Abstract: A linear encoder system includes an encoder magnet having alternating magnetic zones. The end ones of the magnetic zones are tapered. A distance between the centers of the tapered magnetic zones defines a span. First and second encoder sensors, sensitive to the alternating magnetic zones, are spaced apart a distance equal to the span. As the encoder magnet moves into alignment with one tapered magnetic zone, and out of alignment with the other magnetic zone, the decrease in signal from one magnetic zone is approximately equal to the increase in signal from the other magnetic zone. In one embodiment of the invention, a third encoder sensor is positioned midway between the first and second encoder sensors.

Abstract: A linear motor has an epoxy core armature with dual cold plates attached to a top and a bottom of the epoxy core armature to effect cooling of the epoxy core armature. The use of dual cold plates with circulating cooling fluid reduces heat build up by providing paths of high thermal conductivity from any point in the epoxy core armature to the cold plates. Another embodiment of the invention employs ceramic heat sink plates laminated to sides of the epoxy core armature to increase the thermal conductivity and the resultant power dissipation capacity of the epoxy core armature without introducing magnetic or electrically conducting materials. Other embodiments of the invention utilize cold plates formed from extrusions of aluminum or ceramic materials. Still other embodiments have forced air cooling wherein a U-frame of the linear motor has longitudinal flexible seals and air is forced through the U-frame in which the epoxy core armature travel.

Abstract: An X-Y positioning machine has a forcer, with armature coils, that moves around on a platen, supported by an air bearing. Magnets embedded in the motor platen generate a fixed magnetic field with which the armature coils interact. Perpendicular elongated coils interact with the fields of magnets in columns and rows. When a traditional rectangular pattern of the magnets is provided, a packing density and average peak magnetic flux intercepted by the coils are limited to 50%. The present invention provides magnet configurations that provide greater than 50% maximum peak flux density and up to 100% packing density. Several magnet arrangements are provided: a first in which round magnets are used instead of square, and a second in which diamond-shaped magnets are used. The latter can be used at 100% packing density arrangement. In addition to high peak flux density for a narrow coil, these embodiments exhibit low cogging forces. A method of making the magnet is also provided.

Abstract: A flat linear motor has a single row of permanent magnets mounted upon backplate and an armature having non-overlapping flat coils encapsulated in a block of epoxy resin mounted upon an armature backplate comprised of a magnetic material and having anchoring recesses or protrusions. The armature backplate serves to provide magnetic circuits of low magnetic resistance in the flat linear motor thereby increasing a force generated by the linear motor. A length of the armature backplate is a non-integral number of a pitch length of the permanent magnets so as to reduce cogging. The three non-overlapping flat coils are comprised of square wire windings which provide increased thermal conduction. An embodiment of the invention employs software commutation wherein a position sensing device is used by a controller to determine a position of the armature from which a field polarity is found by means of a formula or a look-up table.

Abstract: A linear motor has coil assemblies driven by multiple phases mounted side by side on a base plate such that they do not overlap. The coil assemblies include conductors wound upon teeth such that voids in the coil assemblies are minimized along with path lengths and thermal resistances between windings and the base plate, thus maximizing heat dissipation and the power capacity of the motor. The linear motor may have coil assemblies with teeth composed of a first material having desirable magnetic properties and a base plate composed of an inexpensive second material minimizing costs of materials. The teeth may be of varying lengths in or to further minimize voids. The coil assemblies are compactly mounted with a longitudinal axis normal to an axis of movement. Permanent magnets are mounted upon a back iron plate with axis of symmetry normal to the axis of movement.

Abstract: A positioning device has a shuttle slidably and rotatably supported above a base assembly. A first linear motor moves the shuttle linearly in a first direction while the second and third linear motors move the shuttle linearly in a second direction, normal to the first direction. The second and third linear motors are separated along an axis in the first direction. The linear motors have magnetic arrays including rows of magnets or a checkerboard array of magnets and provide continuously variable positioning. Rotary movement of the shuttle is achieved by operating the second and third linear motors in opposing directions or at differing rates. The positions of three points on the shuttle are determined by three optical encoders, or three interferometers, whose signals provide feedback to a controller which actuates the linear motors accordingly.

Abstract: Apparatus for force restoration of a bearing retainer uses a loop of resilient line around a pulley at an end of the bearing retainer. One end of the loop attached to a slide and the other end is attached to a base of a positioning table. A second loop is similarly attached at the opposite end of the retainer. These loops apply equal tension to both ends of the bearing retainer as long as the bearing retainer remains in its proper position without creep. When the bearing retainer moves out of position, unequal forces are exerted by the two loops, with a resultant force in a direction necessary to return the bearing retainer to its proper position. This controls the position of the bearing retainer relative to the slide. Provision for detecting and controlling broken force restoration lines may be included. In a second embodiment, a positioning table is disposed in a non-level position wherein gravity tends to produce bearing creep in a downward direction.

Abstract: A positioning table includes a pair of parallel rails defining an axis of motion. A movable assembly including a first linear motor assembly disposed for motion along one of the rails. An outboard linear motor assembly on the other rail is rigidly bridged to the first linear motor assembly. The first linear motor assembly includes a plurality of permanent magnets defining a plane at a predetermined angle to the horizontal and an armature defining a plane at the same angle closely spaced from the permanent magnets. The permanent magnets may be disposed on the movable element of the linear motor assembly or on the first rail. The armature is disposed on the other of the movable element and the first rail. First and second bearings on the movable element of the linear motor assembly support loads in the vertical and horizontal directions. The predetermined angle establishes the direction of a magnetic attractive vector between the permanent magnets and the armature.

Abstract: An armature of a linear motor is cooled by a serpentine channel formed in the lower surface thereof and sealed with a sealing plate. In one embodiment, the serpentine channel is formed in a separate cold plate in good thermal contact with laminations of the armature. In another embodiment, the serpentine channel is formed by stacking bundles of laminations having suitably formed notches therein. The bottom of the serpentine channel is sealed with a sealing plate. A sealant layer between the laminations of the serpentine channel prevents coolant leakage from the serpentine channel into the laminations. A sealing interlayer, may be interposed between the surfaces of the lamination bundles and the sealing plate both for sealing against coolant leakage and for affixing the sealing plate in position. The sealant layer and the sealing interlayer may be of the same material and formed at the same time.

Abstract: A positioning table includes a pair of parallel rails defining an axis of motion. A movable assembly including a first linear motor assembly disposed for motion along one of the rails. An outboard linear motor assembly on the other rail is rigidly bridged to the first linear motor assembly for concerted motion therewith. The first linear motor assembly includes a plurality of permanent magnets defining a plane at a predetermined angle to the horizontal and an armature defining a plane at the same angle closely spaced from the permanent magnets. The permanent magnets may be disposed on the movable element of the linear motor assembly or on the first rail. The armature is disposed on the other of the movable element and the first rail. First and second bearings on the movable element of the linear motor assembly, which may be air bearings support loads in the vertical and horizontal directions.

Abstract: A linear motor system includes first and second linear motors driving a load along spaced-apart supports. A positioning table, or a portion of a machine tool, supported between the first and second linear motors includes a device for varying the position of the table or portion along an axis extending between the first and second linear motors. A single motor control system produces a motor drive signal. A proportioning device proportions the portion of the motor drive signal fed to the two motors in a proportion controlled by the position of the table or portion.

Abstract: A positioning table includes a light-weight workpiece supported thereabove on programmed dynamic support assemblies below a beam-generating apparatus. The positioning table performs gross positioning of the workpiece to bring a desired portion thereof under the influence of the beam-generating apparatus. The programmed dynamic support assemblies are actuated in a three-step sequence first for urging stabilizing posts on the workpiece into stabilizing contact with a base structure of the beam-generating apparatus, second for urging spring rods into contact with the bottom surface of the workpiece, and then for leaving the workpiece supported by the spring rods with the stabilizing posts in firm mechanical contact with the base structure of the beam-generating apparatus. Transverse vibrations in the beam-generating apparatus are directly transmitted to the workpiece through the stabilizing posts, whereby relative motion between the workpiece and the beam-generating apparatus is prevented.

Abstract: A linear DC motor adapted for driving a positioning table having a frame and a table displaceable in a linear direction has a toothed assembly affixed to one element thereof and an array of permanent magnets facing the toothed assembly mounted on the other element. Coils wound around the teeth of the toothed assembly and appropriately energized by DC produce a linear force which is effective to displace the table in a desired direction. When used with a position sensor and an appropriate control system, the table is controllable to a desired position. A set of brush members depending from the table contact a developed linear slip ring track for energizing the coils and for switching polarity of voltage to the coils at appropriate locations. In an embodiment where the coils are stationary on the frame and the magnets are disposed on the table, a power pickup arrangement movable with the brush members is incorporated into the brush and developed slip ring apparatus.

Abstract: An armature for a permanent-magnet linear motor is made up of a set of coils retained in a flat armature plate. The armature plate is of non-magnetic material. In one embodiment, the armature plate is of aluminum having parallel grooves machined in one surface to receive the straight runs of the coils. An aluminum plate covers the grooves to create a reinforcing box-like structure. In a second embodiment, the armature plate is dispensed with and the coils are integrally cast into a resin jacket. A further embodiment employs a serpentine cooling coil for supporting the coils prior to casting the resin and for dissipating coil heat during operation.

Abstract: A short-slide positioning table employs precision grooves machined in opposed edges of a slide thereof for receiving preloading forces applied thereto through bearings from similar opposed grooves in arms of a U-shaped frame of a positioning table. A bearing guide moves bearings released from the downstream end of the slide to a bearing-return tube for return to the upstream end of the slide where they are again captured. Tapered transition regions at each end of each groove in the slide permit easy release and capture of the bearings. In one embodiment of the invention, a force-relief portion is disposed between two contact portions of the groove in the slide. The force-relief portion is set back from the contact portions a sufficient distance to reduce preloading forces in these regions to about zero. Tapered transition regions are provided between the contact portions and the force-relief portions.

Abstract: A linear DC motor adapted for driving a positioning table having a frame and a table displaceable in a linear direction has a toothed assembly affixed to one element thereof and an array of permanent magnets facing the toothed assembly mounted on the other element. Coils wound around the teeth of the toothed assembly and appropriately energized by DC produce a linear force which is effective to displace the table in a desired direction. When used with a position sensor and an appropriate control system, the table is controllable to a desired position. A set of brush members depending from the table contact a developed linear slip ring track for energizing the coils and for switching polarity of voltage to the coils at appropriate locations. In an embodiment where the coils are stationary on the frame and the magnets are disposed on the table, a power pickup arrangement movable with the brush members is incorporated into the brush and developed slip ring apparatus.

Abstract: A linear motor of the type having an elongated stator contained in a U-shaped channel includes a linearly moving element connected to its load by a connecting beam which passes out of the U-shaped channel. A flexible seal on each arm of the U-shaped channel seals against the sides of the beam where it passes out of the U-shaped channel and opposed elements of the seal abut each other to provide a barrier in other areas. In one embodiment of the invention, a positive pressure of a clean gas is maintained within the sealed U-shaped channel to prevent entry of atmospheric contaminants. In another embodiment of the invention, the seal in the vicinity of the beam is purposely made less than perfect so that the cooling gas is encouraged to flow toward, and exit in the vicinity of, the region where maximum cooling is required.

Abstract: A linear motor separates the functions of commutating into a first function for enabling a subset of coils in a linear stator which are within the magnetic influence of permanent magnets in the movable element and a second function for applying the drive power to the enabled subset. One pair of sensors produces sine and cosine signals to maintain a controd coils, the fiabout the phase of power which should be applied to the enabled subset. Another sensor produces a proportional signal which varies linearly between zero and one over each electrical quadrant with a short non-changing interval at maximum and minimum. The control system employs the sine, cosine and proportional signals to synthesize a pair of quasi-sinusoidal waveforms for application to alternate coils in the enabled subset of coils. The short non-changing intervals in the proportional signal are employed to ensure that polarity changeover to the enabled coils takes place at zero volts for bumpless drive.

Abstract: Air bearing pads for supporting a one-axis table in a granite bridge positioning apparatus on a thin film of air include machine-thinned sections for providing resilience to the pads in order to permit flexing sufficient to accommodate surface irregularities on the supporting surface. A single air pressure regulator provides a source of pressurized air to flow-control devices of a plurality of air bearing pads supporting a one-axis table. The individual flow-control devices adjust the flow of air to their respective air bearing pads to individually adjust the lift of the pads.

Abstract: A linear DC motor adapted for driving a positioning table having a frame and a table displaceable in a linear direction has a toothed assembly affixed to one element thereof and an array of permanent magnets facing the toothed assembly mounted on the other element. Coils wound around the teeth of the toothed assembly and appropriately energized by DC produce a linear force which is effective to displace the table in a desired direction. When used with a position sensor and an appropriate control system, the table is controllable to a desired position. A set of brush members depending from the table contact a developed linear slip ring track for energizing the coils and for switching polarity of voltage to the coils at appropriate locations. In an embodiment where the coils are stationary on the frame and the magnets are disposed on the table, a power pickup arrangement movable with the brush members is incorporated into the brush and developed slip ring apparatus.