Saturday, March 12, 2011

Pneumatic Fire Alarm Signal -- March 12, 2011

Doctor Peter Henri Van Der Weyde wrote the series of articles which gave this blog its name. Here, thanks to Google Patents, is an example of one of his many patents, in this case for a pneumatic fire alarm signal.

United States Patent Office,



SPECIFICATION forming part of Letters Patent No. 242,803, dated June 14, 1881.

Application filed August 31,1880. (No model.)

To all whom it may concern:

Be it known that I, Peter H. Vander Weyde, of the city of Brooklyn, Kings county, State of New York, have invented some im provements in Pneumatic Fire-Alarm Signals, being an improvement on the invention for which Letters Patent were granted, No. 213,536, dated March 25, 1879, which improvements are set forth in the following specification.

My invention consists in a peculiar method of starting a pneumatic fire-alarm by the melting of a separate piece of an easily-fusible alloy, consisting of four parts bismuth, two of lead, one of tin, and one of cadmium, described in the patent granted to me March 25, 1879, No. 213,536, and which melts at as low a temperature as 140° to 150° Fahrenheit, which can still be lowered by the addition of arsenic, gallium, or mercury in small quantities. I obtain thus an automatic fire-alarm without the intervention of electric currents, in the manner described in the adjoined drawings.

Figure 1 of the drawings illustrates my invention. Fig. 2 is a modification for which I intend to make separate application for Letters Patent.

The piece of alloy may have the form of a small block, A, placed over a hole in a plate, C C, and preventing the plunger B from entering this hole. This plunger may be propelled by a weight, as shown in H, or by springs, as shown in K and O. It may also be retained by suspension from above, the links being secured by a pin of the same alloy. This plunger may enter a cylinder like a pump-piston, and so cause by its descent a wave of compressed air to be propelled in a system of tubes, T T, with which it is connected; but I find it more reliable to cause this plunger to act upon a flexible membrane placed under the plate C C. This membrane may be rubber, or even very thin sheet metal. It is stretched over a funnel-shaped piece, E, attached to the series of tubes T T, and will by its depression send a wave of compressed air through the same. These tubes are at their extremity attached at the office of a hotel or warehouse, cabin of a ship, &c., to the signal-receiving alarm box Q by means of the lever L, acted upon by the flexible diaphragm M, which, by bulging outward by the wave, will start the wound-up alarm-clock contained in the box and ring the bell D or give any other kind of audible or visible alarm.

It is evident that such an alarm will be started as soon as any of the thermostats A supporting the weight H or springs K and O melts by the heat of an incipient fire. If, however, several such thermostats are attached to the same series of tubes, the effect of the compressed-air wave upon the membrane M, working the alarm, would be diminished in case all the other membranes were allowed to expand or bulge out. This, however, is effectively prevented by the rigid perforated plates C C, placed over all the diaphragms except that of the receiver M L Q.

It is evident that, instead of the elastic membranes described or piston arrangement referred to a kind of small bellows could be used, or any other device which will permit of a sudden slight depression of the air and send an air-wave through the tubes.

Experience has shown me that it is desirable not to close hermetically this system of tubes and connecting diaphragms, because in that case atmospheric changes in temperature or pressure will cause the membrane to bulge outward or inward in proportion that the temperature ascends or descends, or the pressure decreases or increases, which in either case interferes with the proper operation. In order to prevent such interference, I make one small pin-hole in the tubes or in an additional short tube, N. This will not in the least interfere with the propagation and proper action of a sudden wave, as this has no time to spend itself through so small an aperture, while it will allow the interior air to be kept always in equilibrium with the external air, whatever be the changes of the thermometer and barometer, because they always take place very gradually and have time to diffuse themselves through the small aperture referred to. It is advisable to place these thermostats at the ceiling, near the staircases or elevator-shafts, and, in general, in such places as are most likely to be reached first by the ascending currents of hot air, which always precede an incipient fire.

The greater reliability of iron tubing over stretched wires for communicating the alarm-signals referred to is self-evident.

What I wish to secure by Letters Patent is —

1. The combination, with a pneumatic fire alarm tube, of a plunger retained by a piece or plate of fusible alloy, which, by its melting, will cause the plunger to be propelled by a weight or spring and act upon a diaphragm, bellows, or on an air-pump, and operate the signal, in the manner set forth.

2. The combination of the pneumatic tube, the flexible diaphragm, plunger, and plate of fusible alloy with a rigid perforated plate, as A, between the diaphragm and the plate of alloy, which prevents reflex action between the various diaphragms, as set forth.



J. W. Lasperre,

L. B. Heuser.

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