Field of the Invention

This invention relates to fluid cylinders. In partic- ular, it relates to a fluid cylinder in which the cylinder tube has two internal cross-sections, a first cross-section which receives the piston and a second cross-section which receives the piston rod in guiding relationship.

Background of the Invention In conventional fluid cylinders, the cylinder tube has a single, uniform cross-section which receives the piston, usually in sealing engagement. An end cap is attached to both ends of the cylinder tube. The end caps have two functions: they guide and steady the piston rod, and they hold packing, usually consisting of an O-ring and a wiper, in sealing engagement with the piston rod to prevent loss of working fluid. These two functions, while related, are not ^" identical, and it requires careful design, manufacture, and assembly of the cylinder tube and the end cap to ensure that the end cap will perform both functions satisfactorily.

Objects of the Invention . It is the general object of the invention to provide a fluid cylinder which separates the guiding and stabilizing function conventionally entrusted to the end cap from the sealing function.

It is a particular object of the invention to provide a fluid cylinder in which the cylinder tube itself performs the piston rod guiding and stabilizing function.

Other objects and advantages of the present invention will become apparent from the detailed description of a preferred embodiment thereof given hereinafter.

Brief Summary of the Invention The invention is a fluid cylinder in which the cylinder tube has two internal cross-sections, a first cross-section which receives the piston and a second cross-section which receives the piston rod in guiding relationship.

Brief Description of the Drawings Figure 1 is a cross-sectional view of the presently preferred embodiment of the invention. Figure 2 is a fragmentary, enlarged cross-sectional view of a portion of the presently preferred embodiment of the invention.

Detailed Description of the Presently Preferred Embodiment The drawings illustrate a fluid cylinder having a piston 10, a piston rod 12 operatively connected to the piston 10, and a cylinder tube 14 which receives both the

-3- piston 10 and the piston rod 12. The cylinder tube 14 has two internal cross-sections, a first cross-section "A" intermediate the ends of the cylinder tube 14 and a second cross-section "B" adjacent at least one of the ends of the 5 cylinder tube 14. In the illustrated embodiment, the first cross-section "A" receives the piston 10 in sealing rela¬ tionship, but there may be space for passage of fluid around the piston insofar as the present invention is concerned. The important- point is that the second cross-section "B"

10 receives the piston rod 12 in guiding relationship. That is, the second cross-section "B" serves as a bearing surface for the piston rod 12.

The cylinder tube 14 flares radially outwardly from the second cross-section "B" towards the end of the cylinder 5 tube 14, and an end cap 16 is received over the flared end 18 of the cylinder tube 14. The end cap 16 has a rod exit hole 20 which recives the piston rod 12 with substantial clearance. Thus, it should be noted that the end cap 16 does not touch the piston rod 12 and therefore serves no 0 rod guiding function. The end cap 16 does, however, sur-

• _* round an 0-ring 22 and a wiper 24, and the end cap 16 is sized and shaped so that the O-ring 22 and the wiper 24 are held in sealing engagement with the piston rod 12. In particular, the axial dimension between the flared end 18 5 of the cylinder tube 14 and the inner surface 26 of the end cap 16 is slightly less than the unrestrained axial dimen¬ sion of the O-ring 22 and the wiper 24. Accordingly, the O-ring is distorted into close engagement with the piston rod 12, when the end cap i6 is placed over the flared end

OMPI ^'

18, as illustrated in Figure 2.

Preferably the cylinder tube 14 and the end cap 12 are both made of metal, and the described shape of the cylinder tube 14 is achieved by cold forming.

Caveat

While the present invention has been illustrated by a detailed description of a preferred embodiment thereof, it will be obviotfs to those skilled in the art that various changes in form and detail can be made therein without departing from the true scope of the invention. For that reason, the invention must be measured by the claims appended hereto and not by the foregoing preferred embodiment.