Animal husbandry – Milkers – Teat compressor or cup
Patent
1997-11-26
1999-10-19
Price, Thomas
Animal husbandry
Milkers
Teat compressor or cup
A01J 504
Patent
active
059670827
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for reception of a teat, comprising a thin flexible wall surrounding a channel for reception of said teat, wherein said wall in a direction towards the channel has an inner side and in a direction from the channel an outer side.
The invention also relates to a method for the manufacture of a device of this kind.
BACKGROUND OF THE INVENTION
A device of the above described kind is previously known from U.S. Pat. No. 1,285,079, which device constitutes a part of a teat liner which is usually made of nitrile rubber.
During manufacture of a rubber product, there always arise, in the material, discontinuities, which may consist of e.g. air or foreign particles. When load is put on the rubber product cracks may arise, which in that case firstly occurs in connection with the discontinuities.
It is commonly known that surface cracks are more dangerous for the strength of the rubber product than cracks inside the rubber product. It is accordingly especially important to hamper growth of cracks in the surface layer of the rubber product.
When a rubber product ages micro cracks also arise in its surface layer because of reduced elasticity of the rubber. These cracks propagate i.e. get larger, especially during loading of the rubber product. One reason for reduced elasticity of rubber in course of time is that this material is hygroscopic.
A newly produced teat liner made of nitrile rubber contains less than 0,3% water. A teat liner is during use contacted by milk during milking and detergent solution during subsequent cleaning. The milk as well as the detergent solution contains water, which is absorbed by the rubber material of the teat liner. The more water that is absorbed by the rubber material the more the teat liner loses its elasticity. Furthermore the tension of the rubber material is increased owing to this. When a known teat liner made of nitrile rubber is worn out, it contains about 3% water.
At this stage surface cracks have already arisen in the teat liner because of the reduced elasticity in combination with the movement that the teat liner has been forced to perform during milking. The movement has caused tensions in the teat liner that have promoted the growth of the cracks.
OBJECT OF THE INVENTION
The object of the present invention is to accomplish a device for reception of a teat, which device has a longer life than previously known such devices.
SUMMARY OF THE INVENTION
This object is obtained by a device of the initially defined kind, which is characterized in that at least a part of the outer side of the wall is provided with a large number of surface enlargements, which have such a form, size and distribution that they form obstructions to propagation of cracks on the outer side of the wall. Hereby is obtained a reduced risk for fatigue of the material in the wall.
The said surface enlargements are formed on the outer side of the wall in order to create intentional discontinuities with small mutual interspaces, which discontinuities are not limited by sharp edges such as normal surface cracks but form gentle transitions between recesses and protrusions of the outer side of the wall.
The intentional discontinuities provide a substantially less risk for crack growth than sharp naturally arisen cracks; the tension at the sharp crack edge is considerably larger than the tension at a rounded off crack edge at the same load level and is therefore more likely to result in fatigue of the material.
If a crack in spite of these intentional discontinuities would arise in the surface layer, the crack must turn at the surface enlargements, disregarding whether these are constituted by recesses or protrusions. Such a turn requires energy and the crack growth can in this way be hampered.
It is thus realized that the more surface enlargements that are arranged per unit area, the better the protection against crack growth.
It should however be noted that intentional discontinuities in the form of ribs, as disclosed in U.S. Pat.
REFERENCES:
patent: 1285079 (1918-11-01), Eklundh et al.
patent: 2079435 (1937-05-01), Dinesen
patent: 2484696 (1949-10-01), Dinesen
patent: 3104647 (1963-09-01), Rackleff
patent: 3308788 (1967-03-01), Noorlander
patent: 4610220 (1986-09-01), Goldberg et al.
patent: 5482004 (1996-01-01), Chowdhury
Flodin Hans
Petterson Torbjorn
Alfa Laval Agri AB
Price Thomas
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