U.S. patent application number 11/346846 was filed with the patent office on 2007-06-14 for low-cost disposable tourniquet cuff.
Invention is credited to Kenneth L. Glinz, Michael Jameson, James A. McEwen, Allen J. Upward.
Application Number | 20070135836 11/346846 |
Document ID | / |
Family ID | 38327103 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070135836 |
Kind Code |
A1 |
McEwen; James A. ; et
al. |
June 14, 2007 |
Low-cost disposable tourniquet cuff
Abstract
A low-cost disposable tourniquet cuff includes: a first sheet
formed of flexible material that is impermeable to gas; a second
sheet facing the first sheet and formed of flexible material
impermeable to gas; a bladder seal joining the first sheet to the
second sheet around a perimeter to form an inflatable bladder
within the perimeter; port means communicating pneumatically with
the bladder and releasably connectable to a tourniquet instrument;
stiffener means contained within the inflatable bladder and formed
of gas-impermeable material less flexible than the first sheet,
wherein the stiffener means has a stiffener width dimension less
than the bladder width dimension and is joined to the first sheet
to form a non-inflatable portion of the first sheet; and securing
means attached to the non-inflatable portion of the first sheet and
adapted to allow a surgical user to releasably secure the cuff
around the limb at the desired location so that the bladder
overlaps upon itself.
Inventors: |
McEwen; James A.;
(Vancouver, CA) ; Jameson; Michael; (North
Vancouver, CA) ; Glinz; Kenneth L.; (Richmond,
CA) ; Upward; Allen J.; (Vancouver, CA) |
Correspondence
Address: |
PATRICK W. HUGHEY
P.O. BOX 6553
PORTLAND
OR
97228
US
|
Family ID: |
38327103 |
Appl. No.: |
11/346846 |
Filed: |
February 3, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11304363 |
Dec 14, 2005 |
|
|
|
11346846 |
Feb 3, 2006 |
|
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Current U.S.
Class: |
606/203 |
Current CPC
Class: |
A61B 17/135 20130101;
A61B 17/1322 20130101; Y10T 156/10 20150115; A61B 2017/0023
20130101 |
Class at
Publication: |
606/203 |
International
Class: |
A61B 17/00 20060101
A61B017/00 |
Claims
1. A low-cost disposable tourniquet cuff, comprising: a first sheet
formed of flexible material that is impermeable to gas; a second
sheet facing the first sheet and formed of flexible material
impermeable to gas; a bladder seal joining the first sheet to the
second sheet around a perimeter to form an inflatable bladder
within the perimeter, wherein the bladder has a bladder width
dimension and a bladder length dimension greater than the
circumference of a patient's limb at a desired location; port means
communicating with the bladder and releasably connectable to a
tourniquet instrument for establishing a pneumatic passageway for
pressurized gas between the bladder and the tourniquet instrument;
stiffener means contained within the inflatable bladder and formed
of gas-impermeable material less flexible than the first sheet,
wherein the stiffener means has a stiffener width dimension less
than the bladder width dimension and is joined to the first sheet
to form a non-inflatable portion of the first sheet; and securing
means attached to the non-inflatable portion of the first sheet and
adapted to allow a surgical user to releasably secure the cuff
around the limb at the desired location so that the bladder
overlaps upon itself.
2. The apparatus of claim 1 wherein the stiffener means is joined
to the first sheet by a gas-tight stiffener seal around a stiffener
seal perimeter to form the non-inflatable portion within the
stiffener seal perimeter.
3. The apparatus of claim 1 wherein the stiffener means has a
stiffener length dimension at least equal to the circumference of
the limb at the location and less than the bladder length
dimension.
4. The apparatus of claim 1 wherein the cuff has sides, side edges
and first and second ends outside the bladder seal, wherein the
cuff includes a tie strap located between the first sheet and the
second sheet near the second end and extending from the side edges,
wherein the tie strap is non-releasably attached to at least the
second sheet, and wherein the tie strap is adapted to assist the
surgical user in releasably securing the first end of the cuff.
5. The apparatus of claim 1 wherein the cuff has sides, side edges
and first and second ends outside the bladder seal, wherein the
cuff includes secondary securing means attached to the second sheet
near the first end, and wherein the secondary securing means is
adapted to allow the surgical user to secure the cuff around the
limb independently of the securing means attached to the
non-inflatable portion of the first sheet.
6. The apparatus of claim 1 wherein the bladder seal is a weld that
includes integral marking visible to the surgical user.
7. The apparatus of claim 1 wherein the stiffener means is sealed
to the first sheet by a weld having integral marking visible to the
surgical user.
8. The apparatus of claim 1 wherein the securing means is a
securing strap attached to the first sheet, wherein the port means
passes through the securing strap at a port location, and wherein
the port means includes means to prevent detachment by a surgical
user of the securing strap from the first sheet near the port
location.
9. A low-cost disposable tourniquet cuff, comprising: a first sheet
formed of a gas-impermeable material having a predetermined
flexibility; a second sheet formed of a flexible material
impermeable to gas; stiffener means formed of gas-impermeable
material having a predetermined stiffener flexibility less than the
predetermined flexibility of the first sheet, wherein the stiffener
means is located between the first sheet and the second sheet and
wherein the stiffener means is joined to the first sheet within a
portion of the first sheet; a bladder seal joining the second sheet
to the first sheet around a perimeter enclosing the stiffener means
to form an inflatable bladder within the perimeter, wherein the
inflatable bladder has a length dimension greater than the
circumference of a patient's limb at a desired location; port means
communicating with the inflatable bladder and releasably
connectable to a tourniquet instrument for establishing a pneumatic
passageway for pressurized gas between the bladder and the
tourniquet instrument; and securing means for securing the cuff
around the limb at the desired location so that the bladder
overlaps upon itself.
10. The apparatus of claim 9 wherein the securing means includes a
securing strip of velcro-type material non-releasably attached to
the first sheet at a strip attachment location and further includes
a securing strap of mating velcro-type material attached to the
securing strip near a first strap end and releasably attachable by
a user to the securing strip near a second strap end to secure the
cuff around the limb.
11. The apparatus of claim 9 wherein the securing strap is further
non-releasably attached to the first sheet at an attachment
location away from the inflatable bladder.
12. The apparatus of claim 11 wherein the second sheet is
non-releasably attached to the first sheet at the attachment
location.
13. The apparatus of claim 9 wherein the portion has a
predetermined area and wherein the stiffener means is joined to the
first sheet by a gas-tight seal having a seal area substantially
equivalent to the predetermined area of the portion.
14. The apparatus of claim 9 wherein the stiffener means is joined
to the first sheet by a plurality of welds located within the
portion.
15. The apparatus of claim 9 wherein the stiffener means is joined
to the first sheet by a gas-tight stiffener seal around a stiffener
seal perimeter within the portion to establish a non-inflatable
area within the stiffener seal perimeter.
16. A low-cost disposable tourniquet cuff, comprising: an
inflatable bladder having a first bladder side and a second bladder
side and a bladder length dimension between first and second
bladder ends that is greater than the circumference of a patient's
limb at a desired location, wherein the first and second bladder
sides extend past the first and second bladder ends; stiffener
means contained within the inflatable bladder and formed of
material less flexible than the first and second bladder sides;
port means communicating with the inflatable bladder and releasably
connectable to a tourniquet instrument for establishing a pneumatic
passageway for pressurized gas between the inflatable bladder and
the tourniquet instrument; and securing means including a securing
strip of velcro-type material non-releasably attached to the first
bladder side and further including a securing strap of mating
velcro-type material extending past the first bladder end and
non-releasably attached to the first bladder side at an attachment
location past the first bladder end, wherein the securing strap is
releasably attachable by a surgical user to the securing strip to
secure the cuff around the limb.
17. The apparatus of claim 16 where the first bladder side is
further joined to the second bladder side at the attachment
location.
18. The apparatus of claim 16 wherein stiffener means is joined to
the first bladder side to form a non-inflatable portion of the
first bladder side.
19. The apparatus of claim 16 and including a tie strap
non-releasably attached to second bladder side at a location past
the second bladder end, wherein the tie strap is adapted to assist
the surgical user in releasably securing the second end of the
bladder.
Description
[0001] This is a continuation-in-part of U.S. patent application
Ser. No. 11/304,363, filed Dec. 14, 2005.
FIELD OF THE INVENTION
[0002] This invention pertains to pneumatic tourniquet cuffs
commonly used for stopping arterial blood flow into a portion of a
surgical patient's limb to facilitate the performance of a surgical
procedure, and for facilitating intravenous regional
anesthesia.
BACKGROUND OF THE INVENTION
[0003] Typical surgical tourniquet systems of the prior art include
a tourniquet cuff which encircles the limb of a surgical patient
and a tourniquet instrument which is releasably connected to an
inflatable bladder within the tourniquet cuff through a length of
tubing, thereby establishing a gas-tight passageway between the
cuff and the tourniquet instrument. The tourniquet instrument
contains a pressurized gas source which is used to inflate and
regulate the pressure in the tourniquet cuff above a minimum
pressure required to stop arterial blood flow distal to the cuff,
for a duration suitably long for the performance of a surgical
procedure. Many types of surgical tourniquet systems have been
described in the prior art, such as those described by McEwen in
U.S. Pat. No. 4,469,099, No. 4,479,494, No. 5,439,477 and McEwen
and Jameson in U.S. Pat. No. 5,556,415 and No. 5,855,589.
[0004] A number of different types of disposable tourniquet cuffs
are known in the prior art. These cuffs are intended to be used
within sterile surgical fields, and are typically sterilized at the
time of manufacture. Examples of multi-layer disposable cuffs in
the prior art are described by Robinette-Lehman in U.S. Pat. No.
4,635,635, and in commercial products manufactured in accordance
with its teachings ("Banana Cuff" sterile disposable tourniquet
cuffs, Zimmer Arthroscopy Systems, Englewood Colo.), and by Guzman
et al. in U.S. Pat. No. 6,506,206, and in commercial products
manufactured according to its teachings ("Comfortor.TM. Disposable
Gel Cuff", DePuy Orthopaedics Inc., Warsaw Ind.). A two-layer
disposable cuff of the prior art is described by Spence in U.S.
Pat. No. 5,733,304. Other disposable cuffs of the prior art have
been constructed using multiple layers of costly materials such as
cloth/thermoplastic laminates and gels. The use of multiple layers
of such materials in prior-art cuffs has increased their overall
thickness and stiffness, making these cuffs difficult for a
surgical user to apply consistently. Thicker and stiffer cuffs of
the prior art may also degrade performance after cuff application
so that higher tourniquet pressures may be required to reliably
occlude blood flow; this is undesirable because higher tourniquet
pressures are associated in the surgical literature with a higher
risk of patient injury.
[0005] Typical tourniquet cuffs of the prior art include a sealed
inflatable bladder that encircles the limb and communicates
pneumatically with a connected tourniquet instrument through one or
more cuff ports, a stiffener that helps direct the expansion of the
bladder radially inwards towards the limb and helps prevent any
twisting or rolling of the cuff on the limb, and one or more
fasteners that secure the cuff around the limb.
[0006] In order to facilitate the attachment of fasteners and cuff
ports, the manufacture of prior art cuffs having multiple layers
typically includes several labor-intensive operations, some of
which require a high level of skill, quality and consistency on the
part of manufacturing personnel. These operations can include
sewing fastener materials to an outer cuff layer, adding a
structural reinforcing patch to the outer layer, sealing one or
more ports to a layer forming part of the inflatable bladder, and
sealing layers around a perimeter to form the bladder.
[0007] Cuff layers consisting of compatible thermoplastic polymeric
materials are typically joined together using a radio frequency
(RF) welding process, which uses a combination of heat and pressure
to cause compatible polymers to flow together by molecular
diffusion. Welding operations to make cuffs of the prior art are
typically completed in multiple steps, each of which typically
requires the involvement of manufacturing personnel. For example,
some cuffs have inflatable bladders formed from two separate sheets
of thermoplastic coated material that are sealed around a perimeter
using an RF welding process. Gas passageways into the bladder are
typically formed using single or multiple ports welded to one layer
before the bladder is formed. Each port provides a gas passageway
into the bladder through a reinforced structure that is attached to
tubing extending outside the sterile surgical field for connection
to a tourniquet instrument. During the manufacturing process, the
port is typically attached to one side of the bladder in a welding
operation before the bladder is formed, to prevent the opposite
bladder surface from being welded at the port location.
[0008] Many tourniquet cuffs of the prior art include a
thermoplastic stiffener, which helps direct the expansion of the
cuff bladder radially inward toward the limb when pressurized and
helps reduce any tendency of the cuff to twist when pressurized or
to roll distally down a tapered limb. The absence of a stiffener
can lead to a reduction of the efficient application of pressure to
the limb and thus can lead to an increase in the level of pressure
required to stop blood flow past the cuff and into the limb. Also,
the absence of a stiffener can lead to additional stresses in the
outer cuff surface due to less constrained bladder expansion.
[0009] In many commonly used types of tourniquet cuffs of the prior
art (such as Zimmer ATS sterile disposable tourniquet cuffs
distributed by Zimmer Inc., Dover Ohio), a non-inflating sheath
contains a stiffener outside an inflatable bladder. This
configuration helps constrain the expansion of the bladder inwardly
into the soft tissues of the limb encircled by the cuff when the
cuff is pressurized, and helps prevent any twisting or rolling of
the cuff on the limb. A second type of stiffener configuration
involves increasing the thickness and rigidity of the material
forming the outer cuff layer, to obtain a stiffening function from
the outer layer in a two-layer cuff design (for example, as
described by Eaton in U.S. Pat. No. 5,413,582, and in tourniquet
cuffs distributed by Oak Medical, Briggs, North Lincs, UK). The
outer layer of these prior-art tourniquet cuffs serves both as a
stiffener and as one side of the inflatable bladder. The thick
outer layer extends to all of the cuff edges, and includes an area
for sealing the inner layer to the thick outer layer to form an
inflatable bladder, resulting in the bladder always having a
bladder width that is less than the width of the stiffener; this is
undesirable because cuffs having narrower bladder widths require
higher tourniquet pressures to stop blood flow, and higher
tourniquet cuff pressures are associated with a higher risk of
patient injury. Also, this second type of stiffener configuration
in cuffs of the prior art, in which the stiffener forms part of the
inflatable bladder, greatly limits the extent to which the cuff can
expand inwardly into soft tissue when the cuff is pressurized; this
limitation increases the pressure required to stop or occlude blood
flow in the encircled limb, especially in obese patients and
patients having large amounts of soft tissue. Further, the thick
and stiff edges formed at the side edges of these prior-art cuffs
may have a tendency to buckle towards the limb when the bladder is
pressurized, leading to a potential soft-tissue hazard. A third
stiffener configuration in tourniquet cuffs of the prior art
includes an unsecured stiffener located within the inflatable
bladder (for example, as described by Goldstein et al. in U.S. Pat.
No. 5,411,518, by Spence in U.S. Pat. No. 5,733,304, and as seen in
"Color Cuff II" sterile disposable tourniquet cuffs distributed by
InstruMed Inc., Bothell Wash.). In this configuration, the
stiffener is unsecured within the bladder and does not constrain
the expansion of the outer cuff surface. This reduces the
effectiveness of the stiffener in directing cuff pressure toward
the encircled limb across the width of the cuff, and it reduces the
extent to which the cuff can expand inwardly when pressurized,
thereby making its performance more sensitive to variations in
application technique and thereby leading to the possible need for
higher tourniquet pressures to stop blood flow past the cuff and
into the limb, particularly in patients having large amounts of
soft tissue and in patients with poor muscle tone. Further, an
unsecured stiffener within the cuff bladder is not as effective as
a secured stiffener in helping to prevent the cuff from twisting or
rolling on the limb. In addition, to reduce the limitations of
performance that are inherent in a cuff having an unsecured
stiffener within the inflatable bladder, the width of the stiffener
in prior art cuffs must be as close as possible to the bladder
width; this can impair cuff performance and requires precise
alignment of the stiffener during manufacture.
[0010] Many cuffs of the prior art include velcro-type fastening
elements, commonly referred to as hook and loop fasteners. The most
common configuration consists of a hook-type fastening strap
adapted for engaging with a loop-type material on the outer surface
of the cuff to form a releasable velcro-type attachment when the
cuff encircles a limb. In U.S. Pat. No. 5,201,758 Glover describes
a multi-layer tourniquet cuff having a bladder contained within a
flexible covering and a backing plate, and a fabric strap of
loop-type material attached at one end to the outer side of the
backing plate, for releasably engaging with a strip of hook-type
material permanently mounted to the outer side of the backing
plate. In U.S. Pat. No. 5,411,518 Goldstein et al. describe a
two-layer tourniquet cuff having a hook or loop fastening strap for
engaging with an outer cuff surface of loop or hook material. In
U.S. Pat. No. 5,413,582 Eaton describes a tourniquet cuff having
two sheets joined at the sides and ends to form an inflatable
bladder, wherein a fabric strap of hook-type material is attached
to the outer sheet of the cuff by welding or by an adhesive, and
wherein one end of a loop-type fabric tongue is attached to the
outer cuff sheet by welding or by an adhesive. Eaton '582 further
describes a flange that passes through an opening in the fabric
tongue to help reduce the potential for a user accidentally pulling
the fabric tongue off the outer sheet while tightening the cuff
about a patient's limb. In U.S. Pat. No. 5,733,304 Spence describes
a tourniquet cuff having a bladder with inner and outer walls and a
fastening strap with anchored and free portions, wherein the
anchored portion is attached to the outer wall of the bladder with
a velcro-type connection and wherein the free portion is adapted to
be releasably anchored by a user to the outer wall with a
velcro-type connection. Spence '304 includes a hole in the
fastening strap to allow the cuff port to help permanently secure
the fastening strap, as described previously in Eaton '582.
[0011] Some tourniquet cuffs of the prior art include secondary
fastening elements to provide increased safety and to facilitate
cuff application. In U.S. Pat. No. 5,312,431 McEwen describes a
tourniquet cuff having a primary fastening means to secure the
bladder and a secondary fastening means which is independent of the
primary fastening means. McEwen '431 provides increased safety by
ensuring the bladder remains overlapped and secured in a
substantially circumferential direction by the secondary
velcro-type fastening means even if the primary fastening means is
not engaged or becomes ineffective while the cuff is inflated. The
primary fastening means of McEwen '431 further facilitates cuff
application and alignment of a cuff end by providing a velcro-type
patch near the cuff end for releasable attachment of the end to a
surface of the cuff. In U.S. Pat. No. 5,193,549 Bellin et al.
describe a tourniquet cuff with a hook-type patch attached to a
loop-type cuff surface near an end by welding, adhesive or sewing,
wherein the patch facilitates releasable attachment of the cuff end
to the surface to secure the cuff around a limb. The two-layer
tourniquet cuff described in Spence '304 includes primary and
secondary fastening means similar to McEwen '431, wherein a
velcro-type fastening patch facilitates releasable attachment of a
cuff end to a mating velcro-type cuff surface as in Bellin '549 so
that the overlapping bladder is secured in a substantially
circumferential direction around the limb, and wherein a
velcro-type fastening strap engages with a mating velcro-type
surface of the cuff to secure the cuff around the limb.
[0012] To help secure the end of the cuff in contact with the limb
and to aid in cuff alignment during application, a number of cuffs
in the prior art include a tie strap attached near one end of the
cuff. Typical cuffs which include a tie strap are described by
McEwen et al. in U.S. Pat. No. 6,682,547 and by Robinette-Lehman in
U.S. Pat. No. 4,635,635. A tie strap allows a surgical user to
achieve a snug application of the cuff to the limb, and when tied
helps assure that the overlapping portion of the cuff remains
aligned, thus helping to prevent twisting, telescoping and rolling
of the cuff when inflated, and thus helping to assure the most
effective transmission of pressure from the cuff to the limb.
Prior-art tourniquet cuffs include tie straps that are attached to
cuffs in a variety of ways, including sewing or bonding to a
surface of the cuff. It is not desirable to attach the tie strap to
the cuff surface facing the patient's limb, where such attachment
may distort the cuff surface and thus lead to uneven pressure
distribution and possible soft-tissue injury. An alternate method
of attaching the tie strap to the end of a cuff is shown in
Goldstein et al. '518. Some prior art cuffs such as Spence '304 do
not include a tie strap, but such cuffs are less conveniently
applied, and may result in an applied cuff that is less snug and
less effective in transmitting pressure from the cuff to the
limb.
[0013] Some prior art cuffs carry marking visible to a surgical
user, as described for example by McEwen in U.S. Pat. No. 4,605,010
and U.S. Pat. No. 5,312,431. Typical markings carried on tourniquet
cuffs of the prior art have included labels sewn to cuff components
and ink lettering and symbols marked on cuff surfaces. Some
tourniquet cuffs of the prior art are marked by manufacturers to
indicate that they are intended for single use only. Unauthorized
reprocessing and reuse of such tourniquet cuffs in multiple
surgical procedures may be hazardous for patients. However, such
marking on prior-art cuffs may be easily removed or obscured if the
cuffs are reprocessed, leading to the possibility that surgical
staff may unknowingly use disposable tourniquet cuffs that have
been reprocessed in a manner not authorized by the manufacturer and
hazardous to patients.
[0014] In general, it is desirable to construct the thinnest
tourniquet cuff possible for a given application. Thinner cuffs
have smaller differences in circumference between inner cuff
surfaces and outer cuff surfaces when encircling a patient's limb,
in comparison to thicker cuffs. Such smaller differences in
circumference reduce folding and wrinkling at the inner cuff
surface. This reduces the possibility of wrinkling, pinching,
bruising and other injuries to the skin and soft tissue encircled
by such cuffs. Further, thinner cuffs tend to be less rigid than
thicker cuffs and thus allow a surgical user to apply the cuff more
snugly and more easily to the limb.
[0015] The manufacturing and assembly process of prior art cuffs
consists of numerous cutting, sewing, and sealing operations which
require substantial investment in both equipment and skilled
operators. The manual labor component of cuff assembly is high,
especially where multiple sewing and sealing operations are
required. It is therefore desirable to reduce the skill and time
required by the cuff assembly process, while continuing to utilize
readily available manufacturing equipment. A reduction in the
amount of time and skill required to manufacture tourniquet cuffs
can be accomplished by reducing the number of manual assembly
operations. This may include the elimination of numerous sewing
operations, and the consolidation of multiple RF sealing steps into
a single operation. Reducing the number of manual operations
provides a savings not only in the labor to construct a cuff, but
also provides the potential for the automation of a number of steps
leading to the single cuff sealing operation.
[0016] In U.S. Pat. No. 6,682,547 McEwen et al. describe a method
for automating the cuff manufacturing process by constructing the
top layer of the cuff in a continuous strip having varying
thickness to provide the stiffening functions described previously
while not limiting the inward radial expansion of the bladder.
McEwen '547 describes a custom manufacturing process which allows
the bottom and top layers to be joined in a continuous process,
whereby the edge of the inner layer is folded over the outer layer
and sealed. The end edges of the cuff are sealed at various
intervals to allow the construction of cuffs of a variety of
lengths. The stiffened top layer therefore extends to the ends of
the resulting cuff. Manufacturing the tourniquet cuff described in
McEwen '547 requires a high level of investment in automated
manufacturing equipment and processes, and necessarily requires a
high volume of cuff manufacture to produce low-cost cuffs.
[0017] There is a need for a disposable tourniquet cuff which
overcomes the hazards, problems and limitations of performance
associated with prior-art cuffs as described above, and which can
be manufactured at substantially lower cost with few changes to
existing manufacturing equipment and processes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a pictorial representation of the preferred
embodiment in a surgical application.
[0019] FIG. 2 is an exploded view of the preferred embodiment.
[0020] FIGS. 3a and 3b are top views of the preferred
embodiment.
[0021] FIGS. 4a, 4b and 4c are section views taken from FIG.
3a.
[0022] FIG. 5 is a section view taken from FIG. 3b.
[0023] FIG. 6 is a top view of the preferred embodiment showing a
securing strip.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] FIG. 1 is a pictorial representation of the preferred
embodiment in a surgical application, showing tourniquet cuff 10
secured circumferentially around patient limb 12 proximal to
surgical site 14. Tie strap 16 described further below, is tied as
shown in FIG. 1 to help prevent the cuff 10 from sliding proximally
or distally on patient limb 12 when cuff 10 is inflated.
[0025] The inflatable portion of tourniquet cuff 10 completely
encircles patient limb 12 and is pneumatically connected to
tourniquet instrument 18 via cuff port 20, cuff tubing 22, cuff
connector 24, instrument connector 26 and instrument tubing 28.
Tourniquet instrument 18 supplies pressurized gas for the inflation
of cuff 10 and is capable of inflating cuff 10 to a pressure that
will occlude the flow of arterial blood in patient limb 12 distal
to cuff 10.
[0026] The perimeter of a sterile surgical field 30 encloses
surgical site 14, a portion of patient limb 12, tourniquet cuff 10,
and a portion of cuff tubing 22. Cuff tubing 22 is of sufficient
length to permit cuff connector 24 to be releasably mated with
instrument connector 26 outside of sterile surgical field 30. In
the preferred embodiment shown, cuff 10 is a single port cuff,
where cuff port 20 provides a single pneumatic passageway into the
inflatable portion of cuff 10. Those skilled in the art will
appreciate that the features described in the preferred embodiment
may also be applied to tourniquet cuffs having more than one port,
such as those described by U.S. Pat. No. 4,469,099, No. 4,479,494,
and No. 5,254,087.
[0027] As described below, cuff 10 is constructed of materials that
are appropriate for a single-use sterile disposable tourniquet
cuff. To permit cuff 10 to be used in a sterile surgical field,
cuff 10 is sterilized at time of manufacture by exposure to a
sterilizing agent within a sterilizing process determined to be
safe and effective. To prevent deterioration of the cuff, and to
maintain the integrity of the pneumatic passageways within cuff 10,
a sterilization agent and process that will not harm the materials
or components of cuff 10 is selected by the manufacturer. In the
preferred embodiment cuff 10 is sterilized by exposure to gamma
radiation or electron beam radiation.
[0028] The cost of materials and labor are important considerations
in the manufacture of tourniquet cuffs intended for a single use
and then disposal. To minimize the cost of materials and assembly
of cuff 10, materials are selected which are not intended to
withstand exposure to subsequent sterilization and cleaning
processes. The subsequent sterilization or cleaning of cuff 10 by
agents and processes commonly used in health care facilities, such
as ethylene oxide gas sterilization, hydrogen peroxide gas
sterilization, high temperature and pressure steam sterilization,
sterilization by other chemical agents, and pasteurization, are all
capable of adversely affecting the integrity of the materials and
pneumatic passageways of cuff 10.
[0029] Cuff 10 includes marking such as symbols or letters to
indicate to that cuff 10 is intended for a single patient use and
is to be discarded after use. Marking may also be present to
identify the manufacturer of cuff 10 and indicate a manufacturing
lot number.
[0030] The preferred embodiment includes marking to indicate that
the cuff is intended for a single use and the marking is
permanently formed in selected welded areas of cuff 10 as described
further below. This permanent marking can be easily read by a user
and cannot be easily obscured or removed from the cuff without
causing damage to the cuff. Typical prior art cuffs include marking
printed with ink onto labels which are then sewn onto the cuff or
printed with ink directly onto the cuff, and marking printed onto
the sterile packaging in which the cuff is provided to the user.
Additionally, marking within bonded areas of a cuff is described by
McEwen et al. in U.S. Pat. No. 6,682,547.
[0031] Printed cuff packaging can be easily lost or thrown away and
sewn on labels can be inadvertently or intentionally removed from
these prior art cuffs. Marking printed with ink directly on the
cuff may be obscured, and ink fragments may come loose and
contaminate the surgical field. If a cuff is not clearly marked as
intended for single use a user or third party could unknowingly
attempt to re-manufacture and re-sterilize the cuff contrary to the
original manufacturer's instructions thereby producing a cuff that
is possibly hazardous to patients.
[0032] FIG. 2 is an exploded view of the individual components that
are joined together as described below to form cuff 10. For
clarity, cuff tubing 22 and cuff connector 24 are not shown in FIG.
2.
[0033] Those skilled in the art will appreciate that many
conventional methods exist for joining the thermoplastic polymers
that comprise the materials of cuff 10. Joining processes can be
separated into two broad groups: adhesive bonding, and thermal or
solvent welding. In an adhesive bonding process, an adhesive layer
is applied between two or more materials and when cured, the
adhesive holds the materials together at their surfaces. In a
thermal or solvent welding process, the surfaces of two or more
materials are made fluid by applying either thermal heating or a
solvent, which allow the thermoplastic materials to molecularly
diffuse into one another forming a weld. For molecular diffusion to
occur the thermoplastic polymers being thermally or solvent welded
must be sufficiently compatible. Thermal or solvent welding will
not occur between incompatible materials, for example, polyurethane
and polyethylene. Thermal welding can be accomplished by numerous
methods, including direct heating (e.g., hot gas, infrared,
extrusion), induced heating (e.g., radio frequency (RF) or
dielectric welding), and frictional heating (e.g., ultrasonic
welding). In the preferred embodiment and as described below, the
thermoplastic polymers comprising components of cuff 10 are joined
together by the dielectric welding process, in which materials are
brought together under pressure in a die and radio frequency energy
is applied to temporarily melt a portion of the thermoplastic
materials causing them to weld together in a selected area.
Dielectric welding relies on the principle of dielectric heating to
induce heat in thermoplastic materials placed within an alternating
electromagnetic field. The amount of potential heating generated is
dependent upon the dielectric properties of the thermoplastic
materials, known as loss factor or dissipation factor.
Thermoplastics with a relatively high dissipation factor such as
polyurethane can be readily dielectrically welded, while
thermoplastics with low dissipation factors such as polyethylene
can not be readily welded by this process. While thermoplastic
polyethylene will not heat substantially during the dielectric
welding process it will still provide a conductive path through
which the alternating electromagnetic field will propagate allowing
welding to occur in adjacent materials.
[0034] Some materials that comprise components of cuff 10 are
attached by stitches formed from nylon thread. It will be apparent
that other types of mechanical fastening methods such as stapling
and riveting could be used to attach selected components of cuff
10. Unlike joints formed by adhesive bonds and welds described
above that can form gas-tight seals, materials that are sewn
together or otherwise mechanically fastened generally do not form
gas-tight seals between components.
[0035] To reduce manufacturing equipment and labor costs it is
desirable to manufacture cuff 10 in a single dielectric welding
operation. This requires that the thermoplastic polymers comprising
the components of cuff 10 be prevented from welding at selected
surfaces. Preventing thermoplastic materials from welding together
can be accomplished by several methods. One method involves coating
the surface of a thermoplastic material with a material that
prevents the molecular diffusion into another otherwise compatible
material. Another method involves selecting thermoplastic materials
that have markedly different dissipation factors, preventing one or
more of the materials from heating during a dielectric welding
operation. As described above, both methods may be employed in the
manufacture of cuff 10.
[0036] Referring to the components of cuff 10 shown in FIG. 2,
securing strap 32 is made of a nylon hook material that is commonly
used in hook and loop velcro-type fastening applications.
Velcro-type fasteners form releasable connections between two
mating surfaces. When the velcro-type surfaces are engaged they
resist shear and tensile forces. The surfaces are typically
released by peeling the surfaces apart from an edge. In use,
securing strap 32 engages with loop material on the outer surface
of top sheet 34. When cuff 10 is applied to a limb, securing strap
32 is engaged by a user to the loop material of top sheet 34 to
secure cuff 10 circumferentially around the limb. The length and
specifications of the hook material comprising securing strap 32
are selected to maintain cuff 10 securely around the limb
circumference when cuff 10 is inflated.
[0037] Top sheet 34 is a thin flexible nylon loop material adapted
for secure engagement with the hook material of securing strap 32.
Top sheet 34 is coated on the inner surface with a thermoplastic
polymer. This thermoplastic polymer coating prevents the passage of
gas through top sheet 34 and allows top sheet 34 to be joined to
cuff port 20, bottom sheet 36 and to stiffener 38 as described
below. In the preferred embodiment the thermoplastic coating on top
sheet 34 is polyurethane. It will be apparent that securing strap
32 could be comprised of a loop material and top sheet 34 could be
a hook material. It will also be appreciated that other velcro-type
materials, including adhesives that have velcro-type properties,
could be selected to comprise securing strap 32 and top sheet
34.
[0038] Bottom sheet 36 is made of flexible woven cloth coated on
the inner surface with a thermoplastic polymer. The thermoplastic
polymer coating prevents the passage of gas through bottom sheet 36
and allows bottom sheet 36 to be joined to top sheet 34 as
described above and below. In the preferred embodiment the
thermoplastic coating on bottom sheet 36 is polyurethane. It will
be appreciated by those skilled in the art that other thermoplastic
polymers, polyvinylchloride for example, may be used as coatings on
top sheet 34 and bottom sheet 36 providing they can be joined with
sufficient strength to maintain the integrity of cuff 10 when
inflated.
[0039] As shown in FIG. 2, cuff port 20 has a right angle
configuration and includes a flange. Cuff port 20 is made of a
thermoplastic polymer that is compatible with and can be joined to
the thermoplastic coating of top sheet 34 to form a gas-tight
seal.
[0040] Tie strap 16 is a soft fabric ribbon material that is shown
in FIG. 2 positioned between bottom sheet 36 and top sheet 34. As
described below, tie strap 16 is secured to the inner coated
surface of bottom sheet 36. This configuration positions the tie
strap 16 away from the surface of the patient limb and promotes
even pressure distribution from the overlapping bladder. Tie strap
16 may also be secured to the inner surface of top sheet 34. Tie
strap 16 provides a means for the user to align and pull cuff 10
snug around the limb when tied as shown in FIG. 1, helps maintain
the overlapping portion of the cuff in alignment around the limb by
preventing the inflated cuff from twisting, telescoping and rolling
on the limb when inflated. Tie strap 16 may be coated with a
thermoplastic polymer that is compatible with the polymer coating
on bottom sheet 36 to permit it to be welded to bottom sheet 36 or
may be comprised of materials that adhere to the coated surfaces of
bottom sheet 36 and top sheet 34.
[0041] Secondary fastener 40 is hook material similar to the hook
material that comprises securing strap 32. Secondary fastener 40 is
attached to the outer surface of bottom sheet 36 and engages with
the loop material of top sheet 34. Secondary fastener 40
facilitates cuff application and alignment of the cuff by providing
a means for maintaining cuff 10 in position around patient limb 12
while securing strap 32 is engaged. Secondary fastener 40 acts
independently of securing strap 32 providing increased safety by
helping to ensure the cuff remains overlapped and secured in a
substantially circumferential direction if securing strap 32 is not
engaged or becomes ineffective while the cuff is inflated.
[0042] Stiffener 38 is made of a gas impermeable thermoplastic
polymer sheet cut to a rectangular shape to fit within the
perimeter of bladder perimeter weld 42 shown in FIGS. 3a, 3b and 6.
The length dimension of stiffener 38 is at least equal to the
circumference of patient limb 12 at the location that cuff 10 is
applied to patient limb 12. Top sheet 34 and bottom sheet 36 are
welded together at bladder perimeter weld 42 to form an inflatable
bladder 44 shown in FIGS. 4a, 4b, 4c, and 5. The length dimension
of inflatable bladder 44 is greater than the circumference of
patient limb 12 at the location that cuff 10 is applied to patient
limb 12.
[0043] Stiffener 38 is less flexible than top sheet 34 and bottom
sheet 36 but is flexible enough to be wrapped around a limb (for
example, 0.020'' thick polyurethane/polyvinylchloride alloy sheet
or polyethylene sheet). The properties of stiffener 38 are selected
such that the forces required to bend stiffener 38 across its width
are significantly greater than those required to bend top sheet 34
across its width by an equal amount. When secured circumferentially
around the limb as shown in FIG. 1, stiffener 38 helps direct the
expansion of inflatable bladder 44 radially inwards towards the
limb upon inflation of cuff 10. The stiffener thus provides
uniformly distributed pressure onto limb. Attaching stiffener 38 to
top sheet 34 prevents top sheet 34 from moving relative to
stiffener 38 and thereby helps prevent cuff 10 from rolling down
patient limb 12 when cuff 10 is inflated. The attachment of
stiffener 38 to top sheet 34 permits the use of thin flexible
materials for top sheet 34 and bottom sheet 36 making for a thinner
overall cuff which is desirable as thin cuffs afford an improved
fit to the patient limb with less wrinkling of materials. Some
prior art cuffs with a stiffener floating within the bladder use
heavier stiffer materials for the bladder walls to resist rolling
along the limb. These thick materials result in increased wrinkling
of the bladder surfaces when the cuff is applied to the limb.
[0044] The width of stiffener 38 is less than the width of
inflatable bladder 44 when cuff 10 is laid flat. The width of
stiffener 38 determines the degree to which bladder 44 can expand
(or reach) to apply pressure into the limb. Unlike prior art cuffs
that have a stiffener extending beyond the width of the inflatable
bladder, cuff 10 has greater reach and thereby results in lower
limb occlusion pressures than those obtainable with prior art
cuffs. In the preferred embodiment a surface of the thermoplastic
polymer that comprises stiffener 38 is compatible with the
thermoplastic coating of top sheet 34 and is welded to the inner
surface of top sheet 34 by the dielectric welding process described
above. Stiffener 38 is prevented from welding to the inner surface
of bottom sheet 36 by an incompatible coating which is applied as
described below to either a surface of stiffener 38 or to a portion
of the inner surface of bottom sheet 36.
[0045] Welds that attach the inner surface of top sheet 34 to
stiffener 38 form gas-tight seals at their perimeters and define a
non-inflatable portion or portions of top sheet 34. In prior art
cuffs with floating or unattached stiffeners within the bladder the
outer surface of the bladder is free to expand outward away from
the limb when the cuff is inflated. This expansion or "ballooning"
of the outer surface of the bladder is undesirable, especially in
areas where velcro-type fasteners are mated to the outer surface to
secure the cuff around the limb. In the preferred embodiment
non-inflatable portions of top sheet 34 and stiffener 38 remain in
substantially the same plane and do not balloon outward when the
cuff is inflated thus providing a more secure attachment area for
velcro-type fasteners.
[0046] FIGS. 3a and 3b are top views of the preferred embodiment
laid flat showing the areas where the inner surface of top sheet 34
are welded to bottom sheet 36, cuff port 20 and stiffener 38. The
separate weld areas shown in FIGS. 3a and 3b are: bladder perimeter
weld 42, cuff port weld 46, tie strap retaining weld 48, and
stiffener retaining weld 52. The dies used to form these welds may
be adapted to produce marking in bladder perimeter weld 42 and
stiffener retaining weld 52. The marking that is formed is integral
to the welded areas and easily visible to a user as described above
to indicate to a user that cuff 10 is intended for a single use
only. Bladder perimeter weld 42 defines inflatable bladder 44 of
cuff 10 which is shown in FIGS. 4a, 4b, 4c, and 5. Cuff port 20,
cuff tubing 22 and cuff connector 24 provide a pneumatic passageway
communicating with inflatable bladder 44 through which bladder 44
may be inflated.
[0047] The perimeters of stiffener retaining weld 52 and cuff port
weld 46 define a non-inflatable portion of top sheet 34. This
non-inflatable portion of top sheet 34 does not form part of
inflatable bladder 44 and pressurized gas does not contact this
portion of top sheet 34.
[0048] FIG. 3a shows non-inflating region weld 50, the perimeter of
which defines a non-inflating region near the end edge of cuff 10.
In FIG. 3a, securing strap 32 is shown sewn at location 54 to the
upper surface of cuff 10 (outer surface of top sheet 34) within the
perimeter of non-inflating region weld 50, in the preferred
embodiment secondary fastener 40 is also sewn to the bottom surface
of cuff 10 (outer surface of bottom sheet 36) at location 54
opposite the attachment point of securing strap 32. It will be
apparent that securing strap 32 and secondary fastener 40 may be
attached by other mechanical fastening means or by welding or
adhesives. It will also be apparent that a surface of securing
strap 32 may be coated with a thermoplastic polymer and joined by
welding in between top sheet 34 and bottom sheet 36.
[0049] In FIG. 3b bladder perimeter weld 42 is shown extended to
near the end edge of cuff 10 eliminating non-inflating region weld
50. It will be apparent that the width of the bladder perimeter
weld 42 may be increased near the end edge of the cuff to join top
sheet 34 to bottom sheet 36 out to the end edge of cuff 10.
[0050] In FIG. 3b securing strap 32 is shown non-releasably
attached to the non-inflatable portion of top sheet 34 within the
perimeter of stiffener retaining weld 52 at location 56. Securing
strap 32 may be sewn or attached by other mechanical fastening
means to top sheet 34 as the attachment is not required to be
gas-tight as it is made within the non-inflatable portion of top
sheet 34. Securing strap 32 may also be welded or adhesively bonded
at location 56 to non-releasably attach securing strap 32 to top
sheet 34.
[0051] The length of securing strap 32 may also be increased to
permit a greater area of engagement of the hook and loop materials
of securing strap 32 and top sheet 34 within the non-inflatable
portion of top sheet 34. If the area of hook and loop engagement is
sufficiently large to maintain cuff 10 secured around a limb when
inflated, the attachment at location 56 may be eliminated.
[0052] When cuff 10 is secured around a limb and inflated, securing
strap 32 comes under considerable tension. The amount of tension
securing strap 32 and its attachment location is subject to is
dependent upon the circumference of the limb and the pressure to
which bladder 44 is inflated. In the configuration of cuff 10 shown
in FIG. 3b securing strap 32 includes a hole formed to allow cuff
port 20 to pass through securing strap 32. When securing strap 32
comes under tension securing strap 32 may stretch and move
slightly. In the preferred embodiment the hole formed in securing
strap 32 is sized, shaped, and positioned to prevent securing strap
32 from transferring load to the sides of cuff port 20 when
securing strap 32 is tensioned.
[0053] As shown in FIG. 3b and shown in cross section in FIG. 5
securing strap 32 is also non-releasably attached to cuff 10 by
retaining ring 58. Retaining ring 58 is formed from rigid
thermoplastic and non-releasably engages within a grove formed in
cuff port 20. Retaining ring 58 has an outer diameter that is
greater than the diameter of the hole that is formed in securing
strap 32 for cuff port 20 to pass through. Retaining ring 58 acts
to prevent detachment of securing strap 32 by a surgical user from
top sheet 34 near the location of cuff port 20.
[0054] The attachment of securing strap 32 within the
non-inflatable portion of top sheet 34 allows loads to be
transferred from securing strap 32 to stiffener 38 by stiffener
retaining weld 52. Top sheet 34 may be joined to stiffener 38 in
additional locations to aid in the transfer of loads from securing
strap 32 to stiffener 38.
[0055] When cuff 10 is configured as shown in FIG. 3b, secondary
fastener 40 may be attached to the outer surface of bottom sheet 36
by welding or by an adhesive.
[0056] Tie strap 16 is permanently attached to cuff 10 by tie strap
retaining weld 48 shown in FIGS. 3a, 3b, and 6. Top sheet 34, tie
strap 16, and bottom sheet 36 are joined together at tie strap
retaining weld 48.
[0057] Cross section 4 from FIG. 3a of cuff 10 is shown in FIGS.
4a, 4b and 4c. FIGS. 4a, 4b and 4c depict the regions where
surfaces of the components of cuff 10 are joined together by welds
and show alternate methods for preventing selected surfaces of the
components of cuff 10 from forming welds during the welding
process.
[0058] Referring to FIG. 4a, top sheet 34 is joined to bottom sheet
36 at bladder perimeter weld 42 forming inflatable bladder 44. In
the preferred embodiment bladder perimeter weld 42 does not extend
to the longitudinal side edges of top sheet 34 and bottom sheet 36
thereby leaving a non-welded edge 60 along the length of cuff 10.
This non-welded edge provides a softer more compliant edge for
patient comfort than can be obtained when the width of the bladder
perimeter weld 42 extends completely to the side edges of top sheet
34 and bottom sheet 36.
[0059] Cuff port 20 is joined to the inner surface of top sheet 34
and outer surface of stiffener 38 at the location of cuff port weld
46.
[0060] As shown in FIGS. 3a and 3b, stiffener retaining weld 52 is
formed around the perimeter of stiffener 38 and acts to
non-releasably attach the outer surface of stiffener 38 to the
inner surface of top sheet 34, thereby preventing stiffener 38 from
moving relative to top sheet 34 when cuff 10 is inflated. As
described above, the perimeter of stiffener retaining weld 52
defines a non-inflatable portion of top sheet 34. Stiffener
retaining weld 52 is shown in FIGS. 3a and 3b as a contiguous weld
defining a single non-inflatable portion of top sheet 34, it will
be apparent that top sheet 34 could be joined to stiffener 38 by
multiple welds forming multiple non-inflatable portions of top
sheet 34.
[0061] As shown in FIG. 4a the thermoplastic polymer of stiffener
38 is compatible with the thermoplastic coating on the inner
surface of top sheet 34 and the two surfaces can be welded to each
another. To permit cuff 10 to be manufactured in a single
dielectric welding operation, a barrier 62 is applied to the inner
surface of stiffener 38. Barrier 62 is a coating of thermoplastic
material (for example polyethylene) that is not compatible with the
thermoplastic coating on the inner surface of bottom sheet 36 and
acts to prevent stiffener 38 from welding to the thermoplastic
coating on the inner surface of bottom sheet 36 at the location of
stiffener retaining weld 52 and cuff port weld 46.
[0062] The cross section of cuff 10 shown in FIG. 4b illustrates an
alternate location for barrier 62. As shown in FIG. 4b barrier 62
is applied to a region of the inner surface of bottom sheet 36 such
that stiffener 38 is prevented form welding with the thermoplastic
coating on the inner surface of bottom sheet 36 at the location of
stiffener retaining weld 52 and cuff port weld 46.
[0063] In FIG. 4c, stiffener 38 is formed from a thermoplastic
which will not weld with the thermoplastic coatings on top sheet 34
and bottom sheet 36, such as polyethylene. To permit a stiffener
made of an incompatible thermoplastic to be attached to the inner
surface of top sheet 34, a stiffener coating 64 of a compatible
thermoplastic such as polyurethane is laminated to the outer
surface of stiffener 38. This laminated coating allows stiffener 38
to be non-releasably attached to the inner surface of top sheet 34.
It will also be appreciated that stiffener 38 may be non-releasably
attached to the inner surface of top sheet 34 by an adhesive bond
by selecting and applying an adhesive compatible with the
thermoplastic surfaces of top sheet 34 and stiffener 38.
[0064] To reduce material costs cuff 10 may be configured as shown
in FIG. 6. In FIG. 6 cuff 10 is shown with a securing strip 66
joined to the outer surface of top sheet 34. Securing strip 66 is a
strip of nylon loop material compatible with the hook material of
securing strap 32. Securing strip 66 is coated on one surface with
thermoplastic polymer material. In FIG. 6 top sheet 34 is
configured as woven nylon fabric with a thermoplastic polymer
coating on both the inner and outer surfaces. The thermoplastic
polymer coating on the outer surface is typically thinner than the
coating on the inner surface and provides a weldable surface for
the attachment of securing strip 66. As shown in FIG. 6, securing
strip 66 is attached to top sheet 34 at securing strip perimeter
weld 68. Securing strip 66 is also attached to top sheet 34 by cuff
marking weld 70. The shape of cuff marking weld 70 is selected to
form the standard symbol for single use only devices to indicate to
a user that cuff 10 is intended for a single use only. Stiffener 38
may also be bonded to the inner surface of top sheet 34 at the
locations of securing strip perimeter weld 68 and cuff marking weld
70 to form non-inflatable portions of top sheet 34.
[0065] A portion of securing strap 32 is non-releasably attached to
securing strip 66 at location 72. Securing strap 32 may be attached
to securing strip 66 by sewing or welding. The length of securing
strap 32 may also be increased to permit a greater area of
engagement of the hook and loop materials of securing strap 32 and
securing strip 66. If the area of hook and loop engagement is
sufficiently large to maintain cuff 10 secured around a limb when
inflated, the attachment at location 72 may be eliminated.
[0066] A hole formed in securing strap 32 as described above allows
cuff port 20 to pass through securing strap 32. As shown in FIG. 6
securing strap 32 is also attached to cuff 10 at location 74 beyond
the end edge of bladder perimeter weld 42. In the preferred
embodiment securing strap 32 is attached at location 74 by sewing
through top sheet 34 and bottom sheet 36. The attachment of
securing strap 32 at location 74 allows loads from securing strap
32 to be distributed to bottom sheet 36 and evenly to both sides of
cuff port 20, it also prevents a user from applying loads to cuff
port 20 when manipulating securing strap 32 during cuff application
and removal. If securing strap 32 is not non-releasably attached at
location 72, the non-releasable attachment at location 74 acts to
maintain securing strap 32 in the correct position and orientation
on cuff 10 and prevents securing strap 32 from being inadvertently
removed from cuff 10 by a user. Securing strap 32 may also be
attached at location 74 by other mechanical fastening methods or by
adhesives or welding. Top sheet 34 and bottom sheet 36 may be
welded together at location 74 to provide a stronger area for the
attachment of securing strap 32.
[0067] The embodiment illustrated is not intended to be exhaustive
or limit the invention to the precise form disclosed. It is chosen
and described in order to explain the principles of the invention
and its application and practical use, and thereby enable others
skilled in the art to utilize the invention.
* * * * *