This invention relates to an improved load cell of the type used to measure tension or compression loads and more particularly relates to a washer type load cell adapted to be used with gap-spanning sensor elements.
Load cells have many applications and are used in the prior art in electronic weighing systems for monitoring force and pressure and so on. As such, these cells employ a suitable sensor element such as piezoelectric, reluctance, capacitive or piezoresistive element which is positioned in a housing to monitor the force or pressure exerted on the housing when the load cell is positioned in a suitable environment.
The most popular types of load cells employ a strain gage element which may be an unbonded or bonded wire gage or a foil or a bonded semiconductor element. These gages provide higher sensitivity while further eliminating mechanical linkages and moving parts. They also enable one to achieve good temperature specifications and serve to reproduce load deflection in the elastic member or housing with good linearity.
A major concern in the design of the load cell resides in the housing arrangement. In this manner, the housing serves to couple or transmit the force or pressure to be monitored by the cell to the sensor associated with the cell. The housing would therefore be capable of transmitting such forces to the sensor in a linear manner without providing undue distortions and improper bending movements when the monitored load is not properly aligned with the axis of the load cell. Some load cells are required to have high overall stiffness. Thus, the load cell housing should provide a high overall stiffness while still allowing sufficient strain to be monitored by the associated sensor element.
It is therefore an object of the present invention to provide a load cell transducer capable of accurately monitoring an external force employing a housing which is simple and relatively inexpensive to fabricate; and which provides a relatively stiff structure, but also allows for adequate strain levels to be transmitted to the sensor element or elements.