Mechanical control by cable sliding axially in a flexible sheath

The invention relates to a mechanical control by cable (10) sliding axially in a flexible sheath (12), equipped with an automatic adjustment device (40) for varying the length of the sheath as a function of the clearances appearing in the control, and of which one end (28) is connected to a receiving member (30) provided with elastic return means (36). According to the invention, the adjustment device (40) includes two telescopic sheath extensions (43,44) inserted between two consecutive portions (41,42) of the sheath to which they are fixed, a wedge-action locking member (62) disposed between the two sheath extensions (43,44) to interlock the latter by wedging during actuation of the mechanical control, and a control member (80) fixed to the locking member (62) and connected to the cable (10) by means of a friction connection (84,11), the control member (80) being entrained, during actuation of the control, in axial translation by the cable (10) in the direction corresponding to wedging of the locking member until the sheath extensions (43,44) are interlocked, the control member being entrained in axial translation by the cable in the direction corresponding to unlocking when the return force applied to the cable becomes less than a predetermined value.

The present invention relates to mechanical control by cable sliding 
axially in a flexible sheath provided with an automatic adjustment device. 
The invention relates more particularly to mechanical controls by cable 
applied to the control of a friction clutch for an automobile vehicle or 
the control of a drum or disc brake for an automobile vehicle. When such a 
type of control is used notably in the case of a friction clutch, wear of 
the friction linings of the clutch resulting from successive engagements 
and disengagements of the clutch induces the appearance of increasing 
clearances between the various elements of the clutch. If no device for 
compensating the clearances is provided, the rest position of the clutch 
actuating pedal varies gradually until it reaches a final position 
corresponding to maximum wear of the friction linings, in which the pedal 
is raised by several centimetres relative to its initial rest position 
corresponding to new friction linings. It is likewise ascertained, after 
installation of such a control on a vehicle and after a short time of use, 
that the cable tends to lengthen under the effect of the traction forces 
applied to it, the sheath tending for its parts to shorten under the 
effect of the compression forces applied to it in reaction. This 
lengthening of the cable and this shortening of the sheath are added to 
each other and induce likewise the appearance of parasitic clearances in 
the control which are harmful to correct functioning of this control. 
European patent application No. 0 030 494 A1 published on June 17, 1981 
presents and describes a mechanical control by cable, provided with a 
device for automatic compensation of clearances mounted at one of the ends 
of the sheath. This device comprises a disengageable connecting system 
with wedging by balls, disposed between one end of the sheath and a fixed 
support attached to the chassis of the vehicle. The device proposed 
effects in a very satisfactory manner automatic compensation of any 
clearances capable of appearing in the control, but presents the 
disadvantage of having to be installed on a fixed part of the vehicle, 
this fixed reference being necessary to control unlocking of the 
disengageable connection with wedging by balls, when the pedal is in its 
normal rest position. 
The object of the present invention is to provide a mechanical control by 
cable provided with an automatic adjustment device capable of compensating 
any clearances appearing in the control, and allowing it to abolish a 
fixed reference to the vehicle frame on which it is installed. 
With this object, the invention proposes a mechanical control by cable 
sliding axially in a flexible sheath equipped with an automatic adjustment 
device for varying the length of the sheath as a function of the 
clearances appearing in the control, and of which one end is connected to 
a receiving member provided with elastic return means, said adjustment 
device including two telescopic sheath extensions inserted between two 
consecutive portions of the sheath to which they are fixed, characterized 
in that said device comprises a wedge-action locking member disposed 
between the two sheath extensions for interlocking the latter by wedging 
during actuation of the mechanical control, and a control member fixed to 
the locking member and connected to the cable by means of a friction 
connection, said control member being driven during actuation of the 
control in axial translation by the cable in the direction corresponding 
to wedging of the locking member until the sheath extensions are 
interlocked, said control member being driven in axial translation by the 
cable in the direction corresponding to unlocking when the return force 
applied to the sliding cable becomes less than a predetermined value.

The mechanical control shown in FIG. 1 comprises a cable 10 mounted in 
axial sliding relationship in a flexible cylindrical sheath of the 
"Bowden" type 12 of which the ends 14 and 16 are anchored to a fixed 
frame18 formed for example by the chassis of an automobile vehicle. The 
first end 20 of the cable 10 is fixed to an actuating member 22 formed in 
the example shown by a pedal 22 mounted pivotally relative to the frame 
18. The pedal 22 is returned to its rest position bearing on a fixed stop 
24 by a pedal return spring 26. The second end 28 of the cable 10 is fixed 
to a receiving member formed in the example shown by a friction clutch 
control fork 30. The fork 30 is mounted pivotally relative to the frame 18 
and is connected to a clutch disc 32. The clutch disc 32 is normally 
maintained in contact with a clutch plate 34 by clutch springs 36 
supported on the frame 18. The disc 32 and plate 34 are both provided 
witch friction linings 35. 
The mechanical control shown in FIG. 1 comprises further an automatic 
adjustment device 40 inserted between two consecutive portions 41 and 42 
of the flexible sheath 12. 
When the driver actuates the pedal 22 and causes the latter to pivot, he 
induces axial displacement of the cable 10 relative to the sheath 12 in 
the direction indicated by the arrow A; axial displacement of the cable 10 
induces pivoting of the clutch fork 30 which entrains with it the clutch 
disc 32 at a distance from the plate 34, while compressing the clutch 
springs 36, to induce disengagement. 
The automatic adjustment device 40 will now be described in more detail 
referring to FIG. 2 to 5. The device 40 includes two sheath extensions 43 
and 44 fixed to the ends of the two consecutive sheath portions 41 and 42, 
respectively. The sheath extension 43 is received telescopically in the 
extension 44 to constitute a variable length device allowing the length of 
the sheath 12 to be adjusted automatically as a function of the clearances 
capable of appearing in the control. The sheath extension 43 is formed by 
a piece of tubular shape, which is fixed by its end 46 to the end of the 
sheath portion 41 and is mounted coaxially wit the latter. The extension 
44 is likewise formed by a piece of tubular shape fixed to the second 
sheath portion 42 in an identical manner. The cable 10 can slide freely in 
the internal bores 45 and 46 of the sheath extensions 43 and 44. The 
sheath extension 43 is provided with a protective collar 48 made of 
material with the extension 43 and coaxial with the latter. The end 50 of 
the protective collar 48 is provided with an annular shoulder in the shape 
of a hook 51 capable of cooperating with a similar shoulder 52 provided at 
the end 53 of the sheath extension 44 to define a device for closing the 
casing formed by the two sheath extensions 43 and 44; the shoulders 51 and 
52 further have the function of limiting relative axial displacement of 
the extensions 43 and 44 in a manner which will be described below. The 
automatic adjustment device 40 likewise includes an adjuster spring 54. 
The adjuster spring 54 is formed in the example shown by a helical 
compression spring disposed between the extension 43 and the extension 44. 
The end 55 of the spring 54 is supported on the inner wall 56 of the 
extension 43. The second end 57 of the helical spring 54 is supported on a 
washer 58 mounted in a radial groove 59 formed in the internal bore of 
large diameter 60 formed in the sheath extension 44. The compression 
spring 54 arranged thus urges the sheath extensions 43 and 44 apart from 
each other in the direction corresponding to a lengthening of the sheath 
12. The adjustment device 40 further comprises a locking member 62 
provided to interlock the extensions 43 and 44 during actuation of the 
mechanical control. The locking member 62 is provided with a releasable 
coupling device 64 with wedging by balls 74. This system includes a 
cylindrical sleeve 66 mounted in axial sliding relationship in the large 
diameter internal bore 60 of the sheath extension 44. A frustoconical 
bearing surface 67 is formed in the internal bore 60 of the extension 44. 
The outer cylindrical surface 68 of the sheath extension of tubular shape 
43 is received in sliding relationship in an internal bore 70 formed in 
the cylindrical sleeve 66. The cylindrical outer surface 68 defines a 
cylindrical bearing surface which cooperates with the frustoconical 
bearing surface 67 to form between them a recess 72 in which are received 
balls 74. The balls 74 are distributed circularly and are disposed in 
radial bores 76 formed in the sleeve 66; the sleeve 66 constituting a cage 
for the balls 74 which are mounted freely in the bores 76. 
The locking member 62 is controlled by a control member, shown 
schematically in FIG. 2 and designated by the general reference 80. The 
control member 80 is formed by a split spring collet 82 in which is formed 
a cylindrical internal bore 84 in which the cable 10 is received in 
sliding motion, the bore 84 cooperating with the outer cylindrical surface 
11 of the cable 10. In the example shown, the spring collet 84 is made of 
material with the locking member 62 which is made in a flexible material. 
The split spring collet 84 is compressed and maintained clamped on the 
cable 10 by means of an element forming a spring 86. It can be understood 
that in this way the control member 82 is connected to the cable 10 by a 
friction connection resulting from contact between the inner wall of the 
bore 84 and the outer surface 11 of the cable 10. 
The control member 80 will now be described in more detail referring to 
FIGS. 3 to 5. FIG. 3 to 5 show the end portion of the locking member 62 
constituting the control member 80. The locking member 80 is shown 
independently of the other elements of the control and notably of the 
cable 10. The member 80 includes a split spring collet 82 comprising a 
body of cylindrical general shape. In order to possess good elasticity, 
the cylindrical body 82 is split in the following manner: it comprises a 
first transverse axial slot 88 extending approximately along a diameter of 
the body 82 and ending at its first end 89 in a slot in the form of a 
circular crown 90 extending over about one-third of the circumference, and 
extending axially from the end 92 of the cylindrical body 82 as far as a 
radial transverse slot 94 extending over about half the cylindrical block 
82. The slot 88 widens in the proximity of its second end 87 to form a 
recess in the form of a circle sector 96 extending transversely over a 
length identical with the slot in the form of a crown 90. The control 
member 80 finally comprises a spring 86 formed by a circlip made of sheet 
metal and exhibiting approximately the shape of an incomplete ring. The 
spring 86 is mounted in an external radial groove 98 in the resilient 
block 82. The spring 86 is mounted tightly on the groove 98 to apply to 
the block 82 a resilient stress inducing wedging of the cable 10 in the 
internal bore 84 of the block 82. In the embodiment shown, the whole of 
the locking member 62 including particularly the control member 80 is made 
of thermoplastic material known under the name of "Delrin" and cooperates 
with the outer surface 11 of the cable 10 which is generally formed by a 
wrapping made of polyethylene or polyamide. 
Operation of the automatic adjustment device mounted on the mechanical 
control will now be described. When the driver actuates the control, for 
example by acting on the pedal 22, he induces axial displacement of the 
cable 10 relative to the sheath 12; during this displacement, the cable 
entrains by friction the control member 80 which is fixed rigidly to the 
locking member 62. It can be understood that in this way, as soon as the 
driver acts on the cable 10, the locking member 62 moves to the right, 
considering FIG. 2, and induces wedging of the balls 74 between the 
bearing surfaces 67 and 68 which then occupy the position shown in FIG. 2. 
As soon as the balls 74 are wedged between the bearing surfaces, the 
locking member interlocks the sheath extensions 43 and 44 to constitute a 
sheath of constant length behaving like a conventional cable sheath. Any 
force applied to the cable 10 is applied by reaction to the sheath 12 and 
hence consequently to the sheath extensions 43 and 44 which are subjected 
to forces acting in the direction corresponding to shortening of the 
sheath. These forces amplify wedging of the balls 74 between the two 
sheath extensions, and stop the two extensions in their relative axial 
position as well as the locking member 62 relative to the two extensions. 
From this moment on, any supplementary displacement of the cable 10 to the 
right induces sliding of the cable relative to the member 80, that is the 
control member 80 is no longer entrained by friction, the wedging forces 
exerted on the balls being greater than the friction force exerted by the 
cable 10 on the control member 80. The driver can therefore control 
disengagement of the clutch 30 with all reliability, the mechanical 
control behaving like a mechanical control of a conventional type in which 
the sheath is continuous. When the driver releases the force applied to 
the pedal 22, the cable is subjected by the return springs of the clutch 
30 to a return force inducing its axial displacement to the left. The 
force applied to the cable 10 by the return springs 36 is likewise 
transmitted by reaction to the sheath in two parts and consequently to the 
sheath extensions 43 and 44. In an identical manner with what has been 
described above, these reaction forces transmitted to the extensions 43 
and 44 amplify wedging of the balls 74 between the two extensions and stop 
these two elements relative to each other as well as the locking member 62 
relative to the two extensions. During the return stage of the cable, the 
latter slides relative to the control member 80 of the locking member 62. 
This sliding continues until the clutch approaches the engaged position. 
During this approach, the return force applied to the cable, and by 
reaction to the sheath, decreases progressively until the clutch is in the 
engaged position, in which the forces applied to the sheath and to the 
cable are zero. It will be understood that during its decrease, the force 
applied to the cable passes through a predetermined value corresponding to 
the boundary force of sliding of the cable 10 relative to the control 
member 80; below this predetermined value, the cable can again entrain the 
control member by friction and consequently induce displacement of the 
locking member 61 to the left. Displacement of the locking member 62 to 
the left induces unwedging of the balls 74 and unlocking of the sheath 
extensions, the wedging force applied to the balls having decreased 
progressively as the return force applied to the cable decreased. 
Displacement of the locking member to the left is limited by the washer 58 
against which the free end 65 of the cylindrical sleeve 66 comes to bear. 
The path of the locking member 62 relative to the extension 44 is also 
limited to a value "1" necessary for unlocking of the member 62. In the 
rest position of the control, the two extensions 43 and 44 can slide 
freely relative to each other telescopically to allow, notably by the 
action of the helical spring 54, automatic adjustment of the length of the 
sheath 10, that is, automatic compensation of any clearances capable of 
appearing in the control. It can be understood that in this way the 
mechanical control provided with the automatic adjustment device 40 
constitutes a "self-adjusting" cable capable of compensating any 
clearances appearing in the mechanical control and capable of being 
installed on any vehicle at all in place of a conventional control cable, 
and this without any adaptation either of the vehicle or of the 
conventional cable fixing means such as stops or cable ferrules. This 
advantage is preponderant particularly for the installation of cables on 
modern vehicles in which the constraints of bulkiness are among the most 
important. It can further be understood that mounting of such a 
self-adjusting cable ensures all reliability as regards correct 
functioning of the receiving member which is associated therewith, this 
being from mounting of the cable on the vehicle onwards, no further 
adjustment nor any adaptation being necessary. Particularly, the rest 
position of the actuating member formed by a pedal is ensured constantly 
in the course of time. The automatic adjustment device proposed further 
allows it to be adapted for any cable length at all, the manufacturer of 
the latter having only to modify the length of the two sheath portions 
between which the device is inserted to adapt to the demand of different 
users. The mechanical control provided with its adjustment device being 
moreover of the type in which the cable is not interrupted, it exhibits 
all the conditions of reliability and safety desirable notably in case of 
a possible defect in the adjustment device. In fact, in case of poor 
functioning, for example of the device with wedging by balls, the driver 
will nevertheless be able to actuate the clutch control, the two sheath 
extensions 43 and 44 then abutting one inside the other, that is, the end 
52 of the extension 44 coming to bear on the inner wall 56 of the 
extension 43 to form again a sheath of constant length, poor functioning 
of the adjustment device then being capable of being detected by the 
driver who will ascertain significant idle travel of his pedal before 
disengagement. The structure of the extension 43 provided with the collar 
48 cooperating with the extension 44 defines a casing of which the 
tightness is ensured by cooperation of the shoulders 51 and 52 which 
define a baffle to prevent entry of impurities into the system. The 
shoulders 51 and 52 likewise allow assembly of the adjustment device 
properly speaking to be ensured by simple resilient nesting of the 
extension 44 in the extenstion 43 to avoid inopportune opening of the 
adjustment device during installation of the cable on a vehicle. 
The invention is not limited to the embodiment which has just been 
described. Numerous variants are possible, particularly as far as concerns 
the different materials used for the control member 80 and the cable 
wrapping 11 so as to ensure a correct coefficient of friction between 
these two elements. The control member may be replaced by a collet of the 
type similar to the mandrels of tools gripping the cable until a 
predetermined value of force applied to the cable opens this collet. In 
the same way, the locking member 62 may be of a different type but always 
acting by wedging to interlock the two pieces 43 and 44, the wedging force 
always having to be proportional to the forces applied to the cable and by 
reaction to the sheath. 
In another embodiment, not shown, the adjuster spring is disposed at the 
outside of the adjusting device. In this embodiment, the spring 54 is 
disposed concentrically with the sheath portion 41 and outside thereof. 
One end of the spring 54 is supported on a shoulder fixed to the sheath 
portion 41 and the other end is supported on a radially extending shoulder 
formed on the sheath extension 44. This second embodiment allows to 
reducing the overall length of the adjusting device and to mounting a 
longer spring.