US3828863A

US3828863A - Combined portable electric impact wrench and chipping hammer

Info

Publication number: US3828863A
Application number: US00376935A
Authority: US
Inventors: W Schmid; K Wanner; R Hahner; G Hansel; M Bleicher; J Falchle
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1972-08-31
Filing date: 1973-07-06
Publication date: 1974-08-13
Anticipated expiration: 1991-08-13
Also published as: JPS4968367A; JPS5613596B2; IT993805B; NL7311947A; BR7306718D0; ES418342A1; DE2242944A1; CH560313A5; DE2242944B2; FR2197680B1; FR2197680A1; AU5984873A; GB1447867A

Abstract

A combined portable electric impact wrench and chipping hammer wherein the tool holder is movable axially by a pneumatic impeller which receives motion from the output shaft of an electric motor by way of a first transmission and a clutch which latter can be disengaged at the will of the user, and wherein the tool holder is rotatable by way of a multi-speed second transmission having a neutral position. By placing the second transmission in neutral position, the user can reciprocate the tool holder by way of the first transmission when the clutch is engaged. When the clutch is disengaged, the user can rotate the tool holder at one of several speeds by way of the second transmission. The second transmission can drive the tool holder at a selected speed while the clutch is engaged so that the tool holder moves axially and rotates about its axis. The second transmission embodies or is combined with a safety clutch which is disengaged when the tool holder offers excessive resistance to rotation.

Description

United States Pa tent [191 Bleicher et al.

1111 3,828,863 51 Aug. 13, 1974 [54] COMBINED PORTABLE ELECTRIC 3,720,269 3/1973 Wanner et al. 173/48 IMPACT WRENCH AND H N 3,774,699 11/1973 Schuclt 173/48 HAMMER 3,789,993 2/1974 Jareck1.... 173/48 3,791,461 2/1974 Rosselet 173/48 [75] lnventorsi Manfred Bleicher, Leinfelden; Jorg al l pfl g i ar Primary Examiner-David H. Brown Kemnat; Germ)t Hansel Attorney, Agent, or Firm-Michael S. Striker Stuttgart-Plieningen; Wolfgang Schmid, Plattenhardt; Karl Wanner, [57] ABSTRACT Echterdmgen, all of Germany A C d Portable 16 p t h d om me e c 1 ac wrenc an Asslgneei RllbertBoSch GmbH, Stuttgart, chipping hammer wherein the tool holder is movable Germany axially by a pneumatic impeller which receives motion [22] Filed. July 6 1973 from the output shaft of an electric motor by way of a first transmission and a clutch which latter can be dis- PP 376,935 engaged at the will of the user, and wherein the tool holder is rotatable by way of a multi-speed second [30] Foreign Application Priority Data transmission having a neutral position. By placing the A 31 1972 G 2242944 second transmission in neutral pos1t1on, the user can "many reciprocate the tool holder by way of the first transmission when the clutch is engaged. When the clutch [52] US. Cl 173/48, 173/109, 1177330111282, is disengaged the user can rotate the tool holder at one of several speeds by way of the second transmis- [511 i Eozd 7/02 Ezlb 5/00 E216 3/02 sion. The second transmission can drive the tool [58] Field of Search 173/48 47 holder at a selected speed while the clutch is engaged 'so that the tool holder moves axially and rotates about [56] References Cited its axis. The second transmission embodies or is com- UNITED STATES PATENTS bined with a safety clutch which is disengaged when 3,114,423 12/ 1 3 Na lun 17 /48 X the tool holder offers excessive resistance to rotation.

3,463,246 8/1969 Bronnert... 173/47 3,507,337 4/1970 Chromy 173/48 x 26 Claims, 7 Drawing Figures PArmmw -r 3.828.863

sum

1 or 5 Fig. 1

PAIENIEDAUBWB" f 3.828.863 sumu nrs I I Fig. 6

COMBINED PORTABLE ELECTRIC IMPACT WRENCH AND CHIPPING HAMMER BACKGROUND OF THE INVENTION The present invention relates to portable power tools in general, especially to electrically operated power tools, and more particularly to improvements in multiple-purpose portable power tools. Still more particularly, the invention relates to improvements in portable power tools of the type wherein a holder for a screwdriver, chisel, drill or another material removing or material penetrating tool is movable axially and is also rotatable about its axis.

A presently known combined portable impact wrench and chipping hammer which is disclosed in Swiss Pat. No. 507,066 comprises a tool holder which can receive axial impulses from a pneumatic impeller and can be rotated at a single speed by way of a transmission which receives torque from the rotary output member of the prime mover. The transmission is a stepdown transmission and the output shaft of the prime mover further serves to actuate the impeller. A drawback of the just described power tool is that the tool holder can only be rotated at a single speed and that the impeller cannot be deactivated when the prime mover rotates its output member. This limits the utility of the power tool, i.e., the latter can be put to a very limited number of uses especially since it is not provided with means for permitting the attachment of a variety of differently dimensioned material removing or material penetrating tools.

U.S. Pat. No. 3,500,696 discloses a portable electric drill wherein the tool holder cannot move axially but can be rotated at two different speed. The utility of this power tool is also limited due to the absence of an impeller mechanism for the tool holder.

SUMMARY or THE INVENTION An object of the invention is to provide a portable power tool which is more versatile than presently known portable power tools because it can be readily converted from use as an impact wrench or the like, to use as a chipping hammer or the like, or to use as a simple power drill or the like.

Another object of the invention is to provide a portable power tool of the just outlined character which can be converted from one type of operation to a selected other type of operation while in actual use, which can rotate a tool at several speeds, and which embodies novel and improved safety features to prevent damage to its parts and/or an injury to the user.

A further object of the invention is to provide novel and improved means of transmitting motion from the prime mover to the axially movable rotary tool holder of a combined chipping hammer and impact wrench.

An additional object of the invention is to provide a portable power tool with a novel and improved multispeed transmission for rotating the tool holder.

Still another object of the invention is to provide a portable power tool with novel and improved control means for changing the speed ratio of and for deactivating the just outlined transmission.

The invention is embodied in a portable'power tool, particularly in a combined electric impact wrench and chipping hammer, which comprises a housing, a prime mover (preferably an electric motor) mounted in the housing and having a rotary output member, a tool LII holder which is rotatably and axially movably mounted in the housing and has'means for removably supporting a chisel, drill or another material penetrating and/or removing tool, impeller means (preferably operating with a cushion of compressed gaseous fluid) which is mounted in the housing and is actuatable to transmit to the tool holder recurring axial impluses, first transmission means which is mounted in the housing and has an input element receiving torque from the output member of the prime mover, a mobile output element for actuating the impeller means, and clutch means for moving the output element in response to rotation of the input element, first control means for disengaging the clutch means at the will of the operator to thereby deactivate the impeller means while the prime mover is free to rotate its output member, multi-speed second transmission means (preferably a two-sp eed gear transmission) mounted in the housing between the tool holder and the output member of the prime mover and having a plurality of different speed ratios and a neutral position, and second control means which is actuatable independently of the first control means to select the speed ratio or the neutral position of the second transmission means. This enables the operator to cause the tool holder to move axially under the action of the impeller means while the second transmission means is in the neutral position (i.e., while the tool holder'does not receive torque from the second transmission means) or while the second transmission means drives the tool holder at one of several speeds, or to disengage the clutch means of the first transmission means (so that the output element of the first transmission means is idle and fails to actuate the impeller means) while the second transmission means rotates the tool holder at a selected speed.

It is further desirable to provide the power tool with a safety clutch which can form part of the second transmission means and serves to disconnect the prime mover from the tool holde when the latter offers excessive resistance to rotation, even when the second control means has been actuated by the operator to assume a position corresponding to one of the several speed ratios of the second transmission means.

To novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved portable power tool itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary longitudinal vertical sectional view of a portable power tool which embodies one form of the invention.

FIG. 2 is a sectional view as seen in the direction of arrows from the line II-II of FIG. 1;

FIG. 3 is a fragmentary sectional view as seen in the direction of arrows from the line III-III of FIG. 2;

FIG. 4 is a fragmentary partly elevational and partly longitudinal vertical sectional view of a second portable power tool;

FIG. 5 is a fragmentary longitudinal vertical sectional view of a third power tool;

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 to 3, there is shown a spadehandle portable power tool which can be used as a chipping hammer and/or as an impact wrench. The housing of the power tool comprises a front section 1, a median section 2 and a rear section 3 which latter is with a spade handle 3a (only partially shown). The

housing sections

1,2 and 3 are separably connected to each other by means of suitable bolts, screws or analogous fasteners, not shown. The lower portion of the median housing section 2 receives a prime mover here shownas an electric motor 4 whose rotor 5 is connected with an output shaft 6 which is mounted in antifriction bearings provided therefor in the front and median housing-

sections

1 and 2. As shown in FIG. 1, the front end portion of the output shaft 6 is rotatable in a front antifriction bearing 7 having roller-shaped rolling elements and being located in front of a fly wheel 6a. The rear portion of the output shaft 6 is rotatable in a rear antifriction bearing 8 having spherical rolling elements. The rearmostportion of the output shaft 6 constitutes or is rigidly connected to a pinion or gear 9 which is in mesh with a gear 11 secured to an intermediate shaft 10. The front end portion of the intermediate shaft 10 is rotatable in a first antifriction bearing 10a which is mounted in an internal partition 2a of the section 2. The rear portion of the intermediate shaft 10 is rotatable in a second antifriction bearing 1012 which is installed in a portion 3b of the rear housing section 3. That portion of the intermediate shaft 10 which extends between the front bearing 10a and the gear 11 carries a smaller gear 12 and a larger gear 13. The

gears

12 and 13 respectively mesh with a larger gear and a smaller gear 16 both rotatably mounted on a hollow shaft 14 which is rotatable in

antifriction bearings

27 and 28 provided therefor in the housing section 2. The

gears

15 and 16 are immediately adjacent to each other and can be moved axially of the hollow shaft 14 by a shifter fork 17 shown in FIGS. 2 and 3. The rear portion of the hollow shaft 14 is provided with an annulus of external torque receiving teeth 18 which can be moved into mesh with the internal torque transmitting teeth of the gear 15 or with the internal torquetransmitting teeth 21 of the gear 16. The space 19 between the

internal teeth

20 and 21 is wide enough to receive the external teeth 18 when the multi-speed transmission including the

gears

12, 13, 15, 16 and hollow shaft 14 is in neutral position. As shown'in FIG. 2, the sleeve 14 is provided with four equidistant external torque receiving teeth 18.

The shifter fork 17 for the

gears

15 and 16 is recipro cable along a guide rod 22 (shown in FIGS. 2 and 3) which is mounted in the housing section 2, The means for moving the shifter fork 17 lengthwise of the guide rod 22 comprises a substantially rectangular leaf spring 23 having two

prongs

23a and 23b which flank an eccentric pin provided on a control shaft 24 having a portion extending from the housing section 2 immediately adjacent to the housing section 3 and being pro- .vided with a handle 26. The handle 26 can be pivoted between three different positions including a lowerspeed setting of the multi-speed transmission, a higherspeed setting, and the aforementioned neutral position. As shown in FIG. 2, the shaft 24 extends substantially at right angles to a vertical portion or wall 2b of the intermediate housing section 2. The parts 17 and 23-26 together constitute a control device which can be actuated by hand to select the speed and the neutral position of the transmission 9-16.

The rear antifriction bearing 28 for the hollow shaft 14 comprises roller-shaped rolling elements and the front antifiction bearing 27 for the hollow shaft 14 comprises spherical rolling elements. The front bearing 27 is immediately adjacent to the front housing section 1. An intermediate portion of the hollow shaft 14 between the

bearings

27 and 28 is provided with several equidistant radially extending openings or cutouts 29 for spherical torque transmitting elements 30 forming part of a safety clutch. The median portions of the torque transmitting elements 30 are normally held in the respective opening 29 by a pressure ring 31 which is biased forwardly by a strong helical spring 32 reacting against a retainer 33 which abuts against an external shoulder of the hollow shaft 14 in front of the rear bearing 28. The front side of the pressure ring 31 is provided with two mutually inclined outwardly and forwardly flaring conical surfaces 34 and 34a. When the outermost portion of the spherical torque transmitting elements 30 are engaged by the inner conical surface 34, their innermost portions are caused to extend inwardly beyond the respective openings 29 so that they extend into axially parallel flutes 35 provided in a sleeve 36. The outer conical surface 34a of the pressure ring 31 tapers to a greater extent that the inner conical surface 34 (i.e., the conical surface 34a makes with the axis of the hollow shaft 14 an acute angle which is larger than the actue angle between the axis of the shaft 14 and the inner conical surface 34) so that the surface 34a enables the torque transmitting elements 30 to move radially outwardly and to thereby abruptly disconnect the sleeve 36 from the hollow shaft 14 in response to a predetermined resistance which the rotary and axially movable tool holder 37 of the power tool offers to rotation. The tool holder 37 has a rearwardly extending portion or shank 37a provided with axially parallel external grooves or flutes 39 for portions of balls 38 which are mounted in radially extending openings of the sleeve 36. The balls 38 compel the sleeve 36 to rotate with the tool holder 37 or vice versa while the flutes 39 allow the shank 37a to move axially relative to the sleeve 36. The front portion of the tool holder 37 is provided with internal threads 37b which can mesh with the external threads of a suitable tool T (see FIG. 4) such as a chisel, screwdriver or the like. A first sealing ring 40 is interposed between the foremost portion of the sleeve 36 and the front housing section 1. A second sealing element 41 is received in an internal groove of the sleeve 36 and engages the peripheral surface of the shank 37a. The foremost portion of the sleeve 36 is further provided with a flange or collar 42 having an annulus of teeth 43 separated by axially parallel grooves each of which can receive a projection 45 provided on a transverse blocking shaft 44 which is rotatably mounted in the front housing section 1. A portion of the blocking shaft 44 extends outwardly from the housing section 1 and is provided with a handle (not shown) similar to the handle 26 of FIG. 2 to enable an operator to move the projection 45 into or from engagement with the adjacent teeth 43 of the collar 42. When the projection 45 engages the adjacent teeth 43, the sleeve 36 and the tool holder 7 are held against rotation with the hollow shaft 14 of the multi-speed transmission 9-16.

The multi-speed transmission 9-16 can rotate the tool holder 37 at two different speeds. Furthermore, and as explained above, the handle 26 of the control device 17, 23-26 can be moved to a position corresponding to the neutral position of the multi-speed transmission in which position the

gears

15 and 16 can rotate relative to thehollow shaft 14 so that the tool holder 37 can be held by the projection 45 of the blocking shaft 44 against angular movement. The wall 21; of the housing section 2 can be provided with indicia to facilitate the solution of a desired position for the handle 26. Analogous indicia (e.g., ON" and OFF can be provided on the front housing section 1 adjacent to the handle for the blocking shaft 44.

THe power tool of FIGS. 1 to 3 further comprise a second transmission serving to actuate at the will of the operator a pneumatic impeller which is installed in the hollow shaft 14 and is adapted to transmit to the shank 37a of the tool holder 37 recurrent axial impulses in a direction to the left, as viewed in FIG. 1, to thereby drive the top of a tool which is removably connected to the holder 37 by threads 37b into a workpiece, such as a piece of concrete, wood, brick or the like. The impeller comprises a cylinder 61 which is movable axially in the interior of the hollow shaft 14 and receives a piston or plunger 62 which is adjacent to the rear end of the shank 37a. When the cylinder 61 is caused to move forwardly, the cushion of compressed air in its chamber 61a urges the piston 62 forwardly and causes it to strike against the rear end of the shank 37a.

The aforementioned transmissioned which serves to reciprocate the cylinder 61 of the

impeller

61, 62 comprises an input element in the form of a bevel gear 46 which is secured to the intermediate shaft 10 adjacent to the gear 11 and is in permanent mesh with a second bevel gear 48 mounted on a hollow clutch shaft 47. The shaft 47 is normal to the intermediate shaft 10 and has radially extending opening 51' for spherical torque transmitting elements 51 portions of which extend into axially parallel internal grooves or recesses 52 of the bevel gear 48 when the positive clutch including the hollow shaft 47, bevel gear 48 and spherical elements 51 is engaged. Portions of the spherical elements 51 are normally held in the grooves or recesses 52 by a conical shoulder of a displacing member or bolt 54 which is movable axially in the hollow shaft 47 between the illustrated operative position and an inoperative position and is biased to the operative position of FIG. 1 by a helical spring 53 which reacts against an internal shoulder of the hollow shaft 47. The control means for engaging or disengaging the positive clutch including the spherical elements 51 comprises a shaft 55 having an eccentric pin 56 which can move displacing member or bolt 54 upwardly, as viewed in FIG. 1, against the opposition of the spring 53 whereby the bolt 54 assumes its inoperative position and maintains its groove 57 in register with the spherical elements 51. This enables the spherical elements 51 to penetrate into the groove 57 whereby the bevel gear 48 is disengaged from the hollow shaft 47. The upper end of the hollow shaft 47 carries a disk 58 provided with an eccentric pin 59 for a connecting rod 60 which constitutes a mobile output element of the transmission for the

pneumatic impeller

61, 62 and is coupled to the cylinder 61 by a pin 60a. The hollow shaft 47 is rotatable in a first antifriction bearing 49 provided therefor in the portion 3b of the rear housing section 3 below the disk 58, and in a second antifriction bearing 50 installed in the housing section 3 above the bevel gear 48. The shaft 55 for the eccentric pin 56 extends from the housing section 3 and is provided with a handle (not shown) similar to the handle 26 of FIG. 2 which enables the operator to engage or disengage the positive clutch between the disk 58 and the bevel gear 46.

The piston 62 of the pneumatic impeller for the tool holder 37 is received in the cylinder 61 with minimal clearance. The hollow shaft 14 can rotate about the cylinder 61.

The operation is as follows:

When the parts of the multi-speed transmission 9-16 for rotating the tool holder 37 at several speeds assume the positions shown in FIGS. 1 and 2, the torque receiving teeth 18 of the hollow shaft 14 are located in the space 19 so that the

gears

15 and 16 can be rotated by the electric motor 4 but cannot drive the hollow shaft 14. Thus, the transmission is in its neutral position and the projection 45 of the blocking shaft 44 can be moved into engagement with the adjacent teeth 43 of the collar 42 so as to prevent rotation of the tool holder 37 and sleeve 36. By moving the eccentric pin 56 of the shaft 55 to the angular position shown in FIG. 1, the operator engages the positiveclutch including the spherical elements 51 so that the bevel gear 48 can drive the hollow shaft 47 and the disk 58. Consequently, when the motor 4 is on, the connecting rod 60 reciprocates the cylinder 61 and the piston 62 transmits recurrent axial impulses to the shank 37a so that the tip of a tool which is removably mounted in the holder 37 can be driven into a workpiece, such as a block of concrete or rock.

If the operator thereupon decides to set the tool holder 37 in rotary motion, the projection 45 is first disengaged from the collar 42 and the shaft 24 for the eccentric pin 25 is rotated in a clockwise direction, as

viewed in FIG. 3, whereby the pin 25 flexes the adja-- cent prong 23b of the leaf spring 23. The leaf spring 23 tends to move the shifter fork 17 along the guide rod 22 so as to move the

gears

15 and 16 in a direction to the right, as viewed in FIG. 3, and to thereby engage the torque receiving teeth 18 of the hollow shaft 14 with the torque transmitting teeth 20 of the larger gear 15 which meshes with the smaller gear 12 of the intermediate shaft 10. The hollow shaft 14 is then rotated by the pinion 9, gear 11, shaft 10, gear 12, and gear 15 and drives the sleeve 36 by way of the spherical elements 30 of the safety clutch. The balls 38 rotate the shank 37a but the shank remains free to move axially under the action of the piston 62 and counter to such action when the connecting rod 60 retracts the cylinder 61. The shank 37a moves rearwardly when the cylinder 61 moves rearwardly because the operator pushes the housing forwardly by way of the spade handle 3a.

If the material of the workpiece into which the tool penetrates is extremely hard, for example, if the material is concrete or rock, it can happen that the tool holder 37 offers excessive resistance to rotation with the hollow shaft 14. The safety clutch including the spherical elements 30 then disengages the sleeve 36 from the hollow shaft 14 so that the shaft 14 can rotate with the gear 15 while the sleeve 36 and the tool holder 37 cease to rotate but the tool holder 37 remains free to move axially. The pressure ring 31 of the safety clutch offers a relatively high resistance to axial movement in a direction toward the retainer 33 as long as the spherical elements 30 are engaged by its inner conical surface 34; however, once the resistance which the shank 37a offers to rotation increases to such an extent that the spherical elements 30 are partially expelled from the flutes 35 of the sleeves 36, they can rapidly travel along the outer'conical surface 34a to thus insure that the safety clutch is disengaged practically instantaneously orabruptly. This is desirable in order to avoid damage to or excessive wear upon the parts of the power tool. If desired, the retainer 33 can be adjusted axially of the hollow shaft 14 to thereby select the exact resistance which the sleeve 36 must offer to rotation before the safety clutch is disengaged. The spherical elements 30 are urged radially outwardly by the axially parallel ribs which separate the flutes 35 of the sleeve 36 from each other.

An important advantage of the leaf spring 23 shown in FIG. 3 is that it enables the torque transmitting teeth or 21 of the

gear

15 or 16 to move into mesh with the torque receiving teeth 18 of the hollow shaft 14 as soon as the teeth 18 move into register with the spaces between the

teeth

20 or 21. Thus, when the shaft 24 is rotated clockwise or counterclockwise, as viewed in FIG. 3, at a time when the teeth 18 do not register with the spaces between the

teeth

20 or 21, the

corresponding prong

23b or 23a of the leaf spring 23 is deformed so that the spring 23 stores energy and is ready to propel the

gears

15 and 16 axially of the hollow shaft 14 as soon as the spaces between the

teeth

20 or 21 move into register with the teeth 18. It will be recalled that the

gears

15 and 16 are rotated continuously by the

gears

12 and 13 whenever the motor 4 is on.

If the tool holder 37 is to be rotated at the higher of two speeds, the

gears

15 and 16 are shifted in a direction to the left, as viewed in FIG. 1, so that .the torque receiving teeth 18 of the hollow shaft 14 move into mesh with the torque transmitting teeth 21 of the smaller gear 16 which is driven by the larger gear 13 of the intermediate shaft 10. The shifting from higher to lower speed ratio, or vice versa, as well as from higher lower speed ratio to neutral position of the multi-speed transmission 9-16 can be effected while the motor 4 is on. It will be noted that the provision of the two control devices including the

shafts

55 and 24 enables the operator to impart to the tool holder 37 axial impulses while the tool holder rotates or while thetool holder is held against rotation. Inversely, the operator can decide to disengage the positive clutch between the bevel gear 46 and disk 58 of the transmission for the

pneumatic impeller

61, 62 and to thereupon drive the tool holder 37 at the higher or lower speed so that the tool holder 37 rotates but does not perform any axial movements. The positive clutch can be disengaged while the hollow shaft 14 rotates at a selected speed. The tool holder 37 can accept a variety of different tools as well one or more adapters which enable it to accept further types or sizes of tools. This enhances the versatility of the power tool.

The portable power tool of FIG. 4 employs a modified positive clutch between the input element 60 and the output element 60 of the transmission for the pneumatic impeller including the cylinder 61 and piston 62. This clutch is a claw clutch having an annulus of claws 67 on the right-hand (rear end face of the input element 66 (which corresponds to the gear 11 of FIG. 1 but is movable axially of the intermediate shaft 65) and an annulus of complementary claws 68 on the left-hand end face of a bevel gear 69 which is rotatable on the intermediate shaft 65. The control means for engaging and disengaging the

claws

67 and 68 comprises a suitable shifter having a handgrip portion 66a (indicated by broken lines) which extends from the housing of the power tool so that it can be manipulated by hand. The bevel gear 69 is in permanent mesh with a bevel gear 69a which replaces the disk 58 of FIG. 1 and carries the pin 59 for the output element or connecting rod 60. The bevel gear 69a is secured to a shaft 69b which is rotatable in antifriction bearings provided therefor in the rear housing section 3.

The intermediate shaft 65 is rotatable in two axially spaced antifriction bearings 65a, 65b having rollershaped rollings elements.

The construction of the multi-speed transmission which rotates the tool holder for the tool T is identical with that of the multi-speed transmission 9-16 of FIG. 1. The control means 66a can be manipulated to engage or disengage the positive claw clutch 67, 68 while the multi-speed transmission is in neutral position or while the multi-speed transmission rotates the tool T at a selected speed. Analogously, the speed ratio of the multi-speed transmission can be changed or the multispeed transmission can be shifted to neutral while the claws 67 engage the claws 68.

FIG. 5 illustrates a portion of a third portable power tool which comprises modified control means for changing the speed ratio of the multi-speed transmission for the tool holder. The intermediate shaft 10 carries two

gears

12, 13 which'respectively mesh with gears 72 and 73, both freely rotatable on the hollow shaft 14. The gears 72, 73 are respectively analogous to the

gears

15, 16 of FIGS. 1 and 3. Instead of being rotatably mounted directly on the hollow shaft 14, the gears 72 and 73 are mounted on a cylindrical or sleevelike shifter 74 which is movable axially of the shaft 14. The shifter 74 is provided with an annulus of external torque receiving teeth or projections 75 and serves to rotate the shaft 14'. The teeth 75 are functional equivalents of teeth 18 on the shaft 14 of FIG. 1 and can be moved into mesh with internal torque transmitting teeth or projections 76 of the gear 72 or with internal torque transmitting teeth or projections of the gear 73, depending upon whether the user of the power tool wishes to drive the tool holder at a lower or higher speed. The control means for moving the shifter 74 axially of the shaft 14' is preferably similar to or identical with the control means 17, 23, 24, 25, 26 of FIGS. 2 and 3. The gears 72, 73 are held against axial movement. The internal teeth 76 and 77 of the gears 72, 73 are separated from each other by a ring-shaped space 78 which is wide enough to accommodate the external teeth 75 of the shifter 74 when the user of the power tool wishes to maintain the multi-speed transmission for the tool holder in neutral position.

The portable power tool of FIG. 6 comprises a third embodiment of a disengageable positive clutch between the input element 46 and the output element 60 of the transmission for the

pneumatic impeller

61, 62.

the clutch comprises a shaft 81 which carries at its upper end a disk 82 for the eccentric pin 59 and can receive torque from a sleeve-like clutch element 83 which is axially movably mounted thereon and is biased downwardly, as viewed in FIG. 6, by a helical spring 81a. The latter reacts against the inner race of an antifriction bearing 81b for the upper portion of the shaft 81. The lower end face of the clutch element 83 carries an annulus of claws 84 which can be moved into mesh with similar claws 85 provided on the upper end face of a bevel gear 86 which is in permanent mesh with the bevel gear 46. The latter is secured to the intermediate shaft 10. The clutch element 83 can be shifted axially by control means similar to that including the

parts

17, 23, 24, 25, 26 shown in FIGS. 2 and 3.

The construction of the multi-speed transmission for the tool T is identical with that of the multi-speed transmission shown in FIGS. 1 to 3.

FIG. 7 illustrates a portable power tool which embodies a modified safety clutch for disengaging the tool holder 37 from the prime mover (not shown) when the tool holder offers excessive resistance to rotation with the hollow shaft 14". The hollow shaft 14 is provided with axially parallel slots or openings 89 for rollershaped torque transmitting clutch elements 90 (only one shown) which extends into the adjacent flutes 35 of the sleeves 36 under the action of the spring 32. The pressure ring 31 of FIG. 1 is replaced by two pressure rings 91, 92 the former of which abuts against a split ring 93 in a peripheral groove of the shaft 14". The rear pressure'ring 92 is biased toward the pressure ring 91 by the spring 32. The axes of the roller-shaped elements 90 are parallel with the axis of the hollow shaft 14". Each of the pressure rings 91, 92 is provided with a conical surface (91a, 92a) into which a portion of each element 90 normally extends. The pressure ring 92 yields and moves in a direction to the right to further stress the spring 32 when the sleeve 36 offers excessive resistance to rotation with the shaft 14". This allows the shaft 14 to rotate relative to the sleeve 36 and tool holder 37 but the parts of the power tool cannot be damaged because the tool ceases to rotate.

in all other respects, the construction of the power tool of FIG. 7 is identical with that of one of the power tools shown in FIG. 1, '4, or 6. i

It is clear that the features shown in FIGS. 4 and 7, 5 and 7 or 6 and 7 can be incorporated in a single power tool.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims. i

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A portable power tool, particularly a combined electric impact wrench and chipping hammer, comprising a housing; a prime mover mounted in said housing and having a rotary output member; a tool holder rotatably and axially movably mounted in said housing; impeller means mounted in said housing and actuatable to transmit to said tool holder recurring axial impulses; first transmission means mounted in said housing and having an input element receiving torque from said output member, a mobile output element for actuating said impeller means, and clutch means for moving said output element in response to rotation of said input element; first control means for disengaging said clutch means at the will of the operator; multispeed second transmission means mounted in said housing between said tool holder and said output member and having a plurality of different speed ratios and a neutral position; and second control means actuatable independently of said first control means to select the speed ratio or the neutral position of said second transmission means so that said tool holder is movable axially by said impeller means while said second transmission means is in said neutral position or drives said tool holder at a selected speed, and that said output element of said first transmission means is idle while said second transmission means rotates said tool holder at a selected speed. rotates said tool holder at a selected speed.

2. A power tool as defined in claim 1, wherein said impeller means comprises a pneumatic cylinder and piston unit including a cylinder which is reciprocable by said output element of said first transmission means and a piston which is reciprocable in said cylinder and is arranged to impart said impulses to said tool holder.

3. A power tool as defined in claim 1, wherein said second transmission means comprises a two-speed transmission.

4. A power tool as defined in claim 1, further comprising a safety clutch installed between said second transmission means and said tool holder and arranged to disconnect said tool holder from said second transmission means when said tool holder offers a predetermined resistance to rotation.

5. A power tool as defined in claim I, wherein said prime mover comprises an electric motor and said clutch means comprises a positive clutch.

6. A power tool as defined in claim 5, wherein said positive clutch comprises a hollow shaft arranged to transmit torque to said output element and having at least one opening, a torque transmitting element provided in said opening and movable between a first position in which it partly extends from said hollow shaft and is driven by said input element and a second position in the interior of said hollow shaft, and a displacing member movable in said shaft axially between an operative position in which said displacing member maintains said torque transmitting element in said first position and an inoperative position in which said torque transmitting element is free to assume said second position, said first control means being arranged to move said displacing member between said operative and inoperative positions.

7. A power tool as defined in claim 6, wherein said torque transmitting element is a sphere and said input element includes a gear having an internal recess which receives a portion of said sphere in said first position of said sphere, said displacing member comprising a bolt having a groove which receives a portion of said sphere in said second position of said sphere when said bolt assumes said inoperative position.

8. A power tool as defined in claim 7, wherein said positive clutch further comprises biasing means or permanently urging said bolt to one of said positions thereof and said first control means comprises an eccentric actuatable to move said bolt to the other of said positions against the opposition of said biasing means.

9. A power tool as defined in claim 5, wherein said positive clutch comprises a first annulus of claws driven by said input element and a second annulus of complementary claws arranged to move said output element, said first control means comprising means for moving one of said annuli of claws toward and away from the other annulus to thereby place the claws of said first annulus into and out of mesh with the claws of said second annulus.

10. A power tool as defined in claim 9, wherein said input element comprises a first gear which receives torque from said prime mover and said output element comprises or is movable by a second gear which is coaxial with said first gear one of said gears being movable axially toward and away from the other of said .gears and said first and second annuli of claws being respectively provided on said first and second gears and being located between said gears.

11. A power tool as defined in claim 5, wherein said positive clutch comprises a shaft which is arranged to drive said output element, a gear rotatably mounted on said shaft and receiving torque from said output member of said prime mover, a clutch element rotatable with and movable axially of said shaft toward and away from said gear, a first annulus of claws provided on said gear and facing said clutch element, and a second annulus of complementary claws provided on said clutch element and facing said gear, said first control means comprising means for moving said clutch element toward and away from said gear to thereby move said second annulus of claws into and from mesh with said first annulus of claws.

12. A power tool as defined in claim 1, wherein said second transmission means comprises a two-speed transmission including an intermediate shaft driven by said output member of said prime mover, a second shaft arranged to transmit torque to said tool holder, coaxial first and second gears rotatably mounted on said second shaft and being driven by said intermediate shaft at different speeds and respectively having first and second torque transmitting portions, and torque receiving means provided on said second shaft, said gears being movable axially of said second shaft and said second control means comprising shifter means actuatable to move said first or second torque transmit ting portion into engagement with said torque receiving means.

13. A power tool as defined in claim 12, wherein said second control means further comprises a manually operable eccentric for moving said gears axially by way of said shifter means.

14. A power tool as defined in claim 13, wherein said second control means further comprises resilient means interposed between said eccentric and said shifter means so that said shifter means can move said gears axially when one of said first and second torque transmitting portions is ready to move into engagement with said torque receiving means of said second shaft.

15. A power tool as defined in claim 1, wherein said second transmission means comprises 'a' two-speed transmission including a first shaft driven by said output member of said prime mover, a second shaft arranged to drive said tool holder, a sleeve-like shifter movable axially of and rotatable with-said second shaft,

first and-second gears driven by said first shaft at different speeds and surrounding said shifter, first and second torque transmitting portions respectively provided on said first and second gears, and torque receiving means provided on said shifter, said second control means comprising means for moving said shifter axially betweena first position in which said torque receiving means receives torque from said first torque transmitting portion, a second portion in which said torque receiving means receives torque from said second torque transmitting portion, and a third portion in which said torque receiving means is disengaged from said first and second torque transmitting portions.

16. A power tool as defined in claim 15, wherein said second control means comprises a manually operable eccentric for moving said shifter axially of said second shaft.

17. A power tool as defined in claim 16, wherein said second control means further comprises resilient means interposed between said shifter and said eccentric so that said shifter can move axially when said motion receiving means thereof registers with one of said first and second troque transmitting portions.

18. A power tool as defined in claim 1, further comprising blocking means actuatable to prevent rotation of said tool holder.

19. A power tool as defined in claim 18, further comprising a sleeve rotatable with said tool holder and having at least one external axially parallel groove, said blocking means comprising a shaft rotatable by hand and having a projection movable into and from said groove, the axis of said shaft being inclined relative to the axis of said sleeve.

20. A power tool as defined in claim 1, further comprising a safety clutch installed between said second transmission means and said tool holder and arranged to disconnect said tool holder from said second transmission means when said tool holder offers a predetermined resistance to rotation, said safety clutch comprising at least one torque transmitting element movable between an operative position in which said second transmission means trasmits torque to said tool holder and an inoperative position in which said tool holder, is disconnected from said second transmission means.

21. A power tool as defined in claim 20, wherein said safety clutch further comprises a sleeve arranged to rotate said tool holder and having a flute which normally receives a first portion of said torque transmitting element in said operative position thereof, said second transmission comprising a hollow shaft surrounding said flute and having a radial opening receiving a second portion of said torque transmitting element in said operative position thereof, said safety clutch further comprising a pressure transmitting member arranged to yieldably urge said torque transmitting element to said operative position and to permit said torque transmitting element to move to said inoperative position, in which latter position said first portion of said torque transmitting element is received in said opening, in response to said predetermined resistance of said tool holder to rotation with said shaft.

22. A power tool as defined in claim 21, wherein said pressure transmitting member is a ring which surrounds and is axially movable on said hollow shaft, said torque transmitting element having a third portion which extends radially beyond said opening and is in abutment 13 with said ring in said operative position thereof, said safety clutch further comprising resilient means for biasing said ring against said torque transmitting element.

23. A power tool as defined in claim 22, wherein said ring has at least one outwardly flaring conical surface which is engaged by said torque transmitting element in said operative position thereof.

24. A power tool as defined in claim 22, wherein said pressure ring has a first radially outwardly flaring conical surface which contacts said torque transmitting element in said operative position thereof and a second torque transmitting element is a roller.

Claims

5. A power tool as defined in claim 1, wherein said prime mover comprises an electric motor and said clutch means comprises a positive clutch.

10. A power tool as defined in claim 9, wherein said input element comprises a first gear which receives torque from said prime mover and said output element comprises or is movable by a second gear which is coaxial with said first gear one of said gears being movable axially toward and away from the other of said gears and said first and second annuli of claws being respectively provided on said first and second gears and being located between said gears.

12. A power tool as defined in claim 1, wherein said second transmission means comprises a two-speed transmission including an intermediate shaft driven by said output member of said prime mover, a second shaft arranged to transmit torque to said tool holder, coaxial first and second gears rotatably mounted on said second shaft and being driven by said intermediate shaft at different speeds and respectively having first and second torque transmitting portions, and torque receiving means provided on said second shaft, said gears being movable axially of said second shaft and said second control means comprising shifter means actuatable to move said first or second torque transmitting portion into engagement with said torque receiving means.

15. A power tool as defined in claim 1, wherein said second transmission means comprises a two-speed transmission including a first shaft driven by said output member of said prime mover, a second shaft arranged to drive said tool holder, a sleeve-like shifter movable axially of and rotatable with said second shaft, first and second gears driven by said first shaft at different speeds and surrounding said shifter, first and second torque transmitting portions respectively provided on said first and second gears, and torque receiving means provided on said shifter, said second control means comprising means for moving said shifter axially between a first position in which said torque receiving means receives torque from said first torque transmitting portion, a second portion in which said torque receiving means receives torque from said second torque transmitting portion, and a third portion in which said torque receiving means is disengaged from said first and second torque transmitting portions.

20. A power tool as defined in claim 1, further comprising a safety clutch installed between said second transmission means and said tool holder and arranged to disconnect said tool holder from said second transmission means when said tool holder offers a predetermined resistance to rotation, said safety clutch comprising at least one torque transmitting element movable between an operative position in which said second transmission means trasmits torque to said tool holder and an inoperative position in which said tool holder is disconnected from said second transmission means.

22. A power tool as defined in claim 21, wherein said pressure transmitting member is a ring which surrounds and is axially movable on said hollow shaft, said torque transmitting element having a third portion which extends radially beyond said opening and is in abutment with said ring in said operative position thereof, said safety clutch further comprising resilient means for biasing said ring against said torque transmitting element.

24. A power tool as defined in claim 22, wherein said pressure ring has a first radially outwardly flaring conical surface which contacts said torque transmitting element in said operative position thereof and a second radially outwardly flaring conical surface which is engaged by said torque transmitting element in said inoperative position thereof, said first and second conical surfaces respectively making with the axis of said hollow shaft a relatively small and a relatively large acute angle.

25. A power tool as defined in claim 22, wherein said torque transmitting element is a sphere.

26. A power tool as defined in claim 22, wherein said torque transmitting element is a roller.