Abstract: A return exhaust assembly 50 for a reverse circulation hammer H comprises return tube 52 having first and second ends and a seat 56 at or near the first end 54. An exhaust sleeve 58 has: a section 60 seated and resiliently supported on the seat 56; and, a portion 62 that extends to and includes an end 64 of the exhaust sleeve 58 distal the section 60. The portion 60 surrounds a length of the return tube 52 with an annular clearance 66 formed between the return tube 52 and the sleeve 58 from a down hole end of the seat 56 to the distal end 64 of the exhaust sleeve 58. This arrangement allows relative movement, and therefore a degree of misalignment between the exhaust sleeve 58 and the return tube.

Abstract: A return exhaust assembly (50) for a reverse circulation hammer H comprises return tube (52) having first and second ends and a seat (56) at or near the first end (54). An exhaust sleeve (58) has: a section (60) seated and resiliently supported on the seat (56); and, a portion (62) that extends to and includes an end (64) of the exhaust sleeve (58) distal the section (60). The portion (60) surrounds a length of the return tube (52) with an annular clearance 66 formed between the return tube (52) and the sleeve (58) from a down hole end of the seat (56) to the distal end (64) of the exhaust sleeve (58). This arrangement allows relative movement, and therefore a degree of misalignment between the exhaust sleeve (58) and the return tube.

Abstract: A return exhaust assembly (50) for a reverse circulation hammer H comprises return tube (52) having first and second ends and a seat (56) at or near the first end (54). An exhaust sleeve (58) has: a section (60) seated and resiliently supported on the seat (56); and, a portion (62) that extends to and includes an end (64) of the exhaust sleeve (58) distal the section (60). The portion (60) surrounds a length of the return tube (52) with an annular clearance 66 formed between the return tube (52) and the sleeve (58) from a down hole end of the seat (56) to the distal end (64) of the exhaust sleeve (58). This arrangement allows relative movement, and therefore a degree of misalignment between the exhaust sleeve (58) and the return tube.

Abstract: A down the hole hammer (10) incorporates: an inner tube assembly (100); a fluid flow control system (200); a bit retaining system (400); a porting sleeve (600); and a piston (700). Each of the: inner tube assembly (100); fluid flow control system (200); bit retaining system (400); porting sleeve (600); and piston (700) in their own right provide benefit to the overall operation and/or reliability of the hammer (10).

Abstract: The invention relates to a method of manufacturing an optical component (800). It also relates to a branching unit and to a method of reducing insertion loss in an optical branching unit. It further relates to a method of reducing stress induced polarization effects in spaced planar waveguides (e.g. couplers) and stress induced tilting of the cores due to strain fields introduced by the top-cladding. It also relates to a method for filling high-aspect-ratio structures with material during reflow. The present invention proposes the use of additional structural elements such as transversal elements (850) connected to or pads (840, 841) or elongate elements located in the vicinity of ordinary waveguide core sections (801, 802). The additional structural elements are typically formed in the same processing step as the ordinary waveguide core sections.

Abstract: An optical component having a combination of optical waveguide elements for modifying the spot size of a mode of an electromagnetic field propagated by an optical waveguide element, the optical waveguide elements being formed on a substrate. The optical component further includes a first section having a first optical waveguide element, and a second section having at least two cooperating optical waveguide elements. The cooperating optical waveguide elements of the second section are configured to maintain optical coupling between the optical waveguide elements to ensure that at least one mode of the electromagnetic field is sustained by the at least two cooperating optical waveguide elements in cooperation.

Abstract: An integrated photonic crystal (IPC) structure and method of producing the same in which the IPC structure includes a first layered sub-structure with a surface and a one-dimensional periodic refractive index variation along the direction perpendicular to the surface, and a second sub-structure with a plurality of essentially straight identical passages arranged in a two-dimensional periodic pattern cutting through the layered structure at an angle ?. First and second defects in the first and second sub-structures, respectively, enable electromagnetic modes to be localized in the vicinity of the defects and allow photonic crystal waveguide to be constructed that can control and filter light very efficiently and minimize radiation losses.