US1962459A - Hydraulic system for automatic machines - Google Patents

Description

June 12, 1934. H. E. OSTLUND 7 1,962,459

HYDRAULIC SYSTEM FOR AUTOMATIC MACHINES Filed Aug. 7, 1931 Harri. Boat Band.

7& M

Patented June 12, 1934 PATENT OFFICE HYDRAULIC SYSTEM FOR AUTOMATIC MACHINES Harry E. Ostlund, Worcester, Mass., assignor to The Heald Machine Company,

Worcester,

Mass., a corporation of Massachusetts Application August 7, 1931, Serial No. 555,747

11 Claims.

The present invention relates to hydraulic mechanisms for automatic machines and particularly to machines in which the movements of a vertical slide member are procured and controlled by fluid under pressure.

In machines having vertical slides mounted for reciprocatory movement and actuated by fluid under pressure, the rate of travel of the slide, when said slide is not mechanically counterbalanced, varies greatly, the downward movement occurring at a rapid rate and the upward movement occurring at a slower rate. In certain machine operations it is desira, to have the movements of the slide both upwardly and downwardly occur at substantially the same rate of speed, a feature which has not heretofore been obtained in slides which were not mechanically counterbalanced. It is accordingly an object of the present invention to provide a mechanism by which a vertically movable slide may be actuated by fluid under pressure so that the travel of said slide in both directions shall occur at substantially the same rate of speed.

Furthermore, it is desirable in machines of the above type to bring the vertically movable slide member to rest in any position of travel. It is difficult to support a slide which is not mechanically counterbalanced in fixed position by fluid under pressure since the weight of the slide would cause the fluid to leak out'of the cylinder and allow the slide gradually to creep downwardly with the possibility of injuring the operator, the work, or the tool. It is accordingly another object of the present invention to overcome this by providing a mechanism by which, in response to fluid under pressure, the slide is maintained in any position regardless of leakage in the slide actuating mechanism.

In case the fluid supply fails, or in the event of a substantial drop in the fluid pressure by which the slide is actuated, an unbalanced vertically movable slide will drop suddenly,causing damage to the tool or to the workand often times to the operator of the machine. Another object of the present invention is to avoid this danger by providing a safety locking device which supports the slide against downward movement in the event that the supply of fluid under pressure should become appreciably lowered. Other and further objects and advantages of the invention will be readily apparent from the following description taken in connection with the accompanying drawing in which- Fig. 1 is a fragmentary view of a machine embodying the invention.

Fig. 2 is a diagrammatic view of the hydraulic actuating mechanism.

Like reference characters refer to like parts throughout the drawing.

Referring to Fig. 1, the machine comprises a base 1 supporting a carriage 2 on which the work is to be mounted, said carriage being suitably mounted for movement on ways 3. The base is provided with an upstanding portion 4 on the upper end of which a slide or carriage 5 is mounted for vertical reciprocation in slideways not shown. The slide 5 is arranged to support a wheelhead 6 in which is mounted a shaft 7, the lower end of which carries a grinding wheel or other tool 8, and the upper end of which is connected to a motor 10 which is also mounted on the slide and which is arrangedto procure rotation of the tool 8. Although the slide or carriage is shown and described as a vertical slide, it will be apparent that the invention is applicable to any slide which has a component of movement in a vertical direction, that is, slides which are reciprocated' obliquely to the vertical.

The carriage is arranged to be reciprocated by fluid under pressure which is alternately directed to opposite ends of a cylinder 11 mounted in the upstanding portion, said cylinder carrying a piston 12 to which is connected a piston rod 13, the upper end of said piston rod being connected to a lug 14 on the slide 5. The piston rod is locked against movement relative to the lug by nuts 15 which engage the piston rod on opposite sides of said lug.

Fluid under pressure is supplied from a suitable source such as a pump 16 to a control valve 17, the latter being connected to said pump by a supply pipe 18 which enters a casing 20 for said valve at the port 21. The fluid supply is normally at a constant pressure as determined by the relief valve 19 of the usual construction. Fluid from the valve 17 is directed alternately to opposite ends of the cylinder 11 by a reversing valve 22, an inlet port 23 to the casing 24 for said reversing valve being connected by a pipe 25 to a port ,26 in the valve casing 20 for the control valve. In addition to the inlet port 23, the casing 24 for said reversing valve is provided with outlet ports 27 and 28 connected by pipes 30 and 31 to the upper and lower ends respectively of the cylinder 11 and an exhaust port 32. Said ports are arranged so that the exhaust port is connected alternately to ports 27 and 28, as the reversing valve is rotated, by channels 33 and 34 which are provided in said valve. In the position shown in Fig. 2, one of said channels provides fluid connection between the outlet port 28 and the exhaust port, and the other of said channels provides fluid connection from the inlet port 23 to the outlet port 27 which connects through pipe 30 to the upper end of the cylinder. Rotation of the reversing valve 22 reverses the connection from the inlet port 23 so that one of the channels then connects said inlet port to the outlet port 28 which connects through pipe 31 to the lower end of the cylinder, the other channel connecting the outlet port 27 to the exhaust. Fluid under pressure is thus admitted to either end of the cylinder as determined by the position of the rotating reversing valve 22 and, since said valve may be actuated in'response to movement or the carriage by any suitable mechanism not shown, thereby alternately to connect opposite ends of the cylinder to the fluid supply, a vertical reciprocatory movement may be imparted to the carriage.

In order that the movement of the slide in both directions of travel shall occur at substantially the same rate of speed, a valve mechanism is provided in the lower end of the cylinder. Vertical channels 35 and 36 provided in the lower end of the cylinder intersect a horizontal channel 37, the end of which connects to the pipe 31. The vertical channel 35 is formed with a valve seat 38 which is engaged by a downwardly closing valve 40, and a coil spring 41 which surrounds the valve stem 42 for the valve 40, normally holds said valve downwardly against said seat, thereby to prevent exhaust of fluid from said cylinder into the horizontal channel 37 and thence to the pipe 31, although admitting fluid readily from pipe 31 into said cylinder, the spring 41 being only sufllciently heavy to maintain the valve in closed position. The vertical channel 36 is formed with a valve seat 43 which receives an upwardly closing valve 44 and a coil spring 45 which surrounds the valve stem 46 for said valve 44, engages the surface of the valve at one end and engages an adjustable plug 47 at the other end. The plug 47 is screw threaded and engages in the lower end of the channel 36, said plug being provided with a vertical bore 48 which receives the depending end of the valve stem 46 to maintain said valve in proper relation to said valve seat. Said plug is adjusted so that the pressure at which said valve is opened is equal to substantially twice the pressure necessary to support the slide, that is, exhaust of fluid from beneath the piston is prevented until the pressure exerted on said fluid by the piston is equal to twice the weight of the slide.

When the valve 17 is now rotated from the position shown to provide fluid connection from the pump 16 to the reversing valve 22, the latter being in the position shown, fluid is directed to the upper end of the cylinder, thereby urging the piston downwardly. Since the only escape for fluid from the lower end of the cylinder is past the valve 44 through the pipe 31, and the reversing valve 22 to the exhaust, the outlet through port 50 being closed as will hereinafter appear, the weight of the slide, in addition to the fluid pressure on the upper side of the piston depresses the valve 44 against the force of the spring 45, thereby permitting fluid to escape through the pipe 31 to the exhaust. Since the valve 44 opens at twice the pressure necessary to support the slide, it will be apparent that the necessary pressure on the upper side of the piston is substantially equal to the weight of the slide, and enough additional pressure to overcome the friction and inertia of the parts of the carriage. When the reversing valve 22 is rotated to reverse the slide movement, whereby the slide is actuated upwardly, the valve 44 is closed by the spring 45 and fluid under pressure from the fluid pump 16 is admitted through pipe 31 underneath the valve 40 opening said valve and admitting fluid under pressure to the lower end of the cylinder. The pressure exerted by the spring 41 is light, being only suflicient to maintain the valve in closed position to prevent leakage of fluid past said valve when the slide is stationary, so that said valve opens readily in response to the fluid under pressure from said pump. The pressure necessary to raise the slide is substantially equal to the pressure necessary to counteract the weight of the slide, and enough additional pressure to overcome the friction and inertia of the parts, since the fluid from above said piston is allowed to exhaust freely. It will thus be apparent that the fluid pressure necessary to move the slide either upwardly or downwardly is substantially the same so that said slide will be actuated in the upward direction'at substantially the same speed that it obtains in the downward direction.

The carriage is arranged to be brought to rest in any position of movement at which time fluid under pressure is constantly admitted to the under side of the piston in order to maintain the slide in position, preventing downward movement of the slide due to leakage of fluid out of the cylinder. A pipe connection 51 is provided from the supply pipe 18 to a. port 52 in a casing 53 for a valve 54 and said valve is provided with intersecting channels 55, 56 and 57 which, in the position of said valve shown in Fig. 2, coincide respectively with the port 52 and ports 58 and 60 provided in said casing. Port 58 is connected by the pipe 59 to the port 50 provided in the lower end of said cylinder, and port 60 is connected by a pipe 61 to an auxiliary relief valve 62, the latter being adjusted for a pressure substantially equal to the fluid pressure necessary to support the weight of the slide. Fluid from the pump passes through said valve 54 into the lower end of the cylinder at the pressure determined by said relief valve 62, thereby exerting a pressure on the under side of the piston substantially equal to the weight of the slide to support said slide against downward movement, the pressure of the fluid from pump 16 being now under the control of relief valve 62.

With the valves in the position shown in which the slide is at rest, being supported, as above described, by fluid through valve 54 from the pump 16, the valve 17 is closed preventing fluid connection from said pump to the reversing valve. When it is desired to actuate the carriage vertically, the valve 17 is rotated to admit fluid to the reversing valve. Since the valves 1'7 and 54 are connected together by a link 63 which engages arms 64 and 65 on valves 17 and 54 respectively, the valve 54 is automatically closed when the valve 17 is opened to admit fluid to the reversing valve 22, thereby cutting oil the connection from the lower end of the cylinder to the relief valve 62. The valves 1'7 and 54 are shown as separate valves connected by the link 63 in the diagrammatic showing of Fig. 2. In the usual construction, however, said valves 17 and 54 are formed in the same rotatable valve member spaced longitudinally thereof, said valves then rotating as a unit without the necessity of the additional linkage shown in the drawing.

A latch 66 is arranged to engage said slide in order to prevent the slide from dropping in case the fluid supply should fail or in case the pressure of said fluid should drop below an amount suflicient to maintain the slide in position. The latch 66 is pivotally mounted on a pin 67 carried by the upstanding portion 4, the upper end of said latch being adapted to engage with a rack 68 mounted on the slide, said rack having ratchet teeth 70 with which the upper end of said latch engages. A spring 71 engages the upper end of said latch tending to urge said latch into engagement with the ratchet teeth and a horizontal pin 72 supports said latch to maintain the upper end of said pawl in correct alinement with the ratchet teeth, the lower end of said latch being bifurcated and straddling said pin 72 so that the latch is held against movement parallel to the axis of said latch. The latch is normally held out of engagement with said rack by a piston '73 which is slidably received in a bore 74 in the upstanding portion 4, the forward end of said piston being in engagement with the latch beneath the axis thereof. Fluid connection is provided from the fluid pump through a pipe 75 to the inner end of the bore 74 for said piston so that the fluid under pressure from the pump normally urges the piston forwardly or toward the left as shown in Fig. 2 to maintain the upper end of the latch out of engagement with the ratchet teeth '70. When the pressure of the fluid fro-m the pump drops below an amount suflicient to maintain the carriage in position or when the fluid supply fails entirely, the latch 66 is swung under the influence of the spring 71 to move said latch into engagement with the ratchet,'thereby to support the slide against downward movement, the fluid pressure on the piston '73 having diminished so that the pressure of the spring 71 is greater than said fluid pressure. The hydraulic system is arranged to permit manual movement of the slide, as by means of the hand wheel 79 which is suitably connected through gearing to the upstanding portion 4, and to this end the valve 17 has a recess '76 which is connected to the exhaust in any suitable manner, said recess coinciding with the port 26 in the casing 20 when the valve 17 is closed. When the slide is moved-manually upward, the valves being in the position shown, fluid from above the piston 12 exhausts through pipe 30 and channel 31 into pipe 25 and through the recess 76 to the exhaust. Manual movement of the slide downwardly forces fluid out through pipe 50 and channels 56 and 57 and through the relief valve 62. If the reversing valve is rotated into the opposite position in which the port 23 is connected to port 28 and port 2'7 is connected to port 32, fluid from above the piston exhausts through pipe 30 and one of the channels in the valve to the exhaust port 32 when the slide is moved manually upward. In the same position of the reversing valve, when the slide is actuated downwardly, fluid is forced out in the manner above set out, that is, through pipe 50 and channels 56 and 57 to the relief valve 62.

From the above, it will be apparent that a vertically movable slide, or a slide having a component of movement in a vertical direction, is arranged for vertical reciprocation in response to fluid under a constant pressure at a uniform rate of speed in either direction of movement. When the slide is brought to rest, fluid under pressure is constantly supplied to one side of the piston which actuates said slide in order to sup,- port the slide in fixed position regardless of any leakage which may occur around the valves or piston. A mechanism is further provided by which the slide is supported in position in case of failure of the fluid supply or a substantial drop in the pressure of said fluid, said mechanism including a latch for engagement with a rack, said latch being normally held out of engagement with said rack by a piston actuated by fluid under pressure.

I claim,

1. In a hydraulic system for actuating a vertically movable carriage, a cylinder and a piston in said cylinder, means connecting one of said parts to said carriage, a fluid supply, valve means to admit fluid under pressure to one end of said cylinder at such a pressure that the force exerted on the piston by said fluid is substantially equal to "he weight of the carriage, thereby to support said carriage against downward movement, a reversing valve to admit fluid under pressure alternately to opposite ends of the cylinder and simultaneously to permit fluid from the other end of said cylinder to exhaust, and means to connect said supply selectively through said valve 1 means or through said reversing valve to said cylinder whereby said carriage may remain in fixed position or may be reciprocated vertically.

2L In a hydraulic system for actuating a vertically movable carriage, a cylinder and a piston in said cylinder, means connecting one of said parts to the carriage, means to admit fluid under pressure alternately to the cylinder on opposite sides of the piston and to permit fluid in the cylinder at the other side of the piston to exhaust, whereby to procure a reciprocatory movement of said carriage, and means to prevent the fluid from exhausting from said cylinder as the carriage moves downwardly until the pressure exerted on said exhausting fluid by said piston is equal to substantially twice the weight of the carriage, whereby the fluid pressure necessary to actuate said carriage downwardly is substantially equal to the pressure necessary to actuate said carriage upwardly.

3. In a hydraulic system for actuating a vertically movable carriage, a cylinder and a piston in said cylinder, means connecting one of said parts to the carriage, a fluid supply, valve means to admit fluid under pressure to one end of said cylinder at suflicient pressure to support said carriage against downward movement, a reversing valve to admit fluid under pressure alternately to opposite ends of the cylinder and simultaneously to permit fluid from the opposite end of said cylinder to exhaust to procure a reciprocatory movement of said carriage, means controlling the fluid exhausting from said cylinder as the carriage moves downwardly to prevent said fluid from exhausting until the pressure on said fluid is substantially equal to twice the weight of the carriage, and means to connect said supply selectively through said valve means or through said reversing valve to said cylinder.

4. In a hydraulic system for actuating a vertically movable carriage, a cylinder and a piston in said cylinder, means connecting one of said parts to said carriage, a fluid supply, valve means to admit fluid under pressure to one end of said cylinder, a relief valve associated with said valve means to maintain the fluid through said valve at suflicient pressure to support said carriage against downward movement, a reversing valve to admit fluid under pressure alternately to opposite ends of the cylinder and simultaneously to permit fluid from the other end of said cylinder to exhaust, and means to connect said supply selectively through said valve means or through said reversing valve to said cylinder, whereby said carriage may remain in fixed position or may be reciprocated vertically, the fluid connection from said cylinder to the relief valve being cut oil. when said supply is connected through said reversing valve to the cylinder.

5. In a machine of the class described, a slide having a component of movement in a vertical direction, and means to actuate said slide comprising, a cylinder and a piston in said cylinder, one of said parts being connected to said slide, a fluid supply, a reversing valve to admit fluid under pressure from said supply to said cylinder alternately on opposite sides of the piston and simultaneously to permit fluid on the opposite side of said piston to exhaust, and an exhaust valve to prevent the exhaust of fluid from one side of the piston until the pressure on said fluid is substantially twice the weight of the slide, the fluid in the other end of said cylinder exhausting freely, whereby the slide is actuated at the same rate of travel in both directions of movement in response to fluid from said supply under a constant pressure.

6. In a machine of the class described, a slide having a component of movement in a vertical direction, and means to actuate said slide comprising, a cylinder and a piston in said cylinder, one of said parts being connected to said slide,

' a fluid supply, a reversing valve to admit fluid under pressure from said supply to said cylinder alternately on opposite sides of the piston and simultaneously to permit fluid on the opposite side of said piston to exhaust, an exhaust valve to restrict the exhaust of fluid from one side of the piston until the pressure on said fluid is substantially twice the weight of the slide, the fluid in the other end of said cylinder exhausting freely, whereby the slide is actuated at the same rate of travel in both directions of movement in response to fluid from said supply under a constant pressure, other valve means connecting said fluid supply to the cylinder at one side of the piston, a relief valve to maintain the pressure of the fluid through said other valve means at such a pressure that the force exerted by said fluid on said piston is substantially equal to the weight of the slide, whereby said slide is supported against downward movement, and means to direct the flow of fluid from said supply selectively through said reversing valve or through said other valve to said cylinder, said relief valve being inoperative when the reversing valve is in operation.

'7. In a hydraulic system for actuating a ver tically movable carriage, a cylinder and a piston.

in said cylinder, means connecting one of said parts to the carriage, a fluid supply, a reversing valve to admit fluid under pressure alternately to the cylinder on opposite sides of the piston and to permit fluid in the cylinder at the other side of the piston to exhaust to procure a reciprocatory movement of said carriage, means to cut off the supply of fluid through said reversing valve to bring said carriage to rest, and to admit fluid under pressure to one side of said piston at such a pressure that the force exerted by said fluid on the piston is substantially equal to the weight of the carriage, whereby said carriage is supported against downward movement, and exhaust means associated with said last means to permit fluid from said cylinder on either side of the piston to exhaust in response to manual movement of the carriage.

8. In a hydraulic system for actuating a vertically movable carriage, a cylinder and a piston in said cylinder, means connecting one of said parts to the carriage, a fluid supply, a reversing valve to admit fluid under pressure alternately to the cylinder on opposite sides of the piston and to permit fluid in the cylinder at the other side of the piston to exhaust to procure a reciprocatory movement of said carriage, a control valve between said fluid supply and the reversing valve to cut oi! the'supply oi fluid to said reversing valve to bring said carriage to rest and to admit fluid under pressure to one side of said piston at such a pressure that the force exerted by said fluid on the piston is substantially equal I to the weight of the carriage, whereby said carriage is supported against downward movement, and exhaust means associated with said control valve to permit fluid from said cylinder on either side of the piston to exhaust in response to manual movement oi. the carriage without movement of said reversing valve.

9. In a hydraulic systemior actuating a vertically movable carriage, a cylinder and a piston in said cylinder, means connecting one of said parts to said carriage, a fluid supply, valve means to admit fluid under pressure to one end of said cylinder at a pressure suflicient to support the carriage against downward movement, a reversing valve to admit fluid under pressure alternately to opposite ends of the cylinder and simultaneously to permit fluid from the other end of said cylinder to exhaust, a valve to prevent the exhaust of fluid from one side of the piston until the pressure on said fluid is substantially twice the weight of the slide, the fluid in the other end of said cylinder exhausting freely, and means to connect said supply selectively through said valve means or through said reversing valve to. said cylinder, whereby said carriage may remain in fixed position or may be reciprocated vertically.

10. In a grinding machine, a grinding memher and a work-supporting member, a vertically movable carriage on which one of said members is mounted, a cylinder and a piston in said cylinder, means connecting one of said parts to said carriage, a fluid Supply, valve means for admitting fluid under pressure to one end of said cylinder at such a pressure that the force exerted on the piston is sufficient to support the carriage against downward movement, a reversing valve to admit fluid under pressure alternately at opposite ends of the cylinder and simultaneously to permit fluid from the other end of said cylinder to exhaust, and means for connecting said fluid supply selectively through said valve means or through said reversing valve to said cylinder, whereby the grinding wheel and a workpiece in the workholding member may be supported in fixed position relative to each other or may be reciprocated vertically relative to each other.

11. In a grinding machine, a grinding member and a work-supporting member, a vertically movable carriage on which one of said members is mounted, a cylinder and a piston in said cylinder, means connecting one of said parts to said carriage, a fluid supply, valve means for admitting fluid under pressure to one end of said cylinder at such a pressure that the force exerted on the piston is suflicient to support the carriage against downward movement, a reversing valve to admit fluid under pressure alternately at opposite ends of the cylinder and simultaneously to permit fluid from the other end of said cylinder to exhaust, a valve to prevent the fluid from exhausting from said cylinder as the carriage moves downwardly until the pressure on said fluid is greater than the exhaust pressure at the opposite end of said cylinder by an amount substantially equal to twice the weight of the carriage, and means for connecting said supply se-

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