Abstract:
Piston actuators and methods of its operation are described. The piston actuators include a housing defining a chamber having a piston therein and a spring seated against the piston to bias it into a starting position. The piston includes a ferromagnetic material, a magnet or both and a secondary magnet or ferromagnetic material, forming a first magnetic/ferromagnetic pair with the piston, is positioned to maintain the piston in a secondary position. A tertiary magnet or ferromagnetic material, forming a second magnetic/ferromagnetic pair with the piston, may assist the spring in maintaining the piston in the starting position. During operation, introduction into or removal from the chamber of an amount of fluid sufficient to overcome the force of the spring (and the tertiary magnet or ferromagnetic material) enables the attraction between the members of the first magnetic/ferromagnetic pair to move the piston to the secondary position as a snap movement.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/752,291, filed Jan. 14, 2013, and U.S. Provisional Application No. 61/894,159, filed Oct. 22, 2013. 
     
    
     TECHNICAL FIELD 
       [0002]    This application relates to piston actuators that snap between the on and off positions, more particularly to pressure activated and magnetically assisted piston actuators for operation of a valve for use in an internal combustion engine to move the valve between open and closed positions with no lag or “floating” in between said positions. 
       BACKGROUND 
       [0003]    In current actuators the on/off operation in a pneumatic device is achieved with an electric solenoid. Vacuum force is applied to the actuator only when the solenoid is “on” and only when the vacuum force is high enough to move the actuator the full length of its travel. Alternately, without a solenoid controlling the actuator&#39;s exposure to vacuum, an actuator exposed to vacuum force under all conditions will “float” between the on position and the off position. Floating is undesirable, inefficient, and provides poor control of the valve attached to the actuator. There is a need to make energy efficient actuators that are effective at controlling a valve without the use of an electric solenoid. The elimination of the solenoid reduces power consumption of the device, its weight, its cost, and complexity. 
       SUMMARY 
       [0004]    Herein actuators are described for the control of valves without the use of a solenoid, but that still have on-off functionality. The actuators will stay in a starting position, which may correspond to either an open or a closed position for an attached valve, until a threshold force is applied to the piston therein. Once the threshold force is reached, the piston will move the full length of its travel to its secondary position, moving the valve to the alternate position from its starting open or closed position, and will remain in this secondary position until a lower threshold force is reached, at which point the piston moves back to its starting position by again moving the full length of its travel. The actuators include a housing defining a chamber and having a port in fluid communication with the chamber, a piston enclosed in the chamber, and a spring seated against the piston to bias the piston into a starting position. The piston at least partially includes one or more of a ferromagnetic material or one or more magnets. A first magnet or a first ferromagnetic material is positioned to assist the spring in maintaining the piston in the starting position and a second magnet or a second ferromagnetic material is positioned to maintain the piston in a secondary position when the piston moves to the secondary position. 
         [0005]    The movement of the piston from its starting position to its secondary position may be described as a “snap” movement. This “snap” is a quick, nearly instantaneous movement of the piston the full length of its travel between the starting and secondary positions without a lag or floating of the piston therebetween. The “snap” action of the actuator as it travels between the starting position and the secondary position is facilitated by the presence of the magnets, which attract and pull the piston between the two positions. This is such a quick movement that without bumpers to reduce the noise, a snap-like sound can be heard as the piston contacts the housing as it arrives in the alternate position, which depending on the configuration of the actuator may be an “on” or an “off” position of the attached valve. 
         [0006]    In one embodiment, the piston actuator includes a housing defining a chamber and comprising a port in fluid communication with the chamber, a piston within the chamber and having a ferromagnetic material, a magnet or both included in the piston, a spring seated against the piston to bias the piston into a starting position, and a secondary magnet or ferromagnetic material forming a first magnetic/ferromagnetic pair with the piston and positioned to maintain the piston in a secondary position once the piston moves to the secondary position. During operation, the introduction into or removal from the chamber of an amount of fluid sufficient to overcome the force of the spring enables the attraction between the members of the first magnetic/ferromagnetic pair to move the piston to the secondary position as a snap movement. The first magnetic/ferromagnetic pair thereafter maintains the piston in the secondary position until the amount of fluid introduced into or removed from the chamber is sufficient to overcome the attraction therebetween. Once the attraction of the first magnetic/ferromagnetic pair is overcome, the spring moves the piston to the starting position. 
         [0007]    In another embodiment, the actuator described above also includes a tertiary magnet or ferromagnetic material forming a second magnetic/ferromagnetic pair with the piston. The tertiary magnet or ferromagnetic material is positioned to assist the spring in maintaining the piston in the starting position. Accordingly, during operation, the introduction into or removal from the chamber of an amount of fluid sufficient to overcome the force of the spring and the second magnetic/ferromagnetic pair enables the attraction between the members of the first magnetic/ferromagnetic pair to move the piston to the secondary position as a snap movement. The first magnetic/ferromagnetic pair thereafter maintains the piston in the secondary position until the amount of fluid introduced into or removed from the chamber is sufficient to overcome the attraction therebetween. Once the attraction of the first magnetic/ferromagnetic pair is overcome, the spring and the attraction between the members of the second magnetic/ferromagnetic pair move the piston to the starting position as a snap movement. 
         [0008]    Methods for operating the piston actuators are also described herein. The methods include providing one of the piston actuators and firstly introducing into or removing from the chamber an amount of fluid sufficient to overcome the force of the spring or the force of the spring and the attraction between a second magnetic/ferromagnetic pair (if present) holding the piston in the starting position, and thereby the attraction between the members of the first magnetic/ferromagnetic pair moves the piston to the secondary position as a snap movement and thereafter maintains the piston in the secondary position. The method also includes, oppositely of whichever firstly introducing into or removing of an amount of fluid was performed, subsequently introducing into or removing from the chamber an amount of fluid sufficient to overcome the attraction between the second magnetic/ferromagnetic pair, and thereby the spring and the attraction between the members of the second magnetic/ferromagnetic pair move the piston to the starting position as a snap movement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a front perspective view of one embodiment of a snap actuator and valve. 
           [0010]      FIG. 2  is a cross-sectional view of the snap actuator and valve of  FIG. 1  taken along the longitudinal axis of the conduit portion of the valve with the valve in a starting position. 
           [0011]      FIG. 3  is a cross-sectional view of the snap actuator and valve transverse to the longitudinal axis of the conduit through the gate member, with the valve in a starting position. 
           [0012]      FIG. 4  is a cross-sectional view of the snap actuator and valve transverse to the longitudinal axis of the conduit through the gate member, with the valve in a secondary position. 
           [0013]      FIG. 5  is a front perspective view of another embodiment of a snap actuator and valve. 
           [0014]      FIG. 6A  is a top plan view of an annular magnet. 
           [0015]      FIG. 6B  is a longitudinal cross-section of the annular magnet in  FIG. 6A . 
           [0016]      FIG. 7  is a longitudinal cross-section of one embodiment of a snap actuator. 
           [0017]      FIG. 8  is a longitudinal cross-section of another embodiment of a snap actuator. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following detailed description will illustrate the general principles of the invention, examples of which are additionally illustrated in the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. 
         [0019]    As used herein “fluid” means any liquid, suspension, colloid, gas, plasma, or combinations thereof. 
         [0020]      FIGS. 1-4  illustrate one embodiment of a device  100  for use in an internal combustion engine. In one embodiment, the device  100  is included in a brake vacuum boost system. The device  100  includes a housing  102  that includes a container portion  130  and a cap  132  defining an internal chamber  103  ( FIG. 2 ) and having a port  108  in fluid communication with the chamber  103 . As seen in  FIGS. 1 and 2 , the port  108  enters the housing  102  through the container portion  130 . However, in the alternate embodiment illustrated in  FIG. 5 , the housing  102 ′ again includes a container portion  130  and a cap  132 , but here the port  108 ′ enters the housing  102 ′ through the cap  132 . Preferably, the cap  132  is sealingly connected to the container portion  130  in both embodiments. 
         [0021]    Referring to  FIGS. 2-4 , housed within the chamber  103  is an actuator  104  that includes a piston  110  having a stem  114  connectable to a valve mechanism  120 . The stem  114  has a proximal end  152  proximate to the valve mechanism  120  and a distal end  154  removed from the valve mechanism  120  (labeled in  FIG. 2 ). The valve mechanism  120 , in this embodiment, includes a conduit  122  having a valve opening  124  and a pocket  126  and includes a gate member  128  at least partially receivable in the pocket  126  and having a passage  129  therethrough. Other valves may be connected to the actuator  104  such as a poppet valve, a butterfly valve, or other known valves. 
         [0022]    As seen in  FIG. 2 , the conduit  122  may be a tube that has a bore  123  that continuously, gradually tapers or narrows from both ends  156 ,  157  toward the valve opening  124 , thereby having its smallest inner dimension at the valve opening  124 . The bore may be any circular shape, ellipse shape, or some other polygonal form and the gradually, continuously tapering inner dimensions may define, but is not limited to, a hyperboloid or a cone. This hour glass-shaped cross-section  125  of the bore  123 , centered at the valve opening  124 , reduces the required gate travel. In another embodiment, as seen in  FIG. 5 , the conduit  122  may have a uniform inner diameter  127  along its entire length. 
         [0023]    In the embodiment of  FIGS. 1-4 , with the valve mechanism  120  having a gate member  128 , the gate member  128  is connected to the piston  110  by a rail system  160 , as most easily understood from  FIGS. 3 and 4 , providing sliding movement of the gate member  128  along the longitudinal axis A ( FIG. 2 ) of the conduit  122  thereby forming a seal within the conduit  122  in response to pressure within the conduit  122 . The rail system  160  (best seen in  FIGS. 3 and 4 ) includes a guide rail  162  near the proximal end  152  of stem  114 . The guide rail  162  includes raceway grooves  164  on opposing sides thereof. The gate member  128  includes a slider  166  shaped and configured to fit over the guide rail  162  and conform to the raceway grooves  164 . 
         [0024]    The actuator  104  controls the opening and closing of the valve mechanism  120 , in particular the gate member  128 , in  FIGS. 2-4 , by the movement of the piston  110 . As seen in  FIGS. 3 and 4 , the piston  110  is movable between a starting position  140  ( FIG. 3 ) and a secondary position  142  ( FIG. 4 ). The starting position  140  in this embodiment ( FIG. 3 ) is an open position of the valve mechanism  120 . In other embodiments, the starting position may be a closed position of the valve. The piston  110  at least partially includes a magnetically-attractable material  111 , also referred to as a ferromagnetic material, such that the piston  110  is attractable to a first magnet  116  and a second magnet  118  (seen in the cross-section of  FIG. 2 ). A spring  112  is seated against the piston  110  to bias the piston  110  generally into the starting position  140  ( FIGS. 2 and 3 ) and the first magnet  116  is positioned to assist the spring  112  in maintaining the piston  110  in the starting position  140 . The second magnet  118  is positioned to maintain the piston  110  in the secondary position  142  ( FIG. 4 ), when the piston  110  moves to the secondary position  142 . 
         [0025]    The stem  114  of the piston may also extend therefrom opposite the valve mechanism, and, as seen in  FIGS. 2-4 , be received in a guide channel  146  within the cap  132 . The cap  132  may also include a seat  148  for the spring  112 . These features of the cap  132  provide alignment to the actuator and prevent twisting and/or buckling of the spring and piston. 
         [0026]    The actuator  104  may include a first bumper  138  positioned to reduce noise between the piston  110  and the housing  102  when arriving in the starting position  140  ( FIGS. 2 and 3 ) and a second bumper  139  positioned to reduce noise between the piston  110  and the housing  102  when arriving in the secondary position  142  ( FIG. 4 ). In one embodiment, opening  150  (between the housing  102  and the valve mechanism  120 ) may be defined by a generally frustoconical surface and the first bumper  138  may be disposed proximate to the opening  150 . The first and second bumpers  138 ,  139  may be seated in annular grooves within the housing  102  or on a component of the piston  110 , such as the stem  114 . 
         [0027]    Still referring to  FIGS. 2-4 , the piston  110  may also include a sealing member  134  about its outer periphery as a lip seal against the interior surface of chamber  103 . The outer periphery of the piston  110  may include an annular groove  136  in which to seat the sealing member  134 . In one embodiment, the sealing member  134  may be an O-ring, a V-ring, or an X-ring. Alternately, the sealing member  134  may be any other annular seal made of sealing material for sealing engagement against another member. 
         [0028]    In operation, the actuator  104  moves the piston  110  by the introduction of fluid into or the removal of fluid from the chamber  103  via the port  108  and the assistance of the magnets  116 ,  118  and the spring  112 . The piston  110  is seated in a starting position  140  ( FIG. 3 ) and remains in this position held there by the spring force and the magnetic force of the first magnet  116 , which may correspond to either an open or a closed position for an attached valve, until a threshold force is applied to the piston  110  that overcomes the spring force and magnetic force of the first magnet  116 . Once this threshold force is reached, the piston  110  will move the full length of its travel to its secondary position  142  ( FIG. 4 ) with the assistance of the magnetic force of the second magnet  118 , which thereafter maintains the piston  110  in the secondary position  142 . The movement of the piston  110  through its full length of travel is a quick, nearly instantaneous movement substantially without pause therebetween, i.e., there is no lag or floating of the piston in between the starting position  140  and the secondary position  142 , which may be described as a “snap” movement of the piston. This “snap,” which without bumpers is an audible sound, is a result of the magnetic attraction of the second magnet  118  attracting the piston  110  to and into contact with the second magnet  118 , which acts to quickly move the piston to the secondary position  142 . The second magnet  118  thereafter holds or maintains the piston  110  in the secondary position until a lower threshold force is reached, at which point the piston moves back to its starting position  140  by again moving the full length of its travel as a snap-type movement. 
         [0029]    In one embodiment, the first magnet  116  and the second magnet  118  both may be one or more discrete magnets. In another embodiment, the first magnet  116 , the second magnet  118 , or both may be an annular magnet. 
         [0030]    In  FIGS. 6A through 7 , an annular magnet  218  in the position of the second magnet  118  in  FIG. 2 , is described as illustrative, but is equally applicable to the first magnet  116 . The annular magnet  218  has an inner diameter ID and an outer diameter OD, and typically has a uniform thickness or height. Any one or more of these dimensions may be selectively varied to change the magnetic force acting to attract the piston. The annular magnet  218  may include a corrosion resistant coating applied to its exterior surfaces  222 ,  224 . As a result of the annular shape of the magnet, the magnetic force generated by the magnet is uniform circumferentially against the piston, which means that the flux, or magnetic force per unit area, of the magnet face can be less than required when the first or second magnets  116 ,  118  are each one or more discrete magnets. This allows the first magnets to be thinner, which also beneficially reduces cost. 
         [0031]    In the embodiment illustrated in  FIG. 7 , the upper portion of the housing  102  of the actuator  100 , which may be part of a cap, includes the annular magnet  218  and, optionally, a plate  226  disposed adjacent to a second surface  224  of the annular magnet  218  that is opposite a first surface  222  that is most proximate the piston  110 . The plate  226  is mounted against the exterior surface of the housing  102  to direct the magnetic flux emanating from the annular magnet  218  (or the one or more magnets illustrated in  FIGS. 2 and 3 ) around toward the inside of the actuator to increase the overall attractive force acting on the piston  110  and as such must be composed of a material suitable for directing the magnetic flux. In one embodiment, the plate  226  may be an annular plate having an inner diameter, an outer diameter, and a thickness or height. The size and shape of the plate  226  is selected to act on the magnetic flux as described above and is tunable by changing the size and shape thereof. In one embodiment, the plate  226  is a steel annular ring. The addition of the optional plate  226  increases the overall force generated by the magnet that is available to act upon the piston  110  by providing a magnetically conductive path for the flux to be redirected toward the piston  110 . This provides the advantage of increasing the magnetic force and increasing the rate of change of the magnetic force as the piston  110  moves away from the annular magnet  218  (or the one or more magnets). This beneficially allows for smaller and/or cheaper magnets in the actuator. 
         [0032]    As seen in  FIG. 7 , the thickness of the annular magnet  218  may have a thickness substantially equal to the height of the portion of the housing in which it is present. Substantially equal, with respect to this embodiment, means that the thickness of the annular magnet  218  is at least 90% of the thickness of the portion of the housing it is included in. The annular magnet  218  is contained as part of housing  102  in a manner that provides a pressure tight seal so that a vacuum can be connected to chamber  103  above the piston  110 . 
         [0033]    The annular magnet  218  may be placed into a mold in an injection molding machine and a plastic material is injection molded thereto. The mold may be constructed to enable the plastic to be injection molded inside the inner diameter of the annular magnet  218  as well as around its outer surface that defines the outer diameter. The annular magnet  218  may include surface features (not shown) to enhance the bond between the injection molded plastic material and the material of the annular magnet. 
         [0034]    In one embodiment, the annular magnet  218  may be a solid ring of ceramic or ferrite magnetic material. In another embodiment, the annular magnet  218  may be formed by injection molding a mixture of a binder, such as a plastic material, and a magnetic powder that includes, but is not limited to, neodymium, ferrite, or mixtures thereof. In one embodiment, the binder may be a Nylon 6, Nylon 6/6, Nylon 12, or polyphenylene sulfide (PPS) mixed with a neodymium material such as neodymium iron boron (NdFeB). Injection molded neodymium iron boron (NdFeB) magnets may be manufactured by an injection process of pre-mixed magnetic powder with thermoplastic binders which produces an accurate and homogeneous magnetic part. A benefit to this method is that various shapes of magnets can be directly molded into or over components of the actuator thereby eliminating some steps in assembly. With the injection mold process very complex shaped magnets can be achieved with extremely tight tolerances and a broad range of magnetic properties and characteristics. Injection molded magnets are also beneficial because they have good corrosion resistance in water and industrial solvents. In one embodiment, the injection molding method includes a hot runner system to minimize waste/scrap of the magnet powder. If this process is used to manufacture just the annular magnet  218 , rather than building it into or on a part of the actuator, the magnet, after formation, may be transferred to a mold in the shape of the housing  102  or a portion thereof in an injection molding machine and over-molded with a selected injection moldable material. 
         [0035]    In an alternate embodiment, the annular magnet  218  may be formed from one of the magnetic powders disclosed above in a sintering process and after formation, the magnet is transferred to a mold in the shape of a portion of the housing  102  in an injection molding machine and is over-molded with a selected injection moldable material. As with the injection molding discussed above, the magnet may include surface features (not shown) to increase the bond between the injection moldable material and the magnet. 
         [0036]    Still referring to  FIG. 7 , the first surface  222  of the annular magnet  218  is flush with a first interior surface  105  of the housing  102  in the portion thereof in which the annular magnet is contained. This first interior surface  105  is the wall disposed above the piston&#39;s upper surface  171 . This construction allows the first surface  222  of the annular magnet  218  to have physical contact with the piston&#39;s upper surface  171 , which increases the force generated by the magnet when the piston is in contact therewith and also provides a seal for the vacuum. As a result, less magnetic material may be used in the magnet, but still have an effective magnetic force. 
         [0037]    The surface features of the magnets in any of the embodiments disclosed herein may include surface texture and/or other irregularities in the surfaces thereof such as protrusion, detents, recesses, etc. so that the injection moldable material attaches firmly to the magnet. 
         [0038]    While the embodiments herein have been illustrated and described as having the magnets in the housing and the ferromagnetic material as part of the piston, the opposite configuration is also suitable. As such, one or more magnets or an annular magnet  317  may be included in the piston  110  and ferromagnetic material  311  may be part of the housing as illustrated in  FIG. 8 . The actuator, designated by the reference number  300 , still operates as described above with respect to the other embodiments. 
         [0039]    An advantage to the present actuator is that it is tunable. The threshold force can be tuned to the magnetic force of the first and second magnets, the spring force and spring rate, the piston diameter, which are balanced against the friction forces and gravitational forces acting on the piston and the valve. 
         [0040]    Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention which is defined in the appended claims.