Abstract: A normally engaged wrap spring clutch includes a helical spring which normally is wrapped down on the outer surfaces of aligned input and output hubs to couple the latter. One end of the spring is anchored on the input hub and the other end is secured to a control collar which is telescoped over the spring so that, by turning the control collar relative to the input hub, the spring is unwrapped from the surfaces of the hubs to disengage the clutch. Pins project longitudinally into radial slots in the input hub and spiral slots in the control collar and have substantial mass so that, when the input hub reaches a preselected speed, the pins move radially outward under centrifugal force and, through a camming action in the spiral grooves, turn the control collar relative to the input hub thereby unwrapping the spring. In an alternative embodiment, the outwardly moving pins turn the control collar to cause the spring to wrap down and cause engagement of a normally disengaged clutch.

Abstract: The rotor of a stepping motor includes two axially spaced sections each formed with radially projecting and angularly spaced teeth. The angular width of the teeth of one section is approximately the same as the angular width of the pole pieces of the stator of the motor and, as a result, the motor possesses good dynamic torque, good damping characteristics and a high response speed. The angular width of the teeth of the other rotor section is greater than the angular width of the teeth of the first section so as to cause the rotor to stop in a stable detent position and to improve the stepping accuracy of the motor.

Abstract: A resiliently flexible strip device mounts the armature of an electrically released brake for movement toward and away from the pole faces of the field shell, the armature either moving with pivotal motion or with linear motion. The resiliently flexible strip device may take the form of one or more leaf springs or may be one or more tongues molded integrally with the flange of a bobbin which forms part of the coil of the brake. A piece of flexible friction material is bonded to a curved pad on the outer face of the armature and automatically takes on the curved shape of the pad.

Abstract: A control unit and method for operating a gap-type electromagnetic clutch or brake is provided which reduces audible chatter, screeching caused by belt slippage and related wear and tear on the driving and driven components. The operating winding of the clutch or brake is energized to cause the gap between an armature and rotor to close, energization of the winding is then reduced to initially reduce the torque coupling between the armature and rotor and finally energization of the winding is gradually increased to full energization so as to provide a gradually increasing torque coupling between the armature and rotor.

Abstract: A magnet assembly is made up by a plurality of magnet modules each having a permanent magnet adapted to attract a rotatable armature into engagement with the pole pieces of the module. Each module also includes an electromagnetic coil having an axis disposed perpendicular to the pole pieces. When energized, the coil produces flux which causes the permanent magnet flux to bypass the armature and enable release of the armature from the pole pieces.

Abstract: An armature of an electromagnetic clutch is connected by a mounting plate to a toothed driven hub of the clutch through the intermediary of an annular elastomeric spider. When the parts are assembled, the spider is precompressed around its entire periphery and all parts of the spider remain in compression when torque is transmitted through the spider.

Abstract: An armature of an electromagnetic clutch is connected to a mounting plate which is coupled to the toothed driven hub of the clutch through the intermediary of an elastomeric spider. If the spider is melted by heat, the mounting plate wedges against the tips of the teeth of the hub and is prevented from flying axially off of the forward end of the hub.

Abstract: A helical spring loosely surrounds the input hub of a clutch and is adapted to be wrapped down on the input hub to couple the input hub to an output hub. Wrap down torque is applied to the spring through the tang thereof by an operating spring which acts through an axially shiftable actuator adapted to turn the tang as an incident to being shifted axially by the operating spring. If the tang of the helical spring breaks, the spring automatically unwinds and releases the input hub to effect automatic disengagement of the clutch.

Abstract: A helical spring clutch-brake unit in which the spring is prevented from wrapping down and momentarily engaging the clutch if the output member of the clutch is manually turned while the clutch is disengaged.

Abstract: Ball nuts are preloaded onto a ball screw by rotating the nuts relative to one another to jam adjacent end faces of the nuts together. Thereafter, the nuts are held against relative rotation by tightening a clamping ring secured to one of the nuts and adapted to frictionally engage the other nut to prevent rotation thereof.

Abstract: The friction face of an electromagnet is formed by a relatively thin sheet of friction material and by magnetic inserts which are secured to the friction material and which define the pole faces of the magnet. The friction face is adapted to be easily removed from the magnet and replaced with a new friction face when the friction face becomes worn.

Abstract: Pilot torque is transmitted from the input member to the output member of a clutch when a shoe is pressed axially against the input member. When initially turned by the input member, the shoe causes a helical spring to wrap down on angularly spaced shoe segments and to contract the shoe segments into radial gripping engagement with the input member. The shoe segments engage angularly spaced drive lugs on the output member to transmit torque to the output member.

Abstract: The helical spring of a wrap spring clutch is formed with a radially projecting protrusion which is spaced 180 degrees from one of the end tangs of the spring. The protrusion and the end tang are connected to the control collar of the clutch and cause the tensile force applied by the spring to be balanced angularly around the collar.

Abstract: A ring is telescoped into the end of a nut of a ball screw and nut assembly and carries a lip which breaks ice away from the screw. The plastic insert of relatively short circumferential length is supported by the ring and is urged into the groove of the screw by a spring so as to wipe mud from the screw. A felt strip coacts with the insert to seal the nut against the entry of foreign particles and to restrict the escape of lubricant from the nut.

Abstract: Torque is transmitted from the input member of a clutch to a primary shoe when the primary shoe is pressed into frictional engagement with the input member by compression springs. When initially turned by the input member, the primary shoe moves a series of balls angularly along inclined ramps to cause a secondary shoe to shift into frictional engagement with the input member and transmit torque to the output member of the clutch. A brake acts through the shoes to retard the output member when the clutch is disengaged.

Abstract: A ball screw nut assembly of the type in which a nut having an internal helical groove is telescoped over a shaft having an opposing helical groove and an endless train of balls is disposed in the grooves so that the nut travels axially along the shaft as the latter is turned relative to the nut. Travel of the nut along the shaft is limited by a stop which is mounted on the shaft and engaged by the nut. As the nut approaches the stop, the balls leave the groove in the shaft and roll on a cylindrical portion of the shaft whereby the nut is no longer positively driven and the force with which the nut impacts the stop is substantially reduced. Return of the balls into the groove on the shaft is aided by making the diameter of the cylindrical portion slightly greater than the root diameter of the shaft grooves and by utilizing a resilient stop.

Abstract: A linear actuator includes a nut threaded onto a rotatable drive screw and adapted to be coupled to and uncoupled from an axially movable driven member by a selectively engageable and disengageable helical spring clutch and a friction clutch connected in series with the spring clutch. When the spring clutch is disengaged, the nut is permitted to rotate with the screw and thus the driven member remains stationary. When the spring clutch is engaged, it acts through the friction clutch to couple the nut to the driven member and prevent rotation of the nut so that the driven member advances along the screw. When the driven member reaches a limit position, a positive stop automatically releases the friction clutch to interrupt the drive to the driven member even though the spring clutch remains engaged.

Abstract: The blades of a rotary lawn mower are driven by a constantly rotating shaft through a clutch-brake assembly which, when the operator leaves the operating station of the mower such as the mower handles, automatically disengages the blades from the shaft and brakes the blades while permitting the shaft to continue to rotate. The clutch-brake assembly is self-energizing and normally is engaged but is held in the disengaged condition by an actuator which also is self-energized and which initially is energized by a spring. The latter is effective to disengage the clutch and actuate the brake thereby to prevent the blades from rotating until the operator moves a manual member at the operating station to overcome the spring which initially energizes the actuator. This de-energizes the actuator so that the brake is disengaged and the clutch is engaged whereby the shaft rotates the blades.

Abstract: The field shell of an electromagnet is formed with angularly spaced flanges which define a magnetic pole and which also serve as a mounting hub for a coil assembly consisting of a bobbin and a multiple turn winding. Resilient fingers on the bobbin snap into openings in the flanges to hold the bobbin and the shell in assembled relationship. Tabs are located between and project inwardly from the flanges and are used to mount the shell in a fixed position.

Abstract: A brush holder and slip ring assembly in which the housing of the brush holder and the rotor body of the slip ring assembly are both made of plastic. Conductive terminal strips have portions encapsulated by the plastic of the housing of the brush holder and are adapted to make contact with axially spaced brushes. Conductive terminal strips and slip rings are partially encapsulated by the plastic of the rotor of the slip ring assembly, the slip rings being disposed in contact with the brushes.