JPS5842670Y2 - Energy absorbing suspension parts for hard hats - Google Patents

Description

[Detailed description of the invention] A normal industrial safety helmet has a rigid cap body that is worn on the head.
The cap body has a so-called hammock, which is a suspension part that rides on the head and supports the upper part of the cap body at a certain distance from the head.

When the rigid cap receives a downward blow, this impact force is transmitted to the hammock at the connection point around the bottom of the cap.

Because the hammock is made with flexible straps, the straps only experience tension, and if the straps are made of molded plastic, they permanently stretch upon impact and absorb the energy of the impact.

The properties of the plastic strap change considerably under this type of dynamic stress condition, and the strap becomes very brittle, especially when the hard hat temperature is below room temperature.

When a strap becomes brittle, it does not absorb or dissipate energy effectively, becomes very stiff or undergoes uncontrollable plastic deformation, or breaks.

Therefore, one of the major drawbacks of this type of hammock is that it absorbs and dissipates energy only by generating tensile stress, so it cannot control the stress generation as desired or generate it effectively. be.

The main objective of the invention is to provide an energy-absorbing suspension component or suspension device that undergoes both bending and elongation, which is more reliable, simpler in construction and cheaper to manufacture than conventional ones.

Preferred embodiments of the present invention will be explained below with reference to the accompanying drawings.

FIG. 1 shows a hard hat having a desired shape and having a rigid cap body 1 that is worn on the head.

A hammock is provided to keep the top of the cap at a certain distance from the head, and the hammock has a flexible strip, or strap 2, that extends so as to come into contact with the upper surface of the head.

The lower ends of the straps are connected to the cap body in a suitable manner, for example by fitting and retaining projections 3 projecting from both ends of each strap into sockets 4 provided in the lower portion of the cap body near the brim.

A clip 5 is attached to the strap 2 directly above this protrusion and supports a head band 6.

This strap is not continuous from one side of the hard hat to the other, but is separated into upper and lower parts by an energy absorbing suspension piece.

The suspension part comprises a generally rigid but non-brittle flat molded plastic ring 8 whose diametrically opposite sections are connected flush with the flat ring to the upper and lower parts of the strap 2, respectively.

The diameter of each ring is greater than the width of the strap. Typically this ring is circular, but may be of any desired shape.

Similarly, the cross-section of each ring may be of any desired shape.

The material forming the ring must be non-brittle and must be able to withstand bending and tensile deformation up to a predetermined load.

This ring is usually made of molded plastic.

The preferred plastic is polyethylene, but polyurethane, PMMA (polymethyl methacrylate), polycarbonate, nylon and other plastics can also be used.

Plastics that are light in weight and insulating are suitable for use in hard hats.

In another application, metal rings can be used in ropes for securing safety belts, such as for window cleaners and construction workers.

When the strap and ring are made of the same plastic, they are integrally molded as shown.

Alternatively, the strap and projection 3 can be molded as a single piece, as shown in FIG.

In most cases, the impact experienced by the illustrated hard hat does not affect the suspension system because the impact force is not very large.

However, if the impact force exceeds the design load of the suspension system,
The hammock absorbs some or all of the excess energy.

Therefore, when the hard hat is subjected to an impact force above a predetermined minimum load, the lower strap pulls the ring downward with great force, bending and elongating it by pulling on the sides as shown by the dotted lines in FIG.

While both sides of the ring are bent and stretched straight, the inner surface of the ring is in tension and the outer surface is under compression.

There is a neutral plane between the inner and outer surfaces of the ring, the tensile force increases from the neutral plane towards the inside of the ring, and the compressive force increases from the neutral plane towards the outside of the ring.

In other words, since the bending stress is large in this state, a tensile stress is generated on the opposite inner surface of the ring, and this stress decreases linearly to zero at the neutral plane, and gradually increases toward the outside of the neutral plane. This results in increased compressive stress.

As the load continues to increase, the tensile force on the inner surface of the ring continues to increase until the yield point of the ring material is reached.

At this time, even if only the innermost part of the ring reaches the yield stress, the remaining part behaves elastically.

If the load increase continues further, the total area of plastically yielded and deformed material increases linearly.

This is contrary to the uniform tensile stress development that occurs in plastically deformable straps.

Complete yielding of the entire cross-section on both sides of the ring occurs only after large deformations such that both sides of the ring become approximately parallel.

The yield stress and the rate of progression of the total plastic deformation of the ring depend on the material forming the ring, the inner and outer diameters of the ring, and the cross-sectional area of the ring.

Each ring is often provided with a tension member 9 which is normally in a sagging condition when aligned with the adjacent strap.

The ends of the tension member are secured to the ring at diametrically opposite locations on the ring.

In molded plastic rings, the tension member is integrally molded with the ring structure.

This tensioning member has the effect of limiting the extension of the ring under load and, after the tensioning member has been pulled and tensioned by the extending ring, preventing further extension of the ring.

Crossed straps 2 of a hard hat as shown in Figure 1
Alternatively, it is also possible to mold the plastic to form a strap as shown in Figure 4, which crosses in a somewhat staggered manner, with the inner or upper end of the strap extending in the longitudinal direction of the hard hat. They are connected together by a short portion 13.

The outer end, ie, the lower end of this strap is provided with a connecting protrusion 14 for attachment to the cap body, similar to the above-mentioned actual case.

A shock absorbing ring 15 is provided on each strap.

The present invention provides a much more effective energy absorbing device than previously known, both at room and low temperatures.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a safety width with a suspension device of the present invention; FIG. 2 is an enlarged partial elevational view of a part of the suspension device of the present invention;
FIG. 3 is a sectional view taken along the line ■--■ in FIG. 2; FIG. 4 is a plan view of the modified suspension device of the present invention. DESCRIPTION OF SYMBOLS 1... Rigid cap body, 2... Flexible strap, 8... Ring, 9... Tensile member.

Claims (1)

[Scope of utility model registration request] a rigid but non-brittle flat molded plastic ring that suspends the load and absorbs energy when the load applied to the hard hat increases above a predetermined minimum limit; and diametrically end areas of the ring. a flexible plastic strap integrally molded with the ring for connecting the support and the load; the flattened ring and the ring connecting ends of the ring and the strap are all in the same plane; wherein the ring is permanently deformed when subjected to a load above the minimum limit, and there is no connecting device at the ring ends between the ring end areas, but the sides protrude along the entire length on either side of the strap; If the load on the ring increases above the minimum limit, the projecting sides of the ring are pulled and permanently stretched, and this stretching of the ring in the direction of the load reduces the transverse diameter of the ring;
An energy-absorbing suspension component for a safety width, characterized in that the energy required for ring deformation is absorbed by the ring.