NL2008496C2

NL2008496C2 - A telescopic ladder assembly.

Info

Publication number: NL2008496C2
Application number: NL2008496A
Authority: NL
Inventors: Caspar Bernard Lampe; Marcel Cornelis Hooiveld
Original assignee: Lampe Holding B V
Priority date: 2012-03-16
Filing date: 2012-03-16
Publication date: 2013-09-18

Description

P31091NL00 A TELESCOPIC LADDER ASSEMBLY.

The present invention relates to a telescopically extendable and collapsible ladder assembly having at least a first, second and third ladder section, each of said ladder sections having two metallic tubular stile members arranged parallel to each other, said stile members each having a lower end and each being interconnected at a top end by a ladder rung to form an 5 inverted U-shaped ladder section. The stile members of each ladder section are telescopically inserted into the stile members of a lower ladder section.

At least the first and second ladder sections further each comprising a locking mechanism for locking the telescopically inserted stile members of an extended second and third ladder 10 section respectively, the locking mechanism being associated with an actuator for unlocking the stile members in order to allow for collapsing of the respective ladder section.

The locking mechanism comprises a locking pin that is biased towards a locking position, wherein the locking pin extends into and through a locking hole provided in a stile member of 15 the extended ladder section.

Telescopic ladder assemblies have become quite popular as portable ladders, such as a straight telescopic ladder or a step ladder, but also for stationary mounting, such as a loft ladder providing access to a loft. The tubular stile members are commonly made of extruded 20 aluminium profiles, e.g. of circular, oval, square, or other cross-sectional shape.

Prior art designs of telescopic ladder assemblies have already been disclosed as early as 1929 in the US patent 1712942 (Smith). More recent designs are for example disclosed in EP 527 766, EP 1 402 143, EP 1 843 005, EP 1 728 966 (Telesteps), W02004/013445 25 (Core Distribution), and W02009057995 (Lampe).

As described in EP 1 843 005 with reference to the prior art, a prior art telescopic ladder assembly has been embodied with a friction damper that is fitted at the lower end of each of the stile members of an extendable ladder section. Each friction damper, made of plastic, is 30 provided with a chamfered surface. These chamfered surface are each being arranged such that - during collapse of the ladder section - each chamfered surface cooperates with a locking pin of a locking mechanism that holds the below positioned ladder section in its extended position. This locking pin is initially in its locking position and is then moved against -2- the biasing force by said cooperation with the chamfered surface of the damper into an intermediate position. In this intermediate position the locking pin still extends into the locking hole and thereby holds the below positioned ladder section in its extended position, yet allows for the further passage of the stile member of collapsing ladder section.

5 EP 1 728 966 proposes to embody not only the dampers on the lower end of the stile members with a chamfered surface but also to embody the locking pins with a chamfered end. This is done in such a manner that the locking pin does not maintain its above described intermediate position but is further retracted in order to be entirely retracted from 10 the locking hole and to release ladder section that was initially locked by the locking pin.

These prior art design ladder assemblies wherein the dampers have a chamfered surface that cooperates with the locking pin are not satisfactory, either with regard to their construction and/or their practical use. In particular problems may arise with the service life 15 of these ladders. Therefore the present invention aims to propose measures that allow for improvements.

The present invention proposes a ladder assembly according to the preamble of claim 1, which is characterized in that the chamfered surface is embodied by a deformed region of 20 the lower end portion of the metallic stile member.

In a preferred embodiment the chamfered surface is embodied by an indented region of the lower end portion of the metallic stile member.

25 The present invention is based on the insight that by deforming a region of the lower end portion of the metallic stile member, preferably an aluminium profile, a durable chamfered surface is obtained that is monolithic and seamless with the tubular stile member. In this manner the metallic chamfered surface is less prone to wear than a chamfered surface formed by the plastic damper body as in the prior art. It is noted that in the prior art such 30 wear becomes problematic in particular when the locking pin crosses the dividing seam between the plastic damper and the metallic stile member. In the inventive design no such dividing seam is present, so if any wear would occur due to the locking pin engagement no collision would take place as would happen at said prior art dividing seam.

A further benefit of the present invention is the ease of manufacturing the chamfered surface, 35 in particular in an embodiment wherein the chamfered surface is embodied by an indented region of the lower end portion of the metallic stile member. By a suitably shaped pressing -3- tool, the form of the indented region may be suited to the particular design of the locking pin and the desired retractive motion thereof.

The invention envisages a preferred embodiment wherein there are no dampers at the lower ends of the stile members. As is then preferred, the stile members each have an open lower 5 end delimited by the tubular stile member with the local deformation forming the chamfered surface. It is noted that lightweight ladders may require no damping at all, or some damping provided by one or more guide collars on the stile members, preferably arranged above the chamfered surface, possibly between the chamfered surface and the locking hole. It is noted that if damping is desired, a damper may be fitted at the lower end of the stile member in 10 combination with the chamfered surface embodied according to the invention.

Preferably the locking pins are made of solid metal, preferably of steel, preferably at least the portion extending into and through the locking hole in locking position.

15 Preferably the locking pin has a non-chamfered end such that in its intermediate position the locking pin locks the stile member of the second ladder section. It is noted that the locking pin may have a marginal chamfering to facilitate entry of the locking pin into the locking hole. In a less preferred embodiment the locking pin has a chamfered end such that the locking pin by cooperation with the stile member of the second ladder section is further retracted from 20 the intermediate position to be entirely retracted from the locking hole, and to release the second ladder section. This is e.g. known from EP 1 728 966.

In a preferred embodiment for at least one ladder section the stile members are each provided with at least one guide collar between the locking hole and the lower end of the stile 25 member, preferably two axially spaced apart guide collars. The guide collars mainly serve to fill the annular gap between the inserted stile members to enhance stability of the ladder assembly and to facilitate the sliding motion during extension and collapse. As is common each guide collar has a dividing gap allowing the guide collar to pass the end of the locking pin that is in sliding contact with the stile member of the collapsing ladder section.

30

In a preferred embodiment the length of the stile members of a ladder section is at least 1.3 times the distance between rungs when the ladder section is extended.

In an embodiment each ladder rung is connected at each end thereof to the stile member via 35 a connector member, the locking pin being reciprocally supported in the connector member, e.g. with a spring between the locking pin and the connector member to bias the pin toward its locking position.

-4-

In an embodiment the one or more actuators are arranged on the front side of the rung, e.g. two actuators, each connected to a corresponding locking pin, arranged centrally on the front side of the rung so as to be operable simultaneously with a single hand.

5 In an embodiment each ladder rung is connected at each end thereof to the stile member via a connector member, the locking pin being reciprocally supported in the connector member, e.g. with a spring between the locking pin and the connector member to bias the pin toward its locking position, and each connector member being provided with an actuator connected to the locking pin, e.g. to allow actuation thereof by a thumb of a user or to allow for actuation 10 by contact with a lower positioned ladder section.

The tubular stile members may have a circular cross-section, but other cross-sectional shapes, e.g. square, rectangular (rounded), triangular, delta shaped, oval, elliptical, etc. are also possible.

15

The ladder assembly may be embodied as a straight telescopic ladder, e.g. having a lower ladder section with feet to rest on the ground and with three or more extendible ladder sections, e.g. 6 or 8 extendible ladder sections.

20 The ladder assembly can also be embodied as a loft ladder, wherein the upper end of the ladder is connected to a carrier structure and the ladder is extended downwards to get access to a loft. The collapse of the ladder is then in upward direction.

The ladder assembly can also be part of a stepladder having a first stepladder assembly and 25 a second stepladders assembly hinged to one another so as to be in a storage position folded against one another and an operative position similar to an inverted V at least one of the stepladder assemblies being a ladder assembly according to the invention.

The ladder assembly can also be part of a work platform.

30

The present invention also relates to a method for manufacturing a telescopically extendable and collapsible ladder assembly according to the invention. As explained above the chamfered surface is made by deforming a region of the lower end portion of the metallic stile member.

The invention will now be explained in more detail under referral to the appended drawings.

In the drawings: 35 -5-

Fig. 1 shows in side view, partly cut away view, an upper part of a straight telescopic ladder according to the invention in extended condition,

Fig. 2 shows a part of the ladder of figure 1,

Fig. 3 shows in cross section - with the locking pin still in its locking position - the 5 cooperation of a chamfered surface of a stile member and a locking pin of the ladder of figure 1,

Fig. 4 shows the view of figure 3 as the locking pin has been moved due to said cooperation into its intermediate position.

10 Figure 1 shows a top part of an example of a telescopic extendable and collapsible ladder assembly according to the invention, here embodied as a straight telescopic ladder 1. As explained above the ladder assembly may also be part of another “ladder product” such as a stepladder or combination ladder, a work platform with ladder like telescopic legs, etc.

15 The figure 1 shows that the ladder assembly has at least a first ladder section 5, a second ladder section 10, and a third ladder section 15 which here is the top ladder section of the ladder. In practice for a straight ladder may have more than 3, e.g. 7 or more ladder sections, with a lower ladder section having ground engaging feet or similar ground engaging members.

20

Each of the ladder sections 5, 10, 15 has two metallic, preferably of extruded aluminium tubing, tubular stile members 5a, 5b, 10a, 10b, 15a, 15b arranged parallel to each other. The stile members each have a lower end. The tubular stile members may have a circular cross-section as is shown here, but other cross-sectional shapes, e.g. square, rectangular 25 (rounded), triangular, delta shaped, oval, elliptical, etc. are also possible.

At their top end the stile members of each section 5, 10, 15 are interconnected by a ladder rung 20, 21, 22, preferably of aluminium, to form an inverted U-shaped ladder section. In this example, as is preferred, a connector member 23, 24 connects the end of each rung to the 30 top end of the stile member, preferably a plastic connector member as is known in the art. The connector member may comprise a portion 23a inserted into the rung and a retaining portion 23b for the top end of the stile member, e.g. clamped onto the top end by a tensioning bolt as depicted here.

35 The stile members of the ladder sections 10, 15 are telescopically inserted into the stile members of a lower ladder section as is common in the art and illustrated in the drawings.

In figure 1 and 2 a part of the stile member 10a and a connector 23 has been cut away to show the parts relevant for the invention.

-6-

The first and second ladder sections 5, 10 further each comprise a locking mechanism 30 5 that is adapted to lock the telescopically inserted stile members of an extended second and third ladder section 10, 15 respectively. Here, as is preferred, two independently operable locking mechanisms are provided per ladder section 5, 10; one for each stile member to be locked. These mechanisms 30 will be explained in more detail below.

10 For each locking mechanisms 30 the depicted ladder assembly has a manually operable actuator 40 that allows to selectively unlock the stile members in order to allow for collapsing of the respective ladder section. Here the actuators 40 are arranged in the centre of the rung to be operated simultaneously with a single hand, here as example by pressing the actuators 40 towards one another. In another embodiment, for example, each actuator 40 is situated 15 close to the end of the rung, e.g. integrated with a connector 23, so as to allow operation with a digit, e.g. thumb, of a hand that grips around the stile of the ladder. In another embodiment the actuators are replaced by a single common actuator, e.g. a rotatable knob centrally on the rung. In yet another embodiment at least some of the actuators are embodied to achieve automatic unlocking upon collapsing of the ladder assembly as is known in the art.

20

As illustrated best in figure 3 each locking mechanism 30 comprises a locking pin 31 that is biased by a spring 32 towards a locking position (see figure 3), wherein the locking pin 31 extends into and through a locking hole 16 provided in a stile member 15a of the extended ladder section 15.

25

At least the third ladder section 15 has at the lower end of each of the stile members 15a, b thereof a chamfered surface 17. These chamfered surfaces 17 are each embodied and arranged such that - during collapse of the third ladder section 15 by unlocking the mechanisms 30 of the second section 10 - each chamfered surface 17 cooperates with a 30 locking pin 31 of a locking mechanism 30 of the first ladder section 5. As depicted in figures 2 and 3 this locking pin 31 is initially in its locking position and is then retracted or pushed back by the cooperation with the chamfered surface 17 into an intermediate position (shown in figure 4). In the intermediate position the locking pin 31 allows for the further passage of the stile member 15a of third ladder section 15 during collapse of the third ladder section 15 35 downward whilst the stile member 10a of the second ladder section 10 is still locked thereby keeping the second ladder section in extended position.

-7-

Only when the actuator 40 coupled to the locking pin 31 is actually operated to unlock the mechanism 30, is the locking pin 31 moved to its fully retracted position out of the locking hole 16 allowing the collapse of the second ladder section 10.

5 The locking pin 31 has a non-chamfered end so that the vertical force exerted on the pin end by the second ladder section stile member 10a is unable to cause the further retraction of the locking pin to its fully retracted position. As explained in an alternative embodiment the pin end may be chamfered to obtain just this effect if desired.

10 The figures 2 and 3 illustrated that the chamfered surface 17 is embodied by a deformed region of the lower end portion of the metallic, here aluminium, stile member 10a, here by making an indented region in the originally circular shaped lower end of the stile member, e.g. using a pressing tool.

15 The stile members are each provided with at least one guide collar 14 between the locking hole 16 and the lower end of the stile member. In this example, as is preferred, two axially spaced apart guide collars 14 are provided on each stile member. The collars 14 generally fill the annular gap between surrounding stile members and so enhance the stability of the ladder assembly. For example each collar 14 is made of suitable plastic material.

20

As is shown each collar can be fitted on the stile member by providing the collar 14 with one or more integral bosses 14a at its inner face, and providing insertion holes in the stile member.

25 As is best seen in figures 3 and 4 each guide collar 14 has a dividing gap in longitudinal direction of the stile member at the side of the locking mechanism 30 allowing the guide collar 14 to pass the end of the locking pin 31 that is in sliding contact with the stile member 10a of the collapsing ladder section.

30 The collars 14 may optionally provide some damping (by friction) of the collapsing motion of the ladder section, but this is not a necessity. As is preferred the ladder section is devoid of any damping member within the telescopic stile members. It is observed that internal dampers as they are now often used in telescopic ladder assemblies show significant reduction or even disappearance of their actual damping effect over time. In this perspective 35 it is envisaged that no such dampers inside the stiles are present and that the stile members are preferably open ended at their lower end.

-8-

The making of the chamfered surface 17 is preferably done by making an indentation in the lowermost region of the stile member. In an alternative design one can envisage that cuts are made in the lowermost region from the lower edge upward, so as to create a tab that is connected to the rest of the stile member at its upper end. This tab is then folded inward to 5 create the chamfered surface that is at said upper end contiguous with the rest of the stile member without a transition seam. The folded inward tab may be retain in position by being supported on the inside by a support member, e.g. of plastic, that has been inserted in the lower end of the stile, e.g. prior to the folding of the tab.

Claims

Telescopic extendable and retractable ladder assembly (1) with at least a first, second and third ladder section (5,10,15), each of said ladder sections having two metal tubular post elements (5a, 5b, 10a, 10b, 15a, 15b) arranged parallel to each other, the post elements each having a lower end and each at an upper end connected by a ladder rung (20, 21, 22) to form an inverted U-shaped ladder section, the post elements of the second and third ladder section are telescopically inserted into the post elements of the first and second ladder section respectively, wherein at least on each of the first and second ladder sections a locking mechanism (30, 31,32) is provided for locking the telescopically inserted post elements of the respective second and third ladder section in the extended position, which locking mechanism is provided with an actuator (40) for unlocking the post elements to allow it to be applied allow the relevant ladder section to retract, wherein at least the locking mechanism (30) disposed on the first ladder section (5) comprises a locking pin (31) which is forced to a locking position, which locking pin - when in the locking position - is in and extending through a locking hole (16) provided in the post element (10a) of the second ladder section (10) when the second and third ladder sections are both in extended position, with at least the third ladder section (15) at the lower end of each of the post elements thereof has a chamfered surface (17), the chamfered surfaces are each arranged such that - during sliding in of the third ladder section - each chamfered surface cooperates with a locking pin (31) of a locking mechanism (30) first ladder section is arranged, which locking pin is initially in its locking position and, by virtue of that cooperation with the beveled surface against the force of force, towards a An intermediate position is moved, the locking pin in that intermediate position allowing the further passage of the post element of the third ladder section during the insertion of the third ladder section, characterized in that the beveled surface (17) is designed as a deformed area of the lower part of the metal style element.

A ladder assembly according to claim 1, wherein the chamfered surface is formed by a dented area of the lower end portion of the metal post element. 5

A ladder assembly according to claim 1 or 2, wherein the locking pin (31) has a non-chamfered end so that the locking pin remains in its intermediate position in the locking hole and locks the post element (10a) of the second ladder section in its extended position.

A ladder assembly as claimed in claim 1 or 2, wherein the locking pin of the locking mechanism disposed on the first ladder section has a chamfered end so that the locking pin is moved further from the intermediate position, through cooperation with the post element of the second ladder section, completely out of the locking hole be retracted into the post element of the second ladder section so as to release the second ladder section.

A ladder assembly according to any one of claims 1-4, wherein the post elements (5a, 5b, 10a, 10b, 15a, 15b) are made from extruded aluminum tube.

A ladder assembly according to one or more of the preceding claims, wherein of at least one ladder section the post elements are each provided with at least one guide collar (14) in an area between the locking hole (16) and the lower end of the post element, preferably two guide collars (14) placed at axial distance from each other.

A ladder assembly according to claim 6, wherein each guide collar (14) has a dividing gap that allows the guide collar to pass through the end of the locking pin that is pressed to be in conductive contact with the post member of the sliding ladder section.

A ladder assembly according to one or more of the preceding claims, wherein the post elements are open at their lower ends and are not provided with damper elements.

9. A ladder assembly as claimed in one or more of the foregoing claims, wherein the one or more actuators (40) are arranged on the front of the sport, for example two actuators (40) centrally arranged on the front of the sport in order to simultaneously to operate with a single hand.

10. Method for manufacturing a telescopically extendable and retractable ladder assembly according to one or more of the preceding claims, characterized in that the beveled surface (17) is made by deforming an area of the lower end portion of the metal post element .