Drier for a vehicle wash and method of controlling same

In a drying device for a vehicle wash with a travelling portion of said drying device movable relative to said vehicle with the aid of a travel motor and a lift motor in a direction of a longitudinal axis and a lifting or vertical axis of said vehicle, said travelling portion carrying a drying means and a light barrier whose light beam passes with clearance under said drying means and with a device controller operating said travel and said lift motors guiding said travelling portion on a path which keeps a guaranteed clearance from the contour of said vehicle, as a result at least the raising and lowering of said portion is controlled by a gating signal, said light barrier including a light source, a light detector and a signal conditioner which transmits said gating signal to said device controller which indicates a light barrier breaking and a light barrier release and which acts on an amplifier to produce an output signal of the detected light beam which contains a threshold circuit acted upon with said output signal of said amplifier and an adjustable voltage generator which transmits a control voltage for adjustment of the amplification factor of said amplifier or said threshold circuit or said light source, the improvement wherein an automatic adjustment is provided for said voltage generator which is activated by said control device at the start of said drying process and which changes said voltage produced by said voltage generator so that with said gating signal present said gating signal reports said light beam breaking and then said voltage produced by said voltage generator varies about a small definite value.

In a method of operating a vehicle washer in which a washer frame is moved along a vehicle to effect washing thereof by brushes carried by said frame and drying of the vehicle is effected by movement of said frame along said vehicle and controlled displacement of drying nozzles in response to a light beam which can be interrupted by the vehicle to maintain a substantially constant spacing of the nozzles from the vehicle the improvement which comprises the steps of:

• before commencement of a drying operation, selecting a value representing a desired response to interruption of said light beam;
• generating a start pulse at commencement of said drying operation;
• in response to said start pulse, transferring said value to a countdown counter and resetting an up/down counter;
• gating to an up-counting input of said up/down counter a sequence of pulses to accumulate a count in said up/down counter whose increase in magnitude corresponds to increasing response to said light beam;
• detecting the response to said light beam and generating a feedback pulse upon said response exceeding a predetermined threshold value, with said feedback pulse blocking the gating of pulses from said clock to said up-counting input and gating pulses from said clock to a down-counting input of said up/down counter and to said countdown counter until said value is reached therein;
• and
• effecting said drying operation with the response to said light beam being determined automatically by the count in said up/down counter when said value has been reached in said countdown counter.