Drive unit for a pressing device

Abstract

Drive unit for a pressing device for pressing a workpiece with a motor with a motor shaft, wherein the motor shaft is rotatable about a rotational axis, an eccentric, wherein the eccentric is connected to the motor shaft, the eccentric having an eccentric element which is eccentric to the axis of rotation of the motor shaft, such that a pump piston connected to the eccentric element is moved back and forth when the motor shaft rotates to pump a hydraulic fluid, characterized by the eccentric is formed from at least a first eccentric part and a second eccentric part.

Description

[0001] The present invention relates to a drive unit for a pressing device for pressing a workpiece and to such a pressing device.

[0002] Common electro-hydraulic pressing tools feature an electro-hydraulic drive unit with a hydraulic pump. The hydraulic pump draws hydraulic fluid from a reservoir into a piston unit, generating the movement of a working piston within the piston unit. This movement is then transferred to a pressing tool connected to the pressing unit to generate a pressing force. The hydraulic pump in the drive unit is typically a piston pump with an eccentric rotating element driven by an electric motor. This eccentric movement causes a piston or pump piston within the piston pump to move the hydraulic fluid.

[0003] Since the pressing tools are hand-operated machines, they are compact and lightweight. However, with known pressing tools, further reduction in size is limited by the space occupied by the piston pump. Reducing the eccentricity or stroke of the eccentric reduces the delivery rate of the hydraulic pump and thus negatively impacts the performance of the pressing tool.

[0004] The object of the present invention is to create a drive unit for a press device which is compact in design with the same or improved conveying performance.

[0005] The problem is solved by a drive unit according to claim 1 and a pressing device according to claim 9.

[0006] The drive unit according to the invention for a press for pressing a workpiece comprises a motor with a motor shaft, wherein the motor shaft is rotatable about an axis of rotation. In particular, the axis of rotation is defined by the motor shaft. Furthermore, the drive unit comprises an eccentric, wherein the eccentric is connected to the motor shaft. The eccentric has an eccentric element which is designed eccentrically to the axis of rotation of the motor shaft, such that a pump piston connected to the eccentric element is moved back and forth when the motor shaft rotates, in order to pump a hydraulic fluid. In particular, the eccentric element has a circular cross-section, wherein the center of this circle is arranged offset from the axis of rotation of the motor shaft. Here, the eccentric is formed from at least a first eccentric part and a second eccentric part.In particular, the eccentric element is formed at least by the first eccentric part and the second eccentric part. In the prior art, the eccentric is usually formed in one piece to reduce the number of components within the drive unit. However, it has been shown that this results in limitations regarding the design of the eccentric element. Specifically, in the prior art, the eccentric element must have a radius such that the radial distance of the outer surface of the eccentric element always projects beyond concentric outer surfaces of the eccentric element, allowing an eccentric bearing to be attached to the eccentric element, particularly by sliding it onto the eccentric element. Thus, in the prior art, the eccentric element must be very robust and large, which also increases the installation space for the drive unit.According to the present invention, the eccentric, or at least the eccentric element, is formed by a first eccentric part and a second eccentric part, so that the drive unit, and in particular an arrangement of an eccentric bearing on the eccentric element, can be assembled before the first and second eccentric parts are joined. Thus, it is no longer necessary for an outer surface of the eccentric element to protrude beyond the concentric outer surfaces of the eccentric. Therefore, the eccentric can be designed to be particularly compact. In particular, the eccentric element can be smaller, i.e., with a smaller cross-section or diameter, thereby reducing the overall size of the drive unit. Specifically, the minimum distance between the drive unit's conveying piston and the axis of rotation of the motor shaft is reduced compared to the prior art.This allows the size of the eccentric to be reduced while maintaining the same stroke. Alternatively, a more compact design can be used to increase the eccentric's stroke and thus boost the hydraulic pump's delivery rate.

[0007] Preferably, the first and second eccentric parts are connected by means of an joining connection. In particular, an eccentric bearing, for example designed as a needle bearing, surrounds the eccentric element, with the first and second eccentric parts being joined within the eccentric bearing. Thus, for the assembly of the eccentric, the first eccentric part can first be provided, followed by the arrangement of the eccentric bearing around the first eccentric part, and subsequently the second eccentric part can be joined with the first eccentric part within the eccentric bearing, and in particular within the inner ring of the eccentric bearing.

[0008] Preferably, the first eccentric part and the second eccentric part have a tenon joint, wherein one of the eccentric parts has a tenon and the other eccentric part has a tenon hole for receiving the tenon of the other eccentric part. This ensures a secure connection between the first and second eccentric parts.

[0009] Preferably, the first and second eccentric parts are screwed together. For example, one eccentric part can have an axial through-hole which, when assembled, aligns with a bore in the other eccentric part. This bore is threaded, allowing a screw to be inserted through the axial through-hole and tightened with the thread of the other eccentric part, thus creating a durable connection between the first and second eccentric parts.

[0010] Preferably, the end faces of the first and second eccentric parts, which come into contact with each other, have alignment features, such as radially arranged grooves and tongues, which interlock when the first and second eccentric parts are joined to increase the torsional stiffness of the first eccentric part relative to the second. Thus, when the first and second eccentric parts are joined, the alignment feature of the first eccentric part is inserted into a correspondingly shaped alignment feature of the second eccentric part, and subsequently, the first and second eccentric parts are firmly connected, for example, by a joining connection, a screw connection, or the like, as described above.

[0011] Preferably, the eccentric has a first section connected to the motor shaft, which is rotationally symmetrical or concentric with respect to the axis of rotation. In particular, the first section has a concentric outer surface that is concentric with respect to the axis of rotation. Furthermore, the eccentric has a second section arranged opposite the eccentric element, which is rotationally symmetrical with respect to the axis of rotation. In particular, the second section also has a concentric outer surface that is concentric with respect to the axis of rotation. The eccentric is supported in the first section and in the second section. Thus, a first bearing, which is, for example, designed as a rolling bearing, is arranged on the first section, and a second bearing, which is also designed as a rolling bearing, is arranged on the second section. The first and second bearings can be identical or different.

[0012] Preferably, the minimum radial extent of the eccentric element, measured from the axis of rotation of the motor shaft, is smaller than the radial extent of the first section and / or the second section. Due to the two-part design of the eccentric, and in particular the eccentric element, it is no longer necessary to slide the eccentric bearing onto the eccentric element via the first section and / or the second section. Thus, the minimum radial distance of the eccentric element can be smaller than the radial distance of the first section or the second section. In other words, the radius of the first section and / or the second section is larger than the minimum distance of the outer surface of the eccentric element to the axis of rotation. Therefore, the eccentric can be designed compactly while maintaining the same stroke. Simultaneously, the weight of the eccentric can be reduced by decreasing the size of the eccentric element.

[0013] Preferably, the maximum radial extent of the eccentric element, measured from the axis of rotation of the motor shaft, is greater than the radial extent of the first section and / or the second section. In other words, the radial extent of the eccentric element is greater than the radius of the first section and / or the second section. This ensures sufficient stroke of the eccentric element.

[0014] Preferably, the diameter of the eccentric element is less than or equal to the diameter of the motor shaft and / or the first section and / or the second section. Thus, due to the two-part design, it is no longer necessary to select a diameter of the eccentric element larger than that of the first section and / or the second section and / or the motor shaft, which would allow an eccentric bearing to be slid onto the eccentric element. The two-part design of the eccentric, and in particular the eccentric element itself, allows for a smaller diameter of the eccentric element, thereby enabling the eccentric bearing to be mounted on the eccentric element.

[0015] Preferably, the stroke of the eccentric is greater than 2 mm and particularly greater than 5 mm. Thus, despite the reduction in installation space, the stroke of the eccentric is not reduced compared to the prior art, and therefore the delivery rate of the drive unit, and in particular of the hydraulic pump of the drive unit, remains the same despite the reduced size. Alternatively, it is possible to utilize the compact design to increase the delivery rate of the hydraulic pump, so that while a reduction in the dimensions of the drive unit cannot be achieved, an increase in performance can be achieved through the two-part design of the eccentric according to the present invention.

[0016] Another aspect of the present invention relates to a pressing device for pressing workpieces with a drive unit as described above. The pressing device further comprises a reservoir for hydraulic fluid, wherein the piston pump of the drive unit is arranged in a supply line that connects the reservoir to a working piston of the pressing device, so that the piston pump conveys hydraulic fluid from the reservoir to the working piston for the movement of the working piston. The movement of the working piston can then be transmitted to a pressing tool permanently or detachably connected to the pressing device for pressing a workpiece.

[0017] Preferably, the pressing device is further developed based on the features of the drive unit described above.

[0018] The invention will now be explained in more detail with reference to preferred embodiments and the accompanying figures.

[0019] They show: Fig. 1 a schematic diagram of a pressing device according to the present invention, Fig. 2 an eccentric of a drive unit according to the present invention and Fig. 3 an eccentric from the state of the art.

[0020] The following refers to the Fig. 1. Fig. Figure 1 shows a schematic representation of a pressing device 10. The pressing device 10 has a piston unit 24 with a working piston 28. Furthermore, the pressing device 10 has a drive unit 20, designed as an electro-hydraulic drive unit. The drive unit 20 has an electric motor 14 with a motor shaft 16. A hydraulic pump 12, in particular designed as a piston pump, is arranged in a supply line 22 between a reservoir 18 and a working chamber 26 of the piston unit 24 via the motor shaft 16. By means of the drive unit 20, and in particular the hydraulic pump 12, hydraulic fluid is pumped from the hydraulic reservoir 18 into the working chamber 26, so that the working piston 28 is moved in the direction indicated by arrow 30. This movement is then transmitted to a pressing tool, which is detachably or permanently connected to the pressing device, for pressing the workpiece.Furthermore, the pressing device 10 has a return line 32 in which a check valve 34 is arranged. When the check valve 34 is closed, the hydraulic pump 12 can build up pressure in the working chamber 26 of the piston unit 24 to generate the pressing force. At the end of a complete pressing operation or when a pressing process is aborted, the check valve 34 can be opened electronically or mechanically, allowing hydraulic fluid to flow from the working chamber 26 back into the reservoir 18 via the return line 32. The working piston 28 can then be pushed back to its starting position in the opposite direction to arrow 30 for a further pressing operation.

[0021] The following refers to the Fig. 2. The Fig. Figure 2 shows a detailed view of the hydraulic pump 12, designed as a piston pump. The hydraulic pump 12 has an eccentric 15 with a concentric connecting element 36, which can be connected to or formed by the motor shaft 16. The motor shaft 16 or the connecting element 36 defines an axis of rotation 17. The eccentric 15 has a first section 45A and an opposing second section 45B. The first section 45A and the second section 45B have concentric outer surfaces, which are arranged concentrically to the axis of rotation 17. The eccentric 15 is rotatably mounted at the respective sections 45A and 45B by corresponding bearings 38A and 38B. These can be, for example, ball bearings, roller bearings, or plain bearings. An eccentric element 42 extends between the first section 45A and the second section 45B.The eccentric element 42 converts the rotational movement of the eccentric 15 into an eccentric back-and-forth movement, which is transferred to a piston 48 that moves in a pump housing 46 to pump the hydraulic fluid from the reservoir 18 towards the working chamber 26 of the piston unit 24.

[0022] Here, the eccentric element 42 has a circular cross-section, the center of which is offset from the axis of rotation 17 of the eccentric 15.

[0023] An eccentric bearing 41 is arranged on the outer surface 44 of the eccentric element 42 for supporting the piston 48. The minimum distance E between the axis of rotation 17 and the outer surface of the eccentric element 42 is smaller than the radius R of the first section and / or the second section. In the illustration of the Fig. In the first section 45A and the second section 45B, the first section 45A and the second section 45B had the same radius. This can, of course, be deviated from, and the present invention is not limited to this, so that the first section 45A and the second section 45B can also have different radii. Thus, sliding the eccentric bearing 41 onto the outer surface 44 via the first section 45A or the second section 45B is initially not possible.

[0024] State of the art, as shown in the Fig. 3. This was made possible by increasing the minimum distance E' between the axis of rotation 17 and the outer surface 44 of the eccentric element 15, such that the outer surface 44 of the eccentric element 15 always protrudes beyond the concentric surface of the first and / or second section. Thus, in the prior art, it is easily possible to slide the eccentric bearing 41 onto the eccentric element 42 via the first or second section. However, this increases the size of the eccentric element 42 and makes the drive unit unnecessarily heavy and large.

[0025] This includes in the Fig. Three identical or identical elements are marked with the same reference symbols.

[0026] The following will refer again to the Fig.2. The disadvantages of the prior art are circumvented according to the present invention by the fact that the eccentric 15 is designed in two parts, comprising a first eccentric part 15A and a second eccentric part 15B, which are joined at a contact surface 47. In particular, the separation of the eccentric 15 into a first eccentric part 15A and a second eccentric part 15B takes place in the region of the eccentric element 42 and, in particular, within the eccentric bearing 41. Due to the two-part design, it is now possible to insert the first eccentric part 15A and the second eccentric element 15B into the eccentric bearing 41 from different sides. A projection of the eccentric surface 44 beyond the first section 45A and / or the second section 45B is therefore no longer necessary.

[0027] A method for assembling the eccentric according to the present invention may include the following steps: - Providing an initial eccentric element, - Inserting the first eccentric element into an eccentric bearing, - Providing a second eccentric element and inserting the second eccentric element into the eccentric bearing, with the first eccentric element and the second eccentric element being inserted into the eccentric bearing from different sides.

[0028] Subsequently, within the framework of the procedure, a first bearing 38A and a second bearing 38B can be connected to a corresponding section of the eccentric 15 for the purpose of supporting the eccentric 15.

[0029] The first eccentric part 15A and the second eccentric part 15B can be connected to each other by means of an insertion joint within an inner ring of the eccentric bearing 41. Alternatively, the first eccentric part 15A and the second eccentric part 15B can be connected to each other, for example, by screwing them together in an outer ring, wherein the eccentric surface 44 is formed by the outer ring and the outer ring has threads on its inner surface into which the first eccentric part and the second eccentric part can be screwed from different sides. Alternatively or additionally, a pin connection can be provided on the contact surface 47 by means of which the first eccentric element 15A is connected to a second eccentric element 15B.

[0030] Thus, the present invention provides a drive unit which can be designed compactly without reducing the power of the drive unit for an electro-hydraulic pressing device.

Claims

[1] Drive unit for a press for pressing a workpiece with a motor with a motor shaft, wherein the motor shaft is rotatable about a rotational axis, an eccentric, wherein the eccentric is connected to the motor shaft, the eccentric having an eccentric element which is eccentric to the axis of rotation of the motor shaft, such that a pump piston connected to the eccentric element is moved back and forth when the motor shaft rotates to pump a hydraulic fluid, characterized by the eccentric is formed from at least a first eccentric part and a second eccentric part. [2] Drive unit according to claim 1, characterized by , that the eccentric element is formed at least by the first eccentric part and the second eccentric part. [3] Drive unit according to claim 1 or 2, characterized by, that the first eccentric part and the second eccentric part are connected by means of a joining connection and / or screw connection and / or pin connection. [4] Drive unit according to one of claims 1 to 3, characterized by , that an eccentric bearing surrounds the eccentric element, wherein the first eccentric part and the second eccentric part are joined in the eccentric bearing. [5] Drive unit according to any one of claims 1 to 4, characterized by , that the eccentric has a first section which is connected to the motor shaft and is rotationally symmetric to the axis of rotation and a second section arranged opposite the eccentric element which is rotationally symmetric to the axis of rotation, wherein the eccentric is supported in the first section and in the second section. [6] Drive unit according to claim 5, characterized by, that the minimum radial extent of the eccentric element is smaller than the radial extent of the first section and / or the second section. [7] Drive unit according to claim 5 or 6, characterized by , that the maximum radial extent of the eccentric element is greater than the radial extent of the first section and / or the second section. [8] Drive unit according to one of claims 5 to 7, characterized by , that the diameter of the eccentric element is none or equal to the diameter of the rotor shaft and / or the first section and / or the second section. [9] Drive unit according to any one of claims 1 to 8, characterized by that the stroke of the eccentric is more than 2 mm and in particular more than 5 mm. [10] Pressing device for pressing workpieces with a drive unit according to one of claims 1 to 9, wherein a piston of a piston pump is connected to the eccentric, wherein the pressing device further has a reservoir for a hydraulic fluid, wherein the piston pump is arranged in a supply line that connects the reservoir to a working piston of the pressing device, so that the piston pump delivers hydraulic fluid from the reservoir to the working piston for the movement of the working piston.

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