Speedup device for reciprocating cylinders

Claim 1

In a machine utilizing a fluid actuated reciprocating piston/cylinder mechanism, a power transmitting rod connected to one side of the piston to define a retraction chamber and the side of the piston opposite the power transmitting rod defining an extension chamber, the volume of the retraction chamber being less than the volume of the extension chamber; a directional control valve for alternately fluidly connecting a source of pressurized fluid and a reservoir with a pair of control valve outlets adapted for controlling alternate extension and retraction of the power transmitting rod; wherein the improvement comprises a two valve speed-up valve unit comprising: a speed-up valve housing; an extension chamber valve inlet in fluid communication with one of said control valve outlets; a retraction chamber valve inlet in fluid communication with the other of said control valve outlets; an extension chamber valve outlet in fluid communication with the piston/cylinder extension chamber; a retraction chamber valve outlet in fluid communication with the piston/cylinder retraction chamber; a first fluid passage interconnecting said retraction chamber valve inlet and said retraction chamber valve outlet; a check valve interposed in said first fluid passage and having a first position wherein fluid flow through said first fluid passage is completely blocked and a second position wherein fluid flow is permitted, said check valve being actuated by fluid pressure in said first fluid passage; check valve biasing means for normally biasing said check valve to said first fluid blocking position; a second fluid passage interconnecting said extension chamber valve inlet and said extension chamber valve outlet; a circulation valve means comprising a single unitary piston element, said piston element comprising a solid cylindrical plug having opposed faces with a centrally located valve stem extending from one of said faces for engaging said housing when said circulation valve means is open, said plug being slidable in a bore opening directly into said first passage upstream of said check valve, said circulation valve means being positioned in a third fluid passage comprising a first portion extending between said piston element and said retraction chamber valve outlet and a second portion element extending between said piston element and said extension chamber valve outlet, said first portion joining with said piston element along a longitudinal side of said piston element, and said second portion joining with said piston element along the other face of said piston element, whereby only fluid pressure in said second portion of said third passage can actuate said circulation valve to an open position wherein said first and second portions of said third passage are joined, said circulation valve being normally biased to a closed position by a single circulation valve biasing means interposed between said housing and said one face and surrounding said valve stem wherein fluid flow in said third fluid passage between said first and second portions is blocked; wherein when said power transmitting rod is retracted, said control valve is actuated to fluidly connect said pump with said first fluid passage and to connect said reservoir with said second fluid passage, said pressurized fluid in said first fluid passage acting on said check valve to cause said check valve to assume said second position, whereby fluid flows to said piston/cylinder retraction chamber and, as said power transmitting rod retracts, fluid flows from said extension chamber through said second passage and control valve to said reservoir, said circulation valve assuming said closed fluid blocking position under the force of said circulation valve biasing means and fluid acting on said one face; and wherein when said power transmitting rod is extended, said control valve is actuated to fluidly connect said pump with said second fluid passage, said pressurized fluid in said second fluid passage acting on said circulation valve means to cause said circulation valve means to assume said open position whereby fluid flow in said third fluid passage between said retraction chamber valve outlet and said extension chamber valve outlet is permitted, said check valve assuming said first position under the force of said check valve biasing means, whereby fluid flows from said pump to said piston/cylinder extension chamber and, as said power transmitting rod extends, fluid flows from said retraction chamber through said third fluid passage to said piston/cylinder extension chamber, whereby an increased volume flow rate of fluid flows to said extension chamber during power rod extension to compensate for the increased volume of said extension chamber.