US396377A

US396377A - Valve gear for engines

Info

Publication number: US396377A
Authority: US
Publication date: 1889-01-15
Anticipated expiration: 1906-01-15

Description

t e e h S s t 6 er ,h S 2 N 0 S D M 0 H T J u m d 0 M o m VALVE GEAR FOR ENGINES.

Patented Jan. 15, 1889.

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(No Model.) I Sheets-+Sheet 2.

J. W. THOMPSON.

VAL E GEAR FOB. ENGINES.

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UNTTED STATES JOSEPH lV. THOMPSON, OF SALEM, OHIO, ASSIGNOR OF ONE-HALF TO THE BUCKEYE ENGINE COMPANY, OF SAME PLACE.

VALVE-G EAR FOR ENGINES.

SPECIFICATION .forming part of Letters Patent No. 396,377, dated January 15, 1889.

Application filed August 4, 1888. $erial No. 281,953. (No model.)

To all whom it may concern..-

Be it known that I, JOSEPH W. THOMPSON, of Salem, in the county of Columbiana and State of Ohio, have invented a certain new and useful Improvement in Valve-Gears for Steam-Engines, of which improvement the following is a specification.

My present invention is an improvement upon that for which Letters Patent of the United States, No. 381,596, were granted and issued to myself and the Buckeye Engine Company, as my assignee, under date of April 24, 1888, and its object is to secure the greatest possible admission capacity at all points of cut off with a minimum valve area, and to obtain from an eccentric of variable throw a correct valve movement which shall not exceed the maximum required in either direction at the maximum throw of the eccentric, and shall also attain a maximum at less degrees of throw within practical range of cut-off variation as nearly as is practicable consistent with the avoidance of movements of ob jectionable violence.

To this end my invention, generally stated, consists in an oscillating cam suitably adapted to transmit movement from a "alve-operating member to an induction valve or valves, and in the combination of a fixed eccentric, an exhaust valve or valves actuated thereby, an adjustable eccentric adapted to modify the movement derived from the fixed eccentric at points of cut off earlier than that due to the unmodified movement of said fixed eccentric, an oscillating cam connected with and moved by the fixed eccentric and by the fixed and movable eccentrics at different points of cut off, respectively, and an induction valve or valves actuated by said oscillating cam.

The improvement claimed is hereinafter fully set fort-h.

In the accompanying drawings, Figures 1 and 2 are views in elevation taken on opposite sides, respectively, of an engine embodying my invention; Figs. and l, transverse sections at the lines .I: .r and 1 y, respectively, of Fig. 1; Fig. 5, a side view, in elevation, and 011 a larger scale, of the cylinder with the covers of the induction-valve chests removed; Fig. 6, a plan or top view of the cylinder and valve-chests; Fig. 7, a view, in elevation, and on a still larger scale, of the oscillating cam and the levers connecting the same with the induction-valve, the parts being shown as seen from the side opposite to that shown in Fig. 5; Fig. 8, a transverse section through the oscillating cam, one half being taken at the line 2' z and the other at the line ,2 w of Fig. 7 and Fig. 9, a View in elevation of one of the cam-sections detached.

The engine illustrated as exemplifying my invention is of the same general type as that described and shown in Letters Patent No. 381,590, before referred to, and as it accords substantially therewith in structure, except as to the elements of my present invention, need not be in other particulars described at length and in detail herein. Steam is, as in the former instance, admitted to the cylinder 20 by a pair of multiported or gridiron-slide induction-valves, 15, each governing a series of ports, 15, in an induction-valve chest, 1t or 16 adjacent to one end of the cylinder, and is exhausted by similar exhaust-valves wor ing over ports in exhaust-chests 6 6 on the opposite side of the cylinder.

The exhaust-valves are actuated by a fixed eccentric, 19, through the intermediation of a wrist-plate, efisecured upon a transverse shaft, 4, journaled in bearings below the cylinder, the valve-stems being pivoted to valve-levers, which are coupled by links to pins on the wrist-plate. The induction-valves are at the latest point of cut off actuated by the unmodified movement of the fixed eccentric 19 and at earlier points of cut off by the compounded movements of said eccentric and of an adjustable eccentric, 17, the latter being varied and controlled in position by a proper centrifugal governor, 18, fixed upon the crankshaft 23, and being substantially concentric with said shaft, and hence inoperative upon the valve at the latest point of cut off, while its movement by the governor into positions of successively-incrcasing eccentricity shortens and advances the movement derived from the fixed eccentric and correspondingly varies the point of cut off without change of induction or change other than may be desired. The movement of the fixed eccentric, or of the fixed and adjustable eccentrics, as the ease maybe, is transmitted to the in duction-valves through an oscillating cam, 12, which constitutes an essential feature of my present invention, the actuating-rod 10 of said cam being preferably connected with the eccentrics by a compound rocker system operatingsimilarly to that set forth in Letters Patent No. 162,715, dated April 27, 1875, (reissued September 24, 1878, No. 8,432,) and in Letters Patent No. 381,596 aforesaid. It will. be seen that the movement of the cam 12 will be the same at all points in the are of traverse of the center of the adjustable eccentric as it operated. directly without the intermediation ot' the compound rocker system, with the adjustable eccentric bearing the same relation to the shaft as to travel and angular position. as it does to the center of the fixed eccentric when the compound rocker system is employed. The movement will vary as to extent and advance similarly to that obtained by the employment of the ordinary link-motion, the movement imparted when the adjustable eccentric is in concentric position corresponding to that due to full gear, and movement when the adjustable eccentric is in the position of maximum eccentricity corresponding to that due to mid-link position, and similarly as to intermediate points.

The oscillating cam 12 is journaled upon a pin or stud, 30, fixed on the side of the cylinder, and consists of a containing-ease in the form of a disk having a central hub and a peripheral rim. The exterior of the hub, the face of the disk, and the inner surface of the rim are turned off truly, forming a wide annular channel, in which are fitted two camsegments, 31, which are secured ad justably to the disk by bolts 32, passing through slotted holes in the disk, so that the segments may be varied in angular position to admit of ready adjustment of lead, &c., as desired. A cam groove or channel, is formed in each of the segments 31, each of said grooves being concentric with the axis of oscillation of the cam 12 and of comparatively long radius for an angular distance from one end corresponding to the traverse of the cam, during which no valve movement is required. The opposite end portions of the cam-grooves are likewise concentric with the axis of oscillation of the cam, but are of comparatively short radius and of comparatively short angular length, and are connected with the first specified concentric portions by intermediate reversed curves in the cam-grooves, the difference of radius between the two concentric portions of the cam-grooves being such as will enable the cam to impart the required amount of traverse to the induction-valve levers 1% 14. Said levers, which are journaled on proper supports fixed to the valve-chests or cylinder, are coupled at one end to the stems 1t; 16 of the induction-valves, and at the other en d are provided with rollers 34, which fit and traverse freely in the cam-grooves 33.

It will be obvious that a projecting flange, corresponding in curvature with the center line of the cam-groove and adapted to move between two rollers on the valve-lever, would constitute the mechanical equivalent of and may be substituted for the cam-groove. Oscillating movement about the axis of its bearing-pin 30 is imparted to the cam 12 bya rod, 10, which is coupled at one end to the pin of a crank, 35, secured upon the hub of the cam 12, and at the other is suitably adapted to be reciprocated by the fixed eccentric 19, the movement of the latter being either unmodified at the point of latest cut off or compounded with that of the adjustable eccentric 17 at earlier points of cut off. The rod 10 is in this instance coupled to the upper pin, 10, of the supplemental rocker 9 of the compound rocker system, which is actuated by the eccentrics 1!) and 17, as in the patents hereinbefore recited.

By reference to Fig. 7, which shows the cam 12 as oscillated to about the left-hand limit of its throw, (the line ,2 10 being vertical at mid-movement,) it will be seen that the valve-lever 14c is depressed, closing the induetion-valve, to which it is connected, and the valve-lever H is raised, opening its induction-valve. Further oscillation of the cam to the left would not impart movement to either valve, and if oscillated to the right, or toward mid-position, the opening movement of the left-hand valve would not begin until the roller of the valve-lever 1t reached the inner terminal of the longer concentric por-' tion of the cam-groove in which it is shown, while the closing movement of the right-hand valve would begin earlier, though its actual closure would be effected later. In the oscillation of the cam to the right the roller of the valve-lever 11 passes from a con centric camgroove section of short radius to one of long radius, depressing the lower end of the valvelever ll and closing the righthand valve, and later in such movement the roller of the valve-lever 1 L passes from a concentric camgroovc section of long radius to one of short radius, elevating the lower end of the valvelever 11 and opening the left-hand valve. The eccentric sections of the cam-grooves which connect the concentric portions thereof are made as short as is practicable relatively to the entire traverse, without involving objectionable suddenness and violence of movement, depending mainly, in this regard, on the rotative speed of the engine, the proportions, when practicable, being such as to reach full opening, or nearly so, when cutting off at on e-quarter, and sufficient opening, in proportion to piston speed, for all. earlier points of cut off.

lVhile I have described and shown the oscillating cam as provided with grooves, portions of which are concentric-such construction being that which I deem most effective and desirable in practice it is not essential that absolute concentricity should be 0bserved in such portions, as the same might, if preferred, be made slightly eccentric, so as to keep the valves moving slightly, without materially enlarging the valve area or other wise departing from the principle of my invention.

The oscillating cam above described is of special value when applied in connection with induction-valves having a movement of variable extent, as the valve movement may be limited to the exact requirements, irrespective of further traverse of the cam, after the required movement is eifected. The advantage attained in thus limiting the valve movement consists in the fact that with valves having two or more ports the width of the spaces or bridges between the ports in the cylinder and valve need not exceed the width of the ports to a degree greater than that sufficient to give the lap required for tight closure, whereas, if the opening or closing movement of the valve continues throughout the entire period of movement of the actuating member, the surplus movement at late points of cut off will be such as to necessitate the widening of the spaces between the ports (to prevent reopening after closure or reclosure after opening) to an extent which will materially reduce the degree of port capacity relatively to a given valve area.

The wrist-plate employed in actuating the exhaust-valves permits the excess of movement to be curtailed in one direction but not in the other, and the exhaust movement being uniform in extent, and the wrist-plate suffieing for the curtailment of unnecessary movement after closure, the correct amount of opening movement may be readily provided for in the proportions of the parts.

Each of the induction-valves is coupled by a link, 26, to an auxiliary piston working in a cylinder, 27, which is open at its top to the valve-chest and communicates below the auxiliary piston with the end of the cylinder, to which steam is admitted by the inductionvalve, the construction being substantially similar in structural detail and corresponding in principle and operation with that of Patent No. 381,596 aforesaid. The advantage of this mechanism in relieving the governor to amaterial degree from the duty of moving an unbalanced slide-virlve is more fully and perfectly utilized when employed in connection with the oscillating cam, by reason of the elimination by the latter of all unnecessary movement after closure.

I claim as my invention and desire to secure by Letters Patent- 1. A cam plate or disk for valve-gears, which is fitted to oscillate upon a central bearing and provided with one or more circu1nferen tially-adj ustable sections, each having a camgroove consisting of substantially concentric portions of longer and shorter radius, respectively, connected by an intermediate eccentric portion, substantially as set forth.

2. The combination of a cam plate or disk having a central. hub fitted to oscillate upon a fixed bearing and a peripheral rim or flange, one or more cam-sections fitting between and abutting against said hub and rim, each having a groove consisting of substantially con centric portions of longer and shorter radius, respectively, connected by an intermediate eccentric portion, and bolts passing through slotted holes in the cam sections or disk and securing the sections adjustably to the disk, substantially as set forth.

3. The combination of a valve governing one or more cylinder-ports, an oscillating cam having a cam-groove, substantially as described, a valve-lever coupled to the valvestem and engaging the cam-groove, and an eccentric actuating a rod coupled to a pin connected with the oscillating cam, substantially as set forth.

4. The combination of an eccentric fixed upon a driving-shaft, an eccentric mounted adjustably upon said shaft, a compound rocker system connected to the rods of the fixed and adjustable eccentrics, a cam fitted to oscillate upon a fixed bearing and provided with one or more cam-grooves, substantially as described, a rod coupling a pin connected to said cam with a pin on the compound rocker system, and an induction valve or valves, each actuated by a lever engaging one of said cam-grooves, substantially as set forth.

JOSEPH W. 'lIlOllIPSON.

lVitnesses:

NETTIE GAILEY, OLIVER TOMLINSON.