US1962549A - Arrangement for tapping steam directly from double-acting reciprocating steam engines - Google Patents

Description

June l2, 1934.

A. BJORKLUND 1,962,549 ARRANGEMENT FOR TAPPING STEAM DIRECTLY FROM DOUBLE ACTING RECIPROCATING STEAM ENGINES Filed March 5, 1930 ngz /n venfon:

`Patented June 12, 1934 UNITED STATESk PATENT ori-ics Alrik Bjorklund, Gottenborg, Sweden Application March 5, 193i), Serial No. 433,447

i In Germany October 30, 1928 2 Claims. (AC1. 137-53) ,Y

This invention relates to a valve for the withdrawal of steam from the cylinders of doubleacting reciprocating steam engines during the Y expansion stage. The object of the invention is so to construct such a valve that at every revolution ofthe crank shaft it enables two uniform withdrawals of steam to take place, one on each side of the piston, through an outlet passage arranged at the middle of the steam cylinder l@ and uncovered from time to time by the reciprocating piston. The withdrawal of steam is therefore effected both during the forward `stroke and during the return stroke of the piston, always under the same conditions as regards quantity of steam and pressure. The regulating of the pressure at which withdrawal ceases is according to the invention effected by axial shifting of the control piston of the withdrawal member,

while the commencement of the withdrawal can be displaced from the centre towards the ends of the cylinder by providing a throttling member which enables the opening movement of the control piston to be retarded when the steam pressure is acting. In this way it is possible to regulate the quantity of steam to be tapped off, and also the withdrawal pressure, within wide limits.

In the accompanying drawing,

"r'igure 1 shows the indicator diagrams for the forward and return strokes, with a withdrawal of steam according to this invention;

Figure 2 shows diagrammatically in section the cylinder of a reciprocating steam engine with an overflow member according to the invention in the middle of the cylinder;

.1 Figure 3 shows one form of construction of the overflow member in section on a larger scale.

In the drawing, l is the cylinder of a reciprocating steam engine. It may be the high-pressure, the medium-pressure or the low-pressure cylinder as required. In the middle of the cylinder is provided an outlet aperture 2, which is alternately covered up and uncovered by the reciprocating piston. To the outlet aperture 2 is attached an overflow member constructed ac- `c'lording to the present invention. This overflow member consists oi a casing 3 closed by a cover 4 and containing in a central bore a sleeve 5.

In this sleeve 5 is slidably supported a piston 7 secured to a rod 8. The piston rod'S passes in al fluid-tight manner through a positioning nut 20 screwed into the cover 4. It has at its outer end a screw thread 8, upon which a plate 10 is displaceable along the rod 8. The plate 10 can be clamped in position by means of a lock nut engaging with the screw thread 8. Between the piston 7 and the positioning nut 20 is arranged a spring 6, and between the positioning nut 20 and the plate 10 is arranged a spring 9.

The unloaded piston 7 is always kept in equin librium by the two springs 6 and 9, independently of the initial stress applied to the springs by shifting the platelo along the piston rod 8, and

independently of the position in the casing 4 assumed by the entire unit comprising the piston v 7, the rod 8, the springs 6 and 9 and the nut 20. 5b By axially shifting the plate 10 and the positioning nut 2U the distance :c of the lower edge ofV the piston 'i from outlet apertures ports 1l in the sleeve 5 can be made greater or smaller. This distance determines the amount by which the spring 6' must be compressed, and therefore the pressure p at which the piston 7 only just closes the apertures 11 when it is exposed to the steam pressure prevailing in the cylinder with the aperture 2 uncovered. If the steam pressure is higher, 75 the piston 'l uncovers the apertures, and a portion of the cylinder steam can escape through the apertures 11 and the pipe union 12 until the steam pressure has fallen to the value p. From the withdrawing connection 12 the steam is then con- `veyed to the place where it is to be used.

Above the piston 7 there is a chamber, closed in a fluidtight manner, which communicates with the withdrawal connection 12 by a by-pass 13 with a shut-off cock 14 inserted therein, so that 85 the fluid enclosed in the chamber can escape when the piston 7 rises if the cock 14 is open. rfhis device serves as a shock-absorber and a pressureequalizer.

The apparatus operates in the following manner:-

The steam supplied to the cylinder expands after the end of the admission in the usual manner. When the piston uncovers the outlet aperture 2 in the middle of the cylinder 1, steam of a pressure p passes into the space underneath the piston 7. 1i the cock 14 is open the piston 'l is immediately raised by the steam pressure, compressing the spring 6, so far that it uncovers the apertures 11, and a portion of the steam can overflow through the apertures 11 into the withdrawal connection 12 until the pressure in the cylinder has fallen to the magnitude p. The piston l then closes the apertures or ports 11 again, and the withdrawal is terminated. As mentioned above, the withdrawal pressure can be varied by axially shifting the piston '7. The withdrawal still begins at the moment at which the piston uncovers the apertures, that is to say, in the middle of the piston stroke.

Now if the withdrawal of steam is to begin later, when the piston has passed beyond the middle of the cylinder l, provision must be made for the piston 7 not to open the apertures l1 suddenly but with retardation. The retardation in the movement of the piston 7 is obtained by partially closing the shut-ofi cock 14, so that the piston 7, in its ascent has to overcome not only the resistance of the springs but also the adjustable damping resistance, During the short time that the piston needs for traversing the path a: against the damping resistance, the steam piston has also moved beyond the centre of the cylinder to right or left, so that in this way, according to the adjustment of the damping resistance, the withdrawal of steam is effected correspondingly later, that is to say, at a lower steam pressure than when the opening occurs without damping resistance immediately upon the uncovering of the passage 2 by the steam piston.

In both cases, through the same withdrawal member,'the same quantity of steam is drawn off in the forward stroke and in the return stroke of the piston, at the same pressure, as a result of which smooth ruiming of the engine is ensured.

What I claim is:-

1. A valve comprising a tubular casing including a pressure chamber in its upper part and having inlet and outlet passages in its lower part, with the inlet passage in axial alinement with the bore of the casing and with the outlet passage extending across the bore; a liner seated in the bore of the casing to separate the inlet and outlet passages from each other, said liner having its upper and lower ends respectively registering with the pressure chamber and the inlet passage, and said liner having ports in its intermediate part to provide communications between the interior of the liner and the outlet passage; a controllable by-pass connecting the outlet passage with the pressure chamber; and a piston slidable in the liner to control the communications through the ports of the liner, a compression spring mounted in the pressure chamber normally operating to press the piston to overlap the ports, said piston and spring being responsive to the pressure fluid entering the inlet passage of the casing to open the ports to discharge the pressure fluid from the inlet passage into the outlet passage and through the by-pass to the pressure chamber to cushion the opening movement of the piston and to augment the pressure of the compression spring in closing the valve.

2. A valve comprising a tubular casing including a pressure chamber in its upper part and having inlet and outlet passages in its lower part, with the inlet passage in axial alinement with the bore of the casing and with the outlet passage extending across the bore; a liner seated in the bore ofthe casing to separate the inlet and outlet passages from each other, said liner having its upper and lower ends respectively registering with the pressure chamber and the inlet passage, and

vsaid liner having ports in its intermediate part to provide communications between the interior of the liner and the outlet passage; a controllable by-pass connecting the outlet passage with the pressure chamber a piston slidable in the liner to control the communications through the ports of the liner, a positioning nut'threaded in the upper end of the casing, a rod extending through the positioning nut and attached to the piston, a main compression spring in the pressure chamber mounted on the rod between the piston and positioning nut normally tending to press the piston to overlap the ports of the liner, said piston and spring being responsive to the pressure fluid entering the inlet passage of the casing to open the l ports of the liner to discharge the pressure uid from the inlet passage into the outlet passage and through the by-pass to the pressure chamber to cushion the opening movement of the piston; and to augment the pressure of the main compression spring in closing the valve; an vadjustable abutment on the upper end of the piston rod, and an auxiliary compression spring on the upper end of the piston rod between the adjustable abutment and the top of the casing, said auxiliary compression spring normally tending to lift the piston rod and piston against the action of the main compression spring, the adjustment of the abutment on the piston rod operating to vary the pressure of the auxiliary compression spring to y regulate the ypressure of the main compression spring on the piston. v v

ALRIK BJORKLUND.

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