US3599239A

US3599239A - Protective headgear

Info

Publication number: US3599239A
Application number: US870507A
Authority: US
Inventors: David Tatum
Original assignee: FIBER METAL PRODUCTS Co
Current assignee: FIBER METAL PRODUCTS Co
Priority date: 1969-10-06
Filing date: 1969-10-06
Publication date: 1971-08-17
Anticipated expiration: 1988-08-17

Abstract

An outer shell and a suspension construction for engagement with a wearer''s head and supporting the shell in spaced relation thereto, the suspension being specifically configured by shape and thickness for directionally controlled distention under impact applied to the shell, and the shell being provided with resilient means by shape and thickness for obliquely deflecting an article impinging on the shell.

Description

United States Patent (72] Inventor David Tatum Swarthmore, Pa.

[21 I App]. No. 870,507

[22] Filed Oct. 6, 1969 [45} Patented Aug. 17,1971

[7 3 Assignee The Fibre-Metal Products Company Chester, Pa.

[54] PROTECTIVE HEADGEAR 11 Claims, 18 Drawing Figs.

[52] US. Cl 2/3 R [51 1 Int. Cl A42b 3/00 [50] Field of Search 2/3, 6

[56] References Cited UNITED STATES PATENTS 3,041,621 7/1962 Brockway 2/3 R 3,422,459 1/1969 Bowers. Jr. 2/3 R Primary Examiner-James R. Boler Attorney-Robert K. Youtie ABSTRACT: An outer shell and a suspension construction for engagement with a wearers head and supporting the shell in spaced relation thereto, the suspension being specifically configured by shape and thickness for directionally controlled distention under impact applied to the shell, and the shell being provided with resilient means by shape and thickness for obliquely deflecting an article impinging on the shell.

PATENTEU AUG! 719m SHEET 1 BF 6 BV/fMK;

A TTOIP/VEX PATENTED AUG] 7 I971 SHEET l} UF'B TATUM QL/JMLA,

.PATENTEU we: 7 |97I SHEET 5 0F 6 MH/E/VraP.

DAVID TA T U M PROTECTIVE HEADGEAR BACKGROUND OF THE INVENTION As IS well known to those versed in the art, protective headgear, sometimes called safety hats and caps, are constructed for protection of the wearer's head against impact, penetration, and electrical shock. In the past, protection against impact has been considered as afforded by yieldability of'the head-engaging part or suspension, while protection against penetration has been considered as provided by the shell and resistance to electrical shock by the insulation characteristics of the materials.

SUMMARY OF THE INVENTION In accordance with the instant invention, it is an important object to provide a unique structure and resultant function wherein protection against impact is afforded not only by head-engaging part or suspension, but also by the outer shell,

, and further by unique cooperative interrelation, both structurally and functionally, between the suspension and shell.

It is a further object of the present invention to provide a protective headgear having the advantageous characteristics mentioned in the preceding paragraph, which transmits considerably less force to the wearer's head than prior constructions without disengagement nor permanent deformation of, or damage to any components of the headgear.

It is a further object of the present invention to provide a protective headgear of the type described wherein both the shell and suspension cooperate to deflect a falling object upon impact, so as substantially to reduce the effective mass of the falling object, and minimize the possibility of injury to a wearer.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings, which form a material part of this disclosure.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, which will be exemplified in the construction hereinafter described, and of which the scope will be indicated by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a bottom perspective view showing a protective headgear of the present invention, with parts broken away for increased clarity of illustration.

FIG. 2 is a side elevational view showing the exterior of a protective cap of the present invention.

FIG. 3 is a bottom plan view, taken generally along the line 3-3 of FIG. 2, partly broken away and omitting certain details of the suspension for purposes of clarity.

FIG. 4 is a sectional elevational view taken generally along the line 4-4 of FIG. 3, with the headband broken away and details of the suspension omitted for clarity.

FIG. -5 is a bottom plan view of the outer shell apart from the suspension and headband, also broken away.

FIG. 6 is a top plan view of the suspension of the instant invention, apart from the remainder thereof, showing the details omitted from FIGS. 3 and 4, the front being leftward.

FIG. 7 is a partial sectional view taken generally along the line 7-7 of FIG. 6.

FIG. 8 is a partial sectional view taken generally along the line 8-8 of FIG. 6.

FIG. 9 is a partial sectional view taken generally along the line 9-9 ofFIG. 6.

FIG. 10 is an exploded fragmentary view showing certain connection elements of the shell and suspension.

FIG. 11 is a fragmentary view showing a certain type of female connection element of the shell.

FIG. 12 is a longitudinal sectional view taken generally along the line 12-12 of FIG. 11.

FIG. 13 is a sectional view taken generally along the line 13-13 of FIG. 11.

FIG. 14 is a fragmentary elevational view showing a male connection element of the suspension.

FIG. 15 is a sectional view taken generally along theline 15-15 of FIG. 14.

FIG. 16 is an end view taken generally along the line 16-16 of FIG. 14.

FIG. 17 is a partial sectional view taken generally along the line 17-17 of FIG. 3 illustrating a connection between the headband and suspension.

FIG. 18 is a partial sectional view taken generally along the line 18-18 of FIG. 17 illustrating certain details of the headband DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the drawings, and specifically to FIGS. 14 thereof, a protective headgear of the present invention is there generally designated 20, and includes a relatively stiff outer member or shall 21, an inner, head-engaging part or suspension, generally designated 22, and a headband 23 circumposed about the interior of the suspension.

The outer shell 21 is best seen in FIGS. 1, 4 and 5, and is advantageously integrally fabricated of any suitable material, say plastic, and is of suitable resilience, for purposes appearing presently. In practice, it has been found preferable to integrally form the shell 21 by molding of plastic material.

The shell 21 is of a hollow, downwardly concave configuration, including an upper, central dome portion 25, and a circumferential sidewall portion 26 extending entirely about and depending from the periphery of the dome portion. In practice, the dome and

sidewall portions

25 and 26 may imperceptibly merge one into the other, preferably having a smooth continuous exterior surface.

The downwardly facing cupped configuration of the dome portion 25, by its shape and resilience, is inherently possessed of a spring action in the nature of a Belleville spring. Enhancing or stiffening this spring action, the dome portion 25 is provided with a generally annular reinforcement or stiffening, such as in the form of internal generally annular ribs 30 defining an annular resilient formation. Of course, the resilient formation defined by annular ribs 30 may alternatively be provided by other suitable means, such as internal reinforcement within the shell wall of dome portion 25, say of glass fibers, spring wire filaments, or other. In any event and by any construction, the resilient formation 30 serves to enhance the Belleville spring action of the dome portion 25.

Spaced generally centrally within the resilient formation 30, there is provided in the dome portion 25 a central resilient formation, say of internal ribs 31, or other suitable construction. The resilient formation 31, as best seen in FIG. 5, is located generally centrally within the outer dome portion resilient formation 30, and is of an ovaloid or elongate configuration in the forwardly and rearwardly direction. More specifically the ribs 31 are of generally concentric ovaloid configuration, being further reinforced at their forward and rearward ends, as by branching ribs 32 in the forward region and relatively short separate lengths of ribs 33 in the rearward region. The forward and rearward and regions of central resilient formation 31 are therefore more stiffly reinforced; and further, the forward end region of the resilient formation 31 is of greater stiffness, by its connected branch ribs, than the rearward region thereof with its separate or unconnected additional length of ribs. By this construction, the resilient formation 31 is of a varying spring constant in the forwardly and rearwardly direction, and specifically, is of a decreasing spring constant in the rearward direction. Also, the location of the resilient formation 31 spaced within the resilient formation 30 is such that the formation 31 is located eccentrically forwardly, so as to further increase the spring constant in the forward region of the dome portion 25. By this construction of resilient formations, as will appear more fully hereinafter, a gravitationally falling object impinging more or less centrally on the exterior of the dome portion-25, is caused to rebound or deflect obliquely by the resilience of the shell, and more specifically to deflect obliquely rearwardly.

In addition, the outer shell 21 is formed with a plurality of reinforcement formations extending radially outwardly from the, resilient formation 30, say the internal ribs 35 formed interiorly on the sidewall portion of the shell. The reinforcing ribs 35 may assume the form of other reinforcement or strengthening, such as by strengthening materials embedded in the' shell, which reinforcement is all in the nature of a columnar formation, serving to reinforce and support the dome portion 25 by columnar action. While the number and arrangement of columnar formations may vary, it has been found suitable to employ a pair of forwardly extending columnar formations 35a, a single rearwardly extending columnar formation 35b, a pair of obliquely rearwardly extending columnar formations 35, a pair of laterally obliquely extending columnar formations 35d, just rearwardly of center, and a pair of laterally obliquely forwardly extending columnar formations 35s, just forwardly of center. The several columnar formations 35 may all terminate at their lower ends in a lower circumferential region of the shell sidewall 26. At the lower end of each columnar formation 35, there is formed internally of the shell sidewall 26, a female connection element or socket 36. Specifically, a pair of forwardmost sockets 36a are each formed adjacent to the lower end of a respective forwardmost columnar formation 35a, a socket 36b being formed adjacent to the lower end of rearmost columnar formation 35);, a pair of sockets 36 each formed adjacent the lower end of a respective columnar formation 350, a socket 36d formed adjacent to the lower end of each columnar formation 35d, and a socket 36c formed adjacent to the lower end of each columnar formation 35a. The female connection elements or sockets 36 are each preferably formed integrally with the shell 21, as by a protuberance on the inner surface thereof, and formed therein with a downwardly and inwardly opening dovetail groove or slot 37. That is, each socket 36 is formed with a slot or groove 37 having an undercut or dovetail configuration, which opens both downwardly and radially inwardly oi the shell. Further, each socket slot 37 tapers upwardly to a closed upper end. The closed upper ends of sockets 36s are designated 38a, and correspondingly the closed upper ends of sockets 36/), 360, 36a and 362 are each respectively designated 38b, 38c, 3811 and 38a.

By way of illustration, the sockets 36a, 3560 and 3641 are of one type, as illustrated in FIGS. 11, 12 and 13. The socket 360 there illustrated has its upwardly convergent, undercut groove or slot 37 terminating at its closed upper end in a downwardly pointed engaging member 38a closing the upper end of the slot. The downwardly pointed engaging member 38a may be relatively weak, as for deflection or breakage under force, for purposes appearing presently.

The sockets or female connection elements 36!) and 361: are substantially identical to the remaining sockets or

female eonnection elements

36a, 36c and 36d, except that the closed upper ends 38b and 380 of the upwardly convergent slots or grooves 37 are defined by downwardly tapering, blunt end on gaging members. An engaging member 38b is shown in FIG. as closing the upper end of slot 37 formed in socket 36b, and being of relatively stout proportions for substantial re sistance to breakage and deflection.

The lower circumferential edge of the shell 21 may be provided with a circumfcrentially extending brim in the manner of a hat, or with a forward peak 40, as illustrated, to define a cap. in the cap construction, as illustrated, it is preferred to reinforce the rearward lower edge region, as by an integral formation of outwardly offset depending flange 41. That is, the integral flange 41 isroutwardly offset, as by a generally horizontal outwardly extending offsetting portion 42, see PK]. 4.

Considering now the suspension 22, best seen in FIGS. 1, 3, 4 and 6, the suspension may advantageously be integrally fabricated of flexible resiliently yieldable material, say by molding of suitable plastic, and includes a sheetlike head engaging part 45, which may be formed of a domed configuration for conforming engagement with the crown of a wearer's head. The sheetlike head-engaging part 45 may have a central through opening 46 bounded by a circumferential bead 47.

Extending generally radially outwardly and depending from the head-engaging part 45, being located in anguiarly spaced relation circumferentially thereabout, are a plurality of flexible suspender extensions 48. The extensions or suspenders 48 may advantageously be of sheetlike formation integral with the head-engaging part 45, and of a number and arrangement corresponding to that of the shell sockets 36. More particularly, the suspension 22 may include a pair of forwardly extending suspenders 48a, a rearward suspender 48b generally along the forward and rearward centerline, a pair of obliquely rearwardly extending suspenders 48c angularly spaced on opposite sides of the rearwardly suspender 48b, a pair of laterally obliquely and rearwardly extending suspenders 48d, respectively on opposite sides of the head-engaging part 45 rearward of the center opening 46, and a pair of obliquely laterally and forwardly extending suspenders 48s on opposite respective sides of the head-engaging part forward of the center opening 46.

The suspenders 48 are each provided on the outer side of its distal end region, as by integral formation therewith, with a male connection element, lug or insertion member, each generally designated 50. By way of specific designation, the male connection elements or lugs 50 are respectively designated by the alphabetical suffix of the corresponding suspcnder. That is, the forwardmost male elements 50 are specifically designated 50a, while the rearmost male connection element is specifically designated 50b, the connection elements of suspenders 480 being specifically designated 50c, the connection elements of suspenders 48d being specifically designated 50d, and the connection elements of suspenders 48a being specifically designated 50c. I

The male connection elements or lugs 50 are all substantially identical in construction, being of a trapezoidal outline configuration and are arranged to taper or converge from s lower larger end 51, sec FIGS. 10 and 15, to an upper smaller and 52. Further, the tapering or COfiVdrg-rni sides 53 are undercut in dovetail fashion, as may be seen in FIG. 16. and elsewhere.

Each of the male elements or lugs 50 may further be formed with a groove, slot or recess 55, which groove may extend up" wardly and inwardly through the lower larger lug end 51, iongitudinally along and between the convergent sidewalls 53, and terminate short of the inner end wall 52 to define a web or wall portion 56 closing the upper, inner end of the groove. As best seen in FIG. 6, the

lugs

50a, 50;- and 50d differ slightly from the lugs 50!; and 50a, in that the former are provided exteriorly on the wall portion or web 56 with a weakening line or groove 57. The weakening lines or grooves 57 are located to respectively receive the pointed engaging members or

wedges

38c, 38c and 38d, to facilitate piercing rupture by the engaging members oftlie engaged wall portions. The relatively blunt engaging members 38b and 38a engage with the nonwcakened walls 56 of corresponding lugs 50]) and 502, to provide greater resistance to relative shell and suspension movement.

in addition to the extending arms or suspenders 48, the suspension 22 includes a plurality of radially extending, circurnfcrentinlly spaced flexible extensions or legs 60, each provided with a row or series of fastener receivers or holes 61, for selective connections to the head band 23.

Additionally, a pair of laterally opposite radial extensions or legs 62 may be provided on the head-engaging part 45 of the suspension 22, having fastener elements 63 of any suitable construction, for connection to opposite ends of a chin strap, if desired.

The flexible sheet material of the head-engaging part 45 is preferably of a gradually varying thickness, being increasing in the forward direction, so as to have increasing yieldability in the rearward direction, as best seen in in FIG. 4. Further, the head-engaging part 45 is provided at a plurality of spaced locations with groups of vent openings, each group being generally designated 65. The vent opening groups 65 are each formed of staggered elongate openings or slots, so that the vented region is yieldably distensible, in the general manner of expanded metal. More specifically, the vent opening groups 65 are each of generally triangular configuration, tapering radially inwardly toward the central opening 46, and each group is located intermediate an adjacent pair of extension arms or suspenders. In particular, a forwardmost vent opening group 65a is formed in the head-engaging part 45 spaced between the forwardmost suspenders 48a, while a pair of laterally spaced rearwardmost vent opening groups 65b are each located on opposite sides of the rearwardmost suspender 48b, intermediate the latter and the respective, next adjacent suspender 48c. Additionally, an obliquely rearwardly disposed vent opening group 65c is formed in the head-engaging part 45 of intermediate each suspender 48c and the adjacent forward suspender 48d, while a pair of side vent groups 65d are each formed between an adjacent pair of

suspenders

48d and 48e. The vent opening groups 65 are thus sufficient in number and size to afford adequate ventilation to wearers head, while further affording resilient yieldability for absorbing impact force.

The haed-engaging part 45 of the suspension 22 is further formed in the rearward region thereof, with a plurality of areas generally designated 68 of deformable formations. As best seen in FIG. 6, it will be apparent that the areas 68 of deformable formations are each in radial alignment with a respective suspender 48b and 480, being correspondingly designated respective areas 68b and 680. More specifically, the formations of each area 68 may comprise a plurality of pairs of laterally spaced integrally formed depressions 69, which pairs of depressions are arranged in alignment with each other to define a pair of generally radially extending rows on opposite sides of a radial suspension portion 70 extending between the adjacent pairs of depressions. That is, the depressions 69 are formed integrally of the head-engaging part 45, and the radial interdepression suspension portion 70 of each group of depressions is generally in radial alignment with a respective suspender 48. The depressions 69 are depressed downwardly for bearing engagement with a wearers head, being of rela tively light gauge for soft cushioning action against the wearer's head. Further, the relatively light gauge of the suspension portions 70 enhances stretchability thereof under force, for purposes appearing presently.

The forward, relatively heavy gauge region of the head-engaging part 45 is formed with relatively large pairs of laterally extending

depressions

72 and 73. That is, a forward pair of laterally extending, spaced depressions 72 are formed in the head-engaging part 45 with the interdepression region 74 generally along the forward and rearward centerline of suspension. A relatively large pair of laterally extending, spaced depressions 73 are formed just rearwardly of the depressions 72, the interdepression space 75 being also along the forward and rearward centerline of the suspension; and, the outer regions of the depressions 73 are formed with further depressions 76 extending generally radially inwardly. The relatively

large depressions

72 and 73, extending laterally of the suspension 22, are engageable with the forward crown portion of a wearer's head for cushioning against the latter, and may have a rolling action thereon upon rearward shifting of the outer shell, as will be described more fully presently.

The headband 23 may include an elongate strip 80 bent upon itself to define a closed loop having overlapping

end portions

81 and 82 detachably secured together by suitable fastener means. A sweatband 83 may be secured along one edge of the strip 80, being folded inwardly to cover the inner side of the headband. A transverse extension 84 may be formed on one end portion 82 of the strip 80, being wrapped about the other end portion 81 and secured in its wrapped condition, as by a fastener 85.

At several locations spaced along the strip 80, there are provided fasteners for detachable connection to the suspension legs 60, as by headed studs 86. The rearward locations of connection to the suspension legs 60 are provided with upward extensions 87 for carrying the fasteners 86. The upward extensions 87 serve to displace the rearward region of the headband downwardly for enhanced gripping action with a wearer's head, especially when a wearer tilts his head forwardly.

In the assembled condition of suspension 22 with the outer shell 20, the forward male engaging elements or lugs 5011 are each inserted upwardly into the forward female connection elements or sockets 36a, as seen in FIG. 3. Similarly, the

male connection elements

50b, 50c, 50d and 50s are respectively engaged upwardly into the female connection elements or

sockets

36b, 36c, 36d and 36a. The male connection elements or lugs are firmly connected to the female connection elements or sockets by frictional engagement therein; or, additional detent means may be provided if desired.

Under the imposition of great impact force, as in the conventional testing procedure with the assembled headgear on a head form, a weight is dropped generally centrally onto the outer shell 21. As discussed hereinbefore, lesser forces applied in this manner will cause obliquely rearward deflection of the weight, as by the individual and combined actions of the

resilient formations

31 and 30. Further, the columnar formations 35 effect transmittal of downward forces through the sockets 36 to the suspension 22.

Tending to absorb or delay the transmittal of such forces to the suspension 22 are a number of structural features described hereinbefore, For example, the upward tapering of the sockets 36 and the wedge configuration of the several lugs 50, together with the yieldability or compressibility of the lugs afforded by the slots 55, permit of displacement between the sockets 36 and lugs 50 to absorb substantial forces.

Further, the pointed engagement members or wedges 38a. 38c and 38d, being impaled against the weakened end wall portions 56 of

lugs

50a, 50c and 50d, as by rupture of the end wall portions and distortion of the engaging members, permits of additional, delayed relative movement between the outer shell 21 and suspension 22 for absorption of additional impact forces.

The bearing engagement of the relatively blunt depending engagement members 381) and 38e with the end walls 56 of lugs 50b and 50e, serves to permit of additional distention and relative displacement, although less than that afforded by the action of wedge shaped

engagement members

38a, 38c and 38d.

Additionally, the deformable formations 68 of the relatively thin rearward region of suspension 22, as by stretching of the interdepression regions 70, permits additional downward movement of the rearward regions of the outer shell and suspension relative to the wearer's head, for additional absorption of impact force. That is, the suspension portions 70, being in alignment with respective suspenders 48, are yieldably extensible, and concurrent flattening of depressions 69 serves to elongate the rearward region of the suspension in the rearward direction. Simultaneously, the

depressions

72 and 73 may permit of rolling action to facilitate rearward shifting of the outer shell.

Also, as discussed above, the groups of vent openings 65 are formed to facilitate distention of the suspension 22 and further effect absorption of impact force.

The above-discussed rearward shifting of the outer shell, as by stretching of the interdepression regions 70, is further enhanced by the provision of several rearwardly located distensible vent areas 65, and also enhanced by the rearward location of several weakened lug end wall portions 56, as by weakening grooves 57. These several coacting structures cooperate to effect a rearward shifting of the outer shell under impact of a falling object. By this means, the transmitted force is substantially reduced and includes a relatively harmless forward component, the falling object being deflected obliquely rearwardly. This obliquely rearward defection enhances that described hereinbefore in connection with the

resilient formations

30 and 31 of the outer shell.

From the foregoing it is seen that the present invention provides a protective headgear which fully accomplishes its intended objects, substantially reducing the apparent mass of a gravitationally impinging object, and which otherwise fully accomplishes its intended purposes.

Although the present invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be made within the spirit of the invention.

What I claim is:

1. A protective headgear comprising a flexible head engaging part adapted to rest on a wearer's head, an outer shell in spaced relation over said head-engaging part, a plurality of suspender elements spaced circumferentially about and depending from said head-engageable part toward a lower region of said shell, and interfitting connection means on said suspender elements and said shell for suspending the latter in said spaced relation, said shell having a dome portion, a sidewall portion extending circumferentially about said dome portion, and an asymmetrical resilient formation generally centrally of said dome portion for obliquely resiliently deflecting a falling object.

2. A protective headgear according to claim 1, said resilient formation being integral with said dome portion and having a spring constant varying in the forwardly and rearwardly direction for effecting said oblique resilient deflection.

3. A protective headgear according to claim 2, said spring constant decreasing rearwardly for effecting Oblique rearward deflection ofa falling object.

4. A protective headgear according to claim 2, in combination with an additional resilient formation in said dome portion surrounding said first-mentioned resilient formation and affording said dome portion an enhanced Belleville spring action.

5. A protective headgear according to claim 4, in combination with a plurality of columnar formations in said shell sidewall extending downwardly from said additional formation toward respective connection means.

6. A protective headgear according to claim 5, said resilient and columnar formations being defined by shell portions of various cross sections.

7. A protective headgear according to claim 4, said resilient formations being defined by internally thickened portions of said shell, the exterior of said shell being smooth to assure predetermined deflection of falling objects.

8. A shell for protective headgear adapted to be suspended in spaced relation over a wearers head and comprising a dome portion, a sidewall portion extending circumferentially about and depending from said dome portion, a resilient formation centrally of said dome portion and configured to provide a spring constant varying in the forwardly and rearwardly direction, for resiliently deflecting a falling object in the forwardly and rearwardly direction, and an additional resilient formation in said dome portion surrounding said first mentioned resilient formation and affording said dome portion an enhanced Belleville spring action.

9. A protective headgear according to claim 8, said spring constant decreasing rearwardly for effecting obliquely rearwardly deflection of a falling object.

10. A protective headgear according to claim 8, in combination with a plurality of columnar formations in said shell sidewall extending downwardly from said additional resilient formation.

11. A protective headgear according to claim 10, said resilient and columnar formations being defined by shell portions of controlled elastic moduli.

Claims

1. A protective headgear comprising a flexible head engaging part adapted to rest on a wearer''s head, an outer shell in spaced relation over said head-engaging part, a plurality of suspender elements spaced circumferentially about and depending from said head-engageable part toward a lower region of said shell, and interfitting connection means on said suspender elements and said shell for suspending the latter in said spaced relation, said shell having a dome portion, a sidewall portion extending circumferentially about said dome portion, and an asymmetrical resilient formation generally centrally of said dome portion for obliquely resiliently deflecting a falling object.

3. A protective headgear according to claim 2, said spring constant decreasing rearwardly for effecting oblique rearward deflection of a falling object.

8. A shell for protective headgear adapted to be suspended in spaced relation over a wearer''s head and comprising a dome portion, a sidewall portion extending circumferentially about and depending from said dome portion, a resilient formation centrally of said dome portion and configured to provide a spring constant varying in the forwardly and rearwardly direction, for resiliently deflecting a falling object in the forwardly and rearwardly direction, and an additional resilient formation in said dome portion surrounding said first mentioned resilient formation and affording said dome portion an enhanced Belleville spring action.