Electrical control selector for controlling at least one actuator between a plurality of discrete positions

A selector is typically arranged to control adjustment of a motor vehicle headlamp between a plurality of discrete, stable positions. It includes a control member arranged to occupy a number of discrete stable positions, a switching member operated by the control member, a voltage generator for giving voltage signals and having two supply inputs, a control output terminal for operating an actuator for the headlamp, and at least one coded network of resistors and electrical contact strips. The output terminal is connected to each supply input through at least one resistor, the coded network comprising at least one collecting strip connected to the output terminal, together with a secondary contact strip, also connected to the output terminal, and a primary contact strip connected to one of the supply inputs. The various contact strips are so arranged that the switching member cooperates with the collecting strip in all of the positions, with the primary contact strip in a smaller number of positions, and with the secondary contact strip in an even smaller number of positions.

FIELD OF THE INVENTION 
The present invention is concerned with electrical control selectors for 
controlling at least one actuator for a member which is movable between a 
plurality of discrete positions, for example a headlamp or a pair of 
headlamps for a motor vehicle. In particular the invention is concerned 
with such a selector comprising a control member adapted to occupy a 
plurality of stable positions; a switching member which is movable under 
the action of the control member: a voltage generator for emitting 
voltages at discrete values and comprising two supply inputs each 
connected to a respective one of the terminals of an electrical supply 
source; a control output terminal for controlling the actuator; and, 
between the said supply inputs and the said output terminal, at least one 
coded network of electrical resistors and contact strips, with the said 
electrical contact strips being adapted to cooperate in a coded manner 
with the said switching member for emission of a command signal to the 
output terminal. 
BACKGROUND OF THE INVENTION 
A selector of this kind is described in the specification of published 
European patent application No. EP 0 367 668A, in which the actuator is a 
voltage responsive generator which is a "mirror image" of the above 
mentioned voltage generator, together with an electric motor which is 
powered through differential amplifiers of limited or fixed gain and 
mounted in opposition to each other. In addition, in the event of damage 
to the control line, the movable member assumes a predetermined position. 
The selector or switching unit includes a switching member in the form of a 
conductive cursor for making electrical contact between one of the contact 
points (or electrical contact strips) and the control output terminal; the 
voltage generator for emitting voltages at a plurality of discrete values 
consists of a voltage splitting bridge with resistors. 
This requires certain precautions to be taken. Thus, it is necessary for 
the cursor, while passing from one stable position to another, to overlie 
the contact strips unless this would produce, at the control output 
terminal, a signal equivalent to a fault in the control line, in which 
case the headlamp is automatically returned to its dipped position. 
In addition, when two contact strips are connected to the supply inputs, it 
is necessary to prevent the cursor from overlying three contact strips at 
the same time when passing from one position to another. Accordingly, 
having regard to the mounting mentioned above, of the actuator (or 
positioning unit), the electric motor of the latter would oscillate. It is 
also desirable for standardization reasons to avoid having to modify the 
actuator, which is overall a more costly component than the selector. 
DISCUSSION OF THE INVENTION 
An object of the present invention is to satisfy the above criteria in a 
simple and economic manner, without having to modify the positioning unit. 
In accordance with the invention, a selector of the kind described above is 
characterized in that the output terminal is connected to each of the 
supply inputs through at least one resistor, in that the said coded 
network of resistors and electrical contact strips comprises: at least one 
collecting strip connected to the output terminal, a secondary contact 
strip connected to the output terminal; and a primary contact strip 
connected to one of the said supply inputs, and in that the said 
electrical contact strips are so arranged and dimensioned that the 
switching member is in permanent cooperation with the collecting strip, 
while the switching member cooperates with the primary contact strip in a 
number of the said positions smaller than the total number of positions, 
and with the secondary contact strip in an even smaller number of the said 
positions. 
The invention enables the switching member, which is for example again a 
cursor, to separate from one contact strip on each change of position 
without leading to any instability in the actuator, due mainly to the fact 
that the collecting contact strip and the secondary contact strip or 
strips are connected to the control output terminal. 
It will be appreciated that this arrangement is economical in cost and 
leads to minimal modification. In addition, it is possible to provide an 
increased number of stable positions, by providing a second series of 
secondary contact strips, longer than the first series of secondary 
contact strips but shorter than the primary contact strip. 
It is also easy to provide an increased number of positions by using a 
symmetrical arrangement in which a second primary contact strip is 
connected to the other supply input and to a second secondary contact 
strip connected to the first secondary contact strip. An appropriate 
resistor is associated with each contact strip, depending on the 
particular application. In a modification, the various contact strips 
could be made with different electrical resistances. 
It will be appreciated that a resistor is brought into or out of circuit as 
between one of the said positions and another, which enables the selector 
to be easily matched to a standard actuator. 
A preferred embodiment of the invention is described below, by way of 
example only and with reference to the accompanying drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
In the drawings, the electrical control selector 20 is intended for 
controlling the action of at least one actuator 21, 22 of a movable member 
23, 24 which is displaceable between a number of discrete positions. The 
selector 20 includes a control member 4 which is adapted to occupy a 
plurality of stable positions, together with: a movable switching member 
11, movable under the action of the control member 4; a voltage generator 
50 for emitting voltages at discrete values and having two supply inputs 
58, 59, which are connected to respective ones of the terminals of an 
electrical supply source; a control output terminal 56 for control of the 
actuator; and, between the supply inlets 58, 59 and the output terminal 
56, at least one coded network comprising a plurality of resistors R1 to 
R6 and electrical contact strips 51 to 55. These contact strips 51 to 55 
are arranged to cooperate in a coded manner with the switching member 11, 
such that a command signal is given at the output terminal 56. 
In this example, the selector 20 is connected through three lines 25 to 27 
to two actuators 21, 22 for controlling the headlamps 23, 24 of a motor 
vehicle. The selector is supplied with power from the battery of the motor 
vehicle, which constitutes the above mentioned electrical supply source. 
Its inputs 58, 59 are connected respectively to the negative terminal of 
the battery (which is earthed to the vehicle) and to the positive terminal 
of the battery at +12 V. 
The actuators 21 and 22 are constructed in the manner described in the 
above mentioned European published patent specification No. EP 0 367 668A, 
and include a voltage responsive generator 28 comprising a plurality of 
resistors, together with an electric motor 29 and two differential 
amplifiers 30 and 31 which are mounted in opposition to each other, with 
resistors 32 being interposed. 
The line 25 is connected to the positive terminal of the vehicle battery, 
while the line 27 is earthed to the vehicle, the line 26 constituting the 
control line. Each actuator 21, 22 may of course be supplied directly from 
the vehicle battery, so that it is not then essential to provide the lines 
25 and 27. 
The control output terminal 56 is connected to each of the supply inputs 58 
and 59 through at least one resistor R2, R1. The coded resistor network R1 
to R5 and electrical contact strips 51 to 55 include at least one 
collecting strip 51 which is connected to the control output terminal 56, 
together with a secondary supply strip 52, 55 connected to the output 
terminal 56 and a primary supply strip 53, 54 connected to one of the 
supply terminals 58, 59. The electrical contact strips 51 to 55 are so 
made and dimensioned that the switching member 11 is in permanent 
cooperation with the collecting strip 51, while it is in contact with the 
primary supply strip 53, 54 in a smaller number of positions, and with the 
secondary supply strip 52, 55 in an even smaller number of positions. 
In the particular arrangement shown in the drawings, the selector is 
arranged to adopt five stable positions (like the actuator), which are 
indicated by the reference numerals 0 to 4 in FIG. 5. The arrangement is 
symmetrical about the middle position 2. The primary supply strips, 
secondary supply strips and collecting strips are all parallel to each 
other. 
More precisely, there are in this example two primary supply strips 53 and 
54, two secondary supply strips 52 and 55 which are connected together 
through a conductive line 57, and a single collecting strip 51. The latter 
is connected through a resistor R3 to the output terminal 56, while the 
secondary supply strips 52 and 55 are connected to the output terminal 56 
through a further resistor R4. The contact strip 54 is connected to the 
supply terminal 58 (i.e. earth or ground) and to a resistor R2, while the 
primary supply strip 53 is connected to the input 59, at 12 V, through a 
resistor R5. The output terminal 56 is connected to ground and to the 
input 58 through the resistor R2, and to the input 59 through the resistor 
R5. The strips extend parallel to each other. 
The switching member 11 comprises a cursor which is displaceable axially 
and which is in the form of a three-pronged comb adapted to cooperate with 
the electrical contact strips in a manner to be described below. The 
cursor 11 is of an electrically conductive material, and in this example 
is of metal. It is fixed to a carriage 10 which is itself movable axially. 
The carriage 10 is generally in the form of an angle piece comprising a 
tubular upper portion having a threaded internal bore for cooperation with 
a thread 12 formed on the outer periphery of the control member 4. 
The control member 4 is a small toothed wheel which has a tubular portion 
on which the external thread 12 is formed. The wheel 4 is mounted for 
rotation about a spindle 9, and is fixed to an insert 5 which carries 
marks to indicate the five stable positions of the wheel 4. 
The primary supply contact strip or strips are offset axially with respect 
to the secondary contact strip or strips, the latter being themselves 
offset axially with respect to the single collecting strip. In this 
example, the primary contact strips 53 and 54 are arranged as axial 
extensions of each other, as are the secondary contact strips 52 and 55, 
and extend parallel to the collecting strip 51 and to the secondary strips 
52 and 55. The primary contact strips 53 and 54 are longer in the axial 
direction than the secondary contact strips 52 and 55, but are shorter in 
the axial direction than the collecting strip 51. The length of the latter 
is equal to the total length of the primary strips 53 and 54, which are 
separated from each other by a non-conducting zone so as to define the 
middle position. 
The generator 50 is carried by a support plate 3 of electrically insulating 
material. The cursor 11 is arranged to cooperate with the resistive 
network. All these components are mounted inside a housing 1, 2, which is 
of an electrically insulating material which in this example is a plastics 
material. The housing 1, 2 comprises a base member 1 having a base portion 
which is constructed as an electrical connector and which is shrouded by a 
cover member 2 which is attached to the base member 1 by a snap-fit or 
clipping attachment. A hooking lug which is fixed to the cover member 2 
can be seen in the lower part of FIG. 4, as can a tongue which is fixed to 
the base member 1. The housing is assembled in a known way by resilient 
engagement of the tongue so that the hooked lug hooks against a fixed 
abutment of the base member 1, which serves as a guide for the carriage 
10. In a modification, fitting of the two components of the housing 
together may be obtained by threaded attachment or by adhesion. 
The housing 1, 2 also includes lugs, one of which can be seen in the left 
hand part of FIG. 3, for mounting on the bulkhead of the vehicle. The 
cover member 2 is suitably styled, and has an opening 17 for access to the 
wheel 4 so that the latter can be actuated by the user. 
The stable positions of the wheel 4 are obtained by virtue of disengageable 
locking means, which in this example comprise teeth 6 formed in the wheel 
4, together with a resilient locking member 16 carried by the base member 
1. This locking member is in the form of a thin metal strip cooperating 
with the teeth 6. Movement from one stable position to another is obtained 
by rotating the wheel 4 and disengaging the strip 16, followed by 
engagement of the latter with a further tooth 6. In a modification, an 
arrangement can of course be used in which a spring-mounted pin is used 
for cooperation with the teeth 6. 
In this example the spindle 9 is carried by the cover member 2, and has a 
thickened portion for mating cooperation with the internal bore of the 
wheel 4 and for coupling with the latter in rotation, as can be seen in 
FIG. 4. 
The support plate 3 carries pins 15 on one of its faces. The pins 15 extend 
through the base portion of the base member 1 and are part of the 
electrical connector of the latter. It also carries, on the same face, 
resistors 13 which are part of the coded network mentioned above. The 
electrical contact strips 51 to 55 are arranged on the other face of the 
insulating support plate 3. The latter carries a lamp 14, and also carries 
the electrical supply means for this lamp. The lamp 14 illuminates the 
insert 5, which is of translucent material, and the lamp 14 is accessible 
from outside. The base portion 1 carries a finger 7 which extends through 
a hole 42 formed in the support plate 3 (see FIG. 6), so as to secure the 
support plate in position and to support the spindle 9. The support plate 
3 is also formed with a notch 40, through which there extends a projection 
which is part of a series of projections 8 for supporting and locating the 
support plate 3. The lamp 14 is mounted in an aperture 41 in the plate 3. 
The carriage 10 has a horizontal lower portion which extends below the 
wheel 4 and carries the cursor 11 for cooperation with the contact strip. 
In this example the cursor 11 has three prongs. The device operates by 
covering an uncovering the contact strips. 
The resistors R1 to R5 have values of resistance which depend on the 
particular application, and a resistor R6 is provided at the output 
terminal 56. This resistor R6 is a safety resistor. In this example the 
resistors R1 to R6 have different values of resistance. Thus, for example, 
movement from the middle position 2 to the position 1 is obtained by 
rotation of the wheel 4 from one tooth to the other, the motion of the 
wheel being converted into axial displacement of the carriage 10 by the 
threaded coupling with the thread 12, so that the carriage displaces the 
cursor 11 axially and is guided axially by the side walls of the base 
portion 1 of the housing (see FIG. 4). During this phase, the cursor 11, 
which was initially in contact only with the collecting strip 51, comes 
into contact with the strip 54 and so connects these two strips together. 
If the movement is now continued (i.e. from position 1 to position 0), the 
cursor 11 comes into contact with the secondary contact strip 55, so as to 
connect the three strips 51, 54 and 55 electrically together. 
It is of course also possible to move the wheel 4 in the opposite 
direction, so as to go from position 2 to position 3, so that it covers 
the secondary strip 52 which is connected to the strip 55 through the line 
57, and vice versa. 
Referring now to FIGS. 7 to 11, these show the resistance values used to 
determine the voltages at the output terminal 56 for various positions of 
the cursor 11. FIG. 7 corresponds to position 4, while FIGS. 8 to 11 
correspond to positions 3 to 0 respectively. As will have been gathered 
from the foregoing, movement from one position to another (as represented 
in FIGS. 8 to 11) causes a resistor to be brought into circuit or out of 
circuit. 
It will be appreciated that the electrical circuit of the actuator has not 
been modified, and that the voltage generator 50 of the selector and the 
generator associated with the actuator may be equally made as "mirror 
images" of each other, by appropriate choice of the resistance values in 
the selector. 
The contact strips 51 to 55 are part of a printed circuit, or in a 
modification, an engraved metallic circuit, with this circuit including 
connection lines for connection with the resistors R1 to R5 and being 
carried by the support plate 3. 
It will be noted that, clearly, all the contact strips are so shaped and 
dimensioned as to cooperate with the cursor 11, and in particular they 
have a width which is greater than that of its prongs, with the axial 
spacings between the collecting strip, the secondary contact strips and 
the primary contact strips being a function of the spacing between the 
prongs of the cursor 11. 
The present invention is of course not limited to the example described 
above and shown in the drawings. In particular, the number of positions 
may be less than five, or greater than five, and depends on the number of 
positions of the actuator. Thus for example, in order to obtain three 
positions, the collecting strip 51 is shortened and the strips 52 and 53 
are omitted. If a larger number of positions is required, then a second 
series of secondary contact strips (or a larger number of the latter) can 
be added, it being understood that in each case, the length of any such 
additional strip is smaller than that of the corresponding primary contact 
strip, but greater than that of the first secondary contact strip. 
Instead of employing linear movement, it is of course possible to design a 
device in which the contact strips are in the form of circular sectors 
arranged on pitch circles of different diameters, with the cursor then 
being arranged to move in circular motion. 
In all cases, the collecting strip has an axial or circumferential length 
which is greater than that of the primary contact strip, the latter itself 
being longer than the secondary contact strip and with the cursor never 
joining the two primary contact strips together.