Pressure washer with pressure bypass

Claim 2

A pressure washer for delivering liquid under pressure, the pressure washer including a spray nozzle for spraying liquid, an outlet conduit connected for delivering liquid to the spray nozzle, an inlet conduit for receiving liquid from a liquid supply, a pump connected between the inlet conduit and the outlet conduit and effective for pumping liquid from the inlet conduit to the outlet conduit, actuation means connected with the spray nozzle for selectively permitting or blocking exit from the spray nozzle of liquid pumped by the pump, a bypass conduit connected between the inlet conduit and the outlet conduit and in parallel with the pump, and a liquid bypass system associated with the bypass conduit for selectively closing and opening the bypass conduit to flow of liquid through the bypass conduit, the bypass system comprising: a bypass chamber in liquid communication with the bypass conduit, the bypass chamber having a bypass chamber inlet in fluid communication with the outlet conduit for receiving liquid from the outlet conduit and having a bypass chamber outlet for delivering liquid through the bypass conduit to the inlet conduit; a shuttle movable in the bypass chamber between a first position in which the shuttle blocks liquid communication between the bypass chamber and the bypass conduit and a second position which permits liquid communication between the bypass chamber and the bypass conduit; the shuttle having a first end surface area in the bypass chamber which is exposed to liquid pressure at the chamber inlet and a second end surface area in the bypass chamber which is exposed to liquid pressure in the chamber outlet wherein the second end surface area is larger than the first end surface area; a liquid passage which extends through the shuttle from the first end surface area to the second end surface area of the shuttle, the liquid passage being tapered in cross-section along substantially the entire distance from the first end surface area tot he second end surface area for producing in the bypass chamber a pressure drop across the shuttle from the first end surface area to the second end surface area when liquid is passing through the liquid passage, the pressure drop being such that the shuttle becomes disposed in the first position when liquid is passing through the liquid passage and out the spray nozzle during which time the liquid pressure at the chamber inlet is greater than the liquid pressure at the chamber outlet by a predetermined amount, and otherwise the shuttle is moved, by the liquid pressures at the chamber inlet and the chamber outlet, toward the second position; and biasing means at the bypass chamber for biasing the shuttle toward the second position.

Claim 3

The pressure washer of claim 1, wherein the shuttle has an axis along which the shuttle moves in the bypass chamber, and the liquid channel passes generally axially through the shuttle.

Claim 4

The pressure washer of claim 2, wherein the shuttle has a substantially circular cross-section.

Claim 5

The pressure washer of claim 2, further comprising first and second seals disposed axially spaced apart and extending circumferentially around the shuttle, the first seal being so placed with respect to the chamber inlet and the bypass conduit and the bypass chamber being so shaped and dimensioned as to seal the chamber inlet from the bypass conduit in the first position of the shuttle; and the second seal being so placed with respect to the chamber inlet and the bypass conduit and the bypass chamber being so shaped and dimensioned as to seal the chamber outlet from the bypass conduit in all positions of the shuttle.

Claim 6

The pressure washer of claim 4, wherein the bypass chamber has first, second and third axially extending axial regions; the first region being toward the chamber inlet and having a smaller cross-section, the second region being toward the chamber outlet and having a larger cross-section, and the third region being disposed between the first and the second regions; the first seal extending around a portion of the shuttle which is movable into the first region and toward the third region of the chamber, and the second seal extending around another portion of the shuttle wherein the second seal is at all times in sealing and sliding contact with a wall surrounding the bypass chamber.

Claim 7

The pressure washer of claim 5, wherein the bypass conduit meets the bypass chamber in the third region thereof.

Claim 8

The pressure washer of claim 6, wherein the first position of the shuttle places the first seal in contact with the wall of the bypass chamber which defines the third region and the third region is so placed that the first seal blocks liquid communication from the bypass chamber to the bypass conduit when the shuttle is in the first position; and the second position of the shuttle places the first seal such that it is radially spaced from the wall of the bypass chamber defining the first region of the bypass chamber and is spaced in a manner for permitting liquid flow from the bypass chamber to the bypass conduit.

Claim 9

The pressure washer of claim 1, wherein the biasing means comprises a spring acting on the shuttle.

Claim 10

The pressure washer of claim 8, wherein the spring is in the bypass chamber and engages the shuttle to push it toward the second position and the spring is so placed and of a type to be tensioned as the shuttle is moved to the forward position.

Claim 11

The pressure washer of claim 4, wherein the liquid passage includes an upstream end that is toward the first surface area and a downstream end that is narrowed in cross-section relative to the upstream end.

Claim 12

A pressure washer for delivering liquid under pressure, the pressure washer comprising: a spray nozzle for spraying liquid; an outlet conduit connected for delivering liquid to the spray nozzle; an inlet conduit for receiving liquid from a liquid supply; a pump connected between the inlet conduit and the outlet conduit and effective for pumping liquid from the inlet conduit to the outlet conduit; actuation means connected with the spray nozzle for selectively permitting or blocking exit form the spray nozzle of liquid pumped by the pump; a bypass conduit connected between the inlet conduit and the outlet conduit and in parallel with the pump; and a liquid bypass system associated with the bypass conduit for selectively closing and opening the bypass conduit to flow of liquid through the bypass conduit, the bypass system including a bypass chamber in liquid communication with the bypass conduit, a bypass chamber inlet in fluid communication with the outlet conduit for receiving liquid from the outlet conduit and a bypass chamber outlet for delivering liquid through the bypass conduit to the inlet conduit; a shuttle in and movable axially along the bypass chamber, the shuttle having an inlet side facing toward the entrance of liquid into the bypass chamber and having an outlet side facing toward the exit of liquid from the bypass chamber into the outlet conduit, the shuttle being so shaped and being movable in the bypass chamber between a first position in which the shuttle blocks fluid communication between the bypass chamber and the bypass conduit and a second position which permits fluid communication between the bypass chamber and the bypass conduit, the shuttle and the bypass chamber being sized so that a surface area of the shuttle inlet side is smaller than a surface area of the shuttle outlet side, for normally urging the shuttle to the second position when the pressure in the bypass chamber at the outlet side of the shuttle approaches the pressure in the bypass chamber at the inlet side of the shuttle; a liquid passage having a length which extends through the shuttle from the inlet side to the outlet side, the passage being tapered over substantially the entire length thereof for creating a pressure drop across the shuttle when liquid flows from the spray nozzle and through the outlet conduit, and the surface areas of the inlet and outlet sides being so sized and the narrowed region of the liquid passage being of such cross-section that the pressure drop reduces the pressure at the outlet side of the shuttle as to cause the pressure at the inlet side of the shuttle to move the shuttle to the first position; and biasing means at the bypass chamber for biasing the shuttle toward the second position.

Claim 13

A pressure washer for delivering liquid under pressure, the pressure washer comprising: a spray nozzle for spraying liquid; an outlet conduit connected for delivering liquid to the spray nozzle; an inlet conduit for receiving liquid from a liquid supply; a pump connected between the inlet conduit and the outlet conduit and effective for pumping liquid from the inlet conduit to the outlet conduit; actuation means connected with the spray nozzle for selectively permitting or blocking exit form the spray nozzle of liquid pumped by the pump; a bypass conduit connected between the inlet conduit and the outlet conduit and in parallel with the pump; and a liquid bypass system associated with the bypass conduit for selectively closing and opening the bypass conduit to flow of liquid through the bypass conduit, the bypass system including a bypass chamber in liquid communication with the bypass conduit, a bypass chamber inlet in fluid communication with the outlet conduit for receiving liquid from the outlet conduit and a bypass chamber outlet for delivering liquid through the bypass conduit to the inlet conduit; a shuttle in and movable axially along the bypass chamber, the shuttle having an inlet side facing toward the entrance of liquid into the bypass chamber and having an outlet side facing toward the exit of liquid from the bypass chamber into the outlet conduit, the shuttle being so shaped and being movable in the bypass chamber between a first position in which the shuttle blocks fluid communication between the bypass chamber and the bypass conduit and a second position which permits fluid communication between the bypass chamber and the bypass conduit, the shuttle and the bypass chamber being sized so that a surface area of the shuttle inlet side is smaller than a surface area of the shuttle outlet side, for normally urging the shuttle to the second position when the pressure in the bypass chamber at the outlet side of the shuttle approaches the pressure in the bypass chamber at the inlet side of the shuttle; a liquid passage having a length which extends through the shuttle from the inlet side to the outlet side, the passage being tapered over substantially the entire length thereof for creating a pressure drop across the shuttle when liquid flows from the spray nozzle and through the outlet conduit, and the surface areas of the inlet and outlet sides being so sized and the narrowed region of the liquid passage being of such cross-section that the pressure drop reduces the pressure at the outlet side of the shuttle as to cause the pressure at the inlet side of the shuttle to move the shuttle to the first position; and biasing means at the bypass chamber for biasing the shuttle toward the second position.

Claim 14

The pressure washer of claim 11, further comprising first and second seals disposed axially spaced apart and extending circumferentially around the shuttle, the first seal being so placed with respect to the chamber inlet and the bypass conduit and the bypass chamber being so shaped and dimensioned as to seal the chamber inlet from the bypass conduit in the first position of the shuttle; and the second seal being so placed with respect to the chamber inlet and the bypass conduit and the bypass chamber being so shaped and dimensioned as to seal the chamber outlet from the bypass conduit in all positions of the shuttle.

Claim 15

The pressure washer of claim 11, wherein the liquid passage includes an upstream end that is toward the first surface area and a downstream end that is toward the second surface area and is narrower in cross-section than the upstream end.