Bunk ladder TECHNICAL FIELD

The present invention relates to a ladder for a bed in a driver's cab, especially the cab of a commercial vehicle, said bed being in a position that is raised in relation to the floor of the cab, wherein the ladder is attached to the bed structure via a linkage mechanism allowing the ladder to be moved between an essentially horizontal stored position under the bed to a deployed upright position for access to the bed.

BACKGROUND OF THE INVENTION

The driver's cab of a commercial long haul transport vehicle includes a sleeping compartment for resting. Driver comfort is essential for effective driver recovery for maintaining traffic safety. When an operator is required to travel for an extended period of days, often a second operator or a companion passenger/co-driver accompanies the driver because of safety concerns. To accommodate two persons, a cab sleeping compartment can be provided with two beds arranged one over the other.

A ladder is required for entry to and exit from the top bed. The ladder will need to be both light and strong. Also, the relatively tight configuration of a sleeping compartment allows little room for maneuvering the ladder in and out of position. For example, limited cab floor space makes it unpractical to have a full length ladder reaching all the way down from the top bed to the floor surface.

EP 1749965 describes a telescopic ladder which is adapted to be stored horizontally under the upper bed and can be pivoted down to an upright deployed position reaching down to the floor. US 6622822 describes a telescopic ladder which is adapted to be stored horizontally under the upper bed and can be pivoted down to an upright deployed position. The ladder can be latched with its low end to the frame of the lower bed.

There is a need for further development of ladders which can be lowered from the underside of an upper bed into a secure self-locked deployed position without the need of support from either the floor or a lower bed frame.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a ladder which can be securely self- locked and self-supported both in a stored and in a deployed position. This object is achieved according to the invention by a ladder as claimed in claim 1. According to the invention, a first end of the ladder is provided with means for sliding said end from one side of the bed toward the other side of the bed, and a second end of the ladder is controlled by a link member which is pivotally attached to the ladder, The configuration according to the invention allows the ladder to be supported both via sliding means and link members for efficient distribution of weight in a self-locking deployed position.

According to an embodiment of the invention, the ladder comprises a first ladder member with a pair of longitudinal rails, wherein the ends of said rails are glidingly arranged in a guide frame.

Preferably, the longitudinal rails are interconnected at said first end by a transverse rod extending through the guide frame. According to an advantageous embodiment of the invention, each rod end is supported in the guide frame by means of a guide sled. Advantageously, the guide sled is longitudinally adapted to distribute load over a section of the guide frame. This weight distribution may reduce the weight of the ladder supporting attachments at the bottom of the upper bed.

Preferably, a second ladder member is slideably arranged in the rails to form a longitudinal extension of the ladder. This allows the ladder to extend to a height above the floor which is comfortable for access to the upper bed.

Each link member can advantageously be hinged to the ladder at a point a certain distance from said first end of the ladder.

Preferably, each link member is hinged to the guide frame at a point adjacent the side of the bed, opposite said first end of the ladder.

If the bed frame is provided with a horizontal flange positioned opposite the first end of the ladder, a free end of the second ladder member can be adapted to be supported by said flange when the ladder is in the stored position. This allows the ladder to be securely stored below the upper bed.

Preferably, the first ladder member is provided with resilient means acting to bias the second ladder member in a direction toward the bed frame when the ladder is in the stored position. Advantageously, the resilient means is a helical spring acting between the inner end of the second ladder member and the rod. The resilient means act to secure the ladder in the stored position supported by the bed frame flange.

Further embodiments of the invention are illustrated and explained in the figures. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of a driver's cab of a commercial vehicle comprising a sleeping compartment with a ladder according to the invention for access to an upper bed, and

Fig. 2 to 7 are perspective views of the ladder in different positions illustrating movement from a stored to a deployed position.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows in a broken view a commercial truck comprising a driver's cab 10 and a cargo compartment 11. The driver's cab is provided with a sleeping compartment provided with two beds 12, 13 arranged one over the other. Access to the upper bed 12 is facilitated by a ladder 14.

A ladder 15 according to the invention is shown in Figs. 2-7. Fig.2 shows the ladder in a storage position. The ladder 15 is attached to the bottom of the upper bed frame of which only a part 16 is shown in Figs. 2-7. In this storage position the free end of the ladder is supported by a horizontal flange 16a of the frame 16. The ladder 15 comprises a load bearing guide frame including two parallel guide frame rails 17 attached to the upper bed frame 16. A pair of parallel ladder rails 18 is arranged alongside the guide frame rails 17 and interconnected at an inner end by a transverse rod 19 to form a first ladder member 20. A second U-shaped ladder member 21 is telescopically arranged in the rails 18 to form a longitudinal extension of the ladder, wherein the horizontal part of the ladder member 21 forms a step for access to the bed. Each rod end is supported in the guide frame 17 by means of a guide sled 22 which is adapted to slide inside a slot 23 in each guide frame rail 17. A helical spring 24 is arranged inside each ladder rail 18 between rod 19 and inner end of the second ladder member 21. Thus, in the storage position shown in Fig. 2, the springs 24 are biasing the second ladder member 21 toward the bed frame 16, so that the ladder is locked in the storage position by the horizontal flange 16a.

Fig. 3 shows how the ladder is released from the storage position by pressing the second ladder member 21 toward the opposite side of the bed against the action of the springs 24. When the free end of the second ladder member

21 has been moved past the edge of the flange 16a, the ladder can be swung down from the bed frame 16 as shown in Fig. 4.

Initially, the ladder will pivot down a slightly on the rod ends. Then a pair of link members 25 will control the movement of the ladder as it is pivoted down. Each link member 25 is hinged with one end to a guide frame rail 17 at a point 26 adjacent the bed frame flange 16a. The opposite end of the link member 25 is hinged to the first ladder member 20 at a point 27 approximately half its length. The link members 25 will pivot down from a horizontal position to a near vertical position as the ladder is moved from the storage position to a deployed position, see Fig. 5 and 6.

When a force is applied to the free end of the ladder to pivot it from horizontal to vertical, the link member 25 hinge point 27 to the ladder will act as a fulcrum point for the ladder to rotate on. This will cause the end of the first ladder member 20, which is connected to the guide sled 22, to slide along the slot 23 in the guide frame rails 17in the direction of the bed frame flange 16a.

Fig. 6 shows the ladder in a position where the sliding movement is completed. Now the ladder is in a near vertical position with the guide sleds

22 abutting the end of the slots 23. This position can be considered as self- locking as any force acting from above or from a point beside the bed will be absorbed by the guide sleds 22 and the link members 25. Now the second ladder member 21 can be extended telescopically to the final deployed position shown in Fig. 7. When a vertical load is applied to the horizontal step of the second ladder member 21 , the load will be absorbed primarily by the guide sleds 22 which provide a wide load bearing contact surface to the guide frame rails 18. The link members 25 provide secondary load support for the ladder 15 to further distribute the load in the guide frame rails 18. This enables the complete design to be slender to reduce weight. Possible materials that can be used in different elements of the design are steel, aluminium and plastics, for example carbon fibre reinforced plastics.

The invention has mainly been described above with reference to the disclosed embodiment. However, as is readily appreciated by the person skilled in the art, embodiments other than the one disclosed above are equally possible within the scope of the invention, as defined by the appended claims. For example, a further transverse step member may be attached between the free ends of the first ladder member 20. Also, the transverse rod 19 can be replaced with short bolts, connecting each ladder rail 18 to the corresponding guide sled 22 in the guide frame rails.