Load Cell for Screw Pililng Power Head
A load pin having a pair of opposing pockets milled a certain distance from the pin's surface, but not extending through the pin. A strain gauge sensor is mounted within the each pocket to measure force. In one embodiment differential bridge network is used to obtain a measurable signal from the strain gauge.
1 . A load pin adapted to be combined with a machine suitable for driving a screw pile into the ground, said load pin comprising:
an outer surface;
a longitudinal axis extending between opposing ends;
a medial portion having a center point along said longitudinal axis;
a sensor combined with the pin for measuring forces applied thereto;
wherein the sensor is comprised of four gauges which are electrically connected using a differential bridge electronic circuit.
2 . The load pin of claim 1 wherein the sensor is a shear type foil strain gauge sensor.
3 . The load pin of claim 1 further comprising a pair of transitional portions, each of said transitional portion being located between each of the two ends and the medial portion, said transitional portions being of slightly smaller diameter than said medial portion and ends, the transitional portions being substantially mirror images of each other.
4 . The load pin of claim 3 wherein the gauges are centered within one of the transitional portions.
5 . A load pin adapted to be combined with a machine suitable for driving a screw pile into the ground, said load pin comprising:
an outer surface;
a longitudinal axis extending between opposing first and second ends;
a medial portion having a center point along said longitudinal axis;
a first side and a second side separated by a center plane which intersects the longitudinal axis to divide the first side and the second side;
at least one pocket in at least one of the top side and the bottom side, wherein the at least one pocket has an interior surface set into the pin a predetermined distance from the outer surface, and wherein the at least one pocket extends less than halfway through the pin such that it does not reach the center plane;
at least one sensor combined with the interior surface of the at least one pocket for measuring forces applied to the pin.
6 . The load pin of claim 5 wherein the interior surface of the pocket is a floor which is generally planer and parallel with the center plane.
7 . The load pin of claim 5 wherein the interior surface of the pocket is a wall which is generally planer and perpendicular to the center plane.
8 . The load pin of claim 5 having two pockets on opposite sides of the same end, each pocket having a floor which is generally planer, parallel with the center plane, and equidistant from the center plane relative to the floor in the opposing pocket.
9 . The load pin of claim 5 having four pockets with the first two pockets on opposite sides of the first end comprising a first pocket pair and the second two pockets on opposite sides of the second end comprising a second pocket pair, each pocket having a floor which is generally planer, parallel with the center plane, and equidistant from the center plane relative to the floor in the opposing pocket.
10 . The load pin of claim 9 further comprising a pair of transitional portions, each of said transitional portion being located between each of the two ends and the medial portion, said transitional portions being of slightly smaller diameter than said medial portion and ends, the transitional portions being substantially mirror images of each other.
11 . The load pin of claim 10 wherein each pocket is centered within one of the transitional portions.
12 . The load pin of claim 11 wherein said transitional portions and their respective pockets are equidistant from said center point.
13 . The load pin of claim 10 wherein the at least one sensor is centered within one of the transitional portions.
14 . The load pin of claim 5 further comprising an internal passage to facilitate electrical connection inside the pin.
15 . The load pin of claim 14 further comprising an access passage for connecting the at least one pocket to the internal passage.
16 . The load pin of claim 5 wherein the at least one sensor is a strain gauge.
17 . The load pin of claim 5 wherein the at least one sensor is a shear type foil strain gauge.
18 . A load pin adapted to be combined with a machine suitable for driving a screw pile into the ground, said load pin comprising:
an outer surface;
a longitudinal axis extending between opposing first and second ends;
a medial portion having a center point along said longitudinal axis;
a first side and a second side separated by a center plane which intersects the longitudinal axis to divide the first side and second side;
a first pocket pair having a first pocket in the first side of the first end and a second pocket in the second side of the first end, wherein the pockets have an interior surface set into the pin a predetermined distance from the outer surface, and wherein the pockets extend less than halfway through the pin such they do not internally connect;
a first sensor having four gauges which are electrically connected, wherein two of the gauges are mounted to the interior surface of the first pocket and two of the gauges are mounted to the interior surface of the second pocket.
19 . The load pin of claim 18 wherein the four gauges within the first pocket pair are electrically connected using a Wheatstone bridge electronic circuit.
20 . The load pin of claim 18 wherein the set of four gauges within the pocket pair are electrically connected using a differential bridge electronic circuit.
21 . The load pin of claim 18 further comprising a second pocket pair having a first pocket in the first side of the second end and a second pocket in the second side of the second end, wherein the opposing pockets have an interior surface set into the pin a predetermined distance from the outer surface, and wherein the pockets extend less than halfway through the pin such they do not internally connect.
22 . The load pin of claim 21 having a second sensor with four gauges, wherein two of the gauges are mounted to the interior surface of the second pocket pair's first pocket and two of the gauges are mounted to the interior surface of the second pocket pair's second pocket.
23 . The load pin of claim 22 wherein the four gauges in each pocket pair are electrically interconnected to provide a single measureable signal using a pair of connected differential bridge electronic circuits.
24 . The load pin of claim 21 wherein the interior surface in each of the four pockets is a floor which is generally planer, parallel with the center plane, and equidistant from the center plane relative to the floor of the opposing pocket in the pocket pair.
25 . The load pin of claim 18 wherein the at least one sensor is a strain gauge having parallel lines.
26 . The load pin of claim 25 wherein said strain gauges are mounted within their respective pockets of the load pin so that the orientation of their parallel lines are substantially parallel to the load pin's longitudinal axis.
27 . The load pin of claim 18 wherein the at least one sensor is a shear type foil strain gauge.
28 . The load pin of claim 18 wherein, the machine has an axis of rotation and wherein, when the load pin is combined with the machine, the floor of each pocket is oriented substantially perpendicular to said axis of rotation of the machine.
29 . The load pin of claim 18 further comprising an internal passage to facilitate electrical connection inside the pin.
30 . The load pin of claim 29 further comprising an access passage in each pocket for connecting each pocket to the internal passage.