U.S. patent application number 11/051896 was filed with the patent office on 2006-09-07 for vent assembly.
Invention is credited to Richard J. Camarota, Richard JR. Hartmann.
Application Number | 20060199493 11/051896 |
Document ID | / |
Family ID | 36944701 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060199493 |
Kind Code |
A1 |
Hartmann; Richard JR. ; et
al. |
September 7, 2006 |
Vent assembly
Abstract
A vent assembly, suitable for marine use including, for example,
venting an enclosure, such as an engine compartment, on a boat. The
vent assembly has substantially the external appearance of a cast
or machined, one piece, stainless steel vent, at a cost very little
more than a molded plastics vent. A molded plastics vent has a head
perforated by a pattern of ventilating slots separated by flanking
strips. A decorative, corrosion-resistant, sheet metal cover shell
lies tight against the front side of the molded plastics vent and
has a pattern of slots and strips mapping substantially on the
pattern of slots and strips of the molded plastics vent. Snap-fit
fasteners fix the cover shell on the vent so that the cover shell
slots are a substantially flush continuation of the vent slots, so
as to provide the decorative appearance of a solid metal vent at
substantially lower cost and without compromising or through flow
capability.
Inventors: |
Hartmann; Richard JR.;
(Holland, MI) ; Camarota; Richard J.; (Holland,
MI) |
Correspondence
Address: |
FLYNN THIEL BOUTELL & TANIS, P.C.
2026 RAMBLING ROAD
KALAMAZOO
MI
49008-1631
US
|
Family ID: |
36944701 |
Appl. No.: |
11/051896 |
Filed: |
February 4, 2005 |
Current U.S.
Class: |
454/81 |
Current CPC
Class: |
B63B 2231/06 20130101;
F24F 13/084 20130101; B63J 2/10 20130101 |
Class at
Publication: |
454/081 |
International
Class: |
B63B 19/04 20060101
B63B019/04 |
Claims
1. A vent assembly, suitable for mounting in a hole in a wall of an
enclosure, to vent such enclosure, and comprising; a molded
plastics vent having a radially extending head, said head having a
radially outward facing edge and having a continuous peripheral
edge portion inboard of said edge, said head being perforated by a
pattern of elongate ventilating slots extending axially
therethrough and laterally to said peripheral edge portion, ones of
said slots having end walls at said peripheral end portion, said
slots being separated by flanking strips defining sidewalls of said
slots, said head having front and back sides separated by said
radially outward facing edge and through which said slots open,
said molded plastics vent having a generally tubular base extending
substantially coaxially from said head back side at said peripheral
edge portion, said base being spaced inboard of said radially
facing edge by a coaxial, radially extending, rear facing,
enclosure wall abutting, annular lip and having a coaxial
throughpassage communicating with said slots; a radially extending,
decorative, corrosion resistant, sheet metal cover shell lying
tight against said front side of said vent head, said shell having
a continuous peripheral edge portion mapping on said head
peripheral edge portion and a pattern of slots mapping on said
pattern of vent head slots in shape, size and relative location,
said cover shell slots being separated by strips substantially
mapping on said vent head strips in shape, size and relative
location, an edge of a given cover shell slot being a substantially
flush, forward continuation of the adjacent edge of the
corresponding vent head slot to minimize disruption of airflow
through the vent assembly, said cover shell including resiliently
bendable, cantilevered tabs angled substantially rearwardly from
ends of ones of said shell slots and extending into adjacent vent
head slot ends, a given said tab having a leg extending along and
adjacent the opposed vent head slot end wall, a heel protruding
from the free end of said leg beyond said vent head slot end and
snugly behind said vent head peripheral edge portion and locking
said cover shell on the front face of said vent head, a foot
extending rearward from the radially outboard end of said heel, and
a toe angled rearward and radially inward from the free end of said
foot, said toe having a cover shell installing position bearing
cammingly on the front of said vent head peripheral edge portion to
assist snap-fit installation of said tab in its said vent head
slot, said cover shell being contoured three dimensionally in a
shallow, cup-like shape having a front wall incorporating said
slots and strips and a peripheral wall covering said radially
outward facing edge of said vent head to give the outside
appearance of a solid metal vent, said peripheral wall having an
enclosure wall approaching, free, peripheral edge rearwardly
approaching the plane of said vent head annular lip.
2. The apparatus of claim 1 in which the axial thickness of said
head strips and cover strips is approximately in the range of
ratios 1/20 to 1/80.
3. The apparatus of claim 1 in which said cover is a stainless
steel stamping.
4. The apparatus of claim 2 in which said front side of said vent
head is convexly rounded and said cover shell is correspondingly
convexly rounded and lies tight against said front side of said
vent head.
5. The apparatus of claim 4 in which said head slots extend
substantially parallel and widthwise of said head, said shell slots
extending correspondingly parallel and widthwise of said head.
6. The apparatus of claim 1 in which said cover shell has at least
one cross strap extending across at least one of said shell slots
and between flanking strips, said strap connecting and minimizing
deflection of said flanking shell strips.
7. The apparatus of claim 6 in which the width of said strap is at
most substantially the width of a said flanking shell strip to
minimize interference with flow through said head.
8. The apparatus of claim 1 in which the thickness of said cover
shell is in the range 0.2 mm to 1.0 mm.
9. The apparatus of claim 8 in which the thickness of said cover
shell is about 0.5 mm.
10. The apparatus of claim 1 in which said cover shall is of type
316 stainless steel sheet.
11. A vent assembly, suitable for marine use and the like, for
covering a vent opening while permitting air flow therethrough, and
comprising: a vent comprising a radially extending head perforated
by a pattern of ventilating holes extending axially therethrough,
said holes being separated by flanking portions defining side walls
of said holes, said head having front and back sides through which
said holes axially extend, said head having a radially outwardly
facing edge and a peripheral edge portion inboard of said edge; a
radially extending, decorative, corrosion-resistant, cover shell of
substantially rigid sheet stock, said cover shell lying tight
against the front of said vent head, said shell having a peripheral
edge portion mapping said head peripheral edge portion and a
pattern of holes mapping on said pattern of vent head holes in
shape, size and relative location, said cover shell holes being
separated by flanking portions substantially mapping on said vent
head portions in shape, size and relative location, an edge of a
given cover shell hole being a substantially flush, forward
continuation of the adjacent edge of the corresponding vent head
hole to minimize disruption of air flow through the vent assembly,
said cover shell being fixed on said vent head, said cover shell
forwardly and sidewardly covering said vent head.
12. The apparatus of claim 11 in which said cover shell has a rear
facing peripheral edge and said vent head has a rear facing surface
substantially flush with said cover shell rear facing edge, the
latter two being adapted to substantially abut an environmental
surface having a vent hole to be covered by the vent assembly.
13. The apparatus of claim 11 in which said vent is a molded
plastics mass and said cover shell comprises a sheet metal stamping
perforated by said holes, said sheet metal stamping including
integral rearward extending fastener elements in snap-fit
engagement with said mass.
14. The apparatus of claim 13 in which said fastener elements are
tabs bent rearward from the peripheral portion of the sheet metal
at edges of said holes, said tabs being elongate leaf spring-like
elements, a given said tab comprising an elongate rearward
extending leg received at the edge of a corresponding vent head
hole, said leg extending rearward through said corresponding vent
head hole and having a heel engaging a rearward surface of said
vent head at said corresponding vent head hole end to positively
hold said cover shell tight against the front of said vent head in
a positive yet resiliently releasable manner.
15. The apparatus of claim 11 in which said vent head has a
substantially dome shaped front portion, said cover shell being
three-dimensionally shaped to conform to said dome shape, said
cover shell continuously abutting and covering said vent head
forwardly and sidewardly.
16. The apparatus of claim 11 in which at least ones of said vent
head and corresponding cover shell holes are elongate slots.
17. The apparatus of claim 16 in which said cover shell slots are
mutually parallel.
Description
FIELD OF THE INVENTION
[0001] This invention relates to slotted vents, and more
particularly to slotted vents usable in marine applications such as
for ventilating a motor enclosure on a boat.
BACKGROUND OF THE INVENTION
[0002] U.S. Pat. No. 5,588,908, assigned to the assignee of the
present invention, discloses a apparatus for fixing a ventilating
hose at an opening in a wall of an enclosure, e.g. for use on a
boat in venting gases from the engine compartment, or venting
cooking odor laden air from the galley, or admitting air. That
apparatus includes a vent fitting comprising a radially extended,
slotted head adapted to rest against the exterior face of the wall
to hide an opening therein and a tubular body extending from the
rear face of the head through the wall opening, to fix the vent
fitting and an attached, rearwardly extending hose to the wall at
the opening, to communicate flow through the hose and slotted head.
To accomplish its various purposes, such vent fitting is of
relatively complex form. Despite this, the assignee of the present
invention has succeeded in forming such fittings of molded plastics
material at relatively low cost and has successfully marketed units
in substantial quantities, for example to boat manufacturers.
[0003] However, the present assignee has found that for more
expensive lines of boats, boat manufacturers and their buyers
prefer more expensive looking fittings, e.g. stainless steel
fittings, rather than less expensive looking molded plastics
fittings.
[0004] With that in mind, the present assignee has marketed molded
plastics fittings of this general type with exposed surfaces
chromium plated, by a conventional process, to achieve the richer,
more expensive appearance of a polished metal fitting. While
generally successful commercially, the present assignee has found
that continuing contact, over a long period of time, with the
elements in a harsh salt water marine environment, may attack, and
eventually degrade the appearance of, the plated visible surfaces
of such fittings.
[0005] Accordingly, the present assignee has considered producing
such fittings of corrosion resistant metal, such as stainless
steel, as by casting or machining, and while such product is
durable and can maintain a rich, expensive appearance over long
periods of use, it is many times more expensive to produce than the
same product of molded plastics material, and because of this
expense would have a very limited market.
[0006] The purposes of the present invention include overcoming
these conflicting prior difficulties.
SUMMARY OF THE INVENTION
[0007] This invention relates to a vent assembly, suitable for
marine uses including, for example, venting an enclosure, such as
an engine compartment, on a boat, which vent assembly has
substantially the external appearance of a cast or machined, one
piece stainless steel vent, at a cost very little more than a
molded plastics vent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a pictorial view of a prior molded plastics vent
substantially as disclosed in U.S. Pat. No. 5,588,908 assigned to
the assignee of the present invention.
[0009] FIG. 2 is an enlarged cross-sectional view of the FIG. 1
molded plastics vent.
[0010] FIG. 3 is a pictorial view of a cover shell of convexly
curved shape, taken from the front side thereof, and in accord with
a preferred embodiment of the present invention.
[0011] FIG. 4 is a pictorial view of the FIG. 3 cover shell taken
from the rear side thereof.
[0012] FIG. 5 is a front view of the FIG. 3 cover shell.
[0013] FIG. 6 is an enlarged fragmentary cross-sectional view
substantially taken on the line 6-6 of FIG. 5.
[0014] FIG. 7 is an enlarged, fragmentary cross-sectional view
substantially taken on the line 7-7 of FIG. 5.
[0015] FIG. 8 is a pictorial view of a preferred embodiment of a
molded plastics vent for which the FIG. 3 cover shell is
intended.
[0016] FIG. 9 shows FIG. 6 cover shell installed on a molded
plastics vent like that of FIG. 8.
[0017] FIG. 10 shows the FIG. 7 cover shell installed on a molded
plastics vent of the type shown in FIG. 8.
[0018] FIG. 11 is an enlarged fragmentary cross-sectional view
substantially taken on the line 11-11 of FIG. 5, and showing the
cover shell installed on the FIG. 8 vent.
[0019] FIG. 11A is a fragment of FIG. 11, but showing the FIG. 3
cover sheet tab at a starting position of installation on the FIG.
8 vent.
[0020] FIG. 11B is similar to FIG. 11A, but showing an intermediate
position of installation.
DETAILED DESCRIPTION
[0021] A vent 40 (FIGS. 1 and 2) is here formed to function as a
hose fitting. The vent 40 is formed (preferably molded) of a
suitable substantially rigid molded plastics material, such as
nylon or polypropylene. The molded plastics vent 40 includes a
radially extending head 42, here in the form of a circular face
plate. The head 42 has a radially outward facing edge 30 and a
continuous peripheral edge portion 43 inboard of the edge 30. The
head 42 is perforated by a pattern of elongate ventilating slots 31
extending axially therethrough and laterally to the peripheral edge
portion 43. The slots 31 have end walls 32 at the peripheral edge
portion 43. The slots are separated by flanking straps 46 defining
side walls 33 of the slots 31. The head 42 has front and back sides
20 and 21 respectively separated by the radially outward facing
edge 30 and to which the slots 31 open.
[0022] The molded plastics vent 40 also has a generally tubular
base 50 extending substantially coaxially from the back side 21 of
the head 42 at its peripheral edge portion 43. The base 50 is
spaced inboard of the radially facing edge 30 by a coaxial,
radially extending, rear facing, enclosure wall abutting, annular
lip 49 and has a coaxial through passage 51 communicating with the
slots 31.
[0023] In the embodiment shown in FIGS. 1 and 2, the generally
tubular base 50 is circumferentially segmented to form
circumferentially closely spaced, alternating lock tabs 45 and
locking fingers 52, all of which extend axially rearwardly from the
head back side at the peripheral edge portion 43. The lock tabs 45
and fingers 52 are of arcuate, circumferentially extending
cross-sectional profile. The rear edges of the lock tabs 45 are
radially inwardly beveled at 47.
[0024] The locking fingers 52 are located slightly radially
outwardly from the lock tabs 45. Each locking finger 52 has one or
more (here three) axially spaced, radially outwardly protruding,
circumferentially extending teeth 54 having a rearward and radially
outwardly beveled, generally rearwardly facing surfaces 56. The
rearwardmost tooth 54 forms the rear edge of the base 50 and its
beveled surface 56a extends the full radial thickness of the tooth.
The rearward end portion of each locking tooth 52 is thickened to
provide a slightly radially inwardly protruding lip 60. The teeth
54 and lip 60 extend circumferentially the width of the locking
finger 52. It will be understood that the locking fingers 52,
including their lips 60, are spaced radially outward from the outer
circumferential plane of the lock tabs 45 and preferably are
circumferentially narrower than the circumferential spaces between
the lock tabs 45. Circumferentially spaced, axially extending,
reinforcing, rib-like webs 58 protrude radially outwardly from the
radially outer face of the locking fingers 52 between the back side
21 of the head 40 and the nearest tooth 54.
[0025] The molded plastics vent 40 can be used as an end
termination for a ventilation hose 10 (FIG. 2), a ventilating
member to provide a finished appearance for a hole 14 in a wall 12,
or both. In the embodiment shown, the hose 10 is formed of a
flexible material in which a coiled wire 64 is embedded for
reinforcement. The front (leftward in FIG. 2) end of the hose is
forwardly inserted into the circumferentially continuous, radially
narrow, annular space between the lock tabs 45 and locking fingers
52 so as to closely approach or abut the back side 21 of the head
42 of the molded plastics vent 40, as permitted by the limited
radial bending capability at least of the fingers 52. So installed,
the radially inwardly protruding lips 60 on the fingers 52 axially
fix the hose 10 to the molded plastics vent 40 and prevent
unintended axial separation thereof. With an intermediate portion
of the hose 10 extending through the hole 14 in the wall 12,
rearward movement of the molded plastics vent 40 toward the wall
12, coaxially of the hole 14, inserts the generally tubular base 50
into the hole 14, such that the teeth 54 slide axially rearwardly
along the peripheral edge of the hole 14, camming and bending the
fingers 52 radially inwardly as needed, until the radially
extending head 42 of the vent 40 abuts the front face of the wall
12, thereby completing installation as seen in FIG. 2.
[0026] During installation, the tapered rearward surfaces of the
teeth 54 assist installation of the vent 40 in the wall 12, whereas
after installation the forward facing radially planar faces of the
teeth 54 resist removal of the vent 40 from the wall 12. The
radially inward bending of the locking fingers 52 by the peripheral
edge of the hole 14 helps the lips 60 of the fingers 60 fixedly
grip the hose 10 between themselves and the circumfererentially
flanking tabs 45.
[0027] To the extent of above discussed, the apparatus is
substantially that disclosed in the present assignees prior U.S.
Pat. No. 5,588,908.
[0028] FIG. 8 shows a further prior art vent 140 which may be
generally similar to the vent 40 above discussed with respect to
FIGS. 1 and 2, except as follows.
[0029] For example, the head 142 (FIG. 8) of the vent 140 has a
front side 120 of shallow, convexly rounded shape. Thus, the strips
146 have correspondingly somewhat convexly rounded front faces
147.
[0030] Turning now to aspects of the apparatus more directly
dealing with the present invention, attention is directed to FIGS.
3-11.
[0031] A radially extending cover shell 201 (FIGS. 3-5) is
preferably of a decorative, corrosion resistant, relatively stiff
material, such as sheet metal. In the preferred embodiment shown,
the cover shell 201 is of stainless steel sheet. Marine grade
stainless steel sheet is sufficiently corrosion resistant, even in
salt water environments, as to maintain a decorative appearance
over a long period of time.
[0032] The cover shell 201 has a continuous peripheral edge portion
205 surrounding a central portion 206 comprising a pattern of slots
211 separating by elongate strips 206, whose edges define
corresponding edges of the flanking slots.
[0033] The cover shell 201 has a front face 220 (FIG. 3) and a back
face 221 (FIG. 4). The cover shell 201 is contoured
three-dimensionally to continuously snugly cover, in a skin-like
manner, the front side of the head of a corresponding molded
plastic vent. Thus, in the embodiment shown, the cover shell 201 of
FIGS. 3-5 is three-dimensionally contoured to cover the convex
front face 147 of the corresponding vent 140 of FIG. 8, it being
understood that similar cover shells can be three-dimensionally
configured to similarly fit, in a skin-like manner, the front face
of the head of otherwise contoured vents, for example such as the
vent 40 in FIGS. 1 and 2 above-described, the front face 20 of
which is not convexly rounded, but rather is flat (or might be
concavely rounded if desired).
[0034] Returning to the particular cover shell 201 shown in FIGS. 3
and 4, same thus is contoured three-dimensionally in a shallow,
cup-like shape having a convexly rounded front wall 226
incorporating the slots 211 and strips 216 and a peripheral wall
continued therefrom and terminating in a peripheral edge 228.
[0035] The cover shell 201 is three-dimensionally contoured so that
its back side 221 can continuously abut the front face 147 (FIG. 8)
of the supporting vent 140, in the manner shown in FIGS. 6, 7 and
9-11. In other words, the cover shell 201 is contoured to fit in a
skin-like manner on the front of the supporting vent head 142.
[0036] The pattern of slots 211 and strips 216 of the cover shell
201, as well as the size, shape and placement thereof, are
preferably identical to those of the slots 131 and strips 146 of
the corresponding vent 140. Thus, with the cover shell 201 properly
oriented on the front face 147 of the vent head 142, the vent head
142 is to be entirely hidden from the front by the cover shell 201,
as in FIG. 5. Thus, the cover shell 201 is to cover the entire
exposed portion (the front and periphery) of the vent head 142,
including the front surfaces of the strips 146, the peripheral edge
portion 143, and the radially outwardly facing peripheral edge 130.
Thus, at least as a casual observer, the external appearance of the
vent assembly, comprising the molded plastic vent 140 and cover
shell 201, is to be that of a monolithic metal (e.g., stainless
steel) vent cast from molten stainless steel or machined from a
block of stainless steel. This visual effect can be enhanced by
reducing the visibility of the molded plastics vent 140. For
example, by molding the plastics vent 140 of a black material with
a non-shiny surface, the sidewalls 133 (FIGS. 8 and 9) of the vent
head strips 146 may visually merge into the shadowed interior
reaches of the vent slots 131.
[0037] In some embodiments, as for example shown in FIG. 8, at
least some of the vent head strips 146 may be, as seen from the
front, several times longer than their width. Despite this, such
strips 146 may be made especially strong by providing same with
substantial front-to-rear depth, as seen for example in FIGS. 8 and
9, wherein the strips 146 crossing the central portion of the head
142, while laterally longer, are also deeper front-to-rear. On the
other hand, the cover shell 201 is preferably of constant thickness
sheet material and indeed very thin compared to any dimension of
the vent strips 146.
[0038] Thus, to avoid accidental bending after the cover shell 201
is formed, the longer cover shell strips 216 may be reinforced by
one or more cross straps 234 (FIGS. 3-7) spanning one or more of
the slots 211 and extending transversely from the flanking strips
216. A given cross strap 234 thus acts to prevent twisting (about
its length axis) or bending (out of its plane or transversely into
or away from a flanking slot) of the attached strip 216. So that
the cross straps 234 do not significantly impede flow through the
slots 211, the cross straps 234 are preferably minimized in number
and length, so that the total frontal area of the cross straps 234
is small compared to the total frontal area of the slots 211.
[0039] The cover shell 201 can be fixed to the front of the vent
head 142 as desired, for example by adhesive bonding. However, in
the preferred embodiment shown, the cover shell 201 is preferably
securely but resiliently releasably snap-fitted to the front of the
vent head 142 by its own monolithically integrated fastening
structure. In the preferred embodiment shown, that fastening
structure comprises resiliently bendable, cantilevered tabs 250
(FIGS. 3, 4, 7, 8, 10 and 11) angled substantially rearwardly from
edges of corresponding slots 211. Advantageously, the tabs 250
extend from ends 251 of one or more of the shell slots 211 and are
hence rearwardly bent from inboard edges of the peripheral edge
portion 205 of the cover shell 201. Such tabs 250 are thus located
to extend into adjacent vent head slots 131 (FIG. 11), here at
opposite ends of the two adjacent longest ones of the vent head
slots 131. A given said tab 250 (FIG. 11) has a leg 254 extending
rearwardly and positioned to lie along and adjacent the opposed
vent head slot end 132. Such tab 250 further includes a heel 256
protruding from the free rear end of the leg 254 and positioned to
lie laterally beyond the vent head slot end 132 and snugly behind
the vent head peripheral edge portion 143 to lock the cover shell
201 against the front face 147 of the vent head 142. Such tab 250
further includes a foot 258 extending rearward from the radially
outboard end of the heel 256 and a toe 260 angled rearward and
radially inward from the free, rear end of the foot 258.
[0040] Applicants found that the cover shell 201 can be
inexpensively produced from stainless steel sheet by a stamping
operation which separates the cover shell 201 from the surrounding
portion of the parent metal sheet (not shown), removes material to
form the slots 211 and flanking strips 216, forms the mentioned
cup-shaped configuration and forms and bends out of plane the
mentioned tabs.
[0041] To install the cover shell 201 on the vent 140, the cover
shell is moved rearward toward the front of the vent 140 to
cammingly engage the rear face of the toe 260 (FIG. 11A) with the
front inboard corner of the vent peripheral edge portion 143 at the
appropriate slot end wall 132. Continued rearward displacement of
the cover shell 201 causes the vent edge portion 143 to cam the
cover shell toe 260 laterally inboard (leftward in FIGS. 11A and
11B), resiliently bending the tab 250 leftwardly and allowing the
heel 256 to slide rearwardly along the corresponding vent slot end
wall 132 toward and past its FIG. 11B partially installed position.
Continued rearward displacement of the cover shell 201 brings same
into the firm, face-to-face contact with the vent 140, as shown in
FIGS. 9-11, whereupon the resiliently bent tab 250 snaps its heel
256 (FIG. 11) laterally outward snugly behind the vent edge portion
143. With the tabs 250 (four being provided in the embodiment
shown) thus deployed, same firmly and fixedly retain the cover
shell 201 tightly against the front of the vent head 142, as
generally shown in FIGS. 9-11.
[0042] Thus installed, it will be noted that the back side 221
(FIGS. 9-11) of the cover shell 201 tightly continuously abuts the
front side 147 of the vent head 142, with the continuous peripheral
edge portion 205 of the cover shell mapping on the head peripheral
edge portion 143 and the shell peripheral edge 228 lying flush with
the rear facing lip 149 of the vent head 142, as seen in FIGS. 9
and 10. Moreover, the pattern of cover shell slots 211 maps on the
pattern of vent head slots 131 in shape, size and relative location
(FIGS. 9 and 11) and the cover shell strips 216 map on the vent
head strips 146 in shape, size and relative location. Thus, the
edges of the shell slots 211 are a substantially flush forward
continuation of the walls of the corresponding head slots, so as to
minimize disruption of air flow through the vent head 142 despite
the covering thereof by the cover shell 201. In the FIGS. 3-11
embodiment, one or more of the cover shell strips 216 is relatively
long and narrow, and one or more rigidifying cross straps 234 are
integrated in the cover shell 201 and span one or more cover shell
slots 211 and corresponding vent slots 131 but, as indicated in
FIG. 9, the cross straps 234 are minimized in width and number, and
so do not significantly, if at all, impede air flow through the
vent 140.
[0043] In a preferred embodiment of the invention, the cover shell
201 was stamped of grade 316 stainless steel sheet material of
thickness about 0.5 mm, though use of similar material of thickness
in the range 0.2-1.0 mm is contemplated.
[0044] The use of thicker material may be desirable where the cover
shell is of greater diameter, has a more flat or otherwise less
inherently rigid cross-sectional shape, has longer and/or narrower
strips 216, has longer and/or wider slots, or has fewer (or no),
narrower and/or longer cross straps 234. The cover shell thickness
may also be varied to compensate for variations in rigidity as
between different cover shell materials.
[0045] While the vent 140 and cover shell 201 here shown by way of
illustration have a pattern of substantially parallel, chordally
extending, uniform width slots 211, the pattern of slots 211 may be
varied as desired in shape, size and relative location within the
broader scope of the invention. For example, the slots 211 could
take the form of a plurality of circular or irregularly shaped
holes, and/or nonparallel (e.g. radiating) elongate openings as
desired.
[0046] In accord with the present invention, the rigidity, frontal
impact resistance, and resistance to denting of the vent assembly
140, 201 is provided primarily by the relatively inexpensive, rigid
molded plastics vent 140 which firmly backs the cover shell 201.
Thus, the thickness of the cover shell 201, including its strips
211, may be a very small fraction (e.g. 1/20 to 1/80) of the
thickness of the vent head strips. For example, in the embodiment
shown, the cover shell strip thickness is about 1/40.sup.th of that
of the thickest vent head strips 146.
[0047] Thus, the vent assembly 140, 201 according to the present
invention, as compared to a monolithic cast or machined vent of
solid stainless steel, is substantially more economical both in
terms of substituting less expensive plastics material for the
great majority of more expensive stainless steel, and in
substituting less costly fabrication methods (e.g., relatively
inexpensive plastic molding and sheet metal stamping operations)
for more expensive stainless steel casting or solid-block
machining.
[0048] Although a particular preferred embodiment of the invention
has been disclosed in detail for illustrative purposes, it will be
recognized that variations or modifications of the disclosed
apparatus, including the rearrangement of parts, lie within the
scope of the present invention.
* * * * *