GB2079935A - Apparatus for orienting non- circular workplaces - Google Patents

Abstract

A piston ring blank 3, before the gap is cut, is centred by a frusto- conical surface 19 which engages the shoulders on either side of the gap region and a point opposite the gap region. A sensor 18 scans the periphery of the ring to find the gap region (minimum diameter) while the ring is held between turntable 17 and damping disc 16. The ring is oriented with reference to the measured position of the gap and removed by a slider 15 for stacking. In alternative constructions the sensor is rotated about the ring axis. The ring may be held in a turret which rotates between a loading station, an orienting station, and an unloading station. In the orienting station it may be rotated by contact with a housing which encloses a light source, the sensor being fixed and responding to passage of light between the centering device and the gap region of the ring. <IMAGE>

Description

SPECIFICATION Apparatus for orienting non-circular workpieces The invention relates to a method and an apparatus which operates in accordance therewith for orienting non-circular piston ring blanks having a closed (i.e. uninterrupted annular) circumference, in which the non-circular characteristic of the circumferential contour serves as a basis for correcting the position of the non-oriented piston ring blank.

A method and a device for controlling the position of non-circular workpieces are already known from DE-OS 28 00 618 and the corresponding published U.K. application No.

2,01 5,727A (7900214). The apparatus consists essentially of a rotatable workpiece holder, a device for scanning the circumference of the workpiece, an electronic calculator for processing the measurements and for controlling the position of the workpiece and a gripping device, which is mounted so as to be rockable and rotatable, for forwarding the workpiece in a positionally oriented condition. The procedure according to the method is approximately as follows: The workpiece - in this case a piston rings mounted on a drivable clamping mandrel which is composed of radially adjustable segments. The mandrel and the piston ring are then rotated in front of a ground glass plate behind which is located a light source.

During the rotation, the circumferential contour of the piston ring is scanned and the measured values are fed to a calculator. By making a comparison with a pre-programmed diagram of required values, the workpiece holder is rotated until the position of the piston ring conforms as far as possible with the diagram of required values.

The piston rings, which are thus oriented individually in the circumferential direction, are then engaged by a gripping device which is rockable about the shaft and rotatable about its own axis and are fed to a magazine or the like. A disadvantage of this method and of the apparatus which operates in accordance therewith is that, on the one hand, a relatively great amount of time is consumed as a result of the separate measurement of the entire circumference of the ring and the subsequent orienting of the latter as well as the conveying of the workpiece which only then takes place and, on the other hand, that a relatively large amount of calculation is necessary having regard to the displacement of the centre of the gripped ring during the comparison of the measured values with the diagram of required values.

Furthermore, an apparatus for positioning noncircular workpieces, especially piston rings, is known from DE-OS 28 40 863 and the corresponding published U.K. application No.

2,032,306A (7932284). This consists essentially of two drivable rollers or cylinders which are located one behind the other in the direction of rotation of the workpiece. The workpiece rests under the action of its own weight on the rollers or cylinders. Between the two rollers or cylinders is arranged a brake shoe having a main surface facing the workpiece, the height of which main surface bears a given ratio to the circumferential surfaces of the rollers or cylinders, so that the workpieces are braked in the region of the surfaces thereof which deviate from the normal non-circular contour and are thus positioned.This purely mechanical method of orienting noncircular workpieces has the disadvantage that differences can occur in the dispositions of the individual workpieces as a result of surfaces deviating to different extents from the normal noncircular contour, which can occur in the cast bodies to be positioned. In the case of surfaces of different sizes, it may happen that the brake shoe either brakes the workpiece and brings it to rest farther forward, or in the middle or farther back. It is thus possible that individual workpieces that have been oriented in this way and assembled in the form of a stack to be machined, will assume different positions with respect to one another, which have an undesirable effect on the machining of the workpieces.

It is apparent that the difficulty in the orienting of closed non-circular piston rings consists in the fact that the piston ring, as seen in the circumferential sense has several raised parts which, with the previously known devices, could be engaged and disposed in a given relationship, so as to discover a given position which holds good as a basis for the orientation of each of the piston rings, only with relatively great difficulty and only by carrying out complicated and timeconsuming operations.

Since moreover continuous progress is taking place in the technology relating to machine tools, and particularly lathes for machining non-circular workpieces, the time available for the main and auxiliary operations is also consequently reduced.

It accordingly follows that the time for the preparation of new stacks of piston rings for machining is becoming progressively shorter, so that the two devices mentioned above can no longer satisfy the advancing technology.

It is accordingly the object of the invention, having regard to the special difficulty of orienting non-circular, closed piston ring blanks, to provide a simple method and an apparatus which operates in accordance therewith, by means of which the time required for preparing oriented and stacked piston ring blanks for subsequent treatment is reduced to a minimum.

This object is achieved according to the invention in that the piston ring blank is centred on a rotational axis, which is the same for each series of rings, by means of the three maximum radius parts of its circumference, one in the region of the back of the ring and the other two on the two sides respectively of the position where the gap is subsequently to be formed and that the required angular correction is determined by scanning the circumference of the said blank until the part of minimum radius, at the position of the gap to be formed between the two maximum radius parts, is reached.

With the aid of this method it is possible to orient the piston rings very rapidly in the correct positions and then, after stacking them, to advance them for further processing. A further advantage over the state of the art, especially as disclosed in DE-OS 28 00 618, is that, in the method according to the invention, although the piston ring blank is likewise displaced from its original axis of rotation, in this case the displacement during orienting of its centre between its original axis of rotation and the axis of rotation which it is forced to assume need not be taken into account, since a given position is sought for each ring and the rings can all be suitably positioned at the same position.

An apparatus which operates in accordance with the invention is characterised in that the centring device consists of a socket with a frustoconical inner surface against which one of the two outer circumferential edges of the piston ring blank can be presented by means of the workpiece holder. Sockets are already known which have a cylindrical inner surface with a frusto-conical entrance portion, but these serve for compressing to a nominal diameter piston rings in which gaps have already been cut, so that they can thus be formed into stacks and held tightly for further processing. The holding of closed non-circular piston rings or even the packaging thereof in an oriented condition in this manner, i.e. by means of a socket having a cylindrical bore, is precluded by the unalterable non-circular contour of the piston rings.

According to a further preferred feature of the invention, either the workpiece holder consists of a plunger which forces the piston ring blanks into the frusto-conical interior of the socket or the workpiece holder feeds the piston ring blank forward and the socket is lowered onto the piston ring blank. In addition, there is advantageously arranged within the socket a clamping disk which is mounted so as to be axially movable towards the plunger, in which case the plunger and the clamping disk are also rotatably mounted and drivable. For example, after the socket has been lowered over the piston ring blank and has centred the latter, the piston ring blank, while still lying within the socket, is clamped axially between the plunger and the clamping disk and the socket is then lifted off the piston ring blank.The plunger and the clamping disk are then caused to rotate while one or more measuring probes scan parts or the whole of the circumference of the piston ring blank. When the required point is found, preferably the position of minimum radius between the two raised parts of the circumference of the piston ring blank in the region of the gap to be formed, the ring is brought to rest and then adjusted to the predetermined angular position from which the piston ring blank so oriented is advanced by means of known conveying devices and is deposited, for example, in an intermediate magazine.

Since the individual piston ring blanks, depending upon their starting positions, must be scanned at least over only a fraction of their circumference and at most over the whole of their circumference, there is obtained, according to the theory of probabilities, a total time factor, for a given number of rings to be oriented, which is substantially more favourable than, i.e. about half as great as, that which can be obtained by the method according to DE-OS 28 00 618.

According to another preferred feature of the invention, the centring socket is made in the form of a workpiece holder for the scanning procedure, this feature being based on the appreciation which follows from the invention that non-circular piston ring blanks have, as seen in the circumferential direction, three parts of maximum radius (raised parts? which enable the piston ring blank to resemble a polygon. According to further features of the invention, use is made of these raised parts which are difficult to determine in that each non-circular piston ring, as a result of being inserted into a circular section frusto-conical socket cavity, is caused to engage corresponding opposing wall surfaces of the latter by means of three parts of its own circumference.

In the region where the gap is to be formed, two raised parts lie relatively close together, as viewed circumferentially, which raised parts slope down towards the position of the gap to be formed later, where the radius of the piston ring is smallest, so that in this region for example a maximum amount of light can be transmitted and the gap position can therefore be easily determined. Another, somewhat more expensive way of precisely determining the gap position is first to determine the positions of the two closely adjacent parts of maximum radius and then to bisect the angle subtended by them.

Furthermore, it may be considered to be advantageous to provide an electro-optical scanning device for scanning the circumference of the ring, the optical axis of which device extends at an inclination corresponding to the conicity of the inner surface of the centring socket.

For the centring and scanning there may be provided at least two consecutive stations which are preferably arranged on a turntable or indexing plate. In the region of the scanning station a light source is arranged on one side of the piston ring blank and a light-intensity measuring device is arranged on the other side of the piston ring blank.

The light source is preferably enclosed within a bell-shaped housing which is movably mounted against the centring socket and is also rotationally drivable. In order to allow the light to shine through substantially only in the region being scanned, a ground glass plate is arranged within the bell-shaped housing. In order to provide for positive driving of the socket by the housing, one or each of the mutually contacting end surface of the centring socket and the housing is provided with a covering of friction material.

In addition, the following practical constructional variants may be considered to be advantageous, namely that the frusto-conical socket is mounted within an approximately L-section machine part - in this case also a machine part in the form of an adapter rings as to be able to accommodate centring sockets of different interior diameters in one and the same apparatus. In this case it is advantageous to provide, not the centring socket, but either one limb of the L-section machine part or the bellshaped housing or each of them with a friction coating.

The apparatus described above which operates according to the method of the invention may thus be fitted as an auxiliary unit not only in various different kinds of processing machines but also in machines for forming piston ring blanks into stacks and subsequently conveying the stacks to a machining station. Likewise, it is also possible for the apparatuses or the processing machines to be fitted with an intermediate magazine for the reception of the oriented workpieces, in which intermediate magazine the individua! workpieces can be assembled into stacks which are then conveyed to a machine for further processing.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a plan view of a non-circular piston ring blank within a centring device, and Figures 2 and 3 are diagrammatic vertical sections of apparatuses for orienting non-circular piston ring blanks.

In order to emphasise the basic idea of the invention, Figure 1 shows on a relatively large scale a centring device 1 against the frustoconical inner surface 2 of which. a non-circular closed piston ring blank 3 is supported so that three supporting zones 4, 5, 6 are formed. In the gap zone 7, i.e. the region within which the piston ring gap will later be formed, two raised parts (parts of maximum radius) 8, 9, which lie close together as seen in the circumferential direction, are visible. If the piston ring blank 3 is now for example electro-optically scanned, the light penetrating between the gap zone 7 (part of minimum radius) and the inner circumferential surface 2 of the socket will be substantially greater than that in the other regions 10, 11.

Consequently, the gap zone 7, which is thus the smallest radius part of the outer circumference of the piston ring blank 3, can be easily determined.

An apparatus for carrying out the present method is illustrated diagrammatically in Figure 2.

The apparatus 12 consists essentially of a centring device 13, a feeding device in the form of a gripper 14 for the piston ring blank 3 and a removing device 1 5 in the form of a slider or the like. In addition, the apparatus 12 has two plungers 16, 17, one 17 of which has the form of a turntable and the other 16 that of a clamping disk, and a measuring probe 18 which is connected with a microprocessor (not shown). The way in which the apparatus 12 operates is as follows: The piston ring blank 3 is placed by the gripper 14 on the turntable 17 (the centring device 13 is in its raised position) and is then centred by the centring device 13, which is formed by a socket with a frusto-conical inner circumferential surface 19, i.e.

it is positioned with its centre-line in alignment with the axis 20 of rotation of the socket 13. The plunger 16 is arranged for sliding movement within the socket 13. After the piston ring blank 3 has been centred, the plunger 16 moves downward and the piston ring blank 3 is clamped axially between the plunger 16 and the turntable 17. The socket 13 is now raised and releases the piston ring blank 3, the outer circumference 21 of which is then scanned by the measuring probe 18 while the turntable 17 is rotating out of contact in order to find the position where the radius of the outer surface of the piston ring blank 3 is smallest, i.e. a position within the gap zone 7. The turntable 17 is then (if necessary) adjusted by the microprocessor (not shown) to the correct position and brought to rest.The plunger 16 is now raised and the piston ring blank 3 is removed from the turntable 17 by means of the slider 1 5 and deposited in a magazine or the like with the gap portion correctly oriented. If holding magnets are provided in the turntable 17, the apparatus 12 will be able to operate in a horizontal position (i.e. with the rotational axis of the turntable disposed horizontally). The time required for orienting each piston ring blank 3 is about one second, so that a relatively rapid positioning of the piston rings followed by stacking thereof for further processing is possible.

An apparatus 22, which constitutes an alternative solution and operates in accordance with the same method, is illustrated in Fig. 3. The apparatus 22 consists essentially of a turntable 23 provided with three rotatably mounted centring devices 24 each of which has a frusto-conical inner surface 25. The turntable 23 is driven by a shaft 26 so that it moves through three work stations: first a loading station 27, secondly an orienting station 28 and thirdly an unloading and stacking station 29. In the loading station 27 a plunger 30 forces the uppermost piston ring blank 3 of a stack 32 of such blanks in an adjustable magazine 31 into the frusto-conical cavity 25 of the centring device 24. When the plunger 30 descends together with the stack 32 of piston ring blanks, the uppermost piston ring blank remains suspended in the cavity 25.During this loading operation the orienting and unloading operations take place simultaneously at the stations 28 and 29. The working procedure at the station 28 the orienting stations as follows: The centring device 24 is mounted within a machine part 33 in the form of an L-section adapter ring. This machine part 33 is driven positively by a bellshaped housing formed by a flange 35 with a hollow cylindrical skirt 34, which bell-shaped housing is illuminated internally, the said flange 35 being driven by a plunger 36 which is rotationally driven by a motor (not shown). Within the upper region of the hollow cylindrical skirt 34 of the bell-shaped housing 34, 35 is a ground glass disk 44.The mutually confronting end surfaces of the machine part 33 and the skirt 34 are provided with layers 37, 38 of friction material to provide a better torque transmission between them. When the turntable 23 is stationary, the skirt 34 of the unit 34, 35 is pressed against the machine part 33. Using a light intensity measuring device 39 and a known calculating device (not shown), the orientation of the piston ring blank 3 takes place according to Figure 1, since the greatest amount of light is measured in the gap region 7 and the position where the gap is to be formed later is thus clearly determined. At the station 29 the ejector plunger 41 acts against the relatively low counter pressure of the plunger 40, so as to force the oriented piston ring blank 3 out of the frusto-conical cavity 25 of the centring device 24, so that this blank comes to rest on top of the stack 42 in the magazine 43 which can be lowered.

In the embodiment of Fig. 3 the piston ring blank is rotated until the measuring device 39 detects light transmission in the gap region 7, which is the only point at which significant light transmission occurs. Thus each blank is brought to the same orientation with respect to the measuring device. In a case where the blank is held stationary while the measuring device is rotated or where the whole periphery of the blank is scanned it may be necessary to correct the orientation of the blank after completion of the measurement.

Claims (14)

1. A method of orienting non-circular piston ring blanks having a closed circumference, in which the non-circular characteristic of the circumferential contour serves as a basis for the correction of the position of the non-oriented piston ring blank, characterised in that the piston ring blank is centred on a rotational axis, which is the same for each series of rings, by means of the three maximum radius parts of its outer circumference, one in the region of the back of the ring and the other two on the two sides respectively of the position where the gap is subsequently to be formed and that the required angular correction is determined by scanning the circumference of the said blank until the part of minimum radius, at the position of the gap to be formed between the two maximum radius parts, is reached.

2. An apparatus for orienting non-circular piston ring blanks having a closed circumference, comprising a centring device, a scanning device mounted for rotation, relatively to a piston ring blank arranged in a workpiece holder, about an axis extending through the centre of the said blank, and a control device for imparting to the said blank a correction movement according to the scanning of the circumference thereof by said scanning device, characterised in that the centr;ing device (1, 12, 24) consists of a socket with a frusto-conical inner surface (2, 1 9, 25) against which one of the two outer circumferential edges of the piston ring blank can be presented by means of the workpiece holder.

3. A device according to claim 2, characterised in that the workpiece holder (17) has the form of a plunger.

4. A device according to claim 2 or 3, characterised in that a plunger (1 6) is provided which is mounted for movement in opposition to a further plunger (17).

5. A device according to claim 3 or 4, characterised in that the or each plunger (16, 17) is rotatably mounted and drivable.

6. A device according to claim 2, characterised in that the centring socket (24) serves as the workpiece holder for the scanning operation.

7. A device according to any of claims 2 to 6, characterised in that an electro-optical scanning device is provided for scanning the circumference of the piston rink blank, the optical axis of which scanning device extends at an inclination corresponding to the conicity of the inner surface (25) of the centring socket (24).

8. An apparatus according to any of claims 2 to 7, characterised in that at least two consecutive stations (27, 28) are provided for the centring and scanning.

9. An apparatus according to any of claims 2 to 8, characterised in that the consecutive stations(27, 28) are arranged on a turntable (23).

10. An apparatus according to any of claims 2 to 9, characterised in that, in the region of the scanning station (28), a light source is arranged on one side of the piston ring blank (3) and a lightintensity measuring device (39) is arranged on the other side of the piston ring blank (3).

11. An apparatus according to claim 10, characterised in that the light source is housed within a bell-shaped housing (34, 35).

12. An apparatus according to claim 11, characterised in that the bell-shaped housing (3,4, 35) is movably mounted against the centring socket (24).

13. An apparatus according to claim 11 or 12, characterised in that the bell-shaped housing (3'4, 35) is rotationally drivable.

14. An apparatus according to any of claims 1 11 to 13, characterised in that one or each of the mutually contacting end surfaces of the centring socket (24) and the bell-shaped housing (34, 35) is provided with a covering (37, 38) of friction material.