As suggested, embodiments of the invention provide for the drive unit and the tool to be accelerated with the same simultaneous acceleration. Thus, the invention involves a considerably slower acceleration of the tool, compared to the acceleration obtained by processes with a drive unit to tool strike as mentioned above. Thereby, there is no need to consider the risk of excessive deformation of the tool caused by a strike from the drive unit. Therefore, the tool may possess a reduced stiffness, and thereby a reduced mass. In addition, drive unit may present a reduced mass, compared to a drive unit in a process with a drive unit to tool strike. As a result, the capacity of the system for driving the drive unit may be reduced.

In some embodiments, the tool is separable from the drive unit. The tool may be arranged to separate from the drive unit during a work material striking process involving the acceleration of the drive unit. The tool may be arranged to separate from the drive unit, before the tool strikes the work material. For example, where the drive unit accelerates upwards, the tool may be arranged to rest on top of the drive unit, without any fastening elements fixing the tool to the drive unit. Thereby, advantageous embodiments exemplified below, are enabled. However, in some embodiments, the tool may be fixed to the drive unit during the work material striking process. Thereby, the tool may be fixed to the drive unit by one or more releasable fastening elements, for example comprising bolts or similar. In such embodiments, the tool may be fixed to the drive unit when the tool strikes the work material.

As suggested, preferably, the drive unit is decelerated, before the tool strikes the work material, so as for the tool to separate from the drive unit before the tool strikes the work material. Thereby, the drive unit may continue towards the work material by means of inertia.

As suggested, preferably, the method comprises guiding the tool towards the work material, after the tool has separated from the drive unit. In some embodiments, the path of the tool may be controlled by a guiding arrangement. In some examples, the guiding arrangement comprises a plurality of pins, which are fixed to the tool. However, alternatives are possible. For example, a frame, surrounding the tool, or the path of the tool, may be arranged to guide the tool. Thereby, one or more guiding devices, which are fixed to the tool, may be arranged to engage with the frame while the tool moves along the frame. The guiding of the tool allows an accurate positioning of the tool onto the work material.

As suggested, preferably, the drive unit is decelerated so that the tool does not come into contact with the drive unit again, until after the tool has stricken the work material. Preferably, the drive unit does not reach a position in which it will be in contact with the tool, when the tool is in contact with the work material. Thereby, the energy imparted to the work material, for forming the work material, is provided by the tool, without any participation of the drive unit. Thus, the separation may provide for the drive unit being absent at the strike of the work material by the tool. Thereby, problems of known system, such as the risk of one or more repeated strokes by the drive unit, are eliminated.

As suggested, the drive unit may be arranged to be driven by a hydraulic system comprising a first chamber for hydraulically biasing the drive unit towards the work material. The method may comprise, for the acceleration of the drive unit, the hydraulic system being controlled so that hydraulic fluid is moved to the first chamber, wherein, for the drive unit deceleration, the hydraulic system is controlled so that the transport of hydraulic fluid towards the first chamber is reduced, but high enough to avoid cavitation of the hydraulic fluid. Thereby, fluid cavitation, which may be harmful to the process, may be effectively avoided.

As suggested, preferably, where the drive unit is arranged to be driven by a hydraulic system, the method comprises, for the deceleration, allowing a part of the drive unit to enter a braking chamber, and allowing thereby hydraulic fluid to be trapped in the braking chamber, whereby an increased pressure in the trapped fluid decelerates the drive unit. As suggested, for example, said part of the drive unit may be a waist. Thus, where the drive unit is arranged to be driven by a hydraulic system, the drive unit may be provided with a waist, the method comprising, for the deceleration, allowing the waist to enter a braking chamber, and allowing thereby hydraulic fluid to be trapped in the braking chamber, whereby an increased pressure in the trapped fluid decelerates the drive unit. Where a second chamber for biasing the drive unit away from the work material is provided, as suggested above, the braking chamber may be formed at an end of second chamber, in the direction towards the work material.

Preferably, the drive unit is accelerated upwards. As suggested, hence, the tool is also accelerated upwards. Thereby, said contact of the tool with the drive unit, during at least a major part of the acceleration, may be provided by the tool resting on the drive unit. Thereby, the tool may be held by the drive unit by gravity, and the acceleration. This simplifies the arrangement for the striking process. It should be noted however, that alternatively the drive unit and the tool may be accelerated in another direction, for example downwards, or sideways.

As suggested, where the drive unit is accelerated upwards, the method may comprise allowing the tool to fall back onto the drive unit after the strike of the work material by the tool. Preferably, the fall of the tool is damped as it approaches the drive unit. For this, a damping arrangement may be provided, as exemplified below. This softens the impact when the tool comes into contact with the drive unit, which may reduce wear.

As suggested, the method steps described above may form parts of a work material striking process. Where the drive unit is arranged to be driven by a hydraulic system comprising a first chamber for hydraulically biasing the drive unit towards the work material, and a valve arrangement for controlling the pressure in the first chamber, the method may comprise receiving signals indicative of one or more of the drive unit position, the drive unit velocity, the drive unit acceleration, the tool position, the tool velocity, the tool acceleration, the pressure in the first chamber, one or more response times of the valve arrangement, the ambient temperature, and a temperature of the hydraulic system oil. The method may further comprise storing at least some of the signals received during at least one work material striking process, and/or storing data provided as a result of processing of at least some of the signals received during at least one work material striking process, and adjusting, for a further striking process, the control of the valve arrangement, based at least partly on the stored signals and/or the stored data. The control of the valve arrangement may also be adjusted based partly on current sensor signals during the further striking process. Thereby the timing of valve actuations during the striking process may be accurate, in view of circumstances such as the temperature and the aging of the apparatus.

The objects are also reached with a computer program, a computer readable medium, or a control unit. The control unit may be provided as a single physical unit, or as a plurality of units, arranged to communicate with each other.

It should be noted that, although, in some embodiments, the method may be controlled by a control unit, in other embodiments, the method may be controlled mechanically. For example, the method may comprise hydraulically pressurizing a first chamber so as to bias the drive unit towards the work material. The method may further comprise, for a deceleration of the drive unit before the tool strikes the work material, allowing a part of the drive unit to enter a braking chamber, and allowing thereby hydraulic fluid to be trapped in the braking chamber, whereby an increased pressure in the trapped fluid decelerates the drive unit. In such embodiments, the step of controlling the hydraulic system so that the transport of hydraulic fluid towards the first chamber is reduced, may be omitted.

The objects are also reached with an apparatus for high velocity forming and/or cutting, by means of a tool and a drive unit, the apparatus being arranged to accelerate the drive unit to provide kinetic energy to the tool, for the tool to strike a work material, so as to form and/or cut the work material, wherein the apparatus is arranged so as for the tool to be in contact with the drive unit during at least a major part of the acceleration of the drive unit. Advantages with such an apparatus is understood from the description above of embodiments of the method according to the invention. In some embodiments, the tool is separable from the drive unit. The tool may be arranged to separate from the drive unit during a work material striking process involving the acceleration of the drive unit. The tool may be arranged to separate from the drive unit, before the tool strikes the work material. As suggested, the drive unit may be a plunger.

As suggested, preferably, the apparatus is arranged to decelerate the drive unit, before the tool strikes the work material, so as for the tool to separate from the drive unit. Preferably, a guiding arrangement is arranged to guide the tool towards the work material, after the tool has separated from the drive unit. Preferably, the drive unit is arranged to be driven by a hydraulic system, the apparatus being arranged to allow, for the deceleration, a part of the drive unit to enter a braking chamber, and to thereby allow hydraulic fluid to be trapped in the braking chamber. Said part of the drive unit may be a waist. Thus, the drive unit may be arranged to be driven by a hydraulic system, wherein the drive unit is provided with a waist, the apparatus being arranged to allow, for the deceleration, the waist to enter a braking chamber, and to thereby allow hydraulic fluid to be trapped in the braking chamber.

An aspect of the invention provides a method for material forming and/or cutting, by means of a tool and a drive unit, the method comprising operating the drive unit to provide kinetic energy to the tool, for the tool to strike a work material, so as to form and/or cut the work material, wherein that the tool is operatively dis-associated from the drive unit before the tool strikes the work material. The drive unit could be arranged to drive the tool electromagnetically. The drive unit could comprise an electromagnetic spool arranged to provide a magnetic field to drive the tool. Operatively dis-associating the tool from the drive unit could comprise controlling, e.g. disengaging, the electromagnetic spool so as to eliminate the electromagnetic field. In other embodiments, operating the drive unit could comprise moving the drive unit, as exemplified above.

The invention also provides a method for material forming and/or cutting, by means of a tool and a plunger, the method comprising accelerating the plunger to provide kinetic energy to the tool, for the tool to strike a work material, so as to form or cut the work material, wherein said method steps form parts of a work material striking process, wherein the plunger is arranged to be driven by a hydraulic system comprising a first chamber for hydraulically biasing the plunger towards the work material, and a valve arrangement for controlling the pressure in the first chamber, the method comprising receiving signals indicative of one or more of the plunger position, the plunger velocity, the plunger acceleration, the tool position, the tool velocity, the tool acceleration, the pressure in the first chamber, one or more response times of the valve arrangement, the ambient temperature, and a temperature of the hydraulic system oil, the method further comprising storing at least some of the signals received during at least one work material striking process, and/or storing data provided as a result of processing of at least some of the signals received during at least one work material striking process, and adjusting, for a further striking process, the control of the valve arrangement, based at least partly on the stored signals and/or the stored data.

Further advantages and advantageous features of the invention are disclosed in the following description and in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Below, embodiments of the invention will be described with reference to the drawings, in which:

FIG. 1 shows an apparatus for high velocity material forming and/or cutting according to an embodiment of the invention,

FIG. 2 is a flow diagram, depicting steps in a striking process of the apparatus in FIG. 1

FIG. 3 shows an apparatus for high velocity material forming and/or cutting according to another embodiment of the invention, and

FIG. 4 shows an apparatus for high velocity material forming and/or cutting according to yet another embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 shows an apparatus for high velocity material forming and/or cutting according to an embodiment of the invention. The apparatus comprises a frame 7. The frame is supported by a plurality of support devices 10. An anvil 6 is fixed to the frame. In this embodiment, the anvil 6 is fixed at the top of the frame 7.

A tool, herein referred to as a fixed tool 5, is mounted to the anvil. The fixed tool 5 is mounted to a lower side of the anvil 6. A movable tool 4, described closer below, is located below the fixed tool 5. The tools 4, 5 present complementary surfaces facing each other. A workpiece W is removably mounted to the fixed tool 5. The workpiece W may be mounted to the fixed tool 5 in any suitable manner, e.g. by clamping, or with vacuum. The workpiece W could be of a variety of types, for example a piece of sheet metal. The movable tool 4 is herein also referred to as a first tool. The fixed tool 5 is herein also referred to as a second tool. It should be noted that in some embodiments, also the second tool 5 could be movable.

In the embodiment shown in FIG. 1, a drive assembly comprising a cylinder housing 2 is mounted to the frame 7. Further, the drive assembly comprises a drive unit, hereinafter called plunger 1 that is arranged in the cylinder housing 2. The plunger 1 is elongated, and has, as understood from the description below, a varying width along its longitudinal axis. Preferably, any cross-section of the plunger is circular. The plunger 1 is arranged to move towards and away from the fixed tool 5, as described closer below.

Before providing kinetic energy to the tool 4 by moving or accelerating the drive unit to accelerate the tool, the tool may be positioned at a distance of at least 5 mm from the work material W. Preferably the tool is at a distance of at least 8 mm from the work material W. Most preferably the tool is at a distance of at least 12 mm from the work material W.

The plunger 1 is arranged to be driven by a hydraulic system. The hydraulic system comprises a first chamber 17 for biasing the plunger towards the workpiece, and a second chamber 18 for biasing the plunger away from the workpiece. The first and second chambers are formed by the cylinder housing 2 and the plunger 1. In this example, the workpiece is above the plunger. Thus, in this example, the first chamber 17 is located below the second chamber 18.

The hydraulic system comprises a hydraulic pump 16, for increasing the pressure of a hydraulic fluid in the system, to what is herein referred to as a system pressure pS. The hydraulic system further comprises a non-return valve 161 downstream of the hydraulic pump 16. The second chamber 18 is permanently connected to the system pressure pS. A hydraulic accumulator 13 is arranged to store hydraulic fluid at the system pressure. As understood from the description below, the accumulator 13 is provided to achieve a rapid pressure increase in the first chamber at a plunger acceleration.

The hydraulic system further comprises a valve arrangement. The valve arrangement comprises a first valve 11, and a second valve 12. The first valve 11 is connected to the first chamber 17 as well as to the second chamber 18. Also, the second valve 12 is connected to the first chamber 17 as well as to the second chamber 18. The valve arrangement is controllable by an electronic control unit CU. The valves 11, 12 are arranged to assume positions, so as to provide the steps described below. It is noted here that the valve arrangement 11, 12 can assume a position in which there is no communication between the first and second chambers 17, 18. The valves may be provided with draining devices for end bushing leaks.

At opposite ends, the cylinder housing and the plunger form axial slide bearings 21, 22. Thereby one of said bearings 21 delimits the first chamber 17, and is herein referred to as a first chamber bearing 21. The other of said bearings 22 delimits the second chamber 18, and is herein referred to as a second chamber bearing 22. At each of the first and second bearings 21, 22, draining conduits 9 are provided. An intermediate axial slide bearing 23 is formed, by the cylinder housing and the plunger, between the first and second chambers 17, 18. The bearings 21, 22, 23 allow an axial movement of the plunger 1 in relation to the cylinder housing 2.

The three bearings 21, 22, 23 are circular, as seen in a direction which is parallel to the movement direction of the plunger. Also, the bearings have mutually different diameters. More generally, the bearings have mutually different areas. In other words, circles formed by the circular shape of the bearings have mutually different areas. As a result, the effective areas of the plunger 1 in the first and second chambers differ. In this example, the area A23 of the intermediate bearing 23 is larger than the area A22 of the second bearing 22. In turn, the area A22 of the second bearing 22 is larger than the area A21 of the first bearing 21. Thereby, for balancing the plunger 1 in a static position, with the system pressure pS in the second chamber and an adjusted pressure pA in the first chamber, the adjusted pressure pA has to be such that

p
⁢

A
⋆

(

A
⁢
23

-

A
⁢
21

)

=

p
⁢

S
⋆

(

A
⁢
23

-

A
⁢
22

)

+

mp
⋆

⁢
g

- where mp is the mass of the plunger and g is the acceleration of gravity.

Reference is made also to FIG. 2, depicting steps in a striking process of the apparatus in FIG. 1, involving a strike by the movable tool 4 against the workpiece W and the fixed tool 5.

Before the strike, the movable tool 4 rests S1 on top of the plunger 1. In addition, before the strike, the movable tool 4 is at a distance from the fixed tool 5. Thereby, the plunger 1 and the movable tool 4 are S1 in, what is herein referred to as, respective starting positions.

The first valve 11 is in this example, a 4 way, 3 position valve. Before the strike, the first valve 11 is closed. Also, before the strike, the second chamber 18 is subjected to the system pressure pS. Simultaneously, the second valve 12 is used to control the adjusted pressure pA in the first chamber 17, so as to keep the plunger 1 is a fixed position, as detailed above. The second valve 12 is preferably a proportional valve. It is understood that, to keep the plunger 1 stationary, the adjusted pressure pA of the first chamber 17 may be lower than the system pressure pS. Thereby, the plunger may be kept in its starting position.

The acceleration of the plunger 1 is affected by adjusting the starting position of the plunger 1 and the system pressure pS.

Before the strike by the movable tool 4 is effected, the workpiece W is fixed S2 at the fixed tool 5. It is understood that in the starting position, the movable tool 4 is at a distance from the workpiece W.

When the strike is to commence, the first valve 11 and the second valve 12 are moved to a respective position, in which the respective ports P, with the system pressure pS, is connected with respective ports A, connected to the first chamber 17. Also, in the first valve 11, in said position, port B, with the system pressure pS, is connected to port T, connected to the first chamber 17. As a result, the plunger 1 will accelerate S3, with the movable tool 4, towards the workpiece W. Thereby, hydraulic fluid will flow to the first chamber 17, from the second chamber 18, and from the accumulator 13. Meanwhile, the second chamber 18 is provided with the system pressure pS. A force F moving the plunger can be expressed as

F
=

p
⁢

S
⋆

(

A
⁢
22

-

A
⁢
21

)

-

mp
⋆

⁢
g