BACKGROUND

[0001] People working on the tops and sides of buildings, as well as other high structures risk falling and suffering injury as a result. In modern society, building maintenance is an area that continues to expose workers to the risk of dangerous falls. According to the U.S. Department of Labor, work related falls are among the most common sources of work related severe injuries and death. (See, e.g., https://www.osha.gov/SLTC/fallprotection/). The Department of Labor's Bureau of Labor Statistics reports that slips, trips and falls resulted in approximately 229,000 injuries per year (201 1-2013) resulting in approximately 700 workplace deaths per year. Death from falls is second only to vehicle related deaths and account for roughly 16% of work related deaths. The

Occupational Safety and Health Administration (OSHA) and the American National standards Institute (ANSI) provide standards to reduce the number and severity of workplace falls. Fall protection equipment must perform under a wide variety of conditions while not hindering the ability of workers to safely perform their jobs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The accompanying drawings illustrate various examples of the principles described herein and are a part of the specification. The illustrated examples are given merely for illustration, and do not limit the scope of the claims.

[0003] Fig. 1 is an isometric top view of a monorail traveler, according to one example of the principles described herein.

[0004] Fig. 2 is an isometric bottom view of the monorail traveler of Fig. 1 , according to one example of the principles described herein.

[0005] Fig. 3 is a front view of the monorail traveler of Fig. 1 , according to one example of the principles described herein. [0006] Fig. 4 is a side view of the monorail traveler of Fig. 1 , according to one example of the principles described herein.

[0007] Fig. 5 is a bottom view of the monorail traveler of Fig. 1 , according to one example of the principles described herein.

[0008] Fig. 6 is a top view of the monorail traveler of Fig. 1 , according to one example of the principles described herein.

[0009] Fig. 7 is an isometric top view of the monorail traveler of Fig. 1 engaged with a monorail, according to one example of the principles described herein.

[0010] Fig. 8 is an isometric bottom view of the monorail traveler of Fig. 1 engaged with the monorail of Fig. 7, according to one example of the principles described herein.

[0011] Fig. 9 is a front view of the monorail traveler of Fig. 1 engaged with the monorail of Fig. 7, according to one example of the principles described herein.

[0012] Fig. 10 is a side view of the monorail traveler of Fig. 1 engaged with the monorail of Fig. 7, according to one example of the principles described herein.

[0013] Fig. 1 1 is a top view of the monorail traveler of Fig. 1 engaged with the monorail of Fig. 7, according to one example of the principles described herein.

[0014] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.

DETAILED DESCRIPTION

[0015] In order to access some areas of buildings such as under overhangs, special equipment and systems may be required. Rope access technicians use climbing and abseiling techniques and this specialized equipment in order to access difficult-to-reach areas from above for various industrial applications like maintenance, construction, inspection, and welding. While close to the ground, lifts and ladders may be options, but at certain heights, they become impractical. To access such areas, specialized suspension access devices such as harnesses, ropes, rail or monorail systems, davit systems, and outrigger beams may be used. These and other devices support workers as they perform their work, and may share features with fall protection systems and similarly function to reduce the number and injuries resulting from falls. However, while a fall protection system may be focused on the impact of a fall by a worker and their equipment, they generally are not load bearing devices designed to continuously support a worker and equipment. In contrast, a system for suspending a worker may need to continuously and safely support the weight of the worker and associated equipment while being capable of dealing with impacts from falls or other unexpected events without deforming or breaking.

[0016] Thus, examples described herein provide a monorail system. The monorail system includes a traveler. The traveler includes a body including a v- shaped cross-section and two diverging appendages. The traveler further includes a plurality of first axles coupled to a distal end of the two diverging appendages, and a plurality of first wheels mounted on each of the first axles. At least two of the first wheels are mounted on opposite diverging appendages [0017] The traveler further includes a number of second axles coupled to the body proximal to an intersection of the two diverging appendages and closer to the intersection relative to the first axles. A number of second wheels are mounted on each of the second axles.

[0018] The monorail system further includes a monorail. The monorail includes a cross-section that includes a first portion that fills a void defined by the v-shaped body of the traveler and the first wheels. The first portion includes at least three sides. The monorail further includes a second portion

monolithically formed with the first portion. The second portion includes a pair of flanges running parallel to each other with respect to a length of the monorail and are for mounting the monorail to a structure.

[0019] In one example, the at least three sides of the first portion of the monorail includes a first side. The second wheels contact the first side. The first portion of the monorail also includes a second side, the first side and second side being formed at an acute angle. At least one of the first wheels contacts the second side.

[0020] The first portion of the monorail also includes a third side. The first side and the third side are formed at an acute angle, wherein at least one of the first wheels contacts the third side. At least two of the second wheels contact the first side of the first portion of the monorail.

[0021] The monorail further includes a coupling ring pivotably coupled to the body on a side of the body opposite the void defined by the v-shaped body of the traveler and opposite the first wheels. A brake is coupled to the v-shaped body to, when engaged with the monorail, stop movement of the traveler along a length of the monorail. In one example, a number of brackets are coupled to the second portion of the monorail to couple the monorail to a structure. In one example, the monorail is made of extruded aluminum.

[0022] Examples described herein further provide a traveler for a monorail system. The traveler includes a body comprising a v-shaped cross- section comprising two diverging appendages, a plurality of first axles coupled to a distal end of the two diverging appendages, and a plurality of first wheels mounted on each of the first axles. At least two of the first wheels are mounted on opposite diverging appendages. A number of second axles are coupled to the body proximal to an intersection of the two diverging appendages and closer to the intersection relative to the first axles. A number of second wheels are mounted on each of the second axles.

[0023] The traveler further includes a threaded recess defined in the v- shaped body, and a brake screw engaged with the threaded recess. The brake screw includes a length to protrude from the threaded recess and engage with a monorail to stop movement of the traveler along a length of the monorail.

[0024] The two diverging appendages and the first wheels form a void in which at least a portion of a monorail may be inserted to retain the monorail within the void with respect to any orthogonal direction relative to a length of the monorail. The traveler further includes a coupling ring pivotably coupled to a spine of the v-shaped body on a side of the v-shaped body opposite a void defined by the v-shaped body of the traveler and the first wheels. [0025] The traveler further includes a coupling ring axle disposed within a spine via defined within the spine of the v-shaped body. A stop screw is included to retain the coupling ring axle within the spine via. At least one coupling ring interface of the coupling ring is coupled to the coupling ring axle through a recess defined within the v-shaped body.

[0026] The first wheels mounted on each of the first axles of the traveler include a chamfered surface that contact a side of the monorail and support the traveler from turning in a direction orthogonal to a length of a monorail to which the traveler is coupled when a side load is applied to the traveler.

[0027] The traveler further includes a number of axle blocks to retain the second axles and the second wheels mounted thereto within the v-shaped body. A number of axle block screws may be used to couple the axle blocks to the v-shaped body. A brake screw retains the coupling ring axle within the spine via on an end of the coupling ring axle opposite the stop screw.

[0028] Examples described herein further provide a monorail for a monorail system. The monorail includes a first portion that fills a void defined by a v-shaped body of a traveler and a number of wheels of the traveler. The first portion includes at least three sides. The monorail further includes a second portion monolithically formed with the first portion. The second portion includes a pair of flanges running parallel to each other with respect to a length of the monorail for mounting the monorail to a structure.

[0029] The at least three sides of the first portion of the monorail include a first side, and a second side, and a third side. The first side and second side are formed at an acute angle. At least one of the wheels of the traveler contacts the second side. The first side and the third side are formed at an acute angle. At least one of the wheels of the traveler contacts the third side.

[0030] The monorail includes a number of voids defined in the second portion of the monorail along the length of the monorail. The voids form an internal support structure monolithically formed in the monorail. The internal support structure includes a number of support ribs. The monorail further includes a main rail void defined within the first portion of the monorail. The number of voids defined in the second portion of the monorail along the length of the monorail include a support structure void defined within approximately the center of the second portion of the monorail, and a number of rib voids defined in the second portion of the monorail within a perimeter of the second portion around the support structure void.

[0031] As used in the present specification and in the appended claims, the term "a number of" or similar language is meant to be understood broadly as any positive number comprising 1 to infinity; zero not being a number, but the absence of a number.

[0032] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present systems and methods. It will be apparent, however, to one skilled in the art that the present apparatus, systems, and methods may be practiced without these specific details. Reference in the specification to "an example" or similar language means that a particular feature, structure, or characteristic described in connection with that example is included as described, but may not be included in other examples.

[0033] Turning now to the figures, Fig. 1 is an isometric top view of a monorail traveler (100), according to one example of the principles described herein. Other figures will be described in connection with Fig. 1 . The traveler (100) is coupled to and used in connection with a monorail (Figs. 7-11 , 200). When engaged with the monorail (200), the traveler (100) is able to move along the length of the monorail (200). A user may couple climbing or safety equipment to the traveler (100) for use in accessing some areas of structures such as under overhangs and along exterior walls. This system allows the traveler to move as the user moves along the exterior of the structure. In this manner, exterior surfaces of windows may be washed, utilities may be serviced, heating, ventilation, and air conditioning (HVAC) systems may be installed and maintained, security systems may be installed and maintained, and building signage may be installed and maintained, among other tasks that may involve accessing areas of the building from which the individual could fall. In some examples, the traveler (100) and the monorail (200) may be installed and used inside the structure as well in order to access areas within vaulted rooms such as within gymnasiums and warehouses, among others.

[0034] Throughout the figures, a three-dimensional Cartesian coordinate indicator is provided to orient the reader as to directions of movement and forces placed on the elements of the present monorail system. Within the Cartesian coordinate indicator, a circle located at the origin of the coordinate indicator indicates that the positive direction is moving or coming out of the page toward the reader such as in Figs. 3, 4, 6, and 1 1. Conversely, a square indicates that the negative direction is moving or coming out of the page toward the reader such as in Figs. 5, 9, and 10. Generally, the X direction indicates a direction of a force applied to a traveler of the monorail system by a user hanging directly from the traveler. In one example, the X direction is normal to a length of the monorail on which the traveler is engaged. In other words, the monorail system as depicted throughout Fig. 1-4, and 7-10 is depicted in an inverted orientation with respect to how the monorail system is actually oriented when installed on a structure (i.e., building).

[0035] The Y direction indicates a direction of travel of the traveler along a straight section of the monorail, where the positive Y direction indicates a front end of the traveler and the negative Y direction indicates a rear end of the traveler as referred to herein. The Y direction also indicates the longitudinal axis of the monorail. The Z direction indicates a direction orthogonal to both the X and Y directions, and may indicate a force of a side load applied to the traveler if a user should apply such a force when coupled to the traveler.

[0036] The traveler (100) includes a body (101 ) with a number of appendages (102). In the example of Figs. 1 through 1 1 , the body (101 ) includes two appendages (102). The appendages (102) diverge from a common spine and form a v-shape when viewed from an end of the traveler (100) as depicted in, for example, Figs. 1 , 2, 3, 7, 8, and 9. In other words, the traveler (100) has an inverted v-shaped cross section as depicted in these figures.

[0037] A coupling ring (103) is pivotably coupled to the body (101 ) of the traveler (100). With reference to Figs. 1 , and 3-6, the coupling of the coupling ring (103) to the body (101 ) may be performed by defining a number of coupling ring recesses (107) in the body (101 ) of the traveler (100). A spine via (108) is also defined in a spine portion of the body (101 ). A coupling ring axle (105) is inserted into the spine via (108) while being engaged with a number of coupling ring interfaces (104) of the coupling ring (103). In this manner, the coupling ring (103) is able to rotate about the coupling ring axle (103) with a rotational movement defined by the coupling ring recesses (107) as indicated by arrow A. The coupling ring (103) and its associated elements allow a user to move relative to the traveler in the Z direction.

[0038] The traveler (100) includes a plurality of first axles (1 1 1 ) coupled to a distal end of the two diverging appendages (102). In one example, at least two first axles (1 1 1 ) are included in the traveler (100). In the examples depicted throughout the figures, four first axles (1 1 1 ) are included in the traveler (100) with two first axles (1 11 ) coupled on a side of the traveler (100) opposite where two other first axles (11 1 ) are coupled. A corresponding number of rail wheels (1 10) are mounted to the first axles (1 11 ) with two rail wheels (1 10) mounted on opposites sides from one another. The rail wheels (1 10) are wheels that continually make contact with the monorail (200) and function to give the traveler (100) locomotion along the monorail (200) with or without a force due to the weight of a user being placed on the traveler (100) in the X direction. The rail wheels (1 10) include bearings (1 12) that interface with the first axles (1 1 1 ) to allow the wheels to freely rotate about the first axles (1 1 1 ). A snap ring (1 13) may be used to secure the rail wheels (1 10) to the axles (1 1 1 ). The rail wheels (1 10) include a chamfered surface or edge (114) that assist in the traveler (100) moving along the monorail (200) even when the force associated with a side load is applied in the Z direction. This aspect of the traveler (100) will be described in more detail in connection with Figs. 7-1 1 below.

[0039] A number of guide wheels (130) may also be included within the traveler (100). The guide wheels (130) will now be described in connection with, for example, Fig. 2. Fig. 2 is an isometric bottom view of the monorail traveler (100) of Fig. 1 , according to one example of the principles described herein. As depicted in Fig. 2, the guide wheels (130) are coupled to the traveler (100) in a number of guide wheel voids (134) defined in the body (101 ) of the traveler (100). The guide wheels (130) are coupled to the traveler (100) by mounting a number of guide wheel axles (131 ) and the guide wheels (130) to the traveler (100) within the guide wheel voids (134). The guide wheel axles (131 ) and the guide wheels (130) are secured to the traveler (100) and retained in the guide wheel voids (134) using a number of axle blocks (132) and a number of axle block screws. The axle blocks (132) may be formed with a recess, or similar recess may be defined within the guide wheel voids (134) of the traveler (100) to accommodate for the guide wheel axles (131 ). In either example, the axle block screws (133) secure the axle blocks (132) to the guide wheel voids (134) of the traveler (100). In this manner, the guide wheels (130) are coupled to the traveler (100) and move freely about the guide wheel axles (131 ). As will be described in more detail below, the guide wheels (130) interface with a first surface of the monorail (200) referred to herein as a domed guide wheel interface (206). As mentioned above, a force associated with a side load may be applied in the Z direction. This may cause the traveler (100) to shift on the monorail (200) to one side or the other. In this case, the guide wheels (130) come into contact with the domed guide wheel interface (206). The guide wheels (130) are coupled to the traveler (100) in a location such that when a side load is applied, the bode (100) of the traveler (100) does not come in contact with the monorail (200) but, instead, glides along the monorail (200) due to the guide wheels (130) interfacing with the domed guide wheel interface (206).

[0040] A stop screw (106) may also be included within the traveler (100). The stop screw will now be described in connection with Figs. 1 , 2, 4-6, 9 and 10. Fig. 4 is a side view of the monorail traveler (100) of Fig. 1 , according to one example of the principles described herein. Further, Fig. 5 is a bottom view of the monorail traveler (100) of Fig. 1 , according to one example of the principles described herein. Still further, Fig. 6 is a top view of the monorail traveler (100) of Fig. 1 , according to one example of the principles described herein. Fig. 9 is a front view of the monorail traveler (100) of Fig. 1 engaged with the monorail (200) of Fig. 7, according to one example of the principles described herein. Still further, Fig. 10 is a side view of the monorail traveler

(100) of Fig. 1 engaged with the monorail (200) of Fig. 7, according to one example of the principles described herein. In each of these figures, the stop screw (106) is depicted as being inserted into a stop screw via (109). In one example, a number of screw threads may be included on the stop screw (106), and corresponding threads may be defined in the stop screw via (109) so that the stop screw (106) may be tightly engaged with the stop screw via (109) defined in the body (101 ) of the traveler (100). In this example, the treading of the stop screw (106) may begin at a portion of the stop screw (106) that projects into the body (101 ) of the traveler (100) located after the stop screw (106) has traveled through the spine via (108) as depicted in Fig. 9. The stop screw (106) retains the coupling ring axle (105) located within in the spine via (108).

[0041] The traveler (100) may further include a brake screw (120). The brake screw (120), when engaged with a portion of the monorail (200), serves to stop the movement of the traveler (100) along the length of the monorail (200), or, in other words, in the Y direction. The brake screw (120) is depicted in, for example, Figs. 2, 3, 5, and 9. Having not yet introduced Fig. 3, Fig. 3 is a front view of the monorail traveler (100) of Fig. 1 , according to one example of the principles described herein. The brake screw (120) may include a number of threads, and a via defined within the body (101 ) that receives the brake screw (120) may include corresponding threads as depicted in Fig. 3 for example.

[0042] A retention ring groove (121 ) may be defined in a portion of the brake screw (120) below the body (101 ) of the traveler (100). A retention ring (122) is coupled to the brake screw (120) at the retention ring groove (121 ) in order to ensure that the brake screw (120) is not capable of being removed from the body (101 ) of the traveler (100) unless the retention ring (122) is removed.

In this manner, the brake screw (120) may be screwed further into the body

(101 ) until it comes in contact with the monorail (200), but, as a safety measure, is unable to be fully removed from the body (101 ). In one example, the retention ring (122) is a snap ring as depicted in Figs. 2, 3, and 5. Further, in one example, the brake screw (120) has a length sufficiently long enough to protrude from the threaded via and engage with the monorail (200) to stop movement of the traveler (100) along a length of the monorail (200).

[0043] Further, the brake screw (120) may further serve to retain the coupling ring axle (105) within in the spine via (108) in a similar manner as described above in connection with the stop screw (106). In this manner, both the brake screw (120) and the stop screw (106) ensure that the coupling ring axle (105) does not wander out of the spine via (108) because of, for example, the movement of the coupling ring (103) back and forth in the Z direction during a load force being applied on the coupling ring (103) in directions along the arc created by the movement of the coupling ring (103) indicated by arrow A (Fig.

1 ).

[0044] As may be best understood in connection with, for example, Figs. 3 and 9, the two diverging appendages (102) and the rail wheels (1 10) form a void (140) in which at least a portion of the monorail (200) may be inserted to retain the monorail (200) within the void (140) with respect to any orthogonal direction relative to a length of the monorail. The description of the interfaces between the monorail traveler (100) and the monorail (200) will now be described in connection with Figs. 7 through 1 1 . Fig. 7 has already been introduced above, but Fig. 7 is an isometric top view of the monorail traveler (100) of Fig. 1 engaged with a monorail (200), according to one example of the principles described herein. Fig. 8 is an isometric bottom view of the monorail traveler (100) of Fig. 1 engaged with the monorail (200) of Fig. 7, according to one example of the principles described herein. Further, Fig. 9 is a front view of the monorail traveler (100) of Fig. 1 engaged with the monorail (200) of Fig. 7, according to one example of the principles described herein. Still further, Fig. 10 is a side view of the monorail traveler (100) of Fig. 1 engaged with the monorail (200) of Fig. 7, according to one example of the principles described herein. Yet further, Fig. 1 1 is a top view of the monorail traveler (100) of Fig. 1 engaged with the monorail (200) of Fig. 7, according to one example of the principles described herein.

[0045] The monorail (200) includes a first upper portion (201 ), and a second lower portion (202). The first portion (201 ) includes a number of protrusions (203) that occupy the void (140) between the body (101 ) and the rail wheels (1 10). In the examples described herein, the monorail (200) includes two protrusions (203). In some examples, the protrusions (203) of the first portion (201 ) are dimensioned to fit between the body (101 ) and the rail wheels (1 10) such that the guide wheels (130) are in continual contact with a domed guide wheel interface (206) of the monorail (200). In another example, the protrusions (203) of the first portion (201 ) are dimensioned to provide an amount of space between the domed guide wheel interface (206) and the guide wheels (130) as depicted in, for example, Fig. 9.

[0046] The rail wheels (1 10) contact the first portion (201 ) of the monorail at a rail wheel interface (204). Since a load is applied to the coupling ring (103) approximately in the positive X direction, the rail wheels (1 10) continually interface with the rail wheel interface (204). In the instance in which a degree of a side load is applied in the negative or positive Z directions to the coupling ring (103), the rail wheels (1 10) may wander along the surface of the rail wheel interface (204) to the point to where at least one of the guide wheels (1 10) contacts the domed guide wheel interface (206) of the monorail (200). Further, in this situation, the chamfered edges (114) of the rail wheels (1 10) come into contact with the connecting walls (212) that couple the first portion (201 ) to the second portion (202). Thus, in this example, the chamfered edges (1 14) ensure that the movement of the traveler (100) in the positive and negative Y directions is not hindered through an increase in friction between a non-chamfered rail wheel (1 10) and surfaces of the monorail (200).

[0047] In one example, the rail wheel interfaces (204) located on opposite sides of the monorail (200) may be angled at approximately 45 degrees in opposite relative to the YZ coordinate plane. In this example, the rail wheels (1 10) match the angle of the rail wheel interfaces (204) such that the edges that contact the rail wheel interfaces (204) are angled at approximately 90 degrees relative to one another. However, any arrangement of angles among these elements may be used to ensure that the traveler (100) cannot separate from the monorail (200) unless the traveler (100) is moved to an end of a length of the monorail (200). [0048] The first portion (201 ) further includes the domed guide wheel interface (206) as mentioned above. The domed guide wheel interface (206) contours with the internal shape of the body (101 ) of the traveler (100) including the appendages (102). Further, the domed guide wheel interface (206) is dimensioned to allow for contact with the guide wheels (1 10) in instances where the side load in the negative or positive Z directions.

[0049] The second portion (202) includes a number of flanges (205) that are used to couple the monorail (200) to the structure either directly or indirectly. In an example in which the flanges (205) are directly coupled to the structure, a number of holes may be formed into the flanges (205) along the length of the monorail (200) through which a number of bolts may be inserted and used to couple the monorail (200) to a joist, beam, or other portion of the structure. In an example, in which the flanges (205) are indirectly coupled to the structure, a bracket system may be coupled to the flanges (205), and the brackets may be coupled to the joist, beam, or other portion of the structure.

[0050] Two connecting walls (212) are included in the second portion (202) to couple the first portion (201 ) to the second portion (202). Thus, in one example, the monorail (200) may be extruded as a single monolithic piece including the first portion (201 ) and the second portion (202). In this example, the monorail may be made of an extrudable metal such as aluminum. In another example, the monorail (200) may be formed by coupling a number of portions of the monorail (200) including the first portion (201 ) and second portion (202).

[0051] A number of voids are defined within the interior of the monorail (200) along the length thereof. The voids defined along the length of the monorail (200) drastically reduce the weight of the monorail (200). However, the voids are arranged such that they do not compromise the strength of the monorail (200) along any axis thereof. With reference to Fig. 9, the first portion may include a main rail void (207) and a number of coupling apertures (213). The main rail void (207) may run the entire length of a section or length of monorail (200). [0052] The coupling apertures (213) may be defined within an end of the monorail (200), but may not extend entirely through the length of the monorail (200). The coupling apertures (213) are used in connection with a number of dowels or other coupling rods to align and couple lengths of the monorail (200).

[0053] The second portion (202) also includes a number of voids. The voids include a support structure void (209) and a number of rib voids (21 1 ). In one example, the support structure void (209) may be defined within

approximately the center of the second portion (202) of the monorail (200). The support structure void (209) and the number of rib voids (21 1 ) form an internal support structure (208) and a number of support ribs (210). The internal support structure (208) and a number of support ribs (210) support to monorail (200) from any bending along the X, Y, and Z-axis, torsional deformations, or other structural deformations due to a load applied to the monorail (200).

[0054] A number of elements of the traveler (100), and all portions of the monorail (200) may be made of a material sufficient to withstand forces placed thereon. In one example, the monorail may be made of any number of metals or metal alloys. In one example, the monorail system (100, 200) is made of aluminum. In this example, aluminum allows the monorail system (100, 200) to be lightweight, but strong. However, any material may be used to make the various elements of the monorail system (100, 200).

[0055] The specification and figures describe a monorail system includes a traveler and a monorail. The traveler includes a body including a v-shaped cross-section including two diverging appendages. The traveler includes a plurality of first wheels mounted on a number of first axles and a number of second wheels mounted on each of a number of second axles. The monorail system includes a monorail. The monorail includes a cross-section including a first portion that fills a void defined by the v-shaped body of the traveler and the first wheels. A second portion is monolithically formed with the first portion including a pair of flanges running parallel to each other with respect to a length of the monorail for mounting the monorail to a structure. This monorail system may have a number of advantages, including (1 ) use of less material due to a number of voids defined in the monorail without a decrease in strength throughout the monorail due to the internal structure; and (2) reliable movement of the traveler along the monorail even with side loads applied to the traveler, among other advantages.

[0056] The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching.