EP1998709A1

EP1998709A1 - Suction machine

Info

Publication number: EP1998709A1
Application number: EP07711761A
Authority: EP
Inventors: Michael Thoms; Jürgen Schnepf
Original assignee: Duerr Dental SE
Current assignee: Duerr Dental SE
Priority date: 2006-03-28
Filing date: 2007-03-03
Publication date: 2008-12-10
Also published as: DE102006014682B4; KR20090007348A; US20090298011A1; DE102006014682A1; JP2009531166A; UA99709C2; WO2007112814A1; CN101410072A; CN101410072B

Abstract

A suction machine intended for a dental or surgical suction installation is specified which comprises a separating unit (20), which contains a rotor (22) and is used to separate liquid and if appropriate solid constituents from a suctioned mixture of air, liquid and if appropriate solids, and a suction fan (60), which is connected to an air outlet (37) of the separating unit (20) and has a housing (61) and an impeller (62). The suction fan (60) is designed as a radial fan whose impeller (62) is driven by an electrically commuted electric motor (43), which drives the rotor (22) of the separating unit (20) via a gearing (36).

Description

suction machine

The present invention relates to a suction machine with a separating unit for separating liquid and optionally solid constituents from a sucked air / liquid mixture and with a suction fan which is connected to an air outlet of the separating unit.

Such a suction machine is known from EP 0 400 431 A1. The suction machine described there consists of a separation unit, which is connected to a suction fan. The separation unit has a cyclone and a centrifuge arranged coaxially.

Suction machines are used in dental or surgical extraction systems. The extracted by the dentist or surgeon from the mouth of the patient or the surgical area air / liquid mixture must first be separated in the separation unit in its liquid and optionally solid components on the one hand and the air portions on the other.

As a suction fan with the air removed from the output of the separation unit and a negative pressure for the suction is generated, currently often quiet running side channel blower are used.

Smaller suction machines can be integrated directly into the treatment unit, while larger, centrally positioned suction machines can be used to simultaneously supply multiple treatment stations. The side channel blowers used today have a relatively poor efficiency of only about 0.25-0.3 per level at best. In addition, their power requirement increases with the desired negative pressure. For example, a suction machine for four dental treatment stations requires an electric motor with a connected load of approximately 1.5 kW.

Typically suction aspirators for dental or surgical suction machines today are powered by single-phase or three-phase motors which achieve a maximum efficiency of 60-70%.

In addition, a demand-dependent regulation of the suction power would be desirable, especially in the case of multi-station devices, in order to avoid having to operate the suction fan constantly in the full-load range. However, this requires a technically complex and expensive control electronics.

The object of the invention is therefore to provide a suction machine of the type mentioned, which has a better efficiency and which is particularly suitable for the supply of multiple treatment stations.

The object is achieved by a suction machine with the features of claim 1.

Advantageous embodiments can be found in the dependent claims.

According to the invention, the suction fan is designed as a radial fan in a suction machine of the type mentioned, the impeller is driven by an electrically commutated electric motor (EC motor). In contrast to a side channel blower, a radial blower has a much higher efficiency of about 0.6-0.7 per level at best. In addition, the power requirement of a radial blower in the partial load range is lower because radial blowers require more power the higher the volume flow. At high negative pressure but low volume flow, as is typically the case with dental or surgical suction, the power requirement is relatively low. In addition, the radial fan in operation is less sensitive to sucked liquid residue, foam or dust. Due to the lower mass of the impeller of a radial fan compared to a side channel blower faster startup is also guaranteed.

The electrically commutated motor has a higher efficiency of about 80-85% compared to conventional single-phase or three-phase motors. As a result, power consumption and waste heat are lower.

Since an electrically commutated motor works brushless, it is virtually wear-free and has a longer service life.

In addition, the electronics required for the operation of an electrically commutated motor permit speed control, by means of which demand-dependent suction power control can be realized without great effort.

According to the invention, the separating unit and the radial fan are mechanically coupled to one another, preferably such that the separating unit runs slower than the radial fan. So can be operated with the EC motor both the radial fan and the separating unit and different speed requirements of the two subunits are taken into account.

Suitably, the coupling can be performed by a gear transmission. Alternatively, however, is also a coupling via a V-belt, a toothed belt or a friction gear into consideration.

Particularly advantageous is the use of a helical gear transmission.

If the one gear made of plastic and an engaging second gear made of metal, so it is possible to realize a particularly quiet gear coupling and the gear is also without lubrication.

If the control electronics of the EC motor is housed in a motor chamber, resulting in a particularly compact design, it is expedient to provide a fan for cooling the engine electronics. The fan can be advantageously arranged on the drive shaft of the separating unit.

The air outlet of the separating unit can be easily connected via an external line with a suction nozzle of the radial fan.

Preferably, the separating unit comprises a cyclone stage and a pump or a centrifugal stage arranged coaxially. As a result, a good separation of the extracted air / liquid mixture is achieved.

If the electric motor is designed as an external rotor motor, the suction machine can be built very compact. In addition, an external rotor motor enables the transmission high torques and can be operated at high speeds.

Further advantages can be found in the description of the following embodiment of the invention, which is explained in more detail below with reference to the drawings. It shows :

Figure 1 is a sectional drawing of a suction machine

FIG. 2 shows an isometric view of the suction machine from FIG. 1 in a view rotated by approximately 120 °,

FIG. 3 shows a side view of the suction machine rotated by 90 ° with respect to FIG. 1,

Figure 4 is a plan view of the suction machine of Figure 1 and

Figure 5 is a view of the suction machine of Figure 1 from below.

The suction machine shown in Figures 1 to 5 has a lower housing cover 11, on the top of a cup-shaped housing segment 21 of a separating unit 20 is screwed.

At the top, the housing segment 21 is closed by an annular intermediate flange 30 which has in the middle a suspended outlet nozzle 92 for air-freed air.

An inlet connection 29 of the separating unit 20 leads tangentially laterally into the housing 21 (see FIG. 2) and opens in a spiral passage 35, which terminates in the interior of the housing 21. On the inlet port 29, a y-shaped branch piece 29 'is screwed to the example, two dental aspirator can be connected separately.

From above, the intermediate flange 30 is screwed to a two-chambered housing segment 31, the lower chamber of which serves as the air outlet chamber of the separating unit 20 and which laterally carries an outlet connection 37 (see FIG. 3). The upper chamber of the housing 31 serves to receive a gear transmission 36.

At the top, the housing segment 31 is closed by a further housing segment 41, which serves as a motor chamber, which is attached laterally offset and whose underside is designed as a cover 47 for the upper chamber of the housing segment 31. At the top, the housing segment 41 is closed by a cover 51.

The lid 51 projects radially beyond the housing segment 41 and at the same time forms the bottom for a spiral housing 61 of a radial fan 60. The spiral housing 61 together with the lid 51 forms a working chamber 67 for an impeller 62.

In the center of the spiral housing 61 is a round air passage 65, which opens into an inlet chamber 66, which communicates with a tubular intake manifold 63. The working chamber 67, which otherwise has a circular cross section, has a tangential air outlet opening 68 (see FIG. 2) which extends into a spiral passage 69 which leads around the working chamber 67 to a tubular air outlet 64. In Figure 4, the course of the spiral passage 69 can be seen in plan view. At the top, the spiral housing 61 is closed by a round upper sheet metal cover (not shown).

Under operating conditions, the air outlet 37 is the

Separation unit 20 via an external line, not shown here, which may be a hose or pipe, connected to the intake port 63 of the radial fan 60.

In the housing segment 21 of the separating unit 20, a pump impeller 23 and a bell-shaped downwardly widening rotor 22 of a cyclone stage are arranged one above the other on a common drive shaft 34.

In the upper region of the rotor 22, a web surrounding the rotor 22 in the form of a ring helix is provided which, together with an opposing web on the inner wall of the housing 21, forms the spiral passage 35, via which the aspirated air / liquid mixture is conducted into the separating unit 20 ,

At the upper edge, the rotor 22 has a larger number of circumferentially distributed radial pump vanes 19 which have a narrow rectangular recess in the middle and together with a correspondingly shaped rib of the intermediate flange 30 form a dynamic seal with a return pumping action, so that no direct flow connection from the interior of the housing 21 to the central passage opening of the intermediate flange 30 consists.

In its interior, the rotor 22 has a plurality (eg, six) in the vertical and radial direction between the drive shaft 34 and the inner wall of the rotor 22 flat extending wings 25, which the interior of the rotor 22 divided into several, laterally closed sectors.

Under the rotor 22 is a ring-shaped pump impeller 23, whose outer wall extends obliquely upwards over the lower edge of the rotor 22. Inside the pump impeller 23 a plurality of radial webs 26 are arranged. At the outer edge of the pump impeller 23 are distributed over the circumference a larger number of pump blades 27, each having a narrow rectangular recess in the middle.

Above the ring of pump blades 27, the diameter of the housing segment 21 decreases in a shoulder 28, which in this way together with the bottom lid 11 delimit a liquid outlet chamber.

From the shoulder 28, a blocking web 81 projects annularly downwards and projects into the rectangular recesses of the pumping blades 27. The pumping blades 27 thus form a dynamic together with the shoulder 28 and the blocking web 81 protruding therefrom into the recess of the pumping blades 27 Poetry.

The pump vanes 27 extend inwardly beyond the shoulder 28 into the pump impeller 23, thus conveying liquid dripping from the rotor 22 into the pump impeller 23 and forced outwardly by the centrifugal force to a liquid outlet port 24 (see Figure 3). which extends tangentially from a lower peripheral wall of the Gehäusegmantes 21, which lies under the shoulder 28.

Sucked air / liquid mixture from the inlet port 29 via the spiral passage 35 in the housing segment 21 enters, flows downwardly under swirl and then under the suction of the connected to the air outlet 37 radial fan 60 from below into the limited by the wing 25 sector-shaped chambers of the rotor 22. Liquid residuals are deposited in this way under centrifugal force at the outer cyclone wall and then drip directly into the pump impeller 23.

In the rotor 22, entrained fine liquid droplets and foam portions are forced against the inner wall of the rotor 22 by the centrifugal action and flow down the inner wall which widens downwards. From there, the liquid drips into the pump impeller 23 and is forced outwards under centrifugal action, where it is conveyed by the pump blades 27 to the liquid outlet port 24.

The drive shaft 34 of the separating unit 20 extends through the air outlet opening in the intermediate flange 30 and the air outlet chamber of the housing segment 31 up to the

Gear 36.

At the upper end of the drive shaft 34 sits a large gear 32 which is driven by a smaller gear 33. The reduction ratio is about 1: 3.

The gear 33 is seated on a shaft 42 which extends centrally through the housing segment 41 up to the impeller 62. Within the housing segment 41 sits on the shaft 42, a rotor 44 of an electrically commutated electric motor

(EC motor) 43, which is designed as external rotor motor.

Usually, an internal rotor rotates in an electric motor, and the outer housing is stationary. In the external rotor motor used here, this is reversed. The outer, permanent magnet motor housing serves as a rotor 44 and rotates, while the armature 45 (stator), which consists of several air coils, stands in the interior. This leads to a particularly compact design and enables high torques. Alternatively, however, an internal rotor EC motor can be used.

Conventional electric motors usually work with brushes to always change the current direction in the winding at the right time. This brush apparatus causes mechanical and electrical losses, is susceptible to wear and causes electromagnetic interference. In electrically commutated motors, however, the current application is realized with a control electronics (motor control), the circulating magnetic field through the

Air coils of the armature 45 generated. The mentioned disadvantages of the brushes do not occur here. As a result, a brushless motor has a better efficiency.

The cup-shaped rotor 44 is at the bottom with the

Shaft 42 connected while it is open on the top.

From the top of the lid 51 is a bearing sleeve 53 down over, in which the shaft 42 is mounted and sitting on the outside of the armature 45 with its air coils.

The motor control is housed on two circuit boards 46 inside the housing segment 41, of which the lower circuit board concentrically extends around the rotor 44 while the other is mounted above the armature 42 on the bearing sleeve 53. Alternatively, of course, the motor control can also be accommodated in an external housing. In order to cool the motor control, a fan, not shown here, can additionally be accommodated in the housing segment 41, which is preferably driven by the shaft 42.

The motor control can be used to regulate the suction power of the suction machine relatively simply by controlling the speed according to the current demand at the treatment stations (for example 1-4 treatment places). For this purpose, the negative pressure in the suction line can be measured and the speed can be regulated accordingly.

In addition, the motor control has a motor current limit (blocking protection).

On the upper end of the shaft 42 sits the impeller 62 of the radial fan 60. It comprises a lower flat disc 72 and an upper frusto-conical disc 72. The disc spacing is thus reduced from the inside to the outside.

Between the two discs 71, 72 are axially parallel generatrices having blades 73 which extend on curved lines from the center radially to the edge of the discs 71, 72. Alternatively, radially ending blades are possible.

The upper disc 71 of the impeller 62 has centrally an air inlet, which opens into the air passage 65 of the spiral housing 61. For better sealing against the working chamber 67, a vertical nozzle 74 is attached to the air inlet, which encloses a corresponding, downwardly reaching collar 75 at the air passage 65 with little play. When the impeller 62 is caused to rotate rapidly by the EC motor 43, air is sucked through the central air inlet in the impeller 62 and forced outward by the curved blades 73 through the gap between the two disks 71, 72, then rotates in the working chamber 67 and flows through the air outlet opening 68 and the spiral passage 69 to the air outlet 64 and from there via a roof-led line to the outside.

Fan 62, shaft 42 and EC motor 43 are designed for very high rotational speeds in the range 12,000 to 15,000 l / min. By means of the gear ratio (gears 32, 33), the drive shaft 34 runs, and with it the rotor 20 and the pump impeller 23 of the separating unit 20 run only at relatively lower rotational speeds in FIG

Range from 2,800 to 4,000 l / min, as preferred for separation.

Due to the lower speeds, the gear 32 may be made of plastic such as plastic. PTFE or PE are running, the gear 33, however, is made of metal, for example made of brass or stainless steel. With this material combination, lubrication of the transmission 36 can be dispensed with.

As an alternative to the toothed gearing 36, it is also possible to use a planetary gearing, a V-belt or a toothed belt gearing or a friction gear for coupling the separating unit 20 and the radial fan 60.

The high speed rotating parts of the radial fan 60 must be well balanced. The ball bearings, not shown here, with which the shaft 42 is mounted, must be kept small in diameter. additionally it may be necessary to have a bearing cooling system, as well as the use of high-temperature grease and a seal on the ball bearings.

By contrast, the axial operating gaps of the radial blower 60 can be relatively large in the range of approximately 1-3 mm. This simplifies assembly, as accurate spacing is not required, and renders the radial fan 60 insensitive to aspirated foam and dust. Housing parts such as the spiral housing 61 or the housing segment 41 can be made of plastic, which leads to lower production costs.

The impeller 62 itself can be relatively easily, preferably made of aluminum. This allows a fast startup of the suction machine. Alternatively, only the lower disc 72 of the impeller may be made of aluminum and the upper disc 71 with the blades 73 made of plastic, wherein the two discs 71, 72 are thermally riveted.

Due to the better efficiency of radial fan 60 and EC motor 43, the engine power for a suction machine designed to supply up to four treatment stations is only 0.95 kW in the exemplary embodiment.

In addition, in a development not shown here, a separation of solid fractions such as drilled amalgam can be carried out.

For this purpose, the pump impeller 23 is replaced by a centrifuge drum, the bottom of which has a sludge discharge opening, through which the solids content can fall when the centrifuge is discharged into a collection container.

Claims

claims

1. suction machine with a rotor (22) containing separating unit (20) for separating liquid and possibly solid constituents from a sucked air / liquid / and possibly solid mixture and with a suction fan (60) connected to an air outlet (37) the separating unit (20) is connected and has a housing (61) and an impeller (62), characterized in that the impeller (62) by an electrically commutated electric motor (43) is driven and the latter via a

Transmission (36) drives the rotor (22) of the separating unit (20) with.

2. Suction machine according to claim 1, characterized in that the separating unit (20) and the radial fan

(60) are mechanically coupled together by the transmission (36) such that the separating unit (20) runs slower than the radial fan (60).

3. Suction machine according to claim 1 or 2, characterized in that it is in the transmission (36) is a gear transmission or a friction gear.

4. suction machine according to claim 3, characterized in that it is in the transmission (36) is a helical gear transmission.

5. Suction machine according to claim 3 or 4, characterized in that the gear transmission (36) has a toothed wheel (32) made of plastic and a gear engaging therein

(33) made of metal.

6. Suction machine according to one of the preceding claims, characterized in that the motor (43) housed together with a motor control (46) in a housing segment (41) and a fan for cooling the motor control (46) is provided.

7. suction machine according to claim 6, characterized in that the fan for the motor control (46) by the drive shaft (42) of the radial fan (60) is driven.

8. Suction machine according to one of the preceding claims, characterized in that the air outlet (37) of the separating unit (20) via an external line to an intake port (63) of the suction fan (60) is connected.

9. Suction machine according to one of the preceding claims, characterized in that the separating unit (20) comprises a cyclone stage (22) and a rotor (22) comprising centrifugal stage (23), which are arranged coaxially.

10. Suction machine according to one of the preceding claims, characterized in that the electric motor (43) is an external rotor motor.