GB1571250A - Hydraulic dynamometers - Google Patents

Description

(54) HYDRAULIC DYNAMOMETERS (71) We, FROUDE ENGINEERING LIMITED of Gregory's Bank, Worcester, a British Company, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to hydraulic dynamometers.

Reference is directed to patent application No. 50136/77 (Serial No. 1,571,249) in which we claim an hydraulic dynamometer comprising a stator supported by a plurality of members with universal joints at top and bottom ends of said members to. enable horizontal adjustment both axially and laterally in the position of the stator, each member forming in combination with the universal joints at the top and bottom ends thereof a support assembly, and each said support assembly incorp orating a load cell for use in torque measurement.

According to the present invention, there is provided an hydraulic dynamometer comprising at least one double-sided rotor, each side of the rotor co-operating with a corresponding stator side, so that in operation opposing axial thrusts are produced between the two rotor sides and the two stator sides, the rotor being capable of limited axial movement whereby imbalance between the two axial thrusts results in axial movement of the rotor, causing compensating adjustment of the spaces between the two rotor sides and the two stator sides, whereby the two thrusts become or tend to become balanced.

The present invention will be described by way of example with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of an hydraulic dynamometer embodying both aspects of the invention, from one corner of the dynamometer; Figure 2 is another perspective view of the dynamometer of Figure 1, from the opposite corner; Figure 3 is a diagrammatic end elevation of the dynamometer of Figure 1; Figure 4 is a diagrammatic plan view ot the dynamometer of Figure 1; Figure 5 is a section through one of three support assemblies in the dynamometer of Figure 1; Figure 6 is an enlarged perspective view d part of the dynamometer of Figure 1, from the same general view point as Figure 1; Figure 7 is a partly-sectioned view of an hydraulic piston-in-cylinder device in the dynamometer in Figure 1; Figure 8 is a section through the stator and rotor od the dynamometer of Figure 1; Figure 9 is an end elevation of part of the dynamometer, related to Figure 8; and Figures 10 and 11 are respectively sections on line A-A and line B-B of Figure 9.

Referring to the drawings, the illustrated hydraulic dynamometer 1 comprises a stator 2 supported by three members 3a, 3b and 3c substantially vertical with universal joints 4a, 4a', 4b, 4b', 4c and 4c' at the top and bottom ends respectively of said members 3a, 3b and 3c to enable horizontal adjustment both axially and laterally in the position of the stator 2.

Each member 3a, 3b and 3c is normally in compression, that is, as a strut, due to the weight of the stator 2, and forms in combination with the universal joints 4a and 4a', 4b and 4b', 4c and 4c' at the top and bottom ends thereof a support assembly 5a, 5b and 5c.

Each said support assembly 5a, 5b and Sc incorporates a (respective) load cell 6a, 6b and 6c for use in torque measurement.

Two of the support assemblies 5a and 5b are on one side of the stator 2 and the third support assembly Sc is on the opposite side of the stator 2, as shown in the drawings, so that the stator 2 is supported at three points.

Each universal joint 4 is a so-called "spherical joint" comprising a pivot pin 7, a partly spherical bearing member 8 mounted on the pivot pin 7 and a hollow member 9 in which the member 8 is rotatably mounted so that the pivot pin 7 can rotate in two or more planes relative to the member 9.

As regards the universal joints 4a, 4b and 4c at the upper ends of the members 3 a, 3b and 3c respectively, the pivot pins 7 are received by forks 10 forming parts of the stator 2, whilst the hollow members 9 are fixed to the top ends of the members 3.

As regards the lower universal joints 4a', 4b' and 4c' at the bottom ends of the members 3a, 3b and 3c respectively, the pivot pins 7 are received in forks 11 of a support bed or bed plate 12, whilst the hollow members 9 are fixed to the bottom ends of the members 3. The forks 11 can be hydraulically raised or lowered, for raising and lowering the stator 2, by hydraulic oil fed under pressure (by means not shown) to an opening 13a in each fork 11, connected via passages 13b and 13c in the fork 11 to a space 13d between the bottom end of the fork 11 and a receiving cup 14 welded to a girder 15 forming part of the support bed or bed plate 12.

The load cell 6a, 6b and 6c in each support assembly 5a, 5b and Sc is incorporated in the (strut) member 3a, 3b and 3c respectively, and is adapted to sense both compression and tension.

The dynamometer 1 includes a doublesided rotor 16 which can be connected by either one of two couplings 17 to a prime mover (not shown). Because of the support assemblies 5 comprising the members 3 and universal joints 4, enabling horizontal adjustment both axially and laterally in the position of the stator 2 and hence in the position of the rotor 16, it is unnecessary to position the support bed or bed plate 12 accurately with respect to the prime mover. However, unacceptable vibration would be produced if the stator 2 were not rigidly located during use.

Accordingly, two hydraulic piston-in-cylinder devices 18 are provided to enable adjustment in the position of the stator 2 and locking of the stator 2 in position. More particularly, each device 18 comprises a double-sided piston 19, with equal piston area on both sides, sliding in a cylinder 20. Passages 21a, 21b and 21c in the cylinder 20 inter-connect spaces 20a and 20b on opposite sides of the piston 19, via a controllable shut-off valve 22. So long as valve 22 is open, the piston 19 can slide freely in the cylinder 20, with hydraulic fluid flowing from one side to the other side of the piston 19 via the passages 21. Accordingly, since one end 19a of the piston 19 is connected to the stator 2 whilst the other end 19b of the piston is connected to the support bed or bed plate 12, the stator 2 can be adjusted horizontally in position, but not after the valve 22 has been shut off.

In order to limit the possible horizontal movement of the stator 2 with the two valves 22 open, each support assembly 5 is fitted with two adjustable screw-threaded bolts 23a and 23b, fitted with lock nuts 24a and 24b respectively. The limit bolt 23a is screwed directly into the respective stator fork 10, whilst the limit bolt 24b is screwed into a plate 25 which is attached by four screws such as screw 26 to the fork 10. The bolts 23a and 23b are adjusted as required, and then secured by means of the lock nuts 24a and 24b, to engage the corresponding member 3a, 3b or 3c whenever the member 3 tilts from a vertical position as far as one wants it to.

In use, the dynamometer 1 is placed in approximately the desired position in relation to the prime mover (not shown) and the coupling 17 is then connected to the prime mover while the two valves 22 are open, so that the stator 2 can adjust itself horizontally to the exact position required, relative to the prime mover. The valves 22 are then both shut, whereupon the stator 2 becomes locked in position.

Referring now more particularly to Figures 8 to 11, the double-sided rotor 16 has rotor pockets 27a at one side of the rotor 16 facing corresponding stator pockets 28a at one side of the stator 2, whilst the rotor 16 has a second ring of rotor pockets 27b, on the opposite side of the rotor 16 from the pockets 27a, and facing a corresponding ring of stator pockets 28b at the opposite side of the stator 2 from the stator pockets 28a. In use, torque is developed between the stator 2 and rotor 16 by the introduction of hydraulic fluid into the pockets 27a and 27b and 28a and 28b via inlet passages 29, due to the rotation of the rotor pockets 27 relative to the stator pockets 28. The hydraulic fluid exits via passages 30 to an annular chamber 30. Ideally, although two mutually opposite axial thrusts are developed between the two sides of the rotor on the one hand and the two stator sides on the other hand, these two axial thrusts are equal and cancel each other out.

In practice, these two axial thrusts are seldom equal and a large thrust bearing would normally be provided in an hydraulic dynamometer.

However, in the dynamometer 1, the rotor 16 is permitted a limited amount of axial movement. This has the effect that if, for example, the thrust developed between the rotor pockets 27a and stator 28a in Figure 8 exceeds the thrust produced between the rotor pockets 27b and 28b, the rotor 16 will tend to move to the right as seen in Figure 8. The effect of this is to increase the axial distance between the rotor pockets 27a and stator pockets 28a, thereby decreasing the axial thrust between them, and decreasing the axial distance between the rotor pockets 27b and stator pockets 28b, thereby increasing the axial thrust produced between them, so that the two axial thrusts become, or tend to become balanced. The rotor 16 is fitted with a rotor shaft 31 which runs in two "deep-groove" ball bearings 32. The advantage of deepgroove ball bearings over, for example, roller bearings is that lubrication is less of a problem, because of the smaller surfaces in con tact, lubricating grease can be used in place of lubricating oil, and higher speeds are permissible.

In order to damp the axial movement of the shaft 31 (with axial movement of the rotor 16) the outer bearing member 32a is fitted with twelve Belleville washer or disc spring assemblies 33, six on one side and the other six on the other side, each constituted by a piston 33a screwed adjustably into the bearing member 32a, a plug 33b screwed adjustably into a part of the stator 2 and a pack of Belleville washers 33c between them.

WHAT WE CLAIM IS:- 1. An hydraulic dynamometer comprising at least one double-sided rotor, each side of the rotor co-operating with a corresponding stator side, so that in operation opposing axial thrusts are produced between the two rotor sides and the two stator sides, the rotor being capable of limited axial movement whereby imbalance between the two axial thrusts results in axial movement of the rotor, causing compensating adjustment of the spaces between the two rotor sides and the two stator sides, whereby the two thrusts become or tend to become balanced.

2. A dynamometer as claimed in Claim 1 wherein disc springs are incorporated to apply additional opposing axial thrusts to the rotor and to control the axial movement of the rotor.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. tact, lubricating grease can be used in place of lubricating oil, and higher speeds are permissible. In order to damp the axial movement of the shaft 31 (with axial movement of the rotor 16) the outer bearing member 32a is fitted with twelve Belleville washer or disc spring assemblies 33, six on one side and the other six on the other side, each constituted by a piston 33a screwed adjustably into the bearing member 32a, a plug 33b screwed adjustably into a part of the stator 2 and a pack of Belleville washers 33c between them. WHAT WE CLAIM IS:-

1. An hydraulic dynamometer comprising at least one double-sided rotor, each side of the rotor co-operating with a corresponding stator side, so that in operation opposing axial thrusts are produced between the two rotor sides and the two stator sides, the rotor being capable of limited axial movement whereby imbalance between the two axial thrusts results in axial movement of the rotor, causing compensating adjustment of the spaces between the two rotor sides and the two stator sides, whereby the two thrusts become or tend to become balanced.

2. A dynamometer as claimed in Claim 1 wherein disc springs are incorporated to apply additional opposing axial thrusts to the rotor and to control the axial movement of the rotor.