US3838571A

US3838571A - Operating device with mechanical linkage for transmission of assisting power

Info

Publication number: US3838571A
Application number: US00360720A
Authority: US
Inventors: P Remillieux
Original assignee: DBA SA
Current assignee: DBA SA
Priority date: 1972-06-01
Filing date: 1973-05-16
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01
Also published as: GB1397881A; GB1400677A; IT988886B; JPS4949073A; DE2326847A1; DE2326846A1; FR2188071A1; IT988887B; JPS4949074A; US3838572A; FR2188071B1

Abstract

The invention relates to an operating device for a vehicle braking system comprising a master-cylinder and a set of wheel brakes. The device comprises a hydraulic portion having an annular boost piston and a mechanical portion connected to an energy accumulator device having a coil spring. The mechanical portion includes two pivoting arms, one of which being a lever cooperative with said boost piston by the intermediary of a push rod. The lever rotates around a pivot fixed to the support of the device and is pivotally secured to the other arm which consists of a link provided with a sliding pivot secured to another push rod biased by the energy accumulator device. The sliding pivot comprises a roller moving between two plane surfaces upon rotation of the two arms. The structure of the mechanical portion being such that, upon a checkwise rotation of the link, the energy accumulator device is unlocked when the axis of pivotment joining the link to the lever passes through the plane comprising the fixed and sliding pivots.

Description

United States Patent 1191 Remillieux Oct. 1,1974

[ OPERATING DEVICE WITH MECHANICAL LINKAGE FOR TRANSMISSION OF [73] Assignee: Societe Anonyme DBA, Paris,

France [22] Filed: May 16, 1973 [21] Appl. No.: 360,720

[30] Foreign Application Priority Data Ill/ll Primary Examiner-Edgar W. Geoghegan v Attorney, Agent, or Firm-Leo H. McCormick, .lr.; William N. Antonis 5 7 ABSTRACT The invention relates to an operating device for a vehicle braking system comprising a master-cylinder and a set of wheel brakes. The device comprises a hydraulic portion having an annular boost piston and a mechanical portion connected to an energy accumulator device having a coil spring. The mechanical portion includes two pivoting arms, one of which being a lever cooperative with said boost piston by the intermediary of a push rod. The lever rotates around a pivot fixed to the support of the device and is pivotally secured to the other arm which consists of a link provided with a sliding pivot secured to another push rod biased by the energy accumulator device. The sliding pivot comprises a roller moving between two plane surfaces upon rotation of the two arms. The structure of the mechanical portion being such that, upon a checkwise rotation of the link, the energy accumulator device is unlocked when the axis of pivotment joining the link to the lever passes through the plane comprising the fixed and sliding pivots.

8 Claims, 2 Drawing Figures OPERATING DEVICE WITH MECHANICAL LINKAGE FOR TRANSMISSION OF ASSISTING POWER The invention relates to an operating device with mechanical linkage for transmission of assisting power.

In known operating devices wherein power is transmitted to a receiver member through a mechanical assembly. a control device is required. The control device is almost always directly worked by an operator.

To reduce operator fatigue in the case of repeated working of the operating device. and also to increase the force transmitted to the receiver member. it is common to use an assisting device comprising, for example, a hydraulic pump, a hydraulic or pneumatic accumulator, or a spring accumulator having means of recharging it.

These various solutions give satisfactory results, but their complexity and cost. particularly in cases where the extra force required is small and where the addition of an auxiliary energy source is debatable, make their use questionable.

It is known, also, that due to the inherent resiliency of material some energy is stored in the various members of the mechanical assembly when the receiver is operated, and this energy is restored when the stressing of these members ceases. An object of the device of the invention is to recover some of this resilient energy restored, and to store it in an energy accumulator so that it can be used as boost during the next operation.

To this end, the invention provides: an operating device with mechanical linkage for transmission of assisting power, comprising a driving member adapted to be associated with a receiver member of a mechanical assembly and responsive both to an operator controlled actuating force and to an assisting force produced by an energy accumulator device. said assisting force being transmitted by the intermediary of a mechanical transmission means comprising means for unlocking the energy accumulator device when said actuating force reaches a predetermined value, said driving member responsive to the reaction force produced by the resiliency of the various members of the mechanical assembly and acting on the mechanical transmission means so as to recharge the energy accumulator device on release of operator controlled actuating force until said energy accumulator device returns to a locked position, said energy accumulator device comprising resilient means capable of storing and restoring energy, said mechanical transmission means comprising a linkage assembly mounted on a support and having two arms which are articulated and pivotable about parallel axes and which are separately connected to the resilient means of the energy acumulator device accumulator to the driving member respectively, said mechanical transmission means and said energy accumulator device constituting a system occupying an unstable equilibrium position when the axis of articulation of the two arms is situated in the plane of the pivot axes of the arms and a stable equilibrium position obtained by resilient engagement of one element of the mechanical transmission means with an abutment attached to the support, this stable equilibrium position corresponding to the locked position of the energy accumulator device.

The invention will now be described in reference to the accompanying drawings, in which:

FIG. 1 represents a cross-section through an operating device embodying the invention, applied by way of example to a vehicle braking system in which the operator-controlled actuating force is transmitted by hydraulic pressure medium.

FIG. 2 is a partial section along a line 22 through the device shown in FIG. 1.

The operating device (FIG. 1) is placed between a control pressure source represented by a mastercylinder 12 and a receiver member of a mechanical assembly represented by a brake actuator 14 of a wheel brake. The device 10 comprises a pressure booster 16 connected to the master-cylinder l2 and brake actuator 14 by

respective orifices

18, 20 in its housing 22, and mechanical transmission means having a linkage assembly 24, cooperating with an energy accumulator device 26.

The booster 16 is provided with a rod 28 having a book 30 and guided firstly, by way of a bushing 32 in the housing 22 and, secondly, by way of a sheath or tube 36 in a piston 34 slidable in the bore 38 in the housing 22. A driving member 40 is slidable in a fluidtight manner in the bore 38 and separates two

chambers

42, 44 in the bore. the chambers communicating respectively with the

orifices

18 and 20. The driving member 40 is slidable on the rod 28 with a clearance 46 enabling fluid to flow between the

chambers

42, 44, and it also acts as a valve on account of an annular seal 48 cooperating with a shoulder 50 on the rod 28. The cross-section of the seal 48 may advantageously be trapezoidal to prevent the pressure from detaching the seal from its housing. In the idle position a spring 54, acting by way of a dished or disc member 56 fixed to the rod 28, biases the driving member 40 on to a circlip or snap ring stop 52 fixed to the housing. The spring 54 is supported on the piston 34, which in turn is biased on to a shoulder 58 in the housing by a spring 60 stronger than the spring 54. The rod 28, when idle, is kept abutting on the circlip or snap ring stop 52 by way of the dished or disc member 56 and driving member 40, so that the seal 48 is off the shoulder 50 and the

chambers

42, 44 can communicate freely. A shoulder 62 on the sheath or tube 36 cooperates with the piston 34 so that when moving to the left in the FIG. 1 the piston 34 urges the rod 28 to the left by way of the sheath or tube 36. Fluid-tightness of the

chambers

42, 44 is ensured by

seals

64, 66 and 68 and during braking periods by the seal 48. i

The mechanical transmission means comprise that portion of the rod 28 situated outside the housing 22, and the linkage assembly 24 which cooperates with the rod by way of its hook 30.

The linkage assembly 24 is mounted on a support 70 fixed to the housing 22 by two pins 72. It includes two pivoting arms, a bell-crank lever 74 and a link 86 respectively. The lever 74 comprises a portion 76 which cooperates with the hook 30 by way of a roller 78 rotatable on a pivot 80, and a lever portion 82 cooperating with a pivot 84 which it shares with the link 86. The lever 74 is articulated on a pivot 88 fixed to the support 70. The link 86 bears a roller 90 capable of running along a ramp 92 on the housing 22 and is guided by the flat end of a threaded stud 94. A pivot 96 is common to the link 86, to the roller 90 and to straps 98 cooperating with the energy accumulator device 26 by way of a stem 100. The lever 74 and link 86 may advantageously be in the form of double metal plates as shown in FIG. 2. When idle the link 86 abuts on a bearing surface 102 on the ramp 92. It should be noted however that, without departing from the scope of the invention, the idle position is obtained in another embodiment of the invention by an abutment cooperating with the rod 28, the sheath 36 and the sleeve of piston 34 which is retained by shoulder 58.

The energy accumulator device 26 comprises a spring 104 enclosed in a sleeve 106 and compressed between a fixed retaining cup 108 and a floating retaining cup 110 cooperating with a shoulder 112 on the stem 100. The fixed cup 108 is screwed into a tapping 114 in the sleeve 106, so that the compression of the spring 104 can be adjusted by altering the position of this cup.

The compact structure of the device should be noted thanks to the fact that the axis of bore 38 converges with the line joining the

pivotaxis

96, 88 and defines an acute angle there with.

An adjuster means is mounted on the housing 22, for initially setting the position of the mechanical transmission means of the energy accumulator device within bore 38. The adjuster means comprises a bolt 116 cooperating with a nut 118 fixed to the housing 22. When the bolt is screwed into its nut, it urges the rod 28 to the right in FIG. 1 by way of a ball 120 fixed to the rod 28 by a sleeve 122. The ball 120 is intended both to prevent unscrewing of the sleeve 122 during operation of the bolt 116 and to preserve the fluid-tightness of the chamber 44. A seal 121 is provided between the sheath 36 and sleeve 122 to assure the fluid tightness with respect to the rod 28.

Furthermore, a line 124 directly connecting the master-cylinder 12 and brake actuator 14 contains a nonreturn valve 126 such that the fluid can flow only in the direction from the master-cylinder towards the brake actuator.

The device described above operates as follows.

When at rest the device is in the position shown in FIG. 1. The lever 86 abuts on the bearing surface 102, and the line joining the centers of the

pivots

96, 84 and 88 is bent and therefore imparts a stable position to the resilient system comprising the linkage 24 and the energy accumulator device 26. The compression of the spring 104 is now slightly lower than its maximum. The rod 28 is urged to the right by the springs 54 and 60 and bears by way of the shoulder 62 on the piston 34, which in turn bears on the shoulder 58 in the housing 22. The driving member 40 abuts on the circlip or snap ring stop 52 so that the fluid can flow freely from the orifice 18 to the orifice 20.

When the operator operates the master-cylinder 12 the fluid passes freely from the orifice 18 to the orifice until the pressure reaches a predetermined value. so that the play in the brakes is taken up. Until this predetermined pressure value is reached, the spring 60 keeps the piston 34 abutting on the shoulder 58, while the spring 54 holds the rod 28 on to the driving member 40 (by way of the dished or disc member 56) and the driving member 40 on to the circlip or snap ring stop 52.

When the pressure exceeds the predetermined value, the piston 34 is urged to the left and compresses the spring 60. The piston 34, cooperating with the shoulder 62 on the sheath or tube 36, moves shoulder 50 on rod 28 into contact with the seal 48 to interrupt the connection between the

chambers

42 and 44.

The stroke of the piston 34 is such that the axis of the pivot 84'passes form one side of the line joining the axes of the

pivots

96 and 88 to the other side. through the unstable equilibrium position whereupon the spring 104 can expand and act by way of the linkage assembly 24 and rod 28 on the driving member 40 to further pressurize the fluid in chamber 44. The fluid under pressure in chamber 44 is communicated to the brakes with appreciably greater pressure than can be achieved through the master cylinder 12 alone.

When the operator stops operating the mastercylinder, the pressure in the chamber 42 falls rapidly. The various members of the brake assembly expand due to their inherent resiliency and release the energy accumulated during braking. The brake actuator restores to the chamber 44 a certain quantity of fluid, depending on the resilient deformation of the brakes. The pressure in the chamber 44 acts on the driving member 40 and piston 34. Since the latter has a smaller effective area than the driving member 40, the driving member 40 moves to the right, returning the rod 28 and urging linkage assembly 24 into the initial, idle position.

It will be appreciated that when the energy accumulator device is first set off the force produced by the spring 104 opposes, during a first phase, the pressure acting on the driving member 40. The locking force holds the energy accumulator device in the charged position. This first phase ends when the axis of the pivot 84 arrives in the plane formed by the axes of the

pivots

96 and 88. When the axis of the pivot 84 crosses over to the other side of this plane, the spring 104, in a second phase. expands and adds its force to the pressure produced by the master-cylinder. In the above described embodiment of the invention the bearing surface 102 is situated so that the travel of the pivot 84 is very slight in the first phase, just enough to give a sub stantial locking force.

As a result, the dimensions of the threaded stud 94 and ramp 92 are calculated according to the travel of the roller in the first and in the second phase respectively, since the roller 90 is subject to a radial force tending to urge it on to the stud 94 in the first phase and on to the ramp 92 in the second phase.

Operation of the device as just described may on occasion be faulty, for example if a slight leak occurs in a brake actuator during prolonged application of the brakes. In this case the pressure in the chamber 44 may become too low to reset the energy accumulator de vice, so that the brakes remain on. In the long run the brakes would be released due to the leak, but to wait for this while driving would be undesirable, and also the energy accumulator device would remain uncooked and braking would be substantially altered. A nonreturn valve 126 has therefore been provided which overcomes this problem.

When the pressures upstream and downstream of the non-return valve 126 are equal, transfer may take place, which is not a disadvantage during the period in which the play is taken up. Once the play has been taken up, the pressure on the brake side becomes higher and the valve 126 therefore closes.

If, for example. due .to a slight leak in the brake actuator, the energy accumulator is uncooked, the return transfer of fluid through the booster 16 being impossible and the brakes being clamped on, vigorous and rapid operation of the master-cylinder causes fluid to pass through the valve 126 and the pressure to rise so that the brakes are deformed resiliently as much as possible, The operator then rapidly releases the mastercylinder pedal, so that the brakes are able to reset the energy accumulator device 126. It should be noted that the driving member 40 acts also As a non-return valve. However due to the notable variation of the load of the spring 54 it has appeared preferable to provide the nonreturn valve 126.

In another embodiment of the invention (not shown), the driving member is secured to the rod and is provided with a passage in which a non-return valve such as valve 126 is mounted. The valve member is provided with a projection which cooperates with a circlip or snap ring stop secured to the housing for permitting fluid to pass through said passage when the driving member is in its rest position. Such a device could be a more sensitive pressure failure indicator than a conventional pressure drop indicator. The assistance ratio, defined as the ratio of the assisting force to the force exerted by the operator on the master-cylinder pedal, is selected so that the operator can still check the braking of the vehicle, as the effort required of him increases progressively during braking. This operator braking check is also obtained by selecting for the operating device control system an effort variation rate similar to the resilient brake deformation rate. i.e., generally a linear rate. Pneumatic accumulators or various types of energy accumulators having one or more springs are suitable for this purpose.

The operating device described above may be used to assist the braking of a private motor vehicle without using an external energy source, or to reduce the energy consumed when braking heavy loads, in which case, however, energy from an external source is still required.

In the latter case, it should be noted that in addition to their other advantages these devices enable the dimensions of conventional assisting equipment to be substantially reduced.

Finally although the above described embodiment of the invention is included in a hydraulic vehicle braking system, the scope of the invention is not limited to such installation. By way of example in another embodiment of the invention (not shown) the mechanical transmission means such as above described are mechanically connected to the receiver, the driving member consisting of the hooked rod. This rod, slidably mounted on the support, is engaged by an operator-actuator input member such as a lever pivoting on said support.

I claim:

1. An operating device with mechanical linkage for transmission of assisting power, comprising a driving member being adapted to be associated with a receiver member of a mechanical assembly and responsive both to an operator controlled actuating force and to an assisting force produced by an energy accumulator device, said assisting force being transmitted by the intermediary of a mechanical transmission means comprising means for unlocking the energy accumulator device when said actuating force reaches a predetermined value, said driving member being responsive to the reaction force produced by the resiliency of the various members of the mechanical assembly and acting on the mechanical transmission means so as to recharge the energy accumulator device on release of operator controlled actuating force until said energy accumulator device returns to a locked position, said energy accumulator device comprising resilient means capable of storing and restoring energy, said mechanical transmission means comprising a linkage assembly mounted on a support and having two arms which are articulated and pivotable about parallel axes and which are separately connected to the resilient means of the energy accumulator device and to the driving member respectively, said mechanical transmission means and said energy accumulator device constituting a system occupying an unstable equilibrium position when the axis of articulation of the two arms is situated in the plane of the pivot axes of the arms and a stable equilibrium position obtained by resilient engagement of one element of the mechanical transmission means with an abutment attached to the support, this stable equilibrium position corresponding to the locked position of the energy accumulator device.

2. An operating device as claimed in claim 1, wherein one of the arms is a lever pivoting on a pivot fixed relative to the support, the other arm being a link pivoting on a pivot capable of translation relative to the support, the plane defined by the two pivot axes being fixed relative to the support, a roller coaxial with the movable pivot being provided to guide the translation of the latter pivot, the roller sliding between two parallel plane portions fixed to the support.

3. An operating device as claimed in claim I, wherein the energy accumulator device comprises a spring compressed between two retaining cups inside a sleeve, one cup being fixed to the bottom of the sleeve and the other cooperating with the mechanical transmission means.

4. An operating device as claimed in claim 3, wherein the cup fixed to the sleeve is screwed into a tapping in the sleeve, so permitting regulation of the spring compression.

5. An operating device as claimed in claim 1, wherein it comprises a mechanical device for the initial setting or emergency resetting of the energy accumulator device, acting on the mechanical transmission means.

6. An operating device as claimed in claim 5, wherein the mechanical device for initial setting of the energy accumulator device comprises-a bolt cooperating with a nut fixed to said support and acting on the force transmission means so that, when the bolt is screwed in, the latter means are biased into a position such that the energy accumulator device is charged.

7. An operating device as claimed in claim 1, wherein the driving member is slidable along a direction that converges with the line joining the pivot axes of said arms and defining therebetween an acute angle.

8. An operating device as claimed in claim 1, wherein the means for unlocking the energy accumulator device comprises a piston forming member subjected to an operator controlled pressure force acting against resilient means, said piston forming member sliding parallelly to said driving member and cooperating with the mechanical transmission means so that when the pressure force exceeds a predetermined value the mechanical transmission means are stressed out of their stable equilibrium position, so unlocking the energy accumulator device.

Claims

3. An operating device as claimed in claim 1, wherein the energy accumulator device comprises a spring compressed between two retaining cups inside a sleeve, one cup being fixed to the bottom of the sleeve and the other cooperating with the mechanical transmission means.

6. An operating device as claimed in claim 5, wherein the mechanical device for initial setting of the energy accumulator device comprises a bolt cooperating with a nut fixed to said support and acting on the force transmission means so that, when the bolt is screwed in, the latter means are biased into a position such that the energy accumulator device is charged.