Patent Application
20180156656
None.
This invention relates to improvements in load-weight sensing systems for lift trucks and other similar load supporting apparatus. Such previous load-weight sensing systems commonly employ electrical load-weight measuring cells, sometimes referred to as strain gauges, interconnecting an underlying cantilever-type load-supporting fork blade member with an overlying simple beam-type load weighing platform. Some such prior systems, as exemplified by U.S. Pat. No. 9,316,528 and other references cited therein, use bendable elongate beam-type load-weight measuring cells. Other prior systems, as exemplified by US published patent applications 2007/0041820 A1 and 2011/0067502 A1, use other types of load-weight measuring cells. Any of such types of prior load-weight measuring cells can be used in the present invention, and are intended to be included herein.
In the present invention, the weight of the load elastically deforms the overlying load weighing platform and the underlying fork blade member downwardly in variable response to the weight of the load. However, the overlying load weighing platform is deformed downwardly differently than the underlying fork blade member, because the overlying platform is not supported in a cantilever fashion as is the underlying fork blade member. Instead the overlying platform is supported by weight-measuring cells in positions adjacent to the load weighing platform's forward and rearward extremities, respectively. This inconsistency results in stressing of the load-weighing platform as a simple beam supported at both ends, while simultaneously stressing the underlying fork blade member as a cantilever beam. Such difference in stressing causes lateral misalignments of the above-described load cells relative to the load-weighing platform, which then causes errors in the sensed load weight because the misalignments introduce load-cell-deforming stresses which are additional to the load weight-caused stresses. The purpose of the present invention is to minimize these error-causing load weight-sensing problems, as well as to minimize the adverse operational and economic effects that result from such problems, by automatically compensating for them.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
Because the fork assemblies 10 and 12 are intended to have a load-weighing function in addition to their load-lifting and lowering function, they are equipped with respective load-weighing platforms 18 as shown in
In contrast, in accordance with the present invention, it has been discovered that a slight loosening of the fastening of a load-weight measuring cell 20 with respect to either a load weighing platform 18 or a fork blade member 22, while maintaining the opposite fastening tight, provides a significant improvement.
However if the bolts 25 are loosened slightly, in accordance with the present invention, so as to provide small gaps which permit resultant small relative movements in the tapered head regions of the bolts 25 with respect to the weight-measuring load cells 20 during their initial load-induced downward movements, the difference between the unequal stresses caused by the dissimilarities of the two beam structures 22 and 18 can be reduced or eliminated. Thereafter, as further bending of the two beam structures 18 and 22 occurs, the initial looseness of the bolts 25 is terminated by contact of the undersides of their bolt heads with collars 26 rigidly mounted on the load cells 20, which thereby prevents them from further downward movement with respect to the weight measuring cells 20 as shown in
Lateral movement of the load weight measuring cells 20 is simultaneously also prevented by the collars 26 in the case of each rearward bolt 25 as seen in
The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.
