US2947180A - Rotary percussive power tool - Google Patents

Description

Aug. 2, 19.60 J, QROS ROTARY PERCUSSIVE POWER TOOL Filed Nov. 4, 1958 JNVENTOR. JOHN OROS ATTORNEY Unite This invention pertains to the art of rotary percussive power tools, and more particularly to a device for applying an axial percussive force to the working end of a rotating, cutting tool.

The invention'is particularly applicable to a device adapted to be mounted between a portable electric drill and a rotating tungsten-carbide tipped drill, and will be described with particular reference thereto although it will be appreciated that the invention has broader applications, and for example, may be incorporated in the portable electric drill itself, or in fixed apparatus if desired.

In the art of drilling cement, masonry, or other nonmetallic substances, it is known that substantially increased drilling speeds and more rapid cutting can be obtained if, while the drill is being rotated in contact with the work, an axial percussive force is periodically applied to the drill. Such percussive force drives'the cutting edges of the drill axially into the cement, or the like, to greatly accelerate the drilling operation.

Various means have been proposed in the past to obtain this result, for example, a cam rotating with the drill and having a gradual axial rise, and an abrupt dropoif, together with a spring biased follower which is pushed back by the cam and allowed to drop'abruptly to impart a hammering action on the cam and thus on the drill. However, the hammering action-on the cam surfaces caused excessive wear on these surfaces with the result that the manufacture of a long-lifetoolwas extremely difiicult and expensive. a v

Furthermore, it has been impossible with previous States Patent 2,947,180 ,Patnted Aug. 2, 1960,

member is spaced from the cam surface of the cam member at the point of abrupt drop-off when the hammer surface engages the anvil surface of the tool holder.

Further in accordance with the invention, means are provided to adjust the cam member toward and away from the follower, to vary the length of stroke of the hammer member and consequently the percussive force applied to the working end of the tool; The cam member is adjustable between a first position in which the cam and follower surfaces just clear each other at the point of drop-off when the hammer and anvil surfaces are engaged, and a second position in which the cam and 01- lower are maintained out of engagement during rotation of hammer member.

Further in accordance with the invention, the tool holder is mounted on a drive shaft'of a rotary drill and is capable of a small degree of axial movement relative to the shaft so that transmission of percussive effects to portions of the device other than the tool holder an tool is minimized or eliminated.

The principal object of the invention is the provision of a new and improved device for applying a percussive. action to a rotating drill which has improved operation, is simple to use, and enables the percussivev actiontogbe readily controlled- Another object of the invention is the provision'of a new and improved device of a general type'described wherein the hammer or percussive action takes place on surfaces other than the cam and follower surfaces.

Still another object of the invention is the provision of a means for varying the percussive force applied to the tool. Z

A further object of theinvention is the provision in such a device of a means for selectively discontinuing the percussive effects. 4

A still further object of the invention is to mount the tool holder of the ,device in a manner such thattransmission offthe percussive effects to parts of said device other than the tool holder and tool is minimized or eliminated.

The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of knowndevices to vary the amount of percussivetorce applied to the tooljor to eliminate the percussion entirely; The inabilityto achieve'this often resulted in break, age of the brittle drill tips when initially starting into work, because of the huge force exerted over a small area of-the drill tip. 1 a

The "present invention contemplates a new and improved device for applying a percussive action to a' rotatingildrill which overcomes the above-mentioned difficultiesofth prior art, and others, and provides a do:

viceywhich is simple in construction, rugged in 'dp'eration, easy tom'anipulate, and which is economical to construct.

ing acam follower surface separate from the hammer surface.v .Thecam follower surface of the hammer mern-f her is adapted to--rotate and cooperates with a stationary cam member having anaxial rise and an abrupt drop-01f.

Spring means biases the hammer member toward the fanvil surfacesand supplies the hammering force when theflcam, follower surface reaches the point of abrupt ,dropofiof-the cam.

j .Eur'ther in accordancewith the invention, the parts are so. arranged, that the cam following surface of the hammer which will be described in detail in this specification, and illustrated in the accompanying drawings which form a part hereof, and wherein: I V l Figure 1 is a sidecross-sectional viewwith portions partly in elevation of a device for applying a percussive action to a rotating drill illustrating a preferred embodia ment of the invention; Figure 2 is a cross-sectional viewof Figure 1 taken approximately on the line 22. thereof; Figure 3 isa cross-sectional view of Figure 1 taken approximately on the line 3-3thereof; and, 1 Figure 4 is a cross-sectional view of 'Figure 1 take approximately on the line 4-- 4 thereof. r

Referring now to the drawings wherein the showings are for the purposes of illustrating a preferred embodiment of the invention only, and not for the purposes of limiting the same, the figuresshow a device for applying a percussive action or effect to a rotating drill comprised of a drive shaft 1i) rotatable in a fixed member in the form of a housing 11 and rotatably driven on the righthand end by suitable power means (not shown), A tool holder 12 is'slidable on, and keyed to the opposite or left-hand end of the shaft 10. This tool holder 12'extends beyond the left-hand end ofthe housing ll and has an opening to receive the shank end of a drill 13 which drill is held in the holder 12 by any suitable hold ing means such as the set screw 14. h V Q Means are provided for applying end thrust from the shaft 10 to thetool holder 12 and for at least partially 3. absorbing thrust from the tool holder to the shaft in the same direction. Such means may be of any suitable type, but as shown herein comprise a thrust collar mountednear the left end of the shaft lflandseated against the,bott om of a counterbore in theright end of ;the,tool holden As illustrated, the thrust collar, consists, of. a pair of c shaped pieces which fit into agroove. near theendof the shaft. A retainingnut 16 is threaded onto-,th'e extreme left-hand end of the shaft 10 to secure thetoolholderlz to the shaft 10. In order to permit a, small degree of axial movement of the tool holder relative to the shaft, the threaded endof the shaft. is

shouldered so that the distance between thethrust collar,

and the retaining nut, when locked imposition, is slightly greater than the distance between opposed shouldersin the tool holder cooperating with the thrust collar and nut 16.

An anvil surface 17 is provided at the right-hand end of, the tool holder 12 to receive periodic, blows from a hammer surface 18 on the left-hand of a hammer member ,1 9. Any suitable means may be provided to pcriodically reciprocate the hammer member :19 to cause the hammer surface 18 to strike the anvil surface 17 of thetool holder and drive the drill 13 into the work. Inthe preferred embodiment shown, the hammer member has a follower surface 20 adapted to cooperate with a cam,surface 21 on a stationary cam member 22 fixed against rotation relative to the housingll, 'Ihehammer member 19 is keyed to andaxiallyslidable'on the shaft 10 and rotates relative to the cam member 22. The surface 21 of the cam member is formed as an axial rise followed by an abrupt drop-01f 23. There are two such cooperating surfaces and drop-offs shown on each thecam member 22 and hammer member 19. Accordingly, as the hammer member 19 is rotated with the drive shaft 10, it is driven each time to the right to lift the hammer surface 18 from the anvilsurface 17.-for each half revolution of the shaft. A helical compressionspring 24 biases the hammer member 19 in'the direction toward the tool. holder 12 and is adapted, when the point of abrupt drop-01f immediately following the high point of the cam surface 21 is reached, to impart a sudden leftward movement to the hammer member to effect a percussive blow against the anvil surface '17 of the tool holder 12. The spring 24 seats between a washer, 25 and the bottom of a counterboreinthehammer member 19.

Means are provided to adjustably move the cam member 22 axially relative to the hammer member 19 so that the effective portion of the cam surface21 engaged by the follower surface 20 may be varied to limit the length of stroke of the hammer member. As shown, the cam member 22 is keyed-to the housing 11 with an elongated keyway being provided in the housing to en ableaxial movement of the cam member. Adjustment of the cam member 22 is accomplished in a rightward direction by rotation of a normally fixed second cam member 26 and in the leftward directionby a pair of springs 27 urging the cam member 22 against the member 26, and the latter against a seat in the housing 11. Theopposite end of the springs 27 seat between the housing 11 and cam member 22. The second cam member 26' has an axially inclined surface 28 mating witha corresponding surface-29 on the cammember 22., The member 26 is capable of 180 rotation-relative to the housing 11, to move thelcamymember 22from a leftwardposition shown in Figure l. in which the surfaces 20 and 21 are maintained out of engagement during rotation of-the hammer member 19, to a second rightwardposition in which these surfaces are closely spaced but separated when the hammer and anvil surfaces 18 and 17 are in engagement. The cam member 22 may be infinitely adjusted between; these two; positions to: enable selection by; the operator-cf the..extent 10f percussive force below the surface.

applied to the anvil surface of the tool holder, by varying the length of stroke of the hammer member. In any position of adjustment, there will preferably always be a clearance between the follower surface 20 and cam surface 21 at the point of abrupt drop-off when the hammer surface 18 strikes the anvil surface 17. The entire force of the spring will therefore be absorbed between the surfaces 17 and' 18 and not between the surfaces 20 v 4 131 21.

It isobvions that means other than the second. cam member 26 may be provided to shift the cam' member 22 axially. The-cam member 26 was selected for this purpose because it can be easily manufactured from the same stock as the cam member 22. They are made from a sleeve which serves not only the functions aforementioned, but also journals the tool holder 12, hammer member 19, and thereby, the left end of the shaft 10.

Any means may be provided to rotate the second cam member 26. Preferably this means is in the form of a sleeve 30 rotatable-on the exterior of the housing 11 between a shoulder in the housing and a retaining nut 31. A set screw 32 is threaded radially into the member 26 with itsv head extending outwardly through the sleeve 30. A circumferential slot 33 is provided about of the housing 11 and also receives the head of the screw 32. The ends of the slot serve as limits of rotation for the second cam member 26.

The adjustable stroke. of the hammer member is provided for the following purpose. The tips of tungsten carbide drills are easily broken when great impact is provided over a relatively small area of the tip. Because. of this, the percussive action is disadvantageous when first starting to drill into a surface. Consequently, it has been necessary inthe past to compensate for the difference between the highest permissible starting force limited by the point at which a drill would break, and the much higher force desirable once the drill tip was completely below the surface of the work. This was done by selecting a spring having a force which was sufficiently low to prevent breaking of the drill tip when starting to drill, but which was also sulficiently high to give a fairly effective percussive action once drilling was under way. I have found that'by eliminating the percussive blows initially and then increasing the force steadily to a much higher force, I'not only prevent breaking of the drill tip, but am able to get much higherpercussion than previously,- oncethe drill tip is into and The force of the spring 24 need no longer be limited, by the breakage point ofthe drill tip when starting. It is now limited only by the maximum permissible percussive force at whicha; drill tip will break'when the full area of the cutting edge .isin contact with the subject being drilled. Therefore, I can get much higher impact force applied tothe drill tip, and consequently much more rapid andefiicient drilling.

In the preferred manner. of operation of the device,

when, the operator is ready to commence drilling, he will grasp the sleeve and rotateit to thatend of its travel in the slot which causesmovement of the cam member to itsposition shown in Figure 1 to prevent reciprocation ,andthereby adjust the cam member 22 toward thefollower surface 20. This will steadily increase the length ofstroke and the percussive force of the hammer member 19. Oncethe'tip of theme! is fully into the work, he may rotate-the sleeve =30 to the other limit permitted by the slot--33 to increase the length-of stroke to-its maximum.- During the entire operation, the full impact of the hammer member 19 will be absorbed by the anvil surface 17 of the tool holder 12 upon being struck. by the hammer surface 18, since the surfaces 20 and 21 cannot engage when the spring ,241rapidly' moves the hammer member 19 leftwardly-at the point of abrupt drop-off.

. It will furtherabe appreciated that in normal operation of'the device, the drill will be forced into the work by "the operator. Therefore, the drive shaft will have a by the-pieces will engage its corresponding shoulder a in the tool holder 12 with a small amount of clearance existing between the nut 16 and its corresponding shoul-' der in the tool holder. Now, after the cam member 22 has lifted the hammer member beyond the point of abrupt drop-off and the spring has caused the hammer surface 18 to strike the anvil-surface 17, the impact will move the tool holder leftwardly relative to the shaft, causing a. slight momentary separation between the thrust collar and its cooperating shoulder in the tool holder. The

movement is permittedby the clearance between the nut 16 and its cooperating shoulder. The percussive blow is thereby imparted primarily or solely to the tool holder 12 and drill 13. Transmission of the blow to other parts of the device will be minimized or possibly eliminated. While the hammer member 19 continues to rotate with the drill and again start its rightward movement, the hammer and anvil surfaces will again be separated and the force of the operator in bearing down on the drill will again cause the thrust collar to engage the shoulder in the tool holder.

The invention has been described with reference to a preferred embodiment. It will be appreciated that modifications and alterations will occur to others upon a reading and understanding of this specification, which modifications and alterations will differ radically inappearance from the preferred embodiment. herein described. It is my intention to include all such modifications and alterations insofar as they come within the scope of the with, said hammer member having a hammersurface cooperating with the anvil surface of the tool holder, and means for imparting an intermittent reciprocation to said hammer member, said last-named means including a fixed cam having an axial rise and an abrupt dropoif, a follower on said hammer member and cooperating with said cam, spring means biasing said follower toward said cam and said hammer surface toward and into pressure engagement with the anvil surface, said cam and follower members having a clearance at thepoint of abrupt drop-off when the hammer and anvil surfaces are in engagement.

2. A device for applying axial percussive effects to a rotating tool comprising in combination a member fixed against rotation, a drive shaft rotatable and axially immovable relative to said fixed member, a tool holder rotatable with said shaft and receiving said tool, said holder having an anvil surface facing in the direction opposite to the working end of said tool, a hammer member axially slidable relative to said shaft and rotatable therewith,

axially toward or away from the follower toincrease or decrease the effective portion of the axial rise of the cam engaged by the follower, to thereby vary the length of stroke of said hammer member and consequently the percussive force applied'to the tool. 7

3. A device according to claim 2 in which the adjusting means is operable to move said cam between a first position in which the cam and follower just clear each other at the point of abrupt drop-off when the hammer and anvil surfaces are engaged, and a second position in which the cam and follower are maintained out of engagement during rotation of the hammer member.

4. A device for applying axial percussive elfects to a rotating tool comprising in combination a housing fixed against rotation, a rotatable drive shaft extending into said housing from one end thereof and being axially im movable relative thereto, a tool holder slidable on and rotatable with said shaft, said tool holder having a tool receiving portion facing outwardlyof the other end of the housing and an anvil surface facing inwardly of the. housing, .a reciprocable hammer member axially slidable on said shaft and rotatable therewith, said hammer member having a hammer surface cooperating with the anvil surface of the tool holder, a cam member coaxial with said shaft and having an axial rise and an abrupt dropoif, said hammer member having a follower portion independent of said hammer surface which follower portion cooperates with said cam member to intermittently drive the hammer member in a direction away from the tool holder during rotation of the .drive shaft, and spring means biasing said hammer member in the direction toward said tool whereby a power stroke is imparted to the anvil. surface of the tool holder by the hammer surface of the hammer member each time the follower portion of the latter drops off the rise of the cam, and said cam member and follower portion of the hammer member have a clearance at the point of abrupt drop-01f when the hammer and anvil surfaces are in engagement.

5. A device for applying axial percussive effects to a rotating tool comprising in combination: a housing fixed against rotation, a rotatable drive shaft extending into said housing from one end thereof and being axially im movable relative thereto, a tool holder slidable on and rotatable with said shaft, said tool holder having a tool receiving portion facing outwardly of the other end of the housing and an anvil surface facing inwardly of the housing, a reciprocable hammer member axially slidable on said shaft and rotatable therewith, said hammer member having a hammer surface cooperating with the anvil surface of the tool holder, a cam member coaxial with said shaft and having an axial rise and an abrupt drop-olf, said hammer member having a follower portion independent of said hammer surface which follower portion cooperates with said cam member to intermittently drive the hammer member in a direction away from the tool holder during rotation of the drive shaft, and spring means biasing said hammer member in V the direction toward said tool whereby a power stroke said hammer member having a hammer surface cooperat- I with the anvil surface, and means for adjusting the cam is imparted to the anvil surface of the-tool holder by the hammer surface of the hammer member each time the follower portion of the latter drops ofi the rise of the cam, and said tool holder is mounted on the shaft between opposed shoulders thereof and is capable of slight axial movement relative thereto.

6. A device for applying axial percussive effects to a rotating tool comprising in combination: a housing fixed against rotation, a rotatable drive shaft extending into said housing from one end thereof and being axially immovable relative thereto, a tool holder slidable on and rotatable with said shaft, said tool holder having a tool receiving portion facing outwardly of the other end of the housing and an anvil surface facing inwardly of the housing, a reciprocable hammer member axially slidable on said shaft and rotatable therewith, said hammer member having a hammer surface cooperating with the anvil surface of the tool holder, a; cammember" coaxial wtih said shaftand'having an axialrise; and an abruptdropoff, said -harnme r member having a follower portion in dependent of said hammer surface which'follower portion cooperates with said cam member to intermittently'd-rive the hammer'member in-la direction away from the; tool holder during rotation of the drive shaft, and'springmeans biasing'said hammer'member in the direction toward said toolholder by the hammer surface of the hammer; member each time, the follower portion of the-latter drops off the rise of the cam, and means for adjusting the cam member axially to increase or decrease the effective portion of the axial rise of 'thecam' engaged by the follower to thereby vary the length of stroke of said hammer member and consequently the percussive force applied to the, tool.,

7. A device according to claim 6 in which the adjusting means are operable to move said cam betweenafirst position in-which thercam and follower just clear each other atthe point of abrupt drop-off'when the hammer and anvil surfaces are engaged, andasecond position in which the cam and follower are maintained'out of 'engagement during rotation of the hammer member.

8 A device according to claim 6 in which said housing is' tubular, and in which said: adjusting'means comprises a rotatable sleeve mounted on said housing'and operatively connected to said cam member. d

9. A device according to claim 8 in'which said cam member is provided with an inclined'surface on its end remote from the follower, and in which a second cam member fixed" tosaid sleeve is rotatable therewith and cooperates with the inclined surface to eifectuate the adjustment of the first cam member. 7

10. A device according to claim 9 in which spring means intermediate said housing and the first cam member urges said cam members in a direction away from the follower portion of the hammer member.

11; A device for applying axial percussive effects to a rotating tool comprising in combination a member fixed against rotation, a drive shaft rotatable in and axially immovable relative to said fixed member, a tool holder rotatable with said shaft and receiving said tool, said holder havingan anvil surface facing inthedirection opposite to" the working'end of-tbetool, a'reciprocable hammer member having a hammer surface engageable at OD'blfld of its reciprocating stroke with said anvil surface to impart a blow to said .anviI surface and there by to said to'ol, means for reciprocating said hammer member, and manually operable means cooperatively associatedwith said reciprocating means for varying'the length of stroke of the hammer-member, said reciprocating means comprising'a cam member fixed' against rotation relative to the fixed member, said cam member having an axial rise and an abrupt'drop-oif, a follower on said' hammer member androtatable with said shaft; and spring'means urging'the hammer surface toward said anvil surface.

12. A device for applying axial percussive effects to a rotating tool comprising in combination amember fixed against rotation, a drive shaft rotatable in and axially immovable relative'to said'fixed member, means for rotating said shaft, a tool holder rotatable with said shaft and receivingsaid tool, said'holder having an anvil surface'facing in the direction opposite to the workingend ofthe tool, a reciprocable hammer member having a .hammer surface engageable at one end of its stroke with said anvil surface and rotatable-with said shaft, means for reciprocating said hammer member asit rotates;

manually operable means for disabling said reciprocating means, said hammer member reciprocating means comprising cooperating cam and follower members, and said disabling means comprising means for adjusting the position of said cam member to alter the effective portion of the cam engaged by the follower, whereby the length of stroke, of the hammer member and consequently the percussive force applied to the working end of the tool maybe varied.

References Cited in the file of this patent UNITED STATES PATENTS 1,665,173 Misener Apr. 3, 1928 2,457,565 Kott Dec. 28, 1948 2,630,723 Gridley Mar. 10, 1953 2,794,621 Beeson June 4, 1957

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