US20140190275A1

US20140190275A1 - Load Cell for Screw Pililng Power Head

Info

Publication number: US20140190275A1
Application number: US14/043,486
Authority: US
Inventors: Wayne McILravey
Original assignee: Concept Torque Solutions Inc
Current assignee: Concept Measurement Inc
Priority date: 2013-01-05
Filing date: 2013-10-01
Publication date: 2014-07-10
Also published as: US20160109310A1; DE202013009782U1; US10067020B2

Abstract

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.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation-In-Part of U.S. patent application Ser. No. 13/736,011 filed Jan. 7, 2013 which is a non-provisional of U.S. Provisional Patent Application Ser. No. 61/749,310 filed Jan. 5, 2013 and entitled, “LOAD CELL FOR SCREW PILING POWER HEAD”, the entirety of these applications is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to equipment and techniques for measuring torque applied to objects and, more particularly, to a load cell to measure torque applied to a screw piling by a rotary drive.

BACKGROUND

The background information discussed below is presented to better illustrate the novelty and usefulness of the present invention. This background information is not admitted prior art.
Screw piling or screwpiles are a steel screw-in piling and ground anchoring system used for building foundations, pipeline tie-downs and in other applications. Screw pile(s), as used herein, includes screw piling, steel screw-in foundations, screw piers, helical piles, helical anchors, screw anchors, screw foundations, helical piers, and other similar devices. They are often necessary for building foundations where the ground is not compacted, or strong enough or of variable capacity to carry a building structure. Screwpiles are typically manufactured using varying sizes of tubular hollow sections for the pile or anchor shaft. The pile shaft transfers a structure's load into the pile. Helical steel plates, or helixes, are welded to the pile shaft in accordance with the intended ground conditions.
To install screw piling, they are typically wound into the ground much like a screw into wood. Screw piles are preferably installed using earthmoving equipment or mobile machinery fitted with drive attachments which may include rotary drives, rotary drivers, powerheads or drive heads, see, for example, FIGS. 1 a and 1 b. The mobile machinery varies from skid-steer loaders to 5 ton through 30 ton excavators. Rotary drives, generally with torque capacities ranging from 5,000 Nm to 300,000 Nm, are custom fitted using various boom configurations. Drive attachments generally connect the screwpile to the machine. Likewise, hinged attachment means, such as a universal joint-type coupler, are often employed to suspend the rotary drive attachment from the boom of the mobile machinery; see, for example, FIG. 1 b. One or more pivot pins may be utilized to connect the coupler to the boom and the drive attachment see, for example, the coupler disclosed in U.S. Pat. No. 6,942,430 (Suver).
The level of torque that is required to turn the screw pile is indicative of the strength of the soil, and can be used to predict the capacity of the pile. Low installation torque indicates a weak soil and low pile capacity, whereas high installation torque indicates a relatively strong soil and greater pile capacity. Where the required installation torque can be accurately measured, the approximate holding capacity of a screw pile can usually be predicted.
Traditionally, estimates of installation torque were made using hydraulic pressure gauges (to measure the amount of hydraulic pressure provided to a rotary drive), assumed or estimated gearbox ratios and compensation for any hydraulic motor losses. However, such estimates are fairly inaccurate and may not reliably predict a screw pile's holding capacity. As such, various devices and systems have been created to more accurately measure the installation torque of a screw pile.
One example is that by Pro-Dig, LLC of Kansas, U.S.A., which markets a screw pile torque monitoring system under the trade-mark INTELLI-TORK™. This system comprises a flanged member that mounts between the rotary drive and the screw piling and, therefore, rotates along with the screw piling as it is driven into the ground. As the rotary drive imparts torque to the screw piling, sensors in the flanged member measure this torque. Because this flanged member rotates along with screw piling it must send its measurements wirelessly to a display or recorder. As such, one disadvantage of this system is that such wireless signals may be subject to interference from the vibrations created during screw piling installation, especially as the screw piling is almost installed and the flanged member is driven closer to the ground.
A further disadvantage of this system is that the flanged member adds additional length to the rotary drive/screw pile assembly, thereby shortening the maximum length of screw pile that can potentially be installed using a particular mobile machinery. Yet a further disadvantage is that the INTELLI-TORK™ system also appears to be subject to interference from downward forces that may be applied by the mobile machinery as it pushes the rotary drive/screw pile assembly downwards during installation.
Another example is that by Russell Heale Engineering Pty Ltd of Burleigh Heads, Queensland, Australia, which markets a screw pile torque monitoring system under the trade-mark TORQATRON™ . This system comprises a load cell member that mounts between the boom of the mobile machinery and the rotary drive. Unlike the flanged member of the INTELLI-TORK™ system, this load cell member does not rotate with the screw piling as it is driven into the ground (since it is mounted between above the rotary drive and to the boom). As such, wired connections can be used to transmit signals from the load/torque sensors in the TORQATRON™ . However, this device and system does suffer from the other disadvantages present in the INTELLI-TORK™ system, namely that the load cell member adds additional length to the boom/rotary drive/screw pile assembly, thereby shortening the maximum length of screw pile that can potentially be installed using a particular mobile machinery that it also appears to be subject to interference from downward forces that may be applied by the mobile machinery as it pushes the boom/rotary drive/screw pile assembly downwards during installation.
Therefore, what is needed is a system and apparatus to measure the installation torque of a screw pile which is simple in design and does not have these and other disadvantages.

SUMMARY

The present invention is directed to overcoming the prior art deficiencies in load cells used to measure torque applied to a screw piling by a rotary drive, such as being subject to interference from downward (crowd) forces, having inconvenient sensor locations on the pin, and adding additional length to the boom, rotary drive, and screw pile assembly during operations.
In one aspect the invention provides a system to measure the installation torque of a screw pile which comprises machinery suitable to drive the screw pile into the ground, said machinery further comprising a rotary drive suspended by means of a universal joint-type coupler. A load pin, having at least one sensor, is mounted through the universal joint-type coupler as a pivot pin and is oriented within the universal joint-type coupler so that at least some of the installation torque is transmitted through said load pin and is measurable by said at least one sensor.
In one embodiment, the load pin further comprises at least one opening (“pocket”) which is milled to be set in the pin a certain distance from the pin's surface, but the pocket does not extend through the pin. Two pockets may be milled into opposing sides of the pin with one pocket being a mirror image of the other. A strain gauge is mounted within each pocket to measure force. In one embodiment a differential bridge network may be used to obtain a measurable signal from the strain gauges.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:

FIG. 1 a is a side view of a PRIOR ART system for installing screw pilings;

FIG. 1 b is a perspective view of another PRIOR ART system for installing screw pilings wherein the rotary drive is suspended from a boom by a universal joint coupler;

FIG. 2 a is a perspective view of one embodiment of the load cell according to the present invention, shown mounted in a universal joint coupler suspended between a boom and a rotary drive;

FIG. 2 b is an enlarged view of the embodiment of FIG. 2 a, taken of area 6 in FIG. 2 a;

FIG. 3 is a perspective view similar to FIG. 2 a showing a different type of universal joint coupler;

FIG. 4 is a sectioned perspective view of an embodiment of the load cell, shown mounted in a universal joint and taken along line 1-1 in FIG. 2 b;

FIG. 4 a is a sectioned perspective view of an embodiment of the pin;

FIG. 4 b is a top view of one end of the pin shown in FIG. 4 a;

FIG. 4 c is a bottom view of one end of the pin shown in FIG. 4 a;

FIGS. 5 a and 5 b are perspective views of an embodiment of the load cell, with access cover being removed in FIG. 5 b;

FIG. 5 c is a perspective view of an embodiment of the load cell similar to 5 a, showing some of the internal structure in phantom lines;

FIG. 6 is a sectioned perspective view of an embodiment of the load cell, taken along line 3-3 in FIG. 5 a;

FIG. 7 is a sectioned perspective view of an embodiment of the load cell, taken along line 4-4 in FIG. 5 a;

FIG. 8 is another sectioned perspective view of an embodiment of the load cell;

FIG. 9 is a perspective view of an embodiment of the load cell showing the sensors mounted in the pockets;

FIG. 10 a is an electrical schematics of how a Wheatstone bridge network electrically connects a preferred embodiment of four strain gauges;

FIG. 10 b is an electrical schematics of a differential bridge network employed by the invention to electrically connect a preferred embodiment of four strain gauges;

FIG. 11 a is an electrical schematics of a preferred pair of Wheatstone bridge networks electrically connecting the eight strain gauges of the load cell of FIG. 10 a; and

FIG. 11 b is an electrical schematics of a preferred pair of differential bridge networks electrically connecting the eight strain gauges of the load cell of FIG. 10 b.

DEFINITION SECTION

Horizontal plane, as used herein, refers to a plane that is horizontal at a given point if it is perpendicular to the gradient of the gravity field at that point, in other words, apparent gravity is what makes a plumb bob hang perpendicular to the plane at that point. In other words a horizontal plane in the plane that is perpendicular to the line that passes through the center of the Earth.
Vertical plane, as used herein, refers in astronomy, geography, geometry, and related sciences and contexts, to a direction passing by a given point if it is locally aligned with the gradient of the Earth's gravity field, i.e., with the direction of the gravitational force (per unit mass, i.e. gravitational acceleration vector) at that point.

DETAILED DESCRIPTION

The following description is of a preferred embodiment by way of example only and without limitation to the combination of features necessary for carrying the invention into effect. Reference is to be had to the figures in which identical reference numbers identify similar components. The drawing figures are not necessarily to scale and certain features are shown in schematic or diagrammatic form in the interest of clarity and conciseness.
In accordance with one embodiment of the present invention and as shown generally in the figures, there is a provided a system 10 to measure the installation torque T of a screw pile 12 which generally comprises at least one load cell 14 having at least one sensor 16 for detecting the load, force or strain on the cell 14. In one embodiment, load cell 14 is in the form of a pin and is placed or positioned, within the machinery used to drive the screw pile 12 into the ground so that all, or substantially all, or at least some of the installation torque T is transmitted through said at least one sensor 16 so as to measure that installation torque. Load cell 14 will also be referred to as load pin 14 when discussing a preferred embodiment of the invention. The machinery used to drive the screw pile 12 into the ground may be a skidsteer loader, excavator or some other suitable machinery.
In one embodiment, the machinery used to drive the screw pile 12 into the ground comprises a suitable rotary drive 18 suspended from a boom 20 by means of a universal joint 22 (see, for example, FIGS. 2 a, 2 b, 3, and 4). The rotary drive 18 can be of the type disclosed in U.S. Pat. No. 6,942,430 (Suver), the disclosure of which is hereby incorporated by reference, or of some other conventional rotary drive.
In the embodiment shown in FIGS. 2 a and 2 b, the rotary drive 18 is shown suspended from the boom 20 by a universal joint-type coupler 22 having an upper section 22 u and a lower section 22 l. Other suitable couplers may also be used. The coupler's upper section 22 u is pivotally connected to the boom 20 between two ears 20 i, 20 ii (having through bores) via pivot pin member 24 in a conventional manner. In one embodiment the rotary drive 18 is pivotally suspended from the coupler's lower section 22 l, via ears 18 i, 18 ii whereby load pin 14 is mounted through an axial passage in the coupler's lower section 22 l and through bores provided in each of said ears 18 i, 18 ii. In one embodiment, and as is conventional in a universal joint-type coupler, pins 14 and 24 have their pivot axis oriented at 90° relative to each other. Wear sleeves, wear members, bushings or bearings may be provided between load pin 14 and through bores to facilitate pivotal movement of the rotary drive 18 with the coupler 22. Likewise, wear sleeves, wear members, bushings or bearings may be provided between pivot pin 24 and through-bores in ears 20 i, 20 ii.
In accordance with normal practice, the tolerances between the parts are selected to prevent binding, to allow the desired pivotal movement and to permit easy assembly and disassembly. As such, load pin 14 functions as a pivot pin to pivotally connect the rotary drive 18 to coupler's lower section 22 l. Preferably lower section 22 l has its pivot axis oriented at 90° to the pivot axis of the upper section 22 u with the boom 20, as is customary in a universal joint. In one embodiment, the load pin 14 is mounted through the coupler's lower section 22 l so that the majority of the load pin 14 is covered or enveloped by the coupler's lower section 22 l and/or any bushings with only the ends of the load pin 14 extending out of the coupler's lower section 22 l (see FIG. 2 b, for example).
In this embodiment, all or substantially all of the installation torque T is transmitted from the rotary drive 18 (as applied to the screw pile 12 during installation) through the coupler 22 and to the boom 20. By virtue of the load pin 14 being used as one of the pivot pins in the universal joint-type coupler 22, some or all of the installation torque T is also transmitted through said pin 14 and detectable or measurable by said at least one sensor 16.
In an alternate embodiment (not shown), load pin 14 may be mounted in the connection between the upper section 22 u and the boom 20 in place of pivot pin 24 and a conventional pivot pin may then be used to pivotally connect the rotary drive 18 to the lower section 22. In yet a further alternate embodiment, the rotary drive 18 is suspended from the boom 20 by only a single pivoting joint (e.g. such as that shown in FIG. 1 a) and then load pin 14 will be used as the pivot pin at such single pivoting connection.
Description of the Load Pin
In one embodiment, and referring now to FIGS. 5 a, 5 b, and 5 c, load pin 14 is an elongate member having an axial body with longitudinal axis A-A extending between opposing ends 14 e, 14 f, preferably formed as one part and in one solid piece. In one embodiment the elongate member is cylindrical, but other suitable symmetrical shapes such as rectangular cuboid may be used. The load pin 14 has a medial portion 14 m, having a center point CP along longitudinal axis A-A, and two peripheral portions, each peripheral portion near one of the opposing ends 14 e, 14 f. Medial portion 14 m is adapted to mount through the axial passage of the coupler's lower section 22 l. The peripheral portions of the opposing ends 14 e, 14 f are adapted to mount through bores provided in each of said ears 18 i, 18 ii and any wear members that may be provided.
In one embodiment, between the medial portion 14 m and the two end portions 14 e, 14 f, the load pin 14 has transitional portions 15 a, 15 b of a slightly smaller outside diameter than the medial 14 m and peripheral portions so as to allow some movement and/or bending of the load pin 14 at these portions 15 a, 15 b when installed in a coupler 22 and when subjected to installation torque T.
In one embodiment, the transitional portions 15 a, 15 b function as force measuring zones, each having at least one sensor 16 arranged or mounted somewhere therein. In one embodiment, transitional portions 15 a, 15 b are between 1 cm and 5 cm in width (i.e. width/spacing between medial and peripheral portions), which allows for movement and/or bending of the load pin (to help the at least one sensor 16 to function) while not weakening the load pin unnecessarily and still allowing it to safely function as a pivot pin within a coupler 22. In one embodiment, transitional portions 15 a, 15 b are positioned along the load pin's longitudinal axis A-A so that they are substantially centered along the interface of the coupler's lower section 22 l and any respective wear members, so that a maximum amount of shear force (between the load pin portion within the coupler's lower section 22 l and the load pin portion that is within the through bores provided in each of said ears 18 i, 18 ii and any wear members) can be directed into said transitional portions 15 a, 15 b (see FIG. 5 a). However, the system 10 will also work if said interface is positioned at any point along the transitional portions 15 a, 15 b. In one embodiment, the transitional portions 15 a, 15 b are the same distance from the center point CP and are substantially mirror images of each other. Other embodiments may only include one transitional portion 15 a or 15 b, said single transitional portion 15 a or 15 b being preferably positioned in the center of the pin 14 (equidistant from both end portions 14 e, 14 f).
In one embodiment, the system 10 comprises a plurality of sensors 16 mounted on the interior of one or more pockets 28 a, 28 b, 28 c, 28 d (as more fully described below), in said one or more of the transitional portions (force measuring zones) 15 a, 15 b. In one embodiment, pockets pairs 28 a and 28 b are equidistant from the center point CP of the medial portion 14 m and are mirror images of each other as are pocket pairs 28 c and 28 d. Pocket pairs 28 a and 28 c are equidistant from a center horizontal plane and are mirror images of each other as are pocket pairs 28 b and 28 d.
In one embodiment, load pin 14 is provided with an internal passage 30 which extends to at least one end (e.g. end 14 e) of the load pin 14. Axial passage 30 is preferably coaxial with the longitudinal axis A-A, but it need not be. Advantageously, electrical conductors (not shown) can be run through axial passage 30 and out toward one of the ends 14 e of the load pin 14, so as to facilitate electrical connection of, and signal transfer from, the at least one sensor 16 to an external display, signal amplifier or recorder (not shown) and/or electrical connection of a plurality of sensors 16 to each other and/or to an external display, signal amplifier or recorder.
In one embodiment the one or more pockets 28 a, 28 b, 28 c, 28 d do not extend deep enough into the pin 14 to connect with the axial passage 30. In this embodiment the pockets 28 each contain an access passage 31 for connecting each sensor 16 to the rest of the system via electrical conductors. The access passages 31 are preferably in the floor 29 of the pockets 28 a, 28 b, 28 c, 28 d and connect with the axial passage 30, however, in other embodiments the access passages 31 are in the walls 33 of the pockets 28 a, 28 b, 28 c, 28 d. As is shown in the figures, the pockets 28 have a wide opening compared with the much smaller openings of the access passages 31. The access passages 31 are much smaller than the pockets 28 and therefore do not compromise the structural integrity of the pin 14. In some embodiments the access passages 31 are only wide enough to allow a few twenty-six gauge wires to pass through.
In one embodiment, axial passage 30 near the end 14 e may be enlarged at said end 14 e so as to accommodate additional electrical circuitry, such as a printed circuit board assembly 32, to assist with sensor signal processing, amplification and/or transmission of the sensor signals to the external display or recorder. In one embodiment, printed circuit board assembly 32 is provided with a conventional level sensor or accelerometer (not shown), to provide sensory data regarding the amount of tilt or displacement (if any) of the load pin's 14 longitudinal axis A-A relative to the horizontal plane H. In one embodiment, a wiring connector or socket 34 is provided to facilitate a removable electrical signal connection between the at least one sensor 16 and any external display, signal amplifier or recorder and to sealable close passage 30; and a cap 36 is provided to sealable close passage 30 once printed circuit board assembly 32 is installed within enlarged end of passage 30.
Description of the Pockets
As shown best in FIGS. 5 a and 9, the pin 14 includes one or more pockets 28 a, 28 b, 28 c, 28 d, each of which is adapted to receive a sensor 16 (or part of a sensor). The pockets are milled, drilled, or otherwise created below the outer surface of the pin 14 a predetermined distance and are preferably centered within their respective force measuring zone 15 a, 15 b. The embodiments shown include four pockets 28 a, 28 b, 28 c, 28 d with pockets 28 a and 28 b being generally the same distance from the longitudinal center of the pin 14 and substantially mirror images of each other relative to a vertical plane that passes through the center point CP. Pockets 28 a and 28 c are generally mirror images of each other relative to a horizontal center plane. As used herein, pockets 28 a and 28 b are on the same “side” but are on opposite “ends”.
Although the embodiment shown comprises four pockets 28 a, 28 b, 28 c, 28 d, other embodiments may have other numbers of pockets. Some embodiments include a single pocket 28 a with an entire sensor 16 mounted therein. Other embodiments include two or more pockets on the same side of the pin 14 such as pockets 28 c and 28 d with a sensor 16 (or part of a sensor 16) mounted in each pocket 28 c, 28 d. Still other embodiments include two or more pockets on opposite sides and opposite ends of the pin 14 such as pockets 28 a and 28 d with a sensor 16 (or part of a sensor 16) mounted in each pocket 28 a, 28 d. It is preferable, however, to have the pockets paired on opposite sides of the same end such as pockets 28 a and 28 c so they are opposing (mirror images) about a horizontal axis. This configuration is preferred because the symmetry allows for easier cancellation of downward forces since errors in pocket 28 a are opposite to downward forces in opposing pocket 28 c thereby allowing the forces to cancel each other and provide a more accurate calculation of torque T. It is even more preferably to have multiple mirror image groups of two on opposite sides of the same end such as mirror image pocket pairs 28 a/28 c and 28 b/28 d shown in the figures.
The pockets 28 are not through-bores (i.e. they do not go fully through the load pin 14). Instead, the pockets terminate a predetermined distance below the surface of the pin 14. This allows sensors 16 to be mounted within the pockets without compromising the strength of the pin 14. In some embodiments the pockets extend between about one eighth (⅛) and one quarter (¼) of the way through the diameter of the pin 14. A shallower pocket may be required if the pin needs to be stronger. In one embodiment the minimum depth of each pocket is about 0.188 inches ( 3/16 of an inch) in order to ensure the gauges and wires are situated in the pocket without protruding therefrom. A clear adhesive (or other suitable cover) may be used to cover and protect the gauges and wires in the pocket.
As shown best in FIGS. 6, 8, and 9, the pockets 28 a, 28 b, 28 c, 28 d preferably comprise a floor portion 29 and one or more wall portions 33. Collectively, the floor 29 and walls 33 are referred to herein as the “inner surface” or “web” of the pocket. In one embodiment, the floor portion 29 sits in a plane that is generally horizontal (when the pin 14 is aligned in its normal orientation described below) and parallel with the longitudinal axis A-A of the pin 14. In one embodiment the one or more wall portions 33 are generally perpendicular to the floor portion 29 and extend outwardly (away from the center of the pin 14). In some embodiments the floor portion 29 may be in a plane other than horizontal and the walls 33 may be in a plane other than vertical, however, these alternate embodiments make it more difficult to align the sensor 16. Further, as shown in FIGS. 4 b and 4 c, some embodiments include fewer than four wall portions 33 in a single pocket.
The sensors 16 are mounted to a portion of the web and are preferably mounted in the center of their respective pocket (which correspondingly means the sensors 16 are preferably centered within their respective force measuring zone 15 a, 15 b.) In one embodiment, the floor 29 of each pocket 28 a, 28 b, 28 c, 28 d provides sufficient surface area to mount the at least one sensor 16 (e.g. as shown in FIG. 8). In one embodiment, the surface area of the floor portion 29 is between two and five times larger than the exposed surface of the sensor 16 to allow for easy placement of the sensor to the floor 29. It is preferable to mount the sensor 16 to the generally horizontal floor portion 29 to measure torque T for the reasons discussed below. In another embodiment, the walls 33 of each pocket 28 a, 28 b, 28 c, 28 d provide sufficient surface area to mount the at least one sensor 16. As will become apparent from the description of the sensors 16 (below), the sensors 16 are preferably mounted to the walls 33 for measuring downward force DF instead of torque T, however, sensors 16 may be mounted to the walls 33 for measuring torque T in some embodiments. The large generally planer surfaces of the floor 29 and side wall(s) 33 make it easy to install the sensors 16 without needing a jig or other placement tool.
Description of the at Least One Sensor
As shown in FIGS. 4 a, 6, and 9, the pin 14 includes at least one sensor 16. Any suitable sensor 16 may be used, including strain gauges and semiconductor gauges. In one embodiment, the at least one sensor 16 is a transducer such as a strain gauge, glued or otherwise mounted to the inner surface (web) of the one or more pockets 28 a, 28 b, 28 c, 28 d as described above. Strain gauges are well known in the art as sensors to transduce deformation (due to application of force) into electrical resistance change. Generally, a strain gauge is a resistive device that increases its resistance value with an increase in the tension force and decreases its resistance value with an increase in the compression force. There are several types of strain gauges including bending strain gauges, axial strain gauges, torsional strain gauges, and shear strain gauges. Any suitable strain gauge may be used with the present invention. In use, as the interior of the pockets 28, 28 b, 28 c, 28 d (including the floor 29 and one or more walls 33) are deformed, any gauges mounted thereon are also deformed, causing the strain gauge's electrical resistance to change. Conventional electronic network circuitry and measurement calculations can then be utilized to translate output from the at least one sensor 16 into corresponding force measurements, such as torque T.
Referring to FIGS. 4 a, 4 b, 4 c, 10 a, and 10 b, typical strain gauge sensors 16 include multiple gauges (e.g., R1, R2, R3, R4) arranged in predetermined configurations as described below. The strain gauge sensors 16 are shown arranged as a long, thin conductive strip in a zig-zag pattern of parallel lines such that a small amount of stress in the direction of the orientation of the parallel lines results in a multiplicatively larger strain over the effective length of the conductor and, moreover, results in the strain gauge being far more sensitive to strain and forces in the orientation of the parallel lines than in the direction that is substantially perpendicular to the orientation of parallel lines.
Each sensor 16 comprises four gauges (R1-R4) which may be arranged in different configurations. In one embodiment, the sensor 16 (all four gauges) may be mounted within a single pocket 28 a. In another embodiment, two of the gauges R1, R3 may be mounted within a first pocket 28 a and the other two may be mounted within a second pocket 28 c or 28 d. As described above, these pocket pairs are preferably mirror images across the horizontal plane of the pin 14 (e.g. 28 a and 28 c on opposite sides of the same end), however, other pocket pair configurations may also be used.
In one embodiment, each gauge R1-R4 is a quarter gauge with each gauge separately and independently mounted within the pocket. In another embodiment, the load pin 14 comprises two half gauges to complete each sensor 16, where each half gauge comprises two gauges. This embodiment is shown in FIGS. 4 b and 4 c wherein gauges R1 and R3 make up a first half gauge and are mounted within pocket 28 a, and gauges R2 and R4 make up a second half gauge and are mounted within pocket 28 c such that pocket 28 a and 28 c are pocket pairs on opposite sides of the same end. The same gauge configuration may be used for pins 14 having additional opposing pocket pairs, such as pockets 28 b and 28 d wherein corresponding gauges R5 and R7 make up a first half gauge and are mounted within pocket 28 b, and gauges R6 and R8 make up a second half gauge and are mounted within pocket 28 d. The use of two half gauges to complete each sensor 16 is preferred since the spacing between gauges is completed by the manufacturer of the gauges and need not be measured at the time the gauges are placed in the pin 14.
For embodiments using traditional strain gauges, R1-R4 are mounted within their respective pockets 28 a, 28 c of the load pin 14 so that the orientation of their parallel lines are substantially parallel to the load pin's longitudinal axis A-A and substantially perpendicular to their respective pocket axis P (see FIG. 5 a). For embodiments using shear gauges, R1-R4 are mounted within their respective pockets 28 a, 28 c of the load pin 14 so that the orientation of their parallel lines are at angled relative to the load pin's longitudinal axis A-A and substantially perpendicular to their respective pocket axis P (see FIGS. 4 b and 5 a). In one embodiment the parallel lines of the shear gauges in R1 and R2 are angled at about 135 degrees relative to the pin's longitudinal axis A-A and the parallel lines in R3 and R4 are angled at about a 45 degree angle relative to the pin's longitudinal axis A-A.

Preferred Orientation of Load Pin Installation within Coupler

In one embodiment, when the load pin 14 is placed within a coupler 22, wherein its longitudinal axis A-A will be oriented substantially parallel to the horizontal plane H (see FIGS. 2 a, 4), and wherein the load pin 14 is rotated or mounted so that pockets 28 a, 28 b (and their pocket axis P) are oriented substantially parallel to the vertical plane V and, hence, also substantially parallel to the axis of rotation of the screw pile 12, which is generally driven into the ground in vertical manner (see FIGS. 2 a, 4). When shear style foil strain gauges are utilized as the sensor 16 the parallel lines thereof are substantially parallel to horizontal H and, therefore, the much less sensitive orientation of the gauge sensor 16 (direction PD) is substantially parallel to vertical V. Any torque T imparted to the screw pile 12 by the rotary drive 18 will be applied in a perpendicular manner to said pocket axis P and can be picked-up, or sensed, by the at least one sensor 16 via the much more sensitive parallel lines. Any downward force DF is directed through the sensors 16 along the much less sensitive direction PD and therefore will not be picked up by overall sensing system and/or the system 10 will overall be less affected by such downward force DF. In one embodiment, the orientation of the pocket axis P does not deviate more than 7 to 10 degrees (plus or minus) from being parallel to the vertical plane V.
In contrast, and as will now be appreciated by those skilled-in-the art, if the orientation of the pocket axis P is further deviated and is substantially parallel to the horizontal plane H, then: (a) any torque T imparted to the screw pile 12 by the rotary drive 18 will be applied in a parallel manner to said pocket axis P and will be sensed by the at least one sensor 16 via the much less sensitive direction PD and (b) any downward force DF is directed through the sensors 16 along the much more sensitive parallel lines PL. Such an orientation of the load pin 14 within the coupler 22 would, therefore, not be desirable and would likely create unknown and unexpected errors; or require significant calibration of the load pin 14 to compensate for such errors and/or unknowns.
In one embodiment, the load pin 14, once mounted within the coupler 22 is the desired orientation, is locked in place using a conventional end-cap (not shown) that may be attached to end 14 f. Alternatively, the load pin 14 may be locked in place (in the desired orientation) via welding, keyed members, cross-pins, locking pins or other conventional means.
Connection of Sensors within Each Pocket
In one embodiment, the sets of gauges in each pocket (e.g. R1 and R3 within pocket 28 a and R2 and R4 within pocket 28 c) may each be electrically interconnected using a conventional Wheatstone bridge electronic circuit or network 40; see, for example, FIG. 10 a illustrating how one set of gauges R1-R4 in pocket 28 a and 28 c may be interconnected in a Wheatstone bridge fashion (gauges R5-R8 in pockets 28 b and 28 d then likewise being interconnected using a second similar Wheatstone bridge network). In one embodiment using this Wheatstone bridge configuration, one branch or leg of the bridge circuit 40 is comprised of two gauges (which act as the resistors within the bridge circuit) that are mounted on the web of pocket 28 a (e.g. R1 and R3 on the web of pocket 28 a; see FIGS. 10 a and 4 b). The other branch or leg of the bridge circuit 40 is likewise comprised of the two remaining gauges that are mounted on the web of opposing pocket pair 28 c (e.g. R2 and R4 on the web of pocket 28 c; see FIGS. 10 a and 4 c).
The Wheatstone bridge network 40 is energized by a suitable source of electric potential 42 and may have additional electronics such as temperature control resistors 46 and calibration resistors 48 as is conventional with such bridge circuits. In one example using shear type foil strain gauges, when no force is applied to the load pin 14, the sensors 16, R1-R8 remain at their normal resistance values (e.g. at 3500 (ohms)), the bridge circuit is balanced and the signal voltage (Vsig) is therefore at zero. However, when a force is applied any unbalance in flow of electric current through the strain gauges R1-R4 of the network circuit 40 creates a measurable signal 44 that may be measured, recorded or amplified by an external display, signal amplifier or recorder (not shown) in a conventional manner to determine and calculate the amount of force or torque T applied.
Although a Wheatstone bridge network 40 will be responsive to, and can be used to measure, installation torque T and provide a measurable signal 44 relating thereto, there are some disadvantages to using a Wheatstone bridge network 40. In particular, the inventor has observed that such a Wheatstone bridge network 40 (as used with the preferred embodiment a set of four gauges within the pocket 28 a, 28 c) is still somewhat sensitive to downward forces DF, even if the downward force DF is directed through the sensors 16 along the much less sensitive direction PD.
Therefore, in a preferred embodiment a set of four gauge sensors 16 are mounted to the web of pocket pair 28 a and 28 c (e.g. R1 and R3 within pocket 28 a and R2 and R4 within pocket 28 c) using a differential bridge electronic circuit or network 50. In particular, in this differential bridge fashion, one branch or leg of the bridge circuit 50 is comprised of two gauges 16 (which act as the resistors within the bridge circuit) that are mounted on the web of pocket 28 a (e.g. R1 and R3 on the web of pocket 28 a; see FIGS. 10 b and 4 b). The other branch or leg of the bridge circuit 40 is likewise comprised of the two remaining gauges that are mounted on the web of opposing pocket pair 28 c (e.g. R2 and R4 on the web of pocket 28 c; see FIGS. 10 b and 4 c).
The differential bridge network 50 is energized by a suitable source of electric potential 52 and may have additional electronics such as temperature control resistors 56 and calibration resistors 58 as is conventional with such bridge circuits. When no force is applied to the load pin 14, the sensors 16, R1-R4 remain at their normal resistance values (e.g. at 3500 (ohms)), the bridge circuit is balanced and the signal voltage 54 (Vsig) is therefore at zero. However, when a force is applied any unbalance in flow of electric current through the strain gauges R1-R4 of the network 50 creates a measurable signal 54 that may be measured, recorded or amplified by an external display, signal amplifier or recorder (not shown) in a conventional manner to determine and calculate the amount of force or torque T applied.
Advantageously, the inventor has observed that a differential bridge network 50 (as used with the preferred embodiment of a load pin 14 having at least one set of four gauges within a pocket or pocket pair and said pin 14 being oriented within coupler as described above in the preferred orientation) is much less sensitive to any downward forces DF than using a Wheatstone bridge network 40.
In one embodiment, during manufacturing or afterwards, the particular electronic bridge network 40 or 50 of a particular load pin 14 is calibrated using a test bed or similar calibration machine, and using conventional calibration techniques.

Example

Now referring to FIGS. 11 a and 11 b, the set of four gauges R1-R4 within each pair of pockets 28 a, 28 c of the preferred embodiment may be electrically interconnected to provide a single measureable signal 44, 54 using either a pair of connected Wheatstone bridge electronic networks 40, 40′ (see FIG. 11 a) or a pair of connected differential bridge electronic networks 50,50′ (see FIG. 11 b).
Using the preferred embodiment of the load pin 14 and oriented in the preferred orientation within the coupler 22, as described herein, and wherein the sensors 16 are shear type foil strain gauges having normal (i.e. no force being applied) resistance values of 3500 (ohms), each pair of sensors mounted on a planar region (as shown in the Figures) and where excitation voltage (Vinput, +EX/−EX) is 10 Volts (although the signal voltage change (Vsig) being reported as millivolts-per-volt (mV/V)), and utilizing either a pair of connected Wheatstone bridge electronic networks 40, 40′ (of the embodiment of FIG. 11 a) or a pair of connected differential bridge networks 50, 50′ (of the embodiment of FIG. 11 b), the inventor observed the following signal values (in millivolts/volt) with respect to a 5000 lb force applied to the pin 14, either as downward force DF or as torque T (as noted), as shown in the table below:


	Downward Force	Torque Force

Wheatstone bridge network	−0.0167 mV/V	0.6643 mV/V
(40, 40′ in FIG. 11a)
Differential bridge network (50,	0.0003 mV/V	0.6605 mV/V
50′ in FIG. 11b)

As can be seen, both types of networks (Wheatstone bridge vs differential bridge) provide a similar magnitude of signal in a response to a 50001 b torque force (i.e. 0.6643 mV/V and 0.6605 mV/V). Therefore, both types of networks 40 or 50 are suitable to detect and measure torque forces T that may be applied to a screw pile 12. Advantageously, however, the differential bridge network provides a significantly lower signal when the load pin 14 is subjected to a downward force than does a Wheatstone bridge network (0.0003 mV/V for differential vs −0.0167 mV/V for Wheatstone). In fact, the observed difference was more than an order of magnitude smaller when using the differential bridge network. Advantageously then, utilizing a load pin 14 of the preferred embodiment as described herein, along with the eight strain gauges R1-R8 electrically connected between four pockets 28 a, 28 b, 28 c, 28 d using a paired differential bridge network 50, 50′, results in a system 10 capable of providing a signal representative of the installation torque T of a screw pile 12 while being unaffected (or only very minimally affected) by any downward forces DF.
More advantageously, the inventor has observed that such preferred embodiment, i.e. wherein pockets 28 a, 28 b on opposing ends are equidistant from the center point CP of the medial portion 14 m, wherein each of pockets 28 a, 28 b is provided with two generally horizontal planar floor portions 29 in a paired arrangement, wherein the floor portions 29 in each pocket 28 a, 28 b are equidistant from the central plane CP, wherein the arrangement of sensors 16 in one of the pockets (e.g. R5-R8 in bore 28 b) is a mirror image of the arrangement of the sensors 16, in the shear pocket on the other end (e.g. R1-R4 in bore 28 a) and wherein the sensors 16, R1-R8 are connected to generate a signal 54 using a pair of differential bridge networks 50, 50′, the load pin 14 and the system 10 are insensitive (or only minimally sensitive) to both downward forces DF and to point loading of the pin, such as if the pin 14 is mounted somewhat off-center within the coupler's lower section 22 l. Thus the preferred embodiment of the pin 14 and system 10 allows for a non-point source measurement of installation torque T that is not affected by downward forces DF. Moreover, now a conventional hinged member, such as a universal joint or simple pivot connector can be adapted or retro-fit to measure installation torque T and no additional devices are necessary which would otherwise lengthen the screwpile installation machinery (as is the case with the above-noted INTELLI-TORK™ and TORQATRON™ systems).
Those of ordinary skill in the art will appreciate that various modifications to the invention as described herein will be possible without falling outside the scope of the invention. For example, although the load pin 14 herein is shown as a single elongate cylindrical member having an axial body 14 a with longitudinal axis A-A extending between opposing ends 14 e, 14 f, preferably formed as one part and in one solid piece, it is also contemplated that the invention will work with a two-part (or split) load pin (not shown), wherein each of the two parts of such pin would correspond to the peripheral portions 14 p, 14 p′ (with corresponding ends 14 e and 14 f) along with the appropriate transitional portions 15 a, 15 b, and wherein with the medial portion 14 m is then split into two parts (and each such parts then corresponding with the relevant transitional portions 15 a or 15 b). In such an embodiment, each of the two parts of the split load pin is then mounted within the coupler 22 in the preferred orientation and wherein each part is mounted substantially the same distance from what would otherwise be the center of the medial portion CM of a single load pin 14.
In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite article “a” before a claim feature does not exclude more than one of the features being present.

Claims

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.