GB2154674A - Shaft seal - Google Patents

Abstract

A shaft seal comprises a holder (16) carrying a carbon seal (56) for rotation against an end surface of a stationary seal ring (60), the holder being coupled to a drive sleeve (18) secured to a shaft (12) which extends through an end wall (66) which mounts the seal ring. The coupling is provided by drive lugs (36) extending from the outboard end of the drive sleeve into slots (48) within the seal holder. A seal (52) is provided between the drive sleeve (18) and the seal holder (16) and is axially movable along a travel land (62) of the drive sleeve (18). The drive sleeve (18) is provided with an annular stress- relieving groove (65) and is sealed to the shelf (12) by a seal (28). <IMAGE>

Description

SPECIFICATION Shaft seal The present invention relates to a shaft seal, and is more particularly concerned with a seal for a shaft which extends through an end wall of a pump machine, such as a bell housing.

A shaft seal is manufactured by Gits Bros Mfg. Co., Tampa, Florida, known as the Type 880, in which a drive sleeve is connected to a shaft and is coupled to rotate a seal holder whose seal member has a seal face which is rotatable against an end surface of a stationary seal ring. The coupling between the drive sleeve and the seal holder comprises a plurality of lugs extending from the seal holder parallel to the axis of rotation and received in slots which are formed in the outer peripheral surface of the drive sleeve. The seal holder includes an internal annular groove which carries an O-ring which bears against the outer surface of the drive sleeve. Also, in order to maintain the sealed relationship between the seal face and the stationary seal ring, springs are provided in the holder to bear against the end of the drive sleeve.

The drive sleeve includes, basically, two portions, an inboard portion which has threaded bores for receiving set screws to connect the sleeve to the shaft, an outboard portion having the slots therein for receiving the drive lugs and a groove for stress relief between the two portions. The outer surface of the second portion serves as a travel land for the O-ring and is limited, at the outboard end, by the stress relief groove and, at the inboard end, by the outboard ends of the drive lug slots.

The object of the present invention is to provide, in a seal structure of the type generally set forth above, a new and improved shaft seal which, for the same combination of lug length and travel land is axially shorter than that heretofore known in the art.

According to the invention, a drive sleeve is adapted for rotation with a shaft and a second sleeve telescopically receive thereover, a seal holder, is provided to hold a rotatable seal against an end surface of a seal ring. In a preferred embodiment, the drive sleeve is divided into two portions including a connection portion for connection to the shaft and a second portion for driving the holder, the two portions being separated by a stress relief groove. The holder driving portion includes a plurality of blind bores each of which mounts a drive lug at its inboard-facing end. The holder sleeve is provided with a plurality of spaced blind bores, each of which includes a spring extending therefrom to engage the outboard-facing end of the drive sleeve so as,to urge the two sleeve apart.The holder sleeve also includes a plurality of slots for receiving the drive lugs which are secured in the drive sleeve. By placing the drive lug slots in the holder sleeve between blind bores for the biasing springs, the travel land, heretofore limited by the slots, now extends from the stress relief groove all the way to the inboardfacing end of the drive sleeve. Therefore, to achieve the same travel land as heretofore available, the drive sleeve can be made appreciably shorter. In one embodiment, this reduced the length of the seal from 1.750 inches to 1.5 inches using the same length of drive lug and the same length of spring.

A second advantage arises in that the use of material is reduced and the use of machining time is reduced.

A third and principle advantage arises concerning the location of the rotational drive closer to the face seal. Ideally, the drive should be centered at the seal face; however, this is not possible because of the use of carbon seal face held in a metal holder. Therefore, the drive connection between the drive sleeve and the holder must be at the metal holder. The closer the drive can be placed to the actual end face, the less tendency for inface wobble or orbit to occur with respect to the rotational movement of the sleeve--radial runout. Orbit or radial runout has the disadvantage of allowing a cocking of the two face seals which can open a halfmoon-shaped leakage path. Additionally, orbiting causes a constant back and forth movement of the O-ring as the holder and drive sleeve are no longer concentric throughout the entire rotational cycle.This increases wear on the O-ring providing an early secondary leakage path.

Other objects, features and advantages of the invention, its organization, construction and operation will be best understood from the following detailed description, taken in conjunction with the accompanying drawing, on which: Figure 1 is a perspective view, shown partially in section, of a shaft seal constructed in accordance with the present invention; Figure 2 is a sectional elevational view of a shaft seal constructed in accordance with the present invention and shown mounted on a shaft within, for example, a pump; Figure 3 is a sectional view taken generally along the parting line Ill-Ill of Fig. 2; and Figure 4 is a sectional view taken generally along the part line IV-IV of Fig. 2.Referring to Fig. 1, a shaft seal is generally illustrated at 10 as being mounted on a shaft 1 2 (phan- tom) and comprises a drive sleeve assembly 14 and a ring seal assembly 16.

As illustrated in greater detail in Fig. 2, the drive sleeve assembly comprises a sleeve 1 8 of. for example, stainless steel, which includes a plurality of threaded bores 20 for receiving a corresponding plurality of set screws 22 for securing the sleeve to the shaft 1 2. The sleeve 18 comprises an inside surface 24 which includes an annular groove 26 having the O-ring 28 therein for sealing the sleeve 18 to the shaft 12.

The sleeve 1 8 includes an outboard end having a plurality of blind bores 30 therein, each of which receives a corresponding cylindrical section 34 of a drive lug 32, the extending portion 36 of the drive lug 32 being generally rectangular.

A second sleeve 38, namely a seal holder, is telescopically received over the drive sleeve 1 8 and includes an annular inside surface 40 and a plurality of blind bores 42 each of which as a spring 44 mounted therein to bear against the end surface 46 of the drive sleeve.

As seen in Fig. 2, and as best seen in Fig.

3, the seal holder 38 comprises a plurality of slots 48, here two, for receiving the outwardly extending portions 36 of the drive lugs 32.

As is apparent, the slots are greater in the actual direction than the corresponding dimensions of the drive lugs.

As illustrated in particular in the lower portion of Fig. 2, the drive sleeve 1 8 includes a surface which constitutes a travel land 62.

Telescopically thereover is a portion of the seal holder 38 which includes a surface 40 having an annular groove 50 therein which carries an O-ring 52 which bears against the surface 62. Therefore, as the holder 38 moves axially, the O-ring 52 seals along the full axial extent of the surface 62.

At its outboard end, the holder 38 comprises an annular recess 54 which seats a seal 56 having an end face 64. The seal 56 may be, for example, carbon. The seal face 64 rotates against a surface 58 of a seal ring 60, which as indicated is secured to a gland 66 by way of a clamp ring 68 and a plurality of machine screws 70.

As mentioned above, the drive sleeve 1 8 may be provided with a stress relief in the form of a groove 65 which extends about the periphery of the drive sleeve and which divides the drive sleeve into a shaft connection portion and a seal holder coupling portion.

Advantageously, the shaft seal is hydraulically balanced. for example at 80:20 by the radial position of the outer diameter of the 0ring 52 with respect to the radial extent of the seal area of the seal face 64. This structure aids the springs 44 in applying closing forces between the seal face 64 and the surface 58 of the stationary seal ring 60.

Claims (5)

1. A shaft seal for sealed rotation against an end surface of a sealing ring with a rotatable shaft extending through the ring comprising: a ring-shaped first sleeve for receiving the shaft therethrough including an axially extending first portion, an axially extending second portion, an outer surface and an inner surface; a first groove in said inner surface and a first O-ring in said first groove for fiuid sealing said first sleeve to the shaft; connection means in said first portion for connecting said first sleeve to the shaft for rotation therewith; a plurality of drive lugs fixed to said second portion of said first sleeve and extending parallel to the axis of rotation; a ring-shaped second sleeve for receiving the shaft therethrough including a first portion, a second portion overlapping said second portion of said first sleeve, an inner surface and an outer surface; a second groove in said inner surface of said second portion of said second sleeve and a second O-ring in said second groove fluid sealing said second sleeve and said first sleeve; a plurality of slots in said inner surface of said first portion of said second sleeve extending parallel to the axis of rotation for telescopically receiving said drive lugs therein; a plurality of spaced-apart blind bores in said first portion of said second sleeve extending parallel to the axis of rotation; a plurality of springs in said blind bores bearing thereagainst and against said second portion of said first sleeve to urge said sleeves axially apart; and an annular seal carried by said second sleeve for receiving the shaft therethrough, said annular seal comprising an end face for fluid-sealed rotation against the end surface of the sealing ring.

2. A shaft seal as claimed in claim 1, wherein said ring-shaped first sleeve includes a plurality of spaced-apart blind bores in said second portion; and each of said drive lugs comprises a first portion secured in a respective blind bore of said ring-shaped first sleeve and a second portion received in a respective slot of said first portion of said second sleeve.

3. A shaft seal as claimed in claim 1 or 2, wherein said connection means comprises: a plurality of radially-extending threaded bores through said first portion of said first sleeve; and a plurality of set screws in said threaded bores for securing said first sleeve to the shaft.

4. A shaft seal as claimed in any preceding claim, and further comprising: an annular stress-relief groove about said first sleeve between said first and second portions, said stress-relief groove and the axial end of said second portion of said first sleeve defining the limits of a travel land for said second O-ring on said outer surface of said first sleeve.

5. A shaft seal substantially as hereinbefore described with reference to the accompanying drawings.