阅读说明：本技术 带有检查舱口组件的回转破碎机底壳 (Gyratory crusher bottom shell with inspection hatch assembly ) 是由 米夏埃尔·斯科格 阿德里安·亨西恩 桑尼·埃克 米卡埃尔·拉尔森 芒努斯·弗雷德里克松 扬 于 2018-01-31 设计创作，主要内容包括：一种回转破碎机底壳和检查舱口组件,所述检查舱口组件能够通过定位在所述底壳的内部区域处的耐磨板而唯一地附接到所述底壳。所述底壳在紧挨着围绕舱口开口的边界区域处的壁厚度大体上等于或小于在所述舱口开口的相同轴向高度位置处的壁的剩余区域上的壁厚度。(A gyratory crusher bottom shell and inspection hatch assembly that is uniquely attachable to the bottom shell by wear plates positioned at an interior region of the bottom shell. The wall thickness of the bottom shell at a boundary region immediately surrounding the hatch opening is substantially equal to or less than the wall thickness over the remaining region of the wall at the same axial height position of the hatch opening.)

1. A gyratory crusher bottom shell (100) comprising:

an annular wall (104) extending about a longitudinal axis (103) of the bottom shell, the annular wall (104) having a radially outwardly facing surface (105), a radially inwardly facing surface (106), an annular axial upper end, and an annular axial lower end;

at least one hatch opening (107) disposed through the annular wall (104);

the method is characterized in that:

at a boundary region (111) of the wall (104) surrounding the hatch opening (107), a radial thickness of the wall (104) is not greater than a radial wall thickness over a remaining region (112) of the wall (104) outside the boundary region (111) at the same corresponding axial position of the hatch opening (107).

2. Bottom shell according to claim 1, wherein the thickness of the wall (104) at the boundary area (111) is substantially equal to the wall thickness at the position of the wall (104) separated from the hatch opening (107) by an angular distance of 90 ° in a circumferential direction around the axis (103).

3. Bottom shell according to claim 1 or 2, wherein the thickness of the wall (104) at the boundary region (111) around the hatch opening (107) does not increase from the remaining region (112) of the wall (104) towards the hatch opening (107) in a circumferential direction and in an axial direction with respect to the longitudinal axis (103).

4. A bottom shell as claimed in any preceding claim, wherein, in a plane perpendicular to the longitudinal axis (103), the shape profile of the radially outward-facing surface (105) is substantially continuously convex at the boundary region (111).

5. The bottom shell of any preceding claim, wherein the radially outwardly facing surface (105) is free of any planar surface at the boundary region (111) and is substantially continuously curved in a circumferential direction about the longitudinal axis (103).

6. Bottom shell according to any preceding claim, wherein the radial thickness of said wall (104) within said boundary region (111) decreases in an axial direction from said axial upper end and/or said axial lower end of said wall (104) towards said hatch opening (107).

7. The bottom shell of any preceding claim, wherein the hatch opening (107) is at least partially defined by a curved region (400,401) extending in a substantially radial direction between the inward-facing surface (106) and the outward-facing surface (105), such that the hatch opening (107) is edgeless.

8. A gyratory crusher inspection hatch assembly for a gyratory crusher, comprising:

-a bottom shell (100) according to any preceding claim;

a frame (201) having an annular protrusion (205), the annular protrusion (205) mountable to sit radially within the hatch opening (107) between the radially inward facing surface (106) and the radially outward facing surface (105); and

a door (202) mountable at the frame (201) to close the hatch opening (107).

9. The assembly of claim 8, further comprising a wear plate (200), the wear plate (200) having an aperture (300), the wear plate (200) being mountable to the radially inwardly facing surface (106) of the bottom shell, a radially inner end of the annular protrusion (205) being fixedly attached to the wear plate (200) so as to extend radially outwardly from the wear plate at the area of the aperture (300) and through the annular wall (104) via the hatch opening (107).

10. The assembly of claim 9, wherein the annular protrusion (205) is secured to the wear plate (200) at the perimeter of the aperture by a weld material.

11. The assembly of claim 9 or 10, wherein the frame further comprises a rim provided at a radially outer end of the annular protrusion (205), and the rim extends at least partially annularly around the annular protrusion (205).

12. The assembly of claim 11, wherein the rim comprises a door mounting face (505) to mate with a complementary surface (506) of the door (202) to mount the door (202) at the frame (201) and to close the hatch opening (107).

13. An assembly according to claim 9 or 10, further comprising a compressible or deformable collar (209) mountable around a region of the annular protrusion (205), at least a portion of the collar being configured to be radially seated between a region of the radially outwardly facing attachment face (203) of the wear plate (200) and a portion of the boundary region (111) of the annular wall (104).

14. The assembly of claim 13, wherein the collar (209) comprises a foam or rubber material.

15. A gyratory crusher inspection hatch assembly for mounting at a hatch opening (107) in an annular wall (104) of a gyratory crusher bottom shell (100), comprising:

a wear plate (200) mountable at a radially inward facing surface (106) of the bottom shell (100) and having an aperture (300);

a frame (201) having a hollow annular protrusion (205), the hollow annular protrusion (205) being fixedly attached to the wear plate (200) such that at least a first end (205a) of the annular protrusion (205) is dimensioned to seat immediately around the aperture (300) or within the aperture (300); and

a door (202) removably mountable to the frame (201) to close the hollow interior of the annular protrusion (205).

16. The inspection hatch assembly according to claim 15, further comprising a compressible or deformable collar (209), the collar (209) being mountable around a region of the annular protrusion (205), at least a portion of the collar (209) being configured to be radially seated between a region of the radially outwardly facing attachment face (203) of the wear plate (200) and a boundary region (111) of the annular wall (104) surrounding the hatch opening (107).

Technical Field

The present invention relates to a gyratory crusher bottom shell and an inspection hatch assembly for cooperation at the bottom shell, which does not require specific modifications at the area around the hatch opening.

Background

Gyratory crushers are used to crush ores, minerals and rocks to smaller sizes. Typically, a crusher comprises a crushing head mounted on an elongated main shaft. A first crushing shell, called mantle section, is mounted on the crushing head and a second crushing shell, called the concave section, is mounted on the frame such that the first and second shells together define a crushing chamber through which the material to be crushed passes. A drive device positioned at a lower region of the main shaft is configured to rotate an eccentric assembly positioned about the shaft to cause the crushing head to perform a gyratory pendulum movement and crush material introduced into the crushing chamber. An exemplary gyratory crusher is described in WO 2010/071565.

The crushing frame is typically formed by a top shell and a bottom shell to accommodate the rotating main shaft and crushing head. Inspection hatches are typically provided through the bottom enclosure wall to allow access to the internal chamber by a service shaft to remove and retrieve the crushable material and periodically (typically monthly) inspect the various internal components. Conventionally, the thickness of the bottom shell wall around the hatch opening is excessive and is also machined to provide a planar surface for mounting the hatch door or hatch frame. An excessively large border around the hatch opening is disadvantageous for several reasons. In particular, the arrangement of the material feeder that introduces the flowable melt into the mold (cast) can be complex, and the restricted flow path can lead to porosity in the final bottom shell casting due to the oversized surrounding hatch opening. In addition, the oversized walls at the hatch opening require machining, which is disadvantageous in terms of additional machining time, tooling, personnel and energy usage. The thickened hatch boundary region also limits the maximum wall thickness of the bottom shell and, therefore, the achievable strength properties of the bottom shell. Therefore, what is needed is a bottom shell and hatch assembly that addresses the above-mentioned problems.

Disclosure of Invention

It is an object of the present invention to provide a bottom shell for a gyratory crusher and a gyratory crusher inspection hatch assembly that facilitates the manufacturing of the bottom shell by avoiding the need for machined and oversized walls at the border area immediately surrounding the hatch opening, by means of its attachment mechanism at the area of the bottom shell. Another specific object of the present invention is to provide a bottom shell and hatch assembly that enables the casting of a bottom shell with enhanced strength and reduces the risk of defects, in particular porosity at the area around the hatch opening, resulting from the casting process.

Another specific object is to provide a bottom shell for a gyratory crusher by a hatch opening assembly and an attachment mechanism at the area of the bottom shell, which does not require specific attachment of the hatch assembly to the bottom shell wall, thereby avoiding the need for: the bottom shell at the area of the hatch opening is machined and drilled in order to mount the hatch door and/or the hatch frame. Therefore, one particular objective is to minimize the occurrence of stress concentrations within the bottom shell during use.

These objects are achieved by providing a hatch assembly that may be mounted at the bottom shell by one of the lining wear plates mounted on the inward facing surface of the bottom shell such that the hatch assembly is not directly mounted to the bottom shell wall. In addition, casting of the bottom shell is greatly facilitated since the bottom shell according to the subject invention does not include an excessive wall thickness immediately at the boundary region around the hatch opening. In this way, in addition to reducing the risk of defects (in particular porosity within the bottom shell at the region of the hatch opening), the complexity of the material feeder is greatly reduced.

Since the inventive bottom shell comprises a substantially uniform wall thickness in a plane perpendicular to the longitudinal axis of the bottom shell, the overall wall thickness in the circumferential direction may be increased relative to conventional arrangements at the axial position of the hatch opening due to the greater clearance provided for the attachment bolts (at the area of the hatch opening) coupling the top shell and the bottom shell.

In this specification, reference to a "border region" encompasses the section of the bottom shell wall immediately adjacent to and extending around each hatch opening. The boundary region may be considered to extend in the axial and circumferential directions by a distance approximately equal to the radius of each hatch opening (or approximately half the width of the opening in the circumferential direction around the bottom shell). The boundary region may extend in a circumferential direction from the hatch opening, in particular from an inwardly facing surface or edge defining the hatch opening, an angular distance in the range of 1 ° to 40 °, 1 ° to 30 °, 1 ° to 20 °, 1 ° to 10 °, 1 ° to 5 °, 5 ° to 40 °, 5 ° to 30 °, 5 ° to 20 °, or 5 ° to 10 °.

References in this specification to "remaining regions" encompass regions of the bottom shell wall that are located outside of the boundary region and at the same axial height as the boundary region with respect to a longitudinal axis extending through the bottom shell. The remaining areas may be considered to include those sections of the bottom shell that extend in the circumferential direction between diametrically opposed hatch openings and are positioned at the same axial position as the respective hatch openings.

According to a first aspect of the present invention, there is provided a gyratory crusher bottom shell comprising: an annular wall extending about a longitudinal axis of the bottom shell, the annular wall having a radially outwardly facing surface, a radially inwardly facing surface, an annular axial upper end, and an annular axial lower end; at least one hatch opening disposed through the annular wall; the method is characterized in that: at a boundary region of the wall surrounding the hatch opening, the radial thickness of the wall is not greater than the radial wall thickness over a remaining region of the wall located outside the boundary region at the same corresponding axial position of the hatch opening.

Preferably, the thickness of the wall at the boundary region is substantially equal to the wall thickness at the remaining region or location of the wall at an angular distance in the circumferential direction about the axis from the hatch opening of 10 ° to 30 °, 20 ° to 40 °, 50 ° to 70 °, 80 ° to 100 °, 110 ° to 130 °, 140 ° to 160 °, 20 ° to 120 °,40 ° to 140 °, 60 ° to 120 °, or an angular distance of 20 ° to 160 °, 30 ° to 150 °,40 ° to 140 °, 50 ° to 130 °, 60 ° to 120 °, 70 ° to 110 °, or about 85 ° to 95 °. The uniform wall thickness at the axial location of the top shell aligned with the hatch opening facilitates uniform distribution of loading forces around the bottom shell and minimizes the occurrence of stress concentrations at specific areas. The uniform cross-sectional area in a plane perpendicular to the longitudinal axis of the bottom shell also facilitates casting and reduces the likelihood of undesirable porosity during casting that continues into the final cast product.

Preferably, the thickness of the wall at the boundary region around the hatch opening does not increase in the circumferential and axial direction from the remaining region of the wall towards the hatch opening. Thus, the hatch opening may be formed by a continuously curved surface and a wall thickness in the boundary area, which wall thickness gradually decreases in the axial direction such that the wall thickness tapers inwardly towards the center of the hatch opening. This arrangement further facilitates casting when feeding casting material into the mold from axially upper and lower positions.

Preferably, in a plane perpendicular to the longitudinal axis, the shape profile of the radially outwardly facing surface is substantially continuously convex at the boundary region. This continuously curved shape profile minimizes stress concentrations and thus extends the useful life of the bottom shell. In particular, the radially outwardly facing surface at the boundary region is free of any planar surface and is substantially continuously curved in the circumferential direction. Advantageously, the boundary region is free of any machined surface. The formation of such surfaces that would otherwise be conventionally required to install hatch frame components (including the hatch assembly and hatch mounting mechanism) is time-inefficient and may weaken the bottom shell because of the potential crack nucleation sites provided. The boundary area is also free of any threaded attachment holes that might otherwise increase the likelihood of stress concentrations and increase the risk of fatigue and cracking of the bottom shell at the area around the hatch opening.

Preferably, the thickness of the bottom shell wall in the boundary region decreases in the axial direction from the axially upper end and/or the axially lower end of the wall towards the centre of the hatch opening.

Preferably, the inner surface of the wall defining the hatch opening between the radially outwardly facing surface and the radially inwardly facing surface comprises a curved region so as to provide an edge-free region. Sharp edges in the bottom shell are disadvantageous because they provide areas from which stress concentrations may originate and may lead to casting defects.

According to a second aspect of the present invention, there is provided a gyratory crusher inspection hatch assembly for a gyratory crusher, comprising: a bottom shell as claimed herein; a frame having an annular protrusion that is mountable to be seated radially within the hatch opening between the radially inward facing surface and the radially outward facing surface; and a door mountable at the frame to close the hatch opening.

Preferably, the inspection hatch assembly further comprises a wear plate having an aperture, the wear plate being mountable to a radially inwardly facing surface of the bottom shell, a radially inner end of the annular projection being fixedly attached to the wear plate so as to extend radially outwardly from the wear plate at the region of the aperture and through the annular wall via the hatch opening. In addition to forming part of the liner assembly, the wear plates may also be considered to form part of the inspection hatch assembly, which in turn is formed from individual liner panels positioned side-by-side around the interior of the bottom shell. The wear plate preferably forms part of a wear plate liner assembly that is attachable to the bottom shell by means of attachment bolts extending through apertures extending radially through the wall of the bottom shell. Preferably, the apertures of the wear plate may be the same or similar in shape and size as the hatch opening of the bottom shell. Preferably, the size of the orifice is considered to account for double casting tolerances of the bottom shell bore. Preferably, the aperture is circular.

Preferably, the annular projection is secured to the wear plate at the periphery of the aperture by a weld material. Optionally, the annular projection is friction fit into mating engagement with the aperture of the wear plate. Optionally, the annular protrusion may be secured within the perimeter of the aperture by bolts, screws, pins, plugs, bayonet mounts, and/or adhesives. Optionally, the frame may be integrally formed with the wear plate.

Preferably, the frame further comprises a rim disposed at a radially outer end of the annular projection and extending at least partially annularly around the annular projection. Preferably, the rim includes a door mounting surface to mate with a complementary surface of the door to mount the door at the frame and to close the hatch opening.

Preferably, the assembly further comprises a compressible or deformable collar mountable around the region of the annular projection, at least a portion of the collar being configured to seat radially between a region of the radially outwardly facing attachment face of the wear plate and a portion of the boundary region of the annular wall. Optionally, the compressible or deformable material comprises a foam or rubber material. The collar material may be elastically deformable, or may be fixed or set into a compressed configuration after the hatch assembly is initially installed at the bottom shell.

According to another aspect of the present invention, there is provided a gyratory crusher inspection hatch assembly for mounting at a hatch opening in an annular wall of a gyratory crusher bottom shell, the inspection hatch assembly comprising: a wear plate mountable at a radially inwardly facing surface of the bottom shell and having an aperture; a frame having a hollow annular protrusion fixedly attached to the wear plate such that at least a first end of the annular protrusion is dimensioned to seat immediately around or within the aperture; and a door detachably mountable to the frame to close the hollow interior of the annular protrusion.

Preferably, the length of the protrusion is configured to account for double casting tolerances in the thickness of the bottom shell.

According to another aspect of the present invention, there is provided a gyratory crusher inspection hatch assembly for mounting at a hatch opening in an annular wall of a gyratory crusher bottom shell, the inspection hatch assembly comprising: a protrusion for attachment to a wear lining panel attachable to a radially inward-facing surface of the bottom shell, the protrusion configured to extend at least partially through the hatch opening from the radially inward-facing surface of the bottom shell toward a radially outward-facing surface of the bottom shell; and a door mountable across and/or within the protrusion to close the hatch opening; wherein the assembly can be mounted at the bottom shell exclusively by means of the wear-resistant lining panel.

According to another aspect of the present invention, there is provided a gyratory crusher comprising an inspection hatch assembly as claimed herein.

Drawings

Particular embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

fig. 1 is a perspective view of a gyratory crusher bottom shell according to a particular embodiment of the present invention;

FIG. 2 is a cross-sectional perspective view of an inspection hatch assembly installed at a hatch opening of the bottom shell of FIG. 1;

FIG. 3 is a perspective view of a portion of the bottom case of FIG. 1, showing selected wear plates mounted within the interior of the bottom case;

FIG. 4 is another cross-sectional perspective view of the bottom case of FIG. 1 including the internally mounted wear plate of FIG. 3;

FIG. 5 is a perspective view of components of the hatch assembly of FIG. 2;

FIG. 6 is another perspective cross-sectional view of components of the hatch assembly of FIG. 2;

FIG. 7 is another perspective view of components of the hatch assembly of FIG. 2;

fig. 8 is another cross-sectional perspective view of the bottom shell of fig. 1 at the area of the hatch opening.

Detailed Description

Referring to fig. 1, a gyratory crusher bottom shell 100 includes an annular wall 104 extending about a longitudinal axis 103 of the bottom shell 100. Wall 104 includes a radially outwardly facing surface, generally indicated by reference numeral 105, and a radially inwardly facing surface 106 that defines an internal chamber within bottom shell 100. The wall 104 is terminated at an axially upper end by an annular rim 108, which annular rim 108 has an annular upwardly facing planar surface 101. A plurality of attachment holes 110 extend axially through the rim 108 to receive attachment bolts for coupling a top shell (not shown) to the bottom shell 100 to form a main frame portion of the gyratory crusher. The corresponding axially lower end of bottom shell 100 similarly includes a generally annular rim 102 for mounting against a base or lower support structure.

A pair of diametrically opposed hatch openings 107 extend through wall 104 to allow inspection access into the interior chamber defined by radially inwardly facing surface 106. Each hatch opening 107 includes a generally circular shaped profile. According to the invention, the boundary region, generally designated by reference numeral 111, immediately adjacent to the bottom shell wall 104 surrounding each hatch opening 107 does not comprise an excessive wall thickness. That is, the radial thickness of wall 104 at boundary region 111 is not greater than, and in particular substantially equal to, the wall thickness at remaining region 112 of bottom shell 100 at the same respective axial position relative to axis 103 outside of boundary region 111. That is, wall 104 includes a substantially uniform radial thickness in a circumferential direction around bottom shell 100, within remaining area 112 and immediately within boundary area 111 around each hatch opening 107.

Referring to fig. 2 and 3, a hatch assembly is installed at each hatch opening 107 of the bottom chassis 100. The hatch assembly includes: a frame generally indicated by reference numeral 201; a gate member generally designated by reference numeral 202; and a liner wear plate 200 secured to the wall 104 by a plurality of attachment bolts 206, the attachment bolts 206 extending through holes 109 provided through the wall 104 between the radially outward facing surface 105 and the radially inward facing surface 106. Wear plate 200 includes a radially inwardly facing wear surface 204 and a radially outwardly facing attachment surface 203 for positioning against inwardly facing surface 106 of bottom case 100. It should be appreciated that wear plate 200 forms part of the liner assembly to protect bottom shell surface 106 from damage by bulk material as it falls from the crushing zone through bottom shell 100. The liner assembly includes a series of individual wear plates positioned side-by-side in an annular configuration around the inner facing surface 106 of the bottom shell. The wear plate 200 referred to herein represents a plate component of such a liner assembly.

The frame 201 includes an annular protrusion 205 having a generally cylindrical shape and configuration. Respective first inner axial ends 205a of the protrusions 205 are positioned substantially coplanar with the wear plate 200, while respective second axial ends 205b extend beyond the bottom housing outwardly facing surface 105. An annular rim 207 is mounted to and extends outwardly from the annular projecting second end 205b to provide a corresponding mounting area for a portion of the door 202, the door 202 being described below.

Wear plate 200 includes apertures 300. According to particular embodiments, the aperture 300 is circular, but other shape profiles may be suitable. The first end 205a of the annular protrusion 205 is suitably dimensioned (in diameter) to seat within the aperture 300 in close fitting contact against the area of the wear plate 200 defining the periphery of the aperture 300. The door 202 is configured to seat within the hollow interior 208 of the annular protrusion 205 and extend the entire length of the cylindrical interior 208 between the ends 205a and 205 b.

As shown in fig. 2, the hatch assembly further comprises a deformable and/or compressible collar 209, which collar 209 may be mounted to partially surround the annular protrusion 205. In particular, the collar 209 is configured to seat against a portion of the wear plate outer surface 203 and an outwardly facing surface 508 (fig. 5) of the annular protrusion 205. The collar 209 is dimensioned such that, at least during initial assembly, the collar 209 is larger than the space or volume available in the area of the hatch opening 107 surrounding the annular protrusion 205. Thus, as wear plate 200 is pulled radially outward by tightening attachment bolts 206, collar 209 is compressed (or deformed) between wear plate 200 and boundary area 111 of bottom case 100 at an area immediately surrounding hatch opening 107. This configuration is advantageous to prevent dust and debris from passing from the interior chamber of bottom shell 100 into the area of hatch opening 107 and past annular protrusion 205. Thus, the collar 209 is configured to provide a dust or debris seal at the hatch opening 107, which is effective for particle containment during the crushing operation. The wear plate aperture 300, to which the door frame 201 is attached, is dimensioned to substantially correspond to the size of the hatch opening 107, in particular slightly smaller than the size of the hatch opening 107, such that when the door 202 is removed from the door frame 201, access to the inner chamber of the bottom shell (defined by the wall 104) is obtained.

Referring to fig. 4 and 8, the radial thickness of the wall 104 immediately surrounding each hatch opening 107 (defined herein as boundary region 111) coincides with the respective wall thickness at the same axial location (or respective plane perpendicular to axis 103) such that the wall 104 at boundary region 111 is not as large as according to conventional bottom shell wall configurations at the region surrounding each hatch opening 107. In particular, the outwardly facing surfaces 105a, 105b within the boundary region 111 at respective axial locations below and above the hatch opening 107 taper radially inward so as to be linear or concave with respect to the axis 103. Corresponding regions 106a, 106b of the radially inward facing surface 106 within the axially below and above boundary regions 111, respectively, of the hatch opening 107 are similarly aligned with respect to the corresponding outward facing surface regions 105a, 105b to taper or curve inwardly. The tapering of the respective outward and inward facing surfaces 105, 106 extends annularly about the hatch opening 107 and is not limited to only a plane axially aligned with the longitudinal axis 103. That is, this tapering of surfaces 105, 106 also exists at bottom case 100 in a plane extending transverse or perpendicular to longitudinal axis 103. Thus, the thickness of the wall 104 within the boundary region 111 tapers annularly, decreasing from a position outside the boundary region 111 towards the axial center of the circular hatch opening 107. Accordingly, the wall thickness within the boundary area 111 is equal to or less than the thickness of the bottom case wall at the remaining area 112 of the bottom case 100 outside the boundary area 111.

Referring to fig. 8, this configuration facilitates the introduction of casting material into the mold during casting of bottom shell 100 through first feed orientation 800a at lower annular rim 102 and second feed orientation 800b at upper annular rim 108. It should be appreciated that conventional hatch openings typically include an increased wall thickness at the boundary region 111 because the wall 104 flares radially outward, providing a planar mounting surface corresponding to the surface regions 105a, 105 b. Such radially extending shoulders increase the risk of porosity within the wall 104 during casting. Due to the tapered wall thickness in the boundary region 111 at least in the axial direction of the wall 104 and the corresponding substantially uniform wall thickness in the boundary region 111 and the remaining region 112, casting is facilitated and the risk of defects and porosity in the wall 104 at the boundary region 111 is significantly reduced. In addition, the general thickness of the wall 104 may be increased relative to conventional bottom case arrangements while still providing sufficient radial clearance to receive attachment bolts (not shown) through the attachment holes 110 without contaminating the outwardly facing surface 105, particularly the outwardly facing surface 105 at the boundary region 111.

The present invention is further advantageous by including hatch opening 107 without angled or sharp edges. In particular, and with reference to fig. 4, inner surface 402 defining hatch opening 107 (extending in a generally radial direction between radially outward-facing surface 105 and radially inward-facing surface 106) terminates at respective radially outer and inner ends defined by respective curved regions 400,401, curved regions 400,401 providing respective interfaces with radially outward-facing surface 105 and radially inward-facing surface 106. Thus, the surfaces defining the hatch opening 107 from the radially outwardly facing surface 105 to the radially inwardly facing surface 106 are free of sharp annular edges or edge regions.

Referring to fig. 5-7, the door 202 includes a disc-shaped inner end plate 503 that provides a base for the generally cylindrical section 502, and the end plate 503 is positioned at one axial end of the section 502. An annular flange 500 is mounted at the second axial end 502b of the section 502 and has a radially outwardly projecting portion, forming a rim 500a, the rim 500a having a mating surface 506, the mating surface 506 being configured for abutting contact with a door mounting face 505 provided at the rim 207 of the frame 201. Accordingly, door 202 is able to be inserted into hollow interior 208 (defined by annular protrusion 205) and removed from hollow interior 208 such that surface 509 of plate 503 is substantially co-planarly aligned with inwardly facing wear plate surface 204, wherein such alignment is established and maintained by abutting contact between respective surfaces 505, 506. As shown, during initial installation of the hatch assembly at the hatch opening 107, the collar 209 is placed around the annular protrusion 205 to contact the generally cylindrical protrusion surface 508. By tightening bolts 206, collar 209 is compressed between the three opposing surfaces 203, 401 and 508 as wear plate 200 is drawn radially outward into touching contact against bottom shell surface 106.

It should be appreciated that the annular protrusion 205, rim 207 and door 202 may be formed from steel, while the wear plate 200 is formed from a high hardness wear resistant material. The annular protrusion 205 at the inner end 205a is attached and permanently secured to the wear plate 200 at the defined perimeter of the aperture 300 by a suitable weld material 504.

To secure the door 202 at the hatch opening 107 (within the hollow interior 208), the attachment bolts 501 may be mounted within "keyhole" shaped bolt receiving holes (or slots) 507 extending through the flange 500 and the door frame rim 207. Bolt 501 is preferably stationary (captive) and includes a washer, spring, etc. at the innermost axial end, so when door 202 is removed, bolt 501 is held in place at rim 207. The door 202 also includes a rod-shaped handle 600 that extends diametrically across the cylindrical section 502 and is attached within the cylindrical section 502.

Thus, the frame 201 and door 202 are secured to the bottom housing 100 by the intermediate wear plate 200 and associated attachment bolts 206. That is, frame 201 and door 202 are not secured directly to bottom shell wall 104 by separate and specific attachment holes and bolts and the otherwise machined mounting surface at boundary region 111 as is the case with conventional bottom shell and hatch assemblies. Bottom shell wall 104 of the subject invention is not suitable for mating with existing hatch assemblies at boundary region 111, but may be optimized to reduce the risk of defects (particularly including porosity) within the internal structure of wall 104, and may additionally be optimized to minimize stress concentrations, thus maximizing the useful life of bottom shell 100. In particular, bottom shell wall 104 at radially outward-facing surface 105 is continuously convex within boundary region 111 and remaining region 112 such that each hatch opening 107 is seamlessly formed within bottom shell wall 104.