Abstract:
A solenoid for an electromagnetically operated valve includes a bobbin having a substantially rectangular or elliptical cross section, a pole plate stationary with respect to the bobbin, and an armature slidable within the bobbin in response to a magnetic field generated by the coil through the pole plate. A coil wound around the bobbin has a rectangular cross section which on a short axis side includes a width W. A relation between width W and a virtual cylindrical iron core of diameter D having the same cross sectional area as an armature cross sectional area is expressed as D=(0.4 to 0.8) W. A ratio of a length A of a long axis side of the armature to a length B of a short axis side of the armature has a range between 3.1≦(A/B)≦4.5.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application Ser. No. 60/599,814 filed Aug. 6, 2004, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates in general to solenoids and more specifically to solenoids used in conjunction with a valve to control operation of the valve.  
       BACKGROUND OF THE INVENTION  
       [0003]     Electromagnetically operated valves are known which include a bobbin supporting a winding formed as a coil of wire. A stationary core or pole plate typically made of a conductive material such as iron is mounted adjacent to a center hole of the bobbin. A movable armature is slidably disposed within the aperture of the bobbin such that when electrical current is passed through the winding of the coil, the armature is induced to translate toward the stationary pole plate. This translation of the armature can be mechanically used to actuate a valve assembly through the use of a pushpin in contact with the armature and which is also in contact with a valve assembly within the valve body. A biasing device is typically provided to return the valve assembly to its original position which also displaces the armature back to its de-energized location. An operating cycle of one of these electromagnetically operated valves is therefore the time from initial energizing of the coil to the time when the armature has returned to its original position.  
         [0004]     When it is desirable to reduce the body size of the valve in order to maximize a quantity of valves for a particular operation, the winding of the coil is necessarily reduced in size, thereby reducing the attraction force between the armature and the pole plate and/or reducing the operating speed of the valve. To resolve this problem, solenoid geometry has changed such that the geometry of the coil is shaped substantially rectangular permitting an equal number of windings of the coil in a width of the solenoid commensurate with the necessary use. An example of a rectangularly shaped coil and its construction is provided in U.S. Pat. No. 6,698,713 issued to Sato et al. on Mar. 2, 2004. The patent to Sato et al. also identifies a known method to calculate the attraction force generated between an armature and a pole plate, and a power consumption.  
         [0005]     The U.S. patent to Sato discloses a ratio of a length “A” of a longer axis or side of a solenoid inner coil to a length “B” of a shorter axis or side of the solenoid inner coil having a relationship expressed as: 1.3≦A/B≦3.0. The limited ratio range of Sato restricts the geometry of the solenoid and therefore can preclude a desired solenoid wattage and/or valve operating speed for narrow or tightly arranged solenoid/valve applications.  
       SUMMARY OF THE INVENTION  
       [0006]     A rapid response solenoid for an electromagnetically operated valve according to a preferred embodiment of the present invention includes a bobbin having a substantially rectangular shaped cross section. A coil is wound around the bobbin. A stationary pole plate is fixed in relation to the bobbin. An armature is slidably disposed within the bobbin and slides toward the pole plate in response to a magnetic field generated by the coil through the pole plate. The armature has a substantially rectangular shape having a short axis side and a long axis side. A ratio of a length A of the long axis side of the armature to a length B of the short axis side of the armature has an operable range of 3.1≦(A/B)≦4.5.  
         [0007]     According to another preferred embodiment of the present invention, the stationary pole plate is positioned at a bobbin first end having a portion of the pole plate extending within a through aperture formed in the bobbin. A bushing is disposed within the through aperture and substantially fixed in relation to the bobbin. The bushing is positioned between the armature and an inner wall of the bobbin and provides a sliding fit between the armature and the bobbin inner wall. A brass or other non-magnetic material used for bushing reduces friction and magnetic attraction of the armature to the bushing and therefore increases a de-energized return speed of a valve connected to the solenoid.  
         [0008]     Advantages of the present invention include the capability of accepting higher operating wattages, a faster cycle time for an attached valve and a solenoid assembly less susceptible to wear from friction of the moving parts. A smaller wire size is also used which provides additional benefit to the solenoid operating force and power generated. By using the geometry for a solenoid of the present invention, an improved cycle time at a given solenoid size is also provided.  
         [0009]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]      FIG. 1  is a perspective view of a rapid response solenoid for an electromagnetic operated valve of the present invention;  
         [0012]      FIG. 2  is a cross-sectional elevational view taken at section  2 - 2  of  FIG. 1 ;  
         [0013]      FIG. 3  is a cross-sectional plan view taken at section  3 - 3  of  FIG. 2 ; and  
         [0014]      FIG. 4  is a cross-sectional elevational view similar to  FIG. 2 , showing a valve energized/open position.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0016]     According to a preferred embodiment of the present invention and referring generally to  FIG. 1 , a valve assembly  10  includes a solenoid  12  connectably attached to a valve body  14  at a valve body mounting face  16 . Internal components of valve body  14  are generally loaded via a valve loading face  18 . A valve body inlet port  20 , and outlet port  22  and an exhaust port  24  are exemplary of fluid ports disposed via a fluid system service face  26  of valve body  14 . The invention is not limited to a particular orientation or quantity of ports.  
         [0017]     Referring next to  FIG. 2 , components of the solenoid  12  include a pole plate  28  which forms an interface between solenoid  12  and valve body  14  via valve body mounting face  16 . A flux frame  30  formed generally at a perimeter of pole plate  28  provides an external limit for individual wires forming a coil  32 . Coil  32  includes at least one or a plurality of individual wires  31  in one or more windings provided in wire sizes ranging from approximately 33.5 to 35.5 gauge. A first portion  33  of pole plate  28  is disposed within an internal cavity of coil  32 . An armature  34  is also positioned within the internal cavity of coil  32 . Both pole plate  28  and armature  34  are typically provided of electrically conductive and magnetic materials such as iron. Armature  34  is slidably disposed within a bushing  36  such that a bushing inner wall  38  is in slidable contact with an armature outer wall  40 .  
         [0018]     Solenoid  12  is also provided with a cover  42  which seals solenoid  12  from the external environment. Cover  42  is connected to flux frame  30  by an adapter  44  and one or more fasteners  46 . Within cover  42  is disposed a current distribution plate  48 , which is in direct contact with a lead pin  50 . Lead pin  50  is disposed within an insulating bushing  52  to electrically isolate lead pin  50  from cover  42 . Electrical current provided to the windings of coil  32  is provided via lead pin  50  through current distribution plate  48  and a coil connector  54 .  
         [0019]     Armature  34  is positioned as shown in  FIG. 2  in a de-energized condition of solenoid  12 . In this condition, an adjustment device  56  is in contact with armature  34 , forming a stop for armature  34  in the de-energized position. Adjustment device  56  can be threaded such that the positioning of armature  34  can be adjusted by changing the engagement depth of adjustment device  56  within cover  42 . Armature  34  displaces from the de-energized position in the direction of arrow “X” when current is supplied to coil  32  such that a magnetic flux is created between coil  32 , pole plate  28  and armature  34 . Armature  34  is thereby drawn towards pole plate  28 . This translation in the direction of arrow “X” of armature  34  also displaces a pushpin  58  which is in direct contact with armature  34 . A clearance aperture  59  is provided within pole plate  28  to allow slidable displacement of pushpin  58  in either the energized direction of arrow “X” or the return (de-energized) direction of arrow “Y”.  
         [0020]     Pushpin  58  directly contacts a first end of a valve member  60  provided within valve body  14 . Valve member  60  is slidably disposed within valve body  14  such that valve member  60  is displaceable in each of the directions of arrows “X” and “Y”. In the solenoid de-energized position shown in  FIG. 2 , valve member  60  is in a closed position wherein fluid pressure in inlet port  20  is isolated from both outlet port  22  and exhaust port  24 . An end retainer  62  slidably receives a second end of valve member  60  and acts as a positive stop for the sliding motion of valve member  60 . End retainer  62  is fastenably connected, generally via threads, to valve body  14 . A biasing element  64  is positioned between and contacts both valve member  60  and end retainer  62 . Biasing element  64  biases valve member  60  away from end retainer  62  and provides a normal biasing force in the direction of arrow “Y” to return valve member  60  and pushpin  58  together with armature  34  in the direction of arrow “Y” when solenoid  12  is de-energized. Biasing element  64  and valve member  60  are positioned within a valve bore  65  of valve body  14 . Valve member  60  is exemplary of a plurality of designs for a valve member. The invention is not limited to a particular design for valve member  60 . Coil  32  is provided in a substantially rectangular or elliptical shape based on winding the individual wires of coil  32  about a bobbin  66  which is itself substantially rectangular or elliptically shaped. Bobbin  66  includes a first end  67  and a second end  68 . A through-aperture  69  is created within bobbin  66  which slidably receives first portion  33  of pole plate  28  and also receives bushing  36 .  
         [0021]     Referring generally now to  FIG. 3 , a cross-sectional geometry of solenoid  12  is provided. A coil width “W” is maximized within a total width of solenoid  12 . A plurality of apertures  70  are also shown, each aperture  70  providing access for a fastener (not shown) used to connectably mount solenoid  12  to valve body  14 . Coil width “W” defines a short length axis of coil  32 . Bushing  36  disposed within through aperture  69  of bobbin  66  defines an inner perimeter for coil  32  and a cross-sectional area “S” of armature  34 . A circle  72  having a diameter “D” represents a virtual cylindrical iron core having the same cross-sectional area as cross-sectional area “S”. Circle  72  therefore represents only a virtual item used to establish a comparison to a theoretical circular iron core. Expressed as an equation, S=(πD 2 /4). Diameter “D” of circle  72  and coil width “W” are related by the equation: D=(0.4 to 0.8)W. A further relationship exists for armature  34  wherein a long axis “A” of armature  34  is related to the short axis or length “B” of armature  34 . The range or limits of a ratio of “A” to “B” for armature  34  are provided by the equation: 3.1≦A/B≦4.5.  
         [0022]     Providing the above range of the ratio of “A” to “B” for armature  34  permits maximizing a length “L” of coil  32  compared to coil width “W” such that a higher current and wattage can be used for coil  32 . It is common in the industry for solenoid operated valves to use an actuation wattage of approximately four to five watts. Faster acting solenoids are available using approximately  16  watts of electrical power. A solenoid  12  of the present invention permits operation up to approximately  215  watts. This is accomplished by the geometry of coil  32  and armature  34  and in part through the use of smaller gauge wire within coil  32 , ranging from approximately 33.5 to 35.5 gauge. Increasing the wattage for solenoid  12  provides a significantly faster acting valve assembly  10  because the higher wattage creates a greater magnetic flux in coil  32  which increases the travel speed of armature  34 . Cycle time can be reduced from known  4  watt solenoid valve designs having cycle times of approximately 3 milliseconds to approximately 340 microseconds using a solenoid design according to the present invention.  
         [0023]     A further improvement of the valve assembly  10  of the present invention is provided by the use of a non-magnetic material, and preferably a brass material, for bushing  36 . A non-magnetic material used for bushing  36  and in particular a material such as brass provides a low coefficient of friction between armature  34  and bushing  36 . In addition, the non-magnetic nature of bushing  36  reduces the likelihood-of magnetic attraction between armature  34  and bushing  36  during its return travel to the non-energized position shown in  FIG. 2 . This further reduces the operating time of valve assembly  10 . The operating time of valve assembly  10 , i.e., its operating cycle, is defined as the time required between the initiation of current flow to coil  32  and the initial displacement of armature  34  until armature  34  returns to the de-energized position shown in  FIG. 2 . An overall reduced cycle time is provided by valve assembly  10  of the present invention, permitting use of valve assembly  10  in operations such as sorting operations which require very high rates of material transfer and very low cycle times of the valves operating the sorting machinery.  
         [0024]     Referring to  FIG. 4 , valve member  60  is shown positioned in an energized condition of solenoid  12 . A flow passage “E” is provided in this position between inlet port  20  and outlet port  22 . Biasing element  64  is compressed and provides biasing force to return valve member  60  to the position shown in  FIG. 2  when solenoid  12  is de-energized.  FIG. 4  further shows an insert  74  having an inner wall  76  which slidably supports an upper end (as shown in  FIG. 4 ) of valve member  60 . A passage  78  is longitudinally provided through valve member  60  allowing fluid at either end of valve member  60  to displace to the opposite end when valve member  60  translates in either the direction of arrow “X” or arrow “Y”. The biasing force in the direction of arrow “Y” provided by biasing element  64  redirects valve member  60  to the position shown in  FIG. 2 . Fluid in a fluid/biasing member chamber  80  which partially encloses biasing element  64  is also displaced via passage  78  to allow translation of valve member  60  in either the direction of arrow “X” or arrow “Y”.  
         [0025]     Advantages of the present invention include the capability of using higher operating wattages to achieve faster cycle times and/or increased solenoid driving force for solenoid actuated valves, and providing a solenoid assembly less susceptible to wear from friction of the moving parts. A smaller wire size is also used which further increases the solenoid operating force and power generated by the solenoid. By using the geometry for a solenoid of the present invention, an improved cycle time at a given solenoid size is also provided.  
         [0026]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. For example, additional ports or ports oriented in a different configuration from those shown in  FIG. 2  can be used. The geometry of valve member  60  can therefore vary to accommodate different valve port designs, locations and quantities. An exemplary size for a valve body of the present invention is approximately 0.81 in long (2.06 cm), 0.66 in high (1.66 cm) and 0.31 in depth (0.79 cm). An exemplary size for a solenoid of the present invention is approximately 0.31 in deep (0.79 cm) substantially matching the depth of the valve body, with a length and height of approximately ¾ of the valve body dimensions. These dimensions are exemplary only and the valve body and solenoid can be varied from these dimensions. Such variations are not to be regarded as a departure from the spirit and scope of the invention.