EP0096029A1 - Electrically driven impact tool - Google Patents

Electrically driven impact tool

Info

Publication number
EP0096029A1
EP0096029A1 EP82900418A EP82900418A EP0096029A1 EP 0096029 A1 EP0096029 A1 EP 0096029A1 EP 82900418 A EP82900418 A EP 82900418A EP 82900418 A EP82900418 A EP 82900418A EP 0096029 A1 EP0096029 A1 EP 0096029A1
Authority
EP
European Patent Office
Prior art keywords
ram
bodies
movement
ram means
moving
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP82900418A
Other languages
German (de)
French (fr)
Other versions
EP0096029A4 (en
Inventor
James D. Cunningham
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0096029A1 publication Critical patent/EP0096029A1/en
Publication of EP0096029A4 publication Critical patent/EP0096029A4/en
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25C—HAND-HELD NAILING OR STAPLING TOOLS; MANUALLY OPERATED PORTABLE STAPLING TOOLS
    • B25C1/00—Hand-held nailing tools; Nail feeding devices
    • B25C1/06—Hand-held nailing tools; Nail feeding devices operated by electric power

Definitions

  • This invention relates to electrically driven impact tools and a method of operating the same, particularly to such tools which may be adapted to drive nails and the like
  • Prior electrically driven impact tools have utilized low amounts of energy and have been used in applications, such as for driving small nails and staples, loosening and tightening nuts or seating deformable fasteners, such as small brass and copper rivets.
  • Substantially all high en ⁇ ergy impact tools particularly those which have been suf- ficiently light to be hand used, have operated on compresse air.
  • Such air tools have required, for supply of air through hoses to the tools, a high volume air compress ⁇ or which is stationary or requires a cumbersome trailer or similar support, for transportation and location at the sit at which the tool or tools are to be used.
  • the impact tool of this invention overcomes the prob ⁇ lem of unbalance wear and accuracy in guiding a ram, as well as more effective acceleration of the ram, by pivot- ing the rotating bodies or flywheels inwardly toward the stationary ram from both sides, and for equal distances.
  • the frictional engagement of the rotating bodies with the ram takes place essentially simultaneously from both sides, producing substantially the same wear on both sides of the ram.
  • the rotating bodies or flywheels are also mounted in an overhang or cantilver arrangement with respect to the driving motors and thus permit greater freedom of ac ⁇ cess to the ram and positioning of guide rods or the like for the ram.
  • the initially engaged surfaces of the ram are each slightly tapered, as on the order of 0.0254 cm.-.
  • the taper of the initially engaged surfaces of the ram should, of course, be less than that at ' which the flywheels tend to "grab" the ram, rather than a smooth frictional en ⁇ gagement.
  • the sides of the ram are beveled at the opposite end, but at a considerably greater angle than the taper of the initially engaged end, to produce disengagement of the flywheels from the ram and also to facilitate the return of the ram between the spinning flywheels.
  • the number of revolutions will diminish as the ram is driven on its impact stroke, but the flywheels will be ⁇ gin to accelerate as soon as the ram has been disengaged.
  • flywheels are returned quickly to their ini ⁇ tial position after disengagement from the ram, as by a spring acting against both pivoted motors or against each.
  • Coil springs are suitable for this purpose, but unsuitable for returning the ram, since the distance of movement of the motors and flywheels is considerably less than that of the ram and the rate of movement of the motors and fly ⁇ wheels is less than that of the ram.
  • the angles of the initial flywheel centers to the centerline of the pivots and the taper of the initial engagement surface of the ram are correlated to produce a regenerative action, such as the ram taper being on the order of that expressed above, and the initial angle of the flywheel centers being within the range of a minimum of 9° to a maximum of 20°, with a range of 10° to 14° being preferred.
  • a balanced pull on the two pivoted motors is produced by a pair of electrical solenoids, which are more readily controlled and vastly quicker in action than a nose piece pressed against a work piece.
  • a power sup ply booster may be used to produce a high amperage pulse to increase considerably the speed of movement and initial pull of the solenoids.
  • Each of the solenoids acts through a pair of pivotally connected links, to maximize the force which presses the flywheels against opposite sides of the ram.
  • the links in a straight line position, have a leverage ratio of almost infinity, which, of course, de ⁇ creases as the links are bent toward each other.
  • the pull of the solenoids is essentially the reverse, being least when the solenoids are just starting movement and be ⁇ coming greater as the solenoids move.
  • the effective leverage of the links counteracts the variation in the pull of the solenoids.
  • the movable ends of the two sets of links are connected together for equalization of movement and simultaneous transmission of movement through cables connected to the pivoted motors, movement of which produces a corresponding movement of the flywheels.
  • cable con nections between the solenoids and the center pivot of the corresponding toggle links has been found advantageous, with aircraft type cable being suitable.
  • a single solenoid may act through a single set of links, or through a cable arrangement in- eluding a first cable fixed at one end and attached at the opposite or movable end to the cables connected to the pi ⁇ voted motors.
  • a second cable, pulled by a solenoid, is connected to an intermediate point on the first cable and exerts a pull transverse to the first cable.
  • a third cabl also transverse to the first cable, is anchored at one sid and is connected to the movable end of the first cable.
  • This tension rod is located adjacent the flywheels and overcomes the necessity for the housing to equalize these forces, thereby reducing considerably the necessary thickness and weight of the housing or per ⁇ mitting the housing to be made of molded plastic, rather than formed aluminum.
  • the tension rod pro ⁇ vides a stable means for maintaining the spaced position between the pivot shafts.
  • a pair of spaced tension rods, the other at the opposite ends of the motors, may also be utilized.
  • the characteristics of the flywheel inertia, the ram inertia, the probable rate of ram wear and the mo ⁇ tor recovery rate, such as from 7,000 to 14,000 r.p.m. are matched to provide adequate acceleration of the ram with a reasonable amount of wear.
  • a brake lining on the sides of the ram provides a friction surface for the flywheels.
  • the brake lining may be bonded by an epoxy resin to the sides of the ram for ade quate retention of the friction surface to the ram.
  • the ram may be provided with wings, which engage guide rods and have a greater surface area for abutment against a bum- per.
  • the motor is equipped with a fan for blowing air past the fly ⁇ wheels and ram, while this air is filtered to prevent for ⁇ eign material from collecting on the friction surface.
  • the friction surface such as brake lining
  • the friction surface may be bonded, as by an epoxy resin, to the periphery of each flywheel, in order to provide a greater cooling effect on the friction material, due to rotation of the flywheel.
  • a resin such as polyurethane or phenolic
  • asbestos fibers as fric- tion material
  • a safety device actuated by a slide on the nose piece may control a microswitc which must be closed by move- ment of the slide engaging the work piece, before the fly ⁇ wheel pivoting solenoids can be energized.
  • An alternative or additional safety device includes a movable stop block which is normally in _- a: -.position preventing downward movement of the ram but moved away from this position through a rod actuated through movement of the nose piece slide through engagement with the work piece.
  • the controller for the motors is selected to cause as great acceleration as possible after the motors and fly ⁇ wheels have slowed down after moving the ram on an impact stroke, but to limit the top speed of the motors to a spee consonant with the kinetic energy to be transmitted to the ram for driving the size and length of nail into the type o wood or other material of the work piece, such as through steel into concrete.
  • the motors are preferably selected so that the maximum obtainable speed exceeds any speed to whic it might be desirable to limit the motors for any expected application.
  • Such a controller may be selected so that it can be adjusted to limit the maximum speed of the motor.to a greater or lesser speed, when different nails or differ ⁇ ent work piece materials are encountered.
  • substitute flywheels such as adapted to produce different weights, may be used for such different applications.
  • access to, removal of and substi ⁇ tution of different flywheels and/or rams should be expedi ⁇ ted by the mounting of these parts and the construction of the enclosing housing.
  • Fig. 1 is a perspective view of an impact tool . of this invention embodied in a nail driving machine.
  • Fig. 2 is a bottom perspective view of a pair of op ⁇ posed, pivoted, oppositely rotating bodies, each compris- ing a flywheel and motors for rotating the flywheels.
  • Fig. 3 is a perspective view of a housing, with cer ⁇ tain parts installed on the housing, the housing being par ⁇ ticularly adapted to receive the rotating flywheels of Fig. 2.
  • Fig. 4 is an end view of the machine of Fig. 1.
  • Fig. 5 is a side view of the machine of Fig. 1, but taken from the opposite side than Fig. 1 and with a portion of a nail feed magazine omitted.
  • Fig. 6 is a partial longitudinal section taken along line 6-6 of Fig. 4, with certain exterior parts omitted for clarity of illustration.
  • Fig. 7 is a cross section taken through the motors, along line 7-7 of Fig. 5, showing particularly the device for pivoting the motors and flywheels.
  • Fig. 8 is a fragmentary horizontal section taken along line 8-8 of Fig. 7, and showing particularly the cable guides omitted from Fig. 7 for clarity of illustration.
  • Fig. 9 is a longitudinal section taken along line 9-9 of one of the motor and flywheel assemblies of Fig. 2, but on an enlarged scale.
  • Fig. 10 is a cross section taken along line 10-10 of Fig. 9.
  • Fig. 11 is a side elevation, partly in central longi ⁇ tudinal section, of a ram which is engaged and accelerated by the flywheels.
  • Fig. 12 is an . end elevation of the ram of Fig. -11, with the flywheels shown fragmentarily in the position of initial engagement with the ram.
  • Fig. 13 is an enlarged view corresponding to a portion of the lower end of the ram, as shown in Fig. 12, to illus ⁇ trate a slight taper.
  • Fig. 14 is a similar enlargement of a portion of the upper end of the ram, illustrating the bevel which produces disengagement of the flywheels with the ram, as the ram reaches the normal end of its travel.
  • Fig. 15 is a bottom view of the ram of Fig. 11.
  • Fig. 16 is a cross section, on a slightly larger scale, of a nose piece slide, shown also in Figs. 1 and 3.
  • Fig. 17 is a condensed side elevation of a driver blad which is attached to the ram for driving nails.
  • Fig. 18 is a condensed rear elevation of the driver blade of Fig. 17.
  • Fig. 19 is a cross section, on an enlarged scale, taken along line 19-19 of Fig. 18.
  • Fig. 20 is a longitudinal section of a flywheel alter ⁇ native to those of Figs. 2 and 9.
  • Fig. 21 is a fragmentary view, on an enlarged scale, showing a safety mechanism, alternative to or in addition to that shown in Fig. 5.
  • Fig. 22 is a fragmentary, diagrammatic view illustra- ting a cable arrangement, for use as an alternative force multiplying means of a device for pivoting the motors and flywheels.
  • Fig. 23 is a fragmentary end elevation of a further alternative safety mechanism.
  • Fig. 24 is a fragmentary side elevation of the safety mechanism of Fig. 23.
  • Fig. 25 is an . enlarged view corresponding to Fig. 13 but showing a modified manner of providing a slight taper.
  • An impact tool of this invention illustrated as em ⁇ bodied in an electric nail driving tool, includes general ⁇ ly a housing H of Fig. 1 having a nose piece N through which the nails are driven into the work piece by a driver blade B of Fig. 6 attached to a ram R which is engaged by rotating bodies or flywheels F and F' of Fig. 2, pivoted into simultaneous engagement with the opposite sides of the ram for propelling the ram and driver blade longitud ⁇ inally toward the nail.
  • Flywheels F and F' are rotated in opposite directions by electrical motors M and M' , the ar ⁇ matures of which may also supply a portion, as on the order of 10%, of the kinetic energy or inertia available for transmission to the ram by the flywheels.
  • Solenoids S and S' of Fig. 3 are utilized, with linkage mechanism and cable connections described below, to pivot the flywheels toward the ram.
  • a nail feeding magazine A of conventional cons ⁇ truction is attached to the nose piece N for moving the nails, in turn, in position to be driven into the work piece, by blade B.
  • the housing H is provided with a handle 10 by which the tool may be held for placement in a desired posi ⁇ tion against the work piece, with electricity being supplied through an electrical cord 11 and an on-off switch 12 of Fig. 5 which, when on, causes current to be supplied to motors M and M* .
  • the solenoids S and S' are actuated only when a trigger 13, provided on the handle, is closed, sub ⁇ ject to a safety device described below which precludes the accidental discharge of a number of nails into the air if the trigger is accidentally pressed.
  • the respective motors M and M" rotate the corresponding flywheels F and F' , which are brought up to a predetermined speed, corre ⁇ lated with the weight of the ram and the necessary inertia of the flywheels for producing an adequate number of foot pounds to drive each nail in turn.
  • Each motor M or M' is provided with a shaft, to the overhanging end of which the corresponding flywheel F or F* is attached by a cap screw 14, as in Fig.
  • the motors and flywheels are pivoted concurrently and simultan ⁇ eously toward each other for simultaneous engagement of the flywheels with the opposite sides of the ram R, adjacent the lower end of the ram R, as viewed in Fig. 6 and assum ⁇ ing that the tool is held in an upright position above the work piece, it being understood that the tool may be held in a horizontal position, as for driving a nail into an up ⁇ right work piece, or even in an upward position, as for driving a nail into an overhead work piece.
  • the entrance edges of the sides of the ram R are each provided with a taper 17 at an angle selected such that the flywheels will engage the ram quickly, but will smoothly impart acceleration thereto.
  • a layer 18 of fric ⁇ tion material, brake lining being highly suitable, will follow the angle of tapers 17.
  • Such entrance taper may also be provided in layer 18 of the friction material, as at 17" in Fig. 25, as in both layers on opposite sides of the ram.
  • An initial engagement of flywheels with parallel sides of a ram tends to produce a grabbing effect and con ⁇ siderable wear at the point of initial engagement.
  • the initial taper of the sides such as a taper of 0.0254 to 0.0635 cm.
  • the gripping force of the flywheels produced by the entrance taper on opposite sides of the ram is most pro- nounced when both flywheels are moved simultaneously into engagement with the ram, since the inertia of each flywheel resists the tendency for the ' initial taper of the sides to push the flywheels apart, as the ram starts its movement produced by the flywheels.
  • This inertia produced force would not be present if a flywheel, which is fixed, were used on one side of the ram and a spring pressed roller on the opposite side, since a fixed center flywheel is unable to exert any inertia effect on the ram, while the opposed roller would not rotate until started by movement of the ram and therefore has a negligible inertia.
  • the opposite end of the ram R is provided with a disengagement bevel 19, on each side, which has a considerably greater inclination than the slightly tapering surfaces 17, and permits a quick disengagment of the ram from the rotating flywheels, so that the ram may quickly stop and be returned, normally up ⁇ wardly between the flywheels.
  • An additional feature of this invention is the tension rod T of Figs. 2 and 10, connected between the pivot shafts 15 and 15* for the motors, as by connectors 20.
  • the ends of rod T may be oppositely threaded for adjustment into hexa ⁇ gon blocks 21 of connectors 20.
  • Tension rod T equalizes the large normal forces required to drive the ram, thus re- lieving the housing of the necessity for equalizing such forces.
  • the tension rod also equalizes the precession for ⁇ ces and the rotational and acceleration reaction forces pro ⁇ cuted by the counter-rotating motor armatures and flywheels.
  • An additional tension rod T' as in Fig. 2, may connect shafts 15 and 15' at the opposite end of the motor.
  • a further feature of this invention includes the simul ⁇ taneous pivoting of the motors M and M* and flywheels F and F* , along with them, through the action of solenoids S and S' mounted in the housing H, as in Figs. 3-5, through a linkage and cable arrangement, including cables 22 connec ⁇ ted to motor brackets 23, as in Fig. 2, and in turn connec ⁇ ted to a block 24.
  • Block 24, as in Fig. 7, is adjustably connected to a yoke 25 whose spaced arms 26 are each pivot ⁇ ally connected to the adjacent end of an inner link 27 or 27'.
  • each inner link 27 or 27' is pivotally con ⁇ nected to an outer link 28 or 28', respectively, the oppos ⁇ ite end of which is pivotally connected to a support block 29.
  • a solenoid cable 30, as in Fig. 8, connects the res ⁇ pective solenoid plunger 31 with a socket 32 at the pivotal connection of the links 27, 28 and 27', 28'.
  • Each solenoid cable 30 passes over a pivoted, arcuate pulley 33 which transfers the pull of the respective solenoid plunger throug 90°, to pull the respective pivot centers between the links away from each other, as in the direction of the arrows of Fig. 8.
  • this engagement of the flywheels with opposite sides of the ram R will start the ram moving in an impact direction, with the acceleration increasing as the flywheels move along the slightly tapered surfaces and continue to engage the parallel sides of the ram, until the disengagement be- vels 19, at the opposite end of the ram, are encountered.
  • Such impact of the ram will also move the driver blade B into engagement with the head of the nail and drive the nail into the work piece.
  • a safety device for preventing actuation of the sole- noids S and S' and a resulting impact movement of the ram, until the tool is in position against the work piece may include an angular rod 35 of Fig. 5 attached to a slide 36 mounted for movement along the nose piece N and provided with a partial ring 37, shown also in Fig. 16, adapted to be pressed against the work piece, when the operator desires to produce another impact, as for driving another nail.
  • An up ⁇ per portion of rod 35 is provided with a plate 38 adapted to engage a button 39 of a mi ⁇ roswitch 40 when the rod 35 is moved upwardly, as viewed in Fig. 5, due to engagement of ring 37 with the work piece.
  • FIG. 3 An enlargement 41 of the upper end of rod 35 extends into a socket 42 for engaging a coil spring 43 which returns the rod 35 and slide 36 to their initial position, when the ring 37 is no longer presse against the work piece.
  • Microswitch 40 is mounted on the housing adjacent the socket 42, while pressure plate 38 on button 39 will close the microswitch and complete the elec ⁇ trical circuit to solenoids S and S' , when the operator presses the trigger 12.
  • slide 36 is provided with slots 44 through which bolts 45 extend, for guiding the slide in its movement, such as upwardly and downwardly, as viewed in Figs. 4 and 5.
  • the ram R is guided by a pair of spaced, parallel rods 47, as in y ⁇ WE Fig. 6, extending through a pair of wings 48 of the ram which extends both above and below the wings in a generally rectangular configuration in cross section.
  • the upper end of the ram in the initial position shown, extends through a corresponding slot in a fixed attachment plate 49 for a flexible cord C and into engagement with a resilient upper bumper 50.
  • the flexible cord C is formed of a series of elastomer cords, such as rubber, encased in a nylon sheath.
  • the cord C stretches equally along its length when an elongation force is applied to it, which property is particularly desirable for the present use, since the rapidity with which the ram is impelled, such as moving over its length of travel in a few milliseconds, tends to deform coil springs, the use of which has been at- tempted.
  • the latter tend to elongate in increments as the stress is applied to the spring, which is reasonably satis ⁇ factory for an elongation stress applied much more slowly, but tends to overstress and deform the spring when the elon ⁇ gation stress is applied as rapidly as it must be for the movement of the ram to be effective in developing the de ⁇ sired amount of power for the impact stroke, such as for driving nails.
  • Each end of the cord C extends through a hole therefor in the attachment plate 49, as shown, and is attached to the plate, as by a suitable fastener or being tied in a knot 51 above the plate.
  • Cord C extends through holes 52 in the wings, indicated also in Fig. 11, along slots 53 below the wings and is looped through the lower end of the ram.
  • the ram R moves downwardly, the impact of the driver blade B against the nail will drive the nail into the work piece, and the head of the nail in the work piece will ordinarily stop the driver blade and ram. How ⁇ ever, if the ram has excess kinetic energy, the underside of the wings 48 will engage lower bumpers 34 which surround the guide rods 47, correspond in area to the underside of the wings and will absorb the remaining kinetic energy.
  • the lower bumpers are formed of resilient but tough material, such as rubber, or a hard plastic, such as polyurethane hav ⁇ ing a hardness of 80-90 Shore.
  • Lower bumpers 54 are ⁇ maintained in the desired parallel relation on the guide rods by a sleeve 55 which surrounds each of the bumpers 54 and is provided with a central aperture 56 into which the lower portion of the ram moves, as the ram is driven downwardly. Additional details of the ram construction will be given below.
  • the housing H may include a forward section having a lateral wing 58 closing each side and in which the motors M and M' and flywheels F and F' are installed.
  • a hollow, rectangu ⁇ lar extension 59 on opposite sides of which the solenoids S and S' are mounted, as in Fig. 3, while below the wings is a rectangular extension 60 having a bottom 61 of Fig. 6 having a central aperture corresponding to the aperture 56 of sleeve 55, as shown, and holes 62 beneath bumpers 54 into which guide rods 47 extend, for abutment by attachment flange 63 of nose piece N.
  • the opposite ends of guide rods 47 extend into corresponding holes 64 in upper bumper 50.
  • the guide rods 47 for the ram R and attached driver blade. B extend centrally of this housing section and be ⁇ tween extensions 59 and 60.
  • Cover plates 65 and 65' having apertures, as shown, for outflow of cooling air moved through and around the motors and rotating flywheels, close the front of the two wings 58 of the front housing section, while a front box 66 covers the central portion thereof.
  • Covers 65 and 65' and box 66 are conveniently integral.
  • a top cover 67 closes the top of the upper extension 59 of the winged housing section, and a flange 68 upstands from the rear edge thereof, while cover boxes 69 for the sole- noids are positioned at opposite sides thereof.
  • Upper bumper 50 is attached to the underside of cover 67, which may be removed, along with front box 66 and plates 65, 65' attached thereto, to permit removal of plate 49, which nor ⁇ mally rests on a shoulder formed in the wall of extension 59, and ram R along with guide rods 47, as for inspection or replacement of the ram. Also, removal of front box 66 and plates 65, 65' permits access to flywheels F and F', as for changing through removal of cap screws 14.
  • a hollow motor hous ⁇ ing section 70 corresponds in contour to the wings 58 and is attached to the rear thereof, with an end cap 71 clos ⁇ ing the cavity.
  • a motor control assembly box 72 extends rearwardly from the central portion of end cap 71.
  • Mounting ribs 73 are formed on the inside of each wing 58 and receive the end of the corres ⁇ ponding pivot shaft 15 and 15' adjacent the flywheels F and F'.
  • An attachment lug 74 at the opposite end of the corresponding pivot shaf 15 and 15* is attached to the in ⁇ side of housing section 70 at an appropriate position.
  • a housing 75 of each motor is pivotally connected to the res ⁇ pective pivot shaft by brackets 76, shown also in Fig. 10, and each provided with a bearing 77 encircling the corres- ponding pivot shaft.
  • end cap 71 with lugs 74 attached to housing section 70, will be sub ⁇ ject to a portion of the normal and precession forces to be equalized by tension rod T.
  • tension rod T* is connected between the pivot shafts 15 and 15' rear- wardly of the motors M and M* , the forces imposed on end cap 71 will become negligible and the two tension rods will tend to receive somewhat similar amounts of forces for equalization.
  • the use of tension rod T, or also rod T f permits the housing to be lighter or to be made of less expensive material.
  • support block 29 is attached to and ex ⁇ tends upwardly from the rear wall of extension 59 of the front housing section.
  • Block 29 is provided with slots 79, as in Fig. 7, through which the pivot pins for the.up- per ends of links 28 and 28' extend, while a center rib
  • a cover box 81 encloses support 29, rib 80. and the linkage arrangement.
  • the arcuate pulleys 33 may be pivoted on brackets 81 which may also be mounted on the rear side of extension 59 of the front housing section.
  • the motors M and M' may be retracted by coil springs 82 connected between ears formed as parts of brac ⁇ kets 23 and ears 83 provided on the inside .of ..adjacent wing 57 .
  • the nose piece N is generally rectangu ⁇ lar on the outside and provided with a cylindrical, central passage 85 of a diameter to accommodate the heads of nails placed in and driven therethrough, with a flat sided abut ⁇ ment 86 at the front for attachment of slide 36 thereto for movement between the extended position of Fig. 3 and the retracted position of Fig. 1.
  • nose piece N is provided with a slot 87 through which the shank of each nail may move and a lateral enlargement 88 of the slot to accommodate the head of the nail.
  • the nails are con ⁇ veniently secured together in side by side relation between spaced pairs of strips of tape, as of paper, with plastic or the like between the tapes and molded against the nails.
  • Such a strip of nails slants downwardly to one side, corres ⁇ ponding to the angularity of the feed magazine A to .
  • the nose piece N through which the nails are fed in succession into the nose piece in a conventional manner.
  • the front end of feed magazine A is attached to the nose piece N by brackets 89 and 89', secure to opposite sides of the nose piece by bolts 90, as shown.
  • each motor includes an armature 92 moun ⁇ ted on a shaft 93 which carries a commutator 94 engaged by brushes 95 mounted in conventional brush holders, as shown.
  • the brush holders are mounted in an end cap 96 for the mo ⁇ tor which may carry a " bearing 97 for the commutator end of the motor and have holes 98 therein, for flow of air into the motor.
  • the field windings 99 of the motor are posi ⁇ tioned by pins 100 extending between annular support rings 101.
  • a sleeve 105 attached to the front of the motor housing 75 is provided with a slot 106 which .
  • a stepped enlarge ⁇ ment 107 of the shaft carries a fan 108, which pulls air through the motor and blows it past the flywheels.
  • the en- largement 107 continues to a bearing 109 which is larger than bearing 97, because of the additional weight and over ⁇ hanging position of the flywheel, a hub 110 of which is mounted on the end of shaft enlargement 107 and retained
  • ram 119 may be provided in the rear wall of housing end cap 71, as in Fig. 5.
  • the air is discharged through the holes in front plates 65 and 65'.
  • the ram is provided with additional elements, as in Figs. 11, 12 and 15, such as holes 120 in the wings 48 for the guide rods 47 and bevels 121 on the outer edges of the wings.
  • a groove 122 is formed at each side of the upper portion of the ram above the respective wings, for readier access to the ends of cord C and to re ⁇ turn weight, while the holes in plate 49 of Fig. 6 for cord C are placed in ears of the plate which extend into the respective groove 122.
  • a transverse bore 123 connects the two grooves. Also, a series of bores 124, for similar pur ⁇ poses, extend laterally through the ram, within the longi ⁇ tudinal extend of the wings and intersect the holes 52 and
  • a socket 126 extends upwardly from the lower end of the ram, and connects holes 127 through which the cord C extends to cross socket 126. From the up ⁇ per edge of the latter, a central socket 128 extends upward ⁇ ly, to receive the upper end of the driver blade B, as through set screws tightened in tapped holes 129 and 130, inclined upwardly toward the driver blade from opposite sides.
  • a steel plate 131 having a central hole corresponding in size to socket 128 is posi ⁇ tioned against the upper surface of socket 126 to trans ⁇ mit forces received from the driver blade over a large area and thereby avoid crushing the surface of aluminum or the like.
  • Cord C may pass around either the front or the back of the driver blade.
  • the driver blade B as in Figs. 17-19, includes an elongated shank 135 having on one side a groove 136 and a bevel 137 at the impact end of the shank.
  • the blade is preferably positioned so that the groove 136 and bevel 137 will face the incoming nails, so that, if the next nail tends to enter the nose piece N before the blade has been returned following an impact stroke, the head of the nail will tend to be cleared by the groove and bevel.
  • the shank is provided with an enlargement 138 at the opposite end, providing a shoulder 139 around a stem 140.
  • the stem may be made separate from the shank, as by forging, and an enlarged lower end 141 of the stem placed in a corresponding socket formed in the shank enlargement 138.
  • the stem and shank may be attached together by forging or by brazing, or in any other suitable manner.
  • the stem 140 is also pro ⁇ vided with oppositely disposed, staggered notches 141 and 142 which correspond in position to the tapped holes 129 and 130 of the ram R, as in Fig. 11.
  • the notches 141 and 142 are engaged by the set screws threaded into the tapped holes 129 and 130, respectively.
  • the stem of the driver blade extends through the hole in plate 131 and into the socket 128 of the ram, until the shoulder 139 abuts against the plate 131.
  • the cross sectional area of the shoulder 139 is such that, with a stem shank- made of alloy steel, it may possibly crush the softer material, such as aluminum or the like, of the ram.
  • the plate 131 which is also formed of steel, is adapted to receive the possibly crushing force of the shoulder 139 without deformation, and to distribute this force over the entire area of the plate 131, which corres ⁇ ponds to the area of the enlarged socket 126, as in Fig. 15, around the socket hole 128.
  • the friction layer such as brake lining 18, bonded to the sides of the ram R, as in Fig. 12, may alternatively be bonded to the periphery of each of the flywheels F and F 1 .
  • the periphery of the rim 115 of each flywheel with a fric- tion layer 145, molded onto the flywheel rim.
  • the molded friction layer 145 may be formed of a mixture of suitable resin, such as polyurethane or pheno ⁇ lic, and asbestos fibers, as a friction material. Fibers, powder or the like of a material having a relatively high heat conductivity, such as copper, may be mixed with the resin to enhance the dissipation of heat produced by the frictional engagement of the flywheels with the ram.
  • the periphery of the flywheel rim 115 is preferably polished and as smooth as possible, since it has been found that the coefficient of friction for cold rolled steel, .of which the flywheel rims may be made, will be increased when the friction sur ⁇ face, such as brake lining, is engaged with a highly po ⁇ lished surface moving at the peripheral speed of the fly- wheels. While such a coefficient of friction is theoretic ⁇ ally on the order of 0.3, in practice, it may be reduced to about 0.15. However, when the friction layer is molded on or bonded to the periphery of each flywheel, the sides of the ram to be engaged by such friction surfaces, for simi- lar reasons, are preferably highly polished and smooth.
  • An alternative or additional safety device may be operated by a rod 35' which may extend -- upwardly from slide 36 and ring 37 in a manner similar to rod 35 of Fig. 5, or may be provided as an extension of the rod 35 which extends upwardly through the enlargement 41 and coil spring 43 of Fig. 5.
  • the upper end of the rod 35' is adapted to engage a base 147 of a block 148 pivotal about a fixed pin 149.
  • An offset nose 150 is nor ⁇ mally positioned beneath a wing 48 of the ram R, so that if the ram is accidentally moved downwardly without the rod 35 and its extension 35' being raised by engagement of slide ring 37 with the work piece, the nose 150 will block downward movement of the ram.
  • the nose 150 will clear the side of the wing 48 and the ram will be permitted to move downwardly for .the desired impact.
  • the block 148 is normally maintained in a position with the nose 150 beneath the ram wing by a coil spring 151, one end .of which abuts a shoulder 152 formed on the block and the other end of which abuts a fixed stop 153.
  • the spring 151 will move the safety block from the dotted posi ⁇ tion back to the full position of Fig. 21.
  • FIG. 22 An alternative force multiplying means, comprising essentially a cable arrangement, is illustrated in Fig. 22.
  • This force multiplying means includes a first cable
  • a se ⁇ cond or solenoid cable ' 30' extends from a plunger 31 of a solenoid and is attached to a connector 159, which conveni ⁇ ently encircles the cable 155 at an intermediate point of the cable.
  • Connector 159 although clamping the cable, has a longitudinally rounded inside surface opposite cable 30', as shown, to avoid injury to the cable 155 when moved by pulling.
  • the solenoid cable 30' may extend directly from the solenoid plunger 31 or may extend around an arcuate pulley, as in the manner illustrated in Fig. 8.
  • a third cable 160 is attached at its movable end to connector 158 and its fixed end to an anchor 161, as by a plug 162, and causes the connector 158, i.e. the movable end of cable 155, to follow an essentially straight line motion, or the equivalent thereof, when solenoid cable 30' is pulled. Such pull moves the first cable 155 to the dotted position shown, thereby to move the connector 158 upwardly, as viewe in Fig.
  • the weight of the flywheels has been reduced from 1.1 kg. each for the nail driving tool, constructed in accordance with- Serial No. 580,246, to 0.158 kg. for each flywheel for a nail driving tool constructed in accordance with the present invention.
  • a corresponding reduction has been secured in the weight of the complete nail driving tool itself, i.e. from 9.5 kg. for the previous tool, to between 5.2 and 5.4 kg. for a tool of this invention, for driving 16-penny nails.
  • lighter motors the weight of the same tool could be reducible to between 3.-6 and 4.5 kg.
  • the angles 170 are between the plane of shafts 15 and 15' and a centerline extending from the cen ⁇ ter of a shaft 15 or 15' to the center of the corresponding motor M or M' .
  • the centerlines 171 approximate the posi ⁇ tion of the latter, when the motors M and M' have been pi ⁇ voted, so that the flywheels will engage the opposite sides of the ram R.
  • the arrows 172 indicate the c normal force exerted by the respective flywheels F and F' against the tapered side portions of the ram.
  • the kg. meters necessary to accelerate the ram and drive the nail must be imparted.to the ram by the flywheels. Calculations have indicated that it requires approximately 0.17 kg. meters per gram, to accelerate the ram, so that 24.19 kg. meters are necessary to accelerate the 141.7 gram ram used.
  • the flywheels should transmit, through the ram, additional kg. meters, such as 8.295 to 16.59 kg. meters, depending on the wood, when driving 16- penny nails. For this purpose, the kg.
  • each cable 22 of Fig. 7 is estimated for cal ⁇ culations to be initially on the order of 186 to 205 kg. due to a solenoid . pull on each cable 30 on the order of 37 to 56 kgs.
  • the initial normal force against the ram indicated by the arrows 172 of Fig. 12, should be approximately 373 kgs.
  • the normal force increases through the reac ⁇ tion of flywheel inertia and as the ram drive becomes re ⁇ generative, the toggle action further increases the normal force to approximately 933 to 1306 kgs. Then, depending upon the coefficient of friction of the friction material, the necessary driving force is developed to set the nail or the like. While the theoretical coefficient of friction for highly polished, cold rolled steel against brake lining or phenolic resin with asbestos fibers is approximately 0.3, in practice it may be found to be between 0.15 and 0.3.
  • the total movement of the ram ui will correspond to a distance slightly greater than the length of the nail, i.e. slightly more than 8.25 cm. for a 16-penny nail, plus the 1.58 cm. clearance. It can be calculated that the time which the ram requires to move this distance, in order to develop the necessary kg. meters of energy for driving the nail, is on the order of 3 to 4 milliseconds.
  • the pulse to the 24 volt solenoids such as from 50 to 80 amperes at 110 volts, may be con ⁇ trolled to be on the order of 8.33 milliseconds, due to the time required to move the flywheels into position against the ram and a slight initial slippage.
  • the time for return of the motors and flywheels to the initial posi ⁇ tion, return of the ram to its initial position and the acceleration of the flywheels to the speed desired prior * to the next impact stroke may be on the order of 128 mil ⁇ liseconds, which is considerably less time than it would require the user of the tool to reposition the tool for driving another nail.
  • the speed of the fly ⁇ wheels may be less, such as a speed on the order of 10,000 to 14,000 r.p.m.
  • the speed of the fly ⁇ wheels may be less, such as a speed on the order of 10,000 to 14,000 r.p.m.
  • excess slippage was apparently occurring above 14,000 r.p.m. for the flywheels, since nails driven at 14,000 r.p.m. and down to 10,000 r.p.m. would not be completely driven at speeds above 14,000 r.p.m.
  • higher ram engaging forces were
  • the speed of the flywheels will, of course, decrease, such as a reduction to approximately 7,000 r.p.m. at the point of disengagement of the flywheels from the ram, i.e. when the flywheels rea.ch the bevels 19 of Figs. 12 and 14.
  • the motors should be able to increase the speed of the flywheels from on the order of 7,000 r.p.m. to 10,000 r.p.m. or 14,000 r.p.m., for example, prior- to driving the next nail..
  • the stress on the tension rod T may be found to be on the order of 559.8 to 1119.6 kg. meters, with an additional 10% of that amount on the end cap 71 of the housing.
  • the stresses will tend to become more nearly equalized on both tension rods.
  • the bumpers 54 of Fig. 6 may be con ⁇ structed to absorb on the order of 93.3 kg. meters, in the event the ram is driven on an impact stroke but does not drive a nail or otherwise perform its impact function.
  • a link 180 mounted on an intermediate pivot 181 below the motors M and M' and extending longitudinally below the space between the motor housings.
  • the link has an upstanding a ⁇ HQ__ 182 having a stop block 183 at its upper end normally dis ⁇ posed between the motor housings to prevent the motors and flywheels being moved toward each other and thereby deter the linear movement of the ram.
  • a tension spring 184 pulls on the link, adjacent its front end, to maintain the link and its stop block in the normal position between the motor housings.
  • a rod 185 is connected to the front end of link 180, while abutments 186 and 186* on the motor housings engage stop block 183 if the motors tend to pivot toward each other.
  • Rod 185 is connected to slide 36 by a rod sim ⁇ ilar, to rod 35 of Fig. 5 and is moved upwardly by engage ⁇ ment with the work piece by ring 37 on slide 36 to move the front end of the link upwardly to pivot the link and move the block downwardly from between the motor housings, thereby rendering the stop block inoperative and permitting the motor housings and flywheels to be pivoted toward each other and cause the flywheels to drive the rams, when the trigger is pressed to energize the solenoids.
  • flywheels of different weights for different wood properties or other variations in kinetic energy required.
  • Another is to uti ⁇ lize a motor control in which the r.p.m. of the motors may be varied, such as between the 10,000 and 14,000 r.p.m. referred to above for different woods or nails, or other variations in impact requirements.
  • Still another is to time the pulse supplied to the solenoids, so that the fly ⁇ wheels will tend to disengage from the ram before the end of the ram is reached.

Abstract

L'un ou les deux corps d'une paire de corps en rotation en sens opposés, tels que des volants entraînés par un moteur (F, F') sont montés avec un mouvement de pivotement contre le côté d'un bélier (R). Une ou plusieurs tiges de tension (T) relient des arbres de pivot (15, 15') pour égaliser les forces de précession et autres forces similaires des corps rotatifs, plutôt que l'enceinte (H). Des solénoïdes à impulsion (F, F') produisent une force augmentée par un dispositif de multiplication de force telle que des organes de liaison pivotants (27, 28, 27', 28') ou un agencement à câble (155, 160) qui possède des avantages mécaniques plus grands lorsque la traction du solénoïde est plus faible au départ, mais diminue au fur et à mesure que la traction du solénoïde augmente. Le bélier (R) possède une conicité d'entrée (17) d'un côté ou des deux côtés. Le bélier (R) est revêtu d'un ensemble ou faisceau (C) de corps élastomères gainés de nylon qui entourent le bélier des deux côtés et sont étirés proportionnellement sur leurs longueurs. Des tiges de guidage amovible (47) pénètrent dans des trous (120) aménagés dans les ailes latérales (48) du bélier (R). Un dispositif de sécurité est actionné par une tige (35), déplacé par engagement avec une pièce à usiner, pour fermer un commutateur de sécurité dans le circuit du solénoïde. Dans un autre mode de réalisation, un bloc (150) engage une aile (48) du bélier pour empêcher la course de choc, mais est retiré par une tige similaire (35'). Dans un autre mode de réalisation, un bloc d'arrêt (183) est placé entre les enceintes du moteur pour empêcher un mouvement contre le bélier (R) jusqu'à ce que la pièce à usiner soit engagée et une tige similaire (185) déplace une ligne pivotante (180) sollicitée par un ressort pour retirer le bloc d'arrêt.One or both bodies of a pair of bodies rotating in opposite directions, such as flywheels driven by a motor (F, F ') are mounted with a pivoting movement against the side of a ram (R) . One or more tension rods (T) connect pivot shafts (15, 15 ') to equalize the precession and other similar forces of the rotating bodies, rather than the enclosure (H). Pulse solenoids (F, F ') produce an increased force by a force multiplier such as pivoting connecting members (27, 28, 27', 28 ') or a cable arrangement (155, 160) which has greater mechanical advantages when the traction of the solenoid is weaker at the start, but decreases as the traction of the solenoid increases. The ram (R) has an inlet taper (17) on one side or on both sides. The ram (R) is coated with a set or bundle (C) of nylon sheathed elastomeric bodies which surround the ram on both sides and are stretched proportionally over their lengths. Removable guide rods (47) penetrate into holes (120) provided in the lateral wings (48) of the ram (R). A safety device is actuated by a rod (35), moved by engagement with a workpiece, to close a safety switch in the solenoid circuit. In another embodiment, a block (150) engages a wing (48) of the ram to prevent shock stroke, but is removed by a similar rod (35 '). In another embodiment, a stop block (183) is placed between the engine enclosures to prevent movement against the ram (R) until the workpiece is engaged and a similar rod (185) moves a pivoting line (180) urged by a spring to remove the stop block.

Description

Description
Electrically Driven Impact Tool and Method of Operating The Same
Technical Field This invention relates to electrically driven impact tools and a method of operating the same, particularly to such tools which may be adapted to drive nails and the like
Background of the Invention
Prior electrically driven impact tools have utilized low amounts of energy and have been used in applications, such as for driving small nails and staples, loosening and tightening nuts or seating deformable fasteners, such as small brass and copper rivets. Substantially all high en¬ ergy impact tools, particularly those which have been suf- ficiently light to be hand used, have operated on compresse air. However, such air tools have required, for supply of air through hoses to the tools, a high volume air compress¬ or which is stationary or requires a cumbersome trailer or similar support, for transportation and location at the sit at which the tool or tools are to be used. The additional pneumatic equipment, such as pressure regulators, lubrica¬ tors, filters and the like, complicate the supply mechanism Electrically driven impact tools which are hand held and es pecially those which are adaptable to nail driving purposes, are quite attractive in view of the fact that, at almost al construction sites, electrical power is normally available in substantially any desired quantity.
It has been proposed, in the James E. Smith and James D. Cunningham U. S. application Serial No. 580,246, now U. S. patent No. 4,042,036, to provide an electrical impact tool having a specific application to a nail driving tool by utilizing one stationarily mounted and one pivotally mou ted motor and rotating flywheel assembly, with the station¬ arily mounted, rotating flywheel being adjacent one side of a ram and the opposite side of the ram being engaged by the pivotally mounted, rotating flywheel. Movement of the lat¬ ter into engagement with the ram is produced by a movable nose piece which is pushed into engagement with the work. Lateral movement of the latter is used to push the ram a- gainst the stationarily mounted, rotating flywheel, which requires-that the ram have sufficient lateral play to ac¬ commodate this movement, with the result that undue wear on one side of the ram is produced. Often, an inadequate force is produced to move the pivoted, rotating flywheel in to engagement with the ram. Thus, this force may vary with different operators and also in accordance with the positio in which the nail is to be driven, i.e. between a downwardl driven nail, an upwardly driven nail. and a laterally driven nail, for which the gravitational force of the weight of th tool may vary from assisting the movement of the nose piece to opposing it. Thus, the force which the operator must supply differs considerably. Other problems have arisen in connection with the practical application of such a con¬ struction to a tool for driving nails, including erratic starting of the ram, undue wear at the impact points of the rotating flywheels, the tendency for the production of for¬ ces which deflect the ram laterally, absence of equaliza¬ tion of the engagement forces of the two flywheels, acciden tal starting of the ram by the stationarily mounted, rotat- ing flywheel, difficulty in disengagement of the ram from the stationarily mounted, rotating flywheel, a tendency for the rotating flywheels to "grab" the sides of the ram, difficulties in producing a smooth acceleration of the ram and undue losses in power effectively transmitted to the ram. Other problems included difficulties in returning the ram to its initial position, including localized elon¬ gation of a coil spring and frequent breakage of a rubber cord attempted to be utilized for that purpose. As a re¬ sult, there has been difficulty in consistent reproduction of the desired nail driving characteristics. The elec¬ trically driven impact tool of this invention is designed to overcome the foregoing difficulties, as well as to pro¬ vide additional novel features. Summary of the Invention
The impact tool of this invention overcomes the prob¬ lem of unbalance wear and accuracy in guiding a ram, as well as more effective acceleration of the ram, by pivot- ing the rotating bodies or flywheels inwardly toward the stationary ram from both sides, and for equal distances. The frictional engagement of the rotating bodies with the ram takes place essentially simultaneously from both sides, producing substantially the same wear on both sides of the ram. The rotating bodies or flywheels are also mounted in an overhang or cantilver arrangement with respect to the driving motors and thus permit greater freedom of ac¬ cess to the ram and positioning of guide rods or the like for the ram. The initially engaged surfaces of the ram are each slightly tapered, as on the order of 0.0254 cm.-. .0.0635 cm-., preferably 0.0381 cm., for 1.27 cm. of length, insuring not only a more uniform frictional en¬ gagement on each side, but also an essentially smooth in¬ itial acceleration'. The initial tapered surfaces also con- tribute to regeneration or "feedback" by the increase of width of the distance between the flywheels and a conse¬ quent increase in the normal force between the flywheels and the sides of the ram, thereby increasing the driving force as the ram is speeded up. Thus, there will be pro- duced a larger force with which the flywheels grip the ram between them, as the flywheels pass along the tapered por¬ tions to the parallel portions of the sides of the ram. The taper of the initially engaged surfaces of the ram should, of course, be less than that at'which the flywheels tend to "grab" the ram, rather than a smooth frictional en¬ gagement. The sides of the ram are beveled at the opposite end, but at a considerably greater angle than the taper of the initially engaged end, to produce disengagement of the flywheels from the ram and also to facilitate the return of the ram between the spinning flywheels. Noriαally, of course, the number of revolutions will diminish as the ram is driven on its impact stroke, but the flywheels will be¬ gin to accelerate as soon as the ram has been disengaged. Of course, the flywheels are returned quickly to their ini¬ tial position after disengagement from the ram, as by a spring acting against both pivoted motors or against each. Coil springs are suitable for this purpose, but unsuitable for returning the ram, since the distance of movement of the motors and flywheels is considerably less than that of the ram and the rate of movement of the motors and fly¬ wheels is less than that of the ram. The angles of the initial flywheel centers to the centerline of the pivots and the taper of the initial engagement surface of the ram are correlated to produce a regenerative action, such as the ram taper being on the order of that expressed above, and the initial angle of the flywheel centers being within the range of a minimum of 9° to a maximum of 20°, with a range of 10° to 14° being preferred.
A balanced pull on the two pivoted motors simultan¬ eously, to move the flywheels into engagement with the ram, is produced by a pair of electrical solenoids, which are more readily controlled and vastly quicker in action than a nose piece pressed against a work piece. Also, a power sup ply booster may be used to produce a high amperage pulse to increase considerably the speed of movement and initial pull of the solenoids. Each of the solenoids acts through a pair of pivotally connected links, to maximize the force which presses the flywheels against opposite sides of the ram. Thus, the links, in a straight line position, have a leverage ratio of almost infinity, which, of course, de¬ creases as the links are bent toward each other. However, the pull of the solenoids is essentially the reverse, being least when the solenoids are just starting movement and be¬ coming greater as the solenoids move. Thus, the effective leverage of the links counteracts the variation in the pull of the solenoids. The movable ends of the two sets of links are connected together for equalization of movement and simultaneous transmission of movement through cables connected to the pivoted motors, movement of which produces a corresponding movement of the flywheels. Also, cable con nections between the solenoids and the center pivot of the corresponding toggle links has been found advantageous, with aircraft type cable being suitable.
As an alternative, a single solenoid may act through a single set of links, or through a cable arrangement in- eluding a first cable fixed at one end and attached at the opposite or movable end to the cables connected to the pi¬ voted motors. A second cable, pulled by a solenoid, is connected to an intermediate point on the first cable and exerts a pull transverse to the first cable. A third cabl also transverse to the first cable, is anchored at one sid and is connected to the movable end of the first cable. When the solenoid pulls on the second cable to shorten the effective length of the first cable, with the third cable maintaining the movable end of the first cable in alignmen .with its fixed end, the cables connected to the motors are also pulled to move the flywheels into engagement with the ram. A similar cable arrangement may be substituted for each of the link pairs used with two solenoids, as describ above. An equalization of large normal forces required to drive the ram, as well as precession forces between the mo¬ tor armatures and flywheels, rotating in opposite direc¬ tions, has been accomplished by the use of a tension rod connecting the pivot shafts on which the motors and fly- wheels are pivoted. This tension rod is located adjacent the flywheels and overcomes the necessity for the housing to equalize these forces, thereby reducing considerably the necessary thickness and weight of the housing or per¬ mitting the housing to be made of molded plastic, rather than formed aluminum. In addition, the tension rod pro¬ vides a stable means for maintaining the spaced position between the pivot shafts. A pair of spaced tension rods, the other at the opposite ends of the motors, may also be utilized. The characteristics of the flywheel inertia, the ram inertia, the probable rate of ram wear and the mo¬ tor recovery rate, such as from 7,000 to 14,000 r.p.m. , are matched to provide adequate acceleration of the ram with a reasonable amount of wear. The problem of the shorter life and delay in reaction of a normal coil spring, for returning the ram to its ini¬ tial position, after completion of the impact stroke, or breakage of a single rubber cord for the same purpose, has been overcome by the use of a bundle of elastomer . cords, such as rubber cords, placed in a nylon sheath. Such elas¬ tomer cords tend to stretch throughout their length upon the imposition of a force tending to elongate them, rather than stretching one increment at a time, as in the case of a coil spring subjected to an extremely short time period of ram movement. The ram is formed of a lighter weight ma¬ terial, such as aluminum, but a steel driver blade, which produces the actual impact, is attached to the ram.
A brake lining on the sides of the ram provides a friction surface for the flywheels. The brake lining may be bonded by an epoxy resin to the sides of the ram for ade quate retention of the friction surface to the ram. Also, the ram may be provided with wings, which engage guide rods and have a greater surface area for abutment against a bum- per. In order to cool the frictionally engaging parts, the motor is equipped with a fan for blowing air past the fly¬ wheels and ram, while this air is filtered to prevent for¬ eign material from collecting on the friction surface. As an alternative, the friction surface, such as brake lining, may be bonded, as by an epoxy resin, to the periphery of each flywheel, in order to provide a greater cooling effect on the friction material, due to rotation of the flywheel. However, it is preferred to bond a mixture of a resin, such as polyurethane or phenolic, with asbestos fibers, as fric- tion material to each flywheel. Such a resin mixture may also include particles or elongated fibers of copper or other material having a relatively high heat conductivity. A safety device actuated by a slide on the nose piece may control a microswitc which must be closed by move- ment of the slide engaging the work piece, before the fly¬ wheel pivoting solenoids can be energized. An alternative or additional safety device includes a movable stop block which is normally in _- a: -.position preventing downward movement of the ram but moved away from this position through a rod actuated through movement of the nose piece slide through engagement with the work piece.
The controller for the motors is selected to cause as great acceleration as possible after the motors and fly¬ wheels have slowed down after moving the ram on an impact stroke, but to limit the top speed of the motors to a spee consonant with the kinetic energy to be transmitted to the ram for driving the size and length of nail into the type o wood or other material of the work piece, such as through steel into concrete. The motors are preferably selected so that the maximum obtainable speed exceeds any speed to whic it might be desirable to limit the motors for any expected application. Such a controller may be selected so that it can be adjusted to limit the maximum speed of the motor.to a greater or lesser speed, when different nails or differ¬ ent work piece materials are encountered. Also, substitute flywheels, such as adapted to produce different weights, may be used for such different applications. For this rea- son, it is desirable that access to, removal of and substi¬ tution of different flywheels and/or rams should be expedi¬ ted by the mounting of these parts and the construction of the enclosing housing.
Brief Description of the Drawings
Fig. 1 is a perspective view of an impact tool . of this invention embodied in a nail driving machine.
Fig. 2 is a bottom perspective view of a pair of op¬ posed, pivoted, oppositely rotating bodies, each compris- ing a flywheel and motors for rotating the flywheels.
Fig. 3 is a perspective view of a housing, with cer¬ tain parts installed on the housing, the housing being par¬ ticularly adapted to receive the rotating flywheels of Fig. 2. Fig. 4 is an end view of the machine of Fig. 1.
Fig. 5 is a side view of the machine of Fig. 1, but taken from the opposite side than Fig. 1 and with a portion of a nail feed magazine omitted. Fig. 6 is a partial longitudinal section taken along line 6-6 of Fig. 4, with certain exterior parts omitted for clarity of illustration.
Fig. 7 is a cross section taken through the motors, along line 7-7 of Fig. 5, showing particularly the device for pivoting the motors and flywheels.
Fig. 8 is a fragmentary horizontal section taken along line 8-8 of Fig. 7, and showing particularly the cable guides omitted from Fig. 7 for clarity of illustration. Fig. 9 is a longitudinal section taken along line 9-9 of one of the motor and flywheel assemblies of Fig. 2, but on an enlarged scale.
Fig. 10 is a cross section taken along line 10-10 of Fig. 9. Fig. 11 is a side elevation, partly in central longi¬ tudinal section, of a ram which is engaged and accelerated by the flywheels.
Fig. 12 is an .end elevation of the ram of Fig. -11, with the flywheels shown fragmentarily in the position of initial engagement with the ram.
Fig. 13 is an enlarged view corresponding to a portion of the lower end of the ram, as shown in Fig. 12, to illus¬ trate a slight taper.
Fig. 14 is a similar enlargement of a portion of the upper end of the ram, illustrating the bevel which produces disengagement of the flywheels with the ram, as the ram reaches the normal end of its travel.
Fig. 15 is a bottom view of the ram of Fig. 11.
Fig. 16 is a cross section, on a slightly larger scale, of a nose piece slide, shown also in Figs. 1 and 3.
Fig. 17 is a condensed side elevation of a driver blad which is attached to the ram for driving nails.
Fig. 18 is a condensed rear elevation of the driver blade of Fig. 17. Fig. 19 is a cross section, on an enlarged scale, taken along line 19-19 of Fig. 18.
Fig. 20 is a longitudinal section of a flywheel alter¬ native to those of Figs. 2 and 9. Fig. 21 is a fragmentary view, on an enlarged scale, showing a safety mechanism, alternative to or in addition to that shown in Fig. 5.
Fig. 22 is a fragmentary, diagrammatic view illustra- ting a cable arrangement, for use as an alternative force multiplying means of a device for pivoting the motors and flywheels.
Fig. 23 is a fragmentary end elevation of a further alternative safety mechanism. Fig. 24 is a fragmentary side elevation of the safety mechanism of Fig. 23.
Fig. 25 is an.enlarged view corresponding to Fig. 13 but showing a modified manner of providing a slight taper.
Detailed Description of the Invention
An impact tool of this invention, illustrated as em¬ bodied in an electric nail driving tool, includes general¬ ly a housing H of Fig. 1 having a nose piece N through which the nails are driven into the work piece by a driver blade B of Fig. 6 attached to a ram R which is engaged by rotating bodies or flywheels F and F' of Fig. 2, pivoted into simultaneous engagement with the opposite sides of the ram for propelling the ram and driver blade longitud¬ inally toward the nail. Flywheels F and F' are rotated in opposite directions by electrical motors M and M' , the ar¬ matures of which may also supply a portion, as on the order of 10%, of the kinetic energy or inertia available for transmission to the ram by the flywheels. Solenoids S and S' of Fig. 3 are utilized, with linkage mechanism and cable connections described below, to pivot the flywheels toward the ram. A nail feeding magazine A of conventional cons¬ truction is attached to the nose piece N for moving the nails, in turn, in position to be driven into the work piece, by blade B. The housing H is provided with a handle 10 by which the tool may be held for placement in a desired posi¬ tion against the work piece, with electricity being supplied through an electrical cord 11 and an on-off switch 12 of Fig. 5 which, when on, causes current to be supplied to motors M and M* . The solenoids S and S' are actuated only when a trigger 13, provided on the handle, is closed, sub¬ ject to a safety device described below which precludes the accidental discharge of a number of nails into the air if the trigger is accidentally pressed. The respective motors M and M" rotate the corresponding flywheels F and F' , which are brought up to a predetermined speed, corre¬ lated with the weight of the ram and the necessary inertia of the flywheels for producing an adequate number of foot pounds to drive each nail in turn. Each motor M or M' is provided with a shaft, to the overhanging end of which the corresponding flywheel F or F* is attached by a cap screw 14, as in Fig. 2, while the motors are pivoted on spaced pivot shafts 15 and 15' disposed in spaced, parallel re- lation and at equal distances from the centerline of move¬ ment of the ram R. In accordance with this invention, the motors and flywheels are pivoted concurrently and simultan¬ eously toward each other for simultaneous engagement of the flywheels with the opposite sides of the ram R, adjacent the lower end of the ram R, as viewed in Fig. 6 and assum¬ ing that the tool is held in an upright position above the work piece, it being understood that the tool may be held in a horizontal position, as for driving a nail into an up¬ right work piece, or even in an upward position, as for driving a nail into an overhead work piece.
Also in accordance with this invention, the entrance edges of the sides of the ram R, as in Figs. 12 and 13, are each provided with a taper 17 at an angle selected such that the flywheels will engage the ram quickly, but will smoothly impart acceleration thereto. A layer 18 of fric¬ tion material, brake lining being highly suitable, will follow the angle of tapers 17. Such entrance taper may also be provided in layer 18 of the friction material, as at 17" in Fig. 25, as in both layers on opposite sides of the ram. An initial engagement of flywheels with parallel sides of a ram tends to produce a grabbing effect and con¬ siderable wear at the point of initial engagement. However, the initial taper of the sides, such as a taper of 0.0254 to 0.0635 cm. preferably 0.0381 cm. in a length of 1.27 cm., permits the flywheels to start the ram on its - movement more smoothly and with less slippage, as well as with a greater rate of increase in acceleration, due to the slight wedging action of the tapered sides, as the ram be¬ gins to move and there is little or no tendency for the flywheels to produce wear at one point.
The gripping force of the flywheels produced by the entrance taper on opposite sides of the ram is most pro- nounced when both flywheels are moved simultaneously into engagement with the ram, since the inertia of each flywheel resists the tendency for the' initial taper of the sides to push the flywheels apart, as the ram starts its movement produced by the flywheels. This inertia produced force would not be present if a flywheel, which is fixed, were used on one side of the ram and a spring pressed roller on the opposite side, since a fixed center flywheel is unable to exert any inertia effect on the ram, while the opposed roller would not rotate until started by movement of the ram and therefore has a negligible inertia. Similarly, the use, on the bottom of a cylindrical ram having a con¬ ical point, of a fixed motor driven roller and, on the top, a motor driven roller supported by springs, while pushing the ram between the rollers, does not produce the desired results, since there is a necessity for a starting force, - i.e. the ram would not be self starting. Also, the lower fixed roller is again incapable of exerting inertia against the ram and the upper roller can, at best, exert only one half the inertia of a similar rotating body on each of the opposite sides of the ram. Since a greater gripping effect, due to the wedging action of the tapered sides, is produced as the ram moves, there is an adequate normal force to pro¬ duce additional acceleration as the flywheels move from the tapered portions to the parallel portions of the sides of the ram. The opposite end of the ram R, as in Figs. 12 and 14, is provided with a disengagement bevel 19, on each side, which has a considerably greater inclination than the slightly tapering surfaces 17, and permits a quick disengagment of the ram from the rotating flywheels, so that the ram may quickly stop and be returned, normally up¬ wardly between the flywheels.
An additional feature of this invention is the tension rod T of Figs. 2 and 10, connected between the pivot shafts 15 and 15* for the motors, as by connectors 20. The ends of rod T may be oppositely threaded for adjustment into hexa¬ gon blocks 21 of connectors 20. Tension rod T equalizes the large normal forces required to drive the ram, thus re- lieving the housing of the necessity for equalizing such forces. The tension rod also equalizes the precession for¬ ces and the rotational and acceleration reaction forces pro¬ duced by the counter-rotating motor armatures and flywheels. An additional tension rod T', as in Fig. 2, may connect shafts 15 and 15' at the opposite end of the motor.
A further feature of this invention includes the simul¬ taneous pivoting of the motors M and M* and flywheels F and F* , along with them, through the action of solenoids S and S' mounted in the housing H, as in Figs. 3-5, through a linkage and cable arrangement, including cables 22 connec¬ ted to motor brackets 23, as in Fig. 2, and in turn connec¬ ted to a block 24. Block 24, as in Fig. 7, is adjustably connected to a yoke 25 whose spaced arms 26 are each pivot¬ ally connected to the adjacent end of an inner link 27 or 27'. In turn, each inner link 27 or 27' is pivotally con¬ nected to an outer link 28 or 28', respectively, the oppos¬ ite end of which is pivotally connected to a support block 29. A solenoid cable 30, as in Fig. 8, connects the res¬ pective solenoid plunger 31 with a socket 32 at the pivotal connection of the links 27, 28 and 27', 28'. Each solenoid cable 30 passes over a pivoted, arcuate pulley 33 which transfers the pull of the respective solenoid plunger throug 90°, to pull the respective pivot centers between the links away from each other, as in the direction of the arrows of Fig. 8. As will be evident, such movement essentially moves the links 27, 28 and 27', 28' from the full to the dotted positions of Fig. 7. In turn, this will move the yoke 25 and motor cables 22 upwardly, as viewed in Fig. 7, to pivot the motors M and M1 toward each other about the shafts 15 and 15', to produce a corresponding movement of the fly¬ wheels with opposite sides of the slight tapers at the ini¬ tial contact end of the ram R. As described previously, this engagement of the flywheels with opposite sides of the ram R will start the ram moving in an impact direction, with the acceleration increasing as the flywheels move along the slightly tapered surfaces and continue to engage the parallel sides of the ram, until the disengagement be- vels 19, at the opposite end of the ram, are encountered. Such impact of the ram will also move the driver blade B into engagement with the head of the nail and drive the nail into the work piece.
A safety device for preventing actuation of the sole- noids S and S' and a resulting impact movement of the ram, until the tool is in position against the work piece, may include an angular rod 35 of Fig. 5 attached to a slide 36 mounted for movement along the nose piece N and provided with a partial ring 37, shown also in Fig. 16, adapted to be pressed against the work piece, when the operator desires to produce another impact, as for driving another nail. An up¬ per portion of rod 35 is provided with a plate 38 adapted to engage a button 39 of a miσroswitch 40 when the rod 35 is moved upwardly, as viewed in Fig. 5, due to engagement of ring 37 with the work piece. An enlargement 41 of the upper end of rod 35 extends into a socket 42 for engaging a coil spring 43 which returns the rod 35 and slide 36 to their initial position, when the ring 37 is no longer presse against the work piece. Microswitch 40 is mounted on the housing adjacent the socket 42, while pressure plate 38 on button 39 will close the microswitch and complete the elec¬ trical circuit to solenoids S and S' , when the operator presses the trigger 12. As in Figs. 3 and 4, slide 36 is provided with slots 44 through which bolts 45 extend, for guiding the slide in its movement, such as upwardly and downwardly, as viewed in Figs. 4 and 5.
During its upward and downward movement, the ram R is guided by a pair of spaced, parallel rods 47, as in y § WE Fig. 6, extending through a pair of wings 48 of the ram which extends both above and below the wings in a generally rectangular configuration in cross section. The upper end of the ram, in the initial position shown, extends through a corresponding slot in a fixed attachment plate 49 for a flexible cord C and into engagement with a resilient upper bumper 50. The flexible cord C is formed of a series of elastomer cords, such as rubber, encased in a nylon sheath. The cord C, as indicated previously, stretches equally along its length when an elongation force is applied to it, which property is particularly desirable for the present use, since the rapidity with which the ram is impelled, such as moving over its length of travel in a few milliseconds, tends to deform coil springs, the use of which has been at- tempted. The latter tend to elongate in increments as the stress is applied to the spring, which is reasonably satis¬ factory for an elongation stress applied much more slowly, but tends to overstress and deform the spring when the elon¬ gation stress is applied as rapidly as it must be for the movement of the ram to be effective in developing the de¬ sired amount of power for the impact stroke, such as for driving nails. Each end of the cord C extends through a hole therefor in the attachment plate 49, as shown, and is attached to the plate, as by a suitable fastener or being tied in a knot 51 above the plate. Cord C extends through holes 52 in the wings, indicated also in Fig. 11, along slots 53 below the wings and is looped through the lower end of the ram. As the ram R moves downwardly, the impact of the driver blade B against the nail will drive the nail into the work piece, and the head of the nail in the work piece will ordinarily stop the driver blade and ram. How¬ ever, if the ram has excess kinetic energy, the underside of the wings 48 will engage lower bumpers 34 which surround the guide rods 47, correspond in area to the underside of the wings and will absorb the remaining kinetic energy.
The lower bumpers are formed of resilient but tough material, such as rubber, or a hard plastic, such as polyurethane hav¬ ing a hardness of 80-90 Shore. Lower bumpers 54 are Ε maintained in the desired parallel relation on the guide rods by a sleeve 55 which surrounds each of the bumpers 54 and is provided with a central aperture 56 into which the lower portion of the ram moves, as the ram is driven downwardly. Additional details of the ram construction will be given below.
The housing H, as in Figs. 1, 3, 4 and 5, may include a forward section having a lateral wing 58 closing each side and in which the motors M and M' and flywheels F and F' are installed. Above the wings is a hollow, rectangu¬ lar extension 59 on opposite sides of which the solenoids S and S' are mounted, as in Fig. 3, while below the wings is a rectangular extension 60 having a bottom 61 of Fig. 6 having a central aperture corresponding to the aperture 56 of sleeve 55, as shown, and holes 62 beneath bumpers 54 into which guide rods 47 extend, for abutment by attachment flange 63 of nose piece N. The opposite ends of guide rods 47 extend into corresponding holes 64 in upper bumper 50. Thus, the guide rods 47 for the ram R and attached driver blade. B extend centrally of this housing section and be¬ tween extensions 59 and 60. Cover plates 65 and 65' having apertures, as shown, for outflow of cooling air moved through and around the motors and rotating flywheels, close the front of the two wings 58 of the front housing section, while a front box 66 covers the central portion thereof.
Covers 65 and 65' and box 66 are conveniently integral. A top cover 67 closes the top of the upper extension 59 of the winged housing section, and a flange 68 upstands from the rear edge thereof, while cover boxes 69 for the sole- noids are positioned at opposite sides thereof. Upper bumper 50 is attached to the underside of cover 67, which may be removed, along with front box 66 and plates 65, 65' attached thereto, to permit removal of plate 49, which nor¬ mally rests on a shoulder formed in the wall of extension 59, and ram R along with guide rods 47, as for inspection or replacement of the ram. Also, removal of front box 66 and plates 65, 65' permits access to flywheels F and F', as for changing through removal of cap screws 14. Rearwardly of the front section, a hollow motor hous¬ ing section 70 corresponds in contour to the wings 58 and is attached to the rear thereof, with an end cap 71 clos¬ ing the cavity. A motor control assembly box 72, as in Fig. 5, extends rearwardly from the central portion of end cap 71. Mounting ribs 73, as in Fig. 3, are formed on the inside of each wing 58 and receive the end of the corres¬ ponding pivot shaft 15 and 15' adjacent the flywheels F and F'. An attachment lug 74 at the opposite end of the corresponding pivot shaf 15 and 15* is attached to the in¬ side of housing section 70 at an appropriate position. A housing 75 of each motor is pivotally connected to the res¬ pective pivot shaft by brackets 76, shown also in Fig. 10, and each provided with a bearing 77 encircling the corres- ponding pivot shaft. It will be noted that end cap 71, with lugs 74 attached to housing section 70, will be sub¬ ject to a portion of the normal and precession forces to be equalized by tension rod T. However, when tension rod T* is connected between the pivot shafts 15 and 15' rear- wardly of the motors M and M* , the forces imposed on end cap 71 will become negligible and the two tension rods will tend to receive somewhat similar amounts of forces for equalization. As indicated previously, the use of tension rod T, or also rod Tf, permits the housing to be lighter or to be made of less expensive material.
As in Fig. 8, support block 29 is attached to and ex¬ tends upwardly from the rear wall of extension 59 of the front housing section. Block 29 is provided with slots 79, as in Fig. 7, through which the pivot pins for the.up- per ends of links 28 and 28' extend, while a center rib
80 extends downwardly between the links. As in Fig. 5, a cover box 81 encloses support 29, rib 80. and the linkage arrangement. As in Fig. 8^ the arcuate pulleys 33 may be pivoted on brackets 81 which may also be mounted on the rear side of extension 59 of the front housing section.
As in Fig. 7, the motors M and M' may be retracted by coil springs 82 connected between ears formed as parts of brac¬ kets 23 and ears 83 provided on the inside .of ..adjacent wing 57 .
As in Fig. 6, the nose piece N is generally rectangu¬ lar on the outside and provided with a cylindrical, central passage 85 of a diameter to accommodate the heads of nails placed in and driven therethrough, with a flat sided abut¬ ment 86 at the front for attachment of slide 36 thereto for movement between the extended position of Fig. 3 and the retracted position of Fig. 1. At the rear, nose piece N is provided with a slot 87 through which the shank of each nail may move and a lateral enlargement 88 of the slot to accommodate the head of the nail. The nails are con¬ veniently secured together in side by side relation between spaced pairs of strips of tape, as of paper, with plastic or the like between the tapes and molded against the nails. Such a strip of nails slants downwardly to one side, corres¬ ponding to the angularity of the feed magazine A to . the nose piece N, through which the nails are fed in succession into the nose piece in a conventional manner. The front end of feed magazine A is attached to the nose piece N by brackets 89 and 89', secure to opposite sides of the nose piece by bolts 90, as shown.
As in Fig. 9, each motor includes an armature 92 moun¬ ted on a shaft 93 which carries a commutator 94 engaged by brushes 95 mounted in conventional brush holders, as shown. The brush holders are mounted in an end cap 96 for the mo¬ tor which may carry a" bearing 97 for the commutator end of the motor and have holes 98 therein, for flow of air into the motor. The field windings 99 of the motor are posi¬ tioned by pins 100 extending between annular support rings 101. A sleeve 105 attached to the front of the motor housing 75 is provided with a slot 106 which . provides clearance for the tension rod T, while a stepped enlarge¬ ment 107 of the shaft carries a fan 108, which pulls air through the motor and blows it past the flywheels. The en- largement 107 continues to a bearing 109 which is larger than bearing 97, because of the additional weight and over¬ hanging position of the flywheel, a hub 110 of which is mounted on the end of shaft enlargement 107 and retained
U in position by washers 111 engaged by socket head screw 14. Bearing 109 is supported within a bearing cap 112 attached to the end of sleeve 105 and also provided with holes 113, for flow of cooling air to the flywheel. The flywheel has a rim 115 mounted on the hub 110, such as through an inside flange 116 and studs 117, spaced circum- ferentially about the hub. As will be evident, the stepped enlargement 107 may be formed integrally with the shaft 93 or formed separately and mounted thereon by a press fit, or by brazing. Air inlet openings 118, provided with filters
119, may be provided in the rear wall of housing end cap 71, as in Fig. 5. After movement past the flywheels F and F* and ram R, the air is discharged through the holes in front plates 65 and 65'. In addition to parts previously described in connec¬ tion with the ram R, the ram is provided with additional elements, as in Figs. 11, 12 and 15, such as holes 120 in the wings 48 for the guide rods 47 and bevels 121 on the outer edges of the wings. A groove 122 is formed at each side of the upper portion of the ram above the respective wings, for readier access to the ends of cord C and to re¬ duce weight, while the holes in plate 49 of Fig. 6 for cord C are placed in ears of the plate which extend into the respective groove 122. A transverse bore 123, for both weight reduction and cooling purposes, connects the two grooves. Also, a series of bores 124, for similar pur¬ poses, extend laterally through the ram, within the longi¬ tudinal extend of the wings and intersect the holes 52 and
120, as in Fig. 11. The side grooves 53 which receive the cord C are widened for weight reduction purposes, while sockets 125 and 125' on opposite sides of the ram con¬ nect with the respective groove 53 adjacent the wings. A socket 126, enlarged as in Fig. 15, extends upwardly from the lower end of the ram, and connects holes 127 through which the cord C extends to cross socket 126. From the up¬ per edge of the latter, a central socket 128 extends upward¬ ly, to receive the upper end of the driver blade B, as through set screws tightened in tapped holes 129 and 130, inclined upwardly toward the driver blade from opposite sides. Since the ram is preferably formed of aluminum or other lightweight metal and the driver blade is prefer¬ ably formed of alloy steel, a steel plate 131 having a central hole corresponding in size to socket 128 is posi¬ tioned against the upper surface of socket 126 to trans¬ mit forces received from the driver blade over a large area and thereby avoid crushing the surface of aluminum or the like. Cord C may pass around either the front or the back of the driver blade.
The driver blade B, as in Figs. 17-19, includes an elongated shank 135 having on one side a groove 136 and a bevel 137 at the impact end of the shank. The blade is preferably positioned so that the groove 136 and bevel 137 will face the incoming nails, so that, if the next nail tends to enter the nose piece N before the blade has been returned following an impact stroke, the head of the nail will tend to be cleared by the groove and bevel. The shank is provided with an enlargement 138 at the opposite end, providing a shoulder 139 around a stem 140. The stem may be made separate from the shank, as by forging, and an enlarged lower end 141 of the stem placed in a corresponding socket formed in the shank enlargement 138. The stem and shank may be attached together by forging or by brazing, or in any other suitable manner. The stem 140 is also pro¬ vided with oppositely disposed, staggered notches 141 and 142 which correspond in position to the tapped holes 129 and 130 of the ram R, as in Fig. 11. Thus, the notches 141 and 142 are engaged by the set screws threaded into the tapped holes 129 and 130, respectively. The stem of the driver blade extends through the hole in plate 131 and into the socket 128 of the ram, until the shoulder 139 abuts against the plate 131. As will be evident, the cross sectional area of the shoulder 139 is such that, with a stem shank- made of alloy steel, it may possibly crush the softer material, such as aluminum or the like, of the ram. However, the plate 131, which is also formed of steel, is adapted to receive the possibly crushing force of the shoulder 139 without deformation, and to distribute this force over the entire area of the plate 131, which corres¬ ponds to the area of the enlarged socket 126, as in Fig. 15, around the socket hole 128. The friction layer, such as brake lining 18, bonded to the sides of the ram R, as in Fig. 12, may alternatively be bonded to the periphery of each of the flywheels F and F1. However, as in Fig. 20, it is preferred to provide the periphery of the rim 115 of each flywheel with a fric- tion layer 145, molded onto the flywheel rim. As indicated previously, the molded friction layer 145 may be formed of a mixture of suitable resin, such as polyurethane or pheno¬ lic, and asbestos fibers, as a friction material. Fibers, powder or the like of a material having a relatively high heat conductivity, such as copper, may be mixed with the resin to enhance the dissipation of heat produced by the frictional engagement of the flywheels with the ram. When the friction layer is provided on the ram, the periphery of the flywheel rim 115 is preferably polished and as smooth as possible, since it has been found that the coefficient of friction for cold rolled steel, .of which the flywheel rims may be made, will be increased when the friction sur¬ face, such as brake lining, is engaged with a highly po¬ lished surface moving at the peripheral speed of the fly- wheels. While such a coefficient of friction is theoretic¬ ally on the order of 0.3, in practice, it may be reduced to about 0.15. However, when the friction layer is molded on or bonded to the periphery of each flywheel, the sides of the ram to be engaged by such friction surfaces, for simi- lar reasons, are preferably highly polished and smooth. Although it would be expected that a rough surface in en¬ gagement with the friction layer would have a higher co¬ efficient of friction, the driving results produced appear to be affected by the relatively high peripheral speed of the flywheels and the desirability of producing a smooth initial engagement, rather than a grabbing effect.
An alternative or additional safety device, as in Fig. 21, may be operated by a rod 35' which may extend -- upwardly from slide 36 and ring 37 in a manner similar to rod 35 of Fig. 5, or may be provided as an extension of the rod 35 which extends upwardly through the enlargement 41 and coil spring 43 of Fig. 5. Thus, the upper end of the rod 35' is adapted to engage a base 147 of a block 148 pivotal about a fixed pin 149. An offset nose 150 is nor¬ mally positioned beneath a wing 48 of the ram R, so that if the ram is accidentally moved downwardly without the rod 35 and its extension 35' being raised by engagement of slide ring 37 with the work piece, the nose 150 will block downward movement of the ram. However, if the rod 35' is raised to pivot the block to the dotted position shown, the nose 150 will clear the side of the wing 48 and the ram will be permitted to move downwardly for .the desired impact. The block 148 is normally maintained in a position with the nose 150 beneath the ram wing by a coil spring 151, one end .of which abuts a shoulder 152 formed on the block and the other end of which abuts a fixed stop 153. As will be evident, if the rod 35' is retracted due to dis- engagement of the slide ring 37 of the work piece, the spring 151 will move the safety block from the dotted posi¬ tion back to the full position of Fig. 21.
An alternative force multiplying means, comprising essentially a cable arrangement, is illustrated in Fig. 22. This force multiplying means includes a first cable
155 which is connected, at its fixed end, to an anchor 156 by a plug 157. The movable end of cable 155 is provided with a connector 158, to which are attached cables 22' ex¬ tending to the respective motors M and M' , such as in a manner corresponding to that illustrated in Fig. 7. A se¬ cond or solenoid cable '30' extends from a plunger 31 of a solenoid and is attached to a connector 159, which conveni¬ ently encircles the cable 155 at an intermediate point of the cable. Connector 159, although clamping the cable, has a longitudinally rounded inside surface opposite cable 30', as shown, to avoid injury to the cable 155 when moved by pulling. The solenoid cable 30' may extend directly from the solenoid plunger 31 or may extend around an arcuate pulley, as in the manner illustrated in Fig. 8. A third cable 160 is attached at its movable end to connector 158 and its fixed end to an anchor 161, as by a plug 162, and causes the connector 158, i.e. the movable end of cable 155, to follow an essentially straight line motion, or the equivalent thereof, when solenoid cable 30' is pulled. Such pull moves the first cable 155 to the dotted position shown, thereby to move the connector 158 upwardly, as viewe in Fig. 22, to pivot the motors M and r and the rotating bodies or flywheels driven by the motors, toward each other, for engagement of the flywheels with the ram, as described previously. It will be noted that a dual cable arrangement actuated by a pair of solenoids may be utilized, in effect being the substitution of the force multiplying cable ar- rangement of Fig. 22 for each of the pairs of links 27, 28 and 27', 28' of Fig. 7. Similarly, one of the link pairs of Fig. 7 may be substituted for the cable arrangement of Fig. 22 but including cable 160 connected as a guide for straight line movement to the free end of the inner link 27, or other suitable mechanism.
Through this invention, the weight of the flywheels has been reduced from 1.1 kg. each for the nail driving tool, constructed in accordance with- Serial No. 580,246, to 0.158 kg. for each flywheel for a nail driving tool constructed in accordance with the present invention. A corresponding reduction has been secured in the weight of the complete nail driving tool itself, i.e. from 9.5 kg. for the previous tool, to between 5.2 and 5.4 kg. for a tool of this invention, for driving 16-penny nails. By the use of lighter motors, the weight of the same tool could be reducible to between 3.-6 and 4.5 kg.
In Fig. 7, the angles 170 are between the plane of shafts 15 and 15' and a centerline extending from the cen¬ ter of a shaft 15 or 15' to the center of the corresponding motor M or M' . The centerlines 171 approximate the posi¬ tion of the latter, when the motors M and M' have been pi¬ voted, so that the flywheels will engage the opposite sides of the ram R. In Fig. 12, the arrows 172 indicate the c normal force exerted by the respective flywheels F and F' against the tapered side portions of the ram. These relationships, as well as the movement of the flywheels by the solenoids and the force multiplying means, are of interest, since tests have indicated that it requires on the order of 8.295 kg. meters of energy to drive a 16- penny nail into pine and on the order of 15.2 to 16.59 kg. meters to drive a 16-penny nail into oak. As will be evi¬ dent, the kg. meters necessary to accelerate the ram and drive the nail must be imparted.to the ram by the flywheels. Calculations have indicated that it requires approximately 0.17 kg. meters per gram, to accelerate the ram, so that 24.19 kg. meters are necessary to accelerate the 141.7 gram ram used. In addition, the flywheels should transmit, through the ram, additional kg. meters, such as 8.295 to 16.59 kg. meters, depending on the wood, when driving 16- penny nails. For this purpose, the kg. meters transmitted to the ram by both flywheels thus should exceed 32.48 to 40.78 kg. meters, or 16 to 20 kg. meters for each flywheel. The pull on each cable 22 of Fig. 7 is estimated for cal¬ culations to be initially on the order of 186 to 205 kg. due to a solenoid . pull on each cable 30 on the order of 37 to 56 kgs. Thus, when the flywheels reach the ram, the initial normal force against the ram, indicated by the arrows 172 of Fig. 12, should be approximately 373 kgs.
As the flywheels drive the ram and tend to be spread apart by the taper, the normal force increases through the reac¬ tion of flywheel inertia and as the ram drive becomes re¬ generative, the toggle action further increases the normal force to approximately 933 to 1306 kgs. Then, depending upon the coefficient of friction of the friction material, the necessary driving force is developed to set the nail or the like. While the theoretical coefficient of friction for highly polished, cold rolled steel against brake lining or phenolic resin with asbestos fibers is approximately 0.3, in practice it may be found to be between 0.15 and 0.3.
For a 1.58 cm. clearance between the driver blade B and the head of the nail, the total movement of the ram ui will correspond to a distance slightly greater than the length of the nail, i.e. slightly more than 8.25 cm. for a 16-penny nail, plus the 1.58 cm. clearance. It can be calculated that the time which the ram requires to move this distance, in order to develop the necessary kg. meters of energy for driving the nail, is on the order of 3 to 4 milliseconds. However, the pulse to the 24 volt solenoids, such as from 50 to 80 amperes at 110 volts, may be con¬ trolled to be on the order of 8.33 milliseconds, due to the time required to move the flywheels into position against the ram and a slight initial slippage. The time for return of the motors and flywheels to the initial posi¬ tion, return of the ram to its initial position and the acceleration of the flywheels to the speed desired prior * to the next impact stroke, may be on the order of 128 mil¬ liseconds, which is considerably less time than it would require the user of the tool to reposition the tool for driving another nail. However, there may be operations, such as factory operations, involving a stationary tool in which the nails can be driven with a 128 millisecond time period between the termination of the driving of one nail and the start of driving the next nail. The 128 mil¬ liseconds is thus an approximate minimum time for the tool to be ready to drive the next nail. In order to develop the necessary kg. meters of energy in the flywheels, it is calculated that, at 20,000 r.p.m. , each 0.13 kg. flywheel will be able to store approximately 93.3 kg. meters of energy. For lesser speeds, the stored energy decreases. Since the total of 186.6 kg. meters is greater than the kg. meters required to accelerate and drive the ram, as described above, the speed of the fly¬ wheels may be less, such as a speed on the order of 10,000 to 14,000 r.p.m. In addition, with the ram engaging forces available, it was found that excess slippage was apparently occurring above 14,000 r.p.m. for the flywheels, since nails driven at 14,000 r.p.m. and down to 10,000 r.p.m. would not be completely driven at speeds above 14,000 r.p.m. However, if higher ram engaging forces were
- y∑E available, speeds over 14,000 r.p.m. would probably be successful. In order to have ample reserve speed and also to provide acceleration at a lower speed, it may prove de¬ sirable to select a motor having a top speed of, say, 22,00 r.p.m. but a development of high torque over a lower speed range, such as 7,000 to.14,000 r.p.m. A universal type mo¬ tor, for which, as the speed drops, full voltage and amper¬ age are applied, is desirable. Also, the initial speed of the motor may be reduced by an SCR type control system, as in the motor control box 72. For battery operation, rather than electricity supplied through a cord, the motors should be selected accordingly.
As the flywheels drive the ram and kinetic energy is transferred from the flywheels to the ram, the speed of the flywheels will, of course, decrease, such as a reduction to approximately 7,000 r.p.m. at the point of disengagement of the flywheels from the ram, i.e. when the flywheels rea.ch the bevels 19 of Figs. 12 and 14. Thus, the motors should be able to increase the speed of the flywheels from on the order of 7,000 r.p.m. to 10,000 r.p.m. or 14,000 r.p.m., for example, prior- to driving the next nail..
For normal forces of the magnitudes referred to, the stress on the tension rod T may be found to be on the order of 559.8 to 1119.6 kg. meters, with an additional 10% of that amount on the end cap 71 of the housing. As indicated, with two tension rods, one intermediate the flywheels and the motors, as shown, and the other beyond the opposite ends of the motors, the stresses will tend to become more nearly equalized on both tension rods. For driving nails as large as 16-penny, the bumpers 54 of Fig. 6 may be con¬ structed to absorb on the order of 93.3 kg. meters, in the event the ram is driven on an impact stroke but does not drive a nail or otherwise perform its impact function. A further alternative or additional safety device, as in Figs. 23 and 24, may include a link 180 mounted on an intermediate pivot 181 below the motors M and M' and extending longitudinally below the space between the motor housings. At its rear end, the link has an upstanding a^HQ__ 182 having a stop block 183 at its upper end normally dis¬ posed between the motor housings to prevent the motors and flywheels being moved toward each other and thereby deter the linear movement of the ram. A tension spring 184 pulls on the link, adjacent its front end, to maintain the link and its stop block in the normal position between the motor housings. A rod 185 is connected to the front end of link 180, while abutments 186 and 186* on the motor housings engage stop block 183 if the motors tend to pivot toward each other. Rod 185 is connected to slide 36 by a rod sim¬ ilar, to rod 35 of Fig. 5 and is moved upwardly by engage¬ ment with the work piece by ring 37 on slide 36 to move the front end of the link upwardly to pivot the link and move the block downwardly from between the motor housings, thereby rendering the stop block inoperative and permitting the motor housings and flywheels to be pivoted toward each other and cause the flywheels to drive the rams, when the trigger is pressed to energize the solenoids.
As will be evident, for driving different'nails in different materials, or for other applications in which the kinetic energy desirable for an impact may vary, there are several variations which may be utilized to accommodate these differences. One variation is to use flywheels of different weights for different wood properties or other variations in kinetic energy required. Another is to uti¬ lize a motor control in which the r.p.m. of the motors may be varied, such as between the 10,000 and 14,000 r.p.m. referred to above for different woods or nails, or other variations in impact requirements. Still another is to time the pulse supplied to the solenoids, so that the fly¬ wheels will tend to disengage from the ram before the end of the ram is reached. This variation would be usable pri¬ marily when there is a large difference between the kinetic energy required for the different operations. Although a preferred embodiment of this invention, as well as alternative constructions, have been illustrated and described, it will be understood that other embodiments may exist and that various changes may be made, without departing from the spirit and scope of this invention.

Claims

Claims What is claimed is:
1. In an impact tool for producing an impact against an object: (a) elongated ram means mounted for movement along a longitudinal path, in opposite directions; (b) a pair of oppositely rotating bodies for storing energy and mounted on opposite sides of said ram means for movement toward and away from said ram path, each said body having an axis of rotation generally perpendicular to the direction of movement of said ram means;
(c) means for moving said bodies substantially simul- taneously toward and into engagement with said ram means on the respective side thereof, whereby said rotating bo- dies impart linear movement to said ram means;
(d) said moving means including force multiplying means and means for moving said force multiplying means;
(e) said means for moving said force multiplying means being electrically actuated;
(f) means for moving said bodies away from the path of said ram means; and
(g) means for returning said ram means to its initial position.
2. In an impact tool as defined in claim 1, 'wherein: said force multiplying means has a greater mechanical advantage at the start of movement and a lesser mechanical advantage as movement continues.
3. In an impact tool as defined in claim 1, wherein: said moving means is constructed and arranged to move both said bodies toward and into engagement with said ram means substantially simultaneously on opposite sides there- of.
4. In an impact tool for producing an impact against an object: (a) elongated ram means mounted for movement along a longitudinal path, in opposite directions; (b) a pair of oppositely rotating bodies for storing energy and mounted on opposite sides of said ram means for movement toward and away from said ram path, each said body having an axis of rotation generally perpendicular to the direction of movement of said ram means;
(c) means for moving said rotating bodies substantial- ly simultaneously toward and into engagement with said ram means on the respective side thereof, whereby said rotat- ing bodies impart linear movement to said ram means;
(d) said moving means including force multiplying means and means for moving said force multiplying means;
(e) said force multiplying means having a greater mechanical advantage at the start of movement and a lesser mechanical advantage as movement continues and including at least one pair of pivoted links in an essentially straight line position when said rotating body is spaced away from said ram means;
(f) means for moving said bodies away from the path of said ram means; and
(g) means for returning said ram means to its initial position.
5. In an impact tool for producing an impact against an object: (a) elongated ram means mounted for movement along a longitudinal path, in opposite directions; (b) a pair of oppositely rotating bodies for storing energy and mounted on opposite sides of said ram means for movement toward and away from said ram means, each said body having an axis of rotation generally perpendicular to the direction of movement of said ram means;
(c) means for moving said bodies substantially simul- taneously toward and into engagement with said ram means, whereby said rotating bodies impart linear movement to said ram means;
(d) said means for moving said bodies toward and into engagement with said ram means includes force multiplyinc means and electrically actuated means for moving said force multiplying means;
(e) said force multiplying means includes at least one essentially non-stretchable cable connected at an intermediate position to said electrically actuated means but in an essentially straight line position when said ro¬ tating body is spaced away from said ram means; (f) means for moving said bodies away from the path of said ram means; and (g) means for returning said ram means to its initial position.
6. In an impact tool as defined in claim 5, including: connections from said non-stretchable cable for moving each rotating body into engagement with said ram.
7. In an impact tool for producing an impact against an object: (a) elongated ram means mounted for movement along a longitudinal path, in opposite directions; (b) a pair of oppositely rotating bodies for storing energy and mounted on opposite sides of said ram means for movement toward and away from said ram means, each said body having an axis of rotation generally perpendicular to the direction of movement of said ram means;
(c) means for moving said rotating bodies substantial- ly simultaneously toward and into engagement with said ram means on the respective side thereof, whereby said rotating bodies impart linear movement to said ram means;
(d) means for returning said ram means to its initial position including a series of cords connected to said ram means extending essentially in the direction of said longi- tudinal path and comprising material having the property of rubber in elongating generally equally along the length thereof during an impacting movement of said ram;
(e) a support for said cords disposed in fixed posi- tion in the direction of movement of said ram, but spaced from the opposite end of said ram; 23 (f) said cords extend from said support longitudinal¬ ly of the direction of movement of said ram to a point on
25 said ram at one side of the central longitudinal axis thereof, thence transversely of said ram to a second point
27 similarly spaced from said axis of said ram but on the op¬ posite side thereof, thence longitudinally to said support;
29 and
(g) means for moving said bodies away from said ram
31 means.
8. In an impact tool for producing an impact against an object, comprising: 3 (a) an elongated ram means mounted for movement along a longitudinal path, in opposite directions; 5 (b) a first rotating body for storing energy and moun¬ ted on one side of said ram means for movement toward and 7 away from said ram means, said body having an axis of rota¬ tion generally perpendicular to the direction of movement 9 of said ram means;
(c) a second rotating body rotating in an opposite di¬ ll rection to the rotation of said first body and about an axis parallel to the axis of said first body; 13 (d) a separate member to which is transmitted forces and components of forces produced by rotation of the cor- 15 responding rotating body;
(e) tension means connecting said members for receiv- 7 ing and equalizing forces and components of forces pro¬ duced by the rotation of said bodies; 9 (f) means for moving said bodies substantially simul¬ taneously toward and into engagement with said ram means 1 on opposite sides thereof, whereby each said rotating body imparts linear movement to said ram means; 3 (g) means for moving said bodies away from the path of said ram means; and 5 (h) means for returning said ram means to its initial position.
9. In an impact tool as defined in claim 8, wherein:
W l said rotating bodies are pivoted on parallel pivot 3 shaf s; and said tension means comprises a tension rod extending 5 between said pivot shafts to equalize forces and components of forces in the direction of said tension rod.
10. In an impact tool as defined in claim 9, wherein: each rotating body comprises a flywheel mounted on a
3 shaft coaxially with a motor for driving said flywheel; and 5 said tension rod is disposed in the space around said shaft between each flywheel and its corresponding motor.
11. In an impact tool as defined in claim 9 , wherein: the angle for each rotating body between a plane ex-
3 tending through said pivot shaft and the axis of rotation of said rotating body prior to movement toward said ram
5 and a plane extending through said pivot shafts and said tension rod, is on the order of 9° to 20°.
12. In an impact tool for producing an impact against an object:
-3 (a) elongated ram means provided with a lateral wing at each side and mounted for movement along a longitudinal 5 path in opposite directions, each said wing having a lon¬ gitudinal slot; 7 (b) a pair of oppositely rotating bodies for storing energy and mounted on opposite sides of said ram means for 9 movement toward and away from said ram means, each said body having an axis of ..rotation generally perpendicular 1 to the direction of movement of said ram means;
(c) means for moving said rotating bodies substantial- 3 ly simultaneously toward and into engagement with said ram means on the respective side thereof, whereby said rotating 5 bodies impart linear movement to said ram means;
(d) guide rods for said ram disposed longitudinally 7 and extending through the corresponding slot in each wing;
(e) means for moving said bodies away from the path of said ram means; and
(f) means for returning said ram means to its initial position.
13. In an impact tool as defined in claim 12, includ¬ ing: shock absorbing bumpers spaced laterally to permit a portion of said ram, between said wings and extending in the direction of movement of said ram, to move between said bumpers on an impact movement; and said bumpers being positioned for engagement by the respective wing of said ram upon movement of said ram be- yond a predetermined distance.
14. In an impact tool as defined in claim 12, includ¬ ing: means for retaining said guide rods laterally with respect to the ram path; and removable means for retaining said guide rods longi¬ tudinally but permitting longitudinal removal of said rods from said lateral retaining means.
15. In an impact tool for producing an impact against an object: (a) elongated ram means mounted for movement along a longitudinal path, in opposite directions; (b) a pair of oppositely rotating bodies for storing energy mounted on opposite sides of said ram means for movement toward and away from said ram, each body having an axis of rotation generally perpendicular to the direc- tion of movement of said ram means;
(c) means for moving said rotating bodies substantial- ly simultaneously toward and into engagement with said ram means on the respective side thereof, whereby said rotating bodies impart linear movement to said ram means;
(d) force multiplying means connected by cable to electrical solenoid means for moving said bodies toward and into engagement with said ram means; ' (e) means for moving said bodies away from the path of said ram means; and (f) means for returning said ram means to its intial position.
16. In an impact tool as defined in claim 15, wherein: said solenoid cable connects a plunger of said solen- oid means to a pivot center of said force multiplying means.
17. In an impact tool as defined in claim 16, wherein: said force multiplying means comprises a pair of links pivoted together and positioned in a substantially straight line relation for the beginning of movement; a movable bar is pivotally connected to a movable end of one said link; a cable connects said bar to said rotating body; and a pivoted arcuate guide engages said solenoid cable.
18. In an impact tool as defined in claim 17, wherein: said force multiplying means includes two pairs of pivoted links mounted in essentially parallel, spaced rela¬ tion, with a cable from a separate solenoid connected to the pivot connection between each pair of links; and the movable end of one link of each pair is pivotally connected to said movable bar.
19. In an impact tool as defined in claim 16, wherein said force multiplying means includes: a first cable having a fixed end and a movable end having cable connections for moving said rotating bodies simultaneously; a second cable having one end fixed and the opposite end connected to the movable end of said first cable, said second cable being essentially transverse to said first cable; said solenoid cable connected to said plunger of said solenoid means and to an intermediate point on said first cable between said fixed end and said movable end; and said first cable being in an essentially straight line position prior to movement of said rotating bodies and said solenoid cable exerting a pull at said inter¬ mediate point substantially transverse to said straight line.
20. An impact tool for producing an impact against an object comprising: (a) elongated ram means mounted for movement along a longitudinal path, in opposite directions; (b) oppositely rotating bodies for storing energy and mounted on opposite sides of said ram means, said bodies having parallel axes of rotation, which axes are generally perpendicular to the direction of movement of said ram means;
(c) means for causing said bodies to engage said ram means on opposite sides thereof substantially simultaneous¬ ly, whereby said rotating bodies impart linear movement to said ram means;
(d) means for moving said bodies from the path of said ram means;
(e) means for returning said ram means to its initial position;
(f) coaxial motors having housings of a diameter cor- responding to said rotating bodies for rotating said bodies;
(g) means including a pivoted lever for deterring said linear movement of said ram, said lever being disposed below the space between said motor housings and having an upward- ly extending arm provided with a block whose normal posi¬ tion is between said motor housings , to prevent said motors and rotating bodies from being moved to a position of en¬ gagement by said rotating bodies with said ram; (h) resilient means for urging said lever in a direc¬ tion to move said block between said motor housings; (i) a movable element engageable with a work piece associated with the operation of said ram; and (j) means associated with said movable . element
- JRE including a rod engageable with said lever for pivoting said lever to move said block from between said motor hous¬ ings a distance sufficient to permit said rotating bodies to be moved into engagement with said ram.
21. An impact tool for producing an impact against an object, comprising: (a) elongated ram means mounted for movement along a longitudinal path, in opposite directions; (b) oppositely rotating bodies for storing energy and mounted on opposite sides of said ram means for movement toward and away from said ram means, said bodies having parallel axes of rotation, which axes are generally per- pendicular to the direction of movement of said ram means;
(c) means for moving said bodies toward and into en- gagement with said ram means substantially simultaneously on opposite sides thereof, whereby said rotating bodies impart linear movement to said ram means;
(d) each side of said ram means being provided with a taper extending outwardly opposite the direction of said linear movement of said ram means at a position of initial engagement of said ram means by said rotating bodies, whereby movement of said ram means initiated by said rotat- ing bodies forces said rotating bodies apart and thereby increases the force normal to the sides of said ram means while said rotating bodies engage said taper;
(e) means for moving said bodies away from the path of said ram means; and
(f) means for returning said ram means to its initial position.
22. An impact tool as defined in claim 21, wherein: said taper of said ram means is on the order of 0.0254 cm. to 0.0635 cm. in 1.27 cm. of length of said ram.
23. An impact tool as defined in claim 21, wherein: said ram means is provided on each side with friction surface means. ^
24. An impact tool as defined in claim 23, wherein: said friction surface means is substantially uniform in thickness; and said ram means includes a body having sides provided with said taper.
25. An impact tool as defined in claim 23, wherein: said ram means includes a body having parallel sides; and said friction surface means is provided with said taper.
26. An impact tool as defined in claim 21, wherein: said ram means includes a body provided with said ta- per; and said rotating bodies are provided with friction sur- face means for engagement with said respective sides of said ram.
27. An impact tool as defined in claim 21, wherein: said ram means is provided at the end opposite . the end of initial engagement with a taper on each side exten¬ ding inwardly in a direction opposite said linear movement of said ram means.
28. A method of operating an impact tool which in¬ cludes a ram movable along a predetermined linear path to produce an impact against an object, comprising:
(a) imparting rotation in opposite directions to first and second bodies rotating about axes perpendicular to the path of movement of said ram; (b) establishing a separate member for each said ro¬ tating body and transmitting forces and components of forces produced by rotation of each body to the correspond¬ ing member; (c) equalizing said forces and components of forces through tension means connecting said members; (d) positioning said ram at an initial end of its \J E path but in position for engagement by said rotating bodies against a corresponding side of said ram;
(e) moving said rotating bodies toward said ram until each said body engages said ram, whereby said bodies move said ram along its path from said initial position to pro- duce said impact, said ram being disengaged from said ro¬ tating bodies for travel for a predetermined distance; (f) returning said rotating bodies to the initial position thereof; and (g) returning said ram to the initial position there¬ of.
29. A method as defined in claim 28, including: establishing a pivotal axis for each rotating body parallel to the axes of rotation of said bodies and spaced equidistantly from the path of said ram; moving each said rotating body about its pivotal axis into engagement with said ram; and transmitting forces and components of forces in direc¬ tions between said pivotal axes through at least one tens- ion bar connecting said pivotal axes of said bodies to equalize said forces.
^TJ £4
EP19820900418 1981-12-10 1981-12-10 Electrically driven impact tool. Ceased EP0096029A4 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1981/001649 WO1983002082A1 (en) 1981-12-10 1981-12-10 Electrically driven impact tool and method of operating the same

Publications (2)

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EP0096029A1 true EP0096029A1 (en) 1983-12-21
EP0096029A4 EP0096029A4 (en) 1984-04-27

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WO (1) WO1983002082A1 (en)

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Publication number Publication date
EP0096029A4 (en) 1984-04-27
WO1983002082A1 (en) 1983-06-23
JPS58502044A (en) 1983-12-01

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