This application claims the priority of German Application No. 197 11 551.9, filed Mar. 20, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a yarn traversing device on a textile machine producing cross-wound packages, comprising at least one traversing rod extending in machine longitudinal direction over a plurality of winding stations and subjected alternately to tension and compression. The traversing rod is driven at one end by means of a traversing drive, and, for aiding its return of motion, at the other end is connected to an energy storer whose spatial position, with reference to the return point of the traversing rod, is fixed.
Traversing rods are alternately accelerated by the traversing gear. The highest tension and compression load occurs with each return of motion or motion reversal. In particular in the case of long machines, there are considerable delays in the return of motion at the machine end facing away from the traversing gear. The mass accelerated in one direction hinders delay-free motion reversal. This inertia must be overcome. With one motion reversal, a considerable elongation of the traversing rods occurs and with the other motion reversal a corresponding compression of the traversing rods occurs. Length changes in the traversing rods measuring several millimeters occur. In the case of a long machine it is to be feared that the traversing motion is increased in both directions at the machine end, caused on the one hand by elongation and on the other by compression, which results in the varying dimensions of the cross-wound packages. The yarn guides located on the traversing rods do not undergo their return of motion (motion reversal) exactly where they should.
Attempts have been made to alleviate this problem by connecting the traversing rod at its end facing away from the traversing gear with a buffer in the form of an energy storer. This was done in such a way that towards the end of the traversing movement in one direction by the traversing rod, a pneumatic spring is compressed, by means of which in the moment of the return motion an additional force is exerted on the traversing rod (for example German published patent application 38 10 734). Such known energy storers primarily serve to compensate the pressure load of the traversing rod and to override an external tensile load during compression. Thus the length change of the traversing rod in one direction is taken into account, even if this is not expressly stated in the publication, but not, however, the length changes in the opposite direction. The known energy storer is effective namely in only one direction.
It has been shown that such energy storers are only effective over a short time. The reason for this is that the machines do not measure the same length daily, in particular over a longer period of time. The same applies to the traversing rod. The climate plays a role here, as well as heat expansion and other factors known in the industry such as the "strain" of the machine. This "strain" applies not only to the height of a machine but also to its length; it is not taken into account in the above mentioned prior art.
It has been shown that as a result of this "strain", the known energy storer can only function as long as it is sufficiently exactly adjusted. Experience has shown that the values drift after a relatively short period of time, due to the above mentioned variations in length of the machine. It cannot be assumed that a machine measures the same length exactly to the millimeter over a long period of time. This means that the energy storer, in relation to the traversing rod, moves to one side or the other, whereby, for example, in the case of the known pneumatic energy storer, the compressions spaces change their volume, so that the repulse is no longer uniform. A pneumatic force exerted at the wrong time loses its desired effect and can in extreme cases even be damaging.
It is an object of the present invention to ensure that the effectiveness of the energy storer is maintained as far as is possible over a longer period of time while taking into account the "strain" of the machine.
This object has been achieved in accordance with the present invention in that the energy storer is effective in both directions of the traversing rod, that a measuring device is provided for the constant monitoring of the point of return of the traversing rod relative to the position of the energy storer and that the energy storer is connected to an adjusting device coupled to the measuring device.
Data concerning the return motion of the traversing rod at its end facing away from the traversing gear is thus collected, and dependent thereon, corrections for the exact position of the energy storers are relayed. The device according to the present invention thus effects that a once established state attained during assembly is maintained even while taking the "strain" of the machine into account. The "breathing" of the machine and/or the traversing rod is balanced out by automatic readjustment of the energy storer in its position relative to the traversing rod. The impulse effective on the end of the traversing rod for facilitating the return motion should remain always constant in both directions.
The present invention can be particularly easily realized when the energy storer comprises in a known way a pneumatic cylinder, into which a piston, arranged on the traversing rod, is inserted and which is adjustable relative to the longitudinal direction of the traversing rod. In this embodiment, the compression spaces of the pneumatic cylinder can be adapted to the actual point of return of the traversing rod in such a way that both compression spaces always have the same volume and thus the same maximum pressure.
In certain preferred embodiments of the present invention, the traversing rod is provided with at least one signal transmitter to which a signal receiver on the pneumatic cylinder, or on a component connected thereto, is arranged. By means of such "test eyes", the current position of the traversing rod in relation to the position of the energy storer is continuously scanned.
In certain preferred embodiments of the present invention the compression spaces of the pneumatic cylinder are each connected to a pressure measuring device. In the present case, the same pressure means the same volume and guarantees that the return point of the traversing rod always maintains the same distance in relation to the two bottoms of the pneumatic cylinder.
The adjusting device according to certain preferred embodiments of the invention comprises a step motor, which is preferably controlled by a computer. The computer can not only process the data from the measuring device and transmit it to the adjusting device, it can also take into account additional traversing movements of the traversing drive and constantly adapt the energy storer thereto.
Normally the pressure attainable by the pneumatic cylinder by means of the movement of the piston is sufficient to aid the return motion of the traversing rod. In preferred embodiments of the present invention, it is possible furthermore to connect the compression spaces of the pneumatic cylinder to compressed air pipes. Thus the pressure can be increased at a desired point in time and the impulse, which facilitates the return motion, is increased.