BACKGROUND OF THE INVENTION Traditional puzzles, usually referred to as"jigsaw puzzles"have a long history and can be traced back to Britain. See http ://www. jigsaw- puzzle. org/jigsaw-puzzle-history. html. Typical jigsaw puzzles comprise an image, design, picture, etc. embedded on cardboard that are cut into random shapes comprising protrusions and recesses.

The following are some examples of U. S. patents relating to jigsaw puzzles.

U. S. Patent No. 1,236, 378 (Ordway) discloses a jigsaw puzzle including irregularly and arbitrarily shaped pieces, as well as"symbolic"pieces. The "symbolic"pieces are scattered throughout the puzzle, and are generally "hidden"within parts of the picture that are of more, or less, uniform appearance, such as skies, roads, etc.

U. S. Patent No. 4,625, 969 (Donnell) discloses a jigsaw puzzle having sets of puzzle pieces with the pieces of a first set being considerably larger than the pieces of a second set. The pieces of the first and second sets are separate from one another by an intermediate set of pieces of graduated size, as shown in Figs. 1 and 2 of that patent. The puzzle may assume the form of a circle, as shown in Fig. 2 of that patent.

U. S. Patent No. 4,792, 138 (Watkins) discloses a novel jigsaw puzzle game wherein points are assigned when players complete particular portions of the puzzle, or placing uniquely-shaped pieces in a particular manner.

Other related U. S. patents are shown in U. S. Patent Nos. 3,540, 732 (Wilson) ; 3,575, 418 (Palmer) ; and 5,743, 741 (Fife).

However, despite the features introduced by these exemplary patents, assembling traditional jigsaw puzzles appeals only to those whose personalities enjoy hours and hours of concentrated effort in"piece placing"and tends to be tedious and boring to many others who are simply not interested in puzzles that do not move more quickly and which do not contain some interesting"twists." Thus, there remains a need for a new type of puzzle that is more easily assembled than a conventional jigsaw puzzle, that is able to be completed simultaneously by multiple users with different skill levels and which employs new mechanisms of puzzle construction.

SUMMARY OF THE INVENTION A puzzle comprising puzzle pieces wherein each of the puzzle pieces has a periphery and comprises at least one protrusion or at least one recess along the periphery and wherein the at least one protrusion and the at least one recess each form a recognizable shape (e. g. , a shaped protrusion, e. g. , a shape such as a star, a triangle, etc. , or a recognizable object such as an ax, pike pole, etc. ).

A puzzle having a plurality of puzzle pieces and having a plurality of zones defined by protrusions and recesses forming recognizable shapes (e. g., shaped protrusions) along the periphery of each puzzle piece in the plurality of puzzle pieces.

A puzzle comprising a plurality of puzzle pieces wherein each of the puzzle pieces comprises a first recognizable shape (e. g. , an object piece) and wherein the plurality of puzzle pieces connect with each other.

A puzzle comprising a plurality of puzzle pieces wherein the puzzle pieces (e. g., puzzle frame pieces) comprise sub-pieces and wherein the sub- pieces are contained within the puzzle pieces.

A method for assembling a puzzle comprising the steps of: providing a plurality of puzzle pieces having protrusions and recesses of recognizable shapes (e. g. , shaped protrusions) along the peripheries of the puzzle pieces; and joining the puzzle pieces by matching protrusions of recognizable shapes with corresponding recesses of the recognizable shapes.

A method for assembling a puzzle comprising the steps of: providing a plurality of puzzle pieces having protrusions and recesses of recognizable and of different sizes (e. g. , shaped protrusions) along the peripheries of the puzzle pieces; and joining the puzzle pieces according to the size of the protrusions and recesses to form different puzzle piece zones within the puzzle.

A method for assembling a puzzle comprising the steps of: providing a plurality of puzzle pieces of a single recognizable shape (e. g. , object pieces); and interconnecting the plurality of puzzle pieces of a single recognizable shape.

A method for assembling a puzzle comprising the steps of: providing a plurality of puzzle pieces of a single recognizable shape but of different sizes (e. g. object pieces); and joining the puzzle pieces according to the size of the puzzle pieces to form different puzzle zones within the puzzle.

A method of assembling a puzzle comprising the steps of: providing a plurality of puzzle pieces each containing at least one removable element and wherein the plurality of puzzle pieces demarcates the puzzle into large subdivisions (e. g., puzzle frame pieces); and interconnecting the plurality of puzzle pieces and installing the at least one removable element into a corresponding puzzle piece.

A method for assembling a puzzle by a plurality of users of different skill levels and wherein the puzzle comprises puzzle pieces having shaped protrusions and recesses of varying kinds (e. g. shaped protrusions) along the peripheries of the puzzle pieces. The method comprises the steps of: assigning the assembly of the puzzle pieces having protrusions and recesses of a first kind to users having a first skill level ; and assigning the assembly of the puzzle pieces having protrusions and recesses of a second kind, different from the first kind, to users having a second skill level.

A method of assembling a puzzle by users having different skill levels and wherein the puzzle comprises a plurality of puzzle pieces. The plurality of puzzle pieces have a first set of pieces of a first recognizable shape which interconnect with each other (e. g. , object pieces) and a second set of puzzle pieces having a second set of pieces of a second recognizable shape, different from said first recognizable shape, that interconnect with each other (e. g., object pieces). The method comprises the steps of: directing users of a first skill level to find puzzle pieces having a first or second recognizable shape; directing users of a second skill level to place such found puzzle pieces of the first recognizable shape in assembling the puzzle ; and directing users of a third skill level to place such found puzzle pieces of the second recognizable shape in assembling the puzzle.

A method of assembling a puzzle by users having different skill levels and wherein the puzzle comprises a plurality of puzzle pieces. The plurality of puzzle pieces having a first set of pieces of a recognizable shape of a first size which interconnect with each other (e. g. , object pieces) and a second set of puzzle pieces having a second set of pieces of a second size of the recognizable size is different from the first size. The method comprises the steps of: directing users of a first skill level to find puzzle pieces having the recognizable shape; directing users of a second skill level to place such found puzzle pieces of the first size in assembling the puzzle ; and directing users of a third skill level to place such found puzzle pieces of the second size in assembling the puzzle.

DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a first embodiment of a puzzle of the present invention utilizing shaped protrusions (SP) and puzzle frame pieces (PFP) and incorporating, for example, a rainbow image thereon; Fig. 2 is a partially-exploded isometric view of puzzle frame pieces (PFP) and their corresponding elements of the puzzle of Fig. 1; Fig. 3 is a plan view of a second embodiment of portions of a puzzle of the present invention utilizing shaped protrusions (SP), interconnected object pieces (OP) and puzzle frame pieces (PFP); Fig. 4 is a plan view of a third embodiment of portions of a puzzle of the present invention utilizing shaped protrusions (SP) and interconnected object pieces (OP); Fig. 5 is a plan view of a fourth embodiment of portions of a puzzle of the present invention utilizing puzzle frame pieces (PFP); Fig. 6 is a plan view of some exemplary interconnected object pieces (OP) depicting air balloons ; Fig. 7 is a partial plan view of other exemplary interconnected object pieces (OP) depicting airplanes ; Fig. 8 is a partial plan view of additional exemplary interconnected object pieces (OP) depicting forks and knives; and Fig. 9 is a partial plan view of exemplary puzzle frame pieces (PFP) having internal elements that utilize shaped protrusions (SP), interconnected object pieces (OP) and traditional jigsaw pieces.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION The puzzle of the present invention is more easily assembled than a traditional puzzle, is able to be completed by multiple puzzlers with different skill levels at the same time and employs new mechanisms of puzzle construction.

Using these new mechanisms, as discussed in detail below, the puzzles of the present invention possess the following characteristics: (1) heterogeneous skill levels ; (2) clearly demarcated subdivisions, and (3) novelty and excitement.

Heterogeneous skill levels provides several benefits to a puzzle. It allows an entire family with different aged children to strive towards a common family goal while interacting socially. Nursing homes or mental health institutions can use such a puzzle to entertain and provide therapeutic benefits to patients of different mental and dexterity abilities.

Subdividing a large puzzle into multiple smaller zones using different techniques to assign areas of a puzzle to which individual pieces belong serves several functions. It reduces a large overwhelming task into multiple smaller more manageable tasks, the completion of each bringing a sense of satisfaction. It allows for different puzzlers to collectively work on the whole puzzle while focusing their individual concentration on"their part". Lastly, by having one subdivision significantlyeasierto complete than anothersubdivision, the characteristic of heterogeneous skill levels is achieved.

As mentioned earlier, the puzzle of the present invention comprises three new mechanisms of puzzle construction: shaped protrusions (SP), interconnected object pieces (OP) and puzzle frame pieces (PFP). The puzzle of the present invention is referenced at 20. Figs. 1-2 depict an example of a complete puzzle utilizing two of the new mechanisms: shaped protrusions (SP) and puzzle frame pieces (PFP). Fig. 3 depicts a second example of puzzle pieces (not a complete puzzle) utilizing these three new mechanisms. Fig. 4 depicts a third example of puzzle pieces (also not a complete puzzle) utilizing shaped protrusions and interconnected object pieces. Fig. 5 depicts a fourth example of puzzle pieces (also not a complete puzzle) utilizing shaped protrusions and interconnected object pieces. It should be understood that the puzzle pieces of Figs. 3-9 depict exemplary puzzle pieces that utilize these three mechanisms and which form the pieces of an overall puzzle, such as those shown in Figs. 1-2.

The first new mechanism of puzzle construction is referred to as shaped protrusions, SP. Traditionally, jigsaw puzzles have interconnected protrusions consisting of a neck and an ovoid/circular head and a receiving recess of complimentary shape. In contrast, SP pieces have protrusions, or recesses, which have recognizable shapes. For example, as shown in Fig. 2, shaped protrusion/recess SP1 are stars; in Fig. 3, shaped protrusion/recess SP2 are fire axes, shaped protrusion/recess SP3 are pike poles, shaped protrusion/recess SP6 are ladders; in Fig. 4, shaped protrusion/recess SP4 are lobster claws and shaped protrusion/recess SP5 are fish tails. The shaped protrusions SP may be in the form of a recognizable object (e. g. , a fire axe, a pike pole, a lobster claw, etc. ), or a recognizable geometric shape (e. g. , a star, etc. ). Thus, shaped protrusions SP1-SP6 (Figs. 1-4) are by way of example only and are not limited to those shown. Moreover, the shape of the protrusions in a puzzle may also have a common theme; for example, the protrusions of the puzzle pieces of Fig. 3 have a common theme of"fire. "And, although not shown, when all of these puzzle pieces are assembled, a recognizable image (e. g. , the rainbow, cloud, sun, etc. as shown in Figs. 1-2) is formed related to fire, e. g. , a fireman's hat, a fire engine, etc.

It should be understood that the term"shape"as used throughout this Specification includes both geometric shapes (e. g. , rectangles, stars, etc. ) and object shapes (e. g., animals, instruments such as axes, pike poles, ladders, fish tails, lobster claws, etc.). It should also be understood that where the phrase"shaped protrusion SP"is used, this covers both the actual protrusion and its corresponding recess in the adjacent puzzle piece that it connects with.

It should also be understood that unlike the puzzle pieces disclosed in U. S. Patent No. 1,236, 378 (Ordway), where the puzzle pieces themselves are of symbolic form, in the present invention it is the shaped protrusion, SP, of the puzzle piece that forms an important aspect of the invention.

There are multiple ways shaped protrusions SP can facilitate heterogeneous skill levels. The first is by having some pieces in the puzzle be of traditional jigsaw shape while others have the shaped protrusion SP.

Interconnecting the pieces using shaped protrusions is much simpler than traditional jigsaw puzzle assembly. Another way is to have the shaped protrusions SP of different sizes extending from a single puzzle piece. For example, in puzzle piece 22 of Fig. 4 the shaped protrusions SP4'and SP4" (as well as their corresponding recesses in puzzle piece 24) are of different sizes.

Although this specific technique of using different size shaped protrusions SP to create heterogeneous skill levels appears to have some similarity to the puzzle pieces disclosed in U. S. Patent No. 4,625, 969 (Donnell), there are significant differences in the present invention 20. In particular, the puzzle pieces of the Donnell patent are traditional jigsaw shaped pieces. In addition, the Donnell patent discloses a series of graduated puzzle pieces that decrease in size, for example, beginning from the periphery of the puzzle extending toward the center. In contrast, in the present invention 20, multiple sizes of the shaped protrusions SP can be used to create heterogeneous skill levels ; this means that a puzzle piece may contain various sized shaped protrusions SP to interconnect with adjacent pieces that have complimentary various sized recesses (Fig. 3). Another way to enhance the ability of puzzlers to place pieces using the shaped protrusions SP is to increase the number of kinds of protrusions on a given piece. For example, as shown in Fig. 3, puzzle piece 26 has a fire axe protrusion, two pike pole protrusions and one pike pole recess.

It can be appreciated that by having both the fire axe and pike pole as protrusions on a puzzle piece, or by having a puzzle piece with different sizes of the same shaped protrusion SP, the number of possible locations that that piece might fit into is decreased, thus making that area of the puzzle that much easier to solve.

One way that the shaped protrusions SP can involve a wide variety of skill levels is where a very young child, or mentally-challenged adult, can help to find the pieces with a specific shaped protrusion SP, while more skilled puzzlers can place the actual puzzle pieces.

The mechanism of shaped protrusions SP can also demarcate a large puzzle into smaller subdivisions by various techniques that are now described.

For example, as shown in Fig. 4, by virtue of the fact that puzzles of the present invention 20 may be subdivided into zones with different shaped protrusions this feature automatically identifies a puzzle piece as either belonging to a shape-A protrusion zone or a shape-B protrusion zone. For example, the shape-A protrusion zone 23 (Fig. 4) is characterized by puzzle pieces having the fish tail protrusions/recesses while the shape-B protrusion zone 25 is characterized by puzzle pieces having the lobster claw protrusions/recesses. Furthermore, where these two zones abut, there are demarcation zone 27 pieces, i. e., puzzle pieces with both shape-A and shape-B protrusions and/or recesses. Thus, in effect, three subdivisions are created: a shape-A protrusion zone 23, a shape-B protrusion zone 25 and a demarcation zone 27. Therefore, for example, if a puzzle of the present invention 20 has three different shaped protrusion zones, there will exist six subdivision zones: shape-A protrusion zone, shape-B protrusion zone, shape-C protrusion zone, demarcation zone shape-A/shape B, demarcation zone shape-A/shape C and demarcation zone shape-B/shape- C.

It should be understood that this technique of subdividing the puzzle into zones differs from the puzzle disclosed in U. S. Patent No. 3,540, 732 (Wilson) which relies on a coding scheme on the opposite face of a puzzle piece to distinguish the appropriate puzzle zone to which that puzzle piece belongs. In contrast, the present invention 20 uses shaped protrusions SP as the mechanism of subdividing the puzzle wherein the similarity or dissimilarity of the shaped protrusions SP assigns the puzzle piece to a particular zone.

As mentioned earlier with regard to Fig. 4, the size of the shaped protrusions SP may effect heterogeneity of skill level. However, the size of the shaped protrusions SP can also create subdivisions clearly demarcated from one another. By having one zone, shape-A/size 1 protrusion zone, and another zone, shape A/size 2 protrusion zone, the puzzle pieces can readily be identified as belonging to one or the other zone. For example, as shown in Fig.

4, the shape-A/size 1 protrusion zone 31 may comprise the fish tail protrusion puzzle pieces having a first size and the shape-A/size 2 protrusion zone 33 may comprise the fish tail protrusion puzzle pieces having a smaller second size.

Use of the different sized shape protrusions of the present invention 20 differ from the puzzle of the Donnell patent in that: first, it is the shaped protrusion SP size and not the size of the puzzle piece itself that forms the basis for where the piece belongs. Secondly, and most importantly, the pieces of the Donnell patent use a piece-size gradation technique where the zones gradually change in size from very large on the outside to very small on the inside of a circular puzzle and from very large on the one side to very small on the other side of a rectangular puzzle. In contrast, in the present invention 20, the shaped protrusion size differences are not gradual but rather are of clearly distinct size disparity, thereby allowing a user to distinctly place a piece in a particular zone with clear demarcation between the zones.

Finally, use of the shaped protrusions SP introduces novelty and excitement into puzzle assembly because more than just the picture/image (e. g. , the rainbow, clouds, sun, etc. ) is used in the piece placement.

Assembling the puzzle of the present invention 20 can be educational by having shaped protrusions SP which can be used as learning tools. For example, using shaped protrusions SP such as triangles, rectangles, squares, etc., children can be asked to find pieces having one or more of these shaped protrusions SP. Another aspect of the present invention 20 is that the invention can be used as a game. For example, instead of having individual players each have their own jigsaw puzzle to assemble in the shortest amount of time (such as that disclosed in the Watkins patent), individual players can be assigned a respective portion or subdivision of the common puzzle of the present invention 20 to assemble in the shortest amount of time.

The second new mechanism of puzzle construction is interconnected object pieces OP. The interconnected object pieces OP differ from those puzzle pieces disclosed in the Ordway patent and the puzzle pieces disclosed in U. S. Patent No. 3,575, 418 (Palmer). In the Ordway patent, puzzle pieces are scattered throughout a puzzle which can individually be recognized as an object. In the Palmer patent, a puzzle game is disclosed where circumferential pieces need to be placed in the correct position in order to form an inner periphery where an identifiable object puzzle piece can then be placed. In contrast, the interconnected object pieces OP (e. g. , see Fig. 4, OP1) of the present invention 20 differ from these other patented puzzles in that the object pieces OP are used as the primary mechanism of puzzle construction. They are used repetitively, wherein each object piece OP1 abuts, or interconnects with, multiple other object pieces OP1, as shown in Fig. 4. These interconnected object pieces may be identical in size and shape, for example, as shown by OP1 in Fig. 4, or by OP4 in Fig. 6; these interconnected object pieces OP may be very similar in size and shape as shown by OP2 in Fig. 4; or they may be vastly divergent in size, but readily identifiable as the same object as shown by OP7 and OP8 in Fig. 7. A puzzle may also be constructed using interconnected object pieces OP readily identifiable as different objects but all having a common theme, such as the interconnected forks OP5 and knives OP6 shown in Fig. 8. These object pieces OP interface, or interconnect, with multiple other object pieces OP of a similar theme to comprise the puzzle or a zone of the puzzle.

Where object pieces OP are used as the mechanism of puzzle construction some irregular pieces IP may be logistically required to complete the puzzle. These, however, comprise a very small portion of the area of the puzzle where object pieces OP are used as the mechanism of construction; in Fig. 4, there is shown an example of such an irregular piece IP.

The mechanisms whereby object pieces OP can create heterogeneity of skill levels are multiple. The very young can simply pick out recognizable objects while the more skilled puzzlers can place them. In addition, a puzzle may have one zone of object pieces OP that are inherently more challenging to place than another zone. Large object pieces with simpler shapes are easier to place than smaller object pieces OP with more complicated shapes. For example, the large air balloon object pieces OP4 (Fig. 6) are easier to place than the small octopus object pieces OP2 (Fig. 4). Furthermore, with regard to object pieces OP shown in Fig. 7, there exists both large airplane object pieces OP7 and small airplane object pieces OP8 interfacing with each other in a single zone of a puzzle of the present invention 20. The large airplane object pieces OP7 are more conducive for the less skilled puzzler to place, while the more skilled puzzler may find a challenge in appropriately placing the smaller airplane object pieces OP8.

The mechanism of object piece OP construction can also create clearly demarcated subdivisions. Similarto shaped protrusions SP, a puzzle can have one zone constructed from interconnected object pieces A while another zone <BR> <BR> <BR> <BR> is constructed from different interconnected object pieces B, e. g. , OP1 and OP2 in Fig. 4. Furthermore, similar interconnected object pieces OP, but of distinctly contrasting sizes, can demarcate a puzzle into various zones, thereby effecting subdivision, e. g., OP3'and OP3"as shown in Fig. 3. As stated earlier with regard to shaped protrusion SP demarcation, and unlike the gradually- decreasing puzzle piece size of the puzzles in the Donnell patent, object piece OP zone demarcation is based upon distinct object piece OP size differences.

Thus, by using clearly distinct size disparity with the object pieces OP in a puzzle of the present invention 20, this allows a user to distinctly place a piece in a particular zone with clear demarcation between the zones of similarly- shaped, but dissimilar-sized, object pieces OP.

In addition, as with the shaped protrusions SP, although not shown, when all of these OP puzzle pieces are assembled, a recognizable image (e. g. , the rainbow, cloud, sun, etc. as shown in Figs. 1-2) is formed that may be related to the shape of these object pieces, e. g. , an image of sea life can be depicted when the object pieces OP1 and OP2 are assembled.

The last mechanism of puzzle construction is known as puzzle frame pieces PFP and are depicted most clearly in Fig. 5. These puzzle frame pieces 1 1 PFP comprise large subdivisions of the entire puzzle, usually from to of<BR> <BR> 8 16 the entire puzzle's surface area. Each PFP has either a large central opening/pieces or multiple interior openings/pieces, all of which can be referred to as"sub-pieces". For example, as shown most clearly in Fig. 2, PFP1 has a large star-shaped central opening 28 and a corresponding star-shaped element 30; furthermore, PFP2 is an example of a PFP having multiple interior openings 32 and 34, with corresponding elements 36 and 38; another example of this is shown by the elements 35,37 and 39 in PFP16-PFP18, respectively, in Fig. 3.

Furthermore, each of the multiple interior openings/elements can themselves have an interior opening/element, which can be referred to as"inner pieces".

For example, as shown in Fig. 5, PFP4 comprises a plurality of multiple interior openings, (one of which is indicated at 40) wherein each of these has its own opening/element (one of which is indicated at 42). Each of these openings can be completed by placing the corresponding element, thereby requiring skill levels from the most basic to very advanced. Thus, heterogeneity of skill level and subdivisions are accomplished using the PFPs.

The construction of the PFPs provide puzzle demarcation into large areas, as shown most clearly in Fig. 5, each of which can act as a"sub-puzzle" to various players and can be assigned to these players based on their skills.

The puzzle frame pieces PFP3-PFP15 are shown by way of example in Fig. 5.

PFPs can be incorporated into the puzzle of the present invention 20 and abut with and connect to other PFPs, such as those shown by PFP3-PFP15 in Fig.

5. The periphery of these PFPs utilize conventional regular jigsaw-shaped puzzle piece cuts 46. Alternatively, PFPs can abut/connect with areas of the puzzle of the present invention 20 comprised of object pieces OP and shaped protrusions SP. For example, as shown in Fig. 3, PFP16-PFP18 comprise shaped protrusions SP along their peripheries for connecting with corresponding shaped protrusion puzzle pieces. Similarly, Fig. 1 shows PFP1 and PFP2 using shaped protrusions SP (e. g., SP1) along their peripheries.

Moreover, interconnected object pieces OP can used as the sub-pieces within the puzzle frame pieces PFP, such as those shown by OP9 in PFP11 of Fig. 5 or OP10 in PFP16 of Fig. 9. Another variation comprises sub-pieces using shaped protrusions SP7. For example, as shown in PFP17 of Fig. 9, shaped protrusions/recesses SP7 form elephant trunks. A further variation is to have the sub-pieces comprise traditional jigsaw puzzle pieces, such as those shown at 48 in PFP9 of Fig. 5 and at 50 of PFP18 in Fig. 9.

In addition, the multiple interioropenings/elements ofthe PFPs may have a common theme with the overall image formed when the puzzle is assembled, e. g. ,"things in the sky"forms the common theme in Figs. 1-2 between the image formed from the assembled puzzle pieces (e. g. , a rainbow, the sun, a cloud) and the multiple interior openings/elements (e. g. , stars 30,36, 38 etc.) of the PFP1 and PFP2.

It should be understood that it is within the broadest scope of the present invention wherein each of the above-identified mechanisms can be integrated into a single puzzle.

As mentioned earlier, using these three new mechanisms of puzzle construction, individuals of different skill levels can participate in putting together the puzzle of the present invention 20. For example, individuals of a first skill level can be asked to find puzzle pieces having particular shaped protrusions SP, or particular object pieces OP. Another group of individuals of a higher skill level can be asked to actually place or assemble the pieces involving the found pieces. Where different sizes/kinds of shaped protrusions and/or different sizes/kinds of object pieces are involved, the higher skill level individuals can be sub-divided to place respective sized shaped protrusion pieces or object pieces; and these sub-divided groups can even compete with each other to assemble their corresponding pieces in the least amount of time. Alternatively, a third group of individuals of even a higher skill level can place or assemble the more complex-shaped object pieces, shaped protrusion pieces or the smaller object pieces which may require a greater skill.

Without further elaboration, the foregoing will so fully illustrate our invention that others may, by applying current or future knowledge, readily adopt the same for use under various conditions of service.