Energy dissipation valves for hydraulic cylinders

Abstract

A hydraulic actuator comprises a cylinder, a piston reciprocatingly received within the cylinder, a piston rod connected to the piston and a pressure release mechanism which allows hydraulic fluid to pass from a first side of the piston to a second side of the piston when the actuator encounters shock loading. This permits the piston to move. The pressure relief mechanism includes a passageway extending from the first side of the piston to the second side of the piston and a valve member adjacent to the passageway which releasably engages the piston. The valve member has a closed position where the valve member closes the passageway and engages the piston. A resilient member biases the valve member towards the closed position. A valve member limiter limits movement of the valve member away from the closed position. The resilient member has a rigidity sufficiently great so that movement of the valve member away from the closed position is more dependent upon the rigidity of the resilient member than upon a preload applied to the valve member.

1 . A hydraulic actuator comprising a cylinder, a piston reciprocatingly received within the cylinder, a piston rod connected to the piston and a pressure release mechanism which allows hydraulic fluid to pass from a first side of the piston to a second side of the piston when the actuator encounters shock loading, thereby permitting the piston to move, the pressure relief mechanism including a passageway extending from the first side of the piston to the second side of the piston, a valve member releasably engaging the piston adjacent to the passageway, the valve member having a closed position where the valve member closes the passageway and engages the piston, a resilient member biasing the valve member towards the closed position, and a valve member limiter which limits movement of the valve member away from the closed position, the resilient member having a rigidity sufficiently great so that movement of the valve member away from the closed position is more dependent upon the rigidity of the resilient member than upon a preload applied to the valve member.  
   
   
       2 . The actuator as claimed in  claim 1 , wherein the resilient member has a rigidity between 600 and 1500 lbs/in.  
   
   
       3 . The actuator as claimed in  claim 1 , wherein the resilient member has a rigidity between 750 and 1000 lbs/in.  
   
   
       4 . The actuator as claimed in  claim 1 , wherein the resilient member is a spring and has a rigidity of generally 875 lbs/in.  
   
   
       5 . The actuator as claimed in  claim 4 , wherein the spring is a coil spring.  
   
   
       6 . The actuator as claimed in  claim 1 , wherein the limiter limits movement of the valve member away from the piston such that fluid flow through the passageway is controlled by a gap between the valve member and the piston.  
   
   
       7 . The actuator as claimed in  claim 5 , the limiter including an elongated spring guide, the coil spring extending about the spring guide, the spring guide contacting the valve member at a first end thereof, the spring guide having a second end, and a stop member, the second end approaching the stop member when the valve member moves away from the piston and the second end contacting the stop member to limit movement of the valve member away from the piston.  
   
   
       8 . The actuator as claimed in  claim 7 , wherein the spring guide includes an enlarged portion adjacent to the valve member, the enlarged portion having a flat surface contacting the valve member.  
   
   
       9 . The actuator as claimed in  claim 8 , wherein the valve member is a poppet.  
   
   
       10 . The actuator as claimed in  claim 8 , wherein the valve member is a ball.  
   
   
       11 . The actuator as claimed in  claim 1 , wherein movement of the valve member away from the closed position is more dependent upon the rigidity of the resilient member after the valve member is initially cracked open than upon the preload applied to the valve member.  
   
   
       12 . The actuator as claimed in  claim 1 , wherein the movement of the valve member away from the closed position is more dependent upon the rigidity of the resilient member than upon the preload applied to the valve member after the valve member is initially cracked open.  
   
   
       13 . A marine craft with a tiltable drive unit at the stern, the drive unit having a hydraulic actuator connected to the craft, the actuator comprising a cylinder, a piston reciprocatingly received within the cylinder, a piston rod connected to the piston and a pressure relief mechanism which allows hydraulic fluid to pass from a first side of the piston to a second side of the piston when the drive unit encounters an obstacle, thereby permitting the drive unit to tilt, the pressure release mechanism including a passageway extending from the first side of the piston to the second side of the piston, a valve member releasably engaging the piston adjacent to the passageway, the valve member having a closed position where the valve member closes the passageway and engages the piston, a resilient member biasing the valve member towards the closed position, and a valve member limiter which limits movement of the valve member away from the closed position, the resilient member having a rigidity sufficiently great so that movement of the valve member away from the closed position is more dependent upon the rigidity of the resilient member than upon a preload applied to the valve member.  
   
   
       14 . The craft as claimed in  claim 13 , wherein the resilient member has a rigidity between 600 and 1500 lbs/in.  
   
   
       15 . The craft as claimed in  claim 13 , wherein the resilient member has a rigidity between 750 and 1000 lbs/in.  
   
   
       16 . The craft as claimed in  claim 13 , wherein the resilient member is a spring and has a rigidity of generally 875 lbs/in.  
   
   
       17 . The craft as claimed in  claim 16 , wherein the spring is a coil spring.  
   
   
       18 . The craft as claimed in  claim 13 , wherein the limiter limits movement of the valve member away from the piston such that fluid flow through the passageway is controlled by a gap between the valve member and the piston.  
   
   
       19 . The craft as claimed in  claim 16 , the limiter including an elongated spring guide, the coil spring extending about the spring guide the spring guide contacting the valve member at a first end thereof, the spring guide having a second end, and a stop member, the second end approaching the stop member when the valve member moves away from the piston and the second end contacting the stop member to limit movement of the valve member away from the piston.  
   
   
       20 . The craft as claimed in  claim 19 , wherein the spring guide includes an enlarged portion adjacent to the valve member, the enlarged portion having a flat surface contacting the valve member.  
   
   
       21 . The craft as claimed in  claim 20 , wherein the valve member is a poppet.  
   
   
       22 . The craft as claimed in  claim 20 , wherein the valve member is a ball.  
   
   
       23 . The craft as claimed in  claim 13 , wherein the actuator is a trim actuator.  
   
   
       24 . The craft as claimed in  claim 13 , wherein the actuator is a tilt actuator.  
   
   
       25 . The craft as claimed in  claim 13 , wherein the movement of the valve member away from the closed position is more dependent upon the rigidity of the resilient member than upon a preload applied to the valve member after the valve member is initially cracked open.  
   
   
       26 . A method for configuring a hydraulic actuator connecting a tiltable drive unit to a marine craft to permit the drive unit to tilt when the drive unit encounters an obstacle, the actuator including a cylinder with a piston reciprocatingly received therewithin, the method comprising: 
 providing the piston with a passageway extending from a first side thereof to a second side thereof;    providing a valve member having an open position where the passageway is open and a closed position where the passageway is closed;    biasing the valve member towards the closed position with a resilient member having sufficient rigidity so that movement of the valve member towards the open position, when the drive unit encounters the obstacle, is more dependent upon the rigidity of the resilient member than upon a preload applied to the valve member.    
   
   
       27 . The method as claimed in  claim 26 , wherein movement of the valve member away from the closed position is limited so as to control flow of fluid from the first side of the piston to the second side of the piston when the valve member is in the open position.  
   
   
       28 . The method as claimed in  claim 26 , wherein the valve member is biased with a resilient member, the resilient member having a rigidity between 600 and 1500 lbs/in.  
   
   
       29 . The method as claimed in  claim 26 , wherein the resilient member has a rigidity between 750 and 1000 lbs/in.  
   
   
       30 . The method as claimed in  claim 26 , wherein the resilient member is a spring and has a rigidity of generally 875 lbs/in.  
   
   
       31 . The method as claimed in  claim 26 , wherein the movement of the valve member away from the closed position is more dependent upon the rigidity of the resilient member after the valve member is initially cracked open than upon the preload applied to the valve member.  
   
   
       32 . A shock absorbing apparatus comprising a fluid actuator having a piston with a passageway therethrough and a valve controlling fluid flow from one side of the piston to another side thereof, the valve including a closure member biased towards a valve seat by a resilient member and a stop limiting movement of the closure member away from the valve seat, the resilient member having a rigidity such that initial opening of the closure member with respect to the valve seat, due to pressure of fluid in the passageway, is determined by preload applied to the closure member by the resilient member, movement of the closure member further away from the valve seat, until limited by said stop, is determined more by the rigidity of the resilient member than the preload and fluid flow through the passageway is limited by an orifice between the closure member and the valve seat when the stop limits movement of the closure member away from the valve seat.  
   
   
       33 . A method of absorbing shock using a fluid actuator with a piston having a passageway therethrough and a valve controlling fluid flow from one side of the piston to another side thereof, the valve including a closure member biased towards a valve seat by a resilient member, the method comprising: 
 applying a preload to the closure member with the resilient member such that initial opening of the closure member with respect to the valve seat, due to pressure of fluid in the passageway, is determined by the preload applied to the closure member by the resilient member;    selecting a rigidity for the resilient member such that movement of the closure member further away from the valve seat is determined more by the rigidity of the resilient member than the preload; and    limiting movement of the closure member away from the valve seat so that fluid flow through the passageway is controlled by an orifice between the closure member and the valve seat when the movement of the closure member away from the valve seat is so limited.    
   
   
       34 . A method for configuring a hydraulic actuator connecting a movable member to a larger body to permit the movable member to move when the movable member encounters shock loading, the actuator including a cylinder with a piston reciprocatingly received therewithin, the method comprising: 
 providing the piston with a passageway extending from a first side thereof to a second side thereof;    providing a valve member having an open position where the passageway is open and a closed position where the passageway is closed;    biasing the valve member towards the closed position with a resilient member having sufficient rigidity so that movement of the valve member towards the open position, when the movable member encounters the shock loading, is more dependent upon the rigidity of the resilient member than upon a preload applied to the valve member.    
   
   
       35 . The method as claimed in  claim 34 , wherein movement of the valve member away from the closed position is limited so as to control flow of fluid from the first side of the piston to the second side of the piston when the valve member is in the open position.  
   
   
       36 . The method as claimed in  claim 34 , wherein the valve member is biased with a resilient member, the resilient member having a rigidity between 600 and 1500 lbs/in.  
   
   
       37 . The method as claimed in  claim 34 , wherein the resilient member has a rigidity between 750 and 1000 lbs/in.  
   
   
       38 . The method as claimed in  claim 34 , wherein the resilient member is a spring and has a rigidity of generally 875 lbs/in.  
   
   
       39 . The method as claimed in  claim 34 , wherein the movement of the valve member away from the closed position is more dependent upon the rigidity of the resilient member after the valve member is initially cracked open than upon the preload applied to the valve member.