BINDING DEVICE FOR A BALING PRESS

Description

[0001] The present invention relates to a binding device for a baling press according to the preamble of claim 1 and to a baling press according to the preamble of claim 13.

[0002] Balers are used in agriculture to compress harvested crops such as hay or straw into bales. The crop is typically picked up from the ground by a pickup integrated into the baler. In the case of a square baler, the compression of the collected crop occurs in two stages. First, the crop, picked up and possibly cut by a cutting device, is conveyed by a conveyor or collecting device within a collection chamber, where it is gathered and pre-compacted. A pressing chamber or press channel follows the collecting chamber. There, an oscillating piston acts on the crop, carrying out the actual compression. Pre-compacted crop is thus transferred in portions into the press channel, where the square bale is gradually formed.

[0003] Once the rectangular bale has reached a predetermined size, it is bound with a binding material before being ejected. The binding material can be, for example, twine or a thermoplastic band. During the binding process, one end of the binding material is held against the top of the bale at one end. The binding strand is then guided along the top to the opposite end, then downwards, and finally back under the bale in the opposite direction. A subsequent section of the binding strand is guided by a binding needle. A number of binding needles are attached to a needle arm that is movable relative to the press channel. This arm can be adjusted, in particular, from a position outside the press channel to a position where the binding needles project upwards into the press channel, with each binding needle carrying a strand of binding material.This can be connected to the secured end section, either by knotting or welding, thus forming a closed loop around the bale. This can be separated from the rest of the binding strand, thereby securing a newly formed end section. The bale can then be ejected, and new bale formation can begin.

[0004] The generally existing requirements for high process speeds lead to rapid movement of the needle rocker. While this is readily achievable from a drive technology perspective, it carries the risk of the needle rocker unintentionally moving beyond its intended end position, i.e., overshooting, which could damage the needle rocker and / or other components. Therefore, it is known in the art to use a braking device that exerts a permanent braking force on the needle rocker. This can prevent overshooting but increases the load on the drive. Furthermore, a braking device optimized for high drive speeds can prevent the needle rocker from reaching its intended end positions at lower drive speeds. To prevent this, the drive power must be increased, which in turn may require an increase in the braking force.Overall, a considerable amount of drive energy is required, which is not converted into kinetic energy of the needle swing arm but is lost in the braking device. Furthermore, the increased load on the braking device leads to increased wear.

[0005] Binding devices with a braking device are known, for example, from the following documents: US 4 062 280 A, US 3 122 991 A, US 2 766 684 A, US 2 897 749 A and DE 11 57 024 B.

[0006] The object of the invention is to enable efficient and precise guidance of a needle swing arm.

[0007] The problem is solved with a binding device for a baling press, having the features of independent claim 1. Advantageous embodiments can be found in the dependent claims.

[0008] For this purpose, a binding device for a baler is created, comprising a needle arm with a plurality of binding needles for supplying a binding agent into a press channel, wherein the needle arm can be driven by a motor drive in such a way that it moves relative to a frame of the baler according to a binding cycle, and comprising a braking device which is designed to exert a braking force acting at least indirectly on the needle arm.

[0009] A baler is typically a square baler or large square baler. It can be self-propelled with its own drive system or a trailer without. It features a compression chamber where the actual bale formation and pressing process take place. The compression chamber has a longitudinal axis, to which it usually runs predominantly parallel. This axis may coincide with a longitudinal axis of the baler, or it may be inclined relative to it. A compression piston is typically located within the compression chamber, designed to compress the crop through an oscillating motion. Regarding crop flow, a collection chamber is usually located upstream of the compression chamber, containing a conveying or collecting device to transport the crop and pre-compact it.

[0010] To secure the shape of the finished bale, it is bound within the press channel. This binding material, also known as binder, can be a yarn or a thermoplastic tape (e.g., made of PET). It is typically wrapped around the bale in multiple separate loops spaced perpendicular to the channel's longitudinal axis. To form each loop, an end of the binding material, held at one end of the bale, is connected to a section that must be inserted into the press channel from the outside. A binding needle is provided to guide each section into the press channel. A needle arm comprises multiple binding needles, which may be attached to a common carrier. The number of binding needles on the needle arm is not limited in principle, but typically ranges from two to eight.Each of the binding needles feeds binding agent into the compression channel, with the feed typically occurring from an underside of the compression channel. The needle arm is part of the binding device according to the invention, which can generally include components directly related to the binding process, as well as components that are not involved or only indirectly involved in the binding process. Therefore, the term "binding device" is not to be interpreted restrictively. The needle arm can be driven by a motor such that it moves relative to a frame of the baler according to a binding cycle. The motor drive comprises at least one motor, which can be, for example, an internal combustion engine, an electric motor, a hydraulic motor, or designed in another manner. Typically, exactly one motor is provided, so the motor drive can also be referred to as a motor.

[0011] The needle arm is driven by the motor, although it is generally not directly coupled to the motor, but rather via various elements for power transmission and / or redirection, and possibly for reduction or overdrive. In particular, it may also be possible to temporarily decouple the needle arm from the drive. The needle arm is movably mounted relative to the frame of the baler, and is normally pivotable about a pivot axis running transversely to the baler. The action of the motor drive causes the needle arm to move according to a binding cycle. This binding cycle typically consists of a movement from a starting position, corresponding to a first dead center position, to a binding position, corresponding to a second dead center position, followed by a movement back to the starting position.In the binding position, the binding needles are inserted as far as possible into the press channel. With the usual arrangement of the needle arm, the first dead center position is bottom dead center and the second dead center position is top dead center.

[0012] The movement of the needle arm within the binding cycle exhibits various acceleration and deceleration phases. The necessary deceleration forces can be partially absorbed, for example, by the motor drive, but this is generally insufficient. Therefore, the binding device incorporates a braking device designed to exert a braking force, at least indirectly, on the needle arm. Normally, the braking force is generated by solid friction, although generation by fluid friction or eddy currents, for example, is conceivable, at least as a supplementary measure. The braking device can exert a braking force either directly on the needle arm, so that the braking force acts directly on the needle arm.Alternatively, the braking force can act indirectly on the needle swing arm, meaning that the braking force is generated at a component that is rigidly connected to the needle swing arm or whose movement is at least directly coupled to the movement of the needle swing arm, so that a braking force acting on the corresponding component inevitably also acts on the needle swing arm. In general terms, the braking device is designed to exert a braking force that slows down the needle swing arm. The braking device can have a single brake or multiple brakes.

[0013] According to the invention, the binding device is configured such that the braking force is automatically varied depending on at least one parameter relating to the binding device. This is typically a parameter that describes the current operating state of the binding device. Generally, this could be a position, a speed, an acceleration, a power, or another quantity. Thus, according to the invention, the braking force is not kept constant but depends on the at least one parameter. If the parameter changes, the braking force changes automatically as a result. It is possible that no change in the braking force occurs within certain value ranges of the parameter. However, there is at least one parameter range in which a corresponding change results.The required braking force generally depends solely on parameters relating to the binding device itself. Therefore, any adjustment of the braking force should be based on at least one such parameter. This makes it possible to control the braking force with regard to its timing and / or intensity, thus avoiding unnecessary or excessively strong braking. The invention therefore enables safe operation of the binding device, minimizing wear and energy consumption. Undesirable processes, such as movement beyond a predetermined dead center position, can be effectively prevented. The needle arm can also be secured, for example, in its lower dead center position, ensuring it remains reliably in one position between binding cycles. Otherwise, it could shift, for example, under the influence of gravity, potentially leading to...coupling to the drive might become impossible during the next binding cycle, or the binding needles might protrude into the press channel between binding cycles.

[0014] There are no restrictions regarding the generation of the braking force within the scope of the invention. For example, it could be generated by an electric or pneumatic actuator. It would also be conceivable for the braking force to be generated by a spring element, wherein the preload of the spring element is varied by a suitable mechanism depending on at least one parameter. A preferred embodiment provides that the braking device is hydraulically actuated. That is, the braking device has at least one hydraulic actuator by means of which the braking force is generated. In a variant, it would also be conceivable, for example, that the braking force is generated by a spring element, whereby a hydraulic actuator counteracts the spring element in order to reduce or completely deactivate the braking force.

[0015] A preferred embodiment provides that the binding device is configured such that the braking force is varied depending on a phase of the binding cycle. The respective phase of the binding cycle corresponds, on the one hand, to a point in time during the binding cycle and, on the other hand, to a position and state of motion of the needle arm. One can also speak of a movement phase of the needle arm within the binding cycle. If, as described below, the needle arm is coupled to a control shaft, the phase also corresponds to the current rotation angle of the control shaft. In any case, the variation depending on the phase of the binding cycle means that the braking force is varied over the course of the binding cycle. Accordingly, it can be adapted to the respective requirements, in particular to whether and how strongly the needle arm should be braked in a specific movement phase.

[0016] As a rule, the binding device is designed to initiate at least one time-limited braking phase, increase the braking force for this phase, and reduce the braking force afterward. Since the binding device undergoes multiple binding cycles in succession during normal operation, with bale formation occurring between each cycle, multiple braking phases result—at least one braking phase per binding cycle. In particular, multiple braking phases per binding cycle may be provided. Compared to the phase preceding each braking phase, which can generally be referred to as the intermediate phase, the braking force is increased during the braking phases. This includes the possibility that the braking force was zero beforehand. During the braking phase, the braking force is maintained, but it does not necessarily have to remain constant. In any case, the braking force is reduced after the braking phase.This in turn includes the possibility that the braking force is reduced to zero. Typically, the braking force is reduced after the braking phase to the value it had before the braking phase, although this is not always the case. Each braking phase corresponds to a time interval. As a rule, however, it also corresponds to a position interval of the needle swing arm. That is, the braking phase lasts as long as the position of the needle swing arm remains within a specific interval or range.

[0017] In most cases, applying a braking force after the braking phase is counterproductive and only leads to unnecessary wear of the braking device. Therefore, the binding device is preferably designed to activate the braking force for at least one braking phase and reduce it to zero afterward. Thus, the braking device is completely deactivated between two braking phases. This intermediate phase can also be referred to as the freewheeling phase. Only for the next braking phase is the braking force increased to a positive value again. It is possible for the braking force to be reduced continuously, i.e., gradually, after the braking phase. Alternatively, it is also possible to reduce the braking force discontinuously to zero, so that it falls to zero in steps.

[0018] Preferably, the binding device is configured to initiate at least one braking phase before the needle arm reaches a dead center position and to terminate this phase no later than when the dead center position is reached. The dead center position refers to a position in which the needle arm is at rest as intended and undergoes a reversal of its direction of movement. Normally, an upper dead center position can be identified, in which the binding needles extend furthest into the press channel and partially through it, as well as a lower dead center position, in which the binding needles are completely retracted from the press channel. However, movement sequences of the needle arm are conceivable in which more than these two dead center positions can be identified. For example, the needle arm could move from the lower dead center position to the upper dead center position, then back to the lower dead center position, and from there to a middle dead center position.Other movement sequences are also conceivable. In the embodiment described here, a braking phase is initiated before reaching a dead center position; that is, the braking force is increased or, if necessary, activated so that the needle arm is effectively decelerated. This prevents overshooting beyond the dead center position. The braking phase can also be terminated before reaching the dead center position, for example, in a state where the needle arm has decelerated sufficiently that further braking is unnecessary. It is advisable to terminate the braking phase at the latest after reaching the dead center position. In particular, the braking phase should end when the needle arm moves out of the dead center position. At this point, the needle arm accelerates, which should be supported by a reduction or deactivation of the braking force. Typically, a total of one braking phase per dead center position can be provided during a binding cycle.

[0019] Advantageously, the braking device can be coupled via a coupling mechanism to a control shaft rotatable relative to the frame, through which the needle arm is coupled to the drive for force transmission, at least during one binding cycle. The coupling mechanism can, for example, include elements for mechanical force transmission, elements for actuator force generation, sensors, and / or wireless or wired signal transmission links. In any case, the coupling mechanism is designed such that the braking force depends on the rotation angle of the control shaft. In other words, the control shaft controls the development of the braking force via its rotation angle. Although other variations are conceivable, the control shaft normally rotates 360° during one binding cycle. At least during the binding cycle, the needle arm is coupled to the motor drive for force transmission via the control shaft.Typically, there is a permanent mechanical connection between the needle arm and the control shaft, for example, via a linkage that translates the rotary motion of the control shaft into an oscillating pivoting motion of the needle arm. In contrast, a coupling is usually arranged between the control shaft and the motor drive, allowing a mechanical connection to be established during the binding cycle and released after its completion. In this embodiment, both the braking device and the needle arm are coupled to the control shaft during the binding cycle, and thus the braking force is automatically synchronized with the movements of the needle arm. This means that the braking force is automatically varied depending on the phase of the binding cycle.

[0020] According to one embodiment, the coupling mechanism has a cam track rigidly connected to the control shaft and a squeegee that can be deflected relative to the frame by the cam track, and the braking force can be varied by its deflection. The cam track is at least rotationally fixed, and usually rigidly connected, to the control shaft. In principle, it would also be conceivable to couple the cam track to the control shaft via intermediate gear components, but this would generally entail increased complexity without any significant advantages. The coupling to the control shaft guarantees, firstly, precise synchronization between the change in braking force and the binding cycle of the needle rocker. Secondly, the cam track can replicate the entire braking force profile during the binding cycle without unnecessary repetition of sections. The cam track can form the outer contour of a disc connected to the control shaft.In this case, the stylus can rest against the outside of the cam track, potentially biased towards the cam track by a spring element. The cam track could also be formed, for example, by a groove into which the stylus engages, or by a rib against which the stylus engages. In any case, the cam track has radially projecting and radially recessed sections, causing the stylus to deflect to varying degrees. The stylus can be slidably and / or pivotally connected to the frame. The deflection of the stylus allows for variable braking force. Normally, a specific deflection of the stylus corresponds to a specific braking force. However, it is also conceivable that the braking force depends on the deflection only within a certain range, and that no further change in braking force occurs beyond this range.Generally, the sensing element is coupled to the braking device, although this coupling does not necessarily have to transmit force. For example, it would also be conceivable to detect the deflection of the sensing element using a sensor, the signal from which would then control an actuator of the braking device.

[0021] A preferred embodiment provides that the sensing element interacts with a hydraulic valve through which the braking device can be actuated. Thus, a deflection of the sensing element causes a change in the state of the hydraulic valve. The hydraulic valve can be designed as a directional control valve, whereby specific connections are opened or closed by the action of the sensing element. However, it is also conceivable that the hydraulic valve opens to varying degrees depending on the deflection of the sensing element. The braking device is actuated by the hydraulic valve, meaning that the braking force depends on the state of the hydraulic valve. For example, a hydraulic actuator, which is part of the braking device, could be pressurized when the hydraulic valve is opened.Instead of a sensing element and a cam track, the rotation angle of the control shaft could also be detected by a sensor, and a hydraulic valve could be electronically controlled depending on the detected rotation angle. In a further variation, the sensing element could be coupled to a piston of a master cylinder in a hydraulic system, so that deflection of the sensing element directly causes a change in hydraulic pressure. This, in turn, causes a change in the braking force at a hydraulically actuated brake device.

[0022] If force generation is achieved using a spring element instead of hydraulic force generation, a mechanism that counteracts the spring element or reduces its preload could be coupled to the cam track. In particular, a mechanical coupling could be used. However, such a mechanism could also include a hydraulic actuator coupled to the sensing element and the cam track in the manner described above.

[0023] According to the invention, the binding device is configured such that the braking force is varied depending on the drive speed. This can preferably be combined with a variation of the braking force depending on the phase of the binding cycle. Normally, in this configuration, a specific braking force is uniquely assigned to a specific drive speed, provided that other potentially relevant parameters, such as the position of the needle arm, are predetermined. In particular, a maximum possible braking force can be uniquely dependent on the drive speed. The term "drive speed" generally refers to a quantity that characterizes how fast the motor drive operates. In particular, this can also be the rotational speed of the drive, or possibly an angular velocity.

[0024] According to the invention, the braking force increases with increasing drive speed.

[0025] A higher drive speed means that the binding cycle is completed in a shorter time. Accordingly, the needle arm must move faster, which in turn requires higher acceleration and deceleration forces. In particular, it can be provided that the braking force increases proportionally to the square of the drive speed.

[0026] In particular, it may be designed so that the hydraulic pressure for actuating the brake increases with increasing drive speed. Such a relationship is often found in hydraulic systems. Specifically, the hydraulic pressure can depend quadratically on the drive speed, i.e., it is proportional to the square of the speed. With a hydraulically actuated brake, the braking force is, in turn, normally proportional to the hydraulic pressure. That is, a braking force is generated that is proportional to the square of the speed. This ensures optimal adaptation to the increasing acceleration and deceleration forces that must act on the needle roller with increasing drive speed. These forces are also proportional to the square of the drive speed, i.e., normally to the square of the speed.

[0027] Preferably, the braking device comprises a disc brake with a brake caliper suspended from the frame and a brake disc that can be coupled to the needle roller at least in a force-transmitting manner. In particular, the brake disc can be force-transmittingly coupled to the needle roller. That is, a permanent coupling can exist. The brake disc can be rigidly connected to the needle roller or even formed integrally with it. However, a movable connection would also be conceivable. In any case, the force-transmitting coupling means that the movement of the brake disc is coupled to the movement of the needle roller. This normally means that the needle roller stops when the brake disc stops. The brake pads are arranged on the brake caliper and interact with the brake disc to generate the braking force. These can be actuated, in particular, by one or more brake pistons.The respective brake piston can preferably be moved hydraulically. It is also expressly possible that several brake calipers are assigned to one brake disc and / or that the braking system has multiple disc brakes.

[0028] Preferably, a brake pad arranged on the brake caliper is movable relative to the frame with at least one degree of freedom. Either the brake caliper is not rigidly connected to the frame, but is movably connected to it, in which case the brake pad is also movable. Alternatively, the brake pad can be movably arranged on the brake caliper. The mobility is generally limited to a certain range of motion. This mobility includes at least one degree of freedom. This can be at least one translational degree of freedom and / or at least one rotational degree of freedom. In particular, at least one translational and at least one rotational degree of freedom can be present. The brake pad (or the entire brake caliper) can – within the aforementioned range of motion – either be freely movable, or it can be returned to a rest position by an elastic return element.In any case, the movable connection allows for adjustment to changes in the position of the brake disc and the frame. These changes can be caused, for example, by deformations of various components, such as those resulting from thermal expansion. If the brake pad could not adapt to these changes in position, this could lead to an unplanned increase or decrease in braking force, unwanted rubbing of the brake pads against the brake disc, etc.

[0029] The problem is also solved with a baling press according to claim 13, which has a binding device according to one of the preceding claims.

[0030] The terms mentioned above have already been explained with reference to the binding device according to the invention and are therefore not explained again. Advantageous embodiments of the baling press according to the invention correspond to those of the binding device according to the invention.

[0031] The invention is described below with reference to figures. The figures are merely exemplary and do not limit the general concept of the invention.

[0032] They show Fig. 1 a perspective view of a part of a baling press according to the invention; Fig. 2 a side view of a binding device of the baling press made of Fig.1 in a first state; Fig. 3 a side view of the binding device in a second state; Fig. 4 a diagrammatic representation of parts of the binding device; and Fig. 5 a diagram showing the relationship between a rotation angle of a control shaft and a pivot angle of a needle rocker as well as a braking force.

[0033] Fig. 1 Figure 1 shows a perspective view of parts of a baler 1 according to the invention, more precisely a rectangular baler. Various components not relevant to understanding the invention have been omitted, such as a chassis and a drawbar by means of which the baler 1 can be coupled to a towing vehicle. The invention is expressly not limited to trailed or mounted balers, but also relates to self-propelled balers. The baler 1 has a frame 2. Within the frame 2, a press channel 3 is defined, which extends along a longitudinal channel axis A. The side and top panels of the press channel 3 are partially omitted in the figure. Within the press channel 3, a rectangular bale (not shown) is successively built up from portions of harvested material, which have been pre-compacted in a collection chamber (not visible here).The harvested crop is compacted in the press channel 3 by an oscillating press piston 4. Once the rectangular bale has reached its predetermined size, it is bound using a binding agent, such as twine or thermoplastic tape. A total of six loops of binding agent, spaced apart from each other perpendicular to the longitudinal axis A of the channel, are placed around the rectangular bale. To form each loop, an end section of the binding agent, which is held at one end of the bale on its upper surface, is connected to a section that is inserted into the press channel 3 from below.

[0034] This is achieved by means of six binding needles 12, which are part of a needle arm 11. The needle arm 11, in turn, is part of a binding device 10 according to the invention. The needle arm 11 has a swing arm support 13 to which the binding needles 12 are attached and which is pivotably connected to the frame 2 of the baler 1 about a swing arm pivot axis B. Eccentrically to the swing arm pivot axis B, a connecting rod 22 is attached to the swing arm support 13 via a first coupling pivot axis C. This connecting rod 22 is pivotably connected at its opposite end via a second coupling pivot axis D to a drive element 21, which in turn is rotationally fixed to a control shaft 20. The control shaft 20 can be connected via a clutch transmission 5 to a (in Fig. 4 The (schematically represented) motor drive 40 is connected so that it rotates about a shaft rotation axis E and the needle rocker 11 is driven for one binding cycle. The needle rocker 11 is initially in a bottom dead center position, in which the coupling pivot axes C, D and the shaft rotation axis E are aligned accordingly. Fig. 1 and 2 The binding needles 12 lie in a plane and are arranged completely outside the press channel 2. From this lower dead center position, the needle rocker 11 is moved to an upper dead center position, in which the coupling pivot axes C, D and the shaft rotation axis E again lie in a plane, with the shaft rotation axis E being arranged between the coupling pivot axes C, D. Fig. 3 This represents a state shortly before reaching top dead center. At top dead center, the binding needles 12 protrude into the press channel 3 and partially extend upwards beyond it, carrying the aforementioned section of the binding material with them. This section is then joined to the end of the binding material to form the loops, and the binding material is separated. These processes are not discussed in detail here.

[0035] Due to the mass or moment of inertia of the needle rocker 11 and the sometimes short cycle times and associated high speeds of the needle rocker 11, considerable forces are required to bring it to a standstill in the respective dead center position as intended. For this purpose, the binding device 10 has a braking device 15, which in this case has two disc brakes 16 arranged on opposite sides of the press channel 3. Each of the disc brakes 16 has a brake disc 17, which is rigidly connected to the rocker arm 13, and a brake caliper 18, which is connected to the frame 2. A brake pad, not visible in the figures, is connected to the brake caliper 18 in such a way that it can perform both translation and rotation relative to the frame 2 within certain limits.This prevents deformations that may occur during the manufacture of the baling press or during its operation from unpredictably affecting the effect of the respective disc brake 16.

[0036] The disc brakes 16 are connected to a directional control valve 32 via a split brake line 35. As is particularly evident in Fig. 2 and 3 As can be seen, a sensing element 30 is associated with the directional control valve 32, which is pivotably mounted on the frame 2. The sensing element 30 is biased by a first spring element 31 towards a rest position, in which it actuates the directional control valve 32, thus connecting the brake line 35 to a main line 34. As can be seen from the schematic representation in Fig.4 As can be seen, the directional control valve 32 is biased by a second spring element 33 into a position in which it isolates the brake line 35 from the main line 34 and connects it to a return line 36. The main line 34 is connected to a pump 37, which is coupled to the drive 40 that drives the needle roller 11 during the binding cycle. A pressure p is generated in the main line 34 by a primary throttle 38, which is proportional to the square of the rotational speed n of the drive 40. If the brake line 35 is disconnected from the main line 34, the disc brakes 16 remain released. Such a condition is in Fig. 2 and 4 shown.

[0037] The sensing element 30 interacts with a cam track 25, which is rotationally fixed to the control shaft 20. The sensing element 30, the cam track 25, and the directional control valve 32 are part of a coupling mechanism 24 by which the brake device 15 is coupled to the control shaft 20. The cam track 25 has two projecting sections 26. When one of the projecting sections 26 reaches the sensing element 30 during rotation of the control shaft 20, the sensing element 30 is deflected from its rest position and relieves the directional control valve 32, thus isolating the brake line 35 from the main line 34 and deactivating the disc brakes 16. Such a condition is present in Fig. 2 shown. Thus, the activation of the disc brakes 16 via the control shaft 20 is coupled to the movements of the needle rocker 11. That is, the braking force F is activated or deactivated depending on a respective phase of the binding cycle. This is shown in Fig. 5 The diagram shows, on the one hand, the course of a pivot angle ϕs (solid line) of the needle rocker 11 and, on the other hand, the course of the braking force F (dashed line) as a function of a rotation angle ϕw of the control shaft. The dead center positions correspond to a pivot angle ϕs of 0° and 90° and are reached in this example at rotation angles ϕw of 0° and 180°. The position of the projecting sections 26 of the cam track 25 is chosen such that the braking force F is activated before each dead center position is reached and deactivated at or shortly before reaching the dead center position. Thus, the braking force F remains deactivated from a rotation angle ϕw of 0° to approximately 95°, corresponding to a pivot angle ϕs between 0° and approximately 50°. Fig. 2 This corresponds to a swivel angle ϕs of approximately 5°, i.e., shortly after leaving the bottom dead center position. Then, a first braking phase is performed at a rotation angle ϕw of 95° to approximately 175°, corresponding to a swivel angle ϕs of approximately 50° to approximately 87°, i.e., shortly before the top dead center position. During this first braking phase, braking is carried out with a maximum braking force F max. Fig. 3This corresponds to a swivel angle ϕs of approximately 80°, i.e., shortly before reaching the top dead center position. Subsequently, the braking force F is deactivated again at a rotation angle ϕw of approximately 175° to approximately 300°. During this time, the swivel angle ϕs increases from approximately 87° to 90° and then decreases again to approximately 27°. A second braking phase then occurs at a rotation angle ϕw of 300° to approximately 355°, corresponding to a swivel angle ϕs of approximately 27° and approximately 2°, i.e., shortly before the bottom dead center position. During this second braking phase, braking is again carried out with a maximum braking force Fmax. In this way, the braking force F assists in the controlled attainment of the dead center position, but does not impede the acceleration of the needle rocker 11 as it moves out of the dead center position.Optionally, a secondary throttle can be provided between the directional control valve 32 and the return line 36, which slows down the pressure drop in the brake line 35 when the connection to the main line 24 is interrupted.

[0038] Since the generated pressure p in the main line 34 and, with appropriate connection, in the brake line 35 is proportional to the square of the rotational speed n of the drive 40, this also applies to the braking force F when the disc brakes 16 are activated, more precisely, to the maximum braking force Fmax. Since, on the other hand, the needle roller 11 is coupled to the drive 20 via the control shaft 20 during the binding cycle, its speed is proportional to the rotational speed n, and the necessary acceleration and deceleration forces increase with the square of the rotational speed n. Thus, the increase in pressure p with increasing rotational speed n ensures a corresponding increase in the braking forces F.

[0039] Since the braking force F in the binding device 10 according to the invention is adapted to the respective phase of the binding cycle with regard to its application and to the rotational speed n of the drive or the cycle time of the binding cycle with regard to its strength, on the one hand, safe guidance of the needle arm 11 is ensured, while on the other hand, unnecessary energy consumption and wear on the part of the braking device 15 are prevented. Because the braking force only acts temporarily and in a targeted manner, the needle arm 11 can be accelerated more effectively. This means, for example, that the top dead center position can be reached precisely when the bale of harvested crop is maximally compressed by the press piston 4. Thus, the bale of harvested crop can have an optimal density when being bound.

Claims

1. Binding device (10) for a baler (1), comprising a needle yoke (11) having a plurality of binding needles (12) for feeding a binding means into a baling channel (3), wherein the needle yoke (11) can be driven by a motor drive (40) such that it moves relative to a frame (2) of the baler (1) according to a binding cycle, and comprising a braking device (15) which is designed to exert a braking force (F) acting at least indirectly on the needle yoke (11), wherein the binding device (10) is designed such that the braking force (F) is automatically varied depending on at least one parameter relating to the binding device (10), characterized in that the binding device (10) is designed such that the braking force (F) is varied depending on a drive speed (n) of the drive (40), wherein the braking force (F) increases as the drive speed (n) increases.

2. Binding device according to claim 1, characterized in that the braking device (15) can be hydraulically actuated.

3. Binding device according to either of the preceding claims, characterized in that said binding device is designed such that the braking force (F) is varied depending on a phase of the binding cycle.

4. Binding device according to any of the preceding claims, characterized in that said binding device is designed to initiate at least one time-limited braking phase, to increase the braking force (F) for the at least one braking phase, and to reduce the braking force (F) after the braking phase.

5. Binding device according to claim 4, characterized in that said binding device is designed to activate the braking force (F) for at least one braking phase and to reduce the braking force (F) to zero after the braking phase.

6. Binding device according to any of claims 3 to 5, characterized in that said binding device is designed to initiate at least one braking phase before a dead center position of the needle yoke (11) is reached, and to end the braking phase at the latest after the dead center position has been reached.

7. Binding device according to any of the preceding claims, characterized in that the braking device (15) is coupled by means of a coupling mechanism (24) to a camshaft (20) which is rotatable relative to the frame (2) and by means of which the needle yoke (11) is force-transmittingly coupled to the drive (40) at least during a binding cycle.

8. Binding device according to claim 7, characterized in that the coupling mechanism (24) has a cam track (25) which is connected to the camshaft (20) for conjoint rotation and a contact element (30) which can be displaced relative to the frame (2) by means of the cam track (25), and by means of the displacement of which contact element the braking force (F) can be varied.

9. Binding device according to claim 8, characterized in that the contact element (30) is coupled to a hydraulic valve (32) by means of which the braking device (15) can be actuated.

10. Binding device according to any of claims 2 to 9, characterized in that a hydraulic pressure for actuating the braking device (15) increases as the drive speed (n) increases.

11. Binding device according to any of the preceding claims, characterized in that the braking device (15) comprises a disk brake (16) having a brake caliper (18) suspended on the frame (2) and having a brake disc (17) which is force-transmittingly coupled to the needle yoke (11).

12. Binding device according to claim 11, characterized in that a brake pad arranged on the brake caliper (18) is movable relative to the frame (2) with at least one degree of freedom.

13. Baler (1) having a binding device (10) according to any of the preceding claims.