Abstract:
The invention provides a portable, collapsible sign stand assembly in which a sign is suspended from a support tube. The support tube is connected to a support base through a connecting member which includes a plurality of weakening members which cause the connecting member to fail upon impact. In other embodiments, the support tube is weakened by weakening members so as to fail upon impact. In one embodiment, the weakened portions are placed under tension.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention pertains to signs such as temporary warning signs which may be collapsed for storage in a reduced space and readily erected upon demand.  
           [0003]    2. Description of Related Art  
           [0004]    Warning signs are provided for a variety of purposes. Among the more demanding applications, is the use of roadside warning signs to advise motorists and pedestrians of activity being conducted at a work site. This type of signage allows those present in the vicinity to be alerted before entering the center of the work area so that appropriate action may be taken. Such signs are used, for example, by utility companies and others who maintain dedicated service in residential areas, and who may be required to perform repairs and other work activities in close proximity to pedestrian or vehicular traffic. With the presence of appropriate warning signs, pedestrian traffic is advised that objects unusual for the area may impede their progress of movement, that objects may be temporarily suspended above them or that other conditions may warrant careful scrutiny while traversing a work area. Vehicular traffic approaching a work site can, with sufficient amounts of properly located signage, be advised that traffic is being diverted or that traffic may be required to stop or slow down to avoid contact with workmen or construction vehicles, for example.  
           [0005]    For long term projects, appropriate signage can be ordered ahead of time and installed in a permanent or semi-permanent fashion, after a detailed study of the particular work area. However, utility companies, highway departments, providers of emergency services and others may be required to establish a work area, virtually on a moment&#39;s notice. For example, management of a traffic accident scene may require appropriate signage to be erected in a traffic lane or at a roadside or other location, on an emergency basis.  
           [0006]    Bearing in mind that such signage must be large enough to present adequate notice to motorists and others passing by an area, consideration of the sign&#39;s size and weight must be taken into account when outfitting a work team. It is impractical in such instances to require work personnel to employ bulky, massive signage. Accordingly, lightweight so-called “roll-up” signs are becoming increasingly popular with a variety of different users. With lightweight collapsible signs, utility construction or repair crews can carry a number of such signs as standard equipment which is maintained in the vehicles at all times.  
           [0007]    One example of a commercially popular collapsible sign panel is the Model No. 3000XP sign panels offered for sale by the assignee of the present invention. The collapsible sign panel employs aluminum tubing arms and a central mounting system which allows the panel to fold together before rolling into a compact bundle that is more easily stored in tight places. The sign panels are made of flexible retro-reflective material which is folded as the arms are pivoted about the hub. The flexible panel is then wound about the collapsed arms to form a compact, cylindrical package of minimal size. Sign panels which are as large as three feet and four feet on a side are typical.  
           [0008]    U.S. Pat. No. 4,694,601 assigned to the assignee of the present invention shows a portable collapsible sign which has also enjoyed commercial success. Various sign stand assemblies employ spring loading features to balance wind deflection forces. Ground-engaging legs for supporting the erected sign panel may be permanently attached to the sign panel or may be provided in a separate assembly which is typically mated to the erected sign panel with a slip fit or other type of engagement.  
           [0009]    With easily portable sign panel assemblies of the above-described type, the use of signage at temporary workplace locations is becoming more consistent due to the practicality and ease of use afforded worksite personnel. However, further improvements are still being sought. For example, continued improvements and simplifications of the sign assembly mechanisms are continually being sought.  
           [0010]    The Transportation Research Board (TRB) is a unit of the National Research Council, a private, nonprofit institution that is the principal operating agency of the National Academy of Sciences (established by Congress in 1863) and the National Academy of Engineering. The mission of the Transportation Research Board is to promote innovation and progress in transportation by stimulating and conducting research, facilitating the dissemination of information, and encouraging the implementation of research results.  
           [0011]    The Transportation Research Board fulfills its mission through the work of its standing technical committees and task forces addressing all modes and aspects of transportation. Duties include conducting special studies on transportation policy issues at the request of the U.S. Congress and government agencies as well as operation of an on-line computerized file of transportation research information and the hosting of an annual meeting that attracts a large number of transportation professionals from throughout the United States and abroad.  
           [0012]    The Transportation Research Board administers two cooperative research programs: The first program, the National Cooperative Highway Research Program (NCHRP) is sponsored by the member departments of the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration, the National Cooperative Highway Research Program and the Transit Cooperative Research Program. The National Cooperative Highway Research Program was created in 1962 as a means of conducting research in acute problem areas that affect highway planning, design, construction, operation, and maintenance nationwide.  
           [0013]    The second program, named the Transit Cooperative Research Program (TCRP), is sponsored by the Federal Transit Administration and is carried out under a three-way agreement among the National Academy of Sciences (acting through the Transportation Research Board), the Transit Development Corporation, Inc. (a nonprofit educational and research organization established by the American Public Transportation Association) and the Federal Transit Administration. The Transit Cooperative Research Program serves as one of the principal means by which the transit industry can develop innovative near-term solutions to meet demands placed on public transit systems.  
           [0014]    Currently, developers of roadside safety hardware are guided by testing requirements using a range of criteria defined by Report 350 of the National Cooperative Highway Research Program (NCHRP), entitled “Recommended Procedures for the Safety Performance Evaluation of Highway Features.” NCHRP Report 350, incorporated significant changes and additions to procedures for safety performance evaluation, including criteria for multiple performance levels, guidelines for testing features not previously addressed, translation to metric units, and updates reflecting the changing character of the highway network and the vehicles using it. Concerns have been raised that some existing hardware, which is observed to be performing adequately in the field, may have difficulty passing new tests and evaluation criteria. Further study and testing has been called for in an attempt to improve roadside safety by establishing crashworthiness criteria that reflects changes to the vehicle fleet and safety hardware technology.  
           [0015]    In its Jul. 25, 1997 guidance memo, “Identifying Acceptable Highway Safety Features,” the Federal Highway Administration established four categories of work zone devices. It also set deadlines requiring devices within each category to be crashworthy under the National Cooperative Highway Research Program Report 350 criteria.  
           [0016]    Work crews, such as those servicing and installing utility equipment, are required to operate at or near operational highways and other roadways. Temporary sign assemblies are typically carried by the work crew and are installed at a roadside location so as to give oncoming motorists time to react to the unexpected appearance of equipment and personnel, at or near the highway roadside. At times, a work crews operations will be very brief. Nonetheless, it is important that roadside warnings in accordance with recent safety regulations, be set up in advance of work commencement. To be commercially successful, a temporary sign assembly must be capable of quick and easy deployment.  
         SUMMARY OF THE INVENTION  
         [0017]    It is an object of the present invention to develop temporary sign assemblies that are good candidates for offering a satisfactory performance when tested under various safety programs.  
           [0018]    It is another object of the present invention to provide sign panel assemblies having an improved ease of operation, with low mass, conformable, dynamically reconfigurable members.  
           [0019]    A further object of the present invention is to make it possible for police vehicles, survey teams and others which typically employ automobile and other similar sized vehicles to carry several signs in the trunks of their vehicles. These and other objects of the present invention are provided in a support arrangement, a base, a force accumulator tube of hollow predetermined cross-section outwardly extends from the base and has a free edge spaced from the base. A support tube of hollow complementary cross-section telescopically engages in a close-sized fit with force accumulator tube so as to have a predetermined portion which extends beyond the free edge of force accumulator tube. An insertion limiter cooperates with force accumulator tube and support tube to limit telescopic engagement of support tube and force accumulator tube, aligns with predetermined portion with the free edge of force accumulator tube, and predetermined portion of support tube includes a plurality of weakening members aligned with the free edge of force accumulator tube. A lateral force applied to sign support arrangement is accumulated at free edge of force accumulator tube and is developed at predetermined portion of support tube.  
           [0020]    Other objects are attained in a support arrangement, a base plate, a force accumulator tube of hollow predetermined cross-section depends from base plate, force accumulator having a free edge spaced from the base plate, support tube of hollow complementary cross-section, has a lower edge. A support plate at the bottom of support tube, support plate spaced from base plate to form a gap therewith. A tension arrangement extends between base plate and support plate, urging said base plate and support plate away from one another, a connecting tube having opposed ends telescopically engaged in a close-sized fit with force accumulator tube and support tube, and spanning the gap between support plate and base plate first and second insertion limiters cooperating with force accumulator tube, connecting tube and support tube to limit telescopic engagement of connecting tube and force accumulator tube limiting telescopic engagement of support tube and force accumulator tube, aligning a predetermined portion of connecting tube with a force accumulator tube free edge, and predetermined portion of connecting tube including a plurality of weakening members aligned with the free edge of force accumulator tube. A lateral force applied to sign support arrangement is accumulated at the free edge of force accumulator tube and is developed at predetermined portion of connecting tube. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a perspective view of a sign and sign stand assembly according to principles of the present invention;  
         [0022]    [0022]FIG. 2 is a fragmentary front elevational view of the sign stand assembly, taken on an enlarged scale;  
         [0023]    [0023]FIG. 3 is an exploded view thereof;  
         [0024]    [0024]FIG. 4 is a cross-sectional view taken along the line  4 - 4  of FIG. 3;  
         [0025]    [0025]FIG. 5 is a cross-sectional view taken along the line  5 - 5  of FIG. 3;  
         [0026]    FIGS.  6 - 8  are fragmentary elevational views showing a connecting tube portion of the sign stand assembly;  
         [0027]    FIGS.  9 - 11  are fragmentary perspective views showing the connecting tubes to FIGS.  6 - 8  installed in the sign stand assembly;  
         [0028]    FIGS.  12 - 15  show alternative embodiments of base plate members of the sign stand assembly;  
         [0029]    FIGS.  16 - 19  show the base plates of FIGS.  12 - 15  installed in a sign stand assembly;  
         [0030]    FIGS.  20 - 22  show the sign stand assembly during an impact event;  
         [0031]    [0031]FIG. 23 is an enlarged fragmentary view of the sign stand assembly immediately after impact;  
         [0032]    [0032]FIG. 24 shows an alternative embodiment of a sign stand assembly and sign stand, immediately prior to an impact event;  
         [0033]    [0033]FIG. 25 is a fragmentary perspective view of a sign stand support of FIG. 24;  
         [0034]    [0034]FIG. 26 shows an indicated portion of the sign stand assembly of FIG. 24, on an enlarged scale;  
         [0035]    [0035]FIGS. 27 and 28 show alternative embodiments of the sign stand assembly of FIG. 24; and  
         [0036]    [0036]FIGS. 29 and 30 show the sign stand assembly during an impact event. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]    Turning now to the drawings, FIG. 1 shows a sign apparatus generally indicated at  10 . Included is a sign panel assembly  12  supported by a sign stand assembly  14  having ground-engaging legs  16  and a spring-loaded pivoting coupling  18 . The sign panel assembly  12  includes a flexible message or sign panel  20  of conventional construction. Sign panel  20  may, for example, comprise a mesh fabric such as vinyl coated polyester mesh or may be of a solid or continuous such as a vinyl coating applied to a polyester fabric backing. It is generally preferred that the sign panel  20  be made of some sort of reflective material, such as a vinyl microprism reflective material so as to provide a high level of retro-reflectivity of a type suitable for traffic applications.  
         [0038]    Federally mandated standards are being developed to ensure that roadside appurtenances such as temporary warning signs are crashworthy under the National Cooperative Highway Research Program Report 350 criteria. Category II Devices are defined as not being expected to produce significant vehicular velocity change, but may otherwise be hazardous. The following is a SUMMARY OF SUPPLEMENTARY EVALUATION FACTORS for crash worthiness according to the National Cooperative Highway Research Program Report 350 criteria:  
         [0039]    Passenger Compartment Intrusion  
         [0040]    1. Windshield Intrusion  
         [0041]    a. No windshield contact  
         [0042]    b. Windshield contact, no damage  
         [0043]    c. Windshield contact, no intrusion  
         [0044]    d. Device embedded in windshield, no significant intrusion  
         [0045]    e. Partial intrusion into passenger compartment  
         [0046]    f. Complete intrusion into passenger compartment  
         [0047]    2. Body Panel Intrusion (yes or no)  
         [0048]    Loss of Vehicle Control  
         [0049]    1. Physical loss of control  
         [0050]    2. Loss of windshield visibility  
         [0051]    3. Perceived threat to other vehicles from debris  
         [0052]    4. Debris on pavement  
         [0053]    Physical Threat to Workers or Other Vehicles  
         [0054]    1. Harmful debris that could injure workers (yes or no)  
         [0055]    2. Harmful debris that could injure workers in other vehicles (yes or no)  
         [0056]    If yes, record the size and approximate mass of the debris, the approximate speed (high or low) and the approximate trajectory (height, direction etc.) of the potentially harmful debris.  
         [0057]    Vehicle and Device Condition  
         [0058]    1. Vehicle Damage  
         [0059]    a. None  
         [0060]    b. Minor scrapes, scratches or dents  
         [0061]    c. Significant cosmetic dents  
         [0062]    d. Major dents to grill and body panels  
         [0063]    e. Major structural damage  
         [0064]    2. Windshield Damage  
         [0065]    a. None  
         [0066]    b. Minor chip or crack  
         [0067]    c. Broken, no interference with visibility  
         [0068]    d. Broken and shattered, visibility restricted but remained intact  
         [0069]    e. Shattered, remained intact but partially dislodged  
         [0070]    f. Large portion removed  
         [0071]    g. Completely removed  
         [0072]    3. Device Damage  
         [0073]    a. None  
         [0074]    b. Superficial  
         [0075]    c. Substantial, but can be straightened  
         [0076]    d. Substantial, replacement parts needed for repair  
         [0077]    e. Cannot be repaired  
         [0078]    [0078]FIG. 1 shows sign panel  20  in a deployed or fully expanded configuration. Two or more arm assemblies  24  span the corners of panel  20  to hold the panel in a preferred planar configuration. The arm assemblies may comprise a pair of rigid aluminum ribs, or alternatively a pair of fiberglass ribs, as is known in the art. Other types of materials may also be employed as well. As an alternative, the arm assemblies may be formed separate one from another and joined at the center to align the arms in a co-planar arrangement, so as to provide a suitable support surface for the flexible panel  20 . A central hub assembly is indicated at  26 . Together, the arm assemblies  24  and center hub assembly  26  comprise a panel supporting system which, together with the sign panel  20  comprise panel assembly  12 . With the sign panel assembly in a fully opened position, panel  20  is maintained relatively taut, and is thus subject to naturally occurring or vehicle induced wind bursts. These forces are applied to a support tube or upright  30 . If desired, one or more arms  24  can span the vertical extent of panel  20 , with support tube  30  being coupled to the arm at a point adjacent the bottom of panel  20 . Alternatively, support tube  30  may be extended to the top of panel  20 , with its upper portion functioning as the vertical support arm(s)  24 .  
         [0079]    A bottom portion  32  of support tube or upright  30  is fitted to a sign stand assembly  14 . With additional reference to FIG. 2, sign stand assembly  14  includes a support tube  36  which is joined to an upright  30  to impart support thereto the preferred embodiment, support tube  36  is hollow, with a central passageway dimensioned to receive the bottom portion of upright  30 . The upright  30  is secured within the upper portion of support tube  36  by bolt fasteners  38 . Alternative construction, may include an upright  30  which is telescopically received within support tube  36  and secured thereto with suitable adhesives or metallurgical joining such as welding or brazing. Alternatively, support tube  36  can be made to comprise the bottom portion of upright  30 , eliminating the need for a special joining arrangement.  
         [0080]    With reference to FIGS.  1 - 3  support tube  36  is joined to support plate  40 . Preferably, support tube  36  is fitted within an aperture formed in plate  40 , with the bottom edge of support tube  36  located adjacent the bottom major surface of support plate  40 . Support tube  36  is joined to support plate  40  using conventional fastening means such as adhesive, shrink fit, brazing and most preferably welding. Together, support tube  36  and support plate  40  form a continuous rigid structure.  
         [0081]    Referring now to FIGS.  2 - 5 , support assembly  14  includes a pair of opposed body plates  44  joined to an intermediate force accumulator tube  48 . Preferably, force accumulator tube is hollow and is joined to body plates  44  using conventional means, such as welding. An optional outer support collar  46  may be employed to assist in the welding operations. For example, collar  46  may be welded between plates  44  with force accumulator tube  48  thereafter being welded to support collar  46 . With reference to FIG. 5, force accumulator tube  48  is fitted within a base plate  52  and has an upper end preferably aligned adjacent the upper major surface of base plate  52 . Force accumulator tube  48  and base plate  52  are joined together using conventional fastening means, such as welding. In a preferred embodiment, base plate  52  is also joined to bottom plates  44  preferably by welding. Accordingly, in a preferred embodiment base plate  52 , force accumulator tube  48  and plates  44  comprise a unitary rigid assembly.  
         [0082]    As indicated in FIGS. 2 and 3, plates  44  include outwardly diverging ears  56  each of which supports a ground-engaging leg  60  (see FIG. 1). Legs  60  have been omitted in FIGS. 4 and 5 for drawing clarity. A connecting tube  70  has an upper end inserted within support tube  36  and a lower end inserted within force accumulator tube  48 . As can be seen in FIG. 3 the mid-portion of connecting tube  70  includes several weakening members  74  which are aligned in a plane generally perpendicular to the longitudinal axis of a connecting tube. In a preferred embodiment, the connecting tube, as with the support tube and force accumulator tube, have generally rectangular and most preferably square cross-sectional shapes. Connecting tube  70  has upper and lower portions dimensioned for a relatively close fit engagement with the support tube and force accumulator tubes, respectively. Accordingly, the connector tube  70  has four outer faces, one of which is visible, for example, in FIG. 3. Preferably, all four outer faces of connecting tube  70  have an identical appearance, that is, each face has a pair of weakening members  74 . As illustrated in FIG. 3 and as can be seen in the enlarged drawings of FIGS. 8 and 11, weakening members  74  comprise round holes located toward the outside corners of the connecting tube, and being separated by an intervening wall portion of the connecting tube.  
         [0083]    Referring again to FIG. 11, force accumulator tube  48  has an upper end surface  80  which, as mentioned, is generally aligned with the upper major surface of base plate  52 . With reference to FIG. 12, base plate  52  has a central opening  82  for receiving the upper end of force accumulator tube  48 . Preferably, opening  82  is dimensioned for a close tolerance fit with the upper end of the force accumulator tube. Preferably, the force accumulator tube  48  is rigidly joined to base plate  52  with a conventional joining means such as welding to maintain the upper edge  80  (see FIG. 11) of the force accumulator tube  48  with the upper surface  52   a  of base plate  52  (see FIG. 12). As shown in FIG. 11, connecting tube  70  is carefully aligned with respect to force accumulator tube  48 , with a controlled insertion depth, such that the upper edge  80  of the force accumulator tube generally overlies only the lower half portions of weakening member  74 . FIG. 11 shows the preferred relative alignment of the force accumulator and connecting tubes, although the relative alignment can be made to vary plus or minus one-half the vertical height of the weakening element as may be desired to “fine tune” the desired response for a particular installation.  
         [0084]    With reference to FIG. 2, the upper and lower ends of connecting tube  70  are secured to support tube  36  and force accumulator tube  48 , respectively by bolt-like fasteners  88 . A plurality of threaded fasteners  90  extend between plates  40 ,  52  and are arrangement so as to apply a force tending to separate plates  40 ,  52  in the direction of arrows  92 . Although not required, it is generally preferred that a gap  94  be formed between plates  40 ,  52 . In a preferred embodiment, threaded fasteners  90  are threadingly engaged with support plate  40  and have lower ends receiving thrust support from the upper surface of base plate  52 . As threaded fasteners  90  are advanced, support plate  40  is urged in an upward direction, away from base plate  52 . Upward travel is restrained by connecting tube  70  which is joined at its upper and lower ends to the support tube  36  and force accumulator tube  48 , respectively.  
         [0085]    In the preferred embodiment, threaded fasteners  90  are advanced until a pre-determined tension load is placed on connecting tube  70 . When subjected to an impact event as indicated by FIGS.  20 - 22 , connecting tube  70  is ruptured in the manner indicated in FIGS. 16 and 23. In a preferred embodiment, the connecting tube has been observed to separate along an imaginary, generally horizontal plane located at or slightly above the upper surface of base plate  52 . In FIG. 23, the direction of applied force is indicated by arrow  102  and, in the impact scenario indicated in FIGS.  20 - 23  it is aligned with the direction of travel of the illustrated vehicle  104 . The sign assembly  10  illustrated in FIGS.  20 - 23  has a support tube  36  extending up to and at least slightly above the point of impact with vehicle  104 , causing efficient transfer of lateral force to the region of weakening of connecting tube  70 , defined by weakening member  74  and located generally in gap  94 , at or between the opposed major faces of plates  40 ,  52 . As mentioned, in an alternative embodiment, the support tube  36  and upright  30  of the sign panel assembly can comprise a continuous unitary member. As indicated in FIG. 23, panel  20  is secured by a conventional rivet fastener  106 .  
         [0086]    Tensioning of the connecting member  70  is believed to greatly enhance energy control or focusing during the impact event. The relatively clean planar rupturing of the connecting member at or slightly above the upper surface of the base plate was observed even with ground engaging legs which are unrestrained and free to travel in a sideways direction, for example. Without the invention herein, as the sign stand travels in a lateral direction, the base rocks or twists altering modes of energy absorption during the critical initial portion of the impact event, which typically occurs in less than a second. It is important during this critical time in the impact event that impact forces be efficiently transferred into the sign stand, and transferred in an advantageous manner which causes the sign stand to rupture with the upper end of the sign stand directed along a path of movement which clears the vehicle windshield. Such important features are provided by the present invention. As indicated in FIG. 22, the support plate  40  has achieved a height generally aligned with the vehicle hood with the upper, freed portion of the sign stand accelerating in an upward direction while rotating in a clockwise direction, timed so as to bring the support plate  40  and support tube  46  above the path of travel of the vehicle windshield. In fact, as has been observed that with the present invention, the entire freed portion of the sign stand reacts to the applied impact force in a manner so as to clear vehicle  104  without making contact with the vehicle during or after the impact event.  
         [0087]    Referring now to FIGS. 6 and 9, an alternative connecting tube is indicated at  120 . Connecting tube  120  is substantially identical to the connecting tube  70  described above, except that weakening members  122  have a generally triangular shape. As indicated, the triangular openings  122  are aligned along a common plane, generally transverse to the longitudinal axis of connecting tube  120 . In a preferred embodiment, triangular openings  122  on a given face of the connecting tube point away from each other, toward outside corners of the connecting tube. As shown in FIG. 9, the upper edge  80  of force accumulator tube  48  is aligned with respect to weakening members  122  such that generally only the lower half of the weakening members is overlaid by force accumulator tube  48 . As with other embodiments, relative orientation of the force accumulator tube and the connecting tube may be adjusted generally plus minus one-half the vertical height of the weakening members.  
         [0088]    With reference to FIGS. 7 and 10, connecting tube  126  has outside corners in which weakening members  128  are formed. Weakening members  128  generally comprise notches extending into the outside corners and are preferably aligned along a common plane generally perpendicular to the longitudinal axis of the connecting tube. Notches  128  extend below the outer surface of the connecting tube and most preferably extend through the walls of the hollow connecting tube penetrating the inner surface  130  (see FIG. 10).  
         [0089]    Referring to FIGS. 13 and 17, an alternative embodiment of the connecting tube indicated at  120  has an elongated, rectangular, cross-sectional shape. Connecting tube  120  is received in a base plate  122  having an elongated rectangular opening  124  dimensioned for a tight fit with the connecting tube. Any of the weakening members described above may be employed. As a further example of optional weakening which may be employed with any of the embodiments disclosed herein, one or more “score” lines may extend into the surface of the connecting tube, preferably along a plane generally perpendicular to the longitudinal axis of the connecting tube. The “score” lines may be continuous or may be spaced-apart or “dashed”.  
         [0090]    As shown in FIGS. 18 and 14 the connecting tube may have a generally cylindrical configuration as indicated at  126 . The corresponding base plate  128  has a circular hole  130  to receive connecting tube  126  in a tight fit relationship.  
         [0091]    [0091]FIGS. 15 and 19 show an arrangement for a connecting tube having a generally triangular cross-section, as indicated at  132 . A connecting tube is received in a triangular opening  136  formed in base plate  134  and is dimensioned for a telescopic fit with the connecting tube in a tight fit relationship. Any of the weakening members described herein may be employed with the alternative connecting tubes and their associated plates.  
         [0092]    Turning now to FIGS. 24 and 25, an alternative sign arrangement is generally indicated at  150 . Included is a sign panel assembly generally indicated at  12 , as described above and an upright or support mast  152  received in a force accumulator tube  154 . As can be seen with reference to FIG. 25, force accumulator tube  154  is supported on an upper saddle member  156  of a conventional spring-loaded sign supporting base of a type known in the art. Force accumulator tube  154  is preferably welded or otherwise rigidly joined to saddle member  156 . The sign support base includes side plates  158  supporting ground engaging legs  160 . If desired, force accumulator tube  154  can receive support in conventional ways other than the base having ground engaging legs. For example, a conventional ground socket can be provided for telescopic mating with the force accumulator tube, or the force accumulator tube itself could be used as a ground socket. Further, provision can be made in timbers, concrete pads, steel plates or other conventional expedients to support force accumulator tube  154  in a generally upright direction. Again, if desired, direct connection can be made to the force accumulator tube or a mounting socket for receiving the accumulator tube can be provided.  
         [0093]    In a preferred embodiment, force accumulator tube  154  is resiliently mounted with respect to the sign supporting base so as to absorb wind energy, as is known in the art. Such torsional mountings have been employed to prevent wind bursts from causing the sign assembly to tip over or “hop” along the ground surface. The torsional mounting may be omitted, if desired.  
         [0094]    The upright mast or support tube  152  may extend to the top of message panel  20  or may be coupled to vertical rib members at the central hub  26  or at some point therebelow, such as adjacent the bottom of sign panel  20 . Upright  152  is telescopically inserted within force accumulator tube  154 , in the manner described above with respect to the aforementioned connecting tubes. The depth of insertion of upright  152  within force accumulator tube  154  is limited by threaded fasteners  168 . With additional reference to FIG. 26, the depth of telescopic insertion is limited such that the upper edge  172  of force accumulator tube  154  is generally aligned with the mid-portion of weakening members  174 . In the embodiment shown, weakening members  174  comprise round holes and the lower portion of upright  152  generally resembles connecting tube  70  and weakening member  74 , described above. Alternative weakening members such as triangular members  180 , four corner-located notch members  184 , similar to weakening members  122  and  128  described above may also be employed, as well as other weakening members mentioned herein.  
         [0095]    During the impact event shown in FIGS. 29 and 30, a lateral force is applied to the sign assembly by a vehicle  104  traveling in the transverse direction  194 . As schematically indicated in FIG. 29, it is generally preferred that force accumulator tube  154  extend to the anticipated height of impact. This efficiently transmits lateral force to the sign assembly to cause a rapid response in the first fraction of a second impact, in which impact forces are efficiently transferred to the horizontal cross-sectional plane of the upright located at or near the horizontal plane containing the weakening members. Most preferably the rapid response includes rupturing of the lower portion of the upright, separation from the base and rotation in the manner indicated, all within 10 msec and most preferably within 3 msec.  
         [0096]    With reference to FIG. 30, it has been observed that the lower free end  152   a  of upright  152  is formed by rupture of the upright along a plane located transverse to the longitudinal axis of the upright. It has further been observed that the planar rupture of the upright lies along or very near a transverse plane containing centers of the weakening members. As with the preceding embodiments, of the present invention, the upright is almost instantly ruptured and with further application of the impact force, the upper, freed portion of the sign assembly is caused to travel along a path of upward and clockwise (as shown in the figure) movement. The rotational movement moves the sign panel in a direction generally aligned with clockwise downstream movement of the vehicle, a motion which raises the ruptured, trailing end in an upward direction. It has been observed that the free end  152   a  is deflected as illustrated in FIG. 30 in a manner which clears the vehicle windshield.  
         [0097]    The drawings and the foregoing descriptions are not intended to represent the only forms of the invention in regard to the details of its construction and manner of operation. Changes in form and in the proportion of parts, as well as the substitution of equivalents, are contemplated as circumstances may suggest or render expedient; and although specific terms have been employed, they are intended in a generic and descriptive sense only and not for the purposes of limitation, the scope of the invention being delineated by the following claims.