US2760707A - Scaffold stair unit - Google Patents

Description

Aug. 28, 1956 A. ANDERSON 2,760,707

SCAFFOLD STAIR UNIT Filed July 9; 1951 INVENTOR. ARVID A. Anoeasom ATToRNEY SCAFFOLD STAIR UNIT Arvid A. Anderson, Milwaukee, Wis., assiguor to Safway Steel Products, Inc., Milwaukee, Wis., a corporation of Wisconsin Application July 9, 1951, Serial No. 235,819

1 Claim. (Cl. 228-45) This invention relates to a stair unit for use in prefabricated sectional scaffolding of the type employing standardized frame sections which may be interconnected to form a rigid structure of the desired size.

In the past ladders, either separate or integral with the frame members, have been employed to afford access to the various levels in the scaffolding. In addition to the obvious objection that ladders are relatively difi"1- cult to climb, it is impractical to attempt to carry a load when climbing a ladder. Recently there have been some efforts directed to provision of a scaffold stairway, but all designs thus far advanced have been objectionable for lack of versatility, erection difliculties and inefficient design so far as use and materials are concerned. The present invention overcomes past objections.

An object of this invention is to provide a simple, economical stairway unit for scaffolding.

Another object is to provide a stair unit which may be rapidly erected.

Another object is to provide a stair unit for scaffolding which is versatile and permits of a number of variations in erection to meet the needs of the particular installatron.

A further object is to provide a stair unit which includes clamp units for securing the unit to the scaffolding in a safe manner.

Still another object is to provide a clamp which normally holds the stair unit to the scaffolding and may be rendered inoperative to facilitate erection.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings, in which:

Fig. l is a side elevation of the stair unit with a portion of scaffolding shown in dot-dash lines;

Fig. 2 is an elevation as viewed from the right of Fig. 1;

Fig. 3 is a side elevation showing the manner of erecting the stair units in scaffolding;

Fig. 4 is an end view of Fig. 3;

Fig. 5 is a plan view of Fig. 3;

Fig. 6 is a side elevation of the clamp partly in section; and

Fig. 7 is a plan view of the clamp of Fig. 6.

Referring to the drawings in detail, the stair unit 10 includes a pair of stringers 12, 12 provided with a clamp 14 at each end. The clamps are designed to permit the stair unit to be rigidly fixed to the horizontal members 16, 16 of the scaffold end frames 18 except that the bottom of the lower stair unit (Figs. 3 and 4) is connected to a horizontal member 20 mounted on the standard end frame for this purpose. It will be noted that the stair unit is bent near its lower end so platform 22 will be horizontal when the unit is mounted between end frames which are interconnected by means of scissors type cross braces 24 which also serve to properly space the end frames.

Usually the stair units would be assembled as shown in Figs. 3 and 4 where the units are staggered and reatent quire changing direction at the end of each flight. Since the platform or stair landing is adjacent the top stair tread 26 when thus erected it is a convenient and easy ascent. Where the scaffold permits and it is desired the stair units may be assembled to provide a practically straight stairway (with the landing at each flight) by mounting one stringer between the stringers of the adjacent unit with successive units passing through the scaffolding in the same general direction. When properly assembled in this manner ascent may be made without changing direction at each landing. It will be appreciated that each unit will be out of alignment with adjacent units by the stringer thickness (usually no more than two inches) but this is of little importance.

The provision of clamps 14 at each end of each stringer 12 makes such versatility in erection possible. Each clamp has a head 28 provided with a U-shaped saddle 3t] and carried on a shank 32 which projects into the tubular stringer. The stringer is struck inwardly at diametrically opposed points to provide semi-elliptical tongues 34 to engage notches 36 in the shank and fix the clamp in the end of the stringer. A shoulder is provided between the clamp head and shank so the stringer may butt this point. Latch pin 38 is reciprocally mounted in the head and urged by spring 40 to project partially across the saddle opening to tangentially engage horizontal frame member 16. When thus clamped the member 16 may not be withdrawn until pin 38 is pulled back by means of actuator 42 pivotally mounted on the end of the latch pin by means of shaft 44. The actuator is provided with a forked nose 46 and may be rocked in the direction shown by the arrow in Fig. 6 to bring the nose into alignment with the axis of shaft 44 and the longitudinal axis of pin 38 as shown in dotted lines in Fig. 6. As may be seen, this movement pulls latch pin 38 back to open the saddle. Since the spring pull is ineffective in this position the pin remains withdrawn until the actuator is started back to its original position, at which time the spring will drive the pin out.

The ability to open the clamp in this manner greatly facilitates erection of the unit. All the clamps are first opened and the lower clamp may then be placed on the member 16, with the unit in a generally vertical position. The pins may then be released (a kick on the actuator will usually suffice) and the unit pivoted until the upper clamp seats on the member 16. The worker may then climb the steps and release the upper latch pins to complete the installation. This method avoids the need for supporting the weight of the unit at an awkward angle but it will be appreciated that all clamps could be seated first and that other methods may be worked out. Taking this unit down is also a simple matter due to the ability to hold the clamps open.

As shown in Figs. 3 through 5 these stair units afford access to plank 48. Planks may be provided at all or any desired level in the scaffolding. The present structure immediately suggests a modification essentially amounting to inverting the unit so the platform is at the top (with the clamp being turned so the saddle still faces downwardly) as if the drawings were inverted. Other changes will of course occur to the art and for this reason the present invention is to be limited only by the scope of the claim.

I claim:

A stair unit for use in scaffolding of the type including horizontally and vertically spaced parallel horizontal members, comprising a pair of parallel stringers adapted to be connected to vertically and horizontally spaced scaffold members, a quick release clamp at each end of each stringer for releasably securing the stringers to the members, a horizontal platform interconnecting said stringers adjacent one end of the pair of stringers,

and a plurality of treads interconnecting said stringers, along the remainder of the stringers, each said clamp comprising a U-shaped saddle the open end of which is adapted to face downwardly to receive a horizontal member of the scaffold frame When the unit is properly positioned in the scaffolding and includes a spring projected latch pin for at least partially closing the open end of said saddle together with manually operable pin retracting means for withdrawing the pin to a position permitting entrance of a scalfold member into the saddle, the manually operable pin retracting means is mounted for pivotal movement about a transverse axis carried by the pin, said pin retracting means including a cam portion eccentrically disposed with respect to said axis and adapted to ride on a cooperating surface provided on the saddle whereby when the pin retracting means is rotated on said axis, the pin is retracted against the bias of said spring, means for maintaining the pin retracting means in a position to retain the pin in retracted position, said pin retracting means being adapted for quick release by reverse rotation thereof to cause the pin to be projected to normal position by said spring.

References Cited in the file of this patent UNITED STATES PATENTS Knight May 6, 1884 Thomson May 6, 1890 Richards July 18, 1893 Chamberlain Feb. 17, 1903 Lillow Jan. 8, 1907 Duncon et a1. Jan. 19, 1909 McLeran Jan. 28, 1913 Auchu June 8, 1915 De Veau et a1. Dec. 15, 1931 Fee Oct. 11, 1932 Bailey Jan. 23, 1934 Uecker Aug. 2, 1938 Jaenichen July 23, 1940 Roney et a1. Jan. 19, 1943 Johnson et al Mar. 23, 1948 Wyscoki Nov. 15, 1949 FOREIGN PATENTS Austria Nov. 26, 1906

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