Abstract:
The invention provides an actuator for actuating a pallet of a pipe organ under the command of a key of an organ. The actuator comprises a movable member, adapted to be connected to the pallet of the organ pipe and a magnetic plunger, mounted on the movable member. It also comprises an electromagnet having a gap within which the magnetic plunger can be inserted and moved, wherein the electromagnet when energized moves the member to thereby actuate the pallet. A controller unit controls a current in the electromagnet to provide a controlled actuation of the pallet that is proportional to a key dip of the key. It also provides for a system based on a digital serial link for controlling an assembly of organ pallets that are actuated by electromagnets.

Description:
RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 11/694,184 filed Mar. 30, 2007, which is a continuation under 35 USC §120 of International patent application no. PCT/CA2005/001521 filed Sep. 30, 2005 entitled PROPORTIONAL ELECTROMAGNET ACTUATOR AND CONTROL SYSTEM, which claims priority of U.S. provisional patent application No. 60/614,463 filed Oct. 1, 2004 entitled PROPORTIONAL ELECTROMAGNET ACTUATOR AND CONTROL SYSTEM under 35 USC §119(e), the specifications of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to field of electromagnet actuators, particularly to those used in pipe organs. 
       BACKGROUND OF THE ART 
       [0003]    Pipe organs can be very large instruments with thousands of pipes. Usually, each organ pipe is equipped with a pallet which closes and opens the pipe to the passage of air therethrough. When the pallet is opened, the air flow can enter the pipe and as a result a sound is produced. The pallet is opened when the organist presses the corresponding key on the organ keyboard. 
         [0004]    Modern pipe organs use electromagnets to open a pallet when the corresponding key is pressed: pressing a key sends a current to the solenoid of the electromagnet that pulls open a moveable armature of the electromagnet. Since the armature is connected to the pallet, moving the armature causes the pallet to open. In order to control the assembly of the electromagnets that actuate the numerous pallets, an electric control system is also a part of the organ as a whole. Because of the numerous pallets an organ can have, current control systems can be however quite cumbersome. 
         [0005]    Current electromagnet systems used for controlling the closing and opening of pallets function according to an ON/OFF principle, i.e. the pallet is either opened or closed. Pipe organs containing such electromagnet systems are therefore insensitive to the subtlety and intensity of an organist&#39;s touch to the keys. 
       SUMMARY OF THE INVENTION 
       [0006]    In one of its aspects, the present invention provides an electromagnet actuator that presents a mechanical structure that is stable and, at the same time, compact enough such that many of these electromagnets can be stacked to control hundreds of pipes. The present invention also provides for a system to control these electromagnet actuators such that each of these electromagnet actuators can provide an opening of a pallet that is proportional to the key dip of the corresponding key that was pressed by the organist. The present invention also provides an efficient and simple control system based on a digital serial link. 
         [0007]    The invention provides an actuator for actuating a pallet of an organ pipe under the command of a key of an organ. The actuator comprises a movable member adapted to be connected to the pallet of the organ pipe; a magnetic plunger, mounted on the movable member; an electromagnet having a gap defined therein for receiving the magnetic plunger when energized, the gap comprising a space between a magnetic north pole and a magnetic south pole of the electromagnet formed when the electromagnet is energized; and a controller unit to control a current in the electromagnet to provide a controlled actuation of the pallet, proportional to a key dip of the key. When the electromagnet is energized with the current, a magnetic field is created between the magnetic north pole and the magnetic south pole of the electromagnet, exerting a force over the magnetic plunger and thereby moving the member to actuate the pallet of the organ pipe. 
         [0008]    Advantageously, the electromagnet and the magnetic plunger of the actuator have similar cross-sections, to provide for a low reluctance magnetic circuit, the magnetic circuit being created when the electromagnet is energized. 
         [0009]    Advantageously, the movable member comprises an arm pivotally mounted on the electromagnet and comprises low permeable material such as to be substantially external to the magnetic circuit. 
         [0010]    Advantageously, the actuator further comprises a controller unit to control a current in the electromagnet to provide a controlled actuation of the pallet. 
         [0011]    The invention further provides a controllable actuator for actuating a pallet of an organ pipe under the command of a key of an organ. The actuator comprises a movable member having a magnetic plunger and an electromagnet having a gap within which the magnetic plunger can be inserted and moved. The electromagnet further has a core comprising at least two parallel portions, and at least two coils respectively wound around the parallel portion, whereby each coils produces partial magnetic field which are added to contribute to a total magnetic field of the electromagnet and thereby control the movement of the magnetic plunger and hence of the member, wherein the electromagnet when energized moves the member to thereby actuate the pallet of the organ pipe. 
         [0012]    The invention further provides a system for controlling an assembly of pallets in an organ, wherein each pallet is actuated by an electromagnet actuator and corresponds to a key of the organ. The system comprises a plurality of key dip measurement units for measuring for each of the keys a dip as a function of time and for providing a plurality of digital key dip statuses. It also comprises a plurality of controllers, wherein each controller is connected to one of the electromagnet actuators. It also comprises a communication unit for receiving the digital key dip statuses and relaying each of the statuses to the corresponding controller via a serial link, wherein the controllers control the electromagnet actuators upon receiving the digital key statuses to thereby provide for each pipe an opening proportional to the corresponding key dip. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0013]    In order that the invention may be readily understood, embodiments of the invention are illustrated by way of example in the accompanying drawings. 
           [0014]      FIG. 1  is a schematic view of an electromagnet actuator to open a pallet in accordance with a one embodiment of the present invention. 
           [0015]      FIG. 2  is a perspective view of the electromagnet actuator of  FIG. 1 , when the member is a pivotal arm and shown without the coils. 
           [0016]      FIG. 3  is a cross-section view of the electromagnet actuator of  FIG. 2 , with the arm in the upper position. 
           [0017]      FIG. 4  is a cross-section view of the electromagnet actuator of  FIG. 2 , with the arm in the lower position. 
           [0018]      FIG. 5  is a schematic view of an electromagnet actuator to open a pallet in accordance with an alternative embodiment; 
           [0019]      FIG. 6  is a block diagram of a system to control an organ in accordance with one embodiment of the present invention 
           [0020]      FIG. 7  is a block diagram of keyboard card according to an embodiment of the invention; 
           [0021]      FIG. 8  is a block diagram of showing the connection of a central processing unit and a plurality of consoles according to an embodiment of the invention. 
       
    
    
       [0022]    Further details of the invention and its advantages will be apparent from the detailed description included below. 
       DETAILED DESCRIPTION 
       [0023]    In the following description of the embodiments, references to the accompanying drawings are by way of illustration of an example by which the invention may be practiced. It will be understood that other embodiments may be made without departing from the scope of the invention disclosed. 
         [0024]      FIG. 1  illustrates schematically an electromagnetic actuator  10  in accordance with one embodiment of the present invention and its relation with an organ pallet (not shown). The electromagnet actuator  10  comprises an electromagnet  14 , a magnetic plunger  16  and a member  18 . In one embodiment of the present invention, the electromagnetic actuator  10  also comprises biasing means to apply a force on the member  18  to keep it normally in an upper position (when the electromagnet  14  is not energized). In  FIG. 1 , such biasing means is a spring  38 , imparting a vertically upward force to the member  18  and thereby helping to keep the pallet closed. The electromagnet  14  comprises a magnetic core  20 , which can have various shapes and usually made of soft iron, at least one coil  22  for creating a magnetic flux in the electromagnet  14 , and a gap  30  defined therein. The plunger  16 , made of a permeable material, is attached to the member  18  and has dimensions such that it can fit inside the gap  30  of the electromagnet  14  while leaving a desired amount of space on either side of plunger  16 . Therefore, when the electromagnet  14  is energized (by having a current flowing through the coil  22 ), a magnetic induction is produced inside the magnetic core  20 , and in the plunger  16  and the gap  30 , creating a magnetic field, whose lines follow roughly the geometry of the core  20  in order to reduce the gap  30  and produce vertical downward movement. The magnetic field defined through the gap  30  exerts a vertically downward attraction force over the magnetic plunger  16 , such that the plunger  16  and the member  18  to which it is attached will be moved towards the gap  30 . If the member  18  is attached by a connector (not shown) to the pallet, the member  18  moving towards the electromagnet  14  will provide an opening of the pallet. When the current of the electromagnet  14  is shut down, the member  18  is brought back to its upper position by means of the spring  38  retaining force, which helps to keep the organ pallet closed. 
         [0025]    While  FIG. 1  illustrates very schematically the principles of the electromagnet actuator  10 , it will become apparent to one skilled in the art that many other geometries of the core  20 , of the member  18 , of the plunger  16  and of the physical relationships between these elements are possible and are intended to be covered by the present invention. 
         [0026]    In an alternative embodiment, for example, the magnetic core  20  can lack the symmetrical geometry of the core  20  illustrated in  FIG. 1 . Similarly, the gap  30  defined in the core may by placed elsewhere in the magnetic field defined by the magnetic core  20 . Similarly, more than one coil  22  can be part of the electromagnet  14  or the coil  22  may be disposed differently with respect to the magnetic core  20 . In short, many configurations of the electromagnet  14  can be realized, without departing from the scope of the present invention. 
         [0027]    One of these configurations is shown in  FIGS. 2 ,  3  and  4  in which an electromagnet actuator  10  having as a member  16  a pivotal arm  24  is illustrated with a pair of coils  22 . The arm  24  comprises a connecting point  29  to which a connector linked to the pallet (not shown) is affixed. The arm  24  is mounted to the core structure  20  by means of a pivot  26 . Hidden inside the arm  24 , is the plunger  16  which is located just behind the two screw holes  17 , just at the level of the core gap  30 .  FIG. 2  illustrates the structure of the electromagnet  10  that was made to receive two coils  22  producing parallel magnetic fluxes. The two coils  22  are shown on two separate and parallel legs of the core. The two coils  22  are electrically connected such that when they are energized, they produce magnetic fields that add up in the core  20 . To increase the magnetic field inside the core  20 , more parallel legs (also referred to herein as parallel portions) with coils can be added to the two existing coils. Thus, in this geometry, the magnetic flux flows around the core from the two coils  22 , to the core&#39;s left part  27 , then to the left top part  23 , and then traverses the plunger  16  and the gap  30  to flow in the right top part  21  to the core&#39;s right part  25  to finally close the magnetic circuit. It can be noted that one advantage of the present structure is that substantially no magnetic flux flows through the arm  24 . The arm is not therefore part of the magnetic circuit which enables to reduce the reluctance of the electromagnet  14 . It can also be noted that one particularity of this electromagnet  14  is having a magnetic core cross-section that is relatively constant along the magnetic circuit, (including the magnetic plunger  16 ), which is another way to reduce the reluctance of the actuator  10 . 
         [0028]    In this particular embodiment, since the arm  24  does not have to be made out of a permeable material, as it is not part of the magnetic circuit of the electromagnet  14 , a polymer material may be used for the arm  24 . That provides a very light arm  24 , easier to pivot than a metallic arm, such as those that can be found in prior art systems. 
         [0029]    A PCB plate  32  can also be seen on the top of the actuator  10  structure, which is just above the arm  24 . This PCB plate  32  is equipped with a Hall effect sensor  36  ( FIGS. 3 and 4 ) that measures the position of the arm  24  by detecting the position of a permanent magnet  34  located on the arm  24 . The PCB plate  32  also has the role of controlling the coil current as a function of position in time in order to provide an opening of the pallet that is proportional to the key dip of the key when pressed by the organist. 
         [0030]      FIG. 3  illustrates the actuator  10  when the arm  24  is in an upper position and  FIG. 4  illustrates the actuator  10  when the arm  24  is in the lower position. The arm  24  is in an upper position when the electromagnet  14  is not energized and the pallet to which it is connected is closed. It is understood that, in the upper position, the plunger  16  must be slightly engaged in the gap  30 . The arm  24  is in a lower position when the electromagnet  14  is energized, and in that case, the pallet to which it is connected is completely open. Naturally, PCB  32  can control the opening of the arm  24  (and of the pallet) to an intermediate position corresponding to an intermediate key dip. As it can be seen, the plunger  16  (illustrated by dashed lines) is almost completely in the gap  30  when the arm  24  is in the lower position such that it fills almost totally the gap space. 
         [0031]    Thus, the present invention provides for an electromagnet actuator  10  that can deliver sufficient work to open the pallet pipe and at the same time be compact, thanks to its dual coil geometry and its low reluctance. The present invention provides also for an electromagnet actuator  10  that presents a very stable structure that is less susceptible to deformation created by very high magnetic flux. 
         [0032]    Naturally, other electromagnet actuators configurations than the one just described, could be thought of, having an equivalent compact and stable structure and without loosing potential in delivering work. An example of another configuration  10 ′ having such characteristics is illustrated in  FIG. 5 , where the pivotally arm  24  is shorter and is made of highly permeable material. In that configuration, the plunger  16  and the arm  24  are corresponding to the same entity and the arm  24  is part of the magnetic circuit. Because the cross-section of the arm  24  is substantially the same as the cross-section of the core  20  the reluctance of the magnet can be kept low. The dual coil configuration allows keeping the electromagnet actuator  10 ′ compact without sacrificing on the deliverable work to open the pallet valve. 
         [0033]    Turning now to  FIG. 6 , the architecture of a system for controlling an organ will be described. For simplicity, only three keys  1  of the organ are schematically illustrated with their accompanying control elements, but obviously, the system  9  can be generalized for the whole assembly of keys  1  of the organ. The system  9  measures, as a function of time, with key measurement units  60 , the key dip of the keys  1  of an organ keyboard  2 . In this embodiment, each key  1  is equipped with its own key dip measurement unit  60 . The unit  60  then converts the analog key dip signal to a digital signal, referred to as a digital key dip status  61 . This digital key dip status  61  is then relayed to a communication unit  62  that manages the input/output of the system  9 . In particular, communication unit  62  relays to each controller  64  of each electromagnet actuator (and eventually to each electromagnet actuator PCB  32 ), the corresponding digital key dip status  61 , such that the actuator  10  can provide the proper proportional action to the pallet  12 . In this particular embodiment, the communication unit  62  relays the digital key dip statuses  61  in accordance with, for example, the RS-485 data transmission standard, so that the digital key dip statuses  61  are relayed via a serial numerical link  69  to the actuators via their respective controllers  64 . In an embodiment, each controller  64  can be mounted on a corresponding PCB  32  (shown in  FIG. 2 ). Each controller  64  has a micro-processor and is addressable by the link  69 . It is also possible to add RF transceivers on controller  64 , for data exchange purposes. 
         [0034]    The use of a numerical serial link  69  facilitates the interconnections between the pallets and the control system. It also enables one to remotely program (or reprogram when needed) each controller associated to each organ pipe actuator. Those controllers could also be controlled by another control system via another type of serial link, as someone skilled in the art will know, which open other application possibilities for the above described electromagnet actuator and controller. 
         [0035]    Now, with respect to  FIG. 7 , an alternative embodiment of a system for controlling an organ will be described. In the embodiment of  FIG. 7 , each keyboard has a digital keyboard card  70  associated therewith. The digital keyboard card  70  may be installed under the keys of the keyboard. In an embodiment of the present invention, the digital keyboard card  70  has 32 channels (more or less channels are also envisaged), having the ability to read the position of 32 keyboard keys. Each key has a permanent magnet installed thereon. A plurality of Hall effect sensors  71 A,  71 B,  71 C,  71 D is used to read the position of each key. The change of position of each permanent magnet produces a variation in the surrounding magnetic field that is detected by the Hall effect sensors  71 . While in the embodiment of  FIG. 7 , only four such sensors  71  are shown, it will be understood by someone skilled in the art that for each key of the keyboard, there is a sensor  71  provided. 
         [0036]    The digital keyboard card  70  comprises a multiplexer  73  that receives the 32 signals from the Hall effect sensors  71 . In an embodiment, the 32:8 multiplexer provides, across 8 channels, the signals to an analog to digital converter  75 . Other multiplexer ratios are envisaged. The sampled signals relating to the pressed keys and their position are sent by the microprocessor  77  through a receiver/transmitter unit  79  to a central processing unit (shown as numeral  83  on  FIG. 8 ). The microprocessor unit  77  sends the information along a serial communication link  72 , which, in an embodiment, is an RS-485 data transmission standard. 
         [0037]    With respect to  FIG. 8 , the digitalization and serialization of information through the use of the digital keyboard card  70  provides the advantage that a plurality of keyboard cards  70 A,  70 B,  70 C,  70 D,  70 E,  70 F, from a plurality of organs consoles  80 A,  80 B, can be connected simultaneously to a same central processing unit  83 . Persons skilled in the art will recognize that the number of connections to the central processing unit  83  is greatly reduced in the configuration shown in  FIG. 8  comparatively to a configuration where each key or each keyboard card  70  is connected directly to central processing unit  83 . 
         [0038]    Although the present invention has been described hereinabove by way of specific embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined herein. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.