Abstract: A printing web tensioning system that is activated in response to a break in the printing web. The system includes a pair of tensioning rollers which bracket the paper web and are movable between a spaced disengaged position and a contacting engaged position. The pair of tensioning rollers are driven by a variable speed motor, the speed of which is synchornized with the speed of the printing cylinders. Hydraulic rams are attached to the tensioning rollers to move them from the disengaged position to the engaged position when a break in the printing web is detected and the printing unit begins to shut down. Since the speed of the tensioning rollers is synchronized with the speed of the printing cylinders, web tension is maintained and a small quantity of paper web is advanced forward and collects on the floor during the shut down process. By maintaining tension on the printing web, paper is prevented from wrapping around the printing cylinders and causing damage to the print blankets.

Abstract: A method and apparatus for splicing a fresh stack of continuous pin-feed forms in a high-speed printer having fed therethrough an expended stock of continuous pin-feed forms, where the printer includes an input station at a recessed area. A slidable tray for supporting the fresh stack is pulled out of the printer, and a splicing station which is hingedly coupled to an upright wall portion attached to the tray is deployed external to the printer for splicing ease. The splicing station includes a spool of splicing tape which is disposed within a locating groove of a controlled depth, the forms being registered on locating pins on either side of the groove for accurate splicing upon pressing them centered on the tape. When the splice is complete, the spliced stack is fan-folded upon the tray, the splicing station folded back against the upright wall portion, and the tray returned within the recessed area.

Abstract: An apparatus for removing an endless paper web folded in a large stack and for feeding the paper web to the printing unit of a high-speed printer, particularly a laser printer applying a removal force, at least above stack and in the removal direction behind the same and in front of the printing unit of the high-speed printer is positioned at least one guide roller. At least one of the guide rollers also serves as a deflection roller and for reducing the removal force and, consequently, prevent the risk of the paper web tearing. At least one deflection roller is provided with an additional continuous drive.

Abstract: The present invention relates to a wire supply sensing apparatus (4) for monitoring the supply of wire (3) to a wire receiver (5) from a wire supply source (1). The sensing apparatus (4) is comprised of a tangled wire sensor (7) and a wire supply continuity sensor (9). The wire supply continuity sensor (9) has a sensing arm (23) which responds to the absence of wire due to wire breakage or depletion of the wire supply from the source (1). Upon wire breakage or depletion the sensing arm (23) controls an electric switch (27) which signals a controller (33) to turn off electric power at the wire receiving apparatus (5). The tangled wire sensor (9) has a plunger (13) including a tension sensing channel (15) for detecting a tangle (37) in the wire. Tension caused by the tangle (37) provides a force against the plunger (13) to move the plunger (13) to a position indicating the presence of a sensed tangle.

Abstract: A printer having a plurality of differently located feed paths for print material including in each instance a feed channel, has also separately positioned feeler and scanning levers projecting into the respective feed path and channel, in the case of absence of print material in the respective feed path and channel, but the respective lever is pushed out of the channel and feed path in the case of presence of the respective print material; the scanning levers and feelers are linked by a slotted cam plus pin linkage and one of the levers carries a single switch actuating element such as a projector; electric contact making and breaking switching means with three point biased and clamped tongues are actuated by said actuating element to provide a first switching state when print material and sheet stock is in one of said feed paths and channels, independently from the particular channel and feed path involved and providing a second switch state when none of said feed paths and channels includes or contains she

Abstract: A method of preventing the subsequent breakage of webs running in a rotary press which would be caused by a first broken web. In this method, when a signal of web breakage is received from any one of web breakage sensors which are provided to sense the breakage of any of the running webs, a nip pressure signal is changed in accordance with the number of webs still running, and is sent to a nip pressure controller to decrease the nip pressure of a triangular former drag pressing roller and nipping roller, to prevent the multiple breakage of webs.

Abstract: Sensing arrangements on material rolls are used to give advance warning when the material web forming the roll approaches its end. Usually this involves the sensing of the reduction of the the roll diameter with the help of a sensing device resting against the roll periphery. In the case of roll suspensions where the center of the roll is not fixed, these sensing arrangements cannot be used. The present invention uses a sensing arrangement which comprises a field-generating element, e.g. a permanent magnet, present in the center of the roll, together with a movable sensing device resting against the periphery of the roll, e.g. a heavy current switch which is acted upon at a certain predetermined field strength, and in a suitable manner indicates that a roll replacement is imminent.

Abstract: This relates to a dispenser for a hot melt material which is supplied in rod-like form from a spool and which is heated to the required semi-liquid dispensing state. The dispensing head is provided with a heating passage which provides for uniform heating of the rod-like hot melt material and there is further provided a special piston having a throughbore through which hot melt material is fed into a pumping cylinder as the piston retracts after a pumping stroke so as to eliminate in the dispensing head downstream of the piston any momentary voids. There is also a feed mechanism which will feed the hot melt material in accordance with the demand of the dispensing head and which will urge the rod-like hot melt material into the heating passage of the dispensing head under a preselected pressure so as to assure flow not only through the heating passage, but also through the piston.

Abstract: A device for use in a tape driving apparatus for detecting the tape end made of transparent material, comprising means for generating signals consisting of a first output and a second output having a delay time behind the first output, a device for emitting light upon the existence of the second output, a sensor for receiving the light emitting from the light emitting device through the tape end of transparent material, and a discriminating means for controlling, by means of the first output, the output supplied from the sensor during the existence of the second output, whereby the tape end is correctly detected without causing trouble in connection with extraneous light to be introduced from the outside.

Abstract: A device for shifting a compensator roller in a printing press, comprising an actuator assembly which may be controlled for either high speed or low speed movement of the compensator roller.

Abstract: To prevent damage to a printing cylinder, typically the blanket cylinder of rotary offset printing machine, upon tearing of a paper web, which usually occurs within a dryer, a paper web seizing apparatus is positioned downstream of the last printing station. The apparatus includes a roller (15) which is driven at the speed somewhat higher than the linear speed of the paper web by a belt drive (20,21,22) from a friction wheel (18) and held out-of-engagement with the other roller (3) of the pair by a latching mechanism (24, 25, 26--FIG. 2). Upon sensing of a tear, the electromagnetic (26) of the latching mechanism permits a spring (23) to disengage the first roller (15) from the friction drive (18), the roller continuing to rotate due to inertia and engaging the web (A) and then being driven by the positive drive (8,9,10) of the first roller, thus wrapping any torn web about the first roller and preventing damage to the printing cylinders of the printing machine.

Abstract: A device for detecting whether or not one end of a belt-shaped sheet is locked having a depressing bar for depressing one end of a belt-shaped sheet perpendicular to the surface of an end thereof when the end is at a locking position where to be locked by an end locking member. A detector is operated when the depressing bar is moved a predetermined distance to produce a signal representative of whether the end of the belt-shaped sheet is satisfactorily locked. The depressing bar is operated in response to a signal representing when the end of the belt-shaped sheet comes to the locking position.

Abstract: A conveying device directs printed products past a stationarily arranged ink jet printer. A control system initiates a printing operation by the printer each time a printed product passes through the effective printing zone or region of the printer. The conveying device comprises an individual conveyor equipped with gripper units arranged in spaced relationship from each other, each of which is structured to take-up or engage one printed product. The control system includes a pulse generator driven by the individual conveyor and transmits a control pulse for each one of the gripper units. The control pulse is suppressed by a monitor responsive to empty gripper units. Since the printed products are conveyed by the gripper units, their reference position relative to the conveying device is defined over the entire product conveying path. The control signal initiating the printing operation thus can be utilized for initiating other operations after passing through a delay element.

Abstract: A sensing system senses web movement and web tension of a photosensitive web moving through a processor. The system includes a sensing arm pivotally attached about a pivot to the processor and a transport roller rotatably attached to one end of the sensing arm. The photosensitive web engages the transport roller such that the roller rotates. The other end of the sensing arm, on an opposite side of the pivot point, is biased in a direction opposing the web tension of the photosensitive web. A tension detecting mechanism detects the movement of the sensing arm when the web tension overcomes the biasing force and transmits an alarm signal indicating that the web tension has increased beyond a predetermined value. A web break detecting mechanism is preferably included and detects the rotation of the transport roller and transmits a signal when the transport roller stops rotating indicating that a web break has occurred.

Abstract: Method and apparatus for web break detection employing a sonic signal generator to generate regularly repetitive sonic signals of selected frequency, duration and time spacing between signals and disposed to direct the sonic signals toward a moving web of selected material so the signals are reflected from the web, a receiver device to receive the reflected signals, a time signal generating device to generate signal pulses during the time period between the generation of a sonic signal and receipt of the reflected signal a counter device to count the time generated between the transmission of the sonic signal and the reflected signal so that the number of time signals generated is indicative of the presence of the web as well as the distance of the web from the signal generator and receiver and a logic system to actuate a cutter mechanism to cut the web if it should fall outside a preselected "window" in which the web is positioned.

Abstract: A device for indicating the triggering of a signal transducer in, for example, thread surveillance and monitoring systems.

Abstract: In a printer, a bail is attached to a wall of a supply chamber which contains a single supply roll. The bail has a pivot which allows the bail to pivot for providing access to the supply roll. A flexible web has one end attached to the wall of the supply chamber and the other end attached to a forward edge of the bail, and moves with the bail to resiliently contain blousing of paper from the supply roll.

Abstract: A measuring device for measuring the distance of feed of cloth in a sewing machine, comprising a wheel driven by the cloth without slippage and located at the presser foot. A plurality of slits on the wheel are arranged to cooperate with two slits in the bracket of the wheel, and thereby form two light gates producing two output signals in the form of a two bit binary code. This light is detected by photo transistors or photo diodes positioned to receive light through the slits from light emitting diodes or lamps. The output signals from the unit are applied to a data unit connected to compute a positive or negative feed of the cloth. The invention is especially useful when a buttonhole is to be sewn totally automatically.

Abstract: Feeding device for the cycled feeding of rod or tape-like material into a press, cutter or the like, which includes a metering wheel which rolls off directly or indirectly on the material being fed, serving as a true value indicator. The metering wheel is coupled with a true value input metering spindle which acts upon a hydraulic control valve device. The exactly maintained feeding path is made possible by the mechanical coupling of the true value feeding with the true value input on the control hydraulic valve device.

Abstract: A bulk material feeder (10) has two rollers (12,14), at least the lower (14) of which is driven (24,26). Strip material (34) is threaded around the side of the upper roller (12) toward the direction of feed, between the rollers (12,14), around the side of the lower roller (14) opposite the direction of feed and to downstream machinery (38) spaced from the feeder (10). Roller (12,14) spacing is greater than material (34) thickness precluding compression of the material (34). Feed is produced by friction between the roller (14) and material (34) only. Feed rate is greater than usage thereby producing a depending loop (40) between the feeder (10) and the downstream machinery (38). In one embodiment, increasing loop (40) size decreases material (34) and roller (14) contact, causing relative slippage and a discontinuance of feed. In another embodiment, both rollers (12,14) are driven and loop (40) size is limited by a photoelectric device (42) and associated control circuitry.

Abstract: An ends-down sensor device for detecting breakage or absence of a cabinet end of filamentary yarn, involving a cylindrical roller seated upon a fixed center post with the center of gravity of the roller causing it to rotate relative to the center post in one direction and activate a suitable signal device when a cabinet end breaks or becomes missing; and upon a cabinet end frictionally engaging the cylindrical roller, causing the roller to rotate relative to the center post in the opposite direction and deactivate the signal device.

Abstract: A photographic film processor including a film dryer through which photographic film is transported under tension and dried, has a film break detection system for detecting photographic film breaks within the dryer. Upper and lower substantially horizontal shafts are positioned in the dryer in a spaced relationship. Each shaft has a plurality of spools, and the photographic film is transported back and forth over the spools and between the shafts in a serpentine fashion. The lower shaft is spatially movable with respect to the upper shaft and is biased in a direction opposite to the force on the lower shaft due to film tension. A film break within the dryer causes a loss of film tension, which in turn causes a change in the spatial position of the lower shaft. A sensor senses this change in the spatial position of the lower shaft, activates an alarm, and shuts off the dryer drive system.

Abstract: A film advance error detection system for synchronizing the operation of shutter cocking and film winding mechanisms with a motor drive unit therefor. This system utilizes three transducers positioned adjacent the sprocket wheel, film perforations and rewinding spindle to pick up signals whose frequencies are related to their speeds. By processing the signals in combination with an output signal of a phase difference compensator, it is made possible to provide, in a selective manner, a display representative of the film advane error and reeling end in the winding and rewinding operations along with the automatic stoppage of rotation of the motor.

Abstract: A device for detecting a travel condition of an inkribbon for printers is disclosed. The device is composed of a rotary member rotatable in response to the travel of the inkribbon and a signal generation means interlocked with the rotary member. The signal generation means generates a detection signal and can not only detect trouble of the detection device but also detect a mode in operation of a carrier on which the detection device is arranged as well as detect the travel of the inkribbon.

Abstract: A sensing device responsive to ballooning motion of textile yarns, and producing electrical sensing signals comprising a hollow or ring-shaped yarn guide body whose interior periphery is provided with motion responsive and non-responsive elements in alternate sequence.

Abstract: A device for withdrawing and gathering a fiber web discharged by a web delivering assembly of a carding machine includes a guide element arranged immediately downstream of the web delivering assembly and has a web guiding face; a support for positioning the guiding face to be movable towards and away from the web delivering assembly; an arrangement for urging the guiding face towards the web delivering assembly into a closed position with a predetermined force; a switch supported adjacent the guiding face for actuation by the guiding face upon movement of the guiding face away from the web delivering assembly in response to a web pressure opposing and exceeding the predetermined force; and an arrangement connected to the switch and responsive to the actuation thereof.

Abstract: Pulses from a motor-driven roto pulser, e.g., primary pulses, and from a roto pulser powered by a moving ribbon, e.g., secondary pulses, are (1) compared to determine if the ribbon is continuous and (2) used to actuate ribbon cross scoring and snapping equipment. When the secondary pulse count exceeds the primary pulse count for a given ribbon displacement by more than a predetermined amount, indications are that a ribbon break has occurred and the scoring and snapping equipment is actuated by the pulses from the ribbon powered roto pulser. When the difference between the secondary pulse count and primary pulse count is less than the predetermined amount, indications are that the ribbon is continuous and the equipment is actuated by pulses from the motor-driven roto pulser.

Abstract: An end of paper roll detection assembly for detecting the end or near-end of a paper roll on a hollow core is provided. The end of paper roll detection assembly includes a detecting bar pivotally mounted on a retaining bar biased towards the side face of the paper roll which is supported on an adjustable paper roll retaining member. When paper is consumed the core is lowered towards the retaining member until the core is aligned with the detecting bar which passes into the hollow core thereby actuating a switch for generating a signal indicating that a predetermined amount of paper remains on the roll. The switch may be a reed switch closed by a permanent magnet secured to the retaining bar or a microswitch operated by the retaining bar. The retaining bar pivots towards the paper roll by action of a pulsating electro-magnet or a spring biasing the retaining bar towards the paper roll.

Abstract: A stop motion apparatus is disclosed for disengaging a drive motion on a carding machine in response to the detection of a desired operating condition wherein the carding machine is of the type having motorized drive means for imparting a drive motion to the carding machine when engaged and actuator means for selectively enaging or disengaging the drive motion. The stop motion apparatus includes a base for attachment to the carding machine and a pivotable arm assembly carried by the base. A linkage assembly connects the pivotable arm assembly to the actuator means of the carding machine. The pivotable arm assembly has a first position in which the actuator means disengages the drive stopping the carding machine and a second position in which the actuator means engages the card drive.

Abstract: Apparatus for feeding seriatim discrete webs of paper, cardboard or synthetic plastic material to one or more processing machines has a pair of continuously driven transporting rolls, a first and a second pair of intermittently driven advancing rolls, and first and second guides which respectively compel webs to travel from the nip of the corresponding advancing rolls into the nip of the transporting rolls. Two photocells are adjacent to each guide and each photocell is shiftable in and counter to the direction of travel of a web from the respective advancing rolls toward the transporting rolls. That photocell of each pair which is nearer to the respective advancing rolls causes the generation of a visible or audible signal in response to detection of the leader of a fresh web, and the other photocell of each pair transmits a signal in response to detection of the trailing end of a running web.

Abstract: This invention relates to an improvement in an apparatus for monitoring the drawing-in operation and the tearing-off of a sheet of material in a dryer, wherein a sheet of material to be dried is guided over continuously-rotating screen-type conveyor belts, particularly jet dryers with conveyor belts positioned in several stages, and with means for transferring the sheet of material from one stage to the next-following stage, the improvement comprising a two-stage construction of the monitoring apparatus, a first stage comprising a first partial means for optically monitoring the path of the sheet of material during the drawing-in operation, and a second stage comprising a second partial means for monitoring the tension of the sheet of material in running operation, said first partial means releasing said second partial means upon completion of a malfunction-free drawing-in operation.

Abstract: A flywheel is provided with a detection wheel which is rotatable relative to the flywheel, and is also provided with a displacement member which is rotatable with the flywheel and is radially movable thereto. The detection wheel forms part of a drive system for a reel mount, and ceases its movement upon termination of tape rewind. The displacement member is provided with a pin which actuates a release lever to stop the operation of a tape recorder when the member moves radially in response to the detection wheel coming to a stop.

Abstract: Apparatus for automatically dispensing material from a roll comprising a base and a cover pivotally mounted thereon, a roller for rotatably supporting a roll of material, and material engaging roller for automatically dispensing the material from the roll for at least two preselected time intervals under the control of an adjustable resistor-capacitor timing control circuit.

Abstract: Apparatus adapted for use in printers for indicating when the paper upon which information is to be printed has been depleted. A pivotable sensing member is slightly biased towards a fixed guide member, the two members being adjacent to one another. The sensing member has a horizontal row of protrusions on its inner wall which entend towards the opposing wall of the fixed member. The opposing wall of the fixed member similarly has a horizontal row of protrusions extending towards the sensing member but being aligned between the protrusions on the sensing member. In the situation wherein no paper is introduced between said members, a switch associated with the sensing member provides an indication to control circuiting that no paper is present for printing.

Abstract: A control for a web processing machine such as for a printing press is described for detecting web breaks, faulty web sensors and inconsistent web threading conditions. A logic network is employed to compare web sensor signals with control signals to detect whether the web sensor signals are consistent with what is called for by associated control signals. Station status signals are produced to stop the machine when inconsistent conditions are sensed and cause appropriate web severing. A bypass control network is provided to inhibit the station status signals for slow speed checkout. However, when the machine speed exceeds a predetermined level, the bypass network is automatically deactivated and full machine control protection restored.

Abstract: A continuous web handling device includes two web storage structures, both of which can receive and discharge web material. A selector mechanism including a rotatable web guide turret directs the web material into a selected one of said structures and simultaneously directs the material previously stored in the other of said structures to be delivered therefrom.

Abstract: A method and apparatus is disclosed for protecting the apparatus employed in the formation of glass fibers, glass fiber strands and the products produced therein. The method involves continuously contacting the moving glass fiber strand during the forming thereof from glass fibers with a strand detecting means provided between a gathering shoe and winding means and automatically deactivating the winding means and spiral assembly associated therewith in addition to protecting the application surface of the applicator when a loss of contact of strand between the gathering shoe and winding means is detected. This deactivation of the winding means and spiral prevents damage from glass beads which may form after a strand breakout in a glass fiber forming operation. The strand breakout is detected by means located between the gathering shoe and collet.

Abstract: A stamp dispensing mechanism has a cylindrical feed wheel, with axially-parallel rows of projections, rotatably mounted on a front portion of a vertical support plate that is constructed to rotatably support a roll of stamps on its rear portion. A Geneva star wheel, rotatably mounted on the plate, is operatively connected to the feed wheel for its step movement with the star wheel. A Geneva driver assembly, rotatably mounted on the plate, has a driver pin on an arm rotated by a motor also mounted on the plate. During one rotation of the arm, the pin moves into and out of a slot of the star wheel for its step movement. An arcuate part of the arm is in a recess in the periphery of a tooth of the star wheel, when the pin is not in the slot, to lock that wheel.

Abstract: A tape recorder, in particular a cassette recorder, with an automatic stop device, which during stoppage of the tape switches off the apparatus and releases the play button. During tape stoppage a rotatably journalled drive wheel is brought into contact with the flywheel with its circumference, after which said flywheel drives a force-transmitting member, preferably via a reduction gear, and the latching slide is released.

Abstract: A sprocket drive device for a computer form feeder for transporting a computer printout web having predeterminedly spaced apertures along the edges thereof along the upper and lower surfaces and about a free end of a copyboard overlying the copy platen of a copying machine, including a pin chain assembly mounted on spaced driven sprocket and idler wheels. The pin chain assembly includes a plurality of predeterminedly spaced pins extending therefrom for receipt in the spaced apertures of the web. The pins travel along an endless path between the wheels spaced from the upper and lower surfaces of the copyboard, respectively. A guide and stripper member is provided on the sprocket drive for guiding the web from the pins to the copyboard surface and vice-versa while avoiding the tearing of the web material about the apertures. The guide and stripper member includes upper and lower central portions extending between the wheels for guiding the web along upper and lower planes passing through the base of the pins.

Abstract: The present invention relates to: process and apparatus for feeding continuous filaments to a continuous multifilament structure utilizing tangentially converging fluid streams to forward the filaments; process and apparatus for detecting breakage of filaments utilizing a rotatable cylinder, or a gap in a three dimensional body, wherein breakage of the filament causes a measurable change in the pressure of fluid flowing to the cylinder or the gap; process and apparatus for the production of continuous multifilament structures wherein, upon breakage of a continuous filament, the breakage detector automatically activates a filament feeder to temporarily insert a substitute filament.

Abstract: Disclosed is apparatus for feeding length stock into a work tool such as a punch press. The feed apparatus includes a pneumatically operated traveling clamp and a pneumatically operated fixed position clamp. The traveling clamp is linearly reciprocated between two positions by a pneumatically operated lever and linkage which varies the velocity of the traveling clamp proportionately with distance from the fixed position clamp to decelerate the traveling clamp as the feed stock reaches the desired position in the work tool. Interdependent pneumatic control systems for sequencing the advancement of the stock with the cyclic operation of the work tool and for sequencing the clamps with the feed advancing mechanism are also disclosed.

Abstract: The apparatus is removably mounted on a copying machine, for feeding a web, such as an output medium of a computer, as it is paid out of a web supply tray. The apparatus comprises pin chains for driving the web, a roller for reversing the direction of movement of the web driven by the pin chains, a conveyor pivotally movable between a horizontal position and a vertical position, an operating device for operating the pin chains, a discharged web receiving tray disposed beneath the web supply tray, and a window for taking readings on the scale attached to the copying machine and indicating the sizes of copy sheets.

Abstract: Stop feed mechanism for feeding continuous stock having uniformly spaced abutments thereon in which a resiliently biased dog is moved rearwardly over an abutment and then is moved forwardly in a feeding stroke in which it engages the abutment. Means are provided for sensing when the supply of continuous stock is nearly exhausted and for interrupting further feed by blocking engagement of the dog with an abutment during the feeding stroke.

Abstract: A drive shaft of an automatic printer engages tractors which, in turn, pull a paper web across a print mechanism. Located on the drive shaft is a drive shaft position cam which is fixed to the shaft and rotates therewith. Additionally, located upon the drive shaft for limited rotational movement thereon is a second cam. The shape of the second cam is similar to the shape of the first cam and formed integral with the second cam is a frictional surface engaged by the paper. During normal paper drive, the cams are out of registration and rotate in unison. In response to a paper jam condition, the first cam driven by the paper locks and the cams are forced into registration actuating a switch, the plunger of which rides on both of the cams. The switch signal thus serves to interrupt the paper drive mechanism in response to a paper jam condition.

Abstract: A system for monitoring the paper feed in printing mechanisms and the like, in which reference signals are derived in response to actuation of the feeding means for the paper web and in synchronism with the feed movement thereof, which signals may be compared with supervisory signals generated in response to advancing movement of the paper web, whereby predetermined abnormal relation between the reference and supervisory signals forms a criterion of improper paper advance conditions.

Abstract: Apparatus for providing metered lengths of adhesive bearing strips, from a supply roll, to a mechanism for fixing each of the metered strips to a different one of a plurality of stacks of sheets comprises: a pair of rollers providing a nip, and means for rotating one of the rollers to advance adhesive strip engaged by the nip. The axial length of the nip is smaller than the width of the adhesive bearing strip and the strip includes a hole which is larger than the nip, the hole being located near the end of the roll. As a result, when the hole is advanced into the nip by the rollers the rollers stop feeding the adhesive bearing strip to the mechanism.

Abstract: A sensing lever, preferably a double-arm lever, is journalled over a fulcrum; one arm is engaged by the thread to be supervised, and further connected to operate an electrical switch; the other arm is subject to electromagnetic force derived from an interrupted, pulsed electromagnet. Pulsed operation of the electromagnet can be obtained by a signal derived from the switch of the lever itself, or from an extraneous source; upon attraction by the magnet, the contacts are opened; during a pulse gap, the thread tension depresses the lever, thus closing the contacts; the lever will, therefore, continuously vibrate and presence of an a-c signal across the switches will be indicative of: (a) presence of thread; (b) thread tension below a predetermined limit (excessive tension would overcome the pulsed reset force of the electromagnet); and (c) proper operation (jamming of the lever would likewise result in a d-c output from the switch).