Abstract:
Actuator controller comprising a body ( 12 ) with an inlet port ( 14 ) coupled to a source of pressurised fluid and in flow communication with primary and secondary spool bores ( 16, 20 ); primary and secondary spools ( 60, 62 ); first and second cross flow ports ( 48, 52 ) communicating said primary and secondary spool bores, compression and expansion outlet ports ( 53, 54 ) for applying pressurized fluid to a return-biased actuator ( 110 ); and a venting outlet port ( 23 ); wherein return action of the working piston of the actuator is facilitated with aid of pressurized fluid already gained in the system.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is generally in the field of controllers for controlling the operation of different actuators. More specifically the present invention is concerned with controllers suited for use in conjunction with return-biased actuators and in particular the invention provides intensification of the return force of the actuator. 
       BACKGROUND OF THE INVENTION 
       [0002]    Controllers for operating and governing the operation of actuators which in turn are coupled to a varsity of valves and other devices are known. Such controllers typically comprise one or more ports connectable to a pressurized fluid source, which by sequential control signals close and open pressure ports and venting ports thereof to thereby impart motion to various valves and the like, articulated thereto. 
         [0003]    A number of differing designs have been formulated for actuator controllers, such as those utilizing dual electromagnetic actuators to move a valve spool in opposite directions. Another example is the use of a double wound actuator, able to energize in both directions. 
         [0004]    An alternative approach is the so called spring return pneumatic actuators which typically comprise one or more cylinders slidingly accommodating therein a spring-biased piston, wherein the piston is spring biased in one direction and pneumatically urged in the opposed direction. Such actuators are at times referred to as single action pneumatic actuators. Accordingly, when compressed air is applied at one end of the piston, the piston is thrust to load the biasing spring so as to provide a useful output bias thrust. However, upon discharging the compressed air the piston is retuned and the spring member is relaxed, with a useful but reversed output linearly reducing thrust, as the spring relaxes. This arrangement offers strong spring-biasing effect at the initial displacement of the piston, whereby the final thrust available as the piston comes to rest is considerably less than the initial return thrust. 
         [0005]    An example of such as design is discussed in GB Patent No. 1373070 to Tugwell disclosing a pneumatic actuator comprising a double-acting piston separating two first chambers, spring means to urge the piston in one direction, and valve means adapted to admit compressed air to one of the chambers and thus to load the spring means, then to transfer some of such air into the other chamber at a selected phase position of the piston, and then to open the said one chamber to atmosphere whereby the combined forces of the spring means and of the compressed air acting on the piston in the other chamber, complete the power stroke of the actuator. 
         [0006]    Hereinafter in the specification and claims, reference will be made to a pressurized fluid useful for operating the controller, with particular reference to pneumatic devices operated by pressurized air. The skilled person will appreciate that such apparatuses are operable with either pressurized air or liquid, the former often being more readily available and suitable for industrial environments. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to provide a fluid-assist actuator controller, for cooperation in conjunction with an actuator of the spring-loaded type, wherein return action of one or more working pistons of the actuator is facilitated by said spring member and with aid of pressurized fluid already gained in the system. 
         [0008]    According to the present invention there is provided an actuator controller comprising a body formed with a pressurized fluid inlet port for coupling to a source of pressurised fluid, and being in flow communication with a primary spool bore and a secondary spool bore extending axially within said body; a primary spool supported and axially displaceable within said primary spool bore; a secondary spool supported and axially displaceable within said secondary spool bore; a first cross-flow port and second cross flow port providing fluid communication between said primary spool bore and said secondary spool bore, at least one compression outlet port and at least one expansion outlet port both extending from said primary spool bore, and a venting outlet port. 
         [0009]    According to a particular design of the present invention, the primary spool bore is formed with a first chamber and an second chamber partitioned from one another by a neck portion sealable by a first seal fixed over the primary spool; said primary spool further comprises a first one-way seal membrane extending in the first chamber and a second one-way seal membrane extending in the second chamber, and admitting fluid flow only in direction from the first chamber towards the second chamber; and a second seal fitted at an end of the primary spool to selectively seal the venting outlet port. 
         [0010]    Furthermore, the secondary spool comprises a small spool head being in flow communication with the pressurized fluid inlet and comprising a small seal; and a large spool head being in flow communication with the expansion outlet port and comprising a large seal. 
         [0011]    The arrangement according to the present invention is such that the secondary spool is displaceable between a first position in which the small seal seals fluid flow between the pressurized fluid inlet and the first cross-flow port, and a second position admitting fluid flow between. Furthermore, the secondary spool comprises a secondary first chamber being in fluid communication with the pressurized fluid inlet and partitioned from an intermediate chamber by the small seal; said intermediate chamber being in flow communication with the first cross-flow port; and a major chamber partitioned from the intermediate chamber by the large seal and being in flow communication with the second cross flow port. 
         [0012]    According to a particular design of the invention the large spool area has a large surface area extending in the major chamber, and a small surface area extending in said intermediate chamber. 
         [0013]    According to a particular arrangement of the invention the second one-way seal membrane is axially displaceable about the primary spool. 
         [0014]    By some further embodiments, the controller may comprise one or more of the following arrangements:
       a manual override for axially displacing the primary spool within the primary spool bore so as to open the venting outlet port. Said manual override may be formed at a sealing plug coaxial with the primary spool bore;   an adjusting member for adjusting axial positioning of the primary spool so as to govern seal engagement of the first seal of the primary spool within the neck portion of the primary spool bore. The adjusting member is screw fitted at a sealing plug coaxial with the primary spool bore.   The at least one compression outlet port and at least one expansion outlet port are fitted with a Namur-type coupling arrangement.   The venting outlet port may be fitted with an adjustable valve for controlling venting rate of the second chamber.   The controller according to the invention may be applied to a variety of mechanisms such as, emergency braking systems, door systems, etc. utilizing a pneumatic lock/return system.       
 
         [0020]    By a further particular design of the controller the first cross-flow port and second cross flow port extend coaxially with the compression outlet port and at least one expansion outlet port, respectively. 
         [0021]    According to the invention, the primary spool is displaceable between a first extreme position where a fore spool head bears against a sealing plug of the primary spool bore, and a second extreme position wherein a shoulder of the primary spool extending intermediate the first seal and the first one-way valve seal bears against a shoulder of the neck portion of the primary spool bore. 
         [0022]    the design of the controller is such that the pressurized fluid inlet port entails full displacement of the primary spool and the secondary spool, into a first position respectively, wherein the primary spool is displaced so as to admit pressurized fluid flow to the compression outlet port and the first chamber and an second chamber are sealingly disengaged from one another; and the secondary spool is displaced so as to seal fluid flow between the pressurized fluid inlet and the first cross-flow port. 
         [0023]    Furthermore, the arrangement is such that terminating pressure through the pressurized fluid inlet port entails displacement of the primary spool so as to seal the venting outlet port and resume fluid flow between the first chamber and an second chamber; and further, the secondary spool displaces so as to resume fluid flow in direction from the first cross-flow port towards the pressurized fluid inlet, until the pressure camber and the second chamber are at pressure equilibrium. 
         [0024]    And further wherein the venting outlet port opens only to exhaust fluid from the second chamber and is otherwise sealed by is a sealing ring mounted on the primary spool, to thereby prevent external fluid from entering the controller through the venting outlet port. 
         [0025]    According to a further aspect of the present invention, there is provided an actuator system comprising an actuator and an actuator controller as described hereinabove, said actuator being formed with one or more pistons displaceable within a piston cylinder, each cylinder being sealingly divided into a first chamber being in flow communication with an compression outlet port of the said actuator controller, and an second chamber being in flow communication with an compression outlet port of said actuator controller; said piston being biased in direction to expand said second chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    In order to understand the invention and to see how it may be carried out in practice, several embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which: 
           [0027]      FIG. 1  is a three-dimensional sectioned illustration of an actuator controller in accordance with the present invention; 
           [0028]      FIG. 2  is an elevation of the primary spool used in the controller in accordance with the illustrated embodiment; 
           [0029]      FIG. 3  is an elevation of the secondary spool used in the illustrated embodiment; 
           [0030]      FIGS. 4A-4C  illustrate consecutive steps of a sequence of operation of the controller in accordance with the present invention cooperating in conjunction with an actuator; 
           [0031]      FIG. 5  is a modification of a controller in accordance with the present invention fitted with a manual override; 
           [0032]      FIG. 6  is a modification of the invention illustrating a controller fitted with a primary spool adjusting member; and 
           [0033]      FIG. 7  is a further embodiment of a controller in accordance with the present invention wherein the venting outlet port is fitted with an adjustable vent valve. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0034]    Attention is first being directed to  FIGS. 1 to 4  for understanding the general construction of the actuator controller in accordance with the present invention generally designated  10 . The controller comprises a body  12  fitted with a pressurized flowing inlet bore  14  adapted for coupling to a source of pressurized fluid, e.g. by a threaded coupling, or otherwise, as known per se. 
         [0035]    Transversely extending within the body  12  there is a primary spool bore  16  sealed at one end by a sealing plug  18  screw coupled at  19  to the body  12 . 
         [0036]    Extending from the pressurized fluid inlet port  14  and in parallel to the primary spool bore  16 , there is a secondary spool bore  20  sealed by a plug  24  screw threaded to the body at  28 . 
         [0037]    The primary spool bore  16  is divided into a first chamber  30  and a second chamber  34  and the secondary spool bore  20  is divided into a secondary first chamber  38  being in flow communication with conduit  120  and the pressurized fluid inlet port  14 , and further there is an intermediate chamber  42  and a major chamber  44 . 
         [0038]    A first cross-flow port  48  extends between the first chamber  30  of the primary spool bore  16  and the intermediate chamber  42  of the secondary spool bore  20 , and a second cross-flow port  52  extends between the second chamber  34  of the primary spool bore  16  and the major chamber  44  of the secondary spool bore  20 , providing controlled fluid flow between said chambers, as will become apparent hereinafter. 
         [0039]    Extending from the first chamber  30  of the primary spool there is a compression outlet port  53  and an expansion outlet port  54  extends from the second chamber  34 . 
         [0040]    Whilst in the present embodiment, and as illustrated in the annexed drawings, there is provided only a single compression outlet port and a single expansion outlet port, it is to be appreciated that there may be more such ports, depending on the desired application. Furthermore, in the particular embodiment, the body  12  is fitted with a Namur-type coupler  57  (i.e. Namur-type interface), configured and sized in accordance with that standard. 
         [0041]    With further reference being made to  FIGS. 3 and 4 , it is noticeable that the primary spool bore  16  accommodates an axially displaceable primary spool  60  and the secondary spool bore  20  accommodates an axially displaceable secondary spool generally designated  62 . The primary spool  60  comprises a substantially flat fore-end  66  fitted for stopping against a substantially flat end  68  of plug  18  ( FIG. 1 ) and further the primary spool  60  comprises a first one-way seal membrane  70  made of resilient material and fixedly retained in position within a groove  72  sized accordingly. A first seal  74 , in the form of an O-ring is fixedly positioned on the primary spool  60  which further comprises a second one-way seal  78  slidingly displaceable over a intermediate portion  80  of the primary spool  60 . Spool  60  is further fitted at its other end with a second seal  82  in the form of an O-ring, fitted for selective sealing of shoulder  84  formed at the venting outlet port  23 . 
         [0042]    Turning back now to  FIG. 1 , it is noticed that the first one-way seal membrane  70  slidingly bears against the substantially smooth wall portion  80  of intermediate portion of the primary spool bore  16  in a sealing engaging manner, allowing fluid to flow only in one direction namely from left to right as visualized in the figure. Similarly, the second one-way seal membrane  78  slidingly bears against a corresponding second substantially flat portion  86  of the primary spool bore  16  to thereby provide sealing engagement therebetween and allow fluid flow over the one-way seal membrane in the same direction, namely from left to right as visualized in  FIG. 1  and as will be explained hereinafter and exemplified with reference to  FIGS. 4A to 4D . 
         [0043]    The first O-ring seal  74  is fitted for sealing fluid flow between the first chamber  30  and the second chamber  34  at an abutting sealing portion  88  of the primary spool bore  16 . 
         [0044]      FIG. 3  illustrates the secondary spool  62  comprises a small spool head  90  formed with a substantially flat forehead  92  and being in flow communication with the pressurized fluid inlet  14  ( FIG. 1 ) and comprising a small O-ring seal  94  fitted for sealing against a corresponding neck portion  98  in the secondary spool bore  20 , partitioning the secondary first chamber  38  from the intermediate chamber  42 . At an opposite end of the secondary spool  62  there is a large spool head  100  formed with a flat head  102  and comprising a large O-ring seal  106  fitted for sealing abutting against smooth wall  108  ( FIG. 1 ) of the secondary spool bore  20  thereby forming a sealed partition between the intermediate chamber  42  and the major chamber  44 . 
         [0045]    Further attention is now directed to  FIGS. 4A-4D  illustrating how the actuator controller  10  in accordance with the present invention cooperates in conjunction with an actuator, in accordance with one particular embodiment designated  110 . Whilst in the particular embodiment the actuator  110  is a double piston actuator, of the so-called spring return type, it is to be appreciated that the controller in accordance with the present invention may be used with a variety of different actuator types such as rack and pinion, skotch yoke, diaphragm and vane types, spring return pistons, etc. as known in the art. 
         [0046]    In the particular example of  FIGS. 4A-4D  a pressure compartment  112  of the actuator  110  is coupled to the compression outlet port  53  of the controller, and two outlet ports  113 , each extending from a spring compartment  114 , are flow coupled to one another by a pressure line  116  which in turn is coupled to the expansion outlet port  54  of the controller  10 . 
         [0047]    Hereinafter in the particular example, particular reference is made to a pneumatic system wherein the working fluid is compressed air. However, it is to be appreciated by a person skilled in the art that the working fluid may be any gas or liquid. 
         [0048]    At an initial state ( FIG. 4A ) pressurized air is introduced into the pressurized fluid inlet port  14  expanding through conduit  119  into the primary spool bore  16 , deforms the first one-way seal membrane  70  resulting in axial displacement of the primary spool  60  until a shoulder  130  of the primary spool  60  (see  FIG. 2 ) comes to rest against a corresponding shoulder  132  formed in the primary spool bore  16 . 
         [0049]    During axial displacement of the primary spool  60  into the position seen in  FIG. 4A , air initially captured within the second chamber  34  and at the major chamber  44  and the cross-flow port  52 , may now be discharged to the atmosphere through venting outlet port  23  since the second O-ring seal  82  disengages from the respective shoulder  84 , to allow a venting aperture therebetween. Pressurized air now flows through the first cross-flow port  48  into the intermediate chamber  42  of the secondary spool bore  20  resulting in pressure applied against the large spool head  100  resulting in further and complete displacement thereof against the stopper plug  24 . 
         [0050]    Upon displacement of the primary spool  60  to the position seen in  FIG. 4A , the first O-ring seal  74  adequately seals against surface  88  of the primary spool bore  16 , thus providing pressure seal between the first chamber  30  and the second chamber  34  of the primary spool bore  16 , resulting in pressure built-up in the first chamber  30  and within pressure compartment  112  respectively. 
         [0051]    During displacement of the primary spool  60 , pressurized fluid (air in the discussed example) from the fluid inlet port  14  expands also through conduit  120  into the secondary first chamber  38  of the secondary spool bore  20 , resulting in axial displacement of the secondary spool  62  in the direction of arrow  124 , until its head surface  102  comes to rest against face  25  of seal plug  24 . At this situation the small seal  94  of the secondary spool  62  seals fluid flow between the pressurized fluid inlet  14  and the intermediate chamber  42  of the secondary spool bore  20 , also sealing fluid flow between duct  120  and first cross-flow port  48 . Displacement of the secondary spool  62  to the position of  FIG. 4A  entails exhaustion of residual air from major chamber  44  through the second cross-flow port  52  and out through the open venting outlet port  23   
         [0052]    Air pressure build up in the actuator pressure chamber  112  of the actuator  110 , results in axial displacement of the double-rack pistons  111  in opposite directions as illustrated by corresponding arrows  131 , against the biasing affect of compression springs  115  in spring chambers  114 . Now the system is in a so-called steady state and standby position. 
         [0053]    It is appreciated that in the standby position, in the event of pressure fluctuations of the pressurized fluid, the pressurized air trapped in the first chamber  30  retains the actuator at its recent position as all outlets from the first chamber  30  are now sealed, namely by the first one-way seal membrane  70 , the small O-ring seal  94  and the large O-ring seal  106  (of the secondary spool  62 ) and by the first seal  74 , respectively. Similarly, any pressure surge will remain trapped within in the actuator such that upon pressure cease, the trapped compressed air is readily available, offering the highest available value of stored energy. 
         [0054]    Upon ceasing the pressurized fluid through the pressurized fluid inlet port  14  ( FIG. 4B ), pressure at the pressure chamber  112  of the actuator  110  and within the first chamber  30  now acts against the non return membrane  70  which results in displacement of the primary spool  60 , in direction of arrow  140  until the fore surface  66  comes to rest against surface  68  of plug  18 . At this state, the first O-ring seal  74  disengages from shoulder  88  and fluid flow is facilitated, from the first chamber  30  towards the second chamber  34 , whilst seal  82  engages with shoulder  84  so as to seal the venting outlet port  23 . Pressurized air from pressure chamber  112  of the actuator  110  now flows into the first chamber  30  and via the gaps formed between the first O-ring seal  74  and the corresponding sealing edge  88  of the primary spool bore  16  thus deforms the second one-way seal membrane  78  such that the compressed air now flows through the second chamber  34 , along arrows  37  ( FIG. 4B ) and via the compression outlet port  54  to the coupling duct  116  and into the spring chambers  114 . 
         [0055]    The compressed air now flowing into pressure line  116  generates pressure in piston chambers  114  which together with the biasing effect of return springs  115  results in force applied on the pistons  111  to contract and thus rotate the pinion  121 . 
         [0056]    Further, pressurized air now flows also through the second cross-flow port  52  resulting in pressure build-up within the major chamber  44  whereby the secondary spool  62  now begins displacement leftwards (arrow  79  in  FIG. 4C ). This occurs as a result of pressure equilibrium between the first chamber  30  and the second chamber  34  and the associated intermediate chamber  42  and major chamber  44 , respectively. This situation is reached as a result of difference in surface area applied on opposite faces of the large spool head  100  namely at the major chamber  44  and the intermediate chamber  42  and the surface area of the small seal  94 . 
         [0057]    Upon displacement of secondary spool  62  leftwards, i.e. into the position of  FIG. 4C , seal  94  disengages from neck portion  98  to allow fluid flow therethrough, and through conduit  120  into pressurized fluid inlet  14 , thus venting the pressure compartment  112  of the actuator  110 , the first chamber  30  (via first cross-flow port  48 ) and the intermediate chamber  42 , along arrow  99 . At this situation, residual pressure remains trapped at second chamber  34  and the pressure line  116 , spring cambers  114 , second cross-flow port  52  and the major chamber  44 , respectively. 
         [0058]    The residual pressure within the system provides additional thrust on the pistons  111  of the actuator  110 , in addition to the biasing effect of the springs  115 . 
         [0059]    The next sequence of operation is similar to the situation disclosed at the initial situation of  FIG. 4A . 
         [0060]    It is noticed from the above disclosure that the above system utilizes compressed air already contained within the actuator and which has been used for activating the pistons in one direction, for operating it in an opposite direction, instead of merely discharging said utilized pressurized air to the atmosphere. 
         [0061]    The controller acts as a built-in automatic sensor for torque increase that will utilize the added energy from residual air in the first chamber to give additional torque for operating the actuator when required. Any delay in the actuator movement that is a result of increasing torque (i.e. resistance applied by a valve or other device articulated thereto), will cause the air pressure to equalize between the first chamber and the second chamber sooner and provide the additional torque required for overcoming said resistance. 
         [0062]    The sealed position of venting outlet port  23  prevents ingress or suction of ambient air and particles into the controller  10  and/or actuator  110  whereby such ambient, untreated air (not to mention dirty air) may cause corrosion and damage the system. 
         [0063]    Another advantage of the a actuator controller in accordance with the present invention is, as mentioned hereinabove, that at the event of non continuous pressure supply (sudden or scattering irregulate pressurized air supply) the actuator retains the highest pressure because of the non return seal valve membranes, and maintains its position so as to retain its last acquired position with maximal stored compressed fluid. 
         [0064]    It is further noticeable that the second one-way seal  78  is displaceable over the primary spool  60  between its first position noticeable in  FIGS. 4A and 4D  and the second position noticeable in  FIGS. 4B and 4C . This enables further displacement of the primary spool  60  with respect to the second one-way seal membrane  78 , in case of residual air pressure within the second chamber  34  and upon applying pressure through the pressurized fluid inlet  14 . 
         [0065]      FIG. 5  illustrates a modification of the invention wherein a manual override system generally designated  150  is provided for axially displacing the primary spool  60  within the primary spool bore  16  so as to open the venting outlet port  23 , thus discharging compressed air within the spring chambers  114  of the actuator (not shown in  FIG. 5 ). 
         [0066]    The manual override system  150  comprises an eccentric wheel  152  fixed to plug  18  and fitted with a manual lever  154  whereby rotating the lever in the direction of arrow  156  entails axial displacement of a pushing rod  158  bearing against fore surface  66  of the primary spool  60  displacing it in the direction of arrow  162 , whereby the second O-ring seal  82  disengages from the sealing shoulder  84 , thus opening the venting outlet port  23 . 
         [0067]      FIG. 6  illustrates still a modification of the invention wherein the plug  18  sealing the primary spool bore  16  is fitted with an adjusting member generally designated  170  comprising a screw threaded boss  172  which may gently be axially displaced with respect to plug  18  by means of an adjusting screw  174 . Such adjustment provides manual readjusting the axial positioning of the primary spool  60  within the primary spool bore  16 , so as to govern the sealing engagement of the first O-ring seal  74  with respect to the sealing shoulder  88  of the primary spool bore  16  so as to delay or advance displacement of the primary spool  60  by changing the point of sealing contact namely, changing the time at which pressure equilibrium between the first chamber  30  and the second chamber  34  is obtained. 
         [0068]    In the embodiment of  FIG. 7  the venting outlet port  23  is fitted with an adjustable nozzle  180  for controlling the venting rate of the second chamber  34  so as to control the actuator operating speed within the system at which the controller is applied. The adjusting nozzle  180  in accordance with the example of  FIG. 7  is screw coupled to the venting outlet port  23  and comprises a tapering outlet nozzle  182 , the outlet section of which is controllable by a screw coupled nozzle end  184 , rotation of which adjusts the size of the outlet orifice. 
         [0069]    It is to be appreciated that a controller in accordance with the present invention may be integrated within a housing of a solenoid pressure supply line. 
         [0070]    Whilst some embodiments have been described and illustrated with reference to some drawings, the artisan will appreciate that many variations are possible which do not depart from the general scope of the invention,  mutatis, mutandis.