Abstract:
A pressure sprayer is pressurized automatically with movement of the sprayer and maintains adequate pressure during non-movement to allow the ejection of an amount of liquid before needing re-pressurization. The pressure sprayer includes wheels that allow the pressure sprayer to be mobile. A cam is attached to the axle of the wheels which rotates with the rotation of the axle/wheels. A pressure pump is associated with the cam such that movement of the cam causes the pressure pump to pump liquid from a holding tank to an accumulator or directly to a spray wand in communication with the pump. The liquid may be sprayed (ejected) from the accumulator during both movement (pumping) and non-movement (no pumping) of the sprayer, while the liquid may be directly sprayed from the holding tank only during movement (pumping) thereof. Thus, as the wheels rotate due to moving the pressure sprayer, the cam causes movement of the pressure pump to fill the accumulator with the liquid under pressure. The pressure pump is adapted to obtain liquid from the holding tank and provide that liquid to the pressure accumulator. A relief valve is provided to relieve the buildup of pressure during movement of the wheels when no spraying is taking place.

Description:
[0001]    This non-provisional U.S. patent application claims the benefit of U.S. provisional patent application serial number 60/189,194, filed on Mar. 14, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to pressure sprayers and, more particularly, to portable, self-pumping pressure sprayers.  
         BACKGROUND OF THE INVENTION  
         [0003]    Pressure sprayers are well known in the art, having been developed many years ago. They essentially consist of a tank that is adapted to hold a liquid and become pressurized with air. The tank becomes pressurized via a pump. When a spray head and/or wand that is attached to the pressurized tank is opened, the liquid within the tank is ejected from the spray head/wand by the pressure in the tank. Eventually, the pressure within the tank decreases with the ejection of liquid therefrom. When the pressure against the liquid within the tank drops to a particular value, the liquid will not be ejected from the tank due to lack of pressure. Therefore, in order to maintain (have) adequate pressure within the tank in order to eject the liquid therefrom, the pressure must be periodically increased. This is accomplished by a manually actuated pump associated with the pressure sprayer.  
           [0004]    Such pressure tanks may be used for spraying insecticides, pesticides, biocides, and herbicides, as well as paints, stains, water, and virtually any other non-viscous liquid. Small, portable (i.e. hand-carried) pressure tanks of one to five gallons in size have been used by the home and business industry. Early pressurized tanks were metal canisters with a manually actuated pump. When these metal tanks were filled with a liquid, and manually pumped to the appropriate pressure, they were quite heavy and cumbersome to carry. Currently, most pressure sprayers are formed from a suitable plastic. While plastic tanks are lighter than metal tanks when filled with a liquid and pumped to an adequate pressure, they are still cumbersome and somewhat heavy.  
           [0005]    Wheels were added to larger pressure sprayers in order to alleviate the above problems by allowing a user to pull or push the pressure sprayer to its intended location rather than carry the pressure sprayer. These portable pressure sprayers were, however, still pressurized by manually actuated pumps. Thus, although these mobile pressure sprayers obviated the need to carry the heavy pressure sprayers, they were still pressurized by manual pumps.  
           [0006]    Still another type of wheeled pressure sprayer in existence includes a pump which is actuated by rotation of the wheels of the sprayer. Upon actuation, the pump generates pressure which causes fluid to be sprayed out of the tank of the sprayer. However, this type of sprayer does not store pressure for spraying when the sprayer is not being moved (i.e. when the wheels are not being rotated). In other words, when movement of the sprayer is stopped so that the wheels are no longer rotating, the sprayer stops pumping fluid from the tank of the sprayer to the environment (e.g. onto a lawn).  
           [0007]    What is needed is a portable pressure sprayer that develops its own pressure for ejecting a liquid and stores such pressure for later use by the sprayer even when the wheels of the sprayer are no longer being rotated.  
           [0008]    What is further needed is a portable pressure sprayer that develops it own pressure for ejecting a liquid wherein adequate ejection pressure is maintained at least transiently.  
           [0009]    What is still further needed is a portable pressure sprayer that develops pressure for ejecting a liquid through movement of the pressure sprayer, wherein adequate pressure is maintained for liquid ejection during periods of nonmovement (i e. during periods when the wheels of the sprayer are no longer being rotated).  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is a self-energizing pressure sprayer in which movement of the sprayer creates and maintains adequate pressure to expel an amount of liquid held therein during both movement and non-movement of the sprayer.  
           [0011]    In one form thereof, a pressure sprayer having a holding tank includes a pressure pump that is adapted to pump a liquid from the holding tank to the accumulator during movement of the sprayer (i.e. rotation of the wheels of the sprayer).  
           [0012]    In another form thereof, a pressure sprayer includes a holding tank, an accumulator and a pressure pump in communication with the holding tank and the accumulator. The pressure sprayer further includes wheels carried on an axle that rotates during pushing and/or pulling movement of the pressure sprayer. The pressure pump is associated with the axle such that rotation of the axle causes the pressure pump to pump fluid from the holding tank to the accumulator wherein the fluid is pressurized for ejection from the sprayer even at times when the wheels of the sprayer are being maintained stationary.  
           [0013]    In yet another form thereof, a pressure pump of a pressure sprayer having a holding tank and an accumulator both in fluid communication with the pressure pump, is coupled to a cam assembly affixed on an axle for wheels of the pressure sprayer that drives the pressure pump during pushing and/or pulling movement of the pressure sprayer. The pump is in communication with a tank adapted to hold a liquid to be ejected and a pressure accumulator. During movement of the pressure sprayer, the cam assembly rotates to cause the pressure pump to reciprocate and thus pump (operate). Once the pressurized fluid has been depleted, movement of the pressure sprayer re-energizes (re-pressurizes) fluid for ejection.  
           [0014]    According to still another embodiment of the present invention, there is provided a pressure sprayer which includes a tank for holding fluid, and an accumulator for storing fluid therein under pressure. The sprayer further includes a number of wheels for supporting the tank. Moreover, the sprayer includes a pump which advances fluid from the tank into the accumulator in response to rotation of the number of wheels. The pressure within the accumulator is increased when fluid is advanced into the accumulator by the pump.  
           [0015]    Yet in accordance with another embodiment of the present invention, there is provided a pressure sprayer which includes an accumulator for storing fluid therein under pressure, and at least one wheel which rotates when the pressure sprayer is moved. The sprayer also includes a pump which advances fluid into the accumulator in response to rotation of the at least one wheel. An increased pressure is generated within the accumulator in response to fluid being advanced into the accumulator by the pump. Further, the increased pressure within the accumulator is maintained when the at least one wheel is stationary.  
           [0016]    In accordance with still another embodiment of the present invention, there is provided a method of spraying fluid with a portable pressure sprayer having a tank, an accumulator, and a number of wheels. The method includes the steps of (i) moving the portable pressure sprayer so as to cause the number of wheels to rotate, (ii) advancing fluid from the tank into the accumulator in response to rotation of the number of wheels, (iii) generating an increased pressure within the accumulator in response to fluid being advanced into the accumulator, and (iv) maintaining the increased pressure within the accumulator after the moving step when the number of wheels are stationary.  
           [0017]    In accordance with yet another embodiment of the present invention, there is provided a method of spraying fluid with a pressure sprayer having at least one wheel. The method includes the step of moving the portable pressure sprayer so as to cause the at least one wheel to rotate. The method also includes the step of generating an increased pressure within the sprayer in response to rotation of the at least one wheel. In addition, the method includes the step of maintaining the increased pressure within the sprayer after the generating step when the at least one wheel is stationary. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiment(s) of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0019]    [0019]FIG. 1 is a perspective view of a design of a mobile pressure sprayer embodying various features in accordance with the principles of the invention set forth herein;  
         [0020]    [0020]FIG. 2 is a sectional view of the pressure sprayer of FIG. 1 taken along line  2 - 2  thereof particularly showing a bottom half view;  
         [0021]    [0021]FIG. 3 is a sectional view of the bottom portion of the sprayer body particularly showing the pump and wheel drive assembly coupled to the pump;  
         [0022]    [0022]FIG. 4 is a sectional view of the lower half of the bottom portion of the sprayer body showing the pump in sectional and the wheel drive assembly in sectional coupled to the pump;  
         [0023]    [0023]FIG. 5 is a perspective view of the pump used in the pressure sprayer of FIG. 1;  
         [0024]    [0024]FIG. 6 is an exploded view of one side of the pump of FIG. 5 and its corresponding valve plate, particularly for describing pump operation;  
         [0025]    [0025]FIG. 7 is an exploded view of another side of the pump of FIG. 5 and its corresponding valve plate, particularly for describing pump operation;  
         [0026]    [0026]FIG. 8 is an exploded view of the pump and valve plate of FIG. 5 and its pressure relief valve, particularly for describing operation of the pressure relief valve;  
         [0027]    [0027]FIG. 9 is a sectional view of an alternative embodiment of a pump;  
         [0028]    [0028]FIG. 10 is top perspective view of an embodiment of the present pressure sprayer having a hose and spray wand attached thereto;  
         [0029]    [0029]FIG. 11 is an enlarged sectional view of the handle assembly/tank interface area taken along circle  11 - 11  of FIG. 2;  
         [0030]    [0030]FIG. 12 is an enlarged view of a cam track of a cam portion of a cam assembly in accordance with the principles of the present invention;  
         [0031]    [0031]FIG. 13 is a sectional view of a pressure accumulator of the pressure sprayer of the of FIG. 1 showing an alternative arrangement for implementation of the pressure relief valve into the pressure sprayer of FIG. 1;  
         [0032]    [0032]FIG. 14. is a sectional view of the pressure relief valve of FIG. 13;  
         [0033]    [0033]FIG. 15 is a fragmentary view of the pump of the pressure sprayer of FIG. 1 showing yet another arrangement for implementation of the pressure relief valve into the pressure sprayer of FIG. 1;  
         [0034]    [0034]FIG. 16 is an exploded view of the pump of the pressure sprayer of FIG. 1 showing the manner of attachment of a support and guide bracket to the pump in an alternative embodiment of the present invention;  
         [0035]    [0035]FIG. 17 is an assembled elevational view of the bracket and pump of FIG. 16 shown positioned at a first orientation; and  
         [0036]    [0036]FIG. 18 is an assembled elevational view of the bracket and pump of FIG. 16 shown positioned at a second orientation. 
     
    
       [0037]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates a preferred embodiment of the invention, and such exemplification is not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0038]    Referring now to the drawings and, more particularly to FIG. 1, there is shown a pressure sprayer generally designated  20 . In the current best mode, the pressure sprayer  20  is formed (e.g. molded) from a suitable plastic that is durable, able to withstand air pressure stress, and other stresses of use. Various thermoplastics may be used such as polyethylene, polypropylene, nylon, and the like. It should be appreciated that one type of plastic may be used for one component of the pressure sprayer  20  while another type of plastic may be used for other components. The pressure sprayer  20  includes a main body or housing  22  defined by an upper or tank portion  23  and a lower or support portion  24 . The tank  23  has a label area  25  on which may be placed an identifying and/or warning label as necessary.  
         [0039]    The lower portion  24  supports the tank portion  23  and is itself movably supported by wheels  30  and  32 . The wheels  30  and  32  are preferably molded from a suitable plastic and include a plurality of ridges along the periphery or diameter of the wheel. The lower portion  24  also includes a hose bore  26  and a support  28 . The support  28  provides a drain housing and serves as one leg in a tri-pod configuration defined by the wheels  30  and  32  and the support  28 . The hose bore  26  allows a sprayer hose to extend from the interior of the body  22  to an exterior of the body  22 .  
         [0040]    With additional reference to FIG. 2, the pressure sprayer  20  further includes a handle assembly  34  that is removably attached to the body  22  via a threaded joining ring  42 . The handle assembly  34  is preferably formed of a solid plastic and is predominantly defined by a shaft  36  that terminates at one end in a grip  38 , and at the other end in an interface  60 . Two sprayer hose clips  40   a  and  40   b  extend from opposite sides of the shaft  36  while a spray wand storage area  54  (see FIG. 1) is located on the shaft  36  proximate the grip  38 . The grip  38  is preferably formed with a plurality of finger recesses  56  in an arch portion  58  thereof for the receipt of fingers of a user.  
         [0041]    The interface  60  is adapted/configured to be received in and releasably retained on the tank portion  23 . The tank portion  23  defines an internal cavity, tank, reservoir or the like  46  that is adapted to hold a liquid for dispensing. A neck  44  is formed on one end of the tank portion  23  and defines an opening  48  through which the liquid is received into the tank  46 . The interface area  60  forms a cap or cover for the tank  46 .  
         [0042]    With additional reference to FIG. 11, the interface  60  of the shaft  36  as it is releasably received onto the neck  44  of the tank portion  23  is shown in enlarged detail. The neck  44  defines the opening  48  by terminating in an essentially annular flange  66 . The shaft  36  includes an enlarged or bulbous portion  68  that has a reduced diameter knob  74  sized to be received and extend into the opening  48  defined by the annular flange  66 . The neck  44  further includes external threads  62  that threadedly mate with internal threads  64  of the joining ring  42 . Preferably, the joining ring  42  is coupled to the bulbous portion  68  of the shaft  36  in a manner that allows the joining ring  42  to freely rotate. In particular, the bulbous portion  68  includes a circumferential groove or slot  70  that receives an annular flange  72  of the joining ring  42 . Once the knob  74  is received into the opening  48 , the joining ring  42  is threaded onto the threads  62  of the neck  44  and tightened. This releasably couples the handle assembly  34  to the body  22  and seals the tank  46 .  
         [0043]    Referring back to FIG. 2, the tank  46  is in communication with a pump  78  via outlet  80 . The outlet  80  includes a filter  84  and allows liquid within the tank  46  to enter the pump  78  for eventual spraying, and also to a drain  86  should it be desired to remove (e.g. drain) the contents of the tank  46 . The drain  86  includes a conduit  90  that is fitted with a plug  88 . When the conduit  90  and plug  88  are in the position shown in FIG. 2, any liquid within the tank  46  will not flow out of the conduit  90  but be drawn into the pump  78  when the pump  78  is active. When the drain  86  is pulled out, the plug  88  does not hold back the liquid and it is allowed to exit via conduit  90  to the environment.  
         [0044]    Internal to the tank  46  is a pressure accumulator  76  that is threadedly coupled to an outlet/inlet  82  and sealed with an O-ring. The pressure accumulator  76  receives liquid from the tank  46  via the pump  78  when the pump  78  is pumping and there is little to no spraying occurring. As the accumulator  76  fills with liquid, the pressure therein increases tending to force out the liquid. When the pump  78  is not pumping, the liquid under pressure within the accumulator  76  may be sprayed. The liquid exits the pump  78  via an exit nozzle  91 . Once the pressure within the accumulator  76  is exhausted, the pump  78  needs to pump again to recharge the accumulator  76 .  
         [0045]    With reference to FIGS. 3 and 4, the pump  78  is caused to pump via action or movement of the wheels  30  and  32  as the pressure sprayer  20  is moved or wheeled from place to place. The wheel  30  includes a hub or sleeve  31  that extends over an axle portion  94  that connects to an axle portion  92 . The wheel  32  includes a hub or sleeve  33  that extends over the axle portion  92 . A cam assembly  96  comprising a cam portion  104  and a cam portion  106  is situated on the axles  92  and  94  respectively. The cam portion  104  includes a cam track  105  that faces a cam track  107  in the cam portion  106 . Both cam tracks  105  and  107  are hexagonal shaped.  
         [0046]    In FIG. 12, the cam portion  106  is depicted particularly showing the cam track  107  thereof. The cam track  107  mirrors the cam track  105  of the cam portion  104  and coacts therewith to provide a hexagonal cam track for the drive pins  110  and  112  of the pump  78  (see FIG. 5). Particularly, the cam track  107  receives drive pin  112  while the cam track  105  receives drive pin  110  (see FIG. 4) each drive pin extending from a shaft  108  coupled to the yoke  114 . Because of the configuration of the cam tracks  105  and  107 , the drive pins  110  and  112 , and thus the yoke  114  of the pump  78  is caused to reciprocate as represented by the arrow  98  in FIG. 5, causing the pump  78  to pump as described below.  
         [0047]    While each of the cam tracks  105 ,  107  is described as possessing a hexagonal shape, it should be appreciated that each of the cam tracks  105 ,  107  may possess a shape other than a hexagonal shape and still achieve many of the benefits of the present invention. For example, each of the cam tracks  105 ,  107  may possess an octagonal shape.  
         [0048]    Referring back to FIGS. 3 and 4, and with additional reference to FIG. 5, as the wheels  30  and  32  turn, rotate or revolve under action of movement of the pressure sprayer  20 , the cam assembly  96  rotates therewith, thereby rotating the cam tracks  105  and  107 . As the drive pins  110  and  112  are constrained to follow the respective cam tracks  105  and  107 , the yoke  114  is caused to move back and forth (i.e. reciprocate). The piston  122  having an O-ring  126  reciprocates in piston cylinder/housing  123  while the piston  124  having an O-ring  128  reciprocates in piston cylinder/housing  125 . As one piston creates suction the other piston creates compression during reciprocation.  
         [0049]    The pump  78  pictured in FIG. 5 also includes drive pins  118  and  120  extending from shaft  116 . The shaft  116  is attached to the yoke  114  and thus moves with the movement of the yoke. This configuration allows the pump  78  to be installed in a different configuration and be driven by the drive pins  118  and  120  in the same manner as the drive pins  110  and  112  attached to shaft  108 .  
         [0050]    With reference now to FIG. 6 the operation of the pump  78  will be described. The numbers within circles in FIG. 6 are referred to herein as “circle #”. Liquid within the tank  46  is gravity fed to the pump  78  via inlet  130  (circle  1 ). As the wheels  30  and  32  are rotated, the “A” side draws the liquid through the port (circle  2 ) pushing the switching valve (circle  3 ) of the valve plate  138  out of the way. The liquid then flows through the port (circle  4 ) and into the piston cylinder  123 . As the piston  122  begins the compression stroke, liquid is passed through the port (circle  6 ) pushing switching valve (circle  7 ) out of the way to allow the liquid to flow to port (circle  8 ) and into the pressure side (“B”) of the pump  78 . In the pressure side of the pump  78 , the liquid can either discharge via the outlet nozzle  91  (circle  16 ) or flow to the pressure accumulator  76  via the outlet  132  (circle  17 ) for later use. The switching valves (circle  3  and circle  7 ) ensure that the liquid only flows in one direction, allowing the pump  78  to operate at peak efficiency.  
         [0051]    With reference to FIG. 7, the “B” side of the pump  78  will be described. The “B” side of the pump  78  operates in essentially the same manner as the “A” side but the timing is exactly opposite thereof (i.e. 180° out of phase). When the “A” side is drawing in liquid, the “B” side is expelling liquid, due to the cam/pump/yoke stagger. The “B” side draws liquid from the tank  46  and passes the liquid through the port (circle  9 ) pushing the switching valve (circle  10 ) out of the way. Thereafter, the liquid flows through the port (circle  11 ) and into the piston cylinder  125  (circle  12 ). As the “B” side begins the compression stroke, while the “A” side is drawing liquid, the liquid in the “B” side is passed through the port (circle  13 ) and into the pressure side of the pump. In the pressure side of the pump, the liquid can either discharge via port  91  (circle  16 ) or flow to the pressure accumulator  76  (via circle  17 ) for later use. In FIGS. 6 and 7, circles  1 ,  16 , and  17  are common channels use by both the “A” and “B” sides of the pump  78 .  
         [0052]    With particular reference now to FIG. 8 there is depicted a pressure relief valve utilizing spring  140  and ball  142 . The pressure relief valve (PRV) helps prevent excessive pressure buildup within the unit that might make the unit difficult to push or could damage the unit. The present PRV is designed to release pressure on the pressure side of the pump when the pump pressure exceeds 35-45 psi. When this pressure is reached, liquid pushes through port A, moving ball  142  (“B”) out of the way by compressing spring  140  (“C”). The liquid can then flow through channel D, through port E, and back to the supply line of the pump via channel F. The pressure passed back to the supply line via this route is safely vented, allowing easy push/pull of the unit without causing damage to the pump  78 .  
         [0053]    In FIG. 9 there is depicted a sectional view of an alternate embodiment of a pump  150 . The pump  150  includes the same inlets and outlets as the pump  78 . The present pump  150  however, is known as a diaphragm pump rather than the O-ring pump  78 . It should be appreciated that either pump may be used in the pressure sprayer  20  as well as other pumps not shown and described herein. The pump  150  includes a reciprocatable yoke  152  that surround pump blocks  156  and  160  which are stationary with respect to the yoke  152 . The yoke  152  includes a piston  154  that extends into the block  156  and is surrounded by a diaphragm sealing cap  164 . A diaphragm overmold  166  is positioned at the end of the piston  154 . The yoke  152  further includes a piston  158  that extends into the block  160  and is surrounded by a diaphragm sealing cap  168 . A diaphragm overmold  170  is positioned at the end of the piston  158 . Disposed between the various chambers and passages of the blocks  156  and  160  is a valve plate  162 .  
         [0054]    In this manner alternating suction and compression is produced by the pistons  154  and  158  due to the reciprocating motion of the yoke  152  as the wheels/cam assembly of the pressure sprayer rotates.  
         [0055]    Referring to FIG. 10, there is shown pressure sprayer  20  with a hose  100  extending through hose bore  26  and coupled to the nozzle  91  (see e.g. FIG. 6). Attached to the hose  100  is a spray wand  102  as is conventionally known in the art. The spray wand  102  is shown in FIG. 10 releasably mounted on hook  40   a . As is well know in the art, the spray wand  102  includes a valve  204  having a control valve  106  (see FIG. 10).  
         [0056]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, of adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.  
         [0057]    For example, it is possible to modify the design of the pump  78  of FIGS.  2 - 8  so that it does not possess a pressure relief valve therein. Rather, a pressure relief valve  300  can be coupled directly to a sidewall of the pressure accumulator  76  as shown in FIG. 13. In particular, in such a modification, the pressure relief valve  300  is located in a recess  304  defined in a sidewall of the pressure accumulator  76 . The pressure release valve  300  includes a plunger  306  as shown in FIG. 14. An elastomeric O-ring  308  is positioned around a lower portion of the plunger  306  and is located in a groove  310  defined in the plunger  306  as shown in FIG. 14. A threaded retainer  314  is positioned around an upper portion of the plunger  306 . The retainer  314  possesses a substantially annular configuration. The retainer  314  includes a number of channels  316  defined therein so as to allow fluid to flow through the retainer  314 . The retainer  314  is threadingly received by a complementary threaded portion  315  defined in the sidewall of the pressure accumulator  76  at a location within the recess  304  (see FIG. 13). A spring  318  is positioned around the plunger  306  and interposed between the retainer  314  and a flange portion  320  of the plunger  306 .  
         [0058]    During operation, if pressure within the pressure accumulator  76  exceeds a certain value (e.g. 35-45 psi), liquid pushes the plunger  306  in the direction of arrow  322  (see FIG. 13) against the spring bias of the spring  318 . This movement of the plunger  306  causes O-ring  308  to become unseated so that liquid flows through a port  324  defined in the sidewall of the accumulator  76 . Once liquid flows through port  324 , it advances around the plunger  306  and the spring  318 , and then though the channels  316  defined in the retainer  314 , and thereafter advances to a location outside of the pressure accumulator  76 . Liquid advances in such a manner until pressure within the pressure accumulator  76  diminishes to a certain value such that the spring bias of spring  318  can urge the O-ring  308  back to its seated position in contact with the sidewall of the accumulator  76  as shown in FIG. 13 whereby fluid flow through the port  324  is occluded.  
         [0059]    The above-identified design could be further modified by providing the pressure relief valve  300  at a neck portion  330  of the pressure accumulator  76 , as opposed to an intermediate sidewall portion  332  as shown in FIG. 13. Obviously, the neck portion  330  would have to be modified to possess the width and length sufficient to accommodate the pressure relief valve  300 .  
         [0060]    Another modification of the pump  78  of FIGS.  2 - 8  which is possible is to alter the configuration of the pump so that the pressure relief flow path as shown in FIG. 8 does not exist but rather a new pressure relief flow path exists as shown in FIG. 15. In particular, each of the piston housings  123 ,  125  would possess a port  500  which leads to a channel  502  defined within the housing of the pump  78 . In turn, the channel  502  is in fluid communication with another port  504  defined in the housing of the pump  78  which leads to the supply line of the pump  78 . Thus, during operation, when a certain pressure is reached within each of the piston housings  123 ,  125 , liquid advances through the respective port  500  thereby moving a respective ball  506  out of the way by compressing a spring  508 . Liquid can then flow through the ports  500 , the channel  502 , and the port  504  and then back to the supply line of the pump  78  as shown by the arrows in FIG. 15. In this manner, excess pressure is safely vented back to the supply line of the pump thereby facilitating easy pushing and pulling of the pressure sprayer  20  and avoiding damage to the pump due to overpressurization of the accumulator  76 .  
         [0061]    Yet a further modification of the pump  78  of FIGS.  2 - 8  which is possible is to provide a bracket  600  which is secured to the outside of the housing of the pump  78  as shown in FIGS.  16 - 18 . The bracket  600  includes a pair of legs  602  extending outwardly from a main body portion  604  as shown in FIG. 16. When secured to the housing of the pump  78  as shown in FIGS.  16 - 18 , the bracket  600  functions to guide the piston shaft  108  during reciprocation thereof. In particular, when the bracket  600  is secured to the housing of the pump  78 , and the piston shaft  108  is reciprocating, a pair of ribs  606  which are attached to the piston shaft  108  slidingly contact an inner surface  607  of the main body portion  604  so as to help guide the piston  122  within the piston housing  123 . Note that while it is possible to provide a bracket  600  on each side of the pump so as to help guide both pistons  122 ,  124  within its respective piston housing  123 ,  125 , in the preferred embodiment only one bracket is provided to help guide the piston  122  within the piston housing  123 . Note that this bracket  600  is provided on the axle side of the pump (i.e. the side of the pump  78  which is closest to the axle portions  92  and  94  - see FIG. 4). It should be appreciated that a significant amount of torque is transferred through the pump  78  during operation of the pressure sprayer  20 . The bracket  600  helps support the yoke  114  including the piston shaft  108  from deflecting or otherwise deforming during such operation.  
         [0062]    Moreover, it is possible to modify the pressure sprayer  20  (see FIG. 10) so that the hose  100  is in fluid communication with a boom assembly  400  (shown in phantom in FIG. 10), as opposed to the spray wand  102 . The boom assembly  400  would function to receive the flow of liquid from the hose  100  and distribute the liquid to a plurality of nozzles  402  located along the length of the boom assembly  400 . Of course, during operation, liquid flow to the boom assembly could be selectively actuated, via a valve mechanism (not shown), so that the liquid flow can occur at the desire of the user.  
         [0063]    Moreover, it is further possible to modify the pressure sprayer  20  (see FIG. 10) so that the number of wheels possessed by the pressure sprayer is greater than or less than two. For instance, the sprayer may have three wheels which actuate the pump  78 . Also, it is possible for the sprayer  20  to have only a single wheel which actuates the pump  78 . In sum, Applicants&#39; invention contemplates the use of any number of wheels.  
         [0064]    Furthermore, it is possible to modify the pressure sprayer  20  of FIGS.  1 - 10  so that the pump  78  does not operate based on movement of a cam. For instance, the sprayer may be modified so that a gear mechanism (not shown) is interposed between the wheel axles  92 ,  94  and the pump  78 . The gear mechanism would be operable to transfer force from the rotating wheel axles  92 ,  94  to the pump  78 . In other words, operation of the pump  78  would be based on movement of at least one gear which is coupled to the wheel axle  92  or  94  (or both). Preferably, in this particular embodiment, a series of gears would be operable to transfer force from the rotating wheel axles  92 ,  94  to the pump  78 .  
         [0065]    There are a plurality of advantages of the present invention arising from the various features of the pressure sprayer described herein. It will be noted that alternative embodiments of the pressure sprayer of the present invention may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the pressure sprayer that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present invention as defined by the appended claims.