Brushing – scrubbing – and general cleaning – Attachments – Optical-member-attachable cleaner
Patent
1996-10-11
1998-10-27
Graham, Gary K.
Brushing, scrubbing, and general cleaning
Attachments
Optical-member-attachable cleaner
1525029, 1525017, 318DIG2, 318444, 318443, B60S 144
Patent
active
058262954
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a straight-line windscreen wiper of the type used on large marine vessels.
BACKGROUND OF THE INVENTION
A straight-line wiper offers the advantage of a swept area that can cover substantially the whole window being wiped. Also it can be constructed in a robust form so as to deal with extreme conditions.
The wiper generally uses a continuous drive means in the form of a belt which runs between two equal sized pulley wheels. Alternatively the continuous drive means may be a chain running on sprocket wheels.
The blade of the wiper is fixed to a wiper carriage which runs and is guided in a casing, and which is attached by an appropriate linkage to the belt. One of the wheels is free to rotate on its bearings while the other is driven by an electric motor, or both may be driven, so that the carriage moves in a linear path along the casing. Referring to FIG. 1 of the accompanying drawings, the motion of the carriage is reversed at each end (a, and b) of stroke by the motion of the carriage attachment point being transferred from the upper to the lower flight and vice versa. The motor is generally run at one speed w, so the velocity V of the carriage (and hence of the wiper blade) is as shown in FIG. 1 of the accompanying drawings.
The rate of change of velocity f (i.e. acceleration) is shown in FIG. 2. The value at the end of stroke is large, typically 5 g. The large value is currently accommodated by the use of damping mechanisms, and by limiting the size of the wiper arm and blade (and hence inertia) to values such that there is an acceptable life and acceptable levels of the physical manifestation of acceleration and deceleration shocks.
The problem of large start up and slow down shock is particularly acute with heavy duty marine wipers, because of the extreme conditions which are encountered. In particular, the system needs to be extremely robust and a high pressure has to be applied to the wiper blade to ensure reliable operation in adverse weather conditions which are accentuated by salt or icing.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a heavy duty wiper device which includes a continuous drive means operating over spaced wheels, a wiper carriage driven by the continuous drive means so as to travel in a to and fro motion between first and second end of travel positions and which is adapted to change the direction of drive by transferring the drive between upper and lower lights of the continuous drive means, and a drive motor for driving at least one of the spaced wheels unidirectionally, characterized by speed profiling means for controlling the speed of the motor, the speed profiling means being arranged to control the motor speed so as to perform an operational to and fro cycle where in a region at each end of the travel of the wiper carriage the motor speed is, over a selected period of time, smoothly increased from a low speed to an operational speed as it leaves each end of travel position and is smoothly reduced from the operational speed to the low speed as it approaches each end of travel position.
A variable speed of operation is often provided in current designs. This is achieved by crude (open-loop) regulation of the motor speed using a speed setting control which reduces the average current fed to the motor (generally either dc or series-wound ac). In conjunction with the essentially constant wiper torque demand, this results in a lower average speed.
By sensing the position of the carriage, it is possible to provide a profiled decrease of motor speed on approach to an end of motion, and a subsequent increase back to the normal speed for the motion across the main travel.
Most systems also incorporate a `park` position sensor, such that on reaching that end of stroke the motor is caused, in a simple control circuit, to be stopped.
One simple method of achieving the smoothed action according to the invention is to make use of this park position sensor P to engage a speed demand profile as shown in FIG. 3. In a propose
REFERENCES:
patent: 3042954 (1962-07-01), Wynn et al.
patent: 4599546 (1986-07-01), Uemura
patent: 4663575 (1987-05-01), Juzswik et al.
patent: 4665488 (1987-05-01), Graham et al.
patent: 5225752 (1993-07-01), Yasuda et al.
Elmhirst John
Kirkby Denis J.
Graham Gary K.
Wynn Marine Ltd.
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