Abstract:
An energy absorber includes a base sheet and a plurality of energy absorbing units with domed countermeasures extending from the base sheet. The countermeasures have slits in a domed portion thereof. The side walls of the energy absorbing units protect an adjacent object by cushioning the blow following repeated impacts in both vehicular and non-vehicular (e.g. helmets) environments. Preferably the side walls are oriented to buckle or bend after absorbing energy when impacted. The countermeasures primarily deaden any associated buzzes, squeaks or rattles. The integrally-formed countermeasures have a lower standing strength than the energy absorbing units. Methods related to the above are also described.

Description:
[0001]    This application relates to U.S. Pat. No. 8,465,087, filed Mar. 23, 2010 and issued Jun. 18, 2013, which claims benefit under 35 U.S.C. §119(e) from provisional application Ser. No. 61/164,700, filed Mar. 30, 2009, entitled ENERGY ABSORBER WITH ANTI-SQUEAK ANTI-RATTLE FEATURE, the entire contents of which applications are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. (1) Technical Field 
         [0003]    The present invention relates to recoverable energy absorbers, such as are used non-destructively and re-usably for absorbing energy in automotive and non-automotive applications. 
         [0004]    2. (2) Background Art 
         [0005]    Vehicle manufacturers spend considerable time and effort to eliminate BSR noises because they can be very irritating and annoying to vehicle drivers and passengers, particularly when the BSR noises come from a location close to a passenger&#39;s head, and/or any component in the vehicle&#39;s passenger compartment, especially when the noises are created near or are amplified by components that effectively form an echo chamber. 
         [0006]    Many different geometrically shaped thermoformed energy absorbers are known, such as those described in U.S. Pat. Nos. 6,017,084; 6,221,292; 6,199,942; 6,247,745; 6,679,967; 6,682,128; 6,752,450; 7,360,822; 7,377,577; 7,384,095; and 7,404,593. These absorbers are said to provide dynamic reaction force characteristics that produce a relatively “square wave” shape when observing their reaction force properties as a function of deflection. 
         [0007]    U.S. Pat. No. 8,465,087 describes a formed energy absorber with an integrated anti-squeak/anti-rattle feature which includes a protrusion (“countermeasure”) that suppresses or dampens buzzes, squeaks or rattles at the end wall of an energy absorbing structure. Such structures typically lie between a Class-A surface (such as a bumper fascia, a headliner, or a door trim panel) and a rigid sheet metal structure in automotive applications. The absorber is typically installed with a 3-5 mm gap from one surface and is attached to another. However, in some instances it becomes necessary to reduce the gap to improve the reaction response time at the primary area of impact prior to secondary impacts as for example the head rolls into adjacent structures. When the absorber contacts the opposing surface, an undesirable buzz or rattle can be heard. This noise occurs because a flat hard plastic surface can tap or vibrate against the opposing structure. The &#39;087 patent describes an anti-buzz, squeak or rattle feature that is formed integrally with energy absorbers during the thermoforming process. However, this feature has proven difficult to form consistently, requires relatively a narrow processing window, and generally lacks the flexibility necessary to fully mitigate the translation of one structure to another that creates a BSR condition. 
         [0008]    Materials such as foam, felt, and flock are often added to absorbers which lack an integrated structure to remedy the issue. A fabric pad, flock material, foam padding, or some other kind of flexible material if added to one of the surfaces responsible for making the noise may lessen or eliminate the severity of the buzzing or tapping or eliminate the possibility of one surface translating into the other. However, this solution requires the purchase and assembly of one or more separate components, and that results in added complexity, cost, and mass. 
       SUMMARY OF INVENTION 
       [0009]    One aspect of the present invention includes a base sheet and a plurality of energy absorbing units extending from the base sheet. Each energy absorbing unit includes a side wall that even when subjected to multiple hits deflects while absorbing energy and at least partially recovers after each hit. The energy absorbing unit includes an end wall. At least one of the base sheet and the end wall of at least one energy absorbing unit includes a number (X) of integrally-formed protruding countermeasures (“ears”) where 1&lt;=X&lt;1000. The protruding countermeasures have a lower standing strength than the energy absorbing units so that the protruding countermeasures dampen movement that may otherwise cause buzzes, squeaks and/or rattles (“BSR”) between the base sheet or end wall and an adjacent structure. 
         [0010]    One aspect of the present disclosure includes a modified end wall structure that is superior to prior structures relative to ease of manufacture, cost, and function. 
         [0011]    The improved energy absorber is created through a combination of designed geometry and tooling that creates a “domed” flexible member (“countermeasure”) extending from the end wall of an energy absorbing unit. The dome is designed and engineered in such a way that it interacts with the reaction surface through a touch or designed interference condition. In one embodiment, the frusto-conical side wall of the energy absorbing unit is maintained, but some or all of the end wall is convex or “domed”. In response to impact the side wall may buckle without reversion to its un-deflected state, but the countermeasure may revert to its initial condition soon after impact. This provides a rapid response to the desire to suppress buzzes, squeaks or rattles (“BSR”) after the hit. 
         [0012]    In one embodiment, the domed countermeasure protrudes from the inner radius of an annular perimeter of the flat end wall. In another embodiment, the dome rises from the top of the side wall. In either embodiment there is tangential point contact between the energy absorbing structures and the adjacent structures that minimizes the surface area in contact with the reaction surface. 
         [0013]    When the energy absorber is manufactured from a material of thickness (T), tooling is used to mold or coin the domed area to a thickness (t) substantially less than 0.5 (T), e.g., 0.1 (T). This makes the dome more flexible the rest of the structure and isolates or localizes preferred flexibility at and around the dome. 
         [0014]    Imagine the dome is represented by part of a hemispherical shell with a pole positioned at its highest point and lines of longitude extending radially therefrom. In one embodiment, the dome may be lanced or cut parallel to the lines of longitude to create flexible “petals” that enable additional flexibility when compared to a non-lanced dome of the same material thickness. By changing the shape and position of the cuts in the dome, in combination with the “coined” thickness of the dome, additionally flexibility or strength may be imparted to meet BSR performance objectives. 
         [0015]    In another aspect of the invention, an energy absorber includes a base sheet and a plurality of frusto-conical energy absorbing units extending from the base sheet. Each energy absorbing unit has a side wall that is oriented so that upon receiving the forces of impact (“incident forces”), the side wall offers some resistance, deflects and partially reverts (springs back) to an un-deflected pre-impact configuration while exerting reaction forces to oppose the incident forces. This phenomenon effectively cushions the blow by arresting the transmission of incident forces directed towards the mass or object to be protected (e.g., an anatomical member, a piece of sheet metal, an engine block, or the head of a passenger or player). 
         [0016]    In another aspect of the present invention, a method includes the substantially simultaneous steps of forming an energy absorber with a base sheet and energy absorbing units extending from the base sheet with associated integral domed countermeasures of a weaker standing strength than the energy absorbing units. 
         [0017]    In still another aspect of the present invention, an assembly method includes the steps of (1) providing a component or other mass to be protected, (2) forming substantially simultaneously an energy absorber including energy absorbing units and optionally at least one domed countermeasure in an end of one or more of the energy absorbing units, the countermeasure being configured to interface with the component or mass when placed adjacently, so that BSR from movement of the energy absorber relative to the adjacent component or mass is reduced or eliminated, and (3) assembling the energy absorber and the component or mass in adjacent positions. 
         [0018]    In yet another aspect of the present invention, a thermoforming apparatus for making the energy absorber includes a heater for heating a flat sheet of a polymeric material, at least one thermoforming die for forming the flat sheet into a three-dimensional energy absorber that absorbs impacting forces non-destructively, the absorber having a base sheet and a plurality of energy absorbing units, and tooling for forming domed BSR countermeasures in at least one of the base sheet and the energy absorbing units. 
         [0019]    These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]      FIG. 1  is a cross-sectional view of opposing thermoforming dies for forming a sheet into an energy absorber with a plurality of energy absorbing units and domed countermeasures extending from recesses formed in the base sheet. At least some of the units have integral domed countermeasure for reducing buzzes, squeaks, and rattles (“BSR”) upon installation. 
           [0021]      FIG. 2  is a cross-sectional view showing the thermoformed energy absorber of  FIG. 1 . 
           [0022]      FIG. 3  is a cross-sectional view showing the energy absorber installed between for example a roof structure of a passenger vehicle and a headliner or a helmet and the head of a wearer. 
           [0023]      FIG. 4  is a cross section through one energy absorbing unit having a coined dome-shaped countermeasure extending from an end wall thereof. 
           [0024]      FIGS. 5-6  are isometric views of a single energy absorbing unit. 
           [0025]      FIGS. 7-8  are top views of the units depicted in  FIGS. 5-6 . 
           [0026]      FIG. 9  is a top view of an alternate embodiment. 
           [0027]      FIG. 10  is a force-displacement graph that illustrates the response of energy absorbing units with and without a countermeasure. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]      FIG. 1  illustrates a thermo forming process step in which an energy absorber  10  is shaped between a male (upper) die and a female (lower) die. If desired the dies could be inverted.  FIG. 2  shows the product so formed.  FIG. 3  depicts the energy absorber interposed between for example a vehicle roof  14  and a headliner  13 . 
         [0029]      FIG. 4  is a cross section through one energy absorber (“EA”)  10  with a coined domed countermeasure  15  whose thickness (t) is substantially less than that of a base  16  or sidewalls  11 . A relatively thin dome  15  promotes flexibility in the interfacial region between the energy absorber  10  and a surface with which it is juxtaposed. 
         [0030]    As shown in  FIGS. 5-9 , if desired, the domed region  15  may be cut or lanced longitudinally and/or laterally to create slits  19  in a manner to be described to enhance flexibility and create pre-engineered zones of weakness. 
         [0031]    In several embodiments of the invention the disclosed energy absorber has a base sheet  16  and a plurality of energy absorbing units  11  that preferably are reusable after exposure to multiple impacts. The energy absorbing units  11  extend from the base sheet  16 . Each energy absorbing unit  11  has an end wall  12  and a side wall  13  that in some cases revert at least partially towards an un-deflected configuration after impact. The sidewall  13  absorbs energy after being impacted. The end wall  12  of at least one energy absorbing unit  11  includes a number (X) of integrally-formed domed countermeasures  15 , where 1&lt;=X&lt;1000. 
         [0032]    In some cases, the energy absorbing unit  11  reverts to an un-deflected or compression set configuration after a first impact. As used herein the term “compression set” means a configuration before impact in which an energy absorbing unit lies after being squeezed or compressed into position between for instance a Class A surface (e.g. a bumper fascia) and a rigid block or sheet of metal (e.g. a bumper frame). In other cases, the energy absorbing unit may revert to or towards the compression-set configuration after multiple impacts. 
         [0033]    To absorb impact forces, the side wall  13  of an energy absorbing unit  11  bends in response to impact like the wall of a concertina or bellows and springs back to an un-deflected configuration in further response to impacting forces. In some cases opposing side walls  13  of an energy absorbing unit bend at least partially convexly after impact. In other cases, opposing side walls of the energy absorbing unit bend at least partially concavely after impact. Sometimes, opposing side walls of the energy absorbing unit  11  bend at least partially concavely and convexly after impact. 
         [0034]    In one embodiment, the energy absorber  10  has an energy absorbing unit  11  with an end wall  12  that includes an annular ring around the perimeter of the end wall  12  of the domed countermeasure  15 . The domed end wall  12  is supported by an upper periphery of the side wall  13  and deflects inwardly, thereby absorbing a portion of the energy dissipated during impact. 
         [0035]    Several alternative designs call for the countermeasure  15  to be formed in the base sheet  16 . In others, the countermeasure  15  is formed in the end wall  12  of an energy absorbing unit  11 . 
         [0036]    Aided by these structures, the disclosed energy absorber can be re-used after single or multiple impacts. For example the hockey or football player or cyclist need not change his helmet after every blow. Most of the recovery occurs quite soon after impact. The remainder of the recovery occurs relatively late in the time period of recovery. 
         [0037]    In a given end wall  12  there is a number (X) of countermeasures  15 , where 1&lt;=X&lt;1000. Some or all countermeasures  15  have slits  19  originating at an imaginary pole of a generally hemispherically shaped domed countermeasure. As used herein the term “hemispherical” is not limited in a geometrical sense to half of a sphere. It may describe or qualify a spheroid or oblate spheroid for example, like a squashed orange or pear or a section of a football. 
         [0038]    As to the shape of the energy absorbing units  11 , it is useful to define an annular perimeter  17  ( FIGS. 7-9 ) of the end wall  12  inside the side wall  13 . The annular perimeter  17  has an inner radius (r) from which the domed countermeasure rises. Alternatively, the domed countermeasure may rise from a collar  21  extending from the end wall. 
         [0039]    It is contemplated that the “soft” BSR countermeasure  15  can be formed integrally with the material of an energy absorbing unit at or near the location(s) of potential buzz, squeak, or rattle BSR noises. 
         [0040]    Where deployed, the BSR countermeasure  15  has a relatively lower longitudinal/standing strength than the associated energy absorbing unit  11 . Though the sidewall of an energy absorbing unit may buckle and assume a permanent deformation following impact, the countermeasure flexes and reverts to its pre-impact configuration. Accordingly, it acts as a dampener, thus greatly reducing the likelihood of significant BSR noises in the final assembled product (such as an automotive vehicle or crash helmet for a motor cyclist or a helmet for the skier, hockey player or football player). Further, a significant assembly cost reduction and mass reduction can be realized with only a minimal or zero increase in the tooling and/or manufacturing cost because various wadding or muffling materials are no longer needed. 
         [0041]    Various headliner constructions are exemplified in the drawings. However, persons skilled in this art will understand that the present disclosure is not limited to headliners, but instead can be applied to many other applications, including but not limited to other locations in a vehicle (e.g., doors, instrument panels, trim components for A, B and C pillars and roof supporting structures of vehicles, and other components), various types of protective headgear, and other protective gear that intercedes between an anatomical member (e.g., a knee, elbow, stomach) and an impacting object. 
         [0042]    In one embodiment, an energy absorber  10  (illustrated in  FIGS. 1-3 ) includes a matrix of hollow frusto-conical, distended frusto-conical (e.g. with an oval or elliptical footprint/lower perimeter/upper perimeter or cross section), cup-shaped (with a wall that is curvilinear—e.g., bowed, convex or concave when viewed from the side—or flat), domed, hemispherical or flat-sided pyramid-shaped) three-dimensional energy absorbing units with side walls  11  extending from a base sheet  16 . At least some of the energy absorbing units  11  have the BSR countermeasure  15  that extends from an end wall  12  of an energy absorbing unit  11 . In some cases the countermeasure  15  may effectively be flattened somewhat so that it resembles a domed end wall  16  that extends between the sidewalls  13  of an energy absorbing unit  11  ( FIGS. 5-6 ). 
         [0043]    The energy absorbing units  11  can be arranged on the energy absorber  10  in any repeating or non-repeating, uniform or non-uniform pattern desired, such as an orthogonal or diagonal matrix of rows (parallel or converging) and columns (parallel or converging) that would partially or totally cover the mass to be protected, for example an area of a vehicle roof from the side-to-side and from the front-to-rear of a vehicle&#39;s passenger compartment. 
         [0044]    Further, the energy absorbing units  11  can be similar to each other or can be varied, so as to have different or similar footprints, widths, heights, and/or cross-sectional shapes (parallel, inclined or perpendicular to the base sheet  16 ). The energy absorbing units  11  can have uniform or non-uniform spacing and/or different lateral relationships and/or be varied to accommodate the spatial constraints imposed by the environment of use, such as the vehicle roof and mating structures as needed for energy absorption in different areas of the assembly. For example, the energy absorber  10  can have different regions, some regions having energy absorbing units arranged or configured a first way, and other regions having energy absorbing units arranged or configured a second or different way. This is often the situation where energy absorbers are used in for example vehicle roof structures, as will be understood by persons skilled in this art. After thermoforming, the base sheet  16  may be flat or bent as desired. 
         [0045]    As an example, the illustrated energy absorber  10  is thermoformed from a heated sheet  16  of a polyolefin polymeric material such as that available from Lyondell Bissell under the product name SV  152 . The sheet is heated to a temperature below its melting point and positioned between by opposing forming dies  17 ,  18  (see  FIG. 1 ), and then cooled to form a three-dimensional energy absorber (see  FIG. 2 ). Opposing forming dies  17 ,  18  are illustrated, but it is contemplated that the present inventive concepts can be made using other forming processes, such as a thermoforming process using only a single sided die (e.g. by vacuum thermoforming). Optionally the absorber is made by softening a sheet of starting material and positioning it across a tool with which it is made to conform under a vacuum. It will be appreciated that the present inventive concepts can be made by other forming processes, such as injection molding, compression molding, and the like. 
         [0046]    Once formed, the illustrated energy absorber  10  is adapted to fit between and generally at least partially bridge a gap between for instance a vehicle headliner  13  and its roof  14  (see  FIG. 3 ). In the exemplary application depicted, the energy absorbing units  11  and the base sheet  12  are generally configured to occupy at least some space between the headliner  13  and roof  14 . The outer ends  16  (also called “end walls” or “base” herein) of the energy absorbing units  11  and the base sheet  12  generally match the contoured mating surfaces on the headliner  13  and roof  14 . 
         [0047]    The illustrated energy absorber  10  has differently shaped energy absorbing units  11  that are configured to meet spatial or aesthetic requirements and cover protruding bolts plus other fittings while optimizing the safe absorption of energy and distribution of impact loads in order to reduce at least in vehicular applications passenger head injury (such as during a vehicle crash or roll-over accident) or in other non-vehicular applications (such as head- or limb-protecting gear). 
         [0048]    As noted above, the (BSR) countermeasure  15  (also called an “ear” or “soft structure” herein) is integrally formed into its end wall  12 , as illustrated. An energy absorber  10  may have energy absorbing units  11  with a collective number (X) of ears  15  that are associated with the energy absorber  10 , where 1&lt;=X&lt;1000. 
         [0049]    The countermeasures  15  have a lower standing strength than the energy absorbing units  11 . Their “softness” reduces the potential for BSR noises caused by repeated noise-generating vibration and/or cyclical movement of the energy absorber  10  against adjacent rigid surfaces on for example the headliner  13  and roof  14 . 
         [0050]    In end wall  16 , the illustrated BSR countermeasure  15  ( FIG. 1 ) preferably is formed by a rounded male protrusion  20  that extends from the top die  17  into a mating recess in the lower die  18 . The protrusions  20  include at least part of a hemispherical dome. As a consequence the sheet material assumes a shape after cooling that resembles a dome-shaped thin-walled hollow BSR countermeasure  15 . It will be appreciated that the dome may be described by an angle of latitude (in terrestrial terms) less than 90 degrees, i.e., the dome need not be a geometrically perfect hemisphere. 
         [0051]    In some cases the base sheet  16  (or roof, depending on orientation) of an energy absorbing unit  11  itself may be domed to form a countermeasure  15  so as effectively to interface with a neighboring structure, thereby reducing an area of contact therebetween and reducing or eliminating BSR. 
         [0052]    The illustrated BSR countermeasures  15  are sufficient in length and strength to maintain their generally hemispherical shape after the starting sheet material is cooled (see  FIG. 2 ). In particular, the height of the BSR countermeasures  15  in combination with energy absorbing units  11  is greater than any expected gap between the headliner  13  and the roof  14  (in vehicular applications), such that the BSR countermeasure  15  contacts the headliner  13  (or roof  14 ) and is compressed during assembly into the vehicle. 
         [0053]    The domed BSR countermeasure  11  also compensates for variations in the gap size due to part tolerance variation, assembly stack-up variations, and other process and part variables that may lead to inconsistent gaps. This results in the BSR countermeasures  15  acting to dampen any cyclical or vibratory movement of the energy absorber  10 , which in turn eliminates most BSR noises. 
         [0054]    As an example, it is contemplated that the BSR countermeasures  15  can be about ⅛ to ½ inch in height (or more typically about ¼ to ⅜ inches), and at their base about 1/32 to ¼ inch in diameter (or more preferably about 1/16 to ⅛ inch in diameter). 
         [0055]    As mentioned earlier, the countermeasure is preferably sufficiently flexible so that it deflects at relatively low loads in a relatively elastic manner. The term “relatively low load” as used herein is defined as less than 2 lb.f at each point of contact. By comparison, the energy absorbing unit itself typically collapses at loads in excess of 10 lb.f (see, e.g.  FIG. 10 ). In this way, flexibility is substantially localized at the countermeasure on the end wall. 
         [0056]    One manufacturing technique involves coining Though other methods may be suitable, coining is done by providing a rigid lower member (typically metal) and an upper coining member. A representative configuration is a matched metal set and a material which is more rigid than the molten plastic (like a rigid silicone rubber). This prompts displacement of material away from the domed countermeasure, preferentially thinning the dome in the contacted area. Other things being equal, the thinner the material, the less resistance is required to displace the dome. Furthermore, by relieving the dome with cross cuts as described above, the resistance required to displace the dome is further reduced. 
         [0057]    It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.