US3409091A - Percussion multi-blow gravity drill - Google Patents

Description

NOV 5, 1968 A. E. BARDWELL PERCUSSION MULTIBLOW GRAVITY DRILL Filed July 2e, 196e United States Patent 3,409,091 PERCUSSION MULTI-BLOW GRAVITY DRILL Allen E. Bardwell, Princeton, NJ., assgnor to Trident Industries, Inc., Princeton, NJ., a corporation of Delaware Filed July 26, 1966, Ser. No. 567,927 Claims. (Cl. 173--119) ABSTRACT OF THE DISCLOSURE A novel gravity drop multiblow percussion drill comprising an elongated casing closed at the upper end by a plug adapted to be attached to a cable connector and at the lower end by a stationary `anvil adapted t0 receive a drill bit at its free lower end, an elongated heavy hammer reciprocably mounted in the casing having reduced extremities about each of which is mounted a heavy compression spring which in rest upright position of said drill maintain said lower end of the hammer spaced a predetermined short distance from the anvil, said springs being yieldable to permit initial and subsequent striking of the anvil by the hammer immediately following striking of a drill bit mounted in the anvil.

The present invention relates generally to gravity drop -percussion drills, and more particularly to a novel percussion gravity drop drill incorporating structure for effecting one or more blows immediately following the gravity drop blow of the bit.

Efforts have long been made to improve gravity drop or churn drilling in the area of multiple vblow structure. It has been recognized for years that the number of feet drilled per hour in Irock, or the like, can be materially increased by striking one or more additional blows through the bit immediately following the gravity blow thereof. Structures heretofore devised by others have had little, if any, practical success.

Hence, an object of the present invention is to provide a novel percussion multi-blow gravity drop drill comprising one solution to the long existing problem.

In brief, the present novel drill includes in a preferred embodiment an elongated casing having an upper plug for attachment to a cable connector and a fixed anvil assembly secured in the lower end thereof comprising an anvil portion and a shank portion having a threaded socket for receiving a drill bit. Within the casing is a reciprocatable hammer having reduced upper and lower extensions, there being a compression spring about each extension. In the normal position of the hammer, with respect to the casing, there is a short gap between the face of the lower extension and the anvil. When the drill descends and strikes the hole bottom the internal hammer continues its descent, closing the short gap and compressing the lower spring to deliver a follow-up blow to the anvil and hence to the drill bit. The hammer may then rebound, compressing the upper spring, `and a series of follow-up blows may result. Upon retraction of the drill up the hole, the two compression springs will return the hammer to the normal position, of a short gap Ibetween hammer and anvil prior to the succeeding dropping of the drill and striking of the hole bottom.

Therefore, other objects of the invention are to provide a novel percussion multi-blow gravity drop drill which is of durable, rugged construction insuring good commercial use of the tool, which incorporates effective multi blow structure that materially increases the per hour drill footage, which is adapted to a variety of drilling uses, and which otherwise fulfills the objects and advantages sought therefor.

The foregoing and other objects and advantages are 3,409,091 Patented Nov. 5, 1968 apparent from the following description taken with the accompanying drawings, in which:

FIGURE 1 is longitudinal cross-sectional view of the upper portion of a gravity drop drill incorporating the teachings of the present invention, portions of the upper plug and of the middle portion of the hammer and casing Ibeing broken away for conservation of space and the upper portion of the plug being 'shown in elevation; and

FIGURE 2 is a longitudinal cross-sectional view through the lower portion of the drill of FIGURE 1, portions of the lower shank portion being omitted for conservation of space and the lower shank portion being shown in elevation.

Referring to the drawings more particularly by reference numerals, 10 indicates generally a gravity drop drill constructed in accordance with the principles of the pre'sent invention. The drill 10 includes an elongated cylindrical tubular casing 12, which may be integral, as shown, and may be any desired length, as some fourteen feet long in an experimental tool. An upper plug 14 of the configuration clearly shown in the drawings is screwed into the upper end of the casing 12, suicient length of threads being provided to effect the total desired compression in two springs, identified below, in the process of screwing the plug 14 to its installed position.

Reciprocally mounted within the casing 12 is a massive hammer unit 16 including a central principal hammer body portion 18, an upper reduced shaft portion 20, and a lower reduced 'shaft portion 22. The free lower end part of the lower reduced shaft portion 22 may be of tough, hardened steel. The upper reduced shaft portion 20 reciprocates in an upper bearing 24 which supports and guides the upper end of the massive hammer unit 16 in its reciprocation in the casing 12. This upper bearing 24 may be made from a nylon tubing, or other suitable long lasting material. Surrounding the upper hammer shaft portion 20 below the bearing 24 is a heavy compression spring 26 which engages a bearing protection shim 28 at its upper end. Surrounding the lower hammer shaft portion 22 is a second heavy compression spring 30 similar to the spring 26 which engages at its lower end a bearing protection shim 32 abutting a lower bearing 34 within which the lower reduced shaft portion 22 reciprocates as a guide and support. Below the lower bearing 34 is a lower bearing support shim 36 having a larger inside diameter 38 at the bottom to provide a debris chamber 40 around a raised anvil surface, identified below. The debris chamber 40 is designed and provided to capture any particles of metal, nylon, or the like, which may fall from various internal components of the drill 10 during its functional life.

An anvil assembly 42 is secured in the lower end of the casing assembly 12 by sweating, by threads, or otherwise, and includes an anvil cap 44 which receives the chatter of impacts from the hammer unit 16, and a lower shank portion 46 including a threaded bit socket 48 which removably receives a bit of selected design.

Inasmuch as in the operation of the drill :10, a bit mounted in the socket 48 of the anvil unit 42 can remain in contact with the surface to be drilled for only a very small fraction of a second during each cycle, precise synchronization and positioning of the hammer unit 16 are critical. For proper operation, the opposing springs 26 and 30 should be maintained under several hundred pounds of compression and the equilibrium position of the hammer unit 16 in free fall should be such as to provide a small fraction of an inch gap between the lower extremity of the hammer unit 16 and the anvil cap 44. That is, the springs 26 and 30 should counterbalance in a position such that the gap between the lower extremity of the hammer unit 16 andthe anvil cap 44 is less than one-half Y L3 inch. If this gap is made much larger than one-half inch, except in soft material, the probability of the hammer unit 16 delivering its impact to the anvil cap 44 during the short period of time when said anvil assembly 42 is still in contact with the bottom of the bore is greatly reduced and the eiciency of drilling suffers. Successful experimental models of this drill 10 have lbeen constructed where this gap is one-quarter inch, The .extent of the gap will lvary, however, in practice depending upon the nature of the ground or rock in which drilling is taking place.

In the operation of the drill, the upper and lower compression springs 264 and 30 are both under compression when the drill is descending to hold the hammer unit 16 raised above the anvil cap 44 to form the short gap described above. Then, when the drill strikes the hole bottom, so that the downward stroke of the casing 12 is arrested, the hammer unit 16 will continue to descend and further compress the lower spring 30. The hammer closes the short gap and strikes the anvil assembly 42a followupblow that is delivered through the drill bit to the hole bottom for additional drilling impact. The' gap length,` mass of hammer and spring forces are selected to have the follow-up below occur while the drill bit is contacting the hole bottom, thereby increasing drilling eciency.

The hammer unit 16 will rebound from the anvil assembly 42, and the upper spring 30 functions to absorb and redirect rebound forces, such that a series of followup blows may occur. The upper spring 30 must also be under such compression and have such a spring constant during descent of the drill as to act as an abutment, or

stop, that resists the upward force of the lower spring 26 to establish the short gap between the lower end of the hammer unit 16 and the anvil cap 42. The lower spring 26 must exert an upward force adequate to support the mass of the hammer unit 16 and to work against the upper spring 30 in establishing the short gap. Adjustment of the spring compression can be made by altering the length' of the bearing protection shims 28, 36, and by selection of the springs 26, 30.

It is clear that this design depends primarily on the inertial follow-through action of the hammer unit 16 subsequent to the initial impact of the anvil assembly 42 with the bottom of the bore and the redirection of the resulting rebound forces to energize its hammer unit 16 to produce a chatter of impacts upon said anvil cap 44. This design offers a substantial increase in eiciency over stanlard churn drills.

It is apparent that there has been provided a drill construction which fulfills the objects and advantages sought therefor,

It is to be understood that the foregoing description and the accompanying drawings have been given by way of illustration and example. It is also t-o be understood that changes in form of the elements, rearrangement of parts, and substitution of equivalent elements, which will be obvious to those skilled in the art, are contemplated as within the scope of the present invention, which is limited only by the claims which follow.

What is claimed isc l 1.` A multi-blow gravity drop drill structure comprising an elongated casing, means closing the upper end of-the casing including means for attachment to a raising and dropping structure, an anvil member secured to and closing the lower end of-said casing, said anvil member including means for detachably receivinga bitya-single hammer member reciprocably mounted in said casing adapted to strike said anvil member immediately following the impact of the drill structure through an attached bit with the bottom of a hole, a first compression spring acting downwardly upon said hammer member, and a -second compression spring acting upwardly upon said hammer mem-ber, said springs in a dropping drilling position of said drill being substantially in equilibrium and maintaining said hammer member spaced a small distance from said anvil member.

2. The combination of claim 11 in which said springs remain under compression.

3. The combination of claim 1 in which said dropping drilling position said springs maintain said spacing between anvil member and hammer member at less than one-half inch.

4. The combination of claim 1 in which the spacing between the hammer and the anvil members at the moment of contact of the drill at the bottom of a hole in hard rock and the like is less than about one-half inch.

5. The combination of claim 1 in which the spacing between the hammer and the anvil members at the moment of contact of the drill at the bottom of a hole in soft material is greater than one-half inch.

References Cited UNITED STATES PATENTS 1,835,189 12/1931 Spencer 175-299 X 2,524,707 10/1950 Koeln 175-299 2,655,825 10/1953 Gendron 173-121 X 2,765,776 10/1956 Pyk 173-118 X 2,835,474 5/1958 OConnor et al 175--299 2,872,158 2/1959 Green 175-299 3,151,912 10/1964 Herrmann 173-121 X 3,303,899 2/1967 Jones et al. 175-299 3,305,034 2/1967 Koeln 175-299 3,307,641 3/1967 Wiggins 175+-56 CHARLES E. OCONNELL, Primary Examiner'.

I. A. CALVERT, A ssistanl Examiner.

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