Mechanism for flat knitting machines and an operating method for the taking down of shaped knitted products

For the purpose of taking down shaped knitted products from a flat knitting machine the take-down mechanism comprises an auxiliary take-down roller (18) disposed in advance of the take-down roller (16), and this can have a superimposed take-down motion intermittently imparted thereto by means of an auxiliary driving device. To increase the effectiveness of the auxiliary take-down roller (18), the last course of separating stitches formed on one needle bed can be pressed off between two successive shaped knitted pieces (43) before the taking down of a double-sided separating knitting section (45).

This invention relates to a mechanism for flat knitting machines for taking 
down shaped knitted products, this comprising a driven main take-down 
roller and an auxiliary take-down roller which precedes it in the 
take-down direction, is arranged adjacent the stitch forming area, and 
coupled to the drive of the main take-down roller, and an operating method 
for taking down the shaped knitted products by a mechanism of this nature. 
It is already known to provide the take-down mechanism of flat knitting 
machines with additional take-down members which are disposed as near as 
possible to the stitch formation area to provide for early engagement of 
the knitted product. The auxiliary take-down members may be take-down 
rollers or belts (DE OS 3025008). In the making of shaped knitted 
products, that is to say knitted products which, to avoid yarn waste, are 
given their basic shape on the flat knitting machines by narrowing and 
widening, particular problems for the take-down mechanism are met with at 
the transition from narrow shaped knitted parts to the wider beginning of 
the part of a succeeding knitted product. It is known on a flat knitting 
machine to make a plurality of shaped knitted parts simultaneously 
alongside and divided from one another by separating knitted pieces, or 
one after another, that is to say in sequence. Where a shaped knitted 
piece finishes with a narrow edge, for example a narrow collar part, the 
tension imposed by the take-down mechanism is first concentrated on this 
narrow end part of the knitted product. Until a wider starting edge part 
of a subsequent shaped knitted piece is engaged by the take-down mechanism 
there is a sharp contraction of the wide starting edge of the next knitted 
piece by the take-down force which has been applied only over the narrow 
terminal edge of the previous shaped piece. The quality of this next 
knitted piece is negatively influenced by a non-uniform straining of the 
starting edge of a shaped knitted piece in this way. 
The object of the present invention is to provide a take-down mechanism and 
a method of taking down shaped knitted products in which the take-down 
strain is distributed over the full width of the oncoming knitted piece 
even in cases where there are large jumps between succeeding knitted 
pieces at the transition between them. 
The object set by this invention is achieved in a mechanism of the type 
first set forth above by the fact that the auxiliary take-down roller to 
impart a superimposed rotary motion is provided, at least in the take-down 
direction, with an auxiliary driving device which can be operated 
intermittently through a control arrangement through a clutch capable of 
assuming a free wheel status. 
This superimposed rotary motion imparts an accelerated drawing off of the 
knitted piece to be taken down. As a result, in the above-mentioned 
transitions from a narrow shaped knitted end to a wider shaped knitted 
beginning there is a rapid take-up of this beginning over the separating 
knitted area between succeeding shaped knitted pieces and, with it the 
application of the take-down force at the beginning of the next successive 
shaped knitted piece over the full width of the latter. Using the 
mechanism constructed in accordance with this invention a superimposed 
take-down motion with the effect of increasing, or perhaps decreasing, the 
take-down loading on the knitted fabric can be applied temporarily at 
other parts of the knitting formed and this can be of advantage in the 
making of other knitting patterns. 
The auxiliary driving device may be a separate motor which, through a 
clutch capable of adopting a free wheel status can be coupled for example 
directly with an auxiliary take-down roller, the control arrangement 
acting either on the motor or on the clutch. The auxiliary driving device 
may however also be a driving part of the knitting machine itself, for 
example a control shaft with which the auxiliary take-down roller is 
directly or indirectly drivingly coupled through a control clutch. Also 
the clutch capable of adopting an idling position can be of different 
construction. An electromagnetically-operated clutch or a so-called loop 
spring clutch can be used. Also the control device can take different 
forms. 
With the problem with which the invention is primarily concerned, viz. that 
of achieving a starting pull as uniform as possible over the full width of 
the wide spread of the now shaped knitted piece where there is an abrupt 
change in width between successive pieces, and avoiding a twisted pull on 
the edge of this new piece, in a particularly advantageous arrangement the 
following operating procedure is used to take down successive shaped 
knitted pieces connected through separating knitted sections: 
(a) after a double-sided separating knitted section has been made the 
stitches of the last course of stitches of the separating section made on 
one needle bed are pressed off and 
(b) at the same time or following thereon the auxiliary driving device for 
the auxiliary take-down roller is operated to produce an additional 
superimposed take-down rotation of the auxiliary take-down roller. 
After pressing off of the stitches of the last separating stitch course 
made on one of the two needle beds, as a result of the strain of the 
auxiliary take-down roller there is a release of the stitch ends 
containing the pressed off stitches, this leading to a longitudinal 
stretching of the separating knitted section to about three times its 
length. During this release of the stitch ends the separating knitted 
section exerts no appreciable resistance to the increased pull-down 
movement of the auxiliary take-down roller so that, even where there is a 
very sizeable jump in width between successive knitted pieces over the 
range of the separating knitting between these successive pieces the 
interposed delay until the wide starting edge of the next shaped piece is 
engaged can be absorbed and the wide starting edge of the shaped knitted 
piece immediately subjected over its full width to the take-down power of 
the take-down mechanism. 
An exemplary embodiment of a take-down mechanism constructed in accordance 
with the invention will now be described in more detail with reference to 
the accompanying more or less diagrammatic drawings.

FIG. 1 shows the two needle beds 10 and 11 of a flat knitting machine and 
the associated needle bed frame supports 12 and 13. Disposed beneath the 
comb gap 14 and thus beneath the knitting area of the machine is a 
mechanism for taking down the fabric, which latter is depicted by the full 
line 15. 
The take-down mechanism comprises a main take-down roller 16 of known type 
and this cooperates with a press roller 17. The take-down mechanism also 
includes an auxiliary take-down roller 18 which is disposed below the comb 
gap 14 between the two frame supports 12 and 13 and cooperates with a 
press roller 19. The driving shafts 16a, 18a of the main take-down roller 
16 and of the auxiliary take-down roller 18 are--as will be fully 
described later--operatively and permanently coupled together and turn at 
the same rotary speed. The main take-down roller 16 is driven, in a manner 
not illustrated, by a rotary field magnet motor. The main take-down roller 
16 and the auxiliary roller 18 each have a profiled surface to engage the 
knitted width or widths 15 to be taken down and these may be made up of 
individual roller sections. 
This also applies to the press roller 19 working with the auxiliary 
take-down roller 18. 
Whilst the auxiliary take-down roller 18 is mounted on rigid carrier arms 
21 the carrier arm 22 for rthe press roller 19 is bifurcated and mounted 
by a pivot pin 23 so that it can be pivoted on the machine by means of an 
electric motor, or manually through a handle 26, so as to lift the press 
roller 19 away against compression springs 24. 
As shown in FIGS. 1 and 2 the auxiliary take-down roller 18 is coupled with 
an additional driving unit by which a take-down speed different from that 
of the main roller 16 can be imparted intermittently to it under the 
command of a control unit not shown. In the embodiment illustrated the 
motivating part of this auxiliary driving means is a control shaft 27 of 
the flat knitting machine. As shown in FIG. 2 this control shaft 27 has 
thereon a driven bearing sleeve 28 on which a chain wheel 29 is rotatably 
mounted. A hub of this chain wheel 29 is coupled to the bearing sleeve 28 
through a so-called loop spring clutch 30. This clutch comprises a 
cylindrical helical spring disposed around the parts which are to be 
coupled. Loop spring clutches of this nature are effective to provide a 
drive coupling in one direction of rotation to allow free wheeling in the 
opposite direction. One end of the loop spring is anchored to a concentric 
stop wheel 31 in a manner not here shown. Engaged in the spaced notches 32 
of this wheel 31 is a catch 34 formed at the end of a two-armed pivot 
lever 33. The lever 33 is subject to the action of an electromagnet 35 
which when energised pivots the locking catch 34 out of the notches 32 of 
the wheel 31. 
The chain wheel 29 is coupled (see FIGS. 1 and 2) with a chain wheel 37 
rotatably mounted on the shaft 16a of the main take-down roller 16 through 
an endless chain 36 shown in dotted lines. 
The chain wheel 37 is coupled, through a loop spring clutch 38 of the 
previously-described character with a coaxial chain wheel 39 which is 
rotatably arranged on a bearing sleeve 40 non-rotatably connected to the 
shaft 16a of the main take-down roller 16. On the other hand the chain 
wheel 29 is coupled through a further loop spring clutch 41 with a driving 
disc 42 rotatably arranged on the shaft 16a. The chain wheel 39 is coupled 
by a chain 53 (shown in dotted lines) with a chain wheel 54 secured on the 
shaft 18a of the auxiliary driving roller 18. 
The two loop spring clutches 38 and 41 associated with the main take-down 
roller 16, which in one direction of rotation will produce a coupling and 
in the other direction of rotation an idling effect, are so constructed 
and arranged that when the chain 36 is stationary the chain wheel 39 is 
only coupled to the ring 42 through the clutch 41 and thereby participates 
in the rotation of the driven shaft 16a of the main take-down roller 16. 
This movement is transmitted through the chain 53 and the chain wheel 54 
to the shaft 18a of the auxiliary take-down roller 18. 
If the stop wheel 31 is released by operation of the electromagnet 35 it 
will participate through the loop spring clutch 30 of the control shaft 27 
through a rotary step determined by the mutual spacing of the notches 32 
of the wheel 31. The chain wheel 29 also participates in this rotary step 
and this motion is transmitted through the chain 36 to the chain wheel 37. 
The rotary step of the chain wheel 37 is transmitted through the loop 
spring clutch 38 to the chain wheel 39 which is already turning at the 
speed of the shaft 16a of the main take-down roller 16. The loop spring 
clutch 41 permits an overtaking movement of the chain wheel 39 relatively 
to the driving ring 42 so that the rotary stepping movement transmitted 
through the clutch 38 to the chain wheel 39 can be transmitted as an 
additive movement to the chain wheel 39. Corresponding to this the 
auxiliary roller 18 makes a faster take-down movment than that of the main 
take-down roller 16 during this rotary stepping period and consequently 
brings about a faster take-down of the knitted web 15 than was previously 
the case. The rotary field motor operating the main take-down roller 16 
adapts itself to this augmented take-down of the knitted web 15. 
The auxiliary driving mechanism is not necessarily confined to a control 
shaft in the flat knitting machine. It could, as indicated by the 
auxiliary motor shown in dotted lines in FIG. 2, be coupled directly to 
the shaft 18a of the auxiliary take-down roller 18 through a clutch 50 
allowing for a clutching or an alternative idling position. 
FIGS. 3 and 4 diagrammatically show the main take-down roller 16 and the 
auxiliary take-down roller 18 and a first shaped fabric piece 43 engaged 
by this take-down mechanism, the marginal area 44 of a second and similar 
succeeding shaped knitted fabric piece and a separating section 45 and 45' 
of the knitted fabric connecting the first shaped fabric piece 43 with the 
next following shaped piece. The shaped knitted pieces 43 end in a narrow 
collar margin 46 on which the take-down force of the take-down mechanism 
is effective and is transmitted through the separating knitted section 45 
to the substantially wider marginal section 44 of the next following 
shaped knitted piece. As a consequence of the fact that the take-down 
effect which is operative only over the narrow collar section margin 46 
there is a contraction of the adjoining starting seam 47 of the separating 
knitted section 45, as can be seen from FIGS. 3 and 4. A corresponding 
pull on the wider marginal section 44 of the next following knitted piece 
must however be avoided and a distribution of the take-down force be 
achieved over the complete width of the marginal section 44. 
As can be seen from the yarn illustrations of FIG. 3, both the shaped 
knitted piece 43 illustrated including its starting selvedge section part 
44, as also the separating knitted section 45, are of double sided knit. 
In accordance with the invention, after knitting the last course of 
stitches of the separating knitted section 45, before the knitting of the 
selvedge section 44 of the next following shaped knitted piece the 
stitches on one of the two needle beds 10 or 11 are pressed off so as to 
provide the yarn structure 48 for this course of stitches shown in FIG. 4. 
After the pressing-off of these stitches the stitch roots are loosened 
under the action of the take-down force of the main take-down roller 16 
and the auxiliary take-down roller 18, which means an increase in the 
length L of the separating knitted section 45 to the length L', about 
three times as much, indicated in FIG. 4. Because of the increased 
take-down speed imparted by the auxiliary take-down roller 18 the 
elongated knitted section 45', at first exerting practically no counter 
pull, is rapidly drawn off, delay originally present and visible in the 
separating knitted section is relieved and a uniform take-down force 
applied over the complete width of the adjoining marginal area 44 of the 
next shaped piece.