Improvements in Vacuum Pumps.
Year: 1892

page_text: Date of Application, 26th Jan., 1892-Accepted, 9th Apr., 1892
COMPLETE SPECIFICATION.
Improvements in Vacuum Pumps.
I, JAMES YATE JOHNSON of 47 Lincoln's Inn Fields in the County of
Middlesex Gentleman do hereby declare the nature of this invention which has
been communicated to me from abroad by Adolph Bornholdt and Joseph Glatz
both of 485 Kent Avenue Brooklyn in the State of New York Chemists and in
what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
This invention has reference to the construction of vacuum pumps for use in
connection with stills, or with engines as a condensing pump or for deep wells or
for other purposes.
The general object of the said invention is to produce a pump capable of main-
taining a very high vacuum, and which therefore can be advantageously used for
the purposes above indicated. The said invention consists in the construction and
arrangement of the vacuum cylinder and auxiliary parts as hereinafter described
whereby the cylinder is absolutely emptied of air and vapour at each forward
stroke of the piston and the inlet valve at the same time sealed against the return
of any air or vapour during the period of compression.
The particular construction and combination of devices whereby these results are
secured can be most conveniently explained in connection with the accompanying
drawings in which
Figure 1 is a horizontal sectional plan shewing the valves and valve movement
and other parts applied to an indirect duplex-pump:
Figure 2 is a side elevation thereof partly in section;
Figure 3 is a detail plan showing a modification of the valve movement and
Figure is a vertical section shewing a special form of valve.
In the drawings A A represent respectively the two pump cylinders, C C¹ the
two pistons, and E E' the piston rods. FF are castings having dovetail guide
rails for the slides G which are connected to the ends of the piston rods. On each
slide G is a curved arm supporting at its end a friction clamp K which may
conveniently be made of a perforated block of ordinary rubber packing. Through
the perforation of the block passes a valve rod L and the grip of the friction
clamp on the valve rod may be tightened or loosened by means of the nut M.
Each friction clamp K moves backward and forward with its piston the full length
of its stroke, but it is desired to give the rod only sufficient movement to operate
the inlet valve N of the pump cylinder A (or A'). Consequently the valve rod is
provided on its ends, or on some other convenient part, with a stop 0, which when
the rod has moved forward a sufficient distance, strikes an abutment O' on the
frame or casting, and thereafter the friction clamp K slips on the rod L.
Similar stops P and abutment P' limit the return movement of the valve rod.
Various means for connecting this positive actuating mechanism with the valve
may be employed. As shewn in Figures 1 and 2 each rod L has a bent arm Q
provided with a small spiral spring which as the rod moves forward presses
elastically upon an arm R. The latter is secured to a stud or plug S which is set
air-tight in a box S' and is capable of- rotation therein. The plug S has a cam
projections which as the plug is turned by the arm Q bears against the end of the
stirrup T connected with the valve stem t and thus closes the valve N positively.
By reason of spring the valve is closed by yielding pressure, preventing injury to
the mechanism. As shewn in Figure 3 the arm Q is provided with a rack which
engages with a pinion q' which is mounted on the plug or stud S and turns the
latter positively in both directions.
It is essential to the efficient operation of the pump mechanism as will be pointed

page_text: out hereinafter, that means should be provided to open and close the inlet valve
positively. The particular actuating means herein before described have been
found operative and efficiert in action. Attempts to close the valve by devices
inside the cylinder have not proved satisfactory. In the arrangement described
access can be had to all parts for adjustment, and when the apparatus is out of use
both valves can be closed by hand.
5
In Figures 1 and 2 the cylinders A. A¹ are shewn as being enclosed in the tank U
which is the receptacle for the cooling liquid, and the receiver for the matters
collected by the pump when used for condensing. The inner ends of the cylinders
open directly into the said tank and are closed only by the piston heads which may
be provided with packing rings, or may have a smooth periphery, according to the
purpose for which the apparatus is to be used. The suction pipe 2 (Figure 2)
leads from the still or the exhaust pipe of the engine, or other apparatus or from a
deep well or other place according to the purpose for which the pump is used.
The pipe 2 communicates with the condenser which consists of a series of
upright tubes 3 open at their upper ends and enclosed in the jacket 4.
The spaces
between the tubes are closed at the top. The pipe 6 admits (when the cock 8 is open
and the cock 7 closed) the condensing liquid to the space within the jacket, and
the said liquid is forced through a series of small perforations in the top of
the tubes (see Figure 2) so that the vapours drawn down through the pipe 2
encomuter the spray and are cut down or partially condensed. The pipe 6 com-
municates as shewn in Figure 2 with the lower part of the tank U and when the
cock is open and the cock 8 is closed the condensing medium is constantly
re-used. By reversing the cocks, the supply of condensing liquid may be drawn
through the pipe 6 in the opposite direction.
The condenser communicates with the two cylinders A A' so that the distilled
matters pass into the said cylinders alternately.
These matters may be only partially condensed and as it is disadvantageous to have
the liquid portions pass through the same valve as the vapours, a pipe 9 is provided
to carry the liquids. It communicates with the cylinder through the small flap
valve 10 which may conveniently be formed of a strip of rubber. Through the top
wall of the cylinder is a number of small perforations 11, through which as the
piston retreats a spray of liquid from the tank U is discharged upon the vapours
entering through the valve N which effects a further condensation. When the
piston moves inward, the liquids and vapours collected in the cylinders are forced
into the tank U through the discharge valve W which may consist simply of a soft
rubber plate resting on a grating, which is found in practice to give excellent
results. When the apparatus is used as a vacuum pump simply the condenser is
not required.
The tank U is shewn as being provided with an inlet opening 13 for use as
required to keep up the supply of liquid and with a discharge opening 14, to draw
off its contents when necessary. It also has a vapour discharge pipe 15 provided
with a small check valve 16. The manner of discharge will depend upon the
purpose for which the pump is used.
If the vapours that collect in the tank U be of no value, the pipe 15 may
discharge into the atmosphere. In using the apparatus to pump the exhaust steam
from a steam engine, the pipe will return to the boiler. Just above the check
valve 16 is a small pipe 17 provided with a cock 18. The pipe 15 may be of
considerable length and height and the liquid that may collect therein will be
drawn off by the pipe 17.
In the operation of the pump (considering it is as a vacuum pump) each cylinder
always contains a certain quantity of liquid.
As the piston moves forward the air is forced into the tank U and the level
of the liquid (being more and more confined) gradually rises until it seals the
valve.
Finally as the piston reaches the forward limit of its stroke, the air has been
entirely squeezed out, and the space in front of the piston is occupied entirely by

page_text: liquid. As the piston retreats air and liquid again enter by their respective
inlets. In ordinary vacuum pumps there is always a thin layer of air in front of
the piston which being under high compression may escape in part, and which
expands as the piston retreats. This prevents a very high vacuum from being
obtained.
By the apparatus constructed according to this invention it is possible to maintain
a vacuum higher it is believed, than has been heretofore obtained by other
means.
In securing this result means such as those indicated for actuating the inlet
valve positively and with certainty are of great importance. The exhaust in the
suction pipe is so complete, that there is not sufficient difference in pressure to
operate the lightest kind of hanging or flap valve.
On the other hand if such a valve were used its opening and closing at the
proper time would be so uncertain as to prevent the desired results being obtained.
In Figure 4 I have shewn the form of inlet valve devised for hot fluids. No
form of valve, hitherto in use, has 1 believe given entire satisfaction when operating
with hot Huids, as the expansion of either the valve itself or its connections, causes
defective working. The valve shewn in Figure 4 is found to give excellent results.
It consists of a plug N' tapering slightly towards the bottom and set in an opening
of corresponding shape in the valve box, which is provided on top with a cup e for
oil, or similar liquid to seal the valve. The valve in its construction and operation
is substantially like a two-way cock. The bottom of the valve box is, however,
closed so that the valve stem is enclosed underneath, and a free space is left between
its lower end and the adjacent part of the casing. The valve moreover is not
screwed down, or otherwise held in place, except by its own weight so that within
sufficiently wide limits, it is free to expand vertically. It will be seen that the
expansion in thickness will, on account of the tapering form of valve, cause it to
rise, adjusting its increased diameter to the size of the opening which contains it.
In using the pump for deep wells the suction pipe 2 instead of leading to the
vessel to be exhausted from air, leads directly down into the well. The condenser
or sprinkler (numbered 3-4) is not required.
The pipe 9 which takes water from the tank U to condenser is attached to the
upper side of the main pipe which contains the valve N and is used only until the
suction pipe leading to the well is entirely exhausted of air, and water from the well
follows to the cylinder. It will then be shut off.
The pump operates the same as with vacuum. If the piston moves back it
will draw up whatever air there is in the suction pipe and finally water. At the
forward stroke the air will first discharge through discharge valve W and water
will follow. If there is no more air, only water can discharge. If the tank U gets
filled up sufficiently the water may discharge through either the pipe 13 or 15.
For deep well pumps the construction of the tank U may be somewhat modified.
It will be obvious from the foregoing explanations, that some of the improve-
ments may be used without others, and may be embodied in a single acting pump,
and that modifications may be made in details of construction without departing
from the spirit of the invention.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is:
1. The combination of the receiving tank and the pump cylinder or cylinders
having at one end an inlet valve, and a discharge valve opening into the said tank,
the arrangement and construction of the parts being such as hereinbefore described
and as illustrated in the accompanying drawings that at the forward stroke of the
piston, the inlet valve is sealed by the liquid compressed in front of the piston and
all air and vapour expelled substantially as hereinbefore described.
2. A vacuum pump of the character herein before described and illustrated in the
accompanying drawings, having a receiving tank communicating through a

page_text: discharge valve with the pump-cylinder a suction pipe leading to the cylinder and
having an inlet valve, and a return pipe 6 leading from the receiving tank to the
suction pipe.
3. A vacuum pump of the character hereinbefore described in which the suction
pipe is connected with the pump cylinder by a branch pipe in addition to the main
inlet pipe, so that vapours and liquid enter the cylinder by independent inlets.
4. In vacuum pumps the construction and use of the particular mechanism
herein before described and illustrated in the accompanying drawings for actuating
the inlet valve of the pump cylinder positively in both directions.
5. In vacuum pumps, the use of an inlet valve constructed and arranged as
hereinbefore described and as illustrated in Figure 4 of the accompanying drawings
the said valve being combined with mechanism for operating it positively.
Dated this 26th day of January 1892.
J. H. JOHNSON & Co.,
Agents.