AU2006203042B2 - Improved latching means for a combination step and extension ladder - Google Patents

Abstract

The invention provides an improved latching device for a dual purpose ladder which can be used as a step ladder or an extension ladder. The latching device comprises at 5 least one latch member mounted on a rotatable shaft which extends between the stiles of one of the ladder sections and being biased towards a latch engaging position, a latch engaging bar or rail secured to the other ladder section, and a manual actuator operatively associated with the latch member for effecting pivotal movement of the latch member so as to disengage same from the latch engaging bar 10 or rail to enable the two ladder sections to pivot relative to one another, the latch member being arranged so that it will automatically engage with the latch engaging bar or rail when the other ladder section is rotated to an extended position. o o Fig 2 o o Fig 3

Description

Regulation 3.2 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant: Hills Industries Limited Actual Inventors: Ronald Thomas Delaforce Douglas Walson Palmer Address for Service: C/- MADDERNS, 1st Floor, 64 Hindmarsh Square, Adelaide, South Australia, Australia Invention title: IMPROVED LATCHING MEANS FOR A COMBINATION STEP AND EXTENSION LADDER Details of Associated Provisional Application No: 2005903835 dated 20 July 2005 The following statement is a full description of this invention, including the best method of performing it known to us.

This invention relates to an improved latching device for a dual purpose ladder which can be used either as a step ladder or as an extension ladder wherein one section of the ladder forms an extension of the other. 5 Dual purpose ladders comprising two ladder sections which are pivotally joined together so as to allow one of the sections to pivot between a first position in which the ladder can be used as a step ladder and a second position in which the section is an extension of the first section, are well-known and have been available in the marketplace for many, many years. When the ladder is being used in the 10 extension mode of use, it is important that the extension section of the ladder is securely locked to the other section to ensure that it does not collapse or twist when the ladder is in use. Several locking or latching devices have been used in order to lock the two ladder sections against relative pivotal movement when the ladder is in its extension position. One such locking system makes use of a pair of retaining loops 15 which slidably engage over overlapping stile portions on each side of the ladder when the ladder sections are parallel. This arrangement requires the user to separately engage each of the retaining loops. The sliding engagement (or disengagement) of each of the retaining loops can be quite awkward. Another latching system known to the applicant makes use of a pair of flat metal hooks which 20 are attached to the outside of the stiles of the lower ladder section adjacent the top end thereof, the hooks being adapted to engage over pins which are fixed to the legs or stiles on the other ladder section. This arrangement once again requires the user to manually engage the hooks over the pins when the two ladders sections are in the extension position. Some users will not use the latching hooks at all, which can lead 25 to accidents. This also applies to the former system using slidable retention loops. It is the main object of the present invention to provide an improved latching mechanism for a dual purpose ladder comprised of a pair of pivotally interconnected ladder sections, which will allow the ladder sections to automatically lock together in 30 the extension position of the ladder.

It is another object of the present invention to provide an improved latching mechanism for a dual purpose ladder which is of simple design, reliable and which can be conveniently and economically fitted to existing ladder designs. 5 It is a still further object of the present invention to provide an improved latching mechanism for a dual purpose ladder wherein not only is the latching of the two ladder sections easily accomplished but also permits easy unlatching so as to allow the two ladder sections to assume the step ladder mode of use. D Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed. 5 Broadly according to this invention therefore, there is provided a latching mechanism for a dual purpose ladder which comprises a first ladder section, a second ladder section pivotally connected to the first section so that it can be pivoted relative to the first section between a first position in which ladder can be used as a step ladder, and a second extended position in which the second section is an 3i extension of the first section approximately parallel therewith, said latching mechanism comprising: at least a pair of spaced apart latch members pivotally mounted on said first ladder section adjacent its upper end, and operatively associated to pivot in unison; a latch engaging member secured to the second ladder section; 5 bias means biasing said latch members towards a latch engaging position; a manual actuator operatively associated with at least one latch member and arranged, when actuated, to effect pivotal movement of the latch members so as to disengage or release same from the or each latch engaging member to thereby enable the second ladder section to pivot relative to the first section; and 0 wherein said latch members, when the second ladder section is rotated to its said extended position, automatically latchingly engage with the or each latch 3 engaging member to securely interlock the two ladder sections together in the second extended position. In one form, the latch members latchingly engage a common latch engaging 5 member. Preferably, the latch engaging member is a latch bar or rail which extends between and is secured to the stiles of the second ladder section near its pivoted end. 3a Preferably, there is a pair of spaced apart spring loaded latch members located between the stiles of the first ladder section adjacent its upper end, said latch members being mounted on a common transverse rotatable shaft extending between the stiles of the first ladder section, 5 said actuator co-acting with one of said latch members, said latch members being movable in unison between a latching position where each lockingly engage the latch bar and a raised unlatched position where each of the latch members is released from the latch bar. 10 Desirably, the actuator is a push-button actuator having a projecting inner end which is in operative engagement with a portion of one of the latch members. Desirably, each of the latch members has a latch body keyed to said common transverse shaft so as to rotate therewith, a forwardly projecting latching arm which 15 terminates at its distal end in a hook portion, and a depending push button engagement limb or arm extending from the latch body on the rear side thereof. Desirably, the hook portion on each of the latch members has an inclined cam surface which makes camming contact with an upper edge of the latch bar to permit 0 the latch members to ride up over the latch bar upper edge and lockingly engage in position, when the second ladder section is rotated to the extended position. Desirably, a channel shaped top cap is secured, eg by rivets, to the upper end of the first ladder section, the top cap having an outer depending flange which 25 extends between the upper ends of the stiles, said flange having an opening formed therein for fitment of the push button actuator. The walls of the top cap provide protection for the latch mechanism and reduce the likelihood of any accidental damage to the mechanism and the actuator. 30 Desirably, the actuator has a housing which is provided with resiliently deflectable fingers which allow the housing to snap-fittingly locate in said opening. 4 Desirably, each of the latch members is slidably and non-rotatably fitted on the support shaft which extends between and is rotatably supported between opposed stiles of the first ladder section. 5 In order to more fully explain the present invention, a preferred embodiment thereof is described hereunder in some further detail with reference to and as illustrated in the accompanying drawings in which: Figure 1 is a fragmentary perspective view of a dual purpose step ladder (shown in the step ladder position) to which is fitted a latching mechanism designed 10 to automatically lock the two ladder sections together when in the extension mode of use; Figure 2 is a fragmentary, partly sectioned, side elevational view showing the two ladder sections in the extension mode, with the latch mechanism in the latched position; 15 Figure 3 is a fragmentary, partly sectioned, side elevational view of the ladder assembly showing the latch mechanism in its unlatched position so that the upper ladder section can be swung downwardly to its step ladder position; Figure 4 are views showing stages of the latching operation of the latching mechanism when the second ladder section is swung upwardly to its extended 20 position; Figure 5 is a perspective view of the latch sub-assembly; and Figure 6 is an elavational view of the actuator button shown in Figure 2. Referring to the drawings, there is shown a dual purpose ladder 10 25 comprising a first ladder section 11, a second ladder section 12 which is shorter in length than the first section 11, pivotally connected to the first ladder section 11 so that it can be pivoted between a first position in which the ladder 10 can be used as a step ladder (as shown in Figure 1) and a second extension position in which the second section 12 is an extension of the first section 11 and approximately parallel 30 therewith (as shown in Figure 2). Each of the ladder sections 11, 12 comprises a pair of transversely aligned stiles 13, 13' and 14, 14' respectively, each of the stiles having inwardly directed parallel flanges, and a plurality of rungs 15, 16 which are secured 5 to and extend between the stiles 13, 13' and 14, 14' respectively. The first ladder section 11 is fitted with a channel section top cap 18 which has a depending outer flange 19 fixed adjacent its opposite ends to the front flanges 20, 20' of the stiles 13, 13'. 5 The two ladder sections 11, 12 are pivotally interconnected by means of a pair of transversely aligned brackets 21 secured to opposite sides of the ladder section 11, and each of which has a projecting portion which is secured to the outer side of a respective stile 14, 14' of ladder section 12 by a pivot bolt 23. 10 The first ladder section 11 is provided with a latching mechanism 24 comprising a pair of pivotal spring loaded latching members 26 adjacent its upper end, each of the latching members 26 being carried on a common profiled shaft 27 which extends between and is rotatably supported between the stiles 13, 13' (refer L5 Fig 5) by means of brackets 28 fixed to the inner sides of the stiles 13, 13'. The latching members 26 are arranged to latchingly engage an upper edge portion of a transverse latching bar 29 which is fitted to the ladder section 12 near its pivoted end. The latching mechanism includes a push button actuator 30 which operatively !0 engages one of the latching members 26 and, when inwardly depressed, effects rotation of the latching member 26 and thereby the shaft 27. The rotation of the shaft 27 causes both latching members 26 to simultaneously rotate to an upwardly raised delatching position wherein the hook portions 32 at the ends of the latching members 26 are clear of the upper edge of the latching bar 29. In this delatching position, the 25 ladder section 12 is free to rotate about its pivot axis 23 to assume its step ladder position. In this embodiment, the push button actuator 30 is slidably housed in a diamond shaped housing 35 which locates within a diamond shaped opening 36 30 formed in the outer flange 19 of the top cap 18. The housing 35 has a pair of resiliently deflectable fingers 35' formed in its opposite side walls and which permit the housing 35 to snap-fittingly locate in position when inserted through opening 36 6 in the flange 19, with portions of the flange 19 surrounding the opening 36 being clamped between the distal ends of the fingers 35' and a perimeter front flange 31 on the housing 35. The push button actuator 30 comprises a slidable push button 37 which has a rearwardly projecting extension portion which engages a depending 5 limb 40 on the latching member 26. Each of the latching members 26 is biased under the influence of a return spring 42 operatively associated therewith, towards its latching position, with the extent of rotational movement of each latching member 26 being restricted by means of a limit stop 46 which projects upwardly from the body of the latching member 26. The limit stop 46, with the push button 37 retracted, bears L0 against the inner side of depending flange 50 of the top cap 18, thereby limiting the extent of clockwise rotational movement of the latching member 26. This is shown in Figure 2 of the drawings. In this embodiment, each hook portion 32 on the latching members 26 is L5 defined in part by an inclined edge 52 which, when the ladder sections are pivoted to assume the extension position of the ladder, makes caning contact with the upper edge of the latch bar 29 so that the latching arm will smoothly ride up over the top edge of the latch bar 289 and thereafter allow the hook portion 32 to latchingly engage with abutment face 54 on the latch bar 29. It is a feature of this invention that !0 the latching arms 26 automatically lockingly engage with the latch striker 29 when the ladder section 12 is swung upwardly to the extension position. It will be appreciated that the top cap 18 fitted to the upper end of ladder section 11 affords protection to components of the latching mechanism against 25 possible damage from external forces. Furthermore, the outer depending flange 19 of the top cap 18 provides a convenient support and location for the push button actuator. It is of course desirable to have two latching members 26, one adjacent each 30 side of ladder section 11 to ensure that when the ladder is in its extension position, both sides of the extension ladder are firmly and securely locked together to minimise any possibility of twisting of the ladder during use. 7 As shown in Figure 1, when the ladder 10 is in its step ladder mode of use, the ladder sections 11, 12 are locked together by a pair of pivoted locking stays or links 58 - in accordance with known art. 5 The above described embodiment is intended to be illustrative and not limiting. Other embodiments of this invention will be obvious to those skilled in the art in view of the above disclosure. For example, the push-button actuator may be replaced by a hand actuated pivotal lever arm operatively connected to the shaft 27 so that it can effect rotation thereof. 0 A brief consideration of the above-described embodiment will indicate that the invention provides a simple, practical and reliable latching mechanism for automatically locking together the two ladder sections of a dual purpose ladder when in its extension position, as well as one which permits simple, quick unlatching 5 of the mechanism when it is desired to convert the ladder from its extension mode of use to its step ladder mode of use. Throughout the specification and the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as .0 "comprising" and "including" will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. The reference to any prior art in this specification is not, and should not be 25 taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge. It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present 30 invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that various modifications can be made without departing from the principles of the 8 invention. Therefore, the invention should be understood to include all such modifications in its scope. 9

Claims (14)

1. A ladder latching mechanism for a dual purpose ladder which comprises a first ladder section, a second ladder section pivotally connected to the 5 first section so that it can be pivoted relative to the first section between a first position in which ladder can be used as a step ladder, and a second extended position in which the second section is an extension of the first section approximately parallel therewith, said latching mechanism comprising: at least a pair of spaced apart latch members pivotally mounted on said first D ladder section adjacent its upper end, and operatively associated to pivot in unison; a latch engaging member secured to the second ladder section; bias means biasing said latch members towards a latch engaging position; a manual actuator operatively associated with at least one latch member and arranged, when actuated, to effect pivotal movement of the latch members so as to 5 disengage or release same from the or each latch engaging member to thereby enable the second ladder section to pivot relative to the first section; and wherein said latch members, when the second ladder section is rotated to its said extended position, automatically latchingly engage with the or each latch engaging member to securely interlock the two ladder sections together in the second D extended position.

2. The latching mechanism according to Claim 1, wherein the latch members latchingly engage a common latch engaging member. 25

3. The latching mechanism according to either Claim 1 or 2, wherein the latch engaging member is a latch bar or rail which extends between and is secured to stiles of the second ladder section near its pivoted end.

4. The latching mechanism according to anyone of Claims 1 to 3, wherein 3O said manual actuator is a push button actuator mounted between stiles of the first ladder section adjacent its upper end, said push button actuator operatively engaging directly with a portion of said latch member. 10

5. The latching mechanism according to anyone of Claims 1 to 4, wherein each latch member has a latch body, a forwardly projecting latching arm which terminates at its distal end in a hook portion, and a depending actuator engagement 5 limb or arm extending from the latch body on the rear side thereof.

6. The latching mechanism according to Claim 5 when appended to Claim 3, wherein the hook portion on each of the latch members has an inclined cam surface which makes camming contact with an upper edge of the latch bar to permit D the latch member to ride up over the latch bar upper edge and lockingly engage in position, when the second ladder section is rotated to the extended position.

7. The latching mechanism according to Claim 1 or Claim 2, wherein the latch members are located between the stiles of said first ladder section adjacent its 5 upper end, said latch members being mounted on a common transverse rotatable shaft extending between said stiles so as to rotate therewith, said latch members being movable in unison by said actuator between a latching position wherein each lockingly engage the latch engaging member and a raised unlatched position where each of the latch members is released from the latch engaging member. 0

8. The latching mechanism according to Claim 7, wherein each of the latch members is keyed to said common transverse rotatable shaft.

9. The latching mechanism according to any one of the preceding claims, 25 further comprising a channel top cap extending between and secured to the upper ends of the stiles of the first ladder section, said top cap having an outer depending flange which extends between said upper ends, said depending flange having an opening for locating said actuator. 30

10. The latching mechanism according to Claim 9, wherein said actuator comprises a housing, having integrally formed resiliently deflectable fingers in 11 opposite side walls and which allow the housing to snap-fittingly locate in said opening.

11. The latching mechanism according to Claim 10, wherein said actuator 5 comprises a push button slidably housed in said housing.

12. The latching mechanism according to Claim 7, wherein each of the latch members is slidably and non-rotatably mounted on said shaft which is rotatably supported between opposed stiles of the first ladder section. D

13. A ladder which includes a latching mechanism according to any one of the preceding claims.

14. A ladder latching mechanism for a dual purpose ladder substantially as 5 herein before described and illustrated in the accompanying drawings. 12