The present invention relates to a device for a vacuum
cleaner comprising a vacuum source in the form of a fan
arrangement comprising a fan unit which, via a shaft, is driven
by a motor unit in the form of a commutator motor.
Vacuum cleaners of the type mentioned above are previously
known. One problem in vacuum cleaners having commutator motors
is that carbon particles are torn away from the carbon brushes
during operation and these particles follow the air flow which
is created by the fan and which is normally used to cool the
electric motor. In order to collect these particles, and to take
care of smaller particles which are not taken up by the dust bag
of the vacuum cleaner, special fine filters which can easily be
exchanged are used at the outlet side of the vacuum cleaner.
However, the fine filters, which are rather expensive, are
quickly filled with carbon particles. The carbon particles
discolor the filter and cause an increased flow resistance and,
hence, need to be changed relatively often.
It is also previously known to use a separate fan to cool
the electric motor. However, using a dedicated motor-cooling fan
complicates the vacuum cleaner and motor design. In order to
achieve a reasonable pressure drop with a limited filter area,
a course mesh filter with a low flow resistance is used. Coarse
mesh filters do not, however, prevent carbon particles from
leaving to atmosphere.
U.S. Patent No. 3,791,774 describes a vacuum cleaner having
a commutator motor in which the carbon particles are collected
on a plate inside the motor. The cooling air flow through the
motor takes up the carbon particles and the direction of the air
flow is abruptly changed, causing the particles to be thrown
against the plate on which they are collected. However, this
arrangement has certain disadvantages. Firstly, there is no
means for taking care of the small carbon particles which will
inevitably follow the air flow to the outlet. Secondly, cleaning
of the plate is problematic since the plate is a part of the
motor. Accordingly, the motor has to be removed from the vacuum
cleaner in order to access the plate.
It should also be mentioned that it is previously known in
connection with electric machines, see GB 2144924, to provide a
closed chamber surrounding the commutator and to blow air through
the chamber in order to expel the carbon particles to atmosphere.
Thus, this arrangement does not relate to a vacuum cleaner and
there is no intention to filter or trap the carbon particles.
An object of the present invention is to provide an
arrangement for a vacuum cleaner which takes care of the carbon
particles from the brushes in a simple way by means of an air
flow in close connection with the commutator, and delivers the
particles to a place where they can be separated from the air
flow. This object is achieved by a small amount of air which
simultaneously assists in cooling the commutator, the brush
holders, and the bearings of the electric motor. Since the
amount of air is very limited, the air is preferably taken in
before the dust bag at the suction side of the fan without
considerably reducing the suction efficiency of the nozzle.
Thus, the carbon powder will also be drawn into the dust bag and
be separated from the air flow in the bag, which means that the
carbon powder will never reach the outlet filter, if any, on the
pressure side of the fan. Thus, replacement of the dust bag
means that the collected carbon powder is also removed from the
vacuum cleaner.
These and further features of the invention will be apparent
with reference to the following description and drawings,
wherein:
FIG. 1 is a schematic vertical section through a vacuum
cleaner which is provided with a device according to the present
invention; and, FIG. 2 is a vertical section through the fan unit of the
vacuum cleaner according to the present invention.
A vacuum cleaner 10 according to the present invention
comprises a shell 11 enclosing a chamber 12 for a dust container
13, a motor housing 14 enclosing a motor-fan unit 15, and a
chamber 16 receiving a cable reel 17. The dust container 13 is
connected, via a sleeve 18, to a vacuum cleaner hose 19. The
vacuum cleaner hose 19 is connected to a tube shaft and a nozzle
(not shown). The dust container 13 comprises a plate 20 of
comparatively stiff material to which an air-pervious bag 21,
preferably of paper, is fixed.
The motor-fan unit 15 comprises a fan unit 22 and a motor
unit 23. The motor unit 23 includes a commutator motor with a
conventional commutator-carbon brush arrangement 24. The inlet
side of the fan unit 22 communicates, via an inlet part 25, with
the chamber 12. The inlet part 25 is covered by a catastrophe
filter 26. The catastrophe filter prevents larger particles or
debris from being drawn into the fan unit 22 if the dust
container 13 should break.
The air flow leaving the fan unit 22 flows over the motor
unit 23 in order to cool the motor before exiting to atmosphere
via openings (not shown) in the shell. The shell 11 also has one
or more openings 27 through which air is drawn into the chamber
16 in order to cool the cable reel 17.
As shown in FIG. 2, the fan unit 22 comprises a two stage
fan with the impellers 28 placed in a fan housing 29 on a common
shaft 30. The shaft 30 is driven by the motor unit 23 provided
with a commutator motor 24. The commutator 24 is arranged in a
closed pocket 31 which also comprises a bearing housing 32 for
one of the bearings 33 on which the shaft 30 is supported. The
closed pocket 31 is thus limited or defined by the motor housing
34, the bearing housing 32 and an annular sealing gasket 35
surrounding the commutator 24. The pocket 31 has two openings,
each of which are provided with a nipple to which two conduits
36 and 37 are connected. One conduit 36 is connected to the
chamber 16, while the second conduit 37 is connected to the
sleeve 18, as shown in FIG. 1.
The device operates in the following manner. During the
operation of the vacuum cleaner, working air is drawn through the
nozzle, and the hose 19, and into the dust bag 13. Dust is
separated from the air in the bag 13 and the cleaned air flows
into the fan unit 22. The cleaned or filtered air flows over the
motor 23 and cools the motor before exiting to atmosphere via an
optional fine filter.
Simultaneously, relatively cold ambient air is drawn through
the opening 27 and into the chamber 16. The ambient air cools
the cable reel 17, and flows through the conduit 36 to the pocket
31. In the pocket 31, the air flow cools the commutator 24, the
carbon brushes and the bearing 33 and, at the same time, takes
up the carbon particles which are released from the commutator
brushes. Thereafter, the air flows through the conduit 37 to the
sleeve 18 wherein it mixes with the working air flowing
therethrough. The carbon particles will follow the working air
into the dust bag 13 and collect on the filter surfaces. The
filtered carbon particles will thus be removed from the vacuum
cleaner when the dust bag 13 is replaced.
It should be observed that it, of course, is possible to
create the air flow through the pocket 31 by other means than
what has been mentioned above. For instance, the air flow could
be created by supplying a minor part of the air flow from the
pressure side of the fan to the pocket, or by using some kind of
pump or fan and simultaneously placing a smaller filter for
taking up the carbon particles after the pocket, as seen in the
direction of flow.
The present invention also makes it possible to not use a
separate outlet filter after the dust bag. Accordingly, there
is no need for a careful sealing arrangement on the pressure side
of the fan which, up to now, has been necessary in order to
prevent the carbon particles from leaking out of the air channels
between the fan and the outlet filter.