A Method of Keeping Uniform Tension on a Moving Thread, Cord, Rope, Chain, Ribbon of Paper or other Material, and the like.
Year: 1891

page_text: Date of Application, 11th Aug., 1891
Complete Specification Left, 2nd May, 1892-Accepted, 4th June, 1892
PROVISIONAL SPECIFICATION.
A Method of Keeping Uniform Tension on a Moving Thread, Cord,
Rope, Chain, Ribbon of Paper or other Material, and the like.
1, ALEXANDER DEY M.A., LL.D. H.M. Inspector of Schools 62 Albert
Drive Pollokshields Glasgow do hereby declare the nature of this invention to be
as follows:-
Let A B be a rod or lever turning freely about a stud or pivot fitting exactly a
hole in it, at any point C between A and B (Fig. 1). Let the end B rest upon a
block D with surface even and of any roughness required. Let the rod be pressed
against the block D by any spring, say an elastic spiral attached to the rod at A
and to some fixed object F. If the moving thread (moving from B to A say) be
passed between the rod at B and the block D it is clear that we can grasp it with
any force we please by varying the distance of C from B or the strength of the
spiral spring. If now the thread be passed through a ring or an eye in the rod
at A and pulled in a direction opposite to the spiral spring it is clear that the limit
of the tension of the string will be the strength or tension of the spiral and we can
make the tension as near to this limit as we please by moving C close to B and
attending to the surfaces between which the thread passes at D. Thus the tension
of the string depends entirely on the spiral spring and is regulated by it.
This is the simplest form of the principle which is capable of numerous variations
in its application.
I have taken a thread for clearness, but the principle applies equally to anything
from a slender thread to an anchor chain, to a ribbon of any material and of any
breadth from a slip of paper to cloth yards wide.
Two important special cases are these. (1) Suppose the moving thread (or other
material) is being unwound from a spool (Fig. 2). (2) Suppose the thread is paid
out at a given velocity and a spool on which it is being wound is driven with a force
which remains constant from beginning till the spool is full and the tension on the
string must remain uniform all the time notwithstanding the increasing diameter of
the spool (Fig. 3).
In case (1) we so arrange that the end of the rod B rests on the rim of the spool
where it forms a drag on the spool and the tension as before will depend on the
spring at A. In case (2) suppose the rim of the spool almost touches the rod at a
point E between A and C, but close to C (everything else remaining as before).
Suppose the thread is moving (now from A towards C) through the eye at A
(approaching the rod in direction opposite to the spiral spring) and is wound on to
the spool. Let the spiral have the strength or tension which is the limit allowed
on the string. It is clear that if the spool is driven too forcibly the slightest
excess of tension of the string over the spiral draws the rod which will then press
on the spool and stop it (the points of contact of the rod and spool being sufficiently
roughened so as to gear if necessary). The constant force driving the spool
evidently should be that which puts sufficient tension on the string when the spool
is full.
Dated this Tenth day of August 1891.

page_text: COMPLETE SPECIFICATION.
A Method of Keeping Uniform Tension on a Moving Thread, Cord,
Rope, Chain, Ribbon of Paper or other Material, and the like.
I, ALEXANDER DEY M.A., LL.D., 62 Albert Drive l'ollokshields in the
County of Renfrew North Britain, H.M. Inspector of Schools, 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 :-
Let A B be a rod or lever turning freely about a stud or pivot fitting exactly a
hole in it at any point C between A and B (sce drawings accompanying Provisional
Specification). Let the end B rest upon a block D with surface even and of any
roughness required. Let the rod be pressed against the block D by any spring,
say an elastic spiral, attached to the rod at A, perpendicular to the rod, and
attached to some fixed object. If the moving thread (moving from B to A say) is
passed between the rod at B and the block D it is clear that we can grasp it with
any force we please by varying the distance of C from B or the strength of the
spiral spring. If now the thread be passed through a ring or an eye in the rod
at A and pulled in a direction opposite to the spiral spring it is clear that the limit
of the tension of the string is the strength or tension of the spiral spring, and we
can make the tension as near to this limit as we please by moving C close to B and
attending to the surfaces between which the thread passes at D. Thus the tension
of the string depends entirely on the spiral spring and is regulated by it.
This is the simplest form of the principle which is capable of numerous
applications and variations.
I have taken a thread as the simplest case but the principle applies equally
to a rope, chain, ribbon of any breadth, or any material, such as a web of cloth or
paper.
Two important cases in which it applies are these (1) suppose the thread is being
unwound from a spool (2) suppose the thread is paid out at a given velocity, and a
spool on which it is being wound is driven with a force which remains constant
from the beginning till the spool is full, and it is required to keep the tension
uniform all the time notwithstanding the increasing diameter of the spool. In
case (1) we make the end of the rod B rest on the rim of the spool, where it forms
a drag and the tension as before will depend on the spring at A. In case (2)
suppose the rim of the spool is almost touching the rod at a point E between A
and C but close to C (everything else remaining as at beginning). Suppose the
thread is moving through the eye at A (approaching the rod in direction opposite
to the spiral spring) and is wound on to the spool. Let the spiral have the strength
or tension which is the limit allowed to the string. It is clear that if the spool be
driven too forcibly the slightest excess of tension of the string will overcome the
spiral and the rod will be pressed on to the spool and will stop it.
The constant force driving the spool evidently should be that which will put
sufficient tension on the string when the spool is full.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, declare that what I
claim is
An improved method of keeping uniform tension on a moving thread, cord, rope,
chain, ribbon of paper or other material, and the like, substantially as herein before
described.
Dated this 30th day of April 1802
ALEXANDER DEY.