TECHNICAL FIELD
The present disclosure relates generally to lightweight scaffolding and, more particularly, to a lightweight, multi-function scaffold with a reversible platform.
BACKGROUND
Lightweight scaffolds made from metal tubing are commercially available for use when working close to the ground. One such scaffold comprises an adjustable height platform supported between two ladder frames. The platform includes two side rails with guide channels at each end that slide up and down along the vertical supports of the ladder frames. Casters insert into the lower ends of the vertical supports so that the scaffold can roll on the floor or other support surface. Also, the scaffolds are configured to be stacked vertically. Stability of the scaffold is provided by a braces that connect the guide channels to the platform.
The design of lightweight scaffold involves a trade-off between the height adjustment range and stability. Lightweight scaffolds tend to be less stable than typical heavy-duty scaffolding. Stability can be increased in two ways: by reducing the amount of play between the vertical supports of the ladder frame and the guide channel makes, and by reducing the flex of the ladder frame at the upper end of the adjustment range. Increasing the length of the guide channels at the ends of the side rails achieves both of these stability enhancements.
While increasing the guide channel length provides greater stability, it comes at the cost of significantly less adjustment range. The movement of the guide channels that slide along the legs is limited by interference with other components of the scaffolding. For example, when the platform is lowered, the guide channels may come into contact with other components. Because the guide channels extend down from the platform, the interference with other components establishes a lower limit on the platform height. Reducing the length of the guide channel would enable the platform to be lowered closer to the ground but would make the scaffolding less stable. Therefore, the length of the guide channels for lightweight scaffolding currently on the market compromises the adjustment range in order to improve stability.
SUMMARY
The present disclosure provides a lightweight scaffold designed to provide a greater range of height adjustment while at the same time greatly increasing stability. Greater stability is achieved in by increasing the length of the guide channels. Greater range of height adjustment is achieved by making the platform reversible so that it can be mounted between the ladder frames in either a first orientation or in a second orientation. Making the platform reversible increases the range of height adjustment in two ways. First, orienting the platform so that the guide channels extend in an upward direction allows the platform to be lowered closer to the ground than conventional designs. When the platform is oriented with the guide channels extending downwardly, the increased length enables the platform to be raised above an upper end of the ladder frame while maintaining stability. The stability can be enhanced by properly clamping the guide channel to the vertical supports of the ladder frame to remove play between the guide channels and the vertical supports.
According to another aspect of the disclosure, further increase in the adjustment range is achieved by providing openings in the guide channels that align with the openings in the vertical supports of the ladder frame used for connecting a caster or other ground engaging member. In a conventional scaffold, the caster or other ground engaging member includes a stem that inserts into the lower end of the vertical supports and is secured by a span pin that passes through aligned openings in the vertical support and in the stem of the caster. The guide channel cannot extend below the span pin so the span pin limits the range of movement. In exemplary embodiments disclosed herein, an opening is provided in the guide channel that aligns with the openings in the vertical support and caster stem when the platform is lowered to a predetermined height. The addition of the opening allows the platform to be lowered below the span pin to further increase the adjustment range.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a scaffold including two ladder frames and an adjustable height platform according to one exemplary embodiment.
FIG. 2A is a side view of the scaffold with the platform adjusted to a top of the ladder frame. In some embodiments, this is the maximum height.
FIG. 2B is a side view of the scaffold with the platform adjusted to a height above the top end of the ladder frame.
FIG. 3 is a side view of the scaffold with the platform adjusted to minimum height.
FIG. 4A is a partial perspective view of a side rail and guide channel for the adjustable height platform.
FIG. 4B is partial perspective view of a side rail and guide channel for the adjustable height platform with the platform extending above the height of the ladder frame.
FIGS. 5A and 5B are cross section views of exemplary side rails for the adjustable height platform.
FIG. 6 is a partial top plan view of the platform showing a locking mechanism to secure the deck to the side rails of the adjustable height platform.
FIG. 7 illustrates compact stacking of two ladder frames for shipment or storage.
FIG. 8 is an exploded perspective view illustrating a first method of mounting a caster to the scaffold.
FIG. 8A is a perspective view illustrating an alternate method for mounting the caster to the scaffold
FIG. 9 is an exploded perspective view of a stacking pin for the scaffold.
FIG. 10 schematically illustrates the adjustment range of the adjustable height platform.
FIG. 11 illustrates a method of adjusting the height of the platform for the scaffold.
FIG. 12 shows a perspective view of an alternative embodiment of a side rail assembly with a curved brace.
FIG. 13 shows a cross-sectional view of the side rail of FIG. 12 taken along XIII-XIII.
FIG. 14 shows a partial perspective view of a scaffold using the side rail assembly of FIG. 12, with the side rail in the second orientation for adjustment of the platform to a minimum height.
DETAILED DESCRIPTION
Referring now to the drawings, FIG. 1 illustrates a multi-purpose scaffold 10 according to an exemplary embodiment. The multi-purpose scaffold 10 comprises two ladder frames 12 and an adjustable height platform 20 supported between the two ladder frames 12. As described in greater detail below, the side rails 22 of the adjustable height platform 20 can be mounted between the ladder frames 12 in two different orientations depending on a height requirement for a task. The first orientation enables the platform 20 to be adjusted to its maximum height. The second orientation enables the platform 20 to be adjusted to its minimum height. In one embodiment, the adjustment range is between a maximum height of about 78.5 inches and a minimum height of about 10 inches providing an adjustment range of 68.5 inches. For comparison, the maximum height for conventional lightweight scaffolds of this type is about 71 inches and the minimum height for conventional lightweight scaffolds is about 27 inches providing an adjustment range of only 44 inches. In this example, the design enhancement yield a 55% increase in the adjustment range. The first orientation is for relatively greater heights, i.e., farther from the ground, and the second orientation is for relatively lower heights, i.e., closer to the ground.
Each ladder frame 12 comprises two vertical supports 14 connected by two or more cross members 16. The vertical supports 14 and cross members 16 are preferably made of a metal tubing or other tubular material. The cross members 16 are preferably welded at each end to respective ones of the vertical supports 14 so that each ladder frame 12 is a unitary structure.
In one embodiment, the vertical supports 14 have a square or rectangular cross-section and the cross members 16 have a circular cross-section. The outside diameter of the cross members 16 is less than the width of the vertical support 14. The cross members 16 can be offset from the center of the vertical supports 14 and the ends of the cross members 16 can be crimped or compressed to facilitate more compact stacking as shown in FIG. 7.
A series of aligned openings 18 extend through the vertical supports 14 perpendicular to the plane of the ladder frame 12 and are spaced 2 inches apart. As will be hereinafter described in more detail, the openings 18 are engaged by a releasable locking mechanism 30 on the platform 20 to secure the platform 20 at a desired height between the ladder frames 12. Additionally, openings 18a extend transversely through the lower end of each vertical support 14. These opening 18a are used to secure casters 50 to the vertical supports 14 when the side rail 22 is in the lowermost position as will be hereinafter described.
Referring to FIG. 4A, the platform 20 comprises two side rail assemblies that extend between the ladder frames 12 and a deck 40 that is supported by the side rail assemblies. Each side rail assembly comprises a side rail 22 and two guide channels 24 at opposing ends of the side rail 22. The side rails 22 are configured to provide a support surface for the deck 40 in both a first orientation and a second orientation. Two variations of the side rail 22 are shown in FIGS. 5A and 5B respectively. In both cases, the cross section of the side rail 22 is symmetrical about a horizontal plane H. In the embodiment shown in FIG. 5A, the side rail 22 comprises a generally C-shaped channel with a central web 22a two parallel flanges 22b. Stiffening flanges 22c extend outwardly from the outer ends of the parallel flanges 22b. In this embodiment, one parallel flange 22b provides a support surface for the deck 40 in a first orientation and the other provides a support surface for the deck 40 in the second orientation. In effect, the stiffening flanges 22c and the parallel flanges 22b form upper and lower bounded notches that include the support surfaces for the first and second orientations, respectively, and these bounded notches are disposed inward relative to the stiffening elements in the form of flanges 22c.
In the embodiments shown in FIG. 5B, the side rail 22 comprises a generally C-shaped channel with a central web 22a and two parallel flanges 22b as previously described with two additional channels 22d attached to the outer ends of the parallel flanges 22b. Like the previous embodiment, the parallel flanges 22b function as support surfaces for the deck 40 in the first and second orientations respectively. Thus, like described above, the channels 22d and the parallel flanges 22b form upper and lower bounded notches that include the support surfaces for the first and second orientations, respectively, and these bounded notches are disposed inward relative to the stiffening elements in the form of the channels 22d. The additional channels 22d provide greater strength and rigidity compared to the design in FIG. 5A.
The side rails 22 are equipped with internal latches 42 to hold the deck 40 down once the deck 40 is put in place. The latches 42 are mounted to the parallel flanges 22b of the side rail 22 and are configured to project up through slots 40a (FIG. 6) in the deck 40. The latches 42 include a catch element 42a connected to a spring-biased latch pin 42b that pulls the catch element 42a down into contact with the top surface of the deck 40. The latch pin 42b with the attached catch element 42a is rotatable. To secure the deck 40 in place, the latch pin 42b and attached catch element 42a are rotated so that the catch element 42a can pass through the slot 40a in the deck 40 while the deck 40 is being lowered into place. Once the deck 40 is in place, latch pin 42b is pushed upward and then rotated so that the catch element 42 engages the upper surface of the deck 40 as shown in FIG. 6. The latch pin 42b is biased by a spring 42c so that when the latch pin 42b is released, the catch element 42b presses the deck 40 down against the support surface, thus preventing the deck 40 from lifting up off the side rail 22.
Referring back to FIG. 4A, the ends of each side rail 22 connect directly or indirectly to a C-shaped guide channel 24 sized to fit around the vertical supports 14 of the ladder frames 12. In one embodiment, a square sleeve 23 is interposed between each end of the side rail 22 and the guide channel 24 for mounting a safety rail to the platform. The sleeve 23 is configured to receive posts P of the safety rail (not shown), which can be secured to the sleeve 23 by locking pins (not shown). In one embodiment, the side rail 22, sleeves 23, and guide channels 24 for each side rail assembly are welded together to form a unitary structure.
The guide channels 24 comprises a C-shaped channel and are configured to slide along the vertical supports 14 of the ladder frames 12 at each end of the scaffold 10 to adjust the height of the platform 20. Two openings 26 are formed in the inner flanges of each guide channel 24 for locking the guide channel 24 at a selected height as hereinafter described. The openings 26 are spaced to align with the openings 18 in the vertical supports 14 of the ladder frame 12 at preselected heights. The openings 26 in the guide channels 24 are engaged by a releasable locking mechanism 30 (described below) on the platform 20 to secure the platform 20 at a desired height between the ladder frames 12. A third opening 28 is formed near a lower end of the guide channel 24 and aligns with an opening 18 in the vertical support 14. A locking pin 29 passes through aligned opening 28 and 18 in the guide channel 24 and vertical support 14 respectively. The locking pin 29 serves as a failsafe and provides additional safety in case the locking mechanism 30 inadvertently disengages. Diagonal braces 25 connect a lower end of each guide channel 24 to the side rail 22 to increase the strength and rigidity of the assembled scaffold 10. The increased stability enhances worker’s confidence when standing on the scaffold.
Each guide channel 24 includes a releasable locking mechanism 30 for locking the platform 20 at a desired height. In one embodiment, the releasable locking mechanism 30 comprises a U-shaped locking pin 32 that engages with the aligned openings 26 and 18 in the guide channel 24 and vertical supports 14 respectively to lock the side rail 22 at a desired height. Each locking pin 32 includes a pair of spaced apart legs 32a connected by a cross member 32b. A bracket 34 supports the locking pin 32. The bracket 34 includes a pair of openings 36 through which the legs 32a of the locking pin 32 extend. Springs 38 surrounding each leg 32a of the locking pin 32 and bias the locking pin 32 to a locked position. The springs 38 are compressed when the locking pin 32 is pulled back to disengage the locking pin 32 and push the locking pin 32 back to an engaged position when the locking pin 32 is released.
The guide channel 24 as herein described is increased in length in comparison to prior art designs. The increased length enables the platform to be adjusted to a height above the top end of the ladder frames as shown in FIG. 4B. By increasing the length of the guide channels 24 from about 18 inches to about 23 inches, the maximum height for the platform can be increased from about 71 inches to about 78.5 inches.
In some embodiments, the scaffold 10 includes casters 50 disposed at the lower end of each vertical support 14 as shown in FIG. 8. Each caster 50 includes a stem 52 that extends into the lower end of a vertical support 14. The stem 52 is sufficiently long to overlap at least two openings 18 in the lower end of the vertical support 14. The stem 52 of the caster 50 includes an opening 54 that is located to align with an opening 18 in the vertical support 14 when the stem 52 of the caster 50 is inserted into the vertical support 14. A locking pin 56 passes through aligned openings 54 and 18 in the caster 50 and vertical support 14 respectively to secure the caster 50 to the vertical support 14.
In one embodiment, the stem 52 further includes a second opening 58 oriented 90 degrees relative to the first opening 54. The second opening 58 is for use when the platform 20 is adjusted to the minimum height as shown in FIG. 3. In this case, the obstruction of the guide rail 20 prevents insertion of the locking pin 56 through the aligned openings 54 and 18 in the caster 50 and vertical support 14. In this case, the second opening 58 aligns with opening 18a in the vertical support and an opening 27 in the guide channel 24 of the side rail 20 so that the locking pin 56 can be inserted through the aligned openings 58, 18a and 27 to secure the caster 50 to the vertical support 14.
FIG. 8A show an alternate embodiment, where the caster 50 includes s single opening 54 as previously described. In this embodiment, the opening 18a in the vertical support 14 is vertically aligned with an opening 18. In this case, the caster 50 can be turned 90 degrees so that the opening 54 aligns with opening 18a in the vertical support and the opening 26 in the guide channel 24 of the side rail 20 when the side rail is in the lowermost position as shown in FIG. 3.
In some embodiments, the casters 50 can be replaced by footpads, level jacks or socket levelers (not shown) or other ground-engaging member. comprising a generally flat pad that contacts the ground or underlying surface and a stem that extends into that extends into the lower end of a vertical support 14.
In a conventional scaffold 10, the guide channel 24 cannot extend below the span pin 56 securing the caster 50 or other ground engaging member the lower end of the vertical supports 14. Thus, the span pin 56 limits the range of movement at the lower end of the adjustment range. In exemplary embodiments disclosed herein, an opening 27 is provided at each end of the guide channel 24 that aligns with the openings 18a and 58 in the vertical support 14 and caster stem 52 respectively when the platform 20 is lowered below the span pin 56. The addition of the openings 27 allows the platform 20 to be lowered below the span pin 56 to further increase the adjustment range. In a conventional scaffold, the span pin 56 is 2.5 inches above the caster flange. Providing the additional openings 27 in the guide channel allow the platform to be lowered by an additional 2.5 inches plus ½ the diameter of the span pin 56.
In some embodiments, the ladder frames 12 include removable stacking pins 60 at the upper ends of the vertical supports 14. As shown in FIG. 9, the stacking pins 60 include a threaded end 60a that screws into an opening 62a in a mounting block 62 at the upper end of the vertical supports 14. The ability to remove the stacking pins enables more compact packaging for shipments and storage. Additionally, the design enables the use of interchangeable stacking pins of different size and/or shape.
When assembled, the scaffold 10 provides a free-standing, self-supporting structure. Outriggers 70 can be used with the scaffold to increase stability by providing a wider base. Conventional outriggers 70 for lightweight scaffolds are designed to extend out from the sides of the scaffold in a lateral direction, i.e., perpendicular to the longitudinal axis. This arrangement reduces the risk of tipping sideways but does not improve stability in the longitudinal dimension.
The multifunction scaffold as herein described provides a greater range of adjustment in the height of the platform 20. To obtain maximum height, the side rails 22 of the platform 20 are mounted between the ladder frames 12 in a first orientation as shown in FIGS. 2A-2B. To obtain the minimum height, the side rails 22 of the platform 20 are inverted and mounted between the ladder frames 12 in a second orientation as shown in FIG. 3.
FIG. 10 is a schematic illustration showing the range of adjustment of the platform 20 in the first and second orientations. For reference, the term first orientation is used as a label for the configuration shown in FIGS. 2A-2B and the term second orientation is used a label for the configuration shown in FIG. 3. In the first orientation, the downward movement is limited by the guide channels 24, which extend downward in this configuration. The lower bound of the downward movement is referred to as the first threshold. In this orientation, the platform 20 is adjustable to a height between the first threshold and a maximum height. In the second orientation, the guide channel extends upward and limit the upward movement of the platform 20. The upper bound of the movement is referred to as the second threshold. In this orientation, the platform 20 is adjustable to a height between the minimum height and the second threshold.
FIG. 11 illustrates an exemplary method of configuring the scaffolding for use. Prior to assembly of the scaffold 10, user determines a height requirement for a particular task (block 110). Based on the height requirement, the user selects either the first orientation or the second orientation (block 120). If the height requirement is greater than the first threshold, the user can install the platform 20 in the first orientation (block 130). If the height requirement is less than the second threshold, the user can install the platform 20 in the second orientation (block 140). If the height requirement is greater than the first threshold and less than the second threshold, the user can install the platform 20 in either the first orientation or the second orientation (block 150).
FIG. 12 shows an alternative embodiment of a side rail assembly, with a curved brace 25. As can be seen in FIG. 13, the brace 25 is located outwardly laterally offset relative to the flanges 22b forming the support surfaces for the deck 40. Thus, for the embodiment of FIG. 13, the brace 25 mates to the side rail 22 at the stiffening element, which is located laterally outward (to the left in FIG. 13) relative to the corresponding flange 22b. This lateral offset of the brace 25 allows the deck 40 to engage the flange 22b closest to the brace 25 (the lower flange 22b in FIG. 13) when the side rails 22 are in the second (or inverted) orientation (see FIG. 3). The braces 25 are advantageously located entirely outside the vertical projection of the perimeter of the deck 40 so that the braces 25 do not interfere with placement of the deck 40 against the support surfaces of the side rail 22 when the side rail assembly is inverted. See FIG. 14. Note that the lateral offset of the brace 25 applies at least to the end of the brace mated to the side rail 22, but that the end of the brace 25 mating to the guide channel 24 may or may not be laterally offset relative to the center of the guide channel, as is desired.
As can also be seen in FIG. 13, a plurality of alignment pins 21 are optionally mounted to the side rail 22 so as to extend from one or optionally both support surfaces of the side rail 22. The alignment pins 21 are intended to extend into/through corresponding holes in the deck 40 to facilitate maintaining alignment of the deck relative to the side rails 22. Also shown in FIG. 14 are alternative embodiments of locking pins 42, which extend through the stiffening element of the side rail 22, and are described more fully in PCT/US2022/030542, filed 23 May 2022 (the disclosure of which is incorporated herein by reference in its entirety). Further shown in FIG. 14 is that the releasable locking mechanism 30 is advantageously vertically spaced from the side rail 22 so that there is a gap between the releasable locking mechanism 30 and the side rail 22. The concepts illustrated in FIGS. 12-14, such as the laterally offset braces 25, the alignment pins 21, and the spacing of the releasable locking mechanism 30 from the side rail 22, may optionally be present in the other embodiments of the scaffold 10 described herein, alone or in any combination.
A lightweight, multi-function scaffold with reversible side rails is more versatile than conventional multifunction scaffolds and enables use of the scaffold over a greater range of height requirements while increasing stability. When the side rails are in the first orientation, the adjustable height platform is vertically movable between a first threshold and a maximum height. When the side rails are in the second orientation, the adjustable height platform is vertically movable between a second threshold and a minimum height. The ranges of movement in the first and second orientations may overlap.
Patent Application
20230151620
