CA1047995A - Ladder - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A foldable ladder is disclosed having a central and two outer parallel support members or "stiles" and a plurality of steps connected between the central and the outer stiles. Each step is arranged to fold between an erected position, in which it extends generally at right angles to the longitudinal direction of the stile to which it is connected, and a storage position in which the step lies generally parallel to the central stile with the outer stile to which it is connected extending parallel to and in close juxtaposition with the central stile. Engaging means are provided adjacent the upper end of the central stile for holding cooperating engaging means of a supporting member such as another ladder section (forming an extension ladder) or a prop extending to ground (forming a step ladder).

Description

~lLo~799S ~
The present invention relates generally to the art of ladders and, in particular, to ladders which may be folded to facilitate portability ;~
and storage. ~ ~
As can well be imagined, the design and~!construction of ladders, ~ - `
in one form or another, may be included among man's oldest technological ~"
arts. Notwithstanding centuries of experimentation in this field, however, man has failed to arrive at the "ultimate" ladder: a ladder which may be extended by any number of available sections to reach any desired height; a ladder which may be opened into the ~step-ladder~ configuration; a ladder which may be stood securely on irregular surfaces or be leaned against an upright surface of any shape without deleterious effect on its stability;
a ladder which may be folded to form a single pole which may be easily carried or stored; a ladder which provides non-slip surfaces and human-engineered handrails for safety and convenience of use; and, finally~ a ladder which may be manufactured and sold in identical modular sections that can be assembled together to fulfill all of the user's needs, including needs that have never been met before.
It is an object of the present invention bo provide a ladder offer-ing various advantages over prior art ladders.
This object, as well as other objects ~hich will become apparent in the discussion that follows, are achieved,i~according to the present in~
vention~ by providing a portable foldable ladder comprising a ladder structure having: an elongate central member, t~o elongate outer members arranged one at each of opposite sides of the central member, a plurality of steps disposed at spaced intervals on each of said opposite sides of the central member, and foldably connected both to the central member and to the respective one of the outer members, each outer member with its associated steps being arranged to fold between an erected position for use with the outer member ~;
spaced from the central member and the steps extending outwardly from the -9S~5 central member, and a storage position in which the outer member and the steps lie adjacent and substantially parallel to the central member, and releasable means for supporting said steps in their erected position; the ladder structure being arranged at one end to engage the ground at two spaced points to support it above the ground or other surface~ and having a foldable support member arranged to engage the ground or other surface at a third point when in an open position so that the ladder is supported at three points in use. The central and the two outer elongate members thus ` constitute the three "stiles" of the ladder.
The above construction of the ladder, according to the present invention, permits the central stile to be spaced from a supporting surface by the support member when the ladder section is in a substantially upright, `~
working configuration. For example, the supporting member may be a second ladder section either identical or different from the first, but having also a central stile which may be held adjacent and substantially parallel to the central stile of the first ladder section at a number o~ extended, partially overlapping positions. The supporting member may also constitute a prop which is pivoted outward from the central stile of the ladder section to form a generally inverted V-shaped ladder configuration.
In the case where the supporting member constitutes another ladder section, the two central members of the two ladder sections may have slidably cooperating parts to provide captive location of one cenkral member behind the other during all, or substantially all~ of their relati~e move-ment. According to a preferred feature, the engaging means on the central stiles of the ladder sections may constitute a self-tightening latch which ;~
will be described in detail hereinbelow.
According to a further preferred feature of the present invention, the central stile of a ladder section ma~ be constructed so that the steps are angled in the horizontal plane when in the erected position to accomodate : 1~47995 ~ ~ :
the natural splay of the feet of a person using the ladder. According to another feature, the outér stiles may be constructed with a U shaped cross --3 section so that the steps may be received within these stiles when folded to the storage position.
The ladder according to the present invention may be supported on the ground in a number of ways. In one preferred embodiment the outer ~
stiles of the supported section extend downwardly beyond the lower end of ~; ;`the central stile to support the ladder. In another preferred embodiment the support for the ladder is provided at the lower end of the central stile.
This may be accomplished by providing at least two leg structures connected to the central stile adjacent its lower end. These leg structures are conveniently provided with means for adjusting the positions of their outer ends, thereby permQtting individual height adjustment to adapt to an uneven supporting surface. Like the ladder itself, the leg structures may be constructed so as to be capable of folding to a storage position in which they lie generally parallel to the central stile. Preferably, the steps and outer members may be foldable upward and the leg structures foldable ;;`
downward on the central stile to the storage position.
When two ladder sections are used together, it is advantageous to provide means for locking the second section to the first when the central stiles thereof are in an aligned, parallel configuration, to permit the two ladder sections to be conveniently transported.
j It will be appreciated that the ladder structure according to the present invention makes possible a so-called Uni-modular design whereby the ladder is comprised of one or more identical ladder sections. In this case, since it is necessary orly to provide supporting leg structures for the lowest section, means may be provided on the central stile of each ladder ~-~
section for detachably retainirg such leg structures.
The invention may be carried into practice in a number of ways but 4~99S
certain specific embodiments will now be described with reference to the accompanying drawings in which: ,~
Figure 1 is a perspective view of two ladder sections in an ex-tended position;
Figure 2 illustrates two ladder sections in inverted V-form to ~ -make a step ladder; `
Figure 3 shows the two ladder sections stored one agains~ the other;
.` Figure 4 is a sectional plan on the line 4-4 of Figure 12;
Figure 5 is a sectional plan on the line 5-5 of Figure 13; ;
Figure 6 is a sectional plan on the line 6-6 of Figure 8;
Figure 7 is a perspective view with certain parts broken away of one section of ladder;
f Figure 8 is a sectional side elevation with certain parts broken .`
away of two sections of ladder in a storage condition; :
Figure 9 shows the two sections of ladder of Figure 8 with the rear section slightly raised and slightly tilted with respect to the front section; -Figure 10 shows the two sections of Figure 9 with the rear section lowered slightly;
Figure 11 shows the two sections of ladder in their inverted V ` .
configuration; ` ` ,, Figure 12 shows two sections o:E ladder in an e~tended position ;~
immediAtely aEter they have been latched in position and with the rear ` ~;
section still supported manuall~
Figure 13 shows the two sections of ladder of Figure 12 with the `~
manual support for the rear section removed; ~:
Figure 14 is a front elevation with certain parts shown in cross- :
section of the lower end of a ladder section the Figure being drawn for clarity in the direction of the arrows A-A of Figure 17 and showing, on the , ' : . - - -~4799S

left, a step partly folded and a leg fully folded and, on the right, a step and a leg in working positions;
.! Figure 15 is a view generally in the direction of the arrow 15 of Figure 14 showing the top of a leg strut;
~ Figure 16 is a sectional plan generally on the line X-X of Figure r 14 but with the left-hand side rail and lower step and strut in a folded position;
Figure 17 is an under plan on the line 17-17 of Figure 14;
Figure 18 is a section on the line 18-18 of Figure 14;
Figure 19 illustrates a further mode of use of four identical ladder sections;
Figure 20 illustrates an alternative mode of use of the sections of ladder to support a work platform;
. Figure 21 illustrates two alternative embodiments~ one on each side of a ladder section;
. Figure 22 illustrates a still further alternative embodiment com-prising a short "step-ladder" section supported by a prop;
Figure 23 shows, in detail, a rear portion of the ladder embodiment of Figure 22;
Figure 24 shows the ladder embodiment of Figure 22 in the half-folded configuration;
Figure 2S shows the ladder embodiment of Figure 22 in the fully ~; folded configuration; and Figure 26 is a section on the line 26-26 of Figure 25.
The ladder illustrated in Figures 1 to 3 has two identical sections generally indicated at 10 and 11. While it will be convenient to refer to the section 10 as the front section and the section 11 as the rear section, it will be appreciated that these sections~ because they are identical, are completely interchangeable. Figure 3 shows the two sections 10 and 11 in a ,. .
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-' storage condition in which they lie in close juxtaposition. From the - :.
storage position the sections can be alternatively moved to the extended position of Figure 1, or to form an inverted V-shaped step ladder, to the position of Figure 2.
Each ladder section includes a longitudinal central support stile . 14 formed as an aluminum extrusion. The cross-section of this ., ~

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~ 7995 J-'' e~t~lsion is sho~n clc.lrl~ in ligurcs ~ 5 alld 6, and will be refcrr~d to :' in dctail later. S~cured at spaccd intcrvals alun~ cach side of tho stile l 14 are stcp braclcets l5 to which arc pi~otcd steps 17 shown in a worlci~
position in Figurcs 1 and ~. Interconnccting~the outcr ends of the steps 17 on each side are a pair of longitudinal generally U-section side or hand rails 19. Each of the lower steps 20 is pivoted at its inner end to the upper end of a support plate 21 instead of a bracket 15. Extending i between a pivot 23 adjacent the lower end of the plate 21 and an outer ' f' region of the step 20 is a step strut 25~ the detail of which will be referred to later. Also mounted to pivot on the pivot 23 is a leg strut 27 which is pivotally mounted at 28 to the outer end of a leg 29 the inner end of which is connected by a pivot 31 to a'leg support bracket 32, the detail of which is shown at the lower end of Figure 7.
It will be noted that the folded form of tha ladder shown in Fi~ure 3 make~ it extremely cotnpact and rcadilJ portable. Tt1e handrails~
~' when folded together with the folded leg assemblies on each side, àre eompact and substanti'ally in line with one another. ¦
Returning to the cross-section of the ladder stiles shown in 1 FiO~Ires 4, 5 and 6, it ~Yill be seen that each stile has two side walls 14A~ r tho two side walls being`inclined to one another as shown in FiO~lre 4, 90 ¦
that the cross-section of the stile is somewhat triangular in shape.
Since tho steps project at right a1~les to the side faces of the stilo, it ~ollows that the steps themsolvos are not in line, in plan view.
In fact thcy subtend an angle of 150, this complying with the natural splayin6 of the user's feot in normal standinO position.
Intogrally cxtruded on cach sidc wall arc a pair of ribs 14B
which definc betwcen thcm spaccd channcls 14C within which thc stcp brackets 15 and tbe plate ~1 aro locatcd. Each stcp brackct is sccurcd to the side wall 14A of thc stilc b~r a pair of rivcts 34 shown in ~iOurcs ? and 7.

~ ~147~1~5 Figure ? shows the detail of the step brackets 15. Each br~clcct llas two ~ outl~ardly dircctcd flal~es 15~ reccivcd in onc of the -two cll.~nnels IIC.
s This accurately locates the brackets 15 with rèspect to the l~dder stile 14 and outward or hori~ontal t~isting movements o~ the irner end of the ;~
~ steps is effectively absorbed by co-operation of the flanges 15.~ ith thc s ribs 14B. Each step bracke~ has a pair of vertical lugs 15C to which thc , irner ends of the steps are secured by means of pivot pins 36. ~¦ .
As has been men~ioned in reference to Figure 2, the lowermost step 20 is mounted at its inner end to a vertical plate 21 secured to the stile and which is also shown in Figure 14. The lowermost step 20 is of : inverted U-form with double side walls 43 and 45. The pivotal comlection ,, .
~ ; between the step 20 and the plate 21 comprises t~o rivets 38. Continuing ,l to refer to Figure 14, the step strut 25 and the leg strut ~ are each ,j . . ~ .
shown pivotally connected at 23 at the lower end of the plate 21. The l upper.end of the step strut 25, as shown in Figure 18, carries a transverse ,j .
j pi~ 40 havi,ng a slider 41 mounted at each end, the sliders being retained , '~
'i within the cross-section of the step 20 by inner walls 45, having at their .
lower ends inturned flanes 47 which slidably retain the sliders 41. ~Thus in the operative position of the steps and the side rail 19, the sliders 20 . abut a pivot 49 by which the lower step 20 is connected to the side rail and in this position the step strut 25 takes loads recei~ed downwards from ., .I the weight of a man on either the step 20, in which case the loads are directly applied to the strut 25, or on the five upper steps 17, in which case the load is transmitted to the step strut ~5 via the side rail 19.
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. The side rail and steps are maintaincd in thcir operative posi- -tions by means of a latch S0 which is pivoted on the pivot 49. The latch :, 50 has a hooked arm 52 to overlic thc pin 40 a~ shown on thc right-hand side in Figurc 14. The latch 50 also has a finaer button portion 54 which can be prcssed im~ards in thc manner indicatcd by thc arrow on the ~ ~
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lcft-l~and sidc of Figurc l4 whcn roleasc of thc strut ~5 is rcquircd to enablc the hand rail and stcps to be pivotcd to an inoperative position, for example as in Figurc 3. For this purpose the sidc rail has an aperturc ` 56 in line with the finger button 54, and the latch is spring-biassed into ,!~ an engagement condition by a spril~ 55.
When the side rail and the steps are pivoted to the inoperative (closed) position for storage the latch 50 can engag0 a hook abutment 53 situated on the stile between the lowest step 20 and the ne~t step above it, as shown in Figure 2. This retains the side rail and steps in the J 10 inoperative position. ~
It has already been mentioned that the leg strut 27 is pivoted ~-- to the plate 21 at the pivot 23. The leg strut basically comprises two ?
telcscopic sections including an upper section 60 of inverted U-channel form, the s1des of the U having inwardly directed flarges 62 to locate an ~ ;
inverted U section 64 which telescopes within the section 60. The uppcr end 66 of the inner section 64 abuts against a moulded plastics abutment 68 carried by the lower end of a screwthreaded rod 70. The rod 70 has mounted on it a knurled knob 72 which is located within an aperture 74 in thc top surface of the strut section 60. This also is shown in F1gure 0 15. The upper side of the knurled knub 72 engages a thrust abutment 76 fixed to the strut section 60 and having a plain bore 78 through which the rod 70 passes. Thc upper end of the rod carries à circlip 80 to pre~ent tho rod passi~ through the thrust abutment 76.
The plastics moulded abutment 68 ha9 a pair of integral spring ton~ues 82 of the form shown in dotted lines in Figure 15. Thesa tongues engage the internal surface of the side walls of the inner strut section 64 so that when the laddcr is liftcd bodily thc section 64 does not tend to slidc out. By rotation of the knurlcd knob 72 the position of thc abutment 68 can be adjusted so as to control the lcngth of the ~holc strut _9_ , 27 for heigtlt ~djustmcnt. In chain dottcd lin~s in l~ ure 1~ an alt~rnati~e adj~st~d pOSitiOn of thc lc~ assembly is s}lown. The leg st~lt ~7 and thc leg 29 are interconnected by a pair of sidc plates 84 of a U-shapcd pressin~
to the base of which a rubber fo~t 86 is secured.
The plastics moulded abutment 68 has a tongue 88 formcd thcreon which projects downwardly from ~he underside of the strut 2~. This serYcs to engage over a hook 90 formed on the leg bracket 32 when the leg assembly is folded down to the storage position shown on the left-hand side of Figure 14. The knurled knob 72 can be adjusted so as to hold the tongue 88 over the hook 9o.
Referring to Figure 16~ this shows a cross-sectional plan throu~h the stile above the pivot of the lowest steps 20 but with the step and side rail folded up into the inoperative positions. It shows that the j plate 21 has a pair of flanges 92 to which the inner and outer walls 45 and 43 respectively of the lower step 20 are connected by the rivets 38 each having a head 94 and a peened-over end 96. It will be seen that the step strut 25 passes between the peened ends of the ri~ets 38 when `;
the parts are in the inoperative (folded storage) position.
Turning again to the cross-section of the ladder stile which is shown in Figures 4 to 7, it will be seen that the side walls 14A of the stile are interconnected at their front ends by a front wall 14D. The rear ends of the side walls are interconnected by a rear wall 14E. Thc front wall 14D has at each end an integral hook 14F which bctween them form a gcnerally opcn channel 100 and wh1ch also afford forwardly and outwardly ; facing surfaces 14C.
Thc rear wall 14E is generally flat but adjacent the upper end of the stile it has a gcnerally rcctangular slot 102 thc lower wall 104 of which is shown in Figure ?.
The upper end of the stilc 14 has a hoad asscmbly comprising a 1(~47~9S
pair of steel pressil~s lOG ~ach of ~hicll affords a rear vertical wall 106A~ a tapercd front wall 106B ~nd a side ~all 106C. Tho prcssit~s at their upper ends are covered by a nosin~ block 109 which affords a central vertieal rectangular eross-section portion lO~A having lead-in surfaces ~ 109 on its lower side, and a pair of inclined spaced wall-et~aging pads ;~ 108B. Between the eentral portion 108A and the pads 108B~ the nosing ¦ bloek has a pair of raised portions tO8C which define rearwardly and inwardly faeing vertical thrust faces 110, the purpose of whlch will later be described. The upper end of each ladder seetion has an angled face whieh has a generally rectangular recess 136A formed therein as shown in Figures 1, 2 and 8-12. This receives the por~ion 108r~ of the nosing bloek of a front ladder seetion in the Figure 11 eonfiguration.
I` ~ .The pressings 106 ectend do~n within the upper end of the stile `
14. The forward lower wall portions 112 of the pressings are shown in dotted lines. At the lower ends of the side w~]ls tO~ of the pressingA there is a further bloclc 116 whieh is seeured by serews 117 that also retain the lower ends of the pressings. The bloek 116 is generally U-section in plan as also shown in Figures 4 and 5. This block has a further pair of inelined vertieal thrust faees 118 the purpose of which i~ill also be deseribed.
Projeeting through the slot 102 is a shoe generally indicated at 120 and which has a rear portion 1~1 provided with a pair of vertieal grooves 12~ the purpose ~f whieh is to reeeive the hoolc portions 14F of the rear ladder seetion as shown in the Figures 4 and S so as to loeate and slidably hold tho rear ladder seetion in position behind the front seetion. The shoe 120 has a front body portion 126 provided with a forked upper end 128 to receiYc the rear end of a flat lit~c 130. The link is pivoted to the body 126 of the shoe 120 by means of a transverse pin 132 whieh appears in Figures 4 and 7. The forward end of tlle linlc 130 is eonneeted to the pressil~s 106 by a pivot pin 134 as shown in ~igutes 4 l ' "' ''~F ' :.

' ~047995 ~ ~nd 7.
., Thc link 130 is thereforc frcc to pi-vot up and down about thc pin 134. Upward movement is limited to a hori_ontal position (as ~icl~ed when the ladder is vcrtical) by a stop 138. The undersidc of the body portion 126 of the shoe 120 is formcd as an arcuate cam 140 terminating in a stop flange 142 which limits rotations of the shoe 120 about thc pin 132 by engagemcnt with the rear of the lower periphery of the slot 102 in the stile 14 and pressings 106.
,~ ~lounted within the shoe 120 is a retractable latch plunger 150, - `;
the detail of which is shown clearly in Figure 5. Thus the plunger 150 is mounted within a bore i52 in the shoe 120 and is capable of limited movement to and fro with respect to the shoe 120 under the influence of `
`; a compression spring 154. Escape is limited by a stop 156. The plunger 150 is thus biased outwards to a projected position shown in Figures 5 and 7~ but can be rctractcd bJ~ ~eans of a Bo~dcn cable Oenerally indicated a~
~ 160, the inner wire 162 of which is connected to the plunger 150 and the ¦ outer casing 164 of which éngages a recess 166 in the shoe 1~0. The lower end of the cable 160 is connected to a latch release levor 168 mounted on a side of the stile. ~lovement of the lever 168 away from the side of the ~' 20 stilc causes the plunger 150 to be withdrawn. The front wall 14D of each stile has in it a mlmbor of holcs 170 (one of which is shown in Figl~rc S) ` ~, ;' to receivo the plunger 150. The holes 170 are spaced along the front wall l~D at stcp-pitch intervals. Whcn the plunger of a front stile is so racciYed in onc of the holes 170 of a roar stile~ the front and rcar stiles ''~
I are locatcd with rcspoct to one another and only slight relative movement i5 possiblo in certain conditions to the oxtent permitted by movcment of `~
thc link l30.
Adjacent tho lowcr cnd of thc rear wall 14E of thc stile, as shown in Figurcs 6 and 7, a third block 172 is pro~idcd. This includcs 12~

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~a~s~s .. .... ~ .
S a pair of outcr portions l,~ and ~ centr~l T-scction portion 176. I`he} bloc~ 172 has on its uppcr edges inclincd lcad-in fac~s 17S. The configura-tion of the T-shaped portion 176 is such that i~ can be receivcd within the lower end of the channel 100 formed at the front of the rcar stile when the rear stile is to be rctained against the front stile in a storage position, as shown in Figure 8. Thus, referring to Figurc 8, it ~Yill be seen that the front and rear stile sections are aligned e~actly one with the o: ier and are retained securely against vertical movement in this relative position by means of the plunger 150, the stop 138 for the link 130 and also by abutment of the lower end of a block plate 180 which is shown in Figure 8 and also~in Figure 7. The block plate 180 is secured within the channel 100 by means of a pair of ~ivets 182. In this way the rear stile is prevented from downward movement by the engagement of the lower end of the block plate lS0 with the upper end of the T-shaped portion 176 of the block 172 and is prevented against rising upwardly because the plunger 150 is engaged in the topmost hole 170 of the rear stile. Upward movement of the shoe 120, which carries the plunger 150, is prevented by the stop 138 which prevents further anti-clockwise rotation o the link 130 in Figure 8. Thus a number of ladder sections can be retain~d one against the other for storage or simple transport by an appropriately posi-tioned handle. When it is desired to shift the rear stile section to the inverted V step ladder configuration of Figures 2 and 11, the plullgor 150 on the front stile is irst withdrawn by means of the lever 168, as shown in Fi~ure 9. This permits the rear stilo to be lifted until it is cloar of the T-shnped por~ion 176. The rear section of the ladder, while held up, can then be rotated slightly anti-clocXwise as shown in Figure 9, at which time the upper end of the lad~er section will still be in engagement witll the shoe 120. Therefore the shoe 120 will rotate slightly anticloc~wise from the position of Figure 8 to the postion of Figure 9. Tho rear SCCtiOII of the iad-~0 der c~n then be lowercd to the Figurc 10 position in ordcr to bring the rear section in line with the ront sec~ion at which time the plunger 150 ~3 ~a0~79yl5 ~ ~ ~san again latch tho uppel ends of thc stilc scctions togetllcr but with :~
their lower ends sep~ratcd. The li~c 130 in ~igurc 10 would now be trcc to rotate in a clockwise direction although it is biased upwardly by a tension spring 186. The rear section can be pivoted outwards to thc Figurc 11 position to form the step laddcr configuration. During rotation of the ladder sections to the inverted V-shape it is necessary to ensurc that, at the end of such rotation, the linlc 130 is held in its uppermost position. Unless this is achieved by the spring 186 it is achieved by means of the cam 140 engagir~ the lower wall 104 of the slot 102.
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As has been mentioned, in the Figure 11 configuration the portion 108A of the nosing block of a front ladder section engages in a rècess 136A in the front faces of the pressings 106 of the rear ladder ~
section so providing a good secondary lateral and vertical location of one ~`
section relative to the other During the rotation of the rear section of la~er the no~in~ block IOR of the rear section w;ll move above the nosing block 108 of the front section. Each nosirg block carries a catch `~
184 which is spring biased dowm~ards. Thq catch of the rcar ladder section ~ . .
can automatically be engaged over the nosing block 108 of the front section ; as shown in Figure 11. This retains the parts of the ladder in the con-~0 fi~uration shown in Figure 11. When it is desired to restorc the ladder to the Figure 8 condition the catch 184 can readily be releasod by manual opcration.
Turnin~ now to Figurcs 1~ and 13, these show the mannor in which the laddor is oxtandod to thc condition of Figure 1. To ~ovo tlle two soctions relatively to one anothcr to the extendod position it is to bo ~; ;
noted that it is thc rcar section which is to be raised. StartinO from a Figurc 8 or Figurc 10 position thc plunOcr 150 will, of coursc, bc with~
drawn whcrcupon thc rcar stilc can be liftcd by hand to any dcsircd dcgrce . ~ .
of c~tcnsion, for c~amplc, to thc condition sho~m in Figurc 12. At this ~4~95a~
~, timc tl~e lil~ l30 will oncc ~gain be biascd to its uppcr position by th~
sprinO 186. It is to bc notcd, that with thc lil~ 130 in a hori-ontal position tllcrc arc slight spacings shown at 188 betwecn the front and rear ~' stile sections as shown in Figure l~. This pcrmits easy slidin~ movement of the rear stile ~ith respect to the shoe 1~0. As soon as thc rear section of the ladder reaches the Fioure 1Z position the latch releasc ... .
lever 168 is released and the plunger 150 can e~tend through one of the holes 170 to locate and support the rear section in its extended position.
The holes 170 are so spaced that overlapping sections of ladder have their steps in alignment, e~cept that the lowest step on the upper section may-`~ be ono step pitch above the upper step on the lower section when the sections are fully e~tended. Extension is also restrictad beyond the Figure 12 position by engagement of the upper end 190 of the block plate 180 with the underside of the shoe 120.
While an up~ard load is imparted to the rear ladder stile section, the spacings 188 will be maintained. In this condition the ladder sections , are not fully stable but as soon as the support for the rear stile section is removed it will drop slightly as permitted by cloclcwise rotation le.~., by 5 - 20) of the lintc 130 to the position shown in Figure 13, For this '0 roason the up~ard bias of tha spring 186 is less than the do~m~ard weiOht impartcd by any single stile. At this tima the out~ardly faci~ angled surfacos 14C move into tight engagemont ~ith thc similarly angled but inward facing thrust faces 110 of the nosing block 108 on the one hand and with the similarly shaped thrust faccs 118 of the block 116, with the linlc 130 in tension, The condition in ~hich the angled contact faces 14G on thc for~ard edge of tlle rear stilc arc slightly spaccd from thc anglcd faces 1l~ and 110 of thc bloc~s 108 and 116 is shown in Figurcs ~
and 12. On thc othcr hand tho condition in wllich thcy are drawn toOothcr to locatc very positivcly is shown in Figuros 5 and 13, The rcar laddcr ~ .

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section is drawn do~n~ardly and inwardly by its o~m wci~hit towards tlle front laddcr section. In this position thc two laddcr sections are auto-matically securely located thus eliminating play and inhibitin~ latcral bcnding and ~orsional movements. The elevated rear section is strongly supported by the latch plunger 150 which is in shear loading in the hole 170 of Figure 13. When in use the link 130 is always in tension but one set of the upper or lower abutment and thrust faces will take the prime bending ioads (i.e. depending upon which way the extended sections are leaning). In order to ensure that the latch plunger 150 has engaged fully a series of inspection holes may be provided in the side walls 14A
adjacent each hole 170. Alternatively a means of visually ascertaining that the lever 168 and also thereby the plunger 150 have returned to their er~aged positions may be provided. Alternatively the plunger may be operated to each of its engaged or disengaged positions by a manually ;~
rcciprccablc lir~;aoo. ~-thermore, lockup means may be used to ensure that the latch plunger cannot be withdrawn when the weight of a rear section is being supported on the latch plunger. For example the latch plunger may be blocked from operating ~henever the lir~ 130 is in a down-w~rd-rotated position as shown in Figure 13.
It is believed that the opera~ion of the ladder will be generally .
apparent from the foregoing description. However it can be stressed that in mov1ng the ladder soctions relatively to one another, cither to and from an cxtended, leaning-ladder configuration, or to and from tho step-ladder confi~uration, the steps and side rails can either be lowered or not. However it is generally envisaged that the setting up of an extended ladder will best be performcd with thc steps and side rails in their closcd confi~uration. It can also be useful for some purposes to lean the stcps and hand rails 19 of an e~tended section folded up to facilitatc access to the work.

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~799S
Whcrc it is dcsircd ~o scparatc Ol1C laddcr scction complctely - from tlle other (or to reintroducc thcm into cngagcmcnt with one another), the s~ctions arc movcd from or into the ligure 9 confiOuration ".~ith thc plunOer 150 held out during appropriate stages of movement. ~s seen on the rear stile of Figure 8, the shoe 120 is tilted outwardly slightly to facilitate engagement of a further section.
While in the embodiment of Figures l to 18 the step strut 25 has been shown associated with the lowest step, it wi1l be appreciated that the strut could be associated with any step, even the top one, in which case the side rail will be placed in tension when steps below the strutted step are used. ~ith a handrail arrargement the outer end of the strut could have sliding engagement on t~e handrail rather than be connected to the step. It is to be noted that the step struts 25 of a rear section, when e.Ytended, are disposed above the foot space of a front section step.
~oreover, with the leg structures of the rear section folded down flS in Figure 1, these are out of the way of the footspace.
A further modification, not sho~n, is that where additional ladder sections are used, such sections need not necessarily have the leg assemblies thereon. It is to be noted however that the leg assembly, ~; 20 whether e.~tended or retracted, does not affect the ability of the sections to be extended with respect to one another. In additian, i~ is not - neccssary that additional ladder sections be all of the same lc1~-th.
FigurQ 19 illustrates an arrangement in which t~lreo ladder sections ~OS are arrangcd in cxtended formation to form a triple section ladder. In addition a fourth section 706 of idcntical form is arranged in in~erted V form with respcct to the top section 705. This illustrates tho e~trcme ~crsatility of thc laddcr and in particular shows a confi~ura-tion l~hicll can bo used on stairs or bctwecn thc ground and a highcr surfacc.
Figurc 70 illustratcs the use of laddèr scctions of thc type ` -17-r ' . . , ~ :

which have been described to support a working platform or scaffold or a gantry, for example carrying an engine liftirg hoist. While only one ladder section is shown a similar ladder section will support the opposite end of a platform grid 200 which is provided with an aperture 2~2 to receive a `
; plunger 150 at the upper end of a ladder section generally indicated at 204. The edge of the grid 200 which abuts the ladder section is formed with a pair of lips or hooks 203 to engage the shoe 120 of the ladder section 204. ~
Figure 21 illustrates two alternative embodiments. On the left- ;
hand side a handrail 219 is connected to four steps, namely two lower steps 220 and two upper steps 221. Two intermediate steps 222 are arranged to be capable of movement independent of the handrail, as shown on the left-hand side in Figure 21. This enables a person using the ladder to be able ~ ~`
to work through this section of the ladder, for example when paintirg, or to be able to stand with knees protruding through the gap formed by the raised intermediate steps 222.
On the right-hand side of Figure 21 further alternative aon-structions are shown. A pair of handrail sections 224 are connected each `
to three steps 225 so that the two handrail sections 224 can be independently operated. The lower handrail section and lower steps are shown supported by a strut 226. While the upper section 224 could be similarly supported~
no strut has been shown~ to indicate that the steps can be of cantilevered form if desired, the loading on the steps being accommodated at the inboard ends of one or more of them.
Furthermore the leg assembly can be modified. For instance the upper end of the leg strut could have sliding engagement on the stile, or the strut and leg could be cornected at their outer ends by a sliding connec-tion.
Figures 22-26 illustrate a still further embodiment of a ladder : . , , . :
- .. .. . : :

~- ~()479~5 according to the present invention. In this case, the ladder is not ex-tendable but has a built-in support member or "prop" which may be opened so that the ladder and prop form an inverted V configuration. In this open $ configuration, the ladder becomes a "step-ladder" of more or less traditional design. Unlike conventional step ladders, however, the ladder according to the invention may be folded together into a single elongate element which is easily portable and requires a minimum amount of storage space.
The ladder according to this embodiment is shown in Figure 22 ; in the open configuration, in Figure 24 in the half folded configuration and in Figure 25 in the fully folded configuration. Figure 23 illustrates how various elements of the ladder are connected while Figure 26 shows the respective positions of certain elements in cross-section when the ladder i9 in the folded configuration.
The ladder of Figures 22-26 comprises two outer stiles 236 and 238 having suitable rubber feet 240, 242, respectively, at their lower ends for providing a cushioned slip-resistant support which will not mar the floor surface on which the ladder rests. The sir~le, pole tyye support member or prop 244 is also provided with a shoe 246 for the same purpose.
In the central part of the ladder, at both front and rear, there are straps 248 and 250 which pi~otally suppo~ the ladder steps 252 and 254 extending outward in both directions at regular intervals along their length. The steps 252 (i.e., the steps on the left-hand side of the ladder as shown in Figure 22) are pivotally connected with outer stile 236 whereas the steps 254 (on the right-hand side of the ladder) are pivotally connected with the outer stile 238. The straps 248 and 250 extend up~ard beyond the topmost ~steps'l 256 and 258 and are pivotally connected at their upper ter-minus with two support struts 260 and 262. As is illustrated in detail in Figure 23, the struts 260 and 262 are in captive sliding connection with the upper steps 256 and 258, respectively, and, when the ladder is in the open or 1 ~4~9~5 erected position, they abut against stops in the region of the outer stiles .
236 and 238, respectively, so that the central straps 248 and 250 are pre-vented from moving downward with respect to the outer stiles beyond a point at which the steps 252 and 254 make an angle of approximately 90 with respect thereto, as shown in Figure 22. In this erected position, the struts 260 and 262 are in compression, whereas the upper steps 256 and 258 as well as the central straps 248 and 250 are in tension.
The prop 244 is pivoted to the strap 250 at a point near its . upper end, for example between the upper steps 256, 258 and the support :
struts 260, 262, as shown in Figure 23. The prop 244 is prevent~a from pivoting outward away from the strap 250 by an angle greater than approxi-mately 45 by means of a stay 264. This stay has a pivotal connection at 1 one end with the strap 250 and a sliding connection at the other with the ,~ prop 244. As the prop is manually moved in the direction of the strap 250 to close the ladder, the lower end of the stay 264 slides downwardly with ~
respect to the prop, tucking itself into the channel provided as illustrated ~;.` ;.
in Figure 26. .~:
Although the prop 244 in the embodiment shown must be moved manually ;
between its open and closed positions, apparatus may be provided to auto-matically open and close this member as the ladder is erected and folded~
respectively.
The two outer stiles 236 and 238 are formed as channel members ; having a U-shaped portion 265~ 266 and an extension portion 268, 270, as shown in Figure 26. ~hen the ladder is ~olded together, the U-shaped portions enclose the steps 252, 254, 256, and 258, the straps 248, 250 and the support struts 260, 262. The extension portions 268 and 270 fold over the prop 244 and stay 264 so that all of the elements of the ladder are covered, as shown in Figure 25, when the ladder is closed While various preferred embodiments have been described above~ it ~
20 - ; .

- . : -.; : ~:
, -~7995 will be understood that the present invention is susceptible to variousmodifications, changes ~nd adapt~tions as will occur to those skilled in the art. By way of example, and not limitation, a few of these variations will now be described:
As explained above in connection with Figures 6-11, a block 172 having a T-shaped portion 176 is provided a~jacent the lower end of the rear wall 14E of the front stile. This T-shaped portion 176 engages the lower end of the channel 100 formed at the front of the rear stile when the rear stile is to be retained against the front stile in a storage posi-tion. This arrangement requires that the rear stile be lifted manually off of the block 172 when the rear stile is to be pivoted outward into the st~p-ladder or inverted V configuration.
It may be desirable in some instances, particularly with small ( ladders intended for household use, to replace the block 172 with a simple detent so that the rear stile may be swung directly outwardly away from the front stile without first unlatching and raising it upward.
While the preferred embodiment disclosed and described in connec-tion with Figures 1-18 contemplates a ~Unimodular~ ladder system; that is, a ladder comprised of one or more identical ladder sections, each of which may be purchased separately and joined together in any desired configur~tion~
it will be understood that the invention is not limited to this concept.
When intended for general household use in particular, it may be desirable to provide a somewhat simpler ladder structure comprised of only two sections which are capable of being extended to form a straight extension ladder, or may be pivoted into the step-ladder or inverted V configuration. In this case, the two ladder sections need not be identical.
For example, in this simplified ladder the front ladder section (which remains the lower section when the ladder is extended), need not be provided with a slanted or cut away portion at the end of the central stile, ~ 21 ~

~47995 or with sliding grooves along the front side of the central stile. ~rther, since the ladder will not be extended beyond two sections, it may not be necessary to provide a self-tightening lakch. ;' ' Similarly, in a two section ladder the rear section will, of i course, not require a latch or any other means of support for retaining a further section on its rear side.
It will be appreciated that the ladder according to the present invention combines various features which contribute to making a common ;`~
device extremely safe and useful. By forming the ladder of three parallel stiles, interconnected by transverse steps, the strength of the ladder is ! considerably increased. This structure also increases the user's safety $
because the feet of the person using the ladder are constrained to the space ;~
between the centre and outer stiles, and therefore cannot slide sideways `~
as i possible with conventional two-stile ladders. ; `
The foldability of the ladder according to the present invention has the obvious advantage of facilitating the portability of the ladder and ~` minimizing the space required in storage.
Finally, the ability to support the upper end of the central stile of the ladder according to the present invention achieves three principal purposes: First, it increases the safety when the ladder is leaned against `
a building or other upright supporting surface because it utilizes the prlnciple of the ~three point~ contact. Second, it frees the design oE
side or outer stiles so that they can be more particularly tailored to their function as handrails and support members for the individual steps. ~nd third, it facilitates the construction of a Uni-modular ladder section which, when combined with other identical sections, form an extremely useful and flexible ladder system. ;~

22 ~
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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A portable foldable ladder comprising a ladder structure having:
an elongate central member, two elongate outer members arranged one at each of opposite sides of the central member, a plurality of steps disposed at spaced intervals on each of said opposite sides of the central member, and foldably connected both to the central member and to the respective one of the outer members, each outer member with its associated steps being arranged to fold between an erected position for use with the outer member spaced from the central member and the steps extending outwardly from the central member, and a storage position in which the outer member and the steps lie adjacent and substantially parallel to the central member, and releasable means for supporting said steps in their erected position; the ladder struc-ture being arranged at one end to engage the ground at two spaced points to support it above the ground or other surface, and having a foldable support member arranged to engage the ground or other surface at a third point when in an open position so that the ladder is supported at three points in use.

2. A ladder as claimed in Claim 1, in which said support member is foldable between a closed position parallel to the central member and an open position to form an inverted "V" formation with the central member in use of the ladder.

3. A ladder as claimed in Claim 2, in which said support member is pivotally mounted on the central member.

4. A ladder as claimed in Claim 2 or 3, including a foldable tension member arranged between the support member and the central member to prevent the support member from swinging beyond a given angle from the central member in use.

5. A ladder as claimed in Claim 1, ? or 3, in which the central member comprises two spaced generally parallel strips.

6. A ladder as claimed in Claim 1, 2 or 3, in which said outer members extend beyond one end of the central member in their erected position to engage the ground or other surface at said two spaced points.

7. A ladder as claimed in Claim 1, in which said outer members each have a cross section which includes a "U" shaped formation, said steps being received within the "U" shaped formation of the respective outer members when they are folded to said storage position.

8. A ladder as claimed in Claim 7, in which the cross section of the outer members further includes a flange disposed so that in the storage position of the outer members their flanges form a channel disposed to receive the support member in its closed position.

9. A ladder as claimed in Claim 1, in which said releasable means for supporting the steps comprises at least one strut means arranged on each side of, and extending outwardly from, the central member for supporting said steps and said outer members when in their erected position, the load on at least one step being transmitted, via the outer member to which it is connected and one of said strut means, to said central member.

10. A ladder as claimed in Claim 9, in which each of said strut means extends between the central member and the outboard region of one of said steps.

11. A ladder as claimed in Claim 10, in which each of said strut means is pivotally connected at the central member and slidably connected to the corresponding one of said steps.

12. A ladder as claimed in Claim 9, in which a single strut means is provided on each side of the central member for a group of steps inter-connected by an outer member, whereby a load on at least one of the steps of said group is transmitted via the outer member to said single strut means.

13. A ladder as claimed in Claim 12, in which all the steps on one side of the central member constitute a group of steps.