WO1999023674A1

WO1999023674A1 - Cascading electromagnetic armature

Info

Publication number: WO1999023674A1
Application number: PCT/US1998/023342
Authority: WO
Inventors: Gary A. Jaminson
Original assignee: Diesel Engine Retarders, Inc.
Priority date: 1997-11-03
Filing date: 1998-11-03
Publication date: 1999-05-14
Also published as: JP2001522140A; EP1029332A1; KR20010031761A; EP1029332A4

Abstract

The present invention is a two or more-piece cascading armature for use in a solenoid. The cascading armature comprises a core (174) of conductive material slidably disposed within at least one conductive sleeve (176), which, in turn, is disposed in the solenoid housing. The core and sleeve are operably linked. In various embodiments, the cascading armature may contain multiple conductive sleeves in varying sizes and proportions to the core. When the cascading armature is installed in the conductive housing, both the sleeve rim (179) and the core face (172) are presented to the pole member face across the working air gap. In the deactivated position the working air gap is different for the core and the sleeve because the rim of the sleeve extends beyond the core and is accordingly closer to the pole member face than the core.

Description

CASCADING ELECTROMAGNETIC ARMATURE

Cross Reference To Related Patent Application

This application relates to and claims priority on provisional application serial number 60/064,035. filed November 3, 1997 and entitled "Cascading Electromagnetic Armature."

Field of the Invention

The present invention relates to solenoids. In particular, the present invention relates to an improved structure for a cascading electromagnetic armature for a solenoid that may be used in the operation of compression release-type engine retarders.

Background of the Invention

Compression release-type engine retarders are well-known in the art. Engine retarders are designed to convert temporarily an internal combustion engine of either the spark ignition or compression ignition type into an air compressor. A compression release retarder decreases the kinetic energy of an engine by opposing the upward motion of the engine's pistons on the compression stroke. As a piston travels upward on its compression upstroke, the gases that are trapped in the cylinder are compressed. The compressed gases oppose the upward motion of the piston. When the piston nears the top of its stroke, an exhaust valve is opened to "release" the compressed gases. The pressure having been released from the cylinder, the piston cannot recapture the energy stored in the compressed gases on the subsequent expansion downstroke. In so doing, the engine develops retarding power to help slow down the vehicle. This provides the operator with increased control over the vehicle. A properly designed and adjusted compression release-type engine retarder can develop retarding power that is a substantial portion of the power developed by the engine on positive power. Compression release-type retarders of this type supplement the braking capacity of the primary vehicle wheel braking system. In so doing, these retarders may substantially extend the life of the primary wheel braking system of the vehicle. The basic design of a compression release type engine retarding system is disclosed in Cummins, United States Patent No. 3,220,392. The compression release-type engine retarder disclosed in the Cummins patent employs a hydraulic system to control the operation of the exhaust valves to effect the compression release event. The hydraulic control system engages the engine's existing valve actuation system, namely, the rocker arms of the engine. When the engine is operating under positive power, the hydraulic control system of the compression release retarder is disengaged from the valve control system, so that no compression release event occurs. When compression release retarding is desired, the engine is deprived of fuel and the hydraulic control system of the compression release brake engages the valve control system of the engine. The valve control system drives the compression release retarder to produce compression release events at the appropriate times.

The hydraulic systems of compression release engine retarders typically have a number of components. A solenoid valve is typically actuated to supply engine oil to fill the hydraulic circuits of the compression release engine retarder. when retarding is desired. Solenoids typically contain some type of slidable armature assembly which is biased in a direction opposite to a magnetic force applied by the coil. When the coil is energized, the magnetic force builds up to attract the armature assembly until the force is sufficient to overcome the bias.

Cylindrical type solenoids typically consist of a coil or winding surrounding a central hollow core in which an armature of soft iron or low carbon steel is slidably located. Figure 1 is an example of a short stroke solenoid actuator 10 having a flat ended armature 170. The solenoid 10 includes a conductive frame 110, a conductive coil 120, a conductive flux member 130, and an end cap 140, all of which define a central bore 150 in the solenoid. Located within the bore 150 are an armature 170 and a pole member 180. A slidable plunger 190 is provided in a central bore through the pole member 180. The conductive frame 110, conductive flux member 130, and the pole member 180 may be made preferably of soft iron or fully annealed low carbon steel.

The armature 170 comprises a solid plug of conductive material slidably disposed in the bore 150. The armature 170 may be cylindrical in shape and may have a conical or flat end 172, depending on the working stroke desired. Flat ended armatures are generally used for short stroke applications. Conical ended armatures may have a 90° cone for medium stroke units or a 60° cone for longer stroke devices. The movement of the armature 170 towards the pole member 180 is restricted by contact with the poie member. In its deactivated position, an air gap 200 is provided between the armature and the pole member 180.

The coil 120 is energized to activate the solenoid 10. When the solenoid 10 is activated the armature 170 is attracted to and slides towards the pole member 180. Movement of the armature 170 towards the pole member 180 displaces the plunger 190 downward. When the coil 120 is energized, magnetic flux is developed within the conductive elements of solenoid. The magnetic flux produces an attractive force across any air gaps (e.g. air gap 200) that occur within the circuit. This force is generally considered to be inversely proportional to the square of the air gap distance. That is, if the air gap distance is doubled, the magnetic attraction force will be reduced by approximately a factor of four. The working air gap 200 that exists between the armature end 172 and the pole face 182 obeys the inverse square law. Thus, the power of the downward stroke of the armature 170 (and the voltage required in coil 120 to produce this stroke) are a function of the air gap 200 distance. In order to maximize the magnetic force of the armature 170, it is desirable to reduce the air gap 200 as much as possible without reducing the distance of the stroke of the armature. As is evident from Fig. 1, in order to increase the stroke of the plunger 190, the air gap

200 must be increased. Increasing the air gap 200, however, has the undesirable effect of reducing the effective downward force of the solenoid in abeyance of the inverse square law. Thus, stroke may only be increased at the expense of force. There is a need for a solenoid in which the increase of stroke has less of a negative impact on force (i.e.. a solenoid with an improved mechanical advantage).

Because the force generated by a solenoid may also be a function of voltage, there is also a need for a solenoid that will produce a given force with a lower voltage than that required by solenoids such as shown in Fig. 1.

The relatively small diametral clearance (air gap) between the conductive flux member 130 and the armature 170 produces a very high side force on the armature as a result of the inverse square law. This side force may create unwanted friction forces that oppose sliding motion of the armature 170 in the bore 150. It is desirable to reduce the effect of this side force by minimizing the coefficient of friction between the armature 170 and the side walls of the bore 150 in which it is disposed. This is may be accomplished by selecting a liner material of plastic or brass that guides the armature 170 and prevents actual contact between the armature and the conductive flux member 130. Lubrication between the armature 170 and the conductive flux member 130 may also be used to reduce friction between the two.

Magnetic circuits, such as those in the solenoid 10. may exhibit a phenomena known as saturation. The conductive material of the circuit can carry only a limited flux density (Maxwells/sq.cm), visualized as so many lines of flux per unit area. Regardless of the magnetic intensity (amp-turns/cm.) exerted by the coil, a given area of the attracting armature and pole member faces may reach saturation and the flux passing through that area will be restricted beyond that value — which may result in magnetic "freeze-up" of the attracted elements. An object of the present invention is to reduce the likelihood of magnetic "freeze-up."

Solenoids may require a certain number of "amp turns" to create the necessary magnetic field around the coil to actuate the armature. Current engine electronic control modules are not generating the required "amp turns" or voltages necessary to actuate the current technology based solenoids. To overcome this problem, either the voltage, or the mechanical advantage of the solenoid, must be increased.

Others have attempted to achieve increased mechanical advantage (Quenneville, U.S. Patent No. 4,251,051) by the introduction of a "flopping armature", but any advantage of the Quenneville invention is countered by a reduction in armature stroke, fill, and overall performance of the solenoid. The present invention suffers less loss of performance and may be used in a solenoid application where voltage is limited. The present invention also provides a working stroke for the armature that is longer than the initial working air gap. Current solenoids can be either on or off, and are not capable of intermediate or variable control. The cascading armature of the present invention permits the solenoid to be on, off, or operate at intermediate levels of activation.

Objects of the Invention

It is therefore an object of the present invention to provide a solenoid with increased mechanical advantage.

It is another object of the present invention to actuate a solenoid valve with lower voltages.

It is a further object of the present invention to provide a working stroke for the armature which is longer than the initial working air gap, and thus is longer for a given solenoid voltage. It is still another object of the present invention to provide, for the same magnetic intensity, increased downward force on the solenoid plunger given a fixed core face area.

It is yet another object of the present invention to reduce the likelihood of magnetic "freeze-up" of the solenoid.

It is still yet another object of the present invention to control the position of a solenoid armature by regulating the solenoid voltage.

It is yet another object of the present invention to reduce the amount of current needed for operation of a solenoid without sacrifices to the working gap, stroke, or returning mechanism. Additional objects and advantages of the invention are set forth, in part, in the description which follows and, in part, will be apparent to one of ordinary skill in the art from the description and/or from the practice of the invention.

Summary of the Invention

In response to the foregoing challenge, Applicants have developed an innovative, economical cascading electromagnetic armature for use in a solenoid. In an electromagnetic solenoid having a conductive housing surrounding a movable armature, the armature may include two members, wherein the two members are adapted to be independently displaced relative to each other towards a pole member. The two members of the armature may include a conductive core and at least one conductive sleeve surrounding the conductive core. The conductive core may be slidably disposed within the conductive sleeve, and the conductive sleeve may be slidably disposed in the conductive housing. The present invention may include multiple conductive sleeves, wherein an inner conductive sleeve surrounds the conductive core, and an outer conductive sleeve surrounds the inner conductive sleeve. In the embodiment of the present invention including multiple conductive sleeves, the inner conductive sleeve may be recessed within and independently slidable relative to the outer conductive sleeve. The conductive core and the conductive sleeve may be cylindrical in shape, or the shape may vary from cylindrical to any number of shapes. The conductive core may include a flat or a conical end spaced from the pole member.

The conductive core may include an internal void. The conductive sleeve includes a means for engaging the conductive core upon displacement of the conductive sleeve. The engaging means may comprise a washer composed of a non-conductive or a conductive material. The washer may be convex or some other type of spring mechanism. The electromagnetic solenoid of the present invention may possess an outer air gap between the conductive sleeve and the pole member, and an inner air gap between the conductive core and the pole member. The conductive core may be recessed within the conductive sleeve such that the conductive core is further from the pole member than the conductive sleeve when the solenoid is not energized. The outer air gap may be in the range of 0.01 and 0.05 inches, and the inner air gap may be in the range of 0.02 and 0.10 inches for certain applications, but the present invention is not intended to be limited to these ranges.

SUBSTΓTUTE SHEET (RULE 26) It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and which constitute a part of this specification, illustrate certain embodiments of the invention, and together with the detailed description serve to explain the principles of the present invention.

Brief Description of the Drawings

Fig. 1 is a cross-section in elevation of an electromagnetic solenoid. Fig. 2 is a cross-section in elevation of a first embodiment of the cascading electromagnetic armature of the present invention.

Fig. 3 is a cross-section in elevation of a second embodiment of the cascading electromagnetic armature of the present invention.

Fig. 4 is a cross-section in elevation of a third alternative embodiment of the cascading electromagnetic armature of the present invention. Fig. 5 is a cross-section in elevation of a fourth alternative embodiment of the cascading electromagnetic armature of the present invention.

Detailed Description of the Preferred Embodiments

Reference will now be made in detail to a preferred embodiment of the present invention, an example of which is illustrated in the accompanying drawings. Figure 2 is an example of an embodiment of the present invention, in which like elements to those in Figure 1 are referred to with like reference numerals. The present invention may utilize a solenoid 10 with a telescoping (cascading) armature 170. The solenoid 10 may include a conductive housing 100. Located within the conductive housing 100, may be a two or more-piece cascading armature 170, and a pole member 180.

The cascading armature 170 comprises a core 174 of conductive material slidably disposed within at least one conductive sleeve 176, which, in turn, is disposed in the housing 100. In various embodiments, the cascading armature may contain multiple conductive sleeves in varying sizes and proportions to the core 174. The core 174 and sleeve 176 may be cylindrical in shape. The core 174 may have a conical or flat end 172, depending on the working stroke desired for the cascading armature. The core 174 may be a solid or hollow cylinder, slidably disposed within the sleeve 176 and arranged so that in the deactivated "resting" position the core face 172 is slightly recessed from the rim 179 of the sleeve 176.

When the cascading armature 170 is installed in the conductive housing 100, both the sleeve rim 179 and the core face 172 are presented to the pole member face 182 across the working air gap 200. The working air gap 200 is different for the core 174 and the sleeve 176 because the rim 179 of the sleeve extends beyond the core and is accordingly closer to the pole member face 182 than the core.

Figure 3 is an example of the preferred embodiment of the present invention, in which like elements to those in Figure 1 are referred to with like reference numerals. The present invention may utilize a solenoid 10 with a telescoping (cascading) armature 170. The solenoid 10 may include a conductive housing 100, which, in turn, may include a conductive frame 110, a conductive coil 120, a conductive flux member 130, and an end cap 140, all of which define a central bore 150 in the solenoid. Located within the bore 150 are a two-piece cascading armature 170 and a pole member 180. A slidable plunger 190 is provided in a central bore through the pole member 180. The conductive frame 110, conductive flux member 130, and the pole member 180 may be made preferably of soft iron or fully annealed low carbon steel.

The cascading armature 170 comprises a core 174 of conductive material slidably disposed within at least one conductive sleeve 176, which, in turn, is disposed in the bore 150. In various embodiments, the cascading armature may contain multiple conductive sleeves. The core 174 and sleeve 176 may be cylindrical in shape. The core 174 may have a conical or flat end 172, depending on the working stroke desired for the cascading armature. Flat ended cascading armatures are generally used for short stroke applications. Conical ended cascading armatures, as shown in Fig. 4, may have a 90° cone for medium stroke units or a 60° cone for longer stroke devices. The sleeve 176 may be a thin walled cylinder having one end partially closed by a lip.

Disposed internally in the same end of the sleeve 176 may be a stop washer (ring) 178 constructed of non-conductive material. The lip of the sleeve 176 engages the edge of the stop washer (ring) 178. The stop washer (ring) 178 may be flat, or may be slightly curved to impart a "spring" action to assist in the downward movement of the cascading armature 170 upon actuation of the solenoid, as shown in Fig. 5. It is also envisioned that the stop washer (ring) 178 may be composed of either a conductive or non-conductive spring mechanism to assist in the downward movement of the cascading armature 170. The core 174 may be a solid cylinder, slidably disposed within the sleeve 176 and arranged so that in the deactivated "resting" position the core face 172 is slightly recessed from the rim 179 of the sleeve 176. When the cascading armature 170 is installed in the solenoid assembly, both the sleeve rim 179 and the core face 172 are presented to the pole member face 182 across the working air gap 200. The working air gap 200 is different for the core 174 and the sleeve 176 because the rim 179 of the sleeve extends beyond the core and is accordingly closer to the pole member face 182 than the core. As an example, it has been found that an initial gap of .025 inches between the sleeve rim 179 and the pole member face 182, and an initial gap of .042 inches between the core face 172 and the pole member face 182 has worked. The coil 120 may comprise a copper winding that is energized with a voltage and produces a current flow in the winding. A magnetic field is developed as current flows through the winding. The magnetic field seeks a path or medium through which to flow, thus setting up a magnetic flux in the solenoid 10. The flux enters the cascading armature 170 through the conductive flux member 130 and causes an attractive force between the cascading armature sleeve 176/core 174 and the pole member 180.

Upon energization of the coil 120 and the establishment of the magnetic flux in the solenoid 10, the flux may be concentrated in the shorter gap between the sleeve rim 179 and the pole member face 182. In abeyance of the inverse square law, the attractive force between the sleeve 176 and the pole member 180 is enhanced by the proximity of the sleeve rim 179 to the pole member face 182. This attractive force may result in the sleeve 176 sliding towards the pole member 180 in the bore 150. As the sleeve 176 moves toward the pole member 180, contact between the end washer (ring) 178 and the core 174 causes the core to advance with the sleeve toward the pole member. The sleeve 176 and core 174 may advance together until the sleeve rim 179 contacts the pole member face 182. Normally, contact between the cascading armature 170 and the pole member face 182 would be undesirable because intimate contact of the cascading armature with the pole member could constitute a magnetic short circuit eliminating magnetic flux. If such a magnetic short circuit occurred, the conditions that create the attractive force would thus be satisfied and the attractive force may be greatly reduced. However, the area of the sleeve rim 179 that contacts the pole member face 182 may be sized to allow saturation to occur, limiting the flux carried by this path. At the point where the sleeve rim 179 contacts the pole member 180, the core 174 has advanced far enough toward the pole member 180 that the remaining flux present (attractive force) is sufficient to complete the working downward stroke of the cascading armature 170. The magnetic flux in the sleeve 176 may be saturated and accordingly seeks another path and begins to flow into an adjacent sleeve or core 174. The movement of the cascading armature 170 towards the pole member 180 is ultimately restricted by contact with the pole member and full displacement of the plunger 190.

In its deactivated position, an upward bias provided by the plunger 190 may cause the cascading armature to return to the deactivated "resting" position.

With regard to Figure 4, in which like reference numerals refer to like elements, the cascading armature 170 may function similarly to a hydraulic or pneumatic telescoping cylinder or rod. The cascading armature may comprise a series of nested sleeves capable of conducting a magnetic flux, arranged so that adjacent sleeves will respond proportionally to changes in the flux magnitude.

As shown in Fig. 3, the alternative embodiment of the present invention may utilize a solenoid 10 with a cascading armature 170 which may consist of more than one sleeve, i.e., an inner conductive sleeve 176 and an outer conductive sleeve 173. The solenoid 10 may include a conductive housing 100, which, in turn, may include a conductive frame 110, a conductive coil 120, a conductive flux member 130, and an end cap 140, all of which define a central bore 150 in the solenoid. Located within the bore 150 are a three (or more)-piece cascading armature 170 and a pole member 180. A slidable plunger 190 is provided in a central bore through the pole member 180. The conductive frame 110, conductive flux member 130, and the pole member 180 may be made preferably of soft iron or fully annealed low carbon steel.

The cascading armature 170 comprises a core 174 of conductive material slidably disposed within an inner conductive sleeve 176, which is slidably disposed within an outer conductive sleeve 173, which, in turn, is disposed in the bore 150. In various embodiments the cascading armature may include any number of sleeves. The core 174, the inner sleeve 176, and the outer sleeve 173 may be cylindrical in shape. The core 174 may have a conical or flat end 172, depending on the working stroke desired for the cascading armature. Flat ended cascading armatures are generally used for short stroke applications. Conical ended cascading armatures, as shown in Fig. 5, may have a 90° cone for medium stroke units or a 60° cone for longer stroke devices.

The inner sleeve 176 and the outer sleeve 173 may be thin walled cylinders having one end partially closed by a lip. Disposed internally in the same end of the inner sleeve 176 may be a stop washer (ring) 178 constructed of non-conductive material. There may also be a stop washer (ring) 177 disposed between the inner sleeve 176 and the outer sleeve 173. The stop washer (ring) 178 and 177 may also be curved or composed of a spring to assist in the downward motion of the cascading armature 170 as previously discussed. The core 174 may be a solid cylinder, slidably disposed within the inner sleeve 176, which, in turn, is slidably disposed within outer sleeve 173 and arranged so that in the deactivated "resting" position the core face 172 is slightly recessed from the rim 179 of the inner sleeve 176, and the rim 179 of the inner sleeve 176 is slightly recessed from the rim 175 of the outer sleeve 173.

When the cascading armature 170 is installed in the solenoid assembly, both the inner sleeve rim 179, the outer sleeve rim 175, and the core face 172 are presented to the pole member face 182 across the working air gap 200. The working air gap 200 is different for the core 174 and the inner sleeve 176 because the rim 179 of the inner sleeve extends beyond the core and is accordingly closer to the pole member face 182 than the core 174. In addition, the working air gap 200 is different for the inner sleeve 176 and the outer sleeve 173 because the rim 175 of the outer sleeve extends beyond the inner sleeve 176 and is accordingly closer to the pole member face 182 than the inner sleeve rim 179.

The coil 120 may comprise a copper winding that is energized with a voltage and produces a current flow in the winding. A magnetic field is developed as current flows through the winding. The magnetic field seeks a path or medium through which to flow, thus setting up a magnetic flux in the solenoid 10. The flux enters the cascading armature 170 through the conductive flux member 130 and causes an attractive force between the cascading armature inner sleeve 176/outer sleeve 173/core 174, and the pole member 180.

Upon energization of the coil 120 and the establishment of the magnetic flux in the solenoid 10, the flux may be concentrated in the shorter gap between the outer sleeve rim 175 and the pole member face 182. In abeyance of the inverse square law, the attractive force between the outer sleeve 173 and the pole member 180 is enhanced by the proximity of the outer sleeve rim 175 to the pole member face 182. This attractive force may result in the outer sleeve 173 sliding towards the pole member 180 in the bore 150. As the outer sleeve 173 moves toward the pole member 180. contact between the outer sleeve 173, the inner sleeve 176, and the core 174, causes the inner sleeve 176 and the core 174 to advance with the outer sleeve 173 toward the pole member 180. The outer sleeve 173, the inner sleeve 176, and the core 174 may advance together until the outer sleeve rim 175 contacts the pole member face 182. Normally, contact between the cascading armature 170 and the pole member face 182 would be undesirable because intimate contact of the cascading armature with the pole member could constitute a magnetic short circuit eliminating magnetic flux. If such a magnetic short circuit occurred, the conditions that create the attractive force would thus be satisfied and the attractive force may be greatly reduced.

However, the area of the outer sleeve rim 175 that contacts the pole member face 182 may be sized to allow saturation to occur, limiting the flux carried by this path. At the point where the sleeve rim 175 contacts the pole member 180, the inner sleeve 176 has advanced far enough toward the pole member 180 that the remaining flux present (attractive force) is sufficient to cause the inner sleeve 176, and the core 174, to continue to move towards the pole face 182. The magnetic flux in the outer sleeve 173 may be saturated and accordingly seeks another path and begins to flow into the inner sleeve 176 and the core 174. At the point where the inner sleeve rim 179 contacts the pole member 180, the core 174 has advanced far enough toward the pole member 180 that the remaining flux present (attractive force) is sufficient to complete the working downward stroke of the cascading armature 170.

As above, magnetic flux in the inner sleeve 176 may be saturated and accordingly seeks another path and begins to flow into the core 174. The movement of the cascading armature 170 towards the pole member 180 is ultimately restricted by contact with the pole member and full displacement of the plunger 190. In its deactivated "resting" position, an upward bias provided by the plunger 190 may cause the cascading armature 170 to return to the resting position.

The cascading armature of the present invention may provide a solenoid with increased mechanical advantage, and allow the solenoid to operate with less voltage. The cascading armature may also provide a working stroke for the armature which is longer than the initial working air gap, and thus is longer for a given solenoid voltage. Further, for the same magnetic intensity, the cascading armature may create a downward force on the solenoid plunger about

20% greater than a one-piece armature having the same equivalent core face area.

Options include the ability to incorporate multiple tiers of cascading sleeves, or armatures composed of powder metal (e.g. P45, FH000, FH008, low carbon alloy, inconal, or magnetic ceramics) or other suitable materials. Composites with different materials on the stop washers are also envisioned. Magnetic flux may also be increased by increasing amperage or the number of coil turns. Also, due to the cascading action of the armature, the position of the cascading armature may be controlled by precisely controlling the voltage. Conventional solenoids are simple on or off devices. The cascading armature allows the solenoid to be on, off, or partially on or off. By regulating the available voltage the cascading armature can be used to operate incrementally to produce specific motion at a specific input voltage or current. The cascading armature allows the solenoid valve to actuate at lower voltages thus reducing the amount of current needed for operation without sacrifices to the working gap, stroke, or returning mechanism.

A further advantage is seen in a reduction of sliding friction by virtue of having two concentric members separated by a film of lubricating oil. During the side load that results from the proximity to the flux ring, the additional oil film between the sleeve and plug creates an essentially frictionless condition during the short actuation period.

It will be apparent to those skilled in the art that various modifications and variations can be made in the construction, configuration, and/or operation of the present invention without departing from the scope or spirit of the invention. For example, in the embodiments mentioned above, various changes may be made to the cascading armature without departing from the scope and spirit of the invention. The number of conductive sleeves can be from one to ten or more.

The core and the conductive sleeves, as well as the stop washer may be composed of any of a number of materials. In addition, the core and the conductive sleeves can be any shape or size, depending upon the specific application. The core need not be completely solid, nor need it be composed of one uniform material. The working air gap is not limited to specific ranges or ratios, and may vary depending on the individual structure and components of the present invention. Further, it may be appropriate to make additional modifications or changes to the solenoid itself without departing from the scope of the invention. The solenoid housing may be constructed in any shape or size to accommodate the cascading armature. In addition, the coils may be modified to provide a more discrete range of voltages to permit the precise actuation of the solenoid. Thus, it is intended that the present invention cover the modifications and variations of the invention provided they come within the scope of the appended claims and their equivalents.

Claims

WHAT IS CLAIMED:

1. In an electromagnetic solenoid having a conductive housing surrounding a movable armature, said armature comprising: two members, wherein the two members are adapted to be independently displaced relative to each other towards a pole member.

2. The electromagnetic solenoid of Claim 1 , wherein the two members of the armature comprise: a conductive core; and at least one conductive sleeve surrounding the conductive core: wherein said conductive core is slidably disposed within said conductive sleeve; and wherein said conductive sleeve is slidably disposed in the conductive housing.

3. The electromagnetic solenoid of Claim 2, wherein said conductive core and said conductive sleeve are cylindrical in shape.

4. The electromagnetic solenoid of Claim 2, wherein said conductive core and said conductive sleeve are non-cylindrical in shape.

5. The electromagnetic solenoid of Claim 2, wherein said conductive core includes a flat end spaced from the pole member.

6. The electromagnetic solenoid of Claim 2, wherein said conductive core includes a conical end spaced from the pole member.

7. The electromagnetic solenoid of Claim 2, wherein said conductive core includes an internal void.

8. The electromagnetic solenoid of Claim 2, wherein said conductive sleeve further comprises a means for engaging said conductive core upon displacement of said conductive sleeve.

9. The electromagnetic solenoid of Claim 8, wherein the engaging means comprises a washer composed of a non-conductive material.

10. The electromagnetic solenoid of Claim 8, wherein the engaging means comprises a washer composed of a conductive material.

11. The electromagnetic solenoid of Claim 9, wherein said washer is convex.

12. The electromagnetic solenoid of Claim 9, wherein said washer is a spring mechanism.

13. The electromagnetic solenoid of Claim 10, wherein said washer is convex.

14. The electromagnetic solenoid of Claim 10, wherein said washer is a spring mechanism.

15. The electromagnetic solenoid of Claim 8, wherein an outer air gap is between the conductive sleeve and the pole member, and an inner air gap is between the conductive core and the pole member.

16. The electromagnetic solenoid of Claim 8, wherein said conductive core is recessed within the conductive sleeve such that the conductive core is further from the pole member than the conductive sleeve when the solenoid is not energized.

17. In an electromagnetic solenoid having a conductive housing surrounding a movable armature, said armature comprising: a conductive core; and at least one conductive sleeve surrounding the conductive core; wherein said conductive core is slidably disposed within said conductive sleeve; and wherein said conductive sleeve is slidably disposed in the conductive housing; and wherein said conductive core and said conductive sleeve are adapted to be independently displaced relative to each other towards a pole member.

18. A cascading armature assembly for use in a solenoid comprising: a conductive core; andat least one conductive sleeve surrounding the conductive core.

19. The cascading armature assembly of Claim 18 wherein an inner conductive sleeve surrounds the conductive core; and an outer conductive sleeve surrounds the inner conductive sleeve.

20. The cascading armature assembly of Claim 19 wherein the inner conductive sleeve is recessed within and independently slidable relative to the outer conductive sleeve.

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SUBST╬ôTUTE SHEET (RULE 26)