Coupling device comprising a polygonal stem

Abstract

The invention relates to a coupling device (1) for conically converging twin-screw extruders which serves for rotational-speed-transmittingly and torque-transmittingly coupling a first shaft (2) and a second shaft (3), comprising a first journal (4) and a hollow shaft (5) which has an opening (6) and a longitudinal axis (7), wherein: the first journal (4) can be coupled to the first shaft (2) or is an integral end portion of the first shaft (2); the first shaft (2) can be coupled to the hollow shaft (5) in a first coupling portion (8) and the second shaft (3) can be coupled to the hollow shaft in a second coupling portion (9); in the first coupling portion (8) and in a normal plane (10) to the longitudinal axis (7), the opening (6) has a first cross section (15) in the form of a polygonal profile (11); and the first journal (4) has a first journal cross section (12) with a shape that complements the polygonal profile (11) of the opening (6). The invention further relates to a twin-screw extruder comprising the coupling device (1).

Description

[0001] COUPLING DEVICE WITH POLYGON SHAFT

[0002] The invention relates to a coupling for connecting shafts in drive systems, in particular for connecting a drive or gearbox-side output shaft to a screw shaft of an extruder. Couplings generally serve to transmit torque and speed from a drive machine to a driven machine.

[0003] The choice of the appropriate coupling depends on various factors, such as the torque, speed, shaft distances, type of torque transmission and operating conditions.

[0004] There are various types of couplings, which differ in their function, design features, and advantages and disadvantages. Well-known coupling types include rigid couplings, friction couplings, form-fit rigid couplings, torque limiter couplings, and special couplings such as hydraulic couplings and magnetic couplings.

[0005] Rigid couplings are characterized by their simple design, cost-effectiveness, high rigidity, and maintenance-free operation. However, they are not suitable for damping vibrations and shaft deviations, nor for shock loads.

[0006] Friction clutches enable smooth starting and engagement, and dampen vibrations and shaft deviations. They also offer overload protection through slippage. However, they are subject to wear, generate heat, and have a limited torque.

[0007] Rigid form couplings offer high stiffness, enable high speeds and backlash-free torque transmission. However, they are sensitive to vibrations and shaft deviations and are susceptible to installation problems.

[0008] Torque limiter couplings protect machines from overload and are characterized by a simple design. However, their torque transmission is reduced and their range of applications is limited.

[0009] Special couplings, such as hydraulic couplings, enable smooth starting and engagement, offer stepless speed control, and are suitable for potentially explosive atmospheres. Magnetic couplings, on the other hand, offer contactless torque transmission, generate no heat, and are also suitable for potentially explosive atmospheres.

[0010] A common example of a widely used coupling is the jaw coupling. It is characterized by a simple and robust design and is available in various sizes and configurations. Jaw couplings are cost-effective, maintenance-free, and offer high rigidity. However, they are not suitable for damping vibrations and shaft deviations, nor for shock loads.

[0011] The present invention describes a coupling that combines certain advantageous properties of the aforementioned coupling types while overcoming disadvantages of individual previously described coupling designs. The new coupling is capable of damping shaft deviations, compensating for axial misalignment, and simultaneously ensuring high stiffness and high efficiency.

[0012] The object of the present invention was to overcome the disadvantages of the prior art and to provide a coupling device by means of which axle offsets can be compensated and at the same time a high torque can be transmitted reliably and safely.

[0013] This problem is solved by a device and a method according to the claims.

[0014] The coupling device according to the invention is particularly suitable for driving a conically tapered twin-screw extruder. A conically tapered twin-screw extruder is understood to be a twin-screw extruder whose first screw shaft has a first longitudinal axis and whose second screw shaft has a second longitudinal axis, wherein the first and second longitudinal axes are oriented so that they intersect each other. In particular, the longitudinal axes can have an angle to each other within a range of 0.5° to 5°. Such screw shafts are coupled by a gearbox, which in turn is coupled to a drive device, in order to drive them. Thus, it is possible that a gearbox output shaft may have an axial offset with respect to at least one of the screw shafts, i.e., an angle between the longitudinal axis of the gearbox output shaft and the longitudinal axis of the screw shaft.This axial misalignment must therefore be compensated for, while a high torque must still be transmitted from the gearbox output shaft to the screw shaft, which is coupled to it via a coupling device. Thus, a coupling device for a conically tapered twin-screw extruder must compensate for axial misalignments and simultaneously transmit a high torque.

[0015] The coupling device according to the invention for conically converging twin-screw extruders for the speed- and torque-transmitting coupling of a first shaft and a second shaft comprises a first journal and a hollow shaft with an opening and a longitudinal axis, wherein the first journal can be coupled to the first shaft or is designed as an integral end section of the first shaft, wherein the first shaft is connected in a first coupling section and the second shaft can each be coupled to the hollow shaft in a second coupling section, wherein the opening in the first coupling section and in a normal plane of the longitudinal axis has a first cross-section designed as a polygon profile, wherein the first journal has a first journal cross-section that is at least partially complementary in shape to the polygon profile of the opening, in particular along the longitudinal axis, so that the first journal can be coupled to the hollow shaft in a speed- and torque-transmitting manner.

[0016] In the context of the device according to the invention, a polygon profile is understood to mean a polygonal contour of the inner shape of the hollow shaft's opening. Thus, the radially inner surface of the hollow shaft has a polygonal cross-sectional shape. In this context, "shape complementary" means that the journal can be received within the hollow shaft's opening, allowing the hollow shaft and the journal to be coupled for torque and speed transmission. This occurs when the forces involved in transmitting torque and speed are transferred from the adjacent surfaces of the polygon profiles or from the first journal and the hollow shaft.

[0017] The hollow shaft can also be referred to synonymously as a sleeve or coupling sleeve. In any case, a hollow shaft within the meaning of the invention is understood to be a shaft that can transmit the torque and speed, which are provided, for example, at the first shaft, to the second shaft.

[0018] It can also be provided that the hollow shaft is designed as an integral part of a gear journal. This can be particularly advantageous in a screw compressor or an extruder screw, where the first journal is designed as an integral part of the screw shaft. The coupling device according to the invention has the advantage that higher torques can be transmitted through coupling via a polygon profile than would be possible with coupling using splined teeth, jaws, or similar devices with the same mean diameter of the coupling device. This reduces the required installation space or allows existing installation space to be used to improve the safety of the new coupling device compared to older designs.

[0019] The fact that the first journal, in particular, can have a first journal cross-section that is complementary to the polygon profile, at least in some areas along the longitudinal axis, means that the journal can also have successive sections with different tolerances or different distances to the hollow shaft in the direction of the longitudinal axis.

[0020] In this sense, it can further be provided, for example, that the first journal is convexly shaped extending in the direction of the longitudinal axis, wherein the first journal is convexly shaped on both sides, particularly with respect to a median plane, and wherein the first journal is specifically accommodated to a predominant extent within the opening of the hollow shaft. This allows for improved compensation of an axial misalignment between the orientation of a first longitudinal axis of the first shaft and a second longitudinal axis of the second shaft.

[0021] Furthermore, it can be provided that the coupling device comprises a second pin, wherein the second pin is couplingable to the second shaft or is designed as an integral end section of the second shaft, and that the opening in the first coupling section and in a normal plane of the longitudinal axis has a second cross-section designed as a polygon profile, wherein the second pin has a second pin cross-section that is complementary in shape to the polygon profile of the opening, in particular along the longitudinal axis at least in certain areas, so that the second pin can be coupled to the hollow shaft in a speed- and torque-transmitting manner.

[0022] This allows for easier assembly and disassembly of the coupling device. This embodiment of the coupling device also offers the advantage of improved compensation for misalignment between the two shafts along their longitudinal axis. Another advantageous feature is a design in which the second journal is convexly shaped along its longitudinal axis, particularly on both sides, and specifically where a significant portion of the second journal is accommodated within the hollow shaft's opening. This allows for improved compensation of axial misalignment between the first longitudinal axis of the first shaft and the second longitudinal axis of the second shaft.

[0023] According to further training, it is possible that the polygon profile, or consequently the cross-section and the tenon cross-section, is designed according to DIN 32711 as a P3G profile or according to DIN 32712 as a P4C profile.

[0024] Provided the polygon profile is designed according to a common standard, this has the advantage that the explosive forces acting on the hollow shaft are limited within a safety range due to high local surface pressures. In conjunction with an extruder, this also offers the advantage of material savings compared to conventional coupling devices, reduced complexity of torque transmission, and a more compact coupling device design. Furthermore, manufacturing a polygon profile according to a common standard, even for a hollow shaft or journal, allows the application of established non-circular turning processes, resulting in cost savings.

[0025] Furthermore, it may be advantageous if the first journal has a support element with a spherical support surface at an end facing the hollow shaft or the second shaft, wherein the spherical support surface can be applied to a shape-complementary counter surface of the second shaft or a buffer element between the first shaft and the second shaft, so that axial forces can be transferred from the first shaft to the second shaft and vice versa.

[0026] Furthermore, the buffer element can be coupled to the hollow shaft in a positionally fixed manner along the longitudinal axis, while the coupling of the first shaft to the hollow shaft in the longitudinal axis is detachable. For example, the buffer element can be a damping plastic element that is fixed to the hollow shaft or within the opening of the hollow shaft. This prevents the first and / or second shafts from running against each other by interposing the buffer element and dampens impacts in the longitudinal axis. Alternatively, the support element can be designed as a ball joint in conjunction with the buffer element, with the coupling of the first shaft to the second shaft via the ball joint being permanent in the longitudinal axis. This provides a simple way to create an axially secured coupling.

[0027] According to a specific embodiment, the Ab support element can be coupled so that it is axially displaceable relative to the first pin, and / or the buffer element can be coupled so that it is axially displaceable relative to the second shaft, allowing for adjustable axial play along the longitudinal axis between the first and second shafts. If the Ab support element and the buffer element are to be in contact with each other to transmit axial forces, this can be easily achieved with this design.

[0028] According to an advantageous embodiment, a radial bore or opening can be provided in the hollow shaft so that the axial play can be adjusted or tuned by adjusting the coupling of the support element with the first pin and / or by adjusting the coupling of the buffer element with the second shaft using a tool that can be inserted through the radial bore.

[0029] Finally, it may also be provided that the first tenon and / or the second tenon and / or any surface of the first tenon cross-section, the second tenon cross-section, the first cross-section and the second cross-section has a surface hardened by surface compaction.

[0030] It can also be advantageous for the coupling device to have at least one axial locking element that can be coupled to the hollow shaft, so that the first shaft is captive coupled to the hollow shaft in the axial direction along its longitudinal axis. Advantageously, this can also be provided for the captive locking of the second shaft to the hollow shaft. When setting up a twin-screw extruder, it can happen that the screw shaft, i.e., in this case the second shaft, tends to move axially away from the gearbox or gearbox shaft, i.e., in this case from the first shaft, so that the second shaft would be pulled out of the hollow shaft if an axial locking element were not provided. This simple measure improves the safety of the coupling device.The invention also relates to a twin-screw extruder for the extrusion of plastics, comprising a gearbox with an output shaft or a first shaft and an extrusion device with a screw shaft or a second shaft, wherein the gearbox and the extrusion device are coupled by means of a coupling device of the type described above. For example, it is provided that the output shaft of the gearbox corresponds to the first shaft of the coupling device, and that the screw shaft of the extrusion device corresponds to the second shaft of the coupling device. In particular, the twin-screw extruder can be a conically tapered twin-screw extruder. In this case, a first longitudinal axis of the first screw shaft can form an angle with a second longitudinal axis of a second screw shaft within an angular range of 0.The two longitudinal axes of the two screw shafts are aligned at an angle of 5° to 5°, such that they intersect each other or at least intersect each other in a projection onto a plane. By coupling the gearbox to the extrusion device using the coupling device according to the invention, an axial misalignment between the first longitudinal axis of the first screw shaft and the second longitudinal axis of the second screw shaft can be compensated for, while still allowing a high torque to be transmitted. Furthermore, by transmitting the torque via surfaces with a polygonal cross-section, a relatively high or even higher torque can be transmitted than would be possible with a different type of coupling device, such as a curved-tooth coupling, with the same mean diameter.

[0031] To better understand the invention, it is explained in more detail with reference to the following figures.

[0032] It shows, in a highly simplified, schematic representation:

[0033] Fig. 1 shows a possible embodiment of a coupling device for conically converging twin-screw extruders.

[0034] It should be noted at the outset that in the differently described embodiments, identical parts are provided with the same reference numerals or component designations, and the disclosures contained in the entire description can be applied analogously to identical parts with the same reference numerals or component designations. Furthermore, the positional designations chosen in the description, such as top, bottom, side, etc., refer to the figure directly described and illustrated, and these positional designations must be applied analogously to the new position if the position changes.

[0035] Figure 1 shows a possible embodiment of a coupling device 1 for conically converging twin-screw extruders in a highly simplified, schematic representation and in a sectional view. The coupling device 1 serves to couple a first shaft 2 with a second shaft 3 in a speed- and torque-transmitting manner, wherein the coupling device 1 comprises a first journal 4 and a hollow shaft 5 with an opening 6 and a longitudinal axis 7.

[0036] The first pin 4 can be coupled to the first shaft 2 or alternatively be designed as an integral end section of the first shaft 2.

[0037] The first shaft 2 or the first journal 4 is coupled to the hollow shaft 5 in a first coupling s from section 8, and the second shaft 3 is coupled to the hollow shaft 5 in a second coupling s from section 9. The coupling can be configured such that the first shaft 2 or the first journal 4 is accommodated within the opening 6 in the first coupling section 8, and that the second shaft 3 is accommodated within the opening 6 in the second coupling section 9. Alternatively, it can also be provided that the second shaft 3 is coupled to the hollow shaft 5 in such a way that the second shaft 3 and the hollow shaft 5 are formed as a single machine element.

[0038] According to the invention, the opening 6 in the first coupling section 8 and in a normal plane 10 of the longitudinal axis 7 has a first cross-section 15 designed as a polygon profile 11, wherein the first journal 4 has a first journal cross-section 12 that is complementary in shape to the polygon profile 11 of the opening 6, so that the first journal 4 can be coupled to the hollow shaft 5 in a way that transmits speed and torque. This is shown in section AA of Fig. 1.

[0039] Specifically, it can be provided that the first journal 4 is only partially complementary in shape to the polygonal profile 11 along the longitudinal axis 7. This can be the case, for example, if the first journal 4 is convex in the direction of the longitudinal axis 7, wherein the first journal 4 is convex on both sides, particularly with respect to a central plane 13, and wherein the first journal 4 is specifically designed to be received for a predominant part within the opening 6 of the hollow shaft 5. This specific embodiment of the first journal 4 is also shown in Fig. 1.

[0040] Furthermore, the coupling device 1 may also include a second pin 14, wherein the second pin 14 may be coupled to the second shaft 3 or may be formed as an integral end section of the second shaft 3, and wherein the opening 6 in the first coupling section 8 and in a normal plane 10 of the longitudinal axis 7 has a second cross-section 16 formed as a polygon profile 11, wherein the second pin 14 has a second pin cross-section 17 that is at least partially complementary in shape to the polygon profile 11 of the opening 6, in particular along the longitudinal axis 7, so that the second pin 14 can be coupled to the hollow shaft 5 in a way that transmits speed and torque. This is shown in section BB of Fig. 1.

[0041] It can also be provided that the second pin 14 is convex in the direction of the longitudinal axis 7, wherein the second pin 14 is in particular convex on both sides, wherein the second pin 14 is specifically to be received to a predominant extent within the opening 6 of the hollow shaft 5.

[0042] Preferably, it can also be provided that the polygon profile 11, or consequently the cross-section 15 or 16 and the pin cross-section 12 or 17, are designed according to DIN 32711 as a P3G profile or according to DIN 32712 as a P4C profile.

[0043] As a useful extension, the first journal 4 can be provided with a support element 19 at one end 18 facing the hollow shaft 5 or the second shaft 3. This support element has a spherical bearing surface 20, and the spherical bearing surface 20 can be applied to a shape-complementary mating surface 21 of the second shaft 3 or a buffer element 22 between the first shaft 2 and the second shaft 3, so that axial forces can be transferred from the first shaft 2 to the second shaft 3 and vice versa. The support element 19 can be designed as a machine element that is coupled to, or can be coupled to, the first journal 4 or the first shaft 2. Alternatively, the support element 19 can be designed as an integral part of the first journal 4 or the first shaft 2. Likewise, the buffer element 22 can also be designed as a machine element that is coupled or can be coupled to the second pin 14 or the second shaft 3.Alternatively, the buffer element 22 can also be designed as an integral part of the second journal 14 or the second shaft 3. Alternatively, the buffer element 22 can also be designed as an independent machine element, wherein the buffer element 22 can be coupled to the hollow shaft 5 in a positionally fixed manner in the direction of the longitudinal axis 7, thereby allowing the coupling of the first shaft 2 to the hollow shaft 5 in the direction of the longitudinal axis 7 to be released.

[0044] In any case, a further embodiment is also conceivable in which the support element 19, in conjunction with the buffer element 22, is designed as a ball joint, wherein the coupling of the first shaft 2 with the second shaft 3 by means of the ball joint in the direction of the longitudinal axis 7 is indissoluble.

[0045] If the buffer element 22 and the support element 19 are each designed as independent machine elements, it may also be useful to provide that the support element 19 is coupled so as to be axially displaceable relative to the first pin 4 and / or that the buffer element 22 is coupled so as to be axially displaceable relative to the second shaft 3, so that an axial play in the direction of the longitudinal axis 7 between the first shaft 2 and the second shaft 3 can be adjusted.

[0046] In order to enable such an adjustment of the axial play in a simple manner, it can be provided that a radial bore 23 is provided in the hollow shaft 5, so that the axial play can be adjusted by adjusting the coupling of the support element 19 with the first pin 4 and / or by adjusting the coupling of the buffer element 22 with the second shaft 3 by means of a tool that can be inserted through the radial bore 23.

[0047] Finally, it may also be provided that the first pin 4 and / or the second pin 14 and / or any surface of the first pin cross-section 12, the second pin cross-section 17, the first cross-section 15 and the second cross-section 16 has a surface hardened by surface compaction.

[0048] The exemplary embodiments show possible embodiments, whereby it should be noted that the invention is not limited to the specifically illustrated embodiments, but rather various combinations of the individual embodiments are also possible, and this possibility of variation lies within the capabilities of a person skilled in the art in this technical field, due to the teaching of the present invention. The scope of protection is defined by the claims. However, the description and the drawings must be consulted for the interpretation of the claims. Individual features or combinations of features from the different exemplary embodiments shown and described can in themselves represent independent inventive solutions. The problem underlying these independent inventive solutions can be found in the description.

[0049] All references to value ranges in this description are to be understood as encompassing any and all sub-ranges thereof, e.g., the reference 1 to 10 is to be understood as including all sub-ranges, starting from the lower limit 1 and the upper limit 10, i.e., all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g., 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0050] Finally, for the sake of clarity, it should be noted that, for a better understanding of the structure, some elements have been shown not to scale and / or enlarged and / or reduced in size.

[0051] Reference numeral list

[0052] Coupling device

[0053] First wave

[0054] Second wave

[0055] First cone

[0056] Hollow shaft

[0057] breakthrough

[0058] Longitudinal axis

[0059] First coupling section

[0060] Second coupling section

[0061] Normal plane

[0062] Polygon profile

[0063] First cone cross-section

[0064] Middle level

[0065] Second cone

[0066] First cross-section

[0067] Second cross-section

[0068] Second cone cross-section

[0069] End

[0070] From support element

[0071] From support surface

[0072] Opposite surface

[0073] Buffer element

[0074] Drilling

Claims

P a t e n t a n s p r ü c h e 1. Coupling device (1) for conically converging twin-screw extruders for the speed- and torque-transmitting coupling of a first shaft (2) and a second shaft (3), comprising a first journal (4) and a hollow shaft (5) with an opening (6) and a longitudinal axis (7), wherein the first journal (4) is couplingable to the first shaft (2) or is designed as an integral end section of the first shaft (2), wherein the first shaft (2) is couplingable to the hollow shaft (5) in a first coupling section (8) and the second shaft (3) is couplingable to the hollow shaft (5) in a second coupling section (9), characterized in that the opening (6) in the first coupling section (8) and in a normal plane (10) of the longitudinal axis (7) has a first cross-section (15) designed as a polygon profile (11), wherein the first journal (4) has a cross-section corresponding to the polygon profile (11) of the opening (6), in particular along the longitudinal axis (7) at least in certain areas,has a form-complementary first journal cross-section (12) so that the first journal (4) can be coupled to the hollow shaft (5) in a speed- and torque-transmitting manner.

2. Coupling device (1) according to claim 1, characterized in that the first pin (4) is convex extending in the direction of the longitudinal axis (7), wherein the first pin (4) is convex on both sides, in particular with respect to a central plane (13), wherein the first pin (4) is specifically to be received to a predominant extent within the opening (6) of the hollow shaft (5).

3. Coupling device (1) according to one of the preceding claims, characterized in that the coupling device (1) comprises a second pin (14), wherein the second pin (14) is couplingable to the second shaft (3) or is designed as an integral end section of the second shaft (3), and that the opening (6) in the first coupling section (8) and in a normal plane (10) of the longitudinal axis (7) has a second cross-section (16) designed as a polygon profile (11), wherein the second pin (14) has a second pin cross-section (17) that is at least partially complementary in shape to the polygon profile (11) of the opening (6), in particular along the longitudinal axis (7), so that the second pin (14) is couplingable to the hollow shaft (5) in a speed- and torque-transmitting manner.

4. Coupling device (1) according to claim 3, characterized in that the second pin (14) is convex in the direction of the longitudinal axis (7), wherein the second pin (14) is in particular convex on both sides, wherein the second pin (14) is specifically to be received to a predominant part within the opening (6) of the hollow shaft (5).

5. Coupling device (1) according to one of the preceding claims, characterized in that the polygon profile (11) or the cross-section (15) is thereby 16) and the pin cross-section (12 or 17) is designed according to DIN 32711 as a P3G profile or according to DIN 32712 as a P4C profile.

6. Coupling device (1) according to one of the preceding claims, characterized in that the first pin (4) has a support element (19) with a spherical support surface (20) at an end (18) facing the hollow shaft (5) or the second shaft (3), wherein the spherical support surface (20) can be applied to a shape-complementary counter surface (21) of the second shaft (3) or of a buffer element (22) between the first shaft (2) and the second shaft (3), so that axial forces can be transferred from the first shaft (2) to the second shaft (3) and vice versa.

7. Coupling device (1) according to claim 6, characterized in that the buffer element (22) can be coupled to the hollow shaft (5) in a positionally fixed manner in the direction of the longitudinal axis (7), wherein the coupling of the first shaft (2) to the hollow shaft (5) in the direction of the longitudinal axis (7) can be released.

8. Coupling device (1) according to claim 6, characterized in that the Ab support element (19) in conjunction with the buffer element (22) is designed as a ball joint, wherein the coupling of the first shaft (2) with the second shaft (3) by means of the ball joint in the direction of the longitudinal axis (7) is indissoluble.

9. Coupling device (1) according to claim 6 or 7, characterized in that the support element (19) is coupled so as to be axially displaceable relative to the first pin (4) and / or that the buffer element (22) is axially displaceable relative to the second shaft (3). is slidably coupled so that an axial play in the direction of the longitudinal axis (7) between the first shaft (2) and the second shaft (3) can be adjusted.

10. Coupling device (1) according to claim 8, characterized in that a radial bore (23) is provided in the hollow shaft (5) so that the axial play can be adjusted by adjusting the coupling of the Ab support element (19) with the first pin (4) and / or by adjusting the coupling of the buffer element (22) with the second shaft (3) by means of a tool that can be inserted through the radial bore (23).

11. Twin screw extruder for extruding plastics, comprising a gearbox with an output shaft or with a first shaft (2) and an extrusion device with a screw shaft or with a second shaft (3), characterized in that the gearbox and the extrusion device are coupled by means of a coupling device (1) according to one of the preceding claims.

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