FIELD OF THE INVENTION

The present invention relates to a collapsible ladder comprising a number of stile sections interconnected by ladder steps to form U-shaped ladder sections, wherein adjacent stile sections have inner and outer diameters adapted to allow telescopic insertion into one another.

PRIOR ART Collapsible ladders of various types have been on the market for several years, and have gained a large market share. Compared to ordinary ladders, they can be easily stowed away and are easy and convenient to transport.

Collapsible ladders typically comprise two parallelly extending telescopically collapsible stiles interconnected by a number of ladder steps. The ladder steps are often connected to the stiles in the top end of a section telescopically insertable into a lower section.

Typical examples of prior art collapsible ladders can be found in e.g. EP 1 516 999 and EP 0 527 766. As can be seen in those patents, a ladder section of such a ladder comprises several U-shaped sections, the stanchions of the U being stile sections, and the bottom of the U being the ladder step. The stile sections of an upper section fits within the stile sections of a lower section, and the upper stile section is held in place by a spring loaded pin arranged in the ladder step of the lower section's ladder step and extending through a hole provided in the upper stile section as the ladder is in an extended position. The upper stile sections extend about 15 centimeters, or about half the distance between two adjacent ladder steps, past the lower ladder step when the ladder is in an extended position.

In order to lock a prior art ladder in an extended position, several known locking mechanisms can be used; both mechanisms allowing for automatic collapsing (such as shown in EP 0 527 766) and manual collapsing (such as shown in EP 1 516 999). A further type of locking mechanism (shown in DE 196 53 003 C2) comprises outwardly extending pins arranged in lower ends of the stile sections. Such pins cooperate with openings in the outer ladder pars section to lock the sections relative one another.

One problem with the prior art ladders is, however, that the rigidity of the ladders is too low for taller ladders; authorities in many countries have demands concerning the deflection of a fully extended ladder resting in a horizontal position on its ends, and being subjected to a weight in a center portion. Although the prior art ladders are convenient to use and efficiently collapsed to a small size, it has proven difficult to design tall ladders that pass the deflection test.

One other possible problem with the known ladders is the small risk of inadvertently collapsing the ladder. On prior art ladders, there is a small risk that a user simultaneously might maneuver the pins of one ladder step. Such simultaneous maneuvering might lead to the ladder being inadvertently collapsed.

Taken the above, the object of the present invention is to provide a ladder having an increased stiffness, i.e. lower deflection, and an increased safety against inadvertent collapsing.

SUMMARY OF THE INVENTION

According to the invention, these and other objects are solved by a ladder wherein at least some of the stile sections have a length equaling at least twice the distance between two adjacent ladder steps when the ladder is in an extended position.

In one embodiment of the invention, locking mechanisms may be placed in the ladder steps and may comprise a spring loaded pin adapted to lock at least one stile section inserted into a stile section adhering to the ladder step comprising the locking mechanism by cooperation with holes arranged in the at least one stile section. Moreover, a starting section comprising two starting stiles interconnected by an upper ladder step, an intermediate ladder step and a lower ladder step may be provided in order to leave room for the above ladder sections as the ladder is in a collapsed state. For this embodiment, locking mechanisms may be provided in the top ladder step.

In order to alleviate problems with inadvertent collapsing of the ladder, locking mechanisms may be provided in the intermediate ladder step. In order to alleviate collapsing, openings arranged to cooperate with the pins of the locking mechanism of the intermediate ladder step may be oblong to allow a certain movement without the pin being retracted.

If a ladder allowing for automatic collapsing is desired, the locking mechanisms may comprise levers connected to withdraw the spring loaded pins upon engagement with an adjacent ladder step.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, the invention will be described with reference to the appended drawings, wherein: Fig. 1 is a schematic front view of a ladder according to the invention in an extended position,

Fig. 2 is a schematic side view showing stile sections and locking mechanisms of the ladder of Fig. 1 in an enlarged view, and Fig. 3 is a schematic view of a ladder in an extended position and a ladder section comprised in the ladder.

DESCRIPTION OF EMBODIMENTS In Fig. 1, a collapsible ladder 100 according to one embodiment of the present invention is shown. The ladder is shown in an extended position, and comprises a number of ladder steps 11 Oa-11On (in the shown embodiment, n=g, but any reasonable number of ladder steps could be used). The ladder steps 1 lOa-c are firmly connected to two starting stiles, or ladder bars, 120a, 120b. The ladder steps 1 lOa-c and the two starting stiles 120a, 120b form a ladder like base section 120. The rung HOc is provided with locking means 111, 114, which each comprise a pin 112a, which is spring-biased towards an extended position. The pins 112a can be retracted, in the shown embodiment by pulling rings 111, 113.

A first collapsible section 130 comprises the ladder step HO d, which is firmly connected to upper ends of two stile sections 130a, 130b to form a U-shaped ladder section. The stile sections 130a, 130b are inserted into the starting stiles 120a, 120b. At lower ends of the stile sections 130a, 130b dampers 140a, 140b are fastened. In the shown position, i.e. the extended position, the stile sections 130a, 130b extend within the starting stiles past both the ladder step 110c and the ladder step 110b. The stile sections 130a, 130b are held in place by interaction between holes (not shown) in the stile sections 130a, 130b and the pins 112a, 112b. For a better understanding of the length of the stiles of the ladder sections, please see Fig. 3, wherein a portion of the ladder 100 is shown in an extended position and a ladder section comprising stile sections 130a, 130b and ladder step 11Od is shown besides the ladder 100. A second collapsible section 150 comprises the ladder step 11Oe, which is connected to upper ends of stile sections 150a, 150b. The stile sections 150a, 150b extend into the stile sections 130a, 130b, past the ladder steps 11Od and 110c. The stile sections 150a, 150b are held in place both by interaction between holes engaged by the pins 112a and 112b, and by holes engaged by pins 142a, 142b, respectively. The pins 112a, 112b can be withdrawn from interaction with the holes in the stile sections 130a, 130b and the stile sections 150a, 150b by pulling the rings 111, 113, whereas the pins 142a, 142b can be disengaged from interaction with the holes provided in the stile sections 150a, 150b by interaction between levers 143 a, 143b and the ladder step HOc.

In order to collapse the ladder 100, a user may pull the rings 111, 113. This pulling of the rings will, as mentioned above, impart a retracting movement of the pins 112a, 112b, which movement will disengage the pins 112a, 112b from the holes provided in the stile sections 130a, 130b, 150a and 150b. The stile sections 130a, 130b will then be free to move into the starting stiles 120a, 120b. The stile sections 150a,

150b will not be released from the stile sections 130a, 130b, since they are held in place by interaction between the pins 142a, 142b and the holes aligned with those pins. Consequently, the only stile sections being initially released by the pulling of the rings 111, 113 are the stile sections 130a, 130b. After the stile sections 130a, 130b have been released, the stile sections 130a,

130b will move into the starting stiles 120a, a20b, for example by the force of gravity. As the stile sections 130a, 130b are almost fully inserted into the starting sections, the ladder step HOc will contact the levers 143a, 143b, hence withdrawing the pins 142a, 142b from engagement with the corresponding holes of the stile sections 150a, 150b. The withdrawal of the pins 142a, 142b from the corresponding holes of the stile sections 150a, 150b will release the stile sections 150a, 150b.

Also, the withdrawal of the pins 142a, 142b will release the stile sections fastened to the ladder step 11Of, but, in the same way as described above, the stile sections fastened to the ladder step 110 f will be held in place by the pins located in the ladder step 11Oe until the ladder step 11Oe contacts the ladder step 110 d, such that levers 163a, 163b are maneuvered to withdraw pins associated with those levers. This pattern will repeat itself for the above stile sections until the ladder is fully collapsed.

One important feature with the ladder according to the present invention is that the risk of collapsing the ladder by accident has been reduced as compared to prior art ladders; on the prior art ladders, it is enough to maneuver the levers on a random ladder step for all above stile sections to collapse. On a ladder according to the invention, it is, however, not possible to collapse the ladder by maneuvering the levers on only one ladder step. Instead, the levers on two adjacent ladder steps must be maneuvered simultaneously in order for the ladder to collapse. This is, however, not the case for the rings 111, 113, since such rings are connected to the pins 112a, 112b, which are the only pins to lock the stile sections 130a, 130b.

In Fig. 2, three ladder steps HOn, 110m, 1101 and their corresponding stile sections 17On, 170m and 1701 are shown in an enlarged scale. Also, a damper 173 and level actuators 143m, 1431 connected to pins 142m, 1421 are shown. As can be seen in this figure, the stile section 17On extends past both pins 142m and 1421, i.e. the length of the stile sections is larger than twice the distance between two ladder steps when the ladder is in an extended state.

Again with reference to Fig. 1, in another embodiment of the invention, locking mechanisms each comprising a pin, some kind of mechanism designed to withdraw the pin and a hole in the stile sections 130a, 130b can be arranged in the ladder step 110b. By providing such a mechanism, inadvertent collapsing of the ladder section 130 by withdrawing the pins 112a and 112b can be avoided, since actuation of either the pins located in the ladder step 110b or the pins 112a, 112b will not cause the stile section 130, 130b to be released from the starting stiles 120a, 120b; only simultaneous withdrawal of the pins 112a, 112b and the pins located in the ladder step 110b will release the stile sections 130a, 130b.

In still another embodiment, the holes located in the stile sections 130a, 130b that are positioned for engagement with the pins located in the ladder step 110b are oblong, such that a certain movement between the stile sections 130a, 130b and the starting stiles 120, 120b is allowed without the pin being withdrawn. By this embodiment, it is possible to release the ladder in two steps: In a first step, the rings 111, 113 are pulled, such that the pins 112a, 112b are withdrawn from interaction with the corresponding holes in the stile sections 130a, 130b. Due to the oblong shape of the holes cooperating with the pins in located within the ladder step 110b, the stile sections 130a, 130b are able to move a certain distance into the starting stiles 120a, 120b. This movement will cause the holes corresponding to the pins 112a, 112b to moved off- center compared to the pins 112a, 112b, and as a result, the pins will not engage the holes after the withdrawing force has been released, and the spring urges the pin towards the stile sections 130a, 130b. In a second step, the pins located in the ladder step 110b is withdrawn, after which the stile sections 130a, 130b are released such that they may be fully inserted into the starting sections. After the stile sections 130a, 130b have been fully inserted, the above ladder sections will be released in the same manner as described above. In still another embodiment of the invention, the stile sections are provided with locking mechanisms protruding outwards, i.e. a pin of the locking mechanism protrudes from a stile section located within a larger stile section through an opening in the larger stile section. An example of such a locking system can be found in e.g. DE 196 53 003 C2.

In order to adapt a locking system according to DE 196 53 003 C2 to a ladder according to the present invention, openings must be arranged in both stile sections wherever three ladder sections overlap one another. This makes a ladder according to this embodiment just as safe against inadvertent collapsing as any of the previously described embodiments.

It should be noted that several modifications of the described embodiments are possible without departing from the scope of the invention, such as it is defined by the appended claims.