US39181A - Improvement in slide-valves for - Google Patents

Description

Ntra STATES PATENT raten.

A. J. STEVENS, OF SAlNT FRANCISCQCALIFORN IA.

IMPROVEMENT IN SLIDE-VALVES FOR STEAM-ENGINES.

Specification forming part of Letters Patent No. 39,181, dated July 7, 1863; antedatezl April 29, 1863.

To all, whom t may concern:

Be it known that I, A. J. STEVENS, of the city of San Francisco, in the county of San Francisco and State of California, have invented a new and useful Improvement in the Slide-Valves of Steam-Engines; and I do hereby declare that the following :is a full, clear, and exact description of the same, reference being had to the accompanying draw ings, forming part of this specification, in which- Figure 1 is a longitudinal vertical section of the valve chest and slide-valve of a steam, engine with my improvement applied. Fig. 2 is a plan of the same with the cover of the chest and follower of the valve removed.

Similar letters of reference indicate corresponding parts in the two figures.

This invention relates to the employment, in combination with the slide-valve of a steamengi11e,of what I have termed, in a patent granted to me June 1S, 1862, an anti-coinpression valve 7 for preventing the compression of the steaml in the cylinder on the eX- haust-side of the piston after the port has been closed by the lap on the inside of the valve, as is the case when the valve has a long lap.

The object of 011e part of the invention is to dispense with any mechanism for operating such a valve; and to this end it consists in the substitution for a single anti-compression valve oftheslidingkind of two puppet-valves, so applied as to be operated upon directly by the steam in such manner as to produce the desired result.

Another part of the invention consists in an improved mode of applying a follower in coinbination with the main valve and anti-compression valves, to serve the double purpose of protecting the back of the main valve from the pressure of the steam to such an eXtent as may be desired, and to form a means of communication between the anticompression valve-chest and the atmosphere or exhaustpipe of the engine.

To enable those skilled in the art to make and use my invention, I will proceed to describe its construction and operation.

A is the valve-chest of the engine.

a a are steam-ports, and b the exhaust-port, constructed in the manner common to engines using a single short slide valve.

B is the slide-valve constructed like an ordinary short slide-valve, except that it has two passages, c c', right through it, like that described in my Letters Patent hereinbefore mentioned, and has formed all round its back a ange, d, which stands up perpendicular to its face for the attachment of the follower (l, the manner of whose application will be presently described.

D is the anttcompression valve-chest having two separate chambers, e e', each of which covers the outer oritice of one of the passages, c c', and a central cavity, d, between the said chambers, the said cavity being open at the back.

g g are the anti-com pression valves, of which there may be two or more-viz., one or more for each of the passages c c. These valves are of the puppet kind and fitted to seats formed in openings z' t', which form means of communication between the chambers c e and central cavity, d, and the said openings are formed opposite each other, and two valves belonging to opposite openings are secured together face to face as represented'in Fig. l, by attaching both to the same stem. The said valves work on fixed guide-pins n u, screwed into the sides of the chest D. The chest D is secured to the back of the main valve B by means of bolts fj'.

The follower C is composed of a frame fitted snugly to the exterior of theliange d, and having a flange, h, all round it fitting to the flat inner surface of the cover A ofthe main valvechest A, such surface being parallel with the main valve-seat. Around the exterior of the rabbet for the reception of a packin g, j, of india-rubber or other material, and of a gland, E, which is fitted around that portion of the is screwed down upon the packing to make a steam-tight joint between the main valve and the follower by means of nuts l l, tting to screwed pins lc k, which are screwed tightly into the main valve and pass through lugs in the interior of the gland. These nuts are reached when it is desirable to screw down the packing by the removal of -a plate, F, which is secured to and covers an opening, m m, in the valve-chest cover A.

l G is a spring applied to the follower C, and

upper part of the iiange el there is formed a iiange and within the follower (l. This glandresting upon the top of the anti-compression valve-chest D, for the purpose of holding the follower up to its seat on the inside of the cover A when the engine is not at work and of preventing it from being drawn down by the act of screwing down the gland. The tension or pressure of this spring is regulated by a set-screw, p, screwing through the spring and pressing on the top of the anti-compression valvecl1est G. When the engine is at work, the follower is held in contact with the plate A `by the pressure of steam on its flange h, and it protects from pressure the whole of the back of the main valve, with the exception of its marginal portion. H is an exhaust-pipe forming a means of communication between the space within the follower C and the main exhaust-pipe ofthe engine or the atmosphere. The main valve B is operated in the usual manner, and during its movement, as soon as it closes either port a or a to the steam, one of the passages c or c arrives over that port and t team rushes from the cylinder through the said passage into its respective chamber e or e', and by its pressure on the valveg org of that chamber closes that valve, and so opens the opposite one g or gf, so that after the other port a. or ce is closed to the exhaustport b and its respective passage c or c arrives over that port the exhaustion of the steam from the cyl inder is continued through that port, through the chamber e or e and open valve g or g, through the space d and the space within the follower', and hence through the pipe hv, and the compression of the steam on the exhaust side of the piston is prevented. This is illus .trated in Fig. l, in which the valve is supposed to be moving to the left, and steam has been cut oft' from the port a., and the port a' has been closed to the exhaust by the lap on the inside of the valve, but steam passing from the cylinder through the port a and passage c into the chamber e has closed the valve g, and thereby opened g', and the exhaust of the steam from the port a is permitted to be continued through the passage c', chamber e', valve g', and passage d, and through thefollower U and pipe H. When the piston moves in the opposite direction, the operation is precisely the reverse of that above described. The follower, it will be perceived, serves not only the purpose of protecting the back of the valves to a desirable extent from the pressure of the steam, but as a means of ci mmunication between the anti-compression valves and the exhaust-pipe or atmosphere.

What I claim as my invention, and desire to secure by Letters Patent, is-

l. The connected puppet-valves g g', applied, in combination with separate chambers e e', and in relation to the main valve, substantially as and for the purpose herein specified.

2. The follower G, combined with the valve by means of an internal gland, E, and otherwise applied as herein specified, to serve not only for the protection of the back of the valve from the pressure of steam but as a means ot' communication between the anticompression valve-chest and the exh aust-pipe or atmosphere, as herein set forth.

A. J. STEVENSV Witnesses M. T. DUsINBURY, A. M. BoYLn.

Images