No grow gas spring

#This invention relates to pneumatic devices, and more particularly to a gas spring having a positive piston stop and a removable end cap with a valve assembly received therein.

#Previously, self-contained gas springs have been constructed with an actuating rod connected to a piston sidably received in a cylinder having a chamber which is precharged at a predetermined pressure, such as 2000 PSI, with an inert gas, such as nitrogen. When the rod and piston are forced into the chamber, the gas therein is compressed to a maximum operating pressure which is usually in the range of about 3,000 to 5,000 PSI, depending on the volume of the chamber and the effective area and stroke of the piston. In normal use, the pressure to which a self-contained gas spring is initially charged is not varied or changed. The spring is initially charged, relieved and recharged through a high pressure valve of the type commonly used in aircraft struts and accumulators.

#Previously, gas springs have been constructed with the rod being slidably received in a bearing and retaining assembly received in a tube cylinder. This assembly has a front housing slidably received in a rear housing with a rod gasket or seal therebetween. In use, the gasket is compressed axially so that it expands radially inward into firm sealing engagement with the piston rod by the force produced by pressurized gas in the piston chamber acting on the rear housing. However, in use the rod seal wears away and permits longer strokes of the piston. This results in the piston rod striking the associated dies and causing damage thereto, and/or a rod retainer on the piston head striking the rear housing and causing them to mushroom and/or be damaged. Thus, these self-contained gas springs require considerable maintenance and repair. Moreover, when repair is needed, these gas springs are not easily disassembled, since the bearing assembly, piston rod and retainer must all be removed and replaced through one end of the cylinder housing because a cap is permanently fixed to the other end.

#These and other objects, features and advantages of this invention will be apparent from the following detailed description, appended claims, and accompanying drawing in which:

#FIG. 1 is a full sectional view of a gas spring embodying this invention;

#FIG. 2 is an enlarged and fragmentary sectional view of the positive stop of the gas spring of FIG. 1; and

#FIG. 1 illustrates a gas spring 10 embodying this invention with a piston rod 12 received in a cylinder housing or tube assembly 14 defining in part a chamber 16. In use, the chamber is charged with gas under pressure to yieldably urge the piston rod to its extended position. This provides a gas spring or cushion permitting the rod to yieldably move toward its retracted position when a force applied externally to the rod exceeds the force produced thereon by the gas in the chamber.

#The piston rod is slidably received in a bearing and seal assembly 18 received in the housing and releasably retained therein by a snap ring 20 removably received in a complimentary groove 22 in the tube 14. This assembly has a front housing 24 slidably received in a rear housing 26 with a rod gasket or seal 28 therebetween. In use, the gasket is compressed axially so that it expands radially inward into firm sealing engagement with the piston rod by the force produced by pressurized gas in the chamber acting on the rear face of the rear housing. To provide a seal between the tube 14 and the rear housing 26, an O-ring 30 and a lockup washer 31 are received in a groove 32 in the rear housing.

#The rod is slidably received in a bearing 34 carried by the rear housing. Preferably, the front housing 24 also provides a bearing for the rod. Preferably, both the front housing and the bearing are made of a suitable bearing material such as sintered bronze and impregnated with a suitable lubricant. A rod wiper 36 is received in a groove 38 in the front housing and a dust cap 40 overlies the bearing assembly and is received and frictionally retained in the end of the tube.