FLOOR CLEANING MACHINE

Abstract: The invention pertains to a floor cleaning machine compris­ ing an electrical means for controlling the operation of the brush head lever motor to maintain the brush pressure at an operator-­ set value. An improved brush pressure regulating system which is operator-adjustable, is provided.

Description: The present invention relates to floor cleaning machines as defined as defined in the preamble of the accompanying Claim 1 and which are used for the cleaning of hard surfaces of large floor areas, such as e.g. in hotels, factories, office buildings, shopping centres and the like. A machine of this kind is disclosed in US-A-4218 798. In general such machines comprise a movable body supported by a pair of drive wheels and one or more caster wheels, the body carrying a brushing means, reservoirs for storing fresh and spent cleaning liquid, means for dosing fresh cleaning liquid onto the floor and a squeegee/vacuum pick-up system for recovering spent cleaning liquid from the floor. The brushing means normally comprises one or more rotatable brushes, a motor for driving the brushes and a means for lifting the brushes off the floor when large areas are traversed without any cleaning action being required. A number of conventional floor cleaning machines also include an option/for adjustment of the brush height with respect to the floor. In general adjustment of the brush height has to be done manually which severely limits the easy controllability during operation. In view of uniform cleaning, wear of the brushes and energy consumption, it is often more advantageous to control not so much the brush heigth, but the brush pressure. In US patent No. 4,218,798 a control system has been disclosed whereby the brush pressure is operator-adjustable. Brush-pressure control is achieved by means of a hydraulic/pneumatic actuator system whereby the pressure level is adjustable by way of a pressure regulator. It is an object of the present invention to provide an electric brush-pressure regulating system. It is a further object to provide such a system for automatic control of the brush pressure which is instantly operator-adjustable. Accordingly, in its broadest aspect the present invention provides a floor cleaning machine comprising a motor-driven movable body carrying a scrubber assembly which comprises a brush head housing one or more rotatable brushes, a motor for driving the brushes, a lever capable of lifting and lowering the brush head, a motor for moving the lever between a lifted and a lowered position in which the brushes engage the floor characterized in that the scrubber assembly comprises a sensing device sensitive to the brush pressure which sends an output signal dependent upon the brush pressure , control means capable of comparing the output signal of the brush pressure sensing device with an operator-set value of the brush pressure, said control means being further capable of electrically controlling the operation of the lever motor to maintain the brush pressure at the operator-set value. In a first preferred aspect of the invention the control means comprises an electronic device which controls the lever motor by way of pulse width modulation. Pulse width modulation is a well-known method of controlling the motor voltage allowing easy electronic adjustment thereof to an operator-set value. Preferably, the control means operates the lever motor on the basis of the feed-back output signal of the sensing device, which is proportional to the instant brush pressure. In general the sensing device will not measure the brush pressure directly, but by way of a related physical quantity proportional to the brush pressure, such as the deformation of parts or portions of parts of the scrubber assembly which are under a stress proportional to the brush pressure, or the instant power consumption of the lever motor. A preferred brush pressure sensing device consists of an ammeter which measures the amperage of the lever motor. Being proportional to the torque of the lever motor, this amperage is proportional to the brush pressure, accordingly providing a suitable feed back to the control means. In a further preferred aspect of the invention the brush pressure sensing device comprises a deformation-sensitive component suitably attached to the surface of or incorporated in a stress-deformable portion of the lever or spring. The deformation-sensitive component may be any electrical or electronic device suitable for the purpose. Preferably it consists of a Hall element. A Hall element is a device which is based on the Hall effect whereby a transverse electromotive force is produced in a current-carrying conductor or semi-conductor subjected to a magnetic field. Instead of a Hall element a deformation-dependent resistance (strain gauge) may also advantageously be used. In a further aspect of the invention the lever is tensioned by an extension spring counter-acting the lever motor. Preferably the lever motor is a stepper motor. The brush pressure is proportional to the extension of the spring which in turn is linear to the number of steps of the stepper motor. Suitably also, a deformation-sensitive component may be incorporated in or connected to the extension spring for measuring the deformation thereof, which is proportional to the brush pressure. The invention will now be further illustrated with reference to the accompanying drawings in which: Figure 1 is a perspective view of an automatic cleaning machine according to the present invention; Figure 2 is a perspective enlarged view of a preferred embodiment of the scrubber assembly according to the present invention; and Figure 3 is a circuit diagram showing a preferred control circuit for the lever motor means. Referring now to Figure 1 an automatic floor cleaning machine is shown, comprising a housing or body (1), a steering and controlling means (2), a scrubber assembly (3) and a squeegee (4). The body (1) has been drawn cut-open for illustration of the interior. It comprises a cover (5) for housing tank, battery, pump and motor parts. A storage tank (6) comprises a first reservoir(7) for storing fresh cleaning liquid and a second reservoir (8) for storing spent cleaning liquid. Although the two reservoirs may have a fixed separation wall, it is preferred that they are separated by way of a flexible membrane. The cleaning machine is supported on main drive wheels (9) and one or more caster wheels (10). The driving motor means for wheels (9) is battery-operated enabling ready manoeuverability over a wide area. Although the use of a battery is preferred, if so desired the motors may also be energized from an external electrical source through a cord, thereby eliminating battery (11). A preferred embodiment of the scrubber assembly (3) is shown in more detailed form in figure 2. A brush head (12) houses two rotatable brushes (13) which are driven by motor means (14). The brush head (12) is carried by lever (15) comprising two arms (16) and (17) pivotably mounted on body (1) around pin pivot (18). To allow small variations in position of brush head (12) with respect to lever (15), elastic bearings (19) are mounted between the brush head and the lever arms. Between the two arms (16) and (17) a gear block (20) is pivotably mounted about pin pivot (18). Gear block (20) and lever (15) are spring-tensioned relative to each other by means of an extension spring (21) mounted between and to pegs (22) and (23). A peg stop (24) on gear block (20) is co-operable with arm (16) for preventing unrestricted backward movement of gear block (20) relative to lever (15). Pinion (25) is co-operable with gear block (20) for transmitting the drive-force of motor means (26) to the tension-force of spring (21). Motor means (26) is electrically connected to an electronic control unit (ECU) (27). Clockwise or anti-clockwise rotation of pinion (25) results in a forward or backward pivoting movement of gear block (20) and, as a result, in an increased or decreased tension in extension spring (21). Proportional to the spring tension is the pressure exerted by lever (15) onto brush head (12) and accordingly, by the brushes onto the floor. By moving the gear block to its fully backward position the brush head is lifted off the floor due to cooperation of the peg stop (24) and lever arm (16). Accordingly control of the operation of lever motor means (26) gives full control of the brush pressure, and lifting or lowering of the brush head (12). A brush pressure sensing device (28) is attached to the lower portion of the lever arm (16). The sensoring device is of the type which is deformation-sensitive, such as a Hall element or a deformation-dependent resistance. With increasing brush pressure the lower portion of the lever arm (16) is proportionally deformed resulting in a proportional fed-back output signal of device (28) to the ECU (27), which on the basis thereof controls the operation, direction and power output of the lever motor means. In an alternative embodiment of the invention the deformation of the extension spring (21) is measured to which purpose similar deformation-sensitive components may be used. In figure 3 a preferred control circuit for motor means (26) is illustrated. The ECU (27) controls the switches (29) and (30) which open and close the energizing circuit of the lever motor means and may establish inversal of the motor current. When no action is required the switches are in the closed position, motor means (26) being short-circuited and remaining in the instant position corresponding to the brush pressure as set by the operator. When the output signal of the brush pressure sensoring device (28) no longer corresponds to the, operator-set value, the ECU opens the appropriate switch (29) or (30) until the operator-set value is reached. In an alternative embodiment of the invention the sensoring device comprises an ammeter which measures the amperage of the lever motor means (26). On a time-interval basis one of the switches (29) or (30) corresponding to lowering of lever (15), is opened and the amperage is measured which is necessary to maintain lever (15) in position. When the amperage does not correspond to the operator-set value, the ECU opens the appropriate switch (29) or (30) until the operator-set amperage is reached.

Claims: A floor cleaning machine comprising a motor-driven movable body (1) carrying a scrubber assembly (3) which comprises a brush head (12) housing one or more rotatable brushes (13), a motor (14) for driving the brushes (13), a lever (15) capable of lifting and lowering the brush head (12), and a motor (26) for moving the lever (15) between a lifted and a lowered position in which the brushes engage the floor, characterized in that the scrubber assembly (3) comprises a sensing device (28) sensitive to the brush pressure which sends an output signal dependent upon the brush pressure , control means (27) capable of comparing the output signal of the brush pressure sensing device (28) with an operator-set value of the brush pressure, said control means (27) being further capable of electrically controlling the operation of the lever motor (26) to maintain the brush pressure at the operator-set value. A floor cleaning machine according to claim 1 which comprises an extension spring (21) counter-acting the lever motor (26). A floor cleaning machine according to claim 2 in which the lever motor (26) is a stepper motor. A floor cleaning machine according to any one of the preceding claims wherein the control means (27) comprises an electronic device which controls the lever motor by way of pulse width modulation. A floor cleaning machine according to claim 1 wherein the brush pressure sensing device (28) consists of an ammeter capable of measuring the amperage of the lever motor. A floor cleaning machine according to claim 1 wherein the brush pressure sensing device (28) comprises a deformation-sensitive component suitably attached to the surface of or incorporated in a stress-deformable portion (19) of the lever (15) or spring (21). A floor cleaning machine according to claim 6 wherein the deformation-sensitive component comprises a Hall element. A floor cleaning machine according to claim 6 wherein the deformation-sensitive component comprises a strain gage.

Inventors: MEILI, HERMANN
Applicants: UNILEVER NV, UNILEVER PLC
Application year: 1985
Main classification: A47L11
IPC codes: A47L11, E01H1, E01H3