Developments and Improvements in Compound Needle

8/3/2019 Developments and Improvements in Compound Needle

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Developments and

Improvements inCompound Needle

Abeera KhannaRoll No. 1

FP- Tech 7


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Introduction A compound needle with a sliding latch

was first patented by JeacockofLeicester in 1856.

Compound needles consist of twoseparately-controlled parts the openhook and the sliding closing element(tongue, latch, piston, plunger).

The two parts rise and fall as a single unitbut, at the top of the rise, the hook movesfaster to open the hook and at the start ofthe fall the hook descends faster to closethe hook.


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Compound needle having reducedsliding resistance and widthwise

extension of a needle

The blades of the slider can be allowed to beadvanced beyond the needle hook with

a reduced sliding resistance of the blades ofthe slider and,

a reduced degree of stretch of the bladesas compared with the conventional compound

needle.

Objective


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It is to be noted that with increase in thickness of the partition wall, the slidingresistance and the stretch of the blades can be made smaller


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Construction

The blades of the slider are supported in a bladegroove formed in the needle body.

A partition wall having thickness smaller thanthat of the needle hook of the needle body isformed in the blade groove.

The blades of the slider are accommodated inthe blade groove to sandwich the partition wallthere-between.


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Features

The partition wall allows the two blades to be advancedalong lines deviating from a dashed line XX passingthrough the front end of the needle hook and can allowthe blades to be stretched to a small extent and can allowthe sliding resistance to reduce.

The blades are prevented from being stretched out to alarge extent.

Also, when the blades are moved to their retractedposition, dirt and dust that may get into the spacebetween the blades are pushed out by the partition wall.


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Compound needle with asymmetrical

divided closing element

A compound needle comprises a closing element with two closingelement springs.

These are designed to be asymmetrical relative to each other or atleast provided with clearances or openings which, during theoperation of the compound needle, are made to overlap with acorresponding cutout or other openings in the basic compoundneedle member.

An asymmetric design of the closing element springs prevents theclosing element from being wedged into the closing elementchannel, even if the deposit removal is incomplete.

As a result, the compound needle wear is reduced considerably and

the operational safety is increased.


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Basis of invention The closing element is composed of two connected closing element

springs, which respectively push past the hook of the compoundneedle on the side and are spread apart in this way.

Dirt that reaches the area between the two closing element springs,

can lead to a gradual spreading apart of the closing element springsinside the closing element channel.

In turn, this leads to increased friction and wear.

In the extreme case where the closing element is extremely hard tomove or is wedged inside the channel, the loop formation, the looptransfer and the loop knock-over are obstructed.

Given another extreme case, the closing elements can no longer bemoved inside the closing element channel of the needle member, sothat a butt break occurs.


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Construction

Openings arranged at different locationsin the closing element springs initiallypermit deposits that have accumulatedbetween the closing element springs tomove from the gap formed between the

closing element springs to the closingelement channel walls and through theopenings in these walls to the outside.

In addition, the closing element springscan also be designed asymmetricalbetween the guide sections and a

respective loop-support section, whichalso leads to a reduced tendency foraccumulating dirt and being wedged in.The closing element springs thus for themost part are not designed to overlap.


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It is advantageous if the

asymmetrically designedsections of the closing elementsprings are primarily arrangedin the closing element channel.

This results in a good sideguidance of the closing elementsprings, which permits areliable operation of thecompound needle even at a

high operating speed

Developments and Improvements in Compound Needle

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