Patent Description:
Graphite electrodes are a necessary consumable in an electric arc furnace and are able to withstand the extremely harsh operating environment of the electric furnace steelmaking operation. Graphite electrodes are typically manufactured by forming cylindrical green carbon bodies. The green carbon bodies are typically formed by mixing and kneading raw materials including coke, such as powdered needle coke, and binder pitch at a high temperature. The raw material mixture is then extruded from a press to form an extruded green carbon body. The green carbon body is subsequently graphitized to form the graphite electrode.

<CIT> discloses an extrusion apparatus according to the preamble of claim <NUM> comprising a frame that is pivotably mounted about a horizontal axis for movement from a generally horizontal position to a generally vertical position. A container is supported by the frame and mounted for pivotable movement about said axis independently of the frame to facilitate loading material into the container.

The present invention is defined by an extrusion apparatus according to claim land a method of extruding according to claim <NUM>.

More particularly, in one embodiment the invention is an extrusion press including a ram having a ram body configured for movement along a ram axis, and a compaction container defining a compaction compartment and having a compaction container axis. The compaction container is rotatable between a first orientation wherein the compaction container axis is not aligned with the ram axis and a second orientation wherein the compaction container axis is aligned with the ram axis such that the ram body is movable into the compaction compartment.

The structure and certain embodiments can be understood by reference to the accompanying drawings, in which:.

Referring now to <FIG>, an extrusion press is shown generally at <NUM>. The extrusion press includes a hydraulic ram or extrusion ram <NUM>, which includes a hollow ram casing <NUM> receiving a ram body <NUM> therein. The ram <NUM> is, in the illustrated embodiment maintained in a generally horizontal orientation (with respect to a gravitational frame of reference) such that the ram body <NUM> is configured for axial movement in the horizontal direction. In the illustrated embodiment the ram casing <NUM> has an annular shape defining a cylindrical inner cavity, and the ram body <NUM> has a generally cylindrical shape (e.g. having a circular cross section) such that the ram body <NUM> is closely received in the ram casing <NUM>. However the ram body <NUM> and ram casing <NUM> can instead have other shapes, including shapes other than circular in cross section.

The ram body <NUM> can be moved forwardly and/or rearwardly in the horizontal direction using, for example, pressurized hydraulics (shown schematically at <NUM>) operatively coupled to the ram casing <NUM> so that the ram body <NUM> can extrude material as described in further detail below. The extrusion press <NUM> can include auxiliary cylinders <NUM> coupled to the ram <NUM> and/or ram body <NUM> for moving the ram body <NUM> along the axial direction via, for example, electrical power, or via a separate hydraulic circuit, when hydraulic pressure is not applied to the ram <NUM> through the ram casing <NUM>.

The ram <NUM>/ram body <NUM>/ram casing <NUM> have a longitudinal axis ARAM disposed in a horizontal orientation. The ram body <NUM> includes a ram face or end face <NUM> disposed at a first end thereof and aligned in a radial plane. The ram body <NUM> can include a series of nozzles or openings <NUM> extending through the ram body <NUM> and terminating at the ram face <NUM>, as shown in <FIG>. In one case the nozzles <NUM> can be pressure activated - e.g. remain closed except when exposed to sufficient pressure. <FIG> illustrates one of the nozzles <NUM> extending through the ram body <NUM>, although the nozzles <NUM> can have any of a wide variety of configurations and paths. As an alternate embodiment <FIG> illustrates the ram body <NUM> as being hollow and having an inner cavity which fluidly communicates with nozzle <NUM>. The nozzles <NUM> can have various other shapes and configurations beyond that shown. The upstream end of the nozzles <NUM> can be coupled to a fluid source (not shown) such as a compressed air source and operate as described in further detail below. Moreover, if desired it may be possible to draw a vacuum through the nozzles <NUM> as described below.

The press <NUM> includes a compaction container assembly <NUM> which includes a compaction container <NUM> having a wall <NUM> (such as a cylindrical wall <NUM>) defining a compaction compartment <NUM> within. The compaction container assembly <NUM>/container <NUM> extend and are oriented along a longitudinal container axis Ac, and have a first opening or first open end <NUM> and a second opening or second open end <NUM> disposed opposite the first open end <NUM>. The compaction container assembly <NUM>/container <NUM> are rotatably mounted to the remainder of the press <NUM> and/or the ram <NUM> such that the compaction container assembly <NUM>/container <NUM> are rotatable about a horizontal axis of rotation AROT as described in further detail below.

The compaction container assembly <NUM> also includes a valve assembly <NUM> at or adjacent to the first open end <NUM>. The valve assembly <NUM> has an actuator <NUM> operably connected to a lid <NUM> for moving the lid <NUM> between a closed position wherein the lid <NUM> engages and sealingly covers the first open end <NUM>, as shown in <FIG> and <FIG>, and an open position, as shown in <FIG> and <FIG>, wherein the lid <NUM> does not engage or cover the first open end <NUM> such that the first open end <NUM> is uncovered. The embodiment of <FIG> show the valve assembly <NUM> as including or taking the form of a rotating valve (also known as a swing valve) in which the lid <NUM> rotates about an axis between the open and closed positions. However the valve assembly <NUM> can include or take the form of various other types of valve assemblies, including but not limited to a gate valve or a sluice valve as shown in <FIG> in which the lid <NUM> is generally flat and planar, and slides open and closed along the plane. The valve assembly <NUM> including the actuator <NUM> and lid <NUM> rotate together with the compaction container assembly <NUM>/container <NUM> as they rotate about the axis of rotation AROT.

The compaction container assembly <NUM> can also include a die <NUM> disposed at the second open end <NUM> of the compaction container assembly <NUM>. The die <NUM> has a die opening <NUM>, through which the material <NUM>/extruded article <NUM> is forced during the extrusion process, as shown in <FIG> and as described in further detail below. The compaction container assembly <NUM> can include a die cover <NUM> is disposed at the second open end <NUM> adjacent to the die <NUM>. The die cover <NUM> is movable between a closed position and an open position. The die cover <NUM> sealingly engages or covers the die opening <NUM> when in the closed position, as shown in <FIG>. When the die cover <NUM> is in the open position as shown in <FIG>, the die cover <NUM> is spaced away from and does not cover the die opening <NUM>, to allow the material to be extruded from the die <NUM> as described in further detail below. The die <NUM> and die cover <NUM> rotate together with the compaction container assembly <NUM>/container <NUM> as they rotate about the axis of rotation AROT, as described in further detail below.

The press <NUM> also includes a generally annular vacuum shroud <NUM> disposed concentrically about and coaxial with the ram body <NUM>. The vacuum shroud <NUM> has an annular front face <NUM> that is adapted to sealingly engage a flange or mating surface <NUM> (<FIG>, <FIG> and <FIG>) positioned at or adjacent to the first open end <NUM> of the container <NUM>. The flange or mating surface <NUM> is positioned on an outer surface of the container <NUM>, and spaced slightly downstream from the first open end <NUM> in the illustrated embodiment. The vacuum shroud <NUM>/face <NUM> is movable along the ram axis ARAM between a retracted position in which the vacuum shroud <NUM>/face <NUM> are spaced apart from and do not engage the mating surface <NUM>, and a sealing or engaged position in which the vacuum shroud <NUM>/face <NUM> sealingly engage the mating surface <NUM> for drawing a vacuum in the container <NUM>, as will be described in further detail below.

As noted above, the compaction container assembly <NUM> and container <NUM> are rotatable about the axis of rotation AROT, between a first or vertical orientation wherein the container axis Ac is oriented generally or strictly vertically and the first open end <NUM> is positioned above the second open end <NUM>, as shown in <FIG>, <FIG>, <FIG> and <FIG>, and a second or horizontal orientation wherein the container axis Ac is oriented generally or strictly horizontally and the first open end <NUM> is generally aligned with the second open end <NUM> as shown in <FIG> and <FIG>. When the compaction container assembly <NUM> is first moved to the horizontal orientation the first open end <NUM> is positioned adjacent to, and faces, the ram face <NUM>, and the container axis Ac is aligned with the longitudinal axis ARAM of the ram body <NUM>. The amount of rotation of the container assembly <NUM>/container <NUM> is about <NUM> degrees in the illustrated embodiment, but is at least about <NUM> degrees in one case or can vary as desired. The axis of rotation AROT can in one case be oriented perpendicular with respect to the ram axis AR, as shown in <FIG>, but the axes of rotation can be at varying different angles if desired.

Referring now to <FIG>, one method for operating of the press <NUM> is now described. The container assembly <NUM> begins in, or is rotated to, the first or vertical orientation, as shown in <FIG>, and arranged such that lid <NUM> is in its open position and the die cover <NUM> is closed. The container assembly <NUM> is secured, locked or blocked into this first orientation. In this orientation the first open end <NUM> is positioned above the second open end <NUM> such that raw material <NUM> to be extruded, such as green carbon raw material <NUM>, can be easily loaded into the container <NUM>. The raw material <NUM> can be loaded into the container <NUM> in any suitable known manner, such as for example by conveyer <NUM> shown in <FIG> having an end <NUM> disposed above the first open end <NUM> such that the raw material <NUM> is naturally fed into the container <NUM>, and retained therein, by gravity. In one case the raw material <NUM> is green carbon raw material <NUM> used to form an extruded green carbon body and includes coke, such as for example needle coke, calcined petroleum coke, calcined anthracite and binder, such as for example pitch, coal tar pitch or petroleum pitch. The green carbon raw material <NUM> is mixed and kneaded at a high temperature and then loaded into the first open end <NUM> of the container <NUM>.

After the desired amount of material <NUM> has been loaded into the container <NUM>, the valve assembly <NUM> is closed, thereby moving the lid <NUM> to the closed position to sealingly cover the first open end <NUM>, as shown in <FIG>. The container assembly <NUM>/container <NUM> is then released, unlocked or unblocked and rotated (<NUM>° in one case) about axis AROT until the container assembly <NUM>/container <NUM> is in the second or horizontal orientation, such that container axis Ac is aligned with the axis ARAM of the ram body <NUM>, as shown in <FIG>. When the container assembly <NUM> is in the horizontal orientation, the first open end <NUM> and/or lid <NUM>, faces, and is adjacent or immediately adjacent to, the ram face <NUM>. The vacuum shroud <NUM> and ram body <NUM> are sufficiently retracted at this stage to allow the compaction container assembly <NUM> to freely rotate to its horizontal orientation. As described above, the valve assembly <NUM>/lid <NUM> and die cover <NUM> rotate with the container <NUM>. The container assembly <NUM>/container <NUM> is then secured, locked or blocked in the horizontal orientation to prevent movement of the container assembly <NUM>/container <NUM> during the subsequent steps, such as during extrusion.

Referring now to <FIG>, the ram body <NUM> is moved forward from its retracted position to an external position where the ram face <NUM> is positioned proximate, near, adjacent or immediately adjacent to the lid <NUM>. The valve assembly <NUM> is then opened, moving the lid <NUM> away from the first open end <NUM> to the open position. In this position, the ram face <NUM> retains the material <NUM> within the container <NUM> preventing most of the material <NUM> from spilling out of the first open end <NUM> of the container <NUM>. The maximum size of the gap between the ram face <NUM> and the first open end <NUM>/container <NUM> at this stage may be relatively small to reduce or minimize spilling, such as less than about <NUM> in one case, or less than about <NUM> in one case, or less than about <NUM> in another case.

Referring now to <FIG>, the ram body <NUM>/ram face <NUM> is then advanced from a position at least partially external to but proximate to the container <NUM>, to a first internal position in which the ram body <NUM>/ram face <NUM> fully enters the container <NUM> through the first open end <NUM>, and is partially positioned in the casing <NUM> without compacting, or without significantly compacting, the raw material <NUM>. For example, in this step the ram body <NUM> may extend less than <NUM>%, or in another case less than <NUM>%, or in yet another case less than <NUM>%, of the axial length of the container <NUM>.

The vacuum shroud <NUM> is then moved towards the container <NUM> until the shroud <NUM>/shroud face <NUM> is in a sealing position where the shroud <NUM>/shroud face <NUM> sealingly engage the mating surface or flange <NUM> of container <NUM> as shown in <FIG>. The shroud <NUM> including an inner sealing member <NUM> that closely, slidably and sealingly receives the ram body <NUM> therein. The shroud <NUM> thus generally closes and seals the container <NUM> and compaction compartment <NUM> so that a vacuum can be drawn in the container <NUM> and compaction compartment <NUM>. A vacuum cycle is then performed by drawing a vacuum within the vacuum shroud <NUM> and to remove air in the container <NUM>/compaction compartment <NUM>. In one embodiment, vacuum shroud <NUM> has one or a plurality of radially-extending openings <NUM> (<FIG> and <FIG>) to which a vacuum source can be coupled to draw down the vacuum. However the vacuum can be formed by various other methods such as possibly in one case applying a vacuum via the nozzles <NUM>. The vacuum can help to facilitate the compaction process as described in the next step.

When a desired level of vacuum is reached (in one case less than about 10kPA, or in another case less than about 2kPA), a compaction cycle is performed wherein the raw material <NUM> is compacted without extruding the material <NUM> through the die <NUM>. During the compaction cycle, the ram <NUM> is moved from the first internal position towards and into the container <NUM>/raw material <NUM> to compact the material <NUM> in container <NUM> while the die cover <NUM> remains closed, as shown in <FIG>. For example, in this step the ram body <NUM> may extend less than <NUM>%, or in another case less than <NUM>%, or in yet another case less than <NUM>%, of the axial length of the container <NUM>, and may extend at least about <NUM>%, or in another case at least about <NUM>% of the axial length of the container <NUM>. The compaction process helps to eliminate voids in the extruded material and provide a more uniform extruded product. Upon completion of compaction, the vacuum shroud <NUM> is retracted, thereby moving the shroud face <NUM> away from the container mating surface <NUM> and breaking the vacuum.

The die cover <NUM> is then moved to the open position to uncover the die opening <NUM> and the extrusion commences by moving the ram body <NUM> further into the container <NUM> as shown in <FIG>. The ram body <NUM> is extended into the container <NUM> and the raw material <NUM> is extruded through the die opening <NUM> to form an extruded article <NUM>, such as an extruded green carbon article <NUM>. The extrusion process can be carried out at various temperatures and pressures, and in one case between about <NUM> degrees Celsius and about <NUM> degrees Celsius, and in one case at a pressure of about least about 20bar in one case, or at least about 50bar in another case, or at least about <NUM> bar in yet another case. The extruded article <NUM> can be cut away or otherwise separated from the press <NUM> and further processed, such as by graphitizing, to form the graphite electrode for use an electric arc furnace.

Upon completion of the extrusion step, the ram body <NUM> is retracted away from the die opening <NUM>. Air or some other fluid can be sprayed against the material <NUM> within the container <NUM> via the nozzles <NUM> in the ram face <NUM> before or as the ram body <NUM> is retracted from within the container <NUM>. The sprayed air acts as a release and prevents the raw material <NUM> from sticking to the ram face <NUM>, which is known as the stick effect. A source of compressed air can be fluidly coupled to the upstream end of the nozzles <NUM> to provide the sprayed air. The die cover <NUM> can also move to its closed position as the ram <NUM> is retracted from the container <NUM>. The ram body <NUM> is then retracted out of the container <NUM> until it is fully retracted out of the container assembly <NUM>/container <NUM>. The container assembly <NUM><NUM>/container <NUM> is then rotated about the axis of rotation AROT back to the first or vertical orientation where it is ready to be loaded again with the raw material <NUM> as shown in <FIG>.

It should be noted that although the figures and description show the container assembly <NUM>/container <NUM> being rotated between a vertical orientation, where it is loaded, to a horizontal orientation, where extrusion takes place, the container assembly <NUM> can be rotated through various different angles and oriented in differing positions. In addition, the loading process can be carried out at various orientations other than vertical, and the extrusion process can be carried out at various orientations other than horizontal. The rotatable nature of the container assembly <NUM> allows freedom in separating the orientation of loading from the orientation of extrusion. In the particular illustrated embodiment, the ability to load in the vertical direction, and then move to the horizontal direction, enables the ram body <NUM> to perform both the compaction and the extrusion, in one case in the horizontal configuration. This avoids the need to use a separate component, device or mechanism to provide compaction of the raw material <NUM>, which enables faster processing and the elimination of additional equipment and steps. Thus such a separate compacting component, device or mechanism can be lacking from the press <NUM> or excluded from the press <NUM>.

Claim 1:
An extrusion press (<NUM>) comprising:
a ram (<NUM>) having a ram body (<NUM>) configured for movement along a ram axis; and
a compaction container (<NUM>) defining a compaction compartment (<NUM>) and having a compaction container axis, wherein the compaction container (<NUM>) has a first open end (<NUM>) and a second open end (<NUM>) positioned opposite to the first open end (<NUM>), wherein the compaction container (<NUM>) is rotatable between a first orientation wherein the compaction container axis is not aligned with the ram axis and a second orientation wherein the compaction container axis is aligned with the ram axis such that the ram body (<NUM>) is movable into the compaction compartment (<NUM>), wherein when the compaction container (<NUM>) is in the first orientation the first open end (<NUM>) is positioned above the second open end (<NUM>);
characterised in that the press (<NUM>) includes a lid (<NUM>) coupled to the compaction container (<NUM>) and movable to a closed position at least when the compaction container (<NUM>) is not in the second orientation, wherein the lid (<NUM>) is configured such that when the lid (<NUM>) is in the closed position the lid (<NUM>) generally covers the first open end (<NUM>) to retain material (<NUM>) in the compaction container (<NUM>).