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(11) | EP 2 255 960 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Press with a pre-stressed frame and method for mounting said press |
| (57) A press provided with a structure comprising a table (2), an upper crossbar (4),
and at least two interposed lateral spacers (3) which define, together with the table
(2) and the upper crossbar (4) a passage (100) having a longitudinal axis (A); the
press structure comprising a stage of predisposed the table (2) and the upper crossbar
(4) at a predetermined reciprocal initial distance defined by the spacers (3) or by
other suitable means, and being characterised in that it comprises further stages of: realising at least a resistance ring (30); coupling
the resistance ring (30) to the press structure such that it envelops at least a portion
of the table (2) and at least a portion of the upper crossbar (4); reciprocally distancing
the table (2) and the upper crossbar (4) in contrast with the resistance ring (30),
such that the resistance ring (30) is subjected to traction, and interposing at least
a further spacer between the table (2) and the upper crossbar (4) in order to impose
therebetween a reciprocal distance which is greater than the initial reciprocal distance,
such as to maintain the resistance ring (30) in traction.
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[0002] The invention relates to all types of press, among which for example presses for cold-forming metals, presses for plastic materials and in particular ceramic presses.
[0003] As is known, presses comprise a rigid structure conformed substantially as a portal, which affords a passage through which the articles to be pressed are progressively passed.
[0004] The inlet and outlet direction of the articles is parallel to the longitudinal axis of the passage.
[0005] In the type of press which most particularly relates to the present invention, the rigid structure of the press generally comprises a table and an upper cross bar which are maintained parallel and reciprocally distanced by at least two uprights or lateral spacers, and which are connected together by a resistance ring comprising one or more windings of a flexible element, such as a steel tape or cable, which envelops both the upper crossbar and the table.
[0006] The rigid structure of the press is destined to support a die, which generally comprises a lower half-die fixed on the table, and an upper half-die which is fixed on a mobile crossbar which mobile crossbar is connected to the fixed upper crossbar of the structure by means of one or more hydraulic actuators destined to move it in a vertical direction.
[0007] During each pressing stage the upper half-die is pressed against the lower half-die, such that by reaction the resistance spring of the press is drawn in traction.
[0008] To improve this traction state, in the prior art the flexible element of the resistance ring is placed in traction during its winding such as to pre-compress the lateral spacers between the table and the upper crossbar.
[0009] In this way, during the application of the pressing load, the traction to which the flexible element is subjected increases, while the compression force to which the lateral spacers are subjected decreases.
[0010] In practice, the traction force, which is the more dangerous force, is entirely supported by the flexible element which exhibits high-level mechanical characteristics and a small section, while the lateral spacers, which possess lesser mechanical characteristics, are subjected only to the compression stress, which creates fewer problems, especially as regards fatigue stresses. Notwithstanding the above, this pre-compression system exhibits some drawbacks.
[0011] A first of these drawbacks consists in the difficultly of realising the resistance ring on structures having large dimensions.
[0012] At present the resistance ring is realised by rotating the rigid press structure and winding the flexible ring about the structure, while keeping the ring tensioned. This implies the need to use sufficiently large binding machines which are also sufficiently resistant and powerful to manage the size and weight of the press. If the dimensions and weight of the press exceed certain limits, the binding machines become so large and expensive as to render the whole operation economically disadvantageous.
[0013] A further drawback consists in the difficulty of adequately pre-compressing the lateral spacers of the rigid structure during winding.
[0014] The pre-compression of the lateral spacers is proportional to the tension applied on the flexible element and to the overall resistant section, i.e. the transversal section of the flexible element multiplied by the number of windings. The desired pre-compression level can be obtained by a few windings of a large-section flexible element, or by many windings of a small-section flexible element.
[0015] To subject a large-section flexible element to traction, very powerful and expensive binding machines are required. However, if a small-section flexible element is used, much time is required in order to perform all of the winding turns needed.
[0016] A further drawback consists in the difficulty of replacing the structural components of the press, once it is assembled.
[0017] As the flexible element is directly wound on the rigid structure of the press, the replacement of a structural element has normally to be preceded by the dismounting of the flexible element following a new binding operation.
[0018] A further drawback consists in the poor accessibility of certain zones of the rigid press structure.
[0019] This is because the flexible element is wound about the rigid structure of the press in such as way as to form a resistance ring the axis of which is parallel to the longitudinal axis of the rigid structure, i.e. parallel to the inlet and outlet direction of the articles into and out of the press.
[0020] The flexible element develops parallel to the upper crossbar, runs adjacent along the lateral spacers, and passes below the table, forming one or more windings which are coaxial and which substantially frame the portal defined by the rigid structure of the press.
[0021] This arrangement enables the passage of the portal to be left completely open, such as to allow inlet and outlet of the articles, which pass internally of the resistance ring which surrounds the portal.
[0022] On the negative side, the windings of the flexible element almost completely cover the sides of the rigid structure, some components of which are therefore hidden and are accessible only if the flexible element is dismounted.
[0023] The components of the rigid structure must also be provided with a receiving channel for the windings of the flexible element, which complicates and further limits the geometry of the press.
[0024] The aim of the present invention is to obviate or at least mitigate the above-mentioned drawbacks, with a solution which is simple, rational and relatively inexpensive.
[0025] These aims are attained by the characteristics of the invention as reported in the independent claims. The dependent claims delineate preferred and/or particularly advantageous aspects of the invention.
[0026] Firstly, the invention makes available a new method for mounting a rigid structure of a press, which comprises stages of:
predisposing the table and the upper crossbar of the press at a predetermined reciprocal initial distance by interposing at least a first spacer or other suitable means;
realising, separately, at least a resistance ring having adequate characteristics of resistance to traction;
coupling the resistance ring to the table and to the upper crossbar such that the ring winds around at least a portion of the table and at least a portion of the upper crossbar;
reciprocally distancing the table and the upper crossbar in opposition to the resistance ring, such as to subject the ring to traction; and interposing, between the table and the upper crossbar, at least a second spacer in order to set a reciprocal distance between them which is greater than the initial distance, such as to maintain the resistance ring in traction.
[0028] Thanks to this solution the main drawbacks in the prior art are obviated. Firstly, the resistance ring can be coupled to the rigid structure without rotating the press in order to wind the flexible element.
[0029] It follows that machines for rotating the rigid structure are not required, which reduces the costs and resolves the difficulties connected with the pre-compression of large-size presses.
[0030] Secondly, the resistance ring can be mounted on the rigid structure of the press without being at the same time set in traction, as it is already set in traction thanks to the following reciprocal distancing between the table and the upper crossbar.
[0031] In a particularly advantageous aspect of the invention, the resistance ring is coupled to the crossbar and the table with the axis of the ring being orientated transversally with respect to the longitudinal axis of the press, such as to realise a configuration in which the inlet and outlet direction of the manufactured articles does not pass through the resistance ring.
[0032] The invention does not however exclude the possibility that the resistance ring be coupled to the crossbar and to the table with the axis thereof orientated parallel to the longitudinal axis of the press, thus obtaining a configuration which is similar to that of the prior art in which the inlet and outlet direction of the manufactured articles passes through the resistance ring.
[0033] The resistance ring can also be a modular ring destined to be stacked in a pack together with other identical resistance rings.
[0034] As mentioned herein above, the resistance ring is realised by one or more windings of a flexible element, such as for example a cable or a steel tape.
[0035] In particular, realising the resistance ring preferably comprises stages of:
predisposing an assembly of rigid components for forming a provisional support frame; and
winding the flexible element about the provisional support frame such as to bind the rigid components making it up together.
[0036] Thanks to this solution, the table and the upper crossbar of the press can be bound simply and rapidly, while preparing the provisional support frame separately with the flexible element wound on it, and then mounting the thus-obtained group directly on the press.
[0037] The shape and dimensions of the group formed by the provisional support frame and the flexible element can be selected and optimised such as not to interfere with the other components of the press and not to create difficulties of accessibility.
[0038] The group formed by the provisional support frame and the flexible element can also be dismounted and remounted on the press without having to repeat the binding operation, thus facilitating maintenance and/or if necessary the replacement of the other structural organs of the press.
[0039] During the winding of the provisional support frame, the flexible element can be subjected to a slight traction, with does not however correspond to the final pre-tensioning which is desired for the press, but serves only to keep the rigid components of the provisional support frame together, and to enable easy movement of the group.
[0040] Therefore the winding of the flexible resistant element on the provisional support frame can be realised using very much smaller, simpler and inexpensive machines with respect to those used in the prior art.
[0042] The press is commonly provided with a rigid portal structure which comprises a table, a fixed upper crossbar and at least two interposed lateral spacers which define, together with the table and the upper crossbar, a passage having a longitudinal axis, which is the longitudinal axis of the press.
[0043] With the invention, the upper crossbar and the table are reciprocally connected by at least two resistance rings, each of which winds about at least a portion of the upper crossbar and at least a portion of table, such that the axes of the resistance rings are orientated transversally with respect to the longitudinal axis of the press, and are preferably perpendicular thereto. The resistance rings are further reciprocally distanced such as to at least partially leave open the passage which is defined by the table and the upper crossbar with the lateral spacers interposed.
[0044] Thanks to this solution, the two resistance rings can effectively bind the table and the upper crossbar, thus significantly reducing problems of accessibility and the geometrical constraints of the press.
[0045] As they develop with a transversal axis, the resistance rings cover only a small portion of the rigid structure of the press, which is thus almost entirely accessible without having to dismount them.
[0046] Further, as they are reciprocally distanced, the resistance rings guarantee a stable binding, while however leaving the passage free for advancing the manufactured articles in both inlet and outlet.
[0047] The resistance rings arranged with a transversal axis also have very much smaller dimensions that the single resistance ring of the prior art, and can therefore be made much more easily.
[0048] Although it is preferable to realise these resistance rings with the innovative method delineated herein above, the invention also includes the possibility of making the rings directly on the press, using traditional modes.
[0049] Further characteristics and advantages of the invention will better emerge from a reading of the following description, provided by way of non-limiting example, with the aid of the figures illustrated in the tables of drawings.
Figure 1 is a schematic frontal view of a press of the invention.
Figure 2 is section II-II of figure 1.
Figure 3 is a schematic frontal view of a resistance ring of the invention.
Figure 4 is section IV-IV of figure 3.
Figures 5, 6, 7 and 8 are schematic frontal views of the press of figure 1, shown during four successive stages for obtaining the precompression.
Figures 5A, 6A, 7A and 8A are respectively section V-V of figure 5, section VI-VI of figure 6, section VII-VII of figure 7, and section VIII-VIII of figure 8.
[0050] In the accompanying figures of the drawings a press 1 for ceramic dies is illustrated, without excluding the possibility for the invention to be applied to other types of press too, for example presses for cold-forming metals and other presses for plastic materials.
[0051] The press 1 comprises a rigid structure substantially shaped as a portal delimiting a passage 100 having a longitudinal axis A.
[0052] The manufactured articles to be pressed are advanced through the passage 100 in an inlet and outlet direction which is parallel to the longitudinal axis A. The rigid structure schematically comprises a table 2 and a fixed upper crossbar 4 which are maintained parallel and distanced by two uprights, or lateral spacers 3.
[0053] A mobile crossbar 5 is connected to the upper crossbar 4, which mobile crossbar is activated by hydraulic actuators 6 to move in a vertical direction with respect to the underlying table 2.
[0054] The rigid structure of the press is destined to support a ceramic die, which generally comprises a lower die which is fixed on the table 2 and an upper die which is fixed on the mobile crossbar 6.
[0055] In the invention the table 2 and the upper crossbar 4 are predisposed at a predetermined reciprocal initial distance.
[0056] In the illustrated example, this operation is obtained by assembling the structure of figure 1 and 2, such that the lateral spacers 3 which are interposed between the table and the upper crossbar 4 define the initial distance.
[0057] Alternatively, the initial distance can be obtained by positioning the table 2 and the upper crossbar 4 on a mounting template.
[0058] The invention then includes predisposing two connecting groups 10 of the type illustrated in figure 3 and 4.
[0060] The shorter sides of the support frame 20 are realised by a pair of semicircular block elements 21 arranged specularly to one another, while the longer sides are realised by a pair of provisional parallel lateral bars 22 separating the two semicircular elements 21.
[0061] Each connecting group 10 further comprises a flexible element 30, provided with good characteristics of resistance and traction, which is wound about the support frame 20 such as to realise overall a resistance ring.
[0062] The resistance ring develops in a plane which is parallel to the lie plane of the support frame 20 and is received and retained in a channel 23 which is delimited by two flanges fashioned along the external sides of the semicircular elements 21.
[0063] In the illustrated example, the flexible element 30 is a small plate or a steel ring-wound tape forming a single circumference about the support frame 20. Alternatively, the flexible element 30 might be constituted by several winding circumferences of a cable or steel tape, or any other suitable element.
[0064] In general terms, the transversal section and the number of windings of the flexible element 30 about the support frame 20 are chosen on the basis of the level of the tension to be borne after being installed on the rigid structure of the press 1.
[0065] In the preparation of the connecting group 10, the flexible element 30 is wound about the support frame 20 such as to bind the semicircular elements 21 and the lateral bars 22 in a pack-form, thus obtaining a structural stability which is sufficient to move the connecting group as a single body.
[0066] This characteristic facilitates the following mounting operations of the connecting group 10 on the rigid structure of the press 1, and renders further fastening means between the semicircular elements 21 and the lateral bars 22 superfluous.
[0067] In order to obtain the binding, the flexible element 30 is preferably subjected to a slight traction during the stage of winding the support frame 20.
[0068] This traction does not correspond to the pretensioning to be obtained on the press 1, but serves only to block the semicircular elements 21 against the lateral bars 22.
[0070] In particular, the tensioning values in play are such as not to lead to substantial technical difficulties, thus enabling the use of very simple and economical binding machines, including in the case in which a flexible element 30 having rather a large section is chosen.
[0071] As illustrated in figure 5, a first connecting group 10 is inserted on a flank of the rigid structure of the press 1, such that the support frame 20 contains a shoulder of the upper crossbar 4, a shoulder of the table 2, and the lateral spacer 3 which is interposed between them.
[0072] The second connecting group 10 is inserted in the same way on the opposite flank of the rigid structure of the press 1.
[0073] In this way, the resistance rings formed by the flexible elements 30 are transversally orientated, i.e. they have axes that are transversal to the longitudinal axis A of the press 1, and in the present example perpendicular. The resistance rings are further reciprocally distanced along the direction of the axes thereof, such as not to obstruct the passage defined by the rigid structure of the press and thus enable the manufactured articles to advance. In particular, the resistance rings are positioned at opposite ends of the upper crossbar 4 and the table 2, where they surround a respective lateral spacer 3.
[0074] As illustrated in figure 5A, the support frames 20 of the connecting groups 10 are initially coupled to the rigid structure of the press 1, with a small amount of vertical play.
[0075] After the coupling of the connecting groups 10, a hydraulic jack 7 is inserted vertically-orientated between the table 2 and the upper crossbar 4.
[0076] In the illustrated example, the hydraulic jack 7 is rested on the table 2 and acts directly against the mobile crossbar 5, which is rested on the upper crossbar 4 by means of interposing two rigid blocks 8.
[0077] The hydraulic jack 7 is activated to raise and distance the upper crossbar 4 from the lateral spacers 3 and the table (see figure 6A), in contrast with the flexible elements 30 of the connecting groups 10.
[0078] In this way, the resistance rings formed by the flexible elements 30 are placed in traction and slightly lengthen.
[0079] The semicircular elements 21 of the support frame 20 thus distance reciprocally, detaching from the relative uprights 22.
[0080] While maintaining the upper crossbar 4 raised, the lateral bars 22 of both the connecting groups 10 are removed, after which two further rigid spacers 9 of equal thickness are predisposed, which are singly inserted in the space left free between each lateral spacer 3 and the upper crossbar 4 of the press (figure 7A).
[0081] When these operations are finished, the hydraulic jack 7 is shortened and removed, such as to leave the upper crossbar 4 to rest on the rigid spacers 9 and 3.
[0082] In this way, the upper crossbar 4 is constrained to be at a distance from the table 2 which is greater than the initial distance by a same quantity as the thickness of the spacers 9.
[0083] This thickness is chosen such that the resistance rings formed by the flexible elements 30 remain in traction, compressing the lateral spacers 3 between the upper crossbar 4 and the table 2, and thus preloading the whole rigid structure of the press 1.
[0084] Naturally the thickness of the spacers 9 is chosen on the basis of the preload value to be applied to the rigid structure of the press 1.
[0085] Obviously a technical expert in the sector could bring numerous modifications of a technical-applicational nature to the press 1 and the relative mounting method, without its forsaking the ambit of the invention as claimed herein below.
[0086] If for example the table 2 and the upper crossbar 4 were initially positioned on a mounting template, it would be possible to place the resistance rings realised by the flexible elements 30 in traction, and thereafter interpose only two height spacers between the upper crossbar 4 and the table 2, equal to the sum of the previously-described spacers 3 and 9.
1. A method for mounting a press structure, the press structure comprising a table (2),
an upper crossbar (4), and at least two interposed lateral spacers (3) which define,
together with the table (2) and the upper crossbar (4) a passage (100) having a longitudinal
axis (A), the method for mounting the press structure comprising a step of predisposing
the table (2) and the upper crossbar (4) at a predetermined reciprocal initial distance
defined by lateral spacers (3)between the table and the crossbar, and being characterised in that it comprises further steps of:
separately realising at least a resistance ring (30), the realization of said resistance ring comprising the step of realizing a support frame (20) comprising at least two block elements (21) separated by two lateral bars (22), and of winding a flexible element about the support frame (20) such as to bind the block elements (21) and the lateral bars (22) making them up together; and
coupling the support frame (20) to the press structure such that the resistance ring (30) envelops at least a portion of the table (2) and at least a portion of the upper crossbar (4); and
reciprocally distancing the table (2) and the upper crossbar (4) in contrast with the resistance ring (30), such that the resistance ring (30) is subjected to traction; and
interposing at least a further spacer (9) between the table (2) and the upper crossbar (4) in order to impose there-between a reciprocal distance which is greater than the initial reciprocal distance, such as to maintain the resistance ring (30) in traction.
2. The method of claim 1, characterised in that the resistance ring (30) is coupled such that an axis thereof is orientated parallel
to the longitudinal axis (A) of the press structure.
3. The method of claim 1, characterised in that the resistance ring (30) is coupled such that the axis thereof is orientated transversally
to the longitudinal axis (A) of the press structure.
4. The method of claim 3, characterised in that it comprises realising at least two of the resistance rings (30), and coupling them
to the press structure such that they are distanced from one another, in order to
leave the passage (100) of the press structure at least partially open.
5. The method of claim 1, characterised in that the resistance ring (30) comprises one or more windings of a flexible element.
6. The method of claim 5, characterised in that the flexible element is a flexible cable.
7. The method of claim 5, characterised in that the flexible element is a flexible tape.
8. The method of claim 5, characterised in that realising the resistance ring (30) comprises stages of:
predisposing an assembly of rigid components (21, 22) for forming a support frame (20); and
winding the flexible element about the support frame (20) such as to bind the rigid components (21, 22) making up the flexible element together.
9. The method of claim 8, characterised in that the support frame (20) comprises at least a receiving channel (23) for the flexible
element which is wound about the said support frame (20).
10. A press comprising a rigid structure which comprises a table (2), and at least two
interposed lateral spacers (3) which define, together with the table (2) and an upper
crossbar (4), a passage (100) having a longitudinal axis (A), characterised in that the upper crossbar (4) and the table (2) are reciprocally connected by at least two
resistance rings (30), each of which resistance rings (30) comprises a flexible element
winding about a support frame (20) that is coupled to the press structure such that
the resistance ring (30) winds about at least a portion of the upper crossbar (4)
and at least a portion of the table (2) and such that the axis of the resistance ring
(30) is orientated transversally with respect to the longitudinal axis (A) of the
press structure, each support frame comprising at least two block elements (21) separated
by two disposable lateral bars (22) made together by the flexible element wound thereon."
11. The press of claim 10, characterised in that the resistance rings (30) are positioned at opposite ends of the upper crossbar (4).
12. The press of claim 10, characterised in that each of the resistance rings (30) winds about a respective lateral spacer (3) of
the press structure.
13. The press of claim 10, characterised in that each of the resistance rings (30) comprises one or more windings of a flexible element.
14. The press of claim 10, characterised in that the lateral spacers comprise two aligned portions (3, 9).