WO2008066480A1

WO2008066480A1 - Teat cup liner

Info

Publication number: WO2008066480A1
Application number: PCT/SE2007/050890
Authority: WO
Inventors: Nils ÄLVEBY
Original assignee: Delaval Holding Ab
Priority date: 2006-11-27
Filing date: 2007-11-22
Publication date: 2008-06-05

Abstract

A teat cup liner according to the invention comprises at least a teat-receiving flexible sleeve (24), adapted to be positioned on/over a teat. It also has at least a first portion comprising a silicone material, and at least a second portion 5 comprising a material different from the silicone material in the first portion. Preferably, both the head portion (22) and the connecting part (27) comprise thermoplastic material, and the flexible sleeve (24) extends between the head portion (22) and the connecting portion (27).

Description

TEAT CUP LINER

The present invention relates to a teat cup liner usable in a milking machine.

Background of the Invention

Machine milking has been available for about a century. The basic construction of a milking device, which is still in use today is based on an invention patented by Gillies in 1902, and comprises a double chambered teat cup designed to operate with a pulsating vacuum. The teat cup comprises a flexible sleeve made of rubber, forming one flexible wall of a chamber, where the teat cup shell forms the other wall. In the space between the two walls a pulsating vacuum is applied whereby the sleeve will expand and contract, thereby causing a massaging action on a teat on which the teat cup has been applied.

The flexible sleeve is provided as a part of a so called teat cup liner (or inflation in US English; in the present specification and claims the term "liner" will be used throughout) .

A milking apparatus as a whole comprises a number of different components, many of which currently are made of different kinds of rubber, e.g. tubing, nozzles, liners etc.

As an example, a modern teat cup system is disclosed in US-6, 176,200 (Petterson). It comprises a tubular head portion capable of receiving a teat, and a shaft portion forming an inner wall of the pulsating vacuum chamber. The shaft portion is flexible and normally made of a rubber compound.

In order to be accepted by the market, devices forming the components of milking apparatus, such as teat cups and liners, must exhibit a number of properties. Examples that can be mentioned are the following:

Good milking performances, e.g., milk speed, milk yield, slip, strip yield Good teat treatment

Long lifetime of the device and capability of functioning at the same high level of performance over the entire lifetime. Uniform quality of the devices. Chemical and physical endurance Devices should be easy to clean Devices should be easy to replace Devices should be environmentally friendly Low energy consumption manufacturing

The product must comply with regulations relating to material and to articles and products that are intended to come into contact with foodstuff.

Currently available components of milking apparatus, such as liners and tubing, are most often made of rubber materials, which do not meet the above requirements to a totally satisfactory degree.

Liners made of silicone, have certain characteristics that are desirable, such as sustained smoothness and a durable surface, and such liners made of silicone are available on the market. The use of silicone rubber for a liner in a teat cup assembly has been disclosed i.a. by Kupres (US-4, 651 ,676; 1987). Some further examples are disclosed in US-6,640,744, US-6,435, 132, US-5,069, 162, UK- 1 ,400,014, just to mention a few. A commercially available teat cup liner is marketed by Westfalia AG, Germany, under the trademark Stimulor^® Silicone Liner, and is disclosed i.a. on their web site.

While silicone has a number of advantages in such applications (wide service temperature range, flexibility etc.), a few disadvantages exist. First, when the whole inflation part for the teat cup assembly is made of pure silicone, the part is very soft and will move easily, which in some cases could prevent efficient milking. This problem was only partly addressed by Kupres, who disclosed the use of adhesives to fasten the silicone liner to the assembly, in order to anchor it tightly to the assembly. However, the use of adhesives is disadvantageous, as it is difficult to find adhesives withstanding the temperature and humidity conditions encountered in the dairy industry. In particular the inherently non-adhesive nature of silicone surfaces makes it difficult to use adhesives for silicone.

Thompson et al (US-5,069,162; 1991) disclosed the use of flutes in the silicone liner, in order to make that part more stable.

Summary of the Invention

The object of the present invention is therefore to provide a liner based on silicone rubber, but with improved properties compared to the prior art silicone liners, in particular in terms of stiffness of selected parts of the liner.

The present invention achieves this object with a liner as defined in claim 1 , having a flexible teat-receiving sleeve, wherein at least a first portion of the liner comprises a silicone material, and at least a second portion thereof comprises a material different from said silicone material.

Currently, in the present invention amorphous and in some cases semi-crystalline thermoplastic polymers are preferred. Currently preferred amorphous materials are Phenylenpolysulphone (PPSU), polysulphone (PSU), poly-amide 12 (PA 12), or acrylonitrile-butadiene-styrene (ABS ).

Suitable semi-crystalline materials e.g. Poly butylene teraftalat (PBT), or poly-amide 6.6 (PA66) may be considered as suitable alternatives.

This solution to the problem with prior art devices is based on the use of integral molding of silicone and a material different from silicone, preferably but not exclusively thermo plastic material, to achieve a liner which can both be firmly anchored to a teat cup, and has an improved stiffness compared to a liner made of pure silicone rubber.

Suitably, at least the second portion comprises a material selected from the group consisting of thermoplastic materials. Alternatively, the second portion comprises a silicone material having a higher stiffness than the silicone material in the first portion. In an embodiment of the invention the second portion of the teat cup liner is a connecting part for connection to external equipment, such as milk tubes, milking claws etc. It also preferably comprises a head portion which includes a hole for positioning on/ over a teat. The head portion is preferably a separate part which is attachable to the teat-receiving flexible sleeve. Both the head portion and the connecting part suitably comprise thermoplastic material.

In a preferred embodiment of the liner the flexible sleeve extends between the head portion and the connecting portion.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus not to be considered limiting on the present invention, and wherein

Fig. 1 shows a prior art teat cup liner; and

Fig. 2 shows a teat cup liner according to the invention.

Detailed Description of Preferred Embodiments

The expression "liner" or "teat cup liner" is taken to encompass a device usable together with a milking apparatus or system, that is to be used in the dairy business e.g. in contact with the milk, and therefore must comply with regulations relating to materials and articles intended to come into contact with foodstuffs. A liner comprises at least a teat receiving flexible sleeve, adapted to be positioned on/over a teat, suitably in a close fit. At the end proximal of the teat receiving end, there can be provided a short milk tube, to be attached to the teat cup central. It can also comprise a supply tubing for pulsating medium, referred to as a "pulsation tubing". It is to be noted that the liner according to the invention may be used for various different animals, e.g. cows, buffalos, sheep and goats and other ruminant animals. "A teat cup" is taken to be a device comprising a housing, "teat cup shell" in which a liner, as defined above is mounted or formed as an integral part thereof. In particular a teat cup can be a milk extracting device, i.e. a device constituting a part or component of a milking apparatus that acts on the teat of an animal, or cooperates with other parts of the milking apparatus, such that the udder will release milk in a controlled manner. A teat cup comprises a liner, which in its turn comprises at least a flexible teat receiving sleeve, adapted to be positioned on/over a teat in a close fit.

For the purposes of the present application, the expression "thermoplastic polymer" is given the ordinary meaning of that term within the field of polymer technology. Currently, in the present invention, amorphous and semi-crystalline thermoplastic polymers are preferred, although other types of thermoplastic polymers are possible. Typical examples of preferred thermoplastic polymers are amorphous polymers like phenylenepolysulphone (PPSU), polysulphone (PSU), poly-amide 12 (PA 12), aciylonitrile-butadiene-styrene (ABS); semi-crystalline polymers like poly butylene teraftalat (PBT) and poly-amide 6.6 (PA66). It can also encompass various types of fillers, such as glass fibers, carbon fibers, mineral fibers, metal fibers etc, or other conventional fillers usable in polymers.

In Fig. 1 , an exemplary prior art teat cup assembly is disclosed. It comprises a teat cup liner 1 which is mounted in a teat cup shell 2. The teat cup liner 1 is essentially rotationally symmetrical with respect to a longitudinal axis 3 and comprises an upper tubular head portion 4 and a tubular, flexible teat receiving sleeve portion 5 extending downwardly from the head portion 4. The head portion 4 comprises a first upper end 6 and a second lower end 7. At the upper end 6, the tubular head portion 4 comprises a lip 8 extending radially inwardly and defining an essentially circular central opening. The tubular head portion 4 forms a passage through the head to the inner space of the teat cup liner for receiving a teat in the sleeve 5. The lower end 7 comprises an annular recess 9 which is engaged by the upper end portion of the teat cup shell 2. The lower part of the sleeve 5 comprises a peripheral surrounding recess 10 which is engaged by the lower end portion of the teat cup shell 2. The recesses 9 and 10 are shaped in such a manner that a closed space 11 is formed between the teat cup liner and the teat cup shell 2, which space 11 forms a pulsating chamber of the teat cup. In its lower part, the teat cup liner 1 connects to prolongation pieces 12 and 13, which form a milk conduit which may be connected to a claw (not disclosed) . The teat cup liner 1 can be manufactured in an elastic material, for instance natural or synthetic rubber

In the upper end 6 of the head portion 4 there is a pre-tensioning member 14 in the shape of a ring, the function of which is to pretension or tighten the upper end 6 of the head portion 4 radially outwardly and in such a manner pull the lip 8 radially outwardly and thus provide a pretension in the lip 8 which extends in the peripheral direction of the lip. In such a manner, weakening of the lip and any deformation, i.e. such as bending upwardly or downwardly of especially radially inner parts thereof is counteracted.

An alternative prior art liner is made entirely of a single silicone material, i.e. there are no parts or portions thereof that differ from each other in respect of the material properties. For example there is no member corresponding to the pre-tensioning member 14 in Fig. 1. Such a liner may suffer from not being rigid enough in certain parts.

In fig. 2 a teat cup liner 20 according to the present invention is shown, mounted in a teat cup shell 21. The liner 20 comprises at least one softer portion made of a silicone rubber, and at least one stiffer portion. The inventive feature of the liner of Fig. 2 with respect to the liner of Fig. 1 is that the at least one stiffer part of the liner is made from a material that is different from the elastic silicone rubber. It could simply be another stiffer grade of silicone, but in particular the liner according to the invention comprises at least one part made from silicone rubber, and a second part made from a material having certain properties such as a higher stiffness than silicone and having chemical resistance to water, fat and detergents (alkali acidic and tensides). Suitably, the material is selected from the class of thermoplastic materials. By using both silicone rubber and another suitable material, different from silicone, such as but not limited to a thermoplastic material, it is possible to tailor the liner so as to exhibit the desired stiffness in different parts thereof. In a preferred embodiment of the present invention, there is provided a teat cup liner 20 which is made of such a material combination. An embodiment of a liner 20 according to the invention is schematically illustrated in cross-section in Fig. 2, as mounted in a likewise schematically represented teat cup shell 21. The liner comprises a head portion 22, a flexible sleeve portion 24 for receiving a teat in a substantially close fit. By "close fit" is meant that there will be no significant amounts of air leaking in from between the teat and the sleeve in operation, i.e. during milking. The sleeve extends from the head portion 22 to a connecting part 27 where a short milk tube is connectable to the sleeve 24. Alternatively the milk tube can be integrated with the sleeve.

In the particular embodiment shown in Fig. 2, the teat cup liner is made as two separate parts connectable by means of a snap fit coupling 28. Thus, the top or head portion 22, including a teat-receiving opening 26, is made as a "lid" that can be connected to the remaining part comprising the actual flexible sleeve 24 of the liner.

Suitably the connecting part 27 is made from the stiffer material, preferably but not necessarily, thermoplastic material, in order that the liner can be rigidly attached to the teat cup shell 21 , so as not to cause leakage. It is important that the sleeve can be fixed in a defined and particular position in the shell.

Furthermore, the teat cup shell is to be connected to a supply of pulsating medium in order that the sleeve of the liner can be able to perform its function. This supply is provided via a pulsation tubing connectable to the teat cup shell 21 at an inlet connector 23, such that the pulsation can act on the sleeve 24.

The most important element of a liner is the flexible sleeve 24, in the sense that it is this element that performs the function by alternatingly collapsing and opening/ expanding, caused by the pulsating vacuum applied. Thus, in order that the liner be able to fulfil its technical function, at least the flexible sleeve must meet certain criteria with respect to material properties. According to a specific embodiment of the present invention, the flexible sleeve 24 is made of silicone rubber, whereas the head portion 22 and the connecting part 27 comprise thermoplastic material. At least the head portion can comprise a combination of silicon and thermoplastic material.

A particular advantage of combining the silicone rubber with another material, in accordance with the invention, is the strong bonding between the materials that is actually achieved. This will enable the device as a whole to accommodate shear forces during use. By making certain parts exposed to such forces from a stiffer material, while ascertaining a strong connection between the materials, this problem is avoided. A further advantage of this design, is that the said parts exposed to shear forces can be made smaller, which enables the construction of a more compact teat cup liner. Accordingly, less material is used in the production of the teat cup liner, which is cost efficient.

A number of embodiments based on material selections and material combinations are possible, wherein different parts are made with different stiffnesses depending on the material selected. All such variations and modifications are applicable to all embodiments within the generic definition of the device according to the invention.

Thus, it is possible to make a device according to the invention (e.g. a liner, possibly comprising a short milk tubing and/ or a short pulsation tubing) by using several variations or modifications in terms of material combinations, to provide for suitable properties for each specific use or application of the device according to the invention. Also, different parts of a device may be provided with different properties, adapted to the kind of environment that the specific part or portion of the device will come into contact with.

In particular it should be noted that it is within the inventive concept to use different silicon rubbers in combination with one or more thermoplastic material. Thereby, e.g. the exterior surface of the flexible sleeve can be given different properties than the inner surface, such as different in terms of hydrophobic/ hydrophilic properties. Amorphous polymers are particularly suitable, but also semi-crystalline polymers are suitable. The reason for these materials being so well compatible with silicone rubber is that they exhibit suitable surface energies. Now a method for making a liner according to the invention will be described.

Suitably a teat cup liner according to the invention is manufactured by injection molding of the selected materials, i.e. silicone fluid (the precursor of silicone rubber) and thermoplastic material, such that the final device will exhibit the desired properties.

Generally, devices comprising two or more materials in combination, i.e. forming a composite material, can be formed together in several ways. Dual injection of two (or more) materials in sequence in one and the same mold can be used. Another option is to make a "precursor" from one material in a first mold, and then move the "precursor" to a second mold in which one or more further materials are injected. It is also possible to injection mold or extrude the different components separately using different materials. For silicone rubber a cross-linking is required after the injection into the mold. It will pertain to the field of the skilled man to design the molding processes in detail to obtain the desired structures and the set ups necessary to obtain them, and such methods will therefore not be discussed further herein.

According to the present invention, the silicon is cross-linked so as to form a bond to the other material. This can be a physical bond or at best a chemical bond. And in some instances a chemical bond from the silocone into a surface layer of the thermoplastic material only. A bond can arise from intertwining of molecules from silicone and the other material, across the interface between the two materials. Furthermore, bonds between the molecules of the two materials can arise from Van der Waals forces. The expression Van der Waals forces refer to those forces which arise from the polarization of molecules into dipoles. This includes forces that arise from fixed or angle-averaged dipoles (often referred to as Keesom forces in the literature) and free or rotation dipoles (often referred to as Debye forces in the literature), as well as shifts in electron cloud distribution (often referred to as London forces in the literature).

For molecules comprising hydrogen and electronegative elements, such as oxygen and nitrogen, interaction can also arise from hydrogen binding. The method for making a teat cup liner according to the invention in a preferred embodiment is a two-step molding process. However, it is possible to perform more than two steps for making more complex structures.

Thus, in a first step a thermoplastic material such as poly butylene teraftalat (PBT) or any other suitable thermoplastic material mentioned initially, is injected in a mold defining only that/ those portion(s) of the device that is/ are to exhibit a higher stiffness or rigidity, such as couplings. The mold comprises a core defining an inner lumen of the liner.

After solidifying of the thermoplastic material the core, now carrying the above mentioned stiffer parts, is demolded from the mold, and placed in a second mold, into which, as a second molding step, a suitable silicone fluid is injected. Alternatively, the core can be moved to a second cavity but in the same mold, or could even be left in the same cavity if the mold is adjustable to a different shape, defining the second molding structure or component. Thus, the second (and further if required) molding step defines the remaining portions of the device to be made.

Silicone fluid requires cross-linking in order to cross-link the constituent molecules to bring about the transformation to a rubber. The "precursor" composite consists of one or more parts of thermoplastic material in contact with silicone fluid. The silicone thereby fills the remainder of the mold to define the final product. This combination of solid thermoplastic material and silicone fluid, is then subjected to conditions that will bring about the desired cross- linking_^ cross-linking of silicone commences when the product is exposed to atmospheric moisture, with elimination of by-products. This reaction, also referred to as cross-linking, begins at the surface of the applied layer of silicone rubber and gradually progresses inwards.

The used cross-linking system can be one of three kinds: Basic or amine systems: Small amounts of an amine are eliminated.

Acidic or acetoxy systems: Small amounts of acetic acid are eliminated.

Neutral, i.e. oxime or alkoxy systems: Small amounts of an oxime or alcohol are eliminated.

Despite the different chemistry of silicone and thermoplastic, there will be a very good connection between the materials. Transitions between the two materials, i.e. between stiffer and softer portions, will be near perfect. By "near perfect" we mean that there will be no perceivable steps or grooves where the two materials meet. Thus, bacteria or other micro-organisms and organic material, such as milk residues, serving as nutrition for bacteria cannot in fact become trapped in these transition regions. From a hygiene point of view this is essential, and an important feature of the method and of the device according to the invention.

Also, load can be carried over from one material to the other.

As an example the silicone materials usable in the invention can suitably exhibit the following properties:

Tensile Strength (Mpa) 3-25

Elongation (%) up to 100-1000 Tear Strength (KN/ m) 10-50

Durometer Range (Shore A) 20-85

Specific Gravity 0.90- 1.2

Suitably, the tensile strength is less than 20 Mpa, preferably less than 15 Mpa, but greater than 5 Mpa, preferably greater than 8 Mpa. The elongation can be greater than 300%, and less than 1000%, but can be as high as 500%. The tear strength is suitably greater than 15 but less than 45, preferably more than 17.5 but less than 44 kN/m. The specific gravity is suitably over 1.0, preferably more than 1.10, more preferably over 1.13, but less than 1.18. The Durometer Range (Shore A) is suitably less than 85, preferably less than 65 but greater than 20, preferably greater than 45.

Claims

CLAIMS:

1. A teat cup liner comprising at least a teat-receiving flexible sleeve (24), adapted to be positioned on/ over a teat, and a head portion (22), characterized in that at least the head portion (22) of the liner comprises a combination of silicone and another material different from the silicone material.

2. A teat cup liner as claimed in claim 1 , characterized in that the at least second portion comprises a silicone material having a higher stiffness than the silicone material in the first portion.

3. A teat cup liner as claimed in claim 1 , characterized in that the at least second portion comprises a material selected from the group consisting of thermoplastic materials.

4. A teat cup liner as claimed in claim 3, characterized in that the thermoplastic material is amorphous.

5. A teat cup liner as claimed in claim 4, characterized in that the amorphous material is any of Phenylenpolysulphone (PPSU), Polysulphone

(PSU), Poly-amide 12 (PA 12), or acrylonitrile-butadiene-styrene (ABS).

6. A teat cup liner as claimed in claim 3, characterized in that the thermoplastic material is semi-crystalline.

7. A teat cup liner as claimed in claim 3, characterized in that the semi-crystalline material is any of Poly butylene teraftalat (PBT), or poly-amide 6.6 (PA66).

8. A teat cup liner as claimed in any of claims 3-7, characterized in that the thermoplastic material further comprises fillers, such as glass fibers, carbon fibers, mineral fibers, metal fibers.

9. A teat cup liner as claimed in any of the preceding claims, characterized in that the silicone material in the first portion is selected from materials having the following properties:

Tensile Strength (Mpa) 3-25

Elongation (%) up to 100-1000

Tear Strength (KN/ m) 10-50

Durometer Range (Shore A) 20-85

Specific Gravity 0.90- 1.2

10. A teat cup liner as claimed in any of the preceding claims, characterized in that the second portion is a connecting part (27) for connection to external equipment.

1 1. A teat cup liner as claimed in any of the preceding claims, characterized in that the liner further comprises a head portion (22) which includes a hole for positioning on/ over a teat.

12. A teat cup liner as claimed in claim 1 1 , characterized in that the head portion (22) is a separate part which is attachable to the teat-receiving flexible sleeve (24).

13. A teat cup liner as claimed in any of claims 1 1-12, characterized in that both the head portion (22) and the connecting part (27) comprise thermoplastic material, and wherein the flexible sleeve (24) extends between the head portion (22) and the connecting portion (27).

14. A teat cup liner as claimed in any of the preceding claims, characterized in that the silicone material forms a physical or chemical bond to the other material, preferably a chemical bond.

15. Milking apparatus characterized in that it comprises a teat cup liner as claimed in any of the preceding claims.