screw conveyor

Abstract

A screw conveyor (1) for transporting products in a downward direction by gravity includes a frame (2) and a screw track (6) extending about a vertical centerline (CL). The screw track (6) is supported by the frame (2) and includes a bottom (7) that carries the products. The bottom (7) has an inclination angle in the direction (X) along the screw track (6). At least a portion of the bottom (7) is formed by a transport surface (7a) of a driveable conveying system (10), such that the transport surface (7a) has a predefined speed in the downward direction (X) along the screw track (6). The inclination angle at the inner bend of the transport surface (7a) of the conveying system is greater than 20°.

Description

Technical Field

[0001] The present invention relates to a screw conveyor for transporting products in a downward direction by gravity, the screw conveyor comprising a frame and a screw track extending about a vertical centerline, the screw track being supported by the frame and including a bottom for carrying the products, wherein the bottom has an inclined angle in the direction along the screw track. Background Technology

[0002] Such screw conveyors are known from US 3,565,226. These known screw conveyors, also called helical chutes, are suitable for conveying products horizontally from a higher height by gravity. In other words, the product slides or rolls automatically on the bottom in a downward direction along the helical track. Sidewalls at the outward bend at the bottom prevent the product from accidentally leaving the helical track in an outward direction due to centrifugal force. In practice, the choice of the tilt angle involves a trade-off between preventing the product from getting stuck in the helical track due to a relatively small tilt angle and preventing the product from gaining excessive speed due to a large tilt angle. Finding a suitable trade-off is difficult when transporting products with a wide variety of characteristics such as weight, shape, size, flexibility, and surface conditions. Summary of the Invention

[0003] One object of the present invention is to provide a screw conveyor that prevents products from reaching undesirable high speeds without the risk of getting stuck in the screw track for products with a wide variety of characteristics.

[0004] This objective is achieved by a screw conveyor according to the invention, wherein at least a portion of the bottom is formed by a transport surface of a driveable conveying system, such that the transport surface has a predetermined speed in the downward direction along the screw track, and the inward curvature angle of the transport surface of the conveying system is greater than 20°.

[0005] Because the inclination angle at the inner bend of the transport surface is relatively large, exceeding 20°, some products, perhaps most in the product range, will automatically slide or roll downwards on the bottom. Some products, such as relatively heavy and large-sized products, may tend to stop moving relative to the bottom under operating conditions, but these products will be forced downwards by the transport surface of the driveable conveyor system. Therefore, the screw conveyor according to the invention provides a combination of transporting products downwards by gravity and by the transport surface of the driveable conveyor system. A screw conveyor is known in the prior art whose bottom includes the transport surface of the driveable conveyor system, such as a screw conveyor including an annular conveyor belt, but with a relatively small inclination angle at the bottom, precisely to prevent products from moving downwards relative to the conveyor belt. Due to the helical track, the inclination angle of the bottom gradually decreases radially outwards from the inner bend relative to the centerline. Therefore, products moving outwards relative to the bottom due to their higher speed may automatically decelerate. It should be noted that the screw conveyor according to the invention is intended to transport various discrete products, i.e., non-bulk materials, such as items in e-commerce warehouses. The centerline can extend vertically, and the helical track can have multiple turns.

[0006] To facilitate easy downward movement of the product by gravity, the upper side of the bottom is preferably smooth and free of obstructions in the downward direction.

[0007] The inclination angle at the inner bend can be greater than 25°, or even greater than 30°.

[0008] In a particular embodiment, the driveable conveyor system includes a driveable annular conveyor belt guided by a frame, wherein the conveyor belt has a transport section and a return section, and wherein a transport surface is formed by the upper surface of the transport section. If the product tends to adhere to the transport surface without sliding or rolling further downward by gravity, the transport surface will carry the product downward.

[0009] The return section can extend below the transport section, causing it to also follow a helical path. In this case, the conveyor belt reverses direction at the upper and lower ends of the transport section, respectively. This embodiment is particularly advantageous when the number of helical windings is limited, as this configuration of the return section requires a relatively long conveyor belt, which is more expensive and requires greater drive power. However, due to the relatively large inclination angle of the transport surface, the helical conveyor according to the invention can have a limited number of windings, such as only a single turn.

[0010] In a practical embodiment, the conveyor belt is provided having elongated slats that are movable relative to each other and have a longitudinal direction perpendicular to the direction extending along the helical track. The slats can be mounted to an annular component, such as a chain, that is driven along the helical track.

[0011] Preferably, at the transport surface, each slat overlaps the upper side of the adjacent slat located downstream of it, as this minimizes the risk of the product getting stuck behind the slat or between adjacent slats.

[0012] The predefined transport speed can be less than 30 meters per minute, preferably less than 20 meters per minute, and more preferably less than 10 meters per minute. In practice, when most products are transported by gravity, the transport speed may be relatively low.

[0013] In a preferred embodiment, the transport surface of the conveyor system is inclined downwards in a direction from its outer curvature to its inner curvature. This inclination is referred to as embankment. The advantage of this embodiment is that when a product moves downwards relative to the transport surface at a relatively high speed, it is forced to move outwards due to its speed; however, because the inclination angle along the direction of the helical track decreases in the outward direction, the product can decelerate and move inwards, thus creating a self-stabilizing effect. Furthermore, when using a conveyor belt comprising elongated slats as described above, embankment appears to minimize the step effect in the height direction between adjacent slats, whereas a step effect could occur due to the torsion of the transport surface within the helical track when the inclination angle along the direction of the helical track is relatively large.

[0014] In one particular embodiment, a portion of the bottom is formed by the transport surface of the conveyor system, and the bottom is also provided with a static inner curved section fixed to the frame, wherein the static inner curved section extends along the transport surface of the conveyor system and is adjacent to its inner curved section. The position of the static inner curved section results in a relatively large inclination in the direction along the helical track. Therefore, when the product reaches the static inner curved section, it will almost certainly slide or roll downwards under the influence of gravity. If the product accelerates on the static inner curved section, it can move outwards relative to the bottom and automatically decelerate, as described above. In the case of embankment construction on the transport surface, the self-stabilizing effect can be enhanced.

[0015] The static inner bending segment may have an upper surface that extends substantially horizontally when viewed in a plane extending radially from the centerline. The static inner bending segment may be a plate.

[0016] The coefficient of friction at the bottom of the conveyor surface of the conveyor system can be increased radially outward from the centerline. An advantage of this embodiment is that heavy products with a bottom having a low coefficient of friction and moving downward at a relatively high speed relative to the bottom of the helical track when their distance from the centerline is relatively small may move away from the centerline due to centrifugal force on the product. Therefore, the product may decelerate due to the smaller tilt angle along the helical track and due to the increased coefficient of friction. Thus, the speed of heavier products can be automatically limited. On the other hand, light products with a bottom having a high coefficient of friction and moving downward relative to the conveyor surface of the driveable conveyor system may decelerate due to their high coefficient of friction, but in this case, the conveyor surface will cause the product to move downward.

[0017] If the bottom is provided with a static inner bend, the coefficient of friction of the transport surface can be higher than that of the static inner bend. In this case, the coefficient of friction of the static inner bend can be substantially constant, while the coefficient of friction of the transport surface can, for example, gradually increase from the centerline in a radially outward direction.

[0018] It is worth noting that in a screw conveyor without a transport surface for a driveable conveying system, an increased coefficient of friction in the radially outward direction from the centerline is also conceivable. In other words, one aspect of the invention is a screw conveyor for transporting products downward by gravity, comprising a frame and a helical track extending around a vertical centerline, the helical track being supported by the frame and including a bottom for carrying the product, wherein the coefficient of friction at the bottom, where the transport surface of the conveying system is located, increases radially outward from the centerline. The bottom may have an inclination angle greater than 20° at its inward bend along the direction of the helical track.

[0019] The present invention also relates to a method of transporting products using a screw conveyor as described above, wherein a first product and a second product are moved downward along a screw track, wherein the first product is moved by gravity at a speed higher than a predefined speed of the transport surface of the conveying system, and the second product is moved by the transport surface of the conveying system at a predefined speed of the transport surface of the conveying system, so as to transport the second product downward while it rests on the transport surface.

[0020] The predefined speed can be less than 30 m / min, preferably less than 20 m / min, and more preferably less than 10 m / min.

[0021] The transport surface can only move in the downward direction because the screw conveyor is not designed to transport products upward.

[0022] The inclination angle of the inner curvature of the conveyor surface can be selected so that more than 50% of the transported products slide and / or roll downwards on the bottom. These products are transported by gravity, rather than by a moving transport surface.

[0023] Each of these products can achieve a stable speed during downward movement, meaning that acceleration or deceleration becomes or approaches zero during movement, allowing the product to exit the helical track with an acceptable speed. This can be achieved, for example, by building a dam on the transport surface. Attached Figure Description

[0024] The invention will now be described with reference to the accompanying drawings, which illustrate embodiments of the invention by way of example.

[0025] Figure 1 This is a perspective view of an embodiment of a screw conveyor according to the present invention;

[0026] Figure 2 It is based on Figure 1 An enlarged cross-sectional view of a portion of a screw conveyor. Detailed Implementation

[0027] Figure 1 and Figure 2 An embodiment of a screw conveyor 1 is shown, which is suitable for transporting products along a spiral path in a downward direction. The screw conveyor 1 can be used, for example, to transport piece-rate goods in an e-commerce warehouse. An input end I is located on the upper side of the screw conveyor 1, and an output end O is located on the lower side. Products can be supplied, for example, from a sorting conveyor (not shown) at a higher height level to the input end I, and then transported downwards via the input end I, the screw conveyor 1, and the output end O to a lower height level toward a downstream unloading conveyor, collection container, etc. (not shown).

[0028] The screw conveyor 1 includes a frame 2, which in this case includes a vertical cylindrical column 3 with legs 4 and radial rods 5 supporting a helical track 6 extending about a vertical centerline CL around the column 3. The helical track 6 includes a bottom 7 for carrying products, an inner sidewall 8 extending inwardly along the bottom 7, and an outer sidewall 9 extending outwardly along the bottom 7. The inner sidewall 8 and the outer sidewall 9 are fixed to the frame 2. In this case, the inner sidewall 8, which curves inwardly along the bottom 7, is formed by the outer surface of the column 3; however, a separate inner sidewall at a distance from the column 3 is also conceivable. In this case, the number of turns of the screw conveyor 1 is approximately one, but this can be different in alternative embodiments.

[0029] Input terminal I is formed by a twisted plate fixed to frame 2, and output terminal O is also formed by a plate fixed to frame 2. It is practically impossible for the product to stop on the plate at output terminal O, but if this happens, it is easily accessible to the operator because it is located at a lower height.

[0030] A portion of the bottom 7 of the helical track 6 is formed by a transport surface 7a of a driveable conveyor system in the form of a driveable annular conveyor belt 10. The conveyor belt 10 is guided by belt supports of the frame 2 and can be driven relative to the frame 2 by an electric motor 11, such that under operating conditions, the transport surface 7a has a predefined speed in the downward direction X along the helical track 6. The conveyor belt 10 has a transport section and a return section. The transport surface 7a is formed by the upper surface of the transport section.

[0031] The transport section of the conveyor belt 10 has an outward bend adjacent to the outer side wall 9 and an inward bend opposite to the outward bend. Due to its helical shape, the transport surface 7a has an inclination angle in the direction X along the helical track 6, which increases in the direction from its outward bend to its inward bend. Therefore, the maximum inclination angle is located at the inward bend of the transport section, which is greater than 20° in this case. This is a rather steep angle, which in fact causes many products to automatically slide or roll on the transport surface 7a in the downward direction X along the helical track 6.

[0032] The conveyor belt 10 is provided with an upper pulley 12 located at the upper end of the spiral track 6 and a lower pulley 13 located at the lower end of the spiral track 6. The transport section of the conveyor belt 10 extends along the spiral track 6 from the upper pulley 12 to the lower pulley 13. The return section of the conveyor belt 10, which does not contribute to the transport surface 7a, is guided below the transport section by a return belt support 14 and extends from the lower pulley 13 to the upper pulley 12. The return section also follows a spiral path, but in the reverse direction.

[0033] In an alternative embodiment (not shown), the return section can be guided back via a non-spiral path. Generally, the latter configuration is advantageous in terms of efficiency because the conveyor belt length can be shorter, resulting in less friction than when both the transport and return sections follow spiral paths. However, in this case, the inclination angle along the direction X of the spiral track 6 is relatively steep, requiring only a limited number of turns. This means the length of the annular conveyor belt 10 is relatively short. Therefore, it is advantageous for the return section to extend below the transport section.

[0034] In such Figure 1In the illustrated embodiment, the conveyor belt 10 is provided with elongated slats 15 that are movable relative to each other and have a longitudinal direction perpendicular to the direction extending along the helical track 6. The slats 15 are coupled to each other by annular connecting members, such as chains (not shown). Within a transport section of the conveyor belt 10, each slat 15 may overlap the upper side of the adjacent slat 15 located downstream of it. This minimizes the risk of products getting stuck between adjacent slats 15. Preferably, the upper surfaces of the slats 15, as well as the upper surfaces of the input end I and the output end O, are smooth to produce suitable sliding characteristics.

[0035] Figure 1 and Figure 2 The conveyor surface 7a of the conveyor belt 10 is shown to be inclined downwards in a direction from its outer bend to its inner bend. This direction is called embankment and produces a balancing effect on products moving downwards at a higher speed than that of the conveyor surface 7a. Due to its higher speed, such products tend to move outwards towards the outer bend of the conveyor surface 7a. As the inclination angle along the direction X of the helical track 6 decreases in the outward direction, the products tend to decelerate and move backwards in the direction from the outer bend to the inner bend of the conveyor surface 7a. Due to the embankment, the return force on the products towards the inner bend is enhanced. For example, the inclination angle can be 15°. The inclination angle and / or embankment angle can be selected such that, in practice, most products sliding or rolling on the bottom 7 achieve a stable speed during their downward movement on the bottom 7, i.e., their acceleration or deceleration becomes or approaches zero before reaching the output end O.

[0036] In such Figure 1 and Figure 2 In the illustrated embodiment, the bottom 7 is further provided with a static inner bend 7b that is fixed to the frame 2. The static inner bend 7b extends along the transport surface 7a and is adjacent to its inner bend. The static inner bend 7b is also adjacent to the column 3, such that the column 3 forms an inner sidewall 8 at the inner bend of the bottom 7, as previously described. In this case, the static inner bend 7b is plate-shaped and has a smooth upper surface. Due to the position of the static inner bend 7b, its inclination angle along the direction X of the helical track 6 is steeper than its inclination angle at the transport surface 7a. For example, the inclination angles along the direction X of the helical track 6 at the inner bend of the bottom 7, the inner bend of the transport surface 7a, and the outer bend of the transport surface 7a can be 55°, 25°, and 15°, respectively. Figure 2 The static inner bending segment 7b is shown to have an upper surface that extends horizontally in a plane extending radially from the centerline CL of column 3.

[0037] Preferably, the plates of the input end I and the output end O are shaped such that their upper surfaces fit into the inclined upper surface of the bottom 7 at the upper pulley 12 and the lower pulley 13.

[0038] Under operating conditions, the conveyor belt 10 can be driven at a relatively low speed, for example, less than 10 meters per minute. In fact, due to the relatively steep incline of the helical track 6, a portion, preferably the majority, of the series of products supplied to the transport surface 7a via the input end I can slide or roll downwards on the conveyor belt 10 by gravity, and have a speed higher than that of the conveyor belt 10. Products remaining on the conveyor belt 10 and transported downwards by it reach the output end O at a speed equal to the speed of the transport surface 7a; in effect, such products will be transported further downwards by gravity. If not, the operator can remove the products from the output end O. Therefore, it may be advantageous when the lower end of the transport surface 7a, in this case at the lower pulley 13 of the conveyor belt 10, is located 2 meters or even 1.5 meters below ground level.

[0039] More typically, in a method of transporting products using a screw conveyor 1, a first product and a second product are moved downward along a screw track 6, wherein the first product is moved by gravity at a speed higher than a predefined speed of the transport surface 7a, and the second product is moved by the conveyor belt 10 at a predefined speed of the transport surface 7a, so as to transport the second product downward while it remains on the transport surface 7a.

[0040] This invention is not limited to the embodiments shown in the accompanying drawings and described above, and can be varied in different ways within the scope of the claims and their technical equivalents. For example, instead of using a circular conveyor belt, the helical track may include alternative means for moving the transport surface relative to the frame in a downward direction, such as a driveable roller. Similarly, the input and / or output may be provided with alternative guiding means, such as freely rotating rollers, etc.

Claims

1. A method for transporting products using a screw conveyor (1) for transporting the products in a downward direction by gravity, comprising a frame (2) and a helical track (6) extending about a vertical centerline (CL), the helical track (6) being supported by the frame (2) and comprising a bottom (7) for carrying the products, wherein the bottom (7) has an angle of inclination in a direction (X) along the helical track (6), characterized in that, At least a portion of the bottom (7) is formed by a transport surface (7a) of a driveable conveying system (10), such that the transport surface (7a) has a predefined speed in the downward direction (X) along the spiral track (6) and the inclination angle at the inner bend of the transport surface (7a) of the conveying system (10) is greater than 20°. In the method, a first product and a second product are moved downward along the spiral track (6), wherein the first product is moved by gravity at a speed higher than the predefined speed of the transport surface (7a) of the conveying system (10), and the second product is moved by the transport surface (7a) of the conveying system (10) at the predefined speed of the transport surface (7a) of the conveying system (10) to transport the second product downward while it remains on the transport surface (7a).

2. The method according to claim 1, characterized in that, The tilt angle at the inner bend is greater than 25°.

3. The method according to claim 1, characterized in that, The tilt angle at the inner bend is greater than 30°.

4. The method according to any one of claims 1-3, characterized in that, The driveable conveying system (10) includes a driveable annular conveyor belt guided by the frame (2), wherein the conveyor belt has a transport section and a return section, wherein the transport surface (7a) is formed by the upper surface of the transport section.

5. The method according to claim 4, characterized in that, The return segment extends below the transport segment, so that it also follows a spiral path.

6. The method according to claim 4, characterized in that, The conveyor belt is provided with elongated slats (15) that are movable relative to each other and have a longitudinal direction that extends perpendicular to the direction (X) along the spiral track (6).

7. The method according to claim 6, characterized in that, At the transport surface (7a), each slat (15) overlaps with the upper side of the adjacent slat (15) located downstream of it.

8. The method according to any one of claims 1-3 and 5-7, characterized in that, The predefined speed is less than 30 meters per minute.

9. The method according to any one of claims 1-3 and 5-7, characterized in that, The predefined speed is less than 20 meters per minute.

10. The method according to any one of claims 1-3 and 5-7, characterized in that, The predefined speed is less than 10 meters per minute.

11. The method according to any one of claims 1-3 and 5-7, characterized in that, The transport surface (7a) of the transport system (10) is inclined downward in the direction from its outer curvature to its inner curvature.

12. The method according to any one of claims 1-3 and 5-7, characterized in that, A portion of the bottom (7) is formed by the transport surface (7a) of the conveying system (10), and the bottom (7) is also provided with a static inner curved section (7b) fixed to the frame (2), wherein the static inner curved section (7b) extends along the transport surface (7a) of the conveying system (10) and is adjacent to its inner curved section, wherein the static inner curved section (7b) has an upper surface that extends horizontally in a plane extending radially from the center line (CL).

13. The method according to any one of claims 1-3 and 5-7, characterized in that, The coefficient of friction of the bottom of the transport surface (7a) of the transport system (10) increases radially outward from the centerline (CL).

14. The method according to claim 12, characterized in that, The coefficient of friction of the transport surface (7a) is higher than that of the static inner curved section (7b).

15. The method according to any one of claims 1-3 and 5-7, characterized in that, The transport surface (7a) moves only in the downward direction (X).

16. The method according to any one of claims 1-3 and 5-7, characterized in that, The inclination angle of the inner bend of the transport surface (7a) of the conveying system (10) is selected such that more than 50% of the transported product slides and / or rolls downward on the bottom (7).

17. The method according to claim 16, characterized in that, Each of the products achieves a stable speed as it moves downward on the bottom (7).

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