US3034300A

US3034300A - Supervising device for hydraulic adjusting apparatus in automatic lathes

Info

Publication number: US3034300A
Application number: US615379A
Authority: US
Inventors: Hachenberg Edmund
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-10-15
Filing date: 1956-10-11
Publication date: 1962-05-15
Anticipated expiration: 1979-05-15
Also published as: GB843396A; DE1107048B

Description

y 1962 E. HACHENBERG 3,034,300

SUPERVISING DEVICE FOR'HYDRAULIC ADJUSTING APPARATUS IN AUTOMATIC LATHES Filed Oct. 11, 1956 SUPERVHSING DEVICE FQR HYDRAULIC ADJUST- ING APPARATUS 1N AUTGMATIC LATHES Edmund Hachenherg, Kola, Germany, assignor to Alfred H. Schutte, Kola-Bouts, Germany, a German company Filed Oct. 11, 1956, Ser. No. 615,379 Claims priority, application Germany st. 15, 1355 Claims. ((11. 60-545) Automatic lathes are known in which the control of the tool slides or other movable parts by any desired cam levers, connecting rods and the like, is eiiected not directly but by way of hydraulic transmission systems. The mechanically-moved parts then actuate a control piston the movements of which are transmitted through two closed pressure oil columns, acting in opposite directions, to a working piston connected to a tool holder or a clamping device as the case may be. It is also known to provide a safeguard against overloading in the form of a pressure relief valve in such a hydraulic transmission sys tern.

The object of the present invention is to avoid the difliculties which must necessarily arise in the known devices because a certain working operation has to be carried out in a specific time while, in addition, it must be ensured that the hydraulically-moved slides, tools or clamping devices have reached the end position reliably determined by a stop andremain at such end position for a suiliciently long time. If this is not the case the machine must be stopped, otherwise the workpieces are not machined accurately or the workpiece is not held sulficiently fast in the clamping device. However, the pressure in the hydraulic transmission system must not be too high.

According to the present invention, in an automatic lathe of the abovementioned type, the existing difliculties are eliminated in that the attainment of the end position of the working piston, at least when it moves in the direction of application, is controlled by supervising the pressure of the pressure oil column which efiects such displacement. One or both of the oppositely acting pressure oil columns is connected to actuate a compensating piston which, when a specific range of movement thereof is exceeded, owing to lack of oil or too high an oil pressure, switches oi the machine and/ or actuates an indicating device. In accordance with an aspect of the invention, in one or both ends of the control cylinder in which the control piston moves, there is provided a spring-loaded compensating piston which takes up a variable position in accordance with the pressure of the pressure oil and which, in turn, is connected to the control means for switching oil? the drive and/or indicating unallowable pressure oil conditions. The travel of such a compensating piston is limited at the side facing in the direction of its spring-urged movement by a fixed stop, and the spring tension expediently is adjustable. Connected to the compensating piston by a feeler there is a multiple switch which, when the compensating piston is in its specific positions, actuates corresponding indicating devices or, in cooperation with a switch operated by a cam rotating synchroniously with the control cam, holds closed or opens a holding contact arranged in the circuit of the driving motor.

An embodiment of the invention is illustrated in the accompanying drawing, wherein the single diagrammatic View shows the application to the control of a tool slide.

The tool is carried by the tool slide 19 the exact end position of which is determined by an adjustable stop 11, while the feed and withdrawal of the tool slide is effected by a piston 12 which is movable in a working cylinder 13. The interior of cylinder 13 at the opposite sides of piston 12 communicates through pipes 14 and 15 with a am ss Patented May 15, 1962 control cylinder 16 at the opposite sides of a control piston 17 movable in cylinder 16. The control piston 17 is actuated by a two-armed lever 18, having an adjustable pivot 46, which is, in turn, actuated by a control cam 19 on a shaft 20 also carrying a control cam 21.

The cylinder chambers at the opposite sides of the control piston 17 are bounded inside the cylinder 16 by slidable compensating

pistons

22 and 23, which are acted upon at the sides remote from piston 17, by compression springs 24 and 24a respectively and the movements of the compensating pistons toward the control piston are limited by

stops

25 and 26, the compression of springs 24 and 24a being adjustable by means of screws 27 and 28..

The cylinder chambers at the opposite sides of the control piston 17 are filled automatically through a pipe 29 which communicates with a high-level tank 30 receiving oil through a pipe 30m from the circulatory lubricating system of the machine, More oil is always delivered than is necessary and the surplus flows out of tank. 30 through an overflow 30b for return to the oil sump. It is not necessary to check the oil level in the high level tank 30 and to replenish it. As soon as the piston 17, in moving in one or the other direction, has closed the inlet duct 29 for the pressure oil, further movement of the piston will compressthe column of oil in front of it so that the working piston 12 will move in the opposite direction. At the same time oil is forced back into the control cylinder 16 from in front of the working piston considered in the direction of movement of the latter.

The compensating piston 22 is engaged at its side tacing away from control piston 17 by a feeder 31 connected to a switch '32 which carries two

contact bridges

33 and 34 arranged in different holding circuits for the driving motor M of the machine. For example, as shown in the drawing, the

bridge contacts

33 and 34 are connected in series between

conductors

47 and 48 forming part of a conventional motor control circuit that includes the secondary of a transformer 49 having its primary energized from supply lines 50 and a relay 51, energized by completion of the control circuit to close the motor circuit made up of conductors 52 and 53 for connecting motor M to supply lines '50.

A switch 35 is actuated by the cam 21 and includes: alternatively closed contacts 36 and 41. The contact 36 is connected in parallel with the bridge contact 33 of.

switch 32 so that the described motor control circuit can also be completed when the bridge contact 33 is open and the

contacts

34 and 36 are simultaneously closed.

The multiple switch 32 further includes

bridge contacts

37 and 38 which are interposed in energizing circuits;

for signal devices 39and 40, and the contact 41 of switch 35 is connected in series with bridge contact 37 so that the related signal 39 is energized only when the contacts 37 and 41 are simultaneously closed.

The

bridge contacts

33, 34, 37 and 38 of multiple switch 32 are disposed relative to the corresponding fixed contacts so that, when the compensating piston 22 and the feeler 31 are displaced toward the left, as viewed in the drawing, in response to continued movement of piston 17 toward the left following engagement of slide 10' with stop 11 under normal operating conditions,

contacts

33 and 34 are simultaneously closed while contacts 37 and- 38 are simultaneously opened (as shown). Further, contacts 33 and '34 are positionally related so that a smaller movement of teeler 31 toward the left, as viewed in the drawing, will cause closing only 'of bridge contact 34,

while contact 33 will remain open. On theother hand,

excessive movement of feeler 31 toward the left, as viewed in the drawing, will cause opening of both

contacts

33 and 34, and simultaneous closing of contact 38.

The cam 21 is arranged with respect to the cam 19 so that, when the radially enlarged portion of cam 19 is with the contacts 36 and 41 intheir open and closed conditions, respectively. On the other hand, when the this way it is possible to adjust the ranges and the positions of the ranges at which the switching arrangements for the indicating means 39 and All come into operation.

If there is too little oil in the pipe 15 and in the cylinder chambers connected therewith, the supply can be replenished by operating a hand pump 42. In the supply replenishing pipe at non-return valve 43 and a shut-elf valve 44 are arranged in series.

The operation of the above described device is as follows: During a predetermined portion of each revolution of the cam19 in the direction of the arrow 45, it

tion in which the contact bridge 34 is opened but the contact bridge 38 is closed. Thus, the control circuit for the motor is interrupted and the driving motor comes to a stop while the indicating device 40 lights up.

In the constructional'form described above a tool slide 10 is controlled, the working position of the tool being determined by a stop '11; The actuation of a clamping device for the workpiece can be effected in a similar presses the control piston 17 towards the left and applies pressure to the pressure oil column in the pipe 15, so that the column advances the working piston 12 with the tool holder 10 so far as to abut the latter against the stop 11. Owing to the pressure of the oil on the left-hand side of the control piston 17, the compensating piston 22 is pushed back from the stop 25 in opposition to the action of the spring .24 and the compensating piston presses back the feeler 31 so that the two

contact bridges

33 and 34 are simultaneously closed, while, on the contrary the two

contact bridges

37 and 38 are opened. Therefore, the oil control arrangement operates as required,

contact 41 is openeda Even though the pressure in cylinder 16 at the left hand side of piston 17 is reduced by reason of the return of piston 17 toward the right, so that contact 33 is opened, the control circuit for the driving motor is still completed by way of the contact bridge 34 and contact 36. The circuits of the indicating

devices

39 and 40 are also interrupted, since the supply of cur- 'rent to the indicating device 39 is interrupted at the open contact 41, and the supply of current to the indicating device 40 is interrupted at the open contact 38. When unallowable oil pressure conditions occur, the following takes place:

If there are excessively great oil losses due to leakage in the pipe 15, the compensating piston 22 will no longer be'lifted away from the stop 25' or will not be moved away to an adequate extent following engagement ofslide 10 with stop 11. The switch 32 is then in a position in position. On the other hand the bridge contact 33 is situated in the o or open position. Then if the control shaft 20 rotates further and the contact 36 is opened and the contact 41 is closed, the holding circuit of the driving motor is interrupted at 36 so that the motor is stopped. At the same time, the indicating device 39 is fed with current through the contacts 41 and 37 so that it lights up. The quantity of pressure oil which is lacking can be added to the system by operating the hand, pump 42.

If the working piston 12 cannot reach its normal end position, the pressure in the pipe 15 and related part of cylinder 16 increases to a value higher than normal, since the control piston 17 is forcibly moved through its full 7 stroke by the cam 19'. As a result, the compensating piston 22 moves further outwards and compresses the spring 24 still further; When the highest permissible pressure" is exceeded in the pipe 15, the compensating piston ,22, by means of the feeler 31-, moves the switch 32 into a posi manner. In that case, movement of the working piston is stopped either by the clamping of the workpiece or by a fixed stop in the clamping device.

I claim:

1. In an automatic lathe having a driving motor and electric control means therefor, the combination of an operating cylinder having an operating piston reciprocable therein through a working and return stroke to actuate a part of the lathe, a control cylinder, a control piston reciprocable in said control cylinder, cam operatedmeans for reciprocating said control piston, conduits connecting said operating andcontrol cylinders at the opposite sides of the pistons therein, said cylinders and conduits being filled with hydraulic fluid to define a closed hydraulic transmis- Sion system for effecting said working and return strokes of said operatingpiston in response to movement of said control piston in one direction and in the opposite direction, respectively, at least the end of said control cylinder toward which said control pistonmoves in said one direction being defined by a compensating piston reciprocably slidable in the control cylinder and subjected to the pressure in said system at the adjacent side of the control piston, spring means opposing the movement of said compensating piston by the pressure in said system, and multiple throw switch means adapted to be interposed in the electric control means for the driving motor and actuated by movement .of said compensating piston to halt the operation of the motor in response to a shortage of fluid in said system at the end of said working stroke and in response to the occurrence of an excessive pressure in said system during the working stroke.-

2. In an automatic lathe, the combination as in claim 1; further comprising first and second indicating means controllable by said switch means to signal the bait of operation of the motor upon a shortage of fluid in Said system at the end of the working stroke and upon the occurrence of an excessive pressure in the system during a working stroke, respectively.

3. In an automatic lathe, the combination as in claim 1; further comprising a fixed stop limiting the movement of said compensating piston in one direction.

4. In anautomatic lathe, the combination as in claim 1; further comprising means. for adjusting the force with which said spring means opposes the movement of said compensating piston by the pressure in said system.

5. In an automatic lathe, the combination as in claim 1; further comprising means for positively limiting said'working stroke of said operating piston.

6. In an automatic lathe, the combination as in claim 1; further comprising normally inoperative pump means for supplying hydraulic fluid to the one of said conduits connected to said control cylinder at the side of said control piston facing in said one direction of movement in the event of a shortage of fluid in said system. i

7. In an automatic lathe, the combination as in claim 1; wherein said switch means includes first and second contacts connected in series to cause operation of the motor when said first and second contacts are simultaneously closed,'said first and second contacts being arranged to close simultaneously only in response to a predetermined pressure acting on said compensating piston and to open individually in response to pressures on said compensating piston which are respectively less than and greater than said predetermined pressure; and further comprising a cam actuated switch operated synchronously with said cam operated means and having a normally open contact con nected in parallel with said first contact and closed following said working stroke to prevent a halt in the operation of the motor by reason of a reduced pressure acting on said compensating piston during said return stroke.

8. In an automatic lathe, the combination as in claim 7; further comprising first indicating means operative to indicate a shortage of fluid in said system at the end of the working stroke, second indicating means operative to indicate an excessive pressure in the system during the working stroke, and control circuits for said first and second indicating means, respectively; and wherein said switch means includes third and fourth contacts which are respectively closed only in response to pressures acting on said compensating piston which are less than, and more than, said predetermined pressure, said third contact being interposed in said control circuit of the first indicating means for operating the latter when said third contact is closed, and said cam actuated switch further having a normally closed contact connected in serieswith said fourth contact in the control circuit of said second indicating means, said normally closed contact being opened following said Working stroke so that said control circuit of the second indicating means can be completed only during said working stroke.

9. An electro-hydraulic control system comprising an operating cylinder having an operating piston reciprocable therein through a working stroke and a return stroke, a control cylinder having a control piston reciprocahle therein, mechanical means for reciprocating said control piston, conduits connecting said operating and control cylinders at the opposite sides of the pistons therein, said cylinders and conduits being filled with hydraulic fluid to define a closed hydraulic transmission system for effecting said working and return strokes of said operating piston in response to movement of said control piston in one direction and in the opposite direction, respectively, at least the end of said control cylinder toward which said control piston moves in said one direction being defined by a cornpensating piston reciprocably slidable in the control cylinder and subjected to the pressure in said hydraulic transmission system at the adjacent side of the control piston, spring means opposing the movement of said compensat- 6 ing piston by the pressure in the hydraulic transmisison system, multiple-throw switch means actuated by said compensating piston, and electric control circuit means having said switch means interposed therein and being interrupted by the latter in response to a shortage of fluid in said hydraulic transmission system at the end of said working stroke and in response to the occurrence of an excessive pressure in said system during the working stroke.

10. An electro-hydraulic control system as in claim 9; wherein said switch means includes first and second contacts connected in series in said electric control circuit means, said first and second contacts closing simultaneously only in response to a predetermined pressure acting on said compensating piston and opening individually in response to pressures on said compensating piston which are respectively less than and greater than said predetermined pressure; and wherein said electric control circuit means further includes second switch means actuated in synchronism with said mechanical means reciprocating the control piston and having a normally open contact connected in parallel with said first contact of the first mentioned switch means, said normally open contact being closed following said working stroke to prevent interruption of said electric control circuit means by reason of a reduced pressure acting on said compensating piston during said return stroke.

References Cited in the file of this patent UNITED STATES PATENTS 1,557,330 Reynolds Oct. 13, 1925 2,400,840 Peters May 21, 1946 2,437,821 Hughes Mar. 16, 1948 2,557,824 I-Iornfeck June 19, 1951 2,583,825 Felt Jan. 29, 1952 2,590,022 Larkin Mar. 18, 1952 2,632,956 Crosby Mar. 31, 1953 2,674,232 Mason Apr. 6, 1954 2,756,563 Bohlman et a1 July 31, 1956 2,766,590 Erwin et a1 Oct. 16, 1956