106 Civil and Mechanical .Engineering.

From tho London Engineerlng, No. 4- °.

HYDRAULIC PRESSURE GAUGE, The accompan3dn ~ engraving is an illustr~,tion of ,~ hy(]rau]ic

pressure gauge constructed by the well known firm of Shaeffer ~: Bu<lenherz, upon B(~ur<h)n's pri,,ciple, modified to suit pressures reaehin~ to five tons p<~r square inch. Ttle majority of our readers are, no doubt, aware that Bourdon's pressure gauge is based upon the property possessed by an elliptical bent tube closed at one of its extremities to uncoil itself when an internal pressure is applied by the medium of some fluid substance, such as water or oil; and tile degree of sensitiveness of the instrument depends upon the following two things simultaneously, namely, the length of the coil and the thickness of the metal of the tube.

For very high pressures, such as arc transmitted by the hydraulic press, considerably less sensitiveness is required than for stcdam pur- poses, and for this reason Messrs. Shaett'er & Budenberg have reduced

Bourdon's coil, which has a length of about of a circumference, to half a circumference

only, and the tube, which in :Bourdon's gauge is made of bm'nished brass, is in this gauge made of solid steel bored out to the shape shown in cross-section. The loose end is made tight by means of a brass nut screwed upon it, and the joint, with the piece which screws to the hydraulic pump or press, is made good by letting the tube slightly into it. A small connecting rod, articulating in ~ socket-joint, is attached to the loose end, and communicates motion to the index by means of a small crank, quad- rant and pinion; a light hair-spring is attached to the index in order to prevent back lash.

Messrs. Shaeffer & Budenberg have pro- vided these gauges with a contrivance, very

simple in its construction, for registering the maximum pressure which has been attained, by means of a. loose index which is pushe<t forward by the principal index, but catches, by means of a small lift, in a kind of ratchet-wheel cut unto the centre of the dial-plate, and, if the gauge is locked, it must remain in the position to which it has beat pushed until the person in the possession of the key moves it back.

The fluid used in these gauges for transmitting tile pressure is oil, with which the tubes are filled, the advantage of oil being that it does not corrode the tube so readily as water.

These ganges have been applied with complete success, more espe- cially in oil mills, and, among others, at the Copenhagan Mills, at Limehouse, and at Messrs. J31undell g Co.'s mills, at tlull. The)' are now coming iato extensive use.