Abstract:
A portable lighting device for providing illumination includes a body dimensioned and sized to the held by one hand, and adapted to contain a power source therein. A head on the body has a recess in which a light source in the recess is electrically as connected to the power source. The recess and the light source are configured to generate a unidirectional light pattern. A switch enables the light source to be selectively energized by the power source, and a volumetric optical unit is configured for attachment to the head over the recess and the light source to generate an isotropic light pattern.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/932,529, filed Jan. 28, 2014, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    There are many products that use DC batteries or power supplies that inherently require more isotropic light or where it may be useful to convert a generally unidirectional light output to a more isotropic light output. Examples where these attributes might be especially beneficial are that of a portable light source such as a flashlight or camping lantern or other similar products where it would be useful to have a generally efficient, isotropic source of light. 
       BRIEF SUMMARY 
       [0003]    One aspect of the invention relates to a portable lighting device for providing illumination. The portable lighting device includes a body dimensioned and sized to the held by one hand, and adapted to contain a power source therein. A head on the body has a recess in which a light source in the recess is electrically connected to the power source. The recess and the light source are configured to generate a unidirectional light pattern. A switch enables the light source to be selectively energized by the power source, and a volumetric optical unit is configured for attachment to the head over the recess and the light source to generate an isotropic light pattern. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    In the drawings: 
           [0005]      FIG. 1  illustrates a conversion of flashlight to a lantern according to an embodiment of the present invention. 
           [0006]      FIG. 2  illustrates a conversion of lantern to a flashlight according to an embodiment of the present invention. 
           [0007]      FIG. 3  illustrates a vertically rotating volumetric optical unit attachment according to an embodiment of the present invention. 
           [0008]      FIG. 4  illustrates a horizontally rotating volumetric optical unit attachment according to an embodiment of the present invention. 
           [0009]      FIG. 5  illustrates an integrated device for flashlight and lantern and light pattern 
           [0010]      FIG. 6  illustrates a sliding protective cover for a volumetric optical unit according to an embodiment of the present invention. 
           [0011]      FIG. 7  illustrates extending a volumetric optical unit inside of a device according to an embodiment of the present invention. 
           [0012]      FIG. 8  illustrates fixed top volumetric optical unit with side unidirectional light and light pattern. 
           [0013]      FIG. 9  illustrates a sliding protective cover for a volumetric optical unit according to an embodiment of the present invention. 
           [0014]      FIG. 10  illustrates light patterns for the volumetric optical unit of  FIG. 9 . 
           [0015]      FIG. 11  illustrates a downward sliding reflector according to an embodiment of the present invention. 
           [0016]      FIG. 12  illustrates a reflector conversion to device stand according to an embodiment of the present invention. 
           [0017]      FIG. 13  illustrates a light pattern for flashlight/lantern device according to an embodiment of the present invention. 
           [0018]      FIG. 14  illustrates a handheld device with isotropic light pattern according to an embodiment of the present invention. 
           [0019]      FIG. 15  illustrates a volumetric optical unit attachment with flexible material according to an embodiment of the invention. 
           [0020]      FIG. 16  illustrates a volumetric optical unit attachment with flexible material according to another embodiment of the present invention. 
           [0021]      FIG. 17  illustrates a volumetric optical unit attachment with compression fit according to an embodiment of the present invention. 
           [0022]      FIG. 18  illustrates a volumetric optical unit attachment with stretch material according to an embodiment of the present invention. 
           [0023]      FIG. 19  illustrates a volumetric optical unit mechanical attachment according to an embodiment of the present invention. 
           [0024]      FIG. 20  illustrates a volumetric optical unit attachment with hook and loop material according to an embodiment of the present invention. 
           [0025]      FIG. 21  illustrates a volumetric optical unit attachment with a stretchable band according to an embodiment of the present invention. 
           [0026]      FIG. 22  illustrates a handheld device with internal storage for a volumetric optical unit according to an embodiment of the present invention. 
           [0027]      FIG. 23  illustrates a handheld device with external storage for a volumetric optical unit according to an embodiment of the present invention. 
           [0028]      FIG. 24  illustrates a volumetric optical unit according to an embodiment of the present invention. 
           [0029]      FIG. 25  illustrates a volumetric optical unit with reflector according to an embodiment of the present invention. 
           [0030]      FIG. 26  illustrates a volumetric optical unit with protruding reflector shapes according to an embodiment of the present invention. 
           [0031]      FIG. 27  illustrates a volumetric optical unit with a central core of different material according to an embodiment of the present invention. 
           [0032]      FIG. 28  illustrates a volumetric optical unit with a smaller lower diameter according to an embodiment of the present invention. 
           [0033]      FIG. 29  illustrates a volumetric optical unit with an open cavity area according to an embodiment of the present invention. 
           [0034]      FIG. 30  illustrates a volumetric optical unit with a top and bottom reflector according to an embodiment of the present invention. 
           [0035]      FIG. 31  illustrates a volumetric optical unit with hemispherical exterior shapes according to an embodiment of the present invention. 
           [0036]      FIG. 32  illustrates alternate shapes for a volumetric optical unit exterior surface. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    The term “flashlight” represents a device which is generally hand held and with a generally unidirectional light output. The term “lantern” represents a device, which is generally hand held, with a generally omni-directional or isotropic light output. Both the flashlight and lantern could also be independently suspended or floor standing. 
         [0038]    Although the disclosure primarily discusses flashlights and lanterns, these terms generally represent a wide range of products that can make use of the items disclosed. These products typically have their own DC power supply and are usually portable. For example, mining helmets, bicycle and other sports helmets, hand held safety lights, emergency lights, boat lighting, reading lights, cameras, automobile lighting and other lighting where a battery is the primary power source. The disclosed devices could also be used in other portable articles like umbrellas, or on ski pole handles. Additionally, the disclosed devices are aptly suitable for portable electronics such as cell phones, tablet computers, electronic readers, hand held electronic games, watches and other portable electronics where a generally unidirectional light can efficiently and conveniently be converted to generally isotropic light. A cell phone is a good example. A cell phone often includes a generally unidirectional light for a camera flash. The light can be kept in the “on” position and adapted with the disclosed device to provide an isotropic light suitable to support reading or created a lantern type lighting distribution pattern. 
         [0039]    Furthermore, disclosed devices can include structures that incorporate the benefits of both a flashlight and a lantern into a single device that can produce both unidirectional and isotropic light and methods for changing from flashlight mode to lantern mode or the reverse. 
         [0040]    The term Volumetric Optical Unit (VOU) represents structures as described in publications US20140078746, US20140078722, and WO2014294044, the disclosures of which are incorporated herein in their entireties. A VOU is generally a structure having an interior volume mostly filled with solid or flexible material useful for the redirection of light, as opposed to a hollow shell. 
         [0041]    In all of the following described embodiments, reference numbers will be used with the intention of providing consistency among the different embodiments. In other words, components that remain unchanged among different embodiments will bear the same reference number in each embodiment. 
         [0042]      FIG. 1  illustrates a structure for the conversion of a flashlight to a lantern with the inclusion or attachment of a VOU.  FIG. 1 a    illustrates a device  10  with a body that contains a battery compartment for the storage of a battery. Preferably the body will be elongated so as to have a longitudinal axis  11 . The body is configured to interconnect the battery to a light source  13 , typically a small incandescent light bulb or LED mounted in a reflector with a lens configured to direct light in a typical unidirectional light pattern  12 .  FIG. 1 b    illustrates the device  10  with the addition of a VOU  14  that converts the light to an isotropic light pattern  16  similar to a lantern. 
         [0043]      FIG. 2  illustrates a structure for the conversion of a lantern, including a VOU, to a flashlight, with the addition of a reflector surrounding the VOU for directing the isotropic light to unidirectional light.  FIG. 2 a    illustrates the device  10  including a VOU  14  that provides a generally isotropic light pattern  16  similar to a lantern.  FIG. 2 b    illustrates the device  10  with addition of a reflector  18  surrounding the VOU and thereby redirecting the light into the unidirectional light pattern  12 . 
         [0044]      FIG. 3  illustrates a configuration of the device  10  wherein the primary lighting function is a flashlight with unidirectional light emitting properties. In  FIG. 3   a,  a VOU  20  is hinged to the device  10  by a hinge  21  that has an axis normal to the longitudinal axis  11 , and can be easily vertically rotated onto the top of the device  10  as shown in  FIG. 3   b.  In  FIG. 3   c,  it will be seen that the light output is changed from unidirectional to isotropic as shown in  FIG. 1   b,  thereby converting the flashlight to a lantern. In flashlight mode, the vertically hinged VOU  20  is located in a down position as in  FIG. 3   a.  In lantern mode the hinged VOU  20  is located in an up position as in  FIG. 3   c.  While in the down position as illustrated in  FIG. 3   a,  the VOU  20  may have a protective cover attached to the flashlight unit and partially, or fully, cover the VOU  20  for protection. The VOU  20  may also have a locking mechanism, e.g. a magnetic or detent latch or catch, in either or both the down and up positions to keep the VOU  20  stationary and in the intended position. 
         [0045]      FIG. 4  illustrates a horizontal hinged mechanism  25  for converting a flashlight to a lantern. In this case  FIG. 4 a    shows the VOU  30  located above a top plane  32  of the device  10  and located to the side, out of the path of the unidirectional light from the device. The hinge  25  has an axis of rotation parallel to the longitudinal axis  11  so that the VOU  30  can be easily rotated into the path of the unidirectional light and convert the light to a generally isotropic light pattern, as illustrated in  FIG. 4   b.  While in the flashlight position as illustrated in  FIG. 4   a,  the VOU  30  may have a protective cover attached to the flashlight unit and partially, or fully, cover the VOU  30  for protection. The VOU  30  may also have a locking mechanism, e.g. a magnetic or detent latch or catch, in either or both the down and up positions to keep the VOU  30  stationary and in the intended position. 
         [0046]    In the structures described in  FIGS. 3 and 4 , the main function of the unit my be considered a flashlight, with the VOU out of the path of the unidirectional light emitted from the flashlight, but then easily converted to a lantern by rotating the VOU into the path of the unidirectional light from the flashlight. Likewise, the main function of the unit could be considered a lantern, with the VOU positioned in the path of the unidirectional light converting it to isotropic light but easily rotated out of position to expose the unidirectional light. In both cases, the VOU is designed to be an integral component with the device  10  that can easily be moved to change the function from one to the other. And in both cases, the same light source  13  is used for both flashlight and lantern mode 
         [0047]      FIG. 5  illustrates a structure that functions as a flashlight and/or a lantern without changing the location of the VOU. In  FIG. 5   a,  the device  40  has a flashlight in located on one end of the structure with its own light source  13 . A lantern is located on the other end of the device  10  with its own light source (not shown) and a VOU  44  fixed to the device over the light source. Each light source may be operated independently by its own switch  46 ,  48 .  FIG. 5 b    illustrates the unidirectional light pattern  12  of the flashlight end, and the generally isotropic light pattern  16  of the lantern end. 
         [0048]      FIG. 6  illustrates a structure similar to  FIG. 5 a    with a sliding cover  50  over the VOU  44  to protect the VOU when not in use.  FIG. 6 a    illustrates the device  40  with the cover  50  over the VOU  44 .  FIG. 6 b    illustrates the structure after sliding the cover  50  away from the VOU  44  to expose the VOU and put the device  40  into lantern mode. Each light source may be operated independently by its own switch  46 ,  48 . As well the light source beneath the VOU  44  may automatically turn on when the protective cover  50  slides open to expose the VOU  44 . 
         [0049]      FIG. 7  illustrates a structure that functions as a flashlight and/or a lantern wherein the VOU is extendible from the side of the structure.  FIG. 7 a    illustrates a device  60  where a VOU  62  is extended outside the walls of the device  60  and ready to radiate light in an isotropic light pattern.  FIG. 7 b    illustrates the device  60  with the VOU retracted into the structure to protect the VOU when the VOU is not in use. The light source (not shown) for the VOU  62  may be movable with the VOU  62  or fixed within the device  60 , and may be switched independently with its own switch  48 , or automatically activated when the VOU  62  is extended outwardly from the device  60 . 
         [0050]      FIG. 8 a    illustrates a device  70  where a VOU  72  is fixed at one end of the device  70 , with a light source  74  for emitting unidirectional light disposed in a recess  76  in the side of the device  60 .  FIG. 8 b    illustrates an isotropic light pattern  77  emanating from the VOU  72  and a unidirectional light pattern  78  emanating from the light source  74 . 
         [0051]      FIG. 9 a    illustrates the device  70  where the VOU  72  is fixed at one end of the device  70 , with the light source  74  for emitting unidirectional light disposed in the recess  76  in the side of the device  60 . A sliding cover  80  is movable between a first position covering the VOU  72  and a second position covering the recess  76  (and the light source  74 ). Preferably, the sliding cover  80  would be in the first position over the VOU  72  when the device  70  is not is use or is in storage, to protect the VOU. The light source for the VOU  72  may be switched independently with its own switch  82 , or it may be automatically activated by moving the sliding cover  80  to the second position. Alternatively or additionally, the light source  74  for the unidirectional light may be switched independently with its own switch  82 , or it may be automatically activated by moving the sliding cover  80  to the first position. 
         [0052]      FIG. 10 a    illustrates the unidirectional light pattern  84  of the activated device  70  in  FIG. 9   a.    FIG. 10 b    illustrates the isotropic light pattern  86  of the activated device  70  in  FIG. 9   b.    
         [0053]      FIG. 11 a    illustrates a device  90  with a VOU  92  fixed at one end of the device  90 . A reflector  94  is movable between a first position surrounding the VOU  92  (see  FIG. 11 a   ) and a second position retracted over the body of the device  90 , fully exposing the VOU  92  (see  FIG. 11 b   ). In the first position, the VOU  92  and the reflector  94  will generate a unidirectional light pattern. In the second position, the VOU  92  will generate an isotropic light pattern. 
         [0054]      FIG. 12 a    illustrates the device  90  of  FIG. 11 a    with the VOU  92  fixed at one end, but with a removable reflector  96  for generating a unidirectional pattern. The structure in this configuration would typically be held in the hand and used as a flashlight. The reflector  96  may be removed and attached to the opposite end of the device  90  to serve a secondary purpose of supporting the device  90  to stand upright independently. The reflector  96  may be attached to the structure by a screw connection, compression fit, bayonet type connection, or other connection suitable for this purpose. 
         [0055]      FIG. 13 a    illustrates a unidirectional light pattern  97  of the device  90  illustrated in  FIG. 12   a.    FIG. 13 b    illustrates an isotropic light pattern  98  of the device  10  illustrated in  FIG. 12   b.    
         [0056]    In many cases, the hand held structure does not need a unidirectional light source but is better served with only an isotropic light source.  FIG. 14 a    illustrates a device  100  with a top mounted VOU  102 , which provides an isotropic light pattern  104  as shown in  FIG. 14   b.  The device  100  also include a sliding protective cover or other covering means to protect the VOU  102  when not in use. The sliding cover may also serve as the off/on switch for the light source. This configuration is useful when there is only a need for an isotropic light pattern. 
         [0057]      FIGS. 15 a  and 15 b    illustrate a device  110  with a VOU  112  attached over a unidirectional light source  114  as in a flashlight. In this case the VOU  112 ,  112 ′ is constructed of a flexible molded material such as silicone comprising a body  116  and a flexible molded skirt  118 ,  118 ′ sized to fit snuggly over the end of the device  110  providing a secure fit for the VOU  112 ,  112 ′ to the head of the flashlight. 
         [0058]      FIGS. 16 a  and 16 b    illustrate the device  110  shown in  FIGS. 15 a  and 15 b    with a differently shaped VOU  120 ,  120 ′over the unidirectional light source  114  of the flashlight. In this case the VOU  120 ,  120 ′ is constructed of a flexible molded material such as silicone but is much wider than the VOU  112 ,  112 ′. The VOU  120 ,  120 ′ also includes a flexible molded skirt  122 ,  122 ′ sized to fit snuggly over the end of the device  110  providing a secure fit for the VOU  120 ,  120 ′to the head of the flashlight. 
         [0059]      FIG. 17 a    illustrates a device  130  with a VOU  132  having an annular flexible protrusion  134  around the periphery of a lower portion thereof. A head  136  of the device  130  defines a recess  138  with a light source  140  therein, and includes an annular slot  142  sized to frictionally receive the annular flexible protrusion  134  in a compression fit.  FIG. 17 b    illustrates the VOU  132  after compression fit into the head  136 . 
         [0060]      FIG. 18 a    and  FIG. 18 b    illustrate a device  150  and a VOU  152  with an integrated flexible/stretchable material  154  that can be stretched over a head  154  of the device  150  to attach the VOU  152  to the device  150 . The flexible/stretchable material  154  may be nylon, spandex or other fabric material or other material, which can be integrated with the VOU  152  and stretched over the head  154  in a secure fit. 
         [0061]      FIG. 19  shows several embodiments of a mechanical attachment of a VOU to a device.  FIG. 19 a    illustrates a device  160  with a head  162  and light source  164  with an internal thread  166  in a recess surrounding the light source. A VOU  168  with an integrated solid ring  170  has an external thread  172  on the solid ring sized to fit the internal thread  166 . The VOU  168  may be screwed into the head and thereby secured to it.  FIG. 19 b    illustrates the device  160 ′ with the head  162  and the light source  164  and an internal bayonet socket  166 ′ in the recess surrounding the light source. The VOU  168 ′ with the integrated solid ring  170 ′ has an external bayonet protrusion  172 ′ on the solid ring sized to fit the internal bayonet socket  166 ′. The VOU  168 ′ may thus be secured to the head by a bayonet fixture.  FIG. 19 c    and  FIG. 19 d    illustrate similar configurations where screw threads  166 ″,  172 ″, or the bayonet structure  166 ′″,  172 ′″ are adapted to fit the exterior of the head  162 .  FIG. 19 e    illustrates a VOU  180  with a spring mounting clip  182  extending therefrom for a spring type of attachment to a device. The VOU  180  may include a plurality of spring clips. Other mechanical mounting schemes are possible such as a magnetic attachment, a compression fit, other hinged methods, other spring clip attachments to either the inside or outside of the flashlight head, clamps or any combination thereof. Additionally, the VOU bottom surface may include an adhesive to enable directly attachment to the light source, or a protective glass or plastic cover. 
         [0062]      FIGS. 20 a    and  FIG. 20 b    illustrate a VOU mounting means that uses a hook and loop fastener. Loop tabs  190  mounted to exterior sides of the head  162  may couple with hook strips  192  attached to a VOU  194 .  FIG. 20 c    and  FIG. 20 d    illustrate an alternate mounting means where the hook and loop attachment material is only on the VOU  194 . The VOU  194  has one or more fixed or flexible tabs  196  extending downward and attached to a strip of material  198  having a hook surface on one side and loop surface on the other side. The strip of material  198  would wrap around the head  162  and attach to itself to secure the VOU  194  to the structure. 
         [0063]      FIG. 21  illustrates a VOU mounting means that uses a stretchable or elastomeric material, such as rubber, or other elongating materials. The stretchable material  200  is attached to a VOU  202 . The VOU  202  is placed on the head of the device  110 , while the stretchable material  200  stretches across the bottom of the device, or other side attachment points, to hold the VOU  202  thereto. The stretchable material  200  may also be fixed to the device and attached to mounting points on the VOU  202 . 
         [0064]    In cases were the VOU is not an integral part of the structure, it may be desirable to have a means for storing the VOU when not in use, but still attached to the flashlight structure and easily accessible when needed. There are several unique ways to store the VOC that not only makes it easily accessible, but can also serve to protect the VOC when not in use. 
         [0065]      FIG. 22 a    illustrates a device  210  with a recessed cavity  212  in the side for the purpose of storing a VOC  214 .  FIG. 22 b    illustrates a device  210 ′ with a recessed cavity  212 ′ located at an end or bottom. 
         [0066]      FIG. 23 a    illustrates a VOU  220  with an integrated flexible/stretchable material  222  that may be stretched over a device head  224  to attach the VOU  200  thereto.  FIG. 23 b    illustrates the same VOU  220  with the flexible/stretchable material  222  folded backwards to act as a storage bag to protect the VOU. 
         [0067]    The primary function of a VOU  300  as previously discussed and as illustrated in  FIG. 24 , is to redirect light from a generally unidirectional light pattern to an isotropic light pattern. As discussed in the aforementioned related patent publications, the VOU includes a scattering medium  302  made of reflective materials or other materials such as down-converting phosphors, fluorescent, quantum dots, nano-particles having similar features relative to a VOU. The light scattering medium could include titanium dioxide. 
         [0068]    It may be preferable for the VOU  300  to include a reflector  304  typically located opposite the light source as illustrated in  FIG. 25 . This will serve to maximize the redirection of light from a generally unidirectional light source to a generally isotropic light pattern as the light exits the VOU. The reflector can be either a specular reflector or a diffuse reflector. A specular reflector can be made of a stamped reflective aluminum or other materials. A diffuse reflector could be injection molded with a reflective material such a titanium dioxide, or made with a film such as White Optics™ 97, or a diffuse metal reflector such as White Optics™ Metal, both with reflectivity of greater than 97%. Other methods and materials can also be used. The reflector  304  may also be made partially translucent allowing a certain percentage of the light to exit through the reflector itself 
         [0069]    The reflector may take many configurations to help optimize the generally isotropic light pattern to a desired light pattern.  FIG. 26 a    illustrates a reflector  306  with hemispherical shape to redirect light outwardly.  FIG. 26 b    illustrates a reflector  308  with a curved shape to perform the same function.  FIGS. 26   c,    26   d  and  26   e  illustrate reflectors  310 ,  310 ′,  310 ″ with conical shapes. The depth of the shape can influence the light output radiation pattern.  FIG. 26 f    illustrates a reflector  312  with a parabolic shape. 
         [0070]      FIG. 27  illustrates a VOU configuration that includes two types of volumetric materials. In this example, there is a central core  320  with scattering medium  322  that is less concentrated than the surrounding material  324 . This structure serves to allow more dissipation of the unidirectional light from the light source, before being scattered by the scattering medium  324 . The central core  320  may include no scattering medium as well. There are many ways to configure a VOU with different materials, different shapes or various scattering medium concentrations to optimize the light output. The central core area  320  can take many shapes. For example, a cylinder, cone, dome, conic, parabola or a combination of these. 
         [0071]      FIGS. 28 a  and 28 b    illustrate reflector configurations that provide the opportunity to optimize the light output. These include depressions in the reflector, one conical  330 , and one curved  332 . 
         [0072]      FIGS. 28 c  and 208 d    illustrate VOUs  330 ,  330 ′ where the exterior shape is such that the portion  332  of each VOU nearer the light source has a smaller diameter than the portion  334  of each VOU further from the light source. This configuration more closely resembles the light pattern emitted by the light source and can help optimize the light pattern from the VOU. A large depression  336 ,  336 ′ in the middle can serve several functions including better scattering of the light from the light source, saving material, and controlling light output which might, by design, exit the upper portion  334  through a partially translucent material. 
         [0073]      FIG. 29 a    and  FIG. 29 b    illustrate VOUs  340 ,  340 ′with an open cavity area  342 ,  342 ′ in each VOU. This open cavity area serves to allow more dissipation of the unidirectional light from the light source, before being scattered by the scattering medium  344 . That open cavity area can take many shapes. For example, the shape may be a cylinder, cone, dome, conic, parabola or a combination of these. 
         [0074]      FIG. 30  illustrates a VOU  350  that includes a reflector  352  at the bottom of the VOU near an opening  354  for a light source. The reflector  352  may be useful in directing the light to optimize the generally isotropic light pattern. 
         [0075]      FIG. 37  illustrates a top down view of a VOU  360  including hemispherical shapes  362  on the outside of the exterior surface. The shapes  362  may be included for decorative purposes, or for functional purposes to help control the dissipation of light from the VOU. As an alternative to the hemispherical shapes shown, the surface may include waves or ribs as shown in  FIG. 38 . Other shapes or textures may also be adapted. These shapes, or similar shapes, can also provide a more textured surface or handgrip to assist when twisting or installing or removing a VOC from a device or other portable lighting source. 
         [0076]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.