US2108771A - Fluid pump - Google Patents

Description

Feb. 15,1938. Y J. P. LAIRD 2,108,771

FLUID PUMP l Filed Jan. 30, 1935 2` Sheets-Shoe?I 2 Patented Feb. 15, 1938 UNITED STATES PATENT OFFICE FLUID PUMP Application January 30,l 1935, Serial No. 4,003

'7 claims.

My invention relates to the art of .pumping heavy 4oils and other relatively thick and viscous iiuids.

In a gear pump having adjustment of the 5 rate of pumping by axial movement of' one of the gears to match Ia variable part of its face against a corresponding part of the face of the mating gear,`one purpose is to provide an equalizing connection between the spaces at opposite ends of the adjustment movement so as to facilitate flow of leakage liquid between the two spaces while the axial adjustment is being made.

In the handling of heavy oils and like uids which are pumped with difficulty, a further purpose is to increase the fluidity of the oil by the use of a primary pump in so close relation to a secondary pump by which itis to be delivered as to give little opportunity between for the oil to increase in viscosity. A

A further purposeis to break up and diffuse and preferably at the same time raise the temperature of heavy oils and other olly viscous materials pumped by a primary pump so as to lower their viscosity and render them of substantially uniform viscosity when delivered to a secondary pump whose pumping action is thus made more nearly uniform.

A further purpose is to break up and diffuse a heavy substance or an accumulation in an oil or other fluid pumped by a primary pump, thereby breaking up the "set of the material pumped, and to deliver it to a secondary pump before the material has had opportunity to again become set.

A further purpose is to provide primary and secondary gear pumps in series in a single unit having the capacity of the first of the series pumps inexcess of the normal capacity of the second and having the capacity of the second pump adjustable by axial movement of one of the gears.

A further purpose is to interconnect primary and secondary pumps within the same pumping unit, of which the primary pump is designed to have the larger pumping capacity and the secondary pump is adjustable for quantity pumped, so as to secure any desired pressure of delivery from the primary pump and varlable'rate of delivery from the second pump.

A further purpose is to provide a primary gear pump having capacity in excess of its .pumping needs and having a short circuit connection about the pump providing leakage against a predeterminable preferably adjustable resistance, to pump from it to a secondary gear pump,

(o1. ros-126) of smaller capacity and having adjustment of the capacity of the secondary pump by axial movement of one of the gears and to facilitate 4leakage between opposite ends of the movable gear of the secondary pump so as to permit easy shifting of the movable gear.

A further purpose is to provide primary and secondary gear pumps, one of them adjustable, within the same pumping unit, whereby conveniently and with a high degree of space econom'y pressure may be maintained between the two pumps, not only to supply the second pump with fluid from the first but to add the pressure fromthe primary to the pressure of the secondary, pump, making 'it possible to secure the desired pressure from the secondary pump at a low energy expenditure in the secondary pump.

A further purpose is to operate a two-stage gear pump with higher volumes pumped by the primary stage, and to continuously by-pass at a selected pressure any excess of liquid pumped by the primary pump back to the inlet side of the primary pump.

In a two-stage gear pump, a further purpose is to by-pass continuously at a predetermined pressure excess liquid pumped by the secondary stage back to the conduit connecting the stages, and, if necessary, from the conduit connecting the stages to the inlet of the primary stage.

The construction shown is a preferred construction only, selected because of its practicability and its excellence in illustration of the invention.

Figure 1 is a section through the axes of the pumps taken upon line I-l of Figure 2.

Figure 2 is a section upon line 2-2 of Figure 1.

Figure 3 is a fragmentary section corresponding generally to Figure 1 but upon a smaller scale than that of Figure 1 and showing a second form of the invention. l

Figure 4 is 'a fragmentary section corresponding generally to Figure 2 but upon a smaller scale than that yof Figure 2 and showing another form of the invention.

Where gear pumps are operated at a relatively high rate of`speed, such, for example, as 1750 -R. P. M., the tolerances or clearances between the gears and their surrounding casings may be relatively large, because the speed of operation is suiiicient to make the leakage through these relatively large tolerances small enough to be considered negligible in ordinary operation. On the other hand, when pumps of this character are greatly reduced in speed, (as for example down to 200 R'. P, M.) it is necessary to operatev the pumps at very much closer tolerances or clearances.

With the axially adjustable gear type of pump, where the adjustable gear unit is moved axially to engage a larger or smaller proportion of the gear faces of its mating gear for larger or smaller pumping capacities, the spaces which must be allowed at the ends of the gear unit to permit movement of the unit axially become much more tightly sealed than where larger clearances have been provided. These spaces soon ll up with leakage from the material pumped.

Whereas clearances suitable for high speed gear operation nave permitted leakage oil from the end of the gear toward which adjustment is being made to ow out past the movable unit-and into thespace at the end of the gear unit from which movement is being made, allowing easy adjustment, this pressure flow from the space at one end ofthe movable gear unit to the space at the other end of the unit requires more and more pressure with the smaller tolerances necessary for lower speeds until with the tolerances which are desirable from other standpoints it becomes i almost impossible to shift the gear without breakage. 'I'his difficulty is, ofcourse, very much increased with increase in viscosity of the fluid pumped. i

- One feature of the invention is intended to relieve this diicultyin adjustment of the gear unit and others provide for primary pump supply under pressure for a gear pump secondary and for the breaking'up and smoothing of the liquid to be pumped, where its character or its initial temperature have given it a set making it difcult to pump smoothly and evenly until this set has been broken up. v'

The casing I0 is preferably made up as shown of two generally at front and back plates or faces II, I2, secured by bolts I3 to an intervening gear I9 keyed to shaft 20. The secondary adjustable gear pump is made up of drive gear 2l and driven (adjustable) gear 22.

For convenience of reference. the material Dumped will hereafter be referred to as oil.

The primary gear pump draws its oil through any suitable pipe 23 leading from a .sump to the suction side of the primary pump at 24 and transmits the oil through passages 25, 26and 21 to the secondary gear pump, by which it is pumped through passages 28 and 29 to'any suitable point of discharge for use. s The shaft'l8 is suitably driven as from a pulley Thev shaftA 20 is keyed to a driving gear 3l, one

of a transmission train which connects and synchronizes the two pumps. Gear 3| meshes with an idler 32 mounted upon a pin-33 and the idler` in turn drives a gear 34 which is keyed to a shaft 35. 'I 'he shaft 35 is 'keyed to the driving gear 2| of the second (secondary) gear pump. The gear 2l meshes to different extents according to the adjustment with the axially .adjustable driven gear 22 mounted upon or about rod 36 and may turn directly upon the rod or upon a bearing sleeve 31 carried by the rod, as preferred.

'I'he gear 22 and its bearing (if it bear upona sleeve rather than upon the rod) is shifted longitudinally as part of a unit comprising pistons 38 and 39, both pinned to the rod 36 and shiftable with it.I The piston 39 yis arcuately recessed to correspond with and form a close fit with the outer surfaces of the teeth of gear 2| and corre-- spondingly to Afit the-cylindrical surface 40 of a cylindrical collar 4I which fills in the block or body at this point. 'Ihe collar isvof the samediameter as the outside of the teeth of gear 2i.

The two pistons and the pump gear 22 between them slide as a unit within a cylinder of uniform diameter, into which project at one end and from the side the surface of the collar 4I and the gear 2|. The teeth of the gear 2i mesh to varying axial extents with the teeth of gear 22, as the adjustable unit is moved to the right (Figure 1) to cause deeper axial extent of meshing, and hence higher pumping capacity, or to theleft (Figure 1) to reduce theextent of meshing and a lower pumping capacity.

The two pistons 38 and 39 are alike except for the cylindrical recess of the piston 39 to correspond with and pass over the teeth of gear 22. It will be noted that a portion of the cylindrical surface of collar 39 projects into the cylinder Within which the pistons slide.

In any position of the two pistons between the ends of their stroke there will be cylinder end spaces 42 and 43 between the respective pistons and the ends 44 and 45 of the cylinder. `Inevitably the oil which is being pumped will leak past the pistons 38 and 39'intopthe spaces 42 and 43 so that at any'time during the. operation of the pumps the spaces 42 and 43 can be assumed to be full of oil with corresponding interference with movement of the adjustable pump unit.

Movement of the unit in either direction must force theoil out of the space toward which the pistons are moving in order'to make it possible to move the pistons, at the same time tending to cause a vacuum in the space at the opposite end of the movable unit. With relatively large tolerances the diiilculty inmoving the pistons has not been a serious one, as the tolerances permit the oil. to be forced back through the same channels by which it reaches these spaces, but. with reduced speed of pump rotation and the consequent necessity for reduced tolerances, this dii'- flculty of moving the pistons becomes so great as to be serious, threatening breakage of the parts.

In order to relieve from trapping of oil in spaces 42 or 43 to the other. On the other hand, since leakage through this passage 46 can do no harm at an time there is no objection to having the resistance to flow through the passage 46 low.

In order that the leakage throughpassage 46' may provide the entire'oil transfer adjustment needed with longitudinal movement of the gear unit, the cross-sections perpendicular to the rod 36 must be equal in the spaces 42 and 43. This can be accomplished readily by making the rod 36 of such lsize that its crosssection equals the cross-section by which the cylindricalI portion 40 of the collar 4I projects into' the cylinder. Approximately equal cross sections are quite desirable and are contemplated..

The rod 35 is made axially adjustable by threading it at 48 into an adjustment wheel 49 rotatably supported at 50 in a bracket 5I secured to the rear plate of the pump at 52. The adjustment wheel 49 is threaded at 53 to receive a nut 54 which holds the wheel 49 in position on the bracket. 'I'he adjustment. wheel 49 is toothed at 55 to engage a spring detentr56 secured at 51 to lthe bracket 5I. The adjustment wheel 49 may be power driven if desired through engagement of a rack with the teeth of the adjustment wheel.

Instead of the passage 46 through' the pump body, a passage may be provided through the interior parts between the spaces 42 and 43. In Figure 3 I show a passage 46' through the rod 36, and equalizing Vpressure between the spaces 42 and 43.

The rod 35 is protected and may be in part supported by a gland 58 compressing packing 59 where the rod passes through the casing face I2. The driving shaft I8 is also protected by a gland shown at 6U, compressing packing -6I. It vhas outboard bearing at 62 and 63 in the face Il of the casing and in the body I4. Pin 20 has bearing at 54 in thefront face, at 65 in the body and at 65 in the rear face.

The bearing of the pin 35 is at B9 in the body and at 10 in the rear face; also at 1I in the collar 4I which in turn is supported at 12 within the body and withinl the4 face plate I I. The bear- f ingsl 62, 53, 64, v66,. 61, 68, 10 and 1Iare all outboard bearings, an'important feature in the construction of the device, so that the driving shaft and all of the pins `are provided with outboard support.

The primary pump is shown as of greater capacity than the secondary pump in order that there may be a full supply of uid for the secondary pump and preferably also inl order that the secondary pump supply may be under pressure so as to increase the pressure of the discharge from the secondary pump.

In order that the primary pump may operate continuously, an overflow is provided between the primary and secondary pumps which overflow is preferably against an adjustable resistance. Two types of overow are shown, the one through passages 13, 14 and 15 about the pump (Figure 2), protected by anadjustable ball check valve 16 whose pressure is applied by a spring 11 bearing against a seat 18 and adjustable by use of different springs and different positions of the plug 19;-and the other through a pipe 80 (Figure 4) to a pressure tank, not shown. The pipe may lead through a check yvalve to the sump side of the pump, as in the other case, \or to a pressure tank in which the mounting pressures check the pumping effect of the primary pump.

The various passages about the pump are closed, by plugs 8l.

' The secondary pump has a by-pass relief similar to that of the primary pump and comprising passages 13', 14 and 15', a ball check'valve 16', spring 11 (which is desirably heavier than spring 11), valve seat 18 and plug 19. Relief is thus provided against excessive pressure von the delivery-side ofthe secondary pump.

In operation the pumping effect of the secondary pump isl adjusted by longitudinal movement of the movable gear to mesh variantly according to the position of the unit with the driving gear of the secondary pumping pair. This alone is broadly old. When the secondary gear adjustment is to be eiected the4 fluid pumped is driven from one space 42 to the opposite 43 or vice versa, allowing free and easy movement of the secondary unit parts. i

The operation of over-pumping by the primary as compared with the secondary will be determined in large measure by the extent of interiitting of the gears of the secondary pair. With adjustment of this secondary pair position fluid in one or other of the spaces 42 and 43 is driven to the other space, allowing free and easy adjustment of the position of the movable gear unit by operation of the adjusting wheel 49.

My novel pump finds wide application in the handling of various liquids, particularly liquids of high viscosity such as oils and chemicals, for example, viscose liquors. -Particularly in handling liquids of this type the feature of equalizing pressure between two ends of the cylinder containing the movable gear is of considerable importance as is also the provision of pressure relief for the primary and secondary pumping stages. It is likewise desirable in this eld to pump a relatively larger volume by the primary stage than that pumped by the secondary stage.

In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, toobtain all or part of the benefits of my invention-without copying thestructure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention'.

Having thus described my invention, rwhat I claim as new and desire to secure by Letters' Patent is:- 1. A gear pump comprising front and back pump plates, a body between the plates, means for connecting the plates againstv the body protecting -driving secondary pump gear, walls forming a cylinder fitting the driven'secondary pump gear, pistons at opposite ends of the driven secondary pump gear, movable inthe cylinder, one of them having an arcuate opening to accommodate the driving secondary pump gear, a filler for the arcuate opening, means for shifting the pistons and drivenusecondary pump gear longitudinally, Walls forming an inlet to the primary pump, an outlet .from the secondary pump and a series connection between the pumps, and the transmission gearing betweenthe pumps being proportioned to operate the secondary pump at a higher speed than the primary pump.

2. A gear pump comprising front and back puxp plates, a body between the p1ates,rneans for connecting the plates, against the body protecting against leakage, a drivingl shaft, bearings therefor, a drivingprimary pumpgear on the driving shaft, a. primary pump driven shaft,

bearings therefor, a driven pump vgear'upon said driven shaft and meshing Awith the driving pump gear, a driving transmission gear driven from said driven shaft, a driven transmission gear driven from the driving transmission gear,- a

shaft and bearings therefor, a driving secondary pump gear mounted upon the driven transmission shaft, a driven secondary pump gear adapted to mesh with and be adjusted axially with respect to the driving secondary pump gear, walls forming a cylinder fitting the driven secondary pump gear, pistons at opposite ends of the driven secondary pump gear, movable in the cylinder, one of them having an arcuate recess to accommodate the driving secondary pump gear, a ller for the recess, a rod for shift-ing the pistons and driven secondary pump gear axially, the section of the rod and filler being approximately equal at the two ends of the cylinder, walls forming a passage equalizing fluid pressures at the two ends of the cylinder, and walls forming an inlet and an outlet for fiuidvpumped and a fluid connection between the pumps, a

v3. A gear pump comprising front and back pump plates, a body between the plates, means for connecting `.the plates against the body protecting against leakage, a driving shaft havingl bearing in the front plate and body, a driving primary gear on the driving shaft, a primary pump driven shaft having bearings in the front plate and body, a driven pump gear upon thedriven primary shaft and meshing with the driving primary gear, a driving transmission gear also upon the driven primary pump shaft, an idler shaft having bearings in the rear plate and body, an idler thereon meshing with the driving transmission gear, a driven transmission gear shaft, a driven transmission gear thereon driven by the idler, the driven transmission gear shaft having bearings in the rear plate and the body at opp'osite ends of the driven transmission "gear, a driving secondary pump gear mounted upon the driven transmission shaft, a bearing for the driven transmission shaft between the secondary pump gear and the front plate, a secondary drivenv pump gear adapted to be adjusted axially of the driving secondary pump gear, walls forming av cylinder within which `the driven secondary pump gear moves, pistons at opposite ends ofthe secondary driven gear movable in'the cylinder, one of them having an arcuaterecess to accommodate the driving secondary* pump gear and sealed by the bearing member for the driven transmission gear shaft, means for shifting the pistons and driven secondary pump gear longitudinally, walls forming a passage for qualizing fluid pressures at the two ends of the cylinder, walls forming an inlet to the primary pump and an outlet from the secondary pump and 'a series yconnection between the pumps, the transmission within the front plate, a driving primary gear on the driving shaft, a primary pump driven shaft having bearings in the front and rear plates, a driven pump gear upon the driven primary shaft and meshing with the driving primary gear,v a driving transmission 'gear alsouponthe Adriven primary pump shaft, an idler shaft hav.

ing bearings -in the rear plate and body, an idler thereon meshing with the driving transmission gear, a' driven transmission gear shaft, a driven .transmission gear thereon drivenby the idler,

the' driven transmission gear shaft having bear- -able gar.

' commodate the driving secondary pump gear and sealed longitudinally of the recess by the bear- .ing member for the driven transmission gear shaft, means for shifting the pistons and driven secondary pump gear longitudinally, walls form- 'ing a by-pass from one end of the cylinder to the' other, walls forming an inlet to the primary pump, an outlet from the secondary pump, fluid series connection between the pumps, and transmission gearing between the pumps operating the secondary pump at high speed with respect to the primary pump.

5. A casing, a. primary pressure pump, a secondary gear pump having series fluid connections with the primary pump, one gear of which secondary pump is shiftable within a cylindrical space in the casing, and of smaller secondary pumping capacity than the capacity ofthe primary pressure pump, whereby a portion only of the fluid discharging from the primary pump is pumped by the secondary gear pump and the secondary gear pump is constantly supplied under pressure from the primary pump, means providing for the discharge of the over-supply of uid, the structure being characterized by a shaft for longitudinally moving the shiftable gear within the cylindrical space, a shield adjacent the second secondary gear, pistons at opposite faces of the shiftable gear fitting the walls of the cylindrical space, one of said pistons surrounding the shaft and the other of which pistons is cut away to pass over the secondary pump gear which is the ends of ,said space and walls forming a bypass within the body of the casing of the pump between opposite ends of the cylindrical space whereby pressure ofv trapped fluid in the cylindrical space interfering with shifting of the gear of the pump is relieved andv shifting is facilitated, the effective cross sectional areas of the shaft surrounded by the one piston and the cut-away part of the other piston being approximately equal, whereby the total volume of the by-pass plus the portions of the said cylindrical space longitudinally beyond the'pistons remains substantially the same at all positions of the shift- 6. vA casing, a primary pressure gear pump, a secondaryv gear pump fed therefrom through series fluid connections between said pumps and of smaller pumping capacity than the capacity of the primary pressure pump whereby a portion only of the fluid discharging from the primary pump is pumped by the secondary gear pump and the secondary gear pump is constantly supplied under pressure from the primary pump, one of the gears of the secondary pump being axially adjustable ing a cylinder in the casing co-axial with and containing the adjustable gear of the secondary pump, a shaft for axially shifting the adjustable gear within said cylinder with respect to the xed gear, a shield in line with the fixed gear and extending into the cylinder from the side, pistons at opposite faces of the adjustable gear sealing against the walls of the cylinder, one piston surrounding the shaft and the other of which pistons is cut away to pass over the fixed gear and seal against it and against the shield to protect against excessive leakage of the liquid pumped into the ends of the cylinder, and walls forming a by-pass between opposite ends of the cylinder whereby pressure ofthe trapped duid v in the cylinder interfering with shifting of the gear of the pump is relieved and shifting is facilitated, the ei'ective cross-sectional areas' of the shaft surrounded by the one piston and the cutt away part of the second piston to seal with the" shield being approximately equal whereby the total volume of the by-pass and of theportions of the said cylinder space longitudinally beyond the pistons remains substantially the same in all positions of the adjustable gear.

1. In a gear pumping device, a casing, walls forming a cylinder therein, interconnecting gears Whichtogether form a secondary pumping element, one of which gears is fixed against axial movement and the other of which is axially movable in the cylinder, means for axially moving said movable gear comprising a shield having a portion extending into the cylinder from its side at one end of the axiallyxed gear, a piston connected with the axially movable gear and adapted to seal with the cylinder and having one side recessed and sealing against the shield, a second piston fitting the cylinder and a shaft upon which the pistons are mounted, passing through the casing and of cross-section approximately that of the recess in the first piston whereby the` total volume of the portions of the cylinder space axially beyond the two pistonsris approximately the same irrespective of the adjusted position of the two pistons, the construction being provided with a by-pass from one end of the cylinder to the other through a part xed during normal operation whereby fluid is free to pass between the two ends of the cylinder and means for shifting said shaft. ,i JOSEPH PAUL LAIRD.

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