Plastic butterfly valve

Details Plastic butterfly valve Plastic butterfly valve

1998-12-02

2001-02-20

Shaver, Kevin (Department: 3754)

Valves and valve actuation

Rotary valves

Butterfly

C251S305000

Reexamination Certificate

active

06189860

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a plastic butterfly valve preferably used in a piping line for a chemical plant, a city water supply or the like and more particularly, to a plastic butterfly valve in which the seat can be easily mounted and demounted in a short time.
BACKGROUND ART
Hitherto, in an eccentric type metallic butterfly valve, a method, as shown in
FIG. 7
, where a cylindrical seat pressure foot
21
is mounted on a body
20
by fixing bolts
23
so that a seat
22
is fixed to the body
20
, has been adopted. Also, in a plastic valve, a method as shown in
FIG. 8
, where a seat pressure foot
25
provided with a tapered projection
28
is pushed into a circular hole portion of a body
24
having an inner diameter slightly smaller than the outer diameter of the tapered projection
28
and provided with an annular projection
27
so that a seat
26
is fixed to the body
24
, has been adopted.
However, in the former butterfly valve, the body must be tapped with tapped holes for bolts to fix the seat pressure foot, thus not only does the cost increase as a result of an increase of working processes, but also a long time is required for fastening the bolts, thus the efficiency of the assembling work is deteriorated.
On the other hand, in the latter butterfly valve, the seat pressure foot is pushed in from the side of the body, thus it is possible that the engaging regions between the seat pressure foot and the body are damaged during disassembly. Thus, in fact, exchanging the seat on-site is impossible, with the result of that the time and the cost of maintenance are increased.
DISCLOSURE OF THE INVENTION
The present invention has been conceived in view of the problems of the conventional technique as stated above and the purpose of this invention is to provide a plastic butterfly valve that does not require the tapped holes in the body and the seat pressure foot, it is not possible to damage the engaging regions during disassembly, and the mounting and the demounting the seat can be easily and rapidly carried out.
The present invention has been conceived in view of the above conventional technique, and relates to an eccentric type plastic butterfly valve characterized in that a seat pressure foot is detachably fitted in the side portion of a body by insertion/rotation means (that is, by a bayonet manner) so that the seat can be easily mounted and demounted in a short time.
A fitting arrangement by the insertion/rotation means (the bayonet manner) in the present invention consist in the following. First, the construction of the seat pressure foot will be explained.
The seat pressure foot is formed with a plurality of arcuate projections at the outer peripheral end surface and is provided with a step portion fitting on and holding the seat at the inner peripheral side of the seat pressure foot.
Next, the construction of a hollow cylindrical body will be explained.
On one side portion of the body is provided arcuate cutout step portions of the same diameter as that of the seat pressure foot, in which the seat pressure foot and the seat are fitted.
The cutout step portion is diametrically provided with arcuate cutout portions having enlarged diameters in which the arcuate projections are fitted, in positions corresponding to the circular arc projections of the seat pressure foot, and is provided at the interior sides of the cutout portions with an annular engaging groove in which the arcuate projections of the seat pressure foot, the foot having been inserted, are circumferentially guided.
In the fitting of both members, first the seat is fitted in the step portion of the seat pressure foot to fit the arcuate projections provided on the outer peripheral end surface of the seat pressure foot into the arcuate cutout portions provided on the side portion of the body. Then, the seat pressure foot is pushed in until the interior side of the seat fitted in the seat pressure foot comes in contact with the interior bottom portion of the arcuate cutout step portions of the body while the seat pressure foot is circumferentially rotated to guide the arcuate projections in the annular engaging groove of the body.
In this way, the seat pressure foot and the seat are fixed on the body. This fitting manner is referred to as insertion/rotation means (bayonet manner) in the present invention.
At least two of the arcuate projections must be provided on the outer peripheral end surface of the seat pressure foot, and the number of the arcuate projections may be suitably selected depending on the size of the diameter of the passage of the butterfly valve. Also, the width of the projections (the length in the axial direction of the seat pressure foot) must be smaller than the thickness of the seat pressure foot, and may be preferably set to 40 to 50% of the thickness of the seat pressure foot.
Further, the forming process of the projections is desirably an integral molding, although any of an integral molding, a fitting manner, a bonding or the like may be used.
The material used in the butterfly valve in the present invention may be any available plastic, and generally hard vinyl chloride resin, polypropylene, and fluorocarbon resin such as PVDF are preferred.


REFERENCES:
patent: 4083529 (1978-04-01), Santy et al.
patent: 4231546 (1980-11-01), Eggleston et al.
patent: 4289296 (1981-09-01), Krause
patent: 4813650 (1989-03-01), Digler
patent: 4-10168 (1992-01-01), None
patent: 4-32363 (1992-03-01), None

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