GB2140370A

GB2140370A - Rotary indexing unit

Info

Publication number: GB2140370A
Application number: GB08314757A
Authority: GB
Inventors: James David Goody
Original assignee: ESTUARY AUTOMATION Ltd
Current assignee: ESTUARY AUTOMATION Ltd
Priority date: 1983-05-27
Filing date: 1983-05-27
Publication date: 1984-11-28
Also published as: GB2140370B; GB8314757D0

Abstract

In a rotary indexing unit of the kind comprising a circular table or turret (2, 3) and a pneumatically operated indexing device (15, 18), the indexing device is operated by a piston (20) of arcuate form the ends of which enter two arcuate cylinders (8, 9 and 10, 11) mounted within the confines of the table, and the table is provided at or adjacent its periphery with a circumferential series of drive pins carrying rollers (39) for successive engagement by the indexing device during each forward stroke of the piston and by locating and locking members (16) spring operable following each forward stroke of the piston to prevent movement of the table between successive indexing operations. <IMAGE>

Description

SPECIFICATION Rotary indexing unit This invention relates to rotary indexing units of the kind comprising a circular table or turret and a pneumatically operated indexing device acting thereon at a point adjacent the periphery of the table and the principal object of the invention is to provide such a unit which is compact in form and operates auto matically with a high degree of accuracy.

To this end, according to the invention, the indexing device is operated by a piston and cylinder assembly which extends in an arc within the confines of the rotary table, and the table is formed, at or adjacent its periphery, with a circumferential series of driven ele ments for engagement by the indexing device and also by locking means for preventing movement of the table between successive indexing operations.

A preferred embodiment of the invention will be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a plan view of the unit with the top removed; Figure 2 is a vertical section on the line B-B of Fig. 1; Figure 3 is a vertical section through one end of the piston and cylinder assembly; and Figure 4 is a vertical section on the line A-A in Fig. 1.

As shown in the drawings, a mounting plate 1 supports the lower end of a ring 2 which is closed at its upper end by a top plate 3 to form a table or turret which is rotatable relative to the plate 1 on bearings 35 running in wire races interposed between the inner face of the ring and inner race rings 4 and 5 secured together and to the mounting plate by screws 56. The centre of the top plate 3 is apertured to receive the upper end of a spigot 6, the lower end of which is received in a central aperture in the plate 1 and is provided with an external flange which is secured to the plate 1 by screws 59. The spigot 6 carries a collar 7 which engages, through a thrust washer 38, the upper end of a needle bearing assembly 24, 36, the lower end of which engages, through another thrust washer, the upper surface of the flange on the spigot.The needle bearing assembly 24, 36 is interposed between the spigot 6 and an arm 1 5 provided at its inner end with a bearing housing 1 4 surrounding the spigot. The outer end of the arm 1 5 carries a pivoted indexing lever 1 8 which is spring-biassed into the path of a circumferential series of drive pins mounted in a recess extending around the inner surface of the ring 2 and carrying upper and lower rotatable rollers 39. The inner end of the arm 1 5 is operatively connected to the mid-portion of an arcuate piston 20 concentric with the rotary table and extending at its ends into two cylinders of corresponding arcuate form which are alternately connectable to a source of air under pressure.Each cylinder is made up of upper and lower sector-like parts 8, 9 or 10, 11 and is closed at its end adjacent the other cylinder by an end plate 12 or 13.

The upper part 8 of the cylinder remote from the indexing lever 1 8 carries pivotally mounted locating and locking members 1 6 and 1 7 of segmental form. The locating member 1 6 is arranged immediately above the upper surface of the cylinder and is springbiassed in a clockwise direction towards the position illustrated in Fig. 1 in which it engages in front of the lower of the rollers 39 on one of the drive pins on the rotary table and the upper end of a pin 26 carried thereby engages the end of a resilient abutment in the form of a rubber tube 29-1.The lower end of the pin 26 carries a rotatable roller 25 which is positioned in the path of a release lever 1 9 pivotally mounted at 23 on the piston 20 and biassed in an anti-clockwise direction by a tension spring 46. The locking member 17 is vertically spaced from the top of the cylinder by a stem portion and a headed liner 42 and is spring-biassed in an anti-clockwise direction towards the position illustrated in Fig. 1 in which it engages behind the upper one of the rollers 39 on the drive pin already engaged by the locating member 16 and a pin 28-1 thereon engages another resilient abutment in the form of a rubber tube 29-2.

In operation, the closed ends of the air cylinders are alternately connected at predetermined intervals to a source of compressed air and in the position illustrated in Fig. 1 compressed air is about to be supplied to the left-hand cylinder while the right-hand cylinder is connected to exhaust. Supply of compressed air to the left-hand cylinder moves the piston 20 in a clockwise direction and the release lever 1 9 thereon engages the roller 25 to swing the locating member 1 6 out of the path of the drive pin engaged thereby to permit that pin to pass the locating member upon forward movement of the table after which the locating member is returned by its spring into the path of the next drive pin.

Movement of the piston 20 is also operative through the indexing arm 1 5 and indexing lever 1 8 to act on one of the drive pins on the opposite side of the table to rotate the table by an amount equal to the distance between successive drive pins and during this advancing movement of the table the locking member 1 7 yields against the action of its spring to permit the next drive pin on the table to pass the locking member.

On completion of the forward stoke of the piston 20, the locating member 1 6 is in engagement with the next drive pin and the locking member 1 7 is returned by its spring 44 into locking position behind said next drive pin to prevent any reverse movement of the table. The fluid connections to the cylinders are then automatically reversed to connect the left-hand cylinder to exhaust and the righthand cylinder to the compressed air source.

The piston then commences its return stroke in which it moves relative to the table and the indexing lever yields against the action of its spring 45 to permit the arm 1 5 to return with the piston to the position illustrated in Fig. 1.

During this return stroke of the piston the release lever 1 9 yields against the action of its spring to pass the roller pin 25 on the locating member 1 6 which has been returned by its spring into the position illustrated in Fig. 1 and the table is once again held firmly in position until the commencement of the next indexing step.

The extent of each indexing step is dependent upon the number and spacing of the driving pins on the table and this may be readily adjusted by increasing or reducing the number of pins.

Although we have referred to clockwise indexing movement of the table it will be understood that the direction of indexing movement may be readily reversed.

Claims

1. A rotary indexing unit comprising a circular table or turret provided with a peripheral series of internal drive members, a pneumatically operated piston and cylinder device which extends in an arc within the confines of the table, indexing means operable on one of said drive members in response to a forward stroke of the piston to rotate said table through a predetermined increment and locking means operable on another of said drive members following each forward stroke of the piston to prevent any movement of the table until the piston commences its next forward stroke.

2. A rotary indexing unit according to Claim 1, wherein said piston and cylinder device comprises an arcuate piston concentric with the rotary table and extending at its ends into two cylinders of corresponding arcuate form which are alternately connectable to a source of air under pressure.

3. A rotary indexing unit according to claim 1 or 2, wherein said indexing mew s comprises an arm angularly movable by said piston about the axis of rotation of said table and a lever pivotally mounted on said arm adjacent its outer end and spring-biassed into the path of movement of said drive members to rotate the table by an amount equal to the distance between successive drive members during each forward stroke of the piston.

4. A rotary indexing unit according to any preceding claim, wherein said drive members are pins mounted in a recess extending around the inner surface of a ring forming the outer wall of the table.

5. A rotary indexing unit according to claim 4, wherein said locking means operates on a part of the periphery of the table remote from that acted upon by said indexing means and includes a locating member of segmental form pivotally mounted on top of the cylinder, said locating member being spring-biassed towards a position in which it engages in front of one of the drive pins and being movable out of the path of said drive pins on commencement of each forward stroke of the piston by a spring-biassed release lever pivotally mounted on the piston.

6. A rotary indexing unit according to claim 5, wherein movement of the locating member into the path of said driving means is limited by engagement of the upwardly projecting portion of a pin thereon with an abutment on the cylinder.

7. A rotary indexing unit according to claim 6, wherein a portion of said pin projects below said locating member for engagement by said release lever.

8. A rotary indexing unit according to any one of claims 5 to 7, wherein said locking means also includes a locking member of segmental form pivotally mounted on top of the cylinder and spring-biassed towards a position in which it engages behind the drive pin already engaged by the locating member.

9. A rotary indexing unit according to claim 8, wherein movement of said locking member into the path of the driving pins is limited by the engagement of a pin thereon with a resilient abutment on the cylinder, said locking member being yieldable against the action of its spring on impact with the next successive drive pin during indexing of the table.

10. A rotary indexing unit substantially as hereinbefore described with reference to and as shown in the accompanying drawings.