DEDE TG4 oil seal is a three-lip rotary shaft seal with an external thread and reinforced metal skeleton, designed to provide oil retention while adding protection against contaminants around the shaft. Compared with a conventional single-lip or double-lip oil seal, the TG4 uses three sealing lips with different functions, so its structure is intended to handle more complicated sealing conditions rather than simply increase contact pressure.
The three-lip arrangement is the most recognizable feature of the TG4. The main sealing lip works on the lubricant side and maintains contact with the rotating shaft to limit oil or grease leakage. Behind it, the auxiliary lip provides an additional contact area around the shaft. This intermediate lip should not be understood as another spring-loaded primary lip; its function is related to supporting the overall sealing arrangement and helping maintain a more controlled sealing zone. The outer lip works mainly as a barrier against dust and particles entering from the outside.
The reason for using several lips is easy to understand when looking at an actual machine. A rotating shaft may be exposed to lubricant on one side and dust, moisture or other contaminants on the other. A single sealing edge has to deal with both directions. With the TG4 structure, these functions are distributed between different lips. The result is a more layered sealing path around the shaft instead of depending on one contact edge for every task.
The external-threaded outside surface is another feature that distinguishes
TG4 from some common smooth-OD oil seals. The external thread is formed on the
outer rubber surface and interacts with the housing during installation. Besides
helping with retention, this structure can contribute to the seal's resistance
to movement in the housing under suitable installation conditions. It is
particularly useful when the sealing design needs a firm relationship between
the seal OD and housing bore.
The metal skeleton serves a different purpose. It supports the elastomer and gives the seal the dimensional stability needed during installation and operation. The skeleton itself is not the dynamic sealing surface. The actual sealing action at the shaft comes from the elastomer lips and their designed radial contact with the shaft.
Material selection also changes how a TG4 seal behaves. DEDE provides TG4 products in different material options, including NBR and FKM. NBR is commonly considered for general oil and grease service, while FKM can be selected when the application involves higher temperatures or more demanding chemical exposure. The appropriate material still depends on the actual lubricant, temperature, speed and surrounding environment rather than simply choosing one material for every application.
For this reason, the TG4 should not be viewed simply as an oil seal with “one more lip.” Its value comes from the combination of three functional lips, an external-threaded OD, metal reinforcement and material selection. These features give engineers another option when a conventional rotary shaft seal does not provide the sealing arrangement required by the working environment.
