Irreversible adjustment mechanism

Details Irreversible adjustment mechanism Irreversible adjustment mechanism

2000-04-13

2001-08-14

Marmor, Charles A (Department: 3681)

192 clutches and power-stop control

Transmission and brake

Torque-responsive brake

C192S038000, C192S044000

Reexamination Certificate

active

06273233

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to irreversible adjustment mechanisms, in particular for vehicle seats.
More particularly, the invention concerns an irreversible adjustment mechanism comprising:
a fixed support,
an input part mounted to pivot relative to the support around an axis of rotation, this input part being resiliently assisted towards a neutral position and being moveable along a first direction from the neutral position, in a first angular sector, and along a second direction opposite to the first direction from the neutral position, in a second angular sector,
an intermediate part pivoting mounted around the axis of rotation,
a driving stage connecting the input part to the intermediate part and adapted:
to positively drive the intermediate part with the input part by means of at least one driving part when the input part is moved by moving away from its neutral position,
and to move the driving part with the input part when this input part returns to its neutral position, with friction of the driving part against the intermediate part,
a locking surface which is integral with the support and which has a shape of revolution centered on the axis of rotation,
an output part which is pivoting mounted around the axis of rotation and which is shaped to radially delimit, with the locking surface, at least one pair of wedge-shaped spaces including first and second hollow wedge-shaped spaces, these first and second wedge-shaped spaces diverging respectively in the first and second angular directions,
and a locking stage connecting the intermediate part to the output part, this locking stage comprising:
at least one pair of clamping bodies including first and second rigid clamping bodies which are arranged respectively in the first and second wedge-shaped spaces and which are resiliently assisted in the first and second angular directions respectively in order to be wedged between the output part and the locking surface,
at least first and second rigid stop surfaces integral with the intermediate part, which are directed in the first and second angular directions respectively, the first stop surface being adapted to abut against the first clamping body by unwedging it when the intermediate part turns in the first angular direction, and the second stop surface being adapted to abut against the second clamping body by unwedging it when the intermediate part turns in the second angular direction, the first and second stop surfaces having a certain angular play relative to the first and second clamping bodies,
and at least first and second counter stops which are integral with the output part, the first counter stop surface being adapted to limit the relative movement of the intermediate part relative to the output part in the first angular direction after said first stop surface has sufficiently moved the first clamping body to unwedge it, so as to then cause the intermediate part to drive said output part, and the second counter stop surface being adapted to limit the relative movement of the intermediate part relative to the output part in the second angular direction after said second stop surface has sufficiently moved the second clamping body to unwedge it, so as then to make the intermediate part drive the output part (in particular by direct contact with intermediate part stops or again by abutment of the clamping bodies against the counter stop surfaces when the stop surfaces of the intermediate part move said clamping body).
BACKGROUND OF THE INVENTION
The document EP-A-0 631 901 describes various examples of such irreversible adjustment mechanisms.
Mechanisms of this type enable continuous adjustment of a component driven by the output part by carrying out one or more alternating “pumping” movements:
either in the first angular sector from the neutral position of the input part to move the component driven by the output part in a certain direction,
or in the second angular sector to move the component driven by the output part in the opposite direction.
For example, such mechanisms can be used in particular to adjust the height of the seat part of a vehicle seat.
These known mechanisms taken as a whole give satisfaction, but however have the disadvantage that, when the input part pivots in one of the angular directions from its neutral position, the output part is itself only driven after a certain dead angular travel which is random (this dead angular travel can have for example a maximum value of 9 degrees, and vary randomly between 5 and 9 degrees under load).
This random variation of the dead angular travel is due to the fact that the positioning of the first and second stop surfaces relative to the first and second clamping bodies is itself random, in view of:
the play existing between said stop surfaces and said clamping bodies (this play is made compulsory to guarantee that the clamping bodies can in every case wedge in the first and second wedge-shaped spaces immobilizing in this way the output part relative to the fixed support whilst the input part does not turn),
and the friction between the driving part and the intermediate part at the time of each return movement of the input part to its neutral position.
OBJECTS AND SUMMARY OF THE INVENTION
The particular object of the present invention is to overcome this disadvantage.
To this end, according to the invention, an irreversible adjusting mechanism of the type in question is mainly characterized in that the intermediate part is braked relative to the support, with a braking torque sufficient to hold the intermediate part fixed at the time of each return movement of the input part to its neutral position, after locking the locking stage.
By means of these arrangements, after the input part has undergone a first alternating “pumping” movement in the first angular sector, the first stop surface remains in contact with the first clamping body, so that it is necessary to carry out a second similar alternating movement of the output part in the first angular sector, this second movement results in an almost immediate movement of the output part, as soon as said first stop surface has sufficiently moved the first clamping body to unwedge it (case of operating empty) or as soon as the intermediate part drives the first counter stop (case of operating under load).
At the time of this second activation, the dead travel is therefore reduced to its incompressible minimum, i.e.:
the small dead travel necessary to drive the intermediate part by the input part, for example about 1 degree,
and if the need arises (if the adjustment mechanism is under load, i.e. if it must overcome an opposing torque) the small dead travel (for example about 2 degrees) necessary in order that the intermediate part engages (directly or indirectly) with the first counter stop of the output part.
The dead travel during said second activating of the input part is therefore reduced to 1 degree when empty and to 3 degrees under load, in the example considered.
The operation is similar when the input part undergoes alternate “pumping” movements in the second angular sector.
In preferred versions of the invention, one and/or other of the following arrangements can possibly be resorted to:
the braking torque sustained by the intermediate part is between 0.2 and 1 Nm (Newton meter);
the intermediate part is braked by means of a braking part which is integral with the support and which is radially friction supported against said intermediate part ;
the braking part is a collar which is in contact with the intermediate part in three support zones;
the support includes a casing which contains at least the intermediate part, which intermediate part is braked by means of at least one braking block which is integral with said casing and which is applied axially with friction against said intermediate part, parallel to the axis of rotation;
the intermediate part is braked by at least three braking blocks which are integral with the casing and which are applied axially with friction against said intermediate part, parallel to the axis of

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