Patent Publication Number: US-10786697-B2

Title: Connection structure for trampoline frames

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from, and incorporates by reference in its entirety, Chinese patent application no. 201710926507.3 filed on Oct. 10, 2017. 
     BACKGROUND 
     Technical Field 
     Various embodiments of the present invention relate to sports equipment, and more specifically, to connection structures for trampoline frames. 
     Description of Related Art 
     It is important that sports equipment be designed to avoid structural failure that could lead to injury. This is especially true of load bearing sports and exercise equipment that comes in close contact with the human user. Weight lifting machines and free weight equipment are two prime examples of the type of equipment that must be designed for structural integrity. Such equipment is often subject to repeated forces, twisting motions and stresses likely to cause structural failure. 
     BRIEF SUMMARY 
     Recognizing the importance of avoiding sports equipment structural failures that could lead to user injuries, the present inventor developed improved structural components to strengthen trampoline frame structures. The various embodiments disclosed herein achieve these goals, and others, which will become readily apparent in view of the drawings and detailed disclosure. 
     Various embodiments disclosed herein are drawn to trampoline frames configured to hold a flexible fabric trampoline bed attached to the frame with a number of torsion springs. The frame has a number of tee joints at the intersection between frame components. The frame components may be curved so that a number of them can be assembled into a circular structure to hold the trampoline bed. The frame components each have slotted holes spaced apart to receive one end of the torsion springs. The other end of each torsion spring is attached to the trampoline bed. 
     In various embodiments the tee joints each have a frame passageway (hole) extending through it lengthwise. The frame passageway is sized to accept an end of one frame component into one side and another frame component into the other side. In various embodiments the end of one frame component slides into the other, adjacent frame component within the frame passageway. The frame components and the tee joints have through-holes in them sized to accept a guard pole. The guard poles extend upward above the level of the trampoline bed to support a guard net or guard rail. In various embodiments the through-holes of adjacent frame components align with the through-hole of their tee joint so that a guard pole (or other component) may be inserted into the through-holes. Inserting the guard pole down into the tee joint via the through-holes aids in strengthening the connection joint where the various parts intersect. 
     In various embodiments each tee joint has a leg holder section configured to receive a leg component that extends beneath the level of the trampoline bed in order to support the trampoline frame. The leg components may either sit directly on the ground, or attach to bottom pipe components that sit on the ground. Some embodiments do not have a guard pole extending from each of the tee joints. Such embodiments may be configured with an internal blocker at each tee joint without a guard pole. The internal blockers extending down into the tee joints via the through-holes to add strength to the connection joint. Some embodiments may additionally have bolts that pass through the various parts to further strengthen the trampoline frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute part of the specification, illustrate various embodiments of the invention. Together with the general description, the drawings serve to explain the principles of the invention. In the drawings: 
         FIG. 1  depicts an oblique view of trampoline frame structure according to various embodiments disclosed herein. 
         FIG. 2  depicts an exploded view of the several trampoline frame components according to various embodiments disclosed herein. 
         FIG. 3  depicts oblique views of tee joints according to various embodiments disclosed herein. 
         FIG. 4A  depicts oblique views of two frame components according to various embodiments disclosed herein. 
         FIG. 4B  depicts side views of three frame components embodiments. 
         FIG. 5  is a flowchart of method steps according to various embodiments disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     Load bearing sports and exercise equipment such as weight lifting equipment must be designed to avoid structural failure that could lead to injury of the user. The present inventor recognized that trampoline frames are also subjected to the type of repeated compression forces and twisting motions that can cause structural failures. Since the forces and structural stress exerted on trampoline frames are dampened by springs, the forces and stresses may not be as apparent as the forces of steel weights slamming together on weight lifting equipment. Nonetheless, trampoline frames are subject to compression forces and twisting forces each time a user jumps up and down on the trampoline. Over time the joints of the trampoline frame may incur many hundreds of thousands of compression and twisting stress forces. The inventor developed the embodiments herein to ensure the structural integrity of trampolines frames and avoid injury due to equipment failure. 
     The present inventor recognized the drawbacks of conventional trampoline frame components that are connected to one another by welded tee joint pieces. For example, the welded tee joint pieces are used to connect the crosspieces to the trampoline leg pipes of conventional trampoline frames. The welded seams tend to be the weakest points in the structure, and often endure the greatest stresses and forces. Over time this may result in welding breakage and tearing due to the repetitive compression forces and twisting stress over the life of a conventional trampoline. In addition, the present inventor recognized drawbacks in the way conventional trampoline leg pipes are connected together using fasteners. The conventional trampoline frame fastener is located at the point of connection, and often becomes loose after repeated usage. This results in an unstable frame structure due to this type of conventional trampoline leg pipe fastener. The unstable frame structure of conventional trampolines tends to cause defects such as wear, breakage and bending. The present inventor recognized these and other drawbacks that cause safety hazards, and in response developed an innovative new solution to the aforementioned problems. 
       FIG. 1  depicts an oblique view of trampoline frame structure  100  according to various embodiments disclosed herein. The various embodiments provide connection structures for trampoline frames aimed at addressing the drawbacks and technical problems existing in the design of conventional trampoline frames. The trampoline connection structures of the various embodiments disclosed herein include components that may be arranged in multiple configurations, depending upon the requirements of the implementation. 
     Various trampoline frame components are arranged to support the flexible fabric trampoline bed  190 . A number of springs such as tension springs  195  are used to span between the trampoline bed  190  and the trampoline frame. Typically, the tension springs  195  are inserted into holes in the frame components on one end, and inserted into metal grommets sewn into the fabric trampoline bed  190 . The tension springs, upon being stretched, exert pulling forces capable of rebounding a user up into the air.  FIG. 1  depicts three tension springs  195  for illustrative purposes. But in practice a trampoline has many more than three tension springs  195 —e.g., one spring spaced from approximately three inches apart to a foot or more apart. In some implementations, connection of the springs may be doubled up—that is, two (or more) springs may be connected either at the connection points on the frame or the connection points on the trampoline bed  190 , or both. 
     The trampoline frame structure  100  depicted in  FIG. 1  is round as viewed from above, and is configured with tension springs that hold a similarly shaped fabric trampoline bed in place. In other embodiments the frame and accompanying trampoline bed may be square, rectangular, oval, arc-shaped, octagonal, or other like shapes known to those of ordinary skill in the art. 
       FIG. 2  depicts an exploded view  200  of the several trampoline frame components according to various embodiments disclosed herein. The depicted trampoline frame structure  200  includes frame components  201 , tee joints  202 , leg components  203  (sometimes called standing pipe components  203 ), bottom pipe components  204 , guard poles  205 , internal blockers  206  and bolts  208 . 
     Each trampoline has a number of curved frame components  201  that fit together to form a circle that encompasses and supports the trampoline bed. Each frame component  201  has a number of tension spring holes or other attachment mechanisms configured to accept tension springs to hold the trampoline bed  190 , shown in  FIG. 1 , in place. A tee joint  202  is positioned between each of the frame components  201  at their connection point to connect them securely together. At least some of the tee joints  202  have a guard pole  205  removably connected to and extending upward from them. In the embodiment depicted in  FIG. 1 , every other tee joint  202  has a guard pole  205  extending upward from it. In other embodiments every tee joint  202  has a guard pole  205  extending upward from it. In yet other embodiments every third tee joint  202  has a guard pole  205  extending upward from it. The guard poles  205  each have a guard connection end  225  that extends down into, and connects with, a tee joint  202 . Some embodiments have one or more internal blockers  206  removably inserted into the tee joints  202 . Some embodiments have internal blockers  206  all the way around, connected to each tee joint  202 . Other embodiments have an assortment of parts connected to the different tee joints  202 . For example, some embodiments have an internal blocker  206  at every other tee joint  202 , with guard poles  205  removably attached to the other tee joints  202 . 
     Each of the leg components  203  has a leg connection end  223  that connects to a tee joint  202 . The leg components  203  each extend downward beneath the tee joint  202  where the leg component  203  connects to a bottom pipe component  204  that rests on the ground or floor. In  FIG. 2  the bottom pipe component  204  is shaped like a low, wide W. That is, the outer portions of bottom pipe component  204  just inside the 45 degree bend rest on the ground while the center portion comes up away from the ground. This aids in allowing the trampoline frame  200  to flex somewhat to accommodate a yard or floor that is not perfectly planar. In other embodiments the bottom pipe component  204  may be flat across its length where it contacts the ground, rather than W shaped. In at least some embodiments the bottom pipe component connects to three or more of the leg components  203 , rather than two as shown in  FIG. 2 . Yet other embodiments have leg components  203  that sit directly on the ground, have detachable feet that sit on the ground, or are inserted into the ground, rather than being tied together with one or more bottom pipe components. 
     Either one or both ends of various components and parts are constricted to a narrower diameter, e.g., frame components  201 , bottom pipe components  204 , guard poles  205 . The constricted section is typically four inches long, plus or minus 1.5 inches, but may be as long as twelve inches or as short as one-half inch in various implementations. In some embodiments the constricted sections of the various components are all approximately the same length, while in other embodiments the constricted sections of some components may be longer than those of other components. The constricted ends are configured to be inserted into an opening of the adjacent component so as to concentrically fit together. In this way the diameter at the connection point of adjacent components remains relatively consistent. However in some other embodiments the component ends may be left with their diameters intact rather than constricting them. In such embodiments the ends of the adjacent components are flaired out or otherwise enlarged, making the end section of them larger in diameter so as to receive the standard sized ends and join the two components. 
     In the embodiment  200  depicted in  FIG. 2  each of the frame components  201  has a first end  212  and a second end  214 . In this embodiment the first end  212  has squared surfaces that fit within the square frame passageway hole of tee joint  202 . The second end  214  of the adjacent frame components  201  fits within the first end  212 , sliding far enough in so that the through-holes  215  of first end  212  and second end  214  line up to receive the constricted guard connection end  225  of guard pole  205 . 
       FIG. 3  depicts oblique views  300  and  350  of tee joints  302  and  322 , respectively, and oblique view  351  similar to view  350 , according to various embodiments disclosed herein. Tee joint  302  is similar to tee joint  202  depicted in  FIG. 1 . In various embodiments the tee joint  302  may be manufactured using a welding-free sheet metal stamping process. A through-hole  315  is arranged on the upper part of tee joint  302  to facilitate penetration of the guard pole  205  shown in  FIG. 2 . 
     Some embodiments may use a tee joint  322  configured with an end that extends further in the lateral direction. That is, one side the tee body  313  of tee joint  322  extends further from leg holder section  307  than the tee body  311  of tee joint  302  extends from its leg holder section  307 . As such the length of the frame passageway  319  of tee joint  322  is longer than the frame passageway  310  of tee joint  302 . The tee joint  322  also has a through-hole  315 . The through-hole  315  may be a raised through-hole as shown in  FIG. 3 , or may be flush to the surface of tee joints  302  and  322 . The guard pole  205  penetrates down via the through-hole  315  into the tee joint  302  or  322 . The raised through-hole  315  provides additional structural support for guard pole  205 , of  FIG. 2 , inserted into it. The oblique view  351  depicts a part similar to tee joint  322  but with the addition of a slotted hole  317  to aid in reinforcing a guard pole  205  inserted into raised through-hole  315 . A reinforcing member may be configured to span between the slotted hole  317  and the guard pole to provide support. 
     With reference to the parts shown in  FIG. 2 , the adjacent frame components  201  each insert into opposite ends of frame passageway  310  of tee joint  302 . The first end  212  of one frame component  201  fits into one end of passageway  310  and second end  214  of the adjacent frame component  201  fits into the other end of passageway  310 . In this way the two frame component ends connect together within the tee joint  302 . For example, the second end  214  may be configured smaller so as to fit within the first end  212 . In such embodiments the first end  212  of one frame component  201  slides far enough into frame passageway  310  of tee joint  302  for the through-hole  215  in first end  212  to line up with the through-hole  315  of tee joint  302 . The second end  214  of the adjacent frame component  201  slides into the opposite side of the tee joint frame passageway  310  and also slides into the first end  212  which is positioned within frame passageway  310 . The second end  214  slides far enough into frame passageway  310  so that the through-holes  215  of the first end  212  and the second end  214  line up with the through-hole  315  of tee joint  302 . In at least some embodiments this allows constricted end  223  of leg component  203  (of  FIG. 2 ) to be inserted up into the lined up through-holes  215  and  315  to extend into the vertical channel of the tee joint. 
     In other embodiments the constricted end  223  of leg component  203  fits up into leg holder  307  but does not extend up into the bottom through-holes of the two frame components  201  inserted into tee joint  302 . Each guard pole  205  has a constricted guard connection end  225  that extends downward via through-hole  315  of the tee joint  302  and into the through-holes of the two frame components  201  inserted into tee joint  302 . In some embodiments the constricted end  225  extends down through the bottom through-holes of the two frame components  201  down far enough so that the bolt hole of constricted end  225  lines up with the top bolt hole of the tee joint  302 . This allows the bolt  208  to be fastened through the bolt hole of constricted end  225 , thus securing guard pole  205  firmly in place. In some embodiments a nut  209  may be used to secure the bolt  208  firmly, but removably, in place. In other embodiments one or more of the components&#39; bolt holes may be configured with internal threads into which the bolt  208  screws, to affix it firmly, but removably, in place. In yet other embodiments a nut  209  may be welded, glued or otherwise attached outside the bolt hole through which the bolt  208  passes to secure the bolt in place, thus removably securing the components together. The various embodiments that use nuts  209  to secure the parts together may also use washers and or lock washers with the nuts  209  to prevent them from loosening over time. 
     In various embodiments the diameter of the leg component  203  constricted end  223  is larger than the diameter of the guard pole  205  constricted end so that the guard pole  205  constricted end fits within the leg component  203  constricted end. Other embodiments are configured so that the leg component  203  constricted end is smaller and fits into the guard pole  205  constricted end. In yet other embodiments either the end of leg component  203  or guard pole  205  may be flaired out or otherwise enlarged, so as to fit on the outside of the tee joint  302 . In the various embodiments end of guard pole  205 , the end of leg component  203  and the leg holder section  307  of tee joint  302  are concentric. Being concentrically fit together, the guard pole  205  fits within the end of leg component  203  which itself fits within the round end (cross-section) of tee joint  302 —that is, within the leg holder section  307 . In some embodiments the frame component  201  has a flaired end that fits around the tee joint  202 , or at least partially around (e.g., around three sides) of tee joint  202  allowing the leg holder section  307  portion to extend downward. 
       FIG. 4A  depicts oblique views of two frame components  401  and  451  according to various embodiments disclosed herein. The frame component  401  has two symmetrical ends, each configured with through-hole  415  and a connection section  411 . In various embodiments the connection sections may either he constricted or flaired out, so as to concentrically fit the adjacent piece or pieces in the trampoline frame. Slotted (or other shaped) holes  197  in the frame components  401  and  451  may serve as spring attachment structures. The frame component  401  can be used with tee joint  302  shown in  FIG. 3 . In such embodiments the connection sections  415  of adjacent frame components  401  are inserted into each side of the frame passageway  310  of tee joint  302 . The connection sections  415  are configured to be slid in far enough until the adjacent frame components  401  concentrically fit together within the frame passageway  310  of tee joint  302  and the through-holes  415  align with through-hole  315  of tee joint  302 . In some embodiments one end of frame component  401  may be configured larger than the outside dimensions of tee joint  302  so as to fit on the outside of it as the three parts—the tee joint  302  and two frame components  401 −are concentrically fitted together. 
     The frame component  451  is configured with a through-hole  415  on connection section  413 , and no through-hole on connection section  422 . The frame component  451  can be used with tee joint  322  shown in  FIG. 3 . In various embodiments the connection section  413  end of frame component  451  with through-hole  415  is inserted into the short side of tee joint  322 &#39;s frame passageway  310  far enough until the parts concentrically fit together and the through-hole  415  of frame component  451  aligns with through-hole  315  of tee joint  322 . The end without a through-hole of adjacent frame component  451  may then be inserted into frame passageway  310  to concentrically fit together with tee joint  322 . In some embodiments the two adjacent frame components  451  do not fit together concentrically. Instead, each of the adjacent frame components  451  fit within the frame passageway  310  of tee joint  322  with their ends facing each other (rather than having the adjacent frame components  451  fit concentrically). That is, each of the adjacent frame components  451  fit concentrically within (or on the outside of) the tee joint  322 , but the adjacent frame components  451  do not themselves fit concentrically together. In other embodiments the connection section  413  is approximately the same length as frame passageway  310  of tee joint  322 . In such embodiments the connection section  413  is inserted into the short side of tee joint  322 &#39;s frame passageway  310  until the connection section  413  extends to the far end of the frame passageway  310  and the parts concentrically fit together. The connection section  422  of adjacent frame components  451  fits within (or outside of) the connection section  413  so the three parts concentrically fit together. 
       FIG. 4B  depicts side views of three frame components embodiments. The frame components  401  and  451  can be implemented with various cross-section shapes at their ends. Component end shapes  431 ,  433  and  435  are three typical embodiments. Component end shape  431  is basically a square cross-sectional shape with angled corners shaped like a square with chamfered corners. Component end shape  431  features a pressed groove  432  that extends the length of its connection section  413  (e.g., connection section  411 ). The frame components  401  and  451  can be implemented in a round such as end shape  433  or a square such as end shape  435 . Frame components  401  and  451  can also be implemented in various other cross-sectional end shapes, including for example, rectangular, triangular, oval, octagonal, star shaped, or other like cross-sectional end shapes known to those of ordinary skill in the art. Any of the various shapes may have one or more grooves  432  extending fully or partially along the connection section. 
       FIG. 5  is a flowchart of method steps according to various embodiments disclosed herein. The method starts at block  501  and proceeds to block  503  where the tee joints are connected to the frame components to form a frame shape that will hold the trampoline bed. In various embodiments the frame components (e.g., frame components  201  of  FIG. 2 ) are inserted into the frame passageway of the tee joint (e.g., frame passageway  310  of tee joint  302 ) so that the parts concentrically fit together. Upon sliding the frame components into the tee joints the method proceeds to block  505 . 
     In block  505  the insertion of the frame components is adjusted until their respective through-holes line up with the through-hole of the tee joint. Once the various through-holes are aligned the method proceeds from block  505  to block  507 . The leg components are inserted into the leg holder section of their respective tee joints. Some embodiments use bolts to further strengthen the trampoline frame. In such embodiments the parts are slide together so that their bolt holes align, allowing insertion of a bolt to be secured firmly with a nut. 
     Upon inserting the leg components in block  507  the method proceeds to block  509  to insert the guard poles. The guard poles are attached to the top of the tee joint, passing through-holes of the tee joint and both frame components that are themselves attached to the tee joint. In some embodiments the guard poles are inserted far enough that they extend down into the leg components. In this way the guard pole, the two frame components and the tee joint are concentrically connected at each intersection. In some embodiments the leg component is concentrically fitted together with the tee joint and the guard pole, but the leg component isn&#39;t typically inserted far enough up into the joint to be concentrically connected to the frame components. 
     In block  511  the internal blockers are installed. Some embodiments do not have a guard pole affixed to each tee joint. For example, the embodiment depicted in  FIG. 1  has a guard pole at every other tee joint, and internal blockers at the tee joints in between. Some internal blockers—for example, internal blocker  206  of  FIG. 2 —are merely caps put over the tee joint through-hole to prevent water and debris from getting inside the pipes. In other embodiments the internal blockers are shaped the same as the guard poles from the level of the tee joint through-hole downward. These embodiments of internal blockers are installed in much the same way as the guard poles, but do not extend upward above the level of the trampoline bed like the guard poles. They do, however, extend downward into the tee joint in order to be concentrically fitted with the tee joint, the two frame components—and in some embodiments, the leg component also. 
     Block  513  involves the installation of the bottom pipe components. In some embodiments the leg components sit directly on the ground. Other embodiments are implemented with a bottom pipe component attached to the leg components. The bottom pipe component sits on the ground and ties together two or more of the leg components, serving to further strengthen the structure. In such embodiments the bottom pipe components are affixed to the leg components in block  513 . Upon completing block  513  the method proceeds to block  515  to insert and tighten the various bolts and nuts. For example, the embodiment depicted in  FIG. 2  has two bolt holes in the leg holder section of tee joint  202 . Both bolts extend through the tee joint  202  and through the leg component  203 . The topmost bolt also extends through the bolt hole on guard connection end  225  of leg component  203  in the embodiment of  FIG. 2 . 
     Once all the bolts have been installed and tightened in block  517  the method proceeds to bock  517  for installation of the trampoline bed. Typically, trampoline beds are made of flexible, but durable, fabric such as a woven nylon fabric. Other embodiments have trampoline beds made of strips of nylon or other material (e.g., 1″ to 2″ wide strips) woven together to form a flexible fabric. However, the trampoline bed may be made of any number of flexible, sturdy materials such as cotton, rayon, or other fabrics man-made or natural fibers known to those of ordinary skill in the art. In block  517  the trampoline bed is installed by stretching springs between the spring attachment structures on the frame and the trampoline bed. The spring attachment structures may be slotted (or other shaped) holes in the frame components, or metal loops affixed (e.g., welded or glued) on the frame components, or eye bolts or hooks inserted through holes in the frame components, or other such mechanical attachment structures suitable for fastening a metal loop as known by those of ordinary skill in the art. The trampoline bed is typically put in place by installing two springs on opposite sides of the bed, then installing two more springs halfway around the bed between the first two spring, then going back and forth filling in the gaps until springs are installed all the way around. This avoids exposing any single spring to an excessive amount of force that would potentially damage the spring. Once all the springs have been installed the method proceeds to block  519  and ends. 
     Some of the method steps or activities may be included or excluded as described above, or performed in a different order than depicted in  FIG. 5 , while still remaining within the scope of at least one of the various embodiments. For example, the bottom pipe components (block  513 ) may be performed after installing the leg components (block  507 ). Further, blocks  509  and  511  may be reversed or performed at the same time. Numerous other steps and activities may be implemented in various different orders or performed at the same time, as is known by one of ordinary skill in the art. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. For the purposes of description herein a trampoline is a type of sports equipment that has a flexible bed (e.g., fabric or woven mesh) connected by tension springs to a frame, allowing a user to jump or bounce up and down on it. As used in the specification and claims the term “substantially” means plus or minus (+/−) ten percent. For example, “substantially one inch” means “one inch plus or minus ten percent.” As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” used in this specification specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The term “plurality”, as used herein and in the claims, means two or more of a named element. It should not, however, be interpreted to necessarily refer to every instance of the named element in the entire device. Particularly, if there is a reference to “each” element of a “plurality” of elements. There may be additional elements in the entire device that are not be included in the “plurality” and are not, therefore, referred to by “each.” 
     The descriptive text in this disclosure includes directional phrases and words such as up, down, above, beneath, below, on top of, or the like. Since the torsion springs of a trampoline are pulled down by the earth&#39;s gravity acting on the mass of a user, the directional phrases and words are relative to the earth. For example, down is the direction towards the center of the earth. The phrase “level of the trampoline bed”, as this term is used herein, means the upper surface of the trampoline flexible fabric bed (or other bed material) in an undisturbed state; i.e., without a user on the trampoline. In embodiments where the frame components are assembled into a planar circle (typical) the level of the trampoline bed is a planar surface. 
     The phrase “concentrically fit together” (or “fits concentrically together”) in regards to two components means that a portion of one of the components fits into an opening on the other component. For example, a bolt and a nut that screw together can be said to concentrically fit together. Turning to the specification,  FIG. 2  depicts frame component  201  having a constricted first end  212  that fits within the frame passageway of tee joint  202 . Thus, the frame component  201  concentrically fits together with tee joint  202 . In some embodiments the frame components have flaired ends so as to fit around the tee joints  202 . Such flaired out frame components are also said to concentrically fit together with the tee joints. Three or more objects can concentrically fit together—e.g., two objects concentrically fit together within a third object. For example, some car antennas used to be made of multiple telescoping sections that concentrically fit together. For two adjacent frame components that concentrically fit together within the frame passageway of the tee joint, the three parts are said to concentrically fit together. 
     The word “removably” as used with affix, attach, secure or the like word in regards to two or more parts, means that the two or more parts are affixed together (or attached, secured, etc.) firmly so they tend not to come apart by themselves, but may be release from each other without damaging the two parts. For example, a bolt and corresponding nut may be used to removably attach two parts. But two parts welded or glued together are generally not said to be removably attached to each other. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements, if any, in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The disclosure of the various embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and gist of the invention. The various embodiments included herein were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. The description of the various embodiments provided above is illustrative in nature inasmuch as it is not intended to limit the invention, its application, or uses. Thus, variations that do not depart from the intents or purposes of the invention are encompassed by the various embodiments of the present invention. Such variations are not to be regarded as a departure from the intended scope of the present invention.