Electromagnetic Cutting Device With Change-over Switch

Abstract

Cutting device for thread, rope, wire and the like actuated electromagnetically with means for holding an end of the material to be cut during and after cutting, the cutting movement being automatically repeated if the material is not cut through completely on the previous movement.

Description

The present invention relates to a cutting device for thread, rope or wire and the like, and includes a cutter which is actuated by the armature of an electromagnet or solenoid.

In order to effect reliable and precise cutting of textile threads, ropes or wires, for example, apparatuses are known in which two cutting edges which are moved towards each other in the manner of scissors, and in which the material remaining after the cut, is caught or pinched fast by a special device separate from the cutting device.

In a further known cutting apparatus, a bank of knives rigidly fixed on the armature of an electromagnet and which has a passage for the material to be cut arranged within the cutter, is lead horizontally and with a traction movement against a cutting edge which is horizontally stationary, together with the passing material to be cut. The cutter is thus vertically pressed against the surface of the knife bank by a pressure spring acting from above so that, as the length of the path of movement of the knife bank increases until it meets with the cutting edge of the cutter, the pressure of the cutter against the knife bank also increases so that the pressure is at its maximum when cutting is effected.

The disadvantage of this apparatus consists in that, under certain circumstances, the knife bank may draw the material to be cut out of its normal running path so that it forms an angle with the cutting and knife edges, whereby, instead of cutting the material, it may pinch the latter between the cutter and knife edges. Furthermore, because of defects such as knots, differences in diameter and so on, which occur in the material to be cut, it may not be possible to advance the same uniformly between the knife bank and the cutter edge because the cutter edge is lifted from the knife, and this may also lead to pinching of the material to be cut.

In another known apparatus, the separation of the threads is effected by the armature of a solenoid by centrally attracting the armature which can be swiveled about one end thereof, whereby a cutter fixed on the other end of the armature strikes a conical anvil with a cutting edge, a thread being led over the anvil by means of a thread leading groove. The cutter is situated on one arm of a U-shaped device on the other arm of which is provided a thread pinching device, which, acting simultaneously with the cutter, fixes the thread on a further anvil. After termination of the cutting step, the cutter is lifted away from the anvil together with the thread pincher by a retraction spring arranged above the swivel center of the armature.

This apparatus also presents the disadvantage that, by hammerlike advancing of the cutter as well as by the cutting faces gliding past each other in an oblique plane, respectively, pinching of the material to be cut may also occur within a wedge-shaped groove of the anvil. Moreover, with continuously moving armatures, there is the danger of armature vibration which is caused by the traction spring as well as by saturation of the magnetic field, being transferred to the cutter. Furthermore, in continuous armature movement, much of the cutting force is absorbed by the preceding friction between cutter and knife bank, so that the remaining cutting force of the armature is reduced for the actual cutting operation.

I have conceived by my present invention, a cutting device which eliminates the foregoing difficulties and disadvantages by means of a cutting device which is actuated electromagnetically, the cutting movement being automatically repeated, should the material not have been cut through completely.

Accordingly, I provide a cutting device for thread, rope, wire or the like, with a cutter actuatable by the armature of an electromagnet, comprising: a slidable and swivellable cutter which, at a free extremity, cooperates with a coupling part rigidly connected with the armature, and which cooperates at its other end with a fixed knife. I further provide a retraction spring for applying a force between the sliding cutter and the stationary knife, as well as for applying a retractive force on the knife and on the armature.

As a further feature of my invention, I provide means for pinching the material to be cut just prior to the cutting and for retaining an end of the material in that condition as long as desired after cutting occurs. Such means may include a member which shifts with the cutter but which precedes it during the protraction excursion; and a pad against which such member presses the material to be cut just prior to the actual cutting.

Another feature of the invention resides in the provision of a resistance which is normally bridged by the solenoid induction coil circuit; but which can be placed in series with the coil by a switch in the bridging circuit. The various parts are so arranged that bridging is interrupted just prior to completion of the protraction excursion wherefor pinching and holding of the material is effected only by a holding current. However, if the material is not cut on the first protraction, its thickness causes an airgap between the coil and core of the solenoid, and this gap, together with the low holding current and the retraction spring, return the cutter to its starting position from which it again strikes at the material and continues to do so until cutting is achieved after which it remains protracted to hold the material end.

Further specific features and advantages of the invention will be hereinafter more fully set forth with reference to the annexed drawings, showing a presently preferred embodiment of the invention and certain modifications thereof, in which:

FIG. 1 is a side elevational view of the apparatus of the present invention in its normal at rest position;

FIG. 2 is a plan view of a part of the cutting device in normal position;

FIG. 3 is a view similar to that of FIG. 1, but showing the apparatus in cutting position;

FIG. 4 is a plan view similar to that of FIG. 2, but showing the cutting device in cutting position; and

FIG. 5 is a circuit diagram of the electrical system.

The cutting device shown in FIGS. 1 and 2 consists of a housing 1 in which a pot magnet 2 and tubular coil 3 are arranged. An armature 4 with a conical attraction surface 5 in which a pin 6 is fixed by means of screws is positioned for axial movement in the coil recess. The enlarged end 7 of the pin 6 has a central opening 8 for vertically swivellable arrangement therein of a cutter 9, and of a pinching member 10 which is rigidly fixed on the upper face of the cutter 9. The cutter 9 is drawn against a knife 14 by a retraction spring 11 which, by one of its extremities, is attached to a hook 12 provided on the housing 1. During advancing of the armature 4 and, therefore, of the cutter 9 when the coil is energized, the pressure against the knife bank 13 and the knife 14 provided thereon is increased as the knife comes forward due to the effect of the spring 11. On one side, the knife 14 is provided with an opening 15 for passage of the material 16 to be cut. During the cutting procedure, the member 10 for pinching the material to be cut, and which slightly protrudes over the cutting edge of the cutter 9, presses the material 16 to be cut against an elastic pad 17 which is fixed on the rear wall 19 of the housing, and there maintains the material 16 to be cut in position.

After cutting has been effected, the cutter 9, together with the member 10, is maintained in the cutting position by the armature 4 and the pin 6 as shown in FIGS. 3 and 4, this condition being maintained as long as the current circuit is closed.

After reinserting the material 16, the cutter 9 and member 10 may be returned to normal position by interrupting the current circuit.

The protractive movement of the armature 4 together with the pin 6 and the cutter 9 together with the material pinching member 10 is effected as follows:

On the free end of armature 4, a metal ring 26 is provided with an insulating ring 27 lining the inner surface thereof. In its normal position, the contact point of a switching contact 25 is in contact with the metal ring 26, so that the resistance 24 in the current supply line for the coil 3 is coil However, in a certain position of the armature 4 within the coil 3, contact point of the switch contact 25 comes into contact with the insulating ring 27, wherefor the bridging of the resistance 24 is interrupted, and the coil 3 is connected in series with the resistance 24. In this circumstance, only a relatively small holding current flows through the coil 3, and the armature 4 is, therefore, during the last portion of its protractive excursion, moved only by the holding current and its mass acceleration.

The advantage of the above lies in the fact that the armature 4, with the cutter 9 and the member 10, is maintained in protracted position by only a very slight holding current, while the cut material is pinched between the member 10 and pad 17 until the current circuit is completely interrupted by the switch 28 (FIG. 5).

When a very thick or very hard material is to be cut, the holding current is not sufficient to hold the armature 4 with the cutter 9 and the member 10 in the cutting position of FIGS. 3 and 4 because of the remaining airgap between the armature 4 and core cap 20. Accordingly, the armature 4 is retracted into its original position (FIGS. 1 and 2) by the spring 11, and the resistance 24 connected in series with the coil 3 is again bridged by the switch contact 25, wherefor full current flows again in coil 3, whereby the cutting procedure is automatically repeated until the material is completely cut through.

From the foregoing description, it will be seen that an essential advantage of the cutting device of the present invention consists in that the cut may be effected in all positions of the thread; that, by a series circuit of the induction coil with a resistance, an undesirable heating of the coil is prevented; and that, when a thick or hard material is incompletely cut, the cutting is automatically repeated until the material is completely cut through.

I believe that the construction and operation of my contribution will now be fully understood, and that its advantages will be appreciated by those persons skilled in the art.

Claims

I claim:

1. Cutting apparatus for thread, rope and wirelike material with a cutter actuated by the armature of an electromagnet, characterized by a cutter having a free extremity, a coupling member rigidly connected to said armature, means for mounting said cutter on said coupling member for horizontal sliding movement and for vertical swiveling movement, a fixed knife cooperating with said cutter to cut material when said cutter is advanced, and a traction spring attached to the cutter for exerting pressure between said cutter and the rigid knife, as well as a retracting force acting on the cutter and the armature.

2. Cutting apparatus for thread, rope and wirelike material with a cutter actuated by the armature of an electromagnet, characterized by a cutter having a free extremity, a coupling member rigidly connected to said armature, means for mounting said cutter on said coupling member for sliding movement in one direction and for swiveling movement, a fixed knife cooperating with said cutter to cut material when said cutter is advanced, and a traction spring attached to the cutter for exerting pressure between said cutter and the rigid knife, as well as a retracting force acting on the cutter and the armature, a material pinching means comprising a member rigidly connected with the cutter for moving therewith, and a pad fixed opposite the end of said member and against which pad the member presses the cut material after cutting has been effected.

3. Cutting apparatus for thread, rope and wirelike material with a cutter actuated by the armature of an electromagnet, characterized by a cutter having a free extremity, a coupling member rigidly connected to said armature, means for mounting said cutter on said coupling member for sliding movement in one direction and for swiveling movement, a fixed knife cooperating with said cutter to cut material when said cutter is advanced, and a traction spring attached to the cutter for exerting pressure between said cutter and the rigid knife, as well as a retracting force acting on the cutter and the armature, contact means arranged at one end of the armature and comprising a conductive member and an insulating member for actuating a switch member to effect a series connection of the induction coil of the electromagnet with a resistance before the armature reaches the full limit of its protrative excursion.

4. Cutting apparatus according to claim 3, characterized in that the induction coil, the armature and the traction spring are so selected that, when the coil is connected in series with said resistance, a current flows in the coil which, when the material to be cut has been separated completely, is just sufficient to hold fast the armature and the cutter in close contact with the magnet core whereas, if the material has not been cut through completely, the current is not sufficient because of the airgap existing due to the thickness of the uncut material between the armature and the core, wherefore the armature and the cutter are retracted into their original position by the spring and a repetition of the cutting movement occurs.

5. Cutting apparatus according to claim 1, characterized by a ring-shaped knife opened to one side which is arranged to cooperate with the moveable cutter.