Control panel with a printed circuit, in particular for a motor vehicle

A control panel or control unit for a motor vehicle heating and air conditioning circuit comprises a body having a front panel, and contains a printed circuit which comprises a front circuit board located behind the front panel and having an aperture, together with a computer circuit board which makes an angle with the front circuit board. The computer circuit board has an extension portion which passes through the aperture in the front circuit board, and this extension portion carries a display device which is located behind an aperture formed through the front panel. Retaining means, for example adjustable fastening means, are interposed between the computer circuit board and the body so as to secure the display device in a defined position with respect to the front panel.

FIELD OF THE INVENTION
 This invention relates to control units, also referred to as control
 panels, of the type having a printed circuit which is intended most
 particularly for use in a motor vehicle, especially for the purpose of
 being actuated by an occupant of the vehicle in order to control some
 function of the vehicle.
 BACKGROUND OF THE INVENTION
 Control panels of this type are already known which comprise a body having
 a front panel, a printed circuit carried by the front panel, and a display
 device which is connected to the printed circuit and which is located
 behind a window formed through the front panel. Such a panel may for
 example be used for controlling an installation for heating and/or air
 conditioning the cabin of a motor vehicle.
 The front panel of the control panel (or control unit) is conventionally
 incorporated in a substantially vertical position within the fascia or
 console of the motor vehicle, so that the display device can be visible to
 the driver. Conventionally again, the front panel contains a keypad
 consisting of a plurality of touch elements such as buttons or the like,
 which are arranged to be operated by the driver of the vehicle. The front
 panel generally contains lighting means for the purpose of illuminating
 the keypad and various symbols or pictorial displays, especially for use
 when driving at night. In addition, the front panel usually contains
 indicator lights such as light emitting diodes, which light up when the
 control unit is in operation.
 Control units of the type just discussed are known in which the printed
 circuit comprises a single circuit board disposed parallel to the front
 panel. This arrangement has the disadvantage that it leaves too little
 space available to accommodate conveniently the electronic components and
 the connecting tracks associated with the printed circuit.
 Control units of the same type are also known in which the printed circuit
 comprises two circuit boards arranged at right angles to each other, and
 also arranged to be able to be separated from each other or in contact
 with each other. This particular arrangement makes it necessary to make
 some kind of special provision for fastening the display device behind the
 front panel of the control unit. These fastening means may for example
 consist of a flexible connection between the display device and one of the
 circuit boards of the printed circuit, and this then makes it necessary to
 provide a connection between the two circuit boards.
 The said means may also consist of a seal or lugs bearing on the display
 device, which then makes it necessary to provide a suitable flexible
 component such as a braid, consisting of connecting wires between the
 display device itself and one of the printed circuit boards.
 All of these arrangements are costly and do not always enable correct
 retention of the display device in engagement behind the front panel to be
 guaranteed. As a result of this, vibrations can be set up, and a gap may
 appear at the perimeter of the display device.
 DISCUSSION OF THE INVENTION
 A main object of the invention is to overcome the above mentioned
 drawbacks. A particular object of the invention is to obtain a control
 panel or control unit of the type discussed above, which enables the
 display device to be held in correct engagement against the front panel,
 regardless of any manufacturing tolerances.
 According to the invention, a control unit, in particular for a motor
 vehicle, comprising a body having a front panel, a printed circuit carried
 by the body, and a display device connected to the printed circuit and
 located behind a window in the front panel, is characterised in that: the
 printed circuit comprises a first circuit board, called a "front circuit
 board" (or keypad interface board), located behind the front panel and
 having an aperture, together with a second circuit board referred to as a
 "computer circuit board", which is disposed in such a way as to define a
 given angle with respect to the front circuit board, the computer circuit
 board including an extension portion adapted to pass through the aperture
 in the front circuit board; in that the said extension portion carries the
 display device; and in that retaining means are interposed between the
 computer circuit board and the body for holding the display device in a
 defined position with respect to the front panel.
 Thus, the control unit of the invention has two printed circuit boards
 which are disposed so as to make an angle between them, and which
 interpenetrate due to the fact that the extension portion of the computer
 circuit board passes through the aperture in the front circuit board,
 which extension portion carries the display device itself.
 Because of the above mentioned retaining means, the position of the
 computer circuit board can be easily adjusted in such a way that the
 display device will be in a position which is defined with respect to the
 front panel, that is to say generally in direct or indirect engagement
 with, and behind, a rear face of the front panel. As a result, the display
 device is held firmly flat against the back of the front panel, avoiding
 any gap or clearance, and this improves sealing against the ingress of
 dust, besides improving the general appearance. In addition, it eliminates
 any risk of noise due to vibration, and enables the effect of
 manufacturing tolerances to be ignored. A further advantage of this
 arrangement is that it reduces the connections between the display device
 and the computer circuit board, and gives improved protection against
 electrical discharges, by separating the connecting system from the front
 panel.
 In a preferred embodiment of the invention, the front circuit board and the
 computer circuit board are disposed at right angles to each other.
 Preferably the front circuit board is substantially parallel to a rear
 face of the front panel, while the computer circuit board is substantially
 at right angles to the same rear face of the front panel.
 The front circuit board preferably carries electrical contacts arranged to
 establish a connection with a control keypad carried by the front panel
 and/or with means for illuminating the front panel.
 Preferably the front circuit board is a single-face printed circuit
 carrying two opposed connecting networks, or it may be a double-face
 printed circuit. As to the computer circuit board, this is preferably a
 printed circuit of the double-face type.
 According to another preferred feature of the invention, the control unit
 includes electrical means for connecting the front circuit board with the
 computer circuit board, this connecting means also determining the mutual
 positioning of the two circuit boards. Such connecting means are arranged
 to provide the required electrical connections regardless of the mutual
 positions of the two circuit boards in space, in order to permit
 adjustment of the position of the computer circuit board.
 In a preferred embodiment of the invention, the connecting means include at
 least one pin-type connector and at least one socket having contacts for
 making mutual electrical contact.
 Preferably, the connecting means comprise at least one connector carried by
 the front circuit board, and at least one socket carried by the computer
 circuit board. In one embodiment, the front circuit board and the computer
 circuit board carry respectively two connectors and two sockets. In that
 case, the pins of the connectors preferably extend at right angles to the
 front circuit board.
 In another embodiment of the invention, the connection means comprise a
 flexible element made up of electrical conductors, such as a braid or the
 like.
 The retaining means may be made in the form of adjustable fastening means.
 Such adjustable means preferably comprise at least one screw which is
 arranged to extend through an oblong hole formed through the computer
 circuit board, the screw then being arranged to engage in a hole in the
 body. In another version, the retaining means may be made in the form of
 means which act as permanent springs.
 According to a further preferred feature of the invention, the control unit
 includes resilient means which are arranged to bias the computer circuit
 board towards the front panel, and therefore also to bias the display
 device towards its predetermined location. These resilient means may
 consist of fitted springs, for example leaf springs, wire springs, spring
 clips and so on, and may render it unnecessary to provide retaining and/or
 fastening screws.
 These resilient means preferably include at least one flexible lug carried
 by the body and arranged to engage against an edge of the computer circuit
 board.
 In one embodiment of the invention, the front circuit board is in direct
 engagement against the front panel.
 In another embodiment, an intermediate block is interposed between the
 front panel and the front circuit board. The purpose of this is
 essentially to guide the various elements of the control unit, with the
 display panel and the actuating touch elements, or to provide walls for
 locating the light, or again, to provide sealing.
 The display device of the control unit of the invention is preferably of
 the liquid crystal type.
 Further features and advantages of the invention will appear more clearly
 on a reading of the following detailed description of some preferred
 embodiments of the invention, which is given by way of non-limiting
 example only and with reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
 Reference is first made to FIG. 1 which shows a control unit or panel 10,
 which in this example is arranged to control an installation for heating
 and air conditioning the cabin of a motor vehicle. The control panel 10
 includes a body 12 made in the form of a casing which is moulded in a
 suitable plastics material. The body 12 includes a front panel, or face
 panel, 14 which is arranged to be incorporated, in a substantially
 vertical position, into the fascia or console of the vehicle.
 The front panel 14 is formed with a window 16 of generally rectangular
 form, behind which a display device 18 of the liquid crystal type is
 placed. In this example, the display device 18 is substantially
 rectangular and its dimensions are generally greater than those of the
 window 16, so that it abuts against a rear face 20 of the front panel 14.
 In another version, the display device may consist of a simple through
 hole or several through holes, the display device itself consisting of one
 or more elements.
 The body 12 carries a printed circuit which comprises a first circuit board
 22, and also a second circuit board 24. The first circuit board 22 is
 called the front circuit board, and is arranged to be located behind the
 front panel 14 in a position substantially parallel to the rear face 20 of
 the latter. The second circuit board 24 is called a computer circuit
 board, and is arranged so as to lie at right angles to the front circuit
 board 22. Thus, in the normal position of use of the control panel 10, the
 front circuit board 22 and the computer circuit board 24 are,
 respectively, in a substantially vertical position and in a substantially
 horizontal position.
 The front circuit board 22 may also be referred to as a keypad interface
 board, because it serves essentially as an interface with the front panel
 14, which carries the controls and essentially constitutes a keypad or
 keyboard. The computer circuit board 24 serves essentially to carry the
 components of the electronic control circuit itself, and possibly
 electronic regulating means for the control panel, and/or other electronic
 components that may be incorporated in the unit.
 The front circuit board 22, as shown in FIGS. 1 to 3, has a form which is
 matched to the window of the front panel 14, with dimensions smaller than
 those defined by the edges of the window 16. In this example, the front
 circuit board 22 is generally rectangular and is bounded by two major
 sides 26 and two minor sides 28, see FIG. 3. It has a central aperture 30
 of generally rectangular form, the sides of which are parallel to the
 sides 26 and 28. The aperture 30 must be sufficiently large to enable the
 display device 18, which is in fact carried by the computer circuit board
 24, to pass through it.
 The computer circuit board 24, as is best seen in FIG. 4, is generally
 rectangular in form. It has an anterior edge 32, a posterior edge 34 and
 two side edges 36. In addition, it has an extension portion 38 of
 generally rectangular form which extends the board beyond the anterior
 edge 32. The extension portion 38 has a width which is smaller than the
 largest dimension of the aperture 30 in the front circuit board 22, so
 that it is able to pass through the aperture 30. The extension portion 38
 supports the display device 18 in a perpendicular position. Side walls 40,
 FIGS. 1 and 4, are carried by the circuit board 24 adjacent to the
 extension portion 38, and have a substantially arcuate cross section as
 shown in FIG. 1. The walls 40 serve to maintain the display device 18 in
 its position perpendicular to the circuit board 24.
 The front circuit board 22 in this example is made in the form of a simple
 single-face printed circuit board, i.e. the circuit is printed on one
 side, having two connection arrays, one at each end as shown, for
 connection of the pattern of connecting strips printed on the board.
 However, this front circuit board could have any other suitable structure.
 The circuit board 22 also includes electrical contacts 42 which are
 arranged to establish connection with lamps or illuminated indicators,
 together with electrical contacts 44 for establishing connection with
 control elements such as touch pads, knobs or the like, which form part of
 the keypad or keyboard incorporated in the front panel 14.
 In addition, the front circuit board 22 includes two connectors 46 which
 are provided with pins 48, each of which is arranged to cooperate with a
 corresponding socket 50 carried by the computer circuit board 24. The
 circuit board 24 is a printed circuit of the double-face type, connected
 to the two sockets 50.
 As can be seen in FIG. 2, the connecting pins 48 of the connectors 46
 project at right angles to the surface of the front circuit board 22
 itself. These pins 48 are arranged to cooperate with contact elements 52
 which form part of the sockets 50, so as to establish electrical
 connection between the two circuit boards 22 and 24 regardless of the
 position of the computer circuit board 24. In this connection, the latter
 is adjustable in position as indicated by the double arrow F in FIG. 2, so
 as to enable the display device 18 to be placed truly flat against the
 back face 20 of the front panel 14 as shown in FIG. 1.
 In this example, two screws 54 are provided for retaining the computer
 circuit board 24 in position. The screws 54 may extend either upwards or
 downwards in the housing of the unit. Each of them passes through an
 oblong hole 56 formed in the circuit board 24, and shown in FIG. 4, and is
 engaged in the further hole 58 formed in a boss 60 of the body 12, shown
 in FIG. 1. In another version, the computer circuit board 24 may be
 retained in position by suitable permanent resilient means, such as clips,
 instead of by means of screws.
 In addition, as can be seen in FIG. 1, a flexible elastic lug 62 carried by
 the body 12 is arranged to engage against the edge 34 of the computer
 circuit board 24. This flexible lug, or leaf, biases the circuit board 24
 elastically in the direction of the arrow G in FIG. 1, i.e. towards the
 left in FIG. 1, which helps to maintain the display device 18 in
 engagement against the back face of the front panel 14. In this way it is
 possible to adjust the circuit board 24 so as to keep it in a defined
 position in which the display device 18 is in engagement against the front
 panel 14. This enables any clearance, and therefore any vibration noise,
 to be eliminated, regardless of variations in dimensions due to
 manufacturing tolerances. During assembly, the flexible lugs 62 enable the
 computer circuit board 24 to be pushed into position so as to obtain
 perfect contact of the display device 18 against the front panel 14
 without any clearance. The two screws 54 can then be tightened so as to
 secure the board 24 in the position which is thereby preadjusted, and
 secure the assembly together definitively.
 Reference is now made to FIG. 5, for a description of a further version of
 a control panel according to the invention. In FIG. 5 those elements which
 are also shown in FIGS. 1 to 4 in relation to the first embodiment just
 described are designated by the same reference numerals.
 In FIG. 5, the body 12 is made in the form of an open cap, in a rigid
 plastics material such as ABS. The liquid crystal type display device 18
 is fixed on the computer circuit board 24. A prism 64 of synthetic glass
 is arranged behind the display device 18. The purpose of the prism 64 is
 that it shall itself be covered by a light box 66, which is preferably
 made of a synthetic plastics material of the ABS type.
 The front circuit board 22 carries three luminous elements 68, such as
 light emitting diodes (LEDs), together with two support elements 70, each
 of which is arranged to support a lamp 72.
 The front panel or face panel 14, which is arranged to be placed in front
 of the mouth of the body 12 in the form of a casing, is made of coloured
 plastics material, for example of the ABS type.
 A light guide 74 and an intermediate block 76 are held trapped between the
 front circuit board 22 and the front panel 14. The intermediate block 76
 has a number of through holes such as those indicated at 78, and portions
 80 of the light guide 74 are arranged to penetrate through these holes 78.
 The intermediate block 76 also has seatings for touch elements, namely, in
 this example, a switch dolly 82 of the vertical tilt type, a switch dolly
 84 of the horizontal tilt type, and a touch button 86. These three touch
 elements pass through appropriate holes formed through the front panel 14,
 and constitute elements of a control keypad. The touch elements 82, 84 and
 86 are mounted on respective support members 88, 90 and 92 carried by the
 intermediate block 76. A saddle clip 94 is arranged to retain the support
 member 92 in position. In addition, a push rod 96 is arranged to extend
 through the intermediate block 76.
 The invention is of course not limited to the embodiments described above
 by way of example, and does embrace other versions. Thus, for example, it
 will be understood that the interconnection between the computer circuit
 board and the front circuit board could be obtained in any other way, for
 example by means of a flexible braid or the like, of conductive wires.
 In addition, although the invention has been described above with
 particular reference to a control unit for a heating and/or air
 conditioning installation for a motor vehicle, it can be applied to other
 kinds of equipment. It may particularly be applicable for example to
 display panels, multi-function screens, clocks, instrumentation panels,
 automatic radios, and so on.