GB2114478A

GB2114478A - Coupling mechanism for coupling a pair of mechanical elements

Info

Publication number: GB2114478A
Application number: GB08303516A
Authority: GB
Inventors: Shiro Shimada
Original assignee: Nakamura Tome Precision Industry Co Ltd
Current assignee: Nakamura Tome Precision Industry Co Ltd
Priority date: 1982-02-10
Filing date: 1983-02-09
Publication date: 1983-08-24
Also published as: JPH0356858B2; FR2521049A1; JPS58137542A; FR2521049B1; DE3304463C2; GB8303516D0; GB2114478B; DE3304463A1; CA1205305A

Abstract

A compound lathe W is provided with a tool post 1 and a tool post slide 2 which are coupled by a coupling mechanism comprising a pressure chamber 10, a columnar member 11 that receives the fluid pressure in the pressure chamber as a uniform tensile stress of axial direction, and a holder 15 integral with tool post 1 that is substantially made of a rigid material and is fixed to the tip 12 of the columnar member so as to be shiftable only in the axial direction, the tool post slide 2 being integral with the base end portion 13 of the columnar member 11 so that control of the fluid pressure in the pressure chamber minutely adjusts the positional relationship between post 1 and slide 2. <IMAGE>

Description

SPECIFICATION Coupling mechanism for coupling a pair of mechanical elements This invention relates to a coupling mechanism for coupling a pair of mechanical elements together and to machinery incorporating such a coupling mechanism. In general the present invention provides a coupling mechanism capable of providing a microdisplacement between the coupled elements that corrects or controls positional error generated due to thermal deformation or abrasion between the coupled elements.The type of elements which may be coupled in accordance with the present invention are for example a coupling portion of the base and the column of the drilling machine or a coupling portion of the tool post or the tail stock and their slides, whereby the positional error due to the thermal deformation or the abrasion of the machinery is corrected without spoiling the rigidity in the coupling portions, and the operation accuracy of the machinery can be maintained, and also, the controlled micro-displacement is applied between the machine elements according to requirements to render more plentiful functions to the machinery.

Heretofore, in a compound lathe, the tool post was either fixed to the tool post slide or was rotatably mounted thereto for rotation around the axis in the vertical direction in the drawing of Figure land transverse motion in the direction (in Figure 1, the vertical direction of the drawing, hereinafter referred to as "Y axis direction") right angle to the spindle and the tool shaft was not allowed. Accordingly, for example, when machining a key way a milling cutter is normally mounted on the tool mounting shaft, and the width of th key way to be machined was controlled by the outside diameter of the milling cutter. When the cutter is worn, the width of the key way becomes narrow. Also, if the width of the key way was desired to be enlarged slightly, it is normally necessary to exchange the cutter.

An object of this invention is to retain the operation accuracy of the machinery by the correction of positional error due to thermal deformation or abrasion of the machinery without spoiling the rigidity in the coupling portions where the machine elements are mutually coupled. Additionally, it is an object to provide controlled micro-displacement between coupled machine elements according to requirements.

Moreover, another object of this invention is to allow the micro-transfer of the tool post in the Y-axis direction without spoiling the rigidity between the tool post and the tool post slide by coupling the tool post and the tool post slide in the compound lathe by means of a coupling mechanism of this invention, and when the key way is to be machined, the correction of error of the dimension of the key way resulting from the abrasion of the milling cutter becomes possible, and as the result, the key way of the accurate width can be machined.

Furthermore, still another object of this invention is to allow the automatic control of the qualtity of micro-transfer of the tool post in the Y-axis direction by coupling the tool post and the tool post slide in the compound lathe by means of the coupling mechanism of this invention, and providing a displacement quantity control unit of the tool post, and is to allow the automatic correction of the error of the cutting dimension of the key way resulting from the abrasion of the milling cutter when the key way is to be machined.

Afurtherobjectofthis invention is to allow the free cutting of key ways of different dimensions using one milling cutter, thereby eliminating the troublesome exchange of the milling cutter.

Reference is now made to the accompanying drawings, in which: Figure 1 is a side view schematically showing a compound lathe; Figure 2 is a partial cross section showing a coupling mechanism according to the present invention incorporated between a tool post and a tool post slide of a compound lathe; Figure 3 is a block diagram showing a displacement quantity control unit for a tool post when coupled to a tool post slide by a coupling mechanism according to the present invention; Figure 4 is a perspective view schematically showing a drilling machine incorporating a coupling mechanism according to the present invention, which couples the column to the base; and Figure 5 is a schematic perspective view of a lathe incorporating a coupling mechanism according to the present invention between the tail stock, and its slide, and the tool post and its slide.

In Figure 1, there is shown a lathe W which is of generally conventional construction except for the coupling mechanism between tool post 1 and a tool post slide 2. The compound lathe W is provided with a bed 3, and is provided with a chuck mounted on the spindle. A cross slide 5 is mounted on the bed 3 so as to be slidable in the axial direction of the spindle, and the tool post slide 2 coupled with the tool post 1 is mounted on the cross slide 5 so as to be slidable in a transverse direction to the axis of the spindle i.e. to the right or left as shown in Figure 1.

The tool post slide 2 is made to move slidably on the cross slide 5 by a motor 6. The tool post 1 is provided with a tool mounting shaft 7, and a milling cutter 8 is mounted on the tool mounting shaft 7, and the tool mounting shaft 7 is rotatably operated by a motor 9.

The tool post 1 and the tool post slide 2 are coupled by the coupling mechanism according to this invention as will be described in detail hereinafter.

In Figure 2, the coupling mechanism for mutually coupling the post 1 and slide 2 (which may be generally described as being machine elements) is shown in detail. The coupling mechanism comprises a pressure chamber 10, an elongate, preferably, columnar member 11 that is acted upon by the fluid pressure in the pressure chamber 10 as a uniform tensile stress in the axial direction, and a holder 15 that is substantially made of rigid material and which is fixed to the tip 12 of the columnar member 11 and is interlocked with the base portion 13 of the columnar member 11 so as to be shiftable only in the axial direction, and being integrally provided on the machine elements 1 and 2 (which in the present case are the tool post and the tool post slide which are mutually coupled with the base end 14 of the columnar member 11 and the holder 15.) Accordingly, variation of the mutual micro-positional relationship of the coupled machine elements 1 and 2 is possible by utilizing the elastic deformation of the columnar member 11 caused by the fluid pressure in the pressure chamber 10. As the base portion 13 of the columnar chamber 11 and the holder 15 are interlocked to be shiftable only in the axial direction by a washer like spring plate 16 or a sliding portion 16a, the cutting reaction force working in the right angle direction of the Y axis is transmitted to the tool post slide 2 in the interlocked portion, and no bending stress works on the columnar member 11, and therefore, the rigidity in the coupled portion is assured, and also, an accurate linearity can be maintained between the fluid pressure in the pressure chamber 10 and displacement quantity of the machine element 1 in the Y axis direction.

Next, this invention will be described by referrring to embodiments shown in Figures 2 and 3.

The columnar member 11 of Figure 2 is constructed in such a way that the base end 14 is fixed to the tool post slide 2 by a bolt (not shown), and the tip 12 is fixed to the tool post 1 by means of the head member 17. The holding member 15 is integral with the tool post 1, and a cylindrical hole centering around the columnar member 11 is formed in the tool post, and a sleeve 18 is fitted within the cylindrical hole to form the pressure chamber 10.

The sleeve 18 is mounted so that the fluid pressure in the pressure chamber 10 does not work directly onto the tool post (which is a casting), and as a result, it is substantially an integral unit with the holder 15, and its lower end portion is slidable on the base portion 14 of the columnar member 11. The base portion 13 of the columnar member 11 and the holder 15 are interlocked so as to be movable only in the axial direction of the columnar member 11 by means of the sliding portion 16a, but in order to increase the rigidity of the interlocking portion, the holder 15 and the base portion 13 of the columnar member 11 are connected by the washer like spring plate 16.The inside diametral portion of the spring plate 16 is sandwiched between the base end 14 of the columnar member 11 and the tool post slide 2, and is fixed to the side of the tool post slide 2, and its outside diametral portion is sandwiched between the lower end portion of the holder 15 and the holding member 19, and is fixed to the side of the holder 15. Referance numerals 20,21,22 denote pressure oil supply holes provided in the tool post slide 2 and the columnar member 11, and numerals 23 and 24 denote liquid sealing units, and numeral 25 shown by imaginary line denotes a workpiece.

In the foregoing structure, when the operating pressure of oil supplied to the pressure chamber 10 is high, the pressure produces a uniform tensile stress in the axial direction of the columnar member 11, and as a result, the tool post 1 is displaced by a micro-quantity in the upper direction in Figure 2 on account of the resulting elastic distortion of the columnar member 11 so that micro-displacement in the Y axis direction can be applied to the tool mounting shaft 7.

The pressure oil supply unit to the pressure chamber 10 and the control system are shown in Figure 3, and numeral 26 denotes a cylinder of the pressure oil supply unit, and 27 denotes a plunger moving back and forth in the cylinder 26, and 28 denotes a screw formed integral with the plunger 27, and 29 denotes a gear meshed with the screw 28, and 30 denotes a gear meshed with the gear 29, and 31 denotes a DC motor for driving the gear 30, and 32 denotes an oil pressure pipe.The DC motor 31 rotates by the servo control that is operated by the control unit to be described hereinafter, and rotates the gear 29 supported by the frame (not shown) by means of the bearing 33, and causes the nonrotating plunger 27 to move back and forth to change the pressure of the operating oil to be supplied to the pressure chamber 10, and change the quantity of displacement of the tool post 1 in the Y axis direction.

The quantity of displacement of the tool post 1 is detected by the differential transformer 34, and is applied to the differential amplifier 36 through the insulated amplifier 35, and on the other hand, the instruction data applied from the NC device or other instruction device (not shown) is applied to the differential amplifier 36 through the D-A converter, and the servo amplifier controls the DC motor 31 by the differential signal. When the output of the differential amplifier 36 becomes within a fixed allowable value, the coincidence signal from the comparator 37 is outputted to the instruction device, and the position in the Y axis direction of the tool post 1 and the tool 8 is set at the instructed position.

As described in the foregoing, the position of the tool post 1 is corrected in the Y axis direction or is displaced, and machining error due to the thermal deformation of the loaded workpiece 25 or machining error due to the abrasion of the tool 8 is corrected or machining with accuracy according to the difference of various fitting dimensions such as a key way or the like can be achieved by the displacement of the tool post 1 in the Y axis direction, but as the uniform tensile stress only is applied to the columnar member 11 by the construction mentioned in the foregoing, the accurate linar relationship between the pressure of the pressure oil to be supplied to the pressure chamber 10 and the displacement of the tool post 1 is assured whereby the control of the quantity of displacement can be carried out easily with extreme accuracy.

The foregoing embodiment is used for correcting or adjusting the position of the tool post 1 in the Y axis direction of a compound lathe W. It will be appreciated that the coupling mechanism according to the present invention is suitable for use in any mechanism or machinery where a high rigidity and accuracy in position of the coupling is required. For example, the drilling machine B shown in Figure 4 is such that the column 38 and the base portion 39 are coupled by the coupling mechanism 40 of this invention, and the angle of the column 38 can be adjusted minutely and correctly by supplying oil pressure selectively to the respective coupling mechanisms 40....40. Numeral 47 of Figure 4 denotes the support plate, and the column 38 is fixed to the support plate 47, and the support plate 47 and the base 39 are coupled by the coupling mechanisms 40....40.Also, in the lathe T shown in Figure 5, the tail stock 41 and its tail stock slide 42 are coupled by using the coupling mechanisms 40....40 of this invention in horizontal direction, so thatthe spindle 43 and the tail stock 41 may be displaced in minute angle in the horizontal plane to perform correction of the taper of the workpiece 25 or degree of its cylindrical shape, and moreover, in case the tool post 44 and the tool post slide 45 are coupled by using the coupling mechanisms 40...40 of this inven- tion in horizontal direction, so that the cutting tool 46 may be statically or dynamically moved back and forth to correct the dimension difference of the outside diameter of the workpiece 25 orto correct its roundness.Numeral 48 of Figure 5 denotes the bed, and 49 denotes the base, and 50 denotes the machine case in which the spindle drive mechanism is built in.

The columnar member 11 in the coupling mechanism of this invention has high rigidity in the axial direction, and the possible displacement quantity of the coupled machine elements is less than 1 milimeter. The control of the displacement quantity is possibly carried out with the accuracy in the order of 1 micron, and the fluid pressure to be supplied to the pressure chamber 10 is practically set at high pressure of about 500 to 700 kg per square centimeter. In this high pressure fluid as mentioned in the foregoing, the compressing property by the air to be mixed into the fluid becomes a major factor of deteriorating the control accuracy of the displacement quantity, particularly, the dynamic control accuracy. In order to avoid the deterioration of the control accuracy by the mixed air, it is effective to minimize the volume of the pressure chamber 10 as small as possible, and the sleeve 51 is inserted into the pressure chamber 10 to minimize the volume of the pressure chamber 10 as shown in the imaginary line in Figure 2 which is effective.

Claims

1. A coupling mechanism for coupling a pair of mechanical elements, the mechanism including a fluid pressure chamber formed in one of said elements and an elongate member housed in said pressure chamber so that fluid pressure applied to said chamber applies tensile stress to said elongate member to cause it to stretch, the elongate member being attached to said members so that axial movement of the elongate member caused by said tensile stress causes relative movement between said members.

2. A coupling mechanism according to Claim 1 wherein the elongate member is in the form of a column.

3. A coupling mechanism according to Claim 1 or 2 wherein the elongate member is attached at one axial end to one of said elements and is attached at its other axial end to the other of said axial elements.

4. A coupling mechanism according to Claim 3 wherein said other axial end is interlocked with said other of said elements via a spring washer.

5. A coupling mechanism according.to any preceding Claim wherein the pressure chamber is defined by a sleeve which in use is inserted into a bore formed in one of said elements.

6. A coupling mechanism according to Claim 5 wherein a further sleeve is incorporated within said pressure chamber in order to reduce the column of the pressure chamber defined by said sleeve.

7. A coupling mechanism substantially as described with reference to and as illustrated in Figure 2 or 3 of the accompanying drawings.

8. Machinery including a pair of mechanical elements coupled together by a coupling mechanism according to any of Claims 1 to 7.

9. Machinery substantially as described and illustrated with reference to any of the accompanying drawings.