DE29609767U1 - Measuring device for recording the insertion depth in a pipe connection - Google Patents

Description

Description; Novopress GmbH Presses and Press Tools & Co. KG, Scharnhorststrasse 1, 41460 Neuss Mannesmann AG, Mannesmannufer 2, 40213 Düsseldorf

Measuring device for measuring the insertion depth in a pipe connection

The invention relates to a measuring device for detecting the insertion depth in a pipe connection, consisting of a pipe and a press fitting, with a device carrier with at least one ultrasound transmitter and ultrasonic receiver arranged on the device carrier and with a measuring circuit for evaluating ultrasonic signals in such a way that a signal dependent on the insertion depth is generated.

To connect pipe ends, it is known to use sleeve-shaped press fittings that are plastically deformable and made of metal, preferably steel. Such pipe connections and the associated press fittings are known, for example, from DE-C-II 87 870 and DE-C-40 12 504. To create the connection, the end area of a pipe is pushed axially into the press fitting and then connected to one another in a force-locking and form-locking manner by means of a pressing tool placed on the press fitting using pressing jaws that can be moved relative to one another.

The reliability of the connection between the pipe and the press fitting depends, among other things, on the pipe being pushed into the press fitting by a certain minimum insertion depth. The insertion depth is limited by a constriction in the press fitting. The axial distance of the constriction to the end into which the pipe is to be pushed is greater the larger

the diameter of the pipe end or the press fitting. The constriction forms a stop against further axial insertion of the pipe.

Since the insertion depth cannot be seen from the outside, a measuring device has been developed to measure the insertion depth. It has a device carrier that can be placed on the outside of the pipe connection, which can also be designed as a pressing device and to which a thickness sensor is attached to record the material thickness of the pipe connection (PCT/WO 95/06232). Ultrasonic, magnetic field and/or eddy current sensors are proposed as thickness sensors. With the help of an evaluation device, the recorded material thickness is displayed at least qualitatively optically or acoustically.

This measuring method has proven to be unreliable. The reason for this is the air gap between the pipe and the press fitting, which varies in size. The sealing rings embedded in the press fitting in the area of the pipe connection also interfere with the received signals. As far as magnetic methods are suggested, they can only be used with magnetizable material and therefore not with stainless steel pipe connections.

Eddy current measuring methods are also known which measure the influence of the eddy current formation through the pipe behind the press fitting. These methods have the disadvantage that the reception signal is different for different pipe or fitting diameters because the wall thickness of the press fitting and pipe also changes with the diameter. In addition, the eddy current is weakened by the wall of the press fitting to such an extent that an accurate measurement of the insertion depth is not guaranteed.

The invention is based on the object of designing a measuring device of the type mentioned at the outset in such a way that the insertion depth can be detected with high reliability.

This object is achieved according to the invention in that the ultrasonic transmitter and the ultrasonic receiver are designed for oblique sounding or oblique reception and the device carrier is designed in such a way that the ultrasonic transmitter and the ultrasonic receiver can be attached to the pipe at a predetermined distance from the press fitting, with the measuring circuit being set up for the evaluation of ultrasonic echoes at the end of the pipe. The ultrasonic transmitter generates transverse waves that are reflected at the end of the pipe and can then be detected by the ultrasonic receiver. The ultrasonic transmitter and the ultrasonic receiver can be designed as a single ultrasonic transducer that is controlled by the measuring circuit so that it works both as a transmitter and as a receiver.

The ultrasonic signal can be made up of a number of individual signals. It can then be displayed qualitatively or quantitatively, for example, or it can be used to control connected devices, e.g. a pressing device. The previously mentioned distance can essentially be arbitrary, but should be significantly smaller than the other end of the pipe. Br can also approach zero.

The basic idea of the invention is therefore to generate transverse ultrasonic waves in the pipe using oblique sounding, which are then reflected from the end of the pipe and detected by the ultrasonic receiver. Care should be taken to ensure that the sounding takes place at the first angle of total reflection according to Schellius' law in order to avoid overlapping of the returned signals and thus to enable meaningful evaluation. Since the ultrasound is preferably sounded directly into the pipe without an auxiliary coupling medium and in front of the pipe connection, measurement value distortions due to air gaps are eliminated. A high level of reliability and measurement accuracy can therefore be achieved with the measuring device.

The reception signals used for the evaluation can be generated in various ways. The interference method known in the state of the art, in which frequencies are superimposed, is a possible option. The resonance method, which is also known, in which frequencies are changed until resonance occurs, is also suitable, as are methods in which a frequency analysis is carried out. In addition, it is possible to use the transit time of the ultrasound signal to the ultrasound receiver as a value corresponding to the insertion depth of the pipe.

To ensure that the distance between the ultrasonic transmitter or receiver and the press fitting is always the same, the device carrier can be designed so that it can rest axially immovably on the press fitting, for example on the round bead characteristic of such fittings or on the front end of the press fitting.

According to the invention, it is further provided that the measuring device can be attached to the pipe at a certain predetermined distance from the pipe end and that the measuring circuit is set up to calculate a value corresponding to the speed of sound in the pipe from the behavior, in particular the transit time of an ultrasonic signal, whereby this value is then used to determine the insertion depth. Due to the known distance to the pipe end, this additional step can be used to determine the speed of sound in the pipe material, which is then used for the subsequent actual measurement. Such a measuring device can also be used with unknown pipe materials.

Alternatively, the measuring device can have a displacement device for axially displacing the ultrasonic transducer by a predetermined distance. This design allows ultrasonic signals to be transmitted into the pipe at two points located at a predetermined axial distance from one another and

received again. Based on the difference between the resulting received signals, the speed of sound in the pipe can be determined, i.e. the difference represents a measure of this speed of sound.

In deviation from this, the measuring device can be designed in such a way that a first ultrasonic transducer as an ultrasonic transmitter and a second ultrasonic transducer as an ultrasonic receiver are arranged at a longitudinal distance from one another and the measuring circuit is also set up to record the transit time of an ultrasonic signal from the ultrasonic transmitter directly to the ultrasonic receiver, whereby this transit time is then adopted as a value corresponding to the speed of sound for determining the insertion depth. However, this requires the presence of two spaced ultrasonic transducers.

The transfer of the quantity corresponding to the speed of sound can be done in a simple way by displaying this quantity and entering it into the measuring circuit via an input device. It is, however, more advisable to design the measuring circuit in such a way that it adopts the quantity corresponding to the speed of sound of the pipe automatically or by manual confirmation for the determination of the insertion depth.

If the measuring device is to be used exclusively for pipes made of tool steel or stainless steel, it is sufficient that the measuring device has a magnetic sensor for detecting the magnetizability of the pipe, whereby the signal generated in each case is used for the measuring circuit as a characteristic value for the speed of sound. This can also be done manually with the help of a display and input device or by automatic transfer. The magnetic sensor responds to the fact that stainless steel, in contrast to tool steel, is practically not magnetizable.

If the measuring circuit for determining the running time of the Ul-

trasonic signal, it can be set up to record and process the shortest ultrasonic signal, since this transit time is directly proportional to the distance between the end of the pipe and the ultrasonic transmitter or receiver and therefore to the insertion depth. However, a measuring circuit is preferable for recording and processing the maximum individual signal of the reflected ultrasonic signal.

In addition, it may be advisable for the measuring circuit to be set up to record the reflection curve by processing several consecutive received signals and to compare the reflection curve with predefined values that are characteristic of at least one pipe diameter. This type of measuring circuit should be connected to a signaling device for signaling that is characteristic of the respective pipe diameter. This signaling can be used to determine whether the measured pipe diameter matches the theoretical values stored in a matrix, for example, or not. If the latter is the case, the signaling device can be used to decide whether the available press tool is suitable in terms of size for the connection between the pipe and the press fitting or not. It is also possible for several groups of predefined values to be present, each of which is characteristic of a specific pipe diameter. This even makes it possible to display the respective pipe diameter not only qualitatively but also quantitatively, whereby the operator can then decide which pressing device is suitable based on the display.

In a particularly preferred embodiment, the device carrier is designed as a pressing tool for radially pressing the pipe connection. As a result of the intended attachment of the pressing device to the pipe connection by enclosing the bead-shaped end of the press fitting, it is automatically ensured that the ultrasonic transmitter is always in

a predetermined distance from the press fitting and is placed on the pipe for the purpose of sounding. This combination of measuring device and pressing tool can be used particularly safely if the measuring circuit mentioned above is present, which is set up to record the reflection curve. A corresponding display informs the operator whether the associated pressing device fits the diameter of the pipe or not.

In a particularly preferred embodiment, the drive usually provided on the pressing tool is connected to the measuring circuit in such a way that the drive is blocked if the received signals that arise when the reflection curve is recorded do not match the specified values. The security against incorrect operation achieved in this way can be further increased by blocking the drive even if the measured insertion depth is smaller than a specified value for an insertion depth. This prevents a pressing process if the insertion depth is too small.

Alternatively, the measuring device can be provided with at least a qualitative display for the insertion depth. This display can, for example, be designed so that an optical display only goes out when a previously stored value for the insertion depth is reached or exceeded. Since the minimum depth for the insertion depth depends on the pipe diameter, the measuring circuit can also be set up so that when a certain pipe diameter is entered, the respective insertion depth to be specified is calculated or assigned. This design of the measuring circuit can also be combined with the previously mentioned detection of the pipe diameter using ultrasonic measurement in such a way that after determining the pipe diameter, an associated value for the insertion depth is assigned or calculated, which is then used for the display.

Irrespective of this, it is of course possible to display the measured insertion depth quantitatively after appropriate processing of the measurement signals, so that the operator has the opportunity to compare the displayed value with values obtained from tables. The aforementioned automatic adjustments, including blocking the drive if the insertion depth is insufficient, prevent reading errors that can occur when comparing with a table.

Finally, the invention provides that the ultrasonic transmitter and the ultrasonic receiver are guided in a spring-loaded manner in the radial direction. This ensures that the ultrasonic transducer or transducers come into contact with the pipe regardless of the respective pipe diameter.

The invention is illustrated in more detail using exemplary embodiments in the drawing. Bs show:

Figure 1 a pressing tool with ultrasonic measuring device in the

Front view with section through a pipe connection;

Figure 2 shows the side view of the pressing tool with the

Pipe connection according to Figure 1;

Figure 3 shows an axial section through the pipe connection and

a part of the pressing tool according to Figures 1 and 2 in a position rotated by 90°;

Figure 4 a Scheniatic representation of another

measuring device on the pipe;

Figure 5 is a graphic explaining the ultrasonic propagation in the pipe;

Figure 6 is a graphic showing the ultrasound

echoes depending on the radius of the pipe and

Figure 7 is a graph showing the ultrasonic echoes as a function of the angle of incidence.

Figures 1 to 3 show a pressing tool 1. Bs has two base plates 2, 3 arranged at a distance from one another, which continue upwards into heart-shaped end plates 4, 5 connected to the base plates 2, 3. Press levers 7, 8 extend in the free space between the base plates 2, 3 and the band plates 5, 6, which are mounted approximately centrally in the band plates 5, 6 via hinge pins 9, 19.

The upper lever arms 11, 12 of the pressing levers 7, 8 have indentations 13, 14 opposite one another. On the inside, the indentations 13, 14 have matching pressing grooves 15, 16. On the outside, the indentations 13, 14 are limited by irregularly protruding ring webs 17, 18, 19, 20.

The pressing levers 7, 8 have lower lever arms 21, 22, the distance between which decreases conically in the direction of the hinge pins 9, 10. Between the base plates 2, 3, two spreading rollers 23, 24 are mounted next to each other on a carriage not shown here. The carriage can be moved in the direction of arrow P by a mountable drive device. The spreading rollers 23, 24 move against spreading surfaces 25, 26 on the lower lever arms 21, 22 and push them apart. This in turn means that the upper lever arms 11, 12 are moved towards each other, i.e. in the pressing direction.

A holder 27 of a measuring device is attached to the base plate 2 on the left in Figure 2, which has a hole 28 that is open at the top. An ultrasonic transducer 29 is inserted telescopically into this hole 28. Br is supported on a helical spring 30 that strives to push the ultrasonic transducer 29 in an outward direction, i.e. upwards. The

Ultrasonic transducer 29 is - although not shown in detail in the drawing - designed in such a way that it can emit ultrasound at an angle in the direction of the pressing tool 1 and also receive reflected ultrasonic signals. An electrical line 31 extends from the underside of ultrasonic transducer 29, which goes via a line channel 32 extending from the bottom of bore 28 to an evaluation device of the measuring device (not shown in detail here) with a measuring circuit for processing the received signals from ultrasonic transducer 29.

As can be seen in particular from Figures 2 and 3, the recesses 13, 14 comprise a pipe connection 33. It consists of a pipe 34 and a press fitting 35, both of a conventional design. The press fitting 35 has annular beads 36, 37 extending around the circumference at the end, into each of which a sealing ring 38, 39 made of elastomer material is inserted on the inside. In the middle, the press fitting 35 has a constriction 40, which forms a stop for the pipe end 41 of the pipe 34. The pipe 34 is pushed into the press fitting 35 up to the constriction 40.

Figure 4 shows a schematic variant of the embodiment according to Figures 1 to 3. Instead of just one ultrasonic transducer 29, two ultrasonic transducers are provided here, arranged one behind the other in the axial direction of the pipe 34, namely an ultrasonic transmitter 42 at a distance L from the pipe end 41 and an ultrasonic receiver 43 arranged at a distance a closer to the pipe end 41, the distance to the pipe end 41 being indicated by b. Both ultrasonic transducers are guided in a holder not shown in detail here, which is firmly attached to the pressing tool 1, also not shown here, in a similar manner to the embodiment according to Figures 1 to 3. In this way, it is ensured that the ultrasonic transmitter 42 and the ultrasonic receiver 43 are always at the same distance from the press fitting 35 when the pressing device is correctly attached to the press fitting 35.

With the help of the ultrasonic transmitter 42, ultrasonic waves can be emitted obliquely towards the pipe end 41, which spread out in the pipe 34 as transverse waves towards the pipe end 41 and are reflected there. The ultrasonic echoes can then be received by the ultrasonic receiver 43 and converted into electrical reception signals. In addition, the sound wave coming directly from the ultrasonic transmitter 42 to the ultrasonic receiver 43 can be detected. The travel time of this sound wave serves in the measuring circuit as the basis for the speed of sound of the pipe material.

In Figure 5, the pipe 34 with the pipe end 41 is shown again, but without the press fitting 35. "A" symbolizes the point at which the ultrasonic transducer 29 shown in Figures 1 to 3 is placed on the pipe 34, namely at a distance L from the pipe end 41. The transmission takes place without an auxiliary coupling medium such as water or jelly. With the help of the ultrasonic transducer 29, oblique ultrasonic pulses of very short duration are transmitted. This creates transverse sound waves across the pipe cross-section, which spread in all directions. The distance L is chosen so that any sound reflections from the left can be blocked out by choosing the distance L to be significantly smaller than the total length of the pipe 34.

The ultrasonic pulse or ultrasonic wave that is emitted travels to the pipe end 41 and is reflected there. The travel time depends on the point of the pipe cross-section between S0 and Sl at which the respective portion of the ultrasonic pulse is reflected, i.e. the larger the angle α , the longer the portion of the ultrasonic pulse needs to return to the starting point A and thus to the ultrasonic transducer 29 after being reflected at the pipe end 41. The portion that runs parallel to the surface of the pipe 34 between A and S0 has the shortest travel time. Its travel time corresponds to the distance L and is

thus a measurement for the insertion depth of the pipe 34 into the press fitting 35 when the pressing tool 1 is placed on the pipe connection 33 in the position shown in Figures 1 to 3 , the pressing grooves 15, 16 thus enclose the annular bead 36.

The parts of the ultrasonic pulse running at an angle to the pipe surface cover partially elliptical distances, as shown in the example of the angle α and thus the distance AQ by projecting the cutting surface downwards through the pipe 34. The ultrasonic pulse starts from A and is divided into a part AG and a part AH. The reflection occurs at G and H. The longest path is from A to Sl. If the angle α is larger than the distance A-Sl, i.e. at an angle A-Sl to AK, the parts of the ultrasonic pulse cancel each other out because they meet along the distance K-Sl and have the same amplitude and phase.

After reflection at the end of the pipe 41, reflections of the ultrasonic pulse arrive at point A one after the other. If they come from the inside of the pipe wall itself, the time is very short in the case of the thin-walled pipes usually used, so that they can be masked out. Conversely, the echoes coming from the other end of the pipe (not shown here) arrive so late in relation to the echoes from the end of the pipe 41 that they can also be masked out.

Figure 6 shows a family of partial ellipses which pass through the components of the sound pulses at a sensor distance L to the pipe end 41 of 32 mm and at a pipe diameter of 27 mm.

In Figure 7, half the distance S covered is plotted against the angle of the respective portion of the sound pulse. At an angle of zero, half the distance S covered is identical to L and thus to the distance of the ultrasonic transducer 29 from the pipe end 41. The larger the angle α (Figure 5), the longer the distances and thus the travel times. The

The ends of the vertical lines, when connected to one another, form a curve that is characteristic of the respective pipe diameter and represents the reflection pattern. The angle at which cancellation occurs is 57° in the present example. It is smaller the greater the distance between the ultrasonic transducer 29 and the pipe end 41.

The characteristic curve shape, which results from the connection of the ends of the vertical lines, is steeper the larger the diameter of the pipe 34. After measuring the distance L - here 32 mm - the diameter of the pipe 34 can be determined based on the curve shape. This can be used to provide an indication of the pipe diameter via the evaluation device so that the operator of the pressing device 1 can decide whether the diameter fits the pressing device 1 or not. To be on the safe side, the determination of the pipe diameter can also be linked to the drive for the pressing device 1 in such a way that the drive is blocked if the determined pipe diameter does not fit the indentations 13, 14 of the pressing device 1.

Claims (19)

Claims: Novopress GmbH Pressen und Presswerkzeuqe & Co. KG, Scharnhorststr. 1, 41460 Neuss Mannesmann AG, Mannesmannufer 2, 40213 Düsseldorf Measuring device for determining the shear depth in a pipe connection 1. Measuring device for detecting the insertion depth in a pipe connection (33), consisting of the pipe end (41) of a pipe (34) and a press fitting (35), with a device carrier with at least one ultrasonic transmitter (29, 34) and ultrasonic receiver (29, 34) arranged on the device carrier (1) and with a measuring circuit for evaluating ultrasonic signals in such a way that a signal dependent on the insertion depth is generated, characterized in that the ultrasonic transmitter (29, 42) and ultrasonic receiver (29, 43) are designed for oblique sounding or oblique reception and the device carrier (1) is designed such that the ultrasonic transmitter (29, 42) and ultrasonic receiver (29, 43) can be attached to the pipe (34) at a predetermined distance from the press fitting (35), the measuring circuit being set up to evaluate the received signal of the ultrasonic receiver (29, 43). 2. Measuring device according to claim 1, characterized in that the measuring circuit is arranged to detect the transit time of the ultrasonic signal. 3. Measuring device according to claim 1 or 2, characterized in that the measuring device is attached to the pipe (34) at a certain predetermined distance from the pipe end (41). ss "j ·1 :&Ggr;:· ^: ··:&Ggr;: settable and the measuring circuit for the calculation of one of the
Sound velocity of the pipe (34) corresponding size
from the behavior of an ultrasonic signal, which value is then used to determine the insertion depth
is taken over. 4. Measuring device according to claim 1 or 2, characterized in that the measuring device has a displacement device for the axial displacement of the ultrasonic transducer by a predetermined distance. 5. Measuring device according to claim 1 or 2, characterized in that the ultrasonic transmitter (42) and
the ultrasonic receiver (43) are arranged at a longitudinal distance from each other and that the measuring circuit is also for the detection
the transit time of an ultrasonic signal from the ultrasonic transmitter (42) directly to the ultrasonic receiver (43), this transit time then being adopted as a value corresponding to the speed of sound for determining the insertion depth. 6. Measuring device according to one of claims 3 to 5, characterized in that the measuring device comprises a display device for the speed of sound and an input device for specifying the speed of sound of the pipe
(34) has. 7. Measuring device according to one of claims 3 to 5, characterized in that the measuring circuit automatically or by acknowledgement takes over the value corresponding to the speed of sound of the pipe (34) for the determination of the insertion depth. 8. Measuring device according to claim 1 or 2, characterized in that the measuring device comprises a magnetic sensor for detecting the magnetizability of the pipe (34). The signal generated for the measuring circuit
as a characteristic of the speed of sound
size is used. 9. Measuring device according to claim 8, characterized in that the measuring device has a display for
which has at least a qualitative representation of magnetizability. 10. Measuring device according to claim 8, characterized in that the magnetic sensor with the measuring circuit
for the automatic adoption of the size corresponding to the magnetizability. 11. Measuring device according to one of claims 1 to 10, characterized in that the measuring circuit is designed to detect and process the maximum individual signal of the reflected ultrasonic signal. 12. Measuring device according to one of claims 1 to 11, characterized in that the measuring circuit is set up for detecting the reflection curve by processing several successive received signals and for comparing the reflection curve with predetermined values which are characteristic of at least one pipe diameter. 13. Measuring device according to claim 12, characterized in that the measuring circuit includes a signal which is used to detect the respective pipe diameter
is characteristic. 14. Measuring device according to claim 12 or 13, characterized in that there are several groups of predetermined values, each of which is for a specific
diameters are characteristic. 15. Measuring device according to one of claims 1 to 14, characterized in that the device carrier is designed as a pressing tool (1) for radially pressing the pipe connection {33). 16. Measuring device according to one of claims 12 to 14 and claim 15, characterized in that the pressing tool (1) has a drive which is connected to the measuring circuit in such a way that the drive is blocked if the measured reflection curve does not correspond to the predetermined values. 17. Measuring device according to claim 15 or 16, characterized in that the pressing tool (1) has a drive which is connected to the measuring circuit in such a way that the drive is blocked if the measured insertion depth is smaller than a predetermined value. 18. Measuring device according to one of claims 1 to 17, characterized in that the measuring device has at least a qualitative display for the insertion depth. 19. Measuring device according to one of claims 1 to 18, characterized in that the ultrasonic transmitter (29, 42) and ultrasonic receiver (29, 43) are guided resiliently in the radial direction.