US3791774A

US3791774A - Vacuum cleaner unit

Info

Publication number: US3791774A
Application number: US00285441A
Authority: US
Inventors: K Vonk
Original assignee: US Philips Corp
Current assignee: US Philips Corp
Priority date: 1971-09-02
Filing date: 1972-08-31
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12
Also published as: JPS4835669A; DE2242572A1; FR2151119A1; NL7112062A; GB1367418A

Abstract

Vacuum cleaner unit comprising a compressor and an electric commutator motor built so as to adjoin the compressor, in which air which in operation emanates from the compressor is used to cool the motor and for this purpose is directed through the motor by means of baffle plates and furthermore is used to conduct away carbon-brush detritus due to wear of the carbon brushes, thereby preventing the detritus from depositing on the motor and in particular on the coils. The commutator with the carbon brushes is positioned between the rotor of the motor and the compressor. A carbon-brush detritus collecting plateau is located at the compressor end of the commutator. The carbon-brush detritus is moved from the commutator circumference towards the compressor by air vorticles produced near the commutator and is deposited on the collecting plateau.

Description

United States Patent 1191 Vonk I Feb/t 12, 1974 [54] VACUUM CLEANER UNIT 2.973.895 3/l96l Brown et al. 1. 417/424 l Kl V k, H [75} mentor zl g oogevu'n Primary Lxammer-C. J. Husar Attorney, Agent, or Firm-Frank R. Trifari [73] Assignec: U.S. Philips Corporation, New

' York NY. {57] ABSTRACT [22] Filed: Aug. 31, 1972 Vacuum cleaner unit comprising a compressor and an electric commutator motor built so as to adjoin the [21] Appl' compressor, in which air which in operation emanates from the compressor is used to cool the motor and for [30] Foreign Application P i it D t this purpose is directed through the motor by means Sept. 2 1971 Netherlands 7112062 of baffle Plates and furthermme is used w away carbon-brush detritus due to wear of the carbon 52 U.S. Cl 417/423 A; 310/63 310/227 brushes hereby Preventing detritus hem deposit- 51 Int. Cl. Fll4b 17/00 ihg the meter and in Petieular the eeils- The [58] Field of Search U 417/424 423 310/227 commutator with the carbon brushes is positioned be- 310f227 152 tween the rotor of the motor and the compressor. A I carbon-brush detritus collecting plateau is located at [56] a' Cited the compressor end of the commutator. The carbonbrush detritus is moved from the commutator circum- UNITED STATES PATENTS ference towards the compressor by air vorticles prog 'zj duced near the commutator and is deposited on the re unn 1 2,297,283 9/1942 Berg 417/424 collectmg plateau 2,309,583 l/l943 Frantz v. 417/423 A 4 Claims, 3 Drawing Figures PAIENIEBFEMIQM 3791774 saw sur 3 VACUUM CLEANER UNIT The invention relates to a vacuum cleaner unit comprising a flow compressor having at least one rotatable fan, and an electric commutator motor which, viewed in the direction of the axial directional component of the air flow through the compressor, is located downstream of the compressor and the commutator of which co-operates with a plurality of carbon brushes, the motor and the compressor being separated from one another by a partition which is provided with an opening for the passage'of the motor shaft and with flow openings for the passage of the compressed air discharged from the compressor, whilst furthennore downstream of these flow openings baffle plates are arranged for directing the compressed air through the motor for the purpose of cooling it in operation.

A vacuum cleaner unit of this construction is described, for example, in United States Patent Specification No. 2,532,264 which shows a unit having a twostage centrifugal compressor and hence comprising first and second fans mounted on the motor shaft. The motor is mounted on the partition by means of a flange. The partition comprises a ring to which the flange of the motor is secured and a baffle plate which is mounted on the ring and directs the air from the space along the circumference of the second fan to the flow openings which are located within the circumference of the motor flange. The motor has a completely closed housing which immediately adjoins the flange, so that the air emanating from the flow openings is compelled to flow through the motor and hence past the stator coils and the stator core before leaving the motor at the other end. Consequently, the baffle plates mentioned at the beginning of this specification form parts of the motor housing in the described known unit.

In vacuum cleaner units commutator motors are commonly used in which the commutator co-operates with carbon brushes. Compared with induction motors which previously have been used in vacuum cleaner units, commutator motors have the advantage that at the usual alternating voltages having frequencies of 50 Hz or 60 Hz they have improved power/weight ratios and improved characteristics.

In practice, however, the use of commutator motors in vacuum cleaner units gives rise to two typical problems, one being the cooling of the motor, which involves increasing difficulty as the power and the ratio between power and motor weight increase, the other being the difficulty involved in discharging the carbon detritus from the brushes. This detritus also contains metal swarf. Because the carbon brushes by reason of their function are excellent conductors for electricity, the brush detritus also is. Consequently it must be prevented from depositing, on the rotor and the stator of the motor and particularly on the coils, for this deposition may considerably reduce the breakdown voltage of the motor. Since in view of the quality and safety requirements to be satisfied by vacuum cleaner units the motor must always have a breakdown voltage higher than a given minimum value, care must be taken to prevent the deposition of carbon brush detritus on the motor.

In the known vacuum cleaner units of the type referred to at the beginning of this specification, for example the mentioned United States Patent Specification No. 2,532,264, the air current produced by the compressor is used both for cooling the motor and for conducting away the carbon brush detritus. Obviously it must be prevented that the cooling of the motor should be effected by means of an air current which already contains such detritus, and hence the commutator and the carbon brushes are always positioned in the unit at a location such-that the air current which flows past the carbon brushes has first passed the motor. This entails that the commutator and the carbon brushes are invariably mounted at that side of the rotor of the motor which is more remote from the compressor. Thus, viewed in the axial direction, the air drawn in by the unit first flows through the compressor, then past the coils of the motor, subsequently past the carbon brushes to be finally discharged from the unit.

A disadvantage 'of this constructional sequence of the unit is that the carbon brushes are mounted at a position at which the transverse dimensions might otherwise be reduced. In other words: the transversely projecting holders for the carbon brushes at this location determine the largest transverse dimension of the unit.

In particular in upright vacuum cleaners this restricts the freedom of design. Upright vacuum cleaners are preferably constructed so as to be as compact as possible and hence the housing is preferentially shaped in a more or less conical form. This shape is of particular importance when the vacuum cleaner housing is made of a synthetic material, for such a housing is always made by injection moulding and preferably should have a shape permitting it to be readily removed from a mould of the simplest possible construction.

It is an object of the present invention to provide a vacuum cleaner unit of the type described at the beginning of this specification in which the transverse dimension at the end more remote from the compressor is not determined by the carbon brushes and which has further advantages to be described hereinafter, and a vacuum cleaner unit according to the invention is characterized in that the commutator is mounted between the rotor of the motor and the aforementioned partition, and in that at the side of the commutator facing this partition there is provided a stationary substantially closed carbon-brush detritus collecting plateau, which is a tray which extends substantially in a direction at right angles to the motor shaft and has transverse dimensions which are substantially greater than those of the commutator and along the circumference of which more remote from the motor shaft the aforementioned flow openings are located, so that in operation of the unit at least substantially at the area at which the carbon brushes make contact with the commutator a local air flow is produced which has a component in the direction from the carbon brushes to the detritus collecting plateau.

In the unconventional location of the commutator and the carbon brushes in the vacuum cleaner unit according to the invention the air vortices which are produced in the part between the partition and the stator and rotor of the motor are intentionally utilized. Part of the air discharged from the flow openings in the partition strikes these elements and hence is compelled to change direction. This gives rise to vortices which in the vicinity of the motor shaft have a component in the direction from the rotor to the partition.

The carbon detritus collecting plateau again compels this air flow to abruptly change direction. The carbonupright rim which extends substantially at right angles to the plateau.

A simple construction of a vacuum cleaner unit according to the invention is characterized in that the said partition also forms an end shield which carries a bearing for the motor'shaft, the carbon-brush detritus collecting plateau being integral with this end shield.

For vacuum cleaner units of the latter type in which in operation of the unit there is produced across the bearing arranged at the commutator end of the motor a pressure drop from the pressure prevailing at the commutator end of the bearing to a lower pressure at the compressor end of the bearing, in view of the possibility of fouling of the bearing due to carbon-brush detritus and consequent rapid wear an embodiment is of importance which is characterized in that at least one pressure equalizing duct is formed in the end shield at the circumference of the bearing, the duct or ducts having an overall air flow resistance which is lower than that of the bearing. This not only enables fouling of the bearing to be prevented but also the effect of the collecting plateau to be increased. Obviously the resistance of the duct must not be excessively reduced, because this would cause the compressor efficiency to be affected too adversely.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a part elevation part axial sectional view of a vacuum cleaner unit having a motor power of 400 W shown in natural size,

FIG. 2 is a similar part elevation part sectional view of the vacuum cleaner unit shown in FIG. 1, but rotated about its axis through an angle of 90 relative to the position shown in FIG. 11, and

FIG. 3 is a perspective view of that end shield of the motor of the vacuum cleaner unit shown in the preceding Figures which faces the compressor, viewed on to the carbon-brush detritus collecting plateau.

The vacuum cleaner unit I of FIG. 1 includes a twostage centrifugal compressor 2 having two double

rotatable fans

3 and 4. An electric commutator motor 5 is shown to the right of the compressor 2. The axial directional component of the air current flowing through the compressor 2 extends from left to right in FIG. 1.

The centrifugal compressor 2 comprises, in addition to the two

double fans

3 and 4, two

diffusers

6 and 7 which at their upstream sides are covered by intake plates 8 and 9 respectively. These plates are secured to the two

diffusers

6 and 7,'which are made of a thermoplastic synthetic material, in a manner not shown, with the interposition of resilient gasket rings 10 and 11 respectively and centered with respect to the diffusers by means of pins 12 and 13 respectively. The intake plates 8 and 9 each have a central intake opening 14 and 15 respectively.

The electric cornmutatormotor 5 comprises a stator 16 and a rotor ll7. The stator comprises a set of laminations E8 on which are wound, with the interposition of thin insulating foils 22, two stator coils 19 by means of metal brackets 21 mounted in slots 20. The rotor 17 comprises a set of laminations 23, a rotor winding 24 the individual coils of which, which cannot be distinguished in the drawing, are connected to a commutator 25, and a'rotor shaft 26. Carbon brushes 27 arranged in brush holders 28 co-operate with the commutator 25. The motor frame in which the stator l6 and the rotor 17 are mounted comprises two

end shields

29 and 30 which are secured to one another by four screws 31. The end shield 29 carries a ball bearing 32 and the end shield 30 carries a ball bearing 33 which together form the bearing system for the rotor 17.

The set of stator laminations 18 is centered in the end shield 30 by means of a centering ring 34 mounted in this shield. The set 18 is radially fixed in that it abuts parts, not shown, which project from the inner surface of the shield 29. The stator set 18 is axially fixed in the motor frame by means of two screws 35 mounted in the shield 29.

A balancing disk 36 is mounted on the right-hand end of the rotor shaft 26. The left-hand end of the shaft 26 includes a threaded part 37 on which a nut 38 is screwed. A spacer ring 39 is interposed between the bearing 33 and the commutator 25. At the other side of the bearing 33 a spacer ring 40 is interposed between the bearing and the fan 4, a spacer sleeve 41 being interposed between the

fans

4 and 3. By means of a ring 42 interposed between the nut 38 and the fan 3, tightening the nut 38 causes the

fans

3 and 4 to be secured to the shaft 26 and also causes the rotor 17 to be axially fixed with respect to the end shield 30 in which the bearing 33 is rigidly secured.

The two

end shields

29 and 30 are made of a zinc al loy. The diffuser 7 is riveted to the end shield 30 by means of pins 43.. Thus, the end shield 30 also serves as a partition between the motor 5 and the compressor 2, and it is formed with a plurality of flow openings 44 for the compressed air emanating from the compressor 2. Downstream of these flow openings 44' baffle plates 45 are located which are integral with the end shield 30 and serve to direct the compressed air to the motor 5 to cool it in operation.

The commutator 25 is mounted between the rotor 17 of the motor and the end shield 30. At the side of the commutator 25 facing this shield there is located a stationary substantially closed carbon-brush detritus collecting plateau 46. This plateau also is integral with the shield 30 and has a diameter which is about twice that of the commutator 25. Flow openings 44 are formed in the shield 30 on the side of the circumference of the plateau 46 more remote from the motor shaft 26, so that in operation of the unit at least substantially at the areas at which the carbon brushes 27 are in contact with the commutator 25 a local air stream isproduced which has a component in a direction from the carbon brushes 27 to the collecting plateau 46. This is illustrated in FIG. 3. Arrows 47 indi: cate the flow direction of the air which emanates from the compressor through the flow apertures 44 to pass through the motor. From the main stream indicated by the arrows 47 smaller air currents indicated by arrows 48 branch off. This is due to the fact that air amanating from the flow openings 44 strikes the set of stator laminations 18, the stator coils l9 wound on this set and also the rotor 17. v

Carbon-brush holders 28 have laterally projecting lugs 49 which permit them to be secured to the end shield 30 by screws 50. Electric current is supplied to the carbon brushes by current supply wires 51 and plug terminals 52.

At the locations at which the two carbon brush holders 28 are mounted on the end shield 30 there are no baffle plates, such as the baffle plates 45, which are integral with the shield 30. However, the air leaving the motor at these locations does not flow through the motor anymore and hence cannot cause fouling of the motor.

To increase the collecting effect the carbon-brush detritus collecting plateau 46 along its circumference remote from the motor shaft 26 has an upright rim 53 which extends substantially at right angles to the plateau 46. It is difficult and may even be impossible to determine exactly how the motor, in particular in the vicinity of the commutator, must be constructed to obtain the desired collecting effect of the plateau 46. Hence, the vacuum cleaner unit shown in the drawing is to be regarded as a possible embodiment of a vacuum cleaner unit according to the invention, but in any case an embodiment which proved highly satisfactory in practice and in life tests was found to be fouled by carbon detritus in an even lesser degree than a similar vacuum cleaner compressor in which in accordance with conventional practice the commutator and the carbon brushes were located on the other side of the rotor. However, possibly the embodiment shown may be modified in a variety of manners without essentially departing from the invention, which is based on the utilization of the air vortices produced at the areas at which the carbon brushes engage the commutator 25 in order to collect the carbon-brush detritus at a location which, with respect to the main pair flow through the unit, lies upstream of the commutator 25. However, it will be appreciated that the collecting plateau 46 at least. locally must have a diameter which is greater than that of the commutatorZS, because otherwise the carbon-brush particles which are detached from the carbon brushes by wear at the areas at which the brushes engage the commutator cannot be collected on the plateau.

With regard to the air flows indicated by

arrows

47 and 48 in FIG. 3 it should be noted that the arrows shown in the drawing do not exactly or even approximately indicate the directions and values of the flows produced in operation. They roughly illustrate these flows, but in actual fact these flows will exhibit great local differences and be of a far more complicated nature. It will be clear that the air flow which moves past the commutator in a direction towards the compressor will have not only an axial component in the direction of the compressor but also a tangential component, i.e., a velocity component in the direction of movement of the commutator 25. Hence, a carbon particle which at some time may be thrown off from the commutator will follow a path which may be termed helical, i.e., simultaneously in the directionof the collecting plateau 46 and in a tangential direction, that is parallel to a tangent to the commutator 25.

The collecting effect of the carbon-brush detritus collecting plateau 46 roughly is based on the same principles as hold in known dust extractors. In certain dust extractors and hence also in the unit according to the present invention abrupt changes in direction of the air stream are utilized owing to which the dust particles, in the present case carbon-brush detritus particles, can no longer follow the movement of the air molecules because of their larger masses and consequently are separated from the air stream. This is the reason why the upright rim 53 of the plateau 46 provides an additional collecting effect,-for by this rim the air flow is abruptly deflected a second time.

Without departing from the scope and the spirit of the invention various steps may be taken to further increase the collecting effect of the collecting plateau 46. Conceivably corrugating the surface of the plateau facing the commutator may slightly increase the collecting effect, as may be expected in view of the principles discussed hereinbefore. An obvious step is to provide the plateau with a sticky surface to ensure that carbon-brush detritus striking the plateau adheres to it. However, it has hitherto been found that in the embodiment of the invention shown in the Figures such a sticky surface is not required, because the carbon particles by themselves adhere satisfactorily to the material of the end shield 30.

In the operative condition of the vacuum cleaner unit shown in the Figuresa pressure drop is produced across the bearing 33 from a pressure at the end facing the commutator 25 to a lower pressure at the side facing the compressor. The bearings 32 and 33 are ball bearings provided with a supply of lubricant sufficient vfor their entire life. However, the pressure drop across the ball bearing 33 causes the lubricant in this bearing to tend to leave the bearing towards the compressor 2. This would not only mean a loss of lubricant for the bearing but also would cause carbon detritus to find its way into the bearing, which naturally would greatly increase the rate of wear of the bearing. The Figures show precautions taken to prevent the supply of lubricant from being urged from the bearing 33 but also to increase the collecting effect of the collecting plateau 46'. These precautions comprise three pressure equalizing ducts 54 formed in the end shield 30. This is shown particularly in FIG. 3. The ball bearing 33 is held in place in the shield by means of a thrust plate 55 and at the end facing the shield is mounted on three projecting rims 56. The thrust plate 55 is secured by three screws, not shown, to projections 57 formed integrally with the shield 30. Opening 58 in the shield 30 has a diameter which is only slightly larger than the diameter of the rotor shaft 26 passing through it, preventing the production of an excessive air stream from the commutator side of the bearing to the final pressure stage of the compressor, which air stream forms a leakage flow and hence reduces the efficiency of the compressor. The inevitable small leakage flow, however, is sufficient to increase the collecting effect of the collecting plateau 46. The resistance which the leakage flow experiences in the pressure equalizing ducts 54 must be lower than the airflow resistance of the ball bearing 33 itself.

What is claimed is:

1. Vacuum cleaner unit comprising a flow compressor having at least one. rotatable fan, and an electric commutator motor located downstream from said compressor when viewed in the direction of the axial directional component of the air flow through the compressor, a commutator of said commutator motor cooperating with a plurality of carbon brushes, a partition separating said motor from the compressor, said partition provided with an opening for the passage of the motor shaft and with a plurality of flow openings for the passage of the compressed air discharged from the compressor, baffle plates arranged downstream of said flow openings for directing the compressed air through the motor for cooling said motor in operation, said commutator being mounted between the rotor of the motor and said partition, and a stationary plateau provided at the side of the commutator facing said partition for collecting carbon-brush detritus, said plateau being a tray which extends in a direction substantially at right angles to the motor shaft and has transverse dimensions greater than those of the commutator, and along the circumference of which more remote from the motor shaft the aforementioned flow openings are located, so that in operation of the unit a local air flow is produced at the area at which the carbon brushes make contact with the commutator, said air flow having a component in the direction from the carbon brushes to the carbon detritus collecting plateau.

2. Vacuum cleaner unit as claimed in claim 1, further comprising an upright rim which extends substan tially at right angles to the plateau along the circumference thereof more remote from the motor shaft.

3. Vacuum cleaner unit as claimed in claim 1, wherein said partition also constitutes an end shield which carries a bearing for the motor shaft, the carbon-brush detritus collecting plateau being integral with this end shield.

4. Vacuum cleaner unit as claimed in claim 3, wherein a pressure drop is produced across the bearing positioned at the commutator end of the motor from a pressure prevailing at the commutator end of the bearing to a lower pressure prevailing at the compressor end of the bearing when said unit is in the operative condition, and along the circumference of the bearing at least one pressure equalizing duct is formed in the end shield, the overall resistance to the air flow of the duct or ducts being lower than that of the bearing itself.

Claims

1. Vacuum cleaner unit comprising a flow compressor having at least one rotatable fan, and an electric commutator motor located downstream from said compressor when viewed in the direction of the axial directional component of the air flow through the compressor, a commutator of said commutator motor cooperating with a plurality of carbon brushes, a partition separating said motor from the compressor, said partition provided with an opening for the passage of the motor shaft and with a plurality of flow openings for the passage of the compressed air discharged from the compressor, baffle plates arranged downstream of said flow openings for directing the compressed air through the motor for cooling said motor in operation, said commutator being mounted between the rotor of the motor and said partition, and a stationary plateau provided at the side of the commutator facing said partition for collecting carbon-brush detritus, said plateau being a tray which extends in a direction substantially at right angles to the motor shaft and has transverse dimensions greater than those of the commutator, and along the circumference of which more remote from the motor shaft the aforementioned flow openings are located, so that in operation of the unit a local air flow is produced at the area at which the carbon brushes make contact with the commutator, said air flow having a component in the direction from the carbon brushes to the carbon detritus collecting plateau.

2. Vacuum cleaner unit as claimed in claim 1, further comprising an upright rim which extends substantially at right angles to the plateau along the circumference thereof more remote from the motor shaft.