Textiles: knitting – Needles – Pivoted latch
Reexamination Certificate
2001-04-16
2002-07-23
Worrell, Danny (Department: 3765)
Textiles: knitting
Needles
Pivoted latch
Reexamination Certificate
active
06422046
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application Nos. 100 18 798.6 filed Apr. 15, 2000 and 100 57 765.2 filed Nov. 22, 2000, which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to a latch needle, particularly for knitting machines and more particularly for circular knitting machines.
Latch needles are utilized, for example, in circular knitting machines. At one end the latch needles have a hook, adjoined by a latch which is pivotally supported in a sawslot of the latch needle. The latch is arranged in such a manner that in its closed state it lies at or on the end of the hook and closes the trapping space partially bounded by the hook. In its open state the latch is swung back to rest on its back and thus opens the trapping space. Such latch needles which are present in large numbers in knitting machines, are supported in needle beds in which, during operation of the knitting machine, they are rapidly reciprocated in their longitudinal direction. During this occurrence, the latches snap open and closed. For this purpose they have to move easily which, as a rule, requires a certain lateral play between the latch and the needle.
During the knitting operation the hook of the latch needle captures a thread while the needle executes its reverse stroke. A thread which is located behind the latch situated in its reverse state, lies on the upper side of the needle and first closes the latch. Upon further needle motion the thread slides off the hook resulting in the formation of a loop. The thread captured by the hook during this occurrence must be able to slide in the inner hook space and the trapping space must be closed by the latch. Only upon the successive movement of the needle in the opposite direction may the thread slide out of the inner hook space, opening the catch and the trapping space. If the latch is lifted from the hook earlier and thus the trapping space is opened and the thread moves out of the trapping space between the hook tip and the latch, loops will be dropped, resulting in a defective knit of unacceptable quality
Latch needles are also frequently used to produce dual-thread knits. To ensure that such knits have a uniform appearance, it is of the utmost importance that the threads do not switch their sequence in the trapping space of the latch needle. Dual-thread knits, so-called plated knit goods, are manufactured frequently with a combination of unlike threads, for example, a natural fiber yarn and an elastomer thread. In such a product the elastomer thread should, as a rule, be situated on that side of the product which is not visible (that is, on the reverse side of the item). Such a requirement is not fulfilled if the threads switch position. Such an occurrence results in an undesired pattern because, as a rule, the two threads have different shapes and/or color as well as other different properties.
Further, particularly monofilaments, such as elastomer threads are reacting very strongly to damages. Deep surface scratches must be definitely avoided, since even the slightest damage to the thread surface may lead to thread breakage.
Latch needles are known, for example, from German Patent No. 1,069,812. The latch needle has a pivotally supported latch, whose latch spoon (noucat) is provided with a groove for receiving the hook tip. The latch is linear along its inner contour which bounds the trapping space in the closed state of the latch and in the closed state the inner contour of the latch adjoins directly the hook tip.
Right-left circular knitting machines, that is, unifacial circular knitting machines have a sinker ring with hold-down sinkers instead of a dial. Such a ring or sinkers are needed to hold the knit product. For this purpose the sinkers, when the knitting machine needles are in their respective uppermost position, are moved past the loop forming portion of the needle and hold down the last-formed loop. During operation the knitting machine needles are exposed to a high degree of wear, for example, because of the high operating speed of the knitting machine, because of the yarns to be handled, or because of abrasive wear or other effects. The wear in most cases leads to an ever-increasing play in the latch bearing both in the axial and the radial direction resulting in lateral excursions of the latch during operation. The Coriolis force which is generated at the latches by the rotation of the cylinder of the knitting machine may amplify the lateral excursion of the latches of the knitting machine needles. If the lateral excursion of the latches is greater than the play between sinker and latch, the two frictionally engage one another, leading to lateral abrasions of the latch head.
Grooved needle latches as described in the above-noted German Patent No. 1,069,812 are particularly prone to such a wear which causes the originally rounded latch head to be transformed into a latch spoon having a groove with sharp edges. These may damage the threads which may lead to a rupture particularly of threads which break or tear relatively easily, such as elastomer threads.
German Offenlegungsschrift (application published without examination) No. 28 34 558 discloses a needle in which the needle hook is provided with a groove. Thus, the needle has a grooveless latch spoon and the latch head is configured such that it is accommodated by the deep groove in the needle hook when the latch is in its closed state. The inner contour of the closed trapping space, bounded by the hook and the latch, has at its transition from the latch to the hook a projection which prevents a thread motion within the inner space defined by the hook.
Such latch needles too, behave critically when simultaneously a plurality of threads are processed, such as, for example, during the manufacture of dual-thread knits.
British Published Patent Application No. 2,232,689 describes a latch needle for dual-thread knits. The latch needle has a pivotally supported latch which at its inner side is provided with a chamfer or step projecting into the inner space of the hook. The latch shank has a substantially constant height starting at the step and extending approximately to the rounded end of the latch shank. At its free end the latch has a latch spoon provided with a groove for receiving a portion of the hook tip. The step is configured as an oblique surface oriented in the direction of the hook tip and serves as a supporting surface for the threads of the dual-thread knit. The supporting surface is oriented toward the inner space of the hook and contacts the thread particularly when the threads lie on that border of the trapping space which is situated at the latch bearing.
During the knitting operation the threads are to be guided by the reciprocating motion of the needle from that end of the trapping space which is at the latch bearing into the inner space of the hook. Plating defects are intended to be avoided in such a needle structure as well.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved latch needle of the above-outlined type which may be used in a diversified manner and which permits the manufacture of knit products having the desired quality.
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 shank; a hook formed at an end of the shank and having a hook tip; and a latch pivotally supported by the shank and cooperating with the hook. The latch has a closed state and a reverse state. In the closed state the hook and the latch together define a closed trapping space and in the reverse state the hook defines an open trapping space constituted essentially by an inner hook space. The latch includes an inner contour facing the trapping space in the closed state, a free end lying on the hook in the closed state and a stepped portion formed on the inner latch contour and adjoining the free latch end.
The latch needle according to the invention h
Groz-Beckert KG
Kelemen Gabor J.
Venable
Worrell Danny
LandOfFree
Latch needle having an improved trapping space does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Latch needle having an improved trapping space, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Latch needle having an improved trapping space will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2870165