U.S. patent number 3,664,435 [Application Number 05/087,965] was granted by the patent office on 1972-05-23 for hydraulic hammer with automatic stopping action.
This patent grant is currently assigned to Worthington Corporation (Worthington Compressor and Engine International. Invention is credited to Ernest F. Klessig.
United States Patent |
3,664,435 |
Klessig |
May 23, 1972 |
HYDRAULIC HAMMER WITH AUTOMATIC STOPPING ACTION
Abstract
An improved hydraulic hammer assembly including an automatically
operable system for connecting the inlet to the outlet and
bypassing the control system of the hammer when the hammer moves
past a predetermined point as when the work performing element of
the assembly is not in contact with the work. In the exemplary
embodiment, a bypass conduit extends from the inlet to the outlet
and is normally closed by a valve. When the hammer does not move
past the position where it would normally encounter the tool, the
application of fluid under pressure to first and third surfaces of
the valve maintains the valve closed notwithstanding the
application of pressure to a second surface thereon in opposed
hydraulic relation to the first and third surfaces. However, when
the hammer moves past the position mentioned above, the third
surface on the valve is vented to the outlet and the application of
fluid under pressure to the second surface causes the valve to open
to establish a bypass flow path for the hydraulic fluid which
avoids entirely the control system used to control reciprocation of
the hammer.
Inventors: |
Klessig; Ernest F. (Racine,
WI) |
Assignee: |
Worthington Corporation
(Worthington Compressor and Engine International (Holyoke,
MA)
|
Family
ID: |
22208308 |
Appl.
No.: |
05/087,965 |
Filed: |
November 9, 1970 |
Current U.S.
Class: |
173/17;
173/DIG.4; 91/220; 173/207 |
Current CPC
Class: |
B25D
9/12 (20130101); Y10S 173/04 (20130101) |
Current International
Class: |
B25D
9/12 (20060101); B25D 9/00 (20060101); B25d
009/18 () |
Field of
Search: |
;173/16,17
;91/220,235 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Claims
I claim:
1. A hydraulic hammer comprising:
a casing having a bore;
a hammer received within said bore for reciprocating movement
therein;
a tool adjacent one end of the bore and normally positioned to be
struck by said hammer, said tool being movably mounted and movable
to a position wherein it cannot be struck by said hammer;
a hydraulic fluid inlet in said casing;
a hydraulic fluid outlet in said casing;
means, including a hydraulically operated control valve for
intermittently directing hydraulic fluid from said inlet to the
hammer to drive the same in one direction within said bore;
means for driving the hammer within said bore in a direction
opposite said one direction; and
means associated with said inlet and said outlet and responsive to
movement of the tool to said position thereof for directing
hydraulic fluid from said inlet to said outlet in a flow path that
bypasses said control valve.
2. A hydraulic hammer according to claim 1 wherein said directing
means includes a bypass conduit within said casing extending from
said inlet to said outlet and a valve normally closing said bypass
conduit.
3. A hydraulic hammer according to claim 1 wherein said directing
means comprises a bypass conduit within said casing extending from
said inlet to said outlet, a valve member positioned to close said
bypass conduit, said valve having a pair of opposed pressure
sensing surfaces with one of said surfaces having a larger area
than the other of said surfaces, said valve further including a
third pressure sensitive surface hydraulically parallel to said
other surface, said pair of surfaces being arranged with respect to
each other and to said inlet and said bypass conduit so that said
valve will be moved to open said bypass conduit whenever pressure
is not applied to said third surface, and means for applying fluid
under pressure to said third surface whenever said anvil is not in
said position wherein it cannot be struck by said hammer.
4. A hydraulic hammer according to claim 3 wherein said means for
applying pressure to said third surface includes conduit means on
said hammer normally establishing fluid communication between said
inlet and said third surface and cooperating means within said
casing for blocking said conduit means when said hammer moves
within said bore past a portion wherein it would normally strike
said tool.
5. A hydraulic hammer comprising:
a casing having a bore;
a tool movably mounted adjacent one end of a bore and normally
positioned to be struck by a hammer;
a hammer received within said bore for reciprocating movement to a
position wherein it would normally strike said tool;
a hydraulic fluid inlet in said casing;
a hydraulic fluid outlet in said casing;
means, including a hydraulically operated control valve for
intermittently directing hydrualic fluid from said inlet to said
hammer to drive the same towards said tool; and
means associated with said inlet and said outlet and responsive to
movement of said hammer past said position wherein it would
normally strike said tool for directing hydraulic fluid from said
inlet to said outlet in a flow path that bypasses said control
valve.
6. A hydraulic hammer according to claim 5 wherein said directing
means comprises a bypass conduit extending between said inlet and
said outlet, a hydraulic operated bypass valve normally closing
said bypass conduit and means for normally directing fluid under
pressure from said inlet to said bypass valve to bias the same to a
closed position, and means on said hammer for blocking the
application of fluid under pressure from said inlet to said bypass
valve when said hammer moves beyond the position at which it would
normally strike said tool.
7. A hydraulic hammer according to claim 6 further including means
on said hammer for directing fluid from said bypass valve to said
outlet when said hammer moves beyond said position at which it
would normally strike said tool; said bypass valve further
including pressure responsive surface means in fluid communication
with said inlet and responsive to the fluid under pressure to cause
movement of said bypass valve to an open position when said hammer
has moved beyond said position wherein it would normally strike
said tool.
8. A hydraulic impact device having a casing having a bore, a
hammer element reciprocable in said bore in a cycle between normal
limit positions by controlled application of pressure fluid to
opposed areas of the hammer, said casing having a pressure fluid
inlet and a fluid outlet, a control valve for controlling the
intermittent application of fluid to one of said areas of the
hammer, a bypass passage in said casing connecting said inlet and
outlet and bypassing said control valve, a bypass valve closing
said bypass passage, and means, including a valve section on said
hammer, responsive to movement of the hammer beyond a normal limit
position to open said bypass valve and stop cycling of the hammer
element.
Description
BACKGROUND OF THE INVENTION
Hydraulic hammers are now available to do work as efficiently and
more economically than air hammers and without the high noise
level. Manually controlled hydraulic hammers include a control
valve for controlling operation. Frequently, a hydraulic hammer
will be mounted on a boom or other support and moved relative to
the work such as concrete or the like. Operation of the boom
requires attention of the operator and rather than also require
attention of the operator to operate a control valve for the
hammer, it is preferable to have the hammer operate automatically
dependent on its engagement with the work. This ensures that the
hammer will only operate when engaging the work and avoids
unnecessary vibrations.
It has been suggested that the problem be overcome by the use of
valve channels on the hammer which will permit fluid under pressure
from the inlet in passing through the control valve to flow about
the hammer to an outlet when the hammer descends beyond a
predetermined point in the bore as, for example, when the tool is
suspended from its mounting means at the end of the bore due to the
fact the tool is not in contact with the work.
One difficulty with the foregoing approach is that the machining of
the valve channels on the hammer is a relatively costly operation.
A second difficulty is that such an approach does not employ a
positive bypass of the hammer control system and the system may be
rendered ineffective if the valve channels, for any reason, become
clogged.
SUMMARY OF THE INVENTION
It is the principal object of the invention to provide a new and
improved hydraulic hammer including means for automatically
terminating operation of the hammer when the hammer descends beyond
a predetermined point within a casing bore, as when the tool
associated therewith is no longer in engagement with the work.
The exemplary embodiment accomplished the foregoing object by means
of a bypass conduit within the hammer casing extending from the
inlet directly to the outlet. A bypass valve normally closes the
bypass conduit and includes three pressure sensitive surfaces. The
first two are associated with the inlet and are hydraulically
opposed while the third is hydraulically parallel to the first and
will be in fluid communication with the inlet whenever the hammer
has not moved beyond the position mentioned previously. The three
surfaces are arranged so that when inlet pressure is applied
against the first and third surfaces, the bypass valve will be
closed while when inlet pressure is applied only against the first
and second surfaces, the bypass valve will be opened.
Fluid communication between the third surface and the inlet is
normally established through the bore in which the hammer
reciprocates by means of a hammer shank having a lesser diameter
than the inside diameter of the bore. Fluid communication between
the third surface and the inlet may be precluded when an end
portion of the hammer, which also serves as a piston, and which has
a diameter equal to that of the bore, descends below a
predetermined point in the bore as when not restricted in movement
by the tool and blocks the fluid path mentioned previously. At the
same time, a reduced diameter portion on the hammer used for other
valve purposes in conjunction with a control valve which controls
the reciprocation of the hammer vents the third surface to the
outlet thereby permitting the bypass valve to open.
Other objects and advantages of the invention will become apparent
from the following specification taken in conjunction with the
accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation, with parts shown in section, of a
hydraulic hammer made according to the invention with the elements
shown in one position wherein the bypass valve is closed; and
FIG. 2 is a side elevation, with parts shown in section with the
elements in the position wherein the bypass valve is opened.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An exemplary embodiment of a hydraulic hammer made according to the
invention is illustrated in FIGS. 1 and 2 and is seen to include a
casing, generally designated 10, having a central bore 12 therein.
Disposed within the bore 12 for reciprocation therein is a hammer
element, generally designated 14, having an upper valve end
including an annular reduced diameter portion 16 and a pressure
responsive piston 18. The hammer element 14 also includes a lower,
enlarged hammer 20 which is disposed within an enlarged diameter
portion 22 of the bore 12.
Secured to the lower end of the casing 10 is a tool mount 24 having
a central bore 26 receiving a movable tool 28 which is disposed to
be struck by the hammer 20 and which has a lower, work performing
end (not shown). Alternatively, that portion of the tool 28
illustrated could be an anvil having its lower end operatively
associated with a selected tool to be used in conjunction with the
hammer. For example, the lower end of such an anvil may ride on the
upper end of the tool. The tool 28 includes a key way 30 and a key
32 which extends through the tool mount 24 and the key way 30 to
restrict the movement of the tool 28 within the tool mount 24 to
the length of the key way 30.
The casing 10 includes an inlet 34 which may be connected to any
suitable source of hydraulic fluid under pressure to serve as a
source of energy for reciprocating the hammer 20 within the casing
10 to impart energy to the tool 28. In fluid communication with the
inlet is a conventional accumulator 36. The casing 10 further
includes an outlet 38 and a second accumulator 40 in fluid
communication with the outlet 38.
A port 42 transverse to the bore 12 in the casing 10 and in fluid
communication with the inlet 34 is arranged to permit the
application of fluid under pressure to a lowermost surface 44 of
the piston 18 of the hammer element 14. As will be seen, this
application of fluid under pressure serves to move the hammer
element 14 upwardly in the bore 12 for its return stroke. A series
of small grooves 45 extend upwardly partially to the port 46 from
the port 42 for purposes to be seen.
A port 46 normally in fluid communcation with the port 42 through
the bore 12 and reduced diameter portion 16 provides fluid under
pressure to a hydraulically operated control valve spool, generally
designated 50, which is operative to control the reciprocation of
the hammer element 14 within the bore 12. The spool 50 includes a
reduced diameter portion 52. The spool 50 is shiftable within a
bore 54 to a first position (illustrated in FIG. 1) wherein fluid
under pressure from the inlet 34 passing through the port 42 and
the port 46 is fed along the reduced diameter portion 52 to the
upper end of the bore 12 via a conduit 56 in communication with
both the bore 54 and the bore 12 and applied to an upper surface 58
on the piston 18 of the hammer element 14. The surface 58 is larger
than the surface 44 so that when fluid under pressure is applied to
the former, notwithstanding the fact that fluid under pressure is
also applied to the latter, the hammer element 14 will be driven
downwardly to strike the tool 28.
A second position of the spool 50 within the bore 54, shown in FIG.
2, is one wherein the spool 50 is shifted upwardly from the
position shown in FIG. 1 and wherein an enlarged lower end 60
blocks off the path of fluid under pressure from the inlet 34 to
the upper end of the bore 12 while an enlarged upper end 62, in
conjunction with the reduced diameter portion 52 permits fluid in
the upper end of the bore above the surface 58 to exit to the
outlet 38 via a conduit 64. Interposed between the conduit 64 and
the outlet 38 and hydraulically prior to the point of connection of
the accumulator 40 to the outlet 38 is a restriction or orifice 65
for purposes to be seen. When the spool 50 is in the just-mentioned
position, the fact that the surface 58 is subjected to outlet
pressure while the surface 44 is subjected to inlet pressure will
cause the hammer to move upwardly for its return stroke.
Positioning of the spool 50 is controlled by a differential pin
device including pins 66 in the lowermost end of the spool 50 and
pins 68 at the opposite end thereof. The pins 66 have a lesser
effective area than the pins 68 and are continuously subjected to
inlet pressure. The pins 68 are intermittently subjected to inlet
pressure dependent upon the position of the hammer 14 within the
bore 12 and when such is the case, the spool 50 will be driven by
the pins 68 to the position shown. When such is not the case, the
pins 68 will drive the spool 50 upwardly to the second-mentioned
position above. For a more detailed statement of the operation and
specific construction of the differential pin device, reference may
be had to U.S. Pat. No. 3,399,602 to Klessig et al., the details of
which are herein incorporated by reference.
As mentioned previously, one of the difficulties encountered in the
operation of hydraulic hammers is variations in the frequency of
operation principally due to varying back pressure. Specifically,
the rate of return of the hammer element during the return stroke
will be generally dependent upon the ratio of the area of the
smaller surface 44 and the pressure supplied thereto to the area of
the larger surface 58 and the pressure applied thereto. Since,
during return, the latter surface is subjected only to outlet
pressure, an increased back pressure will cause a slower rate of
return than would be the case with little or no back pressure
present. Accordingly, the exemplary embodiment of the invention
includes means by which the back pressure against the surface 58
during the return stroke of the hammer element 14 is maintained
constant so that cycling frequency will be constant.
Specifically, a restriction of constant size is located in the flow
path from the upper end of the bore 12 to the outlet 38 and which
is established when the valve 50 is in the second position
mentioned above. More particularly, the restriction is in the form
of a venturi, generally designated 70 and carried on the upper end
of the reduced diameter portion 52 of the spool 50. The venturi 70
is generally defined by a land 72 having a diameter less than the
diameter of the bore 54 and greater than that of the reduced
diameter portion 52; an upstream tapered short side 74; and a
downstream tapered long side 76. That is, the longitudinal extent
of the upstream side 74 of the land 72 is less than the
longitudinal extent of the downstream side 76.
When the spool 50 is moved upwardly to the second-mentioned
position, the same in conjunction with a portion 78 of the bore 54
interposed between the conduit 64 define an annular venturi. The
annular venturi effectively isolates the pressure in the conduit 56
from pressure variations normally encountered in the return conduit
64.
It should be specifically noted that while the exemplary embodiment
employs a venturi on the spool 50, the same could be located at any
one of a variety of downstream points in fluid communication with
the outlet 38. However, because the casing 10 is generally formed
as a casting and the various conduits contained therein are
frequently defined by bores, the forming of a restriction in one of
the conduits would require a rather complex machining or casting
operation. In contrast, the formation of the venturi 70 on the
spool 50 may be accomplished relatively easily during the formation
of the reduced diameter portion 52 thereon.
The exemplary embodiment further includes a bypass conduit 80 which
extends between the inlet 34 and the outlet 38 and which is
normally closed by a bypass valve, generally designated 82. The
bypass valve 82 is mounted for reciprocation within a bore 84 in
the casing 10. One end of the bore 84 is closed by a plug 86 which
serves to position a spring 88 in a recess 90 formed in the body of
the valve member 82 to bias the valve member 82 against a seat 92
surrounding the bypass conduit 80 as shown in FIG. 1.
The bypass valve 82, intermediate its ends, includes a reduced
diameter portion 93 which normally permits fluid under pressure to
flow from the inlet 34 to the port 42 for use in driving the hammer
in the manner mentioned previously. The bypass valve 82 further
includes a pair of pressure responsive surfaces 94 and 96 with the
surface 94 being larger than the surface 96. The recess 90
terminates in a third pressure sensitive surface 98 on the valve
82. The arrangement is such that the combined areas of the surfaces
96 and 98 is greater than the area of the surface 94 but the
surface 94 is greater in size than the surface 96 alone. More
particularly, the surfaces 94, 96, 98 and the spring 88 act such
that when inlet pressure is applied against the surface 96 and the
surface 94 (as will always be the case) and is applied to the
surface 98 (as will usually be the case) the valve 82 will be in
the position shown in FIG. 1. However, when inlet pressure is not
applied to the surface 98, the valve will shift downwardly to the
position shown in FIG. 2 to open the bypass 80 whereupon fluid
under pressure from the inlet 34 will flow directly to the outlet
38 bypassing entirely the control valve 50. As a result,
reciprocation of the hammer element will cease.
Returning to FIG. 2, fluid under pressure from the inlet 34 is
normally applied to the surface 98 via the port 42 and a section
100 of the bore 12 interconnecting the port 42 and a port 102. The
bore section 100 is of slightly greater diameter than the shank of
the hammer element 14 but, for purposes to be seen, is of the same
diameter as the diameter of the piston 18.
Referring now to FIG. 2, the relief of fluid pressure against the
surface 98 so as to permit the valve 82 to open for bypass purposes
is accomplished by means of a port 104 in the bottom of a
stationary sleeve 106 embracing the shank of the hammer element 14.
Also included are a series of small grooves 105 extending upwardly
a short distance from the port 104 to permit the establishment of
fluid communication to the port 104 through the bore section 100
slightly before the reduced diameter portion moves to the upper
boundary of the port 104. A channel 108 is in fluid communication
with the port 104 and a bore 110 which empties into the hollow
center 112 of the spool 50. From the hollow center 112, fluid may
flow through a radial bore 114 in the uppermost end of the spool 50
to the conduit 64 to the outlet 38. The arrangement is such that
when the hammer element 14 has been driven downwardly past a
position wherein it would normally encounter the tool 28 and not
yet has encountered the tool as shown in FIG. 2, the side of the
piston 18 will enter the bore portion 100 thereby blocking fluid
communication between the inlet 34 via the port 42 to the surface
98. Simultaneously, the reduced diameter portion 16 on the hammer
element 14 will establish fluid communication between the port 102
and the port 104 through the grooves 105 thereby permitting the
fluid under pressure bearing against the surface 98 to flow to the
outlet 38 via the path mentioned previously.
This relieving of the pressure against the surface 98 will cause
the inlet pressure to shift the valve 82 downwardly thereby
permitting fluid from the inlet 34 to flow directly to the outlet
38 via the control valve 50. Furthermore, the presence of the
orifice 65 in the return line will, when the accumulator 40 dumps,
cause a large back pressure area 58 of the piston 18 through the
port 64, the venturi 70 and the port 56 to tend to keep the hammer
in its down position. Also, the grooves 45 permit flow of fluid
from the pressure port 42 into the upper portion of the bore 12 to
tend to fill the cavity caused by cavitation as the piston 18 cuts
off flow through the port 46 during downward movement.
As a result of the foregoing, reciprocation of the hammer 14 will
cease. It will therefore be apparent that whenever the tool is at a
predetermined position within its bore 26 and lower than the
desired position, as for example, when it is not bearing against
work, the hammer will automatically cease to operate.
From the foregoing, it will be appreciated that a hydraulic hammer
made according to the invention possesses a number of significant
advantages over those heretofore known. For example, a positive
bypass is provided as opposed to one wherein the hydraulic fluid
will flow through a control system for the hammer. Secondly, the
exemplary construction does not require any special machining
operations on the hammer element. Specifically, the reduced
diameter portion 16 on the hammer element, which is operative to
relieve pressure against the third surface 98 of the control valve
92 when hammer reciprocation is to cease would normally be employed
in the hammer in any event for controlling the application of
hydraulic fluid to the large piston surface 58. It is therefore
believed apparent that the invention provides an improved hammer of
economical construction and which is positive in its operation for
ceasing, automatically, the reciprocation of the hammer when the
same has moved beyond a predetermined point in the bore.
* * * * *