Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BACKGROUND OF THE INVENTION
The tremendous impacts involvecl in the operation
of forging hammers can cause problems, t:he seriousness of
which increases in accordance with the size of the hammer.
With little or no vibrati~n isolation, the impacts of large
forging ham~ers can sometimes be felt o~er a mile away
from the location of the hammers. Often, the shock of an
improperly or unisolated forging har~mer can crack building
walls, damage other equipment in and around the facility
where the hammer is located, creates an environmental
nuisance, affects the accuracy of precision tools and
instruments located at even substantial distances a~ay
and can actually pound the foundation on which the hammer
is located down into the ground, making necessary frequent
releveling.
Effective shock and vibration control systems
for forging hammers have been known and widely used Lor
many years. P. good system will completely eliminate the
transmission of shock betweell the hammer and the oundation
and will, therefore, eliminate all of the problems referred
to aboveO Moreover, a good shock and vibration system will
make the operation of the hammer quieter and actually
increase the efficiency of the hammer.
In some shock and vibration control systems
proposed and used in the past, the vibration isolators
and damping systems have often been ins~alled outside of the
perimeter of the inertia block to facilitate installation and
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maintenance of the isolators and dampers. In many
installations, the isolators are of a type in which the
top plate is connected by a screw to a beam constructed
into the inertia block. This type of isolator can be
installed in unloaded condition and loaded by threading
the screw to lift the inertia block off the foundation.
In a system that has apparently been used in Europe,
isolators constructed in a manner that permits them to be
preloaded prior to installation under the inertia block
and then partially unloaded by loosening the preloading
bolts have been employed~
The damping systems that have been used in shock
and vibration control systems for forging hammers have
been of the type that inherently produce forces of magnitudes
that vary in the course of operation of the system. One
type of dampiny employs a mechanical snubber similar to
snubbers used in the couplings between railway cars. The
construction of such mechanical snubbers is such that ~he
forces that they produce increase as a function of the
extent of compression, and rnechanical snubbers are subject
to ailure under certain conditions, for exa~ple, because
of the buildup of an excessive vertical or horizontal force.
Hydraulic-type snubbers have also been used, but it is well know~
that the seals required to contain hydraulic fluid frequently fail
and require excessive maintenance and result in costly shutdown
time. Moreover, the force output of hydraulic~-type
dampers is dependent on the velocity o~ the vibrating
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e~uipment at any given point in time; accordingly, the
damping forces are low just after impact of the hammer,
increase to effective levels only after the load has
developed some velocity, and then decrease as the load is
decelerated toward the end of one half cycle of vibration.
Accordingly, hydraulic dampers work effectively only during
part of each cycle of vibration, and from this point of
view, hydraulic dampers are inefficient.
In recent years, the tendency has been toward the
use of forging hammers of extremely large size and involving
tremendous impact loads, and the greater size and consequent
heavy static loads and, o~ course, the greater impact forces
have increased the proble~s in providing e~fective shock and
vibration control. The heavy loads and tremendous impacts
involved require a very large number of isolators and highly
reliable damping, particularly when the hammer is designed
for relatively high productio~ rates in terms of operations
per minute. Vibration must be damped as rapidly as possible
using highly reliable dampers. The heavy static loads of
the e~uipment have increased the difficulties involved in
construction and installaticn of the hammer and have, in some
of the very ]arge installations, made systems based on known
technology extremely expensive.
SUMMARY OF THE INVENTION
There is provided, in accordance with the invention,
a greatly improved shock and vibration control system for
forging hammers that overcomes many of the problems and
limitations of previously known systems and offers
important advantages and economies.
One aspect o the invention concerns the use of
isolators having integxal spring-loaded,adjustable friction-
type damping systems. At least some of the great number
of isolators of the system include, more particularly, a
pair of horizontal, spaced-~part pla-tes that extend down
in parallel vertical planes from the underside of the top
plate, each of which is engaged by a brake shce that is
I spring loaded to develop a predeterminec; friction force
between the brake shoe and the vertical plate. Each braking
shoe is restrained by a housing from moving vertically or
horizontally parallel to the plane of the plate. Accordingly,
~ movement of the top plate or the isolator vertically or
horizontally parallel to the planes of the plate is resisted
by frictional force developed by the brake shoes and the
vertical plates. The loading of the brake shoes can be
adjusted by shimming to provide the desired damping orces,
and the spring-loading of the brake shoes produces automatic
0 adjustment to cornpensate for wear.
The shock and vibration control system, according
to ~he invention, employs at least two of the above-described
type of isolators oriented to provide damping of horizon~al
~ibration tshould such vibration occur) of the inertia block
and hammer along one axis and at least two other such isolators
oriented to damp horizontal vibration along an axis perpendicular
to the a~orcmentioned axis. Thus, the system provicles for
damping of any horizontal vibration that mi~ht occur alon~
mutually perpendicular axesl ~t should be apparent that the
springs that load the brakes of an isola-tor afford move-
ment of the top plate of the isolator in a direction parallel
to the axes of the brake loading springs. Energy-absorbing
stops are provided in the isolators to restrict the extent
of such movements.
In most systems, only a few of the many isolat-ors
are of the type having friction damping devlces; the remaining
isolators, usually by far the major proportion of the total
number, are simple spring isolators having no damping and no
loading devices. Both types are known per se, but neither type
has, as far as is known, been used in shock and ~ibration
control systems or forging hammers.
~nother aspect of the inven~ion involves -the method
of installing tne system and the constxuction o~ the founda~ion
that is ancillary to the method. The inertia block on which
the hammer is mounted is a massive structure, usually made of
reinforced or prestressed concrete. (The inertia block is
often considered as part of the foundation for the forging
hammer, and it is part of the shock and vibration control
system for the hammer, but in the terminology employed herein,
it is referred to as the "i~,~rtia blockt" and the term
"foundation" is used to refer to the structural base member
on which the inertia block and forging hammer are mounted,
the isolators being interposed between the inertia block
and the foundation.)
With extremely large forging hammers, the inertia
block o the system may weigh as much as one million pounds
~s~
or more, and it is quite apparent that the inertia block
must, because of its size and weight, be fabricated in place
on the foundation. In accordance with the present invention,
the inertia block is fabricated in place on a multiplicity
S of spaced-apart load-bearing piers which are preferably
constructed as part of the foundation. The height o~ the
p~ers is such that the bottom of the inertia block is
located at a distance "X" above the surfaces on ~hich the
isolators are ~ounted, the distance "X" being established
with a definite relation to the unloaded and the loaded
heights of the isolators and the minimum height of a jack
used to load the isolators in place. In particular, the
distance or dimension "X" is equal to the sum of (1) :he
loaded height of the isolators and (2) the height "S" of
structural spacers that are installed between the top plates
of the isolators and the bottom of the inertia block~ The
structural spacers, in turn, have a height "S" that is not
less than, and preferably slightly greater than, the sum
of (1) the difference between the unloaded height and the
loaded heigh~ of the isolators and (2) the minimum height
of the jack.
The reason for the dimensional relationships
described above is that such dimensional relationships
permit the isolators to be inserted in unloaded condition
while the inertia block and the hamm~r are suppor-ted on the
piers. The procedure for installing each isolator is as
follows: First, the isolator, in unloaded condition (a
condition in which the height of the isolator is, of course,
somewhat greater than the loaded height~ is placed in proper
position on the foundation under the inertia block. A jack,
preferably a hydraulic jack, is then inserted between the top
plate of the isolator and the bottom of the inertia block and
is operated to load the isolator to an extent sufficient to
permit one or more permanent load-bearing spacers to be
installed between the top plate of the isolator and the bottom
of the inertia block. The jack is then lowered and removed.
After all of the isolators have been so installed, the loads
of the inertia block and hammer will have been transferred from
the piers to the isolatars. The piers or parts of the piers
can then be removed to provide su~ficient clearance to permit
normal vibration o~ the inertia block and hammer on the
isolators. An economical and reliable pier may, as described
below, consist of a concrete pier, the top of which is spaced
from the bottom of the inertia block by a distance greater
than the distance that the inertia block moves down in operation
of the hammer (thus permitting controlled vibration of the
inertia block and hammer) and a removable temporary spacer
plate mounted on top of the concrete pier. After the
isolators are installed, the spacer plates are removed.
In accordance with one broad aspect, the invention
relates to a method of constructing a shock and vi~ration
control system ~or a forging hammer mounted on an lnertia
block which is, in turn, mounted on a foundation comprising
the steps of fabricating the inertia block in place at a
vertical height "X" above isolator-supporting portions of the
foundation under the inertia block, supporting the inertia
block on rigid temporary structural supports at said height
"X", inserting a shock and vibration isolator in ~mloaded
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condition under the inertia block and in position on the
isola~or~supporting portion of the foundation, loading the
vibration isolator by inserting a jack between the top of the
isolator and the bottom of the inertia block and operating
the jack to load the isolator, and inserting at least one
permanent structural spacer between the isolator and the
inertia block, the spacer having a height "S" substantially
equal to the difference between the height "X" and the loaded
height "H" of the isolator and the height "S" of the spacer
being greater than the sum of ~1) the difference between the
unloaded height of the isolator and the loaded height of the
isolator and (2) the minimum height of the jack.
For a better understanding of the invention, reference
may be made to the following description of an exemplary
embodiment, considered in conjunction with the accompanying
drawings.
DESCRIPTION OF THE DRAWrNGS
Fig. 1 is a plan view of the foundation on which
the isolators, inertia block and forging hammer are mounted,
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A 5i~5
the positions of the isolators and the types o isolators
being represented by boxes bearing labels;
Fig. 2 is a side view in cross-section of the
oundation taken generally along the lines 2-2 o~ Fig. 1
`5 and in the direction of the arrows and showing the shock
and vibration control system, the inertia block and r
schematically, the lower par~ of the hammer,
Fig. 3 is an end view in cross-section taken
generally along the lines 3-3 of Fig. 2 and in the
direction of the arrows;
Fig. 4 is a ragmentary view in elevation of
one of the piers, the view being on a larger scale than
in Fig. 3 and showing in greater detail the structure
within the circle labelled 4 in ~ig. ~; c~,~
lS Fig. 5A is a top view of a type "A" isolator,
part of the top plate being broken away;
Fig. SB is an elevational view of a type "A"
isolator and the permanent spacers and also shows a jack
in place for loading the isolator;
Fig. 5C is an end view of a type "A" isolator
wi~n spacers in place;
Fig. 6A is a top view of a type "B" isolator,
the top plate being partly broken away;
Fig. 6B is a side elevational view of the type
"B" isolator; and
~:~ Fig. 6C is an end view of the type "B" isolator,
; part of the brake-spring retainer being broken away.
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DESCRIPTION OF E~:MPLARY EMBODI~IENTS
As shown in Figs. l throu~h 3, a typical forging
hammer installation embodying the invention includes a pit
having side walls 10, end walls 12 and a base or foundation 14
on which are located structural pedestals 16, the upper surfaces
of which constitute hori~ontal isolator-mounting surfaces of
the foundation. The placement, dimensioning and structure of
the pedestals will be such that they will support in desired
locations, as indicated by the boxes bearing letter legends
in FigO l, vibration isolators. As described in more detail
below, the system shown in the drawings involves the use of
two types of isolators that, for convenience, are reerred
to herein as l'type A isolatorsl' and l'type B isolators. Il The
type A lsolators are positioned on the pedestals in the
i locations represented by the boxes labelled IIA", in Fig. l,
and the type B isolators are positioned in the locations
indicated in Fig. 1 by the boxes labelled IIBI'.
The foundation 14 of the pit for the forging hammer
installation shown in the drawings further includes a number
) of spaced-apart piers 18, one of which is shown in detail in
Fig. 4. The piers are constructed and arranged to provide
temporary support for the loads of the inertia block 20 and
forging hammer 22 during fabrication of the inertia block and
installation of the forging hammer. In the exemplary embodiment,
as shown in Fig. 4, each pier includes a base portion 24, ~hich
may be of reinforced concrete or structural steel; the portion 24
constitutes the major part of the height of the pier.
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The pier also includes a removable, temporary spacer plate 26
held in position by a temporary peripheral ~rame 28. The
inertia block, which is made of reinforced concrete, prestressed
concrete, or post-stressed concrete/ is fabricated in place by
conventional const~uction techniques involving constructing
temporary forms supported by erection shoring and the piers 18,
placing the reinforcing and pouring the concrete. In reinforced
concrete cons~ructions, bearing plates 30 and 32 are installed
in the forms for the pier and the inertia block and cast in
L0 place at each pier location. Bearlng plates 33 (see Figs. 2
and 3) are cast in place on the bottom of the inertia block
at each isolator location. After the inertia block has been
poured and has set to the strength necessary to support the
for~ing hammer, the forms and erection shoring are removed
and the forging hammer 22 is installed~ From this point,
the loads of the inertia block 20 and the forging hammer are
suppor~ed by the piers 18.
The installation of the shock and vibration control
system requires having access to the space under the inertia
block to permit the isolators physically to be moved in
under the inertia block, inserted in proper position, as
indicated in FigO 1, and loaded. Accordingly, it is preferable
for the pedestals to be spaced apart and to have a height such
that, when added to the height of the isolators and spacers
(described below), there is enough room for workmen to move about~
~eferring now to Figs. 5A to SC, each type A
; isolator consists of a base plate 36, the bottom of which is
provided with a non-skid pad ~not shown), a top p:late 38 and
a number of springs 40. The details of the couplings between
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the springs and the plates are omitted in the drawing,
the drawings showing the springs in schernatic form, but
it will be understood by those skilled in the art that
suitable spring retainers are provided to maintain each
spring in proper position between the plates 36 and 38.
Each type B.isolator (Figs. 6A to 6C) has a top
plate 42 that is supported on a large number of springs44
and has a pair o vertical parallel brake plates 46 extending
down from the underside, one at each end outwardly of the
cluster o springs. Stiffener plates ~7 extend lengthwise
between the rows of springs to stif~en the ~wo brake plates 46
and the top plate 42. The base plate 48 extends some distance
out beyond each of the brake plates 46, and a strong housing
50 is fastened to the base plate 48 at each end portion.
Within each housing axe several brake springs 5? that are
compressed between a retainer 54 and a brake shoe assembly,
which consists of a back-up plate 56 and a brake shoe element
58, bolted to the back-up plate, and urge the brake shoe
element 58 against the corresponding brake plate 46, thereby
to generate substantially constant r~ction damping forces
acting between the base and the top plate of the isolator.
The spring force can be adjusted by using suitable shims
between the retainer 54 and the housing 50~ Each back-up
plate 56 is captured between the base plate 48 and the
top member 57 of the housing 50, thus preventing vertical
movement of the friction brake shoe 58, and lateral
retainer ribs 59 extend back between the interior side ~alls
o the housing of each brake assembly, thus preventing
ho~izontal movement of the brake slloe 58 relative to the
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housing 50~ Accordingly, vibration of the inertia block
and hammer and the consequent movement of the brake plates
on the top plate of the isolator is resisted by frictional
damping forces acting vertically and horizontally parallel
to the.brake plates.
As can be observed in Fig. 1, even numbers of type
B isolators are mounted symmetrically with their longer axes
aligned parallel to the end walls 12 of the pit, and even
numbers of the type B isolators are mounted symmetrically
with their longer axes parallel to the side walls lO of
the pit. In other words, even numbers oE type B isolators
are oriented to provide symmetrical damping orces parallel
to mutually perpendicular, horizontal axes.
Both the type A and type B isolators are constructed
to permit not only vertical vibration, but horizontal vibration,
and the damping assemblies of the type B isolators are
constructed and oriented to provide damping forces to dampen
horizontal components of vibration of the inertia block and
hammer. Each t~pe B vibration isolator includes,.however,
energy-absorbing stops 60 (see Fi~. 6A) that limit the extent
of horizontal vibration, such stops 60 being positi~ned to
be engaged by the back face of the correspondin~ back~up plate 56.
. All of the isolators of the shock and vibration
:: co~ltrol system (i.~., both the type A and type B) are
installed in accordance ~ith the same procedure as ollows:
recalling that the inertia block and forging hammer are
firmly and reliably supported by the piers 1~ o the
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s
~oundation, each isolator is moved through a suitable one
of the access passageways between the pedestals and is
placed in proper position on the pedest~l. A jack is then
moved in through an appropriate passageway and positioned
on top of the top plate. At this point, the isolator is
in an unloaded condition, which means that its height will
be greater than its height will be when it is loaded. Using
the jack, the isolator is loaded, that procedure involving,
of course, the application by the jack of a force acting
between the bottom of the inertia block and the top plate
of the isolator that forces the top plate down and compresses
the sp~ings.
The loaded height of the isolator and the operating
load in static condition of the isolator are, of course,
known in advance. mhus, the measured distance between the
bottom of the inertia block and the top of the top plate and
the force applied to the jack will both be available ways
to determine when the desired load condltion has been reached.
In practice, the jack will be used to load the
J isolator to an extent slightly above the static load that it
will carry in the final installation, thereby to move the
top plate to a position a little bit below that which it
will occupy at the rest position when installedO The reason
for th.at is to provide enough clearance to allow spacers 62
i (see Figs~ 5A to 5C) to be moved into place between the top
plate 38 or 42 and the bottom of the inertia block, the spacers
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beln~ per~anent load-bearing elements of the system. After
the spa~ers are ln place, the jack is lowered and removed.
(Amon~ ~h~ det~ not shown in the drawings are anchor bolts
~or ~uxl~g the ~ase plates 48 of the type B isolators to the
~Qp~S ~ ~he ~e~estals, All of the spacers 62 are bolted
~o ~h~ bearin~ plates 33 on the bottom of the inertia block
and ~o the ~p pla~es of all isolators to ensure against
mov~m~nt ~ ~hc operation of the systemO)
~ iny to Fig. 5B, the dimension between the
LO hçaring plates on ~he pedestals and the bearing plates on
the in~tia ~lQçk at eaçh isolator location (the dimension
~ 11ed "X" i~ Fi~. 5~) is, of course, equal to the sum of
th~ load~d heie~h~ "H" o~ the isolator and the height "S"
o~ ~he ~acex~ 6~. Thç height o the spacers "S" must be
L5 not l~s~ ~han ~hç sum Q (1) the diference between the unloaded
heigh~ o~ ~he isola,~o~s and the loaded height of the isolators
a~d (2) ~h~ minimu~ height of a jack (item "J" in Fig. 5B)
capabl~ of applyi~ the necessary load to the isolator~.
S~t~ mo~e simply, ~hç dimension "X" is established to permit
an unload~d i~ol~x to,be placed on the pedeskal and a suitable
jaclr to be inse~ted between the top plate of the isolator
an~ th~ bo~t~m of ~he inertia block. The known dimension "X"
and ~h~ l~ad~d dimension "H" of the isolator will then determine
~he hei~h~ "S" of the stops.
~he h~hts of the piers, including the temporary
~pa~exs, will ~e established such that when all of the isolators
h~v~ ~een in~talled in the manner described above, the load of
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the inertia block and hammer will ~e carried substantially
~ntirely by the isolators, thereby permit~ing the temporary
spacer plates 26 to be readily removed. To put it another
way, after all of the isolators are installed, the piers
should not support loads that will make it difficul to
remove the spacers. The thickness of the temporary spacers 26
is in excess o the amplitude, i.e., of one half of the
maximum movements of vertical vibration of the inertia block
and hammer on the system. Thus, when the spacers are removed
) from the piers, normal vertical vibration of the shock and
vibration isolation system is accommodated because the tops
o the permanent piers 18 (which are preferahly left in place)
are below the lowest point of movement of the inertia block.
Should it be necessary to remove any of the isolators
for any reason, such as to replace the brake shoes or, eventually,
springs t the procedure described above for installing the isolator
can be reversed. Indeed it is desirable as a matter o normal
maintenance for the entire procedure of installing the isolation
system to be used in reverse to again support the inertia block
~20 and hammer on the piers for replacement of the brake shoes and
any other necessary maintenance of all of the isolators.
In the operation of the shock and vibration control
system, as is, per s , well known, the isolators transform the
impact force of the hammer to a smaller, gradually applied
25 force. In addition, however, vertical and horizontal components
of vibration ~enerated upon impac~ of the hammer are rapidly
damped by substantially constant forces generated by the
frictlon dampers of the type B isolators used in the system.
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A system, according to the invention, can thus be constructed
more efficiently and reliably to dampen substantially all
vibration of the inertia block and hammer bet~een cycles of
operation. The installation procedure, according to the
invention, offers substantial benefits in terms of cost and
ease of fabrication and installation of the forging hammer
isolation system and, therefore, of relatively low initial
cost of the job.
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