Abstract:
A lubrication unit for delivering lubricant in a system and a method for controlling the unit. The lubrication unit includes a reservoir, a motor, and a pump. The lubrication unit has a flow rate sensor mounted downstream from the pump for measuring a flow rate of lubricant. The lubrication unit includes a control unit operatively connected to the flow rate sensor and the motor for controlling operation of the motor. The control unit includes an input selector for selecting at least one characteristic selected from a group consisting of a volume and a flow rate of lubricant pumped by the pump. The control unit adjusts motor speed to obtain the selected characteristic.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to apparatus and method for supplying lubricant, and more particularly to an apparatus and method of controlling lubrication units using flow rate feedback. 
       BACKGROUND OF THE INVENTION 
       [0002]    This invention has particular application to automatic lubrication systems for supplying lubricant to multiple points of lubrication at predetermined intervals and/or in predetermined amounts. Lincoln Industrial sells such automated systems under the Quicklub®, Centro-Matic®, and Helios® trademarks. The Quicklub® system includes a reservoir for holding a supply of lubricant, a stirrer for stirring the lubricant, and an electric or pneumatic pump for pumping lubricant from the reservoir to one or more progressive metering (divider) valves each of which operates to dispense lubricant to multiple points of lubrication. Reference may be made to U.S. Pat. No. 6,244,387, incorporated herein by reference, for further details regarding an exemplary Quicklub® system. The Centro-Matic® system is similar to a Quicklub® system except that lubricant from the pump is delivered through a single supply line to injectors each operating to dispense a metered amount of lubricant to a single lubrication point. Reference may be made to U.S. Pat. No. 6,705,432, incorporated herein by reference, for further details regarding an exemplary Centro-Matic® system. The Helios® system is a dual line system. 
         [0003]    In some lube systems, a known volume of lubricant is typically dispensed during each pump piston stroke. Knowing the volume of lubricant dispensed during a piston stroke enables ready calculation of an aggregate amount of lubricant dispensed and/or a flow rate of lubricant dispensed during a given interval. Under certain conditions, lubricant does not entirely fill the pump cylinder. If lubricant does not fill a total volume of the pump cylinder during each stroke, the aggregate amount of lubricant dispensed and the flow rate cannot be determined absent additional equipment. One such example is when lubricant is required in extreme cold temperatures (e.g., below 20° F.), the lubricant becomes more viscous and frequently results in an inability to draw sufficient suction to fill the pump cylinder. In lube systems where pump operation is controlled by determining the amount of lubricant dispensed or the lubricant flow rate from pump cylinder volume, not filling the cylinder may result in insufficient lubricant being dispensed to the lubrication points. Thus, there is a need for a lube system in which the pump is controlled directly from flow rate measurements. 
       SUMMARY OF THE INVENTION 
       [0004]    In one aspect of the present invention, a method controls a lubrication unit having a motor driven pump and flow rate sensor. The method comprises the steps of driving the pump at a predetermined speed and measuring flow rate provided by the pump when driven at the predetermined speed. In addition, the method includes adjusting the pump speed until the measured flow rate equals a preselected flow rate by increasing the motor speed when the measured flow rate is below the preselected flow rate and decreasing the motor speed when the measured flow rate is above the preselected flow rate. 
         [0005]    In another aspect, a method controls a lubrication unit having a pump and flow rate sensor. The method comprises the steps of driving the pump at a predetermined speed and measuring flow rate provided by the pump at the predetermined speed. A volume of lubricant delivered by the pump is determined from the measured flow rate and the time period during which the pump is driven. Further, the method includes stopping the pump when the determined volume of lubricant delivered equals a preselected lubricant volume. 
         [0006]    In still another aspect, a lubrication unit for delivering lubricant in a system comprises a reservoir for holding a supply of lubricant, a motor, and an axial piston pump in fluid communication with the reservoir and having a piston driven by the motor and a cylinder of a known cross-sectional area. The piston is moveable by the motor to reciprocate axially within the cylinder through a filling stroke in which lubricant is drawn from the reservoir into the cylinder and a pumping stroke in which lubricant is pushed out of the cylinder for delivery to the system. The unit includes a flow rate sensor mounted downstream from the pump for measuring a flow rate of lubricant pushed out of the cylinder. Further, the unit has a control operatively connected to the flow rate sensor and the motor for controlling operation of the motor. The control includes an input selector for selecting at least one characteristic selected from a group consisting of a volume and a flow rate of lubricant pumped by the pump. The control adjusts motor speed to obtain the selected characteristic. 
         [0007]    The above summary is provided to introduce a selection of concepts in simplified form that are further described below in the Detailed Description. The summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Other objects and features will be in part apparent and in part pointed out hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a diagram of a conventional automated lubrication system having divider valves for directing lubricant to points of lubrication; 
           [0009]      FIG. 2  is a diagram of a conventional automated lubrication system having injectors for directing lubricant to points of lubrication; 
           [0010]      FIG. 3  is a diagram of a automated lubrication system having a CAN bus and divider valves for directing lubricant to points of lubrication; 
           [0011]      FIG. 4  is a schematic cross section of a pump unit of the present invention; 
           [0012]      FIG. 5  is a vertical section taken through an exemplary pump used in the pump unit; and 
           [0013]      FIG. 6  is a horizontal section of the exemplary pump taken in the plane of line  6 - 6  of  FIG. 5 . 
       
    
    
       [0014]    Corresponding parts are indicated by corresponding reference numbers throughout the drawings. 
       DETAILED DESCRIPTION 
       [0015]      FIG. 1  illustrates a conventional Quicklub® system, generally designated  100 , comprising a pump unit  110  that operates to pump lubricant through a lube supply line  114  to a master divider valve, generally designated by  118 , having an inlet  120  and multiple outlets  124  connected via lines  128  to the inlets  130  of additional (slave) divider valves, generally designated by  134 . The divider valves  134  are connected via lines  138  to bearings  144  or other points of lubrication. The number of divider valves  134  used will vary depending on the number of lubrication points to be serviced. 
         [0016]      FIG. 2  illustrates a conventional Centro-Matic® system, generally designated  200 , comprising a pump unit  110  that operates to pump lubricant through a lube supply line  114  to a plurality of injectors  250 , each of which has an inlet communicating with the lube supply line  114  via passages in a manifold  252  and an outlet  158  connected via a line  138  to a bearing  144  or other point of lubrication. 
         [0017]      FIG. 3  illustrates a CAN bus and zone valve system, generally designated  300 , comprising a pump unit  110  that operates to pump lubricant through a lube supply line  114  to a series of manifolds  360 , each of which has an inlet  362  communicating with the lube supply line  114  and a plurality of outlets  364  selectively delivering lubricant via corresponding lines  138  to corresponding bearings  144  or other points of lubrication. Electronically controlled valves  370  connected to the manifolds  360  selectively receive power and control signals from a controller  372  in the pump unit  110  via a power field bus  374  to control lubricant distribution. As shown in  FIG. 3 , the system may independently deliver lubricant to multiple points of lubrication. 
         [0018]    General descriptions of these systems, including components and controls, are provided in U.S. patent application Ser. No. 13/271,814, entitled, “Pump having Venting and Non-venting Piston Return,” which is incorporated by reference. As previously described, under certain conditions, the pumps do not fill completely with lubricant during the suction portion of their stroke. As a result, the controller operates the pump as if more lubricant is delivered by the pump than actually is delivered, potentially under lubricating the lubrication points. 
         [0019]      FIG. 4  schematically illustrates a pump unit or lubrication unit, generally designated by  400 , of the present invention. The pump unit  400  comprises a reservoir (generally designated by  402 ) for holding a supply of lubricant (e.g., grease) and a pump housing (generally designated by  404 ) below the reservoir for housing pump and controller components of the unit. A flow rate sensor  410  is mounted on the housing  496 . Although this sensor  410  is mounted directly on the unit  400  and outside the housing  496 , it is envisioned that the sensor may be housed inside the housing or separated from the unit at a convenient downstream location. In addition to the previously mentioned components, the housing  496  houses a pump, generally designated by  412 , a motor  414  for powering the pump, and a control unit, generally designated by  416 , for controlling operation of the pump unit  400  and other lubrication system components such as those shown in  FIGS. 1-3 . 
         [0020]    A stirrer, generally designated  420 , is provided for stirring lubricant in the reservoir  402 . The stirrer  420  rotates about a vertical axis upon operation of a drive motor  422  mounted in the pump housing  496 . The drive motor  422  is operatively connected to the control unit  416  mounted in the housing  496 . The stirrer  420  rotates to fluidize lubricant in the reservoir  402  and break up any air bubbles that may be in the lubricant to minimize the risk that the pump unit  400  will lose its prime. The stirrer  420  includes a blade  424  that pushes lubricant from the reservoir  402  through an outlet, i.e., through passage  430 , of the reservoir. 
         [0021]    The pushing force exerted on the lubricant by the blade  426  is complemented by a pulling force exerted on the lubricant by the pump  412 . Desirably, the control unit  416  is programmed to operate the stirrer  420  and the pump  412  simultaneously so the pushing and pulling forces act together to move lubricant along the defined passage  430  into the pump. When combined, these forces are usually able to move lubricant from the reservoir  402  to the pump  412 . Further, these forces are maximized because the passage  430  from the reservoir  402  to the pump  412  is closed to atmosphere along its entire length. As a result, the pump unit  400  is able to pump more viscous lubricants at lower temperatures than conventional pump units. Desirably, the inlet passage  430  is a generally straight-line path extending generally vertically. Further, the total length of the inlet passage  430  is preferably relatively short. 
         [0022]    As shown in  FIG. 5 , the pump  412  includes a pump cylinder, generally designated by  440 , and a piston, generally designated by  442 , movable back and forth in the cylinder. As shown in  FIGS. 5 and 6 , the pump cylinder  440  comprises a cylinder body  450  and a valve housing  452  in threaded engagement with the cylinder body. The cylinder body  450  is illustrated as being made in two pieces, but it may comprise any number of parts. The cylinder body  450  has a longitudinal cylinder bore  454 , in which the piston  442  reciprocates. 
         [0023]    The cylinder inlet passage  430  has an upper portion that is substantially cylindrical (having only a small taper to facilitate manufacture) and a lower portion that is oblong (e.g., racetrack-shaped) as viewed in horizontal cross-section (see  FIG. 6 ). The oblong configuration of the inlet passage  430  maximizes inlet passage area entering the cylinder bore  454  and reduces the effective length of the piston power stroke (i.e., the segment of the power stroke after the piston  442  has passed the cylinder inlet passage and blocked communication between the bore  454  and the inlet passage  430 ). As a result, the pump unit  400  has a more compact design, but pumps a larger volume of lubricant (e.g., at least 1.5 cubic centimeters) per pumping stroke of the piston  442 . 
         [0024]    Referring to  FIG. 5 , a first ball check valve  460  is mounted in an opening  462  extending through the valve housing  452  for movement between a closed position, in which the ball engages a first valve seat  464  on the housing to block flow through the opening during a return stroke of the piston  442 , and an open position, in which the ball allows flow through the opening during a pumping stroke of the piston. A first coil compression spring  466  reacting at one end against the ball valve  460  urges the ball toward its closed position (as shown). The opposite end of the spring  466  reacts against a second ball check valve  470  mounted along the opening  462  downstream from the first ball valve  460 . The second ball valve  470  is mounted in the valve housing  452  for movement in the opening  462  between a closed position in which it engages a second valve seat  472  on the housing to block flow through the opening during a return stroke of the piston  442  and an open position in which it allows flow through the opening during a pumping stroke of the piston. A second coil compression spring  474  reacting at one end against the second ball valve  470  urges the ball toward its closed position (as shown). The opposite end of the spring  474  reacts against a plug  476  threaded into the downstream end of the opening  462 . Using two check valves  460 ,  470 , instead of one check valve, reduces potential of lubricant flowing back into the cylinder bore  454  during a return stroke of the piston  442 . 
         [0025]    Referring to  FIG. 6 , the pump cylinder  454  has an outlet comprising an outlet port  480  in the cylinder body  450 . The outlet port  480  communicates with the cylinder bore  454  via an annular gap  482  located between the valve housing  452  and the cylinder body  450  and via a connecting passage (not shown) extending between the annular gap and the opening  462  extending through the valve housing  452  at a location downstream from the second ball check valve seat  472 . The flow rate sensor  410  and a pressure sensor  484  are in fluid communication with the outlet port  480  as shown in  FIG. 4 . Both sensors  410 ,  484  send signals to the control unit  416  corresponding to respective sensed characteristics. 
         [0026]    As illustrated in  FIGS. 5 and 6 , a drive mechanism, generally designated  490 , drives the piston  442  to reciprocate in the cylinder bore  454 . In the illustrated embodiment, the drive mechanism  490  is a linear position drive mechanism comprising the stepper motor  414  in driving engagement with a lead screw  492  that is in threaded engagement with a follower  494  in a follower housing  496 . The follower  494  and piston  442  are joined in a non-rotatable manner. The follower  494  and housing  496  are shaped so the follower does not rotate inside the housing as the lead screw  492  rotates. As a result, when the motor  414  rotates the lead screw  492  in one direction the piston  442  moves through a pumping (power) stroke in the cylinder bore  454 , and when the motor rotates the screw in the opposite direction the piston moves through a return stroke in the cylinder bore. The lengths of the strokes are regulated by controlling operation of the stepper motor  414 . Operation of the stepper motor  414  is controlled by the control unit  416  as will be explained below. 
         [0027]    A calibration mechanism, generally designated  500  in  FIG. 5 , is provided for calibrating operation of the stepper motor  414  so the lengths of piston strokes are precisely controlled. In the illustrated embodiment, this mechanism  500  comprises a magnet  502  mounted on the follower  494 , and at least one magnetic field sensor  504  mounted on the follower housing  496 . By way of example only, the sensor  504  may be a reed switch positioned in proximity to the magnet  434 . 
         [0028]    In some embodiments, one motor may be used to drive both the pump and the stirrer. In other embodiments, the stirrer motor  422  and the stepper motor  414  are separate, distinct, independently energized motors. One advantage of using two motors is evident in colder environments when the lubricant may become stiff, resulting in an increased resistance to rotation of the stirrer. The increased resistance can slow down rotation of the motor driving the stirrer. If the motor driving the stirrer is also driving the pump, the slower rotation reduces the rate of operation of the pump and the rate at which lubricant is pumped. In contrast, when two independently energized motors are used, if the lubricant is stiff and slows down the rotation of the stirrer motor, the pump motor continues to operate independently to pump lubricant at a speed independent of the speed of the stirrer motor. 
         [0029]    Referring to  FIG. 4 , the pump unit  400  includes a control unit  416  for controlling operation of the linear position drive mechanism  490 . The control unit  416  receives signals from the pressure sensor  484  and the calibration mechanism  500  (e.g., magnetic field sensor  504 ). In one embodiment, the control unit  416  includes a programmable microprocessor  510  that processes information and controls operation of the stirrer drive motor  422  and the pump stepper motor  414 , as well as other components in the lubrication system as shown in  FIGS. 1-3 . An operator input panel  520  having a display  522  is provided on the pump housing  404  for use by an operator for communicating instructions from the operator to the pump unit  400  and for communicating information from the control unit to the operator. This information may include the type of lubrication distribution system to be used with the pumping unit, the volume of lubricant to be delivered to each point of lubrication (e.g., bearing), and the frequency of lubrication events. Information can also be uploaded and downloaded to and from the control unit  416  via a USB port  524  on the housing  404  of the pump unit  400 . 
         [0030]    In some embodiments, the control unit  416  includes a power field bus  530  having wires for carrying messages from a communications port  532  to an electronically controlled circuit for controlling the operation of electronically-operated valves (not shown) in the lubrication system, and wires supplying power from an external power supply to an electronically-controlled actuators (not shown) for energizing a respective solenoid in the system. The power wires may be connected to a power supply of the apparatus being lubricated, or the power wires may be connected to a separate power supply. The control unit  416  also includes one or more motor drivers  534  for controlling operation of the motors  414 ,  422  in response to signals from the microprocessor  510 . 
         [0031]    The control unit  416  is programmable by an operator via the input panel  520  or the USB port  524  to select a desired lubricant flow rate or a desired volume of lubricant. Further, the operator may use the input panel  520  to select between a normal operation mode and an alternate (cold weather) mode. In the normal operation mode, the lubricant flow rate and volume are determined from the number of piston strokes, the known volume of lubricant pushed out of the cylinder bore  454  during each piston power stroke, and the time period. The total volume of lubricant delivered is calculated by multiplying the number of strokes by the cylinder volume, and the flow rate is calculated by dividing the total volume by the time period. In the alternate mode, the lubricant flow rate is measured by the flow rate sensor  410 , and the volume is calculated by multiplying the measured flow rate by the period of time. 
         [0032]    In some instances, the control unit  416  initiates operation of the stirrer motor  422  before operating the pump stepper motor  414  to reciprocate the piston  442 . This sequence allows the stirrer  420  to fluidize the lubricant and the piston  442  to prime the pump cylinder  440  with lubricant before actual lubricant pumping begins. Stirring and priming can be especially advantageous if the lubricant is in a viscous condition, as in cold-temperature environments. After a suitable delay (e.g., eight to twelve seconds), the stepper motor  414  is energized by the motor driver  534  to drive the piston  442  through a succession of pumping (power) strokes and return strokes to pump a desired amount of lubricant through the feed lines connected downstream from the flow rate sensor  410 . 
         [0033]    The pump unit  400  is capable of pumping viscous lubricants at relatively low temperatures due at least in part to the strong push/pull forces exerted on the lubricant to force lubricant from the reservoir directly into the cylinder bore  454 . As explained above, rotation of stirrer  420  causes the force-feed mechanism  500  to exert a strong downward force on lubricant in the reservoir  402  tending to push it along the defined flow path  386  to the cylinder bore  454 . Further, in some embodiments, a return stroke of the piston generates a force tending to pull this same lubricant along the passage  430 . The combination of these pushing and pulling forces is effective for moving viscous lubricant into the cylinder bore at lower temperatures. 
         [0034]    As will be appreciated by those skilled in the art, the calibration mechanism  500  provides precise piston  442  stroke length information, enabling lubricant flow rate to be determined during the normal mode of operation when the pump is completely primed. By knowing the stroke length and the cross-sectional area of the cylinder bore  454 , the precise volume of lubricant pumped out of the pump cylinder  440  during each piston power stroke can be calculated (i.e., volume=stroke length×bore area). By knowing the precise volume of lubricant pumped during each stroke and the number of strokes during a period of time, the exact flow rate of lubricant delivered from a completely primed pump can be determined (i.e., flow rate=volume per stroke/stroke per time). However, as previously alluded to, when the lubricant is particularly viscous, such as when the pump is operating in an environment below some predetermined temperature (e.g., 20° F.), lubricant may not complete fill the cylinder bore  454 . As a result of the bore  454  being incompletely filled, the volume of lubricant delivered during each stroke is unknown, and the flow rate of lubricant cannot be calculated. Accordingly, the operator can select the alternate mode, in which the flow rate sensor  410  can be used to determine lubricant flow rate. When the flow rate sensor  410  is used, the number of piston strokes per unit of time may be adjusted to obtain a desired flow rate as measured by the sensor. 
         [0035]    In some embodiments, it is envisioned that the control unit  416  may automatically switch to alternate mode when a signal is received from the sensor indicating the sensor is connected to the unit. In some embodiments, it is envisioned the control unit  416  may automatically rely upon calculations from piston stroke calculation until measurements received from the flow rate sensor  410  exceed the calculated flow rate by some predetermined amount (e.g., a set percentage variance or a particular flow rate difference). In still other embodiments, it is envisioned that the control unit  416  may receive signals from a sensor (e.g., a temperature sensor or a viscosity sensor, not shown) and may automatically switch to the alternate mode when the sensor measures a predetermined value. 
         [0036]    As will be apparent to those skilled in the art, when in the alternate mode and a desired flow rate is entered, the control unit  416  adjusts pump speed until the measured flow rate equals a preselected flow rate. The unit  416  increases the motor speed when the measured flow rate is below the preselected flow rate and decreases the motor speed when the measured flow rate is above the preselected flow rate. 
         [0037]    When in the alternate mode and a desired volume is entered, the control unit  416  determines determining a volume of lubricant delivered by the pump by multiplying the flow rate measured by the sensor  410  by elapsed the time period during which the pump is driven. The control unit  416  signals the motor driver  534  to stop the pump  412  when the calculated volume of lubricant delivered equals the preselected lubricant volume. 
         [0038]    Other features and characteristics may be found in previously filed Patent Cooperation Treaty Application No. PCT/US2011/057592, which is incorporated herein by reference. 
         [0039]    As will be appreciated by those skilled in the art, features of each of the previously described embodiments may be combined with features of other embodiments. These combinations are envisioned as being within the scope of the present invention. 
         [0040]    Embodiments of the invention may be described in the general context of data and/or computer-executable instructions, such as program modules, stored one or more tangible computer storage media and executed by one or more computers or other devices. Generally, program modules include, but are not limited to, routines, programs, objects, components, and data structures that perform particular tasks or implement particular abstract data types. Aspects of the invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices. 
         [0041]    In operation, computers and/or servers may execute the computer-executable instructions such as those illustrated herein to implement aspects of the invention. 
         [0042]    Embodiments of the invention may be implemented with computer-executable instructions. The computer-executable instructions may be organized into one or more computer-executable components or modules on a tangible computer readable storage medium. Aspects of the invention may be implemented with any number and organization of such components or modules. For example, aspects of the invention are not limited to the specific computer-executable instructions or the specific components or modules illustrated in the figures and described herein. Other embodiments of the invention may include different computer-executable instructions or components having more or less functionality than illustrated and described herein. 
         [0043]    The order of execution or performance of the operations in embodiments of the invention illustrated and described herein is not essential, unless otherwise specified. That is, the operations may be performed in any order, unless otherwise specified, and embodiments of the invention may include additional or fewer operations than those disclosed herein. For example, it is contemplated that executing or performing a particular operation before, contemporaneously with, or after another operation is within the scope of aspects of the invention. 
         [0044]    When introducing elements of aspects of the invention or the embodiments thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
         [0045]    In view of the above, it will be seen that several advantages of the invention are achieved and other advantageous results attained. 
         [0046]    Not all of the depicted components illustrated or described may be required. In addition, some implementations and embodiments may include additional components. Variations in the arrangement and type of the components may be made without departing from the spirit or scope of the claims as set forth herein. Additional, different or fewer components may be provided and components may be combined. Alternatively or in addition, a component may be implemented by several components. 
         [0047]    The Abstract and Summary are provided to help the reader quickly ascertain the nature of the technical disclosure. They are submitted with the understanding that they will not be used to interpret or limit the scope or meaning of the claims. 
         [0048]    The above description illustrates the invention by way of example and not by way of limitation. When two items or multiple items are illustrated, it is contemplated that the invention may include two or more items. This description enables one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. Additionally, 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 drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it will be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
         [0049]    Having described aspects of the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of aspects of the invention as defined in the appended claims. As various changes could be made in the above constructions, products, and methods without departing from the scope of aspects of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.