Turning – Lathe – Tool rest
Reexamination Certificate
1995-03-17
2001-03-06
Tsai, Henry (Department: 3722)
Turning
Lathe
Tool rest
C082S160000, C409S232000, C409S233000
Reexamination Certificate
active
06196094
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to an improved lock rod clamping apparatus for detachably connecting a tool unit to a tool supporter, and is particularly concerned with such an apparatus having an increased gripping force.
Clamping mechanisms for detachably connecting a tool unit to a tool supporter are well known in the art. One typical use of such mechanisms is in machining operations where the tool unit holds a cutting insert that is moved into and out of cutting engagement with a rotating metal workpiece. The clamping apparatus allows different tool units holding different cutting inserts to be quickly attached to and detached from the tool supporter which in turn is connected to a device that controls the movement of the tool units with respect to the workpiece.
One of the most commercially successful clamping mechanism includes a cylindrically-shaped canister member that is matable with the tubular end of a tool unit and which includes apertures for admitting locking elements into locking engagement with recesses present in the tool unit. The locking elements, which are typically spherical, are radially moved through the apertures in the canister member by means of cam surfaces present on a reciprocating lock rod. Examples of such a clamping mechanism are disclosed in Erickson U.S. Pat. Nos. 4,708,040; 4,747,735; 4,836,068, and 4,932,295, each of which is assigned to Kennametal Inc. located in Latrobe, Pa.
Such a prior art clamping mechanism is illustrated in FIG.
4
. Here, a side, cross-sectional view of the distal end
62
of a canister member
39
is shown which includes an aperture
54
a
in the form of a cylindrical bore through the wall of the member
39
. The inner diameter of the circular bore forming the aperture
54
a
closely approximates the outer diameter of the spherical locking element
57
a
. A reciprocating lock rod
60
includes a cam portion
64
a
having a spherical depression
66
which tapers off into a ramp
68
. When the spherical locking element
57
a
is seated in the depression
66
, and the lock rod
60
is moved against the bias of the springs
74
(shown in
FIG. 3
) toward the distal end of the canister member
39
so that its stop flange
70
is in the position illustrated in
FIG. 3
, the spherical element
57
a
is in a non-locking position. This unlocking position allows the tubular shank
16
of a tool unit
10
to be inserted into the annular recess
59
. However, when the springs
74
are released to pull the lock rod
60
away from this position toward the position illustrated in
FIG. 4
, the ramp of the cam portion
64
a
wedgingly engages and radially raises the spherical locking element
57
a
into the locking position shown. In such a position, the spherical locking element will wedgingly and lockingly bear against the angled wall
30
of the tool unit
10
.
While such a prior art locking mechanism has proven its capability of quickly, conveniently, and rigidly attaching a tool unit to a tool supporter, the applicant has observed an area where the performance of such a mechanism could be substantially improved. Specifically, the applicant has observed that if the clamping mechanism could be modified to increase the clamping force applied to the tool unit without increasing the pull-back force that the spring package applies to the lock rod, then a smaller and shorter spring package could be used to achieve the same holding force. Such a smaller spring package would advantageously shorten the envelope of the tool, which in turn would render the tooling system incorporating the clamping mechanism easier and more convenient to use in a working environment. Additionally, the life span of the springs used in the package (which are typically Bellville washers) would be lengthened. Alternatively, if a spring package of conventional size were used, the holding force between the clamping mechanism and the tool unit would be increased, which in turn would increase tool rigidity and enhance the accuracy of the cutting operation.
Clearly, it would be highly advantageous if a way could be found to increase the holding force that such a clamping mechanism generates with respect to a tool unit for a given pull-back force on the lock rod to make possible either the use of a small spring package, with a consequent reduction in the overall size of the tool envelope or an increase in tool rigidity and cutting accuracy with the use of a spring package of conventional size. Ideally, such a holding force-increasing solution should require only a minimal amount modification to the shapes of existing parts so that a conventional clamping mechanism of the type previously described could easily be converted into an improved clamping mechanism with a minimum amount of disassembly and machining.
SUMMARY OF THE INVENTION
Generally speaking, the invention is a clamping mechanism for detachably connecting a tool unit to a tool supporter with an improved holding force that fulfills all the aforementioned criteria.
The inventive clamping mechanism comprises at least one locking element, which may be in the form of a sphere; a canister matable with a tool unit and having an aperture for admitting a locking sphere through a wall thereof; a lock rod reciprocally movable within the canister member along a longitudinal axis and having a cam portion for moving the locking sphere through the canister aperture into wedging and locking engagement with a wall of the tool unit, wherein the canister aperture walls are not cylindrical, i.e., are not orthogonal to the longitudinal axis of the lock rod, but instead are angled with respect to a line extending radially from this axis for increasing the force of locking and wedging engagement between the locking element and the tool unit.
Such an angling of the aperture walls increases the force of wedging engagement by increasing the mechanical advantage between the locking sphere and the wall of the tool unit that is engaged by this sphere when it is forced radially outwardly by the cam portion of the lock rod. In the preferred embodiment, the aperture walls are angled between about 50 and 20° with respect to a line extending radially from the lock rod axis, and more preferably between 7° and 15° with respect to this radial line. As the wall of the tool unit that engages the locking sphere is engaged between about 50° and 60° with respect to this radial line, the locking sphere wedgingly engages the wall of the tool unit at a shallower angle, thereby increasing the mechanical advantage associated with its engagement against the tool unit.
As the invention may be incorporated into a prior art clamping mechanism by merely boring the canister member apertures obliquely with respect to the axis of rotation of the canister member as opposed to orthogonally, the invention may be easily incorporated into existing clamping mechanisms with a minimum amount of machining operations. Moreover, as the incorporation of the invention into a clamping mechanism increases the holding force by 30%, the invention allows smaller spring packages to be used with all their envelope-reducing and longevity-increasing advantages.
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patent: 4209182 (1980-06-01), Sheldon
patent: 4406195 (1983-09-01), Kruger
patent: 4708040 (1987-11-01), Erickson
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patent: 4726268 (1988-02-01), Erickson
patent: 4726269 (1988-02-01), Erickson
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patent: 4747735 (1988-05-01), Erickson et al.
patent: 4836068 (1989-06-01), Erickson
patent: 4897014 (1990-01-01), Tietze
patent: 4932295 (1990-06-01), Erickson
patent: 4951536 (1990-08-01), Robertson
patent: 5011346 (1991-04-01), Pfalzgraf
patent: 5173017 (1992-12-01), Oshnock et al.
patent: 5193954 (1993-03-01), Hunt
patent: 5245896 (1993-09-01), Erickson et al.
patent: 5261302 (1993-11-01), Erickson et al.
patent: 36 06 331 A1 (1986-02-01), None
patent: 0233321 (1986-02-01), None
patent: 38 29 331 A1 (1988-08-01), None
patent: 2070473 (1981-09-01), None
patent: 8-243814 (
Kennametal PC Inc.
Prizzi John J.
Tsai Henry
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