Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1993-05-06
1996-02-27
Ryznic, John E.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
F15B 910
Patent
active
054939488
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a force transmission device for a pneumatic brake-booster, comprising: displacement through the action of an input force, said rod ending in a feeler having an axial end face forming a first upstream support surface; through the action of a pressure difference controlled by the axial displacement of the operating rod, said piston being able to receive a minimum non-zero thrust for a minimum non-zero active displacement of the control rod and having an annular axial surface which surrounds the first upstream support surface and constitutes a second upstream support surface, face being intended to receive forces applied by the first and second upstream support surfaces, and the downstream face being intended to retransmit these forces, a first downstream support surface bearing against the downstream face of the reaction disk, this rod having a second end adapted to apply an output force greater than the input force, and by regulation of the distance between a support surface and the corresponding face of the reaction disk, said regulation means comprising a cup gripping the reaction disk, having a screw thread, and enabling said distance to be modified by screwing-in or screwing-out, which can be effected downstream of the reaction disk.
A device of this kind is for example described in U.S. Pat. No. 4,984,506, the teaching of which permits regulation of the minimum thrust received by the piston, which is known as "jump", by screwing-in or screwing-out, which is relatively easy because it is effected downstream of the reaction disk, that is to say on the thrust rod side.
Despite its advantages and effectiveness, this known technique nevertheless suffers from a residual defect due to the fact that the regulation leads to prestressing of the reaction disk.
Not only may this prestressing constitute a cause of premature wear of the reaction disk, but it also gives rise to an initial thrust on the thrust rod, which has a parasitic effect in the value of the jump itself.
Moreover, a force transmission device of the type described previously, in which the regulation means are designed to allow the first upstream support surface to be moved away from the first end of the thrust rod without relative displacement of the first downstream support surface in relation to the second upstream support surface is described in U.S. Pat. No. 4,271,670.
Although this known device thus solves the problems previously expounded as regards the device of U.S. Pat. No. 4,984,506, it calls upon four different elements whose relative rotation has to be controlled, namely the cup, an external ring screwed onto the cup, the thrust rod, and a screw for varying the length of the thrust rod.
In this context the object of the present invention is to provide a force transmission device for a booster which will permit the simplest possible regulation of the jump and nevertheless not entail undesirable secondary effects.
To this end the invention is essentially characterized in that the cup has a cylindrical rim, a radial extension in which a central aperture is formed and which has an annular internal surface which constitutes the first downstream support surface, and an internally threaded cylindrical sleeve which leads into the central aperture and into which is screwed the first end of the thrust rod, this end constituting a second downstream support surface.
Other features and advantages of the invention will become clear in the description given below by way of indication and without limitation, with reference to the drawings, in which:
FIG. 1 is a view in section of a booster according to a first, unclaimed, embodiment of the invention,
FIG. 2 is a detailed view in section of a device according to the first embodiment of the invention, and
FIG. 3 is a detailed view in section of a device according to a second embodiment of the invention.
The invention relates to an improvement made to pneumatic brake-boosters, of which one example according to the invention is illustrated in FIG. 1.
However, since the gen
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Patent Abstract of Japan, vol. 8, No. 47 Mar. 2, 1984.
Gautier Jean Pierre
Perez Revilla Miguel
Verbo Ulysse
Bendix Europe Services Techniques
McCormick Jr. Leo H.
Palguta Larry J.
Ryznic John E.
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