Note: Descriptions are shown in the official language in which they were submitted.
CA 02865452 2016-02-22
QUICK CHANGE RAIL FASTENER DRIVING WORKHEAD UNIT
BACKGROUND
The present disclosure generally relates to railroad right-of-way
maintenance machinery, and more particularly relates to machinery used for
driving fasteners into rail ties for securing rail tie plates and rails to the
ties.
Rail fasteners as contemplated herein include cut spikes, lag screws,
hairpin spikes and other types of rail fasteners used for retaining tie plates
upon
ties, and rails upon tie plates, as are known to skilled practitioners. In
some cases
in the specification, "spikes" may be used interchangeably with "rail
fasteners."
The use of the term "spikes" is not intended to limit the scope of the present
invention.
During the course of railroad maintenance work, it is common that
existing rail fasteners are removed for replacement of rail ties, tie plates,
rails and
for other maintenance operations. Once the desired maintenance is complete,
the
fasteners need to be reinstalled. For installing the fasteners, a conventional
spike
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driving workhead unit employs an elongated shaft-like anvil which is
vertically
reciprocating relative to a spotting carriage to drive the fasteners into the
ties.
Under the upward and downward actions of a hydraulic impact hammer, the anvil
repeatedly applies downward pressure upon spikes in a pushing or percussion
function. After extended use, a spike engagement end of the anvil wears out
and
thus it needs to be replaced. To perfolin maintenance on the conventional
spike
driving workhead unit, a hole must be dug in the ballast so that conventional
guide
rods can be lowered below a hammer bushing, which is very inconvenient for
replacement of the worn-out anvil.
Further, because the conventional guide rods are fastened with
transverse threaded fasteners such as bolts, vibrations and impacts caused by
the
percussive actions of the hammer loosen and eventually shear the bolts. Spring
pins are also used to fasten the guide rods to the jaw block, but as with the
bolts
the spring pins also fail due to the same reasons stated above. Failures of
other
moving components are also caused by manufacturing tolerances, thereby
creating
loose connections and improper alignments when assembled. Therefore, there is
a
need for securing a decreased chance of component failure and increasing
serviceability of the conventional spike driving workhead unit during
maintenance.
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SUMMARY
The present disclosure is directed to a railway right-of-way
maintenance machine having a spike driving workhead unit that is quickly
changeable and easily disassembled for maintenance. Specifically, a lower
portion
of the spike driving workhead unit including an anvil assembly and a jaw
assembly is detachable by unfastening associated clamps configured to
releasably
attach the members to the unit. A combination of three clamps with a specific
geometry matingly engages corresponding components of the spike driving
workhead unit.
One aspect of the machine is that, as described in further detail
below, the geometry of each clamp allows securing the corresponding component
in place by pivotally fastening the clamp with a biasing force. An indentation
of
the corresponding component mates with a matching indentation of the clamp to
ensure that the component is properly installed and oriented in the unit. As a
result, the clamp prevents linear and rotational movement of each component,
and
maintains its vertical and rotational alignments during operation.
Another important aspect is that the lower portion can be quickly
and easily removed from the spike driving workhead unit for maintenance
without
ballast excavation. This removal is achieved by unfastening the three clamps
and
disassembling the unit in sequence. More specifically, after the unfastening
of the
clamps, guide rods are removed upwardly from the jaw assembly, and the lower
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portion is released from an impact hammer housing by removing a hammer pin
from the housing. Once the lower portion is released from the unit, a worn-out
anvil inside the anvil assembly is conveniently pulled out and replaced.
In one embodiment, a fastener driving workhead unit is provided for
performing an operation on spikes of a railroad track having a plurality of
ties, and
includes a hammer housing configured for accommodating a hammer, the housing
being attached to a hammer bushing having a hammer bushing clamp. Also
included in the workhead unit is an anvil assembly having an anvil and an
extension coupler, the extension coupler being releasably secured to the
hammer
bushing by fastening the hammer bushing clamp. Further, the workhead unit
includes a jaw assembly having a jaw block, the jaw block having at least one
jaw
block clamp for releasably securing a guide rod to the jaw block by the jaw
block
clamp, such that the anvil freely reciprocates in the hammer housing for
driving
the spikes into the plurality of ties. In another embodiment, a method of
disassembling a fastener driving workhead unit is provided, wherein the method
includes releasing a plurality of jaw block clamps disposed on a jaw block of
the
fastener driving workhead unit; removing a plurality of guide rods connected
to
the jaw block after releasing the plurality of jaw block clamps; releasing a
hammer
bushing clamp disposed on a hammer bushing, which is connected to a hammer
housing of the fastener driving workhead unit; removing a hammer pin from a
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keyway opening machined on a side wall of the hammer housing; and releasing an
anvil assembly and a jaw assembly of the fastener driving workhead unit.
In still another embodiment, a clamp is provided for use in a railway
fastener driving workhead. The clamp includes an elongate body having two
ends,
a finger pull disposed at at least one of the ends, a protrusion extending
from an
inner wall of body adjacent each end, the protrusions defining a central
indentation
therebetween and, with the body, forming a general "C" shape when viewed from
above. A horizontal bore is defined in each protrusion.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top perspective view of the present spike driving
workhead unit;
FIG. 2 is an exploded perspective view of the spike unit of FIG. 1
when jaw block clamps are unfastened;
FIG. 3 is an exploded perspective view of the spike unit of FIG. 2
when a hammer bushing clamp is unfastened;
FIG. 4A is a front exploded perspective view of the spike unit of
FIG. 3 when a hammer pin is removed;
FIG. 4B is a rear exploded perspective view of the spike unit of FIG.
4A;
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FIG. 5A is an inner perspective view of a jaw block clamp of the
present unit;
FIG. 5B is an outer perspective view of the jaw block clamp of FIG.
5A;
FIG. 6A is an inner perspective view of a hammer bushing clamp of
the present unit;
FIG. 6B is an outer perspective view of the hammer bushing clamp
of FIG. 6A;
FIG. 7A is an enlarged perspective view of the present jaw assembly
featuring the present jaw block;
FIG. 7B is a cross-sectional view of the present jaw block taken
generally along the line A-A in FIG. 7A and in the direction generally
indicated;
FIG. 8A is an enlarged perspective view of the present anvil
assembly featuring the present hammer bushing;
FIG. 8B is a cross-sectional view of the present hammer bushing
taken generally along the line B-B in FIG. 8A and in the direction generally
indicated;
FIG. 9A is a front exploded perspective view of the spike unit of
FIG. 3 featuring a second embodiment of the jaw block clamp and a second
embodiment of the hammer bushing clamp;
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FIG. 913 is a rear exploded perspective view of the spike unit of FIG.
9A;
FIG. 10A is an inner perspective view of the jaw block clamp of
FIG. 9A;
FIG. 10B is an outer perspective view of the jaw block clamp of
FIG. 9A;
FIG. 11A is an inner perspective view of the hammer bushing clamp
of FIG. 9A; and
FIG. 11B is an outer perspective view of the hammer bushing clamp
of FIG. 9A.
DETAILED DESCRIPTION
Referring now to FIG. 1, the present spike driving workhead unit is
generally designated 10 and is designed to drive railroad spikes (not shown)
into
railroad ties (not shown). Several types of rail fastener applicators or
drivers are
known, and exemplary models are described in commonly assigned U.S. Pat. Nos.
4,579,061; 4,777,885; 5,191,840; 5,671,679; and 7,104,200. Included in the
unit
is a hammer housing 12 for accommodating a hydraulic impact hammer (not
shown) which is reciprocally vertically movable to drive the spikes into the
ties.
A lower end 14 of the hammer housing 12 is attached to a hammer bushing 16
having a hammer bushing clamp
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18. While other suitable shapes are contemplated, it is preferred that the
hammer
bushing 16 has a substantially cylindrical shape for accommodating an
extension
coupler 20. The extension coupler 20 is releasably secured to the hammer
bushing
16 by pivotally fastening the hammer bushing clamp 18 as described in further
detail below.
An anvil assembly, generally designated 22, includes the extension
coupler 20 at its upper end. Further included in the anvil assembly 22 is a
tube-
like anvil sleeve 24 that defines a passageway for a shaft-like anvil 26 (best
shown
in FIGs. 3-4) within the sleeve. In operation, the anvil 26 travels
reciprocally
vertically inside the sleeve 24 to matingly engage the head of the spike.
Further
included in the anvil assembly 22 is a spring 28 that surrounds the anvil
sleeve 24,
and is connected at one end to the extension coupler 20 and at an opposite end
to a
jaw assembly, generally designated 30. More specifically, the spring 28 biases
at
its upper end the extension coupler 20, and also biases at its lower end the
jaw
assembly 30. When the jaw assembly 30 is in an open position, the sleeve 24
holds the spike inside the sleeve during percussion, and subsequently the
spike is
driven into the tie.
Included in the jaw assembly 30 is a pair of spike gripping jaws 32
mounted to a jaw block 34 via a pair of rod eyes 36 to grasp the spike. In
operation, the jaws 32 are pressurized toward the closed or gripping position
by
the rod eyes 36 which are hydraulically or mechanically biased, e.g., spring
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, .
biased, as is well known in the art. To facilitate the reciprocal movement of
the
anvil 26, the jaw block 34 defines a central opening 38 through which the
anvil
passes to separate the jaws 32 and drive the spike into the tie as taught in
U.S. Pat.
No. 5,191,840.
Also included in the jaw block 34 is a plurality of throughbores 40,
relatively smaller than the central opening 38, and each disposed for the
vertical
passage of the jaw block 34 that moves with a plurality of guide rods 42. The
rods
42 guide a vertical movement of the anvil assembly 22 during percussing
operation of the spike driving workhead unit 10. Also, the rods 42 guide the
downward movement of the jaw assembly 30 to a spiking position. As is known
in the art, the guide rods are slidingly engaged in corresponding bores of a
workhead feeder frame of the type disclosed in US Patent No. 5,398,616. While
other configurations are contemplated, it is preferred that two throughbores
40 are
provided for the accommodation of two guide rods 42 for each spike driving
workhead unit 10. A lower end 44 of each guide rod 42 matingly engages a
corresponding throughbore 40, and is secured to the jaw block 34 by pivotally
fastening a corresponding jaw block clamp 46 as described in further detail
below.
An upper end 48 of each guide rod 42 has a plurality of spaced apertures 50
for
receiving a locking pin 52 to secure the rod to a weldment bracket (not
shown).
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During operation, the lower end 44 of each guide rod 42 is
releasably attached to the jaw block 34 by fastening the corresponding jaw
block
clamp 46 using a transverse threaded fastener 54, such as a bolt. A rod
indentation
56 (best shown in FIGs. 2-4) is disposed at each lower end 44 of the guide rod
42
for mating with a matching indentation of the jaw block clamp 46 as described
in
further detail below.
Typically, the spike driving workhead unit 10 is attached to a
cylinder (not shown) via a sled (not shown) for upward and downward
movements. A stroke range of the cylinder is between 18" and 19.5", but
preferably 19.5". The sleeve 24 is firmly attached to the hammer housing 12
through the extension coupler 20 and the hammer bushing 16. The sleeve 24
travels in upward and downward directions along an operation axis of the
hammer
housing 12. Inside the sleeve 24 is the anvil 26, and it freely reciprocates
in the
hammer housing 12. The sleeve 24 is guided through the central opening 38.
The jaw assembly 30 and the guide rods 42 travel downwardly under
the action of the spring 28 biasing between the extension coupler 20 and the
jaw
block 34. A purpose of the spring 28 is to keep the jaw assembly 30 and the
guide
rods 42 to travel at the same speed as the hammer housing 12, the sleeve 24,
and
the cylinder so that the spike is held securely. A length of the spring 28
does not
change when the spike driving workhead unit 10 moves downwardly to the
spiking position until the locking pins 52 hit the top of a bushing weldment
(not
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shown). At this time, the sleeve 24, the hammer housing 12, and the anvil 26
continue to descend, and the spring 28 starts to compress. Then, the jaws 32,
which are spring biased (not shown), start to open as the sleeve 24 is passing
though the jaws. At this time, the spike driving workhead unit 10 receives
resistance from the spike head, and this triggers the anvil 26 for driving the
spike
into the tie.
Referring now to FIGs. 2, 5A, and 5B, the geometry and functions of
the jaw block clamp 46 are shown in further detail. A vertical bore 58 of each
jaw
block clamp 46 allows the jaw block clamp to pivot laterally about an axis of
the
vertical bore when the jaw block clamp is pushed into or pulled out of a
corresponding jaw block side cavity 60 of the jaw block 34. Preferably, a
finger
pull 62 disposed opposite the vertical bore 58 is used for horizontal
rotational
manipulation of the jaw block clamp 46. Each side cavity 60 is configured to
be
in fluid communication with the throughbore 40 for receiving the guide rod 42.
When the jaw block clamp 46 is fully pushed into the side cavity 60, a clamp
or
central indentation 64 disposed on an inner wall 66 of an elongated body 67
matingly engages the rod indentation 56 of the guide rod 42. Securing the jaw
block clamp 46 into the jaw block side cavity 60 is achieved by rotationally
fastening the bolt 54 through a horizontal bore 68 disposed transverse to the
vertical bore 58 near the finger pull 62.
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In the preferred embodiment, the jaw block clamp 46 has a first
protrusion portion 70 at one end and a second protrusion portion 72 at an
opposite
end. Specifically, the first protrusion portion 70 having the horizontal bore
68 is
generally rectangular or block-shaped and is disposed at one end of the jaw
block
clamp 46, and at an opposite end, the second protrusion portion 72 having the
vertical bore 58. The second protrusion 72 is generally cylindrical in shape.
Preferably, a width of the first protrusion portion 70 along the axis of the
horizontal bore 68 is substantially the same with a corresponding width of the
second protrusion portion 72. It is contemplated that the general shapes of
the
protrusions 70, 72 may vary to suit the application.
Additionally, the jaw block clamp 46 defines a generally "C"-shape
when viewed from above in the orientation of FIG. 5A for fitting over the rod
indentation 56 and locking the guide rod 42 in the throughbore 40. This
configuration enables the jaw block clamp 46 to generate a squeezing force
against
the guide rod 42 when the jaw block clamp is tightened by rotationally
fastening
the bolt 54 through the horizontal bore 68 and into the jaw block 34. As a
result,
the clamp indentation 64 of the jaw block clamp 46 is slightly bent to firmly
directly bias the rod indentation 56 of the guide rod 42, thereby ensuring a
proper
installation and orientation of the guide rod 42 in the jaw block 34.
Referring now to FIGs. 3, 6A, and 6B, the geometry and functions of
the hammer bushing clamp 18 are shown in further detail. Both the hammer
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bushing clamp 18 and the jaw block clamp 46 share similar features, and
components shared with the spike driving workhead unit 10 are designated with
identical reference numbers. As is the case with the jaw block clamp 46, a
vertical
bore 158 of each hammer bushing clamp 18 allows the hammer bushing clamp to
pivot laterally about an axis of the vertical bore when the hammer bushing
clamp
is pushed into or pulled out of a bushing side cavity 74 of the hammer bushing
16.
Preferably, as shown in FIGs. 6A-6B, a finger pull 162 disposed
opposite the vertical bore 158 is used for horizontal rotational manipulation
of the
hammer bushing clamp 18. The side cavity 74 is configured to be in fluid
communication with the hammer housing 12 for receiving the extension coupler
20. When the hammer bushing clamp 18 is fully pushed into the side cavity 74,
a
clamp indentation 164 disposed on an inner wall 166 of an elongated body 167
matingly engages a coupler indentation 76 of the extension coupler 20.
Securing
the hammer bushing clamp 18 into the bushing side cavity 74 is achieved by
rotationally fastening the bolt 54 through a horizontal bore 168 disposed
transverse to the vertical bore 158 and near the finger pull 162.
Similarly with the jaw block clamp 46, the hammer bushing clamp
18 has a first protrusion portion 170 at one end and a second protrusion
portion
172 at an opposite end. Specifically, the first protrusion portion 170 having
the
horizontal bore 168 is disposed at one end of the hammer bushing clamp 18, and
at
an opposite end, the second protrusion portion 172 having the vertical bore
158.
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Preferably, a width of the first protrusion portion 170 along the axis of the
horizontal bore 168 is substantially the same with a corresponding width of
the
second protrusion portion 172.
Additionally, the hammer bushing clamp 18 also defines a generally
"C"-shape when viewed from above in the orientation of FIG. 6A for fitting
over
the coupler indentation 76 and locking the extension coupler 20 in the hammer
bushing 16. Similar methods described above for securing the jaw block clamp
46
are employed here for the hammer bushing clamp 18. Further detailed
description
of the jaw block clamp 46 and the hammer bushing clamp 18 is provided below in
FIGs. 7 and 8.
Referring now to FIGs. 5-6, although both the hammer bushing
clamp 18 and the jaw block clamp 46 share similar features as described above,
an
outer wall 78 of the jaw block clamp 46 has a planar surface, and an outer
wall
178 of the hammer bushing clamp 18 has a contoured surface to conform to the
surrounding surfaces of adjacent components of the spike driving workhead unit
10. Other suitable configurations are also contemplated.
Referring now to FIGs. 2-4, an exemplary disassembling sequence
of the spike driving workhead unit 10 is illustrated. While the following
sequence
is primarily described with respect to the embodiment of FIG. 1, it should be
understood that the steps within the sequence may be modified and executed in
a
different order or manner without altering the principles of the present
disclosure.
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During maintenance, as shown in FIG. 2, the jaw block clamps 44 are initially
loosened by rotationally removing the bolts 54 from the horizontal bore 68 of
the
jaw block 34, thereby releasing the guide rods 42 from the jaw block 34 and
allowing the rods to be removed upwardly.
Next, as shown in FIG. 3, the hammer bushing clamp 18 is similarly
loosened by rotationally removing the bolt 54 from the hammer bushing 16,
thereby releasing the extension coupler 20 from the hammer bushing 16 and
allowing the anvil assembly 22 and the jaw assembly 30 to be lowered
downwardly from the lower end 14 of the hammer housing 12. For example, the
anvil and jaw assemblies 22, 30 can be lowered onto the tie for inspection
without
requiring ballast excavation.
At this stage, both the anvil assembly 22 and the jaw assembly 30
are still connected to the hammer housing 12 via the anvil 26. Releasing of
the
anvil 26 from the hammer housing 12 is achieved, as shown in FIG. 4A, by
removing a hammer pin 180 from a keyway opening 182 machined on one of the
side walls 184 of the hammer housing 12. Specifically, an upper end 186 of the
anvil 26 has an anvil indentation 188 (FIG. 4B) that mates with the hammer pin
180. As best shown in FIG. 4B, the hammer pin 180 preferably has a cylindrical
shape with a guiding planar upper surface and is configured for mating with
the
anvil indentation 188 when the hammer pin is inserted into the keyway opening
182. Upon removal of the hammer pin 180, the anvil and jaw assemblies 22, 30
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are removed from the spike driving workhead unit 10 for maintenance. Thus, the
disassembled components, such as a worn-out anvil, can then be readily
replaced.
Reassembling of the disassembled components is achieved by applying a reverse
sequence of the above-described steps.
Referring now to FIGs. 7A-7B, the detailed geometry and functions
of the jaw block clamp 46 is shown. When the jaw block clamp 46 pivots about a
pivot pin 190 disposed in the vertical core 58 of the jaw block clamp 46, the
clamp
indentation 64 firmly biases against the rod indentation 56 of the guide rod
42 for
securely locking the rod. An important aspect of this configuration is that
when
the jaw block clamp 46 is pushed into the corresponding jaw block side cavity
60,
a first clearance, generally designated 192, is defined between the first
protrusion
portion 70 and a first inner wall 194 of the jaw block side cavity 60.
As a result, the first clearance 192 enables the jaw block clamp 46 to
generate a squeezing force against the rod indentation 56 by bending or
deforming
the elongated body 67 of the jaw block clamp when the bolt 54 is rotationally
fastened through the horizontal bore 68 and into a corresponding bore 196
disposed on the first inner wall 194. A second clearance, generally designated
198, is defined between the second protrusion portion 72 and a second inner
wall
200 of the jaw block side cavity 60, thereby allowing free pivoting actions of
the
jaw block clamp 46 during a clamping process.
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Referring now to FIGs. 8A-8B, the detailed geometry and functions
of the hammer bushing clamp 18 is shown. As is the case with the jaw block
clamp 46, when the hammer bushing clamp 18 pivots about a pivot pin 202
disposed in the vertical core 158 of the hammer bushing clamp 18, the clamp
indentation 164 firmly biases against the coupler indentation 76 of the
extension
coupler 20 for securely locking the coupler. An important aspect of this
configuration is that when the hammer bushing clamp 18 is pushed into the
corresponding bushing side cavity 74, a first clearance, generally designated
204,
is defined between the first protrusion portion 170 and a first inner wall 206
of the
busing side cavity 74.
As a result, the first clearance 204 enables the hammer bushing
clamp 18 to generate a squeezing force against the coupler indentation 76 by
bending or deforming the elongated body 167 of the hammer bushing clamp when
the bolt 54 is rotationally fastened through the horizontal bore 168 and into
a
corresponding bore 208 disposed on the first inner wall 206. A second
clearance,
generally designated 210, is defined between the second protrusion portion 172
and a second inner wall 212 of the bushing side cavity 74, thereby allowing
free
pivoting actions of the hammer bushing clamp 18 during the clamping process.
Referring now to FIGs. 2, 9A and 9B, another embodiment of the
present spike driving workhead unit 10 is generally designated 214. Components
shared with the unit 10 are designated with identical reference numbers. A
major
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difference featured in the unit 214 is that the unit is equipped with another
embodiment of the hammer bushing clamp 18 designated 216, and another
embodiment of the jaw block clamp 46 designated 218. An important feature of
the unit 214 is that the hammer bushing clamp 216 is secured to the bushing
side
cavity 74 using two bolts 54, and similarly, the jaw block clamp 218 is
secured to
the jaw block side cavity 60 using two bolts 54. Notably, both clamps 216, 218
are secured to the workhead unit 214 without pivotal manipulation as is the
case
with the clamps 18, 46 shown in FIGs. 4A and 4B. Detailed description of the
configurations of the hammer bushing clamp 216 and the jaw block clamp 218 is
provided below.
Referring now to FIGs. 9A, 10A and 10B, the geometry and
functions of the jaw block clamp 218 are shown in further detail. The jaw
block
clamp 218 operates generally in a similar manner as the jaw block clamp 46
shown in FIGs. 5A and 5B. For pushing into or pulling out of the corresponding
jaw block side cavity 60 of the jaw block 34, at least one finger pull 220 is
disposed at an end of an elongated body 222 of the jaw block clamp 218. When
the jaw block clamp 218 is fully pushed into the side cavity 60, a clamp or
central
indentation 224 disposed on an inner wall 226 of the elongated body 222
matingly
engages the rod indentation 56 of the guide rod 42. An outer wall 227 is
opposite
the inner wall 226 and is in spaced, parallel relation thereto.
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Securing the jaw block clamp 218 into the jaw block side cavity 60
is achieved by rotationally fastening two bolts 54 through corresponding
horizontal bores 228 disposed in generally rectangular or block-shaped
protrusions
229 at opposite ends of the elongate body 222 near the corresponding finger
pull
220. It will be seen that the protrusions 229 extend from the inner wall 226
of the
elongate body 222 corresponding to the central indentation 224, and each
preferably has radiused portions 229' located above and below the bores 228.
It is
contemplated that the radiused portions 229' can optionally be provided to the
hammer bushing clamp 18 and the jaw block clamp 46 described above in relation
to FIGs. 5A and 5B and 6A and 6B. As is the case with the jaw block clamp 46,
the protrusions 229 and the elongated body 222 combine to define a general "C"
shape when viewed from above as seen in FIGs. 10A and 10 B.
Referring now to FIGs. 9B, 11A, and 11B, the geometry and
functions of the hammer bushing clamp 216 are shown in further detail. The
hammer bushing clamp 216 operates generally in a similar manner as the hammer
bushing clamp 18 shown in FIGs. 6A and 6B. Similarly with the jaw block clamp
218, to push into or pull out of the bushing side cavity 74, at least one
finger pull
230 is disposed at an end of an elongate body 232 of the hammer bushing clamp
216. When the hammer bushing clamp 216 is fully pushed into the bushing side
cavity 74, a clamp or central indentation 234 disposed on an inner wall 236 of
the
elongated body 232 matingly engages the anvil indentation 188 of the anvil 26.
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An outer wall 237 is in spaced parallel relation to the inner wall 236
and defines a general concave portion 237'. Securing the hammer bushing clamp
216 into the bushing side cavity 74 is achieved by rotationally fastening two
bolts
54 through corresponding horizontal bores 238 extending transversely to the
elongated body 232 disposed in block-shaped or rectangular protrusions 239 at
opposite ends of the elongate body near the corresponding finger pull 230. The
generally concave portion 237' is located between the bores 238. Also, as is
the
case with the jaw block clamp 218, the protrusions 239 head define radiused
edges
240 above and below the bores 238. Also, as is the case with the hammer
bushing
clamp 18, and the jaw block clamp 46, the protrusions 229 and the elongated
body
232 combine to define a general "C" shape when viewed from above as seen in
FIGs. 11A and 11 B.
While a particular embodiment of the present spike driving
workhead unit has been described herein, it will be appreciated by those
skilled in
the art that changes and modifications may be made thereto without departing
from the present disclosure in its broader aspects and as set forth in the
following
claims.
