Patent Description:
Rail joining using aluminothermic welding has been employed for many years owing to its robustness, portability, and relatively low cost. The inherent characteristic of the process is the reduction of iron oxide by aluminium. This chemical reaction is highly exothermic and liberates copious quantities of heat, thereby generating high temperatures and inevitably accompanying amounts of fume and potentially flammable gases, largely as by-products of the reaction. With ever-tightening legislation related to welders' health and safety, there is a growing need for a safe, reliable, and cost-effective system by which these by-products can be captured, thereby ensuring welders are not exposed to unnecessarily high levels of these waste products. This is especially the case when the process is deployed underground or in confined spaces where there is an increased risk of fume accumulation.

The conventional filter (see <FIG> and <FIG>) that dates back to <NUM> is tall and extends vertically from the crucible, which leads to structural instability during the filtering process. In addition, the conventional filter tends to rock on the crucible due to the pressure of the waste produced during the aluminothermic reaction.

The conventional filter employs two layers of filter material positioned on top of one another that are of relatively high density. This setup is such that it limits the life of the filters as the lower of the two filters rapidly becomes clogged with the solid particulate. The filter material life is also undesirably reduced when the filter is deployed with more lively aluminothermic welding chemicals. Examples of similar prior art can be found in documents <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

The present invention is aimed at improving the stability of the filter sitting on a crucible.

The invention is defined in independent claims <NUM> and <NUM>. Further aspects are provided in dependent claims.

Although the invention has been explained in relation to its preferred embodiment(s) as mentioned above, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the present invention, as defined by the appended claims.

<FIG> shows an illustrative view of the conventional filter system. <FIG> shows an illustrative view of the conventional filter system of <FIG> sitting on the crucible on a rail. <FIG> shows how a welder applies the filter of the present invention to a crucible during an aluminothermic welding process on a rail. <FIG> shows a perspective view of the filter of the present invention applied to a crucible. <FIG> shows a cross-section view of <FIG>. <FIG> shows a cross-section view of <FIG> with a filter material of the present invention. <FIG> shows a perspective view of the filter of <FIG>. <FIG> shows an exploded view of the filter of <FIG>. <FIG> shows a bottom view of the filter of <FIG>. <FIG> shows a front view of the filter of <FIG>. <FIG> shows a side view of the filter of <FIG>. <FIG> shows a top view of the filter of <FIG>. <FIG> shows a cross-section view taken along line A-A of <FIG>. <FIG> shows an expanded view of the partial body of the filter of <FIG>. <FIG> shows the illustrated view of the mounting plate of the body of the filter of <FIG>. <FIG> shows the workflow of the method for applying the filter of the present invention to a crucible during an aluminothermic welding process on a rail.

Please refer to <FIG> together. <FIG> shows how a welder <NUM> applies the filter <NUM> of the present invention to a crucible <NUM> during an aluminothermic welding process on a rail <NUM>. The crucible <NUM> can be a single-use crucible, a permanent-use crucible, or any kind of crucible for aluminothermic welding. <FIG> shows a single-use crucible <NUM> invented by the Goldschmidt Group. Specifically, <FIG> shows that a welder <NUM> ignites the aluminothermic welding chemicals in a crucible <NUM>. The aluminothermic welding chemical reaction may produce undesirable chemicals from the outlet <NUM> of the crucible <NUM>. The chemicals may include toxic gas such as carbon monoxide, fume, particles, welding slag, and/or debris. In the patent application, these chemicals all refer to "waste". To prevent the welder <NUM> from inhaling the waste <NUM>, the welder <NUM> places the filter <NUM> of the present invention on the top <NUM> of the crucible <NUM> to cover the outlet <NUM> of the crucible <NUM> as soon as the aluminothermic welding chemicals are ignited in the crucible <NUM> (<FIG> shows that the filter <NUM> remains on top <NUM> of the crucible <NUM> for a predetermined duration to capture waste <NUM> produced by the aluminothermic reaction. The filter <NUM> extends perpendicular to the axis <NUM> of the crucible <NUM> and thus lies horizontally with respect to the crucible <NUM>, so that the mould <NUM>, the crucible <NUM>, and the filter <NUM> can be stably placed and balanced on the rail <NUM>. The present invention improves significantly the stability compared to the conventional filter in <FIG> and <FIG>. <FIG> highlights the relatively low centre of gravity of the filter <NUM> of the present invention compared to the conventional filter, thereby ensuring its stability and safety during its deployment. Then, the welder <NUM> removes the filter <NUM> from the crucible <NUM> once the waste <NUM> has been captured to leave the welder <NUM> in a cleaner and safer environment.

Please refer to <FIG> together. The present invention provides a filter <NUM> for filtering waste <NUM> produced from a crucible <NUM> during the aluminothermic reaction when welding rail <NUM>. The filter <NUM> is designed to be placed on the outlet <NUM> of the crucible <NUM>. The filter <NUM> comprises a body <NUM> and two handles <NUM>. The body <NUM> includes a waste passage <NUM>, an inlet <NUM>, a filter material <NUM>, a first protruding portion <NUM>, a second protruding portion <NUM>, a baffle plate <NUM>, a mounting plate <NUM>, a seal felt <NUM>, a felt restraint <NUM>, a latch <NUM> and a hinge <NUM>. The first protruding portion <NUM> includes a first outlet <NUM>. The second protruding portion <NUM> includes a second outlet <NUM>.

Specifically, <FIG> shows that the body <NUM> includes two handles <NUM> symmetrically disposed on the body <NUM> of the filter <NUM>. In another embodiment, the filter <NUM> can only have one handle <NUM> in the middle of the body <NUM>, can have more than one handle <NUM>, or can have no handle. The welder <NUM> can hold the handle <NUM> for placing the filter <NUM> onto the crucible <NUM> easily. Two handles <NUM> are located on the top of the body <NUM> of the filter <NUM> to facilitate its easy and safe positioning and in turn its safe removal at the mandated time after tapping of the steel from the crucible <NUM>.

The body <NUM> extends perpendicular to the axis <NUM> of the crucible <NUM>, allowing the body <NUM> to be placed horizontally on the crucible <NUM> when it is viewed from above. In a preferred embodiment, the body <NUM> is shaped to be a rectangular box when it is viewed from above. For example, the dimensions of the body <NUM> are <NUM>-<NUM> (preferably <NUM>) in length, <NUM>-<NUM> (preferably <NUM>) in width, and <NUM>-<NUM> (preferably <NUM>) in height. The rectangular box design of the body <NUM> allows for the fabrication of the case of the body <NUM> from a single piece of cut steel sheet, thereby reducing manufacturing complexity in terms of the amount of welding required to create a gas-tight seal in the outer skin. Such a design also reduces the cost of manufacture and reduces the risk of leakage of either solid particulate or gaseous fumes. In a preferred embodiment, the body <NUM> is integrally formed.

The first protruding portion <NUM> extends adjacent to the side <NUM> of the crucible <NUM> and includes the first outlet <NUM>. The second protruding portion <NUM> extends adjacent to the side <NUM> of the crucible <NUM> and includes a second outlet <NUM>. The first protruding portion <NUM> and the second protruding portion <NUM> extend out from the cross-section of the crucible <NUM> (when the filter <NUM> is placed on the crucible <NUM> and is viewed from above) and extend further downward adjacent to the side <NUM> of the crucible <NUM> and parallel to the side <NUM> of the crucible <NUM>. The lower part <NUM> of the first protruding portion <NUM> and the lower part <NUM> of the second protruding portion <NUM> of the filter <NUM> lie below the plane of the outlet <NUM> of the crucible <NUM>, resulting in a centre of gravity of the filter <NUM> as a whole lying very close to the top <NUM> of the crucible <NUM> and therefore improving the stability of the filter <NUM> sitting on the top <NUM> of the crucible <NUM>. To secure the placement, the body <NUM>, the first protruding portion <NUM>, and the second protruding portion <NUM> define a crucible receiving area <NUM> for securing the filter <NUM> on the crucible <NUM>. The inlet <NUM>, the first outlet <NUM>, the second outlet <NUM>, and the waste passage <NUM> are communicated. The first outlet <NUM> and the second outlet <NUM> direct the waste <NUM> out of the filter <NUM>. The first outlet <NUM> and the second outlet <NUM> are respectively hinged with the first protruding portion <NUM> and the second protruding portion <NUM> through the hinges <NUM> so that the first outlet <NUM> and the second outlet <NUM> can easily be opened. The first outlet <NUM> and the second outlet <NUM> are configured to be meshes. The meshes of the first outlet <NUM> and the second outlet <NUM> can be made of metal (preferably steel or stainless steel), or any material.

In another embodiment, the first protruding portion <NUM> and the second protruding portion <NUM> are communicably and integrally formed; in this case, the body <NUM> can be a circular box, and the first protruding portion <NUM> and the second protruding portion <NUM> can be circular in shape or essentially an annulus around the periphery of the body <NUM> and adjacent around the side <NUM> of the crucible <NUM>. In another embodiment, the filter <NUM> can have only one protruding portion. In another embodiment, the body <NUM> can also have other shapes, for example, a square box, or a triangular box, when the filter <NUM> is placed on the top <NUM> of the crucible <NUM> and is viewed from above. The body <NUM> allows the filter <NUM> to be balanced on the crucible <NUM>. In a preferred embodiment, the body <NUM> is symmetrically formed, and the body <NUM> extends out from the cross-section of the crucible <NUM>.

The body <NUM> includes a mounting plate <NUM> defined as the bottom <NUM> of the body <NUM> and which is in contact with the top <NUM> of the crucible <NUM>. The inlet <NUM> of the body <NUM> is provided on the mounting plate <NUM>. The mounting plate <NUM> extends horizontally into the first protruding portion <NUM> and the second protruding portion <NUM>. The filter <NUM> includes a latch <NUM> for attaching or securing the first outlet <NUM> and the second outlet <NUM> to the body <NUM>. Specifically, the latches <NUM> can be locked or unlocked to close or open the first outlet <NUM> or the second outlet <NUM>, and the first outlet <NUM> and the second outlet <NUM> can be pivoted around the hinges <NUM>. The latch <NUM> is preferably an over-centre latch or a loop latch, which are made of steel. In a preferred embodiment, two latches <NUM> are provided for the filter <NUM>. The body <NUM> and the mounting plate <NUM> can also be integrally formed in another embodiment.

Please refer to <FIG>. The inlet <NUM> directs the waste <NUM> from the outlet <NUM> of the crucible <NUM> into the waste passage <NUM>. The inlet <NUM> of the body <NUM> lies above the outlet <NUM> of the crucible <NUM> and is preferably larger in area than the outlet <NUM> of the crucible <NUM> so that the inlet <NUM> can capture all waste <NUM> produced from the crucible <NUM>. The inlet <NUM> of the body <NUM> is circular in shape or any shape. The inlet <NUM> is on the bottom <NUM> of the body <NUM>. The inlet <NUM> is a circular hole of <NUM>-<NUM> (preferably <NUM>) in diameter through which the waste <NUM> from the aluminothermic reaction can pass. The waste passage <NUM> allows the waste <NUM> to flow through the filter <NUM> and perform purification. The outlet directs the waste <NUM> out of the filter <NUM>.

The filter material <NUM> is provided in the first protruding portion <NUM> and/or the second protruding portion <NUM>. In another embodiment, the filter material <NUM> may be provided inside the first outlet <NUM>, inside the second outlet <NUM>, or anywhere in the body <NUM>, but preferably away from the inlet <NUM> of the body <NUM>. The filter material <NUM> is made from a combination of fire retardant and non-combustible materials which allows for capturing and filtering waste <NUM>. The filter material <NUM> can be selected from the group of polymer, nylon, glass, mineral stone wool, calcium magnesium silicate, alumina-silica, alumina-zirconia silica, and/or magnesia. There are many possible arrangements of the filter material <NUM>. The waste <NUM> can be filtered by the filter material <NUM>, and then the filtered gas can be released out of the first outlet <NUM> and/or the second outlet <NUM> of the filter <NUM>.

The filter material <NUM> is reusable for multiple welding operations. If the filter material <NUM> becomes worn or blocked, a welder <NUM> can change the filter material <NUM>. Specifically, the first outlet <NUM> of the first protruding portion <NUM> and the second outlet <NUM> of the second protruding portion <NUM> are respectively hinged with the first protruding portion <NUM> and the second protruding portion <NUM> so that the first outlet <NUM> of the first protruding portion <NUM> and the second outlet <NUM> of the second protruding portion <NUM> are openable.

In a preferred embodiment, the first outlet <NUM> and the second outlet <NUM> are welded meshes made of stainless steel. The meshes of the first outlet <NUM> and the second outlet <NUM> have a lattice spacing of nominally <NUM> and act as filter doors. The filter doors (the first outlet <NUM> and the second outlet <NUM>) support the filter material <NUM> and in combination permit the free egress of any residual gaseous products. A hinge <NUM> arrangement permits easy access to change the filter material <NUM>. In particular, the potential use of filter materials <NUM> of lower density offers the ability to allow waste <NUM> to travel deeper into the filter material <NUM>, thereby allowing their consecutive use for a higher number of welds before becoming sufficiently clogged with particulate reducing their efficacy, thereby necessitating their replacement. Particulate penetration into higher-density filter material <NUM> is less, such that particulate builds up more rapidly on the uppermost filter surface leading to a more rapid decrease in its particulate capturing efficiency. Fume analysis has shown the filter material <NUM> to be effective in capturing a variety of oxides resulting from the aluminothermic reaction including those of iron, aluminium, manganese, silicon, and chromium. Furthermore, emissions of potentially flammable gases are reduced to levels considerably below the recommended Work Exposure Levels (WELs).

The first outlet <NUM>, the second outlet <NUM>, and the inlet <NUM> of the body <NUM> face downward when the filter <NUM> is placed on the crucible <NUM>, so filtered gas cannot surge out of the outlet directly into the face of a welder <NUM>. In addition, the downward-facing outlets of the filter <NUM> act as a safety feature. For example, if any flames are present during the chemical reaction and penetrate through the filter <NUM> out of the first outlet <NUM> and the second outlet <NUM>, the flames would be facing downwards and away from the welder <NUM>, thereby minimizing any risk of injury to the welder <NUM>. Also, when the welder <NUM> removes the filter <NUM> after the welding chemical reaction has finished, and if there are any residual flames inside the filter <NUM>, such flames would be facing away from the welder <NUM> and the filter <NUM> acts as a shield against any such flames.

In another embodiment, the inlet <NUM> of the body <NUM>, the first outlet <NUM> and the second outlet <NUM> can also face other directions. In a preferred embodiment, the first outlet <NUM> of the first protruding portion <NUM>, and the second outlet <NUM> of the second protruding portion <NUM> are configured to be meshes made of metal.

<FIG> and <FIG> show the flow of the waste <NUM>. The waste <NUM> including hot particulate and reaction gases essentially rises vertically from the outlet <NUM> of the crucible <NUM> into the inlet <NUM> and is then directed first horizontally and thereafter vertically downwards exiting the two filter materials <NUM> located at the extremes of the filter <NUM>.

The filter <NUM> includes one or more baffle plates <NUM> in the body <NUM>. The baffle plates <NUM> not only prevent slags from hitting the filter material <NUM> directly but also act in combination with the designated waste passage <NUM> inside the filter <NUM> to calm down the waste flow before contacting the filter material <NUM>. Furthermore, the baffle plates <NUM> require waste <NUM> to take a longer path before they reach the filter material <NUM>. In a preferred embodiment, the gap (with a width of <NUM>-<NUM>) through which the gases pass through the baffle plates <NUM> is no smaller than the inlet <NUM> of the filter <NUM> or the outlet of the filter <NUM>, thereby avoiding any bottle neck which would lead to a venturi effect.

The level of activity of the aluminothermic reaction may vary depending on the chemical composition of the portion. In some compositions, the chemical reaction causes slag to surge out of the outlet <NUM> of the crucible <NUM> together with the waste fume and gas. The slag is not desirable for contacting the filter material <NUM> as it tends to adhere to the filter material <NUM> and, in the worst case burn holes through the filter material <NUM>, thereby decreasing the filtering efficiency of the filter material <NUM>. Moreover, the baffle plate <NUM> and the mounting plate <NUM> define a slag precipitation area <NUM>. The length of the slag precipitation area <NUM> and the height of the baffles are configured to inhibit the amount of slag passing or crossing over the baffle and to minimize the risk of the slag sticking to the inlet <NUM> of the body <NUM>. In a preferred embodiment, the baffle plates <NUM> extend perpendicular to the partition plate and guide the air in the waste passage <NUM>.

In addition, the baffle plates <NUM> limit the build-up of potentially flammable gases within the filter <NUM> and reduce the associated risk of their spontaneously combusting once sufficient oxygen becomes available.

The filter <NUM> also improves the effectiveness of the seal between the filter <NUM> and the crucible <NUM> and eliminates the need for luting materials. For example, to avoid waste <NUM> leaking from the interface between the filter <NUM> and the crucible <NUM>, a robust and fume-proof seal between the filter <NUM> and crucible <NUM>, in turn leading to improving filtering efficiency. The filter <NUM> includes a large thermally-resistant seal felt <NUM> disposed around the inlet <NUM> of the body <NUM> that ultimately sits between the underside of the body <NUM> and the top <NUM> of the crucible <NUM> for sealing the filter <NUM> with the crucible <NUM>. The material of the seal felt <NUM> is made of refractory ceramic fibers with high-temperature stability and low thermal conductivity. For example, the seal felt <NUM> is made from refractory ceramic fibers, examples of which include silica, alumina and/or zirconia. The seal felt <NUM> also improves the stability of the filter <NUM> when the filter <NUM> is placed on the crucible <NUM>. The seal felt <NUM> and the weight of the filter <NUM> provides a fume-proof seal with the crucible <NUM> without the need for luting paste. The need for luting paste between the filter <NUM> and the crucible <NUM> when using the conventional filter makes the process cumbersome, with repeated manual removal of the paste serving to increase the time required and increasing the risk of an inadequate seal between the filter <NUM> and the crucible <NUM>. Moreover, the seal felt <NUM> can be used for multiple welds. Also, the large surface area of the seal felt <NUM> allows for easy alignment between the filter <NUM> and the top <NUM> of the crucible <NUM>. The robust nature of the seal also encourages gas and particulate flow toward the filter material <NUM>.

The body <NUM>, the first protruding portion <NUM>, and the second protruding portion <NUM> define a crucible receiving area <NUM> for securing the filter <NUM> on the crucible <NUM>. The inlet <NUM> of the body <NUM> is designed to cover the outlet <NUM> of the crucible <NUM> during the aluminothermic welding reaction and guide the waste <NUM> into the passage. The size of the inlet <NUM> of the body <NUM> is between <NUM> and <NUM> (preferably <NUM>) in diameter. The inlet <NUM> of the body <NUM> can also be other shapes, such as a square. The filter <NUM> includes a felt restraint <NUM> for keeping the seal felt <NUM> on the bottom <NUM> of the body <NUM> when placing the filter <NUM> on the top <NUM> of the crucible <NUM> and/or for guiding the outlet <NUM> of the crucible <NUM> with the inlet <NUM> of the filter <NUM>. In a preferred embodiment, the filter <NUM> has four felt restraints <NUM> forming a diamond shape around the outlet of the body <NUM> and between the first protruding portion <NUM> and the second protruding portion <NUM> in the crucible receiving area <NUM>. The felt restraints <NUM> improve the stability of the filter <NUM> on the crucible <NUM> and effectively eliminate the risk of incorrect placement of the filter <NUM> onto the crucible <NUM>.

In a preferred embodiment, the filter <NUM> can be symmetrically or asymmetrically formed. If the filter <NUM> or the body <NUM> is formed as a circular box, the first protruding portion <NUM> and the second protruding portion <NUM> can be integrally formed. In another embodiment, the body <NUM> includes an additional door (not shown in the drawings) outside of the first outlet <NUM> and an additional door (not shown in the drawings) outside of the second outlet <NUM>.

Claim 1:
A filter for filtering waste produced from a crucible during the aluminothermic welding reaction, the filter (<NUM>) being used for placing on an outlet (<NUM>) of the crucible (<NUM>), the filter (<NUM>) comprising:
a body (<NUM>) including:
a waste passage (<NUM>),
an inlet (<NUM>) for directing the waste (<NUM>) from the outlet (<NUM>) of the crucible (<NUM>) into the waste passage (<NUM>),
a filter material (<NUM>) for filtering the waste (<NUM>),
characterized in that the body (<NUM>) includes: a first protruding portion (<NUM>) extending adj acent to the side of the crucible (<NUM>) and including a first outlet (<NUM>), and a second protruding portion (<NUM>) extending adjacent to the side of the crucible (<NUM>) and including a second outlet (<NUM>).