GB2086778A - Method and apparatus for indexing of a crankshaft - Google Patents

Abstract

The invention provides means for rotatably indexing a crankshaft when mounted in one or more crank head fixtures CH of the grinding machine, through any angle from 0 DEG to 180 DEG by a combination of two movements, one of the main bearings MB, being a rotational one about the crank head spindle axis A1, and one of the pin P2 or set thereof to be ground being one approximately radially of this axis, with the two movements being effected substantially in unison and with the precise radial position of the crankpin to be ground relative to a previously ground pin P1 being established by accurate rotational positioning of the crank head spindle and by the end position of a radial indexer and locator comprising a member LA in contact with and acting against the previously ground pin P1 to effect movement thereof. <IMAGE>

Description

SPECIFICATION Method and apparatus for automatic radial indexing of a crankshaft The present invention relates to a method and apparatus for automatic radial indexing of a crankshaft in a Crankpin Grinding machine of the type referred to, for example, in Patent Number 998,078.

Normally crankshafts are rotated and located by two separate and independently operated means; the rotation being effected through radial index means, such as by a chuck, drive key or key way, and the location being effected by a plunger or abutment to establish the precise radial position.

This present invention provides means for rotating a crankshaft when mounted in one or more crank head fixtures of the grinding machine, through any angle from 0 to 180= by means of a combination of two movements, one rotational about the crank head spindle axis, and one approximately radially of this axis, whereby these two movements occur substantially in unison and the precise radial position of the crankpin to be ground relative to a previously ground pin is established by accurate rotational positioning of the crank head spindle and the end position of a radial indexer and locator comprising a member in contact with and acting against the previously ground pin. The radial indexer and locator may be attached to any part of the machine or structure except the rotatable crank spindle or attachments thereto.

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figures 1A to 1D are sequence diagrammatic sketches in end elevation of a two-throw crankshaft set in a grinding machine and illustrate the movements of the crankshaft in being indexed from a first to a second radial position; Figures 2A to 2E are similar figures to those of Figs. 1A to 1D illustrating, in respect of a three throw crankshaft, the crankshaft movements in indexing thereof from a first radial position to a second radial position;; Figures 3A to 3E show indexing of the three-throw crankshaft from a second to a third radial position, and Figures 4A to 4Eshow an alternative method of indexing the three-throw crankshaft from a second to a third radial position.

In the drawings, it is assumed that the crankshaft generally indicated at W is set in a grinding machine comprising means of safely unclamping the or each crank fixture (not shown) to a latched position (partially open).

This allows the crankshaft to be indexed in the crank fixture at the same time as the fixtutre itself is rotated.

The crankshaft W is loaded into the crank fixtures (manually or automatically) and an initial radial location position is established using some machined datum on the crankshaft i.e. milled pad on shaft web or hole in flange face. The first pin P1 (or set thereof), is ground by grinding wheel G utilising this location.

For the purpose of indexing the crankshaft in accordance with the invention a radial index/locator comprising an arm LA is mounted from the machine bed. When the first pin (or set thereof) is ground, the arm is applied to that crankpin in a preferably straight line motion, although a radial motion could alternatively be used. The important aspect of the path of the arm is that it passes through the axis of rotation of the crankhead CH and is sufficiently rigid to provide a repeatably accurate position of the crank shaft pin relative to this axis.

Referring now to Figs. 1 A to 1 D, before the arm 1A is applied, the crankshaft rotation is stopped so that a line passing through the axes of the ground pin and the main bearings, one of which MB is indicated in the drawings, lies at substantially 90 to the axis of the arm in the position the latter occupies when brought in engagement with the ground pin P1, and the crankhead fixture (or each of them as the case may be) is unclamped.

Pressure is applied to the locator arm when engaged with the ground pin while the crankhead is rotated, in this instance, in the direction shown by the arrow. This causes the ground pin, as viewed in the drawings, to move downwardly and, by the rotation of the main bearings, the further, unground pin P2 to start moving along an arc approximating to a radius of the crankhead spindle axis inwardly towards that axis, indicated at Al in the drawings.

These movements are continued with the ground pin moving still further downwardly and the unground pin inwardly (Fig. 1 C) until the crankhead rotation is accurately stopped to give the required angle of crankshaft rotation (Fig. 1 D). The crankshaft is then reclamped and the arm LA withdrawn.

In the case of the three-throw crankshaft comprising pins P1, P2 and P3 (or respective sets thereof) the crankshaft is indexed from the first radial position to the second thereof Figs. 2A to 2E) in substantially the same manner as the two throw crankshaft. Thus, the crankshaft rotation, after grinding of the first pin P1, is stopped with a line passing through the axes of the ground pin P1 and the main bearings at approximately 90 to the radially disposed arm LA, and the crankshaft unclamped. Then, by the movements as indicated in Figs. 2A to 2D the unground pin P2 is brought to lie on the axis of the crankhead spindle; the crankshaft then being reclamped and the arm withdrawn (Fig. 2E).

In the position in which the crankshaft is stopped in Fig. 2E, the first ground pin and the second pin to be ground are in line with the axis of the locator arm.

With the crankshaft in such a position, the indexing movements shown in Figs. 3A to 3E may be used to index the crankshaft from the second radial position thereof to the third; Fig. 3A showing the crankshaft in the Fig. 2E position with the locator arm engaged with the second ground pin P2. As in the previous indexing operation, the crankshaft is unclamped to permit the arm LA to effect downward movement of the pin the arm is engaged with and to permit rotation of the crankshaft.

In the subsequent movements of the crankshaft, particularly as shown in Figs. 3B to 3D, the mainbearings pass through the plain containing the crankhead spindle axis Al and the axis of the locator arm to bring the third pin P3 to the third radial position of the crankshaft; the clamp then being re-applied and the arm LA withdrawn.

In the alternative method of Figs. 4A to 4E, the rotation of the crankshaft after grinding of the second pin is stopped with the second ground pin and the mainbearing in the position shown in Fig. 2A. Then by the same movements as effected in indexing, the crankshaft from the first to the second radial position, and as shown in Figs. 4B to 4D, the third pin P3 is brought to the third radial position. Again, as indicated in Fig. 4E, the crankshaft is reclamped and the arm LA withdrawn.

The advantages of this melthod are that a positive application of the radial index/locator arm is always possible and for shafts with even angles of index only one accurate crankhead index position is required (i.e. no complex index wheel and plunger mechanism are required).

The first method of indexing for the third pin/s and others is somewhat more complex in that each angle of index is made relative to the first (initial) pin/s ground and therefore the crankhead indexing must comprehend all angles required. However, because every index is made relative to the first pin/s this is potentially a more accurate method.

The sequence diagrams show the arm being applied in a vertical plane. This is not essential and could be at any angle to suit the machine layout.

The direction of rotation of the crankhead during indexing is also not important: that shown is merely the most convenient, being the direction used during grinding. The relative angular position of the arm and the crankhead prior to indexing is not important, the 90 angle shown merely results in the least amount of rotation necessary to accomplish the required index.

It will be evident that greater numbers of indexes of even or odd angles can be achieved by repeated use of indexing movements as above described.

Claims (9)

1. A method for automatic radial indexing of a crankshaft when mounted in one or more crank head fixtures of the grinding machine, through any angle from 0 to 1 80'; wherein the indexing comprises a combination of two movements, one of the main bearings being a rotational one about the crank head spindle axis, and one of the pin or set thereof to be ground being one approximately radially of this axis, with the two movements being effected substantially in unison and with the precise radial position of the crankpin to be ground relative to a previously ground pin being established by accurate rotational positioning of the crank head spindle and by the end position of a radial indexer and locator comprising a member in contact with and acting against the previously ground pin to effect movement thereof.

2. A method according to claim 1, wherein said member is moved in a vertical plane on a path passing through the axis rotation of the or each crank head fixture.

3. A method according to claim 1 or 2, wherein a first indexing operation is carried out by stopping crank head rotation with a line intersecting the axis of the pin or set thereof which has been ground and the axis of main bearings of the crankshaft, passing normal to the line of movement of said member, and then bringing the member into engagement with the or a ground pin on a path passing through the axis of the or each crank head fixture while simultaneously, the main bearings are rotated about that axis, until the axis of the pin or set thereof next to be ground lies on the axis of the crank head fixture or fixtures.

4. A method according to any of the preceding claims, wherein a second indexing operation is carried out by stopping crank head rotation with a line intersecting the axes of the pin or set thereof first ground and the pin or set thereof second ground, lying parallel or in alignment with the path of movement of said member with the second ground pin or set thereof lying first in the direction of movement of the said member, and then moving said member first to engage the or a first ground pin to move the pin in the direction of movement of said member and then to permit return movement of the pin while simultaneously rotating the main bearings about the axis of the crank head fixture or fixtures, until the third pin or set thereof lies on the axis of the crank head fixture or fixtures.

5. A method according to claim 3, wherein a second indexing operation is carried out in substantially the same manner as the first indexing operation with the second ground pin or set thereof and the third pin or set thereof to be ground being moved in the same manner as were the first ground pin and the second pin to be ground in the first indexing operation.

6. A method according to claim 2 or any of the claims 3 to 5 as dependent thereon; wherein said member is moved on a line at 90 to the axis of the crank head or crank heads.

7. A method of automatic indexing of a crankshaft, substantially as hereinbefore described with reference to Figs. 1A to D, or to Figs. 2A to E, or to Figs. 3A to E or to Figs.

4A to E.

8. A grinding machine comprising means for automatically indexing a crankshaft mounted in the crank head fixture or fixtures thereof through any angle between 0 and 1 80' and comprising a radial index and locator member for engaging and moving a pin of the crankshaft radially of the axis of the crank head of crank heads, and means for effecting accurate rotational positioning of the spindle of the or each crank head; said means acting so that an indexing comprises a combination of two movements, one of the main bearings being a rotational one about the crank head spindle axis, and one of the pin or set thereof to be ground being one approximately radially of this axis, with the two movements being effected substantially in unison and with the precise radial position of the crankpin to be ground relative to a previously ground pin being established by accurate rotational positioning of the crank head spindle and by the end position of the radial indexer and locator.

9. A grinding machine comprising means for automatic radial indexing of a crankshaft mounted in the crank head or crank heads of the machine substantially as hereinbefore described with reference to Figs. 1A to D, or to Figs. 2A to E, or to Figs. 3A to E or to Figs.

4A to E of the accompanying drawings.