US3835934A

US3835934A - Impact wrench with automatic shut-off

Info

Publication number: US3835934A
Application number: US00328679A
Authority: US
Inventors: K Schoeps; T Gustavsson
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1972-02-04
Filing date: 1973-02-01
Publication date: 1974-09-17
Anticipated expiration: 1991-09-17
Also published as: NL177091B; CH553625A; DE2304610A1; NL7301377A; BR7300833D0; JPS4888600A; CA997179A; IT977178B; AU464994B2; PL84774B1; DE2304610C2; JPS5623754B2; US3904298A; SE374505B; FR2169974B1; GB1391574A; AU5177873A; BE794782A; ZA73663B; FR2169974A1

Abstract

In an impact wrench, the rotor of a pneumatic sliding vane motor and the hammer are inter-connected to rotate conjointly. On the rear stub shaft of the rotor there is formed an inner race for a ball. A pivot-mounted arm forms an outer race for the ball, and the races diverge in the direction of the rotary impacts so that, at its rolling movement created by the rebound of the hammer, the ball forces the arm to swing. At a pre-determined magnitude of the rebound, the arm forces a trigger for a shut-off valve to release the shut-off valve for movement into its position for shutting off the supply of motive fluid, and the motor stops.

Description

[ Sept. 17, 1974 IMPACT WRENCH WITH AUTOMATIC SHUT-OFF [75] Inventors: Knut Christian Schoeps, Nacka;

Tommy Henning Bruno Gustavsson, Skarholmen, both of Sweden [73] Assignee: Atlas Copco Aktiebolag, Nacka,

Sweden [22] Filed: Feb. 1, 1973 [21] Appl. N0.: 328,679

[30] Foreign Application Priority Data Feb. 4, 1972 Sweden 1300/72 [52] US. Cl. 173/12 [51] Int. Cl B25b 23/14 [58] Field of Search 173/12 [56] References Cited UNITED STATES PATENTS 2,543,979 3/1951 Maurer 173/12 2,768,546 10/1956 Amtsberg ..l73/l2 Primary ExaminerErnest R. Purser Attorney, Agent; or FirmFlynn & Frishauf 5 7 ABSTRACT In an impact wrench, the rotor of a pneumatic sliding vane motor and the hammer are inter-connected to rotate conjointly. On the rear stub shaft of the rotor there is formed an inner race for a ball. A pivotmounted arm forms an outer race for the ball, and the races diverge in the direction of the rotary impacts so that, at its rolling movement created by the rebound of the hammer, the ball forces the arm to swing. At a pre-determined magnitude of the rebound, the arm forces a trigger for a shut-off valve to release the shutoff valve for movement into its position for shutting off the supply of motive fluid, and the motor stops.

16 Claims, 11 Drawing Figures mmmsm 7 1914 v 3.8%5334 sum 3 or a I //I r/////1 IMPACT WRENCH WITH AUTOMATIC SHUT-OFF This invention relates to an impact wrench of the kind with a hammer that is rotated by a fluid motor, particularly but not exclusively by a pneumatic sliding vane motor, and delivers rotary impacts to an anvil, a shut-off valve in the motive air passage of the motor being adapted to be initiated to close when the amplitude of the rebound of the hammer has reached a pre determined value.

In aprior embodiment of such an impact wrench, a conventional freewheel clutch is connected to the rotor of the sliding vane motor. When the rotor rebounds,

the clutch catches hold of the rotor and swings an arm which initiates the closing of the valve when the rebound amplitude reaches a predetermined value. In such a design, it is difficult to provide for a reverse running without negatively influencing the endurance of the rebound measuring device.

It is an object of the invention to provide for an impact wrench which has a simple, reliable and accurate torque controlling device which, furthermore, permits reverse running of the wrench.

The invention will be further described with reference to the accompanying drawings which show an impact wrench in accordance with the invention.

FIG. 1 is a longitudinal section taken substantially along line 1-1 in FIG. 2 and 3,

FIGS. 2-5 are cross sections taken along lines 2-2, 33 and 44, respectively, in FIG. 1,

FIGS. 5 and 6 show on an enlarged scale and in other relative positions some details in FIG. 3,

FIG. 7 is a section taken along line 77 in FIG. 5,

FIG. 8 shows a detail in FIG. 1,

FIG. 9 is a section taken along line 99 in FIGS. 1 and 3 but showing a modified form of some details,

FIG. 10 is a section taken substantially along line 1010 in FIG. 9, and

FIG. 11, finally, is a section corresponding to FIG. 9 but some of the details are in another position.

. The impact wrench in the figures has a housing 11 which in general consists of an intermediate portion 12 with an integral handle 13, a back end portion 14 and a front end portion 15, all held together by three screws. A drive square 16 protrudes from the housing. A nut socket can be attached directly on to the drive square, but usually a torsion bar 17 is inserted between the drive square and the nut socket 18. The drive square is part of a rotatable anvil 19 which extends rearwardly into a hammer 20 adapted to deliver rotary impacts to the anvil so as to rotate the latter. The hammer 20 is connected to a rotor of a pneumatic sliding vane motor 21 which consists of a cylinder 22, two

end plates

23,24, and the rotor 25 which is journalled by means of

roller bearings

26,27 in the end plates. The rotor 25 has six radial slots for vanes 28. The cylinder 22 has two combined inlet/

outlet ports

29,30 which through supply/

exhaust passages

31, 32 are connected to a selector valve 33 which is connected to a supply valve 34 in the handle 13 and to two forwardly directed

alternative exhaust passages

35,36 as well. The supply valve is supplied with compressed air through a passage 37 which is connected to a non-illustrated air hose.

In the supply passage 31 there is a shut-off valve 38 in the form of a slide which is loaded towards its open position by a spring 39. It has an end chamber 40 which is connected to the supply passage 31 through a bore 41 in the slide 38 so that the latter is loaded to the right by the air pressure when the supply passage 31 is pressurized. The spring 39 is weak enough to be overcome by the air pressure. However, the shut-off slide 38 is normally retained in its open position (shown in FIG. 1) by a retainer slide or trigger 42 which is loaded towards a locking position by a spring 43 as well as by the air pressure in an end chamber 44 which through a passage 45 is connected to a mouth 46 that is controlled by the shut-off slide 38. The retainer slide 42 has a shoulder in the form of a screw 47 which abuts the outer end of an arm 48 so as to force the latter to the left in FIG. 3. The arm is pivot-mounted in the housing on a pin 49 which is eccentric on a turnable axle 50. A cylindrical member 52 is affixed to the rear stub shaft 51 of the rotor 25 by means of a screw 53 and a pin 54. This member 52 has an annular groove 55 which fonns an inner race for a ball 56 to which a recess 57 in the arm 48 forms an outer race. The

races

55,57 diverge clockwise somewhat in the figures. A knife 58, loaded by a spring 61, is journalled on a pin 59 and extends into a slot 60 in the arm 48 so as to bias the ball 56 into the position it takes up in FIG. 3. However, the knife 58 can be lifted to the position shown in FIGS. 5 and 6 by a piston 62 which pushes a pin 63 on the knife. The piston 62 lifts the knife 58 when loaded by compressed air through a passage 64 which, like the passage 45, is connected to the mouth 46.

For running down a nut or screw, the selector valve 33 shall be in its position shown in FIG. 2. Since the supply valve 34 is closed, the shut-off slide 38 is in its position shown in FIG. 1 owing to the spring 39, and it is retained there by the spring-biased retainer slide 42. When the supply valve 34 is opened, the passage 31 is pressurized while the passage 32 is connected as an exhaust passage and the motor starts rotating clockwise so that the hammer 20 will deliver rotary impacts to the anvil 19. On account of the opening 46 and the passage 64, the piston 62 will lift the knife 58 to the position shown in FIG. 5 simultaneously with the motor starting its rotation. If the joint has some elasticity, the resistance to rotation will gradually increase and the hammer will start rebounding counter-clockwise after each impact. The rotor 25 and the cylindrical member 52 on the rear stub shaft 51 of the rotor will rebound conjointly with the hammer. The ball 56 will therefore roll counter-clockwise as the hammer rebounds and it will force the arm 48 to swing at every rebound. The arm 48 swings back again as the rotor 25 again starts rotating clockwise and the ball 56 rolls back to its normal position. When the resistance to rotation reaches a predetermined value the rebound will force the arm 48 to move the retainer slide 42 completely out of register with the shut-off slide 38, and because of the air pressure in the end chamber 40 of the shut-off slide 38, this slide 38 will switch over to its closed position so that the impact wrench immediately stops working. Since the passage 31 is oblique to the slide 38, the end chamber 40 will maintain pressurized through the bore 41 in the slide 38 also when the slide has switched over to is closed position.

When the supply valve is released, i.e. has taken up its closed position, the end chamber 40 of the shut-off slide 38 is vented by means of leakage in the selector valve 33 so that the shut-off slide 38 moves back to its open position shown in FIG. 1. During this movement, the shutoff slide 38 opens the mouth 46 so that the piston 62 is vented so as to permit the knife 58 to return the ball 56 to its normal position shown in FIG. 3 by the action of the spring 61. As a result of the ball 56, the spring loaded retainer slide 42 again locks the shut-off slide 38 in its open position, and the impact wrench is ready for another operation.

If instead a screw or nut is to be released and run back, the selector valve 33 shall be moved to the left in FIG. 2 so that the passage 32 will be the supply passage and the passage 31 the exhaust passage. Upon actuation of the supply valve 34, the knife 58 will not be lifted since the opening 46 has only exhaust pressure and the knife 58 will therefore positively hold the ball 56 in the normal position.

The impact wrench will operate also if the knife 58 is dispensed with, since the shut-off slide 38 will remain in its open position during the reverse rotation due to its end chamber 40 having only exhaust pressure so that the spring 39 is able to retain the shut-off slide 38 open also if the retainer slide 42 is moved out of its locking position by the arm 48. When a run-down operation of a nut is started, however, the ball 56 can be in such a position that the shut-off slide 38 is not locked in its open position by the retainer slide 42 and in that case the supply valve 34 must be actuated twice before the wrench starts its operation.

Instead of the knife 58, there can be an arrangement to inhibit the movement of the shut-off slide 38 until the retainer slide 42 is in its position for engagement with the shut-off slide 38. Such a modification is shown in FIGS. 9-11. When the supply passage 31 is pressurized and the shut-off slide 38 is open, air is admitted through an axial groove 66 in the slide to a transverse bore 67 that forms a restriction and ends in a wider coaxial bore 68. Another bore 69 leads axially from this bore to the end chamber 40. The bore 68 registers with a vent passage 70 when the shut-off slide 38 is in its open end-position (its left hand position shown in FIG. 9). The retainer slide 42 is arranged to control the vent passage 70, and, unless it is in its position for engagement with the shut-off slide 38, it holds the vent passage open as can be seen in FIG. 9. The vent passage 70 vents through a sintered bronze plate 71.

If the ball 56 and the arm 48 are in their positions of FIG. when the operator actuates the valve 34 to pressurize the supply passage 31, the retainer slide 42 is in its position of FIG. 11 and blocks the vent passage 70. The shut-off slide 38 is in its open end position its left hand position in which it is shown in FIG. 9. Since the vent passage 70 is blocked by the slide 42, the end chamber 40 is being pressurized through the

passages

66,67,68,69 and the air pressure forces the shutoff slide 38 to abut against the slide 42 as shown in FIG. 11. In this intermediate position of the shut-off slide, the vent passage 70 is isolated from the air chamber 40 since the bore 68 does not any longer register with the vent passage 70. Thus, the shut-off slide 38 is forced into its closed position its right hand position when the retainer slide 42 is withdrawn by the arm 48 as previously described.

Since there is no knife 58 to reset the ball 56, the retainer slide 42 could rest in a withdrawn position as well, as shown in FIGS. 6 and 9, before the operator actuates the valve 34 in order to start a run-down operation. However, there will not be a pressure in the air chamber 40, that can force the shut-off slide out of its end position shown in FIG. 9 since the retainer slide 42 holds the vent passage open as can be seen in this figure. As the motor now starts to rotate, the ball 56 will roll down to its position of FIG. 5 and permit the retainer slide 42 to move into its position of FIG. 11 in which the slide 42 blocks the vent passage 70. As a result, the shut-off slide 38 will be forced into its position shown in FIG. 11 as previously described.

When the shut-ofi' slide 38 and the retainer slide 42 are in their positions of FIG. 9, the air chamber 40 is not only vented, but it has partial vacuum since the restricted bore 67 forms an injection nozzle that draws air from the air chamber 40.

As can be seen in FIG. 10, a weak wire spring 72 is preferably inserted to force the arm against the ball 56 and ensure that the ball always contacts both its

races

55 and 57. Furthermore, this spring 72 permits a play at 73.

The spring 39 ensures that the shut-off slide remains open during the reverse running during which the supply passage 31 is utilized as an exhaust passage as previously described.

The operator can adjust the final torque by turning the axle 50 on the eccentric pin 49 of which the arm 48 is journal-mounted. When the operator needs greater changes in the final torque, he switches from the torsion bar 17 to a bar with other spring characteristics, or he uses an adjustable torsion bar.

What we claim is:

1. An impact wrench comprising an anvil connected to a spindle, a hammer adapted to deliver rotary impacts to the anvil, a fluid motor for rotating the hammer, a motive fluid passage for the motor, a shut-off valve in said motive fluid passage, a member connected to the hammer to rotate conjointly therewith and forming a circular inner race for a rolling member, and a pivotably mounted arm carrying an outer race for said rolling member, said arm being swingable into a position for initiating the shut-off valve to take up a closed position, said outer race diverging relative to said inner race in the direction of the rotary impacts so that, at its rolling movement created by the rebound motion of the hammer, said rolling member forces said arm to swing into its position for initiating said shut-off valve to take up said closed position when the rebound of the hammer from the anvil reaches a pre-determined magnitude.

2. An impact wrench as defined in claim 1 in which the motor is a pneumatic sliding vane motor and the shut-off valve is adapted to be loaded towards said closed position by the live air from the supply passage of the motor and is adapted to be retained in an open position by a trigger, said arm being adapted to release the trigger from the shut-off valve.

3. An impact wrench as defined in claim 2 comprising a spring adapted to load the shut-off valve towards said closed position so as to re-set the valve when the drive air is closed off.

4. An impact wrench as defined in claim 3 in which the shut-off valve is a slide which is parallel with the pneumatic motor and the trigger is a slide which is transverse to the shut-off slide and loaded by a spring to register with the shut-off slide.

5. An impact wrench as defined in claim 4 in which the trigger slide is loaded to register with the shut-off slide also by the air pressure in the supply passage, conveyed through a connection passage.

6. An impact wrench as defined in claim 2 in which the motor is reversible and has an alternative supply passage, and including a selector valve connected upstream of the shut-off valve so as to selectively connect either of the supply passages as an outlet.

7. An impact wrench as defined in claim 6 comprising a piston means connected to either of the supply passages, and a retainer means controlled by said piston means to retain the rolling member when the selector valve is connected for reverse running.

8. An impact wrench as defined in claim 6 comprising a retainer loaded by a spring to bias said rolling member into an inactive position, and a piston means connected to a mouth into the supply passage that includes the shut-off valve, said mouth being located between said selector valve and the shut-off valve, said piston means being adapted to release said retainer from said rolling member when loaded by pressure fluid.

9. An impact wrench as defined in claim 8 in which said mouth is located so as to be closed by the shut-off valve when the latter is in its closed position.

10. An impact wrench as defined in claim 1 comprising a retainer loaded by a spring to bias said rolling member into an inactive position and a piston means adapted to release the retainer from the rolling member when the wrench is started.

11. An impact wrench as defined in claim 1 in which said shut-off valve is a slide arranged in the supply passage of the motor, said shut-off slide being loaded by a spring towards an open end position and having a piston surface in an air chamber in order to be forced towards a closed position by air pressure in said air chamber, a restricted air passage leads from said supply passage to said air chamber, a vent passage is arranged for venting said air chamber whereby to inhibit a movement of said shut-off slide away from its open end position, said shut-off slide isolating said air chamber from said vent passage when out of said open end position, and a trigger is loaded towards a position for retaining said shut-off slide in an intermediate open position when the shut-off slide is forced towards its closed position by the air pressure in said air chamber, said arm being adapted to move said trigger into a position in which it releases the shut-off slide for movement to said closed position, said trigger holding said vent passage closed when in its position for retaining said shut-off slide.

12. An impact wrench as defined in claim 11 in which said trigger is a slide arranged transverse of said shutoff slide is loaded by a spring towards said position for retaining the shut-off slide.

13. An impact wrench as defined in claim 11 in which said restricted passage comprises an ejector nozzle in said shut-off slide and a suction passage from said air chamber to said nozzle, said nozzle being located to be directed into said vent passage when said shut-off slide is in said open end position whereby to provide for a suction in said air chamber.

14. An impact wrench comprising an anvil connected to a spindle, a hammer adapted to deliver rotary impacts to the anvil, a fluid motor for rotating the hammer and having a supply passage, a shut-off valve in the form of a shut-off slide arranged in the supply passage of the motor, said shut-off slide being loaded by a spring towards an open end position and having a piston surface in an air chamber in order to be forced towards a closed position by air pressure in said air chamber, a restricted air passage leading from said supply passage to said air chamber, a vent passage for venting said air chamber whereby to inhibit a movement of said shut-off slide away from its open end position, said shut-off slide isolating said air chamber from said vent passage when out of said open end position, a trigger loaded towards a position for retaining said shut-off slide is an intermediate open position when the shut-off slide is forced towards its closed position by the air pressure in said air chamber, said trigger holding said vent passage closed when in its position for retaining said shut-off slide, and means for forcing said trigger into a released position in response to a rebound of said hammer reaching a pre-determined magnitude.

15. An impact wrench as defined in claim 14 in which said trigger is a slide arranged transverse of said shutoff slide and loaded by a spring towards said position for retaining the shut-off slide.

16. An impact wrench as defined in claim 14 in which said restricted passage comprises an ejector nozzle in said shut-off slide and a suction passage from said air chamber to said nozzle, said nozzle being located to be directed into said vent passage when said shut-off slide is in said open end position, whereby to provide for a suction in said air chamber.

Claims

12. An impact wrench as defined in claim 11 in which said trigger is a slide arranged transverse of said shut-off slide is loaded by a spring towards said position for retaining the shut-off slide.

15. An impact wrench as defined in claim 14 in which said trigger is a slide arranged transverse of said shut-off slide and loaded by a spring towards said position for retaining the shut-off slide.