[0001] The invention relates to an air weaving machine having at least one main blower, a plurality of relay blowers, a storage tank for compressed air which is connected to the at least one main blower and a storage tank for compressed air which is connected to the plurality of relay blowers.

[0002] With air weaving machines of the abovementioned type, the weft threads are inserted into the shed by means of one or usually two main blowers arranged one behind the other. In the shed, the weft threads are kept at least approximately at speed and supported by means of auxiliary or relay blowers. The relay blowers blow air jets into an insertion duct which is formed by lamellae of a reed. The main blowers are supplied with compressed air at a pressure in the order of magnitude of 3 to 7 bar. The relay blowers are supplied with compressed air at a pressure of approximately 4 to 7 bar, with a pressure of 4 to 5 bar being sufficient for a relatively large number of types of weft thread. Air weaving machines of the abovementioned type have a relatively high energy consumption which is mainly determined by the insertion of the weft threads by means of compressed air.

[0003] It is known (WO 2007/071350 Al) to provide a common storage tank for both the main blowers and the relay blowers which is connected to a compressed-air source. The main blowers and the relay blowers are connected to the storage tank via pressure-regulating valves and switchable shut-off valves. Preferably, the relay blowers are arranged together in groups, each time one pressure-regulating valve and one shut-off valve being provided for each group of relay blowers . [0004] It is also known (JP 2007211358 A) to provide separate storage tanks, for the main blowers on the one hand and for the relay blowers on the other hand. Via shut-off valves, the one storage tank is connected to main blowers which are arranged in succession. The other storage tank is connected to the relay blowers via shut-off valves. Both storage tanks are provided with compressed air by a common compressed-air source. A pressure-regulating valve is arranged between the compressed-air source and both storage tanks, respectively, for adjusting the pressure of the compressed air in the storage tank. In this case, the compressed air which is supplied can in addition also be used to cool a heat generator, for example the drive motor for weaving frames.

[0005] It is also known (US 4682636) to supply compressed air having a temperature of between 45 ⁰ C and 120 ⁰ C to the main blowers and the relay blowers. The compressed air emanates from a common compressed-air source and is supplied to the main blowers and the relay blowers via valves without the interposition of storage tanks .

[0006] It is an object of the present invention to improve an air weaving machine of the abovementioned type in such a manner that the energy consumption of this air weaving machine is reduced.

[0007] This object is achieved in that a dedicated compressed-air supply unit is connected to the storage tank to which the plurality of relay blowers is associated and in that the storage tank is connected to the plurality of relay blowers via switchable shut-off valves. Thereby, the dedicated compressed-air supply unit is able to produce compressed air at a pressure which is required for the plurality of relay blowers. [0008] According to an embodiment of the invention, it is provided that the compressed-air supply unit of the air weaving machine is provided with a compressor which is driven by a controllable and/or adjustable drive and which maintains the pressure of the compressed air in the storage tank at a certain value for the plurality of relay blowers .

[0009] According to another embodiment, it is provided that the compressor is directly connected to the storage tank for the plurality of relay blowers. In this case, "directly connected" is intended to mean that no cooling devices for the compressed air are provided between the two.

[0010] According to another embodiment, it is provided that the storage tank for the plurality of relay blowers is directly connected via shut-off valves to the shut-off valves for the plurality of relay blowers and/or to the plurality of relay blowers. In this case, "directly connected" is intended to mean that no cooling devices for the compressed air are provided between the two.

[0011] The invention assumes that the known insertion systems for weft threads consume an unnecessarily large amount of energy since the compressed air required for the relay blowers is supplied by the compressed-air source which supplies the compressed air for the main blowers. Thereby, the total needed amount of compressed air is brought to the pressure required for the main blowers, which requires a considerable supply of energy. Then for a substantial part of the compressed air the pressure is reduced again to the pressure which is required for the relay blowers . The pressure required for the relay blowers may be lower than the pressure required for the main blowers. In this case, the energy necessary to bring the compressed air used by the relay blowers to this high pressure is lost. This portion of the energy which is lost in the case of the known insertion systems for weft threads is saved by the invention, since the compressed air used for the relay blowers is only brought to the pressure which is required for the latter.

[0012] When providing compressed air for air weaving machines, according to the prior art, the compressed air which has been heated by compression using a compressor is cooled to 20 ⁰ C to 3O ⁰ C before being supplied to several air weaving machines. This also requires energy which, according to the insights of the invention, does not have to be supplied, at least not for the compressed air which is supplied to the relay blowers. According to the invention, the compressed air which is supplied to the relay blowers does not have to be cooled, thus making it possible to save a considerable amount of energy.

[0013] Tests have shown that the function of the relay blowers is not impeded, but on the contrary is rather improved, when compressed air of a higher temperature is supplied to the relay blowers. The high temperature has the effect that, at the same pressure of the compressed air, the expelled air mass per unit time is slightly lower, but the speed at which this mass of hot air is expelled is higher. In particular when the relay blowers mainly only serve to keep the inserted weft thread at the insertion speed and not to accelerate it substantially, it is even possible to further reduce the pressure of the hot compressed air made available to the relay blowers, thus making a further energy saving possible.

[0014] By providing a dedicated compressed-air supply unit for the relay blowers of an air weaving machine, i.e. a compressed-air supply unit which is associated with that particular air weaving machine, it is possible to adjust the pressure of the compressed air which is produced by the dedicated compressed-air supply unit to the weft threads to be woven. In most cases, it is possible to opt for a significantly lower pressure than the pressure of the compressed air which is supplied to an air weaving machine according to the prior art.

[0015] According to another embodiment of the invention, it is provided that, upstream of the abovementioned compressor of the compressed-air supply unit with which an air weaving machine is equipped, an additional compressor is fitted which supplies air to the compressor of the compressed-air supply unit with which the air weaving machine is equipped at a pressure which is higher than that of the environment. This additional compressor can supply air of a specific pressure to the compressors of the compressed-air supply unit of several air weaving machines .

[0016] According to yet another embodiment of the invention, it is provided that the storage tank which is associated with the relay blowers is supplied with both compressed air from a dedicated compressed-air supply unit according to the invention and compressed air from a compressed-air supply unit which is associated to at least one other storage tank, for example to several storage tanks of different air weaving machines. In this case, an adjustment or control may be provided for the supplied amount of compressed-air coming from the different compressed-air supply units, for example by adjusting the mutual ratio between the applied amounts of compressed-air coming from the two compressed-air supply units. This can also be used advantageously when starting the air weaving machine. This may also make it possible to limit the temperature of the compressed air supplied to the relay blowers . This may be important for weft threads which are less suited to resist high temperatures.

[0017] Further characteristics and advantages of the invention will appear from the following description of embodiments which are presented in the figures.

Fig. 1 shows a diagrammatic view of an insertion system for weft threads in an air weaving machine which, according to the invention, comprises a dedicated compressed-air supply unit for the relay blowers,-

Fig. 2 shows a variant of the insertion system from Fig. 1 with an additional compressor which can cooperate with the dedicated compressed-air supply unit of several air weaving machines;

Fig. 3 shows a variant of the insertion system from Fig. 2; and

Fig. 4 shows another variant of the insertion system from Fig. 2.

[0018] The insertion system for weft threads of the air weaving machine from Fig. 1 comprises two main blowers 10, 11 and a plurality of relay blowers 12 arranged in succession. A weft thread 13 is taken from a supply bobbin 9 using a prewinder 14 and a specific length thereof is supplied to the main blowers 10, 11. The main blowers 10, 11 blow the weft thread 13 into the shed which comprises an insertion duct 15 of a reed

16 in a known manner. As is known, the shed is formed between planes of warp threads. The insertion duct 15 is of a substantially U-shaped design which is formed in the known manner from profiled lamellae of the reed

16. The relay blowers 12 blow compressed air into this insertion duct 15 substantially in the transport direction of the weft thread. The relay blowers 12 mainly serve to maintain the speed of an inserted weft thread 13 and to guide and keep the weft thread 13 in the insertion duct 15.

[0019] The reed 16 and the relay blowers 12 are mounted on a sley 17 which is driven in a reciprocating manner by drive elements 19, 20 by means of a main drive motor 18 of the air weaving machine. By means of drive elements 21, the main drive motor 18 also drives other devices of the air weaving machine, for example devices for forming a shed, which may comprise weaving frames and the like. The main blower 11 is also mounted on the sley 17, so that the main blower 11 moves along with the relay blowers 12 and the reed 16.

[0020] A compressed-air supply unit 8 is associated to the main blowers 10, 11, which comprises a compressor 22, a pressure-regulating valve 23 and a storage tank 24. The compressor 22 is, for example, placed centrally in a building and serves to provide several air weaving machines with compressed air via a supply line 29. The pressure-regulating valve 23 may be manually adjustable or may be adjustable motor-controlled via a control unit 36. In the storage tank 24 compressed air at a pressure of approximately 3 to 7 bar is stored. The main blowers 10, 11 are connected to the storage tank 24 via a line which comprises a throttle valve 25 and a switchable shut-off valve 26, for example a motor- controlled throttle valve 25 and a magnetically controlled shut-off valve 26. Furthermore, the main blowers 10, 11 are connected to the storage tank 24 via another line which comprises a throttle valve 27 and a non-return valve 28. The throttle valve 27 is set to a value at which the weft thread 13 in the main blowers 10, 11 can remain tensioned between successive insertions. The throttle valve 27 may be manually adjustable. The throttle valve 25 and the switchable shut-off valve 26 may be adjusted and/or operated by a control unit 36. Usually, an air weaving machine is provided with several pairs of main blowers 10, 11 to which in each case a prewinder and a supply bobbin with associated weft thread are assigned. The pressure which is set by the control unit 36 via the throttle valve 25 and/or the pressure-regulating valve 23, at which the main blowers 10, 11 are provided with compressed air, can be set, depending on the material and the properties of the weft threads to be woven.

[0021] A dedicated compressed-air supply unit 7 is arranged for the relay blowers 12, also referred to as auxiliary blowers. This compressed-air supply unit 7 provides the relay blowers 12 with compressed air at the pressure which is required at the relay blowers 12, i.e. compressed air at a pressure of 4 bar. The compressed-air supply unit 7 for the relay blowers 12 has an own storage tank 30 to which compressed air from a compressor 31 is supplied. The compressor 31 may be a compact helical compressor or a scroll compressor. Such a compressor can easily be arranged in an air weaving machine and can be provided with insulation in a simple manner. The storage tank 30 is connected to the relay blowers 12 via shut-off valves 32. The shut-off valves 32 may be controlled by the control unit 36. The compressor 31 maintains the pressure in the storage tank 30 which is necessary for the relay blowers 12. In this case, the compressor 31 is driven by a controllable and/or adjustable drive 37 which comprises a controllable drive motor 33 which is controlled by means of an apparatus 34 in such a manner that the compressor 31 keeps the pressure required in the storage tank 30 as constant as possible. The drive motor 33 may also consist of a switchable reluctance motor, also called a "switched reluctance motor" or "SR motor" , the speed and the drive torque of which are controllable by the apparatus 34. The apparatus 34 is connected to a pressure sensor 35 which is connected to the storage tank 30. The pressure sensor 35 consists, for example, of a mano contact which emits a specific signal from a certain pressure which is present. The apparatus 34 can be designed as a regulating apparatus. The apparatus 34 which cooperates with the control unit 36 keeps the pressure in the storage tank 30 at a predetermined value by controlling the drive motor 33 of the compressor 31 to maintain the necessary speed, depending on the pressure determined by the pressure sensor 35. In this case, the speed may be adjustable in an arbitrary manner or in accordance with discrete values. The volume of the storage tank 30 may be chosen so that pressure variations of the compressed air in the storage tank 30 are limited. This predetermined value may be adjusted on the apparatus 34, on the control unit 36 or on the pressure sensor 35. The apparatus 34 and the control unit 36 may, for example, be incorporated in the control device of the air weaving machine.

[0022] The compressor 31 not only realizes an increase in the pressure of the air supplied to the storage tank

30, but also an increase in temperature. The compressed air at increased temperature is supplied directly to the storage tank 30, that is without passing through a cooling device. The storage tank 30, on the other hand, is connected directly to the relay blowers 12, i.e. no cooling device is involved in this case either. Thus, the relay blowers 12 blow compressed air of a relatively high temperature into the insertion duct 15, that is compressed air at a temperature of, for example, 150 ⁰ C to, for example, 200 ⁰ C. The compressor

31, the storage tank 30 and the connections situated in-between as well as the connections from the storage tank 30 to the relay blowers 12 may be at least partially thermally insulated, so that the relay blowers 12 are supplied with compressed air at basically substantially the same temperature as the temperature which is present at the outlet of compressor 31. The connections between the compressor 31 and the storage tank 30 may, for example, comprise pressure lines, while the connections between the storage tank 30 and the relay blowers 12 may also comprise shut-off valves 32 in addition to, for example, pressure lines. It is clear that these connections have to be able to withstand the high temperature of the compressed air. As a result of the expansion of the compressed air which is expelled by the relay blowers 12, the temperature of the expelled compressed air will be reduced slightly, as a result of which the temperature of the air jet which comes into contact with the weft threads will be lower than the temperature of the compressed air which is supplied to the relay blowers 12. Because of this, the high temperature of the compressed air which is supplied to the relay blowers 12 usually causes no problems for the weft threads.

[0023] As has been explained above, the energy consumption can be reduced substantially by means of a compressed-air supply unit 7 for the relay blowers 12 according to the invention. A reduction is already achieved by the fact that the compressed air is only raised to the pressure which is required for the relay blowers 12. Furthermore, a reduction in the energy consumption is achieved by the fact that part of the energy which is converted into heat upon compression of the air is not lost, but can be used since, with equal pressure at the relay blowers 12, the speed at which the air jet is blown out from the relay blowers 12 at high temperature is higher than at normal temperature. As a result thereof, it is possible, if the former blow-out speed is maintained, to reduce the pressure and thus to reduce the energy consumption of the compressor 31. In addition, the energy consumption is reduced due to the fact that the energy which is required to compensate for the reduction in volume of the compressed air during cooling of the compressed air is omitted.

[0024] The embodiment from Fig. 2 is basically the same as the embodiment from Fig. 1. One difference is the fact that upstream of the compressor 31 which is incorporated into the air weaving machine, an additional compressor 38 is arranged which supplies compressed air to the compressor 31 at a pressure which is higher than that of the environment. Of course, this higher pressure is lower than the pressure which is desired in the storage tank 30 and is, for example, 2 bar. The additional compressor 38 can be stationary placed in a building and can, by means of a supply line 39, supply compressed air to several air weaving machines, more particularly to a plurality of compressors 31 of compressed-air supply units 7 of several air weaving machines . This means that the additional compressor 38 supplies compressed air to compressors 31 which have been incorporated into several air weaving machines. As a result thereof, the compressor 31 which has been incorporated into an air weaving machine is provided with precompressed air. This not only makes it possible to reduce the energy which has to be supplied to a compressor 31 which is incorporated into an air weaving machine, but also to reduce the temperature of the compressed air which such a compressor 31 supplies.

[0025] In the embodiment from Fig. 3, the storage tank 30 for the relay blowers 12 is connected to both an associated compressed-air supply unit 7 and a compressed-air supply unit 40. The compressed-air supply unit 40 comprises a compressor 41 and a supply line 42 which is associated to at least one other storage tank (not shown) , for example a storage tank of another air weaving machine. The compressed air which is supplied to the storage tank 30 by the compressor 41 may be nearly at room temperature. In this embodiment, the supply line 42 is connected to the storage tank 30 via a throttle valve 43 and a shut-off valve 44. The throttle valve 43 and the shut-off valve 44 may be controlled by the control unit 36, for example by means of a control program and/or by means of signals from the pressure sensor 35. According to a possibility, the shut-off valve 44 may be open for a certain percentage of the time required for a weaving cycle and the throttle valve 43 may in this case be in a certain position, so that compressed air from the compressor 41 which is at a higher pressure than the pressure in the storage tank 30 can flow to the storage tank 30. In this case, both compressed air from the compressor 31 and compressed air from the compressor 41 are supplied to the storage tank 30.

[0026] In this case, the temperature of the uncooled compressed air which is supplied by the own compressor

31 is higher than the temperature of the compressed air which is supplied by the compressor 41 which can supply several air weaving machines with compressed air. By adjusting and/or controlling the amount of compressed air supplied to the storage tank 30 coming from the various compressed-air supply units 7, 40, for example by means of the control unit 36, it is possible to adjust the temperature of the compressed air which is supplied to the relay blowers 12 by supplying more or less warm or cold compressed air to the storage tank

30. By suitably mixing compressed air from the compressed-air supply units 7 and 40, compressed air of a desired temperature can be stored in the storage tank 30. For example, a too high temperature of the compressed air at the relay blowers 12 can be disadvantageous in case of weaving with weft threads with a low heat resistance. This also makes it possible to reduce the energy supply for driving the drive motor 33 by supplying only a part of the compressed air required by the relay blowers 12 by means of the compressor 31.

[0027] Providing an additional compressed-air supply unit 40 for the storage tank 30 in addition to the compressed-air supply unit 7 according to the invention also makes it possible to bring the storage tank 30 to the pressure which is required for weaving upon starting the air weaving machine, for example after a weaving stop, without it being necessary for the compressed-air supply unit 7 to be started simultaneously with the air weaving machine. In this embodiment, the control unit 36 can open or close the shut-off valve 44 depending on the pressure measured by the pressure sensor 35, so that the pressure in the storage tank 30 essentially remains at the desired value shortly after the start of the air weaving machine. This can occur while the compressor 31 is being started up and also supplies compressed air to the storage tank 30. Once the compressor 31 gradually supplies sufficient compressed air after start-up, clearly the shut-off valve 44 can be closed, so that only compressed air from the compressor 31 will be supplied to the storage tank 30 from then on.

[0028] In the exemplary embodiment from Fig. 3, a plurality of relay blowers 12 is also provided with a throttle valve 45 next to a shut-off valve 32. This makes it possible to restrict the air flow for certain relay blowers 12, while for the other relay blowers 12, the air flow is mainly determined by the pressure of the compressed air which is present in the storage tank 30. According to a variant (not shown), it is obvious that the shut-off valves 32 may consist of so-called proportional valves which can also act as throttle valves in addition to serving for opening and closing, for example because such valves allow the flow passage to be modified in the open position.

[0029] In the embodiment from Fig. 4, the storage tank 30 for the relay blowers 12 may be supplied with compressed air both via a dedicated compressed-air supply unit 7 according to the invention and via the compressed-air supply unit 8 which has been associated to the storage tank 24. To this end, the supply line 29 of the compressed-air supply unit 8 is connected for example via a shut-off valve 44 and a pressure- regulating valve 46 to the storage tank 30. The pressure-regulating valve 46 is set in such a manner that, when the shut-off valve 44 is open, the pressure of the compressed air in the storage tank 30 is slightly lower than the pressure desired for weaving. When starting the air weaving machine, the shut-off valve 44 may be opened while the drive motor 33 for the compressor 31 is started. As soon as the compressor 31 supplies sufficient compressed air to the storage tank 31, in other words the compressor 31 supplies sufficient compressed air so that the pressure in the storage tank 30 reaches the desired value, no more compressed air will be supplied via the pressure- regulating valve 46 and the shut-off valve 44 can be closed again.

[0030] In the exemplary embodiment from Fig. 4, the outlet of the compressor 31 is arranged directly on the wall of the storage tank 30, i.e. without a pressure line being provided between them. This offers the advantage that the temperature of the compressed air which is supplied by the compressor 31 is identical to the temperature of the compressed air supplied to the storage tank 30. At the same time, the shut-off valves 32 are mounted directly to the storage tank 30 itself, so that no pressure lines have to be arranged between the shut-off valves 32 and the storage tank 30. [0031] In this case, a part of the compressor 31 can also be designed to be common with the storage tank 30. Of course, according to a variant embodiment, the compressor 31 can at least partly be incorporated into a frame of the air weaving machine. The compressor 31 and/or the drive motor 33 of the compressor 31 can also be arranged in the storage tank 30.

[0032] Although only four or five groups of three relay blowers 12 have been illustrated in the illustrated embodiments, it is clear that with an air weaving machine according to the invention, there are usually more than ten groups of relay blowers present, each of these being connected to a shut-off valve 32 and it being possible to connect at least one relay blower to each shut-off valve 32. Usually, two, three or four relay blowers are connected to each shut-off valve 32.

[0033] The shut-off valves 32 for the relay blowers 12 of an air weaving machine according to the invention may be controlled according to known methods, for example according to a method described in WO 2007/057217. The air weaving machine according to the invention also allows to use relay blowers which have a small number of small discharge openings, which relay blowers are particularly suitable for hot air jets.

[0034] It is clear that according to the invention other embodiments are possible in order to provide that with an air weaving machine, having at least one main blower 10, 11 and a plurality of relay blowers 12, a storage tank 30 having a dedicated compressed-air supply unit 7 is added to a plurality of relay blowers 12, wherein the compressed-air supply unit 7 supplies relatively hot compressed air at the pressure which is required at the relay blowers 12. The compressor 31 which is incorporated in the air weaving machine will, for example, be arranged near or partly in a lateral frame of the air weaving machine, for example near the lateral frame of the air weaving machine which is situated opposite the main drive motor and/or opposite the frame drive system.

[0035] The air weaving machine according to the invention defined in the claims is not limited to the exemplary embodiments given and described by way of example, but may also comprise variants and combinations thereof which are covered by the claims .