GB2151954A - Replaceable gang head machine tool - Google Patents

Abstract

In the machine tool, in addition to a spring (12) provided in each of telescopic arms (15, ....) interconnecting moveable rails (6), for carrying a gang head (9), and a working unit (5), there is provision (23, 18a) for supplying pressure fluid to the telescopic arms to add to the arms-contracting effect of the springs thereby to ensure firm connection between the moveable rails and the working unit at a time when the springs have relaxed to a certain extent, to prevent the rails (6) moving when a gang head moves onto them from fixed rails (7). <IMAGE>

Description

SPECIFICATION Replaceable gang head machine tools This invention relates to replaceable gang head machine tools.

A previously proposed machine tool has a machine base on which is provided, through a reciprocable slide table, a working unit having a driving electric motor. An annular rail made-up of a front movable rail and a rear stationary rail is provided around the working unit. Several gang heads are disposed around the annular rail, supported thereon so as to be turnable around a circle moving along the annular rail, by an index table provided thereabove so that any desired one of the gang heads may be selectively positioned on the movable rail such that, if the working unit is then advanced from a retreated end position, the se lected gang head on the movable rail is advanced therewith together with the movable rail for apply ing a predetermined working operation to a workpiece set in front thereof.In this tool, in the course of advance of the working unit, the movable rail has to be stopped once, together with the selected gang head supported thereon, at such a position that the working unit advanced slightly from its retreated end position is in order to join the working unit to the selected gang head. To achieve this the movable rail and the working unit are intercon nected through a telescopic arm made-up of a cyl inder and a piston rod extending from a piston mounted in the cylinder and urged in a contracting sense by a spring. This arrangement, however, is inconvenient in that, if the working unit is advanced relatively to the movable rail, the spring is increased in length and accordingly the resilient force thereof is decreased, and consequently it is inevitable that the movable rail tends to be moved more or less forwards.

According to the present invention there is provided a replaceable gang head machine tool hav ing a machine base on which is provided, through a reciprocable slide table, a working unit having a driving electric motor; an annular rail made-up by a front movable rail and a rear stationary rail provided around the working unit; and gang heads disposed around the annular rail and supported thereon so as to be turnable around a circle, mov ing along the annular rail, by an index table provided thereabove so that any desired one of the gang heads may be selectively positioned on the movable rail; the movable rail and the working unit being interconnected through a telescopic arm which comprises a cylinder and a piston rod extending from a piston mounted in the cylinder and which is urged to contract by a spring; and there being further provided a supply source of pressure fluid connected through a communication passage to the cylinder of the telescopic arm so that the arm may be urged to contract by pressure fluid supplied into the cylinder. In this tool, because the pressure fluid can be introduced into the cylinder of the arm and thereby the arm can be pushed to contract both by the pressure fluid and the spring of the arm, the difficulty that arises where the arm is urged only by a spring is avoided and also there can be obtained a good connection between the movable rail and the working unit. However, the pressure fluid charged in the cylinder is liable to become more or less a load on the working unit in the course of moving the working unit to its retreated end position.In view of this, the tool can be such that a detecting means for detecting a retreated end position of the working unit and a slightly advanced position thereof which is closer to the movable rail so that the telescopic arm is changed over between a condition in which the cylinder thereof is connected to the supply source of pressure fluid, so that pressure fluid is supplied into the cylinder, and a condition in which the cylinder thereof is connected to the exterior so that pressure fluid is discharged from the cylinder. In this case the pressure fluid can be discharged from the cylinder in the course of moving the working unit from a slightly advanced position to its retreated end position, so that the pressure fluid does not become a load on the working unit and consequently the working unit can make a light retreating movement.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a perspective view of a replaceable gang head machine tool, Figure 2 is a perspective view of the machine tool of Figure 1 with a working unit shown in its advanced condition, Figure 3 is a perspective view of part of the machine tool, Figure 4 is a top plan view, partly in section, of an important portion of the machine tool, Figure 5 is a sectional view taken along line V-V in Figure 4, Figure 6 is a sectional view similar to Figure 5 but with the working unit in a slightly advanced condition, Figure 7 is a diagram of a pressure fluid circuit of the machine tool, and Figures 8 and 9 are diagrams for explaining operation of the pressure fluid circuit.

Referring to the drawings, numeral 1 denotes a machine base. The machine base 1 is provided thereon, through a slide table 3 that is receiprocate by an oil pressure operated cylinder 2 with a working unit 5 having a driving electric motor 4. Upper and lower annular rails 8,8 made-up by front movable rails 6,6, and upper and lower rear stationary rails 7,7 are provided around the working unit 5.

Several gang heads 9,9 .... are disposed around the annular rails 8,8 and are supported thereon. In addition these gang heads 9,9 .... are arranged to be turnable around a circle, moving alone the annular rails 8,8 by an index table 10 provided thereabove, so that any desired one of the gang heads 9,9 may be selected to be positioned on the movable rails 6,6. Thus, if the working unit 5 is advanced from a retreated end position, the selected gang head 9 on the movable rails 6,6 is advanced there with, together with the movable rails 6,6, for applying a predetermined working operation thereof to a workpiece set on a jig base 11 provided in front thereof.

The working unit 5 is fixedly provided on the table 3 through a working unit casing 5a provided on its periphery. In the illustrated tool the upper and lower annular rails 8,8 which constitute the upper and lower movable rails 6,6 are interconnected through a connecting bracket 6a, and the upper and lower stationary rails 7,7 are interconnected through a machine frame 7a by which they are fixed to the machine base 1.The movable rails 6,6 and the working unit 5 are interconnected, as shown in Figure 4, through two upper laterally spaced telescopic arms 15, 15 and two lower laterally spaced telescopic arms 15,15 each comprising a cylinder 13 and a piston rod 14 extending from a piston 14a mounted in the cylinder 13 and urged to contract by a spring 12 so that the movable rails 6,6, movable through a slide engagement of the telescopic arms 15 with the working unit 5, are urged towards the unit 5, that is, rearwards, by the springs 12, 12. Of each arm 15, the cylinder 13 is fixed to the working unit 5, the piston rod 14 is fixed to the movable rail 6, and the spring 12 in the cylinder 13 bears through a spring seat 17 on a spacer 16 to push the piston rod 14 rearwards.

In the present machine tool, as shown in Figure 7, there is provided a supply source 18 of pressure fluid such as air or oil under pressure. This supply source 18 is connected through a communication passage 18a to the cylinder 13 of each telescopic arm 15 so that the arm 15 may be caused to contract by pressure fluid supplied into the cylinder 13.

In the illustrated tool, there is used as the pressure fluid air under pressure, and the communication passage 18a for introducing this air is provided with a regulator 24 for keeping the pressure of the air constant.

If the working unit 5 is moved from its retreated end position as shown in Figure 4 and Figure 5 to a slightly advanced position in which it is closer to the movable rails 6,6 as shown in Figure 6, the te lescopic arms 15 .... are changed from a condition shown in Figure 8 to a condition shown in Figure 9. Namely, the cylinder 13 of each arm 15 is advanced together with the working unit 5 on the piston rod 14 of each arm and in accordance therewith the spring 12 of each arm is more or less expanded as shown in Figure 9 with resulting decrease in its resilient force. However, the internal volume of each cylinder 13 open to receive the pressure fluid is increased at the same time, and at this time an amount of pressure fluid corresponding to the increase in volume is supplied from the supply source 18 into the cylinder 13.Thereby each cylinder 13 can be always kept in such a condition that the volume thereof open to receive pressure fluid is filled with the pressure fluid, and thus, as a result, each arm 15 is always kept in such a condition that it is pushed to contract by the pressure fluid. In other words, the movable rails 6,6 have always applied thereto the pushing force of the fluid pressure, so that there can be eliminated the problem that, due to the expansion of the springs 12, the themovable rail is liable to be moved more or less forwards.

It is desirable that pressure fluid in the cylinder 13 be discharged therefrom when occasion demands, in a manner such as not to become an unnecessary load. For example, when the working unit 5 is moved from the slightly advanced position shown in Figure 9 to the retreated end position, it is un avoidable that the internal volume of the cylinder 13 available to the pressure fluid is decreased as shown in Figure 8, and an amount of the pressure fluid that corresponds to this reduction in volume has to be discharged from the cylinder to the exterior through the regulator 24.

Resistance to this discharge at the time of discharging would represent more or less a load on the retreating operation of the working unit, and it is desirable to remove this resistance. To this end there is provided a detector 19 for detecting that the working unit 5 is at its retreated end position, and that the working unit 5 is at its advanced position which is closer to the movable rails 6,6, so that the telescopic arms 15 .... may be changed over between such a condition that, when the detector 19 is in its operative condition, each cylinder 13 is connected to the supply source 18 and as a result the pressure fluid is supplied into the cylinder 13, and such a condition that, when the detector 19 is in its inoperative condition, each cylinder 13 is connected to the exterior and as a result the pressure fluid is discharged from the cylinder 13.

In more detail, as shown in Figure 7, a changeover valve 20 is interposed in the communication passage 18a so that each cylinder 13 may be selectively connected either to the supply source 18 or to an external air open side 21 open to the atmosphere, and the detector 19 is a micro-valve for effecting a changeover control of the changeover valve 20. This micro-valve cooperates with an elongated dog 22 that reciprocates with the working unit 5. As shown in Figure 5, for instance, the detector 19 is provided on the machine frame 7a and the dog 22 is provided on the slidable table so that when the working unit 5 is located at the retreated end position as shown in Figure 5, or at the slightly advanced position as shown in Figure 6, the detector 19 is released from being pushed by the dog 22 and is in its operative condition. In this condition the changeover valve 20 is set such that each cylinder 13 is placed in communication with the supply source 18 to be supplied with the pressure fluid. When the working unit 5 is located at an intermediate position between the two positions just discussed the detector 19 is pushed by the dog 22 to adopt its inoperative condition. In this condition the change-over valve 20 is set such that each cylinder 13 is placed in communication with the external air open side 21 to allow the pressure fluid in the cylinder 13 to be discharged therefrom to the exterior.

As shown in Figures 4 to 6, the changeover valve 20 is provided on the working unit 5 and has an inlet opening 20a which is in communication with the supply source 18, an outlet opening 20b which is in communication with each of the cylinders 13 through a manifold 23, and a discharge opening 20c which is in communication with the external air open side 21, and has also a connecting tube 20d extending to the micro-valve detector 19 for controlling the changeover valve 20.

As mentioned before, the communication passage 18 for introducing the pressure fluid, for instance, air under pressure is provided with the regulator 24 in order that the internal pressure in each cylinder 13 may be always kept constant. A passage for supplying a pressure fluid, for instance, oil under pressure, to the cylinder 2 that drives the slide table 3 is provided with a relief valve 25 in order that the internal pressure in the cylinder 2 may also be kept always constant.

Operation is as follows: In an ordinary condition, the working unit 5 is lo cated at its retreated end position a little apart from the movable rails 6,6 as shown in Figures 1, 4 and 5. When the working unit 5 is at this position, the detector 19 is in its operative condition and ac cordingly each cylinder 13 is supplied and filled with the pressure fluid as shown in Figure 8, so that the telescopic arms 15 .... are urged to con- tract not only by their springs 12 but also by the pressure fluid. In other words, the movable rails 6,6 are strongly pushed rearwards by the springs 12 and the pressure fluid to be firmly connected to the stationary rails 7,7.Under this firm connective connection, when a selected one of the gang heads 9 is turned to be positioned on the movable rail 6,6, these rails are prevented from being advanced unnecessarily even through centrifugal force gen erated during the turning operation by a more or less large weight of the gang head 9 acts on the rails 6.

When the working unit 5 is then advanced to its intermediate position, the detector 19 is brought to its inoperative condition for discharging the pres sure fluid from each cylinder 13 and therafter, when the working unit 5 is advanced to reach its slightly advanced position as shown, for instance, in Figure 6, the detector 19 is again brought into its operative condition for again introducing the pres sure fluid into each cylinder. Thus, at the slightly advanced position the movable rails 6,6, are again acted upon by both the springs 12 and the pressure fluid as shown, for instance, in Figure 9, and thereby the gang head 9 on the movable rails 6,6 is immovably restrained at that position, together with the rails 6,6, and under this condition the working unit 5 and the gang head 9 are joined to gether.Thereafter, as the working unit 5 is further advanced, the gang head 9 is advanced with the working unit under the joined condition to perform a predetermined working on the workpiece. In this example, a mechanical clamp mechanism 26 as shown by dotted lines in Figure 4 may be provided, as occasion demands, for being simultane ously operated.

If the working unit 5 is retreated together with the gang head 9 from the working position, the condition shown in Figure 6 is again reached. If the working unit 5 is further retreated from this condition, the detector 19 is brought to its inoperative condition and thereby each cylinder 13 is brought to the condition that it is connected to the open side 21 and the pressure fluid previously charged therein is discharged therefrom.

Under the liquid discharge condition, each arm 15 is in such a condition that it is urged to contract only by its spring 12 and thus expansion can be effected by a comparatively light force. In other words, when the working unit 5 is being further re treated, the telescopic arms 15 .... do not become a large load on the working unit 5. When the working unit 5 is returned to its retreated end position, the telescopic arms 15 are again placed in condition to be supplied with the pressure fluid, as shown in Figure 8 for instance, and thus are ready for the next operation.

Thus, in the illustrated machine tool, because each telescopic arm interconnecting between the movable rails and the working unit is such that the pressure fluid can be introduced into the cylinder of the arm and thereby the arm can be pushed to contract both by the pressure fluid and the spring of the arm, the difficulty that arise where the arm is urged only by a spring is avoided and also there can be obtained a good connection between the movable rail and the working unit. Furthermore, the pressure fluid can be discharged from the cylinder in the course of moving the working unit from a slightly advanced position to its retreated end position, so that the pressure fluid does not become a load on the working unit and consequently the working unit can make a light retreating movement.

Claims (3)

1. A replaceable gang head machine tool having a machine base on which is provided, through a reciprocable slide table, a working unit having a driving electric motor; an annular rail made-up by a front movable rail and a rear stationary rail provided around the working unit; and gang heads disposed around the annular rail and supported thereon so as to be turnable around a circle, moving along the annular rail, by an index table provided thereabove so that any desired one of the gang heads may be selectively positioned on the movable rail; the movable rail and the working unit being interconnected through a telescopic arm which comprises a cylinder and a piston rod extending from a piston mounted in the cylinder and which is urged to contract by a spring; and there being further provided a supply source of pressure fluid connected through a communication passage to the cylinder of the telescopic arm so that the arm may be urged to contract by pressure fluid supplied into the cylinder.

2. A machine tool as claimed in claim 1, and comprising a detecting means for detecting a retreated end position of the working unit and a slightly advanced position thereof which is closer to the movable rail so that the telescopic arm is changed over between a condition in which the cylinder thereof is connected to the supply source of pressure fluid, so that pressure fluid is supplied into the cylinder, and a condition in which the cylinder thereof is connected to the exterior so that pressure fluid is discharged from the cylinder.

3. A replaceable gang head machine tool, substantially as hereinbefore described with reference to the accompanying drawings.