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Title:
SAFETY LADDER WITH A FALL PROTECTION DEVICE, AND ACCESS BLOCKING MEANS THEREFOR
Document Type and Number:
WIPO Patent Application WO/2009/127980
Kind Code:
A1
Abstract:
The invention relates to a safety ladder with a rail (3) for receiving a runner which can be connected to a harness as fall protection device, with a plurality of ladder rungs (2) which are arranged one above another and run transversely to the rail, and with an access blocking means (20) having a covering device which in the closing state covers a plurality of adjacent ladder rungs (2) and being movable, after release of interlocking means by means of a runner guided in the rail (3), into an opening position by a movement mechanism. In order to improve the safety of the device, the covering device comprises two covering shells (21A, 21B), the distance of which being increasable from the closing position to the opening position by means of the movement mechanism, which especially may comprise swivel arms (23, 24) thertofore.

Inventors:
SZLACHCIKOWSKI MIROSLAW (DE)
GSELL JUERGEN (DE)
EICHWEIN MICHAEL (DE)
HAAS VIKTOR (DE)
Application Number:
PCT/IB2009/051019
Publication Date:
October 22, 2009
Filing Date:
March 11, 2009
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
GREIFZUG HEBEZEUGBAU GMBH (DE)
SZLACHCIKOWSKI MIROSLAW (DE)
GSELL JUERGEN (DE)
EICHWEIN MICHAEL (DE)
HAAS VIKTOR (DE)
International Classes:
E06C7/00
Foreign References:
EP0485489A11992-05-20
DE202007009435U12007-09-20
FR2799501A12001-04-13
Attorney, Agent or Firm:
ALTHAUS, Arndt et al. (Postfach 19 04 08, Köln, DE)
Download PDF:
Claims:

Claims

[Claim 1] 1. Safety ladder with a rail (3) for receiving a runner which can be connected to a harness as fall protection device, with a plurality of ladder rungs (2) which are arranged one above another and run transversely to the rail, and with an access blocking means (20) having a covering device which in the closing state covers a plurality of adjacent ladder rungs (2) and being movable, after release of interlocking means by means of a runner guided in the rail (3), into an opening position by a movement mechanism, characterized in that the covering device comprises two covering shells (21A, 21B), the distance of which being increasable from the closing position to the opening position by means of the movement mechanism.

2. Safety ladder according to Claim 1, characterized in that the movement mechanism comprises at least one swivel arm (23) being connected at one arm end to one covering shell (21A) and at its other end to the other covering shell (21B), or preferably comprising precisely two swivel arms (23, 24) which are connected at one arm end (23A) to one covering shell (21A) and at their other end (23B) to the other covering shell (21B).

3. Safety ladder according to Claim 2, characterized in that the swivel arm(s) (23, 24) is/are connected to the safety ladder, preferably to the back of the rail (3), preferably centrally via a respective swivel joint (34).

4. Safety ladder according to Claim 2 or 3, characterized in that the arm ends on one covering shell (21A) are connected at a different height position from the arm ends on the other covering shell (21B), the swivel arms (23, 24) being oriented in the closing position at an oblique angle to the rail and in the opening position substantially or precisely perpendicularly to the rail.

5. Safety ladder according to one of Claims 2 to 4, characterized in that the interlocking means (30) are associated with a swivel arm, preferably the lower swivel arm (23) in the assembly position on the safety ladder, and/or in that the lower swivel arm (23) consists of a bent swivel bracket.

6. Safety ladder according to Claim 5, characterized in that the swivel arm (23) is connected to a locking disc (35) in a rotationally fixed manner.

7. Safety ladder according to one of Claims 1 to 6, characterized in that the covering shells (21A, 21B) consist of metal sheets which are bent in a U-shaped manner and the free space (22) of which is adapted partially to cover the front and back of the rungs in the closing position.

8. Safety ladder according to one of Claims 1 to 7, characterized in that the rail (3) is provided with windows (7) lying one above another for engagement of a latch on the runner, and in that the interlocking means (30) are coupled to a triggering mechanism (45) having pressure pieces (46) which lie one above another and release the interlocking means (30) on simultaneous actuation by the runner, in particular by guide rollers on the runner.

9. Safety ladder according to Claim 8, characterized in that the pressure pieces (46) of the triggering mechanism penetrate window recesses which are embodied in a laterally offset manner next to the windows on the rail.

10. Safety ladder according to Claim 8 or 9, characterized in that the triggering mechanism (45) has a pressure bridge (47) which is connected to the pressure pieces (46) so as to be fixed in terms of movement and is provided, preferably centrally between the pressure pieces (46), with a pressure pin (48) which furthermore rests, preferably on the side opposing the pressure pieces, against a catch arm (39) which is mounted so as to be tiltable on one side.

11. Safety ladder according to one of Claims 8 to 10, characterized in that the catch arm (39) is pre-tensioned by a restoring means, in particular a compression spring (40), into a catch position in which a locking projection (38) on the catch arm (39) engages with a locking groove (36; 37) on a locking disc (35) fastened to at least one of the swivel arms.

12. Safety ladder according to Claim 6 or 11, characterized in that the locking disc (35) is provided with two locking grooves (36, 37), a first locking groove (36) arresting the swivel arm in the closing position and a second locking groove (37), which is arranged so as to be angularly offset relative to said first locking groove, arresting the swivel arm in the opening position of the covering shells.

13. Safety ladder according to one of Claims 8 to 12, characterized in that the catch arm (39) is connected to a triggering pin (43) with which a remote actuating device (60) is associated to release the interlocking means (30) manually or using the runner.

14. Safety ladder according to Claim 13, characterized in that the remote actuating device (60) comprises a Bowden wire or a pull rod (65) laid parallel to the rail in order to move, by moving the Bowden wire or the pull rod (65), the catch arm (39) into a release position in which no locking engagement of the catch arm (39) with the locking groove takes place and the covering shells can be moved into the respective other position.

15. Safety ladder according to Claim 13 or 14, characterized in that a contour metal sheet (64) can be moved parallel to the rail using the remote actuating device (60), wherein the contour metal sheet (64) is preferably provided with a curved or sliding track (66) with which the triggering pin (43) interacts in a form-fitting manner.

16. Safety ladder according to one of Claims 8 to 15, characterized in that the interlocking mechanism is fastened to a base plate (31) which can be fixedly screwed to the windows (7), which supports the swivel bearing (34) for the lower swivel arm (23) and the tilting bearing (42) for the catch arm (39) and in which the pressure bridge (47) is dis- placeably guided.

17. Safety ladder according to one of Claims 1 to 16, characterized in that the rail (3) has a notch (5) for inserting the runner, the covering shells extending in the closing position to below the notch and a closing metal sheet (70; 170) being mounted on one of the covering shells for covering the notch (5), which closing metal sheet is tiltable or dis- placeable transversely to the safety ladder and can be arrested against movement on the other covering shell using a lock.

18. Access blocking means for a safety ladder with a fall protection device, with a covering device, which can be moved by means of a movement mechanism between a closing position and an opening position, for adjacent ladder rungs of the safety ladder, wherein the covering device is arrested in the closing position by means of interlocking means which can be released by means of a runner which is guided in a rail of the ladder, characterized in that the covering device has two covering shells (21A, 21B), the distance of which can be increased in size by means of the movement mechanism from the closing position to the opening position.

19. Access blocking means according to Claim 18, characterized in that the access blocking means has at least one of the features specified in the characterizing part of Claims 2 to 17.

Description:

Description

Title of Invention: SAFETY LADDER WITH A FALL PROTECTION DEVICE, AND ACCESS BLOCKING MEANS

THEREFOR

[1] The invention relates to a safety ladder with a rail for receiving a runner which can be connected to a harness as fall protection, with a large number of ladder rungs which are arranged one above another and run transversely to the rail, and with an access blocking means having a covering device which in the closing state covers a plurality of adjacent ladder rungs and can be moved, after the release of interlocking means by means of a runner guided in the rail, into an opening position by a movement mechanism. The invention further relates to an access blocking means for a safety ladder with a fall protection device, which access blocking means is provided with a covering device, which can be moved by means of a movement mechanism between a closing position and an opening position, for adjacent ladder rungs of the safety ladder, wherein the covering device is arrested or can be arrested in the closing position by means of interlocking means which can be released by means of a runner which is guided in a rail of the ladder.

[2] Safety ladders, which are provided with a fall protection device so that staff using the corresponding safety ladders are protected from falling both when climbing the safety ladder and during maintenance work carried out from the ladder, are mounted on numerous structures such as for example towers, masts of large-scale wind power stations, facades of office buildings, industrial constructions and the like. In Germany and other countries, official regulations frequently require the provision of a fall protection device once the ladder exceeds a certain length. A particularly effective safety ladder with a fall protection device has been found to be a configuration of ladders in which a central beam is embodied as a rail or is provided with a rail into which it is possible to insert on a notch a runner which is connected to a harness which is carried by a person wishing to climb the safety ladder. A tightening-up of the official approval for corresponding safety ladders demands, inter alia in Italy, that the safety ladder additionally be provided with an access blocking means which on the one hand prevents unauthorized persons, such as for example children, from climbing the safety ladder and also ensures that only persons carrying a harness secured to a runner in the rail can climb the safety ladder.

[3] EP 0 485 489 Bl discloses a safety ladder with a fall protection device having an access blocking means meeting these requirements. The access blocking means consists of a covering metal sheet which is fastened to a lateral beam of the safety

ladder by means of hinges and the width of which is greater than the width of the safety ladder and which covers in the closing position a plurality of ladder rungs, lying one above another, of the ladder. In order to release an interlocking device which arrests the covering metal sheet in the closing position, a control member has to be actuated using a runner inserted into the rail. Displacement of the control member is converted via a Bowden wire into a movement which releases the interlocking means for the covering metal sheet in order to tilt said covering metal sheet into an opening position. In the opening position, the covering metal sheet stands substantially perpendicular to a facade or a wall. At the same time, it is possible to ensure via a lock at the lower end of the covering metal sheet that releasing of the interlocking mechanism is possible in the first place using the runner only when the lock is opened. Drawbacks of the known access blocking means include the fact that the actuating mechanism is relatively easy to manipulate in order to be able to climb the safety ladder even without the runner having been introduced and therefore without protection. Also, the known solution cannot be used under cramped spatial conditions.

[4] The object of the invention is to provide a safety ladder with a fall guard device and access blocking means and also an access blocking means for a safety ladder of this type which does not have the aforementioned drawbacks and offers increased protection against unauthorized use.

[5] According to the invention, this object is achieved in that the covering device has two covering shells, the distance of which is increasable by means of the movement mechanism from the closing position to the opening position or can be reduced in size from the opening position back to the closing position. In contrast to the solution known in the art, use is accordingly not made of a covering plate which is tiltably articulated to a side beam of the ladder and therefore can be built only onto safety ladders having a side beam, in any case in the lower region; instead, the provision of two covering shells, which are pushed apart from each other or pushed back together by the movement mechanism substantially parallel to the ladder rungs, produces a compact access blocking means which can, if appropriate, be built directly onto the ladder. The solution according to the invention can also offer increased protection from unauthorized use, since the covering shells can cover the ladder rungs not only on the front of the safety ladder, but rather also on the back of the safety ladder, so that no ladder rung at all of the ladder is accessible in that region in which the access blocking means extends.

[6] In order to allow the pushing-apart or pushing-together of the two separate covering shells in a particularly simple manner, the movement mechanism has, according to a particularly advantageous configuration, at least one swivel arm which is connected at one arm end to one covering shell and at its other arm end to the other covering shell.

The particularly preferred configuration provides precisely two swivel arms which are arranged so as to be vertically offset relative to each other and are connected at one arm end in each case to one covering shell and at their other arm end in each case to the other covering shell. Two swivel arms, which are arranged vertically offset relative to each other, allow even relatively heavy, extensive covering shells to be supported without difficulty and moved with guidance relative to one another. The two swivel arms form a type of linkage assembly or steering gear which ensures simultaneous, parallel movement of both covering shells relative to each other while at the same time providing good mechanical support. In order to attain a particularly compact design of the access blocking means, it is advantageous if the swivel arm or if the swivel arms are connected to the safety ladder via a respective swivel joint. With regard to the sequence of movement of the movement mechanism, it is particularly advantageous if each swivel arm is connected centrally between its two arm ends to the back of the rail via a swivel joint. The fastening to the back does not impede the movement of the runner within the rail and the central arrangement of the swivel joint ensures an equilibrium of forces of the covering shells relative to one another during movement between the opening position and the closing position or vice versa. The two centrally mounted swivel arms, which are at the same time joined together via their ends and the covering shells connected there, form a steering gear which can be actuated by the application of relatively little force. It is particularly advantageous if the arm ends on one covering shell are connected at a different height position from the arm ends on the other covering shell, the swivel arms being oriented in the closing position approximately parallel to the rail and in the opening position substantially perpendicular or precisely perpendicular to the rail. In the case of an arrangement of this type of the steering gear, the upper and lower front edges of the covering shell are flush with one another in the same height position only in the closing position of the covering shell, whereas in the opening position one covering shell is moved upward from its starting position and the covering shell fastened to the other arm ends is moved downward, and at the same time experiences the outward displacement, in order to free the ladder rungs. The weight forces which have to be exerted on the movement mechanism for this movement manually or using a pre-tensioning means or the like are low, as the downward movement of one covering metal sheet causes the upward movement of the other covering metal sheet. A slight pressure exerted at any point on one of the covering shells may therefore be sufficient to carry out the movement of the covering shells which are guided by the movement mechanism.

[7] The interlocking means can be associated preferably with a swivel arm, in particular the lower swivel arm in the assembly position on the safety ladder. This measure shortens the spacing to be bridged between the position of the runner and the in-

terlocking means to be released. In order to allow the interlocking of the access blocking means in a particularly simple manner, the swivel arm is, in the case of the particularly preferred configuration, connected to a locking disc in a rotationally fixed manner. The locking disc accordingly rotates on movement of the swivel arm and for the purposes of arresting, rotation of the locking discs has merely to be blocked. The lower swivel arm can preferably consist of a bent swivel bracket in order to improve the sequence of movement.

[8] The covering shells can preferably consist of metal sheets which are bent in a U- shaped manner and the free space of which is adapted partially to cover the front and back of the rungs in the closing position. However, the covering shells can also consist of angled metal sheets having, in particular if there are no side beams, a short leg which extends backward in an angled manner in order to prevent, in the case of a safety ladder which is fastened to a structure with the access blocking means closed, any portions of the ladder rungs from being exposed in the region of the access blocking means. If the safety ladder is mounted very tight to a building and if appropriate also has side beams, it may even be sufficient to form the covering shells with flat metal sheets, the spacing of which is increased in size and subsequently reduced in size again by the movement mechanism for opening the safety ladder and rendering it accessible.

[9] A particularly safe configuration of a safety ladder with an access blocking means is ensured if the rail is provided in a manner known per se with windows lying one above another for engagement of a latch on the runner, wherein furthermore the interlocking means are coupled to a triggering mechanism having pressure pieces which lie one above another and release the interlocking means preferably only on simultaneous actuation by the runner, in particular by guide rollers on the runner. A triggering mechanism having a plurality of pressure pieces which are actuated simultaneously is much more resistant to manipulation than the triggering mechanism known in the art. In the case of the particularly preferred configuration, the pressure pieces of the triggering mechanism penetrate not the windows in the rail, but rather window recesses which are embodied in a laterally offset manner next to the windows on the rail. This has not only the advantage that it is more difficult to actuate the triggering mechanism through the opening in the rail, but rather a further advantage consists in the fact that the pressure pieces lie concealed after the front edge webs of a rail formed mostly from a slotted hollow profile. Also preferably, the triggering mechanism can have a pressure bridge which is connected to the pressure pieces so as to be fixed in terms of movement in order to control via the pressure bridge that the interlocking mechanism is released only on simultaneous actuation of all of the pressure pieces. In order to attain this, the pressure bridge can be provided, in particular centrally between the

pressure pieces, with a pressure pin. It is particularly advantageous if the pressure pin is embodied on the side of the pressure bridge that opposes the pressure pieces and rests against a catch arm which is mounted so as to be tiltable on one side. As a result of the interaction of a pressure bridge, which is provided with the pressure pieces preferably on or close to its corners, and a catch arm which is mounted so as to be tiltable on one side, the necessary path for releasing the interlocking means can be adjusted in such a way that the catch arm frees the interlocking of the swivel arm only when the pressure bridge is displaced from its starting position as a result of simultaneous loading of all of the pressure pieces. Expediently, the catch arm is pre- tensioned by a restoring means, in particular a compression spring, into a catch position in which a locking projection on the catch arm engages with a locking groove on the swivel arm or on a locking disc fastened in a rotationally fixed manner to the swivel arm.

[10] As the entire sequence of movement of the movement mechanism is controlled or guided via two swivellable swivel arms, the locking disc can, according to a further advantageous configuration, be provided with two locking grooves, a first locking groove arresting the swivel arm in the closing position and a second locking groove arresting the swivel arm in the opening position of the covering shells, as a result of which the closing position or opening position of the access blocking means is arrested accordingly. In the case of this solution, one and the same mechanism, namely the locking grooves in the locking disc, can accordingly be used to cause both the interlocking of the closing position and arresting in the opening position. The arresting of the covering shells in the opening position makes it easier for staff to climb up and down.

[11] In order to fulfil even higher safety requirements with a safety ladder having an access blocking means, the catch arm can be connected to a triggering pin with which a remote actuating device is associated to release the interlocking means manually or using the runner. Manual releasing or releasing using the runner can be required both when climbing up and when climbing down. If an interlocking mechanism is present for the opening position and it is also desirable to prevent, when one person is present on the safety ladder, a second person from climbing the safety ladder in an unauthorized manner without protective equipment, the catch arm can be moved via the remote actuating mechanism and the triggering pin in order to release the locking connection to the locking disc and to free the covering metal sheets in the opening position, so that the covering metal sheets can resume the closing position. During climbing-down, the same mechanism can in turn be used to release the closing position and to displace the covering metal sheets back into the opening position.

[12] The remote actuating device can comprise a Bowden wire. In the case of the

preferred configuration, a pull rod laid parallel to the rail is provided in order to move, by moving the pull rod, the catch arm into a position in which at any given moment no locking engagement of the catch arm with the locking groove on the locking disc takes place so as subsequently to allow the covering shells, assisted by the movement mechanism, to be moved into the closing position or back into the opening position. The remote actuating device can for this purpose have in particular a contour metal sheet which can be moved parallel to the rail, wherein the contour metal sheet can for example be provided with a curved track or sliding track with which the triggering pin, which is connected to the catch arm so as to be fixed in terms of movement, interacts in a form- fitting manner on movement of the contour metal sheet in order to move the catch arm in accordance with the course of the curved track.

[13] As the interlocking mechanism is relatively compact and can be associated with one of the swivel arms, it is particularly advantageous if the interlocking mechanism is fastened to a base plate which can be fixedly screwed to the windows and which both has the swivel bearing for the lower swivel arm and supports the tilting bearing for the catch arm and also forms the guide for the pressure bridge. The entire interlocking mechanism can then be mounted as a preassembled unit on a ladder, if appropriate on site.

[14] Even greater protection from unauthorized use can be attained if the rail has a notch for inserting the runner, the covering shells extending in the closing position to below the notch and a closing metal sheet being mounted on one of the covering shells, which closing metal sheet is displaceable transversely to the ladder or is hingeably mounted and can be arrested against movement using a lock. Accordingly, provided that no authorized maintenance staff wish to use the safety ladder, the notch can be concealed so that it is then impossible to latch a runner into the rail.

[15] The invention relates not only to a safety ladder having a built-on access blocking means but rather also to the access blocking means itself and protection is claimed for the access blocking means in its own right.

[16] Further advantages and configurations of a safety ladder according to the invention or an access blocking means for a corresponding safety ladder will emerge from the subsequent description of a preferred exemplary embodiment shown in the drawings, in which:

[17] Fig. 1 is a perspective view of a safety ladder according to the invention with an access blocking means in the closing position;

[18] Fig. 2 shows the safety ladder from Fig. 1 with the access blocking means opened;

[19] Fig. 3 is a perspective detailed view of the ladder in the region of the notch with the fall protection runner inserted;

[20] Fig. 4 is a perspective view of the interlocking and triggering mechanism associated

with the lower swivel arm when assembled on the ladder in the closing position of the access blocking means;

[21] Fig. 5 shows the mechanism from Fig. 4 in the opening position of the access blocking means and interlocking means;

[22] Fig. 6 is a horizontal section through the safety ladder in the view according to Fig. 4 without a runner;

[23] Fig. 7 is a horizontal section through the safety ladder in the view according to Fig. 5 without a runner;

[24] Fig. 8 shows an exemplary embodiment for a remote actuating mechanism with the swivel arm interlocked in the opening position;

[25] Fig. 9 shows the remote actuating mechanism from Fig. 8 in the release position for the locking device; and

[26] Fig. 10 shows an alternative exemplary embodiment for a closure device for the notch on the safety ladder.

[27] In the figures, reference numeral 10 denotes as a whole a safety ladder according to the invention consisting in a manner known per se of a central ladder beam 1, which extends over the entire height of a structure (not shown) such as a tower, a facade or the like and is composed usually of a plurality of elements, and also a large number of ladder rungs 2 which are arranged with uniform spacing one above another, run transversely to the ladder beam 1 and are fastened to the back thereof. In the case of a safety ladder 10, either the ladder beam 1 is provided with a C-shaped rail for receiving a runner for a fall protection device or, as illustrated in the exemplary embodiment shown, the ladder beam 1 consists directly of a corresponding rail 3 having an approximately C-shaped, slotted hollow profile, the vertically running slot 4 of which is embodied on the front of the rail 3 lying remote from the ladder rungs 2. The basic construction of this rail 3 may be seen particularly clearly from Fig. 3 which shows not only the rail 3 with two ladder rungs 2 arranged one above the other, but rather also a runner 50 with a carabiner hook for connection of a harness (not shown) which is inserted into the guide 8, which is accessible via the slot 4, inside the rail 3. In order to insert the runner 50 into the guide 8 of the rail 3, there is formed close to the lower end of a ladder 10 what is known as a notch 5, the width and height dimensions of which are adapted in such a way that the runner 50 can be inserted into the rail 3 only there, and is restrictedly guided at all other points with play within the rail 3. Fig. 3 also clearly shows that the back 6 of the rail 3 is provided with windows 7 which lie one above another at regular spacing and serve to allow a latch (not shown), which is embodied on the runner 50, or another locking member to be secured in a form-fitting manner within the windows 7 should a person climbing up the ladder using the harness and runner 50 slip down in order automatically to be intercepted by the runner 50

which is secured in the rail. As the interplay of a rail 3 forming a catching protection device with a runner 50 is known to a person skilled in the art in a broad range of configurations and the invention can in principle be used with all types of runners and rails, this will be described no further here.

[28] Figures 1 and 2 show the safety ladder 10 in the region of its lower end in which there is arranged an access blocking means which is denoted in its entirety by reference numeral 20 and which is intended to prevent unauthorized use of the safety ladder 10. Fig. 1 shows the closing position of the access blocking means 20 according to the invention and Fig. 2 shows the opening position of the access blocking means 20. Figures 1 and 2 clearly show that the access blocking means 20 has as basic constructional elements for preventing unauthorized climbing of the safety ladder 10 two covering shells 21A, 21B which are in this case bent in a U-shaped manner, wherein both covering shells 21A, 21B have the same height and extend in the exemplary embodiment shown over the spacing of eight ladder rungs 2 arranged one above another. Both covering shells 21A, 21B extend in the closing position according to Fig. 1 with their leg metal sheets up to the central rail 3, so that in the closing position of the access blocking means substantially exclusively the slot of the rail 3 is accessible without it being possible for persons in any way to reach the ladder rungs, since the covering shells 2 IA, 2 IB extend, owing to their profile shape, laterally to and after the region of the ladder rungs 2 that projects toward the respective side. The U-shaped covering shells 2 IA, 2 IB shown, which receive the ladder rungs in the closing position in the free space 22 between the leg metal sheets, therefore form an insurmountable access blocking means even when the safety ladder 10 is mounted at a greater distance from a building wall or the like. Nevertheless, depending on the arrangement of the safety ladder 10, it may also be sufficient to have the covering shells consist only of flat or angled metal sheets or the like.

[29] The opening position shown in Fig. 2 of the access blocking means 20 clearly reveals that the two covering shells 21A, 21B are outwardly displaced in opposite directions, in order to free the safety ladder 10 over the entire height, by means of a movement mechanism, comprising two swivel arms 23, 24, parallel to the extension of the ladder rungs 2. The swivel arms 23, 24 are fastened to the back of the rail 3 at a spacing of approximately four ladder rungs 2 relative to each other in each case by a swivel bearing and each swivel arm is fastened at one arm end (23A, Fig. 5) to one covering shell 21A and at the other arm end (23B, Fig. 5) to the other covering shell 21B. In the closing position of the access blocking means 20 in Fig. 1, the fastening axes 25 A, 25B, which are indicated merely by black dots, for the upper swivel arm and 26 A, 26B for the lower swivel arm 23 indicate that the swivel arms 23, 24 stand in the closing position at an angle of approximately 10° obliquely to the longitudinal axis of the rail 3,

whereas they stand in the opening position according to Fig. 2 in principle perpendicularly to the longitudinal axis or parallel to the ladder rungs 2. Coupling of the two swivel arms 23, 24 to the rigid covering shells 2 IA, 2 IB forms a steering gear which ensures the simultaneous and parallel movement of the two covering shells 2 IA, 2 IB between the closing position and the opening position. Starting from the closing position, in this case the covering shell 2 IB, shown on the left in Figures 1 and 2, is moved downward and accordingly the right covering shell 21 A is moved upward until the swivel arms 23, 24 stand substantially perpendicularly.

[30] The access blocking means 20 comprises interlocking means which allow swivelling of the swivel arms 23, 24 only when the runner 50 is inserted into the guide profile of the rail 3 or when a remote actuating mechanism 60, which is arranged with sufficient spacing above the covering shells 2 IA, 2 IB, is actuated. The left covering shell 2 IB is provided at its upper end, in order to move the access blocking means 20 into the opening position when climbing down the safety ladder 10, with a tread arm 61 which a person climbing down can tread on with his left foot after actuating the remote actuating mechanism 60 in order as a result to move the covering shell 2 IB downward and, owing to the coupling to the swivel arms 23, 24, the covering shell 21 A upward. The opening during climbing-up takes place via actuation of the handles on the two covering shells 2 IA, 2 IB. The return movement into the closing position can take place automatically by way of springs (not shown), which are pre-tensioned into the closing position, or a greater weight of the covering metal sheet 2 IB which is to be moved upward.

[31] Figures 4 to 7, to which reference will now additionally be made, each show the lower swivel arm 23, consisting in this case of a swivel bracket curved in an arcuate manner, including the interlocking means, denoted in its entirety by reference numeral 30, on the one hand in the closing position (Figures 4 and 6) of the access blocking means and on the other hand in the opening position thereof (Figures 5 and 7). The interlocking device 30 is provided with a base plate 31 which is fastened to two windows 7 on the back 6 of the rail 3 by means of two screws 32. A bearing receptacle 33, in which a swivel bearing 34 (which is not illustrated in detail) for the lower swivel arm 23 is received and supported, is, as Figures 6 and 7 show in particular, formed in the base plate 31. A locking disc 35 is connected in a rotationally fixed manner, for example welded on or screwed on, to the swivel arm 23 which is mounted so as to be able to rotate relative to the base plate 31 by means of the swivel bearing 34, which locking disc is accordingly moved in conjunction with the movement of the swivel bracket 23. In the exemplary embodiment shown, the locking disc 35 consists of a round plate which has at its centre a piercing for the swivel bearing 34 and is fastened to a corresponding bulging 27 of the swivel arm 23. The locking disc 35 has, as

Figures 4 and 5 reveal in particular, two locking grooves 36, 37 which are arranged angularly offset relative to each other by a little less than 90° and with which a locking projection 38 on a catch arm 39 binds in a form-fitting manner when the swivel arm 23 is in the end location of the closing position or end location of the opening position. The catch arm 39 is in this case pre-tensioned in the direction toward the locking disc 35 by means of a compression spring 40 which is shown in Fig. 6 and 7 and is supported on a carrying arm 41, which is connected to the base plate 31, so as to be able to move in an articulated manner within limits. The catch arm 39 is in turn mounted at its lower end so as to be able to tilt on one side via a tilting hinge 42 or the like, the tilting hinge 42 being embodied at the lower end and the locking projection 38 at the upper end of the catch arm 39. Fig. 4 and 6 show the interlocking means 30 with the swivel arm 23 in the closing position, shortly before the runner 50, which is guided in the guide 8 of the rail 3, reaches a position in which a triggering mechanism 45 is actuated, whereas Fig. 5 and 7 show the runner in the position in which the triggering mechanism 45 is just being actuated.

[32] The construction and the mode of operation of the triggering mechanism 45 will now be described with reference to Figures 6 and 7. Fig. 6 shows the starting position in which the catch projection 38 on the catch arm 39 dips into the locking groove 36 on the locking disc 35 and thus prevents swivelling of the swivel arm 23. Two of a total of in fact four pressure pieces 46 provided of a triggering mechanism may be seen within the guide 8 in the rail 3, wherein the pressure pieces 46 of the window recesses shown penetrate within the back 6 of the rail 3, which are arranged on both sides next to, if appropriate also vertically offset relative to, the windows 7. The position of the pressure pieces 46 is selected in such a way that a runner 50 presses with its sliding or guide elements, such as for example rollers or slide blocks, against the pressure pieces 46 only when the runner is exactly in a position immediately after the interlocking means 30. All four pressure pieces 46 are joined together via a pressure bridge 47, formed at the centre of which is a pressure pin 48 which projects, on the side of the pressure bridge 47 opposing the pressure pieces 46, by a preferably adjustable degree. The tip of the pressure pin 48 rests in this case permanently against the back of the catch arm 39, so that the pressure bridge 47, and thus also the pressure pieces 46, are pre-tensioned by the spring 40 permanently into the position shown in Fig. 6 and can be displaced toward the right only by overcoming the compressive force of the spring 40. The positioning of the pressure pieces 46 is selected in such a way that the pressure bridge 47 can normally be displaced only using a runner 50 which is inserted into the guide 8 of the rail 3, and Fig. 7 shows this state, the runner being omitted. Compared to the starting position in Fig. 6, the pressure pieces 46 are each displaced toward the right and the catch arm 39 is tilted toward the right by the pressure bridge 47 and the

contact with the pressure pin. In this case, the required degree for displacing the catch arm 39 into a release position for the locking disc 35 is selected in such a way that only when in fact both the lower and the upper pressure pieces 46 are displaced is the tilting path of the catch arm 39 sufficient for the locking projection 38 to free the locking groove 37 (or 36). Only when the locking groove 36 or 37 is freed can the swivel arm 23 be swivelled and the covering shells can be swivelled, by actuating the handles or the foot tread or induced by spring force or gravity, from one position into the other. If a person continues to climb up the safety ladder, he displaces the runner 50 further upward and the spring 40 presses the catch arm 39 back into the blocking position, wherein, depending on the position of the swivel arm 23, either the opening position is arrested on engagement of the locking projection 38 with the locking groove 37 or the closing position is arrested on engagement of the locking projection 38 with the locking groove 36. [33] In the case of a safety ladder with a reduced-safety access blocking means, the above-described interlocking means 30 can be sufficient to prevent unauthorized use of the safety ladder in any case when there is no person with a catching protection device on the safety ladder. Increased safety requirements may demand that the access blocking means 20 assume its closing position whenever a person does not specifically wish to climb, using an inserted runner, through the access blocking means 20 from bottom to top or from top to bottom. A remote actuating mechanism 60, the construction and mode of operation of which will now be described with reference to Figures 4, 5 and also 8 and 9, is provided for the increased safety requirements. A triggering means 62, which is automatically actuated on climbing-up and climbing- down with the runner 50, as Fig. 9 illustrates for climbing-up, is mounted, at a certain distance above the covering metal sheets, for actuating the remote actuating mechanism 60. Figures 8 and 9 show the position and function of the remote actuating mechanism 60 when the lower swivel bracket 23 is in the opening position and holds, together with the swivel arm 24, the covering metal sheets pushed apart from one another at the greatest possible distance. A triggering pin 43, which penetrates a transversely running slot 44 in a side metal sheet of the support arm 41 and can jointly perform the tilting movement of the catch arm 39, is, as may clearly be seen from Figures 4 and 5, connected to the catch arm 39. A contour metal sheet 64, which is connected to the triggering means 62 via a pull rod 65, is arranged directly adjacent to the triggering pin 43. In the exemplary embodiment shown, the contour metal sheet 64 has on the right outer edge a curved track 66 with which the triggering pin 43, and thus also the catch arm 39 which is connected to said triggering pin so as to be fixed in terms of movement, can be displaced by displacing the contour metal sheet 64 in the vertical direction. Provided that the contour metal sheet 64 is in the starting position

shown in Figures 4 and 8, the remote actuating mechanism 60 is inactive. In the position shown in Fig. 9, on the other hand, in which the runner 50 actuates the triggering means 62 on climbing-up, the contour metal sheet 64, which is rigidly connected to the triggering means 62 via the pull rod 65, is displaced upward, as a result of which the triggering pin 43 and thus the catch arm 39 are swivelled toward the right and the locking disc 35 frees the swivel arm 23 for swivelling-back of both swivel arms 23, 24 and thus of the covering metal sheets. It is now possible to cause, if appropriate via additional weights or springs which are tensioned during the opening movement, both covering metal sheets automatically to move back, guided by the movement mechanism (steering gear), into the closing position. At the same time, as a person continues to climb, the contour metal sheet 64 will migrate downward back into the starting position, thus allowing the catch arm 39 to arrest the closing position, as shown in Figures 4 and 6.

[34] In the case of the exemplary embodiment shown, exclusively as a result of interaction with the runner 50 as a person climbs up, the access blocking means is not only first opened but rather, after climbing through the access blocking means, automatically closed again. A tilt arm 67, which is arranged on the triggering means 62, automatically draws with an upper entrainment pin, as a result of the upward movement of the runner, the pull rod 65 upward. If the person climbs downward with the catching device introduced, the pull rod 65 can be drawn upward, again via the tilt arm 67 on the triggering means 62, in that the centrally mounted tilt arm 67 is pressed downward and displaces the pull rod 64 with a second entrainment pin 68. This leads in turn to a movement of the contour metal sheet 64, triggering pin 43 and catch arm 34, as a result of which the interlocking means 30 are released again using the remote actuating device 60 in order to free the lower swivel arm 23 for opening of the access blocking means 20. If the person then steps onto the tread arm 61 on the left covering metal sheet 2 IB, the access blocking means 20 is opened and interlocked again in the opening position. If the person climbs down through the access blocking means 20 using the runner and passes the pressure pieces 46 of the interlocking means 30, the swivel arms are freed again so that the covering metal sheets are swivelled back into the starting position and secured there against opening.

[35] In the case of the covering metal sheets shown in Figures 1 and 2, the notch in the rail 3 can be covered by a flap 70 with which no lock is associated. Nevertheless, an eyelet or the like could be arranged on the flap 70 in order to secure the closing position of the flap 70 on the covering metal sheet 2 IB using a lock. Alternatively, a sliding flap 170 could, as shown in Fig. 10, be guided on one of the covering shells, for example on the covering shell 121A, in sliding guides 171, which sliding flap, in the closing position, covers the notch 5 on the rail 3 and is secured in the closing position

on the other covering shell 12 IB using a padlock 172 or another suitable lock. When the notch 5 is covered, the runner, which is crucial for actuating the access blocking means 20, cannot be inserted into the guide of the rail of the catching protection device.

[36] A person skilled in the art will infer from the foregoing description numerous modifications which are to fall within the scope of protection of the appended claims. Instead of U-shaped covering shells, the covering shells used could also be angled metal sheets or if appropriate even flat metal sheets having a width of less than half the width of the ladder, if for example the safety ladder has side beams which prevent the rungs from being accessible from the side. The triggering mechanism could also be operated using a Bowden wire. The blocking of a swivel arm could also take place differently. One or both swivel arms could be pre-tensioned using tensioning springs, so that they are at all times swivelled into the closing position if a force for opening the covering metal sheets or covering shells is not applied counter to the action of these springs or the instantaneous swivelling position of the lower swivel arm is blocked. Instead of a locking disc with locking grooves, other locking means or blocking means could also be used.