GB2036814A

GB2036814A - Improvements in Tufting Machines

Info

Publication number: GB2036814A
Application number: GB7942133A
Authority: GB
Original assignee: Pickering E Ltd
Current assignee: Pickering E Ltd
Priority date: 1978-12-11
Filing date: 1979-12-06
Publication date: 1980-07-02

Abstract

A tufting machine which includes a needle bar 8 which is reciprocated vertically by cams 12 on a main shaft 10 which are so designed as to impart at least two strokes to the needle bar at each revolution of the main shaft. <IMAGE>

Description

SPECIFICATION Improvements in Tufting Machines A tufting machine is normally provided with a main shaft which imparts vertical reciprocating movement to the needle bar of the machine through push rods disposed at intervals, normally of the order of - metre, across the width of the machine through the agency of individual eccentrics on the main shaft. The main shaft normally also carries other eccentrics at its ends from which the necessary rocking movements are imparted to the loopers, which engage the loops of yarn projected through the backing cloth by the needles, and also to the knives in the case of a machine making cut pile fabric.

Modern tufting machines run at a high speed.

Typically the needle bar may be required to make 650 strokes per minute, which requires the main shaft to rotate at 650 r.p.m. Problems arise in balancing a shaft, particularly a shaft carrying numerous eccentrics, when it runs at so high a speed. Such balancing is necessary to avoid undue vibration and can be provided without undue difficulty in the case when the machine is required to run at a single speed only.

Users of tufting machines, however, now require variable speed machines They desire, to ensure maximum output, to run the machine at the highest speed compatible with avoidance of yarn breakage and this speed varies with the nature of the yarn and the backing cloth in use at any particular time. Effective balancing is extremely difficult when the main shaft is required to run at a variety of different high speeds.

With a view to obviating this difficulty the invention provides a tufting machine comprising a needle bar to which vertical reciprocation is imparted by push rods driven from cams on a main shaft, the cams operating to impart n strokes to the needle bar at each revolution of the shaft, n being an integer amounting to 2 or more.

This permits the main shaft to revolve at one half, one third or one quarter of the speed required to impart a given rate of reciprocation to the needle bar in comparison with a machine in which the needle bar is driven by eccentrics. The problems of balancing in a variable speed machine are therefore greatly alleviated.

In one embodiment of the invention, each cam acts on a follower on one arm of a bell crank, the other arm of which is connected by a connecting rod to a push rod, and means are provided for simultaneously adjusting the effective lengths of said other arms of all the bell cranks by the same amount for the purpose of varying the stroke of the needle bar, the bottom dead centre position of the needles remaining the same in all positions of adjustment.

One embodiment of the tufting machine according to the invention is illustrated, by way of example, in the accompanying drawings, in which: Fig. 1 is a sectional front elevation, and Fig. 2 is a section on the line Il-Il in Fig. 1.

The machine includes a needle bar 8 (Fig. 2), carrying a multiplicity of needles 9 and extending transversely to the direction in which the backing cloth (not shown) to be tufted is fed through the machine. The needle bar is reciprocated vertically by a series of spaced push rods 11 operated by a main shaft 10. The main shaft 10 carries, for each push rod 11,acam 12, the track 13 of which is engaged by a follower 14. The push rods 11 are guided for vertical reciprocating movement in fixed guides 1 5.

Each follower 14 is mounted on one arm 1 6 of a bell crank which is mounted on a rocking shaft 1 7 supported in bearings 17A. The other arm 1 8 of the bell crank carries a stud 1 9, to which is pivoted the upper end of connecting rod 20 pivoted at its lower end by a pin 21 to the upper end of the respective push rod 11. In the machine illustrated, the cam tracks 1 3 are so shaped as to impart two strokes to the push rods 11 for each revolution of the shaft 1 0. As will be appreciated by use of cams having different forms of cam track, three or more strokes could be imparted to the push rods 11 per revolution of the shaft 1 0.

Each stud 19 has an enlarged head 22 at one end which engages an arcuate groove 23 in the arm 18, which is struck to a radius from the centre of the pin 21 which is shown in Fig. 1 in the bottom dead centre position. A screw 24 engages a screw threaded hole in the stud 1 9 and is connected at the end remote from the stud by a universal joint 25 to a shaft 26 carrying a bevel gear 27. The bevel gears 27 on all the shafts 26 mesh with bevel gears 28 on a common adjusting shaft 29.

By rotation of the shaft 29, therefore, all of the studs 19 can be moved simultaneously and to equal extents from the positions shown at the outer ends of the arms 18, which correspond to maximum stroke of the needles, to the inner ends of the arms 1 8 when the stroke of the needles is a minimum. In all positions of adjustment the bottom dead centre position of the needles remains unchanged.

Cam-operated mechanisms precisely similar to those illustrated are provided at the extreme ends of the shaft 10 and the push rods of these mechanisms are arranged to impart rocking movement to the looper shaft of the machine and, when the machine is one producing cut pile fabric, to the knife shaft as well.

The invention provides the following advantage in addition to that of enabling the main shaft 10 to be rotated at reduced speed. When the needle bar 8 is driven by eccentrics in accordance with conventional practice, the curve relating displacement of the needles to angular position of the main shaft is sinusoidal and it is impossible to regulate the duration of engagement of the needles with the backing cloth at each machine cycle. It is desirable to reduce this to a minimum owing to the tendency of the advancing backing cloth to bend the needles 9. This reduction can be provided by suitable shaping of the cam tracks 13, which can also be shaped to give optimum dwell times of the needles at the top and bottom centre positions.

Claims

1. A tufting machine comprising a needle bar to which vertical reciprocation is imparted by push rods driven from cams on a main shaft, the cams operating to impart n strokes to the needle bar at each revolution of the main shaft, n being an integer amounting to 2 or more.

2. A tufting machine as claimed in claim 1, wherein each push rod is operated from its respective cam by a bell crank, one arm of which carries a follower engaging the cam and the other arm of which is connected to the push rod by a connecting rod.

3. A tufting machine as claimed in claim 2, which includes means for simultaneously adjusting the effective lengths of all the bell cranks by the same amount to vary the stroke of the needle bar with the bottom dead centre position of the needles remaining the same in all positions of adjustment.

4. A tufting machine as claimed in claim 3, wherein each connecting rod is pivoted to a stud movable in an arcuate groove in the other arm of the associated bell crank, the studs of all the bell cranks being movable by respective screws along their respective grooves by an adjusting shaft geared to all the screws.

5. A tufting machine as claimed in claim 1, which includes a looper shaft operated by push rods actuated by other cams on the main shaft which impart at least 2 strokes to said push rods at each revolution of the main shaft.

6. A tufting machine as claimed in claim 1, which includes a knife shaft operated by push rods actuated by other cams on the main shaft which impart at least 2 strokes to said push rods at each revolution of the main shaft.

7. A tufting machine as claimed in claim 1, subtantially as described herein with reference to the accompanying drawings.