EP2428290A1

EP2428290A1 - A cushioning arrangement for presses

Info

Publication number: EP2428290A1
Application number: EP11180851A
Authority: EP
Inventors: Sancar Yorukoglu; Hakan Demir
Original assignee: Coskunoz Metal Form Makina Enduestrive Tic AS
Current assignee: Coskunoz Metal Form Makina Enduestrive Tic AS
Priority date: 2010-09-13
Filing date: 2011-09-12
Publication date: 2012-03-14
Also published as: TR201007501A2

Abstract

The present invention is a press cushioning arrangement (20) which is embodied in the cushioning housing (11) of a press lower group (10) and which provides support to the blank holder through the rods (13) during the pressing process, characterized by comprising a cylinder body (21) positioned in said cushioning housing (11), and a plurality of pistons (22) whose lower ends are inside the cylinder chamber (211) defined by said cylinder body (21) and whose upper ends contact with the rods (13) corresponding to them during the cushioning process so that equal force is applied to each one by means of the hydraulic oil applied to said cylinder body (21).

Description

The present invention relates to presses and particularly relates to press cushioning arrangements which are embodied within a cushioning housing of the lower body of the press and which support the blank holder through the rods during the pressing process.

PRIOR ART

As known, presses comprise a stationary lower die and an upper die moved by a ram and work pieces are formed between said two dies. In detail, during the pressing application, work pieces are attached to a blank holder which moves downwardly together with the upper die when the upper die contacts the work piece. By means of this, undesired situations such as tearing of the work piece as a result of the sudden impact of the upper die while the work piece is held by blank holder during pressing work are eliminated.
Cushioning arrangements are utilized for absorbing the force from upper die so that the blank holder is moved downwardly in a controlled manner. Referring to prior art figure, such a cushioning arrangement essentially comprises a cushioning pad positioned on the lower part of the press; plurality of rods contacting said cushioning pad from the top and guided within the openings formed on the die coupling plate; two cushioning cylinders contacting said cushioning pad from the bottom; a hydraulic motor pump system providing hydraulic oil to said cylinders; and a guiding system which ensures reciprocating movement of the cushioning pad within a opening formed on the lower part of the press. Relevant inventions of said embodiment are disclosed in JP5057363 and JP11114700 .
Accordingly, cylinders, which are actuated by the hydraulic system, move the cushioning pad and rods on the cushioning pad upwardly prior to pressing work and thus rods hold the blank holder which is within the die. During the pressing work, upper die and blank holder are moved by the hydraulic press so that the sheet piece is formed between the dies. The cushioning pad is moved in the direction of the pressing force by means the pressing force during pressing. During this movement, valves which are present in the hydraulic system and which are already set according to cushioning pressure stabilize the pressure within the cylinders and excessive pressure is discharged via the valve. Thus, blank holder cushioning process is realized.
The embodiment has, however, certain drawbacks as detailed hereunder. Middle section of the lower bridge is emptied for the movement of the cushioning pad and the cushioning pad is guided within this section. Since the guiding embodiment occupies a part of said emptied section, guiding over a wide area cannot be ensured. Moreover, the guiding embodiment subjected to high pressing forces may be damaged in time, resulting in malfunctioning. On the other hand, in order not to face problems resulting from bending, the cushioning pad should be made relatively thick.
Another important drawback is that the cushioning pad cannot apply equal cushioning force to every point of blank holder via rods uniformly since the cushioning pad is supported at only two points by the cushioning cylinders. As a result, the cushioning pad moves with respect to point where higher force is applied and this impairs optimal cushioning functionality and causes guiding problems.
As a solution to this problem, in JP2192829 , a gas line is disclosed which connect gas chambers of cushioning cylinders so as to apply uniform pressure to cushioning pad. By means of this, it is proposed that equal pressure can be applied to the cushioning pad at plurality of points via plurality of cushioning cylinders. However, this system has a complex structure since a plurality of separate cylinder mechanisms is utilized and since these cylinders are connected to each other by means of a gas line.
Consequently, because of the abovementioned drawbacks, an improvement is required within relevant technical field.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is a novel cushioning arrangement for presses, in order to eliminate the above mentioned drawbacks and in order to bring new advantages to the related technical field.
An object of the present invention is to provide a cushioning arrangement which provides application of equal pressure to all of the rods which support the blank holder.
Another object of the present invention is to provide a cushioning arrangement which eliminates the usage of the cushioning pad and the guiding system in connection with it and thereby whose failure probability depending on the unbalanced loadings is less.
In order to realize all of the objects obtained from the abovementioned description and the below mentioned detailed description, the present invention is a press cushioning arrangement which is embodied in the cushioning housing of a press lower group and which provides support to the blank holder through the rods during the pressing process, characterized by comprising a cylinder body positioned in said cushioning housing, and a plurality of pistons whose lower ends are inside the cylinder chamber defined by said cylinder body and whose upper ends contact with the rods corresponding to them during the cushioning process so that equal force is applied to each one by means of the hydraulic oil applied to said cylinder body.
In another preferred embodiment of the present invention, the cushioning arrangement comprises a plurality of pistons in the cylinder body parts corresponding to the points without rod, in order to support the die coupling pad from the bottom during the cushioning process.
In another preferred embodiment of the present invention, said pistons' parts inside the cylinder chamber comprise a step so as to define an end part with a narrower diameter than the remaining part of the piston.
In another preferred embodiment of the present invention, said pistons' end inside the cylinder chamber comprises an upper peripheral surface, and a lower peripheral surface with a wider surface area than said upper peripheral surface. Thus, even if the pistons are rested onto the cylinder body base, when desired, they can be lifted by the hydraulic oil.
In another preferred embodiment of the present invention, there is an upper cover forming the top part of the cylinder body and there is a plurality of trunks which provide the bearing of the pistons on said upper cover.
In another preferred embodiment of the present invention, the pistons comprise a holding tab, in order to prevent the entry of the pistons to the openings in the die pads where the rods are placed.
In another preferred embodiment of the present invention, in order to fix the cylinder body to the cushioning housing, there is a connection plate which is fixed to the base of the cushioning housing and whereon the cylinder body is seated, and a connection element whose one end is fixed to said connection plate and whose other end is connected to said upper cover.
In another preferred embodiment of the present invention, there is at least one support piece which has at least one passage aperture thereon which provides hydraulic oil flow between two compartments and which separates the cylinder chamber into compartments.
In order for the embodiment of the subject matter invention and the advantages thereof together with the additional elements to be understood in the best manner, they should be evaluated with the figures whose description is given below.

BRIEF DESCRIPTION OF THE FIGURES

In Figure 1, the perspective view of a lower group of a press where the subject matter cushioning arrangement is applied is given.
In Figure 2a, the zoomed view of the subject matter cushioning arrangement is given.
In Figure 2b, the zoomed view of a piston in the subject matter cushioning arrangement is given.
In Figure 2c, an embodiment alternative to the embodiment given in Figure 2a is given.

REFERENCE NUMBERS

10: Press lower group
11: Cushioning housing
12: Die connection pad
121: Rod opening
13: Rod
20: Cushioning arrangement
21: Cylinder body
211: Cylinder chamber
212: Upper cover
213: Support piece
214: Passage aperture
215: Base part
22: Piston
221: Upper peripheral surface
222: Lower peripheral surface
223: End part
224: Holder tab
23: Trunk
231: Trunk body
232: Bearing element
233: Sealing element
24: Connection element
25: Connection plate
30: Hydraulic control block
40: Hydraulic pump
50: Drive element

THE DETAILED DESCRIPTION OF THE INVENTION

In this detailed explanation, the subject matter arrangement is explained with references to examples without forming any restrictive effect in order to make the subject more understandable. Accordingly, in the detailed description and figures below, the subject matter invention is assumed to be applied to a press. However, in alternative embodiments, the subject matter invention can also be used in any metal forming machine or system where there is cushioning need.
With reference to Figure 1, the press to which the subject matter cushioning arrangement (20) is applied comprises a press lower group (10) with a cushioning housing (11) wherein the cushioning arrangement (20) is embodied. On the upper surface of the press lower group (10), there is a die connection pad (12) whereon the lower die (not illustrated in the figure) is connected. On the die connection pad (12), there is a plurality of rod openings (121) which are formed in matrix structure, and through these openings (121), rods (13) pass. Each rod (13) is supported from the bottom part thereof by one of the pistons (22) in connection with the cylinder body (21) in the cushioning arrangement (20). As can be seen in Figure 1, in this exemplary application, the rods (13) are positioned so as to define a hollow rectangle. Accordingly, the empty area in the middle corresponds to the lower die, the blank holder (not illustrated in the figure) encompassing the lower die is supported from the part where the rods (13) exist. Accordingly, as known in the art, during the cushioning process, when the pressing process applies downward pressure on the pistons (22), the pistons (22) operate oppositely to the pressing process, and the cushioning process can be realized with the pressing process overcoming the cushioning process. Meanwhile, the blank holder where the work piece (not illustrated in the figure) is connected moves towards the lower die together with the upper die, and during pressing, the blank holder is supported by the cushioning arrangement (20). The drive required for the cushioning process is provided by the hydraulic oil applied to the cylinder body (21). Accordingly, the hydraulic oil is provided into the cylinder body (21) through the hydraulic control block (30) where elements like direction valves, pressure safety valves exist inside the hydraulic pump (40) which is rotated by a drive element (50).
Again with reference to Figure 1 and 2a, the subject matter cushioning arrangement (20) has a single and big cylinder body (21) which is placed to the cushioning housing (11) so as to fill all of the housing substantially. Accordingly, a plurality of pistons (22), where each one is in connection with a rod (13) or which extend until the die connection pad (12) where there is no rod (13), extend towards the cylinder chamber (211) defined by the cylinder body (21). As a result, thanks to this structure, when oil is applied to the cylinder body (21), equal oil pressure can be applied to all of the pistons (22).
With reference to Figure 2b, at each piston's (22) end inside the cylinder chamber (211), an upper peripheral surface (221), and a lower peripheral surface (222) which has a greater surface area than said upper peripheral surface (221) are embodied. Preferably, the lower and the upper peripheral surface (221) are one piece to each other so as to define a tapered end part. Thanks to the surface area difference in between, even if the pistons (22) are rested onto the cylinder body (21) base part (215), they can be lifted by the hydraulic oil when desired. Since, when hydraulic oil is applied to the cylinder body (21), the force of the oil pressure applied from down to up to the lower peripheral surface (222) can overcome the force applied to the upper peripheral surface (221) from up to down. In an alternative embodiment of the subject matter invention, the same process can also be realized only by forming an end part which is narrower than the remaining part of the piston (22).
On the other hand, in order to prevent the pistons (22) from entering into the openings (121) in the die pad (12) where the rods (13) are placed, a holding tab (224) is embodied at the upper end of the pistons (22).
With reference to Figure 2c, in an alternative embodiment of the subject matter invention, the cylinder chamber (211) is separated into plurality of compartments by means of plurality of support pieces (213) which are in plate form and which preferably extend orthogonally. On each support piece (213), there are the passage apertures (214) which provide the flow of hydraulic oil between two adjacent compartments. As a result, thanks to this structure, the cylinder body (21) becomes much more resistant against the pressing forces.
In another alternative embodiment of the subject matter invention, instead of a single cylinder body (21), plurality of cylinder bodies (21) can also be used. In this case, provided that the required sealing precautions are taken, in order for equal oil pressure to be applied to each cylinder body (21), openings permitting oil flow between the cylinder bodies (21) can be embodied. Or the cylinder bodies (21) can be connected to each other by an oil line.
Under the light of the structural details given above, the operation of the subject matter invention is as follows. During the cushioning process, the hydraulic oil applied to the cylinder chamber (211) applies equal force to each piston (22) and thus, equal force is applied to each rod (13) which is in connection to these pistons (22). As a result of this, the blank holder can be cushioned with an equal force from each point thereof. The pistons (22) which do not have a rod (13) at the opposite side thereof continue to move until the die connection pad (12) and at this point, the movements thereof is stopped by the pad. Thus, the pistons (22) which are not in connection with the rod (13) support the die connection pad (12) from below and thereby they increase resistance and strength. Thanks to this, die connection pads (12) with a smaller thickness when compared with the prior art can be used. On the other hand, the blank holder which is moved downwardly by the press during the cushioning process transfers the force through the rods (13) and it moves the pistons (22) inside the cylinder body (21) independently from each other in the pressing direction, thus, flexible cushioning is realized. For the return of the pistons (22) to the beginning position, preferably a spring (not illustrated in the figure) is used.
As a result, thanks to the flexible cushioning function provided, the unbalanced loading on the lower die is decreased, each area on the blank holder is held by a substantial force. In connection with this, since all of the pistons (22) are connected to a single cylinder body (21) during the cushioning process, equal cushioning force is provided at each piston (22). Moreover, in the subject matter cushioning system, since no cushioning pad is used, there is no need to use a guiding system. Thus, cushioning problem in a narrower area resulting from the guiding system is prevented and the possible accidents are prevented, thus, a better cushioning can be realized in a wider area.
In addition to these, in the present applications, in the cushioning process, during the pressing process overcoming the cushioning process, the hydraulic fluid inside the cylinder body (21) is brought to a tank by being taken from valves or hydro-motor and meanwhile, some of the pressing process is transformed into heat energy and discharged outside. Here, by using servo motor and energy transformation modules instead of standard motor, and by using pump-motor functioning in double direction instead of hydraulic pump (40), the energy discharged as heat is transformed into electrical energy, it can be used in the system or it can be fed back to the system by arranging the frequency thereof. Or it can be stored in the storing units in order to be used later.

Claims

A press cushioning arrangement (20) which is embodied in the cushioning housing (11) of a press lower group (10) and which provides support to the blank holder through the rods (13) during the pressing process, characterized by comprising a cylinder body (21) positioned in said cushioning housing (11), and a plurality of pistons (22) whose lower ends are inside the cylinder chamber (211) defined by said cylinder body (21) and whose upper ends contact with the rods (13) corresponding to them during the cushioning process so that equal force is applied to each one by means of the hydraulic oil applied to said cylinder body (21).
A cushioning arrangement (20) according to Claim 1, characterized in that the cushioning arrangement (20) comprises a plurality of pistons (22) in the cylinder body (21) parts corresponding to the points without rod (13), in order to support the die coupling pad (12) from the bottom during the cushioning process.
A cushioning arrangement (20) according to Claim 1 or 2, characterized in that said pistons' (22) parts inside the cylinder chamber (211) comprise a step so as to define an end part (223) with a narrower diameter than the remaining part of the piston (22).
A cushioning arrangement (20) according to Claim 1 or 3, characterized in that said pistons' (22) end inside the cylinder chamber (211) comprises an upper peripheral surface (221), and a lower peripheral surface (222) with a wider surface than said upper peripheral surface (221).
A cushioning arrangement (20) according to Claim 1, characterized by comprising an upper cover (212) forming the top part of the cylinder body (21) and there is a plurality of trunks (23) which provide the bearing of the pistons (22) on said upper cover (212).
A cushioning arrangement (20) according to Claim 5, characterized by comprising a connection plate (25) which is fixed to the base of the cushioning housing (11) and whereon the cylinder body (21) is seated, and a connection element (24) whose one end is fixed to said connection plate (25) and whose other end is connected to said upper cover (212), in order to fix the cylinder body (21) to the cushioning housing (11).
A cushioning arrangement (20) according to Claim 5, characterized in that the pistons (22) comprise a holding tab (224), in order to prevent the entry of the pistons (22) to the openings (121) in the die pad (12) where the rods (13) are placed.
A cushioning arrangement (20) according to Claim 1, by comprising at least one support piece (213) which has at least one passage aperture (214) thereon which provides hydraulic oil flow between two compartments and which separates the cylinder chamber (211) into compartments.
A cushioning arrangement (20) according to any of the preceding claims, characterized in that said cylinder body (21) have a size so as to substantially fill the cushioning housing (11).
A cushioning arrangement (20) according to Claim 1, characterized by comprising plurality of cylinder bodies (21) where each one is positioned so as to be adjacent to each other inside the cushioning housing (11).
A cushioning arrangement (20) according to Claim 10, characterized in that all of the cylinder bodies (21) are hydraulically connected to each other through a fluid line or a passage aperture (214).