A Speed and Direction Indicator for Shafts.
Year: 1896

page_text: Date of Application, 22nd June, 1896-Accepted, 29th Aug., 1896
COMPLETE SPECIFICATION.
A Speed and Direction Indicator for Shafts.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings, in the
County of London Patent Agent, do hereby declare the nature of this invention,
a communication to me from Bradley Allan Fiske of Beresford Hotel, West 81st:
Street, New York, a Lieutenant in the United States Navy, and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement :-
The object of the invention is to produce a simple and efficient device or devices
for indicating at a distant point the speed and direction of rotation of a shaft such, for;
instance, as the driving shaft of an engine, and the invention is mainly designed;
for use on steamships." Heretofore in devices of this character mechanical contact,
or connection was depended upon for obtaining the indication of the speed and-
direction of rotation of the shaft, but all methods of indication employing direct
mechanical contact or connection with the moving shaft were objectionable and
unreliable on account of the wearing of parts where mechanical contact was
involved, or on account of the slipping of belts or the wear of gearing where
mechanical connection was employed, and all such methods required frequent
re-adjustment to compensate for the wearing of parts. Furthermore, the methods
eniploying direct current generators driven by the shaft were found objectionable
on account of the variations in resistance at the commutator brushes producing
variations at the indicator, thus requiring almost constant attention.
In carrying the invention into effect all mechanical contact with the rotating
shaft is avoided and the invention consists in providing a device which will produce
an electric current through the rotation of the shaft, which electric current will
affect an indicator at a distant point, and the preferred form of apparatus for
accomplishing this consists of inductors secured to the rotating shaft and moving in
close proximity to a pole or poles of a magnet provided with coils, whereby an
alternating current is induced in such coils, which current, actuates an indicator
having a pointer which is moved across the face of a scale whose graduations are
obtained empirically to indicate the number of turns of the shaft per minute. To
indicate the direction of rotation of the shaft, it is preferred to provide an
additional indicator which has a periodically moving pointer. This pointer may
be actuated by a galvanometer or other suitable device, but a polarized relay is
preferably employed, the current for energizing which is also produced by the
rotation of the shaft. The device for generating the current for the direction
indicator preferably consists of a permanent magnet carried by the shaft and moved
thereby in proximity to a bar of iron carrying a coil of insulated wire; or the
magnet may be stationary, and the bar and coil carried by the shaft. The direction
indicator also serves as a speed indicator, since by counting the strokes of the
pointer, the number of turns of the shaft per minute can be counted. Thus with
the two indicating devices working together, a perfect indication is obtained, and
the direction indicator acts as a check upon the speed indicator to show whether or
not the speed is correctly indicated...
The invention is illustrated in the accompanying drawings, in which:
Fig. 1 is a perspective view of the combined indicating apparatus;
Fig. 2, an enlarged plan view of the preferred form of direction indicator;
Fig. 3, an enlarged, plan, view of the speed indicator;
Fig. 4, a plan view illustrating the devices for generating the electric currents,
and the circuit connections to the indicators...

page_text: Fig. 5 an elevation showing the devices for generating the current for the speed
indicator; and Fig. 6, a similar view of the devices for generating the currents for
the direction indicator.
Referring to Fig. 1, A is the speed indicator mounted within a case A² carried
by a suitable pedestal A¹, and B is the direction indicator, also supported by the
pedestal, and both indicators are so arranged that the indication of the speed and
direction of rotation may be readily seen at a glance. The indicator A is
preferably an alternating current galvanometer having a stationary coil of wire
and a movable coil carrying the pointer a which moves over the scale a¹ whose
graduations indicate the number of turns made by the shaft per minute, and which
graduations are obtained empirically, or it may be of any other suitable form.
The galvanometer coils are not shown, since their arrangement will be readily
understood. They are so connected with each other that whenever the alternating
current produced at the shaft changes in direction, it changes in direction in both
the stationary and the moving coils, so that the direction in which the moving coil
turns, due to mutual reaction between the two coils, is always the same. Springs
are also employed in the galvanometer, which tend to maintain the moving coil
and its pointer at a certain normal position of rest, but any current traversing the
coils moves the movable coil against the tension of the springs through an angle
which depends on the strength of the current due to the speed of rotation of the
shaft. (This is simply the construction of an alternating current voltmeter.)
In mounting the speed indicator in position, the electrical apparatus of the
indicator is preferably mounted in a watertight case A2 filled with a liquid in order
to steady the pointer. Many different liquids may be employed for this purpose,
such as vegetable oils which do not congeal readily, and I find that poppy oil and
oil of almonds are suitable and give satisfactory results, since they do not congeal
until nearly 0° F. The indicator case A2 is filled from the top by pouring the
liquid through a sort of stand-pipe P (Figures 1 and 3), the level of the liquid in
the pipe P being somewhat above the top of the case A2. The filling-hole in the
pipe P is closed by a screw-plug p, in which is a small hole for allowing the passage
of air into and out of the pipe as the liquid contracts or expands with changes in
temperature.
Other devices, such as expansion chambers like those used in compasses for
allowing for expansion and contraction of the liquid, may be employed.
The device for indicating the direction of rotation of the shaft may be a direct
current galvanometer, or it may be a polarized relay actuating a pointer or any
other suitable direct current indicator. As shown in the drawings, I have
represented the direction indicator B as comprising a polarized relay having an
. armature which is polarized by a permanent magnet. 62. The armature bis
pivoted at 3 between the two poles of the relay b, and carries a pointer b. The
armature and pointer are pivoted upon a plate c which is adjustable by means of
screws c¹ screwing into extensions from the yoke of the magnet. b. The permanent
magnet 62 is secured at d to the yoke of the magnet b. The movement of the
armature toward and away from the poles of the magnet is limited by screw-
stops e.
The devices for inducing the current which actuates the indicators are illustrated
in Figures 4, 5 and 6, in which S indicates the shaft, whose speed and direction of
rotation are to be indicated. Mounted on the shaft S are two rings E and F,
which rings are formed in halves and are clamped to the shaft by means of lugs
and bolts, as shown at e and f. The ring E is provided with a number of flanges e
(six being shown), to which are secured soft iron armatures or inductors E'. These
armatures or inductors when revolved by the shaft, pass across the face of the
poles s and n of the magnet G whose coils are connected with the terminals of the
speed indicator A. When one of the armatures or inductors E' is directly in
front of the poles s and n, the magnetic flux passing through the two coils is at its
maximum, and when no inductor is near the poles, the magnetic flux is at its
minimum. Consequently as these iron inductors revolve before the poles of the

page_text: magnet, the magnetic flux is increased and decreased as many times per revolution
as there are inductors. Each increase and decrease of the magnetic flux produces
an alternating current in the coils according to principles well understood, and the
more rapid the increase and decrease, the greater the electro-motive force induced.
It will be evident that in manufacture, it is possible, with a proper construction of
the apparatus and with a proper proportioning of the parts, to so control the
inductance of the circuit and to so arrange the inductors and the number of them,
that the current in the circuit shall increase very considerably as the speed of
rotation of the shaft increases.
V
It is advisable in the construction of the apparatus, to introduce an adjusting
device for controlling the air-gap between the inductors E' and the poles s and n of
the magnet G, and therefore the magnetic flux and strength of the current
generated. This adjustment may be accomplished by mounting the magnet on two
supports and g', one of which g is stationary on the base g, and the other, g, is
movable longitudinally of the base by means of a screw g. The poles and n of
the magnet G pass through bearings in the support g', and by turning the screw g
in either direction, the poles are moved toward or away from the inductors E¹, as
will be readily understood. By this means the strength of the current generated
can be readily increased or decreased. In practice it is found that the distance
between the inductors and the poles of the magnet should be about one-sixteenth
of an inch, and in installing the apparatus, it is merely necessary to. adjust this
distance until the indicator A gives the proper indication. A similar result is
secured by adjusting the coils nearer to or further away from the poles and n.
For making finer adjustments, a rheostat R is provided in the circuit leading from
the coils of the magnet G to the indicator A. This rheostat may be of any
suitable construction, but it is preferred to employ one having a resistance wire
wrapped around the surface of an insulating cylinder and so -arranged that by
rotating the cylinder a greater or less amount of resistance may be introduced in
the circuit.
The ring F carries a permanent horseshoe magnet F1 having poles ¹ and
and this magnet is adjustably secured to an arm f¹ on the ring F by means of
a clamp The poles of this magnet travel in proximity to the end of a
core of iron H having coils thereon which are connected to the direction
indicator B.
The currents induced in the coils by the revolution of the magnet F1 cause the
pointer of the indicator B (when it is a direct current galvanometer) to make
three movements for each turn of the shaft, that is to say, a right, left, right
movement or vice versa according to the direction of rotation of the shaft. To
illustrate this, let it be supposed that the shaft S is the driving shaft of a ship
rotating in the direction of the hands of a watch, and that the pole of the
magnet F approaches the core H; the approach of this pole will induce a
current of a certain direction in the coils carried by the core, which current will
cause the pointer to move, for instance, to the right with a quick motion, and
which direction of movement we will assume represents the direction of the shaft
when the ship is moving ahead. As the shaft continues to rotate, the pole,
passes away from the core H and the pole n' approaches the core. The approach
of pole n induces in the coil of said core a current opposite in direction to that
induced by the approach of the pole s', and tends to move the pointer of the
indicator in the opposite direétion, that is, to the left. The rotation of the shaft
continuing, draws the pole n' away from the 'core, and this act induces another
current in the coil of said core in the same direction as did the approach of the
pole s, and therefore another movement is given the pointer to the right. Thus
for every turn, of the shaft in the direction of the hands of a watch or the
direction of rotation when the ship is going ahead, 'the pointer of the indicator
is given a quick movement to the right, left and right. If the shaft is moving in
the reverse direction, that is, when the ship is "backing," the results produced
by the rotation of the shaft will be just the reverse of that above indicated, so

page_text: that for every turn of the shaft in the reverse direction, the pointer of the
indicator will make quick movements to the left, right and left. Thus, by a mere
glance at the indicator, an observer can see at once in which direction the shaft is
rotating, and, if necessary, the number of rotations can be counted by the strokes
of the pointer. The indicator B therefore is useful both as a direction and speed
indicator, and may be used in case of accident to the direct reading instrument A
as the speed indicator, and the indicator B also serves as a means of verifying
the indication of the speed indicator A. Thus, if through any cause the adjust-
ment of the speed indicator should change, for instance, if anyone should tamper
with it, the variation between the speed indication on the indicator A and the
number of strokes of the pointer of the indicator B may be readily detected and
the apparatus re-adjusted.
When a "polarized relay" is used as a direction indicator, the alternating
currents generated in the coils carried by core H pass through the coils of the
electro-magnet or relay b and tend to give the armature successive movements for
each rotation of the shaft, as above indicated; but since there is no directing
spring on the armature, and since the magnetized armature when moved to either
side tends to remain there by reason of its greater nearness to one core than to
the other of the coils 7, the armature remains during the whole time of a revolution,
except when the poles and s are actually passing the core H, at the position.
in which it was placed by the last current, or, in other words, it remains in the
position to which it was last moved; for instance, if the movement were right,
left, right the pointer would remain to the right until actuated again upon the
next approach of the magnet F' to the core H. Furthermore, as the last current
produced when the shaft is going in a certain direction is the reverse of the
current produced when the shaft is turning in the opposite direction, the position
of rest of the pointer will be on cne side or the other of its central position
according as the shaft is going ahead or backward, and as the first current
generated in any revolution is the same as was the last current, and as the
armature b cannot move any farther, the first motion cannot take place except
during the first rotation of the shaft. The result of this is that if the shaft be
going ahead, the pointer of the direction indicator will occupy a position of rest
ou one side of the scale, and will make a quick motion to the left and back at each
rotation, whereas if the shaft is backing, the pointer will lie on the other side of
the scale and will make a quick motion to the right and back to the left at each
rotation.
Obviously the relative positions of magnet F1 and core H with its coil may be
reversed, the magnet being held stationary, and the iron core with its coil being
revolved by the shaft. With such a reversal it would be merely necessary to
connect the ends of the coil to two insulated metal rings on the shaft from which
the current would be taken by suitable brushes.
o
In the drawings I have shown the magnet F¹ for producing the currents which
actuate the direction indicator as projecting radially from the shaft. In many
cases, however, it will be more convenient to have the magnet lie parallel with the
shaft or at an angle to it, but it is desirable that in any case, the poles of the
magnet F¹ should not be too close to the shaft. In practice it is found that
the poles should not be closer than two inches to the shaft.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is :-
1. The apparatus for producing indications of the speed of rotation of a shaft,
substantially as herein described.
2. The apparatus for producing indications of the direction of rotation of a shaft,
substantially as herein described.
3. The combined apparatus for producing indications of the speed and direction
of rotation of a shaft, substantially as herein described.

page_text: 4. In apparatus for producing inlications of the speed of rotation of a shaft,
the employment of one or more inductors mounted upon the shaft, and a magnet
whose pole or poles are located in close proximity to said in luctors and providel
with coils in which a current of electricity is induced by the movement of said
inductors in proximity to said magnet for actuating a suitable indicator connected
to a circuit extending from said coils, substantially as set forth.
5. In apparatus for indicating the rotation of a shaft, the employment of a
magnet mounted upon the shaft and revolving therewith, an an iron core located
in proximity to said magnet and provided with coils, in which a current of
electricity is induced by the movement of said magnet in proximity to said core
for actuating an indicator connected to a circuit extending from said coils,
substantially as set forth.
6. In an apparatus for producing indications of the speed or direction of rotation
of a shaft, the employment of a inagnet mounted upon the shaft, and a core located
in close proximity to the poles of said magnet and provided with a coil of wire, in
which currents of electricity are induced by the movement of said magnet in
proximity to said core, in combination with an indicator comprising a magnet,
and a polarized armature carrying a pointer, which magnet is placed in a circuit
extending from the coils referred to, substantially as and for the purpose set
forth.
Dated June 22nd 1896
HARRIS & MILLS,
23 Southampton Buildings, London, W.C., Agents.