Patent Application
20130200003
This disclosure relates generally to filters for filtering foreign debris from fluid flows, and more particularly to filters for filtering circulating automotive fluids such as hydraulic fluid, refrigerant, power steering fluid, and the like.
Filtering fluids as they circulate through automotive systems such as power steering systems, air conditioning systems, hydraulic systems, and the like can significantly increase the lifetimes of such systems and is therefore desirable. In this context, there is a need for a compact in-line or in situ filter that has a single outlet and a first or normal inlet path wherein fluid passes through a filter element before exiting the single outlet and a second or bypass path wherein fluid bypasses the filter element when it becomes clogged before exiting the single outlet. Further, the filter should be easily installable, easily replaceable, and should continue to capture certain types of debris even when operating in its bypass mode. It is to the provision of such a filter that the present invention is primarily directed.
Briefly described, a fluid filter comprises a generally annular base having a central outlet opening and being formed at least partially of a magnetic material. An annular groove in the base receives one end of a cylindrical mesh screen filter element that is bonded to the base and extends therefrom to an inlet end. The filter element is made of a ferrous material as well such that the screen itself becomes magnetized by being in contact with the magnetic base. The inlet end of the filter element carries an at least partially pliable seat having a central opening that may be smaller than the central outlet opening of the base. A conical compression spring is disposed within the filter element with its large end resting on the base and its small end cradling a ball. The force of the compression spring normally biases and urges the ball against the central opening of the seat thereby closing off flow through this central opening. The ball is made of a non-magnetic material so that it is does not become magnetized. The filter is installable in-line or in situ within an inlet port or an outlet port of a component such as a fluid reservoir with its inlet end facing the direction of fluid flow.
The tension or spring constant of the conical spring is selected such that under normal conditions, the ball prevents fluid from flowing through the seat and forces it to flow around the filter, through the mesh openings of the filter element, and exit through the single outlet in a normal mode of operation. If, however, the filter element becomes clogged with debris, the force of the backpressure generated in the fluid by the clog is sufficient to overcome the force of the compression spring and force the ball out of engagement with the seat. This opens up the central opening of the seat, allowing fluid to flow through the seat before exiting from the single outlet of the filter in a bypass mode of the filter. In both modes, the fluid flows past the magnetized filter element and out through the single central outlet opening of the magnetic base so that ferrous debris that may be entrained in the flow continues to be captured by the filter element and the base.
These and other features, aspects, and advantages of the invention will be better understood by the skilled artisan upon review of the detailed description set forth below when taken in conjunction with the accompanying drawing figures, which are briefly described as follows.
a and 2b are perspective views of the filter of
Referring now in more detail to the drawing figures, wherein like reference numerals indicate like parts throughout the several views,
The filter element has an outlet end 24 and an inlet end 26 opposite the outlet end. The outlet end of the filter element is disposed and bonded securely within the annular slot 16 of the base 12 and extends axially away from the base 13 to the inlet end of the filter element. Since the filter element is made of a ferrous material, the mesh screen of the filter element becomes magnetized by being in contact with the annular magnetic base. The outlet end may be bonded with appropriate adhesive, sealant, epoxy, or other mechanisms that insure that the end of the filter element will not separate from the base during use.
An annular seat 31 has a central opening 28 and is bonded to the inlet end of the filter element with its central opening coaxially aligned with the axis of the filter element. The annular seat may be formed of any appropriate material, but preferably is formed of a polymer material that is somewhat compliant, for purposes discussed below. The seat may or may not have a radially projecting rim 27 that extends outwardly from the filter element depending upon the particular application to which the filter is to be applied. A compression spring 32 is disposed inside the filter element 21 and has an outlet end portion 33 and an inlet end portion 34. The compression spring in the illustrated embodiment is conically shaped in that the diameter of the spring at its outlet end 33 is greater than the diameter of the spring at its inlet end 34.
A ball 36 is cradled in the inlet end of the conical spring and the spring constant is selected such that the ball 36 is yieldably biased by the spring 32 against the perimeter of the central opening 28 of the seat. As such, the ball 36 seals the central opening of the seat and defines a normal operating mode of the filter. The ball is made of a non-ferrous or otherwise non-magnetically susceptible material so that it does not become magnetized by being in proximity to the magnetic base or magnetized screen of the filter element. In the normal operating mode, fluid being circulated from the inlet end of the filter toward the outlet end of the filter flows around the seat 31, passes through the filter element 21, and flows out through the single central opening 14 of the base 12 as indicated by arrows 37, 47, and 38. In the process, the fluid is filtered in that the filter element captures particles larger than the mesh size of the filter's mesh screen that are entrained in the fluid. In addition, some ferrous particles entrained in the flow are captured by the magnetized screen through magnetic attraction even if the ferrous particles are smaller than the mesh size of the filter screen. Finally, as the filtered fluid flows through the central opening 14 of the base, the magnet 13 attracts remaining small particles of ferrous material that may have evaded capture by the filter element and still be entrained in the flow. What emerges from the central opening 14 is a filtered fluid with ferrous particles removed or greatly reduced. This filtering and cleaning occurs continuously as the fluid traverses a flow path in line with which the filter 11 is disposed.
After a period of operation, the filter element screen may become clogged with captured particles such that fluid flow through the filter element is choked off to an unacceptable extent. The fluid must nevertheless be allowed to circulate so that the system such as a power steering system supported by the fluid continues to operate. Accordingly, should the filter element become clogged, the resulting back pressure generated in the fluid upstream of the filter rises to an amount sufficient to overcome the force of the spring 32 holding the ball 36 against the seat 31. The ball 36 then moves away from the seat to open a path through the central opening 28 of the seat 31 allowing fluid to flow directly into the filter element without passing through the mesh screen material and exit directly out the central opening of the base 12. In this bypass operating mode of the filter, the now clogged filter element screen is bypassed and the fluid is not filtered by the screen. Nevertheless, damaging ferrous particles entrained in the fluid continue to be removed as the fluid flows past the still magnetized screen and through the central opening 14 of the magnetic base 12. In the process, ferrous particles in the flow are not attracted to the ball 36 since it is made of a non-ferrous material and does not become magnetized. This eliminates contamination of the ball by ferrous particles sticking to its surface. Of course, a clogged condition of the filter should be avoided through regular maintenance and replacement of the filter; but, in the event maintenance is neglected, the bypass mode of the filter element ensures that fluid will continue to circulate and automotive systems supported by this flow will continue to operate.
a is a perspective view of the filter 11 in its normal operating mode wherein the filter element screen is not clogged. The ball 36, which preferably is made of stainless steel, nickel coated metal, PTFE, or some other non-magnetic, non-corrosive, smooth surfaced material, is seen biased against the periphery of the central opening 28 of the seat 31 thereby sealing off the central opening. Under these conditions, fluid is forced to flow around the seat, through the mesh screen material of the filter element, and exit out the single central opening of the base 12, as indicated by arrows 48 and 49 in
The spring constant of the conical spring 32 and thus the force applied by the spring to the ball may be selected to be appropriate for a particular intended application in which the filter 11 is to be used. For example, in lower pressure systems such as a power steering system, the spring constant may be lower so that the bypass mode is initiated by a lower back pressure upstream of a clogged filter. Conversely, in a higher pressure system such as in hydraulic drive systems, the spring constant may be higher so that higher back pressure is required to initiate the bypass mode of the filter.
Finally,
The invention has been described herein in terms of preferred embodiments and methodologies considered by the inventor to represent the best mode of carrying out the invention. It will be understood by the skilled artisan; however, that a wide range of additions, deletions, and modifications, both subtle and gross, may be made to the illustrated and exemplary embodiments without departing from the spirit and scope of the invention set forth in the claims.
