| WO/1986/007006 | METHOD AND APPARATUS FOR EXTRUSION |
| JP60018207 | ROLLING MILL |
| JP59166320 | MANUFACTURE OF LITHIUM SHEET |
RUSSELL, Derek (Algrena Gard 489, Aspa Bruk, S-696 93, SE)
PERSSON, Anders (Segelvägen 25, Vreta Kloster, S-590 77, SE)
RUSSELL, Derek (Algrena Gard 489, Aspa Bruk, S-696 93, SE)
CLAIMS
1. A device for use in a metal extruder, comprising a die block (17) adapted for extrusion of metal into a product (30), such as a strip, said product (30) comprising parts (34a, 34b) designed to be post- extrusion disconnected from each other, c h a r a c t e r i z e d in that said device further comprises a groove former (24a) arranged toform a longitudinal first groove (32a) between said parts (34a, 34b).
2. The device as claimed in claim 1 , wherein the groove former (24a) is arranged to form said first groove (32a) at a location in relation to said die block (17) where said product (30) has not yet been cooled down to room temperature after extrusion.
3. The device as claimed in claim 2, wherein the groove former (24a) comprises a local narrowing of a die aperture (20) of said die block (17), said narrowing having a profile corresponding to a profile of said first groove (32a).
4. The device as claimed in any one of the preceding claims, wherein the groove former is arranged to form the first groove (32a) to be tapered with a tapering depth and a narrow, preferably acute, bottom.
5. The device as claimed in claim 4, wherein the groove former is arranged to form the tapered first groove (32a) to open up at an angle (α) that is in the range of about 60° to about 120°.
6. The device as claimed in any one of claims 4-5, wherein the groove former is arranged to form the first groove (32a) to have a substantially triangular cross section.
7. The device as claimed in any one of the preceding claims, wherein the groove former is arranged to form the first groove (32a) to have a bottom end having a radius that is less than about 1 mm, or less than about 0.5 mm, or less than about 0.1 mm, or less than about 0.05 mm, or less than about 0.01 mm.
8. The device as claimed in any one of the preceding claims, wherein the groove former is arranged to form the first groove such that the product along the bottom of the first groove (32a) has a thickness (t) that is less than about 50% of the thickness (T) of said product (30) adjacent to and longitudinally along said first groove (32a).
9. The device as claimed in any one of the preceding claims, wherein the groove former is arranged to form the first groove such that a maximum lateral width (w) of the first groove (32a) is significantly less, such as less than about 5 %, or less than about 4 %, or less than about 3 %, or less than about 2 %, or less than about 1 % of a largest lateral extension (W) of said product (30).
10. The device as claimed in any one of the preceding claims, said device further comprising a second groove former (24b) arranged to form a second groove (32b), preferably having a substantially identical profile as the first groove (32a) and preferably oppositely arranged the first groove (32a) on an opposite side of said product (30).
11. A method for producing a metal product (30), such as a strip, comprising parts (34a, 34b) designed to be post-extrusion disconnected from each other, said method comprising: feeding (101) metal to a die block (17) of a metal extruder; extruding (103) metal through said die block (17) to form said product
(30); c h a r a c t e r i z e d by forming (105) a longitudinal first groove (32a) between said parts (34a, 34b).
12. The method as claimed in claim 11 , wherein forming (105) of the groove is taking part before said product (30) has been cooled down to room temperature.
13. An extruded metal product (30), such as a strip, comprising parts (34a, 34b) designed to be post-extrusion disconnected from each other, c h a r a c t e r i z e d in that said product (30) has a longitudinal first groove (32a) separating said parts (34a, 34b).
14. The extruded metal product (30) as claimed in claim 13, wherein the first groove (32a) has been formed in said product (30) before said product was cooled down to room temperature after extrusion, and preferably formed during extrusion. |
METAL EXTRUSION OF PRODUCT COMPRISING PARTS DESIGNED TO BE POST-EXTRUSION DISCONNECTED FROM EACH OTHER
Technical field
The present disclosure relates to metal extrusion, more specifically it relates to extrusion of metal into a product, such as a strip, comprising parts designed to be post-extrusion disconnected from each other.
Background
A today predominant continuous metal extruding machine, or simply metal extruder, of rotary extrusion type, well known in the art, is manufactured by the company H. Folke Sandelin® and marketed under the trademark HANSSON-ROBERTSON®.
A conventional HANSSON-ROBERTSON® machine comprises i.a. a motor driven extrusion screw in a housing, a die block, temperature control means, a melting pot and a feed pipe. The extrusion screw is driven to rotate inside the screw housing. The screw is rotatably supported in a bearing housing and extends from the bearing housing towards the die block. Melted metal is arranged to be fed, via the feed pipe, into the screw housing to fill spaces between the outer surface of the screw and the inner surfaces of the screw housing. The temperature control means enables control of the temperature of the metal in the screw housing, i.a. so that it can be transported by the screw (typically by keeping the metal in plastic state), and to allow for control of the extrusion process, and thereby, in the end, also quality of the extruded product. The rotation of the screw transports the metal towards the die block under high pressure and the screw terminates at an inlet to the die block. For extrusion into cable sheath, the die block comprises means for turning the flow of the metal, typically plastic lead, 90-degrees, so that the flow direction becomes substantially perpendicular to the axial (metal transport or extrusion) direction of the screw, thereby enabling forming the cable sheath onto a cable being transported in the perpendicular direction through the die block.
US 6,797,403 discloses production of a lead alloy strip for fabrication of battery electrodes, using a HANSSON-ROBERTSON® extruder instead of more conventional strip production methods such as ram-press extrusion. An
advantage of the HANSSON-ROBERTSON® extruder is that it allows for good control of the process through i.a. machine parameter adjustments, which in turn allows for extrusion products having a desired microstructure and a strip with very accurate physical dimensions can be produced. In US 6,797,403 it is disclosed that a conventional extruder with die block as above for cable sheath production was modified to allow for strip production of planar high-quality lead alloy strip of desired profile. For example, the extruded strip can be produced with strip thickness tolerances of ±0.025 mm and thus an exact width required can be produced without trimming edges that risk to negatively affect properties near the edges. For even better control of, in particular grain sizes, the modified system in US 6,797,403 includes a cooling system for rapidly cooling the strip under controlled conditions. The cooled extrusion strip is slit and expanded into a diamond grid mesh.
Summary of invention
A metal extruder is comparatively expensive and typically a very big investment. Owing to this, such equipment is often operated in production over as long time periods as possible to achieve high throughput and high degree of utilization of the extruder. Parallel production of extruded products using a single extruder is an interesting option instead of duplicating the extruder. However, the difficulty to accomplish multiple product from a single extruding machine may vary depending on the desired profile of the extruded product. Also, in practice it is typically required to extrude a product as a single piece. However, post extrusion separation, e.g. by cutting, has tendency to negatively affect properties near edges of separation and thus it can be hard to reach the same quality degree as when producing a single piece product.
A general object of the invention is thus to present a solution that enables increased throughput of continuous metal extrusion products. A more specific object is to present a solution where products can be extruded in parallel in one piece using a single continuous extruder and which piece can be post extrusion separated into the products with no, or at least with low, negative impact on quality compared to a case where only one product is extruded at the same time. The invention is defined by the appended independent claims.
Preferred embodiments are set forth in the dependent claims and in the following description and drawings.
Hence, according to a first aspect, there is provided a device for use in a metal extruder, comprising a die block adapted for extrusion of metal into a product, such as a strip, said product comprising parts designed to be post- extrusion disconnected from each other. Said device further comprises a groove former arranged to form a longitudinal first groove between said parts. According to a second aspect there is provided a method for producing a metal product, such as a strip, comprising parts designed to be post- extrusion disconnected from each other, said method comprising feeding metal to a die block of a metal extruder; extruding metal through said die block to form said product; and forming a longitudinal first groove between said parts.
According to a third aspect here is provided an extruded metal product, such as a strip, comprising parts designed to be post-extrusion disconnected from each other, where said product has a longitudinal first groove separating said parts.
By "groove between parts" is meant that the groove as such does not belong to any of said parts. By "longitudinal" is here meant along the extrusion output direction. The first groove facilitates post-extrusion disconnection of said parts along said first groove, such as by tearing along the first groove, with less detrimental material impact compared to a case without such groove. In case the disconnected parts are stand-alone sub- products, the first groove thus enables that better quality parts can be extruded in parallel using a single metal extruder, which e.g. improves throughput and can reduce production costs. The groove former may be arranged to form said groove at a location in relation to said die block where said product has not yet been cooled down to room temperature after extrusion. Correspondingly, in the method, forming of the groove may take part before said product has been cooled down to room temperature, and for the product, the first groove may have been formed in said product before said product was cooled down to room temperature after extrusion. The forming of the first groove at such point allows for reduced deformation of edges when the parts are being post- extrusion separated. This is owing to that a groove, before the material has
cooled down, can be made with less microscopic level impact on the material in and near the groove. The material will be more uniform in and near the groove compared to a case where the groove is being made after the material has cooled down. The groove former may comprise a local narrowing of a die aperture of said die block, said narrowing having a profile corresponding to a profile of said first groove. The first groove can thus be formed during the extrusion by said narrowing. Forming the groove like this is a comparatively simple solution that do not require additional parts and the grove is formed as early as is possible and can thereby be made with very low microscopic level impact on the material in and near the groove. (Making the groove before extrusion is typically not possible because of the material deformation taking part during the extrusion.) Low microscopic level impact may be particularly advantageous for electrical appliances, such as when the product is a strip for use as an electrode in a battery.
The first groove may be tapered with a tapering depth and a narrow, preferably acute, bottom. In one embodiment the tapered first groove opens up at an angle that is in the range of about 60° to about 120°. The first groove may have a substantially triangular cross section. The bottom may have an end with a radius that is less than about 1 mm, or less than about 0.5 mm, or less than about 0.1 mm, or less than about 0.05 mm, or less than about 0.01 mm.
The product typically has, along the bottom of the first groove, a thickness that is less than about 50% of the thickness of said product adjacent to and longitudinally along said first groove.
Moreover, preferably a maximum lateral width of the first groove is significantly less, such as less than about 5%, or less than about 4%, or less than about 3%, or less than about 2%, or less than about 1 %, of a largest lateral extension of said product. In the case of an extruded strip, the lateral extension is the width of the strip. In case of e.g. a tube, the lateral extension is the perimeter. Typically is it desirable to keep the width of the groove small, typically as small as possible or practical. This since any remains pertaining to the groove, i.e.
that may remain after the parts have been physically separated from each other along the groove, are typically not desirable.
Said device may further comprise a second groove former arranged to form a second groove, said method may comprise a step for forming such groove and the product may comprise such second groove. The second groove may have a substantially identical profile as the first groove and is preferably oppositely arranged the first groove on an opposite side of said product. Such second groove facilitates post-extrusion disconnection by tearing, allow each groove to be smaller and enables parts that after disconnection are more symmetric and identical, or at least are more similar, on both sides.
Brief description of the drawings
The above, as well as other aspects, objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description, with reference to the appended schematic drawings.
Fig 1. shows a perspective view of an exemplary horizontally oriented HANSSON-ROBERTSON® type of continuous metal extruder having a die block adapted for extrusion into cable sheath.
Fig. 2a shows a schematic die aperture profile of a metal extruder die block for extrusion into a strip for post extrusion separation along a groove into two flat strips.
Fig. 2b shows a schematic strip extrusion product for post extrusion separation along a groove into two flat strips.
Fig. 3 is a flow chart that shows steps in a method according to an embodiment.
Description of preferred embodiments Fig 1. shows a perspective view of an exemplary horizontally oriented
HANSSON-ROBERTSON® type of continuous metal extruder, as discussed in the background, comprising a die block 17 adapted for extrusion of cable sheath. The shown extruder comprises a base frame 1 and a an extension frame 3 acting as floor support and means for bringing the parts of the extruder together. A threaded extrusion screw (not shown in Fig. 1) is located in a screw housing 15, and is therein arranged to transport melted metal to
the die block 17. Although not shown in Fig. 1 , there are typically trolleys arranged to support the die block 17 and screw housing 15 on the extension frame 3 and to facilitate mounting/demounting of these parts. The shown extruder has a screw that is arranged to transport the metal for extrusion horizontally (in the x-direction indicated in Fig. 1), instead of vertically, which often is the case in more conventional extruders. Such metal extruders can also be used with the present invention. The die block is typically replaceable so that the extruder can be used to produce extrusion products of different profile. For example, in US 6,797,403 a conventional extruder with die block as above for cable sheath production was modified to allow for strip production. In such cases it is understood that the extrusion may be performed in a direction that is parallel with the transport direction of the screw, since turning the flow perpendicularly as is the case for the cable sheath die block shown in Fig. 1 makes little sense, although possible. An extrusion product being a tube, such as is the case for the die block in the shown example, is one example of a product that is compatible with the present invention. Another example is a strip, for example as disclosed in US 6,797,403, which will be used next in a more detailed example.
Fig. 2a shows a schematic die aperture profile 22 for extrusion into a product being a strip 30, shown in Fig. 2b, that is designed to be post extrusion separated into two individual flat sub-strips, i.e. sub-products. Before being physically separated, i.e. disconnected, from each other, the sub-strips are thus connected parts 34a, 34b, or portions, of the strip 30. The parts 34a, 34b are separated by two oppositely arranged longitudinal grooves 32a, 32b. The disconnection of the parts 32a, 32b is taking part along the grooves 32a, 32b. The grooves are preferably designed to facilitate disconnecting the sub-strip parts 34a, 34b from each other by tearing along said grooves. In the shown example, the groves 34a, 34b are designed with a triangular cross section having a narrow acute bottom. However, in other embodiments there may be a groove or grooves with other cross-sections, e.g. a similar bottom but with a curved, instead of linear, transition from opening to bottom.
Although not shown in detail in the schematic figures 2a-b, each of the parts 34a, 34b may be formed such that, after being post-extrusion disconnected from each other, each corresponds to the strip as disclosed in US 6,797,403. The narrow bottom opens up at an angle α, which preferably is between about 60° and about 120°.
The shown strip product 30 has a thickness T adjacent to and longitudinally along the grooves 32a, 32b. At the bottom of each the groove the product has a thickness t, which preferably is less than about 50% of the thickness T of said product. Generally, a thinner product in the groove means that disconnecting the parts will be easier, but this also increase the risk for the parts to come apart, fully or partially along the groove or groove, when it is not intended, e.g. by mistake, at an undesirable time and/or place. The risk for the parts coming apart undesirable like this is affected by a number of factors, such as how the extruded product is handled, when the indented disconnection of the parts is going to take place etc. Of course, also the type of metal alloy the extruded product is being made from, at which temperature the groove is formed, the profile etc, are factors that should be taken into account. For a given product it can thus be beneficial to find out, e.g. by routine tests/experiments, how deep groove can be, i.e. how thin the product can be made in the groove, without risking such undesirable separation, and then make the groove with such depth. Another approach, e.g. when is not required to make it particularly easy to disconnect the parts from each other, is to make the product as thick in the groove as is possible, without there being formed edges by the separation in the sub-products that are unacceptable.
Still referring to Fig. 2b, it is understood that the width w of the groove in case of the triangular cross section can be defined as a function of the angle α of the groove and the depth, i.e. here (T-t)/2, of the groove. Hence, in case of two oppositely arranged grooves having substantially the same profile, as in Fig. 2b, w=(T-t)sin(α 12), and in case of a single groove, w=2(T-t)sin(α 12).
In a more detailed example, where the sub-products are battery strips as in US 6,797,403, T is typically in the range of 0.3-1.2 mm and t is typically in the range of 0.2-0.4 mm. In case of an angle α that is 60°, this thus means that the width of each groove 32a, 32b should be in the range 0.05-0.4 mm. Correspondingly, in case of an angle α that is 120°, the width w of each groove should be in the range 0.09-0.7 mm. Since the width of each such sub-strip typically is in the order of 100 mm, and a groove separate two sub- strip parts, it can be understood that the width w of the grooves, or groove, in a general case, should be significantly less than the width W, or lateral extension, of the extruded product, such that less than about one or a few percent thereof.
In order to reach sub-products, such as sub-strips from the parts 34a, 34b in Fig. 2b, that are of higher quality, that have low deformation of edges resulting from disconnecting the parts from each other along the groove, or grooves, and that have lower microscopic level impact on the material near these edges, any such groove should be formed during the extrusion, or as soon as possible thereafter, and at least before the product has cooled down to room temperature. It should be understood that one way to accomplish this is to form the groove, or grooves, by a suitably shaped die block comprising a die aperture having a local narrowing, e.g. accomplished by a protrusion or protrusions from a wall of the die aperture, having a shape that corresponds to the shape of the desired groove, as for example is the case in Fig. 2a. Low microscopic level impact e.g. means that a controlled micostructure can be maintained, which may be desirable in particular for electrical appliances, i.e. when the sub-products are electrical components or for electrical or electrochemical use, such as when the sub-products are strips for use as battery electrodes as in US 6,797,403.
In alternative embodiments there may be only a single groove, and/or one or more grooves at different lateral positions, e.g. in order to accomplish disconnection of more than two extruded product parts into sub-products. In Fig. 2b, the shown grooves 32a, 32b separate the strip 30 into two substantially identical parts so that each of the sub-strips, after separation, will be substantially identical. In the shown example, the parts 34a, 34b and grooves 32a, 32b are symmetrically arranged, however, generally symmetrical and/or asymmetrical parts and/or grooves are possible, e.g. so that the parts being separated by grooves may have different dimensions. It should be understood that other extruded products than a strip 30, i.e. products having other geometrical shapes and profiles than in the shown examples, also are applicable. For example, a tube, such as corresponding to a cable sheath may be produced with a groove, or grooves longitudinally along the sheath, which allow for the tube to be longitudinally opened up and flatten after extrusion, or allow for a portion of the perimeter of the tube to be removed. Of course, there is also a lot of other geometries that can be extruded and furnished with grooves for post extrusion disconnection into individual sub-products. The groove or grooves may be formed so as to allow disconnecting of the parts by hand tearing, i.e. so that the extruded product is suitable to be
disconnected into sub-products by tearing said parts apart along the groove by hand.
The extruded product may be a thin-walled product, or a product comprising a thin-wall structure, with the groove, or grooves, being formed in such wall of the product.
Although it is typically advantageous, for example owing to simplicity, to form the groove by a modified die aperture, for example as schematically shown in Fig. 2a, the groove can also be formed by other means and at other locations in an extruder. It is understood that the groove should not be formed before extrusion since the groove would then be deformed. Instead of forming the groove by physical continuous contact between the product being extruded and a protrusion in the die aperture, such as the tooth-like protrusion as in Fig. 2a, a groove can be formed by temporal such contact, e.g. such that only parts of the extruded product will be furnished with a groove. Also, it should be understood that it is possible to provide mechanical contact for forming the grove also after the product has been extruded and passed through the die aperture. An alternative to mechanical contact for forming the groove can e.g. be by cutting using a laser. A protrusion from a die wall into the die aperture, such as shown in the figure, may be an integral part of the die block or may be a separate part, e.g. releasably attached. Any device arranged to form the groove may be fixed in relation to the die block or be movably arranged, e.g. such that it is possible to control if and when said device shall be in position to form the groove, and/or by that said device comprises a part arranged to move in relation to the die block when forming the groove.
The invention may advantageously be practiced to produce parallel lead alloy strips, which after post-extrusion separation, each may correspond to the type of strip described in US 6,797,403. When there are means for rapidly cooling down the extruded product at a certain location after extrusion, such at the output of the die block, the groove should be formed in the product when the product is located in the die block or between the die block and the location of cooling. The possibility for
Fig. 3 shows a flow chart for illustrating a method according to an embodiment, which is compatible with the foregoing. In a first step 101 , metal, typically in a plastic state, is fed to a die block of a metal extruder. In the die block, the metal is, in a second step 103, being extruded, typically under very high pressure, through a die aperture of the die block, whereby an extruded
product is formed. In a third step 105, a longitudinal first groove is being formed between parts of the product to be post extrusion disconnected from each other. The groove is here being formed before the extruded product has been cooled down to room temperature. As previously discussed, the third step 105 is preferably taking part at the same time as the second step, i.e. the groove being formed during the extrusion.
It should be realized that although a HANSSON-ROBERTSON® type of extruder is advantageous to use, the invention may be operated also using other types of metal extruders. The drawings and the foregoing description are to be considered exemplary and not restrictive. The invention is not limited to the disclosed embodiments.
The present invention is defined by the claims and variations to the disclosed embodiments can be understood and effected by the person skilled in the art in practicing the claimed invention, for example by studying the drawings, the disclosure and the claims. Occurrence of features in different dependent claims does not exclude a combination of these features.