Note: Descriptions are shown in the official language in which they were submitted.
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Title: VIBRATIONAL FINISHING ASSEMBLY
FIELD OF THE INVENTION
The present invention relates to vibratory finishing
machines, and more particularly to an improved vibrational finishing
assembly.
BACKGROUND OF THE INVENTION
Finishing machines are used to perform finishing operations
such as deburring, burnishing, descaling, cleaning and the like. Such
machines include a movably mounted chamber and a drive system for
vibrating the receptacle. Workpieces to be finished are loaded into the
chamber together with finishing media. A finishing action is imparted to
the workpieces by vibrating the chamber so that the mixture of workpieces
and media is effectively maintained in a fluid or mobile state with smaller
components of the mixture dispersed between larger components so that
the larger components receive finishing treatment from the smaller
components. Impulse forces imparted to the mixture not only cause
repeated impacts among its components but also cause the mixture to
churn in a predictable manner as a finishing process is carried out.
Two basic types of unbalanced-mass vibratory finishing
machines are in common use. An earlier type of finishing machine such
as that described in U.S. Patent No. 4,228,619 to Anderson employs an
elongate chamber which defines an elongate, trough-like finishing
chamber extending in a substantially horizontal plane, and which is
vibrated by rotating one or more eccentrically-weighted drive shafts about
one or more substantially horizontally axes extending along the chamber.
This type of machine is known in the art as a "tub machine".
Another, newer type of machine such as that described in
U.S. Patent No 3,161,993 to Balz, uses a substantially toroidal-shaped
chamber which defines an annular, trough-like finishing chamber
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extending in a generally horizontal plane, and which is vibrated by
rotating an eccentrically-weighted drive shaft about a substantially vertical
"center axis" located centrally of the chamber when the chamber is at rest.
This type of machine is known in the art as a "bowl machine".
Both types of machines use inertial centrifugal vibrators (i.e.
unbalanced mass type mechanisms) to provide vibrations excitation. It is
important to be able to increase the amplitude of the vertical velocity
vibrations in order to increase the intensity (i.e. velocity) of the finishing
process. However, unbalanced-mass finishing machines are prone to a
number of operational disadvantages.
First, when the machine power supply is turned off and
braking is applied to the drive shaft, the large machine components
rapidly lose their accumulated energy. When the rotation frequency of the
drive mechanism coincide with the vibrations of the larger machine
components on an elastic suspension there is a corresponding increase in
the non-stationary vibratory load that acts on the floor or foundation of
the building where the finishing machine is mounted. In order to avoid
the horizontal displacement of the machine when it is turned off, it is
necessary to secure the elastic suspension of the chamber to the heavy base
which in turn significantly limits the intensity of the working vibrations
of the machine and, consequently, the finishing intensity.
Generally, the amplitude of the transitional regime is known
to increase with the increase of the amplitudes of the operational regime
and with the increase of the polar moment of inertia of the unbalanced
shaft. Therefore, in practice, in order to achieve an acceptably high
amplitude of the operational vibrations in unbalanced-mass vibratory
machines, the double amplitude of vibrations is limited (e.g. to between 4
and 8 millimetres), and the frequency of operational vibrations is
increased (e.g. above 1200 rpm). However, such increases in frequency
requires the rigidity of the chamber and the machine to be increased and
accordingly the loads acting on the supports and the associated noise level
increase as well.
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Also, designers of both types of finishing machines have
attempted to provide a simple and relatively inexpensive, yet reliable
system which will enable a truly aggressive finishing action to be imparted
to the contents of the chamber. A challenge facing the industry has been to
provide an efficient bowl machine design which is capable of generating
the type of large amplitude velocity vibrations needed to provide an
aggressive finishing action, while minimizing the use of inordinately
massive and costly machine components.
Accordingly, there is a need for an improved finishing
assembly which provides aggressive finishing action while using a low-
energy input drive system, which comprises relatively few parts, and
which is durable and relatively inexpensive to manufacture.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
finishing assembly for vibratory finishing of a group of workpieces within
finishing media, said finishing assembly comprising:
(a) a first chamber adapted to hold the finishing media for
finishing the surfaces of the workpieces;
(b) a crank shaft operably connected to said first chamber,
said crank shaft having a first rotary axis;
(c) a drive shaft driveably operated and operably connected
to said crank shaft for driving said crank shaft, said drive
shaft having a second rotary axis;
(d) a coupling member operably connecting said crank shaft
to said drive shaft with said first rotary axis of said crank
shaft and said second rotary axis of said drive shaft
intersecting with one another at a predetermined angle;
(e) a restraining element coupled to said first chamber for
restraining said first chamber from rotational
movement; and
(f) a reactive mass operative connected to said drive shaft
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for providing vibrational stability to said finishing
assembly.
Further objects and advantages of the invention will appear
from the following description, taken together with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
Fig. 1 is a side cross-sectional view of the finishing assembly
according to a preferred embodiment of the present invention;
Fig. 2 is a side cross-sectional view of the finishing assembly
according to an alternative embodiment of the present invention;
Fig. 3 is a side cross-sectional view of the finishing assembly
according to another alternative embodiment of the present invention;
Fig. 4 is a top plan view of the embodiment of finishing
assembly of Fig. 1;
Fig. 5A is a perspective view of the finishing assembly of Fig.
1; and
Fig. 5B is a perspective view of the chamber of Fig. 1 with its
top removed.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference is first made to Fig. 1 which shows a finishing
assembly 10 made in accordance with a preferred embodiment of the
invention. Finishing assembly 10 includes a chamber 12 for holding
finishing media 13 for treating a group of workpieces 14, a drive assembly
16, a support housing 18, shock absorbers 20, and restraining elements 22a
and 22b.
Chamber 12 is of a conventionally known shape, namely
having a circular toroidal bottom 24 and cylindrical walls 26 extending
from the toroidal bottom 24. Chamber 12 is made of a durable material (e.g.
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hard plastic). It should be understood that the specific shape of chamber 12
is not of principal concern and that a chamber 12 of any other known
shapes may be used in association with the invention.
Drive assembly 16 is actuated by a motor 28 (e.g. an electric
motor) and includes a crank assembly 30, a drive shaft assembly 32 and a
coupling assembly 34. Crank assembly 30 comprises a crank 36 which
rotates in roller bearings 37 in a first bearing hub 38 as well as a crank
journal 40 having a flat flange 42. Drive shaft assembly 32 comprises a
drive shaft 44 which rotates in second bearing hub 46 as well as a drive
journal 48 having a flat flange 50. Drive shaft 44 is coupled to motor 28
through coupling 45.
The operational parameters of finishing assembly 10 depend
significantly on the design of the crank assembly 30 and on the carrying
capacity of the bearing units (i.e. first and second bearing hubs 38, 46 etc.)
when loaded by rotating vectors of forces and moments that are
perpendicular to the axes of crank 36 and drive shaft 44. It is contemplated
that finishing assembly 10 would use automobile wheel supports as the
bearing units as such supports are readily available and are generally
designed to meet the requirements of a kinematic vibrational drive. It has
been observed that wheel supports provide additional convenience due to
their compact size as well as their ease of mounting and operation.
Coupling assembly 34 comprises an adjustable wedge gasket
52 which can be adjusted to change the overall inclination of the axis of
crank 36 (line A) relative to the axis of drive shaft 44 (line B). Coupling
assembly 34 is bolted to flange 42 of crank assembly 30 and to flange 50 of
drive shaft assembly 32 using bolts 43. Coupling assembly 34 provides the
central axis of crank assembly 30 with a different angle of orientation than
the central axis of drive shaft assembly 32, as shown.
The angle o between the rotary axis of crank 36 and the rotary
axis of drive shaft 44 (i.e. the phase angle a~ between lines A and B) can be
adjusted using wedge gasket 52. Specifically, wedge gasket 52 consists of
two separate wedges 53 and 55, such that relative rotation of individual
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wedges 53 and 55 changes the general angle of inclination between crank
36 and drive shaft 44. Also, the radial displacement of crank flange 42 in
relation to the drive shaft flange 50 produces a certain eccentricity between
crank 36 and drive shaft 44 and the required phase displacement can be set
by turning wedge gasket 52 in relation to the direction of the eccentricity.
Flange 42 can be displaced radially about the axis of drive
shaft 44 in respect of flange 50 using various mechanisms including, for
example, the grooves 54 shown formed in flanges 42 and 50. This
displacement determines the eccentricity of crank 36 in respect of drive
shaft 44. The rotation of wedge gasket 52 determines the angle 8 between
the crank shaft 36 and the drive shaft 44. It should be understood that
coupling assembly 34 could also comprise any other type of mechanism
(e.g. a conjugated cylindrical pair) which could be used to change the
overall inclination of crank 36 in respect of drive shaft 44. It should be
understood that the optimal angle of inclination e~ for operation is
determined by the specific parameters (i.e. mass, moments of inertia etc.)
of the various components of finishing assembly 10.
Support housing 18 is used to house part of drive assembly 16
as well as motor 28 and is coupled to a base 56 through shock absorbers 20.
It has been determined that absorbers 20 should be designed to have
rigidity such that the frequency of finishing assembly 10 is many times less
than the rotational speed of the drive shaft 44. Chamber 12 is prevented
from rotating by the attachment of restraining elements 22a and 22b (e.g.
helical coil springs) which are coupled to housing 18 and to chamber 12, as
shown. While motor 28 is shown coupled to housing 18 co-axially with
drive shaft 44, it should be understood that motor 28 could also be
mounted directly on base 56 in order to protect motor 28 from stray
vibrations of finishing assembly 10.
Finishing assembly 10 also utilizes a separator 58 and a chute
60 which are secured to housing 18 by a holder 62 so that finished
workpieces 14 can be delivered out of chamber 12, possibly into a separate
receptacle (e.g. reservoir 64). Separator 58 is secured to the walls of
chamber
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12 above the level of finishing media 13 and has a screen 59 located at its
bottom. During the finishing process a flap 66 is opened to let finishing
media 13 flow through and into separator 58. Due to the inherent head
pressure of the vibrating loose media flow of workpieces 14 and media 13
is driven up above the upper rib of the flap 66 and lands on screen 59 of
separator 58. Granules or particles of finishing media 13 pass through the
openings in screen 59 back onto the bottom of chamber 12, while the
screened workpieces 14 are conveyed by chute 60 out of chamber 12. This
simple separation method is not acceptable in cases, where due to
excessive intensity of vibrations of separator 58 and chute 60, the
workpieces 14 separated from finishing media 13 jump so strongly as to get
damaged. In such cases, damage can be avoided by securing the screen 59
and the chute 60 to housing 18 and not to chamber 12.
When drive shaft 44 is rotated and drives crank 36 within
first bearing hub 38, chamber 12 is provided with kinematic motion
having an adjustable range of angular and circular horizontal vibrations
and phase shift/angle between vibrations. It is possible to increase the
amplitude of the vibrational movement by adjusting the relative angle
and eccentricity between crank 36 and drive shaft 44. Thus, it is possible to
increase the amplitude of vibration without having to increase the
unbalanced masses and moment of inertia of the drive as is necessary in
the case of conventional unbalanced-mass drives. Rather, the amplitudes
can be affected by the angle of wedge gasket 52 and the average distance
between the centre of chamber 12 and the middle of the chamber 12 (i.e.
depends on the dimension of chamber 12).
The angle o between the respective axes of crank 36 and drive
shaft 44, the distance between the respective axes of crank 36 and drive
shaft 44 (i.e. eccentricity therein) along with the location of the centre of
mass of chamber 12 and housing 18 and the ratio of the masses and the
moments of inertia therein, all influence and determine the extent of the
spatial vibrations of chamber 12. The phase angle between the horizontal
projection of the axis of crank 36 and the direction of eccentricity of the
axis
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of crank 36 also affects the dynamics of the machine.
Generally, chamber 12 vibrates in space such that points of
chamber 12 located along one horizontal plane, travel along elliptical
paths having identical circular horizontal projections and having an
amplitude of vertical oscillation that is proportional to the distance
between the specific point and the center of the axis of drive shaft 44.
Accordingly, the character of vibrations of chamber 12 in the present
invention is similar to movement of finishing chambers of known
machines with unbalanced mass drives and the corresponding movement
of loose media contained within chamber 12 is also similar.
Also, housing 18 of finishing assembly 10 serves as a reactive
masse in relation to the mass of chamber 12 and finishing media 13. The
vibration of this reactive mass (i.e. housing 18) about the immobile
common centre of masses of the finishing assembly 10, efficiently balances
the movement of chamber 12 and media 13 which moves independently
within chamber 12. It should be noted that the role of the reactive mass
(i.e. housing 18 in this embodiment) does not have to be as "passive" as it
usually is in typical prior art unbalanced-mass machines. In contrast, the
reactive mass can itself be used to perform further finishing functions as
will be further described in association with alternate embodiments of the
invention.
Moreover, the character and intensity of the vibrations of the
said reactive mass (i.e. housing 18) and the main mass (i.e. chamber 12) are
controllable as it should be appreciated that the respective vibrational
amplitudes of these masses can be set within a wide range, for example, by
appropriately setting the angle a between the drive shaft and the crank
shaft. Thus, the vibrations of housing 18 can be used for performing
additional operations (e.g. separation and/or drying of workpieces inside
container 64 etc.) As another example, if separators (e.g. screens, grates)
are
located inside the chamber are secured not to the container itself but to
housing 18 (as described in respect of Fig. 1), excessive throwing up of the
screened parts on the separator and chute can be avoided (provided that
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the housing weight is larger than that of the chamber).
Accordingly, the design of the present invention achieves a
wide range of vibratory amplitude regulation at a low moment of inertia
between drive shaft 44 and crank 36. Due to the kinematical connection
between the vibrating elements of finishing assembly 10 (i.e. chamber 12
and housing 18) and a low kinematical energy of the rotating elements of
crank 36 and drive shaft 44, finishing assembly 10 can pass through the
resonance zones when finishing assembly 10 is turned off, without any
appreciable increase of the vibrations amplitude. This robustness of
finishing assembly 10 allows for operation within a wider range of
vibration velocities than is the case in typical prior art vibratory finishing
machines. An increase in the velocity of assembly 10 can be achieved by
simultaneously reducing the operational frequency of vibrations (by 1.5 to
2-fold) due to a many fold (3 to 4-fold) increase of the amplitudes.
Accordingly, the velocity of treatment of workpieces 14 increases.
Finally, due to the kinematic connection between chamber 12
and a reactive mass (e.g. housing 18), finishing assembly 10 becomes less
sensitive to changes in the weight of finishing media 13 loaded into
chamber 12. This is because, the change in finishing intensity within
finishing assembly 10 is determined not by the ratio of the change in
weight within chamber 12 to weight of chamber 12 (as is the case with
unbalanced-mass vibratory machines) but is determined by the ratio of the
change in weight to the sum of the weights of chamber 12 and reactive
mass (e.g. housing 18). This results in a much more robust finishing
assembly 10 than has been previously attainable.
Fig. 2 shows an alternative embodiment of finishing
assembly 100 of the present invention wherein a second chamber 102 is
positioned concentrically with chamber 112 in order to provide additional
finishing capacity for finishing assembly 100. Common elements between
the alternative finishing assembly 100 and the finishing assembly 10 will
be denoted by the same numerals but with one hundred added thereto.
By utilizing a second chamber 102, it is possible to further
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exploit the benefits of the kinematical drive as second chamber 102 will
also act as a reactive mass. Essentially, there is no housing, as such, in
this
embodiment and accordingly, the role of the reactive mass is being played
by the second chamber 102 and its mounting plate 104. Second chamber 102
is located concentrically with chamber 112. Chamber 112 is mounted
similarly to chamber 10 of Fig. 1. Generally, both chamber 112 and chamber
102 act as reactive masses for each other and vibrate in the opposite phases
around the centre of mass of finishing assembly 100.
The ratio of intensity of vibrations of the opposite phases is
most simplistic when second chamber 102 is placed concentrically with
chamber 112 (i.e. the centres of gravity of chamber 112 and second chamber
102 are located at the same level). The amplitudes of angular and circular
vibrations will be inversely proportional to the corresponding moments of
energy and masses of the respective chambers.
If the centres of mass of chambers 112 and 102 are on the same
horizontal level, then, in order to ensure identical processing conditions
in both chambers, chambers 112 and 102 must have equal masses, while
the ratio of their moments of inertia about the central horizontal axes has
to be equal to the ratio of the radiuses of the middle of the chutes. It must
be noted that, base 156 serves as a shock absorber for both the dynamic
system comprising chambers 112 and 102 as well as motor 128 of finishing
assembly 100. Also, base 156 supports electric motor 128 which actuates
drive shaft 44 via a conventionally known belt drive 101.
As shown, workpieces 114 can be transferred from chamber
112 to chamber 102 from separator 158a through chute 160a. Granules or
particles of finishing media 113 pass through the openings in screen 159a
back onto the bottom of chamber 112, while the screened workpieces 114
are conveyed by chute 160 out of chamber 112 and into second chamber
102. Workpieces 114 can then be transferred from chamber 102 to a
reservoir (not shown) external to finishing assembly 100, from separator
158b through chute 160b. Granules or particles of finishing media 113 pass
through the openings in screen 159b back onto the bottom of chamber 102,
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while the screened workpieces 114 are conveyed by chute 160b out of
finishing assembly 100.
Figs. 3 and 4 show another alternative embodiment of
finishing assembly 200 wherein chamber 212 and second chamber 202 are
arranged in a two-stored (two-tier) design and shaped differently to allow
for easy access to the contents of chamber 212 and second chamber 202.
Common elements between the alternative finishing assembly 200 and the
finishing assembly 10 will be denoted by the same numerals but with two
hundred added thereto.
Finishing assembly 200 allows for use of identical chambers
212 and 202 and the footprint of finishing assembly 200 (i.e. the floor space
necessary to house finishing assembly 200) becomes smaller. When
chambers 212 and 202 are disposed close to each other, access to chamber
202 one becomes more difficult. Accordingly, it is more convenient to
form chamber 202 in an oval-shaped manner. For example, chamber 202
and 212 can be made of two elongated chutes with cylindrical bottoms and
connected to each other by semicircular ends having toroidal bottoms. The
access to chamber 202 can be provided by placing the long sides of the 212
and 202 perpendicular to each other, as shown.
In finishing assembly 200, each chamber can be used for
separate operations, so that functionally aforesaid machine can be used as
two machines. The two-chamber machine is especially advantageous for
mufti-operation finishing technologies (primary and final grinding,
drying, etc.). Each chamber 202 and 212 can be loaded with the
corresponding finishing media 13 and can be provided with appropriate
screens and flaps (not shown) for separation. As shown, the discharge
chute 260 of the internal or the upper chamber 212, where the first
operation is effected, conveys screened parts to the second chamber 202.
It should be noted that the difference in the moment of
inertia about the parallel horizontal central axes gives certain advantages
for optimization of vibrational characteristics for finishing assembly 200.
As shown, workpieces 214 can be transferred from chamber 212 to chamber
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202 from separator 258 through chute 260. Granules or particles of
finishing media 213 pass through the openings in screen 259 back onto the
bottom of chamber 212, while the screened workpieces 214 are conveyed by
chute 260 out of chamber 212 and into second chamber 202.
Also, it may be noted that in the two-chamber embodiments
of finishing assembly 100 and 200 discussed (Figs. 2, 3, and 4), despite the
absence of a special heavy housing (e.g. finishing assembly 10 shown in
Fig. 1), the stability (or robustness) of the vibratory regimes to changes in
weight contained in chambers 110, 102 and 210, 202, respectively is
sufficiently high. This is because in the case of an equal change of weight
in both chambers 110, 102 and 210, 202, respectively, the kinematical drive
maintains the stability of the corresponding vibrations of the chambers
occurring in opposite phases. The advantage of a two-chamber
embodiment also lies in the fact that second chambers 102, 202 do not
increase the load, acting on the supports, it only requires the double power
of motor 128, 228 for finishing of the double weight charge.
Referring now to Figs. 1, 5A and 5B, in use, a user loads a
sufficient number of workpieces 14 into chamber 12 of finishing assembly
10. Once workpieces 14 are positioned within chamber 12, motor 28 will
provide drive shaft 44 with rotational force and crank 36 will provide
chamber 12 with rotational force along an axis which is oriented at an
angle to the axis of the drive shaft 44. Accordingly, chamber 12 can be
rotated and aggressive finishing can be accomplished using a relatively
low-energy input drive system 16. Once finishing is completed, finishing
assembly 10 can be turned off. Due to the kinematic design of finishing
assembly 10, there is no adverse machine runout characteristic when
finishing assembly 10 is turned off. Finished workpieces 14 can be
removed from finishing assembly 10 either manually, or using a separator
58, screen 59 and reservoir 64 assembly described above.
Since finishing assembly 10 utilizes a kinematical drive to
cause chamber 12 to experience spacial vibrations, the usual disadvantages
associated with an inertia centrifugal drive mechanism are not present.
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Accordingly, finishing assembly 10 provides aggressive finishing action.
Finishing assembly 10 also comprises relatively few parts and is durable in
construction and is relatively inexpensive to manufacture. Loose finishing
media 13 contained within chamber 12 has the same character of
movement as is the case with known prior art finishing machines.
However, chamber 12 provides greater finishing intensity to workpieces 14
at a lower noise level than is conventionally achievable. Finally, due to
the kinematic connection between chamber 12 and a reactive mass (e.g.
housing 18 or second chamber 102), finishing assembly 10 becomes less
sensitive to changes in the weight of finishing media 13 loaded into
chamber 12.
It should be understood that finishing assemblies 10, 100 and
200 can use different types of chambers 12, 112, and 212 (e.g. annular
chamber with toroidal bottom, bowl, etc.) Also, it is possible to provide a
plurality of individual isolated chambers mounted on the periphery of a
platform for finishing small parts (e.g. watch parts). Additional well
known auxiliary devices for separation of finished workpieces 14 can also
be used in association with finishing assembly 10, as is conventionally
known.
As will be apparent to persons skilled in the art, various
modifications and adaptations of the structure described above are possible
without departure from the present invention, the scope of which is
defined in the appended claims.
