[0001] The present invention relates generally to the prevention of particulate contamination
in cleanrooms and pertains, more specifically, to the construction of wipers for use
in a cleanroom, or another similar controlled environment, the construction being
such that the wipers will not release contaminating particles into the controlled
environment.
[0002] Cleanrooms are finding wider use in the manufacture, inspection and maintenance of
precision products where it is essential that various operations be conducted in an
environment as free of undesired small particles as possible. Cleanrooms can function
effectively only when every effort is taken to maintain the close control necessary
to preclude contamination of the controlled environment within the cleanroom. Such
contamination most often is generated by the worker in the cleanroom and by items
brought into the cleanroom. Rigorous standards have been established, and continue
to be developed, for the operation of cleanrooms in such a manner as to exclude unwanted
contaminants from the controlled environment. One potential source of particulate
contamination in cleanrooms has been the wipers used extensively in connection with
operations carried out in the controlled environment of a cleanroom. For example,
in the fabrication of semiconductor wafers, wipers are used for cleaning up spills
which can occur during the procedures carried out in the controlled environment of
a cleanroom. In addition, wipers are used for wiping surfaces of various equipment
and items in the cleanroom, as well as for wiping down the walls and other interior
surfaces of the cleanroom itself. The very nature of a wiper, which requires a high
degree of absorbency and pliability, militates against a construction which resists
shedding and the concomitant release of small particles into the surrounding environment.
[0003] The present invention provides a wiper construction and a method by which a potential
source of particulate contamination of a cleanroom environment, or another such controlled
environment, is eliminated in that particles which otherwise might be generated by
a wiper used in the cleanroom, or other such controlled environment, no longer are
present for release into the controlled environment. The invention attains several
objects and advantages, some of which are summarized as follows: Eliminates a potential
source of particulate contamination of a controlled environment, such as a cleanroom,
by precluding the introduction of particles through the use of wipers in the environment;
provides a wiper structure which eliminates the release of unwanted particles into
a controlled environment, such as that found in a cleanroom, while enabling effective
and efficient wiping procedures; enables the use of wiper materials having the desired
pliability and absorbency characteristics in wipers employed in controlled environments,
such as in cleanrooms, without risk of introducing particulate contamination into
the controlled environment; promotes ease of use as well as effectiveness in wipers
constructed for use in a controlled environment, such as a cleanroom; utilizes commonly
available materials, thereby enabling economy of manufacture and use while eliminating
a source of particulate contamination, as set forth above; provides a strong and durable
as well as an aesthetically pleasing wiper which finds acceptance in a wide variety
of manufacturing, inspection and maintenance procedures; and is readily manufactured
economically in large numbers of consistent high quality.
[0004] The above objects and advantages, as well as further objects and advantages, are
attained by the present invention, which may be described briefly as a method and
a wiper for reducing particulate contamination which otherwise might result from the
use of the wiper in a controlled environment, such as that maintained in a cleanroom,
the wiper being of the type constructed at least partially from a thermoplastic fabric
material by severing the wiper along peripheral edges thereof from a sheet of such
material having indeterminate dimensions, the method and the wiper providing a fused
border in the material along the peripheral edges of the wiper and extending inwardly
into the wiper a distance great enough to provide the fused border with sufficient
area and sufficient tear-strength to maintain therein segments of the material of
the wiper which otherwise might be released from the peripheral edges of the wiper
during use of the wiper, yet small enough to maintain pliability and absorbency in
the wiper for wiping procedures. In one embodiment of the wiper, two plies of the
material are joined along the fused border to establish a sealed envelope within which
is placed an absorbent material isolated from the controlled environment by the plies
of material and the fused border.
[0005] The invention will be understood more fully, while still further objects and advantages
will become apparent, in the following detailed description of preferred embodiments
of the invention illustrated in the accompanying drawing, in which:
FIG. 1 is a plan view of a wiper constructed in accordance with the invention;
FIG. 2 is a somewhat diagrammatic, highly enlarged view of a portion of the material
from which the wiper is constructed;
FIG. 3 is a view similar to FIG. 2, but illustrating a step in the procedure for constructing
a wiper;
FIG. 4 is a view similar to FIG. 3, but showing an alternate configuration;
FIG. 5 is an enlarged cross-sectional view taken along line 5-5 of FIG. 1;
FIG. 6 is a partially diagrammatic view illustrating a procedure for the manufacture
of the wiper; and
FIG. 7 is a longitudinal cross-sectional view of an alternate wiper construction of
the present invention.
[0006] Referring now to the drawing, and especially to FIG. 1 thereof, a wiper constructed
in accordance with the invention is illustrated generally at 10. Wiper 10 is constructed
of one of a variety of generally thermoplastic fabric materials which have found use
in wipers. Among these materials are polyester, nylon, polypropylene and blends of
these materials, as well as blends of natural materials, such as cotton, with synthetic
thermoplastic materials. The materials are in the form of a knitted, woven or non-woven
fabric. The preferred material, and the one described in connection with the embodiment
of wiper 10, is a knitted polyester, preferably knitted from a continuous filament.
As illustrated in FIG. 2, the material of wiper 10 is constructed of filaments 12
knitted together in interlocking loops 14. The loops 14 have a relaxed loop length
L. Preferably, the length L is very small, in the order of about 0.75 mm and the filaments
12, which are made up of a plurality of fibrils, have a diameter of about 0.25 mm,
so that the wiper 10 is provided with the requisite pliability and absorbency.
[0007] Wiper 10 is most economically manufactured by severing the wiper 10 from a larger
sheet of the knitted fabric to establish a wiper of desired dimensions. However, as
illustrated in FIG. 3, severing the fabric of a larger sheet 20 along a cut line 22
leaves a cut edge 24 along which there are free segments 26 of the filaments 12. These
free segments 26 can be released into the ambient atmosphere and become contaminating
particles when the wiper is utilized in a controlled environment, such as is found
in a cleanroom. It has been suggested that cutting be accomplished with a hot knife
or a hot wire so that the segments 26 will fuse and will remain in place within the
remainder of the wiper; however, experience has shown that the localized melting of
the segments 26 is insufficient to prevent the segments 26 from release when subjected
to agitation and other manipulations common in the use of the wiper. Moreover, during
the severing operation, the larger sheet 20 usually is stretched and distorted, particularly
when the material is a knitted fabric, so that the interlocking loops of the material
are somewhat skewed and the cut line is less uniform, as seen at 28 in FIG. 4. The
less-uniform cut line 28 produces odd-shaped free segments 30, in addition to the
aforesaid free segments 26, at locations which do not lend themselves readily to capture
of all of the free segments 26 and 30 within the wiper, thereby increasing the propensity
for contamination by the release of free segments into the surroundings.
[0008] In order to preclude the release of severed segments from the remainder of the wiper,
wiper 10 is provided with a fused border 32 along the peripheral edges 34 of the wiper
10, within which fused border 32 all of the severed segments are captured and retained
throughout the useful service life of the wiper 10. As best seen in FIG. 5, as well
as in FIG. 1, border 32 extends inwardly into the wiper 10, away from the peripheral
edges 34, a distance D. The distance D is chosen so as to be large enough to accomplish
the objective of capturing all of the segments 26 and 30 which otherwise could be
free to escape into the ambient atmosphere and contaminate the controlled environment
within which the wiper l0 is used, while resisting any tendency for tearing of the
wiper l0 at the peripheral edges 34, yet is small enough to retain the desired degree
of pliability in the wiper 10 and to resist any tendency toward abrasiveness in the
wiper 10, while maintaining the necessary absorbency. In the illustrated wiper 10,
the distance D is about 7L, that distance having been determined empirically as providing
an optimum balance between attaining the complete capture of all of the otherwise
free segments 26 and 30 along the peripheral edges 34 and establishing sufficient
tear-strength, while maintaining pliability and resistance to abrasiveness. Thus,
the selected distance D provides a border 32 of minimum area so as not to interfere
with the requisite pliability and absorbency of wiper 10, while capturing potential
contaminants in a construction having sufficient strength and durability to resist
tearing and other deterioration during use. At the same time, abrasiveness is not
introduced at the peripheral edges and an aesthetic appearance is maintained which
provides a visual balance between the area of the border 32 and the area of the remaining
absorbent portions of the wiper 10 to instill confidence in the user that the wiper
10 provides the necessary absorbency to accomplish any wiping job.
[0009] Turning now to FIG. 6, the preferred manufacturing technique for making a plurality
of wipers l0 is to sever the wipers from a sheet 40 of indeterminate dimensions. The
sheet 40 is advanced in the direction of the arrow 42 along a predetermined path of
travel 44. A pattern 46 is fused in the sheet 40, the pattern defining a plurality
of latent wipers 10 including fused and unfused areas, and the sheet 40 is severed
within the fused pattern 46, along sever lines 48 and 50, to establish each individual
wiper 10 with a fused border 32 along the peripheral edges 34 of wiper 10. In this
manner, dimensional stability is maintained for wiper manufacture, while the appropriate
fused border 32 is established in each wiper 10.
[0010] An alternate wiper construction is illustrated in FIG. 7 wherein a composite wiper
60 includes two sheets of material in the form of outer plies 62 and 64 of a thermoplastic
fabric material, chosen from the materials outlined above in connection with the description
of wiper 10, and a third sheet, or inner ply, in the form of pad 66 of highly absorbent
material, such as cotton, a blend of polyester and cellulose, tissue stock or the
like, sealed within the envelope 68 provided by the outer plies 62 and 64. A fused
border 70 extends along the peripheral edges 72 of the wiper 60, all around the periphery
of the wiper, in much the same manner as that described in connection with wiper 10.
In this manner, the fused border 70 secures together the outer plies 62 and 64 and
at the same time precludes the release of any segments of the thermoplastic fabric
material which forms the plies 62 and 64, and together with the remainder of the plies
62 and 64 isolates the pad 66 so that any particles which might otherwise emanate
from the material of the pad 66 are maintained within the wiper 60 and are precluded
from contaminating the environment within which wiper 60 is employed. It is noted
that even in those instances where pad 66 is in the form of a sheet which extends
all the way to the peripheral edges 72, as a result of the particular manufacturing
process in which the pad 66 and the plies 62 and 64 all have essentially the same
length and width and are placed into juxtaposition with one another prior to establishing
the fused border 70, the fused border 70 will preclude the emanation of particles
from the pad 66, as well as from the outer plies 62 and 64, while securing together
the plies 62 and 64 and the interposed pad 66. Thus, wiper 60 makes available the
use of highly absorbent materials in pad 66, while assuring that potentially contaminating
particles, which are prevalent in such absorbent materials, are contained and are
not released to the controlled environment within which wipers 60 are to be used.
[0011] It is to be understood that the above detailed description of preferred embodiments
of the invention are provided by way of example only. Various details of design, construction
and procedure may be modified without departing from the true spirit and scope of
the invention as set forth in the appended claims.
1. A wipe constructed at least partially from a thermoplastic fabric material and
formed by severing the wipe along at least one peripheral edge from a sheet of such
material, the wipe being capable of enabling the reduction of particulate contamination
which otherwise might result from the use of known wipes in a controlled environment,
such as that maintained in a cleanroom, and being provided with a fused border along
its peripheral edges, the fused border extending inwardly into the wipe a distance
great enough to provide the fused border with sufficient tear-strength to maintain
within the border segments of the material of the wipe which otherwise might be released
from the peripheral edges of the wipe during use of the wipe, yet small enough to
maintain pliability and absorbency in the wipe for wiping procedures.
2. A wipe according to claim 1, wherein the sheet of material includes filaments knit
into interlocking loops having a relaxed loop length L and the distance over which
the fused border extends inwardly into the wipe is a multiple of the length L.
3. A wipe according to claim 2, wherein the distance is at least about 7L.
4. A wipe according to claim 2 or 3, wherein L is about 0.75 mm.
5. A wipe according to claim 2, 3 or 4, wherein the filaments in the border are fused
together.
6. A wipe constructed at least partially from a thermoplastic fabric material and
formed by severing the wipe along at least one peripheral edge from a sheet of such
material, the wipe being capable of enabling the reduction of particulate contamination
which otherwise might result from the use of known wipes in a controlled environment,
such as that maintained in a cleanroom, the wipe comprising:
first and second sheets of the material juxtaposed with one another;
a fused border along the peripheral edges of the wipe, the fused border extending
inwardly into the wipe a distance great enough to provide the fused border with sufficient
area and sufficient tear-strength to secure together the first and second sheets and
maintain within the border segments of the material of the wipe which otherwise might
be released from the peripheral edges of the wipe during the use of the wipe, yet
small enough to maintain pliability and absorbency in the wipe for wiping procedures;
an envelope between the first and second sheets, the envelope being sealed by the
fused border; and
an absorbent material placed within the envelope and isolated from the controlled
environment by the first and second sheets and the fused border such that particles
from the absorbent material in the envelope will remain sealed within the envelope.
7. A wipe according to claim 6, wherein, the sheets of material include filaments
knit into interlocking loops having a relaxed loop length L and the distance over
which the fused border extends inwardly into the wipe is a multiple of the length
L.
8. A wipe according to claim 7, wherein the distance is at least about 7L.
9. A wipe according to claim 8, wherein L is about 0.75 mm.
10. A method of making a wipe severed from a sheet constructed of filaments of thermoplastic
material, the filaments being knit into interlocking loops having a relaxed loop length
L, the wipe being capable of being used in a controlled environment, such as that
maintained in a cleanroom, without releasing unwanted particles of the knit filaments
which otherwise might be formed in the vicinity of the peripheral edges of known wipes
as a result of severing such wipes from such a sheet, which method comprises fusing
the sheet along areas of the sheet to establish fused areas and unfused areas defining
latent individual wipes, and severing the fused areas to form actual individual wipes
having severed edges and a border in which the filaments are fused together, the border
extending from the severed edges inwardly into each wipe a distance which is a multiple
of the length L so as to provide the border with sufficient tear-strength while maintaining
within the fused border all segments of the filaments which otherwise might be present
as a result of severing the fused areas, thereby precluding the release of severed
segments into the controlled environment.