DE4207292C2 - paper shredder - Google Patents

Description

The invention relates to a document shredder according to the preamble of claim 1 with an informa Cutting carriers such as paper or paper-like material nernen cutting or tearing and one of these cutting or Tear mechanism via an asynchronous motor driving a gear.

Usual document shredders can be cut according to their or tear performance and speed in two classes len: on the one hand, shredders that are at high speed and work with less torque and the other shredder, which have a large torque at lower speeds.

There was an earlier solution to increase device flexibility in it, between the drive motor and the cutting or tearing roller to provide manually or automatically switchable transmission, the an increased speed of the cutting or tearing rollers at verrin enabled torque.  

From CH-655 866 A5 is a genus intended for high performance Appropriate tear mechanism known, which has a drive motor with two Has stator windings, of which the second stator winding if the drive motor is overloaded by a switching device the first stator winding temporarily connected in parallel becomes. After the limited parallel connection has expired the direction of rotation of the drive motor for another limited Reverse time. In normal operation, the stator winding is in three corner switched. In the event of an overload, the triangle is used stator winding in two star windings connected in parallel switched. However, this is only possible for short-term operation or does not exhaust the full possible performance.

From "Dubbel", paperback for mechanical engineering, 14th edition, page 1212 ff., It emerges that with asynchronous motors, the internal torque increases with an increase in the number of poles. However, such a motor is not suitable for operating a document shredder which is connected to a conventional single-phase network in an office.

It is an object of the invention, a generic file shredding ter so that he without the need for a Manual transmission in its speed is switchable and in all Load cases enables continuous operation and the maximum for ver performance exhausted.  

This task is done with a generic document shredder solved according to the invention in that the asynchronous motor is a polum switchable single-phase 2/4-pole motor with a motor capacitor which is to increase the motor at least in reverse operation its initial torque is switched on, its stator winding lungs are designed so that its torque with increasing pole number grows.

The subclaims 2-11 form the Article according to claim 1 further.

Pole-changeable 2/4-pole asynchronous motors, in which the Polum circuit forms a possibility of the speed setting are on known (e.g. in machine tool drives, in blowers and pumps as well as for rolling mill drives). The stator windings of the 2/4-pole motor used according to the invention are now so designed tet that this drive motor for use in a file ver is not suitable, in which the higher number of pole pairs, the one allows lower speed, exerts a higher torque and still allows continuous operation.

The advantage is that so far different Device types can be combined in a single document shredder can. That means e.g. B. that for a document shredder for Computer continuous forms, low number of sheets and high speed, and on the other hand a document shredder for larger numbers of sheets and thus higher torque and still sufficient Betriebsge speed can be combined in a single device.  

A motor capacitor is also provided which min at least in reverse operation to increase the current torque is switched on.

The stator winding of the motor is expediently so guaranteed kelt that the speed-torque characteristic of the 2/4-pole motor a predetermined target speed-torque characteristic by the ge appropriate choice of the number of pole pairs and the winding parameters adapted is.

Automatic pole switching is provided for pole switching that an automatic engine-dependent or load-dependent Pole switching takes place.

A pole-dependent motor load can be used to switch poles electronic signal are generated. A preferred solution ar however works with a mechanical transmission of a load dependent deformation of the engine suspension on a switching element. In the In this case, the drive motor is resilient on the drive shaft side suspended. Depending on the load caused by the tear mechanism so the drive motor has an angular displacement that over a ver Extension lever on the switching device effecting the pole changeover gan acts.

Preferably, the switching element that executes the pole changeover is equipped with switching hysteresis.  

A torque-dependent electronic engine shutdown can occur partly with the preferred electromechanical motor pole switching can be combined.

In an advantageous development, a reversing switch control provided when blocking the cutting or tearing factory automatically switches the motor to reverse operation.

Furthermore, the automatic reversing advantageously switches switching on the number of pole pairs of the motor during reversing operation the maximum value around. This ensures that at maxi Painter number of pole pairs present increased torque in the reversing urged to come to fruition.

According to a further advantageous embodiment is a transmission clutch provided that the block impact torque of the engine like.

The motor fan must be designed so that it has a high pair of poles number the motor, which should be designed for continuous operation, cools sufficiently. So the cooling performance of the fan is Two-pole operation too high and causes you to ho in office equipment high, intolerable noise level. That is why a polum switchable asynchronous motor in the case of a motor shaft directly driven motor fan when operating with only one pole some very loud running noise, which is mainly caused by the engine fan is created.  

With one sitting on the motor shaft and directly on it driven fan according to the invention is one around the fan arranged noise insulation unit made of a special porous and air-permeable noise insulation material provided, which the Airflow of the fan brakes so that it runs with the motor lower speed just enough for continuous operation cools and its air throughput at low number of poles significantly is reduced.

This advantageously turns the noise level on measured level without the function of the An drive motor and the fan is impaired.

Alternatively, a separately driven, quiet engine fan can also be used ter can be used, which runs at constant speed and kei ne extra noise insulation unit needed.

In the following the invention is in a preferred and further Embodiment described in more detail. Show it:

Fig. 1 graphically a required for a paper shredder speed-torque characteristic with a pole-changing by 2 / X asynchronous achievable values;

FIG. 2 graphically the same target characteristic and the work fields required for an EDP document shredder and for a conventional office document shredder;

Fig. 3 graphically measured with a 2/4-pole motor sound pressure level before and after sound insulation optimization;

Fig. 4 graphically measured with a 2/4-pole motor air throughputs of the fan before and after sound insulation;

Figure 5 schematically illustrates the structure of a first embodiment of a shredder with the preferred sound insulation.,

6A and 6B, a further embodiment of a shredder with electromechanical Polumschaltgliedern. and

Fig. 7 pole switching characteristics of the embodiment shown in Figs. 6A and 6B.

In Fig. 1, a target characteristic curve 1 is not shown for a Aktenver. The target characteristic curve 1 specifies the paper feed speed v in m / s required by a paper shredder, which is influenced by the motor speed, depending on the number of sheets to be torn by the cutting or tearing unit, which is a measure of the required torque of the drive motor ,

This target characteristic curve, as Darge also shows in Fig. 1, approximate by a 2 / X-pole motor. This motor has a high speed and a low torque when it is operated with the lowest number of poles (2 poles). If the number of poles is high, the motor runs more slowly and has an increased torque.

In FIG. 2, the same target characteristic is shown 1, through which the corner points of a working area a for a computerized document shredder and a working field b for an office shredder proceeds.

For example, an EDP file produced by the applicant shredders have a sheet capacity of 20 to 22 sheets with one Working speed of 0.35 m / s. The one of that as the drive motor Tor used asynchronous motor consumed engine power be carries 0.75 kW.

Another so far manufactured by the present applicant The office shredder has a sheet capacity of 42 to 45 Sheet at a working speed of 0.2 m / s. The one there motor power consumed by the drive motor is 1.0 kW.

The document shredder according to the invention combines the operational characteristics values of both machines through the pole switching according to the invention possible drive motor.

Figs. 1 and 2 show that the various requirements represented by the nominal characteristic curve 1 of the difference handy operating conditions of a computer shredder and an office shredder by a pole-changing Asyn nous motor can be achieved with respect to.

In the preferred embodiment, the Ak tenvernichter invention has an electromechanical pole switching device described below with reference to FIGS . 6A, 6B and 7, which performs a power or load-dependent pole switching of the motor. Furthermore, an automatic reversing switch control, not shown, is provided, which automatically switches the motor to the Reversierbe when the cutting or tearing mechanism is blocked. The reversing circuit can also connect an additional capacitor to the motor in reversing mode, where it needs more power after blocking, the cutting or tearing unit. Furthermore, the automatic reversing circuit in reversing mode switches the number of pole pairs of the drive motor to the maximum number of pole pairs. In reverse operation, the motor therefore runs with the highest number of pole pairs, with the highest torque being generated.

The additional capacitor is also connected to the starting torque the engine as high as possible, and thus to a flatter torque-speed characteristic of the engine to come. The means that one immediately after switching on can shred large numbers of sheets without overloading the motor becomes.

When the rotor is running faster, the two-pole operation creates the Motors a higher block impact torque. This is preferred by compensated a clutch, as be DE 37 24 404 C2 writes.

Of course, in addition to the service or bela Depending on the position, automatic pole switching, a user also perform a manual pole switching on a control panel of the device ren.

A possible embodiment of a purely electronic automati The pole changeover switches when a current is exceeded limits a high-speed two-pole motor automatically the next highest number of pole pairs. If the power consumption of the Motors again below a certain time after a predetermined time Level, the automatic pole switching switches to a lower pole number of pairs and therefore faster speed.

The pole-changing drive motor, which runs in two-pole operation, has a very loud running noise, which cannot be tolerated in office equipment because the fan driven directly by the motor shaft then runs too fast. In Fig. 3 measured values of the sound pressure level for a drive motor in each case in the two-and four-Polbetrieb Polbetrieb are displayed graphically. The partial diagram 7 shows the measured values without additional noise insulation. The dashed straight line 9 indicates a desired sound pressure level Lp to be achieved by the noise insulation at 60 dB. The partial diagram 7 'shows that after noise insulation has been achieved, the sound pressure level sought is achieved with good approximation.

Fig. 5 shows schematically a first embodiment 20 of a document shredder according to the invention. In particular, the arrangement of the noise insulation unit around the fan which is seated on the motor shaft and is driven directly by it is illustrated. The Ge räusdämmeinheit consists of a two parts 23 and 24 of ordered porous noise insulation material, which is permeable to air, but reduces the air flow so that it is just designed enough for continuous operation in the engine with a higher number of pole pairs and is significantly reduced at a low number of pole pairs. The first part 23 of the noise insulation unit is seen axially in the air flow 25 sucked in by the fan in front of a fan housing 22 .

A ring-shaped second part 24 of the noise insulation unit insulates noises radially emerging from the fan. The air flow 25 drawn in by the fan sweeps through the motor and past the outside of the motor (arrows 26 'and 26 ") and exits again at a housing opening of the document shredder which is provided approximately radially to the motor shaft (arrow 26 ). The shaft of the pole-changing Asyn chronmotors 21 is connected via a gear 28 to the drive shaft egg nes cutting or tearing mechanism 27 .

Instead of placing the fan directly on the motor shaft, it can also have a separate drive that is also speed-controlled can run.

In FIG. 4, for the fan and the motor 21, which was a 2/4-Polmotor in the measurement, measured Luftdurchsatzgeschwindig speeds Vair in m / s in each case before the noise reduction (Part Diagram 8) and after the noise reduction (partial diagram 8 ') shown. A dashed line 10 represents the amount of air required for continuous operation with four-pole switching of the drive motor.

In the measurement shown graphically in FIG. 4, the parameters were the idle speeds 2800 revolutions per minute for the two-pole circuit, and 1400 revolutions per minute for the four-pole circuit. The partial diagram 8 'shows that the fan after the noise insulation by the noise insulation unit 23 , 24 ( Fig. 5) even in four-pole operation at 1400 revolutions per minute promotes a sufficient amount of air for continuous operation with a throughput speed of about 3 m / s , The partial diagram 8 'also shows, in comparison with the partial diagram 8 in FIG. 4, that the air throughput in two-pole operation is significantly reduced by the use of the noise insulation unit 23 , 24 compared to operation without the noise insulation unit, of approximately 10 m / s to about 7 m / s.

A preferred electromechanical pole-changing device will now be described with reference to FIGS. 6A, 6B and 7.

FIG. 6A shows a plan view, comparable to FIG. 5, of a preferred embodiment 30 of the file shredder. The drive motor 31 drives a tear mechanism 37 via its drive shaft 32 and a chain gear 38 . The Antriebsmo gate 31 is resiliently suspended on the machine base or machine housing by means of a mounting plate 39 . The drive motor he drives depending on the load of the tearing mechanism 37 from an elastic steering from its basic position and then takes for example the position shown by a dash-dotted line. This load-dependent deflection of the drive motor 31 is transmitted to a pole changeover switch 34 via an extension lever 35 and a switching arm 33 .

FIG. 6B shows the drive motor 31 , the extension lever 35 , the switching arm 33 and the pole changer 34 in the direction of the arrow B in FIG. 6A.

The switching arm 33 and the pole changeover switch 34 are preferably designed in such a way that a switching hysteresis H is achieved, which is shown in FIG. 7. Fig. 7 shows, for example, characteristic curves, which switches the function of the electromechanical pole switching according to FIGS. 6A and 6B when switching from two poles to four poles and vice versa depending on the load on the tear mechanism. The abscissa represents the motor poles and the ordinate the number of sheets drawn into the tearing mechanism. From FIG. 7 it can be seen that switching hysteresis H causes the drive motor to switch from two-pole to four-pole operation when 30 sheets are torn. Conversely, the motor only returns to two-pole operation when there are 20 blades. Advantageously, the switching hysteresis H ensures that motor vibrations do not cause the pole switches to flutter.

In order to transmit the respective load from the tearing mechanism 37 to the drive motor 31 with a larger lever arm, so that this is deflected clearly from its rest position, a drive chain 38 is preferably used ( FIG. 6A).

Claims (11)

1. Document shredder with a cutting or tearing mechanism that shreds information media such as paper or paper-like material and a asynchronous motor that drives it via a gear, characterized in that the asynchronous motor is a single-phase, 2/4-pole motor with a motor capacitor, which the motor is switched on at least in reversing mode to increase its initial torque, the stator windings ( 11 , 16 ) are designed so that its torque increases with an increasing number of poles. 2. Document shredder according to claim 1, characterized in that the motor stand is designed so that the speed-torque characteristic of the 2/4-pole motor to a given target speed-torque characteristic curve ( 1 ) adapted by suitable choice of the number of pole pairs and the stator winding parameters is. 3. Document shredder according to one or more of the preceding Claims, characterized in that an automatic pole changeover for power-dependent switching of the poles of the drive motor is provided.   4. Document shredder according to one or more of the preceding claims, characterized in that the drive motor ( 31 ) on the side of its output shaft ( 32 ) is resiliently suspended and on the output shaft ( 32 ) opposite side is unsecured, and that one on a switching element ( 34 ) acting extension lever in extension of the motor longitudinal axis on the motor housing on the side of the motor ( 31 ) facing away from the motor shaft ( 32 ), the switching element ( 34 ) depending on the load acting on the drive motor ( 31 ), which is an elastic , De deformation of the engine suspension causes, the poles of the drive motor ( 31 ) switches. 5. Document shredder according to claim 4, characterized in that a switching element ( 34 ) with switching hysteresis is provided. 6. Document shredder according to one or more of the preceding Claims, characterized in that one depends on the torque existing electronic engine shutdown is provided. 7. Document shredder according to one or more of the preceding claims, characterized in that a Reversierschaltsteue tion for switching the motor direction of rotation when blocking the cutting or tearing mechanism ( 27 ) is provided, which automatically switches to the reversing mode when blocking. 8. Document shredder according to at least one of the preceding An sayings, characterized in that the automatic reversing switching the number of pole pairs in reverse operation to maximum value the number of pole pairs switches. 9. Document shredder according to one or more of the preceding Claims, characterized in that a gear coupling for Compensation of the starting torque of the drive motor is provided is. 10. Document shredder according to one or more of the preceding Claims, characterized in that one of the motor shaft di right driven fan and a ring around the fan Orderly noise insulation unit are provided, the air flow of the fan brakes so that it reduces the motor operation Speed just enough for continuous operation and its cools Noise effect at a lower number of poles is significantly reduced. 11. Document shredder according to one or more of claims 1 to 9, characterized in that an independent of the motor shaft hanging external fan is provided for ventilation of the drive motor is.