Abstract:
An oral irrigator has a pump, a discharge nozzle and a pressure control. The pump has a generally constant operating speed and feeds the discharge nozzle. The pressure control is adapted to modify a discharge pressure at the nozzle without a significant change in pump speed. The pressure control modifies a level of fluid flow restriction between the pump and the nozzle. The modification of the level of fluid flow restriction is accomplished by modifying aspects of a fluid flow path extending through the pressure control. The aspects modified include the diameter, length and/or number of direction changes of the fluid flow path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation patent application of U.S. patent application Ser. No. 11/483,376, filed Jul. 7, 2006 and entitled “Oral Irrigator,” the disclosure of which is hereby incorporated herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to health and personal hygiene equipment and methods of controlling such equipment. More particularly, the present invention relates to oral irrigators and methods of controlling such equipment. 
       BACKGROUND 
       [0003]    Oral irrigators for discharging a high-pressure fluid stream into a user&#39;s oral cavity are well known in the art and are useful for promoting oral hygiene and health. For example, a particularly effective oral irrigator is disclosed in U.S. patent application Ser. No. 10/749,675 which is hereby incorporated by reference in its entirety into the present application. 
         [0004]    It is advantageous for an oral irrigator to discharge a fluid stream at a select pulse rate that is generally constant. For example, a particularly useful constant pulse rate is 1200 cycles per minute. 
         [0005]    Depending on the user and the part of the oral cavity being impacted by the fluid stream, a high-pressure fluid stream or a low-pressure fluid stream may be preferred. Thus, it is preferable to offer oral irrigators with an ability to vary the pressure of the fluid stream discharging from the oral irrigator. Prior art oral irrigators have attempted to meet this need by adjusting pumping speed. Unfortunately, this approach results in an inability of the oral irrigator to provide a generally constant pulse rate. 
       SUMMARY 
       [0006]    A handheld oral irrigator general includes a fluid reservoir, a pump, a pressure control assembly, and a nozzle. In an implementation disclosed herein, the pump may include a suction side and a discharge side. The suction side is in fluid communication with the fluid reservoir. The pressure control assembly may include a casing and a member displaceable within the casing. The casing has an inlet and an outlet. The inlet is in fluid communication with the discharge side of the pump, and the nozzle is in fluid communication with the outlet of the casing. In one embodiment, the member is longitudinally displaceable within the casing. 
         [0007]    In some embodiments, the oral irrigator may also include an actuator for displacing the member within the casing. The member may have a portion that extends through the casing to couple to the actuator. In one embodiment, the portion of the member is an arm that extends through a longitudinally extending slot in the casing. A fluid flow path may extend from the inlet to the outlet and may be modifiable between a first route that extends along at least a portion of the member and a second route that does not. 
         [0008]    In another implementation, an oral irrigator may have a pump, a discharge nozzle and a pressure control. The pump may have a generally constant operating speed and feeds the discharge nozzle. The pressure control may be adapted to modify a discharge pressure at the nozzle without a significant change in pump speed. The pressure control modifies a level of fluid flow restriction between the pump and the nozzle. The pressure control may modify the diameter of a fluid flow path extending through the pressure control. The pressure control may also modify the length of a fluid flow path extending through the pressure control. The pressure control may also modify the number of direction changes of a fluid flow path extending through the pressure control. 
         [0009]    In a further implementation, an oral irrigator has a pump and a pressure adjustment assembly. The pump supplies a nozzle. The pressure adjustment assembly may be configured to provide a first fluid flow path associated with a high nozzle discharge pressure and a second fluid flow path associated with a low nozzle discharge pressure. The pressure adjustment assembly may be located between the pump and nozzle. 
         [0010]    In one embodiment, the first fluid flow path offers a more direct route to the nozzle than the second fluid flow path. In another embodiment, the first fluid flow path has a length that is shorter than a length of the second fluid flow path. In a further embodiment, the second fluid flow path has a diameter that is smaller than a diameter of the first fluid flow path. 
         [0011]    The pressure adjustment assembly may have a casing and a member displaceable within the casing. The casing defines a first orifice and the member a second orifice. The second fluid flow path extends through both orifices. The first fluid flow path extends only through the orifice of the casing. 
         [0012]    In one embodiment, the pressure adjustment assembly may have a casing and a member displaceable within the casing. A portion of the second fluid flow path extends circumferentially about at least a portion of the member. The member may be generally cylindrical and define a groove extending about at least a portion of the circumferential outer surface of the member. The casing may define an inlet orifice that aligns with the groove to form a portion of the second fluid flow path. The member may also have a longitudinally extending center lumen in fluid contact with the groove via an orifice extending through a wall of the member. 
         [0013]    In another implementation an oral irrigator may have a pump and a pressure adjustment assembly. The pump supplies a nozzle. The pressure adjustment assembly may have a first fluid flow friction setting associated with a high nozzle discharge pressure and a second fluid flow friction setting associated with a low nozzle discharge pressure. 
         [0014]    In a further implementation, a method of controlling a nozzle discharge pressure of an oral irrigator having a pump that feeds a nozzle is described. The method includes modifying a fluid flow friction value of a fluid flow path between the pump and nozzle by modifying the fluid flow path. The fluid flow path may be modified by one or more of the following actions: changing its length, changing its diameter or by changing its number of direction deviations. 
         [0015]    While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a top isometric view of the handheld oral irrigator. 
           [0017]      FIG. 2  is a top isometric view of the handheld oral irrigator. 
           [0018]      FIG. 3  is a control side elevation of the handheld oral irrigator. 
           [0019]      FIG. 4  is a reservoir side elevation of the handheld oral irrigator. 
           [0020]      FIG. 5  is a right side elevation of the handheld oral irrigator as if viewed from the direction of arrow A in  FIG. 3 . 
           [0021]      FIG. 6  is a left side elevation of the handheld oral irrigator as if viewed from the direction of arrow B in  FIG. 3 . 
           [0022]      FIG. 7  is a top plan view of the handheld oral irrigator. 
           [0023]      FIG. 8  is a bottom plan view of the handheld oral irrigator. 
           [0024]      FIG. 9  is a section elevation of the handheld oral irrigator as taken along section line  9 - 9  in  FIG. 4 . 
           [0025]      FIG. 10  is an isometric view of a motor side of the handheld oral irrigator with the outer housing of the handle portion removed to show the internal elements of the irrigator. 
           [0026]      FIG. 11  is the same type of view as illustrated in  FIG. 10 , except of a pump side of the handheld oral irrigator. 
           [0027]      FIG. 12  is a longitudinal section through the pump. 
           [0028]      FIG. 13  is an isometric of view of the motor/pump/transmission arrangement with the rest of the irrigator  10  hidden for clarity purposes. 
           [0029]      FIG. 14  is an isometric view of the pressure control valve assembly  85  with the majority of the rest of the handheld oral irrigator  10  hidden for clarity purposes. 
           [0030]      FIG. 15  is a side elevation of the same elements depicted in  FIG. 14 , as viewed from the same direction as  FIG. 6 . 
           [0031]      FIG. 16  is a side elevation of the same elements depicted in  FIG. 14 , as viewed from the same direction as  FIG. 4 . 
           [0032]      FIG. 17A  is a longitudinal cross section of the pressure control valve assembly as taken along section line  17 - 17  in  FIG. 15  and wherein a spool is in a rearward location (i.e., a high discharge pressure position) within the valve cylinder. 
           [0033]      FIG. 17B  is the same view depicted in  FIG. 17A , except the spool is in a forward location (i.e., a low discharge pressure position) within the valve cylinder. 
           [0034]      FIG. 18A  is a longitudinal cross section of the pressure control valve assembly as taken along section line  18 - 18  in  FIG. 16  and wherein the spool is in a rearward location (i.e., a high discharge pressure position) within the valve cylinder. 
           [0035]      FIG. 18B  is the same view depicted in  FIG. 18A , except the spool is in a forward location (i.e., a low discharge pressure position) within the valve cylinder. 
           [0036]      FIG. 19  is a side view of the pressure control valve assembly as shown in  FIG. 15 , except the discharge tube, nozzle and control button are hidden for clarity purposes. 
           [0037]      FIG. 20  is an isometric view of the valve assembly wherein the discharge tube, nozzle and control button are hidden for clarity purposes. 
           [0038]      FIG. 21  is an isometric view of the spool and yoke. 
           [0039]      FIG. 22  is an isometric latitudinal cross section taken along section line  22 - 22  in  FIG. 15 . 
           [0040]      FIG. 23  is a similar view as illustrated in  FIG. 10 , except various components are shown in an alternate configuration. 
           [0041]      FIG. 24  is a similar view as illustrated in  FIG. 11 , except various components are shown in an alternate configuration. 
           [0042]      FIG. 25  is a bottom perspective view of a reservoir of the handheld oral irrigator. 
           [0043]      FIG. 26  is a rear perspective view of a removable faceplate of the handheld oral irrigator. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    In one embodiment, a handheld oral irrigator  10  allows a user to adjust the discharge pressure of the irrigator generated fluid stream while maintaining the pulse rate of the fluid stream. Thus, the handheld oral irrigator  10  is advantageous over the prior art because it allows a user to adjust the fluid stream discharge pressure to suit the user&#39;s comfort preference, while still allowing the oral irrigator to supply the fluid stream at a preferred or most effective pulse rate (e.g., 1200 cycles per minute). 
         [0045]    For a discussion of the overall external configuration of one embodiment of the handheld oral irrigator  10 , reference is made to  FIGS. 1-8 .  FIGS. 1 and 2  are top isometric views of the handheld oral irrigator  10 .  FIG. 3  is a control side elevation of the handheld oral irrigator  10 .  FIG. 4  is a reservoir side elevation of the handheld oral irrigator  10 .  FIG. 5  is a right side elevation of the handheld oral irrigator  10  as if viewed from the direction of arrow A in  FIG. 3 .  FIG. 6  is a left side elevation of the handheld oral irrigator  10  as if viewed from the direction of arrow B in  FIG. 3 .  FIG. 7  is a top plan view of the handheld oral irrigator  10 .  FIG. 8  is a bottom plan view of the handheld oral irrigator  10 . 
         [0046]    As shown in  FIGS. 1-7 , in one embodiment, the irrigator  10  includes a handle portion  15  and a nozzle  20  with an orthodontic tip at its distal end. The nozzle  20  extends from a top end of the handle portion  15 . The nozzle  20  is detachable from the handle portion  15  via a nozzle release button  25  located on the top of the handle portion  15 . 
         [0047]    As illustrated in  FIGS. 1-6 , in one embodiment, the handle portion  15  has a modified hourglass shape that gradually narrows from a wide base  30  (the proximal end of the irrigator  10 ) to a narrow gripping area  35  and gradually widens from the narrow gripping area  35  to a moderately wide top  40  (the distal end of the irrigator  10 ). The hourglass shape is aesthetically pleasing and ergonomically shaped to accommodate a user&#39;s hand, which in one embodiment will be a child or adolescent hand. 
         [0048]    As indicated in  FIGS. 1 ,  2  and  4 - 8 , in one embodiment, the handle portion  15  includes a reservoir  45  that forms a part of the base  30 . The reservoir  45  is removable from the rest of the handle portion  15  and includes a fill port  50  near the bottom of the reservoir  45 . To fill the reservoir with fluid, the reservoir  45  may be disengaged and removed from the rest of the handle portion  15 , the cap of the fill port  50  is opened, and a fluid is flowed into the reservoir  45  via the open fill port  50 . Once the reservoir  45  is filled, the cap is closed on the fill port  50  and the reservoir  45  is reattached to the rest of the handle portion  15 . 
         [0049]    As can be understood from  FIGS. 1 ,  2  and  4 - 8 , the reservoir  45  may be filled while still attached to the rest of the handle portion  15 . To do this, the cap of the fill port  50  is opened and a fluid is flowed into the reservoir  45  via the open fill port  50 . Once the reservoir  45  is filled, the cap is closed. 
         [0050]    For a discussion regarding disengaging the reservoir  45  from the rest of the handle portion, reference is made to  FIGS. 8 and 25 , wherein  FIG. 25  is a bottom perspective view of the reservoir of the handheld oral irrigator. As best shown in  FIGS. 8 and 25 , the reservoir  45  includes a leaf spring latch  47  molded into a lower portion of the reservoir  45  to releasably secure the reservoir  45  to the handle portion  15 . The leaf spring latch  47  is biased to engage the handle portion  15  when the reservoir  45  is joined with the handle portion  15 . To disengage the leaf spring latch  47  from the handle portion  15 , the user moves a latch portion  49  of the leaf spring latch  47  in the direction indicated by an arrow formed, printed, or placed on the leaf spring latch  47 . In one embodiment, the reservoir  45  moves downwardly relative to the handle portion  15  when the leaf spring latch  47  is disengaged from the handle portion  15 . 
         [0051]    Referring again to  FIGS. 1 ,  3  and  5 - 7  for a continued discussion of the overall external configuration of the handheld oral irrigator, in one embodiment, a control side of the gripping area  35  includes an on/off control  52 , a pressure control  54 , and a removable faceplate  56  that surrounds the locations of the two controls  52 ,  54 . The on/off control  52  allows a user to turn on or shut off the irrigator  10 . To turn the irrigator  10  on, the on/off control  52 , which can be a slide, button, etc., is moved (e.g., slid or depressed) to complete an electrical circuit between the irrigator&#39;s internal power source and its motor. To turn the irrigator  10  off, the control  52  is moved again to break the electrical circuit. 
         [0052]    The pressure control  54  allows a user to adjust the discharge pressure of a fluid stream discharging from the distal tip of the nozzle  20 . In one embodiment, the nozzle release button  25  is located on the reservoir side opposite from the controls  50 ,  52 , which helps limit accidental release of the nozzle  20  by accidental pressing or other engagement of the nozzle release button  25  when the user operates the controls  50 ,  52 . 
         [0053]    The removable faceplate  56  can be replaced with other faceplates having other colors or designs, thereby allowing the user to customize the appearance of the irrigator  10  as preferred. In one embodiment, the handheld oral irrigator  10  is sold or provided with multiple faceplates  56  of various designs and colors. The user selects their preferred faceplate and mounts it on the handle portion  15 . 
         [0054]    As shown in  FIG. 26 , which is a rear perspective view of the removable faceplate of the handheld oral irrigator, the removable face plate  56  has two or more L-shaped tabs  410   a ,  410   b  for receipt in corresponding slots or grooves defined in the handle portion  15  of the oral irrigator  10  to join the removable faceplate  56  to the handle portion  15 . When joined together, the short legs of the tabs  410   a ,  410   b  are received in the slots or grooves defined in the handle portion  15  to maintain the joined relationship between the removable faceplate  56  and the handle portion  15 . 
         [0055]    To disconnect the removable faceplate  56  from the handle portion  15 , the removable faceplate  56  is sufficiently flexible such that a user can deflect the edges  415 ,  420  of the removable faceplate  56  inward in order disengage the tabs  410   a ,  410   b  from the handle portion  15  to pull the faceplate  56  away from the handle portion  15 . As a user moves the edges  415 , 420  of the removable faceplate  56  inwardly, the short legs of the tabs  410   a ,  410   b  are removed from the slots or grooves in the handle portion  15 , thereby allowing the user to remove the removable faceplate  56  from the handle portion  15 . 
         [0056]    To join the removable faceplate  56  to the handle portion  15 , a user deflects the edges  415 , 420  of the removable faceplate  56  inwardly and abuts a rear facing surface  425  of the removable faceplate  56  against the handle portion  15 . When the removable faceplate  56  abuts the handle portion  15  in the proper location and orientation, the short legs of the tabs  410   a ,  410   b  generally align with the grooves or slots in the handle portion  15 . In one embodiment, the handle portion  15  has a recessed surface surrounding the controls  50 ,  52  to aid a user in properly locating and orienting the removable faceplate  56  relative to the handle portion  15 . Once the removable faceplate  45  abuts the handle portion  56  in the proper location and orientation, the user stops squeezing the edges  415 ,  420  of the removable faceplate inwardly, thereby causing the short legs of the tabs  410   a ,  410   b , which are biased to move outwardly by the internal forces generated by inward movement of the edges  415 ,  420  of the removable faceplate  56 , to enter into the grooves or slots defined in the handle portion  15 . 
         [0057]    Referring again to  FIGS. 1 ,  3  and  5 - 7  for a continued discussion of the overall external configuration of the handheld oral irrigator, the reservoir side of the gripping area  35  includes a soft over molded grip area  58 , which in one embodiment, includes gripping bumps  60 , a textured gripping surface, or other grip enhancing features. 
         [0058]    As illustrated in  FIGS. 1 and 3 , in one embodiment, a charging plug  63  exits in the handle portion  15  near the base  30 . The charging plug  63  is used to place an external power source in electrical communication with an internal power source (e.g., battery) located within the handle portion  15 . 
         [0059]    For a discussion of the overall internal configuration of one embodiment of the handheld oral irrigator  10 , reference is made to  FIGS. 9-11 ,  23  and  24 .  FIG. 9  is a section elevation of the handheld oral irrigator  10  as taken along section line  9 - 9  in  FIG. 4 .  FIG. 10  is an isometric view of a motor side of the handheld oral irrigator  10  with the outer housing  65  of the handle portion  15  removed to show the internal elements of the irrigator  10 .  FIG. 11  is the same type of view as illustrated in  FIG. 10 , except of a pump side of the handheld oral irrigator  10 .  FIG. 23  is a similar view as illustrated in  FIG. 10 , except various components are shown in an alternate configuration.  FIG. 24  is a similar view as illustrated in  FIG. 11 , except various components are shown in an alternate configuration. 
         [0060]    As shown in  FIG. 9 , the irrigator  10  includes an outer housing  65  that forms the exterior surface of the handle portion  15 . The housing  65  encloses a motor  70 , a pump  75 , a transmission  77 , a rechargeable NiCad battery  80 , and a pressure control valve assembly  85 . In one embodiment as illustrated in  FIGS. 10 and 11 , the motor  70  and pump  75  are located in a side-by-side arrangement near the base  30 , the transmission  77  is located below the motor  70  and pump  75 , the battery  80  is located above the motor  70  and pump  75 , and the valve assembly  85  is located above the battery  80 . In another embodiment as illustrated in  FIGS. 23 and 24 , the battery  80  is located near the base  30 , the motor  70  and pump  75  are located above the battery  80 , the transmission  77  is located above the motor  70  and pump  75 , and the valve assembly  85  is located above the transmission  77 . The transmission  77  couples the motor  70  to the pump  75  to convert the rotational output of the motor  70  into the longitudinally reciprocating movement of the pump&#39;s piston  120 . 
         [0061]    As illustrated in  FIG. 9 , the removable reservoir  45  forms a significant part of a lower side of the handle portion  15 . The fill port  50  opens into the reservoir  45 , and the reservoir  45  extends under a portion of the housing  65  enclosing the motor  70  and pump  75 . A transfer tube  90  extends from a bottom level of the reservoir  45  to a seal coupling  95 . In one embodiment, the transfer tube  90  is part of the reservoir. In another embodiment, the transfer tube  90  is separate from the reservoir  45 . When the reservoir  45  is coupled to the rest of the handle portion  15 , the seal coupling  95  sealing mates with a bottom end of a suction tube  100 , which leads to a suction port  105  of the pump  75 , as best understood from  FIGS. 11 and 24 . Thus, the reservoir  45  is placed in fluid communication with the suction side of the pump  75 . 
         [0062]    As indicated in  FIGS. 10 and 11 , and  FIGS. 23 and 24 , the motor  70 , pump  75 , transmission  77  and valve assembly  85  are coupled to a chassis plate  110  longitudinally extending through the housing  65  of the handle portion  15 . In one embodiment, the controls  52 ,  54 , motor  70  and the battery  80  are located on one side of the plate  110 , and the pump  70  and valve assembly  85  are located on the other side of the plate  110 . 
         [0063]    As can be understood from  FIGS. 9 and 11 , the suction tube  100  is detachably sealably coupled to the seal coupling  95  by coupling the reservoir  45  to the rest of the housing  65  of the handle portion  15  such that the free end of the suction tube  100  is received in the seal coupling  95 . As shown in  FIG. 11 , fluid traveling form the reservoir  45  to the distal end of the nozzle  20  is drawn through the transfer tube  90 , into the suction tube  100  at the seal coupling  95  and to the suction port  105  of the pump  75 . 
         [0064]    As can be understood from  FIG. 12 , which is a longitudinal section through the pump  75 , when a piston  120  moves rearwardly in a cylinder  115  of a cylinder casing  118  (rearward movement indicated by arrow X in  FIG. 12 ), a discharge wafer  121  of a discharge wafer valve arrangement is forced against a discharge valve seat  122  and the fluid is drawn through the suction port  105  of a suction casing  107  of the pump  75 , past a suction wafer  108  forming a suction wafer valve arrangement, and into the cylinder  115 . When the piston  120  moves forwardly (as indicated by arrow Y in  FIG. 12 ), the suction wafer  108  is forced against the suction valve seat  125  and the fluid is forced past the discharge wafer  121 , into a discharge port  130  of a discharge casing  135  of the pump  75 , and into a discharge tube  140  leading to the valve assembly  85 , as illustrated in  FIGS. 11 and 24 . 
         [0065]    In one embodiment, as depicted in  FIGS. 11 and 12 , the pump  75  is formed from three casings (e.g., the suction casing  107 , cylinder casing  118  and discharge casing  135 ). In one embodiment, the three casings  107 ,  118 ,  135  are held together via a joining mechanism. For example, in one embodiment, a screw  145  (illustrated in  FIG. 11 ) is received in screw receiving holes  146  (shown in  FIG. 12 ) in the three casings  107 ,  118 ,  135 . 
         [0066]    For a discussion of the motor/pump/transmission arrangement, reference is made to  FIG. 13 , which is an isometric of view of the motor/pump/transmission arrangement with the rest of the irrigator  10  hidden for clarity purposes. As shown in  FIG. 12 , a pinion gear  150  extends from the motor  70  to drive a gear  155  carrying a cam  160 . A piston rod  165  (see  FIGS. 12 and 13 ) extends between the piston  120  and a cam follower end  170  of the piston rod  165 . The cam follower end  170  receives the cam  160 , and as the cam  160  is caused to rotate, the cam follower  170  and cam  160  act to convert the rotational movement of the motor  70  into longitudinal reciprocal displacement of the piston  120  within the cylinder  115 . 
         [0067]    For a discussion of the pressure control valve assembly  85 , reference is made to  FIGS. 14-22 .  FIG. 14  is an isometric view of the pressure control valve assembly  85  with the majority of the rest of the handheld oral irrigator  10  hidden for clarity purposes.  FIG. 15  is a side elevation of the same elements depicted in  FIG. 14 , as viewed from the same direction as  FIG. 6 .  FIG. 16  is a side elevation of the same elements depicted in  FIG. 14 , as viewed from the same direction as  FIG. 4 .  FIG. 17A  is a longitudinal cross section of the pressure control valve assembly  85  as taken along section line  17 - 17  in  FIG. 15  and wherein a spool  180  is in a rearward location (i.e., a high discharge pressure position) within the valve cylinder  185 .  FIG. 17B  is the same view depicted in  FIG. 17A , except the spool  180  is in a forward location (i.e., a low discharge pressure position) within the valve cylinder  185 .  FIG. 18A  is a longitudinal cross section of the pressure control valve assembly  85  as taken along section line  18 - 18  in  FIG. 16  and wherein the spool  180  is in a rearward location (i.e., a high discharge pressure position) within the valve cylinder  185 .  FIG. 18B  is the same view depicted in  FIG. 18A , except the spool  180  is in a forward location (i.e., a low discharge pressure position) within the valve cylinder  185 .  FIG. 19  is a side view of the pressure control valve assembly  85  as shown in  FIG. 15 , except the discharge tube  140 , nozzle  20  and control button  54  are hidden for clarity purposes.  FIG. 20  is an isometric view of the pressure control valve assembly  85  wherein the discharge tube  140 , nozzle  20  and control button  54  are hidden for clarity purposes.  FIG. 21  is an isometric view of the spool  180  and yoke  190 .  FIG. 22  is an isometric latitudinal cross section taken along section line  22 - 22  in  FIG. 15 . 
         [0068]    As can be understood from  FIGS. 14-18B  and  22 , fluid pumped through the discharge tube  140  from the pump  75  enters an inlet  210  of the pressure control valve assembly  85 . As depicted in  FIG. 19  and  FIG. 22 , in one embodiment, to enter the valve cylinder  185 , the fluid passes through slot openings  215  in the cylinder wall  220 . 
         [0069]    As can be understood from  FIGS. 17A-18B , a spool  180  is located in the cylinder  185  and longitudinally displaceable within the cylinder  185 . As illustrated in  FIG. 21 , the spool  180  is cylindrically shaped with a pair of arms  257  extending outwardly and rearwardly from a middle portion of the spool  180 . A lumen  258  extends longitudinally through the length of the spool  180 . The free ends of the arms  257  are received in pivot holes  259  in a yoke  261 . The distal end of the spool  180  includes a pair of o-ring receiving grooves  260 , a fluid groove  265  positioned between the o-ring grooves  260 , and an orifice  275  extending between the fluid groove  265  and the lumen  270 . The proximal end of the spool  180  includes an o-ring receiving groove  277 . 
         [0070]    As indicated in  FIGS. 17A and 18A , when the spool  180  is located rearwardly in the cylinder  185 , the fluid passes through the slot openings  215  (see  FIGS. 19 and 20 ) and directly from the front of the cylinder  185 , through the valve assembly outlet  225 , through the lumen  230  of the nozzle  20 , and out the distal tip of the nozzle  20  as a high discharge pressure fluid stream. As indicated in  FIGS. 17B ,  18 B and  21 , when the spool  180  is located forwardly in the cylinder  185 , the fluid passes through the slot openings  215  (see  FIGS. 19 and 20 ) and between the fluid groove  265  and the inner circumferential surface of the cylinder  185 , through the orifice  275 , into the lumen  258  of the spool  180 , through the valve assembly outlet  225 , through the lumen  230  of the nozzle  20 , and out the distal tip of the nozzle  20  as a low discharge pressure fluid stream. 
         [0071]    As can be understood from  FIGS. 17A-20 , when the spool  180  is in the forward position within the cylinder  185  (i.e., the low discharge pressure position), the fluid flow passing through the pressure control valve assembly  85  must overcome a substantially increased frictional resistance as compared to when the spool  180  is in the rearward position within the cylinder  185  (i.e., the high discharge pressure position). Accordingly, when the spool  180  is in the low discharge pressure position, the pressure control valve assembly  85  creates a substantially high-pressure drop in the fluid flow passing through the assembly  85  as compared to when the spool  180  is in the high discharge pressure position. Thus, without having to adjust the operating speed of the pump  75 , a user may adjust the discharge pressure of a fluid stream emanating from the nozzle  20  of the oral irrigator  10  by adjusting the position of the spool  180  within the cylinder  185 . Accordingly, the discharge pressure may be substantially modified by a user without causing a substantial change in the preferred pulse rate of the fluid stream. 
         [0072]    As can be understood from  FIGS. 17A-20 , moving the spool  180  from the high discharge pressure position (see  FIGS. 17A and 18A ) to the low discharge pressure position (see  FIGS. 17B and 18B ) modifies, in several ways, the fluid flow path through the discharge pressure control assembly  85  and, as a result, the fluid flow path between the pump  75  and the nozzle  20 . First, moving the spool  180  from the high to the low discharge pressure position increases the length of the fluid flow path because the flow is diverted about the fluid groove  265 , through the orifice  275  and through the lumen  258  before the flow can pass through the cylinder outlet  225  to the nozzle  20 . Second, moving the spool  180  from the high to the low discharge pressure position substantially decreases the diameters or flow areas of the fluid flow path because the diameters or flow areas of the fluid groove  265 , orifice  275 , and lumen  258  are substantially smaller than the internal diameter or flow area of the cylinder  185 . Third moving the spool  180  from the high to the low discharge pressure position increases the number of direction deviations the fluid flow must undergo because the fluid must travel a tortuous route around the groove  265  and through the orifice  275  and lumen  258  before the flow can pass through the cylinder outlet  225  to the nozzle  20 . 
         [0073]    Each of these modifications to the fluid flow path brought about by moving the spool  180  from the high to low discharge pressure position increases the magnitude of the fluid flow friction between the pump  75  and the nozzle  20 . Accordingly, although the pump  75  continues to operate at generally the same speed and provides a fluid stream at generally the same pulse rate, because the spool  180  moves from the high to the low discharge pressure position within the cylinder  185 , the discharge pressure of the fluid stream at the distal end of the nozzle  20  decreases from a high to low discharge pressure. 
         [0074]    Research has indicated that some fluid stream pulse rates are more effective than other pulse rates. For example, in one embodiment, the pump  75  of the oral irrigator  10  cycles at a rate such that it discharges a fluid stream out the nozzle  20  that has a pulse rate of 1000-1600 pulses per minute and, in one embodiment, 1100-1400 pulses per minute and, in one embodiment, 1200 pulses per minute. As discussed in U.S. Pat. No. 3,227,158 issued to Mattingly, which is incorporated by reference herein in its entirety, a pulse rate of 1000-1600 pulses per minute has been found to be the most effective pulse rates for the purposes of oral hygiene and health. Other highly effective pulse rates for the purposes of oral hygiene and health also include 1100-1400 pulse per minute and 1200 pulses per minute. 
         [0075]    The pressure control feature is advantageous because it allows a user to adjust the fluid stream discharge pressure to suit the user&#39;s comfort preferences while maintaining the pulse rate generally at a preferred pulse rate. For example, regardless of whether the pressure control valve assembly  85  is set to cause a low or high discharge pressure fluid stream to emanate from the nozzle  20 , the fluid stream will have a preferred number of pulses per minute (e.g., 1000-1600 pulses per minute, 1100-1400 pulses per minute, 1200 pulses per minute, etc.). 
         [0076]    For a discussion of the cylinder&#39;s configuration, reference is again made to FIGS.  14  and  17 A- 20 . As best understood from  FIGS. 14 ,  19  and  20 , the cylinder  185  of the pressure control valve assembly  185  includes a proximal portion  185   a  received within a collar portion  185   b  of a distal portion  185   c . A slot  300  extends longitudinally along the sides of the cylinder  185 , and the arms  257  of the spool  180  extend through the slots  300  to couple with the arms of the yoke  261 . As indicated in  FIGS. 17A-18B , the cylinder  185  is hollow to receive the spool  180 , and the proximal end of the cylinder proximal portion  185   c  is walled-off such that when a fluid flows into the lumen  258  of the spool  180 , the fluid impacts the proximal end of the cylinder proximal portion  185   c  to establish a back pressure condition within the pressure control valve assembly  85 . As can be understood from  FIGS. 17A and 17B , the o-rings  260 ,  277  prevent fluid from escaping the cylinder  185  through the slots  300 . 
         [0077]    For a discussion of the linkage  305  used to cause the spool  180  to displace within the cylinder  185 , reference is again made to  FIGS. 9 ,  14 ,  15 ,  18 A- 21 . As best understood from these figures, the linkage  305  includes the yoke  261  and the pressure control  54 . The yoke  261  includes a pair of arms, and each arm has a pivot hole  259  near its free end. The pivot holes  259  pivotally receive therein the free ends of the spool arms  257 . The yoke includes an arcuately slotted tongue  310  opposite the yoke arms for pivotally receiving therein a ball  315  extending from the pressure control  54 . 
         [0078]    As indicated in  FIG. 9 , in one embodiment, the pressure control  54  is a slide supported by the housing  65  of the handle portion  15  of the irrigator  10 . As illustrated in  FIGS. 19 and 21 , the yoke  261  has a rocker portion  320  from which the tongue  310  extends. As shown in  FIGS. 18A and 18B , the rocker portion  320  resides within a hole or slot  325  in the chassis plate  110 , which allows the tongue  310  to rock towards the nozzle  20  or towards the base  30 , depending on how the slide  54  is displaced along the housing  65 . 
         [0079]    As indicated in  FIG. 18A , when the slide  54  is shifted towards the nozzle  20 , the tongue  310  is rocked towards the nozzle  20  thereby causing the yoke  261  to pivot about the hole  325  in the chassis plate  110  such that the yoke arms move towards the base  30  and pull the spool arms  257  towards the base  30 , which causes the spool  180  to move towards the base  30  (i.e., the spool  180  moves into the high discharge pressure position). As indicated in  FIG. 18B , when the slide  54  is shifted towards the base  30 , the tongue  310  is rocked towards the base  30  thereby causing the yoke  261  to pivot about the hole  325  in the chassis plate  110  such that the yoke arms move towards the nozzle  20  and pull the spool arms  257  towards the nozzle  20 , which causes the spool  180  to move towards the nozzle  20  (i.e., the spool  180  moves into the low discharge pressure position). 
         [0080]    For a discussion regarding the elements of the nozzle release, reference is again made to  FIGS. 9 ,  14 ,  15  and  18 A- 20 . As illustrated in these figures, the nozzle release button  25  is coupled to a collar  350  having an opening  355  centered about the hole  360  of the nozzle base receiving cylinder  368 , which extends from the cylinder outlet  225 . The proximal end of the nozzle  20  is received in the receiving cylinder  368  and the collar  350 . The collar  350  is biased into a nozzle base groove  370  by a spring  380 . The groove  370  extends about the circumference of the nozzle base. To release or disengage the collar  350  from the nozzle base groove  370  to allow the nozzle  20  to be withdrawn from the receiving cylinder  368 , the nozzle release button  25  is depressed against the biasing force of the spring  380 , which causes the collar  350  to shift out of engagement with the groove  370 . The nozzle  20  is then withdrawn from the cylinder  368 . 
         [0081]    As can be understood from the preceding discussion, the oral irrigator of the present invention is advantageous because it allows a user to adjust the discharge pressure of the fluid stream emanating from the oral irrigator without bringing about a significant change in the pulse rate of the fluid stream. Thus, the oral irrigator can continue to supply a fluid stream at a preferred pulse rate regardless of the discharge pressure selected by the user. 
         [0082]    Although the present invention has been described with reference to preferred embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. The invention is limited only by the scope of the following claims.