MXPA00008488A - Inductive loop sensor and method of manufacturing same - Google Patents

Abstract

A flat or round cable used in an inductive loop sensor. The inductive loop sensor may be installed in a saw-cut groove made in a roadway or positioned in a new roadway. The inductive loop sensor includes an inductive loop having a conductor with one or more turns covered with a protective jacket. First and second ends of the loop conductor are connected in a connection area to a pair of wires in a lead-in cable. The connection area is sealingly encased in a molded connector. This inductive loop may be made from round cable.

Description

INDUCTIVE CHART SENSOR AND METHOD TO MANUFACTURE IT DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION This invention relates generally to an inductive frame sensor for determining the movement or presence of an object, in particular to an inductive frame sensor having improved resistance and more particularly to an inductive frame sensor that It is used on a road or roadway to sense or detect the movement or presence of automobiles. Due to their proven performance characteristics, reliability and low cost, the sensors of return, curl or inductive box are widely used for monitoring systems or monitoring and traffic control. For example, many traffic-light signals have inductive box sensors embedded within the asphalt to determine when to change the traffic light with base, for example, in a detected number of cars waiting for the light to change. In general, the inductive panel sensor is installed permanently either under a new road during construction or in a cut of groove or cutting ditch or saw line, or sawing, inside the surface of the road.

In any installation, the inductive sensor frame can be exposed to very high temperatures. The inductive box sensor embedded in the road must survive repeated compression forces due to the passage of traffic, because replacing an inductive box embedded within the asphalt or concrete is, at best, difficult, and interrupts traffic on the road while the repair takes place. During the construction of a new road, the inductive box sensor is usually placed on the road bed, then hot asphalt is laid on the inductive box sensor, covering the inductive box sensor. As the road deteriorates, the road can be paved over the inductive box sensor. For this reason, it is necessary that the inductive panel sensor survive the paving and resurfacing process intact. Most inductive, conventional preformed cabinets are sufficiently fragile that they frequently break and become inoperative due to the normal traffic moving on the inductive panel or the paving / resurfacing of the road during the installation of the inductive panel sensor or during road repair operations. On existing roads, the inductive box sensors are placed in a sawing groove that is cut off on the road. Once placed in the groove, the inductive box sensor is covered and sealed on the road with hot asphalt or with chemical sealants. As cars travel over the groove, the sealant or asphalt will break, allowing the exposure of the inductive box sensor to changes in environmental conditions, such as temperature and humidity. Most conventional preformed frame sensors are rigid and their size or circumference can not be adjusted, therefore, the sawing groove must be larger than required to allow manufacturing tolerances. Ideally, the sawmill groove should be as narrow as possible. The permanent installation of an inductive box sensor under a new road, or the temporary installation of an inductive box sensor on the top of an existing road, does not impose any of the specific dimensional requirements to the inductive box sensor as The process of installing sawmill does it. However all of them must survive the installation process. Most failures of inductive switchgear sensors occur during the installation process, due to exposure to high temperatures from the melted asphalt, which is laid on top of the inductive switchboard sensor, or due to the repaving of the road. In addition, the inductive panel sensor must allow strict control of the geometry of the cross section of the panel and of the electrical properties, since these properties affect the accuracy of the signal generated by the inductive panel sensor. Accordingly, it is desirable to provide an inductive frame sensor that can survive repeated compression forces due to traffic crossings, that is unaffected by changes in environmental conditions, such as temperature or humidity, that can withstand abrasive materials and High temperature encountered by the frame during paving or sealing processes, and resistant to the sealing chemicals often used in paving and petroleum-based contaminants generated by vehicles traveling over the inductive box sensor. Finally, for the sawing installation, it is desirable that the inductive box sensor have a narrow cross section and be adjustable to fit within the groove formed by the sawing.

BRIEF SUMMARY OF THE INVENTION The invention provides a traffic box sensor, inductive, preformed and robust, based on the use of cables that are readily available in quantities produced in mass, which reduces the total cost of the inductive frame sensors. Inductive box sensors are installed either in furrows formed by sawing on the road surface or under new roads and paved roads and paved with material such as asphalt or concrete. The inductive panel sensor can be exposed to very high temperatures during installation, so insulating materials are used for elevated temperatures in order to protect the internal wires and conductors. In addition, during the resurfacing of a road, when the road surface is scraped to form a rough surface for the new asphalt, the inductive box sensor has a vertical profile or cut sufficiently low, so that the scraping process does not destroy the inductive box sensor. For installation by sawing, a frame with a narrow cross section (eg, <6.35 mm (<0.25 inch)) is constructed, either with a flat cable design or a thin round cable that is flexible enough to adjust inside a groove formed by the sawing. Because most inductive box sensor failures occur during the installation process, the inductive box sensor is robust or rugged. The inductive frame is also resistant to environmental conditions, such as temperature or humidity, due to the selection of insulation and fleece materials and the unique construction. In addition, the inductive box sensor uses a prefabricated cable for the inductive switch cable, so that the cross section and electrical properties of the switchboard can be controlled in a tight manner. Also, the cost of the sensor is reduced by the use of materials and manufacturing processes that are normally used in the production of cables and assemblies or cable assemblies. For example, the cable components of the preformed box are produced using standard extrusion methods and can be produced economically in large quantities even when using high performance installation / plywood materials. In sum, the inductive box sensors according to the invention are relatively inexpensive, easily manufactured, easily used in any type of frame sensor installation, employ high performance materials that have records or proven tread marks and are easily available, are designed to survive road resurfacing operations and are designed to have a long service life.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a flat cable inductive box sensor incorporating an illustrative example of the invention for installation by sawing; Figures 2A to 2C are detailed diagrams showing a flat cable inductive box sensor for installation by sawing, according to one embodiment of the invention; Figure 3 is an enlarged view of an inductive round cable box sensor incorporating another illustrative example of the invention for installation by sawing; Figures 4A to 4C are detailed diagrams showing a round cable inductive box sensor for installation by sawing, according to another embodiment of the invention; Figure 5 is a perspective view of an inductive box sensor incorporating an illustrative example of the invention for installation on the top or under a new road surface; Figures 6A to 6D are detailed diagrams showing a flat lower cable inductive box sensor for new road installation, in which the internal conductors are stacked vertically; Figures 7A to 7D are detailed diagrams showing an inductive round cable box sensor for new road installation, in which the internal conductors are in a triangular configuration; Fig. 8 is another embodiment similar to Fig. 7 showing a flat-bottom cable inductive box sensor, in which the internal conductors are in a triangle configuration; Fig. 9 is an enlarged view illustrating the adjustable section of the inductive box sensor for a sawing installation; Figure 10 is a cross-sectional view of a round inductive cable box according to the invention; Figure 11 is a graph illustrating the inductance of the flat and round cables with 1 to N turns of the cable frame; Figure 12 is a graph illustrating the sensitivity of the inductive frame sensor according to the invention, with one to N turns of the cable frame; Figure 13 shows examples of sawing configurations in which the inductive box sensor can be installed; and Figures 14A to 14D show several cross sections of a road with various inductive frame sensor modes installed.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY The invention is particularly applicable to an inductive box sensor and to the method for manufacturing it, for installation in a sawing groove on an existing road or under a new road, used to measure the presence or movement of the flow of traffic. Figure 14 shows several roads with the inductive box sensor installed. Figure 14A shows an existing road with a sawing furrow, with the inductive box sensor installed. Figure 14B shows a new road where an inductive box sensor is placed on a firm bed of the road and then paved. These are the two types of inductive box sensors that will be described below. In addition, there are other road facilities, in which the present invention can be used. Figure 14C shows the inductive box sensor placed on an existing road with new pavement covering the sensor (this would be similar to Figure 14B). Figure 14D shows the inductive box sensor placed on top of an existing road without having been paved. This is focused on being used for short periods of time, because the sensor is in direct contact with vehicles and the environment. It will be appreciated, however, that the sensor and the method or manufacture according to the invention have great utility. For example, the inductive box sensor can also be used to detect the presence or movement of an aircraft or a land vehicle at an airport. Figure 1 is an illustrative embodiment of an inductive box sensor 30 which is designed to fit within a plurality of saw blades 32 made within a surface of a road 33. In this first embodiment, the inductive cable is a cable of flat box 36 that fits inside the saw blades 32. The flat box cable 36 can be made from prefabricated cable and have any number of curls, loops or turns of internal conductors, but three turns are shown in the figures. In the preferred embodiment of the inductive frame sensor 30, the frame cable 36 has three internal conductors connected together to form the three turns within the frame. In this embodiment, as described in more detail below, the inductive box sensor 30 consists of the flat box cable 36 and an input wire 40, each having a protective cover, with a box / input connector 38 that surrounds the conductors of the box cable 36 and the wires of the input cable 40 where they are joined together. As shown, the connector 38 is narrow or narrow and fits into the interior of the saw or saw cut 32, which is typically 1/4"wide 6. The connector 38 is not a" T "connector. , as used with most preformed conventional frames, but instead is a linear joint, in which the wires of the input cable 40 enter one end of the connector 38 and the ends of the conductors in the cable box 36 enter the other end of the connector 38. This unique design of the inductive box sensor allows the adjustment of the circumference of the loop or loop to fit or correspond to the sawing. In Figure 9 the first end 36a and the second end 36b of the frame cable 36 are shown entering the connector 38 from the same side. The first end 36a is positioned above the second end 36b in a plane oriented substantially vertically. Due to this placement, when the first end 36a and the second end 36b are pushed together to fit in the sawdust, they are aligned in a vertical plane. This makes the frame cable 36 fully adjustable to conform to a variety of saw configurations, shown in Figure 13. During use, the frame cable 36 is placed in the sawdust 32. Any excess frame wire 36 is placed consequently placed in the entry hole 31. Since the first end 36a and the second end 36b are stacked vertically, there is no need to make the inlet sacking 31 wider than the frame sawn 32. Figures 2A, 2B, 2C and 2D show several detailed views of the conductor connection area of the inductive frame sensor 30. The sensor 30 includes a flat cable 36 and an input cable 40. The inductive box sensor 30 also includes the connector 38, made of a molded plastic housing, which protects from damage the connection area for the flat box cable 36 and for the cable 40. Shown in the preferred embodiment, the flat frame cable 36 has three conductors 42, 44 and 46 inside the cable, which when connected form three turns. As described above, the invention is not limited to any particular number of turns of the conductor. In accordance with the embodiment described above, to form the inductive sensor 30 having three turns, the flat frame cable 36 is used having the two ends 36a and 36b. Each of the internal conductors also has two ends. To form the turns, each of the internal conductors are joined together and to the input wires. In order to do this, a first end 42a of the conductor 42 is attached to a first wire 48 of the input cable 40 in a first connection 52 and a second end 42b is joined to a first end 44a of the conductor 44, in 54, forming the first round A second end 44b is attached to a first end 46a of the conductor 46, at 56, forming the second turn. And finally, a second end 46b is joined to a second wire 50 of the input cable 40 in a second connection 58, forming the third turn. By joining the conductors in the flat cable and the wires in the input cable in this manner, a continuous path is formed from the input wire 48 through the first conductor 42 ("first turn"), through the second conductor 44 ( "second round"), through the third conductor 46 ("third turn") and finally towards the input wire 50. The various conductors and wires can preferably be welded or spliced together. Figure 2B illustrates a cross-sectional view along line A-A, as shown in Figure 2A. As shown and described above, the flat frame cable 36 has three conductors 42, 44 and 46 within the cable. In this mode, the conductors are aligned to form a flat cable. As shown, the cable 36 has a jacket layer 60 that protects the cable from damage. The choices of materials that can be used for this jacket layer will be described below. Figure 2C is a cross-sectional view along the line B-B as shown in Figure 2A. As shown, the input cable 40 has a first wire 48 and a second wire 50. In addition, the input wire 40 has a jacket layer 62, which protects both input wires. The jacket layer 62 and the materials used for the insulating layer will be described in more detail below.

This type of flat cable has a high sensitivity to the presence of objects, which will be described below, and fits within a 1/4"saw. Figure 3 is another illustrative embodiment of the invention showing a sensor inductive box 130 which can be inserted into a sawing insulation The inductive box sensor 130 is similar to the inductive box sensor 30, described above with reference to figures 1 and 2, the difference being that a box cable is used round 136 instead of the flat box cable 36. In particular, as shown in Fig. 3, a plurality of saw blades 132, typically with 1/4"width, house the round box cable 136 of the frame and a sawmill Inlet 131, which may also have a width of 1/4", houses a portion of the round box cable 136, a connector 138 and an input wire 140. The connector 138 is made of a molded plastic, which surrounds the the cond uctores of the box cable 136 and the wires of the input cable 140 where they are soldered or joined together. The connector 138 also insulates the internal conductors in the frame cable 136 and the wires of the input cable 140 from the fatigue of the external environment. In this embodiment, the box cable 136 is constructed of round cable with a protective cover. The ends 136a and 136b of the round frame cable 136 are stacked on top of each other as they enter the input hack 131, as shown in FIG. 3. As with the first embodiment shown in FIG. Inlet 140 leaves connector 138 opposite the frame wires 136a and 136b. Additional details regarding this round inductive box cable 136 according to the invention will be described in more detail below. Figures 4A, 4B and 4C show several views of an inductive frame sensor 130 mode. As shown in Figure 4A, the inductive box sensor 130 includes a molded connector 138, which surrounds and seals the round box cable 136 and the input cable 140, which are connected together. As described above, the round box cable 136 forms the inductive box, which measures the presence or movement of an object close to the inductive frame, while the input wire 140 transmits the signals generated by the inductive frames to a detector . In this embodiment, the inductive frame sensor 130 has three conductor turns. However, it should be apparent that the inductive frame sensor is not limited to any particular number of conductive turns and may be increased or decreased. The structure of the round box cable 136 and the input cable 140 will be described in more detail below with reference to Figures 4B and 4.C. The connector 138 houses the connections of the various conductors in the round-box cable 136 and the wires in the input cable 140. As shown, the round-box cable 136 has three conductors 142, 144 and 146 within the cable. Thus, to form the sensor with three turns, each of the internal conductors are connected to each other and to the input cable. To do this, a first end 142a of the conductor 142 is attached to a first input wire 148 of the input cable 140 at 152, and a second end 142b is joined to a first end 144a of the conductor 144 at 154, forming a first turn . A second end 144b is attached to a first end 146a of the conductor 146 at 156, forming a second turn. And finally, a second end 146b is joined to a second input wire 150 of the input cable 140 at 158, forming a third turn. By thus joining the conductors in the round cable 136 and in the input cable 140, a continuous path is formed from the first input wire 148, through the first conductor 142 ("first turn"), the second conductor 144 ( "Second round"), the third conductor 146 ("third turn") and finally the second input wire 150. Thus, with this configuration, an inductive sensor is formed with three turns. As described above, the invention is not limited to a driver with three turns and a different number of turns can also be used. The conductors and the wires can be welded or spliced together. The connector 138 can be a molded plastic housing, which can surround and protect against damage to connected conductors and wires during installation or use. The connector 138 also insulates the conductors and wires from the environment. Figure 4B is a diagram illustrating a cross-sectional view along the line A-A, as shown in Figure 4A. As described above, each round box cable 136 has three conductors 142, 144 and 146 within the cable. In this embodiment, the conductors can be twisted together and form a type of triangular configuration, which when surrounded by the jacket or envelope layer 160, form a round cable. The details of the jacket layer 160 of the cable will be described below.

Figure 4C is a cross-sectional view along a line BB as shown in Figure 4A showing the connector 138 with the input cable 140. As described above, the input cable 140 has a first wire 148 and a second wire 150. To protect against damage to the input wire 140, the input wire 140 also has a jacket or wrap layer 162. The materials for the jacket layer 162 will be described later. As described above, connector 138 may be thin enough to fit in a 6.35 mm (1/4") wide sawing groove together with frame 136 and inlet wire 140 because the ends of the box cable round 136a and 136b are stacked on top of each other as they enter connector 138. Figure 5 is an illustrative embodiment of the invention showing an inductive, cable box sensor 230 that can be installed on top of a bed of a new road, which will then be paved with some type of paving material, such as asphalt With this embodiment of the invention, the adjustment of the circumference of the frame is not critical as in the previously discussed sawing modes, Since the frame can be adjusted before laying the asphalt, the narrow width of the sawing is not necessary as previously required. adro inductive 230 has a box cable 236, which is secured to the surface of the roadbed before paving. The frame sensor 230 can be made from a frame cable 236 with any number of turns formed by conductors within the cable. The box cable 236 can be made from a prefabricated cable. • »In the preferred embodiment, the frame cable 236 has three conductors forming three turns. Drivers can be insulated and caged or wrapped for protection. In this embodiment, a connector 238 can be used forming a "T" junction, in which an input cable 240 leaves the connector 238 from one end of the T, while one end of the round cable 236 enters from one end, while the other end of the round cable 236 enters an opposite end of the connector 238 on each leg of the T. Further details about this and other embodiments of the present invention will be described in greater detail below. Figures 6A to 6D are diagrams illustrating a first mode of the inductive box sensor above the pavement 330. In particular, with reference to Figure 6A, a molded connector 338, configured in "T" houses the junction of the cable conductors of frame 336 with the input wires of the input cable 340. The connector 338 protects the frame cable conductors and the input wires against damage during installation and / or during use, and insulates the conductors and wires of the environment. The frame cable 336 includes a first conductor 342, a second conductor 344 and a third conductor 346, which are interconnected with each other to form an inductive box sensor with three turns. The frame cable 336 has a first end 336a and a second end 336b with each inner conductor also having first and second ends. To form the turns, the internal conductors are connected to each other and to the input wires. To accomplish this, a first end 342a of the conductor 342 is attached to a first input wire 348 of the input cable 340 in a first connection 352 and a second end 342b joins a first end 344a of the conductor 344 in 354, forming a first round. A second end 344b joins a first end 346a of the conductor 346 at 356, forming a second turn. And finally, a second end 346b is joined to a second input wire 350 of the input cable 340 in a second connection 358, forming a third turn. As seen in the figure, each end of the cable 336 enters opposite sides of the connector 338 with the first connection 352 opposite the second connection 358. As described above, in the event that an additional turn or fewer turns of the conductors are required, the connections between the various drivers will have to be modified. The conductors can be welded or spliced together. In this mode for installation above the pavement, the used configuration of the "T" connector 338, has each end 336a and 336b of the cable 336 entering the connector 338 on opposite sides and the input cable 340 leaving the connector from a lateral direction . Figure 6B is a cross-sectional view along line A-A, as shown in Figure 6A. As shown, the frame cable 336 includes the three conductors 342, 344 and 346. Furthermore, as shown in Figure 6D, the flat frame cable 336 also includes a jacket layer 360, which protects the conductors against damage during installation or use. In this particular embodiment, the frame cable 336 is formed in a domed configuration having a flat bottom 337. However, the configuration is not critical to the invention. Figure 6C is a cross-sectional view along the line B-B, as shown in Figure 6A. As shown in Figure 6C, the input wire 340 has a first input wire 348 and a second input wire 350, which are connected to the various conductors of the frame cable to form the various turns of the sensor. In addition, the input cable 340 also includes a jacket layer 362, which protects the input wires from damage during use or installation. The details of the jacket layer and its materials will be described in more detail later. Now, a second embodiment of the inductive box sensor according to the invention that can be paved over during installation will be described. Figures 7A to 7D illustrate a second embodiment of an inductive box sensor to be paved 430, including a molded connector 438, a box cable 436 and an input cable 440, as shown in Figure 7A. as shown in Figure 7C, the frame cable 436 includes three conductors 442, 444 and 446 and a jacket or wrap layer 460, which protects the conductors against damage during installation and / or during operation. In this embodiment, the triangular array of the three conductors and the jacket layer 460 form a round cable. The details of the jacket layer 460 will be described later. Figure 7D is a cross-sectional view along the line BB, as shown at 7B, of the connector 438 and the input cable 440. As shown, the input cable 440 includes a first input wire 448 and a second inlet wire 450 and a jacket layer 462. The details of the jacket layer 462 will now be described in more detail. The frame cable 436 has a first end 436a and a second end 436b with each inner conductor having a first end (442a, 444a, 446a) and a second end (442b, 444b, 444c). The connections of the conductors and the input wires to form the turns are the same as those described for the previous mode shown in Figure 6A. Figure 8 shows another embodiment of the inductive frame sensor 430 shown in Figures 7A to 7D. The difference is that the triangular arrangement of the three conductors (442, 444, 446) form a frame cable having a flat bottom 437, similar in cross section to that of Figure 6D. Now, the construction of the inductive box sensors will be described, including the potential materials for the jacket layer, the (coil) design details of the frame sensor, the input cable specification, the connector design and the Complete design of the frame assembly. First, the possible materials for cable insulation and for the jacket layer will be described. Materials There is a huge and growing variety of synthetic materials that are used for wire insulation and for veneering. Taking into account the wide range of properties of materials that can be obtained by each of the basic plastics through changes in the formulation, the resulting list of potentially acceptable materials for the inductive box sensor can be quite extensive. Some of the key parameters for material selection include resistance to stress, Shore hardness, temperature range during use, water absorption resistance, abrasive resistance, weather resistance, chemical resistance and price. Temperature variations, other environmental factors and aging can also lead to large variations in the properties of plastics. Due to the wide variation in material properties for each of the materials, the most common names will be used. Most of the candidate materials considered for wire insulation and the protective jacket layer are either thermoplastic materials (ie, these materials do not harden or cure under heat), or thermosets. Thermoplastic wire insulation can be easily produced through a standard extrusion process, providing thermoplastics with a cost advantage over thermosetting materials. The thermoplastics can be remelted and are therefore suitable for making sealed, molded connections between parts made of the same material or similar material. In general, thermoplastics tend to be more robust and less brittle than thermoplastics, but they are much less stable dimensionally and thermally. It is a common practice in the manufacture of electrical cable to use different materials for the electrical insulation of conductors and wires, and for the wrapping or wrapping (environmental protection), thus combining the benefits of two different materials and often reducing the cost. In the inductive box sensor for an application in traffic, the requirements of the electrical insulation are not very strict, since the box operates under low current and low voltage, so that usually an insulation is used is rated for 500V. It is important, however, that the electrical properties of the material do not change significantly with time. Materials that can be used for veneer / insulation include polyvinyl chloride (PVC), polyurethane, polyolefin, polyethylene, polypropylene, polyester, interlaced polyolefin, fluoroplast, ETFE (Tefzel® brand), elastomers, silicone, neoprene, hypalon and thermoplastic elastomers. A large number of materials for insulation and the jacket or cable sheath are suitable for the construction of an induction frame preformed according to the invention. Continuous improvements in the formulation and processing of plastics almost ensures that better and less expensive materials will become available in the future. It seems that almost all of the materials listed above may be suitable for at least some inductive box sensor applications. For low temperature applications (ie for installation under concrete) or in a sawing, polyurethanes with higher hardness appear to be preferred due to their mechanical properties and previous successful underground applications. To allow the same material to be used in a high temperature application, the polyurethane must be interlaced to raise its working temperature. Also, for high-temperature installation (that is, installed under hot asphalt), Tefzel® appears to be another selectable material. Preferred designs Interlaced polyurethane seems to be the preferred material for the construction of jacket layers due to its superior properties and relatively low cost. The interlacing process improves the physical properties of the polyurethane and in particular its thermal resistance. Thus, the interlaced polyurethane is suitable for installation of high temperature under the asphalt. Making the connectors of the same material as the jackets / insulation is preferred since it ensures a monolithic and integrated construction. Also, the irradiation process increases the assembly price just a little. The interlaced polyurethane jacket can be used for both the cable and the construction of the connector. The preferred wire insulation is interlaced polyethylene because of its superior insulating properties and its water resistance. Inductive Panel Cable Specification Due to wide differences in installation procedures and associated stresses that the frame cable has to withstand for sawing and pavement installations, we consider two different specifications for the box cable, one for a sawing, and one for the paved or paved above.

Installation in a Sawdust Traditionally installed sawing frame sensors are usually made from a single wire wound several times around the sawing to form a multi-turn frame to match the circumference of the sawing. Preformed frames are rarely installed in sawmills due to the large cross-section of the frame, and the large size of the frame / input wire joint. Therefore, there is a need for a narrow profile preformed frame according to the present invention that can be installed in a sawmill.

In general, the preformed box for sawing according to the invention must fit within a 6.35mm (1/4") saw.This limitation dictates either a flat cable construction (shown in Figure 2) or a cable thin round (shown in Figure 4) of the multi-round frame Stacking the ends of the frame wires in the connector allows widths less than 6.35mm (0.25"), for example, as shown in Figure 2, which shows the cross section of flat cable, and Figure 4, which shows the cross section of thin round cable, both with a sturdy, thin layer of Insulation jacket The frame cable conductors are typically 16 gauge or 18 AWG gauge with multiple threads for increased flexibility. Wire insulation and cable jacket also need to be flexible enough to allow the cable to be installed in sharp turns of the sawing. Molding a connector housing around the conductor and the wire connections also helps to minimize the width of the sensor by eliminating the need for a separate housing and sealant. The preformed sawdust frame has an adjustable perimeter that is used to accommodate variations in the length of the sawing. To make the frame adjustable and minimize road damage during installation, the ends of the box cable are stacked on the upper part between them in the connector and are installed in a short section of the inlet saw before they are separated to go around the frame sawing circle, shown in FIG. Figure 1. Sawdusting modalities, as described above with reference to the figures, allow adjustability without a wider input sawing. Installation Under a New Road Surface Currently, preformed inductive panels are installed predominantly under new road surfaces or roadways. As in the case of the sawing board, one of the main challenges for the inductive box sensor is to survive the installation process. For installation with pavement on top, the size of the frame sensor cable is not a limitation. Therefore, cable with standard round cross section can be used, for example as shown in Figure 10. The frame cable is constructed of a round cable 536 with three individually insulated copper wire conductors 542, 544, 546. wires in this case can be multiple or solid wires to increase the rigidity of the frame assembly. In order to simplify the construction of the joint, each wire has the insulation 561 of "a different color." A 560 veneer material covers and protects the conductors.The preformed inductive box installed under new road surfaces must also have a low profile, so that when coating operations are carried out, the painting will not be damaged.This requirement emanates from a common problem, after the painting has been under the road for many years, the cold flattening of the road for the The coating often damages the existing preformed panels.The designs currently available in the field have large junctions or box / wire joints, which do not have enough road material to cover them to protect them during cold flattening. Invention, the board / wire entry board should also be low profile as possible.

The inductive frame must withstand the high temperature of heated asphalt from 150 ° C to 180 ° C (300 ° F to 350 ° F). This requirement requires the use of materials resistant to high temperatures in the construction of the frame. The frame must not interfere with the asphalt paving equipment. When the asphalt is laid, the machine that spreads the asphalt often digs up the currently available frames that have been laid to be covered. If the frame is of a low profile, then the asphalt machinery will not rough it and will not ruin the installation. The frame must withstand the passage over it of construction vehicles before being covered with new road material. When preformed frames are installed under new road surfaces, they are laid in their positions before the final road covering. Between the time they are laid and the time they are covered, it is to be expected that heavy equipment will pass over them many times. In a preferred embodiment, an interlaced polyurethane cable will be the most feasible to withstand loads associated with construction traffic. Specification of the Input Cable The input cable is a simple cable of twisted pair wires, preferably insulated and enchaquetados with the same material as that used for the sensor box and must meet the same resistance requirements as the box cable. The thickness of the jacket will be the same as that used for the box cable to ensure the same mechanical properties. The input cable will consist of a pair of twisted wires. The wires will also be shielded or wrapped if required, the shield or wrap is made of a thin sheet aluminum turn. Additionally, for the sawing installation, the inlet cable must fit within the 6.35mm (1/4") sawdust.A cable of twisted pair wires that meets this specification is easily manufactured with an outside diameter of less than 6.35mm. (1/4"). The input cable should have low impedance and should not be a noisy transmission line. The twisted pair leads give the design low impedance and the optional shield adds rejection to the noise to the design. The insulation of the input cable must adhere to the connector housing to maintain a sealed unit.

The manufacture of the input cable of the same material as the frame cable and connector housing satisfies this requirement. Connector Specification The connection between the frame cable and the input cable can potentially be the weakest point of the preformed frame assembly. To ensure the necessary mechanical integrity, environmental protection, and a small size of the connector, a wrap molded around the welded or spliced connectors of the conductors and the input wires can be used as described above. The mold will be made of the same material as the coil or spool box cable and the insulation of the input cable or jacket. This will allow the molten housing material to melt with the insulation of the cable and completely isolate the conductor and wire connections from the outside environment. While being robust, this design has the advantage of being easily manufactured and has the greatest opportunity to withstand many years under the road surface. The combination of the connector housing and the seal in a mold reduces the number of parts and the time required to assemble the frame. This simplification actually reduces the cost of the frame sensor, while at the same time making it more robust. Manufacturing The inductive box sensor according to the invention can include an input cable, a box cable and a connector that electrically connects the box cable and the input cable in a multi-turn box surrounded by a molded housing material . To manufacture the inductive box sensor, a longitudinal input cable is cut and the longitudinal frame cable is cut. The conductor and inlet wires are peeled and soldered or spliced together to form the turns, as described above. The connection of the wires is covered for protection and then a final housing is formed around the entire area, forming the connector. The connector can be formed using injection molding, which is a process where the molten insulation material is injected into a metal mold that has the wires passing inside through channels from the outside. Inductive Frame Sensor Geometry The developed frame design requires strict control of the geometry of the frame conductors and therefore the inductance of the frame. This, in general, is not true for the currently available preformed frames, where the mutual position of the frame conductors is controlled only to the point where all the turns must fit within a conduit. A simplified expression for the frame inductance can be determined to obtain approximate measurements of the sensitivity of the frame with geometric parameters. These measurements provide a better discernment of the properties of the frame and are supported by means of calculations. We show this from the point of view of the frame sensitivity, the preferred design is a frame with multiple drivers. In the following, we use the expressions for inductance of a square or circular curl, but the same general conclusions are obtained for other forms of painting. For this discussion, three winding geometries are considered: a ribbon cable with N conductors; a round cable with N conductors; and a single tape driver. The frame inductance is calculated as the inductance of a short winding or short coil, which is expressed in terms of the inductance value for an infinite solenoid multiplied by a factor that gives a measure of the extreme effects. To calculate the inductance of a square made of a ribbon cable with N conductors, we use the formula of a circular single-layer circular coil, given by Grover: Lf = 0. 002N2p2 (2r / b) K (b / 2r). (1) where N is the number of turns, r is the radius of the square or curl, b is the height of the square (that is, of the current sheet). and -2ß / p. { ln [(4 / ß) -l / 2] + ß2 / 8 [ln (4 / ß) + l / 8] - ß4 / 64 ln [(4 / ß) -2/3] + 5ß6 / 1024 [ln (4 / ß) -109/120] + ....}. 2) «(b / pr) ln (8r / b) Therefore, for ß = b / 2r« 1, Lf «0.0047prN2ln (8r / b) (3) For the cable, bf = Ndw, where dw is the spacing between wires (or, approximately, the diameter of a single wire). The inductance of a square made of a round cable with N conductors can be calculated using the formula for a square or round curl with square cross section: Lf = 0. 001 rN2Po (4i where Po = 4p { 0.5 [l + ß2 / 6] ln (88 / ß2) -0.84834 + 0.204 lß2.}. (5) In this case, b is the height (equal to the width) of the coil, and is given roughly as br = N1 / 2dw For ß = ¿/ 2r «1: and the same approximate expression for the inductance is obtained as above for the flat cable.Thus, a box made of a round cable has greater inductance for a given number of turns due to the lower value of j (effective coil height) .This result is illustrated in Figure 11, which gives the results of exact calculations of Equations 1 to 4. The parameter that must be To be taken into account to determine the number of turns is the detection sensitivity that depends on the mutual inductance between the frame and the vehicle.The apparent change in the frame inductance due to the passage of the vehicle is given by? L! = - (M12) 2 / L2, (7) where L2 is the effective inductance of a closed frame representing the body of the vehicle, and M? 2 is the inductan between the frame (Li) and the vehicle frame. The sensitivity of the frame is therefore equal to S =? L1 / L1 = - (M12) 2 / (L2L1). (8) The mutual inductance between the frame and a vehicle is a sum of the mutual inductances between the single return of the traffic frame and the vehicle and, therefore, is proportional to N: M? 2 =? M12 «Nm12, ( 9) where mi2 is the mutual inductance between a single frame or curl and the vehicle. The sensitivity is therefore approximately equal to S «(m? 2) 2 / [L20.004prln (8r / b)]. (io: Thus, in the first-round approximation, the sensitivity depends exclusively on the height of the frame (current sheet) and not on the number of turns.Figure 12 shows the exact relative sensitivity of the frames made of flat and round cables The sensitivity increases as the frame wires are separated, and is larger for a frame made of vertical ribbon cable (slot) than for a round wire frame. There is also a slight increase in sensitivity with the number of turns that have been made. have been omitted from the approximate expression.As an alternative design for a multiple conductor panel, one can consider a single conductor ribbon cable (ie, with a single conductor in the form of a ribbon), even though a single conductor has more inductance low (by a factor of N2) than a multiple conductor, there is no gain in sensitivity because the mutual inductance between the frame and the vehicle is reduced by a factor of N. Thus, u A single conductive tape has the same sensitivity as a multi-conductor ribbon cable.

The inductance of the input cable also needs to be taken into account in the evaluation of the directing sensitivity. This inductance reduces the sensitivity by a factor of (1 + L / L?), Where L is the inductance of the input cable and li is the inductance of the frame. It is common practice to make the number of turns sufficiently large, so that the inductance of the frame cable is greater than the inductance of the input cable (L? »L), which, for a multi-turn construction, is achieved by increasing the number of laps As discussed above, a larger number of turns also results in an improved sensitivity of the "primary" frame. The substantially lower inductance of a single conductor would require the use of an additional transformer to reduce the effect of inductance of the input cable on the magnitude and sensitivity of the signal. Therefore, it seems that increasing the inductance of the frame by increasing the number of turns, as in the preferred embodiment, will be more effective with respect to cost. Noise Considerations It is reported that sometimes the traffic box detectors suffer from electromagnetic noise produced by power lines and electrical installations. Cables shielded with stainless steel or copper mesh can provide increased immunity to noise sources. To determine if shielded cables are required, two frames were constructed, each with a diameter of 1.8288m (six feet) and with four turns. One was made with a shielded cable, with four wires of 20 AWG wire, the other with an unshielded wire, with four conductors of 20 AWG wire. Each had the same length of paired, twisted and shielded input cable. The shield of the frame was landed through the shield of the input cable and the detector, in such a way that a closed frame was not formed. The frames were connected to a unit, which gives a digital measure of the inductance. A location where there was a high level of environmental electromagnetic noise was found. The location was in an auto repair shop where electric motors and power lines created significant noise. The two test frames were then taken to that location and data was collected in the noisy region. There was no significant difference in the signal between the shield and no shields. Preferred Designs Interlaced polyurethane appears to be the preferred material for the construction of the jacket layer due to its superior properties and relatively low cost. The interlacing process improves the physical properties of the polyurethane and in particular its thermal resistance. Therefore, the interlaced polyurethane is suitable for installation at high temperature under the asphalt. It is preferred to make the connectors of the same material since this ensures an integrated monolithic construction. Also, the irradiation process only slightly increases the assembly price. The interlaced polyurethane jacket can be used for both the cable and the construction of the connector. The preferred wire insulation is interlaced polyurethane due to its superior insulating properties and its water resistance. While the foregoing has been established with reference to a particular embodiment of the invention, it will be appreciated by those skilled in the art that changes can be made in this embodiment without departing from the principles and spirit of the invention.

Claims (7)

2. 2. An inductive loop sensor with an inductive cable and an input cable, characterized in that: the inductive cable has a frame conductor with one or more turns ending in first and second conductor ends, the turns of the frame conductor are surrounded by a first cable jacket with the first and second conductor ends extending from the first cable jacket; the input cable has first and second input wires surrounded by a second protective cable jacket, the first and second input wires have ends extending beyond the second protective jacket, the first input wire is connected in a first connection to the first conductor end of the frame conductor and the second input wire is connected in a second connection to the second conductor end of the frame conductor; A molded connector covers the first and second connections in a sealed manner. The inductive box sensor of claim 1, wherein the first and second connections are in a plane oriented substantially vertically with the first connection positioned above the second connection in the molded connector.
3. 3. The inductive box sensor of claim 2, wherein said one or more turns of the conductor are stacked in a vertical plane. The inductive box sensor of claim 1, wherein the first and second connections are in a plane oriented substantially vertically with the first connection positioned opposite the second connection in the molded connector. 5. The inductive box sensor of claim 1, wherein the first protective jacket has a height greater than the width. 6. The inductive box sensor of claim 1, wherein the inductive box cable is a flat cable. The inductive box sensor of claim 1, wherein the inductive box cable is a round cable.