Abstract: A method of returning a movable machine element having a flat dog to a zero point includes advancing the movable machine element in the direction of the flat dog, stopping the movable machine element after a changeover signal (S.sub.D) produced by the flat dog is detected, reversing the direction of the movable machine element, moving the movable machine element a first predetermined distance (L) and stopping it after the changeover signal (S.sub.D) is received again, then moving the movable machine element in the opposite direction a second predetermined distance (l) shorter than the first predetermined distance (L) and stopping the movable machine element, thereafter moving the movable machine element at a low velocity and stopping it at an initial one-revolution signal of a servomotor, which operates the movable machine element, after the changeover signal produced by the flat dog is detected.

Abstract: A monitoring circuit for a door operating D.C. electric motor, the circuit comprises a first means for detecting a back EMF of the motor and producing a load signal indicative of the magnitude of the back EMF, a second means for detecting the time rate of change of the load signal and issuing an obstruction signal if the magnitude of the time rate of change of the load signal exceeds a predetermined value.

Abstract: As a driving power source for an automatic door, a brushless D.C. motor is employed, and the position and the speed of a door member are determined by making use of detection pulses issued from magnetic pole position detectors which are associated with the brushless D.C. motor without providing any additional detector means separately. On the basis of the current position and the current speed of the door as determined from the detection pulses and of a programmed sequence of opening and closing operations for the door as stored in a control system, the opening and closing movements of the door member are controlled.

Abstract: An antenna motor drive system for raising and lowering an antenna. Response to a user input for raising or lowering a vehicle antenna is delayed to avoid rapid reversals of the antenna drive motor. This avoids the large surge currents associated with the prior art. The circuit monitors drive circuit response and de-energizes the motor if an inappropriate response is sensed after a certain period. Use of switching transistors rather than a relay facilitates implementation of the invention in integrated circuit form.

Abstract: A control for an electrically powered, motor vehicle windshield wiper system with independent drive motors for the wiper blades which produces an opposing wiper pattern with overlapping park and which is simple and inexpensive to manufacture by providing a unique switching system which coordinates the blades to prevent interference therebetween and converts simply and effectively, when the system is turned off, to a blade parking control which allows continuation of normal blade movement into a predetermined park position. The control provides switch control for the motor of each wiper blade in response to certain predetermined positions of the other blade, including, in particular, a position adjacent but outside the wipe pattern of the other blade wherein the controlled blade may be stopped if necessary to avoid interference.

Abstract: A drive mechanism comprises a support upon which a drive member is mounted for movement relative to a frame. The drive member comprises first and second elements which are relatively movable, the one of which may be mounted on the other. The elements are interconnected by a resilient member which transmits the drive therethrough, a drive input being coupled to a one element, a drive output to the other element. A detector generates a signal output responsive to relative movement of the elements which may serve to control a drive transmitted through the mechanism. In a preferred embodiment, the support is a rotatable screwed shaft and the first element a traveller thereon upon which the second element is slidably mounted, the elements being interconnected by helical springs.

Abstract: A vehicle to loading dock releasable locking unit includes a hook for engaging a coupling on the vehicle, a motorized drive system for rotating the hook back and forth between locked and unlocked positions, and a hook position sensor for sensing whether the hook is in the locked, the unlocked or an unsafe position between the locked and unlocked positions. The automatic control system includes a hook position selector for generating lock or unlock signals in response to a hook position command selected by an operator and for storing the selected hook position command. A first actuator control unit energizes the hook actuator to reposition the hook into the locked position in response to the lock signal. A second actuator control unit energizes the hook actuator to reposition the hook into the unlocked position in response to the unlock signal.

Abstract: Load position limits and incremental lowering of a load are controlled by a microprocessor forming an interface between an operator's control station and the hoist. Other hoist status conditions such as underspeed and overspeed of the hoist motor are detected by the microprocessor based upon hoist speed during the position limit setting cycle. Still other hoist status data such a motor overheating, number of power-up cycles, number of under and overspeed shut-downs, number of power failures, etc. are input to the microprocessor and all such data as up-dated are entered into a non-volatile memory which, when extracted, permits maintenance scheduling.

Abstract: For a sliding roof device (100) having a panel transfer mechanism (11, 12, 13b, 31, 33, 34, 7, 21) for moving a roof panel (2), which is adapted to open and close a roof opening (3a) of a roof (1), between a close position and an open position, a tilt-up mechanism (11, 12, 13a, 32, 33, 34, 7, 21) for moving the roof panel between the close position and a tilt-up position, and a reversible electric motor (51) for actuating the panel transfer mechanism and the tilt-up mechanism, there is provided a control circuit (50) including a first operation switch (58) for actuating the motor to thereby have the roof panel moved from the close position to the open position and the tilt-up position, and a second operation switch (57) for actuating the motor to thereby have the roof panel moved from the open position and the tilt-up position to the close position.

Abstract: A voltage supply for a servomotor (9) is effected via a wiper (10) which slides on two conductive paths (5, 6) which are displaceable in longitudinal direction. The conductive paths (5, 6) have, at their opposite ends, a driver (15, 17) against which the wiper (10) can come in its end positions upon further displacement, in order to be able to carry the corresponding conductive path (5, 6) along with it. Directly before the driver (15, 17) is reached, no voltage is tapped off from the corresponding conductive path (5, 6), so that the servomotor (9) then stops.

Abstract: A system for controlling the reciprocation of a scanning apparatus which includes a scanning device for scanning an original from a home position across the original to a scanned position and returning it from the scanned position back to the home position, a D.C. motor for driving the scanning device, and a switching circuit for providing electric power to the D.C. motor. The system further includes a home switch for detecting when the scanning device is in the home position, a counter for counting a distance of movement of the scanning device, and a speed detector for detecting the speed of the scanning device. A control device is coupled to the switching circuit for controlling the movement of the scanning device such that during the return of the scanning apparatus, a braking action is initiated when the scanning device returns to a preselected position, and the braking lasts until the returning speed is reduced to a predetermined low speed as detected by the speed detecting device.

Abstract: A control unit for operating the motor of a motor driven headlamp carrier mechanism includes oscillator circuitry for generating a series of pulses for energizing the motor, voltage responsive means for sensing a motor counter-EMF related voltage as an indication of motor rotation, output circuitry for interrupting motor energization when the voltage responsive circuitry senses motor stall, and start circuitry for energizing the motor independent of the oscillator circuitry for a period of time sufficient to produce motor counter-EMF. Such control permits sensing of the engagement of the headlamp carrier with fixed mechanical stops without the use of position or torque limit switches.

Abstract: Apparatus for electrically controlling actuation and deactuation of a hydraulic fluid directional control valve between centered, forwardly-moved and reversely-moved positions thereof includes a reversible electric motor whose drive train is connected to the valve control member for forward and reverse rotation thereof and an arrangement of two forward and two reverse electric circuits between an electrical source and the motor, two manual switches each in associated forward and reverse circuits, four limit switches positioned each in one circuit, and cams mounted on the motor drive train to open and close the limit switches in relation to the rotational disposition of the drive train to provide for manual actuation by the manual switches of selected forward and reverse rotation of the motor drive train and valve control member, for automatic deactuation of the electric motor by the limit switches at each of the two predetermined rotated dispositions of the valve member, for selective holding of the valve mem

Abstract: A system for control of movement of a cross sled which follows movement in an X-Y coordinate system according to a stored program, and for extending or shortening the path of movement either in the X-direction or Y-direction, or both directions.

Abstract: In an apparatus for controlling operation of an automatic door with minimum error in a detected door position, a motion sensor is positioned relative to a movable driving member coupled to the door. Pulses having a pulse repetition rate are created in direct proportion to a velocity of movement of the driving member. The pulses are counted and current position of the door determined. Any error arising from a loss or slip in an intermediate transmission mechanism which couples a motor with the final driving member is substantially eliminated. A pair of motion sensing elements as opto-electronic couplers may be provided for sensing a phase relationship between the sensing elements defining a direction of door movement. A pulse interval monitor adapted to generate a signal indicative of a long lapse of time between adjacent pulses from the sensing element may be provided. A sequence control circuit responsive to this generated signal generates a stop command for the motor.

Abstract: Disclosed is an automatic door actuator which comprises arithmetic unit for calculating a weight of a door, a distance of movement of the door and braking points of the door through learn control of door actuation which is effected once every time a power supply switch is turned on and irrespective of the on-off condition of a normal door actuation start switch; first memory for storing results of calculation by the arithmetic unit; second memory for previously storing various phase angles for starting operation, for deceleration braking operation and for predetermined low velocity control, corresponding to various weights of the door; whereby the control unit is responsive to the first memory to read out from the second memory the phase angles for starting operation, for deceleration braking operation and for predetermined low velocity control corresponding to the actual weight of the door determined in the learn control to thereby supply a trigger signal to semiconductor controlled rectifying elements in ac

Abstract: A method and apparatus for operating and monitoring the opening and closing cycle of electrically operated units such as electric windows and electric slide roofs which both eliminates the danger of body parts getting caught in the window and permits a complete opening and closing of the window automatically. In accordance with the invention, the speed of the drive motor is measured, directly or indirectly, and the first obtained measured value is compared with all following measured values. More particularly, this first measured value is used to detect momentary electrical and mechanical factors which change over the entire time of operation of the window, such as self-heating of the drive motor, the voltage charge of the battery, and the state and condition of the window. The processing or comparing of the measured values is carried out by a microcomputer. The actual measuring of the speed is by means of a sensor. The changes furnished by those sensors are utilized to determine the position of the window.

Abstract: A circuit arrangement for a reversible electric motor supplied from a voltage source, which motor drives a combined window-lifter and door-locking installation in motor vehicles. The motor is switched on by way of a first operating switch developed as a reversing switch and by way of a second operating switch serving as a central switch. A position switch is assigned to the motor and is developed as a two-way switch which is operated by the motor. When the window is completely closed, the position switch may be changed over from a first switching position into a second switching position and after an unlocking operation, or before the window is opened, the position switch may again be changed over from the second switching position into the first one. During a locking operation the second input of the position switch is applied to a pole of the voltage source other than the pole used during the other adjusting operations.

Abstract: A wiper control device for a vehicle capable of accurately stopping wiper blades always at the lowermost position of a wiping range regardless of the rotating speed of a wiper motor. The wiper control device automatically stops the wiper motor at the lowermost position of the wiper blades with a control circuit which obtains a sliding angle corresponding to the rotating speed of the wiper motor from the rotating speed of the motor and controls to flow an electric current continuously in the motor during the time while the motor reaches a rotating position even after the motor is interrupted by selecting the cam contact position with respect to the annular electrode. Thus, this wiper control device can eliminate to disturb the visual field of a driver with the wiper blades.

Abstract: A drive arrangement for a motor vehicle top having an outwardly movable sliding cover driven by an electric motor through a transmission and at least one threaded cable engaging a pinion of the transmission, a manually-actuated switch and a limit switch with a contact arm being provided in a circuit of the electric motor, the contact arm cooperating with a cam of a trip gear to interrupt the current supply to the electric motor in a closed position of the sliding cover, is improved by a construction of the indexing gear transmission for changing the operation of the drive arrangement in a manner increasing the time available for actuation of the limit switch independently of the degree of mobility of the top and ambient temperature conditions when the top reaches a position near the fully closed position.

Abstract: A seat position automatic adjusting device used for an automotive vehicle motor-powered front seat comprises a single reversible motor for actuating the adjusting mechanism to adjust each seat member to a desired position. A control circuit counts and stores the number of rotations of the reversible motor and outputs a control signal by calculating the difference between the current seat position data from the stored value and the original seat position data. A drive circuit drives the reversible motor to automatically return the current seat position to the original seat position to the original seat position in response to the control signal from said control circuit.

Abstract: An improvement in oscillatory line transfer switches of the type having mechanical drive between a drive motor and the shafts of two such switches plus a manual mechanical switch to supplement the drive motor and having a third shaft mechanically connected into the same drive which controls a neutral position. An oscillatory switch system is used to switch from utility power sources to emergency power sources when the normal line supply is temporarily not available. This condition is sensed, an emergency generator activated, and, when the latter is up to needed voltage, the line transfer switches are thrown. After normal line voltage is restored, the switches oscillate back to normal power sources. A gear train causes at least two switches to turn simultaneously.

Abstract: Closing and opening movements are effected by a reversible motor M. The motor M receives its power from a supply U via a feed circuit which includes switch contacts r.sub.1, r.sub.2 controlled by a relay R. The arrangement is such that a closing movement takes place when the relay is energized and an opening movement when the relay is deenergized. To select these two movements there is provided a selector switch S in the feed circuit which has two operative positions and an intermediate neutral position. The excitation winding of the relay R is included in a monitoring circuit in parallel with a strip-like safety switch SL. The strip-like safety switch SL is positioned in the path of the closing movement and has two strip-like contact bands 1, 2 which are pressed together if an object should become trapped in the path of the closing movement. If this occurs the excitation winding of the relay is short circuited and it automatically reverses the motor to convert the closing movement into an opening movement.

Abstract: A logic control and safety circuit for an electrically actuated gate, or the like. Upon command, a counter directs pulses from a free running oscillator of selective frequency to timer and motor control circuitry, effecting sequential gate operations. The normal gate sequence includes open, pause, and close cycles. Electro-mechanical and electrical safety features are included should the gate encounter an obstruction during either the open or the close cycles, or fail to complete a cycle for any reason. Automatic reset circuitry advances the gate through a "close" cycle following a power failure.

Abstract: An automated tire inspection system employs penetrative emanation such as X-radiation to inspect the integrity of portions of tires fed sequentially along a feed path through a centering station and into a shielded enclosure where an inspection station is defined. An inspection apparatus within the shielded enclosure includes an X-ray emitting tube and an imaging system for producing signals representing the pattern of X-rays directed through the tire by the X-ray tube. A control apparatus for the system includes:(1) A protection apparatus for preventing overtravel of movable components of the system, including apparatus for sensing the positions of the movable components and controlling elements for moving the movable components and responding to the sensing apparatus to limit movement of the movable components to within a first predetermined range of positions.

Abstract: A fully-automatic antenna driving device comprises a radio switch consisting of a push type switch which is on only during being pushed, a self-holding circuit for self-holding an excited condition by the turning on of the push type switch, and a further push type switch which is off only during being pushed, thereby preventing an antenna from being extended only by turning on an ignition switch.

Abstract: An apparatus for actuating a slidable and pivotally movable cover for use with an automobile roof opening comprises a control element, e.g. a disc, driven by an electric motor. A plurality of switch cones are preferably secured at equal radial distances from the rotational axis of the control disc. An actuating plunger is radially displaceable by each cam to move a biased actuating element which then operates a switching member of a control switch. This switches off the motor when specific portions of the cover are reached.In a first position of the actuating element, in which it is held against its bias by energized electromagnetic means, the actuating element is operable to displace the switch pin to switch off the motor. In a biased second position of the actuating element, with the electromagnetic means de-energized in consequence of the motor being switched off, the actuating element holds the switching member in its displaced position until the energizing circuit is again energized.

Abstract: A door operator includes a motor-driven mechanism to move a door between an open position and a closed position in response to activation of an improved control circuit. The improved control circuit includes circuitry to initialize the sequence of operation of the motor upon connection of power after installation of the door operator or upon restoration of power after a power outage. Obstruction detection circuitry is also included in the control circuit to stop or reverse the motor if the door encounters an obstacle during movement between the open and closed positions. Time delay circuitry cooperates with the obstruction detection circuitry so as to prevent stopping or reversing the motor due to the inertia of the door and of the drive mechanism as the door starts to open or close upon activation of the control circuit. During the time delay period, however, further manual activation of the control circuit is operative to stop and/or reverse movement of the door.

Abstract: The servo apparatus includes a series resistor string connected in parallel with the body of the servo slidewire resistor. Upscale and downscale travel limit voltage points, corresponding to upscale and downscale travel limit positions for the slidewire contact, are established along the resistor string. The limit voltages on the limit voltage points are separately compared with the slidewire contact voltage, and appropriate motor drive signal interrupting signals are produced when the slidewire contact voltage exceeds the upscale limit voltage or drops below the downscale limit voltage. The interrupting signals effect their motor drive signal interrupting action by reversing the output polarity of motor drive comparators which produce the motor drive signals under the control of an error amplifier which compares the apparatus input voltage to the slidewire contact voltage.

Abstract: The shaft driven by a reversible motor for opening and closing a door is provided with at least one reflective surface. An optical source/detector senses rotation of the shaft and generates a pulse each time one of the reflective surfaces passes. A programmable counter circuit counts the pulses in one direction when the door is opened and de-energizes the motor when a predetermined count is reached without the use of mechanical switches. The counter is decremented when the door is closed, and de-energizes the motor when the count returns to zero. Any obstruction will cause the system to stop the door if sensed during opening, or to reverse the door's direction if sensed during closing. Provision is made to account for any "coasting" the door may experience due to inertia; and the system will also track and permit small changes in the closed position of the door, as might occur if snow accumulates beneath the door.

Abstract: A movement controlling device for the movement of a movable member such as a table in a machine tool which is capable of doing a rapid feeding, a normal feeding for cutting, and a rapid returning. The movable member is driven by a fluid pressure cylinder and engaged, at a predetermined position in the forward movement stroke, with a rack which is linked to a motor by way of the gearing mechanism including a worm and a worm-wheel. The motor is so driven, due to a signal from a sensor for sensing the engagement between the rack and the movable member, as to shift the rack at the speed of cutting feed in the same direction as that of the forward movement of the movable member, and the movable member which is driven by the fluid pressure cylinder is also shifted in response to the shift of the rack.

Abstract: A control circuit for an electrically adjustable patient chair that is adapted when actuated by the momentary depression of a start button, to automatically return the chair to its fully down and tilt forward position. The control circuit includes a multiple-pole relay that is latched in the closed position to energize both motor windings by a solid state switching device that is gated to the on state by a current transformer that senses the load current in a conductor that passes through the core of the transformer. The adjustment motors remain energized until a pair of limit switches are opened upon the chair attaining its exit position. The resulting current drop to zero in the load line is sensed by the current transformer which turns off the solid state switching device which in turn unlatches the relay.

Abstract: The limit switch includes a diode which is connected through a spring-operated switch in circuit with a d-c motor such that, when the motor is commanded to operate in one direction and its limit is reached, the diode is placed in blocking direction in the circuit but, upon reversal of polarity of supply to the motor to reverse its direction, the diode becomes conductive so that a closed circuit is immediately established therefor, the conductive direction of the diode being maintained until a reverse limit is reached, at which time the then conductive diode will be connected in blocked direction. During operation in the normal operating zone of the motor, the diode is short-circuited. The switches themselves can readily be constructed to be cam-operated, for example from a rotating shaft which, selectively, connects the diode in a double-pole, double-throw, center-ON circuit arrangement.

Abstract: The invention provides snubbing apparatus for a D.C. motor in which a capacitor which is charged while the motor is rotating in a first direction is discharged into the gate of a thyristor to initiate the snubbing action. When the thyristor goes on a field coil is connected in series with the motor armature, so as to place the motor in a regenerative mode and snub the motor.

Abstract: A control device is disclosed for controlling the drive means and consequently the oscillation range of a periodically oscillating member particularly when it is necessary to maintain the speed of the periodic oscillation movement such that it corresponds to the average speed of another drive unit. Two movably mounted sensors are located near opposite ends of a predetermined oscillation range of the oscillating member. When either of the sensors senses the presence of the oscillating member beyond the predetermined oscillation range, a signal is generated by the sensor which is transmitted to control means adapted to adjust the speed of the drive means operating the oscillating member.

Abstract: Control apparatus is provided for an electromechanically operated closure panel such as used for sun roofs of automobiles and the like. The control apparatus includes a reversible electric motor drivingly connected to move the closure panel between a closed position and respective slidably retracted and pivoted open positions. In order to accommodate for the differences in relative movement between the electric motor and the closure panel during movement between the closed position and the tilted position, as compared to the movement between the closed position and the slidably retracted position, the invention provides a control mechanism for controlling the speed of the electric motor so as to reduce the same during tilting movement of the closure panel.

Abstract: A position sensor disposed on an elevator car has a first rotatable shaft connected to a secondary winding of a transformer or a switch actuating member, and a second rotatable shaft coaxial with the first shaft and connected to a primary transformer winding or to a switch position changing member. A first roller engages a rod-shaped cam mounted at an angle to a guide rail for the car toward the end of the path of travel of the car to rotate the first shaft in a direction to decrease the voltage across the secondary winding or successively actuate the switches. If the car moves horizontally, the first shaft is rotated to change the voltage and a second roller engaging the rail rotates a second shaft to compensate for this change in voltage.

Abstract: An antenna adapted to be extended and retracted for car radio receivers, which is actuated by means of an on-off switch of the radio receiver and is driven by an electric motor reversible in its direction of rotation; the control circuit for the electric motor includes two limit switch contacts adapted to be opened by switching cams on a disk that moves proportional to the movement of the antenna, and a further switching contact which is adapted to be actuated by a further switching cam of the disk; the further switching contact is thereby opened at and above a predetermined extended length of the antenna while a manual switch with push-button function and possibly with detent function is provided for the further selective extension or retraction of the antenna.

Abstract: A method of driving a door of an automatic door assembly by a linear motor mounted within the automatic door assembly. The method comprises the steps of driving the door by at least a normal propulsion force of the linear motor, driving the door by a propulsion force which may range from zero to nearly the normal propulsion force, and then driving the door by the normal force again thereby reducing the speed of travel of the door during its opening and closing intervals.

Abstract: An automated tire inspection system employs penetrative emanation such as X-radiation to inspect the integrity of portions of tires fed sequentially along a feed path through a centering station and into a shielded enclosure where an inspection station is defined. An inspection apparatus within the shielded enclosure includes an X-ray emitting tube and an imaging system for producing signals representing the pattern of X-rays directed through the tire by the X-ray tube. A control apparatus for the system includes:(1) A protection apparatus for preventing overtravel of movable components of the system, including apparatus for sensing the positions of the movable components and controlling elements for moving the movable components and responding to the sensing apparatus to limit movement of the movable components to within a first predetermined range of positions.

Abstract: An apparatus for adjusting a mirror or a similar flat planar element around two mutually perpendicular axis. The apparatus has a mounting plate for mounting the mirror thereon, the mounting plate being connected to a support by means of a universal joint. On the support is mounted a single reversible electric motor and a transmission system having two planetary gear systems, each having a sun pinion wheel and planet wheels meshing with the sun wheel, the sun wheels of the planetary gear systems being disposed coaxially with the motor shaft. An electromagnetically controlled coupling selectively couples the motor to one or the other of the two pinion sun wheels.

Abstract: A control device for a motor-driven closure panel, for instance an automobile sunroof panel whose closed position is an intermediate position between an open, retracted position and another open, pivoted position, the circuitry for the reversible motor including an impulse relay operating a control switch in one of the two motor connections, the relay coil being connected in parallel to the motor and between the control switch and the pole reversing switch, a position-responsive switch cutting off the relay circuit whenever the panel moves out of its closed position and energizing the impulse relay whenever the panel reaches the closed position. An improved switch arrangement prevents the panel from being stuck in a position in which the reversible motor becomes inoperative.

Abstract: Testing of integrated circuit components of the silicon wafer type for grading purposes is accomplished by supporting the wafer matrix on a platform type work table which is indexed in an x-y coordinate fashion, with the work table being moved vertically to a test position such that the test probes make contact with a precise predetermined position corresponding to the precise location of that portion of the integrated circuit to be tested. The work table is movable vertically with reference to a predetermined axis and rotatable with respect thereto such that the surface of the table remains perpendicular to the reference axis. The chuck assembly for moving the table includes a housing having a bore whose center forms the axis, with a chuck plate mounted for sliding movement in the bore. The end of the chuck plate is in the form of a flanged spool which receives bearing-eccentric assembly for effecting vertical movement while permitting rotation of the spool and the attached chuck plate.

Abstract: In a camera a moveable member moves under control of a motor towards a mechanical stop member provided to accurately position the moveable member. The moveable member may have an objective focusing lens riding thereon and the stop position may correspond to the position of focusing at infinity. The motor energization circuit is connected to the moveable member and the stop member. When the moveable member contacts the stop member the electrical current flowing therebetween operates a switching mechanism to cut off current to the motor.

Abstract: The control device comprises an electric motor whose rotor drives a rotary spindle which shifts the closure member of a valve. Means are provided for detecting the stoppage of the rotation of the spindle. Switching means for opening the supply circuit of the motor are responsive to the detecting means so as to stop the supply when the spindle stops rotating.

Abstract: A storage unit divided into a plurality of stations, is rotatable about a vertical axis to allow any given station to be turned to a position where the articles at that station can be retrieved. A control circuit is provided to allow an operator to select a station, provide an input indicative of that selection, and have the unit rotate through the shortest distance to provide access to the selected station.

Abstract: A stack damper control arrangement for use in a heating system including a furnace having a fuel-fired burner apparatus and a vent stack for conducting combustion products away from the burner apparatus and a damper plate pivotally mounted within the stack and movable between a fully open and a fully closed position, includes a reversible drive motor which is energizable in response to a request for heat to drive the damper plate to the open position, a first limit switch operated when the damper plate reaches the open position to effect the deenergization of the motor, the motor being reenergized at the end of the heating cycle to drive the damper plate to the closed position, and a second limit switch operated when the damper plate reaches the closed position to effect the deenergization of the motor.

Abstract: An annular frame having a biased target plate thereon is mounted in a selected path of advance of each of the usual plurality of tools of a N.C. machine. Two micro-switches are mounted for operation in sequence upon selected movement of the target plate by each advancing tool. Actuation of the first of these micro-switches slows the advance of the tool, while actuation of the second arrests tool advance and notifies the computer of the N.C. machine that such tool is then in a selected, zero position, from which position all further computer controlled operations of the tool are programmed.

Abstract: By actuating a momentary contact switch, an energizing circuit applies an AC voltage directly to one of the two field windings of a two-phase reversible AC induction motor to drive that motor in one of its two directions. As the motor begins to rotate, the shifted phase voltage appearing at the other field winding has a relatively high magnitude and this is employed to energize a neon photo coupler which then completes a holding or latching circuit for maintaining the motor energized so that it continues to rotate. If the motor stalls or if its rotation is purposely stopped, which may be caused by a limit-of-travel switch actuated by apparatus driven by the motor, the magnitude of the shifted phase voltage decreases and the neon photo coupler de-energizes, thereby disabling the holding circuit. By actuating another momentary contact switch, motor rotation in the opposite direction occurs and another holding circuit effects continued motor rotation until the motor stalls or is purposely stopped.