U.S. patent number 3,892,279 [Application Number 05/422,259] was granted by the patent office on 1975-07-01 for reciprocating hydraulic hammer.
This patent grant is currently assigned to Chicago Pneumatic Tool Company. Invention is credited to Lester A. Amtsberg.
United States Patent |
3,892,279 |
Amtsberg |
July 1, 1975 |
Reciprocating hydraulic hammer
Abstract
A pavement breaker having a reciprocating piston hammer to pound
a work steel, wherein a jacket about the tool provides a reservoir
of constantly pressurized oil, which pressurized oil drives the
hammer on a work stroke, operates a plunger to return the hammer,
operates dampers to dampen excessive movement of the hammer beyond
its usual impacting point, operates a dump valve to relieve the
pressurized condition of the reservoir when the tool is lifted out
of pressed relation to the work, and operates a ram to shift a
control valve in one direction to interrupt reservoir oil flow to
the hammer, the control valve being mechanically shiftable in the
opposite direction by the hammer on a return stroke to reestablish
reservoir flow to the hammer.
Inventors: |
Amtsberg; Lester A. (Utica,
NY) |
Assignee: |
Chicago Pneumatic Tool Company
(New York, NY)
|
Family
ID: |
26861475 |
Appl.
No.: |
05/422,259 |
Filed: |
December 6, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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165539 |
Jul 23, 1971 |
|
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Current U.S.
Class: |
173/13; 92/85R;
173/207; 60/371; 92/85B; 173/127 |
Current CPC
Class: |
B25D
9/12 (20130101); F03C 1/035 (20130101); F01L
23/00 (20130101) |
Current International
Class: |
B25D
9/12 (20060101); B25D 9/00 (20060101); F01L
23/00 (20060101); F03C 1/03 (20060101); F03C
1/00 (20060101); B25d 009/04 () |
Field of
Search: |
;92/144 ;91/227,5,300
;175/93 ;173/13,14,15,134,139,127 ;60/413,417,371 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Abbott; Frank L.
Assistant Examiner: Pate, III; William F.
Attorney, Agent or Firm: Rudy; Stephen J.
Parent Case Text
BACKGROUND OF THE INVENTION
This application is a division of patent application Ser. No.
165,539, filed July 23, 1971.
Claims
What is claimed is:
1. In a reciprocating hydraulic hammer including a housing to which
a fronthead is attached adapted to receive a slidable work steel,
and including a piston hammer reciprocable in the housing to pound
the work steel, an outer jacket within which the housing has a
fixed position defines a reservoir in surrounding relation to the
housing, an inlet to the reservoir adapted for connection to a
pressure oil supply system for filling and maintaining the
reservoir constantly pressurized with oil, the piston hammer having
a driving end, a first chamber in the housing about the driving end
of the piston hammer, valve means in the housing having response to
a return stroke of the piston hammer to communicate the reservoir
with the chamber, a pressure oil discharge line in the housing
adapted for connection with an external sump of the supply system,
the valve means having response to movement of the piston hammer on
a work stroke to communicate the chamber with the discharge line
and to block communication of the chamber with the reservoir, a
slidable return plunger constantly subject to pressure of oil in
the reservoir so as to constantly abut a bottom face of the piston
hammer, the piston hammer having a lower section defining a hammer
member providing said bottom face, the housing having a lower
section defining an air chamber in which the hammer member
reciprocates, and the return plunger having response to pressure of
oil in the reservoir following blocking of communication of the
said first chamber with the reservoir to move the piston hammer on
a return stroke.
2. In a reciprocating hydraulic hammer as in claim 1, wherein the
jacket is a cylinder defining the reservoir, and the fronthead has
an annular shoulder serving as a supporting base for both the
cylinder and the housing.
3. In a reciprocating hydraulic hammer as in claim 1, wherein the
fronthead has an axial bore communicating with the air chamber
through which bore the work steel is receivable into the air
chamber.
4. In a reciprocating hydraulic hammer as in claim 3 wherein the
return plunger is slidable in a bore in the fronthead in parallel
relation to the axis of the hammer member, which bore opens into
the air chamber below the hammer member and is connected below the
return plunger with the reservoir.
5. In a reciprocating hydraulic hammer as in claim 3 wherein a
damping plunger is slidable in a bore in the fronthead in parallel
relation to the axis of the hammer member, which bore connects by a
restricted passage with the reservoir, the damping plunger being
adapted under pressure of reservoir oil to normally project a
predetermined distance from its bore into the air chamber below the
hammer member.
6. In a reciprocating hydraulic hammer as in claim 3, wherein the
housing has a backhead section fixed atop the lower section and the
piston hammer has a piston section of a reduced diameter relative
to the hammer member, which piston section is slidable in the
backhead section, the said driving end of the piston hammer being
defined by an end of the piston section.
7. In a reciprocating hydraulic hammer as in claim 6, wherein the
backhead section has a dump port connected with the discharge line
and has a bore intersecting the dump port opening at one end into
the reservoir and opening at its opposite end into the air chamber,
a plunger valve slidable in the bore in parallel relation to the
axis of the hammer member having one end subject to pressure of
fluid in the reservoir and having its other end constantly abutting
and end face of the hammer member under said pressure, the plunger
valve normally blocking communication of the dump port with the
reservoir and as a consequence blocking communication of the
reservoir with the discharge line, the plunger valve being adapted
under said pressure of fluid in the reservoir to follow the hammer
member on a work stroke and adapted upon moving over a
predetermined distance to uncover the dump port relative to the
reservoir.
8. A reciprocating hydraulic hammer including a fronthead having an
annular shoulder at a rear end thereof, an outer housing fixed at
one end to the shoulder, an inner housing confined within the outer
housing and also fixed at one end to the shoulder, the outer
housing defining a reservoir surrounding the inner housing and
filled with pressurized hydraulic fluid, an inlet through the outer
housing connected with an external hydraulic fluid supply system
for maintaining the reservoir continuously filled and pressurized
with hydraulic fluid, a hammer reciprocable in the inner housing to
pound a work steel received in the fronthead, a plunger biased by
pressure of the fluid in the reservoir against a bottom end of the
hammer urging the hammer on a return stroke, the plunger being
reciprocable in an individual cylinder sealed from the inner
housing, the hammer having an opposite piston portion of greater
diameter than the plunger subject to pressure of hydraulic fluid
from the reservoir to drive the hammer on a work stroke, and valve
means having response to movement of the piston portion on a work
stroke of the hammer to block commmunication of the reservoir with
the said piston portion.
9. A reciprocating hydraulic hammer as in claim 8, wherein said
valve means has response to movement of the piston portion on a
return stroke to communicate the reservoir with the said piston
portion.
10. A reciprocating hydraulic hammer as in claim 8, including a
pressure fluid discharge passage in the inner housing connected
with an external sump of the supply system, a bore in the housing
connecting the reservoir with the discharge passage, and a dump
valve slidable in parallel relation to the axis of the hammer in
the bore normally blocking communication of the reservoir with the
discharge passage.
11. A reciprocating hydraulic hammer as in claim 10, wherein the
dump valve has one end subject to pressure of fluid in the
reservoir and has its opposite end abutting an upper face of the
hammer under pressure of said fluid so as to follow movement of the
hammer on a work stroke, the dump valve being adapted upon
following movement of the hammer beyond a predetermined distance to
communicate the reservoir with the discharge port.
12. A reciprocating hydraulic hammer as in claim 8, wherein plunger
means having one end subject to pressure of fluid in the reservoir
and having an opposite end projecting a limited distance under said
pressure into the path of movement of the hammer on a work stroke
is adapted to yieldably resist movement of the hammer on a work
stroke beyond a predetermined distance.
13. In a reciprocating hydraulic hammer comprising an outer
housing, an inner housing within the outer housing having a hammer
chamber, a fronthead having an annular rear shoulder upon which
both the outer and inner housing are mounted, the fronthead having
an axial bore communicating with the hammer chamber, and a work
steel slidably received in the fronthead having a retracted
condition projecting at its rear into the hammer chamber into the
path of movement of the hammer when in pressed relation to a work
surface, the outer housing defining a reservoir in surrounding
relation to the inner housing, the reservoir being continuously
filled and pressurized with hydraulic fluid, the hammer having a
piston end subject to pressure of fluid from the reservoir to drive
the hammer on a work stroke against the work steel; a return
plunger having a diameter relatively smaller than that of the
piston, the plunger constantly abutting an underside of the hammer
under pressure of fluid in the reservoir, and valve means for
blocking the piston end of the hammer from the pressure of the
fluid in the reservoir, the plunger being adapted under the
pressure of fluid in the reservoir when the piston end of the
hammer is in said blocked condition to move the hammer on a return
stroke.
Description
This invention is concerned with an hydraulically operable tool
having a hammer which is hydraulically reciprocable to pound a work
steel against the work.
While the invention is illustrated in a tool designed especially
for use as a pavement breaker, it is understood that the invention
is subject to other applications.
A feature of the invention lies in the employment of an
hydraulically operable piston for driving the hammer on a work
stroke, and in an hydraulically operable plunger for automatically
returning the hammer and piston to starting position.
Another feature lies in a pressurized oil reservoir defined by a
jacket in surrounding relation to an end portion of the tool,
whereby the paths of fluid flow to effect operation of various
elements of the tool are shortened to a minimum with consequent
reduction of energy losses that would otherwise arise from leakage
and friction.
Another feature of the invention lies in a slide valve incorporated
in the tool to control flow of reservoir oil to and from one end of
the driving piston. The valve is shifted mechanically near the end
of the return stroke by means of the returning piston; and is
shifted under hydraulic pressure from the reservoir during the work
stroke.
A further feature lies in the use of plungers hydraulically
dampened by reservoir oil to absorb energy of the moving hammer
beyond its usual impacting position.
Another feature lies in a dumping plunger valve which is responsive
to pressure of reservoir oil to cause dumping of fluid from the
reservoir and dissipation of its energy, when the hammer has moved
to a predetermined low position as when the tool is removed clear
of the work or when the work steel has suddenly dropped into a void
area.
A still further feature of the invention lies in the organized
arrangement of the return plunger, the damping plungers, the
dumping valve, and an hydraulically operable ram for shifting the
control valve in one direction whereby this arrangement they are
all directly subject to constant pressure of oil in the reservoir
for their operation.
Other advantages and features will become apparent as the
description of the invention proceeds in greater detail.
BRIEF DESCRIPTION OF DRAWING
In the accompanying drawing:
FIG. 1 is a longitudinal section of an hydraulic hammer
illustrating the invention, which view is taken on line 1--1 of
FIG. 2;
FIG. 2 is a plan view of the top end of FIG. 1;
FIG. 3 is a section taken on line 3--3 of FIG. 1;
FIG. 4 is a section taken on line 4--4 of FIG. 1;
FIG. 5 is a section taken on line 5--5 of FIG. 1;
FIG. 6 is a longitudinal section taken on line 6--6 of FIG. 5;
and
FIG. 7 is an enlarged detail of the valve mechanism shown in FIG.
6.
DESCRIPTION OF PREFERRED EMBODIMENT
The hydraulically operable hammer illustrating the invention is
designed primarily for use as a pavement breaker. The tool is
mountable to a boom (not shown) on a motor vehicle by means of
brackets 10 (FIG. 5) fixed to a side area of the tool's housing 11.
The boom is hydraulically operable to selectively raise or lower
the tool so as to bring a work steel 12 into or out of pressed
relation with the work.
The general housing 11 includes a fronthead 13 bolted at 14 in end
relation to an elongated cylinder or jacket section 15. The
cylinder provides a chamber 16 which serves as a pressure oil
reservoir. The reservoir is sealed at its rear by means of an end
wall 17 and is sealed at its opposite end by means of an annular
shoulder 18 provided by the fronthead 13. An inlet 19 to the
reservoir is connected by means of a hose line 21 with an hydraulic
pressure supply system 20 mounted upon the motor vehicle. The
supply system is equipped with suitable controls which enable it to
be employed, not only for hydraulically filling and pressurizing
the reservoir, but also for hydraulically operating the boom.
Axially arranged within the reservoir in spaced relation to the end
wall 17 and to the surrounding wall of the reservoir is an internal
or second housing 22. The latter includes a lower section 23 having
an annular wall, the bottom end of which is seated upon the
shoulder 18.
Housing section 23 defines a cylindrical air or hammer chamber 24
which connects directly with a coaxial bore 25 extending through
the fronthead. A heavy cylindrical hammer portion 26 of a combined
piston and hammer, or piston hammer, is reciprocable in chamber 24
to pound a tail end 27 of the work steel. The work steel is
slidably received in the front head and it projects at its tail end
into the hammer chamber where it is subject to being pounded by the
hammer.
A retaining cap 28 threadedly engaged over the forward end of the
fronthead has an internal shoulder 29 which is cooperable with a
flange or collar 31 located intermediately of the ends of the work
steel to retain the latter within the tool against endwise escape.
The collar 31 is also cooperable with a second shoulder 32 within
the fronthead to limit the extent of projection of the work steel
into the hammer chamber.
There is a slight clearance 33 spacing the hammer from the
surrounding wall of the hammer chamber. This is of advantage in
that whatever ambient air enters the hammer chamber through the
fronthead will freely circulate about the hammer and escape around
the drill steel back to atmosphere. Accordingly, neither a vacuum
nor trapped air can develop in the hammer chamber to impede
reciprocation of the hammer.
The hammer is caused to be driven on a work stroke under pressure
of reservoir hydraulic fluid applied to an integral piston portion
34 of the hammer and it is adapted to be mechanically returned
under pressure of the reservoir fluid applied to an end of a return
plunger 35.
The piston 34 is defined by means of an elongated stem that is
fixed axially to the hammer but is of relatively reduced diameter.
The piston is slidably received in a bushing 36 fixed by bolting in
a backhead section 37 of the internal housing. The backhead 37
seals over the rear end of the hammer chamber 24 and it is rigidly
seated upon an annular rear end wall 38 of the lower housing
section 23 by means of a group of bolts 39. The bolts pass through
side ears 41 of the backhead and are threadedly tightened in the
annular shoulder 18. The bolts not only secure the backhead to
section 23, but also the latter seated upon the shoulder 18. The
backhead defines a piston chamber 42 rearwardly of the piston.
A shuttle valve 43 (FIGS. 1, 6, 7) axially slidable in the piston
chamber rearwardly of the piston, controls the application to and
relief of reservoir hydraulic pressure fluid from the piston. The
valve is slidable between a pair of axially spaced annular
shoulders 44 and 45 of the piston chamber to open and closed
positions relative to a ring of oil feed ports 46 and a ring of oil
discharge ports 47 formed in a valve bushing 48. The rearwardly
disposed shoulder 45 is defined by the inner face of a plug 49
bolted to the upper end of the backhead over the piston
chamber.
The feed ports 46 connect through an annulus with a group of larger
feed ports 51 communicating with the reservoir 16. The discharge
ports 47 connect through an annulus with a larger discharge port 52
that opens laterally into a return line passage 53. The latter
leads to an outlet 54 provided by an adapter 55. The adapter is
bolted to the external face of the end wall 17. The outlet connects
by means of a hose line 56 with a sump (not shown) in the external
hydraulic pressure supply system.
The return passage 53 is defined in part by means of a tube 57
(FIG. 1) that is fixed at its lower end in an offset portion of the
backhead 37 (FIG. 4), extends through the back wall 17 and is fixed
in the adapter 55. The return passage also connects by means of a
second large discharge port 58 with an annulus 59 surrounding the
piston bushing 36. A group of relief ports 61 in the piston are
registrable during a work stroke of the piston with a group of
drain ports 62 in the piston bushing 36 to relieve pressure oil
from a cavity 63 in the piston through the annulus 59 to the return
passage 53, as in FIG. 1. During a return stroke of the piston, the
relief ports 61 are blocked off and a group of feed ports 64 in the
piston become connected with the piston chamber 42 to admit
reservoir pressure oil to the piston cavity 63, as in FIGS. 6 and
7.
The shuttle valve 43 is defined by an open ended cylindrical body
or skirt which is slidable to cover and uncover the several feed
and discharge ports 46 and 47. The body of the valve is joined by
means of a group of radial spokes 65 (FIGS. 4, 7) with an axially
extending valve operating rod 66. As the valve is shifted from one
position to the other, pressure oil within the piston chamber 42
freely passes through the spaces between the spokes. An upper
section of the valve rod rearwardly of the spokes extends alidably
into an axial bore 67 of the plug 49. The bore is extended by means
of a relatively reduced counterbore 68 through a terminal stem 69
of the plug. A ram 71 slidable in this counterbore 68 constantly
abuts the upper end of the valve rod under ambient pressure of
reservoir fluid. During the progress of a work stroke of the
piston, the ram 71 functions under pressure of reservoir fluid to
slide the valve forwardly or donwardly so as to uncover the
discharge ports 47 and to cover the feed ports 46 preparatory to a
subsequent return stroke, as appears in FIG. 1.
A longer oppositely lower extending section of the valve rod
extends slidably through a bushing or adapter 72 into the piston
cavity 63. The valve rod is of reduced diameter relative to that of
the cavity so as to provide a surrounding clearance allowing
communication of the cavity with the piston feed ports 64. The
adapter 72 includes a flange which is bolted over the end of the
piston. The adapter has a lower sleeve or stem portion which guides
the valve rod and extends into the piston cavity. This stem is of
reduced diameter relative to the piston cavity so as not to block
communication of the piston cavity with the ports 64.
The adapter 72 has an oppositely upper extending sleeve or stem 72
which also guides the valve rod and projects with a substantial
surrounding clearance into the piston chamber 42 rearwardly of the
piston. On a return stroke of the piston, the stem 73 is carried
freely into the interior of the valve 43 so as to abut the spokes
65 and slide the valve to a partially shifted condition, as appears
in FIGS. 6 and 7. In this partially shifted condition of the valve,
the drain or return ports 47 are covered and the feed ports 46 are
uncovered.
As the piston is returning and shifting the valve, the side ports
64 of the piston are brough into communiation with chamber 42; and,
as the valve is being shifted pressure fluid enters through ports
46 to chamber 42 from where it enters ports 64 to fill and
pressurize the piston cavity 63. The pressure developing in chamber
42 and the cavity 63 decelerates the returning piston and causes
its return movement to stop slightly short of and before the face
75 of the hammer can bottom against the stationary flange 74. The
pressurization of cavity 63 exerts a bias over the lower end of the
valve rod to shift the valve away from the piston for a slightly
further distance until the valve abuts the upper shoulder 45.
Reservoir pressure acting over the smaller diameter end of the ram
71 is insufficient to resist this further shifting action. The
hydraulic bias in cavity 63 acting on the valve rod serves to hold
the valve in its open and fully shifted condition until the
pressure in the cavity 63 is subsequently relaxed which occurs at
about the time of impacting action of the hammer during a work
stroke. Following shifting of the valve to its open condition,
rapid pressurization of chamber 42 acts upon the piston to drive it
over a forceful work stroke.
The manner in which the piston hammer is returned and in which the
valve is shifted to its open conditon is of decided advantage. The
hydraulic deceleration and stopping of the returning piston before
the hammer can contact the stationary flange 74 avoids undersirable
forces being imparted by the hammer to the internal housing 22. The
hydraulic stopping of the piston before it can shift the valve into
abutment with the end shoulder 45 also is of decided advantage in
that undesirable compressive forces of the piston upon the valve
are avoided.
While the hammer and piston are shown in a preferred form as an
integral unit, they may be incorporated in the tool as separate
elements.
MEANS FOR DAMPING HAMMER MOVEMENT WHEN THE WORK STEEL IS NOT IN
IMPACTING POSITION
Damping means is provided to absorb the energy of the hammer on a
work stroke when the work steel is not in its impacting position.
This means is provided by a pair of diametrically spaced damping
plungers 76 (FIGS. 3, 6). Each is slidable in a separate bore 77
formed in a housing 78 fitted in the wall 18 of the fronthead. Each
projects in parallel relation to the axis of the hammer part way
into the hammer chamber 24 under bias of reservoir oil pressure. To
this end, the reservior 16 connects separately with each plunger
bore by means of a restricted passage 79 in the wall of the
fronthead with ports 82 that are located a short distance above the
bottom of the plunger bore. Reservoir pressure fluid entering the
plunger bore biases the plunger upwardly until a tapered upper
shoulder abuts a complementary shoulder of the bore. In this
condition, a reduced diameter stem 81 of the plunger projects into
the hammer chamber. The upper end of the stem 81 of each plunger
will normally be cooperable with the opposed underface of the
hammer during a work stroke after the work steel has dropped to a
position below the level of the plungers. This dropped condition
will be obtained when the work steel encounters a void or soft area
or when the tool is lifted out of pressed relation to the work. The
work steel, when pressed against the work, will normally project
axially into the hammer chamber above the biased level of the
plungers, as in FIG. 6.
The plungers 76 have a slight taper about their lower ends normally
positioned opposite the ports 82 so as to restrict flow through the
latter back to the reservoir as the plungers are pressed downwardly
by the hammer. This flow is further restricted as the plungers are
moved further down by the hammer to carry their tapered ends in
further restricted relation to the ports 82.
HAMMER RETURN PLUNGER
The hammer 26 is caused to be returned upon completion of its work
stroke by means of the hydraulically biased return plunger 35
(FIGS. 6, 3). The plunger is slidable in parallel relation to the
axis of the hammer in an eccentrically located bore provided by a
bushing 83 fitted in the shoulder 18 of the fronthead. The
underside of the bore is connected with the reservoir by a passage
84 opening into the reservoir through the shoulder 18 of the
fronthead. Pressure fluid from the reservoir constantly filling the
passage 84 continuously pressurizes the plunger into abutment with
the underface of the hammer. The passage 84 is sufficiently large
enough to allow rapid escape to the reservoir of fluid displaced by
the plunger when the hammer is moving downward on a work
stroke.
When the shuttle valve 43 is caused to be shifted toward the end of
a work stroke by the arm 71 so as to discontinue application of
reservoir oil to the piston and to open the piston chamber 42 to
the return line 53, the pressure of oil in the reservoir then
effectively acts through the passage 84 upon the return plunger 35
to move the hammer on a return stroke. The diameter of the return
plunger is relatively small so as to permit a desired easy or
slowed return of the hammer.
DUMPING VALVE
A dumping plunger valve 85 (FIGS. 5, 6) is provided to cause the
reservoir oil to be dumped and its energy relieved through the
return line 53 when the tool is lifted from the work. This dumping
action prevents the piston from being returned from a work stroke
by the return plunger 35. This is desired to immediately stop
further undesirable reciprocation of the hammer. The dumping valve
extends parallel to the piston and hammer and is slidable in a
bushing 86 fitted in an offset side portion of the backhead 37. The
dumping valve has and upper flat end which normally projects into
the reservoir 16; its opposite lower end projects through the
bushing 86 and is in constant contact with the upper surface of the
hammer 26 under bias of reservoir oil pressure. The dumping valve
normally blocks communication of the reservoir through the bushing
86 with a dumping port 87. The latter is connected by the annulus
59 with the return passage 53.
It can be seen that, when the tool is lifted from its pressed
relation to the work, the work steel will drop to its low position
upon the shoulder 29 of the cap 28. Then, as the hammer moves
donward on a work stroke below the level of normal impacting
relation with the work steel and as it forces the damping plungers
76 substantially to their limits, the dumping valve under the
constant pressure of resevoir oil follows the hammer sufficiently
to open or communicate the reservoir with the dumping port 87. The
dumping port and return passage 53 are of substantial diameter so
as to allow, when the dumping valve is open, rapid escape of
reservoir oil to the return passage 53 and the outlet hose line 56
with consequent rapid dissipation of the energy of the pressurized
reservoir oil. This condition will prevent return of the piston and
hammer from the work stroke.
A conventional pressure surge accumulator 88 (FIGS. 1, 2) is
connected with the outlet passage 54 as a protective measure to
reduce the pressure of the returning fluid on the return hose
56.
It is to be noted that the inlet feed line 21 is continuously open
so that the reservoir 16 in which the internal housing 22 is fully
immersed is completely filled and constantly pressurized with fluid
continuously being supplied to it from the hydraulic system. This
huge volume of reservoir oil serves as an accumulator due to its
compressibility. It is of such volume that it will feed one stroke
of the piston with a pressure drop of less than 800 p.s.i. in the
reservoir. The close proximity of the reservoir to the internal
housing and to the piston chamber therein facilitates an extremely
high flow rate that occurs when the hammer has attained its maximum
velocity just prior to impacting. The annulus style reservoir 16 in
surrounding relation to the internal housing provides very
convenient access of pressure fluid for obtaining the auxiliary
functions of the return plunger 35, the damping plungers 76, the
dumping valve 85, and the ram 71, all of which are directly exposed
to reservoir fluid.
In summary of the operation of the tool, let it be assumed that the
tool is being held by the boom in pressed relation to the work,
that the reservoir 16 is being constantly pressurized with oil from
the supply system, and that the tool has obtained the condition
shown in FIG. 1 following completion of a work stroke of the piston
and hammer. Since both the piston cavity 63 and the piston chamber
42 are at this time connected with the discharge or return passage
53 and are closed by the shuttle valve 43 to reservoir pressure
fluid, the reservoir pressure fluid acts upon the return plunger 35
to return the hammer and piston.
On this return stroke, the piston displaces the relief ports 61 to
block the piston cavity 63 from drain ports 62; and by means of the
stem 73 of the adapter 72, the piston slides the shuttle valve 43
to its open and partially shifted condition, as in FIGS. 6 and 7.
As the valve is shifted, fluid trapped at the juncture of the upper
end of the valve rod and the ram 71 is drained through a passage 89
to the return line so as to avoid sluggish shifting of the
valve.
Reservoir pressure fluid then flows through feed ports 46 to
chamber 42 and through the piston feed ports 64 to pressurize the
piston cavity 63. The fluid pressure then developing about the
returning piston acts to decelerate its movement and brings it to a
stop before its end wall 75 can abut against the stationary wall 74
and before its stem portion 73 can shift the valve into abutment
with the upper shoulder 45, all as earlier explained. The pressure
developing in the piston cavity 63 acts to bias the valve to its
fully shifted condition and to hold it there until the subsequent
work stroke of the piston is substantially completed. The pressure
developing over the piston finally drives the piston on a forceful
work stroke into impacting relation with the work steel 12.
On the work stroke, the return plunger 35 is moved ahead by the
hammer to force the oil below it through passage 84 back into the
reservoir. The energy being imparted by the return plunger to the
oil forced back to the reservoir is added to the energy of the
reservoir fluid acting upon the piston to further increase the
drive and impacting force of the hammer.
As the piston moves away from the shuttle valve during the work
stroke, the piston registers its relief ports 61 with the drain
ports 62 to relieve the pressure fluid from the piston cavity 63 to
the return passage 53. As the pressure of fluid in the piston
cavity on the lower end of the valve rod relaxes, reservoir fluid
pressure acting upon the ram 71 shifts the shuttle valve 43
downward to close the feed ports 46 and to open the discharge ports
47.
The reservoir pressure now acting over the bottom end of the return
plunger 35 returns the hammer and piston to starting position. As
the piston regains its returned condition, as in FIG. 6, it is
again driven through a work stroke, as earlier described.
The piston and hammer automatically recycle until the work steel
obtains a low condition wherein its collar 31 abuts the shoulder 29
of the retaining cap. The work steel may obtain this low or dropped
condition wherein the return plunger is disabled from returning the
hammer and piston, not only when the work steel drops into the void
or soft ground area, but also which the tool is lifted by the
operator out of its pressed relation to the work. As the work steel
drops in this action below the level of the damping plungers 76,
the hammer is progressively dampened by the plungers 76, as earlier
explained. Should the hammer move downwardly to a point where the
dumping valve 85, which follows its movement under reservoir
pressure, uncovers the dumping port 87, pressure oil in the
reservoir and its pressure will be relieved through the dumping
port and return passage 53, as earlier explained, to disable the
return plunger 35 from returning the hammer and piston.
The hammer will automatically resume its cycling when the operator
actuates the boom to carry the tool to a new position in pressed
relation of the work steel to the work.
During the time that the hammer is reciprocating, the dumping valve
85 is held in constant abutment with the hammer under pressure of
the reservoir fluid and moves in unison with the hammer.
A stop 91 projecting from the side of the internal housing 22
overhangs the upper end of the dumping valve 85 in the normal
returned position of the latter, as in FIG. 6. The stop serves to
prevent the dumping valve from sliding free of its bushing 86 and
dropping into the reservoir should the tool, for some reason, be
turned front end up, as may occur during portage of the tool apart
from the boom.
Appropriate seals against leakage are provided where needed.
* * * * *