The present invention relates in general to a knitting machine, in particular to a synchronizing device for the selection of knitting needles in flat or straight and circular knitting machines of the type having two pairs of needle beds arranged in tandem, knitting carriage circulating in one direction above the needle beds, each carriage supporting a device for selecting the knitting needles according to a desired pattern, the selecting device including a set of selection cams movable between a neutral and an active position, a set of solenoids for controlling the position of respective cams, means including a pulse generator for controlling actuation of selected solenoids, a pin board arranged in the path of movement of the selection cams and guiding a set of selection pins, and blade beds arranged on the needle beds and each including a set of Jacquard-type sinking blades assigned to respective knitting needles and being controlled by the selection pins.
From prior art it is known how to select by means of selecting devices arranged on knitting carriages sinking blades for an auxiliary needle bed so as to control the individual knitting needles. In order to insure correct time points of the generation of control pulses by the selection devices, there are provided synchronizing devices consisting of pulse generators and synchronizing rails. The synchronizing rails have been integrally formed in the needle- or sinking blade beds or can be arranged on the knitting machine separately. For example, according to the German publication DE-OS No. 2919369 there is provided a pulse generator in the form of a disc cooperating with at least one, usually with two, pulse generators. The disc is arranged above the needle beds and is driven by a transmission chain synchronously with the carriages. From the German Pat. No. 2,114,013 known are also optical means for generating synchronizing pulses. In practice, such prior art solutions have been successful in flat knitting machines because they guarantee an error-free selection of the knitting needles, and consequently a high knitting quality.
However, in straight and circular knitting machines operating with two beds of knitting needles arranged one after the other and using circulating carriages, the application of prior art solutions of selecting devices is not possible without further measures. Due to the two independent pairs of needle beds with corresponding different guiding tracks for the carriages, there result higher mechanical tolerances leading to higher timing tolerances for synchronization. Consequently, limitation of operating speed of the straight and circular knitting machines using circulating carriage would result. In addition, in the prior art solution using a chain power transmission from a drive to the knitting carriage, undesirable irregularities in the run of respective knitting carriages may occur especially upon braking the knitting machine a certain amount of kickback takes place. In order to reduce errors resulting from this kickback, it has been necessary to use always two spatially staggered pulse generators in order to recognize the direction change. In the case of straight and circular knitting machines it would be necessary to further increase the number of pulse generators and further component parts, which would impair the reliability and the efficiency of the knitting operation. So far, no measures have been devised how to improve the situation in circular knitting machines.