US2821276A - Rotary impact tool - Google Patents

Description

Jan 2%, 195% H. c. REYNOLDS ROTARY IMPACT TOOL Filed Feb. 10,. 1354 'lllllllmm lllIlll INVENTOR HAROLD C REYNOLDS HlS ATTORNEY United States ROTARY IMPACT TOOL Application February 10, 1954, Serial No. 409,403

4 Claims. (Cl. 192-305) This invention relates to rotary impact tools, and more particularly to air-operated impact tools of the type adapted to rotate screws, nuts and similar work.

One object of this invention is to provide an impact tool of such type which is relatively inexpensive to construct and maintain.

A further object of this invention is to provide an airoperated dog, or jaw, for engaging and disengaging the hammer with the anvil.

Other objects of this invention will become obvious from the following specification and drawings in which,

Figure 1 is a vertical elevation, partly in section, of an impact tool constructed in accordance with the practice of this invention,

Fig. 2 is a transverse view taken through Fig. 1 along the line 2-2 looking in the direction of the arrows,

Fig. 3 is a view in perspective of the anvil,

Fig. 4 is a perspective view, partly in section, of a valve element for controlling the flow of pressure fluid for actuating the hammer dog, and

Fig. 5 is a transverse view taken through Fig. 4 along the line 5-5 looking in the direction of the arrows.

Referring to Fig. l of the drawings, the impact tool disclosed comprises, in general, a casing housing a motor 12 connected to rotate a hammer 14 adapted to deliver a series of rotational hammer blows in rapid succession for rotating an anvil 16. In the tool shown, the hammer 14 and anvil 16 remain engaged and are rotated continuously at a relatively high speed whenever the work is relatively loose or easily rotated. When, however, the work reaches some predetermined degree of tightness, the hammer is alternately disengaged and engaged with the anvil such that the hammer delivers a series of high velocity blows to the anvil to rotate the work.

In furtherance to this end the hammer includes a re- I ciprocatory dog or impact pin 18 constantly urged by a spring 22 into one limiting position such that it will strike, or engage, a jaw 17 on the anvil 16. Immediately after impact of this blow, the dog 18 is retracted into its other limiting position to disengage the anvil from the hammer by pressure fluid valved thereto by a valve 20. Upon such disengagement the hammer is rotated rapidly by the motor 12 to strike another hammer blow. During this free rotation of the hammer 14, the valve 20 exhausts pressure fluid from the dog 18 and the spring 22 actuates the dog 18 into its forward limiting position for engagement with the anvil.

Referring now in greater detail to the construction of the impact tool, the motor 12 shown is of the air-operated type connected to a spindle 26 piloted in a transverse bore 28 in the hammer 14. The gearing 24 shown may, if desired, be connected between the motor 12 and spindle 26. The driving connection between the spindle 26 and hammer 14 is of the type adapted to limit the atent ice impact shock of the hammer transmitted to the motor. The connection shown by way of illustration comprises a cone clutch 30 having a splined connection at 32 with the spindle 26 and a frictional connection at its peripheral surface with the surface of a cone-shaped recess in the rearward end portion of the hammer 14. The clutch 30 is constantly urged into frictional contact with the hammer by a spring 38 biased between the rearward end of the clutch 30 and a retaining ring 40 mounted in the hammer 14. With this construction, limited relative movement between the spindle 26 and the hammer 14 is permitted at the time of impact of the hammer 14 with the anvil 16 so as to limit the amount of shock transversed through the spindle to the gears 24 and motor 12.

The hammer 14, shown by way of illustration only, is of generally triangular shape and having in one corner a longitudinal chamber 42 for the reception of the impact pin or dog 18. The chamber 42 is somewhat enlarged at its rearward end portion 44 thereby providing a shoulder 46 for limiting the forward movement of the dog 18. In furtherance to this end the dog 18 is similar in its outside dimensions to the chamber 42 thereby providing a head 48 reciprocable in the chamber portion 44 and a shoulder 50 defining a pressure surface 52.

The dog 18 is constantly urged into its forward limiting, or hammer engaging, position by the spring 22 positioned in a recess 51 in the dog and bearing at its rearward end against a spring seat 53. The dog 18 is periodically actuated into its rearward limiting position and out of engagement with the anvil 16 by a pressure fluid intermittently supplied to the surface 52. In furtherance to this end an annular groove 54 is cut in the periphery of the chamber 42 immediately adjacent the shoulder 46. This groove 54 is communicated with the interior of the hammer bore 28 by a port 55. The bore 28 in turn is communicated with a pressure fluid source (not shown) through a central bore 56 in the spindle 26 and passage 57 in the motor 12 and casing 10.

The flow of pressure fluid to and from the chamber 42 for actuating the dog 18 is controlled by means of the rotary valve 20. The valve shown by way of illustration is in the shape of a cylinder with the forward portion fitted in a recess 58 in the anvil 16. The rearward end portion of the valve 20 extends into the hammer bore 28 and has a longitudinal passage 60 leading from the rear end surface of the valve 20 to a peripheral cut or notch 62 in the valve 20 lying in the same horizontal plane as the port 55 in the hammer.

Positioned 180 degrees from the cut 62 is a similar cut 64 registering with a longitudinal groove 66 leading forwardly to a transverse hole 68 in the valve 20. When the valve 20 is placed in its operative position as shown in Fig. 1 the transverse hole 68 is in alignment with a pair of cuts 70 in the anvil 16 for the reception of a pin 72 securing the valve 20 against rotation relative to the anvil 16. The pin 72 is preferably of cruciform shape or some similar shape such that clearance is provided to communicate the groove 66 through the hole 68 and cut 70 with the atmosphere.

With this valve construction, whenever the hammer 14 rotates relative to the anvil 16 such that the dog 18 contacts the anvil jaw 17 (see Fig. 2, right-hand rotation being assumed), the cut 62 will register with the port 55 to valve pressure fluid to the dog surface 52. The cut 62 does not, however, register fully with the port 55 in this hammer position and accordingly, a relative short period of time is required for the pressure in the groove 54 to build up to the pressure in the passage 60. Thus the pressure acting on the surface 52 does not build up suflicientiy-to 're'tract'the dog '18 against the pressure of the spring '22 after the hammer has strucka blow.

Immediately after the blow is struck the force of pressure fluid acting against the surface 52 will retract the dog 18 disengaging the hammer from the anvil, and the hammer will then be rotated some 360 degrees prior to striking the next blow. During .thisiree, .rotation of .the hammer and some 181). degrees. after ztheldog misretracted, theperipheral -cnt.;64 registers with .theport 55 thereby exhausting pressure fluid from the groove 54 through the groove 66,'l1ole 68 and cut 70 to the latmospher'etherebypermittingthe spring'2'2 toreturn .thedog 18 .toits'forwardlimit'ingposition preparatory to.striki1 1g the nexthammerhlow.

The. anvil shown, isprovided witha single few 17 such that the hammer strikes. only one .blow per revolution. Two or more jaws .cou1d,,of course, ;be provided if more blows ,per hammer revolution .is. desired. The jaw 17 shown has. curved portions 74. andjfi omits opposite sides, the curve of each portion having .a radius corresponding to the radius of the. dog 18. sons. to provide surface contact between the surfaces of .the..dog '18, .and. the jaw 17-. The curved portion'74 serves as=ast1iiking surface :on the jaw 157v during right-hand rotation..-of the hammer 14, the surface '76 is the striking surface .for left-hand rotation. An extension 78 on theanvil istconnected'througha socket "80 or similar connectingelement with the work .82.,

Reviewing briefly the operation of. the impact tool, .the tool is s'tartedby opening the control valve84in the .tool handie '88 to supply air to themotor 12 and valve 20. Assuming that during. thev initial portion. of the. tightening cycle that the nut '82 runs relatively free. on the 'bolt 83, -the dog 1-8 will remain in engagement with the anvil jaw 17 and thehamrner'and anvil, will be. rotated at the speed of the spindle 26 until the resistance. to. rotation of the nut reaches some predetermined torque. The. reason the 'dog 18 is not intermittently engaged to and disengaged from'the anvil during this .portion of'the tightening cycle is due to an operating characteristic of an .air-motor which makes 'itserve as a means for automatically controlling the pressure of'air supplied'to the valve Z253. Specifically, when there is little resistance to rotation of an air-motor it runsat "a relatively high speede. g., 6,000 revolutions per'minute (R. P. At this speed there is very -little resistance to air flowing through the motor, and the air pressure downstream of the. motor. control valve 84, as 'inthe airsupply passages 86 and 57' for the motor 12 and valve '20, respectively, is relatively low as compared to "line pressure upstream of valve '84. 'When, however, the

motor is running at a slower speed, as when resistance "to rotation of the work' is above said prcdeterminedvalue, the pressure downstream of'the valve '54 builds up to a value more nearly equal t-olinepressure. Thus, the pressurelavailabl'e'to actuate the do g '18- is not 'snfiiciently high during the run-down period to actuate the dog 1'8 against the force of -the spr-ing '22. When-,'-however, the resistance to rotation of the work slows the speed of the motor 12 down to, say for example, 1,000 P. average, the pressure of the air between the motor control valve 84 and the motor '12 is sufficient-lyhigh to actuate the dog 1 8.

Accordingly, Whenever the Work reach-es some predetermined degree of tightness: and the anvil rotates to a positionto register thecut 62 with the .port 55, pressure fluid is conducted to the pressure surface 52 on the dog 18 to retract 'thet dog- 18 immediately after a hammer blow is struck. Movement of the dog 1*8out'o'f'engagement with the anvil frees the hammer tobe'rotated' by the spindle '26 through some 360 degrees preparatory to striking a succeeding hammer blow. During the free rotation of the hammer, the groove 54 is communicated through the port 55, peripheral cut 64, groove 66,- hole e68:and 'cut10'with the atmosphere-such that the spring 22 tactuates' the dog 18 into. its forward limiting position *for engagementrwiththe anvil'lfi.

While. I have shown and described a specific form of the spirit of the invention as set forth in the appended claims.

I claim:

1. An impact tool comprising a pressure fluid motor, an anvil, a hammer for connection with the motor and rotated thereby for delivering a series of rotational blows to the anvil, said hammer having a chamber, and a dog mounted in said chamber has ing -a pressure surface thereon and being movable intoone position .for engagement with the anvil and movable into a second position out of such engagemenr, means tccmstantly urging the. dog into one of said positions, --valve means mounted on the anvil and cooperating with the hammer to valve pressure-fluid to said surface whenever thehammeris 11km location relative to the anvil and to exhaust pressure fluid from said surface to the atmosphere whenever the hammer is in another location relative to the anvil, and means for supplying pressure fluid to said valve means.

2., An impact tool. forrotating .a work-piece comprising, a pressure fluid". motor, an. anvil, a hammer for-con,- nection with the motorand rotated thereby 'for delivering a series of rotational blowsfi'to the anvil, said. hammer having a chamber and, abore formed therein and a port communicating said chamber andbore, a dog reciprocable in said chamber and having a pressuresur'face thereon, said 'd'og being actuated .into one, position for engagement with the anvil andactuated into another position. out of such engagement, means for constantly urging the dog into one of saidpositions, a valve in saidbore held. against rotation relative to said anyfiLfbr' intermittently communicating saicl' port with a source o'fpr'essure. fluid to supply pressure iluid'to' said surface for, actuating thedog into the other of said positions and intermitten'tlyicommurficating said port with the atmosphere to exhaust-pres.- sure fluid-fromsaid chamber, means for .supplyingpressure fluid to said motor and "valve,v and means for automatically reducing the pressure of fluid supplied to the valve whenever the turning force supplied to the work piece is below a predetermined value.

3.A rotary impact tool comprising, an air motor, an anvil, a hammer adapted to be rotated by the motor for deliver-inga series of'rotational hammer blows *to the anvil, said hammer including a dog having a pressure surface thereon and movable relative to the hammerin one direction for engagement with the'anvi-l' and retractable in the other direction todi'sengage the hammer from the anvil, spring means for constantly urging the 'dog in the direction for engagement with the anvil, means for valving pressure fluid' to said pressure surface immediately prior to-engagemen't of thedog with the anvil for disengaging the hammer from theanvil after a blow is struck and for exhausting such fluid to-the atmosphere after the'dog retracted to permit the spring-to actuate the doginto-emgagingaposition'prior to theneart hammerblow; and a -conduitfor supplying-'pressure-iiuid to themotor and the l-a'st said means. 7

4.. An impact tool compni sing, a pressurefluid motor; a rconduit i 01: supplying fluid 'u'nder pressure-to said motor; means. an controlling flow'through said conduit, an anvil havinga jaw, ahammer for connectionthe motor and rotated thereby: forde'liver-in-g aseries-of rotational blows .to theianviil jaw,.-'said hammer having a chamber and a bore. formed therein and a port communicating said chamber "and bore, aadogreoiprocabl'e in saidchamber and having, a pressuresurface; thereon, means; vfor constantly urging the dog into a position for engagement with the anvil jaw, avalve. in, said boreheld against rotation, relativeto the anvil, .saidvalve having a cut therein, adapted to be constantly. communicated. with .a pressure fluid source and arranged to rxister. with. said. port. to. supply pressure 'iluid to, actuate the, dog out of; said. engagement whenever the hammer location relative to the anvil places the dog in contact. with the anviPjaw, VaIYQQhaYing-n" second cut therein adapted to be constantly communicated References Cited in the file of this patent with the atmosphere and arranged to register with said port at a point in the hammer cycle subsequent to said UNITED STATES PATENTS contact of the dog with the jaw, and a passage leading 2,128,761 Thomas Aug. 30, 1938 from said conduit from a point downstream of said means 5 2,476,632 Shaff July 19, 1949 to supply pressure fluid to said valve. 2,693,867 Maurer Nov. 9, 1954

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