U. B. HODGBS &'T. MGGAFFREY.

FUSIBLE PLUG FOR AIR OOMPRESSOBS.

APPLICATION FILED 0013.25, 1911.

13.2.6521, Patented Aug.2 i,1912. 4

MTNESSES. mvENTORs {A} 11 K A? as: 5%

exact description thereof.

UNITED STATES PATENT OFFICE.-

ennnrns B. HOIDGES, or PITTSBURGH, AND THOMAS MGCAFFREY, or BRIER HILL,

PENNSYLVANIA.

FUSIBLE PLUG FOR AIR-COMPRESSORS.

Specification of Letters Patent.

Patented Au g. 27, 1912.

Application filed October 25, 1911. Serial No. 656,641.

of the United Hill, in the ThomashlCCxrrurY, a citizen States, and resident of Brier State of Pennsylvania, have invented a new i and useful Improvement in Fusible Plugs and We do hereby defor Air-Compresso-rs clare the following to be a full, clear, and

Our invention relates air-compressors.

The object of our invention is to provide a fuiible plug located adjacent to the discharge valve of the compressor to indicate by the melting out of the fusible metal abnormally high temperatures of the air. As is of course well known, the air is always heated by compression and if the temperature rises to an excessive degree, it will cause evaporation of the necessary lubricating oils in the cylinder resulting in an explosive compound of the evaporated oil and air which may a little later be ignited by an increased temperature due to compression, resulting in serious explosions which in the operation of air compressors has resulted in the loss of life and injury in addition to the loss occasioned by the destruction of property.

Our invention therefore consists in a plug located at the discharge of the compressor and adjacent tothe discharge valve, said plug having a button of metal fusible at a higher temperature than the normal temperature of the air when discharged under proper conditions, whereby an outlet is afforded through said plug to the atmosphere to reduce the temperature and so give the proper warning to the operator that the compressor is working inefliciently.

In the accompanying drawings Figure 1 is a sectional view of a single acting compression cylinder with our invention applied thereto; and Fig. 2 is an enlarged vertical section of our improved safety plug.

Referring to the drawings we have illustrated our invention in connection with a single acting compressing cylinder 2 although it will be apparent that the invention is equally applicable in connection with a double acting compressing cylinder or with two or three-stage air-compressors and we to fusible plugs for county of Allegheny and State of Pennsylvania, and:

and adapted have selected the single simplicity of illustration. The piston 3 opcrates within the cylinder 2 and said piston compresses air only when traveling in the direction of the arrow, the other side of the piston being open to the atmosphere. Located within the cylinder head is the inletactuated puppet-valve and through which the air is drawn as the piston withdraws. The discharge valve 5 isalso a spring-ac tuated puppet-valve of the usual construction which is open when the piston is advanced and the compressed air is forced through said valve to the discharge pipe .6. The cylinder is assist in preventing excessive temperatures. The plug 8 formed of brass or other suitable metal is provided with the passage 9 which communicates with the cap 10 threaded onto said plug. The cap l'0'is provided with the vents or apertures 11. The tubular extension 12 is screwed into the plug 8 and at the lower end of said extension is inserted the fusible metal 13. forming this fusible button is of such compositionthat it will melt at a temperature higher than the normal temperature of the air when discharged under the conditions of This temperature may be 50 or 100 higher than such normal temperature of the air. An alloy of tin and lead hasbeen found suitable for the purpose under many conditions. lVe do not, however, wish to confine ourselves to any particular alloy or metal as there may be many suitable for our purpose. I

The plug 8 is located adjacent to the discharge valve and in the case of the compressor illustrated, an opening is formed in the discharge. pipe 6 and the threaded portion 14 of the plug is screwed into said opening. The extension 12 extends into the pipe a suflicient distance to remove the. fusible metal from the cooling influence of the external air, and accordingly the inner end of said extension is indicated as at the center or substantially center of the discharge pipe 6. In the using of our invention and Working under normal conditions the fusible plug remains intact. In the operation of airacting cylinder for" valve at which is an ordinary type of spring provided with the Waterchambers 7 for the circulation of waterto The metal selected for the 'normal operation of the compressor."

compressors the increased temperature of the air may be caused by leaky valves such as the'discharge valve 5 forit is clear that if the valve 5 leaks the cylinder Will not be filled with cool, fresh air from the outside through the valve 4,'but will be filled b the hot compressed air rushing back under the valve 5, if said valve is in a leaky condition.

This excessive temperature of the air in the cylinder Will cause evaporation of the lubrieating oils in said cylinder and the result Wlll be an ex losive compound Which is cause of the abnormal operation in time'to preventexplosions or material loss due to the continued operation of the compressor in an ineflicient manner.

What We claim is:

1. The combination with an air-compressor, of a plug located adjacent to the outlet of said compressor, said plug having a passage connecting the atmosphere with the passage conveying compressed air, and a fusible metal closing said passage.

2. The combination With an air compressor, of a plug located adjacent to the outlet of said compressor, having an eXten-' sion in the path of the discharged air, said plug having a passage connecting the atmosphere With the passage'conveying compressed air, and a fusible metal in said extension.

3. The combination with an air compressor,'ofa vertical plug beyond the outlet ofsaid compressor, said plug having a passage connecting the atmosphere with the passage conveying compressed air, and a fusible metal in said plug. n

4. The combination with an air compressor, of a vented discharge passage closed by a fusible metal.

In testimony Cwhereof, we the said CHARLES B. Honors and THOMAS MoCAr- FREY have hereunto set our hands.

CHARLES E. HODGES. THOMAS MGGAFFREY. Witnesses:

ROBERT C. ToTrnN, JOHN F. Wm.

Gopies of this patent may be obtained for five cents each, by addressing the Uommissioner of Patents.

Washington, D. S.-