Sealing Boot

The present invention relates to sealing boots, and more particularly to a sealing boot of elastomeric material for hermetically closing an annular opening between support and movable members in relatively reciprocable relationship, the sealing boot including a bellows portion which is integrally formed at the opposite ends thereof with a pair of cylindrical sealing portions respectively attached to the support and movable members.

In general, such a sealing boot as described above has been adapted for use with sliding portion in an hydraulically operated disc brake assembly of the pin-slide type, a sliding portion in a piston and wheel cylinder assembly or the like to prevent entry of water and dirt into an annular opening at the sliding portion. For example, in a conventional sealing boot as shown in FIG. 7, a cylindrical sealing portion 2 integrally formed therewith has a cylindrical sealing surface 2a to be tightly attached within an annular groove 1a of a pin-bush 1 and an inner side-surface 2b substantially perpendicular to the inner end 2a.sub.1 of surface 2a. When, upon assembly, the pin-bush 1 is inserted in the direction of the arrow in the figure, the cylindrical sealing portion 2 is inverted in the annular groove 1a due to abutment against a tapered end of pin-bush 1 at its inner side-surface 2b and remains as it is. This requires attachment of the cylindrical sealing portion 2 within the annular groove 1a by hand as is illustrated by an imaginary line in the figure, resulting in time consumption during the assembling process of the sealing boot.

It is, therefore, a primary object of the present invention to provide an improved sealing boot of elastomeric material the cylindrical sealing portion of which is naturally coupled in place within an annular groove of a support or movable member by its self-return force even when inverted during the assembling process.

According to the present invention there is provided a sealing boot of elastomeric material for hermetically closing an annular opening between support and movable members in relatively reciprocable relationship, the sealing boot includes a bellows portion which is integrally formed at the opposite ends thereof with a pair of cylindrical sealing portions respectively attached to the support and movable members, and wherein one of the cylindrical sealing portions is formed with a cylindrical sealing surface to be tightly in contact with the outer circumference of either the support or movable member and is further formed at its inner end with an annular flank which is curved radially away from the cylindrical sealing surface. Preferably, the one of the cylindrical sealing portions is further formed at its outer end with an annular flank which is curved radially away from the cylindrical sealing surface, and a joint portion beween the bellows portion and the cylindrical sealing portion is thickened radially inwardly, in necessity.

Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments thereof when taken together with the accompanying drawings in which:

FIG. 1 is a part sectional view of parts of a hydraulically operated disc brake assembly, including support and movable members provided with a pair of sealing boots in accordance with the present invention;

FIG. 2 is an enlarged cross-sectional view of the sealing boot of FIG. 1;

FIGS. 3 to 6 each illustrate cross-sectional views of modifications of the boot of FIG. 1 in an enlarged scale;

and

FIG. 7 is an enlarged cross-sectional view of a conventional sealing boot.

Referring now to the drawings, FIG. 1 illustrates a sliding portion in an hydraulically operated disc brake assembly of the pin-slide type for vehicles, where a movable member in the form of a pin-support portion 20 of a movable calliper (not shown) is coupled over a support member in the form of a pin-bush 10 and is axially reciprocable on pin-bush 10 through a metal bearing 30 fixed therein, the metal bearing 30 being formed with axial slits 30a. The pin-bush 10 is formed at the opposite end portions thereof with a pair of annular grooves 11, 11 and a pair of tapered annular shoulders 12, 12. The pin-bush 10 has an axial bore 13 through which a bolt (not shown) is inserted to connect the pin-bush 10 to a mounting structure (not shown) of the disc brake assembly. On the other hand, the opposite end portions of pin-support portion 20 are formed therein with a pair of annular grooves 21, 21.

In such an arrangement at the sliding portion as described above, a pair of tubular sealing boots 40, 40 are assembled between pin-bush 10 and pin-support portion 20 respectively. Each tubular sealing boot 40 is made of elastomeric material such as synthetic rubber and includes a bellows portion 41 which is integrally formed at the outer end thereof with a cylindrical sealing portion 42 and at the inner end thereof with a cylindrical sealing portion 43. The cylindrical sealing portion 42 of bellows 41 is attached within the annular groove 11 of pin-bush 10, while the cylindrical sealing portion 43 of bellows 41 is attached within the annular groove 21 of pin-support portion 20 in such a manner that the bellows portion 41 is arranged to prevent entry of water and dirt into an annular opening A between pin-bush 10 and pin-support portion 20. The cylindrical sealing portion 42 is formed at its inner periphery with a cylindrical sealing surface S.sub.1 to be tightly in contact with the annular groove 11, the cylindrical sealing surface S.sub.1 being formed with two parallel annular grooves 44. The cylindrical sealing portion 43 is slidably in contact with the outer circumference S.sub.0 of pin-bush 10 to prevent adhesion of dirt on pin-bush 10. For this purpose, the cylindrical sealing portion 43 is formed at its inner periphery with two parallel annular grooves 46, 46 and axial slots 47. The cylindrical sealing portion 43 is further formed at its outer periphery with a cylindrical sealing surface S.sub.2 to be tightly in contact with the annular groove 21, the cylindrical sealing surface S.sub.2 being formed with two parallel annular grooves 45, 45.

As can be well seen in FIGS. 1 and 2, the tubular sealing boot 40 in this embodiment is characterized in that the cylindrical sealing portion 42 is formed at its inner end with an annular flank S.sub.3 which is curved radially away from the cylindrical sealing surface S.sub.1 and that a joint portion between portions 41 and 42 is thickened radially inwardly toward the interior of boot 40. During the assembling process of each boot 40, the inside cylindrical sealing portion 43 is previously attached within the annular groove 21 of pin-support portion 20, and the pin-bush 10 is inserted into the outside cylindrical sealing portion 42 in the direction of the arrow in FIG. 2. At this assembling stage, even when inverted temporarily as is illustrated in FIG. 2, the outside cylindrical sealing portion 42 will be naturally coupled in place within the annular groove 11 of pin-bush 10 by its self-return force. In such instance, the annular flank S.sub.3 causes rotation of the cylindrical sealing portion 42 toward the bottom of annular groove 11 under a self-return force of joint portion 48. This serves to eliminate time consumption for attachment of the cylindrical sealing portion 42 in place.

In the actual practice of the present invention, as is shown in FIG. 3, the cylindrical sealing portion 42 may be formed at its outer end with an annular flank S.sub.4 which is curved radially away from the cylindrical sealing surface S.sub.1. With such a construction, when inverted in an opposite direction, the outside cylindrical sealing portion 42 will be naturally coupled in place within the annular groove 11. Alternatively, as is shown in FIG. 4, the cylindrical sealing portion 42 may be formed at its opposite ends with a pair of annular flanks S.sub.5, S.sub.6 which are respectively curved radially away from the cylindrical sealing surface S.sub.1, and further may be formed with a pair of tapered annular side-surfaces S.sub.7, S.sub.8 radially extending from annular flanks S.sub.5, S.sub.6 respectively. In the case that the cylindrical sealing portion 42 exerts a sufficient self-return force therein, it is not necessary to thicken the joint portion 48 between bellows 41 and cylindrical sealing portion 42. It is also noted that as is illustrated in FIGS. 5 and 6, the present invention may be applied to other sealing boots wherein the cylindrical sealing portion 42 is connected at its outside or inside end to the bellows portion 41.

Although certain specific embodiments of the invention have been shown and described, it is obvious that many modifications thereof are possible. The invention, therefore, is not intended to be restricted to the exact showing of the drawings and description thereof, but is considered to include reasonable and obvious equivalents.