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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus and method for the removal of
flashing from elastomeric elements after they have been molded. More
particularly, it is directed to a refrigerating and tumbling device for
achieving deflashing of such elements.
2. Description of the Prior Art
The manufacture of molded elements from elastomeric materials, such as,
synthetic and organic rubbers, as well as silicone rubbers, is well known.
In the manufacture of such materials, a thin extraneous membrane (called
"flashing") of the elastomer forms about the edges of the main body of the
molded part. In the finishing of the molded part, it is necessary that the
flashing be removed.
In the past, flashing was removed by manual methods which, of course,
proved to be extremely slow and economically unfeasible. Cryogenic
deflashing methods have been developed which utilize the principle that
the very thin flashing membranes freeze much more quickly than the body of
the molded element. When frozen, the flashing becomes extremely brittle,
and when impacted with other molded parts or appropriate media, e.g., sand
or other particulate material, the frozen, brittle flashing membrane
breaks cleanly at the edge of the molded element. This results in a smooth
surface, free from the undesirable flashing membrane.
The devices and methods used heretofore for cryogenic deflashing of such
elements have relied on quick freezing of the elements using extremely
cold temperatures, i.e., temperatures in the range from -32.degree. C. to
-150.degree. F. For this purpose, the art has used solid or liquefied
carbon dioxide or liquid nitrogen. Typically, the molded parts to be
deflashed are immersed in the solid or liquid carbon dioxide or liquid
nitrogen in a vessel which contains, if desired, an appropriate deflashing
media. The vessel is rotated or vibrated so as to cause impact between the
parts and/or media. The flashing membrane freezes to brittleness and
easily breaks away upon impact.
Because of the nature of the cryogenic materials, e.g., liquid nitrogen,
liquid carbon dioxide, and solid carbon dioxide, the devices for use with
such materials are necessarily relatively complicated and expensive.
Because such materials are or become gaseous, they generally result in
pressure build-ups so that the apparatuses must be sufficiently
structurally strong to withstand the higher pressures resulting from these
materials. In addition, substantial insulating must be used with the
devices because of the "quick freeze" aspect of the cryogenic materials.
Because of the extremely low temperatures accompanying their use as well as
the pressure build-up, there is also a safety problem and the devices must
be equipped with appropriate safety mechanisms to avoid accidents. Also,
of course, appropriate storage tanks must be provided with such devices to
provide for holding the cryogenic materials during their use.
All of this contributes to the increased complexity and costs of these
prior art devices. In addition, the use of the cryogenic materials, in and
of itself, provides a storage and handling problem for the user. Normally,
smaller elastomer finishing operations do not have or cannot afford to
maintain the expensive facilities needed to store significant amounts of
the cryogenic materials on site. As a result, the cryogenic materials must
be delivered shortly before their use. This can cause supply problems if
the cryogenic materials cannot be provided at the time necessary for their
use in the deflashing apparatus. Of course, the cryogenic materials
themselves are relatively expensive.
An additional problem with the prior devices is that their use is
accompanied by an extremely high noise level, particularly, when a number
of the machines are being used at the same time. Usually, workers in the
area are required to wear ear protection because of the intensity of the
noise. In addition, these machines generate a substantial amount of dust.
Each of these disadvantages results in the machines normally being kept in
a separate room in order to isolate both the noise and the dust from other
areas of the workplace.
Also, because of the relative complexity of the machines and the necessity
for having a source of liquid nitrogen close at hand, as well as the
pressures which are generated in the devices, the machines are normally
fixed in place. Thus, they are not easily movable from one area to
another.
SUMMARY OF THE INVENTION
I have discovered a device for the removal of the thin flashing membrane
resulting from the molding of elastomeric elements which avoids the costly
apparatus, operations and dangers of the prior art cryogenic devices. It
further avoids the need to have a constant supply of liquid nitrogen or
liquid or solid carbon dioxide near at hand and is superbly suited for the
smaller molder. Moreover, the device of the present invention represents a
substantial cost saving as compared to the complicated cryogenic devices
presently used.
In particular, the apparatus of the present invention comprises a tumbling
barrel which has a closable opening so that molded elastomeric elements
and, if desired, deflashing media, can be introduced to the barrel. The
device further comprises a refrigeration chamber which is larger than the
barrel so that the barrel can be placed therein. The refrigeration chamber
has an appropriate cooling means for lowering the temperature of the
interior of the chamber and further has means for imparting an impacting
movement to elements to be deflashed which are placed within the barrel.
As used herein, the expression "impacting movement" means motion which is
sufficient to cause the elements which are to be deflashed to collide with
each other and/or with media within the barrel with sufficient force to
effect deflashing.
This "impacting movement" may be achieved by having means for rotatably
mounting the tumbling barrel within the chamber with appropriate drive
means for rotating the barrel when it is so mounted. Alternatively, the
apparatus can have means for vibrating the barrel while it is in the
chamber or rotating the barrel through reciprocal rotation cycles wherein
the barrel is rotated in any given cycle less than 360 degrees.
The present invention also comprises a method for deflashing elastomeric
elements by introducing the elastomeric elements into a tumbling barrel,
movably mounting the tumbling barrel within a refrigeration chamber, the
interior of which has been cooled to the desired deflashing temperature,
and moving the barrel within said chamber toimpart an impacting movement
to the contents of the barrel.
With the present invention, when the refrigeration chamber is insulated,
substantial reduction in the noise produced when operating the apparatus
is effected. In addition, because of the fact that the tumbling barrel is
within an enclosed chamber, namely, the refrigeration chamber, there is a
substantial reduction in the dust production in the room in which the
operation is being carried out.
Finally, because of the apparatus of the present invention need only be
plugged into an appropriate electrical outlet and does not need
accompanying piping and/or pressurized connections to gas sources, the
apparatus is easily movable from one location to another within a working
site. This greatly enhances the flexibility of the apparatus as compared
to prior art devices.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of an apparatus in accordance with the present
invention.
FIG. 2 is a partial perspective of a detail of the apparatus of FIG. 1.
FIG. 3 is an exploded perspective view of another embodiment of the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an apparatus in accordance with the present invention,
designated generally as 10, comprises a first chamber 12, having
refrigeration means for cooling the interior of the chamber. In the
drawing, the refrigeration means are shown as cooling coils within the
walls constituting the chamber. Such refrigeration systems are known and
normally comprise refrigeration coils connected to an appropriate
compressor/motor arrangement (not shown) and a refrigerant gas system,
e.g., freon, and the like. The walls 16 forming chamber 12 contain
insulation sufficient to assist in temperature control in the interior of
the chamber and for noise abatement.
Chamber 12, as shown in the drawing, also has two apertures 18 and 20 with
appropriate closures 22 and 24. These closures 22 and 24 are doors which
would have appropriate locking means (not shown) and are attached in a
conventional manner by hinges. The openings allow access to the interior
of the refrigeration chamber. Two openings may be provided for
convenience, although, of course, a single opening would be sufficient.
The doors are also appropriately insulated in order to maintain the
desired low temperature of the interior of the chamber.
If desired, a circulating means may be provided for the interior of the
chamber shown as fan 26 for purposes of circulating the cooled atmosphere
within the chamber to assist in uniform cooling. The refrigerating means
should be capable of reducing the interior of chamber 12 to a temperature
sufficiently low to effect freezing of the flashing membrane so that it
will be removed during the operation. The desirable deflashing temperature
depends on the particular elastomer being treated. A preferred temperature
range is from about -32.degree. to -180.degree. F., most preferably, about
-32.degree. to about -150.degree. F. Moreover, the refrigerating mechanism
desirably possesses control means, conventional in the art, so as to be
able to maintain the temperature within .+-.10.degree. F. of the desired
temperature for a given deflashing operation. Thus, depending upon the
particular elastomeric material being deflashed, a temperature within the
above-specified range with the variation of .+-.10.degree. F. would
normally be used. One of the distinct advantages of the present system
utilizing conventional refrigeration means is the improved temperature
control that can be attained, as compared to, for example, liquid nitrogen
systems.
Mounted in the interior of chamber 12 is a tumbling barrel 28. The tumbling
barrel shown is hexagonal in shape, although other conventional shapes may
be used. Typically, such a tumbling barrel may have a length of
approximately 30 inches with each side being approximately 14 inches wide.
Of course, larger or smaller tumbling barrels may be utilized depending
upon the amount of elastomeric elements to be treated as well as the
amount of deflashing media to be used. One of the sides 30 of barrel 28
constitutes a door with hinges (not shown) to provide access to the
interior of barrel 28. This side may be opened for introducing elastomeric
components and media to the interior of barrel 28 and then secured in the
shut position for the tumbling operation.
Barrel 28 has extending therefrom a shaft 32 which is securely mounted to
the side of barrel 28 via bolted plate 34. Shaft 32 is attached to the
barrel at its axis of rotation and extends therefrom through circular
aperture 36 in the side wall of refrigerating chamber 12. Shaft 32 and
aperture 36 are in an isulatingly sealed relationship to avoid
interference with the maintenance of the decreased temperature within
chamber 12. Also, however, shaft 32 is able to rotate in aperture 36.
Shaft 32 is supported exterior of chamber 12 by supporting bearings 38 as
shown. In the drawing, the bearings are attached to a supporting chassis
indicated generally at 40. The entire combination of supporting bearings
38 and shaft 32 are sufficiently strong such as to support in a rotatable
manner, tumbling barrel 28 within the interior of chamber 12.
Shown generally at 42 is a drive means composed of a motor 44 having a belt
or drive chain 48 attached to the motor drive shaft which is, in turn,
connected to a rotary gear 46, mounted on shaft 32. Drive means 42 has
appropriate control means, conventional in the art for activting the motor
as well as controlling the speed of rotation of tumbling barrel 28.
Preferably, drive means 42 is sufficient to rotate tumbling barrel 28 at
speeds of up to about 200 rpm. The desired speed of rotation will
necessarily depend on the particular elements which are being deflashed.
Alternatively, the drive means can be such so that tumbling barrel does not
rotate through a full 360 degree cycle. Thus, drive means 42 can be
adapted to effect reciprocal rotary movement of the tumbling barrel
through rotations of less than 360 degrees. In essence, this means that
the barrel would rotate a given number of degrees in one direction and
then rotate back through that same number of degrees in the opposite
direction.
The time period for tumbling depends on the particular elements to be
deflashed. Normally, the tumbling will be carried out for a period from
about 15 minutes to 4 hours.
Tumbling barrel 28 may also, if desired, have apertures 50 in the side
walls thereof providing access of the cooled atmosphere within chamber 12
into the interior of the tumbling barrel. These apertures would be
suitably screened so as to prevent loss of any tumbling media or the
elements during operation of the apparatus. This aids in cooling of the
interior of the tumbling barrel. As is clear, however, no special gas or
atmosphere is maintained within the barrel or chamber. Thus, only
atmospheric air is present. Consequently, there is no need for the chamber
walls, tumbling barrel or other elements of the invention (except, of
course, for the internal aspects of the sealed refrigeration system) to be
especially designed or structured so as to withstand pressure other than
normal atmospheric pressure. In this manner, the cooling mechanism of the
present invention is indirect in that the actual refrigerant does not
directly contact the elastomer elements.
As shown in FIG. 1, the drive means 42 as well as the shaft 32 are placed
exterior of refrigeration chamber 12. It is possible, of course, to locate
the entire drive means including the shaft supports 38 within chamber 12.
However, the embodiment shown is desirable from the standpoint that the
drive mechanism does not interfere with the refrigeration of the interior
of chamber 12.
In operation, the elements to be deflashed and any deflashing media
therefor are introduced into tumbling drum 28 which is rotatably mounted
within chamber 12. It should be noted that tumbling barrel 28 can be
removably mounted in chamber 12 so that tumbling barrels of different
sizes and/or shapes may be used as desired.
A variety of mechanisms may be used for removably mounting tumbling barrel
28 within chamber 12. For example, a mounting plate could be secured to
the side of tumbling barrel 28 and shaft 32 can have a flange
corresponding to the mounting plate attached to its end. The mounting
plate and mounting flange are simply bolted to one another to secure the
tumbling barrel to the shaft. To replace the tumbling barrel with another,
the bolts are simply undone and a new tumbling barrel having its own
mounting plate secured thereto can be introduced to and secured in the
chamber. The mounting plate on the barrel is shown in greater detail in
FIG. 2. Plate 31 is secured to the side of barrel 30 by means not shown.
Extending from plate 31 are bolts 33 which can be threaded. Plate 34 (FIG.
1) which is securing the end of shaft 32 can have holes therein in
registration with bolts 33. When the two plates 31 and 34 are married,
they can be secured to one another through nuts. (not shown).
The removability of tumbling barrel 28 is advantageous since additional
tumbling barrels can be maintained in a refrigerated state exterior of
chamber 12, i.e., in a separate conventional refrigeration unit. Also, the
deflashing media can be kept in a refrigerated state. In use, a precooled
tumbling barrel with its precooled ingredients can then be introduced to
chamber 12, thus reducing the amount of time to bring the contents of the
tumbling barrel down to the desired temperature. This procedure is
advantageous in reducing the overall deflashing time, so that while one
barrel is being utilized within apparatus 10, other tumbling barrels with
their ingredients are being cooled.
FIG. 3 shows yet another embodiment of the present invention wherein rather
than imparting rotary movement to the tumbling barrel, it is made to
vibrate so as to place the contents of the barrel into motion. As shown in
FIG. 3, this can be accomplished by having the apparatus generally shown
at 110 with tumbling barrel 112 attached to vibrating means shown
generally at 114. Vibrating means 114 is composed of a mechanical or
electromagnetic vibrator 116 which supports a pair of plates 118 secured
to each other by springs and sandwiched therebetween. Mounted on the top
plate of plates 118 is a shaft 120 which protrudes through the bottom of
refrigeration chamber 122. Shaft 120 is secured, preferably in a removable
manner by flange 124 to the bottom of tumbling barrel 112. Insulating boot
128 is provided to cover the area where shaft 120 protrudes through the
bottom wall of refrigeration chamber 122. Also shown exterior of the
refrigeration chamber is the cooling means indicated as being a compressor
refrigerant.
In use, the elements to be deflashed and/or media are introduced to the
tumbling barrel 112, the contents cooled within the refrigeration chamber
and set into motion with the vibrating means. In this connection, it is
noted that it is not necessary for media to be used in every instance.
Thus, depending on the nature and size of the elastomeric elements, it is
possible to effect deflashing without the presence of media.
An alternative procedure is to place the media into the barrel and cool the
barrel and its contents to the desired deflashing temperature. The
elements are then placed into the barrel with the precooled media and
subjected to impacting movement by rotation, vibration, etc., until they
are completely deflashed. The elements are then removed from the barrel
and the next batch of elements is subjected to the same treatment. In this
manner, the media is continuously maintained at the desired temperature
and the newly introduced elements cool quickly to the deflashing
temperature. This procedure greatly reduces the time for deflashing.
The following example illustrates the present invention.
Using a tumbling device as shown in FIG. 1 hereof, tumbling media composed
of 1/4 inch thick triangular shaped stones having a side surface of
approximately 3/8 inch in length was placed into a tumbling barrel and the
media in the tumbling barrel was cooled to -100.degree. F. This took from
about 6 to 8 hours. As of this point, the tumbling unit will maintain the
barrel and media temperature.
1000 pieces of a molded neoprene washer having a 1 inch outside diameter, a
1/4 inch inside diameter and a thickness of 3/4 inches were placed into
the tumbling barrel. With the barrel closed and refrigerating chamber
closed, the barrel was rotated at a speed of approximately 60 rpm for a
period of from 30 to 45 minutes. The neoprene washers were then removed
from the tumbler and all flashing thereon had been removed.
As shown, the apparatus of the present invention is highly advantageous in
that it completely avoids the need for the refrigeration chamber to be
sufficiently strong so that it can withstand the build-up of pressure
within its interior. This, in turn, avoids the dangers of utilizing
cryogenic materials, such as, liquid nitrogen and dry ice. The present
apparatus provides both economic as well as safety advantages over prior
art devices.
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Description |
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