Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE XNVE~TION
Field of the Invention
This application relates to vibratory machines,
and, more particularly, to the resilient members for ico-
lating said machines from a supporting member.
Description of the Prior Art
. ~In one well-known type of vibratory machine, a
working member is movably mounted on a base. A drive
member is connected between the base and the working mem-
ber to impart vibratory motion to the working member. Tne
working member may, for example, be an elongated trough
which receives material to be conveyed longitudinally
along the trough as the trough is vibrated. Or the ~70r'.~irAg
member may be a screen which receives a load to be sif~d
through the vibrating scxeen~ Other types of machines
also employ a base member, a working memberD and a drive
member connected between the base member and the working
member to impart a vibratory motion to the wor~iny me~ber~
Despite efforts to limit ~he vibratory motion
to the working member, vibration in the base is inevitable~ .
I~ the machine is installed. on the ground, no serious
problems will be created by the vibration o~ the base.
If, however, the machine is installed in a building, or on
some other supporting structure or member, the vi~ra~ion
of the machine can weaken or damage the building or other
structure, particularly if the vibrations are o~ a Ire-
quency at or near the natural frequency of the sup~orting
structure.
Because of the destructive effect a vibrating
base of a ~ibratory machine can have on the supporting
` structure on which the machine is mounted, it is well
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known to provide isolati.on springs between the base and
the supporting structure to insulate the latter from the
vibrations of the former.
A typical vibratory machine of the type des-
cribed is show.n in the United States patent to Musschoot
et al 3,3~5,861 wherein coiled steel isolation springs 12,
on vertical axes, are provided between the base 10 and the
supporting structure 11. The United States patent to
Gilbert 2,918,590 shows the base of a vibratory machine
mounted on "rubber feet" 2, and a United States patent to
Dahlquist 3,108,408 shows a ~ibratory machine having a
base mounted on "elastomer feet" 11. Other vibratory
machines having apparently similar isolation pads are
shown in United States patents to Petrea 3,087,603; Allen
et al 3,165,197; Maeder et al 3,212,629; and Wahl
3,297,304. In all of these patents, the feet, or pads, have
contact surfaces which are horizontal for engagement with
the base member. In other words, a central axis perpendi-
cular to the interface with the base i5 vertical in each
of these isolation pads.
The United States patent of Muskat 2,333,435
shows vertical coil springs 28 mounted between a base 27
and a sub-base 24 of a viblatory machine, and shows rubber
pads 25 with horizontal contact faces between ~he sub~base
and the supporting structure 19.
It should be noted that rubber or elastomer pads
are used in other places in vibratory machinery. For
example, pads are shown in the resilient mounting of a
work member on a base in ~nited States patents of
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Musschoot 3,056,488; Maeder et al 3,212,629; and
~lusschoot et al 3,134,483. The United Stakes patent to
Maeder et al 3,212,629 also sho~s rubber pads in the dri~e
connection between the base and the ~orking member. It
will be noted that many of the rubber ox elastomer pads
- used in other than an isola-tion function (that is, in
some application where the pad is not mounted on sup?or.ing
structure but is, instead, used internally in .he vibra-
tory machine) have contact surfaces not in a horizontal
plane.
The book ubber Spri~L~esiqn by E. F. C-obel,
John Wiley & Sons, New York, ~.Y. 197~ shows vaxious
arrangements or flat rubber springs.
- Block~ made of elastomers (which term as used
herein shall be understood to include rubber and any
elastic substance resembling rubber) are quite yieldable
in shear but much less yieldable under compression. Thus 9
an elastomer block (that is, with parallel upper and lo~er
surfaces) constitutes a stiff spring when resisting forces
directed perpendicularly to said upper and lower sur aces,
but constitùkes a soft spring when resisting lateral
forces tthat is, any force parallel to the upper an~
lower surfaces of the blocX).
The principal vibratory force which must ~2 iso-
lated from the supporting structuxe in the usual v~bra~ory
machine ~such as a material conveyor) is the longitudinal
- vibration created by the reaction to the driving oscilla-
tions which propel the material forward in steps. The
soft resistance of the rubber blocks when oriented with
horizontal conkact faces, as common in the prior art, to
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this longitudinal vibration effectively isolates the vibra-
: tion from the supporting structure.
~ owever, the elastomer springs with horizontal
contact faces, because of the characteristics of the
elastomeric material, also present little resistance to
lateral forces which permits an undesired lat~ral sway to
the conveyor. Moreover, the stiffness of the elastomeric
springs to vertical forces when the contact faces are hori-
zontal, although effective to support the conveyor, results
in poor isolation of vertical vibrations and permits these
destructive vibrations to be transmitted to the supporting
structure.
SUMMARY OF THE I~ TIO~
In accordance with the present invention there is
15 provided in a structure for mounting, in a stationary sup-
porting member, a vibratory machine ~aving a base with a
longitudinal centerline and having a work member, said
: machine having means to support the work member for longi-
tudinal movement parallel to said centerline and relative
to the base, said machine also having a drive member to
effect longitudinal vibration of said work member relative
to the base, said mounting structure including elastomer
isolation blocks having opposing parallel faces engaging,
respectively, parallel and spaced apart support faces on
the base and said stationary support member, said blocks
offering stiff resistance in compresslon to forces tra~s-
mitted from said base to said stationary supporting member
normal to said engaging faces and offering soft resistance
in shear to forces transmitted from said base to said
stationary member parallel to said engaging faces, said
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blocks mounted between said base and said supporting member
on each side of the longitudinal centerline of the base,
the improvement in such mounting structure wherein said
support surfaces on the machine base are on each side of
said centerline and face downwardly and outwardly and
wherein said support surfaces on said stationary support
member face upwardly and inwards, said surfaces on the base
and on the stationary supporting member lying in planes
parallel to the longitudinal centerline of the base, each
of said elastomer isolation blocks thereby oriented by
said support surfaces to resist the vertical ~o~ce of
gravity in both compression and shear thereby to support
said machine while minimizing compression forces trans-
mitted to said stationary supporting member, and to resist
transverse vibrations in both compression and shear,
while limiting to shear the resistance to longitudinal
reaction of the base to said longitudinal vibration of
said work member thereby to continue to permit relatively
free movement thereof along said longitudinal centerline.
BRIEF DESCRIPTIO~ OF THE DRAWINGS
Figure 1 is a side view of a vibratory machine
with portions being broken away, incorporating the mount-
ing arrangement of the present invention.
Figure 2 is a view taken on the line 2-2 of
Figure 1.
Figures 3A, 3B and 3C are schematic diagrams
illustrating three different arrangements of isolation
blocks for a vibratory machine.
- DESCRIPTION OF T~E PREFERRED EM~ODIMENTS
There is shown in Eigure 1 a ~ibratory machine 10
havin~ a base 12 and a work member 14. Although the machine
may be any vibratory machine in which a work member is
oscillated longitudinally with respect to a base, we have
shown for illustrative purposes a material conveyor. The
work member 14 of the material conveyor 10 is in the form
of a trou~h which receives material 15 at the lef-t end
(as viewed in Figure 1) and transports the material to the
right end.
The work member 14 is mounted for movement rela-
tive to the base by means of leaf springs 16. Each leafspring is secured at one end, by bolts 18, to the work
member and is secured, at the opposite end, by bolts 20,
to the base. The leaf springs, which are inclined
slightly from the vertical, define the path of movement of
the work member as perpendicular to the inclined leaf
springs. Thus, at each end, the work member moves in the
direction of the arrows 22.
A drive unit 24 is connected between the base 12
and the work member 14. The drive unit includes a motor
26 mounted on the base and a crankshaft 28 rotatably
mounted in bearing blocks 30 which are also mounted on the
base. The crankshaft 28 is driven by the motor through
pulley 32, secured to the crankshaft, and belt 34. Rota-
tion of the crankshaft imparts to work member 14 a vibra-
tory motion through a crank 36 which is rotatably receivedon the crankshaft and pivotally connected to the work
member 14.
Since the vibratory motion of work member 14 is
in the direction of arrows 22, the work member vibration
will have a horizontal, or longitudinal, component 22h and
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a vertical component 22v. The horizontal and vertical
components of the vibratory motion of the work member
create reac~ionary horizontal and vertical components of
v.ibration in the base.
The elements of Figure 1 described above are well-
known conventional vibratory machine elements used hereto-
fore.
The base 12 is elongated and, as shown best in
Figure 2, of rectangular cross-section with a longitudinal
centerline ~0 extending therethrough. The base 12 is
supported on a member 46, which is usually stationary and
is frequently a structural unit such as the floor of a
building, or a built up platform or stand to support the
conve~or. The vibratory reaction to the oscillations
of the conveyor create longitudinal and vertical vibrations
in the base. These base vibrations, particularly lf close
to the natural frequency of the support member, can be
destructive if not isolated from the support structure.
It is well known to provide elastomer bloc~s
between the base and the supporting member, but these
blocks are conventionally oriented in an upright, Gr ver-
tical, position ~that is, wit~ the upper and lower surfaces
thereof lying in parallel horizontal planes). It is also
known, as shown in Figure 3.3 of Rubber Spring Desiqn, that
the orientation of the elastomer block will affect the
spring characteristics thereof.
~s shown in Figure 3A of the present disclosure
when the contact face F of an elastomer block B, which is
supported on memher S, is horizontal, the weight of a
vertically acting load ~ (such as gravity) acts to compress
~f
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the block. In this orientation, the block B acts as a
stiff spring to this vertical force.
As shown in Figure 3B of the present disclosure
when the contact face F of an elastomer block, which is
- 5 supported on mem~er S, is vertical, the weight of a verti-cally acting load L (such as gravity) acts in shear. In
this orientation, the block B acts as a soft spring to the
vertical load. It should be noted that when the block B is
too soft to vertical forces, the block must be increased
in area to support the weight of the machine. The increase
in size of the block increases the longitudinal stiffness
of the block, thereby transmitting a greater longitudinal
force to the support surface S. The transmission of a
greater force to support surface S defeats the objective
of reducing forces transmitted to the support member.
As shown in Figure 3C of the present disclosure
when the contact face F of an elastomer block, which is
supported on member S, is inclined at an angle between the
vertical and horizontal (say, at an angle of 45 to each),
the weight of a vertically acting load (such as gravity)
acts partly in compression and partly in shear. In this
" orientation, the characteristics of the spring to vertical
forces fall between the stiffness of the orientation of
` Figure 3~ and the softness of the orientation of Figure 3B.
The orientation of the block shown in Figure 3C does not
- increase the stiffness of the block to longitudinal forces.
As shown in Figures 1 and 2, L-shaped brackets
42L and 42R are secured at two or more points along each
side~ respectively, of -the base. In accordance with the
present invention, the lower surfaces 44L and 44R of the
` ?`'
`` .?
~.
brackets define contact sur~aces which are inclined to
face downwardly and outwardly (away from the centerline 40
of the base). Preferably, the contact surfaces define an
angle of approximately 45 from the horizontal, although
angles of from 30 to about 70 can be used under some
circumstances depending on the specific vertical and hori-
zontal spring characteristics required.
Two or more brackets 48R, 48L (one for each base
bracket 42R, 42L) are mounted on the stationary support on
each side, respectively, of the centerline 40 of the base in
registration with the brackets on the base as shown in
Figures 1 and 2. Each bracket 48R, 48L has an upper surface
50L inclined to face upwardly and inwardly (toward the cen-
terline 40 of the base), parallel, respectively, to the sur-
faces 44R, 44L of the base brackets 42R, 42L.
An elastomeric block 52 is received between eacho~ the pairs of complementary surfaces 4~R-50R, 44L-50L to
support the vibratory machine 10 on the stationary support
member 46. It is believed that a comparison of the
schematic diagrams of Figure 3C to Figures 3A, 3B will
clearly demonstrate the desirable effects of our elastomer
isolation block orientation, which is similar to the
arrangement illustrated in Figure 3C.
By placing the block 52 at an intermediate angle
(Figure 2), we have created a spring less stiff than the
prior art springs but yet less soft than a block totally
in shear. By adjusting the angle of inclination (relative
to the horizontal) from between 30 and 70, we can make
the spring stiffer (than a block at 45) to either vertical
or horizontal forces or softer.
_g_
:'
Thus, it will be understood that the stiffness
o~ the elastomeric springs acting in the vertical direction
can be softened by placing the blocks at an angle (say,
45), with the upper faces of the blocks facing upwardly
and inwardly. It should also be noted that in the prior
art arrangement of Figure 3A, where the upper surfaces of
the blocks are horizontal, the springs defined thereby are
soft in the lateral direction~ This softness in the
lateral direction subjects the vibratory machine to lateral
sway. However, our orientation of the blocks at an angle
(as shown in Figures 2 and 3C) not only acts to soften
the springs in the ~ertical direction but acts to stiffen
the springs in the lateral direction.
The difficulty with the prior art arrangement of
the springs of Figure 3A is that the springs are so stiff
in the vertical direction that destructive vibratory
forces are transmitted through the springs to the stationary
support. The arrangement of Figure 3B would substantially
eliminate the transmission through the springs of the
destructive vertical vibratory force but would produce
springs too soft to adequately support the conveyor. Our
arrangement of Figure 3C and Figure 2 softens the springs
hut leaves them stiff enough to adequately support the
conveyor.
An examination of Figure 1 will show that the
longitudinal vibrations of the work members act on the
elastomer blocks in shear so that the springs remain soft
to these forces and do not transmit them to the support
structure.
It should be noted, as shown in Figure 2, that
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central axes 54L and 54R through the blocks and perpendicu-
lar to the faces thereof intersect at a point identified
as a roll center RC. These points (which de~ine a roll
center axis extending through two or more RC points)
constitute roll centers because they are the points about
which the elastomer blocks 52 offer the least resistance
to roll. In order to prevent an undesirable roll, we
arrange the angle of inclination of the blocks to assure
that the axes 54L and 54R intersect above the center of
gravity CG of the vibratory machine (when under normal
load) so that the vibratory machine will not have a ten-
dency to lean.
Although the best mode contemplated Eor carrying
out the present invention has been herein shown and
described, it will be apparent that modification and varla-
tion may be made without depa.rting from what is regarded
to be the subject matter of the invention.
~WE:cds
