said arm member is positionable at an angle of substantially 45° to a longitudinal axis of said vehicle and said link means comprises a longitudinal link extending in a direction substantially parallel with said longitudinal axis of said vehicle.

5. A suspension apparatus as defined in any one of the preceding claims, characterised in that said arm member is arranged to be connected to said vehicle by way of joint means located at one end of said arm member.

6. A suspension apparatus as defined in claim 5, characterised in that said joint means comprises first bracket means connected to said arm member and second bracket means connectable to said vehicle, said first and second brackets being provided with respective pin means, said pin means defining said first and second axes.

7. A suspension apparatus as defin d in claim 6, characterised in that one said pin means passes through an aperture in the other said pin means.

8. A suspension apparatus as defined in any one of the preceding claims, characterised in that said first axis and said second axis are substantially at right angles to one another.

9. A suspension apparatus as defined in any one of the preceding claims, characterised in that said first axis is positioned substantially 45° to the horizontal and said second axis is positioned substantially 45° to the vertical.

10. A suspension apparatus as defined in any one of the preceding claims, characterised in that an additional link means is provided which is connected to the arm member at a location remote from said first location, said additional link means being connectable to said vehicle such that said additional link means is substantially parallel to said arm member.

11. A suspension apparatus as defined in claim 10 characterised in that said additional link means comprises an elongate member.