US3516512A - Mobile scaffold - Google Patents

Description

June 23, 1970 R. M. KUPKE ETA!- 3,516,512

' MOBILE SCAFFOLD Filed March 6, 1968 3 Sheets-Sheet 1 INVENTORS RUDOLF M. KUPKE KARL-HEINZ LADWIG PETER LADWIG C. A. MANFRED MORTENSEN H. HARRY HANDSHACK ATTORNEY June 23,1970 R. M. KUPKE ETI'AL MOBILE SCAFFOLD 3 Shgets-Sheet 3 Filed March 6, 1968 INVENTORS m mwwm Mmm mmm FIT LEED 0 P w F Rm N M A. C.

' HARRY ELKIDSFA-Ch \Ukf ATTORNEY June 23, 1970 R. M. KUPKE ETAL MOBILE SCAFFOLD Filed March a, 1968 3 Sheets-Sheet 5 United States Patent US. Cl. 18216 25 Claims ABSTRACT OF THE DISCLOSURE A mobile scaffold wherein a wheel-mounted carriage supports a multi-section upright tower which guides a vertically movable rectangular work platform provided with hingedly mounted auxiliary platforms. The tower is ec centric with reference to the carriage and one longer side of the platform has a recess for the tower. The drive for the platform comprises a row of teeth provided on one standard of the tower, a wheel which carries an annulus of rollers engaging with successive teeth during movement of the platform and two reversible electric motors mounted on the platform to rotate the wheel by way of self-locking transmissions. Stabilizing arms are detachably connected with the carriage so as to be movable between extended and retracted positions in response to detachment from, inversion by 180 degrees, and renewed attachment to the carriage.

Bridges can be employed to connect the platform with the platform or platforms of one or more adjoining scaffolds. Such bridges are pivotable with reference to the platform so that they can be moved to or from horizontal positions.

BACKGROUND OF THE INVENTION The present invention relates to scaffolds in general, and more particularly to improvements in mobile scaffolds of the type wherein a work platform is movable up and down along a tower or mast.

Presently known scaffolds of the just outlined character normally comprise a work platform which fully surrounds the tower from all sides and wherein the height of the tower can be changed by adding or removing sections at its upper end. The drive for the platform comprises a rack on the tower and a pinion mounted on the platform and meshing with the rack. A serious drawback of such scaffolds is that the parts of the drive undergo excessive wear, that their operation is affected by impurities in the surrounding atmosphere, and that they require frequent and extensive maintenance. Furthermore, and since the platform surrounds the tower from all sides, the latter cannot be readily attached to a building front or the like in order to enhance the stability of the scaffold when the tower is very tall. Still further, such scaffolds cannot be moved sufficiently close to buildings or like edifices which are provided with wings, balconies or other protuberances. Additional problems arise when the drive for the platform employs an electric motor because the conductors serving to supply electrical energy to a motor which is mounted on and moves with the platform must receive current by way of brushes, slip rings and like parts which undergo considerable wear. Furthermore, conventional scaffolds are not sufficiently versatile in that their personnelor work-supporting area cannot be enlarged or reduced to the extent necessary to insure economical operation in construction, building or bridge maintenance, wire laying, painting, plastering, cleaning and/ or like work. As a rule, the area of the work platform is changed by resorting to extensible 0r retractible panels which are connected with counterweights serving to stabilize the scaffold when ice the panels are moved to extended positions. The counterweights add to the bulk of the scaffold and limit the maximum height of the tower as well as the capacity of the work platform to accommodate personnel and/or other loads.

SUMMARY OF THE INVENTION It is an object of our invention to provide a mobile scaffold which can be hitched to trucks, trailers or like prime movers for transport to and from the locale of use, whose dimensions are such that it can be transported on public roads, and whose height can be readily and rapidly altered by a small number of workmen.

Another object of the invention is to provide a mobile scaffold which can be used indoors or outdoors, which can be readily and rapidly converted to accommodate larger or smaller groups of workmen and/or smaller or heavier and bulkier loads, and which can be transported along or in the interior of buildings or other edifices by or without resorting to a prime mover and without necessitating even partial dismantling for transport over relatively short distances.

A further object of the invention is to provide a mobile scaffold which can be assembled with one or more similar scaffolds to form therewith a chain of scaffolds adapted to extend along one or more sides of large buildings or groups of buildings, around a chimney or mast, as well as into recesses between the wings of buildings or into similar hard-to-reach areas.

An additional object of the invention is to provide a scaffold which can be used in all types of climates, in snow, sleet, rain, on icy roads or grounds, in mud or on grounds covered with fragments of construction material, and which can be moved sufficiently close to an edifice or the like to enable the workmen to perform their tasks without leaving the platform or platforms of the scaffold.

A concomitant object of the invention is to provide a rugged scaffold which requires little maintenance, which comprises a relatively small number of simple parts, which is provided with simple, compact and reliable means for moving workmen and materials to a desired level, and which is sufficiently safe to meet the regulations of authorities which determine the standards for construction, building maintenance, repair, bridge maintenance, wire laying and like equipment.

Still another object of the invention is to provide a mobile scaffold which is provided with stabilizing devices capable of being moved to and from retracted positions in which they cannot interfere with transportation of the scaffold on narrow roads, and which is also provided with a novel system of means for supplying electrical energy to its motors and/ or other current-consuming units.

An ancillary object of the invention is'to provide a mobile scaffold which, in addition to serving as a highly versatile piece of equipment in construction, building maintenance, lighting installation or repair, wire laying, painting, plastering, cleaning and/or like work, can be used to facilitate the work of personnel in changing its overall height.

A further object of the invention is to provide a mobile scaffold whose manipulation is very simple and which is provided with a novel drive system for moving the workmen and/or materials to a desired level above the ground.

An additional object of the invention is to provide a scaffold whose height can exceed or at least equals that of presently known scaffords and wherein the area which be coupled to a tractor or the like, and several adjustably mounted stabilizing arms provided with ground contacting legs and/or wheeled trucks, an upright tower which is eccentrically mounted on the carriage and comprises a stack of superimposed sections consisting of three or more parallel standards of tubular steel stock or the like and stiffening braces connecting the standards, a work platform having an eccentrically located recess for and being movable up and down along the tower whereby the platform partially surrounds the tower cooperating guide means provided on the tower and on the platform to guide the latter during movement toward or away from the carriage and preferably including clusters of rolls mounted on the platform and rolling along two or more standards of the tower, and drive means for moving the platform with reference to the tower. Such drive means preferably comprises a row of teeth provided on one of the standards, a wheel rotatably mounted on the platform and having an annulus of rollers engaging with successive teeth when the platform is in motion, and a pair of electric motors mounted on the platform and arranged to drive the wheel by way of self-locking transmissions. Such motors may receive current through a cable the upper end of which is mounted on the platform and the lower portion of which is convoluted on a cable drum fixed to the carriage. The cable is being collected on or withdrawn from the drum in automatic response downward or upward movement of the platform.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved scaffold itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary side elevational view of a mobile scaffold which embodies one form of our invention;

FIG. 2 is a top plan view of the scaffold with certain parts broken away;

FIG. 3 is a side elevational view of a bridge which connects two scaffolds of the type shown in FIGS. 1 and 2; and

FIG. 4 is a fragmentary top plan view of a modified mobile scaffold.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 and 2, there is shown a mobile scaffold which comprises an underframe or carriage 1 having two road wheels 2 with inflated tires and a vertically adjustable hitch 3 by means of which the scaffold can be attached to a truck, tractor or other suitable prime mover. The carriage 1 supports the lowermost section 9 of a multi-section tower or mast 4 which is of triangular cross-sectional outline and extends into a triangular recess 10b provided in one longitudinal side 10a of a main work platform 10, namely, in that side which is adjacent to the front of a building or other edifice which is being erected or repaired by workmen employing our scaffold. As shown in FIG. 1, the tower 4 is installed eccentrically midway or nearly midway between the longitudinal ends of the carriage 1 and one of its three sides is parallel to and flush with or closely adjacent to the side 1011. Each section 9 of the tower 4 comprises three vertical uprights or standards 5', 5, 6 and diagonal stiffening braces 7 a few of which are shown in FIG. 2. The sections 9 are coupled to each other, endto-end, by quick-release couplings 8 of any known design. The main work platform which is movable up and down along the tower 4 is preferably employed to transport sections 9 upwardly so that workmen standing on 4 the platform can manipulate the couplings 8 to assemble a tower of desired height.

Each corner portion of the substantially rectangular carriage 1 can be connected with an elongated stabilizing arm 11 by means of bolts 12 or analogous fasteners. FIG. 2 shows two of the arms 11 by solid lines in their normal or extended positions in which they extend laterally and well beyond the platform 10 (see the two upper arms 11 in FIG. 2). The other two arms 11 are shown by solid lines in their retracted or concealed positions 13 in which they extend in substantial parallelism with the adjacent longer side 10a of the substantially rectangular platform 10. The extended positions of these two other arms 11 are indicated by phantom lines. In order to move an arm 11 from extended position to the retracted position 13, the arm must be detached from the carriage 1 (removal of bolts 12), inverted about its longitudinal axis by degrees, and reattached to the carriage in retracted position. This will be readily understood by observing the positions of bolts 12 in FIG. 2. All of the arms 11 are moved to extended positions when it is necessary to assemble a tall tower 4 so as to prevent tilting and eventual over-turning of the scaffold. However, when the work platform 10 must be moved close t the front of a building or the like, two of the arms 11 are moved to retracted positions 13 in a manner as shown in FIG. 2 so that the tower 4 may be moved close to the front of the building and, if necessary, attached thereto at one or more points. In other words, when the two lower arms 11 of FIG. 2 are moved to the retracted positions 13, each section or one or more sections 9 of the tower 4 can be secured to an edifice which requires repair or other treatment. This is possible because the braces 7 between the standards 5 of the tower 4 are readily accessible.

The outer end portion of each arm 11 carries a vertical spindle 14 and the end portions 15 of each spindle constitute female coupling elements which can be connected with male coupling elements provided on groundengaging legs 16. The spindles 14 are externally threaded and mesh with nuts in the outer end portions of the respective arms 11 so that they may be moved axially to adjust the inclination and/or height of the carriage 1. A crank or a like tool (not shown) can be coupled to the upper end portion 15 of each spindle 14 to facilitate its rotation with reference to the arm 11. As shown in FIG. 1, the end portions 15 are provided with diametral slots 17 which can receive a complementary rib or a like projection on the crank. Each leg 16 can be connected to either end portion 15 of the respective spindle 14, i.e., these legs can be applied to the spindles irrespective of whether the arms 11 are mounted in extended or retracted positions. In order to move an arm 11 from extended position to retracted position or vice versa, the operators simply detach the cranks from the upper end portions 15 and the legs 16 from the lower end portions 15 of the respective spindles 14 and thereupon detach the arms 11 from the carriage 1 prior to inversion of arms and reattachment to the corresponding corner portions of the carriage.

If the ground which supports the scaffold is solid, e.g., if the scaffold is used in a hall or on a paved street for repair of building fronts, it is often desirable to roll the scaffold along the building or from a building to the next locale for use. Such rolling or transport can be effected without necessitating and dismantling or shortening of the tower 4. To this end, a wheeled truck 18 can be mounted below each leg 16 and secured thereto by mating male and female threads or by one or more bolts and nuts or the like. The legs 16 and the trucks 18 are free to swivel about the axes of the respective spindles 14 so that the scaffold can readily change the direction of its travel. In order to prevent uncontrolled changes in direction during transport, each truck 18 preferably comprises two coaxial rolls or Wheels 19a and a third centrally located steering wheel or roll 19 which is offset with reference to the wheels 19a. The wheels 19a are located at the opposite sides of the respective spindle 14.

The work platform 10 comprises a profiled rectangular frame 21 which is reinforced by longitudinally, transversely and/or otherwise extending stiffening braces 20. The inclined braces 20a shown in FIG. 2 are adjacent to longer side 10a of the platform 10 and define between themselves a substantially triangular recess or passage for the tower 4. The outer ends of the inclined braces 20a are adjacent to two vertically extending supporting tubes 22 which are sufficiently strong to withstand substantial bending, twisting and other stresses. The lower end portions of the supporting tubes 22 are connected to the opposite corner portions of the frame 21 by diagonal braces 23. The supporting tubes 22 form part f a guide means for the platform 10 and each thereof carries four pairs or clusters of guide rolls 24, 2'5 rotatable about horizontal axes and arranged to roll along the adjoining standards of the tower 4. Two pairs or clusters of rolls 24, 25 are disposed at each end of each supporting tube 22 and the axis of each roll 24 makes with the axis of the adjoining roll 25 an angle of 12.0 degrees. The axes of the rolls 24 are parallel with the adjacent longer side a of the platform 10 (see FIG. 2). The rolls 24 take up the major part of the weight of the platform 10 whereas the rolls 25 prevent sidewise movements of the platform. The area between the left-hand and righthand rolls 24 is accessible so that the braces 7 between the standards 5 can be readily attached to a building front or the like for reasons which were explained herein before. Such tying of the tower 4 to the building front is often desirable to prevent swaying and/ or to counteract excessive bending and/or other stresses. The tower 4 can be attached to a building at regular or irregular intervals.

The drive which serves to move the platform 10 up and down along the tower 4 comprises a row of teeth 26 provided on the standard 6 at regular intervals and having top faces of epicycloidal outline. The teeth 26 cooperate with an annulus of six equidistant rollers 27 provided on a driven wheel 28 which is formed or rigid with a peripheral spur gear meshing with-two pinions 30. The wheel 28 is mounted in a bearing bracket 29 which is affixed to the underside of the longitudinally extending central stiffening brace 20 of the frame 21. Each pinion 30 is mounted on the output shaft of one of two self-locking transmissions 31 receiving torque from two braked reversible electric motors 32. The transmissions 31 and motors 32 are mounted at the underside of the centrally located brace 20 at the opposite sides of the bearing bracket 29. Two such motors and two transmissions are provided for the sake of safety. The distance between the teeth 26, the diameters of rollers 27, the configuration of top faces on the teeth 26, the diameter of the circle on which the axes of the rollers 27 are located and certain other characteristics of the just described drive for the platform 10 are selected in such a way that the platform can be moved at a constant rate of speed. At least one tooth 26 engages with at least one roller 27 in each position of the platform 10. The torsional moment exerted by the eccentrically mounted platform 10 upon the guide rolls 24, 25 is taken up only in part by the rollers 27 to thus insure movements of the platform without any wobbling. Since the rollers 27 merely roll along the top faces of the teeth 26, these teeth need not be lubricated and deposition of dirt or dust on such top faces does not influence the operation of the drive. Also, the wear on the parts 26, 27 is rather negligible. The feature that the teeth 26 need not be lubricated is of particular importance when the scaffold is used at construction sites where the air is laden with dust.

The frame 21 of the platform 10 carries four auxiliary platforms including two end platforms 33 which are hingedly connected to the shorter sides of the platform 10 and two lateral platforms 34 which are hingedly connected to the longer side 10a and flank the tower 4. The end platforms 33 are moved from their raised or inoperative positions (see the left-hand platform 33 in FIG. 1) to the operative positions shown in FIG. 1 in order to form with the main platform 10 an enlarged composite platform of greater length. The later platforms 34 can be folded upwardly above or downwardly below the main platform 10. These lateral platforms are shown in FIG. 2 in operative positions in which they extend toward a building or the like and enable the workers to move closer to the front of the building. When moved to inoperative positions, the lateral platforms 34 enable the scaffold to bypass wings, balconies and other protuberances on the building or buildings without necessitating movement of the carriage 1 further away from the build ing front. The lateral platforms 34 are shown as having solid floors of wooden planks, sheet metal or the like. The floors 35 of the platforms 10 and 33 are preferably made of wire mesh, interlaced steel bars or the like. Guard rails 37 are provided along the other longer side of the main platform 10 and along the shorter sides of each end platform 33. The guard rail 37 of the main platform 10 has a centrally located opening 36 which is normally closed by the uppermost rung of a ladder 38 which can be suspended on the upper rod of the guard rail. The uppermost rung of the ladder 38 can be suspended on the lowermost part of the guard rail 37 for the main platform 10 or on the frame 21 when a workman wishes to enter or leave the main platform.

Our scaffold can be coupled with one or more similar scaffords to form therewith a chain or train of scaffolds which may extend along the front of a wide building, along the fronts of two or more buildings or in a circle or semicircle around a mast, chimney or another elevated structure. FIG. 3 shows, by way of example, a connection between two scaffolds A and B having main platforms 10 and and end platforms 33, 133. The connection includes a bridge 39 provided with guard rails 39a and having a bottom or floor 39b with extensions or bars 41 which can pass through transversely adjustable sockets 40 provided on the end platforms 33 and 133. Spring-biased or gravity-actuated locking devices 43 are pivotally connected to the ends of bars 41 to prevent unintentional separation of the bridge 39 from the two scaffolds. The locking devices 43 normally engage stops 42 provided at the ends of bars 41 to thus prevent withdrawal of bars from the respective sockets 40. In order to detach the bridge 39, the workmen must pivot the locking devices 43 into recesses 4112 provided therefor in the bars 41 whereupon the bars can be readily withdrawn from the respective sockets 40. Other types of connectors between the bridge 39 and platforms 33, 133 can be used just as well. The sockets 40 are preferably free to swivel relative to the platforms 33, 133 about vertical, horizontal and otherwise inclined axes so that the bridge 39 can be installed in horizontal or inclined position. One or more additional bridges can be employed to connect the scaffold A and/or B with one or more additional scaffolds. As stated before, the bridge 39 can be used with one or more bridges to connect two or more scaffolds in a circle or semicircle around a tower, mast, chimney or the like or to form an L-shaped, rectangular, triangular or like chain around other types of tall buildings. When the chain comprises two or more scaffolds, the exposed sides of their towers 4 (between the standards 5) can be connected to each other by fiexure-resistant braces or like stiffeners, not shown. The length of rods 41 on the bridge 39 is preferably such that this bridge can connect two closely adjacent scaffolds or a pair of scaffolds which are located at a relatively large distance from each other. Furthermore, the bridge 39 can be used to enable workers to enter a tall building through a window or to move onto or from balconies or like projections. The sockets are preferably arranged to permit mounting of the bridge 39 in horizontal as well as in strongly inclined position, for example, when the platform 33 of the scaffold A is located at a level well above or well below the platform 133 of the scaffold B. The connection between the scaffolds A and B may comprise two or more bridges 39 which can be rigidly or articulately coupled to each other.

Referring again to FIGS. 1 and 2, the means for supplying electrical energy to the motors 32 and, if necessary, to other electrically operated equipment on the platform 10, 33 and/or 34 comprises a flexible cable 44 which extends from the carriage 1 upwardly to the main work platform 10. The upper end ofthe cable 44 is connected with a box 45 which may accommodate switches or other electrical components and is electrically connected with the motors 32. The lower end portion of the cable 44 is convoluted around the core of a vertical cable drum 46 mounted on the carriage 1. The cable passes through an eye 47 provided at the free end of a rotary and vertically movable winding member 48 whose purpose is to wind or unwind the cable off the drum work platform 10. The upper end of the cable 44 is con- 46 in response to rotation about the axis of the drum whereby the eye 47 orbits about the drum and moves up or down, depending on the direction in which the winding member rotates. The winding member 48 is connected to the upper end of a vertical spindle 49 which extends axially through and meshes with the core of the drum 46. The lower end portion of the spindle 49 is rigid with a worm wheel 50 which is freely rotatable in one direction but is self-locking in the other direction. The lower end portion of the spindle 49 further carries a reel or spool 51 which carries a supply of convoluted cord or rope 52. The diameter of the core of the drum 46 is the same as that of the core of the reel 51. The rope 52 is trained around a pulley 54 which is mounted on the carriage 1 and its free end 53 is attached to the main platform 10, for example, to the lower end of one of the supporting tubes 22. When the spindle 49 rotates with reference to the drum 46, it causes the winding member 48 to rotate and to move up or down whereby the eye 47 insures accurate winding or unwinding of cable 44 off the core of the drum. When the motors 32 are driven in a sense to move the platform 10 downwardly, the tension in the cord 52 slackens whereby the pulley 54 changes its position under the action of a suitable spring (not shown) and actuates a switch 55 which starts a motor 57 mounted for up and-down movement wtih the spindle 49 and having an output shaft provided with a worm 56 which meshes with the worm wheel 50 on the spindle 49. The motor 57 then drives the spindle 49 in a sense to cause the winding member 48 to convolute the cable 44 on the cable drum 46. If the motor 32 cause the platform 10 to move upwardly, the tension in the cord or rope 52 increases and the pulley 54 opens the switch 55 to arrest the motor 57. The rising platform 10 rotates the reel 51 by way of the cord 52 and causes the winding member 48 to rotate in a sense to unwind the cable 44 from the drum 46. An important advantage of the just described means for supplying electrical energy to the motors 32 is that the cable drum 46 need not .rotate and, therefore, the lower end of the cable 44 need not receive current from slip rings or like parts which undergo considerable wear. The rate at which the spindle 49 rotates the winding member 48 during upward or downward movement of the platform 10 is such that the cable 44- is not subjected to excessive tensional stresses but is sufficiently taut to prevent the formation of large unsupported loops. The eye 47 convolutes the cable 44 in the form of a series of closely adjacent convolutions.

FIG. 4 illustrates a portion of a modified scaflold wherein a rectangular or square tower or mast 204 comprises four standards including three standards 205 and a standard 206. Each of the standards 205 is engaged by several pairs or clusters of guide rolls 224, 225 whose axes are located in horizontal planes and preferably make with each other an angle of about degrees. The rolls 224 may but need not be located at the same level as the rolls 225. A portion of the main platform is shown at 210. The tower 204 is eccentric with reference to the platform 210, i.e., the mounting of the platform is similar to that of the platform 10.

It is clear that the improved scaffold may have a tower of pentagonal or other polygonal outline without departing from the spirit of our invention. Also, the carriage 1 may be provided with two or more pairs of road wheels 2 (with solid or inflated tires) or the wheels 2 can be replaced by endless treads.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A scaffold, particularly a mobile scaffold, comprising a ground supported carriage having a center; an upright tower of polygonal cross-sectional outline eccentrically mounted on said carriage and comprising a plurality of upright standards and braces connecting said standards, one of said standards extending upwardly from said carriage in the region of the center thereof; a work platform having a center in substantially vertical alignment with the center of said carriage and an eccentrically located recess for and being movable up and down along said tower, the latter being partially surrounded by said platform; cooperating guide means on said platform and said tower to guide said platform during movement along said tower, said guide means including at least two of said standards and clusters of rolls mounted on said platform and arranged to travel along said two standards; and drive means on said platform for moving said platform along said tower and engaging means provided on said one standard.

2. A scaffold as defined in claim 1, wherein said drive means comprises electric motor means mounted on said platform and means for supplying electrical energy to said motor means, said energy supplying means comprising cable means having an upper end portion connected with said platform and a lower portion convoluted on a stationary cable drum mounted on said carriage, and means for paying out and collecting said cable on said stationary drum in response to upward and downward movement of said platform.

3. A scaffold as defined in claim 2, wherein said drum has a vertical axis and said last mentioned means comprises a winding member rotatable with reference to and movable axially of said drum and having means for winding the cable on or for unwinding the cable from said drum, and means for rotating and moving said winding member axially with referennce to said drum in response to movement of said platform with reference to said tower.

4. A scaffold as defined in claim 3, wherein said last mentioned means comprises a threaded spindle meshing with said drum and rigid with said winding member, a reel fixed to said spindle, a flexible element convoluted on said reel and having an end portion aflixed to said platform to rotate said spindle in one direction when said platform moves upwardly, and second motor means for driving said spindle in the opposite direction in response to downward movement of said platform.

5. A scaffold as defined in claim 4, wherein said second motor means drives said spindle by way of a one 9 way worm drive and further comprising means for starting said second motor means in response to reduced tension in said flexible element when said platform moves downwardly.

6. A scaffold, particularly a movable scaffold, comprising a ground supported carriage; an upright tower eccentrically mounted on said carriage and comprising a plurality of upright standards and braces connecting said standards to each other; a work platform having an eccentrically located recess for and being movable up and down along said tower, the latter being partially surrounded by said platform; cooperating guide means provided on said platform and said tower to guide said platform during movement toward and away from said carriage; and drive means for moving said platform with reference to said tower and comprising a row of equidistant teeth provided on one of said standards, a driven member rotatably supported by said platform and having an annulus of rollers engaging with successive teeth on said one standard in response to rotation of said driven member, and reversible motor means for rotating said driven member.

7. A scaffold as defined in claim 6, wherein said platform has an elongated side and said recess is provided in said side, said one standard being located in said recess remote from said side of said platform.

8. A scaffold as defined in claim 6, wherein said teeth have faces of epicycloidal shape and said rollers are arranged to engage with and to roll along said faces when the platform is moved with reference to said tower.

9. A scaffold as defined in claim 8, wherein said faces are the top faces of said teeth and wherein at least one of said rollers engages with one of said teeth in each position of said platform.

10. A scaffold as defined in claim 6, wherein said driven member comprises a gear and said drive means further comprises a plurality of pinions meshing with said gear and receiving torque from said motor means.

11. A scaffold as defined in claim 10, wherein said motor means comprises a plurality of motors, one for each of said pinions, and self-locking transmission means interposed between each of said motors and the respective pinion.

12. A scaffold as defined in claim 11, wherein said platform comprises a reinforced frame and wherein said motors and said transmission means are mounted at the underside of said frame.

13. A scaffold, particularly a movable scaffold, comprising a ground supported carriage; an upright tower eccentrically mounted on said carriage and comprising a plurality of upright standards and braces connecting said standard to each other; a work platform having an elongated side and an eccentrically located recess extending inwardly from said elongated side, said tower extending through said recess and two of said standards being adjacent said elongated side of said platform and the latter being movable up and down along said tower; cooperating guide means provided on said platform and said tower to guide said platform during movement along said tower, said guide means comprising a pair of elongated supporting members provided on said platform and each adjacent to one of said two standards, and clusters of guide rolls provided on said supporting members and arranged to roll along the respective standards; and drive means for moving said platform with reference to said tower.

14. A scaffold as defined in claim 13, wherein said tower is of rectangular outline and comprises four standards connected by said braces, said guide means comprising further a third upright supporting member on said platform adjacent to a third of said standards and a cluster of guide rolls being also provided on said third supporting member, each of said clusters comprising a pair of rolls rotatable about substantially horizontal axes making an angle of approximately 90 degrees.

15. A scaffold as defined in claim 13, wherein said supporting members extend downwardly from said platform and further comprising stiffening elements connecting the lower end portions of said supporting members with the frame of said platform.

16. A scaffold as defined in claim 15, wherein said tower is of triangular outline and comprises three standards, each of said clusters comprising a pair of rolls rotatable about axes located in substantially horizontal planes and making an obtuse angle with each other.

17. A scaffold, particularly a mobile scaffold, comprising a ground supported carriage; an upright tower eccentrically mounted on said carriage and comprising a plurality of superimposed sections detachably secured to each other end-to-end; a work platform having an eccentrically located recess for and being movable up and down along said tower, the latter being partially surrounded by said platform; bridge means; coupling means for detachably connecting said bridge means to said platform and comprising sockets adjustably and turnably mounted on said platform and extensions provided on said bridge means and receivable in said sockets; cooperating guide means provided on said platform and said tower to guide the platform during movement toward and away from said carriage; and drive means for moving said platform with reference to said tower.

18. A scaffold as defined in claim 17, further comprising locking means for releasably holding said extensions in the respective sockets.

19. A scaffold as defined in claim 17, wherein said coupling means is arranged to permit movements of said bridge means to and from a horizontal position with reference to said platform.

20. A scaffold, particularly a mobile scaffold, comprising a ground supported carriage having a center and a plurality of corner portions; a plurality of elongated stabilizing arms each fixedly connectable to said corner portions of said platform in an extended and in a retracted position in which it respectively projects laterally from and is-nearer to said carriage; an upright tower eccentrically mounted on said carriage; a work platform having a center in substantially vertical alignment with the center of said carriage and being movable up and down along said eccentrically mounted tower, the latter being partially surrounded by said platform; cooperating guide means provided on said platform and said tower to guide the platform during movement toward and away from said carriage; and drive means for moving said platform with reference to said tower.

21. A scaffold as defined in claim 20, wherein said stabilizing arms are detachable from said carriage and are connectable with said carriage in first positions corresponding to said extended positions and second positions corresponding to said retracted positions, each of said arms being inverted by approximately degrees upon detachment from said carriage in one of said first and second positions and prior to placing it into the other of said first and second positions.

22. A scaffold as defined in claim 20, wherein each of said stabilizing arms has an end portion remote from said carriage, an upright spindle rotatably mounted in the end portion of each of said arms, and a ground-contacting le-g detachably affixed to the lower end of each spindle.

23. A scaffold as defined in claim 22, wherein each of said spindles meshes with the respective end portion and comprises coupling means at its upper end to facilitate connection with a device which causes the spindle to rotate and to change its axial position with reference to the respective end portion.

24. A scaffold as defined in claim 22, further comprising a wheeled truck detachably affixed to and located below each of said legs.

25. A scaffold as defined in claim 24, wherein each of said trucks comprises a pair of coaxial wheels mounted at the opposite sides of the respective spindle and a steering 1 1 12 7 Wheel located midway between and offset with reference 2,978,062 3/1961 Di Camillo- 182.63. to said pair of wheels. 3,016,989 1/1962 vLindmark 18263 I d 3,318,414 5/1967 Meek 182146 References FOREIGN PATENTS UNITED STATES PATENTS 5 1,255,562 1/1961 France. 2,196,511 3/1940 Wagner 182-625 2,402,579 6/1946 Ross 18263 REINALDO P. MACHADO, Primary Examiner 2,787,278 4/1957 Mitchell 1322 2,857,994 10/1958 Sheard 182178 US. Cl. X.R. 2,957,592 10/1960 Thacker. 10 182-63, 141, 131

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