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Title:
SAFETY EXTENSION DEVICE FOR A LADDER
Document Type and Number:
WIPO Patent Application WO/2014/078950
Kind Code:
A1
Abstract:
A safety extension device for a ladder is provided. The safety extension device comprises a frame having a lower section for engaging the ladder and an upper section located above the lower section. The safety extension also comprises a clamping assembly mounted to the lower section of the frame, the clamping assembly having a lower and an upper ladder engaging support separated along the frame by a clamping distance. At least one of the ladder engaging supports is movable along the frame. The safety extension further comprises an actuation mechanism mounted to the upper section of the frame and connected to the movable support by a connecting member. The actuation mechanism is operable to move the movable support along the frame and thereby vary the clamping distance.

Inventors:
PARKER MICHAEL (CA)
Application Number:
PCT/CA2013/050206
Publication Date:
May 30, 2014
Filing Date:
March 15, 2013
Export Citation:
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Assignee:
9105 0732 QUEBEC INC (CA)
International Classes:
E06C1/12; E06C7/02
Foreign References:
GB191200897A1912-03-21
JP2000273886A2000-10-03
GB2214220A1989-08-31
CA2638357A12010-02-19
GB684420A1952-12-17
CA2748480A12013-01-25
Attorney, Agent or Firm:
ROBIC, LLP (Square-Victoria Bloc E - 8th floorMontréal, Québec H2Z 2B7, CA)
Download PDF:
Claims:
CLAIMS

1 . A safety extension device for a ladder, the safety extension device comprising:

a frame having a lower section and an upper section located above the lower section;

a clamping assembly mounted to the lower section of the frame, the clamping assembly having a lower ladder engaging support and an upper ladder engaging support separated along the frame by a clamping distance, at least one of the lower and upper ladder engaging supports being a movable support movable along the frame; and

an actuation mechanism mounted to the upper section of the frame and connected to the movable support by a connecting member, the actuation mechanism being operable to move the movable support along the frame and thereby vary the clamping distance.

2. The safety extension device according to claim 1 , wherein the frame comprises a pair of parallel vertical sidepieces connected by a plurality of horizontal crosspieces.

3. The safety extension device according to claim 1 or 2, wherein the upper ladder engaging support of the clamping assembly is fixedly mounted to the frame and the lower ladder engaging support of the clamping assembly is the movable support.

4. The safety extension device according to claim 2, wherein the movable support is provided with a pair of lower connecting rods projecting transverally from respective extremities of the movable support, each lower connecting rod being telescopically engageable with a corresponding one of the vertical sidepieces.

5. The safety extension device according to claim 2, wherein the actuation mechanism comprises an upper crosspiece vertically movable with respect to the vertical sidepieces.

6. The safety extension device according to claim 5, wherein the upper crosspiece is provided with a pair of upper connecting rods projecting transverally from respective extremities of the upper crosspiece, each upper connecting rod being telescopically engageable with a corresponding one of the vertical sidepieces.

7. The safety extension device according to claim 5 or 6, wherein the connecting member comprises a pair of cables, each cable having opposite ends respectively connected to the upper crosspiece and to the movable support.

8. The safety extension device according to any one of claims 5 to 7, wherein the actuation mechanism further comprises an abutment crosspiece separated from the upper crosspiece along the frame by an actuation distance and connected to the upper crosspiece by a displacement mechanism operable to vary the actuation distance.

9. The safety extension device according to claim 8, wherein the displacement mechanism of the actuation mechanism comprises a displacement shaft connecting the upper crosspiece and the abutment crosspiece and a displacement handle operatively connected to the displacement shaft to vary the actuation distance between the upper crosspiece and the abutment crosspiece.

10. The safety extension device of claim 9 wherein the displacement shaft has a threaded portion and the displacement handle has an opening therethrough provided with complementary inner threads, the handle being rotatable along the threaded portion of the displacement shaft and engageable with one of the upper crosspiece and the abutment crosspiece to vary the actuation distance.

1 1 . The safety extension device of claim 9 or 10, wherein the actuation mechanism further comprises a locking member configurable in a locked configuration where rotation of the displacement handle is prevented.

12. The safety extension device of claim 1 1 , wherein the locking member is a locking handle displaceable along the displacement shaft and engageable with the displacement handle.

13. The safety extension device of any one of claims 1 to 12, wherein the upper ladder engaging support has a set of hooks horizontally aligned and facing downward and the lower ladder engaging support has a set of hooks horizontally aligned and facing upward.

14. A method of operating a safety extension device for a ladder, the method comprising the steps of :

adjusting a clamping distance between an upper ladder engaging support and a lower ladder engaging support located on a lower section of a frame of the safety extension device such that the clamping distance is greater than a distance between a first rung and a second rung of the ladder;

engaging the upper ladder engaging support of the safety extension device with the first rung;

positioning the safety extension device such that the lower ladder engaging support is vertically aligned with the second rung; operating an actuation mechanism located on an upper section of the frame of the safety extension device to decrease the clamping distance until the lower ladder engaging support engages the second rung.

15. The method of claim 14 wherein, the method further comprises the step of locking the actuation mechanism in a locking configuration for preventing accidental disengagement of the safety extension device from the ladder.

Description:
SAFETY EXTENSION DEVICE FOR A LADDER

FIELD OF THE INVENTION

[0001] The present invention relates to the field of safety devices. More particularly, it relates to a safety extension device attachable to a ladder and a method of operation thereof.

BACKGROUND

[0002] In the field of vertical passageways such as manholes, ground or floor openings, access walls or other similar structures, it is common to provide a fixed ladder accessible from above the passageway. Oftentimes, the ladder is wholly confined within a manhole or a passageway and therefore does not impede with the cover when closing the entrance. However, since such confined ladders do not extend above the upper edge of the hole, they normally present a security threat for the users entering or exiting the manhole, as a result of the lack of proper support outside of the manhole that can cause a user to fall or slip in the initial and final stages of interaction with the ladder, at the upper extremity thereof. Similar problems can also occur with other types of ladders mounted to a wall and where the ladder does not extend substantially over the upper edge of the structure.

[0003] To address this issue, it is known to use an extension device attachable to the ladder or to a wall of the manhole and capable of extension when being used and of retraction to a position below the entrance level when not in use. For example, such a device is described in United-States Patents nos. 4,546,855 and 4,729,453, where an extendable extension rod is provided.

[0004] Known extension devices are usually mounted to the rungs of the ladder using methods or assembly, such as nuts and bolts, that require a user to be in the vicinity of the rungs of the ladder in order to secure the extension device thereon. Therefore, the initial securement of the extension device to the ladder usually constrains the user to enter the manhole without the use of the extension device, at least once, or to lean inside the manhole from the street level, which can lead to accidents. Moreover, attachment of known extension devices to the ladder of a manhole tends to be tedious and time consuming. Consequently, known extensions cannot easily be mounted and removed from a ladder to allow a single device to be used in association with a plurality of manhole ladders simultaneously.

[0005] In view of the above, there is a need for an improved extension device and method of operation thereof which would be able to overcome or at least minimize some of the above-discussed prior art concerns.

SUMMARY OF THE INVENTION

[0006] According to a first general aspect, there is provided a safety extension device for a ladder. The safety extension device comprises a frame having a lower section and an upper section located above the lower section and a clamping assembly mounted to the lower section of the frame. The clamping assembly has a lower ladder engaging support and an upper ladder engaging support separated along the frame by a clamping distance. At least one of the lower and upper ladder engaging supports is a movable support movable along the frame. The safety extension device further comprises an actuation mechanism mounted to the upper section of the frame and connected to the movable support by a connecting member. The actuation mechanism is operable to move the movable support along the frame and thereby vary the clamping distance.

[0007] In an embodiment, the frame comprises a pair of parallel vertical sidepieces connected by a plurality of horizontal crosspieces.

[0008] In an embodiment, the upper ladder engaging support of the clamping assembly is fixedly mounted to the frame and the lower ladder engaging support of the clamping assembly is the movable support. [0009] In an embodiment, the movable support is provided with a pair of lower connecting rods projecting transverally from respective extremities of said movable support. Each lower connecting rod is telescopically engageable with a corresponding one of the vertical sidepieces.

[00010] In an embodiment, the actuation mechanism comprises an upper crosspiece vertically movable with respect to the vertical sidepieces.

[00011] In an embodiment, the upper crosspiece is provided with a pair of upper connecting rods projecting transverally from respective extremities of said upper crosspiece, each connecting rod being telescopically engageable with a corresponding one of the vertical sidepieces.

[00012] In an embodiment the connecting member comprises a pair of cables. Each cable has opposite ends respectively connected to the upper crosspiece and to the movable support.

[00013] In an embodiment, the actuation mechanism further comprises an abutment crosspiece separated from the upper crosspiece along the frame by an actuation distance and connected to said upper crosspiece by a displacement mechanism operable to vary the actuation distance.

[00014] In an embodiment, the displacement mechanism of the actuation mechanism comprises a displacement shaft connecting the upper crosspiece and the abutment crosspiece and a displacement handle operatively connected to the displacement shaft to vary the actuation distance between the upper crosspiece and the abutment crosspiece.

[00015] In an embodiment, the displacement shaft has a threaded portion and the displacement handle has an opening therethrough provided with complementary inner threads. The handle is rotatable along the threaded portion of the displacement shaft and engageable with one of the upper crosspiece and the abutment crosspiece to vary the actuation distance. [00016] In an embodiment, the actuation mechanism further comprises a locking member configurable in a locked configuration where rotation of the displacement handle is prevented.

[00017] In an embodiment, the locking member is a locking handle displaceable along the displacement shaft and engageable with the displacement handle.

[00018] In an embodiment, the upper ladder engaging support has a set of hooks horizontally aligned and facing downward and the lower ladder engaging support has a set of hooks horizontally aligned and facing upward.

[00019] According to another general aspect, there is provided a method of operating a safety extension device for a ladder. The method comprises the step of adjusting a clamping distance between an upper ladder engaging support and a lower ladder engaging support located on a lower section of a frame of the safety extension device such that the clamping distance is greater than a distance between a first rung and a second rung of the ladder, The method further comprises the steps of engaging the upper ladder engaging support of the safety extension device with the first rung and positioning the safety extension device such that the lower ladder engaging support is vertically aligned with the second rung. Finally, the method comprises the step of operating an actuation mechanism located on an upper section of the frame of the safety extension device to decrease the clamping distance until the lower ladder engaging support engages the second rung.

[00020] In an embodiment, the method further comprises the step of locking the actuation mechanism in a locking configuration for preventing accidental disengagement of the safety extension device from the ladder.

BRIEF DESCRIPTION OF THE DRAWINGS

[00021] Other objects, advantages and features will become more apparent upon reading the following non-restrictive description of embodiments thereof, given for the purpose of exemplification only, with reference to the accompanying drawings in which:

[00022] Figure 1A shows a perspective view of a safety extension device, according to an embodiment, the safety engagement being shown engaged to a fixed ladder and to an embedded ladder.

[00023] Figure 1 B shows a side elevation view of the safety extension device of Figure 1 A engaged to a fixed ladder.

[00024] Figure 2 is a perspective view of the safety extension device shown in Figure 1A.

[00025] Figure 2A is a close up view of the displacement handle and the locking handle of the actuation mechanism of the safety extension device of Figure 2.

[00026] Figure 3 is a side elevation view of the safety extension device of Figure 2.

[00027] Figure 4 is a cross-sectional view taken along line 4-4 of Figure 3. DETAILED DESCRIPTION

[00028] In the following description, the same numerical references refer to similar elements. The embodiments, geometrical configurations, materials mentioned and/or dimensions shown in the figures or described in the present description are preferred embodiments only, given solely for exemplification purposes.

[00029] Moreover, although the embodiments of the safety extension device and corresponding parts thereof consist of certain geometrical configurations as explained and illustrated herein, not all of these components and geometries are essential to the invention and thus should not be taken in their restrictive sense. It is to be understood, as also apparent to a person skilled in the art, that other suitable components and cooperation thereinbetween, as well as other suitable geometrical configurations, may be used for the safety extension device, as will be briefly explained herein and as can be easily inferred herefrom by a person skilled in the art. Moreover, it will be appreciated that positional descriptions such as "above", "below", "upper", "lower", "top", "bottom", "left", "right" and the like should, unless otherwise indicated, be taken in the context of the figures and should not be considered limiting.

[00030] Generally speaking, embodiments of the present invention provide a safety extension device for a ladder. As explained above, such devices may be particularly useful for ladder provided in passageways such as manholes, ground or floor openings, access walls or other similar structures.

[00031] Referring generally to Figures 1A and 1 B, in accordance with an embodiment, there is shown a safety extension device 10 for a ladder 50 according to one embodiment. The illustrated safety extension device is mounted to a wall 52 or a similar structure. The safety extension device 10 is engageable with the ladder 50 such that, when secured thereon, the safety extension device 10 extends beyond the upper edge 54 of the wall 52, and provides a sturdy support that can thereby be used to securely access the ladder 50 from the upper edge 54 of the wall 52 or any entry surface. One skilled in the art will understand that the ladder 50 could be affixed to outside surfaces of, or be located within, different type of constructions where the ladder 50 does not extend significantly beyond the upper edge 54 of a wall 52. For example and without being limitative, in an embodiment the ladder 50 can be a ladder confined within a manhole.

[00032] As can be seen in Figure 1A, the ladder 50 can be a traditional fixed ladder where substantially vertical sidepieces are joined by substantially horizontal rungs 51 spaced apart from one another (as illustrated on the left side of Figure 1A) or an embedded or rung only ladder (as illustrated on the right side of Figure 1A) where each rung 51 of the ladder 50 is an independent bar embedded into or otherwise affixed to the wall 52. [00033] Now referring to Figure 2, the safety extension device 10 according to the illustrated embodiment is formed of a frame 12 provided with a clamping assembly 20 at a lower section 14 and an actuation mechanism 30 at an upper section 16 thereof. In the illustrated embodiment, the lower section 14 extends over a length of the frame 12 at the bottom extremity thereof, while the upper section 16 is located above the lower section 14, over a length of the frame 12 positioned at the top extremity thereof. One skilled in the art will however understand that, in alternative embodiments, the lower section 14 and the upper section 16 can be sufficiently spaced apart from one another, without being necessarily positioned at the bottom extremity and the top extremity respectively. In other words at least one of the lower section 14 and the upper section 16 could be positioned at a distance from the bottom extremity and the top extremity respectively, as long as their positioning allows a user to operate the actuation mechanism 30 while remaining above the ladder 50 with which the safety extension device 10 is being engaged.

[00034] In the illustrated embodiment, the frame 12 presents a ladder like configuration with a pair of parallel vertical sidepieces 17 connected by a plurality of horizontal crosspieces 18. Such a configuration provides a secure support that a user can easily grasp and climb when accessing or withdrawing from a ladder located in a hard to reach space, such as a manhole.

[00035] In an embodiment, the crosspieces 18 located in the lower section 14 of the frame 12 are configured to allow the user to easily climb the safety extension device 10 and access the ladder 50 to which the safety extension device 10 is secured, while additional crosspieces 18 located above the lower section 14 are easily graspable by a user and thereby contribute to minimize the existing security issues. As can be seen in the illustrated embodiment, the crosspieces 18 located in the lower section 14 of the safety extension device 10 can be provided with an anti-slip or antiskid surface in order to offer better traction and reduce the risks of slippage. One skilled in the art will however understand that the antiskid surface is not mandatory and that, in an alternative embodiment, lower crosspieces 18 without anti-slip or antiskid protection can be provided.

[00036]As can be seen in Figure 2, in the illustrated embodiment, the clamping assembly 20 is positioned in the lower section 14 of the frame 12 and is composed of a fixed upper ladder engaging support 21 and a movable lower ladder engaging support 22. The mobility of the lower ladder engaging support 22 along the frame 12 allows a clamping distance 23 separating the upper ladder engaging support 21 from the lower ladder engaging support 22 to be varied. Such a variation in the clamping distance 23 enables the engagement/disengagement of the safety extension device 10 with the ladder 50, as will become apparent from the description below. One skilled in the art will understand that even though the illustrated embodiment presents a configuration where the upper ladder engaging support 21 is fixedly mounted to the frame and the lower ladder engaging support 22 is movable, in alternative embodiments, either one or both of the ladder engaging supports could be movable along the frame, to allow the clamping distance to be varied.

[00037] In the embodiment illustrated in Figures 2 and 3, the upper ladder engaging support 21 and the lower ladder engaging support 22 are each formed of a set of horizontally aligned hooks 24. The hooks 24 forming the upper ladder engaging support 21 are oriented downward to form a downward open groove 25 for receiving a first rung therein. The hooks 24 forming the lower ladder engaging support 22 present an inverted configuration and are oriented upward to form an upward open groove 26 for receiving a second rung therein. It should be understood that the term "horizontally aligned" is used herein to indicate that the hooks 24 substantially follow a common horizontal line. However the term "horizontally aligned" should not be interpreted in a restrictive sense and one skilled in the art would understand that the alignment of the hooks 24 could vary from a perfectly straight line and from a perfectly horizontal orientation. [00038] In an embodiment, each one of the hooks 24 may present a tapered configuration towards the extremity in order to facilitate the guiding of a corresponding rung within one of the grooves 25 or 26. Similarly, the hooks 24 may form a progressive opening, which offer a versatility regarding the rungs receivable therein. Moreover, the upper extremity 27 of the downward open groove 25 and the lower extremity 28 of the upward open groove 26 may present a rounded configuration in order to match the shape of a corresponding rung. Such a complementary configuration of the upper extremity 27 and the lower extremity 28 of the grooves 25, 26 with the corresponding rungs allows a better engagement of the safety extension device 10 with the corresponding ladder 50. One skilled in the art, will however understand that in alternative embodiments, the hooks may not present a tapered configuration towards the extremity and the configuration of the upper extremity 27 and the lower extremity 28 of the grooves 25, 26 may differ from a rounded configuration.

[00039] In an embodiment, the set of horizontally aligned hooks 24 forming the upper ladder engaging support 21 and the lower ladder engaging support 22 each involve two horizontally aligned hooks 24. One skilled in the art will however understand that, in alternative embodiments, a single wide hook or more than two hooks may be provided, as long as each one of the upper ladder engaging support 21 and the lower ladder engaging support 22 can offer an adequate stability when engaging a rung.

[00040] It should also be understood that, in alternative embodiments, the configuration of the horizontally aligned hooks 24 forming the upper ladder engaging support 21 and the lower ladder engaging support 22 could be adapted to the distance between the wall 52 and the ladder 50 affixed thereon. Therefore, the hooks 24 forming the upper ladder engaging support 21 and the lower ladder engaging support 22 could extend of a variable distance from the corresponding sidepieces 17 such that the safety extension device 10 can be mounted to ladders 50 that are located closer or further away from the wall 52. In an embodiment, the elements forming the upper ladder engaging support 21 and the lower ladder engaging support 22 could also be adjustable or interchangeable such that a single safety extension device 10 could be adaptable to be used in combination with different configurations of ladders 50 and corresponding walls 52.

[00041]As can be seen in the illustrated embodiment of Figures 2, 3, 4 and 4A, the lower ladder engaging support 22 can be telescopically connected to the frame 12 in order to provide the desired mobility. Indeed, in the illustrated embodiments, the hooks 24 forming the lower ladder engaging support 22 are attached to lower connecting rods 29 projecting transverally from respective extremities of the lower ladder engaging support 22. The lower connecting rods 29 are preferably sized and shaped to be telescopically engageable with the corresponding vertical sidepieces 17, i.e. the lower connecting rods 29 are slideable into the sidepieces 17 of the frame 12. This assembly allows the lower ladder engaging support 22 to be movable towards or away from the fixed upper ladder engaging support 21 , thereby varying the clamping distance 23. The length of the lower connecting rods is preferably selected such that they remain engaged with the vertical sidepieces over a desired range of clamping distance. In order to prevent the lower connecting rods 29 from being inserted into the sidepieces 17 beyond a certain limit, a blocking ring 60 can be provided along each lower connecting rod 29. Blocking rings 60 are located at a similar position along each lower connecting rod 29 such that when the predetermined limit is reached, the blocking rings 60 prevent each lower connecting rod 29 from moving further upward into the corresponding sidepiece 17.

[00042] It will be readily understood that the telescopic engagement shown herein between the lower ladder engaging support and the frame is given by way of example only and that other types of arrangements may be considered. For example and without being limitative, the lower ladder engaging support 22 could slide over the frame 12 or be pulled towards the frame by a cable or the like. [00043] Now referring to Figures 2, 2A, 4 and 4B, an embodiment of an actuation mechanism 30 for moving the movable support along the frame, and thereby vary the clamping distance, will be described. As previously mentioned, in the illustrated embodiment, the actuation mechanism 30 is positioned in an upper section 16 of the frame 12 of the safety extension device 10 which extends over a length of the frame at the top extremity thereof. One skilled in the art will however understand that, in alternative embodiments, the actuation mechanism 30 could be provided in an upper section 16 of the frame 12 at a distance from the top extremity.

[00044] In the illustrated embodiment, the actuation mechanism 30 includes an upper crosspiece 19 and an abutment crosspiece 38. The upper crosspiece 19 and the abutment crosspiece are spaced apart from one another of an actuation distance 35 and are connected by a displacement mechanism 37. In the illustrated embodiment the displacement mechanism 37 includes a displacement shaft 36 and a displacement handle 32 operable to vary the clamping distance 35 between the upper crosspiece 19 and the abutment crosspiece 38.

[00045]As can be seen in Figures 2, 2A, 4 and 4B, in an embodiment the upper crosspiece 19 is vertically movable along the frame 12 with respect to the sidepieces 18, to be moved closer or further from the abutment crosspiece 38 and thereby vary the actuation distance 35. In the illustrated embodiment, the upper crosspiece 19 is provided with a pair of upper connecting rods 31 projecting transverally from respective extremities of the upper crosspiece 19. Each upper connecting rod 31 is telescopically engageable with a corresponding one of the vertical sidepieces 17 in order to provide the desired mobility. As can be seen in the figures, the telescopic engagement between the upper connecting rods 31 of the upper crosspiece 19 and the vertical sidepieces 17 is provided by the upper connecting rods 31 being sized and shaped to be slideable into the corresponding sidepieces 17 of the frame 12. [00046] In the illustrated embodiment, the upper crosspiece 19 is supported by the combination of the displacement shaft 36 and the displacement handle 32 abutting on the abutment crosspiece 38. The displacement shaft 36 is connected at a first end to the upper crosspiece 19 and runs downward through an aperture 39 formed in the abutment crosspiece 38. The displacement handle 32 is a handle mounted to the displacement shaft 36, directly above the abutment crosspiece 38. The lower portion of the displacement handle 32 is larger than the aperture 39 formed in the abutment crosspiece 38 such that it abuts the abutment crosspiece 38 and prevents further downward movement of the displacement shaft 36.

[00047] In an embodiment, the displacement shaft 36 has a threaded portion and the displacement handle 32 is rotatable and provided with an opening therethrough having complementary inner threads, such that it can be moved on the threaded portion of the displacement shaft 36 by rotation thereon. Hence, when the displacement handle 32 is rotated in a first direction, for example in a clockwise direction, the displacement handle 32 is driven downward on the displacement shaft 36. During such a rotation of the displacement handle 32, the abutment of the lower portion of the displacement handle 32 with the abutment crosspiece 38, causes the displacement shaft 36 to move upward and consequently increase the actuation distance 35 by driving the upper crosspiece 19 upward and away from the abutment crosspiece 38.

[00048] Similarly, when the displacement handle 32 is rotated in a second direction opposite to the first direction, for example in a counter clockwise direction, the displacement handle 32 is moved upward on the displacement shaft 36 which causes the displacement shaft 36 to move downward and consequently decrease the actuation distance 35 by driving the upper crosspiece 19 downward, towards the abutment crosspiece 38.

[00049] In an embodiment, a locking handle 34 is further provided. In the illustrated embodiment, the locking handle 34 is also rotatable and provided with threading complementary to the threaded displacement shaft 36 and is located above the displacement handle 32. The locking handle 34 is operable to be rotated along the shaft 36 between a locked configuration, where the locking handle 34 is tightened against the displacement handle 32, and an unlocked configuration where the locking handle is distal from the displacement handle 32. The tightening of the locking handle 34 against the displacement handle 32 prevents the displacement handle 32 to be accidently rotated when in the locked configuration. Therefore, when the locking handle 34 is in the locked configuration, a variation of the clamping distance 23, by rotation of the displacement handle 32, requires the locking handle to be previously moved to the unlocked configuration.

[00050] Referring to Figures 4, 4A and 4B, a connecting member 40 is provided for connecting the actuation mechanism 30 to the lower ladder engaging support 22 (which is the movable support) so that the clamping distance 23 can be varied by the operation of the actuation mechanism 30. In the illustrated embodiment, the connection between the actuation mechanism 30 and the lower ladder engaging support 22, is provided by the lower connecting rods 29 of the lower ladder engaging support 22 being connected to the upper crosspiece 19 by a connecting member 40. In the illustrated embodiment, the connecting member 40 is a pair of cables 44 running through each sidepiece 17. Each cable 44 of the pair of cables 44 is connected at a first end 41 to the upper crosspiece 19 of the actuation mechanism 30 and at a second opposite end 42 to the corresponding one of the lower connecting rods 29. One skilled in the art will understand that, in alternative embodiments, other connecting mechanism 40 could be provided. For example and without being limitative, the lower connecting rods 29 could extend upward to the upper crosspiece 19 of the actuation mechanism 30, thereby preventing the need for the cables connecting these elements.

[00051]As will be easily understood, in the above-described assembly, the downward movement of the upper crosspiece 19 drives the lower ladder engaging support 22 downward through the effect of gravity, and consequently increases the clamping distance 23. However, given that the upper crosspiece 19 is connected with the lower ladder engaging support 22 by the connecting member 40, the upward movement of the upper crosspiece 19 consequently drives the lower ladder engaging support 22 upward and decreases the clamping distance 23.

[00052] One skilled in the art will understand that, in alternative embodiments, a different actuation mechanism 30 resulting in the variation of the clamping distance 23, upon actuation by a user, may be provided. For example and without being limitative, the lower crosspiece (or abutment crosspiece 38) could be movable rather than the upper crosspiece 19 and necessary adjustments to the displacement mechanism 37 could be made, the displacement shaft 36 could cooperate directly with a threaded aperture in the abutment crosspiece 38 to move the upper crosspiece 19, without the need for a displacement handle 32, or a pulley system could be used such that a displacement handle would pull or release cables directly, without the need for movement of the upper crosspiece 19 in the variation of the clamping distance 23.

[00053] Now that the structure of the safety extension device has been described, a method of operation for engaging the safety extension device, according to an embodiment, will be described below.

[00054] In this method of operation, the clamping distance is adjusted such that the distance between the upper ladder engaging support and the lower ladder engaging support is greater than the distance between a first rung and a second rung that the safety extension device will engage. The safety extension device is lowered towards the ladder such that the upper ladder engaging support engages the first rung. In an embodiment, the engagement between the first rung and the upper ladder engaging support occurs as the first rung is received within the downward open groove formed by the hooks of the upper ladder engaging support. [00055] Subsequently, the safety extension device is positioned such that the lower ladder engaging support is vertically aligned with the second rung. In an embodiment such a positioning of the safety extension device is effected by pivoting the safety extension device about the first rung to align the upward open groove formed by the hooks of the lower ladder engaging support with the corresponding second corresponding rung.

[00056] Next, the actuation mechanism located on an upper section of the frame of the safety extension device is operated to decrease the clamping distance until the lower ladder engaging support engages the second rung. In an embodiment, the operation of the actuation is effected by rotating the displacement handle in the appropriate direction to decrease the clamping distance until the second rung abuts the lower extremity of the upward open groove and the safety extension device is solidly engaged on the ladder.

[00057] In an embodiment, the first rung engaged by the upper ladder engaging support and the second rung engaged by the lower ladder engaging support are two successive rungs located at the upper extremity of the ladder. However, one skilled in the art will understand that, in alternative embodiments, the upper ladder engaging support and the lower ladder engaging support may engage rungs located further down on the ladder and may engage non-successive rungs as long as the distance between these non-successive rungs is smaller than the maximum clamping distance that can be reached.

[00058] In an embodiment where a locking handle is provided, the method of operation may further comprise the step of locking the actuation mechanism. Locking of the actuation mechanism occurs as the locking handle is brought in the locking configuration, in order to lock the displacement handle in place and prevent a user from accidentally disengaging the safety extension device from the ladder.

[00059] As can be seen form the above description and in reference to Figure 1A and 1 B, the safety extension device 10 can be rapidly and easily engaged/disengaged on the ladder 50, without the need of tools, which facilitates the use of the described safety extension device 10 with more than one ladder 50 simultaneously. Moreover, it will be noted that, as shown in Figure 1A, since the actuation mechanism 30 is located on an upper section of the frame 12, the safety extension device 10 can be engaged on the ladder 50 by a user 1 1 standing on the upper edge 54 of the wall 52 to which the ladder 50 is affixed. Therefore, in an embodiment, a user standing on the street could secure the safety extension device 10 to a ladder 50 of a manhole without having to previously enter the manhole.

[00060] Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person skilled in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person skilled in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the scope of the invention as defined in the appended claims.