Note: Descriptions are shown in the official language in which they were submitted.
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Prior rock drills have commonly been provided with
a striking bar assembly including an elongated striking bar
which is retained within and extends outwardly of the forward
end of the drill for actuation in one or more drilling modes
- such as simultaneous percussive and rotary actuation to drill
~ a bore hole by means of an elongated drill string secured to the
,~"~ free end of the striking bar. Such prior drills generally may
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be classified as open front end drills if the structure of
the striking bar retention means therein permits removal or
insertion of the striking bar without any drill disassembly.
Examples of known open front drills are the lug types wherein
lugs formed intermediate the ends of the striking bar cooperate
, with groove means in the drill chuck to secure the striking bar
in the manner of a bayonet lock, and the latching type-wherein
, a latch member is carried adjacent the forward end of the drill
to secure the striking bar by engaging a peripheral portion
thereof.
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Although heretofore known striking bar assemblies
for open front type drills have generally served the intended
purposes, they have nevertheless often been subject to serious
deficiencies. For example, in many open front drills striking
- bar removal and replacement requires the striking bar to be
; passed axially through the bearing portion of the forward
bushing, and the maximum striking bar diameter thus has often
been limited to the internal bearing diameter of the forward
- bushing. In such cases it has been impossible to provide a
striking bar with a desirably enlarged rearward end portion. -~
Other striking bar design considerations arising from the
~; requirement for compatibility with open front drills have
seriously limited the available design options for striking bar
lubrication, venting and rotary driving in such drills.
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These and other deficiencies of the prior art are
alleviated by the present invention which in a specific form
provides a novel striking bar assembly for an open front end
type drill wherein the striking bar includes an enlarged rear-
ward end portion and enlarged intermediate driver portion, both
of which are ab~e to be passed axially through a forward support
bushing having a bearing surface diameter smaller than the
nominal diameter of either such rearward end portion or driver
portion. The novel striking bar assembly of this invention ~
additionally provides improved venting and lubrication through ~ -
axially extending passageway means formed in the enlarged
diameter rearward end portion thereof.
The present invention is defined as a working member
assembly in an impact tool means comprising: an elongated
working member having at least a pair of axially aligned
support portions and a rotary driver portion; elongated
bearing means adapted to be carried by such impact tool means
and cooperable with the working member to supportingly engage
the support portions of the working member; the bearing means
including a pair of bearing portions with each of the bearing
portions being formed to supportingly encompass a respective
one of the pair of support portions for support of the working
member in a manner to permit rotation thereof with respect
to the bearing portions; and one of the support portions of
the working member having a transverse extent greater than
the transverse extent of the other of the support portions and
being cooperable with the bearing portion which supportingly
encompasses the other support portion to be movable axially
therethrough for removal and insertion of the working member
from and into the bearing means.
These and other features of the invention are
more fully specified in the following description of the invention
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with reference to the accompanying figures in which:
Fig. 1 is a central axial section of a rock drill
forward end portion including a striking bar assembly according
to one embodiment of the instant invention;
Fig. 2 is a fragmentary transverse section of the
drill of Fig. 1 taken on line 2--2 of Fig. 1 and showing the
striking bar assembly in the open or nonretained state;
Fig. 3 is a transverse section similar to Fig. 2
with portions broken away to show the striking bar assembly in
the closed or retained state; and
Fig. 4 is a fragmentary transverse section of
Fig. 1 taken on line 4--4 of Fig. 1.
There is generally indicated at 10 in Fig. 1 the
forward end portion of a powered actuator or tool means, shown
as a percussive rock drill and including a yoke portion 13 which
carries therewithin an elongated generally cylindrical striking
bar 34 retained within yoke portion 13 by means generally
indicated at 12 and more completely described and claimed in
U.S. Patent No. 4,106,573 issued on August 15, 1978 to E.A.
Bailey entitled "Drill" which is assigned to the same assignee
as the instant application.
Yoke 13 comprises an elongated, generally cylindrical
housing 14 rigidly secured coaxially intermediate a generally
annular front cap 16 and an elongated percussion portion 18
(forward end only shown) by any suitable means for example, a
plurality of longitudinally extending conventional side rods
(not shown) secured by threaded fasteners 19.
In operation a hammer piston 17 suitably reciprocably
carried within portion 18 is actuated to repetitively impact
the rearward end of striking bar 34 simultaneously with
independent axial rotation of striking bar 34 by means described
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hereinbelow to provide a rotary, percussive drilling action
for drilling bore holes in hard formations such as rock.
Striking bar 34 is supported coaxially within an elongated
~nnalar chuck
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member 20 which, in turn, is rotatably journaled within housing
14 by axially spaced, annular roller bearing assemblie,s 22 for
rotation by any suitable drive means such as an annular motor
means 21 and planetary gear train 23 which are more fully
described in U.S. Patent No. 3,858,666.
Member 20 incLudes a stepped cylindrical inner
periphery 25 wherein a generally annular rear chuck bushing
24 is press-fitted coaxially ad~acent the rearward end thereof.
An elongated annular chuck driver 28 is similarly press fitted
10~ within periphery 25 coaxially forwardly adjacent bushing 24 f
' and additionally i8 nonrotatably keyed to chuck member 20 '
; ~ for rotary driving thereby as by respective pluralities of
intermeshed splines 30 spaced circumferentially about ad~acent
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peripheral portions of driver 28 and member 20. A generally
annular elongated~forward bushing or bearing member 26 is
loc-ted coaxially~forwardly; ad~acent driver 28 such that a rear-
ward end portion~26A thereof ls engaged in rotary driving
eogagement within~the forward end of chuck inner periphery 25
and a~forward end portion 26B thereof is rotatably supported
20 ~ within;~a cylindrical inner periphery 11 of cap 16. Cap 16,
when~assembled to housing 14, cap~tively retains chuck member 20
and béarings 22 within bousing 14 with bushing 24 and driver 28 '.
carried therewithin~as described. Cap 16 additionally captively
rètains bushing 26 coaxially intermediate a rearwardly facing
annular thrust bearing surface 29 thereof and driver 28.
The coaxially aligned inner peripheries of rear
bushing 24, driver 28 and forward bushing 26 are sized to
receive striking bar 34 therewithin with axially aligned rear-
- ward and forward striking bar portions 34A, 34C rotatably
~30~ supported within respective bushings 24, 26. An enlarged
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striking bar portion 34B axially intermediate portions 34A,
' 34C includes a plurality of circumferentially spaced, radiallyoutward extending drive splines 36 which are engaged in rotary
i driving engagement with cooperably formed splines 38 spaced i~
circumferentially about the inner periphery of driver 28 whereby
striking bar 34 may be driven in axial rotation by motor 21. ~ ~ -
In order to permit removal and insertion of striking
bar 34 in yoke portion 13 without disassembly of cap ~6 from the
drill, all portions of the striking bar 34 located within yoke
portion 13 are able to pass axiaIly through bushing 26. Accord- ,s~
ingly, the inner periphery of bushing 26 includes a radially
inner, circumferentially segmented bearing surface means S2 ~-
which rotatably supports formed striking bar portion 34C, and a
~- ~ plurality of circumferentially spaced, axially extending
grooves 40 (Figs. l and 2) sized and located to receive splines
36 such that when the spline~ 36 are circumferentially aligned
with~grooves 40 as in Fig. 2 striking~bar 34 may be passed
xially through bushing 26 a8 desired. When splines 36 are
circumferentially misaligned with grooves 40 (Fig. 3) str~king
20~ ~ bar 34 is retained within chuck portion 13 by abutment of a for-
ward axial end 36A of splines 36 upon circumferentially spaced
; rearward end surface portions 42 of bushing 26 formed cir-
cumferentially ineermediate grooves 40.
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Bushing 26 rearward end portion 26A is keyed in '~
rotary driving engagement with chuck member 20 by respective
cooperative pluralities of circumferentially spaced splines 44
and 46 (Figs. l, 2 and 3) to be driven in axial rotation at
the same rotary speed as striking bar 34. As shown in Fig. 2,
the circumferential spacing "S" between adjacent splines 46
is approximately twice the width "W" of splines 44 and the
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resulting lost motion rotary connection therebetween permits
sufficient rel~tive axial rotation between bushing 26 and
striking bar 34 to provide the desired alignment and misalign-
ment of grooves 40 and splines 36 as described in the hereinabove
referenced U.S. Patent . . ;
Like the striking bar driver portion 34B, end portion
34A is of a larger nominal diameter than inner periphery 52 of
bushing 26 through which striking bar 34 is passed during removal
and replacement thereof. More specifically, rearward end portion
34A is of larger nominal diameter than the forward end portion
34C by virtue of having a plurality of circumferentially spaced,
axially extending lands 54 (Fig. 1 and 4) aligned with ones of
splines 36, and intervening, axially extending undercut grooves
; 56, the diameter across which grooves 56 is substantially the
same as or smaller than the diameter of forward end portion 34C. 1 ;
The nominal outer diameter of rearward end portion 34A as de- - -
fined by the diameter across lands 54 thus is larger than the
diameter of bearing surface 52 in bushing 26. During striking
bar removal and replacement the lands 54, which are aligned
with ones of splines 36, register with respective grooves 40
and therefore do not interfere with smaller diameter bearing
surface portions 52. Likewise, grooves 56, being of the same
or smaller diameter than portion 34C, pass through forward
bushing 26 in register with bearing surface portion 52 whereby
the entire striking bar 34 including enlarged diameter rear-
ward end portion 34A is able to be passed axially through forward
bushing 26.
The described striking bar assembly affords numerous
advantages not available heretofore in open front drills. For
example, throughout the axial engagement of portion 34A within
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~ rear bushing 24, the grooves 56 cooperate with the bearing I -
; surface area 53 of bushing 24 to provide axially extending
clearance spaces 58 circumferentially intermediate adjacent
lands 54 through which otherwise isolated regions such as at
60 adjacent the impact end of piston 17 (Fig. 1) may be ~
vented to the atmosphere to preclude fluid pressure accumulationi~ l -
therein. Clearance spaces 58 additionally may be used to
conduct lubricant, perhaps in the form of an air-oil mist, to ~ -
~ ; lubricate wear surfaces in yoke portion 13. Furthermore, the ,~ I0~ striking bar rearward end portion 34A is not limited to the
standardized nominal diameter of the forward end portion 34C
which is determined in part by the dimensions of commercially '~ -
available drill steels and couplings. The enlarged nominal
diameter of portion 34A provides added material mass and
strength which is highly desirable to better sustain the impact
blo~ws of piston 17, particularly in view of such known mass
and strength teficiencies as resulting from an enlarged coaxial
bo* (not shown) commonly formed in the striking bar rearward
end to receive a flushing fluid tube.
20 ~ According the the description hereinabove the present l;
invention provides a novel striking bar assembly particularly
well~suited for use in an open front rock drill wherein a ' -
rearward end bearing portion and an intermediate driver portion ~ -
of the striking bar forward end portion, are able to be passed
through a forward bushing which rotatably supports such forward
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5; ~ ~ ~ end portion. Notwithstanding the description hereinabove of a
particular preferred embodiment of the invention it is to be
; uhderstood that this invention may be practiced in numerous
alternative embodiments with various modifications thereto
without departing from the broad spirit and scope thereof.
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For example, various alternative configurations and numbers
of the splines 36 on striking bar 34 may be employed; striking :
bar portions 34A, 34B and 34C are generally axially aligned but
need not necessarily be coaxially aligned, various alternative
striking bar securing and release means may be employed as
well as alternative rotation motors and drill actuating means;
tbe particular configuration of rearward end portion 34A and of
the inner periphery of bushing 26 may be varied within a wide
design latitude;:and the like.
~10~These and other embodiments and modifications having
been envisioned and anticipated by the inventors, the invention
should be construed broadly and limited only by the scope of
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~ the claims appended hereto. ~ -
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