Improvements in Sewing Machine Trimmers.
Year: 1898

page_text: Improvements in Sewing Machine Trimmers.
I, WILLIAM HARVEY INSLEE, Manager of the Singer Manufacturing Company,
Kilbowie, Dumbartonshire, do hereby declare the nature of this invention and in
what manner the same is to be performed as communicated to me, to be particularly
described and ascertained in and by the following statement:-
This invention relates to certain improvements on the sewing machine trimmer
embraced in the Specification of Letters Patent No. 8133 of 1897, the object of the
present invention being to improve the shear trimmer, to provide means for more
effectively preventing lint or trimmings from working down through the trimmer
slot or opening in the work-plate than could be done with my former construction,
and also to provide an adjustable feed-dog section which will be moved laterally
with the trimmer when the latter is adjusted to vary the distance between the line
of trimming and the line of stitching, so that there will be no difficulty in "chaining
off" the last stitches of a seam when the trimmer is adjusted farthest from the
needle of the machine.
In the accompanying drawings Fig. 1 is a plan view of the lower part of
a Singer single-thread chain-stitch sewing machine embodying my invention.
Fig. 2 is a similar view of the same with the work-plate removed. Fig. 3 is an
end view of the same with the work-plate removed. Fig. 4 is a section on line 4-4
of Fig. 2. Fig. 5 is a detail sectional view of the feed dog and of the adjustable
device for securing the lower blade in place.
A denotes a portion of the frame of the machine, and B the rotating driving
shaft carrying the single-thread chain-stitch looper 6 and the feed and trimmer-
operating eccentrics. C is the feed-bar carrying the feed-dog c, said bar being
jointed at e² to the upwardly extending arms d of a feed-operating rock-shaft Ď
having at its rear end au arm d¹ to which is adjustably connected one end of a
pitman d, the other end of which is provided with a strap ds surrounding an
eccentric on the shaft B and which eccentric, through said pitman, imparts rocking
or feeding movements to said shaft D. The feed bar is forked, at c³, to embrace a
feed raising and lowering eccentric on said shaft B. -.
E is the rocking trimmer shaft mounted, as before, in the feed-bar C carrying
the feed-dog c¹ and provided with a rigid arm e forked to embrace an eccentric b¹
on the shaft B to impart rocking movements to said trimmer shaft. Said trimmer
shaft is also provided with a rigid arm or plate e¹ (preferably formed rigid therewith)
tapped at its upper end for the reception of a set screw e by means of which and
the clamping plate and guard e³ the segmental upper shear blade or knife e' is held
....מ

page_text: in any desired position of adjustment, said blade being pivotally mounted on the
said shaft E so that its position may be changed to compensate for wear.
The lower trimmer blade e³ is also pivotally mounted on the shaft E so that it
may be adjusted to compensate for wear, and is normally held rigid with or
stationary relative to the feed bar and feed dog. To this end a rear extension e of
said blade is provided with a slot e' to embrace an adjustable hollow pin or sleeve e¹4
formed integral with and extending outward from a slide e³ movable in an undercut
groove c¹ formed in the side of the feed bar C, said hollow pin or sleeve being tapped
for the reception of a set-screw e which impinges, to hold the said slide and sleeve
in place, against the bottom of the slot c¹.
F is a sliding block movable in a suitable guideway in the frame of the machine
and provided with a notch or recess fentered by a depending lug e¹o formed on the
hub e of the arm e of the rock-shaft E. The block Fis provided with a depending
lug fentering an annular groove formed between flanges g on an adjusting screw G
tapped in the machine frame and provided with a milled head g' by which it may
be readily turned to adjust the trimmer rock-shaft E and the trimmer blades et ande³,
mounted on said shaft, laterally or toward and from the needle. The block F and
the trimmer connected therewith are held in any desired position of adjustment
against accidental displacement by any suitable retaining device which, in the
present instance, consists simply of the friction washer f placed beneath the head
of the steadying or holding screw f³.
H is a sliding lint guard plate suitably mounted, to be moved back and forth or
from and toward the needle, on the work-plate A', the forward end of said guard-
plate being closely adjacent to the arm or plate e' of the trimmer shaft E so that
there will be no appreciable opening for the passage of lint between the forward
end of said guard plate and the arm or plate e'. The sliding block F is provided
with an upwardly projecting lug which enters a slot in the plate so that the
latter will be adjusted back and forth with the trimmer which is movable with said
block, as has been described. This adjustable lint guard H is similar to the lint
guard I in the specification of Letters Patent before referred to, but in the machine
shown in said specification no provision was made for keeping the front side of the
slot in the work-plate closed when the trimmer was adjusted away from the needle.
This omission is remedied in the present instance by extending the lint guard
around to the front or outer side of the trimmer, and for convenience in getting at
the trimmer blades, when it is necessary to remove the same for sharpening, this
extension of the lint guard consists, preferably, of an independent plate H
removably mounted on the plate H by means of the arm having holes to engage
the upper ends of the screws h' which pass through slots in the work-plate A¹ and
between the lower side of which work-plate and the heads of said screws friction
washers are preferably placed to give the plate H a frictional sliding connection
with the work-plate.
To keep the rear part of the slot in the work-plate, into which the rear part of
the blade et extends, closed when said blade has been adjusted so far forward (when
said blade has been partly used up) that it will not fill said slot, the clamping
plate es, by which the said blade is held in place, is extended down to and a little
below the upper surface of the work-plate A¹, this clamping plate thus serving also
as a lint guard at this point.
It is desirable that a portion of the feed-dog should work on the side of the
needle away from the operator or on what (considering the progress of the work)
may be termed the front side of the needle, and it is also desirable, to effect the
"chaining off" of the end of the seam properly, at all times, that there should be
no opening between the lower trimmer blade and the feed or other support for the
work adjacent to said blade. To keep the slot in the work-plate closed at the
point referred to I have provided an adjustable feed-dog cs carried by an arm co
which encircles the trimmer shaft E. The auxiliary feed-dog c' is connected with
the main feed-dog c¹ by means of a lip on the former engaging an under-cut notch
or groove in the latter, as shown in Fig. 3, and said auxiliary feed-dog is also

page_text: connected with the feed bar through the arm c' the rear end of which encircles the
trimmer shaft E mounted in said feed bar, and thus the said auxiliary feed-dog will
move up and down and back and forth with the feed bar and main feed-dog. The
arm c is pressed against the lower trimmer blade e', and the said lower blade is
pressed against the upper blade e and the latter held against the arm e', by the
spiral spring e interposed, on the shaft E, between the said arm c' and a nut els on
the outer end of said shaft. Thus the sectional or auxiliary feed dog c', while
moving up and down and back and forth with the main feed dog c¹, is adapted to be
adjusted back and forth laterally with the trimmer blades and will always be held
in contact with the lower trimmer blade so as to keep the slot in the work-plate
closed adjacent to said blade when the trimmer is adjusted away from the needle.
The operation of my improved trimmer is essentially the same as that shown and
described in the specification of Letters Patent hereinbefore referred to. Both
blades of the trimmer being mounted on the feed bar follow the movements thereof,
the rocking upper blade closing, to effect the cutting, when the feed is moving
forward to advance the work; and the entire trimmer, including both blades and
the trimmer operating rock-shaft, being adjustable towards or from the needle, to
vary the distance between the line of stitching and the line of trimming, either
when the machine is in operation or at rest, as in the former specification, while
the trimmer slot in the work-plate is at all times kept closed by the lint
guards H, H¹ and e³ surrounding the trimmer blades.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. The combination with the stitch-forming mechanism of a sewing machine, of
a laterally adjustable shear trimmer device, a work-plate slotted for the reception
of said shear trimmer device, and a laterally adjustable lint guard extending closely
adjacent to both sides of said shear trimmer to close said slot, and connections
between said trimmer and said guard whereby the latter will be adjusted
co-incidently with the former to keep the said slot closed at all times on both sides
of the trimmer regardless of the position of adjustment of said trimmer.
2. The combination with the stitch-forming mechanism of a sewing machine, of
a laterally adjustable trimmer, the guard plate H connected with said trimmer to
be laterally adjustable therewith, and the independent guard plate H¹ removably
attached to said plate H and adjustable therewith and with said trimmer.
3. In a sewing machine trimmer, the combination with an operating rock-shaft,
of upper and lower trimmer blades one of which is connected with said shaft to
oscillate therewith and the other of which is stationary relative to said shaft, and
both of which are pivotally mounted on said shaft so that they may be adjusted
about the same to compensate for wear, and means for securing both of said blades
in any desired positions of adjustment.
4. The combination with the stitch-forming and feed-operating mechanism of a
sewing machine, of a trimmer which is laterally adjustable relative to said stitch-
forming mechanism, and a feed-dog which is laterally adjustable with said
trimmer.
5. The combination with the stitch-forming mechanism of a sewing machine, of
a laterally adjustable trimmer, a feed bar and its operating mechanism, a feed-dog
which is fixed relative to said feed bar, and a second feed dog which is connected
to and laterally adjustable with said trimmer.
6. The combination with the stitch-forming and feed-operating mechanism of a
sewing machine, of a laterally adjustable shear trimmer comprising upper and lower
blades, and a laterally adjustable feed-dog placed closely adjacent to said lower.
blade and connected with said trimmer to be laterally adjustable therewith.
7. The combination with the stitch-forming mechanism of a sewing machine, of
a laterally adjustable shear trimmer comprising upper and lower blades, a feed bar
and its operating mechanism, a feed dog which is fixed relative to said feed bar,

page_text: and a second feed dog placed closely adjacent to said lower blade and connected
with said trimmer to be laterally adjustable therewith.
Dated this 81st day of January 1898.
WALLACE FAIRWEATHER,
Of the Firm of Cruikshank & Fairweather,
Chartered Patent Agents, 62, St. Vincent Street, Glasgow,
Agent for the Applicant.