LADDER

Abstract: A ladder (10) including: mobility means (12) displaceable between a ladder immobile position and a ladder mobile position in which the mobility means extends downwardly beyond the foot of the ladder; and manually actuable means (30, 20, 14) for displacing the mobility means from the ladder immobile position to the ladder mobile position, wherein, when the manually actuable means is released, the mobility means returns to the ladder immobile position.

Description: "LADDER" TECHNICAL FIELD The present invention relates to ladders. The invention has particular utility with A-frame ladders having an elevated work platform, however the invention is not limited to this particular type of ladder. A- frame ladders having an elevated work platform are often referred to as "order pickers" or "platform steps" and are used in the warehousing of stores. BACKGROUND ART It is known to mount A-frame ladders on castors for the purpose of mobility. The castors have been mounted for movement between a mobile mode in which the castors extend beyond the feet of the ladder to engage the supporting surface and an immobile mode in which the castors are retracted and the feet of the ladder engage the supporting surface. In one known ladder the castors have been mounted to the ladder by compression springs so that the castors are biased to extend beyond the feet of the ladder when the ladder is unloaded, and yet compress to allow the feet of the ladder to engage the supporting surface when the ladder is loaded. A major drawback with these known ladders is that they lack stability, particularly when loaded eccentrically. Furthermore, when stepping onto such a ladder there is a tendency for it to "skate". In other known ladders the castors can be moved by the operator between their extended and retracted positions via some lever or pedal arrangement. With these ladders the operator must be careful to ensure that the castors are returned to their retracted position before stepping onto the ladder to avoid "skating". DISCLOSURE OF INVENTION In one aspect the invention resides in a ladder including:- mobility means displaceable between a ladder immobile position and a ladder mobile position in which the mobility means extends downwardly beyond the foot of the ladder; and manually actuable means for displacing the mobility means from the ladder immobile position to the ladder mobile position, wherein, when the manually actuable means is released, the mobility means returns to the ladder immobile position. Preferably, the manually actuable means includes a link pivot member associated with the mobility means such that pivoting of the link pivot member displaces the mobility means to the ladder mobile position. Preferably, the mobility means is pivotably mounted relative to the link pivot member and guided for sliding vertical movement. Preferably, the manually actuable means further includes a lever member and wherein manual pivoting of the lever member causes pivoting of the link pivot member. Preferably, transmitting means is disposed between the lever member and link pivot member. In one embodiment there are a pair of mobility means and a pair of manually actuable means and wherein the pair of lever members constitute the arms of a U-shaped member such that pivoting of the U-shaped member simultaneously urges both mobility means to the ladder mobile position. Preferably, the ladder is an A-frame ladder and there are two pairs of mobility means and two pairs of manually actuable means, each pair of manually actuable means including a U-shaped member. Preferably, the two pairs of manually actuable means are linked in a master/slave relationship such that pivoting of one of the U-shaped members urges both pairs of mobility means to the ladder mobile position. Preferably, respective individuals of the two pairs of manually actuable means are linked by bar members. Preferably, the bar members are disposed between the link pivot members of the respective individuals of the two pairs of manually actuable means. BRIEF DESCRIPTION OF FIGURES In order that this invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention, wherein:- FIG 1 is a schematic view of the master-slave mechanism of an A-frame ladder according to the invention in the ladder immobile position; FIG 2 is a schematic view of the master-slave mechanism of FIG 1 in the ladder mobile position; FIG 3 is a perspective view of FIG 1; FIG 4 is a perspective view of FIG 2; FIG 5 is a perspective view of an A-frame ladder according to the invention in the ladder immobile position; FIG 6 is a perspective view of the A-frame ladder of FIG 5 in the ladder mobile position; FIG 7 is a reverse perspective view of the A-frame ladder of FIG 5 in the ladder mobile position; FIG 8 is a perspective view of another A-frame ladder according to the invention in the ladder immobile position; and FIG 9 is a schematic side elevation of the A-frame ladder of FIG 8. BEST MODE Referring firstly to FIG 5, there is shown a ladder 10 having a first pair of mobility means 12a and 12b and a second pair of mobility means 12c and 12d. In the embodiment illustrated the mobility means take the form of castors. Referring now to FIGS 1 to 4, there is illustrated the mechanism whereby the mobility means 12a and 12c may be simultaneously displaced from the ladder immobile position (FIGS 1 and 3) to the ladder mobile position (FIGS 2 and 4) . It should be noted that whilst the mobility means are illustrated as being spaced from the supporting surface in FIGS 1 and 3, the mobility means will, in fact, contact the support surface when in the ladder immobile mode, albeit without carrying load. Referring firstly to FIG 1, there is shown a schematic illustration of the mobility means 12a and 12c in the ladder immobile position. In this position the legs of the ladder are in contact with the supporting surface. Accordingly, the ladder is stable and immobile. Referring to FIGS 3 and 4, mobility means 12 is pivotably mounted about a vertical axis on up-standing post 26 so that the ladder can be wheeled in any direction. Up-standing post 26 is guided for vertical movement in a bore in housing 28 and is pivotably linked to link pivot member 14 at pin 22. Housing 28 is fixed to the ladder frame. Link pivot member 14 is pivotably mounted relative to housing 28 at pin 16. Transmitting means 20, which in the illustrated embodiment consists of a bar, is pivotably mounted to link pivot member 14. It will be appreciated that upward movement of transmitting meanε 20 causes rotation of link pivot member 14 about pin 16 thus urging post 26 and mobility means 12 vertically downwardly into load bearing engagement with the supporting surface as illustrated in FIGS 2 and 4. This has the effect of raising the feet of the ladder out of contact with the supporting surface and rendering the ladder mobile. Furthermore link pivot members 14a and 14c are linked by bar member 18ac such that pivoting of one link pivot member is reflected in the other link pivot member in a master/slave relationship. A second bar member 18bd similarly extends between link pivot members 14b and 14d. The bar members are pivotably mounted to the link pivot members 14 at 24. In some embodiments the bar member can be replaced by a cable, chain or the like as discussed hereunder. Referring to FIG 5, the upper end of transmitting means 20 is pivotably mounted to lever member 30. In the illustrated embodiment the upper end of transmitting means 20 includes a slot adapted to receive a pin disposed on lever member 30 so that the slave transmitting means 20 can move upwardly relative to the pin without displacing the slave lever member. Alternatively, transmitting means 20 can be in the form of a chain or cable which will not transmit compression forces. Lever members 30a and 30b (FIG 5) constitute the arms of U-shaped member 32 as do lever members 30d and 30c. As previously mentioned FIG 5 shows ladder 10 in the immobile orientation. In contrast, FIGS 6 and 7 show ladder 10 in the mobile orientation. Manual actuation of U-shaped member 32ab from the orientation shown in FIG 5 to the orientation shown in FIG 6 displaces transmitting means 20a and 20b upwardly which in turn pivots link pivot members 14a and 14b to urge mobility means 12a and 12b downwardly to the ladder mobile position. Simultaneously, due to pivoting of link pivot members 14a and 14b, link pivot members 14c and 14d are pivoted due to the mechanical linkage provided by bar members 18ac and 18bd. Thus, mobility means 12c and 12d are simultaneously urged downwardly to the ladder mobile position. Referring now to FIG 7, the equivalent operation has been performed by displacing U-shaped member 32cd on the other side of the ladder. Thus, the master/slave relationship has been reversed. In this instance transmitting means 20c and 20d have been pulled upwardly thereby urging mobility means 12c and 12d downwardly to the ladder mobile position. Again, due to the master/slave relationship provided by bar members 18ac and 18bd, mobility means 12a and 12b are simultaneously forced downwardly to the ladder mobile position. When U-shaped member 32 is released the mobility means 12 return to the ladder immobile position due to gravity and the U-shaped member returns to a position where it does not impede access to the ladder. Whilst the embodiment illustrated in FIGS 5 to 7 shows U-shaped members on both sides of the ladder, U- shaped member 32cd together with transmitting means 20c and 20d could be eliminated to provide another preferred embodiment in which there is only a single U-shaped member which can be used to displace all four mobility means to the ladder mobile position. Such an embodiment is shown in FIGS 8 and 9. In this embodiment bar member 18 need only be capable of transmitting compression or tension depending on which side the U-shaped member is retained. In the illustrated embodiment, the bar member must be capable of transmitting compression and accordingly the bar member is a solid or hollow bar. However, if the U-shaped member was on the opposite side of the ladder, then the bar member would only need to be capable of transmuting tension and accordingly the bar member could be a cable, chain or the like. Referring to FIGS 8 and 9 there is illustrated an A- fra e ladder having one U-shaped member 32ab. On the opposite side of the ladder is guide frame 42 which mounts platform 40 for sliding vertical movement. Platform 40 can be moved up and down by hand winch 46 via cable 44 which is routed by a series of pulleys. Of course, the hand winch and cable may be replaced by any other appropriate drive system, eg. electric motor. The provision of the platform saves the operator from having to carry a package or the like down the ladder. Rather, the operator can select the desired package from shelving, place it on platform 40, dismount the ladder and then lower the platform. The ladder can then be made mobile and wheeled to the desired location. The reverse operation, of course, applies when the package is being placed on shelving rather than removed. It will be understood that the preferred embodiment of the invention provides a ladder which is convertible between a fully stable default mode in which all four legs are in contact with the supporting surface to a non- default fully mobile mode in which all four mobility means are in contact with the supporting surface. An additional benefit of the preferred embodiment of the present invention is that the ladder can be converted to the mobile mode whilst loaded. In this regard packages or stores can remain on the ladder whilst the operator manually actuates the U-shaped member to convert the ladder to the mobile mode. Thus, in addition to providing a stable or mobile ladder, the present invention also provides a ladder which can be used to transport loads horizontally. The invention provides a mobile ladder which is easily and ergonomically transported. The ladder is easily controlled and steered by means of the U-shaped lift handle which places the operator in a safe, comfortable walking position relative to the ladder eliminating accidental body contact or striking of the ladder. It should be noted that the invention provides a default status which renders the ladder immobile and therefore safe to climb, and eliminates the possibility of accident due to an operator commencing ascent of the ladder when in the mobile mode. In this regard the ladder is stable and totally inert in the default status and the operator must actively make the ladder mobile. The ladder provides a mechanical advantage to enable transportation of load and thereby offers a combination of both an acces and materials handling device for vertical and horizontal transportation of goods. It will of course be realised that whilst the above has been given by way of an illustrative example of this invention, all such and other modifications and variations hereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of this invention as is herein set forth.

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS;- 1. A ladder including:- mobility means displaceable between a ladder immobile position and a ladder mobile position in which the mobility means extends downwardly beyond the foot of the ladder; and manually actuable means for displacing the mobility means from the ladder immobile position to the ladder mobile position, wherein, when the manually actuable means is released, the mobility means returns to the ladder immobile position. 2. A ladder as defined in claim 1, wherein the manually actuable means includes a link pivot member associated with the mobility means such that pivoting of the link pivot member displaces the mobility means to the ladder mobile position. 3. A ladder as defined in claim 2, wherein the mobility means is pivotably mounted relative to the link pivot member and guided for sliding vertical movement. 4. A ladder as defined in claim 2, wherein the manually actuable means further includes a lever member and wherein manual pivoting of the lever member causes pivoting of the link pivot member. 5. A ladder as defined in claim 4, wherein transmitting means is disposed between the lever member and link pivot member. 6. A ladder as defined in claim 4, wherein there are a pair of mobility means and a pair of manually actuable means and wherein the pair of lever members constitute the arms of a U-shaped member such that pivoting of the U-shaped member simultaneously urges both mobility meanε to the ladder mobile position. 7. A ladder as defined in claim 6, wherein the ladder is an A-frame ladder and wherein there are two pairs of mobility means and two pairs of manually actuable means, each pair of manually actuable means including a U-shaped member. 8. A ladder as defined in claim 7, wherein the two pairs of manually actuable means are linked in a master/slave relationship such that pivoting of one of the U-shaped members urges both pairs of mobility means to the ladder mobile position. 9. A ladder as defined in claim 8, wherein respective individuals of the two pairs of manually actuable means are linked by bar members, cables, chains or the like. 10. A ladder as defined in claim 9, wherein the bar members, cables, chains or the like are disposed between the link pivot members of the respective individuals of the two pairs of manually actuable means.

Inventors: MOFFAT WILLIAM, MOFFAT, WILLIAM
Applicants: CUSTOM LADDER CO PTY LTD, MOFFAT WILLIAM, CUSTOM LADDER COMPANY PTY. LTD., MOFFAT, WILLIAM
Application year: 1996
Main classification: E06C1
IPC codes: E06C1, E06C5