EP0833061A1 - Hydraulic press with automatic oil compensation - Google Patents
Hydraulic press with automatic oil compensation Download PDFInfo
- Publication number
- EP0833061A1 EP0833061A1 EP97115451A EP97115451A EP0833061A1 EP 0833061 A1 EP0833061 A1 EP 0833061A1 EP 97115451 A EP97115451 A EP 97115451A EP 97115451 A EP97115451 A EP 97115451A EP 0833061 A1 EP0833061 A1 EP 0833061A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- piston
- aperture
- shutting
- hydraulic apparatus
- hydraulic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B1/00—Presses, using a press ram, characterised by the features of the drive therefor, pressure being transmitted directly, or through simple thrust or tension members only, to the press ram or platen
- B30B1/007—Presses, using a press ram, characterised by the features of the drive therefor, pressure being transmitted directly, or through simple thrust or tension members only, to the press ram or platen using a fluid connection between the drive means and the press ram
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
- F15B7/06—Details
- F15B7/10—Compensation of the liquid content in a system
Definitions
- the present invention refers to a hydraulic press for forming, mainly by deep-drawing and/or bending, sheet-metal plates, sheets or blanks.
- Such presses are implemented by combining hydraulically the hydraulic pressure generating means, which are usually constituted by a piston, which is driven so as to hermetically slide within the sealed space of a cylinder containing a hydraulic medium, and the actual working means, which comprise the forming or final tool.
- An apparatus for sheet-metal processing applications comprising a plurality of hydraulic balancing cylinders and corresponding pistons having their respective hydraulic chambers in communication with each other, in view of a more precise and synchronous operation of said pistons in precision forming operations, is further known from EP 0 718 055 to TOYOTA.
- the rise in the temperature of the oil depends, further to the actual working load, by a number of other variable and basically uncontrollable elements such as the initial transient state of the apparatus until the latter reaches steady-state conditions, the ambient temperature and the heat dissipation.
- a control module associated to a press in which a power cylinder is provided with an auxiliary compartment adapted to be connected with the working and pressure volume being defined by the displacement of a piston inside the same cylinder at least in the top dead center of said piston; in such a position of the piston, the hydraulic liquid contained in said working volume can therefore transfer its possible excess volume, brought about by the thermal expansion, towards said compartment.
- FIG. 2 Another generally known practice, so as this is shown in Figure 2, calls for the use of an oil reservoir associated to a stop valve, or electromagnetic stop valve, installed between the two above cited cylinders.
- a stop valve or electromagnetic stop valve, installed between the two above cited cylinders.
- Such a valve is opened for a very short period of time between the moment in which the piston (pump) relating to the die terminates its return stroke, and the moment in which the same piston starts its subsequent delivery stroke; during such a period of time, any possible increase in the volume tending to occur in the hydraulic fluid is practically counteracted and neutralized by a sufficient amount of fluid passing automatically from the hydraulic circuit to the oil reservoir, which thing is effective in restoring correct pressure conditions in the fluid and, as a result, maintaining a correct volume thereof.
- the present invention describes a type of apparatus having the characteristics as substantially described with particular reference to the appended claims.
- the apparatus comprises two working chambers 1 and 2 wherein in the first chamber 1 the hydraulic fluid contained therein is put under pressure by the respective piston 3, which may be driven in any of the plurality of manners known in the art.
- the so generated pressure is transmitted to the fluid contained in the chamber 2 through the conduit 4 which connects the inner volumes of said two chambers 1 and 2 so as to enable them to communicate with each other.
- the so transferred pressure actuates the working piston 5 associated to the chamber 2 and, therefore, the tool (not shown) that is solidly applied on to said piston 5.
- any variation in the volume of the hydraulic fluid will bring about a corresponding variation in the container that may be defined here as the aggregate of the volumes occupied by the fluid which is put under pressure , and in particular in the position and/or shape of the walls of said chambers, and therefore only in the position of the pistons, since it is assumed that the geometry of the chambers remains fixed and unaltered, except for the position of the pistons.
- the present invention therefore proposes the herein described solution , which does not propose a compensation of the total volume being occupied by the fluid, but rather the use of means capable of ensuring the constancy of the volume of the container , so as the latter has been defined above, and in particular of the two chambers 1 and 2 and the conduit 4, regardless of the overall volume of the fluid which may on the contrary vary within even relatively wide limits.
- This solution is based essentially on the fact that, for the volume of the container to be kept constant, the therein contained fluid in excess of a pre-determined volume is expelled or, better, purged out through at least an aperture that is provided in a wall of the same container, said aperture leading into an expansion (or even feeding) reservoir adapted to receive the excess amount of fluid flowing out through said aperture or, conversely, to feed in an amount of fluid as appropriate to restore the ideal conditions of total filing of said container when the fluid contracts.
- the pre-determined amount of fluid is established in accordance with the geometry of the volumes involved, the general architecture of the apparatus, the initial working position, and all other factors that intervene in the process and are generally well-known and normally considered by anyone skilled in the art when identifying and setting the operational conditions of the apparatus for achieving the desired results.
- a third chamber 16 that might be defined as a compensation chamber, which is totally enclosed, but provided with an aperture 17 capable of being closed with any shutting means 18 known in the art.
- Said shutting means 18 are elastically connected to the motion transmission means 13, or directly to the piston, by an elastic element 19 that is capable of transferring each movement and each position of the piston 11 to said shutting means 18 up to the point at which the latter tightly closes and seals said aperture 17.
- the so arranged apparatus needs following initial settings and adjustments: an initial position is first of all defined for the piston 11, to which a coinciding initial position is then found for the actuation piston.
- This enables an inner volume to be defined for the chambers 10, 16, as well as the expansion chambers and the related connections (in other words, the "container"), which has then to be kept not only constant under any operational condition whatsoever, but also, and in particular, independent from any volumetric variation of the hydraulic fluid contained therein.
- an advantageous solution consists in the use of a constructional and functional architecture as illustrated in Figures 5 and 5a.
- an aperture 20 is provided in the bottom of the piston 11 to enable the working chamber to be put in communication with the inner volume of the same piston.
- an element 21 which is adapted to shut said aperture and is provided with a rod 22 that protrudes from the upper outer perimeter 23 of the piston.
- the outer end portion of said rod is arranged so as to protrude from said outer perimeter by a length H that is similar to the distance which the same rod must cover in order to shut the aperture 20, when the thrust element 12 is separated from both said rod and the piston 11.
- the thrust element By continuing with its downward displacement, the thrust element then reaches a position in which it enters into contact with the upper outer perimeter 23 of the piston and, at the same time, the shutting element 21 shuts the aperture 20, thereby hermetically sealing the "container" of the hydraulic fluid, as shown in Figure 7.
- said thrust element then presses at the same time upon said rod 22 of the shutting element and the piston 11, which therefore start displacing from such a position in perfect synchronism thanks to the geometry of said component parts and the described initial settings (see Figure 8).
- shutting element 21 will by no means be capable of unduly clearing the aperture 20, owing to the rod thereabove being locked in its position relative to the piston by the resistance opposed by the thrust element 12.
- FIG. 12 Another variant may be as illustrated in Figure 12, wherein said elastic element is made to consist of one or more elastic reeds 30 attached with one end thereof against the side inner surface of the piston and with the other end against said rod.
- Figure 13 teaches to arrange the contact zone between the thrust element 12 and the rod 22 in a position which, under any operational condition, is situated inside the volume of the cylinder 11.
- the first problem relates to the difficulty lying in the actual ability of making the moment at which the thrust element 12 touches and starts to push the top edge of the piston 11 (and therefore starts the compression of the fluid in the working chamber 10) exactly coincide with the moment at which the lower end portion of the rod 22 hermetically shuts the aperture 20 in the bottom of the same piston, thereby once and for all defining the fixed volume of the afore defined container .
- the second problem is inherent to the illustrated configuration which makes use nof a flexible conduit 4 to connect the working chamber 10, which sustains the pressure induced by the piston 11, with the chamber 2 which converts such a pressure into a force acting upon the head portion of the working piston 5.
- Such a flexible conduit although useful in view of a more convenient operability and arrangement of the involved organs, is inherently provided with walls that are not totally rigid, so that the absolute constancy of the volume of the container , when the latter is under pressure, is seriously impaired by said walls of the conduit 4 yielding in a slight, but anyway still perceptible manner.
- the present invention proposes a solution that is based on a more compact, one-piece configuration of the press.
- a portion 2/16 which might be defined as an equalization oil passage portion, and which is therefore included in said container , has a completely sealed construction, but for the provision of an aperture 2/17, which is best to be seen in Figure 17, where the thrust element 2/12 has been considerably raised with respect to such an aperture.
- Said aperture 2/17 is capable of being closed with any appropriate shutting means 2/18 known in the art.
- Motion transmission means 2/13 are provided between said thrust element 2/12 and said shutting means 2/18 and are so configured as to be capable of detecting whether said thrust element is sufficiently, ie. by an appropriate value, raised from the piston 2/11 or is in its lowest position from which it starts to press upon said piston.
- the thrust element 2/12 is so arranged as to be able to first act, while moving downwards, on the motion transmission means 2/13 and, only after it has fully actuated such means, it then actuates also said piston 2/11 in correspondence of the contact zones 2/11a and 2/11b thereof.
- the means 2/13 are adapted to transfer the movement imparted thereto by said thrust element to said shutting means 2/18 up to the extent of causing the latter to fully and tightly shut the aperture 2/17.
- the thrust element 2/12 and the motion transmission means 2/13 are two organs that move orthogonally, and their movement is transferred by means of two mating surfaces 2/12a and 2/13a, that are inclined with respect to the angle formed by the movement of said organs, so that the cam effect originated by their rubbing against each other brings about the desired displacement of the motion transmission means 2/13, which are represented as a slide in this case, in the desired direction, ie. rightwards in the Figures which reference is being made to.
- Said slide 2/13 is adapted to move within a respective guide 2/20 which is open on a lower portion thereof and from which there is protruding a projection 2/21 that is provided with an inclined lower side, too.
- Such a projection, the aperture 2/17 and the shutting means 2/18 are sized and arranged so that, according to the position of the thust element and, as a consequence, the slide 2/13, said projection 2/21 presses said sphere 2/18 downwards for the latter to clear the aperture 2/17 or enables said sphere 2/18 to rise until it eventually shuts said aperture.
- an initial position is first of all defined for the piston 2/11, to which a coinciding initial position is then found for the actuation piston 2/15.
- This enables an inner volume to be defined for the chambers 2/10 and 2/14, the conduit 2/4 and the portion 2/16 (in other words, the "container"), which has then to be kept not only constant under any operating condition whatsoever, but also, and in particular, independent of any volumetric variation of the hydraulic fluid contained therein.
- shutting means 2/18 it is at this point necessary for a position of the shutting means 2/18 to be adjusted, along with the position of the therewith associated organs, ie. the slide 2/13 and the thrust element 2/12, in such a manner that the same shutting means are then able to hermetically shut the aperture 2/17.
- said associated organs it is also necessary for said associated organs to be articulated in such an initial position in such a manner that, each time that the thrust element 2/12 rises starting from said initial position, it causes said sphere 2/18 to move downwards, owing to the pushing effect exerted by said projection 2/21, so as to clear the aperture 2/17.
- the shutting means 2/18 represented by a sphere, are contained in an enlargement 2/23 of the top end of the portion 2/16 extending from said conduit 2/4, and said enlargement comprises walls 2/24 oriented towards said aperture 2/17; furthermore, an elastic separation means 2/19, preferably a cylindrical spiral spring, is engaged between said shutting means 2/18 and said walls, so that said shutting means is in all cases forced to shut the aperture 2/17 when so enabled by the position of the slide 2/13.
- an elastic separation means 2/19 preferably a cylindrical spiral spring
- Second elastic means 2/26 are further provided which are adapted to act on said motion transmission means 2/13 in such a manner as to force it to take the position to which a state of the aperture 2/17 corresponds in which the same aperture is not shut by said shutting means 2/18 appropriately pushed inwards by said projection 2/21, when said shutting means 2/18 are not moved away from said position by said thrust element 2/12.
- the shutting means can be advantageously constituted by a wedge 2/28 capable of sliding within the enlargement 2/23 of the top end of said portion 2/16; when the motion transmission means are pushed backwards, it releases the movement of said wedge which, by making also use of the side walls of said enlargement 2/23 as a guide, perfectly fits into the aperture 2/17, thereby shutting it tightly.
- the shutting means are constituted by the same motion transmission means 2/13 that are formed by an actuator capable of sliding, also as a small piston, within the respective guide 2/20.
- Said small piston is configured with two prominent and opposite portions 2/38 and 2/48, which are arranged and sized in such a manner that, in a first operational position shown in Figure 20, said portions plug the passage between the portion of conduit 2/16 and either the outside ambient or an appropriate sealed expansion chamber 2/200.
- Such a configuration is of course made to correspond to the position of the slide displaced by the lowering motion of said thrust element 2/12, whereas, with reference to Figure 21, when said thrust element is raised and separated from the slide 2/13, the latter elastically moves into such a position as to clear the respective passages toward the expansion chamber 2/200 and the portion of conduit 2/16 from the respective plugging prominent portions 2/38 and 2/48.
- FIG. 22 and 23 A further embodying variant is illustrated in Figures 22 and 23, wherein the clearness and the simplicity of the afore given illustrations and explanations are such as to exempt from giving further explanations.
- the motion transmission means 2/13 are formed by a rocker lever hinged on an axis 2/35 and having the tappet end 2/36 adapted to be actuated by the inclined surface 2/12a of said thrust element 2/12, whereas the opposite end 2/37 is adapted to actuate said plugging means 2/18, which may in turn be configured exactly as the sphere that is substantially represented in Figures 14 to 17.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- General Engineering & Computer Science (AREA)
- Press Drives And Press Lines (AREA)
- Presses And Accessory Devices Thereof (AREA)
- Actuator (AREA)
- Reciprocating Pumps (AREA)
- Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
Abstract
Description
- Figures 1 and 2 are schematical views of two different configurations of an apparatus according to prior-art technique;
- Figure 3 is a schematical view of the main component parts of an apparatus according to the prior art and not provided with any means for the correction of variations in the volumes of the hydraulic fluid;
- Figure 4 is a schematical view of the architecture and the function of the sub-assemblies of a press according to the present invention;
- Figures 5 and 5a are views of two subsequent operating states, respectively, of an improved variant of the organs of the cylinder (pump) shown in Figure 4;
- Figures 6 through to 10 are views illustrating a sequence of five subsequent operating states of the apparatus shown in Figures 5 and 5a;
- Figure 11 is a view of a variant in the construction of the cylinder (pump) shown in Figure 5;
- Figure 12 is a view of a further variant in the construction of the cylinder (pump) of Figure 5;
- Figure 13 is a view of yet another variant in the construction of the cylinder (pump) of Figure 5;
- Figure 14 is a schematical view of the architecture and the arrangement of the component parts of a module according to a further variant of the present invention, in a first operational state thereof;
- Figures 15 and 16 are schematical views of the arrangement of the component parts of the above cited module, in a second and third operational state thereof, respectively;
- Figure 17 is a magnified view of a detail of the module of Figure 14;
- the pairs of Figures 18-19, 20-21 and 22-23 are views of corresponding constructive and operational variants of the solution illustrated in the preceding Figures 16 and 17.
Claims (18)
- Hydraulic apparatus comprising:a first chamber (10) for the compression of the hydraulic fluid,a second chamber for the expansion of the same hydraulic fluid,a sealed conduit connecting the inner volumes of said two chambers with each other,a piston slidably arranged within said first chamber, adapted to slide hermetically relative to the inner walls thereof and tightly compress the hydraulic fluid contained therein,a thrust element (12) adapted to press upon the outer perimeter (23) of said piston,a container adapted to delimit the surfaces containing the hydraulic fluid that is put under pressure,
characterized in thatsaid container is provided with an aperture (17) that enables the inner volume thereof to communicate with the outside ambient, or with a tightly sealed expansion chamber (2/200),shutting means (18, 2/28) are provided that are capable of shutting said aperture (17),said shutting means are linked with motion transmission means (13) comprising move-away means (19, 2/25, 2/26) adapted to automatically keep said shutting means open when said means (13) are disengaged from said thrust element, said motion transmission means being adapted to transfer the positions that can be taken by said piston (11) to said shutting means until the latter eventually tightly shut the aperture (17, 20). - Hydraulic apparatus according to claim 1, characterized in that it is capable of going into a first operational state in which said thrust element does not act either on said motion transmission means (13) or on said piston, a second operational state in which said thrust element acts on said means so as to induce said shutting means (18) to shut said aperture (17), while however not acting on said piston yet, and a third operational state in which said thrust element eventually acts on said piston, thereby inducing it to reduce the inner volume of said first chamber (10), while keeping said shutting means (18) in their shut condition.
- Hydraulic apparatus according to claim 2, characterized in thatsaid piston is a hollow tubular element,said aperture (20) is provided in the hydraulic thrust wall of said piston and said shutting means (18) are a shutting element (21) provided with a rod (22) protruding from the upper outer perimeter (23) of the piston.
- Hydraulic apparatus according to claim 3, characterized in that said move-away means (19) or lifting means (25) consist of at least an elastic element arranged to act between said piston and said rod.
- Hydraulic apparatus according to claim 4, characterized in that said elastic element consists of a spiral spring accomodating said rod and retained on one side by appropriate retaining means (26) arranged thereon, and on the other side on a portion of the inner surface of the piston circumscribing said aperture (20).
- Hydraulic apparatus according to any of the preceding claims, characterized in that said elastic element is formed by at least an elastic reed (30) arranged between said shutting means or element (18, 21) and a point which is integral with the press.
- Hydraulic apparatus according to claim 4, characterized in that said move-away or lifting means are formed by at least an elastic reed (30) arranged between a point of said rod and a zone on the inner surface of said piston.
- Hydraulic apparatus according to any of the preceding claims, characterized in that said move-away means are formed by at least a floating element (29) applied to said rod or said motion transmission means (13).
- Hydraulic apparatus according to any of the preceding claims 3 to 8, characterized in that the contact and thrust zone between said thrust element (12) and the rod (22) is in all cases kept inside said piston.
- Hydraulic apparatus according to claim 1 or 2, characterized in that said aperture is provided on an enclosed portion (2/16) extending from said sealed conduit (2/4).
- Hydraulic apparatus according to claim 10, characterized in that said shutting means comprise a valve in the shape of a sphere (2/18) or of a wedge (2/28) contained in said enclosed portion (2/16) and adapted to take at least two distinct positions, ie. a first position in which said aperture is not shut, and a second position in which said aperture is shut by said valve.
- Hydraulic apparatus according to claim 11, characterized in that said valve is contained in an enlargement (2/23) of said enclosed portion (2/16), said enlargement being provided with walls (2/24) oriented towards said aperture, and that said elastic separation means (19) are engaged between said walls and said valve.
- Hydraulic apparatus according to claim 12, characterized in that said elastic separation means (19) are formed by a cylindrical spiral spring.
- Hydraulic apparatus according to any of the claims 1, 2 or 10, characterized in that a side (2/12a) of said thrust element is adapted to engage a corresponding side (2/13a) of said motion transmission means (2/13) comprising a slide, with respect to which it acts in a cam-like manner, said sides (2/12a, 2/13a) being inclined relative to the direction of movement of said means and said thrust element so as to be able to slide on at least a portion of the respective surfaces.
- Hydraulic apparatus according to claims 14, characterized in that there are provided second elastic means (2/26) acting on said motion transmission means (2/13) and adapted to force the latter to automatically move into a position enabling the passage of hydraulic fluid through said aperture during said first operational state in which said thrust element is not acting on said motion transmission means.
- Hydraulic apparatus according to claim 14 or 15, characterized in that said motion transmission means (2/13) are themselves forming said shutting means, which are provided with prominent portions (2/38, 2/48) that are arranged and sized so that, in a first operational position of said motion transmission means, said prominent portions plug the passageway between said enclosed portion (2/16) and the expansion chamber (2/200) and, in a second operational position thereof, a passage of hydraulic fluid between said enclosed portion (2/16) and the expansion chamber (2/200) is on the contrary enabled.
- Hydraulic apparatus according to any of the claims 1 2 or 10, characterized in that the motion transmission means (2/13) comprise a rocker lever hinged on an intermediate axis (2/35) and having a tappet end (2/36) adapted to be actuated by said inclined side (2/12a) of said thrust element (2/12), whereas the opposite end (2/37) thereof is adapted to actuate said shutting means (2/18), which are preferably configured in the shape of a sphere.
- Hydraulic apparatus according to any of the preceding claims, characterized in that said expansion chamber (2/200) is kept at a pressure which is slightly above the atmospheric pressure.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IT96PN000055 IT1289394B1 (en) | 1996-09-26 | 1996-09-26 | Hydraulic press for forming sheet metal plates or blanks by deep-drawing and bending - has arrangement which compensates the oil level by ensuring the constancy of the volume of the oil container by expelling or feeding fluid out of or into the container |
ITPN960055 | 1996-09-26 | ||
ITPN970012U | 1997-02-19 | ||
IT97PN000012 IT243413Y1 (en) | 1997-02-19 | 1997-02-19 | HYDRAULIC OPERATING MODULE WITH AUTOMATIC OIL VOLUME COMPENSATION |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0833061A1 true EP0833061A1 (en) | 1998-04-01 |
EP0833061B1 EP0833061B1 (en) | 2001-11-14 |
Family
ID=26331932
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP97115451A Expired - Lifetime EP0833061B1 (en) | 1996-09-26 | 1997-09-06 | Hydraulic press with automatic oil compensation |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0833061B1 (en) |
AT (1) | ATE208857T1 (en) |
DE (1) | DE69708242T2 (en) |
ES (1) | ES2167656T3 (en) |
PT (1) | PT833061E (en) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB542871A (en) * | 1940-07-26 | 1942-01-29 | James Henry Pratt | Improvements in hydraulic control mechanisms |
DE3002850A1 (en) * | 1980-01-26 | 1981-07-30 | Audi Nsu Auto Union Ag, 7107 Neckarsulm | Hydraulic cylinder for vehicle clutch - has piston sealed to cylinder by bellows to reduce wear and prolong life |
EP0251796A2 (en) * | 1986-06-27 | 1988-01-07 | Rodney Linval | Improvements in or relating to punches and presses |
WO1994025260A1 (en) * | 1993-04-26 | 1994-11-10 | Danly Corporation | Press-driven tool module, in particular press-driven cross-punching or bending unit |
-
1997
- 1997-09-06 EP EP97115451A patent/EP0833061B1/en not_active Expired - Lifetime
- 1997-09-06 DE DE69708242T patent/DE69708242T2/en not_active Expired - Fee Related
- 1997-09-06 ES ES97115451T patent/ES2167656T3/en not_active Expired - Lifetime
- 1997-09-06 AT AT97115451T patent/ATE208857T1/en not_active IP Right Cessation
- 1997-09-06 PT PT97115451T patent/PT833061E/en unknown
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB542871A (en) * | 1940-07-26 | 1942-01-29 | James Henry Pratt | Improvements in hydraulic control mechanisms |
DE3002850A1 (en) * | 1980-01-26 | 1981-07-30 | Audi Nsu Auto Union Ag, 7107 Neckarsulm | Hydraulic cylinder for vehicle clutch - has piston sealed to cylinder by bellows to reduce wear and prolong life |
EP0251796A2 (en) * | 1986-06-27 | 1988-01-07 | Rodney Linval | Improvements in or relating to punches and presses |
WO1994025260A1 (en) * | 1993-04-26 | 1994-11-10 | Danly Corporation | Press-driven tool module, in particular press-driven cross-punching or bending unit |
Also Published As
Publication number | Publication date |
---|---|
DE69708242T2 (en) | 2002-05-02 |
PT833061E (en) | 2002-04-29 |
ATE208857T1 (en) | 2001-11-15 |
DE69708242D1 (en) | 2001-12-20 |
ES2167656T3 (en) | 2002-05-16 |
EP0833061B1 (en) | 2001-11-14 |
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