Abstract:
A peristaltic pump for dispensing liquid includes a front casing portion, a rear casing snap-fitted together with the front casing portion, a rotor confined between the front casing portion and the rear casing portion, a plurality of rollers mounted in the rotor, and a flexible tube compressed at equally spaced intervals by the plurality of rollers. The pump is resistant to constant torques and vibrations caused by a machine to which it is attached so that the pump does not become loose and fall apart. In a first embodiment for low torque and low vibration operations, the pump is screwless. In a second embodiment for high torque and high vibration operations, two screws secure a synchronous gear motor to the pump.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is a continuation-in-part and claims the filing benefit of U.S. patent application Ser. No. 12/283,930 entitled “Fluid Pump Systems” filed on Sep. 17, 2008, which is a continuation-in-part of U.S. patent application Ser. No. 11/197,381 entitled “Peristaltic Pump” filed on Aug. 5, 2005. The &#39;930 application and the &#39;381 application are both incorporated herein by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The invention relates to peristaltic pumps, in particular to a small pump for dispensing liquid detergent into a dish washing machine. 
       BACKGROUND OF THE INVENTION 
       [0003]    Peristaltic pumps are well known in the prior art and may be defined as pumps which produce pulse-like contractions that propel matter along inside a tube. 
         [0004]    In  FIG. 1 , there is shown a prior art device that was manufactured by Knight Equipment International, Inc., of Costa Mesa, Calif., now Knight, Inc. of Northbrook, Ill. 
         [0005]    Inside a casing  10 , there is a pump  12  in which a triangular rotor  14  rotates to compress a flexible rubber tube  16  against a curved wall  30  at points A and B. These points A and B change along the length of the tube  16  as the rotor  14  rotates around its central axis  18 . Three pins  20  hold three rollers  22  at tips X, Y and Z of the rotor  14  while four screws  24  hold front and back portions of the casing  10  together. The tube  16  has an inlet suction branch  16 C and an outlet delivery branch  16 D. Arrows I and  0  indicate the direction of flow of liquid detergent into and out of the tube  16 . A clear, hard plastic cover  26  with a tab  28  allows a user to view and to have access to the interior of the casing  10  in order to replace or repair any parts of the pump  12  and the rotor  14  which may break. 
         [0006]    One disadvantage of this prior art device is that the constant vibration of an industrial washing machine in which it is used tends over time to cause the screws  24  to work loose from the casing  10 , thus causing the pump  12  inside to fail. Also, the constant vibration causes the pins  20  holding the rollers  22  in the rotor  14  to work loose and push up against the cover  26  until the cover  26  pops off. Once again the pump  12  fails. Thus, it is a problem in the prior art to develop a peristaltic pump which is resistant to constant vibrations that eventually caused earlier devices to become loose and fail. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention may be summarized as a small screwless peristaltic pump which is resistant to constant vibrations caused by a machine to which it is attached so that the pump does not become loose and fall apart. 
         [0008]    A primary object of the invention is to hold the pump together without screws when the pump is used in low torque and low vibration operations. 
         [0009]    A secondary object of the invention is to support a motor onto a rear casing portion of the housing. 
         [0010]    A tertiary object of the invention is to make the pump, its internal rollers and a flexible tube impervious to deleterious ingredients contained in liquid detergent. 
         [0011]    A key advantage of the present invention is that only a predetermined amount of the liquid detergent enters the pump because the synchronous motor, as controlled electronically, meters the detergent to prevent waste in the dish washing machine. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention and its other advantages may be best understood by reference to the accompanying drawings and the subsequent detailed description of the preferred embodiments. 
           [0013]      FIG. 1  is a front elevation view of a known prior art device. 
           [0014]      FIG. 2  is an exploded front perspective view of a first embodiment of the invention. 
           [0015]      FIG. 3  is an exploded front perspective view of a rotor and rollers inside the first embodiment. 
           [0016]      FIG. 4  is a top end view of a front portion of a casing of the first embodiment. 
           [0017]      FIG. 5  is a front inside elevational view of a back portion of the casing of the first embodiment. 
           [0018]      FIG. 6  is an assembled perspective view of the first embodiment. 
           [0019]      FIG. 7  is an exploded rear perspective view of a second embodiment of the invention. 
           [0020]      FIG. 8  is an exploded front perspective view of a rotor and rollers inside the second embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    There are two basic preferred embodiments: a first embodiment for low torque and low vibration operations; and a second embodiment for high torque and high vibration operations. 
         [0022]    In  FIG. 2 , the first embodiment is illustrated. There is a small plastic peristaltic pump  112  contained in a main housing which has a front casing portion  100  and a cover or a rear casing portion  110 . The front casing portion  100  and the rear casing portion  110  are snap-fitted together in a manner described below. A bracket  164  is formed integrally with a side of the front casing portion  100 . This bracket  164  attaches the main housing containing the pump  112  to a dish washing machine (not shown). An electrical plug  174  allows alternating current to be carried through wires  176  from an activator (not shown) when it is switched on by a user who desires to wash a load of dishes. Upon activation, an inlet suction branch  106  brings a predetermined amount of liquid detergent flowing from a reservoir (not shown) in a direction I into a flexible rubber U-shaped tube  116  held in place at an inlet to the pump  112  by a U-shaped inlet channel  104  integrally formed on a top surface of the front casing portion  100 . Inside the pump  112 , there is a plurality of plastic rollers  122  on tips X, Y and Z of a triangular plastic rotor  114  confined between the front casing portion  100  and the rear casing portion  110 . The rollers  122  compress the flexible tube  116  at equally spaced intervals against an interior side of a curved wall  130 . Although three rollers  122  are shown, a manufacturer may choose to use more or less rollers, for example, four or two rollers instead. Nevertheless, three rollers  122  are preferred. The rollers  122  are rolled along the flexible tube  116  as they are rotated by the rotor  114  which is turned by an output shaft  118  extending from a synchronous gear motor  132 . Ears  166  project from opposite sides of the motor  132 . Bosses  142  on an outer periphery of the front casing portion  100  extend through hollow cylindrical sleeves  144  into upper and lower holes in the ears  166  and are ultrasonically heated until they melt to spot weld the motor  132  to the rear casing portion  110 . 
         [0023]    As seen in  FIG. 2 , only a predetermined amount of the liquid detergent enters the pump  112  because the synchronous motor  132  meters the detergent to prevent waste in the dish washing machine. The amount of liquid is predetermined by the signal sent to the motor  132  which then turns its shaft  118  and the rotor  114  mounted thereon a predetermined number of times. 
         [0024]    The motor  132  is rated at 120 volts of alternating current (AC) at 60 hertz (Hz). The rated current is 0.05 amps and the rated speed is 20 revolutions per minute (rpm), plus or minus 10%. 
         [0025]    Pulse-like contractions are produced inside the flexible tube  116 . These contractions propel the liquid detergent in spurts along the inside of the flexible tube  116  held in place at an outlet from the pump  112  by a U-shaped outlet channel  108  until the liquid detergent is dispensed by being squirted out of an outlet delivery branch  160  in a direction  0  into the dish washing machine (not shown). The U-shaped outlet channel  108  is formed integrally on a top surface of the front casing portion  100 . 
         [0026]    Instead of the metal pins used in the prior art device shown in  FIG. 1 , the pump  112  in  FIG. 2  is secured together against the constant vibrations of the dish washing machine by three types of plastic devices for snap-fitting the front casing portion  100  together with the cover or rear casing portion  110 . The first type is a C-shaped groove (not shown) in a circular recess  135  into which a C-shaped tongue  136  is inserted. In an alternate embodiment, at least a pair of straight grooves and a mating pair of straight tongues  136  may be used. The second type of plastic device is a trio of square, open-ended boxes  138  into which a trio of springy, plastic clip pairs  140  are inserted. At least two of these boxes  138  and clip pairs  140  are needed for the front casing portion  100  and the rear casing portion  110  to be snap-fitted together. The third type of plastic device is the pair of bosses  142  on each side of the front casing portion  100 . The bosses  142  are inserted through the pair of hollow cylindrical sleeves  144 . In an alternate embodiment, only one boss  142  and one sleeve  144  may be used. Note that the groove in the recess  135 , the boxes  138  and the bosses  142  are positioned on an outer periphery of the front casing portion  100  while the tongue  136 , the clip pairs  140  and the sleeves  144  are positioned on an outer periphery of an interior wall of the rear casing portion  110 . However, in an alternate embodiment, the groove in the recess  135 , the boxes  138  and the bosses  142  may be positioned on the rear casing portion  110  while the tongue  136 , the clip pairs  140  and the sleeves  144  may be positioned on the front casing portion  100 . An ultrasonic welding rod (not shown) is applied to three areas on an exterior wall of the rear casing portion  110  where the bosses  142  are inserted through the sleeves  144  into the ears  166  in order to heat and melt each boss  142  into its aligned sleeve  144  and ear  166  so that the boss  142 , the sleeve  144  and the ear  166  are fused together. Thus, the pump  112  is not jarred apart by the constant vibrations caused by the dish washing machine. 
         [0027]    In  FIG. 3 , the triangular rotor  114  for low torque and low vibration operations is illustrated. The rotor  114  and its rollers  122  are exploded apart to show how they are connected together. A front face  146  of the rotor  1   14  has formed integrally on its inner side three stepped male inserts  148 . A rear face  150  has formed integrally on its inner side three aligned cylindrical barrels  152  with which the male inserts  148  mate. Each roller  122  has a cylindrical bore  156  through its center along its longitudinal axis  158 . Note that a dowel  154  is mounted inside the rotor  114  and aligns the plurality of mated inserts  148  and barrels  152  around a central D-shaped bore  172 . A single central large cylindrical barrel  170  carries the dowel  154  and surrounds the D-shaped bore  172  through which the shaft  118  of  FIG. 2  with its D-shaped cross section passes in order to rotate the rotor  114 . 
         [0028]    In  FIG. 3 , the rotor  114  is assembled in the following manner. First, the rollers  122  are slipped onto the barrels  152 . Second, the inserts  148  are plugged into the bores  156  of the barrels  152  so that the mated inserts  148  and the barrels  152  carry the rollers  122 . Simultaneously, the dowel  154  is inserted into a bore (not shown) made in the inner side of the front face  146 . An ultrasonic welding rod (not shown) is applied to three areas on an outer side of the rear face  150  where the inserts  148  are plugged into the barrels  152  so that the inserts  148  and the barrels  152  are fused together. However, care must be taken so that too much heat is not applied in order to prevent the rollers  122  on the barrels  152  from being deformed. 
         [0029]    In  FIG. 4 , there is shown a top end view of the front casing portion  100  which functions as part of the main housing for both the first and second embodiments. The U-shaped inlet channel  104  secures an entrance for the flexible tube (not shown) while the U-shaped outlet channel  108  secures an exit for the flexible tube. A top of one box  138  is also seen. In the first embodiment for low torque and low vibration operations, a pair of bosses  142  on each side, of which only the top boss  142  is seen, is insertable through the pair of hollow cylindrical sleeves  144  on each side shown in  FIG. 5  on the interior wall of the rear casing portion  110 . In  FIG. 4 , the bracket  164  attaches the front casing portion  100  to the dish washing machine (not shown). The front casing portion  100  is also secured to the rear casing portion  110  of  FIG. 5  by the trio of clip pairs  140  which are inserted into the boxes  138  of  FIG. 4 , of which only one box  138  is shown in  FIG. 4 . Likewise, in  FIG. 5 , the circular tongue  136  arranged on the interior wall of the rear casing portion  110  is inserted into the groove (not shown in  FIG. 4 , but see the back of the groove in the recess  135  illustrated in  FIG. 2 ). In  FIG. 5 , an opening  162  through the center of the rear casing portion  110  allows the output shaft  118  seen in  FIG. 2  to extend therethrough to engage with and drive the rotor  114  of  FIG. 3 . 
         [0030]    In  FIG. 6 , the pump  112  is shown to be assembled with the motor  132 . The operation of the pump  112  and the motor  132  in this first embodiment may be understood by following the path of movement of the liquid therethrough. Note that the liquid may be other than a detergent. Initially, the motor  132  is turned on when it receives a signal through the wires  176  of the plug  174  to meter the flow of liquid in the direction I into the inlet suction branch  106  which leads to the flexible tube  116  that is held securely by the U-shaped inlet channel  104 . To prevent waste of liquid detergent in the dish washing machine, the signal energizes the motor  132  to turn its shaft  118  seen in  FIG. 2  a predetermined number of times depending upon whether a small, medium or large amount of detergent is needed to clean the load in the dish washing machine. A predetermined amount of the liquid then enters the pump  112  where the rollers  122  of  FIGS. 2 and 3  intermittently compress the flexible tube  116  so that the even flow of liquid is converted into pulses of liquid. These liquid pulses exit the pump  112  through the flexible tube  116  that is held securely by the U-shaped outlet channel  108 . The liquid is then squirted out of the outlet delivery branch  160  in the direction  0  into the dish washing machine (not shown). While the rotor  114  of  FIGS. 2 and 3  is driven by the motor  132 , the pump  112  is seen in  FIG. 6  to be held together by the front casing portion  100  and the rear casing portion  110  which are secured by the two clip pairs  140  in the two boxes  138 . Another clip pair  140  in its box  138  is hidden from view. The pairs of sleeves  144  on the rear casing portion  110  and the pairs of bosses  142  on the front casing portion  100  stuck therein are also hidden from view. In this first embodiment for low torque and low vibration operations, the groove in the recess  135  and its mating tongue  136  of  FIG. 2  are not illustrated in  FIG. 6  because they are hidden inside the front casing portion  100  and the rear casing portion  110 , respectively. The bracket  164  is shown for attaching the entire assembly to the dish washing machine (not shown). 
         [0031]    Note in  FIG. 2  that there are no screws holding the pump  112  together with its housing which includes the front casing portion  100  and the rear casing portion  110 . Also, in this first embodiment for low torque and low vibration operations, there are no screws supporting the motor  132  onto the exterior wall of the rear casing portion  110 . Note further that the pump  112 , the rollers  122  and the tube  116  are all impervious to deleterious ingredients contained in the liquid detergent. 
         [0032]    In  FIG. 7 , the second embodiment for high torque and high vibration operations is illustrated. The pump  112  is contained in the main housing which has the front casing portion  100  and the cover or rear casing portion  110 . The front casing portion  100  and the rear casing portion  110  are snap-fitted together in the manner described below. The bracket  164  is formed integrally with a side of the front casing portion  100  and attaches the main housing containing the pump  112  to the dish washing machine (not shown). The electrical plug  174  allows alternating current to be carried through the wires  176  from the activator (not shown) when it is switched on by a user. Upon activation, the inlet suction branch  106  brings a predetermined amount of liquid detergent flowing from a reservoir (not shown) in the direction I into the flexible tube  116  held in place at the inlet to the pump  112  by the U-shaped channel  104  integrally formed on the top surface of the front casing portion  100 . Inside the pump  112 , there is a plurality of rollers  122  on tips X, Y and Z of the rotor  1   14  confined between the front casing portion  100  and the rear casing portion  110 . The rollers  122  compress the flexible tube  116  at equally spaced intervals against the interior side of the curved wall  130 . The rollers  122  are rolled along the flexible tube  1   16  as they are rotated by the rotor  114  which is turned by the output shaft  1   18  (not shown but see  FIG. 2 ) extending from the motor  132 . Ears  166  of which only one is seen in  FIG. 7 , project from opposite sides of the motor  132 . Screws  168  are inserted into upper holes in the ears  166 , extend through the upper sleeves  144  on the rear casing portion  110  and pass through bores  178  in the front casing portion  100  where the screws  168  are secured at their ends by bolts  182  of which only one is shown. The bosses  142  extend from the front casing portion  100  through the lower sleeves  144  into the lower holes in the ears  166  and are ultrasonically heated until they melt to spot weld the motor  132  to the rear casing portion  110 . Of course, in an alternate embodiment, the screws  168  may be inserted into the lower holes in the ears  166  and the bosses  142  may be extended through the upper holes in the ears  166  to achieve the same result. Note that this combination of screws  168  and bosses  142  is intended for high torque and high vibration operations. 
         [0033]    Pulse-like contractions are produced inside the flexible tube  1   16  as the rotor  114  rotates the rollers  122  along the curved wall  130  to compress the tube  116 . These contractions propel the liquid detergent in spurts along the inside of the tube  116  which is held in place at the outlet from the pump  112  by the U-shaped channel  108  until the liquid detergent is dispensed by being squirted out of the delivery branch  160  in the direction  0  into the dish washing machine (not shown). The channel  108  is formed integrally on a top surface of the front casing portion  100 . 
         [0034]    Instead of the metal pins used in the prior art device shown in  FIG. 1 , the pump  112  in  FIG. 7  is secured together against the constant vibrations of the dish washing machine by three types of plastic devices for snap-fitting the front casing portion  100  together with the cover or rear casing portion  110 . The first type is the C-shaped groove  134  into which the C-shaped tongue  136  is inserted. The tongue  136  is not shown in  FIG. 7 , but see  FIG. 2 . In an alternate embodiment, at least a pair of straight grooves  134  and a mating pair of straight tongues  136  may be used. The second type of plastic device is the trio of square boxes  138  into which a trio of springy clip pairs  140  are inserted. Only one pair of the clips  140  is seen in  FIG. 7 . At least two of these boxes  138  and clip pairs  140  are needed for the front casing portion  100  and the rear casing portion  110  to be snap-fitted together. The third type of plastic device is the pair of bosses  142 , one on each side of the front casing portion  100 . The bosses  142  are inserted through the lower sleeves  144  into the lower ears  166  on the motor  132 . Note that the groove  134 , the boxes  138  and the bosses  142  are positioned on an outer periphery of the front casing portion  100  while the tongue  136  (not shown in  FIG. 7  but see  FIG. 2 ), the clip pairs  140  and the sleeves  144  are positioned on an outer periphery of an interior wall of the rear casing portion  110 . However, in an alternate embodiment, the groove  134 , the boxes  138  and the bosses  142  may be positioned on the rear casing portion while the tongue  136  of  FIG. 2 , the clip pairs  140  and the sleeves  144  may be positioned on the front casing portion  100 . An ultrasonic welding rod (not shown) is applied to three areas on the exterior wall of the rear casing portion  110  where the bosses  142  are inserted through the lower sleeves  144  into the lower holes in the ears  166  in order to heat and melt each boss  142  into its aligned lower sleeve  144  and lower hole of the ear  166  so that the boss  142 , the sleeve  144  and the ear  166  are fused together. Thus, the pump  112  is not jarred apart by the constant vibrations caused by the dish washing machine. 
         [0035]    In this second embodiment shown in  FIG. 7 , there is a skirt  180  at least partially surrounding the sleeves  144  on each side of the rear casing portion  110  to form a recessed area into which the ears  166  may fit so as to prevent wobbling of the motor  132  when it is activated. There are also skirts  180  in the first embodiment for low torque and low vibration operations. However, the skirts  180  are not seen in the first embodiment because  FIG. 2  is a front perspective view which hides the skirts  180 . 
         [0036]    In  FIG. 8 , the triangular rotor  114  for high torque and high vibration operations is illustrated. Three T-shaped supports  184  reinforce the rotor  114  against high torque and high vibrations. In the first embodiment shown in  FIG. 3  for low torque and low vibration operations, there are no T-shaped supports  184  reinforcing the rotor  114 . 
         [0037]    In  FIG. 8 , the rotor  114  and its rollers  122  are exploded apart to show how they are connected together. The front face  146  of the rotor  114  has formed integrally on its inner side three stepped male inserts  148 . The rear face  150  has formed integrally on its inner side three aligned cylindrical barrels  152  with which the male inserts  148  mate. Each roller  122  has a cylindrical bore  156  through its center along its longitudinal axis  158 . The dowel  154  is mounted inside the rotor  114  and aligns the plurality of mated inserts  148  and barrels  152  around the central D-shaped bore  172 . The single central large cylindrical barrel  170  carries the dowel  154  and surrounds the D-shaped bore  172  through which the shaft  118  of  FIG. 2  with its D-shaped cross section passes in order to rotate the rotor  114 . 
         [0038]    In  FIG. 8 , the rotor  114  is assembled in the following manner. First, the rollers  122  are slipped onto the barrels  152 . Second, the inserts  148  are plugged into the bores  156  of the barrels  152  so that the mated inserts  148  and the barrels  152  carry the rollers  122 . Simultaneously, the dowel  154  is inserted into a bore (not shown) made in the inner side of the front face  146 . The ultrasonic welding rod (not shown) is applied to three areas on the outer side of the rear face  150  where the inserts  148  are plugged into the barrels  152  so that the inserts  148  and the barrels  152  are fused together. However, care must be taken so that too much heat is not applied in order to prevent the rollers  122  on the barrels  152  from being deformed. 
         [0039]    Although the present invention has been described by way of two preferred embodiments, other modifications will be realized by those persons skilled in this particular technology after reading this disclosure. However, these modifications may be considered within the scope of the appended claims if such modifications do not depart from the spirit of this invention.