Abstract:
A folding chair has a support frame with a back support portion, front leg portions, and rear legs. A seat is pivotally coupled to the support frame. A flexible back support is coupled to the support frame, and has a lumbar support member extending down from the back support to reach a lumbar region of a user&#39;s back. The lumbar support member extends from the back support into a space between the back support and seat. The seat pivots in a downward direction away from the back support and lumbar support ID member, so that the seat folds without interfering with the lumbar support member. The back support also has a perimeter flange disposed across the rigid back support perimeter, and free to move with respect to the rigid support frame in response to a load applied to the flexible back support. The perimeter flange extends across a gap created between the flexible back support and the support frame, such that when a load is applied to the back support and the back support flexes, causing the gap to open, the perimeter flange conceals the gap as the flexible back support goes from a loaded position to an unloaded position, thereby preventing pinching of articles of clothing or skin of a user.

Description:
BACKGROUND OF THE INVENTION 
     1. The Field of the Invention 
     The present invention relates generally to a folding chair, and/or a stackable/storable folding chair system. More particularly, the present invention relates to a folding chair having a flexible back support which displaces under a user&#39;s weight for comfort, and having a lumbar support member extending downwardly from the back support to the lumbar region of the user&#39;s back. 
     2. The Background Art 
     Folding chairs are often used in situations in which it is desirable or necessary to provide varying numbers and/or varying layouts of chairs, such as during conventions, seminars, conferences, etc. In addition, folding chairs are often used in multipurpose areas in which patron seating is required for some functions, but a large open space is required for other functions necessitating storage of the chairs. For example, some organizations have buildings with a multipurpose room which may be used for banquets, seminars, conventions, etc., with chairs set up, or for a dance, sporting event, etc., with the folding chairs removed. 
     It is desirable that the folding chairs be capable of being folded and stacked for storage so that the chairs take up less room when they are not required. It will be appreciated that some situations or events will require thousands of folding chairs, all of which may need to be folded and stored at any given period. Thus, the chairs must be folded and stored such that they have a high storage density to minimize the storage space required. It will be appreciated that any extra thickness of a chair when folded becomes significant when numerous folding chairs are involved. For example, with a thousand stacked folding chairs, a folding chair which saves one extra inch in the folded position results in over 80 linear feet of saved storage space. 
     One disadvantage with many prior art folding chairs is the bulk or thickness of the chair in the folded position. Many typical folding chairs still remain several inches thick in the folded position, and thus are less dense when stored. For example, many typical folding chairs have seats which fold adjacent to or abutting the legs, and/or have front and back legs which fold against one another, such that the thickness of the chairs in the folded position comprises the thickness of both the front and rear legs, and/or the thickness of the legs and the seat. Another disadvantage of many conventional folding chairs is that they fold awkwardly, with bulky folded configurations and/or various protruding members. 
     In addition, it is desirable that the folding chairs be easily storable or stackable, and be stable when stored/stacked. Many typical prior art folding chairs are stored merely by leaning one chair against a wall and subsequent chairs in a series against the first chair. It will be appreciated that a plurality of folding chairs stacked against a wall have a potential domino effect, with all of the chairs subject to being knocked over. Other prior art folding chairs have complicated and expensive hanging rack systems. For example, a wheeled cart might have a plurality of support arms from which a plurality of folding chairs are suspended. One disadvantage of these types of systems is that chairs on the end of the hangers tend to fall off the rack, and the wheeled racks are difficult to move and maneuver. 
     Some types of prior art folding chairs have back rest portions which protrude from the chair and into an adjacent folding chair. For example, a folding chair may have a back portion which curves outwardly to protrude from the frame of the chair, and into the frame of and adjacent folding chair. Although this relationship allows the chairs to be stored with greater density, the chairs tend to be unstable in a stored position. The broad rounded backs of the chairs act as ramps which fail to resist movement of an adjacent chair. In addition, the chairs are still relatively thick and bulky. 
     It also is desirable that the chairs be easy to set up and take down, or fold and unfold. It will be appreciated that there is considerable time involved in setting up and taking down thousands of chairs. One disadvantage of many prior art folding chairs is that they are difficult to both unfold and fold. For example, most folding chairs require the person to use both hands to fold and unfold the chair. One hand usually has to grasp the back of the chair while the other hand has to grab and pivot the seat in or out. 
     It also is desirable that the chairs be comfortable. Typical prior art folding chairs have rigid metal seats and seat backs which can be hard and uncomfortable. One disadvantage of many prior art folding chairs is that the chairs either fold well and are uncomfortable, or are comfortable, but are awkward in folding. Thus, there tends to be a trade off between comfort and foldability. Some chairs provide a cushion. But these chairs still utilize the rigid metal seat bottoms and seat backs, and the cushions tend to make the chairs even thicker when folded. 
     In addition, it is desirable that the chair provide proper id support, or be ergonomically designed. One disadvantage of many prior art chairs is that the angle between the back rest and the seat is dictated by the folding mechanism of the chair. Thus, in an effort to create a folding chair, the proper ergonomic design of the back rest and seat is often compromised in order to obtain a chair that folds more easily. 
     Another disadvantage of many typical prior art folding chairs is that they have a relatively small back support which may not adequately support a user&#39;s back. The small back support is often a function of the folding configuration of the chair. Again, the back support is often compromised in order to obtain a chair that folds. For example, the seat may be configured to fold upwardly or towards the back support, so that a relatively large space must exist between the back support and the seat so that the seat may fold into that space. That space is usually located where a user requires back support. 
     It also is desirable that the folding chair be durable. It will be appreciated that the chair will be alternately stored and used, folded and unfolded, innumerable times. Similarly, it is desirable that the folding chair be strong. The chair must be able be to support persons of various weight, often in potentially abusive conditions. 
     It also is desirable that the folding chair be safe. It will be appreciated that as the various parts of the chair fold, there is a potential for fingers and the like to become pinched within the folding mechanisms. 
     Therefore, it would be advantageous to develop a folding chair capable of folding for high density storage, as well as being comfortable and providing proper support. It also would be advantageous to develop such a folding chair which is more stable and safe in the folded and stored position. It would further be advantageous to develop a folding chair which (i) may easily be folded and unfolded; (ii) is comfortable and safe; and (iii) is durable, strong, and cost effective. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a folding chair which is comfortable, and folds relatively thin to maximize storage density. 
     It is therefore an object of the present invention to provide a folding chair which provides proper support. 
     It is another object of the present invention to provide such a folding chair which stores safely and is stable when stored, and/or stacked. 
     It is another object of the present invention to provide a folding chair which is easily folded and unfolded. 
     It is yet another object of the present invention to provide a folding chair which is safe and comfortable. 
     It is yet another object of the present invention to provide a folding chair which is durable, strong, and cost effective. 
     The above objects and others not specifically recited are realized in a specific illustrative embodiment of a folding chair having a flexible back support with a lumbar support member, and with a perimeter flange protruding from a front surface of the back support and extending across a front portion of a support frame. The support frame has a back support portion, front leg portions, and rear legs. A seat is pivotally coupled to the support frame. 
     The flexible back support is coupled to the support frame. The back support is flexible and displaces in response to the user&#39;s weight. 
     In accordance with one aspect of the present invention, the back support has a lumbar support member extending down from the back support to reach a lumbar region of a user&#39;s back. The lumbar support member extends from the back support into a space between the back support and seat. The seat preferably pivots in a downward direction away from the back support, and the lumbar support member, such that the seat folds without interfering with the lumbar support member. In addition, the lumbar support member preferably has a horizontal concave curvature integrally formed with a vertical convex curvature to support a user&#39;s lumbar region, and to provide several comfortable seating positions. Thus, the lumbar support is unique to folding chairs. 
     In accordance with another aspect of the present invention, the flexible back support has a perimeter flange protruding from a front surface of the back support, and extending across a front portion of the support frame. The perimeter flange displaces across the front portion of the support frame in proportion to a load applied to the back support, thus allowing the back support to flex and conform to a user. The perimeter flange extends across a gap created between the flexible back support and the support frame. Thus, when a load is applied to the back support and the back support flexes, causing the gap to open, the perimeter flange conceals the gap as the flexible back support goes from a loaded position to an unloaded position. Therefore, the perimeter flange advantageously prevents pinching of articles of clothing or skin of a user. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the invention without undue experimentation. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the invention will become apparent from a consideration of the subsequent detailed description presented in connection with the accompanying drawings in which: 
     FIG. 1 is a perspective view of a preferred embodiment of a folding chair in accordance with the present invention in a first open unfolded position; 
     FIG. 2 is a side view of the preferred embodiment of the folding chair in accordance with the present invention in the first open unfolded position; 
     FIG. 3 is a side view of the preferred embodiment of the folding chair of the present invention in a second closed folded position; 
     FIG. 4 is a side view of the preferred embodiment of a storable/stackable folding chair system of the present invention showing two folding chairs in the folded position which are disposed adjacent one another in a nesting or indexing relationship; 
     FIG. 5 is a perspective view of the preferred embodiment of the folding chair in accordance with the present invention shown in the closed, folded position; and 
     FIG. 6 is a partial cross sectional view of a preferred embodiment of a back support of the folding chair in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles in accordance with the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the invention as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention claimed. 
     As illustrated in FIG. 1, a folding chair, indicated at  10 , in accordance with the present invention, is shown in a first, open, unfolded orientation or position. The folding chair  10  advantageously has a flexible back support  156 , and a lumbar support member  160 , as discusses more fully below. 
     As indicated above, typical prior art chairs fold into a thick, awkward or bulky shape or configuration, or have significant protruding members, such that typical prior art folding chairs are less dense when stored, and require more space for storage. The folding chair  10  of the present invention utilizes a new approach in which the chair  10  is designed or configured to fold or collapse into a minimum thickness, such that the chairs  10  of the present invention have a very high storage density, while still providing strength, comfort, and durability. Thus, when folded, the chair  10  of the present invention advantageously is thin or presents a minimal profile, as shown in FIG.  3 . In addition, the thin profile of the chair  10  advantageously is shaped or configured to facilitate nesting or indexing with adjacent chairs, as shown in FIG.  4 . 
     Also as discussed above, typical prior art chairs are hard, uncomfortable, and fail to provide adequate back support. The folding chair  10  of the present invention utilizes a new approach in which the chair  10  is designed or configured to provide self-adjusting back support, and lumbar support, while still providing a folding chair which folds thinly and may be stacked with high density and stability. 
     The shape of the thin profile of the chair of the present invention  10  may take various configurations, as described in co-pending U.S. patent application Ser. No. 09/425,586, filed Oct. 22, 1999, which is herein incorporated by reference. 
     Referring to FIGS. 1 and 2, the folding chair  10  has a rigid support frame  14  including left and right, or first and second, rigid side supports  18  and  20 , as shown in FIG.  1 . As indicated above, it is desirable that the chair  10  be durable and strong. Thus, the rigid nature of the support frame  14  increases the durability and strength of the chair  10 . 
     Preferably, the support frame  14  is formed from a tubular material to optimize strength and weight. In addition, the tubular material preferably has an elongated cross-sectional shape which is oriented generally vertically to increase the weight capacity of the chair  10 . Furthermore, the tubular material preferably has rounded corners, or most preferably has an oval cross-sectional shape, giving soft edges to the frame  14  which are more comfortable. 
     The support frame  14 , and side supports  18  and  20 , have an upper back support portion  24  forming the back of the chair  10 , and a lower front leg portion  28  formed integrally and continuously with the upper back support portion  24 . The back support portion  24  extends forwardly from the back of the chair  10  to the lower front leg portions  28 . Thus, the first and second side supports  18  and  20 , or the upper and lower portions  24  and  28  thereof, are unitary, integral, and rigid structures to increase strength and durability. The front leg portion  28  preferably includes left and right, or first and second, front legs  32  and  34 . In addition, the support frame  14 , or side supports  18  and  20 , may be a single integral member with a broad curved back member  36  formed at the tops of the side supports  18  and  20 , as shown. 
     As indicated above, the rigid support frame  14  preferably is shaped to form a curved spline profile. As used herein, the term “curved spline” is used broadly to describe an elongated member with at least a curved portion, and which may include multiple curves and/or straight portions as well. The profile is an elongated continuous profile having a substantially uniform thickness which is relatively thin when all elements are collapsed within the profile. The thin uniform profile contributes to a higher storage density of the chairs. 
     The chair  10  also includes a rear leg portion  38 , which preferably includes left and right, or first and second, rear legs  40  and  42 , as shown in FIG.  1 . The rear leg portion  38 , or rear legs  40  and  42 , are pivotally coupled to the support frame  14  at leg pivot points  46 . The leg pivot points  46  are preferably fixed pivot points, such that the rear legs  40  and  42  pivot with respect to the support frame  14  or front legs  32  and  34 . 
     In addition, the chair  10  includes a seat or seat portion  50  pivotally coupled to the support frame  14 , and between the side supports  18  and  20  at seat pivot points  54 . Again, the seat pivot points  54  are preferably fixed pivot points such that the seat  50  pivots with respect to the support frame  14 , rather than sliding. The seat  50  and rear legs  40  and  42  also are pivotally connected as discussed in greater detail below. 
     The seat  50  may comprise a seating surface  51  secured to a seat frame  52 . The seat frame  52  may extend generally around the perimeter of the seat  50 , or along the sides, front and back of the seat  50 . This provides an advantage where the seat may flex in response to a load, as discussed below. The seating surface  51  is disposed on the seat frame  52 , and spans the distance between the perimeter of the frame  52 . Preferably, the seating surface  51  is formed of a flexible material, and flexes, bends, or deflects downwardly and into the seat frame  52  in response to, and proportional to, a user&#39;s weight. The flexibility of the seating surface  51  is enabled because of the perimeter location of the seat frame  52 , and allows the seating surface  51  to cup or curve, and thus conform to the user for a custom fit. In addition, the seating surface  51  preferably is coupled to the seat frame  52  only at the front and back, and not at the sides, to further allow the seat surface  51  to deflect. 
     The seat  50  and rear legs  40  and  42  pivot with respect to the support frame  14  between (i) the first, open, unfolded position, as shown in FIGS. 1 and 2, and (ii) the second, closed, folded position, as shown in FIG.  3 . 
     Referring to FIG. 3, the seat  50  and rear legs  40  and  42  advantageously pivot such that a majority of the seat  50  and a majority of the rear legs  40  and  42  collapse within a volume defined by the support frame  14 . In addition, a majority of the back support  156  is contained within the volume of the support frame  14 . Thus, in the folded position, the chair  10  substantially maintains the curved spline profile of the support frame  14 . The chair  10  (or the support frame  14 , seat  50  and rear legs  40  and  42 ) also advantageously has a curved spline profile in the closed position, with the profile having a substantially uniform thickness which is relatively thin. The volume defined by the support frame  14  is the space between the side supports  18  and  20 . Thus, the seat  50  and rear legs  40  and  42  pivot such that a majority of the seat  50  and rear legs  40  and  42  fold directly between the side supports  18  and  20 . 
     The seat  50  and rear legs  40  and  42  collapsing within the volume of the frame  14 , and the back support  156  being contained within the volume, provides a distinct advantage over prior art folding chairs, in which the seat and legs fold inwardly and onto the frame such that the frame, legs and seat form a relatively thick stack. In addition, the curved spline profile of the chair  10  in the folded position provides a distinct advantage over the prior art chairs, in which the profiles are straight and/or bulky. The chairs  10  of the present invention are capable of not only folding into a relatively thin profile in order to save storage space, but also forming a continuously and similarly shaped profile in which the profiles of adjacent chairs may be matched or nested to increase stability of the chairs in a stacked and stored relationship. 
     As illustrated in FIG. 4, a storable folding chair system, indicated generally at 60, may include a plurality of the above described chairs, including, for example, a first chair  10  and a second chair  62 . The curved spline profile of the first folded chair  10  nests or indexes with the curved spline profile of the second folded chair  62  to resist relative motion of the two chairs  10  and  62  when disposed adjacent one another in an adjacent storage relationship. Referring again to FIG. 3, the curvature of the profile creates a protrusion or protruding portion  66  of the profile and an opposite matching indentation or recess  68  in the profile as the profile deviates from a straight line into a curvature. Thus, referring to FIG. 4, the protrusion  66  of the profile of the first chair  10  nests or indexes within the indentation or recess  68  of the profile of the second chair  62 . Unlike many prior art folding chairs, which include a backrest portion which protrudes from the straight thick profile of the chair into the straight thick profile of an adjacent chair, the entire profile of the chair  10  of the present invention simultaneously forms the protrusions  66  and indentations  68  such that it is the entire profile of the chairs  10  and  62  which match to nest. 
     Referring again to FIGS. 1 and 2, the front legs  32  and  34  are preferably curved, and may be convex, as shown. The rear legs  40  and  42  are advantageously similarly curved so that the rear legs  40  and  42  may substantially collapse within the volume defined by the front legs  32  and  34 . Both the front and rear legs  28  and  38  have a radius of curvature, with the radius of curvature  27  of the rear legs  40  and  42  being smaller than the radius of curvature  29  of the front legs  32  and  34 . The smaller radius of curvature  27  of the rear legs  40  and  42  allows a greater portion of the rear legs  40  and  42  to collapse within the volume defined by the front legs  32  and  34 . 
     Referring to FIG. 3, the smaller radius of curvature of the rear legs  40  and  42  also allows a portion of the bottom ends  72  of the rear legs  40  and  42  to protrude or extend outside the volume defined by the front legs  32  and  34 . Although it is desirable to have a majority of the seat  50  and rear legs  40  and  42  collapse within the profile of the frame  14 , the bottom ends  72  of the rear legs  40  and  42  extend outside of the volume of the front legs  32  and  34  to increase the stability of multiple stacked chairs. Referring to FIG. 4, it can be seen that the bottom ends  72  of the rear legs  42  of the first chair  10  protrude slightly from the profile, specifically of the front legs  34 , of the first chair  10 , and into the profile of the second chair  62 . Therefore, the curved spline profile of the chairs  10  and  62  resists relative movement between the two chairs  10  and  62  in a longitudinal direction (or top to bottom direction), and the bottom end  72  of the first chair  10  protruding into the profile of the second chair  62  resists lateral relative motion (side-to-side) between the two chairs  10  and  62 . 
     The folding chair  10  also includes left and right, or first and second folding systems, represented by the second or right folding system  100 , formed by and pivotally coupling the frame  14 , seat  50  and respective first and second rear legs  40  and  42  together. The folding system  100  allows the various components of the chair  10  to fold as thinly as possible in the folded position, and provides strength to the seat in the open position. 
     Referring again to FIG. 1, the chair  10  has a back support  156  coupled to the upper back support portion  24  of the support frame  14 , and/or coupled to and between the side supports  18  and  20 . The back support  156  is supported between the side supports  18  and  20 , or the rigid frame  14 . The back support  156  advantageously is flexible and bends or flexes inwardly or rearwardly as force is applied, such as when a person leans back against the back support  156 . Thus, the back support  156  displaces or bends rearwardly in response to an amount of weight or force applied thereon, to provide an automatic response or adjustment, and to be more comfortable. Thus, the back support is self adjusting. The flexible back is a significant improvement over prior art folding chairs which have rigid metal backs, or inflexible backs. 
     In addition, the back support  156  advantageously includes a lower lumbar region  160  which extends downwardly from the back support  156  to a lumbar region of a user&#39;s back. The lower lumbar region  160  of the back support  156  is a significant advantage over prior art back rests. As indicated above, many typical prior art seats have a relatively small space between the seat and the back because the seat folds upward into the space below the back support. Thus, the back support of many prior art chairs tends to be a thin, high portion which only supports the upper region of a user&#39;s back, not the lumbar region. Because the seat  50  of the present invention folds downwardly and out of the way of the back support  156 , the lumbar support member  160  is able to extend downwardly without interfering with the folding motion of the seat  50 . 
     The lumbar support member or protrusion  160  is secured to the support frame  14  only through the back support  156 , without being directly attached to the support frame  14 , or side supports  18  and  20 . Preferably, the lumbar support member  160  is integrally formed with the back support  156  and is similarly flexible so that the lower lumbar member may flex or move with respect to the back support  156  and with respect to the support frame  14 . Therefore, not only does the entire back support  156  displace rearwardly in response to the user&#39;s weight, but the lower lumbar support member  160  itself displaces rearwardly with respect to the back support  156  to further provide a cushioning response to the user&#39;s lumbar region. 
     The back support  156  preferably is shaped to have a horizontally concave curvature  157  integrally formed with a vertically concave curvature  159 . The lumbar support member  160  advantageously has a horizontally concave curvature  161  integrally formed with a vertical convex curvature  162  to provide support for the user&#39;s lumbar region. The lumbar support member  160  also may have a reduced cross sectional area for providing greater flexibility with respect to the back support  156 . The concave and convex contour, along with the flexibility, allows for comfortable seating in both an upright, and a relaxed position of the user. 
     Referring to FIG. 6, the support frame  14  has an inner surface  170  which faces into the volume defined by the frame  14 , and a forward facing surface  172 . The back support  156  extends between the inner surface  170  on the support frame, and across the forward facing surface  172  of the support frame  14 , as described in greater detail below. The back support  156  has a rear flange  176  or protrusion extending from the back of the back support  156  rearwardly into the volume defined by the support frame  14 . The rearward flange  176  is formed generally near the perimeter of the back support  156 , and around at least a portion thereof, such that the rearward flange  176  also extends along a portion of the support frame  14  on either side, or along the side supports  18  and  20 . Thus, the rearward flange  176  extends along the inner surface  170  of the support frame  14  on both sides. The back support  156  is attached to the support frame  14  by fasteners  180 , such as rivets, bolts, screws, snaps, inserts, etc., which couple the rearward flange  178  to the inside or inner surface  170  of the support frame  14 . Attaching the back support to the inner surface  170  of the support frame  14  allows the back support  156  to displace under a force, such as the user&#39;s weight. 
     The back support  156  advantageously also includes a perimeter flange  184  formed about at least a perimeter of the back support  156 , and protruding or extending across a portion of the forward facing surface  172  of the support frame  14 . The perimeter flange  184  advantageously extends over the gap or space formed between the back support  156 , or rearward flange  176 , and the support frame  14 . As the back support  156  deflects rearwardly, the gap between the back support  156  and support frame  14  increases. The perimeter flange  184  advantageously displaces across the forward facing surface  172  of the support frame  14  as the back support  156  flexes rearwardly, allowing the back support  156  to flex while continuing to cover and conceal the gap. Thus, as the back support  156  returns to an unflexed position, the perimeter flange  184  prevents the back support  156  and support frame  14  from pinching any articles of clothing or skin which might otherwise have entered the gap. 
     Referring again to FIG. 1, the chair  10  may also have a handle  188  for a user to grasp the chair. As indicated above, the support frame  14 , and thus the side supports  18  and  20 , may be formed by a single integral member as shown. Thus, the handle  188  may be formed by the support frame itself at the top of the chair. Otherwise, additional support structures extending from the side supports  18  and  20  form the handle. In addition, an indentation  190  may be formed at the top of the back support member  156  such that a cavity or gap is formed between the top of the back support member  156  and the top of the support frame  14  for a user&#39;s fingers to extend through as the user grasps the handle  188 . 
     As indicated above, the seat surface  51  may also be flexible and suspended between a perimeter seat frame  52 . Thus, the seat surface  51  also deflects in response to a user&#39;s weight, and to cup or curve, and thus conform to the user for a custom fit. Therefore, the flexible seat  50  and back support  156  combine to provide a chair  10  which is both comfortable and foldable. 
     It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements. Thus, while the present invention has been shown in the drawings and fully described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiment(s) of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.