Patent Application
20060210409
This invention generally relates to a fluid pump and, more particularly, to a portable, externally driven fluid pump for pumping fluids such as lubricant, as in a handheld, externally driven grease pump.
Centralized lubrication systems for machinery have relatively large grease reservoirs that periodically require refilling. Refilling may be achieved, for example, with a bulk pump, a manual grease gun, or a handheld powered grease gun. Bulk pump systems are not always available and generally lack portability, and in some cases may be cost prohibitive to add to the centralized lubrication system. Manual grease guns and handheld powered grease guns, on the other hand, are portable and use a cartridge form of grease which may be preferred by many users.
In general, manual grease guns and powered grease guns have a piston and valve arrangement to pump grease. Such a design provides for relatively high pressure discharge and low flow rates. Conventional manual grease guns and handheld battery-powered grease guns generally comprise a housing including a head portion and a handle portion extending transversely from the head. A cylindrical barrel holding a supply of grease is removably secured to the head and extends from the head alongside the handle. The head portion includes a pump mechanism including a piston that reciprocates in a bore that forms a pump cylinder. The head portion has an inlet port in communication with the bore and the material in the barrel and an outlet port at one end of the bore connected to a flexible hose for delivering grease to a point of lubrication.
In a conventional powered grease gun, an electric motor is accommodated in the housing and a gear transmission mechanism is provided between the motor and the pumping mechanism. The gear transmission mechanism changes the rotating motion of the motor output shaft to the linear reciprocating motion of the piston while reducing the rotational speed and increasing torque.
In order for the grease gun to perform satisfactorily, significant force must be exerted. Unfortunately, manual grease guns may require hundreds of strokes in order to fill the centralized lubrication system reservoir because of the relatively large volume of grease required, which is burdensome on the user. This force requirement has also led to the development of large, heavy power transmission mechanisms in powered grease guns, resulting in awkward and difficult to handle grease guns. The power requirement also reduces the life cycle of a rechargeable battery. Moreover, since the transmission drive system includes numerous components, the manufacturing is relatively complicated and costly. Both manual and powered grease guns can pump air into the centralized lubrication system, which is undesirable.
For the foregoing reasons, there is a need for a powered grease pump which generates a high flow rate for filling centralized grease system reservoirs. There is a need for a pump that eliminates the need for translation of rotary tool movement to a linear reciprocating piston arrangement. There is also a need for a design that prevents pumping of air into centralized grease system reservoirs. Ideally the grease pump is externally driven by a battery-powered rotary tool.
According to the present invention, a grease pump is provided for pumping of grease from a source of grease. The grease pump includes a housing having an inlet passage adapted to be in fluid communication with the source of grease, and an outlet passage. A gerotor pump is disposed in the housing and has an inlet in fluid communication with the inlet passage and an outlet in fluid communication with the outlet passage. Operation of the gerotor pump causes pumping of grease through the outlet passage.
Also according to the present invention, a grease pump for pumping grease is provided. The grease pump includes a housing, a gerotor pump, and a source of grease. The housing has an inlet passage and an outlet passage. The gerotor pump is disposed in the housing and is hydraulically interposed between the inlet passage and the outlet passage. The gerotor pump has an inlet in fluid communication with the inlet passage and an outlet in fluid communication with the outlet passage. The source of grease is secured to the housing, with a seal provided, and is in fluid communication with the inlet passage. In another embodiment a discharge conduit in fluid communication with the outlet passage may be provided. The discharge conduit may include an air vent valve.
Also in accordance with the present invention, a combination of a grease pump, grease cylinder and a rotary power tool are provided. The grease pump includes a housing having an inlet passage and an outlet passage and a gerotor pump. The gerotor pump is disposed in the housing and is hydraulically interposed between the inlet passage and the outlet passage. The gerotor has an inlet in fluid communication with the inlet passage and an outlet in fluid communication with the outlet passage. The grease cylinder is secured to the housing, with a seal, and is in fluid communication with the inlet passage. The rotary power tool is operably connected to the gerotor pump.
Also in accordance with the present invention, a method of pumping grease is provided. The method includes providing a housing having an inlet passage and an outlet passage, and disposing a gerotor pump in the housing. The gerotor pump is hydraulically interposed between the inlet passage and the outlet passage. The gerotor has an inlet in fluid communication with the inlet passage and an outlet in fluid communication with the outlet passage. The source of grease is secured to the housing, with a seal, and is in fluid communication with the inlet passage. The gerotor pump is operated to pump the grease.
For a more complete understanding of the present invention, reference should now be had to the embodiments shown in the accompanying drawings and described below. In the drawings:
Certain terminology is used herein for convenience only and is not to be taken as a limitation on the invention. For example, words such as “front,” “rear,” “upper,” “lower,” “left,” “right,” “horizontal,” “vertical,” “upward,” and “downward” merely describe the configuration shown in the Figures. Indeed, the components may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise.
Referring now to the drawings, wherein like reference numerals designate corresponding or similar elements throughout the several views, an embodiment of the present invention is shown, designated generally at 30. It is understood that, although the present invention will be described in detail herein with reference to the exemplary embodiment of a grease pump 30, the present invention may be applied to, and find utility in, pumping fluids or materials other than grease, and in particular those with high viscosity. The present invention may be used in applications ranging without limitation from, for example, industrial to home appliance uses.
Certain pumps operate based on rotary rather than linear reciprocating motion. Rotary pumps having pumping elements consisting of a driving inner rotor and a driven outer rotor are generally referred to as internal rotary gear pumps. One particular class of internal rotary gear pumps is commonly known as internal gerotor pumps. Gerotor-type pumping elements are characterized by an inner rotor having one less tooth than the outer rotor, with each tooth of one rotor always being in contact with some portion of the other rotor. This interaction between the rotors results in continuous driving contact. When the gears are rotated, a series of expanding and contracting chambers is formed which, when connected with appropriate passages, provides pumping action.
In operation, a rotating shaft drives the inner rotor which in turn drives the outer rotor. The axis of the outer rotor is positioned at a fixed eccentricity from the axis of the inner rotor and shaft. The teeth on the respective gears cooperate to define a plurality of variable volume pumping chambers whereupon during rotation of the gear rotors, a pumping chamber increases in volume to a maximum volume, then decreases in volume. Fluid from the pump's low pressure inlet port is drawn into pumping chambers that are increasing in volume. Upon further rotation of the gerotor pump, when the pumping chambers are decreasing in volume, the fluid is pushed out through the pump's outlet port at a higher pressure. Gerotor pumps may be designed to provide relatively high flow rates at low pressures. One example of a gerotor pump that may be used in the present invention is model 10010-Z0170 manufactured by Nichols Portland, a division of Parker Hannifin Corp., of Portland, Me.
Referring now to
One end of the grease cylinder 34 is removably secured to the head 32 at the rear of the head 32 for holding a supply of grease. The cylinder 34 is aligned substantially coaxial with the longitudinal axis of the head 32. The head 32 has a knurled portion 52 at the rear of the head 32. The inside of the knurled portion 52 is threaded for screwing the head 32 to the cylinder 34. The knurled surface is provided for convenience in gripping and screwing the head 32 onto the cylinder 34. The cylinder 32, as the source of the pumped material, is shown as a conventional grease cylinder, but could be any shape or size appropriate to serve as a supply for pumped material. It is understood that a wide variety of fluids other than grease, motor oil, or other lubricant, can be dispensed according to the present invention, such as, for example, sealants such as caulk, glue, and cake frosting as well as other high viscosity fluids or semi-solid materials when relatively low pressure and high flow rates are desired. There is a spring and follower inside the cylinder 34 that applies pressure to direct the grease to the head 32. The spring and follower ride along a rod 54 that extends outside the cylinder 34. A handle 56 allows manipulation of the follower. An end cap 58 might be used to seal the outer end of the cylinder 34, but the cylinder including the sides and bottom may also be of single piece construction without a separate end cap 58.
The discharge conduit 36 extends from the front end of the head 32 for delivering grease to desired points of lubrication. The discharge conduit 36 includes an air vent valve 59 threaded to the front end of the head 32, a coupler 60 connected to the air vent valve 59, an adapter 62 connected to the coupler 60, and a flexible hose 64 connected to the adapter 62. The air vent valve 59 is closed during normal operation and may be closed when filling the cylinder 34 with grease through the grease fitting 50. This air vent valve 59 is used to eliminate air trapped by the gerotor pump but not transmitted through the discharge conduit 36. The air vent valve 59 is opened to release pressurized air, and closed once the air is discharged.
The materials of the various components may be selected as known by one of ordinary skill in the art. For example, the head 32 may be machined aluminum, steel, or other metal. Likewise, the gerotor pump may be a machined metal. The cylinder 34 may be made of aluminum, steel, other metal, or paperboard. Other metals may be selected based on the application or preference of the designer. Optionally the materials could include plastic.
The plate 70 includes recesses 90, 92 that correspond to the inlet and outlet of the gerotor pump 76, as will be described below. The recesses 90, 92 serve to balance pressure across the width of the gerotor pump 76. A plastic thrust bearing 94 may be provided in a recessed central area of the plate 70 to abut the inner end 146 (
An inlet-side air vent valve 96 is provided. This air valve vent 96 is sealingly connected to the head 32 and is in fluid communication with an inlet passage 98, described below. The inlet-side air vent valve 96 may be opened to allow discharge of unwanted air that might be trapped in the cylinder 34 during cartridge loading, and also to help prime the gerotor pump 76.
Referring now to
As best seen in
The gerotor pump 76 by design will not pump air, so if and when air accumulates in the outlet side of the gerotor pump 76, pumping of grease will stop. It is a preferred design feature of the present invention to prevent the delivery of air to the delivery point of the grease. One such delivery point may be a centralized lubrication system. The present invention accomplishes this by ceasing to pump grease if more than a nominal amount of air accumulates in the gerotor pump 76 housing. The air vent valve 59 on the discharge conduit 36 and in fluid communication with the outlet passage 132 is opened to release the air. Design considerations include building the inlet 120 and outlet 122 of the gerotor 76, and specifying the clearances between the outer rotor 84 and the head 32, based on the viscosity and compressibility of grease, oil, or other thick fluids that are to be pumped. When air accumulates in the inlet passage 98 or the outlet passage 132, the pumping efficiency of the gerotor pump 76 changes dramatically due to the much lower viscosity and much higher compressibility of air. The clearances between parts allow internal bypass of air within the gerotor pump 76 that stall the pumping action. Also, as the rotor turns, it can compress the air without discharging it, thus providing a reservoir for the air before it bleeds across the gerotor pump clearances. In one embodiment, the cumulative clearance between the gerotor components, the head 32, and the plate 70 add up to a range of 0.0005 inches to 0.0013 inches (0.0127 mm to 0.0330 mm).
The shaft bore 46 passes though the head 32 as shown in
In use, the user connects the discharge conduit 36 to a centralized lubrication system. The user grips the cylinder 34 or the head 32 in one hand, and a powered rotary tool such as a battery powered hand drill 42 in the other. The user fits the socket 48 of the hand drill 42 to the shaft 44, and turns on the hand drill 42. The shaft 44 turns the gerotor pump 76 for pumping grease from the cylinder 34 to the centralized lubrication system; there are no moving parts other than the shaft 44 and the gerotor pump 76. Alternatively, the grease pump 30 could be laid on a flat surface or otherwise mounted to a fixture for use.
Although the present invention has been shown and described in considerable detail with respect to only a few exemplary embodiments thereof, it should be understood by those skilled in the art that we do not intend to limit the invention to the embodiments since various modifications, omissions and additions may be made to the disclosed embodiments without materially departing from the novel teachings and advantages of the invention, particularly in light of the foregoing teachings. Such modifications may include, but not be limited to, integrating the outlet air vent valve into the housing such that a separate part is not required, and combining the inlet filler fitting with the inlet air vent valve so that only one part is required. Accordingly, we intend to cover all such modifications, omission, additions and equivalents as may be included within the spirit and scope of the invention as defined by the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures.
