Abstract:
An arc tube light source supported by a discontinuous two-part (top and bottom) frame inside a bulb of an HID lamp is ruggedized to reduce weld breakage under vibration and shock. Each of the top and bottom frames is substantially U-shaped, with the open end of the U-shape being attached by a strap to a pinch of the arc tube. For ruggedization a bracing strap is fixed to, and extends between, two sides of the frame and is welded to a lead wire extending from the pinch. Strength is enhanced if two lead wires extend from the pinch, and the bracing strap is welded to both. Advantageously the two lead wires are sides of a U-shaped wire such as a “U-pin”. Further stabilization may be achieved by using braces attached to both of the top and bottom frames and extended out against surrounding parts of the bulb.

Description:
TECHNICAL FIELD 
     The invention relates to lamps and, more particularly, to lamps having an encapsulated light source, particularly a two-ended (electrodes at two opposite ends rather than two electrodes at the same end) type of light source, such as a filament (which may be in its own enclosure) or an arc tube of a high intensity discharge (HID) lamp, and to “mount” structures for mounting the two-ended light sources within an outer envelope (or “bulb”). 
     BACKGROUND 
     Some lamps comprise an encapsulated light source mounted by brackets, braces, straps and the like within an outer envelope (bulb). The encapsulated light source may comprise a filament tube or an arc tube, and may be of the “two-ended” type having at least one terminal (or electrode, or lead wire) at each of two opposite ends of the encapsulated light source. The two-ended light source may comprise a filament, which may be enclosed. In the main hereinafter, high intensity discharge (HID) lamps having an arc tube may be described, as exemplary of such lamps having two-ended light sources. 
     A high-intensity discharge (HID) lamp is a type of electrical lamp having a two-ended encapsulated light source, such as an “arc tube” containing a mixture of gases. The arc tube may be suspended (held in place) by various mechanical elements (such as clips, frames, straps, braces, brackets, etc., which collectively may be referred to as the “mount”) inside a translucent or transparent protective outer envelope (“bulb”). The bulb may be somewhat cylindrical, having a “dome” at one end (which may be referred to as the top end) and a “neck” portion at the other end (which may be referred to as the bottom end). The top end of the bulb is generally sealed (not open). A separate “stem” element may be provided at the open, bottom end of the bulb, sealing the bottom end of the bulb. A “base” may be provided at the bottom end of the bulb, such as for screwing the lamp into a socket for mounting and providing electrical current (from an outside source) to the lamp. Electrical current is provided via the base, via various elements of the mount (and or a “fly wire”) to terminals or electrodes of the arc tube. 
     The arc tube is typically elongated, having two opposite ends, and has electrodes (or terminals, or lead wires) at its two ends. Electricity is applied to these electrodes to create (start, initiate) and to sustain a plasma (or discharge) in the arc tube. Generally, a higher voltage may be required to start the plasma than to sustain it. There are generally two categories (or types) of HID lamp that will be discussed herein:
         (i) “pulse-start”, having only two distinct electrodes, one at each end of the arc tube, and which may use an igniter located in a ballast pod, external to the lamp, to start the lamp (initiate the plasma).   (ii) “probe-start”, which uses an additional electrode in the form of a starting probe (or “starter wire”, or “starter lead”) at one of the ends of the arc tube (typically at the bottom end) to facilitate starting the lamp. A simple starting (or starter) circuit such as comprising an inductor and a bimetallic switch may be located within the bulb for initiating the plasma in the arc tube, and the proximity of the starter wire to the electrode at the same end of the arc tube facilitates initiating the plasma. Once the plasma is started, heat generated by the arc tube may cause a bimetallic switch in the starter circuit to open, thereby terminating flow of electric current through the starter wire.)       

       FIG. 1  illustrates the construction of an exemplary HID (High intensity Discharge) lamp  100  of the prior art. The lamp  100  is illustrated in a generally vertical orientation, or “base-down”, although it may be inverted or held horizontal in use (such as for overhead lighting applications). In some of the descriptions set forth herein, terms such as “top” and “bottom” may be used to describe the location or position of various elements, such as relative to other elements, and should be evident from the drawings. Other terms such as “left” and “right”, or “front” and “back” may also be used to indicate relative positions of elements as viewed in a referenced drawing figure. 
     A generally cylindrical arc tube  110  (or capsule) has two end portions  110   a  and  110   b , a central (“chamber”) portion  110   c  between the end portions  110   a  and  110   b , a length and diameter, and contains one or more gases which, when excited by an appropriate electrical current arcing through the gases, produce light. The end portions  110   a  and  110   b  of the arc tube  110  may be flattened (“pinched”) to seal around one or more electrical conductors passing therethrough, and may be referred to as “pinches”. The central portion  110   c  remains generally cylindrical, and is hollow to contain the gas(es) in a closed chamber. 
     As is known in the lamp-making arts, other light sources are provided in similarly fashioned capsules which may also be similarly mounted in an outer envelope—for example high pressure halogen atmospheres are contained along with an incandescent filament in a capsule that may be called a filament tube. Therefore, although the present disclosure is focused on an arc tube embodiment of an encapsulated light source, that should be treated as an exemplary embodiment of an encapsulated light source which may be held in a mount structure according to the present invention, as will be disclosed hereinbelow. 
     At both the top and bottom ends (not specifically labeled) of the arc tube  110 , a lead wire (or electrode) extends from external to the arc tube  110 , through the respective pinch  110   a  and  110   b , to the interior  110   c  of the arc tube. The portion of the lead wire external to the arc tube  110  may be referred to specifically as a “lead wire”, and the portion of the lead wire internal to the arc tube  110  may be referred to specifically as the “electrode”. (A similar, additional separate “starter lead” or “probe lead” may also be provided at one end of the arc tube  110 , as described below, for probe-start type HID lamps.) 
     The arc tube may have a band of white coating surrounding the electrodes on one, or both, ends of the arc tube. The coating reflects the heat from the arc and electrode back into the bottom of the end-chamber where the chemicals settle when the arc tube cools. This additional heat helps to vaporize the chemicals into a gas so that they will enter into the arc stream. The vaporized chemicals fuel the arc making it very strong and brilliant. The white coating material may stay white through the lamp life, maintaining optimum end-chamber temperature and resulting in superior lumen maintenance and color consistency. 
     The arc tube lead wires may be provided in the form of U-pins (U-shaped elements). Generally, any “U-shaped” element may be described as having two “side” or “leg” portions (or simply “legs”, or “sides”) extending substantially parallel (and coplanar) with one another and joined at a common end to each other by a “bow” (or “bend”, or “bight”) portion (or simply “bow”, “bend” or “bight”). 
     A U-pin  112  is shown extending into the top pinch  110   a  of the arc tube  110 . A U-pin  114  is shown extending into the bottom pinch  110   b  of the arc tube  110 . The bight portions of the U-pins  112  and  114 , including a portion of their respective leg portions (or sides), are external to the arc tube  110 , and serve as lead wires. Remaining portions of the legs of the U-pins  112  and  114  extend into the respective pinch  110   a  and  110   b , where they are welded to a thin metal foil which is sealed in the pinch. On the interior side of the pinch, an electrode wire/shank is also welded to one of the foils and extends into the interior of the arc tube, to serve as electrodes, in contact with gas(es) contained in the central portion  110   c  of the arc tube  110 . The U-pins  112  and  114  may be formed of wire, such as approximately 0.6 mm (0.020 inch) diameter molybdenum wire. 
     The U-pins  112  and  114  may also serve a mechanical function. Generally, the U-pin construction with two legs embedded in the pinch of the arc tube may provide a sturdier mechanical interface with the arc tube than would otherwise be realized if only a single pin (lead wire) were to be embedded in the pinch. 
     The U-pins  112  and  114  also serve as terminals, or electrodes, for providing electrical current to the gases inside the arc tube to initiate and sustain the plasma discharge. For a pulse start lamp, each U-pin connects to one of the two electrodes at opposite ends of the of the arc tube. For a probe start lamp, one of the U-pins, such as the bottom U-pin  114  may be cut (or clipped, such as in half, at the bight) so that one leg of the U-pin constitutes an electrode lead wire (as before), and the other leg is connected to a “starter” or “probe” wire for starting the discharge in the arc tube. This may be referenced as a probe lead wire. Details of a cut bottom U-pin will be shown and described below ( FIG. 3B ). 
     In a finished lamp, a protective outer envelope (bulb)  120  surrounds the arc tube  110  which is located and supported more-or-less centrally within the bulb  120  by a “mount structure”  130  comprising various metal wires, frames, bands and straps, as may be described in greater detail hereinbelow. Mechanical and/or electrical connections or attachments of metal components one to another is typically accomplished by welding, but other connection means are possible, therefore the term “welded” should be considered as including other suitable and comparable attachment means within its scope. 
     The bulb  120  is elongate, somewhat “pear shaped”, having an overall length “L”, is initially open at one end (the bottom end), and has three main portions. A top end portion of the bulb  120  may be referred to as a “dome” portion  122  of the bulb  120 . The dome portion  122  may constitute approximately 10% of the overall length “L” of the bulb  120 , and is closed. An opposite, bottom end portion of the bulb  120  may be referred to as a “neck” portion  124  of the bulb  120 . The neck portion  124  may constitute approximately 20% of the overall length “L” of the bulb, and is initially open (but will be sealed with the “stem”, described hereinbelow). Both of the neck and dome portions  122  and  124  are generally cylindrical, each having a diameter of approximately “D 1 ”. A central portion  126  (or “bulb portion”) of the bulb  120  is disposed between the neck and dome portions  122  and  124 . The central portion  126  may constitute approximately 70% of the overall length “L” of the bulb  120 , and may have a diameter “D 2 ” greater than “D 1 ”, which gives the bulb  120  its characteristic “pear shaped” (bulbous) appearance. For example, “D 2 ” may be approximately twice as large as “D 1 ” (D 2 ˜=2*D 1 ), and “L” may be approximately twice as large as “D 2 ” (L˜=2*D 2 ). The length “x” of the arc tube  110  may be approximately 60% of the overall length “L” of the bulb  120 , and the diameter “d” of the arc tube  110  may be approximately 50% of the smaller (neck, dome) diameter “D 1 ” of the bulb  110 . As an example, the overall length “L” of the bulb may be approximately 30 cm (12 inches). In other examples, the bulb length may range between 21-38.5 cm. 
     A mount structure  130  supports the arc tube  110  within the bulb  120 , and also delivers electrical current from the base of the lamp (described below) to the lead wires (essentially, the U-pins  112  and  114 , or portions thereof) for the electrodes of the arc tube  110 . 
     The mount structure  130  includes a “top” U-shaped frame  132  disposed in the bulb  120  and extending from within the dome portion  122  into the central portion  126  and a similar “bottom” U-shaped frame  134  disposed in the bulb  120  and extending from within the neck portion  124  into the central portion  126 . The top and bottom frames  132  and  134  may be considered to be two parts of a discontinuous two-part frame. The top and bottom frames  132  and  134  may be formed of wire (and may be referred to as “wire frames”), such as approximately 1.6 mm (0.060 inch) diameter stainless steel rod material. 
     The top U-shaped frame  132  comprises two legs portions (or sides)  132   a  and  132   b  extending parallel with one another and joined at one end by a bow (or bend, or bight) portion  132   c . Similarly, the bottom U-shaped frame  134  comprises two legs portions (or sides)  134   a  and  134   b  extending parallel with one another and joined at one end by a bow (or bend, or bight) portion  134   c . The top and bottom frames  132  and  134  may be substantially coplanar with one another, and may be substantially coplanar with the U-pins  112  and  114 . The U-shaped frames  132  and  134  are larger than the U-shaped U-pin elements  112  and  114 . 
     The two legs  132   a  and  132   b  of the top frame  132  may extend longitudinally downward, slightly beyond the top pinch end  110   a  of the arc tube  110 , generally parallel to the axis of the (cylindrical) arc tube  110 , and spaced a small (radial) distance away from (adjacent to) the arc tube  110 —in other words, extending adjacent the arc tube  110  adjacent opposite sides thereof. A pair of metal pinch straps (or braces)  142   a  and  142   b  (which may collectively be referred to as “ 142 ”) extend across the top pinch  110   a  (on opposite sides thereof), from leg-to-leg of the top frame, and may be fixed (such as by welding) to the two legs  132   a  and  132   b  of the top frame  132 , thereby securing a top portion of the arc tube  110  in the mount structure  130 . 
     In a similar manner, the two legs  134   a  and  134   b  of the bottom frame  134  may extend longitudinally upward, slightly beyond the bottom pinch end  110   b  of the arc tube  110 , generally parallel to the axis of the (cylindrical) arc tube  110 , and spaced a small (radial) distance away from (adjacent to) opposite sides of the arc tube  110 . A pair of metal pinch straps (or braces)  144   a  and  144   b  (which may collectively be referred to as “ 144 ”) extend across the bottom pinch  110   b  (on opposite sides thereof), from leg-to-leg of the bottom frame  134 , and may be fixed (such as by welding) to the two legs  134   a  and  134   b  of the bottom frame  134 , thereby securing a bottom portion of the arc tube  110  in the mount structure  130 . 
     A person of ordinary skill in the related lamp-making and design arts will understand that the references herein to a “pinch strap” (in the singular) is intended to encompass various forms such as, for example, a single ribbon of strapping metal that is wrapped around the pinch; and such as, for example, a pair of ribbons that sandwich the pinch and are attached together (in various ways, e.g., welding) at the two sides of the pinch. 
     As illustrated, the legs of the top and bottom frames  132  and  134  extend towards each other, and may extend at least to (and possibly slightly beyond) the respective pinches  110   a  and  110   b  of the arc tube  110 . The leg  132   a  of the top frame  132  may be in line with the leg  134   a  of the bottom frame  134 , and the leg  134   b  of the top frame  134  may be in line with the leg  134   b  of the bottom frame  134 . However, the top and bottom frames  132  and  134  are physically and electrically separated from one another, and neither extends longitudinally to adjacent the central portion  110   c  the arc tube  110 . It is generally not desirable that any portion of the mount structure  130  be located adjacent the central portion  110   c  of the arc tube. (A “fly wire”, described hereinbelow, may pass by the central portion  110   c  of the arc tube  110 , at a suitable distance therefrom.) 
     A pair of top frame braces (or “supports”)  136   a ,  136   b  (which may collectively be referred to as “ 136 ”) are disposed in the dome portion  122  of the bulb  120  to support the top wire frame  132 . The braces (supports)  136  may each may comprise an elongated metal strip having a length of approximately “D 1 ” and may extend at right angles with respect to a plane defined by the top wire frame  132 . One brace  136   a  may be fixed (such as by a weld) to one of the legs (or sides) of the wire frame  132 , at a longitudinal position near the bight end of the top wire frame  132 . The other brace  136   b  may similarly be fixed (such as by a weld) to the other leg (or side) of the wire frame  132 , at a longitudinal position near its bight end. The ends of the frame braces  136   a  and  136   b  may be slightly bent and/or dimpled, so as to be “snugly” received within the dome portion  122  of the bulb  120  to stabilize the top frame  132  in the dome portion  122  of the bulb  120 . The top frame braces  136   a  and  136   b  serve a mechanical function, and may be formed of sheet metal, such as 0.5 mm (0.020 inch) thick spring steel material. 
     U.S. Pat. No. 4,990,819, incorporated by reference herein, discloses a HID lamp having a canted arc tube with rotary locking joints, and discloses what appears to be a set of frame braces (not numbered) similar to the braces  136   a  and  136   b  in the dome portion of the bulb and a set of similar looking bottom frame braces (also not numbered) in the neck portion of the bulb. 
     Referring again to the prior art shown in  FIG. 1 , a metal strap or wire  152  may extend between the leg  132   b  of the top frame  132  to a leg of the top U-pin  112 , for conducting electrical current from the frame  132  to the arc tube  110 . A metal strap or wire  154  may extend between the leg  134   b  of the bottom frame  134  to a leg of the bottom U-pin  114 , for conducting electrical current from the frame  134  to the arc tube  110 . This is representative of a pulse-start type HID lamp. 
     A stem component  160  may be formed of glass (or the like), and may have a diameter approximately equal to the diameter “d” of the arc tube  110 , which is less than the diameter “D 1 ” of the neck portion  124  of the bulb. Two stem leads  162  and  164  protrude from the top of the stem component  160 . A base component  166 , such as a conventional screw-type base (for screwing the lamp into a socket) is disposed around a bottom part of the stem component  160 . Leads (not shown) within and exiting the bottom of the stem component  160  electrically connect the stem leads  162  and  164  to the base component  166 . 
     The base component essentially comprises a shell (formed with screw threads), a ceramic insulator, and an eyelet (or button) extending from the bottom. The shell may be nickel-plated brass. The shell and the eyelet constitute what may be considered to be two “terminals” for the overall device (i.e., the lamp). 
     The bight portion  134   c  of the bottom frame  134  may be fixed (such as welded) to the stem lead  164 . This provides support for the bottom frame  134 , hence the arc tube  110 , and the top frame  132  attached thereto. Also, the connection of the bottom frame  134  to the stem lead  164  provides electrical current from the base component  166 , via the bottom frame  134 , via the bottom strap (wire)  154 , via the U-pin  114  to the arc tube  110 . 
     A “fly wire”  158  may extend from the other stem lead  162  to a leg  132   b  of the top frame  132  to provide electrical current from the base component  166 , via the top frame  132 , via the top strap (wire)  152  via the U-pin  112  to the arc tube  110 . The example set forth herein is representative of a pulse-start type HID lamp. For a probe-start type HID lamp, a starting circuit (not shown) may be located in the neck portion  124  of the bulb  120 , near the stem component  160 , and a separate probe lead would be provided, as is known, and as is described hereinbelow. 
     U.S. Pat. No. 3,623,134, incorporated by reference herein, illustrates a lamp having a unitary (one-piece), generally rectangular frame, rather then the two-piece frame comprising separate top and bottom frame elements  132  and  134 , as disclosed herein. Generally, a unitary frame would be more rugged, but there are disadvantages to having a portion of the frame located abreast of the central portion  110   c  of the arc tube  110 . 
       FIGS. 1A and 1B  illustrate the lamp  100  with the arc tube  110  supported in the bulb  120  between the separate (rather than unitary) top and bottom frame elements  132  and  134 , the pinch straps  142  and  144  on respective pinches  110   a  and  110   b  of the arc tube  110 , the stem component  160 , the stem leads  162  and  164 , and the base component  166 . The fly wire  168  from the stem lead  162  to the top frame  132  is omitted, for illustrative clarity, and since it does not form part of the mount structure ( 130 ) per se. 
     In  FIG. 1A , the top and bottom frames  132  and  134  are aligned with one another. Since the top and bottom frames  132  and  134  are not a unitary structure (compare the one-piece rectangular frame in U.S. Pat. No. 3,623,134), this allows for some distortion, bending, pivoting, misalignment and/or breakage of welds, stem, or arc tube pinches when the lamp is subjected to vibration and/or mechanical shock. The articulated frame arrangement in U.S. Pat. No. 4,990,819 may address and alleviate such problems, albeit with added complexity. 
     In  FIG. 1B , the top and bottom frames are shown misaligned, such as may result from vibration or mechanical shock. Such misalignment can lead to failure of welds and/or cracking (not shown) of the glass stem  160 , ultimately in failure of the lamp  100 . Note the severe misalignment where the top and bottom frames  132  and  134  are welded to the top and bottom pinch straps  132  and  134 , respectively. Resulting stress is likely to result in breakage of the welds, and consequent failure of the lamp  100 . Also likely to happen is a broken weld of the bottom frame  134  to the stem lead  164 . These problems can result not only in mechanical failure, but also the breaking of these welds may interrupt the flow of electrical current to the arc tube (light source)  110 . 
     It is an object of the present invention to provide an improved mount structure and method of mounting for encapsulated light sources such as are in HID lamps (or the like), particularly those having separate top and bottom frames, the improvements making the lamp more rugged (or ruggedized) by improving shock and vibration resistance, and reducing some opportunities for lamp failure. 
     SUMMARY 
     It is an object of the invention to provide an improved construction for lamps, particularly lamps having a two-ended encapsulated light source disposed within a bulb, thereby providing improved shock and vibration resistance. The two-ended encapsulated light source may comprise an arc tube or a filament, with electrodes at opposite ends. In the main hereinafter, high intensity discharge (HID) lamps having an arc tube will be described, as exemplary of various embodiments of the invention. The improvements disclosed herein generally pertain to modifications or additions to the mount structure (straps, braces, etc.) holding the arc tube in place within the bulb to make the lamp more “ruggedized” (such as resistant to shock and vibration distortion/damage). 
     An arc tube light source supported by a discontinuous two-part (top and bottom) frame inside a bulb of an HID lamp is ruggedized to reduce weld breakage under vibration and shock. Each of the top and bottom frames is substantially U-shaped, with the open end of the U-shape being attached by a strap to a pinch of the arc tube. For ruggedization a bracing strap is fixed to, and extends between, two sides of the frame and is welded to a lead wire extending from the pinch. Strength is enhanced if two lead wires extend from the pinch, and the bracing strap is welded to both. Advantageously the two lead wires are sides of a U-shaped wire such as a “U-pin”. Further stabilization may be achieved by using braces attached to both of the top and bottom frames and extended out against surrounding parts of the bulb. 
     Generally, a mount structure supporting an arc tube in a bulb of an HID lamp is ruggedized to reduce weld breakage and to provide the possibility of welded elements remaining in electrical (and some mechanical) contact with one another even in the event of up to a few welds breaking. For example, U-pin braces extending from legs (sides) of the top and/or bottom frame elements may be “woven” through the two legs (sides) of the U-pins extending from ends of the arc tube and serving as its lead wires. In the case of a cut U-pin, such as in a probe-start type lamp, the brace may be woven around the single U-pin leg serving as the electrode lead, being woven with respect to two frame element legs, one on either side of the U-pin leg. This is stronger than prior art which only connects an arc tube lead to a single frame element leg using a wire to complete an electrical circuit. 
     Although the present disclosure may refer to arc tube lead wire(s) as “U-pin leads” or simply as a U-pin, and may refer to its brace as a “U-pin brace”, such terms should be considered inclusive of one or more individual arc tube lead wires, but not necessarily equivalent, since the U-pin has added strength and rigidity due to the extra interconnection provided by the bight portion of the U-shape. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference may be made to embodiments of the invention, non-limiting examples of which may be illustrated in the accompanying drawing figures (FIGs). Some elements in the figures may be exaggerated, others may be omitted, for illustrative clarity. Similar elements in various figures may be similarly numbered, such as element  215  being similar to element  115 , where the most significant digit(s) of the reference numeral may correspond to the figure number (such as FIG. “ 2 ”). Terms of orientation such as “top”, “bottom”, “left”, “right”, “front”, “back”, and the like may be used to indicate relative positions of elements with respect to one another, or portions of a given element with respect to one another. 
         FIG. 1  is a perspective view of a prior art lamp. 
         FIG. 1A  is a diagram with a portion of the base cut out to view the stem, of a prior art lamp. 
         FIG. 1B  is a diagram with a portion of the base cut out to view the stem, of a prior art lamp. 
         FIG. 2  is a perspective view of a lamp, illustrating some embodiments or features of the invention, which may be shown in greater detail in subsequent figures. 
         FIG. 2A  is a diagram of a portion of a lamp, generally in front- or side-view, illustrating some embodiments or features of the invention. 
         FIG. 2B  is a diagram of a portion of a lamp, generally in a view perpendicular to that of  FIG. 2A , illustrating some embodiments or features of the invention. 
         FIG. 2C  is a diagram of a lamp, illustrating some embodiments or features of the invention. 
         FIG. 3A  is a diagram of a portion of a lamp, generally in perspective view, illustrating some embodiments or features of the invention. 
         FIG. 3B  is a diagram of a portion of a lamp, generally in perspective view, illustrating some embodiments or features of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments will be described to illustrate teachings of the invention(s), and should be construed as illustrative rather than limiting. Although the invention may be described in the context of various exemplary embodiments, it should be understood that it is not intended to limit the invention to these particular embodiments, and individual features of various embodiments may be combined with one another. 
       FIG. 2  shows a pulse-start type HID lamp  200  and illustrates various features or embodiments of the invention, some of which will be discussed in greater detail hereinbelow. The lamp  100  illustrated in  FIG. 1  and the lamp  200  illustrated in  FIG. 2  are both representative of pulse-start type lamps. Many of the features of the pulse-start type lamp  200  are applicable to probe-start type lamps which may be described below, for example with respect to  FIG. 3B . 
     Generally, the lamp  200  comprises the following elements and features which may be similar (or identical) to those described with respect to the lamp  100 , and therefore need not be discussed in detail, the previous description of similar (comparable) elements being referenced as though fully set forth herewith, namely:
         an arc tube  210  (compare  110 ) having top, bottom portions or “pinches”  210   a  and  210   b , and a central portion  210   c;      a top U-pin  212  (compare  112 ) extending out of the top pinch  210   a;      a bottom U-pin  214  (compare  114 ) extending out of the bottom pinch  210   b;      a bulb  220  (compare  120 ) having a dome portion  222  (compare  122 ), a neck portion  224  (compare  124 ) and a central portion  226  (compare  126 );   a mount structure  230  (contrast  130 ) comprising a top U-shaped frame  232  (compare  132 ) and a bottom U-shaped frame  234  (compare  134 ), and other elements, details of which may be discussed hereinbelow;   a pair of top frame braces  236   a  and  236   b  (compare  136   a  and  136   b ) which may collectively be referred to as “ 236 ” (compare  136 );   a pair of top pinch straps  242  (collectively) (compare  142   a  and  142   b ) extending across the top pinch  210   a  of the arc tube  210 ;   a pair of bottom pinch straps  244  (collectively) (compare  144   a  and  144   b ) extending across the bottom pinch  210   b  of the arc tube  210 ;   a stem component  260  (compare  160 ) having two stem leads  262  and  264  (compare  162  and  164 );   a base component  266  (compare  166 ); and   a fly wire  268  (compare  168 ) extending from the stem lead  262  to the top frame  232 .       

     Some features of the lamp  200  distinguishing (differentiating) the lamp  200  from the lamp  100  will now be discussed in detail, and reference may be made to subsequent figures ( FIGS. 2A ,  2 B,  2 C,  3 A,  3 B) which may show in greater detail some of these features as they may be applicable to pulse-start and/or to probe-start type lamps. 
     The lamp  200  may comprise a pair of bottom frame braces  238   a  and  238   b  (which may collectively be referred to as “ 238 ”) which were not shown in the lamp  100  of  FIG. 1 . By having both top and bottom pairs of frame braces  236  and  238 , the top part and the bottom part of the two-part frame (the top frame  232  and the bottom frame  234 ) are braced in position against inside walls of the bulb  220 , in the dome and neck portions  222  and  224 , respectively. 
     U.S. Pat. No. 4,990,819 has been referenced as showing bottom frame braces in an HID lamp, but it should be noted that the HID lamp in that patent has an articulated frame, and the top frame (analogous to the top frame  232 ) and bottom frame (analogous to the bottom frame  234 ) are not in line with one another. The top and bottom frames are not substantially coplanar. In the bulb  200  disclosed herein, the top and bottom frame elements  232  and  234  are substantially coplanar. The frame in the HID lamp of the patent is essentially one-piece, continuous, and continues alongside of the arc tube in manner which is specifically being avoided by the two-part, discontinuous frame described herein comprising separate, non-unitary top and bottom frames  232  and  234  (compare  132  and  134 ). 
     The pair of bottom frame braces  238  may be very similar (including substantially identical) to the pair of top frame braces  236 , but they are disposed in the neck portion  224  of the bulb  220  (rather than in the dome portion  222 ) to support the bottom wire frame  234  (rather than the top wire frame  232 ). The braces  238  may each may comprise an elongated metal strip having a length of approximately “D 1 ” and may extend at right angles with respect to a plane defined by the wire frame  234 . One brace  236   a  may be fixed (such as by a weld) to one of the legs of the wire frame  234 , near its bight. The other brace  236   b  may similarly be fixed (such as by a weld) to the other leg of the wire frame  234 , near its bight. The ends of the frame braces  238   a  and  238   b  may be slightly bent and/or dimpled, so as to be “snugly” received within the neck portion  224  of the bulb  220  to stabilize the bottom frame  234  in the neck portion  224  of the bulb  220 . The bottom frame braces  238   a  and  238   b  serve a purely mechanical function. The bottom frame braces  238  may be formed of the same material as the top frame braces  236 . 
     The lamp  200  may comprise a top ribbon or strap of bracing material  272  extending from one leg (side) of the top frame  232  across the top U-pin  212  and to the other leg (side) of the top frame  232 , and a bottom ribbon or strap of bracing material  274  extending from one leg (side) of the bottom frame  234  across the bottom U-pin  214  and to the other leg (side) of the top frame  232 . The top and bottom straps  272  and  274  may be woven around or through the (one or) two sides (legs) of the top and bottom U-pins  212  and  214 , respectively, and fixed (such as by welding) thereto, as described in greater detail hereinbelow, for example with respect to  FIGS. 3A ,  3 B. 
     Generally, a probe-start type lamp can readily be distinguished from a pulse-start type lamp by virtue of the bottom U-pin of a probe-start type lamp being cut (clipped) so that there is both a lead wire and a starter lead extending into the bottom pinch of the arc tube. In other words, the two legs (sides) of the U-pin are not electrically shorted with one another when the U-pin is clipped. Also, a starting circuit (not shown) may be located within the bulb of a probe-start type lamp. 
       FIGS. 2A ,  2 B,  2 C and  3 A illustrate in greater detail some embodiments or features of the invention as they relate primarily to pulse-start type lamps.  FIG. 3B  illustrates in greater detail an embodiment or feature(s) of the invention as it relates particularly to a probe-start type lamp. Generally speaking, the features of various embodiments of the invention which will be described relate to improving the “ruggedness” of the lamp, thereby reducing mechanical and electrical failures of the lamp. 
       FIGS. 2A and 2B  illustrate in greater detail, the arc tube  210 , the top U-pin  212 , the bottom U-pin  214 , the top frame  232 , the bottom frame  234 , the pair ( 236 ) of top frame braces  236   a  and  236   b , the pair ( 238 ) of bottom frame braces  238   a  and  238   b , the top pinch straps  242   a  and  242   b , the bottom pinch straps  244   a  and  244   b . The circles represent areas where two elements may be joined together, such as by a weld (such as spot weld). The bulb  220 , stem component  260  and base component  266  are omitted from the views of  FIGS. 2A and 2B , for illustrative clarity. 
     The top U-pin  212  is U-shaped, comprising two substantially parallel (and coplanar) side (leg) portions  212   a  and  212   b , connected at one end by a bow (or bight) portion  212   c . The bottom U-pin  214  is U-shaped, comprising two substantially parallel (and coplanar) side (leg) portions  214   a  and  214   b , connected at one end by a bow (or bight) portion  214   c.    
     Note that the top and bottom U-pins  212  and  214  may be offset from center (off-center), so that one of their leads (legs)  212   b  and  214   b  may be substantially on-center with respect to a longitudinal axis of the arc tube  110 . One U-pin may be offset in one direction, the other U-pin may be offset in the other direction. Both U-pins are shown offset in the same direction (to the left, as viewed), in the illustration of  FIG. 2A . Additionally, as best viewed in  FIG. 2B , the pinch straps  242   a/b  and  244   a/b  may wrap around the side edge(s) of the respective pinches  210   a  and  210   b.    
     The top frame  232  is U-shaped, comprising two substantially parallel (and coplanar) leg portions  232   a  and  232   b , connected at one end by a bow (or bight) portion  232   c . The legs  232   a  and  232   b  are illustrated as extending downward, but do not extend past the pinch  210   a  so that they are not adjacent the central portion  210   c  of the arc tube  210 . 
     The bottom frame  234  is U-shaped, comprising two substantially parallel (and coplanar) leg (side) portions  234   a  and  234   b , connected at one end by a bow (or bight) portion  234   c . The legs  234   a  and  234   b  are illustrated as extending upward, but do not extend past the pinch  210   b . The legs  234   a  and  234   b  may extend slightly beyond the pinch  210   b , but should not be adjacent the central portion  210   c  of the arc tube  210 . (The same situation applies to the top frame  232  with respect to avoiding a portion of the frame being adjacent the central portion  210   c  of the arc tube  210 .) 
     The top U-pin  212 , bottom U-pin  214 , top frame  232  and bottom frame  234  may be substantially coplanar with one another. 
     The pair ( 236 ) of top frame braces  236   a  and  236   b  are fixed to a longitudinal position which is at an upper (near the bight  232   c ) portion of the legs (sides)  232   a  and  232   b , respectively, of the top frame brace  232 , such as by spot welding (note the circle in  FIG. 2B ). 
     The pair ( 238 ) of bottom frame braces  238   a  and  238   b  are fixed to a longitudinal position which is at a lower (near the bight  234   c ) portion of the legs (sides)  234   a  and  234   b , respectively, of the bottom frame brace  234 , such as by spot welding (note the circle in  FIG. 2B ). 
     The top set of pinch straps  242   a  and  242   b  are fixed to a longitudinal position which is at a lower (distal from the bight  232   c ) portion of the legs  232   a  and  232   b , respectively, of the top frame brace  232 , such as by spot welding (note the circles in  FIG. 2A ). 
     The bottom set of pinch straps  244   a  and  244   b  are fixed to a longitudinal position which is at an upper (distal from the bight  234   c ) portion of the legs  234   a  and  234   b , respectively, of the bottom frame brace  234 , such as by spot welding (note the circles in  FIG. 2A ). 
     A top ribbon or strap  272  extends from a longitudinal position which is at a middle portion (between the upper and lower portions) of the legs (sides)  232   a  and  232   b  of the top frame  232  to and through the top U-pin  212 , as described in greater detail hereinbelow ( FIG. 3A ). A bottom ribbon or strap  274  extends from a longitudinal position which is at a middle portion (between the upper and lower portions) of the legs  234   a  and  234   b  of the bottom frame  234  to and through the bottom U-pin  214  as described in greater detail hereinbelow ( FIG. 3A ). The straps  272  and  274  may be referred to as “fastening straps” or “U-pin braces”, may be formed of sheet metal, such as 0.4 mm (0.016 inch) thick stainless steel material. 
     Reference has been made herein to various elements attached (fixed, such as by welding) to various “longitudinal positions” of the legs (sides) of the top and bottom frame elements  232  and  234 . The arc tube  210  is generally cylindrical, and has a longitudinal axis which may be coincident with a longitudinal axis of the bulb  220 . The legs of the top and bottom frame elements extend parallel to the longitudinal axis (of the arc tube and bulb), and longitudinal position refers to positions along the length of the legs (sides) of the top and bottom frame elements. 
     To provide power to the arc tube  210 , the bottom frame  234  may be mounted (such as welded) to the stem lead  264 , and a fly wire (not shown) may extend from the stem lead  262  to the top frame  232 . Electrical current is conducted from the top frame  232  to the top U-pin  212  by the top strap  272 , and is conducted from the bottom frame  232  to the bottom U-pin  212  by the bottom strap  274 . The bottom strap arrangement illustrated in  FIGS. 2 ,  2 A and  2 B is exemplary of a pulse-start type lamp. A different arrangement for the bottom strap applicable to a probe-start type lamp is described hereinbelow with reference to  FIG. 3B . 
       FIG. 2C  shows the lamp  200 , and may be contrasted with  FIGS. 1A and 1B  as illustrating that the construction of the lamp  200  is more rugged than the construction of the lamp  100 . Some similarities and differences will now be discussed. 
     Both of the lamps  100  and  200  have a pair of top frame braces  136  and  236 , respectively. The lamp  200  has an additional pair ( 238 ) of bottom frame braces  238   a  and  238   b ). 
     Both of the lamps  100  and  200  have a pair of pinch straps  142   a,b  and  242   a,b  extending across the top pinch  110   a  and  210   a , respectively, and both of the lamps  100  and  200  have a pair of pinch straps  144   a,b  and  244   a,b  extending across the bottom pinch  110   b  and  210   b , respectively. 
     Both of the lamps  100  and  200  have an electrical conductor connected between the frame  132 / 134 ,  232 / 234  and an associated arc tube lead  112 / 114 ,  212 / 214 , for the top/bottom structures respectively. The lamp  100  uses a wire conductor  152 / 154  between the lead wire and only one side of the frame, e.g., frame side  132   a / 134   a  as shown. The lamp  200  uses its novel top and bottom fastening straps  272  and  274  to additionally provide the electrical conductor. (The fastening straps  272  and  274  are mentioned above, and described in greater detail hereinbelow.) 
     These features of the lamp  200 —the fastening straps  272  and  274 , and the pair of bottom frame braces  238 —cooperate to securely hold the arc tube  210  in position (in the middle of the bulb  220 ), even during heavy shock and vibration. 
       FIG. 3A  illustrates an arc tube  310  (compare  210 ), a top U-pin  312  (compare  212 ) extending from a top pinch  310   a  (compare  210   a ) of the arc tube  310 , a bottom U-pin  314  (compare  214 ) extending from a bottom pinch  310   b  (compare  210   b ) of the arc tube  310 , a top frame  332  (compare  232 ) having two substantially parallel legs (sides)  332   a  and  332   b  (compare  232   a  and  232   b ), a bottom frame  334  (compare  334 ) having two substantially parallel legs (sides)  334   a  and  334   b  (compare  234   a  and  234   b ), a pair of top pinch braces  342   a  and  342   b  (compare  242   a  and  242   b ) extending from one leg  332   a  to the other, opposed leg  332   b  of the top frame  332  across the top pinch  310   a , a pair of bottom pinch braces  344   a  and  344   b  (compare  244   a  and  244   b ) extending from one leg  334   a  to the other, opposed leg  334   b  of the bottom frame  334  across the bottom pinch  310   b , a top U-pin brace  372  (compare  272 ) extending from one leg  332   a  to the other, opposed leg  332   b  of the top frame  332 , across (and may be woven through) the top U-pin  312 , and a bottom U-pin brace  374  (compare  274 ) extending from one leg  334   a  to the other, opposed leg  334   b  of the bottom frame  334 , across (and may be woven through) the bottom U-pin  314 , and welds between various elements are indicated by circles, all in the manner described hereinabove with respect to  FIGS. 2A and 2B . 
     The top U-pin  312  comprises two substantially parallel legs (sides)  312   a  and  312   b  joined by a bight portion  312   c . As noted above, the legs  332   a  and  332   b  of the top frame  332  are also substantially parallel to one another, and the top U-pin  312  and top frame  332  may be substantially coplanar with one another. The top U-pin  312  may be referred to as a “connection element”. The two legs (sides)  312   a  and  312   b  of the top U-pin  312  may each be referred to as a “wire”. The two legs or wires  312   a  and  312   b  may both function as “lead wires” for the arc tube, i.e., encapsulated light source. 
     The bottom U-pin  314  comprises two substantially parallel legs (sides)  314   a  and  314   b  joined by a bight portion  314   c . As noted above, the legs  334   a  and  334   b  of the bottom frame  334  are also substantially parallel to one another, and the bottom U-pin  314  and top frame  334  may be substantially coplanar with one another. The bottom U-pin  314  and bottom frame  334  may be substantially coplanar with the top U-pin  312  and top frame  332 . The bottom U-pin  314  may be referred to as a “connection element”. The two legs (sides)  312   a  and  312   b  of the top U-pin  312  may each be referred to as a “wire”. The two legs or wires  312   a  and  312   b  may both function as “lead wires” for the arc tube, i.e., encapsulated light source. (Or, as described below with respect to  FIG. 3B , if the bottom U-pin is cut, one leg may function as a lead wire and the other leg may function as a starter lead.) 
     The top U-pin brace (or fastening strap)  372  has two ends  372   a  and  372   b  and may be “woven” through the top U-pin  312  by passing under (behind) one leg  312   a  of the U-pin  312 , and over (in front of, as viewed) the other leg  312   b  of the U-pin  312  and fixed (such as welded) thereto. More particularly, the left end  372   a  of the top U-pin brace  372  may be disposed in front of and may be welded to a front surface of the left leg  332   a  of the top frame  332 , then may pass under and may be welded to a back surface of the left leg  312   a  of the top U-pin  312 , then may pass over and may be welded to a front surface of the right leg  312   b  of the top U-pin  312 , and the right end  372   b  of the top U-pin brace  372  may be disposed behind and may be welded to the bottom surface of the right leg  332   b  of the top frame  332 . “Left” and “right” refer to the positions of elements in the figure, and the welds are indicated by dots (circles). As used herein, “front” and “back” are relative terms, simply designating two opposite surfaces of an element (such as the U-pin legs or frame legs). 
     In a similar manner, the bottom U-pin brace (or fastening strap)  374  has two ends  374   a  and  374   b  and may “woven” through the bottom U-pin  31   b  by passing under (behind) one leg  314   a  of the U-pin  314 , and over (in front of, as viewed) the other leg  314   b  of the U-pin  314  and fixed (such as welded) thereto. More particularly, the left end  374   a  of the bottom U-pin brace  374  may be disposed in front of and may be welded to a front surface of the leg  334   a  of the bottom frame  334 , then may pass under and may be welded to a back surface of the left leg  314   a  of the bottom U-pin  314 , then may pass over and may be welded to a front surface of the right leg  314   b  of the bottom U-pin  314 , and the right end  374   b  of the bottom U-pin brace  374  may be disposed behind and may be welded to the bottom surface of the right leg  334   b  of the bottom frame  334 . “Left” and “right” refer to the positions of elements in the figure, and the welds are indicated by shaded dots. As used herein, “front” and “back” are relative terms, simply designating two opposite surfaces of an element (such as the U-pin legs or frame legs). 
     A benefit of the woven configuration of the top and bottom U-pin braces  372  and  374  through the legs (sides) of the top and bottom U-pins  312  and  314 , respectively, may be that even if both welds on a given U-pin fail, such as a result of shock or vibration, adequate contact surface area and contact pressure between the brace ( 372 ,  374 ) and the U-pin ( 312 ,  314 ) may remain to maintain electrical conduction for continued operation of the lamp. 
     A person of ordinary skill in the related lamp-making and design arts will understand that the references herein to “U-pin brace” (or fastening strap) can take a variety of forms (e.g., 1 or 2 ribbons or wires) which are mechanically bonded (such as welded) to both sides of the frame plus the lead wire or wires (such as a U-pin) that extend out of the arc tube pinch (end). 
     Adding extra fastening straps (top and/or bottom U-pin braces) creates a much stronger mount structure that compensates for the lack of continuous vertical (longitudinal) frame side wires (contrast U.S. Pat. No. 3,623,134) by providing two longitudinally spaced-apart connections between each arc tube end and the corresponding top/bottom U-shaped frame. The top end  310   a  of the arc tube  310  is supported by pinch braces  342   a/b  and fastening strap(s)  372 . The bottom end  310   b  of the arc tube  310  is supported by pinch braces  344   a/b  and fastening strap(s)  374 . 
     In essence, the single pivot point of the pinch strap welded to both sides of a frame, as shown in the lamp  100 , is eliminated (supplanted) by adding a second fastening strap welded to both sides of the frame and longitudinally spaced apart from the pinch strap. 
     The extra fastening straps (top and/or bottom U-pin braces) are positioned for welding to the arc tube leads (such as in the form of U-pins) extending out from the arc tube end, thereby securely holding the arc tube in alignment with a longitudinal axis in the middle of the bulb (determined by the plane of the frame which is attached in two places to the arc tube end and leads), even during heavy shock and vibration. 
     Regarding the construction of the arc tube leads, as described herein, the arc tube leads may be in the form of U-pins. This is readily implemented in a pulse start lamp which has intact U-pins extending from both arc tube ends (pinches). For a probe-start type lamp, two separate leads are needed at one (typically the bottom) end of the arc tube. The bottom leads may be formed separately by cutting (clipping) a U-pin type lead. 
     Although using a pulse start lamp with the bottom U-pin intact may provide better structural strength (by weaving through and welding to both sides of a U-pin), lesser but still significant improvement should result from implementing the top U-pin brace and the bottom frame brace, but without the bottom U-pin brace when a starter lead must be used. Alternatively, strength will be even better if the bottom U-pin brace&#39;s strap that extends between both sides of the frame is still welded to the bottom arc tube lead, and the only difference then being that the starter lead (cut away from the electrode lead) would be bent away from the U-pin brace to make a separate electrical connection as required. 
     This also exemplifies a novel embodiment that can be applied to lamps having individual lead wire(s) into an arc tube pinch (not a U-pin). In this case, the improvement over prior art includes having a strap like the U-pin brace&#39;s strap  272 ,  274  that is welded to an individual arc tube lead plus two opposed sides of the frame  232 ,  234 . 
     The example shown in  FIG. 3A  is representative of a pulse-start type HID lamp. For a probe-start type HID lamp (described below with  FIG. 3B ), the bottom U-pin may be cut (or clipped, such as in half, at the bight) so that one leg of the bottom U-pin constitutes an “electrode lead wire”, and the other leg is a “starter lead wire” connected to a probe wire for starting the discharge in the arc tube. 
       FIG. 3B  illustrates an embodiment of a semi-woven bottom U-pin brace structure for a probe-start type HID lamp. Only a relevant portion of the lamp is shown, namely an arc tube  310 , a bottom U-pin  316  (which is cut, as described below) extending from a bottom pinch  310   b  of the arc tube  310 , a bottom frame  334  having two substantially parallel legs (sides)  334   a  and  334   b , a pair of bottom pinch braces  344   a  and  344   b  extending from one leg  334   a  to the other leg  334   b  of the bottom frame  334  across the bottom pinch  310   b , and a bottom U-pin brace  376  (compare  374 ) extending from one leg  334   a  to another leg  334   b  of the bottom frame  334 , across the bottom U-pin  316 . Welds between various elements are indicated by circles in the manner described hereinabove. 
     The U-pin  316  may be referred to as a “connection element”. Similar to the U-pin  314  ( FIG. 3A ), the U-pin  316  ( FIG. 3B ) has two legs  316   a  and  316   b . In contrast with the bottom U-pin  314  ( FIG. 3A ), the U-pin  316  ( FIG. 3B ) has been cut (or clipped, such as in half, at the bight) so that one leg  316   a  of the bottom U-pin constitutes an “electrode lead wire” (or “bottom electrode lead”), and the other leg  316   b  is electrically independent therefrom and may be used as a “starter lead wire” (or “probe lead”, or “starter wire”, or “probe wire”). (Of course, the two legs  316   a  and  316   b  could be formed independently as two elements, rather than by cutting one element.) 
     The legs (sides)  334   a  and  334   b  of the bottom frame  334  are substantially parallel to and coplanar with one another, and the lead wire leg  316   a  of the cut U-pin  316  is substantially coplanar with the two legs  334   a  and  334   b . The other, probe lead leg  316   b  of the cut U-pin  316  is bent, out-of-plane, so that the bottom U-pin brace  376  can pass by it without touching it, remaining electrically isolated therefrom. 
     The bottom U-pin brace (or fastening strap)  376  has two ends  376   a  and  376   b  and may be “woven” by passing under (behind) one leg  316   a  of the U-pin  316  and being fixed (such as welded) thereto. More particularly, the left end  376   a  of the bottom U-pin brace  376  may be disposed in front of and may be welded to a front surface of the left leg  334   a  of the bottom frame  334 , then may pass under and may be welded to a back surface of the lead wire leg  316   a  (which is the left leg) of the bottom cut U-pin  316 , pass by without contacting the starter lead (which is the right leg) of the bottom cut U-pin  316 , and the right end  376   b  of the bottom U-pin brace  376  may be disposed in front of and may be welded to a front surface of the right leg  336   b  of the bottom frame  334 . 
     The top U-pin brace  372  may be woven through the two legs  312   a  and  312   b  of the top U-pin  312 , in the manner described hereinabove (reference  FIG. 3A ). The bottom U-pin brace  376  is “woven” (in a manner of speaking) through only one leg  316   a  of the bottom U-pin  316 , the other leg  316   b  being bent out of the way (out of plane). 
     Because of the “woven” (in and out of plane) configuration of the top U-pin brace  372  through the top U-pin  312 , and the bottom U-pin brace  374  ( FIG. 3A ) or  376  ( FIG. 3B ) through the bottom U-pins  314  or  316 , respectively, even if one or both welds on a given U-pin fail, such as a result of shock or vibration, adequate (sufficient) contact surface area and contact pressure (due to the “weaving”) between the brace and the respective U-pin may remain to maintain electrical conduction between the U-pin brace and the respective U-pin for continued operation of the lamp. 
     When the legs of any of the U-pins ( 212 ,  214 ,  312 ,  314 ,  316 ) referred to herein are referred to as “wires”, it should be understood that they may be substantially rigid wires performing a mechanical function of supporting the arc tube ( 210 ,  310 ) in addition to their electrical function of carrying current into the arc tube ( 210 ,  310 ). 
     The bottom frame  334  may be connected to a stem lead ( 264 ,  FIG. 2 ) and a fly wire ( 268 ,  FIG. 2 ) may be connected to the other stem lead ( 262 ,  FIG. 2 ). The probe (starter) lead leg  316   b  of the bottom cut U-pin  316  may be connected to a starting circuit  380  (illustrated schematically), which may be also be connected by a lead  382  to the other stem lead ( 262 ,  FIG. 2 ). 
     Several and various elements and aspects of an improved, ruggedized lamp mount structure have been disclosed, including but not limited to top and/or bottom U-pin braces and bottom frame braces. 
     While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as examples of some of the embodiments. Those skilled in the art may envision other possible variations, modifications, and implementations that are also within the scope of the invention, based on the disclosure(s) set forth herein.