US2879038A

US2879038A - Under-reamer

Info

Publication number: US2879038A
Application number: US692677A
Authority: US
Inventors: Chester F Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-10-28
Filing date: 1957-10-28
Publication date: 1959-03-24
Anticipated expiration: 1976-03-24

Description

March 24, 1959 c. F. JOHNSON 2,879,038

UNDER-REAMER Filed Oct. 28, 1957 lN-VENTOR ATTORNEY United States Patent UNDER-REAMER Chester F. Johnson, Los Angeles, Calif.

Application October 28, 1957, Serial No. 692,677

Claims. (Cl. 255-76) This invention relates to under-reamers of the type employed in forming channels in bores produced in walls fabricated of concrete, brick, stone and the like for the reception of expansion bolts employed in the attachment of structures to the walls.

An object of the invention is to provide an underreamer of the above character embodying a shank for engagement with a power driven rotary chuck, in which the shank is equipped with under-reaming cutters mounted for movement in and out of an under-reaming position and in which means are provided for actuating the cutters through rotation of the shank adapted to advance the cutters on rotation of the shank in one direction and to retract the cutters on reversing the rotation of the shank.

A particular object is to provide yieldable resilient means interposed between the shank and cutters for actuating the latter such as to obviate sudden impact on the cutters as might cause the latter to excessively dig into the wall being cut and thereby stall the motive power or damage the cutters or their mountings.

Another object is to provide a simple and effective means for cushioning operation of the cutters.

Another object is to provide a construction in the under-reaming cutters and a mounting therefor such that the cutters may be readily removed and replaced and whereby the cutters may be so economically constructed as to render them expendible; the cutters being designed to be sharpened when slightly worn and to be discarded and replace when excessively Worn.

A further object is to provide an under cutter of the above character comprising few simple parts that may be readily manufactured and assembled.

With the foregoing objects in view together with such other objects and advantages as may subsequently appear, the invention resides in the parts and in the combination, construction and arrangement of parts hereinafter described and claimed, and as illustrated by Way of example in the accompanying drawing in which:

Fig. l is a view of the under-reamer as seen in side elevation; v

Fig. 2 is a horizontal section and plan view as seen on the line 2-2 of Fig. 1 showing the under-reamer cutters v continuous screw threads 6 on its outer end portion on which is loosely screwed an internally threaded cylindrical sleeve 7 having a fiat inner end 8 extending perpendicular to the axis of the shank A. The shank A has a reduced diameter portion 9 at the inner end of the threads 6 which reduced diameter portion has extending therethrough a diametrical slot 10 in which is mounted a plate spring 11 comprising a normally straight strip of flat stiff but resilient metal having a thickness slightly less than the width of the slot 10 so as to permit lateral but limited movement of the spring 11 in the slot 10. The end margins of the side wall of the slot 10 are rounded as indicated at 12.

Projecting from the flat end face of the sleeve 7 is a pair of cylindrical pivot pins 1414 disposed on diametrically opposite sides of the shank A on radii extending at an angle clock-wise relative to radii extending perpendicular to the slot 10. Mounted on the pivot pins 1+-14 is a pair of end-to-end under-reaming cutters BB particularly shown in Fig. 5 each of which cutters comprises an arcuate flat sided arm 15 having an arcuate inner margin 16 normally in spaced relation to the reduced diameter portion 9 of the shank A and having an arcuate outer margin 17 normally lying inwardly of the outer margin of the sleeve 7 on the flat end faces 8 of which the arm B slidably seats. The outer margin 17 of each of the arms B converges toward the inner margin 16 along the length of the arm between the point of engagement of the arm with the pivot pin 14-14 to a point adjacent but spaced from the outer end of the arm, which convergent portion 18 terminates in an outwardly projecting under-reaming tooth 19 presented toward the pivot pin 1414. The pivotal connection between the arm B and pivot pin is located adjacent to but spaced from the inner end 20 of the arm which inner end is designed to abut at its juncture 20 with the margin 16 with the reduced diameter portion 9 when the arm is swung outwardly to its fully extended position shown in Fig. 4. The inner margin of each of the arms BB has an open ended slot 21 located adjacent the outer end of the arm with which slots the outer ends of the spring 11 are slidably and normally loosely engaged as shown in Fig. 2.

Mounted on the shank A at the inner end of the reduced diameter portion 9 is an adjustable collar 22 for limiting advance of the sleeve 7 on the threads 6, the collar 22 being adapted to be positioned adjacent to the outer ends of the pivot pins 1414 to afford an abutment therefor and also serve to hold the under-reamer arms B against displacement longitudinally of the shank A, which arms have a thickness slightly less than the length of the pivot pins so as to afford a clearance between the arms B and the adjacent flat face of the collar 22. As a means for facilitating adjustment of the collar 22 longitudinally of the shank A, which is necessary in order to permit assem blage of the spring 11 in the slot 10, the shank A is formed with screw threads 23 leading from the inner end of the reduced diameter portion 9 on which threads 23 the collar 22 is screwed. On rotating the collar 22 it may be advanced or retracted on the threads 23.

In assembling the parts of the under-reamer, collar 22 is initially screwed on the shank A over the threads 6 which correspond to the threads 23, and is then screwed onto the latter to a retracted position as indicated by the dotted lines a in Fig. 3. The sleeve 7 is then screwed onto the threads 6 until the flat end face 8 of the sleeve is aligned with the outer end margin of the slot 10. One of the arms B is then engaged with one of the pivot pins 14 by positioning the inner end portion of the arm over the pin then manipulating the arm to pass a cylindrical opening 24 therein over the pin so as to seat the arm on the fiat end face of the sleeve. The spring 11'is then inserted in the slot 10 from the side of the shank opposite the assembled arm B and its advancing end is passed through the slot 10 and projected into the slot 21 of the assembled arm B. The other arm B is then assembled in like fashion on the other pivot pin 14 and in so doing is manipulated to engage the slot 21 of such arm with the other end of the spring 11 then projecting from the shank A. The assemblage will then appear as shown in Fig. 2 with the arms BB seated on the adjacent fiat end face 8 of the sleeve 7 and with :the upper ends of the pins 14 projecting slightly above the adjacent faces of the arms BB and slightly above the plane of the upper margin of the spring 11. The collar 22 is then advanced on the threads 23 and brought into slightly spaced relation to the upper ends of the pins 1414 thus completing the assemblage.

In the operation of the invention, the shank A is engaged in a power driven rotary chuck in a usual fashion, whereupon the under-reamer with the arms BB re- .tracted as shown in Figs. 1 and 2 is inserted in a bore to be reamed which bore has a diameter slightly larger than the diameter of the sleeve 7 so as to slidably receive the sleeve 7. On thus disposing the under-reamer in the desired position in the wall bore, the shank A is rotated.

The sleeve 7 being loosely engaged by the threads 6 of the shank, initial turning movement of the latter which ,is sudden and swift will occur for an instant independent of the sleeve 7 such as to cause the ends of the spring 11, carried by and advancing with the shank A, to exert an outward thrust on the arms BB such as to bring the under-reaming teeth 19 thereon into contact with the surfaces of the wall bore thereby imposing a drag on the sleeve 7 tending to initially resist rotation of the sleeve until such resistance is overcome by the thrust of the end portions of the spring 11 against the side wall of the slots 21 against which the outer ends of the spring .11 bear. When this occurs the sleeve 7 will rotate at least substantially in unison with the shank A and at the same time the end portions of the spring 11 will exert .an outward thrust on the arms BB and thereby cause .the under-reaming teeth 19 to effect cutting engagement with the surface of the wall bore such as to effect a cutting action thereon and thereby form a channel around the wall bore.

Initial thrusts of the ends of the spring 11 on the arms BB in forcing the latter outward are cushioned since the spring will yield in opposition to its tension under resistance offered to outward movement of the arms when the teeth abut the surface of the wall bore. This action coupled with outward movement of the arms being under spring pressure minimizes possibility of stalling of the motor utilized in driving the under-reamer.

Outward movement of the arms BB is limited by the inner end portions 20 of the arms being brought into abutting engagement with the diametrically reduced portion 9 of the shank A under the thrust of the end portions of the spring 11 as shown in Fig. 4.

Back pressure imposed on the .ends of the spring 11 during their forward movement relative to the arms BB flexes the spring as illustrated in Fig. 4 thereby placing it under tension such that on cessation of the driving ,force and/or slight retrograde turning of the shank A the spring will return to its normal straight condition thereby causing the opposite ends of the spring 11 toride into the slots 21 and engage the outer side walls of the latter such as to effect retraction of the arms BB to their normal position shown in Fig. 2 whereupon the under-reamer may be withdrawn from the wall bore. This retraction of the arms is facilitated by reason of the wall of the slots 21 then engaged by the ends of the spring 11 extending in such angular relation to the spring as to present upwardly inclined planes to the advancing ends of the spring so that the latter will exert a wedge action such as to draw the outer ends of the arms BB inwardly.

In event it becomes necessary to remove the under- Iearner arms BB for sharpening or replacement, such maybe. readily accomplished by retracting the collar 22 on the threaded portion 23 so as to permit lifting of the arms BB from the pivot pins 1414 and thusfreeing the arms from engagement by the end portions of the spring 11.

While I have shown and described a specific embodiment of the invention, I do not limit myself to the exact details of construction set forth, and the invention em braces such changes, modifications and equivalents of the parts and their formation and arrangement as come within the purview of the appended claims.

I claim:

1. In an under-reamer, a shank having continuous screw threads on an end portion thereof and a reduced diameter portion at the inner end of said screw threads, and having a slot extending diametrically through said reduced portion, a cylindrical sleeve loosely screwed on said threads for free rotation relative to said shank, said sleeve having a flat end presented to said reduced portion of said shank, a pair of end-to-end arcuate arms pivoted on said fiat end for swinging movement laterally of said shank and sleeve, an outwardly extending under-reaming tooth on the outer end portion of each of said arms arranged to overlie said flat end within the margins thereof when said arms are in their innermost positions, actu ating means carried in said slot engaged with said arms operable on rotating said shank relative to said sleeve to swing said arms out and in relation to said shank and sleeve, and means on said shaft limiting advance movement of said sleeve on said threads.

2. The structure called for in claim 1 in which said actuating means comprises a metallic strip having end portions protruding from said slot slidably engaging the inner margin of theouter end portions of said arms, said strip being stiff yet yieldable and resilient.

4. The structure called for in claim 1 in which said actuating means comprises a metallic strip having end portions protruding from said slot slidably engaging the inner margin of the outer end portions of said arms, said strip being stiff yet yieldable and resilient and said arms each having a slot on its inner margin into which an end of said strip extends.

5. In an under-reamer, a shank having screw threads on an end portion thereof and a reduced diameter portion at the inner end of said threads and having a slot extending diametrically through said reduced portion, a cylindrical sleeve loosely screwed on said threads for free rotational movement thereon, said sleeve having a flat end presented to said reduced portion, a pair of diametrically opposed pivot pins projecting from said flat end, a pair of end-to-end arcuate arms pivoted on said pins for swinging movement laterally of said shank and sleeve, an outwardly projecting under-reaming tooth on the outer end portion of each of said arms arranged to overlie said flat end within the margins thereof when said arms are in their innermost retracted positions and adapted to project laterally from the outer margin of said sleeve when said arms are in an advanced position, a plate spring in said slot having its ends projecting laterally from opposite sides of said shank and slidably engaged with the outer end portions of said arms for advancing and retracting said arms on turning said shank and sleeve relative to each other, and a collar adjustably mounted on said shank at the inner end of said reduced portion for seating on the outer ends of said pivot pins to thereby retain said arms and said plate spring in their assembled position on said shank and sleeve.

6. In an under-reamer, a shank, a sleeve loosely threaded on said shank and having an inner end, a pair of arms pivoted on said inner end each having an underreaming tooth projecting outwardly from the outer end portion of the arm, stiff but resiliently yieldable projections on saidshank slidably engaging said arms for advancing and retracting said arms on relative rotation of said shank and sleeve, and means on said shank limiting advance movement of said sleeve relative to said shank.

7. In an under-reamer, a shank having a slot extending therethrough having opposed side walls, a sleeve loosely threaded on said shank having an inner end, a pair of arms pivoted on said inner end each having an under-reaming tooth projecting outwardly from the outer end portion of the arm, stiff but resiliently yieldable projections on said shank slidably engaging said arms for advancing and retracting said arms on relative rotation of said shank and sleeve; said projections comprising the end portions of a plate spring carried by said shank extending between the side walls of said slot and adapted to bear on either of said side walls according to the direction of rotation of said shank and sleeve relative to each other, and means on said shank limiting advance movement of said sleeve relative to said shank.

8. In an under-reamer, a shank having screw threads on an end portion thereof and a reduced diameter portion at the inner end of said threads, a cylindrical sleeve loosely screwed on said threads for free rotatable movement on said shank, said sleeve having a flat end presented to said reduced portion, a pair of end-to-end arcuate arms pivoted at their inner ends on said flat end for swinging movement laterally of said shank and sleeve, an outwardly extending under-reaming tooth on the outer end portion of each of said arms arranged to overlie said fiat end within the margins thereof when said arms are in their innermost positions and adapted to project laterally from the outer margin of said sleeve into under-reaming position when said arms are swung outwardly relative to said shank, means carried by said shank engaged with said arms operable on rotating said shank relative to said sleeve to swing said arms out and in relative to said shank and sleeve, and means on said shank limiting advance movement of said sleeve on said threads.

9. In an under-reamer, a shank having screw threads i on an end portion thereof and a reduced diameter portion at the inner end of said threads, a cylindrical sleeve loosely screwed on said threads for free rotatable movement on said shank, said sleeve having a fiat end presented to said reduced portion, a pair of end-to-end arcuate arms pivoted at their inner ends on said flat end for swinging movement laterally of said shank and sleeve, an outwardly extending under-reaming tooth on the outer end portion of each of said arms arranged to overlie said fiat end within the margins thereof when said arms are in their innermost positions and adapted to project laterally from the outer margin of said sleeve into underreaming position when said arms are swung outwardly relative to said shank, yieldable tensioned means carried on said shank and engaged with said arms operable on turning said shank relative to said sleeve to advance and retract the outer end portions of said arms relative to said shank and sleeve, and means on said shank limiting advance movement of said sleeve on said threads.

10. In an under-reamer, a shank having a diametrical slot adjacent one end thereof, an abutment collar screwed on said shank adjacent the inner margin of said slot, a cylindrical sleeve loosely threaded on said shank at the outer margin of said slot for free rotation relative to said shank; a pair of under-reamer arms pivoted on the inner end of said sleeve, a plate spring extending through said slot having its ends slidably engaged with said arms and adapted to swing said arms on turning said shank relative to said sleeve, and pivot pins on said sleeve carrying said arms having outer ends presented to said collar and adapted to abut the latter to then limit advance move ment of said sleeve on said shank and also serve to retain said arms on said pins.

Newell Sept. 2, 1902 Berkman Nov. 8, 1938