Patent Description:
The invention relates to an electromagnetic actuation assembly for operation in a powertrain assembly for a vehicle movable using electric motive power, in particular in accordance with the preamble of claim <NUM>. More particularly, the invention relates to an electromagnetic actuation assembly using magnets that are axially secured within the stator housing.

Electromagnetic actuation assemblies are utilized throughout industry. An electric current is sent through a conductive coil of wire to create a magnetic field. This magnetic field acts on a translator to move it in one direction or two directions, depending on the design. A lightweight, compact electromagnetic actuation assembly utilizing a simplified design is necessary as more and more devices are powered by electricity. Electromagnetic actuation assemblies of the type identified above are known from, e. , <CIT>, <CIT>, or <CIT>.

An improved linear actuation assembly is defined by the features of claim <NUM>. A linear actuation assembly includes an electromagnetic coil configured to allow electric current to pass therethrough in either direction creating magnetic flux based on the electric current and its direction. The electromagnetic coil defines a center axis, an inner diameter, and first and second sides. A first set of magnets is disposed in end-to-end relation adjacent the first side of the electromagnetic coil at the inner diameter thereof. A second set of magnets is disposed in end-to-end relation adjacent the second side of the electromagnetic coil about the inner diameter thereof. The linear actuation assembly further includes at least one translator disposed adjacent the first and second sets of magnets opposite the electromagnetic coil. The at least one translator is latchable between a first position adjacent the first set of magnets and a second position adjacent the second set of magnets in response to the magnetic flux and the direction in which the electric current is flowing.

Advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:.

For purposes of this discussion, elements will be identified by reference characters, typically reference numerals. There are several embodiments shown in the Figures that will be described in detail below. For purposes of simplicity, similar elements between the various embodiments will be offset by the hundreds digit, unless otherwise indicated. If an element has characteristics that are different from one embodiment to another, those differences will be discussed when introducing the same element for the new embodiment.

Referring to <FIG>, one embodiment of a linear actuation assembly is generally indicated at <NUM>. The linear actuation assembly <NUM> uses a magnetic field created by a current to physically move an element axially in one or two linear directions.

The linear actuation assembly <NUM> includes an electromagnetic coil <NUM> wrapped around a bobbin, generally indicated at <NUM>. The electromagnetic coil <NUM> includes a conductive wire <NUM> wrapped about a bobbin base <NUM> and between two bobbin side walls <NUM>, <NUM>. In this embodiment, the bobbin <NUM> is fabricated of a non-ferrous material, such as a thermoplastic. It should be appreciated by those skilled in the art that the bobbin <NUM> extends through a continuous loop. In the embodiment shown, the continuous loop is circular, defining a center axis <NUM>, as is best seen in <FIG>. The electromagnetic coil <NUM> defines an inner diameter <NUM>, which is held in place by the bobbin base <NUM> and first <NUM> and second <NUM> coil sides defined by the two bobbin side walls <NUM>, <NUM>.

A first set of magnets <NUM> are disposed adjacent the first side <NUM> of the electromagnetic coil <NUM> at the inner diameter <NUM> thereof. The bobbin base <NUM> extends between the first set of magnets <NUM> and the inner diameter of the electromagnetic coil <NUM>. Each of the first set of magnets <NUM> extend along a portion of the electromagnetic coil <NUM> in an end-to-end manner to complete the continuous loop created by the electromagnetic loop. through an arc, with the total number of the first set of magnets <NUM> completing the continuous loop defined by the electromagnetic coil <NUM>. In the embodiment shown, each of the first set of magnets <NUM> extend through an arc, the total of which defines a circle have a diameter substantially equal to the inner diameter of the electromagnetic coil <NUM>.

A second set of magnets <NUM> are disposed adjacent the second side <NUM> of the electromagnetic coil <NUM> at the inner diameter <NUM> thereof. The bobbin base <NUM> extends between the second set of magnets <NUM> and the inner diameter of the electromagnetic coil <NUM>. Each of the second set of magnets <NUM> extend along a portion of the electromagnetic coil <NUM> in an end-to-end manner to complete the continuous loop created by the electromagnetic loop. through an arc, with the total number of the second set of magnets <NUM> completing the continuous loop defined by the electromagnetic coil <NUM>. In the embodiment shown, each of the second set of magnets <NUM> extend through an arc, the total of which defines a circle have a diameter substantially equal to the inner diameter of the electromagnetic coil <NUM>. The electromagnetic coil <NUM>, together with the bobbin <NUM>, the first set of magnets <NUM>, the second set of magnets <NUM> and the ring <NUM>, discussed subsequently, are collectively referred to as a stator <NUM>.

The linear actuation assembly <NUM> includes a translator, generally indicated at <NUM>. The translator <NUM> is disposed adjacent the first <NUM> and second <NUM> sets of magnets. Said another way, the first <NUM> and second <NUM> sets of magnets and the ring <NUM> are disposed between the electromagnetic coil <NUM> and the translator <NUM>. At least a portion of the translator <NUM> is fabricated from a ferromagnetic material such that it receives forces due to the magnetic field created by the first <NUM> and second <NUM> sets of magnets and the current flowing through the electromagnetic coil <NUM>. The description of the magnetic field and how it acts on the translator <NUM> will be discussed in greater detail subsequently. The translator <NUM> typically has a hollow center (not shown) allowing something to extend therethrough, such as a shaft, a hub, etc..

The translator <NUM> is shown to have a plunger <NUM> extending out therefrom parallel to the center axis <NUM>. The translator <NUM> will have at least one plunger <NUM> and it is contemplated that the translator <NUM> will have a plurality of plungers <NUM> (even though only one is shown in any given Figure). When the translator <NUM> has a plurality of plungers <NUM>, they are spaced equidistantly about a translator edge <NUM> of the translator <NUM>. The translator edge <NUM> will complement the continuous loop created by the bobbin <NUM>. Not all the translator <NUM> needs to be ferromagnetic. However, at least a translator sleeve <NUM> is ferromagnetic. The translator sleeve <NUM> may be a continuous layer about the translator <NUM> or it can be discreet pieces fixedly secured to the translator <NUM> spaced equidistantly thereabout. In the embodiment shown, the translator sleeve <NUM> is a full cylinder having a circular cross section.

The plunger <NUM> has a pointed distal end <NUM>. It should be appreciated by those skilled in the art that the distal end <NUM> of the plunger <NUM> may have a shape other than pointed without adding to the disclosure set forth herein. The plunger <NUM> is fixedly secured to the translator <NUM> such that it moves linearly, parallel to the center axis <NUM>.

The ring <NUM> extends between the two sets of magnets <NUM>, <NUM>. The ring <NUM> may be unitary in construction or it may consist of a composite of ringlets that form the ring <NUM>. In the embodiment shown in <FIG>, the ring <NUM> is unitary in construction and is fabricated from a non- ferromagnetic material. In other embodiments, the ring <NUM> may be fabricated from ferromagnetic material. Alternatively, the ring <NUM> may be fabricated from one or more ringlets, wherein ferromagnetic ringlets and non-ferromagnetic ringlets may be used together to form the ring <NUM>. In the embodiment shown in <FIG>, the ring <NUM> extends between the bobbin base <NUM> and the translator <NUM>. Laterally, the ring <NUM> extends between the first <NUM> and second <NUM> sets of magnets.

Referring to <FIG>, a magnetic field line plot, also referred to as a magnetic flux line plot, is shown in the cross-sectional view as it flows through the linear actuation assembly <NUM>. For purposes of this illustration, the linear actuation assembly <NUM> a circularly symmetric assembly, with the axial movement of the translator <NUM> (also the line of axial symmetry) shown in the x- direction. The radial direction is shown as the y-direction. Since this machine is completely symmetric about its axis, operation (linear motion of the translator <NUM>) does not depend on any given rotational position of the translator <NUM> with respect to the center axis <NUM>. Thus, the linear actuation assembly <NUM> can operate with the translator <NUM> either when it is rotating or when it is not rotating.

The stator <NUM>, shown in cross-section, includes a stator cover <NUM>, fabricated of ferromagnetic material, enclosing the single electromagnetic coil <NUM>, the first <NUM> and second <NUM> sets of magnets, separated by the continuous rectangular cross section ferrous metal (steel/iron) ring <NUM>. The stator cover <NUM> is open in that the first <NUM> and second <NUM> sets of magnets, along with the ring <NUM> are exposed to the translator <NUM>. In a practical application, the ring <NUM> is fixed secured to the bobbin <NUM> (not shown in <FIG> for purposes of simplicity), which is mostly non-ferrous material.

The magnetic field lines <NUM> that are shown in <FIG> have been determined by a commercial magnetic finite element analysis (MFEA) software package. The magnetic field solution shown in <FIG> is for the case of no coil current in the electromagnetic coil <NUM>, and the axial position of the translator <NUM> is somewhat past, to the right of, the "neutral" or center position. Translator locations on this side of the center position will be termed "on" side locations, as it is assumed that translator movement to this side of center will turn the motor mechanical load (typically a clutch mechanism) "on. " It is further assumed that movement of the translator <NUM> to positions left of center will turn the load "off. " Note that the structure of the stator <NUM> shown in <FIG> is depicted as symmetrical about the center, x=<NUM>, axial position. It should be appreciated by those skilled in the art that the linear actuation assembly <NUM> need not be symmetric, and in certain applications would in fact lead to undesired operation due to an unbalanced magnetic material environment surrounding or near the location of the linear actuation assembly <NUM> within its application housing. The remainder of the discussion of the linear actuation assembly <NUM> will assume a symmetric construction, as a simplification for explanation purposes. In addition, the discussion will assume the absence of any neighboring magnetic material bodies.

The magnetic field lines <NUM> are focused or concentrated in closed paths with the majority of the lines flowing through the first <NUM> and second <NUM> sets of magnets, the ring <NUM> and the translator <NUM>. In general, these lines <NUM> of force tend to flow in paths with a majority of iron content due to the ease of the magnetic field production within the iron material. Examining the field lines that do cross the air gap between the stator <NUM> and the translator <NUM>, it can be seen that some of them follow a path, to or from the first set of magnets <NUM> to the translator <NUM>, and some of them follow a path to or from the second set of magnets <NUM> to the translator <NUM>. Flux lines from the second set of magnets <NUM> dominate since the translator <NUM>, in the position shown, is closest to the second set of magnets <NUM>. Because the translator <NUM> is toward the right side in this Figure, there are more magnetic field lines <NUM> to the right, rendering a net force pulling the entire translator <NUM> to the right Shearing stress to both the right side and the left side is seen in <FIG>, which can be matched to the distribution of air gap field lines which "lean" to both the right and left along the air gap. However, the total force (the integrated shear over the air gap x-directed extent surface) shows a net force on the translator <NUM> to the right, for this particular translator position.

If the translator <NUM> is swept from left to right, and the magnetic field lines <NUM> are recalculated at each position, the a "slide show" of the magnetic field line production due to the translator <NUM> and sets of magnets <NUM>, <NUM> as a function of translator position can be produced. Such a presentation would show that when the translator <NUM> is located to the left of the center or neutral position, the dominant number of air gap crossing flux lines flow radially up and to the left of the position of the translator <NUM>. As such, a left-directed force would be imposed on the translator <NUM>. And conversely, as is the case shown in <FIG>, when the translator <NUM> is located to the right of the center position, the majority of air gap flux line flow is radially up and to the right, so a right-directed force on the translator <NUM> is expected. A plot of the MFEA computed total axial force on the translator <NUM> as a function of axial position, given in pounds, is shown in <FIG>. As can be seen, if the translator <NUM> is positioned to the right of center, it is pushed, due to the second set of magnets <NUM>, to the right, and if positioned to the left of center, it is pushed further to the left due to the first set of magnets <NUM>. This is referred to as the "latching" action of the linear actuation assembly <NUM>. The exact center position, where the left-right pushing force exactly balances to zero, is an unstable equilibrium point, at which even minute movements will result in forces tending to push the translator <NUM> away for the center position. The two other points shown, near the two axial ends of the stator <NUM>, where the net translational force also passes through a zero value, are stable equilibrium points, where minute movements result in position restoring force production. In practice, there are non-ferrous material mechanical stops placed in the translator axial movement path that limit the extent of the translator travel path to values approximately between the locations of the maximum force production, referred to as the "latch" points of the linear actuation assembly <NUM>. As can be seen in the example shown in <FIG>, the "on" latch point is approximately at a translator x-position of <NUM>, and the "off" latch point in this balanced structure is at x = -<NUM>. The distance between the two latch points is the maximum travel or "strake" length of the linear actuation assembly <NUM>.

Axial Translation Forces in the Linear Actuation Assembly <NUM> with Electric Current.

Consider the same example of the linear actuation assembly <NUM> as shown in <FIG>, but with the addition of steady electrical current in the electromagnetic coil <NUM>. A typical MFEA solution for the magnetic field lines <NUM> for this situation is shown in <FIG>. A steady current, assumed uniformly distributed in the winding cross section, is assumed to flow into the page, away from the viewer, for the portion of the wires of the electromagnetic coil <NUM> shown in <FIG>. The axial magnetization direction of the sets of magnets <NUM>, <NUM> does not matter Uust as long as they were the opposite of each other) in the pure latching force situation of <FIG>, but it matters very much in this case of "dual" magnetic excitation as a result of current passing through the electromagnetic coil <NUM> in one direction or the other.

For the case shown in <FIG>, the axial magnetization of the first set of magnets <NUM> is stipulated to be to the right, in the plus x-direction, and the axial magnetization of the second set of magnets <NUM> is stipulated to be to the left, in the minus x-direction. The direction or polarity of the magnetic lines of force in their respective closed "flow" paths, due to the magnets alone, would then be dictated by the particular source set of magnets <NUM>, <NUM>. The polarity direction of the circulating magnetic lines of force due to an electric current is given by the "right hand rule," which states that if the thumb of one's right hand is made to point in the direction of the current flow in a wire, or a coil of wires, with the fingers encircling the cross section of the wire or the coil, the magnetic field lines or flux lines due to the current also encircle the wire or coil cross section and have a circulating direction in the same direction as the curling fingers. In <FIG>, the magnetic flux lines <NUM> due the current in the electromagnetic coil <NUM> in the direction away from the viewer and into the page would flow in the clockwise direction.

The net or total production of magnetic field lines, as shown in <FIG>, is due to all three magnetic sources, the current in the electromagnetic coil <NUM> and the two sets of magnets <NUM>, <NUM>, resulting in regions in the linear actuation assembly <NUM> where the individual sources of magnetic excitation enforce and add with each other; and there are regions where the excitation sources buck or subtract from each other. Since the coil current is assumed to be reversible (plus or minus), the dual source enforcement and bucking regions within the linear actuation assembly <NUM>, and most importantly between the sets of magnets <NUM>, <NUM>, can be changed or adjusted with respect to each other. This is the basis of the controllable/reversible direction of the linear actuation assembly <NUM>.

The flow of the majority of the flux lines <NUM> produced by the sets of magnets <NUM>, <NUM> alone resulted in a net force on the translator <NUM> to the right for the position of the translator <NUM> shown in <FIG>. But for the same translator position, with the addition of the stipulated coil current, stipulated both in magnitude and direction, the case shown in <FIG>, the left/right leaning of the flow of the majority of air gap the flux lines <NUM> has shifted. The majority of the flux lines <NUM> now cross the air gap leaning to the left with respect to the translator <NUM>. Thus, the net translational force on the translator <NUM> also shifts to the left. If the translator <NUM>, by means of a "stop" was, previous to the introduction to coil current, latched in the right hand side "on" position and held there against the "stop" by the continuous "latching" force due to the second set of magnets <NUM>, introduction of coil current as in the case of <FIG> would then overpower the latching force to the right and produce a net motoring force to the left, inducing the translator <NUM> to move to the left. And if the translator <NUM> does move and subsequently crosses over the center or neutral position, the current could be removed, as the now left directed latching directed force, due to the first set of magnets <NUM> alone, will enforce the remaining left movement to a similar off- state latching position to the left of the center or neutral position.

The results for the total magnetic flux lines <NUM> within the linear actuation assembly <NUM> with the same coil current drive as in the case shown in <FIG>, as a function of the axial position of the translator <NUM>, similar to that given for the previous case of magnet excitation alone, is given in <FIG>. These solutions show that for the level of coil current assumed the net force on the translator <NUM> is always negative, to the left, no matter the assumed value of the position of the translator <NUM>. This particularly the case for translator movement limited to the strake length distance between the "on" and "off" latch points, that is, positions between plus and minus <NUM> for the example shown. Finally, since the linear actuation assembly <NUM> considered here is symmetric with respect to the translator center position, the results given in <FIG> for the latch- off direction current drive, apply also for a reverse or latch-on direction current drive, simply by reversing both the translator position (i.e., the sign of x) and the net drive force. A combined plot for both of the current drive cases and the passive case (zero current drive) is given in <FIG>.

Referring to <FIG> and <FIG>, one embodiment of the stator <NUM> is shown in perspective view. The stator <NUM> includes the steel casing or cover <NUM> including an <NUM>-plate <NUM> and in L-plate <NUM>. The L-plate <NUM> includes a side plate <NUM> and a cover plate <NUM> designed to cover the electromagnetic coil <NUM> in the bobbin <NUM>. The two plates <NUM>, <NUM> have inner diameters <NUM>, <NUM> matching the inner diameter <NUM> of the electromagnetic coil <NUM> and are fabricated from a ferromagnetic material. In one embodiment, the ferromagnetic material is steel. The two plates <NUM>, <NUM> complement each other to form three sides of the stator case <NUM> for the stator <NUM> leaving the bobbin base <NUM> exposed. The two plate <NUM>, <NUM> forma cylinder to house the bobbin <NUM> therein and allow the translator <NUM> and any other mechanical parts that are not a part of the linear actuation assembly <NUM> that happened to extend therethrough. The ring <NUM> can be seen exposed to where the translator <NUM> would be positioned. The <NUM>-plate <NUM> includes fastening flanges <NUM> designed to secure the stator <NUM> to a transmission housing <NUM>, discussed subsequently. The <NUM>-plate <NUM> also includes a plurality of recesses <NUM>, designed to receive a plurality of extensions <NUM> extending out from the L-plate <NUM>.

Referring to <FIG>, an alternative embodiment of the linear actuation assembly <NUM> is shown wherein the primary difference between this stator <NUM> and the stator <NUM> of the prior embodiment is that the first set of magnets <NUM> includes magnets that are larger than the magnets of the second set of magnets <NUM>. Having different size magnets between the first <NUM> and second <NUM> sets of magnets may be done for a couple of reasons. One reason they would be different sizes is because the linear actuation assembly <NUM> may have a default latched position that would require the plunger <NUM> to be in a particular position when there is no current passing through the electromagnetic coil <NUM>. A second reason they would be different sizes would be that the sizes were designed to compensate neighboring electromagnetic forces that may be generated by other components designed to be adjacent the linear actuation assembly <NUM>.

Referring to <FIG> and <FIG>, and an enlarged view of the bobbin <NUM> is shown to include a first channel <NUM>. The first channel <NUM> receives the first set of magnets <NUM> therein. Each of the first set of magnets <NUM> extends through an arc such that the first set of magnets <NUM> will form a circle within the first channel <NUM>. In the embodiment shown, the first channel <NUM> includes a plurality of partitions <NUM> that separate each of the first set of magnets <NUM>. The bobbin <NUM> includes a second channel <NUM> having partitions <NUM> (one shown in <FIG>). Although not shown, the second channel <NUM> also includes the partitions that will separate each of the second set of magnets <NUM>. In one embodiment, the two bobbin sidewalls <NUM>, <NUM> are sonically welded to each other and to the ring <NUM>. It should be appreciated by those skilled in the art that the fabrication of the bobbin <NUM> with the ring <NUM> may be completed using any method known in the art.

Referring to <FIG>, wherein like primed reference characters represent similar elements, two linear actuation assemblies <NUM>, <NUM>' are shown fixedly secured to each other and to a device <NUM> being operated on by the linear actuation assembly <NUM> (the linear actuation assembly 1O' operates on a device not shown in these Figures and is only shown to depict how these linear actuation assemblies <NUM>, <NUM>' may be packaged and work together). These Figures show the entire translator <NUM>, <NUM>' extending along the entire inner diameter of the electromagnetic coil <NUM>, <NUM>'. Although not shown, the translators <NUM>, <NUM>' have a hollow center to allow devices to pass therethrough. The linear actuation assemblies <NUM>, <NUM>' are shown to be positioned by a positioning pin <NUM>. There is a plurality of positioning pins <NUM> extending through the linear actuation assemblies <NUM>, <NUM>'; however, only one is shown in these Figures due to the cross-sectional view. Likewise, there is only one plunger <NUM> shown extending from the linear actuation assembly <NUM> even though there is a plurality of plungers <NUM> equidistantly spaced thereabout. None of the plungers for the linear actuation assembly <NUM>' are shown in these Figures.

Both <FIG> show the leftmost linear actuation assembly <NUM>' in an "ON" state. In <FIG>, the rightmost linear actuation assembly <NUM> is in the "OFF" state. In <FIG>, the rightmost linear actuation assembly <NUM> is in the "ON" state. Regardless of the state each of these linear actuation assemblies <NUM>, <NUM>' are in, the operation of the electromagnetic coils <NUM>, <NUM>' cannot be determined because the design of these linear actuation assemblies <NUM>, <NUM>' provide the function of latching in either state.

The device <NUM> is a packet plate of a radial clutch. It includes a plurality of struts <NUM> (one shown), one strut <NUM> for each plunger <NUM> of the linear actuation assembly <NUM>. In <FIG>, the linear actuation assembly <NUM> is in the "OFF" state; the plungers <NUM> are retracted and the struts <NUM> are flush with the rest of the packet plate <NUM>, allowing the packet plate <NUM> to rotate. In <FIG>, the linear actuation assembly <NUM> is in the "ON" state; the plungers <NUM> are extended forcing the struts <NUM> to extend out from the outer diameter <NUM> of the packet plate <NUM>, preventing the packet plate <NUM> from rotating with respect to mechanism/piece that is disposed immediately adjacent the outer diameter <NUM> of the packet plate <NUM>.

A particularly desirable feature of the described electromagnetic actuation assembly <NUM> is its ability to function as an axial force and movement machine while at the same time having the translator <NUM> rotating in synchronous or even asynchronous with an axially adjacent load mechanism, such as a clutch controlling an epicyclic gear train.

Referring to <FIG>, a second alternative embodiment of the linear actuation assembly is generally indicated at <NUM>, wherein like elements from the first two embodiments are indicated by reference characters offset by <NUM>. In this embodiment, the plunger <NUM> is spring loaded with a spring <NUM>, which is compressed between the pointed distal end <NUM> of the plunger and a plunger frame <NUM>. A nut <NUM> is secured to the end of the plunger <NUM> opposite the pointed distal end <NUM> and provides a stop for axial movement of the plunger <NUM> with respect to the plunger frame <NUM>. In operation, this linear actuation assembly <NUM> provides lost motion between the translator <NUM> and the plunger <NUM> should the pointed distal end <NUM> of the plunger <NUM> not align perfectly with an opening in the packet plate <NUM>. The translator <NUM> and plunger frame <NUM> move axially even if the plunger <NUM> is stopped from axial movement due to its abutment against the packet plate <NUM>. Once an opening in the packet plate <NUM> is made available, the spring <NUM> forces the pointed distal end <NUM> of the plunger <NUM> into the packet plate <NUM> to move a strut <NUM> (not shown in this Figure).

Referring to <FIG>, the two linear actuation assemblies <NUM>, <NUM>' are shown operating in a transmission, generally shown at <NUM>, including the transmission housing <NUM>. The second embodiment <NUM> is also used in this transmission <NUM>. A third version of the linear actuation assembly <NUM>" is also designed into the transmission <NUM>. The transmission <NUM> is the subject of a <CIT>, the disclosure of which is hereby expressly incorporated into this patent application.

Referring to <FIG>, a graph of forces required to operate the linear actuation assembly <NUM> in the transmission <NUM> are shown. The graph represents force (y-axis) as a function of position of the translator (x-axis). The forces are measured in Newtons and the distance is measured in millimeters.

A line <NUM> is a horizontal line representing the force required to magnetically latch the translator <NUM>. This force does not vary. This magnetically latching force will be discussed in greater detail subsequently.

A discontinuous line, generally shown at <NUM> represents the mechanical resistance required to be overcome to move the translator <NUM>. For the first approximately <NUM>, the force is relatively small and constant. This portion of the line <NUM> is shown as line segment <NUM>. Once the translator <NUM> has moved <NUM>, the force required to move the translator <NUM> increases. The slope of the linear segment <NUM> is much greater than the first <NUM>. The increase in required force is due to the requirement to overcome the centrifugal force working on the cam (strut <NUM>) as well as the compression of a return spring <NUM> (if present). Once the translator <NUM> reaches approximately <NUM>, the mechanical resistance increases, but at a lower rate. This is represented by line segment <NUM>. At approximately <NUM> of translator <NUM> axial displacement, the mechanical force required drops, as is represented by the line segment <NUM>. This is due to the design profile of the cam. As the translator <NUM> moves past approximately <NUM>, the mechanical resistance returns to a relative constant. For the translator <NUM> to move across this length, forces generated by the linear actuation assembly <NUM> have to be greater than the mechanical resistance represented by the discontinuous line <NUM> at all points therealong. A second discontinuous line <NUM> has similar line segments as those of the first discontinuous line <NUM>. The second discontinuous line <NUM> is offset from the first discontinuous line <NUM> by a factor of <NUM>. This is a factor of safety built into the linear actuation assembly <NUM>.

When operating the linear actuation assembly <NUM>, the electromagnetic forces created thereby are represented by a first force line <NUM>. These are the forces generated by current passing through the electromagnetic coil <NUM>. At any point on along the length of movement of the translator <NUM>, the electromagnetic forces generated by the linear actuation assembly <NUM> must be greater than the mechanical resistance of the translator <NUM>. As is shown with the data represented by the graph in <FIG>, this is the case.

First <NUM> and second <NUM> dashed lines represent the forces required if the translator <NUM> were advanced or retracted from its ideal position by ± <NUM>, respectively. As can be seen when viewing the data represented in the graph of <FIG>, even with the translator <NUM> out of position, the electromagnetic forces created by the linear actuation assembly <NUM> are sufficient to overcome the worst case scenario mechanical resistance forces generated by the operation of the translator <NUM>.

A second force line <NUM> represents the magnetic latch force of the linear actuation assembly <NUM>. More specifically, this is the magnetic force required to latch the translator <NUM> into a position. As the translator <NUM> moves from its original position (<NUM>), the magnetic force increases due to the position of the magnets <NUM>, <NUM>. Two dashed lines <NUM>, <NUM>, similar to the dashed lines <NUM>, <NUM>, represent the forces required if the translator <NUM> were advanced or retracted from its ideal position by ± <NUM>, respectively. Regardless of whether the translator <NUM> is in its ideal position (line <NUM>) or some other position (between lines <NUM> and <NUM>), the magnetic forces of the linear actuation assembly <NUM> are greater than the magnetic latch force requirement as represent by force line <NUM> when the translator <NUM> has moved almost to one end or the other. (<FIG> represents forces in one direction. Forces to move the translator <NUM> in the other direction are not shown as the forces acting on the translator <NUM> in the opposite direction are much higher resulting in a much faster movement eliminating the need to track the position or forces.

Referring to <FIG>, wherein like reference characters as those described above are offset by <NUM>, a second alternative embodiment of a linear actuator <NUM> is shown. The difference between the linear actuation assembly <NUM> and the linear actuator <NUM> is that the second linear actuator <NUM> has only one set of magnets <NUM> centered below the electromagnetic coil <NUM>. The translator <NUM> will still move based on the direction of the current flowing through the electromagnetic coil <NUM>. Likewise, it will also latch in place even when the current passing through the electromagnetic coil <NUM> has stopped. The ring <NUM> is on one side of the first set of magnets <NUM> whereas a second ring <NUM>' is on the other side of thereof, thus positioning the first set of magnets <NUM> in the center between the two sides <NUM>, <NUM> of the electromagnetic coil <NUM>.

Referring to <FIG>(, a third alternative embodiment of the linear actuation assembly is shown at <NUM>, wherein like reference characters are offset from those in the first embodiment by <NUM>. This linear actuation assembly <NUM> has many of the same elements as described in the embodiment disclosed above. This linear actuation assembly <NUM> includes two electromagnetic coils <NUM> separated by a non-ferromagnetic barrier <NUM>. The non-ferromagnetic barrier <NUM> may be fabricated from aluminum. The non-ferromagnetic barrier <NUM> inhibits the electromagnetic fields from each of the electromagnetic coils <NUM> from intermingling.

Another difference between this embodiment <NUM> and the prior embodiment is that the two electromagnetic coils <NUM> share the two sets of magnets <NUM>, <NUM>, with the first set of magnets <NUM> under the leftmost electromagnetic coil <NUM> (based on the orientation of <FIG>) and the second set of magnets <NUM> is under the rightmost electromagnetic coil <NUM>. And yet a third difference is that the ring <NUM> includes a plurality of ringlets <NUM>, <NUM>. The first ringlet <NUM> is steel, similar to the ring <NUM> in the first embodiment. The second ringlet <NUM> is non-ferromagnetic and fabricated from aluminum. The barrier created by the second ringlet <NUM> forces the electromagnetic field to flow down below the stator <NUM>.

The electromagnetic field extending down below the stator <NUM> is received by a plurality of translators <NUM>. Each translator <NUM> is identical to the other and spaced apart from each other. In other words, there is a space <NUM> between each of the translators <NUM>.

This linear actuation assembly <NUM> is designed to latch in more than two positions. The number of positions it is able to latch in is defined by the equation:.

Number of Latches = Number of Translators - <NUM> Equation <NUM>.

The linear actuation assembly <NUM> that is capable of operating in more than two latching positions requires four more translators <NUM> than latching positions. <FIG> show the linear actuation assembly <NUM> moving between three distinct positions. As such, the linear actuation assembly <NUM> includes seven translators <NUM>.

The invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation.

Claim 1:
A linear actuation assembly (<NUM>) comprising:
an electromagnetic coil (<NUM>) configured to allow electric current to pass therethrough in either direction creating magnetic flux based on the electric current and its direction, said electromagnetic coil defining a center axis (<NUM>), an inner diameter (<NUM>), and first (<NUM>) and second (<NUM>) coil sides;
a first set of magnets (<NUM>) disposed end-to-end adjacent said first coil side of said electromagnetic coil at said inner diameter thereof, said first set of magnets fixedly secured with respect to said electromagnetic coil;
a second set of magnets (<NUM>) disposed end-to-end adjacent said second coil side of said electromagnetic coil about said inner diameter thereof, said second set of magnets fixedly secured with respect to said electromagnetic coil; and
a translator (<NUM>) disposed adjacent said first and second sets of magnets opposite said electromagnetic coil, said translator latchable between a first position adjacent said first set of magnets and a second position adjacent said second set of magnets in response to said magnetic flux and the direction in which the electric current is flowing, characterized in that the electromagnetic coil is wrapped around
a bobbin (<NUM>) having first (<NUM>) and second (<NUM>) channels complementing each other for receiving said first and second sets of magnets therein, respectively.