Portable step stool

Abstract: The invention relates to a portable step stool (1) comprising a pair of U-shaped frames (2, 3) hinged to each other and supporting a plurality of steps (4) pivotally connected to the front frame (2) and to pairs of lateral stays (7), each step comprising a plane of stamped sheet metal (23), peripherally defined by a folded rim (25), each of said steps being provided on the surface of its plane with a reinforcing rib (22, 27) formed at the crossing of two elongated ribs (22, 22a) disposed along the diagonals of the step and by a third rib (27) of circular shape centred at the crossing of said diagonals.

Description: The present invention relates to a well known portable step stools or stepladders comprising two parallel rectangular load-bearing frames hinged to each other at their upper ends that can be opened with a caliper-like movement, provided with a plurality of transverse steps pivotally connected to one of the two frames and angularly foldable. Examples of such a portable step stool are disclosed in US-A-5 722 507 and in FR-A-2 319 004. US-A-2 562 564 discloses a step ladder with steps comprising a rectangular plane of stamped sheet metal peripherally defined by a folded rim and additionally provided with pressed ribs for increased rigidity. The object of the present invention is to provide a portable step stool with steps of increased rigidity, which can withstand a considerable load without being irreversibly deformed, although having characteristics of lightweight and being easy and cheap to be manufactured. Accordingly, the present invention provides a portable step stool as defined in the appended claim 1. A preferred feature of the step stool of the invention is that the lower ends of the frame carrying the steps are diverging to ensure an improved stability of the step stool, particularly in the taller models equipped with three or more steps. Moreover the front frame, in the upper portion extending above the topmost step, forms a loop projecting towards the rear frame, also called safety arch, so that when the step stool is open i.e. in an operating position, such loop constitutes a comfortable safety handrail while leaving the surface of the top step tread panel completely free and practicable. Advantageously a shallow receptacle or tray, collapsible to occupy less space when not in use, and adapted to contain tools and small objects can be mounted to the handrail. Further characteristics of the step stool according to the present invention are disclosed hereinbelow with reference to the attached drawings for an easier understanding. Of course it is to be understood that a step stool according to the invention is not limited to that shown in the Figures, but encompasses all variations and modifications which lie within the scope defined by the appended claims. With reference to the attached Figures: Figure 1 is a perspective view of a step stool according to the present invention, in an operating position; Figure 2 is a bottom view of a step of the step stool; Figure 3 is a cross section view of the step shown in Figure 2. With reference to Figure 1, reference 1 generally indicates a portable step stool or stepladder formed by two frames 2, 3, preferably tubular steel frames having circular or polygonal cross section, each frame being folded to a substantially U-shaped configuration and either coated with a thermoplastic material or painted. The upper ends of the legs forming the rear frame 3 are hinged or pivotally connected at 10, 11 to a pair of tabs 12, 13 that in turn are welded to the front frame 2. In correspondence with the hinges 10, 11 both legs of the front frame are slightly curved or folded towards the rear frame to form a pair of inclined and parallel arms 2a that together with a transverse section 2b form a comfortable safety handrail, cantilevering towards the rear of the step stool so as to leave the the tread surface of the top step 4 completely practicable. All the steps 4, 4a, 4b are pivotally connected at their front side portions and rear side portions to the parallel legs forming the frame 2 and to a pair of parallel stays 7, respectively. A second pair of stays 14 having ends hinged to the parallel legs of the rear frame 3 and to the stays 7, respectively, as well as to the sides of a step - in the illustrated embodiment step 4a - define the extent of the frames 2, 3. Each step, shown with more details in Figures 2 and 3, is formed by a panel of stamped sheet metal 23, peripherally defined by a folded rim 25, and with an anti-slip layer 24 applied to the panel upper surface. Figure 2 is a detailed bottom view of a step 4 having a rectangular shape and rounded corners. More precisely a first rib 20 forming a channel extends along the whole peripheral edge of the step 23. The sheet metal 23 of the panel is provided with a plurality of holes 21, preferably spaced from one another over the whole surface of the step, in which holes corresponding projections 26 of substantially cylindrical shape of the anti-slip layer 24 are snap-fitted. The anti-slip 24 is a rectangular plastic or rubber sheet provided with a knurled upper surface and a plurality of projections 26 on the lower surface, adapted to engage the holes 21 of the metal panel 23. The step or tread panel 4 is further provided with a reinforcing rib members 22, 27 extending at a lower position in respect of the tread plane, formed by the joining of two elongated ribs 22, 22a, extending along the diagonals of the rectangle of the step, and a third rib 27 having a circular or elliptical shape with centre at the (notional) crossing of the two diagonals. The three ribs 22, 22a, 27 form a single X-shaped stiffening rib with an opened central portion that is enlarged to a circular or elliptical shape. In the illustrated embodiment such single reinforcing rib extends below the tread plane of the step to prevent any interference with the anti-slip layer 24, however an equivalent reinforcing function could be achieved also with a rib protruding above the step tread plane. The lengths of the elongated ribs 22, 22a are preferably slightly shorter than the length of the diagonals, while the circular rib has a diameter that can be for example about one third of the length of the step minor side. Of course the size of the ribs can be changed while maintaining the their stiffening characteristics. The ribs can be formed simultaneously with the forming of the step, through a single sheet metal stamping or die forming operation in accordance with known techniques. The purpose of the ribs 22, 27 is to stiffen the step so as to achieve increased strength and resistance to deformations. Tests carried out by the applicant showed that a step provided with the above disclosed rib can withstand, with a minimum deformation, a loads up to 260 Kg, thus achieving a considerable advantages over a conventional step. The step deformations comply the requirements of DIN 4569/7. Figure 3 shows a cross section view of the step 4. The Figure shows in detail the peripheral channel 20, the circular rib 27 and the projections 26 of the anti-slip layer 24 fitted into the holes of the sheet metal 23. Turning back to Figure 1, a second characteristic of the step stool of the invention is that the lower ends of the front frame 2 are slightly diverging to impart an improved stability to the step stool. This device is very useful, particularly in respect of the taller models having three or more steps. Still with reference to Figure 1, to the handrail 2b there can be secured a small tray 30, collapsible to occupy a lesser space when not in use, and adapted to contain tools and small objects. Both frames 2, 3 are provided with lower terminal means or feet, for safely resting the stool and preventing any slip thereof. The lower portion of rear frame 3 is provided with angled portions 9 of plastic material, snap fitted to the opposed elbows of the tubular frame, and secured in such position, preferably by riveting. Besides the anti-slip function these portions increase the width of the rear frame resting base and impart a greater stability to the step stool. Feet 15, of rubber or suitable plastic material are applied to the ends of the front frame.

Claims: A portable step stool comprising a pair of frames (2, 3) folded to a substantially U-shaped configuration, a front frame (2) and a rear frame (3) hinged to each other, supporting a plurality of steps (4) pivotally connected to said front frame (2) and to pairs of lateral stays (7), each step comprising a rectangular plane of stamped sheet metal (23), peripherally defined by a folded rim (25), and at least one step (4) being provided on its plane surface with a reinforcing rib member (22, 27) formed by two elongated ribs (22, 22a) joining to one another, disposed along the diagonals of said step and by a third rib (27) of circular or elliptical shape with its centre located at the crossing of said diagonals. A portable step stool as claimed in claim 1, characterised in that said three ribs (22, 22a, 27) form a single X-shaped rib with the central portion that is enlarged to form a circular or elliptical shape. A portable step stool as claimed in claim 2, characterised in that said at least one step (4) has a further rib (20) forming a channel extending along the periphery of said step. A portable step stool as claimed in claim 3, characterised in that the stamped sheet metal of said step (4) is provided with a plurality of holes (21) in which corresponding projections 26 of substantially cylindrical shape of the anti-slip layer 24 are snap fitted. A portable step stool as claimed in claim 4, characterised in that said single rib extends below the tread plane of the step. A portable step stool as claimed in claim 5, characterised in that all said steps are equipped with equal reinforcing ribs. A portable step stool as claimed in claim 6, characterised in that the lower portion of said rear frame (3) is provided with angled portions (9) of plastic material, snap fitted to the opposed elbows of the tubular frame that increase the width of the rear frame resting base and impart a greater stability to the step stool while accomplishing an anti-slip function. A portable step stool as claimed in claim 7, characterised in that said frames (2, 3) are formed by metal tubes having a circular or polygonal cross section. A portable step stool as claimed in claim 8, characterised in that the lower ends of said front frame (2) are slightly diverging to impart an improved stability to the step stool. A portable step stool as claimed in claim 9, characterised in that the upper part of said front frame (2) forms a loop projecting towards the rear frame and constituting a safety handrail at least sixty centimeters above the topmost step. A portable step stool as claimed in claim 10, characterised in that a tray (30) for containing tools and/or small objects is mounted to said handrail.

Inventors: COGGIOLA DAVIDE, COGGIOLA, DAVIDE
Applicants: FRAMAR S P A, FRAMAR S.P.A.
Application year: 1998
Main classification: E06C1
IPC codes: E06C1, E06C7