Pipes and tubular conduits – Reinforced – With embedded element
Reexamination Certificate
1999-06-22
2001-07-24
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Reinforced
With embedded element
C138S172000, C138S133000, C156S143000, C156S429000
Reexamination Certificate
active
06263921
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a composite plastic pipe, the method and apparatus for fabricating the same, particularly to an improved composite plastic pipe with netted steel wire skeleton, as well as method and apparatus for fabricating the same.
BACKGROUND OF THE INVENTION
Plastic pipes are widely used in various engineering fields. For its advantages of no contamination of carried media, resistance to corrosion, light in weight, and convenience in transportation and installation, the prospect of the application thereof is becoming even more brilliant.
However, the conventional plastic pipe is restricted in some industrial fields due to its poor performance in mechanic strength, rigidity and heat resistance. So far, many forms of composite steel-plastic pipes, as well as the manufacturing methods and devices, have been proposed, in order to improve the mechanic strength, rigidity and heat resistance of plastic pipes to be applied to the fields with higher pressure. For example, U.S. Pat. No. 3, 526, 692 granted to Osaka, U.S. Pat. No. 4, 657, 049 to Forty et al. and U.S. Pat. No. 4, 167, 953 to Carlstrom et al. have disclosed methods for fabricating reinforced plastic pipes with spiral steel wires to improve the strength thereof. The apparatus for manufacturing reinforced plastic composite pipes has been provided by U.S. Pat. No. 4, 017, 232(Holden et al.) and U.S. Pat. No. 4, 135, 869 (Loyer et al.).
The method for fabricating the conventional composite plastic pipes is, as disclosed by U.S. Pat. No. 3, 526, 692, comprises the following steps: forming a spiral steel wire; inserting the spiral steel wire into a plastic extrusion mold in the direction of the axis; forming a plastic pipe body in mold so that the spiral steel wire is embedded in the plastic pipe body and protruded outwardly from the outer surface of the plastic pipe body; and putting the resulted structure through a second extrusion mold so that a plastic layer is adhered to the periphery of the plastic body to cover the protruding spiral steel wire. There are two drawbacks in this method. Firstly, the process is complicated, since twice extrusions of plastic have to be performed to get a desired product. Secondly, What is embedded in the plastic pipe is a spiral steel wire. Although the measure has reinforced the plastic pipe to a certain extent, the effect is not satisfactory.
The Chinese patent ZL94104509.9 held by the inventor of the present invention provides another method and device for fabricating a netted steel wire skeleton—composite plastic pipe, which has overcome the drawbacks of insufficient strength and complicated process in the prior art. The commercialized product has been obtained by the patented method. The compressive strength of the product is from 1 to 6.5 Mpa. This patent is incorporated herein as reference.
The inventor has discovered on the basis of study that the composite netted steel wire skeleton—plastic pipe made according to the Chinese patent ZL94104509. 9 have also some shortcomings, though it is obviously superior to other similar products. The netted steel wire skeleton, according to the patent, is configured by intersecting longitude lines and latitude lines. Both take 50% respectively. As matter of fact, the longitudes have little effect in bearing interior pressure or reinforcing rigidity. The effect for increasing strength by steel wire skeleton has been reduced by about one third. In the other hand, since longitudes have almost nothing to do with bearing interior pressure, the diameter of the latitudes has to be increased to enhance the strength of the pipes. Large diameter latitudes result in inevitably a thicker pipe wall, thus increasing the production cost. Moreover, the purpose of welding is to secure the two groups of steel wires to form a netted skeleton. This results in he manufacturing device with a complicated structure, great dimension, and large energy consumption.
SUMMARY OF THE INVENTION
The object of the present invention is, on the basis of preserving the advantages of the composite plastic pipe with the netted wire skeleton and to overcome the drawbacks in the prior art, to provide a composite plastic pipe by a simply process, which can conveniently and rapidly fill plastic into the skeleton, so as to increase the utilization of the steel wires and reduce the cost. The method can meet the requirements of automatic production of the composite plastic pipe with netted wire skeleton.
An another object of the present invention is to provide a composite plastic pipe with netted steel wire skeleton with an improved structure.
A further object of the present invention is to provide a method for fabricating a composite plastic pipe with netted steel wire skeleton. A still further object of the present invention is to provide an apparatus for fabricating a composite plastic pipe with netted steel wire skeleton.
To achieve above objects, the netted steel wire skeleton in the composite plastic pipe, according to the present invention, is a cylindrical steel wire netting, comprising a group of left coiled wires and a group of right ones. Each includes a plurality of wires respectively. The two groups of left and right coiled wires are winded inside and outside alternatively each other to form the netted skeleton. The spiral angle of the coiled wires can be varied within a certain range to meet the desired diameter and/or strength of the composite plastic pipe.
To achieve above objects, the present invention also provides a method for fabricating the composite plastic pipe with the netted wire skeleton. The method comprises the following steps: forming cylindrical netted wire skeleton by winding the two groups of left and right coiled steel wires each other inside and outside alternatively; filling melted plastic on both sides of the cylindrical netted wire skeleton to make the melted plastic uniformly filled in skeleton as well as both sides thereof; and cooling the skeleton-plastic composite in a fix shape to obtain desired composite plastic pipe with netted steel wire skeleton. The method can be carried out continuously and automatically. The cylindrical netted wire skeleton is obtained by the following manner. Firstly, two groups of wire coiled reels move in reverse direction along two tracks, which are similar to sinusoidal curve (hereafter called sinusoid tracks) and distributed evenly according to a circle. One sinusoid track is of opposite phase to another. The reels will exchange their positions outside and inside alternatively once they reach the intersection of the two tracks so as to realize simultaneous winding and netting.
In other words, the cylindrical netted wire skeleton is formed according to the following method. A plurality of mutually engaged gears with the same modules and the same teeth' number are distributed evenly along a circle. These gears are rotating at the same rate in reversed direction. The movements of two groups of left and right coiled wire reels are driven along the two tracks. Once the reels reach the intersection of the two tracks, they will exchange their position outside and inside alternatively. The left and right coiled wires will be netted around the axis to form the skeleton.
The present invention also provides a device for fabricating the composite plastic pipe with netted wire skeleton. The device includes a netting means for forming the cylindrical netted wire skeleton; a extruding means for extruding the molten plastic; a pipe-molding chamber and a cooling jacket for fill uniformly the molten plastic into the netted skeleton and both sides of the skeleton, and cooling the result structure to be fix shape; and a drawer for pulling the skeleton out of the netting means and pulling the final product out of the above described device. The netting means is positioned upstream of the pipe-molding chamber and the cooling jacket. Said netting means includes a main shaft, two groups of left and right coiled steel wire reels with axis parallel to the one of said main shaft; a chute pla
Arent Fox Kintner & Plotkin & Kahn, PLLC
Brinson Patrick
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