HK1118030A - Cleaning device and method for cleaning workpieces - Google Patents

Description

Cleaning device and method for cleaning a workpiece

Technical Field

The invention relates to a cleaning device for cleaning workpieces, comprising at least one workpiece holder for the workpiece to be cleaned.

Background

Such cleaning devices are known from the prior art.

In particular, cleaning devices of this type are known in which the correct position of the workpiece on the workpiece holder is controlled by means of a shadow mask on the inlet of the cleaning device. In this regard, the transport device transports the workpiece in a transport direction across the silhouette plate. The silhouette plate has a blanking opening corresponding to the contour of the workpiece. In the event of an incorrect workpiece position, the silhouette plate deflects and operates a touch sensitive sensor.

Such a silhouette plate must be replaced when changing the type of workpiece to be cleaned. It is also difficult to transport workpieces of different outer contours alternately through the cleaning device, since each silhouette plate can only detect certain workpiece types having certain outer contours. In addition, the silhouette plate can only control the position of the workpiece on the inlet of the cleaning device. Having additional silhouette panels inside the washing apparatus may hinder access to the treatment stations and treatment apparatus of the washing apparatus.

Furthermore, cleaning devices are known in which the correct position of the workpiece to be cleaned on the workpiece holder is detected by means of a tuyere, from which compressed air is blown in such a way that it flows into the workpiece when the workpiece is correctly positioned on the workpiece holder. In the event of an incorrect workpiece position, the workpiece is at least partially displaced out of the flow path of the blast, whereby the wind stagnation pressure of the blast drops. By monitoring the wind stagnation pressure, it is therefore possible to detect that the workpiece is positioned incorrectly. However, this method for detecting an incorrect position of the workpiece can only be used in cases where the workpiece is at a small distance from the tuyere (e.g. at most 3 mm). This method cannot therefore be used in situations where the workpiece holder and the tuyere are moved relative to each other while the cleaning device is in operation. In addition, proper verification of the tuyere is difficult and time consuming.

Disclosure of Invention

The object of the invention is therefore to provide a cleaning device of the type mentioned at the outset in which a simple, flexible and reliable control of the workpiece position is possible.

This object is achieved according to the invention in a cleaning device having the features of the preamble of claim 1 in that the cleaning device comprises at least one distance sensor from which it can be determined whether the workpiece is in the correct position on the workpiece holder.

The distance sensor generates a signal which varies as a function of the distance between the workpiece and the distance sensor, so that it can be determined from the signal whether the distance lies within a predetermined target range.

The signal of the distance sensor preferably varies monotonically with increasing distance between the workpiece and the distance sensor.

The signal generated by the distance sensor is preferably an electrical signal, which is characterized by, for example, voltage, current strength, phase and/or frequency.

The distance sensor can be designed in this respect, for example, as a capacitive or inductive sensor.

The capacitive sensor detects a change in permittivity by the presence of the workpiece.

The inductive sensor detects changes in magnetic permeability through the presence of the workpiece.

In particular for controlling the workpiece position of metallic workpieces in environments which are filled with contamination and cleaning media, it has proven advantageous for the distance sensor to be designed as an inductive sensor.

In this respect, the distance sensor preferably does not touch the workpiece whose position is to be controlled, but rather the distance sensor determines the distance of the workpiece from the sensor surface in a contactless manner.

Particularly reliable workpiece position control is achieved if at least two distance sensors are assigned to at least one workpiece holder, from the signals generated by which it can be determined whether the workpiece is in the correct position on the workpiece holder. In this way, this deviation from the nominal position of the workpiece, which is a constant distance of the workpiece from the distance sensor, is also determined, wherein the change in distance relative to the second distance sensor is then detected.

In this respect, it is preferred that at least two distance sensors are arranged on mutually opposite faces of the same workpiece holder.

It has proven to be particularly advantageous if at least two distance sensors are arranged on the same workpiece holder radially, in particular diagonally, opposite one another.

In principle, the distance sensor can generate a digital or analog output signal.

It has proven particularly advantageous, however, for the at least one distance sensor to generate an analog output signal.

In a preferred embodiment of the invention, the cleaning device comprises at least one evaluation device for evaluating the signal generated by the at least one distance sensor.

The signals generated by the at least one distance sensor can in principle be analyzed electronically by means of a processor with suitable software (for example SPS) or by hardware circuits.

In a preferred embodiment of the cleaning device according to the invention, the evaluation device is designed as a hardware circuit. Such hardware circuits can be produced in particular at low cost and can be designed to be particularly resistant to environmental influences.

In a preferred embodiment of the cleaning device according to the invention, the evaluation device determines that the position of the workpiece is incorrect if the signal of at least one distance sensor indicates that the distance between the workpiece and the associated distance sensor is too great, i.e. that the distance exceeds a maximum permissible limit distance.

The limit values assigned to the respective output signals to the distance sensors can be predefined by hardware for the evaluation device, transmitted via a data line and stored in the evaluation device or learned by the evaluation device by the "Teach-in" method.

The evaluation device can preferably store at least one signal value of at least one distance sensor, which corresponds to the maximum permissible limit distance between the workpiece and the associated distance sensor.

Furthermore, the cleaning device preferably comprises a control device which at least partially switches off the cleaning device in the event that an analysis of the signal of the at least one distance sensor shows that the workpiece is not in the correct position on the workpiece holder. In this way, damage to the cleaning device and associated workpieces due to collisions of incorrectly positioned workpieces with the processing device or other components of the cleaning device can be avoided.

In a preferred embodiment of the cleaning device according to the invention, the at least one distance sensor has at least one protection class IP 67, preferably a protection class IP 68.

These protection classes are defined in the first part of the standard DIN VDE 0470, EN 60529 and IEC 592.

Distance sensors employing protection class IP 67 are dust proof and prevent the ingress of hazardous components with wires. An access probe with a diameter of 1.0mm must not be accessed. Furthermore, no dust should enter. The distance sensor using the protection class IP 67 also has a protective effect when submerged for a short time. It must therefore have the ability to prevent the water from entering in quantities that would cause a damaging effect when the casing is submerged under the pressure and time conditions determined according to the above criteria.

The distance sensor using the protection class IP 68 furthermore has a protective effect when submerged continuously. For this purpose, it is required that the water does not enter in quantities that cause damaging effects when the enclosure is kept under water under more severe conditions than those defined in the above-mentioned standard for protection class IP 67.

The aim of maintaining the proper functioning of the distance sensor even in the event of continued use in the area of the cleaning device to which the liquid cleaning medium is applied is achieved by the distance sensor being designed according to a protection class IP 67, preferably a protection class IP 68.

Furthermore, the at least one distance sensor advantageously comprises a sheath, preferably of plastic material.

In particular, the sensor electronics are in a plastic housing (e.g. Hostaform)^®) The inner part adopts artificial resin for injection molding.

By means of such a sheath, the distance between the sensor electronics and any dirt that may be present on the surface of the distance sensor (for example swarf, etc.) is increased, so that the distance sensor is prevented from reacting to the presence of such dirt.

Furthermore, the sensor electronics are protected by the outer skin against mechanical damage and contamination as well as against moisture and cleaning medium deposits used on the cleaning device.

In order to prevent dirt, such as swarf, which could lead to incorrect operation of the distance sensor, from collecting on the surface of the distance sensor, the cleaning device may comprise at least one spray device for spraying the at least one distance sensor with a cleaning liquid, in particular with water.

In order to ensure that only a correctly positioned workpiece can reach a predetermined nominal distance from the at least one distance sensor, it is advantageous if the at least one workpiece holder has at least one slide which prevents a workpiece which is not in the correct position of the workpiece holder from being at the same distance from the at least one distance sensor as a workpiece which is in the correct position of the workpiece holder.

Such mechanical skids may include, for example, columns, brackets, and precision alignment pins.

By means of such a slide, a workpiece which is incorrectly positioned can be kept at a distance from the at least one distance sensor.

The at least one workpiece holder on which the correct position of the workpiece is determined may be a stationary or a movable workpiece holder.

The at least one workpiece holder, on which the correct position of the workpiece is determined, is therefore arranged essentially stationary in a treatment station of the cleaning device.

Alternatively or additionally, the cleaning device may also comprise at least one transport device, by means of which the workpiece is transported through the cleaning device, and at least one workpiece holder, on which the correct position of the workpiece is determined, is arranged on the transport device.

The conveying device can be designed in particular as a slide-plate multi-station automatic feed device.

Another object of the present invention is to provide a method for cleaning a workpiece on a cleaning device comprising at least one workpiece holder for the workpiece to be cleaned, which method comprises a simple, flexible and reliable workpiece position control.

This object is achieved according to the invention in that a signal from which it is determined whether the workpiece is in the correct position on the workpiece holder is generated by means of at least one distance sensor.

The special embodiments of the method according to the invention are the subject matter of claims 21 and 22, the advantages of which have been explained in connection with the special configuration of the cleaning device according to the invention.

Drawings

Further features and advantages of the invention are the subject of the embodiments described in the following description and the figures. Wherein:

FIG. 1 shows a schematic side view of a slide-type multi-station automatic feed conveyor, viewed in a horizontal direction perpendicular to the conveying direction, with a movable workpiece holder and a processing station with a fixed workpiece holder;

FIG. 2 shows a schematic front view of the slide-type multi-station automatic feed device and the treatment station of FIG. 1, viewed parallel to the conveying direction;

FIG. 3 shows a top view of a moving workpiece holder and a fixed workpiece support of a processing station of the slide-plate multi-station automatic feeder;

FIG. 4 shows a schematic cross-sectional view of a workpiece holder and a distance sensor arranged on the workpiece holder and a spray device for cleaning the distance sensor;

FIG. 5 shows a schematic side view of a workpiece holder and a workpiece in the correct position of the workpiece holder;

FIG. 6 shows a schematic side view of a workpiece holder, i.e., a workpiece in an incorrect position of the workpiece holder; and

fig. 7 shows a schematic side view of a workpiece holder and a workpiece held in the correct extreme position of the workpiece holder by a spacer during the execution of the "Teach-in" method for adjusting the evaluation device as a function of the distance sensor output signal, which is still tolerable.

Identical or functionally equivalent parts are denoted by the same reference symbols in all the figures.

Detailed Description

The cleaning apparatus shown in fig. 1-7, generally designated 100, includes a plurality of processing stations 102, each of which performs a processing step of workpiece cleaning and one of which is shown in fig. 1-3.

Each processing station 102 includes a fixed workpiece holder 104 as shown in fig. 1-3 and a processing tool, such as a tuyere, nozzle, movable spray gun, or the like, for performing workpiece cleaning (not shown).

In order to be able to move the workpieces 106 to be cleaned (see fig. 5 to 7) in the conveying direction 108 (see fig. 1 to 3) from the fixed workpiece holders 104 of the first processing station 102 to the fixed workpiece holders 104 of the second processing station 102 following the first processing station in the conveying direction 108, the cleaning device 100 comprises a conveying device 110 in the form of a slide-type multi-station automatic feed device 112, which comprises two webs 114 extending in the conveying direction 108 and carrying a number of movable workpiece holders 114 corresponding to the number of fixed workpiece holders 104 of the first processing station 102, one of which is shown in fig. 1 to 3.

Each movable work holder 114 includes a substantially rectangular base 116 having upper faces 118 with four corners having posts 120 projecting upwardly from the upper faces 118.

Generally inboard of the upright 120, the base plate 116 further has four generally cylindrical legs 122 projecting upwardly from the upper face 118 of the base plate 116.

At least one of the brackets 122, and preferably a plurality of the brackets 122, has a respective precision alignment pin 124 that is upwardly spaced from the upper surface of the respective bracket 122.

As best seen in fig. 3-5, two distance sensors 126 are provided on the movable workpiece holder 114 adjacent to each of the supports 122 having precision alignment pins 124.

As best seen in the enlarged view of fig. 4, each distance sensor 126 passes through a through hole 128 in the workholder base plate 116.

The distance sensor 126 comprises a substantially cylindrical outer skin 130 of plastic material, for example synthetic resin, which has an inclined surface 132 on its upper end face adjacent to the workpiece 106, which surface may in particular have a sinusoidal shape.

The outer skin 130 has a radially offset stop 133 or a radially offset retaining ring on its outer lateral surface, which fixes the distance sensor 126 in a predetermined vertical position relative to the base plate 116 of the workpiece holder 114.

The sensor electronics 134 of the distance sensor 126 are molded into the skin 130 and are therefore protected from contamination and other environmental influences.

A signal cable 136 leads from the sensor electronics 134, through the sheath 130 and out to an evaluation device (not shown) which receives the analog output signal from the sensor electronics 134 of the distance sensor 126.

Furthermore, in the area of the rest position of the movable workpiece holder 114 shown in fig. 1 to 3, a spray device 138 with spray nozzles 140 is arranged in such a way that the spray nozzles 140 are directed at the inclined surface 132 of the distance sensor 126, so that the upper part of the distance sensor 126, including the inclined surface 132, can be cleaned by spraying or spraying a liquid cleaning medium, for example water, with the aid of the spray nozzles 140.

By means of the spray device 138, in particular oil and/or collected chips or other contaminants from the workpiece 106 to be cleaned or from a cleaning medium used on the cleaning device 100 can be removed from the distance sensor 126, in order to prevent in particular metallic contaminants from adversely affecting the function of the distance sensor 126.

The fixed workpiece holder 104 of the processing station 102 is similar in construction to the movable workpiece holder 114 provided on the slide-type multi-station automatic feeder 112, but is not integral but rather is constructed in two parts.

Each fixed workpiece holder 104 comprises two partial workpiece holders 142a and 142b, which are spaced apart from one another in a horizontal direction oriented perpendicular to the conveying direction 108, wherein the distance between the two partial workpiece holders 142a, 142b exceeds the extension of the movable workpiece holder 114 in the horizontal direction perpendicular to the conveying direction 108, so that the movable workpiece holder 114 can be moved through between the two fixed partial workpiece holders 142a, 142b in order to remove the workpiece from the fixed workpiece holder 104 by means of the movable workpiece holder 114.

Each of the fixed part workpiece holders 142a, 142b includes a substantially rectangular base plate 144 having posts 148 projecting upwardly from an upper face 146 at two corners thereof.

The inner sides of the uprights 148 have upstanding legs 150 depending upwardly from the upper face 146 of the base plate 144, with a respective one of the legs having a precision locating pin 152 thereon.

Adjacent to the carriage 150 with the precision alignment pins 152, a distance sensor 154 is arranged on the base plate 144 of the respective part of the workpiece holder 142a or 142 b.

In this regard, the distance sensors 154 of the fixed workpiece holder 104 are constructed in the same manner as the distance sensors 126 of the movable workpiece holder 114 which are arranged on the base plate 116 of the movable workpiece holder 114 and are arranged on the respective base plate 144.

Furthermore, one or more spray devices 138 are assigned to the distance sensors 154 of the fixed workpiece holder 104 for cleaning the parts of the respective distance sensors 154 projecting from the base plate 144.

The distance sensor 154 is also connected to the analysis device of the cleaning device 100 via a signal cable.

Fig. 5 schematically shows the workpiece 106 with the holes 156 in the correct position of the movable workpiece holder 114, wherein the workpiece 106 rests with its bottom surface 158 on the top of the support 122 of the workpiece holder 114 and the precision alignment pins 124 of the workpiece holder 114 engage in the respectively associated hole 156 of the workpiece 106.

In this case, the distance sensor 126, which is designed as an inductive sensor, generates an analog output signal which is dependent on the distance between the workpiece 106, which is made of an electrically conductive material, on the one hand, and the sensor electronics 134 of the distance sensor 126, on the other hand.

The output signal is preferably an electrical signal characterized by its voltage, amperage, phase and/or frequency.

The analog output signal of the distance sensors 126 (for example, current intensities of 4mA to 20mA) is evaluated electronically on an evaluation device, which is embodied in particular as a hardware circuit, and compared with a limit value assigned to the respective distance sensor 126, which corresponds to a tolerable distance between the workpiece 106 and the respective distance sensor 126.

In the case of a correctly positioned workpiece 106 on the workpiece holder 104, the analog output signal generated at the distance sensor 126 is above the respective limit value, which indicates that the distance between the workpiece 106 and the distance sensor 126 is below a tolerable limit distance. The evaluation device therefore emits an evaluation signal, which indicates that the workpiece 106 is in the correct position on the workpiece holder 114 and no further control measures are to be taken.

Depending on the type of distance sensor 126 used, the analog output signal increases with increasing distance of the workpiece 106 from the distance sensor 126, so that in this case it is indicated that the correct position of the workpiece 106 on the workpiece holder 114 is below the respective limit value.

If the workpiece 106 on the workpiece holder 114 is in the incorrect position shown in fig. 6, in contrast, in which the workpiece 106 is tilted relative to the correct position, for example, because one of the precision alignment pins 124 of the workpiece holder 114 cannot be inserted into the associated opening 156 in the bottom 158 of the workpiece 106, for example, because one of the tolerance tolerances on the workpiece holder 114 and/or on the workpiece 106 is exceeded or because the workpiece holder 114 and/or the workpiece 106 is damaged, the distance between the workpiece 106 and the distance sensor 126 in such an incorrect position of the workpiece 106 on the workpiece holder 114 exceeds a limit distance which is tolerable in connection with the at least one distance sensor 126, so that the associated distance sensor 126 emits an analog output signal which indicates a lower limit value than the limit value assigned to the associated distance sensor 126.

In this case, the evaluation device generates an evaluation result which is below the permissible limit value of the analog output signal associated with the at least one distance sensor 126 of the workpiece holder 114, so that the evaluation device generates an evaluation signal which indicates that the workpiece 106 is in an incorrect position on the workpiece holder 114.

The evaluation signal is transmitted to a control device (not shown) of the cleaning device 100 and causes the control device to disconnect the cleaning device 100 at least partially, i.e. at least in the region of the associated workpiece holder 114 in which the workpiece 106 is incorrectly positioned, in order to prevent the processing device of the processing station 102 or other components of the cleaning device 100 from colliding with the incorrectly positioned workpiece 106.

The limit values assigned to the analog output signals to the distance sensors 126 can be predefined on the evaluation device by hardware, transmitted via a data line and stored on the evaluation device, or input by the "Teach-in" method described below with reference to fig. 7.

In this "Teach-in" method, the workpiece 106 is thus deliberately moved into the limit position on the workpiece holder 114 that is still acceptable, i.e. a spacer 160 is placed on the support 122 of the workpiece holder 114 with the precision positioning pins 124 before the workpiece 106 is placed.

After the subsequent placement of the workpiece 106, the workpiece 106 is adjusted with respect to its correct position on the workpiece holder 114 in accordance with the spacer 160 arranged between the workpiece 106 and the workpiece holder 114 in such a way that the distance between the workpiece 106 and the distance sensor 126, which is adjacent to the carrier 122 with the spacer 160 placed, corresponds to a still tolerable limit distance of, for example, 3 mm.

The value of the analog output signal generated by the relevant distance sensor 126 in this case is stored in a memory of an evaluation device, which is operated, for example, according to a "Teach-in" switch, as the limit value assigned to the relevant distance sensor as the analog output signal.

In this manner, the limit value assigned to the analog output signal is stored on the analysis device for each distance sensor 126 by placing the spacers 160 on all of the supports 122 adjacent to one of the accumulated pieces 126 of the workpiece holder 114 in turn.

If the cleaning device 100 is operated below one of the limit values due to an incorrect position of the workpiece 106 on the workpiece holder 114, the evaluation device generates an evaluation signal which indicates an incorrect position of the workpiece 106 on the workpiece holder 114 and at least partially disconnects the cleaning device 100.

The support 122, the precision positioning pin 124 and the upright 120 of the workpiece holder 114 in this respect act as a mechanical slide 162, which limits the placement possibilities of the workpiece 106 on the workpiece holder 114 in such a way that only workpieces 106 correctly positioned on the workpiece holder 114 with respect to all distance sensors 126 of the workpiece holder 114 can reach such distances that they do not exceed the respective permissible limit distances. An incorrectly positioned workpiece 106 is instead held by the mechanical slide 162 at a distance from the distance sensor 126 that exceeds the permissible limit distance associated with at least one distance sensor 126.

When the workpieces 106 are moved correctly by the cleaning device 100, they are each transferred from a movable workpiece holder 114 of the slide-type multi-station automatic feed device 112 to a fixed workpiece holder 104 of the processing station 102 and, after the end of the processing operation at this processing station 102, to the respectively next movable workpiece holder 114 in the conveying direction 108.

This change over by the vertical upward movement of the slide-type multi-station automatic feed device 112 with the movable empty workpiece holder 114 continues until the movable workpiece holder 114 has removed the workpiece 106 from the fixed workpiece holder 104 of the processing station 102, whereupon the slide-type multi-station automatic feed device 112 continues to move in the transport direction 108 at a distance of two successively fixed workpiece holders 104 and again descends vertically, wherein the workpiece 106 is placed on the next fixed workpiece holder 104. Subsequently, the slide-type multi-position automatic feed device 112 emptying the workpieces 106 is returned to its starting position opposite to the conveying direction 108, and a further conveying cycle of the slide-type multi-position automatic feed device 112 can then begin.

The distance sensor 154 of the stationary workpiece holder 104 can likewise be designed as an inductive sensor and operate in the same manner, as described above with reference to the distance sensor 126 of the movable workpiece holder 114.

The analog output signal limit values of the distance sensors 154 respectively associated with the fixed workpiece holders 104 can be input or stored in the same manner as those of the distance sensors 126 of the movable workpiece holders 114.

Furthermore, the support 150, the precision alignment pins 152 and the columns 148 of the workpiece holder 104 can also be used as a mechanical slide 162 on the fixed workpiece holder 104, ensuring that the incorrectly positioned workpiece 106 exceeds the permissible limit distance from the at least one distance sensor 154 of the fixed workpiece holder 104.

Claims (22)

1. Cleaning device for cleaning a workpiece (106), comprising at least one workpiece holder (104, 114) for the workpiece (106) to be cleaned, characterized in that the cleaning device (100) comprises at least one distance sensor (126, 154) which generates a signal from which it can be determined whether the workpiece (106) is in the correct position on the workpiece holder (104, 114).

2. The cleaning device according to claim 1, wherein the distance sensor (126, 154) is designed as an inductive sensor.

3. A cleaning device according to claim 1 or 2, wherein the distance sensor (126) does not contact the workpiece (106).

4. A cleaning device according to one of claims 1 to 3, wherein at least one workpiece holder (104, 114) is assigned at least two distance sensors (126, 154), from which signals it can be determined whether the workpiece (106) is in the correct position on the workpiece holder (104, 114).

5. The cleaning device according to claim 4, wherein the same workpiece holder (104, 114) is arranged on the sides of the distance sensors (126, 154) which face one another.

6. The cleaning device according to claim 5, wherein at least two distance sensors (126, 154) are arranged on the same workpiece holder (104, 114) diametrically opposite one another.

7. Cleaning device according to one of claims 1 to 6, in which at least one distance sensor (126, 154) generates an analog output signal.

8. Cleaning device according to one of claims 1 to 7, in which the cleaning device (100) comprises at least one evaluation device for evaluating the signal generated by the at least one distance sensor (126, 154).

9. The cleaning apparatus defined in claim 8, wherein the analysis device is configured as a hardware circuit.

10. The cleaning device according to claim 8 or 9, wherein the evaluation device determines that the position of the workpiece (106) is incorrect if the signal of at least one distance sensor (126, 154) indicates that the distance between the workpiece (106) and the associated distance sensor (126, 154) is too great.

11. Cleaning device according to one of claims 8 to 10, wherein the evaluation device can store the signal value of at least one distance sensor (126, 154) which corresponds to the maximum permissible limit distance between the workpiece (106) and the associated distance sensor (126, 154).

12. Cleaning apparatus according to one of claims 1 to 11, wherein the cleaning apparatus (100) comprises a control device which at least partially switches off the cleaning apparatus (100) in the event that an analysis of the signal of the at least one distance sensor (126, 154) reveals that the workpiece (106) is not in the correct position on the workpiece holder (104, 114).

13. Cleaning device according to one of claims 1 to 12, wherein at least one distance sensor (126, 154) has at least a protection class IP 67, preferably a protection class IP 68.

14. Cleaning device according to one of claims 1 to 13, in which the at least one distance sensor (126, 154) comprises a skin (130), preferably of a plastic material.

15. The cleaning device of claim 14, wherein the outer skin (130) of the distance sensor (126, 154) has a sloped surface (132).

16. Cleaning device according to one of claims 1 to 15, wherein the cleaning device (100) comprises at least one spray device (138) for spraying the at least one distance sensor (126, 154) with a cleaning liquid, in particular with water.

17. The cleaning apparatus as claimed in one of claims 1 to 16, wherein at least one of the workpiece holders (104, 114) has at least one slide (162) which prevents a workpiece (106) which is not in the correct position of the workpiece holder (104, 114) from occupying the same distance as the workpiece (106) which is in the correct position of the workpiece holder (104, 114) from the at least one distance sensor (126, 154).

18. Cleaning apparatus according to one of claims 1 to 17, wherein the at least one workpiece holder (104, 114) on which the correct position of the workpiece (106) is determined is arranged essentially stationary in a processing station (102) of the cleaning apparatus (100).

19. Cleaning device according to one of claims 1 to 18, in which the cleaning device (100) comprises at least one transport device (110) by means of which the workpiece (106) is transported through the cleaning device (100), and at least one workpiece holder (114) is provided on the transport device (110), on which the correct position of the workpiece (106) is determined.

20. Method for cleaning a workpiece (106) in a cleaning device (100) comprising at least one workpiece holder (104, 114) for the workpiece (106) to be cleaned, characterized in that a signal is generated by means of at least one distance sensor (126, 154), from which signal it is determined whether the workpiece (106) is in the correct position in relation to the workpiece holder (104, 114).

21. The method according to claim 20, wherein the signal generated by the at least one distance sensor (126, 154) is analyzed by means of an analysis device.

22. The method according to claim 21, wherein at least one value of the signal of at least one distance sensor (126, 154) is stored on the evaluation device, which value corresponds to a maximum permissible limit distance between the workpiece (106) and the associated distance sensor (126, 154).