Drawing press having two couplable rams

The invention relates to a drawing press (10) having a first ram (17) and a second ram (18). The first ram (17) is moved in a working direction (A) by an electromotive first ram drive (25) and the second ram (18) by an electromotive second ram drive. The drawing press (10) also has a coupling means (35) which can be switched between an uncoupling state and a coupling state. In the uncoupling state, the two rams (17), (18) can move independently of one another in the working direction (A). In the coupling state, the coupling means (35) ensures that a relative movement between the two rams (17, 18) is prevented. The drawing press (10) can therefore be operated as a single-acting or double -acting press.

CROSS REFERENCE TO RELATED APPLICATION

The present patent application is based upon and claims the benefit of German patent application no. 102011 001 314.8 filed Mar. 16, 2011 and PCT application no. PCT/EP2012/054716, filed Mar. 16, 2012.

BACKGROUND OF THE INVENTION

The invention relates to a drawing press, which serves to produce molded sheet metal parts, such as auto body parts, for example.

Double-acting presses are known for deep-drawing sheet metal parts. In the case of such presses, a sheet metal holding ring is arranged so as to be capable of being moved relative to a drawing punch. The sheet metal holding ring bears on the circuit board, which is to be deformed, and exerts a holding force of clamping force, while the drawing punch subsequently deforms the circuit board in cooperation with a mold. Such a press is known from DE 24 19 389, for example. Provision is made therein for a hydraulic drawing press, in the case of which a drawing punch as well as a sheet metal holding ring12are provided on a ram, which can be moved in working direction. In response to the downwards movement of the ram, the sheet metal holding ring thus initially impacts the circuit board and a deformation of the circuit board by means of the drawing punch takes place only in response to a continued downwards movement.

A double-acting molding machine comprising an inner ram and an outer ram is further known from DE 199 43 441 A1. An eccentric drive encompasses an eccentric shaft, which is connected to the outer ram via connecting rods. A toggle joint drive having two joint levers connects the inner ram to the eccentric shaft via a further lever.

SUMMARY OF THE INVENTION

Based on the known presses, it can be considered to be a task of the instant invention to design the possible applications of the press to be more flexible and to ensure a high quality of the produced molded parts.

For this purpose, the drawing press encompasses a first ram, which can be driven in a working direction by means of a first ram drive. The drawing press furthermore has a second ram, which can be driven by means of a second ram drive. The two ram drives in each case encompass an electric motor. Both ram drives can be activated independent from one another, so that the movements of the first ram and of the second ram relative to the lower die or to the circuit board, respectively, can be carried out and provided independently. A control unit serves to drive the ram drives. The drawing press furthermore encompasses a coupling means, which can be switched between a coupling state and an uncoupling state. In the coupling state, a kinematic coupling is established between the two rams, which prevents a relative movement of the first ram relative to the second ram. Preferably, the coupling means is a mechanical coupling means, which establishes a direct mechanical connection between the two rams in the case of one exemplary embodiment, and which effects a kinematic coupling of the two ram drives in the case of another exemplary embodiment. The drawing press can therefore be switched between a single-acting mode of operation in the coupling state and a double-acting mode of operation in the uncoupling state via the coupling means.

In the uncoupling state, the second ram can be used as a holding-down device, for example. Its position, its movement speed and/or its clamping force, with which it holds the circuit board, can be provided freely and independent from the position and/or the speed, at which the first ram moves, which can serve as drawing punch, for example. The sheet metal holding force, which is exerted by the second ram in the case of this mode of operation and its course during the drawing process are significant for the quality of the produced molded part. Due to the independence of the two ram movements, the sheet metal holding force, which the second ram exerts on the circuit board, can be adapted to the requirements of the drawing process, such as, e.g., the material and the thickness of the circuit board. In addition, it is possible to adjust this sheet metal holding force completely independently from the current position of the drawing punch, which is formed by the first ram. The sheet metal holding force can be adjusted to the speed of the first drawing punch, for example, in this manner. Independent on the movement control of the first drawing punch, the possibility further arises to provide a switching between a position-controlled or position-regulated and a force-controlled or force-regulated control of the second ram drive via the control unit.

In the event that the coupling state is established via the coupling means, the two rams move together in working direction. It is thus possible to press the two rams against the circuit board using a high molding force. The forces, which are provided by the first ram drive and by the second ram drive in working direction, can be added to form a high total force in the coupling state. As a function of the processing task, it can also be sufficient in the coupling state, if only one of the ram drives is moved. In the coupling state, the two rams preferably form a common enlarged clamping surface. In the coupling state, the drawing press interacts as a single-acting press with a drawing tool, which is attached to the press frame in this operating mode.

It is advantageous, if the two ram drives are kinematically identical. They can be embodied as eccentric drives or joint drives, for example. Due to the identical embodiment of the two ram drives, it is attained that the same control of both ram drives can take place very simply in the case of the coupling by means of the control unit, when the drawing force, which is required for the drawing process, is larger than the force, which can be exerted by an individual ram drive. A complex control with different parameters for each ram drive is avoided in this case.

The coupling means can establish a kinematic connection between the two ram drives, for example. In this case, said coupling means can be embodied as switchable shaft coupling or as intermediate drive between the two ram drives. The coupling means is controlled in particular by means of the control unit, so as to switch between the coupling state and the uncoupling state. The operating state of the drawing press can be changed particularly quickly and easily in this manner.

The electric motors of the ram drives can be embodied as servomotors or as torquemotors. They make it possible to accurately adjust the position and/or force of the rams in working direction. In a manner of speaking, the ram drives are “dry” and do not require any hydraulic liquid. In the case of the preferred exemplary embodiment of the drawing press, the two ram drives are embodied as top drives and are therefore arranged above the two rams on the press frame. The lower die, which is located opposite the rams in working direction, can be embodied so as to be completely free of drives.

Advantageous embodiments of the drawing press according to the invention follow from the dependent patent claims as well as from the description. The description is limited to significant features of the invention. The drawing should be used as a supplement.

Other objects and advantages of the present invention will become apparent to those skilled in the art upon a review of the following detailed description of the preferred embodiments and the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2illustrate a drawing press10, which encompasses a press frame11, which encompasses a plurality of stands12, which run substantially vertically and which support a head13. The lower part of the press frame11includes a base14, to which the supports12are connected. The base14, the stands12and the head13form a closed, stiff frame.

A first ram17as well as a second ram18are arranged on the press frame11in a working direction A and so as to be movable substantially vertically, for example. In the exemplary embodiment described herein, the first ram17is embodied as an inner ram, which is surrounded by the second ram18in a ring-shaped manner. The two rams17,18are arranged coaxially to one another. An upper tool element19, for example. which cooperates with a lower tool element20of a bottom die21, to mold a circuit board22, is arranged on the first ram17.

A first ram drive25is present for driving the first ram17. The first ram drive25encompasses a first electric motor26, for example a servomotor or a torquemotor, which drives a first eccentric shaft27. At least one eccentric28, and two eccentrics28for example, on which a connecting rod29is in each case rotatably supported, is arranged on the first eccentric shaft27. On the opposite side of the eccentric28, each connecting rod29is connected to the first ram17in an articulated manner. In response to a rotation of the eccentric shaft27, the connecting rods29are displaced in working direction A, which can bring about the upwards and downwards movement of the first ram17in working direction A.

A second ram drive30having a second electric motor31serves to drive the second ram18. The two ram drives are designed so as to be kinematically identical. The second electric motor31therefore drives a second eccentric shaft32, on which at least one and for example two eccentrics28are arranged in a torque proof manner. Analogously to the first eccentric drive25, two connecting rods29, which are connected to the second ram28in an articulated manner, are rotatably supported on these eccentrics28. The two ram drives25,30are designed so as to be kinematically identical. They encompass the same electric motors26,31and the same translations, so that the same movement of the respective assigned ram17,18is effected in working direction A in response to the control of the ram drives25,30with the same control variable. The connecting rods29of the ram drives25,30have the same length. Substantially the same forces of the rams17or18, respectively, also result in working direction A in the case of the same control variable of the two ram drives25,30.

The two ram drives25,30are controlled by means of a control unit33. The control unit33can adjust and provide the movement and/or position and/or force of each ram17,18independently. The first ram17and/or the second ram18can be position-controlled or position-regulated or force-controlled or force-regulated, for example, in this manner. The corresponding control of the ram drive25,30or of the respective electric motor26,31, respectively, takes place by means of the control unit33.

A coupling means35will furthermore be switched between a coupling state and an uncoupling state via the control unit33. In the uncoupling state, the two rams17,18can move completely independent from one another in working direction A. In the coupling state, the coupling means35prevents a relative movement between the two rams17,18in working direction A. In the latter case, the two rams17,18move only together.

In the case of the exemplary embodiments described herein, the coupling means35establishes a mechanical and/or kinematic coupling between the two rams17,18. In the case of a first exemplary embodiment according toFIG. 3, the two ram drives25,30are coupled kinematically for this purpose. In the coupling state, it is possible, for example, to connect the two eccentric shafts27,32of the two ram drives25,30to one another in a torque-proof manner by means of a shaft coupling36. The shaft coupling36is embodied so as to be capable of being switched and separates the two eccentric shafts27,32from one another in the uncoupling state. The shaft coupling36can be switched by means of the control unit33. As an alternative to this preferred exemplary embodiment, it is also possible to embody the shaft coupling36or another coupling means35so as to be capable of being operated or switched, respectively, mechanically by means of an operator, so that a manual switch between the coupling state and the uncoupling state takes place.

FIG. 4illustrates an alternative embodiment of the coupling means35. A mechanical connection is established directly between the first ram17and the second ram18by means of the coupling means35, when the latter is in the coupling state. In the uncoupling state, the coupling means35releases the relative movement between the two rams17,18. The mechanical connection in the coupling state can be attained, for example, by means of a non-positive and/or position connection between the two rams17,18, for example by means of locking means and/or clamping means. In the case of this embodiment, as is illustrated schematically inFIG. 4, the coupling means35can also be embodied so as to be capable of being switched by means of the control unit33or, in the alternative, as being capable of being switched manually.

The drawing press10can either be operated as double-acting press or a single-acting press as a function of the state of the coupling means35. For the operation as a single-acting press, the lower die21encompasses a drawing device40(FIG. 2). According to the example, the drawing device40encompasses a table cushion41having a suspended intermediate plate42, which can be positioned and/or moved in working direction A of the drawing press10via a table cushion drive43. A plurality of pressure rods46, which permeate a press table44and which encompass a ring-shaped sheet metal holder45on their end, which faces the upper tool element19or the rams17,18, respectively, are arranged on the intermediate suspended plate42. The lower tool element20is arranged on the press table44, below the sheet metal holder45.

The upper tool element19and the lower tool element20are embodied so as to be complementary to one another. It is possible to embody the lower tool element20or the upper tool element19as a shape having a concave recess, as is shown in an exemplary manner inFIGS. 1 and 2.

The drawing press10operates as follows:

With reference toFIG. 1, the operation of the drawing press10is explained in the uncoupling state of the coupling means35. Here, the drawing press operates as double-acting press. In this case, the second ram18serves as holding-down device. Prior to the molding process of the circuit board22, the second ram18is initially moved downwards until it rests against the circuit board22. The movement to the circuit board22in working direction A is carried out by means of the control or regulation of the position of the second ram18. As soon as it has reached the circuit board22, the control unit33switches to the control or regulation of the clamping force, which the second ram18exerts on the circuit board22. It is held between the second ram18and a clamping surface, which is present on the lower die21.

The control unit controls the second ram drive30independent from the first ram drive25such that it only reaches the circuit board22when the first ram18acts on the circuit board22with the desired clamping force. The actual drawing process of the circuit board22is carried out via the control or regulation of the position and/or of the speed of the first ram17in working direction A. For this purpose, the upper tool element19and the lower tool element20cooperate and bring the circuit board22into the desired shape. During this molding process, the clamping force, which the second ram18exerts onto the circuit bard22, can vary. The clamping force can be adjusted so as to be adapted to the position and/or the speed of the first ram17. Due to the independence of the two ram drives25,30and due to the fact that the ram drives25,30are embodied as electric drives, a corresponding control by the control unit33is possible very simply and accurately.

The drawing press10can also be operated as single-acting press, as it is illustrated inFIG. 2. In the case of this embodiment, the drawing device40is additionally attached to the lower die21. In the mode of operation of the drawing press10as single-acting press, the sheet metal holding ring45and the pressure rods46are connected to the suspended intermediate plate42. In the event that the mode of operation is to be adjusted as double-acting press, the pressure rods46and the sheet metal holding ring35can be removed easily. The mode of operation as a single-acting press is further adjusted in that the coupling means35is switched into its coupling state. The two rams17,18are thereby movement-coupled. On its side, which faces the lower die21, they form a common clamping surface50. The moments of the two electric motors26,31of the two ram drives25,30can be added in this state, so that the force, with which the two rams17,18can be moved together against the circuit board22, can be larger than the force, which can be exerted solely by the first or by the second ram drive25,30. Molding processes, which require a large force of the ram17,18in working direction A and which cannot be created in the mode of operation of double-acting press, can thus also be carried out by means of the drawing press10. Due to the coupling of the two rams17,18, they simultaneously move in working direction A and simultaneously impact the circuit board22, which bears on the sheet metal holder45. The two rams17,18move the circuit board22, together with the sheet metal holder45, the pressure rods46and the suspended intermediate plate42in working direction A against the force of the sheet metal holder, which is applied via the table cushion drive43, wherein the upper tool element19and the lower tool element20cooperate and a molding of the circuit board22takes place.

In the case of the exemplary embodiments described herein, the two ram drives25,30are embodied as top drives. According to the embodiment according toFIGS. 1 and 2, the ram drives25,30are formed by means of eccentric drives. As a modification to the illustrated embodiment, each ram drive25,30can also encompass more than one electric motor26,31.

Instead of the eccentric drives25,30, a joint drive51can also be used as ram drive. A joint drive51encompasses two levers52, which are connected to one another in an articulated manner, wherein the one lever52is connected in an articulated manner to the assigned ram17or18, respectively, and the respective other lever52is connected in an articulated manner to the press frame11. A drive lever53, which is driven by means of an eccentric54, is located at the joint connection between the two levers52.

The invention relates to a drawing press10having a first ram17and a second ram18. The first ram17is moved by means of an electromotive first ram drive25and the second ram18is moved by means of an electromotive second ram drive in a working direction A. The drawing press10further encompasses a coupling means35, which can be switched between an uncoupling state and a coupling state. In the uncoupling state, the two rams17,18can move independent from one another in working direction A. In the coupling state, the coupling means35ensures that a relative movement is prevented between the two rams17,18. The drawing press10can thus be operated as a single-acting or double-acting press.

LIST OF REFERENCE NUMERALS

The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims.