DE29604276U1 - Tester - Google Patents

Description

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Description;

Hovopress GmbH Presses and Press Tools & Co. KG, Scharnhorststr. 1, D-41460 Neuss

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Test device

The invention relates to a testing device for checking the driving force of tool drives, in particular press tool drives.

To connect pipes, it is known to use sleeve-shaped press fittings which are pushed over the pipe ends to create a pipe connection and then pressed together radially, whereby both the press fitting and the pipe are plastically deformed. Such pipe connections and the associated press fittings are known, for example, from DB-C-II 87 870 and* EP-B-0 361 630.

The pressing is carried out using pressing devices, as are known in various embodiments, for example in DE-C-21 36 782, DE-A-34 23 283, EP-A-0 451 806 and EP-B-0 361 630. The pressing devices have at least two, sometimes more pressing jaws, which are moved radially inwards during the pressing process in order to form an essentially closed pressing chamber. A tool drive is provided for this movement, for example in the form of a hydraulic pressure cylinder or an electric motor or a combination of both.

Such tool drives have end force limiters, for example in the form of a pressure relief valve in a hydraulic pressure cylinder, a torque coupling in a rotating drive or an overcurrent release in an electrically operated

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Drive. Since such a final force limiter does not directly measure the force emanating from the tool drive, but rather a converted value (pressure, torque or current) that represents only a fraction of the actual drive force, any inaccuracy in this final force limiter has a major impact on the final force that can actually be achieved. Minor tolerances in the final force limiter therefore have a significant effect on the final force.

Since the quality of the pipe connection, especially its tightness, depends significantly on the final force achieved, it is necessary that the pressing tool used actually achieves the required final force, i.e. that the final force limiter does not stop the pressing process too early. This gives rise to the need to check pressing devices for the purpose mentioned here before they are first used - and then at regular intervals to check for wear - to see whether they still achieve the specified final force.

The invention is therefore based on the object of designing a testing device for checking the final force of tool drives.

This object is achieved according to the invention by the following features:

a) the test device has a pressure cylinder with a hydraulic piston guided therein;

b) the hydraulic piston is connected to a force transmission element;

c) the power transmission member extends to a connection for the attachment of the tool drive;

d) Hydraulic piston and pressure cylinder form a pressure chamber for

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a hydraulic oil;

e) the pressure chamber is connected to an outlet valve, the outlet side of which opens into a reservoir;

f) the valve has a valve closure element which is controlled in such a way that its flow resistance increases with increasing piston stroke in the test direction;

g) the pressure chamber is connected to a pressure measuring device.

The basic idea of the invention is not to record the force curve of the tool drive by direct measurement, but to simulate the pressing process using a test device. This is done hydraulically in the test device according to the invention in such a way that the tool drive is connected to the test device so that the force exerted by it acts on a hydraulic piston. During the test process, the hydraulic piston works due to the effect of the tool drive against the effect of an outlet valve, which is controlled in such a way that the pressure in the pressure chamber increases with increasing stroke. This characteristic of the outlet valve simulates the force curve when pressing press fittings, and the pressure measuring device can be used to determine whether the tool drive is able to develop a sufficiently large final force, i.e. whether the final force limiter does not switch off too early.

In the embodiment of the invention, it is provided that the outlet valve is designed as an electronically controlled linear valve. Such valves are known in the prior art. They can be used to simulate a very specific force-displacement curve with exceptional accuracy. However, such linear valves and their control are still very expensive.

Alternatively, it is proposed that the valve closure member is loaded with a closing spring which is connected to the hydraulic piston.

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ben is coupled in such a way that its closing force increases with increasing piston stroke in the test direction. This can be done in such a way that a kinematic transmission from the hydraulic piston to the end of the closing spring facing away from the valve closure member is effected in a corresponding manner, for example in such a way that the closing spring is acted upon directly by a port set of the hydraulic piston. For this purpose, the closing spring can be arranged in a sleeve which is supported on the extension and in which the valve closure member is slidably received. In a special embodiment of the invention, it is provided that the sleeve is slidably guided in a guide bore which runs parallel to the hydraulic cylinder. This results in a particularly compact design of the testing device.

The valve closure element is expediently designed as a valve needle, via the shape of which - as well as through the characteristics of the closing spring - the force-displacement curve can be adjusted according to the respective requirements.

In a further embodiment of the invention, it is proposed that a return spring acting on the hydraulic piston against the direction of the test is provided. After the test process has been completed, this return spring causes the hydraulic piston to move back to its starting position so that another test process can take place. It is expedient for the reservoir to be connected to the pressure chamber via a check valve which opens towards the pressure chamber but closes in the opposite direction. When the piston is returned, the displaced hydraulic oil can therefore flow back into the pressure chamber.

According to the invention, it is further provided that the force transmission element consists of two telescopic rods that protrude outwards from the housing of the test device. However, other force transmission elements can also be provided, expediently in such a way that they are optimally adapted to the respective tool attachment.

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drive are adapted.

Finally, according to the invention, it is proposed that the pressure measuring device has a memory for the maximum pressure reached. This can be provided in a simple form as a trailing pointer. But electronic memories are also possible.

The invention is illustrated in more detail using an embodiment in the drawing. It shows:

Figure 1 shows a pressing device in the front view in the open position with press fitting and pipe end;

Figure 2 shows a cross section through the pressing device according to Figure 1 in the plane A-A and

Figure 3 shows a longitudinal section through a test device for

Checking the driving force of the tool drive for the pressing device according to Figure 2.

The pressing device 1 shown in Figures 1 and 2 has two T-shaped bearing plates 2, 3 which - seen from the front - are arranged exactly one behind the other. In the lower part, the bearing plates 2, 3 are penetrated by a connecting bolt 4. Support plates 5, 6 are placed on both sides of this connecting bolt 4 (in Figure 1, the front support plate 5 is omitted), which belong to the tool drive, designated as 7. They are only shown with their upper part. An electric drive motor (not shown here) is attached to the lower ends of the support plates 5, 6, which also belongs to the tool drive 7 and acts on a drive rod. The upper end of the drive rod is provided with a fork-shaped drive head 8 on the top. Inside the drive head 8, two drive rollers 9, 10 are mounted next to each other so as to be freely rotatable about a horizontal axis. With the help of the drive motor, the drive

head 8 can be moved vertically (and of course also moved back again). The connecting bolt 4 is designed to be removable so that the entire tool drive 7 can be removed in a simple manner.

In the upper area, the bearing plates 2, 3 are penetrated by bearing bolts 11, 12 arranged next to one another at a distance. On each of the bearing bolts 11, 12, a pivot lever 13, 14 is mounted between the bearing plates 2, 3. The two pivot levers 13, 14 are designed with mirror symmetry. They have drive arms 15, 16 extending downwards from the bearing bolts 11, 12 and jaw arms 17, 18 extending upwards. The drive arms 15 _and 16 have drive surfaces 19, 20 which - viewed from the outside inwards - are only slightly inclined to the horizontal and then transition into a steeply upward area. Semicircular recesses which form the contour of the press jaws 21, 22 are formed in the opposing sides of the jaw arms 17, 18.

Figures 1 and 2 show the pressing device 1 in the open position, in which the drive head 8 assumes its lowest position, in which it does not rest on the drive arms 15, 16. The pressing device 1 is attached to a pipe connection so that it lies between the pressing jaws 21, 22. The pipe connection has a pipe end region 23 over which a press fitting 24 is partially slide. This can be seen in particular from Figure 2. The press fitting 24 has a cylinder section 25 with a central constriction 26 serving as a stop for the pipe end region. At the free ends, the press fitting 24 has outwardly curved annular beads 27, 28, into the inside of which an elastomer sealing ring 29, 30 is inserted. The press jaws 21, 22 are at the level of the annular bead 28 on the right-hand side in Figure 2.

For the pressing process, the drive motor of the tool drive 7 is switched on so that the drive rod together with the

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the attached drive head 8 extends upwards. The drive rollers 9, 10 initially come into contact with the flatly inclined sections of the drive surfaces 19, 20. As the drive arms 15, 16 are spread apart, which results in the jaw arms 17, 18 coming closer to one another and the pressing jaws 21, 22 coming into contact with the annular bead 28. As the drive head 8 is raised further, the actual pressing process begins, in which the annular bead 28 and the immediately adjacent area of the cylinder section 25 are plastically deformed radially inwards, with the pipe end area also being plastically deformed radially inwards in the last pressing stage. The drive rollers 9, 10 - as can be seen from Figures 3, 4 - move into the area between the drive arms 15, 16, where the drive surfaces 19, 20 only form a very acute angle, i.e. are very steeply inclined to one another. The pressing process is finished when the upper end faces 31, 32 and the lower end faces 33, 34 of the press jaws 21, 22 come into contact or only have a defined minimum distance.

The drive motor of the tool drive 7 is provided with a torque clutch that opens when a torque is applied and thus limits the final force acting on the drive head 8. The torque clutch is set or designed in such a way that, under perfect conditions, a complete closing of the press jaws 21, 22 is reliably achieved in the sense described above. In order to be able to check whether the torque clutch actually only opens when the designed final force is applied, the test device shown in Figure 3 was developed.

The test device 35 has a housing 36 in which a horizontal pressure cylinder bore 37 is formed, which is closed on the left side and open on the right side. A hydraulic piston 38 is guided horizontally in the pressure cylinder bore 37. Br delimits a pressure chamber 39, whereby a ring seal 40 on the hydraulic piston 38 is used for the piston-side sealing of the

pressure chamber 39. A helical spring 41 under pressure, which is supported at one end on the front side of the pressure chamber 39 and at the other end in an axial bore 42 of the hydraulic piston 38, strives to push the hydraulic piston 38 in the direction of the open side of the pressure cylinder bore 37.

A connector 44 is screwed to the open side of the housing 36 using screws 43, 44, in which two telescopic rods 45, 46 are mounted at a distance from one another so that they can move axially. The telescopic rods 45, 46 are supported on the side of the hydraulic piston 38 facing away from the pressure chamber 39 and protrude from the connector 44 towards the other side. Their distance corresponds to the axis distance of the drive rollers 9, 10 of the tool drive 7. Between the two telescopic rods 45, 46, the connector 44 has a connection hole 47 which is suitable for inserting the connecting bolt 4. In the present case, the tool drive 7 is removed from the pressing device 1 by removing the connecting bolt 4 and is attached to the connecting piece 44 in such a way that the support plates 5, 6 enclose the connecting piece 44 on both sides and their holes for the connecting bolt 4 are aligned with the connection hole 47. The drive rollers 9, 10 rest on the outer end faces of the telescopic rods 45, 46.

The pressure cylinder bore 37 has a recess 48 in the upper area towards the open end, into which an extension 49 of the hydraulic piston 38 protrudes. On the inside, the recess 48 forms a shoulder from which a guide bore 50 extends parallel to the pressure cylinder bore 37. A sleeve 51 is guided in an axially movable manner in this guide bore 50, which is supported with its closed end on the extension 49 of the hydraulic piston 38. A compression-loaded helical spring 52 is inserted into the sleeve 51, which is supported at one end on the closed end of the sleeve 51 and at the other end on the thickened end of a valve needle 53, which is slidably received in the sleeve 51.

The valve needle 53 extends with its conical pointed end partially into a valve bore 54, namely while resting on the opening edge of the valve bore 54. The valve needle 53 and the valve bore 54 form an outlet valve 55.

The outlet valve 55 is connected to the pressure chamber 39 via the valve bore 54 and via a horizontal channel section 56 and an adjoining, vertical channel section 57. From the guide bore 50, in the immediate vicinity of the outlet valve 55, an outlet channel 58 leads vertically up into a hydraulic oil reservoir 59, which is closed at the top with a cover 60 with a ventilation opening 61 and contains hydraulic oil 62.

A return channel 63 extends from the horizontal channel section 56, which reaches into the hydraulic oil reservoir 59 and ends there in a check valve 64. This check valve 64 blocks the return channel 63 in the direction of the hydraulic oil reservoir 59. A connection opening 65 extends from the vertical channel section 57, to which a pressure gauge with a drag indicator (not shown here) can be connected.

Using the test device 35 described above, a test procedure is as follows.

The drive motor of the tool drive 7 is switched on so that the piston rod extends together with the end drive head 8, in the illustration according to Figure 3 in the direction of the test device 35. This causes the telescopic rods 45, 46 and thus also the hydraulic piston 38 to be moved to the right against the action of the coil spring 41. The hydraulic oil displaced in the pressure chamber 39 thereby reaches the valve bore 54 via the vertical channel section 57 and the horizontal channel section 56 and then flows to a defined extent past the valve needle 53 into the guide bore 50 and from there

from the outlet channel 58 into the hydraulic oil reservoir 59. The shape of the valve needle 53 and the coil spring 52 are designed such that a certain initial pressure is required in the pressure chamber 39 to overcome the resistance generated by the valve needle 53.

As the test process continues, i.e. when the hydraulic piston 38 is moved in the test direction, the sleeve 51 is carried along by the extension 49 and therefore moved in the direction of the outlet valve 55. The end of the valve needle 53 located in the sleeve 51 is pushed further and further into the sleeve 51, whereby the spring force increases continuously in accordance with the characteristic curve of the coil spring 52. This in turn results in the pressure in the pressure chamber 39 increasing accordingly, because the valve needle 53 is pressed with an ever increasing force in the direction of the valve bore 54. By appropriate design, a force-displacement curve can be simulated in this way, which essentially corresponds to that when the pivoting levers 13, 14 on the pressing device 1 are acted upon. The pressure increase via the connection opening 65 is recorded by the pressure measuring device (not shown).

At some point in time, such a pressure will be reached in the pressure chamber 39 that the torque clutch will disengage. The final pressure prevailing in the pressure chamber 39 is recorded and stored by the pressure gauge. This pressure can then be used to decide whether the torque clutch opens within the design tolerance range or whether it opens too early. In the latter case, the clutch is not functioning properly.

Once the test procedure is complete, the hydraulic piston 38 is moved back to the starting position shown by the coil spring 41. The check valve 64 opens so that hydraulic oil 62 from the hydraulic oil reservoir 59 flows into the pressure chamber 39 in accordance with the increase in volume of the pressure chamber 39.

can flow.

The force-displacement curve can be adjusted as desired within wide limits using the test device 35. The preload of the coil spring 52 in the sleeve 51 can be adjusted using an adjusting screw 66, which is screwed into the extension 49 and on which the closed end of the sleeve 51 rests. In particular, the characteristic curve can be used to adjust this. Another option is the coil spring 52 itself, i.e. its spring characteristic curve, which can be designed not only linearly, but also progressively or degressively. Finally, the shape of the needle tip of the valve needle 53 itself can also influence the force-displacement curve during the test process.

Claims (11)

Claims: Novopress GmbH Pressen und Presswerkzeuqe & Co. KG, Scharnhorststr. 1, D-41460 Neuss Test device 1. Test device (35) for checking the driving force of tool drives (7), in particular press tool drives, characterized by the following features a) the testing device {35} has a pressure cylinder (37) with a hydraulic piston (38) guided therein; b) the hydraulic piston (38) is connected to a force transmission member (45, 46); c) the power transmission member (45, 46) extends to a connection (44) for the attachment of the tool drive (7); d) hydraulic piston (38) and pressure cylinder (37) form a pressure chamber (39) for a hydraulic oil (62); e) the pressure chamber (39) is connected to an outlet valve (55), the outlet side of which opens into a reservoir (59); f) the outlet valve (55) has a valve closure member (53) which is controlled in such a way that its flow resistance increases with increasing piston stroke of the hydraulic piston (38) in the test direction; g) the pressure chamber (39) is connected to a pressure measuring device. 2. Test device according to claim 1, characterized in that the outlet valve (55) is designed as an electronically controlled linear valve. 3. Test device according to claim 1, characterized in that the valve closure member (53) is loaded with a closing spring (52) which is coupled to the hydraulic piston (38) in such a way that its closing force increases with increasing piston stroke of the hydraulic piston (38) in the test direction, 4. Test device according to claim 3, characterized in that the closing spring (52) is directly acted upon by an extension (49) of the hydraulic piston (38). 5. Test device according to claim 4, characterized in that the closing spring (52) is arranged in a sleeve (51) which is supported on the extension (49) and in which the valve closure member (53) is slidably received. 6. Test device according to claim 5, characterized in that the sleeve (51) is slidably guided in a guide bore (50) which runs parallel to the hydraulic cylinder (37), 7. Test device according to one of claims 1 to 6, characterized in that the valve closure member is designed as a valve needle (53). 8. Test device according to one of claims 1 to 7, characterized in that a return spring (41) acting on the hydraulic piston (38) against the test direction is provided. 9. Test device according to one of claims 1 to 8, characterized in that the reservoir (59) is connected to the pressure chamber (39) via a check valve (64) which opens towards the pressure chamber (39). 10. Test device according to one of claims 1 to 9, characterized in that the force transmission member consists of two telescopic rods (45, 46) which protrude outwards from the housing (36) of the testing device (35). 11. Test device according to one of claims 1 to 10, characterized in that the pressure measuring device has a memory for the maximum pressure reached.