|1.||A device of a suction mouth piece (1) comprising an extraction duct (4) and at least one side channel (10, 12) projecting outwards from the extraction duct (4) , where the side channel (10, 12) is provided with an elongated inlet slot (18) , c h a r a c t e r i z e d i n that the inlet slot (18) is arranged tangentially relative to the cross section of the side channel (10, 12), the inlet slot (18) being located between a generally vertical edge and a bulb projecting outwards to the vertical centre line of the side channel (10, 12), whereby fluid that is drawn into the side channel (10, 12) through the inlet slot (18) assumes a rotating flow pattern in the side channel (10, 12) , and where the outlet from the side channel (10, 12) is connected substantially tangential to the extraction duct (4) .|
|2.||A device according to Claim 1, c h a r a c t e r i z e d i n that the upstream end of the extraction duct (4) has an inlet (16) with a smaller cross sectional area than that of the extraction duct (4) outlet.|
|3.||A device according to Claim 2 , c h a r a c t e r i z e d i n that the cross section of the extraction duct (4) at least over a portion of the length of the extraction duct (4) is formed by a cone.|
|4.||A device according to one or more of Claims 1 to 4, c h a r a c t e r i z e d i n that the extraction duct (4) and the at least one side channel (10, 12) form a mouth piece (1) for a vacuum cleaner.|
This invention regards a suction mouth piece. More particularly, it regards a suction mouth piece comprising an extraction duct and at least one side channel projecting from the extraction duct. The side channel is provided with an elongated inlet slot, where the inlet slot is arranged tangentially relative to the cross section of the side channel. Thus a rotating flow pattern is imparted to fluid flowing into the side channel through the inlet slot. The device of the invention is especially suited for use as a suction mouth piece or nozzle on a vacuum cleaner.
The description below generally uses air as the fluid flowing through the suction mouth piece. However, the operation of the suction mouth piece is not limited to air, as it may be used for any fluid, such as a combination of water and air.
A prior art suction mouth piece, typically for use with a vacuum cleaner, is normally designed with an extraction duct and two diametrically opposed side channels projecting outwards from the extraction duct. The side channels have an elongated opening or slot through which air is drawn in with
the purpose of entraining particles from e.g. a floor to be cleaned.
In the case of particle transport in a flowing gas it is essential to maintain a high flow velocity to prevent the particles from falling out of the air flow. In the case of prior art mouth pieces, especially in industrial applications where the length of the mouth piece may exceed one metre, the power required to achieve a satisfactory cleaning result is relatively high.
It is well known that a fluid which assumes a rotary flow pattern during flow in a duct has a greater relative velocity than fluid flowing in a straight line along the same duct, given an equal flow rate.
Thus JP patent 4 272 730 regards an impeller shaped suction mouth piece in which a plurality of side channels curved in the direction of the direction of flow lead tangentially into an extraction duct. Thus a rotating flow pattern is imparted to the air flowing out through the extraction duct. The performance of the device of the JP publication is believed to be somewhat better than that of conventional suction mouth pieces, however it is relatively space-requiring and not particularly well suited for use in houses.
The object of the invention is to remedy or reduce at least one of the disadvantages of prior art.
The object is achieved in accordance with the invention, by the characteristics stated in the description below and in the following claims.
The invention is implemented by providing a suction mouth piece which comprises an extraction duct and at least one
side channel projecting from the extraction duct, with an inlet slot arranged tangentially relative to the cross section of the side channel. This imparts a rotary flow pattern to air that is drawn into the side channel through the inlet slot.
The efficiency of the suction mouth piece is improved further in that the extraction duct upstream is provided with a smaller flow area than at its outlet. During flow, a vortex- like flow usually arises, helping to impart a rotary flow pattern to the fluid flowing through the extraction duct.
It is further preferable that the cross section of the extraction duct, at least over part of the length of the extraction duct, constitutes a cone.
Most preferably the side channel is connected to the extraction duct in a substantially tangential manner in order to further enhance the rotation of the air in the extraction duct.
When the rotation of the air stream, and with this the relative velocity of the air, increases, particles flowing into the mouth piece along with the air will to a much greater extent be kept suspended in the air, compared with prior art. In particular, this applies to the side channel of the mouth piece, with experiments showing that the motor power may be reduced by as much as 50% while maintaining a similar cleaning effect. The comparison has been carried out using previously known suction mouth pieces.
The following describes a non-limiting example of a preferred embodiment illustrated in the accompanying drawings, in which:
Figure 1 is a perspective view of a suction mouth piece according to the invention, where the flow of air is indicated by helical dashed arrows;
Figure 2 is a perspective view of the same as figure 1, but showing a longitudinal section through a side channel;
Figure 3 shows a section A-A through figure 1; and
Figure 4 shows a section B-B through figure 1.
In the drawings, reference number 1 denotes a suction mouth piece made from an appropriate material such as a light alloy, wherein an extraction duct 4 is provided in the central part 2 of the suction mouth piece, with a first side arm 6 and a second side arm 8 projecting from the central part 2 in diametrically opposed directions. The extraction duct 4 is arranged to be connected to a vacuum cleaner (not shown) .
The first side arm 6 has a first side channel 10, while the second side arm 8 has a second side channel 12.
The side arms 6, 8 are formed with a contact surface 14 arranged to bear against a surface (not shown) to be cleaned.
The lower portion of the extraction duct 4 is formed with an inlet 16 having a smaller diameter than that of the extraction duct 4 outlet. The lower portion of the extraction duct 4 from the inlet 16 has been given a conical shape, see figure 3.
The smaller diameter of the inlet 16, relative to the diameter of the rest of the extraction duct 4, ensures that a
desired volume of air is drawn into the extraction duct 4 from the side channels 10 and 12, and also the creation of a vortex-like rotating flow in the inlet 16.
The side channels 10 and 12 lead tangentially into the extraction duct 4, see figures 2 and 3, with the purpose of further enhancing the rotation in the extraction duct 4.
Figure 4 shows the shape of the first side channel 10 in the first side arm 6. An inlet slot 18 running along the side channel 10 is arranged tangentially relative to the cross section of the side channel 10. This design helps to ensure that the air which is drawn in via inlet slot 18, starts to rotate in the first side channel 10, as shown by the dashed arrows in figure 4.
Similarly, the second side channel 12 is provided with an inlet slot 18.
The suction mouth piece 1 may be provided with brushes (not shown) that are known per se.