Electronically controlled swell shutter operator for pipe organs

#The present invention relates, in general, to pipe organs, and more particularly to a system for electronically positioning the volume-controlling shutters for a pipe organ swell chamber.

#In pipe organs the various tones are derived from wind blown pipes. Each pipe is capable of sounding at only a single intensity (volume) level; and if an attempt is made to control the loudness, as for example by changing the air pressure, an unacceptable variation in tuning will result. In order to surmount this limitation, it is customary in a pipe organ to place the pipes of at least some of the divisions of the organ in a box or room called a (swell box or swell chamber) separated from the main listening room by a set of moveable shutters (sometimes called shades). When closed, these shutters effectively close off the chamber from the listening room and substantially attenuate the sound that is heard. A swell pedal (or swell shoe) is provided at the console and can be adjusted to several positions for controlling the extent that the shutters are opened. Patents that relate to swell shutters and swell boxes include U.S. Pat. Nos. 500,040 issued to E. M. Skinner in 1893, and 2,005,643 issued to H. Willis et al. in 1935.

#In early swell devices the shutters were mechanically linked to the swell pedal by means of operating rods or cables. With the development of electrically controlled key actions it became common to place the console at a remote location from the chambers, and it became difficult to arrange the necessary mechanical linkage to the swell chamber shutters. The next step was the development of electrically controlled pneumatic swell shutter operators, an example of which is shown in U.S. Pat. No. 2,072,844. Such pneumatic devices have been employed for decades and have been reasonably successful; however they have many limitations, the most important of which is their large size. Pipe organs operate on low wind pressures, and in order to achieve sufficient force to move the relatively heavy shutters with promptness, operating pneumatics of great bulk are necessary. In past decades wind pressures of up to 15 inches water gauge were commonly used. This is in fact a relatively low pressure (about one-half pound per square inch), and created problems in driving prior swell shade operators. However, the problem of rapidly and accurately moving swell shade operators is now greatly exacerbated by the current trend back to the very low pressures used in early organs, where the pipes speak on pressures in the order of one and one-half (11/2) or two (2) inches water gauge.

#The foregoing and additional objects, features and advantages of the present invention will become apparent to those of skill in the art from the following detailed description of a preferred embodiment, taken in conjunction with the accompanying drawings, in which:

#FIG. 1 is a perspective view of a swell shutter operator according to the invention;

#FIG. 2 is a schematic circuit diagram of the swell shoe potentiometer circuit board assembly;

#Referring to the drawings, FIG. 1 is a perspective view of a preferred form of the swell shutter operator 10 of the invention. As illustrated, the operator incorporates a DC electric motor 11 having an output shaft 12 connected to a speed reducer 13. The speed reducer has an output shaft 14 to which is connected a crank arm 15, the outer end of which carries a connector 16 for use in connecting the output of the swell shutter operator to the shutters, or shades, of a swell chamber (not shown). The speed reducer is a conventional gear mechanism which reduces the speed of rotation of motor shaft 12 by about 50 to 1 and causes the output crank arm 15 to rotate either in a clockwise or a counterclockwise direction, as viewed in FIG. 1, depending upon the polarity of the voltage supplied to the motor.

#Also connected to the output shaft 14 of the speed reducer is a position indicator cam 18 which is connected to the shaft by a suitable set screw and which is shaped to produce from a potentiometer to be described a voltage which corresponds to the rotational position of shaft 14. A cam follower 19 is secured to and supported by a wall 20 which forms a part of a housing for motor 11, the cam follower being held in position by suitable brackets 21 and 22. A coil spring 23 surrounds cam follower 19 and is mounted between bracket and a flange 24 on a first, contact end of the cam follower so that the spring presses the cam follower into contact with the camming surface of cam 18. A suitable bearing 25 is mounted within bracket 22 to hold the cam follower so that as the cam 18 rotates, the cam follower 19 slides laterally through the bearing 25.

#The second end of the cam follower opposite to the contact end and spaced from cam 18, passes through bracket 21 and rides in a tube 26 secured to the bracket. The cam follower fits snugly in the near end of tube 26 so that ambient light does not enter, the distal end of the tube being closed by a photocell housing 28 mounted on the tube. The photocell is exposed to the interior of tube 26, and the end of the cam follower carries a light emitting diode (not shown) which is connected by leads 29 to a terminal block 30. The light emitting diode rides in tube 26 with the cam follower 19, sliding back and forth in a horizontal direction as viewed in FIG. 1 as the output shaft 14 rotates, and moving toward and away from the photocell.