Patent Application
20100278668
1. Field of the Invention
The present invention relates to fluid pumps, and, more particularly, to reciprocating piston type fluid pumps.
2. Description of the Related Art
Fluid pumps are utilized for various purposes. One such use is to pump an epoxy into a crack in concrete, such as in a wall or floor of a building. The epoxy typically is a two-part epoxy with a catalyst and a base. The catalyst is kept in one supply hopper and the base is kept in another supply hopper. Separate pumps are usually used to separately pump the catalyst and base to a mixing unit immediately before application within the crack(s). An example of a pump arrangement used to pump an epoxy is disclosed in U.S. Pat. No. 4,828,148, also invented by the inventor of the present invention.
A problem with known pump arrangements of the type described above is that they tend to be relatively large, complex and expensive.
What is needed in the art is a fluid pump which can accommodate fluids of different viscosities, simple to assemble, clean and operate, and economical.
The present invention provides a fluid pump with a reciprocating piston which is sealed within the pump body using a pressure loaded seal (e.g., chevron seal) and a wiper seal positioned on a side of the chevron seal opposite the pump chamber.
The invention in one form is directed to a fluid pump assembly including a double acting fluid cylinder, a first pump and a second pump. The fluid cylinder includes a housing, a piston reciprocally disposed within the housing, and a piston rod carrying the piston and extending from opposite ends of the housing. The piston rod has a first end and a second end. The first pump includes a pump body, a pressure loaded seal and a wiper seal. The pump body has a pump chamber and a rod port. The piston rod extends through the rod port and the first end is positioned within the pump chamber. The pressure loaded seal is positioned within the rod port around the piston rod and has a pressure loaded end face toward the pump chamber. The wiper seal is positioned within the rod port around the piston rod on a side of the pressure loaded seal opposite from the pump chamber. The second pump likewise includes a pump body, a pressure loaded seal and a wiper seal. The pump body has a pump chamber and a rod port. The piston rod extends through the rod port and the second end is positioned within the pump chamber. The pressure loaded seal is positioned within the rod port around the piston rod and has a pressure loaded end face toward the pump chamber. The wiper seal is positioned within the rod port around the piston rod on a side of the pressure loaded seal opposite from the pump chamber.
The invention in another form is directed to a fluid pump assembly including a double acting fluid cylinder and a pump. The fluid cylinder includes a housing, a piston reciprocally disposed within the housing, and a piston rod carrying the piston and extending from the housing. The piston rod has an end. A pump includes a pump body, a pressure loaded seal and a wiper seal. The pump body has a pump chamber and a rod port. The piston rod extends through the rod port and the end is positioned within the pump chamber. The pressure loaded seal is positioned within the rod port around the piston rod and has a pressure loaded end face toward the pump chamber. The wiper seal is positioned within the rod port around the piston rod on a side of the pressure loaded seal opposite from the pump chamber.
An advantage of the present invention is that during the return stroke of the piston rod, the chevron seal does not effectively operate as a seal and allows the fluid which is wiped by the wiper seal to flow back into the pump chamber.
Another advantage is that the pumps may be directly mounted to the fluid cylinder, thereby alleviating alignment and deflection problems of the piston rod.
Yet another advantage is that the fluid flow into each fluid pump is positively controlled using a selectively actuated piston check, rather than a ball type check valve.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
Fluid cylinder 12 is configured as a double acting pneumatic cylinder in the embodiment shown, but could also be configured as a hydraulic cylinder, depending on the application. Fluid cylinder 12 generally includes a housing 22, piston 24, and piston rod 26. Housing 22 includes a pair of end caps 28 mounted to opposite ends of a cylinder 30. End caps 28 and cylinder 30 are constructed from a metal in the illustrated embodiment, but could also be constructed from a different type of material, such as a composite material. Piston 24 is reciprocally disposed within housing 22. Piston rod 26 carries piston 24 and extends through opposite ends 32 of housing 22 defined by end caps 28. Piston rod 26 has a first end 34 associated with first pump 14 and a second end 36 associated with second pump 16, as will be described in greater detail below.
In a preferred embodiment, each of first pump 14 and second pump 16 are directly mounted to respective end caps 28 to avoid alignment and deflection problems as piston rod 26 reciprocates during operation. First pump 14 and second pump 16 are configured substantially identical to each other in the illustrated embodiment. Accordingly, only first pump 14 will be described in detail herein, with it being understood that second pump 16 is substantially the same.
First pump 14 generally includes a pump body 38, a pressure loaded seal 40, a wiper seal 42, and a piston check 44. Pump body 38 defines a pump chamber 46, a rod port 48, a piston check port 50, an inlet 52, and an outlet 54. Piston rod 26 extends through rod port 48 and first end 34 of piston rod 26 reciprocates within pump chamber 46. Piston rod 26 is sealed within rod port 48 using pressure loaded seal 40 and wiper seal 42, as will be described in greater detail below.
Piston check 44 is mounted within piston check port 50 and functions to selectively fluidly interconnect inlet 52 with pump chamber 46 during operation. Conventional piston pumps typically use a ball check allowing one way flow of the fluid through the inlet to the pump chamber. However, a ball check can be strongly influenced by the viscosity of the fluid flowing through the inlet. A thicker fluid tends to quickly close the ball check while a thinner fluid may allow an appreciable amount of the fluid to flow past the ball prior to being seated. Piston check 44 is controlled using a cylindroid valve or other suitable actuator to positively open and close the flow path between inlet 52 and pump chamber 46. Piston check 44 is sealed within piston check point 50 using suitable seals carried by seal holders 56.
Pressure loaded seal 40 and wiper seal 42 together function to effectively seal pump chamber 46 during a compression stroke of piston rod 26. Pressure loaded seal 40 and wiper seal 42 also function together to effectively wipe any of the fluid from the outside periphery of piston rod 26 during a return stroke of piston rod 26.
As used herein, a “pressure loaded seal” is intended to mean an annular seal with an axial end face which expands to seal between a rod and surrounding body. For example, a pressure loaded seal may have an axial end face which is generally U-shaped or V-shaped in cross section. Fluid under pressure adjacent the end face causes the seal to expand radially, thereby providing an effective seal. One such seal, known in the industry as a “chevron seal”, and shown in the embodiment illustrated in
Referring to
Wiper seal 42 is positioned within rod port 48 around piston rod 26 on a side of pressure loaded seal 40 which is opposite from pump chamber 46 (i.e., closest to fluid cylinder 12). Wiper seal 42 has an annular lip 62 which functions to wipe fluid (e.g., epoxy component) from the outer periphery of piston rod 26 during a return stroke.
With a conventional wiper seal, lip 62 is usually oriented toward the outside of the pump body and simply acts to prevent foreign matter from entering the annular area around piston rod 26 and contaminating the interior of pump 14. However, with the present invention, the orientation of wiper seal 42 is reversed such that lip 62 is at the axial end of wiper seal 42 which is closest to pump chamber 46. This allows the epoxy component or other fluid to be effectively wiped from the outer periphery of piston rod 26.
Pressure loaded seal 40 and wiper seal 42 can be respectively carried within annular recesses which are directly formed in rod port 48. However, for manufacturing purposes, a seal holder 64 forming part of housing 22 can be formed with the internal recesses for holding pressure loaded seal 40 and wiper seal 42.
During a return stroke of piston rod 26, first end 34 is drawn toward fluid cylinder 12 and piston check 44 is open to allow the epoxy component to flow into pump chamber 46. During the return stroke, there is no pressure within pump chamber 46 and, in fact, may be a slight vacuum pressure to assist in pulling the epoxy component into pump chamber 46. Without pressure within pump 46, pressure loaded seal 40 does not radially expand to prevent the epoxy component from flowing therepast toward wiper seal 42. Lip 62 of wiper seal 42 effectively wipes the epoxy component from the outer periphery of piston rod 26 and the epoxy component returns past the relaxed chevron seal 40 to pump chamber 46.
During a compression stroke within first pump 14, first end 34 of piston rod 26 moves away from fluid cylinder 12 and the pressurized epoxy component is pumped from outlet 54. Piston check 44 is closed during the compression stroke to prevent the epoxy component from flowing back out inlet 52.
When fluid pump assembly 10 is configured with both a first pump 14 and a second pump 16 as illustrated, first pump 14 pumps the epoxy component through outlet 54 while second pump 16 draws the epoxy component through inlet 52, and vice versa. This provides a continuous flow of the epoxy component to other downstream devices, such as a mixing device for mixing the two epoxy components together. To this end, each piston check 44 is selectively actuated such that when one piston check is open, the other piston check is closed. During a compression stroke, the piston check is closed to force the epoxy component from the corresponding outlet, and during a return stroke the piston check is open to draw the epoxy component into pump chamber 46.
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
