Locking joint for collapsible ladders and other structures

Abstract

A rigid structure such as a ladder is disclosed having rotating hinges that allow the ladder to fold up and/or be disassembled and assembled. The hinge or hinges can be provided between ladder sections with one ladder section having a male hinge element, and another having a female hinge element. A cam element provided with the female hinge element can be moved between an unlocked position in which the ladder sections can rotate with respect to each other, and a locked position in which the structure is rigid.

Claims

1. A ladder comprising: a first ladder section including two rails and at least two rungs, each rung extending between the two rails, the first ladder section including a first ladder section connecting end having a first ladder section locking feature; a second ladder section including at least one rail and having a second ladder section connecting end having a second ladder section locking feature; a cam element linearly, slidably along a rail of the second ladder section at the second ladder section connecting end, the cam element having a cam surface; and a male hinge element provided on the first ladder section connecting end, extending transversely from a rail of said ladder section, and having a cam follower that extends transversely from the male hinge element, the cam follower and the cam element being located such that the cam follower selectively contacts the cam surface; wherein sliding movement of the cam element to an unlocked position allows the first and second ladder sections to rotate relative to each other while sliding movement of the cam element to a locked position causes relative motion between the cam follower and the cam surface to move the first ladder section locking feature with respect to the second ladder section locking feature in a direction along the male hinge element such that the first ladder section locking feature and the second ladder section locking feature to engage each other to prohibit relative rotation between the first and second ladder sections.

2. The ladder of claim 1, wherein the male hinge element transverse connector is provided on a rail and is transverse to the rail.

3. The ladder of claim 2, further comprising a female hinge element provided on the rail along which the cam element is slidably disposed, the female hinge element including an opening that extends through the rail and is configured to receive a portion of the male hinge element.

4. The ladder of claim 1, wherein the cam element further comprises a handle disposed on an end of the cam element that is opposite to an end of the cam element in which the cam surface is disposed.

5. The ladder of claim 1, wherein the locking features include a plurality of positive and negative locking features configured so that the ladder sections can be locked in only one orientation.

6. The ladder of claim 1, wherein the locking features include positive and negative locking features that are configured to provide zero backlash upon locking.

7. The ladder of claim 6, wherein the positive and negative locking features include complementary tapers that result in zero backlash upon locking.

8. The ladder of claim 1, wherein the second ladder section consists of two rails and includes first and second connecting ends with a second cam element slidably disposed along one of the two rails provided at each of the two second ladder connecting ends and locking features provided at each of the two second ladder connecting ends, the second cam element having a cam surface, and the ladder further comprising: a third ladder section including two rails and at least two rungs, each rung extending between the two rails, the third ladder section including a third ladder section connecting end having a third ladder section locking feature; and a male hinge element provided on third ladder section connecting end, extending transversely from a rail of said ladder section, and having a second cam follower that extends transversely from the male hinge element, the second cam follower and the second cam element being located such that the second cam follower selectively contacts the cam surface of the second cam element; wherein sliding movement of the second cam element to an unlocked position allows the second and third ladder sections to rotate relative to each other while sliding movement of the second cam element to a locked position causes the second ladder section locking feature and the third ladder section locking feature to engage each other to prohibit relative rotation between the second and third ladder sections.

9. The ladder of claim 1, wherein moving the cam element to a disassembly position allows the cam follower and the cam surface to be engaged to assemble the ladder or disengaged to disassemble the ladder.

10. The ladder of claim 1, further comprising a spring configured to preload at least one of the male hinge element and the cam element towards the locked position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

(2) FIGS. 1A and 1B provide a view of the joint employed in a ladder, with the joint disassembled and also assembled and locked;

(3) FIGS. 2A and 2B show several ladder sections that can be extended to 10 feet in length, both folded for stowage and deployed and locked, ready for climbing;

(4) FIGS. 3A and 3B provide detailed views of the hinge and cam elements of the ladder of FIGS. 1A and 1B;

(5) FIGS. 4A and 4B provides a detailed view of the elements of FIGS. 3A and 3B in unlocked and locked positions;

(6) FIG. 4C provides a detailed view of the locking features illustrated in FIG. 3A;

(7) FIGS. 5A through 5G provide views of another hinge useful with the ladder of FIGS. 1A and 1B; and

(8) FIGS. 6 and 7 illustrate alternative cam elements for use with the hinges of FIGS. 3A and 3B.

DETAILED DESCRIPTION

(9) The invention provides a rigid structure, in particular a ladder, having rotating hinges that allow the ladder to fold up and/or be disassembled and assembled. The hinge or hinges can be provided between ladder sections with one ladder section having a male hinge element, and another having a female hinge element. A cam element provided with the female hinge element can be moved between an unlocked position in which the ladder sections can rotate with respect to each other, and a locked position in which the structure is rigid.

(10) Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the systems and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the systems and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.

(11) FIGS. 1A and 1B illustrate a rigid member 100 of the invention, in this case, a ladder 100. The ladder 100 is illustrated as three separate parts (first ladder section 102, second ladder section 112, and third ladder section 122) in FIG. 1A, and assembled in FIG. 1B. While the embodiment of these Figures shows three ladder sections, two ladder sections or more than three ladder sections may be employed in keeping with the invention.

(12) A first ladder section 102 has right and left rails 104, 106, as well as top and bottom rungs 108, 110. Each of the rungs extends across from one rail to the other, in this case with each rung being perpendicular to each rail. While many ladders have two rails, it should be understood that the invention can be applied with a rigid member having at least one rail, and possibly having more than two rails. Configurations other than perpendicular could also be provided. Further, while the illustrated ladder section 102 has two rungsother ladder sections may have zero, one, or more than two rungs. First ladder section 102 also has a connecting end 130, which may be connected to additional ladder sections. As illustrated, first ladder section has two identical connecting ends, one at the top and one at the bottom, but only one connecting end 130 is used in the Figure. On the connecting end 130, the first ladder section has a male hinge element 134. As illustrated, the first ladder section has four such male hinge elements, the details of which will be described further below.

(13) A second ladder section 112 is also illustrated in FIGS. 1A and 1B. This section consists of two railsright and left rails 114, 116. More or fewer rails may be provided and the second ladder section might also have one or more rungs in some embodiments. The second ladder section also has a connecting end 132 having a female hinge element 136. As illustrated, the second ladder section includes two connecting ends, both of which are used in the exemplary embodiment, and 4 female hinge elementsone each on each connecting end of each rail in the section.

(14) A third ladder section 122 is also illustrated in FIGS. 1A and 1B. The third ladder section 122 includes right and left rails 124 and 126 with top and bottom rungs 128, 140 extending perpendicularly between the two rails. As with the first ladder section, other configurations of ladder section may be used within the spirit of the invention.

(15) The ladder sections 102, 112, 122 are assembled to create the ladder assembly of FIG. 1B. The rails of the first and third ladder sections are inside rails, while the rails of the second ladder section are outside rails in the sense that when the hinges are assembled, the second ladder section rails are place laterally outside with respect to the first and third ladder assembly rails. In the illustrated embodiment, a portion of the rungs in the first and third ladder assemblies may extend through the inner rails to become the male hinge portions. The female hinge elements of the outer rails can then slide over the male hinge portions to complete the assembly. In addition, the hinges and locking features can be arranged so that the ladder sections are not locked in a perfectly straight line, but rather in a slight arc that makes the ladder stronger and more stable.

(16) FIGS. 2A and 2B illustrate a ten foot ladder 200 built using four ladder sections 202 having two rails and two rungs (in this case, each of these ladder sections is substantially identical to the first or third ladder sections above) and three ladder sections 204 having only two rails (the outer rails in the figures, and these are substantially identical to the second ladder section above). In FIG. 2A, the ladder 200 is folded up about its hinges so that in the X and Y dimensions, the ladder assembly is the same size as a single first ladder section 102/202. In FIG. 2B, the ladder 200 is unfolded about its hinges and locked into its configuration for use as a ladder.

(17) FIG. 3A illustrated an exploded view of a hinge that can be used with the invention. The figure shows right rail 104 and bottom rung 110 of the connecting end 130 of first ladder section 104, as well as the right rail 114 of the connecting end 132 of second ladder section 112. Male hinge element 134 is a transverse connecting element extending from rung 110 through rail 104, and includes a pin 142 extending through the male hinge element transversely to act as a cam follower. The pin 302 can extend outward from both of opposed sides of the male hinge element. The male hinge element 134 can extend into female hinge element 136 in rail 114. In this way, male hinge element 134 can act as an axle about which the second ladder section 112 can rotate about the first ladder section 102.

(18) Disposed at least partially within rail 114 and aligned with an opening in the rail to form part of the female hinge element 136 is a rotating cam element 302. The rotating cam element 302 is illustrated in isolation in FIG. 3B. The rotating cam element 302 includes a body 304 and a handle 306 that can be used to rotate the body. The body 304 includes a central opening 316 for receiving the male hinge element 134. The opening 316 can include slots 308 that allow the pin 142 (or cam follower) to pass in and out when the cam is rotated to an assembly or disassembly position. Such a position is illustrated in FIG. 3A where the slots 308 in the rotating cam element 302 are aligned with similar slots in the opening in rail 114, and further the pin 142 on male hinge element 134 is aligned with slots 308 so that male hinge element can slide into (or out of) the female hinge element in this orientation.

(19) A cam profile 310 is provided internally along the opening 316 in the rotating cam element 302. In general, an internal cam surface or profile, as used herein, refers to a cam surface that is provided within the outer perimeter of the element on which it is located. An internal cam surface does not refer to rotating cam elements that use their outer perimeter as the cam surface when they rotate about an axis that is transverse to the direction of the camming motion. When the illustrated ladder sections are not moving with respect to each other, relative rotation of the rotating cam element 302 with respect to the rail 114 in which it is positioned will cause relative movement between the cam profile 310 and the cam follower (or pin) 142. This rotation results in relative movement between the ladder sections in a direction that is transverse to a plane parallel to a major surface of rail 114, which, in the illustrated embodiment, is also transverse to a plane parallel to a major surface of rail 104 and along the longitudinal axis of rung 110.

(20) In the illustrated embodiment, rotating the rotating cam element 302 to an unlocked position, allows the rails 104, 114 to move apart, which allows them to rotate with respect to each other. Rotating the rotating cam element 302 to a locked position, pulls the rails 104, 114 together, causing locking features on the rails to engage each other and prevent relative rotation between the rails.

(21) As shown in FIG. 3A, outer rail 114 is provided with positive locking features 312, while inner rail 104 includes corresponding negative locking features 314. A person of ordinary skill will understand that other configurations are possible, including switching the locations of the positive and negative locking features. In addition, while three sets of complimentary locking features are illustrated, in other embodiments, more or fewer locking features may be provided. Further, the illustrated positive locking features 312 are provided in three different shapes (as are the complementary negative locking features 314). This feature can be useful in that it allows the ladder sections to rotate freely with respect to each other without risk of the locking features engaging until the ladder sections reach the desired locking positionfor a ladder, this will generally be the extended position in which the ladder can be climbed. Other configurations of locking features can be provided, however, it may be preferred to provide at least one locking feature that is differentiated in shape from any other locking features so that the hinge can be locked in only one position.

(22) FIGS. 4A and 4B show rails 104 and 114 in unlocked and locked conditions respectively, in both isometric and side views. In FIG. 4A, the rotating cam element 302 is in the unlocked position, the positive locking features 312 have not engaged with the negative locking features 314, and the ladder sections may rotate freely with respect to each other. In FIG. 4B, the rotating cam element 302 has been rotated to the locked position, and it has drawn the rails 104 and 114 together to engage the locking features. In this position, the ladder sections are locked and no relative rotation is possible.

(23) FIG. 4C shows positive 312 and negative 314 locking features coming together under the cam force to lock the relative positions of rails 104, 114. Preferably the locking features provide zero or minimum backlash when engaging. For example, both the positive 312 and negative 314 locking features illustrated are tapered so as to lock the joint with zero backlash when pressed together by the cam.

(24) A similar hinge arrangement is further illustrated in FIGS. 5A (isometric view) and 5B (side view) in a disassembled or exploded state. This arrangement includes a ladder section having a rail 502, rung 526, and male hinge element 506. Another ladder section includes rail 504 and female hinge element 510. A rotating cam element 512 is provided as part of the female hinge element and including a handle 524 and body 522. The body 522 defines a central opening having slots 514 to accept the male hinge element 506 having a transverse pin or cam follower 508. An internal cam profile 516 is provided on the body 522 to interact with cam follower 508. Positive 518 and negative 520 locking features are provided on the rails such that the hinge can be locked into position only in an extended-ladder orientation. FIG. 5B shows a side view with the direction of assembly of the ladder sections illustrated.

(25) FIGS. 5C and 5D illustrate the elements of FIGS. 5A and 5B where the ladder sections have been assembled and the cam element 512 has been rotated to an unlocked position; the views are isometric and side respectively. In this position, the ladder sections are free to rotate with respect to each other, however, the ladder sections cannot be disassembled. As can be seen most clearly in FIG. 5C, the cam follower 508 is resting at the lowest spot on the cam profile 516, allowing the maximum distance between rail 502 and 504 so that the positive 518 and negative 520 locking features are not engaged.

(26) FIGS. 5E and 5F illustrate the elements of FIGS. 5A and 5B where the ladder sections have been assembled and the cam element 512 has been rotated to a locked position; the views are isometric and side respectively. In this position, the ladder sections may not rotate with respect to each other. As can be seen most clearly in FIG. 5C, the cam follower 508 is resting at the highest spot on the cam profile 516, pushing the relative elements to a minimum distance between rail 502 and 504 so that the positive 518 and negative 520 locking features engaged to lock the orientation of the ladder.

(27) FIG. 5G provides an isometric view of rotating cam element 512. In this Figure, the cam profile 516 is clearly visible and the lowest cam position 532, corresponding to the unlocked position, and the highest cam position 534, corresponding to the locked position can readily be seen.

(28) FIG. 6 provides an alternative sliding cam element 602. This cam element has a body 604 and a handle 606. The body has a cam profile 608. As with the other cam profiles, the cam profile 608 is internal as it is within the perimeter of the body 608. The profile includes a lowest point 610, which corresponds to the unlocked position, and a highest point 612, which corresponds to the locked position. This cam element can, for example, slide along rail 504 underneath pin 508 so that pushing the cam element 602 in locks the relative positions of the ladder sections, while pulling the cam element 602 out allows the ladder sections to rotate relative to each other, and removing the cam element 602 allows the ladder sections to be disassembled.

(29) FIG. 7 provides another alternative cam element 702 having a body 704 and a handle 706. In this embodiment, the body hooks the pin 508 and rotates about it. The cam profile 708 in this embodiment is provided on the outside of the body and is thus external. The minimum camming or unlocked position of the cam profile is illustrated at 712, while the maximum camming or locked position of the cam profile is illustrated at 710. This cam element could be flipped over, hooked on the pin 508 so that the cam element could rotate about the pin, and then the cam element could be rotated about the pin with the cam profile sliding against rail 504 until the handle rests up against rail 504 in order to lock the relative positions of the ladder sections.

(30) Although the invention has been described by reference to specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.