US1089248A - Centrifugal pump. - Google Patents

Description

A. G. M. MICHELL.

CENTRIPUGAL PUMP.

APPLIOATION FILED sEPT.18, 1912.

Patented, Mar. 3, 1914.

2 SHEETS-SHEET I.

'Mal/)Legg @ef A. G. M. MICHBLL'.

GENTRIFUGAL PUMP.

APPLIGATION FILED sBPT.1a, 1912.

190899240 Patented Mar. 3, 1914.

2 SHEETS-SHEET 2.

ANTHONY' GEORGE MALDGN MICHLL, OF MELBOURNE, VICTORIA, AUSTRALIA.

CENTRIFUGAL PUMP.

insaeie.

Specification of Letters Patent. i

Application filed September 18, 1912. Serial No. 721,096.

pel an auxiliary pump-wheel, which acts on the fluid in series .with the primary wheel.

The invention consists in a special arrangement and construction of these elements by which they are combined in a single external casing, and thus a simplification of the apparatus is attained, together with certain other advantages which willv be referred to later.

Briefly stated the invention comprises a compound centrifugal pump having contained in a common external casing a primary pump wheel actuated by motive-power from an external source, a turbine-wheel actuated by the water vdischarged from the primary Wheel and an auxiliary pumpwheel actuated by the turbine-wheel by means of connecting bars which couple the turbine-wheel and auxiliary wheel together and which form ports through which the water enters the primary wheel after pass-y ing through the secondary wheel.

One of the features of the improvements y is the arrangement in a compound centrifugal pump of a turbine wheel and an auxiliary pump wheel rigidly coupled together and rotating on a kcommon fixed spindle.

For a better understanding of the invention the following description is given by way of illustgating the method of carrying same into effect, although 1A do not restrict myself to the specific details hereinafter de scribed.

The invention is illustrated vby the accompanying drawings, which comprisey Figure 1 a central vertical section through the pump, Fig. 2 a half transverse section on line Ill-11 Fig. 1, Fig. 3 a half transverse section on line 111-111 Fig. 1, Fig. 4 a half transverse section on line IV Fig. 1. 1

The invention may be appliedlto pumps arranged with eitherl vertical or horizontal shafts. rlhe following description and drawings relate to a pump of the former class.

Fig. shows the vertical primary spindle 1 carrying the primary wheel 2v at its lower end. This primary wheel is furnished with blades 3 and is otherwise substantially similar to the. single Wheel ofordinary centrifugal pumps. Surrounding the primary wheel' is the turbine wheel 4 with blades 5 which receive the Water discharged from thev primary wheel and deliver it into the cham-l. ber 6 and thus to the outlet branch 7 of the pump. Rigidly connected to the turbine wheel 4 by the bars 8 is the auxiliary wheel 9 which like the primary wheel is furnished with blades 10 and is otherwise constructed as a centrifugal pump wheel. The turbine wheel 4` and auxiliary pump wheel .9 may be cast in one piece as shown in Fig. 1 or may be of separate parts rigidly coupled together. In either case these combined wheels are mounted upon a fixed spindle l1 secured in a. vertical position to the lower part of the pump casingas by the collar 12 and nuts 13 as shown in Fig. .1 and the aux- Patented iuai.e,1914-.

iliary wheel 9 is furnished for this purpose thrust bearing 16 may also be fitted upon the upper end of the spindle 11. In order to lubricate these bearings the spindle 11 has a hole 30 drilledthroughout its length adapted to receive oil from a port 17 in the base 18 of the casing to which oil is conveyed by the pipe 19. The oil thus introduced is delivered first to the thrust bearing 16 and is then discharged between the sleeve 15 and the spindle 11 and escapes between the flange 20 'of the'sleeve 15 and collar'12 on the Yspindle 11 into the-chamber 21 of the pump. This chamber being directly in communication with the suction branch 22 the water in it is usually at lowery than atmospheric pressure so that oil will be drawn in through the pipe 19 from a suitable reservoir placed at a convenient level.

1n the operation of the pump, as in previous pumps of this type, the primary spindle 1 is driven by external motive power while the turbine wheel 4 and auxiliary wheel 9, are rotated in the same direction as the primary wheel but at lower velocity by the water passing through the pump. The water passes throughj the two pump ber 2l in a purelyradial inward direction.l

This chamber is likewise furnished with blades 28, attached to an. upper wall 29 and a lower wall 3l. The water then passes between the bars 8, connecting the auxiliary pump wheel with theturbine wheel, into the inlet of the primary pump wheel 3, whence it is delivered outwardly through the pri- 'mary pump wheel 2 and the turbine wheel et tothe outlet branch 7 of the pump asv already described.

One of the advantages ofthe present invention over previous pumps of this `type arises from the fact that the water may be allowed to retain the velocity with which it is discharged from the auxiliary wheel practically unchanged in amo/unt though altered in direction until its entry into the primary wheel. The loss of energy due to a reduction of velocity' which takes place in the -outer'chamber of the auxiliary pump of the known type of pump referred to, as in ordinary centrifugal pumps, is thus avoided. The introduction of the water first into the comparatively large and slowly revolving auxiliary pump inmany Acases enables a centrifugal pump of this type t0 be used where a pump having a single wheel or several wheels revolving at a common high velocity would not operate satisfactorily on account of the liability ofv cavitation occurring in the inlets of such high speed wheels, particularly with considerable suction lifts.

l Under such conditions also the arrangement herein described possesses the advantage that no stuffing box involving risk of admitting air is required on the suction chamber of the pump. In cases how'ever in which for any reason, such as the existence of a pressure in the water entering the pump, the lubrication of the internal xed spindle shown may'present difficulties the boss of the auxiliary pump may be further extended and brought out through a stuiiingbox in the case of the pump, the Aspindle being supported at its outer end beyond the stufling-box as by a rigid bracket. Or alternatively if desired the combined auxiliary wheel and turbine wheel herein described may be rigidly mounted on a rotating shaft brought out through a stuffingbox and carried in external bearings in the usual way.

The thrust of the primary wheel, which in the case of the construction shown is downward, may be provided for by means of a combined thrust bearing and gland consisting of a collar 25 fixed on the spindle l and bearing steps 26 carried by the casing, the area of the collar 25 being such that the fluid pressure of the water in the pressure chamber is suici'ent to counteract the thrust of the pump according to a well known mode of construction.

The steps 26 may consist of an annular series of ilat segments each secured to the casing of the pump or may form a continuous ring similarly secured and in' either case will have aipracticably vwater-tight connection with the surface on which they rest for which purpose a packing ring 26a may be employed. A slight clearance isallowed between the casing of the pump and the neck 25a of the collar 25. The water under pressure in the chamber 6 has thus access to the bearing surface between the collar 25 and the steps 26 and, as already mentioned, the area of this surface is such that the-collar and'pump spindle will rise under this pressure against the thrust of the pump. As soon, however, as the collar 25 has risen lslightly the water being throttled between the Iteck 25EL and casing will escape at reduced pressure between the Acollar 25 and the steps 26 and thus the pump spindle will cease to rise. In such an equilibrium position the collar will rotate freely on the film of water escaping below it, and thus serves as a thrust collar, while at the same time the flow of water is limited and no separate 'gland is required. Alternatively an ordinary stufling box may be employed for the primary shaft, with an independent thrust bearing of any usual form. The journal bearing for the. primary shaft may be mounted on the cover of the stuffing box, or combined stuiiing box and thrust bearing, as shown in Fig. l. Lugs 27 may be provided on the upper part of the pump casing.

to serve for the 'support of an electric or other motor for driving the primary pump shaft, the spindle of such motor being cou-- pled to the primary spindle l.

With suitable modifications of detail the same as described above.

' In the application of the invention to pumps with horizontal shafts, the mode of operation and arrangement of parts is precisely as above described, such differences Aof constructive'detail being arranged as the horizontal position requires.

I claim 1. In a centrifugal pump and in combination with a primary pump-wheel, a rotating member comprising a turbine element receivingthe fluid discharged by said' primary wheel, an auxiliary pump element acting on the fluid in series with said primary pumpwheel, and a coupling element consisting of bars through which the fluid passes, coupiing said auxiliary pump element to said to said primary pump, and a common casing turbine element. wherein said parts are arranged.

2. In a centrifugal pump and in combina- In testimony whereof I have hereunto set tion with a primary pump-Wheel, a turbine my hand in presence of two subscribing wit- 5 element receiving the fluid from said prinesses.

mary pump Wheel an auxiliar centrifugal pump element'f colipledto sai turbine ele- ANTHONY GEORGE MALDON MICHELL' ment and dellvering `the Huid to said pri- Witnesses:

mary pump Wheel, fixed guide-venes con- WALTER C. HART,

10 Veying the Huid from said auxiliary pump WILLIAM G. HOLDEN.

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