Patent Publication Number: US-6981852-B2

Title: Strainer and valve release

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   Reference is made to the following copending and commonly assigned U.S. Patent Applications by the same inventors, each of which was filed on the same day as the instant application, and each of which is hereby expressly incorporated by reference: 
   i) IMPROVED SWASHPLATE PUMP, Ser. No. 10/427,447; and 
   ii) FAN BAFFLE, Ser. No. 10/427,448. 

   FIELD OF THE INVENTION 
   This invention relates to the field of pumps for paint and related coating materials. 
   BACKGROUND OF THE INVENTION 
   In the past, it has been known to provide strainers for preventing foreign solids over a certain size from being ingested into a paint pump. It has further been known to provide a mechanism for releasing a moveable element in an inlet check valve of a paint pump which has become stuck in a closed position due to inadequate cleaning. 
   Heretofore, however, there has not been an apparatus that has combined the features and functions of a strainer with a valve release. The present invention provides such a combination with attendant reduction in the complexity and cost associated with the prior art approach of using separate parts to perform the separate functions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a paint pump apparatus useful in the practice of the present invention. 
       FIG. 2  is a fragmentary cutaway view, partly in section, of a portion of the apparatus of FIG.  1 . 
       FIG. 3  is a perspective view of a combined strainer and valve release part useful in the practice of the present invention. 
       FIG. 4  is a top plan view of the combined strainer and valve release part of FIG.  3 . 
       FIG. 5  is a bottom plan view of the combined strainer and valve release part of FIG.  3 . 
       FIG. 6  is a side section view along line  6 — 6  of FIG.  5 . 
       FIG. 7  is a side section view similar to that of  FIG. 6 , except showing an alternative embodiment for the combined strainer and valve release part of the present invention. 
       FIG. 8  is a side elevation view of the combined strainer and valve release part of FIG.  3 . 
       FIG. 9  is an enlarged fragmentary view of a portion of the combined strainer and valve release part of  FIG. 4  illustrating a preferred hole pattern for the strainer. 
   

   DETAILED DESCRIPTION 
   Referring to the Figures, and most particularly to  FIGS. 1 and 2 , a paint pump apparatus  20  useful in the practice of the present invention may be seen. Apparatus  20  is intended to pump paint and similar coatings at high pressure to a spray gun (not shown) for application to a surface to be coated via airless spraying. 
   Apparatus  20  includes a paint reservoir  22  and a pump assembly  24  carried by a frame  26 . Reservoir  22  may have a cover  28 . Frame  26  preferably has a handle portion  30  and a pair of foot portions  32 ,  34 . Foot portions  32  and  34  are received in a base  36  which supports pump assembly  24 . It is to be understood that a high pressure hose (not shown) is connected to an outlet  38  of the pump assembly  24  after a cap  40  is removed. The high pressure hose is also connected to an airless spray gun (not shown) for delivering paint or other coating material to a surface (not shown) desired to be coated. An inlet  42  of the pump assembly  24  is in fluid communication with reservoir  22 , and sealed against leakage therebetween by one or more O-rings  44 . It is to be understood that paint (or other similar coating material) is delivered by gravity from reservoir  22  to inlet  42  of the paint pump assembly  24 . As is conventional, a return tube  46  is provided from a pump and valve housing  48  containing inlet  42  and outlet  38 . Return tube  46  will return paint from the pump to the reservoir during a “priming” mode. A mechanical switch  50  enables transfer from the “priming” mode to a “run” mode wherein paint is delivered to the outlet  38  instead of the return tube  46 . An ON-OFF electrical switch (not shown) enables power from a power cord  54  (when connected to electrical supply, not shown) to be delivered to an electric motor (not shown). The motor or another form of prime mover, such as a gasoline engine (also not shown) provides mechanical power for pump assembly  24  which includes a piston  84  axially reciprocating in a cylinder or pumping chamber  119 . An inlet check valve  74  is positioned in inlet  42 . Similarly an outlet check valve  76  is positioned in outlet  38 . 
   The inlet check valve has a valve member in the form of an inlet poppet  60  carrying an O-ring  62  and urged by a spring  64  to seal against an inlet seat  66 . An inlet seat lid  68  supports the inlet poppet  60  and spring  64 . Spring  64  is retained by a spring stop  70  which is preferably secured to a stem  72  of the inlet poppet by a pushnut  78  or by thermally fusing the stem  72  to the stop  70 . 
   Referring now to  FIGS. 3-6  and  8 , a strainer and valve release part  80  is preferably made in the form of a single molded part preferably formed entirely of polyethylene. Part  80  preferably has a screen side wall  82 , a pushrod  84 , an actuator tab  86 , and a screen top wall  88 . The side wall  82  and top wall  88  are preferably about 0.090 inches thick and preferably each have a perforation pattern of through holes  90  to provide the function of a strainer. When the part  80  is installed as shown in  FIG. 2 , actuator tab  86  may be depressed to move the pushrod  84  against the stem  72  of the inlet check valve  74 , to break any adhesion of the inlet poppet  60  or O-ring  62  with seat  66 , as, for example that which may occur when valve  74  is incompletely cleaned. In addition to functioning as a strainer, the top wall  88  of part  80  also acts both as a support for pushrod  84  and tab  86 , and further acts as a return spring for pushrod  84  to move pushrod  84  away from the stem  72  of the inlet check valve  74  when the tab  86  is released, to avoid interference with the normal operation of valve  74 . In the embodiment shown, the pushrod  84  extends 2⅛ inches below the bottom surface of top wall  88 ; however, it is to be understood that the pushrod  84  is preferably designed to extend to be close to, but not touch the top of stem  72 , when the valve  74  is closed, and the part  80  is in its rest or “relaxed” or unactivated state. Tab  86  in the embodiment shown extends 7/16 inch above the upper surface of top wall  88 ; however, it is to be understood that tab  86  may be sized and shaped as desired, to direct a user to depress the top wall  88  of part  80  preferably immediately above pushrod  84 , for most efficient and convenient operation of the valve release function of part  80 . 
   Referring now to  FIG. 7 , an alternative embodiment of strainer and release part  80 ′ may be seen in which the actuator tab  86 ′ is elongated. With this embodiment, the tab  86 ′ may be sized to project up sufficiently high so that when reservoir  22  is filled with paint, the tab  86 ′ projects above the top surface of the paint in the reservoir, enabling a user to actuate the pushrod  84  without having to reach below the top surface of the paint. 
   A side view of the strainer and release part  80  may be seen in  FIG. 8. A  plurality of stiffening ribs or pillars  90  may be provided to add strength and rigidity to the part  80 . 
   Referring now also to  FIG. 9 , a preferred hole pattern for part  80  may be seen. In the embodiment shown, a diagonal hole-to-hole dimension  92  is preferably 0.078 inches, and a “square” hole-to-hole dimension  94  is preferably 0.110 inches, with a hole diameter  96  of 0.040 inches. It is to be understood that these dimensions may be varied while still remaining within the scope of the present invention defined by the claims. 
   The combined strainer and valve release of the present invention may thus be seen to be a strainer positionable with respect to the inlet check valve and having at least one surface with apertures therethrough to permit flow of liquid to the check valve and to prevent movement of solids larger than the apertures from passing through the surface to the check valve; and a pushrod connected to the strainer and located in a rest position adjacent a movable member of the check valve wherein the pushrod is movable to an actuated position to displace the movable member wherein at least a portion of the strainer returns the pushrod from the actuated position to the rest position when the pushrod is released from the actuated position. The portion of strainer that returns the pushrod is made up of a resilient surface of the strainer. The strainer includes a perforated enclosure with a portion of the strainer having deformable resiliency to allow movement of the pushrod from the rest position to the actuated position. An actuator tab connected to the strainer for moving the pushrod from the rest position to the actuated position, with the actuator tab preferably aligned with the pushrod and the perforated wall interposed between the actuator tab and the pushrod and wherein the perforated wall is the portion of the strainer that returns the pushrod to the rest position when the pushrod is released from the actuated position. Preferably, at least a portion of the perforated wall is disposed generally perpendicularly to the pushrod. The actuator tab extends a predetermined distance away from the perforated wall. In the embodiment shown, the strainer and pushrod are formed as a molded part made of generally homogeneous polyethylene material. 
   In another aspect, the present invention may be seen to be a combined paint pump inlet check valve and unitary strainer and valve release structure wherein the inlet check valve has a movable member and the unitary strainer and valve release structure including a strainer located at an inlet of the inlet check valve; and a pushrod formed integrally with the strainer and extending to a location adjacent the movable member of the inlet check valve in a rest position and displaceable to an actuated position wherein the pushrod displaces the movable member of the inlet check valve wherein the strainer has a resilient portion which returns the pushrod from the actuated position to the rest position when the pushrod is released. The strainer has a perforated wall and the pushrod is mounted on the perforated wall and integrally formed of the same polyethylene material. 
   In still another aspect, the present invention includes a method of releasing a stuck inlet check valve in a paint pump comprising the steps of locating a combined strainer and valve release structure at an inlet of an inlet check valve of a paint pump wherein the strainer has a pushrod extending to a rest position adjacent a movable member of the inlet check valve; manually displacing the pushrod from the rest position to an actuated position by pressing on the strainer to dislodge the movable member of the inlet check valve from a valve seat in the inlet check valve; and manually releasing the strainer and causing the strainer to return the pushrod to the rest position. In practicing this method, the strainer and valve release structure may include an actuator tab. The step of manually displacing the pushrod may include manually urging the actuator tab to press on the strainer. 
   The invention is not to be taken as limited to all the details thereof as modifications and variations thereof may be made without departing from the spirit or scope of the invention.