US 3311012 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
March 1967 c. l. WILLIAMS PRESSUREACTUATED EXPANDING ANCHOR 2 Sheets-Sheet 1 Filed March 11, 1965 //VVE/V7'0.
CHESTER Z. W/LL/AMS March 28, 1967 c. l. WILLIAMS PRESSURE-ACTUATED EXPANDING ANCHOR 2 Sheets-Sheet 2 Filed March 11, 1965 B) gym United States Patent 3,311,012 PRESSURE-AUIUATED EXPANDING ANCHOR Chester I. Williams, 347 Greenbriar SE., Grand Rapids. Mich. 49506 Filed Mar. 11, 1965. Ser. No. 438,881 8 Claims. (CI. 85-65) This invention relates to the construction of anchor devices of the type used in conjunction with rock bolts. These bolts are primarily long rods inserted in holes drilled in a rock formation. The inner end of these rods is commonly provided with an anchor that can be expanded into sufiiciently solid engagement with the wall of the hole to resist tensile stresses established in the bolt rod' to hold the rock formation in position. It is the usual practice to fill the hole around the rod and the anchor with grout after the rod has been properly pre-stressed.
The most common forms of anchors are expanded, or setjeither by rotation of the bolt rod, or by inward axial movement of the bolt rod. Either of these arrangements results in a complex and time consuming series of operations to install the rock bolts. This invention utilizes pressure to set the anchor, the pressure being derived from compressed air, grout pressure, water pressure, or from the gas pressure provided by an exploding cartridge at the surface end of the rock bolt. This invent-ion is preferably associated with hollow bolt rod material that functions as a conduit as well as a stress carrier. The pressure necessary to actuate the anchor is therefore preferably supplied via the bolt rod itself.
The several features of the invention will be analyzed in detail through a discussion of the particuular embodiments illustrated in the accompanying drawings. In the drawings:
FIGURE 1 is a sectional elevation of one modification of the invention, showing a rock bolt provided with a pressure-actuated anchor device as it is inserted in the hole.
FIGURE 2 illustrates the condition of the device shown in FIGURE 1 after the anchor has been actuated by grout pressure, and after the hole around the rock bolt has been .filled with grout.
FIGURE 3 illustrates a modified form of the invention, as it is inserted in the hole.
FIGURE 4 illustrates the completely installed condition of the device shown in FIGURE 3.
FIGURE 5 illustrates a further modification of the invention, as it is inserted in the hole.
FIGURE 6 illustrates the actuated condition of the device shown in FIGURE 5.
FIGURE 7 illustrates a schematic form of a device using an explosive cartridge to generate pressure at the surface that is conducted through the bolt rod to actuate the anchor device.
FIGURE 8 is a perspective view of an expansible shell of the type shown in the preceding views.
The device shown in FIGURES 1 and 2 includes a tubular bolt rod 10 installed in the hole 11 in the rock formation 12. Theinner end of the bolt rod is provided with an anchor device generally indicated at 13, which is expanded into engagement with the wall of the hole 11. Tension in the bolt rod 10 is established by the nut 14 bearing against the surface plate 15 through the beveled washer 16. The stresses generated at this point are resisted by the action of the anchor 13 against the wall of the hole 11. i
The anchor device 13 includes a ring 17 resting against a suitable shoulder on the bolt rod 10, and acting as an abutment preventing axial movement of the expansib-le shell 18. The conformation of this sleeve is well-known, and is generally C-shaped in cross section. The inner -the cylinder 21.
surface is preferably substantially conical, and engages a similar surface on the cone member 19. The righthand portion of the cone member, indicated at 20, forms a piston engaging the cylinder 21. This cylinder is essentially cup-shaped, and is in threaded engagement with the end of the bolt rod 10. A transverse diametral hole 22 in the end of the bolt rod forms a port communicating between the interior 23 of the bolt rod and the inside of A plug 24 obstructs the interior 23 at the end of the bolt rod, and it is preferable that this plug 24 be dischargeable on exceeding a predetermined pressure within the bolt rod.
The expanded condition of the anchor is shown in FIGURE 2. The cone member 19 has moved axially to the left as a result of the presence of pressure within the cylinder 21 acting against the piston 20. In the illustrated form of the device, the cone member 19 and the piston 20 are preferably formed as a single integral piece, but this arrangement is by no means necessary. The advance of the cone member 19 to the left results in increasing the circumscribed diameter around the shell 18, and this movement has continued until the piston 20 has moved completely out of the cylinder 21. This results in an unobstructed passage from the interior of the rock bolt out into the space defining the hole 11. The anchor may be placed in this condition by any source of pressure. After it has been properly set, and the bolt 10 placed in a proper degree of tension, the hole 11 around the bolt rod can be filled with grout injected through the interior 23. This grout forms a protective mass 25 surrounding the bolt rod, and bonding it to the surrounding rock formations.
In the condition illustrated in FIGURE 2, the actuation of the anchor has proceeded to the point that the piston 20 has moved out of the cylinder 21 without developing sufiicient pressure to blow the plug 24. If the anchor had encountered solid resistance from the surrounding rock prior to the movement of the piston 20 out of the cylinder 21, the discharge of the plug 24 would have permitted a flow of grout outwardly at this point, and back along the bolt rod through the peripheral discontinuity of the shell 18. The general configuration of this shell is shown in FIGURE 8. This is a preferred form, and forms no part of the present invention. The C-shaped configuration results in a discontinuity 26. The expanding action of the shell 18 is facilitated by the provision of the flattened area 27 and the axially-extending slot 28. This produces a weakened section at the point indicated at 29 which functions in the manner of a hinge as the cone member moves with respect to the shell to induce the expansion.
When the device has been set as shown in FIGURE 2, and after the grout has hardened into the mass 25, tensile stresses extending to the inner end of the bolt (adjacent to the anchor) will have a tendency to be transferred through the cylinder 21 to the cone member 19 via the hardened grout, and from the cone member 19 through the shell 18 into the surrounding rock formation. Much of the tensile stress of the bolt will normally have been taken out by direct transfer through the grout over to the wall of the hole along the length of the bolt rod. The residual tension, however, must pass through the anchor device into the surrounding rock formation directly.
In the modifications shown in FIGURES 3 and 4, the presence of the end ring 30 hearing directly against the inner end of the shell 31 provides a more direct transfer of stress in the expanded condition of the anchor. To provide this feature, the piston 32 is placed at the axially outer end of the anchor device, and drives the pistoncone unit 33 from the position shown in FIGURE 3 to that of FIGURE 4. In the FIGURE 4 position, the
piston has moved out of the cylinder, leaving a passage for the movement of grout through the device and into the hole 34. The port 35is appropriately located for the position of the cylinder 32 in this modification of the invention. It should be noted that the modification shown in FIGURES 3 and 4 does not require that any of the stresses be transferred from the end ring 30 through either grout or through the piston-cone unit in order to pass through the shell 33 and into the rock formation. The condition shown in FIGURE 4 corresponds to the full actuation of the device prior to the development of sufiicientpressure to discharge the plug 36.
Referring to FIGURES and 6, a further modification of the invention is illustrated, and which utilizes a fixed cone 37 having threaded engagement with the end of the bolt rod 38, with the expansible shell 39 being moved to the right along the cone 37 by the piston 40 acting within the cylinder 41. The transverse port 42 is provided for communicating between the cylinder 41 and the hollow interior 43 of the bolt rod 38. The expanded condition of the device is shown in FIGURE 6. Preferably, the left end of the shell 39, as showniln the drawings, is formed on a concave conical surface, so that the reaction of the forces, as the piston 40 forces the shell 39 to the right, will be to neutralize frictional restraint on the radial expansion. The presence of lubrication between the surfaces Will also consume less of the available energy in friction.
In all of these modifications, it is possible to reverse the action of the piston and cylinder so that the piston remains axially fixed, and the cylinder moves. Regardless of whether the piston or the cylinder is axially fixed, the two together form an actuator for expanding the shell.
FIGURE 7 illustrates a schematic arrangement for an auxiliary pressure sourcethat may be used for setting the anchor devices shown in these drawings. Essentially, the unit 44 is similar in construction to the receiver of a boltaction rifle. The bolt itself is not shown, but the unit 44 can be screwed onto the outer extremity of the bolt rod. An explosive cartridge 45 can be detonated by a conventional firing system, with the pressure thus generated being delivered through the interior passage 46 of the bolt rod 47 to the anchor device at the inner extremity of the bolt rod. After the setting of the anchor device has been completed, the unit 44 is detached, followed by tightening of a nut 14 and the subsequent application of a grouting coupling. The size of the cartridge 45 may be matched to the particular anchor device being set., Under ordinary conditions, there will be no substantial tendency for the pressure delivered to the unit to blow the bolt rod out of the hole, as the anchor device will normally have been set prior to the emergence of the pressure into the area surrounding the rock bolt.
The particular embodiments of the present invention which have been illustrated and discussed herein are for illustrative purposes onlyand are not to be considered as a limitation upon the scope ofthe appended claims. In these claims, it is my intent to claim the entire inventiondisclosed herein, except as I am limited by the prior art.
1. A pressure-actuated expanding anchor including in combination with a tubular bolt rod having an axial passage throughout the length thereof, an anchor device for 4 engaging the wall of a hole in a rock formation, comprising:
a cone member having an externally tapered portion and an expansible shell member surrounding at least a portion of said cone member and having an internally tapered portion receiving the externally tapered portion on said cone member, said shell member being axially restrained by radially projecting means on said bolt rod, one of said members being normally axially fixed with respect to said bolt rod, and the other axially movable with respect thereto; means forming a cylinder fixedly mounted on and ex tending axially with respect to said bolt rod, said rod having a radially extending port communicating between the interior of said rod and said cylinder;
piston means having a portion received in said cylinder and adapted to induce relative axial movement between said members in cooperation with said cylinder to expand said shell member, said piston means being mounted on said rod and defining an integral extension of said cone member with the portion thereof which is received in said cylinder being normally axially spaced from said shell member, said cylinder and piston means together forming portions of an-actuator, one of said portions being axially fixed with respect to said bolt rod; and
a plug closing the inner end of the axial passage in said bolt, said plug being dischargeable upon exceeding a predetermined pressure within said bolt rod.
2. A combination as defined in claim I, wherein said piston and cone member are portions of a single integral piece.
A combination as defined in claim 1, wherein said cylinder is a cup-shaped member secured to the end of said bolt rod.
4. A combination as defined in claim 1, wherein said plug is dischargeable on exceeding a predetermined pressure within said bolt rod.
5. A combination as defined in claim 1, wherein said piston is movable to a position providing exhaust from said cylinder.
6. A combination as defined in claim 1, wherein said shell member is axially restrained by a ring engaging the end of said bolt rod, and said piston is movable toward said ring by pressure in said cylinder.
7. A combination as defined in claim 1, wherein pressure for moving said cylinder is derived from an explosive cartridge device engaging the outer extremity of said bolt rod.
8. A combination as defined in claim 1, wherein said cylinder is axially fixed with respect to said bolt rod.
References Cited by the Examiner UNITED STATES PATENTS 2,573,880 11/1951 Temple -65 2,807,184 9/1957 Miller 85-65 2,842,022 7/1958. Semmion 8565 CARL W. TOMLIN, Primaly Examiner.
R. S. BRITTS, Assistant Examiner.