US3779536A - Buffer or fender - Google Patents

Abstract

A buffer of elastomeric material forming a hollow body which has two legs spaced from each other in the direction in which the buffer exerts its main cushioning action and also has two additional legs arranged opposite and in spaced relationship to each other while interconnecting the end portions of said first legs, one of said first legs having bendable elastic insert means therein limiting the elasticity to about half of the flexibility of said additional legs.

Description

United States Patent [191 Kumazawai 267/140 Lachmann 1 Dec. 18, 1973 1 BUFFER 0R FENDER 3,563,525 2/1971 Narabu 267/140 [75] Inventor: Hans-Peter Lachmann, Cologne,

Germany Primary Examiner-James B. Marbert [73] Assignee: Clouth Gummiwerke AG, Cologne, Atmmey waher Becker Germany .[22] Filed: Jan. 3], 1972 [57] ABSTRACT [21] App]. No.: 222,079 A buffer of elastomeric material forming a hollow body which has two legs spaced from each other in the l 30] Forelgn Apphcatlon Pnomy Data direction in which the buffer exerts its main cushion- I ing action and also has two additional legs arranged Jan. 29, 1971 Germany ..P 21 04 212.6 pp and in spaced relationship to each other 52 US. Cl. 267/140 While imemnnecfing end of Said first 511 int. Cl Fl6f 7/12 Rigs, 0f Said first having bendable elastic [58] Field of se'archnw 7a [41 152 sert means therein limiting the elasticity to about half 2677153 of the flexibility-of said additional legs.

[56] References Cited i Q 7 Claims 9 Drawing Figms I UNITED STATES PATENTS 3,418,815 12/1968 .PATENTEBHEB 18 I973 SHEET 3 BF 3 Fig. 6

BUFFER OR FENDER The invention concerns a buffer or fender made of elastomeric material, which comprises a hollow body having parts preferably extending transversely and parallel to the direction of the main force or slightly inclined thereto. The purpose of such buffer or fender consists in permitting the impacting of large moved masses on walls, posts, or the like, for example with the docking of ships at quay sides, without damaging the surfaces of the moved masses and the walls, and to realize this by means of as large as possible a spring deflection and the highest possible energy absorption.

Since the simple compression of elastomeric solid bodies yields insufficient spring deflections and too great reaction forces, such buffers or fenders are mostly so designed that at certain places, in addition to the compression of the elastomer, also its bending or buckling ability istaken advantage of in an effort to obtain the flattest possible extended spring characteristics. To this end, such buffers or fenders mostly represent hollow bodies in which some parts extend preferably parallel and other parts extend preferably transverselyto the main direction of the forces.

Buffers or fenders are known which, when viewed in cross section, have legs parallel or slightly inclined to the direction of force. The free buckling length of these legs is limited by non-extensible or hardly extensible cross-stays connecting them' together at suitable distances to a'degree which permits the buckling process to occur with still sufficient force absorption. As a result thereof, practically a closed I-I-cross-sectional buffer or fender is obtained. In this way, however, the energy absorbing buckling process is limited exclusively to the legsextending parallel or slightly inclined to the direction of force. The use of elastomeric materials inthe cross-stays is, therefore, meaningless for the energy absorbing effect in such constructions of buffers or fenders. Thus, in some of these buffers or fenders, the cross-stays are formed, e. g., by iron plates only, which are merely enveloped by elastomers, and only the legs are intended to take up the spring work. There fore, they must be very thick. In other constructions, the'upper and lower cross-staysare for example firmly screwed to abutting further fenders or abutting fixed walls, so that the same limited effect is present.

If as is likewise known for buffers or fenders of the mentioned kind only particularly short and thick legs with sufficiently high spring work are selected without cross connections being present in the range of their buckling centers (this yields a rectangular or trapezoidal shape in cross section), then here too the upper and lower cross-stays, which absorb the impact or pass it on to the structure involved,,are constructed by inserts so rigid in transverse direction that they themselves practically do not share in the spring work. Constructions are also known, which for example do not provide for any kind of inserts in the upper cross-stays, so that the premature and sudden buckling of the legs with a great collapse of force is made easier.

In the mentioned constructions, it is thus disadvantageous that the necessary spring work is performed only in the legs partly by compression, partly through buckling and that, therefore, when compression predominates (with thick legs) the characteristics exhibit force collapses with insufl'icient energy absorption.

With the above mentioned constructions, it is, therefore, very difficult to maintain the desired characteristic, which should be very extended and should have as long as possiblea horizontal section. This, however, is possible only when precisely designing and maintaining the length-width relationship of the legs and maintaining the technological values of the elastomer employed. Moreover, the desired effect can be achieved only with a relatively large quantity of elastomers.

It is, therefore, an object of this invention to provide a buffer or fender of the above mentioned general type which will overcome the drawbacks outlined above.

This ojbect and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 shows a cross section through a known fender in unloaded condition. I

FIG. 1a shows the fender of FIG. 1 in loaded condition.

FIG. 2 shows a cross section through another known fender in unloaded condition.

FIG. 2a shows the fender of FIG. 2 in loaded condition.

FIG. 3 shows characteristics resulting when loading one of the fenders shown in FIGS. 1 or 2.

. FIG. 4 shows a further characteristic obtained when loading a fender according to FIGs. 1 or 2.

FIGS represents a cross section through a fender according to the invention in unloaded condition.

FIG. 5a shows the fender according to FIG. 5 in loaded condition.

FIG. 6 shows a characteristic obtained when loading the fender shown in FIG. 5 and also shows a further characteristic of the fender according to the invention.

The buffer or fender according to the present invention which comprises a hollow body with parts extending preferably transversely and parallel or slightly inclined to the direction of the main force is characterized primarily in that at least one of the parts which extend preferably transverse to the direction'of the main .force is flexible and as to its bending resistance is by means of elastic reinforcing inserts so'dimensioned' that, when applying the same scale, it is about half as flexible as the parts extending preferably parallel or slightly inclined to the direction of the main force.

As tests have proved, even with a precise design, the change in the loading speed has a disadvantageous effect. With a very slow increase in load (at least than about 30 cm/min), compression will prevail for a very long time and the line of characteristics is too steep.

- With a faster increasing load (higher than about 40 mm/min), a sudden buckling occurs and the line of characteristics collapses. At a substantially greater speed (for example 0.1 m/s), as it may occur in practice, the spring hardens considerably (more than 25 percent due to the flow inertia of the elastomeric masses.

By means of the limited bending resistance of the cross-stays, it will be realized that these stays will actually take part in the spring work and thus a smaller quantity of material will be necessary in the legs. Furthermore, due to their own bending movement controlled by the dimensioning, the stays will from the start initiate an outward bulging of the legs so that the characteristic after the rise flattens out and no longer shows buckling collapses. This course of the curve is attained by the accurate dimenisoning of the flexibility of the cross-stays which corresponds to the respective given load.

According to a further development of the invention, the parts extending preferably parallel or slightly inclined to the main force direction are locally reduced in thickness at more than one place, so that the bulging of the legs does not occur only at one place but preferably at those places where the thickness has been locally reduced. These several places thus practically take part in the bulging-out movement. Since this bulging-out movement takes place from the very start due to the limited flexibility of the cross-stays, and moreover causes little increase in stress, the spring characteristic is thereby further stretched.

Finally, inasmuch as the limited flexibilty of the cross-stays strongly affects the mentioned processes, the speed dependency of the characteristic of the whole buffer or fender will also depend on the speed dependency of the limited flexibility of the cross-stays. According to a further development of the invention, the elastic reinforcement inserts which bring about the limited bending resistance of the parts which preferably extend transversely to the direction of the main force,

possess a substantially lower speed dependency of their bending force characteristic than does the elastomeric material enveloping the reinforcing inserts and forming the buffer or fender. Preferably torsion springs of steel or other highly elastic materials may be employed which have a damping effect as to bending. Tests have proved that thespeed hardening of the buffers or fenders can thereby be lowered to substantially below 25 percent.

Referring now to the drawing in detail, it will be seen from FIGS. 10 and 20 that exclusively the legs 2 and 3 extend parallel or slightly inclined to the direction of force and buckle under load. The cross-stays 4 and 5 are designed so stiff or rigid that they practically do not take part in the spring work.

With slowly increasing load acting on the fenders according to FIGS. 1 and 2, the characteristic shown in FIG. 3 will be obtained. When quickly increasing the load, the buckling of the legs 2 and 3 occurs suddenly, so that as indicated in FIG. 4, the characteristic collapses. Since at considerably higher speeds, due to the flow inertia of the elastomeric masses, the fender hardens, there results a characteristic indicated in dash lines in FIG. 3. I

The fender shown in FIGS. 5 and 5a comprises two legs 7, which are slightly inclined to the direction of force 6. The thickness of legs 7 is reduced at the places 8. The fender further comprises a rigid cross-stay 9 and a cross-stay 10 of limited flexibility. The limitation of the flexibility is in the above example brought about by elastic metallic inserts 11. The mean thickness of the legs 7 is designated by the letter d. The inserts 9a may consist of metallic plates or plates of hardsynthetic, e. g., plastic, material so as to make the cross-stay 9 rigid.

FIG. 6 shows the characteristic of the fender shown in FIGS. 5 and 5a. The dash line represents the characteristic of a fender, the dimensions of which correspond to the fender according to FIGS. 5 and 5a, which however, has no inserts limiting the flexibility and which has no local reduction in thickness of the legs. A fender with a characteristic as indicated by the dash line is obviously useless.

The characteristic shown in FIG. 6 as a solid line will with the load acting in the direction of force 6 (FIG. 5a) occur in view of the fact that initially the legs 7 are compressed (the characteristic ascends; region A); then the cross-stay l0 begins to bend whereby the bulging of the legs 7 is initiated which occurs with practically constant reaction force (the characteristic is approximately horizontal; region B); and finally the bulge areas of the legs increase due to their reduced thickness at the locations 8, so that the meeting of the inner faces of the cross-stays 9 and 10 is retarded (the characteristic rises; region C).

It is, of course, to be understood that the present invention is, by no means, limited to the specific showing in the drawings but also comprises any modifications within the scope of the appended claims. Thus, under some circumstances the rigid reinforcement or insert may be replaced by an elastic metallic reinforcing insert, e. g., of the type of insert 11.

It may also be mentioned that the inclination or angle of the legs 7 may vary over that shown in FIG. 5. More specifically, the legs 7 may be parallel to each other or may be inclined relative to each other until no compression phase exists.

What I claim is:

l. A buffer of elastomeric material which includes: two first legs spaced from each other in and extending transverse to the main force direction in which said buffer is to exert its main cushioning action, two additional legs spaced from each other and respectively interconnecting the end portions of said first legs, said first legs and said additional legs together defining a cavity with each other, and elastic reinforcing insert means in at least one of said first legs and limiting the flexibility of the latter to bending stiffness only about half the'flexibility of said additional legs.

2. A buffer according to claim 1, in which one of said first legs has bendable elastic reinforcing insert means arranged therein whereas the other one of said first legs has rigid reinforcing means arranged therein.

3. A buffer according to claim 1, in which said additional legs are approximately parallel to each other and substantially parallel to the axis in which said buffer is to be compressed for exerting its cushioning action.

4. A buffer according to claim 1, in which the additional legs flare from one of said first legs to the other one of said first'legs.

5. A buffer according to claim 1, in which the addi tional legs vary in thickness along their length.

6. A buffer according to claim 1, in which the additional legs are thinner near their end portions than at the portions therebetween.

7. A buffer according to claim 1, in which the speed dependency of the bending force characteristic of the elastomeric material of the buffer is higher than that of the elastic reinforcing insert means.

Claims (7)

1. A buffer of elastomeric material which includes: two first legs spaced from each other in and extending transverse to the main force direction in which said buffer is to exert its main cushioning action, two additional legs spaced from each other and respectively interconnecting the end portions of said first legs, said first legs and said additional legs together defining a cavity with each other, and elastic reinforcing insert means in at least one of said first legs and limiting the flexibility of the latter to bending stiffness only about half the flexibility of said additional legs.

2. A buffer according to claim 1, in which one of said first legs has bendable elastic reinforcing insert means arranged therein whereas the other one of said first legs has rigid reinforcing means arranged therein.

3. A buffer according to claim 1, in which said additional legs are approximately parallel to each other and substantially parallel to the axis in which said buffer is to be compressed for exerting its cushioning action.

4. A buffer according to claim 1, in which the additional legs flare from one of said first legs to the other one of said first legs.

5. A buffer according to claim 1, in which the additional legs vary in thickness along their length.

6. A buffer according to claim 1, in which the additional legs are thinner near their end portions than at the portions therebetween.

7. A buffer according to claim 1, in which the speed dependency of the bending force characteristic of the elastomeric material of the buffer is higher than that of the elastic reinforcing insert means.

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