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Device and method for thread positive feeding

Device and method for thread positive feeding description/claims

The invention relates to a control device for at least one thread feeding device of a thread processing machine, especially a knitting machine. The invention also relates to a method for positive thread feeding to a textile machine, especially a knitting machine with changing thread requirements.

Circular knitting machines and flat knitting machines are known, which are designed for stitching patterned goods. With respect to patterned goods, different stitching positions must be supplied with thread intermittently rather than continuously.

One example of a circular knitting machine for creating patterned goods is seen in EP 0 724 033 A1. The circular knitting machine has a cutting device in order to cut away unnecessary thread. If thread of the corresponding color is needed again, the previously cut thread is fed again to the stitching position.

In addition, a so-called striping attachment for a circular knitting machine and for a circular machine is seen in DE-PS 2024 341. The striping attachment contains devices to lay threads in and out, i.e., to feed the stitching positions selectively.

Knitting machines that stitch plain-weave goods, i.e., to whose stitching positions continuous thread is fed, are usually supplied with thread by means of so-called positive feed wheel mechanisms, which feed a certain amount of thread to the stitching position for every rotation of the machine cylinder. Thus, the mesh size is uniform independent of tolerances of the stitching positions. Such positive feed wheel mechanisms are usually driven by means of a toothed belt or the like and thus are forced to run in sync with the knitting machine.

Knitting machines used to create patterned goods cannot be supplied with thread with such positive feed wheel mechanisms. Instead, so-called friction feed wheel mechanisms are usually used, as seen in DE 100 06 599 A1. Such friction feed wheel mechanisms have a thread feed wheel that is driven so that it rotates. The thread contacts this thread feed wheel over a wrapping angle, which changes as a function of the thread tension at the point using thread. For this purpose, a so-called feeder lever is provided, which carries on its end an eyelet through which the thread runs. The lever is mounted so that it can pivot and is biased by a spring in the feeder direction, i.e., away from the thread feed wheel. If the thread tension breaks down, the feeder lever lifts the thread away from the thread feed wheel and drastically reduces at least the wrapping angle.

Such thread feeding devices have been proven in practice. Unlike positive feeding devices, however, they do not directly create a uniform mesh size.

The goal of the invention is to present a system, as well as a method, with which thread-processing machines, especially circular knitting machines, can be fed with thread in a way that allows increased stitch quality despite changing thread requirements.

To control the one or more thread feeding devices the control device according to the invention uses a pattern memory, which is used for controlling the knitting machine or some other textile machine. The pattern memory contains data for turning the thread feeding devices on and off at various positions of thread use, for example, stitching positions. Thus, the pattern memory controls, e.g., the lock of a knitting machine, in order to activate or deactivate individual needles, the thread feeder lever to lay thread in and out, cutting devices and the like. The control device has a pattern interface, by means of which it is connected to the pattern memory. In addition, the control device receives from a position sensor information on the current machine position. For a circular knitting machine, the term “machine position” is understood to be primarily the rotational angle of the needle cylinder. Here, the machine position can be detected either as an absolute position or as a relative position in the form of a pulse sequence or otherwise.

The central component of the control device is a processing module, which can also be designated as a machine interpreter, especially when it is realized in software. The processing module obtains data from the pattern memory according to the position of the machine and converts this data according to a set of given logic rules into control commands for the one or more thread feeding devices. The “set of given logic rules” can be a delay command in the simplest case. When the position sensor delivers, for example, a pulse sequence specifying the angular steps of the needle cylinder, and when the needle cylinder must rotate by a preset angle between the activation of a stitching position and the resulting thread requirements, there is the logic rule of waiting an appropriate number of pulses of the position sensor until a further request for thread is issued from the pattern memory to the thread feeding device. This can be realized with a gate circuit, which, after counting the relevant pulse number, forward the step pulses of the position sensor of the needle cylinder to the thread feeding device in order to cause the synchronous rotation between the thread feed wheel and needle cylinder with the desired delay.

The number of angular steps that pass between the activation of a certain point in the pattern and the required start of feeding can be viewed as the lag angle. In other cases, advance angles may also be necessary. This is easier to set when the position sensor is an absolute value sensor. The advance angle and/or lag angle are machine-specific and depend on, for example, the distance between a thread supply and feeder lever and a stitching position. For a given machine, they can be constant or dependent on settings or add-on parts. Preferably, they are stored in a data memory for machine data.

“Machine data” is, for example, a number of angular steps of the stitch cylinder or a number of other machine cycles that are executed after receiving a pattern command until the thread requirements actually change according to the pattern. Thus, the machine interpreter accesses both the pattern data memory and also the machine data memory and links these together (for example, through addition or subtraction of the advance angle or lag angle from the data of the pattern memory) and ensures that the feed wheel mechanisms are activated or deactivated at the correct point of the rotation of the needle cylinder. Instead of the access to the pattern memory, the machine interpreter can also be connected to a line that carries the pattern switching signals. Such lines are, for example, lines controlling switching elements of the knitting machine for activating or deactivating stitching positions. Thus, easily detectable control signals can be used that are used for controlling switching elements. In addition, signals of sensors that poll switching elements, needles, or other mechanical parts for executing pattern-specific actions can be used.

While activated thread feeding devices run-in sync with the needle cylinder, deactivated thread feeding devices are stationary. In addition to this switching operation, it can also be necessary to create at least temporary operating states in which the thread feeding devices are run at reduced rotational speed or also at overspeed.

For a simple embodiment, the advance and lag angles can be determined beforehand and programmed by service personnel or the machine manufacturer or the feed wheel mechanism manufacturer. However, it is also possible to provide an input interface, by means of which corresponding data, for example, screen masks, can be input. It is thus possible to test certain start and stop points relative to the rotation of the machine cylinder, and in this way to optimize the quality of the stitching to be created. It has also been found to be useful to establish positive thread feeding for jacquard circular knitting machines, wherein the thread feeding is not dependent on the current thread tension.

In addition, it is possible to provide thread tension sensors for simplifying the gathering of the machine data and to monitor the thread tension in a test operating mode as well as to activate the thread feeding devices only when tension appears in the thread. The rotational angle of the needle cylinder at which the thread tension appears can be compared to the associated pattern data. The angle differences between the pattern data and the rotational angles at which tension appears in the thread can be stored as advance angles or lag angles. After completing the test run, the thread tension sensor can be deactivated and pure positive operation can be performed with reference to the obtained data. If necessary, however, thread tension monitoring can be continuous or intermittent, e.g., in order to identify error states.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:

• Provisional Patent
• Utility Patent

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