HYDRAULIC PRESSES
United States Patent 3808859
A method and apparatus for detecting relative displacement of hydraulic press components such as stem, container die and mandrel. Measurements are taken using suitable detectors such as wide-gap air gauges.
US Patent References:
Alignment and orientation detector for extrusion press dummy block
Gardner - November 1966 - 3282074
Safety apparatus for extrusion press dummy block
Zhookoff - November 1966 - 3282075
Cold extrusion press
Hoffmann - August 1960 - 2949051
Alignment and orientation detector for extrusion press dummy block
Gardner - November 1966 - 3282074
Safety apparatus for extrusion press dummy block
Zhookoff - November 1966 - 3282075
Cold extrusion press
Hoffmann - August 1960 - 2949051
Application Number:
05/276447
Publication Date:
05/07/1974
Filing Date:
07/31/1972
View Patent Images:
Export Citation:
Assignee:
Cefilac, Compagnie Du Filage Des Metaux Et Des Joints Curty (Paris, FR)
Primary Class:
Other Classes:
72/253.100
International Classes:
B21C23/21; B21C31/00; B30B15/16; B21C23/00; B21C51/00
Field of Search:
72/31,23,22,21,35,253
Primary Examiner:
Lanham, Charles W.
Assistant Examiner:
Rogers, Robert M.
Attorney, Agent or Firm:
Brisebois & Kruger
Claims:
I claim
1. Apparatus for facilitating correct operation of a press having a work-receiving container and a pressing stem, the apparatus comprising first means for detecting the relative displacement of the axis of the container and the axis of the stem, said means comprising two detectors arranged substantially at right-angles and disposed adjacent the upstream end of the container, said detectors being adapted to indicate any relative movement of the outer peripheral surface of the stem towards or away from said detectors during passage of the stem into the container.
2. Apparatus as claimed in claim 1 in which the detectors are mounted in grooves provided in the upstream end face of the container.
3. Apparatus as claimed in claim 1, in which the detectors are wide gap air gauges.
4. Apparatus as claimed in claim 1 in which the apparatus further comprises second means for detecting the relative displacement between the downstream end face of the container and the upstream face of the press platen or bolster, said second means comprising two detectors arranged substantially at right-angles and disposed adjacent the upstream face of the press platen or bolster, said detectors being adapted to indicate any relative movement of the downstream end face of the container towards or away from the detectors.
5. Apparatus as claimed in claim 4, in which the detectors of said second means are mounted in grooves provided in the upstream end face of the bolster or platen.
6. Apparatus as claimed in claim 4, in which each detector of the second means is adapted to indicate relative displacement of one end of a corresponding probe member, the other end of which is adapted to abut the downstream end face of the container.
7. Apparatus as claimed in claim 6, in which each probe member is carried by a rotatable holder for the press die assembly.
8. Apparatus as claimed in claim 7, in which the holder has two die assembly stations, two probes being associated with each station.
9. Apparatus as claimed in claim 6, in which each probe member comprises a rod, one end of which is spring-biased towards engagement with the container and the other end of which is provided with an axially adjustable member.
10. Apparatus as claimed in claim 4 in which the detectors of the second means are wide gap air gauges.
11. Apparatus as claimed in claim 1 in which the apparatus further comprises third means for detecting relative displacement between the press stem or the moving crosshead or the main ram and the press-bed during extrusion, said third means including a number of detectors mounted on the moving crosshead and adapted to indicate any relative displacement towards or away from the bed in two directions lying substantially at right-angles.
12. Apparatus as claimed in claim 11, in which said third means includes six detectors, two of which are adapted to detect relative displacement from a vertical plane, the other four detectors being placed two on either side of the crosshead to detect any relative displacement from a horizontal plane.
13. Apparatus as claimed in claim 11, in which the detectors of the third means are wide gap air gauges.
14. Apparatus as claimed in claim 1 in which the apparatus further comprises fourth means for detecting relative displacement between the press platen relative to the press-bed during extrusion, said fourth means including a number of detectors mounted on the press platen and adapted to indicate any relative displacement towards or away from the bed in two directions lying substantially at right-angles.
15. Apparatus as claimed in claim 14, in which the fourth means includes six detectors, two of which detect relative displacement from a vertical plane, the other four detectors being placed two on either side of the platen to detect any relative displacement from a horizontal plane.
16. Apparatus as claimed in claim 14, in which the detectors of the fourth means are wide gap air gauges.
17. Apparatus as claimed in 1 in which the apparatus further comprises fifth means for measuring any stretch or bending of each press column, said fifth means including a number of strain gauges or linear transducers.
18. A method of facilitating correct operation of a press having a work-receiving container and a pressing stem including the step of measuring, in two directions substantially at right-angles, relative displacement of the axis of the stem and the axis of the container during passage of the stem into the container.
19. A method as claimed in claim 18, including the further step of measuring the relative displacement between the downstream end face of the container and the upstream face of the main bolster or platen in two directions substantially at right-angles.
20. A method as claimed in claim 18, including the further step of measuring the relative displacement between the press stem or moving crosshead or main ram and the press-bed during extrusion in two directions substantially at right-angles.
21. A method as claimed in claim 18, including the further step of measuring the relative displacement between the press platen and the press-bed during extrusion in two directions substantially at right-angles.
22. A method as claimed in claim 18, including the further step of measuring any stretch or bending of each press column.
1. Apparatus for facilitating correct operation of a press having a work-receiving container and a pressing stem, the apparatus comprising first means for detecting the relative displacement of the axis of the container and the axis of the stem, said means comprising two detectors arranged substantially at right-angles and disposed adjacent the upstream end of the container, said detectors being adapted to indicate any relative movement of the outer peripheral surface of the stem towards or away from said detectors during passage of the stem into the container.
2. Apparatus as claimed in claim 1 in which the detectors are mounted in grooves provided in the upstream end face of the container.
3. Apparatus as claimed in claim 1, in which the detectors are wide gap air gauges.
4. Apparatus as claimed in claim 1 in which the apparatus further comprises second means for detecting the relative displacement between the downstream end face of the container and the upstream face of the press platen or bolster, said second means comprising two detectors arranged substantially at right-angles and disposed adjacent the upstream face of the press platen or bolster, said detectors being adapted to indicate any relative movement of the downstream end face of the container towards or away from the detectors.
5. Apparatus as claimed in claim 4, in which the detectors of said second means are mounted in grooves provided in the upstream end face of the bolster or platen.
6. Apparatus as claimed in claim 4, in which each detector of the second means is adapted to indicate relative displacement of one end of a corresponding probe member, the other end of which is adapted to abut the downstream end face of the container.
7. Apparatus as claimed in claim 6, in which each probe member is carried by a rotatable holder for the press die assembly.
8. Apparatus as claimed in claim 7, in which the holder has two die assembly stations, two probes being associated with each station.
9. Apparatus as claimed in claim 6, in which each probe member comprises a rod, one end of which is spring-biased towards engagement with the container and the other end of which is provided with an axially adjustable member.
10. Apparatus as claimed in claim 4 in which the detectors of the second means are wide gap air gauges.
11. Apparatus as claimed in claim 1 in which the apparatus further comprises third means for detecting relative displacement between the press stem or the moving crosshead or the main ram and the press-bed during extrusion, said third means including a number of detectors mounted on the moving crosshead and adapted to indicate any relative displacement towards or away from the bed in two directions lying substantially at right-angles.
12. Apparatus as claimed in claim 11, in which said third means includes six detectors, two of which are adapted to detect relative displacement from a vertical plane, the other four detectors being placed two on either side of the crosshead to detect any relative displacement from a horizontal plane.
13. Apparatus as claimed in claim 11, in which the detectors of the third means are wide gap air gauges.
14. Apparatus as claimed in claim 1 in which the apparatus further comprises fourth means for detecting relative displacement between the press platen relative to the press-bed during extrusion, said fourth means including a number of detectors mounted on the press platen and adapted to indicate any relative displacement towards or away from the bed in two directions lying substantially at right-angles.
15. Apparatus as claimed in claim 14, in which the fourth means includes six detectors, two of which detect relative displacement from a vertical plane, the other four detectors being placed two on either side of the platen to detect any relative displacement from a horizontal plane.
16. Apparatus as claimed in claim 14, in which the detectors of the fourth means are wide gap air gauges.
17. Apparatus as claimed in 1 in which the apparatus further comprises fifth means for measuring any stretch or bending of each press column, said fifth means including a number of strain gauges or linear transducers.
18. A method of facilitating correct operation of a press having a work-receiving container and a pressing stem including the step of measuring, in two directions substantially at right-angles, relative displacement of the axis of the stem and the axis of the container during passage of the stem into the container.
19. A method as claimed in claim 18, including the further step of measuring the relative displacement between the downstream end face of the container and the upstream face of the main bolster or platen in two directions substantially at right-angles.
20. A method as claimed in claim 18, including the further step of measuring the relative displacement between the press stem or moving crosshead or main ram and the press-bed during extrusion in two directions substantially at right-angles.
21. A method as claimed in claim 18, including the further step of measuring the relative displacement between the press platen and the press-bed during extrusion in two directions substantially at right-angles.
22. A method as claimed in claim 18, including the further step of measuring any stretch or bending of each press column.
Description:
This invention relates to hydraulic presses, for example, extrusion and billet piercing presses and more particularly provides a method and apparatus for detecting relative displacement of a press component from its desired position.
In presses used for the hot extrusion of tubes, loss of production and spoiled products may be caused by misalignment of the press, or by relative movement of the press tools whilst under load. A number of other factors associated with the process may also cause the press to produce an eccentric product. It is at present difficult to differentiate between the various factors and detect which of them have been responsible for product inaccuracy. As a result, it often happens that much time is spent adjusting the alignment of the press with no improvement in the resulting product. Few, if any, data are provided by press builders to assist in either checking or correcting alignment.
Measurement of the relative positions of stem, container, die and mandrel, etc., during extrusion would present the press user with a picture of press alignment during extrusion. Such a picture would assist the press user in determining the causes of product eccentricity and would enable press mis-alignment to be corrected.
According to one aspect of the present invention there is provided apparatus for facilitating correct operation of a press having a work-receiving container and a pressing stem, the apparatus comprising the first means for detecting the relative displacement of the axis of the container and the axis of the stem during extrusion, said means comprising two detectors arranged substantially at right angles and disposed adjacent the upstream end of the container, said detectors being adapted to indicate any relative movement of the outer peripheral surface of the stem towards or away therefrom. The detectors can be mounted in grooves provided in the upstream end face of the container. The detectors are preferably wide gap air gauges.
The apparatus can further comprise second means for detecting the relative displacement between the downstream end face of the container and the upstream face of the press platen or bolster, said second means comprising two detectors arranged substantially at right-angles and disposed adjacent the upstream face of the press platen or bolster, said detectors being adapted to indicate any relative movement of the downstream end face of the container towards or away therefrom. The detectors of the second means can be mounted in grooves provided in the upstream end face of the bolster or platen. Each detector of the second means can be adapted to indicate relative displacement of one end of a corresponding probe member, the other end of which is adapted to abut the downstream end face of the container. Each probe member can be carried by a rotatable holder for the press die assembly. The holder can have two die assembly stations, two probes being associated with each station. Each probe member can comprise a rod, one end of which is spring-biased towards engagement with the container and the other end of which is provided with an axially adjustable member. Preferably, the detectors of the second means are wide gap air gauges.
The apparatus can further comprise third means for detecting relative displacement between the press stem or the moving crosshead or the main ram and the press-bed during extrusion, said third means including a number of detectors mounted on the moving crosshead and adapted to indicate any relative displacement towards or away from the bed in two directions lying substantially at right-angles. The third means can include six detectors two of which are adapted to detect relative displacement from a vertical plane, the other four detectors being placed two on either side of the crosshead to detect any relative displacement from a horizontal plane. Preferably, the detectors of the third means are wide gap air gauges.
The apparatus can further comprise fourth means for detecting relative displacement between the press platen relative to the press-bed during extrusion, said fourth means including a number of detectors mounted on the press platen and adapted to indicate any relative displacement towards or away from the bed in two directions lying substantially at right-angles. The fourth means can include six detectors, two of which detect relative displacement from a vertical plane, the other four detectors being placed two on either side of the platen to detect any relative displacement from a horizontal plane. Preferably, the detectors of the fourth means are wide gap air gauges.
The apparatus can further comprise fifth means for measuring any stretch or bending of each press column, said fifth means including a number of strain gauges or linear transducers.
According to a second aspect of the invention, there is provided a method of facilitating correct operation of a press having a work-receiving container and a pressing stem including the step of measuring the relative displacement of the stem relative to the container during extrusion in two directions substantially at right-angles.
The method can include the further step of measuring the relative displacement between the downstream end face of the container and the upstream face of the main bolster or platen in two directions substantially at right-angles.
The method can include the further step of measuring the relative displacement between the press stem or moving crosshead or main ram and the press-bed during extrusion in two directions substantially at right-angles.
The method can include the further step of measuring the relative displacement between the press platen and the press-bed during extrusion in two directions substantially at right-angles.
The method can include the further step of measuring any stretch or bending of each press column.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings of which:
FIG. 1 is an explanatory diagram showing a typical tool arrangement of an extrusion press;
FIG. 2 is a diagrammatic side elevation of an extrusion press incorporating the tool arrangement shown in FIG. 1 with certain modifications;
FIG. 3 is a section on the line 1--1 of FIG. 2;
FIG. 4 is a section on the line 2--2 of FIG. 2;
FIG. 5 is a view on the line 3--3 of FIG. 2;
FIG. 6 is an enlarged view of the container shown in FIG. 2 illustrating the position of one of the wide gap air gauges;
FIG. 7 is an enlarged view of the container shown in FIG. 4 illustrating the position of both wide gap air gauges;
FIG. 8 is an enlarged view of part of the die wheel shown in FIG. 2 illustrating the probe and gauge arrangement; and
FIG. 9 is an end view of the die wheel.
Referring to the drawings, the tool arrangement of a tube extrusion press is shown in detail in FIG. 1 and consists of a cylindrical container 1 into the bore 2 of which a billet 3 to be extruded is loaded. One end of the container is closed by a circular hole die assembly 4 which is located concentrically with the container axis by an accurately machined recess in the container end face into which the die assembly fits. The billet is pushed into the container bore and against the die assembly 4 by the stem 5, a cylindrical pressing disc 6 being interposed between the billet and the stem.
A mandrel 7, which passes through a preformed hole in the billet and which enters the die to leave an annular orifice through which the billet is extruded, is carried in a mandrel holder 8 which is housed within the stem 5.
As shown in FIG. 2, the tool assembly described is mounted within the hydraulic press used for extrusion. The press consists of a bed-plate 9 mounted on a massive concrete foundation block 10. The bed-plate carries at one end a main hydraulic cylinder assembly comprising a main cylinder 11 mounted in a crosshead 12, and a ram 13 secured to a moving crosshead 14. The latter is fitted with guide surfaces 15 (see FIG. 3) which are adapted to slide in guideways 16 provided on the bedplate.
The cylinder crosshead 12 is connected to the press platen 17 arranged at the other end of the bed-plate by means of four columns 18. The container 1 is mounted within a holder 19 which is guided and slides axially in the slideways 16 provided on the bed-plate (see FIG. 4).
The press illustrated is for extruding steel and in common with such presses the die assembly 4 is held in a rotatable die wheel 20. As shown in FIG. 8, this wheel is made in two parts but it can be, and in fact more usually is, of unitary construction. The wheel 20 has two diametrically opposed die-receiving stations 21 and 22 (see FIG. 9) and is mounted on a rotatable shaft (not shown) lying parallel to the centreline of the press so that whilst one die assembly lies along the centreline of the press, the other die assembly lies outside the press where it may be conveniently changed.
In order to make it possible to detect movement of press components out of alignment during extrusion, a system of gauges as shown in FIG. 2 is proposed, the various groups of gauges being used to detect different types of movement which occur under load conditions. Referring to FIG. 2, the measurements taken by each gauge group are as follows, the lettered items corresponding with the reference letters on the drawing:
A. Alignment of stem to container measured on rectangular co-ordinates;
B. Angle of tilt of container relative to tool bolsters or platen;
C. Alignment of stem or moving crosshead or main ram assembly relative to bed-plate;
D. Alignment of platen relative to bed-plate;
E. Stretch and bending (if any) of each press column.
To measure the deviation of the container mouth relative to the stem axis, two wide gap air gauges g 1 , g 2 are positioned in rectangular grooves 23 machined in the end face of the container. (See FIGS. 4, 6 and 7). Instead of forming grooves, the gauges could be mounted in and protected by strips welded on to the end face of the container. Gauge g 1 is mounted to lie along the vertical centreline of the container and gauge g 2 along the horizontal centreline. The two gauges are capable of measuring a gap of up to 10 m.m. and the measurement taken by each is converted into an electrical signal by means of a strain gauge type transducer, not shown, and used to operate a moving coil indicator, not shown, or an instrument equipped with a chart recorder. The stem 5 itself is used as the measuring datum and, consequently, it should be truly cylindrical, but if it is of tapered form, two small flats can be provided on its outer periphery from which measurements are taken. In the former case, a slight inaccuracy occurs in measurement when deviations occur other than those on rectangular co-ordinates, but for all practical purposes, this inaccuracy may be neglected.
Wide gap air gauges are used for this particular measurement for the following reasons. Firstly, the gauge nozzles may be mounted slightly below the container bore surface so that they cannot be damaged during container changing. Secondly, the air supplied to the gauges can be kept on at all times except perhaps during the period the hot billet passes the gauge nozzles. Thirdly, the continuous passage of air through the nozzles will assist in keeping them clear of particles of dust and scale and also tends to keep the nozzles reasonably cool. Fourthly, no rubbing contact occurs between the gauge and the stem. Finally, either simple manometers, moving coil electrical meters or recording chart type meters may be used depending upon conditions and the speed of response required.
The system described above provides absolute measurements of container displacement. It would also be possible to take differential measurements by arranging four gauges in two diametrically opposite pairs angularly spaced by 90°. Such a system would be self-compensating with regard to temperature changes, but it can give rise to difficulties. In particular, because of the conditions obtaining in and around the area of the press container, the gauges situated below the press axis would be susceptible to clogging by molten glass, glass dust, etc. in the atmosphere.
The above arrangement enables any parallel mis-alignment of the container to the stem axis to be measured. Measurement of "tilt" or inclination of the container axis to the stem axis would be ideally made by two further gauges measuring between the container and stem and spaced at some appreciable distance from the gauges g 1 and g 2 . However, such a system is not practically possible for a number of reasons, notably wear of the container bore, difficulties in fitting measuring devices on the stem, and clogging of the nozzles by the billet material glass lubricant or scale.
Since a direct measurement of "tilt" by two pairs of gauges placed on rectangular co-ordinates cannot be applied for the above reasons, another system of indirect measurement must be adopted. This involves taking the measurement of displacement of the container mouth relative to the stem as described above and also measuring the tilt of the container relative to the main platen or bolster as described below. Further refinements can also be employed, viz. monitoring the stem and platen alignment to the press bed-plate and monitoring the load in each press column also described below.
In order to measure container tilt relative to the bolster or platen face in the press construction illustrated, it is necessary to transmit any container movement past or through the die wheel 20. This is achieved essentially by push rods mounted at approximately 90° to one another and as near to the vertical and horizontal axes of the press as is permitted by the construction of the die wheel, main bolster and platen. More particularly, the equipment which is shown in FIG. 2 and in more detail in FIGS. 8 and 9 consists of two pairs of spring-loaded push rods P 1 , P 2 ; P 3 , P 4 , housed in bush-holders 24 bolted to the die rotate wheel 20. The push rod assemblies are completely enclosed by metal bellows 25 to protect the bearing bushes from seizure by glass dust, scale, etc. The push rods have hardened hemispherical ends 26 which bear against the die end face of the container. At the main bolster end, the push rods have hard-faced screwed cap-nuts 27 and lock nuts 28 to enable the two push rods to be adjusted to identical lengths one to the other. One pair of push rods are fitted at each die station 21 and 22.
Two wide gap air gauges, only one of which g 3 is illustrated, are mounted in recesses 29 machined in the main bolster 30 and are angularly spaced by about 90°, the nozzles of the air gauges being positioned about 2 m.m. below the face of the main bolster. Alternatively, the gauges could be mounted in the press platen 17.
The push rods mounted in the die rotate wheel are arranged so that when the container closes against the die, it pushes the rods towards the platen so that when the container is sealed, there is a gap of about 3 m.m. between the nozzles of the gauges and the cap nuts at the end of the push rods.
The air pressure signals from the gauges will be converted into electrical signals by means of a strain gauge type transducer (not shown) and used to operate a moving coil electrical indicator or an instrument equipped with a chart recorder.
As in the case of the container mouth deviation gauges described above, visual measurements may be taken from either manometer or moving coil indicators, or the measurements may be recorded on a chart type instrument.
Wide gap air gauges have been chosen for this application for the same reasons as in the case of the container mouth to stem deviation measurement.
To monitor the deviation of the stem, moving crosshead or main ram assembly relative to the bed-plate, six wide gap air gauges are mounted in gauge-holders 31 attached to the moving crosshead 14. The six air gauges, only five of which, g 4 , g 5 , g 6 , g 7 , and g 8 are illustrated, are mounted as shown in FIGS. 2 and 3 and will measure off two rectangular gauge bars 32 shown diagrammatically in FIG. 3 secured to the press bed-plate. The gauge bars are accurately fitted to the bed-plate by brackets (not shown) so that their two datum faces are parallel to the press centreline.
Two of the gauges g 4 , g 5 , measure any departure from accurate alignment of the crosshead in a vertical plane and are connected to an instrument which will indicate the differential between the two gauges.
The other four gauges, only three of which g 6 , g 7 and g 8 are illustrated, are placed two on either side of the crosshead and indicate any departure from a horizontal plane of the crosshead either in the form of a departure from the press axis or any tendency for the moving crosshead to roll on the bed-plate guide surface.
The six gauges proposed are wide gap air gauges, and as with the previously described measurements, each gauge measurement is converted into an electrical signal by means of a strain gauge type transducer, not shown, and used to operate a moving coil electrical indicator or an instrument equipped with a chart recorder. Wide gap air gauges have been chosen for this application for similar reasons as those given above in the case of the deviation of container mouth to stem measurement. However, it would be possible in this case to use gauges working on a narrow gap, since here the gauges are mounted in a more protected position on a press component which is not subjected to crane handling during tool changing.
To monitor the position of the platen axis and the seating face of the main bolster during extrusion, a similar method of measurement is proposed to that for monitoring main ram alignment. (See FIGS. 2 and 5). Again, six gauges are used, only five of which, g 9 , g 10 , g 11 , g 12 and g 13 , are illustrated.
The gauges are mounted in gauge-holders 33 secured to the platen and measure off two rectangular gauge bars 34 secured to the bed-plate, as shown in FIGS. 2 and 5.
Two of the gauges g 9 and g 10 measure any departure from accurate alignment of the platen in plan view and are connected to an instrument which will indicate the differential between the two gauges.
The other four gauges, only three of which, g 11 , g 12 and g 13 , are illustrated, are placed two on either side of the platen and indicate any departure from the horizontal of the platen. The six gauges may be of the same type used for measuring the displacement of the moving crosshead relative to the bed-plate.
Although in the measurements described above it is preferable to use wide gap air gauges for reasons already specified, it would, of course, be possible to use conventional air gauges or other types of detectors such as photocells, electrical contact gauges, etc.
A number of strain gauges or linear transducers are affixed to the press columns and the readings for each column are compared during extrusion. Four such gauges, g 14 , g 15 , g 16 and g 17 , illustrated in FIG. 2, are mounted on each column to measure both the stretch and bending of the columns, the four gauges being mounted in two diametrically opposite pairs.
In presses used for the hot extrusion of tubes, loss of production and spoiled products may be caused by misalignment of the press, or by relative movement of the press tools whilst under load. A number of other factors associated with the process may also cause the press to produce an eccentric product. It is at present difficult to differentiate between the various factors and detect which of them have been responsible for product inaccuracy. As a result, it often happens that much time is spent adjusting the alignment of the press with no improvement in the resulting product. Few, if any, data are provided by press builders to assist in either checking or correcting alignment.
Measurement of the relative positions of stem, container, die and mandrel, etc., during extrusion would present the press user with a picture of press alignment during extrusion. Such a picture would assist the press user in determining the causes of product eccentricity and would enable press mis-alignment to be corrected.
According to one aspect of the present invention there is provided apparatus for facilitating correct operation of a press having a work-receiving container and a pressing stem, the apparatus comprising the first means for detecting the relative displacement of the axis of the container and the axis of the stem during extrusion, said means comprising two detectors arranged substantially at right angles and disposed adjacent the upstream end of the container, said detectors being adapted to indicate any relative movement of the outer peripheral surface of the stem towards or away therefrom. The detectors can be mounted in grooves provided in the upstream end face of the container. The detectors are preferably wide gap air gauges.
The apparatus can further comprise second means for detecting the relative displacement between the downstream end face of the container and the upstream face of the press platen or bolster, said second means comprising two detectors arranged substantially at right-angles and disposed adjacent the upstream face of the press platen or bolster, said detectors being adapted to indicate any relative movement of the downstream end face of the container towards or away therefrom. The detectors of the second means can be mounted in grooves provided in the upstream end face of the bolster or platen. Each detector of the second means can be adapted to indicate relative displacement of one end of a corresponding probe member, the other end of which is adapted to abut the downstream end face of the container. Each probe member can be carried by a rotatable holder for the press die assembly. The holder can have two die assembly stations, two probes being associated with each station. Each probe member can comprise a rod, one end of which is spring-biased towards engagement with the container and the other end of which is provided with an axially adjustable member. Preferably, the detectors of the second means are wide gap air gauges.
The apparatus can further comprise third means for detecting relative displacement between the press stem or the moving crosshead or the main ram and the press-bed during extrusion, said third means including a number of detectors mounted on the moving crosshead and adapted to indicate any relative displacement towards or away from the bed in two directions lying substantially at right-angles. The third means can include six detectors two of which are adapted to detect relative displacement from a vertical plane, the other four detectors being placed two on either side of the crosshead to detect any relative displacement from a horizontal plane. Preferably, the detectors of the third means are wide gap air gauges.
The apparatus can further comprise fourth means for detecting relative displacement between the press platen relative to the press-bed during extrusion, said fourth means including a number of detectors mounted on the press platen and adapted to indicate any relative displacement towards or away from the bed in two directions lying substantially at right-angles. The fourth means can include six detectors, two of which detect relative displacement from a vertical plane, the other four detectors being placed two on either side of the platen to detect any relative displacement from a horizontal plane. Preferably, the detectors of the fourth means are wide gap air gauges.
The apparatus can further comprise fifth means for measuring any stretch or bending of each press column, said fifth means including a number of strain gauges or linear transducers.
According to a second aspect of the invention, there is provided a method of facilitating correct operation of a press having a work-receiving container and a pressing stem including the step of measuring the relative displacement of the stem relative to the container during extrusion in two directions substantially at right-angles.
The method can include the further step of measuring the relative displacement between the downstream end face of the container and the upstream face of the main bolster or platen in two directions substantially at right-angles.
The method can include the further step of measuring the relative displacement between the press stem or moving crosshead or main ram and the press-bed during extrusion in two directions substantially at right-angles.
The method can include the further step of measuring the relative displacement between the press platen and the press-bed during extrusion in two directions substantially at right-angles.
The method can include the further step of measuring any stretch or bending of each press column.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings of which:
FIG. 1 is an explanatory diagram showing a typical tool arrangement of an extrusion press;
FIG. 2 is a diagrammatic side elevation of an extrusion press incorporating the tool arrangement shown in FIG. 1 with certain modifications;
FIG. 3 is a section on the line 1--1 of FIG. 2;
FIG. 4 is a section on the line 2--2 of FIG. 2;
FIG. 5 is a view on the line 3--3 of FIG. 2;
FIG. 6 is an enlarged view of the container shown in FIG. 2 illustrating the position of one of the wide gap air gauges;
FIG. 7 is an enlarged view of the container shown in FIG. 4 illustrating the position of both wide gap air gauges;
FIG. 8 is an enlarged view of part of the die wheel shown in FIG. 2 illustrating the probe and gauge arrangement; and
FIG. 9 is an end view of the die wheel.
Referring to the drawings, the tool arrangement of a tube extrusion press is shown in detail in FIG. 1 and consists of a cylindrical container 1 into the bore 2 of which a billet 3 to be extruded is loaded. One end of the container is closed by a circular hole die assembly 4 which is located concentrically with the container axis by an accurately machined recess in the container end face into which the die assembly fits. The billet is pushed into the container bore and against the die assembly 4 by the stem 5, a cylindrical pressing disc 6 being interposed between the billet and the stem.
A mandrel 7, which passes through a preformed hole in the billet and which enters the die to leave an annular orifice through which the billet is extruded, is carried in a mandrel holder 8 which is housed within the stem 5.
As shown in FIG. 2, the tool assembly described is mounted within the hydraulic press used for extrusion. The press consists of a bed-plate 9 mounted on a massive concrete foundation block 10. The bed-plate carries at one end a main hydraulic cylinder assembly comprising a main cylinder 11 mounted in a crosshead 12, and a ram 13 secured to a moving crosshead 14. The latter is fitted with guide surfaces 15 (see FIG. 3) which are adapted to slide in guideways 16 provided on the bedplate.
The cylinder crosshead 12 is connected to the press platen 17 arranged at the other end of the bed-plate by means of four columns 18. The container 1 is mounted within a holder 19 which is guided and slides axially in the slideways 16 provided on the bed-plate (see FIG. 4).
The press illustrated is for extruding steel and in common with such presses the die assembly 4 is held in a rotatable die wheel 20. As shown in FIG. 8, this wheel is made in two parts but it can be, and in fact more usually is, of unitary construction. The wheel 20 has two diametrically opposed die-receiving stations 21 and 22 (see FIG. 9) and is mounted on a rotatable shaft (not shown) lying parallel to the centreline of the press so that whilst one die assembly lies along the centreline of the press, the other die assembly lies outside the press where it may be conveniently changed.
In order to make it possible to detect movement of press components out of alignment during extrusion, a system of gauges as shown in FIG. 2 is proposed, the various groups of gauges being used to detect different types of movement which occur under load conditions. Referring to FIG. 2, the measurements taken by each gauge group are as follows, the lettered items corresponding with the reference letters on the drawing:
A. Alignment of stem to container measured on rectangular co-ordinates;
B. Angle of tilt of container relative to tool bolsters or platen;
C. Alignment of stem or moving crosshead or main ram assembly relative to bed-plate;
D. Alignment of platen relative to bed-plate;
E. Stretch and bending (if any) of each press column.
To measure the deviation of the container mouth relative to the stem axis, two wide gap air gauges g 1 , g 2 are positioned in rectangular grooves 23 machined in the end face of the container. (See FIGS. 4, 6 and 7). Instead of forming grooves, the gauges could be mounted in and protected by strips welded on to the end face of the container. Gauge g 1 is mounted to lie along the vertical centreline of the container and gauge g 2 along the horizontal centreline. The two gauges are capable of measuring a gap of up to 10 m.m. and the measurement taken by each is converted into an electrical signal by means of a strain gauge type transducer, not shown, and used to operate a moving coil indicator, not shown, or an instrument equipped with a chart recorder. The stem 5 itself is used as the measuring datum and, consequently, it should be truly cylindrical, but if it is of tapered form, two small flats can be provided on its outer periphery from which measurements are taken. In the former case, a slight inaccuracy occurs in measurement when deviations occur other than those on rectangular co-ordinates, but for all practical purposes, this inaccuracy may be neglected.
Wide gap air gauges are used for this particular measurement for the following reasons. Firstly, the gauge nozzles may be mounted slightly below the container bore surface so that they cannot be damaged during container changing. Secondly, the air supplied to the gauges can be kept on at all times except perhaps during the period the hot billet passes the gauge nozzles. Thirdly, the continuous passage of air through the nozzles will assist in keeping them clear of particles of dust and scale and also tends to keep the nozzles reasonably cool. Fourthly, no rubbing contact occurs between the gauge and the stem. Finally, either simple manometers, moving coil electrical meters or recording chart type meters may be used depending upon conditions and the speed of response required.
The system described above provides absolute measurements of container displacement. It would also be possible to take differential measurements by arranging four gauges in two diametrically opposite pairs angularly spaced by 90°. Such a system would be self-compensating with regard to temperature changes, but it can give rise to difficulties. In particular, because of the conditions obtaining in and around the area of the press container, the gauges situated below the press axis would be susceptible to clogging by molten glass, glass dust, etc. in the atmosphere.
The above arrangement enables any parallel mis-alignment of the container to the stem axis to be measured. Measurement of "tilt" or inclination of the container axis to the stem axis would be ideally made by two further gauges measuring between the container and stem and spaced at some appreciable distance from the gauges g 1 and g 2 . However, such a system is not practically possible for a number of reasons, notably wear of the container bore, difficulties in fitting measuring devices on the stem, and clogging of the nozzles by the billet material glass lubricant or scale.
Since a direct measurement of "tilt" by two pairs of gauges placed on rectangular co-ordinates cannot be applied for the above reasons, another system of indirect measurement must be adopted. This involves taking the measurement of displacement of the container mouth relative to the stem as described above and also measuring the tilt of the container relative to the main platen or bolster as described below. Further refinements can also be employed, viz. monitoring the stem and platen alignment to the press bed-plate and monitoring the load in each press column also described below.
In order to measure container tilt relative to the bolster or platen face in the press construction illustrated, it is necessary to transmit any container movement past or through the die wheel 20. This is achieved essentially by push rods mounted at approximately 90° to one another and as near to the vertical and horizontal axes of the press as is permitted by the construction of the die wheel, main bolster and platen. More particularly, the equipment which is shown in FIG. 2 and in more detail in FIGS. 8 and 9 consists of two pairs of spring-loaded push rods P 1 , P 2 ; P 3 , P 4 , housed in bush-holders 24 bolted to the die rotate wheel 20. The push rod assemblies are completely enclosed by metal bellows 25 to protect the bearing bushes from seizure by glass dust, scale, etc. The push rods have hardened hemispherical ends 26 which bear against the die end face of the container. At the main bolster end, the push rods have hard-faced screwed cap-nuts 27 and lock nuts 28 to enable the two push rods to be adjusted to identical lengths one to the other. One pair of push rods are fitted at each die station 21 and 22.
Two wide gap air gauges, only one of which g 3 is illustrated, are mounted in recesses 29 machined in the main bolster 30 and are angularly spaced by about 90°, the nozzles of the air gauges being positioned about 2 m.m. below the face of the main bolster. Alternatively, the gauges could be mounted in the press platen 17.
The push rods mounted in the die rotate wheel are arranged so that when the container closes against the die, it pushes the rods towards the platen so that when the container is sealed, there is a gap of about 3 m.m. between the nozzles of the gauges and the cap nuts at the end of the push rods.
The air pressure signals from the gauges will be converted into electrical signals by means of a strain gauge type transducer (not shown) and used to operate a moving coil electrical indicator or an instrument equipped with a chart recorder.
As in the case of the container mouth deviation gauges described above, visual measurements may be taken from either manometer or moving coil indicators, or the measurements may be recorded on a chart type instrument.
Wide gap air gauges have been chosen for this application for the same reasons as in the case of the container mouth to stem deviation measurement.
To monitor the deviation of the stem, moving crosshead or main ram assembly relative to the bed-plate, six wide gap air gauges are mounted in gauge-holders 31 attached to the moving crosshead 14. The six air gauges, only five of which, g 4 , g 5 , g 6 , g 7 , and g 8 are illustrated, are mounted as shown in FIGS. 2 and 3 and will measure off two rectangular gauge bars 32 shown diagrammatically in FIG. 3 secured to the press bed-plate. The gauge bars are accurately fitted to the bed-plate by brackets (not shown) so that their two datum faces are parallel to the press centreline.
Two of the gauges g 4 , g 5 , measure any departure from accurate alignment of the crosshead in a vertical plane and are connected to an instrument which will indicate the differential between the two gauges.
The other four gauges, only three of which g 6 , g 7 and g 8 are illustrated, are placed two on either side of the crosshead and indicate any departure from a horizontal plane of the crosshead either in the form of a departure from the press axis or any tendency for the moving crosshead to roll on the bed-plate guide surface.
The six gauges proposed are wide gap air gauges, and as with the previously described measurements, each gauge measurement is converted into an electrical signal by means of a strain gauge type transducer, not shown, and used to operate a moving coil electrical indicator or an instrument equipped with a chart recorder. Wide gap air gauges have been chosen for this application for similar reasons as those given above in the case of the deviation of container mouth to stem measurement. However, it would be possible in this case to use gauges working on a narrow gap, since here the gauges are mounted in a more protected position on a press component which is not subjected to crane handling during tool changing.
To monitor the position of the platen axis and the seating face of the main bolster during extrusion, a similar method of measurement is proposed to that for monitoring main ram alignment. (See FIGS. 2 and 5). Again, six gauges are used, only five of which, g 9 , g 10 , g 11 , g 12 and g 13 , are illustrated.
The gauges are mounted in gauge-holders 33 secured to the platen and measure off two rectangular gauge bars 34 secured to the bed-plate, as shown in FIGS. 2 and 5.
Two of the gauges g 9 and g 10 measure any departure from accurate alignment of the platen in plan view and are connected to an instrument which will indicate the differential between the two gauges.
The other four gauges, only three of which, g 11 , g 12 and g 13 , are illustrated, are placed two on either side of the platen and indicate any departure from the horizontal of the platen. The six gauges may be of the same type used for measuring the displacement of the moving crosshead relative to the bed-plate.
Although in the measurements described above it is preferable to use wide gap air gauges for reasons already specified, it would, of course, be possible to use conventional air gauges or other types of detectors such as photocells, electrical contact gauges, etc.
A number of strain gauges or linear transducers are affixed to the press columns and the readings for each column are compared during extrusion. Four such gauges, g 14 , g 15 , g 16 and g 17 , illustrated in FIG. 2, are mounted on each column to measure both the stretch and bending of the columns, the four gauges being mounted in two diametrically opposite pairs.