DE29505149U1 - Filter cleaning in vacuum cleaners - Google Patents

Description

Filter cleaning for vacuum cleaners

Description State of the art:

Industrial vacuum cleaners or similar vacuum cleaners for home and hobby use use paper filters or filters made of fiber material or foam. These must be removed for cleaning. Depending on the material being vacuumed, shaking or brushing produces dust emissions that are more or less unpleasant or harmful to health. Filters are used depending on the different areas of application of vacuum cleaners. The particle size and consistency of the material being vacuumed are crucial. The shape of the filters is designed to have the largest possible surface area in order to keep flow losses to a minimum.
Problem:

The suction material can get stuck on the surface of the filter. This is especially true for fine dust from plaster, concrete, etc. The suction material clogs the filter. The suction power is reduced to an unusable level within a short period of use (1-5 minutes). To avoid this phenomenon, the device presented in the protection claims is described in more detail.
The filters in high-quality industrial vacuum cleaners are currently vibrated for cleaning. Put simply, the filter or a combination of several filters is shaken when installed so that the accumulation of vacuumed material falls back from the surface of the filter into the collection container.

This shaking movement is currently generated by an electromagnetic coil which is operated with mains voltage. The oscillation corresponds to the mains frequency of 50 Hz or corresponding harmonics. The coil is mechanically firmly connected to the filter and flexibly mounted in relation to the rest of the device.

The cleaning system therefore consists of an electrical switch which connects the coil to the power supply, the coil itself and the oscillating system - consisting of the coil, filter and spring-loaded suspension of the filter.

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Filter cleaning for vacuum cleaners

Solution:

To create a cleaning effect for the filters in vacuum cleaners, the filter is also set into vibration. In contrast to existing systems, this vibration is not achieved with a mains-powered coil, which only vibrates at a constant frequency (50 Hz), that of the alternating current network.

An eccentric disk is also mounted on the motor shaft or a flexibly mounted shaft, which rotates the fan wheel to suck in the air and the suction material. This therefore rotates at the same speed as the motor.

The eccentric disc creates an imbalance at speeds below a defined range (speed < RPM2). This range is below the smallest nominal speed. The smallest nominal speed is the speed of the fan wheel, which is required for suction operation or can be set to a minimum in speed-controlled motors. The imbalance is caused by a radially movable mass that is pressed by a spring towards the center of the axis (Figure 3: Pos.P1). Below the smallest nominal speed, the mass distribution is uneven in relation to the axis of rotation, the eccentric disc and the balancing mass Figure 3 Pos.7, which is also mounted on the eccentric disc. The eccentric disc is unbalanced.

If the eccentric disk is rotated, the spring and centrifugal force counteract the eccentric mass. The masses (spring and eccentric mass) and the spring force are dimensioned in such a way that the spring force is greater than the centrifugal force below the lowest nominal speed.

If the lowest nominal speed is exceeded, the centrifugal force is greater than the spring force. The eccentric mass is then pressed against the stop P2 (Figure 3: Pos.P2). The stop P2 (Figure 3 Pos.5) is adjusted in such a way that at these speeds the eccentric mass and balancing mass produce an even mass distribution of the eccentric disk. The eccentric disk is now balanced.

This means that the vacuum cleaner will operate at all speeds of its motor above the lowest rated speed (+ tolerances) with a centered

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Filter cleaning for vacuum cleaners

Eccentric disc operated. The vacuum cleaner has no disturbing vibrations in normal operation (suction mode).

The cleaning effect therefore only occurs at low engine speeds (below the lowest rated speed).

This means that when the vacuum cleaner motor is started and switched off, the effect of the vibration excitation occurs through the eccentric disc and thus the filter cleaning is activated.

The time it takes for the vacuum cleaner motor to start up is short. This time should therefore be extended for filter cleaning. For speed-controlled or regulated motors (or other motor start-up delays (NTC resistors, etc.)), the stay time below the lowest rated speed can be extended. This means that the filter is exposed to the "cleaning" vibrations for longer. For uncontrolled vacuum cleaner motors, the duration of the vibration cleaning can also be extended by slowing down the movement of the eccentric mass between the stops P1 and P2 when the speed increases or decreases (when the motor is switched on/off) using a fluid (air, water, oil...). This means that the radial movement of the eccentric mass is slowed down by a fluid. This means that when the motor starts up, the eccentric mass remains between the stops P1 and P2 for a period that depends on the damping of the movement of the eccentric mass and is therefore unbalanced even at speeds above the lowest rated speed. This improves the effect of the filter cleaning. However, the stress due to the higher motor speed, the greater amplitude and frequency reached up to that point must be taken into account in the design.

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Filter cleaning for vacuum cleaners

Benefits achieved:

The eccentric disc can be mounted on the fan wheel or integrated into the structure.

The high-speed rotating fan wheel can be balanced together by adjusting the eccentric mass in a structural design according to claim 5, in which the eccentric disk and the fan wheel are combined to form one component.

If the speed changes (acceleration or deceleration of the motor) below the lowest nominal speed of the eccentric disk, the system or parts of the system are caused to vibrate at several frequencies (so-called frequency band). The filter as a whole is caused to vibrate due to the flexible suspension. Furthermore, the filter vibrates in such a way that parts of the filter and the suction material adhering to the surface are each subject to a separate shape-changing vibration. These respective resonance frequencies or partial resonance frequencies or their harmonics with corresponding node points depend on the mass and the specific spring constant of the filter and also of the suction material. The filter and suction material therefore do not have the same vibration or resonance behavior. The force caused by the mass inertia of the filter and suction material breaks the adhesive force of the suction material. The suction material is virtually blown off. Ultrasonic cleaning is comparable to this.

As is well known, this results in the effect of significantly larger amplitudes and thus a much stronger vibration and associated cleaning effect. This means that the spring-mass system, consisting of filter, eccentric disk and spring bearing, oscillates at frequencies or their frequencies proportional to the engine speed. The design of the spring-mass system is therefore optimal when the system or when many of the dirty parts of the system oscillate at their own resonance frequencies.

The suction material that clogs the filter by depositing on the surface is essentially shaken off. This means that the filter becomes permeable again and the suction power is restored.

In contrast to the previous cleaning process with a frequency (coil with mains frequency), it can now be ensured that the filter and parts of the filter are excited to oscillate.

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Filter cleaning for vacuum cleaners

the filter vibrates as part of the system, as do parts of the filter with the adhering suction material.

Since the mass (filter, quantity and density of the suction material) and the spring constant of the filter, as well as the ductile connection of the adhering suction material and the filter, are not constant, the exciting vibration must also vary in frequency and amplitude for an optimal cleaning result. This is made possible by the variable speed and thus vibration excitation.

The above can ideally be used to roughly determine the frequencies using the simple physical principle:

&ohgr;.. angular frequency

ω = \ c / m c. Spring constant m .. mass

The flexible mechanical suspension of the components serves as a spring system. It decouples the elements that are excited to vibrate and the housing of the vacuum cleaner. The spring suspension must have vibration-damping (absorbing) properties through the appropriate choice of material so that the oscillating system is limited in its amplitude and the duration of the vibration (aperiodic).

This property also serves to reduce the transmission of the structure-borne noise of the motor and the suction noise to the housing and the surroundings of the vacuum cleaner (protection claim point 4).

Due to its simple design, the eccentric disc can be manufactured as a plastic injection-molded part and is therefore more cost-effective than a solution using an electromagnetic coil as a vibration exciter.

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Filter cleaning for vacuum cleaners

Description and design of several embodiments:

Conceptually, there are two possible implementation options:

The choice depends on the design, size and intended use of the vacuum cleaner and the intended suction material.

1. Example

The motor, fan wheel, eccentric disc and filter with filter holder are mechanically rigidly connected to one another and flexibly connected to the rest of the vacuum cleaner housing. The motor, fan wheel, eccentric disc and filter with filter holder are exposed to the vibrations caused by the rotating eccentric disc. At speeds below the lowest rated speed, the eccentric disc generates a bending moment on the flexible bearing 4 in Figure 1 due to its imbalance and the distance from the flexible holder. This creates a wobbling movement around point Y in Figure 1.

2. Example

The eccentric disc and the filter with filter holder are connected to each other rigidly but rotatably by the pivot bearing (item 3 in Figure 2). They form the oscillating system, together with a flexible connection (item 4 in Figure 2) (holder) to the other components of the vacuum cleaner. The eccentric disc is driven by the motor of the vacuum cleaner via a flexible connection (item 11 in Figure 2) (rubber sleeve or spring steel coil).

The knurled nut 8 is used to fasten the filter and to press it onto the seal. The seal and the flexible suspension of the filter are shown as one part in Figure 2

In the first version, the entire unit is exposed to the oscillating movements. This requires more complex bearings and a more stable design of the motor and the fan wheel.

The second version with a separate vibration unit is more complex in terms of construction and costs, but can be designed to be more effective and durable for vacuum cleaners with large filters and powerful motors, since fewer components are exposed to vibration loads.

Destruction of the filter and the other parts due to excessive vibration loads, especially in the case of resonance, must be prevented

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Filter cleaning for vacuum cleaners

The resonance amplitude must be limited by appropriate choice of materials and design measures.

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Filter cleaning for vacuum cleaners

Explanations for Figure 3:

P1 .. Position of the eccentric mass at standstill or low speed P2 .. Position of the eccentric mass below the nominal speed

1 ... Guide of the eccentric mass

2 ... Motor or eccentric axis 3... Spring

4 ... eccentric mass (e.g. ball)

5 ... End stop possibly with adjustment

6 ... Mounting opening for eccentric mass 7... Mass balance

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Filter cleaning for vacuum cleaners

Explanations for Figure 1:

1 .. Eccentric disc

2 .. Engine

3 ,. Engine mount

4 .. Damping element (flexible bracket)

5 .. Air outlet

6 .. Container
7.. Filter

8 .. Knurled screw

9 .. Engine cover

10 .Fan wheel

12 .Suction opening for suction material

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Filter cleaning for vacuum cleaners

Explanations for Figure 2:

1 .. Eccentric disc

2 .. Engine

3 .. Pivot bearing for eccentric shaft

4 .. Damping element (flexible bracket)

5 .. Air outlet

6 .. Container

7 .. Filter

8 .. Knurled screw

9 .. Engine cover

10 .Fan wheel

11 .flexible shaft connection (sleeve)

12 .Suction opening for suction material

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Claims (1)

Filter cleaning for vacuum cleaners Eccentric disc S1 for generating a variable imbalance to stimulate an oscillating system, consisting of a motor, fan wheel, filter, spring/damping element and suspension or housing, which is used to clean vacuum cleaner filters (filters of industrial vacuum cleaners), characterized, that the imbalance is generated by the masses M1 and M2, whereby mass M1 is mounted on the disk S1 in a movable manner and the displacement of the mass in the radial direction is possible or in a direction with the same effect, so that the masses rotate with the disk. Mass M2 is fixedly mounted on the disk S1. The mass M1 on the disk S1, according to claim 1, is pressed on its displacement path by a spring F1 in the direction of the center of the rotation axis of the disk S1. The path by which the mass M1, according to claim 1, can be displaced, is limited by two stops (inner stop P1 and outer stop P2), which are located at different distances from the axis of rotation of the disk S1, according to claim 1. The eccentric disc according to claims 1 to 4 and 7 is driven in its rotational movement by the motor, which also drives the fan wheel. The fan wheel and eccentric disk according to claims 1 to 4 can be structurally combined into one component. 30.07.1995 295 05 149.3 Harald Reibnagel Page 1/17 Filter cleaning for vacuum cleaners When the eccentric disk rotates, the centrifugal force of the mass M1 is opposite to the spring force, according to claim 2, so that at a speed of the disk (and thus of the masses), according to claim 1, below a speed RPM1, the spring force is greater than the centrifugal force. The mass M1 remains in position P1 according to claim 3. If the speed is between RPM1 and RPM2, where RPM2 is greater than RPM1, the mass on the disk moves according to claim 1, between the stops P1 and P2 according to claim 3. At a speed equal to RPM2, the mass reaches the stop P2 according to claim 3. This speed RPM2 is the lowest speed (lower nominal speed) at which suction operation is still possible The mass remains in position P2 even if the speed is greater than RPM2 The mass M2 is mounted on the eccentric disk according to claims 1 to 3 or is structurally integrated. The mass M2 is designed in its shape, position and partial, radial mass distribution such that it acts as a balancing mass for the displaceable mass M1 of the eccentric disk S1 as soon as the disk S1 rotates about the axis of rotation at a speed equal to or greater than RPM2 (mass M1 at position P2 according to claim 3), whereby the eccentric disk balances to its axis of rotation. The imbalance which arises when the eccentric disk rotates below the speed RPM2, according to claim 7, causes the spring-mass system according to claim 1 to oscillate in accordance with the embodiments described below. The spring-mass system can be constructed in the following versions: The motor, fan wheel, filter and eccentric disc form a rigid mass system that is coupled to the housing via a system consisting of spring and damping elements. The filter and eccentric disc form a rigid mass system that is connected to the engine via a system consisting of spring and damping elements. 30.07.1995 295 05 149.3 Harald Reibnagel Page 2/17 Filter cleaning for vacuum cleaners fan wheel and the housing. The eccentric disc S1 is driven by a flexible shaft. The fan wheel, filter and eccentric disc form a rigid mass system, which is coupled to the motor and the housing via a system consisting of spring and damping elements. The eccentric disc S1 is driven by a flexible shaft. The eccentric disk according to claims 1 to 8 stimulates the system to produce (periodic-aperiodic) oscillations or resonances superimposed on the rotary movement. The vibrations, according to the requirements of claim 7, are proportional to the speed of the eccentric disk, according to claims 1 to 7, or to the speed of the motor driving the eccentric disk. By varying the speed of the eccentric disc, the system is excited to oscillations and partial oscillations in the frequencies, frequency bands, harmonics of the frequencies and resonances corresponding to the speed, or parts of the system, and in particular the filter with the suction material. The speed or speed range of the motor driving the eccentric disc is chosen specifically to stimulate the type of vibration (see above) so that the optimum cleaning effect of the filter is achieved. According to claims 6, 8 and 10, the filter or parts of the filter and the adhering suction material oscillate in such a way that the suction material, depending on its nature (mass, structure, adhesiveness, etc.), is partially or completely detached from the filter. The function according to claims 10 and 11 is caused by the change in speed during switching on/off or the acceleration or deceleration of the motor driving the eccentric disk S1 according to claims 1 to 3, or is generated by a speed control of the motor. 30.07.1995 295 05 149.3 Harald Reibnagel Page 3/17 Filter cleaning for vacuum cleaners In order to extend the duration of the cleaning function in an uncontrolled motor, according to claims 10 to 12, the movement of the displaceable mass M1, according to claims 1 to 3, is braked in its speed. Since, depending on the functions according to claim 11, the partial system consisting of filter and suction material is a spring-mass system that is variable in itself (from a physical point of view), the property according to claim 10 is an essential functional feature of claims 1 to 3. The system structures according to claims 8.1 to 8.3 reduce the transmission of structure-borne sound by decoupling the vibrating system from the housing by means of the spring and damping elements. 30.07.1995 295 05 149.3 Harald Reibnagel Page 4/17