Technical Field

The invention relates to an exhaust line for removing gases from a working area, and which at a first end communicates with a vacuum source, and at a second end is provided with a suction opening and comprises at least two tube sections and a pivotal connection arranged therebetween interconnecting the interior of the tubes.

Background Art

Such exhaust lines are used in numerous situations, where it is desirable to remove gases, for instance fumes, from a working area, and are described inter alia in WO 93/04791 and US-A-4,860,644.

Moreover, it is commonly known that electrostatic charging of products, working surfaces, production systems or persons may cause problems: Products, in particular electronic components, may be damaged; problems may arise in microprocessor controls for robots and handling equipment; the electrostatic charged surfaces attract particles of dust, which may be a problem in so-called clean rooms, etc.

For discharging an exhaust line of the above type formed of anodized aluminium tubes and chromium-plated plastic pivot joints, it has been suggested to ground the outer tube or nozzle by means of a copper cable extending through the interior of the tube. However, this solution has proved inadequate to prevent an electrostatic charging of the outer surface of the exhaust line and is less advantageous with respect to manufacture thereof.

Brief Description of the Invention

The object of the invention is to provide an exhaust line of the above type, which reliably ensures a discharge of the outer and inner surfaces of the exhaust line and which is easy to implement.

The exhaust line according to the invention is characterised in that the pivotal connection is made of a polymer comprising an electrically conductive material, and is in electrically conductive connection with the tubes, at least the outer and inner surfaces thereof being conductive and grounded.

As result of all of the parts of the exhaust line having conductive surfaces and being in conductive, mutual contact and grounded, it is ensured that the exhaust line is continuously discharged and that the surfaces thereof are not significantly charged. Moreover, by using a polymer comprising a conductive material as the pivotal connection between the tubes, the advantageous manufacture thereof by injection moulding is obtained, at the same time as no special measures are needed to obtain a conductive connection between the pivotal connection and the tubes, and thus to obtain the desired electrically conductive connection between the parts of the exhaust line.

According to the invention, the tubes may be made of a polymer comprising a conductive material. In particular, the tubes may be made of the same material as the pivotal connection therebetween. By using a polymer filled with a conductive material the desired conductive properties are obtained directly, an expensive surface coating with a conductive material thereby being avoided.

Furthermore, according to the invention, the conductive material may be graphite and/or carbon black. Naturally, the electrically conductive material in the pivotal connection and/or in the tubes may also be a metal, such as aluminium, silver, copper or nickel.

Moreover, according to the invention, the inner and outer surfaces of tubes may be provided with an electrically conductive surface coating. This surface coating may for instance be an electrically conductive lacquer or paint. Optionally, the surface coating may be a metal coating. Further, according to the invention, the surface coating may be a chromating, which is particularly preferable, when the tubes are made of aluminium.

Finally, according to the invention, the exhaust line may be grounded by means of a grounding cable with a 1 M Ω resistance.

Brief Description of the Drawings.

The invention is explained in greater detail below with reference to the figure on the drawing illustrating an exhaust line according to the invention in perspective.

Best Mode for Carrying Out the Invention

The exhaust line shown in Fig. 1 comprises a first suction tube 1 provided with an inclined outer end 2 forming the mouth or suction opening of the exhaust line and adapted to be arranged near the working area, from which gases are to be removed. The second end of the first suction tube 1 is connected to a first pivot joint 3 connected to a first end of a second suction tube 4, the second end of which being connected to a second pivot joint 5 corresponding to the first pivot joint 3. More¬ over, the second pivot joint 5 is connected to a first end of a third suction tube 6, the second end of which being connected to a third pivot joint 7 corresponding to the first pivot joint 3. Finally, the third pivot joint 7 is connected to a first end of a fourth suction tube 8, the second end 9 of which being connected a vacuum source (not shown). A flange 10 is secured about the fourth suction tube 8 for securing the exhaust line e.g. to a tabletop (not shown). Finally, a grounding cable 17 with a 1 M Ω resistance is connected to both the inner and outer surface of the fourth suction tube 8.

The three pivot joints 3,5,7 are formed of two identical halves 11 comprising a cup-shaped part 12 and a sleeve 13 extending from the cup-shaped part 12 and adapted to receive the ends of the suction tubes in a circumscribing manner. With edges of the cup-shaped parts 12 facing each other, the two halves 11 forming the pivot joint are bolted to each other by means of a through-going metal bolt, illustra¬ ted by means of the axis 15 thereof, a thumbscrew 16 being screwed onto the projecting end thereof. A sealing ring (not shown) is arranged between the edges 14 of the two halves 11 to obtain a tight connection between the halves 11. The pivot

joints 3, 5, 7 allow for a turning of the suction tubes 1, 4; 4, 6; 6, 8 connected therewith about an axis perpendicular to the axis of the tubes, 4, 6; 6, 8. In relation to the pivot joint 3, the axis is determined by the axis of the bolt 15. Finally, the ends of the tubes 1, 4, 6, 8, received in the sleeve 13 of the pivot joints may either be received fixedly therein or such that a turning about the axis of the tube in question is possible.

The halves 11 of the pivot joints 3, 5, 7 are made of a polymer comprising an electrically conductive material, such as POM containing graphite or carbon black, and the tubes 1 , 4, 6, 8 are made of aluminium, chromatised on the inner and outer faces. However, the tubes may also be made of any other material provided that both the inner and outer face thereof is electrically conductive. Moreover, the two halves 11 of each pivot joint are interconnected, either by abutment between portions of the edges 14 of the sleeves 13 or by means of the metal bolt 15 extend¬ ing therethrough.

In consequence of the tubes being provided with electrically conductive surfaces and the pivot joints being made of an electrically conductive material, the halves 11 of each pivot joint 3, 5, 7 and the tubes 1,4; 4,6; 6,8 interconnected by means of the pivot joints are in contact with each other, whereby any electrostatic charging of one of the parts of the exhaust line is conducted away to the ground through the ground- ing cable 10. In this connection, instead of being connected to the tube 8, the grounding cable 10 may be connected to any of the electrically conductive parts of the exhaust line.

Finally, instead of being formed of the outer end of the first suction tube 1, the suction opening of the exhaust line may also be formed of a nozzle provided with at least one electrically conductive outer and inner surface and being of any shape or form, e.g. slit-shaped.