Safety switch

The present invention relates to a safety switch of the normally closed kind for vehicle engines, and more particularly pertains to a safety switch inserted in the fuel pump electric circuit. The function of the switch is to open responsive to acceleration or deceleration exceeding a predetermined intensity to which the vehicle is subjected in a horizontal plane.

At the same time, the switch must not be responsive to jerks or vibration of normal intensity.

Switches of this kind are well known, for example those disclosed in US-A-2206067 and EP-A-0038328. These devices have a drawback in that they are rather complex and costly from a constructional point of view.

Some of them are also rather difficult to reset in their original position after they have been activated.

FR-A-2 620 855 discloses a safety switch inserted in an electric circuit of a vehicle. The switch comprises:

• a housing fixed to the vehicle;
• a spherical inertia mass movable from a first unstable position of normal operation, whereby the spherical mass allows current passage in said circuit, to a second stable position whereby current in the circuit is interrupted responsive to sharp acceleration or deceleration in a horizontal plane;
• a first electric contact for opening or closing on a second electric contact responsive to the position of the spherical mass. In said first position the spherical inertia mass is interposed between a concave retaining seat and a convex retaining means. The mass is retained by said seat and said means in opposite ways along a substantially vertical axis by means of gravity of a mass.

From other patent publications (CH-A-351011, FR-A-2151585, DE-A-3128594, CH-A-486345) it is known to retain the inertia mass by resilient biasing means.

None of the above cited references provide a safety switch wherein resetting operation is possible also when the vehicle is considerably slanting after a crash. In such a condition, the prior art resetting means are not capable of taking the spherical inertia mass from the second, open circuit position back to the first, current conductive position.

The present invention seeks to provide an improved safety switch capable of overcoming the above problem.

According to this invention, there is provided a safety switch as specified in claim 1.

Preferred but not-limiting embodiments of the switch according to the invention are described hereinafter with reference to the accompanying drawings, in which:

• Figure 1 is a sectional view of a first embodiment of a safety switch according to this invention; and
• Figures 2 and 3 are sectional views of a second embodiment of the safety switch of this invention in first and second working positions, respectively.

Referring at first to figure 1, the safety switch comprises a fixed housing 1, preferably made of plastic material, consisting of a bottom portion 53 and a downwardly tapered side wall portion 43 on top of which a cap 40 is fitted. The cap 40 forms a cylindrical portion 43 extending upwardly from a base 42, in the centre of which a central dead hole 44 and four openings 45 (of which only two are visible in the drawing) are obtained. A push button 46 is slidably accommodated in the upper part of the cap 40. The push-button 46 rests on the base of the cap by means of a returning spring 47. The openings 45 let through four projections 48 (of which only two are visible in the drawing of figure 1) that are integral with the push-button 46 and have lower outwardly diverging inclined surfaces 49.

An inner cup 50, consisting of a bottom portion 51 and a cylindrical wall 52, is fixed between the frustoconical portion 43 of the lower body 1 and the base 42 of the cap 40. The bottom 51 of the cup 50 provides a central bore for accommodating a floating pin 54 that is interposed between the spherical mass 22 and the contact in form of elastic lamina 11. This lamina is fixed in bottom portion 53 of the body 1 and is movable between a lower fixed contact 12 of normally closed kind and an upper contact 13 of normally open kind fixed to the bottom portion 53. The elastic lamina 11 and the floating pin 54 are biased upwardly by means of a spring 30 resting on the bottom portion 53 of lower body 1.

The lower body 1 also forms a watertight connector 55 for electric connection to the fixed contact 13.

The top of the switch is covered by a gasket 56 that renders the inner parts of the switch watertight.

Operation of the switch of figure 1 is as follows. In normal conditions, the spherical mass 22 is kept in its unstable position (see full line in the drawing) resting on the bottom of the dead hole 44 biased by floating pin 54.

The resistance offered by the ball in this position keeps the lamina 11 onto contact 12.

In case of an accident occurring, the consequent crash causes the ball to move away from of the central position (full line) to a side position 22a (dotted line in the drawing). Therefore, the spring 30 is released and pushes up the floating pin 54 and the lamina 11, thereby disconnecting the fixed contact 12 and interrupting the electric circuit feeding an apparatus, i.e. the pump of a fuel injection apparatus. Those skilled in the art will appreciate that the safety switch may also be utilised for other devices, providing the same advantages. At the same time, the contact 13 is closed so that a warning light (not shown) located in the passenger cabin is lit up to indicate the operation of the switch.

Also in this case, to reset the electric current to pass through the contact 12, it is necessary to press the push-button 46, in order to lower the inclined surfaces 49 and take the spherical mass 22 into its central position, pushing down the floating pin 54 and compressing the spring 30. Upon releasing the push-button, the returning spring 47 pushes it back into its original position as shown.

It should be appreciated that the reset of the switch is very simple to accomplish and it is also possible when the vehicle is considerably slanting, as the inclined surfaces 49 can engage the ball 22a in any place it has ended within the cup 50 after the crash.

The embodiment shown in Figures 2 and 3 differs from that of Figure 1 in that the floating pin 54 is arranged having an upper narrow shaft portion 54a and a lower downwardly open larger cup portion 54b. Floating pin 54 is no longer interposed between the spherical mass 22 and the elastic lamina 11, (as shown in Figure 1), as shaft portion 54a is inserted in a corresponding bore obtained in the elastic lamina 11. Bottom spring 30 is fitted within cup portion 54b and urges the upper end of shaft portion 54a directly against mass 22. Lamina 11 is arranged so as to normally close upon lower fixed contact 12 (Figure 2).

When mass 22 moves away due to a crash, spring 30 biases pin 54 upwardly through the bottom 51 of cup 50. The cup portion 54b engages lamina 11 pushing it up, thereby opening contact 12 and closing contact 13 (Figure 3). Vertical movement of floating pin 54 is stopped by lamina 11. This particular arrangement and the shape of the floating pin prevents it from falling out of its seat in case the vehicle should be slanting or tilted after an accident.

The invention is not limited to the aforegoing description, which is to be considered purely as an illustration of the best mode of implementing the switch, and modifications are possible in the terms of the shape, dimensions and arrangement of the parts and of the constructional and operational details. The invention includes all modifications which fall within its scope, as defined by the following claims.