US3839944A

US3839944A - Transducer mounting arrangement

Info

Publication number: US3839944A
Application number: US00202317A
Authority: US
Inventors: E Swift
Original assignee: Davy Loewy Ltd
Current assignee: Davy Loewy Ltd
Priority date: 1968-12-13
Filing date: 1971-11-26
Publication date: 1974-10-08
Anticipated expiration: 1991-10-08
Also published as: GB1295636A

Abstract

Mounting for transducers whose electrical output is proportionate to the relative position of two moving parts comprises hydraulic means for adjusting the transducer to a datum position after load has been applied to one of the parts.

Description

States Patent [191 TRANSDUCER MGUNTING ARRANGEMENT Inventor: Eric Owen Swift, Rotherham,

England Assignee: Davy-Loewy Limited, Sheffield,

England Filed: Nov. 26, 1971 Appl. No.: 202,317

Related US. Application Data Continuation-impart of Ser. No 5,255, Jan. 23, 1970, abandoned.

10.8. C1 92/5 1R, 72/21, 33/125, 33/172 E, 33/DIG. 15

Int. Cl..... B211) 37/08, F01b 31/12, GOlb 7/00 Field 01' Search...... 33/169, 182, 180 R, 172 E, 33/172 F, DIG. 2, DIG. 5, 143 L, 174 L, 147 L, 147 R, DIG. 15, 125; 72/21, 19, 240; 241/37, 231; 92/28, 5 R

[ 1 Oct. 8, 1974 Primary Examiner-John W. Hucrkert Assistant Examiner-John M. Jillions Attorney, Agent, or Firm-Brisebois & Kruger [57] ABSTRACT Mounting for transducers whose electrical output is proportionate to the relative position of two moving parts comprises hydraulic means for adjusting the transducer to a datum position after load has been applied to one of the parts.

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TRANSDUCER MOUNTING ARRANGEMENT This invention relates to mounting arrangements for electrical transducers whose electrical output is proportionate in magnitude and polarity to the relative position of two opposed moving parts. The application is a continuation-in-part of my application Ser. No. 5,255 filed Jan. 23, 1970 now abandoned.

There are many applications in which fluid operated pressure capsules which comprise a piston displaceable by hydraulic fluid in a cylinder are employed to displace one member relative to another. For example hydraulic capsules may be positioned between the rigid housing and a chock supporting one end of a roll of a metal rolling mill in order to displace the chock and roll relative to the housing. In such an application it is usually desirable to have an accurate knowledge of the separation of the chock from the housing at all times and it is usual to employ an electrical transducer arranged to provide an electrical signal which is representative of this separation. In another application one or more pressure capsules may be positioned between the chocks supporting a pair of rolls of a rolling mill. Again it is desirable to employ an electrical transducer to give an electrical signal representative of the separation between the chocks. A fluid operated pressure capsule which is suitable for use in a rolling mill usually has a stroke which is relatively long and it is desirable that the stroke of the piston is sufficient to allow for rolls of different diameter to be fitted into the mill. In order for the transducer associated with the capsule to be capable of producing an electrical signal representative of the entire stroke of the pressure capsule it has heretofore been necessary to employ a transducer which has a maximum stroke of approximately the same length as that of the capsule. Long stroke transducers have the disadvantage that their linearity is a function of their overall stroke, thus the linearity in absolute terms becomes worse as the overall stroke is increased. It is therefore desirable for the degree of accuracy required in rolling mills to employ a transducer the stroke of which is as small as possible.

It is an object of the present invention to provide a mounting arrangement for a transducer which permits a transducer to be employed with a pressure capsule the stroke of which is large compared with that of the transducer.

According to the present invention a transducer mounting arrangement comprises a housing defining an opening therein, an electrical transducer having an outer casing and an inner core projecting out of one end of the casing, the core being displaceable in a direction parallel to its length relative to the casing, the transducer producing an electrical signal representative of the relative position of the core and the casing, a body rigidly supporting the transducer casing, the body being accommodated in the opening and displaceable therein in a direction parallel to the length of the casing, means acting between the body and the housing to retain the body in a desired position in the opening and hydraulic means for displacing the body and the transducer casing against the action of the re taining means to a desired position in the opening.

The transducer comprises an elongate outer casing having an inner core projecting out of one end of the casing. The core is displaceable in the direction parallel to its length and electrical means associated with the casing and the core produce an electrical signal which is proportionate to the relative position of the core and the casing. The electrical means may take the form of a differential transformer having a primary coil and a pair of oppositely wound secondary coils or it may take the form of a potentiometer which is steplessly variable or it may be a capacitive-type of transducer.

The hydraulic means for displacing the transducer casing is preferably arranged to be capable of displacing the casing by an amount considerably in excess of the maximum relative displacement of the transducer core and easing.

When the transducer is associated with a pressure capsule the signal produced by the transducer may, be employed to position the core and easing of the transducer relative to one another in order to produce a predetermined datum signal from the transducer. When the signal produced by the transducer is other than the datum signal, this signal may be used to automatically position the parts of the transducer relative to one another to produce the predetermined datum signal or alternatively it may be used to indicate to an operator the relative positions of the two parts of the transducer and the operator may bring about adjustment of the positions of the two parts in order to produce the datum signal. Once the two parts of the transducer have been moved relative one to the other in order to produce the datum signal, one part of the transducer is then held stationary with respect to the other part and if the other part is displaced relative to the fixed part an output signal is produced which is representative of the displacement of the movable part of the transducer from the datum position.

In order that the invention may be more readily understood it will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a sectional side elevation of a hydraulic capsule having an electrical transducer associated therewith,

FIG. 2 is a sectional side elevation of a transducer mounting arrangement suitable for use with a hydraulic pressure capsule, and

FIG. 3 shows diagrammatically a control arrangement for displacing one part of the transducer of FIG. 1 relative to another part.

Referring to FIG. 1, a hydraulic pressure capsule comprises a member 1 defining a cylinder 2 with a piston 3 displaceable in the cylinder. An annular sealing ring 4 mounted on said piston prevents loss of hydraulic fluid between the walls defining the cylinder and the piston. The maximum stroke of the hydraulic capsule is indicated by the arrow a and this may be of the order of 1 inch or more.

An opening in the form of a bore 5 is provided axially of the piston 3 and a finger 6 secured to the member 1 extends along part of the bore into an enlarged portion 7 thereof. The piston 3 serves as a housing for an electrical transducer which has a cylindrical casing 8 and a cylindrical core 9 extending into an axial opening in the casing. The electrical output signal of the transducer is representative of the relative position of the core and the casing. The casing 8 is mounted in support means 10 which is free to slide as a piston in the enlarged bore portion 7 of the piston 3. The core 9 has an enlarged head 11 which is urged towards one extremity of its stroke relative to the casing by a coil spring 12. The enlarged head 11 abuts against the finger 6. The

stroke of the transducer is less than the dimension a. An insert 20 introduced into the lower end of the enlarged portion 7 of the bore has an inwardly extending part 13 with a sealing ring 14 which engages with a part of the sleeve which is of reduced diameter, and annular spaces 15 and 16 are formed on either side of the part 13 in the bore of the piston 3. The lower end of the space 16 is closed by an annular ring 60 fitted on to the sleeve 10 and held in position by a nut 61 secured to the sleeve 10. A fluid line 17 extends from the outside of the piston 3 to the annular space 15 and a separate fluid line 18 extends to the fluid space 16. An annular friction pad 19 secured to the outerv wall of the sleeve 10 engages with the bore of the insert 20. The friction pad 19 grips the bore of the sleeve 20 and the transducer casing is prevented from moving relative to the piston 3 unless the friction force between the sleeve and the pad is overcome by hydraulic forces in one of the spaces 15, 16.

Consider now the case where the hydraulic capsule is positioned between a rigid part of the housing of a rolling mill and one of the chocks supporting one end of a roll of the mill with the piston 3 in engagement with the housing and the cylinder 1 abutting the chock. When fluid is introduced under pressure into the cylinder 2 of the capusle, through a fluid line not shown, in order to apply forces to the roll chock, the relative displacement of the piston and cylinder may be such that the finger 6 moves away from the transducer casing and in the absence of the present invention the core of the transducer which tries to follow the finger 6 would be positioned at or close to one end of its stroke relative to the transducer housing and consequently further variations in the position of the piston and cylinder of the capsule when the mill is in operation may not be accommodated by the transducer because the transducer is at or close to the end of its working stroke. With an arrangement in accordance with the invention and with the control circuit of FiG. 3, when the mill is first set up with no material in the gap between the work rolls the signal from the transducer is employed as one imput B to a comparator 65 and is compared with a reference signal C from a potentiometer 66 and the difference signal A is applied to valve means 67 which is used to control the flow of hydraulic fluid to one or other of the spaces 15 and 16 in order to cause displacement of the sleeve and the transducer casing relative to the core in a direction to reduce the signal from the transducer to a predetermined value. The forces set up in the spaces 15 or 16 are sufficiently high to overcome the friction force between the sleeve and the pad. When the signal from the transducer has been adjusted to its predetermined value, the flow of fluid to the space 15 or 16 is stopped and the friction pad 19 holds the transducer casing. The transducer is now in its datum position and any variations in the relative position of the piston 3 and the cylinder 1 of the hydraulic capsule due to material passing between the rolls causes displacement of the core of the transducer relative to the casing and this produces a signal, other than the predetermined value, from the transducer. This signal indicates the thickness of the material in the gap between the work rolls of the mill. The signal from the transducer can be used on any subsequent occasion to reset the position of the transducer casing relative to the core to restore, if necessary, the transducer to its datum positron.

FIG. 2 illustrates a mounting arrangement for a transducer and comprises a fixed housing 30 having a central opening 31. A cylindrical tubular member 32 extends through the opening and out of the lower end of the housing. The lower end of the member 32 is secured to a transversely extending member in the form of a crosshead 33. The member 32 is slidable in the opening 31 and a self-lubricating bush 34 is provided in the housing to permit the member 32 to slide relative thereto. Inside the tubular member 32 there is a further tubular member 35 which carries at its upper end a metal block 36 into which the casing 37 of an electrical transducer is rigidly secured by means of the grub screw 65. The axis of the transducer is aligned with that of the members 32 and 35. The transducer casing 37 receives a core 38 which has an enlarged head portion 39. A coil spring biases the head portion 39 away from the casing of the transducer. A cap 41 fits over the end of the transducer and encloses the core 38. The cap 41 and the core 38 are displaceable against the action of the spring relative to the casing 37 through a stroke which may be in the order of say 5/8 inch. The crosshead 33 is connected to one end of a piston rod 42 which is connected in turn to a piston 43 inside a cylinder 44 within the housing 30. The axis of the cylinder 44 and hence the line of action of the piston 43 is parallel to the direction of displacement of the member 32 and the

transducer

37, 38. Hydraulic fluid under pressure is introduced into opposite ends of the cylinder 44 through fluid lines not shown on opposite sides of the piston 43 to displace the piston relative to the cylinder and the displacement of the piston causes the member 32 and the transducer to be displaced relative to the housing 30. Between the housing 30 and the upper end of the member 32 there is a bush 45 which is a hydraulically operated clamping device. The device sold under the trade name LAMALOCK by Sykes Manufacturing (Simplex) Ltd. Barkby Road, Leicester, England, takes the form of a bush having a wall with portions of reduced thickness. On introducing hydraulic fluid under pressure to the outside of the wall, the portions of reduced thickness are deformed inwardly and grip the member 32 and prevent it from moving in the opening 31.

2 may be associated with a hydraulic pressure capsule mounted either between the roll chocks or between the housing and one roll chock of a rolling mill. The cap 41 of the transducer arrangement abuts against the movable part of the capsule and the housing 30 is secured to the stationary part of the capsule so that movement of the capsule causes the core 38 of the transducer to be moved. The electrical signal from the transducer is representative of the displacement of the parts of the mill between whicl the capsule acts.

The transducer mounting arrangement shown in FIG.

In a similar manner to that described above in connection with FIGS. 1 and 3, the signal from the transducer may be employed to actuate the piston-

cylinder device

43, 44 in order to displace the casing of the transducer relative to the core until the output from the transducer is at a predetermined value. The device 45 then clamps the casing of the transducer relative to the housing and any further displacement of the core 38 relative to the casing 37 is represented by a change in the output signal from the transducer.

I claim:

1. A transducer mounting arrangement comprising a support means fitted around the transducer cas-, ing and rigidly supporting it, the support means.

being a sliding fit in the opening in the housing and slideably displaceable therein in a direction parallel to the direction of movement of the transducer core,

frictional retaining means comprising a friction member (19) extending around the outer surface of the support means and opposed portions of said outer surface and the adjacent wall in the opening between which said friction member engages to retain the support means in a desired position in the opening, and hydraulic means (15, 18) for displacing the support means and the transducer casing against the action of the frictional retaining means to a desired position in the opening, said hydraulic means being separate from said frictional retaining means. i 2. A transducer mounting arrangement as claimed in claim 1 in which the support means is in the form of a hollow piston fitted around the transducer casing and displaceable hydraulically in said opening.

3. A transducer mounting arrangement as claimed in claim 2 in which the piston has a pair of spaced apart outwardly projecting flanges which engage the wall of the opening on opposite sides of a member projecting inwardly from the wall of the opening and engaging the piston to thereby define a pair of annular chambers and means for supplying hydraulic fluid under pressure to said chambers.

4. A transducer mounting arrangement as claimed in claim 1 in which the support means comprises a cylindrical tubular member slidably mounted in said opening and projecting outwardly from one end of the open ing, a metal block surrounding and secured to said transducer casing, the block being fixedly located within the tubular member adjacent the end thereof opposite to that which projects from the opening and a cross head secured to the end of the tubular member outside of the opening, said cross head being connected to a piston rod displaceable hydraulically in the direction parallel to the length of the tubular member.

5. A transducer'mriunting arrangement as claimedin j 6. A transducer.mountingarrangement as claimed in claim 4 in which the piston rod is connected to a piston displaceable in a cylinder located within the housing.

Claims

1. A transducer mounting arrangement comprising a housing (3) defining an opening (5,7) therein, an electrical transducer having an outer elongate casing (8) and an inner core (9) projecting out of one end of the casing, the core being displaceable in a direction parallel to its length relative to the casing and the transducer producing an electrical signal representative of the relative position of the core and casing, support means (10) fitted around the transducer casing and rigidly supporting it, the support means being a sliding fit in the opening in the housing and slideably displaceable therein in a direction parallel to the direction of movement of the transducer core, frictional retaining means comprising a friction member (19) extending around the outer surface of the support means and opposed portions of said outer surface and the adjacent wall in the opening between which said friction member engages to retain the support means in a desired position in the opening, and hydraulic means (15, 18) for displacing the support means and the transducer casing against the action of the frictional retaining means to a desired position in the opening, said hydraulic means being separate from said frictional retaining means.

2. A transducer mounting arrangement as claimed in claim 1 in which the support means is in the form of a hollow piston fitted around the transducer casing and displaceable hydraulically in said opening.

4. A transducer mounting arrangement as claimed in claim 1 in which the support means comprises a cylindrical tubular member slidably mounted in said opening and projecting outwardly from one end of the opening, a metal block surrounding and secured to said transducer casing, the block being fixedly located within the tubular member adjacent the end thereof opposite to that which projects from the opening and a cross head secured to the end of the tubular member outside of the opening, said cross head being connected to a piston rod displaceable hydraulically in the direction parallel to the length of the tubular member.

5. A transducer mounting arrangement as claimed in claim 1 wherein said housing is in the form of a piston displaceable in a cylinder and including a finger secured to the cylinder and projecting into the opening in the piston into engagement with the core of the transducer.

6. A transducer mounting arrangement as claimed in claim 4 in which the piston rod is connected to a piston displaceable in a cylinder located within the housing.