Note: Descriptions are shown in the official language in which they were submitted.
-
~;~6~7~7
YOK~ OR THE HARNESS OlF A Rl~SPIRATOR
~IELD O~ TEIE INVE~TION
This invention related to a yoke by means of which a harness of elastic
straps may be attached to the face piece of a respirator, the straps being
employed for securing the face piece over the nasal and oral areas of a
user's face in surrounding sealing relationship with those areas.
BACKGROUND OF THE INVENTION
Respirators commonly include a face piece molded from a soft, pliable,
rubber-like material, the face piece supporting members for attaching one
or more air-purifying cartridges to the face ~iece, and îor attaching an
exhalation valve, the said members being accommodated in apertures through
the face piece.
In order to secure the face piece over the user's nasal and oral areas,
straps are attached to rearward portions of the mask, the straps usually
being of an elastic material for them to be passed over or around the
user's head, and then adjusted for them to draw the mask into sealing
relationship with the nasal and oral areas of the user's face in a continuous
line or zone extending around the user's nose and mouth.
.
TF113 PRIO~ ART
A typical example of such a respirator is disclosed in United States
Patent 4,414,973, Matheson et al. The respirator of that patent includes
dual members for attaching air-purifying cartridges to the face piece and
which are arranged at the lateral sldes of a face piece, and, a centrally
~V
79~7
arranged exhalation valve. rhe face piece of this patent is to be helcl
positioned on the user's head by a plurality of straps, the straps bein~
secured to the mask by eyelets received over button-lilce members formed
integrally with the face piece at positions adjacent to the peripheral edge
thereof.
In this construction, any stresses imposed on or generated in the straps
must be absorbed by the face piece itself. As a consequence, the face
piece must be made of enhanced strength and resistance to distortion for
it to resist such stresses.
It has been proposed to relieve the face piece from such stresses by
attaching the harness of straps to a yoke that is attached to the face piece
at a single point at the front of the face piece. While this construction
has the advantage of relieving the face piece from distortions in lateral
directions resulting from stresses set up in the straps7 it tends to be less
stable in its intended purpose of immobilizing the face piece in continuous
sealing engagement with the user's face.
THE I~VleNllON CONOEPT
In accordance with the present invention, there is provided a yoke for
securing a harness of straps to the face piece of a respirator, which, in
addition to locatin~ the face piece over the user's nasal and oral areas
with greater stability and immobility, also acts to equalize the stresses
produced in the straps, and to transfer those stresses to the face piece and
to the user's face in a manner enhancing the seal provided by the face
piece against the face of the user, despite facial differences of the user,
;or~
who may be broad-featured, or sharp-featured, and have either a long or
short facial profile.
According to the present invention, the yoke is comprised by a unitary
laminar member of inverted butterfly shape formed from a stiff and
relatively inflexible material, the wings of the butterfly shape being
interconnected by a stiff and relatively in1exible central portion of the
yoke through the intermediary of webs of lesser thickness than the thickness
of the wings and central portion, and which act as spring-hinge members
permitting resiliently restrained movement of the wings relative to the
central portion.
The stief and relatively inflexible central portion is attached to a planar
front surface of the face piece at spaced positions lying in a vertical plane
bisecting the face piece, for the wings to diverge outwardly from the face
piece and be cantilevered and resiliently restrained against displacement.
Accordingly, the face piece is readily positionable in lateral directions
for it to be brought into the required sealing relationship with the user's
face, but is restrained from angular or rotational movement relative to the
yoke. The interconnections of the yoke and face piece act to inhibit
relative rotational movement between those members, other than about an
axis lying in said plane and whieh passes through the said spaced positions
of attachment of the yoke and face piece.
The stresses produced by the straps attached to the yoke also pass
through that axis, and are equally and symmetrically dissipated in the face
piece in a manner minimizing flexure and distortion of the face pieae, the
resilient interconnection of the wings of the yoke and the central portion
thereof, also acting to dissipate and equalize such stresses.
The face piece can thus be formed from an extremely soft and pliable
material and of relatively li~lt weight, the danger of collapsing of the face
piece under the stresses imposed thereon being eliminated by the equalization
and distribution of the stresses.
Preferably, the yoke is apertured in order to reduce its weight and in
order to accommodate the attachment of air-purifying cartridges to the
face piece, and, in order that it may lie positioned between the face piece
and the adjacent air-purifying cartridge. The yoke is also apertured to
accommodate a frontly positioned exhalation valve~ or a speaking diaphragm
or cartridge if such device is provided.
Also, preferably, the yoke is in the form of three open interconnected
trapezoidal shapes,which in combination act to stabilize the positions of
the yoke under the stress loading of the straps.
Also, preferably, the yoke is a molding of plastics material which has
been molded in a substantially flat or planar condition, and which has been
subsequently bent about axes extending through the webs to permanently
deform the webs and enhance their resilient resistance to further flexing
moments.
D~SCRIPTION Ol~ THE DRAWINGS
The invention will now be described with reference to the accompanying
drawings, which illustrate a preferred embodiment of the invention, and,
in which:
FIGURE 1 is a perspective view of the yoke of the present
invention shown attached to a respirator face piece;
~2tj~ 7
FIGIJRES 2 and 3 are front and rear elevations of the yoke,
respectively, in the flattened or planar condition in which it is
manufactured; and,
FIGURE 4 is a plan view of the yoke of the present ;nvention,
shown attached to a face piece, as illustrated in ~igure 1.
D~SC~IPTION OF THlE PRE~ERRED ~MBODIME~TS
In the drawings, the face piece is indicated at generally at 10, and the
yoke is indicated generally at 12. The face piece may be formed from
any soft pliable and ~lexible elastomeric material, such as a soft rubber, as
is well-known in the art9 a preferred material for use in the face piece
being a soft and pliable silicone rubber. As is also well known in the art,
the face piece is provided with flexible flanges 14 at the rear edges thereof
for engagement with the user's face in a continuous line or area extending
about the nasal and oral areas of the user's face, for the user's nose and
mouth to be located within the confines of the face piece. The face piece
extends forwardly of the user's face to provide a confined air space 15
within the face piece, and is suitably apertured to accommodate supporting
members 16 for air purifying cartridges (not shown) which are attachable
to threaded portions 17 of the supporting members. The face piece is also
suitably apertured to accommodate an exhalation valve 18.
The front face of the face piece is formed with a substantially flat
and planar surface 20, from which extend two securing members or buttons
22, the buttons 22 being molded integrally with the face piece and thus
being of the same pliable and flexible material as the face piece. Preferably,
797
the buttons are of forwardly conical shape, as illustrated, to facilitiate
their insertion through apertures in the yoke 12, as is later described.
The buttons 22 are spaced vertically of the planar surface 20, for them
to lie in a vertical plane which includes the axis ~-A indicated in Figure 1,
and which bisects the face piece 10.
The yoke 12 is comprised of a unitary lamina and includes a central
or medial portion 3U, which, as is more clearly illustrated in Figures 2 and
3, is apertured at 32, for it to receive the buttons 22, the buttons hav;ng
suitably undercut portions to restrain them from removal from the apertures
32,32, and for them to retain the yoke 12 firmly attached to the face
piece 10 with the said central portion ~0 engaged by and firmly seated on
the planar surface 20 of the face piece. The yoke 12 may be formed
from any suitable plastics material, such QS hard nylon, polyolefin, or a
similar materi~l, and preferably is formed as a substantially planar molding
of that material, as illustrated in Figures 2 and 3, which is subsequently
bent to form dihedrals, as illustrated in Figure 4. Typically, the yoke 12
will have a thickness in the order of O.OS inches, but may be of greater
or lesser thickness depending on the specific plastics material employed in
its manufacture.
Extending from each side of the central portion 20, are wing portions
34, the wings being Q mirror image in shape of each other. The wings 34
are respectively connected with the central portion 30 through the
intermediary of hinge portions 3~ which are positioned slightly beyond the
side edges of the planar surface 20, the hinge portions 3~ being of lesser
thickness than that of the central portion 30 and that of the wings 34, for
example, of a thickness of 0.025 inches.
1~:6(~7~37
~ s will be more clearly apparent from Figure 3, the hinge portions 36
at the opposite sides of the medial portion 30 are arranged in lines that
are inclined relat;ve to each other and which are also inclinecl relative to
the said plane ;ncluding the axis A-A. Thus, upon flexure of the yoke 12
about the hinge lines 36, compressive stresses are set up in the wings 34
which tend to cause the wings to assume an outwardly dished concave shape
instead of being substantially planar.
The formation of the hinge portions 36 for them to be of lesser
thickness than that of the central portion 30 or the wings 34, and thus of
greater flexibility, insures that the yoke will flex predominantly or
exclusively along the lines of the hinge portions 36. Upon the assembly of
the yoke onto the face piece and the orientation of the wings 3~ as
dihedrals, the wings 34 become accurately oriented and positioned at the
sides of the face piece in an entirely predictable manner, as is illustrated
in Figure 4. Additionally, the wings tend to assume a concave shape, more
readily conforming the wings to the exterior configuration of the mask and
further equalizing the stresses produced by the straps.
Subsequent to the assembly of the yoke onto the face piece, air-
purifying cartridges (not shown) are attached to the face piece 10 by
threading them onto the threaded portions 17 of the supporting members
16. In order to provide access to the threaded portions 17, the respective
wings 34 are apertured at 38 for the wings to lie located and confined
between the face piece 1û and the respective air-purifying cartridges. In
this position, the wings of the yoke are constrained against outward
movement, but are still moveable between a position in which they engage
the adjacent air-purifying cartridge, and a position in which they engage
~LXÇ~ 7
the adjacent outer surface of the face piece. This is illustrated in Figure 4
as permitted resiliently restrained hinging movement of the wings through
the angle "~", the probability belng that prior to the positioning of the
respirator over the user1s head, the wings will be resiliently biased outwardly
into engagement with the adjacent air-p~lrifying cartridge.
Bails 40 are provided on the yoke for the attachment of the usual
elastic straps (not shown) used for holding the respirator positioned on the
user's head.
As will be apparent, within a range determined by the permitted
movement "X" of the respective wings 34, the straps will exert a direct
pull on the respective wings to place them in tension, to the exclusion of
any lateral bending movements exerted on the wings, the wings themselves
being capable of movement into alignment with the forces exerted by the
straps.
In this manner, it is arranged that the forces exerted by the straps on
the respective wings 34 are transmitted through the respective hinge portions
36 and directly to the central portion 20, where they are resolved as
opposing inclined tensional forces. The resultant of those forces acts to
draw the face piece 10 perpendicularly into intimate sealing engagement
with the user's face, to the substantial exclusion of any forces acting
laterally of that plane and which could cause the face piece to lift or
distort at the peripheral edge thereof. By this construction, improved
protection factors can be obtained, since the effect of changes in strap
tension and angular vectors created predominately in the lower (neck) strap
as the wearer turns his/her head from side to side are more compensatingly
resolved thus adding to face piece stability. ~urther, by attaching the
)7137
yoke 12 to the face piece tO at positions spaced vertically in the plane of
the flXiS A-A, and by seating the central portion 30 of the yoke 12 on the
planar surface 20 of the face piece, unequal stresses imposed on the wings
by the elastic straps are further equalized and uniformly distributed within
the yoke. The forces are resolved in the face piece 10 as a substantially
uniform force acting perpendicularly of the front face of the face piece,
and thus throughout the entire perimeter of the mask, this resulting in the
elimination of high pressure spots or zones, such as can cause severe
discomfort and annoyance to the wearer of the respirator.
This equalization of the forces will occur even in the event -that the
face piece sholdd be positioned slightly of-center on the user's face, in
that the central portion 30 of the yoke is free to pivot about the hinge
portions 36 and redistribute and equalize the pressures exerted by the face
piece on the user's face, again resulting in the force transmitted by the
yoke being in the direction of the plane of the axis A-A.
Of importance in this respect is the securing of the yoke 12 to the
face piece 10 at vertically spaced positions medially of the face piece, the
face piece being oppositely symmetrical on both sides of the plane including
the axis A-A. In the presence of rotation of the yoke and face piece
relative to each other in the plane of the surface 20, then, the face piece
10 would move out of symmetry with respect to the yoke 12, and, forces
would be produced in the face piece on opposite sides of a plane transverse
to the axis A-A and extending through the point of relative rotation between
the yoke and the face piece, with consequential discomfort to the wearer
of the respirator.
7g7
As the wings 34 are hingecl to the central portion 20 of the yoke,
albeit resiliently restrained, the wings 34 can move between the extremes
of the angle "X". In this manner, within a determined range of skull widths
of various users, the advantages of equalization of the forces transmitted
to the face piece is retained, the wings assuming a widely splayed position
i-f the respirator is worn by a person having a broad skull, and moving
towards a more narrowly splayed position if the user has a lesser skull width.
As illustrated in the drawings, yoke 12 in addition to being provided
with apertures at 38, also is provided with a central aperture 42 which
extends entirely through the central portion 30 and into the respective wing
portions 34. In this manner, yoke 12 is of universal application to ~ace
pieces having lateral support members for the attachment of air-purifying
cartridges, or, ones in which the air-purifying cartridge replaces the
exhalation valve 18, the exhalation valve then being located in the planar
surface 20 and intermediate the securing members 22.
A considerable advantage arises from this triptych arrangement of the
apertures 38 and 42, and the resulting open framework form of the yoke
12. Not only is the yoke 12 of reduced weight, but, to the greatest possible
extent its strength und rigidity is preserved, while at the same time
facilitating the transrnission and equalization of the stresses produced in
the yoke.
As so formed, the yoke 12 is of inverted butterfly shape, the respective
apertures effectively dividing the yoke into three interconnected
substantially trapezoidal portions.
The outermost ones of those portions are provided by a major portion
of the wings 34, the bails 40 for connection of the straps being located at
.
3'7~7
the outermost adjacent pairs of corners of the respectlve wing portions 34.
The innermost sides of the outermost pair of trapezoidal portions are
comprised by the bridging members 34a of the wing portions 34, the bridging
portions 34a constituting opposite sides of a trapezoidal portion intermediate
the outer trape~oidal portions The intermediate portion is comprised by
the central portion 30 and the interconnected portions of the wing members
34.
By this construction, stresses exerted by straps attached to the
respective bails 40 are transmitted directly to both of the securing members
22. In the absence of the dual securing members 22, the resulting forces
would tend to rotate the yoke relative to the face piece, with the
consequences previously described. Any such attempted relative rotation
is prevented by the dual attachment of the yoke to the face piece, with
the result that the forces produced by each one of the straps is resolved
in both of the securing members, with better equalization of the forces
transmitted to the face piece. ~urther, any tendency of the respective
pairs of bails to move towards or away from each other is effectively
resisted by the bridgin~ portions 34a and 34b, which act as struts maintaining
the respective bails a~o in correctly spaced positions relative to the adjacent
bail.
It will be appreciated that the structure described above is a preferred
embodiment of the present invention~ and, that various modifications of
the structure may be made without departing from the scope of the appended
claims. For example, in the event that the yoke is to be employed solely
with a face piece having dual air-purifying cartridges, then, the central
aperture 42 could be omitted. Conversely, if the face piece is to have a
;(t~7
single air-purifying cartridge and a centrally arranged exhalation valve,
then, the shape of the apertures 38 could be approximately modified to
decrease the extent of the lower lobes of the wings 34.
12
