Pressure relief valve for a grease gun

#This invention relates to grease guns and particularly to a pressure relief valve for high pressure grease guns. More particularly, this invention relates to a pressure relief valve for use with high pressure grease guns of the type having a coupling secured to the outlet end of the gun which prevents grease from being ejected from the gun except when the coupling is properly located over a grease fitting.

#Grease guns of the type with which the invention of this application is utilized are conventionally used in automobile service stations to grease bearings of motor vehicles. The gun is in reality a manually operated control handle for controlling a valve which in turn controls the flow of grease through the handle. When the valve of the gun or control handle is manually opened, it connects the outlet end of the gun to a high pressure grease pump. The pump is usually operable to supply grease to the gun at a pressure of approximately 7,000 pounds per square inch depending upon the resistance encountered by the grease in the bearing to which the grease is supplied. The greater the resistance, the higher the pressure of the grease ejected from the gun.

#In addition to lubricant flow control handles of the type just described, there are also so-called "booster" control handles or guns for lubricating motor vehicles. Booster control handles are used for supplying grease at still higher pressures to vehicle bearings. A conventional booster control is operable to boost the ratio of grease pressure from the inlet to the outlet by a two-to-one ratio, i.e., from 7,000 to 14,000 p.s.i. Generally, booster control handles or guns are used to grease bearings of trucks or motor vehicles which are heavily loaded.

#FIG. 1 is a side elevation view of a grease gun control handle upon which there is mounted a coupling and a pressure relief valve.

#FIG. 2 is a cross-sectional view of the pressure relief valve showing the valve in its closed position.

#FIG. 3 is a cross-sectional view through the pressure relief valve showing the valve in its open position.

#Referring first to FIG. 1, the high pressure grease gun 10 includes a control handle 11 and a handle extension tube 12. The handle 11 has a manual trigger 13 operated control valve for controlling the flow of grease from a high pressure hose 14 to and through the extension tube 12. The hose 14 is conventionally a double wire braid hose which interconnects the handle 11 to a source of grease or hydraulic lubricant through a high pressure pump (not shown). Conventionally, the pump is an air operated reciprocating piston pump which is operated by approximately 150 pounds air pressure and is operable to dischare grease or a lubricant at a pressure on the order of 7,000 p.s.i.

#The valve mechanism contained within the handle 11 for controlling the flow of lubricant through the gun or handle comprises a ball 16 type valve which is normally urged by a spring 18 to a closed position. To open the valve and permit the throughput of high pressure grease from the hose 14 the trigger 13 actuates a valve plunger 20 which is slidably mounted above the ball 16 in the body of the handle 11. The trigger is pivotally mounted on the top of the handle, as indicated at 22, and has a first cam surface 24 engageable with the top of the plunger 20 so that movement of the trigger 13 from the position illustrated in FIG. 1 toward the body of the handle 11 (i.e., squeezing of the trigger) causes the cam surface 24 to engage the plunger 20 and move the plunger downwardly thereby opening the ball valve 16. Upon release of the handle, the valve is automatically closed by the spring 18.

#At the opposite end of the extension tube is a coupling 26 which is operable to be secured to hydraulic grease fittings. A bore 28 (FIGS. 2 and 3) extends axially through the extension tube 12 and through the coupling 26 whereby grease can be delivered from the handle body 11 to the grease fitting. A suitable coupling is that described in the aforementioned U.S. Pat. No. 3,788,427. The pressure relief valve 30 for relieving grease pressure in the handle extension 12 is located in the extension tube 12 between the trigger 13 and the coupling 26.