Labor stirrer

Abstract

Laboratory stirrer, in particular overhead stirrer, with a housing, a stirrer shaft (11) rotatably mounted in the housing about an axis (A) and a drive for driving the stirrer shaft (11) to a rotary movement about the axis (A), wherein the stirrer shaft (11) can be coupled to a stirring tool via a coupling device such as a chuck, characterized by a blocking device (15) to block the agitator shaft (11) against rotation about the shaft axis (A), wherein the blocking device (15) comprises a shaft-side ring element (17) with an external toothing (22) coupled in a rotationally fixed manner to the agitator shaft (11), a housing-side ring element (27) with an internal toothing (28) arranged coaxially to the shaft-side ring element (17), and a housing-fixed guide section (10) on which the housing-side ring element (27) is adjustably guided in the axial direction of the agitator shaft (11), wherein the housing-side ring element (27) is axially adjustable between a release position of the blocking device (15), in which it is disengaged from the shaft-side ring element (17), and a blocking position of the blocking device (15), in which it is engaged with the shaft-side ring element (17).

Description

The present invention relates to a laboratory stirrer, in particular an overhead stirrer, having a housing, a stirring shaft mounted rotatably in the housing about an axis, and a drive for driving the stirring shaft to rotate about the axis, wherein the stirring shaft can be coupled to a stirring tool in a drive-effective manner via a coupling device such as a chuck.Laboratory stirrers are used to stir a medium in a container. The stirring operation serves in particular to achieve a uniform material distribution. For example, solid substances can be dissolved in liquids or different liquids can be mixed with one another. Frequently, a so-called overhead stirrer is used for this purpose, in which the drive is arranged above the container and the stirring shaft with the stirring tool extends vertically downwards.EP 2 055 372 A1 describes a stirrer unit with an adapter in which the stirrer shaft of the stirrer is mounted. The adapter has a plurality of recesses into which a lever-like detent can be engaged, which is connected to a guide sleeve which is connected to a motor housing. By changing the engagement of the lever-like locking mechanism into another recess, the stirring shaft can be raised or lowered in the container.Furthermore, DE 20 13 513 A discloses a laboratory agitator whose agitator is driven by a motor which is connected via a flexible shaft to a planetary gear train, to which a clamping chuck for fastening the agitator is attached.The coupling device usually makes it possible to undertake a change of the stirring tool if required. In particular, the stirring shaft can carry a chuck, as is known, for example, from portable drilling machines. In order to remove the chucked stirring tool during a desired tool change, a user must hold one part of the chuck and rotate another part about the axis in a known manner. However, the user then no longer has a hand free to hold the stirring tool. In particular in the case of an overhead stirrer, there is thus the risk that the tool falls down. Also, when inserting the stirring tool, the user cannot simultaneously hold the stirring tool and operate the chuck. Furthermore, the possibility of accidental switching on of the drive during the tool change presents a considerable risk of accidents.The object of the invention is to provide a laboratory stirrer of the type mentioned at the beginning which is simple and convenient to operate and in particular enables a reliable tool change.This object is achieved by a laboratory stirrer having the features of claim 1.According to the invention, a laboratory stirrer comprises a blocking device in order to block the stirrer shaft against rotation about the shaft axis, wherein the blocking device comprises a shaft-side ring element with an external toothing, which is coupled to the stirrer shaft in a rotationally fixed manner, a housing-side ring element with an internal toothing, which is arranged coaxially to the shaft-side ring element, and a guide portion fixed to the housing, on which guide portion the housing-side ring element is guided so as to be adjustable in the axial direction of the stirrer shaft, wherein the housing-side ring element is axially adjustable between a release position of the blocking device, in which it is disengaged from the shaft-side ring element, and a blocking position of the blocking device, in which it is engaged with the shaft-side ring element.The stirring shaft can be securely blocked, if necessary, by the toothed engagement between the shaft-side ring element and the housing-side ring element. That is, a rotational movement of the stirring shaft can be stopped. This makes it possible that a user does not have to hold the stirring shaft or the corresponding part of the chuck during a tool change. The user can actuate the rotatable component of the chuck with one hand and hold and remove the stirring tool with the other hand or insert a new stirring tool into the chuck. The blocking device thus enables a particularly simple and reliable tool change. The activation and deactivation of the blocking device can take place in a simple and quick manner by axial displacement of the housing-side ring element. The axial movement can be overlaid by a rotational movement. Specifically, the axial adjustment of the housing-side ring element can comprise a linear displacement movement. Preferably, the housing-side ring element is guided on the housing-fixed guide section by means of a sliding guide. This enables a particularly simple construction.A ring element with an external toothing or an internal toothing within the meaning of the present application is not limited to a conventional gearwheel or a conventional toothed ring, but comprises all ring elements which have one or more individually outwardly or inwardly projecting parts such as teeth, serrations or tines. A plurality of protruding parts of a toothing can be arranged evenly distributed or symmetrically in the circumferential direction of the respective ring element. However, this is not absolutely necessary. In particular, a respective protruding part of the external toothing can engage between two respective protruding parts of the internal toothing, and vice versa. The engagement can be in particular a loose engagement such that a rotational movement of the ring element with the internal toothing relative to the ring element with the external toothing is still possible to a limited extent until the two toothings abut one another. In principle, it is also possible for the external toothing and the internal toothing to each have only a single part projecting outwards or inwards, which in a relative rotational position abut against one another and thus block the rotational movement of the stirring shaft.The housing-side ring element can have blocking teeth, the axial sides of which, in the release position, point toward the shaft-side ring element, are beveled or pointed on one side. Alternatively or additionally, the shaft-side ring element can have shaft teeth, the axial sides of which pointing towards the housing-side ring element in the release position are beveled or pointed on one side. As a result, even in a "tooth-on-tooth" position of the two ring elements, an easy adjustment of the housing-side ring element into the blocking position is possible. In the case that both the blocking teeth and the shaft teeth are axially beveled or pointed, a particularly easy sliding of the teeth against one another is possible.It is not necessary and generally also undesirable for there to be a play-free or particularly play-free toothed engagement between the housing-side ring element and the shaft-side ring element. Rather, it is preferred that the two ring elements are in loose toothed engagement in the blocking position of the blocking device. Specifically, the housing-side ring element and the shaft-side ring element can have respective toothings, the tooth spacing of which in the circumferential direction is at least twice, preferably at least three times, the tooth thickness in the circumferential direction. This is advantageous in that a "tooth-on-tooth" position occurs only relatively rarely. The existing rotational movement play is not critical with regard to a tool change, since the stirring shaft can be rotated without problems by a rotational angle of, for example, a maximum of 30° up to the stop. Finally, during a tool change, the aim is less to completely prevent a rotational movement of the stirring shaft, rather than stopping a rotational movement of the stirring shaft at a stop.The blocking device can have an actuating section coupled axially fixedly to the housing-side ring element for manually axially adjusting the housing-side ring element, so that the housing-side ring element and the actuating section can be axially adjusted jointly between the release position and the blocking position. Such an operating section enables convenient manual operation of the blocking device. The actuating portion can be designed in a special manner for manual operation and in particular have radially outwardly facing, e.g. corrugated grip surfaces which can be easily gripped. Depending on the application, the actuating section can be formed integrally with the housing-side ring element or can be designed as an independent component which is coupled axially fixedly to the housing-side ring element, for example, via a driver device.The actuating section can comprise a sleeve section which at least partially encloses the housing-side ring element and optionally the shaft-side ring element. Preferably, both in the release position of the blocking device and in the blocking position of the blocking device, a complete enclosure of the housing-side ring element and of the shaft-side ring element is provided. The toothings are therefore not directly accessible from the outside, which is preferable for safety reasons. A special embodiment of the invention provides that the actuating section is overall sleeve-like, wherein the stirring shaft is passed through a central passage of the sleeve-like actuating section.The actuating section can engage in the guide section fixed to the housing and cooperate therewith in such a way that the axial adjustment of the actuating section on the housing side from the release position into the blocking position is possible only after the actuating section has been rotated by a predetermined angle of rotation from an operating position of the blocking device into the release position. The blocking device can thus be actuated like a bayonet lock.An embodiment of the invention provides that the guide section fixed to the housing is traversed by at least one circular arc-shaped slot in the axial direction, wherein the respective slot has a radial widening at one end of the circular arc, and that the actuating section has at least one extension extending in the direction of the release position, wherein the respective extension has a radial projection at its free end, wherein the extension engages into the slot in such a way that the radial projection engages behind the guide section fixed to the housing in the operating position and is located in the region of the radial widening in the release position. As soon as the radial projection is located in the radial widening, the extension can be guided in the axial direction in the slot or through the slot, so that an axial displacement of the actuating section is possible. This enables, in a structurally simple manner, the guide section fixed to the housing and the actuating section to cooperate in the manner of a bayonet lock.According to a further embodiment of the invention, a switching device is provided which deactivates the drive of the stirring shaft when the actuating section is rotated from the operating position into the release position. This ensures that the stirring shaft does not run when the tooth arrangements of the ring elements are brought into engagement.It can be provided here that the switching device comprises a switch arranged fixed to the housing, in particular a microswitch, wherein the actuating section has at least one extension which engages into the guide section fixed to the housing and actuates a closer of the switch or is spaced apart from the latter depending on the rotational position of the actuating section. This makes it possible in a particularly simple manner to automatically shut off the drive before axial adjustment of the ring element fixed to the housing. As an alternative to a switch, the automatic switching on and off of the drive could also be effected by means of bridgeable contacts, reed contacts or the like.According to a further embodiment of the invention, the housing-side ring element is coupled axially fixedly to a guide element, wherein the housing-side ring element is guided via the guide element on the housing-fixed guide section so as to be adjustable in the axial direction of the stirring shaft. In other words, the housing-side ring element can be guided indirectly on the housing-fixed guide section. Such decoupling between the blocking function and the guiding function may be advantageous in certain applications.Preferably, a latching device is provided in order to latch the guide element to the guide section fixed to the housing in the release position. This prevents an undesired automatic sliding down of the assembly comprising the guide element, the ring element fixed to the housing and optionally an actuation section and thus ensures that an axial adjustment of the ring element fixed to the housing into the blocking position takes place only upon an active actuation by the user.The guide element can be designed in particular as a guide sleeve which is arranged coaxially with respect to the housing-side ring element. The stirrer shaft can thus be passed in a simple manner from a manufacturing standpoint through the arrangement of the housing-side ring element and guide sleeve.According to a special embodiment of the invention, the stirring shaft is connected to a freewheel, which releases a rotational movement of the stirring shaft in a freewheel direction and blocks it in a blocking direction. Such a freewheel may be provided by drivingly coupling one or more freewheel couplings to the agitator shaft. In certain applications, it may be advantageous to restrict the rotation of the stirring shaft to a single predetermined direction of rotation. This is the case, for example, in a laboratory stirrer, in particular an overhead stirrer, which comprises a motor with a motor shaft that can be changed over in its direction of rotation and a 2-speed transmission with an output shaft, wherein the output shaft has the same direction of rotation for both gears, wherein a gear change is effected by a reversal of the direction of rotation of the motor shaft.According to a preferred embodiment of the invention, the housing-fixed guide section defines a helical movement path for the guide element with respect to the shaft axis, wherein the rotational movement component of the helical movement path is directed against the blocking direction when the guide element is adjusted in the direction of the release position. Due to the helical movement path, an axial adjustment of the guide element is always connected to a rotation of the guide element or of the ring element coupled thereto and fixed to the housing. This facilitates disengagement of the meshing in the case where the stirring shaft is connected to a freewheel. In the presence of a freewheel, the tooth flanks of the ring elements that abut each other tend to become jammed, in particular when a relatively strong torque is exerted on the stirring shaft during the tool change. In such a case, the frictional engagement between the tooth flanks would conventionally be so pronounced that axial pulling apart of the ring elements by hand would be difficult or even not possible at all. Due to the fact that the ring element fixed to the housing is rotated counter to the blocking direction immediately at the beginning of the axial adjustment in the direction of the release position, however, the tooth flanks separate from one another and make possible an easy movement apart of the two ring elements.The housing-fixed guide section can have at least one helically running guide slot, in which a guide projection arranged on the guide element is accommodated in each case. Preferably, a plurality of helically extending guide slots and a plurality of corresponding guide projections are provided, which are arranged distributed, for example, with respect to a circumference of the sleeve-like guide element. A slotted guide can be provided simply and cost-effectively. In general, a relatively weak helical course of the guide slot is sufficient to successfully counteract jamming of the tooth flanks.In particular, a helically extending web can be provided as the projection. This enables a particularly stable and reliable guidance.A further embodiment of the invention provides that the housing-side ring element is mounted on the guide element such that it can rotate with respect to the shaft axis, wherein in particular the rotatably mounted housing-side ring element is prestressed by a spring device with respect to the guide element in the blocking direction of the freewheel. It has namely been found that a constellation in which the tooth flanks already abut against one another before the blocking position is finally reached is problematic in the case of an existing freewheel. A further axial adjustment of the housing-side ring element is made more difficult or completely prevented in such a case by the tooth flanks pressed against one another. This situation is taken into account by a rotation of the housing-side ring element relative to the guide element counter to the spring force. The tooth flanks can then slide against one another while overcoming the spring force until the ring element on the housing has reached the final blocking position.According to a further embodiment of the invention, the housing-side ring element has a further internal toothing which is arranged axially offset with respect to the internal toothing which can be brought into engagement with the external toothing of the shaft-side ring element and engages in recesses formed on the guide element, wherein the recesses form stops for the further internal toothing. The stops limit the rotational movement of the housing-side ring element relative to the guide element. This is favorable since the spring device is thus protected from overloading and, in addition, the blocking function does not depend on the action of the spring device.Preferably, compression springs are arranged between tooth flanks of the further internal toothing of the housing-side ring element and corresponding flanks delimiting the recesses. This ensures a particularly simple construction.The shaft-side ring element can have shaft teeth whose flanks pointing counter to the blocking direction are inclined in the blocking direction with respect to the shaft axis at their ends pointing in the release direction, and that the housing-side ring element has blocking teeth whose flanks pointing in the blocking direction are inclined in the complementary manner with respect to the shaft axis to the flanks of the shaft teeth. That is to say that the flanks of the shaft teeth are inclined in such a way that their ends pointing in the direction of the release position are in each case offset in the blocking direction with respect to the ends pointing in the direction of the blocking position. This generally assists in the ring elements sliding into and out of each other. In particular, tooth flanks beveled in this way facilitate a release of the tooth engagement in the case of an existing freewheel, preferably in cooperation with a helical movement path of the guide element as described above.Display means can be provided which indicate whether the ring element on the housing side is in the release position or in the blocking position. This facilitates the operability of the laboratory stirrer insofar as a user can recognize at all times whether or not the stirring shaft is blocked.The display means may comprise an electronic display integrated into the housing. In particular, a display provided in any case on the laboratory stirrer can be used in an advantageous manner for displaying the current operating state of the blocking device.However, the display means can also comprise a marking which identifies the position of the housing-side gearwheel element relative to the housing-fixed guide portion. Such a type of display can be provided particularly cost-effectively.Advantageous embodiments of the invention are also described in the dependent claims, the further description and the drawing.The invention further relates to a blocking device as described above, wherein the advantageous embodiments of the laboratory stirrer according to the invention can be transferred analogously to the blocking device according to the invention.A non-limiting embodiment of the invention is shown in the drawing and is described below. FIG. 1 ashows a part of a laboratory stirrer according to the invention with a blocking device located in an operating position, in a side view, a lateral sectional view and a top view. FIG. 1 bshows the laboratory stirrer according to FIG. 1 awith a blocking device located in a release position, in a side view, a lateral sectional view and a plan view. FIG. 1 cshows the laboratory stirrer according to FIG. 1 awith a blocking device located in a blocking position, in a side view, a lateral sectional view and a plan view. Fig. 2a is an exploded view of a portion of the arrangement shown in Fig. 1a. FIG. 2b is an exploded view of the remaining part of the arrangement shown in FIG. 1a. FIG. 3 is a side view of a first assembly of the laboratory stirrer shown in FIG. 1 a. FIG. 4 is a top view of the assembly of FIG. 3. FIG. 5 is a perspective partial illustration of the laboratory stirrer shown in FIG. 1 a, which illustrates the interaction between a guide section fixed to the housing and an actuating section of the blocking device. FIG. 6 is a perspective view of a second assembly of the laboratory stirrer shown in FIG. 1 a, which comprises a stirrer shaft and a shaft-side ring element. FIG. 7 shows the cooperation of the housing-side ring element shown at the bottom and 4 in FIGS. 2 aand the shaft-side ring element shown in FIG. 6 in a bottom view. FIG. 8 shows in schematic form three different ways of engaging the housing-side ring element and the shaft-side ring element.The arrangement shown in FIGS. 1 a- 1 cand also FIGS. 2 aand 2 bform part of an overhead stirrer according to the invention, which comprises a guide section 10 formed as part of a housing, not otherwise shown, a stirrer shaft 11 mounted rotatably about an axis A in the housing, and a drive, not shown, including a gear arrangement. The drive, for example in the form of an electric motor, is accommodated in the housing 10 and serves to drive the stirring shaft 11 to rotate about the axis A. The drive can be switched on and off by means of a switch 12.The stirring shaft 11 can be coupled in a likewise known manner by means of a coupling device, not shown, such as a chuck, in a drive-effective manner to a stirring tool. The coupling device is usually seated at the lower end of the stirrer shaft 11 as shown in FIG. 2 b. The coupling of a stirrer tool to the stirrer shaft 11 or the decoupling of a stirrer tool from the stirrer shaft 11 usually requires a manual rotation of a component of the coupling device while holding the stirrer shaft 11, optionally via another component of the coupling device.In order to make the holding of the stirrer shaft 11 unnecessary during the tool change, the overhead stirrer is equipped with a blocking device 15, by means of which a user can block the stirrer shaft 11 against rotation about the axis A if required. The blocking device 15 can assume three different states or positions, which correspond to the representations of FIGS. 1a-1c. FIG. 1a corresponds to an operating position of the blocking device 15, in which the drive is switched on and a rotational movement of the stirring shaft 11 is enabled. FIG. 1 b corresponds to a release position of the blocking device 15, in which the drive is switched off and a rotational movement of the stirring shaft 11 is released. FIG. 1 c corresponds to a blocking position of the blocking device 15, in which the drive is switched off and a rotational movement of the stirring shaft 11 is blocked.The blocking device 15 comprises a shaft-side ring element 17 shown in more detail in FIG. 2 b, in particular a shaft-side toothed ring or toothed wheel element, having a sleeve-like base body 19 which is coupled in a rotationally fixed manner via a spline-like web 21 (FIG. 7 ) to the stirring shaft 11 which is provided with a corresponding groove 99 (FIG. 6 ) and carries an external toothing 22 having shaft teeth 25. The blocking device 15 furthermore comprises a housing-side ring element 27 (FIG. 2 a ) arranged coaxially with the shaft-side ring element 17, in particular a housing-side ring gear or gearwheel element, on which an internal toothing 28 with blocking teeth 29 is formed. As illustrated, the upward-pointing axial sides 30 of the shaft teeth 25 in FIG. 2 bare beveled on one side. In a corresponding manner, the axial sides 31 of the blocking teeth 29 pointing downward in FIG. 2 aare beveled on one side.The housing-side ring element 27 is coupled axially fixedly to a guide sleeve 33 (FIG. 2 b ) arranged coaxially with respect thereto and is guided via said guide sleeve on the guide section 10 of the housing 10 so as to be adjustable in the axial direction with respect to the axis A. For this purpose, the guide sleeve 33 is provided with a plurality of guide webs 35 which are arranged distributed along its outer circumference and extend helically and are accommodated in guide slots 37 of the guide section 10 which likewise extend helically. On the guide sleeve 33, latching notches 39 are provided, which are situated between the guide webs 35 and into which resilient latching tongues 40 of a spring plate 43 can latch. The spring plate 43 provided with fastening holes 45 is screwed to the underside of the guide section 10 and serves to hold the guide sleeve 33 in a predetermined axial position as required.The blocking device 15 also comprises an actuating section 47, which is here sleeve-like and is guided on the housing 10 both rotatably and axially displaceably, as will be explained in more detail below. The actuating portion 47 can be gripped and rotated or axially displaced by a user in order to bring the blocking device 15 into the various positions according to FIGS. 1 a- c.During the assembly of the blocking device 15, the housing-side ring element 27 is first introduced into the actuating section 47 from below until it abuts against inwardly projecting retaining webs 50 thereof. Here, a radially outward-pointing bead 51 of the housing-side ring element 27 is engaged behind by snap fasteners 53 of the actuating section 47, so that the housing-side ring element 27 is held axially fixedly on the actuating section 47. Subsequently, the guide sleeve 33 is inserted into the actuating section 47 from below until it abuts against inner projections 57 of the housing-side ring element 27. The guide sleeve 33 is then fastened axially fixedly to the housing-side ring element 27 by a snap ring 59 being inserted between the underside of the guide sleeve 33 and projections 60 of the housing-side ring element 27. The actuating portion 47, the housing-side ring element 27, the guide sleeve 33 and the snap ring 59 then form an assembly 65 shown in FIGS. 3 and 4, which is provided as a whole for axial displacement with respect to the guide portion 10. The assembly 65 is slid over the stirring shaft 11 and inserted into the guide portion 10. Finally, the shaft-side ring element 17 is placed on the stirring shaft 11, pushed against a circumferential shoulder 67 thereof and axially fixed by means of a securing ring, not shown. The shaft-side ring element 17 fixed in this way acts as a lower stop for the assembly 65. the blocking device 15 is then fully assembled. In the sectional views of FIGS. 1 a- c, it can be seen that the sleeve-like actuating portion 47 encloses the housing-side ring element 27 and the shaft-side ring element 17 in all positions of the blocking device 15 shown.With reference to FIGS. 2 aand 2 band FIG. 4, it should be noted that the housing-side ring element 27 is rotatable about the axis A with respect to the guide sleeve 33. The housing-side ring element 27 also has a further internal toothing 88 which is arranged axially offset with respect to the internal toothing 28 and engages in recesses 89 formed on the guide sleeve 33. The recesses 89 form stops for the further internal toothing 88 and thus limit the rotational movement of the housing-side ring element 27 relative to the guide sleeve 33. Compression springs 95 are arranged between the tooth flanks 90 of the further internal toothing 88 and corresponding flanks 91 limiting the recesses 89, which bias the housing-side ring element 27 in the clockwise direction according to FIG. 4.The cooperation between the operating portion 47 and the guide portion 10 will be described below with reference to FIG. 5. As shown, the housing 10 is traversed in the axial direction by two mutually opposite, circular-arc-shaped slots 70. The slots 70 each have a radial widening 71 at one end of the circular arc. In addition, two columnar protrusions 75 protrude from an upper side of the operating portion 47. Each of the extensions 75 is provided with a radial projection 77 in the region of its free end. The slots 70, the extensions 75 and their radial projections 77 are dimensioned in such a way that, on the one hand, the extensions 75 can be axially passed through the radial extensions 71 and, on the other hand, the radial projections 77 engage behind respective retaining ribs 79 of the housing 10 when the extensions 75 are not located in the radial extensions 71. This means that, starting from the operating position shown in FIGS. 1 aand 5, an axial adjustment of the assembly 65 is only possible after a rotation of the actuating section 47 by an angle of rotation predetermined by the slots 70. Thus, the blocking device 15 can be actuated via the actuating section 47 in a similar manner to a bayonet lock.It can be seen from FIGS. 1 aand 1 bthat one of the extensions 75 actuates a closer 80 of the switch 12 in the operating position of the blocking device 15, but is spaced apart from the blocking device 15 in the release position thereof. In order to ensure reliable actuation of the closer 80 in the operating position of the blocking device 15, an engagement depression 81 is formed on the relevant extension 75. The different lengths of the extensions 75 are purely exemplary and without any further significance.Both in the operating position of the blocking device 15 and in the release position of the blocking device 15, the blocking teeth 29 are axially spaced apart from the shaft teeth 25, so that there is no toothed engagement between the housing-side ring element 27 and the shaft-side ring element 17. The stirring shaft 11 is thus rotatable about the axis A in these positions.If a user wishes to block the stirring shaft 11 starting from the operating position of the blocking device 15 shown in FIG. 1 a, for example because of a tool change to be made, he grasps the actuating portion 47 and rotates it in the counterclockwise direction according to the lower part of FIG. 1 auntil the extensions 75 of the actuating portion 47 strike the ends of the slots 70 and the release position according to FIG. 1 bis reached. One of the extensions 75 releases the closer 80 of the switch 12 so that the drive is switched off and the stirring shaft 11 runs out. The switch 12 should switch sufficiently fast that any follow-up of the stirring shaft 11 subsides before the user transfers the blocking device 15 from the release position according to FIG. 1 bto the blocking position according to FIG. 1 c. This transfer of the blocking device 15 into the blocking position takes place by pulling down the assembly 65 via the actuating section 47 in the axial direction, overcoming the holding force of the latching tongues 40. In the blocking position of the blocking device 15, the housing-side ring element 27 is in toothed engagement with the shaft-side ring element 17, so that any rotational movement of the stirring shaft 11 is stopped and subsequently blocked (FIG. 7 ).The stirring shaft 11 can be connected to a freewheel, which is not shown in the figures, however. Such a freewheel releases a rotational movement of the stirring shaft 11 in one freewheel direction, while blocking it in the opposite blocking direction. In order to prevent a flank-side jamming of the blocking teeth 29 with the shaft teeth 25 in such a configuration, the helical guide slots 37 ensure that the axial adjustment of the guide sleeve 33 and of the housing-side ring element 27 axially coupled thereto takes place according to a helical movement path with respect to the axis A, wherein the rotational movement component of the helical movement path is directed counter to the blocking direction of the freewheel when the guide sleeve 33 is adjusted in the direction of the release position (FIG. 1 b ). Thus, the ratchet teeth 29 immediately separate from the shaft teeth 25 when the operating portion 47 is pushed in the axial direction from the ratchet position toward the release position, so that the meshing engagement is easily released.While the tooth position of the housing-side ring element 27 is firmly defined on account of the guidance on the housing 10, the stirring shaft 11 comes to a standstill in any desired rotational position in the event of a shutdown of the drive, so that the tooth position of the shaft-side ring element 17 is undefined. There are three different ways in which the ratchet teeth 29 and the shaft teeth 25 meet, these ways being contrasted in the upper, middle and lower parts of Fig. 8. In solid lines, the position of the relevant teeth at the beginning of the engagement process is shown, while in dashed lines, the position of the relevant teeth towards the end of the engagement process, corresponding to the blocking position of the blocking device 15, is shown. The free-wheeling direction of the free-wheeling device is indicated with F, while the blocking direction of the free-wheeling device is indicated with S.The upper part of FIG. 8 shows a constellation in which the blocking teeth 29 meet gaps between two shaft teeth 25. In this case, which will occur relatively frequently because of the large tooth spacing, the meshing can take place completely unimpeded. After the blocking position is reached, the stirring shaft 11 can be rotated manually counter to the blocking direction S of the freewheel until the shaft teeth 25 abut against the blocking teeth 29. A subsequent disengagement of the toothing engagement is assisted, as mentioned above, by the helical movement path of the guide sleeve 33. In addition, the flanks 85 of the shaft teeth 25 pointing counter to the locking direction S are inclined in the locking direction S as shown with respect to the axis A at their upper ends, i.e. pointing in the direction of the release position. The flanks 87 of the blocking teeth 29 pointing in the blocking direction S are inclined in a manner complementary thereto. This also assists in releasing the toothed engagement.The middle part of Figure 8 shows a "tooth-on-tooth" constellation. In this case, the blocking teeth 29 and the shaft teeth 25 slide against one another on account of their beveled axial sides 30, 31, wherein the shaft-side ring element 17 with the shaft teeth 25 is rotated away in the free-wheeling direction F. Subsequently, the stirring shaft 11 can be rotated further in the free-wheeling direction F until the shaft teeth 25 abut the respective next blocking tooth 29.The lower part of FIG. 8 shows a constellation in which the flanks 87 of the blocking teeth 29 come to rest on the flanks 85 of the shaft teeth 25 already before the blocking position is reached. In this case, with an unrestricted rotationally fixed coupling between the guide sleeve 33 and the housing-side ring element 27, no further axial adjustment of the housing-side ring element 27 would be possible because of the beveled flanks 85, 87 and the helical movement path of the guide sleeve 33, since the freewheel locks. The housing-side ring element 27 can, however, be rotated against the force of the compression springs 95 (FIG. 4 ) so far relative to the guide sleeve 33 until the blocking position is reached.Thus, in any possible tooth position, the toothing engagement can be brought about easily and the toothing engagement can also be released easily. The invention thus enables a simple and rapid blocking of the stirring shaft 11 if required, which is advantageous in particular when a tool change is to be carried out.

Claims

Laboratory stirrer, in particular an overhead stirrer, having a housing, a stirring shaft (11) mounted rotatably in the housing about an axis (A) and a drive for driving the stirring shaft (11) to rotate about the axis (A), wherein the stirring shaft (11) can be coupled to a stirring tool in a drive-effective manner via a coupling device such as a chuck, characterized a blocking device (15) for blocking the stirrer shaft (11) against rotation about the shaft axis (A), wherein the blocking device (15) comprises a shaft-side ring element (17), which is coupled to the stirrer shaft (11) in a rotationally fixed manner and has an external toothing (22), a housing-side ring element (27), which is arranged coaxially with the shaft-side ring element (17) and has an internal toothing (28), and a guide portion (10), which is fixed to the housing and on which the housing-side ring element (27) is guided so as to be adjustable in the axial direction of the stirrer shaft (11), wherein the housing-side ring element (27) is axially adjustable between a release position of the blocking device (15), in which it is disengaged from the shaft-side ring element (17), and a blocking position of the blocking device (15), in which it is engaged with the shaft-side ring element (17).Laboratory stirrer according to claim 1, characterised in that the ring element (27) on the housing side has blocking teeth (29), the axial sides (31) of which pointing towards the ring element (17) on the shaft side in the release position are beveled or pointed on one side, and / or in that the ring element (17) on the shaft side has shaft teeth (25), the axial sides (30) of which pointing towards the ring element (27) on the housing side in the release position are beveled or pointed on one side.Laboratory stirrer according to claim 1 or 2, characterised in that the housing-side ring element (27) and the shaft-side ring element (17) have respective toothings (28, 22), the tooth spacing of which in the circumferential direction is at least twice, preferably at least three times, the tooth thickness in the circumferential direction.Laboratory stirrer according to one of the preceding claims, characterized in that the blocking device (15) has an actuating section (47), which is coupled axially fixedly to the housing-side ring element (27), for manually axially adjusting the housing-side ring element (27), such that the housing-side ring element (27) and the actuating section (47) are axially adjustable jointly between the release position and the blocking position.Laboratory stirrer according to claim 4, characterised in that the actuating section (47) comprises a sleeve section which at least partially encloses the housing-side ring element (27) and optionally the shaft-side ring element (17).Laboratory stirrer according to claim 4 or 5, characterised in that the actuating section (47) engages in the guide section (27) fixed to the housing and interacts with the latter in such a way that the axial adjustment of the actuating section (27) on the housing side from the release position into the blocking position is only possible after rotation of the actuating section (47) by a predetermined angle of rotation from an operating position of the blocking device (15) into the release position.Laboratory stirrer according to claim 6, characterised in that the guide section (27) fixed to the housing is traversed by at least one circular arc-shaped slot (70) in the axial direction, wherein the respective slot (70) has a radial widening (71) at one end of the circular arc, and that the actuating section (47) has at least one extension (75) extending in the direction of the release position, wherein the respective extension (75) has a radial projection (77) at its free end, wherein the extension (75) engages into the slot (70) in such a way that the radial projection (77) engages behind the guide section (10) fixed to the housing in the operating position and is located in the region of the radial widening (71) in the release position.Laboratory stirrer according to claim 6 or 7, characterised bya switching device (12) which deactivates the drive of the stirrer shaft (11) when the actuating section (47) is rotated from the operating position into the release position.Laboratory stirrer according to claim 8, characterised in that the switching device (12) comprises a switch, in particular a microswitch, arranged fixed to the housing, wherein the actuating section (47) has at least one extension (75) which engages in the guide section (10) fixed to the housing and which actuates a closer (80) of the switch (12) depending on the rotational position of the actuating section (47) or is spaced apart from the latter.Laboratory stirrer according to one of the preceding claims, characterized in that the housing-side ring element (27) is coupled axially fixedly to a guide element (33), wherein the housing-side ring element (27) is guided via the guide element (33) on the housing-fixed guide section (10) so as to be adjustable in the axial direction of the stirrer shaft (11).Laboratory stirrer according to claim 10, characterised in that a latching device (39, 43) is provided in order to latch the guide element (33) to the guide section (10) fixed to the housing in the release position.Laboratory stirrer according to claim 10 or 11, characterised in that the guide element (33) is designed as a guide sleeve which is arranged coaxially to the housing-side ring element (27).Laboratory stirrer according to one of claims 10 to 12, characterised in that the stirrer shaft (11) is connected to a freewheel which enables a rotational movement of the stirrer shaft (11) in a freewheel direction (F) and blocks it in a blocking direction (S).Laboratory stirrer according to claim 13, characterised in that the guide section (10) fixed to the housing defines a helical movement path for the guide element (33) with respect to the shaft axis (A), wherein the rotational movement component of the helical movement path is directed against the blocking direction (S) when the guide element (33) is adjusted in the direction of the release position.Laboratory stirrer according to one of claims 13 and 14, characterised in that the guide section (10) fixed to the housing has at least one helically extending guide slot (37), in each of which a guide projection (35) arranged on the guide element (33) is accommodated.Laboratory stirrer according to claim 15, characterised in that the projection (35) is a helically extending web.Laboratory stirrer according to one of claims 13 to 16, characterised in that the housing-side ring element (27) is mounted on the guide element (33) rotatably with respect to the shaft axis (A), wherein in particular the rotatably mounted housing-side ring element (27) is prestressed by a spring device (95) relative to the guide element (33) in the blocking direction (S) of the freewheel.Laboratory stirrer according to claim 17, characterised in that the housing-side ring element (27) has a further internal toothing (88), which is arranged axially offset with respect to the internal toothing (28), which can be brought into engagement with the external toothing (22) of the shaft-side ring element (17), and engages in recesses (89) formed on the guide element (33), wherein the recesses (89) form stops for the further internal toothing (88).Laboratory stirrer according to claim 18, characterised in that compression springs (95) are arranged between tooth flanks (90) of the further internal toothing (88) of the housing-side ring element (27) and corresponding flanks (91) delimiting the recesses (89).Laboratory stirrer according to one of claims 13 to 19, characterised in that the shaft-side ring element (17) has shaft teeth (25), the flanks (85) of which pointing counter to the blocking direction (S) are inclined in the blocking direction (S) with respect to the shaft axis (A) at their ends pointing in the direction of the release position, and in that the housing-side ring element (27) has blocking teeth (29), the flanks (87) of which pointing in the blocking direction (S) are inclined in the blocking direction (A) in a complementary manner with respect to the flanks (85) of the shaft teeth (25).Laboratory stirrer according to one of the preceding claims, characterized in that display means are provided which indicate whether the ring element (27) on the housing side is in the release position or in the blocking position.Laboratory stirrer according to claim 21, characterised in that the display means comprise an electronic display integrated into the housing.Laboratory stirrer according to claim 21 or 22, characterised in that the display means comprise a marking which identifies the position of the housing-side toothed wheel element (27) relative to the housing-fixed guide section (10).Blocking device for blocking a stirrer shaft (11) of a laboratory stirrer, in particular an overhead stirrer, which is rotatably mounted about an axis (A), against rotation about the shaft axis (A), wherein the blocking device (15) comprises a shaft-side ring element (17), which is coupled to the stirrer shaft (11) in a rotationally fixed manner and has an external toothing (22), a housing-side ring element (27), which is arranged coaxially to the shaft-side ring element (17) and has an internal toothing (28), and a housing-fixed guide portion (10), on which the housing-side ring element (27) is guided in an adjustable manner in the axial direction of the stirrer shaft (11), wherein the housing-side ring element (27) is guided between a release position of the blocking device (15), in which it is disengaged from the shaft-side ring element (17), and a blocking position of the blocking device (15), in which it is engaged with the shaft-side ring element (17).

Images