LINEAR ELECTRIC MOTOR FOR MACHINE TOOL

Abstract: In the synchronous linear motor (10), the coil block (20) exhibits low inertia and therefore good dynamic performance, thanks to being constrained to slide with respect to the support structure (11), which comprises a plurality of magnets (13), on a single mechanical guide (16), which is arranged advantageously on an opposite wall with respect to the fixed magnets, which are immobile. The solution of the invention, especially suitable for actuating tool chucks, also offers high-level protection with regard both to external impurities and to the magnetic field emitted by the magnets themselves. The support structure (11) of the motor can be of a closed type with four sides.

Description: LINEAR ELECTRIC MOTOR FOR MACHINE TOOL Technical Field The invention relates to a synchronous electric motor, suitable in particular for driving machine tools, or automatic machines. Background Art In recent years, linear electric motors have been more and more frequently used in the field of machine tool drive. In this field as in many others, linear motors exhibit considerable advantages, with respect to traditional powering methods, essentially thanks to the absence of transmission organs of any kind which, as is well known, reduce the overall performance of the machine. Electric motors also guarantee that the moving block is driven at the speed and acceleration times required, as motion transmission is in no way affected by friction or adherence coefficient variables necessary for traditional mechanical transmissions, which use kinematic chains. This last-described characteristic is especially useful in the actuating of tool-heads or in machines designed for various tasks, where often these tasks require both high dynamic capabilities and considerable precision. A classic example of application of a linear motor of this type is illustrated in figure 3 of the accompanying figures of the drawings, in which the tool-head or kworkpiece jig 1, is solidly constrained to the coil block 2 of the motor and, together with the coil block 2, is constrained to slide on two guides 3, which are anchored to the structure of the fixed magnets 4. This solution, immediate and effective in conception, is without doubt sturdy, simple and reliable; it is, however, susceptible to development, with the emergence of new solutions directed at improving dynamic performance which, as we have already mentioned, is of primary importance in this field. Simplifying the structure of these applications is also a priority, not least as it would bring with it a reduction in production costs. The main aim of the present invention is to provide a linear motor, applied in particular to a drive for machine tools, or automatic machines, which has a simplified structure in relation to prior art motors and which offers an improvement in both dynamic performance and actuation. A further aim of the present invention is to provide a linear electric motor for actuating machine tools which is economically advantageous and reliable. The above aims are all attained by a synchronous linear electric motor in which the coil block is compelled to slide with respect to the stator comprising the magnets, on a single mechanical guide. The guide is constrained to the shell of the motor, on a side opposite the side where the magnets are located. The support shell of the motor has a U-shaped transversal section, though it can be closed on all four side. The lie plane of the coil block can, in both cases, be arranged either vertically or horizontally. It is immediately obvious that me above-described solution is innovative: as we shall see herein below, the solution is based on he original concept of using the high force of attraction developed in these motors between the fixed block and the mobile block to guarantee correct positioning of both, though adopting only one mechanical sliding constraint. The flexibility of application and the structural simplicity of the solution proposed herein appear equally evident from the above description. Disclosure of Invention Further characteristics and advantages of the present invention will better emerge from the detailed description that follows of a preferred but non-exclusive embodiment of the invention, illustrated purely by way of non-limiting example in the accompanying figures of the drawings, in which: figure 1 is a partially-sectioned perspective view of the linear electric motor of the invention; figure 2 is a view in horizontal longitudinal section of the motor of figure 1; figure 3 is a perspective view relating to a traditional solution, of a linear motor applied to actuation of machine tools; figure 4 is a detailed view of a linear motor according to the present invention. With reference to figure 1, 10 denotes in its entirety a linear electric motor in a configuration which is suitable for application to machine tool drive. The motor is comprised within a U-shaped support structure 11, to a lateral wall 12 to which magnets 13 of the motor are fixed, while a mechanical guide 16 is fixed by screws 15 to an opposite wall 14. In the present embodiment two slides 17, 18 are constrained to and mobile on the mechanical guide 16. The coil block 20 of the motor is anchored to a plate 19, which plate 19 is solidly constrained to the two slides 17, 18. As we can observe in figure 2, the coil block 20 comprises a known lamination pack 21 made of a ferrous-magnetic material, shaped so as to form a series of cores 22 about which single coils 23 are wound (illustrated in figure 4). In figure 4 the longitudinal halfway-line of the coil block is positioned vertically, while in figure 1 it is horizontal. The motor of the invention can operate either vertically or horizontally. The perfect perpendicularity of the longitudinal halfway-line of the coil block 20 to the lie plane of the fixed magnets is guaranteed by the elevated force of attraction exerted by the magnets 13 on the coil block 20, thanks to the very strong magnetic field generated by the magnets themselves (in the cores 22 of the coil block 20). The coil block 20 is subject to a traction force, which is developed parallel to the axes of the cores 22 and is generated by the above-described constraining force of reaction of the guide 16. This traction is of sufficient entity to overcome (in the case a horizontal positioning illustrated in figure 1) the weight force tending to rotate the core block 20 downwards, about the axis of rotation constituted by the guide 16. The horizontal positioning in figure 1, or vertical positioning in figure 4, can therefore be adopted with no reservations about the operation of the motor. It can be chosen freely according to the architecture of the machine tool it is to be applied on and/or the workpiece-jig thereon. The U-shape adopted in the present embodiment for the support structure 11 affords a good level of protection, both of the motor (from the outside environment) and of the machine operator. Complete protection can be provided by using a support structure of the completely closed kind, on all four sides. This protects the motor from outside impurities, i.e. mechanically, and also limits the action of the magnetic field created by the fixed magnets with regard to the surrounding environment, when the material of the support structure 11 is made of a ferrous-magnetic material. Obviously the use of one solution or another depends on the specific applications, taking into consideration, for example, the direction of action of the tool or chuck, the reciprocal positioning of the actuator and the tool, or other variables. The solution shown in figure 1, for example, can be adapted for supporting and moving sheet steel, or a sheet of other material, in a horizontal direction, with application of special vertical attachments or similar to the plate 19. Frontal attachments could also be applied, for example a single or multiple shaft. Both the above solutions and the possible solution employing a closed structure on all four sides can also be used in a vertical position, with the tool or workpiece in a vertical plane. In all cases it is evident that with the solution herein proposed the moving coil block 20 exhibits decidedly less inertia in comparison to the moving block of figure 3; at the same time the energy needed to actuate the displacement is reduced, considering the smaller overall contact surface between the fixed and the moving part. Also, the total cost of actuation is reduced, as the invention is notably uncomplicated. These and other advantages connected to the motor of the invention are not compromised by any modifications or embodiment variations which might be different from the present description. The sliding between the guide 16 and the slides 17, 18, is achieved through ballbearing skates or similar low-friction elements. The means of attachment of the tools or workpieces to the plate 19 can obviously vary according to the applications. The shape of the guide 16 and the slides attached thereto can also be varied. If the length of the coil block 20 is limited, one slide 17 or 18 alone could be used on the guide 16; this would give the advantage of eliminating any possible misalignment of the slides 17 or 18, and consequent risks of sticking during motion.

Claims: Qai-ms. 1). A synchronous electric motor (10) comprising a containing support structure (11), a plurality of magnets (13) fixed to a wall (12) of the structure, a coil block (20), constrained to slide with respect to the plurality of magnets (13) on a single mechanical guide (16), the guide (16) being arranged on an opposite wall (14) with respect to the wall (12) on which the plurality of magnets (13) is fixed. 2). The synchronous linear electric motor of claim 1, wherein the coil block (20) is constrained to the guide (16) by means of a plate (19) to which plate (19) at least one slide (17) is fixed, which slide (17) is mobile along the guide (16). 3). The synchronous linear electric motor of claim 1 or 2, wherein the containing support structure (11) is U-shaped, the plurality of magnets (13) being anchored on the wall (12) of the support structure (11) which is opposite to the wall (14) on which the guide (16) is constrained. 4). The synchronous linear electric motor of any one of the preceding claims, wherein the plate (19) is a tool-holder or workpiece jig of a machine tool. 5). The synchronous linear electric motor of claim 3 or 4, wherein the opposite walls (12, 14) of the U-shaped support structure (11) can be arranged either vertically or horizontally. 6). The synchronous linear electric motor of claim 2, 3, 4 or 5, wherein the at least one slide (17 or 18) is slidably constrained to the guide (16) by a ballbearing coupling. 7). The synchronous linear electric motor of claim 1 or 2, wherein the containing support structure (11) is tubular and closed on all four sides. 8). The synchronous linear electric motor of claims 1 or 2, wherein the guide (16) is anchored to a wall (14) of the containing support structure (11) which wall (14) is aranged on an opposite side with respect to the wall (12) to which the plurality of magnets (13) is fixed.

Inventors: ANCESCHI STEFANO, ANCESCHI, STEFANO
Applicants: ANCESCHI STEFANO, MOTOR POWER COMPANY S R L, ANCESCHI, STEFANO, MOTOR POWER COMPANY S.R.L.
Application year: 2001
Main classification: H02K41
IPC codes: H02K41