Housing With a Pressure-Equalizing Element Which Is Retained Water-Tightly Around the Edges Within a Housing Wall Opening

This invention relates generally to a housing with a pressure-equalizing element for preventing water from entering the housing, while still allowing for gaseous pressure to equalize on either side of the element. More particularly, the invention relates to a mechanically simple and reliable device for providing such selective sealing for a gear housing.

A pressure-equalizing element in the form of a conventional GORE-TEX.RTM. PTFE (polytetrafluoroethylene) membrane is disclosed in DE-U1-87 07 254. In this device, the membrane is inserted from the outside into the counterbored hole of a gear housing for a vehicle window actuator until it reaches a support shoulder. Further movement of the membrane in the opposite direction is prevented by use of a sealing ring placed in between the membrane and a counter-pressing spring lock washer. The spring lock washer locks into the counterbored housing hole when it reaches its final position. The dish-shaped spring lock washer is provided with a curved dish base which arches into the area of the dish.

Although this seal works well, the problem of further developing a pressure equalizing sealing structure that is simpler in construction and provides a more reliable seal against water, is still presented.

The invention solves this problem by providing a retainer and pressure equalizing element for an opening in a housing. The pressure equalizing element is a gas-permeable membrane that is both impermeable to water and permeable to gas. Such a membrane, properly positioned within the housing opening, prevents water from infiltrating into the housing while allowing for the equalization of pressure on both sides of the membrane.

The membrane is held in place by a retaining ring that holds the membrane about its edges. For ease of construction and to facilitate insertion of the membrane into the housing opening, the membrane is preassembled onto the retaining ring. The retaining ring has at least one circumferential elastic sealing lip disposed about its outer portion adapted for insertion into the housing opening. This lip serves both to lock the membrane in place within the opening, and to prevent any liquid from leaking across the periphery of the water impermeable membrane. By combining the membrane, retaining, locking, and sealing functions in one easy to insert pre-assembled element, one reduces the likelihood that the membrane will be damaged during insertion. No further separate sealing element need be inserted.

In order to preassemble the membrane within the retaining ring in a simple manner, the retaining ring is provided with a circumferential contact shoulder to which the outer periphery of the membrane is affixed during preassembly. This attachment of the membrane to the retaining ring is done in a watertight manner. Such well known means of attachment as bonding, welding, injection, caulking, or a combination of these methods, can be employed to affix the membrane to the retaining ring.

The retaining ring may be designed in two pieces instead of one. In this case, both parts of the retaining ring may be fitted together during preassembly, so that the membrane is effectively sandwiched between the contact shoulders of both retaining ring parts in a watertight manner.

In order to protect the membrane from external damage during assembly or operation, the retaining ring or the retaining ring parts are provided on their outer faces with coverings--in particular in the form of struts--which protect the membrane face. The protective coverings, as well as the external sealing lips, are molded in one piece as plastic injection molded parts during the production of the retaining rings.

FIG. 1 is an axial part-sectional view of a window actuating drive mechanism for a vehicle with a pressure equalizing element mounted in a gear housing constructed according to the principles of the invention;

FIG. 2 is a partial sectional view taken along line II--II of FIG. 1, showing a sealing structure constructed according to a first embodiment of the invention;

FIG. 3 is a partial sectional view taken along line II--II of FIG. 1, showing a sealing structure constructed according to a second embodiment of the invention; and

FIG. 4 is a frontal top view of the housing wall opening with the inserted retaining disk according to FIG. 2 or FIG. 3.

FIG. 1 shows a window actuating drive mechanism with a gear housing 1 that accommodates a worm gear and the motor housing 2 of a commutator motor that is screwed onto this gear housing. The gear housing 1 has a wall opening, which is closed by a pressure-equalizing element 6 in the form of a PTFE membrane. This membrane allows an exchange of gas to take place across the membrane, thus equalizing pressure on the inside and outside of the housing, while preventing water from penetrating into the gear housing. To prevent such leakage of water, the membrane must also be retained about its periphery within the housing wall opening in a watertight manner.

FIGS. 2 and 3 show two different embodiments of a retaining ring according to the invention that has been inserted into the wall opening of the gear housing 1, whereby the housing wall opening is connected to the interior of the gear housing by way of a through-hole 11.

FIG. 2 shows a one-piece retaining ring 3 with a support shoulder 33. The PTFE membrane has been bonded onto this support shoulder 33 so as to establish a watertight seal between these elements. The retaining ring 3 with the preassembled PTFE membrane 6 is inserted from the outside into the housing wall opening until reaching the base of the housing wall opening. The retaining ring 3 is fixed in this final position against movement in an axially opposing direction (i.e., to the right in the figures) by means of a circumferential elastic sealing lip 31. This lip is angled with respect to the direction of insertion of the retaining ring 3 in the housing wall opening, and has a greater outer diameter before insertion than the inside width of the housing wall opening. The insertion of such structure to its final position assures both a press fit of the retaining ring 3 in its final position and the watertight mounting of the retaining ring 3 within the housing.

FIG. 3 shows a second embodiment of the retaining ring. This embodiment uses a two-piece retaining ring that consists of a first retaining ring part 4, and a second retaining ring part 5. The retaining ring parts 4 and 5 have axially protruding clamping ridges or corresponding clamping grooves such that both retaining rings 4 and 5 can be fitted together axially. As with the embodiment of FIG. 2, a PTFE membrane 6 is affixed to a contact shoulder 43 or 53 of the retaining ring 4 or 5 in a watertight manner. The membrane is then sandwiched between the retaining ring parts.

It is desirable to provide external mechanical protection of the PTFE membrane during assembly or in later operation. Such protection may be obtained by providing the retaining rings of the first or second embodiments with protective struts 32, 42, or 52. Such struts serve to protect the face of the PTFE membrane. These protective struts, as can be seen in FIG. 4, are arranged in a cross shape.

The retaining rings advantageously consist of plastic injection molded parts with sealing lips that are molded in one piece. The protective struts too, may be molded as one piece with the rest of the retaining ring .