Improved Needle Driving Mechanism for Sewing Machines.
Year: 1896

page_text: Date of Application, 10th Nov., 1896-Accepted, 20th Mar., 1897
[Communicated from abroad by EDWIN LORING SPRAGUE, of 103 Summer Street,'
Boston, Massachusetts, United States of America, Manufacturer.]
Improved Needle Driving Mechanism for Sewing Machines.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,"
45 Southampton Buildings, in the County of Middlesex, 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:-
The present invention relates to an improvement in sewing machines and is
applicable to the well known McKay sewing machine, in connection with which it
will be hereinafter shown and described.
The invention consists in an improved mechanical connection between the driving
shaft and the needle-bar actuating lever, its object being to produce a relatively
slower movement of the needle near the ends of its strokes both up and down and a
relatively more rapid movement near the middle part of its strokes than is produced
by the actuating mechanisin therefor heretofore commonly used.
By thus reducing the speed of movement of the needle near the end of its stroke
the laying of the thread in the hook by the whirl is rendered more certain, and the
tightening of the last stitch is effected with less of a jerk and sudden strain on the
thread, thus improving the operation of the machine and also improving the quality
of the sewing.
The change in the relative speed of movement of the needle in different portions
of its stroke is accomplished in accordance with the present invention by connecting
the usual eccentric rod or pitman which actuates the needle lever with said lever by
devices which in effect change the position of the point of application of the force
from said pitman on said lever with relation to the fulcrum of the lever, so as to
correspondingly change the effective length of the lever arm during the reciprocation
of the said pitman. The arrangement is such that the pitinan operates upon the
greatest length of lever arm when at or near the ends of the stroke, thus causing the
opposite end of the lever which carries the needle bar to move.a shorter distance in a
given time, the movement therefore being slower, and conversely the pitman acts
upon a shorter length of lever arın during the middle part of its stroke, thus
accelerating the movement of the needle during the middle part of its stroke both up
and down.
Fig. 1 is a side elevation of a sufficient portion of a McKay sewing machine to
illustrate the present invention;
Fig. 2 a rear elevation of the portion thereof to which this invention relates, showing
the driving shaft, the reciprocating rod or pitman carried thereby and the connection
between said pitman and the needle bar lever; and
Fig. 3 a diagram view showing the relative positions of the parts in different
positions of the needle, dotted lines of different character being used to show the
relations at the middle position and both end positions of the needle bar respectively.
As has been stated, the construction of the main portions of the machine is well
known and therefore needs no detailed description in connection with the present
invention, which consists in a novel construction of the actuating nechanism for the
needle. bar lever a fulcrumed at a 2 and connected at a 3 by the link a 4 with the
needle bar a 5 in the usual manner.

page_text: The said lever is arranged to reciprocate the needle bar by a rocking movement on
the pivot a 2 and such movement is caused by means of a rod or pitman b which may
be the same as heretofore used in these machines and is reciprocated by means of the
usual eccentric b 2 upon the main shaft B of the machine. The connection between
said pitman & and the lever a is made in accordance with the present invention by a
link c connected at c 2 to the lever a, and at c 3 to the rod 6, the end thereof which is
pivoted at e 3 being connected with a movable guide in this case shown as a link or
radius bar d pivotally supported at one end in a bracket or extension d 2 from the
frame of the machine and pivotally connected at its other end with the rod or pitman b.
As the rod moves up and down therefore in response to the action of the eccentric
the link d will move on an are as indicated in Fig 3, thus carrying the upper end of
the pitman 6 toward the fulcrum a 2 of the lever a in the middle part of the stroke
thus practically shortening the arm of said lover and accelerating the movement of the
opposite end thereof during the middle part of the stroke, and correspondingly retarding
the movement near the ends of the strokes, both up and down.
The axis of fulcrum d3 of the guiding link or radius bar d is at an intermediate
point between the upper and lower positions of its end that is jointed at c3 to the
pitman b, the result being that it throws the said joint furthest inward towards the
falerum a 2 of the needle bar lever at an intermediate point in its stroke and throws
said joint c 3 outward or away from said fulcrum a 2 in the movement from the middle
towards the ends of the strokes in both directions. In other words, the fulcrum d 3
of the guiding link is at the opposite side of the pitman & from the fulcrum 2 of the
needle bar lever a, and is at a distance from the actuating shaft B approximately equal
to the-length of the said pitman.
In Fig. 1, the lever is shown at the end of a complete downward movement of the
needle, and the end of the rod d is practically in line with the outer end of said lever,
so that as said rod begins to move down it will operate upon the lever arm of maximum
length, causing a slow movement of said lever at first, said movement being gradually
accelerated as the movement of the guided carries the pivot c 3 towards the fulcrum a 2.
Following the line of movement of the point e3 as shown in Fig. 3, it will be seen that
at about the centre of the stroke the said point c 3 is nearest the tulerum a 2 thus giving
a maximum speed of movement to the lever, and as the rod b continues its movement
the point e 3 again recedes from the fulcrum a 2 increasing the effective length of the
lever a and causing the slower movement of the needle.
The retardation of the movement near both ends of the stroke relative to the speed
produced by the usua! crank or eccentric is of great advantage; that at the end of
the down stroke affording more time for the whirl to lay the thread into the hook
of the needle, and thus insuring greater certainty of this operation; while the
slowing down near the upper end of the stroke causes the thread to be finally drawn
tight by a slow, steady, and powerful pull of the needle, so that the machine does
better work and with much less liability of breaking the thread than when the needle
bar lever is actuated directly from a pitman, as , pivotally connected directly
to the end of the lever as has been heretofore the construction in McKay sewing
machines.
As shown herein, the link d is mounted upon a transverse shaft d 3 and is forked as
shown in Fig. 2, the rod & extending upward between the said forks and being
connected thereto by means of a pintle c 3. The links c are made in duplicate, one
of said links being connected to one side of the needle lever a and the other to the
opposite side thereof, the said links extending down to the pivot e 3 between the rod b
and the forked extension of the moveable guide or link d. Thus the end of the lever
the connecting links, and the guide arm or link d may all fall together as it were as
they descend in making the upstroke of the needle.
It is obvious that the construction of the variable connection between the pitman
and the needle lever can be varied considerably while retaining the same essential
relations between the same. The specific construction illustrated is of advantage
because it can be readily applied to existing machines, it being necessary only to
substitute a new lever for the needle actuating lever commonly employel and to add

page_text: the links c, guide arm d. and supporting brackets for the latter to the existing
machines, said parts co-operating properly with the same pitman or eccentric rod as
employed in connection with the original lever. The brackets d 2 which support the
guiding mechanism may be connected with the usual frame over the usual uprights
or posts connecting the upper and lower plates of the frame. For this purpose the
brackets are secured over the ends of the uprights by tubular or thimble-like ants d 4
see Fig. 1, which take the place of the nuts commonly employed to fasten the top
frame plate to the uprights. The foot portion of the bracket that rests on the top of
the frame plate is preferably provided with an elongated opening d5 to receive the
tubular shank of the nut d 4, thus enabling the position of the bracket to be adjusted
to vary somewhat if desired the effect of the guide arm d in modifying the action of
the pitman on the lever a.
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 correspondent, I declare that what I claim is :-
1. The combination with the needle bar actuating lever of a sewing machine; of
the main shaft and pitman actuated thereby; and means for operatively connecting
said pitman and needle har lever; and a guide link pivotally connected at one end
with the said pitman and pivotally connected at its other end with the frame work
at a point on the opposite side of said pitman from the fulcrum of said needle bar
actuating lever, and at a distance from said main shaft approximately equal to the
length of said pitman; whereby the movement of the needle bar, lever is retarded
near both ends of the stroke and accelerated in the middle part of its stroke relative
to the speed that would be produced if the pitman were directly connected therewith,
substantially as and for the purpose described.
2. The combination with the needle bar actuating lever; of the main shaft and
pitman actuated thereby; a link pivotally connected at one end with the pitman,
and at the other end with the needle bar lever; and a guide link or radius bar
pivotally connected at one end with the joint between the pitman and link, and pivotally
connected at its other end with the frame of the machine, as set forth, said guide link
causing the joint between the pitman and link to be carried towards the fulcrum of
the needle bar lever during the movement from the end to the middle part of its
stroke, and to be carried from said fulcrum during the movement from the middle to
the end of the stroke in both directions, substantially as described.
3. The combination of the needle bar lever a, and its fulcrum a 2; and links c
pivotally connected to one end thereof; with the main shaft, and actuating pitman b,
connected by a pivoted joint with said links c; the forked guide link pivotally
supported at one end on the frame work, and pivotally connected at the other end
with, the joint between the pitman band links c, substantially as and for the purpose
described.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.