Abstract: A multi-dimensional adjustable forklift driving system includes a cab in which a steering wheel control system, a base plate control system and a pedal system are provided; where the steering wheel control system includes a steering wheel diverter and a first telescopic adjustment device, which is connected to the steering wheel diverter to drive the steering wheel diverter to move; the base plate control system includes a base plate assembly and a second telescopic adjustment device connected to the base plate assembly to drive the base plate assembly to move up and down; the pedal system includes a pedal body and a third telescopic adjustment device connected to the pedal body to drive the pedal body to move. The multi-dimensional adjustable forklift driving system is capable of creating a relatively large space, thereby facilitating the driver getting on or off the vehicle.

Abstract: A method for compensating parameter imbalance induced current harmonics in a synchronous motor drive includes receiving a command current signal corresponding to a generated command current. The method also includes receiving a position estimate signal indicating an estimated position of the synchronous motor drive and, in response to at least one current harmonic being induced by a parameter imbalance, determining a voltage adjustment value using the command current signal and the position estimate signal. The method also includes generating a voltage adjustment signal using, at least, the voltage adjustment value, the voltage adjustment signal being applied to the synchronous motor drive to compensate for the current harmonics induced by the parameter imbalance.

Abstract: A method and system of reducing/eliminating ripple in an electric motor. An electric parameter, such as current is sensed in an input electric signal. Ripple is detected in the signal using one or more current sensors and a discrete Fourier transform calculation. Ripple is reduced by adjusting the electric signal being sent from a drive control to an electric motor, using a closed-loop configuration. The electric motor might be a regenerative electric motor that is configured to sink or supply electricity to a power grid.

Abstract: System controller and method for protecting a power converter. The system controller includes a first controller terminal configured to output a drive signal to a switch to affect a first current flowing through a primary winding of a power converter. The power converter further includes a secondary winding coupled to the primary winding, and the drive signal is associated with one or more switching periods. Additionally, the system controller includes a second controller terminal configured to receive a sensing voltage from a sensing resistor. The sensing voltage represents a magnitude of the first current flowing through the primary winding of the power converter. The system controller is configured to process information associated with the sensing voltage and a reference voltage, and determine whether an average output current of the power converter is larger than a current threshold.

Abstract: A power conversion apparatus includes: an inverter unit having high and low potential-side switching elements corresponding to each phase of a winding of a rotating electrical machine; a current detecting unit; and a control unit controlling the switching elements based on a PWM reference signal and a duty instruction value. The control unit includes: a phase current computing device; and a voltage instruction value computing device. The control unit computes an active voltage vector interval in first and second half periods of one or multiple cycles of the PWM reference signal to be a predetermined period or longer, and computes first and second half duty instruction values to set first and second voltage vector intervals equal to or longer than minimum time to be in the first or second half period.

Abstract: A method of normalizing phase measurements for a motor using a normalizing phase measurements (NPM) algorithm that a processor implements to cause a motor controller coupled to stator terminals of the phases to execute forcing a set of input current or voltage vectors (set of input vectors) including repeating the forcing after rotating the rotor through a full mechanical cycle to generate resulting current or voltage samples (resulting samples) of non-normalized phase A and phase B waveforms. The magnitude of the input vectors are sufficiently small to not move the rotor. A maximum value (x_max) and a minimum value (x_min) are determined for each of the non-normalized phase A and phase B waveforms. An offset value and normalization scale factor (NSF) are determined from the max and min values. The offsets and NSFs are applied to the non-normalized phase waveforms to generate normalized phase A and phase B waveforms.

Abstract: The driver seat unit and the other-seat unit are connected by the single signal line. A direction of a current passed through a motor is switched using contacts of a window opening switch and a window closing switch in the other-seat unit. When a window closing manipulation is performed by the driver seat unit, the current is passed through a coil of a relay via the contacts of the window closing switch, and a contact of the relay is switched to pass a forward current through the motor. When a window opening manipulation is performed by the driver seat unit, the current is passed through a coil of a relay via the contacts of the window opening switch, and a contact of the relay is switched to pass a reverse current through the motor.

Abstract: A trash can with a power operated lid can include a sensor assembly and a lifting mechanism. The sensor assembly can include at least one light emitter and at least one light receiver, the viewing area of the at least one light receiver being limited in size. The lifting mechanism can include a controller, a drive motor, and a lifting member. The trash can with power operated lid can further include at least one position sensor for detecting the position of the lid.

Abstract: The present invention relates to a door drive comprising electrically operated components which are supplied with electrical energy via a mains connection. In accordance with the invention, a control and an electrical energy store are provided, with the control separating the door drive from the mains and the electrical energy store providing the electrical energy in a first operating mode and with the control connecting the door drive to the mains in a second operating mode.

Abstract: A turning drive control apparatus that controls a drive of a turning mechanism of a construction machine driven to turn by an electric motor, includes: a drive command creation part that creates a drive command to drive the electric motor based on an amount of operation input through an operation part of the construction machine; a turning motion detection part that detects a turning motion of the turning mechanism; and a drive command correction part that corrects the drive command, when a turning motion in a direction opposite to a turning operation direction input to the operation part is detected by the turning motion detection part, to suppress the turning motion in the direction opposite to the turning operation direction in response to a degree of the turning motion in the direction opposite to the turning operation direction.

Abstract: Method for protection of a switching device controlled by a control unit, through which an electric drive can be disengaged during the period of an overvoltage surge caused by a load dump in the electrical system of a vehicle, in which the drive current rises to a maximum value in a first slot within the duration of the overvoltage surge and drops in the second slot connected to the first time slot, with the following process steps: recognition of a load dump by recording a limit voltage value in the electrical system by the control unit, disengagement of the electric drive in the event of a load dump at a switching time stipulated by the control unit, which lies after the first time slot.

Abstract: In a closure panel control apparatus, an ECU controls a rotational speed of an electric motor, which provides a drive force to drive a closure panel in an opening movement and a closing movement thereof. The ECU obtains a vehicle speed measured with a vehicle speed sensor and receives a command signal from a switch, which is operable by an occupant of a vehicle to command the opening movement or the closing movement of the closure panel. The ECU controls the rotational speed of the electric motor based on the measured vehicle speed that is obtained at the time of receiving the command signal from the switch.

Abstract: A turning drive control apparatus that controls a drive of a turning mechanism of a construction machine driven to turn by an electric motor, includes: a drive command creation part that creates a drive command to drive the electric motor based on an amount of operation input through an operation part of the construction machine; a turning motion detection part that detects a turning motion of the turning mechanism; and a drive command correction part that corrects the drive command, when a turning motion in a direction opposite to a turning operation direction input to the operation part is detected by the turning motion detection part, to suppress the turning motion in the direction opposite to the turning operation direction in response to a degree of the turning motion in the direction opposite to the turning operation direction.

Abstract: A trash can can include a sensor for detecting the presence of an object near a lower portion of the trash can. The detection of the object can be used to signal the trash can to open its lid. The trash can can include an electric drive unit for opening and closing the lid.

Abstract: A motor receives power through two or more relays connected to a power source. A switch-operated logic circuit is powered by a relay power source and connects to the relays. To start the motor, the switch is pressed, causing the logic circuit to close the relays sequentially. When all the relays are closed, the motor will start. If the motor starts before the logic circuit closes all of the relays, the motor is stopped and an indication is provided that the relays that have not yet been closed have failed. Otherwise, the motor runs until the switch is pressed again, causing the logic circuit to open the relays and stop the motor. The sequence in which the relays are closed is then changed. Each relay is alternately made the last in the closing sequence, therefore testing each relay in turn for failure.

Abstract: A hand-held power tool has an electric drive motor having a drive shaft and a tool connected to the drive shaft and rotatably driven by the drive shaft. The drive motor has a control device that has correlated therewith at least a first operating curve and a second operating curve. The control device operates the electric drive motor in idle according to the first operating curve and operates the electric drive motor under load according to the second operating curve. The first operating curve covers the low power range at low speed and the second operating curve covers a large power range at high speed.

Abstract: The present invention concerns a method for the position-dependent control of a mobile element in a motor vehicle, wherein the element is movable in a drive movement by an electrically powered positioning device, wherein the positioning device has several different operational modes, and characteristics of a drive signal of the positing device, in particular a waviness of a drive current, are used for the determination of the position of the element. According to the invention, a characteristic variable, which influences the drive movement of the positioning device, and/or a specific value, which characterizes the positioning device, are evaluated for the determination of an error value of the determined position of the mobile element, and that the operating modes of the positioning device are controlled in dependence of the determined error value.

Abstract: A transactional printer having a wheel interconnected to a knife cutting assembly for frictionally engaging a severed slip and ejecting it into a receiving bin. The wheel is moved out of engagement with an ejected slip during the cutting operation of the knife. As the knife blade is restored to its pre-cut position, the wheel is moved into engagement with the slip and rotated to eject the slip into the bin. A depression in the printer housing prevents contact between the housing and the wheel when the wheel is in frictional engagement with a slip. A stop interconnected to the wheel prevents contact between the wheel and the depression.

Abstract: PWM methods and apparatus are provided for loss minimized control of AC motors taking into consideration inverter non-linear limitations. The method comprises providing a voltage to the AC motor based on a switching cycle, adding a duty cycle of a zero vector to each phase leg of the switching cycle when a duty cycle of a first phase leg of the switching cycle is less than a minimum duty cycle, and subtracting the duty cycle of the zero vector from each phase leg of the switching cycle when a second duty cycle of a second phase leg is greater than a maximum duty cycle. The minimum duty cycle and maximum duty cycle indicate distortion regions.

Abstract: The power window system moves a window glass in opening and closing directions in response to operation of an opening and closing instruction switch. The power window system includes a measurement device for obtaining an open degree of the window glass and a control device for controlling movement of the window glass in response to operation of the switch. The control device moves the window glass in the closing direction when an open degree obtained by the measurement device is not less than a predetermined degree and in the opening direction when the open degree is less than the predetermined degree.

Abstract: Improvements in human interaction with barrier movement operators are disclosed. A controller of the barrier movement operator is capable of a number of learning modes in which the controller cooperates with a user to learn operating parameters. The controller guides and corrects the necessary actions by the user. The barrier movement operator also includes an input/output unit remote from the main controller of the operator. Human interaction with the remote input/output unit enables diagnosis of operator faults remotely.

Abstract: A method of controlling a motor (106) used to drive a screwdriver bit (105) such that screws (107) are seated to the optimum point of grip between the screw (107) and the work piece material. An electronic control circuit controls the speed and output torque of the motor (106). The control system utilizes pulse width modulation (PWM) to control motor (106) speed and torque. The PWM signal controls the duty cycle of the transistors that supply current to the motor (106). The amount of current flowing through the motor (106) coils is proportional to the amount of torque the motor (106) is producing. Motor (106) current is measured as voltage produced across a precision resistor that is in series with the motor (106) coils. As the current in the motor (106) increases, the voltage across the resistor increases (V=IR).

Abstract: A garbage container includes a base section for collecting garbage and a lid section attachable to the base section. The lid section includes an access door pivotally operable therewith. The garbage container further includes a sensor connected to the top surface of the lid section and for determining when an object has reached a predetermined distance therefrom. The garbage container further includes a housing and a motor disposed therein and connected to the sensor. A plurality of arm members each have a first end portion passing through a corresponding one of a plurality of slots and are operable by the motor. The plurality of arm members each further has a second opposed end portion connected to the access door respectively. The plurality of arm members are preferably selectively pivotable about the first end portions and in a generally arcuate path to thereby move the access door between open and closed positions based upon signals transmitted by the sensor.

Abstract: A vehicle power window and power door lock system includes a vehicle pillar adapted for use between openable and closable vehicle doors and a single lock actuation assembly in the pillar adapted for engagement with a front door lock latch assembly on a front door and a rear door lock latch assembly on a rear door for locking and unlocking the doors. The vehicle power window and power door lock system further includes a single reversible electric motor in the pillar adapted for selective engagement with a front window on an adjacent front door and a rear window on an adjacent rear door for driving the windows up and down. A vehicle side door assembly includes a door lock latch assembly, a latch rod operatively connected to the latch assembly, a window, and a driven gear operatively connected to the window. The latch rod is operably connectable to a lock actuation assembly located in a body pillar adjacent to the door when the door is positioned against the body pillar.

Abstract: A three phase motor starting system is provided to reduce the in-rush current to the motor in order to obtain a soft start of the motor. The soft start of the motor equates to reduced impact forces on motor parts and device components connected to the motor during startup of the motor, especially a startup resulting from a reversal of the direction of rotation of the motor. The system uses an impedance load in series with the motor windings of the motor to reduce the in-rush current to the motor windings, which results in a reduced acceleration of the motor shaft and a soft start to the motor. The impedance loads used by the system can be a resistive load, a capacitive load or an inductive load, depending on the type of impedance load that is desired for the soft start of the motor.

Abstract: A method of operation for a motor-driven worm gear actuator coupled to a load device energizes the motor in a series of pulses during an initial period of motor operation when reversal of the motor is commanded. The pulsed energization produces a slow initial axial movement of the motor armature without moving the load device, minimizing the contact force between the armature shaft and a mechanical end stop of the motor. Rotation of the motor is determined by identifying and counting motor current pulses due to commutation, and the pulse count is adjusted at each reversal of motor rotation to compensate for motor current pulses due to the pulsed energization.

Abstract: In a power window device an MCU detects motor torque values one by one when a window is opened and closed, compares the detected motor torque values with base values set to the travel regions and stops or reverses a motor determining that an object is pinched in the window when the former values exceed the latter values.

Abstract: A compact drive mechanism for both driving a paper web and severing a printed receipt in a transaction or point-of-sales printer. Both driving the paper web and cutting the printed receipt is accomplished through a bi-directional stepper motor that is operative through a one-way clutch.

Abstract: A method of minimizing the torque ripple produced by unbalanced phase currents in a sinusoidally excited motor is disclosed. The method comprises measuring the position of the motor; sampling the phase currents of the motor generating thereby at least one phase current; synchronizing the at least one phase current of the motor with the position of the motor; determining the imbalance in the magnitudes of the at least one phase current of the motor; generating a set of modulation index terms for reducing the imbalance in the magnitudes of the at least one phase current to ensure acceptable torque ripple characteristics over the operating velocity of the motor; and generating a set of minimized line-to-ground voltage commands.

Abstract: A motor control apparatus for a reversible motor of a railway switch machine includes a conditional power source having an output voltage. A motor control circuit includes inputs for inputting the voltage from the power source, inputs for inputting a normal signal and a reverse signal, two output terminals for electrical connection to two input terminals of the reversible motor, and a relay logic circuit including a pair of double pole, double throw relays. The contacts of these relays: (a) output the voltage to the two output terminals in response to the normal signal, (b) output an inverted polarity of the voltage to the two output terminals in response to the reverse signal, and (c) short the two output terminals in response to absence of both of the normal and reverse signals.

Abstract: The present invention relates to an electronic circuit that interrupts the application of electrical power to a motor after a predetermined period of time. The electronic circuit is disposed between a motor which drives a device from an initial position to a final position and a switch movable from a first position to a second position. A battery which supplies the electrical power for the motor is engaged with the switch. The control circuit includes at least two energy storage devices. Depending on the position of the switch, one of the energy storage devices will be fully charged by the battery source. Altering the position of the switch will cause the fully charged energy storage device to begin its discharge and the alternate energy storage device will be “instantly” charged. During the time that both energy storage devices have a significant charge on them, a control signal is generated.

Abstract: A method and system for directly determining the presence of an object between a window and its respective frame during closing of the window is disclosed. A sensor is provided within the frame to determine a length of the frame being compressed when the window is closed against the frame. This length is compared to a predetermined value. If the compressed length is less than the predetermined value, an object is detected so that the window can be controlled to stop and change direction so as to release the object before injury or damage occurs.

Abstract: A full-bridge driver, and especially an entirely integrated bridge driver, for driving DC motors in either direction is capable of automatically braking the motor when the motor direction is to be reversed. The bridge circuit is of "H" configuration and has four transistor switches connected in bridge configuration and has two bridge output terminals to which a motor may be connected. A differential window comparator has the input connected to the two bridge output terminals, producing a high level binary signal only when the voltage across the two output terminals is within a small voltage range centered at about zero volts. A pulse-width filter circuit having an input connected to the window comparator produces a high binary output signal only when the comparator-produced binary signal remains high for greater than a predetermined time.

Abstract: The present invention provides controls for driving roller blinds, rolling shutters and doors. The controls include a two directional motor, a control panel, switches, power supply, and a logic processing unit which are all interconnected to allow the user to partially or fully raise and lower the blinds. The direction of the blinds can be changed at any time and also stopped at any time.

Abstract: An elevator door control apparatus includes at least one door safety device for detecting whether elevator doors are safe; an elevator control circuit for outputting a door-open/close command; and a door control circuit for controlling the opening/closing of doors on the basis of a door-open/close command issued from the elevator control circuit and for outputting a door reversal request to the elevator control circuit on the basis of the operation signal of the door safety device, wherein the door control circuit outputs a door reversal request to the elevator control circuit upon reception of the operation signal of the door safety device while the doors are being closed on the basis of a door-close command from the elevator control circuit, switches the door speed command pattern to a brake pattern from the door-close command speed pattern and thereafter switches the door speed command pattern from the brake pattern to the door-open command speed pattern when the door-open command is received from the elev

Abstract: The improvement of a remotely controlled ceiling fan is achieved mainly by means of a function control IC communicating with TRIAC Q.sub.8, TRIAC Q.sub.9 and TRIAC Q.sub.10 of the speed-changing device via lines Q.sub.5, Q.sub.6 and Q.sub.7 connecting respectively with points 11, 12 and 13 of the function control IC, so as to transmit a command from the function control to the speed-changing device which in turn controls the speed of motor. The function control IC is additionally provided at point 16 thereof with a delay device, which in turn is connected to a relay via line Q.sub.11. The primary line coil of the motor communicates with the relay intended to initiate a change in the polarity of the primary line coil of motor at the time when the function control IC receives a command to put the operation of motor in reverse and the speed-changing device is halted temporarily.

Abstract: A synchronous motor is divulged whose direction of rotation may be chosen, comprising a rotor with permanent magnet and a stator with homopolar field, including a winding fed with an AC voltage. In response to a stopping order, a circuit controls the switch for opening the connection of the winding when the voltage is decreasing in absolute value or is cancelled out and stores the sign of its slope at the time of opening. The circuit controls the switch for closing the connection when the voltage is cancelled out or is increasing in absolute value, with a sign slope identical to, respectively opposite, the stored sign, in accordance with an order for setting in rotation in a direction identical to, respectively opposite, the preceding direction of rotation.

Abstract: A control for an automatic washing machine with a reversing permanent split capacitor (PSC) drive motor. Separate ferrite core sensors surround each of two PSC motor windings. A sense winding is threaded through both sensors. A brief output voltage is generated whenever the alternating current in either PSC motor winding passes through a zero-crossing and when the sense winding is wound with proper mutual polarity, an output voltage is generated in response to zero-crossings of a brief, residual alternating current which flows in both PSC motor windings and the capacitor when the rotating PSC motor is cycled OFF.

Abstract: An electromechanical A.C. motor reverser having a timed cam-driven SPDT switch with the side terminals thereof connected to separate motor stator coils. The movement of the transfer blade between contacts to break one motor coil circuit and complete the other reversing motor coil circuit is delayed sufficiently by the cam to permit the motor rotor speed to decay enought to enable reversal of rotation upon completion of the reversing coil circuit. The minimum contact transfer time is set at the period corresponding to two cycles of power line current.

Abstract: Motor control systems are commonly associated with motors found on electric industrial vehicles, such as lift trucks. Advantageously, the control of such motors should be optimized such that current is timely supplied to the motors in conjunction with selection of the appropriate motor direction. The instant apparatus 10 includes a logic device 24 for receiving speed and direction demand signals from respective speed and direction selection devices 20,22. The logic device 24 responsively produces respective motor speed and direction command signals. A motor control device 26 receives the command signals and directs the electrical current from a power source 18 through the motor 12. A transducer device 38 senses the actual direction of electrical current flow through the motor 12 and produces responsive feedback signals. The logic device 24 produces at least one motor direction interrogation pulse in response to receiving the speed and direction demand signals and prior to delivering the motor command signals.

Abstract: The invention is directed to an apparatus for resetting the vibration amplitude of a hydraulically driven vibration device having two eccentric weights arranged on a rotating shaft and rotatable relative to each other. The amplitude-resetting arrangement includes a hydraulic directional valve for resetting the vibration device between high and low amplitudes. The valve is electrically operated and the electric control circuit incorporates a time-delay relay for delaying the amplitude change until the speed of the rotating shaft has been reduced to an acceptable level.

Abstract: An anti-plug reversing circuit for use with a variable speed D.C. motor which provides safe and fast motor reversing with dynamic braking. The circuit, by sensing counter-EMF, prevents the premature application of a voltage of opposite (reversing) polarity until the motor armature has come to a full stop. The circuit advantageously utilizes a three-wire control input, is low cost, easily manufactured and applicable for use with low cost D.C. motors.

Abstract: A commutator-type d-c motor has its line current connected through a sensing resistor (18) or transformer (18'), the pulses of which, upon energization, are counted in a counter (C) and also passed to a speed sensing circuit (S) in a control circuit (30), energization of the motor being disconnected if the frequency of undulations or waviness of the motor current drops, thus indicating that the positioned element, for example an antenna, window, or sliding roof of an automobile has reached a limiting position. The counter can be used to establish intermediate positions, upon suitable control by a selector switch (27) or a reference count number stage (C-Ref) controlled, for example, by a potentiometer (P) or from the selector switch (27). A timing circuit (T) prevents short-circuit through the motor upon manual sudden reversal of command of direction of rotation.

Abstract: An apparatus and method for position control by a DC servomotor having improved stiffness. An electric current (i.sub.R) of the servomotor is interpreted anew and defined as follows: ##EQU1## where .theta. is an observed rotation angle of the load (L), .theta..sub.c is a precommanded value, K.sub.F is a feedback coefficient, and K.sub.V is a velocity coefficient. After normalizing the above equation, stiffness (S) can be increased by incorporating a limiter into the control system, thus providing prompt response and smooth covergence of .theta. to .theta..sub.c with a high degree of stiffness maintained at the precommanded angle (.theta..sub.c).

Abstract: A plugging defeat system for use with a reversible electric motor having a motor shaft. A slipping clutch-type mechanism is used to sense the speed and direction of the motor and to selectively open forward or reverse enabling switches when the motor reaches a predetermined speed. If operating in the forward direction, the clutch mechanism will open the reverse enabling switch, once the predetermined speed is reached, preventing motor reversal until the speed has fallen to a safe level, and vice versa.

Abstract: A d.c. motor control system, intended primarily for use in battery powered vehicles, includes a control switch (RL2a, RL2b) for varying the connections of the motor field winding (24) to determine the mode of operation of the motor and speed interlock means for preventing said control switch being operated to change the motor mode while the motor is actually running. Instead of using a mechanical speed transducer the speed interlock means includes means for supplying current to the motor field winding (24) when current would not otherwise be flowing therethrough and means (BR1, T.sub.1, P.sub.16 etc.) connected to detect the voltage across the armature which occurs in these circumstances if the motor is in motion.

Abstract: A power screwdriver that is equipped with a spring coupling between the motor drive and the tool spindle, a signal that indicates that a certain value of torque has been overstepped, at which the screwdriver must be sopped, first causes reversal of the motor, but before the motor appreciably turns in the reverse direction, powers shut-off, allowing the motor to coast. After another brief interval, power is reapplied to the motor in the original direction, again briefly. In this way it is possible for the final shut-off to occur when the motor is stopped and the spring is unstressed, avoiding oscillations of the motor-spring system. A triac bridge circuit makes possible quick reversals and brief applications of power. In such a bridge circuit, precautions must be taken to be sure one pair of triacs is extinguished before the other pair is ignited.

Abstract: An electric starting system for cranking an internal combustion engine by an electric cranking motor. The system prevents energization of the cranking motor following initial energization and subsequent deenergization by sensing the voltage generated by the cranking motor when it is deenergized and preventing reenergization of the cranking motor until this voltage drops to some value indicative of a low cranking motor speed.

Abstract: A method and apparatus for controlling the rotational speed of an electronically controlled power tool in both the forward and reverse direction. When the reversing switch is placed in the reverse direction, the electronic speed control circuit automatically limits the speed of the motor to a predetermined maximum value. The speed control circuit also is adapted to sense a change in the state of the reversing switch and remove power to the motor until it coasts down to a relatively slow speed or to zero before reapplying power in the opposite direction. The speed control circuit monitors the rotational speed of the motor by means of a tachogenerator comprising a ring magnet mounted on the rearward end of the rotor shaft of the motor outboard of the commutator-end bearings and a Hall effect device mounted to the peripheral flange of a carrier which encircles the ring magnet so that the ring magnet and Hall effect device are separated by a small radially extending gap.

Abstract: An improvement for electrically driven floor maintenance apparatus including means for varying the speed of the driving motors is disclosed. Two speed ranges are provided by switching means which change the interconnection of the drive motors from series for the low speed range, and parallel for the high speed range. Within each speed range, intermediate speeds are provided by placing resistors with shunt in series with the motors. Time delay circuitry is also included to prevent immediate operation of the vehicle in the high speed of each range until the vehicle has had some time to accelerate. Additionally, means are provided for detecting whether a vehicle is rolling in a forward or reverse direction and circuits are provided to prevent the operator from driving the vehicle in an opposite direction until the vehicle has slowed down to a near stop. A deadman control is provided to prevent the energizing of the drive motors when the operator is no longer seated on the driver's seat.