Improvements in Thread Tension and Let-off Mechanisms for Sewing Machines.
Year: 1891

page_text: "Date of Application, 17th July, 1891-Accepted, 29th Aug., 1891
COMPLETE SPECIFICATION.
Improvements in Thread Tension and Let-off Mechanisms for
Sewing Machines.
A communication from JOSEPH ELI BERTRAND, of Boston, in the County of
Suffolk and State of Massachusetts, United States of America, Machinist, and
MELLEN BRAY, of Newton, County of Middlesex, Massachusetts, aforesaid,
Manufacturer.
1, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
M.I.M.E., 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 thread tension and let-off mechanisms for sewing
machines and is an improvement upon the invention described in the British
Letters Patent No. 11015 dated July 15, 1890, and it consists in certain novel
features of construction arrangement and combination of parts, which will be
readily understood by reference to the description of the drawings hereinafter
given, and in which the invention is clearly pointed out.
Fig. 1 of the drawings is a sectional elevation of so much of a sewing machine as
is necessary to illustrate the present invention.
Fig. 2 is a plan of the same parts.
Fig. 3 is a sectional elevation of a portion of the same parts the cutting plane
being on linea on Fig. 1.
Fig. 4 is an elevation of the tension wheel its supporting stand and the stop pawl,
and showing the locking pawl cut in transverse section.
Fig. 5 is a sectional elevation the cutting plane being on line y y on Fig. 4.
The sewing machine to which the present improvement has been applied is
substantially the same as that shown and described in the British Letters Patent
No. 11015 dated July 15, 1890 to which a reference may be made for information
regarding parts not shown in the drawings forming a part of this application in
which C is the upper tie girt of the machine and C' the forward extension of the
same, D is the cam shaft, J is a stand carrying the thread guiding sheave, is
the thread carrier mounted on the lower end of the vertical rod k upon which is
secured the pinion to which an oscillating motion is imparted by the recipro-
cating rack bark, Pis the take-up lever; only a portion of which is shown having
adjustably secured to its movable end the slotted block p³ carrying the grooved
sheave p; Qis the locking lever carrying at its front end the locking pawl q³
and is the cam for vibrating said locking lever and pawl, all constructed
arranged and operating in the same manner as described in said Letters Patent
No. 11015 of 1890 except as will be hereinafter mentioned.
The tension wheel 9 has formed in its periphery a groove the bottom of which is
polygonal or composed of a series of flat sides meeting each other at angles
precisely as in the Letters Patent No. 11015 of 1890.
In the Patent No. 11015 of 1890 the tension wheel a had formed thercon at one
side of the thread receiving groove the ratchet wheel q' with the teeth of which
the pawl engaged to lock said tension wheel against rotation when the take-up
lever P' was drawing the loop into the work after the shuttle had passed through
the same, and said wheel was prevented from revolving freely on its axis when not
locked only by friction caused by the tension of a spring which tended to clamp
said wheel between the head of its axial pin and supporting stand or car and

page_text: the thread for forming the loop above the work was drawn out by the looper finger
against the friction caused by said spring which caused more or less chafing of the
thread according to the amount of friction applied.
To obviate this tendency to wear the thread I dispense with the spring pressure
on the tension wheel, mount or form thereon a second ratchet wheel a having its
teeth formed with their radial shoulders facing in the opposite direction to those
of the ratchet wheel 2 and provide the stop pawl which is pivotted to the
ears formed upon and projecting from the stand in which is set the stud c upon
which the tension wheel is mounted.
1
The pawl is made to automatically engage the teeth of the ratchet wheel a at
its upper end by the tension of the spring d and serves to prevent the rotation of
said tension wheel in the direction indicated by the arrow 2 and also as a shield or
guard to disengage the let-off pawle which is also arranged to engage the teeth of
the ratchet wheel a at the proper time to rotate the tension wheel in the opposite
direction to that indicated by the arrow 2 for the purpose of delivering the desired
length of thread to form the next loop.
The pawle is secured upon a short shaft mounted in a bearing in the arm f
depending from the lever said shaft having secured upon its opposite end the
lever to the free end of which is connected one end of the spiral spring g the
opposite end of which is connected to a pin or hook set in the lever Q as shown in
Figs. 1, 2 and 3.
A.stand A is bolted to the tie girt C in such a position that its upper end over-
hangs the lever Q in front of its pivotal axis and has set therein the adjustable stop
screw to limit the upward movement of the front arm of said lever Q and con-
sequently of the pawle whereby the length of thread delivered for each loop may
be regulated according to the thickness of the stock being sewed, the rear end of
the lever being moved towards the cam g' by the spring r³ as described in the
before cited Patent.
A stand is secured to and depends from the tie girt C and carries at its lower
end the thread guiding sheave i as shown in Figs. 1, 2 and 3.
The needle thread indicated by the dotted line tt passes from the spool or
bobbin (not shown) to under and partially around the sheave i over and one or more
times around the tension wheel q thence over the sheave p³ carried by the take-up
lever P¹, then down around the front side of the sheave through an eye in the
thread carrier k³ and thence to the work (not shown).
The operation of my invention is as follows:-
--
The parts being in the position shown in the drawings the tension wheel being
locked by the engagement of the pawl q with the ratchet wheel and the take-up
lever P being at the extreme of its upward movement having just completed the
drawing up of the loop through which the shuttle has previously passed.
As the shaft D continues to revolve in the direction indicated by the arrow 3 the
throw 4 of the cam 97 passes from beneath the truck carried by the rear end of
the lever Q which is moved downward by the spring thus raising the front arm
of said lever and the locking pawl so as to disengage said pawl from the ratchet
wheel and at the same time moving the pawl e upward into engagement with the
teeth of the ratchet wheel a and moving said wheel about its axis in the direction
opposite to that indicated by the arrow 2 this motion continuing until the truck at
the rear end of the lever Q comes in contact with the smaller portion of the cam q
or the front arm of the lever Q comes in contact with the stop screw / thus
delivering the requisite length of thread to form the next loop the tension wheel g
being locked against backward movement by the stop pawl b.
When the cam g' has revolved until the throw 5 comes in contact with the
truck the pawl q is again brought into engagement with the ratchet wheel to
lock said wheel, the pawl e is moved downward until disengaged from the teeth of
the ratchet wheel a by the nose of the stop pawl band then the take-up lever P¹ is
moved upward again to draw up another loop.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents, I declare that what I claim is: :-
1. In combination with a thread tension wheel having a thread receiving groove
the bottom of which is polygonal or composed of a series of flat sides meeting each
other at angles, two ratchet wheels formed thereon or secured thereto the radial
shoulders of the teeth of which face in opposite directions, a pivotted lever, a cam
for vibrating said lever, two pawls carried by said lever one of which is arranged
to engage one of said ratchet wheels to lock said tension wheel, and the other
arranged to engage the teeth of the other ratchet wheel to move said tension wheel
about its axis substantially as and for the purposes described.
2. The combination of the tension wheel y having a polygonal section between
its flanges, the ratchet wheels a and connected to said wheel, the lever Q, the
cam, the spring r³, the pawl to engage the ratchet and the pawl e to
engage the ratchet a both carried by the lever Q, and the stop pawl 6 to engage
the ratchet a all constructed and arranged to operate substantially as described.
9.
3. The combination of the tension wheel having a polygonal section between
its flanges, the two ratchet wheels a and having teeth facing in opposite directions
and formed upon or secured to said tension wheel, the lever Q, the cam, the
spring, the pawls g³ and e carried by said lever and constructed and arranged to
engage the former with the ratchet and the latter with the ratchet u, the
adjustable screw stop h, and the stop pawl 6 constructed and arranged to engage
the ratchet a and to serve as a shield to disengage the pawl e from the teeth of the
wheel a substantially as described.
Dated this 17th day of July 1891.
W. P. THOMPSON & BOULT,
Agents for the Applicants.