Opening e has no effect, its upper end being now closed by the valve. Opening h effects the exhaust. In the actual machine a covered passage leads the exhaust steam from the port is to the passage o, so that the exhaust from the two ends of the cylinder escapes to the air through a single outlet w of Fig. 2. In Fig. 6 the piston has just uncovered the port d leading to the lower end of the valve-ehest, and it has thus established the conditions which will re verse the valve and insure the next upward stroke. As the port d is just uncovered, and no more, the piston is at the point marking the termination of its shortest working stroke. Should the piston stop short of the position shown (by reason of excessive feed), the port d would not be uncovered, the valve would not reverse, and the machine would stop. As will be seen, the piston is at some distance from the lower cylinder-head, this distance represent ing the latitude of irregularity permitted in the feed. The piston may stop anywhere be tween the end of the cylinder and the position of Fig. 6, and the action will continue. In order to effect the third improvement (the unenshioned blow), it is necessary to provide an arrangement which, notwithstanding the passage d is always opened at the position shown in Fig. 6. shall yet, when full-length strokes are made. permit the piston to pass on and complete its stroke without the movement of the valve actually taking place until the delivery of the blow. This is effected by simply constricting a portion of this passage d, making it of such small size that the passage through it of the steam necessary to move the valve shall lie delayed until the piston has had time to pass on and complete its stroke. In the machine as actually made, most of the ports opening Into the cylinder are arranged in pairs, and diamet rically opposite one another, to obviate side pressure on the piston.
In Fig. 7 are shown indicator diagrams taken with the machine operated by compressed air, and photographically the original pencil-lines. anil being taken at work ing pressure, with wide-open throttle, unrestricted speed. and full-lengili stroke, illustrate the action of the machine. At p in the upper diagram the piston is in the position of Fig. :1.
At q the exhaust port II is dosed and compression begins; at r the port k is opened, steam enters, stops the piston at a, and reverses the valve: at / the port i is closed and expansion begins: at it the port It is opened std exhaust takes place. At the lower end of the cylinder there is no gradnal rise of pressure like that from y to r. At this end the rise of pressure is practically instantaneous, and the result is the undulations of the lower diagram. While. however. the upper side of the latter diagram is about valueless, the lower side renders clear the action which it is desired to show: as stated, the machine was running at its full stroke—as near to its lower head VIS was considered safe—nevertheless, there is no lead what ever shown. At c the exhaust from the upper each of the cylinder occurs, and the crossing of the two exhausts pro duces the flutter shown. The port d is also opened at r, but it is clear that steam is not admitted until the end of a the stroke is reached.
It will he observed that the point of cut-off depends upon the position of the ports e lengthwise in the eylinder, and can be varied at will in the design and in the two ends of the cylinder independently. 'clic effect of the cut-off on the striking strpke is to diminish the force of the blow, while the effect of the absence of cushion is to increase it. The former man be adjusted to the hitter. so that the blow struck is precisely the same as in enshioned-liloW machines. but of course obtained with a smaller consumption of steam. On the other hand, a late cid-off may be employed on the striking stroke, thus giving the full effect of the un cushioned blow to increased power. It is freely recognized that fuel is but one of many items of expense. and that in many situations speed of execution far outweighs any economy iii fuel that might be realized through the use of the expansion principle. To meet both situations
—t hose where economy and ea pacity, respectively, are lead ing objeets—two classes of ma chines are being made, line haying cut-off on both strokes and the other on the up-stroke only. The first machine is named the “Econounizer " and the second the "Slugger," and either is furnished as the sitna requires.
Figs, 8 and 9 illustrate the latest modification of the yell known Little Giant drill. The construction will be manifest from the figures. The object of this change is to obtain renewable bearings for the rocker-pin, and thereby provide for wear.
The Ingersoll (Fig. 10 and lull page plate).—For a clear under standing of the valve-motion of this drill, refer to the cut lin the following page. The prin cipal parts 22f the machine are the cylinder a. the piston B. the valve and chest C.
The cylinder it is in form a common steam-eylinder, with its live-steam ports I' and I', and exhaust-port E. The two (lotted circles FP represent open passages hi the cylinder, which are conuceted with the exhaust port E, and hence the interior of the cylinder bet ween F is at all times open to the atmosphere. The two passages .1) /Y are brass tubes opening a passage from the space in the steam-ehest at each end of the valves to the interior or the cylinder within the space between and P. The piston II, a common engine-piston. moves back and forth in the cylinder, and has a stroke from X to Y. This piston has a long bearing in the cylinder, broken in its center by the annular spare S 5', making an open sluice or chamber all around it. The length of the space is such that, wherever the piston may be in the cylinder. this spaee is at all lilacs open to one of the inissages D I)'. and hence to unit of the holes FP. which leads by way of the exhaust port to the open air. S 5' therefore is an exhaust-eliamber earried tip and down with the piston. When the piston is on the up stroke it is open to one of these passages. and when on the down-stroke to the other. The valve is spied-shaped, and has it hole through its longitudinal axis. through which passes the bolt T. which serves to guide the valve in its motion hack arid forth, and which by means of a spline prevents its rolling nn its seat. In the hollow of the steam-chest there c•ore?l passages connect ing the tithes D and bY frith the coils /t' and 11 of the valve. These passages cross each (uher, so D. is connected with // and It" with D. Now refer to the above illustration. The piston has ,,,ph.ted 1he up-stroke: this valve has been reversed, and the drill is ready to strike a blow. We admit the steam through the chest to the valve at a point —say 0. As the spaces at 0 Nand .N" are in one, the steam will eneirele the valve. bearing it down upon its seat t hrongh the excess of pressure at 0. Escaping over the top of the valve S 8' approaches the passage D, and when the distance from D to If is traversed, the piston exhaust-passage is open to D; and at the same instant 1)' is shut off by the upper piston-head. The result is that D is suddenly opened to the atmosphere, and the chamber R', being con nected with it. is exhausted. The live-steam around the valve rushes toward this exhaust opening, carrying the valve with it, and pressing it against the upper head of the chest at H; thus the valve is reversed, the machine exhausts, and the motion of the piston is reversed. We here have an intermittent and reciprocative action of piston and valve; one being dependent upon and regulated by the other, yet each is separate and removed from the other, and with out direct mechanical connection. The valve motion admits of a variable piston-stroke. By simply feeding down the cylinder the piston will work entirely in the upper part, cutting off so soon as the blow is delivered and increasing its stroke as the hole is driven. This is of value. especially in starting or pointing holes.