Cartridge Seal Stack

A cartridge seal stack utilizes a plurality of rotary cartridge seals each including a cold flowable plastic ring having a body for sealably engaging a housing bore and a lip for sealably engaging a shaft rotating within the housing bore.

A spring is provided and disposed between the body and the lip for biasing the lip against the shaft and a separable metal retainer is provided for fixing the plastic ring within the housing bore and around the shaft. The separable metal retainer includes a surface of revolution with a rear portion having a radius suitable for press fitting into the housing bore and a front portion of lesser radius ending the ring. An internal groove is provided in the body of the plastic ring for engaging the ring in order to latch the plastic ring and metal retainer together. A spring portion connecting the retainer rear portion and the ring is provided for controlling residual stress in a radial direction within the plastic ring and preventing shrinkage of the plastic ring toward the shaft.

The present invention generally relates to a stack of cartridge rotary seals that are pressed into a housing and provide a seal around a shaft at relatively low pressures under various fluid environments. More particularly, the present invention is directed to a stack of cartridge seals mounted in a housing or on a shaft, which are designed primarily for use in reciprocating, rotary and static applications.

Cartridge rotary seals have been used for many years in a variety of applications for the sealing of various types of fluids and gases. Generally these seals use an elastomer as the seal material and such elastomer is molded and bonded to a supporting metal ring.

The materials described in this application utilize various types of plastics, such as ploytetrafluoroethylene PTFE because it exhibits relatively low friction and it is chemically inert and can withstand a variety of temperatures, thus enabling their use under conditions with no lubrication. Other plastic materials may be used, such as ultra high molecular weight polyethylene, but it has limited temperature capabilities and limited chemical compatibility with a high degree of friction.

The prior art cartridge seals utilized the elastomer in a bonded relationship and continuous tube bears around the shaft.

As hereinabove noted, when plastics are utilized, like PTFE, the plastic is mechanically retained to the metallic ring and the entire assembly is pressed into the housing with a high degree of interference between the OD of the seal and the housing to permit retention of the seal assembly into the housing and at the same time, providing static sealing against the housing. Dynamic sealing between the seal and the shaft is provided by the contact between the plastic and the shaft.

A common problem with the prior art is that the elastomer when subjected to heat, produced a high degree of friction and wear and also have limited chemical compatibility that limits the life of the seal and can cause seal failure.

Heretofore seals have been stacked between a housing and the shaft in order to enhance overall sealing therebetween. Generally, the type of seals that have been used for stacking are known as "V-Rings". Such rings are circular and have a "V" cross section. The rings are stacked with a hard support ring that bears against a housing end. The V-Rings stack is generally made from the elastomeric materials or combinations of elastomeric materials as well as plastics, such as PTFE and combinations thereof. Unfortunately, fluid pressure applied to the stack is transmitted equally throughout the entire seal stack so all seals were subject to the fluid pressure. In addition, heretofore, seals stacks utilizing V-Rings provide for no radial adjustment. Accordingly, as the seals wear, leakage increases and eventually the replacement of the seals is necessary due to such leakage.

The present invention provides for a seal stack assembly in which pressure is concentrated on a primary seal while other seals in the stack provide other functions, such as better sealing, longer life of variations and design, etc. Accordingly, the seal stack in accordance with the present invention can withstand fluid pressure with little deformation.

The rotary cartridge seal stack assembly in accordance with the present invention generally includes a plurality of rotary cartridge seals disposed in an abutting relationship with one another, the plurality of cartridge seals being disposed between a housing bore in a shaft.

In one embodiment, each of the cartridge seal include a cold flowable plastic ring having body means for sealably engaging a housing bore and lip means for sealably engaging a shaft rotating within the housing bore. Separable metal retainer rings are provided for fixing the plastic ring between the housing bore and around the shaft with the separable metal retainer means each having a surface of revolution with a rear portion having a radius suitable for press fitting into the housing bore.

Although there has been hereinabove described a specific embodiment of a rotary cartridge seal stack in accordance with the present invention, for the purpose of illustrating the manner in which the invention may be used to advantage, it should be appreciated that the invention is not limited thereto.