Fluid pump with rotary seal assembly

Abstract

A fluid pump having a rotary seal assembly adapted to reduce wear between the pump impeller and the assembly while maintaining a seal between the pump housing and drive connecting means to the impeller, is disclosed. The rotary seal assembly includes means for anchoring the assembly, preferably resiliently, to a rotating component to positively preclude rotation of the impeller with respect to the assembly upon acceleration of the impeller. The rotary seal assembly may include a coil spring to bias the assembly into sealed relation, and resilient anchoring of the assembly for absorption of shock is preferably accomplished by means of a recess or opening formed in the impeller or drive connecting means and an end or extension of the coil spring which is seated in the recess.

Description

Most fluid pumps, particularly liquid pumps which employ a rotating impeller, have had to provide a seal between the housing and the drive connecting means which connects the impeller to the pump motor. In fluid pumps having a rotating impeller, this has often been accomplished by employing a rotary seal assembly mounted to extend around the drive connecting means and coaxially therewith. Such rotary seal assemblies are usually constructed to rotate with the impeller while bearing against a stationary seat portion mounted to the housing and simultaneously bearing against the drive connecting means.

Acceleration of the impeller by the pump motor during starting, and to some degree during deceleration during stopping of the pump, has been found, however, in such prior rotary seal assemblies to cause substantial wear between the rotary seal assembly and the impeller. The mass of the rotary seal assembly tends to keep the assembly at rest when the impeller rapidly accelerates until friction between the assembly and impeller causes the assembly to rotate at the same velocity as the impeller.

In a similar manner the drive connecting means rotates within the rotary seal assembly on rapid acceleration of the impeller causing slippage and friction between the assembly seal and the drive connecting means until the assembly reaches the same angular velocity as the impeller and drive connecting means. These two sources of friction result in substantial wear over a period of time which in turn necessitates replacement of the rotary seal assembly or impeller.

Accordingly, among the objects of my invention are:

1. To provide a novel and improved fluid pump;

2. To provide a novel and improved rotary seal assembly for a fluid pump in which the wear in the assembly and the pump parts contacted thereby is reduced; and

3. To provide a novel and improved rotary seal assembly for a fluid pump which is durable, easy to manufacture, and easy to install.

Additional objects of my invention will be brought out in the following description of a preferred embodiment of the same taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view, partially broken away and in cross-section of a fluid pump embodying the present invention;

FIG. 2 is an enlarged, fragmentary, side elevational view in cross-section of the rotary seal of FIG. 1; and

FIG. 3 is a fragmentary end view in cross-section taken substantially along the plane of line 3--3 in FIG. 2.

Referring to the drawing for details of my invention in its preferred form, the same is shown incorporated into a fluid pump, generally designated 21, of the type particularly well suited for pumping liquids. The pump 21 includes a housing 23 with an impeller 25 mounted rotatably in the housing. Mounted to connect the impeller 25 to a motor 27 is drive connecting means 29, which in this case is a shaft integrally formed with the impeller 25 that extends outwardly from the housing 23. The drive connecting means is formed with a cylindrical bore 31 dimensioned for receipt of a shaft 33 extending from the pump motor. Mounted proximate and preferably about or surrounding and coaxially aligned with the drive connecting means 29 is a rotary seal assembly 35, best seen in FIG. 2. This rotary seal assembly includes flexible spring biasing means, preferably in the form of a coil spring 41, and an annular spring seat 43 in pressure contact with the impeller 29. At the opposite end of and mounted inside the coil spring is an annular ferrule 45 adapted for receipt of sealing means therein.

It is preferred that the sealing means take the form of two sealing elements, an O-ring seal 47 in sealed relation with the drive connecting means and an annular seal element 49 having a nose portion 51. Mounted to the pump housing is a grommet 53 which carries an annular seal seat 55. Both the seal seat and grommet are stationary. The nose portion 51 of the seal element 49 rotates with the drive connecting means and impeller.

The passage of liquids from the housing, proximate the drive connecting means, is prevented by the rotary seal assembly by reason of engagement of the nose portion 51 with the seal 55 and the engagement of the O-ring 47 with the drive connecting means 29. It is preferable that the seal seat 55 be formed of a ceramic material having a low coefficient of friction and high abrasion resistance and that the nose portion 51 be formed of carbon or similar material.

In operation, water is drawn in through the inlet opening 61 in the housing and in through the eye 63 of the impeller means. Curved radially extending impeller blades 65 then accelerate the water rapidly out to the peripheral volute channel 67 of the housing from which the liquid tangentially discharges through opening 69.

While the vast majority of the water is urged to the peripheral channel 67 and out the discharge opening 69, invariably some water will pass along the space 71 between the impeller and the housing, best seen in FIG. 1, to the area 73 of the rotary seal assembly. The assembly, therefore, prevents the further passage of the water along the drive connecting means out the opening 75 between the drive connecting means and the housing.

It might be noted further that the spring biasing provided by the coil spring 41 maintains the impeller means seated for rotation in the seat 77 provided in the opposite side of the pump housing. Thus, while effecting sealing on one side of the impeller, the coil spring also urges the impeller into the impeller seat 77 for proper rotation in the pump housing.

Rotary fluid pumps of the type thus far described are old in the art and normally employ a motor which can drive the impeller at a relatively high angular velocity, and accordingly the pump motor is capable of and does accelerate the impeller rapidly to full pumping speed.

In prior fluid pumps, the rapid impeller acceleration will cause the rotary seal assembly 35 to slip or the impeller 25 to rotate with respect to the assembly for a period of time until friction between the annular spring seat 43 and the impeller 25, and the friction between the O-ring 47 and the drive connecting means 29, cause the mass of rotary seal assembly to have the same angular velocity as the impeller and drive connecting means. Such slippage occurs notwithstanding the fact that the coil spring tends to urge the spring seat against the impeller and increase the frictional forces by increasing the normal force between the spring seat and the impeller.

During repeated usage, the spring seat, preferably being formed of metallic material, causes substantial wear on the end wall 83 of the impeller adjacent the drive connecting means, the impeller preferably being formed of a glass impregnated high strength plastic. Similarly, the drive connecting means 29 would begin to cause wear on the O-ring 47. The result was that either the rotary seal assembly had to be replaced because the O-ring was worn, or the impeller had to be replaced because the end wall of the impeller was abraded and grooved, or both.

In order to prevent excessive wear and the need for periodic replacement of parts, the fluid pump of the present invention and the rotary seal assembly are provided with means for anchoring the assembly to a rotatable component proximate the assembly to positively preclude rotation of the impeller means with respect to the seal assembly upon acceleration of the impeller. The rotatable component can be the impeller, the drive connecting means or impeller shaft, or even the motor shaft, if it protrudes into the pump proximate the rotary seal assembly.

While in general the problem of slippage can be solved by positively locking the rotary seal assembly to the impeller, it is preferred to anchor one end 85 of the spring 41 to the impeller means to obtain the added advantage of a shock absorbing function.

In terms of specific structure the proximate end 85 of the spring may be passed through an opening 89 in the spring seat 43 and anchored in a recess or opening 87 in the impeller. Such a positive or interlocked mounting of the rotary seal to the impeller prevents relative slippage or rotation between the coil spring, and particularly the spring seat 43, and the impeller and also between the O-ring 47 and the drive connecting means 29, as will be more fully set forth hereinafter.

Once relative slippage or rotation between the impeller and the rotary seal are eliminated by positive interlocking engagement between the same, it would be possible to eliminate the spring seat 43, at least as to its function in reducing wear between the seal and the end wall of the impeller. The spring seat, however, also acts to contain and locate the spring coaxially with the drive connecting means. Additionally, the spring seat prevents localized abrasion when acceleration causes the spring to wind or unwind to a small degree during its shock absorbing function. Accordingly, it is preferable to retain the spring seat and merely form the opening 89 therein which is aligned with the opening 87 in the end wall 83 of the impeller.

Positive interlocking of the rotary seal could also be accomplished by forming a recess or opening in the drive connecting means or impeller shaft 29 generally perpendicular to the longitudinal axis of the impeller shaft means and impeller. The end 85 of the coil spring could then be formed for insertion into the impeller shaft. Since the impeller shaft is preferably integrally formed with the impeller or at least is rigidly secured for rotation therewith, positively connecting the rotary seal assembly 35 to the impeller shaft will similarly prevent slippage and frictional abrasion or wear.

It should be noted, however, that an additional advantage accrues from securing the rotary seal assembly to the impeller by a recess 87 parallel to the axis of rotation of the impeller. This orientation of the end 85 of the coil spring and the opening 87 in the impeller end wall 83 enables rapid assembly of the rotary seal assembly onto the drive connecting means and into positive interlocked relation to the impeller without the use of special tools or difficult manipulation of parts.

In order to minimize wear of the O-ring seal 47, the end of the coil spring 41 opposite the means 85 for positively interlocking the rotary seal to the impeller is formed to have an interference fit with the annular ferrule 45. In addition, the sealing element 49 is positively locked for rotation with the ferrule 45 by having a protrusion 91 which extends to an opening 93 in the ferrule, causing the assembly to rotate as a unit.

As will be noted in FIG. 2, the opening 93 in the annular ferrule 45 extends axially to a length greater than the protruding portion 91 of the annular sealing element 49. This allows the annular sealing element to be pushed backwardly against the O-ring 47, which in turn compresses the O-ring against the bevelled portion of the ferrule and simultaneously compresses the O-ring inwardly to effect a seal with the impeller shaft 29.

It would be possible, although it has not been found necessary, to provide an additional opening in the annular ferrule 45 into which the second end 95 of the coil spring could be inserted. Moreover, it would also be possible to positively secure the O-ring 47 to the annular ferrule 45, but again it has been found that the slippage is virtually eliminated by positive securement of the other end of the coil spring to the impeller.

As will be understood from the foregoing, the exact form of the drive connecting means is not critical to the present invention. As shown in the drawing and particularly FIG. 1, the pump motor is formed with a stepped shaft 33 having a threaded end which mates with the step cylindrical bore 31 having a threaded end 97 in the drive connection means. The pump housing is bolted to a face plate 99, which in turn is secured to the pump motor by fasteners 101 or the like.

This construction allows the drive connecting means 29 to be assembled over the stepped shaft 33 for driving by the same. The pump housing is preferably formed in two halves which may be bolted together by fasteners 103 with a gasket 105 being in position between the halves of the housing to effect sealing of the pumping channel 67.

Claims

We claim:

1. A fluid pump comprising: a housing, impeller means rotatably mounted in said housing and including drive connecting means adapted to connect said impeller means to an external source of power, and a rotary seal assembly mounted about said drive connecting means between said impeller means and said housing and adapted to effect sealing against the passage of fluid from said housing proximate said drive connecting means, said rotary seal assembly further including means for anchoring said rotary seal assembly to positively preclude rotation of said impeller means with respect to said rotary seal assembly upon acceleration of said impeller means whereby wear between said rotary seal assembly and said impeller means as a result of relative slippage or rotation is essentially eliminated.

2. A fluid pump in accordance with claim 1, characterized by said rotary seal assembly being resiliently anchored against torsional forces to a rotatable component in proximity to said rotary seal assembly to enable absorption of shock during acceleration of said impeller means.

3. A fluid pump in accordance with claim 2, characterized by said rotary seal assembly being formed with a coil spring mounted in axially aligned relation to said drive connecting means, said means for anchoring being formed by an end of said coil spring and a recess in one of said impeller means and said drive connecting means adapted for receipt of said end therein to effect resilient anchoring of said rotary seal assembly.

4. A fluid pump in accordance with claim 3, characterized by said coil spring having an annular sealing element mounted thereto and encircling and in sealed relation with said drive connecting means whereby rotation of said annular sealing element relative to said drive connecting means is minimized.

5. A fluid pump in accordance with claim 3, characterized by said rotary seal assembly further including an annular spring seat having an opening therein, and said end of said coil spring being mounted through said opening in said spring seat and extending therebeyond into said recess.

6. A rotary seal assembly for use in a fluid pump having a housing, impeller means rotatably mounted in such housing, and drive connecting means adapted to connect such impeller to an external source of power, said rotary seal assembly being adapted for installation proximate such drive connecting means between such impeller means and such housing to effect sealing against the passage of fluid from such housing proximate such drive connecting means, the improvement in said rotary seal assembly comprising:

means for anchoring said rotary seal assembly to a rotatable component in proximity to said rotary seal assembly when said rotary seal assembly is mounted in such pump to positively preclude rotation of such impeller means with respect to said rotary seal assembly upon acceleration of such impeller whereby wear between said rotary seal assembly and impeller means as a result of relative rotation is essentially eliminated.