DE9109120U1 - paper shredder - Google Patents

Description

19 042 S/ago

company

Ideal-Werk

Krug & Priester GmbH & Co. KG

Schickhardtstrasse 13-19 7460 Baiingen

paper shredder

The invention relates to a document shredder with a cutting or shredding mechanism that shreds an information carrier, such as paper or paper-like material, and an asynchronous motor that drives this cutting or shredding mechanism via a gear.

Common document shredders can be divided into two classes according to their cutting or tearing performance and speed: Firstly, document shredders that work at high speed and

smaller torque and on the other hand, document shredders, which have a large torque at lower speeds.

An earlier solution to increase the flexibility of the device was to provide a manually or automatically switchable gear between the drive motor and the cutting or tearing roller, which enabled an increased speed of the cutting or tearing rollers with reduced torque.

CH-655 866 describes a high-performance shredder of this type, which has a drive motor with two stator windings, of which the second stator winding is temporarily connected in parallel to the first stator winding by a switching device when the drive motor is overloaded. After the time-limited parallel connection has expired, the direction of rotation of the drive motor is reversed for a further limited time. In normal operation, the stator winding is connected in a delta. In the event of an overload, the stator winding connected in a delta is switched into two star windings connected in parallel. However, this is only possible for short-term operation or does not utilize the full possible performance.

The object of the invention is to enable a generic document shredder in such a way that its speed can be switched without the need for a gear box and that it enables continuous operation in all load cases and the maximum

- 6 makes full use of the available performance.

This object is achieved according to the invention in a document shredder of this type in that the asynchronous motor is a pole-changing 2/X-pole motor whose stator windings are designed in such a way that its torque increases with the number of poles.

Pole-switchable 2/X-pole asynchronous motors, in which pole switching provides a possibility for setting the speed, are known per se (e.g. in machine tool drives, in fans and pumps as well as in rolling mill drives). The stator windings of the 2/X-pole motor used in the invention are now designed in such a way that this drive motor is suitable for use in a document shredder, in which the higher number of pole pairs, which enables a lower speed, exerts a higher torque and still allows continuous operation.

The advantage is that previously common different device types can be combined in a single document shredder. This means, for example, that on the one hand a document shredder for continuous computer paper, with a small 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 operating speed can be combined in a single device.

The stator winding of the motor is designed so that

wound so that the speed-torque characteristic of the 2/X-pole motor is adapted to a specified target speed-torque characteristic by selecting the appropriate number of pole pairs and the winding parameters. A 2/X-pole asynchronous motor is any motor whose smallest number of pole pairs is one, including motors with multiple pole switching, such as 2/4/6/8-pole asynchronous motors.

The drive motor is preferably a single-phase 2/4-pole motor.

For this switching, an automatic pole switching system is provided so that the pole switching takes place automatically depending on the motor power.

In an advantageous further development, a reversing control is provided, which automatically switches the motor into reversing mode when the cutting or tearing device is blocked.

In this advantageously further developed embodiment, a motor capacitor is also provided, which is connected to the motor at least in reversing operation to increase the instantaneous torque.

Furthermore, the automatic reversing circuit advantageously switches the number of pole pairs of the motor to the maximum value during reversing operation. This ensures that the increased torque present at the maximum number of pole pairs in the reversing

- 8 sier operation comes into play.

According to a further advantageous embodiment, a transmission clutch is provided which compensates for the block shock torque of the engine.

The motor fan must be designed in such a way that it cools the motor sufficiently with a high number of pole pairs, which should be designed for continuous operation. The cooling capacity of the fan is therefore too high in two-pole operation and results in a noise level that is too high and intolerable for office equipment. This is why a pole-changing asynchronous motor with a motor fan that is directly driven by the motor shaft when operated with only one pole pair has a very loud running noise, which is mainly caused by the motor fan.

In the case of a fan that is mounted on the motor shaft and driven directly by it, the invention provides a noise insulation unit made of a special porous and air-permeable noise insulation material that is arranged around the fan, which slows down the air flow of the fan so that it is just cooled sufficiently for continuous operation when the motor is running at a lower speed and its air throughput is significantly reduced when the number of poles is low.

This advantageously reduces the noise level to an appropriate

reduced to a certain level without affecting the function of the drive motor and the fan.

Alternatively, a separately driven, quiet motor fan can be used, which runs at a constant speed and does not require an additional noise insulation unit.

In the following, the invention is described in more detail in a preferred and further embodiments. They show:

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

Fig. 2 graphically shows the same target characteristic curve and the working fields required for a computer document shredder and for a standard office document shredder;

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

Fig. 4 graphically shows the air flow rates of the fan measured for a 2/4-pole motor before and after sound insulation; and

Fig. 5 schematically shows the structure of a document shredder with the

- 10 preferred sound insulation.

Fig. 1 shows a target characteristic curve 1 for a document shredder. The target characteristic curve 1 indicates the paper feed speed v required by a document shredder in m/s, which is influenced by the motor speed, depending on the number of sheets to be shredded by the cutting or shredding mechanism, which is a measure of the required torque of the drive motor.

This target characteristic curve can be approximated, as also shown in Fig. 1, by the 2/X-pole motor provided according to the invention. This motor has a high speed and a low torque when it is operated with the smallest number of poles (2 poles). With a high number of poles, on the other hand, the motor runs slower and has an increased torque.

In Fig. 2 the same target characteristic curve 1 is shown, through which the corner points of a working field a for a computer document shredder and a working field b for an office document shredder pass.

For example, a computer document shredder manufactured by the applicant has a sheet capacity of 20 to 22 sheets at a working speed of 0.35 m/s. The motor power consumed by the asynchronous motor used as the drive motor is 0.75 kW.

Another invention previously produced by the present applicant

The office document shredder has a sheet capacity of 42 to 45 sheets at a working speed of 0.2 m/s. The motor power consumed by the drive motor is 1.0 kW.

The document shredder according to the invention combines the operating characteristics of both machines through the polarity-switchable drive motor according to the invention.

Figures 1 and 2 show that the different requirements represented by the target characteristic curve 1 with regard to the different operating conditions of a computer document shredder and an office document shredder can be achieved by a pole-changing asynchronous motor.

In the preferred embodiment, the document shredder according to the invention has an automatic pole switching system (not shown) that carries out a pole switching of the motor depending on the motor power. Furthermore, an automatic reversing switch control (also not shown) is provided that automatically switches the motor into reversing mode when the cutting or shredding mechanism is blocked. The reversing circuit can also connect an additional capacitor to the motor in reversing mode, where it needs more power after the cutting or shredding mechanism is blocked. Furthermore, the automatic reversing circuit switches the number of pole pairs of the drive motor to the maximum in reversing mode.

number of pole pairs. In reversing mode, the motor therefore runs with the highest number of pole pairs, generating the highest torque.

The additional capacitor is also switched on to increase the starting torque of the motor as much as possible and thus to achieve a flatter torque-speed characteristic curve for the motor. This means that a high number of blades can be destroyed immediately after switching on without the motor being overloaded.

When the rotor runs faster, an increased block shock torque occurs in two-pole operation of the motor. This is preferably compensated by a clutch as described in DE Patent 37 24 404.3.

Of course, in addition to the power-related automatic pole switching, which switches depending on the current consumption of the drive motor, a user can also carry out a manual pole switching on a control panel of the device.

In automatic pole-changing operation, the automatic pole-changing system switches to the next higher number of pole pairs if a current limit is exceeded in the fast-running two-pole motor. If the motor's power consumption falls below a certain level again after a specified time, the

the automatic pole switching to a lower number of pole pairs and thus to a faster speed.

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

Fig. 5 shows a preferred 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 driven directly by it, is illustrated. The noise insulation unit consists of a porous noise insulation material arranged in two parts 23 and 24, which is permeable to air*, but reduces the air flow so that it is just sufficient for continuous operation in the case of a motor with a higher number of pole pairs and is significantly reduced with a lower number of pole pairs. The first part 23 of the noise insulation unit is arranged axially in the air flow 25 sucked in by the fan in front of a fan housing 22.

see. A ring-shaped second part 24 of the noise insulation unit dampens noises that emerge radially from the fan. The air flow 25 sucked in by the fan passes through the motor and past the outside of the motor (arrows 26' and 26'') and exits again at an opening in the shredder's housing, which is provided approximately radially to the motor shaft (arrow 26). The shaft of the pole-changing asynchronous motor 21 is connected to the drive shaft of a cutting or shredding device 27 via a gear 28.

Of course, the structure in Fig. 5 is only a schematic representation of an example. Instead of arranging the fan directly on the motor shaft, it can also have a separate speed-controlled drive.

In Fig. 4, the measured air flow velocities VAir in m/s are shown for the fan and the motor 21, which was a 2/4-pole motor during the measurement, before the noise insulation (partial diagram 8) and after the noise insulation (partial diagram 8'). A dashed straight line 10 represents the air quantity sufficient for continuous operation with a four-pole connection of the drive motor.

In the measurement shown graphically in Fig. 4, the parameters were the idle speeds of 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) also delivers a sufficient amount of air for continuous operation at 1400 revolutions per minute in four-pole operation. 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, from approx. 10 m/s to approx. 7 m/s.

Claims (9)

19 042 S/ago claims 1. Document shredder with an information carrier, such as paper
or paper-like material and a cutting or shredding device which drives this cutting or shredding device via a gear
driving asynchronous motor, characterized in that the
Asynchronous motor is a pole-changing 2/X-pole motor whose
Stator windings (11-16) are designed so that its torque increases with increasing number of poles. 2. Document shredder according to claim 1, characterized in that the motor stator is designed such that the speed-torque characteristic curve of the 2/X-pole motor is adapted to a given target speed-torque characteristic curve (1) by suitable selection of the number of pole pairs and the stator winding parameters. 3. Document shredder according to claim 1 or 2, characterized in that the drive motor is a single-phase 2/4-pole motor. 4. Document shredders according to one or more of the preceding
Claims, characterized in that an automatic pole-changing for power-dependent switching of the poles of the drive motor. 5. Document shredder according to one or more of the preceding claims, characterized in that a reversing switch control is provided for switching the direction of rotation of the motor when the cutting or shredding mechanism (27) is blocked, which automatically switches to reversing operation when blocked. 6. Document shredder according to at least one of the preceding claims, characterized in that a motor capacitor is provided which is connected to the motor at least in reversing operation to increase its initial torque. 7. Document shredder according to claim 5 or 6, characterized in that the automatic reversing circuit switches the number of pole pairs in reversing operation to the maximum value of the number of pole pairs. 8. Document shredder according to one or more of the preceding claims, characterized in that a gear coupling is provided to compensate for the starting shock torque of the drive motor. 9. Document shredder according to one or more of the preceding claims, characterized in that a fan driven directly by the motor shaft and a ring-shaped fan arranged around the fan A sound insulation unit is provided which slows down the air flow of the fan so that it cools just enough for continuous operation when the motor is running at a reduced speed and its noise effect is significantly reduced when the number of poles is lower.