US2858804A

US2858804A - Power piston with control valve

Info

Publication number: US2858804A
Application number: US623102A
Authority: US
Inventors: Oscar H Banker
Original assignee: New Products Corp
Current assignee: New Products Corp
Priority date: 1956-11-19
Filing date: 1956-11-19
Publication date: 1958-11-04
Anticipated expiration: 1975-11-04

Description

O. H. BANKER POWER PISTON WITH CONTROL VALVE Nov. 4, 1958 8 Filed Nov. 19, 1956 United tates Patent Ofihce 2,858,804 Patented Nov. 4 1958 POWER PISTON WITH CONTROL VALVE Oscar H. Banker, Evanston, Ill., assiguor to New Products Corporation, Skokie, Ill., a corporation of Delaware Application November 19, 1956, Serial No. 623,102

8 Claims. (Cl. 121-45) The improved hydraulic control mechanism comprising the present invention has been designed for use primarily in connection with metal working machines for feeding a cutting or abrading tool to the work or vice versa in such a manner that the movement of the tool against the work will be varied substantially in inverse proportion to the resistance encountered by the tool. The invention is, however, capable of other uses and may, if desired, with suitable modification if necessary, be employed in the manner of a power'transmission or servo-mechanism for effecting application of increments of power to a movable member to shift its position in substantially inverse proportion to the resistance offered against such movement.

It is an object of this invention to provide a hydraulic piston and cylinder assembly wherein the rate of admission of fluid under pressure to the cylinder for pistondriving purposes is a function of the mechanical resistance encountered by the piston against longitudinal displacement thereof within the cylinder.

A similar and related object of the invention, in a power cylinder assembly of this character, is to provide such an arrangement wherein the variable porting necessary to effect such variable admission of fluid under pressure into the cylinder for piston-driving purposes is wholly contained in and carried by the piston assembly itself and is operated solely under the control of the mechanical resistance offered to the pistonagainst displacement thereof, thereby eliminating the necessity for employing external pressure sensing devices such as pressure-sensitive switches and the usual solenoid actuated valves controlled thereby. Stated more generally, it is an object of the invention to provide a power cylinder assembly of the character briefly outlined above which is entirely hydraulic in its operation and is completely devoid of electrically operating instrumentalities.

Other objects and advantages of the invention, not at this time enumerated, will become more readily apparent as the following description ensues.

In the accompanying single sheet of drawings forming a part of this specification a preferred embodiment of the invention has been shown. in these drawings:

Fig. l is a fragmentary sectional view taken substantially centrally and longitudinally through a power cylinder assembly constructed in accordance with the principles of the present invention;

Figs. 2 and 3 are fragmentary sectional views similar to Fig. 1 showing the operative parts of the assembly in different positional relationships; and

Fig. 4 is a cross-sectional view taken substantially along the line 4-4 of Fig. 1.

Referring now to the drawings in detail, a fragment of the power cylinder assembly of the present invention is shown at and comprises a cylinder 12 within which there is slidably disposed a piston assembly 14 mounted on the free end of a piston rod 16. The hydraulic motive fluid i applied to the system, as schematically shown in Fig. I, through a flexible intake and return line 18 under relatively high pressure from a control valve 20 operatively connected to a source of fluid or reservoir 22 through a feed line 24 and a pump 26. A return line 28 serves to conduct ex= haust fluid back to reservoir 22. One end of cylinder 12 is shown closed by a cylinder head 30 which may be threadedly received as at 32 on the cylinder and which, in combination with the piston assembly 14', provides'a variable volume pressure chamber 34.

The piston rod 16 constitutes a thrust member operatively connected to a cutting tool or other work engaging member (not shown). Alternatively, the rod 16 may be operatively connected to the work undergoing cutting and the movements of the rod thus imparted to the work to force the same against the "tool. Rod 16 is formed with a longitudinally extending central bore 36 therein in communication with the line 18 at or adjacent one end of the rod and, at the othe'r end of the rod, the bore is closed by a threaded plug 38 having an Allen wrench socket 40 formed therein. The right hand end of the piston rod 16, as viewed in Figs. 1 to 3 inclusive, is reduced to provide a cylindrical surface 42 on which is slidably mounted the piston as sembly 14.

The piston assembly 14 includes a cylindrical piston 44 having a central bore 46 therein closely fitting around the cylindrical surface 42 on the piston rod 16 but slidable thereon as aforesaid and sealed thereto by one or more O-rings 48 disposed in circumferential grooves preferably formed in the reduced portion of the rod 16. The piston 44 is also slidable within bore 50 of cylinder 12 and may be sealed thereto by expansible sealing rings 52 in the form of V-rings or the like.

Piston 44 is movable on the cylindrical surface 42 of the piston rod 16 between an extreme retracted posh tion in which it abuts against a snap ring '5 received within a circumferential groove 56 formed near the end of rod 16, and an advanced position wherein the opposite side thereof abuts against a thrust washer or plate 58 which surrounds the reduced end of the rod 16 and, in turn, abuts against a shoulder 60 formed on the latter.

As best seen in Fig. 4, the rear face of the piston 44 is formed with a series of circumferentially spaced sockets, alternate sockets being designated at 62 and 64, respectively. While any number of

such sockets

62 and 64 may be provided in piston 44, t.ree of the sockets 62 and three of the sockets 64 have been illustrated here? in. Disposed in each socket 62 and compressed between thrust plate 58 and piston 44 is a spring 66, the three such springs normally serving to yieldingly urge piston 44 to the right as viewed in Fig. 1 against the snap ring 54 to its fully retracted position. Compressed in each socket 64 is a spring 68, one e d of which bears against the bottom of the socket and the other end of which bears against a radial flange 76 formed on a plunger 72 having a nose portion or button 74 formed thereon which projects outwardly of the socket 64. A snap ring 76 serves to retain each plunger 2 in position within its respective socket 64. When piston 44 is in its fully retracted position as shown in Fig. i, the outer end of the nose portion 74 of each plunger '72 is maintained slightly spaced from the rear face of thrust plate 58 for a purpose that will be made clear presently.

The bore 36 formed centrally in the piston rod 16 communicates through one or more radial passages 80 with an annular groove 82 formed in the cylindrical surface 42 of the rod 16 near the forward free end there of. The bore 46 of piston 44 is formed with an internal groove 84 which may be of slightly greater width than the width of the groove 82 and which normally fully registers with the latter groove when piston 44 is in fully retracted position. Groove 84 communicates with chamber 34 through an inclined passage 86.

In the operation of the herein described hydraulic control mechanism, a constant and relatively high head of pressure is maintained within the bore 36 by valve 20 so that when the cutting tool is idling, as for example, prior to the time the work is engaged thereby, a maximum volume of fluid will be delivered to chamber 34 (Fig. 1) through the bore 36, radial passages 80,

grooves

86 and 84, respectively, which, at this time, are in full register, and inclined passages 86. Since little or no resistance is offered to the movement of the piston rod 16 to the left as viewed in Fig. 1 rapid entry of fluid under pressure into chamber 34 will force the entire piston assembly and piston rod 16 to the left as viewed in Fig. 1 without compressing the spring 66 or otherwise altering the relative positions of the various parts of the assembly as depicted in Fig. l and such movement will continue until the tool engages the work. In this manner all initial lost motion between the operating or cutting tool and the work will be rapidly and completely taken up.

As soon as the cutting tool strikes the work to make its initial cut, a resistance to further advance movement of the piston rod 16 will be built up, and the rod will be held against its free floating advance movement so that an increase in pressure within the chamber 34 will take place. Such an increase in pressure within chamber 34 will cause piston 14 to move to the left as viewed in Fig. l relative to rod 16 against the action of springs 66 until such time as the extreme forward ends of the nose portions or buttons 74 of the plungers 72 engage the thrust plate 58. During such relative movement between piston 44 and reduced cylindrical portion 42 of the rod 16, the

grooves

82 and 84 will move to a position of partial register as shown in Fig. 2 to reduce the rate of flow of fluid into chamber 34 through the previously described path provided for it.

Grooves

82 and 84 thus, in effect, provide a restriction in the normal path of flow of the motive fluid so that the rate of expansion of the volume of the pressure chamber 34 is reduced to an extent which is commensurate with the cutting rate of the tool on the particular work involved. Thereafter the pressure of the plungers 72 acting on the thrust plate 58 under the influence of the springs 68 and of the advancing piston body 44 will serve to continue the advancing motion of the piston rod 16 at the desired rate.

It will be understood, of course, that the design of the various fluid passages and of the springs 68 will be calculated according to engineering exigencies so that for any given tool and any given work the desired rate of advancement of the tool will be effected. It will be observed that under normal operating conditions slight increases or slight decreases in the resistance of the work to the advance movements of the tool will be absorbed by the combined resistance of the compressed or preloaded springs 68 without materially compressing them further. Thus a slight increase in this resistance will cause the plungers 72 to increase their pressure against the thrust plate 58 to advance the piston rod 16 and consequently the tool. Conversely, a slight decrease in this resistance will cause the plungers 72 to decrease their pressure upon the thrust plate 58.

When an unexpected obstruction is encountered, as for example, a hard spot in the work, or a change in the cutting angle of the tool, the inability of the piston rod 16 to continue to advance will cause the plungers 72 to be retracted into their respective sockets 64 against the resistance of springs 68 to such an extent that the

grooves

82 and 84 move out of register (Fig. 3), thus shutting off the supply of fluid under pressure to chamber 34 and terminating the tool feed, but holding the tool against the work with the locked-in pressure in chamber 34. This steady pressure will obtain until the resistance is overcome and rod 16 may move forward again relative to piston 44 to cause

grooves

82 and 84 to come into at least partial registry. This allows fluid to enter chamber 34 again and resume movement of piston 44 to the left.

In instances where successive cuts are to be made progressively on a particular work, as the tool breaks through or otherwise completes each successive entire cut, resistance to advancement of the tool will substantially cease and springs 68 and subsequently springs 66 will expand so that piston 44 is slid on rod 16 to its fully retracted position on the rod 16 and thus the ports or

grooves

82 and 84 are moved into full register and cause unobstructed flow of fluid into the pressure chamber 34 rapidly to advance the piston rod 16, and consequently the tool, to its succeeding work-engaging position.

The foregoing description is illustrative of a preferred form of the invention, but it should be understood that the scope of the invention is not to be limited thereto, but is to be determined by the appended claims.

I claim:

1. In a hydraulic control mechanism of the character described, in combination, a cylinder member closed at one end, a piston .rod member projecting into said cylinder member in axial alignment therewith, said members being axially movable relative to each other, one of said members being designed for operative connection to a cutting tool or the like whereby movement of the member in one direction relative to the other member will cause the tool to be advanced proportionately, a piston body slidable on said piston rod toward and away from said closed end, said piston body also being slidable within the cylinder and, in combination with the closed end of the latter, providing a variable volume fluid pressure chamber, a source of fluid under pressure, said piston rod having a longitudinal passage therein communicating with a radial port at the piston body and said piston having a passage leading from the chamber to a radially disposed port at the piston rod, manually controlled means for directing fluid under pressure from said source to said longitudinal passage in the piston rod, said ports on the piston body and piston rod varying in registry with one another from full registry when the piston body is in its fully retracted position to zero registry when the piston body is in its advanced position to control the admission of fluid under pressure to said chamber, means for exhausting the fluid under pressure from said chamber through said piston rod and piston body passages, and spring means interposed between said piston body and piston rod for yieldingly maintaining said piston body in its fully retracted position on the piston rod.

2. In an hydraulic control mechanism of the character described, in combination, a cylinder member closed at one end, a piston rod member projecting into said cylinder member in axial alignment therewith, said members being axially movable relative to each other, one of said members being designed for operative connection to a cutting tool or the like whereby movement of the member in one direction relative to the other member will cause the tool to be advanced proportionately, a piston body slidable on said piston rod between advanced and retracted positions thereon, said piston body also being slidable within the cylinder and, in combination with the closed end of the latter, providing a variable volume fluid pressure chamber, said piston rod and piston body being provided with cooperating ports which are in full register with each other when the piston body is in its retracted position and which are out of register when the piston body is in its advanced position, said piston rod and piston body functioning as a valve for admission of motive fluid to said chamber by virtue of varying degrees of registry between said ports, means on said piston rod establishing a rearwardly facing surface, means on said piston body establishing a forwardly facing surface, a coil spring interposed between said surfaces yieldingly maintaining said piston body in its fully retracted position, and additional spring means interposed between said piston body and piston rod and effective when the former is in an intermediate position on the latter for transmitting further forward movements of the piston body to the piston rod.

3. In an hydraulic control mechanism of the character described, in combination, a cylinder closed at one end, a piston rod projecting into said cylinder in axial alignment therewith and adapted to be operatively connected to a cutting tool or the like whereby movement of the piston rod forwardly in one direction will elfect advance movements of the tool, a piston slidable on said piston rod between advanced and retracted positions thereon, said piston also being slidable in the cylinder and, in combination with the closed end of the latter, providing a variable volume fluid pressure chamber, said piston rod and piston being provided with cooperating ports which are in full register with each other when the piston is in its retracted position and which are out of register when the piston is in its advanced position, said piston and rod functioning as a valve for admission of motive fluid to said chamber by virtue of varying degrees of registry between said ports, spring means interposed between said piston and piston rod for yieldingly maintaining said piston in its fully retracted position, and additional spring means interposed between the piston and piston rod and effective when the former is in an intermediate position on the latter for transmitting further movements of the piston toward its advanced position directly to the piston rod.

4. In an hydraulic control mechanism of the character described, in combination, a cylinder closed at one end, a piston rod projecting into said cylinder and adapted to be connected operatively to a cutting tool or the like whereby movement of the piston rod forwardly in the cylinder will effect advance movements of the tool, a piston slidable on said piston rod between advanced and retracted positions thereon, said piston also being slidable in the cylinder and, in combination with the closed end of the latter, providing a variable volume pressure chamber, said piston and rod being provided with cooperating ports which are in full register with each other when the piston is in its retracted position, said piston and rod functioning as a valve for admission of motive fluid to said chamber by virtue of varying degrees of registry between said ports, means providing an annular rearwardly facing surface on said piston rod, a plurality of longitudinally extending, circumferentially spaced springs interposed between said rearwardly facing annular surface and said piston for yieldingly maintaining said piston in its fully retracted position, and a second set of longitudinally extending circumferentially spaced springs interposed between said rearwardly facing annular surface and said piston and effective when the former is in an intermediate position on the piston rod for transmitting further forward movements of the piston to the piston rod.

5. In an hydraulic control mechanism of the character described, the combination set forth in claim 4 wherein said second set of springs are mounted on and wholly supported by said piston.

6. In an hydraulic control mechanism of the character described, in combination, a cylinder closed at one end, a piston rod projecting into said cylinder and adapted to be operatively connected to a cutting tool whereby movement of the piston rod forwardly in the cylinder will effect advance movements of the tool, a piston slidable on said rod adjacent the rear end thereof between advanced and retracted positions thereon, said piston also being slidable in the cylinder and, in combination with the closed end thereof, providipg a variable volume fluid pressure chamber, there being a longitudinally extending bore in said piston rod, said piston rod being formed with an external annular groove adjacent the rear end thereof and with a radial passage establishing communication between said bore and groove, said piston being formed with an internal annular groove in communication with said external groove in the piston rod when the piston is in its fully retracted position, said internal groove being out of communication with said external groove when the piston is in its advanced position, said piston also being formed with a passage establishing communication between said internal groove and the pressure chamber, spring means interposed between said piston and piston rod normally urging the former to its retracted position on the latter, and second spring means interposed between said piston and piston rod and effective when the former is in a predetermined intermediate position on the piston rod for yieldingly transmitting further forward movements of the piston to the piston rod.

7. In an hydraulic control mechanism of the character described, in combination, a cylinder closed at one end, a piston rod projecting into said cylinder and having a reduced rear end providing a cylindrical surface, said piston rod being adapted to be operatively connected to a cutting tool whereby the movements of the rod in a forward direction will effect advance movements of the tool, a piston slidable on and sealed to said cylindrical surface and, in combination with said closed end, providing a pressure chamber, a radial shoulder formed on said piston at the forward end of said cylindrical surface, means providing an abutment on said piston rod adjacent the rear end thereof, said piston being movable between a retracted position wherein it effectively bears against said abutment to an advanced position wherein it effectively bears against said shoulder, a plurality of circumferentially spaced coil springs each effectively hearing at one end against said shoulder and at the other end against said piston and serving to yieldingly urge said piston toward its retracted position, said piston and piston rod being provided with cooperating ports which are in full register with each other when the piston is in its retracted position and which are out of register when the piston is in its advanced position, said piston and rod functioning as a valve for admission of motive fluid to said pressure chamber by virtue of varying degrees of registry between said ports, and a second set of circumferentially spaced springs interposed between said piston and shoulder and efiective when the former is in a predetermined intermediate position to yieldingly transmit further forward movements of the piston to the piston rod.

8. In an hydraulic control mechanism of the character described, the combination set forth in claim 7 including a second set of circumferentially spaced springs interposed between said piston and shoulder and effective when the former is in a predetermined intermediate position to yieldingly transmit further forward movements of the piston to the piston rod.

References Cited in the file of this patent UNITED STATES PATENTS