Patent Application
20160104588
This application claims priority to and benefits of French Patent Application Serial No. 1459769, filed on Oct. 10, 2014, the entire content of which is incorporated herein by reference.
The proposed technique relates to an actuator. The technique relates more particularly to an actuator for electrical contacts. Such actuators are used in electronic devices to make or break electrical contact in a printed circuit board at a place where the printed circuit track is deliberately interrupted precisely in order to detect this electrical current. Such actuators are used for example to generate electrical contacts on a board when keys of a keyboard are pressed or in order to detect the breaking of a pre-established electrical contact.
Actuators are very practical and are used in a great variety of electronic devices. Actuators are chiefly of two types: switches and pucks. These terms can be immediately recognized by those skilled in the art.
A switch is a component to be soldered or glued to a printed circuit board at a position where the electrical contact must be set up. The switch however has the disadvantage of requiring soldering or bonding, and this is not necessarily always possible or desirable.
A puck generally has the shape of a pebble. The base of the pebble can be round or have the shape of a metallic imprint on which it is supposed to make a contact. The puck comprises a conductive surface at one of its ends. This conductive surface is generally made by means of conductive ink or any other relatively inexpensive conductive material. Indeed, with a view to cost reduction, since pucks are not essential elements of the electronic device, low-cost materials are used. Besides, a puck is actuated by a rod (situated opposite the conductive part). The rod must be firm enough to ensure pressure on the electrical contact. When the rod is elastic, it can more easily accept dimensional variations. Whether elastic or not, this rod is often directly integrated with another element situated on the surface of an electronic device and accessible to the user. The puck can then be actuated by means of this rod.
In another example, a puck can also be directly integrated with the keys of the keyboard or keypad. These are for example silicone keypads of computers, remote control units, certain payment terminals, etc.
One of the problems of a puck is that it does not necessarily age very well: in the long term, repeated action on a key of the keypad can damage the conductive surface of the puck and make the key inoperative. Indeed, a puck does not ensure quality electrical contact when a low-cost conductive material is used. Besides, this is why large-sized pucks are often seen with metal imprints that are also large in size. Now, such configurations are not always possible. In addition, the puck is not necessarily “coupled” with another element. This means that, at assembly, difficulties can arise in ensuring an accurate position of a puck which is, so to speak, floating: there can be problems with the final position of the puck. Finally, very often, the deformable material of the puck is used as a return means (like a spring) to ensure that the puck resumes its initial position after having been acted upon. This plays a role in the rapid deterioration of the puck.
There is therefore need for an actuator that can have the advantages of the puck while at the same time avoiding its drawbacks.
An exemplary embodiment of the present application pertains to an actuator (A) for creating an electrical contact between two tracks of a printed circuit board.
Such an actuator comprises:
Thus, such an actuator makes it possible to provide high flexibility of implementation while at the same time ensuring high electrical conductivity.
According to one particular characteristic, the metal part (PM) has the shape of a spherical cap.
Thus, when it receives pressure, this spherical cap is capable of getting deformed at its center to enable contact to be made with the tracks of the printed circuit and when the pressure stops, it is capable of resuming its initial shape. This spherical cap shape plays a role in the longevity of the actuator.
According to one particular embodiment, the polymer part (PSM) is made out of silicone with a hardness of 60 Shores A.
Thus, electrical contact can be made as soon as the actuator exerts sufficient force on the actuator. This part is thus slightly deformable but rigid enough for the metal part to be pressed.
According to one particular embodiment, the metal part (PM) is fixedly attached to the contact end (E1) by means of a glue whose tear strength is substantially equal to 100 grams.
Thus, the actuator withstands a great number of strains and offers high resistance to attempts at sabotage such as for example during an operation to hack into a terminal containing sensitive data, such as a payment terminal. In this case, the actuator is used to make a normally closed contact throughout the duration of use of the terminal except during dismantling (when the electrical circuit is opened) for example by a user who tries to open the terminal fraudulently to place a snooper device therein.
According to one particular characteristic, the metal part (PM) is formed by a gold-plated spring steel sheet.
Thus, the conductivity of the electrical contact is high and its reaction (its deformation) is immediate in the case of dismantling, even after a very lengthy period of time in the actuated position.
According to one particular embodiment, the end (E1) of the actuator supporting the metal part (PM) is surrounded by an enclosure (EP) extending up to a contact base (BPM) of the metal part (BPM), the enclosure (EP) forming a recess.
Thus, a protective barrier is formed around the metal part, especially against dust.
According to one particular embodiment, the enclosure (EP) has the overall shape of a cone whose vertex is a point of the straight line passing through the central axis of the polymer part (PSM).
Other features and advantages of the proposed technique shall appear more clearly from the following description of a preferred embodiment given by way of a simple illustratory and non-exhaustive example and from the appended drawings, of which:
Reminder of the principle of an exemplary embodiment The general principle of the technique of an exemplary embodiment is explained with reference to
More particularly, this metal part (PM) does not have any specific shape. This metal part has the general shape of a cap which can be spherical or elliptical or rectangular as shown in
The function of the metal part is twofold: the metal part is used to provide high electrical conductivity, making it possible to differentiate between the actuator of the present technique and that of the traditional puck. The geometry (i.e. the geometrical shape) of this metal part is also adapted to reproduce operation close to that of the switch, namely the force exerted on the metal part to make electrical contact with the metal imprint is rendered at least partially by the metal part itself (and not by a molded silicone part) in order to prolong the service life of the actuator. Thus, the force used to set up electrical contact deforms or changes the shape of the metal part: this part therefore seeks to resume its initial shape by rendering the initially provided energy.
Indeed, the actuator (A) also has a polymer part (PSM), possibly molded, taking for example the form of a cylinder or a rectangular parallelepiped. This polymer part (PSM) forms an arm comprising one contact end (E1) and one end for setting in motion (it is through this end that the pressure is exerted, for example from a key of a keyboard). The size of this polymer part is adapted to each case, depending on position. This polymer part (PSM) gives the actuator sufficient elasticity to accept differences in position due to errors of manufacture of the parts, and to deformations that can occur during the life of the product (through impacts, falls, ageing or temperature variations).
One contact end (E1) of this cylinder is attached to the metal part (PM) of the actuator (A). This attaching can be done by any necessary means such as for example glue. This end (E1) can have a diameter different from that of the cylinder. More particularly, the diameter of this gluing end can be adapted to the shape of the cap.
As a complement to these embodiments, the end (E1) of the actuator bearing the metal part (PM) is surrounded by an enclosure (EP) which serves as a protection for all handling operations during assembly. This enclosure (EP) is flexible enough so as not to disturb the operation of the actuator and more particularly the setting up of electrical contact by the metal part. This enclosure (EP) also enables the creation of a tight-sealing barrier between the metal part (PM) and the external environment. According to at least one embodiment, the enclosure is a part of the polymer part (PSM), in which it is integrated; thus the enclosure is also in polymer, as explained above. The enclosure creates a recess within which the metal part takes position. If necessary, the base of this enclosure which comes into contact with a printed circuit can itself be covered with conductive ink. Indeed, a known technique for hacking this type of the device consists in using conductive ink to set up a short-circuit between two rings (for example D2 and A1). The ink maintains contact even when the actuator is removed. The guard ring then serves to detect a short-circuit between the ring EMP and itself. If necessary, a protective countermeasure for protecting the terminal is also triggered. The presence of the guard ring therefore sets up a normally open electrical contact which serves to detect hacking by the addition of conductive ink (or any other electrically conductive liquid). A protective countermeasure can then be triggered.
Thus, unlike the pucks and switches of the prior art, the actuator as proposed integrates excellent conductivity (thus providing a real advantage for establishing electrical contact). This conductivity is ensured by the metal part of the actuator. In addition, the proposed actuator is simple to implement and especially does not require any gluing or soldering operation, unlike in the case of the switch. In a certain way, the proposed actuator combines both the advantages of both the switch and of the puck without having their drawbacks.
Here below, we present one embodiment of the actuator in which the metal part takes the form of a spherical cap (CS). The use of such an actuator is of course not limited to printed circuits. It can also be used in any other situation where it is of interest.
As explained here above, the actuator of the described technique is intended to come into contact with the metal imprint, deposited for example on an electronic board.
Such a metal imprint (E0), described with reference to
The signal for activating the key is initiated by putting for example the external ring (A1) and an internal disk (D2) into contact. When contact is set up, a microprocessor or any other arrangement of electronic components receives an electrical impulse and interprets this impulse according to functions embedded in the device in question.
There are numerous existing variants of the metal imprint. For example, a metal imprint can comprise one or two guard rings (AG), which can be internal, external or both, as described with reference to
Be that as it may, as indicated here above, it is necessary to have an actuator available to set up contact between the disk and the ring. To this end, the prior-art techniques are generally content with using a switch glued or soldered to the electronic circuit board or again a puck (when a switch is used, it replaces the imprint on the board as well as the actuator). The actuator is used to set up electrical contact between the external ring (A1) and the internal disk (D2).
The actuator of the present technique works according to the same principle.
In addition, in this embodiment, the end (E1) of the actuator supporting the metal part (PM) is surrounded by an enclosure (EP) which serves as protection during handling operations during assembly. This enclosure has the overall shape of a cone, the vertex of which is a point of the straight line passing through the central axis of the molded silicone cylinder (the vertex of the cone represented in dashes). The enclosure forms a part of the polymer part. The radius of this cone is greater than the radius of the spherical cap (CS), i.e. greater than four millimeters. The base of this cone also ensures the stability of the actuator when it is placed on the printed circuit board.
In
Other embodiments can clearly be envisaged. It is for example quite possible for the polymer part (PSM) to take the form of a rectangular parallelepiped instead of a cylinder and for the enclosure (EP) to then have a pyramid shape. In addition, the shape of the metal part can be modified according to need. Although the spherical shape of the cap is advantageous in certain situations. this cap shape can also be modified (hyperbolic cap, etc.). Thus, any metal part, whether deformable or not, can be used as needed.
The proposed technique thus has several advantages in all its embodiments, among them:
An exemplary embodiment of the proposed technique does not have the drawbacks of the prior art.
Although the present disclosure has been described with reference to one or more examples, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the disclosure and/or the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1459769 | Oct 2014 | FR | national |
