Note: Descriptions are shown in the official language in which they were submitted.
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Description
Material Fracturing Apparatus
Technical Field
This invention relates generally to impact
apparatus for fracturing material and, more
particularly, to a relatively reciprocatable
shank/housing configuration which facilitates sealing
therebetween.
Background Art
Numerous apparatus are available for
fracturing rock formations and other materials in
mining, excavation, and earthmoving in general.
Fracturing materials by blasting with explosives can be
an efficient technique, but may, under some
circumstances, present an unacceptably high risk when
used near population centers.
Mechanical impact apparatus such as jack
hammers and/or crank driven impactors are known but are
relatively slow and inefficient or constitute bulky
devices which are not easily manipulated into limited
access places.
U.S. Patent 3,868,145 which issued
February 25, 1975, and U.S. Patent 3,922,017 which
issued November 25, 1975, both being assigned to the
present invention's assignee, illustrate two highly
efficient, compact, manipulatable material fracturing
devices. Each of the devices includes a fracturing
shank which is reciprocatably mounted adjacent a power
supply housing. The shank, during operation,
reciprocates between a first impact receiving position
and a second, material fracturing position where the
fracturing shank is in penetrating contact with the
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fracturable material. In U.S. Patent 3,868,145 the
fracturing shank has an impact receiving portion which
protrudes into the housing and is intermittently
impacted by a rotatable eccentric to provide such
reciprocating motion. In U.S. Patent 3,922,017, an
intermediate hammer member extends into the energy
supply housing and is used to transfer energy generated
and stored within that housing to an impact receiving
portion of the shank which is external to the housing.
Such intermediate hammer member extends into and is,
likewise, reciprocably mounted relative to the housing.
In each of the aforementioned apparatus the
reciprocatable member which extends into the energy
supply housing must be sealed to the housing to retain
lubricant within the housing and prevent foreign
particle intrusion into the housing. Moreover, seal
apparatus providing such sealing must be attached to
the reciprocatable member (shank or intermediate
hammer) to avoid transporting foreign debris into the
housing on the surface of the reciprocatable member
when it moves from its second to its first position.
Sliding seals such as are commonly used in hydraulic
cylinder applications and are illustrated in U.S.
Patent 4,121,845 which issued October 24, 1978, U.S.
Patent 2,188,106 which issued January 23, 1940, U.S.
Patent 2,881,015 which issued April 7, 1959, U.S.
Patent 4,021,049 which issued May 3, 1977, U.S. Patent
3,403,932 which issued October 1, 1968, U.S. Patent
3,285,632 which issued November 15, 1966, U.S. Patent
3,317,215 which issued May 2, 1967, U.S. Patent
4,003,666 which issued January 18, 1977, and U.S.
Patent 4,003,667 which issued January 18, 1977, are,
thus, not suitable for use in such material fracturing
apparatus since they can permit transportation of such
foreign debris into the housing.
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A type of boot seal, illustrated in U.S.
Patents 3,868,145 and 3,922,017, is attached to both
the housing and the reciprocatable member which extends
into the housing. While the impacting apparatus
described in the immediately herebefore U.S. Patents
have, in general, fractured material in an efficient
manner, the life of the boot seals has been erratic. A
short boot seal life is highly undesirable since repair
or replacement of such boot seal can be a time
consuming process which must often be performed under
field conditions. Moreover, during such repair, the
impact fracturing apparatus utilizing the boot seal
must be shut down.
Disclosure of the Invention
In one aspect of the present invention a
material fracturing impact apparatus is provided which
has a fracturing shank which is arcuately,
reciprocatably mounted about a pivot axis and which has
a cylindrically shaped sealing surface which is
arranged about a longitudinal sealing surface axis
which is perpendicular to a radial line extending from
the pivot axis to the sealing surface's longitudinal
axis. An annular seal which is connected to both the
shank's sealing surface and a housing into which the
shank is arcuately reciprocatable has a flexible
portion which is bounded by an inner margin that lies
along the radial line. When in an unstrained
configuration, the annular seal is symmetrically
disposed about a longitudinal seal axis extending
therethrough. The seal assumes such unstrained
configuration only when the shank's sealing surface
occupies a position along the arcuate reciprocation
path in which the longitudinal sealing surface axis
coincides with the longitudinal seal axis.
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l67
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Non-symmetric disposition of the seal due to radial
deflection thereof relative to the longitudinal seal
axis necessarily obtains for all other shank positions
along such arcuate reciprocation path as a result of
securing the seal to both the housing and the sealing
surface which is arcuately reciprocatable relative to
the housing. Such radial deflection of the seal during
the shank's arcuate reciprocation is minimized by
arranging the longitudinal sealing surface axis
perpendicular to the pivot axis' radial line and
arranging the seal's flexible portion's inner margin
along such radial line. Minimization of the seal's
radial deflection contributes to a longer seal life,
provides greater fracturing apparatus reliability, and
improves the productivity thereof.
Brief Description of the Drawings
The invention will be more fully understood
from the following detailed description of a preferred
embodiment taken in connection with the accompanying
drawings in which:
Fig. 1 is a partial transverse sectional view
of a material fracturing apparatus illustrating one
embodiment of the present invention;
Fig. 2 is an enlarged view of a portion of
Fig. l;
Fig. 3a is a front elevational view of a
portion of a seal used in the apparatus illustrated in
Fig. 1 and 2;
Fig. 3b is a transverse sectional view of the
seal illustrated in Fig. 3a;
Fig. 4 is a front elevational view of a seal
retaining ring used to secure the seal to a housing
illustrated in Fig. 1 and 2; and
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Fig. 5 is a rear elevational view of a portion
of a shank illustrated in Fig. 1 and 2.
Best Mode for Carrying Out the Invention
Referring now to the drawings in detail, Fig.
1 illustrates an impact fracturing apparatus 10 having
an arcuately reciprocatable shank member 12, a housing
14 having an interior 15 into which the shank 12 is
arcuately reciprocatable, and an annular seal member 16
connected to the reciprocatable shank 12 and the
housing 14 and having a longitudinal seal axis 16a.
The shank 12 is reciprocatable between a first, extreme
impact receiving position (illustrated in full) and a
second, extreme material fracturing position
(illustrated in phantom). Arcuate reciprocation of the
shank 12 to the right (as viewed in Fig. 1) beyond its
first, extreme impact receiving position is precluded
by a stopping member 18 which abuts the shank 12 when
it reaches its first extreme position. Likewise, a
stopping member 20, which is disposed on the opposite
side of the shank 12 and is preferably attached to a
stationary casing member 21 (attachment not shown),
abuts the shank 12 when it reaches the second, extreme
material fracturing position. A pin 22 pivotally joins
the shank 12 to the casing member 21 which also
supports the housing 14 to constrain the reciprocation
of the shank 12 along an arcuate path about a pivot
axis 24.
The shank 12 includes a sealing portion 26, an
impact receiving portion 28, and a fracturing tip 29.
As better illustrated in Fig. 2, the shank's sealing
portion 26 has a cylindrical sealing su~face 26a and a
longitudinal axis 26b about which the cylindrical
sealing surface 26a is disposed. The impact receiving
portion 28 has a longitudinal axis 28b and an impact
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receiving surface 28a which is engageable at
intermittent times with a rotatable eccentric impacting
member 30. A shank guide structure 31 includes two
shank guides 32 (the one nearer the viewer having been
removed to provide better visibility of the impact
receiving portion 28) which are fixedly attached to the
housing interior 15 and together transversely define an
opening within which the impact receiving portion 28 is
receivable. The shank guides 32 are arranged in
closely spaced, transverse relation with the impact
receiving portion 28 so as to direct the impact
receiving surface 28a into an optimum impact receiving
relationship with the impact member 30 and to resist
transversely directed forces exerted on the shank 12 by
the impacting member 30 and by the fracturable
material. The shank guides 32 have an axial length 32a
which is greater than the distance separating the
extreme reciprocation positions of the shank's impact
receiving surface 28a as illustrated in Fig. 1. The
mechanism for intermittently engaging the impacting
member 30 with the impact receiving surface 28a is
better described in U.S. Patent 3,868,145 which issued
February 15, 1975, and is assigned to the present
invention's assignee. The sealing surface's
longitudinal axis 26b is perpendicular to a line 33
which extends radially from the pivot axis 24. As a
result, the longitudinal axis 26b remains perpendicular
to the radial line 33 for all positions assumable by
the shank 12 along its arcuate reciprocation path. The
sealing surface's longitudinal axis 26b is inclined
relative to the impact receiving portion's longitudinal
axis 28b by an angle of approximately 10 by example.
The annular elastomeric seal 16 (best
illustrated in Fig. 3A and 3B) has a relatively rigid
inner terminating portion 36 and a relatively rigid
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outer terminating portion 38 which are respectively
fixedly attached to the sealing surface 26a and the
housing 14 so as to prevent debris intrusion into the
housing's interior 15 and to prevent lubricant leakage
out of the housing's interior 15. When the shank 12
assumes the position illustrated in Fig. 2 which is
intermediate its extreme reciprocation positions, the
seal apparatus 16 is unstrained symmetrically disposed
about the longitudinal seal axis 16a and the sealing
surface's longitudinal axis 26b coincides with the
seal's longitudinal axis 16a. The seal 16 includes an
annular flexible portion 40 which is disposed between
and joined to the relatively rigid terminating portions
36 and 38. A plurality (in this case two) of
concentrically arranged interconnected convolutions 42
and 44 together constitute the flexible seal portion
40. The convolutions 42 and 44 have a convoluted
centersurface 16b which appears as a centerline in Fig.
3B. It is to be understood that the centersurface 16b
is the locus of points traced by the centerline
illustrated in Fig. 3 as it is rotated about the
longitudinal axis 16a. It is to be further understood
that the centersurface 16b is an imaginary surface
which is introduced for reference purposes only.
The convolutions 42 and 44 respectively
include an inner and an outer margin 46 and 48 which
bound the flexible portion 40, interface with the inner
and outer terminating portions 36 and 38 respectively,
and have exemplary thicknesses perpendicular to the
centersurface 16b of 4 mm and 3 mm, respectively. The
inner margin 46 constitutes the effective inner edge of
the flexible portion 40 and is disposed along the
radial line 33. The inner convolution 42 has a smaller
radius of curvature Rl of 17.77 mm by example as
measured from an axis of curvature l to the
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centersurface 16b than does the outer convolution 44
whose radius of curvature R2 of 23.69 mm by example
is measured from an axis of curvature 2 to the
centersurface 16b. The axes of curvature l and 2
(illustrated in Fig. 3B) are separated, or offset, by a
distance which is designated generally by the reference
letter 0 and, by example, equals 16.0 mm.
It is to be understood that the previously
` mentioned sizes and dimensions for the seal 16
correspond to a seal which utilizes an elastomer
material commonly known in the trade as Hytrel. A
suitable alternative seal material constitutes fabric
reinforced neoprene rubber which varies in exemplary
thickness from 7 mm at the inner margin 46 to 5 mm at
the outer margin 48. The offset 0 of the radii of
curvature by example equals 10.0 mm while the radii of
curvature for the inner and outer convolutions 42 and
44, respectively, constitute 16.78 mm and 22.37 mm for
such fabric reinforced neoprene seal material.
The inner and outer margins 46 and 48
respectively interface with and are connected to the
inner and outer terminating portions 36 and 38. The
thickness of seal 16 perpendicular to the centersurface
16b varies from the inner margin 46 to its outer margin
48 with decreases rrom the inner margin's thickness
being proportional to the radial distance H
(illustrated in Fig. 3B) separating the centersurface
16b at the inner margin 46 from the centersurface 16b
at the seal location in question. The seal's
terminating portions 36 and 38 have thicker cross
sections (as measured perpendicularly to the
centersurface) than the flexible portion 40 since the
terminating portions 36 and 33 are actually joined to
the relatively reciprocatable shank 12 and housing 14.
The flexible seal portion 40 has isolation faces 50 and
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g
52 which are equidistant from the convoluted
centersurface 16b and are respectively exposed to the
environment surrounding the impact apparatus 10 and
that existing in the housing's interior 15.
The seal 16 further includes an annular
connection member 54 of U-shaped cross section which is
disposed about and vulcanized bonded to the inner
terminating portion 36. The U-shaped connection member
54 is open along the axial end adjacent the inner
margin 46 and is closed on the opposite axial end. The
connection member 54 has a radially inwardly facing
surface 56 which is threadably engageable with the
sealing surface 26a. A plurality (two in the
illustrated case) of openings 57 in the connecting
member 54 are provided to receive a tightening tool
used to relatively rotate and threadably engage the
seal 16 and the sealing surface 26a with a
predetermined torque. A cylindrical locking extension
58 protrudes from the connection member 54 and is
deformable into a plurality of restraining slots 59
(best illustrated in Fig. 2) formed in the shank 12 to
prevent relative rotation of the connection member 54
and the sealing surface 26a in a threadably disengaging
direction.
A retainer ring 60, illustrated in Figs. 1, 2,
and 4, is engagable with the seal's outer terminating
portion 38 and is securable to the housing 14 by a
plurality of threaded screw bolts 62. The retaining
ring 60 is annular relative to the longitudinal seal
axis 16a except in the vicinity of a vertical
centerline therethrough where the retaining ring's
radial thickness is reduced to permit disposition
thereof between the seal's outer terminating portion 38
and the casing member 21. The retaining ring 60 and
the outer terminating portion 38 are engageable along
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cooperatively ramped interfacing surfaces 38a and 60a
which are respectively disposed thereon. Tightening
the screw bolts 62 displaces the retaining ring 60
relative to the outer terminating portion 38, increases
the interference therebetween as a result of the
cooperative inclination of the ramped surfaces 38a and
60a, compresses the seal's outer terminating portion
38. Optimum sealing of the seal's outer terminating
portion 38 with the housing 14 and the retaining ring
60 obtains when the retaining ring 60 engages the
housing 14. A securing bead 38b of the terminating
portion 38 extends radially inwardly and is receivable
in a circular notch 14a formed in the housing 14.
An enlarged view of the impact receiving
portion 28 is illustrated in Fig. 5 as viewed from a
vantage point A as indicated in Fig. 1. The impact
receiving portion 28 has an outer periphery 28c which
constitutes a four-sided figure whose corners have been
rounded. The longest protrusion of the outer periphery
28c from the impact receiving portion's longitudinal
axis 28b is the radius 28d which is smaller than the
radius separating the sealing surface 26a from the
sealing longitudinal axis 26b. Such size differential
enables axial displacement of the seal 16 over the
impact receiving portion's outer periphery 28c.
Industrial Applicability
With the fracturing apparatus 10 assembled as
previously described, highly effective sealing is
provided between the arcuately reciprocatable shank 12
and the housing 14 by the seal 16 which is fixedly
joined to both. When the impact receiving portion 28
of the shank is in its first extreme position (furthest
intrusion into the housing's interior 15 between the
shank guides 32), the sealing surface's longitudinal
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axis 26b is skewed relative to the seal's longitudinal
axis 16a. A coincident relationship between the seal's
longitudinal axis 16a and the sealing surface's
longitudinal 26b axis obtains when the shank 12
occupies the position illustrated in Fig. 2. Arcuate
reciprocation of the shank 12 in either direction from
the position illustrated in Fig. 2 results in a
pivoting of the sealing surface's longitudinal axis 26b
relative to the seal's longitudinal axis 16a. Such
relative pivoting of the longitudinal axes 16a and 26b
necessarily occurs since the sealing surface 26a is
constrained to pivot about the pivot axis 24 while the
seal's longitudinal axis 16a remains fixed since it is
defined by the configuration of seal 16 when it is
unstrained. The seal's longitudinal axis 16a thus
occupies a stationary position relative to the housing
14. The center of the shank's impact receiving surface
28a is displaceable between the extreme reciprocation
positions illustrated in Fig. 1 through a distance of
approximately 70 mm by example. When the shank 12
occupies the second or extreme material fracturing
position, the maximum strain on the seal 16 is
approximately 9.6% which is significantly lower than
the strain levels encountered in previous seals used in
similar material fracturing apparatus.
Canting the shank's sealing portion 26
relative to the shank's impact receiving portion 28,
providing a concentric relationship between the seal 16
and the sealing portion 26 for one position of the
shank 12, and arranging the seal's inner margin 46
along the radial line 33 as well as utilizing the seal
geometry previously described results in greatly
reduced strain levels in the seal 16 which are
substantially equal at the points of maximum strain.
Oscillation of the shank about the pivot axis 24 is
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necessary to provide the desired reciprocating motion
thereto. At the seal's inner terminating portion 36,
this oscillation produces an arcuate motion which may
be resolved into two perpendicular components of
displacement: an axial displacement component parallel
to the longitudinal axis 16a of the unstrained seal 16
and a radial displacement component perpendicular to
the unstrained seal axis 16a. Such radial displacement
can be visualized by noting that the top (as viewed in
Fig. 1) of the seal's terminating portion 36 will
slightly approach the top of the seal's terminating
portion 38 simultaneously with the bottom of the seal's
terminating portion 36 moving away from the bottom of
the seal's terminating portion 38. Seal strain
produced by the combined axial and radial displacements
is greater than that produced by the axial displacement
alone, primarily because the radial displacement
deforms the seal into an unsymmetrical configuration
relative to the longitudinal axis 16a of the unstrained
seal. It was found that the additional strain
resulting from such radial deflection of the seal 16
could be minimized by: (1) canting the seal 16 and the
sealing portion 26 to provide perpendicularly between
the radial line 33 and the longitudinal axis 26b; and
(2) arranging the seal's inner margin 46 (located where
the seal 16 becomes rigid or is effectively attached to
the shank 12) along the radial line 33. Cooperatively
canting the longitudinal axes 26b and 16a to provide
coincidence thereof when the shank configuration of
Fig. 2 occurs reduces the strain in the seal 16 during
arcuate reciprocation of the shank 12 while the seal's
tapered wall thickness and convoluted shape equalizes
the maximum strains induced therein. The geometrical
features of seal 16 which are responsible for providing
such substantially equalized maximum strains are the
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tapered thickness which is a function of the radial
distance H, the convolutions' different radii of
curvature Rl and R2, and the offset distance 0
between the axes of curvature.
The seal 16 may be removed from the material
fracturing impact apparatus 10 by extracting the screw
bolts 62, removing the retaining ring 60, disengaging
the deformed areas of the locking extension 58 from the
locking slots 59, and rotating the seal 16 and integral
connection member 54 to threadably disengage them from
the sealing surface 26a. After moving the stopping
member 20 to an unobstructing position, the shank 12 is
arcuately displaced to a convenient position where the
impact receiving portion 28 is disengaged from the
shank guides 32 and is resident outside the housing's
interior 15. The seal 16 is then axially displaced
along the outer periphery 28c of the impact receiving
member 28 until it passes the impact receiving surface
28a and can be removed to a remote location. Assembly
of the seal 16 is accomplished in the opposite order as
just described: the stopping member 20 is moved to an
unobstructing position; the shank 12 is arcuately
displaced to a position where the impact receiving
portion 28 is exterior to the housing 14; the seal 16
is slidingly displaced over the impact receiving
portion's outer periphery 28c; the seal 16 and integral
connection member 54 are rotated relative to the
threaded sealing surface 26a until they are threadably
engaged to a suitable tightness; areas of the locking
extension 58 which are aligned with the restraining
slots 59 are deformed thereinto; the terminating
portion 38 of seal 16 is engaged with the housing 14
such that the restraining bead 38b is inserted in the
notch 14a to secure the seal 16 in place and facilitate
assembly of the retaining ring 60; the retaining ring
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60 is disposed on the opposite side of the seal's
terminating portion 38 from the housing 14; and the
screw bolts 62 are inserted through the retaining ring
60 and torqued into the housing 14 to provide the
desired sealing between the seal's terminating portion
38 and the housing 14.
During shank reciprocation, the cross section
of the flexible seal portion 40 flexes between an
"S-shape" and a nearly straight line as illustrated in
Fig. 1. The respective orientation of the convolusions
42 and 44 toward and away from the housing 14 cause
fracturable material and other debris exposed to the
isolation face 50 to be expelled therefrom during seal
flexure and thus avoid potentially debilitating, seal
immobilizing debris accumulation on the isolation face
50. The U-shaped cross section of the connection
member 54 shields the vulcanized bond from direct
impingement by fracturable material during shank
reciprocation and maximizes the bonding area between
the seal material (preferably Hytrel) and the
connection member 54 (preferably carbon steel) for the
purpose of reducing the stress (and thus increasing the
life) imposed thereon during shank reciprocation.
While the seal 16 has been illustrated as
providing sealing between an arcuately reciprocatable
shank 12 and a stationary housing 14, it is to be
understood that the seal 16 may be used with equal
facility with the purely translatably reciprocatable
intermediate hammer member described in U.S. Patent
3,922,017 which issued November 25, 1975.
It will now be apparent that a material
fracturing impact apparatus 10 and associated seal
apparatus 16 have been provided in which the following
obtain: excellent sealing, exceptionally long seal
life, and high reliabllity. Such attributes are
necessary for practical operation of the impact
apparatus 10 and seal apparatus 16 in the hostile
environments to which they are customarily subjected.
