US3112010A - Safety ladder - Google Patents

Description

R. MlHALlK SAFETY LADDER Nov. 26, 1963 3 Sheets-Sheet 1 Filed Oct. 10, 1961 INVENTOR Poms-W7 4/0944 BY v aux, W/AW ATTORN s:

R. MlHALlK SAFETY LADDER Nov. 26, 1963 3 Sheets-Sheet 2 Filed Oct. 10, 1961 INVENTOR 435?)- All/mak- BY M %w ATTORN s:

Nov. 26, 1963 R. MIHALIK SAFETY LADDER INVENTOR 1%55/97? M/Mz //r 5 Sheets-Sheet 5 Filed Oct. 10, 1961 United States Patent 3,112,011 SAFETY LADDER Robert Mihaiiit, Uniontown, Pa, assignor to The Patent Scaffolding Co. inc, Long Island City, N.Y. Filed 0st. 10, 1961, Ser. No. 144,184 2 Qlainrs. (1. 182-106) The present invention relates to ladders and more particularly to a ladder assembly consisting of a base and an extension ladder mounted on the base.

In the use of step ladders it is important that safety and utility exist concurrently. Too often facility of use or of folding for storage or economy have been attained only at some sacrifice of safety.

In the specification and the accompanying drawings I describe a ladder which combines these qualities to an extraordinary degree. I have also described certain modifications thereof.

It is to be understood that these are not intended to be exhaustive; on the contrary, these are supplied for purposes of illustration so that others skilled in the art may fully understand the invention, the principles thereof, and the manner of applying it in practical use, and will thus be enabled to modify and adapt it in various forms, each as may be best suited to the conditions of a particular use.

In the drawings:

FIGURES 1, 3, 4 and 6 are side elevation views of a safety step-ladder with an upper extension locked in operative upright position in FIGS. 1 and 4 and, folded down in FIGS. 3 and 6, illustrating the safety step ladder of the invention and, in FIGS. 4-6 a modified embodiment of the invention.

FIGURE 2 is a front elevation of the same structure as FIG. 1, and FIG. 5 is a front elevation of the same embodiment as is shown in FIGS. 4 and 6.

FIGURE 7 is a diagrammatic fragmentary detail view in side elevation showing the construction of the extra step and path of its swing.

FIGURE 8 is an isometric view partly broken away illustrating a platform structure suitable for use between the lower frame members.

FIGURE 9 is a fragmentary sectional detail of the telescoping extension lock device also shown in FIGS. 4, 5 and 6.

FIG. 10 is a detailed view in front elevation showing the leg and caster elevating structure.

FIG. 11 is a similar detailed view partly in side elevation, partly broken away, and partly in section.

FIG. 12 is a fragmentary detail partly in section and partly in elevation similar to FIG. 11 but showing the parts with the caster retracted.

Referring to FIGS. 1 and 2 there is shown a ladder assembly which comprises a rigid frame 11, comprising a plurality of upstanding members 12 and 13 with legs spaced apart, and each spaced from the straight line through others so as to give stable stance. These :members, in the ladder shown in FIGS. 1 and 2 are, respectively, guard rails 12. and rear uprights 13, and are connected by cross pieces 14, shown in these figures as running between guard rails 12 and rear uprights 13 a little above their bottoms.

The uppermost step 15 of the ladder connects the tops of said members 12 and 13 and forms a step platform which can be used either to support a workman or as a shelf for his tools, equipment and work materials. The other steps 16 are secured on at least one of the uprights, advantageously, as shown, engaging side rails at their ends which also serve to reinforce the frame structure 11.

The rear uprights 13 run from the back of the upper step platform 15 to the wheels 18.

An upper extension 26 to the ladder adds operative 3,112,010 Patented Nov. 26, 1963 height without sacrificing safety or compactness for moving through doors and for temporary storage. The upper step platform 15 serves as a base for a swivel mounted extra step 17 which can also be used as a shelf for tools, etc. When it is being used as an extra step, safety is maintained for the user by the provision of upper guard rails 12. A hinged shelf 21 is provided which may be collapsed flat against the rear upright extensions 13' when not in use. This increases the versatility of the ladder.

At each corner of the frame 11 is a wheel 13- whereby the =ladder can be readily rolled from place to place. As shown two of these wheels 18' are casters and two are mounted on fixed and parallel horizontal axes. This is advantageous for best guiding, and the casters are advantageously located at the side of the ladder where the operator will push or pull the ladder frame. Since it is most often convenient to do this from the front, grasping both hand rails 12, I have shown the casters 18 at the front corners and the fixed-position wheels at the rear corners.

In order to give stability in use it is desirable to have at least one of these wheels, and preferably the two casters, mounted over an elevating device which provides for elevating the frame on the wheels for rolling and lowering it so that its weight is supported directly on the legs 19, (which may be the lowermost parts of the hand rails 12) and lifting the casters off the floor. The drawing embodies such a device which is an invention of Arthur C. Borgman, claimed in his copending application Serial No. 144,183, filed October 10 1961.

FIGURES 10 and 11 illustrate this mechanism by which the casters are lifted off the floor leaving the weight of the ladder resting on legs 19, which securely fix its position during use, and by which the ladder is lifted again onto the wheels for rolling it from place to place. The caster is lowered to the floor, and the ladder elevated so as to be carried thereby, by putting pressure on a pedal 50.

The pedal 51 is on a bell crank lever 51, the shorter arm of which engages the top of caster stem 53 as a fulcrum pushing it down against the resilient lifting force of spring 55 and prying up the ladder. An extension 57 on bell crank 51 is engaged under rollers 61 on swing latch 58 to hold the caster down in rolling position. This latch 58 is urged into locking position by spring 59.

In this condition of the device, as shown in FIGS. 10, 11 and 12, the ladder is 1116614301116 for rolling; but, when a user steps on the first step 16, it swings down about pivot 61;, com-pressing spring 6 2 and engaging the projection 63 on latch 53 to swing back the latch and release bell crank 51, allowing the caster to be lifted by spring 55 and the leg 19 to drop the floor.

The fixed wheels 18 are advantageously on the rear legs 13 so that a workman coming down the steps can stand at the front of the ladder, grasp the hand rails 12 and roll the ladder in whatever direction is required. With the casters on the front legs, a pull to one side or the other will swing the casters and thus guiding the ladder is easy and natural. It is also possible to omit the casters, in which case the workman would pick up the front of the ladder by hand rails 12 and move it like a wheel barrow; but, with large ladders this may be quite difiicult.

FIGURE 3 represents the above described ladder when the upper extension has been folded down by rotation about its hinge into a position which decreases the height of the ladder so that it can pass through doors and be stored in closets of limited height. When the upper extension is so positioned, the upper platform on shelf 21 can be used as a wide shelf for tools.

In FIGURE 3, it will be seen that the extra swivel step axis of attachment 20. Thus, when not in use, this step may be folded down and out of the way beneath the upper platform 15.

Comparing FIGS. 1 and 3; the rest of the upper extension i.e., the upper guard rails 12' and the folding step 17 are pivoted forward to the position shown in FIGURE 3.

The curved braces 22 pass through a bushing 23. Both the bushing 23 and the arcuate braces 22 are provided with registering holes 24 and with a pin 25 on a chain or lanyard so that it can be pushed through the holes, when in alignment, to serve as a lock against rotation of the upper extension.

Another type of upper guard rail is illustrated in FIG- URES 4 to 6 and 9. In these, the folding top section is extensible. Upper members 27 of the guard rail 12a telescope onto an intermediate rod 29. By the use of the spring pin 30, the telescoped members are locked in a desired relation as shown in FIGURE 9. Each pin 36 is retracted when the guard rail 27 is lowered by telescoping, and is pushed into the hole 32 (FIG. 9) in the intermediate guard rail member 29 through an aligned hole in the front leg 28 at the desired position of extension. Thus when the guard rail is to be extended it only needs to be pushed up until the belt 36 snaps into place in hole 32. For retraction of the guard rail, the pin 30 is pulled out and gravity effects the telescoping. The back legs 13" may be fully secured by pins 33 on chains or lanyards inserted into corresponding holes in the back legs 13". With this structure the extension and retraction and locking can all be done by one man.

As FIGURE illustrates, the upper extension may be locked into an upright position by a lock pin 35 which will prevent the curved member 22 from sliding through the bushing 23 and hence prevent rotation.

The general construction of the extra swivel step 17 is shown in FIGS. 4 and 7. The folded-under position is indicated in FIGURE 7. FIGURE 4 shows the extra step 17 in a position ready for use as a step or shelf. It comprises basically four tubular legs attached to a rectangular top. The front legs 64 are unattached to the step upon which they rest, while the rear legs 66 are hinged for the swing-motion described.

In this embodiment a ring 36 has been attached to the back of the step assembly, which can be engaged with a hook 37 to secure the swivel-step in folded position below the upper step-platform.

A platform 38 is provided between the lower members 14 of the frame 11 for carrying tools and materials close to the floor so as to minimize danger of dropping off or spilling when the ladder is rolled from place to place. Such a platform is more clearly illustrated in FIGURE 8 where a part of its expanded metal floor 39 is broken away to show the peripheral frame 40 and cross frame members 41.

I claim:

1. A ladder structure comprising a rigid lower frame of limited height having interconnected uprights, hand rails and transverse members, a flight of steps secured in said frame between said hand rails, a platform at the top of said flight secured to the top of said lower frame, and a rigid extension pivotally secured to a top edge of said lower frame for swinging into upright position for effective vertical extension of the ladder structure and down into a lowered position for passage of the ladder into limited clearance spaces, said extension comprising an open frame at each side thereof disposed laterally beyond the planes of the sides of said lower frame whereby to overlap said sides when the extension is folded down, and cross members at the back between said side frames whereby to provide a support cell in which one can safely work while standing on said platform.

2. A ladder structure comprising a rigid lower frame of limited height having interconnected uprights, hand rails and transverse members, a flight of steps secured in said frame between said hand rails, a platform at the top of said flight secured to the top of said lower frame, and a rigid extension pivotally secured to a top edge of said lower frame for swinging into upright position for eiiective vertical extension of the ladder structure and down into a lowered position for passage of the ladder into limited clearance spaces, said extension comprising parallel polygonal side frames including front and back members, said frames being rigidly connected by cross members and pivotally connected to the main frame near its rear upper corner, a bottom member of said polygonal frame, when the latter is in its upright position, lying substantially parallel with and secured to the top member of said main frame, and, when in its lowered position, having its back member adjacent to and supported upon said top member of the main frame, and when in its upright position, having its front members substantially aligned with said hand rails of the main frame to form in effect extensions thereof.

References Cited in the file of this patent UNITED STATES PATENTS 818,484 Terry Apr. 24, 1906 1,439,388 Willet Dec. 19, 1922 2,479,736 Fieroh Aug. 23, 1949 2,604,251 Caughan July 22, 1952 2,798,652 Easton Jan. 12, 1955 2,897,910 Steely Aug. 4, 1959 2,923,373 Ledgerwood Feb. 2, 1960 FOREIGN PATENTS 128,182 Sweden May 9, 1950 791,282 Great Britain Feb. 26, 1958

Claims (1)

1. A LADDER STRUCTURE COMPRISING A RIGID LOWER FRAME OF LIMITED HEIGHT HAVING INTERCONNECTED UPRIGHTS, HAND RAILS AND TRANSVERSE MEMBERS, A FLIGHT OF STEPS SECURED IN SAID FRAME BETWEEN SAID HAND RAILS, A PLATFORM AT THE TOP OF SAID FLIGHT SECURED TO THE TOP OF SAID LOWER FRAME, AND A RIGID EXTENSION PIVOTALLY SECURED TO A TOP EDGE OF SAID LOWER FRAME FOR SWINGING INTO UPRIGHT POSITION FOR EFFECTIVE VERTICAL EXTENSION OF THE LADDER STRUCTURE AND DOWN INTO A LOWERED POSITION FOR PASSAGE OF THE LADDER INTO LIMITED CLEARANCE SPACES, SAID EXTENSION COMPRISING AN OPEN FRAME AT EACH SIDE THEREOF DISPOSED LATERALLY BEYOND THE PLANES OF THE SIDES OF SAID LOWER FRAME WHEREBY TO OVERLAP SAID SIDES WHEN THE EXTENSION IS FOLDED DOWN, AND CROSS MEMBERS AT THE BACK BETWEEN SAID SIDE FRAMES WHEREBY TO PROVIDE A SUPPORT CELL IN WHICH ONE CAN SAFELY WORK WHILE STANDING ON SAID PLATFORM.

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