FR2634926A1 - DEVICE FOR DETECTING SUPPORT ON A SURFACE, BY CARBON-CHARGED RUBBER - Google Patents

Abstract

The present invention relates to a support detection system on one face, consisting of a deformable element made of carbon-loaded rubber 5 which comes into mechanical contact with conductors 3 deposited on an insulator 2 by causing the electrical resistance between the conductors 3 to drop. from infinity to a few thousand Ohms. Applications to the detection of passing vehicles or pedestrians.

Description

The present invention relates to an electrical detection device

  support or passage. its production methods and applications

  detection of passage and presence of vehicles and pedestrians. and in reali-

  sation of pressure sensitive "remote control switches".

  ) * -This device consists partly of conductive tapes

  planes and carbon-laden rubber with low linear electrical resistance.

  It is known, for example, to carry out detection measurements

  of vehicles by pneumatic tubes inside which the variation is measured

  pressure when passing vehicles. Such devices are not generally

  only sensitive to pressure variation. but do not detect a presence.

  which considerably limits its use.

  Devices are also known comprising two deformable metal blades glued or held by any means with two opposite faces

  a rubber element. These two metallic elements constitute an inter-

  mechanical breaker: when one of the two rubber supports is pressed.

  it deforms and the metal blades come into contact.

  Such devices are difficult to achieve because of the pro-

  sticking problems between metal and rubber and present problems of

  reliability over time due to their mechanical non-homogeneity.

  Systems for measuring the variation in resistance of layers of carbon-filled rubber foam are also known. These systems have the disadvantage of having slow response times after prolonged compression over time. and this due to the low resistance

  mechanics of these rubber foams.

  The subject of the present invention is the production of devices

  detection using the surface resistance of carbon charged rubber.

  of varying hardness between 50 and 100 ShoresA. associated with the mechanical properties of rubbers. It relates to a device for detecting axles or wheels of vehicles on a roadway of the type comprising on the same side of the device two fixed long conductors, placed opposite a deformable conductive rubber element also of great length. The assembly may have the shape of a very long profile which can be extruded. Profile can be rectangular or trapezoidal to be fixed

mechanically on the ground.

  The present invention also relates to the realization of "remote control switches" of great tightness characterized in that they comprise a block of conductive rubber coming into contact under the force of a finger with 2 -

  conductors placed for example on a printed circuit.

  The present invention also relates to the production of carpets sensitive to the passage or stay of an object or a pedestrian, characterized in that a flat conductive rubber element is deformed through an insulating plate to come into contact. with one or more conductors, the other side of the rubber plate being. depending on the case. electrically isolated

  or in contact with a second driver.

  Other characteristics and advantages will appear during the description

who will sweat.

  To the drawings given only as examples

  - Figures la and lb constitute a description of the principle

of the invention.

  - Figure 2 is a schematic view of an electro-

  nique allowing the detection of the contact of carbon-laden rubber with

the 2 conductors.

  - Figure 3 is a schematic sectional view of a device

linear according to the invention.

  - Figure 4 is a schematic view of the application of such a system to a closing safety of automatic sliding doors - Figures 5a. b. vs. are schematic sectional views of a circular device according to the invention constituting a second variant of the invention. - Figures 6a, b and c are schematic views of a

  third variant according to the invention.

  - Figures 7a. b and c are schematic views of a

  fourth variant according to the invention.

  FIG. 1 describes the basic system according to the invention which comprises - a rigid or semi-rigid support (1) - electrical conductors (3) placed on an insulating material (2) - the carbon-laden rubber (5) of hardness greater than 50 shores A. - This rubber (5) is linked to the support (1) by a system

(4) rigid or deformable.

  -3- When no force is applied to (5) in direction (5)

  to (1). the resistance between conductors 31 and 32. or 32 and 33 is infinite.

  A weak force and which depends on the mechanical rigidity of the system formed by (4) and (5) will allow the resetting in mechanical contact of the rubber (5) with the conductors 31. 32 33 then the resistance measured between these conductors

  will be several hundred thousand Ohrns. When the effort increases. the resistance

  electrical tance measured between conductors 31. 32 'or 32 and 33 drops very

  quickly to become less than a few thousand Ohms.

  A very simple electronic detection circuit can be

  realized in which the resistance of the system (8) is compared to that of a poten-

  tiometer (9) by a comparator (10). The response (12) from this comparator (10) will be instantaneous. A time delay system can be added: then the signal at 13 will only appear after (12) has been maintained for a period of time

  greater than the time delay defined by (11).

  The present invention applies to the measurement of the passage of vehicles on a roadway using a piece of great length and narrow width. deformable rubber loaded with carbon which comes into contact with two conductors and whose resistance is measured using a more or less sophisticated electronic circuit. the two elements being connected by a cable to two

  conductors not shown. Following the example shown in. Figures 3a and 3b.

  a piece of conductive rubber (14) with a hardness greater than or equal to 50 Sho-

  resA. of small section and of great length, includes a cavity (19) in which the two conductors (16 and 17) are placed on an electrical insulator (18). The two conductors (16 and 17) can be flat or rounded. They can be laminated and glued on an insulating support. The assembly of the insulating support (18) and of the two conductors (16 and 17) can also be in the form of a flexible or "flex-rigid" suppressed circuit. The assembly formed by the two conductors and their insulating support adheres to the lower surface of the profile (14) by any known means. such as cold glue. hot, double-sided adhesive,

  chemical adhesion of rubber ...

  The profile (14) is installed in a mechanical system (15)

  itself sealed in the roadway (20).

  When a wheel passes over the profile which is installed as described above. it exerts pressure (21) on the bead and deforms the profile (14); the upper part of the cavity (19) comes into contact with the two conductors (16 and 17) and strongly presses on these conductors: the resistance (e measured between the two conductors (16 and 17) therefore changes from infinity to a value of a few thousand Ohms which is detected by an electronic system from -4 -

  type of that described in figure 2.

  The dynamic and static properties of such a system can

  can be adjusted by varying. the hardness of the rubber between 50 and

  Shores A. used to make the profile (14). or the shape of the cavity (19).

  either the distance at rest (22) between the upper face of the cavity (19) and the face

  upper conductors (16 and 17).

  Such a detection system can have other applications,

  such as door closing detection for example in railroad cars

  vialres. or from Metropolitan, or for motorized gate doors. This system is described in Figure 4 o a sensitive element (23) of the type described in Figure 3 is placed on the side of a sliding door (24). Any object (26) will be easily detected when the door (24) is closed in the direction

  (25) so as to avoid any accident.

  As a variant. flexible detection systems of small dimensions can be made that are perfectly waterproof and can easily replace remote switches. The device according to Figures 5a. b. c and d. is made by molding or molding and gluing one or two rubber blocks (27) in which is placed a flexible or non-flexible printed circuit (28) on which two

  conductors (29 and 30) arranged for example in a spiral.

  Pressing on the upper surface of the block (27) allows

  tra to mechanically contact the carbon-laden rubber with the conductors (29 and 30). Pressure detection will always be performed with

  a system of the type described in FIG. 2.

  As a variant, the device can be produced by placing the conductors on each side of the carbon-laden rubber as shown in FIGS. 6a. b and c. o the carbon-loaded rubber plate (34) is in contact on one side with a conductive plate (36) secured to a support

  rigid (32) and on the other with a sheet of insulating material pierced with holes.

  Another conductive plate (33) integral with another rigid support (32) is

  placed on the insulating plate. At rest, the resistance between the two planes

  teurs (33 and 36) is infinite: if a compression force is applied. the rubber deforms through the holes in the plate (35) to come into contact with the upper conductive plane (33), the electronic system described in Figure 2 will detect this contact. As a variant. and as shown in figure 7, we can

  arrange the two conductors (33) and (36) on one side of the rubber

  conductor (34) by isolating them therefrom by the plate (35). When pressure is exerted on (34) by means of a plate (37). the rubber deforms through the holes to come into mechanical contact with the two conductors

  (33) and (36) so as to allow detection.

  Such plates can be used for detection and

  the location of heavy objects. pedestrian crossing approach.

  people near areas where robots or self-propelled machines move

ques. -6 -

Claims (6)

  1 / Device for detecting support on a surface, characterized in that it comprises a deformable rubber element. shore hardness greater than 50 ShA. charged with carbon (5) coming into mechanical contact with two electric conductors (3) insulated from each other. by passing the electrical resistance between these two conductors from infinity to a few thousand Ohms: the drop in resistance is detected by an electronic comparator system   (10) compared to an adjustable resistance (9).   2 / Device according to claim I characterized in that it is formed of a hollow section of rubber loaded with carbon. of great length and small section (14) comprising on one side of the cavity and in the great length. two conductors (16 and 17) insulated (18) from the rubber and placed opposite the other rubber face of the cavity. the latter comes into mechanical contact with the two conductors when a force (21) is applied to the outer surface of the profile. the drop in resistance between the two conductors allows detection   of the support (21) on the external surface of the profile.   3 / Device according to claims 1 and 2 characterized in   that the profile (14) is placed in a roadway (20) directly or through the   medial of a metal part (15) perpendicular to the direction of movement   vehicles to determine the passage or presence of the axles.   4 / Dispositlf according to claim 1. characterized in that the couple formed by the insulator (18) and the conductors (16 and 17) consists of   a flexible or rigid printed circuit.   / Device according to claim 1. characterized in that   its small size makes it comparable to a push button: the drop in resistance   tance being caused by the deformation of a carbon-charged rubber cavity (27) one face of which comes into mechanical contact with two conductors   (29 and 30) placed on an insulating support opposite the bearing face of the force.   6 / Dispositlf according to vendîcat: zi 1. characterized in that   the carbon-laden rubber (34) deforms at the trzaver5 of pre-   -7 ticked in a plate of insulating materials (33) to come into contact with the electrically conductive surfaces (33 and 36) between which is observed resistance drop.   7 / Device according to claims 1 and 6. characterized in   that the conductive surfaces are placed either on one side of the rubber   loaded with carbon. or on both sides of the carbon-laden rubber.