Abstract:
The invention relates to a solenoid housing fabricated by a method which allows a manufacturer to produce a high performing product while minimizing manufacturing complexity and time. The instant invention uses cold-forging techniques to reduce the need for fine machining processes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of and claims priority to U.S. patent application Ser. No. 14/146,122, filed Jan. 2, 2014 and titled “Solenoid Housing and Method of Making the Same,” which is a continuation-in-part of and claims priority to U.S. patent application Ser. No. 13/439,409, filed Apr. 4, 2012, now U.S. Pat. No. 8,643,452, issued on Feb. 4, 2014 and titled “Solenoid Housing with Elongated Center Pole,” which claims priority to and the benefit of U.S. Provisional Patent Application No. 61/472,844, filed Apr. 7, 2011 and titled “Solenoid Housing with Elongated Center Pole.” The contents of the above-referenced patent applications and issued patent are relied upon and incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of the invention relates to advantageous methods of fabricating solenoid housings. 
       BACKGROUND OF THE INVENTION 
       [0003]    Solenoid assemblies are typically found in a myriad of modern products, from the control of anti-lock braking systems and automatic transmissions in automobiles, to pressurized water control in irrigation systems, to more general uses such as in doors, windows, many hydraulic controls, and the like. 
         [0004]    Solenoid housings are typically used in car control systems, such as doors, windows, hydraulic controls, engine control, and the like. Other uses include refrigerators, washers, and dryers. Further uses include electrically actuated valves/switches, door holders, speakers, and CRT monitors. 
         [0005]    Solenoids typically make use of a high magnetic reluctance region to facilitate movement of an armature along a set path in response to the application of an electric current. This region can be referred to as an “air gap” because empty space is commonly used as the high magnetic reluctance region. Such an arrangement with a literal air gap, however, may lead to certain difficulties in both construction and operation of the solenoid. Certain prior art teachings disclose the air gap may be achieved through a two piece construction of the solenoid with a gap left between the two pieces. Each piece may have a different conformation, meaning that separate, specialized manufacturing processes could be required for each piece. Further, if the two pieces need to be aligned properly to allow for easy movement of the armature through each piece and across the air gap, extra calibration and alignment procedures may be necessary. All of these additional steps generally increase manufacturing complexity, meaning more time and cost may be necessary to produce a single solenoid than if said extra calibration and alignment procedures were eliminated. 
         [0006]    There may be the fear of decreased manufacturing efficiency and operational lifetimes associated with these prior art solenoids as well. For example, if a solenoid were produced in a two-piece arrangement with a certain degree of allowed deviation from the ideal alignment of the first and second piece, solenoids may be produced outside of this tolerance, and the time and cost necessary to produce said solenoid would have been wasted. Further, since a two-part construction like the one described above may be unlikely to produce ideal alignments on a consistent basis, the average operation lifetimes of the solenoids may decrease by general wear and tear (caused by frictional forces of the armature on the solenoid housing after days, months, or years of repeated rubbing due to misaligned solenoid components). 
         [0007]    Further, traditional solenoid housing manufacturing and assembly is typically a multi-stage machining and welding process requiring a series of highly specialized machines, skilled manufacturing personnel, and time to perform each manufacturing step to produce a quality, reliable product. For example, the lathes which can be used for machining a central armature path in prior art processes are often expensive and require a large amount of space for proper operation, and welding methods may need to be completed in tight spaces and with little room for error or inconsistency in the weld. The imprecision and complexity of the prior art processes may produce solenoids and solenoid housings with inherent structural weaknesses, and produce them at a disadvantageously high rate. These manufacturing deficiencies may lead to premature operational failure of the prior art solenoid housings or a high rejection rate during the assembly process. 
         [0008]    What is desired, therefore, is a method of making a solenoid housing which eliminates much of the manufacturing complexity found in the prior art. It is further desired that this novel method of making a solenoid housing improve the operation and increase the expectant operational lifetime of said solenoid housing. 
       SUMMARY OF THE INVENTION 
       [0009]    It is therefore an object of the invention to provide a method of producing a solenoid housing utilizing cold-forging methods to eliminate multi-component fabrication and assembling, as well as provide a suitable analogue for the air gap. 
         [0010]    In one embodiment, the method of providing a solenoid housing of the instant invention comprises the steps of providing a cylinder of malleable material having a first part and a second part, said first part having a first-part perimeter and said second part having a second-part perimeter, reducing a size of the first-part perimeter to be less than a size of the second-part perimeter, compressing at least a portion of said second part in a direction towards said first part to produce a flattened disk, providing said cylinder of malleable material with a non-magnetic region, extending a bore from said first part toward said second part to at least a distance beyond said non-magnetic region. In a further embodiment, the step of compressing at least a portion of said second part in a direction towards said first part to produce a flattened disk also comprises the step of providing a protrusion on said second part. 
         [0011]    In another embodiment, a cup is provided around the cylinder of malleable material. In another embodiment, the above-mentioned cup is produced using a method comprising the steps of providing a sheet of malleable material, raising a perimeter of said sheet to produce a raised perimeter, extending said raised perimeter to define a cup with a base, and providing a recess in said base of said cup. In one embodiment, the cup is produced through a machining method which provides a cup-bore into a cylinder of suitable material. In a further embodiment, the cup is provided to the cylinder of malleable material though a method selected from the group consisting of assembling, riveting, press-fitting, and combinations thereof. In one embodiment, the riveting method further comprises the steps of inserting said protrusion into said recess and compressing said protrusion in a direction towards the first part. In yet another embodiment, the non-magnetic region is provided by selecting from the group consisting of: a perforated region, an area comprised of non-magnetic material, a region wherein said region has a smaller cross-sectional area than a cross-sectional area of the remainder of the cylinder of malleable material, and combinations thereof. 
         [0012]    In a further embodiment, the method includes annealing the housing after at least one of the steps of any of the following: providing a cylinder of malleable material having a first part and a second part, said first part having a first-part perimeter and said second part having a second-part perimeter; reducing a size of the first-part perimeter to be less than a size of the second-part perimeter; compressing at least a portion of said second part in a direction towards said first part to produce a flattened disk; providing said cylinder of malleable material with a non-magnetic region; and extending a bore from said first part toward said second part to at least a distance beyond said non-magnetic region. 
         [0013]    In yet another embodiment, the method includes a step of providing said cylinder of malleable material with said region wherein said region has a smaller cross-sectional area than a cross-sectional area of the remainder of said cylinder of malleable material further comprises the following step: reducing said cross-sectional area of said region to be approximately 10%-20% of said cross-sectional area of the remainder of the cylinder. 
         [0014]    In one embodiment, this invention is a solenoid housing comprising a raised wall having a first end and a second end; a center-piece having a first end and a second end; a flattened disk at said second end of said raised wall and said second end of said center-piece; and wherein said center-piece, flattened disk, and raised wall are formed of a one-piece construction. In another embodiment, the center-piece includes a bore. In yet another embodiment, the bore extends from the first end of the center-piece to a point between the first end and the second end of the center-piece. In yet another embodiment, the raised wall includes a flange. In yet another embodiment, the flange is generally perpendicular to the flattened disc. 
         [0015]    In one embodiment, the invention is a method of providing a solenoid housing, comprising the steps of: providing a solid cylinder of malleable material having a first part and a second part; reducing a diameter of said first part of the cylinder to be less than a diameter of said second part of the cylinder; compressing said second part in an axial direction toward said first part, resulting in a flattened disc; cold forging an entire outermost perimeter of said flattened disc in a direction toward said first part for defining a first solid, raised wall; extending said first part of the cylinder in a direction away from said second part of the cylinder for creating a center piece; cold forging an entire outermost perimeter of the center piece for defining a second solid, raised wall; extending the first solid, raised wall to define an annular recess having a depth; and wherein the first part, second part, center-piece, first solid raised wall, and second solid raised wall are all integrally connected as a single piece. In yet another embodiment, there is a further step of extending the second solid raised wall to define an annular recess having a depth. In yet another embodiment, there is a further step of extending a bore in the center-piece from a first end of the center-piece to a point between the first end and a second end of the center-piece. In yet another embodiment, the method of providing a solenoid housing includes a step of extending a third part of the cylinder away from the first and second parts. In yet another embodiment, there is a further step of extending a flange from the first solid raised wall. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the claims. The figures are for illustration purposes only. The invention itself, however, both as to organization and method of operation, may be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which the drawings show typical embodiments of the invention and are not intended to be limited of its scope. 
           [0017]      FIG. 1  shows a method of providing a solenoid housing consistent with one embodiment of the instant invention. 
           [0018]      FIG. 2  shows a further embodiment of the method of providing a solenoid housing from  FIG. 1 . 
           [0019]      FIG. 3  shows a method of providing a solenoid housing consistent with one embodiment of the instant invention. 
           [0020]      FIG. 4  shows a further embodiment of the method of providing a solenoid housing from  FIG. 3 . 
           [0021]      FIG. 5  shows a further embodiment of the method of providing a solenoid housing from  FIG. 3 . 
           [0022]      FIG. 6  shows a further embodiment of the method of providing a solenoid housing from  FIG. 5 . 
           [0023]      FIG. 7  shows a further embodiment of the method of providing a solenoid housing from  FIG. 3 . 
           [0024]      FIG. 8  shows a further embodiment of the method of providing a solenoid housing from  FIG. 2 . 
           [0025]      FIG. 9  shows a further embodiment of the method of providing a solenoid housing from  FIG. 3 . 
           [0026]      FIG. 10  shows a flowchart depicting the production of a solenoid housing consistent with the method as depicted in  FIG. 1 . 
           [0027]      FIG. 11  shows a flowchart depicting the production of a solenoid housing consistent with the method as depicted in  FIG. 3 . 
           [0028]      FIG. 12  shows a flowchart depicting the production of a solenoid housing consistent with the method as depicted in  FIG. 3 . 
           [0029]      FIG. 13  shows a flowchart depicting the production of a solenoid housing consistent with the method as depicted in  FIG. 6 . 
           [0030]      FIG. 14  is a side view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0031]      FIG. 15  is a side view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0032]      FIG. 16  is a side view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0033]      FIG. 17  is a top-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0034]      FIG. 18  is a top-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0035]      FIG. 19  is a top-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0036]      FIG. 20  is a side-view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0037]      FIG. 21  is a side-view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0038]      FIG. 22  is a side-view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0039]      FIG. 23  is a side-view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0040]      FIG. 24  is a side-view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0041]      FIG. 25  is a top-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0042]      FIG. 26  is a top-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0043]      FIG. 27  is a top-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0044]      FIG. 28  is s a flowchart depicting the production of a solenoid housing consistent with the method as depicted in  FIG. 1 . 
           [0045]      FIG. 29A  is a bottom-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0046]      FIG. 29B  is a bottom-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0047]      FIG. 29C  is a bottom-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
           [0048]      FIG. 29D  is a bottom-down view of an embodiment consistent with the method of providing a solenoid housing from  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0049]    In describing the various embodiments of the instant invention, reference will be made herein to  FIGS. 1-29  in which like numerals refer to like features of the invention. 
         [0050]    The instant invention generally relates to an improved method of making a solenoid housing, including fabrication of features such as the center pole for providing a path along which an armature will actuate and an outer cup enclosing the center pole as well as a space in which a solenoid coil will be held. In one embodiment of the instant invention, a cold-forging method has been found which allows for simplified fabrication of the solenoid as a one-piece construction from a single billet of malleable material. This embodiment is shown in  FIG. 1 , which depicts the step of providing  100  a cylinder of malleable material having a part. The cylinder is comprised of any malleable material suitable for use as a solenoid housing. In some embodiments, the malleable material is a low carbon steel. Herein, the cylinder of malleable material and all method steps for modifying said cylinder of malleable material will be described and portrayed as having a basic, curved cylindrical shape; that is to say that the ends of the cylinder are circles. However, the specific shape of the cylinder is not meant to be limited to this embodiment. In other embodiments, the outline of the cylinder is selected from the group consisting of a square, rectangle, triangle, pentagon, hexagon, octagon, polygon, and combinations thereof. The specific shape of the cylinder of malleable material is a design choice well within the abilities of one of ordinary skill in the art. In some embodiments, the part is provided as a region at or near the one of the ends of the cylinder of malleable material. In a further embodiment, the cylinder can be defined as having a first part and a second part, wherein the first part is subjected to the various cold-forging and machining steps that will be described herein, and the second part is in most cases held immobile. 
         [0051]    After the cylinder is provided  100 , a flange is extended  110  from the part. In one embodiment, this is performed by compressing part of the cylinder in a direction towards the remainder of the cylinder and holding said remainder of the cylinder of malleable material stationary in a form which only allows movement by the material comprising the part. In some embodiments, the flange is a raised perimeter which extends from the part in an axial direction, a radial direction, or both. In one embodiment, the flange expands to provide a constant perimeter around a circumference of the part. 
         [0052]    At least a portion of the part is then raised  120  to form a raised wall. In some embodiments, the first part is raised by immobilizing a portion of the cylinder in a form and compressing the part in a direction towards the remainder of the cylinder with a die having a smaller diameter than the cylinder itself. When axially aligned with the cylinder of malleable material, compression of the die into the part forces material to extrude upwards around the outer edges of the die itself. The form, meanwhile, substantially prevents movement of the remainder of the cylinder of malleable material. The result of this compression step is a raised wall which extends the more the die compresses the part. The height of the raised wall is a function of the amount of material in the cylinder and the desired design of the solenoid housing. After raising step  120 , the cylinder has been transformed into a hollow, cup-shaped housing with a flange around the top and a base of some thickness at the bottom. 
         [0053]    A center pole is then raised  130  from the part. An annular die is used to raise this center pole from the material within the hollow, cup-shaped housing itself. Compression of the part in raising step  120  as described above moved the part of the cylinder to the bottom or floor of the hollow cup. In raising step  130 , a hollow die again compresses the part. Material displaced by the compression in raising step  130  is extruded through the cavity within the hollow die in a direction opposite the direction of compression. The compression step continues until the center pole is raised to the desired height. 
         [0054]      FIG. 10  is provided to pictorially demonstrate an embodiment of method steps  100 - 130  from  FIG. 1 . For the purposes of disclosing the following embodiment, the cylinder of malleable material will be described has having a first part and a second part. However, this description is not meant to provide any additional limitations into the embodiments described above or as claimed. In this embodiment, cylinder of malleable material  1  is subjected to force A at first part  1000  in a direction towards second part  1001 . By immobilizing second part  1001  and a desired length of cylinder  1 , first part  1000  is extended in directions B, resulting in flange  1002 . A force C, brought by a die (not pictured) having a diameter which is less than that of cylinder  1 , causes a section of first part to extend in a direction D and produce a first-part raised wall  1003 , while the remainder of first part  1000  is compressed towards second part  1001 . Center pole  1004  is then created by application of a force E by a hollow die (not pictured). Again, with second part  1001  held stationary, material displaced by said annular die will cause first part  1000  to extend in a direction F. In one embodiment, first annular recess  1005  which results from this method step becomes the receptacle for the solenoid coil (not pictured). 
         [0055]    In one embodiment as shown in  FIG. 10 , flange  1002  is generally perpendicular to first raised wall  1003 . This embodiment offers the most control over dictating a flow of energy through the solenoid housing because it allows the greatest disbursement of magnetic energy in a radial direction away from the solenoid housing after passing through the first raised wall  1003  and contributes to the best life expectancy of the solenoid housing. Flange  1002  includes other angles between approximately 0° and approximately 180° with respect to first raised wall  1003 . In one embodiment, flange  1002  includes an angle approximately 30° with respect to first raised wall  1003 . This embodiment slightly disburses the flow of magnetic energy in a direction radially away from the solenoid housing and helps contribute to a much longer life-expectancy of the solenoid housing. In one embodiment, flange  1002  includes an angle approximately 60° with respect to first raised wall  1003  for moderately disbursing the flow of magnetic energy in a direction radially away from the solenoid housing but results in a slightly longer life-expectancy. In another embodiment, flange  1002  includes an angle at approximately 120° with respect to first raised wall  1003  for slightly disbursing magnetic energy in a direction axially away from the solenoid housing helps contribute to a slightly longer life-expectancy of the solenoid housing. In another embodiment, flange  1002  includes an angle at approximately 150° with respect to first raised wall  1003  for moderately disbursing magnetic energy in a direction axially away from the solenoid housing helps contribute to a much longer life-expectancy of the solenoid housing. 
         [0056]    Flange  1002  may include a plurality of angles. In a preferred embodiment as shown in  FIG. 15 , flange  1002  includes two angles with respect to first raised wall  1003 . In one embodiment as shown in  FIG. 15 , first angle  2200  is smaller than second angle  2300  and is ideal for directing the flow of magnetic energy axially away from the solenoid housing. Second angle  2300  is greater than first angle  2200  and is ideal for directing the flow of magnetic energy radially away from the solenoid housing. In this embodiment where first angle  2200  is smaller than second angle  2300 , there is a greater need for magnetic energy to flow radially away from the solenoid housing while still maintaining some axial flow of magnetic energy away from the housing. In other embodiments, first angle  2200  is greater than second angle  2300 . In this embodiment, there is a greater need to direct the flow of magnetic energy radially away from the solenoid housing while still maintaining some axial flow away from the solenoid housing. 
         [0057]    In one embodiment, before or after at least one of method steps  110 ,  120 , and  130 , cylinder  1  is annealed  160 . The annealing step  160  is performed to reduce stress on the malleable material during each of these steps, lessening the risk that the material will become brittle and liable to crack or fail in subsequent cold-forging steps. In some embodiments, annealing step  160  is performed by heating cylinder  1  to approximately 850° C., allowing said cylinder  1  to stay at that temperature before cooling said material to 720° C., and subsequently allowing said cylinder  1  to stay at that temperature before cooling cylinder  1  down to room temperature. In one embodiment, an annealing step is performed before and after each of method steps  110 ,  120 , and  130 . 
         [0058]    In some embodiments, center pole  1004  created by method step  130  is modified to provide a path through which an armature is actuated. As depicted in FIG.  1 , a bore  1105  is machined  140  into said center pole  1004  to produce a center-pole raised wall  2500 . In alternative embodiments, the bore  1105  is provided via a cold-forging step, or a combination of a cold-forging step and a machining step. 
         [0059]    In a further embodiment, the center-pole raised wall  2500  is provided  150  with a non-magnetic region. The non-magnetic region is used to approximate an air gap and generate the force which actuates an armature through the solenoid assembly. In one embodiment, the air gap is approximated by providing  200  said center-pole raised wall with a perforated region, providing  210  said center-pole raised wall with a region comprised of non-magnetic material, or providing  220  said center-pole raised wall with a region wherein said region has a smaller cross-sectional area than a cross-sectional area of the remainder of the center-pole raised wall  2500 , and combinations thereof. 
         [0060]    In one embodiment, providing step  220  is performed by reducing the cross-sectional area of said region to be approximately 5-25% of the cross-sectional area of the remainder of the center pole raised wall  2500 . In a further embodiment, the cross-sectional area of the region is reduced  800  to be approximately 10-20% of the cross-sectional area of the center-pole raised wall  2500 , as depicted in  FIG. 8 . Providing non-magnetic regions within these ranges strikes an optimal balance between performance and manufacturing ease and time. As has been previously discussed, the non-magnetic region on the center-pole raised wall approximates an air gap to facilitate movement of an armature through the solenoid assembly. The relative saturation of the air gap to its surroundings creates an electromotive force which acts upon the armature within the solenoid assembly. Due to air&#39;s high magnetic reluctance, an actual air gap saturates immediately. In the instant embodiment, thinning a region of the center-pole raised wall  2500  creates an air gap analogue by reducing said region&#39;s ability to hold magnetic flux. The magnetic reluctance of region is effectively increased, the result being that the magnetic flux saturates much quicker through the thin-walled region than the remainder of the center-pole raised wall. 
         [0061]    When the center-pole raised wall  2500  is thinned to a width of about 30% or higher, said region remains permeable enough for magnetic flux so as to be an unsuitable air gap analogue; performance of the solenoid suffers significantly. The resulting electromotive force is weak and the response time delayed, sacrifices which are not offset by the ease of manufacturing gained by eliminating the complicated air gap fabrication process. However, by thinning the cross-sectional area of a region on the center-pole raised wall to approximately 5-25%, and more particularly to approximately 10-20%, the air gap is approximated to a degree such that performance closely mirrors that of an actual air gap. Non-magnetic regions with a cross-sectional area of approximately 25% that of the remainder of the center-pole raised wall provide a sufficient analogue to an air gap. However, performance increases are achieved with walls approximately 20% the cross-sectional area of the remainder of the center-pole raised wall or lower. Further, these thin walls of approximately 20% the cross-sectional area of the remainder of the center-pole raised wall maintain the increased structural rigidity and durability inherent in the substantially continuous path along which the armature may actuate. A one piece construction is significantly more resistant to misalignment than a two piece construction and results in a longer operational lifetime. 
         [0062]    Complications arise when the relatively thin walls of the non-magnetic region are fabricated to widths less than 5% of the remainder of the center-pole raised wall. As thinner and thinner walls are achieved, the likelihood of introducing structural weaknesses to the solenoid housing increases. When producing walls with widths less than 5% of the remainder of the center-pole raised wall, there is a significant increase in the likelihood that the forces exerted on the solenoid housing by the fabrication method itself will result in warping or fracturing of the center pole. A solenoid which suffers this warping or fracturing is inoperable and must be rejected. By manufacturing the non-magnetic region at widths of 5% or above, however, the housing retains sufficient structural rigidity to survive the fabrication process, resulting in a low rate of failure during production. The rate of failure decreases even further when the center-pole raised wall is provided at a width greater than 10%. Levels of performance for those solenoid housings with non-magnetic regions between 10-20% remain acceptably high compared to their air gap analogues. 
         [0063]      FIG. 3  depicts another embodiment of the instant invention for providing a solenoid housing comprising a step of providing  300  a cylinder of malleable material having a first part and a second part, said first part having a first-part perimeter and said second part having a second-part perimeter. As described above, the cylinder of malleable material may be comprised of any suitable material and any suitable shape. In one embodiment, the malleable material is low carbon steel. 
         [0064]    In some embodiments, the method of the instant invention comprises the step of reducing  310  a size of the first-part perimeter to be less than a size of the second-part perimeter. At least a portion of the second part is then compressed  320  in a direction towards the first part. In one embodiment, such as the one depicted in  FIG. 4 , compression step  320  provides  410  a flattened disk to said second part, provides  400  a protrusion on said second part, or both. Steps  310  and  320  are advantageous with certain sizes of starting billet cylinders of malleable material. Whether method steps  310  and  320  are advantageous is determined by the ratio of the axial length of the cylinder (L) to the width of the cylinder (D), or the value of L/D. Where the cylinder is provided with an L/D of less than or equal to 2, the above method steps  310  and  320  are useful.  FIG. 11  pictorially shows method steps  310  and  320 , as well as an alternative embodiment where L/D is greater than 2. In this latter embodiment, second part  1001  is compressed upwards towards first part  1000 , with the displaced matter of cylinder  1  forced into a generally conical formation. Further compression of the second part in a direction of the first part with an appropriately shaped die (not pictured) yields the same housing conformation as that from method steps  310  and  320 , including flattened disk  1108  and protrusion  1103 . In some embodiments, protrusion  1103  is a stabilizing feature in subsequent fabrication steps, as will be discussed below. These two methods allow for greater freedom when selecting the starting cylinder of malleable material for performing the instant invention. 
         [0065]    A non-magnetic region is then provided  330  on said cylinder  1 . As previously described in connection with  FIG. 2 , in one embodiment the non-magnetic region is provided through use of a perforated region, a region comprised on non-magnetic material, a region with a smaller cross-sectional area than the cross-sectional area of the remainder of cylinder  1 , and combinations thereof. In one embodiment, production of the non-magnetic region begins by providing a notch about the circumference of cylinder  1 . A bore is then extended  340  through said first part  1000  in a direction towards said second part  1001 . In one embodiment, said bore is extended a distance from said first part towards said second part such that said bore goes beyond the non-magnetic region. 
         [0066]    This series of steps is best exemplified in  FIG. 11 . In one embodiment, the notch  1104  is provided to cylinder  1  through a cold-forging method, a machining method, or a combination of both. The depth and shape of notch  1104  is a matter of design choice. A bore  1105  is applied and extended to some distance beyond notch  1104 . In one embodiment, bore  1105  is extended via a machining step. In a further embodiment, bore  1105  is extended substantially all the way through cylinder  1 . The width of bore  1105  is a matter of design choice and depends heavily on the armature to be utilized in the solenoid and the depth of notch  1104 . 
         [0067]    As described above, in one embodiment, the non-magnetic region is provided through use of a region with a smaller cross-sectional area than the remainder of cylinder  1 . The cross-sectional areas of the non-magnetic region and the remainder of cylinder  1  refer to the cross-sectional areas of  1106  and  1107  respectively after a bore is extended  340  in cylinder  1 . Bore  1105  turns cylinder  1  into a hollow tube at least as far as bore  1105  is made in cylinder  1 . In one embodiment, the cross-sectional area of non-magnetic region  1106  is at least 5-25% of the cross-sectional area of the remainder  1107  of cylinder  1 . In a further embodiment, the cross-sectional area of non-magnetic region  1106  is 10-20% of the cross-sectional area of the remainder  1107  of cylinder  1 . In other embodiments, notch  1104  is filled with non-magnetic material, such as aluminum-bronze. In these embodiments, the cross-sectional area of region  1106  is advantageously reduced to zero or at least near zero. Region  1106  is therefore exclusively non-magnetic material in this embodiment, with the original malleable material of cylinder  1  completely removed. 
         [0068]    In much the same way as described above, in some embodiments, the solenoid housing is annealed  370  before or after at least one of the steps of  300 ,  310 ,  320 ,  330 , and  340 . In a further embodiment, annealing step  370  occurs before and after each of steps  310 ,  320 ,  330 , and  340 . 
         [0069]    In one embodiment, a cup is provided  350  for assembly with or placement around cylinder  1 . In some embodiments, such as the embodiment shown in  FIG. 7 , the cup is provided by a cold-forging method. In this embodiment, a sheet of malleable material is provided  700 . A perimeter of the sheet is then raised  710  to produce a raised perimeter. In some embodiments, said raised perimeter extends around at least a portion of said sheet of malleable material. In a further embodiment, the raised perimeter extends around the entire perimeter of the sheet. The raised perimeter is then extended  720  to define a cup with a base. A recess is then provided  730  is said base of said cup. In one embodiment, the recess is provided by a punching method or a machining method. The size of the recess is a matter of design choice. However, the purpose of the recess is to accept the protrusion provided in method step  400 , as will be discussed below. Therefore, the recess is at least large enough to accept the protrusion. In further embodiments, the perimeter of the recess is also smaller than the perimeter of the flattened disk. 
         [0070]    In one embodiment, a flange is then expanded  740  on said raised perimeter. In some embodiments, expansion step  740  provides a flange by expanding the material already present in said raised perimeter. In further embodiments, expansion step  740  is combined with a step of removing excess material from the raised perimeter (not pictured). Excess material is removed to produce a solenoid housing with the desired shape or dimension. In one embodiment, for example, excess material is removed from the cup such that the heights of the cup and the cylinder of malleable material are approximately the same. 
         [0071]    In another embodiment, as depicted in  FIG. 9 , the cup is provided  900  through a machining method which machines a cup-bore into a cylinder of suitable material. 
         [0072]    The cup provides the outer housing for the solenoid assembly, encloses the solenoid coil, and provides protection for the coil and armature assembly. The shape and size of the sheet of malleable material is a matter of design choice and greatly depends on the shape of cylinder  1  and the intended use of the solenoid itself. 
         [0073]    The application of the cup to cylinder  1  is pictorially demonstrated in  FIG. 12 . As can be seen in this figure, cylinder  1  has already been provided with bore  1105 , non-magnetic region  1106 , and protrusion  1103 . Cup  1200  is provided with an inner diameter at least large enough to accept flattened disk  1108 . In some embodiments, the outer diameter of flattened disk  1108  and the inner diameter of cup  1200  are essentially equal to ensure a tight fit between the two pieces. Cup  1200  is also provided with a recess  1201 . In some embodiments, recess  1201  is at least large enough to accept all of protrusion  1103 . In one embodiment, protrusion  1103  has a length greater than the depth of recess  1201 . As depicted in  FIG. 12 , cup  1200  is inserted along direction G so as to fit snuggly around cylinder  1 . 
         [0074]    The interaction between recess  1201  and protrusion  1103  holds cylinder  1  and cup  1200  in alignment. In one embodiment, cup  1200  and cylinder  1  are then held in place via a riveting step, a press fitting step, an assembling step, and the like, as seen in  FIG. 5 . In one embodiment, cup  1200  is attached through a riveting method as shown in  FIG. 6 , which provides a more secure and permanent fit between the two pieces. In this embodiment, protrusion  1103  is inserted  600  into recess  1201  and the perimeter of protrusion  1103  is compressed  610  in a direction towards first part  1000 , such as via a cold-forging method. In some embodiments, compression step  610  enlarges the perimeter to a size larger than the perimeter of the recess (also known as the recess perimeter), thus preventing cup  1200  from disengaging from cylinder  1 . This embodiment is also depicted in  FIG. 13 , where cup  1200  is already in place on cylinder  1 . Application of force H causes expansion of protrusion  1103  in direction I. The resulting protrusion-end perimeter  1300  holds cup  1200  securely in place and limits movement of cup  1200  in relation to cylinder  1 . 
         [0075]    In another embodiment, cup  1200  and cylinder  1  are held together via a press-fitting step  510 . Press-fitting step  510  relies on the frictional interaction between the outer perimeter of protrusion  1103  and the inner circumference of recess  1201 . In yet another embodiment, cup  1200  and cylinder  1  are assembled  520 , and are kept stationary relative to each other by interaction with other components in the solenoid assembly or apparatus into which the solenoid assembly is incorporated. 
         [0076]    As shown in  FIG. 28 , another embodiment of the method comprises steps of providing  2000  a cylinder of malleable material having a first part and a second part, reducing  2010  the diameter of the first part of the cylinder to be less than the diameter of the second part of the cylinder, compressing  2020  the second part in an axial direction toward the first part, resulting in a flattened disc generally perpendicular to the first part; raising  2030  an entire outermost perimeter of the flattened disc in a direction toward the first part for defining a first raised wall; extending  2040  the first raised wall to define a first annular recess  1005  having a first depth; extending  2050  the first part in a direction away from the second part for creating a center piece; raising  2060  an entire outermost perimeter of the center piece for defining a second raised wall; extending  2070  a bore in the center piece; extending  2080  the second raised wall to define a second annular recess  1105  having a second depth; extending  2090  a third part of the solid cylinder away from the first and second parts; extending  2100  a flange from the first raised wall; orienting  2110  a plurality of grain lines of the flattened disc; orienting  2120  a plurality of grain lines of the first part; orienting  2130  a plurality of grain lines of the second part; orienting  2140  a plurality of grain lines of the third part. 
         [0077]    In some embodiments, the compressing  2020  step resulting in a solid, flattened disc  1108 . In other embodiments, the flattened disc  1108  is hollow. In yet other embodiments, the flattened disc  1108  is generally perpendicular to the first and second parts. In yet other embodiments, the flattened disc  1108  is generally parallel to the first and second parts. 
         [0078]    In some embodiments, the step of raising  2030  a first raised wall  1003  is performed by a method of cold forging. In other embodiments, the step is performed by a method of extruding. In yet another embodiment, step  2030  may be performed by compressing the first part in a first location toward the second part in an axial direction for defining the first raised wall  1003 . In some embodiments, the first raised wall  1003  is solid. In other embodiments, it is hollow. 
         [0079]    In some embodiments, the step of extending  2050  the first part of the cylinder in a direction away from the second part of the cylinder creates center-piece  1004 . Center piece  1004  includes second raised wall  2500  as shown in  FIGS. 17-25 . In other embodiments, this center piece  1004  is of a generally circular shape. In yet other embodiments, the center piece  1004  is generally square shaped. In yet other embodiments, the center piece  1004  is generally triangle shaped. The center piece  1004  may be of any shape depending on the preference of the manufacturer and the objectives sought. 
         [0080]    Center piece  1004  aids in directing the flow of magnetic energy through the base of the solenoid housing and into the first raised wall  1003 . The flow and direction of magnetic energy is dictated by the size and shape of center piece  1004 . In one embodiment, center piece  1004  has a bore  1105  as shown in  FIGS. 20-25 . In yet other embodiments, center piece  1004  does not have a bore as shown in  FIGS. 17-19  and is instead solid but still includes second raised wall  2500 . 
         [0081]    Center piece  1004  may extend any distance from a first location of the second part to a point between the first location of the second part and an upper portion of the first raised wall  1003 . In one embodiment as shown in  FIG. 20 , center piece  1004  extends approximately one-quarter of an axial length of the first raised wall  1003 . A center piece  1004  of approximately this axial length is best for distributing magnetic energy toward the first raised wall  1003 . In some embodiments, center piece  1004  extends approximately halfway between a first location of the second part and an upper portion of the first raised wall  1003 , which provides the best balance of retaining magnetic energy within the center piece  1004  and distributing magnetic energy toward the first raised wall  1003 . In yet other embodiments, center piece  1004  shares a generally even plane with the upper portion of first raised wall  1003 . A center piece  1004  that shares a generally even plan with the upper portion of first raised wall  1003  is best for retaining magnetic energy within the center piece  1004  and distributing very little magnetic energy toward the first raised wall  1003 . 
         [0082]    In a further embodiment, the center-piece  1004  is provided  150  with a non-magnetic region. The non-magnetic region is used to approximate an air gap and generate the force which actuates an armature through the solenoid assembly. In one embodiment, the air gap is approximated by providing  200  the center piece  1004  with a perforated region, providing  210  the center piece  1004  with a region comprised of non-magnetic material, or providing  220  the center piece  1004  with a region wherein said region has a smaller cross-sectional area than a cross-sectional area of the remainder of the center piece  1004 , and combinations thereof. 
         [0083]    In one embodiment, providing step  220  is performed by reducing the cross-sectional area of said region to be approximately 5-25% of the cross-sectional area of the remainder of the center piece  1004 . This range provides a substantial dampening in the flow of magnetic energy but is more difficult to achieve. In a further embodiment, the cross-sectional area of the region is reduced  800  to be approximately 10-20% of the cross-sectional area of the center piece  1004 , as depicted in  FIG. 8 . This range provides less dampening of the magnetic energy than the 5-25% range but is easier to manufacture. Providing non-magnetic regions within these ranges strikes an optimal balance between performance and manufacturing ease and time. 
         [0084]    In one embodiment, the first annular recess  1005  created by extending  2040  step has a first depth and the second annular recess  1105  created by extending  2060  step has a second step. In one embodiment, the first depth of first annular recess  1005  is substantially similar to the second depth of second annular recess  1105  as shown in  FIGS. 20-22 . This embodiment is ideal for inhibiting the flow of magnetic energy from the center piece  1004  to the first raised wall  1003 . In another embodiment, the first depth of first annular recess  1005  is different from the second depth of second annular recess  1105  as shown in  FIGS. 23-24 . This embodiment is ideal for distributing the flow of magnetic energy through from the center piece  1004  to the first raised wall  1003 . 
         [0085]    In some embodiments, the step of raising  2060  a second raised wall  2500  is performed by a method of cold forging. In other embodiments, the step is performed by a method of extruding. In yet another embodiment, step  2060  may be performed by compressing the center-piece  1004  in a first location toward the second part in an axial direction for defining the second raised wall  2500 . In some embodiments, the second raised wall  2500  is solid. Second raised wall  2500  may extend any distance from a first location of the second part to a point between the first location of the second part to an upper portion of the first raised wall  1003 . In one embodiment as shown in  FIG. 20 , second raised wall  2500  extends approximately one-quarter of an axial length of the first raised wall  1003 . Second raised wall  2500  of approximately this axial length permits the greatest amount of magnetic energy flow through the solenoid housing. In some embodiments, second raised wall  2500  extends approximately halfway between a first location of the second part and an upper portion of the first raised wall  1003 . Second raised wall  2500  of approximately this axial length permits some flow of magnetic energy but not the most possible. In yet other embodiments, second raised wall  2500  shares a generally even plane with an upper portion of first raised wall  1003 . Second raised wall  2500  that shares a generally even plan with an upper portion the first raised wall  1003  provides the greatest inhibitory effect of the magnetic flow and direction. 
         [0086]    In some embodiments, step  2070  of creating a bore  1105  in the center piece is performed by a method of extruding. In other embodiments, it is performed by a step of compression. Bore  1105  may be extended  2070  from a first end of the center piece to a point between the first end and a second end of the center piece. In one embodiment as shown in  FIG. 24 , bore  1105  is an indentation in a top surface of the center piece  1004 . In this embodiment, bore  1105  is best at distributing a flow of magnetic energy through the solenoid housing. In another embodiment, bore  1105  extends approximately one-third through the center piece. In this embodiment, bore  1105  is best at permitting a slight amount of magnetic energy flow through the solenoid housing. In another embodiment as shown in  FIG. 23 , bore  1105  extends approximately halfway through the center piece and offers the best balance between retaining magnetic energy in the center piece  1004  and distributing it toward the first raised wall  1003 . In yet other embodiments as shown in  FIGS. 20-22 , bore  1105  extends from the first end of the center piece to the second end of the center piece  1004 , allowing the greatest amount of magnetic energy flow through the solenoid housing. 
         [0087]    In one embodiment, a third part  1103  is extended  2090  in a direction away from the first and second parts. Third part  1103  may be a solid protrusion as shown in FIGS.  11 - 12  and  FIGS. 29A-29D . In some embodiments, third part  1103  has a generally triangular shape as shown in  FIG. 29A . In other embodiments, third part  1103  has a generally octagonal shape as shown in  FIG. 29B . In yet other embodiments, third part  1103  has a generally square shape as shown in  FIG. 29C . And in yet other embodiments, third part  1103  has a generally hexagonal shape as shown in  FIG. 29D . And in yet other embodiments, third part  1103  has a generally circular shape. 
         [0088]    In one embodiment, third part  1103  has a circumference that is less than a circumference of the first raised wall  1003  as shown in  FIGS. 29A-29D . In yet another embodiment, third part  1103  has a circumference that is approximately equal to a circumference of the first raised wall  1003  as shown in  FIGS. 11-12 . In yet another embodiment, third part  1103  has a circumference that is greater than a circumference of the first raised wall  1003 . 
         [0089]      FIGS. 14-27  represent the physical embodiments of steps  2060 ,  2070 , and  2080  for forming a second raised wall  2500 . In one embodiment as shown in  FIGS. 25-27 , the second raised wall  2500  is shown to be a cylindrical cup, having a bore  1105  in the middle for accepting actuator assemblies and the like. However, in other embodiments, as shown in  FIGS. 17-19  the second raised wall  2500  could be center piece  1004 , having no bore in the middle and remaining substantially solid throughout for substantially inhibiting magnetic flow. In one embodiment, the second raised wall  2500  is reverse extruded through a die. The specific size and shape of the die will determine the physical dimensions of the second raised wall  2500 , and the design and control of each of these variables is well within the ability of one of ordinary skill in the art. An additional embodiment could have the second raised wall  2500  fashioned using a machining method as is well known in the art. In this embodiment, there would be no need to raise the second part of the cylinder to define the raised wall or compress the second part of the cylinder with an annular die to create the raised wall. Instead, the second part of the cylinder would be machined away in the desired areas to define the second raised wall  2500 . 
         [0090]    In a further embodiment, the second raised wall  2500  is provided  150  with a non-magnetic region. The non-magnetic region is used to approximate an air gap and generate the force which actuates an armature through the solenoid assembly. In one embodiment, the air gap is approximated by providing  200  the second raised wall  2500  with a perforated region, providing  210  the second raised wall  2500  with a region comprised of non-magnetic material, or providing  220  the second raised wall  2500  with a region wherein said region has a smaller cross-sectional area than a cross-sectional area of the remainder of the second raised wall  2500 , and combinations thereof. 
         [0091]    In a further embodiment, the method orients a plurality of grain lines of the flattened disc to be in a generally radial direction extending outwardly from a general center of the flattened disc. In some of these embodiments, the method further orients a plurality of grain lines of the first part to be in a generally axial direction extending along a length of the first part. Orienting the plurality of grain lines of the flattened disc in a generally radial direction further facilitates transmission of the electromagnetic field because the electromagnetic field passes along the generally radial direction of the grain lines as the energy moves toward either raised wall. The grain lines may be oriented in a randomized, perpendicular, or angular relation relative to the travel of the electromagnetic field, in which case the grain lines inhibit the flow of the electromagnetic field rather than facilitate the flow. 
         [0092]    Once again, it is contemplated that the features of the solenoid housing may be provided in any particular order. Reversing these steps will not substantively change the integrated valve sleeve produced by the instant method. 
         [0093]    While the present invention has been particularly described, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications, and variations as falling within the true scope and spirit of the present invention.