The present invention relates to a telescopic or collapsible ladder or stepladder of the type comprising U-shaped ladder sections being telescopably inserted in each other, and more specifically to a locking mechanism for such ladders.
Ladders having collapsible and expandable ladder sections are used in order to make the ladder smaller for storage and transport purposes.
In the European patent EP-B1-0 527 766 a collapsible ladder is described comprising ladder bars divided into sections interconnected by rungs. In each ladder section is provided retaining or locking mechanisms, designed to automatically release the upper ladder sections, when a rung reaches a lower rung. This means, that subsequent to the release of the lowermost ladder section, the following ladder sections are automatically released, whereby the ladder collapses.
In the European patent EP-B1-1 402 143 another collapsible ladder is described comprising a retaining or locking mechanism on each ladder section. The locking mechanism is provided at both sides of a ladder section and is designed to be manually and individually released at both sides of a ladder section to collapse a ladder section. The locking mechanism on every ladder section needs to be released to completely collapse the ladder.
One drawback with the ladder described in EP-B1-0 527 766 is that the locking mechanism is positioned on the second lowermost ladder section, which makes it rather uncomfortable to release the ladder. One drawback with the ladder described in EP-B1-1 402 143 is that every ladder section needs to be released individually by the user, which could be rather tiresome for the user. Yet another and greater drawback is if any of the locking mechanisms of EP-B1-0 527 766 or EP-B1-1 402 143 are used in a step-ladder, since both locking mechanisms enable a stepladder having any of these locking mechanisms to be used even though they are not completely extended or if one side of the stepladder is folded or extended more or less than the other side of the stepladder.
There is a wish to provide a locking mechanism for a collapsible ladder or stepladder that combines the benefits of the described prior art solutions without their drawbacks and that ensures the collapsible ladder or stepladder can only be used when the ladder is completely extended.
An object of the present invention is to provide a locking mechanism for telescopably collapsible ladders and stepladders, which enables the user to comfortably release the locking mechanism and automatically collapse the ladder by a single locking mechanism arranged on the upper ladder sections, but also secure that the ladder can only be used when fully extended.
This object is attained according to the invention described in the characterizing part of claim 1.
In a further embodiment of the invention, the retaining mechanism enables to completely fold the ladder by using the retaining mechanism of any bar section.
In still a further embodiment of the invention, the locking mechanism is included in a collapsible ladder.
In another embodiment of the invention, the locking pin position is indicated by a field, preferably with red color, when the locking pin is withdrawn from the respective ladder bar, and by another field, preferably with green color, when the locking pin is in the locking position.
In yet another embodiment of the invention, the locking mechanism is included in a collapsible stepladder.
In the following, the invention will be explained with reference to the accompanying drawings, where:
a is a front view of an extended ladder according to the third embodiment of the invention;
b is a front view of an extended ladder according to the second embodiment of the invention;
As can be seen by briefly reviewing the drawings, there are many similarities between
In
The lowermost ladder section 15 is besides the rung 7 suitably provided at the bottom with a stationary rung 6, designed to provide an extra foot support and a more stable lowermost ladder section. The rungs are suitably made of an extruded aluminum profile.
Each rung 7-13 houses at each end a locking or retaining mechanism 20, 41 (not shown in
A completely extended ladder 1 according to the second embodiment is shown in
The ladder 1 of
A completely extended ladder 1 according to the third embodiment is shown in
Now the retaining or locking mechanism 20 used in the first and second embodiment will be described in detail. In
In
The retaining mechanism 20 comprises a locking pin 24, which is received in a shell 21, where the shell 21 is press-fitted into the rung. The locking pin 24 is displaceably mounted in the shell 21 and is in one end biased by a spring 25. The locking pin 24 is provided with a waist or recess portion 26 in the mid portion of the locking pin 26 and a slot or slit 27 in the fore portion of the locking pin 24. The waist or recess 26 serves to receive an actuator or button 30, 32 (see
The ladder locking indicator 31, 42 is, as earlier described, provided with a green field to indicate that the retaining mechanism associated with that locking indicator 31, 42 is activated, and with a red field to indicate that the retaining mechanism associated with that locking indicator 31, 42 is inactivated. These fields are provided on a plate made of plastic or metal attached to the other end of the locking indicator 31, 42, where the plate is vertically arranged in relation to the connecting part. The locking indicator is completely housed in the shell 21, but the plate with the green and red fields is visible through a recess 29 (see
When the locking pin 24 is in the position shown in
Alternatively the locking indicator 31, 42 can be arranged as colored portions of the locking pin 24. The rear portion of the locking pin 24, which visible through the recess 29 when the retaining mechanism is activated, see e.g.
The locking pin 24 is furthermore provided with a chamfered end 33 in the end opposite to the end biased by the spring 25. The locking pin 24 interacts with a locking hole 34 of the bar section 5b to keep the extended position of the ladder.
The slot or slit 27 serves to prevent the locking pin 24 from projecting too far into the locking hole 34 and can for that reason be provided with a washer or can the making of the slit 27 create raisings on the locking pin that fulfills that purpose.
In
In
In
Now the functionality of the retaining or locking mechanism 20 used in the first and second embodiment will be described in detail.
The user inactivates the retaining mechanism 20 of top rung 13 by withdrawing the locking pin 24 from the locking hole 34 by means of the actuator or slide button 30, 32 positioned on the front side of the rung 13. The bar section 5, associated with the rung 14 and kept in position by the retaining mechanism 20 of the rung 13, is lowered by gravity. In
According to the second embodiment the folding of the ladder is made in two steps, firstly the bar sections 5 are associated with the rungs 8-11 folded by actuating the actuators 32 and secondly the bar sections 5 are associated with the rungs 12-14 folded by actuating the actuators 30. According to the first embodiment the folding of the ladder 1 and the bar sections 5, associated with the rungs 8-14, is made in one step by actuating the actuators 30.
Similar to
Similar to the first embodiment every bar section 5, except the lower most bar sections, is provided with a damper 22 at its lower end. The damper 22 is provided with an inclined surface 23.
The actuator 40 is a rotary button and is pivotably mounted spindle 45 on the shell 21 and having a connecting part (fork-shaped) of the button 40 clasps or jams about the waist or recess 26 of the locking pin 24. The rotary button 40, which is roughly L-shaped, extends through a recess 43 of the bottom of the shell 21 projecting out of a recess on the underside face of the rung. In a locking position, one of the legs of the rotary button projects obliquely out from the recess, whereas the other leg, e.g. having a fork-shaped and rounded end, grasps the recess portion 26 of the locking pin 24. Other structure of the retaining mechanism 41 is similar to the retaining mechanism 20.
The functionality of the retaining mechanism 41 is similar to the functionality of the retaining mechanism 20. The user inactivates the retaining mechanism 41 of bar section 5c by withdrawing the locking pin 24 from the locking hole 34 by means of the actuator or rotary button 40 positioned on the underside of the rung associated with the bar section 5c. The bar section 5b associated with the rung positioned above the inactivated of released the bar section 5c and kept in position by the retaining mechanism 41 of bar section 5c and its associated rung is lowered by gravity. In
Simultaneously thereto the folding of the bar sections, associated with rungs that have been released and lowered, i.e. the initially released bar section and every bar section positioned below the initially released bar section of the third embodiment as described above, the folding of the bar sections associated with the rung positioned above the initially released bar section will be initiated. The initiation of the folding of the bar sections associated with the rungs above the initially released bar section is due to the functionality of the retaining mechanism 41. As the rung of a released bar section reaches a lower rung of an immediately below positioned bar section, the retaining mechanism 41 of the upper positioned bar section is released when the rotary button is pushed into the recess of the upper rung by the lower rung, and thereby releases the retaining mechanism 41. This will be repeated until every bar section positioned above the actuator has been folded.
It is vital that the chamfering has a depth from the end of the locking pin to the end of the chamfering that exceeds the total length measure of the space between two adjacent ladder bars and the thickness of the ladder bars. Beside this a security margin is needed to match any tolerances. This total length measure of the chamfering is crucial for the locking mechanism to function and for the locking pin to be further retracted, after that the chamfering of the damper has retracted the locking pin in the first phase of the releasing of the ladder sections.
In previous solutions some of the collapsible ladders are provided with locking pins having a rounded end, but the rounded end serves as a soft surface as the locking pins slide against the inner surface of the bars by means of the spring. The rounded end solves the problem of enabling a smooth sliding of the locking pins against the inner surface of the bars.
Even though the actuators to inactivate the retaining mechanism have been shown being arranged on the underside or the front of the rungs, it is evident that other solutions also are possible. For example can the actuators be arranged on topside of the bar sections associated with the upper most rung 14, where each actuator is connected to a link arm or a system of link arms that enable the actuators inactivate the upper most retaining mechanisms and thereby enabling the folding of the ladder. Another possible solution would be to arrange the actuators on the outside of the bar sections, at least on the upper most bar section, where each actuator again is connected via some sort of an arrangement to the upper most retaining mechanisms and thereby enabling the folding of the ladder by means of the actuators.
Even though it has not been shown by the detailed embodiment or the drawings it is evident that the claimed locking mechanism can be used on a stepladder. A collapsible stepladder comprises a first and a second ladder leg. The legs are hingedly connected to each other in one end, and where each of the ladder legs can be seen as an individual collapsible ladder as the ladders shown in
The invention according to the claims secures that a stepladder is provided the claimed locking mechanism can only be used when both ladder legs are fully extended. If any of the locking mechanism of any of the ladder section or ladder legs are released or inactivated, all ladder section of that ladder leg will collapse or fold entirely by means of the claimed invention.
The invention is not limited to the embodiments described above and shown on the drawings, but can be supplemented and modified in any manner within the scope of the invention as defined by the enclosed claims.
Number | Date | Country | Kind |
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05011809.0 | Jun 2005 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/062676 | 5/29/2006 | WO | 00 | 11/30/2007 |