This invention relates to windscreen wipers, particularly heavy duty windscreen wipers of the type used on large marine vessels.

Such wipers, usually straight line wipers, can be installed in ships and a particularly convenient control system is described in our co-pending U.K. Patent Application No. 9407111.5. This uses a pre-selected velocity profile for the windscreen wiper motor speed so that end of travel shocks are minimised. Alternatively or in addition other functions such as screen washers and heaters may need to be controlled and supplied with current.

A problem with such systems is that power needs to be supplied to an operator control means such as a control panel controlling such a motor and the power then has to be fed to the motor, at which point a synchronisation unit such as a park switch is located and then has to be wired back to the control panel and then subsequently back to the motor. This requires considerable heavy current supply cables in the installation of such a system. Generally at least two

sets of cables, that is to say at least from the control means to the motor and back, are required and the problem may be accentuated by the use of a three phase AC supply.

The present invention aims to solve the problem of providing additional functions for a wiper system with a minimum of additional wiring.

Referring to our co-pending Application No. 9407111.5, a power supply which incorporates a velocity profile can be supplied to the motor. This can be achieved with an AC supply by use of a central processing unit and a solid state inverter which is controlled by a signal from the park switch of the motor drive system. A DC motor with programmed speed control is an alternative which can be used.

According to the present invention, a central processing unit for controlling the motor is located in or on a casing in close adjacency with the motor. By being located in close adjacency with the motor, we mean that it is either located in a casing also housing the motor or is located on or within a casing which is closely adjacent thereto and attached as an extension to the motor casing. Being in close adjacency has a number of important advantages in practice. One such is that

the heat sink cooling of any solid state devices can be obtained from the motor itself which will have fan, or fin cooling. Another is that the wiring for that part of the system will be at a minimum, and the main components will be carried as one unit so simplifying installation. Thus the invention provides a control system for a windscreen wiper comprising a windscreen wiper motor, a casing for housing said motor, a central processing unit having circuitry for generating a speed control function for said motor, heavy current supply cabling between said motor and a power supply, and an operator control means for controlling said motor, said central processing unit being mounted to said casing so as to be in close adjacency with said motor, thereby enabling the circuitry to be cooled by the motor and data supply means being provided for provision of data from said operator control means to said central processing unit, thereby reducing or eliminating the need for heavy current supply cabling between the operator control means and the motor.

With such a system it is only necessary to have a light duty operator control means located at a location remote from the motor and connected to the motor and its processing unit by a light duty data supply means, for example light weight two-wire data supply cabling instead

of the heavy current supply cabling.

The heavy current supply cabling for the motor can go directly to the motor without being fed to and from the operator control means and various ancillary operations can also be powered from the location of the motor, for example a park switch, a heater which might be needed in conjunction with the windscreen wiper for de-icing or a solenoid valve for operating a wash and air purge system associated with the wiper.

Moreover, with such an arrangement the operator control means can be arranged to control a multiplicity of outlets, that is to control a number of separate composite motors and central processing units located in different places.

In each case all that is needed from the operator control means is a two wire or other light duty data supply means, for example multi-wire communication cabling, fibre optic data supply cabling, infra-red or radio or optical remote control, or computer LAN (local area network) wiring. Such a system thus further reduces the use of doubled up wiring and becomes much easier and less costly to instal. Also, reduced wiring with current running through it reduces electro magnetic radiation and

fields and electrical noise.

An embodiment of the invention will now be described by way of an example with reference to Figures 1, 2 and 3 of the drawings which show a schematic diagram of a wiper mechanism incorporating the present invention, a functional circuit arrangement, and a speed profile.

Continuous drive means 1 in the form of a continuous belt operates over spaced pulley wheels 2 and 3 to carry a wiper carriage 4 including a wiper blade 5 to cause it to travel in a to and fro motion between end of travel points 6 and 7 while running on a slide track (not shown) . The mechanism is essentially as described in our earlier British patents numbers 1490597 and 1502199 and uses a motor 10 which draws the pulley 3. With this arrangement the upper flight of the continuous belt 1 drives the carriage from left to right until it reaches an end of travel position 7 when it is brought back on the lower flight of the belt until it again reaches the end of travel position 6.

A park sensor 8 in the form of a reed switch is located at the first extremity position 6 and is operated by a magnet 9 carried by the carrier 4, (although it would operate equally well if located at the second

extremity position 7). In a normal wiper mechanism the reed switch 8 is wired into a park control mechanism which when activated enables the carrier to continue movement until it reaches its end of travel at which point the reed switch opens and signals that the motor 10 should be cut off. The present embodiment makes use of this reed switch 8 operating in conjunction with a speed profiling means to synchronise the end of travel position.

The speed profiling means is shown schematically as a block diagram. This is generated by circuitry on a printed circuit board, PCB, which can be located either in the casing of the motor 10 or within an extension casing firmly attached to motor 10. A central processing unit CPU, into which a timer T and the reed switch output are fed, generates a speed profile in which at the end of travel the motor accelerates smoothly between a low speed for the period when the blade carrier changes direction and a higher speed for travel between the two positions and decelerates. This profile is fed to an inverter I which then feeds the speed controlled supply from an AC supply to the motor 5.

Figure 3 shows the speed profile as the blade moves from the extreme position 6. The reed switch 8 provides

a signal S each time the system reaches the first end position 6, and any difference between the time of receipt of this signal and the actual minimum speed at the end of cycle is used to adjust the length of the next cycle so as to maintain synchronisation.

Referring to Figure 2, the PSU is linked by data supply means to an operator control means in the form of a multi function switch box SW. The switch box SW comprises low voltage switching circuitry and an operator controlled external control switch selector which allows the system to operate to provide any of the following functions:

high speed run (including profiled speed at ends of travel) low speed run switch off and park electrical heating screen wash and purge.

The switch box SW can be set up to operate a single wiper system or may have further data supply means linking to further units and the whole can be operated on a low voltage two wire system with a form of encoding to identify the unit to which control signals are to be

sent

The data supply means need not be a low voltage two wire system, but can be multi-wire communication cabling, fibre optic cabling, an infra-red, radio or optical remote control system, or a local area network (LAN) computer wiring.

An AC supply (single phase or three phase) will be fed into the PCB by heavy current supply cabling and within the PCB a rectifier, an inverter and the timed synchronised C.P.U. will change this into an AC whose frequency is varied to vary the speed.

This profiled AC will vary between that providing a slow speed for the motor as the blade carrier crosses over from left to right travel (and vice versa) and accelerating up to a high speed for the main period of travel and then decelerating back down to the low speed again.

This same profiled AC, or AC without profile can be fed to each of the functions which is selected, as set out above, and the signals from the switch unit will determine which of the functions receives current.

It is not necessary that a variable frequency AC supply should be used. An alternative is to use a DC supply operating a variable speed motor whose speed has the same profile (e.g. that of Figure 3).