US 3287754 A
Description (OCR text may contain errors)
Nov. 29, 1966 D, PRlCE ET AL coLLAPsIBLE suRFBoARD 4 Sheets-Sheet 4 Filed Oct. 9, 1964 JJN 6, n?! f gy M@ Hemi JIM?? United States Patent Ofce 3,287,754 Patented Nov. 29, 1966 3,287,754 COLLAPSIBLE SURFBOARD Thomas D. Price, 234 Valencia, San Clemente, Calif., and Karl D. Pope, 3210 Colorado Place, Costa Mesa,
FledOct. 9, 1964, Ser. No. 402,856 9 Claims. (Cl. 9-310) This invention relates to an improved Surfboard of the type adapted to be arranged in a collapsed and disassembled condition for compact storage and ease in handling without losing any desirable feature of the non-collapsible type of board.
Although the sport of surfing or surf boarding is one of an increasing popularity, the storage and transportation problems associated with surfboards due to their considerable length inhibit the practice of this sport. Thus, the board is ordinarily carried on the exterior of an automobile where it is highly susceptible to loss by theft when the automobile is left unattended or to damage because of failure of the auto carrier. Further, it is difficult and expensive to carry a Surfboard on public modes of transportation. By Way of specific example, a surfing enthusiast is charged an extra fee of $40 by a major airline to transport his Surfboard roundtrip between Los Angeles and Hawaii.
The plastic foam and fiber glass construction of a surfboard gives it an inherent lightness of weight so that a multi-section board can be easily carried by one person. However, the soft foam interior and thin sheet ber glass exterior, while providing a light-weight construction, makes it very difficult to removably secure together the individual sections of a multi-section board since any fastener extending through or into the foam material will tend to enlarge the Opening formed in the foam when the board is subjected to the stresses and strains caused by the surfing activity. Prior -to this invention, means have not been known in the art for constructing a collapsible board which will satisfactorily withstand the substantial loading forces applied thereto during the surfing activity while maintaining full maneuverability in the water with respect to paddling and surfing.
Accordingly, one lof the important features of the invention resides in the provision of means for securely locking the disconnectable Surfboard sections together in such a manner as to withstanding the stresses and strains to which the sections are subjected when connected together and placed in use, and yet at the same time, permits the Surfboard sections to be readily and conveniently Separatedwhen so desired.
Another object of the present invention is to provide an improved collapsible Surfboard characterized by its simplicity of construction and in its adaptability to economical manufacture.
Other and further objects, features and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings in which:
FIG. 1 is a perspective view of a preferred embodiment of a collapsible Surfboard constructed in connection with this invention;
FIG. 2 is a perspective view of the collapsible surfboard of FIG. 1 shown in a collapsed or folded state;
FIG. 3 is an enlarged cross-sectional view taken along the line 3--3 of FIG. 1;
FIG. 4 is a view taken along the line 4-4 of FIG. 3;
FIG. 5 is an enlarged cross-sectional view taken along the line 5-5 of FIG. 4, particularly illustrating the indexing means;
FIG. 6 iS a cross-sectional view taken along the line 6-6 of FIG. 5;
FIG. 7 is a cross-sectional view taken along the line 7-7 of FIG. l, particularly illustrating the detachable skeg inserted into a mating recession provided in the rear section of the Surfboard;
FIG. 8 is a cross-sectional view taken along the line 8 8 of FIG. 7, illustrating the means for fastening the detachable'skeg to the Surfboard;
FIG. 9 is a partial plan view of an alternative embodiment of the present invention;
FIG. l0 is an elevation view of the end of one of the Surfboard sections;
FIGS. 11, 12 and 13 illustrate successive stages of manufacture of the collapsible Surfboard of the present invention;
FIGS. 14 and 15 illustrate perspective and cross-sectional views, respectively, of a mold adapted to form the plastic foam bodies for the collapsible Surfboard;
FIG. 16 illustrates the convenient manner in which the Surfboard may be transported by a person on either public or private modes of transportation; and
FIG. 17a illustrates the loading forces applied at the joints of the collapsible Surfboard and FIG. l7b is a free body diagramy to facilitate understanding of theimproved structural rigidity of collapsible surfboards constructed according to the present invention.
Referring now to FIGS. 1 and 2, a preferred embodiment of the collapsible surfboard constructed in accordance with the teachings of this invention comprises a Surfboard 10 comprised of three separate sections, i.e., a front section 11, a center section 12, and a rear section 13. The latter section includes a Skeg 14 which may be detached therefrom. These three Sections are advantageously of substantially equal length and are adapted to be rigidly connected in longitudinal alignment with each other as shown in FIG. l. FIG 2 illustrates the Surfboard in a collapsed or folded condition wherein the three sections 11, 12 and 13 are detached one from another and the skeg 14 is detached from the rear section 13.
The Surfboard sections 11, 12 and 13 are retained together by pairs of laterally spaced clamp assemblies 1S disposed on the upper and lower sides of the respective sections. Each clamp assembly advantageously comprises a cam action type clamp whereby the sections may be quickly assembled and disassembled. As shown in FIG. 2 and described below, the assembly is facilitated by respective mating index pins 17 and sockets 18 formed in the adjacent board sections for facilitating longitudinally aligning thesections during assembly.
An enlarged sectional view illustrating the details of the clamp assemblies is shown in FIGS. 3 and 4.l The board Sections are seen to comprise anl inner plastic core 20, usually formed of a polyurethane foam, and a covering of resin impregnated fiber glass 21. A metal bracket 24 having extending horizontal and vertical flanges 24a, 24b is disposed in each of the mating recesses 22, 23 formed in the cores of the respective sections 11, 12 and permanently afiixed therein providing a support for the cam action clamp'assembly 25. Sheet aluminum alloy 0.060 inch thick has been found to be quite satisfactory for constructing the brackets 24. As shown, the depth of each recess 22, 23 is small compared to the thickness of the board at the joint assembly. By way of specific example, the recesses 22, 23 advantageously have a depth of the order of 3/16 inch for a board having a thickness of 31/2 inches at each joint.
Each cam assembly advantageously comprises a lever 30 pivoted at 31 to respective trunnions of yoke 32 affixed to one of the clamp brackets 24 by bolts 41 and latch arm 33 pivotable about axis 34 defined by respective trunnions of lever 30. Latch arm 33 includes an adjustable lock piece 35 adapted to engage a permanent lock piece 36 aixed to the adjacent clamp bracket 24. Each of these clamp parts should be of stainless steel or like rust-resistant alloy. Preferably, each of the clamp brackets 24 includes threaded stainless steel inserts 40 secured to their underside faces which are threadedly engaged by mounting bolts 41. In this manner, any of the latch assemblies may be easily replaced if they should become damaged or worn.
The operation of the clamp assembly will be seen to be such that the pivot axis 34 is translated away from the permanent lock piece 35 when the lever 30 is rotated on axis 31 in a clockwise direction (as seen in FIG. 3) to a position parallel the Surfboard surface. The cam action provided by the pivotal movement of axis 34 with respect to axis 31 enables a substantial tension to be exerted by a relatively small clamp member, which tension has been found to be completely satisfactory for rigidly securing together respective sections of the surfboard.
The tension supplied by the clamp assemblies may be varied by providing the latch arm 33 with a threaded portion 38 receiving an engaging threaded end portion 39 of the lock piece 35. The tension provided by the clamp may then be increased or decreased by rotating the lock piece 35 relative the threaded portion 33 in the appropriate direction to either decrease or increase the distance between the end of the lock piece and the pivot axis 34.
An alternative embodiment of the present invention is shown in FIG. 9 wherein four clamp assemblies 82 are utilized on both sides of the board for retaining together the respective board sections. The additional number of clamps would be particularly useful when the width of the board is wider than average. Also, for a given size of board, each of the clamps 82 could be physically smaller than when only two clamps are employed and still obtain the same tension between the respective board sections. In this manner, the depth of each of the recesses 22, 23 may be decreased to lengthen the moment arm D of equation 3.
It will be apparent that the Surfboard will be subjected to numerous bending moments during the surfing activity which will produce maximum tension on one horizontal surface of the board and maximum compression on the other horizontal surface. An important feature of the present invention is that a substantial tension can be applied near the surface of the board for retaining the respective sections in longitudinal alignment while locating the entire clamping structure flush or beneath the board surface so as to obviate any interference with the user of the board.
The mechanical advantage derived from this structure will be apparent from a simple stress analysis. As shown in FIG. 17a, forces F1 and F2 are applied to respective board sections, tending to rotate the boards around point R and separate the boards at the upper edge of the joint. In order to prevent this separation, a tension force T must be applied by the clamping means. For the exaggerated case shown in FIG. 17a, the free body diagram of FIG. l7b may be drawn, where T is equal to the tension force resisting separation, F is some force applied at a distance X from the center of rotation R, resulting in a moment M1=FX acting about R; C is' a compression force acting through the center of rotation R and producing no moment; and D is the distance the tension force acts through to produce the moment M 2=TD.
When the body shown in FIG. l7b is in equilibrium, the summation of moments about any point in that body is equal to zero, i.e.
M1-M2=0 Substituting the moment values gives TD=FX or T :FX /D n From the Equation 3, it may be seen that the distance D between the tension producing means and the axis about which the board sections tend to pivot must be maximized in order to minimize the tension force T required to maintain equilibrium. Conversely, as the distance D is reduced, the tension force required to maintain equilibrium follows a hyperbolic relationship. Therefore, the tension should be applied as close as possible to the upper and lower surface of the board as provided by the present invention.
Consider, for example, an extreme loading condition wherein a 250 lb. man is standing on a board solely supported at its end points. The tension force which must be exerted along an axis midway between the upper and lower board surfaces to prevent separation is of the order of 5,000 lb., whereas the tension force at the lower board surface required to prevent separation under these conditions is of the order of 2,500 lb., which force may be provided by plural clamps. For example, if four clamps are used, each clamp need only provide some 625 lb. of tension force.
FIGS. 4, 5 and 10 illustrate in greater detail the indexing pin and socket. Referring to FIG. 10, one of the upper brackets 24a and a laterally disposed lower bracket 24b are respectively provided with a circular aperture 50 concentric with an indexing pin 0r a socket 18. As shown in FIG. 5, a relatively flexible indexing pin 17 formed of a material such as polypropylene and having a diameter of the order of 1/2 inch is inserted through the aperture 50 of bracket 24a into a slightly oversized bore 5S filled with a resin 56 such as isothalic polyester resin. Oppositely disposed grooves 57 are formed at the circumference of pin 17 whereby the resin produces a mating shoulder for assuring that the pin is permanently secured to the core section. A mating socket 18 is provided and comprises a bore 60 long enough to accommodate the extending end of pin 17. As shown, the bore is made slightly oversize and the exposed surface of the foam coated with isothalic polyester resin 61 after which the polypropylene pin 17 is inserted until the resin sets. The polypropylene material is self-lubricating so that the resin does not bond itself to its smooth exterior surface so that the pin may be withdrawn after the resin sets, thereby forming a close tolerance socket 18.
A particular feature of the present invention is that the indexing pins and the sockets are utilized solely for properly positioning the sections in longitudinal alignment during assembly of the multi-section board. All shear, torsion, and longitudinal tension and compressive loading forces are opposed solely by the tension provided by the clamping means; accordingly, no stresses are placed either upon the index pin 17 or socket openings 18 when the board is assembled. This obviates any wearing of the soft inner core 20 of the Surfboard which inevitably occurs if a member such as pin 17 is relied upon for opposing of the bending moments which tend to separate the board sections. For example, if the pin and socket are used as strength members, the pin will have to be a rigid member adapted for resisting bending moments irl-I stead of the relatively exible pin preferably employed in this invention. Since the rigid pin and socket must be located within the interior portion of the core 20, the moment arm D is reduced, thereby increasing the tension forces which must be provided by the pin structure. As a practical matter, a rigid pin will inherently tend to enlarge both the socket opening 18 and also the bore 55 within which it is retained, eventually compressing the foam material in these areas and thereby undermining the structural integrity of the board and nullifying the usefulness of such a pin and socket as stress members. Contrariwise, a collapsible Surfboard may be constructed according to the present invention having incorporated therewith clamping means which accomplishes both longitudinal rigidity of the board and which obviates separation between the board sections. Any separation between the sections, however small, is highly undersirable, both because it inherently lessens the rigidity of the board and also because of the danger of the surfer that his skin or clothing may become pinched between abutting sections.
The Structure of the removable skeg 14 is shown in detail in FIGS. 7 and 8. Skeg 14 is located in a longitudinal groove 65 formed in a resin-filled cavity 66 on the underside surface of the board core (FIG. 8). A second cavity 67 generally orthogonal to the cavity 66 is also filled with resin and has formed therein an arcuate bore 68 generally orthogonal to the groove 65 and terminating at opposite apertures 72, 73 in the underside section 13 and at oppositely disposed surfaces 74, 75 of the groove 70. An aperture 80 is formed through the skeg 14 and so located that when the skeg is positioned in groove 70, the aperture 80 is in alignment with bore 71. The skeg may then be secured lto the board by pushing a fiexible plastic pin 76 through one end of the bore 71 and aperture 80, thereby locking the skeg 14 into position. Removal of the skeg is quickly accomplished by applying a force to either end of the pin 76 until a portion of it extends above the surface of the board, which end may then be grasped and withdrawn from the bore 71. Both groove 65 and bore 68 are advantageously formed by pouring isothalic polyester resin into the cavities 66, 67 after the skeg 14 and a exible rod (both formed of a self-lubricating plastic) until the resin sets. The skeg and rod may then be withdrawn, leaving a groove and bore whose dimensions very accurately conform to skeg 14 and pin 76, respectively. Accordingly, the skeg can be very rigidly retained to the board, While being very easily removed therefrom. Besides affording a very compact package, a further advantage of a removable skeg adapted to be rigidly retained to the board is that a damaged skeg can be very easily replaced.
FIGS. 11, 12 and 13 illustrate the method of constructing the individual board sections described hereinabove. As shown in FIG. 11, the recesses 22, 23 for the clamp means are advantageously formed Simultaneously in opposing board Sections. One method for constructing these recesses is to initially form the core 20 of the Surfboard in the customary manner, then form the recesses 22, 23 in a single routing operation, and subsequently cut thro'ugh the core 20 as Shown at 85. After cutting the board into the three sections shown in FIGS. 1 and 2, the edge portions proximate the recesses 22, 23 are routed. Each recess 22 (and 23) therefore comprises a longitudinal groove 22a, a shallow mortise 22b formed in the exterior surface of the core, and another shallow mortise 22e in the edge surface of the core proximate groove 22a. Each of the other recesses is formed in the Same manner toproduce the multi-section core, one section of which is shown in FIG. 12.
Another method for producing the respective sections of the board is by forming the recesses and each core section when the core is molded. A mold for producing the sections in this manner is described hereinafter. It will be apparent that the core section shown in FIG. 12 illustrates the core formed by either of these two methods.
The finishing stages of a representative section are accomplished in the manner shown in FIG. 13. Initially, each recess 22 is coated with a suitable resin such as the isothalic polyester resin and the metal bracket 24 positioned in place. The depth of longitudinal groove 22a and shallow mortises 22b and 22C match the dimensions of the bracket 24 whereby the exterior surface of the bracket 24, including ange surrfaces 24a, 24b, is essentially ush with the surface of the core as shown in FIG. 3.
Each board section is then covered by laminating fiber glass over both the core and flanges 24a, 2411 of the bracket, a very firm bond being obtained between the fiber glass laminate and metal brackets of sheet aluminum by anodizing or iriditing the surface of the aluminum. It has been found that this structure distributes the tension forces applied to the clamp means and :their associated brackets and prevents excessive stress upon the core material immediately adjacent the bracket 24. Without Such a force distribution, the stresses and Strain applied to the core material will be suiicient to quickly cause the deleterious wear at each joint, thereby destroying the utility of the board even though its remaining structure is unblemished.
After the brackets have been secured into position, the respective bores 55, 60 (FIG. 5) are drilled, using the preformed apertures 50 for defining their respective locations. These apertures are accurately located when the brackets 24 are stamped or otherwise formed from sheet metal stock. Thus, by accurately forming the recesses 22, 23 in the core for each pair of brackets, either in the manner shown in FIG. l1 or by the mold described below, the apertures 50 serve to self-align the respective indexing pins 17 and sockets 18.
A preferred embodiment of a mold for preparing the respective sections of the Surfboard is illustrated in FIGS. 14 and 15. As Shown, the mold comprises upper and lower halves 100, 101 forming an elongated cavity 102 having the shape of the desired finished Surfboard core. Spaced lateral grooves 103, 104 are formed at onethird intervals in the bottom surface of each cavity half, which grooves are adapted to accommodate respective partitions 105, 106. These partitions are thus placed at one-third intervals along the mold cavity to produce a foam body 20 cast into three separate sections. Each partition is provided with plural extending mold cores shaped according to the interior surface of a juxtaposed pair of brackets 24. Consequently, both recesses 22 land 23 are formed simultaneously with the formation of the core Sections. Further, mutually orthogonal longitudinal rectangular cores 111, 112 are provided at the bottom and rear of mold cavity 102 to form respective cavities 66, 67 used for forming the removable skeg retaining structure.
FIG. 16 illustrates the manner in which the Surfboard of this invention can be carried as a piece of luggage 120. As a result, the surfing enthusiast can carry his Surfboard in the trunk of an automobile and on any form of public transportation.
Although exemplary embodiments of the invention have been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiments disclosed may be subjected to various changes, modifications and substitutions without necessarily departing from the spirit of the invention.
1. A Surfboard adapted to be arranged in a collapsed and disassembled condition for compact storage and ease of handling comprising front, center and rear molded plastic foam Sections of approximately equivalent length, with one end of said center Section being adapted to abut one end of Said front section in longitudinal alignment and the other end of said center section being adapted to abut one end of said rear section in longitudinal alignment, and
means for detachably securing said sections including at least two laterally spaced tension clamps located in the upper surface and at least two laterally Spaced tension clamps located in the bottom surface of said sections at their respective abutting ends, said clamps being disposed in recesses formed in the surface of said plastic foam and means for distributing the forces applied to said tension clamps for preventing the application of excessive stress upon the plastic foam material immediately adjacent thereto So that substantial tension can be applied near the upper and lower Surfaces of the board for opposing the loading forces produced by the surfing activity which tend to separate said board sections while locating the entire clamping structure flush or beneath the board surface, thereby obmeans for detachably securing said sections including at least two laterally spaced tension clamps located in the upper surface and at least two laterally spaced tension clamps located in the bottom surface of said viating any interference with the user of the sections at their respective abutting ends, said clamps board and maintaining full maneuverability in being disposed in recesses formed in the surface of the water with respect to paddling and surfing. said plastic foam and 2. The Surfboard defined in claim 1 wherein means for distributing the forces applied to said tension said meansfor detachably securing said sections inclamps for preventing the application of excessive cludes a thin metal clamp support bracket having 10 stress upon the plastic foam material immediately integral flange portions substantially flush with the adjacent thereto so that substantial tension can be surface of the plastic foam and applied near the upper and lower surfaces of the said means for distributing the forces applied to said board for opposing the loading forces produced by tension clamps comprises a sheet of fiber glass lamithe surfing activity which tend to separate said board nated both to the surface of said plastic foam and l5 sections while locating the entire clamping structure to the exposed surfaces of the flange portions of Said flush or beneath the board surface, thereby obviating metal brackets. any interference with the user of the board and 3. The Surfboard defined in claim Zwherein maintaining full maneuverability in the water with said thin metal brackets are constructed of sheet respect to paddling and surfing.
aluminum whose surface is anodized or iridited t0 20 9. A Surfboard adapted to be arranged in a collapsed effect a firm bond between the fiber glass laminate and disassembled condition for compact storage and ease and the metal bracket. of handling including 4. The Surfboard defined in claim 1 comprising first and second molded plastic foam sections of apmeans for positioning said front, center and rear secproximately equivalent length, adapted to be contions in longitudinal alignment including an indexing nected in an assembled condition in end abutment pin in one section and a mating socket in the abutting and longitudinal alignment with each other, and section. means for detachably securing said sections including 5. The Surfboard defined in claim 4 wherein at least two laterally spaced tension clamps located said indexing pin has a grooved portion located Within in the upper surface and at least two laterally a bore formed in the plastic foam material, said spaced tension clamps located in the bottom surbore being filled with a resin which produces a matface of said sections at their respective abutting ing shoulder for permanently securing the pin to ends, said clamps being disposed in recesses said Surfboard section. formed in the surface of said plastic foam and 6. The Surfboard defined in claim 4wherein means for distributing t-he forces applied to said said socket comprises a bore in said core material tension clamps for preventing the application of covered with a protective and sealing resin coating. excessive stress upon the plastic foam material 7. A collapsible Surfboard comprising, in combination, immediately adjacent thereto so that substantial a front section, a center section and a rear section tension can be applied near the upper and lower adapted t0 be connected in an assembled condition surfaces of the board for Opposing the loading in end abutment and longitudinal alignment with one forces produced by the surfing activity which another, said sections being made of foam and tend to separate said board sections while locathavin g bracket recessions formed therein laterally ing the entire clamping structure flush or beneath spaced on the top and bottom side of adjacent secthe board surface, thereby obviating any intertions, ference with the user of the board and mainmeans for connecting said sections together including taining full maneuverability in the water with tension clamps affixed to thin metal clamp mounting respect to paddling and surfing. brackets secured in said bracket recessions, said bracket recessions having substantially the same con- RGfel'enCeS Cited in 'the file 0f this patent figuration as said clamp mounting brackets, d UNITED STATES PATENTS means for indexing the longitudinal alignment of sai sections comprising mating pin and socket connec- 1853159 4/1932 Welsh 9 310 tions between said abutting ends, and, 2929 104 3/1960 Hutton 18-39 a glass fiber material laminated over said separable sec- 293 6466 5/1960 SZymcZyk et a1 9 310 X tions and said mounting brackets bonded thereto. 3021569 2/1962 Lyman 156 245 8. A Surfboard adapted to be arranged in a collapsed 3091562 5/1963 Berlepsch et al' 156-245 and disassembled condition for compact storage and ease 3132382 5/1964 Magester 19-39 0f handling Comprising 3,137,873 6/1964 GaITOlU 9-310 a plurality of molded plastic foam sections of approxmately equivalent length, adapted to -be connected in an assembled condition in `end abutment and longitudinal alignment with one another, and
MILTON BUCHLER, Primary Examiner. ALFRED E. CoRRrGAN, Examiner.