Note: Descriptions are shown in the official language in which they were submitted.
Disclosure
The present invention relates to the art of presses
and, more particularly, to a hydraulic fluid shoc~. dampening
system for a shearing press
In a shearing press, as is well known, cooperable
cutting die or shearing components are mounted on the press
slide and bed to achieve cutting or shearing of material there-
between in response to movement of the press slide through
the downward portion of its total stroke. Upon engagement
of the die component on the slide with the material to be
severed a load is placed on the press which progressively
increases to a maximum which is reached at the point of break-
through of the die components with respect to the material
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therebetween. This load is imposed on the press through
the slide, and movement of the slide toward the press bed
is restrained during the severing operation. This restraint
is removed upon breakthrough, whereupon slide movement toward
the press bed is accelerated as a result of the load build up.
In the absence of a restraining force with respect to such
accelerated movement of the slide, objectional shock loads
and vibration forces are set up within the press. Such
shock and vibration is detrimental to press life as well
as maintenance expenses in connection with component parts
of the press. Moreover, these shock and vibration forces
result in objectionably high noise levels and impar~ un-
desirable vibration to otner equipment and to the personnel
working in the vicinity of the press. Moreover, it will
be appreciated that these undesirable characteristics are
repeated with each stroke of the press and are related in
degree of objectionability to the size of the press
Efforts have been made heretofore to dampen such
shock and vibration forces experienced with the operation
of a shearing press. While some success has been achieved
in connection with reducing shocX and vib~ation, the systems
heretofore proposed for ~his purpose do not provide optimum
efficiency with regard to vibration and noise abatement over
a desirable period of continuous use of a given press, Addi-
tionally, systems heretofore proposed have characteristicswhich are detrimental to press life and economical press
operation. With regard to such prior art efforts, it has been
proposed, for example, to employ a hydraulic shock absorbing
syS~eM including one or more piston and cylinder units inter-
po~ed betwaen the press bed and slide to define chambers
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receiving hydraulic fluid under pressure. During movement
of the slide toward the bed to achieve a shearing operation~
fluid is expelled from the chamber or chambers through a vari-
able restricted passageway incorporated in the piston component
and adjusted to provide a predetermined restriction to flow
from the chamber at the point of breakthrough of the material
being severed. Such a system enables continuous, though re-
stricted, movement of the slide following breakthrough and,
thus, the imposition of some shock and vibration forces on
the press. Moreover, if two or more such piston and cylinder
units are employed in a given press, the adjustment thereof
must be extremely accurate to avoid eccentric loading of the -
slide as a result of different pressure drops across the
restrictions of the different units. Still further, the -
accuracies required in these units makes the system extremely
expensive, and continuous operation of the press results in
a requirement fbr frequent adjustment of the units ~hereby --;-
down time of the press is undesirably high as is maintenance ~ -
time and expense. Additionally, continuous operation of
the press with continuous flow of hydraulic fluid from the --
cylinder chambers each time the slide strokes results in
undesirably high fluid temperatures which may necessitate
the use of a cooling system therefor, thus adding to the ~
cost of production and expensive operation of the press. -~-
Still further, even if just one piston and cylinder unit is
- employed to avoid the possibility of eccentric loading of the
slide, the accuracy required with regard to adjusting the --
point of maximum restriction to coincide with the point of
material breakthrough is impractical.
Other systems heretofore proposed have included
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a ~ixed orifice in the hydraulic system operable to pass
hydraulic fluid from a fluid receiving chamber to a tank
or the like by a low pressure drop during initial cutting
of the material and at a high pressure drop when break-
through occurs. The high pressure drop provides a restrain-
ing force against the slide. Systems of the latter character
have poor efficiency with regard to reducing shock and noise
and, additionally, generate excessive heat in the fluid due
to the substantially continuous flow thereof under pressure.
In accordance with the present invention, the
disadvantages of previous shock dampening systems provided
in connection with shearing presses, including those speci-
fically enumerated hereinabove, are minimized or overcome.
In this respect, maximum restraint of slide movement following
breakthrough is achieved by quickly and positively blocking
fluid flow from hydraulic fluid receiving chambers inter-
posed between the press slide and bed. This maximum re-
straining force provides increased efficiency in reducing
shock and noise by minimizing the load energy released and
thus slide movement following breakthrough. Moreover, by
positively blocking fluid flow from the chamber or chambers
there is very little heat generated in the system fluid.
Accordingly, the necessity of cooling systems are avoided as
is the danger of excessive heat in the system without such a
cooling system.
Preferably, such shutoff of fluid flow from a fluid
chamber at the point of breakthrough is achieved by a flow
sensitive valve in the fluid system whîch is responsive to
acceleration of the slide at the point of breakthrough to
block fluid flow from the chamber or chambers. Further,
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the shock and v-~bration loads imposed on the press by
energy release at breakthrough can be further reduced
by using a minimum volume of hydraulic fluid in the system,
by using a fluid having a high bulk modulus, and by rapid
response of the flow sensitive valve. Preferably, the
flow sensitive shutoff valve provides restricted flow
from the chamber or chambers with minimal pressure drop
during the cutting operation up to the point of breakthrough.
At the point of breakthrough, acceleration of the slide posi-
tively shuts the valve producing a rapid counterload againstslide movement, thus reducing the energy release experienced
at breakthrough and maintaining the load on the press through
the slide, thus to minimize shock, vibration and noise. -~
It is accordingly an outstanding object of the
present invention to provide an improved hydraulic shock
dampening system for shearing presses.
; Another object is the provision of a shock dampening
system of the foregoing character which minimizes energy
release, with respect to the load on the press, upon break-
through of the material being severed.
Yet another object is the provision of a shock
dampening system of the foregoing character which effficiently -~
minimizes the imposition of shock and vibration forces on a -
press and the resultant noise level of the press during shearing
operations.
Still a further object is the provision of a shock
dampening system of the foregoing character ~hich positively
blocks fIuid flow from an expansible chamber unit interposed
between the press slide and bed at breakthrough of the material
being severed, thus to minimize energy release with respect
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1063925
to the slide at the point of breakthrough and maximize slide
restraining force.
Yet another object lS the provision of a shock
dampening system of the foregoing character in which a flow
5 . sensitive valv~ is employed to permit restricted flow of -
hydraulic fluia from the expansible chamber device duri~g
cutting of material up to the point of brea~through and which
is responsive to acceleration of the slide at the point of
breakthrough to close the valve and thus block further fluid .
flow from the expansible chamber device
Still another object is the provision of a shock
dampening system of the foregoing character which i9 in- . .
expensive to manufacture and install and which is highly
efficient in operation throughout long periods of continuous
use, thus minimizing down time of the press and maintenance : -
time and expense.
According to a broad aspect the present invention
relates to a hydraulic shock dampening system for a shearing !;
. . . ~
press having fra~e means including bed means and supporting :
reciprocable slide means and wherein material is severed between .
cooperable shearing means supported by said bed and slide means, ~.-
- said system including hydraulic fluid receiving variable volume chamber means between said bed means and slide means and con-
nected to a source of hydraulic fluid under pressure, said - i
25 chamber means being operable under compression in response to ,-
breakthrough of material being sneared by said sl-earing means
supported by said slide means to restrain the resulting
accelerated movement of said slide means, the improvement ~::
comprising: shutoff valve means in fluid flow communication
with said chamber means, said valve means having opened and
closed modes, and means completely closing said valve means
in response to said accelerated movement of the press slide ~
to prevent any fluid flow from said chamber means. . .
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The foregoing objects, and others, wlll ln part
be obvious and in part pointed out more fully hereinafter
in con~unction with the written description of preferred
embodiments of the invention shown in the accompanying drawings
in which:
FIGURE 1 is a schematic illustration of a shock
dampening system in accordance with the present invention
associated with the slide and bed components of a shearing
press;
` FIGURE 2 is a graph showing slide displacement and
press load curves during the working stroke of a shearing
press without shock dampening;
FIGURE 3 is a graph showing slide displacement
and press load curves during the work stroke of a shearing
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press having a shock dampening s~stem in accordance with the
present invention; and,
FIGURE 4 is a schematic illustration of a modifica-
tion of the system sho~n in FIGURE 1.
Referring now in greater detail to the drawings
wherein the showings are for the purpose of illustrating
preferred embodiments of the present invention onl~ and
not for the purpose of limiting the same, a hydraulic fluid
shock dampening system is schematically illustrated in
; FIGUR~ 1 and in conjunction with a shearing press 10 operable,
fo~ example, to cut blanks from metal sheets. The structure
and operation of presses of this character are of course
well known in the art, and details regarding the structure
and operation are not necessary to an understanding of the
present invention. It will be sufficient to appreciate that
the press has a ~rame 12 providing a press bed 14 and that
the frame supports a slide 16 for reciprocation toward and
away from bed 14, a suitable drive arrangement being provided
to achieve such reciprocation. As is further well known in
the shearing press art, bed 14 supports a shearing component
18 and slide 16 supports a shearing component 20 cooperable
with component 18 to cut material therebetween during down-
ward movement of slide 16 to the bottom dead center position
thereof. Cutting takes place, of course, from a point along
tne slide stroke above the bottom dead center position at which
shearing component 20 engages the material to a second point
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along the slide path ~ust ahead of bottom dead center at which
shearing components 18 and 20 cooperatlvely break through the
material being cut. As is well known to those skilled in the
art of presses, engagement of material to be cut between
shearing components 18 and 20 during downward movement of
the slide imposes a load on the press through the slide and
which load is suddenly released upon breakthrough of the
material, whereupon down~ard movement of the slide is
accelerated in the direction toward the bottom dead center
position thereof. This is of course accompanied by release
of the energy stored by loading of the press during the
shearing operation.
In accordance with the present invention, a shock
dampening system is associated with the slide and frame
components of the press to minimize downward displacement
of the press slide following breakthrough, thus to minimize
; the release of energy resulting from loading of the press
up to the point of breakthrough. The shock dampening system,
designated generally by the numeral 22 in FIGURE 1, is a
hydraulic system including hydraulic fluid receiving variable
volume devices 24 mounted on or supported relative to the
press bed for actuation by slide 16 during downward movement
thereof toward the bottom dead center position. In the
embodiment shown, each variable volume device 24 is in the
form of a piston-cylinder assembly including a cylinder 26
supported on the press bed and a piston 28 supported within
cylinder 26 for vertical reciprocation relative thereto.
The space in cylinder 26 behind piston 28 defines a fluid
receiving chamber 30, and cylinder 26 is provided with a
common inlet and outlet passage 32 opening into chamber 30.
106392S
Slide 16 carries an actuator pin 34 for each piston, and
each pin 34 has its upper end threadedly interengaged wit'n
a support collar 36 on the slide so that the pin is vertically
adjustable relative to the slide for the purpose set forth
hereinafter.
Chambers 30 of variable volume devices 24 are con-
nected to a common source of hydraulic fluid under pressure.
~lore particularly, in the embodiment shown in FIGURE 1 a
motor-pump unit 38 is adapted to deliver hydraulic fluid
under pressure to cha~bers 30 fr~m a source 40 through a
flow line system including a flow line 42 and branch lines
44 and 46 connected thereto and to one of the passageways 32
of variable volume devices 24. A one way check valve 48
- prevents backflow to source 40, and a pressure responsive
unloading valve 50 is operable at a predetermined pressure
between valve 48 and the motor-pump unit to return hydraulic
fluid to the source when valve 48 is closed and the pressure
between the latter valve and motor-pump unit 38 exceeds the
setting of valve 50.
A noramlly open fluid flow sensitive shutoff valve
52 is provided in flow line 42 to control fluid flow through
the latter line. Valve 52 includes a restricted passageway
54 permitting restricted fluid flow in the direction between
chambers 30 and source ~0 when valve 52 is in the open
position illustrated in FIGURE 1. Valve 52 further includes
a closed passageway 56 which is adapted to blocX fluid flow
through line 42 when valve 52 is in the closed position in
which pa~sage 56 would be shifted to the right in FIGURE 1
to a position in ~lignement with flow line 42. Valve 52 is
normally biased to the open position such as by a spring 58
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and is adapted to be biased to the right in FICURE 1 by fluid
under pressure from branch lines 44 and 46 acting thereagainst
tlrough a feed line 60, as described in greater detail here-
inafter. For the purpose set forth hereinafter, a low pressure
hydraulic fluid receiving accumulator 62 is connected to flow
line 42 between valves 48 and 52, and a high pressure hydraulic
fluid receiving accumulator 64 is connected in fluid communi-
cation with line 42 and branch lines 44 and 46 between valve
52 and chambers 30 of variable volume devices 24.
Operation of the shock dampening arrangement described
above will be best understood by referring to FIGURES 2 and 3
of the drawing together with FIGURE 1. Briefly, FIGURES 2 and
3 are graphs showing slide displacment and press load during
movement of the slide through the shearing stroke. FIGURE 2
shows the effect of no shock dampening of the slide, and
FIGURE 3 shows the effect of the shock dampening system
described above and the effect of prior art shock dampening
: systems. In both graphs, the point 1 represents the time
during the slide stroke at which, in the system disclosed
herein, pins 34 engage pistons 28 during movement of the
slide toward the bottom dead center position thereof which
is indicated BDC in FIGURES 2 and 3. Point 2 represents the
time at which the shearing components engage the material
to be severed, and point 3 represents the time at which
breakthrough of the material by the shearing components .
occurs. Curve L represents the load imposed on the press
during a severing operation, and curve D represents the
position of the slide during the severing operation relative
to bottom dead center. If the press was not loaded by the
interposition of material to be cut between the shearing
-- 10 --
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components, slide displacement curve D would be arcuate
throughout its extent and thus would follow the arcuate
portion D' between point 2 and BDC in FIGURE 2 and between
points 2 and 4 in FIGURE 3. The significance of point 4
is set forth hereinafter.
- With regard now to the operation of the shock dampening
arrangement described hereinabove, the components of the press
and hydraulic system are in the positions illustrated in PIGURE
1 prior to a shearing operation. Hydraulic fluid is delivered
under pressure from source 40 to chambers 30 through flow line
42, restricted passage 54 of valve 52 and branch lines 44 and 46,
and the fluid under pressure in chambers 30 biases pistons 28
upwardly. As slide 16 moves downwardly toward bed 14, pins 34
engage pistons 28 just before shearing components 18 and 20
engage the material therebetween to be severed. The ad~ustability
of pins 34 enables setting the pins in this respect. As
mentioned above, the material is engaged at point 1 in the
graphs of FIGURES 2 and 3 and at this time the slide is located ~-
,~
a distance S above BDC. Continued downward movement of slide 16
causes downward movement of pistons 28 in cylinders 26 thus
forcing the hydraulic fluid in chambers 30 into branch lines 44
and 46 through cylinder passages 32. This fluid from chambers
30 flows back toward source 40 through restricted passage 54 of
valve 52 and, since one way valve 48 is closed against return of
fluid to source 40, accumulator 62 receives the back flow fluid
- under pressure and stores the latter for return towards chambers
30 as set forth hereinafter. During this movement of the slide
toward its bottom dead center position the slide has a normal
velocity which is a known factor in connection with a given press
and
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shutoff valve 52 is structured for this normal velocity to
produce a minimal pressure drop through restricted passage
54, whereby the opening bias is sufficient to maintain valve
52 open.
Continued downward movement of slide 16 brings shearing
components 18 and 20 into engagement with the material there-
between, thus initiating the imposition of a losd on the press
through the slide. This engagement with the material is re-
presented by point 2 in the graphs, and at this time the slide
is spaced a distance W above the bottom dead center position
thereof. As the shearing components cut the material, pins 34
continue to depress pistons 28 and the loading of the press
restrains advancement of the slide and reduces the velocity
thereof. Accordingly, the piston displacement is gradual
causing a continuance of the foregoing fluid flow from chambers
30 through restricted passage 54 of valve 52 to accumulator 62.
As will be seen from load curve L in the graphs, the press is
loaded from zero to a maximum as the shearing components move
through the material during the period of slide displacement
represented between points 2 and 3. At the same time, it
will be seen that the material between the shearing components
restrains displacement of the slide in the downward direction
towards bottom dead center, as represented by portion D2 of
the displacement curve in the graphs.
The shearing components breakthrough the material
at point 3 whereby the load is removed from the press and
the stored energy of the load is imposed on the slide causing
a rapid acceleration of the slide towards its bottom dead
center position. In the absence of any shock dampening
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o~ the slide a~ this point, the slide is immediately acceler~ted
to bottom dead center, thereby imposing shock on the press
and bounce of the slide resulting in the imposition of a
series of reverse direction loads on the press as indicated by
the portion of load curve L to the right of point 3 in FIGU~E 2.
A shock dampening system in accordance with the
present invention advantageously restrains slide displacem~nt
toward BDC following breakthrough and minimizes the energy
release so as to maintain a load on the~press during completion
of the severing operation. In this resp,ect, with reference
to FIGURE 1, acceleration of the slide which occurs upon
breakthrough is transmitted to pistons 28, thus suddenly
accelerating displacement of the pistons in the direction
to reduce the volume of chambers 30. This sudden displace-
ment increases the velocity of the hydraulic fluid ~lowing from
; chambers 30, whereby valve 52 is actuated through feed line 60
to close the valve and thus positively ~lock fluid flow from
chambers 30. Thus, as seen in FIGURE 3, load energy release
is stopped at point 5 following breakthrough and the slide ~-
is restrained from reaching BDC, as represented by portion ~3
of the slide displacement curve. Accordingl~, a major pro-
portion of the load is maintained on the press following
breakthrough. From the point of time in normal slide displace-
ment at which B~C is reached the press load i5 progressively
decreased as a result of movement of the slide drive components
which would normally cause upward displacement of the slide
from ~DC. At point 4 in the graph of ~IGURE 3, the slide
drive components are in slide displacement positions corres-
pondin~ to the displacement position in which the slide is
held by the piston-cylinder units 24. Thereafter, the slide
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drive components move the slide up~ar~ly and thc load on
the press is reduced to zero.
The load maintained on the press in this rnanner
maintains the hydraulic fluid between chambers 30 and valve
5~ under pressure to maintain valve 52 closed. Upon upwa-d
movement of slide 16, the fluid pressure in the system biases
pistons 28 upwardly to reduce s~stem pressure and thus provide
for spring 58 to open valve 52. Thereafter, fluid accumulated
under pressure in accumulator 62 is released to flow through
L0 restricted passage 54 of valve 52 back into branch lines
44 and 46 and chambers 30 to fully bias pistons 28 to their
uppermost positions. Motor-pump unit 38 is operable to
replenish any fluid leakage from the system which might
occur during operation o~ the press.
High pressure accumulator 64 is a safety device to
prevent damage as a result of press overload. If, far example,
there is some breaXdown which causes the press slide to impose
a high pressure on the hydraulic system between piston-cylinder
units 24 and check va}ve 48, accumulator 64 is actuated to
receive fluid under such excess pressure.
The embodiment of the present invention illustrated
in FIGURE 4 is the same in many xespects as that shown in
FIGURE 1 and, accordingly, like numerals are employed in
FIGU~ES 1 and 4 to designate li~e components. In the embodi-
ment of FIGURE 4, restricted passageway 54 of shutoff valve 52
is in communication with source 40 and piston-cylinder units
24 through flow line 42 and a branch line 66 leading to the
valve. Additionally, fluid flow through restricted passage 54
in respon~e to downward movement of pistons 28 prior to
sO material brea~through is released by a low pressure ch~ck
,
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1~63g25
valve 68 for flow to a sump or the ]ike 70 leadlng back
to source 40. In further comparison of this embodlment
with that shown in FIGURE 1, high pressure accumulator 64
in FIGURE 1 is replaced by a pressure responsive relief valve
72 which is operable in response to an undesirably high
fluid pressure in the system to dump fluid to a sump or
the like 74 for return to source 40. Further, low pressure
accumulator 62 in FIGURE 1 is replaced by a low pressure
accumulator 76 positioned between motor-pump unit 38 and check -~
valve 48 to accumulate fluid under pressure when shutoff valve
52 is closed to provide sufficient fluid for the system to
return pistons 28 to their uppermost positions following a
severing operation. It will be appreciated that accumulator
76 works in conjunction with motor-pump unit 38 in replenishing
the system in this respect.
Operation of the system shown in FIGURE 4 insofar
as blocking fluid flow from chambers 30 of piston-cylinder
units 24 is the same as that for the system shown in FIGURE 1.
In this respect, initial downward movement of pistons 28
prior to breakthrough is at the velocity of the press slide,
whereby valve 52 remains open and fluid expelled from chambers 30
flows through check valve 68 to sump 70. Upon breakthrough,
the sudden acceleration of slide 16 and the resulting velocity
increase in the fluid flow closes valve 52 to block further
flow of fluid from chambers 30 and thus stop downward displace-
ment of the slide. When the slide reaches point 4 in the
graph of FIGURE 3, system pressure is reduced whereby valve
52 is biased open and pistons 28 are biased to their upper-
~- most positions in preparation for the next severing operation.
It will be appreciated in conjunction with both
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of the embodiments herein disclosed that the magnitude of
the load energy release at point 3 in the graph of FIGUR~ 3
can be controlled toward minimization by using a minimum volume
of hydraulic fluid in the piston-cylinder units and flow line~,
by using a hydraulic fluid having a high bulk modulus, by
using a rapid response flow sensltive shutoff valve, and by
various combinations of these control possibilities.
While considerable emphasis has been placed on the
specific embodiments herein illustrated and described, it
will be readily understood that many modifications will be
obvious and suggested upon reading the foregoing description .
and can be made without departing from the principles of the
present invention. In this respect, for example, while two
piston-cylinder units 24 are illustrated, one or more than
two such units can readily be associated with a given press
structure to provide the desired slide restraint function
; in response to breakthrough, Further, it will be appreciated
that variable volume devices other than piston-cylinder
units can be employed and that, in connection with piston-
cylinder units, the piston-cylinder relationship can be
reversed so that the cylinder is a movable component engaged
by the press. Still further, while it i~ preferred to employ
a flow sensitive shutoff valve permitting restricted fluid
flow therethrough prior to breakthrough of the material being
severed, it will be appreciated that other shutoff valve
structures could be employed, Moreover, it will be appreci-
ated that the shutoff valve could be controlled other than
by system fluid. For example, the valve could be solenoid
actuated to close at the point of breakthrough. It is only
; 30 necessary in accordance with the present invention that the
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shutoff valve b^ act~lated at the point of acceleration of
the slide upon breakthrough to positively block fluid flow
from the chambers of the variable volume devices.
As many possible embodiments of the present invention
may be made and as many changes may be made in the em~odiments
herein illustrated and described, it is to be distinctly
understood that the ~oreqoing descriptive matter is to be
interpreted merely as illustrative of the present invention
and not as a limitation.
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