US 3238731 A
Description (OCR text may contain errors)
March 8,1966 H. c. SEIFERT ETAL MINE ROOF SUPPORTING ASSEMBLY I Filed m 4, i965 INVENIOR HAROLD C; SEIFERT GEORGE. W. ALLEN A ORNEY United States Patent 3,238,731 MINE ROOF SUPPORTING ASSEMBLY Harold C. Seifert, Westlake, and George W. Allen, Hudson, Ohio, assignors to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey Filed May 4, 1965, Ser. No. 453,097 3 Claims. (Cl. 61-45) This is a continuation-in-part of our application, Serial No. 248,529, filed December 31, 1962, and now abandoned.
This invention relates generally to mine roof plates and bolts for attaching these plates to the overhead roof structure of mines and other types of underground excavations requiring shoring means to insure against collapse of the ceiling.
More particularly, this invention concerns me roof plates of relatively small size and intended to be used to cover localized surfaces within subterranean areas such as a mine roof, as opposed to larger forms of plates as utilized to completely cover extensive portions of a mine roof.
Preferably, in the present invention, a single fastening bolt provided with novel head construction passes through the center of a substantially square mine roof support plate and is provided with suitable conventional means for anchoring the bolt within the roof structure of the nnne.
It is known to provide a substantially square support plate with a single fastening bolt for attachment to a mine roof; however, most of these prior arrangements fail to produce a mine roof supporting plate which may be securely attached to the usual roof surface encountered by means of the conventional form of fastening bolt.
Even using the most desirable form of fastening bolt and anchoring means in combination with many of the known forms of roof plates has led to many shortcomings. Two general types of roof plates are presently in common use. One is the peripheral contact type while equally popular is the peripheral and center contact plate. In the former instance, only the peripheral edge portion of the plate engages the roof surface as the center of the plate surrounding the bolt receiving opening 1s normally displaced downwardly well below the plane of the per pheral edge so that as the bolt is tightened by turning mto its anchor within the roof hole, the center portion of the plate will be biased upwardly by the bolt head to place the assembly under a constant spring tension. This structure is thought to offer continued protection following minor shifting in the roof strata due to the constant biasing of the sprung center portion of the plate. The disadvantages of this form of plate are that the exact stress condition of the plate is not readily discernible and accordingly the tendency to overtighten the bolt and permanently deform the plate is very prevalent and also, fatigue in the plate due to time and varying stress causes a loss of installed tension upon the bolt.
The latter mentioned peripheral and center contact form of plate includes a center portion adapted to be drawn into abutting relationship with the mine roof surface. The present invention may be broadly classed as this type of plate but includes an improved construction precluding the failure so often encountered when using the prior known devices which exhibit a tendency to be deformed as the bolt is tightened. This is due to the unsupported disposition of the center portion of the plate immediately adjacent the plate hole which results in this plate material being drawn up into the mine roof hole upon tightening of the bolt.
After selecting the location for a roof plate, a drill is used to produce the necessary hole in the mine roof structure for receiving the plate fastening bolt and suitable anchoring means therefor. It is not too difficult to drill a straight hole in the roof, but even with todays drill supporting carriages, or by aligning the drilling apparatus by means of measuring devices, it is virtually impossible to provide a bolt fastening hole which is exactly perpendicular to the exposed mine roof surface immediately surrounding the bolt hole and which underlies the support plate. This situation is compounded by the fact that hardly ever is the surrounding roof surface perfectly flat or even smooth.
The result is that when applying conventional support plates and using typical fastening bolts, the plate is practically always disposed at an angle other than normal to the axis of the bolt hole, due to the irregularity of the roof surface. Upon the tightening of the bolt, the off-center relationship between the bolt and plane of the plate causes a distortion of the support plate due to the unequal or uneven seating engagement between the head of the bolt and the center of the plate.
Accordingly, one of the objects of the present invention is to provide an improved mine roof plate assembly adapted to provide a rigid non-yielding engagement between a support plate and roof surface.
Another object of the present invention is to provide a universal full contact engagement between a mine roof support plate and bolt fastener.
Another object of the present invention is to provide a mine roof bolt having a convex spherical head for cooperation with a mine roof support plate provided with a mating spherical seat.
A further object of the present invention is to provide a mine roof support assembly including a roof plate providing peripheral and center engagement with the mine roof surface.
With these and other objects in view which will more readily appear as the nature of the invention is better understood, the invention consists in the novel construction, combination, and arrangement of parts, hereinafter more fully described, illustrated, and claimed.
A preferred and practical embodiment of the invention is shown in the accompanying drawing, in which:
FIGURE 1 is an elevational view, partly in section, showing the roof plate and fastening bolt of the invention, in relation to a mine roof structure.
FIGURE 2 is a perspective view of the roof plate and bolt of the invention illustrating more clearly the universal or spherical seat of the fastening bolt and plate.
FIGURE 3 is a bottom plan View of the bolt head and support plate as shown in FIGURE 1.
Similar reference characters designate corresponding parts throughout the several figures of the drawing.
The mine roof support plate, generall esignated 1, is preferably of square construction and is provided with a centrally disposed opening 2 for receiving the bolt fastener generally designated 3. Alternatively, a circuit or other shape of plate may 'be used in connection with the present invention.
The lower or bottom face 4 of the plate is formed with a downwardly projecting annular reinforcing rib 5 adjacent to and concentrically disposed with respect to the opening 2.
Said annular rib is substantially medially disposed between the center of the plate opening 2 and the nearest peripheral edge of the plate and is formed with a convex outer side wall 5a adjacent the plate edge while its inner side wall provides an arcuate concave seating surface 6, the imaginary projection of which, if carried across the opening 2, would comprise a spherical are having a constant radius. The upper or top surface 7 of the support plate 1 is preferably disposed in a single plane to provide a fiat or coplanar anchoring surface adjacent the periphery of the plate and intended to be disposed in abutting relationship with the exposed upper mine roof surface 8.
The fastening bolt 3 is adapted to be inserted in a suitable hole 9 which is drilled by conventional means into the strata of the mine roof. Any of several conventional anchoring devices generally designated may be employed to secure the fastening bolt 3 in the opening 9.
The circumferential edge 11 of the support plate opening 2 may have its upper edge 12, which is coplanar with the surface 7, at an angle away from the centeriaxis of the opening 2 for reasons which will hereinafter be more fully described.
The mine roof fastening bolt 3 is provided with a specially constructed head 13 for cooperating with the spherical seat 6 and inclined circumferential edge 11 of the support plate.
An important feature of the present assembly is the relationship between the bolt head 13, plate opening 2 and mine roof hole 9. The diameter of the opening 2 is at least as large as the diameter of the roof hole 9 with the bolt head 13 having a diameter greater than either. In this manner it will be seen that the upper edge 12 adjacent the opening 2 will contact the roof surface 8 to insure firm engagement by both of the coplanar surfaces 7 and 12.
The inner spherical surface 14 of the bolt head is curved to form a convex surface having a radius substantially identical to the radius of the spherical seat 6 surrounding the opening 2 of the mine roof plate.
Thus, it will be noted, as particularly illustrated in FIGURE 1, that regardless of the angle between the longitudinal axis of the bolt 3 and the plane of the support plate 1, a positive full engaging contact will be maintained between the spherical convex surface 14 of the bolt head 13 and the spherical seat 6 of the plate 1, whereby irrespective of the unevenness of the mine roof surface 8 with respect to the upper surface 7 of the plate 1, a positive supporting engagement will be maintained between the bolt head, plate, and mine roof without any possibility of deforming the plate or drawing any part thereof into the roof hole. In other words, since rarely, if ever, is the longitudinal axis of the bolt hole 9 normal to the plate of the upper surface 7 of the support plate, it is necessary to provide for a universal type engagement between the bolt head and plate in order to achieve positive non-rocking engagement between these elements.
As previously described, the circumferential edge 11 forming the opening 2 may be inclined at an angle coinciding with the longitudinal axis of the bolt shank 3a when at an angle in abutment with this edge 11. This would permit maximum pivotal movement of the bolt 3 by increasing the diameter of the opening 2 across the upper edge 12.
Suitable means are provided to permit turning of the bolt to expand the anchoring means 10 and draw the plate up against the mine roof 8. FIGURES 1 and 3 show a square-shaped recess 15 in the bolt head 13 for receiving a similarly shaped turning tool.
It is to be understood that the invention is not limited to the specific features shown, but that the means of construction herein disclosed comprise the preferred form of several modes of putting the invention into effect and the invention will therefore be understood in any of its forms or modifications within the legitimate and valid scope of the appended claims.
1. A mine roof support assembly comprising, in combination, a support plate having an upper roof engaging surface and a lower outer face, said plate provided with a central opening having a diameter no less than the diameter of a hole formed in the roof, an outward-1y projecting annular rib adjacent and concentric to said opening and including outer and inner side walls, said inner side wall providing a concave spherical seating surface surrounding said opening; the upper edge of said inner side wall coplanar with the upper roof engaging surface of said plate and providing a second roof engaging surface surrounding the hole in the mine roof structure which edge combined with said first mentioned roof engaging surface prevents distortion of said plate when said plate is in assembled supporting position, a fastening bolt having a shank portion insertable through said opening in said plate and adapted to extend into a hole provided in the mine roof structure, means on said shank portion to anchor said bolt in said roof hole, said bolt provided with a head portion having a convex spherical surface facing said shank portion, the radii of said plate and bolt head spherical surfaces being substantially equal, whereby, regardless of the relative angle between said bolt shank and the upper surface of said plate, a positive full contact engagement is provided between said bolt head and the seating surface of said plate.
2. A mine roof support assembly for a mine roof structure having an exposed support surface, said roof structure provided with a hole having an opening in said support surface, a support plate having a continuous fiat peripheral coplanar upper roof engaging surface and a lower outer face, said plate provided with a central opening at least as large as said roof opening and positioned around said roof opening with the upper circumferential edge of said plate opening in abutment with the exposed surface of said roof structure, said plate having an outwardly projecting annular rib adjacent and concentric to said opening and including outer and inner side walls, said inner side wall providing a concave spherical seating surface surrounding said plate opening, the upper edge of said inner side Wall forming said plate opening and coplanar with said upper roof engaging surface of said plate which edge combined with said upper roof engaging surface prevents distortion of said plate, a fastening bolt having a shank portion inserted through said opening in said plate and extending into said hole provided in the mine roof structure, means on said shank portion anchoring said bolt in said roof hole, said bolt provided with a head portion having a convex spherical surface facing said shank portion, the radii of said plate and bolt head spherical surfaces being substantially equal whereby regardless of the relative angle between said bolt shank and the upper surface of said plate or the degree of tension applied by said bolt, a positive full contact engagement is maintained by said bolt head between the two coplanar roof engaging portions of said plate and the roof support surface without deformation of said inner side wall into said roof opening.
3. A mine roof support assembly comprising, in combination, a support plate having a fiat peripheral coplanar upper roof engaging surface and a lower outer face, said plate provided with a central opening adapted to be positioned around a hole formed in a roof structure, the diameter of said opening at least as large as said roof hole, the upper circumferential edge of said opening adapted to be mounted in abutment with the exposed outer face of the roof structure, an outwardly projecting annular rib adjacent and concentric to said opening and including outer and inner side walls, said inner side wall providing a concave spherical seating surface surrounding said opening, the upper edge of said inner side wall coplanar with said upper roof engaging surface of said plate which edge combined with said roof engaging surface prevents distortion of said plate when staid plate is in assembled supporting position, a fastening bolt having a shank portion inserted through said opening in said plate and adapted to extend into said hole provided in the mine roof structure, means on said shank portion adapted to anchor said bolt in said roof hole, said bolt provided with a head portion having a convex spherical surface facing said shank portion, the 'radii of said plate and bolt head spherical surfaces being substantially equal whereby regardless of the relative angle between said bolt shank and the upper surface of said plate or the degree of tension applied by said bolt, a positive full contact engagement is maintained by said bolt head between the two coplanar roof engaging portions of said plate and the roof structure.
References Cited by the Examiner UNITED STATES PATENTS 2,862,368 12/ 1958 Dempsey 61--45 5 FOREIGN PATENTS 1,222,640 1/ 1960 France.
924,624 3 1955 Germany.
CHARLES E. OCONNELL, Primary Examiner.
1O JACOB SHAPIRO, Examiner,