STAIR-CLIMBING HAND TRUCK

Abstract: A stair-climbing hand truck comprises a body (10), including a generally rectangular frame (11), and a supporting arrangement for said body (10), including two parallel horizontal shafts (21, 35) extending transversally to said frame (11) and forming a lower shaft (21) and an upper shaft (35), each shaft (21, 35) having a pair of opposite spiders (19, 33) mounted thereon, the spiders (19) of the lower shaft (21) carrying freely rotatable supporting wheels (18), while the spiders (33) of the upper shaft (35) carry auxiliary supporting means (32), electrically powered driving means (22-28, 36, 37) being provided for bringing both pairs of spider members (19, 33) into rotation. In order to make the truck more stable and reliable, the auxiliary supporting means (32) are secured in fixed positions to their spiders (33) and located in laterally offset positions with respect to said wheels (18) to be able, during rotation of the spiders (19, 33) to move along circular paths partially overlapping the movement paths of said wheels (18).

Description: Stair-climbing hand truck The present invention relates to a stair-climbing hand truck. More particularly, the invention relates to a stair- climbing hand truck of the kind comprising a body, in¬ cluding a generally rectangular frame which, at an upper end thereof, is provided with handle means, while, at a lower end thereof, it is provided with load-supporting means for forming a load-supporting surface extending generally perpendicular to the frame in a forward direction therefrom, and a supporting arrangement for movably sup¬ porting said body, said arrangement including two shafts which are rotatably carried by said body and extend trans- versally to said frame in mutually parallel horizo ' ntal directions and which are spaced apart from each other in a direction nearly parallel to the longitudinal direc¬ tion of the frame in order to form a lower shaft and an upper shaft, each of said two shafts being provided with a pair of opposite spider members, each of which comprises a central hub portion, mounted on the appurtenant shaft, and at least three equally spaced arms extending in generally radial outward directions from said hub portion, each arm of each spider member mounted on the lower shaft being provided with a supporting wheel which is mounted freely rotatable at an outer end of said arm, while each arm of each spider member mounted on the upper shaft is provided with an auxilliary supporting means mounted at an outer end of said arm, electrically powered driving means being provided to permit the spider members mounted on both said shafts to be brought into simul¬ taneous rotation. A hand truck of said kind is previously known through U.S. patent specification No. 2,400,824. However, this known hand truck suffers from several disadvantages making it inconvenient and unreliable in practical use. Firstly, the auxilliary supporting means carried by the arms of the spider members mounted on the upper shaft consist of freely rotatable wheels. This results in that the truck may easily tend to move in an uncontrollable manner when travelling up or down a flight of stairs. Secondly, the upper shaft is located near the upper end of the body frame in order to avoid any interference between the wheels' carried by the spider members of the different shafts. As a consequence, the resultant centre of gravity of the truck is located at a comparatively high level which makes the truck unstable. The invention has for its purpose to provide an im¬ proved stair-climbing hand truck which avoids the disadvan¬ tages of the above-mentioned known hand truck. In accordance with the invention, for this purpose there is provided a hand truck of the kind initially specified, primarily characterized in that said ^ auxilliary supporting means are secured to the arms of the spider members of the upper shaft in stationary fixed positions relatively to said arms and that they are located in laterally offset positions with respect to the wheels carried by the spider members mounted on the lower shaft and adapted, during rotation of the spider members by means of said driving means, to move along circular paths partially overlapping the movement paths of the wheels carried by the spider members mounted on the lower shaft. As a result of the invention, the hand truck will not have any tendency to move in an uncontrollable manner when travelling along a flight of stairs: Moreover, the upper shaft may be located at a comparatively short dis- tance from the lower shaft, thereby permitting the result¬ ant centre of gravity of the truck to become located at a comparatively low level and hence rendering the truck more stable and easy to handle. In a preferred embodiment of the invention, the driving means comprise a single electric driving motor provided in permanent driving connection with all spiders through a transmission which is capable of holding all spiders against rotation when the driving motor is not energized. Said transmission may suitably include a self- braking worm gear connected to the output shaft of the driving motor. In order to keep the total width of the truck at a minimum, the spider members may preferably be mounted in axially retracted positions on the shafts and inside brackets which extend in a rearward direction from the « body frame at opposite sides thereof and which serve to carry the shafts mounted therein. Advantageously, the auxilliary supporting means may have curved contact surfaces having a generally arc- circular shape. Below, the invention will be described in further detail with reference to the accompanying diagrammatic drawing, in which:- Figure 1 shows a rear end view of a hand truck accor¬ ding to a preferred embodiment of the invention, illustra¬ ting the truck in an upright vertical position, while Figure 2 shows a part-sectional side elevation view, illustrating the truck in a backwardly inclined position during movement of the truck on a horisontal substrate. The hand truck shown in the drawing comprises a body, generally designated 10. Said body 10 mainly consists of a rigid rectangular frame 11, a front cover plate 12 and two side plates 13 which extend in a backward direction from frame 11 at opposite sides thereof and near the lower end of the frame. At its upper end, frame 11 is provided with a yoke-shaped handle 14, while, at its lower end, it is provided with a load-supporting means 15 serving to form a load-supporting surface extend¬ ing in a forward direction from the frame and generally perpendicular thereto. Said load-supporting means 15 may for instance consist of two parallel arms which to- gether may serve as a lifting fork to enable the truck to be used for the transportation of goods loaded on pallets. Both said arms may preferably be mounted for limited pivotal movement and longitudinal displacement on a transversally extending rod 16 in order to permit an adjustment of their relative positions in the trans¬ versal direction of frame 11 and enable them to be swung in an upward direction to retracted positions in which they will extend parallel to frame 11 adjacent to the latter. To provide a favourable support for body 10 during movement of the truck on a plane substrate 17, there are provided totally six supporting wheels 18 which are divided into two sets, each comprising three wheels 18 which are mounted on a common carrier 19. Each carrier 19 is formed by a spider member consisting of a central hub portion and three equally spaced arms which extend in generally radial outward directions from said hub portion. At. its radially outer end, each spider member arm carries one wheel 18 which is mounted freely rotatable on a stub axle 20. The two spider members 19 are rigidly mounted on a common shaft 21 which is rotatably journalled in the two side plates 13 at its opposite ends. Reference numeral 22 designates a sprocket wheel which is rigidly mounted on shaft 21 and serves to permit said shaft to be driven from an electric motor 23 through a self-braking worm gear 24 and a chain transmission provided between said gear and sprocket wheel 23. Said chain transmission comprises another sprocket wheel 26 rigidly mounted on the output shaft 25 of worm gear 24 and an endless chain 27 passing over sprocket wheels 23 and 26. Reference numeral 28 designates an operating switch by which motor 23 may be connected to an electric accumu¬ lator 29, which is carried on a holder 31, rockably mounted on a rod 30. The operating switch 28 is of a kind permit¬ ting an alteration of the polarity of the voltage supplied to motor 23 from accumulator 29 and, hence, a reversion of the rotary direction of the motor. Naturally, motor 23 may also be completely disconnected from accumulator 29 by means of switch 28 in order to receive no driving power therefrom. When switch 28 is set in a position to interrupt the voltage supply to motor 23, shaft 21 will be held safely in a stationary position due to the self-braking function of worm-gear 24. Hereby, it is possible, when moving the truck on a substantially plane substrate, to adjust and lock the two spider members 19 in stationary positions such that the resultant centre of gravity of the truck and the load carried thereon may be placed .in a vertical plane located between two pair of wheels 18 by which the truck rests on the sub¬ strate. The operator will then not have to bother him with constantly trying to hold the truck in a balanced position. The illustrated truck, which is intended to be moved solely by manual force on a plane substrate, is also suited for use in connection with the transportation of goods along a flight of stairs. In order to provide sufficient stability during such use of the truck, the latter is also provided with auxilliary supporting means which are utilized only when using the truck as a stair- climbing transport aid. These auxilliary supporting means are formed by six additional wheels 32 which are mounted in stationary fixed positions on two additional rotary spider members 33. These spider members 33 are almost identically equal to spider members 19 which serve as carriers for the freely rotatable wheels 18. In order to ensure that wheels 32 will be held in fixed positions with respect to the corresponding arms of spider members 33, they may be locked against rotation by suitable locking pins or screws 34. Both spider members are rigidly mounted on an upper shaft 35 which is rotatably journalled in side plates 13 at its opposite ends. Reference numeral 36 designates a sprocket wheel which is rigidly mounted on shaft 35 and drivingly connect¬ ed to a cooperating sprocket wheel on the output shaft motor 23 is energized, it will bring both shafts to rotate at equal speeds and in equal directions. This makes it possible, when moving the truck along a flight of stairs, to effect said movement in a safe manner as said movement may take place under the control of a precise rolling action of the curved contact surfaces of the auxilliary supporting means formed by fixed wheels 32. In order to avoid any undesired slip between wheels 32 and consequ- tive stairs, said wheels may preferably be provided with tires of rubber or other similar material. Similar tires may also be provided on rotary wheels 18. As may be seen from the drawing, the distance between the lower shaft 21 and the upper shaft 35 has been made comparatively short. This has been made possible by placing fixed wheels 32 in laterally offset positions with respect to rotary wheels 18 and permitting the different types of wheels to move along partially overlapping paths, when brought into rotation by the driving motor 23. As a result, the truck may easily be designed so as to permit one wheel 32 to rest on one step of a staircase while the corresponding wheel 18 rests on the next lower step. When climbing up or down along a flight of stairs, the truck is preferably held in a more inclined position than when moved on a plane substrate. Hereby, it may assume a stable position also during its powered climbing movement. The invention is not restricted to the embodiment above described and shown in the drawing. Thus, many modifications are feasible within the scope of the inven- tion. For instance, it is possible to replace the fixed wheels 32 by other auxilliary supporting means which may have arcuately curved contact surfaces extending only through an angle of about 120°.

Claims: Claims 1. A stair-climbing hand truck of the kind comprising a body (10), including a generally rectangular frame (11) which, at an upper end thereof, is provided with handle means (14), while, at a lower end thereof, it is provided with load-supporting means (15) for forming a load-supporting surface extending generally perpendicular to the frame (11) in a forward direction therefrom, and a supporting arrangement for movably supporting said body (10), said arrangement including two shafts (21, 35) which are rotatably carried by said body (10) and extend transversally to said frame (11) in mutually parallel horizontal directions and which are spaced apart from each other in a direction nearly parallel to the longi¬ tudinal direction of the frame (11) in order to form a lower shaft (21) and an upper shaft (35), each of said two shafts (21, 35) being provided with a pair of opposite spider members (19, 33), each of which comprises a central hub portion, mounted on the appurtenant shaft (21, 35), and at least three equally spaced arms extending in gene¬ rally radial outward directions from said hub portion, each arm of each spider member (19) mounted on the lower shaft (21) being provided with a supporting wheel (18) which is mounted freely rotatable at an outer end of said arm, while each arm of each spider member (33) mounted on the upper shaft (35) is provided with an auxilliary supporting means (32) mounted at an outer end of said arm, electrically powered driving means (22-28, 36, 37) being provided to permit the spider members (19, 33) mounted on both said shafts (21, 35) to be brought into simultaneous rotation, characterized in that said auxil¬ liary supporting means (32) are secured to the arms of the spider members (33) of the upper shaft (35) in sta- tionary fixed positions relatively to said arms and that they are located in laterally offset positions with respect to the wheels (18) carried by the spider members (19) mounted on the lower shaft (21) and adapted, during rota¬ tion of the spider members (19, 33) by means of said driving means (22-28, 36,37), to move along circular paths partially overlapping the movement paths of the wheels (18) carried by the spider members (19) mounted on the lower shaft (21). 2. A hand truck according to claim 1, characterized in that said driving means (22-28, 36, 37) comprise a single electric driving motor (23) provided in permanent driving connection with all spider members (19, 33) through a transmission (24-28, 36, 37) capable of holding all spider members (21, 35) against rotation when the driving motor (23) is not energized. 3. A hand truck according to claim 2, characterized in that said transmission (24-28, 36, 37) includes a self-braking worm gear (24) connected to the driving motor (23) . 4. A hand truck according to claim 1, characterized in that the spider members (19, 33) are mounted in axially retracted positions on the shafts (21, 35) and inside brackets (13) which extend in a rearward direction from the body frame (11) at opposite sides thereof and which serve to carry the shafts (21, 35) mounted therein. 5. A hand truck according to claim 1, characterized in that the auxilliary supporting means (32) are provided with curved contact surfaces having a generally arc-circu¬ lar shape.

Inventors: OERTENHEIM AOKE BJOERN, OERTENHEIM, AOKE, BJOERN
Applicants: OERTENHEIM AOKE BJOERN, OERTENHEIM, AOKE, BJOERN
Application year: 1985
Main classification: B62B5
IPC codes: B62B5