US495173A - James a - Google Patents

Description

(No Model.)

J. A. VANDEGRIFT. VACUUM PUMP.

No. 495,173. Patented Apr. 11 1893. w

75 aecolzdary rum/1,.

772M565 Inventor Jig/5 UNITED STATES PATENT EEioE.

JAMES A. VANDEGRIFT, OF NEW YORK, N. Y.

VACUUM-PUMP.

SPECIFICATION forming part of Letters Patent No. 495,173, dated April 11, 1893.

Application filed January 20, 1892. Serial No. 418,638. (No model.)

To all whom it may concern.- Beit known that I, JAMES A. VANDEGRIFT,

a citizen of the United States, residing at New for exhausting incandescent lamp globes and analogous purposes, more or less difficulty has always been encountered with the means provided for operating the valves. In some instances valve rods reciprocated by some part of the mechanism and working through stuffing-boxes have been employed, and various kinds of packing materials have been relied upon to prevent leakage of air or gas, either from the outside atmosphere into the interior of the pump, or from the eduction to the induction sides of the piston. In other cases the pressure of the air or gas on the eduction side of the piston has been depended upon for opening the eduction valves, the closing of the valves being effected by the atmospheric pressure. been to cause the piston to strike at a given point in its course or stroke, the valve stem, and to gradually open the valve during the remaining portion of its stroke, and gradually close it in the same way during a certain portion of its return stroke, but necessarily in such manner that the complete closing and prevention of leakage depended upon the weight of the valves and atmospheric pressure. In other pumps slide valves have been employed which worked between plane surfaces in which ports or passages were out for the induction or eduction of the air or gas. With all of the means previously devised, however, for mechanically operating the valves in pumps of this class, there is either a tendency to leakage through the stuffingboxes, or between the slide valves and surfaces upon which they work, or that portion of the stroke of the piston which is most essential for the production of high vacua is rendered inoperative.

The object of my present invention is mainly to prevent entirely the leakage which the ordinary valves, stuffing-boxes and the like in- Still another plan has volve, and to utilize the full and complete stroke of the piston, particularly of that portion most essential for theproduction of high vacua. I furthermore prevent the leakage around or through the packing rings of the piston from adecting the induction side of the piston, and provide special means for reducing the usual wide difference of pressure between the induction and eduction portions .of the pump, and for opening and closing the valves suddenly and positively. These several features I attain by means of a pump constructed and operated as illustrated in the accompanying drawing, which illustrates the pump in central vertical section.

The particular pump here shown is provided with two cylinders O, O, and pistons reciprocated therein by connecting rods and eccentrics carried bya power-driven shaft A. The tubes or pipes a, a, are the induction pipes leading from the cylinder to the lamps or other devices to be exhausted. The pistons P, P, are hollow cylinders of any preferred construction but closed air tight except through certain openings. These pistons form primary exhaust chambers and are constantly in communication with and exhausted by a secondary exhaust pump (not shown in the drawing) through the eduction pipes B, B, which enter the tops or covers of the pistons. A sufficient length of rubber tubing is used for these pipes to permit of the full and free movement of the pistons.

In the bottom of each cylinder 0, O, is located an induction. valve. While the specific construction of these valves may be very considerably varied, I prefer to use a conical valve proper D, fitting into a correspondingly shaped seat and provided with a stem D, which has an enlargement or head D". Over the valve there is secured to the outside of the cylinder a small metal cylinder 0r valve .by a flexible head or diaphragm E, of indiarubber, corrugated copper or other impervious flexible material of sufficient strength. All the joints in and about the valve chamlOO ' induction valves.

. shaft A are reoiprocated through a predeter- I bers,being permanent, may be made perfectly air-tight. In the bottom of each piston is an eduction valve F, provided with a stem F, that extends up through the hollow piston and through a perforation in the cover of the same into a chamber F" secured to the outside of said cover over the projecting stem. This chamber coutainsa perforated partition f, and is closed by a flexible diaphragm f, the construction in these respects being the same as the chambers over or containing the The stem F is also provided with a head f" and is actuated by a spiral springGthat exerts a tendency to open the valve.

On the shaft A are carried two disks G, with cam grooves G cutin their faces. With these cam grooves engage the pins or studs of two valve rods H, H, supported in guides or brackets e, e, and which by the rotation of mined but short distance.

Pivoted to a bracket or arm 6', attached to the bottom of each cylinder, is a lever I that carries a socket or block 1, bearing upon the diaphragm opposite to the head D". This lever has a certain play, limited by a stud t.

A spring K is connected to the free end of being pivotally connected to the rod L. A

second lever M is pivoted to the said bracket, one end being connected to the free end of leverllby a spring N, and the other being prolonged so as to intercept in its movement two studs 0, 0, set in the controlling rods H or H.

The operation of the device thus far de-' scribed is as follows: The piston P at the left is shown in the position in which it has just completed its downward stroke, and the eduction valve F has just been closed. As the piston descends the leversL and M are in the relative positions occupied by the corresponding levers attached to the piston P, but after a given movement the lever M encounters the stud O'. The effect of this, inasmuch as the piston P is moving at a much greater rate of speed than the rod H, is to raise the outer or free end of lever M and compress the spring T. This continues until the end of the lever M has moved past the end of lever L", and this permits the spring N to suddenly expand, and by a positive and sudden reaction to turn the lever L on its fulcrum, depress the rod L and close the "carries the end of the spring K attached thereto across the line of the point or fulcrum of the lever I. The first'part of such movement merely stores up energy by compressing the spring K, but the instant that the point of connection of the spring K with the rod [1 moves past the end of lever I, the spring expands, and raises the end of lever I. This withdraws the block or head I from the diaphragm E and permits the spring (1 to open the valve D. The valves remain in this condition until the piston has completed its upward stroke. The secondary pump during this time is exhausting the air or gas contained in the hollow piston. At the completion of the upward stroke of the piston, the

above described operations are reversed and the parts brought into the positions shown in the other side or part of the pump. That is to say, the induction valve or cylinder 0 is closed and the eduction valve of piston P is then opened by the engagement of the lever M with the stud O.

In order to prevent, during the operation'of the pump, any leakage of air or gas, past the packing rings R, R, of the pistons, passages S are formed through the side walls of the pistons between the packing rings and into the interior of the pistons, from whence any air leaking in is abstracted by the secondary pump.

In operating the pump it is desirable to use a small quantity of oil in the pistons, as this facilitates the action of the valves.

Having now described myinvention and the manner in which it is or may be carried into effect, what I now claim is 1. In an apparatus of the kind described, the combination with a valve of a pivoted lever for operating the same and capable of a limited movement or play, a reciprocating valvecontrolling rod and a spring, the ends of which are connected to the valve lever and to a point on the controlling rod movable past the limits of movement of the point on the valve lever to which the opposite end of the spring is connected, as set forth.

2. In a vacuum pump, the combination of a cylinder provided with an induction valve, a hollow piston having an eduction valve and a passage of communication from the interior IIO of the piston for connection with a secondary exhaust pump, as set forth.

3. The combination in a vacuum pump, of a cylinder provided with an induction valve, a hollow piston provided with an eduction valve, and having air passages through its side walls between the packing rings thereon, and a pipe or passage from the interior of the piston forming a connection for a secondary exhaust pump, as set forth.

4.. In a vacuum pump, the combination with the cylinder, of a piston working therein and an eduction valve in the piston, a pivoted valve-operatin g lever moving with the piston, a supplemental lever also moving with the piston, a spring connecting the two levers and adapted to be shifted across the dead point or line of fulcrums of the two, by the engagement of the supplemental lever with stops independent of the piston, as set forth.

5. In avacuum pump, the combination with a cylinder, an induction valve in the same, a lever for operating the valve, a reciprocating rod and a spring connecting the valve lever and rod movable by the latter across the dead point of the lever, of a piston working in the cylinder, an eduction valve therein, a lever for operating the valve, asupplemental or trip lever, both levers being carried by a part moving with the piston, a spring connecting the two levers, and stops in the path of the trip lever by engaging with which the spring

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