Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3605914 A
Publication typeGrant
Publication dateSep 20, 1971
Filing dateAug 23, 1968
Priority dateAug 23, 1968
Also published asDE1939262A1, DE1939262C2
Publication numberUS 3605914 A, US 3605914A, US-A-3605914, US3605914 A, US3605914A
InventorsKramer Leo
Original AssigneeIngersoll Rand Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Rotary impact wrench mechanism
US 3605914 A
Images(5)
Previous page
Next page
Description  (OCR text may contain errors)

Sept. 20, 1971 L. KRAMER ROTARY mmcr WRENCH MECHANISM 5 Sheets-Sheet 1 Filed Aug. 23. 1968 INVENTOR L E 0 KRAMER ATTORNEY Sept. 20, 1'97! L. KRAMER noun-1 mmc'r wax-men uscnmsm 5 Sheets-Sheet 3 Filed Aug. 25, 1968 FIG. 6

INVENTOR LEO mam-n BY M w .Tm

-FIG. 7

ATTORNEY Sept. 20, 1971 L. KRAMER noun! mnc'r vmmuca uncumsu 5 Sheets-Sheet 5 Filed Aug. 23, 1968 m T N E V N LEO KRAMER J BY W wfrzum ATTORNEY Sept. 20, 1911 L. mm 3.

ROTARY IMPACT 'WRENGH- IIEGHANISM Filed Aug. 23. 1968 5 Sheets-Shoot INVENTOR LEO KRAMER ATTORNEY Sept. 20, 1971 I Kfi 3,605,914

7 ROTARY IMPACT WRENCH IECHANISM Filed 1mg. 2a, 1968 5 Sheets-Sheot-i INVENTOR LEO KRAMER ATTORNEY United States Patent O 3,605,914 ROTARY IMPACT WRENCH MECHANISM Leo Kramer, Skillman, N.J., assignor to Ingersoll- Rand Company, New York, N.Y. Filed Aug. 23, 1968, Ser. No. 754,824 Int. Cl. B25d /00 U.S. Cl. 173-93 31 Claims ABSTRACT OF THE DISCLOSURE A rotary impact wrench clutch mechanism including a rotary anvil adapted to deliver a rotary blow to a fastener, a rotary hammer carrier mounted around the anvil and connected to a motor, and a pair of diametrically opposed hammer dogs pivoted on the carrier to tilt inwardly to strike a blow to the anvil. The clutch mechanism includes a cam operative to tilt the hammer dogs inwardly to strike a blow and then to allow the dogs to pass the anvil without striking a blow during the following rotation of the carrier. The hammer dogs are proportioned and pivoted so that they automatically remain in the non-impact position until they are cammed inwardly and they are returned to the nonimpact position during their rebound by inertial forces following impact with the anvil. The tool clutch is operative in either direction of rotation and includes stop means for automatically preventing the dogs from tilting in the wrong direction in either direction of rotation. During the instant of impact inertial forces hold the hammer dogs against sliding out of engagement with the anvil.

BACKGROUND OF INVENTION This invention relates to a power-operated rotary impact wrench or impact tool for applying rotary or angular impacts to fasteners such as threaded nuts, bolts, etc. In particular, this invention relates to a rotary impact tool mechanism for changing the rotating torque of a rotary motor, such as an air-driven motor, to a series of rapid rotary impacts which can be applied to a threaded nut for either driving it tight or for removing it.

Most rotary impact mechanisms in use today contain an anvil adapted to be connected to a wrench socket and a hammer rotated by a motor. The hammer is alternately engaged and disengaged from the anvil, being engaged to impact the anvil, thereafter being disengaged from the anvil to gather rotary speed again, prior to striking another impact to the anvil. Various means are used for accomplishing this alternate engagement and disengagement between the anvil and hammer.

One well known impact mechanism used today is known as the Pott mechanism, being named after the inventor who received US. Pat. Nos. 2,012,916, 2,049,- 273 and 2,158,303. A modern version of the Pott mechanism is shown in the US. patent to Jimmerson No. 2,160,150. In the Jimmerson patent, the hammer is mounted on a shaft driven by a motor and cam balls are mounted between the hammer and the shaft with the cam balls resting in V-shaped grooves formed on the shaft with the cam balls resting in V-shaped grooves formed on the shaft. Normally, a coil spring biases the hammer into engagement position with the anvil wherein the cam balls rest in the apexes of their grooves. After the hammer strikes the anvil, the shaft continues to rotate and the relative rotation between the shaft and hammer causes the cam balls to ride up their groves and pull the hammer axially rearward to disengagement position, thus compressing and storing potential energy in the hammer biasing spring. When the hammer is disengaged from the anvil, the combined energy in the compressed spring and the rotating Patented Sept. 20, 1971 "ice shaft turns the hammer forward to deliver another impact to the anvil.

The Pott mechanism has several disadvantages, one being that when a pair of diametrically opposed hammer dogs are used, the hammer strikes an impact each halfturn which prevents it from gaining sufiicient speed between impacts.

Another well known impact mechanism is disclosed in the US. patent to Amtsberg, No. 2,881,884. In this mechanism, the hammer is spring-biased axially away from the anvil to a disengaged position and cams operated by the relative rotation between the anvil and hammer cause the hammer to be periodically thrown axially forward to strike a rotary impact with the anvil. This mechanism is known as the ski-jump mechanism.

One disadvantage of the above Amtsberg ski-jump mechanism is that if the hammer is driven slower than its design speed, the hammer teeth will not be thrown far enough anxially forward to engage the anvil teeth properly upon impact. When the hammer teeth are not thrown far enough forward, they top, dub or barely strike the anvil jaws or teeth which causes rapid wear of such teeth. Another disadvantage of the above skipump mechanism is that under certain conditions, it will rebound and strike the anvil jaws several times after an initial impact before rotating past the anvil jaws and gaining speed for a following impact. Rebounding is wasteful of power and time and, thus, is undesirable.

A third mechanism is known as the swinging weight mechanism and is disclosed in the US. Pat. No. 2,285,638 to Amtsberg. This mechanism uses a pair of diametrically opposed tilting hammer dogs which rotate around a lobed anvil and are cammed into an impact position with the lobes or jaws on the anvil by engagement with the anvil. The hammer dogs are released by the cams on the anvil immediately before impact and means is provided for applying a drive torque to the dogs to cause them to rotate to a disengaging position following an impact.

The swinging weight mechanism has the disadvantage of impacting each half turn of the ham-mer, when two hammer dogs are used, thus preventing the hammer from gaining sufficient speed between impacts. It is desirable to provide a pair of hammer dogs so that the anvil will receive a balanced blow, i.e., a pair of impacts delivered to the opposite sides of the anvil.

Another disadvantage of the swinging weight mechanism is that it often rebounds after impact and strikes a blow on its reverse stroke, which is very undesirable, because not only is it inefiicient, but it is acting in the reverse rotary direction.

SUMMARY OF INVENTION The principal object of this invention is to provide a rotary impact mechanism which overcomes the undesirable features of the foregoing impact mechanisms and, in general, significantly advances the art of rotary impact wrenches.

Other important objects of this invention are: to provide a rotary impact tool which does not top or dub its dogs or teeth; to provide a rotary impact tool which provides a balanced impact to the anvil while driving the hammer one full turn between impacts; to provide a rotary impact tool which does not strike any blows in either rotary direction during rebound from an impact blow; to provida an impact mechanism using radially tilting hammer dogs surrounding an anvil and having a non-impact position of the dogs wherein the hammer can rotate free of the anvil; to provide an impact mechanism having radially tilting hammer dogs and an automatic means for preventing the hammer dogs from tilting in the wrong direction in either direction of operation; to

provide an impact mechanism having a radially tilting hammer dog which automatically tilts to its non-impact position following impact without the application of torque to the pivot of the hammer dog; to provide an impact mechanism having a radially tilting hammer dog which is shaped, proportioned and has a mass which causes the creation of inertia forces that prevent the hammer dog from disengaging during the instant of impact; to provide an impact mechanism which can strike an initial blow which is stronger than the following normal blows; and to provide an impact mechanism having a hammer dog shaped and positioned to create inertial forces acting to move the hammer dog to its non-impacting position relative to the anvil during rebound of the hammer dog following impact with the anvil.

In general, the foregoing objects are attained in a rotary impact mechanism including an anvil carrying a pair of jaws, teeth or detents, a hammer carrier surrounding the anvil and carrying a pair of diametrically opposed tilting hammer dogs. Tht hammer dogs have a middle position where they can rotate around the anvil without engaging it and can be tilted to impact the anvil jaws in either direction of rotation. The hammer dogs are linked together by a yoke means causing them to move in unison and a cam or actuation means cooperating with the anvil and hammer dogs, is operative to tilt the hammer dogs inwardly to their impact positions once, each revolution of the hammer carrier. An automatic stop or limit means prevents them from tilting to the wrong impact position in each direction of rotation. The dogs are proportioned and mounted so that they automatically swing to their non-impact positions following an impact during rebound of the hammer dogs. This automatic return of the hammer dogs to their non-impact positions is caused by inertial forces resulting from the shape, mass and location of the dogs in conjunction with the rebound and subsequent acceleration of the dogs following their impact with the anvil. In addition, during impact of the dogs with the anvil, inertial forces act on the dogs to prevent their disengagement movement which would reduce the efiiciency of the impact energy delivered to the anvil.

BRIEF DESCRIPTION OF DRAWINGS The invention is described in connection with the accompanying drawings wherein:

FIG. 1 is an elevational view of a rotary impact wrench having portions cut away to show the impact clutch of this invention in section;

FIGS. 2 to 5 are sections taken on corresponding lines 2-2 to 5--5 in FIG. 1;

FIG. 6 is a section taken on line 66 in FIG. 1 except that the hammer dogs are shown in their free or nonimpacting position;

FIG. 7 is an axial section taken on line 77 in FIG. 3;

FIGS. 8, 9 and 10 are schematic views showing the hammer dog, anvil and cam systems in sequential positions prior to and at the moment of impact;

FIGS. 11 to 13 are sequential views showing the hammer dog and anvil during and following impact;

FIGS. 14 and 15 are schematic views similar to FIGS. 8 to 10 illustrating the components when the impact mechanism is rotated in the opposite direction from that shown in FIGS. 8 to 10; and

FIG. 16 is a schematic view illustrating the path of the eccentric pin as it moves past the hammer cam tang and the hammer stop pin.

DESCRIPTION OF PREFERRED EMBODIMENT The rotary impact wrench 1 shown in FIG. 1 conventionally includes a casing 2 including a nose portion 3, a motor portion 4 and a handle portion 5. The nose portion 3 carries a spindle 6 projecting from its front end, the motor portion 4 houses an air motor having a drive shaft 7 and the handle portion carries an op a i g gg 8 and an inlet connection 9 adapted to be attached to an air hose for feeding air to the motor. The spindle 6 carries flats 10 adapting it to be attached to a conventional wrench socket (not shown). All of the foregoing structure is conventional in the rotary impact wrench art.

The motor shaft 7 is connected to the wrench spindle by a novel rotary impact clutch 12 which is the subject of this invention. In general, the clutch 12 includes a hammer 14 rotating around an anvil 15. The hammer 14 is driven by the motor shaft 7 and the anvil 15 is integrally fixed to the spindle 6.

The hammer 14 includes a hammer cage or carrier 17 having a rear plate 18, a front plate 19 and a pair of interconntcting braces 20. The rear plate 18 is journaled on a stub shaft 21 at the rear end of the anvil 15. This stub shaft 21 has a reduced diameter. The front plate 19 is journaled on an enlarged annulus 22 provided on the forward portion of the anvil 15. To this point in the description, the hammer cage 17 is free to rotate around the anvil 15.

The anvil 15 carries a pair of axially extending fanshaped jaws, teeth, detents or abutments 24 located diametrically opposite each other. These jaws 24 are positioned intermediate the rear and front plates 18 and 19 of the hammer cage 17. In describing the jaws 24 as fan-shaped, it is meant that they project generally radially outward from the anvil 15 with their sides diverging outwardly like a sector of a cylinder. The jaws 24 are adapted to receive rotary impacts or blows from the hammer 14.

The hammer cage 17 carries a pair of arcuate shaped hammer dogs 25 tiltably mounted on longitudinal pivot pins 26 extending between the rear and front plates 18 and 19 of the cage 17. The hammer dogs 25 are located at opposite diametrical locations in the cage 17 with the cage braces 20 positioned degrees from the pivot pins 26 so the dogs 25 are free to tilt without interference with the braces 20. The hammer dogs 25 carry radially diverging end surfaces 27 adapted to substantially conform to the jaws 24 on the anvil 15 so that they can tilt inwardly as shown in FIG. 5 and engage the jaws 24, to strike an impact or rotary blow to the anvil 15. It will be noted that the surfaces 27 have a slight arcuate curve. The hammer dogs 25 have three positions including a midposition as shown in FIG. 6, wherein the hammer 14 can rotate freely around the anvil without the dogs 25 striking a blow, a clockwise impact position, as shown in FIG. 3, wherein the dogs 25 tilt forwardly and inwardly to strike a blow in the clockwise rotary direction and a counterclockwise direction wherein they tilt forwardly and inwardly in the counterclockwise direction. As shown FIG. 2, the rear plate 18 of the cage 17 is cruciform-shaped and has a pair of larger diametrically extending arms 29 which carry the hammer dog pins 26. A driver fork 30 is keyed to the motor shaft 7 and includes fingers 31 projecting longitudinally forward between the cruciform-shaped projections of the rear plate 18 of the hammer cage 17. The fingers 31 are positioned to engage the side edges of the large arms 29 on the cage rear plate 1 8 to drive the hammer 14. The fingers 31 are spaced to provide an amount of lost motion between the driver fork 30 and the hammer 14.

Each finger 31 of the driver fork 30 carries a stop pin 32, as shown in FIG. 7, projecting forward from the end of the finger 31 and adapted to engage against a shoulder 33, shown in FIG. 8, provided on the end of a hammer dog 25 to prevent the dog from tilting in the Wrong direction when rotating in a given direction. The lost motion of the driver fork 30 on the hammer 14 allows the pins 32 to move from one stop position to another relative to the hammer dogs 25 when the rotation of the hammer 14 is reversed.

The hammer dogs 25 are interconnected by a barshaped yoke 35 having its middle pivoted on the stub shaft 21 at the rear end of the anvil 15 and having diametrically extending arms carrying yoke pins 36. The

yoke pins 36 are straddled by bifurcated tongues 37 which are fixed to and project inwardly from the hammer dogs 25. The yoke 35 holds or locks the hammer dogs 25 in identical positions. In addition, the yoke 35 can be pivoted to move the hammer dogs 25 to their impact position. This movement is accomplished by a unique cam system.

The middle of the anvil carrying the jaws 24 is joined or interconnected to the rear end stub shaft 21 by an anvil eccentric 39. An eccentric ring 40 is journaled on the anvil eccentric 39 and carries a pair of eccentric cam pins 41 located at diametrically opposed positions and projecting rearwardly into the circular path of the yoke 36. One side of the yoke 35 carries a pair of hookshaped cams 44 located near the opposite ends of the yoke 35. The hammer cage rear plate 18 carries a hammer cam tang 45 projecting forward into the circular path of the yoke 35 and the eccentric cam pins 41.

As the hammer rotates, the entire cam system rotates with it. This includes the yoke 35, the eccentric ring 40 and the hammer cam tang 45. As the eccentric ring 40 rotates, it also orbits eccentrically around the hammer axis. This eccentric movement will eventually cause the cam pins 41 to engage between an edge of the hammer cam tang 45 and a hook cam 44 on the yoke 35 forcing the yoke 35 to tilt the hammer dogs forwardly and inwardly to an impact position. The eccentric 39 is positioned so that this tilting of the hammer dogs 25 will occur as they near the jaws 24 on the anvil 15. This tilting of the hammer dogs 25 inwardly to their impact position, will occur only once during a full revolution of the hammer 14. After the hammer dogs 25 are tilted inwardly, the eccentric pins 41 release the yoke before the dogs 25 impact the anvil jaws 24 so the dogs 25 are free to move to their mid-position following impact.

The sequential FIGS. 8, 9 and 10 illustrate the operation of the cam system. FIG. 8 shows a hammer dog 25 in its non-impact position passing over one of the anvil jaws 24 and about 100 degrees from its position of impact with the opposite anvil jaws 24. At this time, one of the eccentric pins 41 is beginning to engage a hook-shaped yoke cam 44 while the other eccentric pin 41 is engaging the hammer cam tang 45. Both of the eccentric pins 41 must engage their respective cam surfaces 44 and 45 before they can apply any force in moving the hammer dogs 25 inwardly to their impact positions.

As the hammer dog 25 continues to rotate, the yoke 35, the eccentric ring and the hammer cam tang also rotates with the hammer dog 25. FIG. 9 shows the hammer dog 25 about 30 degrees from its position of impact with the anvil jaw 24. At this time the hammer dog is tilting inwardly toward an impact position. This tilting movement is caused by the stationary eccentric 39 forcing the eccentric ring 40 to translate to the left (as shown in FIG. 9) of the hammer axis 47 which forces the yoke 35 to rotate counterclockwise relative to the hammer dog a slight amount which is sufficient to tilt the dog 25 inwardly. As soon as the hammer dog 25 completes its inward tilting movement, which occurs on the inner peak of the hook-shaped cam 44, the cam 44 is contoured so as to stop the relative movement of the yoke 35 and the hammer cam tang 45 releases its eccentric pin 45 so that the yoke 35 is free from the application of further tilting forces. The moment of release is selected so that the hammer dog 25 is still tilting inwardly and will continue tilting inwardly until just before it strikes the anvil jaw 24 as shown in FIG. 10. In this way, the hammer dog 25 cannot begin tilting outwardly prior to impact with the anvil 15.

At the moment of impact, as shown in FIG. 10, the eccentric pins 41 are disengaged from the hook-shaped yoke cam 44 and the hammer cam tang 45 so that the hammer dog 25 is free to tilt outward following impact. The hammer cage rear plate 18 carries a stop pin 48 located outwardly of the hammer cam tang 45 to prevent the eccentric ring 40 from rotating past the hammer cam tang 45 to the other side of the hammer cam tang during rebound of the hammer dog 25 following impact.

At this point it may be well to more fully explain the action of the hammer dog 25 during impact and following the impact. The hammer dog 25 is shaped and sized so that the surface 27 will not lock against the anvil jaw 24 in case the tool motor is started when these surfaces are in engagement. This is accomplished by sizing the hammer so that the engagement line of force action between the hammer dog surface 27 and the anvil jaw will extend radially outward from the axis of the pivot pin 26. This force line is shown in FIG. 10 as dotted line 50 and is normal to the line of engagement between the hammer dog surface 27 and the anvil jaw 24. Due to the arcuate curvature of the surface 27, the engagement between the surface 27 and jaw 24 is limited to line contact extending generally parallel to the axis of the tool. Actually, this line contact will be enlarged from a true line contact due to the resiliency of the metal surfaces. This engagement force line 50 is called a non-locking force line.

As a result of the non-locking force line 50, one could presume that the impact engagement between the hammer dog 25 and the anvil jaw 24 would tend to cam these surfaces out of engagement and thereby reduce the efficiency of the impact blow. However, this is not true. Instead, the hammer dog 25 is subject to forces which tend to tilt it further inwardly at the moment of impact. This result is attributed to the fact that the center of percussion 49 of the hammer dog 25 is located radially outwardly from the engagement force line 50 and the axis of the pivot pin 26, as shown in FIG. 10.

In general, it can be said that the inertial forces of the hammer dog 25 form a resultant force acting forwardly through the center of percussion 49 of the hammer dog 25 at the moment of impact. This resultant force acting through the center of percussion 49 is strong enough at the instant of impact to overcome the force of engagement acting along the force engagement line 50 and the torque force delivered by the pivot pin 26 to form a force couple tending to tilt the hammer dog 25 further inwardly toward its impact position. This force couple is illustrated in FIG. 10 and is the combination of the resultant force acting through the center of percussion 49 and the moment arm of the resultant force relative to the axis of the hammer dog 25. The mass and proportions of the hammer dog 25 are such that will provide a sufficient resultant inertial force to prevent the hammer dog 25 from disengaging during impact.

FIGS. 11, 12 and 13 illustrate the sequence of movement of the hammer dog 25 following impact. FIG. 11 shows the hammer dog 25 at the moment of impact. FIG. 12 shows the hammer dog 25 during its rebounding movement in a counterclockwise direction. Following impact, the hammer dog 25 is driven backwardly or rearwardly in a counterclockwise direction, as a result of the resiliency of the elements placed under stress by the impact. These elements will include the anvil 15, the socket (not shown) attached to the spindle 6 and the fastener being driven by the wrench 1. At the same time, the motor is applying a clockwise torque force to the hammer dog 25 attempting to slow down its rebounding travel and eventually to drive it forwardly in the clockwise direction. The combination of these actions forms a force couple tending to tilt the hammer dog 25 radially outward to its non-impact position. This force couple is explained as follows.

When the hammer dog 25 is moving in the rebounding direction, as shown in FIG. 12, and is subject to a deceleration force, inertial forces are created which form a resultant force acting rearwardly generally through the center of percussion 49. This deceleration or slow-down force is applied by the motor through the axis of the pivot pin 26. These two forces form a force couple which is illustrated in FIGS. 12 and 13.

This force couple continues to act on the hammer dog during its rebound and after it begins moving forward again. When the hammer dog 25 stops moving rearwardly, in the counterclockwise direction, its inertial forces resist acceleration by the pivot pin 26 to continue creating the same force couple. This force couple causes the hammer dog 25 to complete its outward tilting movement to its non-impact position well before the leading end 27 of the hammer dog 25 approaches and passes the anvil jaw 24 as shown in FIG. 13 so that the hammer dog 25 is free to pass the anvil jaw 24 without again engaging it.

It should be clear that the action of the hammer dog 25 in automatically tilting outwardly to its non-impact position following impact is the result of locating the center of percussion of the hammer dog 25 radially outwardly from the axis of the pivot pin 26.

At this time, we want to make it clear that the resultant force of the hammer dog 25 probably does not act exactly through the center of percussion 49 due to the effect of other mass forces connected in the hammer system. However, we have found that this resultant is near enough to the center of percussion 49 to presume that it is at the center of percussion 49 for the purposes of explaining and claiming this invention. The center of percussion 49 has a definite relationship to the center of mass of the hammer dog 25 and therefore this invention can also be explained in terms of the center of mass.

Following impact, the hammer dog 25 will rotate one full turn about the anvil 15 before again impacting the anvil 15. This action is due to the fact that the cam system will only tilt the dogs 25 inwardly to their impact position once during each revolution of the hammer 14.

It should be noted that the hammer 14 can rebound two full turns before striking an impact in the reverse direction. Since the maximum rebound of a rotary impact tool is normally less than a one-half turn, this mechanism will never strike a reverse blow during rebound.

The reason why the mechanism will not strike a reverse blow during less than two full turns of rebound movement, will be understood by explaining the movement of the hammer in a reverse direction.

If we assume that the clutch mechanism 12 is positioned as shown in FIG. and the motor is reversed, the hammer 14 will rotate in the counterclockwise direction almost two full turns before the hammer dog 25 is again tilted inwardly to strike the opposite side of the anvil jaw 24. During one full turn, the eccentric ring 40 swings relatively clockwise past the hammer stop pin 48. In order for this to occur, the eccentric ring 40 must be translated to the left as shown in FIG. 10 in order for the eccentric pin 41 to clear the hammer stop pin 48 and this can only occur during one full revolution of the hammer 14 around the anvil.

FIG. 14 shows the eccentric pin 41 clearing the stop pin 48 during its first revolution in the counterclockwise direction. FIG. 16 illustrates the path of the eccentric pin 41 betwen its position shown in FIG. 10 and the position shown in FIG. 15, when the hammer dog 25 strikes an impact to the anvil 15. After eccentric pin 41 clears the stop pin 48, it is captured in the concave rear side of the hammer tang 45 for a portion of the travel of the hammer 14. Finally, after the hammer rotates about one revolution, the eccentric pin will move to the left of the hammer tang 45, as shown in FIG. 16, wherein it can operate to tilt the hammer dog 25 into impact position during the next revolution of the hammer 14.

One advantage of the requirement of two turns before striking the first impact blow, is that the motor can accelerate the hammer to a higher speed to create a stronger first blow. This action can be useful in removing fasteners when a very strong first blow is necessary to start moving the fastener. If the first blow does not move the fastener, an operator can again reverse the motor to rotate a few turns in the opposite direction and then reverse it to obtain another strong blow. This operation can be performed again and again when necessary. The point is that the wrench is capable of providing a much stronger blow than its normal blow or impact, and that this capability is useful at times.

Although a single embodiment of the invention is illustrated and described, it should be understood that the invention is not limited thereto and that various changes may be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as set forth in the claims.

I claim:

1. An impact mechanism comprising:

a rotary carrier adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a jaw;

a hammer dog movably mounted on said carrier adjacent said anvil and movable radially inwardly from a first position wherein it clears said anvil jaw as the carrier rotates around said anvil to a second position wherein it will engage and strike a blow to said anvil jaw; and

actuation means interconnected between said anvil and hammer dog for moving said hammer dog inwardly to said second position to strike an impact blow to said anvil, said means allowing said hammer dog to pass said anvil jaw without engaging it during a portion of the rotation of said carrier following the striking of a blow.

2. The impact mechanism of claim 1 wherein:

said anvil carries a second jaw which is circumferentially spaced from said first jaw and said actuation means allows said hammer dog to pass said second jaw without striking it following an impact with said first jaw.

3. An impact mechanism comprising:

a rotary carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw;

a hammer dog pivoted on said carrier adjacent said anvil and movable radially inwardly from a first position wherein it clears said anvil jaw as it rotates around said anvil to a second position wherein it will engage and strike a blow to said anvil jaw; and

actuation means interconnected between said anvil and hammer dog for swinging said hammer dog inwardly to said second position to strike an impact blow to said anwil, said means allowing said hammer dog to pass said anvil jaw without engaging it during a portion of the rotation of said carrier following the striking of a blow.

4. A rotary impact tool clutch mechanism comprising:

a rotary hammer carrier adapted to be driven by a rotary motor;

an anvil rotatably and coaxially mounted adjacent said hammer carrier and having a pair of diametrically opposed jaws;

a pair of hammer dogs movably mounted on said hammer carrier on the opposite sides of the hammer carrier axis and adapted to move inwardly to strike simultaneous impact blows to said jaws on said anvil; and

actuation means interconnected between said anvil and hammer dogs for automatically moving said hammer dogs inwardly as they approach said anvil jaws to strike said impact blows, said means allowing said hammer dogs to pass said anvil jaws without engagement on the next time they approach said anvil jaws following the striking of said impact blows.

5. A rotary impact tool clutch mechanism comprising:

a rotary hammer carrier adapted to be driven by a rotary motor;

an anvil rotatably and coaxially mounted adjacent said hammer carrier and having a pair of diametrically opposed jaws;

a pair of hammer dogs pivotably mounted on said hammer carrier on the opposite sides of the hammer carrier axis and adapted to pivot inwardly to strike simultaneous impact blows to said jaws on said anvil; and

actuation means interconnected between said anvil and hammer dogs for automatically pivoting said hammer dogs inwardly as they approach said anvil jaws to strike said impact blows, said means allowing said hammer dogs to pass said anvil jaws without striking impact blows during a portion of the rotation of the carrier following the striking of said impact blows.

6. The impact mechanism of claim wherein:

said anvil is surrounded by said carrier.

7. The impact mechanism of claim 6 wherein:

said hammer dogs are pivoted on axes which extend parallel to the rotation axis of said hammer carrier.

8. The impact mechanism of claim 6 wherein:

said hammer dogs have non-impact positions wherein said hammer carrier can rotate around said anvil without said hammer dogs engaging said anvil.

9. The impact mechanism of claim 8 wherein:

said hammer carrier includes front and rear plates journaled on portions of said anvil.

10. An impact mechanism comprising:

a carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw;

a hammer dog pivoted on said carrier adjacent to said anvil and tiltable between a middle and first position wherein it clears said anvil jaw as it rotates around said anvil, a second position wherein it will engage and strike a blow to said anvil jaw as said carrier rotates in a clockwise direction and a third position wherein it will engage and strike a blow to said anvil jaw as said carrier rotates in a counterclockwise direction; and

limit means mounted on said carrier and operative to prevent said hammer dog from swinging to said third position when said carrier is driven in a clockwise direction.

11. The impact mechanism of claim 10 wherein:

said limit means also serves to drive said carrier.

12. The impact mechanism of claim 10 wherein:

said limit means is operative to prevent said hammer dog from swinging to said second position when said carrier is driven in a counterclockwise direction.

13. The impact mechanism of claim 12 wherein:

said limit means engages said carrier and includes a stop means adapted to engage said hammer dog to prevent the hammer dog from moving to said second or third positions depending upon the direction of rotation of said carrier.

14. The impact mechanism of claim 13 wherein:

said limit means is a driver which engages said carrier for driving it in a manner providing a limited amount of rotary lost motion between said driver and said carrier, whereby said stop means will move between two different positions relative to said carrier depending on the rotary driving direction of said driver.

15. The impact mechanism of claim 14 wherein:

said driver includes a pair of circularly spaced stop pins moving to alternate positions relative to said hammer dog in opposite driving directions of the carrier.

16. An impact wrench mechanism comprising:

a carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw with an impact surface;

a hammer dog pivoted on said carrier on an axis extending substantially parallel to said carrier axis adjacent to said anvil and tiltable radially inward from a non-impact position to an impact position to engage said anvil jaw as said carrier rotates, said hammer dog having an impact surface adapted to impact said anvil jaw impact surface, and said hammer dog being positioned, proportioned and having a mass and a center of percussion location which will cause the creation of a resultant inertial force couple acting on said hammer dog during the rebound of said hammer dog and carrier following an impact which will urge said hammer dog to tilt outwardly to its non-impact position and to remain in that position as the carrier begins rotation forward.

17. The impact mechanism of claim 16 including:

a second hammer dog similar to the first hammer dog pivoted on said carrier diametrically opposite said first hammer dog and a second jaw similar to the first jaw located on said anvil diametrically relative to said first jaw.

18. An impact mechanism comprising:

a carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw;

a hammer dog pivoted on said carrier adjacent said anvil and tiltable between a middle and first position wherein it clears said anvil jaw as it rotates around said anvil, a second position wherein it will engage and strike a blow to said anvil jaw as said carrier rotates in a clockwise direction and a third position wherein it will engage and strike a blow to said anvil as said carrier rotates in a counterclockwise direction; and

actuation means interconnected between said anvil and hammer dog and operative to tilt said hammer dog to said second position when said carrier is driven in a clockwise direction to cause said hammer dog to strike an impact blow to said anvil jaw.

19. The impact mechanism of claim 18 wherein:

said actuation means is operative to tilt said hammer dog to said third position when said carrier is driven in a counterclockwise direction to cause said hammer dog to strike an impact blow to said anvil jaw.

20. A rotary impact tool clutch mechanism comprising:

a rotary hammer carrier adapted to be driven by a rotary motor;

an anvil rotatably and coaxially mounted within said hammer carrier and having a pair of diametrically opposed jaws;

a pair of hammer dogs pivotably mounted on said hammer carrier on the opposite sides of the hammer cage axis and adapted to pivot inwardly to strike simultaneous impact blows to said jaws on said anvil;

cam means interconnected between said anvil and hammer dogs for automatically pivoting said hammer dogs inwardly as they approach said anvil jaws to strike said impact blows, said cam means allowing said hammer dogs to pass said anvil jaws without striking impact blows during a portion of the rotation of the carrier following the striking of said impact blows and including a link member interconnecting said hammer dogs together for simultaneous rotation.

21. The impact tool mechanism of claim 20 wherein:

said cam means includes a cam surface on said anvil and interconnecting means interconnecting said cam surface to surfaces on said carrier and said link member to pivot said hammer dogs inwardly to impact position.

22. The impact tool mechanism of claim 21 wh r in:

said interconnecting means rotates on said anvil surface.

23. The impact tool mechanism of claim 22. wherein:

said cam surface is an eccentric fixed on said anvil and said interconnecting means is a ring journaled on said eccentric.

24. The impact tool mechanism of claim 23 wherein:

said link member is journaled on said anvil and rotates with said hammer dogs.

25. The impact tool mechanism of claim 24 wherein:

said ring journaled on said eccentric is disengaged from said surfaces on said carrier and said link member after said hammer dogs are pivoted inwardly and before said hammer dogs engage said jaws.

26. An impact mechanism comprising:

a carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw;

a hammer dog pivoted on said carrier adjacent said anvil and tiltable between a middle and first position wherein it clears said anvil jaws as it rotates around said anvil, a second position wherein it will engage and strike a blow to said anvil jaw as said carrier rotates in a clockwise direction and a third position wherein it will engage and strike a blow to said anvil as said carrier rotates in a counterclockwise direction; and

actuation means interconnected between said anvil and hammer dog and operative to tilt said hammer dog to said second position when said carrier is driven in a clockwise direction to cause said hammer dog to strike an impact blow to said anvil jaw at least once each complete revolution of said carrier;

said actuation means being operative to allow said car rier to rotate more than one revolution before striking an impact when initially reversed after rotating in the opposite direction, thus enabling said hammer dog to strike an initial impact which is substantially more powerful than its normal impact.

27. An impact wrench mechanism comprising:

a carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw;

a hammer dog pivoted on said carrier on an axis extending substantially parallel to said carrier axis adjacent to said anvil and tiltable radially inward to engage said jaw as said carrier rotates, said hammer dog being positioned and shaped so that it impacts said jaw generally along a force line displaced radially outward from the axis of the hammer dog pivot causing the creation of a camming force acting on the hammer dog tending to cause it to tilt outwardly to disengage said jaw during said impact, and said hammer dog being also positioned, proportioned and having a mass and a mass center location which will cause the creation of inertia forces acting on said hammer dog during the instant of said impact which will overcome said camming force and will prevent said hammer dog from tilting outwardly during the instant of impact.

28. An impact wrench mechanism comprising:

carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw with an impact surface;

a hammer dog pivoted on said carrier on an axis extending substantially parallel to said carrier axis adjacent to said anvil and tiltable radially inward to engage said jaw as said carrier rotates, said hammer dog having an impact surface adapted to engage said anvil jaw impact surface, the impact surfaces of said hammer dog and anvil jaw being shaped so that during the impact of said hammer dog with said anvil, a camming force is created acting on the hammer dog tending to cause it to tilt outwardly to disengage said jaw during said impact, and said hammer dog being also positioned, proportioned and having a mass and a mass center location which will cause the NILE C. BYERS, ]R.,

12 creation of inertia forces acting on said hammer dog during the instant of said impact which will overcome said camming force and will prevent said hammer dog from tilting outwardly during the instant of im pact.

29. An impact wrench mechanism comprising:

a carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw with an impact surface;

a hammer dog pivoted on said carrier on an axis extending substantially parallel to said carrier axis adjacent to said anvil and tiltable radially inward to engage said jaw as said carrier rotates, said hammer dog having an impact surface adapted to engage said anvil jaw impact surface, the impact surfaces of said hammer dog and anvil jaw being shaped so that during the impact of said hammer dog with said anvil, a camming force is created acting on the hammer dog tending to cause it to tilt outwardly to disengage said jaw during said impact, and said hammer dog being also positioned, proportioned and having a mass and a center of percussion location which will cause the creation of a resultant inertial force couple acting on said hammer dog during the instant of said impact which will prevent said hammer dog from tilting outwardly during the instant of impact.

30. An impact wrench mechanism comprising:

a carrier rotatably mounted on an axis and adapted to be driven;

an anvil rotatably and coaxially mounted adjacent said carrier and having a radially projecting jaw with an impact surface;

a hammer dog pivoted on said carrier on an axis extending substantially parallel to said carrier axis adjacent to said anvil and tiltable radially inward to engage said jaw as said carrier rotates, said hammer dog having an impact surface adapted to engage said anvil jaw impact surface, the impact surfaces of said hammer dog and anvil jaw being shaped so that during the impact of said hammer dog with said anvil, a camming force is created acting on the hammer dog along a force line located relative to the hammer dog axis to cause it to tilt outwardly to disengage said jaw during said impact, and said hammer dog being also positioned, proportioned and shaped to have a center of percussion location which provides a greater moment arm about said hammer dog axis for an inertial force opposing said camming force and acting through said center of percussion than the moment or of said camming force about said hammer dog axis.

31. The impact wrench mechanism of claim 28 where- References Cited UNITED STATES PATENTS 5/1939 Jimerson 173-93.6 6/1942 Amtsberg 17393.-5 5/1959 Madsen 173-935 8/1964 Reynolds 173-935 4/1968 Kaman 173-93.5 6/1942 Amtsberg 173--93.5

Primary Examiner

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5199505 *Apr 24, 1991Apr 6, 1993Shinano Pneumatic Industries, Inc.Rotary impact tool
US5435398 *Sep 1, 1994Jul 25, 1995Chiu-Yu Wang ChengElectrical wrench
US5740892 *Aug 26, 1996Apr 21, 1998Huang; Chen Shu-HsiaPower wrench torque transmission mechanism
US5784934 *Jan 30, 1997Jul 28, 1998Shinano Pneumatic Industries, Inc.Ratchet wrench with pivotable head
US5887666 *Aug 4, 1997Mar 30, 1999Chen; KennethImpact wrench structure
US6311583Apr 13, 2000Nov 6, 2001S. P. Air Kabusiki KaishaRatchet wrench with pivotable head
US6443239Feb 29, 2000Sep 3, 2002S.P. Air Kabusiki KaishaPneumatic rotary tool
US6491111Jul 17, 2000Dec 10, 2002Ingersoll-Rand CompanyRotary impact tool having a twin hammer mechanism
US6938526Jul 30, 2003Sep 6, 2005Black & Decker Inc.Impact wrench having an improved anvil to square driver transition
US7036406Mar 26, 2004May 2, 2006Black & Decker Inc.Impact wrench having an improved anvil to square driver transition
US7249638Jan 7, 2005Jul 31, 2007Black & Decker Inc.Impact wrench anvil and method of forming an impact wrench anvil
US8480453Jan 11, 2007Jul 9, 2013Sp Air Kabushiki KaishaDie grinder with rotatable head
US8505648May 7, 2009Aug 13, 2013Milwaukee Electric Tool CorporationDrive assembly for a power tool
US20130112449 *Nov 9, 2011May 9, 2013Sing Hua Industrial Co., Ltd.Torsion increasing pneumatic tool percussion hammer
EP0808694A1Nov 6, 1996Nov 26, 1997Yotaro TagaSilencer mechanism for use in an impact wrench
WO2009137684A1 *May 7, 2009Nov 12, 2009Milwaukee Electric Tool CorporationDrive assembly for a power tool
Classifications
U.S. Classification173/93
International ClassificationB25B21/02, B25B21/00
Cooperative ClassificationB25B21/026, B25B21/002
European ClassificationB25B21/02C, B25B21/00C