The invention relates to an access assembly which is movable between a retracted position and an extended position. Further, the invention relates to a cargo system or door access system, in particular a vehicle door system comprising a retractable access assembly at a door access.

EP3542768A in the name of Masats discloses a retractable ramp assembly for people to access a mass transit vehicle. The ramp assembly is suitable to be mounted integrated in the floor of the vehicle and flush at the top in an area adjacent to a door of the vehicle. Two end positions can be adopted, a resting position and a ramp position. In the resting position, an access platform which is essentially rectangular and that forms part of the ramp assembly is hidden inside the vehicle. The ramp assembly comprises a framework with an oblong front opening for the access platform to pass through. In the ramp position, the access platform is arranged on an inclined plane from the floor of the vehicle to a surface located at a lower height level from which people access the vehicle.

Movement transmission means are linked to the rear side of the platform through which the platform moves linearly along the framework. The movement transmission means comprise a sliding unit configured as a plate that is linearly movable along the framework on a plane parallel to the floor of the vehicle and to a base of the framework. A direct current motor including a brake and an encoder is provided to drive the access platform. By means of an angular gearbox, a spindle nut mounted on a spindle receives the generated movement in order to transmit it to the access platform. The spindle nut is fastened to the sliding unit, and the sliding unit is in turn articulately joined to a rocker piece enabling the extraction and storage of the access platform. The axial direction of the spindle is arranged parallel and between two chrome linear guide bars which form part of a secondary transmission system. The two linear guide bars oriented in the longitudinal direction of the access platform support ball bushings that contribute to the sliding movement and transmit the stresses of the mobile portions of the ramp assembly to the static portions. The ball bushings are coupled to the sliding unit for the guiding thereof, and the movement of the sliding unit causes the push and pull of the access platform.

A drawback of this known ramp assembly is that this ramp assembly is vulnerable for contaminations. Contaminating particles may intrude the framework and damage the movement transmission means which may cause a poor operation and necessitate maintenance. A more robust design of the ramp assembly is desired.

W02009/111084 discloses a cargo system including an extendable ramp which is designed to collapse in a scissoring fashion and to be stored in a small enclosure in or on a tailgate or flatbed. The ramp system includes a collection box with slots therein. A sliding member is provided with anchors in the sides of the collection box. A lattice-like extendable ramp is provided comprising folding structural members 15 that are coupled together via pivot members 17. Other structural members 13 are interspaced in a horizontal and parallel fashion to the collection box and coupled to the folding structural members 15 throughout the length of the ramp via the pivot members 17. Further, reinforcement members 19 are provided to add strength the ramp.

This known extendable ramp is designed to serve as a ramp to access a cargo area of a pickup truck. The ramp can be manually pulled out from a collection box and restored again by pushing the ramp back into the collection box. Instead of a manual operation, it is desired to provide a driveable access platform. However, this known extendable ramp is not suitable to be driven by an actuator. The in and out movement of this extendable ramp is too in accurate and includes too large tolerances which are problematic when providing this extendable ramp with an own drive.

The general object of the present invention is to at least partially eliminate the above mentioned drawback and/or to provide a usable alternative. More specific, it is an object of the invention to provide a retractable access ramp having a driveable access platform which operates smoothly.

Regarding the above-mentioned prior art, it is remarked that any discussion of documents, acts, materials, devices, articles or the like included in the present specification is for the purpose of providing a context for the present invention, and is not to be taken as an admission that any such matters form part of the prior art or were before the priority date of each claim of this application common general knowledge in the field relevant to the present invention.

In a first aspect, according to the invention, this object is achieved by a retractable access assembly according to claim 1 .

According to the invention a retractable access assembly is provided including an access platform which is driveable to slide out to bridge a separating space between a first and second object to allow a person or a load to be displaced across the access platform to move from the first object to the second object.

The retractable access assembly according to the invention is in particular suitable to be mounted to a chassis of a public vehicle, like a train or a passenger bus. In particular, the access assembly is mountable to a floor area at a public vehicle door. The access assembly may form a wheelchair access ramp. The retractable access assembly is suitable for bridging a separating gap between the public vehicle and a station platform to allow a passenger to move across the access platform to enter our exit the public vehicle. In other appliances, the retractable access assembly may be mounted to a building entrance, a theatre stage, serve as an aircraft or ship gangway, etc.

The retractable access assembly comprises a framework for mounting the access assembly to a main structure. The main structure is in particular a chassis, in particular a floor area, of a public vehicle.

The retractable access assembly comprises an access platform being slidable connected to the framework. The access platform is extendable away from a distal end of the framework. The access platform is movable back-and-forth between a retracted position and an extended position.

The retractable access assembly comprises an actuator, preferably a linear actuator, like a hydraulic cylinder or screw spindle, for retracting the access platform from the extended position to the retracted position. The linear actuator is connected to the framework and includes an actuator member which is movable about a actuator stroke.

The retractable access assembly comprises a link mechanism. The link mechanism is positioned in between the access platform and the actuator member. The link mechanism couples the access platform with the actuator member. The link mechanism has a pantograph configuration. The link mechanism may also be called a pantograph link mechanism.

A pantograph configuration is commonly known from a hand-tool used by designers for drafting enlarged drawings. The panthograph configuration has a pair of long links in a V-shape which long links are at a mid region interconnected by a pair of short links. The design tool is used in drafting sketches to make enlarged views. One end of the tool is kept in a fixed position, an intermediate point is used to draw and the enlarged view is rendered by the movable free end. The link mechanism of the retractable access assembly according to the invention is configured as such a pantograph design tool.

In comparison with a scissor mechanism which is built by multiple interconnected equal links in an X-shape -as known from the prior art pickup truck access ramp-, the link mechanism according to the invention which is configured as a pantograph may strongly reduce a total amount of play provided by a cumulation of coupled components. Due to the reduction of play, the access platform may smoothly run back and forth between the retracted and extended position. The pantograph link mechanism is beneficial to obtain an accurate and smooth movement of the access platform which allows the access platform to be driven by an actuator.

In addition, the pantograph configuration of the link mechanism may be beneficial in contributing to a rigidity of a coupling of the access platform to the framework. In particular when the access platform is arranged as a pivotable access ramp in which the access platform is arranged to pivot at the end of the stroke, a linear guidance alone may be insufficient robust to withstand forces acting on the access platform. According to the invention, besides a linear guidance, the connected pantograph link mechanism may also transfer at least a portion of the forces exerted on the access platform to the framework. Herewith, the pantograph link mechanism contributes by increasing a rigidity of the coupling of the access platform to the framework.

According to the first aspect of the invention, the link mechanism comprises a first, second, third and fourth link. Preferably, the link mechanism is a four link mechanism which consists of four coupled links.

The first and second link are long links. Preferably, the long links have a substantially equal length. The third and fourth link are short links. Preferably, the short links have a substantially equal length. The first and second link are coupled to each other to form a pair of long links. The pair of long links includes the fixed end and a free end of the link mechanism. In the access assembly, these long links form in a V-shape. The third and fourth link are coupled to each other to form a pair of short links. In the access assembly, the short links form a V-shape. The pair of short links is coupled to the pair of long links to form a window shape, in particular a parallelogram. The V-shape of the pair of short links is directed away from the V-shape of the pair of long links. Due to the window shape, at the free movable end of the link mechanism, an enlargement of a stroke is obtained when a certain displacement of the link mechanism is introduced by the actuator. ln particular, in the parallelogram, the first link of the pair of long links is positioned substantially in parallel with the third link of the pair of short links. And, in particular, in the parallelogram, the second link of the pair of long links is positioned substantially in parallel with the fourth link of the pair of short links.

In an embodiment of the retractable access assembly according to the first aspect of the invention, the short links are substantially of half a length of the first long link. The short links are coupled to the long links at half a length of the respective long link. Herewith, the actuator stroke of the actuator is doubled by the link mechanism, such that the access platform moves about a double stroke.

In an embodiment of the retractable access assembly according to the first aspect of the invention, the link mechanism has a fixed end which is coupled to the framework. The fixed end of the link mechanism remains in a fixed position relative to the framework. The link mechanism has a displaceable free end which is connected to the access platform. The free end is movable to another position. The actuator member is connected to the link mechanism at a position in between the fixed end and the movable free end. The link mechanism is configured as a pantograph which is beneficial to enlarge the actuator stroke of the actuator member, such that the access platform moves about an enlarged stroke.

In an embodiment of the retractable access assembly according to the first aspect of the invention, the link mechanism has a first end being connected to the actuator member and a second end being connected to the access platform. Herewith, both the first end and the second end of the link mechanism are moving during operation of the access assembly.

To move the access platform to the extended position, the first end is retracted by the actuator to a rear region of the framework. In particular, the actuator is a linear actuator. Preferably, the linear actuator is arranged by a spindle shaft and a screw bearing engage with the spindle shaft, wherein the spindle shaft is mounted to the framework.

The link mechanism has a pantograph configuration and is preferably a four link mechanism. Preferably, a pair of link mechanisms is arranged in mirror symmetry for guiding the access platform. When a load is exerted on the platform in a lateral direction, forces are transferred to the framework via a linear guidance, but also by the link mechanism. Herewith, the pantograph configuration of the link mechanism contributes to a rigidity of the guidance of the access platform. ln an embodiment of the retractable access assembly according to the first aspect of the invention, the actuator member is connected to the pair of short links. Preferably, the actuator member is connected to a pivot point connecting the third link to the fourth link.

In an embodiment of the retractable access assembly according to the first aspect of the invention, the actuator is a linear actuator having a longitudinal axis. In particular, the linear actuator is oriented by its longitudinal axis in a direction of movement of the access platform.

In an embodiment of the retractable access assembly according to the first aspect of the invention, the displaceable free end of the link mechanism is connected to a proximal region of the access platform. Preferably, the access platform comprises a base member positioned at the proximal region. The base member may have a beam structure to provide rigidity to the access platform.

In an embodiment of the retractable access assembly according to the first aspect of the invention, the actuator member is connected to the link mechanism by a travel member. The travel member is positioned in between the actuator member and the link mechanism. Preferably, the travel member is guided by a linear guidance. The linear guidance is mounted to the framework. The linear guidance extends in a direction of movement of the access platform.

In an embodiment of the retractable access assembly according to the first aspect of the invention, the access assembly comprises a first and second link mechanism. The first and second link mechanism are arranged in mirror symmetry. The first and second link mechanism form a pair of link mechanisms.

The actuator may be centrally positioned in between the first and second link mechanism. The fixed end of each link mechanism may be directly mounted to the framework or indirectly to the framework via an actuator housing. Preferably, the first and second link mechanism are interconnected by the travel member such that the link mechanisms move together. The travel member may be elongated. The travel member may have an L-shaped end which is slidably connected to the linear guidance. The travel member is preferably connected to the pair of short links of each link mechanism in which the travel member has a U-shape. Preferably, the travel member is connected to the pivot point of the third and fourth link of each link mechanism.

In particular, the actuator is a linear actuator, e g. a cylinder unit or a screw spindle. Preferably, the actuator is a double acting actuator, such that both retracting and extending the access platform are driveable by the actuator. Instead of manually extending and a powered retracting of the access platform, both movements may be actuated by the linear actuator. The linear actuator has a longitudinal axis which is preferably oriented in a direction of movement of the access platform. The linear actuator has an actuator member which may be formed by a piston rod or screw nut.

In an embodiment of the retractable access assembly according to the first aspect of the invention, the framework forms a housing for receiving the access platform. The framework may be designed to be mounted on top of a floor area at a door access of a passenger vehicle. Alternatively, the framework may be designed to be mounted to a bottom side of a floor area. Preferably, the framework is box-shaped including a cover panel. In the retracted position of the access platform, the cover panel covers the access platform.

The housing has a slot-shaped opening at a distal end to allow a passage of the access platform when moving to the extended position. The slot -shaped opening is preferably covered by a cover plate. The cover plate is closed when the access platform is stored in the housing. The cover plate is movable, in particular pivotable, away from the slot-shaped opening to allow the passage of the access platform.

Further, the invention relates to a door access system, in particular a vehicle door system, more in particular a passenger vehicle door system. The door access system comprises an access assembly according to the first aspect of the invention which is positioned or to be positioned at a doorway in which the access assembly is retractable from an extended position by an actuator. The access assembly of the vehicle door system is mountable to a chassis of the vehicle, in particular on top or to a bottom of a vehicle floor at a door access. Herewith, the retractable access assembly can be used as a wheelchair ramp to provide access to the vehicle for disabled passengers.

In an embodiment of the vehicle door system, the retractable access assembly may be a retractable access ramp which includes an access platform which is movable to an extended position in which the access platform is in an inclined position. The inclined position may be obtained by downwardly pivoting the access platform in the extended position.

Further, the invention relates to a cargo system for loading and unloading cargo to a cargo area comprising a retractable access assembly according to the first aspect of the invention. In particular, the cargo system is arranged for moving objects to a pick-up truck bed. The access platform may be formed by an elongated ramp plate, or by a pair of ramp plates. ln a second aspect, according to the invention, a retractable access assembly is provided which has an improved obstacle detection.

The retractable access assembly is arranged to bridge a gap between a public vehicle and a station platform to allow a passenger to walk across the access assembly to enter or exit the public vehicle. The retractable access assembly comprises a framework for mounting the access assembly to a main structure and an access platform being connected to the framework. The access platform is extendable from a distal end of the framework and movable back-and- forth between a retracted position and an extended position. An actuator is connected to the framework for retracting the access platform from the extended position to the retracted position. The actuator is fluidly connected to an actuator pump for pressurising the actuator. In particular, the actuator is a hydraulic actuator, more in particular a double acting hydraulic cylinder.

Further, the access assembly comprises a control unit for operating the actuator. The control unit comprises at least one processor for executing computer program instructions. The computer program instructions are configured to detect an obstacle which might cause an improper functioning of the access assembly.

Such an obstacle might be formed by a kerb along a road side which kerb might prevent a full extension of the access platform, or an obstacle might be a load acting on the access platform during motion, e.g. a load formed by a passenger stepping onto the moving access platform. In case of detecting an obstacle, the access platform motion should be interrupted.

Many solutions are known from the prior art, e.g. from WO2013/121185, to detect whether a ramp abuts an obstruction. Sensors and microswitches may be implemented, or a current drawn by an electric motor may be monitored to detect an obstacle to warrant a proper functioning of the access assembly.

WO2019/017845 discloses an obstacle avoidance algorithm in a microcontroller which detects a presence of an immovable object that may be in the passage of a ramp board. The algorithm can be programmed into the microcontroller by using various input devices like a front face camera, a proximity sensor, a pressure sensor and a microphone.

A main problem of obstacle detection is that an implementation of a plurality of sensors increase a technical complexity of the access assembly. Another problem is that wear ora contamination of components may change a dynamic behaviour of the access assembly over time, such that initial settings are no longer valid. The changing dynamic behaviour causes known solutions in obstacle detection to get unreliable over time and requires frequent re-calibration.

According to the second aspect of the invention, an improvement in detecting an obstacle is provided by a control method being implemented by the control unit.

The control method comprises a step of determining an operating pressure of the access assembly. The operating pressure of the access assembly varies during a movement of the access platform from the extended position to the retracted position and vice versa.

In the computer program instructions, also called code, a baseline pressure profile may be stored, e.g. by an algorithm, which baseline pressure profile corresponds with a predetermined access platform motion. The baseline pressure profile may contain a pressure range defining an upper pressure threshold and/or a lower pressure threshold defined in dependence of an access platform stroke. Within the pressure range of the baseline pressure profile, a proper access platform motion can be carried out. Outside the pressure range, a situation is assumed to occur in which the access platform should stop moving, an obstacle is detected.

According to the second aspect of the invention, the control method is improved in that the computer program instructions determine a time dependent pressure variation. During operation of the access platform, a pressure increase or decrease is measured over a predetermined time period, a so-called time sample. Preferably a pressure variation is measured over a time sample of at most 3 seconds, in particular at most 1 second, more in particular at most 0,5 seconds.

In the computer program instructions, a baseline time dependent pressure profile may be stored which corresponds with a proper access platform motion. The baseline time dependent pressure profile defines a variation, meaning an increase or decrease, of operating pressure in dependence of a predetermined access platform stroke. A deviation from this baseline time dependent pressure profile is evaluated by the computer program instructions to determine whether an obstacle is detected. In case of an unallowed deviation of the baseline time dependent pressure profile, an obstacle is detected and the control unit provides a control signal to interrupt a motion of the access platform.

In an embodiment according to the second aspect of the invention, the baseline time dependent pressure profile may be stored in the computer program instructions by an algorithm. The algorithm may be a formula including at least one variable parameter, e.g. a temperature parameter. The temperature parameter in the algorithm may be beneficial to adapt the baseline time dependent pressure profile to anticipate on another dynamic behaviour of the access ramp in hot or cold circumstances.

In an embodiment according to the second aspect of the invention, the control unit is provided with a baseline pressure profile, in particular programmed by a first algorithm to determine a crossing of an upper pressure threshold and/or a lower pressure threshold defined in dependence of an access platform stroke. In addition, the control unit is provided with a baseline time dependent pressure profile, in particular programmed by a second algorithm to determine the crossing of a time dependent pressure profile.

Further, according to the second aspect of the invention, a package comprising a data carrier is provided which comprises a computer program instructions that when run on a control unit carries out the steps of the control method.

In particular, according to the second aspect of the invention, a computer-implemented method is provided for controlling a retractable access platform and being configured to detect an obstacle. In the method, at least one signal is received from at least one pressure sensor. A time dependent pressure data is acquired based on the received sensor signal. In the method, the acquired time dependent pressure data is compared with a baseline time dependent pressure data to evaluate whether or not an obstacle is detected. In particular, the method comprises a step of running an algorithm on the acquired time dependent pressure data to determine whether an obstacle is detected. Preferably, a sample time of at most one second is used in the evaluation.

In particular, according to the second aspect of the invention, a computer program product comprising a computer readable medium is provided. The computer readable medium having computer readable code embodied therein. The computer readable code is configured such that on execution by a suitable computer or processor, the computer or processor is caused to perform the computer-implemented method.

In an embodiment of the retractable access assembly, the retractable access assembly further comprises any of the above described features regarding the first aspect.

Further, the invention relates to a door access system, in particular a passenger vehicle door system, comprising a retractable access assembly according to the second aspect, wherein the access assembly is mountable at a floor area, in particular on top of a vehicle floor, at a door access.

Further, the invention relates to a cargo system, in particular a pickup truck that system for loading and unloading cargo to a cargo area comprising a retractable access assembly according to the second aspect of the invention.

The invention will be explained in more detail with reference to the appended drawings. The drawings show a practical embodiment according to the invention, which may not be interpreted as limiting the scope of the invention. Specific features may also be considered apart from the shown embodiment and may be taken into account in a broader context as a delimiting feature, not only for the shown embodiment but as a common feature for all embodiments falling within the scope of the appended claims, in which:

Fig. 1 shows a perspective view of an embodiment of a retractable access assembly according to the invention in which an access platform is housed in a box shaped framework;

Fig. 2 shows the retractable access assembly of Fig. 1 in which the access platform is in an extended position;

Fig. 3 shows a cross-sectional view of the retractable access assembly showing a link mechanism for moving the access platform;

Fig. 4 schematically shows the link mechanism which has a pantograph configuration;

Fig. 5 schematically shows the arrangement of the pantograph link mechanism of the retractable access assembly;

Fig. 6 shows another embodiment of the retractable access assembly in which a pair of link mechanisms is arranged;

Fig. 7-9 show successive operational steps in which the access platform moves from a retracted position to the extended position; and

Fig. 10-12 show another embodiment of the access assembly in three successive views in which an actuator is coupled to an access platform by a panthograph link mechanism in which a reverse movement of an actuator member causes the platform to move to the extended position.

Identical reference signs are used in the drawings to indicate identical or functionally similar components. To facilitate comprehension of the description and of the claims the words vertical, horizontal, longitudinal, cross-sectional - with reference to the gravity and to the coordinate system X,Y, Z shown in the drawings - are to be understood in a practical sense of normal use and in a non-limiting way.

Fig. 1 shows a coordinate system including a X-, Y-, Z-axis. The Z-axis defines a height or vertical direction. The X- and Y-axis define a horizontal plane, in which the X-direction defines a length direction and the Y-direction defines a width direction. The X- and Z axis define a XZ- plane which is a vertical plane in length direction. The Y- and Z-axis define a YZ-plane which is a vertical plane in width direction.

In Figs. 1-3, an access assembly is denoted overall by reference numeral 1. Fig. 1 shows the access assembly 1 in a retracted position RP. The access assembly is arranged to bridge a space between two objects, e.g. a gap between a public vehicle and a station platform to allow a passenger to walk across the access assembly to enter or exit the public vehicle.

The access assembly has a framework 2 for mounting the access assembly to a main structure. The main structure may for example be formed by a chassis of a public vehicle or a building entrance. To install the access assembly, the framework 2 may be mounted onto a floor area in an access opening.

Here, the framework 2 is box-shaped. The framework forms a housing for storing an access platform 3. The housing comprises a cover panel 21 which forms a closed top surface allowing passengers to walk over. The framework 2 has a framework opening 20 at a distal end to allow a passage of the access platform. Here, the framework opening 20 is covered by a cover plate 22 to close the framework opening when the access platform is in the retracted position RP. The cover plate is pivotable connected to the framework and is pushed away by the access platform when the access platform moves from the retracted position RP to an extended position EP.

Fig. 2 shows the access assembly 1 in which the access platform 3 is positioned in the extended position EP. The access platform 3 is slidable connected to the framework. The access platform 3 is extendable from a distal end of the framework 2. The access platform 3 is movable out of the framework opening 20. Here, the access platform is plate shaped. The access platform has a closed top surface. The access platform 3 has a substantially same width and length as the width and length of the framework 2. Fig. 3 shows a cross-sectional view of the access assembly 1 illustrating an actuator 4 and a link mechanism 5 inside the box-shaped framework 2. The actuator 4 is a linear actuator. The linear actuator has a longitudinal axis which is oriented in a direction of movement of the access platform 3.

Here, the actuator 4 is a piston rod cylinder. The actuator 4 has an actuator housing 40 which is mounted to the framework 2. The actuator 4 has an actuator member 41 which is movable about an actuator stroke. The actuator member 41 is connected to a link mechanism 5 by a travel member 42 at a point of engagement E. The travel member 42 is guided by a linear guidance 43 in the direction of movement of the access platform 3. Here, the travel member 42 has an oblong body with L-shaped ends. The oblong body is oriented in a transversal direction. Here, the travel member has an U-shaped body, which L-shaped ends are guided by the linear guidance.

The link mechanism 5 has a pantograph configuration. The pantograph configuration contributes to a stability of the slidable movement of the access platform 3. In the extended position EP of the access platform 3, acting forces may be transferred the link mechanism

Here, the pantograph configuration is arranged to enlarge the actuator stroke. The pantograph configuration is shown in further detail in Fig. 4. In the configuration as shown in Fig. 3, the link mechanism 5 has a fixed end F which is fixed in position and - as indicated by the arrow- a displaceable free end M. The link mechanism 5 is rotatable about the fixed end F. The fixed end F remains in position and the free end M displaces during operation. The free end M is movable to another position when the link mechanism 5 is engaged and moved.

The link mechanism 5 is engaged at a point of engagement E - as shown in Fig. 3 - in between the fixed end F and the free end M. By displacing the point of engagement E about an actuator stroke, the free end M will move about an enlarged stroke. The actuator stroke at the point of engagement E is multiplied to an enlarged stroke at the free end M.

As shown in fig. 4, the pantograph configuration is formed by a first I, second II, third III and fourth link IV. The link mechanism is a four link mechanism. The four link mechanism is made up of four links. The first and second link are long links. These long links are coupled to each other at a pivot point A to form a pair of long links. The long links I, II have a substantially equal length. In the link mechanism, the long links are positioned in a V-shape. One end of the pair of long links is fixed forming the fixed end of the link mechanism, and the other end of the pair of long links forms the movable free end of the link mechanism. The third and fourth link III, IV are short links. The short links have a substantially equal length. The short links III, IV are substantially of half a length of the first long link I. These short links are coupled together at a pivot point B and form a pair of short links. In the link mechanism, the short links are being positioned in a V-shape. The pair of short links is coupled to the pair of long links. The pivot point A of the pair of long links is positioned opposite the pivot point of the pair of short links B. The V-shape of the pair of short links is directed away from the V-shape formed by the pair of long links. Each short link III, IV is coupled to one of the long links at a pivot point C,D. The coupled links l-IV form a window shape which is here a parallelogram. The first link I is positioned in parallel with the third link III, and the second link II is positioned in parallel with the fourth link IV.

Fig. 5 shows in a schematic view an arrangement of the link mechanism 5 for moving the access platform 3. The fixed end F is connected to the framework 2 and the free end M is connected to a base member 30 of the access platform 3. The base member 30 is positioned at a proximal region of the access platform 3. The actuator 4 has an actuator housing 40 which is mounted to the framework 2. The actuator 4 is a linear actuator to provide a linear motion, like a pneumatic or hydraulic cylinder or a screw jack. The actuator 4 has a movable actuator member 41 which is here connected at a point of engagement E to the pair of short links S.

The point of engagement E here coincidences with the pivot point B. When rotating the link mechanism 5 about the fixed end F, the actuator housing 40 rotates too. Due to a length ratio between the pair of short links and the pair of long links, an actuator stroke is enlarged at the free end M to move the access platform 3.

Fig. 6 shows in a schematic view a preferred embodiment in which a first and a second link mechanism 51, 52 are connected in parallel to an access platform 3. The first and second link mechanism 51 , 52 form a pair of link mechanisms which are arranged in mirror symmetry. Each link mechanism has a pantograph configuration as shown in fig. 4.

Here, the fixed ends F of each link mechanism 51, 52 are connected to the framework 2 by a stationary arranged actuator housing 40. The access platform 3 is connected to the free ends M of each link mechanism 51, 52.The actuator 4 has an actuator member 41 which is connected to a travel member 42. The travel member 42 is connected at both ends to the pair of link mechanisms 51, 52 at the point of engagement E which here coincidences with the pivot point B of the coupled short links III, IV. The travel member 42 is guided by the linear actuator 43. Herewith, both link mechanisms 51 , 52 are simultaneously actuated and the access platform 3 is smoothly movable. Fig. 7-9 show successively in three views, an access assembly 1 having an access platform 3 in a retracted position RP, an intermediate position and an extended position EP. The configuration of the access assembly 1 is as schematically shown in Fig. 6. In the retracted position RP, the access platform 3 is housed inside the framework 2. By actuating the actuator 4, the access platform moves out of a framework opening at a distal end until the extended position EP.

Fig.10-12 show another embodiment of the access assembly in three successive views in which an access platform 3 is shown in respectively a retracted position RP, an intermediate position and an extended position EP. The access assembly has a framework 2 for mounting the access assembly to a main structure.

Here, as shown in figures 1 and 2, the framework 2 is box -shaped. The framework 2 forms a housing for storing the access platform 3. The access platform 3 is slidable to and fro the extended position EP. In operation, the access platform 3 is guided by a linear guidance 43.

Fig. 10 shows a cross-sectional view of the access assembly 1 illustrating an actuator 4 and a link mechanism 5 inside the box-shaped framework 2. The actuator 4 is a linear actuator. The linear actuator has a longitudinal axis which is oriented in a direction of movement of the access platform 3.

Here, the actuator 4 comprises a linear drive 44. The linear drive 44 includes a spindle shaft 441 and an electric motor- not shown- for driving the spindle shaft. The spindle shaft 441 is mounted to the framework 2. The actuator 4 has an actuator member 41 which is movable about an actuator stroke. Here, the actuator member 41 comprises a screw bearing 442 which is engaged with the spindle shaft 441. Another embodiment of a linear drive 44 is also conceivable, for example a belt driven linear actuator. In operation, the actuator member 41 runs from one end to another end of the spindle shaft 441 to move the access platform 3 to and fro the retracted and extended position.

At a point of engagement E , the actuator member 41 is connected to a link mechanism 5 which has a pantograph configuration. The link mechanism has a first end M1 which is connected to the actuator member 41 and a second end M2 which is connected to the access platform 3, in particular to a base member 30 at a rear region of the access platform. During operation, both the first and second end M1 , M2 are moving. As shown in figures 10-12, to move the access platform 3 to the extended position EP, the first end M1 is retracted by the linear actuator 4 to a rear region of the framework 2. The link mechanism 5 is a four link mechanism. The link mechanism 5 is rotatable about the first end M1. The link mechanism 5 has a pair of long links I, II being positioned in a V-shape. The V- shape is oriented in a forward direction. The long links I, II are interconnected at a pivot point A and at pivot points C, D by a pair of short links III, IV. The pair of short links are positioned in a V-shape which the V-shape is oriented in a backwards direction. The pair of short links is coupled to the pair of long links forming a window shape. When retracting the first end F1, due to the pantograph configuration, the link mechanism 5 is forced to rotate in a forward direction, as shown in fig. 11 and 12. Here, a first and second link mechanism 51 , 52 are arranged in mirror symmetry. During a movement of retraction, in a first stage, the V-shape first narrows, and subsequently opens in a second stage of the movement along the actuator stroke.

The pantograph configuration of the link mechanisms 51, 52 contribute to a stable sliding movement of the access platform 3. In particular at the end of the actuator stroke, the access platform 3 may be guided along a relative small portion of the linear guidance 43 which might render the access assembly 3 vulnerable to get damaged by a lateral force onto the access platform. According to the invention, the link mechanism 5 having a pantograph configuration provides additional stability to the access platform when in reaching the extended position EP. A lateral force onto the access platform 3 is transferred via the linear guidance 43 and via the link mechanism 5 to the framework 2.

Thus, the invention provides an access assembly for bridging a space between objects including an access platform which is slidably connected to a framework and retractable by an actuator from an extended position, wherein a link mechanism having a pantograph configuration is coupled with the access platform, which link mechanism has a fixed and being connected to the framework and a displaceable free end connected to the access platform, and wherein the actuator which is connected to the link mechanism at a position in between the fixed end and the displaceable free end, such that an actuator stroke is enlarged by the link mechanism to move the access platform about an enlarged stroke.

Although the present invention has been described in detail, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as hereinafter claimed. It is intended that all such changes and modifications be encompassed within the scope of the present disclosure and claims. Reference signs list:

EP extended position 441 spindle shaft

RP retracted position 442 screw bearing

1 access assembly 5 link mechanism

51 first link mechanism

2 framework 52 second link mechanism

20 framework opening F fixed end

21 cover panel M free end

22 cover plate M1 first end

M2 second end

3 access platform A,B, C, D pivot point

30 base member E point of engagement

4 actuator I first link

40 actuator housing II second link

41 actuator member III third link

42 travel member IV fourth link

43 linear guidance L pair of long links

44 linear drive S pair of short links