Device and method for forming U-shaped dough strands from essentially straight dough strands, in particular for pretzel production

Abstract

Device for forming U-shaped dough strands from substantially straight dough strands, in particular for pretzel production, which is arranged between a feeding device for the substantially straight dough strands and a pretzel twisting device and has a first conveyor belt (1) and a second conveyor belt (2), which can each be driven at different conveying speeds, wherein the plane formed by the upper run of the first conveyor belt (1) is, in the assembled state of the device, higher by a predetermined amount than the plane formed by the upper run of the second conveyor belt (2), wherein the longitudinal axes of the two conveyor belts (1, 2) are arranged parallel to one another, wherein the conveyor belts (1, 2) are arranged in such a way,that the upper run of the second conveyor belt (2) extends beyond the projection of the upper run of the first conveyor belt (1) onto the plane formed by the upper run of the second conveyor belt (2), perpendicular to the projection of the longitudinal center axis of the first conveyor belt (1) onto the plane formed by the upper run of the second conveyor belt (2), on both sides in each case by at least half the desired length of a straight dough strand minus half the width of the first conveyor belt plus an offset, wherein the width of the upper run of the first conveyor belt corresponds to the width of the U of the U-shaped dough strands to be produced, wherein the conveyor belts are designed such that the static friction coefficient of the dough on the first conveyor belt (1) is higher than the static friction coefficient of the dough on the second conveyor belt (2),wherein the substantially straight dough strands can be fed to the device at the end of the device facing the feed device with their longitudinal axes substantially perpendicular to the longitudinal axes of the upper runs of the first and second conveyor belts (1, 2) and mirror-symmetrically about the longitudinal center axis of the upper run of the first conveyor belt (1), and during the transport of the dough strands, at a conveying speed of the second conveyor belt (2) that is higher than the conveying speed of the first conveyor belt (1), U-shaped dough strands can be produced with the legs leading in the conveying direction, characterized in that the second conveyor belt (2) is longer than the first conveyor belt (1) and feeds the U-shaped dough strands directly to the pretzel twisting device, wherein the ends of the two conveyor belts (1, 2) are arranged substantially one above the other at the end of the device facing the feed device for the substantially straight dough strands.

Description

[0001] The present invention relates to a device for forming U-shaped dough strands from substantially straight dough strands according to patent DE 10 2015 121 604 B3. Furthermore, the invention relates to a method for forming U-shaped dough strands from substantially straight dough strands, in particular using the device according to the invention according to patent DE 10 2015 121 604 B3.

[0002] The patent DE 10 2015 121 604 B3 describes a device for forming U-shaped dough strands from substantially straight dough strands, in particular for pretzel production, which is arranged between a feeding device for the substantially straight dough strands and a pretzel twisting device, which has a first conveyor belt and a second conveyor belt, each of which can be driven at a different conveying speed, wherein the plane formed by the upper run of the first conveyor belt is higher by a predetermined amount than the plane formed by the upper run of the second conveyor belt in the assembled state of the device, wherein the longitudinal axes of the two conveyor belts are arranged parallel to one another, wherein the conveyor belts are arranged in such a way thatthat the upper run of the second conveyor belt extends beyond the projection of the upper run of the first conveyor belt onto the plane formed by the upper run of the second conveyor belt, perpendicular to the projection of the longitudinal center axis of the first conveyor belt onto the plane formed by the upper run of the second conveyor belt, on both sides in each case by at least half the desired length of a straight dough strand minus half the width of the first conveyor belt plus an offset, wherein the width of the upper run of the first conveyor belt corresponds to the width of the U of the U-shaped dough strands to be produced, wherein the conveyor belts are designed such that the static friction coefficient of the dough on the first conveyor belt is higher than the static friction coefficient of the dough on the second conveyor belt,wherein the substantially straight dough strands can be fed to the device at the end of the device facing the feeding device with their longitudinal axes substantially perpendicular to the longitudinal axes of the upper runs of the first and second conveyor belts and mirror-symmetrically about the longitudinal center axis of the upper run of the first conveyor belt, and during the transport of the dough strands, at a conveying speed of the second conveyor belt that is higher than the conveying speed of the first conveyor belt, U-shaped dough strands can be produced with the legs leading in the conveying direction.

[0003] According to one embodiment, a stopper is arranged at the end of the device facing the pretzel twisting device, which stopper is connected to a control system and can be actuated hydraulically, electrically or pneumatically, comprising a contact surface against which the dough strands arriving with the legs first come to rest with their middle part and are released in a cycle corresponding to the cycle of the downstream pretzel twisting device by a vertical movement of the stopper upwards for transfer to the pretzel twisting device, wherein the stopper is arranged by means of a holder above an intermediate conveyor belt which feeds the U-shaped dough strands to the pretzel twisting device.

[0004] The provision of an intermediate conveyor belt results in additional manufacturing, assembly and maintenance costs and increases complexity.

[0005] From DE 195 27 116 C1, a device for producing pretzels from pre-formed dough strands is known, comprising a feed arrangement for the dough strands to a work platform provided with several curved stops, a frame that is movable in and against the transport direction of the dough strands, a holder arranged on the underside of the frame so as to be rotatable and lowerable about a central axis, two grippers for the dough strands arranged on the underside of the holder, an arrangement for measuring the position of the dough strands, an arrangement for controlling the grippers as a function of this position, wherein the work platform has a smaller width than the width of the feed arrangement for the dough strands and is connected to the latter symmetrically to the longitudinal axis of the feed arrangement, two support surfaces extending on both sides of the work platform, two vertical stationary pins,which extend from the work platform near the two outer edges and, viewed in the transport direction, directly next to the two support surfaces, with two sensors connected to the control arrangement, and with two holding clamps for the dough strand, each provided in the immediate vicinity of each sensor and outside the work platform, connected to the control arrangement, and operable by the latter. It is provided that each unit formed by the holding clamp and the associated sensor, which has a defined distance from the respective clamp, can be moved back and forth in the longitudinal direction of the respective support surface, and that each unit can be controlled by the control arrangement independently of the other unit in such a way that, after reaching the associated end of the dough strand, each sensor transmits a signal to the control arrangement, which causes the control arrangement to close the holding clamp.so that it grasps the end of the dough strand at a predetermined point near the end of the dough strand, after which it returns, together with the associated sensor, to its starting position near the work platform. Furthermore, DE 198 52 046 C1 discloses a device for producing pretzels, comprising a feed arrangement, a discharge arrangement for the finished, looped pretzels, a work platform, a robot arm or linear robot, and a control device. The feed arrangement has a conveyor belt above the work platform, the width of which is smaller than the length of the dough strand, so that the two dough strand ends hang laterally from the conveyor belt. Guides are provided next to the conveyor belt, in which guides a carriage with a pivoting plate is arranged, on which sensors and retaining clamps are located.

[0006] The present invention is based on the object of specifying a device and a method for forming U-shaped dough strands from substantially straight dough strands, in particular for pretzel production, starting from a device for forming U-shaped dough strands from substantially straight dough strands, in particular for pretzel production, in which the manufacturing, assembly and maintenance costs and the complexity are reduced.

[0007] This object is achieved for a device by the features of patent claim 1. A method is the subject of patent claim 9.

[0008] Accordingly, a device for forming U-shaped dough strands from substantially straight dough strands, in particular for pretzel production, is proposed, which is arranged between a feeding device for the substantially straight dough strands and a pretzel twisting device, which has a first conveyor belt and a second conveyor belt, each of which can be driven at a different conveying speed, wherein the plane formed by the upper run of the first conveyor belt is higher by a predetermined amount than the plane formed by the upper run of the second conveyor belt in the assembled state of the device, wherein the longitudinal axes of the two conveyor belts are arranged parallel to one another, wherein the conveyor belts are arranged in such a way thatthat the upper run of the second conveyor belt extends beyond the projection of the upper run of the first conveyor belt onto the plane formed by the upper run of the second conveyor belt, perpendicular to the projection of the longitudinal center axis of the first conveyor belt onto the plane formed by the upper run of the second conveyor belt, on both sides in each case by at least half the desired length of a straight dough strand minus half the width of the first conveyor belt plus an offset, wherein the width of the upper run of the first conveyor belt corresponds to the width of the U of the U-shaped dough strands to be produced, wherein the conveyor belts are designed such that the static friction coefficient of the dough on the first conveyor belt is higher than the static friction coefficient of the dough on the second conveyor belt,wherein the substantially straight dough strands can be fed to the device at the end of the device facing the feed device with their longitudinal axes substantially perpendicular to the longitudinal axes of the upper runs of the first and second conveyor belts and mirror-symmetrically about the longitudinal center axis of the upper run of the first conveyor belt, and during the transport of the dough strands, at a conveying speed of the second conveyor belt that is higher than the conveying speed of the first conveyor belt, U-shaped dough strands can be produced with the legs leading in the conveying direction, according to patent DE 10 2015 121 604 B3, in which the second conveyor belt is longer than the first conveyor belt and feeds the U-shaped dough strands directly to the pretzel twisting device, wherein the ends of the two conveyor belts are arranged substantially one above the other at the end of the device facing the feed device for the substantially straight dough strands.

[0009] This eliminates the need for an intermediate conveyor belt, reducing manufacturing, assembly and maintenance costs.

[0010] In this case, the second conveyor belt can have a continuous upper run viewed perpendicular to the projection of the longitudinal center axis of the first conveyor belt onto the plane formed by the upper run of the second conveyor belt.

[0011] Alternatively, the second conveyor belt can have a first and a second partial conveyor belt, wherein the arrangement of their upper runs and the projection of the upper run of the first conveyor belt onto the plane formed by the upper runs of the first and second partial conveyor belts is perpendicular to the projection of the longitudinal center axis of the first conveyor belt onto this plane, as viewed from above: upper run of the first partial conveyor belt - projection of the upper run of the first conveyor belt - upper run of the second partial conveyor belt. This configuration enables an embodiment in which the lower run of the first conveyor belt, in the assembled state, lies below the plane formed by the upper runs of the first and second partial conveyor belts.

[0012] In a further embodiment, the upper runs of the first and second partial conveyor belts can each partially overlap with the projection of the upper run of the first conveyor belt onto the plane formed by the upper runs of the first and second partial conveyor belts.

[0013] In a preferred embodiment of the invention, the central longitudinal axes of the first and second conveyor belts are arranged one above the other in the assembled state.

[0014] The first conveyor belt can be arranged above the second conveyor belt in such a way that the lower run of the first conveyor belt, in the assembled state of the device, is higher by a predetermined amount than the continuous upper run of the second conveyor belt or, in the event that the second conveyor belt has two partial conveyor belts, higher than the plane formed by the upper runs of the first and second partial conveyor belts, wherein the upper runs of the first and second partial conveyor belts can each partially overlap with the projection of the upper run of the first conveyor belt onto the plane formed by the upper runs of the first and second partial conveyor belts. The dimension is preferably selected such that the upper run of the second conveyor belt and the lower run of the first conveyor belt just do not touch orin the event that the second conveyor belt has two partial conveyor belts, the lower run of the first conveyor belt is arranged just above the plane formed by the upper runs of the first and second partial conveyor belts.

[0015] As already explained, a feeding device for the essentially straight dough strands is provided at one end of the device according to the invention, which feed device transfers the essentially straight dough strands to the device according to the invention, wherein the longitudinal axes of the essentially straight dough strands during transfer are essentially perpendicular to the longitudinal axes of the upper runs of the first and second conveyor belts and thus to the conveying direction of the conveyor belts, and wherein the dough strands are fed to the device essentially mirror-symmetrically about the longitudinal center axis of the upper run of the first conveyor belt. Thus, during transfer, the middle part of the dough strands lies on the upper run of the first conveyor belt, wherein the ends of the dough strands each lie on one side of the upper run of the first conveyor belt on the upper run of the second conveyor belt.In the following, the terms “upper run of the second conveyor belt” and “second conveyor belt” are also used in the case where the second conveyor belt has two partial conveyor belts.

[0016] At the end of the first conveyor belt facing the pretzel twisting device above the first conveyor belt, or in the area between the end of the first conveyor belt facing the pretzel twisting device and the pretzel twisting device above the second conveyor belt, a stopper comprising a contact surface is optionally provided, against which the dough strands arriving leg-first rest and are released at a rate corresponding to the rate of a downstream pretzel twisting device. The stopper is preferably arranged by means of a holder above the first conveyor belt or above the second conveyor belt.

[0017] Furthermore, a gripping device can be provided above the first conveyor belt at the end of the first conveyor belt facing the pretzel twisting device. This gripping device sorts out dough strands that do not meet defined specifications with regard to dimensions and / or shape. The evaluation of whether a pretzel blank meets the specifications is performed using a sensor device or a camera. The first conveyor belt can be a conveyor belt comprising several conveyor belts, allowing the gripping device to easily grasp the dough strands using fingers that grip between the conveyor belts.

[0018] The device according to the invention functions as follows: By means of the upstream feed device, the essentially straight dough strands are transferred to the device, wherein the conveying speed of the second conveyor belt is higher than the conveying speed of the first conveyor belt, so that the ends of the dough strands, i.e. the parts of the dough strands that lie on the upper run of the second conveyor belt, are transported at a higher speed in the conveying direction than the middle parts that lie on the upper run of the first conveyor belt, whereby after a period of time that depends on the conveying speed difference of the two conveyor belts, the ends of the dough strands, i.e. the parts of the dough strands that lie on the upper run of the second conveyor belt are aligned parallel to the conveying direction of the second conveyor belt and a U-shaped dough strand is formed with the legs in the conveying direction.Accordingly, during transport, at a conveying speed of the second conveyor belt that is higher than the conveying speed of the first conveyor belt, a U-shaped dough strand can be produced with the legs leading in the conveying direction.

[0019] Accordingly, within the scope of the method according to the invention, the essentially straight dough strands are fed to a device comprising a first conveyor belt and a second conveyor belt, which can each be driven at different conveying speeds, wherein the plane formed by the upper run of the first conveyor belt is higher by a predetermined amount than the plane formed by the upper run of the second conveyor belt and the longitudinal axes of the two conveyor belts are arranged parallel to one another, wherein when the dough strands are transferred to the device, the middle part of the dough strands lies on the upper run of the first conveyor belt and the ends of the dough strands each lie on one side of the upper run of the first conveyor belt on the upper run of the second conveyor belt, wherein the conveying speed of the second conveyor belt is higher than the conveying speed of the first conveyor belt,so that during the transport of the dough strands, U-shaped dough strands are produced with the legs leading in the conveying direction. The U-shaped dough strands are fed directly to the pretzel twisting device by means of the second conveyor belt.

[0020] According to the invention, the conveyor belts are designed such that the static friction coefficient of the dough on the first conveyor belt is higher than the static friction coefficient of the dough on the second conveyor belt. After forming the dough strands, with the legs leading in the conveying direction, they are transported at the speed of the first conveyor belt. The legs lying on the second conveyor belt are held by the middle section of the dough strand lying on the first conveyor belt, and sliding friction acts between the upper run of the second conveyor belt and the legs.

[0021] According to the invention, the transport time of the dough strands after forming the dough strands with the legs leading in the conveying direction corresponds at least to the required resting time for the dough.

[0022] According to the invention, the width of the first conveyor belt corresponds essentially to the width of the U-shaped dough strand to be formed; in this case, if pretzels of different sizes are to be produced, the first conveyor belt can be exchanged depending on the desired width of the pretzel blanks to be produced.

[0023] Within the scope of a further development of the invention, the dimensions and shape of the dough strands are measured at the end of the device according to the invention facing the pretzel twisting device using a close-range photogrammetry device. If the deviation in dimensions and shape exceeds predetermined threshold values, the respective dough strands are sorted out by the gripping device. As an alternative to the close-range photogrammetry device, a thermal imaging camera can be used to measure the dough blanks.

[0024] Within the scope of a further embodiment, the length of the legs of the U-shaped dough strands formed by means of the device can be determined by means of two sensors for detecting the legs of the incoming dough blanks, wherein the sensors are each arranged on one side of the device at the same height and are damped when a leg of a dough blank is detected, wherein the length of the respective leg is determined based on the time of damping of a sensor and the known conveying speed of the second conveyor belt.If the difference in length between the two legs exceeds a predetermined threshold and / or if the sum of the lengths of both legs falls below a further predetermined threshold, the pretzel is sorted out by means of the gripping device, since in the first case the shape of the pretzel pretzel does not correspond to the desired shape and in the second case the proportion of dough in the middle part of the pretzel pretzel, which is not detected by the sensors, is much too high.

[0025] In the event that U-shaped dough blanks are to be formed, which are to be fed to a pretzel twisting device with the U-shaped part and not with the legs first, the conveying speed of the first conveyor belt is correspondingly higher than the conveying speed of the second conveyor belt.

[0026] The invention is explained in more detail below by way of example with reference to the attached figure, which shows a schematic perspective view of an embodiment of the invention.

[0027] The drive shafts of the conveyor belts are not shown in the figure.

[0028] According to the invention and with reference to the attached figure, the device for forming U-shaped dough strands from substantially straight dough strands comprises a first conveyor belt 1 and a second conveyor belt 2, each of which can be driven at a different conveying speed. In the assembled state of the device, the plane formed by the upper run of the first conveyor belt 1 is higher by a predetermined amount than the plane formed by the upper run of the second conveyor belt 2, the longitudinal axes of the two conveyor belts 1, 2 being arranged parallel to one another. The conveying speed of the second conveyor belt is higher than the conveying speed of the first conveyor belt.The second conveyor belt 2 is longer than the first conveyor belt 1 and feeds the U-shaped dough strands directly to a pretzel twisting device (not shown). The ends of the two conveyor belts 1, 2 are preferably arranged one above the other at the end of the device facing the feed device for the essentially straight dough strands. Thus, viewed in the conveying direction, the second conveyor belt 2 extends beyond the projection of the upper run of the first conveyor belt 1 onto the plane formed by the upper run of the second conveyor belt 2 as far as a pretzel twisting device (not shown).

[0029] The conveyor belts 1, 2 are arranged such that the upper run of the second conveyor belt 2 extends beyond the projection of the upper run of the first conveyor belt 1 onto the plane formed by the upper run of the second conveyor belt 2 and its imaginary continuation up to the pretzel twisting device, viewed perpendicular to the projection of the longitudinal center axis of the first conveyor belt 1 onto the plane formed by the upper run of the second conveyor belt 2, on both sides by at least half the desired length of a straight dough strand minus half the width of the first conveyor belt 1 plus an offset. According to the invention, the width of the upper run of the first conveyor belt 1 essentially corresponds to the width of the U of the U-shaped dough strands to be produced by means of the device.

[0030] In the example shown in the figure, the second conveyor belt 2 has a continuous upper run viewed perpendicular to the projection of the longitudinal center axis of the first conveyor belt 1 onto the plane formed by the upper run of the second conveyor belt 2, wherein the central longitudinal axes of the first and second conveyor belts 1, 2 are arranged one above the other in the assembled state.

[0031] The first conveyor belt 1 is arranged above the second conveyor belt 2, wherein the lower run of the first conveyor belt 1 is higher by a predetermined amount than the continuous upper run of the second conveyor belt 2 and wherein the predetermined amount is selected such that the upper run of the second conveyor belt 2 and the lower run of the first conveyor belt 1 just do not touch.

[0032] The device according to the invention is arranged between a feed device for substantially straight dough strands and a pretzel twisting device, which correspond to the prior art and are not the subject of the invention; the conveying direction of the conveyor belts 1, 2 leads from the feed device for substantially straight dough strands to the pretzel twisting device.

[0033] The essentially straight dough strands are transferred to the device according to the invention in such a way that their longitudinal axes during transfer are essentially perpendicular to the longitudinal axes of the upper runs of the first and second conveyor belts 1, 2 and thus to the conveying direction of the conveyor belts, wherein the dough strands are fed to the device essentially mirror-symmetrically about the longitudinal center axis of the upper run of the first conveyor belt 1. Accordingly, during transfer, the middle part of the dough strands lies on the upper run of the first conveyor belt 1, wherein the ends of the dough strands each lie on one side of the upper run of the first conveyor belt 1 on the upper run of the second conveyor belt 2.The substantially straight dough strands can therefore be fed to the device at an end 3 of the device facing the feed device (not shown) for the substantially straight dough strands, with their longitudinal axes substantially perpendicular to the longitudinal axes of the upper runs of the first and second conveyor belts 1, 2 and mirror-symmetrically about the longitudinal center axis of the upper run of the first conveyor belt 1.

[0034] Since, according to the invention, the conveying speed of the second conveyor belt 2 is higher than the conveying speed of the first conveyor belt 1, the ends of the dough strands lying on the upper run of the second conveyor belt 2 are transported at a higher speed in the conveying direction than the middle parts lying on the upper run of the first conveyor belt 1 after being transferred to the device according to the invention, as a result of which the ends of the dough strands lying on the upper run of the second conveyor belt 2 are aligned parallel to the conveying direction of the second conveyor belt during transport and a U-shaped dough strand is formed with the legs leading in the conveying direction, the width of which strand essentially corresponds to the width of the upper run of the first conveyor belt.

[0035] The conveyor belts are designed in such a way that the static friction coefficient of the dough on the first conveyor belt 1 is higher than the static friction coefficient of the dough on the second conveyor belt 2. After the dough strands have been formed with the legs first in the conveying direction, they are transported at the speed of the first conveyor belt, whereby the legs lying on the second conveyor belt 2 are held by the middle part of the dough strand lying on the first conveyor belt 1 and sliding friction acts between the upper run of the second conveyor belt and the legs.

[0036] According to the invention, the transport time for a dough strand after the formation of the dough strand with the legs leading in the conveying direction until the transfer to the pretzel twisting device corresponds to the required resting time for the dough.

[0037] In the example shown in the figure, in the area 4 between the end of the first conveyor belt 1 facing the pretzel twisting device (not shown) and the pretzel twisting device above the second conveyor belt 2, a stopper 5 is provided which is connected to a control system and can be actuated hydraulically, electrically or pneumatically and comprises a contact surface 6, against which the dough strands arriving with the legs first come to rest and are released in a cycle corresponding to the cycle of the downstream pretzel twisting device by a vertical movement of the stopper 5 upwards for transfer to the pretzel twisting device, wherein the stopper 5 is preferably arranged by means of a holder 7 above the second conveyor belt 2, which feeds the U-shaped dough strands produced by the device according to the invention to the pretzel twisting device.

[0038] In the example shown, at the end of the first conveyor belt 1 facing the pretzel twisting device, a gripping device 8 is connected to a controller and can be actuated hydraulically, electrically or pneumatically, and is arranged above the first conveyor belt 1 by means of a holder 9. This gripping device sorts out dough strands that do not meet defined specifications. The evaluation of whether a pretzel blank meets the specifications is carried out using a sensor device or a camera, as explained above. The gripping device 8 is vertically movable in order to grip, lift and deposit a dough strand, and horizontally movable in order to transport the gripped dough strand away from the conveyor belts 1, 2 of the device. In the example shown, the gripping device 8 is shown in a position in which a gripped dough strand is transported away from the device.The first conveyor belt 1 may preferably be a conveyor belt comprising several conveyor belts, whereby the gripping device 8 can easily grasp the dough strands by means of fingers which grip between the conveyor belts.

[0039] Within the scope of further embodiments, if the second conveyor belt 2 has a continuous upper run, the first conveyor belt can be designed such that its width increases toward the end facing the pretzel twisting device, with the maximum width corresponding to the width of the U-shaped dough strands. The width of the upper run remains constant, with the increase in width being realized by immovable edges of the conveyor belt between which the upper run is arranged.

Claims

[1] Device for forming U-shaped dough strands from substantially straight dough strands, in particular for pretzel production, which device is arranged between a feeding device for the substantially straight dough strands and a pretzel twisting device and has a first conveyor belt (1) and a second conveyor belt (2), which can each be driven at a different conveying speed, wherein the plane formed by the upper run of the first conveyor belt (1) in the assembled state of the device is higher by a predetermined amount than the plane formed by the upper run of the second conveyor belt (2), wherein the longitudinal axes of the two conveyor belts (1, 2) are arranged parallel to one another, wherein the conveyor belts (1, 2) are arranged in such a way,that the upper run of the second conveyor belt (2) extends beyond the projection of the upper run of the first conveyor belt (1) onto the plane formed by the upper run of the second conveyor belt (2) perpendicular to the projection of the longitudinal center axis of the first conveyor belt (1) onto the plane formed by the upper run of the second conveyor belt (2), viewed on both sides by at least half the desired length of a straight dough strand minus half the width of the first conveyor belt plus an offset, wherein the width of the upper run of the first conveyor belt corresponds to the width of the U of the U-shaped dough strands to be produced, wherein the conveyor belts are designed such that the static friction coefficient of the dough on the first conveyor belt (1) is higher than the static friction coefficient of the dough on the second conveyor belt (2),wherein the substantially straight dough strands can be fed to the device at the end of the device facing the feeding device with their longitudinal axes substantially perpendicular to the longitudinal axes of the upper runs of the first and second conveyor belts (1, 2) and mirror-symmetrically about the longitudinal center axis of the upper run of the first conveyor belt (1), and during the transport of the dough strands at a conveying speed of the second conveyor belt (2) that is higher than the conveying speed of the first conveyor belt (1), U-shaped dough strands can be produced with the legs leading in the conveying direction, characterized by that the second conveyor belt (2) is longer than the first conveyor belt (1) and feeds the U-shaped dough strands directly to the pretzel twisting device, wherein the ends of the two conveyor belts (1, 2) are arranged substantially one above the other at the end of the device facing the feed device for the substantially straight dough strands. [2] Device for forming U-shaped dough strands according to claim 1, characterized by that the second conveyor belt (2) has a continuous upper run when viewed perpendicular to the projection of the longitudinal center axis of the first conveyor belt (1) onto the plane formed by the upper run of the second conveyor belt (2), or that the second conveyor belt (2) has a first and a second partial conveyor belt, wherein the arrangement of the upper runs of the partial conveyor belts of the second conveyor belt (2) and the projection of the upper run of the first conveyor belt (1) onto the plane formed by the upper runs of the first and second partial conveyor belts when viewed perpendicular to the projection of the longitudinal center axis of the first conveyor belt (1) onto this plane is upper run of the first partial conveyor belt - projection of the upper run of the first conveyor belt (1) - upper run of the second partial conveyor belt. [3] Device for forming U-shaped dough strands according to claim 1 or 2, characterized bythat the central longitudinal axes of the first and second conveyor belts are arranged one above the other in the assembled state. [4] Device for forming U-shaped dough strands according to claim 1, 2 or 3, characterized by that the first conveyor belt (1) is arranged above the second conveyor belt (2) in such a way that the lower run of the first conveyor belt (1) in the assembled state of the device is higher by a predetermined amount than the continuous upper run of the second conveyor belt (2) or, in the case that the second conveyor belt (2) has two partial conveyor belts, higher than the level formed by the upper runs of the first and second partial conveyor belts. [5] Device for forming U-shaped dough strands according to claim 1, 2, 3 or 4, characterized bythat at the end of the first conveyor belt (1) facing the pretzel twisting device above the first conveyor belt (1) or in the area between the end of the first conveyor belt (1) facing the pretzel twisting device and the pretzel twisting device above the second conveyor belt (2), a stopper (5) connected to a control system and hydraulically, electrically or pneumatically actuated is arranged, comprising a contact surface (6) against which the dough strands arriving with the legs first come to rest and are released in a cycle corresponding to the cycle of a downstream pretzel twisting device by a vertical movement of the stopper (5) upwards for transfer to the pretzel twisting device, wherein the stopper (5) is arranged by means of a holder above the first or above the second conveyor belt. [6] Device for forming U-shaped dough strands according to one of the preceding claims, characterized bythat at the end of the first conveyor belt (1) facing the pretzel twisting device, above the first conveyor belt 1, there is arranged a gripping device (8) connected to a control system and hydraulically, electrically or pneumatically actuated, which sorts out dough strands that do not correspond to defined specifications of dimensions and / or shape. [7] Device for forming U-shaped dough strands according to claim 6, characterized by that the dimensions and shape of the dough strands are measured by means of a device for close-range photogrammetry, wherein, if the deviation with regard to dimensions and shape exceeds predetermined threshold values, the respective dough strands are sorted out by the gripping device (8). [8] Device for forming U-shaped dough strands according to claim 6, characterized byin that it has two sensors for detecting the length of the legs of the U-shaped dough strands formed by means of the device, wherein the sensors are each arranged on one side of the device at the same height and are damped when a leg of a dough blank is detected, wherein the length of the respective leg is determined on the basis of the damping time of a sensor and the known conveying speed of the second conveyor belt (2), wherein if the length difference between the two legs exceeds a predetermined threshold value and / or if the sum of the lengths of both legs falls below a further predetermined threshold value, the blank is sorted out by means of the gripping device (8). [9] Method for forming U-shaped dough strands from substantially straight dough strands, in particular for pretzel production, wherein the substantially straight dough strands are fed to a device comprising a first conveyor belt (1) and a second conveyor belt (2), wherein the first and second conveyor belts (1, 2) are each drivable at different conveying speeds, wherein the ends of the two conveyor belts (1, 2) are arranged substantially one above the other at the end of the device facing the feeding device for the substantially straight dough strands, wherein the static friction coefficient of the dough on the first conveyor belt (1) is higher than the static friction coefficient of the dough on the second conveyor belt (2), wherein the plane formed by the upper run of the first conveyor belt (1) is higher by a predetermined amount than the plane formed by the upper run of the second conveyor belt (2), wherein the longitudinal axes of the two conveyor belts (1,2) are arranged parallel to one another, wherein during the transfer of the dough strands to the device, the middle part of the dough strands lies on the upper run of the first conveyor belt and the ends of the dough strands each lie on one side of the upper run of the first conveyor belt on the upper run of the second conveyor belt, wherein the conveying speed of the second conveyor belt (2) is higher than the conveying speed of the first conveyor belt (1), so that during the transport of the dough strands, the ends of the dough strands are aligned parallel to the conveying direction of the second conveyor belt (2) and U-shaped dough strands are formed with the legs leading in the conveying direction, wherein after the formation of the dough strands with the legs leading in the conveying direction, these are transported at the speed of the first conveyor belt (1),wherein the legs lying on the second conveyor belt (2) are held by the middle part of the dough strand lying on the first conveyor belt (1) and sliding friction acts between the upper run of the second conveyor belt (2) and the legs, , characterized by that the second conveyor belt (2) is longer than the first conveyor belt (1) and that the U-shaped dough strands are fed directly to the pretzel twisting device by means of the second conveyor belt (2). [10] Method for forming U-shaped dough strands from substantially straight dough strands, in particular for pretzel production, according to claim 9, characterized by that the transport time for a dough strand after forming the dough strands with the legs in the conveying direction corresponds at least to the required resting time for the dough.

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