IMPROVEMENTS IN AIR COMPRESSORS
Year: 1887

page_text: Date of Application, 20th-Oct., 1887
Complete Left, 28th Apr., 1888
Complete Accepted, 15th June, 1888
I, WILLIAM A. PITT, of Glenbrook, in the county of Fairfield, and State of
Connecticut, one of the United States of America, Gentleman, do hereby declare the
nature of my
"IMPROVEMENTS IN AIR COMPRESSORS" to be as follows:-
The purpose of my improvement is to provide means whereby an equivalent in
compressed air is obtained, in volume and pressure for the power expended in the
compression. To accomplish this, I provide two cylinders of equal dimensions, with
pistons, and piston rods, each of which has a tooth rack on its outer end, and
between these racks is placed a gear wheel or pinion having teeth meshing in
the racks.
Where I employ two cylinders placed on the same plane with each other, two
cranks are mounted on a cross shaft, and each has a connecting rod which has a rack
on its lower end, similar to the rack on the piston rods, the two racks engaging with
the centrally mounted pinion.
The pinions are each provided with an axle set at a desired distance from the centre
of each of them, which axles rotate in sliding boxes their motion being in a horizontal
direction. The journal boxes are held in position by traverse bars placed on the frame
and provided with roller carriages and rollers. In the rotation of these pinions, their
periphery being confined between the piston rod and the opposite connecting rod
racks, the eccentric axles cause the journal boxes in which they turn and forming
their fulcrum to slide back and forth on the traverse bars and rollers. The fulcrum
of the pinions, in rotating being constantly changing, as well as different portions
of their periphery coming into contact with the racks, the leverage is also constantly
changing.
1001
WILLIAM A. PITT.
By K. Newell, his Agent.

page_text: COMPLETE SPECIFICATION.
Improvements in Air Compressors.
I, WILLIAM AUGUSTUS PITT, of Glenbrook, in the County of Fairfield, State of
Connecticut, one of the United States of America, Gentleman, do hereby declare the
nature of my invention for "IMPROVEMENTS IN AIR COMPRESSORS," and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement :-
My invention relates to the construction of air compressors, and the object of my
improvement is to provide means whereby an equivalent of compressed air in volume
and pressure is obtained for the amount of power expended in compressing it, and so
overcome the great waste of power which takes place in the ordinary form of engines;
and to accomplish this I employ, in conjunction with the steam and air cylinders, a
constantly changing leverage, whereby a constant change of power is effected, as may
be desired.
In the accompanying drawings, which clearly illustrate the mechanism employed
by me :-
Figure 1, is a front elevation of an air compressing engine embodying my
improvements:
"
Figure 2, is a detail sectional view of the gear wheel and adjoining parts and
Figure 3, is a side elevation of the rack movement, shown applied directly to the
steam and air cylinders of a horizontal engine.
Referring first to Figure 1, a represents a portion of the bed or frame of the
engine. and are two cylinders of equal dimensions and c c the piston rods
carrying the respective pistons of the same." Each piston rod is formed with a rack d
on its outer end."
In the top part of the frame a is journaled a cross shaft e. On this shaft are set, in
line with each other, but in opposite directions, the two cranks ff whose connecting
rods g glare each provided with a rack on the outer end, corresponding to the
racks dd on the two piston rods c c.
Between each piston rod rack and connecting rod rack, is mounted a gear wheel i
adapted to engage therewith. These gear wheels i are each mounted on a shaft o
which is journaled in the blocks jj, which latter are so placed and fixed as to move
in a horizontal direction between two bars kk placed on each side of the engine
frame, to form a guide way for the journal boxes j j, which traverse to and fro
on roller carriages 11, placed on the bars kk, whereby each of the wheels ii have
a movable bearing, so that its axis o becomes a constantly changeable fulcrum, from
the beginning to the finish of the stroke of pistons.

page_text: mm are roller carriages placed on the engine frame a on which the rack ends of the
piston rods c c move, and similar roller carriages n n are provided on the standard a¹
for the rack ends of the cranks ff"
Figure 3, shows the same principle applied directly to an air and steam cylinders a,
and a.
As is seen in both of the figures, I place the axis or shafts o, o, of each of the
gear wheels, or pinions, i, i, near the periphery of the same, so that it becomes a
leverage between the two racks, the fulcrum of which is so located as to give a much
longer stroke of the piston in one cylinder than is made in the other cylinder. These
shafts o, o, rotate in the sliding journal boxes j,j, each of which forms a bearing for
one end of the shaft, as seen in Figure 2, while the boxes, as before stated, are held
in position by the traverse bars k, k, and the rotation of the wheels or pinions
causes them to slide back and forth on the said traverse bars, and interposed roller
carriages, 1, 1.
Thus, as each of the gear wheels or pinions begins to revolve, its axis becomes a
constantly changing fulcrum, and different parts of the periphery of each gear wheel
or pinion coming into contact with the respective racks, effects a constantly changing
leverage.
Thus I provide a changeable leverage to operate between the steam and air cylinders,
with its fulcrum set, at the commencement, at four points from the weight and one
point from the power ends of the lever, and in effecting a balance of pressure in the
air with that of the steam, I cause a three-fourths movement of the air piston with
only a one-fourth movement of the steam piston, at which point in the steam cylinder
the steam may be cut off, and the fulcrum having secured a position midway between
the weight and power ends of the engine, causes a balance all round. Any further
movement of the steam piston causes the steam to expand, and all loss of power due
thereto is compensated for by a still further increasing leverage, which is effected by
a further movement of the fulcrum toward the air piston end of the lever. By this
means is provided a constantly increasing power, in the same increase ratio as and
for the loss that takes place in the engine due to loss of heat or pressure in the steam
by such expansion, and causing the pressure of the piston rod upon the resistance to
become uniform, and further, if desired, to increase toward the end of the stroke,
notwithstanding the decrease of pressure upon the piston by the expanding steam.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed I declare that what I
claim is:
1. In an air compressor, the combination and arrangement of levers between the
steam cylinder and air cylinder, which have a constantly changing fulcrum, whereby
all loss of power due to the expansive use of the steam is compensated for by a
proportionate increase of leverage, as set forth.
2. The combination in an air compressor, of two cylinders having their piston rods
each provided with a rack end, and cranks with connecting rods provided with rack
ends, and gear wheels having movable axes arranged to engage with said racks, as
set forth.
3. The combination with two cylinders and piston rods each having a rack end, and
cranks with connecting rods each with a rack end, of gear wheels arranged to engage
said racks, each mounted in a block 50 fixed as to move to and fro in the frame of
the engine during the movement of the wheel, whereby its axis becomes a changeable
fulcrum from the beginning to the end of the stroke of the pistons, thereby effecting
a constant change in leverage, as set forth.
4. The combination of the cylinders 661, piston rods c c with rack ends d.
cranks ff, and connecting rods g g with racks h h, and gear wheels ii mounted in
movable blocks jj, all arranged and operating as set forth.
5. In an engine, a leverage connecting two cylinders, having a constantly changing

page_text: fulcrum, whereby any portion of the stroke may be effected on the one end of
the engine by a lesser or greater given portion of the stroke on the other end, as
set forth.
6. The cylinders 6 6, piston rods cc with racks d, d, cranks of f1 connecting
rods gg, with racks hh, gear wheels i i, shafts o o, movable blocks ; j, roller
carriages m m and n n, and bars kk, all arranged and operating as set forth.
WILLIAM AUGUSTUS PITT.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.
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