Retaining ring for a seal ring of a mechanical seal assembly

A retaining ring for a seal ring of a mechanical seal assembly comprises a recess (8) inserted at the side of one of its axial ends for a sealing receipt and force-fit assembly of the seal ring (2). In the recess (8), an engaging ring (10) made of a flexible material and having a corrugated profile at its inner periphery is retained, wherein at least the elevations (15) of the corrugated profile may be brought in a force-fit engagement with the outer periphery of the seal ring, when the seal ring is moved into the engaging ring by an external mounting force. Each elevation has a leading flange in direction (P) of the mounting movement having a inclination angle α2 larger than α1 of a lagging flange (18).

The invention relates to a retaining ring for a seal ring of a mechanical seal assembly.

In particular, the invention relates to an enhancement of mechanical seal assemblies to be used in sterile methods, e.g. medical engineering or food processing. In applications of that kind, often the sealing of fluids having a particularly high degree of purity is concerned, as e.g. ultra-pure water, in which the mechanical seal assembly should not affect the degree of purity. An effective measure in this sense is to avoid deposits at the regions of the mechanical seal assembly exposed to the fluid as far as possible, e.g. the avoidance of dead spots. In the context of mechanical seal assemblies, it is known to mount the rotating seal ring by press-fit, adhesion or soldering in a spring-biased retainer housing, however, these dead spot reducing connecting methods prove to be not practicable in view of the specific materials often used for sterile applications for parts of the mechanical seal assembly, said materials having a very low ferrite content. A force transmission (DE 202 02 177 U) between retainer housing and seal ring by means of engagement pins at the retainer housing engaging into recesses of the seal ring proves to be disadvantageous in some cases of sterile applications, since therewith not only undesirable dead spots are formed, but also no sufficient discharge of heat from the seal ring is secured, and therefore an overheating often occurs. This may result in a failure of the mechanical seal assembly after a short period of time. Due to the low or lacking lubrication effect of ultra-pure water, the thermal stress of the seal rings is high.

It is an object underlying the invention to avoid the mentioned difficulties in the application of mechanical seal assemblies of the aforementioned type. In particular, the invention shall provide a retaining ring for a seal ring, which enables the creation of a mechanical seal assembly being particularly suited to be used in sterile applications, in particular in the presence of low-lubrication to non-lubrication fluids to be sealed.

According to the invention, this object is solved by the features of patent claim1. Concerning the advantages and specific effects obtained by the invention, reference is made to the following description of an embodiment. The invention solves the aforementioned object efficiently with surprisingly simple means, such that the structure and the mounting of a mechanical seal assembly is simplified. It is known from DE 102 16 140 A to mount a seal ring at a housing by means of a engaging ring made of flexible material, which engaging ring has a corrugated profile at the engaging surface facing the seal ring, however, same has no formation of elevations and recesses corresponding to the features of patent claim1, such that this arrangement could not obtain the advantageous effects of the invention for the use in sterile applications.

Although the invention is preferably used in connection with sterile applications, in particular for sealing fluids having a high degree of purity such as ultra-pure water, it is obvious that the invention is not restricted to this field of application, but may basically be used in an advantageous way for mechanical seals.

Reference numeral1inFIG. 1designates a substantially tubular retainer housing1which preferably has a smoothly finished or polished outer periphery without any notches or steps, at which deposits could form. A seal ring2held at the retainer housing1includes a slip or seal surface3which co-operates with a like surface4of a stationary seal ring5in order to seal a portion at the outer periphery of the seal surfaces3,4with respect to a space at the inner periphery. The seal ring5is held rotationally fixed at a shaft passage region of a housing6of a device to be sealed, e.g. a pump (not shown), wherein a secondary sealing member creates a sealing between the housing6and the seal ring5. Suitable secondary sealing members for sterile applications are known to the skilled person, such that a detailed explanations is not necessary.

At the side of an axial end of the retainer housing1(right end in the drawing), a recess8is introduced, said recess including a plane radial end face9and an outer periphery (no reference numeral) into which a groove for receiving an engaging ring10is inserted.

At the side of the other axial end (left end in the drawing), a further recess is provided in order to arrange and mount a rotatory force transmission device which is generally designated by reference numeral11and does not need to be described in more detail here. It shall only be pointed out that the rotatory force transmission device11serves to connect a mounting ring13, which may be mounted rotationally fixed on a rotating component12, e.g. a pump shaft, to the retainer housing1such that a rotation of the rotating component12or the mounting ring13causes a like rotation of the retainer housing1.

Between the mounting ring13and the retainer housing1, a biasing spring14, e.g. a corrugated spring, is arranged, which has the effect that the retainer housing1, which is axially movable with respect to the mounting ring13, is biased against the stationary seal ring5in order to retain the co-operating seal surfaces3,4of the seal rings2,5in a sealing engagement with each other. Concerning the detailed structure of corrugated springs, reference is made to BURGMANN, ABC der Gleitringdichtung, 1988, Selbstverlag, page 80. A further secondary sealing member21is provided to create a sealing between the mounting ring13and the retainer housing1.

The engaging ring10is shown in more detail inFIG. 2. The engaging ring10constitutes a compact made of a flexible material, such as an elastomer, and comprises, as shown, a corrugated or saw-toothed profile at its inner periphery facing toward the seal ring2, said profile consisting of a plurality of axially spaced and circumferentially extending elevations15and recesses16provided between adjacent elevations.

Each elevation has a leading flange17in direction of the arrow P inFIG. 2and a lagging flange18, wherein an angle α2of the leading flange17is larger as the angle α1of the lagging flange18. The angle α1may range between 15° and 60°, wherein a value of α1is preferably 45°. The angle α2may range between 80° and 110°, wherein a value of 90° is preferred. The angles α1, α2respectively constitute an opening angle enclosed by a tangent toward the respective flange17,18and a center longitudinal axis of the engaging ring10, opposite to the direction of the arrow P.

The outer cones19of the elevations15forming a transition between the lagging and leading flanges are preferably rounded, however, also a transition configured otherwise may be provided. If desired, the flanges17,18may also abut on each other directly.

A lug portion20having a smaller outer diameter protrudes from an axial end of the engaging member10and extends into an outer entrance bore (not shown) to the recess8receiving the engaging ring10in the retainer housing1, as it is shown inFIG. 1. The inner periphery of the lug portion20may also have a profile of the aforementioned kind, if desired, or may be formed as a smooth cylinder, as shown inFIG. 2.

The circle circumscribed by the cones19of the elevations15has a diameter adapted to the diameter of the outer periphery of the seal ring2such that the elevations15are somewhat deformed or compressed in the radial direction when the seal ring2is moved in direction of the arrow P into the engaging ring10by a suitable external axial mounting force, such that a force-fit engagement of the engaging ring10and the outer periphery of the seal ring2occurs. Preferably, the elevations15are simultaneously deformed radially and axially, to effect a displacement of material of the elevations15into the adjacent recesses16, such that the recesses15are completely or mostly filled in the assembled state and a visible differentiation between recesses16and elevations15ceases to exist.

The seal ring6may be pushed forward in the engaging ring10until its radial end face facing away from the sealing surface3abuts at the abutting surface9of the recess8of the retainer housing1. This abutting relationship is maintained unchanged due to the inventive embodiment of the elevations15, even if the external mounting forces are removed from the seal ring. The narrow abutting relationship between the adjacent surfaces of the seal ring9and the retainer housing1enables an effective heat transfer from the seal ring2to the retainer housing1, in order to avoid an overheating of the seal ring2during operation. At the same time, the engaging ring10enables a safe and simple insertion assembly of the seal ring2at the retainer housing1and a non-slip transmission of a torque from the retainer housing1to the seal ring2.