This invention relates generally to down-hole hammer drills and more particularly to a down-hole compressed fluid driven hammer drill as described below.
Down-hole hammers generally comprise a drill bit as the lowermost component in the hammer assembly. The drill bit has a major diameter portion referred to as the bit head, and determines the diameter of the hole drilled. The bit head is traditionally integral with an upper, splined bit shank, which is slidably engaged and retained within a driver chuck. The driver chuck has an internal spline for engagement with the drill bit shank spline, and an outer threaded portion to engage a down-hole hammer barrel.
The bit shank splined section, when engaged within the driver chuck, is mechanically engaged rotationally, but is free to slide axially. To limit the extent of axial travel, and to prevent the drill bit from sliding out of engagement altogether, the drill bit shank has a section of reduced diameter above the spline, for a distance equivalent to the desired travel length of the spline plus the thickness of a retaining mechanism. This retaining mechanism is a bit retainer ring, made of two semi-circular sections with inner and outer diameters that are placed from each side around the reduced diameter of the bit shank thereby forming a near complete ring. The final section above the reduced diameter is the bearing land, which varies in form but is always of substantially larger diameter than the reduced diameter, so as to limit the axial travel as the bearing land comes to rest on the bit retainer ring.
In use, the driver chuck is lowered onto the drill bit shank, with the mating splines engaged. The two halves of the bit retainer ring are fit to the reduced diameter portion of the bit shank and rest atop the driver chuck. The drill bit, chuck and retainer ring sub assembly are threaded into the down-hole hammer casing/barrel. The bit retainer ring, now encased circumferentially within the down-hole hammer barrel, driver chuck below, and drill bit guide bush above, permits limited axial travel of the splined engagement.
It would be desirable to reduce the manufacturing cost of drill bits. The most effective way of doing so is to redesign the product so as to reduce its mass and length, while maintaining a robust and practical product.
EP1757769A1 discloses splines machined into the casing, a chuck fitted from above and a drill bit screwed into the chuck from below, providing for a shorter and more cost effective drill bit.
WO2008044458A2 discloses a type of drill bit for down-hole hammer use that is designed to be short and efficient to manufacture and use.
WO2009124051A2 discloses two embodiments of drill bits for down-hole hammer use that are designed to be short and efficient to manufacture and use.
WO2007077547A1 discloses a drill bit with a shorter shank than conventional types, also having threaded attachment.
My prior application, identified in the first paragraph above, disclosed embodiments of the invention illustrated in
In its broadest sense, the present invention includes: a hammer casing; a free piston motor in the casing; a drill bit having a separable bit shank extending from a bit head to an anvil end, the bit shank being keyed for reciprocating and driven rotation in the bore of a casing or chuck; and a number of keys or pins rotationally connecting the bit shank to the casing or chuck.
The check valve tube may comprise a perforate cylinder or the like functioning as a debris screen. Alternatively, the upper poppet check valve may be independent of the lower check valve in that the check valve tube and poppet valve may be associated with a spring and form a poppet valve assembly locatable at the upper end of the porting tube, seating onto said check valve tube and located directly adjacent the pressure supply ports of said porting tube, spring actuated from above by a connecting rod or from below by a spring supported by choke plug.
The pins may be considered sacrificial drive engagement pins, or keys, and may be of any suitable cross sectional shape as is practical and of any number as is practical. For example, the pins may be round section drive pins or may be of a section more like a keyway key.
In my prior application, I described the use of alternating long and short pins, whereas in the new embodiment of
The invention will be further described with reference to a embodiments of the invention as illustrated in the accompanying drawings and wherein:
In the hammer of
At this point the driver chuck and drill bit are engaged rotationally, and with the shorter pins 4 now no longer visible but engaged internally, extending axially and spaced circumferentially, the bit may freely slide a desired distance due to the internal engagement of the shorter pins. The shorter pins, which determine the allowable sliding movement, may be formed integral with either the drill bit or driver chuck. The longer pins, or keys, provide the majority of rotational drive engagement.
The embodiment of
In operation, as shown in
In
The lower check valve arrangement is made possible by the hollow porting tube 6 extending from its upper support in the central bore of top adapter sub 13 into the central bore of drill bit 2, and may be utilized as either an upper pressure check valve 11 or lower check valve 7, or both in unison via connecting rod 9. The co-operation of the porting tube within the drill fortifies alignment of the porting tube and permits an advantageous location of an exhaust check valve. The lower exhaust check valve positively and instantly prevents debris contamination at the first possible point of entry. This design is therefore considerably more resistant to entry of potentially damaging debris than prior down-hole hammers.
Additionally, the porting tube 6 controls the piston return chamber 23 volume, thereby eliminating requirement of a component known as a foot valve or exhaust tube, as described in prior art such as that described above.
In the present invention, cooperation of the hollow porting tube and drill bit is made practicable due to the driver chuck and drill bit combination design, in that the drill bit shank 2 is well supported in alignment within the driver chuck 1, and has a substantial wall thickness and a bore able to accommodate a porting tube of sufficient cross-sectional area for the required airflow, the drill bit bore fashioned to provide sufficient cross-sectional area for passage of exhaust fluid through the check valve 7.
A piston compression chamber 14 is formed integrally within the top adapter sub 13.
Internal transfer ports 20 are fly-cut into the barrel bore in a known manner. The effect on torsional rigidity is minimal and acceptable because only about six percent of the barrel circumference is affected per channel since the porting channel 19 need have only a cross sectional area equal to any one of the supply or delivery ports, and much of the removed metal is restored as a cover cap 24. Furthermore, it is not necessary to fashion a cover cap flush fitting with the barrel outside diameter; however, it would be entirely acceptable to do so if the cover cap were to protrude the barrel outside diameter up to but not exceeding the diameter of the drill bit.
With this design, I have found there to be ample material thickness to accommodate a fluid conduit 19 in the manner described. This is advantageous in that material input is kept at a minimum since manufacturing of an inner cylinder is negated, as are the problematic methods of retaining the inner cylinder.
The present invention described thus far is of non-ported piston type design. While the general flow characteristics of this type of porting are known and not part of this patent application, it has a bearing on how some of the components are designed. Another embodiment of the invention, shown in
The embodiment of
Compressed air enters porting tube 6 and directly engages the hammer via pressure supply port 12 to begin operation. In turn, the check valve 7 is forced open by exhaust fluid against its spring 8 via connecting rod 9. The spring is supported by choke plug 10. The check valve arrangement may also be a sliding piston 11 atop the spring which is forced down against the spring by incoming compressed fluid, thus exposing the pressure supply port 12. The check valve arrangement is thus mounted internally within the hollow porting tube, and may be either or both of the aforementioned arrangements in unison. See
With reference particularly to
The piston 18 is ported from its upper and lower extremities via porting conduits 21a and 22a, such porting conduits cooperating with porting apertures in hollow porting tube 6 to effect reciprocal motion, and may be fashioned to slidably co-operate at the top of its stroke with the bore of said piston compression chamber at 14a in
In the present invention, for reasons of safety and ease of handling, are provided longitudinal flats on the outer surfaces of the barrel and driver chuck (see
The further embodiment of
The further embodiment differs from that of
The pin drive and linear retention mechanism design permits the loading of the shank/anvil 2a from either end of the casing but preferably from the lower end, as would be generally convenient in field use. In that case, the drive/stroke limiting pins 5a are inserted into the corresponding grooves within the casing, the shank/anvil 2a then pulled downward to engage the pins, and thus the shank/anvil is engaged rotationally with the casing via the pins but may not be pulled out of the casing longitudinally due to the engagement of the pin ends in the lower end of the casing grooves and the upper end of the shank/anvil grooves.
The drive/stroke limiting pins 5a of the embodiment of
With the shank/anvil in place with the pins, the drill head may then be threadably attached to said shank/anvil, thus the assembly becomes complete.
The reader and those skilled in the art should be aware that in almost all cases, a worn drill bit of the down-hole hammer type is discarded because the drill bit head is worn to below serviceable diameter, while the shank/anvil portion is generally in good serviceable condition but must be discarded regardless, thus the advantages of the present chuckless, casing mounted, shank/anvil embodiment are evident:
Another feature of the embodiment of
A symmetrical, or double ended piston costs no more to produce and may provide up to double the usual service life.
A further feature of the embodiment of
The description above, and the drawings, describe presently preferred embodiments of the invention. Inasmuch as the invention is subject to modification and improvement, the preferred embodiments should be regarded as examples of the invention defined by the claims below.
Number | Date | Country | Kind |
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2006905840 | Oct 2006 | AU | national |
This application is a continuation-in-part of copending application Ser. No. 12/445,850, filed Apr. 16, 2009, which was the U.S. national stage of international application PCT/AU2007/001580, filed Oct. 17, 2007.
Number | Date | Country | |
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Parent | 12445850 | Apr 2009 | US |
Child | 13351454 | US |