Protection mechanism on an implement

Abstract

An implement on a power machine includes at least first and second auxiliary couplers configured to be coupled to a source of hydraulic fluid on the power machine, an hydraulic actuator having a base end coupled to the first auxiliary coupler and a rod end coupled to the second auxiliary coupler and a protection mechanism that is configured to receive hydraulic fluid during normal retraction and extension of the hydraulic actuator. When an unintended external tension force causes the hydraulic actuator to forcibly extend, the protection mechanism is configured to provide hydraulic fluid to the base end of the hydraulic actuator. When an unintended external compression force causes the hydraulic actuator to forcibly retract, the protection mechanism is configured to receive excess hydraulic fluid from the base end.

What is claimed is: 
     
         1 . An implement on a power machine comprising:
 at least first and second auxiliary couplers configured to be coupled to a source of hydraulic fluid on the power machine;   a hydraulic actuator having a base end coupled to the first auxiliary coupler and a rod end coupled to the second auxiliary coupler;   a protection mechanism that is configured to receive hydraulic fluid during normal retraction and extension of the hydraulic actuator;   wherein when an unintended external tension force causes the hydraulic actuator to forcibly extend, the protection mechanism is configured to provide hydraulic fluid to the base end of the hydraulic actuator and wherein when an unintended external compression force causes the hydraulic actuator to forcibly retract, the protection mechanism is configured to receive excess hydraulic fluid from the base end.   
     
     
         2 . The implement of  claim 1 , wherein the protection mechanism comprises an accumulator situated between a plurality of check valves, wherein the accumulator is charged with hydraulic fluid during normal retraction and extension of the hydraulic actuator after pressure in the hydraulic circuit reaches a threshold pressure. 
     
     
         3 . The implement of  claim 2 , wherein when the unintended external tension force causes the hydraulic actuator to forcibly extend, a vacuum condition occurs and hydraulic fluid is taken from the accumulator to fill the base end of the hydraulic actuator, and when the unintended external compression force causes the hydraulic actuator to forcibly retract a differential volume of hydraulic fluid is accounted for by allowing the accumulator to receive excess hydraulic fluid from the base end. 
     
     
         4 . The implement of  claim 2 , wherein when the implement comes up against an immovable object during normal extension of the hydraulic actuator, hydraulic fluid builds up pressure on the base end of the actuator until exceeding a first check valve pressure threshold, fills the accumulator to an extent that the accumulator is not already fully charged and proceeds through a second check valve and through the second auxiliary coupler back to the power machine. 
     
     
         5 . The implement of  claim 4 , wherein when the implement comes up against the immovable object during normal retraction of the hydraulic actuator, hydraulic fluid builds up pressure on the rod end of the actuator until exceeding a third check valve pressure threshold, fills the accumulator to the extent that the accumulator is not already fully charged and proceeds through a fourth check valve and through the first auxiliary coupler back to the power machine. 
     
     
         6 . The implement of  claim 1 , wherein the protection mechanism comprises a case drain line connected to a case drain coupler that is coupled to the source of hydraulic fluid on the power machine. 
     
     
         7 . The implement of  claim 6 , wherein the case drain line includes an actuator relief valve that during at least a portion of normal retraction and extension of the hydraulic actuator is configured to prevent the case drain line and the case drain coupler from being used. 
     
     
         8 . The implement of  claim 7 , wherein when the unintended external tension force causes the hydraulic actuator to forcibly extend a vacuum condition occurs and hydraulic fluid is taken from the power machine through the case drain line to fill the base end of the hydraulic actuator and wherein when the unintended external compression force causes the hydraulic actuator to forcibly retract a differential volume of hydraulic fluid is accounted for by allowing the case drain line to receive excess hydraulic fluid from the base end of the hydraulic actuator to deliver to the power machine. 
     
     
         9 . The implement of  claim 7 , wherein when the implement comes up against an immovable object during normal extension of the hydraulic actuator, hydraulic fluid builds up pressure on the base end of the actuator until exceeding a pressure threshold of the actuator relief valve and causing the actuator relief valve to receive hydraulic fluid from the first auxiliary coupler, direct a first portion of the hydraulic fluid from the first auxiliary coupler to the case drain line and direct a second portion of the hydraulic fluid from the first auxiliary coupler through the second auxiliary coupler back to the power machine. 
     
     
         10 . The implement of  claim 9 , wherein when the implement comes up against the immovable object during normal retraction of the hydraulic actuator, hydraulic fluid builds up pressure on the rod end of the actuator until exceeding a pressure threshold of the actuator relief valve and causing the actuator relief valve to receive hydraulic fluid from the second auxiliary coupler, direct a first portion of the hydraulic fluid from the second auxiliary coupler to the case drain line and direct a second portion of the hydraulic fluid from the second auxiliary coupler through the first auxiliary coupler back to the power machine. 
     
     
         11 . The implement of  claim 1 , wherein the protection mechanism comprises a case line drain situated between a plurality of check valves and connected to a case drain coupler that is coupled to the source of hydraulic fluid on the power machine, wherein during at least a portion of normal retraction and extension of the hydraulic actuator a first check valve and a second check valve of the plurality of check valves are configured to prevent the case drain line and the case drain coupler from being used. 
     
     
         12 . The implement of  claim 11 , wherein when the unintended external tension force causes the hydraulic actuator to forcibly extend a vacuum condition occurs and hydraulic fluid is taken from the power machine through the case drain line to fill the base end of the hydraulic actuator e and wherein when the unintended external compression force causes the hydraulic actuator to forcibly retract a differential volume of hydraulic fluid is accounted for by allowing the case drain line to receive excess hydraulic fluid from the base end of the hydraulic actuator to deliver to the power machine. 
     
     
         13 . The implement of  claim 12 , wherein when the implement comes up against an immovable object during normal extension of the hydraulic actuator, hydraulic fluid builds up pressure on the base end of the actuator until exceeding a pressure threshold of the first check valve of the plurality of check valves and causing the first check valve to receive hydraulic fluid from the first auxiliary coupler and direct a first portion of the hydraulic fluid from the first auxiliary coupler to the case drain line and causing the second check valve of the plurality of check valves to direct a second portion of the hydraulic fluid from the first auxiliary coupler through the second auxiliary coupler back to the power machine. 
     
     
         14 . The implement of  claim 12 , wherein when the implement comes up against an immovable object during normal retraction of the hydraulic actuator, hydraulic fluid builds up pressure on the rod end of the actuator until exceeding a pressure threshold of a third check valve of the plurality of check valves and causing the third check valve to receive hydraulic fluid from the second auxiliary coupler and direct a first portion of the hydraulic fluid from the second auxiliary coupler to the case drain line and causing a fourth check valve of the plurality of check valves to direct a second portion of the hydraulic fluid from the second auxiliary coupler through the first auxiliary coupler back to the power machine. 
     
     
         15 . A power machine comprising:
 a frame;   tractive elements supporting the frame;   an implement coupled to the frame and having a tool;   a hydraulic actuator coupled to the tool and at least first and second hydraulic lines, wherein the hydraulic actuator includes a base end coupled to the first hydraulic line and an rod end coupled to a second hydraulic line;   a protection mechanism that is configured to receive hydraulic fluid during normal retraction and extension of the hydraulic actuator;   wherein when an unintended external tension force causes the hydraulic actuator to forcibly extend, the protection mechanism is configured to provide hydraulic fluid to the base end of the hydraulic actuator and wherein when an unintended external compression force causes the hydraulic actuator to forcibly retract, the protection mechanism is configured to receive excess hydraulic fluid from the base end.   
     
     
         16 . The power machine of  claim 15 , wherein the protection mechanism comprises an accumulator and a plurality of check valves. 
     
     
         17 . The power machine of  claim 15 , wherein the protection mechanism comprises a case drain line and an actuator relief valve. 
     
     
         18 . An implement on a power machine comprising:
 a tool having a rotatable bar;   a hydraulic actuator having a base end and an actuator end and being coupled to the tool;   a protection mechanism coupled to the rotatable bar of the tool and to the hydraulic actuator and configured to be in a stationary position during normal operation of the tool and in a tripped position upon an occurrence of a high force event exceeding a threshold torque on the protection mechanism, wherein the protection mechanism includes one or more spring-loaded trip plates that rotate relative to each other in response to the high force event so that the rotatable bar of the tool is temporarily decoupled from the hydraulic actuator and is allowed to rotate without causing the hydraulic actuator to forcibly extend or forcibly retract.   
     
     
         19 . The implement of  claim 18 , wherein the tool comprises a scarifier having a plurality of teeth extending from the rotatable bar. 
     
     
         20 . The implement of  claim 19 , wherein the actuator end of the hydraulic actuator is extended when the teeth of the scarifier are lowered to contact a ground and the actuator end of the hydraulic actuator is retracted when the teeth of the scarifier are raised and spaced apart from the ground.