Light-emitting deceleration and stopping indicator for motor vehicles

The invention relates to a light-emitting deceleration and stopping indicator for motor vehicles, of the type defined in the preamble of Claim 1.

An indicator according to the preamble of Claim 1 is known from the document US-A-3 019 415. The indicator according to this document includes an elongate hollow body for installation at the rear of a motor vehicle body, which contains a row of flashing light units. As the pressure in the braking system of the motor vehicle increases, increasing numbers of these light units are energized by means of an electro-hydraulic transducer which is sensitive to the pressure in the system. The indicator according to the document US-A-3 019 415 cannot be produced as a compact unit, since its transducer must be located remote from the body which contains the light units. Moreover, the hydraulic connections of the transducer to the braking system require the services of an expert.

Brake-light repeaters or so-called anti-collision lights have been used for some years, particularly in the United States of America, and consist of a lamp which may be mounted in a high position, for example, inside the rear window of a motor car, and includes a bulb connected in parallel with the normal brake lights of the motor vehicle. Indicators of this type are very useful when lines of vehicles are travelling close together, whereby the bonnet of a following vehicle prevents its driver from seeing the normal brake lights of the vehicle in front. An example of this is the repeater known from the document US-A-4 575 782. This repeater is a compact unit which is easy to install and to connect electrically, even by a relatively unskilled person.

The object of the present invention is to provide a light-emitting deceleration and stopping indicator which fulfils the functions of known indicators, which is constituted by a compact unit, and which can be installed and connected electrically even by a relatively unskilled person, like the indicator of document US-A-4 575 782.

According to the present invention, this object is achieved by means of an indicator essentially as defined in the characterising part of Claim 1.

By virtue of this concept and particularly by virtue of the fact that the transducer according to the invention is housed in the body of the indicator, a compact unit is obtained whose installation and electrical connection are just as easy as those of the repeater according to the document US-A-4 575 782, as will be better understood from the description with reference to the drawings.

Another indicator of the type in question is known from document US-A-3 528 056, the transducer of which is constituted by a plurality of separate mercury switches each arranged at a different inclination to the horizontal. In this indicator, which is intended to make the normal brake lights of a motor vehicle flash at a variable frequency, the mounting of the various mercury switches is complicated by the need to adjust their inclinations individually, and the wiring necessary for connection of the switches is relatively complicated and expensive.

Other indicators according to the preamble of Claim 1, and including a mercury transducer of the multiple contact type, are known from various documents, among which US-A-3 157 854, US-A-4 275 378, US-A-4 591 954, DE-A-2 056 212 and FR-A-1 509 574. None of these documents suggests to provide a compact unit incorporating a transducer in a hollow body of the unit.

Documents FR-A-1 487 351 and DE-A-2 360 733 disclose rear light units for motor vehicles which include a hollow body, a single light bulb and an inertial switch fixedly mounted within the body. The inertial switch is adapted to close when the brake pedal is pressed and the deceleration rate of the vehicle exceeds a predetermined threshold to give an intense light warning in addition to that of the normal brake lights of the vehicle. The inertial switch of DE-A-2 360 733 is of the mercury type.

Although the units of FR-A-1 487 351 and DE-A-2 360 733 are easy to install like that of US-A-4 575 782, on the one hand they do not have an array of lights and, on the other hand, their inertial switches cannot be adjusted with respect to the body of the unit to make them more or less sensitive to the deceleration forces.

Transducers such as those mentioned in Claim 1 are also known from the documents US-A-2 108 791, US-A-3 157 854, FR-A-1 509 574, AU-A-56 954 and DE-A-1 555 792.

In these known transducers, as the degree of positive or negative acceleration increases, the mercury rises to higher levels in the ascending arm to establish electrical contact between the input electrode and an increasing number of output electrodes.

The FR-A-1 509 574 discloses a transducer which is tiltable on a support so as to oscillate like a pendulum. This known transducer has no provision for the permanent setting of its inclination.

The known transducers have no provision to enable easy calibration of the various positive or negative acceleration thresholds at which electrical contact is established between the input electrode and the succession of output electrodes.

Such provision would instead be desirable in order to make the transducer more or less sensitive to the acceleration forces and is achieved in an indicator as claimed.

The possibility of adjustment of the inclination of the transducer in an indicator according to the invention enables easy calibration of the various positive or negative acceleration thresholds at which electrical contact is established between the input electrode and the succession of output electrodes.

The invention will be more clearly understood from a reading of the description which follows with reference to the appended drawings illustrating its preferred embodiments, given by way of non-limiting example, and in which:

• Figure 1 is a perspective view of the mercury inertial transducer as to be mounted in the indicator according to the invention,
• Figure 2 is a longitudinal section thereof taken in the median plane indicated II-II in Fig. 1,
• Figure 3 is an exploded perspective view thereof,
• Figure 4 is a cross-section thereof taken in the plane indicated IV-IV in Figure 2.
• Figure 5 is a perspective view of a light-emitting deceleration and stopping indicator according to the invention,
• Figure 6 is a rear view of a motor car, showing possible positions of installation of the indicator,
• Figure 7 is a side elevational view of the indicator, in which part of the window and part of the parcel shelf of the motor car are shown in longitudinal section,
• Figure 8 is a front elevational view of the indicator,
• Figure 9 is a horizontal section thereof taken in the plane indicated IX-IX in Figure 8,
• Figure 10 is a cross-section taken in the plane indicated X-X in Figure 9, and
• Figure 11 is an electrical diagram of the indicator and of its connection to the electrical system of a motor vehicle.

With reference to Figures 1 to 4, the mercury inertial transducer, which is to be housed in the indicator according to the invention, generally indicated 10, includes a casing 12. The casing 12 is constituted by a pair of mirror-imaged half-casings 12a, 12b, for example, of rigid moulded plastics material. The two half-casings 12a and 12b are in the form of essentially triangular or trapezoidal plates and mate at flat faces 14a, 14b which are joined together by glueing or ultrasonic welding. Recesses are formed by moulding in the mating faces 14a, 14b of each of the half-casings 12a and 12b and, when the half-casings are joined together, form an essentially L-shaped cavity in the casing 12. Respective protrusions on the outside of the two half-casings 12a, 12b correspond to these recesses. For simplicity, the various parts of the cavity, the recesses which define them, and the corresponding protrusions are indicated by the same reference numerals.

The cavity of the casing 12 includes, with reference to its position of use, a substantially horizontal lower arm 16 and a substantially vertical ascending arm 18. The lower arm 16 is of relatively large section and in the rest condition contains a volume of mercury A, as illustrated in Figure 2. This volume of mercury essentially does not occupy the ascending arm 18.

The charge of mercury A is introduced into the casing 12 through a threaded hole 20. A protective gas, for example nitrogen, is preferably introduced into the cavity through the same hole 20 and occupies the part of the cavity not occupied by the mercury. The hole 20 is closed hermetically by a threaded plug 22.

The cavity of the casing 12 also includes a third arm 24 which interconnects the remote ends of the lower arm 16 and the upper arm 18.

The transducer includes an input electrode 26 and a series of output electrodes 28₁, 28₂, 28₃, 28₄, 28₅, 28₆, 28₇. The input electrode 26 is produced by the blanking and bending of a piece of sheet metal. It comprises a blade part 30 which projects like a pin from the casing 12 on the outer side of the ascending arm 18 and is permanently immersed in the mercury A. The blade part 30 is extended within the ascending arm 18 by an enlarged appendage 32 which is curved like a tile and is applied against the wall of the ascending arm 18 on its inside.

The output electrodes 28₁ ... 28₇ are all constituted by blades of the same sheet metal as the input electrode 26.

Both the blade part 30 of the input electrode 26 and the blades 28₁ ... 28₇ penetrate the cavity of the casing 12 between the two mating faces 14a and 14b. Facing notches 34 are formed in these faces 14a, 14b for the passage of the electrodes. In correspondence with these notches, the input electrode 26 has a narrow part 36 and the electrodes 28₁ ... 28₇ have narrow parts 38. These narrow parts 36 and 38 are fitted into the paired notches 34 to anchor the electrodes firmly.

As can be seen, the outer parts 40 of the output electrodes 28₁ ... 28₇ are aligned like a comb and project like pins from the casing 12 along the outer side of the ascending arm 18 for coupling, together with the blade part 30 of the input electrode 26, to a common female connector.

Naturally, the electrodes could be arranged differently, but their preferred arrangement is that illustrated. They could, for example, be constituted by rod-shaped elements of round section instead of by blades.

As can be seen, the inner ends of the output electrodes 28₁ ... 28₇, indicated 42, face the tile-shaped appendage 32 of the input electrode 26.

For use, the transducer 10 is intended to be fixed to the stopping indicator of the present invention. For its fixing, the transducer 10 includes a pair of opposing flanges or lugs 44. Each of these flanges 44 is produced by moulding with a respective half casing 12a, 12b. The flanges 44 extend at right angles to the general plane of the respective half-casing and are flush with that edge of the half-casing which corresponds to the outer side of the ascending arm 18. Each flange 44 has a slot 46 for the passage of the shank of a fixing screw.

The plastics material of the casing 12 is preferably transparent to enable the correct functioning of the transducer to be checked.

The operation of the transducer 10 will now be described.

In Figures 1 and 2, the arrows B indicate the path and direction of motion of a movable object on which the transducer 10 is mounted with its lower arm 16 substantially horizontal and its ascending arm 18 substantially vertical. In these conditions, the transducer is sensitive to inertial forces directed along the lower arm 16 and towards the ascending arm 18.

When the movable object, for example, a motor vheicle, is stationary or moving at a constant speed along a horizontal path B, all the mercury A is situated in the lower arm 16 and only the input electrode 26 is immersed therein.

When the movable object decelerates, the mercury A is displaced forwardly (towards the left in Figure 2) and rises in the ascending arm 18 of the cavity. The greater the degree of deceleration, the higher the level the mercury A reaches in the ascending arm 18. The mercury therefore establishes electrical contact between the input electrode 26 and a number of output electrodes 28₁ ... 28₇ which increases as the degree of deceleration increases.

To give an idea, the volume of mercury A, the sections of the arms 16 and 18, and the heights of the output electrodes 28₁ ... 28₇ may be calculated so that contact with the successive electrodes 28₁ ... 28₇ takes place in steps of 0.1 g.

A good electrical contact along the shortest and thus least resistive path through the mercury is ensured by the presence of the appendage 32 which faces the ends 42 of the output electrodes.

The third arm 24, which is preferably of smaller section than the other two arms 16 and 18 and therefore restricted, enables the gas to circulate according to the movements of the mercury A, with a certain damping effect to make the transducer 10 relatively insensitive to negative or positive accelerations of brief duration.

Alternatively, the damping could be made adjustable by the extension of the screw plug 22 so that it obstructs the corresponding opening in the third arm 24 to a greater or lesser extent.

As will be understood, the establishing of the connection between the input electrode 26 and successive output electrodes 28₁ ... 28₇ may be used to obtain electrical signals in order to display distinct negative (or positive) acceleration values, or in order to control a device in dependence on these signals.

The light-emitting deceleration and stopping indicator according to the invention will now be described with reference to Figures 5 to 11.

With reference first of all to Figures 5, 8, 9 and 10, the indicator 50 includes an elongate hollow body or case 52 of moulded plastics material. The body 52 is provided with means for fixing to a relatively high rear part of the bodywork of a motor vehicle. As shown, the fixing means preferably include a pair of legs 54 of the same plastics material as the body 52. The legs 54 are articulted to the body 52 near their ends which are uppermost in the drawings, by means of screws 56. Fixing feet 58 of the same plastics material are associated with the legs 54. The feet 58 are articulated to the legs 54 near the ends thereof which are lowermost in the drawings, by means of screws 60.

The body 52 is in the shape of a recumbent elongate box and has an open side which, as will be seen, faces rearwardly in its position of use.

The body 52 also has transverse walls 62 produced by moulding, which divide it into two opposite end compartments 64 and a long central compartment 66.

Respective optical or light units 68, each having, for example, an incandescent bulb 70 and its parabolic reflector 72, are mounted in the end compartments 64.

The compartments 64 are closed by respective transparent, red dioptric screens or plates 74 which are inserted with a tight fit.

A panel 76 is fitted in the central compartment 66 and, as will be described below, in the embodiment illustrated carries a plurality of light-emitting diodes (LEDs).

The indicator 50 is mounted as illustrated in Figures 6 and 7. Figure 6 shows a motor car seen from behind. Its normal brake or "stop" lights are indicated C. The indicator 50 is mounted (Figure 7) on the parcel shelf D in front of the rear window E. Alternatively, as illustrated in broken outline at 50a in Figure 6, the indicator may be mounted upside down near the top of the frame of the window E.

Once the most convenient or necessary position of fixing of the feet 58 to the parcel shelf D or to something else has been selected, the casing 52 can be arranged in the most convenient position nearer to or further from the window E, by virtue of its articulation about the horizontal transverse axis defined by the screws 60, as indicated by the double-ended arrow F in Figure 7. Thus, it is also possible to regulate the horizontal position or any inclination of the body 52, as indicated by the double-ended arrow G in Figure 7, by virtue of the articulation about the horizontal transverse axis defined by the screws 56.

Once the adjustments according to the arrows F and G have been made, the indicator 50 can be clamped permanently in the desired configuration simply by the tightening of the screws 56 and 60.

The transducer 10 is mounted in the central compartment 66. The transducer 10 is supported by the body 52 so that its lower arm 16 is substantially horizontal and its ascending arm 18 is situated forwardly with respect to the direction of travel, again indicated B in Figure 10.

As shown in Figure 10, the casing 52 has a semi-cylindrical front wall 77 (with respect to the direction of travel) with a horizontal axis. In correspondence with the middle of the central compartment 66, this front wall 77 has a circumferential slot 78. Means for fixing the transducer 10 are provided in correspondence with the slot 78 and comprise a pair of arcuate tile-shaped members. One of these, indicated 80, is fitted to the outer surface of the wall 77. The other tile-shaped member, indicated 82, is fitted to the inner surface of the wall 77. The two tile-shaped members 80 and 82 are interconnected by a screw 84 whose shank passes through the slot 78. The screw 84 is screwed into a metal insert 86 which acts as a nut and is countersunk in the plate 82.

The transducer 10 is fixed to the inner plate 82 by means of screws 86 whose shanks pass through the slots 46 (Figures 1 to 3) in its flanges or lugs 44. Between the flanges 44 and the plate 82, the shanks of the screws 86 are surrounded by tubular spacers 88 which leave a space between the plate 82 and the transducer 10 for a multipolar female connector 90 connected to all the pins 30, 40 of the electrodes 26, 28₁ ... 28₇.

The means for fixing the transducer 10 to its support formed by the casing 52, which are constituted by the two tile-shaped members 80, 82 and their connecting screws 84, enable the attitude of the transducer 10 to be adjusted, with the screw 84 slackened, in the direction of the double-ended arrow H in Figure 10. This attitude adjustment enables the inclination of the lower arm 16 to the horizontal and the inclination of the ascending arm 18 to the vertical to be adjusted to make the transducer less or more sensitive to the deceleration forces. Once the desired sensitivity has been achieved, the setting of the attitude of the transducer 10 is made permanent by the tightening of the screw 84. Thus, by the same adjustment, it is also possible to reset the horizontal position or most convenient inclination of the lower arm 16, if the body 52 is not horizontal as a result of the adjustments in the directions of the arrows of Figure 7.

With reference to Figures 5 to 8, the panel 76 carries an array of light units, each of which is preferably constituted by a set of light-emitting diodes (LEDs). This array is divided into left- and right-hand half-arrays, plus a central unit. The respective light units of the two half-arrays are indicated 92_1S ... 92_6S for the left-hand one and 92_1D ... 92_6D for the right-hand one. The central light unit is indicated 92₇. In the embodiment illustrated, each light unit of each half-array comprises five LEDs arranged so as to form a pattern of dotted arrows pointing towards the central unit 92₇. In the embodiment illustrated, the central light unit 92₇ comprises eight LEDs arranged in a diamond pattern.

The diodes of the units 92_1S ... 92_6S and 92_1D ... 92_6D emit red light, whilst those of the central unit 92₇ emit orange light.

The entire indicator 52 can be connected electrically to the electrical system of the motor vehicle by means of only two terminals 94 and 96 (Figure 8) housed on one of the feet 58 (the left-hand one in Figure 8). One of these terminals, for example 94, is intended to be connected by a lead to earth, which is constituted by the metal bodywork of the motor vehicle. The lead may, for example, be connected to a screw in the bodywork by means of an eyelet terminal.

The other terminal, for example 96, is intended to be connected in parallel with the brake lights C of Figure 6. For example, a lead may connect the terminal 96 to the corresponding non-earth terminal (normally positive) of one of the brake lights C. The electrical circuit incorporated in the body 52 of the indicator 50 is illustrated in Figure 11, to which reference will now be made.

The normal brake lights of the vehicle are again indicated C. The positive pole of the battery is indicated "+" and is connected to the terminals I of the brake lights C through the normal switch J associated with the brake pedal K. The earth of the bodywork is indicated L and is connected to the negative pole, indicated "-", of the battery.

The terminal 94 is also connected to the earth L through a lead 98. The other terminal 96 is connected to one of the terminals I of the brake lights C through a lead 100.

The two lights 68 are interconnected in parallel with each other and are also connected directly in parallel with the brake lights C through the terminal 96 and the lead 100.

The terminal 96 is connected directly to the input electrode 26 of the transducer 10.

The outermost light units 92_1S and 92_1D of each half-array are electrically in parallel with each other and connected to the bottom output electrode 28₁ of the transducer 10. Progressively more inward pairs of units 92_2S ... 92_6S, 92_2D ... 92_6D of the two half-arrays are electrically in parallel with each other and connected to progressively higher output electrodes 28₂ ... 28₆ of the transducer 10. The central unit 92₇ is connected to the top output electrode 92₇ of the transducer. A flasher is preferably interposed electrically between the top output electrode 92₇ and the central light unit 92₇ and mounted in the body 52 of the indicator 50. This flasher has been represented symbolically in Figure 11 as a bimetal switch 102.

The circuit of Figure 11, which is housed in the body 52, may for the most part be a printed circuit carried on the back of the panel 76.

The resistors through which the LEDs are connected to the output electrodes and which may be carried by the printed circuit have not been shown in Figure 11 for simplicity.

The use of LEDs is convenient both for their cheapness and their low current consumption. Amongst other things, the low current consumption has the advantage that it enables a small transducer 10 to be used and at the same time enables the formation of electric arcs between the output electrodes 28₁ ... 28₇ and the mercury A to be avoided.

The LEDs, however, have the disadvantage that they emit light in a beam of limited spread. From this point of view, the adjustability of the attitude of the body 52 in the direction of the double-ended arrow G of Figure 7 is convenient, since it enables the optical axes of the beams emitted by the LEDs of the light units to be directed to the height of the eyes of the driver of a motor car which is following the car provided with the indicator 50 at a distance of 10-20 m.

The operation of the indicator is as follows.

When the driver brakes lightly with the pedal K, the normal brake lights C and the red lights 68, which act as repeaters, are switched on.

When the driver brakes a little more energetically, so as to make the vehicle achieve a deceleration of 0.1 g, the mercury reaches the bottom output electrode 28₁ and the outermost light units 92_1S, 91_1D are switched on. With even more energetic braking, such as to achieve 0.2g, for example, the mercury reaches the immediately higher output electrode 28₂ and the immediately inward pair of light units 92_2S, 92_2D are switched on, and so on.

As the deceleration increases the driver of a following vehicle sees fixed red arrow patterns which get closer and closer together, and the ever closer points thereof give the impression of a decrease in distance from the preceding vehicle.

When, upon extremely sharp braking, for example, to 0.7 g, the mercury reaches the highest output electrode 28₇, the central unit 92₇ flashes with an orange light, giving the driver of the following vehicle a sense of danger.