The RTR garmentlength machine

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This fully-automatic garment-length rib machine was introduced in 1938 by Wildt (Mellor Bromley) as a replacement for their RSB model of 1936, which had no facilities for rib loop transfer. Its anti-clockwise revolving cylinder and dial cam-box has cam sections of equal size whether they are for knitting feeders or rib loop transfer. A unit set in advance of the section can select the cylinder needles for the knitting or transfer action. The original RTR has six cam sections, four for knitting (2 and 3; 5 and 6) and two for transfer (1 and 4). Section 4 also has facilities via the back butt set-out of the dial needles for changing the rib, either by collective dial-to-cylinder loop transfer or by dial needle loop press-off. Four Brinton trick-wheel units provide selection for the cylinder needles - one for each transfer section and one for every two knitting sections, with the selection at section 2 being repeated at 3 and the selection at 5 being repeated at 6.

In Figures 20.5 and 20.6, section 4 contains the cams for selective cylinder-to-dial loop transfer (cams R and Y) and collective dial-to-cylinder loop transfer (cams X, P and Q).

In section 1, cam T may be set to raise cylinder needles to clearing height and, as there is no feed position in this section, when lowered by cam U they will pressoff their loops (for the end of the garment sequence). In a similar position at section 4 are raising and lowering cams P and Q, which act as receiving cams for the collective transfer of dial loops when cam I acts on the back transfer butts of dial needles.

It soon became apparent that the machine's garment-length knitting sequence of drawthread separation course, tubular welt, 1 x 1 or 2 x 2 rib border or waist, body panel section, and press-off locking courses could be used for knitting jacquard, double-jersey, or coarse-gauge knitwear as well as stitch-shaped underwear. A six knitting-section model, with each section having its own selection unit, thus became available for jacquard with interchangeable transfer sections. For double jersey, the dial shogging was adapted for interlock knitting. Depending upon the end-use of its

Interlock Knitting StitchLoop Tuck Miss Png
Fig. 20.5 Cylinder cam system of an RTR rib loop transfer machine.

model, panels can thus be knitted in 1 x 1 rib, dial-only knit, interlock milano rib, rib jacquard, or half- or full-cardigan, with selective patterning in rib transfer, coloured stitches, miss, tuck, knit or raised cloque relief stitch. Articles that can be knitted include vests and panties, cut and sewn sweater dresses and trouser suits, jumpers, coarse-gauge cardigans, and sweaters.

As well as the original 13- and 15-inch diameter models, other diameters were introduced, including 18, 20 and 22 inches to cater for more than one panel width (separated by a needle-out line) and the knitting of high-shrinkage synthetic yarns

Over Knit Cam
Fig. 20.6 The RTR dial cam system.

or coarse gauges. This concept was extended to a 33-inch diameter machine, with flexibility of knitting width and economy in cutting waste achieved by removing the block of needles not required, thus leaving a panel of floating threads.

Machine speeds range from about 16 to 32rpm, according to machine design and type of stitch being knitted, with the cam sections being between eight and twelve in body diameters (and up to eighteen in the 33-inch diameter model). Gauges extend to 16npi for underwear or jerseywear down to 7npi for knitwear, with the coarse model having gauges of 3 and 6npi.

20.3.1 The basic elements and camming arrangement of the RTR machine

The geometric selection employed on this machine has been previously described (Section 11.9). Figures 20.5 and 20.6 illustrate the arrangement of cams for a six-section machine; other models are similar. On the 33-inch diameter model, however, each presser has 79 butts, with a maximum of 73 available for patterning. One is removed to leave a gap. The remaining five are used for isolation purposes as follows: all butts on, 2 out of 3,1 out of 3, odd needles only, even needles only. The dial needles are usually set-out with every third needle having a back butt for dial-to-cylinder transfers or press-off for achieving 2 x 2 rib. Cylinder needle butts may be set-out 1 short 2 long for 2 x 2 rib in the waist.

There is a jack-raising cam associated with each cylinder selection unit raising any jack butts whose pressers are not selected (Fig. 11.6). As empty needles may be required to re-start knitting, in sections 2, 3, 5 and 6, cams A and B, C and D raise and lower the cylinder and dial for latch opening. Cylinder cam G is a swingclearing cam that can be set for knit or miss and is split into two sections; the top section acts on all butts, the bottom section acts only on long butts. In the dial, odd needles usually have long back knitting butts and are raised by cam H, whilst cam I raises even needles with long front knitting butts.

The front part of cam N is fixed, the back part J is shown in a solid line for delayed timing and in a dotted line for synchronised timing. The upthrow cam is K; L and M are the stitch and upthrow cams in the dial. The two cams L and M are adjusted together and have three pre-set positions for automatic alteration during the garment sequence for the welt, rib border and body panel.

In both cam sections 1 and 4, cylinder cam R is aligned with dial cam I as the delivering and receiving cams for cylinder dial rib loop transfer. In section 4, cam O in action will cause all cylinder needle loops to be transferred to the dial for dial-only knit, by means of the middle butt of the jack. If cam S is in action, long butt jacks will be lowered before transfer can occur. This is used for producing a 2 x 2 rib set-out for the waist at section 4.

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