Crankcase breather assembly

A breather assembly for ventilation and pressure control within a crankcase of a positive displacement motor or pump. The breather assembly includes an intake/exhaust port through the crankcase with a valve seat for the port on an exterior surface of the crankcase. A flexible valve membrane is positioned over the port on the valve seat on the exterior of the crankcase for flexing outwardly to exhaust air under positive pressure from the crankcase to atmosphere and to close the port when the crankcase pressure is neutral or negative. An irregular surface is provided on the face of the valve membrane facing to and engaging the valve seat and this surface is provided with a texture which permits air to flow over the valve seat and into the port in a controlled quantity when a negative air pressure condition is attained in the crankcase whereby a predetermined small vacuum level may be maintained in the crankcase. A filter is positioned over the membrane whereby air egressing from and ingressing into the crankcase from atmosphere to the port is filtered.

BACKGROUND OF THE INVENTION

The present invention relates to a breather assembly for ventilation of the crankcase of a motor or pump. More particularly, the present invention relates to a breather assembly for the crankcase of a piston motor or pump to maintain pressure control within the crankcase.

During operation of a positive displacement pump, or engine, pressure variations within the crankcase occur. These pressure variations can produce inefficiencies or other operational problems within the pump or engine. To accommodate these pressure changes, crankcases are commonly fitted with a breather assembly. In most cases the breather assembly includes a filter that removes dirt or other debris from the air being draw into the crankcase and oil or other contaminates from the air that is being discharged.

Ideally, the pressure within the crankcase should be maintained at a low negative pressure level, as for example from between 1/16th to ⅙th psi, which equates to a vacuum level of approximately a negative 0.08 to a negative 0.15 psi.

It is a principal object of the present invention to provide a breather assembly which satisfies these conditions yet is simple in construction and inexpensive to manufacture and maintain.

SUMMARY OF THE INVENTION

The breather assembly of the present invention for ventilation and pressure control within a crankcase of a positive displacement motor or pump is comprised of an intake/exhaust port through the crankcase with a valve seat for the port on an exterior surface of the crankcase. A flexible valve membrane is positioned over this port on the valve seat on the exterior of the crankcase for flexing outwardly to exhaust air under positive pressure from the crankcase to atmosphere and to close the port when the crankcase pressure is neutral or negative. An irregular surface is provided on the face of this valve member which faces to and engages the valve seat. The irregular surface has a texture which permits air to flow over the valve seat and into the port in a controlled quantity when a negative air pressure condition is attained in the crankcase whereby a predetermined small vacuum level is maintained in the crankcase. A filter is positioned over the membrane whereby air egressing from and ingressing into the crankcase from atmosphere through the port is filtered.

The texture of the valve membrane is designed whereby the predetermined vacuum level in the crankcase is preferably maintained, though not definitely required, to be in the approximate range of a negative 0.08 to a negative 0.15 psi.

To provide fast response, the breather assembly may further include a closely spaced pair of these ports through the crankcase with a respective pair of valve seats, and the valve membrane is secured to the crankcase between these ports whereby the valve membrane overlies both of the ports on the respective valve seats.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings, the breather assembly10of the present invention includes two intake/exhaust ports11which penetrate through crankcase12of compressor pump13, which is a positive displacement pump including a reciprocating piston (not shown) of conventional type which reciprocates within cylinder14. While the breather assembly of the present invention is illustrated for use on a pump, nevertheless the present invention is also applicable for a breather assembly to be used on a motor.

The breather assembly10further includes flexible valve membrane15which is positioned over port11on valve seat16on the exterior17of crankcase12. Flexible valve membrane15is constructed of a flexible material, such as plastic or rubber. For example, it may be constructed of Buna N sheet rubber. The valve membrane15flexes outwardly to exhaust air under positive pressure from the crankcase12to atmosphere and to close the ports11when the crankcase pressure is neutral or negative.

FIGS. 4 and 5illustrate the texture or pattern on the bottom side19of valve membrane15thereby providing an irregular surface wherein the texture permits air to flow over the seat16into ports11in a control quantity when the valve is closed and a negative air pressure condition is attained in the crankcase12, whereby a predetermined vacuum level is maintained in the crankcase. Accordingly, the flexible membrane prevents either a strong vacuum or a high crankcase pressure. This bottom surface texture18of bottom surface19is illustrated in an enlarged view inFIGS. 4 and 5. The texture18is provided in the form of a cross stitch pattern.

Flexible valve membrane15is maintained in position overports11on valve seat16by means of the breather housing20which is secured to the crankcase12by machine screw21. In addition, filter22is also retained in housing20over flexible valve membrane15by means of housing20in order to filter air egressing from and ingressing into the crankcase12from atmosphere through the ports11.

The texture18of the bottom surface19of valve membrane15is designed to maintain a predetermined small vacuum level within the crankcase12, for example, of an approximate range of a negative 0.08 to a negative 0.15 psi. Of course this texture may be varied to provide a different range if desired.

Housing20is provided with two air ports23for ingress and egress of air into breather housing20.