WO2004090806A1

WO2004090806A1 - Radio-frequency position and/or limit switch sensor

Info

Publication number: WO2004090806A1
Application number: PCT/IT2004/000156
Authority: WO
Inventors: Giuseppe Bellandi
Original assignee: Gimatic S.P.A.
Priority date: 2003-04-08
Filing date: 2004-03-29
Publication date: 2004-10-21
Also published as: ITBS20030035A1

Abstract

The invention concerns a position and/or limit switch which includes a codified identifier circuit (11) associated by means of an antenna (12) with a radio-frequency power and reader module or transmitter (15), such as a transponder. A control switch (13) is placed in series with the antenna to open/close said circuit in response to the action of an external activator (14) positioned on an element capable of movements in relation to said switch to enable and disable the identifier.

Description

"RADIO-FREQUENCY POSITION AND/OR LIMIT SWITCH SENSOR"

* * * *

Field of the Invention

This invention concerns the field of the position and/or limit switch sensors, and refers in particular to an improved sensor for the automation and industrial equipment. State of the Art.

Electronics already provides us with codified reading and recognition systems, the so-called "transponders". They are electronic identifiers which are made up of passive electronic circuits which do not require feed batteries and which contain an identification number (code) guaranteed to be unique, unchangeable or programmable.

A transponder is made up in particular of a chip with a unique code, connected to a ferrite with a copper antenna. The chip is read by means of a module or radio-frequency transmitter connected to the antenna. This module sends a low frequency wave which, with a certain level of electromagnet energy charges the chip, passing through the antenna. In this way, the chip discharges and sends a wave which, returning through the antenna with a different modulation reaches a bar code reader assigned to the element to be recognised. Such an electronic circuit, given that it is always connected to the transmitter and consequently it is always energized, cannot be used for a configuration and a closed/open, that is, on/off application.

On the other hand there are well known and widely used position and/or limit switch sensors of various types, based on different construction technologies and activation methods, such as sensors activated by mechanical contact, magnetic sensors activated by variations in a magnetic field, etc. These sensors operate principally on an ON-OFF type binary function, by simply making a contact available which can be on or off to close or open a corresponding electric circuit.

In particular, the industrial automation field and/or automatic handling systems to detect and consequently manage the position of a part in movement in regard to a locator part, as for example an alternative piston in a cylinder, an unit which must reach and stop in different positions, etc., position and/or limit switch sensors as mentioned above are usually used.

The use of these traditional sensors is however not without drawbacks, above all those regarding construction.

In the first place, these sensors normally require electric power and a control means to be physically attached to the sensor. Therefore, they need a wiring system so as to connect them directly to a source of power and to the control unit provided to manage them. Furthermore, the wiring, besides making installation of the sensors and consequently the equipment they are applied to more complex and costly, if not carried out accurately, often represents the cause of malfunctions, stops and maintenance work due to jamming, torn cables, cable conduits, etc., given that the sensors are on board moving parts, which sometimes carry out complex movements and which may be in positions which are cramped, difficult to reach and to fit out. Objects and Summary of the Invention

One object of this invention is to provide a position, presence and/or limit switch sensor in the configuration of an electronic identifier, such as a transponder, but modified for its ON-OFF use and function and which does not require direct electric power.

Another object of this invention is therefore to simplify installation and control of the sensors, at least for the abovementioned purpose, avoiding the drawbacks tied to wiring thanks to the elimination of the physical connection between the sensor power source and control unit, so as to reduce in this way the complexity of the installations on equipment to be managed.

These objects are achieved, according to the invention, by a sensor using a codified transmitter/receiver circuit associated by means of an antenna with a power and reader radio-frequency module or transmitter, and a switch of any type, placed in series with the antenna to open/close said circuit in response to the action of an external activator placed on an element susceptible to movements related to said switch.

The transmitter/receiver circuit is permanently irradiated by the radio- frequency module or transmitter, but as long as the switch remains open it does not emit a return response. Only when the switch changes status, closed by the respective external activator on the moving element, does the circuit send a signal in response to the reader module for detection and viewing of the code assigned to the circuit itself and which will be indicative of the position of the element holding the activator to be recognised. Brief description of the drawings

This invention will however be described more in detail in the description that follows made with reference to the attached drawings, which are indicative and not limiting, in which: Fig. 1 shows a block diagram of the radio-frequency position sensor according to the invention; and

Fig. 2 shows the block diagram of an example of an application using several sensors on a drive of a piece of equipment.

Detailed description of the invention As shown, the position or limit switch sensor proposed here includes essentially an electronic identifier made up of a programmable chip 11 which is connected to a circuit with an antenna 12, and a switch 13 positioned in series to the circuit itself and able to take up the open and closed positions.

An external activator 14 is provided for the change of status command from one position to another of the switch. The switch 13 may be of any type and the activator 14 will be compatible with the switch to be controlled.

The radio-frequency sensor configured in this way is managed by a radio-frequency module 15 provided both for power and interrogation of the identifier unit. The radio-frequency module irradiates the sensor, which then may or may not send a return signal depending on the switch status 13 caused by the external activator 14. In this way either one or the other of the following conditions has taken place: the switch is in the open position: the identifier circuit is interrupted and the sensor is not able to dialogue with the control module; the switch is in the closed position: the identifier circuit is enabled and the sensor is able to dialogue with the control module.

In a typical application, where the activator 14 is on a moving element 16 whereas one or more sensors are installed in static positions, continually irradiated by the radio-frequency module 15, it is possible to control the movements and positions of the element by monitoring the answer or failure to answer of the sensors following interrogation on the part of the irradiating module 15.

An example of an application is shown in Fig. 2, where several radio- frequency sensors according to the invention and a module which irradiates them, permit identify and manage the positions of several moving elements 16 each of which is equipped with an activator 14.

Then, to its advantage, it is possible to power all the sensors, eliminating any physical contact with a power source, by exploiting the recharging system of the identifier circuit, which exploits the wireless connection between the antenna and radio-frequency module.

Claims

"RADIO-FREQUENCY POSITION AND/OR LIMIT SWITCH SENSOR"* * * *C L A I M S

1. A position and/or limit switch sensor characterised in that it comprises a codified identifier circuit (11) associated by means of an antenna (12) with a radio-frequency power and reader module or transmitter (15), and a control switch (13) placed in series with the antenna for opening/closing of said circuit in response to the action of an external activator (14) positioned on an element capable of movements in relation to said switch.

2. The sensor according to claim 1 , in which the codified identifier circuit includes a programmable chip and a circuit antenna, and in which the control switch is piloted by an external activator during its movement and depending on the position of the moving element it is associated with.

3. The sensor according to claims 1 and 2, in which the control switch is driven either mechanically, magnetically or in some other similar way.

4. An electronic identifier including a programmable chip and a circuit antenna in combination with a radio-frequency power and reader module or transmitter (15), characterised by a control switch (13) placed in series with the antenna to open/close said circuit in response to the action of an external activator (14) positioned on an element capable of movements in relation to said switch to enable and disable the identifier.