Note: Descriptions are shown in the official language in which they were submitted.
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This invention relatec; to a synchrono~s vibra-
tory hammer employing a driving and a driven eccentric
weight arranged to produce vibratory action which may
be used for impacting a tool upon a work surface.
The art of vibratory hammers, of the type with
which this invention is concerned, is well developed
and many different designs have been proposed and
employed with varying degrees of success. Patent
3r866,693, dated February 18, 1975 to Bernard A. Century,
iO is representative of one such vibratory hammer.
The subject invention has certain elements in
common with the device of the Century patent, however,
it dif~ers in at least one important respect, namely,
it has no mechanical restraints which can absorb energy,
such as would be caused by the guides 186 and 188 of
Centuryls patent. The mechanical restraints in the
Century patent are used to control non-linear motion
of the hammer element being driven by a single eccentric.
The device o~ the subject invention eliminates the need
for such mechanical restraints because of the act that
two eccentrics are used.
The device of the subject invention requires
less maintenance than vibratory hammers having non-
linear impacting vihrations, which not only shake the
hammer supporting mechanism, but are subject to greater
wear and breakage.
A primary ohject of the invention is to provide
a vibratory hammer with improved operating efficiency,
and which minimize.s maintenance costs.
The presenl: invention provides a vibratory im-
pact hammer including a support frame, a hammer body
assemblage suspendecl within the support frame by
resilient means arl-anged to provide guiding and damping
action in either direction of axial movement o~ the
ha~mer body zssemblage, said hamm~r body having a given
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stro~e t the xesilient means being the sole means engaglng
the hammer body assemblage so that extraneous frictional
forces are avoided, vibration dri~e means arranged to de-
velop a forcing frequency to vibrate the hammer body as-
semblage in an axial direction, said forcing frequency setto lead the vibrated ~requency of the hamrner body assem-
blage by 135, and a tool reciprocably mounted in the sup-
port frame and positioned to receive impact blows of the
hammer body assemblage when reciprocated by the vibratory
drive means.
These and further objects and features of the
invention will become more apparent from an understanding
of the following disclosure.
In drawings which illustrate embodiments of the
invention,
Fig. 1 is a side elevation view of a vibratory
hammer embodying the principles of the in~ention;
Fig. 2 is an enlarged section view as seen from
line 2-2 in Fig. l;
Figs. 3, 4 and 5 are cross section views as seen
from lines 3-3, 4-4 and 5-5 respectively in Fig. 2;
Fig. 6 is an exterior view of a hammer body com-
ponent used in the device of Fig. l;
Fig. 7 is an end view of the eccentric weights
mounted on a shaft.
Referring now to Figs. 1 to 5, numeral 1 identi-
fies a vibratory hammer having a support frame consisting
of a pair of side plates 3, which are maintained in par-
allel position by means of tubular space bars 5, welded to
the plates~ as well as a tool holder element 7, similarly
welded thexeto. A hammer body assemblage 9, as shown in
Fig. 6, is suspended between the side plates 3 by resilient
means consisting of four rubber mounts 11 affixed to thc
side plates and the hammex body assemblage by means of
bolts 13 and 15~ As will be apparent, the mounts serve as
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the sole guiding and damping mea~ns for the assemblage
when the latter is vibrated duri.ng t~l operation.
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The hammer body assemblage 9 includes an
eccentric weight chamber 17, shown in Fig. 7~ enclosing
a pair of eccentric weights 19 and-21, mounted upon
shafts 23 supported in roller bearings 25 positioned
in end caps 27 r the latter being secured by bolt means
29 to side members 31 of -the eccentric weight chamber
15 by bolts 32~ Projecting from the top surface of
the eccentric weight chamber 17 and affixed theretol
is an upper axm member 33 adapted to be affixed to the
rubber mounts 11 by the bo]ts 15.
Projecting from the bottom surface of the eccen-
tric weight chamber 7 and aEfixed khereto, is a lower
arm member 35 adapted to be affixed to the rubber mounts
11 by the bolts 15. Brace members 37 are secured to
the sides of the lower arm member 35 and the hammer
body assem~lage 9, to stabilize the arm member. An
hydraulic motor 39, affixed to the end of shaft 23, is
provided to rotate the eccentric weight 19. A pair
of gears 41, mounted upon the shaft 23, ~s arranged to
transmit rotary motion from the shaft which supports
eccentric weight 19, to the sha~t which supports eccen-
tric weight 21, so that both weights are rotated at the
same speed but in opposite directions. Hose means 43
5uppiy pressurized hydraulic fluid to the motor 39
when desired, from a power source, not shown.
At the lower extremity of the arm member 35 is
a striker plake 45 affixed thereto by means of pin 47.
The striker plate is arranged to impact upon a conical
tool 49 mounted in the tool holder element 7 as best
seen in Fig~ 2~ Retaining means, including a key 51
projecting into a slot 53 formed in the tool 49, allow
reciprocal movement of the tool~ The tool slides in
bushi.ngs 55 supported in a bushin~ housing 5?, the
latter positionally maintained against axial movement
hy a tool stop plate 59,affixed to the end of the tool
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holder by means of cap screws 61~
Support means for the vibratory hammer 1, are
provided by a pivotally attached linkage assemblage 63,
which may be operatively positioned by power machinery,
e.g. tractor, not shown.
The desi.gn parameters of a vibratory hammer
built in acco.rdance with the invention disclosed herein,
obviously will vary in accordance with the work impact
output desired.
It is to be recognized -that when a forcing
frequency vibrates a mass at its natural frequency, the
mass of the forcing frequency generator leads the
vibrated mass by 90. When the forcing frequency is
much higher than the natural frequency, the forcing
frequency mass could lead the vibrated mass by 180.
Accordingly, if the leading phase is 135, the vertical
componen-t of centrifugal force of the vibrated mass,
coupled with the stored energy of the rubber mounts,
will produce maximum impacting on the tool 49.
The optimum phase angle of 135 l~) is deter-
mined by the following equation:
2 ~
tan ~ = fn
1 f2
fn
where ~ - phase anqle
~ = damping factor
f = forcing frequency CPM,RAD/SEC
fn = natural frequency
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It can be demonstrated by plottiny frequency
ratio vs. ~ wi.th varying damping factors, that any-
thing less than a critically damped system gives phase
angles of a~proximately 180 at any frequency ratio
greater than 1, hence, critical damping of the system
is essential for optimum operative results. Critical
damping by definition means no over oscillation when
a mass is deflected from its static position and re-
turned to the same static position. Critical damping
is achieved by a preload, in the present vibratory
hammer, by use of the rubber mounts ll.
It is essential, for optimum operation, that
the stroke of the hammer be equal to the -in the air
displacement (S ), which is provided by the following
equation:
S = 2 wr
W
Where w - unbalanced weight
r = radius where unbalanced weight is
located from the center of
rotation
W = total weight vibrated
By application of these formula, a vibratory
hammer in accorclance with the invention will have the
followirlg numeral values, if a work impact output of
200 ft.-lbs. at 1200 rpm is to be achieved:
Stroke 0.4144 inches
Weiyht of hammer body assemblage (9) 485.52 lbs.
w = 60.69 lbs.
r = 1.6576 inches
wr2 - 100.59 in lbs.
wr - 166.76 in2 lbs.
K - 3gO0 #/in.
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While an embodimenk of the invention has been
illustrated and described in detail to enable any
person skilled in the art, to which it pertains, to
make and use the same, it is expressly understood that
the invention is not limited thereto~ Various changes
in form, design, or arrangement may be made in its
parts without departing from the spirit and scope of
the invention; it is my intention, therefore, to claim
the invention/ not only as shown and described, but
also in all such forms and modifications thereof as
might be reasonably construed to be within the spirit
of the invent.ion and the scope of the appended claims.
