Improvements in Tension Spools, applicable for Use in Photographic Cameras and for other purposes.
Year: 1894

page_text: Date of Application, 4th Dec., 1894-Accepted, 12th Jan., 1895
COMPLETE SPECIFICATION.
Improvements in Tension Spools, applicable for Use in Photographic
Cameras and for other purposes.
I, THEODORE MINOT CLARK of No. 1 Mount Vernon Terrace, Newton, in the
County of Middlesex and State of Massachusetts, United States of America,
Gentleman, 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, that is to say:―
The object of this invention is to provide an improved construction of spool,
bobbin, or reel, with provision for placing a tension on the commodity carried by
it and maintaining a stretch of the same always taut by a tendency to re-wind it.
The invention is capable of embodiment in many different forms for many different
It is here shown in a form adapted for holding the sensitive film commonly
used in cameras, and the invention may be said to be particularly useful in this
connection, as it provides for keeping the stretch of film extending across the
camera perfectly smooth and at the same time no tension device bears against the
film and it is not in any way impaired.
uses.
The accompanying drawings, forming part of this Specification, illustrate an
embodiment of the invention.
Figure 1 shows the complete spool in side elevation.
Figure 2 shows a longitudinal section of the same.
Figure 3 shows a central cross-section.
Figure 4 shows the spindle and spring in side elevation, without the casing.
Figure 5 shows the same in end elevation.
The letter a designates a cylinder of suitable material, as thin sheet metal,
pasteboard, or the like, whose ends are closed by heads 6 having central openings
for a spindle c which is round throughout the greater portion of its length, the
cylinder being designed to rotate upon it. The ends of this spindle are flattened
to fit correspondingly formed sockets in a suitable support which prevents the
spindle from turning.
Spiral springs & surround the spindle, and one end of each spring is secured thereto
by being passed through it.
The normal compass of the springs is such as to require their compression to a
certain extent in order to insert them in the cylinder, and hence they will press
against the interior surface of the cylinder.
Unwinding of the film or whatever else may be wound upon the spool is resisted
by the springs, so that when the device is in use, these springs constantly tend to
turn the spool back and wind up the film by reason of their torsional action.
Hence a stretch of the film drawn off from the spool will always be kept taut.
The frictional engagement of the spring with the walls of the cylinder caused by
its expansive tendency is sufficient to produce a torsional strain on the spring when
the cylinder is turned, and a tendency of the spring to re-wind the film.
In filling the spool, it will be supported so that the spindle and cylinder may turn
together and the spring will not offer any resistance.
The heads b of the cylinder may be provided with holes 6¹ to receive the forked
ends of suitable trunnions or other supports which may be used to hold the spool
while it is being filled.
When the cylinder is made of sheet metal, it will be covered with paper to which
the film can be conveniently attached.

page_text: It will be observed that the heads 6 extend beyond the cylinder to form confining
flanges for the film.
While the device is of special utility for holding films in cameras, it can also be
advantageously employed for other purposes, as for holding yarn or the like.
While I prefer to use two springs, as shown, secured at their inner ends to the
spindle so as to cause a uniform action throughout the length of the spool, yet it is
obvious that a single spring could be used to accomplish the purpose.
It is also preferable to taper the springs as shown, so that the several con-
volutions successively release their hold on the cylinder.
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 ;-
A tension-spool comprising a cylindrical shell having heads with circular holes
through their centres, a spindle extending through the cylinder and fitting said
holes, leaving the cylinder free to rotate on said spindle, and a spiral retracting
spring or springs fastened to said spindle and surrounding the same and extending
longitudinally within the cylinder in frictional engagement with the walls thereof.
Dated this 3rd day of December 1894.
THEODORE MINOT CLARK,
Per Samuel Hey,
Agent.