Textiles: knitting – Needles – Pivoted latch
Reexamination Certificate
2001-10-10
2002-08-27
Worrell, Danny (Department: 3765)
Textiles: knitting
Needles
Pivoted latch
Reexamination Certificate
active
06439001
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a latch needle, particularly for use in knitting machines.
Knitting machine needles are used in great numbers in flat bed knitting machines, as well as circular knitting machines. The latch needles have a needle shank which, at one end, terminates in a hook (needle head). A pivotally supported latch cooperates with the hook and may swing back and forth between two end positions. In one end position the latch lies with its noucat (latch spoon) against the hook tip and thus closes the inner hook space. In its other end position the latch is in a reverse orientation and thus opens the inner hook space.
In some knitting machines it is desired to maintain the needle latch in a stable position of rest in the vicinity of the respective two end positions. Thus, for example, only one staple end position for the latch may be desired which is in the vicinity of the reverse end position and in which the latch is not in contact with the the needle shank. It is an exemplary purpose of such an arrangement that the thread of a loop which closes the latch may glide in the intermediate space between the latch and the needle shank without being impaled by the tip of the latch (latch spoon).
Occasionally, it may also be required that the latch assume a stable position of rest adjacent the closed end position. This is the case, for example, when the latch is guided from its closed position into its reverse, open position by a brush carried by the knitting machine. The brush may better engage the latch if the latter is slightly spaced from the hook. In any event, however, the latch must not have an excessive distance from the hook to securely avoid damaging of the latch. By moving the latch from its closed position into its reverse position, the thread trapping since is opened and thus a thread for forming a loop may be inserted.
Springs are used for setting the stable positions of rest of the latch. For example, U.S. Pat. No. 3,050,968 describes a latch needle having a needle shank, a hook provided at one shank end and a pivotally supported latch disposed adjacent the hook. The latch projects, with the latch shank, into a saw slot which is traversed by a bearing pin. The bearing pin pivotally supports the latch for swinging motion between a closed end position in which the latch engaged the hook end with the latch spoon and a reverse end position in which the inner hook space is open. In the saw slot a flexion spring is positioned which engages the end of the latch shank. The end of the latch shank has a flattened region which serves as an engagement face and which is contacted by a pressing face of the spring. This arrangement determines a stable position of rest of the latch in which the latch spoon is slightly spaced from the hook tip.
It has been found to be very difficult to apply by a flexion spring of the above-outlined type the relatively large resetting force needed for lifting the latch off the hook tip.
Further, latch needles having spring-supported latches are known, such as shown in
FIGS. 7 and 8
. The latch needle
1
has a needle shank
2
terminating in a hook
3
having a hook tip
4
. The hook
3
is adjoined by a shank region in which a latch slot which is synonymously a saw slot
5
is formed. A latch
6
is pivotally supported in the saw slot
5
by a bearing pin
7
. A leaf spring
8
positioned in the saw slot
5
has spring ends
11
and
12
which engage respective seats
14
and
10
formed in the saw slot
5
. The spring
8
has flexing locations
15
and
16
on either side of the bearing pin
7
. The flexing locations
15
,
16
, as shown in
FIG. 7
, may contact the reverse side
17
of the latch
6
as shown in
FIG. 7
or may contact an inner side
18
of the latch
6
as shown in FIG.
8
. Thus, the flexing locations
15
,
16
form pressing faces.
In such a basic construction the position of rest of the latch
6
set by the flexion spring
8
is essentially dependent from the positioning of the bearing pin
7
relative to the flexing locations
15
and
16
. The smallest tolerances in the making of the spring
8
or the bearing pin
7
substantially affect the position of rest of the latch
6
. A tolerance in the position of the bearing pin
7
in the longitudinal direction of the latch needle
1
also results in a significant error in the position of rest of the latch
6
. It is a disadvantageous result of these circumstances that in case that latch
6
is in its reverse end position, a thread, during the return motion of the latch needle
1
, may be impaled by the latch spoon or, when the latch is in its closed end position, the brushes may not arrive in contact therewith. Therefore, a proper functioning of the latch needle is not ensured.
In addition, a tolerance in the position of the bearing pin
7
between the needle back
9
and the check
19
results in a significant deviation of the resetting forces from their optimal value. If the resetting forces are too small, the latch cannot be moved into its positions of rest, whereas in case the resetting forces are too large, the latch swings beyond the positions of rest and may be damaged. Again, a reliable operation of the latch needle cannot be ensured.
The position of the latch in its respective position of rest and the force with which the latch is moved and retained in such a position of rest affect the quality of the loops of the knit fabric.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved latch needle of the above-outlined type for obtaining an ameliorated knit fabric.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the latch needle includes a needle shank; a hook formed at one end of the needle shank; a saw slot formed in the needle shank adjacent the hook; and a latch supported in the saw slot for pivotal motion about a pivot axis. The latch has first and second end positions and a position of rest situated between and end positions adjacent one of the end positions. Further, the latch has first and second engagement faces spaced from one another. A spring situated in the saw slot has a first pressing face which is contact with the first engagement face when the latch is in the position of rest and a second pressing face spaced from the first pressing face. The second pressing face is in contact with the second engagement face when the latch is in the end position adjacent the position of rest.
Thus, the latch needle according to the invention has a spring, determining for the needle latch at least one stable position of rest which is different from an end position. Two engagement faces forming part of the latch and two pressing faces forming part of the spring are provided for this purpose. As a result of this arrangement a position of rest for the latch may be set by the cooperation between the first pressing face and the first engagement face and also, the latch may be moved out from its adjoining end position. For example, the latch may be lifted off the hook by the cooperation between the second engagement face and the second pressing face. This has the advantage that lifting the latch off the hook may be effected by means of a relatively large resetting torque, while the setting of the position of rest may occur with a lesser resetting torque. This, on the one hand, ensures a reliable, secure lifting of the latch off the hook and, on the other hand, a loop gliding over the latch may very easily press the latch against the hook. This occurs at least as long as the latch is exposed to a larger counter torque in the vicinity of its end position. Therefore, the latch has a much lesser tendency to expand the loop sliding thereon than in the prior art arrangement of
FIGS. 7 and 8
in which a single engagement face and a single pressing face cause the latch to move from its end position into the respective position of rest.
Further, the latch needle according to the invention is significantly less sensitive to manufactur
Groz-Beckert KG
Kelemen Gabor J.
Venable
Worrell Danny
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