The invention relates to a side channel blower, especially for use as a combustion air blower in vehicle heaters, with a blower housing forming at least one side channel, in which one intake opening and one exhaust opening terminate, as well as with a blower wheel provided with a plurality of blades disposed immediately adjacent to the side channel.
Such blowers are known to have the disadvantage of developing a considerable amount of noise. In order to combat this, the installation chamber of the blower has been lined with noise-absorbing material or large volume intake mufflers. These measures are costly, however, and require a great deal of space, if the noise is to be reduced to a tolerable level, e.g., a value of approximately 60 dB(A) or less.
A principle object of the invention, therefore, is to provide a side channel blower with reduced noise emission.
This object is achieved according to a preferred embodiment of the invention by virture of the fact that at least the edge of the intake opening, which is located rearward in the rotational direction of the blower wheel, is made elastic.
To explain the source of the noise generation problem and the manner in which the present invention reduces same, the process by which gas, e.g., air, is delivered by a blade chamber located between two blades of the blower wheel during one complete revolution of this wheel will now be described. Firstly, the blade chamber draws in the gas at the intake opening. Pressure is generated in the blade chamber and, as soon as the blade chamber reaches to outlet opening, gas is released through this opening. However, during its movement from the intake opening to the exhaust opening, the blade chamber is always under pressure. Thus, when the leading edge, in the rotational direction, of the blade chamber reaches the rear edge of the intake opening, in the rotational direction of the blower wheel, gas suddenly escapes from the blade chamber under pressure. This produces a pressure pulse which enters the environment. This process is repeated for each individual blade. The resultant pressure pulse train is the basic reason for the disturbing noise generation. The measure according to the present invention gradually reduces the pressure in the individual blade chambers as these chambers move toward the outlet opening by virtue of deflection of the elastic trailing edge. This is because the gas can escape from the blade chamber with less of an impact, so that the pressure decline in the blade chamber is produced gradually instead. In this way, the compression impacts upon the environment are considerably reduced.
The elastic edge of the intake opening may be formed in an especially simple fashion from a plate of elastic material inserted in the blower housing. In particular, the plate can be made of sponge rubber, soft foam rubber, or a thin piece of sheet metal mounted partially on the blower housing.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention.