GB2303921A - Sensor for controlling the adjustment of spray nozzles of spray-cleaning installations for workpieces - Google Patents

Description

2303921 Sensor for controlling the adjustment of the spray nozzles of

spray- cleaning installations for workpieces Above all, previously machined workpieces from which chips are removed often have to be subsequently cleaned in order to remove chips and/or other foreign substances such as, for example, residual cooling and cutting liquids, abrasive grains and the like from the workpieces. The cleaning of components of internal combustion engines, gears and the like is particularly critical. A typical example are cylinder heads which not only have a surface with many fissures but also a number of bores, also threaded bores.

In practice, so-called spray-cleaning installations have proved suitable for cleaning such workpieces. Herein, the workpieces to be cleaned are sprayed by spray nozzles and thereby cleaned. These spray nozzles are supplied with cleaning liquid under high pressure which is usually an aqueous cleaning liquid containing surfactants. In order for the cleaning to be carried out in a reliable way, the spray nozzles must not only generate a relatively sharply focused jet of liquid but, above all, the jet of liquid must reliably impinge on the places on the workpieces which are critical with respect to cleaning, as it is otherwise not possible to, for example, completely remove chips from a threaded bore.

In general, it is only identical workpieces that are cleaned one after the other in such spray-cleaning installations, i.e., workpieces of the same configuration, each of which has to be positioned exactly in relation to the spray nozzles for the cleaning, as reliable cleaning of the workpieces is otherwise not guaranteed in spite of precise adjustment of the spray nozzles.

It, therefore, follows that in series production there is the danger that even slight erroneous adjustments of the spray nozzles and/or a slight erroneous positioning of the workpiece to be cleaned relative to the spray nozzles may result in inadequate cleaning of the places on the workpiece which are critical with respect to cleaning, such as threaded. bords and the like, and this is then often ascertained too late.

The aim underlying the invention is, therefore, to provide simple and insensitive means with which a reliable check can be made as to whether the spray nozzles are correctly oriented in relation to a workpiece to be cleaned by spray-cleaning in order to thus avoid the disadvantages explained above.

The invention is based on the fact that in a spray-cleaning installation usually only workpieces of identical configuration, for example, only cylinder heads for a certain engine, are cleaned at least over a certain period of time, e.g., on one workday. An initial consideration in solving the set object is to use one of these workpieces as model workpiece and to provide it at each of its places which are particularly critical with respect to cleaning with a sensor for checking the correct adjustment of the spray nozzle directed at the respective places which are critical with respect to cleaning and to then subject this model workpiece to a cleaning operation, in particular, at the start of a workday or a shift so that, if necessary, the spray nozzles can be readjusted.

Diirr GmbH had already contemplated providing such a model workpiece at its critical places with respect to cleaning such as, for example, blind bores, threaded bores and the like, with sensors which respond to the action of pressure and generate an electric signal which is, for example, proportional to the pressure acting thereon and is then transmitted via a line or in a cordless manner to an evaluating station in order to ascertain whether the pressure values determined by the pressure sensors correspond to those measured with correctly adjusted spray nozzles. Such pressure sensors are available on the market and are designed so as to be insertable in, for example, a threaded bore in such a way that the pressuresensitive surface of the sensor is flush with the workpiece surface at the pertinent place which is critical with respect to cleaning. It has, however, been shown that, in practice, such measuring devices are much too prone to failure, and, in this connection, the rough operating conditions prevailing in a spray-cleaning installation have to be borne in mind, and, in addition, such measuring devices are, of course, extremely expensive.

Using a model workpiece for a spray-cleaning installation in which workpieces of identical configuration to.be cleaned are cleaned by at least one spray nozzle directed at a place on the respective workpiece which is critical with respect to cleaning, the spray nozzle being supplied with a cleaning liquid and generating a jet of liquid, the set object is accomplished in accordance with the invention by the model workpiece being provided at the place which is critical with respect to cleaning with a recess which is closed at least substantially by a pressure sensor, and by the sensor being a - 4 sensor which is permanently mechanically alterable by the jet of liquid of the correctly aligned spray nozzle.

As will be apparent from the following, such a mechanical sensor can be readily designed such that it is only permanently mechanically altered if the jet of liquid to be checked impinges at the correct place on the model workpiece, and, in particular, also with the minimum pressure sufficient for adequate cleaning. Therefore, checking not only as to whether the pertinent spray nozzle is correctly adjusted but also as to whether it generates a jet of liquid with sufficient pressure is possible with such a sensor.

In the simplest and least expensive form, such a sensor is a film or foil which is adapted to be adhesively bonded to the workpiece and perforated by the jet of liquid of the correctly aligned spray nozzle, for choice of a suitable film or foil material will always ensure that the piece of film or foil forming the sensor is perforated by a jet of liquid correctly impinging on the critical place with respect to cleaning and also having the necessary minimum pressure. Even with workpiece surfaces of relatively complicated design, it is still always possible to adhesively bond a relatively small piece of film or foil to each of the places on the model workpiece that are critical with respect to cleaning, and such a sensor is not only inexpensive but also easy to handle and usable under the adverse conditions of use in a spray-cleaning installation.

However, also proposed by the invention is a reusable sensor which is characterized by having a housing which is insertable in a recess provided at the pertinent place on the model workpiece which is critical with respect to cleaning and held stationarily therein, and by a sensor element which is adapted to be acted upon with pressure by the jet of liquid being movable in the housing, more specifically, by the jet of liquid of the correctly aligned spray nozzle against the action of a return force from a rest position to a stable indicating position. Insofar as the critical places with respect to cleaning are threaded bores, the sensor housing could, for example, have the shape of a threaded bushing with an external thread which is screwable into such a threaded bore. However, the housing could also be designed so as to be insertable with a press fit into a smooth bore of the model workpiece. Finally, it is possible to provide the model workpiece at each of its critical places with respect to cleaning with a recess which is adapted to the sensor housing and in which the sensor is then suitably inserted so that it does not become displaced or move in another way in relation to the actual workpiece during the test cleaning operation.

The sensor element of such a reusable sensor could, for example, have an end face inclined in relation to the incident jet of liquid and be held movably, whether it be slidably or pivotably, transversely to the direction of this jet of liquid in the sensor housing against the action of a return spring, so that it is moved into the stable indicating position by a jet of liquid impinging on the critical place with respect to cleaning with the correct orientation and the correct minimum pressure.

The indicating position could, for example, be made stable by the sensor element only being able to move an overcoming considerable friction. However, embodiments of the inventive - 6 reusable sensor in which a releasable detent device for the sensor element is associated with the indicating position are operationally more reliable and, therefore, preferable.

Further features of preferred embodiments of the inventive reusable sensor will be apparent from the appended claims.

As will be evident from the aforesaid, the subject matter of the present invention is not only a model workpiece with one or several inventive sensors but also such a sensor as such, with which one of the workpieces to be cleaned is fitted by the operator of a spray-cleaning installation.

Further features, advantages and details of the invention will be apparent from the following description and the appended drawings of an inventive model workpiece and a particularly advantageous embodiment of an inventive reusable sensor. The drawings show:

Figure 1 Figure 2 a longitudinal section of the sensor; and a schematic view of a gear housing as model workpiece which is provided at.several places which are critical with respect to cleaning with sensors designed in accordance with the invention, the model workpiece being shown cut open at these places, and the spray nozzles associated with these places which are critical with respect to cleaning also being illustrated in Figure 2.

- 7 The sensor illustrated in Figure 1 and denoted in its entirety by 10 has a housing 12 in the form of a hollow circular cylinder with a circular- cylindrical outer wall 14 and a likewise circular-cylindrical inner wall 16. The latter terminates at a housing bottom 18, whereas the sensor housing is open at the top. A sensor element 20 is displaceably guided in the guide formed by the circular-cylindrical inner housing wall 16. The sensor element 20 has the shape of a likewise circular-cylindrical piston, at the rear end face 22 of which a return spring 24 in the form of a helical Pressure spring is supported. The other end of the return spring 24 rests against the housing bottom 18. The construction could be designed such that the return spring 24 is relieved from pressure when the sensor element 20 with its front end face 26 is flush with the front end face 28 of the sensor housing 12. However, the alternative illustrated in Figure 1 is preferred. Herein, a piston rod 30 is attached to the piston-shaped sensor element 20. The piston rod 30 crosses a guide opening 32 in the housing bottom 18 and has at its end facing away from the sensor element 20 a head 34, the diameter of which is larger than the diameter of the guide opening 32. Consequently, the head 34 can form a stop which rests against the outer surface of the housing bottom 18 under the action of the return spring 24. A stop delimiting the path of the sensor element 20 upwardly according to Figure 1 is, therefore, a particularly advantageous feature of the inventive sensor.

In its upper end region, the piston-shaped sensor element 20 has a circumferential groove 36 of V-shaped cross section, i.e., with two inclined flanks 36a and 36b. This circumferential groove 36 constitutes a first element of a detent device with which a detent eement 40 cooperates. The - 8 latter is designed as a kind of slide or piston and is displaceably held in a radial bore 42 of the sensor housing 12. The detent element 40 is provided with a projection 44 which can engage the circumferential groove 36 of the sensor element 20 when the circumferential groove is located opposite the detent element. The radial bore 42 lies in the region of a circumferential groove 46 of the sensor housing 12 which receives a ring- shaped spring 48 in the form of a conventional rubber O-ring which attempts to urge the detent element 40 radially inwardly. The circumferential groove 46 is constructed to such a depth that the ring- shaped spring 48 allows the projection 44 to fall into the circumferential groove 36 of the sensor element 20 when this circumferential groove is located opposite the detent element.

When a jet of liquid represented by arrow S strikes the front end face 26 of the sensor element 20 with the minimum pressure required for adequate cleaning of the workpiece, this jet of liquid displaces the sensor element 20 downwardly according to Figure 1 against the action of the return spring 24 to such an extent that the detent element 40 can fall into the circumferential groove 36. The sensor element has then reached its stable indicating position within the meaning of the appended claims whereas Figure 1 shows the sensor element 20 in its rest position.

In order to make the sensor "sensitive" again, i.e., to bring the sensor element 20 into its rest position illustrated in Figure 1, the head 34 can be pressed upwards. This is adequate since the flank 36a of the circumferential groove 36 of the sensor element 20 forms a sliding surface for the projection 44 of the detent element 40. If, however, on account of the design of the model workpiece, the head 34 is not accessible, the sensor element 20 can also be pulled upwards with a suitable tool. To do so, it is merely necessary to provide a point of application for a tool, a finger or the like on the front end face 26 of the sensor element 20. In the illustrated embodiment, the sensor element 20 has an axial threaded bore 60 into which a screw can be screwed as "tool" to pull the detent element 20 upwards out of its detent or indicating position. In this embodiment, the jet of liquid S which actuates the sensor element strikes the bottom of the threaded bore 60, and so, in this embodiment, the pressure- sensitive surface of the sensor element is set back in relation to the front end face of the sensor.

It is obvious that the responsiveness of the sensor 10 is determined at least essentially by the spring constant of the return spring 24, which, of course, can be optionally selected by choice of a corresponding spring.

Figure 2 shows a gear housing 100 forming a model workpiece which is provided with sensors 10 at three places which are critical with respect to cleaning. The spray nozzles directed at these places which are critical with respect to cleaning and at the sensors 10 are denoted by 102, the jets of liquid generated by these spray nozzles by S. The adjustable holders for the spray nozzles 102 are not illustrated as these and, in the same way, the other components of a spray-cleaning installation, are elements belonging to the prior art.

In connection with Figure 2, it is to be noted that the sensor housings 12 (see Figure 1) of the sensors 10 can be inserted in bores 104 of the gear housing 100 which are originally 1 - 10 provided, or corresponding bores 104 for insertion of the sensors 10 therein have to be made at those places on the gear housing 100 serving as model workpiece which are critical with respect to cleaning and require checking.

Claims (17)

CLAIMS:

1. Model workpiece for a spray-cleaning installation in which workpieces of identical configuration are to be cleaned, the said workpieces being cleaned by means of at least one spray nozzle directed at a place on the respective workpiece which is critical with respect to cleaning, the said spray nozzle being supplied with a cleaning liquid and generating a jet of liquid, wherein the model workpiece is provided With a recess at the place which is critical with respect to cleaning, the said recess being closed at least substantially by a pressure sensor, and the sensor is a sensor which is adapted to be permanently mechanically altered by the jet of liquid of the correctly aligned spray nozzle.

2. Model workpiece as defined in claim 1, wherein the sensor is a film or foil which is adhesively bonded to the model workpiece and is adapted to be perforated by the jet of liquid of the correctly aligned spray nozzle.

3. Model workpiece as defined in claim 1, wherein the sensor has a housing which is insertable into the recess and is held stationarily therein, and a sensor element which is adapted to be acted upon with pressure by the jet of liquid is movable in the housing by the jet of liquid of the correctly aligned spray nozzle against the action of a return force from a rest position to a stable indicating position.

4. Model workpiece as defined in claim 3, wherein a releasable detent device for the sensor element is associated with the indicating position.

5. Model workpiece as defined in claim 3 or 4, wherein the sensor element is displaceably guided in the housing.

6. Model workpiece as defined in claim 5, wherein the sensor has a front end face adapted to be acted upon by the jet of liquid, and the sensor element is displaceable approximately perpendicularly to this end face.

7. Model workpiece as defined in claims 4 to 6, wherein the sensor element is a piston which is displaceably guided in the housing.

8. Model workpiece as defined in claim 7, wherein a pressure spring which urges the piston in the direction towards the front end face of the sensor is arranged between the piston side facing away from the front end face of the sensor and an abutment formed by the housing.

9. Model workpiece as defined in claim 4 and in one or several of claims 5 to 8, wherein the detent device has a detent element which is movable between an ineffective position and a detent position under the action of a spring transversely to the direction of displacement of the sensor element the detent element being held in its ineffective position by the sensor element between the rest position and the indicating position thereof, and the detent element being urged in the indicating position of the sensor element by the spring into its detent position in which it holds the sensor element in the indicating position thereof.

10. Model workpiece as defined in claim 9 and claim 7 or 8, wherein the piston has a circumferential groove for engagement of the detent element therein.

11. Model workpiece as defined in claim 10, wherein the housing has a ring-shaped circumferential groove which receives a ring-shaped spring and a radial bore which extends from the ring-shaped circumferential groove and opens into the piston guide for guiding the detent element which is acted upon by the ring-shaped spring.

12. Model workpiece as defined in claim 10 or 11, wherein the circumferential groove of the piston has at least on its side facing away from the front end face of the sensor a groove side wall which acts as an oblique surface for the detent element to run thereon.

13. Model workpiece as defined in one or several of claims 5 to 12, wherein the sensor element has on its side which is adapted to be acted upon by the jet of liquid a point of application for an actuating element serving to pull the sensor element forward into its rest position.

14. Model workpiece as defined in one or several of claims 3 to 13, wherein the housing is inserted into a bore of the model workpiece, the bore forming the recess and extending transversely to the surface of the workpiece at the place which is critical with respect to cleaning.

15. Sensor with the features of one or several of claims 3 to 13 for attachment to a model workpiece for a spray-cleaning installation.

16. Model workpiece for a spray-cleaning installation substantially as hereinbefore described with reference to the accompanying drawings.

17. Sensor for attachment to a model workpiece for a spraycleaning installation substantially as hereinbefore described with reference to the accompanying drawings.