Relief valve unit for hydraulic pressure lines

Claim 2

A safety valve unit for hydraulic pressure lines, comprising a body provided with an inlet and an outlet duct, a relief piston valve mounted in said body and defining two separate chambers, i.e., a front-pressure chamber defined by the front piston face and communicating directly with the inlet duct and A rear or back-pressure chamber communicating with the front chamber through a throttle flow duct, means for maintaining the said relief valve closed whenever the pressure of the liquid is steadily equal in both said separate chambers, an automatic pilot valve in the form of a needle valve disposed in a third chamber connected to the liquid outlet duct, said pilot valve being urged by a spring to closing position and adapted to be opened by the pressure of the liquid in said back-pressure chamber when said pressure exceeds a limit value considered safe, whereafter the said relief piston valve is first instantaneously fully opened by the momentarily prevailing pressure on its front face, due to the automatically reduced back pressure promoted by the opening of said pilot valve and thereafter, after the automatic closing of the said pilot valve, the said back pressure is rebuilt and the relief valve is again closed, and plunger means connected to said relief valve for damping its motion so as to prevent shocks and chatter, said relief and pilot valves, said damping plunger and said body constituting a single unit provided with said inlet and outlet ducts for connecting same to the pressure line of a hydraulic system, means being also provided for connecting said unit to a supporting and connecting block forming an integral part of the said hydraulic system, said block having a partly screw-threaded cylindrical blind bore in which ports are provided in correspondence of the said ducts in said valve unit when the same is fully screwed into operating position.

Claim 3

A safety valve unit for hydraulic pressure lines, according to claim 1, wherein the means for maintaining the relief valve closed whenever the pressure of the liquid is equal on both faces of the relief piston valve are spring means.

Claim 4

A safety valve unit for hydraulic machinery, according to claim 1, wherein said relief valve is of the differential-piston type, having a rear piston face larger than its front piston face.

Claim 5

A safety valve unit for hydraulic machinery, according to claim 1, wherein said relief valve is of the differential-piston type, with its rear face larger than its front face, spring means being provided for additionally urging the valve towards closing position.

Claim 6

A safety vale unit for hydraulic pressure lines, comprising a body, a bore in said body defining a cylindrical cavity closed near its upper end by a partition having a through bore with a valve seat, duct means opening in the sidewall of said bore for the inflow and outflow of fluid, a plug closing said bore above said partition, a spring-urged automatic pilot valve mounted in said plug and cooperating with said valve seat to close it, a tumbler-shaped piston valve having a closed bottom slidably mounted with a tight fit in the upper portion of said cylindrical cavity below the partition, a sleeve fitted into the lower portion of said cylindrical cavity so as to define a second cylindrical cavity of smaller sectional area, the upper edge of said sleeve forming a second valve seat against which the closed bottom of said tumbler-shaped piston valve may bear with a tight fit, a motion-damping plunger rigidly attached in spaced relation to said closed bottom of said tumbler-shaped piston valve and slidably mounted within the lower end section of said sleeve, passage means in the motion-damping plunger for permitting the throttled flow of fluid thereacross, a fluid inlet chamber communicating with said inflow duct means and positioned between the bottom of said tumbler-shaped piston valve and the facing side of said motion-damping plunger, a second chamber in said first cylindrical cavity below said partition and extending into said tumbler-shaped piston valve, a fluid duct through the closed bottom of said tumbler-shaped piston valve, permitting throttled fluid flow between the inlet chamber and said second chamber, and duct means through the wall of said bore above the partition for communicating the piston valve controlled through boRe in the partition with said fluid outflow duct means, said tumbler-shaped piston valve cooperating with said second valve seat to close and open communication between said fluid inlet chamber and said fluid outflow duct means.

Claim 7

A safety vale unit for hydraulic pressure lines, comprising a body, a bore in said body defining a cylindrical cavity closed near its upper end by a partition having a through bore with a valve seat, duct means opening in the sidewall of said bore for the inflow and outflow of fluid, a plug closing said bore above said partition, a spring-urged automatic pilot valve mounted in said plug and cooperating with said valve seat to close it, a tumbler-shaped piston valve having a closed bottom slidably mounted with a tight fit in the upper portion of said cylindrical cavity below the partition, a sleeve fitted into the lower portion of said cylindrical cavity so as to define a second cylindrical cavity of smaller sectional area, the upper edge of said sleeve forming a second valve seat against which the closed bottom of said tumbler-shaped piston valve may bear with a tight fit, a motion-damping plunger rigidly attached in spaced relation to said closed bottom of said tumbler-shaped piston valve and slidably mounted within the lower end section of said sleeve, passage means in the motion-damping plunger for permitting the throttled flow of fluid thereacross, a fluid inlet chamber communicating with said inflow duct means and positioned between the bottom of said tumbler-shaped piston valve and the facing side of said motion-damping plunger, a second chamber in said first cylindrical cavity below said partition and extending into said tumbler-shaped piston valve, a fluid duct through the closed bottom of said tumbler-shaped piston valve, permitting throttled fluid flow between the inlet chamber and said second chamber, and duct means through the wall of said bore above the partition for communicating the piston valve controlled through boRe in the partition with said fluid outflow duct means, said tumbler-shaped piston valve cooperating with said second valve seat to close and open communication between said fluid inlet chamber and said fluid outflow duct means.