CA1127807A - Reinforced elastomer products - Google Patents

Abstract

Abstract The resistance of structural elastomer products, such as bearing blocks, to compressive forces is reduced by incorporating therein a plural ity of small, separate, reinforcing elements of relatively hard, water-insoluble material. Such materials include crushed rock, concrete, glass or certain slags and small metal pieces. the reinforcing elements are ???
gregated in an interior section or core which is preferably covered on all sides by a marginal section substantially free from reinforcing elements Preferably the reinforcing elements are irregular in shape, i.e. elongated in one direction.

Description

REINFORCED EL,ASTOMER PRODUCTS
This invention relates to the production of reinforced elastomer mater-ials and products made therefrom and is particularly concerned with struc-tural elastomer products. Rubber and related or similar elastomers have previously been employed in the manufacture of load-bearing devices, such as bearing blocks for bridges and the like, in cases where resilience and flexibility are desirable. A disadvantage of such use has been that under conditions of high loading the elastomer is squeezed and deforms, in some instances resembling a very viscous liquid, thereby losing its desirable struc-tural qualities. To minimize or prevent such deformation it has been custo-mary when molding large structural products of rubber or other elastomer to embed in the molded product a plurality of spaced metal plates so arranged as to prevent excessive deformation of the product lmder load or compression.
In many cases this measure presents molding difficulties. However, since in some instances the load on such structural products is quite high, 1000 psi or more, reinforcement is required.
By the present invention the deformation of structural elastomer pro-ducts under compressive stresses is prevented, minimized, or controlled by incorporating in the product a plurality of small) separate, reinforcing ele-ments. These elements, which are of relatively hard material compared to ~0 the elastomer may be formed of a variety of water-insoluble materials. Frag-ments of crushed rock, concrete, glass, and certain slags are convenient and inexpensive. Also in many cases, a substantial number of such fragments are irregular in shape, i. e. elongated i~ one direction, 13y reason of their irregular shape and surface such fragments are mechanically bonded by the elastomer and tend to interlock throughout the elastomer when subjected to sompressive force. Small particles, which may be regular in shape, of metal can also be used. The separate reinforcing elements are congregated in a central, interior portion or core of the product and surrounded on all sides by a marginal portion substantially free from reinforcing elements.

Figure 1 is a fragmentary elevation of a conventionalized bridge show-ing an elastomeric bearing block for a bridge girder; and Figure 2 is a perspective view, partially broken away, showing a bear--1- ~

`
` ~ ' ing block, of the type illustrated in Figure 1, according to the present inventi on.
~lthough structural elastomer products according to the present inven-tion may take various shapes and be of various sizes, there is illustrated in the accompanying drawing and hereinafter described a bearing block of the ~ type employed on the tops of piers or posts for supporting the longitudinal . girders of bridges or overpasses. There are, of course, many other uses !~ for structural elastomer products. For example, they are employed in the : support of buildings to reduce the transmission of vibration and similar use is made of them for mounting machines and instruments. Reinforcement of elastomer products employed for these and other purposes where there is - need for control of deformation and dimensions under load is also possible in accordance with the present invention.
In the drawingsJ which illustrate a typical embocliment of the present invention, Figure 1 shows, somewhat diagrammatically, a portion of a bridge that is designated generally as 11. The bridge has a pavement slab 13, a pavement surfacing 15, horizontal railings 17 carried by vertical posts 19, and longitudinal girders 21 which rest on bearing blocks 25 of suitable elasto-meric material carried on supporting posts or piers 27. As shown in Figure

2, the elastomeric bearing block Z5 comprises a central interior section or core 31 in which separate reinforcing elements 33 are congregated and a sur-rounding, marginal section 35 adjacent its outer faces which is substantially free from such elements.
The composition of the elastomer used in carrying out the present in-vention may vary. Natural rubber may be used, as well as synthetic rubbers, L for example butyl, e-thylene-propylene, and silicone rubbers. Polyurethane is also usable. Neoprene is often preferred because of its resistance to sol-vents as well as its resistance to weathering under the influence of environ-mental factors such as sunlight and ozone and to attack by soil bacteria.
The reinforcing elements 33 should be harder than the elastomer em-ployed and not easily crushed. Fragments of a crushed rock, such, for ex-ample as granite, are suitable. ~;ince in many cases a substantial number of such fragments are irregular in shapeJ that is elongated in one direction, ~,~LZ~

-they tend to interlock through the elastomer of the block 25 when subjected to cs)mpressive force whereby the elastomer is restrained and prevented from flowing freely. Thus9 even under high compressive stress, the verti-cal dimension or deflection of the elastomer block is at least controlled or predictable. Reinforcing elements of other materials can, of course, be used, for example crushed concrete9 glass, or certain slags and small metal pieces - which may, in some cases, be regular in shape. The reinforcing effect of the elements is increased when the elements are wet by the elastomer. It is, therefore, desirable to employ a combination of elastomer and reinforcing elements in which the latter are wet by the former or to provide a treatment for the elements which will enhance their wetability. Such treatments are known. It is not, however, desirable to employ reinforcing elements that are hygroscopic or water soluble since the effect of water will produce alteration in the structural properties of the products.
Although the reinforcing elements may vary widely in si~e, depending upon the intended use, satisfactory results may be obtained when they are of such si~e that substantially all pass a No. 3 sieve and are held on a No. 7 sieve, both of the U. S. Standard Sieve ~;eries. In some cases, however, ele-ments having an average diameter of from about 0. 5 in. ~1 27 c m) to 0. 75 in.
tl. 91 c m) are more suitable.
It will be understood that the proportion of reinforcing elements present in an elastomer product may be varied to achieve the desired structural prop-erties in the -product. The proportion of and hardness of the elements used will depend upon the type of elastomer and the purpose of the product. It will be evident that reinforcing with hard materials permits the use for structural products of relatively soft elastomers, for example oil extended rubber, since the resistance to deformation by compressive forces of such products may - thereby be greatly increased. This illustrates a coincidental matter, that, by suitable choice of elastomer and reinforcing elements, products with different specific gravities and structural characteristics may be readily produced It should also be noted that the reduction in the amount of elastomer possible in products produced according to the present invention will permit shorter cur-ing times and thus increase the production rate.

-3-It is important for the block Z5 to have the marginal section 35 around . the reinforcing element-containing core or interior section 31 This pre-vents loss of elements from the block during handling and dislodgement of elements by frictional, vibrational~ or shock forces during use, thus caus-ing change in the structural properties of the block.
~ lthough in the foregoing specification and the accompanying drawings there is described and illustrated a bearing block for bridges and overpasses, it will be recognized that the invention is not so limited and that the invention should be construed as broadly as permitted by the following claims.

Claims (19)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A reinforced elastomer product suitable for use as a resilient but pressure resistant bearing block comprising a body of relatively soft elastomer having embedded therein a plurality of separate crushed reinforcing elements of relatively hard, not easily crushed material, said elements being present in sufficient quantity as to be effective to reduce the deformation of said product by compressive forces.

2. A product as defined in claim 1 wherein said elements are particles of crushed rock.

3. A product as defined in claim 1 wherein said elements are congregated in a core section of said body and a marginal section of elastomer substantially free from such elements surrounds said core section on all sides.

4. A product as defined in claim 2 wherein said elements are congregated in a core section of said body but are separated one from another.

5. A product as defined in claim 4 wherein a marginal section of elastomer substantially free from such elements surrounds said core section on all sides.

6. A product as defined in claim 3 or 5 wherein a major portion of said elements are elongated in one direction.

7. A process for increasing the resistance of an elastomer body to deformation by compressive forces which comprises in-corporating therein a plurality of separate crushed reinforcing elements of relatively hard, not easily crushed material in such quantity as to be effective to reduce the deformation of said body by compressive forces.

8. A process as set forth in claim 7 in which said elements are particles of crushed rock.

9. A process as set forth in claim 8 in which a major portion of said elements are elongated in one direction.

10. A process as set forth in claim 8 in which said elements are congregated in a core section of said body but are separated one from another.

11. A process as set forth in claim 10 in which a marginal section of elastomer substantially free from such elements surrounds said core section on all sides.

12. In a bridge or the like, the combination of a supporting member, a supported member, and an intermediate load-bearing member in contact with both said supporting member and supported member; wherein the load-bearing member comprises a body of elastomer having embedded therein a plurality of separate crushed reinforcing elements of relatively hard material, said elements being present in sufficient quantity as to be effective to reduce the deformation of said load-bearing member by compressive forces.

13. A combination as set forth in claim 12 in which a major portion of said elements are elongated in one direction.

14. A combination as set forth in claim 12 in which said elements are congregated in a core section of said body and a marginal section of elastomer, substantially free from said elements, surrounds said core section on all sides.

15. A combination as set forth in claim 14 in which a major portion of said elements are elongated in one direction.

16. A combination as set forth in claim 12 in which said elements are particles of crushed rock.

17. A combination as set forth in claim 13 in which said elements are particles of crushed rock.

18. A combination as set forth in claim 14 in which said elements are particles of crushed rock.

19. A combination as set forth in claim 15 in which said elements are particles of crushed rock.