Gear pump or hydraulic gear motor with helical toothing provided with hydraulic system for axial thrust balance

Abstract

A gear pump has a toothed driving wheel, a toothed driven wheel, a front flange from which a projecting portion of the shaft protrudes, being connected to the shaft of the driving wheel, a back lid fixed to the case, and an intermediate flange between the case and the front flange. The intermediate flange has first and second chambers connected by a connection duct to the inlet or outlet fluid duct of the pump. A compensating ring is mounted in the first chamber and inserted on the shaft of the driving wheel to compensate the axial forces of the driving wheel and transmit the motion on the shaft of the driving wheel. A piston is mounted in the second chamber in order to stop against one end of the shaft of the driven wheel, in such manner to compensate the axial forces imposed on the toothed driven wheel.

Claims

1. A gear pump or hydraulic gear motor comprising: a first shaft; a first toothed wheel joined to said shaft; a second shaft; a second toothed wheel joined to said second shaft and engaged with said first toothed wheel, said first and second toothed wheels each having helical teeth; a plurality of supports revolvingly supporting said first and second shafts of said first and second toothed wheels; a case containing said plurality of supports and defining an inlet fluid duct and an outlet fluid duct; a front flange from which a projecting portion of said first shaft protrudes frontally, said front flange being connected to said first shaft of said first toothed wheel, said projecting portion of said first shaft being adapted to be connected to a motor or to a load; and a back lid fixed to said case; an intermediate flange disposed between said case and said front flange, said intermediate flange comprising a first chamber connected by a connection duct to said inlet fluid duct or said outlet fluid duct; a compensating ring mounted in said first chamber of said intermediate flange and inserted on a portion of said first shaft of said first toothed wheel; in such manner to compensate for axial forces imposed on said first toothed wheel and to allow for motion transmission on said first shaft of said first toothed wheel, wherein said compensating ring comprises an internally empty cylinder and a collar radially protruding from said cylinder, wherein an external diameter of said cylinder and said collar are selected to compensate for the axial forces imposed on said first toothed wheel.

2. The gear pump or hydraulic gear motor of claim 1, further comprising: a second chamber formed in said intermediate flange and connected by said connection duct to said inlet fluid duct or said outlet fluid duct of the pump; and a piston mounted in said second chamber of said intermediate flange in order to stop against one end of said shaft of said second toothed wheel, in such manner to compensate for axial forces imposed on said second toothed wheel.

3. The gear pump or hydraulic gear motor of claim 1, wherein said portion of said first shaft of said first toothed wheel whereon said compensating ring is inserted is an end portion and the gear pump also comprises a mechanical connection connecting said end portion of the toothed wheel to another shaft so as to transmit motion.

4. The gear pump or hydraulic gear motor of claim 1, wherein said compensating ring is keyed on said portion of said first shaft so as to eliminate relative friction.

5. The gear pump or hydraulic gear motor of claim 1, further comprising: a plurality of dynamic seals disposed in said first chamber of the intermediate flange to support said compensating ring in such manner to avoid leakage from high pressure areas towards low pressure areas.

6. The gear pump or hydraulic gear motor of claim 1, wherein said back lid comprises: a first chamber and a second chamber connected by ducts to inlet fluid duct or to said outlet fluid duct; a first piston mounted in said first chamber of back lid in order to stop against an end of said first shaft of said first toothed wheel so as to compensate for axial forces imposed on said first toothed wheel; and a second piston mounted in said second chamber of said back lid in order to stop against an end of said second shaft of said second toothed wheel so as to compensate for axial forces imposed on said second toothed wheel.

7. The gear pump or hydraulic gear motor of claim 1, further comprising: a mechanical connection connecting said first shaft of said first toothed wheel to a drive shaft comprising said projecting portion that protrudes from said front flange.

8. The gear pump or hydraulic gear motor of claim 1, wherein said projecting portion of said first shaft is connected to a motor such that said first toothed wheel is a driving wheel and said second toothed wheel is a driven wheel.

9. The gear pump of hydraulic gear motor of claim 1, wherein said projecting portion of said first shaft is connected to a load.

10. The gear pump or hydraulic gear motor of claim 1, wherein said gear pump or hydraulic gear motor is multiple and comprises: at least one front stage comprising said first toothed wheel and said second toothed wheel; a rear stage comprising another said first toothed wheel and another said second toothed wheel and said back lid; and a mechanical connection connecting said first shaft of said first toothed wheel of said front stage to the first shaft of another said first toothed wheel of said rear stage; wherein said intermediate flange is disposed between said case of said front stage and said mechanical connection and said compensating ring of said intermediate flange compensates for an axial thrust of said first toothed wheel of said front stage.

11. The gear pump or hydraulic gear motor of claim 10, further comprising: at least one intermediate stage between said front stage and said rear stage, the intermediate stage comprising a first toothed wheel and a second toothed wheel with each helical teeth, the first toothed wheel of said intermediate stage receiving motion from an end section of the shaft of said first toothed wheel of said front stage and moves said rear stage through the mechanical connection connecting said shaft of said first toothed wheel of said intermediate stage to said first shaft of said first toothed wheel of said rear stage, wherein an additional intermediate flange is disposed between the case of said intermediate stage and the mechanical connection, said additional intermediate flange comprising a compensating ring to compensate for axial thrust of said first toothed wheel of said intermediate stage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional characteristics of the invention will appear evident from the detailed description below, with reference to the attached drawings, which have an illustrative, not limitative purpose only, wherein:

(2) FIG. 1 is an axial view of a gear pump with straight toothing according to the prior art;

(3) FIG. 1A is a cross-sectional view along section plane A-A of FIG. 1;

(4) FIG. 2 is the same view as FIG. 1, which shows the radial transmission forces;

(5) FIG. 2A is the same view as FIG. 1A, which shows the radial and transverse pressure forces;

(6) FIG. 3A is an axial view of a gear pump with helical toothing, which shows the radial and axial transmission forces;

(7) FIG. 3B is the same view as FIG. 3A, which shows the radial and axial pressure forces;

(8) FIG. 3C is the same view as FIG. 3A, which shows the axial transmission and pressure forces when the pump is in left-hand rotation;

(9) FIG. 3D is the same view as FIG. 3A, which shows the resultants of the axial transmission and pressure forces directed towards the back lid of the pump;

(10) FIG. 4 is an axial view of a bi-helical gear pump according to the prior art;

(11) FIG. 5 is an axial view of a helical gear pump according to the prior art, which corresponds to FIG. 1 of U.S. Pat. No. 3,658,452;

(12) FIG. 6A is the same view as FIG. 3C, which shows the axial transmission and axial pressure forces when the pump is in right-hand rotation;

(13) FIG. 6B is the same view as FIG. 6A, which shows the resultants of the axial transmission and pressure forces directed towards the front flange of the pump;

(14) FIG. 7 is a diagrammatic exploded view of two stages of a multiple pump according to the prior art;

(15) FIG. 8 is an axial view that shows a gear pump of bi-directional type according to the present invention, wherein some high-pressure channels connected to the inlet duct of the pump are shown in bold;

(16) FIG. 9 is a cross-sectional view of the pump of FIG. 8, wherein the inlet area is shown in bold;

(17) FIG. 10 is the same view as FIG. 9, after inverting the motion, wherein the inlet area is shown in bold;

(18) FIG. 11 is the same view as FIG. 9, after inverting the motion, wherein some high-pressure channels connected with the inlet duct of the pump are shown in bold;

(19) FIG. 11A is an axial exploded view of some elements of the compensation system of the axial thrusts of the pump of FIG. 11;

(20) FIG. 12 is an axial view of a multiple stage pump according to the present invention, comprising two stages; and

(21) FIG. 13 is an enlarged view of a detail of FIG. 12, which shows the compensation system of the axial thrusts; and

(22) FIG. 14 is a partially axial view of a multiple stage pump according to the present invention, comprising three stages.

DETAILED DESCRIPTION OF THE INVENTION

(23) Referring to FIGS. 8 to 11, a bi-directional gear pump according to the invention is disclosed, being generally referred to with numeral (100).

(24) Hereinafter elements that are identical or correspond to the elements described above are indicated with the same reference numbers, omitting their detailed description.

(25) The pump (100) comprises a first toothed wheel (1), a second toothed wheel (2), a back lid (7) in closing position and a front flange (6) from which a projecting portion (13) of the shaft protrudes frontally, being connected to the shaft (10) of the first toothed wheel (1). Both toothed wheels (1, 2) are provided with helical toothing.

(26) The projecting portion (13) of the shaft is connected to a motor (M) that can make a kinematic mechanism rotate in clockwise or anticlockwise direction. In such a case, the first toothed wheel (1) is the driving wheel and the second toothed wheel (2) is the driven wheel.

(27) With reference to FIG. 9, when the motor (M) makes the driving wheel (1) rotate in anticlockwise direction, an outlet area (high pressure), which is shown in bold, is generated in the left-hand side of the case (3), whereas an inlet area (low pressure) is generated in the right-hand side of the case (3).

(28) With reference to FIG. 8, in such a case, respective axial forces (A, B) facing towards the back lid (7) are generated on the toothed wheels (1, 2).

(29) The precepts of U.S. Pat. No. 3,658,452 were followed to balance the axial forces (A, B) acting on the back lid (7). Two chambers (70,71) are obtained in the back lid (7), wherein a first piston (270) and a second piston (271) are disposed. The pistons (270, 271) axially actuate on the rear end border of the shafts (10, 20) of the toothed wheels (1, 2).

(30) Two ducts (72, 73) are obtained in the back lid (7), which put the outlet chamber (shown in bold in FIG. 9) of the pump in communication with the chambers (70, 71) of the two pistons (270, 271). In view of the above, the pistons (270, 271) push against the shafts (10, 20) of the toothed wheels, exercising forces (A, B) that balance the axial forces (A, B) acting on the toothed wheels.

(31) With reference to FIG. 10, when the motor (M) inverts the rotation direction and puts the driving wheel (1) in clockwise rotation, an outlet area (high pressure), which is shown in bold, is generated in the right-hand side of the case (3), whereas an inlet area (low pressure) is generated in the left-hand side of the case (3).

(32) With reference to FIG. 11, in such a case, respective axial forces (A, B) facing towards the front flange (6) are generated on the toothed wheels (1, 2).

(33) An intermediate flange (8) is disposed between the case (3) and the front flange (6) in order to compensate said forces (A, B).

(34) With reference to FIG. 11A, said intermediate flange (8) is provided with a through hole (85) in order to allow for the passage of an end portion (T) of the shaft (10) of the toothed driving wheel.

(35) The intermediate flange (8) comprises a first chamber (80) with annular shape, obtained around the through hole (85) and a second chamber (81) with cylindrical shape, in axial position to the shaft (20) of the driven wheel (2).

(36) A duct (82) is obtained in the intermediate flange (82) that puts the two chambers (80, 81) in communication with the outlet duct of the pump (shown in bold in FIG. 10).

(37) A compensating ring (9) is provided in the first chamber (80). The compensating ring (9) is inserted on the end portion (T) of the shaft (10) of the driving wheel. To that end, a shoulder (15) is obtained in proximal position to the end portion (T) of the shaft of the driving wheel, against which the compensating ring (9) is stopped. Advantageously, the compensating ring (9) is splined on the end portion (T) of the shaft (10) to avoid undesired friction that may cause fluid leakage from the high-pressure area to the low-pressure area of the pump.

(38) The compensating ring (9) comprises a cylinder (90) and a collar (91) that radially protrudes outwards from the cylinder (90). The compensating ring (9) is internally empty and is provided with a through hole (92) to allow for the passage of the end portion (T) of the shaft of the driving wheel. The through hole (92) has a splined female section, whereas the end portion (T) of the shaft (10) has a splined male section.

(39) Two dynamic seals (95, 96) are disposed in the first chamber (80) of the intermediate flange (8) to support the compensating ring (9) in such way to eliminate possible leakage from the high-pressure areas to the low-pressure areas.

(40) A cylindrical piston (88) is disposed in the second chamber (81) of the intermediate flange.

(41) When the rotation direction of the toothed wheels is as shown in FIG. 10, the chambers (81, 80) of the intermediate flange are in communication with the outlet duct (high pressure), and consequently the fluid pushes the compensating ring (9) and the piston (88) in the direction of the arrows (A, B) (see FIG. 11) in such manner to compensate the axial forces (A, B) exerted on the gears.

(42) With reference to FIG. 11, the collar (91) of the compensating ring has an external diameter (d1) and the cylinder (90) of the compensating ring has an external diameter (d2).

(43) The annular area defined by the diameters d.sub.1 and d.sub.2 is such to completely compensate the axial force (A). The values of the diameters d.sub.1 and d.sub.2 are calculated with the formula (7) considering an annular section with equivalent area instead of a circular area. One of the diameters is fixed according to the constructional requirements and the other diameter is calculated with the following formula:

(44) $\begin{array}{cc}\frac{}{4}\left(d_1^2-d_2^2\right)=2.Math.\sqrt{\frac{10.Math.A}{.Math.P}}\left[\mathrm{mm}\right]& \left(9\right)\end{array}$

(45) The piston (88) has an external diameter (d3). The dimension (d.sub.3) of the piston (88) is such to completely compensate the axial force (B). The d.sub.3 value can be directly calculated from the following formula:

(46) $\begin{array}{cc}{d}_3={}_B=2.Math.\sqrt{\frac{10.Math.B}{.Math.P}}\left[\mathrm{mm}\right]& \left(10\right)\end{array}$

(47) According to a preferred embodiment of the present invention, the axial forces are balanced both on the shaft of the toothed driving wheel (1) and on the shaft of the toothed driven wheel (2), respectively by means of the compensating ring (9) and the piston (88). However, it must be considered that the resultant (A) of the axial thrusts on the shaft of the driving wheel (1) is much higher than the resultant (B) of the axial thrusts on the shaft of the driven wheel (2). Therefore the piston (88) is optional and may be omitted.

(48) As shown in FIGS. 8 and 11, the end portion (T) of the shaft of the driving wheel externally protrudes from the intermediate flange (8) and is connected by means of a mechanical connection (500) to a drive shaft (12) provided with said projecting portion (13) connected to the motor (M).

(49) The mechanical connection (500) can be a splined coupling, an Oldham coupling or a coupling of any other type. The mechanical connection (500) is housed in a plate (501) that is stopped against the intermediate flange (8).

(50) An intermediate plate (600) whereon bearings (601) that revolvingly support the shaft (12) can be optionally provided. The intermediate plate (600) is disposed between the front flange (6) and the plate (501) that houses the mechanical connection (500).

(51) Although FIGS. 8 to 11 refer to a pump, said figures may also refer to a hydraulic motor wherein the pump outlet (high-pressure area) corresponds to the inlet of the motor fluid and the pump inlet (low-pressure area) corresponds to the discharge of the motor fluid. In the case of a hydraulic motor, there are no driving wheel and driven wheel, but simply a first toothed wheel (1) and a second toothed wheel (2). Moreover, the projecting portion of the shaft (13) is adapted to be connected to a load, not to a motor (M)

(52) FIGS. 12, 13 illustrate a multiple gear pump (200).

(53) The multiple gear pump (200) comprises a front stage (S.sub.A) and a rear stage (S.sub.B). Each stage comprises toothed wheels with helical toothing.

(54) The rear stage (S.sub.B) is the last stage of the pump and therefore is closed with the back lid (7), from which no shaft protrudes. A projecting portion (13) of the shaft frontally protrudes from the front flange (6) to be connected to a motor (M).

(55) The end portion (T) of the shaft of the driving toothed wheel of the front stage (S.sub.A) is connected to the end portion (T) of the shaft of the toothed driving wheel of the rear stage (S.sub.B) by means of the mechanical connection (500) housed in the plate (501) disposed between the two stages (S.sub.A, S.sub.B).

(56) In such a case, the toothed wheels of the front stage and of the rear stage are subject to respective axial forces (A, B, C, D), which are all directed towards the back lid (7).

(57) Consequently, the axial forces (C, D) on the toothed wheels of the rear stage (S.sub.B) are balanced by the action of the pistons (270, 271) disposed in the back lid (7).

(58) Instead, the axial forces (A, B) on the toothed wheels of the front stage (S.sub.A) are balanced by the action of the compensating ring (9) and of the piston (88) disposed in the intermediate flange (8). As shown in FIG. 13, the compensating ring (9) and the piston (88) generate respective axial forces (A, B) that compensate the axial forces (A, B) exerted on the toothed wheels (1, 2) of the front stage (S.sub.A).

(59) The plate (501) that houses the mechanical connection (500) is disposed between the intermediate flange (8) and the rear stage (S.sub.B).

(60) Referring to FIG. 14, the multiple gear pump (200) may comprise one or more intermediate stages (S.sub.I) disposed between the front stage (S.sub.A) and the rear stage (S.sub.B). Each intermediate stage (S.sub.I) comprises a first toothed wheel (1) and a second toothed wheel (2) with helical toothing. The first toothed wheel (1) of the intermediate stage (S.sub.I) receives the motion from the end portion (T) of the shaft of the driving wheel (1) of the frontally positioned stage (S.sub.A) and in turn gives motion to a posterior stage (S.sub.B) by means of the mechanical connection (500) that connects the shaft of the first toothed wheel of the intermediate stage to the shaft of the first toothed wheel of the posterior stage (S.sub.B).

(61) In such a case, an additional intermediate flange (8) is disposed between the case of the intermediate stage (S.sub.I) and the mechanical connection (500). The compensating ring (9) of the intermediate flange (8) compensates the axial thrust (A) of the first toothed wheel (1) of the intermediate stage (S.sub.I).

(62) Variations and modifications can be made to the present embodiments of the invention, within the reach of an expert of the field, while still falling within the scope of the invention.