US3245354A

US3245354A - Pump

Info

Publication number: US3245354A
Application number: US289940A
Authority: US
Inventors: Gregor Wilhelm
Original assignee: Licentia Patent Verwaltungs GmbH
Current assignee: Licentia Patent Verwaltungs GmbH
Priority date: 1962-06-22
Filing date: 1963-06-24
Publication date: 1966-04-12
Anticipated expiration: 1983-04-12
Also published as: CH425472A

Description

A ril 12, 1966 w. GREGOR 3,245,354

PUMP

Filed June 24, 1963 ti )7 T v a j}, I MOTOR f .I if V I J Q 9 7nvenlor:

WILHELM GREGOR 3 owcun fim g nttomefss United States Patent Wilhelm Gregor, Hamburg-Hausbruch, Germany, assignor to Licentia Patent-Verwaltungs-G.m.b.H., Frankfurt am Main, Germany Filed June 24, 1963, Ser. No. 289,940 Claims priority, application Germany, June 22, 1962,

L 42,286 3 Claims. (Cl. 103-57) The present invention relates generally to the pump art, and, more particularly, to infinitely variable axial piston pumps designed to provide maximum output.

In the manufacture of groups of infinitely adjustable multicylinder axial piston pumps having cylinders which may be tilted and wherein the groups each have different outputs, the output magnitudes of the units of a group with respect to that of other groups had been provided in such an arrangement that they were successive in accordance with a geometrical or arithmtical'progression, or the stroke volumes of the groups formed an arithmetical progression.

When such axial piston devices are driven directly by an electric motor having a speed of rotation which is determined by the frequency of the electric mains providing the driving current, they are operated with various maximal rates of flow of the pressure fluid. Such rates of flow many times either do not attain the critical or limit value which is permissible, or even exceed this critical value. In the first case .the pumps are not fully utilized hydraulically and in the second case they are no longer properly operable over the entire range through which the cylinders may be tilted.

The main object of the present invention is to provide axial piston pumps of the above-mentioned type which can be fully utilized hydraulically when, as is normally the case, their drive is provided by an electric motor having a speed of rotation which is determined by the frequency of the electric mains.

Another object of the invention is to provide a device of the character described Which is simple in construction.

These objects and others ancillary thereto are accomplished according to preferred embodiments of the invention wherein the pitch diameter of the ball-type hearing of the cylinder pistons is such that a rate of flow which is as great as possible, considering the viscosity of the pressure fluid is obtained, and this large flow rate is a maximum rate of flow of the axial piston pump and is provided at that time when the drive of the pump is carried out directly by an electric motor having a predetermined speed of rotation which is correlated with the frequency of the electric mains providing current to the motor.

In all hydraulic motors, the maximum rate of flow of the operating or driving medium is given by the viscosity, the form of the channels, and the low pressure in the suction line. These factors are constant in all pumps of different structural sizes if the conditions are otherwise the same. The variable factors are the driving speed of rotation and the pitch diameter.

Since the speed of rotation of the electric motors is provided by the frequency of the mains, the result is that, for example, with a four pole drive motor the driven hydraulic device must be provided with double the pitch diameter as in the case of a two pole drive motor. Furthermore, in an eight pole drive the pitch diameter must be four times as large as that of a two pole drive or twice as large as in the case of a four pole drive motor.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawing in which the sole figure is a schematic sectional view providing an example of an axial piston pump constructed in accordance with the present invention.

When axial piston motors operate using filler pumps, then substantially high rates of flow can be used. A particular feature of an axial piston pump according to the present invention is the use of a filler pump. The oil pressure of the filler pump is such that a rate of flow which is as great as possible considering the viscosity of the pressure fluid is attained as a maximum rate of flow of the axial piston pump at the time when the drive of the axial piston pump is carried out directly by an electric motor having a predetermined speed of rotation which is coordinated with the frequency of the mains providing the electric current.

Such a pump is illustrated in the drawing, and with more particular reference now to the drawing, a drive shaft 1 is supported in a bearing body 3 and the drive shaft has a drive flange 2. The left front side of the bearing body carries the level control which is not shown and by means of which the pressure fluid is fed to or carried away from the cylinders 4 through the piston rods 5 which are hollow. At the bottom of cylinders 4, balls 6 are provided which are mounted in a flange 7 in a manner which allows pivotal motion between the cylinders and the flange. Flange 7 is in turn rotatably mounted on the stationary pivot frame 8. By means of frame 8 the pitch angle a can be adjusted.

The hollow piston rods 5 are supported in drive flange 2 by a type of ball and socket connection to allow pivotal movement. The geometrical position on which the centers 9 of the balls of the piston rod bearings lie is the pitch diameter 10. In accordance with the present invention,

pitch diameter 10 is so large with a given maximum setting of the tilting angle a that the maximal permissible rate of flow of the axial piston pump is obtained at a speed of rotation which at least approximately corresponds with the rated speed of an electric motor whose rotational speed is coordinated with the frequency of the mains providing the motor with current.

By the use of axial piston pumps of this type, structural groups can be built which, coordinated with the usually used frequency, contain only pumps which always have only one electric motor as the drive unit and by means of which they can always be fully utilized hydraulically and mechanically.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

The pitch diameter of a variable delivery pump according to the invention is actually fixed by the speed of the driving motor (frequency of electric supply) and by the critical Reynolds number which, as is known, results from its attached factors which, for their parts, result again from the construction of the concerning variable delivery pump and from the hydraulic medium used as well as from the pressure in the suction lead. At a viscosity of the hydraulic medium of about degrees Engler, with smooth, cylindrical supply leads, with little resistance, at an open circuit flow and at a tilting angle of degrees, the following figures show to be the most favourable values for the pitch diameter from a design point of view, e.g. for a frequency of the electric supply of 50 and 60 c.p.s.

Pitch Diameter 50 cps. Pitch 60 c.p.s. E 'cctric Electric Diameter,

Motor, r.p.n1. Motor, cm.

Cm. Inches r.p.m.

At variable delivery pumps of this design, which work with filling pump and therefore with prepressure, higher critical Reynolds numbers are applicable, i.e. higher flow speeds are permissible and consequently the variable delivery pumps with the before-stated pitch diameters can be run at considerably higher speeds.

However, as the majority of the pumps work without filling pumps it is expedient to fix the pitch diameter for a design series of these variable delivery pumps for open circuit flow.

What is claimed is:

1. A group of related articles of manufacture comprising a series of infinitely adjustable axial piston pump devices having similar parameters and each having drive means including a drive shaft and an electric motor each having a predetermined speed of rotation different than the other and which is coordinated with the frequency of the mains providing current thereto; and driven means connected to be rotated by said drive means and including (a) a member connected to and coaxial with said drive shaft, (b) a plurality of pistons, pivotally mounted to said member, (c) a plurality of cylinders parallel to each other and in axial symmetry to each other in which said pistons are operable, and

l (d) a cylinder holding element to which said cylinders are connected, said cylinder holding element being pivotally mounted with respect to said member so that the axes of the member and of the element can define an angle therebetween, the pitch diameter of said pistons being dependent upon the speed of said motor such that a rate of flow which is as great as possible is reached considering the viscosity of the pressure fluid as the maximum rate of fiow of the axial piston pump at the time when the drive is carried out directly by said electric motor. 2. The group defined in claim 1 wherein said motor speed in r.p.m. and said pitch diameter in cm. is related as follows:

R.p.m.: Pitch diameter (cm.) 3600 2.5 3000 3.0 1800 5.0 1500 6.0 1200 7.5 1000 9.0 900 750 12 0 600 l5 0 500 18 0 450 20.0 375 25.0 360 25.0 300 30.0

3. The group as defined in claim 2 wherein the related motor speeds and pitch diameters are considered at a viscosity of the hydraulic medium of about 5 degrees Engler, with smooth, cylindrical supply lines having little resistance at an open circuit flow and at a tilting angle of 20 degrees.

References Cited by the Examiner UNITED STATES PATENTS 2,146,133 2/1939 Tweedale 103-162 3,040,672 6/1962 =Foerster et al. 103162 3,066,609 12/1962 Hann 103-5 ROBERT M. WALKER, Primary Examiner.

Claims

1. A GROUP OF RELATED ARTICLES OF MANUFACTURE COMPRISING A SERIES OF INFINITELY ADJUSTABLE AXIAL PISTON PUMP DEVICES HAVING SIMILAR PARAMETERS AND EACH HAVING DRIVE MEANS INCLUDING A DRIVE SHAFT AND AN ELECTRIC MOTOR EACH HAVING A PREDETERMINED SPEED OF ROTATION DIFFERENT THAN THE OTHER AND WHICH IS COORDINATED WITH THE FREQUENCY OF THE MAINS PROVIDING CURRENT THERETO; AND DRIVEN MEANS CONNECTED TO BE ROTATED BY SAID DRIVEN MEANS AND INCLUDING (A) A MEMBER CONNECTED TO AND COAXIAL WITH SAID DRIVE SHAFT, (B) A PLURALITY OF PISTONS, PIVOTALLY MOUNTED TO SAID MEMBER, (C) A PLURALITY OF CYLINDERS PARALLEL TO EACH OTHER AND IN AXIAL SYMMETRY TO EACH OTHER IN WHICH SAID PISTONS ARE OPERABLE, AND (D) A CYLINDER HOLDING ELEMENT TO WHICH SAID CYLINDERS ARE CONNECTED, SAID CYLINDER HOLDING ELEMENT BEING PIVOTALLY MOUNTED WITH RESPECT TO SAID MEMBERS TO THAT THE AXES OF THE MEMBER AND OF THE ELEMENT CAN DEFINE AN ANGLE THEREBETWEEN, THE PITCH DIAMETER OF SAID PISTONS BEING DEPENDENT UPON THE SPEED OF SAID MOTOR SUCH THAT A RATE OF FLOW WHICH IS AS GREAT AS POSSIBLE IS REACHED CONSIDERING THE VISCOSITY OF PRESSURE FLUID AS THE MAXIMUM RATE OF FLOW OF THE AXIAL PISTON PUMP AT THE TIME WHEN THE DRIVE IS CARRIED OUT DIRECTTLY BY SAID ELECTRIC MOTOR.