GB2196924A - Assembling head arm stack subassemblies - Google Patents

Abstract

An assembly station for assembling head arm stack subassemblies in a a disk file comprises an assembly table (45) for supporting a stack (35) of head arms and other components of the subassembly. The table has an initial position in which it is adapted to receive the components in inverted order for bolting together and is pivotable about a horizontal axis from the initial position to a final position at which the subassembly is delivered to a rotary actuator platform (31). The assembly table is provided with gripping means e.g. (60, 61) for gripping the subassembly initially and during travel of the table and for subsequently releasing it to the actuator from the final position. The preferred gripping means is spring biassed towards a retracted position from which it is initially displaced by a stop (101). A sensor (102) senses disengagement from the stop to confirm correct operations of the gripping means and that the subassembly is securely held on the table. <IMAGE>

Description

SPECIFICATION Assembly station for assembling head arm stack subassemblies in a disk file Technical field of the Invention The present invention relates to assembly stations for assembling head arm stack subassemblies to a disk file rotary actuator.

Background Art A rotary actuator for positioning the heads of a magnetic disk file over selected tracks on the disk is shown in European patent 0031876-B1. This type of actuator resembles a conventional electric motor whose spindle is provided with an extension in the form of a platform. The platform is designed to support a head arm stack subassembly for rotation across the recording surfaces of a disk stack.

A subassembly of this type is described in European patent 0060358-B1 and in European patent application no 86303938.2. As can be seen from the referenced documents, each subassembly consists of a number of support arms each carrying at their ends magnetic heads on respective# spring flexures.

The general principles of assembling this type of head arm stack subassembly on such a rotary actuator platform in correct alignment are described in an article "Assembly of Head/Arm Stacks on Rotary Actuator" by T P Brew and H G Dickie (IBM Technical Disclosure Bulletin, Vol 25, No 2, July 1982, page 835). A later article entitled "Arm Stack Assembly Method" by G P Boswell, H G Dickie and P A Mundye (IBM Technical Disclosure Bulletin, Vol 27, No 10A, March 1985, page 5617) describes a refinement of this process to overcome space constraints in mounting the stack to a rotary actuator which is already in place in a disk file. The article also mentions a temporary head retraction system for holding the heads out of the contact with the adjacent disks while the arm stack is merged with the disk stack.A suitable head retraction tool is shown in an article entitled "Head Unload Device" by G P Boswell (IBM Technical Disclosure Bulletin, Vol 22, No 9, February 1980, page 4204).

While the assembly methods described could be carried out entirely manually, the risk of damage to critical components such as disks or heads makes automation desirable.

Because the actuator sits close to and slightly below the disk stack, the space available for tooling is very confined. Use of a conventional robot would not be easy because of the size of its jaws, drive mechanism and service connections.

Disclosure of the Invention Accordingly, the present invention provides an assembly station for assembling head arm stack subassemblies to a disk file rotary actuator comprising an assembly table for supporting a stack of head arms and other components making up the subassembly, the table being pivotable about a horizontal axis between an initial position, in which it is adapted to receive said components in inverted order for bolting together, and a final position for delivery of the bolted subassembly to a platform portion of such a rotary actuator when located in a predetermined position in the station, the assembly table including gripping means for gripping the first received component of the subassembly when the table is in its initial position and during said pivoting, and for releasing the component and subassembly onto the actuator platform when the table is in its final position.

By assembling the arm stack subassembly in inverted order on a table pivotable vertically about a horizontal axis, the subassembly may be relatively easily delivered in the correct orientation to the actuator within a confined space.

Preferably, the bolting action is such as to raise the first received component from the table and the gripping means is spring biased towards a retracted position. In this case it is also preferred that the station further includes a stop for engaging the gripping means-when the table is in its initial position so as to drive the gripping means to an extended position in which it can grip the first received component.

When the bolting action raises this component, it will also raise the gripping means against the spring bias and this can be detected by a sensor sensing disengagement of the gripping means from the stop. The sensor output thus indicates correct operation of the gripping means and of the bolting step prior to movement of the assembly table from its initial position.

Another preferred feature of the invention is a further sensor, mounted on the assembly table, and arranged to sense the presence of the gripping means in its retracted position.

This sensor indicates release of the subassembly by the gripping means at the final position of the assembly table.

In order to work within the space requirements the preferred form of gripping means is an expandable collet. On expansion, the collet grips the interior of a hollow mandrel which is the first received component of the subassembly.

Preferably, the assembly table is a turntable rotatable about an axis normal to its plane.

This enables the merging of the head arm stack subassembly with a corresponding disk stack prior to the release operation of the gripping means.

Another critical problem of the assembly process is the unloading and unloading of the heads, which are supported on spring flexures attached to the arms, the flexures being preformed so as to bias the heads towards a loaded position on the disks. Manual loading and unloading with a tool such as that of the prior art has been found very likely to damage the heads or disks. Accordingly, it is a preferred feature of the invention that the station further comprises an unloading mechanism for collapsing the head flexures to an unloaded position, the unloading mechanism being supported by the turntable for rotation therewith.

The unloading mechanism is arranged to collapse the flexures prior to the merge operation. The flexures remain collapsed by the mechanism as the arm stack is merged with the disk stack because the unloading mechanisms also rotates with the turntable.

It is preferred that the unloading mechanism should include a plurality of arcuate fingers movable relative to the table about a centre to collapse the flexures. The centre need not be that of the table. Such a mechanism allows collapsing of the flexures in a carefully controlled manner.

It is preferred that the unloading mechanism is arranged to collapse the spring flexures when the head arms are placed on the assembly table located in the initial position.

This and a further preferred feature that at least two of the arcuate fingers are movable independently of each other enables the heads to be collapsed and protected from damage during the building of the arm stack.

Brief Description of the Drawings Figure 1 is a perspective partly exploded view of an inverted head arm stack subassembly; Figure 2 illustrates a bush employed in an additional head arm stack subassembly of the type generally illustrated in Figure 1; Figure 3 is an outline plan view of a portion of a disk file during assembly of one of the subassemblies of Figures 1 and 2 to a rotary actuator; Figure 4 is a schematic plan view of the layout of an assembly station according to the present invention; Figure 5 is a plan view of a precision tooling appendage forming part of the assembly station of Figure 4; Figure 6 shows a cross section through the tooling of Figure 5 and adjacent portions of the assembly station; Figure 7 shows a cross section of a collet assembly forming part of the precision tooling of Figure 5;; Figure 8 shows a cross section of a locating pin assembly forming part of the precision tooling of Figure 5.

Figures 9 and 10 show schematic elevations of high and low arm stack head loading mechanisms respectively; and Figures 11, 12 and 13 are cross sections through a head load mechanism forming part of the precision tooling of Figure 5, taken on the lines A-A, B-B and C-C respectively.

Detailed Description of the Invention Figure 1 illustrates the components of a 'high' head arm stack subassembly for a disk file employing a rotary actuator of the type generally described in European patent 0031876-B 1. The components are shown inverted, as the stack is assembled in inverted order. The first component of the stack is a mandrel 1 over which are an upper arm 2 and a middle arm 3, located on the mandrel by means of a bore 7. A counterbalance weight 4 is bolted to the upper arm. An extension block 5 is bolted to the uppermost face of the middle arm 3 and tape cable connectors 6 are attached to each arm. The stacked components are themselves held together by means of a bolt 8 which engages an inner threaded portion of mandrel 1. A number of magnetic heads 9 are mounted on the ends of arms 2 and 3 by means of spring flexures 10.The flexures are preformed to load the heads towards the disks one of which will locate between the arms 2 and 3.

As illustrated, the heads on adjacent arms are biassed into contact with each other. As will be explained below, the assembly process ensures that adjacent heads are never actually allowed to contact each other in this way.

The purpose of the extension block 5 is to raise the high arm stack sufficiently above the platform of a secondary actuator to be able to access the upper half of the disk stack. Figure 2 illustrates a bush 20 and bolt 21 which replace the extension block 5 in the case of a 'low' arm stack intended to be mounted on a primary actuator to access the lower half of the disk stack. The only other significant difference between high and low arm stacks is that the heads are distributed differently between the arms so that middle arms carry four heads while upper or lower arms carry only two heads.

Figure 3 shows in outline a portion of the disk file during assembly of either head arm stack to its respective actuator. The top disk 30 of a stack of three disks is shown partly broken away and overlying a rotary actuator 31. The actuator 31 is below the level of the disk stack and is mounted, like the stack, in a base casting 32 of the file. For obvious reasons, the actuator is as close to the stack as possible and rotates about a centre 33. A connector pillar 34, to which the head arm tape cables must be attached, further restricts the space for assembly.

The final position of the head arm stack 35 with respect to the disk stack is shown in outline at 35'. Clearly, it is impossible to assemble the arm stack directly to this position and it must therefore be placed initially in the position shown by full lines 35 and subsequently rotated to its final position before being bolted to the actuator through three bores 11 (Figure 1). During such a rotation the heads 9 must be in their unloaded state with the flexures 10 collapsed to an orientation parallel to the plane of the head arms. The arm stack is located on the actuator by means of or features on its underside which are described in the above referenced IBM Technical Disclosure Bulletin (Vol 27, No 10A, March 1985, page 5617).

An automated head arm assembly work station for carrying out the necessary assembly steps is shown schematically in Figure 4. The station consists of an enclosed cell 44 to which a part assembled disk file 42 (known as a Disk Enclosure or "DE") is delivered by a carousel fork lift device 41. The DE has the cover removed to reveal the disk stack 30 and two rotary actuators 31. Semi-automated arm stack assembly tooling is located in area 43. The automatic operations are controlled by an IBM Series 1 control unit via keyboard 46. The major components of the assembly tooling are assembly tables 45 on which the head arm stacks are assembled. The assembly tables 45 are pivotable on arms 47 about horizontal axis 48 to deliver assembled head arm stacks 35 to the platforms of actuators 31. The arms 47 are driven by respective motors (not shown).Ancillary assembly tooling 49 includes a head unload mechanism (Figures 5, 9-13) and a head arm alignment pin mechanism (Figure 8#). Both these appendages are in fact mounted on the respective rotary tables 45 and are rotatable with the tables about their centres. Omitted from Figure 4 is a collet assembly (Figures 6 and 7) set into the table 45. The assembly and merge operation will first be described in general terms, following which a detailed description of the ancillary assembly tooling will be given.

The head arm assembly workstation (Figure 4) is designed to assemble and align a high arm stack (Figure 1) and a low arm stack (Figure 2). The assembled and aligned arm stack assemblies are then merged with the disk stack and secured to their respective DE actuator motor platforms. At this point, the heads are now loaded onto the respective disk surfaces. Following the merge operation for each stack, the tape cable is released from retaining clips on each arm and connected to a connector 34.

A DE 42 is delivered to a common base assembly 50 of the station via the carousel 41 where it is automatically located, clamped and identified. A disk- stack orientation fixture (not shown) automatically locates on the hub of the DE spindle. It then rotates the spindle and disk stack until the disks are presented in a known orientation to the tooling.

Mandrels 1 are then fitted in area 43 to the high and low stack arm assembly tables 45 and held in place on the l/D by a collet device (Figures 6 and 7). An upper arm 2 is mounted on a temporary fixture and a counterbalance weight 4 is attached by means of a screw.

The upper arm 2 and counterbalance weight are then transferred to the high arm stack assembly fixture where they are assembled over the mandrel 1 and located by a tooling pin (Figure 8) through a hole 12 (Figure 1).

On a command from the keyboard 46 high stack head load fingers (Figure 9) advance and collapse (unload) the suspensions 10 of the upper head arm. A middle arm 3 is now placed on the high stack assembly table 45 over the mandrel and locating on the tooling pin. The middle arm 3 now lies over the upper arm on the high stack assembly table.

A second middle arm for the low stack is now placed on the temporary fixture and another counterbalance weight is assembled and secured to it. The middle arm is then transferred to the alternate (low stack) assembly fixture where it is assembled over the mandrel and located by a tooling pin, similarly to the high arm stack. On a command from the keyboard, low stack head load fingers advance and unload the suspensions of the middle arm. A lower arm is now placed on the low stack assembly fixture by assembling over the mandrel and locating on the tooling pin so that it now lies over the middle arm.

The high arm stack is now completed with the addition of an extension block 5 and alignment peg (this is a loose tooling appendage which assists during the stack alignment phase) and the low arm stack is completed with the addition of a bush 20.

On the next keyboard command, arm stack alignment tools (not shown) are activated and the arms of each stack (and the extension block on the high stack) are automatically aligned. Following alignment, the operator screws the stacks together. The high arm stack alignment tool is now removed, and the high arm stack head load mechanism unloads the uppermost arm suspensions. A cover remove tool also removes the DE cover.

The high stack merge operation now takes place to transfer the assembled and aligned arm stack from the arm assembly table onto the respective actuator motor platform, to merge the arm stack assembly to locations on the actuator platform and secure it in position.

To avoid applying high loads onto the actuator end stop during torquing up of fasteners, a lock tool is used to hold the actuator spindle platform away from the outer end stop.

The high stack assembly table 45 is then automatically vertically rotated by arm 47 clockwise through 180 degrees, to a preset stop position over the secondary actuator 31 (high stack) adjacent to the disk stack 30. The arm location tooling pin is now retracted and the table 45 is rotated horizontally and anticlockwise, orientating the arm stack with respect to the actuator motor platform. This motion also positions the heads within the disk stack, with the head load mechanism preventing the heads from coming into contact with the disk surfaces. The collet is now released and a merge preload mechanism (not shown) is activated. The merge preload mechanism is essentially two pneumatically operated compliant 'pushers' which ensure the high stack assembly extension block is firmly located against the location features on the actuator platform.

The high arm stack is now secured in position with screws and washers in a strict torquing sequence. The head load mechanism now withdraws slowly from the arm stack, loading the heads onto the disk surface. The high stack arm assembly fixture (table 45 and arm 47) is now returned to its initial assembly position by rotating vertically and anticlockwise through 180 degrees, leaving the high arm stack assembly secured to the DE.

During this rotation the table 45 rotates clockwise to its initial assembly position.

The actuator lock tool is now manually transferred from the secondary actuator to the primary actuator. The high stack tape cables are removed from the clips on the high stack arms, and plugged into adjacent connectors 34 in the DE.

The low (or primary) arm stack is now merged to the primary actuator in a very similar way to the high stack merge. On completion of low arm stack merge the actuator lock tool is returned to its holder and the DE cover is automatically replaced. The common base clamps are released and the DE can now be collected by the carousel forks 41.

Varius aspects of the semi-automated arm stack assembly tooling located in area 43 of the head arm assembly workstation of Figure 4 will now be described in detail with reference to Figures 5 to 13.

Figure 5 shows a plan view of a precision tooling appendage including table 45 which is supported at one end of arm 47. Figure 6 is a simplified cross section showing how the precision tooling appendage of Figure 5 is mounted on a base plate 100 of the head arm assembly station. As generally described above, these two appendages enable the respective arm stacks to be accurately assembled and aligned at an initial assembly position, rotated through 180 degrees to a merge position and located and secured to the respective actuator motor platform. They also enable the arms to merge with the disk stack and, finally, the heads to be loaded onto the disks.

The major components of the precision tooling appendages, are similar for both high and low arm assembly and will not be separately described. They include, in addition to an assembly table 45, a seating block 60 in the centre of which is a collet assembly 61. A two stage pin assembly 62 and a head load mechanism 63 are supported on a secondary arm fixture 64. Also visible is a portion 65 of an arm stack preload mechanism. A low head arm stack subassembly 35 of the type illustrated in Figures 1 and 2 is shown in outline.

Thus the secondary arm fixture 64 carries the main precision tooling such as collet 61, two stage pin assembly 62, head load mechanism 63, arm alignment posts and on the low stack, arm merge preloads 65. The fixture 64 is able to partially rotate with the table 45 in order to merge arm stacks with the disk stack.

The secondary arm fixture 64 is located at the free end of the fixture arm 47. The assembly table 45 is mounted in ball bea which are in turn retained in the fixture arm 47. The second fixture 64 is retained on the table by cap screws to form a c assembly about a centre 67.

An arm stack is built up around a mandrel (Figure 1) on the seating block 60. The seating block is a hardened tool steel block, the top face of which forms a secondary datum for the arm stack build. Its centre is offset from the centre of rotation of the assembly table 45. In the initial assembly position, the clearance hole for the left hand rear arm stack fixing screw (right hand rear in the merge position), coincides with centre of rotation of the assembly table. The reason for this offset is to provide the optimum approach angle for the arm actuator spindle platform locations.

On alignment and assembly of the arm stack the fixture arm 47 rotates vertically through 180 degrees, positioning the arm stack over the actuator spindle platform. At this stage there should be a minimal gap, under all material conditions, between the arm stack and the actuator platform. The two stage pin (Figure 8) retracts and a pneumatic cylinder (not shown), pivoting about a fixed pin on the fixture arm 47 is activated, rotating a bracket fixed to the assembly table. Thus the table and secondary fixture 64 rotate, merging the arm stack with the disk stack. The angular position and rotation of the secondary fixture is controlled by stops fixed to the fixture arm, and the pneumatic merge rotation cylinder 65 holds the secondary fixture against the appropriate stop. With the merge operation now activated the collet 61 releases the mandrel and the merge preload mechanism is operated.

A collet assembly 61' substantially similar to the collet 61 of Figure 6, is shown in Figure 7. in fact, the collet of Figure 7 is that used for high arm stack assembly, thus, the seating block 60', shown in outline is much lower than block 60 shown in Figure 6 to allow for the height of extension block 5. The collet 61', for the same reason, is more deeply recessed within table 45' (Figure 8) just beneath the seating block 60'. The collet is an assembly of a pneumatic cylinder 80 with a piston rod 81 having a reverse cone 82 at its free end. When the cylinder 80 is energised, the reverse cone 82 is pulled into a split col let 83 which then expands to grip and centralise the mandrel. The mandrel forms the primary datum for the build of the arm stack.

The pneumatic cylinder 80 is, in turn, free to slide in a hardened steel bush 84 which is fastened to the table 45. However, a return spring 85 fitted over the cylinder body and constrained by the cylinder end cap 86 and the end of the bush, exerts a constant preload to bias the collet to a retracted position within the seating block 60' and table 45'.

The purpose of the collet assembly is threefold, namely: (1) to locate the mandrel accurately and securely for subsequent arm stack assembly; (2) to indicate correct assembly and torquing of the arm stack assembly; and (3) to hold the arm stack in place during inversion.

As best shown in Figure 6, with the arm assembly table 45 latched into an initial assembly position, an adjustable stop 101 on the arm assembly platform 100 (Figure 6) contacts the end cap of the collet and against the return spring pressure, holds the collet in the correct dimensional relationship to the seating block 60. Thus with a mandrel located correctly onto the collet, there is a clearance of approximately 1 mum between the mandrel flange 13 and the seating block, illustrated by arrows 71 in Figure 6.

Fitted adjacent to the adjustable stop 101 is a proximity sensor 102, the purpose of which is to detect correct assembly and torquing of the fastening bolt. The mandrel is fitted to the collet, which when the cylinder 80 is energised, grips the mandrel counterbore 14.

The arm assemblies are then built up and aligned about the mandrel. Each stack is fastened by screwing a bolt (8,21) through the extension block 5, in the case of the high stack, and through the bush 20 in the case of the low stack, into the mandrel. As the torque builds up, the mandrel is drawn upwards until the clearance between the flange 13 and seating 60 is eliminated. Since the collet 61 is still in engagement, the main collet body follows the mandrel and in doing so lifts off the proximity sensor 102 thereby confirming correct assembly to the Series 1 computer. This enables the subsequent operations to commence. The sensor also confirms that the collet is still expanded into the mandrel.

The spring loaded collet assembly 60 ensures that the arm stack assembly 35 is held safely against the seating 61 whilst the table 45 is rotating vertically to the 'merge position'. Following the 'merge rotate' operation of table 45, just prior to applying a 'merge preload' to finally position the arm stack with respect to actuator datums, the collet 60 is released and withdrawn by the spring loading to its fully retracted position. This is sensed by a second proximity sensor 72, mounted beneath table 45, prior to continuing with subsequent operations. When the table 45 rotates back to the initial assembly position, the collet assembly is reset by the stops 101 in preparation for the next stack build, the sensor 102 detecting correct resetting.

The pin assembly 62 on the secondary arm fixture is shown in further detail in Figure 8.

The pin assembly 62 is a concentric two stage pneumatic cylinder, the inner cylinder 90 acting as the piston for the outer cylinder 91.

There is a piston rod 93 in the inner cylinder only, which is double ended. The top end of the rod is tapered and radiused for location purposes and the other end is used to trigger two optosensors.

The pin assembly 62 is located in the secondary fixture 64 adjacent to the assembly table 45. Its purpose is to act as a location datum during arm stack build and merge. On fitting mandrels to the collet assemblies both stages of the pins 93 are extended in preparation for assembly of the arms. The arms are located, two per stack, over the mandrel and the two stage pin 93, which locates in tooling hole 12 in the arm casting stiffening webs.

With the lower of the two arms sitting on the seating block 60 surface and the upper of the two arms sitting on the lower, the two stage pin 93, passes through the tooling holes 12 in both arms. During the arm stack assembly process, the arms require alignment and are then fastened together as a stack. To enable the respective arms within the stack to move relative to each other against the alignment tool, the two stage pin is fully retracted. Following alignment and fixing together as a stack the first stage of the pin is operated.

This is to orientate the stack into a known position for the merge operation. The assembly table 45 on arm 47 then rotates vertically and is clamped into the merge position, the two stage pin is fully retracted and the table rotates horizontally to merge the arms between the disks. The two stage pin is operated through three ports in the outer cylinder.

The uppermost port 94, through the fixing flange, is a common return supply to both stages of operation. The centre port 95 activates the inner cylinder only i.e extends the pin. The lower port 96 activates both stages, inner and outer cylinders.

There are three opto-sensors used to detect correct operation of the pin. One sensor 97 is mounted directly to the pin assembly end cap 98 via a bracket and senses full retraction of the pin. The other two sensors 103 and 104 (Figure 6) detect correct operation of the first and second stages respectively and are mounted on a common bracket which is fixed directly to the assembly station base 100.

The head load mechanisms 63 are also mounted in the secondary arm fixtures 64.

One of them is illustrated in Figure 5 and in further detail in Figures 9 to 13.

The purpose of the head load mechanism 63 is to unload the head flexures 10 during arm stack build to ensure heads 10 are always separated, and to prevent disk/head interference during merge of arms to disk stack.

The head arm suspensions 10 are angled with respect to the arm so that the read/write heads 9 are biased towards the disk surfaces.

It is necessary to temporarily restrain the suspensions in a parallel attitude for assembly and merge operations. This is termed 'head unloading' When a head arm stack is merged to the DE, the suspensions are allowed to return to the angled attitude, thus depositing the heads on the disk surface. This is termed 'head loading' As mentioned above, the high and low arm stacks are assembled in two differing configurations. Using the convention that the level of a head 9 in the stack is denoted by a number in parenthesis so that 9(0) denotes the lowest pair of heads and 9(5) the highest pair of heads, heads 9(0) and 9(2) are supported by the low arm stack and heads 9(3) 9(4) and 9(5) are supported by the high arm stack as seen in Figures 9 and 10.

Head unloading is performed as the arm stack assembly is built up. On locating the mandrel and upper arm counterbalance weight on the high stack assembly table seating and after operating the two stage pin, the head load fingers 106 advance unloading head 9(5).

Also, this head load mechanism carries the head load fingers for head 9(4), such that locating the middle arm on top of the upper arm, head 9(4) is automatically unloaded to prevent interference with head 9(5). The extension block, screw and alignment peg complete the stack and the alignment tool is then operated. This tool initially clamps the stack together. The head load finger for head 9(3) now operates so that now all three sets of heads on the high stack are 'unloaded'.

Similarly the low arm stack heads are unloaded, however, there is only a need for one set of head load fingers in this case. Thus the low stack build commences by placing a middle arm and counterbalance weight over mandrel on the low arm assembly table seating.

The head load fingers advance, simultaneously unloading heads 9(1) and 9(2), and positioning the fingers for head 9(0) in the unload position. Hence when the lower head arm is located on the stack, head 9(0) and head 9(1) are prevented from touching. A schematic representation of the relationship of the load fingers to the heads and disks is shown in Figure 9 for the high arm stack and in Figure 10 for the low arm stack. Unload fingers have been numbered parenthetically corresponding to the heads. When each stack has been aligned, assembled, merged and screwed in position on the actuator platform, the head load fingers 106 are retracted to the 'load' position. The heads are thus deposited onto the disk surface.

As shown in Figure 5 and in further sectional detail in Figures 11, 12 and 13 the head load mechanism 63 is rigidly supported on the secondary arm fixture 64. It consists of a precision slide plate 107 (two on the high stack) which is arcuate in shape and rectangular in section with 'V' edges. The slide plate(s) 107 rotate freely between two pairs of journals 108. Each journal 108 has two free running bearings mounted on an eccentric bolt 109 which in turn is screwed into a roller block 110. It will be noted that the centre of rotation of the slide plates does not coincide with that of assembly table 45.

The O/D cage of the two bearings 108 forms a 'V' groove which matches the 'V' edges of the slide plate 107. The eccentric feature 109 is adjustable to ensure drive is engaged and to minimise free movement in the mechanism. Drive is supplied by miniature geared motors Ill retained in motor block 112 on the secondary arm fixture by a grubscrew.

The drive is transmitted to the slide plates by a set of drive rollers. There are three drives in all, two high stack, one low stack. Each set is different in configuration but the principle of all three is the same. A drive shaft 114 is located over the slotted gearbox output shaft 115 of the miniature geared motor 111. A small dowel pin locates in the ouput shaft 115 transmitting drive to the drive shaft 114 which is supported by bearings 116 either end, located to the motor block by bearing plates. Part of the drive shaft is a fixed drive roller 117 which has a urethane faced flange bevelled to match the 'V' angle of the slide plate. A further drive roller 113, also having a bevel to match the side of the 'V', is assembled over the drive shaft such that it sits adjacent to the fixed drive roller 117. The drive roller 113 also has a urethane facing.It has limited axial free movement but is keyed radially to the drive shaft 114 by a dowel. The drive roller 113 is axially preloaded in the direction of the fixed drive shaft roller 117 by a spring restrained on the shaft by an external circlip. The purpose of this preload is to ensure drive is imparted to the slide plate but enables the drive to slip when a stop is engaged, thereby acting as a clutch mechanism 120. The preload is adjustable by varying the number of washers between the spring and the circlip.

The slide plate 107 has a limited angle of roatation which is set by stops 130 and optical sensors 131 and 132. Each slide plate carries a stop block to each side of which are fitted adjusting screws. The adjusting screws strike the side of the front and rear blocks respectively at the extremes of forward and reverse travel. A flag 133 which is an integral feature of a spacer blade attached to the leading end of the slide plate, simultaneously breaks the optical sensor 131 which in turn stops the geared motor. During the lag between mechanical stops being made, preventing further movement of the slide plate and the motor being switched, the clutch mechanism 120 allows the drive to slip.

Claims (9)

1. An assembly station for assembling head arm stack subassemblies to a disk file rotary actuator, comprising an assembly table for supporting a stack of head arms and other components making up the subassembly, the table being pivotable about a horizontal axis between an initial position, in which it is adapted to receive said components in inverted order for bolting together, and a final position for delivery of the bolted subassembly to a platform portion of such a rotary actuator when located in a predetermined position in the station, the assembly table including gripping means for gripping the first received component of the subassembly when the table is in its initial position and during said pivoting, and for releasing the component and subassembly onto the actuator platform when the table is in its final position.

2. An assembly station as claimed in claim 1 in which the first received component is raised from the table by the bolting action and in which the gripping means is spring biased towards a retracted position, the station further including a stop for engaging the gripping means when the table is in its initial position so as to drive the gripping means to an extended position in which it can grip said first received component whereby the bolting action raises not only the first received component but also the gripping means against the spring bias, and a sensor for sensing disengagement of the gripping means from the stop to indicate correct operation of the gripping means and completion of the bolting step prior to movement of the assembly table from its initial position.

3. An assembly station as claimed in either claim 1 or claim 2 in which a further sensor, mounted on the assembly table, is arranged to sense the presence of the gripping means in its retracted position thereby to indicate release of the subassembly by the gripping means at said final position of the assembly table.

4. An assembly station as claimed in any preceding claim in which the gripping means is an expandable collet adapted on expansion to grip the interior of a hollow mandrel, which is the first received component of such an assembly,

5. An assembly station as claimed in any preceding claim in which the assembly table is a turntable rotatable about an axis normal to the plane of the table to merge a head arm stack subassembly with a corresponding disk stack prior to the release operation of the gripping means.

6. An assembly station as claimed in claim 5 for use with head arms of the kind in which magnetic heads are supported by spring flexures attached to the arms, the flexures being preformed so as to bias the heads towards a loaded position on the disks, the station further comprising an unloading mechanism for collapsing the head flexures to an unloaded position, the unloading mechanism being supported by the turntable for rotation therewith and arranged to collapse the flexures prior to said merge operation.

7. An assembly station as claimed in claim 6 in which the unloading mechanism includes a plurality of arcuate fingers movable relative to the table about a centre to collapse the spring flexures.

8. As assembly station as claimed in claim 7 in which the unloading mechanism is arranged to collapse the spring flexures when the head arms are placed on the assembly table located in its initial position.

9. An assembly station as claimed in claim 8 in which at least two of the arcuate fingers are movable independently of each other.