Many construction and earth moving machines use hydraulic or pneumatic cylinders to move work tools such as buckets on backhoes, loaders, and excavators. The cylinders may include a cylinder chamber at least partially filled with hydraulic fluid. A cylinder rod may be configured to slide along an axis of the cylinder chamber, and hydraulic fluid may be introduced into the chamber or removed from the chamber to extend or retract the rod. Often, the rod position must be known so that movement of the work tool can be monitored and controlled.
Cylinder rod surface markings, such as bar codes, may help to determine the position of the rod. The surface markings may be positioned at predetermined intervals along the cylinder rod, and each marking may correspond to a different location on the rod. In operation, a sensor positioned near the cylinder rod may identify a specific surface marking, which may correspond with a specific rod location.
Over time, surface markings on any material may wear or fade due to friction, heat, and/or corrosion. Further, a certain degree of wear may make the surface markings unrecognizable to a sensor, thereby preventing accurate determination of the rod position. Thus, there is a need for surface markings that are more resistant to wear and corrosion.
One method for producing a surface marking on a material is disclosed in U.S. Pat. No. 5,632,916 issued to Lappalainen on May 27, 1997 (hereinafter the '916 patent). The '916 patent describes a method for marking a chromium-plated metal bar. The method includes producing a series of overlapping, colored spots on the bar by exposing the bar to successive laser pulses.
While the method of the '916 patent may produce a suitable marking for some applications, the method has several drawbacks. The surface marking produced by the method of the '916 patent may not withstand repeated exposure to friction and wear produced on a hydraulic cylinder rod. Further, the chromium-plated surface of the metal bar may cause more wear on cylinder-head seals as compared to other materials. In addition, operation of the marking laser may be expensive and time consuming.
The present disclosure is directed to overcoming one or more of the problems or disadvantages in the prior art cylinder rod surface markings.
USPTO Backgrounds
USPTO Backgrounds