US 1703424 A
Description (OCR text may contain errors)
Feb. 26, 1929.
F. HOFFMAN ET AL SCAFFOLD 2 Sheets-Sheet Filed Dec. 1, 1927 WIINEs 5135: W
ww N T w 5 ,A wmm I MW A g M fi Patented Feb. 26,1929.
UNITED STATES I 1,703,424 PATENT OFFICE.
Application filed Ileeember 1, 1927. Serial No. 236,950.
Our invention relates to scaffolds and more particularly to that type adapted to be suspended from an overhead support and having means for changing its elevation.
Scaifolds of this type often carry heavy loads and, when being. raised, their cables tend to pile up at the ends of the drums. One of the objects of the invention is to provide a scaffold having means for guiding the cables on the drums and preventing them from piling up thereon.
Another object is to provide a scafi'oldhaving means for raising or lowering both ends simultaneously and means for leveling the scaffold whenever the supporting cables are so attached to a supporting structure that one end of the scaffold is higher than the other. 7
A further object is to mount the lifting mechanism in a rigid overhead structure'and to suspend the platform support therefrom in such a manner as to provide free access to the wall of the building or other structure upon which the workmen are engaged.
These and other objects and advantages will be apparent from the following description when read in conjunction with the accompanying drawings, in which Figure lis a top plan view of a scaffold embodying our invention,
Figure 2 a side elevation thereof,
Figure 3 an end view, looking'from the right of Figure 2, and
Figure lan enlarged sectional view taken on the line 4-4 on Figure 3.
Briefly, the invention consists of a scaffold having a rigid upper frame in which the lifting mechanism is housed and from whichithe platform support is suspended; drums rotatable in the upper frame for carrying the cable by which the scaffold is supported; a cable guide threaded onto a shaft rotatable above each drum; springs'on each end of each of the shafts for forcing the cable guide away from the flange of the drum so that the cable will not pile up at tlllS point; worm shafts and worm wheels for rotating the drums, and a shaft for rotating the worms and adapted to be detached from them so that one drum may be rotatedindependently of the other for the purpose of leveling the scaffold.
Referring now in detail to the drawings, the scaffold is rovided with a rigid upper frame composed of a top strut 5 having a pair of drum supports 6 and 7 fixed on one of its ends and a pair of drum supports 8 and 9 fixed on its other end; the drum supports on one end of strut 5 being opposite hand to those on its other end. .1.
A rod 10, having an eye in each end, depends from a single pin or bolt 11 extending through the lower parts of drum supports 8 and 9 and a bar 12 depends from a pin or bolt 13 extending through the lower parts of drum supports 6 and 7 rod 10 and bar 12 being swingable on pins 11 and 13 and prevented from being clamped between the drum supports by suitable shoulders 14 formed thereon. A platform support 15 is preferably swingably supported by rod 10 and bar 12 and may consist of a pair of small channels disposed back to back on either side of the rod and bar, as shown in Figure 3.
A drum 17 is rotatably. mounted in each pair of drum supports and has secured thereto one end of a cable 18 which is windable thereon and adapted to have its upper end secured to any suitable overhead support, such as the Lbeam 19 shown in Figure 3, for the pur dose of suspending the scaffold. The shaft 0 one drum 17 extends through drum support 6 and has a worm wheel 20 fixed thereon and meshing with a worm 21 rotatably mounted in bearings 22 and 23 secured to or formed integral with drum support 6.
A worm 24 is rotatably mounted in bearings 25 and 26, fixed to or formed on drum support 8, and meshes with a worm wheel 27 fixed on the shaft of the other drum 17 the threads thereon being opposite hand to those on worm 21 so that cables 18 may be led from the outside of each drum 17. The ends of the shafts of worms 21 and 24 are flattened and con-- nected to one another by a shaft 28 which has a bifurcated head on each end straddling the flattened ends of the worm shafts and held in engagement tlierewith by means of suitable pins or bolts, as shown in Figures 1 and 2.
A chain wheelv 30 is fixed on shaft 28 and encircled by a hand chain 29 by means of which the scaffold maybe raised or lowered after it has been swung from a structure. If one end of the scaffold is higherthan the other, shaft 28 may be; disconnected from worm 24 and the scaffold leveled by rotating worm 21 by means of chain wheelBO, the free end of shaft 28 being manually supported during this operation.
While the load on cables 18 could not cause worm wheels 20 and 27 to rotate worms 21 and 24 and thuscause the scaffold to work wheel, and a pawl 33 pivoted on the drum" support immediately above it.
Pawl 33 may be brought into and out of engagement with ratchet wheel 32 in any suitable manner but has been shown as being fixed on a shaft 34 which extends through the drum support and has a handle 35 fixed on its outer end so as to be accessible to the workmen upon the scaffold platform. Ratchet wheel .32 may be cast integral with drum 17 or made separately and v-s'ecured thereto by suitable bolts or rivets, as shown in Figure 4.
\Vhen the scaffold is in use and being raised, cable 18 will feed along the barrel of drum 17 in the well known manner until the layer being formed is complete, at which time, it is inclined to make several concentric turns adjacent the flangeiof the drum as there is no surface to feed it along the barrel of the drum, as is the case when the cable being wound on the drum comes in contact with the side of the contiguous turn of cable thereon.
In order to overcome this tendency, a threaded shaft 36 is rotatably mounted immediately above drum 17 and has threaded thereon a cable guide 37 having a bifurcated end 38 straddling cable 18 and an apertured end 39 slidable on a guide rod 40 fixed in the upper part of the drum supports. Threaded shaft 36 is held against axial movement by a collar 41 fixed on one of its ends and a hand wheel 42, having an enlarged hub, fixed on its other end and adapted for manual operation.
The pitch of the thread on shaft 36 is very steep so that cable 18 may move. cable guide 37 and cause it to rotate shaft 36 when the scaffold is being raised or lowered. In case cable 18 does not wind correctly on drum 17, it may be forced to do so by rotating hand wheel 42.
As stated above, cable 18 generally winds uniformly on the barrel of drum 17 except when in contact with one of its flanges and it is therefore advantageous to provide means for starting the cable winding across the barrel of the drum in the opposite direction.
We accomplish this by means of short coiled springs 43 which encircle the ends of shaft 36 and abut the inside faces of the drum support, as shown in Figures 1 and 3. As long as the cable being wound on the barrel of the tudinally of the drum and spring 43 will force cable guide 37 away from the flange and cause it to start on its return journey across the barrel of the drum.
When scaffolds of this type are in use, a number of them are suspended from the side of the structure upon which work is to be performed and a platform built by extending planks between the platform supports of'adjacent scaffolds soas to form a continuous platform along the side of the structure. \Vith our improved scaffold in use, free access is had to the side of the structure as rod 10 is the only part of the scafiold between the workmen on the platform and the side of the building. I 7
As it is preferable to provide a back rail along the outside of the scaffolding so erected, a rail bracket 44 is rigidly secured to bar 12, at a suitable distance above platform support 15, and a suitable rail, such asa piece of two by four framing supported in adjacent rail brackets. A hook 45 is also preferably secured to bar 12 above rail bracket .44 to provide a suitable support for tools so that they do not need to be laid upon the platform or hung over the back rail, as the custom when using ordinary scaffolds. 1
VVhile we have described our invention as taking a particular form, it' will be understood that modifications may be made without departing from the spirit thereof, and hence we do not limit ourselves to the precise construction set forth, but consider that we are at liberty to make such changes and alterations asfairly appended claims.
We claim 1. A scaffold including a top strut, a pair. of drum supports rigidly secured on each end of the strut, a drum rotatable in each pair of drum supports in alignment with the center line of the strut, a worm wheel secured to ea'eh drum, a worm meshing with each worm wheel, a shaft "separabiy connecting" the worms, means for rotating the-shaft, cables for supporting the scaffold windable'on the drums, and a platform support swingably depending from the drum supports. 7 I
2. A scaffold including a top strut, a pair of drum supports rigidly secured on each end of the strut, a drum rotatable ineach pair of drum supports in alignment with the center line of the strut, a worm wheel secured to each drum, a worm meshing with each worm wheel, a shaft separably connecting the come within the scope of the worms, means for rotating the shaft, cables for supporting the'scafi'old wind-able on the drums, a rod swingably depending from one pair of drum supports, a bar swingably depending from the other pair of drum sup ports,.and a pair of channels swingably. sup-. ported by the bar and rod.
3. In a scafiold having a drum and a cable windable thereon, means for guiding the cable longitudinally of the drum including a threaded shaft rotatable adjacent the drum, a guide rod fixed adjacent. the shaft, a cable guide, havinga bifurcated end straddling the cable, threaded onto the shaft and slidable on the rod, and means for manually rotating the shaft; the threads on the shaft having a sufliciently steep pitch to allow the cable tomove the cable guide along the shaft.
4. In a scaffold having a drum and a cable windable thereon, means for preventing the cable from piling up including a shaft rotatthe shaft and slidable on the rod and adapted to be moved along the shaft by the cable,
means for-manually rotating the shaft, and means for moving the cable guide away from the sides of the drum.
In testimony whereof we have signed our names to this specification.
- FRANK HOFFMAN.