The invention relates to a conveyor, comprising an elongated casing having side walls, a bottom, a first end and a second end, conveying means inside said casing, a compressed air distribution pipe having a pipe wall, a first end and a se- cond end, compressed air supply means for feeding compressed air in to the air distribution pipe and outfeed devices for leading compressed air out of the air distribution pipe in to the casing, which outfeed devices include holes in the pipe wall of the air distribution pipe.

Pipe belt conveyors comprise a pipe inside which a belt conveyor is installed. The- se kind on conveyors are used to transfer granular and/or powder-like material, such as crushed rock or ore stone, gravel, cement, etc. The pipe forms an elongated dustproof casing aroung the belt conveyor preventing dust and fallen material spreading around the conveyor. The pipe can also be a part of the load bearing frame of the conveyor. A problem relating to the known pipe belt conveyors is, that material failed from the conveyor belt and dust accumulated inside the pipe is difficult to remove from the pipe.

Compressed air can be used for removing dust and dropped material from the pipe of a pipe belt conveyor. Know pressure cleaning systems comprise blowers installed at the first end of the pipe and/or extractors installed at the second end of the pipe. Some cleaning systems may also include pipe angles with nozzles, through which compressed air is led in to the pipe through the bottom wall of the pipe.

Several problems are related to known pressure cleaning systems. The pipe con- veyors are usually very long. Therefore the transport distance of the material that has dropped from the conveyor belt to the other end of pipe can be quite long. For this reason, the air pressure created by blowers and extractors at the ends of the pipe is not sufficient to remove the material from the bottom of the pipe for the entire length of the pipe. Pressure cleaning systems where several compressed air supply pipes and nozzles are installed directly to the bottom of the pipe is expensive to manufacture and difficult to maintain. In some know devices the problem is, that compressed air blows part of the material that has dropped to the bottom of the pipe up along the walls of the pipe instead of moving the material towards the end on the pipe. Document JP2001294313 discloses a pneumatic levitation type belt conveyor. This conveyor comprises compressed air distribution pipe having holes in the upper surface of the pipe wall. Compressed air is supplied to a gap between the upper surface and the conveyor belt through the holes. The object of the invention is to introduce a conveyor, in which problems relating to the prior art is eliminated. The objects of the invention are achieved with a conveyor, which is characterized in what is presented in the independent claims. Some advantageous embodiments of the invention are described in the dependent claims. The object of the invention is a conveyor, comprising an elongated casing having side walls, a bottom, a first end and a second end. Inside the casing there are conveying means, preferably a belt conveyor. The conveyor further comprises a compressed air distribution pipe having a pipe wall, a first end and a second end, compressed air supply means for feeding compressed air in to the air distribution pipe and outfeed devices for leading compressed air out of the air distribution pipe in to the casing. The outfeed devices include holes in the pipe wall of the air distribution pipe. In the invention said holes are in the part of pipe wall facing the side walls and/or bottom of the casing.

In an advantageous embodiment of the conveyor of the invention said pipe wall of the air distribution pipe comprises an upper wall, bottom wall and edge walls and said holes are in the edge walls of the pipe wall. The air distribution pipe may have a rectangular cross section.

In a second advantageous embodiment of the conveyor of the invention inside the air distribution pipe there are tubes having a first end connected to a hole on the first side of the air distribution pipe. The tubes have a tube wall comprising at least one orifice for the inflow of the compressed air. Preferably the holes are arranged on the opposite sides of the air distribution pipe and said tubes inside the distribution pipe have a second end connected to a hole on the second side of the air distribution pipe. The tubes may extend through the air distribution pipe in a trans- verse direction of the air distribution pipe.

In a third advantageous embodiment of the conveyor said outfeed devices comprise nozzle pipes inserted in the tubes in a rotatable manner, which nozzle pipes comprise a nozzle wall having a perforation in a way, that by rotating the nozzle pipe inside the tube the perforation in the nozzle wall and the orifice in the tube wall may coinside, i.e. to settle alingned forming a flow route for the compressed air.

In yet another advantageous embodiment of the conveyor said nozzle pipes have a first portion inserted in to the tube and at least one second portion extending outside said tube, which second portion has an outflow hole for the outflow of compressed air. The second portion may have an open end forming said outflow hole and said second portion may comprise a curved section for directing said open end of the second portion towards the first or second end of the air distribution pipe. Alternatively, said second portion may be a substantially straight pipe having a side wall and said outflow hole is in said side wall. Preferably, at least one of the nozzle pipe's second portions is detachable.

In yet another advantageous embodiment of the conveyor said outfeed devices comprise operating means for rotating the nozzle pipes in the tubes. Preferably said operating means comprise a lever fixed to the nozzle pipe and a cable con- nected to the lever for rotating the nozzle pipe by pulling the cable.

Said cable may be connected to the levers of several nozzle pipes and the cable may be configured to rotate said nozzle pipes in sequential order when the cable is pulled. For example nozzle pipes in the first end on the casing may open first, the neighbouring nozzle pipes may open next and finally the nozzle pipes in sec- ond end of the casing will open last. By this manner it is possible to create a series of air blow pulses propagating from the first end of the casing to the second end of the casing.

In yet another advantageous embodiment of the conveyor above the air distribution pipe there is a roof shaped to cover the air distribution pipe or the air distribu- tion pipe and the cable.

In yet another advantageous embodiment of the conveyor said outfeed devices are grouped to at least two separate groups, which groups can be operated independently. A separate spring may be installed for each outfeed device group. The spring may be operated with a so-called crankshaft at the other end of the casing, either manually or electrically.

In yet another advantageous embodiment of the conveyor the second end of the air distribution pipe is closed. In yet another advantageous embodiment of the conveyor the air distribution pipe is located inside said casing at the bottom of the casing.

In yet another advantageous embodiment of the conveyor said conveying means comprise a belt conveyor above the air distribution pipe, said belt conveyor ex- tending from the first end of the casing to the second end of the casing.

In yet another advantageous embodiment of the conveyor in the bottom of the casing there is an openable hatch for removing material from the casing. Preferably the hatch is in the first or in the second end of the casing.

In yet another advantageous embodiment of the conveyor said casing is a pipe forming a part of the load bearing frame of the conveyor. Preferably said pipe has a substantially round cross-section and a substantially constant wall thickness.

An advantage of the invention is that the fallen material can be removed from the casing in a reliably manner. Also the conveyor according to the invention is structurally simple and easy to maintain. The invention is next explained in detail, referring to the attached drawings in which,

Figurel a illustrates in an exemplary manner a conveyor of the invention as a cross sectional-view in the longitudinal direction of the conveyor,

Figure 1 b illustrates the conveyor shown in Figure 1 a as a cross sectional view in the transverse direction of the conveyor,

Figures 2a, 2b, 2c and 2d illustrate in an exemplary manner a part of the air distribution pipe 2 of the conveyor of the invention and

Figure 3 illustrates an advantageous embodiment of the conveyor of the invention.

In Figure 1 a there is shown in an exemplary manner a conveyor according to the invention, as a cross-section in a longitudinal direction of the conveyor and in Figure 1 b the same conveyor as a cross-section in a transverse direction on the conveyor. In the following both figures are explained simultaneously.

The conveyor is so-called pipe belt conveyor comprising an elongated casing 8 in form of a metal pipe. The pipe has a round cross-section and a substantially con- stant wall thickness. The diameter of the pipe may be 50-200 cm and the wall thickness may be 5-20 mm. Inside the casing there is a belt conveyor 30, which extends from the first end of the casing to the second end on the casing, i.e. the length on the casing and the length on the belt conveyor are substantially equal. The length on the conveyor can be chosen freely according to transport needs of the conveyor. The length may be for example 5-500 m.

The part of the casing wall underneath of the belt conveyor is here called a bottom 7 of the casing 8 and the part of the casing above the belt conveyor is here called a top wall. The parts of the casing wall on the lateral sides of the belt conveyor are here called side walls 5 of the casing. Since the casing has a round cross-section, there is no clear borderline between the aforementioned parts of the casing wall. Above the bottom and underneath the belt conveyor there is an air distribution pipe 2. The air distribution pipe has a first end at the first end of the casing 8 and a second end at the second end of the casing. The air distribution pipe is a hollow metal pipe. In figures 1 a and 1 b the cross section of the air distribution pipe is rec- tangular but also other than rectangular pipe profiles can be used. In the first end of the air distribution pipe there are air supply means for feeding compressed air in to the air distribution pipe. (Air supply means are not shown in the figures). The second end of the air distribution is closed.

Between the first and second ends of the air distribution pipe there are several outfeed devices for leading compressed air out of the air distribution pipe in to the casing. The outfeed devices include nozzle pipes 16 for directing the compressed air towards the second end on the casing. A lever 24 is fixed to each nozzle pipe 16 and the free ends of the levers are connected together with a cable 26. In the first end of the cable there is a spring 27, which is connected to the first end of the casing. The second end of the cable 26 extends outside the casing through the second end of the casing. The nozzle pipes 16 are opened by pulling the cable towards the second end on the casing. When the nozzles pipes are open, compressed air flows from the air distribution pipe 2 through nozzle pipes 16 in to the casing causing an air flow, which moves the dust and any loose material on the bottom 7 of the casing 8 towards the second end of the casing. Near the second end of the casing there is an openable hatch 32 in the bottom 7 for removing the material from the casing.

When the conveyor is in use, conveyed material falls to the bottom of the conveyor casing from the belt conveyor on both sides of the air distribution pipe. With the help of the compressed air the material that has fallen to the bottom is blown towards the hatch at the bottom of the casing. Advantageously the nozzle pipes are steered to blow the material at a slight angle towards the air distribution pipe, in which case the air distribution pipe acts as a guide for the material to be removed, and the material does not rise along the side walls of the conveyor's casing pipe.

In figure 1 a there is only one air distribution pipe 2. It is also possible to arrange several successive air distribution pipes inside the casing each having an own compressed air supply device.

In Figures 2a, 2b, 2c and 2d there are shown in an exemplary manner a part of the air distribution pipe 2 of the conveyor of the invention. Figure 2a shows the air distribution pipe as a side elevation and figure 2b as a top view. In figures 2c and 2d the air distribution pipe is shown as a cross-section in the transverse direction of the conveyor. In the following all figures are explained simultaneously.

The air distribution pipe 2 is a hollow metal pipe having rectangular cross-section. The pipe wall has an upper wall 14a, bottom wall 14b facing the bottom 7 of the casing and two edge walls 14c. In the edge walls there are holes 12 at regular in- terval along the whole length of the air distribution pipe. The holes in both edge walls are aligned, i.e. the holes are in the same place in the longitudinal direction of the air distribution pipe. Tubes 10 having a cylindrical tube wall are inserted into the holes in a way that the first end of the tube is connected to the hole in the first edge wall and the second end on the tube is connected to the hole in the second edge wall in an airtight manner. Thus the tubes extend through the air distribution pipe in a transverse direction of the air distribution pipe. In the tube wall there is an orifice 18 through which air can flow from the air distribution pipe in to the tube 10.

In connection of each tube 10 there is a nozzle pipe 16, having a cylindrical first portion 21 inserted inside the tube and two second portions 23 extending outside the tube. The first portion of the nozzle pipe is dimensioned to fit inside the tube 10 with a small play, which allows the first portion to rotate inside the tube around its axis. The nozzle wall of the first portion has a perforation 20. At both ends of the first portion there is a second portion 23. The second portion has a curved section 22, which bends the free end of the second portion towards the second end of the air distribution pipe 2. The free end of the second portion 23 is open. By rotating the nozzle pipe inside the tube the perforation 20 in the nozzle wall and the orifice 18 in the tube wall may be set aligned, which opens a flow route for the compressed air from inside the air distribution pipe to the nozzle pipe and through the open end of the second portion further in to the casing. The second portions are attached to the ends of the first portion in a detachable manner, which enables an easy repair of the nozzle pipes, because the entire nozzle pipe does not need to be replaced.

A rod-like lever 24 is attached to one second portion of each nozzle pipe 16. The free ends of the levers are connected together with a cable 26. Pulling the cable towards the second end of the casing causes the first portion of nozzle pipe 16 to rotate inside the tube 10. When the pulling is stopped, the spring returns the cable back to its original position. The orifices 18 in the tube wall and perforations 23 in the nozzle pipe are arranged in a way, that nozzle pipes in the air distribution pipe open and close in a sequential order, when the cable is pulled. In this way, a series of air blow pulses propagating from the first end of the casing to the second end on the casing can be created. These air blow pulses move the loose material on the bottom 7 of the casing towards the hatch at the second end of the casing.

In the invention described in figures 2a to 2d the second portion 23 of the nozzle pipe 16 has a curved section 22 and an open free end for the outflow of the compressed air. The outflow hole or holes for the compressed air can also be in the side wall of the second portion and the free end of the second portion can be closed. In this embodiment of the invention there is no curved section in the second portion and the whole nozzle pipe may be a straight pipe with a constant di- ameter.

In Figure 3 an advantageous embodiment of the conveyor of the invention is show. This embodiment contains all the features of the conveyor disclosed in the previously explained figures 1 a to 2d. Additionally, the conveyor comprises a ridged roof 28 which is supported by brackets 34 above the air distribution pipe 2 and cable 26 and below the belt conveyor 30. The roof extends in the longitudinal direction of the air distribution pipe and is shaped to cover the air distribution pipe, the nozzle pipes 16 connected to the air distribution pipe and the cable entirely. The roof prevents the material falling from the belt conveyor to damage the opening mechanism of the nozzle pipes and the nozzle pipes itself. The longitudinal edges of the roof extend close to the bottom 7 of the casing leaving a narrow gap for the material to spread to the lowest place on the bottom. Also the roof forms, together with the bottom 7 and the side wall 14c of the air distribution pipe 2, a partially closed channel, along which loose material travels towards the second end on the casing. Some advantageous embodiments of the conveyor according to the invention have been explained above. The invention is not limited to the solutions explained above, but the inventional idea can be applied in different ways within the limits set by the patent claims.