Electric Actuator Assembly

Abstract

To provide an improved electric actuator assembly. An electric actuator assembly (20) having a support housing (28, 124), a first stator magnetic field generating assembly (26) fixed to the support housing (28, 124), and a movable armature assembly (22). The movable armature assembly (22) includes a plate assembly having a central support (150). The electric actuator assembly also includes a first armature magnetic field generating assembly configured to cooperate with the first stator magnetic field generating assembly to provide a magnetic field to provide linear motion of the movable armature assembly (22) along a reference axis, the first armature magnetic field generating assembly including first and second magnetic assemblies fixed to opposite sides of the central support.

Description

[Technical field]

[0001] The following discussion is merely provided for general background information and is not intended to be used as an aid in the scope of the present subject matter.

[0002] Aspects disclosed herein relate to actuators, and in particular to electromagnetic actuator designs that require the application of a linear force possibly in combination with the provision of a torque. [Background technology]

[0003] A particularly advantageous application of such actuators is in testing machines or apparatus used to test parameters and / or performance of materials, components, consumer products, and medical and other devices (i.e., test specimens).Typically, testing machines include one or more actuators for applying input loads and displacements. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE DISCLOSURE It is therefore an object of the present invention to improve an actuator of the type mentioned at the outset. [Means for solving the problem]

[0005] One general aspect includes an electric actuator having first and second stator magnetic field generating assemblies secured to a support housing. . electric machine a The assembly is disposed within a support housing and is aligned along a reference axis. Telephone machine a a first armature magnetic field generating assembly configured to cooperate with the first stator magnetic field generating assembly to provide a magnetic field to linearly move the assembly; and , electricand a second armature magnetic field generating assembly configured to cooperate with the second stator magnetic field generating assembly to provide a magnetic field to provide rotational motion of at least a portion of the armature assembly, the second armature magnetic field generating assembly being longer or shorter than the second stator magnetic field generating assembly.

[0006] Implementations may include one or more of the following features: The magnetic field generating assemblies may be formed of windings or magnets. In particular, the first stator magnetic field generating assembly includes windings, the first armature magnetic field generating assembly includes permanent magnets, the second stator magnetic field generating assembly includes windings, and the second armature magnetic field generating assembly includes windings.

[0007] The first armature field generating assembly can have a cylindrical or planar shape. The electric actuator assembly can include a bearing rotatably coupling the second armature field generating assembly to the first armature field generating assembly. The bearing can include a thrust bearing, an angular contact bearing, or a tapered bearing spaced apart from an additional bearing configured to react to lateral loads.

[0008] In one embodiment, the electric actuator assembly is configured such that the first armature magnetic field generating assembly includes a central support, and the first and second magnetic assemblies are secured to opposite sides of the central support. Optionally, the central support can be made of a softer material than the first and second magnetic assemblies. In one embodiment, the second armature magnetic field generating assembly is secured to the central support with fasteners, and the second armature magnetic field generating assembly is spaced apart from the central support to bear against the first and second magnetic assemblies. In another embodiment, the shaft extends into a bore extending along a longitudinal length of the first armature magnetic field generating assembly. The electric actuator assembly can include an end member secured to the central support with fasteners, and the end member is spaced apart from the central support to bear against the first and second magnetic assemblies. It should be noted that the central support refers to both the support shaft and the central support plate as described herein.

[0009] In yet another embodiment, the bearing supports the second armature field generating assembly on a shaft that extends at least partially within the first armature field generating assembly, while in another embodiment the shaft extends within a bore that extends along the longitudinal length of the first armature field generating assembly.

[0010] Another general aspect is a support housing and a support member secured to the support housing. Stator Winding Assembly and , electric machine a and an electric actuator assembly having . electric The armature assembly includes a plate assembly having a central support. The electric actuator assembly also has a reference axis. Telephone machine a To move the assembly in a straight line Stator Winding configured to cooperate with the assembly to provide a magnetic field Magnetic Including assembly, Magnetic The assembly includes first and second magnetic assemblies secured to opposite sides of a central support.

[0011] Implementations may include one or more of the following features: An electric actuator assembly, the central support being made from a softer material than the first and second magnetic assemblies. The electric actuator assembly includes end members secured to the central support by fasteners, the end members being spaced apart from the central support for support by the first and second magnetic assemblies. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of an exemplary testing machine having an actuator as disclosed herein. [Figure 1A] 1A-1D are perspective views of an actuator having different operating configurations. [Figure 2A] FIG. 2 is a schematic cross-sectional view of a first actuator. [Figure 2B] FIG. 4 is a schematic cross-sectional view of a second actuator. [Diagram 3] FIG. 2 is a perspective cross-sectional view of one embodiment of a first actuator. [Figure 4] FIG. 2 is a schematic cross-sectional view of a rotating component of an actuator having a first bearing arrangement; [Diagram 5] FIG. 13 is a schematic cross-sectional view of a rotating component of an actuator having a second bearing arrangement. [Figure 6] FIG. 13 is a schematic cross-sectional view of a rotating component of an actuator having a third bearing configuration. [Figure 7] FIG. 13 is a schematic cross-sectional view of a fourth actuator. [Figure 8] FIG. 13 is a schematic cross-sectional view of a fifth actuator. [Figure 9] FIG. 2 is a schematic perspective view of the actuator of FIG. 1. [Figure 10] 10 is a schematic cross-sectional view of the actuator of FIG. 9 taken along an axis parallel to the longitudinal axis of the actuator. [Figure 11] 10 is a schematic cross-sectional view of the actuator of FIG. 9 taken along an axis perpendicular to the longitudinal axis of the actuator. [Figure 12] FIG. 2 is a schematic cross-sectional view of an end of an actuator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present disclosure provides an electric actuator capable of linear and / or rotational displacement. The actuator can be used in a variety of applications. In one advantageous, but non-limiting, embodiment, the electric actuator is provided in a testing machine 10, as shown in FIG. 1. Generally, the testing machine 10 includes a crosshead 12 movable on a vertical column 14 by a crosshead drive (motor, reducer, drive belt, etc.), not shown, and the column 14 is supported by a base 15. An electric actuator 20 having the aspects described herein is attached to the crosshead 12 for movement on the vertical column 14. A housing 21 surrounds the electric actuator 20 and is attached to the crosshead 12 for movement therewith. A user interface 24 is provided to at least partially control the electric actuator 20 and the testing machine 10, although typically the testing machine 10 further includes a computing device for generating a graphical user interface (GUI) by which a user can further control the testing machine 10. In another embodiment, the testing machine 10 may be sized to be supported on a tabletop. In FIG. 1, the actuator 20 has a lower end to which an object, such as a test specimen, is operably coupled. In FIG. 1A, the actuator 20 has an upper end to which an object is operably coupled. Of course, the actuator 20 can be oriented as needed having regard to the application in which it is to be used. As will be appreciated by those skilled in the art, the components of the powered actuator 20 are sized as necessary to provide the desired load.

[0014] 2A and 2B show schematic diagrams of an embodiment of an electric actuator 20 having a linear motion component 25 and a rotational or torsional motion component 27. In the schematic diagram of FIG. Electric machine a The assembly includes a fixed first armature magnetic field generating assembly 22 having a magnetic field of alternating polarity suitable for operation as a linear motor. 32The first stator magnetic field generating assembly 26 is secured to a support housing 28 which may be secured, for example, to the crosshead 12 shown in FIG. 1 or to any other base or fixture depending on the manner in which the actuator 20 is to be used.

[0015] Located at an end, here the lower end, of the armature assembly 22 is a rotary or torsional motion component 27. The rotary or torsional motion component 27 includes a rotatable (partial and / or full rotation) and linearly movable armature 34 having a fixed second armature magnetic field generating assembly 31 with a magnetic field of alternating polarity suitable for operation as a rotary motor, and a second stator magnetic field generating assembly 30 fixed to a support housing 28. The rotatable armature 34 rotates about a central support shaft 33 on bearing assemblies 35A, 35B. In the illustrated embodiment, a support plate 36 generally represents a support structure that can be coupled to the bearings 35A, 35B to enable the armature 34 to rotate about the support shaft 33.

[0016] The winding controller 40 controls the armature assembly The winding controller 40 energizes at least one of the first armature magnetic field generating assembly 26 and the first stator magnetic field generating assembly 26 on the armature 22, and at least one of the second armature magnetic field generating assembly 31 and the second stator magnetic field generating assembly 30 on the armature 34. Thus, each energized magnetic field generating assembly includes windings in a configuration suitable for generating magnetic poles in a desired pattern suitable for operation as a linear or rotary motor. For example, in one embodiment, the winding controller 40 is capable of energizing the windings of the first stator magnetic field generating assembly 26 and the second stator magnetic field generating assembly 30, and energizing the windings of the armature 34. assembly First armature magnetic field generating assembly on 22 32and the second armature field generating assembly 31 on the second armature 34 may include permanent magnets. Similarly, in another embodiment, one or both armature field generating assemblies include windings that are energized by the winding controller 40 and one or both stator field generating assemblies include magnets. If one or both of the armature field generating assemblies include windings, appropriate contacts are provided to allow excitation in the presence of movement of the respective armatures.

[0017] By way of example only, if first stator magnetic field generating assembly 26 and second stator magnetic field generating assembly 30 each include a winding, winding controller 40 may control one or more stator windings of linear motion component 25 to achieve the desired motion of armature assembly 22 relative to support housing 28. Lines and , one or more stator windings 30 of the rotary or torsional motion component 27, and in particular one or more stator windings 31 of the linear motion component 25. Line Controlled excitation is Armature This causes axial displacement (up and down in the views of FIGS. 2A and 2B ) of the assembly 22, and in particular the rotatable armature 34. If it is also desired to rotate the rotatable armature 34, the winding controller 40 energizes one or more stator windings 30 to rotate the armature 34 about the support shaft 33.

[0018] With reference to either of Figures 2A and 2B, the second armature magnetic field generating assembly 31 on the armature 34 and the second stator magnetic field generating assembly 30 have different axial lengths. This structure allows the magnetic fields of the armature 34 and the stator 30 to interact with each other, thereby causing the armature 34 to rotate, even if the axial position of the armature 34 is displaced by the linear motion component 25. In Figure 2A, the second armature magnetic field generating assembly 31 on the armature 34 is axially longer than the second stator magnetic field generating assembly 30, while in Figure 2B, the second armature magnetic field generating assembly 31 on the armature 34 is axially shorter than the second stator magnetic field generating assembly 30. In an advantageous embodiment of the type shown in Figure 2A, the second armature magnetic field generating assembly 31 on the armature 34 includes magnets and the second stator magnetic field generating assembly 30 includes windings. This embodiment is advantageous because it will generally be less expensive due to the reduced amount of windings in the embodiment of FIG. 2A compared to the similarly configured embodiment of FIG. 2B.

[0019] It is also noted that the shape of the armature in the linear motion component 25 may be tubular, as shown in Figure 2A, or in the form of a movable plate, as shown in Figure 2B. The armature of the linear motion component 25 is guided, for example, by a linear guide, indicated diagrammatically at 29. In the embodiment of Figure 2B, the first armature field generating assembly on the armature and the first stator field generating assembly are not shown due to the schematic cross-sectional view provided. The first armature field generating assembly is attached to plate members 37 (one of which is shown) on either side of the linear guide 29.

[0020] 3 is a cross-sectional view of an exemplary rotatable or torsional component 27 configured in a manner similar to that shown generally in FIG. 2A. The rotatable or torsional component 27 includes a support collar 50 fixed to the crosshead 12 or integrally formed therewith as a single unitary structure. The support collar 50 supports the second stator field generating assembly 30. The armature 34 includes an end mounting plate or member 52 for applying a force to, for example, a test specimen. In the illustrated embodiment, the end member 52 includes a cylindrical wall 54 of sufficient diameter to overlap the support collar 50 for various linear positions of the armature 34 relative to the second stator field generating assembly 30, in one embodiment including a winding. The cylindrical wall 54 prevents contaminants or other debris from contacting the armature 34.

[0021] In one embodiment where the individual magnets are coupled to the second armature field generating assembly on the armature 34, the end member 52 is secured to one end of the cylindrical support 60 of that assembly. At the opposite end from the end member 52, an upper mounting ring 62 is secured to the cylindrical support 60 of the armature 34. The support shaft 33 extends through the armature 34 and allows the cylindrical support 60 of the armature 34 to rotate relative to the support shaft 33 by means of bearing assemblies, generally designated 35A, 35B, mounted thereon. In this embodiment, each bearing assembly 35A, 35B includes an axial thrust bearing 70 configured to transmit axial forces through the support shaft 33 and the cylindrical support 60 of the armature 34. The axial thrust bearings 70 may include, for example, needle bearing assemblies. The thrust bearings 70 are operatively coupled between the cylindrical support 60 and a support plate 74. A fastener such as a nut 75 engages threads on the support shaft 33 to hold the armature assembly together.

[0022] At the upper end of the armature 34, a thrust bearing 70 is operatively connected between the cylindrical support 60 and an annular shoulder 80 provided on the support shaft 33. Considering that the thrust bearing 70 is generally not suitable for supporting lateral loads perpendicular to the axis of rotation, an additional bearing assembly 72 suitable for acting on such lateral loads is also provided. Without being limited thereto, for example, the additional bearing assembly 72 may include a roller bearing. The inner race of the additional bearing 72 is fixed to the support shaft 33 and the outer race is fixed to the cylindrical support 60, by way of example only, using a retainer ring 86 which secures the outer race to an annular flange 88 of the cylindrical support 60.

[0023] Preferably, the components of the rotational or torsional motion component 27 are axially preloaded from the linear motion component 25 with a load greater than the maximum axial load applied, for example, by the actuator 20 to the test specimen, thereby maintaining accurate linear positioning of the armature assembly 22, armature 34 and end member 52. In the illustrated embodiment, fasteners 90 (some of which are shown) secure the end member 52 to the end of the cylindrical support 60, and a fastener 92 similar to fastener 92 secures the mounting ring 62 to the end of the cylindrical support 60 opposite the end member 52. Similarly, a nut 75 preloads the thrust bearing 70 to exceed the axial force applied by the actuator 20. In the illustrated embodiment, fasteners, one of which is shown at 77, attach the support shaft 33 to the end 104 of the linear motion armature.

[0024] The rotational sensor is operatively configured to provide an output signal indicative of the rotation of the armature 34. The rotational sensor can take many forms. In the illustrated embodiment, an encoder is shown with an encoder ring 102 having position markings mounted on and rotating with the mounting ring 62. The sensing components of the encoder, not shown, are suitably mounted to sense the movement of the encoder ring 102. Optionally, or alternatively, an analog resolver can be provided to measure the absolute rotational position of the armature 34. In the illustrated embodiment, the resolver includes a fixed component 106 mounted in a cavity in the support shaft 33, with a rotating element 108 extending through a bore 110 in the support shaft 33 and secured to the end member 52 with a fastener 81 such that the rotating element 108 rotates with the rotation of the armature 34. Each of the illustrated rotational sensors moves linearly with the armature 34. In alternative embodiments, the rotational sensors may be mounted to the ends of the armature 34, if desired, rather than being positioned as shown.

[0025] 4, 5 and 6 show schematics of other bearing configurations for the torsional motion component 27, with the same reference numbers being used for components having the same functions as above. The example of FIG. 4 shows schematic bearings 35A and 35B that allow rotation of the support 60 relative to the spindle shaft 3. A nut 75 fixed to the support shaft 33 preloads the bearings 35A and 35B. The embodiment of FIG. 5 is similar to the embodiment of FIG. 4, with the bearings 85A and 85B being angular contact bearings. The embodiment of FIG. 6 is similar to the embodiment of FIG. 4, with the bearings 87A and 87B being tapered roller bearings. These embodiments are further exemplary bearing configurations and assemblies that may be used but should not be considered limiting. Any of these bearings can be stacked in series on top of each other for additional load-bearing capacity.

[0026] Figures 7 and 8 allow for both linear and rotary motion. Electricity machine a2A and 2B , there is shown another configuration of an electric actuator having an armature assembly 93. Referring first to the embodiment of FIG. 7 , an electric actuator 91 includes an armature assembly 93 that is movable relative to a support structure 95. The electric actuator 91 includes a linear motion component 97 and a rotational or torsional motion component 99. Unlike the previous embodiment in which the rotational or torsional motion component directly supports an end member 101 that is used to apply a load to a test specimen or other part, the rotational or torsional motion component 99 is attached to an opposite end of the armature assembly 93. It should be noted that while the rotational or torsional motion component 99 is shown generally, it may include any of the features discussed above, particularly those described with respect to FIGS. 2A and 2B .

[0027] A support shaft 111 is mounted and configured to rotate within the armature assembly of the linear motion component 97, with a rotary or torsional motion component 99 attached to the opposite end of the end member 101. An upper bearing assembly 103A and a lower bearing assembly 103B enable rotation of the support shaft 111 relative to the armature assembly of the linear motion component 97. Generally, at least one bearing assembly is preloaded to sustain a maximum axial load applied by the actuator 91, for example to a test specimen. In the illustrated exemplary embodiment, the lower bearing assembly 103B includes thrust bearings 105A and 105B and a radial or lateral load support bearing 107. A fastener 109, such as a nut, threadably engages the end of the support shaft 111 and further engages spring elements 113, such as Bellevue type washers, which apply a preload force to the thrust bearings 105A and 105B. Upper bearing 103A may include radial or lateral load supporting bearings that allow support shaft 111 to rotate relative to the armature of linear motion component 97. Linear bearings, indicated generally at 115, guide armature assembly 93 for linear motion relative to support structure 95. A suitable armature and stator field generating assembly, not shown but functionally similar to that shown in FIG. 2A, is attached to armature assembly 93 and support structure 95 to control the linear motion of armature assembly 93.

[0028] A portion of another motorized actuator assembly 131 is shown diagrammatically in FIG. 8. In this embodiment, the rotary or torsional motion component 133 directly supports the end member 135. Unlike the embodiment of FIG. 7, in which the support shaft 111 passes completely through a bore in the armature of the linear motion component 97, the support shaft 137 extends only partially into the bore 139 of the armature 141 of the linear motion component 143. A single bearing assembly 145 allows the support shaft 137 to rotate. In the illustrated exemplary embodiment, the bearing assembly 145 is similar to the bearing assembly 103B and includes thrust bearings 151A and 151B and radial or lateral load support bearings 153. Any of the bearing assemblies shown in FIGS. 4-6 can be used. A fastener 155, such as a nut, threadably engages the end of the support shaft 137 and further engages a spring element 157, such as a Bellevue washer, which applies a preload force to the thrust bearings 151A and 151B. A rotational sensor 161 optically monitors an indicator 163 mounted on the support shaft 137 to measure its rotational position. Also shown are the armature and stator field generating assemblies having the reference numbers identified in Figure 2A.

[0029] 9, 10 and 11, the electric actuator 20 includes a support structure 120 including opposing side rails 122 and an upper cross member 124 joining the ends of the side rails 122 together. The side rails 122 and the cross member 124 may comprise separate elements fastened together with fasteners or welding. In further embodiments, the side rails 122 and the cross member 124 are integrally formed from a single unitary structure. The ends of the side rails 122 opposite the cross member 124 are joined to the cross head 12. In a preferred embodiment, the cross head 12 includes a recess 130 through which the side rails 122 extend and is attached to the underside 132 of the recess 130. In this manner, the overall height of the assembly can be reduced.

[0030] 10 and 11, the armature assembly 22 of the electric actuator 20 includes a plate assembly 138 having a major surface that includes magnets, and a planar stator winding assembly 142. The stator winding assembly 142 is mounted to the support structure 120 in an opening 144 defined by opposing side rails 122, cross members 124 and crosshead 12 on each side of the plate assembly 138 in a preferred embodiment.

[0031] The plate assembly 138 includes a central support plate 150 preferably made of a lightweight material such as aluminum. Linear bearings 152 connect side flanges 154 of the central support plate 150 to the side rails 122 to provide guided linear motion of the plate assembly 138 relative to the side rails 122. Magnetic assemblies 156 are secured to both sides of the central support plate 150. Each magnetic assembly 156 includes a backplate 158 to which a magnet (not shown) is coupled. Fasteners 160 secure each backplate 158 to the central support plate 150. Optionally, cooling plates 162 having internal channels 164 for cooling fluid can be secured to both sides of the support structure 120 and positioned proximate at least each stator winding assembly 142 to remove heat therefrom.

[0032] The structure of the plate assembly 138 is particularly advantageous. Generally, the structure is a "sandwich" structure that includes a central support plate 150 and magnet backing plates 158 attached to either side of the central support plate 150. Generally, it is important that the plate assembly 138 is very stiff. The central support plate 150 is made of a relatively lightweight material, such as aluminum, that does not have a very high bending stiffness, yet because of the magnet backing plates 158 attached to the opposite sides, the overall structure is very stiff due to its geometry.

[0033] To prevent uncontrolled movement of the armature assembly 22 when power is removed, a brake assembly 170 (FIG. 9) is configured to block or stop movement of the armature assembly 22 in the event of a power loss. The brake assembly 170 includes at least one caliper assembly 172 having spaced apart plates that form a gap therebetween when power is applied to the electric actuator 20. In the illustrated embodiment, two caliper assemblies 172 are provided. Each caliper assembly 172 is secured to the support structure 120, here one of the side rails 122, between openings 174 provided in the side rails 122. A brake band 178 is coupled at both ends to the central support plate 150, where mounting brackets at the ends of the brake band 178 extend through the openings 174. The brake band 178 is attached to the central support plate 150 such that the brake band 178 is substantially vertical and disposed substantially parallel to the linear motion of the armature assembly 22.

[0034] As the armature assembly 22 moves along a linear path, the brake band 178 also moves along a parallel path. While power is applied to the electric actuator 20, the brake band 178 does not contact the caliper plates, and therefore the caliper plates do not provide resistance to the brake band 178 when power is applied to the electric actuator 20. However, when power is removed, the caliper assembly 172 moves its plates towards each other. As the plates move towards each other, they frictionally engage the brake band 178, thus causing the armature a Prevent assembly 22 from moving any further.

[0035] It should be noted that the rotational or torsional motion component 27 of the electric actuator 20 is not necessary. Rather, an electric actuator having only a linear motion component 25 may be desirable in some applications. In such an embodiment, the configuration of the linear motion component 25 may include the structure described above. Since there is no rotational or torsional motion component in such an embodiment, the support shaft 33 includes a standoff 190 as shown in FIG. 10. The end member 52 is fixed to or integrally formed with the end of the standoff 190 from a single unitary structure using suitable fasteners. Preferably, the standoff 190 is attached to the plate assembly 138 in a manner that does not create backlash. In other words, the standoff 190 is preloaded when attached to the plate assembly 138. However, instead of attaching the standoff 190 directly to the center support plate 150 so that the center support plate 150 carries the axial load, the standoff 190 engages an end face of the backplate 158 to apply the axial load directly to the armature component having the magnets. 12, a space 200 is provided between the end of the standoff 190 and an end face 202 of the central support plate 150. Suitable fasteners 204 attach the standoff 190 to the central support plate 150, such as by using bolts that extend upwardly within the standoff 190 and engage threaded holes 208 in the central support plate 150. The bolts 204 are tightened until a desired preload force is achieved that is greater than the axial force exerted by the actuator 20 during actuation.

[0036] It should be noted that in a similar manner to attaching the standoffs 190 to the central support plate 150 as described above, this technique can also be used to attach the support shafts 33 of the rotation and torsion components 27 so that they engage the backplate 158 rather than the central support plate 150. Also, a space 200 is provided between the end faces of the support shafts 33 and the end faces of the central support plate 150. Suitable fasteners are used to secure the support shafts 33 to the central support plate 150. In one embodiment, two bolts are provided. The bolts are located on either side of the rotation axis and extend upward to engage threaded holes in the central support plate 150.

[0037] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention.

Claims

1. A support housing; a stator winding assembly secured to the support housing; an armature assembly; Equipped with The armature assembly includes: a plate assembly having a central support; a magnetic assembly secured to the central support for linear movement therewith and configured to provide a magnetic field in cooperation with the stator winding assembly to linearly move the armature assembly along a reference axis, the magnetic assembly comprising first and second magnetic assemblies secured to opposite sides of the central support; Equipped with the central support is made of a softer material than the first and second magnetic assemblies; an electric actuator assembly including end members secured to said central support by fasteners, said end members spaced from said central support for support by said first and second magnetic assemblies;

2. A support housing; a stator winding assembly secured to the support housing; an armature assembly; Equipped with The armature assembly includes: a plate assembly having a central support; a magnetic assembly secured to the central support for linear movement therewith and configured to provide a magnetic field in cooperation with the stator winding assembly to linearly move the armature assembly along a reference axis, the magnetic assembly comprising first and second magnetic assemblies secured to opposite sides of the central support; Equipped with an electric actuator assembly including end members secured to said central support by fasteners, said end members spaced from said central support for support by said first and second magnetic assemblies;

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