Vacuum boost apparatus

#1. Field of the Invention

#The invention relates to a device for improving the vacuum in an auxiliary device of a motor vehicle. The auxiliary device uses vacuum for various applications. Such an auxiliary device is often connected to the inlet manifold of a vehicle via a duct having a one-way valve directing the flow from the auxiliary device to the inlet manifold.

#2. Background Information

#For a complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein:

#FIG. 1 shows a schematic view of the present invention with an outlet duct directed to an inlet manifold;

#FIG. 2 shows a schematic view of the present invention with an outlet duct directed to ambient air;

#The figures are simplified and show the present invention schematically in order to facilitate the understanding.

#The device according to FIG. 1 comprises a flexible member 1 and a chamber 2. The chamber has an inlet duct 3 with a one-way valve 5. Further, there is an outlet duct 4 with a one-way valve 6. The inlet duct 3 is connected to the vacuum chamber 8 of an auxiliary device. The chamber 2 is separated from the inlet manifold 10 with the flexible member 1. When the pressure in the inlet manifold 10 decreases the flexible member 1 is drawn inwards the inlet manifold 10, thereby increasing the volume of the chamber 2. The pressure decreases in the chamber 2 and the one-way valve 5 arranged in the inlet duct 3 opens and this creates a flow from the vacuum chamber 8 of the auxiliary device. Next the pressure in the inlet manifold 10 increases and the flexible member 1 of the device is pushed back into the chamber 2 and the pressure increases in the chamber 2. At this point the one-way valve 6 in the outlet duct of the chamber 2 opens and the system reaches equilibrium. This cycle is repeated and this increases the vacuum in the vacuum chamber 8 of the auxiliary device. A one-way valve 7 is preferably arranged between the inlet manifold 10 and the vacuum chamber 8 of the auxiliary device in order to maximize the vacuum in the vacuum chamber 8.

#The working pressure of the inlet manifold 10 is normally below atmospheric pressure. To facilitate the release of pressure from the outlet duct 4 of the chamber 2, said duct 6 is connected to the inlet manifold 10, see FIG. 1. When, as in this example, the pressure of the inlet manifold 10 is lower than the atmospheric pressure the one-way valve 6 in the outlet duct 4 more easily opens to release the pressure. An alternative to directing the outlet duct in to the inlet manifold is to make a connection just before (not shown) the throttle 9 in the hose in order to have a more constant resistance.