U.S. patent number 3,867,892 [Application Number 05/468,630] was granted by the patent office on 1975-02-25 for underbed thread trimmer for chainstitch sewing machines.
This patent grant is currently assigned to The Singer Company. Invention is credited to Heinrich Ciecior, Rolf E. Kessler.
United States Patent |
3,867,892 |
Ciecior , et al. |
February 25, 1975 |
Underbed thread trimmer for chainstitch sewing machines
Abstract
An underbed thread trimmer for a chainstitch sewing machine in
which a pair of ledger blades are adjustably mounted on the machine
bed, a thread catcher being carried pivotably by said bed having
needle thread and looper thread catching hooks and a pair of
cutting edges cooperable with respective ones of said ledger
blades. Means are provided for cyclically pivoting said thread
catcher from an at rest position beyond the eye of the looper past
the looper butt so as to seize the needle and looper threads and
cut same and to return the thread catcher to its at rest position
while thread retaining means retains a length of said looper thread
at the ledger blade.
Inventors: |
Ciecior; Heinrich (Ettlingen,
DT), Kessler; Rolf E. (Karlsruhe, DT) |
Assignee: |
The Singer Company (New York,
NY)
|
Family
ID: |
23860585 |
Appl.
No.: |
05/468,630 |
Filed: |
May 9, 1974 |
Current U.S.
Class: |
112/288 |
Current CPC
Class: |
D05B
65/00 (20130101); D05B 73/12 (20130101); D05B
57/02 (20130101) |
Current International
Class: |
D05B
65/00 (20060101); D05B 73/00 (20060101); D05B
57/02 (20060101); D05B 73/12 (20060101); D05B
57/00 (20060101); D05b 065/02 () |
Field of
Search: |
;112/252,252.5,253,129,130 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Guest; Alfred R.
Attorney, Agent or Firm: Williams, Jr.; Chester A. Breen;
Marshall J. Halpern; Joel
Claims
Having thus set forth the nature of the invention, what is claimed
herein is:
1. An underbed thread trimmer for a chainstitch sewing machine,
comprising a pair of ledger blades adjustably mounted on the bed of
the machine, a thread catcher pivotably mounted on said bed having
needle thread and looper thread engaging means and cutting edges
cooperable with respective ones of said ledger blades, means for
effecting cyclical pivotal movement of said thread catcher from an
at rest position on one side of the sewing machine needle to a
position on the other side of said needle where said needle and
looper threads are engaged and transported in the same general
direction to said ledger blades for cutting, thread retaining means
being provided in association with one of said ledger blades for
retaining a predetermined length of looper thread subsequent to
cutting.
2. An underbed thread trimmer according to claim 1, wherein said
thread engaging means on said thread catcher comprise a pair of
hook members, said thread retaining means being urged towards
yielding engagement with said one ledger blade and separable
therefrom by movement of one of said thread engaging hooks
therebetween.
3. An underbed thread trimmer according to claim 2, wherein said
thread retaining means includes a leaf spring connected at one end
to said one ledger blade, a spiral spring being secured adjacent
the free end of said leaf spring urged towards engagement with said
one ledger blade.
4. An underbed thread trimmer according to claim 1, wherein said
ledger blades are secured to said machine bed to one side of the
throat plate of the machine, each of said blades being provided
with at least one elongated slot and fastening means passing
through said elongated slots thereby securing said blades
adjustably longitudinally to said machine bed.
5. An underbed thread trimmer according to claim 1, wherein a
bearing block is secured to said machine bed, a control shaft is
rotatably carried by said bearing block, a crank arm is secured to
the upper end of said control shaft and the lower end of said
control shaft is connected to means for cyclically rotating same in
timed relationship to the reciprocation of the needle of the
machine and the looper of the machine, the end of said thread
catcher remote from said thread catching hooks being secured to
said crank arm for pivotal movement thereby.
6. An underbed thread trimmer according to claim 5, wherein the
lower end of said control shaft carries a control lever, said
control lever being provided with an aperture dimensioned to
receive one end of a ball stud member, the other end of said ball
stud member being operatively connected to a linear double acting
solenoid adapted to cyclically rotate said control lever and
control shaft in predetermined timed relation to the sewing machine
needle and looper.
7. An underbed thread trimmer according to claim 5, wherein said
thread catcher is pivotable by said crank arm from an at rest
position at the opposite side of said throat plate from that at
which said ledger blades are located across said throat plate but
beneath same to a position where said cutting edges are cooperable
with said ledger blades and thence back to said at rest
position.
8. An underbed thread trimmer according to claim 1, wherein said
ledger blades are mounted in side-by-side relation, said thread
catcher comprising a pair of side-by-side mounted thread catching
hooks, each of said hooks having an inclined cutter edge cooperable
with respective ones of said ledger blades.
9. An underbed thread trimmer according to claim 8, wherein one of
said thread catching hooks is more forwardly disposed than the
other and is located so as to seize the looper thread.
10. An underbed thread trimmer for a chainstitch sewing machine in
which a looper including a blade having a beak and butt at opposed
end regions thereof is driven in timed relation with the
reciprocation of the needle of the machine in the formation, of
chainstitches, comprising a pair of ledger blades adjustably
mounted on the bed of the machine, a thread catcher pivotably
mounted on said bed having needle thread and looper thread engaging
means and cutting edges cooperable with respective ones of said
ledger blades, means for effecting cyclical pivotal movement of
said thread catcher from an at rest position beyond the beak of
said looper past said beak to a point where said needle and looper
threads are seized before being transported in the same general
direction beyond the butt of the looper to said ledger blades where
said threads are severed, said means for effecting cylical pivotal
movement of said thread catcher then being adapted to return said
thread catcher to its at rest position, thread retaining means
being provided in association with one of said ledger blades
retaining a predetermined length of longer thread subsequent to
cutting.
Description
BACKGROUND OF THE INVENTION
Underbed thread trimmers for sewing machines are well known. It has
likewise been known heretofore that in the formation of chain
stitches it is desirable, subsequent to the cutting of the needle
and looper threads, to retain the remaining looper thread so as to
afford a sufficient length of such thread to begin the next stitch
whereby upon descent of the needle it can penetrate the triangle
formed in part by the looper thread which extends from the eye of
the looper and in part by the needle thread from the preceding
stitch. Unless the looper thread is claimed or otherwise prevented
from pulling out of the looper eye the proper formation of the next
stitch becomes uncertain.
Various chainstitch thread trimming or cut-off devices have been
employed; however, the need still exists for a simple yet reliable
thread trimmer. One commonly used prior device employs a
reciprocable thread catcher with a pair of thread catching hooks,
one of the hooks catching the needle thread and the other of such
hooks catching the looper thread on the forward stroke of the
thread catcher towards the eye of the looper from the butt end
thereof, the return reciprocation of the thread catcher carrying
both needle and looper threads into engagement with a cutting
blade. It is also known to utilize with such a device a spring clip
which, in cooperation with the looper thread catching hook, clamps
the looper thread followed by cutting of the threads. The thread
catcher and/or the spring clip must be specially formed in order to
provide for clamping of only the looper thread. In such devices,
where reciprocation of the thread catcher is necessary to first
seize the needle and looper threads and then transport such threads
to the cutting blade, there must be precise coordination in order
to effect both correct seizure and cutting of the threads. As wear
increases the tolerances between the parts, such precision becomes
less than optimum. The requirement for reciprocation of the thread
catcher in order to accomplish both correct seizure and cutting of
the needle and looper threads thus becomes more difficult to attain
and, therefore, the need arises for a thread trimmmer which can
effect the seizure and cutting steps by a less complex technique
whereby there is greater assurance of reliability with increased
age of the machine. Also, with prior thread trimmers of the type
referred to it has been necessary to provide adequate space within
the bed of the machine for positioning of the thread catcher in an
at rest stage which will not interfere with the stitch forming
process. The bed must also afford the necessary space requirements
for the thread catcher to move sequentially into and from thread
seizure and thread cutting positions. As will be readily
appreciated by persons versed in the art, space is at a premium in
the stitch forming area of the bed; thus, a thread trimming
technique and mechanism which requires less space in the critical
area of the bed would be advantageous.
SUMMARY OF THE INVENTION
It is accordingly one object of the invention to provide an
underbed thread trimmer for a chainstitch sewing machine by which
the needle and looper threads are seized and carried to the cutting
blades for trimming in a single direct movement of the thread
catcher.
It is another object of the invention to provide an underbed thread
trimmer for a chainstitch sewing machine by which the looper thread
only is clampable during cutting and separate adjustable ledger
blades are utilized whereby the length of the uncut needle and
looper threads may be regulated.
A further object of the invention is to provide an underbed thread
trimmer for a chainstitch sewing machine which requires less space
to effectuate the thread seizing and cutting steps and for at rest
storage for the thread catcher.
Yet another object of the invention is the provision of an underbed
thread trimmer for a chainstitch sewing machine in which the thread
catcher is stored at a point beyond the eye of the looper and is
adapted to traverse beyond the other extremity of the looper to
seize and trim the threads before returning to its storage
position.
Other objects and advantages of the invention will become readily
apparent from the following description of the invention.
According to the present invention there is provided an underbed
thread trimmer for a chainstitch sewing machine, comprising a pair
of ledger blades adjustably mounted on the bed of the machine, a
thread catcher pivotably mounted on said bed having needle thread
and looper thread engaging means and cutting edges cooperable with
respective ones of said ledger blades, means for effecting cyclical
pivotal movement of said thread catcher from an at rest position on
one side of the sewing machine needle to a position on the other
side of said needle where said needle and looper threads are
engaged and transported in the same general direction to said
ledger blades for cutting, thread retaining means being provided in
association with one of said ledger blades for retaining a
predetermined length of looper thread prior and subsequent to
cutting.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more fully comprehended it will
now be described, by way of example, with reference to the
accompanying drawings in which:
FIG. 1 is a top plan view of the thread trimmer of the invention in
the bed of the sewing machine illustrating, inter alia, the
relationship between the ledger blades and the throat plate of the
machine;
FIG. 2 is a side elevational view, partly in cross-section, taken
in the direction of line 2--2 of FIG. 1;
FIGS. 3, 4 and 5 are enlarged diagrammatic views showing the
relationship between the thread retaining means, the thread catcher
and the blade for trimming the looper thread in successive stages
of the trimming operation;
FIG. 4 depicts the elements at the moment the thread is cut;
FIG. 5 shows the retaining of the thread at the ledger knife;
and
FIGS. 6 through 9 are diagrammatic views showing the thread
trimming operation in successive stages.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGS. 1 and 2 there is shown the bed 10 of a sewing
machine. Mounted on the bed of the machine, such as by mounting
screws 12, is a throat plate 14 which may be of the conventional
type. Also mounted on the machine bed 10 to one side of the throat
plate are a pair of trimming knives or ledger blades 16, 18. As
will be described in greater detail hereafter, one of the knives if
employed to cut or trim the needle thread whereas the other of such
knives is utilized in conjuction with the cutting or trimming of
the looper thread. As can be seen clearly from FIG. 1, each of the
knives is provided with at least one elongated slot 20 dimensioned
to receive fastening means such as screws 22 which secure the
knives adjustably to the bed of the machine. Loosening of the
screws thus permits longitudinal movement of the knives and thereby
the length of needle or looper thread subsequent to cutting. The
cutting edges of the knives are shown at 24, 26. Adjusting screws
28 are provided in the knives for adjusting the height of the
cutting edges as desired.
Secured to the underside of one trimming knife is a thread
retaining means 30 which comprises a leaf spring 32 connected at
one end to knife 16 and looper thread nipping means in the form of
a tightly wound spiral spring 34 which is secured adjacent the free
end of the leaf spring such that it is spring urged towards
yieldable engagement with knife 16. As will be hereinafter
described, movement of a thread catcher 36 between the thread
nipping means 34 and knife 16 will result in movement of the spiral
spring and leaf spring away from the knife. The leaf spring 32 is
longitudinally adjustable relative to the trimming knife by means
of screw 38.
A bearing block 40 is carried by the front end of the bed 10 by
fastening means such as screws or studs 42. Journaled rotatably in
the bearing block is a control shaft 44. The upper end of the
control shaft carries a crank arm 46 which may be restrained from
axial displacement preferably by abutting against the bushing (not
shown) within which the upper end of the control shaft is
journaled. Crank arm 46 is desirably formed as a generally U-shaped
or channel member, the base of the channel being dimensioned to
receive a thread catcher member 36. The thread catcher may be
secured fixedly to the crank arm by fastening means such as screws
50.
The lower end of control shaft 44 has a control lever 52 mounted
thereon. As will be described hereafter, control lever 52 is
operatively connected to means which may include a solenoid and
appropriate linkage in order to provide for cyclical pivotal
movement of the thread catcher in timed relation to the
reciprocation of the sewing needle of the machine and the looper 76
of the machine. A clamping screw 54 secures the control lever to
the control shaft and may be utilized to establish the limits for
the rotational movement of the control shaft and thereby of the
pivotal movement of the crank arm and thread catcher.
The lower end portion of the control lever 52 is given a socket
opening dimensioned to receive one end of a ball stud member 56.
The other end of the ball stud member is confined within a sleeve
58 which connects the control lever operatively to reciprocating
rod 59 of means such as a double acting linear solenoid 60 which in
turn is carried by the bed 10 of the machine by a bracket 62 and
screws or studs 64. The solenoid may be, in any known manner,
coupled to the sewing machine drive system so as to effectuate a
timed actuation of sleeve 58 and consequent rotation of control
lever 52, control shaft 44 and pivotal movement of crank arm 46 and
thread catcher 36 in proper timed relationship to the sewing
machine needle and looper.
As may be observed most clearly in FIGS. 1 and 6, the thread
catcher 36 is mounted on crank arm 46 so as to pivot through an arc
located beneath the plane of throat plate 14 from a storage or at
rest position which is located beyond the beak of looper 76 to a
position beyond the other extremity or butt of the looper to seize
the needle and looper threads without having to penetrate the
needle thread loop. The thread catcher, in its arc of travel,
continues with the threads to the cutting edges of the knives where
they are severed. The thread catcher is then returned to its at
rest or storage position. It will thus be seen that in a single
direct sweep the thread catcher seizes the needle and looper
threads and carries them to the cutting edges of the knives where
they are severed, the reciprocation of the thread catcher serving
to return same to storage.
The thread catcher comprises a base section 66 dimensioned for
positioning within the channel section of the crank arm and an
offset portion 68 which carries at its extremity a pair of thread
catching hooks 70, 72. Each of such hooks 70, 72 is formed to
present an inclined cutter edge 74 which cooperate with respective
ones of said cutting edges 24, 26 of the knife elements 16, 18.
The sewing machine is provided, as aforestated, with a looper 76
carrying a looper thread 80 which may be driven in known manner in
timed relation to the reciprocation of a sewing machine needle 78
carrying a needle thread 84; so as to form chainstitches which
comprise loops 86 of looper thread and looper 88 of needle thread
passed alternately one through the other. The looper 76 as shown in
the drawings includes a blade 90 which extends from a butt 92 at
which the blade is attached to the looper drive mechanism to a beak
94 located at the free end of the blade beyond the thread carrying
eye 96.
Referring to FIGS. 3, 4, 5, 6, 7, 8 and 9 it will be seen that as
the thread catcher 36 approaches the looper 76 from its at rest
position to the left of sewing machine needle 78, with the needle
in its "up" position, one of hooks 70, 72 will seize the needle
thread running from the needle hole to the looper blade whereas the
other hook will seize the looper thread running from the needle
hole to the eye of the looper adjacent the point of the looper. The
looper thread 80 is thus carried by the thread catcher hook 70
between the thread nipping means 34 and knife 16 thereby urging the
nipping means out of engagement with the knife and permitting the
looper thread 80 to slip between the windings of the spiral spring
34. Continued movement of the thread catcher 36 with both the
needle and looper threads causes such threads to be brought into
engagement between the cutter edges of the hooks 70, 72 and the
respective cutting edges of the knives. The threads are thus
trimmed, leaving one severed end 98 of the looper thread running to
the stitched seam and another severed end 100 running to the eye of
the looper, and the thread catcher begins its traverse back to the
at rest position to the left of the needle. However, as the hook 70
is retracted from between the nipping means 34 and knife 16 the
leaf spring urges the spiral back into engagement with the
underside of the knife and thereby retains the desired severed end
100 of looper thread. Retention of such looper thread insures
against slippage of such thread through the looper eye and
encourages immediate formation of a looper thread loop 86 when
stitching is next commenced.
The needle thread 84 is similarly severed by the hook 72
cooperating with the knife 18 but neither severed needle thread end
is nipped.
It will thus be seen that the thread catcher 36 in a single direct
movement from its at rest position to the left of the needle
effectuats a seizure of the needle and looper threads, cutting of
both threads with retention of the desired length of looper thread
before returning to its at rest position. The knives, as
aforestated, are capable of simple adjustment in order to establish
the desired lengths of the trimmed threads.
Numerous alterations of the structure herein disclosed will suggest
themselves to those skilled in the art. However, it is to be
understood that the present disclosure relates to a prefered
embodiment of the invention which is for purposes of illustration
only and not to be construed as a limitation of the invention. All
such modifications which do not depart from the spirit of the
invention are intended to be included within the scope of the
appended claims.
* * * * *