1. Field of the Invention
The present invention relates to rotary mechanical fluid seals of the type used for effecting a fluid-tight seal between a rotatable shaft and a housing. In particular, this invention relates to a reinforced two-member seal assembly which rotates with the shaft and in which one member is a replaceable insert which is resiliently pressed in an axial direction against a stationary surface on the housing. Such seals are used to contain corrosive fluids.
2. Description of the Prior Art
The present invention is an improvement over the rotary mechanical fluid seal disclosed in U.S. Pat. No. 3,391,942, which is incorporated hereby by reference. The prior ar device of the '942 patent is shown in FIGS. 1-3 to include a bellows member 10 having one end 12 clamped by a clamp ring 13 in fixed sealing relationship with a rotatable shaft 14 and the second end 16 fixed in sealing relationship with one portion 18 of a replaceable insert 20. Screws 21 are used to tighten clamp ring 13 around shaft 14. A second portion 22 of replaceable insert 20 rotates against a sealing surface 24 on a housing 26. The radially inner surface of the second end 16 of bellows member 10 is provided with a rigid restraining ring 28 for rigidifying the end of bellows member 10 which is in contact with replaceable insert 20. Second end 16 of bellows member 10 and replaceable insert 20 are biased toward sealing surface 24 by a cylindrical member 30 and springs 32 so that second portion 22 of replaceable insert 20 is in tight sealing contact with sealing surface 24 of housing 26.
Although this arrangement represented a considerable improvement over the then prior art, there were some disadvantages with this design. Since seals of this nature are used to contain corrosive liquids, the composition of the restraining ring is limited to materials which are resistant to the corrosive fluid with which it comes in contact. Unfortunately metal rings have not been corrosion resistant in the design shown in the '942 patent. This limitation cuuses the seal design to be constrained by dimensional and structural configurations which would not be occasioned if a metal ring were useable in a corrosive environment. In addition, the arrangement shown in the prior art has been known to incur premature weakening of the bellows member and, therefore, requires replacement of the bellows member upon wear and relacement of the replaceable insert. Besides the obvious additional cost of replacing both members, it is considerably more time-consuming and inefficient to remove and replace the bellows member each time that the replaceable insert is removed and replaced.
Accordingly, it is an object of this invention to provide a rotary mechanical fluid seal with a replaceable insert in which the composition of the restraining ring is not limited to materials which are resistant to corrosive fluids being contained by the seal.
It is another object of this invention to provide a seal design which is not constrained by dimensional and structural configurations of prior art devices.
It is a further object of this invention to provide a seal design which does not incur premature weakening of the bellows member and, therefore, does not require replacement of the bellows member upon wear and replacement of the replaceable insert.
Additional objects and advantages will be set forth in the description which follows and in the drawings, and in part will be obvious from the description of the invention or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.