Note: Descriptions are shown in the official language in which they were submitted.
60 MP 1042
The present invention relates to broach systems
and particularly to a new and improved broach cutter assembly
having disposable carbide inserts.
Broach tools have been used for many years for
the machining of metal, and for specific operations such as
broaching slots, openings or channels of specialized
cross-section which are typically formed in turbine wheel
discs. The conventional broaching tool has been a unitary
broach having a plurality of cutting teeth formed on a single
solid stick-like member. Several shortcomings, however, have
been associated with the use of such stick-like broaches. For
example, the quality of the overall tool is only as good as
the worst tooth, with the existence of an undersiæed tooth
resulting in an overloading of the next tooth, as well as
making it necessary, through wear or otherwise, to discard
the entire tool even though there is still useful life left
in many or all of the other teeth. Of aourse, the entire
tool is also lost as the result of any tooth damage or cracking
with respect to any one tooth or any one part of the tool. In
addition, the type of material ~rom which the tool is made is
restricted. More particularly, while high speed steels have
been used to form the stick-like broaches~ tougher, more
expensive materials such as carbides cannot be used because of
the prohi~itive costs associated with the initial
manufacture of the tool, as weI1 as the cost of replacements
necessitated by the fact that damage to any one part of the
tool requires that it be discarded.
Another type of broaching tool which has been used
is one which includes a plurality of separate cutting
inserts which are fixed to the` tool body. Typically, the
inserts are formed from a cemented carbide or other hard metal.
The conventional design for tools of this type is generally
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of brazed construction, i.e. carbide blanks are permanen-tly
fastened to a steel holder with braze material and ground
after brazing to the required cutter configuration. Proper
brazing of the carbide to the steel along with grinding the
carbide after brazing is critical, yet due to space limit-
ations, is extremely difficult. The brazing of the carbide
tips requires that each be held in proper position during
the braze procedure to ~acilitate grinding to form after
brazing. Furthermore, it is necessary for a successful
broaching operation that each tip is securely and properly
brazed to the steel body. Unfortunately, it is often common
for a brazed joint to come apart in the grindin~ operation or
in the actual broaching of the part. In either event, if
the carbide tip breaks, a new tip must be rebrazed and the
form reground. The conventional brazed construction thus
offers little advantage over high speed tooling since
downtime and requalifying of a broach set is a len~thy process.
In addition to broaches having brazed inserts, there are tools
in which the cutting inserts are in some way clamped to the
tool. Examples of such tools are disclosed in U.S. Patent No.
3,707,748 - issued ~anuary 2, 1973 - Price et al, and
entitled "Cutting Tool for Holdlng a Plurality of Disposable
Cutting Inserts"; U.S. Patent No. 3,548,474 - issued
Decem~e~ 22, 1970 - Meyerj and entitled "Machine Tool",
U.S. Patent No. 3,641,642 - issued February 15, 1972 -
Schmidt, and entitled "Individual Tooth Broach"; U.S. Patent
No. 3,528,154 - issued March 28, 1968 - Schmidt, and entitled
"Individual Tooth Broach"; and Russion Patent 727357/25 to
Komler, issued April 19, 1961 and entitled "Assembled Broach
For Complex Profiles".
It is an object o~ the present invention to provide
a new and improved broach system having disposable carbide
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inserts which are mounted in a series within a slot in a
holder and cammed into position by clamp means.
A more specific object of this inven-tion is to
provide a new and improved broach system for broaching
dovetail slots in turbine wheel discs wherein disposable
carbide inserts are positioned within a slot in a broach
holder and clamped in place by means of side and front clamps
which also precisely position the inserts against
particularly configured surfaces of the holder,
The present invention pertains to a new and
improved broach system having disposable carbide inserts
precisely positioned and fastened withln the slot of a
holder. Accordingly, a series of disposable inserts are
placed within the slot o~ a holder and cammed into position
against the opposed walls o~ the slot by an elongated side
clamp and bolt arran~ement. The contact surface of the side
clamp automatically forces the inserts against the side and
bottom locating surfaces of the holder. A ~ront clamp is also
employed to force the inserts against a rear stop. Thus, the
broach system is rapidly assembled without the time-consuming
operatlons required by brazed assemblies or the complicated
arrangements of the prior art. The broach assembly is
ideally suited for broaching dovetail grooves particularly
;n gas turbine engine, turbine wheel discs.
FIG. l is a perspective view of the broach system
comprising the invention r
FIG. 2 is a plan view showing the broach system of
the invention,
FIG. 3 is a rear end view of the broach system with
3Q the end clamp in place,
FIG. 4 is a rear end view of the broach sys-tem '
similar to FIG. 3 with the end clamp removed,
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FIG. 5 is a rear end view of -the broach system
looking in the opposite direction from FIG. 3 which shows a
rear end view, and,
FIG. 6 is a partial side view showing two holders
arranged in series as is customary in performing a complete
broaching operation.
Referring now to the fi~ures, the broach cutter
assembly of the subject invention is designated generally by
reference numeral 10, and it includes an elongated holder
~ember 13 having a base 14, an upper end surface 21 opposed
to base 14, and upwardly extending side walls 18 and 19 joining
base 14 and upper end surface 21. Wall 18 is preferably
substantially perpendicular to base 14 and terminates at an
upper surface 21. Wall 19 preerably extends inwardly from
base 14 at an angle of approximately 10 from the vertical and
terminates at a sloped wall 22 of an outwardl~ protruding
portion 23. In addition, i~ is preferable that base 14
include chamfered edges 16 and 17.
Referring specifically to the Figures 1 and 4, end
surface 21 of ~older 13`includes a longitudinal, generally
: U-shaped slot 12 for receiving a plurality of cutting
nserts 11. Typically, inserts 11 are formed from a cemented
carbide or other hard metal block and they include a base
portion 38, a pair of opposed end walls 54, a pair of opposed
side walls 61 and 62, and a cutting portion 51. Preferablyl
side wall 61 of each insert includes a placement wall portion
39 which is disposed substantially perpendicular to insert
base portlon 38. In addition, it is preferable that insert
side wall 62 include a sloped clamping wall portion 37
opposed to placement wall portion.39, clamping wall portion
.37 sloping inwardly relative to insert base portion.38. As
indica-ted in the~Figures,.U-shaped slot 12 includes a generally
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horizontal support portion 26 for engaging insert base
portion 38; a first wall member 24 for engaging insert
placement wall portion 39 and serving as a stop against
which the inserts may be positioned; and a second wall member
27 which is spaced for a distance from sloped clamping wall
portion 37 of the insert. Preferably, first slot wall
member 24 is perpendicular to slot base 26 and has a length
substantially equal to that of insert placement wall portion
39. In addition, it is preferable that first slot wall 24
be longer than second slot wall 27 with upper terminal point
28 of slot wall member 27 being disposed below holder end
surface 21.
Still referring to Figures 1 and 4,holder 13
preferably includes a clamp support surface 29 which slopes
downwardly from point 28 along the upper surface of
protruding portion 23, and terminates at an upwardly
extending stop wall 31. Preferably stop wall 31 is disposed
substantially perpendicular to clamp support surface 29. A
downwardly sloping wall 32 and a generally vertical
downwardly extending wall member 35 complete the outer
perimeter of projecting portion 23.
Turning now to Figures 2 - 5, the subject assembly
10 further includes a first elongated clal~ping member, i.e.
side clamp 33 which is mounted onto clamp support surface 29,
typically by screw means such as bolts 34. Clamping member
33 includes a clamping surface 36 which exerts a force
against clamping wall portion 37 of inserts 11 so as to cam
the inserts against slot support portion 26 and first slot
wall 24, respectively. Preferably, clamping surface 36 is
substantially parallel to sloped clamping wall portion 37 of
the insert. In addition, it is preferable that a generally
rectangular shim member 51, formed from a soft metal such as
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brass or copper be disposed between clamping surface 36 and
insert clamping wall 37. Shim 51 compensates for
irregularities which may cause surfaces 36 and 37 to not be
flush against one another and thus, prevents slipping of the
~nsert.
Rear end portion 41 of clamping member 33 rests
a~ainst stop wall 31 for purposes of-support. As shown in
FIG. l, a plurality of inserts 11 are positioned and held in
place by the clamping member 33 which is secured, in this
case, by fi~e bolts 34 set in spaced recesses 40, which
engage apertures in the holder 13/ the recesses being
disposed in an upper surface 47 which extends substantially
parallel to clamp base por~ion 52. The inserts 11 are, in
effect, cammed into position against the side and bottom
sur~aces 24 and 26 of the slot 12, wi~h each end wall of one
insert being secureIy flush against the end wall of another
insert.
A second clamping member, i.e. front clamp 44 is
mounted to the holder 13 at one end thereof and ti~htened by
means of bolt 49 so as to force the inserts ll against a stop
member 42. Preferably, clamp member 44 comprises a pair of
bracket-like members 56 and 57 and transverse portion 48
which is secured in position by bolt 49. Stop member 42
Which ;s disposed at the other end of holder 13 is generally
rectangular in cross-section, an upwardly protruding portion
45 sealing off the rear end of slot 12 and masking the
portion of the insert ll below the cu-tting portion 51.
Preferably, protruding portion 45 has substantially the same
configuration as insert end wall 54.
In a particular operation, one or more broach
holders 13a and 13b may be utilized in series, as part of a
system lO', as shown in FIG. 6. The cutting portions 51 of
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the inserts are then graduated accordingly over the total
number of holders 13. The inserts ll shown in the drawings
are typical and thus have not been described in detail
although it has been noted that such inserts ll may be used
to form dovetail alots in super high strength materials used
in gas turbine engines. The clamps 33 and 44 permit the
rapid set-up of the broaching tool and provide improved tool
performance as well.
In summary, the subject invention provides a new
and improved broaching assembly which includes a plurality
of separate disposable shelling insert members. The subject
assembly is very simple in construction, yet assures a
quick and accurate indexing and~or removal of the individual
inserts.
It is to be understood that the above-described
arran~ements are merely illustrative examples of the
application. Numerous other arrangements may be readily
devised by those skilled in the art which will embody the
principles of the invention and fall within the spirit and
scope thereof.
