US2935821A

US2935821A - Traverse control device for grinding machines

Info

Publication number: US2935821A
Application number: US644176A
Authority: US
Inventors: Allemann Hugo
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-03-06
Filing date: 1957-03-05
Publication date: 1960-05-10
Anticipated expiration: 1977-05-10

Description

May 10, 1960 H. ALLEMANN TRAVERSE CONTROL DEVICE FOR GRINDING MACHINES Filed March 5. 1957 3 Sheets-Sheet 1 WWI/1 Inventor! Md. M

M ay 10, 1960 H; ALLEMANN 2,935,821

TRAVERSE CONTROL DEVICE FOR GRINDING MACHINES Filed March 5. 1957 3 Sheets-Sheet 2 May 10, 1960 H. ALLEMANN 2,935,821

TRAVERSE CONTROL DEVICE FOR GRINDING MACHINES Filed March 5. 1957 3 Sheets-Sheet 3 FIG. 5

INVENTOR. Hue-o Hw HnN v BY Hana-em. S- S'WQKE/Z,

MTQKNEY TRAVERSE CONTROL DEVICE FOR GRINDING MACHINES Hugo Allemann, Schaanwald FL, Switzerland Application March 5, 1957, Serial N6. 644,176 Claims priority, application Switzerland March 6, 195 6 16 Claims. or. 51-44 The present invention refers to grinding machines and more particularly to a device for controlling the traverse movement of either the spindle carrier or the work carrier.

j 2,935,821 Patented May 1Q, 1960 The novelfeatures which are considered as characteris- I tic for the invention are set forth in particular in the ap' 5. additional objects and advantages thereof, will be best The invention is particularly suitable for those grinding devices which are driven by compressed air and are used for internal grinding. Frequently this type of internal grinding machines are constructed so as to be adapted to bemounted for instance on the cross slide of a lathe. In

grinding devices of this type usually the grinding spindle with respect to the workpiece, or the work carrier with respect to a stationary grinding spindle. Means are known for producing the reciprocating movement or traverse of either the work carrier or the spindle carrier manually or mechanically. However, in the case of manual operation the quality of the ground surface is usually not good enough and uniform enough to meet standards. Automatic means for controlling the traverse movement are known but have been found to be comparatively complicated and very expensive. 6

It is a main object of this invention to provide a device for controlling the traverse movement of either the work carrier or the spindle carrier of a'grinding machine fully automatically.

It is a further object of this invention to provide a device of the type set forth which is simple in structureand therefore comparatively less expensive than known devices.

It is still a further object ofthis invention to providea device of the type set forth which can be adjustedwith respect to the length of the stroke of the moved part and which also can be adjusted with respect to thespeed of movement of the moved part. j

It is still another object of this invention to provide a device of the type described which is composed of simple understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Figure 1 is a perspective view of the entire arrangement of a grinding device according to the invention;

Figure 2 is a diagrammatic sectional view of the device with some of the control means; Figure 3 is another diagrammatic sectional view of the same device showing other parts of the control means; 1 Figure 4 is a diagrammatic sectional view of adevice for controlling the speed of the moving parts of the machine; 6 a 1 Fig. '5 is a fragmentary front elevation of a machine incorporating an embodiment of the invention; and i Fig. 6 is a plan view of the machine shown in Fig. 5.-

Referring to Figs. 1, 5 and 6, the grinding device'is mounted on a support plate 1 which may be attached for instance to the cross slides of a lathe L having a work carrier C to hold a work piece W. A housing block 2 is hingedly attached to the support plate 1 sothatthe device with all of the elements contained in the housing block 2 can be tilted into and from an operative position with respect to the rest of the machine on which the device is mounted. In the housing block 2 all of the working memhers and the control means'are mounted as well as the grinding spindle carrier 3 which surrounds the actual grinding spindle '4 and which carries at its rear end an air turbine 5. The housing of the turbine 5 has a projecting lug 6 which is adapted to engage either one of the two

collars

8 and 9 adjustably mounted on a shank 10 which is part of a control valve 7 which will be described later on. The handle 11 serves to operate a speed control which will also be described further below.

In the housing block 2 is mounted the spindle carrier 3 for sliding movement in its axial direction. The spindle carrier 3 is rigidlyconnected by a rod 27 to a main piston and sturdily constructed parts and therefore is likely to give reliable and long lasting service;

With above objects in view, a grinding machine according to the invention includes a spindle carrier and a work carrier one of these carriers being movable with respect to the other in axial direction of said spindle between two end positions. It further includes a main cylinder and a main piston movable within this cylinder between two and positions and adapted to impart a corresponding reciprocating movement to one of said carriers. The machine further includes means for introducing a fluid under pres- .1

26 which is movable between end positions in a'corresponding'bore 22 or main cylinder of the housing block 2.

Compressed air is introduced by an inlet 12 into'a chamber 13 which is connected by a duct 15 to a chamber 19 surrounding a main vaive l4, and to a chamber 16 surrounding the control valve 7. Fig. 2 shows the device in a position in which the spindle carrierS is in its rearward end position. In the position shown: in Fig. 2, the lug 6 of the turbine housing 5 has engaged the collar 8 and thereby moved the control valve 7 together with the spindle carrier3 into its rearward end position. In this position the. compressed air can flow from the chamber 16 through a groove 17 in the valve 7 and through a duct 18 in the housing block zinto the spacebehind one end of the main valve 14. Hereby, the main valve 14 is forced to the right, as seen'and shown in Fig. 2, so that the compressed air in the cham ber 19 can flow through the groove 20 in the main valve the main piston 26 from the position shown in Fig. 2

in direction towards right as v seen in Fig. 2, whereby the spindle carrier 3, as shown in Fig. 3, is carried along by means of a connecting rod 27 and likewise moved in .right.

: direction to the left.

hand position, the air from chamber 19 flows through I

valves

35 and 38 can be adjusted so as to predetermine block, through the transverse bore 29 of the main valve 14 and through a duct 30 shown in dotted lines into 6 the silencer chamber 25.

Shortly before the spindle carrier 3 reaches its righthand end position the lug 6 engages the collar 9 so that the control valve 7gis also moved in direction to the flows through the groove 17 of the control valve 7 and through the duct 23 into the opposite end of the bore containing the main valve 14 and moves the latter in When the valve 14 is in its leftthe groove 20 of the main valve 14 and through the duct 28 into the space at the right-hand end of 'the main cylinder 22 whereby the main piston 26 is returned to 7 ,its previous position at the left end of the main cylinder Now the compressed air from the chamber 16 10 I, portion of each of

chambers

33 and 37 due to the shape of the chambers. Such air may be introduced for example when filling sleeve 48 with hydraulic fluid. The air bubbles may further be replenished by leakage of air from space 13 which'is permenently filled with compressed air past piston 32 into that one of the chambers which is temporarily under negative pressure during movement of piston 32.

This entrapped air bubble acts as a resilient cushion in the otherwise non-compressible hydraulic circifit. The bubble is compressed towards the end of thestroke of piston 32 and accelerates initial movement of the piston 32 during its expansion "after reversal of piston movement.

As has been mentioned before the function of the the speed of the axial movement of the spindle carrier 3. For this purpose control means are devised and diagrammatically illustrated in Figure 4. A control rod 42 is 22, the spindle carrier 3 being hereby also moved back 20 turnably mounted in the housing block 2 and ends atone ,into the previous position as shown in Figs. 2 and 3.

This movement towards left continues until the lug 6 engages the collar 8 shortly before the spindle carrier .3 reaches its end position. As soon as the control valve 7 reaches its left-hand end position the whole cycle as 2 described repeats.

The

collars

8 and 9 can be set to selected positions on the threaded stem 10 for-adjusting the stroke of the spindle carrier 3. All the air consumed in the various devices described above is caused to'flow into the silencer 30 chamber 25. From this chamber the air enters the bore in which the spindle carrier 3 travels so that the air blowing out at that end of this bore which faces toward the grinding wheel prevents the entrance of grit or dust into this bore.

speed control device. The piston 32 is movable between end positions within a cylinder sleeve 48. At either end 'of the cylinder 48 are portions of slightly enlarged diameter constituting the

end chambers

33 and 37, respectively. When for instance the piston 32 is moved by the movement of the main piston 26 from the position shown .-in Figure 3 towards the right end of its cylinder 48 then the oil contained in the chamber 33 is forced through a 45, conduit 34 and through a valve 35 into an oil chamber 36. As will be described later, 'the'va'lve 35 can be adjusted in such a manner that the cross sectional area'" of the passage through this valve and thereby the amount of oil passing through the valve can be regulated in such a manner that depending upon the larger or smaller restriction in this passage the speed-of the movement of I the main piston 26 is controlled. In the position shown and under the circumstances just mentioned the oil is sucked into the opposite oil chamber 37 through the valve 38 and the conduit 39 from the oil chamber 36. When the direction of movement of the spindle carrier and the main piston 26 is reversed as described further above, then the function of the

chambers

33 and 37 "is also reversed because now the chamber 33 is a suction chamber while 37 is a pressure chamber. It can be seen from Figure 3 that when suction is applied to the

valves

35 and 38, respectively, through the conduits 34 and'39, respectively, the valve opens under the suction against side with a handle 11 as mentioned above. A portion of the control rod 42 is turned down eccentrically as indicated at 42. The

valve balls

43 and 44, respectively, of the two

valves

35 and 38, respectively, are suported on the eccentric portion 42. When by means of the handle 11 the control rod 42 is turned the

individual balls

43 and 44, respectively are more or less lifted or lowered. In this manner the cross section of the area of thevalves 3S and 38, respectively, around the

balls

43 and 44, respectively, ischanged. The exit bores 45, 46, respectively, of the two

valves

35, 38, respectively, are connected with the above mentioned conduits 34, 39, respec' tively. One end of the control rod 42 is supported in an excenterbushing 47 which is tunrable in the housing 5 block 2. By turning this bushing 47 the effect of the control rod 42 on the two valves is influenced in such a manner that the passage of one of the valves and thereby the actual speed of the spindle carrier 3 in opposite directions can be adjusted so that the speed in one direction is fasteror slower than in the opposite direction. For obvious reasons suitable seals are provided around the outer ends of the control shaft 42 and if necessary around the bushing 47 but have been omitted in the drawing for the sake of clarity.

It is advisable to provide a certain play between the piston-32 and its cylinder 48 so that a small portion of the oil may leak out there and may gather at the bottom 13' of the air chamber 13 so that it is forced from there "by-the'compressed air to all those portions of the whole device which require lubrication. It should be understood that in certain cases it may be desirable to modify the device described above in such manner that the pressure fluid operates to move the spindle carrier or work carr'ieronly in one direction and that the control means are'us'ed only for controlling this movement while the return movement is controlled by'resilient means as for instance a spring acting against the force exerted on the 'moved par-ts in the first mentioned direction.

It 'will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of traverse control de- Tvices differing from the types described above.

While the invention has been illustrated and described the spring supporting the ball which is the closing elegrinding machines, it is not intended to be limited to the ment of the valve.

The above mentioned

enlarged end chambers

33 and 37, respectively, serve for holding air cushions in order to increase the speed of the axially directed movement details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully of the spindle carrier at the reversal points of its movereveal the gist of the present invention that others can ment, but only over a small portion of its travel. The

size of these air cushions can be chosen in order to select a certain length of ,the accelerated movement of the spindle carrier.

' by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic 'or specific aspects of this inven- A'bubble of air is trapped permanently in at least-a tion and, therefore, such adaptations should and arcintended to be comprehended within the meaning and range of equivalence of the following claims. What is claimed as new and desired to be secured by Letters Patent is:

1. In .a machine tool, incombination, a tool carrier and a work carrier, one of said carriers being movable with respect to the other between two end positions; a main cylinder; a main piston movable within said main cylinder between two end positions and adapted toimpart a corresponding reciprocating movement to onei-of 'said carriers; means for introducing a fluid under. pressure into said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; and actuating means-connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers; and hydraulic speed control means connectedto said'one of said carriers for regulating the speed of movement of said main piston, said speed control meanscomprising a closed hydraulic circuit, a 'solid member'and a fluid jointly movable in said circuit, said solid member being connected tosaid main piston for joint movement therewith, and adjustable valve means for regualting the flow of hydraulic fluid through said cir- -cuit, so that whenever said one of said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as to 'cause said carrier to move automatically in opposite direction towards its other end position at a predetermined :speed. 3 2. In a grinding machine, incombination, a spindle carrier and a work-carrier,1one of said carriers beingmov aisle with respect to the other between two end positions; :"amain cylinder; a main piston movable within. saidim'ain cylinder between two end positions and adapted to-impart :a corresponding reciprocating movement to one of said -carriers; means for introducing a fluid under pressure into ssaid main cylinder at either end thereof, including fluid "directing means for alternatingly directing said fluid to one 'or the other end of said mairr cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positionsof said one of said carriers; and speed control means connected to said oneof said carriersfor regulating the speed of the movement of said main piston, said speed control means comprising a closed hydraulic circuit, a solid member and a fluid jointly movable in said circuit, said solid member being connected to said main piston for joint movement there with, adjustable valve means for regulating the flow of hydraulic fluid through said circuit and turnable excenter means for controlling the degree of opening of said valve means, so that whenever said one of said carriers is moved towards one if its end positions and reaches one selected position saidfluid directing means are actuated so as to cause-said-carrier to move automatically in opposite di- 'rection towards its other end position at a predetermined speed. i y l 3. In a grinding machine tool, in combination; a tool carrier and a work carrier, one of said carriers being movable with respect to the other between two end positions; a main cylinder; a main piston'movable within said main movement therewith, adjustable valve means ifor regulating the flowof hydraulic fluid through said circuit and turnable excenter means for controlling the degree of opening of said valve means, so that whe'never said one of said carriers is moved towards one ofits end positions and reaches one selected position said fluid directing means are actuated so as to cause said carrier to move automatically in opposite direction towards its other end position at a predetermined speed. 7 r r 4. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said spindle between two end positions; a main cylinder;. a main piston movable within said main cylinder between .two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers; and hydraulic speed control means connected to said one of said carriers for regulating the speed'of the movement of said main piston, said speed control means comprising a hydraulic circuit including a control cylinder, a double-acting control piston movable between end positions in said control cylinder and connected with said main piston for movement conjointly. therewith, a fluid chamber, and conduit means connecting said chamher with the end portions of said control cylinder and incylinder between two end positions and adapted to impart a corresponding reciprocatingmovernent to one otv means connected to one of said carriers for actuating said' fluid directing means-in selected positions of said one of said carriers; and hydraulic speed control means con-.

nected to said one of said carriers for regulating the speed or the movement of said main piston, said speed control ;-means comprising a closed hydraulic circuit, asolid memher and a fluid jointly movable int-said circuit, said-solid .Lmember beingconnected-to said main piston forrjoint eluding adjustable valve means for regulating the resistance to the flow of hydraulic fluid through said conduit means and turnable excenter means for controlling the degree of opening of said valve means, so that whenever said one of said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as to cause said carrier to 'move automatically in opposite direction towards its other end position at a predetermined speed.

5. Ina grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction, of said spindle between two end positions; a main cylinder; a main piston movable within said main cylinder between two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers; and hydraulic speed control means connected to said 'one of said carriers for regulating the speed of the movement of said main piston, said speed control means comprising a hydraulic circuit including a-control cylinder, at double-acting control piston movable between end positions in said control cylinder and connected with said main piston for I movement conjointly therewith, a fluid chamber, and separate conduit means connecting said chamber with each end portion, respectively, of said control cylinder 'in opposite direction towards its other end position at a predetermined speed. i

6. In a grinding machine, in combination, .a spindle carrier and a work carrier, one. of said carriers being movable with respect to the other in axial direction of said spindle between two end positions; a "main cylinder; a gmain piston movable within said main cylinder between two end positions and adapted to impart a corersponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said main cylinder 'at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers; and hydraulic speed control means connected to said one of said carriers for regulating thespeed of the movement of said main piston, said speed control means comprising a hydraulic circuit including a control cylinder, a doubleactin'g control piston movable between end positions in said control cylinder and connected with said main piston for movement conjointly therewith, a fluid chamber, and

separate conduit means connecting said chamber with each end portion, respectively, of said control cylinder that whenever said one of said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as to cause said carrier to move automatically in opposite direction towards its other end position at a predetermined speed.

7. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said spindle between two end positions; a main cylinder; a main piston'movable within said main cylinder between two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into "said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers; and hydraulic speed control means connected to said one'of said carriers for regulating the speed of the movement of said main piston, said speed control means comprising a hydraulic circuit including a control cylinder, a double-acting control piston movable between end positions in said control cylinder and connected with said main piston for movement conjointly therewith, a fluid chamber, and separate conduit means connecting said 'chamber with each end portion, respectively, of said control cylinder and including one independentiy adjustable valve means in each of said conduit means for regulating the resistance to the flow of hydraulic fluid through said i 55 conduit means and turnable excenter means ,for controlling the degree of opening of said valve means, so that whenever said one of said carriers is moved towards'one of its end positions and reaches one selected position said fluid directing means are actuated so 'as to cause said carrier to move automatically in opposite direction towards its other end position at a predetermined speed adjusted separately for the forward and for the return stroke.

8. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said-spindle between two end positions; a main cylinder; -a main piston movable within said main cylinder between ;=means for alternatingly directing said fl uid'to one or the :other 'end of said 'main cylinder; actuating means connected to one of said carriers for actuating-said fluid di- 'recting means in'selected positions of said one of said carriers; and hydraulic speed control means connected to said one ofsaid carriers for regulating the speed of the movement of said main piston, said speed control means comprising a'hydraulic circuit including a control gree of opening of said valve means for regulating the resistance to the flow of hydraulicfluid through said conduit means, so that whenever said one of said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as to cause said carrier to move automatically in opposite direction towards'its other end position at a predetermined speed adjusted separately for the forward and 'for the return stroke.

9.1m a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of saidspindle between two end positions; a main cylinder; a main piston movable within said main cylinder between two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for' introducing a fluid under pressure into said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers; and hydraulic speed control means connected to said one of said carriers for regulating the speed of the movement of said main piston, said speed control means'comprising a hydraulic circuit including a control cylinder, a double-acting control piston movable between end positions in said control cylinder and connected with said main piston for movement conjointly therewith, a fluid chamber, and conduit means connecting said chamber with the'end portions of said control cylinder and including adjustable valve means for regulating the resistance to the flow of hydraulic fluid through said conduit means, said end portions of said control cylinder 'having a larger diameter than the main portion of said control cylinder whereby air can be enclosed in said end portions'for being compressed when said control piston reaches one of said end positions and for imparting to said main piston and said one of said carriers an accelerated speed at the beginning of the next stroke, so that'whenever said one of said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as to cause said carrier to move automatically in opposite direction towards its other end position at a' predetermined speed.

10. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said -spindle between two end positions; a maincylinder; a

main piston movable within said main cylinder between two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said main "cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid .directing means in selected positions of said one of said carriers, said fluid directing means including a control actuatingmeans, and a main valve movable between end positions, said control valve directing in each, of its end so as to move said main piston from'one of its end positions to its other end position; and hydraulic speed control means connected to said one of said carriers for regulating the speed of movement of said main piston, said speed control means comprising a closed hydraulic circuit, a solid member and a fluid jointly movable in said circuit, said solid member being connected to said main piston for joint movement therewith, adjustable valve means for regulating the flow of hydraulic fluid-through .said circuit and turnable excenter means for controlling thedegree of opening of said valve means, so that whenever said one of said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as to cause said carrier tomove automatically in opposite direction towards its other end position at a predetermined speed.-

11. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said spindle between, two end positions; a main cylinder; a main piston movable within said main cylinder between two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers, said actuating means including an actuating member attached to one of said carriers and moving to-' gether with the latter along a path, and engagement means connected to said fluid directing means and-projecting into said path for engagement with said actuating member when said one of said carriers'approaches its end positions whereby said fluid directing means are actuated every time said actuating member and said engagement means engage each other; and hydraulic speed control means connected to said one of said carriers for regulating the speed of movement of said main piston, said speed control means comprising a closed hydraulic circuit, a solid member and a fluid jointly movable in said circuit,

said solid member being connected to said main piston for joint movement therewith, adjustable valve means for regulating the flow of hydraulic fluid through said circuit and turnable excenter means for controlling the degree of opening of said valve means, so that whenever said one of said carriers is moved towards one of its end positions and reaches one selected positionsaid fluid directing means are actuated so as to cause said carrier to move automatically in opposite direction towards its other end position at a predetermined speed.

12. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said spindle between two end positions; a main cylinder;

a main piston movable within said main cylinder between two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers, said actuating means including engagement means attached to one of said carriers and moving together with the latter along a path, and an actuating member connected to said fluid directing means and projecting into said path for engagement with said engagement means when said one of said said main piston, said speed control means comprising a closed hydraulic circuit, a solid member and a fluid jointly movable in said circuit, said solid member being connected to said main piston for joint movement therewith, adjustable valve means for regulating the flow of hydraulic fluid through said circuit and turnable excenter means for controlling the degree of opening of said valvemeans, so that whenever said one of said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as tocause said carrier to move automatically in opposite di-- rection towards its other end position at a predetermined speed.

13. In a grinding machine, in combination, a spindle: carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said spindle between two end positions; a main cylinder; a main position movable within said main cylinder be-- tween two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said: main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers, said actuating means including an actuating member attached to one of said carriers and moving together with the latter along a path, and engagement" means connected to said fluid directing means and project-'- ing into said path for. engagement with said actuating: member when said one of said carriers approaches its: end positions whereby said fluid directing means are actu ated every time said actuating member and said engagement means engage each other, said engagement means: comprising two engagement members spaced from each other indirection of said path, at least one of said engagement members being adjustable in said direction for determining the selected positions of said one of said carriers in which said fluid directing means are to be actuated; and hydraulic speed' control means connected to said one of said carriers for regulating the speed of movement of said main piston, said speed control means comprising a closed hydraulic circuit, a solid member and a fluid jointly movable in said circuit, said solid member being connected to said main piston for joint movement therewith, adjustable valve means for regulating the flow of hydraulic fluid through said circuit and turnable excenter means for controlling the degree of opening of said valve means, so that whenever said one of said carriers is moved towards one of its end positions and reaches one selected position said-fluid directing means are actuated so as to cause said carrier to move automatically in opposite direction towards its other end position at a predetermined speed.

14. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to'the other in axial direction of said spindle between two end positions; a main cylinder; a main piston movable within said main cylinder between two end positions and adapted to impart a corresponding recting means in selected positions of said one of saidcarriers, said actuating means including engagement means attached-to one of saidcarriers and movingi'torgether with the latter along a path, and an actuating mem- :ber connected to said fluid directing means-land projecting into 'said path for engagement with said engagement :means when said one of said carriers approaches its end positions whereby said'fluid directing means are actuated every time said actuating member and said engagement means engage each other, said engagement means comprising two engagement members spaced from each other in direction of said path, at least one of said engagement members being adjustable in said direction for determining the selected positions of said one of said carriers in which said fluid directing means are to be actuated; and hydraulic speed control means connected to said one of said carriers for regulating the speed of movement of said main piston, said speed control means comprising a closed hydraulic circuit, a solid member and a fluid jointly movable in said circuit, said solid member being connected to said main piston for joint movement therewith, adjustable valve means for regulating the :flow

of hydraulic fluid through said circuit and turnable excenter means for controlling the degree of opening of said valve means, so that whenever said one of .said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as to cause said carrier to move automatically in opposite direction towards its other end 1 position at a predetermined speed.

15. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said spindle between two end positions; a main cylinder; asmain piston movable within said main cylinder between two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end of said main cylinder;.actuating means connected to one of said'carriers for actuating said fluid directing means in selected positionsof said one of said carriers; and hydraulic speed control means connected to said one of said carriersfor regulating the speed of movement of said main piston, said speed control means comprising a closed hydraulic circuit, a solid member and a fluid jointly movable in saidcircuit, said solid member being connected to said main -.piston for joint movement therewith, adjustable valve means for regulating'the flow of hydraulic fluid through said circuit passage means for permitting said fluid to flow from said main cylinder and from said fluid directing means to other parts :of themachine and pneumatic means for lubricating said other parts of the machine, so that whenever'saidloneof'saidcarriers is moved-towards one of its end positions'an'clreaches one selected position said fluid directing means are actuated so as to cause sald carrier to move "automatically in opposite direction towards its other end position.

:16. In a grinding machine, in combination, a spindle carrier and a work carrier, one of said carriers being movable with respect to the other in axial direction of said spindle between two end positions; a main cylinder; a main piston movable within said main cylinder. between two end positions and adapted to impart a corresponding reciprocating movement to one of said carriers; means for introducing a fluid under pressure into said main cylinder at either end thereof, including fluid directing means for alternatingly directing said fluid to one or the other end .of said main cylinder; actuating means connected to one of said carriers for actuating said fluid directing means in selected positions of said one of said carriers; and hydraulic speed control means connected to said one of said carriers for regulating the speed-of'the movement of said main piston, said speed control means comprising a hydraulic circuit including a control cylinder, a double-acting control piston movable between end positions in said controlcylinder and connected with said main piston for movement conjointly therewith, a fluid chamber, and conduit means connecting said chamber with the end portions of said control cylinderiand including adjustable valve means for regulating the resistance to the flow of hydraulic fluid through said conduit means, said control piston being guided in said control cylinder with suflicient play for permitting part of the hydraulic fluid to escape and to be available for lubrication of other parts of the machine, so that whenever said one vof said carriers is moved towards one of its end positions and reaches one selected position said fluid directing means are actuated so as to cause said carrier to move automatically in opposite direction towards its other end position at a predetermined speed.

References Cited in the file of this patent H UNITED STATES PATENTS Moulden Dec. 23, 1952