EP0914896A2 - Piston-cylinder for welding gun - Google Patents

Abstract

A double-acting piston/cylinder unit, provided with three pressure chambers for respectively performing a hollow piston advance stroke, a work piston work stroke and a piston return stroke, has an additional pressure chamber which performs the work piston return stroke and which is at least partially located between the hollow piston and the work piston. A double-acting piston/cylinder unit is equipped with a first pressure chamber (7) which is located between a hollow advance stroke piston (3) and a cylinder head (6) and which performs the hollow piston advance stroke, a second pressure chamber (8) which is located between the hollow advance stroke piston (3) and a work piston (5) and which performs the work piston work stroke and a third return stroke pressure chamber (11) which is located between the hollow advance stroke piston and work piston assembly (9) and a cylinder base (10) and which encloses the piston rod (4). The novelty comprises the provision of a fourth pressure chamber (12) which produces the return stroke of the work piston (5) and which is at least partially located between the hollow advance stroke piston (3) and the work piston (5).

Description

The present invention relates to a piston-cylinder arrangement to carry out a double stroke (preliminary stroke, working stroke), especially for driving a welding electrode a welding gun consisting of a cylinder, an in the pre-stroke hollow piston guided in the cylinder, and an in the preliminary stroke hollow piston, with a piston rod connected working piston, being between the preliminary stroke hollow piston and a cylinder head a first pressure chamber, between the forward stroke cabbage piston and the working piston second pressure chamber and between that from the working piston and the pre-stroke cabbage piston formed piston assembly and a third cylinder bottom enclosing the piston rod Pressure room is formed and the pressure rooms optionally can be acted upon with a pressure medium, in particular compressed air are, namely the first pressure chamber for executing the Forward stroke of the preliminary stroke hollow piston, the second pressure chamber for Execution of the working stroke of the working piston and the third pressure chamber for at least one return stroke of the pistons.

Such a piston-cylinder arrangement is, for example known from German utility model DE 94 19 815 U1 and has proven itself in practice. It serves at Spot welding devices, the so-called spot welding electrodes Welding guns, closing and opening, being the entire cylinder unit, the welding gun cylinder, - usually through a robot arm - on the respective one Welding spot is moved. The cylinder is rigid with the an electrode connected during the piston assembly The movable electrode is actuated via a piston rod. The robot gun body is made of high-strength aluminum plates, on modern CNC-controlled processing machines can be produced according to the modular system assembled.

In the piston-cylinder arrangement, this is usually the total movement stroke of the movable electrode in at least divided two areas, namely a preliminary stroke to the welding device first in the welding area of the to position and partially close the respective workpiece to be able to, and a quite small compared to the preliminary stroke Working stroke in which the actual welding processes take place. To make these movements, i.e. the forward stroke, the working stroke and to control the respective return stroke is a valve arrangement provided over which the pressure chambers of the piston-cylinder arrangement controlled with pressure medium, in particular with compressed air.

According to the German utility model DE 94 19 815 U1 Pneumatic valves directly on a corresponding base plate integrated into the cylinder and thus as a completely exchangeable Unit set up. Annoying air hoses can be omitted in this way. Avoiding tubing is achieved in particular in that to apply the pressure medium to the second pressure chamber a starting from a port opening in the cylinder head centric and axial through the pre-stroke hollow piston tube extending into the second pressure chamber is provided.

This takes place in the known piston-cylinder arrangement "Suppression Principle" application, i.e. stands at the forward stroke the third until at least the start of the working stroke Pressure chamber, which is used both for the return stroke of the working piston as well as for the return stroke of the preliminary stroke hollow piston is under pressure. This prevents the working piston executes the working stroke movement prematurely. Of the The pre-stroke hollow piston always moves against a pressure cushion in the third pressure chamber, the stroke movement by the difference the opposite in the axial direction with the pressure medium areas in the first and in the third pressure chamber comes about. Since the pressurized area in the first pressure chamber larger than that under the counter pressure Is in the third pressure chamber, a resulting force that causes the advance stroke. The one Working speeds achievable in such a piston-cylinder arrangement are very slow; for example the time for a work cycle at 500 ms. To higher Reaching working speeds must be one Piston-cylinder arrangement with an additional vent valve be equipped.

The invention has for its object a piston-cylinder arrangement of the type described in the introduction, with the one without an additional vent valve higher working speed can be achieved.

According to the invention, this is achieved by a piston-cylinder arrangement of the type described at the outset fourth, optionally with the pressure medium Has pressure space for the return stroke of the working piston, wherein the fourth pressure space, at least partially, between the Pre-stroke hollow piston and the working piston is arranged.

The piston-cylinder arrangement according to the invention is a Two-chamber cylinder that only has two valves up to 45 Percent runs faster than the well-known welding gun cylinder. Each of the two chambers comprises two pressure spaces - on the one hand for the respective advance stroke, on the other hand for the respective return stroke of the working piston and the preliminary stroke hollow piston. The speed advantage over the known arrangement is achieved in that the Pre-stroke of the pre-stroke hollow piston, the third pressure chamber depressurized can be without the working piston prematurely Stroke movement because this is done by an im fourth pressure chamber pending pressure can be prevented can.

The supply of the fourth pressure chamber with the pressure medium can - like supplying the other pressure rooms - Via internal channels running into the cylinder head and is therefore advantageously due to a compact Marked construction.

In particular, can advantageously be applied to the second and fourth pressure chamber with the pressure medium one Double tube arrangement can be provided, the first tube, that starts from a channel opening in the cylinder head centrically and axially through the pre-stroke hollow piston in extends the second pressure chamber and comprises a second tube, starting from another channel opening in the Cylinder head inside and coaxial to the first pipe the pre-stroke hollow piston and through the working piston extends into the fourth pressure chamber. At a working pressure of about 10 bar can be used for spot welding with a Welding gun that a piston-cylinder arrangement according to the invention contains, depending on the version, cylinder forces of 3500 to 11000 N are generated, the working cycle itself For example, can reduce from 500 ms to 180 ms.

Further advantageous design features of the invention are in the subclaims and the following description contain.

Using a preferred shown in the drawing The invention is intended to illustrate the exemplary embodiment below are explained. 1 to 4 each show in Axial section of a piston-cylinder arrangement according to the invention in different work phases.

The same in the different figures of the drawing Parts with the same reference numerals so that they in usually only be described once.

Fig. 1 represents a working phase of an inventive Piston-cylinder arrangement, from which in particular the Structure and location of the various pressure rooms very much is clear. It gets more specific on that which phase of work is involved acts.

The piston-cylinder arrangement according to the invention is a double-acting arrangement, ie it is designed to carry out a double stroke, namely a preliminary stroke VH and a working stroke AH. The piston-cylinder arrangement according to the invention is used in particular to drive a welding electrode 1 of a welding gun and consists of a cylinder 2, a pre-stroke hollow piston 3, which is axially movably guided in the cylinder 2, and a piston rod 4, which is axially movably guided in the pre-stroke hollow piston 3 connected working piston 5. The length of the axial guide path of the preliminary stroke hollow piston 3 in the cylinder 2 corresponds to the preliminary stroke VH or the corresponding return stroke RH _V. The length of the axial guide path of the working piston 5 corresponds to the working stroke AH or the corresponding return stroke RH _A. In a welding gun, the cylinder 2 is connected to a fixed welding electrode (not shown) and the piston rod 4 is connected to the movable welding electrode 1.

There is a first pressure chamber 7 between the preliminary stroke hollow piston 3 and a cylinder head 6, a second pressure chamber 8 between the preliminary stroke hollow piston 3 and the working piston 5, and between the piston arrangement 9 formed from the working piston 5 and the preliminary stroke hollow piston 3 and a cylinder base 10 is a third pressure chamber 11 enclosing the piston rod 4. The individual pressure chambers 7, 8, 11 can optionally be acted upon with a pressure medium, in particular with compressed air. The first pressure chamber 7 is pressurized with the pressure medium for performing the forward stroke VH of the preliminary stroke hollow piston 3. The second pressure chamber 8 is pressurized with the pressure medium to carry out the working stroke AH of the working piston 3, and the third pressure chamber 11 is pressurized with the pressure medium to carry out the return stroke RH _V of the preliminary stroke hollow piston 3.

According to the invention, the piston-cylinder arrangement has a fourth pressure chamber 12, which can optionally be pressurized with the pressure medium, for the return stroke RH _{A of} the working piston 5. Part of the fourth pressure chamber 12 is arranged between the preliminary stroke hollow piston 3 and the working piston 5. Another part of the fourth pressure chamber 12 is formed by an inner chamber 13 of the piston rod 4. This is particularly important from the point of view of the special feeding of the printing medium into the fourth printing space to be described in detail below.

To apply the pressure medium to the first pressure chamber 7 is a starting from the cylinder head 6 in the first pressure chamber 7 extending channel opening 14 is provided.

To apply the pressure medium to the second pressure chamber 8 is following an outgoing from the cylinder head 6 Channel opening 15 is centered and axially through the Pre-stroke hollow piston 3 extending into the second pressure chamber 8 Tube 16 provided. The second pressure chamber extends through a centrally arranged opening 17 in Working piston 5 into an inner chamber 18 of the piston rod 4 in. As a result, the second pressure chamber 8 has in view to the supply of the pressure medium through the pipe 16 a particularly favorable aerodynamic training.

To apply pressure medium to the third pressure chamber 11 is a starting from the cylinder bottom 10 in the third pressure chamber 11 extending channel opening 19 is provided.

To apply pressure medium to the fourth pressure chamber 12 is - starting from a beginning in the cylinder head 6 Channel opening 20 - another tube 21 is provided. This second tube 21 extends coaxially within the in the second pressure chamber 7 leading tube 16 through the Vorhub hollow piston 3 and through the central opening 17 in Working piston 5 into the fourth pressure chamber 12. Das Pipe extends into the above-mentioned inner chamber 13 of the Piston rod 4, which also here - similar to the second Pressure chamber 8 - a particularly favorable in terms of fluid mechanics Training the pressure medium supply for the fourth Pressure chamber 12 is given.

The different channel openings 14, 15, 19, 20 can advantageously with a valve arrangement, not shown with a valve control block attached to the cylinder head 6 be connected, the pressure spaces 7, 8, 11, 12 via the internal, through the valve control block and the Cylinder head 6 extending channel openings 14, 15 and pipes 16, 21 are connected to the valve arrangement. The channel opening 19 in the cylinder base 10 to act on the third Pressure chamber 11 with the pressure medium can - with all Advantages of tubeless routing of the print medium - also, namely via an outside, not shown of the cylinder 2 guided pipeline, with the cylinder head 6 be connected.

The individual pressure rooms 7, 8, 11, 12 are against each other and sealed pressure-tight against the atmosphere:

To seal the first pressure chamber 7 against the second Pressure chamber 8 is on the outside diameter of the second Pressure chamber 8 extending tube 16 a sealing ring 22 in Area of the wall or the unspecified Head of the preliminary stroke hollow piston 3 arranged. For sealing of the first pressure chamber 7 against the third pressure chamber 11 another on the outer diameter of the preliminary stroke hollow piston 3 Sealing ring 23 arranged.

The working piston 5 is inside the preliminary stroke hollow piston 3 forming the second pressure chamber 7 and the fourth Pressure chamber 12 chambered pressure-tight and - as already mentioned - guided axially. For pressure-tight closure of the second pressure chamber 8 against the fourth pressure chamber 12 a third on the outer diameter of the working piston 5 Sealing ring 24 and on the outer diameter of the fourth pressure chamber 12 extending tube 21 another Sealing ring 25 arranged. To seal the third Pressure chamber 11 against the fourth pressure chamber 12 is also on Outside diameter of the piston rod 4 in the area of the wall or the unspecified bottom of the preliminary stroke hollow piston 3 a sealing ring 26 is arranged.

Another sealing ring 27 is for sealing of the third pressure chamber 11 on the electrode side against the atmosphere on the outside diameter of the piston rod 4.

1 shows, the working piston 5 with the piston rod 4 via a releasable connection 28, in particular via a screw connection. That way is one Manufacture of the working piston-piston rod unit from the individual parts of simpler construction (working piston 5, piston rod 4) possible. In particular, the piston rod can be so 4 easier to manufacture with their inner chambers 13, 18.

1 to 4, the operation of the Piston-cylinder arrangement according to the invention described become.

Fig. 2 shows the basic position of the piston-cylinder arrangement according to the invention, which is characterized by the smallest axial extent (length) of the arrangement. Both the preliminary stroke hollow piston 3 and the working piston 5 guided in the preliminary stroke hollow piston 3 and connected to the piston rod 4 are in an end position on the side of the cylinder head 6, so that the first pressure chamber 7 and the second pressure chamber 8 are each one Have volume that is almost zero or minimal. This basic position is reached when the third pressure chamber 11 and the fourth pressure chamber 12 are acted upon by the pressure medium and so both the forward stroke hollow piston 3 and the working piston 5 have carried out their return stroke RH (RH _V or RH _A ).

Fig. 2 illustrates in a special way the constructive Advantageousness of the piston-cylinder arrangement according to the invention. Through the double pipe feed 16, 21 of the pressure medium becomes a very space-saving telescopic nesting of the individual components achieved: pre-stroke hollow piston 3 in the cylinder 2, working piston 5 in the pre-stroke hollow piston 3, first tube 16 in the central opening 17 of the working piston 5 and in the inner chamber 18 of the piston rod 4, second tube 21 within the first tube 17 and in the inner chamber 13 of the piston rod 4. The depth of the Inner chambers 13, 18 is exactly on the length of the tubes 21, 16 matched.

3 shows the piston-cylinder arrangement according to the invention in a work phase at the end of the preliminary stroke VH before the start of the AH work stroke. The preliminary stroke hollow piston 3, is in an end position on the side of the cylinder bottom 10, so that the first pressure chamber 7 is at its maximum Has volume, while the volume of the third pressure chamber 11 is almost zero or minimal. The working piston 5 is - seen relative to the preliminary stroke hollow piston 3 still in its end position shown in Fig. 2. The working piston 5 is on the cylinder head side on the preliminary stroke hollow piston 3 and works together with it a pressure in the first pressure chamber 7, the preliminary stroke VH. The constant working of the working piston 5 am Pre-stroke hollow piston 3 during the entire advance stroke VH can thereby by acting on the fourth pressure chamber 12 can be achieved with the print medium. The second pressure room 8 still has a volume that is almost zero or is minimal. The third pressure chamber 11 is depressurized.

4 shows the welding position of the piston-cylinder arrangement according to the invention, by the greatest axial extent the arrangement is marked. Both the pre-stroke hollow piston 3, as well as the working piston 5 in an end position on the side of the cylinder bottom 10, so that the first pressure chamber 7 and the second pressure chamber 8 each have a maximum volume, while the Volume of the third pressure chamber 12 and the fourth pressure chamber 12 is almost zero or minimal. This Welding position is achieved if in addition to the first Pressure chamber 11 the second pressure chamber 12 with the pressure medium is applied.

The table below shows the working phases of the piston-cylinder arrangement according to the invention with steps 0 to 8, step 0 of the basic position shown in FIG. 2, step 1 of the position shown in FIG. 3 after execution of the advance stroke VH and Step 3 corresponds to the welding position shown in FIG. 4 after execution of the forward stroke VH and the working stroke AH. In the individual fields of the table, it is entered whether or not the corresponding pressure spaces 7, 8, 11, 12 are pressurized. 0 means that the corresponding pressure chamber 7, 8, 11, 12 is depressurized, 1 symbolizes the presence of pressurization. The pressure spaces 7, 8, 11, 12 are identified in the table by their reference numerals. Pressure room step 0 1 2nd 3rd 4th 5 6 7 8th 7 0 1 1 1 1 0 0 0 0 8th 0 0 1 1 0 0 0 0 0 11 1 0 0 0 0 1 1 1 1 12th 1 1 0 0 1 1 1 1 1

The most important advantage achieved by the invention is in that the third pressure chamber 11, as the table shows, depressurized when performing the advance stroke VH (step 1) can be because the working piston 5 - relative to the preliminary stroke hollow piston 3 - by the pressure in the fourth pressure chamber 12 in its end position shown in Fig. 2 is held. This is in a known, based on the principle of suppression working piston-cylinder arrangement, for example has a cycle time of about 500 ms, not the case, whereby the duration of a work cycle is comparable to a comparable one arrangement according to the invention without an additional Bleed valve can be shortened to about 180 ms.

To carry out the working stroke AH, after the Vorhub VH the fourth pressure chamber 12 relieved of pressure and second pressure chamber 8 is acted upon by the pressure medium (Steps 2 and 3). If the working stroke AH is available the welding process can be carried out.

After the welding process has been carried out, the second pressure chamber 8 is first depressurized, while the fourth pressure chamber 12 is again pressurized with the pressure medium (step 4). The working piston 5 thereby executes its return stroke RH _A , ie it is moved again in the direction of its basic position shown in FIGS. 2 and 3.

Finally, the first pressure chamber 7 is relieved of pressure, while the third pressure chamber 11 is again acted upon by the pressure medium (step 5), as a result of which the preliminary stroke hollow piston 3 now also executes its return stroke RH _V and moves back into its basic position (FIG. 2). From all this it can be seen that the working phase shown in FIG. 1 shows an intermediate position of the piston-cylinder arrangement according to the invention, which corresponds approximately to step 6 or 7 in the table.

The invention is not based on the illustrated embodiment limited, but also includes all in the sense of Invention equivalent effects. For example the The size of the strokes vary: this is how the size of the forward stroke VH in a range from 10 to 100 mm and that of the working stroke AH are in a range from 5 to 50 mm. Especially it also falls within the scope of the invention, for example, if the shape of the pressure spaces 7, 8, 11, 12 that on a Pressure medium network pressure of up to 12 bar can, deviates from the shape shown in the drawing. Furthermore, the invention is not limited to that in the claim 1 defined combination of features limited, but can also by any other combination of certain Characteristics of all of the individual characteristics disclosed defined be. This means that basically practical each individual feature of claim 1 omitted or by at least one disclosed elsewhere in the application Single feature can be replaced. To that extent Claim 1 only as a first attempt at formulation to understand for an invention.

Reference numerals

1

Welding electrode

2nd

cylinder

3rd

Pre-stroke hollow piston

4th

Piston rod

5

Piston

6

Cylinder head

7

first pressure room

8th

second pressure room

9

3 and 5

10th

Cylinder bottom

11

third pressure room

12th

fourth pressure room

13

Inner chamber of 4, part of 12

14

Canal opening between 6 and 7

15

Canal opening between 6 and 8

16

Tube between 6 and 8

17th

central opening in 5

18th

Inner chamber of 4, part of 8

19th

Canal opening between 10 and 11

20th

Canal opening between 6 and 12

21

Tube between 6 and 12

22

Sealing ring on 17

23

Sealing ring on 3

24th

Sealing ring on 5

25th

Sealing ring on 21

26

Sealing ring on 4

27

Sealing ring on 4

AH

Working stroke

VH

Advance stroke

RH

Return stroke in general, consisting of RH _A and RH _V

RH _A

Return stroke of 5

RH _V

Return stroke of 3

Claims (9)

Piston-cylinder arrangement for performing a double stroke (forward stroke VH, working stroke AH), in particular for driving a welding electrode (1) of a welding gun, consisting of a cylinder (2), a preliminary stroke hollow piston (3) guided in the cylinder (2) , and a working piston (5) which is guided in the preliminary stroke hollow piston (3) and is connected to a piston rod (4), a first pressure chamber (7) between the preliminary stroke and between the preliminary stroke hollow piston (3) and a cylinder head (6) - Hollow piston (3) and the working piston (5) a second pressure chamber (8) and a third, the piston rod between the piston assembly (9) formed from the working piston (5) and the preliminary stroke hollow piston (3) and a cylinder base (10) (4) enclosing pressure chamber (11) is formed and the pressure chambers (7, 8, 11) can optionally be acted upon by a pressure medium, in particular compressed air, namely the first pressure chamber (7) for performing the forward stroke (VH) of the preliminary stroke hollow piston (3), the second pressure chamber (8) for execution tion of the working stroke (AH) of the working piston (5) and the third pressure chamber (11) for at least one return stroke (RH) of the pistons (3, 5)
characterized by a fourth pressure chamber (12), optionally pressurizable with the pressure medium, for the return stroke (RH _A ) of the working piston (5), the fourth pressure chamber (12), at least partially, between the preliminary stroke hollow piston (3) and the working piston ( 5) is arranged. Piston-cylinder arrangement according to claim 1,
characterized in that the fourth pressure chamber (12) is, at least partially, formed by an inner chamber (13) of the piston rod (4). Piston-cylinder arrangement according to claim 1 or 2,
characterized in that the second pressure chamber (12) is, at least partially, formed by an inner chamber (18) of the piston rod (4). Piston-cylinder arrangement according to one of claims 1 to 3,
characterized in that, to act upon the second pressure chamber (8) with the pressure medium, starting from a channel opening (16) in the cylinder head (6) centrally and axially through the preliminary stroke hollow piston (3) into the second pressure chamber (8), in particular in the inner chamber (18) of the piston rod (4), extending tube (17) is provided. Piston-cylinder arrangement according to claim 4,
characterized in that to act upon the fourth pressure chamber (12) with the pressure medium, starting from a channel opening (20) in the cylinder head (6) inside and coaxial to the tube (17) extending into the second pressure chamber (8) through the preliminary stroke - Hollow piston (3) and through the working piston (5) into the fourth pressure chamber (12), in particular in the inner chamber (13) of the piston rod (4), extending tube (21) is provided. Piston-cylinder arrangement according to one of claims 1 to 5,
characterized in that the working piston (5) within the pre-stroke hollow piston (3) with the formation of the second pressure chamber (8) and the fourth pressure chamber (12) is pressure-tight and axially movable. Piston-cylinder arrangement according to one of claims 1 to 6,
characterized in that the working piston (5) is connected to the piston rod (4) via a releasable connection (28), in particular via a screw connection. Piston-cylinder arrangement according to one of claims 1 to 7,
characterized in that the pressure chambers (7, 8, 11) are connected to the cylinder head (6) via internal channel openings (14, 15, 20) and / or pipes (16, 21). Piston-cylinder arrangement according to one of claims 1 to 8,
characterized in that the cylinder (2) is connected to a fixed welding electrode (1) and the piston rod (4) is connected to a movable welding electrode.

Images