The present invention relates to a breather assembly for a casing. More particularly, the present invention relates to a breather assembly for a piston housing that inhibits air exchange between the atmosphere and the piston housing.
During operation of a pump, or engine, pressure variations within the piston housing or crankcase often arise. These pressure variations can produce inefficiencies or other operational problems within the pump or engine. To accommodate these pressure changes, piston housings, or crankcases, are often fitted with a breather assembly. In most cases the breather assembly includes a filter that removes dirt or other debris from the air being drawn into the piston housing and filters oil, debris, or other contaminants from the air that is being discharged.
Without the filter, dirt or debris could be drawn into the engine or pump and could contaminate the oil and cause damage to the moving components of the pump or engine. Thus, the filter must be maintained and cleaned periodically.
Piston housings are often shipped to users with lubricant in the piston housing. As such, it is generally necessary to plug the breather opening provided in the piston housing to inhibit leakage of lubricant during shipping. The user is then required to remove the plug and install the breather before the pump can be used.
The invention provides a breather assembly that maintains the pressure within a piston housing or crankcase at a pressure that is substantially within a suitable range. The breather inhibits air exchange between the interior of the piston housing or crankcase and the atmosphere. The breather assembly varies the volume of the piston housing or crankcase to maintain the pressure therein.
In one embodiment the invention provides a breather assembly for a crankcase including a chamber having a chamber pressure. The breather assembly includes a base coupled to the crankcase and having an interior. The base defines a first aperture to allow fluid communication between the chamber and the interior, and a second aperture to allow fluid communication between an atmosphere and the interior. A a movable membrane is disposed substantially within the interior to define a crankcase-side of the interior and an atmosphere-side of the interior.
In another embodiment the invention provides a breather assembly for a crankcase including a chamber having a chamber pressure. The breather assembly includes a base coupled to the crankcase and including an interior. The base defines a first aperture to allow fluid communication between the crankcase and the interior. A cover is coupled to the base and includes a second aperture that provides fluid communication between an atmosphere and the interior. A movable membrane is disposed substantially within the interior to define a crankcase-side of the interior and an atmosphere-side of the interior.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
Before proceeding, it should be noted that while the breather assembly 10 has been described attached to a pump 15, it should be understood that the breather assembly 10 could also be attached to an engine crankcase. Furthermore, as one of ordinary skill will realize, the breather assembly 10 described herein could be used in many other applications where it is desirable to maintain a pressure within a substantially enclosed chamber or space with a variable volume or temperature. As such, while the invention is best suited to use with a positive displacement pump or piston engine, the invention should not be limited to these uses.
As illustrated in
The body portion 65 defines most of the interior 70 such that the interior 70 provides the necessary space for the bellows 45. The interior 70 is sized to define a sufficient volume to allow the breather assembly 10 to function properly under the expected operating conditions of the pump 15 (or other component to which the breather assembly 10 is attached). A seal portion 95 is formed at the end of the body portion 65 opposite the attachment portion 60. The seal portion 95 extends around a perimeter 100 that defines a second aperture 105 opposite the first aperture 75. The second aperture 105 is larger than the first aperture 75 with a center located substantially along the central axis 80 of the base 40.
Turning to
The seal portion 95 also includes a cover slot 125 disposed above the bellows groove 110 (i.e., opposite the attachment portion 60). The cover slot 125 extends around the central axis 80 and is sized to receive a cover lip 130. The cover slot 125 defines a shoulder 135 that is substantially planar and is normal to the central axis 80. The shoulder 135 is spaced a predetermined distance from the bottom of the arcuate slot 120 and the surface 121. A tapered surface 140 is disposed immediately above the cover slot 125 (i.e., opposite the attachment portion 60) to facilitate assembly as will be described.
Returning to
The bellows 45 and the interior 70 are sized to provide enough volume to compensate for at least a portion of the expected pressure changes within the piston housing 30. However, the bellows 45 and the interior 70 are generally not so large as to compensate for all of the possible pressure change. For example, one piston housing 30 may experience pressure fluctuations of 5 pounds per square inch (psi) above and below atmospheric pressure during operation. A suitable bellows 45 and interior 70 may be sized to accommodate sixty percent (3 psi) of these pressure changes, thus still allowing some pressure change within the piston housing to facilitate lubrication of the moving parts.
The cover 50, illustrated in
The leg portion 170 extends substantially normal to the plate portion 165 and defines the cover lip 130 and a bellows clamp surface 180. The cover lip 130 extends radially outward and is sized to engage the cover slot 125 to couple the cover 50 to the base 40. The bellows clamp surface 180, best illustrated in
The cap 55 does not seal the apertures 175 but rather allows for the substantially free flow of air into and out of the interior 70. The cap 55 also inhibits clogging or plugging of the apertures 175 in the cover 50.
To manufacture the breather assembly 10, the individual components are first formed. The base 40 can be formed from metal, plastic, ceramic, composite, or other material suitable for use in the operating environment of the breather assembly 10. In preferred constructions, the base 40 is injection molded from a plastic material. Similarly, the cover 50 can be manufactured using any suitable material with injection-molded plastic being preferred. The cap 55 is also generally formed from an injection-molded plastic, with other materials and manufacturing processes also being suitable for use. The bellows 45 is generally formed from a rubber material (e.g., synthetic, or natural) or another resilient, flexible material that is suited to use in the environment of the breather assembly 10.
The bellows 45 is inserted into the interior 70 of the base 40 such that the bellows tongue 115 rests within the bellows groove 110. The cover 50 is positioned above the second aperture 105 of the base 40 such that the cover lip 130 rests on the tapered surface 140 of the base 40. The cover 50 is then pushed downward until the cover lip 130 engages the cover slot 125. The tapered surface 140 serves to guide the cover 50 into its operating position. As the cover 50 is pushed downward, the bellows tongue 115 is compressed and a seal between the pump-side interior 145 and the atmosphere-side interior 150 is established. The cap 55 is then positioned over the cover 50 and is pushed downward until the engagement tabs 205 engage the cap grooves 210.
When positioned for operation, the breather assembly 10 is in fluid communication with the chamber 35 of the piston housing 30 as illustrated in
A pump employing the breather assembly 10 described herein can be shipped with lubricant in the piston housing and the breather assembly 10 installed in an operating position. Because the breather assembly 10 does not allow for the passage of fluid into or out of the piston housing, the pump can be shipped without fear of spilling oil from the breather assembly. In addition, the user does not need to remove a shipping plug and install the breather assembly before use.
Thus, the invention provides, among other things, a breather that maintains the pressure within an enclosed chamber without discharging air or drawing in air by varying the volume of the chamber. Various features and advantages of the invention are set forth in the following claims.
This application claims priority to co-pending U.S. Provisional Application No. 60/679,311 filed on May 10, 2005 and fully incorporated herein by reference.
Number | Date | Country | |
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60679311 | May 2005 | US |