HK1091957B - Aquarium pump - Google Patents

Description

Aquarium pump

Technical Field

The invention relates to an aquarium pump.

Background

Synchronous machines are often used in applications where a robust and fault-tolerant construction of the machine and low-noise operation of the machine are important. A typical field of application for this type of motor is the drive motor for aquarium pumps.

It is known for synchronous machines that the direction of operation of the machine from a standstill cannot be easily predefined. Depending on the relative position of the rotor with respect to the stator, the electric machine starts up in one or the other direction of rotation when the supply voltage is applied. For applications in which the electric machine has to be started in a defined direction of rotation, mechanical starting devices are known which produce, for example, a slight starting movement of the rotor in the correct direction of rotation. Such a starting device, known from a synchronous clock, can be a driving rod operating by means of a ratchet transmission acting on a gear wheel connected to a stator.

However, such mechanical starting devices are subject to failure and are not suitable for use in conditions where contamination must be considered, for example in aquaria.

Disclosure of Invention

The invention thus makes it possible to provide a synchronous machine with a starter device which has a simple mechanical construction and is also suitable for use in environmental conditions which can lead to pollution.

This object is achieved according to the invention by the aquarium pump described below. The aquarium pump comprises an electric motor and a propeller driven by the electric motor, the electric motor having a stator and a rotor and a starter device for starting the rotor in a defined direction of rotation, wherein the rotor is mounted axially movably and co-operates with a screw/thrust device for axially displacing the rotor from the stator when operation in the wrong direction of rotation is initiated, characterized in that the propeller is rotationally coupled to the rotor such that the screw/thrust device is formed by interaction between the propeller and the water surrounding the propeller, and in that the propeller pump comprises a stop device for limiting the axial displacement path of the rotor to a distance between 30% and 70% of the maximum axial magnetic overlap between the rotor and the stator.

In the synchronous machine according to the invention, the rotor is pulled out of the stator in the axial direction when the rotor starts in the wrong direction. The pulling out takes place until the magnetic coupling between stator and rotor becomes so small that the rotor can no longer be kept in motion by the magnetic field. The axial (pull-out) stroke may be smaller or larger, depending on whether the working load of the rotor is larger or smaller.

If the rotor reaches a standstill, the rotor is pulled back into the stator magnetic field again by the axial component of the magnetic field acting on the rotor. The return movement takes place asynchronously to the magnetic field, so that there is the possibility that, when there is a relative angular position between the rotor and the stator which exists when the magnetic coupling between the stator and the rotor is again sufficient for driving in the angular direction, this is the relative position which allows the start to take place in the correct rotational direction. If this is not the case, the rotor is again moved axially away from the stator and the cycle is repeated again. In this way it can be ensured that the rotor, in some cases after several wrong attempts, is running in the correct direction.

The synchronous machine according to the invention has a mechanically very simple construction. The motor has no mechanically complex parts whose function is easily impaired by contamination as occurs in aquarium water.

Advantageous developments of the invention are given below.

Advantageously, the rotor has a bearing bore, with which the rotor can be moved on a fixed shaft. This makes it possible to ensure a simple low-friction bearing for the rotor, which also makes it possible to self-clean when the rotor is axially displaced on the shaft at certain (time) intervals and the rotary movement is continued.

According to the invention, the screw/thrust unit has a propeller which is rotationally engaged with the rotor and therefore, in the event of a starting direction error, a propeller wheel for generating an axial force is used for axially displacing the rotor, which propeller wheel is also provided for fluid-conveying purposes. The pump according to the invention therefore differs from conventional propeller pumps only in that the support of the rotor and the propeller connected thereto on the shaft is axially movable and not axially rigid. Thereby adding virtually no cost.

According to the invention, the rotor is embedded in the hub portion of the propeller, which allows the rotor and the propeller to be designed as a one-piece component. This simplifies the assembly and reduces the production costs, in particular when the rotor is injection molded directly into the plastic propeller. This also automatically ensures a good centering of the two components on the common shaft when the unit formed by the propeller and the rotor is manufactured in this way. Imbalance can be substantially avoided without the need for mechanical finishing.

According to the invention, the screw/thrust device comprises a threaded connection between the rotor and the motor shaft, which is suitable for applications using synchronous motors for driving mechanical loads. According to this development, the axial relative movement is provided by a screw/thrust device which allows axial and angular relative movement between the rotor and the driven shaft.

According to the invention, the screw/thrust device can be formed by a threaded connection comprising a steep thread, wherein the slope of the thread ensures that the driving movement can be terminated already after a small angular starting travel in the wrong direction of rotation.

With the invention, the screw connection comprises screw ridges connected to the stator and a screw sleeve connected to the motor shaft or vice versa, whereby the screw/thrust unit is well protected against contamination, since the cooperating screw surfaces are located inside a sleeve.

The aquarium pump according to the invention comprises a stop device which limits the axial travel of the rotor in the direction away from the stator, whereby the rotor, when an external force is exerted on the propeller or on the shaft connected to the load, is not moved axially far from the stator, i.e. reaches a distance from the stator at which the axial force acting between the stator and the rotor is no longer sufficient to pull the rotor back into the stator. In this way, a separate rotor return device for axially pressing the rotor back into the stator can be dispensed with.

According to the invention, the stop means limit the axial travel of the rotor to a path which is between 30% and 70%, preferably approximately 45%, of the maximum axial magnetic overlap between the rotor and the stator, thereby ensuring, on the one hand, that in the axially extended position the rotor is magnetically decoupled from the stator to such an extent that the rotor is moved back into the stator in other relative angular positions with respect to the stator. On the other hand, it is ensured that the magnetic restoring force acting in the axial direction is still sufficiently large.

For applications where it is not possible to ensure that the axial magnetic force is sufficient to pull the rotor back into the stator due to high friction or other structural reasons, special return means may be provided, i.e. there may be pull back means by which the rotor may be pre-tensioned into axial alignment with the stator so that the rotor may be returned into the stator.

Drawings

Embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Wherein:

fig. 1 shows: axial section of a propeller pump for an aquarium, which contains a synchronous motor in normal operation;

fig. 2 shows: a cross-sectional view similar to fig. 1, but showing the rotor in a position when the rotor is starting in the wrong direction;

fig. 3 shows: a view similar to that of figure 1, but wherein a synchronous motor is used to drive a motor shaft engageable with a mechanical load, wherein the axial position taken up by the rotor after starting in the correct direction of rotation is shown; and

fig. 4 shows: a cross-sectional view similar to that of figure 3 but showing the axial position occupied by the rotor after starting in the wrong direction of rotation.

Detailed Description

In fig. 1, a propeller pump is generally designated 10, which is arranged in a volume 12 of aquarium water, which is only schematically illustrated. The propeller pump 10 draws water from the water volume 12 in the direction indicated by arrow 14 and delivers it back to the aquarium in the direction indicated by arrow 16.

The propeller pump 10 has a housing, generally indicated at 18, which is divided into a pump housing 20 and a motor housing 22.

A stator 24 is arranged in the motor housing 22, which stator has a lamination stack (Lamellenpaket)26 and a field coil 28.

Lamination stack 26 has an aperture 30 that receives a separation bucket 32. A rotor 34 made of permanent-magnetic material, which may have a plurality of magnetic poles distributed in the circumferential direction, for example, is arranged in the separating funnel 32 with a radial gap.

When a signal is applied to the exciting coil 28 from an external ac power supply, not shown, the rotor 34 starts rotating in the alternating magnetic field.

The rotor 34 has a central bore 36 that rotatably seats against a shaft 38.

The shaft 38 has an end flange 40 at one end which rests on the outside of the bottom of the separating funnel 32, wherein the shaft 38 passes through a central opening of the separating funnel 32.

The second end of the shaft 38 is mounted in the hub part 42 of a star mount 44 which is fixedly connected via radial arms 46 to an outlet nipple 48 which is formed by an integrally formed section of the pump housing 20.

Furthermore, the pump housing 20 has an inlet screen 50 in the transition to the motor housing 22, which is similar to a truncated cone, and which is produced in conjunction with the injection of the pump housing 20.

The pump housing 20 thus defines a working chamber 52 between the inlet screen 50 and the outlet nipple 48 in which a propeller, generally indicated at 54, operates. The propeller 54 has a hub portion 56 which supports three blades 58 which are inclined relative to the propeller axis. The direction of inclination of the blades 58 is arranged so that, when the propeller 54 is turned in the correct direction of rotation, indicated by arrow 60, water is sucked in through the inlet screen 50 and discharged through the outlet nipple 50.

As shown in FIG. 1, the rotor 34 is embedded in the hub portion 56. This embedding can suitably be carried out by placing the rotor 34, which is already provided with the holes 36, in an injection mould, by means of which the propeller 54 made of thermoplastic material is injection-formed. This ensures accurate alignment of the central bore 62 of the propeller 54 with the central bore 36 of the rotor.

In addition, the portion of the hub portion 56 to the right in the drawing may serve as a spacer that specifies the maximum axial position of the rotor 34 that moves into the dividing bucket 32. In contrast, the end face of the hub portion 56 located to the left in the figure, together with the hub portion 42 of the star-shaped outlet 44, defines the maximum axial position of the rotor 34 out of the way.

As shown in fig. 1, the rotor 34 in its maximum retracted position is symmetrical about the mid-plane of the stator 24.

As described above, the entire unit consisting of rotor 34 and propeller 54 is arranged on shaft 38 not only rotatably but also axially displaceably.

When the propeller pump 10 is operated with the rotor 34 and the propeller 54 rotating in the direction of the arrow 60, a force to the right in fig. 1 is obtained as a reaction force to supply momentum to the water on the unit formed by the rotor 34 and the propeller 54. This force is absorbed by the axial support structure or inward stop formed by the right end face of the hub portion 56 and the bottom of the divider bucket 32.

When the rotor is moved in the correct rotational direction, the rotor therefore has a defined axial position and behaves like a rotor supported by an axial/radial support structure.

Conversely, if the rotor 34 is rotated in the wrong rotational direction when the field coil 28 is energized, as indicated by arrow 64 in FIG. 2, the propeller 54 draws water through the star shaped outlet 44 and returns the water through the inlet screen 50 back into the aquarium. As a reaction force for providing momentum to the water, an axial force distributed in an axially outward direction acting on the unit formed by the rotor 34 and the propeller 54 is obtained, and thus the unit formed by the rotor 34 and the propeller 54 is moved leftward in fig. 2.

This leftward movement ends when the magnetic coupling between the stator 24 and the rotor 34 becomes so small that it is no longer sufficient to rotate the propeller 54 against the load of water. Under such conditions, there is no longer angular synchronization between the rotor 34 and the alternating magnetic field. There is also an axial component of the magnetic field that attempts to pull the rotor 34 axially back into the divider hopper 32.

During this return movement, the magnetic coupling between the stator 24 and the rotor is again increased, wherein, when the rotor is in a relative position with respect to the stator that is advantageous for starting in the correct direction, whether the coupling is again of sufficient magnitude for driving purposes is completely random.

If the relative position between rotor and stator is a position which is advantageous for starting in the correct direction of rotation, the rotor starts in the correct direction and is moved back again into full magnetic overlap with the stator by the reaction force which is now to the right in fig. 1 and 2 (state) ((berlapp), in which the hub of the propeller 54 isThe end face of the portion 56 abuts the bottom of the divider hopper 32.

When the rotor 34 is axially reset to the magnetic field of the stator 24, the momentum flow against the blades 58 of the propeller 54 serves to slightly rotate the rotor 34 in the opposite direction to the previously started rotational direction, i.e., in the correct rotational direction. This can improve the chance of the rotor 34 starting in the correct rotational direction when the magnetic coupling between the stator 24 and the rotor 34 is reestablished to achieve the drive torque available.

The same reference numerals are also used for the parts of the motor, generally designated 10', which correspond to the components of the propeller pump 10 described above in the embodiment according to fig. 3 and 4.

In the bearing wall 44 'of the housing part 20', the motor shaft 66, which bears the threaded sleeve 68 on its end facing the rotor, is now supported by a radial/axial bearing 74. The threaded sleeve is provided with a steep thread groove on its inner face.

The steep thread groove of the threaded sleeve 68 cooperates with a steep thread ridge 70 integrally injection-molded on the outer surface of the hub portion 56.

The motor 10' shown in fig. 3 and 4 operates similarly to the propeller pump 10 described above in starting. The screw/thrust device which merely converts the rotary movement of the rotor in the wrong direction of rotation into an axially outward movement of the rotor is not formed by a propeller 54 with inclined blades 58 which interacts with the water volume as a load, but by a screw/thrust transmission formed by a threaded sleeve 68 and a steep threaded edge 70. In the screw/thrust transmission, the load connected/associated with the motor shaft 66 acts as a brake on the threaded sleeve 68 against the steep thread edges 70, so that a screw-slip (Schraub-Schlupf) is obtained which generates the desired axial force.

If the motor is operated in the correct rotational direction, a defined axial relative position between the rotor 34 and the motor shaft 66 and thus a torque-locking connection between the two components is obtained.

In contrast, when the rotor 34 is operated in the wrong direction, the hub part 56 with its steep thread edge 70 is screwed into the screw sleeve 68 braked by the load connected to the motor shaft 66. The rotor 34 is thus moved out of the magnetic field of the stator 24 until the movement of the rotor stops, and then the rotor is pulled back into the stator and can be restarted in the correct direction of rotation, as described above.

In the event that the magnetic return force obtained at the position of the rotor 34 axially remote from the stator 24 is not sufficient to pull the rotor 34 back into the stator 24, in order to ensure a strong return force, a return spring 72 can be provided which is designed as a helical spring and is arranged between the hub portion 56 and the opposite end face of the bearing wall 44.

To ensure good insensitivity of the motor to moisture effects, the interior of the motor housing 22 may be filled with a filler/spacer 76.

Claims (6)

1. An aquarium pump, which comprises a motor and a propeller driven by the motor, the motor has a stator (24) and a rotor (34) and a starting device for starting the rotor (34) in a defined direction of rotation, wherein the rotor (34) is mounted so as to be axially movable and interacts with a screw/thrust device which, when operation is initiated in the wrong rotational direction, can axially displace the rotor away from the stator (24), characterized in that the propeller is rotationally engaged with the rotor (34) such that the screw/thrust means is formed by the interaction between the propeller and the water surrounding the propeller, and comprising stop means (44, 56) which limit the axial travel of the rotor (34) to a path, the path is between 30% and 70% of a maximum axial magnetic overlap between the rotor (34) and the stator (24).

2. An aquarium pump as claimed in claim 1, characterised in that the rotor (34) has bearing bores (36) by means of which the rotor runs displaceably on a fixed shaft (38).

3. An aquarium pump as claimed in claim 1, wherein the rotor (34) is embedded in a hub portion (56) of the propeller (54).

4. An aquarium pump as defined in claim 1, wherein the stop means (44, 56) defines the axial travel path of the rotor (34) as about 45% of the maximum axial magnetic overlap between the rotor (34) and the stator (24).

5. An aquarium pump as claimed in claim 1, characterised in that there is a pullback means by which the rotor (34) can be pretensioned into axial alignment with the stator (24).

6. An aquarium pump as defined in claim 1, wherein the stop means (44, 56) is axially aligned with the rotor.