A piston rod is used in combination with a piston and is positioned within a cylinder. The piston rod and piston move in a linear motion within the cylinder in response to a hydraulic force being applied to the piston. There is a need in the fluid power industry to reduce the weight of the piston rod in hydraulic cylinders to make the systems, in which they are used, lighter and more energy efficient. The primary criterion for determining diameter of the piston rod for a given hydraulic application is the column buckling requirements for the rod. While it is possible to manufacture a hollow piston rod, the resultant rod would sacrifice in buckling resistance. As an example, a hollow steel piston rod would reduce overall rod weight by forty percent but would reduce column buckling resistance by thirty percent as compared to a solid steel piston rod.
The present disclosure relates to piston rods for use in hydraulic applications. The piston rod is coupled to a piston and positioned within a hydraulic cylinder. The piston rods and piston move in reaction to a hydraulic pressure being applied to the piston. The force of the piston rod can be used in various hydraulic operations.
In illustrative embodiments, the hybrid piston rod includes an outer metallic jacket or sleeve bonded to a pultruded composite core. The hybrid piston rod is coupled to a piston and is positioned with a hydraulic cylinder. The resultant hydraulic cylinder can be used for construction equipment or in other applications where hydraulic cylinders are used. The weight savings achieved by using the hybrid piston rod is approximately thirty percent with only a twelve percent reduction in buckling properties. The ratio of weight reduction to column buckling is significantly greater with the hybrid piston shaft. Since the piston rod weight often represents half the weight of the complete hydraulic cylinder, a reduction in rod weight is a significant factor in reducing the overall cylinder weight.
Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived.
The detailed description particularly refers to the accompanying figures in which:
A hybrid piston rod 10 is adapted to be used in a hydraulic cylinder 12, as shown, in
The core 24 of the hybrid piston rod 10 is manufactured by using a pultrusion process in one embodiment. To manufacture the core using the pultrusion process, strands of fiberglass material, that are pre-coated with a thermoset resin, are passed through heated curing dies that shape and cure the rod core 24. The forming dies can control the dimension of the outer diameter of the core 24. Alternatively, the outer surface of the core 24 can be machined to a desired diameter. While thermoset resins are preferred, it may be possible to use thermoplastics, however the resultant structure would not be as resistant to buckling.
Alternatively, the fiberglass or carbon fiber strands can be dipped into a resin bath to coat the fibers before pulling them through the forming dies. The use of resin acts as a substitute to the thermoset plastic material being used to form the core 24. The outer diameter of the core is either the same diameter or slightly less than the inner diameter of the sleeve if an adhesive is used or slightly oversized if a resistance fit is to be used to secure the components together. While graphite and fiberglass strands are described, it is contemplated that other types of fibers could also be used to form the core. Also, it is contemplated that the core could be manufactured using a unidirectional molding process as opposed to a pultrusion process.
The weight savings by using hybrid piston rod 10 is 30% with only a 12% reduction in buckling properties. The ratio of weight reduction to column buckling is significantly greater with the hybrid piston rod 10 than a hollow metal piston rod. Since the piston rod weight often represents half the weight of the complete hydraulic cylinder 12, a reduction in rod weight is a significant factor is reducing the overall cylinder weight. Listed below are several analytical scenarios for samples of the hybrid piston rod 10.
The hybrid piston rod 10 can be used in place of traditional all steel piston rods to provide for a significant savings in weight but provide for similar strength properties. The ends of the piston rod 10 can be finished with couplings to allow the rod 10 to be coupled to the piston on one end and to other components on the second end. The couplings can be either welded to the jacket 22 of piston rod 10 or secured by threading, pinning, adhesive, or resistance fit. The couplings can be either butted up to the end of the position rod 10 or positioned within the jacket 22. If positioned within the jacket 22, the core 24 would be positioned to lie against the coupling.
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
This application claims priority to U.S. Provisional Application Ser. No. 61/044,522 that was filed on Apr. 14, 2008 and is incorporated in its entirety by reference herein.
Number | Date | Country | |
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61044522 | Apr 2008 | US |