Improvements in Chronographs for Indicating Minute Intervals of Time.
Year: 1891

page_text: Date of Application, 16th May, 1891-Accepted, 1st Aug., 1891
COMPLETE SPECIFICATION.
Improvements in Chronographs for Indicating Minute Intervals
of Time.
I, CARL WILHELM SCHMIDT of 4 Place Vendôme, Paris, France, Clockmaker,
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 chronographs of simple construction
and of great accuracy for indicating very small or minute intervals of time such for
example as the thousandths of a second. To this end an indicator or pointer is
mounted directly or indirectly upon the axis of the hair-spring or balance in such
a manner that it has an oscillatory motion from right to left and from left to
right.
The annexed drawings illustrate by way of example two forms of chronograph
constructed according to this invention.
Fig. 1 is a front elevation of one form, a part of the case being removed to show
the details of the mechanism.
Fig. 2.is a cross section thereof.
Fig. 3 is a rear elevation of internal arrangements and
Figs. 4 and 4 illustrate respectively in elevation and plan, a mode of supporting
the chronograph.
Fig. 5 is a front elevation, and
Fig. 6 is a rear elevation of a modified form of chronograph.
Fig. 7 is a transverse vertical section of the same.
The arrangement shewn in Figs. 1 to 4 is applicable to the ordinary uses of a
chronograph.
Figs. 5 and 7 illustrate a form adapted for use in measuring great velocities such
as those of projectiles, wind, light, etc.
In Fig. 1 to 4 a is the hand or pointer mounted upon the axis of the balance b
and indicating on a dial thousandths or still smaller parts of a second; this hand
being subject to the action of the balance makes a series of oscillations to the right
and to the left alternately, and in order to prevent it from exceeding a complete
revolution, it strikes at the end of each movement against an elastic stop c. As the
balance acts as a pendulum the speed of the hand varies, and consequently the
distances between the divisions are made smaller and smaller the nearer they are to
the turning point for the hand or to the elastic stop c where also the zero of the
dial will be found as well as the figure which indicates the time the balance has
taken to complete one oscillation. The graduation is made alike on the left and
right hand side of the stop c and an indicator d fixed to the stop c points out
When
whether the graduation shall be read to the right or to the left of the zero.
the hand moves from left to right it moves the stop c on striking the same over to
the right. The indicator d is moved correspondingly and becomes placed with its
points away from the dial which means that as long as it has that position the
graduation shall be read from zero to the left. The hand having finished its
oscillation strikes the stop and moves the point of the indicator towards the dial
which then points out that the graduation must be read in the opposite direction.
A movable piece o guided by a fixed piece and operated from the outside by a
pusher serves to replace the hand a to zero if required.
"
This is done in the following manner. By moving the pusher and thereby the
piece o so that its end comes in front of the hand a when the same during-its

page_text: oscillations happen to be between c and o, the oscillation of a is stopped and by
continuing the movement of the hand a is brought to zero or to the stop c.
The balance with its hairspring can be connected to an ordinary clock move-
ment the construction of which therefore need not be described here.
The number of oscillations made by the hand a can be indicated as in Fig. 1 by
the hand g indicating seconds and fifths of a second or by any other arrangements
of hands and dials Fig. 1 also shows an hour dial h.
The mechanism can be stopped or set in operation by means of an electro-
magnet i, into which a current is sent at the desired moment. The armature of
this electro-magnet carries a finger which bears upon the balance, thereby
instantly arresting the movement so as to allow of the indication being read on
the dial.
In order to avoid oscillation of the chronograph it may be mounted upon the
inner one of a system of three rings m pivotted one within the other by means of
pivots n, somewhat after the manner of a ship's compass, the said pivots n being six
in number and arranged in pairs in planes at right angles one to the other as shown
in Figs. 4 and 4ª.
Figs. 5 to 7 illustrate an arrangement of chronograph according to this invention,
suitable for use in measuring the speed of firing, or the path described by all kinds
of projectiles, or in various experiments or observations of physical phenomena in
which considerable speeds have to be noted. In this special application, my
chronograph may indicate directly both the duration of the travel of the projectile,
and the distance traversed during a unit of time. This latter scale is easily found
by taking the time for a projectile to travel a certain known distance when the
velocity is found by dividing this distance by the time.
It will be seen that in this arrangement there are no toothed wheels. The
indicator or pointer a is mounted on the axis of balance b, which is actuated by a
spiral spring the balance is arranged to serve as an armature for an electro
magnet c. This electro magnet c, acts to release the mechanism on the discharge
and to arrest it on the projectile having travelled the required distance. It is to
be understood that I may use a number of electro magnets instead of one only if
desired.
By the arrangements generally employed for measuring velocities of projectiles
one current is broken when the projectile passes a certain point on its travel and
another current when it passes another point.
In order to be able to use this same arrangement for my instrument I employ an
electro-magnet which so breaks and closes the currents that the magnet c ceases to
act upon the balance & when the projectile passes its first point and again acts upon
it to arrest its oscillation when the projectile passes its second point.
This arrangement of electro magnets I sometimes place within my instrument.
Although I do not limit myself to such division, the dial d in the example shewn,
represents the value of one fifth of a second divided into two hundred parts, but
these divisions may be still further reduced if desired. Besides this graduation I
apply a scale indicating either the degrees of the circle or the distances in metres
traversed during the unit of time. The last graduation is for speed and is found
by dividing the figures giving the time into the figures giving the distances the
projectile has traversed. In order to obtain a scale this distance must be. constant.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. A chronograph in which an indicator or pointer moving over a suitable dial is
mounted directly or indirectly upon or in connection with the axis of the balance,
in combination with one or more electro magnets which serve for instantaneously
arresting the said balance.
"
2. The arrangement of chronograph, in which an indicator or pointer arranged

page_text: to move over a suitable dial, is mounted upon the axis of a spring balance, this
balance constituting the armature of one or more electro magnets by which the
starting and stopping of the indicator or pointer is controlled."
Dated this 16th day of May 1891
C. W. SCHMIDT.
By L. W., per F. B.