US 28957 A
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qnarran srxrns @Param carica W. BIRKBEGK, OF JERSEY CITY, NElV JERSEY.
Specification of Letters Patent No. 28,957, dated July 3, 1860.
To all whom it may concern:
Be it known that I, WILLIAM BIRKBECK, of Jersey City, in the county of Hudson and State of New Jersey, have invented a new and useful Improvement in Steam-Engines which Reciprocate Freely without cranks; and I do hereby declare that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings, making a part of .this specification, in which- Figure l, is a longitudinal vertical section of an engine with my improvement. Fig. 2, is a transverse vertical section in line A, of Fig. l. Fig. 3, is a plan view of the steam cylinder with the valve chest removed.
Similar letters of reference indicate like partsvin the several figures.
My improvement is applicable to all donble acting reciprocating steam engines which are operated without a crank to steady the motion.
The nature of my invention consists in providing an extra exhaust valve and opening the same by the excess of pressure in the port over that which is nishing the stroke of the working piston, whereby the entrance into the working` cylinder is retarded until the slide valve is well open, and the exhaust is also made more distinct and the area of the ports under the slide valve may be reduced and consequently the friction of the latter may be diminished.
The nature of my invention also consists in connection with the above in so constructing and arranging the valves, ports and passages that the extra pistons or equivalent parts which receive motion from such excess of pressure, are themselvespuppet valves for the exhaust, and make a tight contact with suitable seats at the termination of their motion, whereby any leakage of steam past their peripheries is prevented except at the instant of changing the motion and the Vnecessity of packing the pistons is avoided.
In the use of steam pumps reciprocating without a crank a difliculty is experienced in terminating the strokes properly. The initiatory steps of the process by which the action of the steam is changed so as to induce a motion of the piston in an opposite direction, must necessarily be made by the mot-ion of the piston itself, and the operation must consequently commence before the stroke is completed.
I/Vith any ordinary mechanical connection by simple arms and stops, the steam is liable to flow in ahead of the piston and prevent the completion of the stroke and consequently prevent a proper opening of the valve. To overcome this difficulty a spring has been tried, so arranged as to receive and treasure up the force until kitbecome sufficient to throw the valve suddenly, but this is uncertain and ineffective under varying pressures of steam. By substituting therefor a piston and cylinder so arranged as to act obliquely at each end of the throw, the device has been made to operate, but it is obviously desirable to make the mechanism as simple as possible and especially to avoid a duplication of pistons, stuffing boxes, or any rubbing surfaces which require to be packed. Pistons and cylinders or equivalent devices have also been arranged so as to act directly in lieu of obliquely, and to feel the pressure ofl thesteam intermittently in lieu lof constantly and some of these devices and of those employed in other departments of engineering, as Nasmyths steam hammer, are capable of allowing ample time for the piston to complete its stroke before the valve is effectively thrown, but none are the equivalent of my invention, inasmuch as mine accomplishes this desirable end and secures an effective and smooth action in the machine without any duplication of packed parts or any increase of steam tight rubbing surface. My improvement in fact involves less of such surface than the ordinary simplest form of slide valve engine, as my slide valve requires no cavity in its face and the ports beneath it may be smaller than usual, and my secondary valve is composed, not of two pistons requiring to be packed, as may at first sight appear, but of solid disks or rather of short solid cylinders, which need to t steam tight only when their faces are pressed against the annular stop at the end of their motion.
To enable others to make anduse my invention, I will proceed to describe its oo nstruction and operation.
C is the steam cylinder.
P is the piston.
P is a piston rod, and P is a tapper arm attached to the piston rod.
B, is a valve chest consisting of a double arch, the inner of which is open at one side with closed ends, containing within the double farchl three, chambers; viz., a cylindrical chamber a, in which work two valves V, V, which are both rigidly secured on the single stem VX, the whole constituting what will in the succeeding paragraphs be designated as the secondary valve. On each side of the cylindrical chamber a, are chambers c, c. Under the inner arch is a chamber CZ, which incloses a slide valve S, which is fitted to work on a flat seat e, on the top of the steam cylinder C.
The valves V, V, though in the form of pistons and fitting the cylindrical chamber c, are in reality puppet valves. They fit to two seats w, w, in the cylindrical chamber a. The ends of the chamber a, are closed by heads a', 0,, which contains steam which serves as cushions to the valve stem, and which are movable for the purpose of taking out and replacing the valves. At one end of the valve chamber a, there is are two ports b, and at the opposite end two similar ports the port Z9, communicating through a passage f, which partly surrounds the said chamber and passes under the seat e, e, of the said valve S, with a port g, in the said seat, and the ports communicating through a passage f, with a port g, in the said seat. Near the ports b and ZJ, there are in the sides of the chamber a, nearer the middle thereof two ports Zt, It, from which passages z', and i', z" lead to the ends of the steam cylinder C.
The slide valve S, has a passage y', clear through its center of a width equal to or a little greater than that of the ports g, g, the said passage being of about the same width as the bridge t, between said ports. The said valve S, has a stem n, which passes through a stung box in the end of the chamber CZ, and on the stem are two tappets n, n2, between which the tappet arm P, works.
I is the induction steam pipe leading to a chamber Z, in the cylinder casting from which there is a communication with the chamber c, of the valve chest by a passage s. The chamber 0, has a communication with the slide valve chamber (Z, through a liberal opening in the inner arch on that side as represented, see Fig. 2. The chamber c', has a communication with the eduction chamber Z, through a passage 0', and the cylindrical chamber a, has a communication from between its seats fw, w, to the chamber 0, through a liberal opening on that side as represented, see Fig. 2.
The operation is as follows: Steam being admitted by the pipe T, passes through the chamber Z, passage 0, chamber c, and lls the slide valve chamber cZ, from whence it passes through the passage j, into the port (g) or (g), whichever is open, suppose for example (g), along the passage f', and through the port (ZD), into the right hand end of the valve chamber a, andacting' on. the face of V, moves the secondary valve until V, meets its seat or contracted s ace w', and thereby shuts the steam out rom the middle part of the chamber a. This movement of V, uncovers the ports L, and passages z", i', allowing the steam to pass freely through these into the cylinder C, and drive the piston P, to the left toward the passages z', z'. The corresponding movement of V, also puts the opposite extremity of the cylinder C, into free communication with the atmosphere (or with the condenser if the steam is worked condensingly) by allowing the steam freely to escape through the passages z', z', ports ZL, h, and the contracted space fw, into the middle portion of the chamber c, from whence it descends through o, 0, and Z, into the exhaust pipe E. As the piston P, arrives near the end of the cylinder the tappet arm P2, strikes the tappet n, and carries the valve S, along with it until said valve closes the portv g, after which the piston P, continues to be impelled by the expansion of the steam already in the cylinder and by its slight momentum and commences opening g. The live steam stopped in the chamber CZ, the pressure of which at this juncture,accumulates by continual accessions from the boiler, soon commences to enter g, and passes rapidly along the passage f, through the port b, and acts upon the outer face of the puppet valve V, and quickly fills that end of a, to a higher pressure than that in the other end of a, and almost immediately moves the secondary valve, until V makes a tight contact with Iw. The steam then enters the cylinder through ZL and z', to stop the motion of P, and induce a return stroke. But these several operations consume a little time, and the piston P, has consequently been allowed to very nearly meet'the end of the cylinder C, and consequently to move the slide valve S, t0 such extent that its opening (j), coincides with the port g, and gives a suflicient opening through which the steam can flow in a continuous current through g, f, ZL, z', to effect the return stroke of P. The steam on the opposite side of P, of course escapes through z", b, ZL, v', into the center of a, and thence out as before described.
The movement of the secondary valve while pressed in both directions by the steam may require explanation. The pressure of steam in the boiler must obviously be equal to that required on the piston P, to overcome the resistance opposed to the motion of the latter. 1n practice it is always sensibly greater, the steam being retarded and its pressure reduced in flowing through the screw valve and the several pipes and passages. This condition exists in all steam engines, the amount of contraction or throttling and the velocity of the piston having,
as is well known a certain relation to each other.
In my invention, however, the excess of pressure in the boiler over that existing in the cylinder C, is availed of to perform an important function. These portions of the chamber a, in which V and V, reciprocate in this manner are finished very nicely in a cylindrical form and V and V', should correspond very accurately therewith, but should be suiiiciently smaller' to move freely therein. The escape of steam through the extremely narrow opening thus provided between the valve V or V, and its inclosing case is slight, because the opportunity afforded for such leakage is very brief.
The movement of the valve S, by entirely closing one port g, before it commences to open the other g, allows the steam to accumulate in the chamber d, at a higher pressure than before.
The gradual opening of g, allows the steam to How through f, at a rate which causes the pressure in f, and Z), at rst very slight to rapidly rise until the pressure in that end of chamber a, exceeds that in the other end suiiciently to induce the secondary valve VX, to leap into its opposite position. The time required to produce this effect, an`d allow the steam to flow through z', z', and meet the piston P, is only suiiicient to allow the latter to complete that small portion of its stroke which remains to be performed after P2, has touched and eifected half the movement of n', and it is only during this very brief period or in fact a still shorter period that any steam is allowed to leap past V. The valves V, and V, consequently require no packing and may be allowed to run with perfect freedom and even to wear so as to become quite loose without appreciable waste of steam.
In order to guard against thepercussive eect of the secondary valve V", the ends thereof are allowed to project beyond the parts V and V, and are fitted into corre- Y s ondin sockets in a and a2 as re resented in Fig. l. When the valve is thrown, the steam in one of these cavities is very suddenly compressed and by its superior elastic force it overcomes the inertia and avoids any violent blow.
In consequence of the passages f, f, being only used for the induction instead of as usual for both the induction and the eduction of the steam they may be made considerably smaller than usual without detriment to the effect of the steam in the cylinder.
The reception of steam into an engine of this character, where the steam is worked non-expansively is continuous and slow, no more steam being taken during any short period than is required to fill the space left by the movement of the piston P, during that period: but the eduction of the steam should be performed more rapidly, as the surplus of a whole cylinder full must escape in the early portion of the stroke.
In my engine the passages z', z', z", and the corresponding ports h, h, h, h, are large enough for a free exhaust but the ports g, g', are only large enough for the easy induction of the steam.
In consequence of the small area of the ports g, g, and of the absence of the ordinary hollow throat or cavity in the face of S, and of the ordinary exhaust port between the other ports in the cylinder face, the slide valve is less violently pressed upon the cylinder than is usual in engines of the same capacity, and the motion of the piston is for this reason less retarded by the contact of P2, against the tappets a', 91,.
My improved engine works steadily and smoothly at all velocities and involves no trouble in its management.
The secondary valve may if desired be provided with a slender stem projecting through a stuffing box to allow it to be moved by hand, but the position of such on the exterior of the valve chest allows it to be readily tightened at will by the simple turn of a nut and involves none of the difliculties incident to the adjustment of packed parts in the interior of the machine, the duplication of which is referred to above.
The small area of ports under the valve S, allows the valve and the corresponding face e, e, of the cylinder to endure for a longer period than the corresponding parts in any other engine of this character without requiring attention.
My invention is capable of working under any required pressure and of pumping any material which can be worked in any other machine. My invention is also capable of being applied to the working of other mechanism than pumps and in general of working against any resistance which is or may be made tolerably uniform.
The secondary valve and its inclosing chamber may if preferred be mounted below or at the side instead of above the steam chest d, and the invention may by a proper disposition of this valve and of the several passages be applied to upright or inclined as well as to horizontal engines. But I prefer the form and arrangement shown and described herein in everyparticular and as thus constructed my invention is in successful use in a variety of different situations.
Having now fully described my invention what I claim as new therein and desire to secure by Letters Patent, is-
1. Operating the secondary valve VX, by the excess of pressure in the newly open port f or f', over that which is actin@ in the cylinder to complete the stroke of? the piston, substantially in the manner herein set forth.
2. In connection therewith, so constructing and arranging the valves, ports and pas- In Witness whereof, I have hereunto set sages, that the pistons or equivalents V, V', my name. Which are moved in the chamber a, by such WM. BIRKBECK. excess of pressure are themselves puppet 5 valves for the exhaust and make a tight oon- Witnesses:
tact with the seats w, fw', substantially as and M. HUGHES,
for the purposes herein set forth. J. F. BUCKLEY.