Fast change top jaw system

A quick changing jaw carrier assembly for mounting a top jaw. The jaw carrier assembly includes a main jaw carrier slidably confined for radial movement within a slot of a rotatable housing. An auxiliary jaw carrier or locking wedge is radially slidably mounted on the main jaw carrier. The auxiliary and main jaw carriers define radially opposed wedges for defining a dovetail structure which lockingly engages a similar such structure on the top jaw. The auxiliary jaw carrier is spring urged outwardly into a jaw-engaging position, and can be manually moved inwardly from this position when release of the jaw is desired. A manually-controlled locking cam is rotatably supported on the main jaw carrier and can be rotatably displaced into a locking position wherein the locking cam projects radially beneath a shoulder formed on the auxiliary jaw carrier when the latter is in its jaw-engaging position.

FIELD OF THE INVENTION 
This invention relates to a jaw-type chuck and, more specifically, to an 
improved mounting arrangement for facilitating the fast changing of the 
top jaws. 
BACKGROUND OF THE INVENTION 
Conventional jaw chucks as associated with rotary machine tools, such as 
lathes, employ a rotatable chuck housing which mounts thereon a plurality 
of radially displaceable jaw carriers, and these in turn removably mount 
jaws which are adapted for gripping a workpiece. The jaws assume many 
shapes and sizes, and hence are interchangeably mountable on the jaw 
carriers to facilitate use of the chuck in conjunction with a wide variety 
of workpieces. One conventional mounting technique for removably securing 
the jaws to the jaw carriers involves the use of threaded fasteners, 
specifically screws or bolts. Such arrangements, however, are time 
consuming when changing of the jaws is desired, increase the size, mass 
and complexity of the jaw arrangement, and often result in structures 
which reduce the rigidity of the jaw assembly but increase the undesired 
centrifugal force effect. 
In an attempt to facilitate the mounting of the jaws on the carrier 
assemblies, several arrangements have been developed employing a carrier 
assembly having main and auxiliary carrier members which are relatively 
movable with respect to one another to facilitate the mounting or removal 
of the jaw. Most of these arrangements, however, have still possessed 
features which have resulted in structural and operational complexities. 
One such arrangement is illustrated by U.S. Pat. No. 3,868,120 (Blaettry). 
This patent illustrates a main jaw carrier having an auxiliary carrier 
slidably mounted thereon. In this arrangement, however, all of the opposed 
surfaces of the jaw carriers must be rigidly joined together to permit 
proper utilization of the arrangement, and hence this restricts the 
changing of the jaws. 
Another arrangement is illustrated by U.S. Pat. No. 3,219,356 (Wilterdink) 
which discloses a rotary cam for locking the upper and lower jaw carrier 
portions together, although the joining of the carrier portions is through 
interfitting serrated surfaces. This type of arrangement increases the 
manufacturing cost and decreases the efficiency of the apparatus as 
regards its convenience of use. 
Other arrangements of this general type are disclosed by U.S. Pat. Nos. 
3,833,232, 2,667,358, 3,679,221 and 4,352,500. The arrangements of these 
latter patents involve complex structural and functional arrangements 
which hence minimize their desirability. 
Accordingly, this invention relates to an improved jaw carrier arrangement 
for permitting rapid and efficient removing and/or mounting of a top jaw. 
The improved jaw carrier arrangement is believed to possess a highly 
improved and more desirable structural and functional arrangement so as to 
facilitate both economical manufacture and efficient utilization thereof. 
In the improved jaw carrier arrangement of this invention, there is 
provided a main jaw carrier which slidably supports thereon an auxiliary 
or locking carrier. The main and auxiliary carriers are radially 
spring-urged apart, with the auxiliary carrier being radially outermost 
and slidably supported on the main carrier. A locking cam is rotatably 
mounted on the main carrier for locking the auxiliary carrier in an outer 
position in which position the carriers are adapted to rigidly support a 
jaw thereon. The auxiliary and main carriers have oppositely directed 
dovetail grooves to facilitate rapid but secure engagement with opposed 
grooves formed on the jaw. The locking cam can be rotated into a release 
position wherein the auxiliary carrier can be easily manually displaced 
inwardly in opposition to the spring to facilitate mounting or removing of 
the jaw. Release of the manual pressure on the auxiliary carrier results 
in the spring urging the auxiliary carrier outwardly to securely grip the 
jaw by the opposed dovetail guides, and thereafter the locking cam is 
rotated to engage the auxiliary jaw carrier and prevent inward movement 
thereof. 
The improved jaw carrier arrangement, as aforesaid, permits a jaw to be 
rapidly mounted on or removed from the assembly, and the rotational 
centrifugal force imposed on the auxiliary carrier acts through the 
dovetail guide to create a more secure gripping of the jaw. This 
arrangement also permits the jaw, and its point of engagement with the 
workpiece, to be positioned more closely adjacent the front of the chuck 
housing and hence closer to the main spindle bearings so as to provide 
improved overall rigidity. The arrangement also possesses a limiting stop 
which cooperates between the auxiliary and main carriers for maintaining 
the auxiliary carrier in an outermost limit position, due to the urging of 
the spring, when the jaw is removed from the carrier assembly. 
Other objects and purposes of the invention will be apparent to persons 
familiar with structures of this type upon reading the following 
specification and inspecting the accompanying drawings.

Certain terminology will be used in the following description for 
convenience in reference only, and will not be limiting, for example, the 
words "rightwardly", "leftwardly", "upwardly", and "downwardly" will refer 
to directions in the drawings to which reference is made. The word "front" 
will refer to the exposed face of the chuck, namely the rightward side 
thereof as appearing in FIG. 2. The words "inwardly" and "outwardly" will 
refer to directions toward and away from, respectively, the geometric 
center of the chuck and designated parts thereof. Said terminology will 
include the words specifically mentioned, derivatives thereof, and words 
of similar import. 
DETAILED DESCRIPTION 
Referring to the drawings, there is illustrated a chuck assembly 10 which 
includes a housing 11 having thereon a plurality, here three, of jaw 
carrier assemblies 12 disposed in uniformly angularly spaced relationship 
around the housing. Each carrier assembly 12 is adapted to have a jaw 13, 
normally referred to as a top jaw, removably mounted thereon. A 
conventional actuator or draw bar assembly 14 connects to the carrier 
assemblies 12 for controlling the radial movement thereof, and hence the 
positioning of the jaws 13 for engagement with a workpiece. The chuck 
assembly 10 having an overall configuration as described above is 
conventional and is adapted to be mounted on and rotatably supported 
adjacent the front face of a machine tool, such as a lathe, for supporting 
a workpiece which is to be machined. 
The housing 11 includes a main annular housing part 15 which, in the 
illustrative embodiment, has an inner liner or sleeve 16 concentrically 
mounted therein, the latter defining a central bore 17 which projects 
through the housing part. An annular front plate 18 is fixed to the 
housing part 15, as by fasteners 19. The radially inner portion of this 
plate 18 radially overlaps the front end of the bore 17 and effectively 
defines a front stop for the drawbar assembly 14. A plurality of elongated 
fasteners 21 extend completely through the housing for permitting its 
attachment to a rotatable front plate associated with the spindle of the 
lathe. 
The housing assembly 11 has a plurality of T-shaped slots 22 formed 
therein. These slots 22 project radially outwardly from the bore 17 
through the outer periphery of the housing, and also open axially 
outwardly through the front face 25. These T-shaped slots 22, there being 
three such slots which mount therein carrier assemblies 12, project 
radially outwardly of the housing in uniformly angularly spaced 
relationship therearound. Each slot 22, when viewed in cross section has 
an enlarged head portion 23 which is spaced axially rearwardly from the 
front plate 18. The head portion 23 is joined to a narrower stem portion 
24 which projects axially through the front plate 18. The T-shaped slot 22 
projects radially through the outer peripheral wall 26 of the housing, and 
is conventionally provided with a bushing or slide plate 27 fixed to the 
rear wall thereof to facilitate the free radial sliding movement of the 
respective carrier assembly. 
The carrier assembly 12 includes a main jaw carrier 31 (often referred to 
as a master jaw) which is also T-shaped in cross-section and sized so as 
to be snugly but radially slidably disposed within a respective one of the 
T-shaped slots 22. The main jaw carrier 31 has the leg or stem portion 
thereof projecting outwardly of the slot past the front face of the front 
plate 18 for releasable engagement with the top jaw 13, as explained 
hereinafter. 
A wedge or cam portion 32 is fixedly, here integrally, formed on the 
radially inner end of the main jaw carrier 31, which wedge portion 32 
projects into the bore 17 and is slidably engaged within a wedge-shaped 
groove formed on the piston 33 associated with the draw bar assembly 14. 
This piston 33 is axially slidably supported within the bore 17 and has a 
bar 34 fixed thereto and projecting rearwardly therefrom, the latter being 
connected to the standard axially movable drawbar as associated with a 
lathe. The connection of the main jaw carriers to the drawbar assembly by 
means of wedgelike cams, whereby the jaw carriers are moved radially in 
response to axial movement of the drawbar assembly, is conventional and 
well known, and one typical construction of such arrangement is 
illustrated by U.S. Pat. No. 3,424,467. 
Jaw carrier 31 has a groove 36 formed therein, which groove projects 
radially inwardly from the outer end of the carrier through a 
predetermined extent and terminates at an inner end wall 37. This groove 
36 is also T-shaped in cross-section so that the narrower or stem portion 
of the T-shaped groove opens axially outwardly through the front face of 
the jaw carrier 31. This T-shaped groove 36 hence extends parallel to the 
T-shaped slot 22. 
The jaw carrier assembly 12 also includes an auxiliary jaw carrier 38, 
hereinafter referred to as a locking member or wedge, the latter being of 
T-shaped cross-section and slidably supported within the groove 36 of the 
main carrier 31. This T-shaped locking wedge 38 has the leg or stem 
portion thereof projecting axially forwardly of the groove 36 so that both 
the main carrier 31 and the locking wedge 38 have the front faces thereof 
disposed substantially coplanar with one another and closely adjacent the 
front face 25 of the housing. The main jaw carrier 31 has a jaw mounting 
structure 41 thereon, specifically a dovetail guide structure which opens 
downwardly. The locking wedge 38 has a similar jaw mounting structure 42 
thereon, specifically an upwardly directed dovetail guide structure. These 
dovetail guides 41 and 42 extend substantially parallel to one another and 
are disposed so that they are substantially perpendicular to the radially 
extending centerline of the carrier assembly. The rear sloped wedge 
surface on each dovetail guide extends at an angle of 45.degree. relative 
to the rotational axis 20 of the chuck assembly. Further, the dovetail 
guide 42 associated with the locking wedge is disposed radially outwardly 
from the guide 41 associated with the main carrier. 
The locking wedge 38 is continuously urged radially upwardly relative to 
the main carrier 31 by a conventional compression spring 43, the latter 
being disposed between the locking wedge 38 and the lower end of the 
groove 36, such as by having the ends thereof confined within appropriate 
bores. Hence, the spring exerts a continuous radially outward biasing 
force on the locking wedge. A stop or limiting screw 44 is threadably 
engaged with and projects through the main carrier 31 into the groove 36. 
The inner end of this limiter screw 44 has a nose portion which projects 
into a radially elongated slot 45 formed in the side wall of the locking 
wedge 38. This slot 45 has shoulders at opposite ends thereof which 
effectively function as stop surfaces for defining the radially inner and 
outer limit positions of the locking wedge 38 relative to the jaw carrier 
31. 
The rear surface of the locking wedge 31 has a relief slot or groove 48 
formed thereon, which slot projects radially outwardly from the radially 
inner end of the locking wedge, with this release slot 48 terminating in 
an inwardly directed shoulder or stop surface 49. This latter shoulder 49 
is designed to cooperate with a lock assembly 51 to permit the locking 
wedge 38 to be fixedly locked in its outermost limit position relative to 
the main jaw carrier. 
To accommodate and define the lock assembly 51, the main jaw carrier 31 has 
a bore 52 which projects radially inwardly form the outer peripheral 
surface thereof, this bore 52 being parallel with and spaced axially 
adjacent the rear surface of the T-shaped slot 22. Bore 52 has a 
screw-type seat or cam 53 threadably engaged with the jaw carrier 31 
adjacent the lower end of the bore. This cam or seat has an upper surface 
which can be elevationally adjusted by rotation of the cam, and which is 
adapted to function as a support for the lower axial end of a rotatable 
locking cam 54. This locking cam is formed substantially as a cylindrical 
element which is closely but rotatably supported within the bore 52 so 
that the lower end of the cam bears against the seat member 53. Locking 
cam 54 has a reduced diameter stem 55 which projects axially thereof, and 
hence outwardly of the bore 52 so that the free end of this stem 55 is 
disposed closely adjacent the radially outer surface of the main jaw 
carrier. Stem 55 has a suitable structure, such as an opening 56, 
associated therewith for accommodating a conventional tool, such as an 
Allen wrench, to permit selective rotation of the cam 54. The stem 55 
projects through an end plate 57 which closes off the outer end of bore 52 
for confining the locking cam within the bore, which end plate is fixed to 
the jaw carrier by fasteners such as screws. 
The locking cam 54 defines thereon an upper axial end surface 61 which 
functions as a shoulder or abutment, and which is adapted to be disposed 
directly under the shoulder 49 of the locking wedge to permit securement 
of the locking wedge in its radially outer limit position. 
The locking cam 54 has a substantially cylindrical outer peripheral wall 62 
of a radius such that, coupled with the positioning of the cam relative to 
the locking wedge, results in the cam projecting into the relief passage 
48 below the shoulder 49 when fixing of the locking wedge 38 in its outer 
limit position is desired. To permit release of the locking wedge 38, 
however, the locking cam 54 has a peripheral wall portion thereof removed 
so as to form a flat 63. Hence, when the locking cam is rotated so that 
this flat 63 is disposed in opposed facing (i.e. parallel) relationship to 
the axially rear surface of the locking wedge 38, then the locking cam 54 
no longer projects under the shoulder 49 and hence the locking wedge can 
be manually displaced radially inwardly of the groove 36. 
Top jaw 13 is provided with structure thereon which compatibly cooperates 
with the jaw carrier assembly 12. For this purpose, the top jaw 13 has 
opposed lower and upper mounting structures 65 and 66 which are formed as 
dovetail guides, and these are designed to respectively engage the 
dovetail guides 41 and 42 so that the rear face 67 of the top jaw will 
hence be drawn snugly against the front face 68 as defined on the jaw 
carrier assembly. The top jaw 13 also has, adjacent the upper and lower 
ends thereof in the vicinity of the dovetail guides 65 and 66, pairs of 
rearwardly projecting legs 69 which project outwardly beyond the dovetail 
guides and effectively snugly straddle the opposite sides of the jaw 
carrier when the top jaw is mounted thereon. 
OPERATION 
To mount a top jaw 13 on a jaw carrier assembly 12, an appropriate wrench 
is inserted into the opening 56 of stem 55, whereby locking cam 54 is 
rotated through about one-third of a revolution, whereby this effects 
withdrawal of the locking cam 54 from beneath the shoulder 49 by causing 
the flat 63 to be disposed in opposed facing relationship to the rear of 
the locking wedge 38. The locking wedge will still remain in its radially 
outer limit position due to the urging of the spring 43. The operator then 
applies finger pressure against the radially outer surface 71 of the 
locking wedge so as to slidably radially displace the locking wedge 38 
inwardly against the urging of spring 43. This causes the dovetail guide 
42 to be moved inwardly toward the guide 41 and reduces the spacing 
therebetween so that it is less than the dimension or mouth opening 
between the guides 65 and 66 on the top jaw 13. The radially inward 
movement of the locking wedge 38 is limited by the engagement of the 
limiter screw 44 with the upper end of the slot 45. While manually 
maintaining the locking wedge 38 in its radially inner position, the 
operator then moves the top jaw 13 axially toward the front face of the 
chuck assembly so that the side legs 69 effectively straddle the jaw 
carrier 31, and the dovetail guides 41 and 42 project into the mouth of 
the top jaw as defined between the guides 65 and 66. This movement of the 
top jaw by the operator hence occurs straight toward the chuck assembly 
and substantially parallel with the rotational axis 20. The operator then 
relieves the finger pressure on the locking wedge 38 so that spring 43 
urges the locking wedge radially outwardly, whereupon the dovetail guide 
42 engages the upper dovetail guide 66 on the top jaw, and continual 
radial outward movement of the locking wedge due to the urging of spring 
43 results in the top jaw 13 being properly engaged with the guides 41 and 
42. Thereafter the operator manually rotates the locking cam 54 in the 
reverse direction back to its original position which hence results in the 
upper shoulder 61 on the locking cam moving into a position directly 
beneath the shoulder 49 on the locking wedge so as to prevent radial 
inward movement of the latter. This hence results in the locking wedge 
being fixedly secured in its radially outermost position, and hence 
positively maintains the top jaw securely mounted on the carrier assembly 
12 due to the interfitting relationship of the dovetail guides 65 and 66 
on the cooperating guides 41 and 42. 
During operation of the chuck assembly, the effect of centrifugal force as 
caused by rotation of the chuck assembly is such as to tend to urge the 
locking wedge 38 radially outwardly, and hence this further assists in 
maintaining a secure holding of the top jaw 13 due to the manner in which 
the top jaw is confined by the dovetail guides 41 and 42. 
While the shoulder or end surface 61 formed on the locking cam 54 is 
normally flat, nevertheless this end surface 61 can be provided with a 
slight slope or ramp thereon, such as resembling a spiral ramp, if such is 
deemed necessary or desirable in order to wholly eliminate any clearance 
between the surfaces 49 and 61 when the locking cam is in its locked 
position. 
Although a particular preferred embodiment of the invention has been 
disclosed in detail for illustrative purposes, it will be recognized that 
variations or modifications of the disclosed apparatus, including the 
rearrangement of parts, lie within the scope of the present invention.