GB2098520A

GB2098520A - Apparatus for the mechanical processing of annular workpieces

Info

Publication number: GB2098520A
Application number: GB8214348A
Authority: GB
Original assignee: Goetze GmbH
Current assignee: Goetze GmbH
Priority date: 1981-05-16
Filing date: 1982-05-17
Publication date: 1982-11-24
Also published as: FR2505711A1; GB2098520B; IT1150536B; DE3119533A1; IT8220836A0; DE3119533C2

Abstract

An apparatus (11) for lapping the joint edges of stacked piston rings (1) possesses a rotatable and drivable lapping rod (8) which, on the one hand, has a substantially greater axial dimension than the workpieces and, on the other hand, executes an axially oscillating movement relative to the workpieces. The lapping rod is preferably mounted, in the region of its ends, between at least three hard- metal plates which are adjustable as a function of the diameter of the exchangeable lapping rods. The workpieces are introduced into the apparatus by means of a vice (30), which serves as a bearing weight (35) for the workpieces, acting through elastic layer (37), and provides axial guidance by its jaws (33, 34). A single lapping rod with a diameter greater than the width of the piston ring gap or a pair of counter- rotating rods of smaller diameter may be used. <IMAGE>

Description

SPECIFICATION Apparatus for the mechanical processing of annular workpieces The invention relates to an apparatus for the mechanical processing, especially lapping, of the joint edges of annular workpieces cut open at a point on their periphery, especially individual piston rings or piston rings assembled into a stack, this apparatus consisting of at least one processing tool mounted so as to be rotatable and drivable.

Both when annular workpieces, especially piston rings, are cut open radially and when, in particular, piston-ring running faces are coated with wear-resistant materials such as chromium or molybdenum or with other hard alloys, burrs or excess material occur in the region of the joint edges. Precisely in the case of piston rings the problem arises that for functional reasons these must be made as sharp-edged as possible in the joint region, in order to keep the blow-by in this region as low as possible during operation.

To obtain burr-free edges between the axisparallel joint faces and the outer peripheral face of a piston ring, the piston rings were stacked with their joints aligned with one another and were clamped axially and the two joint faces were processed by means of a rotating profiled grinding wheel with an axis of rotation extending perpendicularly to the piston-ring axis. It happened very frequently, under these circumstances, that, due to the grinding tool, breaks in the wear-resistant running-face layer occurred in the region of the outer joint edges of the piston rings and consequently the rings in question became useless.

Furthermore, it is known from British Patent Specification 300,185 to remove burrs from piston rings in the region of their joint by means of a rotating grinding wheel, the axis of rotation of the grinding wheel here extending parallel to the piston ring axis. Either the piston rings are drawn onto a mandrel (processing of the outer peripheral face) or they rest individually under their own weight on the peripheral face of the grinding wheel by means of their inner joint edges. In the case of piston rings processed in this way, breaks in the running-face layer occurred in the same way during deburring or chamfering of the outer joint edges.

The object on which the invention is based is to improve an apparatus with a rotatable and drivable tool for the mechanical processing of the joint edges especially of coated piston rings or similar workpieces, so that layer breaks or other damage to the edges are prevented and, at the same time, relatively sharp joint edges are maintained.

This object is achieved, according to the invention, due to the fact that the processing tool consists of a lapping rod which has a substantially larger axial dimension than the workpiece, and that an axially oscillating relative movement can be executed between the lapping rod and the workpiece. As a result of the combined rotating and oscillating movement of the lapping rod, together with the relatively small removal of material in the lapping operation, which can be controlled via the lapping medium to be used, it is guaranteed that, on the one hand, burrs and excess material are removed completely and without breaks and, on the other hand, the processed workpiece edge remains virtually sharp-edged.This is, above all, due to the fact that not a relatively hard grinding tool, but a lapping rod is used, and in this case liquid or pasty, relatively soft lapping medium is added and the amount of burr material to be removed can be controlled by means of the lapping time.

Individual processing of the workpiece is possible in principle. Preferably, several axially relatively low piston rings are assembled into a stack and rest on the lapping rod by means of the two outer joint edges, the diameter of the lapping rod being greater than the joint width. This ensures a uniform burr removal on both joint edges simultaneously. It also appears appropriate if the workpiece is arranged to be stationary and the lapping rod to be movable. As a rule, piston rings are provided with a layer of especially wearresistant material only in the region of the outer peripheral face, namely the running face. By means of this apparatus, the inner joint edges of the piston rings or similar workpieces, such as synchronous rings, tension rings and the like, can, of course, also be processed.

In order, during processing of the two joint edges, to ensure uniform loading especially of the running-face layer and uniform wear of the lapping rod, it is proposed that the latter should, in addition to the axially oscillating movement, also execute an oscillating rotary movement.

For normal applications, the lapping rod is made cylindrical. When, for example, cut-open workpieces permitting or even requiring a more pronounced chamfer are to be processed, a conical lapping rod with an axis of rotation extending at an angle to the axis of the workpiece can be used.

According to a further idea of the invention, when cylindrical lapping rods are used, the axial ends of these are designed to taper conically, so that the central working region of the rod has a greater diameter than the two bearing points of the lapping rod at its ends. Thus, the tool wear which occurs to an intensified degree in the oscillating region of the lapping rod is counteracted, the rod then remaining essentially cylindrical over its entire operating life.

In order to remove burrs from the joint edges especially of piston rings and to smooth over fine breaks, the diameter of the lapping rod is designed in such a way that the fine chamfers arising extend approximately at an angle of 450.

A further advantageous design of the apparatus is to be seen in the fact that the lapping rod is mounted, in the region of its two axial ends, respectively between at least three hard-metal plates which are arranged at a specific angle to one another and which can be adjusted radially relative to the lapping rod. This results in the advantage that lapping rods of different dimensions can also be used for different workpiece diameters and/or joint widths.

When several workpieces, especially piston rings, are to be processed in one operation, their joints are aligned with one another on a separate apparatus and they are clamped axially by means of a vice and are introduced in this way into the apparatus according to the invention. There, the vice is released axially and the workpieces then extend with an axial play between the two jaws of the vice. The clamping jaws of the vice thus constitute, at the same time, axial guide stops for the piston rings during the lapping of the joint edges. In particular, because of their greater natural weight, relatively large workpieces rest on the lapping rod under their own weight only, whilst smaller and lighter workpieces can be pressed onto the latter by means of an additional weight arranged diametrically to the lapping rod.To prevent damage to the preferably coated outer peripheral face of the workpieces and to achieve uniform pressure on all the workpieces, the weight is provided with an elastic layer in its bearing region.

To simplify the apparatus as a whole, it is expedient to design the vice in such a way that the region connecting the two jaws is designed as an additional weight, so that only one part is necessary for clamping, guiding and weighting the workpieces.

In order to obtain not only axial but also radial guidance of the workpieces, plates extend on both sides of the workpieces and parallel to their axes with a radial play and can be adjusted radially, preferably as a function of the workpiece diameter.

According to a further advantageous idea of the invention which can be applied especially to relatively large workpieces with a relatively wide joint, two axis-parallel lapping rods, which can preferably be driven in opposing directions of rotation, are used for processing the joint edges, the diameters of these lapping rods being smaller than the joint width of the workpiece.

The invention is illustrated in the drawing and is described in more detail below. Figures 1 a and 1 b show basic diagrams of the processing operation with one or two lapping rods.

Figures 2 and 3 show two views of the apparatus according to the invention.

Figures 1 a and 1 b illustrate basic diagrams of the actual processing operation. Preferably piston rings 1 are to be processed, and these are provided, in the region of their outer peripheral face of the running face, with a wear-resistant layer 2 made, for example, of chromium. The piston rings 1 are cut open at a point on their periphery, resulting in a gap 3, the so-called joint.

After the piston rings 1 have been coated and/or rough-ground, there often remains on the edges 4, 5 excess material (burr) 6, 7 which would have a negative effect on the piston ring 1 during operation. It is important to remove this burr 6, 7 in such a way that edges which are as sharp as possible, that is to say only slight and scarcely noticeable chamfers, are obtained.

During this time, the piston rings 1 rest under their own weight either on one (Figure 1 a) or two (Figure 1 b) lapping rods 8, 9 and 10 by means of their joint edges 4, 5. During the processing operation, the lapping rods 8, 9 and 10 execute both a rotating and an axially oscillating movement. If there is only one lapping rod 8 (Figure 1 a), this executes, in addition to the oscillating axial movement, also an oscillating rotary movement. In this way, breaks in the edges are avoided when the burr 6, 7 is removed. When two axis-parallel lapping rods 9,10 (Figure 1 b) are used, these execute, in addition to the oscillating axial movement, opposing rotary movements. Two lapping rods 9, 10 of smaller diameter are used when the joint exceeds-a certain width, for example 20 mm.

Figures 2 and 3 show, in a front view and side view respectively, an apparatus 11 according to the invention which is designed according to the basic diagram of Figure 1 a. It essentially consists of plates 13, 14, 15 and 16 which are mounted on a base plate 12 and are adjustable relative to the workpiece 17 and between which the workpiece 17, here a stack composed of several piston rings, is retained both with an axial and with a radial play. Seen in an axial direction, recesses 18, 1 9 having the same distance from the base plate 12 and receiving the lapping rod 8 are made in the plates 13 and 14 carried by angle pieces 13a, 14a and located at the end faces of the workpiece.The plates 15, 16 extending parallel to the workpiece axis are carried by angle pieces 15a, 16a and are vertically adjustable so that they can be adapted in this way to different workpiece diameters, that is to say so that they can radially retain or guide the different workpieces. Starting from one end 21, the plates 1 3, 14 guiding the workpiece 17 axially are each provided with a slot 22. Hard-metal plates 24 forming part of the lapping-rod mounting are located at the bottom 23 of the slot 22. The lapping rod 8 resting on the hard-metal plates 24 is surrounded by two further hard-metal plates 26, 27 which are connected to a guide 25, rest against the periphery of the lapping rod 8 and are vertically adjustable according to the diameter of lapping-rod 8. A simple mounting for different lapping-rod diameters, which also still has relatively low wear, is provided in this way. The lapping rod 8 is connected via a coupling 28 to a drive 29 not shown in any more detail, which produces both an oscillating rotary movement and an oscillating axial movement. The workpiece 17 is introduced by means of a vice 30 into the apparatus 11 in such a way that the individual piston rings, their joints aligned with one another, rest on the lapping rod 8 by means of their outer joint edges 4, 5. At the same time, the vice 30 is guided in the slots 22 already mentioned.After the workpieces 17 have been introduced into the apparatus 11, the vice 30 is released axially, and the workpieces 17, here piston rings, rest with an axial play both between the jaws 33, 34 of the vice 30 and between the plates 13, 14. In order, especially in the case of piston rings with relatively large diameters (at least 60 mm), to prevent springing-up and an associated irregular deburring of the edges 4, 5, these are additionally pressed onto the lapping rod 8 by means of a weight 35, for example made of aluminium, connected to the vice 30. Both to prevent scratches or similar damage to the coated running face of the piston rings 17 and to press all the workpieces uniformly onto the lapping rod, the bearing face 36 of the weight 35 is provided with an elastic layer 37. When the piston rings 17 are arranged, as described above, in the apparatus 11 with a radial and axial play, the lapping rod 8 is moved via the drive 29 in such a way that, for example in the case of a workpiece length of 200 mm, the lapping rod 8 executes a stroke of approximately 60 mm and, at the same time, is rotated once through 360O during each stroke. Either the lapping medium is added continuously via lines not shown in any more detail or the lapping rod is smeared with this before the operation.

Claims

1. Apparatus for the mechanical processing of the joint edges of annular workpieces cut open at a point on their periphery, especially of individual piston rings or piston rings assembled into a stack, this apparatus comprising at least one rotatable processing tool in the form of a lapping rod, and means for effecting an axially oscillating relative movement between the lapping rod and the workpiece.

2. Apparatus according to claim 1, characterised in that the workpiece is arranged to be stationary and the lapping rod to be movable.

3. Apparatus according to claim 1 or 2, characterised in that during the axially oscillating movement the lapping rod executes an oscillating rotary movement.

4. Apparatus according to any of claims 1 to 3, characterised in that the lapping rod is made cylindrical.

5. Apparatus according to any one of claims 1 to 4, characterised in that in the region of its axial ends the lapping rod is made conical in such a way that the central working region has a greater diameter than the bearing points of the lapping rod at its ends.

6. Apparatus according to any of claims 1 to 5, charaterised in that in the region of its two axial ends the lapping rod is mounted between at least three hard-metal plates.

7. Apparatus according to claim 6, characterised in that the hard-metal plates are radially adjustable relative to the lapping rod.

8. Apparatus according to any of claims 1 to 7, characterised in that during the processing operation the workpiece is retained with an axial play between the jaws of a vice.

9. Apparatus according to claim 8, characterised in that there is diametrically to the lapping rod an additional weight pressing the workpiece onto the latter.

10. Apparatus according to claim 9, characterised in that the additional weight is provided with an elastic layer in its region facing the workpiece.

11. Apparatus according to claim 9 or 10, characterised in that the additional weight interacts with the vice.

12. Apparatus according to any of claims 1 to 11, characterised in that there are plates which extend on both sides of the workpieces, parallel to their axes and with a radial play.

13. Apparatus according to claim 12, characterised in that the plates are radially adjustable as a function of the workpiece diameter.

14. Apparatus according to any of claims 1 to 13, characterised in that the diameter of the lapping rod is only slightly greater than the width of the joint present in the workpiece.

1 5. Apparatus according to any of claims 1 to 13, characterised by the use of two axis-parallel lapping rods, the diameter of which is smaller than the joint width of the workpiece.

16. Apparatus according to claim 15, characterised in that the lapping rods can be driven in opposing directions of rotation.