A cryogenic deflashing apparatus removes residual flash from molded articles. A cryogenic chamber establishes and maintains cryogenic temperatures from an injected cryogenic fluid. A parts basket is removably disposed within the cryogenic chamber for imparting a tumbling action to the molded articles. The basket has an external perforated shell and an open end and a closed end, where the closed end has a conical surface disposed within the perforated shell effective to enhance the tumbling action for the molded articles for exposure to the cryogenic temperature for embrittling the residual flash. A throw wheel directs shot media toward the articles tumbling within the parts basket for impacting and removing the residual flash from the articles that is embrittled by the cryogenic temperature.

FIELD OF THE INVENTION 
This invention relates to apparatus for removing residual flash from molded 
articles, and, more particularly, to portable apparatus for removing 
residual flash from molded articles at cryogenic temperatures. 
BACKGROUND OF THE INVENTION 
When parts are produced by a molding process, the molded article frequently 
has residual material that is extruded at mold interfaces, which is 
referred as residual flash material or "flash." This flash must be removed 
in a finishing operation. One technique that can be used to remove flash 
is machining and/or hand trimming, which is expensive and time consuming. 
It is frequently possible for small articles to use a shot blasting 
operation where the shot impacts the relatively thinner flash and removes 
the flash without significant damage to the underlying article. See, e.g., 
U.S. Pat. No. 5,676,588, U.S. Pat. No. 4,648,214, and U.S. Pat. No. 
4,312,156, incorporated by reference, for basic teachings on flash 
removal. 
One approach to shot blasting for flash removal uses the property of many 
materials to become embrittled at low or cryogenic temperatures. For 
example, many rubbers and plastics become brittle at temperatures obtained 
from cooling by evaporating liquid nitrogen in the material surroundings. 
Since flash is conventionally very thin, the flash will be cooled to 
brittle temperatures before the body of the material so that the flash 
will be readily removed by shot blasting that does not damage the article. 
In order to be effectively cooled and exposed to the shot, articles are 
conventionally placed in a rotating drum so that the articles are 
continuously picked up and dropped from rotating projections, or 
"flights", in the drum. It is conventional to place the rotating drum at 
an angle to enhance the tumbling action of the flights. The design of 
conventional drums causes some articles to aggregate in the downhill comer 
of the drum, with a resulting loss in deflashing of the articles. 
The deflashing shot is expelled by a throw wheel that accelerates the shot 
through an opening in the housing that contains the rotating basket and 
into the rotating basket. Conventional throw wheels have an even number of 
vanes for accelerating the shot and are subject to harmonic vibrations 
which reduce the life of the equipment Further, the expended shot merely 
collects in the bottom of the housing, which can impede the rotation of 
the drum and which requires a large supply of shot. 
A particular problem for operating deflashing apparatus at cryogenic 
temperatures is the design of adequate seals for closures and for rotating 
shafts that penetrate the cryogenic housing. Conventional closure seals 
are formed of materials that become brittle at the operating temperature 
of the cryogenic deflashing apparatus or that become stuck together 
through freezing of ambient water vapor. Seals for rotating shafts, and 
the like, also become brittle at cryogenic temperatures with a limited 
operating lifetime or excessive leakage of the cooling nitrogen. 
Conventional cryogenic equipment is generally provided as a fixed device. 
With fixed devices, batches of manufactured must be diverted from the 
production line to the devices, unless many of these devices are provided 
integral with the production lines. It would be desirable to provide 
portable deflashing apparatus that can be readily moved when a production 
line is not in use. 
These problems are addressed by the present invention and an improved 
deflashing apparatus is provided. Accordingly, it is an object of the 
present invention to provide a rotating drum that maintains the articles 
in a continuous movement in the drum for improved flash removal. 
Another object of the present invention is to provide for the reuse of shot 
to reduce the quantity of stored shot that is required. 
Still another object of the present invention is to improve the flow of 
shot to the throw wheel and to reduce vibration in the throw wheel. 
One other object of the present invention is to provide improved seal 
designs for operation at cryogenic temperatures. 
Additional objects, advantages and novel features of the invention will be 
set forth in part in the description which follows, and in part will 
become apparent to those skilled in the art upon examination of the 
following or may be learned by practice of the invention. The objects and 
advantages of the invention may be realized and attained by means of the 
instrumentalities and combinations particularly pointed out in the 
appended claims. 
SUMMARY OF THE INVENTION 
To achieve the foregoing and other objects, and in accordance with the 
purposes of the present invention, as embodied and broadly described 
herein, the apparatus of this invention may comprise a cryogenic 
deflashing apparatus for removing residual flash from molded articles. A 
cryogenic chamber establishes and maintains cryogenic temperatures from an 
injected cryogenic fluid. A parts basket is rotatably disposed within the 
cryogenic chamber for imparting a tumbling action to the molded articles. 
The basket has an external perforated shell and an open end and a closed 
end, where the closed end has a conical surface disposed within the 
perforated shell effective to enhance the tumbling action for the molded 
articles for exposure to a shot media. A throw wheel directs shot media 
toward the articles tumbling within the parts basket for impacting and 
removing the residual flash from the articles that is embrittled by the 
cryogenic temperature.

DETAILED DESCRIPTION 
Referring first to FIG. 1, there is shown a pictorial illustration of a 
cryogenic deflashing apparatus 10 according to one embodiment of the 
present invention. Parts basket 12 is provided to receive articles having 
flash from a manufacturing operation. Parts basket 12 has an open end for 
inserting and removing manufactured articles and a closed end for contact 
with a driving mechanism. Parts basket 12 is removably and rotatably 
mounted within insulated cryogenic chamber 14, and is preferably mounted 
within cabinet 20 at an angle with respect to horizontal to better tumble 
the articles for exposure to a stream of cryogenic fluid and shot for 
removing the flash. Basket 12 may be rotatably supported by bearing 
supports 22, 24, which are preferably formed of a material that maintains 
lubricity at cryogenic temperatures, e.g., polytetrafluoroethylene (PTFE) 
such as teflon.RTM.). U.S. Pat. No. 4,979,338, incorporated herein by 
reference, describes many of the basic components of a cryogenic 
deflashing apparatus. 
Load door 16 includes a seal 18 for sealing against chamber 14 to provide 
an enclosed environment for the cryogenic deflashing. Parts basket 12 is 
engaged by drive wheel 28, which is turned by the shaft of drive motor 26 
that extends into cryogenic chamber 14 through seal 32. Hand clutch 34 
(e.g., De-Sta-Go, Model 6.0, from Rutland Tool, Houston, Tex.) is 
connected to slidably translate motor 26 and drive clutch 28 to engage 
basket 12 and to urge the open end of basket 12 against bearing surfaces 
64, 66 (FIG. 5) mounted on an opposed wall of chamber 14. Bearing surfaces 
64, 66 are sized to provide a tolerance between the end of basket 12 and 
the wall of chamber 14 that does not permit the parts to escape from 
basket 12 during the deflashing operation. 
For the cryogenic deflashing operation, a cryogenic fluid, such as nitrogen 
(N.sub.2), is controllably introduced by solenoid valve 36 though feed 
line 38 into cryogenic chamber 14 and basket 12. The fluid vaporizes and 
expands to cool the articles in basket 12 toward the temperature of the 
fluid. The gas exits through vent 50 in cryogenic chamber 14. 
A suitable shot media, such as plastic pellets, is also introduced into 
basket 12 by the action of throw wheel assembly 42. Shot media is fed from 
shot media basket 56 though feed line 44 onto the vanes of a throw wheel, 
described below, in throw wheel assembly 42. Motor 48 rotates the throw 
wheel at a high speed, e.g., 1,000 to 10,000 rpm, for accelerating the 
shot media into basket 12. 
In accordance with one aspect of the present invention, expended shot and 
finite removed flash pass through perforations in parts basket 12 into the 
bottom, or sump, of insulated chamber 14. Removed flash pieces that are 
larger than the perforations in basket 12 remain contained within basket 
12 and are removed with the parts. Finite flash particles pass through the 
perforations and simply circulate with the shot medium, as discussed 
below. Such finite flash particles are comminuted to very small particle 
sizes, e.g., dust, and are eventually removed with the cryogenic gas 
through vent hole 50. These materials are moved by auger 52, driven by 
motor 54, to media basket 56 for return to throw wheel assembly 42. 
It will be understood that a complete cryogenic deflashing apparatus 
includes numerous sensing and safety components which are conventionally 
provided in the art and are not discussed herein for purposes of clarity. 
Control panel 62 provides for controlling the temperature of the 
operation, the speed of rotation of the various components and for 
monitoring the condition of the overall system as is well known in the 
art. 
In a particular embodiment of the present invention, the above components 
are kept to a minimum size to permit portability of the deflashing 
apparatus. Cryogenic chamber 14 is kept to a minimum size by continuously 
moving shot media and removed flash from the sump of the chamber. The use 
of auger 52 and direct feed of shot media from hopper 56 to throw wheel 
assembly 42 minimizes the size of the feed system, where conventional feed 
systems use many external components. Finally, control panel 62 is mounted 
directly on cabinet 20 so that the entire system is self-contained. 
Portability is obtained without significantly reducing the size of parts 
basket 12 since the surrounding and supporting components are reduced in 
size without affecting the deflashing within parts basket 12. 
In a particular aspect of the present invention, parts basket 12 
incorporates particular improvements as shown in cross-section in FIG. 2. 
Perforated shell 72 is provided to conventionally permit expended shot and 
removed finite flash to fall from within basket 12. The purpose of parts 
basket 12 is to tumble the parts for deflashing, i.e., to keep the 
articles of manufacture falling within the volume defined by shell 72 as 
much as possible to maximize exposure to both the cryogenic fluid flow and 
to the accelerated shot. In conventional baskets, the articles tend to 
accumulate in comer portions of lower basket volumes as the basket is 
rotated and many articles are not sufficiently deflashed. 
In the present invention, conical deflector shell 74 acts to keep the 
articles from accumulating in the lower corners and to maximize the fall 
time of the articles. Conical angle .theta. with respect to the surface of 
perforated shell 72 is selected at the closed end of basket 12 to provide 
the bottom of deflector shell 74 in a nearly horizontal position when the 
axis of parts basket 12 is installed at an angle .theta. within cabinet 20 
with respect to horizontal. An angle in the range of 
20.degree.-25.degree., with a preferred angle of 22.degree., has been 
found to best tumble articles while preventing accumulation of the 
articles in the bottom of shell 72. 
A second conical shell 76 is provided at the open end of shell 72 to direct 
the cryogenic fluid and the deflashing shot along shell 72 to dislodge 
articles from shell 72 for falling within the enclosed volume. Conical 
shell 76 acts to retain the tumbling parts within shell 72. A preferred 
angle for this shell is 30.degree.. 
Tumbling action within perforated shell 72 is caused by flights 78, 82, 
which are deflector ribs that extend parallel to the axis of shell 72, 
except within conical shell 74, where the flights are parallel with the 
side of shell 74. A preferred number of flights is three (3) in order to 
maximize flight times without too much churning of the enclosed articles. 
The action of the angled basket 12, conical deflector shell 74, and 
flights 78, 82, along with the impacting action of the shot media causes 
the particles to circulate in a "figure 8" pattern within shell 72 to 
provide an enhanced time of flight for flash removal. It will be 
appreciated that each new article configuration requires some experimental 
regime to determine the best rotation speeds for parts basket 12 and throw 
wheel assembly 42 for optimum flash removal. 
As shown in FIG. 1, there are penetrations into cryogenic chamber 14 for 
rotating shafts, e.g., the drive shafts for parts basket 12 and for auger 
52. These penetrations must be sealed to prevent the loss of cryogenic 
fluid from the cryogenic chamber. Conventional sealed bearings do not 
perform well at cryogenic temperatures and it is a feature of the present 
invention to provide low leakage cryogenic bearings, as shown in FIG. 3. 
Bearing block 84 is attached to the stationary component and seal block 88 
is attached to a rotating shaft, e.g., by set screw 94. Bearing block 84 
defines concentric seal groove 86 and seal block 88 defines concentric 
seal extension 92 that mates with seal groove 86. Extension 92 and groove 
86 are in bearing contact and form a high resistance path for any fluid 
leakage therethrough. Suitable materials will be materials that have a low 
sliding coefficient of friction at cryogenic temperatures, such as PTFE. 
The present invention further incorporates improvements in the shot media 
feed system to provide a smooth flow of shot media onto the parts in parts 
basket 12 (FIG. 1). FIG. 4 more particularly depicts a shot media feed 
system in accordance with one embodiment of these improvements. Auger 52 
pushes expended media from the sump of cryogenic chamber 14 (FIG. 1) into 
media hopper 56. Media level control switch 96 controls auger drive motor 
54 (FIG. 1) to maintain a selected shot media level within media hopper 
56. The action of throw wheel assembly 42 creates a pressure differential 
for delivering shot media to throw wheel 110 through feed line 44. Shot 
media enters into pick-up tube 98 through a first opening below the level 
of the shot media in hopper 56 and is delivered to feed line 44. Pick-up 
tube 98 is preferably provided with flow metering port 102, which is above 
the level of the media in hopper 56. Port 102 acts to prevent media 
blocking within pick-up tube 98 and provides a smooth delivery of shot 
media to throw wheel 110 rather than a pulsating flow that is obtained 
without flow metering port 102. 
The shot media system described above is based on a system described for 
FIG. 1, where removed flash is generally retained within a parts basket. 
In one alternative embodiment, the removed flash is dropped through the 
basket perforations into the sump of the cryogenic chamber and picked up 
with auger 52. Then the flash must be separated from the shot media. Since 
the removed flash will be larger than the shot media, separation is 
readily done by delivering the material from the auger onto a vibrating 
screen so that the shot media passes through the screen into hopper 56 and 
the flash is moved into a flash container by the vibratory motion of the 
flash on the screen. 
Shot media is delivered onto vanes 108 of throw wheel 110 through feed port 
106 of flow control cage 104. The rate of delivery of shot media onto 
vanes 108 is controlled by varying the rotation speed of throw wheel 110. 
Feed line 44 is preferably formed of a transparent material so that media 
flow may be observed and the rotation of throw wheel 110 adjusted to 
maintain feed line 44 about half full of media. 
Flow control cage 104 mates within rotating vanes 108 to deliver shot media 
directly onto vanes 108 for acceleration into parts basket 12 (FIG. 1). 
Flow control cage 106 has a frusto-conical end for extending within vanes 
108 In a preferred embodiment, the frusto-conical end of flow control cage 
104 defines feed port 106 at an angle of about 60.degree. relative to the 
axis of throw wheel 110 to efficiently load shot media onto each vane 108 
as the vane passes feed port 106. In another preferred embodiment, throw 
wheel 110 has an odd number of vanes 108, e.g., 5 vanes rather then the 
conventional 6 vanes, to reduce harmonic vibration at the high rotation 
speeds. 
FIG. 5 is an isometric view of cryogenic chamber 14 with parts basket 12 
(FIG. 1) removed The relative positions of auger 52, bearing surfaces 22 
and 24, and cryogen feed line 38 are illustrated for reference. Shot media 
exits throw wheel 110 through an exit port 112 defined by a wall of 
cryogenic chamber 14. Exit port 112 is offset with respect to the center 
line of rotation of parts basket 12 to direct the shot media toward the 
volume of basket 12 where the articles begin to flip off of the flights, 
e.g., flights 78, 82 (FIG. 2) in the rotating basket. The impact of the 
shot media with the articles acts to deflash the articles and also to 
maintain the parts in a falling pattern for maximum exposure. 
In another aspect of the present invention, shown in FIG. 6, an improved 
cryogenic seal 18 is provided for sealing between load door 16 and 
cryogenic chamber 14. With conventional seal designs, ambient water vapor 
may penetrate the seals and freeze so that opening a sealed door may be 
difficult. The seal design shown in FIG. 6 alleviates this problem. 
Internal tadpole seal gasket 122 and external tadpole seal gasket 124 
(e.g, tetraglass seals from Darco, Independence, Va.) are fixed to load 
door 16. Seal gaskets 126 and 128 are provided on cryogenic chamber 14. 
Spring loaded seal 134 with insulation 136 acts to protect the door seal 
components from erosion from the constant impact of the shot media. 
Inner seal gasket 126 is preferably formed of a material that does not 
stick to frozen water vapor, e.g., PTFE, so that any ice formed between 
gasket 122 and gasket 126 will not cause the parts to adhere together. 
External gasket 124 is preferably formed of a sponge neoprene material. A 
barrier seal 132, such as aluminum, is formed between internal gasket 122 
and external gasket 124 to minimize the contact of water vapor with mating 
seal gaskets 122 and 126 and to minimize the exposure of gaskets 124 and 
128 to cryogenic temperatures. The combination of components provides a 
seal that opens readily during operation of the cryogenic deflashing 
apparatus. 
The component parts of the present invention, described above, cooperate to 
provide efficient removal of flash from molded articles. The overall 
operation of the deflashing apparatus is best described with reference to 
FIGS. 1, 2, 4, and 5. Parts basket is removed from cryogenic chamber to 
load manufactured parts having flash to be removed. The parts are loaded 
through open conical shell 76 and parts basket 12 is placed within 
cryogenic chamber 14 supported by bearing surfaces 22 and 24. Hand clutch 
34 is operated to translate motor 26 and drive wheel 28 for operatively 
engaging parts basket 12. 
Load lid 16 is closed and sealed and motor 26 is energized to rotate basket 
12 at a selected speed while a cryogenic fluid is introduced through feed 
line 38 to cool the parts to a suitable cryogenic temperature for 
embrittling the flash. Throw wheel 110 is brought to a speed for 
accelerating a shot media through shot opening 112 into basket 12. 
The rotation of basket 12 with internal flights, such as flights 82 and 78, 
operates with conical shell 74 at the closed end of basket 12 to maintain 
the parts in a flight pattern whereby the parts do not aggregate in a 
comer of basket 12. Further, shot opening 112 is offset to direct the shot 
along an interior surface of basket 12 and toward a location in basket 12 
where the parts begin to fall from the included flights so that parts are 
exposed to the deflashing shot media for a maximum time. The accelerated 
shot media also impacts the parts to further maintain the parts in flight. 
Expended shot media and removed flash pass through perforations in parts 
basket 12 into a bottom portion, or sump, of cryogenic chamber 14. Auger 
52 is energized as necessary to move shot media into media hopper 56 for 
reuse by throw wheel 110. The speed of rotation of throw wheel 110 is 
adjusted to maintain a suitable delivery of shot media to parts basket 12 
through pick-up tube 98. Flow metering port 102 acts to prevent blocking 
of pick-up tube 98 so that a continuous flow of shot media is obtained. 
The delivery of shot media onto vanes 108 of throw wheel 110 is smoothed 
by the angle of feed port 106 in media flow control cage 104. 
The foregoing description of a cryogenic deflashing apparatus according to 
the present invention has been presented for purposes of illustration and 
description and is not intended to be exhaustive or to limit the invention 
to the precise form disclosed, and obviously many modifications and 
variations are possible in light of the above teaching. 
The embodiments of components of the deflashing apparatus were chosen and 
described in order to best explain the principles of the invention and its 
practical application to thereby enable others skilled in the art to best 
utilize the invention in various embodiments and with various 
modifications as are suited to the particular use contemplated. It is 
intended that the scope of the invention be defined by the claims appended 
hereto.