Fig. 7. Valve and Valve Seat, Hope-Jones Electric Action
The valve-seat H has formed on its lower surface two crescent shaped long and narrow slits. A very slight movement of the armature disc J, therefore, suffices to open to the full extent two long exhaust passages. The movement of this disc is reduced to something less than the 1/100 part of an inch. It is, therefore, always very close to the poles of the magnet, consequently a very faint impulse of electricity will suffice (aided by gravity) to draw the disc off the valve-seat H. The zinc plate K being in intimate contact with the iron poles of the magnet N, protects the latter from rust by well-known electrical laws. All the parts are made of metal, so that no change in the weather can affect their relative positions. R is the point at which the large motor B is hinged. G is a spring retaining cap in position; O the wires leading from the keys and conveying the current to the magnet N; Q the removable side of the box A.
Fig. 7 represents a larger view of the plate K in which the magnet poles N are rigidly fixed—of a piece of very fine chiffon M (indicated by a slightly thicker line) which prevents particles of dust passing through so as to interfere with the proper seating of the soft Swedish charcoal iron armature disc J—of the distance piece L and of the valve seat H.
On the upper surface of this valve seat H another piece of fine chiffon is attached to prevent possible passage of dust to the armature valve J, from outside.
As all parts of this apparatus are of metal changes in humidity or temperature do not affect its regulation.
The use of this action renders it possible for the console (or keyboards, etc.) to be entirely detached from the organ, moved to a distance and connected with the organ by a cable fifty or one hundred feet or as many miles long. This arrangement may be seen, for example, in the College of the City of New York (built by the E. M. Skinner Co.), where the console is carried to the middle of the platform when a recital is to be given, and removed out of the way when the platform is wanted for other purposes.
As all the old mechanism—the backfalls, roller-boards and trackers—is now swept away, it is possible by placing the bellows in the cellar to utilize the inside of the organ for a choir-vestry, as was indeed done with the pioneer Hope-Jones organ at St. John's Church, Birkenhead.