Turbo drying through air knife

Abstract

Device (1) for drying a workpiece (18) that has been previously subjected to a liquid application and is rotationally symmetrical about a longitudinal axis of the workpiece, preferably in the form of a shrink-fit chuck, wherein the device (1) has at least one air guide device encompassing the workpiece (18) for directing an airflow in the direction along the longitudinal axis of the air guide device and at least one blowing device that directs a radial airflow onto the workpiece (18), wherein the radial airflow flows approximately in the direction normal to the longitudinal axis of the air guide device, characterized in that the air guide device is housed within an air duct (7), wherein the air guide device is inserted into the interior of the air duct (7).

Description

The invention relates to a technology for drying a workpiece which has previously been subjected to heat application and subsequently cooled again using a liquid, in particular a multi-part shrink-fit, preferably in the form of a tool holder for the central shrink-fitting of the shank of a rotary tool (so-called shrink-fit chuck), such as a drill, milling cutter or reaming tool.There are numerous prior art which deals with the solution of the problem of re-cooling a tool holder subjected to heat application with the aid of a liquid and then drying it effectively.In rough summary, three different cooling principles have been proposed so far. Namely, air cooling, liquid cooling and solid contact cooling, i.e., by intimately bringing the surface of the tool holder to be cooled into contact with a highly heat-conducting heat sink in which the heat drains.The technologies known in this respect and their disadvantages are described in detail in the earlier but not prepublished German patent application of the applicant, which bears the file reference DE 10 2009 034 730.In order to solve the problems of the known prior art, the applicant proposes in said earlier but not prepublished application a device using a circulated carrier gas stream into which a cooling liquid is misted in fine droplets. In this way, it is possible to effectively and very uniformly cool the workpiece to be cooled without wetting it excessively.However, in-house experiments by the applicant have shown that this device, which in itself already operates very well, can also be improved even further. This is because this device is capable of quite effectively drying the workpieces which are only slightly wetted in any case, by the misting of the cooling liquid being stopped and the pure carrier gas stream which is no longer supplied with cooling liquid droplets flowing around the workpiece in a turbulent manner for a period of time and drying it in the process.During drying with the aid of the device known from these earlier applications, the main flow direction of the fast, turbulent carrier gas flow is oriented substantially in the direction of the longitudinal axis of the workpiece. This naturally leads to the formation of "lee zones" at the level of depressions, such as circumferential grooves or depressions for adjusting screws and the like, in figuratively speaking (in the case of a rapidly flowing body of water, one would say "dead water zones"), in which coolant residues can collect beyond the end of the drying cycle without being entrained and removed by the carrier gas stream flowing around the workpiece in a turbulent manner.As shown by in-house tests, this problem was also not completely avoided by means of swirling devices which were installed in the carrier gas stream shortly before the region of the workpiece to be dried and which had the task of still swirling the carrier gas stream, which as a whole flows mainly in the direction of the longitudinal axis of the workpiece, even more intensively and / or of equipping it with a swirl.U.S. Pat. No. 1,605,839 A describes an air nozzle for drying purposes, and DE 10 2008 051 282 A1 describes a method for the thermal clamping of tools in shrink-fit chucks.In view of this, it is the object of the invention to specify a device for air drying a workpiece which has previously been subjected to liquid application (washing and / or cooling), with which device the workpiece can be dried even more quickly and reliably. This object is intended to be achieved primarily, but not exclusively, for workpieces which exhibit substantially rotational symmetry about a workpiece longitudinal axis and have a region which is difficult to dry and which narrows towards one end. In a tool chuck for which this object is preferably to be achieved, this is that region which extends from the maximum diameter of the tool chuck towards the sleeve part holding the tool shank.To achieve this object, the invention provides an apparatus having the features of the main claim, namely an apparatus for drying a workpiece which has previously been subjected to liquid application and is rotationally symmetrical about a workpiece longitudinal axis, preferably in the form of a shrink chuck, wherein the apparatus has at least one air guide apparatus which engages around the workpiece and is intended for guiding an air flow in the direction along the longitudinal axis of the air guide apparatus, and at least one blowing device which directs a radial air flow onto the workpiece, wherein the radial air flow flows approximately in the direction of the normal to the longitudinal axis of the air guide apparatus, characterized in that the air guide apparatus is accommodated within an air duct, wherein the air guide apparatus is inserted into the interior of the air duct.The term "air" is understood here, as will be explained later, preferably in a broad sense.The air guiding device is preferably a separate component with respect to the pipe wall which forms the channel within which the air flow circulates and which receives the workpiece to be dried.The air guiding device is designed such that it creates or maintains a (pronounced) air flow which flows substantially in the direction along the longitudinal axis of the workpiece (deviations of up to 25 degrees, better only up to 15 degrees with respect to the longitudinal axis, for example in the case of workpieces which are conical in a certain way, are easily non-critical, larger deviations only if the function according to the invention is achieved, for example because the deviation is locally limited).The decisive point is that a pronounced flow in the longitudinal direction, which surrounds the workpiece, as it were, and at least one flow which intersects this flow in the longitudinal direction and meets the workpiece for the first time in the substantially radial direction are superimposed.The apparatus therefore has at least one blowing device which blows the workpiece with a radial air flow. A radial air flow is an air flow which at least also has a pronounced velocity or movement component in the radial direction, i.e. in the direction of a normal to the workpiece longitudinal axis. Such a radial air flow ideally impinges on the workpiece surface for the first time in a direction (substantially, i.e. + / - 10 degrees) parallel to this normal. If the radial air flow impinges obliquely within the scope of the less optimum embodiments of the invention, it impinges for the first time on the workpiece surface at an angle α of at least ≤60 degrees, preferably ≤45 degrees and ideally ≤30 degrees.Such a radial air flow can also set in motion those liquid residues which have remained at "lee points" which are not swept sufficiently intensively by the flow which is established in the direction of the longitudinal axis of the workpiece. As soon as the radial air flow has captured such liquid residues and set them into motion out of their shaded position ("lee position" or "dead water position"), these are entrained by the air flow which flows substantially in the direction along the workpiece longitudinal axis and discharged in the flow direction past the entire remaining workpiece surface-an air flow which, in cooperation with the at least one radial air flow, performs such a removal function is understood as a pronounced air flow substantially in the direction along the workpiece longitudinal axis.This distinguishes the device according to the invention from those devices in which, although at least one radial air flow is likewise directed onto the workpiece, which however serves predominantly only for evaporation of the liquid residues and / or to swirl them up, so that they sink predominantly under the influence of gravity-as is the case, for example, in devices in which the workpiece to be dried is accommodated in a three-sidedly closed, downwardly open bell and is then shot at least with a radially directed compressed air jet, the volume flow of which is sharply bundled or initially flows rapidly, but is nevertheless so low that after its first impact on the workpiece surface it only causes a comparatively slowly flowing air flow to be produced which flows away in the longitudinal direction and is not capable of actively entraining larger liquid droplets (for example with an average diameter of more than 0.5 mm).Insofar as reference is made here to directions of movement or components or to velocity components, it must be clear that it is not a micro viewing of individual particles in the turbulent flow, but rather the viewing of the overall resulting movement or velocity-as the person skilled in the art makes it visible, for example, with the aid of filaments or smoke particles which are free at one end introduced into the flow.The said pronounced air flow in the direction along the workpiece longitudinal axis is preferably generated in that an air flow which substantially already flows in the said direction flows into the air guiding device and is then superimposed-preferably downstream-with the at least one radial air flow. Alternatively, although not preferred, it is also possible to use only one radial air flow which is so strong that, after the first, radially directed impingement on the workpiece surface, it causes a pronounced air flow to be produced substantially in the direction along the workpiece longitudinal axis.In the context of a preferred embodiment, it is provided that the air guiding device which surrounds the workpiece is designed such that it guides the air flow along a region of the workpiece which is close to the surface.This preferred air guiding device is designed such that, when the workpiece is correctly positioned, it guides or guides the predominant part of the air flow forming around the workpiece along the critical points of the workpiece surface with respect to drying.Preferably, the air guiding device engages around the workpiece at least in sections.The air guiding device according to the invention is not just a part of the smooth cylindrical pipe with constant diameter, which receives the workpiece to be dried and feeds the drying air in and optionally also discharges it again, but a component to be distinguished from this, which is designed such that it deflects or guides the air in a specific manner.Unlike in the case of the mere blowing on of the workpiece accommodated in the said circular cylindrical tube, the air guiding device ensures that the turbulent air flow can at least very intensively and at a continuously high speed scan the critical points of the circumferential surface of the workpiece to be dried-because it is then just not such that the predominant part of the air flow passes the critical points of the workpiece to be dried at a greater distance and therefore a good part of the air flow is without effect "puffed", but rather because the entire air flow is instead guided past in the vicinity of a point of the workpiece critical for drying.Advantageously, the air guiding device has different inner diameters, as seen in the main flow direction of the flow which occurs overall. The air-guiding device is preferably designed such that it forms, at least at one or the critical points of the workpiece to be dried, around the circumference of the workpiece to be dried, a gap through which the drying air flows, having a gap height of ≤5 cm, better ≤3 cm and ideally ≤1 cm. In this case, this gap height preferably only has to be substantially maintained, i.e. it is harmless if there is a larger gap height to a locally limited extent. Typically, the flow which the air guiding device is intended to be guided along the surface of the workpiece to be dried is substantially a flow which flows off in the shortest way or with a certain swirl substantially in the direction of the workpiece longitudinal axis.In the context of a first preferred embodiment, it is provided that the air-guiding device is designed as an air-guiding bell that engages over the workpiece to be dried (preferably extends continuously and surrounds the workpiece to be dried substantially on three sides), i.e. as an air-guiding bell that receives the entire workpiece in its interior at least during the drying cycle, preferably also already during the optional cooling cycle.The diameter of the interior space formed by an air guiding bell preferably to be used is not constant. Instead, the inner diameter of the air guiding bell varies along its longitudinal axis-preferably such that the air guiding bell offers the possibility of introducing workpieces of different sizes to be dried with the device as intended into its interior space such that the air guiding bell forms a gap, through which the drying air flows, with the above-mentioned maximum heights around the circumference of the workpiece to be dried, which gap runs through in the longitudinal direction, all of the statements above applying analogously here. Especially when designing the air guiding bell for drying tool chucks, the following procedure is preferably adopted in order to give the air guiding bell its shape: a group of tool chucks having different diameters and lengths is formed, which are intended to be dried with the device as intended. The air guiding bell is now shaped in such a way that all the chucks to be dried as intended can be introduced into the air guiding bell in such a way that the air guiding bell forms a gap with the above-mentioned maximum heights, which gap is continuous in the longitudinal direction and through which the drying air flows around the circumference of the tool chuck to be dried.The air guiding bell can be used in such a way that smaller tool chucks must be inserted deeper into the air guiding bell until they have found their optimum position than tool chucks with a larger diameter.Alternatively, the air guiding bell can be used in such a way that all the tool chucks to be received by it are placed on one and the same base surface and the air guiding bell, which is movable in the direction of the workpiece axis, is pushed over the tool chuck until it comes to a stop-preferably at the level of said base surface.The receiving of the workpiece to be dried and specifically of a tool chuck in the device is preferably effected in an orientation such that the workpiece longitudinal axis is oriented at least substantially parallel or equal to the longitudinal axis of the air guiding bell. Certain angular deviations (up to about 15 degrees) between the longitudinal axis of the workpiece and the longitudinal axis of the air guiding bell are somewhat non-critical, but rather a theoretical in any case.The diameter of the receiving space formed by the interior of the air guiding bell increases downstream, preferably continuously. This enlargement takes place at least in sections, so that the downstream cross section of the air guiding bell marking the end of the receiving space for drying the workpiece, which is provided as intended by the air guiding bell, is greater than the upstream cross section marking the beginning of the receiving space. It is not excluded (although not practical) that a certain narrowing of the air guiding bell adjoins the end of the receiving space.The air guiding bell is equipped in such a way that at least a portion of the drying air flowing through the air guiding bell flows into the air guiding bell through at least one first opening, which in the optimum case opens directly into the workpiece receiving region within the air guiding bell. This at least one first opening forms the above-mentioned blowing device and is therefore oriented such that it generates a radial air flow. The definitions set out above apply analogously.In the context of a preferred embodiment, it is provided that the at least one first opening is formed and fed in such a way that it shapes the radial air flow into an air knife, i.e. into an elongated flat jet, which intersects the air flow flowing away in the air bell tend to in the direction of its longitudinal axis and penetrates as far as the surface of the workpiece to be dried.In the context of a preferred embodiment, it is provided that the at least one first opening is designed as an elongated slot, the longitudinal axis of which forms a plane with the longitudinal axis of the air-guiding bell or the longitudinal axis of which runs in a helical line around the longitudinal axis of the air-guiding bell, preferably with an angle of inclination of greater than 20°, ideally greater than 40°, with respect to the respective local circumferential line of the air bell.Each of these elongated slots preferably extends over a predominant part of the length of the receiving space available in the air guiding bell as intended for the workpiece to be dried. Generally speaking, a long slot can be said to be possible if the slot length is greater than the slot width by at least a factor of 5. Irrespective of this, it is to be mentioned in any case that a long slot is used in the sense of the invention if the slot has a slot length of preferably >2 cm, better >4 cm, with a slot width of <2 mm, better <1 mm. It is possible to arrange a plurality of comparatively short elongated slots one behind the other along a common line without departing from the spirit of the invention.For the sake of completeness, it should be noted that the effect is the decisive criterion--as an equivalent to a long slot, therefore, also such groups of openings are to be designated which are only spaced apart from one another by webs to such an extent that they generate a common knife-like or bar-like air jet, instead of discharging loud individual air jets.The purpose of the at least one elongated slot is to ensure that the radial air flow used according to the invention is available substantially in the entire receiving space provided as intended for the workpiece to be dried, because of the length of the elongated slot, regardless of whether a shorter workpiece protrudes less deeply into the receiving space of the air guiding bell or whether a longer workpiece protrudes more deeply into the receiving space of the air guiding bell. It should therefore be ensured that each of the workpieces to be dried with the device as intended can be positioned in the workpiece receiving space of the air guiding bell without having to specifically take care in this case that the radial air flow according to the invention sweeps over the workpiece to the required extent.In the context of another preferred embodiment, it is provided that the air guiding bell guides the cooling air such that, after it has first impinged on the workpiece surface to be dried, it swirls there in order to subsequently flow past the workpiece with a movement which is increasingly oriented in the direction along the longitudinal axis of the workpiece to be cooled.It is preferably provided that the air flow used for drying is guided in a substantially closed circuit which consists of at least one pump, preferably in the form of a blower or radial blower, and an air duct which connects the pressure side and the suction side of the pump with the interposition of a workpiece receiving chamber and optionally the air guiding bell. The air bell is arranged in the interior of the air duct in such a way that at least a portion of the air stream used for drying is brought up to the outer circumferential surface of the air bell in order then to flow into the air bell via the at least one opening and to flow away via the interior of the air bell. This substantially closed circuit is preferably characterized in that a large quantity of air circulates therein at high speed and at a comparatively low overpressure.To improve the drying effect, the air stream can be heated, preferably by 5 to 25° C., better by 5 to 10° C. This can be done by an additional heating device or preferably by the waste heat of the pump.In the context of another preferred exemplary embodiment, it is provided that the diameter of the air bell, optionally following a section having a substantially constant diameter, increases substantially continuously or stepwise toward the outflow side and there preferably, but not necessarily, merges into a further section having a substantially constant diameter. Ideally, the air guiding bell has an inner diameter at its downstream end which is greater than its inner diameter at the upstream end by at least a factor of 1.5, more preferably even by at least a factor of 1.8.A further preferred embodiment provides that the air guiding bell is mounted and driven such that it rotates at least temporarily about its longitudinal axis during the application of the air used for drying. It is favorable if the air guiding bell rotates at a rotational speed of >50 U / min, better even at a rotational speed of >200 U / min. Such a rotating air guide bell generates a beam-like or air knife-like air flow which runs around the workpiece to be dried, whereby the workpiece surface is swept with great uniformity. The drive can be effected by electric motor or by utilizing a part of the energy of the drying or cooling air stream. The air guiding bell then has corresponding blades which generate a corresponding drive torque under the influence of the air flowing past.In the context of another preferred embodiment, it is provided that the air guiding bell has at least one second opening in a region upstream of the workpiece receiving region, through which opening, alternatively or in addition to the air flow flowing into the air guiding bell through the at least one first opening, a further air flow flows in, which flows substantially in the longitudinal direction past the surface of the workpiece. In this way, a relatively intensive flow in the longitudinal direction can be produced in the interior of the air bell, which flow inherently has a relatively good drying effect and is capable of effectively discharging the liquid expelled from the problem regions of the workpiece by the radial air flow additionally provided according to the invention.The at least one second opening is preferably designed as a window in the upstream end of the air guiding bell, and specifically best as a window in the circumferential surface of the air guiding bell there. Ideally, the at least one second opening can be opened or closed in order to influence or "switch on and off" the quantity of air entering through it.The air guiding bell is preferably arranged in the interior of the air channel surrounding it in such a way that at least a portion of the air flow used for drying is brought up to the outer side of the air guiding bell-and in the majority of cases flows along there a part-in order then to flow into the air guiding bell via the at least one opening and to flow off via the interior of the air guiding bell.In this case, the air guiding bell is preferably installed in the air duct in such a way that, in effect, the (substantially) entire air stream circulating in the device enters the interior of the air guiding bell at any point and flows through at least a portion of the interior of the air bell.In the context of another preferred embodiment, it is provided that the outer periphery of the air guiding bell communicates with at least two different chambers which are not simultaneously or at least not permanently simultaneously connected to the air stream impinging on the air guiding bell. In this way, it is possible to generate in the air guiding bell (quasi-) at least one circulating air jet or at least one circulating air knife, although the air guiding bell as such is immovable. For this purpose, at least two, preferably at least three, first openings are provided in the wall of the air guiding bell, each of which openings communicates with a different chamber. As soon as the chambers are alternately connected to the air flow acting on the air guiding bell and separated from it again, revolving air jets or air knives are produced in the chamber.In order to be able to alternately connect and disconnect each of the chambers from the air flow, a circumferential control disk is preferably provided, which has at least one window and at least one closed surface section, which are successively brought into overlap with the at least one opening of the chambers, via which an air flow enters the chamber.Preferably, a spacer is attached to the inner surface of the air guiding bell, which ensures that a certain minimum distance remains free between a workpiece introduced into the air guiding bell and the inner surface of the air guiding bell (everywhere or except for locally limited exceptions). In this way, it is prevented that a workpiece to be dried is introduced into the air guiding bell in such an unfavorable manner that the distance between the workpiece and the inner surface of the air guiding bell is at some locations so small that the flow of the surface of the workpiece at this location is no longer sufficiently strong-which possibly leads to inadequate drying. Instead, such a spacer simplifies the introduction of the workpiece into the air guiding bell. The air bell is always lowered onto the workpiece until it has reached the end position or it comes to rest against the spacer.Since the spacers can come into contact with hot regions of the workpiece, they consist of heat-resistant material, for example particular types of plastics, metal, ceramic or carbon fibre material.The spacer preferably consists of at least one, preferably a plurality of strips extending along the surface in the longitudinal direction or along a helical line, which strips are not in contact with the surface of the air guiding bell or are in contact with the surface of the air guiding bell only locally at their anchoring points, so that a substantially unhindered air flow can be established between the strips and the inner surface of the air guiding bell in the remaining regions.In the context of another preferred embodiment, it is provided that a cooling liquid for cooling the workpiece can be applied to the air guiding bell during a cooling phase temporally preceding the drying process.Preferably, the air guiding bell can be acted upon with a cooling mist for the purpose of cooling, most preferably in that at least one atomizer or nebulizer is mounted on or in the region of the upstream end face of the air guiding bell, which nebulizer, if required, loads an air stream entering the air guiding bell with finely distributed cooling liquid.This may be done in advance to the concrete description of the exemplary embodiments illustrated by the figures.Further modes of operation, advantages and possible embodiments result from the exemplary embodiments described below with reference to the figures.FIG. 1 shows an overall view of an apparatus according to the invention in the drying operation.FIG. 2 shows an overall view of the device according to the invention in the cooling mode.FIG. 3 shows a detail of a device configured according to FIGS. 1 and 2 in the region of the receiving space for introducing and holding the workpiece to be dried, in longitudinal section.FIG. 4 shows a partial view of FIG. 3, uncut, obliquely from above.FIG. 5 shows a planar section through the device shown by FIGS. 3 and 4.FIG. 6 shows a detail of a second installation according to the invention, which is constructed in principle like those shown in FIGS. 1 and 2, but which differs from the first exemplary embodiment in the details shown in FIG. 6.FIG. 7 shows a third exemplary embodiment, which serves to illustrate how a spacer can look, which can be used in all exemplary embodiments according to the invention.The apparatuses shown within the scope of the exemplary embodiments are all designed as combination apparatuses which can both cool and dry the workpiece. However, unless expressly stated otherwise, the following statements also apply to apparatuses which are designed exclusively as apparatuses for drying.The exemplary embodiments given for the purpose of explaining the invention all function according to the same basic principle, which is explained in more detail below with reference to FIGS. 1 and 2.A substantial part of the entire device 1 is the pump 2, which is designed here as a radial fan. The use of a radial fan is particularly expedient since cooling medium separated or condensed from a radial fan in the interior of the fan can be very easily discharged. However, in principle, the use of another blower or a pump based on a quite different principle is also conceivable. The pump may also consist of a combination of several fans, which may be connected in parallel and / or in series.The radial fan generates a powerful air flow which, in the case of the exemplary embodiment described, serves as a carrier air flow 3 for the cooling mist droplets in the cooling phase and as a drying air flow 4 in the drying phase. The term "air" is understood in a broad sense within the scope of the invention-although it primarily denotes, because it is most easily manipulated and available, "normal" ambient air, but optionally also any other gas which is suitable for blowing on the workpiece in order thereby to at least dry it.The pump output of the blower is relatively high, preferably controllable or controllable, and is preferably above 5 m 3 / min, more preferably even above 10 m 3 / min. The average flow velocity of the air flow on the workpiece used for drying and or as a carrier is preferably above 0.5 m / s, better above 1.5 m / s or even 2.5 m / s. The overpressure within the closed system in which the air flow circulates is preferably <0.4 bar, better still <0.15 bar. In order to realize the invention, unlike in some cases proposed in the prior art, it is preferable not to use a jet of compressed air which is fired onto the surface of the workpiece to be dried, but rather to use an amount of air which is introduced at a high speed but (compared to the pressure at which compressed air is introduced, usually between 3 and 10 bar) at a low pressure.The drying air stream 4 and optionally also the carrier air stream 3 are conducted in a substantially self-contained circuit, wherein particularly when using air corresponding to the ambient air, smaller leakage losses can be harmless in individual cases. For this purpose, the pressure side 5 of the blower is connected to the suction side 6 of the blower via a gas channel 7, so the gas channel 7 ensures that the air flow circulates continuously at substantially the speed that is to be measured in the vicinity behind the pump.In the present exemplary embodiment, the air duct 7 is formed by a round tube, which preferably has an inner diameter of >10 cm. However, the use of a round tube is not obligatory; theoretically, a flexible tube, a flat channel or a channel with a polygonal cross section can also be used.In the present exemplary embodiment, the air duct 7 is designed such that the air flow circulating therein is initially guided in the vertically upward direction on the delivery side of the pump, is then deflected by 180° via a pipe elbow in order now to be guided in the vertically downward direction as a falling flow.As can be seen easily from FIG. 1, a receiving space 8 for the workpiece is provided in the air duct at least at one point. This receiving space can be loaded with the workpiece after opening a sliding sleeve 9 and can then be closed again at least substantially air-tightly.Optionally, a feed device is provided, which in the present case is designed as a rotary plate 16, which is provided with a plurality of correspondingly designed workpiece holders 17, on which the workpieces 18 to be cooled can be placed. The rotary plate moves it stepwise in succession through the receiving space 8, in which it rotates further by the corresponding angle upon each change.The air guiding device 10 is accommodated within the air duct 7, which is designed here in the form of an air guiding bell for which the reference numeral 10 has just been selected.Therefore, only air guiding bell is referred to throughout the following, but the term can be read generally as an air guiding device, unless the context clearly indicates otherwise, although the term air guiding device generally has a meaning to be interpreted further than the term air guiding bell.The air guiding bell is accommodated completely within the air channel 7, i.e. the air channel 7 completely surrounds the air guiding bell. The air guiding bell 10 is accommodated in the air duct 7 in such a way that it can be acted upon from its outside by the air circulating in the air duct. The air guiding bell delimits the receiving space 8 with respect to the air channel 7.Below the air guiding bell there is provided a device for lifting the workpiece, here in the form of a small lifting table 19 which optionally cooperates with the rotary plate 16 in such a way that it can lift its respective workpiece receptacle 17 together with the workpiece 18 placed thereon. With this or with other positioning means, the workpiece is lifted into the workpiece receiving space 23 of the air guiding bell until it has reached its correct position.Alternatively (significantly preferred), it is also possible to design the air guiding bell in such a way that it can be raised for re-loading the receiving space and then lowered again over the workpiece introduced in the meantime into the receiving space 8.As can be seen at least roughly from FIG. 1, the air guiding bell has openings 11, 12 via which the air flow circulating in the air channel 7 enters the interior of the air guiding bell.The air guiding bell has at its upstream end-in the uppermost third, preferably still above the boundary of the region of the receiving region provided as intended for receiving the workpieces to be dried-at least one second air inlet opening 11, via which a not inconsiderable part of the total available air flow enters the air guiding bell, as what is known as a second partial air flow 13. Preferably, instead of one or more (usually uniformly) distributed second air inlet openings, ideally three or even at least four, are provided on the circumference of the air guiding bell.Another not inconsiderable part of the total available air flow passes through the air guiding bell on its outer side until this so-called first partial air flow 14 has arrived at or downstream of the boundary of the region which is provided within the air guiding bell for receiving the workpieces to be dried here as intended. Here, at least one blowing device is located in the form of a first air inlet opening 12 which shapes this first partial air flow 14 to form at least one radial air flow in the abovementioned sense and allows it to enter the interior of the air guiding bell. The partial air flow 14, which is temporarily configured as a radial air flow, also intensively sweeps the problem zones of the workpiece (grooves, recesses, depressions, points with sudden diameter changes) when it initially impinges on the workpiece surface, and entrains the cooling liquid droplets still adhering there. In the course of its first impingement on the workpiece surface, the partial air flow 14 changes its direction and, with entrainment of the coolant droplets captured by it, combines with the partial air flow 13 already flowing in the longitudinal direction of the workpiece, in order then to flow off together with the latter.Preferably, said blowing device is formed by at least one, preferably at least three, more preferably six to ten first openings 12 in the wall of the air guiding bell. This at least one first opening is dimensioned and configured such that it generates a radial air flow according to the above-mentioned definition.In all these cases, it should be noted that it is advantageous, but not absolutely necessary, for the partial air flow 13 and the partial air flow 14 to flow simultaneously.Rather, the device can also be operated according to the invention in such a way that (at least in the drying phase) the entire available air stream is guided along the path which has been described above for the first partial air stream 14. Alternatively, the device can also be operated in such a way that only the first partial air flow 14 flows at one specific time and only the second partial air flow 13 flows at another time.Despite the merely schematic illustration, it can be seen quite well with reference to FIG. 1 that the air guiding device 10, which is realized here as an air guiding bell, guides that air flow which flows along the workpiece substantially in the longitudinal direction (i.e. here from top to bottom) of the air guiding bell such that it is forced along the surface close to the surface, preferably within a predefined maximum distance.As mentioned, the exemplary embodiments, on the basis of which the invention is explained, also serve at the same time for cooling the workpiece. For this purpose, a spraying device 15 is provided. In the simplest case, this operates as a liquid shower. However, it is preferably designed as a nebulizer and then operates as described in the application DE 10 2009 034 730 (this application also designates the nebulizer as an injector). The misting of a cooling liquid into the carrier air stream produces an air / cooling liquid dispersion, which preferably consists predominantly of air in terms of its volume.Ideally (although not obligatory), such a nebulizer is attached in the region of the upstream end of the air guiding bell, preferably within the latter.The apparatus then operates during the refrigeration cycle as illustrated in Figure 2.The nebulizer is mounted such that the droplets generated by it are entrained by the air stream entering the air guiding bell in a turbulent manner through the at least one second air inlet opening 11 and are transported past the workpiece in a finely distributed manner, preferably without dropping out of the carrier air to a significant extent.In this way, the workpiece is cooled gently but uniformly and yet quickly, without excessive liquid wetting of the workpiece.Further details regarding the optional possibility of configuring the apparatus according to the invention as a combination device, with which the cooling cycle and the drying cycle can be realized within a single device (preferably without having to handle the workpiece in between), are described below.FIG. 3 shows the details of the air guiding bell 10 according to the invention. It is fastened upstream by a first collar 21 to the inside of the air duct 7 and downstream by a second collar 22, which second collar is preferably designed to prevent a part of the air flow from bypassing the air guiding bell. The air guiding bell is preferably made of plastic.The region 23 of the air guiding bell intended for receiving the workpiece can be clearly seen. It is provided here with a total of six first air inlet openings 12 which are uniformly distributed on the circumference of the air guiding bell and here form the so-called blowing device.These first air inlet openings 12 each extend substantially in the direction of the longitudinal axis of the air guiding bell 10, and they are each configured as an elongated slot in the wall of the air guiding bell, which extends substantially over the entire receiving space 8 for the workpiece to be dried.Above the region provided for the regular reception of the workpieces to be dried, the air guiding bell is provided with second air inlet openings 11 which here form a number of spaced-apart windows through which at least a second part of the air flow can enter the air guiding bell. These air inlet openings 11 can be opened and closed by means of a control slide 24. The control slide 24 is designed as a cylinder sleeve which is rotatably fastened on the air guiding bell and overlaps the section thereof which carries the second air inlet openings 11. The control slide 24 is provided with openings 25 which at least substantially correspond to the second air inlet openings 11. Depending on the position of rotation of the control slide 24, the openings 11 and 25 are completely or partially aligned or do not come into alignment with one another at all ("completely closed"). In this way, the air flow entering the air guiding bell via the at least one second opening can be "switched on and off" or optionally even controlled. The slide 24 is preferably actuated by an electric motor.The upstream first collar 21 of the air guiding bell has third openings 26. On the collar there is a rotatable control disc 27 which in turn has fourth openings 28 which correspond substantially to the third openings 26. Depending on the rotational position of the control disc, these openings are completely or partially aligned or do not come into register at all. In this way, the air flow entering the air guiding bell via the at least one first air inlet opening 12 can be controlled or even controlled.The control disk 27 is preferably used to supply a plurality of first air inlet openings 12 with air one after the other in such a way that a circular movement is produced-preferably in the form of one or more air knives rotating in the air guiding bell.For this purpose, at least two or more preferably at least three partitions or ribs 34 are provided on the outer periphery of the air guiding bell, which partitions or ribs run in the longitudinal direction of the air guiding bell and together with the air duct 7 (or a further wall) form a plurality of chambers which surround the air guiding bell 10. At least one first air inlet opening 12 or an elongated slot of the air guiding bell is connected to each chamber. Each of the chambers can be supplied with an air stream via at least one third opening 26 of the control disk 27 and can be separated from the air supply with the aid of a window-free section of the control disk 27. By rotating the control disk, the plurality of first air inlet openings 12 can be supplied individually or in groups successively with air, so that a circulating radial air flow is formed in the air guiding bell, which is particularly effective because each part of the surface of the workpiece to be dried is swept by the radial air flow in the shortest way at a specific point in time.Preferably, the control disc 27 and the control slide 24 are actuated by a common electric motor 31. For this purpose, the electric motor is fixed to the control slide 24 and "travels" therewith. On the other hand, the electric motor drives the second pulley 30, which is formed on the control slide 24, preferably via a gearwheel or with the aid of a first pulley 29 via a belt, not shown here. For driving the control slide 24, the reaction torque which arises at the motor housing when the motor applies a torque to the control disc 27 is used-if the motor is driven in a leftward rotating manner, then its reaction torque rotates the control slide 24 until it comes to a stop in the "open" or "closed" position, then the motor is driven in a rightward rotating manner, then its reaction torque rotates the control slide 24 until it comes to a stop in the "closed" or "open" position.The electric motor 31 may be housed inside the air duct 7.For the sake of completeness, it should also be mentioned that it is also possible to see in detail with reference to FIG. 3 how the spraying device 15 is fastened to the air guiding bell-with the aid of a cap which closes the upstream end face of the air guiding bell.The sliding sleeve 9 can also be seen in FIG. 3.FIG. 4 shows a representation corresponding to FIG. 3 of the first exemplary embodiment, but in a non-sectioned view.FIG. 5 likewise shows an illustration of the first exemplary embodiment corresponding to FIG. 3, but in a perspective viewed perpendicularly from the side. Here, the main directions of the expected turbulent partial air streams are illustrated once again.It can be seen here how the first partial air flow 14 generated by the blowing devices or the first air inlet openings 12 forming them enters the air guiding bell 10, which impinges there at an angle α to the normal on the longitudinal axis L of the workpiece or the air guiding bell only indicated here.FIG. 6 shows a second exemplary embodiment of the invention. In this exemplary embodiment, unlike before, the air guiding bell 10 is not mounted in a fixed position in the air duct 7, but is mounted rotatably therein, preferably with the aid of a number of ribs 34 which project into the interior of the air duct 7 and form corresponding bearing rings or bearing seats and preferably hold rolling bearings. Between these ribs, spacings are provided so that at least a part of the air flow available for drying can pass the ribs and only underneath it can enter the interior of the air guiding bell.The air guiding bell is driven to rotate at least temporarily during the drying cycle. Before the beginning of the rotary movement, the air guiding bell is raised somewhat in order to avoid any frictional contact with the workpiece. An electric motor 32 and a gearwheel 33 which is mounted on the air-guiding bell act on said gearwheel as a rotary drive. The gear wheel projects outwardly from the air duct 7 and is driven by the motor located outside the air duct. Alternatively, it is possible to accommodate the motor within the air duct.Due to the fact that the air guiding bell rotates at least temporarily during the drying cycle, it may be sufficient to equip the air guiding bell only with a single blowing device, which is designed here in the form of a single first air inlet opening 12 in the wall of the air guiding bell 10. Nevertheless, in the specific case, it can also be advantageous in the case of a rotatable air guiding bell to equip it with a plurality of first air inlet openings 12 distributed over its circumference.Again, reference numeral 15 designates the spraying device which is fixedly mounted in the air duct 7 here and is arranged outside the air guiding bell in the region of the upstream end thereof. The spray device 15 sprays or mists the cooling liquid into the interior of the air guiding bell via at least one second opening 11 preferably provided in the end face of the air guiding bell.FIG. 7 illustrates an exemplary embodiment of the spacer according to the invention, as can be used in all of the exemplary embodiments described here.The spacer is designed here as a type of "cage" 37, the outer contour of which substantially corresponds to the contour of the inner surface of the air guiding bell, but with a smaller diameter. The cage consists of longitudinal strips 36 and, in the present case, strips which are arranged along a helical line and function as spacers 35. This cage is introduced into the air guiding bell and fastened to it in such a way that (apart from possible fastening points) at least the spacer or spacers 35 are at a distance from the inner surface of the air guiding bell. The "mesh width" or the "grid spacing" of the cage is smaller than the smallest workpiece to be introduced into the air guiding bell as intended, so that the cage also reliably maintains it at a distance from the inner surface of the air guiding bell.Finally, as stated above, it is still possible to proceed to further details of the optional possibility of simultaneously also implementing cooling of the workpiece with the device.The invention is based on the idea with regard to cooling of the liquid coolant not to be used substantially undiluted, as is the case with immersion or surge cooling, but rather to be dissolved into comparatively fine droplets, so as to be able to be diluted virtually and then to transport these droplets by means of the already available air stream, which is used for this purpose as carrier air stream. This makes it possible to guide the coolant droplets past the object to be cooled at an increased speed, so that a rapid but not too sharp cooling results, which is moreover extremely uniform. The transport by means of the carrier gas (which ideally circulates in a closed loop) has the advantage that substantially finer droplets can preferably be used than in the known spraying or spraying, which relies-if dissolution into individual droplets takes place at all-on a comparatively large droplet size, since the individual droplets can only be sufficiently accelerated to be able to overcome the path up to the object to be cooled.In this case, it is generally such that it is the finely distributed liquid cooling medium which absorbs the predominant part of the thermal energy to be dissipated.An advantage of the cooling according to the invention is that the droplets can be selected such that even if the droplets spontaneously evaporate when they strike the surface of the object to be cooled, no uneven cooling results-unlike in a immersion or surge cooling, where the evaporating cooling medium forms more or less large local vapor bubbles, which temporarily impede the heat transfer and thus create the risk of irregularities. In addition, in the procedure according to the invention, vapor formed is immediately entrained by the carrier gas stream, discharged, cooled again and recondensed. The latter is also important when using water with corrosion inhibitors, since the latter form health-threatening vapors.Ideally, the atomization or the nebulisation of the cooling medium is so fine that its droplets are not only transported into the cooling chamber by the carrier gas stream, but are also transported substantially out of it again. In this way, the article to be cooled is not excessively wetted, but comes into continuous contact with new, fresh droplets. The droplets are at least predominantly so fine that their movement is not substantially determined by the force of gravity or the forces which the surface of the object to be cooled exerts on them, but rather substantially by the forces which the carrier gas stream exerts on them.In this way, the intensity of the cooling can be influenced quite well by briefly varying the velocity of the carrier gas stream and / or the quantity of the liquid cooling medium added to the carrier gas stream.At the same time, the fact that the coolant flow flows at an increased speed and, in terms of volume, predominantly consists of the carrier gas and not of the liquid coolant makes it possible to shape the coolant flow without particular effort, for example to focus it on the object to be cooled and / or to impart a swirl to it.A general, generally valid measure for the size of the coolant droplets can only be given with difficulty, since their ideal size depends strongly on the individual conditions.As a rough indication, it can be said that the coolant droplets should in most cases have a diameter which is at least less than 1 mm or, much better, at least predominantly less than 0.5 mm. Ideally, the coolant droplets are at least predominantly smaller than 0.1 mm or are atomized so finely that they form a true mist together with the carrier gas. The coolant droplets preferably already have the diameters mentioned during their initial atomization or misting. In principle, however, it is sufficient if coolant droplets having the above-mentioned diameters are formed only in the course of the further swirling, but substantially before the impingement on the object to be cooled.Water is used as the cooling medium in the present case, because water is cost-effective, easy to handle and physiologically harmless as such. It is of course possible to add corrosion inhibitors or other additives to the water, for example those which influence the wetting of the article to be cooled or the formation of droplets. This naturally also applies when using liquid cooling media other than water.Preferably, the cooling device comprises a cooler downstream of the object to be cooled. Such a cooler not only reduces the temperature of the coolant flow and thus ensures more efficient cooling during its next circulation. Rather, it is generally the case that the cooler also contributes to separating the cooling medium, in particular the water used for this purpose, from the carrier gas stream again. In this way, a relatively "dry" carrier gas stream has always been available on the pressure side of the blower. This opens up the possibility of metering a specific amount of cooling medium into the carrier gas stream again during each circulation and thus influencing the cooling process in a specific manner.Instead of or in addition to a cooler, a mechanical droplet separator can also be used, for example in the form of a centrifugal separator or in the form of an optionally multistage deflecting device which deflects the air stream in such a way that the air stream and the droplets separate. If necessary, a radial fan can also be used which acts at the same time as a droplet separator because of the centrifugal forces to which it is exposed. The liquid coolant which has been separated by the centrifugal force exerted by the rotor of the radial fan on the carrier gas stream can then be collected quite simply with the aid of the correspondingly designed casing of the radial fan and subsequently be drawn off by means of a pump.In this way, moisture is also prevented from being discharged to a significant extent from the device. This moisture could condense in the environment of the device and contaminate the workplace.For the sake of order, it should be noted quite generally that the invention is not exclusively, but preferably directed to a device for drying tool chucks or even (even more specifically) shrink chucks, so that wherever the term "workpiece" has so far been used, the term "tool chuck" or "shrink chuck" can optionally also be used if only a narrower range of application of the invention is to be addressed.Independently of the limiting features of the proposed main claim, protection is also claimed for a device for drying a workpiece which has previously been subjected to liquid application and is rotationally symmetrical about a workpiece longitudinal axis, preferably in the form of a shrink chuck, characterized in that the device has at least one hood or bell 10 which engages over the workpiece and in the circumferential wall of which the workpiece engages at least one slot through which a radial air flow enters the hood or bell, which ideally impinges on the workpiece surface for the first time in a direction (substantially, i.e. + / - 10 degrees) parallel to this normal or impinges on the workpiece surface for the first time obliquely in the sense defined above.The hood is a component which is similar to the air guiding bell described above, but can also be designed, for example, as a cylindrical "pot" with a substantially constant diameter which is open on only one or both end sides.List of reference numbers:1 Device 2 Pump 3 Carrier air flow 4 Drying air flow 5 Pressure side 6 Suction side 7 Gas channel 8 Receiving space 9 Sliding sleeve 10 Air guiding device / air guiding bell 11 Second air inlet openings 12 First air inlet openings 13 Second partial air flow 14 First partial air flow 15 Spray device 16 Rotary plate 17 Workpiece receptacle 18 Workpiece 19 Lifting table 20 Liquid cooling medium 21 First collar 22 Second collar 23 Workpiece receiving space 24 Control slide 25 Openings 26 Third openings 27 Control disc 28 Fourth openings 29 First belt pulley 30 Second belt pulley 31 Electric motor 32 Electric motor 33 Gearwheel 34 Ribs / separating walls 35 Spacer 36 Longitudinal strips 37 Cage

Claims

Device (1) for drying a workpiece (18), preferably in the form of a shrink-fit chuck, which has previously been subjected to liquid application and is substantially rotationally symmetrical about a workpiece longitudinal axis, wherein the device (1) has at least one air-guiding device, which engages around the workpiece (18), for guiding an air flow in the direction along the longitudinal axis of the air-guiding device, and at least one blowing device, which directs a radial air flow onto the workpiece (18), wherein the radial air flow flows approximately in the direction of the normal to the longitudinal axis of the air-guiding device, characterized in that the air-guiding device is accommodated within an air duct (7), wherein the air-guiding device is inserted into the interior of the air duct (7).Device (1) according to Claim 1, characterized in that the air-guiding device (10) which surrounds the workpiece (18) is designed in such a way that it guides the air flow along a region of the workpiece (18) which is close to the surface.Device according to claim 1, characterised in that the air guiding device (10) is an air guiding bell (10), which receives the workpiece (18) at least during the drying cycle, wherein the diameter of the interior space formed by the air guiding bell (10) is not constant.Device according to claim 3, characterised in that the diameter of the receiving space (8) formed by the interior of the air guiding bell (10) increases - preferably continuously - towards the outflow side.Device according to claim 3 or 4da, characterised in that at least a part of the drying air flowing through the air guiding bell (10) flows into the air guiding bell (10) through at least one first opening (12), which is aligned such that the part of the air flow flowing through it into the air guiding bell (10) impinges as a radial air flow on the workpiece surface to be dried.Device according to claim 5, characterised in that the at least one first opening (12) is formed and fed in such a way that the air flow flowing through it into the air guiding bell (10) forms an air knife which penetrates the air flow which builds up in the air guiding bell (10) and flows substantially in the longitudinal direction along the workpiece surface to be dried and impinges as a radial air flow on the surface to be dried.Device according to claim 5 or 6, characterised in that the at least one opening (12) is formed as an elongated slot, the longitudinal axis of which forms a plane with the longitudinal axis of the air guiding bell (10) or the longitudinal axis of which forms a plane in a helical line about the longitudinal axis of the air guiding bell (10), preferably with an angle of inclination of > 20 degrees and ideally > 40 degrees with respect to the respective local circumferential line of the air guiding bell (10).Device according to one of the preceding claims 3 to 7, characterised in that the air guiding bell (10) guides the cooling air in such a way that, after it has initially hit the workpiece surface to be dried, it flows substantially in the direction along the longitudinal axis of the workpiece (18) to be cooled past the latter.Device according to one of the preceding claims, characterized in that the air flow (4) used for drying is guided in a substantially closed circuit which consists of at least one pump (2), preferably in the form of a fan or radial fan, and an air duct which connects the pressure side (5) and the suction side (6) of the pump (2) to one another with the interposition of a workpiece receiving chamber (23).Device according to one of the preceding claims 3 to 8, characterised in that the air guiding bell (10) is arranged in the interior of the air duct in such a way that at least a part of the air flow (4) used for drying is brought up to the outer side of the air guiding bell (10) in order then to flow into the air guiding bell (10) via the at least one opening and to flow away via the interior of the air guiding bell (10).Device according to one of the preceding claims 3 to 8 and / or 10, characterised in that the diameter of the air bell (10), optionally following a section with a substantially constant diameter, increases towards the outflow side and there preferably but not necessarily merges into a further section with a substantially constant diameter.Device according to one of the preceding claims 3 to 8 and / or 10 to 11, characterised in that the air guiding bell (10) is mounted and driven in such a way that during the application of the air flow (4) used for drying it rotates at least temporarily about its longitudinal axis, preferably at a rotational speed of more than 0.25 revolutions per second.Device according to one of the preceding claims 3 to 8 and / or 10 to 12, characterized in that the air guiding bell (10) has, in a region upstream of the workpiece receiving region (23), at least one second opening (11), through which, alternatively or in addition to the air stream flowing through the at least one first opening (12) into the air guiding bell (10), an air stream flows in, which air stream flows substantially in the longitudinal direction past the surface of the workpiece (18).Device according to one of the preceding claims 3 to 8 and / or 10 to 13, characterised in that the air guiding bell (10) has a plurality of first openings (12) which are provided at different points on its circumference and which can be activated or deactivated separately from one another in such a way that an air stream can flow or cannot flow via them into the interior of the air guiding bell (10), wherein the first openings (12) are preferably activated and deactivated in such a way that a circular movement results therefrom.Device according to one of the preceding claims 3 to 8 and / or 10 to 14, characterized in that the outer periphery of the air guiding bell (10) communicates with different chambers which are not simultaneously or at least not permanently simultaneously connected to the air stream acting on the air guiding bell (10).Device according to one of the preceding claims 3 to 8 and / or 10 to 15, characterised in that a spacer (35) is attached to the inner surface of the air guiding bell (10), which spacer ensures that a certain minimum distance remains free between a workpiece (18) introduced into the air guiding bell (10) and the inner surface of the air guiding bell (10), wherein the spacer (35) preferably comprises a number of strips (36) extending along the surface in the longitudinal direction or along a helical line.Device according to one of the preceding claims 3 to 8 and / or 10 to 16, characterized in that the air guiding bell (10) can be acted upon with a cooling liquid (20) for cooling the workpiece (18) during a cooling phase which is temporally upstream of the drying process.Device according to one of the preceding claims 3 to 8 and / or 10 to 16, characterized in that an air-liquid dispersion can be applied to the air-guiding bell (10), preferably in that at least one atomizer (15) or nebulizer (15) is attached to or in the region of the upstream end face of the air-guiding bell (10), which nebulizer, if required, loads an air stream entering the air-guiding bell with finely distributed cooling liquid (20).Device according to one of the preceding claims, characterized in that the air stream can be heated, preferably by 5 to 10°C, in order to improve the drying effect, wherein the heating is preferably effected by an additional heating device and / or ideally in that at least part of the waste heat of the pump is used.

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