A safety switch intended to be fitted in an electrical circuit of a motor vehicle

IS 2 178 331 T3

DESCRIPTION

Safety switch intended to be adjusted in an electrical circuit of a car.

The present invention is related to a safety switch intended to be adjusted in an electrical circuit of a car, according to the preamble of claim 1.

The invention was conceived as a function of its application to a safety switch intended, in the event of a collision, to cut the electrical circuit for supplying an electric pump for supplying fuel to the automobile engine, but it is not limited to this application.

A safety switch according to the preamble of claim 1 is known from EP-A-0 644 568.

In this known switch, the inertial mass is constituted by a metallic sphere. The wall covering the cavity has a circular central seat in the shape of a hole. When the ball is in the center position, the elastic momentum of the push rod keeps a small part of the crown-shaped ball embedded in the seat. The diameter of the hole and the crown must be small enough with respect to the maximum diameter of the sphere in order to allow the latter to disengage from the seat in the event of a collision of a predetermined force.

Despite its fit in the seat of the wall that covers it, the sphere in the central position is in a relatively unstable equilibrium as it is engaged by the push rod with a substantially punctual contact in the position opposite the seat in the wall that covers it.

It has been shown in practice that this unstable equilibrium means that the sphere moves frequently from its central position with the consequent tripping of the switch, even when the car experiences a very slight collision that does not justify cutting off the electrical power to the electrical pump. , or even when the driver stops very abruptly.

It has also been shown that, due to continuous vibrations, the ball erodes the push rod to such an extent that the operation of the device is impeded.

On the other hand, when the ball is in one of the eccentric positions after tripping of the switch, it is not held firmly in this position. It is therefore possible that if the car experiences a second collision following the first collision, the sphere can spontaneously return to the centered position, thus restoring the circuit, which is completely unacceptable.

The main object of the invention is to provide a safety switch which, while having the sensitivity required for collisions, is not likely to experience abrupt unnecessary changes in the direction of both interruption and restoration of electrical power to the electric pump. , but also, in order to allow the vehicle to restart, to ensure that the switch remains closed once the button has been pressed, regardless of the lean of the vehicle.

Another object of the invention is to avoid the aforementioned drawback of erosion of the push rod by the eccentric mass through the effect of vibrations.

According to the invention, these objects are achieved by means of a safety switch as claimed.

In a safety switch according to the invention, it is ensured that the inertial mass is firmly held in the centered position by the fact that, in this condition, the push rod is engaged in the central depression of the mass. Furthermore, the stable maintenance of the inertial mass in the eccentric position is ensured by means of the firm engagement of the push rod in the annular groove.

Erosion of the push rod by the effect of vibration can no longer take place thanks to the fact that the end of the push rod is normally inserted into the central depression and prevents lateral vibrations of the inertial mass.

A further advantage of the invention is based on the fact that, during development, the profiles of the central depression and the annular groove of the inertial mass can be designed to calibrate the sensitivity of the switch for each specific use. Such a calibration was practically impossible to obtain with a spherical inertial mass.

Thanks to the claimed combination, which includes, among other things, on the one hand the annular bevel at the top that separates the central depression from the annular groove and, on the other hand, the pushing means that interconnect the push button with the connecting rod. thrust, the guarantee is obtained that the inertial mass remains in the centered position when it has been firmly brought to that position by pressing the pushbutton, and regardless of the inclination of the vehicle.

In the present description, it is emphasized that for electrical reasons, certain parts described and illustrated are understood to be made from insulating material and certain other parts from electrically conductive material, even in the absence of specific indications of their nature.

The invention will be understood more clearly from the following detailed description, offered by way of a non-limiting example, with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a safety switch incorporating the features of the invention;

Figure 2 is an exploded perspective view of the switch of Figure 1;

Figures 3 and 4 are sections on an enlarged scale in the diametrical plane indicated as IIIIII in Figure 1, showing the switch in the first and second states of the circuit, respectively;

Figures 5 to 9 are sections in a diametrical plane at 45 ° with respect to plane III, in which figure 5 corresponds to the second state of the circuit of figure 4, and figures 6 to 9 show four successive states of restoration of the first state of the circuit of figure 3; Y

Figure 10 shows a diametrical section on an enlarged scale of the illustrated inertial mass

ES 2 178 331 T3 in Figures 2 to 9.

With reference to Figures 1 to 9, a safety switch comprises a hollow body indicated generally at 10 in Figures 1 and 3 to 9.

The body 10 comprises a base part 12 with which fixing lugs 14 and a tubular projection 16 are integrally formed which houses the pins of a connector for connecting to an external electrical circuit.

The lugs 14 are intended for fixing the switch on a wall of a car so that the general axis of the switch is vertical and its inertial mass, about which will be discussed more below, can be displaced horizontally in all directions.

An insert 18 defining a transverse base wall 20 of a cavity indicated 22 in Figures 3-9 forms part of body 10.

A cap 24 snap-fit ​​with base portion 12 and holding insert 18 captively also forms part of body 10. Cap 24 defines a transverse wall 26 to cover cavity 22.

On its side remote from the cavity 22, the cap 24 has a sleeve-like portion 28.

Mounted within the socket-shaped portion 28, is a reset push button 30, slidable along the axis of the switch.

Pushbutton 30 comprises a disk top 32 and a plurality of rigid strip-shaped projections 34 (four positioned at 90 ° to each other in the illustrated embodiment).

For reasons that will become clear later, the projections 34 are capable of penetrating the cavity 22 through respective slits 36 (Figures 5 to 9) in the transverse cover wall 36.

Each projection 34 has an active inclined surface 38 (Figures 5 to 9), the function of which will become clear later.

Between the disk portion 32 of the push button 30 and the cover wall 26, there are interposed opposing elastic means in the form of a wound spring 40 of compression that tends to keep the push button 30 in the rest position of Figures 3 to 5. .

Around the base part 12 and the cover 24, there is fitted a cap-shaped element 42, made of rubber or similar flexible material, this cap maintaining the tightness of the interior of the switch. The cap 42 comprises, among other things, a deformable upper wall 43 through which it is possible to act on the disk 32 to press the push button 30 against the force of the opposing spring 40 when, as will become clear later, the normal state is restored. switch circuit.

Contained within cavity 22 is an inertial mass 44 made of a relatively heavy material.

In a preferred embodiment, the mass 44 may be made of turned brass with a nickel plated surface.

The inertial mass 44 is guided by the base wall 20 and the covered lid 26 in such a way that it can move horizontally (in the installed condition) in all directions.

The inertial mass 44 is shaped as a body of revolution that is substantially cylindrical about an axis that is perpendicular to the base wall 20 and the cover wall 26.

With particular reference to FIG. 10, a surface 45 of the base of the mass 44, which is slidably engaged with the base wall 20, has a central depression 46 and an annular groove 48 concacentric with the depression.

The flatness and parallelism of the base flat surface 45 and the upper surface 50, which are relatively large, makes it possible to avoid vibrations of the inertial mass 44 between the base wall 20 and the wall 26 of the cover.

For purposes that will become clearer below, the central depression 46 has a substantially flat, canonical shape and the indentation 48 has a depth that is greater than that of the depression 46.

More details of the inertial mass 44 will be described later with reference to FIG. 10.

The inertial mass 44 further has a flat upper surface 50 with a rounded peripheral edge 51 (Figure 10) which, as will be seen better later, is adapted to engage with the inclined active surfaces 38 of the projections 34 of the push button 30.

Top surface 50 slidably engages with cover wall 26 of cavity 22.

Numerical reference 52 designates a lower wall of the base part 12 of the body 10.

Between this bottom wall 52 and the base wall 20 of the cavity 22, there is arranged a system of electrical contacts, generally indicated as 54 in Figures 2 to 9.

Contact system 54 includes movable plate-shaped contact 56 that extends diametrically through body 10.

The contact system 54 further includes (Figures 2 to 4) a first fixed contact 58 in the form of a strip having (see Figure 2) a loop 60 in which a first end 62 of the plate is movably retained. 56.

The other end 64 of the plate 56 is adapted to cooperate in its front part, either with a second fixed contact blade 66 or, alternatively, with a third fixed contact blade 68.

Between the base wall 20 and the plate 56, there is interposed pressure means in the form of a wound compression spring 70, in order to maintain the latter in a first state of the circuit in which the first fixed contact 58 connects with the second fixed contact 66.

When the switch is used as a safety switch in a car, this first state of the circuit corresponds, for example, to the closure of the electrical supply circuit to the fuel pump.

Referring to Figures 2 to 9, the bottom wall 52 of the lower body 12 has a hollow central bulge 74 in which a pushrod, generally indicated 76, is slidably mounted along the axis of the switch.

The push rod 76 comprises a lower tubular section 78 slidably mounted as a piston rod in a cylindrical cavity of the shaft.

ES 2 178 331 T3 ting 74, and a rod-shaped upper section extending upward through the corresponding hole 79 in the base wall 20, the rounded upper end of which 80 engages the base surface of the inertial mass 44 in particular and, depending on the conditions, in its central depression 46 or its annular groove 48.

The push rod 76 is forced to engage with the base surface 45 (FIG. 10) of the inertial mass 44 through opposing elastic means in the form of a wound compression spring 82 contained in the cavity of the tubular part 78. of the push rod 76.

A lateral projection 84 (Figures 2 and 5 to 9) in the form of a rigid blade that has a square shape in plan and that reaches a peripheral area of ​​the base part 12 of the body 10, is attached to the push rod 76.

An area adjacent to the free end of the boss 84 has a guide lug 86 attached to it, which can slide into a blind hole 88 in the bottom wall 52 of the base portion 12.

In figure 3, the switch is illustrated in the condition that corresponds to the first state of the circuit in which the inertial mass 44 is centered on the axis and the rounded upper end 80 of the push rod 76 is engaged in the depression 46 due to to the force of the opposing spring 82.

In its application to an automobile, when the automobile experiences a collision from any direction greater than a predetermined acceleration threshold, for example on the order of 10 to 14 g, the opposing spring 82 is calibrated so that the choanic profile of the depression central 46 is designed in such a way that (figure 4), due to a cam effect, the inertial mass 44 is able to move in the direction corresponding to the impact (arrow A) and the push rod 76 moves backwards against the force of its opposing spring 82, and then jumps upwards leaving its upper part 80 inserted in the peripheral annular groove 48.

When raised upward, as illustrated by arrow B in FIG. 4, a surface of the shoulder of the push rod 76, constituted by the upper face of the shoulder 84, carries with it the movable contact plate 56 which, although it remains electrically connected to the first fixed contact 58, moves away from the second fixed contact 66 and makes contact with the third fixed contact 68.

This condition, called the second state of the circuit, can be used, for example, to close an auxiliary electrical circuit to signal the disconnection of the electric pump, for example by illuminating a warning lamp on the dashboard of the car.

In many cases, especially in the application to a power circuit for a fuel pump in a car, if the car has not suffered severe damage after impact and is able to move using its own engine, it is desirable that the switch is reset. to the first state of the circuit in which electrical continuity is established between the first contact 58 and the second contact 66.

Pushbutton 30 is available for this purpose.

By exerting pressure on the push button against the force of its opposing spring 40, the projections 34 descend into the cavity 22 and their inclined surfaces 38 engage with the peripheral edge 51 of the inertial mass 44 (figure 6), tending to carry the latter to its centered position in figure 3.

However, this return of the mass 44 to the centered position will be impossible due to the fact that the upper part 80 of the push rod 76 is inserted into the annular groove 48, as in Figures 4 and 5.

In order to allow the restoration of the first state of the circuit of figure 3, which allows the vehicle to move under its own power, specific means are provided for the deliberate disengagement of the upper end of the push rod 76 from the groove. void 48.

A preferred embodiment of these disengagement means is illustrated in Figures 2 and 5 to 9.

The disengagement means is in the form of a push means that interconnects the push button 30 with the push rod 76.

These drive means comprise at least one push rod 90 that extends parallel to the axis of the switch and out of the cavity 22, so that it does not interfere with the movements of the inertial mass 44.

The push rod 90 is preferably a turned piece of steel.

A lower end of stem 90 extends through a hole 92 in base wall 20 and is adapted to bias engagement with an end region of boss 84, in alignment with guide pin 86.

The stem 90 is provided with a head 94 at its upper end, with a peripheral shoulder 96 at the base.

A wound compression spring 98, which surrounds the head 94, is interposed between the shoulder 96 and the disk portion 32 of the push button.

30.

The stem 90 has a peripheral collar 100 on the shoulder that is adapted to come to bear on the base wall 20 to constitute an end stop for the stem 90.

According to the invention, push button 30 and push rod 76 may be interconnected by several push members having the same overall function as push rod 90.

In Figure 10, reference 102 indicates an annular top that separates central depression 46 from annular groove 48 from inertial mass 44.

The top 102 is preferably at some distance from the general plane of the flat base surface 45 of the inertial mass 44 in order to reduce the friction surface that hinders the horizontal sliding of said mass.

The annular groove 48, in its lower region, has a profile with parallel sides to prevent the inertial mass 44 from accidentally returning to the centered position of Figure 3.

The radially inner annular side of the groove 48 has an annular chamfer 104 that is contiguous with the top 102.

The function of the bezel 104 will be clarified later.

IS 2 178 331 T3

The restoration of the safety switch to the first state of the circuit illustrated in figure 3 takes place in the sequence illustrated in the figures

6a9.

In Figures 5 and 6, as already stated, the inertial mass 44 is displaced to one side (in either direction) and the electrical connection between the first fixed contact 58 and the second fixed contact 66 is cut, although the possible contact Electricity between the first fixed contact 58 and the third fixed contact 68 is established.

The pressure on the push button 30 in the direction of the arrow C of figure 6 initially has the effect that the impulse rod 90 descends, which when pressing on the projection 84, causes the push rod 76 to descend, against the force of its opposing spring 82, to a partially retracted position in which it has been brought to the level of the bevel 104 of the annular groove 48.

At that point, the inertial mass 44 is still engaged in the slot 48 and the projections 34 of the push button 30 are about to engage the peripheral edge 51 of the inertial mass 44.

Spring 98, which is stiffer than spring 82, is not substantially deformed in transition from the condition of Figure 5 to that of Figure 6.

In the condition of figure 7, the stem 90 has reached an end stop, due to the fact that the collar 100 of the projection comes to bear on the lower wall 20.

An additional pressure on the push button 30 causes it to descend (Figure 7) until at least one of the inclined surfaces 38 engages, by means of a cam action, with the peripheral edge 51 of the inertial mass 44 and moves the latter in the direction centripetal, as indicated by arrow D in figure 7.

This centripetal movement of the mass 44 results in the engagement of the chamfer 104 with the upper end of the push rod 76 (FIG. 7).

The resulting cam action produces a further lowering of the push rod 76, against the force of its opposing spring 82.

During this further lowering of the push rod 76, the push rod 90 cannot lower further because its collar 100 was resting on the base wall, but the push button 30 can continue its descent due to the spring 98 giving way.

As the push button 30 continued to descend, the camming of the bevel 104 repels the push rod 76 to a position such that it allows the annular top 102 to overtake the push rod (FIG. 8).

When the inertial mass 44 has finally reached the centered position due to the inclined surfaces 38 of the push button 30, as illustrated in Figure 9, the push button 30 can be released and the system returns to the condition of Figure 3, leaving the upper end of the push rod 76 fitted in the depression 46 and the movable contact plate 56 being engaged with the fixed contacts 58 and 66.

The configuration and operation described with reference to Figures 6 to 9 has the advantage of ensuring that the inertial mass, once it has been intentionally returned to the central position of Figure 9 (and subsequently to the position of Figure 3) , it does not accidentally return to the eccentric position by sliding, due to the effect of gravity, between the base wall 20 and the cover wall 26, even when the vehicle is tilted or even upside down.

This behavior is due to the fact that the inertial mass 44, in the repositioning operation of Figures 6 to 9, can never freely slide radially outward, but is instead forced to move toward the center, the the first time by engaging the annular bevel 104 with the upper end of the push rod 76 (FIG. 7), and the second time by engaging the inclined surfaces 38 with the peripheral edge 51.

The applicant has arrived at the solution described and illustrated after several experimental attempts. In one of these attempts an annular groove, such as that indicated with 48 in the figures, had straight and parallel sides throughout its depth and, in a repositioning operation, the upper end of a push rod, such as that indicated with 76, was completely retracted from a cavity such as that indicated with 22, under the action of a push rod such as that indicated with 90.

Such an experimental solution proved to be undesirable because the inertial mass, when the vehicle was not level (and therefore the base wall and the deck wall, one in front of the other, were not in a horizontal position) slid. from the centered position as soon as the push button was released once a condition similar to that of figure 9 was reached.

This drawback was due to the fact that, although the pushbutton protrusions were moving away from the inertial mass, the push rod was still kept disengaged from the central depression of the eccentric mass by the force of a spring such as that indicated as 98 in Figures 1 and 5a9.

With the solution according to the invention, this drawback no longer occurs due to the fact that the push button 30 is not capable of causing the push rod 78 to lower below the partially retracted position. In reality, the lowering of the push rod 76 beyond this position is not produced by the push rod 90 or equivalent disengagement means, and is instead produced by a cam action that is exerted by the inertial mass. 44 on push rod 76 through annular chamfer 104.