US329288A - dayis - Google Patents

Description

lpv nq OR 33,288

(No Mddel.) 4 Sheets-Sheet 1.

P. M. DAVIS.

VALVE GEAR.

No. 329,288, ted Oct. 27, 1885,

@WLQWW- T 4 Sheets-Sheet 2.

(No Model.)

F. M. DAVIS. VALVE GEAR.

Patented Oct. 27, 1885.

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(No Model.) 4 Sheets-Sheet 3. F. M. DAVIS.

. VALVE GEAR.

Patented Oct. 27

(No Model.) 4 Sheets-Sheet 4.

- P. M. DAVIS.

VALVE GEAR. No. 329,288. Patented Oct. 27, 1885.

. Iwezaor N. PETERS. Plwlo-Litbogrlpinr, Wnlu'nzlnn. D. C.

.lowing is a full, clear, and exact description UNITED STATES PATENT f OFFICE.

FRANCIS M. DAVIS, OF DENVER, COLORADO.

VALVE- GEAR.

SPECIFICATION forming part of Letters Patent No. 329,288, dated October 27, 1885 Application filed July 3. 1885. Serial No. 170,614. (No model.)

To all whom it may concern:

Be it known that I, FRANCIS M. DAVIS, of Denver, in the county of Arapahoe and State of Colorado, have invented a new and useful Improvement in Valve-Gears for Steam-Engines; and I do hereby declare that the folof the same.

My invention relates to trip valve-gear of steam-engines, having for its object, first, to reduce the number of valves and thereby simplify the construction; second, to lessen the work of the governor, so as to leave it free to adjust itself at any point of the stroke; and, third, to provide a valve-gear which can cut off steam at any point between the beginning of the stroke up to seven-eighths, or more, of thestroke.

In the accompanying drawings, Figure 1 is a plan view of a cylinder with my improved valve-gear attached, and also a plan view of i the operating-cams. Fig. 2 is a side elevation of the same. Fig. 3 is an enlarged side elevation of the governor, Fig. 4 is an enlarged side elevation of the trip mechanism, showing also a section through the valve-chest and the steam-passages. Fig. 5 is an enlarged view and side elevation of the cylinder and its connections, shown at the left-hand end of Fig. 2.

The motion of the valve-gear and trippingcams is communicated from the shaft Z by means of two eccentricsone a loose eccentric, R, which rotates the tripping-cams F, and the other a fixed eccentric, O, which is connected to the valve-gear. To one side of the loose eccentric R are attached rods T by means of pins U, the rodsT being pivoted to the ends of rods Y, the other ends of which are pivoted upon arms of the spider at Y. The rods Y are provided with weights W, the tendency of which is to draw the arms outward under the centrifugal force generated by the revolution of the spider, and the arms are drawn in against this force by the springW, which connects the rod Yto the periphery of the spider. The eccentric, being provided with the spider, as described, revolves with the shaft to which the spider is fixed, and when the rotary speed of the spider exceeds the amount of centrifugal force on the weights and the tension on the springs the outward movement of the weights advances the eccentric B, thereby giving it a more or less forward position in the circle of rotation as compared with the spider, according as the centrifugal force on the weights exceeds the tension on the springs. A rod, I, is connected to the eccentric by an ordinary strap, R and this rod is reciprocated by a motion equal to the throw of the eccentric. This rod P is extended to and connected with a cam, F, carried on bracket F fixed to the side of the cylinder F. The reciprocation of the rod P imparts a rotary reciprocation to the cam F on its axis. This gives to the lower face of the cam F, which is the high part of the cam, an alternate advance and retreat toward and away from the trip D. It will be observed by an inspect-ion of Fig. 1 that there are two of these cams-one for the valve at each end of the cylinder-and the cam-arms are connected by rod G. The stems of the cylinder-valves are shown at A, and work through packing -boxes, as shown in Figs. 1, 2, and 4. To each stein A is fixed a double wiper turning with said stem. The fixed eccentric on the shaft Z, through an in- 'tervening lever, is connected by the rods M N to a' rod, 0, the ends of which are slotted, as shown in Fig. 1, and more clearly in Fig. 4. The slotted ends of these bars are'connected to the wipers by means of pins B", fixed in the upper arms of the wipers. Boxes B work on these pins and slide in slots in the. ends of the rod 0. On the pin D fixed in the rod 0, is-pivoted a trip-lever, D. The free end of this lever is curved upward in line with the face of the cam F. The other end rests in a recess above the slot in the end of the rod 0, and has a projecting piece, D, the face of which projects below the upper surface of the box B when said box is at the end of the slot, as shown in Figs. 1 and 4. When the free end of lever D is depressed, the projecting piece D is raised above the box B leaving the box free to slide in the slot, and this free end of the lever D is depressed at the proper instant by the advance of the face of the cam F. The other arm of each wiper is connected to a dash-pot, L, by means of rods H K. The

lower end of rod H is formed with a piston, rco

' sages, is regulated by the position of the cams shifting of the cams.

as shown at theleft end in Fig. 1, which works within the rod K, which is tubular, and within the rod K, between the piston and the bottom of the tubular cavity, is a spring which reacts against the piston end of the rod H.

In the operation of the engine the rod 0 has a uniform reciprocating motion imparted to it by means of the eccentric 0, so that the motion imparted to the valve-stem by this eccentric is uniform; but the cams F have a motion reguated by the governor, and reach their extreme point of travel in either direction at a point in the revolution of the shaft Z determined by the degree of expansion on the weights W. Then the rod 0 is moved forward, it carries the wiper B at the forward valve with itself by reason of its contact with the extension on the trip-lever as well as the wiper in contact with the end of the slot in the other valve, and thus rotates the valve-openings and steam-passages. It also by the same motion raises the dash-pot L at the forward end. As the rod 0 nears the end of its travel the cam,depressing the lever D,liberates the box B and thereby the weight of the dash-pot causes this box to slide back in slot in the rod 0, allowing the weight of the dash-pot to reverse the movement of the valve-stem and shut off the steam. The box B and the wiper B then come to a state of rcst until in its backward movement the rod 0 brings the forward end of the slot in contact with the box B and the wiper B is then moved backward to the extreme rear limit of its travel. By this movement the valve is rotated upon its seat and the exhaustport is opened. During this last-described motion the motion of the rod H is taken up by the spring in the tubular rod K.

The operation of the rear valve and its connecting mechanism in the backward movement of the rod G is the same as that just described. It will be understood that the trip, and therefore the closing of the steam-pas- F, which cams are regulated by the governor, the governor having no other work than the Thus the opening of the steam-ports and the opening and closing of the exhaust-ports are controlled by movement of the rod 0, while the closingof the steamports is controlled by movement of the cam F, and the trip only being performed by the eccentric, which is regulated by the governor, it is independent of the movement of the mam eccentric. The valves themselves are of ordinary construction, and are shown clearly in Fig. 4c, in which the exhaust-port is shown at X and the steam-port at S. As the free end of the lever is depressed by the advance of the cam F, instead of tripped by striking a stationary cam, it follows that the lever D can be tripped in whatever direction it is moving, thus having the great advantage of being able to cut off at any part of the stroke, instead of only durin g the first half of the stroke, as in the majority of other trip valve-gears.

I claim as my invention- 1. The slotted rod'O, operated by a fixed cam, box B connected to the wipers and sliding in the slots in the rod 0, in combination with trips D and cams F, moved by the eccentric controlled by the governor, substantially as described.

2. In combination with the rotary valve V, the stems A, having wipers B fixed thereon and carrying pins, box B sliding in slots in the rodO, and the trips D, pivoted upon the rod 0 and operated by cams which are moved by an eccentric controlled by the governor, the box B being provided with means for leaving them in the slots in the rod 0, substantially as described.

3. In combination with the wipers on the valve-stems carrying the boxes sliding in slots with trips that are controlled by a governor, regulated eccentric, dash-pot L, having a piston-head, rod H, and tubular rod K, and spring, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

rnANors M. DAVIS.

WVitnesses:

LUCIUS P. Manse, H. R. STEAVENSON.

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