Hydraulic device
United States Patent 2396052

This invention relates to improvements in hydraulic devices, of the kind having a rod and piston for reciprocating motion, as in hydraulic motors. The improvement centers on the way provided for cushioning the piston action. Its utility increases when the piston speed increases and the idea...

Light, George S.
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Light, George S.
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Other Classes:
92/85A, 92/85R, 123/90.41
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This invention relates to improvements in hydraulic devices, of the kind having a rod and piston for reciprocating motion, as in hydraulic motors. The improvement centers on the way provided for cushioning the piston action. Its utility increases when the piston speed increases and the idea of the invention involves a very high speed for the piston.

A prior art patent to compare with this invention is my Patent #2,222,819 of 1940. As the present invention is applied, it will perform the purposes of the prior one and a lot more. Not the only one, but the main purpose of this invention is to provide new structure for a high speed motor. The detail disclosure of the drawings and the description of examples will make my invention clear for any one to practice it in the future.

In the drawings: Fig. 1 is only a schematic diagram indicating a general hydraulic system and circuit in which my invention may be put to work in the form of a hydraulic motor; Fig. 2 is a sectional view of a form of my hydraulic motor structure; Figs. 3 and 4 are sections similar to Fig. 2 but of other forms; Fig. 5 is a view with enough detail to show the application of my invention in one. way as a hydraulic motor to operate an airplane engine valve stem, only one being shown of the many needed on a single engine; Fig. 6 is a view similar to Fig. 5 but showing my hydraulic motor applied to operate the engine valve stem in a more extended way than in Fig. 5. A well known system is indicated in Fig. 1 merely for reference in the discussion of hydraulic motor operation. As valve 6 is rotated, fluid under pressure from pump 3 is alternately admitted to opposite sides of a piston in cylinder 4 7. This reciprocates piston rod 1. The exhaust is through valve 6 to tank 2. Other usual parts are the by-pass relief valve 4, and accumulator 5. The plan of such a system is that piston rod I will reciprocate in accordance with the turnIng of valve 6. The valve 6 is arranged to turn automatically as a control valve for the hydraulic motor to drive piston rod I back and forth and give a desired Character of reciprocating motion to a machine part. If further details of description are desired there are hundreds of examples in the published and commercial prior art.

The invention here is in the hydraulic device or motor. One form is shown in Fig. 2. It consists of the cylinder 8, its end walls 9 and 10, piston II, piston rod I, inlet and outlet conduits 12 and 13, and cushion disks, one set 14 on the left and a corresponding set 15 on the right with the piston II arranged between these sets. The surfaces of the disks may.be made rough enough to prevent sticking against adjacent surfaces or a spring 21, as shown in Fig. 3, may be provided for this purpose. When provision is made against sticking, there will always be a path for fluid to act against all disk surfaces. Then all disks may be put in hydraulic balance with layers of fluid between. The separation of the disks is caused in the following manner. The adjacent disks do not fit together smoothly enough to preclude the presence of a liquid film between them at all times. The cushioning squeeze between them, at the end of the stroke does not result in entirely freeing the spaces between of liquid. What is left is a very thin film but enough space is provided by that film to admit more fluid when admitted to the cylinder for the return stroke. The action then is for the high pressure fluid to get on both sides of the disks for the pressure to equalize. This puts each disk in hydraulic balance with equal pressure on opposite sides. The disks float apart ready for the return stroke of the piston to cushion such stroke.

Consider the right hand disk 14, Fig. 2, its film with the next disk is at exceedingly high pressure at the end of the cushioning stroke. Then the pressure at the right of the piston is exhausted, working pressure is admitted from pipe 12 to space 14', is equalized with the film spaces adjacent each pair of squeezing surfaces and the disks are relieved from the squeezing together forces and float apart in their reaction. Each adjacent pair of disk surfaces, and the surfaces of the cylinder end wall and piston wall with respect to their adjacent disks are, in Fig. 2, all arranged for purposes of squeezing layers of liquid. The piston cushioning effect to stop a piston stroke is caused by the squeezing action of the piston, disk, and end wall surface arrangement.

This arrangement of Fig. 2 is one of the simplest forms of the invention. It could be made still simpler by providing only two disks, one on each side of the piston. Sets are shown to multiply the action desired in cushioning strokes of the piston.

The effect of the parts shown in Fig. 2 is this.

The piston II will be cushioned at each end of its stroke. In the positions of Fig. 2 all disks are indicated as in hydraulic balance, pressure being equal on opposite sides with free flow through the openings 14' and 15' to or from conduits 12 and 13. Assume piston I is traveling at high speed to the right. On close approach to disks 15 they are forced to the right. They were previously merely "floating" in hydraulic balance. They should have a leaking fit to slide freely in the cylinder. They are of metal or strong material. They will pack together very closely. They will begin to pack as they are forced to the right by the piston. They are moved suddenly from an inert position, with the layers of liquid between them, which layers because of their width can discharge liquid easily through openings 15' to conduit 13. From the positions of Fig. 2, the disks 15 are slapped by piston II against end wall 10. Then as the liquid layers are thinned out, the resistance to liquid flow increases and it requires a substantial amount of work to overcome this resistance. Such work is to done by the force of the moving piston acting through the distance of the pack of liquid layers. The end effect is to bring the piston to a stop, in doing the work similar to that of a hydraulic press for squeezing out liquid between $5 movable spacer plates. It is a cushioning effect, useful in meeting the inertia of the mass carried by the piston at any speed, or meeting the energy in high speed. The idea is to consider the work necessary to stop the mass and proportion the number of disks accordingly. The principles of construction may be applied in the form of Fig. 2 and with simple structure. These principles as applied avoid complicated or massive construction to meet the shock of high speed pis- 3., ton reciprocation.

When the piston moves to the left instead of the right, the set of disks 14 will give substantially the same cushioning effect as the described effect of disks 15. It can be made identical or it can be varied by varying the number of disks, and in other ways. As the piston starts movement to the left,.the piston pressure is taken off disks 15. Fluid pressure entering from conduit 13 will find its way between all face to face surfaces. So disks 1i5 will take their positions of "floating" balance, ready for the return stroke of the piston.

Referring to Fig. 3, the principle of the spring action there indicated at 21 and 19 is merely to keep the disk surfaces from sticking. It is sometimes desirable to have the disk surfaces very smooth. They are then likely to stick together.

But with a helical spring 21 of a little more than a single turn, adapted to lie wholly within the recesses shown, when the surfaces are pressed tightly together, the disks will be moved apart, when the main pressure is released. The spring 21 is strong enough for the stated purpose as is also spring 19. and altogether too weak for any material effect in cushioning the piston stroke. This Cushioning effect is due to squeezing the liquid layers between the surfaces. By this I mean the relative effect of cushioning by spring action and by the action of squeezing the liquid between adjacent surfaces. The forces are such that when the piston comes to the end of its stroke it need not be cushioned to any substantial extent by the action of the springs but may be cushioned instead by the action of the disks and liquid.

In Fig. 2, I have shown positions and sizes of openings 14' and 15', merely to show the idea of one arrangement. The cushioning effect of the structure may be varied by changing the sizes or positions or both of such openings. It is sometimes desirable to have the cushioning effect different at opposite ends of the stroke and this is easily provided for. The ease with which a desired arrangement can be made to fit various kinds of piston strokes, with the structure of Fig. 2, is one of the useful features of the invention.

After cushioning one stroke, its reverse stroke will be started with exactly the same effect as if the disks were not in the cylinder. Thus the disks do not interfere with the desired character of the start and the acceleration of the return stroke.

The form of Fig. 3 will apply the broad principles in the operation of the Fig. 2 form. It will also apply other principles of operation useful in combination. In this form the piston 16 has tapered end faces to match complementary faces in adjacent disks II and 18. The arrangement will increase the area used for squeezing out liquid between such surfaces. Thus the cushioning effect is increased in one particular way.

The disks II and 18 are of larger diameter than piston 16 and slide back and forth in larger cylindrical surfaces as shown. One effect is that If the disks 17 or 18 should stick to the piston surface they will be positively stripped off by shoulders 17' or 18'. Another and important effect is to provide for a quick start back after the piston comes to rest at the end of the stroke.

The pressure will act on the larger area of the disk as compared to the effective area of the piston. This will give more force to get started faster. And when a disk is stripped off the piston end, the fluid acting through the narrowed bore of the piston slide will give a jump in the velocity. Altogether the arrangement is adapted to improve the action of a high speed piston reciprocation.

In Fig. 3 the coiled spring 19 is merely for the purpose of stripping disk T1 off the surface 20 to avoid sticking. It does not have strength enough to give any substantial cushioning action.

In the same way the coiled spring 21 adapted to lie within recesses 21' when the disks are pressed together is merely to avoid adjacent surfaces of disks 18 and 22 sticking. On the left of piston 16, the two disks 18 and 22 as compared to the single disk 17 on the right merely indicate variations. These may be used for the purpose of arranging a functioning area on the left as compared to that on the right, to compensate for the fact that the piston rod I does not extend from both ends of the piston. The piston head areas are not equal. Or the two disks 18 and 22 may be used to give more cushioning effect at the end of one stroke than at the end of its opposite stroke in the piston action.

It is important for applying the invention in the preferred way to provide for fluid pressure access at practically all times between the cushion functioning surfaces. AsI have said, this may be done by having the surfaces rough enough so they can not stick under pressure. But the roughness prevents their squeezing out layers of liquid to the exhaust port as effectively as may be desired. So I indicate in the form of Fig. 3, an arrangement by which all these surfaces may be as smooth and accurately fitted together as may be desired. If they then squeeze out practically all liquid between them under the piston pressure at the end of the stroke the following action may take place.

If the area of the piston head to which the pressure has immediate access, that is the area never covered by surface 23 is large enough, direct action will form a crack between surfaces 23 and 22 where they can contact. If such area is not large enough, in any particular instance, a spring, like the one 19 on the right may be provided to make such crack between surfaces 23 and 22. When the crack is made, the pressure has the maximum area on that side to commence the return stroke with the maximum force. Shoulder 18' will strip off the disks 18 and 22. Spring. 21 will separate these disks. From the above it will be seen that 14 the stroke is started from the right according to the same principles of operation although the structure is a little different.

The structural form of Fig. 4 is for amplifying the disclosure still further. In this form, the cyl- 1 inder end walls, the cushioning disks 25 and 26 and the piston head surfaces are all increased in area by their tapered forms which match for the liquid squeezing function. The disks are connected by rods 27 on which piston 28 slides freely 2 between disks. Rods 27 are fast to the disks.

The latter must move together. Thus the disks can stick to cylinder end walls or to the piston surfaces sometimes and without giving trouble.

In Fig. 4, consider that pressure from conduit 13, 2 acting on the exposed piston head area, is sufficient to instantly "crack" the space between sticking surfaces of 26 and 28. Then pressure acts on the whole piston head moving it to the left.

The piston picks up disk 25 and rods 27 pull disk 3 26 off the cylinder head area if it is sticking there.

On the reverse stroke, pressure from conduit 12 acting on disk 25 will start it to the right, the pressure area being sufficient for this purpose.

The instant disk starts to move its whole area takes the pressure. The disk may push the cylinder until disk 26 reaches its abutment wall, where its stopping will stop disk 25. The piston then moves alone until it hits disk 26 and the latter cushions the piston stroke. In this way neither roughened surfaces or springs are needed to keep the surface areas ready when needed to begin their cushioning function.

I have in Figs. 1 to 4 disclosed my invention and described its application in various forms. In Figs. 5 and 6 I show two ways adapted to operate the valve of an airplane engine. By disclosing considerable detail in this specific use, I believe -the invention will be better understood.

An airplane considered as a single machine has many of its parts hydraulically operated. The fluid pressure apparatus is already in the machine and my hydraulic device is conveniently applied to operate cylinder valves in the airplane's engine, which will be a new kind of operation, so far as I know. This should be done with a net saving in weight, space, and cost. But more important and one purpose of my invention in this use is to provide for improved valve operation. The engine development has reached the point where the valve operations are so rapid and need such accurately timed control that further improvements in valve operating means is :eagerly desired and aimed at. My invention is particularly useful under these circumstances.

The arrangement in Fig. 5 indicates my hydraulic motor for opening the engine valve, a spring to close the valve, and the cushioning action of the hydraulic motor for cushioning the closing action of the valve. Some of the advantages from this somewhat composite arrangement are; both the valve opening and closing operations may be timed by the hydraulic motor operation; the force of the hydraulic motor acts directly to open the valve; the force of the closing operation is supplied by a spring, but the spring can act only as the operation of hydraulic motor permits it to do so, that is on the back or exhaust stroke of the motor permits the spring to act; the cushioning of the motor stroke, according to the principle I have applied, will permit very rapid spring action without banging the valve closed on its seat; the valve closure is brought about quickly but just before the valve actually can hit its seat, the motor cush0 ioning action takes place and the valve will be cushioned as the motor piston is cushioned. This will be further explained after describing the detail of the arrangement shown in Fig. 6.

Referring to Fig. 6, E is a portion of one engine cylinder, V one of the valves, P the piston in the engine cylinder, and S the valve stem.. This valve stem, as shown, extends through the adjustable cylinder ends 30 and 31 and all through my hydraulic device. The casting 32 is removably fas0 tened to the engine block. This casting provides the stepped chambers from end to end; for adjustable end plug 30, for manifold chamber 33, sliding chamber for cushion disk 34, piston sliding chamber 35, and corresponding chambers for :5 cushion disk 37, adjustable end plug 31 and manifold passages to pipe 12. The piston 36 of my device has outward sloping heads and tubular end extensions 38. Thus the piston and the piston rod may be in one piece and that piece provided with a 0 bore to slide over valve stem S as shown. At the bottom it abuts a shoulder S' of the valve stem S.

At the top it abuts a suitable snap ring fastening means as indicated. The piston rod, piston and valve stem S are thus fastened to move as a unit.

3 Assuming the closed position for valve V, its opening and closing cycle is this; pressure from pipe 12, when admitted, acts on top piston head of 36, in the crack made between the disk 37 and lower surface of plug 31 and thus on an effective 40 area equal to that bounded by the circumference of said disk 37 minus that area bounded by the circumference of tube 38. The pressure action on such effective area on piston and disk gives a quick start and over the short starting range up to the 45 lower abutment for disk 37. The liquid under disk 37 will pass over to the top by nassage 37' through the disk, or by leaking around its circumference or any similar way. Of course tre pressure area is large enough one way so that this little back pres60 sure will not be substantial. When disk 37 hits its lower abutment the restriction of the piston cylinder wall as compared to the wall for disk 37, causes increased velocity of the piston because of the displacement. The lower piston head picks 55 up disk 34, which is hanging in hydraulic balance and slaps it toward the upper surface of plug 30 or the lower cylinder wall as an abutment. The layers of liquid are squeezed out between surfaces of considerable area as before described and the 60 piston stroke stopped with the cushioning effect applied here similarly to that in all forms of the *4nvention before described. The upstroke is made practically identical to the downstroke. The upstroke starts as socn as pressure is applied by pipe 05 13 and exhausted by pipe 12. In this form it will be seen that the structure and surfaces of the coacting parts are exactly balanced on each side of the piston. As shown, it makes a balanced arrangement with simple inexpensive structure. By 70 it the valve V of the engine cylinder can be opened and closed with lightning-like rapidity. The action may be controlled by the rotary action of-a four-way valve which alternates in applying and exhausting liquid pressure through pipes 12 and 76 13 in the desired timed relation. In this use the stroke of the hydraulically operated piston is short and its reciprocation very rapid. The cushioning pffect is given according to the principles already described. It can be increased and varied by changing the "floating" disk arrangements in many ways, some of them described, and all applying the wanted application of principles explained.

As compared to a cam for mechanically operating the valve stem, my hydraulic device is used for the purpose of smoother operation or a better control in timing exact rapid changes in the movements or both. The fluid pressure has good characteristics for transmitting a driving force in the circumstances of this use and the driven member, in this case the valve stem, can be tuned to the fluid drive in a better way than to the motion of a cam. I am considering high speed motions and in speaking of the cam I mean that mechanically the cam follower has a tendency to get out of position with the cam surface, which results in trouble at high speed. But there is not the same action In hydraulic drives where the force is applied differently. The difficulty in hydraulic drives is that the prior art so far as I know, does not show the structure or principles of operation to do work as heavy as engine valve operation in the high speed range that I am here concerned with. This is what led me to work out the present invention for the hydraulic drive art. While the cushioning effect I have described is important in itself, for cushioning, I believe it contributes substantially to the accuracy in controlling movements in the high speed work. This is, of course, important whenever, as in engine work, the valve movement is desired to be under the best conceivable controlling means.

With what has been said about the structure and operation of the engine valve in Fig. 6, the form of Fig. 5 will be understood as a variation which some might prefer to that of Fig. 6. Most of the parts are shown the same way and some of these have primed references. The parts which might pocket liquid need to be vented; and bleed hole ventilation is indicated. The difference is that fluid pressure is admitted and exhausted from; one pipe to one side only of the hydraulic motor. The downstroke of its piston 40 is caused by hydraulic force. The, upstroke is caused by the spring 41 expanding after being compressed by the downstroke. The preferred arrangement is to time the exhaust cpening of the motor, to permit practically full and free snap closing action of the spring 41, except for a small increment of movement when the valve is just about to hit its seat.

Instead of hitting its seat the valve is cushioned, it being fast to its stem and its stem being fast to the hydraulic piston and the piston being cushioned by the squeezing surfaces between the piston head disk 42, and abutment 43. In the structure of Fig. 5 provision is made for a very effective adjustment to get the desirable actions stated, particularly that cushioning action at the end of the valve closing step which will avoid pounding the valve on its seat. And this can be done with- c out interfering with the fast action and proper control of the valve.

To indicate the wide scope of my invention herein disclosed, and its range of use, I refer to the use with the airplane engine on the one hand. On 7 the other hand it may be used in an automatic machine for making the ordinary household pin.

The structure of my aforesaid issued patent is one I have applied in automatic pin making machines. The form of structure herein disclosed 7 can be readily put to the same use and for reciprocating parts by hydraulic driving means in machines of as widely differing character as a pin making machine and an airplane engine.

Having described my invention I claim: 1. A hydraulic device of the kind having a rod and piston reciprocable. within a liquid holding cylinder, a port opening through the end wall of the cylinder, an abutment to stop the piston adjacent the end wall of the cylinder, at least one disk formed for free passage of liquid at all times to opposite faces and freely slidable into hydraulic balance in the liquid between the end face of the piston and the abutment, the opposite faces of said disk being formed to match large complementary faces on the piston and abutment respectively for establishing friction between them, the disk being movable by the stroke of the piston to apply its faces in such close proximity to the adjacent faces of the piston and abutment as to render the total friction of the liquid between the adjacent faces of the disk, piston, and abutment, effective to absorb a substantial part of the shock as the abutment stops the piston movement in its direction.

2. A hydaulic device of the kind having a rod and piston reciprocable within a liquid holding cylinder, port openings, one through each of the cylinder end walls, two abutments to stop the piston adjacent the cylinder end walls, disks, at least one disk on one side and another disk on the other side of the pistoh, each of said disks formed for free passage of liquid at all times between its opposite faces, each disk being freely slidable into hydraulic balance in the liquid between the adjacent end face of the piston and the adjacent abutment, the opposite faces of each disk being formed to match large complementary faces on the piston and abutment respectiVely for establishing friction between them, each disk being movable by the stroke of the piston in its direction to apply its faces in such close proximity to the adjacent faces of the piston and abutment, as to render the total friction of the liquid between the adjacent faces of each disk, piston, and abutment, effective to absorb a substantial part of the shock as the abutment stops the piston movement in the direction of such disk.

5o 3. A hydraulic device comprising in combination a rod adapted to be fastened to a part for reciprocating it, a piston member carried by the rod between its ends, a cylinder member having end bearings in which said rod reciprocates, fluid passage means to the cylinder at the opposite sides of the piston to alternately admit and exhaust pressure operating fluid, said cylinder having an enlarged chamber beyond each end of the piston sliding surface, at least one cushion i0 disk mounted to slide in each enlarged chamber, such disk having a surface on one side to match a substantial part of the adjacent piston surface and a surface on the other side to match a substantial surface backed up by the abutment sur15 face all constructed and arranged to operate in the manner and for the purpose described.

4. A hydraulic device comprising in combination a piston adapted to actuate a work part and having rod-like extensions at opposite ends, cush0 ioning disks, a cylinder with a middle portion fitting the piston and directly communicating portions fitting the disks, adjustable end walls for the cylinder serving as end abutment to stop the strokes of piston and disks, said extensions 5 passing through bearings in said walls, a port at each end of the cylinder to admit and exhaust fluid pressure beyond the piston ends and on either side of the disks, said disks on opposite sides having cooperating liquid squeezing surfaces to fit corresponding surfaces of the piston and cylinder end walls, said ports and the spaces between said squeezing surfaces being connected for fluid passage during each piston stroke, said piston and disks being relatively movable, the former for the work strokes and the latter to and between mere hydraulic balance on the one hand and on the other hand to liquid squeezing position relatively to the surfaces of the cylinder end walls under the impact of the piston stroke and for cushioning the stopping action of the piston.

5. A hydraulic device comprising in combination a motor in the form of cylinder, piston and piston rod and with inlet and outlet ports at the ends, said cylinder having liquid chambers at each end between the end walls and piston head, cushioning disks mounted in said chambers to slide under the impact of the piston stroke to make impact with the end walls, and to move out of abuting relation when the piston moves away, said disks having surfaces to cooperate with piston head and end wall surfaces in squeezing liquid between them for the cushioning function, said surfaces being proportioned to the amount of cushioning desired and particularly adapted to make it large, said ports having substantially constant communication with the spaces between said squeezing surfaces during all squeezing and cushioning action so to avoid an abrupt stop.

6. A hydraulic device comprising in combination a cylinder body, adjustable end walls, a piston rod extending from end to end, three aligned chambers for sliding parts, a piston carrying the piston rod in the middle chamber, cushloning disks of larger diameter than the piston, at least one mounted in each end chamber, said end chambers being larger than the middle chamber, said disks being mounted for free sliding and with suffcient passages for liquid to their opposite sides to move them out of any abutting relation, said disks on their sides facing said heads having matching seats to fit said heads, end abutment means to limit the movement of said disks, the latter on the sides facing said outer abutment means having matching surfaces to cooperate for squeezing liquid between them, ports to admit and exhaust liquid at the ends of the cylinder body, all constructed and arranged for said cushioning disks to meet the end impacts of the piston strokes and cushion them by squeezing out liquid between said surfaces, the ports having constant communication with the spaces between such surfaces during all movement of the parts.

7. A hydraulic device comprising in combination a motor in the form of cylinder, piston, and piston rod, cushioning disks, one on each side of the piston and arranged to slide free of the piston between the end wall and piston head, cooperating liquid squeezing surfaces on the piston heads and disks and on the disks and the cylinder end walls, ports at the ends of the cylinder to admit and exhaust pressure, one disk being mechanically connected to another disk on the opposite side SO of the piston so they must move together, said disks being spaced a fixed distance apart which is less than the stroke of the piston, said piston being movable independently of either disk until it impacts one of the disks to bring them into action for cushioning close to the end of the piston stroke. GEORGE S. LIGHT.