This application claims the priority of German Patent Document 100 14 366.0, filed Mar. 20, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a yarn cutting device for mechanical looms having a first blade carrier with an end-side blade and a second blade carrier with an end-side blade, at least one of said blade carriers being in an operative connection with a drive in order to carry out a yarn cutting function between the blades.
In the case of mechanical looms, the woof yarn is withdrawn from supply coils, is fed to a woof element and is fed by the latter into the shed. In the area of the selvages, special yarn cutting devices are provided which cut off the woof yarn withdrawn from the supply coil, fed into the shed and looped by hand to the selvage. Yarn cutting devices are also used for cutting off yarn projections on the selvages. For example, scissors are used as woof yarn cutting devices which are arranged close to the selvage. Scissors are known which are driven directly mechanically by the mechanical loom as well as those which are operated by a separate electric-motor drive or a pneumatic drive.
In German Patent Document DE-PS 37 03 638, a woof yarn cutting device is disclosed with a stationary scissors part and a scissors part movable by an eccentric arrangement, the eccentric arrangement being coupled with the main drive of the mechanical loom and being operated by the latter.
From German Patent Document DE 40 00 856 A1, a yarn cutting device is known for cutting off the fed woof yarn in the case of mechanical looms, which is mechanically coupled by way of a cam mechanism or the like also with the main drive of the mechanical loom. The yarn cutting device operates synchronously with respect to the loom rhythm. The point in time of the cutting operation is therefore firmly defined with respect to the weaving cycle and cannot be changed or can be changed only by major mechanical modifications.
A significantly more flexible cutting device for woof yarns is known from European Patent Document EP 0 284 766 B1. This cutting device has a drive which is independent of the main drive, so that the point in time of the cutting operation with respect to the weaving cycle can be arbitrarily defined by means of a programmable control. The drive consists of a stepping motor on whose shaft the movable blade is fastened, the stepping motor being driven in an oscillating manner in both rotating directions. However, the oscillating drive has the disadvantage that the stepping motor is subjected to high stress and high wear by continuous acceleration and braking operations. Furthermore, the cutting device is not monitored with respect to the operation or with respect to damage.
In German Patent Document DE 197 13 089 A1, similar yarn scissors are disclosed driven by a stepping motor in mechanical looms, in which case, however, the stepping motor is not driven in an oscillating manner but permanently in one rotating direction. This reduces the wear and the stress of the motor in comparison to the cutting device according to European Patent Document EP 0 284 766.
Disadvantages of the above-mentioned constructions of cutting devices with the above-mentioned drives are, for example, the high space requirement and the fact that the devices for the mechanical power transmission to the at least one shears part are subjected to relatively high wear.
An object of the present invention is to provide a yarn cutting device for mechanical looms which operates with relatively little wear while the space requirements are low.
According to the invention, this object is achieved by a yarn cutting device for mechanical looms having a first blade carrier with an end-side blade and a second blade carrier with an end-side blade, at least one of said blade carriers being in an operative connection with a drive in order to carry out a yarn cutting function between the blades, wherein the drive is constructed as an electrically energized linear motor.
The invention provides that the drive of the yarn cutting device is constructed as an electrically energized linear motor.
According to the invention, a compact flat construction of the yarn cutting device is achieved with reduced friction, a small play and a favorable pivot position of the blade carriers. Another advantage is the high starting thrust of linear motors which reaches it maximal value immediately after the switching-on of the motor.
Preferred embodiments and further developments of the invention are indicated in the dependent claims.
In a preferred embodiment according to the invention, it is provided that one of the blades is arranged on a blade carrier which is stationary with respect to the mounting surface of the yarn cutting device but can preferably be adjusted in its position.
In another advantageous embodiment of the invention, it is provided that at least one of the blades is arranged on a linearly movable blade carrier which can be operated by the linear motor. The blade of this linearly moved blade carrier is moved with respect to the blade of the other, preferably fixedly arranged blade carrier between an open position and a closed position. In this case, the moving direction of the moved blade carrier, thus the dynamic effect of the linear motor, coincides approximately with the longitudinal axis of the blade carrier.
In another embodiment of the invention, at least one of the blades is arranged on a blade carrier rotatably disposed in a pivot, the rotatably disposed blade carrier being movable by the linear motor. The moving direction of the rotatable blade carrier, thus, the dynamic effect of the linear motor, is directed essentially perpendicularly to the longitudinal axis of the blade carrier.
It can also be provided that both blade carriers of the yarn cutting device are linearly movable with respect to one another by one linear motor respectively.
In another embodiment, both blade carriers can be disposed in one pivot and can be moved by one linear motor respectively.
As a further development of the invention, it is provided that, for monitoring the position of at least one of the blades or blade carriers, the yarn cutting device is equipped with a path measuring system. For this purpose, the path measuring system may be integrated in the linear motor or may be coupled directly with the movable blade carrier or carriers.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.