IMPROVEMENTS IN ROTARY BLOWERS AND PUMPS
Year: 1881

page_text: LETTERS PATENT to Francis Marion Roots, of Connersville, Fayette County,
State of Indiana, United States of North America, but now of No. 52,
Chancery Lane, London, for an Invention of "IMPROVEMENTS IN ROTARY
BLOWERS AND PUMPS."
COMPLETE SPECIFICATION filed by the said Francis Marion Roots at the
Office of the Commissioners of Patents on the 27th September 1881.
FRANCIS MARION ROOTS, of Connersville, Fayette County, State of Indiana,
United States of North America, but now of No. 52, Chancery Lane, London.
"IMPROVEMENTS IN ROTARY BLOWERS AND PUMPS."
My Invention relates to rotary blowing engines and pumps in which two or
more rotating abutments coact together and with the shell in which they are
encased to force a current of air, gas, or fluid in one direction without permitting
backward escape of the same under pressure, and is similar to my improvements
in rotary blowers patented 9th May, A.D. 1866, and 23rd April 1807.
The objects of my present improvements are,-
First. To insure perfect contact of the abutments with each other during their
entire revolution, so that there can be no backward escape of the air or other fluid
acted upon.
Second. To reduce the friction between the necessary points of contact.
avoid concussion in use, lessen the surface necessary to be finished, and savo
material.
Third. To provide a means to pack the ends or tips of the pistons, so as to
secure perfect contact between them and the shell when the machine is to be used
under heavy pressure, or as a pump or hydraulic engine.
Fourth. To facilitate the readjustment of the abutments and replacement of the
journal linings to bring the pistons to their proper relative position.
Fifth. To protect the abutments and inside of the shell against injury by
extraneous substances entering the induction port.

page_text: $
Sixth. To facilitate the removal of the gear wheels and the housing in which
they are encased.
To more fully describe my said improvements reference is made to the accom-
panying Drawings, in which
Fig. 1, Sheet 1, is a longitudinal vertical section of a machine embodying my
improvements taken through the line x, of Fig. 2, which is a central vertical
transverse section of the machine.
Figs. 3 and 4 are similar sections, showing the abutments in different
positions.
Fig. 5 is an end elevation of my improved cog wheel.
Fig. 6 is an axial section of one of the abutments fitted with the templets
preparatory to dressing the convex arcs and concave points of contact.
Fig. 7 is an end elevation of the mechanism for dressing the abutments.
Fig. 8 is a diagram illustrating my system for obtaining the centres from which
the convex arcs and concave points of contact are described.
Fig. 9 is a perspective view of my improved journal bearing.
Fig. 10 is a detail view in perspective of the lower box and its lining, and
Fig. 11 is a similar view of the cap and lining.
Similar letters refer to the same parts throughout the several views.
The case or shell of the blower consists of two semi-cylindrical-flanged-shells-A
-secured between-end-plates-B.;-C,-C,.arc-the-co-acting-rotating-abutments-mounted
one above the other within the case A.
The method of constructing my improved abutments is as follows:-The
abutment shafts D, D, are placed the requisite distance apart, depending upon the
size of the machine to be constructed; two equal circles are described from the
shaft centres by a radius equal to half the distance between said centres; these are
the pitch line circles; these circles are divided into cight equal parts by radial
lines, one of the dividing lines c, a, passing through the centres of both shafts
within each of these circles, and described from the same centres are two smaller
circles, usually about one twelfth less in diameter than the pitch circles, although
. the size of the inscribed circles may be varied without materially affecting the
result. Thus far the steps taken are the same as the Patent granted to me,
Francis Marion Roots, and Philander Highley Roots, May 9th, A.D. 1866, No. 1333,
but the convex arcs and concave surfaces in that case were respectively described
from points in the central dividing line X, X, and the radial line y, y, at right
angles to it.
I have discovered that in order to insure perfect contact during the entire
revolution the radius by which the convex surfaces and concave points of contact
are described must extend across the central dividing line X, to a point within
the pitch circle.
The points from and the radius by which the convex surfaces and the concave
points of contact in my improved abutting pistons are described I obtain as
follows:-(referring now particularly to the diagrain, Fig. 8) from the point i
where line X cuts the inscribed circle I draw a line to a point 12 where the line =
intersects the pitch circle, then by a radius equal to one fifth of the line just
obtained, and with one point of the compass on point i (in line X and the inscribed
circle), I obtain two points in the inscribed circle equi distance from line X.
From these points as centres the opposite arcs of the pistous are described by a
radius r extending from point is across line X to point 3, where line cuts the
pitch circle. With this radius all the convex surfaces as well as all the concave
points of contact are described from centres, as when the abutments are in tho
position shown in the diagram (their respective dividing lines X, X, at right angles
to each other) the convex arcs of one abutment are in perfect contact with the
concave contact points in the other.
I do not.limit myself to the exact location described for point, as this
point may be somewhat varied without departing from the principle of my
Invention

page_text: The extreme ends of tips c of the pistons are described from the shaft centres.
Coacting abutments thus constructed will maintain perfect contact with each other
during the entire revolution, as appears clearly from Figs. 2, 8, and 4.
The ends of the pistons upon each side of the central contact point c are cut
away and the concaves between the concave abutting points are cut back, thus
leaving only the requisite surface to keep the contact during the revolution of the
abutments. I thus reduco the surface which requires finishing more than three
fourths, effecting a great saving of labor and material, giving more clearance to
the parts and greatly reducing the friction, and when the machine is used as a
pump for water or denser fluids it will operate without concussion. When used
for this purpose, or as a water meter or hydraulic engine, it is desirable that the
contact between the pistons and the case should be perfect. In Figs. 2, 3, and 4
is shown a means by which this end is accomplished. A packing strip c² of
leather, rubber, or other anitable material is clamped between a metal retaining
strip and the tip of the piston by screw bolts. The strip may also serve
without other packing to keep up contact with the case should the ends of
the pistons become worn. When used for this purpose the bolts should pass through
transverse slots in the metal strip to admit of its radial adjustment.
To attain the best results great accuracy is required in fitting the parts together,
in order that the abutment shafts may be given and maintain the proper relative
position to each other, any change in the relative position of the shafts to each other
or the case either as to parallelism or circumferentially will impair the effectiveness
of the machine, heretofore the labor of adjusting the pistons in the first place, and
readjusting them when the bearings became worn from use, has been difficult and
tedious, requiring great skill and care. By my present improvements these
difficulties are in a great degree obviated.
I have provided means to prevent the driving shaft D from being drawn out of
line by the tension of the driving belt by furnishing a rigid bearing G for the end
of the driving shaft outside of the driving pulley. Depending from the table which
supports the journal boxes is a plate E, cast with the end plate of the blower case,
and rigidly supported by brackets E' also cast with the end of the case; the plate E
is planed off parallel with the inside of the end plate. F is an iron frame
having upon its outer end a table to support journal boxes. The shape of the
frame in vertical cross section is semi-cylindrical; it has openings of sufficient size
to permit free play of the belt from the countershaft; the inner end of the frame F
is planed to accurately fit the plate E, to which it is securely bolted. After it has
been properly adjusted and secured in place on the end of the case, tapering holes
are bored through the plate E and the end of frame F to receive tapering steady
pins e; by means of these pins as guides the frame F may be removed when
desired and readily replaced in its original position; this frame gives a rigid support
to the shaft outside of the pulley.
I have also made provision to quickly readjust the shafts D in line should their
journal bearings become unevenly worn. This I accomplish by the devices
illustrated in Figs. 9, 10, and 11. The journal boxes G, G¹, are bored out exactly
concentric with the axis of revolution; the, linings H are turned off upon the
outside to fit the boxes, and on the inside bored to fit the journals, thus leaving the
shell linings of uniform thickness in cross section, so constructed the linings may
be turned around in their boxings and be evenly worn all round, and when so much
worn as to require replacing the cap G' is removed, the old lining slipped around
the shaft, and a new lining made to follow it while being removed, thus restoring
the original position of the abutments; a set screw may be passed through the
top G₁ of the box to prevent the linings from slipping.
It is evident that by continued use or from negligence (not keeping the parts
properly lubricated) the teeth of the gear wheels will become worn and permit the
abutment to "lag." In Fig. 5 is shown an arrangement to compensate for the wear
of the teeth and facilitate the adjustment of the abutments when fitting up the
machine; by this means the abutment may be advanced or retracted in its path of

page_text: travel around its shaft. This object I accomplish by means of a cog wheel,
consisting of an outer rin I and an inner hub J accurately fitted together. The
keyway in the hub is cut just wide enough to fit the key while the keyway.in tho
rim I is cut about one sixteenth of an inch larger, more or less, the spaces between
the key and the sides of keyway in the rim are filled with thin strips of rolled iron
or steel from one sixty fourth of an inch, more or less in thickness, the rim can
thus be circumferentially adjusted upon its hub by changing one or more of these
strips from one side to the other of the key.
In use, the pistons and interior of the shell are liable to be injured by extraneous
substances being drawn into the induction port. Attempts have been made to
overcome this difficulty by covering the port with a wiro gauze screen, but it is
found that substances too large to pass through the meshes would be held by
suction against the screen, and thus obstruct the free flow of air to the machine. I
overcome this difficulty by the hooded port K, the outer end of which is inclined, so
that anything dropping in front of the hood or falling upon it is or will be carried
out of the line of draft. The port is also guarded by a grate L located within the
hood; should any
substance get within the hood its passage to the machine will be
obstructed;
--
My improved housing for protecting the gearwheels is constructed as follows:-
Flanges Gare.cast-upon-the-outer-end-of-the-journal_boxes_G,-(see Figs. 1, 9, and.
10), these are turned off parallel with the inside of the end plate; the inner plate M
of the housing is divided vertically in the plane of the axis of the two shafts D, D;
it has cast upon its projections m corresponding to the flanges G². These projections
are planed off true to fit the flanges, and the plate is secured in the position shown
in Fig. 1 by screws passing through the flanges G into the projections m.
The
shell N of the housing is secured to plate M by screws passing through the plate
and into the inwardly projecting Blange upon the rim of shell N. The purpose of this
arrangement is to facilitate the removal of the cog wheels or of the housing without
disturbing the coga; this is accomplished by removing the shell N, taking out the
screws in flange G³, and removing the divided back plate M; the keys are now
easily accessible from the back, and the cogs may be readily taken off or the rim of
the adjustable cog wheel set around upon its hub.
I will now describe the method by which my improved abutments are accurately
dressed. For each size of abutment I construct two templets P, P, according to
the formal givena for constructing my abutments; these templets are dressed to
the exact size and shape of a cross section of the abutment; the four centres in
each templet from which the peripheries are described are bored out and accurately
fitted with journal pins p; the pins when in position form the axis of the piston,
a hole is bored in the centre of the templets to accurately fit the shaft of the
abutments; two or more holes are bored in each templet opposite each other when
the templets are in position; through these clamping bolts 7 are passed. The shafts
and the ends of the abutments being turned down true the templets are slipped
over the shafts upon each end of the abutment, the clamping bolts passed through
the templets and the hollow abutments. The templets are adjusted exactly
opposite each other and out of "wind," and the abutment tightly clamped between
them; the abutment is then mounted in standards R on the bed of the planer (see
Fig. 7), the journal pins p of the templets resting in V shaped bearings and held
in place by caps. The opposite tip of the piston is clamped in the end of a yoke s
which is jointed to a travelling nut S upon a screw T, the lower conical end of the
screw rests in a step on the bed plate of the machine; by this screw and its nut
the abutment is turned upon the pin p, and the convex surface of the piston fed
to the cutting tool and dressed down to the templets. The concave contact points
being only about one fourth to one half inch in width are dressed down to the
templets by a tool of proper shape, while the abutment remains stationary in
standards R. When one of the convex arcs and one of the concave points_aro
dressed the abutment is removed from the standards R, the pins p changed to
other holes in the templets, and the abutment replaced in the standards preparatory

page_text: to dressing another side in the same way. The operation is repeated until all the
convex arcs and concave contact points are dressed down to the templets. I have
described my method of dressing my improved piston abutment upon an iron
planer, but they may also be dressed upon a milling machine or other dressing
tool in substantially the same way, as the principal feature in my method is the
centering of the abutments upon the points from which the arcs are described for
making the edge of the cutting tool describe an arc from said centres, or around
them as an axis. It is also evident that instead of the pins pa shaft may be
passed through the pin holes, or centre bearings may be made in the templets at
said points to receive centering points secured in the standards R.
My improved abutments are cored out hollow, and in some cases are cast with
the shafts in position.
By my improvements I am enabled to construct a blower entirely of metal as
cheaply as those having wood covered abutments, and as my improved blower will
not be affected by different conditions of atmosphere, ordinary variations of tempe-
rature, dust, or other abrading substances that would injure wood covered abutments,
less clearance is required between the surfaces of contact, and hence a more
accurate fit may be made and maintained between the parts, and a more durable
and effective machine is produced.
Having now described the mode of constructing and operating my said improve-
ment, what I claim is,-
1st. Abutments for rotary pressure blowers constructed substantially as described,
that is, having the convex arcs of the pistons and the concave points of its recesses
described from a point, as within the pitch circle by a radius extending from
said point across the central dividing line X to a point in the pitch circle.
2nd. Abutments for rotary blowers having their convex arcs and concave points
of contact described substantially as hereinbefore set forth, and having the ends of
the pistons upon each side of the central point c, and their concave surfaces between
the concave points of contact cut away to lessen the friction, avoid concussion, and
reduce the surface of the abutments necessary to be finished.
3rd. The abutments of a rotary blower such as described, having its ends cut
away upon each side of the central point c in combination with a packing strip c².
secured to one end of said central tip c to make an air tight fit between the case
and piston, substantially as described.
4th. In a rotary pressure blower, the combination, substantially as specified, of
the coaching abutments and their shafts with journal boxes G, G', and the two
part lining H, H, the bearings in the boxes and the interior and exterior of the
linings being concentric with the axis of the shafts, so that in case of uneven wear
the said abutments may be in contact by turning said linings, and the linings
removed and replaced without disturbing the position of the abutments.
5th. The rotary pressure blower having co-acting rotary abutments encased and
operating within the shell A, B, in combination with the hooded part K and
grating L, for the purpose set forth.
6th. In a housing for rotary blowers, the combination, substantially as specified,
of the flanged journal box, the dividing inner plate M adapted to be readily secured
to or removed from said flange G2 independent of the gear wheels, and the shell N
secured to plate M for the purpose of protecting the goar wheels and readily
removing them when desired.
In witness whereof, I, the said Francis Marion Roots, have hereunto set
my hand and seal, this Fourteenth day of September, in the year of our
Lord 1881
FRANCIS MARION ROOTS. (L.S.)