CHEMICAL BATH PROCESS FOR THE TREATMENT OF SEALING RINGS PROVIDED WITH A LIP

Abstract: The invention relates to a chemical bath process, particularly for the treatment to which a sealing ring provided with a lip (generally made of natural or synthetic elastomeric material) has to be subjected before its mount­ ing on a rotary shaft, so that it can perform its functions to the best and have a long life of service. Said process comprises, in succession, the steps of halogenation (0.2-1 part by weight of free halogen) and of neutralization (1-7 parts by weight of alkalis as OH⁻) and it allows to considerably reduce the coefficient of friction of the elastomeric material, which involves a lower wear of the same ring and the requirement of less power by the engine which causes the rotary shaft to rotate.

Description: Chemical bath process for the treatment of sealing rings provided with a lip The present invention relates to a chemical bath process for the treatment of sealing rings provided with a lip, and more particularly it relates to the chemical treatment to which said ring must be subjected so that it is in a position to perform its functions to the best and has a long life of service. It is known that by the definition "sealing ring provid ed with a lip" it is meant a particular type of seal mounted on a rotary shaft, which projects from the casing of a machine, the purpose of which is to protect the members connected to said shaft and placed inside the casing (bearings, bushings, etc.) from dust and other impurities. According to the known art, said lip-provided sealing ring is made of natural or synthetic elastomeric material; it comprises a cylindrical or otherwise shaped body and a body in the shape of a truncated cone which are coaxial and crossed by a tubular cavity in which the rotary shaft of the machine is disposed. SÅaid body in the shape of a truncated cone is joined to one of the bases of said cylindrical body by means of its small base; the generating line of said body in the shape of a truncated cone forms an angle of a variable width with the axis of said tubular cavity, owing to the possibility of said elastomeric material to become deformed. Furthermore, the diameter of said tubular cavity is such that said lip-provided sealing ring can be forced, always due to the possibility of deformation of the elastomeric material, on the rotary shaft, becoming consequently integral thereto. When the shaft is at rest, the free end of said body in the shape of a truncated cone is in contact with a fixed surface (generally made of metal) provided with a wide opening through which said rotary shaft passes; said contact gives the inner parts of said machine the necessary protection against impurities. When the shaft rotates, and therefore also the lip-provided sealing ring rotates as it is integral thereto, the free end of said body in the shape of a truncated cone slides against said fixed surface till the centrifugal force exerted on said body in the shape of a truncated cone reaches a certain value, which causes said end to disjoin from the same surface. In other words, the rotation of the lip-provided sealing ring gives rise to a centrifugal force which tends to vary the angle that the generating line of the body in the shape of a truncated cone forms with the tubular cavity and therefore, it finally causes the free end of said body in the shape of a truncated cone to disjoin from the fixed surface. However, this disjunction does not occur immediately, but only when the rotational speed reaches a rather high value; of course, this disjunction also depends upon the fact that the lip-provided sealing ring is subject to deformation, owing to the elastomeric material of which it is made. In fact it can be easily understood that said disjunction is promoted when the possibility of deformation is high, but at the same time the members placed inside the machine do not have the necessary protection, owing to the fact that said body in the shape of a truncated cone can be easily subjected to deformation. In any case however, at the starting step of the shaft and till the time at which the shaft reaches said value of centrifugal force, the free end of said body in the shape of a truncated cone slides against said fixed surface. This sliding is the main drawback as it causes the lip-provided sealing ring to wear and to damage. All known lip-provided sealing rings have the disadvantage of a quick wear and tear of the free end of said body in the shape of a truncated cone and therefore the whole lip-provided sealing ring needs to be replaced often.Furthermore, owing to the high value of said friction, a high power is required by the engine, above all during the starting step. Said too quick deterioration of lip-provided sealing rings in practice involves technical problems (bad protection, necessity of frequent maintenance, etc.) as well as economical problems (cost of the rings, frequent stoppage of the service, etc.). The aim of the present invention is to obviate the drawbacks of the lip-provided sealing rings of the known art, and therefore to considerably reduce the friction which occurs both during the starting step of rotation of the shaft, and during the step of slow running when the rotation is carried out within reduced values and the lip is kept in contact with the fixed surface. It is therefore an object of the present invention to provide a chemical bath process for the treatment of sealing rings provided with a lip, made of natural or synthetic elastomeric material, comprising a cylindrical or otherwise suitably shaped body and a body in the shape of a truncated cone, the small base of said body in the shape of a truncated cone being joined to the base of said cylindrical body, said cylindrical body and said body in the shape of a truncated cone being coaxial and crossed by a tubular cavity; the generating line of said body in the shape of a truncated cone forming an angle of a variable width with the axis of said tubular cavity, characterized in that it comprises, in succession, the steps of halogenation and neutralization, said halogen ation step being carried out in a water bath containing at least 0.2 to t part by weight of a free halogen and said neutralization step being carried out in a water bath containing at least 1 to 10 parts by weight of free alkalis, expressed as OH The present invention will best be understood from the following description taken in connection with th accompanying drawing in which the only figure reF-tsents a cross-sectional diagrammatic view of said lip-provided sealing ring according to the invention. Referring to said figure, the lip-provided sealing ring A appears integrally mounted on shaft 10 which rotates about the axis X-X. Said lip-provided sealing ring A comprises a generally cylindrical body 11, which however can be also different ly shaped, and a body in the shape of a truncated cone 12, the latter being joined by its small base to one of the bases of the former. The two bodies 11 and 12 are coaxial and crossed by a tubular cavity 13 which in turn is coaxial to the shaft. The generating line a of said body in the shape of a truncated cone (for the sake of simplicity said generating line is drawn in the figure in the middle portion of the section showing the thickness of the body in the shape of a truncated cone) forms an angle with the axis X-X. Said angle ¯ has a variable width , by virtue of the degree of deformation of the elastomeric material composing said lip-provided sealing ring. When the shaft 10 is at rest or when it is rotating at a very low speed, the free end 14 of said body in the shape of a truncated cone urges against the fixed surface 15. However, when the shaft is rotating, owing to the centrifugal force exerted on said body in the shape of a truncated cone, the generating line a gradually reaches the position shown as a' in the figure, forming the angle cil with the axis X-X, and gradually causing the disjunction of the free end 14 of said body in the shape of a truncated cone from said fixed surface 15. As already said, the gradual reduction of pressure and the possible disjunction-of said free end from the fixed surface does not only depend upon the rotation speed of the shaft, but also upon the facility of deformation of the elastomeric material cf which said lip-provided sealing ring is made. Particularly, it has been found that said material has a dynamic behavior which is particularly satisfactory for this purpose when the ratio between the density of 3 said material (indicated in g/cm ) and the stress (indi- cated as CAO1 according to UNI 6065 specification) is equal to or higher than 4.5. As to the possibility of reducing the friction which occurs between the free end of said body in the shape of a truncated cone and said fixed surface and which is stronger when the rotation starts but gradually decreases till it reaches the condition of disjunction of the two parts, it has been found that said friction can be considerably reduced if said lip-provided sealing ring is at least subjected, in succession, before its assembl ing on the shaft, to the steps of halogenation and neutralization; advantageously said steps can be preceded and followed by the further steps of a first and a second washing in water. It has been found that important results can be achieved when said halogenation step is carried out in a water bath containing at least 0.2 to 1 part by weight of a free halogen while said neutralization step is carried out in a water bath containing at least 1 to 10 parts by weight of alkalis, expressed as OH Both the steps are carried out at room temperature and for a period varying from 2 to 10 minutes. According to a preferred embodiment, said halogenation water bath comprises 0.5 to 10 parts by weight of hypochlorite, 0.5 to 2 parts by weight of hydrochloric acid and 0.5 to 1 part by weight of a surface-active agent, while said neutralization water bath comprises 2.5 to 10 parts by weight of ammonia. According to the object of the present invention it is understood that said treatment can be accomplished either on the whole lip-provided sealing ring or on the free end only of said body in the shape of a truncated cone, the latter procedure being particularly advantageous when said lip-provided sealing ring has middle or big sizes (for example the diameter of the cylindrical body is longer than 6 cm). The advantages of the present invention reside in the fact that the chemical treatment with halogen elements involves an important reduction of the friction coefficient of the elastomeric material; as a result, the free end of the body in the shape of a truncated cone is less worn during the starting step, that is until the disjunction of said free end from said fixed surface takes place. Furthermore, it has to be noted that a further advantage is given by the fact that the engine requires less power, due to the reduced friction. The purpose of the subsequent neutralization step is to stop the aggressive action of the halogen. It will be understood by those skilled in the art that although preferred embodiments have been shown and described, the invention is not limited thereto or thereby.

Claims: CLAIMS 1) A chemical bath process for the treatment of sealing rings (A) provided with a lip, suitable to be mounted on a rdtary shaft in order to protect the members connected thereto (bearings, bushings, etc.) from dust and other impurities and made of natural or synthetic elastomeric material, comprising a cylindrical or otherwise suitably shaped body'(11) and a body (12) in the shape of a truncated cone, the small base of said body in the shape of a truncated cone being joined to the base of said cylindrical body(11), said cylindrical body (11) and said body(12) in the shape of a truncated cone being coaxial and crossed by a tubular cavity (13), the generating line (a) of said body (12) in the shape of a truncated cone forming an angle ( & ) of a variable width with the axis (X-X) of said tubular cavity (13), characterized in that it comprises, in succession, the steps of halogenation and neutralization, said halogenation step being carried out in a water bath containing at least 0.2 to 1 part by weight of a free halogen and said neutralization step being carried out in a water bath containing at least 1 to 10 parts by weight of free alkalis, expressed as OH .2) A chemical bath process according to claim 1, characterized in that said chemical treatment comprises, upstream of said halogenation step and downstream of said neutralization step respectively, the further steps of a first and a second washing in water. 3) A chemical bath process according to claim 1, cha racterized in that said halogenation and neutralization steps are carried out at room temperature and for a period varying from 2 to 10 minutes. 4) A chemical bath process according tq claim 1, characterized in that said halogenation step is carried out in a water bath containing 0.5 to 10 parts by weight of hypochlorite, 0.5 to 2 parts by weight of hydrochloric acid and 0.5 to 1 part by weight of a surface-active agent. 5) A chemical bath process according to claim 1, characterized in that said neutralization step is carried out in a water bath containing 2.5 to 10 parts by weight of ammonia.

Inventors: BASSI, ANGELO CARLO
Applicants: INTERMARP (ITALIA) S.P.A.
Application year: 1982
Main classification: F16J15
IPC codes: C08J7, F16J15