WO1987002161A1

WO1987002161A1 - System for registering and reading data stored in cards based in electrical field variation

Info

Publication number: WO1987002161A1
Application number: PCT/BR1986/000018
Authority: WO
Inventors: Dalson Artacho
Original assignee: Dalson Artacho
Priority date: 1985-10-02
Filing date: 1986-10-01
Publication date: 1987-04-09
Also published as: PT83484B; PT83484A; BR8504950A; MX161458A

Abstract

System for registering and reading data stored in cards based in electric field variation and applicable to electronic equipment having circuits assembled in removable boards or cards containing a plurality of input and output points of connection which are connected in a non permanent way to corresponding points of connection located in the circuitry assembled in the equipement body, or in other removable circuit board, being the invention here described characterized by the fact that the transferring of electrical signals between the points of connection is effected through capacitive coupling between them, provided by a pair of coupling terminals (12) for each desired connection, each pair being formed by first terminal (14) connected to a circuit board or card (10) and a second terminal (13) connected to the circuitry (11) assembled in the equipment body, or to another circuit board, said terminal being arranged in such a way that when a circuit board is inserted in the equipment the mating terminal surfaces (17, 17') are separated by a gap (16) to form a non permanent connection that may function as a coupling capacitor, so that the transferring of electrical signals through this coupling takes place as a consequence of the varying electrical field generated in the coupled terminals when subjected to the action of a varying electrical signal.

Description

SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION.

The invention here described is related to a system for registering and reading data applicable to electronic equipment which.incorporated removable circuit boards having a plurallity of electrical i put and output points of connection.

More specifically the invention is related to anelectric coupling system between the imput and output connection points of said circuit boards and the corresponding points in the circuits assembled in the equipment body, said coupling system being capable of transferring electrical signals between corresponding points without physical contact, the electric continuity resulting from a capacitance effect between the pair of mating terminals in each connection point. It is well known that electronic equipment comprises a number of circuits usually assembled in boards or cards which are interconnected or connected to circuitry in the equipment body. A practical way of building said electronic equipment is to conveniently divide the complete circuitry in sections in which the components are assembled in removable boards or cards, this construction simplifying manufacturing, permitting standardization and interchangeability as well as facilitating maintenance. To assemble a complete circuit the boards are interconnected, or connected to the wiring assembled to the equipment body, by means of coupling devides which generally consist of two mating parts of non conductive material which nest a number of metallic pins or blades to provide non permanent physical contact between terminal points of the sections.

^■ The non permanent nature and dependence of physical contact of the type coupling described above is continually requiring use of connector materials of higher conductivity , higher contact pressures, enlarged contact surfaces, etc to improve the reliability of the connections. Such measures , although they contributed considerable to reduce failures due to insufficient electrical contact, do not obviate terminal wear, distorsion or breakage resulting from continued removal and reinsertion to which circuit board or cardsmay be subjected.

In view of the above considerations the objective of the present invention -is to provide a registering and reading data system in which the non permanent electrical contact between two points is made without physical contact between these points.

Based in the principles of the present invention the aimed objectives are attained by providing each imput or output point of connection, belonging to a removable board or to the body of the system, with blade type terminals conveniently located so that when a circuit board is inserted in the equipment the mating electrically conductive blades do not touch, an air gap beeing kept between them to form a capacitor, said capacitor providing the means of effecting the electrical coupling between the connection points in the boards an thebody of the system, due to variation of the electrical field in the connector when a variable electrical signals flows through it. The desired electrical coupling is by this means provided without physical contact betweenterminals, thus avoiding wear,distorsion, breakage and resultant contact failures as usually occurs in the conventional systems previously described. To further improve the reliability of the coupling thus achieved, applying the principles of this invention, the blade type terminals may be covered with a layer of insulating material which, contrary to what occurs with the electro-mechanical connectors, will avoid electro-physical contact in the type of connector object of this invention.

This invention will be better understood after reading the detailled description that follows and referring to the drawings attached.

Figure 1 is a sectioned perspective view which illustrates the coupling between a circuit board or card and the circuitry of the equipment to which it belongs, in accordance with the principles of the present invention.

Figure 2 is a sectioned perspective view which illustrates the coupling between a circuit board or card and the circuitry of the equipment to which it belongs, in accordance with another modality of making practical use of this invention.

Figure 3 is a section of a wiring diagram showing one application of the principles of this invention.

As shown in Fig. 1 the electrical coupling between a circuit board or card (10) and the circuitry (11) to which it belongs is provided by a number of pairs of blade type terminals one or eac connec on, eac pa r e ng cons u e y a first terminal (13) directly connected to a point in the system circuitry (11) and a second terminal (14) fastened to the surface (15) of the board (10) , said terminals being placed in such a way that when the circuit board is inserted in the equipment an air gap (16) is maintained between the surfaces of the mating blades (17, 17"), forming a capacitor which permits the transferring of electrical signals between the connection points in the circuit board and those in the equipment, through the variation of the electrical field generated between the two terminals (13, 14) when a varying electrical signal flows through them.

So that on electrical signal may be conducted from a circuit board or card to the circuitry in the body of the system, and vice-versa, at least two connections are required, which in accordance with the principle of the present invention are constituted of two pairs (12) of terminals (13, 14) one of them being an earthing point. Consequently in order that a plurallity of signals may be transferred an equivalent number of pairs of terminals is required plus one of earthing of all the signals.

Due to the inexistance of physical contact between the perminal blades and to the high impedance of the capacitor formed them, which stops continuous electric signals,the constant feed current as well as the analog and digital signals of long duration will require high frequency modulation to be transmitted from stationary circuitry to the removable boards, andvice-versa, through the capacitor formed by the terminal blades,the sign-als being restaured with rectification and filtering. The fitting of a board in the electronic equipment requires some clearances to facilate insertion and removal which will cause variation of the air gap (16) between the terminals blades, (13, 14) and, as a result in the connector capacitaBce, which will cause a proporcional variation in the level of the electrical signal being transmitted, that is, a displacement of the board which cause reduction in the gap between the terminals will increase the signal being tr.ansmitted, and decrease it if the board displacement is in the opposite direction increasing the air gap. A way of assuring a constant level of transmission consists in alternating the location of the pairs of terminals correspondent to the involved connection points, in such a way that the capacitors formed when the board is inserted in the equipment are assembled alternativelly above and below the surface of the board as shown in Figure 2. This arrangement of the terminals will result in compensating capacitance variations when a transverse shift of the board in relation to. the stationary terminals in the equipments occurs.

Figure 2 illustrates an application of the arrangement above described, when a sinusoidal electrical sign is transferred from the equipment circuitry (11) to the circuit in a board (10) inserted in the system.

As shown in Figure 2, the two connection points involved in transferring a signal, have their respective pairs of terminals arranged in staggered position in opposite sides of the board surface (10), that is, while the first pair of terminals is above the board surface the second pair (12) is below it, forming a first capacitor Ca (12) which terminals

(13, 14) are separated by a gap "a" (16) , and a second capacitor

Cb (12') which terminals (13' 14') are separated by a gap "b" (16").

If we assign "s" to indicate the area of each termina¹, "k" the dieletric constant of the capacitors, Ca and Cb their respective capacitance values, we may write the following relationships:

Ca = K -^a- (I)

Cb = K -b- ⁽H⁾

As can be seen in Figure 2 the two capacitors (12,12'), formed when a board is inserted in the equipment, are connected in series and the resultant capacity is expressed as follows:

1 = a + b = (a + b) (III) c k . s k . s k.s

where (a + b) has a constant value since, as result of the terminal pairs (12, 12") arrangement, a shifting in the board reduction in gap "b" and vice-versa, keeping constant the sum of the two terminals areas and the connector capacitance, as shown below:

C = K —-2— (IV) α

where "d = (a + b)

Consequently, as demonstrated above, the positioning of the terminals in a removable circuit board (10) between the stationary terminals (13, 13') in the equipment has no influence in the resultant connector capacitance "c", so that the sinusoidal electric signal transferred is not affects by mislocation of a board, being also important to bring up the fact that the thickness of the terminals and of the board also do not have any influence in the connection capacitancy, and in the transferred signal as a consequence. Concerning the influence in a signal transferred to a board shifted in any direction parallel to the terminals surfaces, this influence is obviated by making one terminal larger than the other in each coupled pair. This procedure assures that the area common to both terminals in the pair is keptconstant. As an example, if we make the terminal blades (14,14") located in the surface of a board (10) smaller in area than the blades (13, 13") located in the stationary circuitry, the capacitance (Ca, Cb) of the connection capacitors (12, 12')formed after the insertion of the board in the equipment, which is a function of the areas of the smaller terminals (14, 14') will be kept constant in spite of board shift.

This way, in accordance with the principles of the present invention, the removable board or card may be shifted in relation to the stationary terminals of the system, without affecting the signals being transferred, provided that certain limits established in the project are not exceeded.

Although the preceeding description was based in a particular modality of transferring an electric signal from stationary circuitry to circuits in a removable board involving only two pairs of coupling terminals, it must be understood that the same procedure may be extended to a plurallity of signals involving any number of terminal pairs.

In Figure 3 is an example of an application following principle of this invention showing a simplifyied diagram of a simple eletric circuit assembled in a detachble board or card (10) intended to monitor and visually indicate the presence of a signal fed to a board from an external source (18) .

As shown in Fig. 3, the circuit is fed by a sinusoidal tension signal coming from a generator (19) transferred to a board (10) through the capacitor (20) formed by the coupling terminal blades in this connection point, when the board is inserted in the equipment. The referred feed signal which is earthed by the capacitor (21) formed by the coupling terminal blades in this connection point, after being rectified by the diodes Dl and D2 and subsequently filtered by the electrolitic capacitor Cl, is fed to the monitor circuit formed with Rl, R2, DLl and Tl. The signal to be monitored, coming from a square wave generator (23) , is transferred to the boardthrough capacitor (24) formed by the connection terminal blades, exciting transistor Tl to switch on a LED (DLl) which lighting follows the pace of the applied signal earthed in the same capacitor (21) used to earth the feed signal.

Although the description of this invention was based in one particular version it must be inferred that modifications and additions are practible without extrapolating the principle of this invention, the objective of the description being explanatory other than to stablish limits. herefore, although, in the example described above, the terminal blades are shown as having a rectangular shape, it must be understood that they could be shaped in many different ways, these variatios not resulting in any new or original physical behavior in relation to what was described in this report. Also, although the coupling terminals contained in the circuit board are shown placed at one edge of the board, these terminals .could be placed in the middle of it without affecting the described characteristics of the invention.

Claims

1. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION aplicable to electronic equipment having circuits assembled in removable boards or cards containing a plurallity of imput and output points of connection which are connected in an non permanent way to corresponding points of connection located in the circuitry assembled in the equipment body, or in other removable circuit board, being the invention here claimed characterized by the fact that the transferring of electrical signals between the points of connecticn is effected through capacitive coupling between them provided by a pair of coupling terminals (12) far each desired interconnection, each pair being formed by a first terminal (14) connected to a circuit board or card (10) and a second terminal (13) connected to the circuitry (11) in the body of the equipment, or to another circuit board, said terminal being arranged in such a way that when a circuit board is inserted in the equipment the mating terminals surfaces (17, 17') are separated by a gap (16) to form a non permanent connection that may function as a coupling capacitor, so that the transferring of electrical signals through this coupling takes place as a consequence of the varying electrical field generated in the coupled terminals when subjected to the action of a varying electrical signal.

2. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1, characterized by the fact that the pairs of coupling terminals are formed by pairs of blade type terminals made of electrically condutive material.

3. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1, characterized by the fact that the mating surfaces of mating terminals are covered with a layer of non conductive material.

4. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1, characterized by the fact that the transferring of each electrical signal from/to a given circuit board is provided through the use of two pairs of coupling terminals.

5. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1 or 4 characterized by the fact that the transferring ofa pluralllly of electrical signals from/to a given circuit board is provided through the use of a number coupling terminal pairs equal to the number of signals to be transferred plus one addiαnal e.arthing terminal. 5 6. SYSTEM FOR REGISTERING AND READING DATA STORED IN

CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1 , characterized by the fact that the pairs of coupling terminals involved in the transferring of a given electrical signal from/ to a given circuit board are arranged over one surface of the ° board.

7. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1 , characterized by the fact the pairs of coupling terminals required to transfer the electrical signals are fastened alternativelly 5 above a below the surface of a circuit board in a staggered arrangement.

8. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1, characterized by the fact that in the coupled terminals the mating blades have equal shape and area.

9. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1, characterized by the fact that the one blade of a given pair of coupling terminals is larger in area than the mating blade of the same pair.

10. SYSTEM FOR REGISTERING AND READING DATA STORED IN CARDS BASED IN ELECTRICAL FIELD VARIATION as claimed in 1 , characterized by the fact that the transferring of non varying electrical signals is made through modulation of these signals by a high frequency signal.