WO2001083134A1

WO2001083134A1 - Impact machine ii

Info

Publication number: WO2001083134A1
Application number: PCT/SE2001/000895
Authority: WO
Inventors: Håkan OLSSON
Original assignee: Morphic Technologies Aktiebolag
Priority date: 2000-04-28
Filing date: 2001-04-26
Publication date: 2001-11-08
Also published as: AU2001252817A1

Abstract

The invention concerns an impact machine comprising an impact unit (1) with a ram (13) and an anvil (3) provided under the impact unit, on which anvil a tool unit (2) can be placed. More particularly the invention concerns an impact machine for working by the employment of a high kinetic energy, characterised in that the anvil assembly, which includes the anvil (3) and the tool unit (2) with tool an abject to be worked, is movable in the vertical direction, and that means are provided to move the anvil assembly upwards towards the ram to meet the ram as it is moving, simultaneously with the ram being moved downwards.

Description

IMP ACT MACHINE II

TECHNICAL FIELD

The invention concerns an impact machine comprising an impact unit with a ram and an anvil provided under the impact unit, on which anvil a tool unit can be placed. More particularly the invention concerns an impact machine which employs kinetic energy during its working.

PRIOR ART Impact machines for working by the employment of high kinetic energy are machines for working in the first place metal, such as cutting, punching, forming metal components, powder compaction, and similar operations, in which the velocity of a ram, which may consist of a press piston, may be essentially higher than in conventional presses. The working principle is based on the development of a very high kinetic energy of short duration instead of a high press force of long duration. The dynamic forces of short duration which are generated at the ram impact and which in impact machines of prior art are conveyed around in the system via stand and foundation may be several thousand times larger. In order to be able to absorb such large force pulses, impact machines of prior art are equipped with very strong and heavy stands and foundations according to principles which are common in connection with conventional presses. Nevertheless the dynamic, chock type force pulses that are developed in impact machines are not damped in such heavy, conventional systems. The stress on all joints therefore become very large, as well as on sensitive components, e.g. electronic components for controlling those hydraulic valves which usually form part of impact machines, which may cause a great risk of failure. Large, unwieldy stands also give rise to problems in connection with service, change of tool unit or of tool insets in the tool unit, changing the height of the impact machine above the tool unit, etc.

BRIEF DISCLOSURE OF THE INVENTION It is the purpose of the invention to address the above complex of problems. More particularly, the invention aims at achieving in the first place the following advantages:

- to counteract chock waves from the impact via the machine stand, and

- to reduce the total mass of the machine in comparison with known comparable impact machines. By counteracting the chock waves from the impact via the stand and instead utilizing the kinetic energies of the movable masses for the working of an object to be worked, the working can be made more efficient and increased working length of the entire machine be achieved.

Preferably it is also an object of the invention to design means for counteracting said chock waves, comprising replaceable units, so that the same impact machines can be used for anvil assemblies with varying masses, wherein the concept anvil assembly includes the anvil and a tool unit, which preferably is stationary relative to the anvil assembly, said tool unit comprising a tool, e.g. a die, and an object to be worked.

It is also a purpose to offer a solution of the above mentioned problems, particularly in connection with large impact machines, where normally very large and heavy stands and/or foundations are required.

It is a characteristic feature, according to an aspect of the invention, that the anvil assembly, in which, as mentioned, the anvil and a tool unit with tool and object to be worked are included, is movable in the vertical direction, and that means are provided to move the anvil assembly upwards towards the ram to meet the ram as it is moving, simultaneously with the ram being moved downwards.

In the tool assembly there can be provided an impact body which rests on a movable tool part, e.g. an upper punch, in the tool unit and transmits the kinetic energy of the ram to the tool part in connection with the working operation. The ram and the impact body are denominated a ram unit in the following. The impact body also may be integrated with the upper, movable tool part (punch). The machine may also be void of a separate impact body, wherein the ram is provided to strike directly on the upper, movable tool part (punch). Further it is conceivable that the ram is integrated with the upper movable tool part (punch) which in this case is included in the ram unit by definition.

It is also typical that said anvil assembly preferably has at least ten times larger mass than the impact piston and that the upwards directed velocity of the ram is essentially smaller, preferably at least ten times smaller than the downwards directed velocity of the ram when the upwards and the downwards directed, movable masses simultaneously hit the object to be worked in the tool unit.

More particularly there should for the momentums of the ram unit and for the anvil assembly (the said possible impact unit is not included in the anvil assembly), i.e. the momentums of the from above and from below, respectively, movable masses, apply a proportional condition which satisfies the following formula: mi x vi = m₂ x v₂, where mi is the mass of the ram unit, V! is the velocity of the ram unit when it hits the tool in the anvil assembly from above, m₂ is the mass of the anvil assembly, and v₂ is the velocity of the anvil assembly when it hits the tool in the tool unit from below.

More particularly the following should apply for the said formula mi x Vi = m₂ x v₂, namely that mi is the total mass of the units movable from above, vi is the velocity of the units movable from above when they hit the object to be worked in the tool, m₂ is the mass of the units movable from below, and v₂ is the velocity of the masses movable from below, when the masses movable from above hit the object to be worked.

In impact machines there is employed a technique which often is referred to as high velocity forming, because high velocities of the rams of impact machines generally are considered to be a prerequisite for the achievement of intended results in terms of forming a work. High velocities of the movable forming units, however, may imply a complication when working according to the counter striking principle, i.e. work with impact units which move towards one another during the striking/impact operation. The complication lies in the fact that the movements of the units which are movable towards one another must be synchronized and coordinated with great accuracy in terms of velocity (momentum) and position in order that the stroke shall be performed simoultainously with correct momentum of the masses which move towards one another, something which becomes increasingly difficult the higher the velocities of the moving units are.

An aspect of the invention is based on the consideration that the velocities of the movable units in the impact machines, which move against one another during the impact operation, need not at all be as large as has been considered necessary because of what is taught by prior art. Nor should the kinetic energies need to be correspondingly high, i.e. lower velocity shall not necessarily need to be compensated by correspondingly larger movable masses. With the same masses, according to this aspect of the invention, the velocity thus can be reduced from about of 5 to 10 meters per sec. of said ram to the order of 1 meter per sec, or more generally 0.5-2 meters per sec. The lower velocities thus improve the possibility to synchronize the movements of the movable units during the impact operation. Even though the velocities are radically reduced, the forming work nevertheless can be perfect, whether the working material is a powder or a solid body. Without binding the invention to any specific theory, it can be assumed that this is due to the good synchronization of the counter directed movements, which in turn has the result that the kinetic energy of the movable masses essentially can be used as effective forming work with small losses of energy to the machine foundation and stand.

Another favourable effect with the lower velocities of the movements that are movable towards one another, is that the ram travels can be shortened. This makes it possible to design the impact devices/the rams and the punches to form integrated units, as above mentioned. The punches in this case may be inserted into the upper and lower openings, respectively, of the die in the starting position for an impact operation, even if the punches are integrated with the impact devices/rams or corresponding, wherein the ram travels, i.e. the acceleration lengths, will be shorter than the axial length of the mould cavity of the die.

It shall thus be understood that the expressions high kinetic energy or very high kinetic energy are relative conceptions and shall be interpreted to mean adequate kinetic energy for the achievement of the effect in terms of forming work, which has been mentioned in the foregoing and which will be described more in detail in the following, detailed description of the invention.

Said means for moving the anvil assembly upwards, comprise at least a hydraulic lifting cylinder with a hydraulic piston for lifting the anvil by the action of the hydraulic pressure in a working chamber in said lifting cylinders. In order to provide an adequate hydraulic pressure in the working chamber/chambers of the lifting cylinder/cylinders suitably the pressure in the return chamber of the impact cylinder is employed, the return chamber being connected to the working chamber of the lifting cylinder/cylinders via a hydraulic circuit.

In the said hydraulic circuit there is preferably included a hydraulic pressure-/flow converter between the return chamber of the impact cylinder and the working chamber of the lifting cylinder/cylinders, said converter comprising a primary cylinder with a working chamber and a return chamber; and a secondary cylinder, the working chamber of the primary cylinder having an essentially larger cross-section area than the secondary cylinder which is connected to the working chamber of the lifting cylinder/cylinders. A particular advantage with the provision of such a pressure-/flow converter is that a unit of that type can be made exchangeable, wherein a possibility is created to chose converters adapted to varying demands owing to the total mass of the anvil assembly, which can vary because the impact machine preferably shall be possible to be used for different, heavy tool units or because of other circumstances. Through the arrangement of exchangeable hydraulic pressure-/flow converters it will also be possible, in the same machine, or with the use of the same lifting cylinders, to use different anvils, which may have different masses. However, a non-return valve with a parallel constriction should be provided after the outlet from the secondary cylinder in order to avoid reverse pressure pulses to the impact piston after the stroke.

Another possibility to adapt the machine so that an adequate chock wave counteraction is achieved for anvil assemblies having different masses, is to make also said lifting lifting cylinders exchangeable, or to make said cylinders exchangeable instead of said hydraulic pressure-/flow converter, in which case the exchangeable lifting cylinders have different hydraulic characteristica in terms of cross-section areas of the working chambers of the cylinders.

According to a preferred embodiment of the invention, the impact unit is suspended in a stand, on at least to stationary vertical columns, which extend through the movable anvil, which is movable relative to the stationary columns, which function as guides for the movable anvil. The anvil suitably has the shape of a rectangular slab; the columns, when they are four in number, suitably being located in the four corners of the anvil. The number of the columns, however, also may be fewer, however at least two. In the latter case, also a pair of guides in excess of the columns should be provided for guiding the impact unit and the anvil.

The lifting cylinders also should be at least two, preferably at least three and most preferably four, in order to avoid jamming. Also as far as the lifting cylinders are concerned, the four corners of the movable anvil is a suitable location. In the case when the columns are provided in the corners, it is conceivable that the columns extend through the lifting pistons in the lifting cylinders. Another conceivable location is in the centre between the columns, a short distance inside of the edges of the anvil.

A foundation can be provided under the anvil. According to an embodiment of the invention, the lifting cylinders are provided in such foundation, wherein the lifting cylinders can be caused to move upwards in order to perform the upwards directed movement of the anvil.

It is also possible to use the columns as stationary, through pistons in the lifting cylinders which in this case are provided in, or constitute integrated parts of the movable anvil. The columns in this case are secured in the foundation or corresponding under the anvil.

The impact unit can, as has been mentioned, be suspended on said columns. The impact unit in this case can be raised and lowered along the columns, which then can be utilized as through stationary piston rods in hydraulic cylinders which are mechanically connected to the impact unit. The hydraulic medium in these hydraulic cylinders therein also work as absorbers of said chock waves in connection with the stroke of the impact piston against the tool unit to the extent that such chock waves are not completely eliminated because of the counter-movement of the movable anvil in connection with the stroke, as has been described above. These functions - the possibility of lowering and raising the impact unit along the columns and the chock absorbing affect of the hydraulic medium in the lifting cylinders - are described in detail in the Swedish patent application No.: 0001560-2 of the same applicant, said patent application being incorporated in the present text by reference.

Further characteristic features, aspects of and advantages of the invention will be apparent from the following detailed description and from the appending patent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed description of the invention, reference will be made to the accompanying drawings, in which

Fig. 1 is a perspective view of the impact machine according to a preferred embodiment of the invention,

Fig. 2 is a side view of a movable anvil with a tool unit and a schematically shown impact piston, impact cylinder, and a hydraulic circuit for lifting the anvil,

Fig. 3 shows a view along the line rπ-ILT in Fig. 2 at a larger scale,

Fig. 4 illustrates a modified embodiment of the invention, and Fig. 5 is a view along the line V-V in Fig. 4 at a larger scale. In the drawings, only elements and functions of essential importance for the invention are shown, while other details have been omitted in order to that which is essential of the invention shall be more clear.

DESCRIPTION OF PREFERRED EMBODIMENTS

The impact unit according to the embodiment shown in Fig. 1 consists of the following main components: an impact unit 1, a tool unit 2 under the impact unit 1, resting on an anvil 3 which is movable in the vertical direction, a stand consisting of four vertical columns 4a, 4b which are secured in a foundation 6 under the anvil 3, and on each such column an elevator- and damping shock absorbing unit 5a, 5b slidably mounted on each said column and connected to the impact unit 1 via an arm 10. How these units are designed is described in detail in said Swedish patent application No. 0001560-2 and will not be described further in this text. The columns 4b are partitionable through a coupling 9, such that the entire impact unit 1 can be turned aside through rotation about the column 4a.

The central part 7 of the impact unit contains an impact cylinder 12 schematically shown in Fig. 2, said impact cylinder having an impact piston 13 which constitutes a ram and which can be accelerated hydraulically very quickly in order to be stricken with a sufficiently high, i.e. an adequate velocity, against an impact body 8 in the tool unit to perform the intended working of an object to be worked in a tool in the tool unit through a single stroke. The impact body 8 according to the embodiment rests on a movable tool part, more particularly on a movable, upper punch, and transmits the kinetic energy of the ram at the stroke to said movable tool part/punch and hence to the object to be worked in the tool. The impact piston/the ram 13 is designed as a through piston rod. The real piston, which is integrated with the piston rod, is designated 14. In the impact cylinder 12 there are a working chamber 15 and a return chamber 16. The working chamber 15 can be connected to a hydraulic pump or other pressure source P or to a tank T via a first conduit 18 and an electrically operated two-way valve 19. A second hydraulic conduit connected to the return chamber 16 is designated 20.

With reference now also to Fig. 3, a lifting cylinder is designated 25 and a lifting piston is designated 26, said lifting cylinder being secured in the foundation but is possibly exchangeable. The lifting piston 26 has the shape of a tubular sleeve. The column 4b extends through the lifting piston and is secured in the foundation 6. At the top the lifting piston 26 has a collar 27. The anvil 3 rests on the collars 27 of the four lifting pistons 26 which are identically designed. The columns 4a and 4b also extend through the movable anvil 3 which has a through hole 28 for the columns in each of the corners of the anvil. The anvil carries a lower, movable tool unit, which is not shown, more particularly a lower punch, which extends into the tool/die in the tool member 2.

The placing of the lifting devices of the anvil 3, i.e. the lifting cylinders 25 and the lifting pistons 26 in the corners is advantageous, because it provides the best condition for a good balance in connection with lifting and lowering of the anvil, which counteracts jamming. It is particularly advantageous in this connection to provide the lifting cylinders and the lifting pistons such that they become concentric with the columns 4a, 4b.

In the lifting cylinder 25 there are a working chamber 3 and a return chamber 31, which have a very small extension in the axial direction. Any larger extension is not required because the length of the stroke of the lifting pistons 27 need not be long.

In the embodiment according to Fig. 4 and 5, the columns 4a, 4b are employed as stationary piston rods in a lifting cylinder 25', which simply consists of a through boring in the movable anvil 3. Possibly said through boring may be provided with a lining, which then forms a lifting cylinder, which however is not shown in the example. In the ends, the cylinder 25' is provided with sealing end walls 33, 34 which are secured to the movable anvil 3. A working chamber is designated 30' and a return chamber is designated 31 '. It should be noted that these chambers are placed the other way round in comparison with the embodiment according to Fig. 3, because the hydraulic piston in this case consists of the stationary column 4b and the anvil 3' is provided to be lifted through development of the pressure in the working chamber 30' against the very piston 35, which in this case consists of a portion of the column 4b having larger diameter than within the regions of the chambers 30' and 31' .

A hydraulic pressureVflow converter 14 is provided in the hydraulic circuit between the return chamber 16 of the impact cylinder 12 and the working chambers 30 and 30' of the lifting cylinders 25 and 25', respectively. The converter is provided with two hydraulic cylinders; a primary cylinder 41 and a secondary cylinder 42. The latter one has a much smaller cross-section area than the primary cylinder 41. In the primary cylinder 41 there is a piston 43 with a piston rod, the end portion of which is designed as a plunger 44 which extends down into the secondary cylinder 42. A working chamber on the side turned from the piston rod is designated 45, and a return chamber on the opposite side is designated 46. A connection 52, including a constriction, is provided in the piston 43 between the working chamber 45 and the return chamber 46.

The working chamber 45 in the converter 40 is connected to the return chamber 16 of the lifting cylinder 12 via the hydraulic conduit 20. The return chamber of the converter 40 is connected to the two-way valve 19 via an hydraulic conduit 47. The secondary cylinder 42 of the converter 40 is connected to the working chamber 30 and 30' of the lifting cylinders 25 and 25' , respectively via a conduit 45 in which there is provided a constriction-non-return valve 53. The return chambers of the lifting cylinders, which chambers in these cylinders only work as drainage chambers, are connected to the drainage tank T for hydraulic fluid via conduits 49. A conduit from the valve 19 to the same tank T is designated 50. The hydraulic pump P or other pressure source is connected to the two-way valve 19 through a conduit 51.

The described impact machine and its system for counteracting chock waves when the machine operates, functions in the following way. The starting position is the position shown in Fig. 2 - Fig. 5. By manoeuvring the valve 19, the hydraulic pump 9 or other pressure source is connected to the working chamber 15 of the impact cylinder 12 via the conduits 51 and 18. The return chamber 46 of the converter 40 at the same time is connected to the drainage tank T via the conduit 47, the valve 19 and the conduit 50. When the working chamber 15 of the impact cylinder 12 is pressurized, the impact piston 13 is moved downwards and is accelerated to achieve a very high velocity. Hydraulic oil in the return chamber 16 is pressed by the piston 14 via the conduit 20 into the working chamber 45 in the primary cylinder 41 of the converter 40. This develops a pressure in the working chamber 45, which forces the piston 43 and hence the plunger 44 down into the secondary cylinder 42. Due to the fact that the ratio between the cross-section areas of the piston 43 and the plunder 44 is very large, the displacement of the piston 43 during the working stroke of the impact piston will be comparatively small and hence also the movement of the plunger 44 down into the secondary cylinder 42. The amount of hydraulic fluid that is displaced by the plunger 44 is forced through the conduit 48 and is distributed to and is pressed into the working chambers 30 and 30' of the lifting cylinders 25 and 25' , respectively. The total cross- section area of the working chambers 30, 30' can for example be equal with the cross- section area of the secondary cylinder 42. This causes the anvil 3 to be lifted by the lifting pistons 27, and directly in the embodiment according to Fig. 4 and 5, upwards at the same velocity as the plunger 44 is moved into the secondary chamber 42 in the converter 40. Through a suitable choice of the cross-section areas of the working chamber 15 and the return chamber 16 of the impact cylinder, of the working chamber

45 and the secondary cylinder 42 of the converter 40, and of the working chambers 30,

30' of the lifting cylinders, and under consideration of the counter pressures in the return chambers 16 and 46, the entire anvil assembly, which includes the anvil 3 and the tool unit 2, can be moved upwards and be accelerated such that the impact piston 13 will strike the impact body 8 with a velocity of the, impact piston 13 and of the anvil assembly satisfying the formula mj x vi = m₂ x v₂, where mi is the total mass of the units which are movable from above, vi is the velocity of the units which are movable from above, when they strike against the object to be worked, m₂ is the total mass of the units which are movable from below, and

V2 is the velocity of the masses which are movable from below when the from above movable units strike against the object to be worked.

EXAMPLE In a conceived case, the masses, the cross-section areas, and the stroke lengths were the following:

The pressure in the working chamber of the impact cylinder = 300 bar. The total mass mi of the impact piston 13, the impact body 8, and the upper punch =

350 kg.

The stroke length si of the impact piston 13 = 100 mm.

The displaced volume in the return chamber 16 of the impact cylinder = 500 cm^.

The cross-section area Ai of the working chamber 45 of the converter = 200 cm². The cross-section area A₂ of the secondary chamber 42 of the converter = 10 cm².

The cross-section area AB of the four working chambers 30, 30' of the four lifting cylinders 25, 25' = 50 cm².

The pressure in the working chamber 45 of the converter = about 19 bar.

The total mass of the anvil assembly __ 7000 kg.

When the above conditions apply, the anvil assembly, i.e. the anvil with the tool unit 2, will move upwards about 5 mm and achieve a velocity of 0,5 m/s when the ram unit (the impact piston 13 and the impact body 8) hits the punch under the impact body 8 at a velocity of 8 m/s. Thus the following applies for the formula mi x vi ≡ m₂ x v₂

350 x 8 « 7000 x 0,4 At the meeting between the ram unit and the object to be worked in the tool, the ram unit and the anvil assembly thus will have the same momentum which implies that any essential chock waves do not come off.

When the stroke has been performed, the valve 19 is immediately switched back to the starting position shown in Fig. 2. Herein the return chamber 46 of the converter 40 is connected to the hydraulic pump P via the conduit 47, the valve 19 and the conduit 51, and the working chamber 15 of the impact cylinder is connected to the drainage tank T via the conduit 18, the valve 19 and the conduit 50. The return- or drainage chamber 31, 31' is continuously connected to the drainage tank T via the conduit 49. The anvil assembly 2, 3 drops down under the influence of its large mass and forces the hydraulic fluid from the working chambers 30, 30' in the lifting cylinders back to the secondary chamber 42 of the converter 40 via the conduit 48. This causes the piston 43 to be lifted by the plunger 44, which drives the hydraulic fluid from the working chamber 45 via the conduit 20 to the return chamber 16, returning the impact piston 13 to its starting position. Also the pressure in the return chamber 46 of the converter, which chamber during this phase is connected to the hydraulic pump P, contributes in this return movement. In case of possible functional disorders, it is secured that the impact piston 13 is returned to its starting position because of the fact that the return chamber 45 of the converter slowly is pressurised by the hydraulic pump P via the constricted connection 52 in the piston 43 in the converter. The filling of the secondary chamber 42 is suitably secured through an adapted leakage in concerned gaps.

Claims

1. An impact machine comprising an impact unit (1) with a ram (13) and an anvil (3) provided under the impact unit, on which anvil a tool unit (2) can be placed, more particularly an impact machine which employs kinetic energy during its working, characterised in that the anvil assembly, which includes the anvil (3) and the tool unit (2) with tool and object to be worked, is movable in the vertical direction, and that means are provided to move the anvil assembly upwards the ram to meet the ram being moved downwards.

2. An impact machine according to claim 1, characterised in that the anvil assembly has at least ten times larger mass than the ram, and that the upwards directed velocity of the anvil is essentially lower, preferably at least ten times lower, than the downwards directed velocity of the ram, when the ram and the tool unit meet.

3. An impact machine according to claim 1 or 2, characterised in that the following formula apply for the velocities and the masses of the units which are movable from above and from below, respectively: mi x vi ≡ m₂ x v₂, where mi is the total mass of units which are movable from above, vi is the velocity of the units which are movable from above, when they strike against the object to be worked, m₂ is the total mass of the units which are movable from below, and

V₂ is the velocity of the masses which are movable from below when the from above movable units strike against the object to be worked.

4. An impact machine according to any of claims 1-3, characterised in that said means for moving the anvil assembly comprise at least a hydraulic lifting cylinder (25, 25' ) with a hydraulic piston (26, 35) for lifting the anvil under the influence of the hydraulic pressure in a working chamber (30, 30') in said lifting cylinder.

5. An impact machine according to any of claims 1-4, characterised in that a hydraulic pressure-/flow converter (40) is provided in a hydraulic circuit between an impact cylinder (12) for bringing about the movements of the ram (13) and said at least one lifting cylinder, that said converter comprises a primary cylinder with a working chamber, a return chamber, and a secondary cylinder, that the working chamber (45) has an essentially much larger cross-section area than the secondary cylinder (42) according to a certain proportional ratio, which is related to the masses of the impact piston and the anvil assembly in such a way that the anvil assembly is given a velocity in the opposite direction, which velocity is inversely proportioned to the ratio between on one hand the mass of the ram and any possible impact body and on the other hand the mass of the anvil assembly, and that the return chamber of the impact cylinder is connected to the working chamber of the converter, and that the secondary cylinder of the converter is connected to the working chamber of said at least one lifting cylinder.