Firing process and method

Abstract

The present invention provides a method and apparatus for firing a ceramic component e.g. a ceramic core, within a firing receptacle containing firing powder. The method comprises using a shaping element to shape and/or define an upper surface of a first portion of firing powder at a predetermined height within the firing receptacle. The ceramic component is subsequently placed on the upper surface of the first portion of firing powder e.g. within a depression formed using the shaping element and covered with a second portion of firing powder. The shaping element may comprise a gridded/meshed plate.

Claims

1. A method of firing a ceramic component within a firing receptacle containing firing powder, the method comprising: using a shaping element to shape and/or define an upper surface of a first portion of firing powder at a first predetermined height within the firing receptacle prior to placing the ceramic component on the upper surface of the first portion of firing powder; using a levelling element to shape and/or define an upper surface of the second portion of firing powder at a second predetermined height within the firing receptacle, the second portion of firing powder covering the ceramic component; and positioning the levelling element within the firing receptacle with the levelling element being supported above a base of the firing receptacle at the second predetermined height using at least one support, wherein the or each support of the levelling element is a strut depending from the levelling element, such that, in use, the base of the or each strut rests on the base of the firing receptacle or wherein the or each support of the levelling element is a hook such that, in use, the hook(s) rest on a rim of the firing receptacle to suspend the levelling element within the firing receptacle, and the shaping element and/or the levelling element is a respective meshed/gridded plate.

2. A method according to claim 1 further comprising positioning the shaping element within the firing receptacle with the shaping element being supported above the base of the firing receptacle at the first predetermined height.

3. A method according to claim 2 further comprising adding the first portion of firing powder such that it abuts the shaping element.

4. A method according to claim 1 wherein the method further comprises removing the shaping element prior to positioning the ceramic component on the upper surface of the first portion of firing powder.

5. A method according to claim 1 wherein the shaping element comprises a protrusion on its lower or upper surface and the method further comprises forming an indentation or protrusion in the upper surface of the first portion of firing powder using the protrusion and positioning the ceramic component in the indentation or on the protrusion.

6. A method according to claim 1 further comprising covering the ceramic component with a second portion of firing powder.

7. A method according to claim 1 wherein the levelling element is the meshed/gridded element and the method comprises adding the second portion of firing powder such that it abuts the levelling element.

8. A method according to claim 7 wherein the method further comprises removing the levelling element prior to firing the ceramic component.

9. A method according to claim 1 further comprising agitating the firing receptacle after addition of the first and/or second portion(s) of firing powder.

10. An apparatus for firing a ceramic component within a firing receptacle containing firing powder, the apparatus comprising: a shaping element, the shaping element being insertable into the firing receptacle, such that, in use, it shapes an upper surface of a first portion of firing powder at a first predetermined height within the firing receptacle prior to placing the ceramic component on the upper surface of the first portion of firing powder; a levelling element, the levelling element being insertable into the firing receptacle, such that, in use, it shapes an upper surface of a second portion of firing powder at a second predetermined height within the firing receptacle, the second portion of firing powder covering the ceramic component; and at least one support for supporting the levelling element spaced from a base of the firing receptacle by the second predetermined height, wherein the or each support of the levelling element is a strut depending from the levelling element, such that, in use, the base of the or each strut rests on the base of the firing receptacle or wherein the or each support of the levelling element is a hook such that, in use, the hook(s) rest on a rim of the firing receptacle to suspend the levelling element within the firing receptacle, and the shaping element and/or the levelling element is a respective meshed/gridded plate.

11. Apparatus according to claim 10 further comprising at least one support for supporting the shaping element spaced from the base of the firing receptacle by the first predetermined height.

12. Apparatus according to claim 11 wherein the or each support of the the shaping element is a strut depending from the shaping element, such that, in use, the base of the or each strut rests on the base of the firing receptacle or wherein the or each support of the shaping element is a hook such that, in use, the hook(s) rest on a rim of the firing receptacle to suspend the shaping element within the firing receptacle.

13. Apparatus according to claim 10 wherein the shaping element comprises a protrusion on its lower or upper surface which, in use, forms an indentation/imprint or protrusion in the upper surface of the first portion of firing powder.

14. Apparatus according to claim 13 wherein the lower or upper surface of the shaping element is convex.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 shows a ducted fan having a series of turbines each having a plurality of aerofoil blades formed using a method according to an embodiment of the present invention.

(3) FIGS. 2A-2G show various steps in a method and an apparatus according to an embodiment of the present invention.

DETAILED DESCRIPTION AND FURTHER OPTIONAL FEATURES OF THE INVENTION

(4) With reference to FIG. 1, a ducted fan gas turbine engine incorporating a series of turbines each having a plurality of aerofoil blades formed using a method according to an embodiment of the present invention is generally indicated at 10 and has a principal and rotational axis X-X. The engine comprises, in axial flow series, an air intake 11, the propulsive fan 12, an intermediate pressure compressor 13, a high-pressure compressor 14, combustion equipment 15, a high-pressure turbine 16, an intermediate pressure turbine 17, a low-pressure turbine 18 and a core engine exhaust nozzle 19. A nacelle 21 generally surrounds the engine 10 and defines the intake 11, a bypass duct 22 and a bypass exhaust nozzle 23.

(5) During operation, air entering the intake 11 is accelerated by the fan 12 to produce two air flows: a first air flow A into the intermediate pressure compressor 13 and a second air flow B which passes through the bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 13 compresses the air flow A directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.

(6) The compressed air exhausted from the high-pressure compressor 14 is directed into the combustion equipment 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 16, 17, 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low-pressure turbines respectively drive the high and intermediate pressure compressors 14, 13 and the fan 12 by suitable interconnecting shafts.

(7) FIGS. 2A-2G show an apparatus and method for firing a ceramic component according an embodiment of the invention.

(8) FIG. 2A shows a firing receptacle 25 and a shaping element 26.

(9) The shaping element 26 comprises a meshed/gridded shaping plate 27 which is supported on two support struts 28 depending from the lower surface of the shaping plate 27.

(10) The shaping plate 27 is positioned within the empty firing receptacle 25 with the ends of the struts 28 resting on the base 29 of the firing receptacle 25.

(11) The shaping plate 27 is supported by the support struts 28 within the firing receptacle at a predetermined height above the base 29 of the firing receptacle 25.

(12) The shaping plate 27 is contoured to define a protrusion 30 on its lower surface (the lower surface is the surface proximal the base of the firing receptacle).

(13) As shown in FIG. 2B, a first portion of firing powder 31 is added to the firing receptacle until it abuts the lower surface of the shaping plate 27. In other embodiments (not shown), the shaping element may be positioned within a firing receptacle already containing a first portion of firing powder and the upper surface of the first portion of firing powder shaped by pressing the shaping element into the first portion of firing powder.

(14) The firing receptacle 25 is agitated to homogenise the first portion of firing powder 31 within the firing receptacle.

(15) The upper surface of the shaping plate (distal the base of the firing receptacle), is scraped to ensure the upper surface of the first portion of firing powder is flush with the shaping plate 27.

(16) As shown in FIG. 2C, the shaping plate 27 is removed from the firing receptacle 25 to leave an upper surface 32 of the first portion of firing powder 31 at the predetermined height defined by the shaping plate 27 and having a surface shape matching the contour of the shaping plate 27 i.e. with an indentation 33 matching the shape of the protrusion 30 on the lower surface of the shaping plate 27.

(17) As shown in FIG. 2D, a ceramic component 34 is positioned within the indentation 33 on the upper surface 32 of the first portion of firing powder 31. Accordingly, the position of the ceramic component 34 i.e. the spacing from the base 29 of the firing receptacle 25 and from the rim 35 of the firing receptacle 25 can be reliably and repeatedly controlled.

(18) Next, as shown in FIG. 2E, a levelling element 36 is positioned within the firing receptacle 25.

(19) The levelling element 36 comprises a meshed/gridded shaping plate 37 which is supported on two support struts 38 depending from the lower surface of the levelling plate 37.

(20) The levelling plate 37 is positioned within the firing receptacle 25 with the ends of the struts resting on the base 29 of the firing receptacle 25.

(21) The levelling plate 37 is supported by the support struts 38 within the firing receptacle at a second predetermined height above the base 29 of the firing receptacle 25.

(22) The levelling plate 37 is planar and sits parallel to the base 29 of the firing receptacle. In other embodiments (not shown), the levelling element/plate may have a contoured lower surface.

(23) As shown in FIG. 2F, a second portion of firing powder 39 is added to the firing receptacle 25 until it abuts the lower surface of the levelling plate 37.

(24) The firing receptacle 25 is agitated to homogenise the second portion of firing powder 39.

(25) The upper surface of the levelling plate (distal the base of the firing receptacle), is scraped to ensure the upper surface of the second portion of firing powder 39 is flush with the shaping plate 27.

(26) Next, as shown in FIG. 2G, the levelling plate 37 is removed from the firing receptacle 25 to leave an upper surface 40 of the second portion of firing powder 39 at athe second predetermined height defined by the levelling plate 37 and having a planar surface matching the lower surface of the levelling plate 37. Accordingly, the amount of firing powder covering the ceramic component 34 can be reliably and repeatably controlled to eliminate/ameliorate dimensional variations in the fired ceramic component.

(27) While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.