Improvements in Dynamometers.
Year: 1895

page_text: Date of Application, 19th Mar., 1895-Accepted, 8th June, 1895
Improvements in Dynamometers.
I, BENJAMIN FRANKLIN PERKINS, of No. 250 Pine Street, in the City of
Holyoke, County of Hampden and State of Massachusetts, United States of
America, Manufacturing Machinist, do hereby declare the nature of this invention
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
This invention relates to improvements in dynamometers or power measuring
apparatus, the object being to improve the mechanism to the end of rendering
it more readily available and efficient; and the invention consists in constructions
and combinations of parts all substantially as will hereinafter fully appear and be
set forth in the claims.
In the accompanying drawings,
Figure 1 is a perspective view showing the driving-shaft, a pulley driven by the
shaft and the dynamometer applied so as to show the force in transmission, and
as exerted by the shaft to carry around the pulley, a speed indicator being also
shown.
Figure 2 is a side elevation of the same, the parts which are especially
comprised in the dynamometer mechanism being, however, shown substantially in
central, or axial vertical section.
Figures 2 and 28 illustrate the pressure indicators, externally.
Figure 3 is a vertical, transverse section taken on the line 3-3, Figure 2.
Figure 4 is a perspective view showing the different parts of the diaphragm,
diaphragm-casing, and diaphragm operating element here employed.
Similar characters of reference indicate corresponding parts in all of the views.
In the drawings, A represents a shaft which may be driven by the belt and
pulley seen at a. This shaft is the dynamic element, or primary movable part,
and B represents a pulley which is loose on the shaft, A, but which constitutes
the secondary part which is driven, and around this shaft is shown a driving belt
which may run to the machine, or machines, for which the power is desired to
be determined.
This loose pulley is driven by the shaft through means of a part of the
dynamometer shown as interposed between an arm, b, fixed to move as one with
the shaft, and a stud, d, extended from a web, or spoke, of the driven pulley.
Said stud, d, engages with a rod connected to a diaphragm, below described,
whereby the latter is deflected by a piston-like movement thus given to said rod.
The said arm, b, is extended to one side of a hub, 2, which is by a set-screw, or
key, fixed to the shaft, A, and another arm, 63, is extended at the opposite side
of the hub and carries, or has, as a part of its end the counterweight, 4, which
is effective in balancing the dynamometer parts to be next described.
A part of the dynamometer which constitutes the medium of the transmission
between the arm, b, of shaft, A, and the stud, d, of the pulley, B, will be now
described in detail, the same consisting of a diaphragm casing supported and
carried by the arm, b, a diaphragm in, or forming a side of, the casing, and a
diaphragm-compressing element which is borne upon by the stud.
The diaphragm casing consists of casing-sections, ff, of hemi-spheroidal form
having edge flanges, f, respectively, externally and internally screw-threaded, to
be screw-united, and each has an axially extended hub, 3, which is centrally bored,
as seen at f*.

page_text: The hub, 3, of the casing section, f, screws into the threaded orifice of a hole, g,
which is bored through the thickness of the shaft-arm, b. The opposite end of this
hole is closed by the screw-stopper, g².
h represents the flexible diaphragm which is clamped between the two sections
of the casing, a washer, or clamping ring, f, being provided, as usual, at the
margin of the diaphragm and a rod, or piston-like element, j, is attached to, and
projects axially from, the diaphragm through and beyond the hole, 78, in the hub
of the casing-section, f2:.
The manner of engagement of this stud, j, with the diaphragm, consists in the
flange of the stud lying against one side of the diaphragm, its attenuated and
threaded inner end passing through the central hole of the diaphragm, while the
nut screws against the washer 7 and presses it against the inner side of the
diaphragm.
Within the chamber constituted by the diaphragm and the casing-section, f; a
body of liquid is placed which is subject to displacement in a greater or lesser
degree according to the extent of the deflection of the diaphragm, and which
will consequently operate the scale, or indicator, which determines the amount of
the power in transmission, which scale, or indicator, is seen at D:.and it comprises
an arc-formed chamber, m, the walls of which are yielding, and resilient, or
reactive.
"
This are-shaped chamber is mounted in a casing, m², at its one end and opens to
the hub,,m³, thereof, while its other end, m, is closed, as seen in Figure 2..
This arc-chamber, m, is in communication with the space behind the diaphragm
through means of conduits, as follows:
From the hole, g, which is open to the diaphragm chamber, the tube, i, leads
which has the elbow coupling, 2, and angular tube section, 3, which radially com-
municates with the axial passage, , within the said shaft, A, at an end portion
thereof which is beyond the part surrounded by the pulley, B.
The hub of the indicator casing (through which is the orifice of the chamber, m,)
screws axially into the enlarged mouth of the passage,
The liquid, a, is of such quantity as not only to fill the diaphragm chamber, but
also the chamber, m, and intermediate connecting, conduits, i, 3,
This pressure of the liquid as induced by the deflection of the diaphragm,
ensures the tendency of the arc-chamber to straighten out thereby swinging,
through the link, the lever, on one arm of which is the sector-gear, k; this sector
meshes with the pinion, k, the arbor, k, of which is mounted in the casing, m², and
which arbor carries the pointer, k³, at the outer dial face of the pressure indicator
casing.
As here arranged the casing rotates as one with the shaft, A. and it is preferably
painted, or enameled, white, its figures and graduations, and the pointer, being
black.
By reason of the persistence of the vision to retain intermittently exposed
objects, the bodily rotating indicator apparently becomes resolved into a graduated
and figured dial face baving a pointer which may be easily read. .
In order to increase the clearness, or intensity, of this effect, I place upon the
rear side of the casing an exact duplicate of the dial-face, as seen in Figure 2B.
In conjunction with this, dynamometer it is necessary to know the speed of
rotation of the shaft and pulley, and a speed indicator of any of the well known
descriptions may be used for this purpose.
In the present illustrations a speed indicator of a very common type is shown in
a general way at F, it not being necessary to describe or show its detailed
construction.
It will be understood, however, that this speed indicator has the casing, n, to
contain the mechanism which is held stationary relative to that part, the rotations
of which it is to determine, while its operating shaft, n², is rotatable within the
casing and derives its rotation by having a suitable manner of engagement with the
rotating part.

page_text: Now, as indicated in Figures 1 and 2; the shaft, n², enters a socket, m°, in the
outer hub of the indicator casing, n. The end of the shaft is of diamond pointed,
or other angular form so that when pressed inwardly to the sent of the socket, m³,
the shaft must rotate as one with the socketed part.
By reason of a spring suitably applied as usual, the shaft, n², is designed to
recede from within the socket so as normally to be out of a rotating engagement.
As shown in these drawings, the speed indicator casing has a handle-bar, ³,
which is extended, trunnion-like, radially opposite the shaft, n², and the stand, o,
may he provided to support this arm and also the socketed hub, m³, of the
pressure-indicator.
By forcing the handle, ³, endwise and maintaining it in its position of
engagement, the rotational velocity may be determined.
In lieu of mounting the speed indicator in a stand therefor, as shown, of course
the same may be presented momentarily properly relative to the shaft, as is
common among mechanical engineers and others for determining, by an indicator
of this description, the rotational velocity.
Of course there is a great variety of speed indicators which might be utilized
other than the one of the character here superficially illustrated.
The resistance element in the pressure indicator, or scale, is to be originally by
the constructor adjusted, or regulated, in a determinate manner to accord with
the power applied or transmitted through the diaphragm. That is to say, in
explanation, in the present illustrated instance, every pound of force transmitted
by the shaft-arm, b, through the diaphragm to the driven pulley, B, will, of course,
before being transmitted to said pulley, ensure a deflection of the diaphragm and a
consequent and corresponding straightening of the resilient chamber, m, in such
a degree as to register in a corresponding number of pounds upon the face of
the dial.
Now, the process of computation, making use of the data established by the
mechanism here contemplated, is as follows:
Multiply the circumference of the pulley, in feet, (which is the travel of the
working belt) by the number which is found to indicate the rotations per minute of
the shaft and the driven pulley, and multiply this product by the number shown
by the pressure indicator representing pounds, whereby we learn the number of
foot pounds carried per minute, and dividing this by 33,000, the quotient gives the
horse power developed.
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. The combination with the shaft, A, having the passage, 4, therein which
opens to its end, and the pulley, B, loose on the shaft having the projecting stud, d,
of the arm, b, fixed on the shaft and having the hole, g, transversely through it, a
diaphragm casing having a hollow hub screwed into one orifice of said hole, and a
reciprocatory stud engaging the diaphragm and in turn engaged by the said
stud, d, of the pulley, the removable stopper, g², screwing into the other orifice of
said hole, g, the tube section communicating with said hole, g, and the tube
section, 3, coupled to said section, i, and communicating with the shaft passage, i*,
and a pressure indicator connected with the said passage, i, all substantially as
described and shown.
2. In combination, the shaft, A, with hole, , extended to its end and having the
fixed arm,
b, with hole, g, and conduits, i, 3, leading therefrom to said hole, *, and
the diaphragm-casing and diaphragm supported by said arm and having its
chamber in communication with said hole, g, the screw stopper at one end of said
hole, and the diaphragm-stud, j, the loose pulley, B, having the projection, d, in
engagement with said stud, j, the reactive casing, m, having the hollow hub, m³,
screwing into the open end of shaft, A, and the enclosing casing, m², movable as a
part of said hub and having double dial faces, the diaphragm-operating liquid, and

page_text: the pointer over one of the dials, operated by said reactive casing, all substantially
as described and shown.
Dated this 18th day of February 1895.
BENJAMIN FRANKLIN PERKINS.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.