Patent Application
20100126782
The present invention relates to a weigh-in-motion scale for the measurement of wheel and/or axle loads of road vehicles. More particularly, the present invention relates to weigh-in-motion scales utilizing load sensing structures for generating electrical signals indicative of a load on the weigh-in-motion scale.
Wheel and/or axle load measuring plates are known to the art, which utilize one or more strain gauges, which can be associated with appropriate circuitry responding to the distortion of the measuring plate for signaling, indicating, recording or registering the wheel or axle load. Additionally, wheel scales which utilize strain gauge sensors fixed to deflectable load cells are known. However, the specific configuration of the load cells utilized in prior art scales, the placement of the load cells in the housing structures of these scales, and the cooperation of the active and inactive elements of these prior art wheel scale devices often yield complex and bulky wheel scales, which are inaccurate and unrepeatable under many conditions of use.
In one known wheel load indicator of this kind, the webs are formed between circular enlargements of a pair of recesses, and strain gauges are adhered to the opposed walls of these enlargements, i.e., to the two opposed web walls. The recesses themselves are closed.
In another known wheel load indicator, the recesses forming a web between them are of slot-like design starting from the lateral edges of the plate. The strain gauges are adhered to the webs in the plane of the upper surface of the plate. With such an arrangement nothing, but bending stresses of a plate loaded by a wheel can be determined. U.S. Pat. No. 4,098,365 issued Jul. 4, 1978 to L Pietzsch for “Device for the Measurement of Wheel or Axle Loads of Road vehicles” provided a device for measuring the wheel or axle load of a road vehicle. The device comprised a plate supported along its periphery at selected points or by knife edges in a frame. At least two pairs of wire strain gauges were provided along two imaginary lines of the plate, and which were spaced apart by a distance greater than the length of a contact zone of a wheel on the plate. Each pair of wire strain gauges included a wire strain gauge extending in the direction of displacement of the wheel, i.e. perpendicular to the imaginary lines, and a wire strain gauge parallel thereto.
U.S. Pat. No. 4,333,543 issued Jun. 8, 1982 to L Pietzsch for “Wheel or Axle Load Measuring Device for Road Vehicles” provided a measuring plate with at least one strain gauge. A wheel of a vehicle could rest on that plate to generate a signal, which was used to indicate or register the wheel load or axle load of the road vehicle. The measuring plate was received in a frame and had edges, which extended transversely of the direction of vehicle travel. Those edges were beveled or partly cut away so as to be overhung by complementarily shaped sides of the frame. Those edges were also provided with elastic bars or ribs along the bottom of the plate. The elastic bars or ribs rested upon and supported the center of the plate above a support plate or body, which was disposed below the measuring plate.
U.S. Pat. No. 4,616,723 issued Oct. 14, 1986 to Ing Ludwig Pietzsch GmbH & Co for “Wheel Load Indicator” provided a wheel load indicator, which comprised a rectangular flat plate of a light material having measuring properties. A series of recesses forming webs were provided along two lateral edges of the plate. Strain gauges were adhesively bonded to walls of bores in the area of the webs to determine the shearing stress under the load of a wheel which has been driven on the bending portion.
U.S. Pat. No. 4,775,018 issued Oct. 4, 1988 to W. P. Kroll et al for “Load Cell Assembly” provided a sealed shear load cell assembly for direct mounting to the load transfer portion of the weighing platform of a scale assembly. The load cell assembly cooperated with the weighing platform to provide a structural load-bearing component for the scale assembly. The top surface section of the beam load cell structure provided a predetermined shear segment in the beam structure. A pair of axially aligned, opposing circular apertures were provided to form stress isolation webs along the longitudinal axis of the beam structure. That structure included parallel end walls, which were spaced apart and which were oppositely and vertically centered adjacent the predetermined shear segment in the beam structure. Strain gauges were mounted to each parallel end wall of the stress isolation webs, and bearings were operative on the beam structure at predetermined locations outside each said stress isolation web. An interiorly disposed channel structure was further provided in the beam structure for housing the electrical communicative wiring of the strain gauges. The channel structure further included a centrally disposed aperture extending through the lateral sides of the beam, an aperture through each stress isolation web, and a longitudinally extending channel extending from one of each pair of the opposing circular apertures to the centrally disposed aperture. A sealing material in the interiorly disposed channel structure was further provided for isolating and protecting the electrical communicative wiring from environmental interaction.
U.S. Pat. No. 4,848,493 issued Jul. 18, 1989 to R. W. Hitchcock for “Load Sensing Structure for Weighing Apparatus” provided a load sensing structure for a weighing scale deck, which included two or more low profile flexure members, each of which was shaped like the letter “E”, with two outer legs secured to the deck and the inner leg to the platform. The inner leg had twice the bending strength and stiffness of the two outer legs. All legs had their ends connected in cantilever fashion, either to a common base or to one or the other of the deck and platform. Strain gauges on one leg provided complementary inputs to a bridge circuit under weight loads, but tend to cancel their effects on the bridge circuit under other load conditions.
The present invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest sense and more specific forms will then be further described and defined, in each of the individual claims, which conclude this specification.
A principal aim of the present invention is to provide such a weigh-in-motion scale, which is capable of weighing of heavier loads than previously known weigh-in-motion scales.
The present invention is based on the surprising discovery that, by making a slight increase in the thickness of the bending plate coupled with a change in the lateral locations of the load cells, the improved weigh-in-motion scale can be provided, which is capable of accurate weighing of heavier loads than previously known weigh-in-motion scales.
Thus, the present invention, in one broad aspect, provides a weigh-in-motion scale comprising: a rectangular parallepiped frame for installation into the pavement of a roadway and a thin, flexibly-deformable plate system secured within that frame. The thin, flexibly-deformable plate system is of rectangular parallepiped shape and comprises a combination of interrelated elements. Those elements include an upper, flexibly-deformable metal plate and a bottom or lower metal plate with a hollow volume therebetween. The upper flexibly-deformable metal plate has a thickness of about 0.604 inches to about 0.756 inches. The bottom or lower metal plate includes at least two parallel, longitudinally-extending, strain gauge channels, each of the strain gauge channels being spaced by an amount of about 52% to about 54% of the distance from the center line of the bottom or lower metal plate to the respective longitudinal edge of the bottom or lower metal plate. One or more strain gauges are bonded within an associated one of the longitudinally-extending strain gauge channels in an environmentally-isolated manner, while being capable of movement. At least two transversely-extending cross-channels are also provided in the bottom or lower metal plate, the transversely-extending cross-channels providing conduits. One or more wiring harnesses, which include electrical communicative wires or cables, are operatively associated with an associated one or more strain gauges, each wiring harness being secured within an associated one of the transversely-extending cross-channels in a manner, which isolates and protects the electrical communicative wires or cables from environmental interaction. The electrically-conductive wires or cables are electrically connected to the one or more strain gauges in an electrical bridge circuit, for example, Wheatstone bridge circuit, to provide input signals to the electrical bridge circuit.
By one feature of this invention, the upper, flexibly-deformable, metal plate comprises a steel plate having a thickness of about 0.720 inches.
By another feature of this invention, each of the strain gauge channels is spaced by an amount of about 53% of the distance from the center line of the bottom or lower metal plate to the respective longitudinal edge of the bottom or lower metal plate.
By another feature of this invention, each strain gauge is encapsulated in a rubber putty, e.g., plastic putty, butyl rubber putty, polyurethane rubber putty, epoxy rubber putty, and silicone rubber putty, so as to be secured, in an environmentally-protected manner, within its associated longitudinally-extending channel.
By another feature of this invention, each of the wire harnesses is encapsulated in a rubber putty, e.g., plastic putty, butyl rubber putty, polyurethane rubber putty, epoxy rubber putty, and silicone rubber putty, to be secured, in an environmentally-protected manner, within its associated transversely-extending channel.
By another feature of this invention, the bottom or lower metal plate comprises a thin steel plate, which is thicker than the thickness of the upper, flexibly-deformable, metal plate.
By another feature of this invention, each of the longitudinally-extending strain gauge channels, which encapsulates an associated strain gauge within a rubber putty, includes an upper surface thereof, the upper surface comprising the top of the rubber putty, the upper surface being covered with a foil tape, and including a rubber overlay atop the bottom or lower metal plate in the areas surrounding the foil tape over each of the strain gauge channels.
By another feature of this invention, each of the longitudinally-extending strain gauge channels, which houses the one or more strain gauges, also includes associated electrically-conductive wires or cables to wiring harnesses.
By another feature of this invention, each of the longitudinally-extending strain gauge channels, which houses the one or more strain gauges and which also includes associated electrically-conductive wires or cables to the one or more wiring harnesses, further includes a first lower layer of a suitable elastomeric material, which is superposed atop each associated strain gauge, and a second upper layer of a suitable elastomeric material encapsulating each associated strain gauge.
By another feature of this invention, each of the transversely-extending cross-channels, in which each of the wire harnesses is encapsulated in a rubber putty, includes a foil tape atop an upper surface of the rubber putty, and a rubber overlay atop the metal plate in the areas surrounding the foil tape, which is atop the transversely-extending cross-channels.
By another feature of this invention, each of the transversely-extending cross-channels, in which each of the wire harnesses is encapsulated in a rubber putty, includes a foil tape atop an upper surface of the rubber putty, and a rubber overlay atop the metal plate in the areas surrounding the foil tape, which is atop the transversely-extending cross-channels, in which each of the one or more wiring harnesses is supported on a first lower layer of a suitable elastomeric material, and in which a second upper layer of a suitable elastomeric material encapsulates each associated wire harness.
By another feature of this invention, the suitable elastomeric material comprises a rubber putty, e.g., plastic putty, butyl rubber putty, polyurethane rubber putty, epoxy rubber putty, and silicone rubber putty.
By another feature of this invention, the bottom or lower metal plate includes an oblique channel, through which electrically-conductive wires or cables are electrically connected to the wiring harnesses.
By another feature of this invention, the transverse edges of the thin, flexibly-deformable plate system are perpendicular to the upper plate.
By another feature of this invention, the transverse edges of the thin, flexibly-deformable plate system are beveled to merge as planar longitudinally-extending edges at the bottom or lower metal plate.
By another feature of this invention, the thin flexibly-deformable plate system is bonded to the substantially rectangular parallelepiped frame by an elastomeric material, preferably a pad of Neoprene™.
By another feature of this invention, the thin flexibly-deformable plate system is encapsulated by an elastomeric material, preferably Neoprene™.
In operation, as weight is applied to the weigh-in-motion scale, the upper flexibly-deformable metal plate bends, wherein the degree of bending is indicative of the weight applied, and applies force to the strain gauges, which thus provide a changing resistive value, which is indicative of the bending of the flexible element and the weight applied.
Preferably, the bending of the metal plate is elastic, and changing resistive value is proportional to the degree of bending and the weight applied. This generates input signals to the Wheatstone bridge circuit, which then generates output signals from the Wheatstone bridge circuit, which are indicative of, and preferably proportional to, the force applied to the upper, flexibly-deformable metal plate. This provides a numerical value of the weight applied.
In the accompanying drawings,
The present invention in its broad aspect as above described, provides a weigh-in-motion scale (10), which includes a rectangular parallepiped frame (12) for installation into the pavement of a roadway. A thin, flexibly-deformable plate system (20) is secured within the rectangular parallepiped frame (12). The thin, flexibly-deformable plate system (20) is in the form of a rectangular parallepiped (13) shape. The thin, flexibly-deformable plate system (20) includes an upper, flexibly-deformable metal plate (16) and a bottom or lower plate metal (24) with a hollow volume space (15) therebetween. The bottom or lower metal plate (24) includes at least two parallel, longitudinally-extending, strain gauge channels (52). At least one strain gauge (82) is bonded within an associated one (52) of the longitudinally-extending strain gauge channels (52) in an environmentally-isolated manner to provide environmental protection (73), while being capable of movement. At least two transversely-extending cross-channels (54) are provided in the bottom or lower metal plate (24), each of the transversely-extending cross-channels (54) thus providing conduits. At least one wiring harness (72) including electrical communicative wires or cables (58) is operatively associated with an associated strain gauge (82). Each wiring harness (72) is secured within an associated one of the longitudinally-extending channels (52) and within an associated one of the cross-channels (54) in a manner (73, 81), which isolates and protects the electrical communicative wires or cables (58) of the wiring harness (72) from environmental damage. The electrically-conductive wires or cables (58) are connected to an associated strain gauge (82) in an electrical bridge circuit, preferably Wheatstone bridge circuit 90, to provide input signals to the Wheatstone bridge circuit. In one embodiment of the present invention, the lower or bottom metal plate (24) comprises a thin steel plate, which is thicker than the thickness of the upper, flexibly-deformable metal plate (16).
Description of
As seen in
Description of
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Description of
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The strain gauge channels 52 are each spaced by a distance “B” of about 52% to about 54%, preferably about 51%, of the distance from the centre line “C” of the bottom or lower metal plate 24 towards the longitudinal edge 28 thereof. In other words, if the distance from the center line “C” to the longitudinal edge 28 is 100% the distance from the centre line “C” to the strain gauge channel 52 is about 52% to about 54%, preferably about 51% of that distance.
For example, for a lower metal plate 24, which is 19.961 inches wide, the strain gauge channels 52 are spaced 5.316 inches from the center line “C” of the bottom or lower metal plate 24.
A comparison of the critical dimensions of the thin flexibly-deformable plate system 20 of one embodiment of the present invention with the critical dimensions of the prior art gives the following results:
The width of the lower metal plate 24 is 19.961 inches;
The spacing “B” of the strain gauge channels from the center line “C” of the lower metal plate is 5.316 inches; and
The thickness of the upper flexibly-deformable metal plate 16 is 0.720 inches.
Critical Dimensions of the Thin Flexibly-Deformable Plate System of the Prior Art
The width of a lower metal plate is 19.961 inches;
The spacing “B” of strain gauge channels from a center line “C” of the lower metal plate is 4.941 inches; and
The thickness of the upper flexibly-deformable metal plate is 0.630″.
The Maximum Weight Measurable is as Follows:
15 Tonnes/axle+10%
For the Thin Flexibly-Deformable Plate System of the Prior Art
10 Tonnes/axle+10%
Thus, the thin flexibly-deformable plate system 20 of one embodiment of the present invention provides an unexpected dramatic improvement (i. e., about 50%) over the prior art by making only a slight increase in the thickness of the bending plate coupled with a change in the lateral locations of the load cells
Description of
As seen in
The thin flexibly-deformable plate system 20 of one embodiment of the present invention is bonded to the substantially rectangular parallelepiped frame 12 by an elastomeric material. For example, this may be done by means of a lower pad 74 of Neoprene™ rubber. The thin flexibly-deformable plate system 20 of one embodiment of the present invention may be alternatively encapsulated (not shown) by the same Neoprene™ rubber.
These two elastomeric material encapsulations 74, 76 are identified as environmental protection 73. This provides protection against the ingress of moisture and dirt.
Description of
As seen in
These two elastomeric material encapsulations 86, 90 are identified as environmental protection 81. This provides protection against the ingress of moisture and dirt.
Thus, to summarize, strain gauges 82 are bonded to the bare metal of the longitudinally-extending channels 52 of the bottom or lower metal plate 24. The strain gauges 82 are encapsulated in a rubber putty, 86, e.g., Neoprene™, which does not hinder the movement of the strain gauges 82. The bottom or lower metal plate 24 also includes two longitudinally-extending channels 52, within which are secured the wiring harnesses 72. The wiring harnesses 72 are also encapsulated in a rubber putty 76, e.g., Neoprene™. Additionally, the lower metal plate 24 includes an oblique channel 56 (best seen in FIG. 5) through which electrically-conductive leads or cables 58 from an electrical signal receiving cabinet (not shown) are connected to the wiring harnesses 72.
Description of
As noted hereinabove,
R1-R14: 12 Ohms Strain gauge;
R15-R18: 33 Ohms;
R19, R20: 84 Ohms; and
R21,R22: resistive wire (nulling)
According to one embodiment of the present invention, the bridge resistance is as follows, measured in Ohms:
In use, as weight is applied to the weigh-in-motion scale 10, the upper flexibly-deformable metal plate 16 of the thin, flexibly-deformable plate system bends, and its deformation is indicative of the force of the weight applied, preferably bending elastically so that the deformation is proportional to the weight applied. The strain gauges 82 provide a changing resistive value, associated with the bending, preferably proportional to the bending, of the upper flexibly-deformable metal plate 16. The weight, through the force thus detected, applies input signals to the Wheatstone bridge circuit. The Wheatstone bridge circuit 100 then generates output signals, which are indicative, preferably proportional, to the force applied to the upper flexibly-deformable metal plate 16 and thus, provides a measure of the weight applied.
The Wheatstone bridge circuit is a preferred implementation, other types of electrical bridge circuits, e.g., Kelvin double bridge circuit, or other known electrical circuits for measuring resistance may also be suitable.
Although Neoprene™ has been used as a preferred elastomeric material in the embodiments of the present invention, it is understood that other elastomeric materials, e.g., variations of the rubber putty can also be used, e.g., plastic putty, butyl rubber putty, polyurethane rubber putty, epoxy rubber putty, and silicone rubber putty.
Conclusion
The foregoing has constituted a description of specific embodiments showing how the invention may be applied and put into use. These embodiments are only exemplary. The invention in its broadest, and more specific aspects is further described and defined in the claims, which follow.
These claims, and the language used therein are to be understood in terms of the variants of the invention, which have been described. They are not to be restricted to such variants, but are to be read as covering the full scope of the invention as is implicit within the invention and the disclosure that has been provided herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,644,875 | Nov 2008 | CA | national |
