Annular sealing element

Details Annular sealing element Annular sealing element

1998-08-21

2001-03-20

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Circumferential contact seal for other than piston

C277S437000, C277S560000, C060S589000, C092S16500R

Reexamination Certificate

active

06203022

ABSTRACT:

TECHNICAL FIELD
The invention relates to an annular sealing element according to the preamble of claim
1
.
BACKGROUND OF THE INVENTION
Sealing elements having a rigid supporting component and an elastomer part arranged thereon are known in principle. In conjunction with valve elements, there is the problem that the point in time at which a valve opens and closes is not defined precisely since that part of the valve which, by virtue of displacement, causes the valve to be opened and closed is pushed into the elastomer material of the sealing element to a more or less pronounced extent, depending on the fluid pressure acting on it, as a result of which the point in time at which the valve opens and closes varies. This is undesirable in a large number of applications since the valve is intended to have constant, precisely defined opening and closing behavior.
U.S. Pat. No. 3,282,594 discloses a sealing element according to the preamble of claim
1
. A similar sealing element is known from GB 2 256 687 A. The factor which is common to both sealing elements is that the elastomer constituent of the sealing element is injection molded in one piece with the rigid supporting body. This is intended to ensure good sealing between the elastomer material and the material of the rigid supporting body.
OBJECT OF THE INVENTION
The object of the invention is to provide an annular sealing element that [sic] is suitable for interacting with a displaceable body of a valve and, in particular, for ensuring that the opening and closing behavior of the valve is as constant as possible. Furthermore, with a view to using it in mass production, the sealing element is intended to be produced cost-effectively without the sealing function of the sealing element being adversely effected as a result.
Taking as departure point an annular sealing element of the type mentioned in the introduction, this object is achieved according to the invention in that the part made of rigid material and the part made of elastomer material are connected to one another in a releasable manner, the protrusion, which is formed on the part made of rigid material and runs around in the form of a ring, passes just more or less to the full extent in the axial direction through the part made of elastomer material, the part made of elastomer material covers over the end surface of the protrusion to the full extent, and the wall thickness S
i
is approximately equal to the wall thickness S
a
. “More or less to the full extent” here means that the axial, free end of the protrusion, which is formed on the part made of rigid material and runs around in the form of a ring, is located not in the end surface of the elastomer part but rather some way beneath this, i.e. that the elastomer part, which covers over the protrusion, projects beyond the latter. The resulting, thin elastomer layer which rests on the free end of the protrusion ensures that a moveable valve body can always be positioned in a smooth and lightly damped manner on that end side of the sealing element which is directed towards it, and then, following a negligible compression phase, can be supported, virtually without delay, on the protrusion, which is formed on the part made of rigid material. The support which is achieved in this way ensures defined opening of the valve irrespective of the pressure counter to which the valve has to be opened.
The abovedescribed design of the sealing element according to the invention results in a more or less rigid stop for the displaceable valve body without the sealing function of the sealing element being impaired as a result. On the other hand, the fact that the elastomer part covers over the protrusion, which is formed on the rigid part of the sealing element, to the full extent ensures excellent sealing even under critical conditions. Since the largest radial extent of the annular protrusion is only, for instance, at most 70% of the sum of the wall thicknesses S
i
and S
a
and the wall thicknesses S
i
and S
a
are approximately equal, sufficient elastomer material for a good, even radially elastic sealing remains inside and outside the protrusion in the radial direction. The radial extent of the annular protrusion is preferably only at most approximately 50% of the sum of the wall thicknesses S
i
+S
a
.
The protrusion of the part made of rigid material, said protrusion running around in the form of a ring, may, for example, be in the form of a closed ring. It is alternatively possible for the annular protrusion to be formed by a plurality of ring segments between which space is left for connecting webs. According to a further modification, it is possible for at least the free end of the annular protrusion to be formed by a series of stud-like continuations which are spaced apart from one another, preferably uniformly, in the circumferential direction and extend in the axial direction. In the case of such an embodiment, the more or less rigid stop is formed by an annular arrangement of approximately punctiform abutment surfaces.
One configuration provides that, on its free end surface, the elastomer part has a plurality of circumferentially spaced apart, preferably dome-like elevations. Such a configuration achieves even gentler, better damped interengagement of the displaceable valve body with the sealing element since, at the start of interengagement, the valve body only comes into contact with the elastomer part at certain points, but then immediately comes up against a rapidly increasing resistance. If the protrusion, which is provided on the rigid part of the sealing element and runs around in the form of a ring, is formed by a series of stud-like continuations, the preferably dome-like elevations on the free end surface of the elastomer part are preferably arranged over the stud-like continuations, i.e. in axial extension thereof.
Irrespective of the design of the annular protrusion the radial extent of the protrusion preferably decreases towards its free end. In this case, the radial extent of the protrusion can decrease continuously or else in a stepwise manner. Reduction in the radial extent achieves an even better sealing action since, toward the free end of the protrusion, more and more elastomer material is present inside and outside said protrusion in the radial direction, this resulting in better radial compensation of the sealing element in the region of its elastomer part.
It is preferable if, on its end side which is directed away from the part made of elastomer material, that part of the sealing element which is made of rigid material has a hollow-cylindrical continuation. This continuation serves for better guidance of the displaceable piston.
In order to ensure a good sealing action of the sealing element even at relatively high pressure, that part of the sealing element which is made of rigid material is intended to have, in particular, no through-passages in the region of the surfaces by which it butts against the part made of elastomer material. Otherwise, regions of the elastomer part could, under corresponding pressure loading, be pushed into such through-passages, as a result of which the elastomer material would be missing at other sealing locations.
The annular sealing element according to the invention is particularly suitable for use in a main cylinder of a hydraulic vehicle braking system. Such a main cylinder, which is often also referred to as main braking cylinder, has a housing with a bore, which extends along a longitudinal axis and of which one end is closed off by an end wall belonging to the housing of the main cylinder and the other, opposite end is closed off by an annular sealing element. Guided in a sealing manner through the sealing element is an axially displaceable piston which is arranged concentrically with the bore and has a central valve, which permits a fluid connection between a fluid reservoir and a pressure chamber, delimited in the bore by the end wall and piston. When the piston is not actuated, the central valve is kept in the open position by an abutment comp

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