US 672638 A
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Description (OCR text may contain errors)
' Nu. 672,638; Patented Apr. 23, |901.
. J. DUNLOP.
(Application led le`e'hr 26, 1901.)
\\\\\\\\ x my ATIOMEYG lo, 672,638. PatentedlApr. 23, |901., J. DUNLOP.
" (No Model.) (Applimim med Feb' 26'. um.) 2 Sheets-Sheet 2.
UNITED STATES PATENT QEETCE..
JAMES DUNLOP, OF MANCHESTER, ENGLAND, ASSIGNOR TO CHARLES HENRY SCHILL, OF SAME PLACE.
SPECIFICATION forming part of Letters Patent N o. 672,638, dated April 23, 1901.
Application med February 26, 1901. semi No. 48,951. (No model.)
This invention relates to pneumatic and like percussive hammers of the differentialpiston inertia-valve type, and has for its object an improved. construction of the inertiavalve and air-passages whereby the action of the valve in distributing the compressed air or other motive fluid will be rendered` more certain and the resulting action of the hammer itself be such that very little jarring or vibration will take place.
Hitherto the use of inertia-valves in pneumatic and like percussive hammers has resuited in faulty and uncertain action, owing to the excessive rebound of the valve from its terminal stops at either end of its travel, and consequently an objectionable amount of jarring and vibration has taken place.
The means taken to prevent unnecessary or excessive rebounding of the inertia-valve and the improved construction and arrangement of parts necessary therefor constitute the chief features of this invention.
In the accompanying drawings, Figure l is a longitudinal sectional elevation of the improved pneu matic or like percussive hammer adapted for use as a hand-tool. Fig. 2 is a similar View, but showing the parts in the relative positions they occupy when the piston has reached the other end of its stroke.
In the views, A designates the barrel or cylindrical body of the hammer, and B a differential piston fitted to slide therein.` The annular space C formed by the difference in the two diameters of the piston B is supplied with compressed air or other motive iiuid, at such times as it is desired to work the hammer, through a passage D, drilled in the body A and communicating with a starting-valve E, placed in the handle F.
The handle F is secured to the body A by means of a screwed collar G, mounted loosely on the body, and when screwed up the parts are locked together by teeth on a springcatch I, engaging a ring of teeth formed on the collar G.
The compressed air or other motive i'luid is supplied to the handle F through a flexible pipe (not shown) attached to the nozzle H, and the starting-valve E is opened when required against the pressure of the motive luid by the operator depressing the triggerlever J with his thumb.
Within the piston B is drilled a valve-race K, in which is iitted with a sliding fit a hollow inertia piston-valve L, having fitting parts at such a distance apart as to cover and uncover almost simultaneously the two rows of holes M and N, drilled through the smaller diameter of the piston B. That part of the inertia-valve L which lies between the litting parts has holes O drilled through it, and at the end of the valve farthest awayv from the handle F a very small hole P is drilled. A plug Q is screwed into the end of the piston B, and this plug limits the travel of the inertia-valve L toward that end of the piston, the travel toward the other end being limited by the opposing wall of the small chamber R. (See Fig. l.)
On the end of the piston B is a projection S for striking any tool placed in the tool-socket T, and between the tool-socket T and that part of the barrel A Which iits the smaller diameter of the piston B is a chamber U, communicating with the atmosphere through the exhaust-ports V.
The action of the parts is as follows: The motive fluid admitted by depressing the trigger J and opening the valve E ows through the passage D into the annular space C and pressing on the annular area of the piston B tends t-o move it into the position shown in Fig. l. In this position and with the inertiavalve L in the position there shown the motive fluid will pass from the annular space C through the holes N and O to the space behind the larger end of the piston, and there, acting on its full area, will drive it into the position shown in Fig. 2, where the projection S is shown in contact with a tool in the tool-socket T, the blow having been delivered and the motion of the piston arrested. When the motion of the piston is thus suddenly ar- IOO rested, the momentum of the inertia-valveiL will carry it also into the position shown in Fig. 2 or into an approximate position. In moving into this position the valve L will compress the motive fluid in the small chamber R to a higher pressure than that acting on thelarger'end of the pi-ston, and thus prevent the valve L fromV striking violently against the opposing wall of the chamber R, and so obviate jarring,as well as excessive rebound of the valve, as the compressed iiuid can escape gradually through the small hole P. When the inertia-,valve Lhas moved into the position shown in Fig. 2,' communication between the annular space() and the space behind the larger end of the piston B is cu-t oit by the iitting part-of the valve L covering the 4holes N and communication between the atmosphere, and the space beh-ind the larger end of the piston is established by the other fitting part of the valve L uncovering theholes M. .The exhaust of the-motive fluid now takes place through the holes O and M, chamber U, land, ports V. When the fluidpressure in the space behind the larger end of the piston 'B is sufliciently reduced, the motive fluid, acting on the annular area of the piston, will again move it into the position shown in Fig. 1, and during thatmovement the holes M in the smaller part of the piston B will pass into the. fitting part of the barrel A, and thereby communication between the atmosphere and the space behind theV larger end of the pistonwill be cutoi. The motive' fluid remaining in the spacebehind the larger end of the piston B will thenbecompressed during the remainder of the stroke until the pist0n is brought to a stop in the position shown in Fig. 1. Just previous to reaching that position the holes M will passk into the annular space C and mot-ive ilui-d will flow through the holes M and O and acting on the full area of the piston B will suddenly arrest its motion and then drive it back on the reverse stroke already described. The motion of the piston B bein-g thus suddenly arrested the momention the valve L will cause a slight reduction of fluid-pressure in the small chamber R, and this'prevents the valve L from striking violently against the plug Q and so prevents any excessive rebound. The hammer will continue working as described so long as the thumb of the operator remains pressing down the trigger J and motive uid continues to enter through the starting-valve E.
Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is- 1. In a pneumatic or like percussive hamme-r, in combination, a barrel or cylindrical body provided with passages for the supply of motive Huid under pressure, a differential piston'fitted to slide therein, an annular space formed by the difference'in the two diameters of the piston, a hollow inertia piston-valve fitted inside the piston, and having fitting parts at each end adapted to alternately cover and uncover almost simultaneously two sets of, holesinthe smaller diameter ofl thepiston, the said inertia-valve having a set of holes between its fitting ends communicating with the spacev between it and the piston, and a single small hole in its end communicating with a small chamber formed between the valve'and the interior of the striking end of the piston, and an enlargedchamber with eX- haust-ports beyond that part of the barrel which fits the smaller diameter of thepiston,
. allv arranged and operating substantially as and for the purposes herein described with reference to the drawings.
2. In a pneumatic or like percussive hammer having a barrel fitted witha differential piston,.the combination with the inertia-valve L provided with a small hole'P, of the chamber R andthe motive-fiuidpassages and ports forming a fluid-pressure check at each end of `the traverse of the inertiavalve substantially as herein set forth.
In witness whereof'I have hereunto set my hand inpresence of two witnesses.