GB2282887A - Means detecting relative positions in extrusion apparatus - Google Patents

Abstract

Detection means D, FIG 1, detecting the relative positions of two relatively rotatable members, particularly a pad 10 and a stem 12 of a metal extrusion apparatus 14 comprises a pressurised fluid system, part of which is shown generally at 16 defined by conduits 18 and an annular space 20 defined between the pad 10 and the means 40 mounting the pad 10 on the stem 12. The system is further defined by a series of annular grooves 54 in the pad 10, the face 36 of which abuts and seals against the stem 12. The grooves 54 are coaxial and equi-spaced about the axis of rotation of the members 10, 12, and each connects a respective conduit 18 and hence a fluid supply and sensing means 22, FIG 4, with the space 20. The sensing means 22 is operable to sense the pressure of the fluid at at least two points in the space so as to detect variations of pressure within the system and thereby detect and monitor the relative positions of the pad 10 and the stem 12. <IMAGE>

Description

Improvements in or Relating to Extruding Apparatus The present invention concerns improvements in or relating to extruding apparatus, and particularly but not exclusively to direct metal extruding apparatus.

Conventional direct metal extruding apparatus operates by forcing a heated billet of metal, such as aluminium, directly through a die to form an extrusion product. The billet is forced through the die by a hydraulically driven ram which acts on the billet through a stem. At the end of the stem is a pad or block, which in use contacts the billet.

There are several conventional types of pad or block, each being provided to generally protect the end of the stem during operation and also to provide a seal against the inside of a liner of a container through which the billet is being pushed and guided as it is being forced through the die. The seal prevents the metal from seeping backwards through the container over the stem.

One type of block, conventionally termed a dummy block, is removably locatable on the end of the stem by location of a projection on the stem in a recess in the block. During the extrusion process, the projection is held in the recess. However, when each extrusion process is complete and the stem is withdrawn, the block falls off the stem. It is then necessary for the block to be collected and separated from any residual part of the billet, to be remounted on the stem. This is inconvenient and time consuming.

A further type of known block is conventionally termed a fixed pad. This type is fixed to the end of the stem to remain thereon even during withdrawal of the stem following an extrusion process. It is often found that these pads are difficult to align with the liner for efficient operation. Moreover, checks for alignment often involve optical equipment, the use of which is time consuming, inconvenient and requires specialist skills. Furthermore, optical alignment requires the apparatus to be substantially cold, and consequently production time is lost during such alignment procedures.

A further disadvantage of fixed pads is that they become hot through continual use and this detrimentally affects the quality of the extrusion product. During extrusion impurities such as oxidation products tend to move to the back of the billet. If the pad or block is relatively cool, which is generally the situation when dummy blocks are used, the impurities tend to remain at the back of the billet. However, when the pad or block is relatively hot, the impurities tend not to remain at the back of the billet but migrate into the main body of the billet such that they become incorporated in the extrusion product.

A further type of known pad, conventionally termed a floating fixed pad, is of generally similar design and function as the aforementioned fixed pad, but is designed to have limited radial movement on the stem, thereby permitting the pad to "float" to facilitate alignment. These pads suffer from the disadvantage that when the stem and pad are withdrawn from the container, the pad tends to fall under gravity to a position of non-alignment. It is often found that re-alignment from this fallen position is difficult and moreover detection of the relative position of the pad on the stem is normally only possible when the pad is outside the liner.

It is an object of the present invention to obviate or mitigate some or all of the above disadvantages.

According to the present invention there is provided means for detecting the relative positions of two members, the detecting means comprising a fluid system which permits fluid to continuously flow through a space between the two members, and sensing means operable to sense the pressure of the fluid at at least two points in the space, to enable the detecting means to detect variations of pressure within the system and thereby detect the relative positions of the members.

The system preferably comprises an outlet of sufficiently large diameter to present no significant back pressure in the system.

Preferably the sensing means senses the pressure in the system on substantially opposite sides of a one of or a part of one of the members. The sensing means may sense the pressure at a plurality of points in the space so located to enable the means to detect relative movement of the members in all possible directions.

Preferably the means senses the pressure at four points to enable the detection means to detect movement in all directions in two dimensions.

The sensing means preferably communicates with said points in the space through separate conduits.

A fluid supply may be provided in communication with each of said conduits. The fluid supply may be pressurised such that the said fluid system is pressurised in use. Supply pressure control means may be provided to enable selective control of pressure of fluid supplied to the system.

Preferably the detecting means is operable to detect the relative positions of members when one of said members is surrounded, at least in part, by the other of said members. Preferably the space between the members is defined generally between the part of the said one member surrounded by the said other member, and the other member. Preferably the sensing points are equi-spaced around the space. Preferably each conduit communicating with the space at said points comprises a first part which extends from said space to a fluid supply, and a second part connecting the space and pressure sensing means. Preferably each conduit extends, at least in part, through both members. Each conduit preferably comprises a first section which extends from the said space through the said other member, and a second section extending through the one member to preferably connect to sensing means.

Preferably the detecting means is operable with members that are relatively rotatable. Preferably the first and second sections of each conduit are so formed to communicate with one another at any relative rotational position of the members.

Each first section may be defined by at least part of an annular recess formed in said other member, and a passage extending between the recess and the said space.

The annular recesses are preferably coaxial with the direction of rotation. Preferably each annular recess is at a different radial spacing about the said axis.

Sealing means may be provided to provide a fluid seal between the members, whilst permitting relative rotation between the members.

Means may be provided to cause relative movement between the members. The movement means may comprise a fluid pressure system operable to exert pressure between the members at one or more locations between the members, desirably within the said space, to cause said relative movement. The movement means may be provided, at least in part, by the system of the detection means.

The alignment means is preferably automatically actuated by the detection means.

Means may be provided for cooling fluid prior to supply to said fluid system.

Preferably the system is automated, and may be controlled by a computer.

Means may be provided to hold the members in general alignment. The means may comprise an elongate member which extends between said members, preferably generally along the axis of rotation. Preferably the elongate member is removable. The elongate member is preferably resilient, and preferably sufficiently resilient to hold the members in general alignment when no external forces are applied thereto.

The said one member may comprise a stem of a hydraulic ram, for example of extruding apparatus. The said other member may comprise a pad or dummy block, and desirably a collar of a pad of the type conventionally referred to as a floating fixed pad.

According to a further aspect of the present invention there is provided means substantially as defined in the preceding thirteen paragraphs for detecting the position of a movable member on a stem of a ram of extruding apparatus, the detecting means comprising a fluid system which permits fluid to continuously flow through a space between the member and the stem or means mounting the member on the stem, and sensing means operable to sense the pressure at at least two points in the space to enable the detecting means to detect variations of pressure within the system and thereby detect the relative positions of the member and the stem.

Preferably the pressure at the sensing points is substantially constant when the members pre correctly aligned.

Preferably the member is mounted on the stem to have limited radial movement but substantially no axial movement. Preferably the member is mounted on the stem by means extending between the member and the stem. The member may comprise an adaptor or collar removably fixed to a pad.

According to a still further aspect of the present invention there is provided a method of detecting the relative positions of two members, the method comprising providing a flow of fluid through a fluid system as defined in any of the preceding fourteen paragraphs, and sensing the pressure of the fluid at at least two points in a space between the two members, to enable detection of variations of pressure within the system and thereby detection of the relative positions of the members.

Extruding apparatus comprising detection means as defined in any of said preceding fourteen paragraphs.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a cross-section of the end of a stem of metal extruding apparatus with a floating fixed pad mounted thereon according to the present invention; Fig. 2 is a view in the direction II-II of the pad of Fig. 1; Fig. 3 is a schematic representation of extruding apparatus according to the present invention, incorporating the stem of Fig. 1; and Fig. 4 is a diagrammatic representation of part of detection means according to the present invention.

With reference to the drawings, there is provided detection means D for detecting the relative positions of two members, particularly a pad 10 and a stem 12 of direct metal extruding apparatus 14. The detection means D comprises a pressurised fluid system, part of which is shown generally at 16 (Fig. 4) defined generally by conduits 18 and an annular space 20 defined between the pad 10 and mounting means 40 mounting the pad 10 on the stem 12. Sensing means 22 is provided which is operable to sense the pressure of the fluid at at least two points in the space so as to detect variations of pressure within the system and thereby detect and monitor the relative position of the pad 10 on the stem 12.

In more detail, the detection means D is operable to detect the alignment of the pad 10 on the stem 12 of extruding apparatus 14, in which the pad 10 is of the type conventionally termed "a floating fixed pad". As with conventional floating fixed pads the pad 10 comprises an outer body 24, termed the main pad, which is generally bell-shaped. Inside the flared end 26 of the main pad 24 is a bell shaped engaging insert 28 hereinafter referred to as "the bell" as is conventional.

The bell 28 comprises a generally frusto-conicai portion 30 from which extends a projection 32 and a smaller diameter threaded projection 33 which extends into the main pad 24. A retaining nut 34 is located on the threaded projection 32 to cooperate with a collar formation 31 on the inside of the main pad 24 to retain the bell 28 in the main pad 24. Limited axial movement of the bell 28 in the main pad 24 is provided to enable the pad 10 to function. In use, the pad 10 pushes against a billet of metal, forcing it through a die to form an extrusion product. As it forces the billet, the bell 28 moves into the main pad 24 to flare the end 26 of the pad 10 out, to seal against the inside of a liner in a container, as will be hereinafter described.

The pad 10 also comprises a collar 36 threadedly attached to the main pad 24 by engagement of a threaded projection 37 on the collar 36 in a corresponding bore 39 in the other end 41 of the main pad 24. The collar 36 is provided to facilitate removal of the nut 34 and subsequent removal of the bell 28 for maintenance.

The pad 10 would conventionally be mounted on the stem 12 in the following manner. Before the collar 36 is attached to the main pad 24, it is rotatably mounted on the stem 12. The stem 12 comprises a threaded recess 38 in which the mounting means, in the form of a threaded pin 40 is engagable. The pin 40 comprises a threaded section 42 on the free end of a smooth shank 44 and an enlarged head 46. The collar 36 is rotatably mounted on the stem 12 by passage of the shank 44 of the pin 40 through a central bore 48 in the collar 36. The section 42 threadedly engages in the stem 12 such that the collar 36 is held between the stem 12 and the head 46. The pin 40 is tightened into the stem sufficiently to substantially restrain the collar 36 against axial movement, whilst enabling limited radial movement about the shank 44. The collar 36 is held against the end 62 of the stem to which the pad 10 is mounted sufficiently tightly to provide a fluid tight seal between the collar 36 and the stem 12, but to permit rotational and limited lateral movement. Sealing means (not shown) may be provided.

The pad 10 may then be threadedly engaged on the collar 36 and secured thereon by a retaining plate 50 fixed by a grub screw 52 across the outside of the junction between the pad 10 and the stem 36.

Referring particularly to Fig. 1 and Fig. 2, the collar 36 comprises a series of annular grooves 54 in the face 56 thereof which in use abuts and seals against the stem 12. The grooves 54 are coaxial and equispaced around the axis R. A passage 58 extends from each groove 54 to open at the wall of the bore 48 to provide communication between the grooves 54 and space 20. The passages 58 are located in the respective grooves 54 at generally 900 intervals around the collar 36.

With reference to Fig. 4, passages 60 are provided in the stem 12. Each passage 60 extends axially from the end 62 of the stem 12 to a radial fluid inlet 64 and a further conduit 66. The passages 60 are all differently radially spaced such that each passage 60 communicates with a respective groove 54, and hence passages 58.

An exhaust passage 68 is provided centrally in the stem 12 to communicate at one end with an exhaust passage 70 provided centrally in the pin 40. The exhaust passage 70 communicates with the space 20 by virtue of four radially extending branches 71. The exhaust passage 68 carries fluid out of the stem 12, for instance to a recycling container or to atmosphere.

The exhaust passages 70, 68 are of relatively large cross-section, such that the fluid exhausting therethrough provides negligible back pressure into the area 20.

Each inlet 64 comprises a restrictor 72 which can be used to control the pressure of fluid being inputted into the passages 60.

The further conduits 66 each extends from respective passages 60 to connect with a pressure sensor 22. Each further conduit 66 extends to a single sensor 22, such that the sensor 22 indicates variations in the distribution of the pressure with reference to four points within the system.

A retaining pin 74 is removably located in a recess 76 formed in the threaded projection 32 of the bell 28. The pin 74 extends from the threaded projection 32 to locate, in use, in a further recess 78 in the head 46 of the pin 40. The pin 74 may be pointed with the recess 78 shaped correspondingly. The pin 74 is resilient, and may be made of spring steel.

In use, the collar 36 is mounted on the stem 12 as described above, and the pad 10 mounted on the collar 36 such that the pin 74 locates in the recesses 76 and 78.

The pad 10 is fixed against movement relative to the collar by the retaining plate 50 and grub screw 52. The pad 10 and collar 36 are able to "float" on the end of the stem 12. That is, limited radial movement about the stem 12 is possible. Moreover, the collar 36 and pad 10 are able to rotate, as one, on the stem 12.

The pin 74 holds the pad 10 and collar 36 generally in alignment with the stem 12, by preventing the pad 10 and collar 36 falling downward relative to the stem 12, under gravity. The pin 74 however, does permit some forced radial movement of the pad 10, due to its resilience.

The alignment of the pad 10 on the stem 12 is then checked with reference to the sensor 22. Pressurised fluid is fed into each inlet 64 such that the system of conduits and the space 20 is pressurised. When the pad 10 is in coaxial alignment with the stem 12, the distance between the outer surface of the shank 44 of the pin 40 and the inner surface of the bore 48 is equal all the way around the circumference, such that the pressure of fluid in each passage 60 will be the same.

If the pad 10 moves out of alignment, then the pressure in the respective passages 60 will differ, and this is detected by the sensor 22. With reference to Fig. 1, if the pad 10 and collar 36 fall relative to the stem 12, then the distance between the pin 40 and the upper part of the pad 10 is reduced and the distance between the lower part of the pad 10 and the pin 40 increases. As a consequence, the pressure in the upper passage 60 increases, with a concomitant decrease in the pressure in the lower passage 60. This is detected by the sensor 22 which provides an indication of the misalignment, preferably along with the direction and degree of misalignment. The provision of four or more conduits 60 communicating with the space 20 enables accurate determination of misalignment, although any number of sensing points may be used, with accuracy increasing with the member.

It is to be appreciated that the grooves 54 enable the system to operate at all rotational positions of the collar 36 and pad 10 on the stem 12.

The arrangement can be controlled wholly or partially by computer.

Once the stem 12 and pad 10 are correctly aligned the extrusion process can begin. With reference to Fig. 3 in particular, a billet B of metal such as aluminium, is placed between the stem 12 and a container C. The stem is then driven by a ram R to push the billet B through the container C until it abuts a die D.

The ram R then exerts further pressure, for example in the order of 1800-2000 tons of force on the billet B to force it through the die E to form an extrusion product.

As the stem 12 forces the billet B, the pad 10 flares as described above, to provide a slideable seal against the liner of the container C, thereby preventing seepage of metal back past the pad.

The detection system permits the relative alignment to be monitored throughout the extrusion process, such that should significant misalignment occur during extrusion, the ram R can be withdrawn to prevent expensive damage of the extruding apparatus.

Moreover, the flow of fluid, such as air, will act to cool the pad during extrusion. This effect will be increased if the fluid is cooled prior to supply to the system. This will help mitigate some of the problems of the prior art described above.

Various modifications may be made without departing from the spirit or scope of the present invention. For example, the fluid could be inputted along the passage 68 and 70 and exhausted through the respective passages 60.

If the sensor 22 detects misalignment, then the system may be adapted to input pressure along the appropriate passage or passages 60 to exert a required pressure between the pin 40 and the collar 36 at the appropriate place to cause relative movement of the collar 36 and pad 10 on the pin 40, and thereby align them.

Whilst endeavouring in the foregoing Specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims (50)

1. Detection means for detecting the relative positions of two members, the detecting means comprising a fluid system which permits fluid to continuously flow through a space between the two members, and sensing means operable to sense the pressure of the fluid at at least two points in the space, to enable the detecting means to detect variations of pressure within the system and thereby detect the relative positions of the members.

2. Detection means according to claim 1, in which the system comprises an outlet of sufficiently large diameter to present no significant back pressure in the system.

3. Detection means according to claim 1 or claim 2, in which the sensing means senses the pressure in the system on substantially opposite sides of a one of or a part of one of the members.

4. Detection means according to any preceding claim, in which the sensing means senses the pressure at a plurality of points in the space so located to enable the means to detect relative movement of the members in all possible directions.

5. Detection means according to claim 4, in which the means senses the pressure at four points to enable the detection means to detect movement in all directions in two dimensions.

6. Detection means according to any preceding claim, in which the sensing means communicates with said points in the space through separate conduits.

7. Detection means according to claim 6, in which a fluid supply is provided in communication with each of said conduits.

8. Detection means according to claim 7, in which the fluid supply is pressurised such that the said fluid system is pressurised in use.

9. Detection means according to claim 8, in which supply pressure control means is provided to enable selective control of pressure of fluid supplied to the system.

10. Detection means according to any preceding claim, in which the detecting means is operable to detect the relative positions of members when one of said members is surrounded, at least in part, by the other of said members.

11. Detection means according to claim 10, in which the space between the members is defined generally between the part of the said one member surrounded by the said other member, and the other member.

12. Detection means according to claim 10 or claim 11, in which the sensing points are equi-spaced around the space.

13. Detection means according to any of claims 6 to 12, in which each conduit communicating with the space at said points comprises a first part which extends from said space to a fluid supply, and a second part connecting the space and pressure sensing means.

14. Detection means according to any of claims 6 to 13, in which each conduit extends, at least in part, through both members.

15. Detection means according to claim 14, in which each conduit comprises a first section which extends from the said space through the said other member, and a second section extending through the one member to preferably connect to sensing means.

16. Detection means according to any preceding claim, in which the detecting means is operable with members that are relatively rotatable.

17. Detection means according to claim 16, in which the first and second sections of each conduit are so formed to communicate with one another at any relative rotational position of the members.

18. Detection means according to any of claims 15 to 17, in which each first section is defined by at least part of an annular recess formed in said other member, and a passage extending between the recess and the said space.

19. Detection means according to claim 18, in which the annular recesses are coaxial with the axis of rotation.

20. Detection means according to claim 18 or claim 19, in which each annular recess is at a different radial spacing about the said axis.

21. Detection means according to any of claims 16 to 20, in which sealing means is provided to provide a fluid seal between the members, whilst permitting relative rotation between the members.

22. Detection means according to any preceding claim, in which means is provided to cause relative movement between the members.

23. Detection means according to claim 22, in which the movement means comprises a fluid pressure system operable to exert pressure between the members at one or more locations between the members to cause said relative movement.

24. Detection means according to claim 23, in which the pressure system is operable to exert pressure within said space.

25. Detection means according to any of claims 22 to 24, in which the movement means is provided, at least in part, by the system of the detection means.

26. Detection means according to any of claims 22 to 25, in which the movement means is controlled by the detection means.

27. Detection means according to any of claims 7 to 26, in which means is provided for cooling fluid prior to supply by said fluid system.

28. Detection means according to any preceding claim, in which the system is automated.

29. Detection means according to any preceding claim, in which the system is computer controlled.

30. Detection means according to any preceding claim, in which means is provided to hold the members in general alignment.

31. Detection means according to claim 30, in which the means comprises an elongate member which extends between said members.

32. Detection means according to claim 30 or claim 31, in which the member extends generally along the axis of rotation.

33. Detection means according to any of claims 30 to claim 32, in which the holding means is removable.

34. Detection means according to any of claims 30 to 33, in which the holding means is resilient.

35. Detection means according to claim 34, in which the member is sufficiently resilient to hold the members in general alignment when no external forces are applied thereto.

36. Detection means according to any preceding claim, in which the said one member comprises a stem of a hydraulic ram.

37. Detection means according to any preceding claim, in which the one member comprises a ram of extruding apparatus.

38. Detection means according to any preceding claim, in which the said other member comprises a pad or dummy block.

39. Detection means according to claim 38, in which the other member comprises a collar of a pad of the type conventionally referred to as a floating fixed pad.

40. Detection means for detecting the position of a movable member on a stem of a ram of extruding apparatus, the detecting means comprising a fluid system which permits fluid to continuously flow through a space between the member and the stem or means mounting the member on the stem, and sensing means operable to sense the pressure at at least two points in the space to enable the detecting means to detect variations of pressure within the system and thereby detect the relative positions of the member and the stem.

41. Detection means according to any preceding claim, in which the pressure at the sensing points is substantially constant when the members are correctly aligned.

42. Detection means according to claim 40 or 41, in which the member is mounted on the stem to have limited radial movement but substantially no axial movement.

43. Detection means according to any of claims 40 to 42, in which the member is mounted on the stem by means extending between the member and the stem.

44. Detection means according to any of claims 40 to 43, in which the member comprises an adaptor or collar removably fixed to a pad.

45. A method of detecting the relative positions of two members, the method comprising providing a flow of fluid through a fluid system as defined in any of the preceding claims, and sensing the pressure of the fluid at at least two points in a space between the two members, to enable detection of variations of pressure within the system and thereby detection of the relative positions of the members.

46. Extruding apparatus comprising detection means according to any of the preceding claims.

47. Detection means substantially as hereinbefore described with reference to the accompanying drawings.

48. A method substantially as hereinbefore described with reference to the accompanying drawings.

49. Extruding apparatus substantially as hereinbefore described with reference to the accompanying drawings.

50. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.