CA2028001C - Tool chuck - Google Patents

Abstract

A tool chuck according to this invention com-prises a locking device disposed between a chuck body and chuck claws slidable by screw feeding. The lock-ing device presses and locks to the chuck body by a reaction force occurring when the chuck claws clamp a tool. The tool chuck further comprises a torque amplifying device disposed between the locking device and a control ring rotatably mounted on the chuck body. When the locking device is locked to the chuck body, the torque amplifying device reduces rotation of the control ring to output an amplified torque to a screw ring which screw-feeds the chuck claws. The chuck claws are slidable fast until the chuck claws clamp a tool inserted in position to realize a quick clamping action. When the chuck claws contact and hold the tool, the chuck claws are slidable with an increased torque, thereby holding the tool with a strong clamping force.

Description

~2~

TOOL CHUC~

BAC~GROUND OF THE I~-E~TION
(1) Field of Application This invention relates to tool chuchs for attachment to power drills, power drivers and the like, to hold tools such as drill bits and driver bits, and more particularly to the type of tool chuck that is manually tiohtened withcut using a chuck handle.

(2) Description of the Prior Art A conventional tool chuck of the type having a turn ring rotatable with a chuck handle to extend and retract chuck claws involves a cumbersome handle . operation, maintenance of the chuck handle under care 1~ and other inconveniences. To eliminate such disadvan-taoes, a tool chuck has already been developed which has a turn ring rotated manually without using a chuck handle to tiohten the chuck claws, and a locking ~ device for preventing the chuck claws from loosenino durino an operation.
~-ith the tool chuck having such a locking device, 2028~1 however, the tool will rotate idlv to the detriment of an effective operation if the chuck claws impart an insufficient clamping force In order to obtain a strong tightening force, it is conceivable to increase the torque by reducing the rotation of the turn ring throuoh a suitable reduction mechanism Ho~ever, this would give rise to the problem that the chuck cannot be operated quickly since the chuck claws are caused to slide at a reduced speed even when an inserted tool is not clamped by the chuck claws.

OBJECTS OF THE INVENTION
A primary object of this invention is to provide a tool chuck comprising a locking device disposed 1~ between a chuck bodv and chuck claws slidable by screw feeding, the locking device pressing and locking to the chuck body by a reaction force occurring when the chuck claws clamp a tool, and a torque amplifying de~-ice disposed between the locking device and a control ring rotatably mounted on the chuck body, the torque amplifyino device reducing rotation of the - 202~

control ring to output an amplified torque to a screw ring which screw-feeds the chuck claws when the lock-ing device is locked to the chuck body, whereby the chuck claws are slidable fast until the chuck claws contact a tool inserted in position to realize a quicl;
clamping action.
.~ secondary object of this invention is to provide a tool chuck wherein the rotation of the control ring is provided with an automatically in-creased torque when the chuck claws contact and hold the tool, therebv causing the chuck claws to slide ~-ith the increased torque for holding the tool with a strong clamping force.
Other objects of this invention will be apparent 1v from the following description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DR~INGS
The drawings show embodiments of this invention, in which:-Fig. 1 is a view in vertical section of a tool chuck in a first embodiment, 2028~01 Fig. '2 is an e~ploded perspective view of a torque amplifving mechanism, and Fig. 3 is a schematic view illustrating rolling grooves, Fig. ~ is a ~-iew in vertical section of a tool chuck in a second embodiment, Fig. 5 is a section taken on line I-I of Fig.
and illustrating an operation, Fig. 6 is a section taken on line II-II of Fig.
and illustrating an operation, Fig. 7 is a view in vertical section of a tool chuck in a third embodiment, Fig. 8 is a section taken on line III-III of Fig.
7, Fig. 9 lS a view in vertical section of a tool chuck in a fourth embodiment, Fig. 10 is a view in vertical section of a control ring, Fig. 11 is a side view of the control ring, Fig. 12 is a view in vertical section of a tool chuck in a fifth embodiment, Fig. 13 is an enlarged partial view in vertical 202~001 section of a torque amplifying mechanism in an inoperative position, Fig. 1~ is an enlar~ed partial view in vertical section of the torque amplifyin~ mechanism in an v operative position, and Fig. 15 is an enlarged partial view in vertical section of a tool chuck in a si~ embodiment.

DET~ILED DESCRIPTION OF THE PREFERRED E~BODI~IENTS
(First Embodiment) A first embodiment of this invention will be described in detail hereinafter with reference to the drawings.
Figs. 1 through 3 show a tool chuck in the first embodiment. This tool chuck is used with a power 1~ drill or a power driver for holding a tool such as a drill bit or a driver bit.
Referring to Figs. 1 and 2, the tool chuck 10 comprises three chuc~ claws 1~ slidably mounted cen-trallv of the forward end of a chuck body 11. The chuck claws 12 are inclined with respective forward ends thereof converging toward the a~is of the chuck `- 202~0~1 bodv 11.
~ ore particularly, the chuck cla~is 12 are mounted only slid~blv in slide arooves 13 formed in the chuck body 11 as inclined relati~-e to its aYiS~ respective-ly. Each claw 12 defines a partial male screw 1~ on aperipheral position thereof, with threads of the screw arranged to constitute a continuous whole. The re-spective partial male screws 1~ are meshed with a female screw 16 ~efined in a screw rina 15. With turnino of the screr~ rin~ 15 in opposite directions, the chuck claws 1~ are slidable toward and away from one another for clamping and releasing a tool.
A torque amplifying mechanism 17 is mounted peripherally of t~le screw ring 15, and a control ring 18 is mounted peripherally of the torque amplifying mechanism 17. When the control ring 18 is turned forward or backward, i.e. in a direction to clamp or release the tool A, the torque is transmitted to the screw ring 15 through the torque amplifying mechanism 17.
The torque amplifving mechanism 17 is constructed as follows.

20280Gl The mechanism 1, includes three annular elements, i.e. an output ring 20 press fit in and fi~ed to the screw ring 1~, an input ring 21 relatively rotatably supported in the control ring 18 and offset a prede-termined amount of eccentricit~ e, and a locking ring22 movable into pressure contact with a rearward posi-tion of the chuck body 11 through tapered peripheral surfaces. These annular elements are arranged a~ially of the chuc~ bod 11.
The input ring 21 defines a hypocycloidal rolling groove 23 having an arcuate section on a surface thereof opposed to the locking ring 22. The locking ring 22 defines an epicvcloidal rolling groove 24 having arcuate sections on a surface thereof opposed to the input ring 21. A plurality of balls 25 are arranged between these rolling grooves 23 and 24 to roll along the grooves 23 and 2~.
As also shown in Fig. 3, the rolling grooves 23 and 24 have an amplitude corresponding to the amount of eccentricity e of the input ring 21. The input ring 21 has ten waves, and the locking ring 22 twelve waves. The number of balls 25 arranged therebetween ~ 2~12~0~L

is eleven or less.
~hen a revolution due to the amount of eccentric-ity e is applied to the input ring 21 having the roll-ing grooves 23 and 2~, the balls 25 roll along the rolling grooves 23 and 24 to rotate the input rina 21.
Since the rotation is significantlv reduced with respect to the revolution, the rotation of the input ring 21 results in output of an amplified torque.
Since, in this embodiment, the rolling groove 23 of the input ring 21 has 10 waves and the rolling groove 24 of the locking ring 22 has 12, the differ-ence in the number of waves being 2, the reduction ratio is 2/10 waves = 1/5.
A greater reduction ratio may be obtained by increasing the numbers of waves. Where, for e~ample, the input ring 21 has 40 waves and the difference in the number of waves is 2, 2/40 waves = 1/20, to output a greatly amplified torque.
To transmit the rotation of the input ring 21 to the outpllt rin~ 20, a pluralitv of balls 26 are ar-ranged between opposed surfaces thereof.
~ore particularly, the input rina 21 defines 202~01 recesses (not shown) for receiving the balls 26, while the output ring 20 defines recesses 27 opposed there-to. The recesses 2l of the output ring 20 have a size (ring-shaped) for allowing the balls 26 to move round 5 b~- the same amount of eccentricity e, so that power transmission is possible despite the eccentric turning of the input ring 21.
For fixing the loc~ing ring 22 to the chuc~ body 11, the locking ring 22 defines, centrally thereof, a tapered pressure contact surface 28 diverging rear-wardly, while the chuck body 11 defines a pressure contact surface 29 corresponding thereto. These sur-faces move into pressure contact with each other when the locking ring 22 is pushed by a backlash of the screw ring 15 (with retraction of the chuck claws 1~), whereby the lockino ring 22 is fi~ed to the chuck body 11 .
The locking ring 22 defines teeth 30 on the circular rear end thereof. ~n elastic ring 33 is disposed on the rear end of the locking ring 22, the elastic ring 33 defining a plurality of elastic elements 32 having pawls 31 elastically engaging the 2~GO~

teeth 30. The elastic ring 33 further defines fixing bosses 3~ for press fitting into grooves 35 defined on an inside wall of the control ring 18, whereby the elastic ring 33 is retained in position and against rotation.
The elastic elements 32 perform at least three functions. One of them is application of an urging force to separate the above-mentioned pressure contact surfaces 28 and 29. The second function is to engage the locking ring 22 and cause it to rotate with the control ring 18 since, otherwise, the locking ring 22 would be freely rotatable when out of pressure contact with the chuck body 11. The third function is a locking function to fiY the locking ring 22 which may become loose by reaction even when the locking ring 22 is pressed against the chuck body 11.
A cover 36 is mounted on the rear end of the controi ring 18, and is press fit at a base thereof on a rear position of the chuck body 11.
The elastic ring 33 is fixed to the control ring 18 in this embodiment, but may be fixed to the chuck body 11.

2028û01 ..

The screw ring 15 consists of two parts which are rigi~ly interconnected by the press fitting the output rina 20 after the two parts are assembled to the chuck bod~; 11. The interconnection may be achieved by any other means, such as by defining screws on the two elements for screwin tight together, or by a spline engagement therebetween with an E-ring provided for pre~-enting separation.
In Figs. 1 and 2, numeral 37 denotes a bearing provided in the input ring 21 for smooth rotation of the control ring 18.
The way in which the tool chuck 10 as constructed above operates will be described ne~t.
Assume that the chuck claws 12 are wide open to be ready to hold the tool A. The tool A is placed in position, and the control ring 18 is turned in the tightening direction for causing the chuck claws 12 to clamp the tool A.
Since, in the initial stage of this ring turning opera~ion, the chuck claws 12 are free from the load resulting from the clamping of tool A, the locking ring ~2 of the torque amplifying mechanism 17 is in a 2~28û~1 free state relative to the chuck body 11. Further, since the locking ring 22 is engaged bv the elastic elements 32, the output ring 20, input ring 21 and locking ring 22 are interconnected as a unit and are rotated to~ether. As a result, the rotation of the control ring 18 directly causes an equal-rate rotation of the screw ring 15, which provides a fast screw feed for projecting the chuck claws 12.
A load acts on the chuck claws 12 when the claws 12 contact and begin to clamp the tool A. This load causes a backlash of the screw ring 15, which rear-wardly pushes the locking ring 22 through the output ring 20 and input ring 21.
As a result, the pressure contact surfaces 28 and 29 of the locking ring 22 and chuck body 11 move into pressure contact with each other. The elastic ele-ments 32 vield to this pressure contact, which results in slippage thereof. The locking ring 22 is then fi~ed to the chuck body 11, to place the torque ampli-fving mechanism 17 in an operable state.
That is, the rotation of the control ring 18 causes revol-ltion of the input rina 21, whereby the ~2~
.

balls 25 roll along the rolling grooves 23 and 2~ to rotate the input ring 21. The rotation of the input ring 21 is transmitted to the output ring 20 as a high torque resulting from reduction of the input, to 5 rotate the screw ring 15 for projecting the chuc~
claws 12 and causin~ them to clamp the tool A with the high torque.
In carrying out an operation with the tool A held bv the chuck claws 12 as described above, the tool A
which may be a driver bit, for e~ample, is turned in opposite directions depending on the nature of the operation.
If this operation involves forward rotation of the tool A which acts on the control ring 18, torque amplifying mechanism 17 and screw ring 1~ in the direction to tighten the chuck claws 12, then backward rotation acts on these components 18, 17 and 15 in the direction to rela~ the chuck claws 12. Even though a reaction occurs with reversal of the rotation acting in the direction to rela~ the chuck claws 12, actually no rela~ation will occur because the locking ring 22 is engaged by the elastic elements 32 to rigidlv 20~a~
.

connect the control ring 18, torque amplifying mecha-nism 17 and screw ring 15 to the chuck body 11.
When releasing the tool A, the control ring 18 needs onlv to be rotated in the rela~ing direction.
Then the chuck claws 12 are rela.Yed under a high torque since the torque amplifying mechanism 17 is in the operative state in the initial stage of rotation.
~hen the chuck claws 12 are further rela~ed to elimi-nate the backlash of the screw ring 15, the elastic elements 32 push back the lockino ring 22. Conse-quently, the pressure contact surfaces 28 and 29 of the locl~ing ring 22 and chuck body 11 move out of the pressure contact. The screw ring 15 rotates fast at the same speed as the control ring 18, to move the chuck cla~-s 12 fast in the rela~ing direction.
According to this embodiment, the tool ~ is held with the tightening force amplified by the torque amplifying mechanism 17. Thus the tool A is held ri~idly in a manner equivalent to the case of using a chuch handle.
Further, the torque amplifying mechanism 17 includes the three rings, i.e. the output ring 20, input ring ~1 and locking ring 22. This construction is compact and capable of easily interlockind with the chuck claws 12. Despite the simple construction, a great torque can be transmitted.
The urging engagement provided by the elastic elements 32 is effective to prevent loosening of the control ring 18 and chuck claws 12 against vibrations occurring during an operation. This promotes clamping of the tool A with increased rigiditv.
Besides the function to pre~-ent relaxation, the elastic elements 32 have the functions to engage the control ring 18 for ri~id connection, to retain the control ring 18 on the chucl. body 11, and to release the chuck body 11 and chuch claws 12 from mutual pressure contact when removing the tool A from the chuck claws 12. This single component fulfilling these functions enables the construction to be compact with a reduced number of components.
In the foreaoing first embodiment, the output of input ring 21 is transmitted to the screw ring 15 througll the output ring 20. Alternatively, the output may be made through a gear coupling operatively inter-2D~8û~1 connectina the input ring 21 and screw ring 15 and capable of absorbing the eccentric rotation of the input ring 21.
Further, in the first embodiment, the chuck claws 12 are fed by the action of screw ring 1~ fitted peripherally thereof. The torque amplifyina mechanism 1/ is applicable to the type of chuck claws which are pushed and pulled by a bush provided at the rear ends of the chuck claws and driven by screw feeding.
(Second Embodiment) Figs. 4 through 6 show a tool chuck in a second embodiment. In Fi8. 4, the tool chuck 40 comprises three chuck claws 42 slidably mounted in a chuck body 41, to be projectable and retractable by opposite rotations of a screw ring ~3, as in the first embodi-ment shown in Fig. 1. A detailed description of such arrangement i5 omitted here.
The screw ring 43 consists cf two parts which are rigidly interconnected by press-fitting a sleeve 44 peripherally thereof.
The chuck body 41 carries a cylindrical control ring 45 rotatablv mounted on an intermediate peripher-al position thereof. A cylindrical co~er ~6 is fitted and fiYed to the periphery at a pro~imal end of the chuck body ~1.
A torque amplifying mechanism 47 is pro~ided in a power transmitting path between the scre~- rino 43 and control rin~ 45 for transmitting torque of the control ring ~5 to the screw ring ~3.
The torque amplifying mechanism 47 includes an input/output ring ~8 rotatabl~ fitted in the control ring 48, and a lockin~ rin~ 4g rotatablv mounted on the chuck body 41.
The input/output ring ~8 has a forward inside ~-all fitted through a needle bearing 50 on the outer peripheral surface of a tubular control section 51 formed centrally of the control ring 45.
As also shown in Fia. 5, the outer peripheral surface of the tubular control section 51 is formed about an a~is C which is offset an amount e with respect to an a.~;is B of the chuck body ~1.
The input/output ring 48 has an intermediate inside wall in drivin~ en~a~ement throuah a gear couplin~ 52 ~iith an outer periphery of a rear end of 20280~1 the screh ring ~3.
~ lore particularl~, this gear coupling 52 is loosel-- meshed ~-ith a gear 53 formed on the inter-mediate inside wall of the input/output ring ~8, and 5 h-ith a ge2r 5~ formed on the outer periphery at the rear end of the screw ring ~3, to allow eccentricitv in the amouni e.
Further, the input/output ring ~8 has a rear inside wall defining a gear 55 which, as also shown in Fig. 6, is meshed with a gear 56 formed peripherally of the locking ring ~9.
These gears 55 and 56 form cycloidal gears for making a ccloidal motion. When the control ring ~5 is turned to revolve the input/output ring 48 through the eccentricit~ of the tubular control section 51, a difference in the number of teeth between the gear ~5 formed on the input/output ring 48 and the gear 56 formed on the locking ring 49 results in rotation of the input/output ring ~8 corresponding to the e~tra number of teeth. As a result, the rotation of the input/output ring ~8 is greatly reduced, and the rota-tion of the input/output ring 48 pro~-ides an amplified torque output.
~ here, for e.~ample, the gear 56 of the locking ring ~9 has 66 teeth and the gear 55 of the input/out-put rin~ ~3 has 68, the difference in the number of teeth being 2, the reduction ratio is 2/66 teeth =
1/33. Thus, the reduction ratio of 1/33 is obtained with respect to an input, whereby the input/output ring ~8 provides a greatly amplified torque output.
A suitable number of thrust balls are mounted for rolling movement between opposed surfaces of the screw ring ~3 and locking ring 49.
The locking ring 49 has an inside peripheral wall defining a tapered pressure contact surface 58 diverg-ing rearwardlv, ~hile the chuck body 41 has an inter-mediate outer peripheral wall defining a taperedpressure contact surface 59 opposed to the contact surface 58 and divergina rearwardl~, to correspond thereto.
These pressure contact surfaces 58 and ~9 move ~0 into pressure contact with each other when the screw ring 43 is retracted by a backlash of the chuck claws ~2 resultin~ from tightening of the screw ring 43 for 2028~

clamping the tool A, whereby the lockina rino 49 is fi~ed to the chuck body ~1.
An elastic ring 60 is fitted in a peripheral inside wall of the control ring ~ to be opposed to 5 the rear end of the locking rin~ ~9. The elastic ring 60 incl~des elastic elements 61 formed around inside peripheral positions thereof and engaging a toothed surface at the end of the locking ring ~9. In this ~-av, the control ring 45 and lockina ring ~9 are ri~idly interconnected and the lockina ring ~9 and chuck body ~1 are urged in a direction to separate the pressure contact surfaces 53 and 59.
A retainer ring 63 is fi~ed by press fit rear-wardly of the elastic ring 60 to hold the elastic ring 60 in positicn and against rotation.
The way in which the tool chuck ~0 as constructed according to the second embodiment is tightened and loosened will be described ne.Yt.
~ hen the tool A is clamped by the three chuck claws ~2, the control ring ~5 is turned in a tighten-ino direction D (indicated by solid line arrows in Fias. 5 and 6~ for clamping the tool A, with the co-~er 202~001 ~6 locked aaainst rotation.
Since, in the initial staoe of this turning operation, the chuck claws ~2 are free from the load resulting from the clamping of tool A, the lockino 5 ring ~9 forming part of the torque amplifying mecha-nism ~, is rotatable relative to the chuck body ~1.
F~lrther, since the locking ring 49 is connected to the control ring ~5 by the elastic elements 61, the control ring 45, input/output ring ~8 and locking ring lg rotate to~ether. As a result, the rotation of the control ring ~5 directly causes an equal-rate rotation O,r the screw ring ~3, which provides a fast screw feed for rapidly projecting the chuck claws 42 to clamp the tool ~.
Subsequently, a load acts on the chuck claws ~2 when the claws 42 contact and begin to clamp the tool . Then the screw ring ~3 is retracted by a backlash due to the tightenin~, which rearwardly pushes the locking ring ~9 through the thrust balls 5/. As a result, the pressure contact surfaces 58 and 59 of the locking ring ~9 and chuck body 41 move into pressure contact with each other. The elastic elements 62 - ` 2~280~1 yield to this pressure contact, which results in slip-page thereof. The locl.ing ring 49 is then fi~ed to the chuck body ~1, to place the torque amplifying mechanism ~l in an operable state to produce the speed reducing effect.
That is, the rotation of the control ring 45 causes the tubular control section 5l to revolve the input/output ring ~8 the amount of eccentricity. This produces rotation of the input/output ring 48 based on the difference in the number of teeth between the gear 55 formed on the input/output ring 48 and the gear 56 formed on the locking ring 49. This rotation is output as a high torque resulting from reduction of the input, to rotate the screw ring 43 and screw-feed the chuck claws 42, therebv causing them to clamp the tool A with the high torque.
In carrying out an operation with the tool A held by the chuck claws ~2 as described above, the elastic elements 61 engaging the locking ring ~9 act to stop the rela.~ation resulting from rotation in the direc-tion to relav~ the chuck claws 42.
~ihen releasing the tool A, the control ring ~5 202~001 needs only to be rotated in the rela~ing direction E
(indicated by dotted arrows in Figs. 5 and 6).
When the chuc~ claws 42 are retracted to elimi-nate the backlash due to the tightening and actina on the screw ring ~3, the locking ring ~9 is advanced by the urging force of elastic elements 51. Consequent-ly, the pressure contact surfaces 58 and 5~ of the locking ring ~9 and chuck body 4l move out of the pressure contact. Then the reduction effect of the torque amplifying mechanism ~ is canceled, whereby the control rino ~5, input/output ring ~8 and loc~ing ring ~g rotate to~ether. The screw ring ~3 rotates at the same speed as the control ring ~, to screw-feed the chuck cla~s ~2 fast in the rela~ing direction. As 1~ a result, the chuc~ claws ~2 rapidl~- slide away from each other to release the tool A.
~ hen the tool A is held, the torque undergoes the speed red~lction and amplification by the torque ampli-f~-ing mechanism ~l as described above. Thus, a higher torque is obtained than where the torque of the con-trol ring 4~ is transmitted directly to the screw ring 43 meshed with the respecti~e chucl claws 4 . By simply turning the control ring ~5 in the tightening direction, the tool ~ may be rigidly clamped and fi~ed in position.
~oreover, the control rino ~5, input/output ring 5 ~8 and lockino, ring ~9 may be rotated together in opposite directions during the turning operation carried out until the tool A is clamped in position and the turning operation after the release thereof.
The chuc~ claws ~2 are rapidly screw-fed toward and away from one another by the screw ring ~3 to clamp and release the tool A. Thus, this construction has e~cellent operability.
The following construction may be provided in place of the tubular control section 51 of the second embodiment.
The control ring ~5 may have an inside peripheral ~-all offset the amount e with respect to the a~is B of the chuck bodv ~1, with the input/output ring ~8 loosely fitted in this eccentric inside peripheral wall, the input/output ring ~8 being revolvable along the eccentric inside peripheral wall of the control ring ~5.

- 2~ -- 202~

Such a construction will be described ne~t as a third embodiment, with emp~asis placed on the torque amplifying mechanism.
(Third Embodiment) Figs. 7 and 8 show a tool chuc~ in the third embodiment. This tool chuck has the same basic construction as in the second embodiment, and like components are affixed with like reference numerals ~-ithout describing the particulars thereof.
The control ring 45 has an inside peripheral wall formed about an a~is C which is offset an amount e with respect to the a.~is B of the chuck body 41. The input/output ring 48 of the torque amplifying mecha-nism ~7 is rotatably fitted in the concentric inside 1~ peripheral wall 70 of the control rino ~8 through a plurality of balls 71. When the control ring ~5 is turned, the input/output ring ~8 is revolvable along this eccentric peripheral inside wall 70.
A sleeve 72 is press fitted peripher~llv of the screw ring 43. The gear coupling 52 comprises a gear 53 formed on an inside wall at the forward end of the input/output ring 48 and a gear 54 formei on the outer - 2~ -periphery of the slee~-e 5~.
~ urther, the input/output ring 48 has a rear inside wall defining a gear ~5 which is meshed with a gear 56 formed peripherallv of the locking rin, ~9.
These gears 55 and 56 form cvcloidal gears. The numbers of teeth of these gears 55 and 56 are selected as in the second embodiment.
When the control ring 45 is turned, the torque amplifying mechanism 47 causes the tool A to be clamped as in the second embodiment.
In the initial stage of this turning operation when the chuck claws ~2 are not clamping the tool A
yet, the control ring 45, input/output rino 48 and locking ring 49 rotate together to rotate the screw 1~ ring 43 at the same speed as the control ring 45 as described in the second embodiment. The fast screw feed by the screw rino 43 causes the chuck claws 42 to mc~-e toward one another rapidly to clamp the tool A.
Subsequently, a load acts on the screw ring 43 when the chuck claws 42 contact and begin to clamp the tool A. Then the screw ring 43 is retracted by a backlash due to the tightening, which rearwardly 2028~01 pushes the loc~ing rin~ 49 through the thrust balls 5~. As a result, the pressure contact surfaces 58 and 59 of the locking ring 49 and chuc~ body 41 move into pressure contact with each other. The elastic ele-5 ments 62 yield to this pressure contact, which resultsin slippage thereof. The locking ring 49 is then fi~ed to the chuck body ~1, to place the torque ampli-f~;ing mechanism 47 in an operable state to produce the speed reducing effect.
10That is, the rotation of the control rin~ 46 causes the eccentric inside wall 70 to revolve the input/output ring 48 the amount of eccentricity. This produces rotation of the input/output ring 48 based on the difference in the number of teeth between the gear 1555 formed on the input/output rin~ ~8 and the gear 56 formed on the locking ring 49. This rotation is out-put as a high torque resulting from reduction of the input, to rotate the screw ring 43 through the gear couplina 5Z and screw-feed the chuck claws 42, thereby causing the chuck claws 4~ to clamp the tool A with the high torque.
When releasing the tool A, the control rin~ 45 needs only to be rotated in the rela~ing direction E
(indicated by the dotted arrow in Fig 8), as already described in the second embodiment. A detailed description thereof will therefore be omitted.
Functions and advantages may be expected from the third embodiment as constructed above, which are equi-~-alent to those of the second embodiment.
(Fourth Embodiment) Fi~s. g, 10 and 11 show a tool chuck in a fourth embodiment. This fourth embodiment relates to another e~ample of the bearing for the input/output ring 48 in the third embodiment. The torque amplifying mechanism ~, and other basic constructions are the same as in the third embodiment, and like components are affixed 1~ with like reference numerals without describing the particulars thereof.
As in the third embodiment, the control rin~ 4~
has an inside peripheral wall offset with respect to the axis of the chuck body ~1. The input/output rina 48 of the torque amplifying mechanism 47 is rotatably fitted in the concentric inside peripheral wall 70 of the control ring 48. When the control ring ~ is - 2~ --2028~)01 turned, the inpu./o-ltput ring ~8 is revolvable along this eccentric peripheral inside wall 70.
The input/output ring 48 revolvable as above is supported by a plurality of needle bearings ~. These 5 needle bearings 7~ are arranged only along a partial circumferential range.
That is, the cycloidal gear 56 of the loc~ing ring ~g revolves and rotates while partiallv engaging the cycloidal gear 55 of the input/output ring ~8.
This engagement takes place in a fi~ed range as far as the control ring 45 is concerned. The load produced by clamping of the tool A results in a radial pressure acting only in the above ranae of engagement.
Thus, the needle bearings 7~ are provided along the partial circumferential range of the control ring ~5 where the gears 55 and 56 engage each other and the load is applied.
The needle bearings 7~ have ends slightly proj-ecting to~ard the locking ring ~9. The locking ring ~9 defines a fittino groove 75 e~tending circumferen-tiallv therecf and opposed to the projecting portions of the needle bearings 7~. This fitting groove 7 20280~1 receives the projecting portions of the needle bear-ings 7~ so as to allow mo~-ement due to the rotation (movement relative to the locking ring ~9) of the needle bearings 7~.
The load produced by the clamping of the tool A
acts on the needle bearings 7~ and radiallv presses the needle bearings 7~ as noted above. Therefore, where the control ring ~6 is formed of a synthetic resin, the pressing force will tend to partially e~pand and deform the control ring ~5. Such outward deformation of the control ring ~5 is suppressed since the ends of the needle bearings 7~ are snugly fitted in the fitting groove 75 against out~-ard spread under the pressure.
1~ ~hen the control ring ~5 is outwardlv e~panded, this will fill the gap between its outer periphery and the cover ~6, which is effective to prevent entry of dust and other foreign matter through the gap.
~hen the force is applied to radially spread the needle bearings 7~ as noted above, this load is appLied to the inward position of the control ring ~.
~s a result, an internal stress is produced in the control ring ~ to cause a twist with its outward portion.
To counteract the twist, needle bearin~s 76 are pro~-ided on an inside peripheral wall in the outward portion of the control ring ~5 to be opposed to the needle bearings ~. These needle bearings 16 prevent the twist of the control ring ~5.
The needle bearin~s 74 and 76 may be provided in a small number. ~ith the projecting portions of the needle bearings 7~ held in the fitting groove 76 of the locking ring ~9, the deformation of the control ring ~5 due to the tool clamping load may be avoided.
The bearing structure described above may be applied also to the tool chuc~ in the first embodiment shown in Fia, 1.
In Fig. 9, the elastic rin~ 60 comprises a spring material formed into an inclined flange shape and retaining a plurality of balls 7~ at a pluralit~- of positions thereof. These balls ~1 engage and spring-load the toothed face 62 e.~tending over the entireperiphery of the locl~ing ring ~9.
The elastic ring 60 thus formed provides func-.

2o`28QDI

tions and ad~antages equivalent to those provided bythe third embodiment.
In Fig. 11, recesses 78 serve to lock the elastic ring 60, and the latter defines projections (not shown) engageable with these recesses.
(Fifth Embodiment) Figs. 12, 13 and 14 show a tool chuck in a fifth embodiment. In Fig. 12, the tool chucl~ 100 comprises three chuc~ claws 102 slidably mounted in a chuck body 101, to be projectable and retractable by opposite rotations of a screw ring 103, as in the first embodi-ment sho~in in Fig. 1. A detailed description of such arrangement is omitted here.
The screw ring 103 consists of two parts which 1~ are rigidly interconnected by press-fitting a sleeve 10~ peripherally thereof.
A cover 105 having a U-shaped section is fi:~ed to the outer periphery of a pro~imal end of the chuck body 101. The chuck body 101 carries a cylindrical control ring 106 rotatably mounted on an intermediate peripheral position thereof. The control ring 106 has the o--ter periphery of an open end thereof relatively ~. 2o28ool rotatabl~- fitted in the inner periphery of the pro~i-mal end of the cover 10~.
A torque amplifying mechanism 10/ is provided bet~ieen the control ring 106 and screw ring 103 for transmittino torque of the control ring 106 to the screw ring 103.
The torque amplify-ing mechanism 10/ includes an input ring 108 interlocked with the control ring 108, an output retainer 112 fi~ed to the screw ring 103, and a locking ring 115.
The input ring 108 is rotatably mounted on an intermediate outer periphery of the screw ring 103. A
plurality of metallic rolling balls 109 are arranged between opposed surfaces of the input ring 108 and 1~ sleeve 10~. The input ring 108 includes a plurality of projections 110 on the outer periphery thereof for engagement with a plurality of grooves 111 defined in the inside wall of the control ring 106. In this way, the input ring 108 is interlocked with the control ring 106 to be capable of a slight a~ial movement.
The output retainer 112 is fi~ed to the outer perlphery of a pro~imal portion of the screw ring 103.

202~01 The output retainer 112 includes ball holders 113 provided at, for example, 16 equidistant positions peripherally thereof. Each ball holder 113 holds a metallic ball 11~.
The locking ring 115 is rotatably supported between the output retainer 112 fixed to the screw ~ing 103, and a stepped portion defined on an inter-mediate periphery of the chuck body 101. The locking ring 115 is constantly urged for pressure contact with the balls 11~ of the output retainer 112 fi~ed to the screw ring 103, by a coil spring 116 housed in the proximal portion of the cover 105.
The coil spring 116 is compressed between a sprinG stopper 11, fixed to the inside wall of the proximal portion of the cover 105 and a presser plate 118. A plurality of metallic balls 119 are arranaed between opposed s-lrfaces of the locking ring 115 and pressure plate 118.
Thus, the coil spring 116 constantly presses the presser plate 118, balls 119, locking ring 115, the balls 11~ held bv the output retainer 112, input ring 10~, balls 109, sleeve 10~ and screw ring 103 a~ially ~ 202800I

against a peripher~l inside wall at a forward end of the control rina 106.
.~s shown in Fig. 13, a leaf spring 121 is fi~ed to the inside wall of the control rin~ 106 and opposed to the outer periphery of the loc~ino ring 115. When the locl.{ing rino 11~ is permitted to rotate in oppo-site directions, a projection 122 formed on the leaf spring 12i en~ages a toothed surface 123 formed on the outer periphery of the locking ring 115 to rotate the locking ring 115 in the same direction as the control rin~ 106. ~hen the locking ring 115 is locked aoainst rotation, this en~agement is broken to allow rotation of the control ring 10~ only.
The engaging arrangement between the projection 122 of leaf spring 121 and the toothed surface 123 is equivalent and performs a similar function to the arrangement between the toothed surface 30 and elastic elements 32 in the first embodiment shown in Fig. 3.
However, the leaf spring 121 does not act to separate the loc~ing ring 115 from the stepped portion 120, and the fifth embodiment relies for this function on the coil spring 116.

2028~01 The lccking ring 11~ includes a pressure contact surface 1~ on an inside periphery thereof for pres-sure contact with the stepped portion 120. This pres-sure contact surface 12~ may have a tapered shape.
The wa~- in which the tool chuck 100 as con-structed according to the fifth embodiment operates to clamp the tool A will be described ne~t.
First, the tool A is inserted into the chuck body 101 through the chuck claws 102 kept wide open. Then the control rino 106 is turned in a tool clamping direction relative to the chuck body 101.
During the turning operation before the chuck claws 102 move into contact with the tool A, only a minor recistance is applied to the screw ring 103, and 1~ the loc~ing ring 11~ of the torque amplifying mecha-nism 107 is in a free state relative to the chuck body 101. Further, since the locking ring 11~ is connected to the control ring 106 by the leaf sprin~ 121, the control ring 106, input ring 10~, balls 11~ of the output retainer 112, and locking ring 11~ rotate to-gether. The rotation of the screw ring 103 which is at the same speed as the control ring 106 provides a 202gO~l fast scre~ feed for rapidlv projecting the chuck cla~s 102 to clamp the tool A.
Subsequentlv, as shown in Fig. 1~, a load acts on the chuck claws 102 when the claws 10 contact and begin to clamp the tool A, therebv producing a back-lash of the chuch claws lOZ. Then the screw ring 103 is a~ially retracted by the backlash, which a,~ially retracts, through the sleeve 10~ and balls 109, the input ring 108, balls 11~ held by the output retainer 11~, and locking rin~ 115 of the torque amplifying mechanism 10l which have been axially pressed. As a result, the pressure contact surface 124 of the locl,-ing ring 115 moves-into pressure contact with the stepped portion 120 of the chuck body 101, and the leaf sprin,g 121 for locking the locking ring 115 against rotation undergoes slippage.
W'hen the locking ring 115 is locked against rotation, the balls 11~ of the output retainer 112 act ~s i~lers to roll, with the rotation of the input ring 108, along the opposed face of the locking rina 115.
This rolling movement pro~-ides a reduced rotation of the output retainer 112, which reduces the rotation of 3t --202~01 the control ring lU6 to rotate the screw ring 103 with high torque, thereby causing the chuck claws 102 to firml~J clamp the tool A.
In carr~ing out an operation with the tool A, the leaf sprino 121 providing the locking engagement acts to stop rela~ation due to reactions of opposite rota-tions of the tool chuck 100, which is the same as in the preceding embodiments.
When releasing the tool A, the control ring 106 is turned in the relaYing direction relative to the chuck bod-~ 101. In the initial stage of the turning operation, a momentarv high torque occurs since the locking ring 115 of the torque amplifying mechanism 10l is locked against rotation. This facilitates rotation of the screw ring 103 in th~ rela~ing direc-tion.
Once rela~Yed, the resistance to the rotation diminishes, and the coil spring 116 releases the lock-ing ring 115 from the pressure contact, with the lock-ing ring 11~ connected to the control ring 106 through the leaf spring 121. Then, the control ring 106 and torque amplifying mechanism 107 rotate together. The 2`o2~oDl rotation of the control ring 106 causes the screw ring 103 to rotate at the same speed, whereby the chuck claws 102 rapidly slide away from each other to release the tool A.
When the tool A is held, as described above, the rotation of the control ring 106 is reduced by the rotating balls 11~ forming part of the torque ampli-fying mechanism 107, for transmission to the output retainer 11~. Thus, a higher torque is obtained than the torque for rotatin~ the control ring 106, for the tool A to be clamped firmly.
Moreover, the resistance of the load is small, and the control ring 106 and the respective components of the torque amplifying mechanism 107 can rotate 1~ together in opposite directions by the action of leaf spring 121 during the turning operation carried out until the tool .~ is clamped in position and the turn-ing operation after the release thereof. The chuck claws 102 are rapidly screw-fed toward and away from one another by the screw ring 103 to clamp and release the tool A. Thus, this construction has e~cellent operabilitv, 20280~I

For facility of operation, the relative rotation between the chuck body 101 and control ring 106 may be effected by opposite rotations of the power drill or power driver to which the ch-~ck bodv 101 is attached.
This applies to the other embodiments as well.
In the fifth embodiment, the torque amplifying mechanism 107 includes the balls 11~ rotatable to cause reduced rotation of the output retainer 112.
These balls 114 may be replaced bv gears.
Such a construc-tion will be described as a si~th embodiment next.
(Si~th Embodiment) Fig. 1~ shows a tool chuck in the si~th embodi-ment. This tool chuc~ has the same basic construction as in the fifth embodiment, and like components are affixed with like reference numerals without describ-ing the particulars thereof.
As illustrated, the torque amplifying mechanism 10, includes a plurality of bevel gears 12~ provided between the screw ring 103 and output retainer 112 fi~ed thereto. The bevel gears 125 are meshed with a gear surface 126 formed on the input ring 108 and a -- ~0 --'_, , 2028~1 ge~r surface 1 ~ formed on the locking ring 115, respectivel~-.
With this construction, when the locking rina 115 is locked against rotation by the pressure contact 5 with the stepped portion 120, rotation of the input ring 108 causes rotation and rolling movement of the be~-el g~ars 125. The rotation of the control ring 106 is reduce~ b~,r this rolling movement for transmission to the OUtp-lt retainer 112. Thus, the bevel gears 11~
perform a function equivalent to that of the balls 114 in the fifth embodiment, and this construction pro-vides a high torque as in the fourth embodiment.

-- ~1 --

Claims (12)

1. A tool chuck having a plurality of chuck claws mounted centrally of a forward end of a chuck body to be slidable toward and away from one another, and a control ring mounted peripherally of the chuck body to be rotatable in opposite directions to rotate a screw ring for screw-feeding the chuck claws toward and away from one another, said tool chuck comprising;
lock means disposed between said chuck body and said chuck claws for pressing and locking to said chuck body by a reaction force occurring when said chuck claws clamp a tool, and releasable upon removal of the reaction force, and torque amplifying means disposed between said lock means and said control ring for reducing rotation of said control ring to output an amplified torque to said screw ring when said lock means is locked to said chuck body, and transmitting rotation of said control ring to said screw ring when said lock means is released from said chuck body.

2. A tool chuck as claimed in claim 1, wherein said torque amplifying means includes an input ring loosely mounted eccentrically in said control ring and inter-locked with said screw ring, said input ring and said lock means lockable to said chuck body being arranged axially of said chuck body, said input ring and said lock means having mutually opposed surfaces defining cycloidal rolling grooves having different numbers of waves, and balls mounted between said rolling grooves.

3. A tool chuck as claimed in claim 1, wherein said torque amplifying means includes an output ring fixed to said screw ring, and an input ring relatively rotatably- and eccentrically supported in said control ring, said output ring, sand input ring and said lock means being arranged axially of said chuck body, said input ring and said lock means having mutually opposed surfaces defining cycloidal rolling grooves having different numbers of waves. balls mounted between said rolling grooves, and power transmitting balls mounted between said input ring and said output ring.

4. A tool chuck as claimed in claim 1, wherein said torque amplifying means includes an input/output ring loosely mounted eccentrically in said control ring and interlocked with said screw ring, said input/output ring and said lock means lockable to said chuck body having opposed inner and outer faces defining cycloi-dal gears having different numbers of teeth and meshed with each other.

5. A tool chuck as claimed in claim 4, wherein said control ring includes a tubular control section formed on an intermediate inside wall thereof eccentrically with respect to an axis of said chuck body for rota-tably supporting said input/output ring through a bearing provided peripherally of said tubular control section.

6. A tool chuck as claimed in claim 4, wherein said control ring includes an inside wall formed eccentri-cally with respect to an axis of said chuck body for rotatably supporting said input/output ring.

7. A tool chuck as claimed in claim 1, wherein said torque amplifying means includes an input ring fixed to said control ring, an output retainer disposed between said input ring and said lock means lockable to said chuck body and fixed to said screw ring, said input ring and said output retainer being arranged axially of said chuck body, and rotatable means held by said output retainer to be rotatable with a rela-tive movement between said input ring and said lock means.

8. A tool chuck as claimed in claim 7, wherein said rotatable means comprises rollers.

9. A tool chuck as claimed in claim 7, wherein said rotatable means comprises bevel gears, said input ring and said lock means defining toothed surfaces for engagement with said bevel gears.

10. A tool chuck as claimed in any one of claims 1 to 4, 7 and 9, wherein said lock means comprises pressure contact surfaces defined on a locking ring and said chuck body to be opposed to each other.

11. A tool chuck as claimed in any one of claims 1 to 4, 7 and 9, wherein said lock means comprises tapered pressure contact surfaces defined on a locking ring and said chuck body to be opposed to each other.

12. A tool chuck as claimed in any one of claims 1 to 4, wherein said locking ring defines a toothed surface circumferentially of a rear end face thereof, said toothed surface being in engagement with an elastic element secured to said control ring.