Abstract:
A grease pump including a gerotor pump. The grease pump includes a head, a source of grease, and a discharge conduit. The head has bores defining an inlet passage and an outlet passage, and additional bores in communication with the inlet passage that lead to an air vent valve and a grease fitting. The gerotor pump is disposed in the head and is caused to rotate by an external, separate rotary power tool. By design, the gerotor pump will stop pumping grease when air accumulates in the outlet passage, and air vent valves in fluid communication with the inlet passage and outlet passage may be used to relieve air from the device.

Description:
BACKGROUND  
       [0001]     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.  
         [0002]     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.  
         [0003]     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.  
         [0004]     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.  
         [0005]     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.  
         [0006]     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.  
       SUMMARY  
       [0007]     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.  
         [0008]     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.  
         [0009]     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.  
         [0010]     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. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     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:  
         [0012]      FIG. 1  is a perspective view of a grease pump according to the present invention;  
         [0013]      FIG. 2  is partially exploded reverse perspective view of a portion of the grease pump shown in  FIG. 1 ;  
         [0014]      FIG. 3  is a perspective view of the head of the grease pump shown in  FIG. 1 ;  
         [0015]      FIG. 4  is a perspective view of the head of the grease pump shown in  FIG. 1  with internal bores shown in phantom line.  
         [0016]      FIG. 5  is a right side elevation view of the head of the grease pump shown in  FIG. 1 ;  
         [0017]      FIG. 6  is a left side elevation view of the head of the grease pump shown in  FIG. 1 ;  
         [0018]      FIG. 7  is a top plan view of the head of the grease pump shown in  FIG. 1 ;  
         [0019]      FIG. 8  is a bottom plan view of the head of the grease pump shown in  FIG. 1 ;  
         [0020]      FIG. 9  is a rear elevation view of the head of the grease pump shown in  FIG. 1 ;  
         [0021]      FIG. 10  is a front elevation view of the head of the grease pump shown in  FIG. 1 ;  
         [0022]      FIG. 11  is a section of the head of the grease pump shown in  FIG. 1  taken along line  11 - 11  of  FIGS. 4 and 7 ;  
         [0023]      FIG. 12  is a cross section of the head of the grease pump shown in  FIG. 1  taken along line  12 - 12  of  FIG. 4 ;  
         [0024]      FIG. 13  is a cross section of the head of the grease pump shown in  FIG. 1  taken along line  13 - 13  of  FIG. 4 ;  
         [0025]      FIG. 14  is a section of the head of the grease pump shown in  FIG. 1  taken along line  14 - 14  of  FIGS. 4 and 5 ; and  
         [0026]      FIG. 15  is an elevation view of a shaft that drives the gerotor of the grease pump shown in  FIG. 1 . 
     
    
     DESCRIPTION  
       [0027]     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.  
         [0028]     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.  
         [0029]     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.  
         [0030]     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&#39;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&#39;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.  
         [0031]     Referring now to  FIG. 1 , the grease pump  30  comprises a housing or head  32 , a tubular reservoir or grease cylinder  34 , and a discharge conduit  36 . As will be discussed further below, the head  32  has an inlet passage at its rear and an outlet passage at its front. The head  32  houses a gerotor pump, which is driven by a conventional rotary tool  42 , such as a battery-powered hand drill. A shaft  44  extends from a bore  46  and is accessible externally of the head  32 . A socket  48  mounted to the rotary tool  42  turns the shaft  44  causing the gerotor pump to rotate. As with all bores through the outside of the head  32  in the present invention, a seal is provided as known by one of ordinary skill in the art. A grease fitting  50  is provided for filling the head  32  with grease for priming the pump at the beginning of use, and for bulk-filling the cylinder if so desired by the user.  
         [0032]     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 .  
         [0033]     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.  
         [0034]     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.  
         [0035]      FIG. 2  shows a portion of the grease pump  30  from a view of the opposite side of the head  32  from that of  FIG. 1 . A plate  70 , which may be fastened to the head  32  with screws (not shown) through openings  72  in the plate and openings  74  in the head, is removed to expose the gerotor pump  76  and the top surface  78  of the head  32 . The gerotor pump  76  is disposed in a bore  80  in the head  32  and has in inner rotor  82  and an outer rotor  84 . Both the inner rotor  82  and outer rotor  84  turn. The inner rotor  82  has a central keyed opening  86  for nonrotatably accommodating the shaft  44  for driving the inner rotor  82 . The inner rotor  82  drives the outer rotor  84 . An annular void  88  is provided in the head  32  for accommodating a gasket to provide a seal between the top surface  78  of the head  32  and the plate  70 .  
         [0036]     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  ( FIG. 15 ) of the shaft  44  as the shaft  44  passes through the gerotor pump  76 .  
         [0037]     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 .  
         [0038]     Referring now to  FIGS. 3 and 4 , the rear portion of the head  32  defines the inlet passage  98  having an annular recess  100  provided for a gasket (not shown) to form a seal between the head  32  and the cylinder  34 . Although for clarity threads are not shown, the inlet passage bore  102  is threaded for connecting to the externally threaded end of the cylinder  34 . The inlet passage  98  then narrows into a substantially oval shaped chamber  104 . All of the bores in the head, except those for screws to fasten the plate  70  ( FIG. 2 ), are shown in  FIG. 4  in solid or phantom line. The grease filler fitting bore  106  may be seen on the inside of the head, and the exterior of the air vent valve bore  108  may be seen from the outside of the head  32 ; both open into the inlet passage  98 . A pressure balancing bore  110  extends longitudinally from inlet passage  38  to the opening for the shaft  44 . The pressure balancing bore  110  helps prevent the seal between the shaft bore  46  and the shaft  44  from blowing out by allowing grease to flow from the shaft bore  46  to the inlet passage  98  as pressure increases in the shaft bore  46 .  
         [0039]      FIGS. 5-15  show views of all the bores, with no phantom lines. As shown in  FIGS. 4 and 7 , the gerotor pump bore  80  is in fluid communication with an arcuate inlet opening  120  and an arcuate outlet opening  122 . The sliver shapes of the inlet opening  120  and outlet opening  122  conform to those generally used with gerotor pumps. As shown in  FIGS. 4, 11 , and  14 , the inlet opening  120  is in fluid communication with the inlet passage  98  in the rear end of the head  32 . As previously noted, the shape of the inlet passage  98  is first defined by a circular bore  102  and then an ovular bore  104 . As best seen in  FIGS. 4 and 14 , the inlet passage  38  further narrows to a smaller oval shaped opening  124  having forwardly extending circular bores  126 ,  128  at each end that together form an inlet chamber  130  with the smaller oval bore  124 . The inlet opening  120  to the gerotor pump  76  ( FIG. 2 ) opens into the inlet chamber  130 .  
         [0040]     As best seen in  FIGS. 4, 11 , and  14 , the gerotor pump outlet opening  122  opens into the outlet passage  132 . The outlet passage  40  is defined by a circular outlet passage bore  134 . The outlet passage bore  134  increases in diameter while extending toward and terminating at the front end of the head  32 . Although threads are not shown for clarity, the outlet passage bore  134  is threaded and receives the externally threaded end of the air vent valve  59  ( FIGS. 1 and 2 ).  
         [0041]     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).  
         [0042]     The shaft bore  46  passes though the head  32  as shown in  FIGS. 4, 8 ,  11 , and  14 . The shaft bore  46  is coaxial with the axis of the gerotor pump bore  80 , and is perpendicular to the longitudinal axis of the head  32 . The air vent bore  108  extends laterally through the head  32  to the inlet chamber  130  as best seen in  FIGS. 4, 5 ,  13 , and  14 . The grease filler fitting bore  106  extends laterally through the head  32  to the inlet passage  98  as best seen in  FIGS. 4, 11 ,  12 , and  14 . The pressure balancing bore  110  extends from the inlet passage  98  to the shaft bore  46 , substantially parallel to the axis of the head  32  as best seen in  FIGS. 4 and 11 .  
         [0043]      FIG. 15  shows the shaft  44  for driving the gerotor pump  76 . The upper end  140  of the shaft  44  is adapted to fit a standard socket that could connect to a rotary tool. The portion below the upper end  140  is the shank  142 , which includes a groove  144  for making a seal in the shaft bore  46 . At the lower end of the shaft is a keyed portion  146 , shaped to allow the shaft  44  to fit in the keyed opening  86  in the gerotor pump  76 .  
         [0044]     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.  
         [0045]     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.