Mixer with a closure lid connected to a machine stand via a coupling gear

Abstract

The present invention relates to a mixer having a closure lid (1) which is connected to a machine stand (7) via a coupling gear.

Description

[0001] Maschinenfabrik Gustav Eirich GmbH & Co. KG

[0002] Our reference number: 240927WO

[0003] Mixer with a lid which is connected to a machine stand via a coupling mechanism.

[0004] The present invention relates to a mixer with a mixing vessel held in a machine stand, wherein the mixing vessel has an outlet opening in its base which is surrounded by a wall. Furthermore, a circular closure lid with a diameter of / and a thickness of ( / ) is provided, which can be moved back and forth between a closed position, in which the closure lid is at least partially arranged within the outlet opening and closes it, and an open position, in which the closure lid releases the outlet opening.

[0005] Such mixing devices are known. They often feature a container that can be rotated about a container axis. Furthermore, a rotatable mixing tool is frequently arranged inside the container. This mixing tool is rotatable about a mixer shaft arranged parallel to the container's axis of rotation, with mixing vanes, for example, attached to the mixer shaft.

[0006] Such a mixing device is known, for example, from EP 1 103 492 A1. In the known variant, the closure lid is held on a support arm which is rotatable about a pivot shaft. Therefore, the closure lid can only be moved along a circular path. However, since the closure lid, which is attached to the end of the pivot arm, must enter a circular opening of a certain depth, the part of the lid closest to the pivot arm will usually be the first to touch the lower edge of the opening. If the lid were fixed and immovably connected to the pivot arm, it would catch in the opening and could not be closed, because the last section of the path the closure lid has to travel is no longer on the pivot radius, but runs parallel to the axis of the outlet opening.

[0007] In other words, the center of the closure lid must be forced onto a curved path at the end of its circular path in order to move the last section as parallel as possible to the opening axis. In the cited prior art, the closure lid is therefore still tiltable relative to the pivot arm, with a spring assembly acting as a return element holding the lid in place.

[0008] However, the process of positioning the lid during closing is still subject to wear and tear. Furthermore, the circular movement of the arm with the lid requires a significant amount of space.

[0009] From EP 3 946 703 B1, a four-bar linkage for guiding the closure lid is known. The lid is moved by a lever along a cam track that is nearly circular over a wide area. The four-bar linkage is designed such that the movement of the closure lid upon impact with the opening in the bottom of the mixing container is nearly linear, i.e., parallel to the axis of rotation of the mixing container. However, the known lid cannot be opened too far because, due to the four-bar linkage, which is located in the center of the closure lid, the edge of the lid abuts the corresponding rod elements. Therefore, the opening of the outlet is limited in this embodiment.

[0010] Based on the described prior art, it is therefore an object of the present invention to provide a mixer which has improved and space-saving mobility of the closure lid.

[0011] According to the invention, this is solved by a mixer comprising a mixing vessel held in a machine stand, the mixing vessel having an outlet opening arranged in the bottom of the mixing vessel, which is surrounded by a wall, and a circular closure lid with a diameter and thickness d, which can be moved back and forth between a closed position in which the closure lid is at least partially arranged inside the outlet opening and closes it, and an open position in which the closure lid does not close or opens the outlet opening, wherein the closure lid is connected to the machine stand via a planar linkage, wherein M is the center point of the circular closure lid and an axis defined as vertical runs through M, wherein a direction perpendicular to this axis is defined as horizontal.wherein the coupling mechanism has two movable pivot joints attached to the locking cap, namely a first movable pivot joint and a second movable pivot joint, and a first and a second fixed pivot joint, wherein the first fixed pivot joint is in a position offset relative to M by a horizontal distance j and a vertical distance k, wherein the first movable pivot joint is at a vertical distance c from M and at a horizontal distance / from M, wherein the second movable pivot joint is at a horizontal distance a from the first movable pivot joint and is spaced b from the first movable pivot joint in the vertical direction,so that the second movable pivot joint has a vertical distance (c + b) and a horizontal distance (a + / ) relative to M. The second fixed pivot joint has a horizontal distance e and a vertical distance f relative to the first fixed pivot joint. Furthermore, the first fixed pivot joint is connected to the first movable pivot joint via a first rod of length g, and the second fixed pivot joint is connected to the second movable pivot joint via a second rod of length h, wherein,

[0012] 1.) > / / 2,

[0013] 2.) J+e > i / 2 and

[0014] 3.) c < i / 2.

[0015] A planar linkage is a mechanical transmission in which several rigid links are connected to each other via joints in such a way that their movement remains confined to a common plane. If the linkage has four pivot joints, it is also referred to as a four-bar linkage in the prior art. The center point M is defined here as the point where the axis of symmetry of the circular cover intersects the plane located midway between the two outermost axial surfaces of the component. The axis of symmetry of the cover is uniquely defined as the axis that runs perpendicularly through the geometric center of the cover's circumference.The outermost axial boundary surfaces are those points that define the component at the greatest axial distance from one another, regardless of whether they are flat, spherical, or otherwise curved. The center point lies exactly at half the axial distance between these two outermost points. The upper surface of the closure lid, facing the interior of the mixing container and forming a base surface of the container when closed, can, in principle, be of any shape, e.g., flat or spherical. However, a flat design is preferred, as this forms a continuous, flat surface with the base of the mixing container when closed.

[0016] If the closure lid is flat on both sides, the center point M lies on the vertical axis of symmetry and is spaced from both the inner and outer surfaces of the closure lid by half the thickness, i.e., by d / 2. Preferably, the inner and outer surfaces of the closure lid are flat. A fixed pivot joint is understood to be one that is arranged in a stationary position. Movable pivot joints are fundamentally designed like fixed pivot joints, except that they are connected to the movable closure lid and are therefore movable together with it.

[0017] Even when referring to a horizontal or vertical direction, it is understood that the lid does not necessarily have to be perfectly horizontal in the closed position. The mixing container can also be slightly tilted or inclined. However, the terms horizontal and vertical define a reference system that is independent of the actual orientation of the lid in the closed position. The vertical axis is perpendicular to the horizontal direction. Positive values ​​for the vertical distance then mean that the corresponding distance lies below the mixing container. The fixed pivot joints are both spaced from the vertical axis in the same horizontal direction. Positive values ​​for a horizontal distance then mean that the corresponding point is spaced from the vertical axis in the direction of the fixed pivot axes.Negative values, on the other hand, mean that the distance exists in the opposite direction.

[0018] According to the invention, both fixed pivot joints are positioned horizontally more than half the diameter i of the closure lid from the vertical axis. Furthermore, the vertical distance c of the first movable pivot axis from the center point M is less than or equal to half the diameter i. This ensures that the space required by the closure lid in the vertical direction is not excessive.

[0019] In a further preferred embodiment, it is provided that 0.15 xi < c < 0.5 xi and preferably 0.3 xi < c < 0.5 xi.

[0020] It has been shown that the distance c is best within the specified intervals to obtain the best movement pattern.

[0021] In a further preferred embodiment, it is provided that e > 0, wherein preferably e > d and particularly preferably 0.15 xi < e < 0.5 xi.

[0022] The distance e between the second fixed pivot joint and the first fixed pivot joint is chosen such that the second fixed pivot joint, which is located further away from the center point in the vertical direction than the first fixed pivot joint, should also have a greater horizontal distance from the center point M. The distance e is preferably greater than the thickness d of the closure of the lid.

[0023] This measure ensures that the horizontal space required when moving the lid into the open position is as small as possible.

[0024] Furthermore, it is advantageous if both g and h are > i / 2.

[0025] In a further preferred embodiment, it is provided that b < i / 2, wherein preferably 0.05 xi < b < 0.45 xi and best 0.1 xi < b < 0.3 xi.

[0026] This feature also results in a lower vertical space requirement.

[0027] In a further preferred embodiment, the value of | / 1 < i / 2 and preferably / 0 and particularly preferably / < 0 is provided. This reduces the complexity of the transmission and the drive force required to open and close the closure cover can be reduced.

[0028] In another preferred embodiment, g < i is provided, wherein preferably g > h and bestly 0.75 xg < h < g.

[0029] This measure optimizes the tilting direction of the lid during opening. Since material from the mixing container also falls out during the opening process, it will fall onto the lid, which is partially extended from the outlet opening. It is therefore important that the lid remains tilted in the same direction throughout the opening process to prevent the material from spreading over a wide area. Preferably, the top of the lid tilts away from the fixed pivots to shield the coupling mechanism from material falling out of the outlet opening and to prevent contamination of the coupling mechanism by material deflected onto the top of the lid towards it.

[0030] In a further preferred embodiment, it is provided that k < i / 2, wherein preferably 0.85 x (c + < k -

[0031]

[0032] < 1.15 x (c + is. Particularly preferred is 0.9 xk < c < 1.1 xk and / or 0.9 x (k + f) < (b + c) < 1.1 x (fc + ). This creates a sufficient, but not excessively large, pivoting field of the closure cover and avoids collisions.

[0033] In a further particularly preferred embodiment, it is provided that b < e 2 + f 2 , preferably 0.5 xe 2 + f 2 < b < e 2 + f 2 is particularly preferred 0.9 xb < f < 1.1 xb , so that in this case the rods g and h are almost horizontally aligned when the closure lid is closed.

[0034] Furthermore, it is advantageous if |a| <0.5b, preferably |a| <0.35b, and particularly preferably |a| <0.3b. The length of a should be significantly smaller than b.

[0035] This measure also led to an improvement in the movement of the closure lid.

[0036] In a preferred embodiment, the closure lid is rotatable about the vertical axis. For example, the closure lid, attached to a stationary machine stand, could be inserted into a rotating container. Once the closure lid is seated in the outlet opening and seals it, the friction between the wall of the outlet opening and the edges of the closure lid, or any elastic seals attached to it, will cause it to rotate with the mixing container and thus about the vertical axis. Since the machine stand does not rotate, in such an embodiment the closure lid must be rotatable relative to the machine stand about the vertical axis.

[0037] In a further preferred embodiment, the closure lid has a cross member on its side facing away from the mixing container. This cross member has a first retaining section projecting beyond the edge of the closure lid in a direction orthogonal to both the vertical and horizontal axes, with the first and second movable pivot joints being arranged on the first retaining section. Because the two movable pivot joints are arranged on the projecting first retaining section, the closure lid can move through the axes of rotation of the movable pivot joints without colliding with them.

[0038] However, since in this embodiment the closure cover is only held on one side of the closure lid, this can lead to static problems, especially with large closure lids. Therefore, in a further preferred embodiment, the crossbeam has a second holding section which projects horizontally opposite the first holding section over the edge of the closure lid, wherein the closure lid is additionally connected to the machine frame via another planar linkage, wherein the further planar linkage also has four pivot joints whose axes of rotation are identical to the axes of rotation of the pivot joints of the planar linkage, and wherein two movable pivot joints of the further planar linkage are arranged on the second holding section.

[0039] This measure ensures that the cover is held on opposite sides, which offers static advantages. The two linkage mechanisms are fundamentally identical, so the movement sequence defined by the planar linkage remains unchanged. Only an additional planar linkage is provided, which has exactly the same horizontal and vertical distances to the center point M and moves in the same manner.

[0040] A drive is provided for moving the closure lid, which is advantageously connected to the first fixed axis of rotation or the second fixed axis of rotation.

[0041] Preferably a stop element is provided which is arranged in such a way that it comes into contact with a section of the coupling mechanism in the closed position and limits movement of the closure cover, wherein the stop element is particularly preferably adjustable.

[0042] In a further preferred embodiment, the drive has an actuator that performs a linear lifting movement, preferably a pneumatic or hydraulic cylinder, wherein the first fixed axis of rotation or the second fixed axis of rotation has a lever on which the actuator acts, wherein the actuator is particularly preferably connected at one end to a pivot joint mounted on the machine stand and at the other end to a pivot joint arranged on the lever.

[0043] Furthermore, when using two linkage drives, it is advantageous if either the two linkage drives are connected to each other via a drive shaft, with the drive shaft connecting the first or the second pivot joints so that the drive powers both linkage drives, or if the second linkage drive has a second drive, with a synchronizing device provided which synchronizes the second drive with the drive of the first linkage drive. The selection of the linkage drive parameters according to the invention ensures that the radially outermost edge of the cover does not collide with the drive shaft when opened.

[0044] Further advantages, features and applications of the present invention will become clear with reference to the following description of a preferred embodiment and the accompanying figures. These show:

[0045] Figure 1 shows a perspective view from a low angle of an embodiment of a mixer according to the invention.

[0046] Figure 2 shows a perspective view of the coupling mechanism of the embodiment shown in Figure 1 and

[0047] Figure 3 shows a schematic representation of the coupling mechanism.

[0048] Figure 1 shows a perspective view from a low angle of an embodiment of a mixer according to the invention. The mixer has a mixing container 6 which is rotatable about its central axis. For this purpose, the mixing container 6 is rotatably mounted on the machine stand 7.

[0049] In the bottom 21 of the mixing container 6 is an outlet opening 22, which can be closed by a cover 1. The cover 1 is connected to the machine stand 7 via a flat linkage mechanism with movable pivot joints 2 and 3, each attached to a side wall 10, and via fixed pivot joints 4 and 5. Since the mixing container 6 rotates relative to the machine stand 7, the cover 1, in the embodiment shown here, is also rotatable about the cover axis relative to the machine stand 7 via the bearing shaft 8 when open, and in this embodiment it has no drive mechanism of its own.

[0050] In principle, the lid could also have its own drive, allowing it to rotate even when open and thereby, for example, eject adhering material. The bearing shaft 8 is mounted on a crossbeam 9. When closed, with the outlet opening 22 completely filled by the lid 1, the lid 1 is rotated over the mixing vessel base 21 by the contact of its outer edges or the sealing elements attached there (not shown in the drawing), which are arranged around the entire circumference of the lid. Ideally, when closed, the mixing vessel axis and the lid axis are directly aligned.

[0051] The planar coupling mechanism, together with the cover 1, is shown in perspective in Figure 2.

[0052] A housing with an internal bearing shaft 8, held by bearings and supported by a cross member 9, is attached to the closure cover 1. A retaining section, designed as a side flange 10, 10', is attached to each of the opposite outer edges of the cross member 9. The retaining section projects beyond the edge of the closure cover in a direction orthogonal to both the vertical and horizontal axes. Both retaining sections, designed as side flanges 10, 10', are symmetrical and each supports a first movable pivot joint 2, 2' and a second movable pivot joint 3, 3'. Furthermore, the sides of the side flanges 10 and 10' facing the closure cover are preferably spaced at least by the diameter i of the closure cover to allow unrestricted movement of the closure cover during its movement along the intended cam track.The rods 17 and 18 are preferably arranged further away from the center of the closure cover than the side cheeks 10 and 10', respectively. This means that at no point during the movement do parts of the closure cover come into contact with the first or second rod 17 or 18, and thus the closure cover can pivot open particularly wide.

[0053] Furthermore, a drive shaft 15 is provided, which is held in the machine stand 7 by means of sliding bearings 16. The drive shaft 15 forms a first fixed pivot joint 4, which is connected to the first movable pivot joint 2 via a first rod 17.

[0054] The drive shaft 15 is connected at one end to a locking lever 13, to which an actuator, preferably a hydraulic or pneumatic cylinder 12, is attached. The actuator is connected at one end to a pivot joint 23 fixed to the machine stand (not shown) and at the other end to a pivot joint 24 arranged on the locking lever 13. The drive 12 thus allows the drive shaft 15, and consequently the first fixed pivot joint 4, to be rotated via the locking lever 13. Alternatively, for example, a geared motor is connected to the drive shaft 15.

[0055] It is also possible to attach the drive 12 to the second fixed pivot joint 5, which is connected to the second movable pivot joint 3 via a second rod 18. The drive shaft 15, which synchronizes the two coupling gears, could remain clamped between the first fixed pivot joints 4 and 4' or be arranged between the two second fixed pivot joints 5 and 5'. Alternatively, two drive shafts could be installed, each connecting the fixed pivot joints 4, 4' and 5 and 5' respectively, with only one of them then being connected to a drive 12. It is also possible, in principle, to omit the synchronizing drive shaft and equip each of the two coupling gears with its own drive.However, to prevent the entire unit from twisting or becoming strained due to slight deviations in the speed of movement of the two coupling gears, the two drives should be synchronized differently, e.g. electrically.

[0056] Furthermore, a stop element 14 is provided, which limits the rotational movement of the locking lever 13. This ensures that the drive 12 can bring the locking cover 1 into a precisely defined end position, corresponding to the closed position. Without the stop element 14, there would be a risk that the locking lever 13 would be rotated too far and, as a result, the locking cover 1 would penetrate too far into the outlet opening of the mixing container 6, where it could collide with rotating, lower parts of the mixing tool. The exact position of the stop element 14 is adjustable. A second stop element 14' limits the movement of the locking cover in the open position to prevent the locking cover 1 or the second rod 18 from colliding, for example, with the crossbeam 11 or the bottom of the mixing container 21.If the movement is achieved via a hydraulic or pneumatic cylinder, the end position of the fully retracted piston rod of the cylinder can be used to limit the movement instead of a second stop element 14'. Alternatively, e.g., when using a geared motor, the movement can be limited, e.g., by means of position switches.

[0057] A crossbeam 11 is attached to the machine stand 7 to increase the rigidity of the structure. A second fixed pivot joint 5 can now be attached to the machine stand 7 or to the crossbeam 11. The second fixed pivot joint 5 is connected to the second movable pivot joint 3 via a second rod 18. When the drive 12 is actuated, it rotates the locking lever 13, causing the first rod 17 to rotate about the first fixed pivot joint 4, thereby moving the locking cover 1 out of the outlet opening 22. However, to prevent the locking cover 1 from describing a perfect circular path, the second rod 18, which connects the second fixed pivot joint 5 to the side plate 10 via the second movable pivot joint 3, ensures that the side plate 10 is simultaneously pivoted about the first movable pivot joint 2.To illustrate the geometry and dimensions of the coupling mechanism according to the invention, a schematic representation is provided in Figure 3. The closing cover 1, which is inserted into an outlet opening 22 in the bottom of the mixing container 21 and closes it, is shown. The closed position is thus depicted. The closing cover 1 has a circular cross-section with diameter i. Furthermore, the closing cover 1 has a thickness d.

[0058] A side panel 10 and the positions of the first movable pivot joint 2 and the second movable pivot joint 3 are shown schematically. The positions of the first fixed pivot joint 4 and the second fixed pivot joint 5 are also shown schematically. For easier reference, a reference system is defined starting from the center point M of the cover. This system has a first axis, designated as the vertical axis 19, and a second axis oriented in a so-called horizontal direction 20. As already explained, the horizontal direction does not have to be exactly horizontal. The essential point is that the vertical axis 19 and the second, horizontally oriented axis 20 are perpendicular to each other.

[0059] In this reference frame, the first movable pivot joint 2 has the coordinates (I, c). This means that the first movable pivot joint 2 is offset from the horizontal axis 20 by a length c and from the vertical axis 19 by a length I. The second movable pivot joint 3 is offset from the first movable pivot joint 2 by a distance b in the vertical direction and by a distance a in the horizontal direction. As a result, in this reference frame, the second movable pivot joint 3 has the coordinates (I + a, c + b).

[0060] The first fixed pivot joint 4 has coordinates (j, k) in the reference frame. This means that the first fixed pivot joint 4 is located a distance j from the center point in the vertical direction and a distance k in the horizontal direction. The first fixed pivot joint 4 is connected to the first movable pivot joint 2 via a first rod 17. The first rod 17 has a length g.

[0061] A second fixed pivot joint 5 is offset from the first fixed pivot joint 4 by length f in the vertical direction 19 and by length e in the horizontal direction. This results in the second fixed pivot joint 5 having coordinates (j + e, k + f) in the reference frame. The second fixed pivot joint 5 is connected to the second movable pivot joint 3 via a second rod 18 of length h. (Reference symbol list)

[0062] I Closure lid

[0063] 2.2' First movable pivot joint

[0064] 3, 3' Second movable pivot joint

[0065] 4, 4' First fixed pivot joint

[0066] 5.5' Second fixed pivot joint

[0067] 6 mixing containers

[0068] 7 machine stands

[0069] 8 Bearing shaft

[0070] 9 Crossbeam

[0071] 10, 10' side cheek

[0072] II T traverse

[0073] 12 Drive

[0074] 13 locking levers

[0075] 14 End stop

[0076] 15 Drive shaft

[0077] 16 plain bearings

[0078] 17, 17' First pole

[0079] 18, 18' Second pole

[0080] 19 Vertical axis

[0081] 20 Horizontal axis

[0082] 21 Mixing container bottom

[0083] 22 Outlet opening

[0084] 23 Swivel joint

[0085] 24 Swivel joint

[0086] M Center of the lid

Claims

Patent Application 1. Mixer comprising a mixing vessel held in a machine stand, the mixing vessel having an outlet opening arranged in the bottom of the mixing vessel and surrounded by a wall, and a circular closure cover (1) having a diameter and thickness d, which can be moved back and forth between a closed position in which the closure cover (1) is at least partially arranged inside the outlet opening (22) and closes it, and an open position in which the closure cover (1) does not close the outlet opening, the closure cover (1) being connected to the machine stand via a planar linkage, wherein M is the center point of the circular closure cover (1) and an axis (19) defined as vertical passes through M, a direction perpendicular to this axis being defined as horizontal, the linkage having two movable pivot joints (2, 3) attached to the closure cover (1),namely, comprising a first movable pivot joint (2) and a second movable pivot joint (3), and a first fixed pivot joint (4) and a second fixed pivot joint (5), wherein the first fixed pivot joint (4) is in a position offset relative to M by a horizontal distance j and a vertical distance k, wherein the first movable pivot joint (2) is at a vertical distance c from M and a horizontal distance / from M, wherein the second movable pivot joint (3) is at a horizontal distance (a + I) from M and is spaced vertically b from the first movable pivot joint (2), such that the second movable pivot joint (3) is at a vertical distance (c + b) relative to M, wherein the second fixed pivot joint (5) is at a horizontal distance e and a vertical distance f relative to the first fixed pivot joint (4),and wherein the first fixed pivot joint (4) is connected to the first movable pivot joint (2) via a first rod (17) of length g and the second fixed pivot joint (5) is connected to the second movable pivot joint (3) via a second rod (18) of length h, wherein, 1.) j > i / 2, 2.) j + e > i / 2 and 3.) ci / 2 is.

2. Mixer according to claim 1 , characterized in that 0.15 xi < c < 0.5 xi and preferably 0.3 xi < c < 0.5 xi is.

3. Mixer according to one of the preceding claims, characterized in that e > 0, wherein preferably e > d and particularly preferably 0.15 xi < e < 0.5 xi.

4. Mixer according to one of the preceding claims, characterized in that both g and h are greater than i / 2.

5. Mixer according to one of the preceding claims, characterized in that b < i / 2, wherein preferably 0.05 xi < b < 0.45 xi and best 0.1 xi < b < 0.3 xi.

6. Mixer according to one of the preceding claims, characterized in that the amount of | / | < i / 2 and preferably / S 0 and particularly preferably / < 0.

7. Mixer according to one of the preceding claims, characterized in that g < i, wherein preferably g > h and preferably 0.75 xg < h < g.

8. Mixer according to one of the preceding claims, characterized in that k < i / 2, wherein preferably 0.85 x (c + d / 2) < k - d / 2 < 1.15 x (c + d / 2) and particularly preferably 0.9 xk < c < 1.1 xk and / or 0.9 x (fc + ) < (fe + c) < 1.1 x (fc + ).

9. Mixer according to one of the preceding claims, characterized in that b < / e 2 + f 2 , preferably 0.5 xe 2 + f 2 < b < e 2 + f 2 and especially preferred is 0.9 xb < f < 1.1 xb .

10. Mixer according to one of the preceding claims, characterized in that the closure lid (1) is rotatable about the vertical axis.

11. Mixer according to one of the preceding claims, characterized in that the closure lid has a transverse traverse (9) on its side facing away from the mixing container, which has a first retaining section projecting beyond the edge of the closure lid in a direction orthogonal to the vertical axis and the horizontal direction, wherein the first and the second movable pivot joint are arranged on the first retaining section. 12.Mixer according to claim 11, characterized in that the crossbeam (9) has a second retaining section which projects in the orthogonal direction opposite the first retaining section over the edge of the closure cover, wherein the closure cover is additionally connected to the machine stand via a further planar coupling mechanism, wherein the further planar coupling mechanism also has four pivot joints whose axes of rotation are identical to the axes of rotation of the pivot joints of the planar coupling mechanism, wherein two movable pivot joints of the further planar coupling mechanism are arranged on the second retaining section.

13. Mixer according to one of the preceding claims, characterized in that the first fixed axis of rotation or the second fixed axis of rotation is connected to a drive, wherein preferably an additional stop element is provided which is arranged such that it comes into contact with a section of the coupling mechanism in the closed position and limits movement of the closure cover, wherein the stop element is particularly preferably adjustable.

14. Mixer according to claim 13, characterized in that the drive has an actuator which performs a linear stroke movement, preferably a pneumatic or hydraulic cylinder, wherein the first fixed axis of rotation or the second fixed axis of rotation has a lever on which the actuator acts, wherein the actuator is particularly preferably connected at one end to a pivot joint fixed to the machine stand and at the other end to a pivot joint arranged on the lever.

15. Mixer according to claim 13 or 14, insofar as dependent on claim 12, characterized in that either the two coupling gears are connected to each other via a drive shaft, wherein the drive shaft connects the first or the second rotary joints to each other, so that the drive drives both coupling gears, or the second coupling gear has a second drive, wherein a synchronizing device is provided which synchronizes the second drive with the drive of the first coupling gear.

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