Counterflow gas flow delivery structure for apparatus for the layer-by-layer formation of three-dimensional objects
A structure for delivering a flow of gas across a window or aperture of an imaging or measurement device within an apparatus for the manufacture of three-dimensional objects by layer-by-layer consolidation of particulate matter, the structure comprising: a hollow body having an upper aperture for mounting in correspondence with the window/aperture of said device, a gas flow intake region below the upper aperture, and a lower aperture; wherein the gas flow intake region is provided on opposing sides of the hollow body when viewed in cross-section along a longitudinal axis that runs from the upper aperture to the lower aperture, and comprises one or more channels configured to allow, in use, a flow of intake gas to enter the hollow body from the opposing sides of the hollow body with a flow component that predominantly lies in a plane parallel to the plane of the upper aperture, and to come into confluence within the hollow body; and wherein the hollow body is symmetrically shaped about the longitudinal axis so as to redirect the confluent flow of intake gas to form a substantially axial flow of gas along the longitudinal axis, and a backflow of gas near the internal wall of the hollow body, wherein the upper aperture is substantially shielded from the backflow by the intake flow, and wherein the velocity of the backflow is relatively low in comparison to the velocity of the intake flow. Also provided is an apparatus for the manufacture of three-dimensional objects by layer-by-layer consolidation of particulate matter, incorporating such a structure, and a method of delivering a flow of gas using such a structure.
1 . A structure for delivering a flow of gas across a window or aperture of an imaging or measurement device within an apparatus for the manufacture of three-dimensional objects by layer-by-layer consolidation of particulate matter, the structure comprising:
a hollow body having
an upper aperture for mounting in correspondence with the window or aperture of said device,
a lower aperture,
a primary gas flow intake region and a secondary gas flow intake region, each arranged along at least part of a perimeter line of the hollow body and provided below the upper aperture and on opposing sides of the hollow body, when viewed in cross-section along a longitudinal axis that runs from the upper aperture to the lower aperture, wherein the primary gas flow intake region comprises one or more channels configured to allow, in use, a flow of intake gas to enter the hollow body from the opposing sides of the hollow body with a flow component that predominantly lies in a plane parallel to the plane of the upper aperture, and to come into confluence within the hollow body;
wherein the one or more channels are each configured as an elongate through-hole extending in a direction of elongation along the perimeter line of the hollow body and being bounded by two side walls, wherein one of the two side walls is arranged at an acute angle to the perpendicular to the longitudinal axis such that the flow component enters the hollow body at an acute angle to a perpendicular to the longitudinal axis to create a circulating flow of gas into the hollow body;
wherein the secondary gas flow intake region is provided on opposing sides of the hollow body when viewed in cross-section along the longitudinal axis, and comprises one or more secondary channels configured to allow, in use, a secondary flow of intake gas to enter the hollow body with a secondary flow component that is predominantly parallel to the internal wall of the hollow body, and wherein the secondary channels are arranged such that, in use, the secondary flow of gas flows in a rotational sense opposite to that of the primary flow of gas; and
wherein the hollow body is symmetrically shaped about the longitudinal axis so as to redirect the confluent flow of intake gas to form a substantially axial flow of gas along the longitudinal axis and a backflow of gas near the internal wall of the hollow body, wherein the velocity of the backflow is relatively low in comparison to the velocity of the intake flow such that the upper aperture is substantially shielded from the backflow by the intake flow.
2 . The structure of claim 1 , wherein the elongate through-hole extends substantially perpendicular to the longitudinal axis of, and through the wall of, the hollow body.
3 . The structure of claim 1 , wherein the elongate through-hole includes side edges that are angled away from the perpendicular to the internal wall surface of the hollow body so that, in use, the flow component that predominantly lies in a plane parallel to the plane of the upper aperture is created.
4 . The structure of claim 1 , wherein the elongate through-hole is bounded by a lower edge and an upper edge connecting the two side walls, and one of the edges is angled away from the perpendicular to the internal wall surface of the hollow body so that, in use, the flow component that predominantly lies in a plane parallel to the plane of the upper aperture is created.
5 . The structure of claim 1 , wherein the elongate through-hole narrows in its cross-sectional area from the outer wall of the hollow body towards the internal wall of the hollow body.
6 . The structure of claim 1 , wherein, in use, the intake flow creates a continuous curtain of high velocity circulating gas parallel to and underneath the upper aperture, or angled down from the plane of the upper aperture, with respect to the velocity of the backflow of gas.
7 . The structure of claim 1 , wherein all of the channels are configured as elongate through-holes, and wherein the side walls between adjacent channels form a vane, each vane being arranged at an acute angle to the perpendicular to the longitudinal axis, such that the channels extend along the majority of the perimeter line of the hollow body and are separated by the vanes.