JPS593112Y2 - telescopic ladder - Google Patents

Description

[Detailed description of the invention] The present invention relates to a telescoping ladder consisting of a lower ladder A and an upper ladder B that ascends and descends along the lower ladder A, as shown in Fig. 4. The left and right side columns 1, 1, which have a U-shaped cross section, are fitted with the left and right side columns 2, 2, which have a U-shaped cross section. One end of the rope 7 is attached to the crosspiece 6, and a pulley 9, through which the rope 7 passes, is installed on the stepper 8, which is placed between the left and right side columns 1.1 of the lower ladder A, and the other end of the rope 7 is pulled or relaxed. By operating the upper ladder B, the upper ladder B is raised or lowered relative to the lower ladder A while being guided by the pillars 1 and 2 on both sides, and the ladder is maintained at a desired height by a hooking device 10 provided on the upper ladder B. Regarding telescoping ladders.

In the conventional extension ladder of this kind, as shown in FIG. 1, the cross-sectional area of the U-shaped side post 1 of the lower ladder is larger than that of the side post 2 of the upper ladder, and
A reinforcing rib 4 is provided protruding from the inner surface of the side walls 3, 3 of the lower ladder side post 1.

In this way, it is natural that the cross-sectional area of the lower ladder side pillar 1 is made larger than that of the upper ladder side pillar 2, considering the fitting structure of the two, but in addition, the side wall 3 of the lower ladder side pillar 1 is made larger than that of the upper ladder side pillar 2. , 3, the cross-sectional area of the lower ladder side column 1 becomes larger than that of the upper ladder side column 2, and there is an increase in strength between the lower ladder side column 1 and the upper ladder side column 2. This creates an imbalance, making it difficult to ensure safety in use.

Generally, in a telescopic ladder, it is ideal that the second moment of inertia of the side column 1 of the lower ladder and the side column 2 of the upper ladder are equal, and this case is the most stable in terms of strength. Making the next moments equal means making both substantially equal in their cross-sectional shapes and cross-sectional areas.

However, in reality, as mentioned above, due to the fitting structure of the two, it is impossible to make the cross-sectional shapes and areas of the two equal, and the cross-sectional cross-section of the side post 1 of the lower ladder is impossible. The area inevitably has to be larger than that of the side pillar 2 of the upper ladder.

The present invention solves the above-mentioned difficulties, and instead of providing reinforcing ribs on the side posts of the lower ladder as in the past, the side posts 11 of the lower ladder are simply U-shaped in cross section as shown in Figure 2. The side wall 13.13 of the side column 12 is made of an aluminum alloy molded material having a U-shaped cross section and is fitted onto the upper ladder. Reinforcing ribs 14, 14 are integrally provided at both ends, and the side posts 12 of the upper ladder are fitted into the side posts 11 of the lower ladder so that the openings of these U-shaped side posts 11, 12 are opposed to each other. The reinforcing ribs 14, 14 are in contact with the inner surfaces of both side walls 15, 15 constituting each side post 11 of the lower ladder.

This makes it possible to minimize the difference in cross-sectional area between the side columns 11 and 12 of the upper and lower ladders, and to obtain an extendable ladder with a stable structure in terms of strength.

In other words, see Figure 3 a-c for the cross-sectional moments of inertia of the side columns 2 and 12 in the case (■) where the reinforcing rib 4 is not provided on the side wall 5 of the side column 2 of the upper ladder and in the case (■) where it is provided. To further explain the comparison, in the case of ■ (see Figure 3 a)
, Second moment of area: ■1,,l)1=2mm,1)2mm,k1=31.5mm Therefore, in the case of I1-" 15.69 cm' (see Figure 3, C), Second moment of area: ■2 28 mm, h 1 = 65 mm, h 2 = 2
0, bl, b2. hl, h2 are the same as in the case of ■, b3-
6mm, h3=6mm, and 2:34.5mm, I 2 ” 24.40 cm4, therefore, I
2-I = 8.71 cm', and in the case of ■, the moment of inertia of area is increased by about 55% compared to the case of ■.

Therefore, according to the present invention, when the upper ladder is raised or lowered relative to the lower ladder by operating the rope 7, the side posts 12 of the upper ladder
Since the reinforcing ribs 14 are interposed instead of directly contacting the side columns 11 of the lower ladder, the sliding resistance is reduced and it can be moved up and down smoothly. In this case, preferably the reinforcing ribs 14, 1
4 at both ends of the side column 12 in the width direction, as shown in FIG. 2, the occurrence of backlash can be reduced as much as possible.

Particularly, as described above, the present invention provides that the outer surface of the side wall 13.13 constituting the side post 12 of the upper ladder is
Since a plurality of reinforcing ribs 14 that contact the inner surface of the upper ladder are integrally provided in the longitudinal direction, the cross-sectional area of the side pillar 12 of the upper ladder is increased, and the difference in cross-sectional area with the side pillar 11 of the lower ladder is increased. It is possible to make the difference as small as possible, and therefore to reduce the difference in the second moment of area between the two, thereby preventing an imbalance in strength between the two, making it possible to obtain an extension ladder with a stable structure in terms of strength. .

Further, a plurality of reinforcing ribs 14 are protruded from the outer surface of each side wall 13 of the side column 12 so as to come into contact with the inner surface of each side wall 15 of the side column 11 of the lower ladder, and the side column 12 is connected to the side column 11 of the side column 11. Since these side columns 11 and 12 are internally fitted so that their openings face each other, the side columns 11 and 12 do not come into surface contact but are in line contact by the opening edge of the side column 12 and the reinforcing rib 14. Therefore, there is little sliding resistance and it is possible to slide smoothly.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the side post of a conventional telescopic ladder, Fig. 2 is a sectional view showing the basic structure of the side post according to the present invention, and Fig. 3a is a side post of an upper ladder without reinforcing ribs. Figure 3 is a cross-sectional view showing the cross-sectional shape of the same side column with reinforcing ribs, Figure 3C is a partially enlarged view of Figure 3, and Figure 4 is this type of expansion and contraction. FIG. 2 is a partial front view showing an example of a ladder. A: Lower ladder, B: Upper ladder, 1
1... Side post of lower ladder, 12... Side post of upper ladder, 13... Side wall of side post of upper ladder,
14... Reinforcement rib, 15... Side wall of side post of lower ladder.

Claims (1)

[Scope of utility model registration request] A lower ladder having left and right columns with a U-shaped cross section, and left and right sides of the U-shaped cross section that are fitted into the left and right columns of the lower ladder so that the openings of the U-shaped side columns face each other. In a telescopic ladder consisting of an upper ladder having columns, a plurality of reinforcing ribs are provided on the outer surfaces of both side walls constituting each side column of the upper ladder that contact the inner surfaces of both side walls constituting each side column of the lower ladder. , an extension ladder formed by integrally protruding in the vertical direction of the side pillars.