Abstract: An electric motor for an appliance includes a rotor coupled with a drive shaft. The rotor includes a plurality of rotor magnets that each define a magnet assembly including a plurality of magnet portions having different magnet pole orientations. A stator is in electromagnetic communication with the rotor. A gap is defined between the stator and the rotor. The stator comprises a stator core. A plurality of stator poles define the gap. Stator magnets are positioned within the stator core and are located to partially define the gap. Each stator magnet defines a pair of flux paths that extend around an outer perimeter of the stator magnet and onto the gap. The different magnet pole orientations of the plurality of rotor magnets operate to direct an effective magnetic flux toward the gap.

Abstract: Systems are described for converting the angular position of a shaft or an axle of a rotary motor to an analog or a digital code indicative of the angular position. The systems may include a magnetic disk encoded with first magnetic transitions and second magnetic transitions, where the first magnetic transitions are on a first circumference of the magnetic disk, the second magnetic transitions are on a second circumference of the magnetic disk, the first magnetic transitions represent regions on the magnetic disk, and the second magnetic transitions represent locations on the magnetic disk within each of the regions. The systems may include a first sensor to detect a region based on the first magnetic transitions and a second sensor to detect a location based on the second magnetic transitions. The systems may also include a decoder to identify an absolute location on the magnetic disk based on the region detected by the first sensor and the location detected by the second sensor.

Abstract: The invention relates to a method of adjusting a brush holder (41) of a slip ring and brush assembly comprising at least one slip ring (50) with a radius of curvature R. With the method a test tool (80) is used to simulate a brush in the brush holder with the important difference that the test tool is able to indicate to the operator whether full contact between the slip ring and the contact surface of the test tool is obtained.

Abstract: A charger, especially a chargeable mobile device for an inductive wireless charging system, is provided which includes at least one coil having a core part formed of a soft magnetic material, wherein the coil is embedded in a polymer bonded soft magnetic material.

Abstract: Methods are provided herein for orientation-independent, wireless charging of devices. The methods disclosed herein comprise transmitters and at least one receiver to transmit power wirelessly. The methods described herein comprise generating rotating magnetic fields to induce an electric current in a device.

Abstract: A torque sensor for a steering mechanism having an input shaft joined to an output shaft by a torsion bar. A first coupler is connected to the input shaft while a second coupler is connected to the output shaft. A first and second receiving coils, each having a plurality of oppositely wound loops, are arranged adjacent the first and second coils, respectively, while a circuit determines the angular offset between the couplers.

Abstract: Systems and devices for a high-efficiency magnetic link for implantable devices are disclosed herein. These devices can include a charging coil located in the implantable device and a charging coil located in a charge head of a charger. The charging coils can each include an elongate core and wire windings wrapped around a longitudinal axis of the elongate core. The charging coil of the charge head can be attached to a rotatable mount, which can be used to align the longitudinal axis of the charging coil of the charge head with longitudinal axis of the implantable device such that the axes of the charging coils are parallel.

Abstract: Systems and devices for a high-efficiency magnetic link for implantable devices are disclosed herein. These devices can include a charging coil located in the implantable device and a charging coil located in a charge head of a charger. The charging coils can each include an elongate core and wire windings wrapped around a longitudinal axis of the elongate core. The charging coil of the charge head can be attached to a rotatable mount, which can be used to align the longitudinal axis of the charging coil of the charge head with longitudinal axis of the implantable device such that the axes of the charging coils are parallel.

Abstract: A soil compacting device has an upper mass and a lower mass that is coupled to the upper mass by a spring device and that has a soil contact element. In addition, a drive is provided for producing a working movement of the soil contact element. The drive has an electric motor, a drive frequency of a drive movement produced by the electric motor being equal to a frequency of the working movement of the soil contact element.

Abstract: A system for treatment of gait disorders includes an external device in the form of a pulse generator (4) with an integrated rechargeable battery and a device adapted to be implanted in the human body. The system features an external to the body placed antenna (3) for the inductive link between the external device and the implanted device. This antenna further incorporates an additional secondary coil (24), for inductively charging the battery in the pulse generator. The fixture on the antenna for mounting the antenna on the skin of the person is reused for being received in a charger fixture (20) on the charger, containing the primary coil (22) for the transfer of charging power.

Abstract: An inductive power transfer apparatus is disclosed. A transmitter generates a first time varying magnetic field. A receiver is separated from the transmitter by a gap, but is located with the first time varying magnetic field. The receiver comprises: a conductor; and a receiver magnet located in the first time varying magnetic field and supported for movement in response to the first time varying magnetic field. The conductor and receiver are positioned relative to one another such that movement of the receiver magnet creates a second time-varying magnetic field in a vicinity of the conductor to thereby induce current in the conductor.

Abstract: An induction generator for a radio switch having a magnet element as well as an induction coil with a coil core wherein the coil core is U-shaped, wherein a first rest position and a second rest position are in each case defined for the magnet element, in contact with the limbs of the coil core, and a flux direction reversal takes place in the coil core, whenever a change takes place between these positions, wherein a movement path for the magnet element is predetermined for a movement between the rest positions, wherein the induction generator has a first mechanical energy storage device which is operatively connected to the magnet element and first of all stores energy in the course of forcing a movement from a rest position and, after reaching an intermediate position, which is defined along the movement path and corresponding to which the magnetic forces on the coil core suddenly decrease, emits this energy to the magnet element in order to mechanically accelerate the movement of the magnet element to the

Abstract: A device wherein food can be warmed by means of induction, said device comprising at least one secondary coil which is formed from a current conductor, whereon at least one heating element is connected. The invention also relates to a device which is used to transfer energy in a device in order to warm food by means of induction, said device comprising a primary coil which is connected to a voltage source and which is formed from a current conductor. According to the invention, the primary and secondary coil is cast into a coil body by casting means, and the insulating casting means exhibits a coefficient of thermal expansion which essentially corresponds to the coil body.

Abstract: A generator, such as for a gas turbine engine, includes an integrated auto transformer unit having secondary windings connected to a main windings.

Abstract: An electromagnetic energy transducer configured to convert mechanical energy into electrical energy comprises two magnetic elements including a permanent magnetic element and a soft-magnetic element and an electrical coil. The permanent magnetic element and the soft-magnetic element are arranged to form a magnetic circuit and one of the two magnetic elements is movable in relation to the other of the two magnetic elements. The electrical coil surrounds a part of the soft magnetic element. The movable magnetic element is held in a first position by a spring force and moved into a second position by applying an external mechanical force exceeding the spring force, and at the first position the magnetic flux within the soft magnetic element is different than the flux at the second position.

Abstract: The invention relates to a conducting line protection device for an industrial robot having at least one power line, having a basic ring section, a hollow cylinder section whose diameter is matched to an inside diameter of a pipe component of the industrial robot that rotates relative to the conducting line protection device, an inner edge rounding section whose rounding radius is matched to a diameter of the power line, and a radial bearing section for rotatable support of the conducting line protection device relative to the pipe component of the industrial robot. The invention also relates to an industrial robot having such a conducting line protection device.

Abstract: An electromagnetic energy transducer configured to convert mechanical energy into electrical energy comprises two magnetic elements including a permanent magnetic element and a soft-magnetic element and an electrical coil. The permanent magnetic element and the soft-magnetic element are arranged to form a magnetic circuit and one of the two magnetic elements is movable in relation to the other of the two magnetic elements. The electrical coil surrounds a part of the soft magnetic element. The movable magnetic element is held in a first position by a spring force and moved into a second position by applying an external mechanical force exceeding the spring force, and at the first position the magnetic flux within the soft magnetic element is different than the flux at the second position.

Abstract: A robust method for detecting a relative position of a feedback device, such as an encoder or resolver, coupled to a shaft, such as a motor shaft, is provided. To detect the relative position, electrical commands are issued in an open loop mode to spin the motor shaft an amount greater than the apparent rotational angle between two consecutive markers of the position feedback device, such that the net mechanical rotation is equal to or greater than the total rotational angle between two consecutive markers.

Abstract: A system includes a first coil mechanically coupled to a first component and electrically coupled to a power source. The system further includes a second coil mechanically coupled to a second component and configured to receive power from the first coil via a magnetic field. At least one of the first and second components includes a rotatable component. The system also includes a field focusing element disposed between the first coil and the second coil and configured as a self resonant coil having a standing wave current distribution to focus the magnetic field onto the second coil and enhance the coupling between the first coil and the second coil.

Abstract: Flux-switching electrical machines. In particular, a flux-switching electrical machine having a stator and a rotor. The stator has permanent magnets, armature windings and excitation windings, and the rotor has no winding or permanent magnet but includes a plurality of flux-switching teeth. The stator is generally formed by a succession of elementary cells, each cell being intended to interact with only a single tooth of the rotor at a time. Each cell includes one of the permanent magnets; a first slot for at least partly housing one of the excitation windings at least; and second slots for housing one of the armature windings.

Abstract: In a ring body of a stator, permanent magnets are arranged in alternate inter-pole magnetic path portions located between an even number of stator poles so that magnetic fields pointing in the circumferential direction of the ring body are generated. Coils are wound around alternate inter-pole magnetic path portions where permanent magnets are not provided so that magnetic fields that oppose the magnetic fields generated by the permanent magnets are generated. When electric power is not supplied to the coils, a ring-shaped magnetic circuit is formed by the permanent magnets, and therefore, magnetic flux does not leak to a rotor. When electric power is supplied to the coils, the magnetic flux of the magnetic fields of the permanent magnets and that of the coils combine with each other and flow from the stator poles to rotor poles of the rotor, whereby strong attraction force is obtained.

Abstract: In a magnet cover caulking method of an electric motor, the method achieves caulking and fixation by forming a taper-shaped outer peripheral portion, a diameter of which is reduced toward an outer side in an axial direction, in an outer periphery of a magnet holder, arranging an annular caulking jig in an outer periphery of a rotating shaft, pressing a taper-shaped forming portion a diameter of which is increased toward an outer side in an axial direction, provided in one end side of an inner periphery of the caulking jig to a straight end portion of a magnet cover installed to the outer periphery of the magnet and the magnet holder from the axial direction, and forming the end portion of the magnet cover according to the taper-shaped outer peripheral portion of the magnet holder.

Abstract: An electromagnetic energy transducer comprising a permanent magnet (1), a soft-magnetic element (9), an electrical coil (6) and stop points (8a-8d). The electrical coil surrounds a part of the magnetic circuit, wherein the permanent magnet (1) and the soft-magnetic element (9) are arranged to form a magnetic circuit with a first flux direction. At least one of the soft-magnetic element (9) and the permanent magnet (1) is mounted for rotary movement about an axis (4) with respect to the other. End points of the rotary movement are formed by the stop points (8a-8d).

Abstract: The present invention relates to electrically magnetized synchronous machine comprising an electrically magnetized rotor, and electrically supplied sator windings, whereby it further comprises non-linear means, optionally controllable, such as rectifying means in a series with three sator phase windings, whereby a rotor field winding is arranged to be fed from said non-linear means.

Abstract: An electrical power generator is provided which is a direct drive induction generator capable of being directly connected to the power grid for the creation of electrical power. The rotor of the induction generator is located along the outside periphery of the stator and the stator may be provided with a plurality of poles. The number of poles provided on the stator may be adjusted to obtain an optimal rotational speed required to generate power. Using this arrangement, a low cost, efficient, reliable and easy to build wind generator may be provided.

Abstract: An inductor-type synchronous machine includes field stators having field elements by which an N-pole and an S-pole are concentrically formed, rotors to which a rotating shaft is fixed and has N-pole inductors disposed so as to face the N-pole of the field elements and S-pole inductors disposed so as to face the S-pole of the field elements, and an armature stator having armature coils disposed so as to face the N-pole inductors and the S-pole inductors.

Abstract: It is possible to provide a brush-less type rotation detector shielding structure capable of reducing the interference of magnetic flux leaking from a rotation transformer to a stator iron core and rotor iron core and suppressing lowering of the angle detection accuracy. As shown in FIG. 1, the shielding structure is used for a brush-less type rotation detector including: a rotation transformer having a rotor transformer (3) and stator transformer (4); a signal modulation section having a stator iron core (2) and a rotor iron core (1); and a case (5) for containing them. The shielding structure has a main configuration having a stator magnetic shielding section (44) capable of magnetically shielding between the stator iron core (2) constituting the signal modulation section and the stator transformer (4).

Abstract: A wind driven electric generator apparatus includes a pair of wind-driven, counter-rotating propeller units placed back to back with each other. A first power transmission system is connected to the pair of counter-rotating propeller units for converting wind energy into mechanical energy. A second power transmission system is connected to the first power transmission system. A generator is connected to the second power transmission system for converting mechanical energy into electrical energy. Propeller unit orientation means are supported by a first transmission housing for orienting the pair of counter-rotating propeller units with respect to wind that is sensed. Self-adjusting propeller blade angle adjustment means are supported by the pair of counter-rotating propeller units for adjusting propeller blade angles in response to wind that is sensed.

Abstract: A power system for a motor vehicle having an internal combustion engine and an electric machine is disclosed. The electric machine has a stator, a permanent magnet rotor, an uncluttered rotor spaced from the permanent magnet rotor, and at least one secondary core assembly. The power system also has a gearing arrangement for coupling the internal combustion engine to wheels on the vehicle thereby providing a means for the electric machine to both power assist and brake in relation to the output of the internal combustion engine.

Abstract: An electric machine (40) has a stator (43), a permanent magnet rotor (38) with permanent magnets (39) and a magnetic coupling uncluttered rotor (46) for inducing a slip energy current in secondary coils (47). A dc flux can be produced in the uncluttered rotor when the secondary coils are fed with dc currents. The magnetic coupling uncluttered rotor (46) has magnetic brushes (A, B, C, D) which couple flux in through the rotor (46) to the secondary coils (47c, 47d) without inducing a current in the rotor (46) and without coupling a stator rotational energy component to the secondary coils (47c, 47d). The machine can be operated as a motor or a generator in multi-phase or single-phase embodiments and is applicable to the hybrid electric vehicle. A method of providing a slip energy controller is also disclosed.

Abstract: A single-pole type generator with low loss magnetic core is excited by a field coil that is part of a low loss series resonant circuit tuned to a desired AC power frequency, which may be frequencies such as 50 Hz or 60 Hz or 400 Hz. The series resonant circuit is excited at the resonant frequency. The resulting resonant behavior of the excitation circuit automatically provides the high driving voltages and sinusoidal energy storage patterns needed to efficiently modulate the magnetic field at the desired power frequency. This modulation of the excitation field is amplified by mechanical power from a rotating shaft and modulates the output current and voltage of a single phase output circuit of the single-pole type generator at that power frequency in a sinusoidal pattern thus delivering alternating current power without any requirement for further electronic rectification, commutation or processing.

Abstract: An electric machine (40) has a stator (43), a permanent magnet rotor (38) with permanent magnets (39) and a magnetic coupling uncluttered rotor (46) for inducing a slip energy current in secondary coils (47). A dc flux can be produced in the uncluttered rotor when the secondary coils are fed with dc currents. The magnetic coupling uncluttered rotor (46) has magnetic brushes (A, B, C, D) which couple flux in through the rotor (46) to the secondary coils (47c, 47d) without inducing a current in the rotor (46) and without coupling a stator rotational energy component to the secondary coils (47c, 47d). The machine can be operated as a motor or a generator in multi-phase or single-phase embodiments and is applicable to the hybrid electric vehicle. A method of providing a slip energy controller is also disclosed.

Abstract: An electric machine selectively operates as a generator mode or a motor mode. The electric machine includes a stator core, a multi-phase armature winding, a field coil, a moving core having a plurality of salient poles so as to move relative to the stator core to cross the magnetic field. Field current is supplied to the field coil differently according to operation mode. A portion of the armature winding is short-circuited to form an additional magnetic field that has a phase different from the magnetic field of the field coil. Therefore, the rotary core moves relative to the stator core when the operation mode is in the motor mode.

Abstract: An electric machine (40, 40?) has a stator (43) and a rotor (46) and a primary air gap (48) has secondary coils (47c, 47d) separated from the rotor (46) by a secondary air gap (49) so as to induce a slip current in the secondary coils (47c, 47d). The rotor (46, 76) has magnetic brushes (A, B, C, D) or wires (80) which couple flux in through the rotor (46) to the secondary coils (47c, 47d) without inducing a current in the rotor (46) and without coupling a stator rotational energy component to the secondary coils (47c, 47d). The machine can be operated as a motor or a generator in multi-phase or single-phase embodiments. A method of providing a slip energy controller is also disclosed.

Abstract: An inner core 62 and a resolver rotor 63 are secured to a rotary shaft 68 so that they are coaxial. A spacer 2, is provided between the inner core 62 and the resolver rotor 63. The spacer 2 and the inner core 62 are formed as a unit with separation, or space, between the spacer 2 and flange 41 of the inner core 62. The thickness of flange 41 is greater than the corresponding width of the corresponding part of the outer core, on which a rotary transformer input winding is wound. The resolver rotor 63 is a separate unit from the spacer 2 and the inner core 62, which facilitates automatic winding of the rotor. Grooves 3, 42 are formed in the spacer 2 and the flange 41 to accommodate a crossover wire 60.

Abstract: A synchronous machine (10), in particular, for a starter-generator of an internal combustion engine, includes a stator, a rotor (22) having a rotor shaft (24), a stack of sheets (28), and squirrel cage (30) non-rotatably connected with the rotor shaft (24) and the stack of sheets (28). The squirrel cage (30) has a short circuit ring (36) on its opposite front ends, which is secured to an annular reinforcement element (40, 42). The reinforcement elements (40, 42) do not overlap adjacent, outer circumferential surfaces of the squirrel cage (32) or the short circuit rings (36).

Abstract: A multi-pole electric pulse generator contains poles having a pseudo-random distribution. Preferably, poles are equally sized and spaced, and polarity corresponds to a pseudo-noise binary sequence, which is specifically a primitive polynomial m-sequence. At one point in the rotor's revolution, all rotor poles are aligned with corresponding stator poles to provide maximum net magnetic flux through the armature windings. At all other rotor positions, the poles are misaligned so that the net flux through the armature windings is small. In operation, rotation through the misaligned rotor positions produces essentially no flux change so that no electric power is generated. When the rotor reaches the aligned position, there is a sudden, large flux change which generates a high-energy electric pulse. The exemplary application is for generating an ignition spark of an internal combustion engine.

Abstract: The invention relates to a rotor for an electric machine, especially a synchronous machine with transverse flux, especially a synchronous generator, especially a TFM rotor.

Abstract: A flux generator base unit electromagnetically coupled with a receiving unit to transfer energy into the receiving unit. The base unit includes one or more permanent magnets that produce a magnetic flux, which passes through a receiver coil in the receiving unit. The receiver coil is either disposed in a separate housing that is electrically connected with a portable device, or integrated into the housing of the portable device. Either the permanent magnets or a flux shunt is moved in the base unit to produce the varying magnetic flux that is coupled to the receiver coil. As a result of the varying magnetic field experienced by the receiver coil, an electric current is induced in the receiver coil, which is conditioned (e.g., rectified, filtered, and regulated) by a conditioning circuit to charge a battery or energize electronics contained in the portable device.

Abstract: A mangle magnetic structure is composed of a plurality of transversely magnetized parallel cylindrical rods forming a cylindrical shell defining an interior cavity filled with insulated wires in parallel to the mangle's principal axis. Two semicircular sections composed of the solid copper wires, within the interior cavity, are physically separated and insulated from each other by a barrier. The transversely magnetized parallel cylindrical rods are rotatable around each rod's individual axis, causing an interior magnetic field within interior cavity and the semicircular sections. The transversely magnetized parallel cylindrical rods are rotated so that the lines of force emanating from them produce an Alternating Current axial electromotive force to drive current through the semicircular sections and to an external load. In one embodiment, two sets of concentric transversely magnetized parallel cylindrical rods form the magnetic shell.

Abstract: This switched reluctance machine has at least six magnet yokes (11) on the stator side. The yokes are placed circularly and they carry windings (112). These yokes (11) can be placed at the inner side and/or the outer side of the rotor (12). These yokes which are magnetically insulated to each other interact with the salient poles (121) of the rotor (12). The two phases (X, Y) of this machine are push-pull controlled by a Hall sensor (31). This way the electronic circuitry becomes very simple.

Abstract: A flux generator base unit electromagnetically coupled with a receiving unit to transfer energy into the receiving unit. The base unit includes one or more permanent magnets that produce a magnetic flux, which passes through a receiver coil in the receiving unit. The receiver coil is either disposed in a separate housing that is electrically connected with a portable device, or integrated into the housing of the portable device. Either the permanent magnets or a flux shunt is moved in the base unit to produce the varying magnetic flux that is coupled to the receiver coil. As a result of the varying magnetic field experienced by the receiver coil, an electric current is induced in the receiver coil, which is conditioned (e.g., rectified, filtered, and regulated) by a conditioning circuit to charge a battery or energize electronics contained in the portable device.

Abstract: A method and apparatus for heating substances such as beverages, soups, chemicals, etc., with heat produced by circulating electrical eddy currents. In one form of the device, a magnetic flux generating base produces a varying magnetic field by using an electric motor to move a plurality of permanent magnets. The varying magnetic field induces the eddy currents to circulate in a ferromagnetic conductor that is sealed in the bottom of a container resting on the magnetic flux generating base. Losses due to the eddy current produce heat that is transferred into the substance within the container. In another embodiment, the motor moves one or more magnetic flux shunts to vary the magnetic field experienced by the ferromagnetic conductor. The presence of the container on the magnetic flux generating base can be detected and used to control the operation of the electrical motor.

Abstract: The invention relates to a single-phase autonomous machine, which comprises: A P-pole pairs rotor, a P-pole pairs stator which comprises two windings, an excitation winding and a single-phase power winding; and an external source for providing current to the said excitation winding, for, creating a magnetic field that interacts with a time-varying inductance caused by the rotor rotation.

Abstract: A flux concerning electrical machine has a stator and a rotor, the stator including on its face a series of notches housing a series of stator coils, and further including a series of housings for excitation means, and the rotor including a plurality of flux commutator teeth for selectively making pairs of closed magnetic circuits through the stator coils. In accordance with invention the stator includes a plurality of independent stator coils defining as many phases and located in a series of individual cells angularly distributed on its circumference and the rotor teeth are equi-angularly spaced so that the angular positions of the various pairs of teeth have predetermined phases relative to the various individual cells. The invention is applicable in particular to brushless alternators for motor vehicles.

Abstract: A brushless resolver comprising a housing, a rotor rotatably mounted in the housing, a rotary transformer comprising a primary winding carried by the housing and secondary winding on the rotor and operatively associated with the primary winding, a resolver comprising a stator winding carried by the housing and a rotor winding on the rotor and operatively associated with the stator winding, characterized by an electromagnetic flux absorber in the housing between the rotary transformer and the resolver for absorbing leakage electromagnetic flux from the rotary transformer so as to reduce any deviation between the indicated electrical position of the rotor and the actual mechanical position of the rotor during each revolution of the rotor. The flux absorber comprises a copper ring between the rotary transformer primary winding and the resolver stator winding so that the leakage flux creates eddy currents in the ring thereby absorbing or reducing the leakage flux.

Abstract: An external power head is energized by a motor causing movement of an element that produces a varying magnetic field, thereby inducing power in an implanted receiver coil within a patient's body. The external power head includes either one or more moving permanent magnets, or one or more moving elements that vary the magnetic flux coupled to the implanted receiver coil. As a result of the varying magnetic field experienced by the implanted receiver coil, an electric current flows from the implanted receiver coil to energize an implanted medical device.

Abstract: An electrical machine includes a stator and a rotor. The stator includes on its internal face at least one induction winding housed in a pair of recesses and a series of housings for excitation means. The rotor does not have windings and includes teeth for establishing variable magnetic fluxes in the induction winding. The excitation brings into play permanent magnets adapted to establish a closed circumferential magnetic flux in the stator and excitation windings locally establishing an adjustable magnetic flux in the reverse circumferential direction. The rotor teeth are adapted to effect a flux commutation in the stator and the, or each, permanent magnet occupies an angular position located between the angular positions of the two arms of a common induction winding. In this way an alternating magnetic flux is produced in the induction winding or windings during the rotation of the rotor.

Abstract: An external power head is energized by a motor causing movement of an element that produces a varying magnetic field, thereby inducing power in an implanted receiver coil within a patient's body. The external power head includes either one or more moving permanent magnets, or one or more moving elements that vary the magnetic flux coupled to the implanted receiver coil. As a result of the varying magnetic field experienced by the implanted receiver coil, an electric current flows from the implanted receiver coil to energize an implanted medical device.

Abstract: A switched reluctance motor is provided with a rotor position detecting apparatus for detecting a rotor position wherein the apparatus comprises a rotor position-sensing mechanism removably mounted in a ventilator hole formed in a side wall of a motor housing for enabling an easy replacement of printed circuit boards and photo-interrupters when they need to be repaired and maintained. The sensing mechanism includes a fixing member having spaced slots for receiving respective circuit boards.