Scale lightning protection system

Claim 2

A weighing scale, comprising a. a scale support unit; b. a load platform; c. at least one electrically conductive load responsive member mounted between said scale support unit and said load platform; d. transducer means for providing a variable electrical characteristic which is a function of the magnitude of a load applied to said load platform, said transducer means including a plurality of strain gauges mounted on said electrically conductive load responsive member; e. a plurality of electrical transducer leads, each said transducer lead being connected at one end to one of said strain gauges; f. surge voltage protection means for protecting said strain gauges from surge voltages developed in said transducer leads, said surge voltage protection means including a plurality of protection units corresponding to the number of transducer leads, each unit having a first terminal and a second terminal separated by a high resistance to leakage current and a low resistance to voltage surges, said first terminals being respectively connected to said transducer leads within the confines of said load platform; and g. lead means for maintaining said second terminals and said load responsive member at substantially the same electrical potential, said lead means including a single conductive lead electrically connected at one end with said second terminals of said protection units and directly connected at the other end to said electrically conductive load responsive member.

Claim 3

The weighing scale of claim 1, wherein said load responsive member is a beam element adapted to bend in response to load applied to said load platform, said beam element having one end secured to said load platform and the opposite end secured to said scale support unit, said electrical resistance strain gauges being connected in a bridge circuit arrangement with said transducer leads connected to the terminals of said bridge circuit.

Claim 4

The weighing scale of claim 1, wherein said load responsive member is a metallic beam element with one end connected to said scale support unit and the opposite end connected for deflection by the application of a load to said load platform, said electrical strain gauges being bonded to the surface of said metallic beam element, and further wherein said single conductive lead includes an electrically conductive housing mounted on and in electrical contact with said metallic beam element, said housing enclosing said strain gauges.

Claim 5

The weighing scale of claim 3, wherein said protection units are mounted within said housing, and wherein said first terminals of said protection units are connected with said transducer leads within said housing.

Claim 6

The weighing scale of claim 1, wherein said scale support unit is electrically grounded and said load responsive member is electrically grounded through said scale support unit.

Claim 7

A weighing scale including a transducer lightnIng protection system, comprising a load platform; a scale support unit; at least one electrical strain gauge transducer means mounted between said load platform and scale support unit and operative to provide an electrical output which is a function of the magnitude of a load applied to said load platform, each such electrical strain gauge transducer means including at least one electrically conductive load responsive element; mounting means for mounting said load responsive element to said load platform and said scale support unit to cause a load applied to said load platform to stress said load responsive element; strain gauge means secured to said load responsive element to sense stresses resulting from the forces applied thereto and operative to provide a variable electrical characteristic indicative of said forces, said strain gauge means including a plurality of electrical resistance strain gauges connected to form a Wheatstone bridge array having a plurality of terminals; transducer leads connected to the terminals of said Wheatstone bridge array; surge voltage protection means mounted beneath and within the confines of said load platform and electrically connected to said transducer leads to become conductive in the nanosecond range in response to lightning induced surges on said transducer leads, said surge voltage protection means including a plurality of protection units corresponding in number to the number of transducer leads, each said protection unit having a first terminal and a second terminal separated by a high resistance to leakage current and a low resistance to voltage surges, said first terminals being electrically connected to said transducer leads, respectively; first circuit means providing a first conductive path from said electrically conductive load responsive element through said scale support to ground, and second circuit means providing a second conductive path separate from said first conductive path between said second terminals of each protective unit and said electrically conductive load responsive element on which the associated strain gauges are mounted.

Claim 8

A weighing scale including a transducer lightnIng protection system, comprising a load platform; a scale support unit; at least one electrical strain gauge transducer means mounted between said load platform and scale support unit and operative to provide an electrical output which is a function of the magnitude of a load applied to said load platform, each such electrical strain gauge transducer means including at least one electrically conductive load responsive element; mounting means for mounting said load responsive element to said load platform and said scale support unit to cause a load applied to said load platform to stress said load responsive element; strain gauge means secured to said load responsive element to sense stresses resulting from the forces applied thereto and operative to provide a variable electrical characteristic indicative of said forces, said strain gauge means including a plurality of electrical resistance strain gauges connected to form a Wheatstone bridge array having a plurality of terminals; transducer leads connected to the terminals of said Wheatstone bridge array; surge voltage protection means mounted beneath and within the confines of said load platform and electrically connected to said transducer leads to become conductive in the nanosecond range in response to lightning induced surges on said transducer leads, said surge voltage protection means including a plurality of protection units corresponding in number to the number of transducer leads, each said protection unit having a first terminal and a second terminal separated by a high resistance to leakage current and a low resistance to voltage surges, said first terminals being electrically connected to said transducer leads, respectively; first circuit means providing a first conductive path from said electrically conductive load responsive element through said scale support to ground, and second circuit means providing a second conductive path separate from said first conductive path between said second terminals of each protective unit and said electrically conductive load responsive element on which the associated strain gauges are mounted.

Claim 9

The weighing scale of claim 6 wherein said electrical resistance strain gauges are bounded to the surface of said load responsive element by a thin layer of bonding material, said surge voltage protection means operating to prevent electrical arcing between said load responsive element and the electrical resistance strain gauges bonded thereto across said thin layer of bonding material in response to lightning induced surges on said transducer leads.

Claim 10

The weighing scale of claim 7, wherein said second circuit means includes an electrically conductive housing enclosing each electrical strain gauge transducer means, said housing being mounted in electrical contact with the load responsive elements enclosed thereby, and an electrical connection between said housing and the protection units for the electrical strain gauge means enclosed within said housing.