US3462763A

US3462763A - Impact absorbing protective headgear

Info

Publication number: US3462763A
Application number: US672561A
Authority: US
Inventors: Richard C Schneider; Elwyn R Gooding
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-10-03
Filing date: 1967-10-03
Publication date: 1969-08-26
Anticipated expiration: 1986-08-26

Description

Aug. 26, 1969 R. c. SCHNEIDER ET AL 3,462,763

IMPACT ABSORBING PROTECTIVE HEADGEAR 3 Sheets-Sheet 1 Filed Oct. 5, 1967 INVENTORS ichard C .Schneider,

g n n 0 Y 0 M nm J R m n T V A w E 2 3 Aug. 26, 1969 c SQHNElDER ET AL 3,462,763

IMPACT ABSORBING PROTECTIVE HEADGEAR Filed Oct. 5, 19s? a Sheets-Sheet 2 INVENTORS Richard C. Schneider,

and

Elwyn R. Gooding g- 1969 R. c; SCHNEIDER ETAL 3,462,763

IMPACT ABSORBING PROTECTIVE HEADGEAR Filed Oct. 5, 1967 3 Shams-Sheet 5 INVENTORS Richard C. Schneider,

and

Elwyn RyGooding I wwjgw ATTORNE United States Patent 3,462,763 IMPACT ABSORBING PROTECTIVE HEADGEAR Richard C. Schneider, 2110 Hill St. 48104, and Elwyn R. Gooding, 98 Valhalla Drive 48103, both of Ann Arbor, Mich.

Filed Oct. 3, 1967, Ser. No. 672,561 Int. Cl. A421) 1/08 U.S. Cl. 2-3 8 Claims ABSTRACT OF THE DISCLOSURE A protective headgear assembly consisting of an impact absorbing and distributing outer shell and a multicellnlar inflatable inner support crown therefor positioned in surface-to-surface engagement with and secured to the outer shell. The inner support crown is formed of a yieldable resilient material and consists of a plurality of air or inert gas filled chambers which engage selected areas of the Wearers head. The inner support crown is positioned between the outer shell and the wearers head so that forces applied to the outer shell are transmitted to the head only through the yieldable inner support crown. The outer shell has relatively firm sections which function like a frame and cover critical brain areas and more resilient sections which cover less critical brain areas and will yield to an impact force so as to absorb and distribute the force before it is transmitted to the wearers head. An impact absorbing inflatable chin cup with an adjustable and self-retractable chin strap, all formed of a yieldable resilient material is secured with suitable fasteners to the above protective headgear.

Background of the invention The protective headgear of this invention is useful as a helmet for athletic participants, construction workers, electrical linemen, firemen, police, rescue squads, miners, mountain climbers, skiers, motorcyclists, motor vehicle operators and occupants, sky divers, aircraft personnel, armed forces personnel and the like. The rigid plastic and metal helmets, which are presently being used by such people, are usually mounted on various types of suspension systems that engage the wearers head and are not adequate for preventing head injuries. U.S. Patent 2,250,275 illustrates a type of football helmet which is presently being used extensively. Such a helmet consists of a rigid outer shell mounted by means of rivets on an inner multiple strap suspension system. The straps are usually formed of non-stretchable fabric material and engage the head of the wearer with line or point contact so that any impact from blows applied to the outer shell is directly transmitted to the head of the wearer with little diminution of the force of impact. Another type of protective headgear used as a football helmet employs a composite padding type liner. Such a liner is very slow in effecting any distribution of the shock energy applied to the helmet so that as a result blows applied to the helmet are substantially directly transmitted to the wearers head. In addition, such helmets are objectionable because they are very heavy and tend to affect the balance and movement of the head of the wearer. U.S. Patent 2,150,290

' illustrates a helmet with inflatable cushions spaced from a fibre board outer shell. An inner tube type cushion is secured to a non-stretchable material ring which is secured to the outer shell so as to hold the outer shell in a spaced relationship to the cushion. An impact force applied to the outer shell causes it to move with a bouncing ball action on the wearers head and thereby induce a rebound of the brain within the skull. Due to a lack of resiliency of the outer shell and the inability of the present suspension systems to absorb the force of such impact, there is a transmission of such force to the intracranial contents perhaps resulting in the tearing of blood vessels with fatal hemorrhage or destruction of the brain.

It is an object of the present invention, therefore, to provide a protective headgear assembly constructed specifically on the basis of an anatomical knowledge of the skull, intracranial membranes and brain and an understanding of the mechanical principles involved in head injuries coupled with an extensive experience in the adaptation of various materials to accomplish the desirable distribution and absorption of impact forces applied thereto to thereby reduce brain damage due to head injuries.

Summary of the invention It has been found that the worst damage to the brain occurs in those closed head injuries in which skull fracture does not occur. There is no dissipation of the impact of the blow but there is a direct transmission of the force to the underlying area of the brain or to the opposite side of the head resulting in a contre coup injury (that is, damage to the skull or brain on the side opposite the side of the blow). In closed head injuries where fracture occurs there is some dissipation of the force of the blow as the bone breaks resulting in less damage to the underlying brain than if the skull had not been fractured. The protective headgear assembly of this invention consists of an initial impact force absorbing and distributing outer shell and an impact force distributing and absorbing multicellular inflatable inner support crown therefor which coact to absorb impact forces and distribute these forces throughout an extensive area of the headgear assembly so as to minimize the localized forces applied to the wearers head. The outer shell has areas provided with relatively different degrees of resiliency. Some sections of the outer shell constitute firm sections and these cover and protect critical brain areas where damage is most likely to cause neurologic disability, and other sections of the outer shell constitute more resilient sections and these cover the relatively silent areas of the brain. When positioned on a wearers head, the outer shell firm section has an annular portion which overlies and protects the inferior and posterior walls of the bony frontal sinus, the dural lateral sinuses and confluens at the base of the skull. This annular section is positioned at the back of the wearers head substantially above the cervical spine to avoid having this part of the protective headgear outer shell driven into the cervical spine causing severe cervical hyperextension injuries which result in cervical fractures or spinal cord damage. The firm section of the outer shell also includes a medial arcuate strip which runs longitudinally of the protective headgear in a direction fore and aft of the wearers head, overlying the longitudinal sinus and bridging veins, and arcuate strips which run transversely of the protective headgear overlying the brain motor strips. The resilient sections are bounded by the firm sections so as to form arcuate shaped quadrants in the outer shell which overlie the relatively silent areas of the brain, namely, those regions of the brain which might absorb some stress without danger of as much residual neurologic deficit. These resilient sections of the helmet are thus capable of yielding and deforming under the force of a blow so as to absorb the initial impact of the blow, distribute the resultant force to the surrounding firm sections and not transmit it directly to the brain.

The protective inner support crown is removably mounted on the inner surface of the outer shell so as to be disposed circumferentially between the outer shell and the wearers skull. The inner support crown is preferably formed of a resilient yieldable plastic which can be air or inert gas inflated to the desired degree and which consists of a plurality of inflated chambers or cells. These chambers or cells are located in protective relation relative to the brain and are arranged so that when an impact force is applied to any area of firm portion of the outer shell it is quickly distributed throughout the outer shell frame structure and transmitted to the multicellular inner support crown which instantaneously reacts to absorb the forces applied, throughout its entirety. This construction of the protective headgear assembly also provides for absorption of noise resulting from impact blows to the outer shell, so as to eliminate undesirable noises such as reverberation of sound resulting in ringing in the ears which is relatively common in protective headgears now in use.

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims, and the accompanying drawings in which:

FIGURE 1 is a pictorial perspective cutaway view of one embodiment of the protective headgear assembly of this invention, illustrating the physical relationship of the protective headgear assembly to the head and important intracranial contents of the wearer;

FIGURE 2 is a side elevational view of the protective headgear assembly shown in FIG. 1, illustrating the protective headgear assembly secured in position on the head of a wearer with an impact absorbing inflatable chin cup and an adjustable and self-retractable chin strap;

FIGURE 3 is a top plan view of the protective headgear assembly shown in FIG. 1;

FIGURE 4 is a front elevational view of the protective headgear assembly shown in FIG. 1, showing the assembly mounted on the head of a wearer;

FIGURE 5 is a bottom plan view of the protective headgear assembly shown in FIG. 1, with the chin cup and chin strap removed;

FIGURE 6 is an enlarged longitudinal sectional view of the protective headgear assembly as seen from substantially the line 66 of FIG. 3;

FIGURE 7 is a perspective view of the impact absorbing multicellular inflatable inner support crown in the protective headgear assembly of this invention shown in FIG. 1;

FIGURE 8 is a perspective view of an impact absorbing multicellular inflatable temporal, aural and mandibular element in the protective headgear assembly of this invention;

FIGURE 9 is a fragmentary sectional view of a portion of the protective headgear assembly of this invention depicting relative thicknesses of different areas of the impact absorbing and distributing outer shell and an impact distributing and absorbing multicellular inflatable inner support crown in exaggerated style for purpose of illustration;

FIGURE 10 is a fragmentary sectional view illustrated similarly to FIG. 9, showing the inner support crown detached from the outer shell;

FIGURE 11 is a sectional view like FIG. 10, showing a modified form of inner support crown in the protective headgear assembly of this invention;

FIGURE 12 is a transverse sectional view of a portion of the inner support crown as seen from substantially the line 1212 in FIG. 7;

FIGURE 13 is a sectional view, like FIG. 12, illustrating a modified form of the inner support crown in the protective headgear assembly of this invention; and

FIGURE 14 is a fragmentary detailed sectional view of a portion of another form of the protective headgear assembly of this invention as formed to adapt it for a construction worker or the like.

With reference to the drawing, the protective headgear assembly of this invention, indicated generally at 10, is illustrated in FIG. I mounted on the head 12 of an athlete such as a football player. The protective headgear assembly 10 consists of an outer shell 14 and a yieldable inner support crown 16 which is removably mounted on the inner surface 18 of the shell 14 in a manner to be described in detail hereinafter and an impact absorbing inflatable chin cup with an adjustable and self-retractable chin strap.

The outer shell 14, which in the illustrated embodiment of the invention shown in FIG. 1, is preferably molded from a resilient plastic material so as to be of one piece, is provided with a section 20 which is relatively firm and sections 22 of relatively greater resiliency, so that

sections

20 and 22 are hereinafter sometimes referred to as firm and resilient sections, respectively. In the illustrated embodiment of the invention, these

sections

20 and 22 are provided with relatively different degrees of resiliency by making the section 20 of increased thickness relative to the section 22. In a preferred embodiment of the invention, the material for the impact absorbing and distributing outer shell is a polymer blend of acrylonitrile-butadiene-styrene, such material being commonly known as ABS material.

The firm section 20 is designed to overlie either the areas of the skull, which might fracture, or cover specific portions of the intracranial contents, which most frequently are damaged in head injuries. The firm section 20 includes an annular portion 24 which, when the headgear assembly 10 is mounted on the head 12, encircles the head and is positioned in a protective covering relation with the inferior and posterior Walls of the bony frontal sinus 26 in the skull 28 of the head 12.

The firm annular portion 24 covers the branches of the middle meningeal artery 42 which is captive in a bony groove of the thin temporal bone. If these vessels are transected with or without a fracture of the skull, the result is a hemorrhage on the surface of the membrane surrounding the brain (i.e., an extradural hemorrhage). The annular portion protects the lateral sinuses 46 and the site at which they join the longitudinal sinus 48 to form a reservoir (i.e., the confluens of the sinuses or torcula Herophili) Which must be protected for they are a source of extradural hemorrhage, although they are less frequently a cause than the middle meningeal artery. The portion 24 also protects the base of the skull 28 directly behind the frontal sinus 26 (i.e., the cribiform plate) which may be very thin and, if fractured, bone fragments may tear the membranes of the brain permitting a leakage of watery fluid (the cerebrospinal fluid which bathes the brain) providing a pathway for infection with the possibility of meningitis or a brain abscess. The outer shell 14 is shaped so that the portion 24 has its posterior edge 30 (FIG. 2) positioned above and in a clearance relation with the wearers cervical spine 32. In other words, the rear edge 30 of the headgear assembly 10 is positioned high on the wearers head to avoid the guillotine effect of this part of the protective headgear assembly outer shell 14 being driven into the cervical spine 32 causing severe hyperextension injuries which result in cervical fractures or spinal cord damage.

The outer shell firm section 20 also includes an elongated arcuate strip portion 34 which extends medially fore and aft of the protective headgear assembly 10 and the head 12 and is integral at its ends to the annular portion 24. The strip firm portion 34 also protects the longitudinal sinus 48 and the bridging vein which drain the blood from the upper surface (vertex 50) of the brain into the longitudinal sinus. These bridging vein are thinwalled and are the most frequent source of bleeding underneath the membranes which encircle the brain (i.e., subdural hemorrhage). The firm section at the top of the protective headgear outer shell also overlies and protects the parietal brain area 51. Firm curvate side strip portions 36 extend from the top of the outer shell 14 in a downwardly and forwardly direction, as seen in FIG. 2, and are integral at their lower ends with the annular portion 24. These firm portions overlie and protect the motor strip areas 40 of the brain. The remaining sections of the outer shell 14 are the resilient sections 22 which are thus of arcuate quadrant shape and are bounded by the

firm portions

24, 34 and 36.

The firm section 20 of the outer shell 14 also includes vertical side portions 52 which extend downwardly from the annular portion 24 bilaterally, overlying and protecting the temporal, aural and mandibular areas. Circular openings 54 are provided in the sections 52 to coincide with the aural canals 56 and external ears of the wearer to facilitate hearing. The vertical side sections 52 are designed to resist horizontal inward movement of the outer shell 14 and also provide a firm anchor for a chin strap 59 secured at its ends to the vertical side portions 52. Air circulating holes 68 are located in the

firm strip portions

24, 34 and 36 of the outer shell 14 so as to be adjacent the inner support crown 16 and create a positive air circulation throughout the protective headgear assembly 10, thereby reducing perspiration of the head thus alleviating the possibility of an upset in the electrolyte balance of the body and affording greater comfort to the wearer. As shown in FIGS. 1 through 6, inclusive, the outer shell 14 has no ridges, bumps, protrusions, projections or irregularities or its external surface and a Teflon plastic coating can be readily applied to the entire outer surface of the outer shell, thereby providing a surface with as low a coefficient of friction as possible to permit the protected head to seek the path of least resistance on impact and thereby lessen the possibility of torsional injury, namely, injury to the head 12 due to twisting of the protective headgear assembly 10.

It can thus be seen that the firm section 20 of the shell 14 is shaped to conform to the head 12 so as to overlie and protect the vertex 50 and extend downwardly in all directions over the parietal brain area 51, the frontal brain area 53, the temporal brain area 44, the occipital brain area 55 and including the mandibular, the aural canal 56 and the ear bilaterally. As shown in FIG. 2, the annular portion 24 increases in width in a front to rear direction for this important purpose. The resilient sections 22 cover the relatively silent brain areas 57 at positions between the firm portions.

The yieldable resilient inner support crown 16 functions to dissipate forces applied to the outer shell 14 over a large area so as to prevent the transmission of localized impact forces to the wearers head 12. The support crown 16 is formed of a yieldable resilient material, and in a preferred embodiment of the invention this material is a vinyl plastisol. Design configurations incorporating various combinations of wall thicknesses, durometers and elasticity can be readily employed to obtain the desired degree of resilience in the support crown 16 to adapt the headgear to a specific application.

As shown in FIG. 7, the inner support crown 16 is of generally open frame crown shape, and includes an annular portion 70 and arcuate portions 72 which extend upwardly therefrom and are integral at their lower ends to the portion 70 at circumferentially spaced points thereon. At their upper ends the arcuate portions 72 are integral with each other so as to provide a relatively large portion 74 in the support crown 16 which overlies the vertex 50 and the parietal brain area 51. As shown in FIGS. 10 and 12, the

support crown portions

70 and 72 are of a cellular construction. The portion 70 has an inner wall 76 curved to conform to the shape of the wearers head, an outer wall 78 and an inner partition 80, which is of increased thickness relative to the

walls

76 and 78 and forms a pair of inflated chambers or

cells

82 and 84 in the portion 70. Likewise, each arcuate portion 72 has its inner wall 86 curved to conform to the shape of the wearers head, an outer wall 88, and an inner partition 90 which coacts with the

walls

86 and 88 to form internal inflated chambers or

cells

92 and 94. The cells in the

portions

70 and 72 communicate as shown in FIG. 6, at the junctures of the

portions

70 and 72 so that air or inert gas can flow therebetween to distribute forces throughout the support crown 16.

The inner support crown 16 is positioned against the inner surface 18 of the outer shell 14 and is removably secured thereto in a suitable manner. In the illustrated embodiment of the invention, a plastic hook and loop assembly 96 (FIG. 9), of well known type, is utilized to secure the support crown portion 70 to the shell portion 24. The assembly 96 includes a pair of

plastic tapes

98 and 100 secured, by suitable adhesives, molded-in, or heat sealed, to the inner surface of the shell portion 24 and the outer wall 78 of the support crown portion 70, respectively. One of the tapes contains a myraid of tiny nylon loops and the other tape contains a similar number of tiny hooks. One suitable product of this type is marketed by Charles Mayer Studios, Inc. of Akron, Ohio, under the name Hook N Loop. As shown in FIG. 9, the

tapes

98 and 100 readily adhere to each other, by virtue of the hooks and loops therein, when the tapes are pressed against each other. As shown in FIG. 10, the tape 100 can be readily disengaged from the tape 98, which makes removal of the inner support crown from the outer shell a simple operation and thereby permits ready cleaning and sanitation of the protective headgear assembly. This type of fastening assures full contact of the exterior surface of the vertical wall circumferentially around the bottom of the inner support crown. This feature also makes it possible to use various sizes of inner support crowns with but one size outer shell being required.

FIGURES 11 and 13 illustrate a modified form of the inner support crown 16 in which the annular and arcuate portions 70a and 72a, corresponding to the

portions

70 and 72, are formed with two internal partitions so as to form three chambers or

cells

102, 104 and 106 in the portion 70a and

similar cells

108, 110 and 112 in the portion 720:. Such a construction is illustrated to indicate that more than two cells can be satisfactorily employed in each inner support crown portion.

The inner support crown 16 is preferably formed to a one piece construction by a suitable rotational molding process so as to form a fail-safe (i.e., incapable of deflation or collapse of all cell portions simultaneously under stress conditions.

Impact absorbing multicellular inflatable temporal, aural and mandibular elements, one of which is indicated at 111, FIG. 8, are formed of a yieldable resilient material, and in a preferred embodiment of the invention this material is vinyl plastisol. As shown in FIG. 8, these elements are of cellular construction. The inner wall 113 is shaped to fit the mandibular of the wearer, the outer wall 114 conforms to the inside contour of vertical side portion 52 of the outer shell 14, the inside surface 116 provides clearance around the external ear, the outside surface 115 is shaped to the outer edge of side portion 52 and the upper surface lies adjacent the bottom surface of section 70 of the inner support crown. The inner wall 113, partition 107, outer wall 114, inner surface 116 and top surfaces 117 form a pair of

inflated cells

118 and 119. The temporal, aural and mandibular elements are secured by plastic hook and loop so as to extend in contiguity with the inner surfaces of the vertical side portions 52 of the outer shell 20'.

With the inner support crown 16 attached to the shell 14, as shown in FIGS. 9 and 10, blows applied to the outer shell 14 have the energy therein absorbed in various degrees in the

cells

82, 84, 92 and 94. These cells can be placed under pressure by employing a needle and heat seal to inject air or inert gas into the cells prior to use of the headgear 10 so as to obtain the desired degree of energy absorption in a headgear designed for a specific purpose.

The cells in the inner support crown 16 react instantaneously to absorb the force energy. When an impact force is applied to one of the resilient sections 22 in the shell 14 the impact is instantly partially absorbed by deforming of the section 22, with any over pressure force being quickly distributed to adjacent firm sections 20 for further distribution and transmission to the impact absorbing multicellular inner support crown 16 which again instantaneously reacts to distribute and absorb the force applied. One important advantage of the inner support crown 16 is that it can readily be deflated by piercing with a sharp pointed instrument or tool to facilitate removal of the entire protective headgear assembly in cases of severe internal and external head, membrane, dental and cervical spine and spinal cord injuries.

As shown in FIG. 1 and FIG. 2, the impact absorbing inflatable chin cup 58 and integral adjustable and selfretractable chin strap 59 are formed of a yieldable resilient material, and in a preferred embodiment of the invention this material is vinyl plastisol. As shown in FIG. 2, the chin cup is of a cellular construction. The inner wall 60 is compound curved to conform to the shape of the wearers chin 13 and an outer wall 61 and an inner partition 62, which is of increased thickness relative to the

walls

60 and 61 forms a pair of

inflated cells

66 and 67. The upper wall 63 and lower wall 64 taper in plain form at the sides of the chin cup so as to become integral with the inner wall 60, the partition 62 and the outer wall 61 which also taper as they wrap around the chin to form the integral chin strap 59 at a point 65 just forward of the front edge of side section 52 of the outer shell firm section 20. Suitable metal fasteners are used to attach the adjustable and self-retractable chin strap 59 to the mating fastener anchored to the side section 52 and thereby make it possible to quickly secure the protective headgear in position on ones head. Although the protective headgear in normal use is held firmly in position by a properly adjusted chin strap, it can be lifted upward and backward without applying severe shock forces to the cervical spine as other present rigid chin cups and chin straps do.

The modified form of headgear assembly indicated at 120, in FIG. 14, is an adaptation of the assembly for use by construction workers and the like. The assembly 120 includes an outer shell 122 having a metal section 124 at the top of the wearers head, a brim section 126, similarly formed of metal, and resilient sections 128 which are secured to and extend between the

sections

124 and 126. The

sections

124 and 126 correspond to the firm section in assembly 10 and the sections 128 correspond to the resilient sections 22. In the protective headgear assembly 120, the resilient sections 128 are secured to the

section

124 and 126 by means of internal flanges 130. An inner support crown 16 like that previously described is secured by a hook and loop assembly 96 circumferentially to the inner surface of the shell 122, exactly as in the assembly 10.

From the above description, it is seen that this invention provides improved protective headgear assemblies which effectively prevent brain injury by virtue of the unique construction and assembly of the outer shell 14 and the resilient inner support crown 16.

We claim:

1. In a protective headgear assembly, an outer shell shaped to overlie a human head, said outer shell being formed with a firm section of low resilience and sections of relatively greater resilience, said firm section including a first annular portion adapted to be disposed in a horizontally inclined position on a wearers head, a second portion of arcuate strip shape extending fore and aft of said shell and having a pair of ends connected to substantially diametrically opposite areas of said first portion, third portions secured to said strip portion intermediate the ends thereof and extending downwardly and forwardly therefrom, said third portions being secured at the lower ends thereof to said first portion, said resilient sections being of arcuate substantially quadrant shape and being located in said shell at positions bounded by said first, second and third portions.

2. In a protective headgear assembly having the structure according to claim 1 wherein said outer shell is of one piece plastic construction, said firm section being of increased thickness relative to the thickness of said sections of greater resilience.

3. A protective headgear assembly according to claim 1 further including an inner support positioned within said outer shell in surface-to-surface engagement therewith, said inner support being formed of a yieldable resilient material and including a hollow annular section disposed within said annular portion of said outer shell, partition means in said annular section forming a plurality of side-by-side chambers, and a plurality of hollow arcuate sections secured to circumferentially spaced portions of said annular section and extending upwardly therefrom into said outer shell so as to form an open generally crown shape structure.

4. A protective headgear assembly according to claim 3 further including partition means in each of said arcuate sections forming a plurality of chambers in said arcuate sections which communicate with said chambers in said annular section.

5. A protective headgear assembly according to claim 1 wherein the lower edge of said annular portion of the outer shell is located so that it is in a clearance relation with the cervical spine of the wearer at the back of the wearers head.

6. A protective headgear assembly according to claim 3 further including a chin cup formed of a yieldable resilient material shaped to include a hollow section conforming to the shape of the chin of a wearer, partition means in said chin section forming a plurality of enclosed cells arranged in a side-by-side relation in a direction extending outwardly from the wearers chin and strap means connecting said chin section to said outer shell.

7. In a protective headgear assembly, a relatively rigid outer shell, means forming a first fluid filled hollow chamber disposed inwardly of and spaced from said outer shell so as to be located between said outer shell and the head of a wearer, and means forming a second fluid filled hollow chamber disposed between said outer shell and said first chamber and operable to transmit forces from said outer shell to said first chamber.

8. A protective headgear assembly according to claim 7 wherein said chambers are formed in an inner crown support positioned within and disposed in engagement with said outer shell, said inner crown support comprising a hollow annular section formed of a yieldable resilient material, partition means in said annular section forming said chambers, a plurality of hollow arcuate sections secured to circumferentially spaced portions of said annular section and extending upwardly therefrom, and partition means in said arcuate sections forming said chambers.

References Cited UNITED STATES PATENTS 1,072,321 9/1913 Fitch 23 2,140,716 12/1938 Pryale 23 2,618,780 11/1952 Cushman 23 2,632,173 3/1953 Lyon.

2,717,384 9/1955 Frothingham 23 2,867,811 1/1959 Jones 29 XR 3,186,004 6/1965 Carlini 23 3,344,433 10/1967 Stapenhill 23 JAMES R. BOLER, Primary Examiner