Step ladders provided a means for an individual to climb
The current invention relates to the field of household step ladders , and to the design of step ladders to permit a folding structure to be used as a self-supporting, or free-standing ladder, while maintaining an adequate degree of stability to prevent over-tipping and dangerous falls.
Step ladders provided a means for an individual to climb to a height for manipulating objects or performing work where the ladder is essentially free-standing; that is, the ladder depends solely upon its construction and erection to insure its stability, in comparison to standard extension ladders which are braced against a structure to be climbed.
A typical step ladder is designed to be folded into a convenient size for storage and carrying, and the requirement that it be portable is a further constraint, restricting the total weight of the ladder. Thus, a typical step ladder will be found to weigh thirty pounds or less weight, in order to insure that it may be easily handled, and it is typically designed to be folded into an essentially flat package of not much increased size over a fixed ladder of similar size.
The classic Aluminum step ladder has a front ladder portion having two vertically ascending parallel members with angled steps periodically interposed between to permit climbing. At an upper end a rear leg section is pivotally attached, and a folding brace member is used to extend the ladder into an expanded, climbable configuration. The front and rear leg members and the cross-brace form the classic letter "A" in the extended position.
Using a ladder that's too short can put stress on your back as well as expose you to the danger of toppling. Always choose a ladder that allows you to reach your work area safely.
Familiarize yourself with the ladder's load capacity. Light-duty ladders are designed to hold 200 lbs.; medium-duty ladders hold 225 lbs.; heavy-duty ladders hold up to 250 lbs.; and extra-heavy-duty ladders hold weights of up to 300 lbs.
The stability of such a ladder is totally dependent upon the user's movement upon the ladder during use. The requirement that the ladder be portable tends to reduce the static weight of the ladder to as low a level as is consistent with minimum structural strength, and it will typically be found that such a step ladder will weigh under thirty pounds; when considering that a typical user will weigh one hundred and fifty pounds or more, this implies that in use practically all the weight involved in the dynamic couple of step ladder and user will be concentrated in the user and that there will be very little static weight tending to Ladder stabilizer .
Use a stepladder for most household purposes. This type of ladder is available in heights of 4 to 16 feet and has a hand foldout shelf on the side opposite the rungs.
Use an extension ladder outdoors to reach high branches or the roof. These are made to reach 20 to 40 feet..
Try an articulated or multipurpose ladder for a variety of uses. This aluminum alloy ladder can be a stepladder or straight ladder or act as a scaffold, and comes in lengths of 12 to 16 feet.
The dynamic motion coupled from the user's motion imposes two separate forces to the ladder. The first is asymmetrical side thrusts. To the extent that the force of the user's weight is projected along the force of gravity but off centered from the center of gravity of the ladder a differential vertical loading is established downward along the leg. Since the total of the downward gravitational component along the leg must equal the total combined weight of the user with load and the static weight of the ladder, it should be apparent that significantly increasing the side thrust loading along one leg can result in a significant decrease in the thrust loading along an opposite leg. This can be observed in wooden step ladders of relatively filmsy construction on an uneven surface as an actual lifting of one leg off the ground; it is quite naturally an alarming condition to the user and occurs immediately before overturning and toppling. Furthermore, since ladders involve at least one lattice structure of vertical legs and steps, such uneven loading produces actual sideways stress upon the bottom portion of the parallel legs where they touch the ground. It has been observed by testing agencies that when Household ladders of typical construction are tested for this condition that some ladders will actually bend and fall at the forced detachment point of the leg and the lowest step due to the side thrusts generated.
The current invention discloses a step ladder of innovative design in which stability is enhanced by providing, in lieu of the standard paired, parallel rear legs, two individually extensible rear legs, coordinated by extension braces, and installed so that upon extension they form an expanding triangular footprint of increased stability in comparison to the rectangular footprint of a classic step ladder.
In addition, the individual rear legs are braced with a unique rigidified truss brace having a rigid cross-section and having means for fixation in the vertical plane, the legs are hinged with relatively wide torque resistant hinges to a rigid top plate from which descend fixed, vertical brace support which provides a point of leg brace fixation nearly in line with the center of gravity of the Ladder Manufacturer . This novel brace significantly decreases bending moment and movement possible within the legs and braces.
The result is an extremely rigid structure having a wide base footprint and a significantly decreased susceptibility to both static instability and to walking effects. The angles of extension of the rear legs produce a ladder which has a reduced tendency to walk as the user mounts to a higher step, due to the increased motion required of the user to produce an unloading effect on the triangularly extended legs.
Step ladders provided a means for an individual to climb to a height for manipulating objects or performing work where the ladder is essentially free-standing; that is, the ladder depends solely upon its construction and erection to insure its stability, in comparison to standard extension ladders which are braced against a structure to be climbed.
A typical step ladder is designed to be folded into a convenient size for storage and carrying, and the requirement that it be portable is a further constraint, restricting the total weight of the ladder. Thus, a typical step ladder will be found to weigh thirty pounds or less weight, in order to insure that it may be easily handled, and it is typically designed to be folded into an essentially flat package of not much increased size over a fixed ladder of similar size.
The classic Aluminum step ladder has a front ladder portion having two vertically ascending parallel members with angled steps periodically interposed between to permit climbing. At an upper end a rear leg section is pivotally attached, and a folding brace member is used to extend the ladder into an expanded, climbable configuration. The front and rear leg members and the cross-brace form the classic letter "A" in the extended position.
Using a ladder that's too short can put stress on your back as well as expose you to the danger of toppling. Always choose a ladder that allows you to reach your work area safely.
Familiarize yourself with the ladder's load capacity. Light-duty ladders are designed to hold 200 lbs.; medium-duty ladders hold 225 lbs.; heavy-duty ladders hold up to 250 lbs.; and extra-heavy-duty ladders hold weights of up to 300 lbs.
The stability of such a ladder is totally dependent upon the user's movement upon the ladder during use. The requirement that the ladder be portable tends to reduce the static weight of the ladder to as low a level as is consistent with minimum structural strength, and it will typically be found that such a step ladder will weigh under thirty pounds; when considering that a typical user will weigh one hundred and fifty pounds or more, this implies that in use practically all the weight involved in the dynamic couple of step ladder and user will be concentrated in the user and that there will be very little static weight tending to Ladder stabilizer .
Use a stepladder for most household purposes. This type of ladder is available in heights of 4 to 16 feet and has a hand foldout shelf on the side opposite the rungs.
Use an extension ladder outdoors to reach high branches or the roof. These are made to reach 20 to 40 feet..
Try an articulated or multipurpose ladder for a variety of uses. This aluminum alloy ladder can be a stepladder or straight ladder or act as a scaffold, and comes in lengths of 12 to 16 feet.
The dynamic motion coupled from the user's motion imposes two separate forces to the ladder. The first is asymmetrical side thrusts. To the extent that the force of the user's weight is projected along the force of gravity but off centered from the center of gravity of the ladder a differential vertical loading is established downward along the leg. Since the total of the downward gravitational component along the leg must equal the total combined weight of the user with load and the static weight of the ladder, it should be apparent that significantly increasing the side thrust loading along one leg can result in a significant decrease in the thrust loading along an opposite leg. This can be observed in wooden step ladders of relatively filmsy construction on an uneven surface as an actual lifting of one leg off the ground; it is quite naturally an alarming condition to the user and occurs immediately before overturning and toppling. Furthermore, since ladders involve at least one lattice structure of vertical legs and steps, such uneven loading produces actual sideways stress upon the bottom portion of the parallel legs where they touch the ground. It has been observed by testing agencies that when Household ladders of typical construction are tested for this condition that some ladders will actually bend and fall at the forced detachment point of the leg and the lowest step due to the side thrusts generated.
The current invention discloses a step ladder of innovative design in which stability is enhanced by providing, in lieu of the standard paired, parallel rear legs, two individually extensible rear legs, coordinated by extension braces, and installed so that upon extension they form an expanding triangular footprint of increased stability in comparison to the rectangular footprint of a classic step ladder.
In addition, the individual rear legs are braced with a unique rigidified truss brace having a rigid cross-section and having means for fixation in the vertical plane, the legs are hinged with relatively wide torque resistant hinges to a rigid top plate from which descend fixed, vertical brace support which provides a point of leg brace fixation nearly in line with the center of gravity of the Ladder Manufacturer . This novel brace significantly decreases bending moment and movement possible within the legs and braces.
The result is an extremely rigid structure having a wide base footprint and a significantly decreased susceptibility to both static instability and to walking effects. The angles of extension of the rear legs produce a ladder which has a reduced tendency to walk as the user mounts to a higher step, due to the increased motion required of the user to produce an unloading effect on the triangularly extended legs.
