US2857087A - Extensible step ladder - Google Patents

Description

EXTENSIBLE STEP LADDER I voct.v 21, 195s'-V Filed oct. 4, 1954 Oct. 21, 1958A B. PRATT 2,857,087 I EXTENSIBLE STEP LADDER Filed oct. 4, 1954 3 sheets-sheet 2 lie/Z527 fw??? iff/ vocbz, 195s y B F. PRATT 2,857,087 l v EXTENSIBLE STEP LADDER 3 sheets-'sheet s Filedoct. 4,v 1954 United States Patent() EXTENSIBLE STEP LADDER Bancroft F. Pratt, Quincy, Mass.

Application October 4, 1954, Serial N o. 459,917

2 Claims. (Cl. 228-21) This invention relates to a step ladder having a front ladder part with steps or treads and `a rear prop part hinged to the front part at the upper end of both. Each of these parts is independently extensible, the front part having extra steps for use when the part is extended. f It is an object of the invention to provide an extensiblev Figure 4 is a fragmentary section, on an enlarged scale,

von the line 4 4 of Figure 2;

' Figure 5 is a section on the line 5 5 of Figure 2;

Figure 6 is a side elevation of the ladder in its extended condition;

Figure 7 is a section on the line 7 7 of Figure'6;

Figure 8 is an enlarged section on the line 8 8 of Figure 7;

Figure 9 is an enlarged Figure 7;

Figure 10 is a perspective view of the principal member vofthe front part of the ladder;

Figure ll is a perspective view of the side members of said front part;

Figure 12 is a perspective view of the upper one of the two movable steps;

Figure 13 is a perspective view of the lower movable step;

Figure 14 is an enlarged section on the line 14 14 of Figure 7;

Figure 15 is an enlarged section on the line 15 15 of Figure 7; and

Figure 16 is an enlarged section on the line 16 16 of Figure 7.

The step ladder illustrated in the drawings consists essentially of the two customary parts, namely, a front or step part 20 and a rear or prop part 22. These parts are hinged together at their upper ends so that the ladder section on the line 9 9 of l can be closed for compact storage or open for use. The

front part 20 comprises two side channel members 24 and 26, these members being in the form of channels to combine lightness and strength.

The channel members 24 and 26 are permanently joined by a top platform 28 and one or more treads, two such treads 30 and 32 being shown in Figure 10. The treads are also preferably inverted channel members and are riveted or otherwise permanently secured at their ends to the side members 24 and 26. Each of the latter is reinforced by a rail 34 which extends longitudinally thereof and is permanently secured to the outer face thereof. Mounted on the lower portion of each rail 34 is a plate 36 which extends longitudinally of the rail and is wider than the rail so that its side margins project outl beyond the .side edges of the portion of the rail coveredv by the plate. The rails 34 reinforce the side members 24 and 26 and also serve as guides for extensions 40 and 42, such as are illustrated in Figure l1. Each of these extensions consists of a pair of angle irons 44 and 46 permanently connected in spaced relation by a cross member 48 at the lower ends thereof and by a bridge member 50 at the upper end.

The angle irons 44 and 46are parallel land are spaced apart so as to form a channel having a longitudinal ycenay tral slot 52. The width of this slot is slightly greater than the rail 34 so that when the extension member40 is slidably mounted on the outer faceof the side member'24,

the rail 34 fits Within the slot 52 and maintains the extension 40 aligned with the side member 24. The overhanging margins of the plate 36 overlap portions of the angle irons 44 and 46 so as to maintain the extension member 40 in assembled relation with the side member 24. In like manner the extension member 42 is slidably mounted on the side channel 26. Each of the rails 34 is provided with a series of holes 54 into which can enter a latch pin 56 mounted on the bridge 50 of each extension member 40 and 42. This latch pin 56 is movableginward to enter a selected hole 54 so as to lock the extension member against, sliding movementv relative to the .side member on Iwhich it is mounted. The pin 56 can'be retracted outward tto release the extension member for sliding movement to different positions relative to its .side

member. For this purpose each locking pin 56 may have a knurled head 58 which can be turned'to unscrew'` a threaded part 60 (Figure 15) in the bridge 50 so as to retract the locking pin 56 from a hole 54 orto move it into such hole. The extension `members 40 and-42 are preferably identical in structure sothat the description of oneservesras a description of the other. If the ' treads 30 and 32 are riveted to the side channels 24 and 26 so that the rivet heads project from the front and rear walls of the side channels, the extension members 40 and 42 are made of suficient width to allowclearances as at 62 fornsuchvrivet heads. p Thus the extensionV members 40. and-42 may be independently adjusted to Iany desired extent in order to increase the overall length of the front portion of the step ladder.

Additional treads are provided for use when the step ladder is in its extended position. Two such additional treads are shown in Figures l2 and 13. The upper tread 66 consists of a channel 4member adapted to extend horizontally between the side members 24 and 26. This tread has two hangers 68 and 70 extending up therefrom and adapted to slide within the side channels 24 and 26 respectively. These hangers extend through clearances 72 between the ends of the tread 32 and the .adjacent walls of the side channels 24 and 26 (Figure l0). The upper ends of the hangers are turned inward as at 74 to form elements adapted to catch on the upper face of the tread 32 when the tread 66 is moved down to its extended or lower position. The hangers support the tread 66 spaced suitably below the tread 32. The hangers 68 and 70 are substantially parallel to each other but are preferably bent slightly outward at their upper ends for frictional engagement with the side channels 24 and 26 so that when the tread 66 is pushed up to its inactive position immediately below the tread 32 as indicated in Figure 5, the tread 66 will be frictionally supported there.

A second movable tread is shown in Figure 13. This tread is ordinarily stowed immediately beneath the tread 66 when in its idle position but can be moved down to an active position spaced from the tread 66. The

movable tread 80 preferably consists of a piece of inverted channel to the ends of which are attached hangers 82 and 84. Each of these hangers has a longitudinal central slot 86 which is open at the bottom but closed `at its upper end 88. The hangers 82 and 84 are each disposed between one of the hangers `68 or 70 and the adjacent side channel 24 or 26. These hangers extend through the clearances 72 when the tread 80 is in its upper or idle position. When the tread 80 is moved to its lowered position as indicated in Figure 7, the slots 86 f thehangers 82 and 84 receive fixed buttons 90 which are secured to the inner faces of the side channels 24 and 26 at a suitable height as indicated in Figures 7, 10 and 16. As the tread 80 moves downward with its hangers, the fixed buttons 90 ride in the slots 86until the tread reaches its lowermostor active position. The buttons 90 are then at the upper ends of the slots 86 and thus support the tread 80 since no further downward movement is permitted. The hangers 82 and 84 are preferably sprung or slightly bent for frictional engagement of the side channels so as to hold the tread 80 in its idle position when it is pushed upward to such position.

The rear or prop part 22 lof the ladder may consist of a pair of parallel legs 92 which are hinged to a platform 94 at the top and on which an extension frame is slidable. This extension frame consists of a pair of tubular members 96 slidably fitted to telescope on the legs 92. The legs 92 and tubes 96 preferably, but not necessarily, have square cross-sections. In addition to thetubular members 96 the extension frame is also provided with cross braces 98 disposed as desired for strength and lightness. The extension frame can be moved downward from the position shown in Figure 3 to increase overall length of the prop part 22 and may be secured in a plurality of positions of adjustment relative to the legs 92. For this purpose locking pins 100 are provided, each of these pins being carried by a link 102 or 104 which are pivotally joined together as at 106 to form a toggle joint.

The links 102 and 104 are each pivoted at their remote ends to their respective 'tubular members 96 as at 108 and 110, these pivot points being oiset downward from the axis of the aligned links as illustrated in Figure 3 so that when the links are moved out of alignment to the position shown in broken lines in Figure 3, the locking pins 100 will be simultaneously retracted from notches 112 in the legs 92 (Figure 4). Each locking pin 100 projects through a suitable hole in the side of the respective tubular member 96 so as to be able to enter any selected notch 112 in the corresponding leg 92.

Thus the overall length of the prop part of the ladder can be made to correspond to that of the front part or can be shorter `or longer if it is desired, for example, to mount the ladder on a stairway.

I claim:

l. A step ladder having a front part comprising side channels, a plurality of treads extending between said channels and permanently secured thereto, the lowermost of said treads having clearances between its ends and the adjacent portions of said side channels, a reinforcing rail extending along the outer surface of each said side channel andpermanently secured thereto, a guide plate mounted on the lower portion of each said rail, each said guide plate having side margins projecting beyond the edges of the rail to which it is secured, an elongated extension member slidably mounted on each side channel, each said extension member having a longitudinally extending central slot with edges abutting the side edges of one of said rails, portions of each said extension member being overlapped by one of said plates, means for locking each said extension member in a plurality of positions relative to its respective side channel, and a movable tread extending between said side members, said movable tread having hangers extending upward through said clearances, and means on the upper end of each said hanger to catch on the lowermost ixed tread so as to support said movable tread.

References Cited in the le of this patent UNITED STATES PATENTS 722,409 Paskell Mar. l0, 1903 947,409 Hudson Jan. 25, 1910 1,040,313 Handy Oct. 8, 1912 1,269,142 Wilcke June 11, 1918 2,538,501 Bianchi 1 Ian. 16, 1951

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