Pneumatic sand conveying device for a sanding system of a rail vehicle, sanding system, and method for operating a pneumatic sand conveying device

Abstract

A pneumatic sand conveying device (100) for a sanding system (500) of a rail vehicle comprises an obstacle device (105) which is fluidically coupled to a sand input (200) for receiving sand from a sand storage container (505), the obstacle device (105) being shaped to form an obstacle between the sand input (200) and a mixing device (110) fluidically coupled to the obstacle device (105). In addition, the sand conveying device (100) has the mixing device (110) for receiving and forwarding sand from the obstacle device (105) by means of compressed air and a discharge device (115) fluidically coupled to the mixing device (110) to dispense the sand from the sand conveying device (100) through a sand outlet (203). The obstacle device (105), the mixing device (110) and the discharge device (115) are arranged in a horizontal plane when the sand conveying device (100) is in a state (140) ready for operation.

Description

[0001] The present approach relates to a pneumatic sand conveying device for a sanding system of a rail vehicle, a sanding system with a pneumatic sand conveying device and a method for operating a pneumatic sand conveying device.

[0002] Sanding systems on rail vehicles are used to apply sand to the rail in front of the wheel rolling over it or directly into the wheel gap to increase the coefficient of friction between the wheel and the rail. For this purpose, sand is drawn from a sand storage container, ideally at its lowest point, using sand conveying devices or sand dosing and conveying devices. The sand is metered accordingly and conveyed further. The distance between this lowest point and the outlet of the sand conveying device directly influences the volume of the sand storage container and should therefore be as small as possible. EP 0 816 129 A2 discloses a pneumatically operated discharge device for a spreader. DE 195 47 746 A1 and EP 1 312 488 A2 disclose a spreader.

[0003] Against this background, the object of the present approach is to provide an improved pneumatic sand conveying device for a sanding system of a rail vehicle, an improved sanding system with a pneumatic sand conveying device and a method for operating an improved pneumatic sand conveying device.

[0004] This object is achieved by a pneumatic sand conveying device, a sanding system with a pneumatic sand conveying device, and a method for operating a pneumatic sand conveying device having the features of the main claim. Advantageous embodiments and further developments of the invention are set forth in the following subclaims.

[0005] The advantages achievable with the approach presented are primarily that a particularly compact sand conveying device is created in which a distance between a position of a sand inlet, at which sand is taken from a sand storage container during operation of the sand conveying device, and a position of a sand outlet of the sand conveying device is particularly small, thus enabling, for example, the use of a larger sand storage container, which can also be referred to as a sandbox.

[0006] A pneumatic sand conveying device for a sanding system of a rail vehicle is presented, wherein the sand conveying device has the following features: a hurdle device fluidically coupled to a sand inlet for receiving sand from a sand storage container, wherein the hurdle device is shaped to form a hurdle between the sand inlet and a mixing device fluidically coupled to the hurdle device. Furthermore, the sand conveying device has the mixing device for receiving and conveying sand from the hurdle device by means of compressed air and an outlet device fluidically coupled to the mixing device for discharging the sand from the sand conveying device through a sand outlet. The hurdle device, the mixing device, and the outlet device are arranged in a horizontal plane when the sand conveying device is in an operational state.

[0007] The horizontal arrangement, in particular, has the advantage that the sand conveyor can be designed very compactly, and the height difference between the sand inlet and the sand outlet is significantly smaller than is possible with a vertically aligned arrangement when ready for operation. Accordingly, when mounted on a rail vehicle with the largest possible sand storage container, the greatest possible distance from the rails can be maintained. The sand conveyor can also be designed to convey a free-flowing material other than sand.

[0008] According to one embodiment, the hurdle device, the mixing device, and the outlet device can be arranged within a common housing. For example, these devices or parts of the devices can also be incorporated directly into the housing, thereby achieving a one-piece and, additionally or alternatively, cuboid-shaped design of the sand conveying device. This has the advantage that the sand conveying device can be constructed as compactly as possible.

[0009] According to a further embodiment, a maximum height of the sand conveying device can be smaller than a maximum depth and, additionally or alternatively, a maximum width of the sand conveying device. For example, the hurdle device, the mixing device, and the outlet device can be arranged next to one another on a horizontal plane in the ready-to-use state, whereby the width and, additionally or alternatively, the depth of the sand conveying device is greater than the height. The position from which the sand conveying device draws the sand should ideally correspond to the lowest point of the sand storage container so that the sand supply can be fully utilized. Consequently, the deeper the lowest point of the sand storage container is, the larger the volume of the sand storage container can be, with otherwise identical dimensions.On the other hand, the position of the sand conveyor's sand outlet should not be too low, as otherwise the height difference between this sand conveyor's sand outlet and a sand hose or pipe outlet near the rail will be too small for optimal and reliable sand application. Advantageously, in the embodiment described here, the distance between the sand inlet and the sand conveyor's sand outlet can be kept to a minimum.

[0010] According to a further embodiment, the diameter of the sand outlet can essentially correspond to a maximum height of the sand conveyor. Thus, the height of the sand conveyor can be determined solely by the diameter of the sand outlet and a sand hose or pipe connected there, which advantageously allows the height of the sand conveyor to be very low and the overall design of the sand conveyor to be very compact. Within the framework of the approach presented here, the term "essentially" can, in particular, refer to a deviation in length specifications of up to + / - 20%.

[0011] According to a further embodiment, the sand inlet and the sand outlet can be arranged substantially perpendicular to each other. In an operational state, the sand inlet can be arranged, for example, on the main surface of the sand conveyor to receive the sand from the lowest point of the sand storage container arranged above. The sand outlet can be arranged, for example, on one side of the sand conveyor. Such an arrangement has the advantage that the previously described distance between the sand inlet and sand outlet can be minimized. Within the scope of the approach presented here, the term "substantially" can, in particular, include a deviation in angle specifications of up to + / - 20°.

[0012] According to a further embodiment, the hurdle device can comprise a labyrinth unit arranged towards the mixing device, comprising a plate and a step. The labyrinth unit can be shaped to prevent the sand from leaking from the hurdle device into the mixing device. For example, the hurdle device can have a recess milled into the housing, with the step being shaped towards the side of the mixing device. The plate can protrude slightly offset from this step so that a square gap or channel remains open. Advantageously, the labyrinth unit arranged in this way can prevent sand from the hurdle device from penetrating the mixing device on its own, while at the same time ensuring that the sand can be sucked into the mixing device, which can also be referred to as the mixing chamber, for example by means of negative pressure.

[0013] According to a further embodiment, the hurdle device can have a drain plug for draining the sand from the hurdle device. The drain plug can, for example, be arranged on the side of the hurdle device opposite the sand inlet and, additionally or alternatively, can be flush with the housing of the sand conveying device when closed. Advantageously, the drain plug can be opened when the sand is to be completely drained from the hurdle device, for example, for servicing purposes.

[0014] According to a further embodiment, the sand conveying device can have a throttle arranged between a sanding compressed air connection for providing the compressed air and the mixing device, wherein the throttle is designed to throttle the compressed air. For example, the throttle can be used if the supplied compressed air is to be reduced to a certain level or if the flow velocity of the compressed air is to be reduced. This has the advantage that the sand discharge can be metered as precisely as possible by possibly throttling the compressed air supply.

[0015] According to a further embodiment, the outlet device can have a hose nozzle arranged at the sand outlet, which is arranged axially to a nozzle arranged in the mixing device for supplying compressed air, in particular wherein the hose nozzle tapers in its interior and can additionally or alternatively be shaped as a Laval nozzle and additionally or alternatively can comprise a Laval nozzle. For example, the compressed air can flow from the sanding compressed air connection and optionally through a throttle through the nozzle. The nozzle can create a negative pressure in the mixing device in conjunction with the hose nozzle shaped, for example, as a Laval nozzle. This negative pressure can suck sand through the labyrinth unit from the hurdle device, into which the sand may have previously reached from the sand storage container by gravity.In the mixing device, the sand can mix with the air from the nozzle and be accelerated toward the sand outlet, where it can be conveyed further through the hose connector and a connected sand hose. Configuring the hose connector as a Laval nozzle or integrating a Laval nozzle is particularly advantageous for generating the required negative pressure.

[0016] According to a further embodiment, the sand conveying device can comprise a blow-out compressed air connection for providing blow-out compressed air for blowing out the mixing device, wherein the blow-out compressed air connection can be arranged substantially perpendicular to the hose nozzle and the nozzle.

[0017] For example, the blow-out compressed air can be connected to the blow-out compressed air connection, which can also be referred to as the blow-out compressed air connection. The air flow can be divided towards the outlet device and the hurdle device. This means that part of the air can flow through the hose connector and, for example, a connected sand hose, and blow out any sand still present in that area. This advantageously allows for easy cleaning of the hose connector and any connected sand hose.

[0018] At the same time, another portion of the air can flow through the labyrinth unit, for example, into the sand storage container, thereby loosening or fluidizing the sand present in the hurdle system and in the vicinity of the sand conveying system. At the same time as applying blow-out compressed air to the blow-out compressed air connection, compressed air can optionally also be applied to the sanding compressed air connection. This has the advantage that no sand grains can enter the nozzle and thus prevent it from clogging. Furthermore, it can influence the distribution of the air flow in favor of the air flow through the hose nozzle. This can be advantageous with long sand hoses, which represent higher air resistance.

[0019] According to a further embodiment, the sand conveying device can have a heating element arranged at the sanding compressed air connection and additionally or alternatively at the blow-out compressed air connection for heating the supplied compressed air and additionally or alternatively the blow-out compressed air. Thus, the air can be heated, and the sand can be warmed and dried by the warm air. This has the advantage that the sand can be protected from penetrating moisture and additionally or alternatively from cold, for example, during the winter months.

[0020] According to a further embodiment, the sand conveying device can comprise a compensating air duct for compensating negative pressure generated in the mixing device, in particular wherein the compensating air duct can be fluidically coupled to the hurdle device via a second labyrinth unit. The compensating air duct can also be referred to as a false air duct and can be arranged, for example, on one side of the hurdle device. Via a second labyrinth unit, which, as in the previously described labyrinth unit, can comprise a step and a plate, the compensating air duct can connect a compensating air inlet, which can also be referred to as a false air inlet, to the hurdle device. Advantageously, this second labyrinth unit can prevent sand from escaping into the environment via the compensating air duct, while at the same time allowing air (false air) to flow from the compensating air inlet to the compensating air duct.The compensating air duct can, for example, be designed to be closable, advantageously allowing pressure equalization in the hurdle system when needed. Additionally or alternatively, an undesirable negative pressure in the hurdle system can also be compensated by incoming air from the sand storage container and, for example, from the environment via false air vents in the sand storage container.

[0021] Furthermore, a sanding system comprising a variant of the previously described pneumatic sand conveying device and a sand storage container for storing sand is presented, in particular, wherein a main surface of the sand conveying device can be coupled to the sand storage container or can be coupled thereto. The main surface of the sand conveying device can be sealed to the sand storage container, for example, via a suitable seal to prevent unwanted air ingress. Such a combination allows the previously described advantages to be optimally implemented.

[0022] In addition, a method for operating a variant of a previously described pneumatic sand conveying device is presented, wherein the method comprises the following step of supplying compressed air to the mixing device of the sand conveying device in order to cause sand to be ejected from the outlet device of the sand conveying device. Alternatively or additionally, the supplying step can include supplying compressed air to the hurdle device of the sand conveying device in order to cause sand to be blown out of the hurdle device, mixing device, and outlet device of the sand conveying device. Alternatively or additionally, the supplying step can also include supplying compressed air to the mixing device of the sand conveying device while simultaneously supplying compressed air to the hurdle device of the sand conveying device in order to cause sand to be ejected from the outlet device of the sand conveying device with increased conveying air.This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

[0023] Examples of the approach presented here are explained in more detail in the following description with reference to the figures. They show: Fig. 1 is a schematic representation of an embodiment of a pneumatic sand conveying device with hurdle device, mixing device and outlet device; Fig. 2 is a schematic representation of an embodiment of a sand conveying device; Fig. 3 is a schematic representation of an embodiment of a sand conveying device with a compensating air channel; Fig. 4 is a schematic representation of a top view of an embodiment of a sand conveying device with a throttle and a blow-out compressed air connection; Fig. 5 is a schematic representation of an embodiment of a sanding system; and Fig. 6 is a flow diagram of an embodiment of a method for operating a variant of a sand conveying device presented here.

[0024] In the following description of advantageous embodiments of the present approach, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0025] Figure 1shows a schematic representation of an embodiment of a pneumatic sand conveying device 100 with a hurdle device 105, a mixing device 110, and an outlet device 115. These three main components of the sand conveying device 100, which can also be referred to as hurdle, mixer, and outlet for short, are shown separated from each other in this embodiment by indicated lines. The hurdle device 105, mixing device 110, and outlet device 115 are arranged in a horizontal plane in an operational state 140 of the sand conveying device 100, as shown here.By way of example only, the hurdle device 105, mixing device 110 and outlet device 115 according to this exemplary embodiment are further arranged in a housing 120, wherein the height 125 of the housing 120, and thus of the entire sand conveying device 100, according to this exemplary embodiment is smaller than the depth 130 of the housing 120 and here, by way of example, also smaller than the width 135 of the housing 120. The housing 120 is here, by way of example only, formed as a whole in a cuboid shape and / or in one piece.

[0026] Figure 2 shows a schematic representation of an embodiment of a sand conveying device 100. This can be the Fig. 1 described sand conveying device 100, with the difference that the boundaries of the hurdle device 105, mixing device 110 and outlet device 115 are not as in Figure 1 are highlighted by additional lines. This can be seen in Fig. 2that the hurdle device 105 is fluidically coupled to a sand inlet 200 for receiving sand from a sand storage container (not shown here), wherein the hurdle device 105 is shaped to form a hurdle between the sand inlet 200 and the mixing device 110 fluidically coupled to the hurdle device 105. The mixing device 110 is designed to receive and convey sand from the hurdle device 105 by means of compressed air. The outlet device 115 is fluidically coupled to the mixing device 110 and is shaped to discharge the sand from the sand conveying device 100 through a sand outlet 203.

[0027] In this exemplary embodiment, a main surface 204 of the housing 120 comprises a seal 205 for sealing the sand conveying device 100 from the sand storage container. According to this exemplary embodiment, the main surface 204 of the housing 120 is the largest surface compared to other surfaces of the housing 120. The main surface 204 is shown partially open to allow a detailed view of the components arranged underneath. Using mounting holes 207, the main surface 204, and with it the entire sand conveying device 100, can be coupled to the sand storage container.

[0028] In this exemplary embodiment, the hurdle device 105 is formed as a recess in the housing 120, which according to one exemplary embodiment is milled into the housing 120. According to this exemplary embodiment, a drain screw 210 is arranged in the lower region of the hurdle device 105, which makes it possible to drain sand for servicing purposes. On a side of the hurdle device 105 arranged essentially centrally in the sand conveying device 100, there is a step 215 protruding from a base of the housing 120 and a slightly offset plate 220 protruding in the opposite direction. In the arrangement shown here, the step 215 and the plate 220 represent a labyrinth unit 225. If, for example, sand is located in the hurdle device 105, the labyrinth unit 225 can prevent the sand from unintentionally flowing further into the mixing device 110.At the same time, however, it is possible to actively suck the sand, for example by means of negative pressure, through an opening between the step 215 and the leaf 220.

[0029] According to this exemplary embodiment, the mixing device 110 arranged next to the hurdle device 105 comprises a nozzle 230 by means of which compressed air can be introduced into the mixing device 110. According to various exemplary embodiments, the mixing device 110 is, for example, drilled or milled into the housing 120 like the hurdle device 105, with the nozzle 230 arranged axially to the mixing device 110. With this system consisting of the mixing device 110 and the nozzle 230, sand can be sucked from the sand storage container via the hurdle device 105 using negative pressure, metered accordingly, and conveyed further through the outlet device 115.

[0030] In this exemplary embodiment, the outlet device 115 comprises a hose connector 235 arranged at the sand outlet 203, which is axially aligned with the nozzle 230. According to this exemplary embodiment, the hose connector 235 is, for example, tapered internally or designed as a Laval nozzle, so that the suction effect of the nozzle 230 can be enhanced. According to an alternative exemplary embodiment, a Laval nozzle is installed as a separate part in a cavity of the hose connector 235.

[0031] According to this exemplary embodiment, the sand conveying device 100 shown here advantageously implements a compact sand dosing and conveying device with a horizontal sand outlet 203.

[0032] Figure 3 shows a schematic representation of an embodiment of a sand conveying device 100 with a compensating air duct 300. This can be an embodiment of the device shown in Fig. 1 or 2described sand conveyor device 100. With such a compensating air duct 300 within the sand conveyor device 100, pressure equalization can be achieved. In this exemplary embodiment, the compensating air duct 300 is arranged on a side of the hurdle device 105 opposite the labyrinth unit 225 and is formed as a second labyrinth unit 305 with a second step 310 and a second plate 315. Through a compensating air inlet 320, which can also be referred to as a false air inlet, air can be guided into the hurdle device 105 from an outer region of the sand conveyor device 100 to a compensating air outlet 325, which can also be referred to as a false air outlet. The second labyrinth unit 305 represents a hurdle, so that no sand from the hurdle device 105 can escape into the environment via the compensating air duct 300.

[0033] Figure 4shows a schematic representation of a plan view of an embodiment of a sand conveying device 100 with a throttle 400 and a blow-off compressed air connection 405. This can be an embodiment of the in Fig. 1 , 2 or 3 described sand conveying device 100. In this exemplary embodiment, the throttle 400 is arranged between a sanding compressed air connection 410, which can also be referred to as a sanding compressed air connection, and the nozzle 230.

[0034] The throttle 400 can, if necessary, reduce the pressure at the sanding compressed air connection 410 and thus achieve the desired lower suction power and corresponding sand dosage. As an additional complement to the sand conveying device 100, in this exemplary embodiment the blow-out compressed air connection 405 is arranged on the mixing device 110. This can also be referred to as the blow-out compressed air connection, wherein the blow-out compressed air connection 405 is arranged perpendicular to the nozzle 230 according to this exemplary embodiment. Blow-out compressed air can be applied to the blow-out compressed air connection 405, by means of which sand can be blown out of the sand conveying device 100, for example for cleaning purposes. A heating element 415 is also arranged at the blow-out compressed air connection 405 in order to heat the blow-out compressed air and thus dry the sand and / or the sand conveying device 100 and / or protect the sand conveying device 100 and the sand from icing.

[0035] The air flow can, for example, be split toward the outlet device 115 and toward the hurdle device 105, so that a portion of the compressed air blowing out can flow through the hose connector 235 and blow out the sand still present in this area. Another portion of the compressed air blowing out can flow through the hurdle device 105 and the sand inlet 200 into the sand storage container and loosen the sand present in the hurdle device 105. If the air is additionally heated by the heating element 415, the sand can also be heated and dried by the warm compressed air blowing out.

[0036] Figure 5shows a schematic representation of an embodiment of a sanding system 500. The sanding system 500 has the pneumatic sand conveying device 100 described in one of the preceding figures and the sand storage container 505 for storing sand. According to this embodiment, the main surface of the sand conveying device 100 is coupled to the sand storage container 505 merely as an example. In this embodiment, the sand storage container 505 is arranged on a rail vehicle 510 and coupled to the sand conveying device 100 at its lowest point. A sand hose 515 leads from the sand conveying device 100 to a wheel 520 of the rail vehicle 510, wherein the wheel 520 is arranged on a rail 525. By supplying sand to the rail 525 in front of the wheel 520, the coefficient of friction between the wheel 520 and the rail 525 can be increased or brought to an originally higher value.This measure can improve the traction and braking of the rail vehicle 510.

[0037] Figure 6shows a flow diagram of an embodiment of a method 600 for operating a variant of one of the sand conveying devices 100 described in one of the preceding figures. The method 600 comprises a step 605 of supplying compressed air to the mixing device of the sand conveying device in order to cause sand to be ejected from the outlet device of the sand conveying device. Optionally, the method 600 according to this embodiment further comprises, before the supplying step 605, a provisioning step 610 in which the sand conveying device is provided. Alternatively or additionally, the supplying step can include supplying 615 compressed air to the hurdle device of the sand conveying device in order to cause sand to be blown out of the hurdle device, mixing device, and outlet device of the sand conveying device.Alternatively or additionally, in the feeding step, compressed air can be fed 605 into the mixing device of the sand conveying device while simultaneously feeding compressed air into the hurdle device of the sand conveying device in order to cause sand to be ejected from the outlet device of the sand conveying device with increased conveying air. LIST OF REFERENCE SYMBOLS

[0038] 100Pneumatic sand conveyor 105Hurdle device 110Mixing device 115Discharge device 120Housing 125Height of the sand conveyor 130Depth of the sand conveyor 135Width of the sand conveyor 140Ready for operation 200 Sand inlet 203 Sand outlet 204 Main surface of the sand conveyor 205 Seal 207 Mounting holes 210 Drain plug 215 Step 220 Leaflet 225 Labyrinth unit 230 Nozzle 235 Hose connector 300 Compensation air duct 305 Second labyrinth unit 310 Second stage 315 Second leaflet 320 Compensation air inlet 325 Compensation air outlet 400 Throttle 405 Blow-out compressed air connection 410 Sanding compressed air connection 415 Heating element 500Sanding system 505Sand storage container 510Rail vehicle 515Sand hose 520Wheel 525Rail 600Method for operating a pneumatic sand conveying device 605Step of supplying compressed air to the mixing device of the sand conveying device 610Step of providing 615Step of supplying compressed air to the hurdle device of the sand conveying device

Claims

1. Pneumatic sand conveying device (100) for a sanding system (500) of a rail vehicle (510), wherein the sand conveying device (100) has the following features: a barrier device (105), which is fluidically coupled to a sand inlet (200) for receiving sand from a sand storage container (505), wherein the barrier device (105) is shaped to form a barrier between the sand inlet (200) and a mixing device (110) coupled fluidically to the barrier device (105); a mixing device (110) for receiving and forwarding sand from the barrier device (105) by means of compressed air; and an outlet device (115) coupled fluidically to the mixing device (110) for dispensing the sand from the sand conveying device (100) through a sand outlet (203), characterized in that the barrier device (105), the mixing device (110) and the outlet device (115) are arranged in a horizontal plane when the sand conveying device (100) is in a state of readiness for operation (140).

2. Pneumatic sand conveying device (100) according to claim 1, wherein the barrier device (105), the mixing device (110) and the outlet device (115) are arranged inside a common housing (120).

3. Pneumatic sand conveying device (100) according to any one of the preceding claims, wherein a maximum height (125) of the sand conveying device (100) is smaller than a maximum depth (130) and / or a maximum width (135) of the sand conveying device (100).

4. Pneumatic sand conveying device (100) according to any one of the preceding claims, wherein the diameter of the sand outlet (203) corresponds substantially with a maximum height (125) of the sand conveying device (100).

5. Pneumatic sand conveying device (100) according to any one of the preceding claims, wherein the sand inlet (200) and the sand outlet (203) are arranged substantially perpendicular to one another.

6. Pneumatic sand conveying device (100) according to any one of the preceding claims, wherein the barrier device (105) comprises a labyrinth unit (225) arranged towards the mixing device (110) having a leaf (220) and a step (215), wherein the labyrinth unit (225) is configured to prevent the sand from running out of the barrier device (105) into the mixing device (110).

7. Pneumatic sand conveying device (100) according to any one of the preceding claims, wherein the barrier device (105) has a drain screw (210) for draining the sand from the barrier device (105).

8. Pneumatic sand conveying device (100) according to any one of the preceding claims, having a throttle (400) which is arranged between a sanding compressed air connection (410) for supplying the compressed air and the mixing device (110), wherein the throttle (400) is configured to throttle the compressed air.

9. Pneumatic sand conveying device (100) according to any one of the preceding claims, wherein the outlet device (115) has a hose connection piece (235) which is arranged at the sand outlet (203), which hose connection piece is arranged axially with respect to a nozzle (230) arranged in the mixing device (110) for supplying compressed air, in particular wherein the hose connection piece (235) is tapered in its interior and / or is configured as a Laval nozzle and / or comprises a Laval nozzle.

10. Pneumatic sand conveying device (100) according to claim 9, with a blowout compressed air connection (405) for providing blowout compressed air for blowing out the mixing device (110), wherein the blowout compressed air connection (405) is arranged substantially perpendicular to the hose connection piece (235) and the nozzle (230).

11. Pneumatic sand conveying device (100) according to any one of the preceding claims 8 to 10, having a heating element (415) arranged at the sanding compressed air connection (410) and / or at the blowout compressed air connection (405) for heating the supplied compressed air and / or blowout compressed air.

12. Pneumatic sand conveying device (100) according to any one of the preceding claims, having a compensating air duct (300) for compensating reduced pressure forming in the mixing device (110), in particular wherein the compensating air duct (300) is fluidically coupled to the barrier device (105) via a second labyrinth unit (305).

13. Sanding system (500) having a pneumatic sand conveying device (100) according to any one of the preceding claims and a sand storage container (505) for storing sand, in particular wherein a main surface (204) of the sand conveying device (100) is coupled or configured to be couplable to the sand storage container (505).

14. Method (600) for operating a pneumatic sand conveying device (100) according to any one of claims 1 to 12, wherein the method (600) comprises the following step: - supplying (605) compressed air into the mixing device (110) of the sand conveying device (100), in order to cause sand to be ejected from the outlet device (115) of the sand conveying device (100) and / or supplying (615) compressed air into the barrier device (105) of the sand conveying device (100), in order to cause sand to be blown out of the barrier device (105), mixing device (110) and outlet device (115) of the sand conveying device (100) and / or supplying (605) compressed air into the mixing device (110) of the sand conveying device (100) while simultaneously supplying (615) compressed air into the barrier device (105) of the sand conveying device (100), in order to cause sand to be ejected from the outlet device (115) of the sand conveying device (100) with increased conveying air.

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