The present invention generally relates to a hydraulic or pneumatic auxiliary valve, and more particularly the invention is concerned with such a valve intended to be connected in a hydraulic or pneumatic fluid system and co prisinσ a reverse valve and to cylinders or motors or groups of cyl nders and motors connected to a hydraulic pump or an air pressure supply means, especially intermittently operating cylinders or motors for providing an operation function of a first cylinder or group of cylinders for each operation cycle whereas a second cylinder or group of cylinders is actuated to an operation function only once per a predetermined multiple of operation cycles, for instance for every second, every third etc. operation cycle.

The invention is useful in many different technical fields and both for hydraulic and pneumatic operation machines of different kinds like piston-cylinder apparatus, rotatable motors, oscillating motors etc. For a better understanding of the invention it will in the following be described only with reference to hydraulic piston-cyl nder apparatus, named hydraulic cylinders. It should, however, be noted that the invention is not limited thereto and that the scope of the invention is defined only by the appended claims.

In co-operating systems of hydraulic cylinders which are fed from one and the same hydraulic pump the cylinders are actuated on with the same relative pressure. If the power need in such case varies for the different cylinders one cylinder may be loaded relatively much stronger than the other cylinder. In other

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cases the power need may occasionally be higher for one cylinder than for the other cylinder. In still other cases there may be a need for one of the cylinders to increase the flew of power from a minimum to a maximum and thereafter to reduce the flew of power to a minimum successively or in one step.

Previously attempts have been made to solve the above mentioned problem with temporarily changed demands on power for the different hydraulic cylinders in one and the same hydraulic system by introducing manually or electronically actuatable shutvalves in the supply conduit for one cyl nder or cylinder group. The manually actuatable shutvalves necessitate a substantial manual operation and give an unsafe result. The electronically actuatable valves, in turn, must rely on complicated electronic components, and hence there is a risk of failures and following false functions depending thereon. In the case that the power demand can be considered as more permanent the above mentioned problems may in some cases be solved by substituting the cylinder in which the power demands have been reduced to a weeker cylinder and/or the other cylinder may be substituted by a stronger cylinder, but generally this measurement causes large costs and much work, and also there is no longer a possibility of reverting to the original cylinder system. It also may show that there is a demand on the capacity of the original cylinders whereas there is a demand for a less frequent function for one of the cylinders than for the other cylinder in order to obtain the best function.

The object of the invention therefore has been to solve the problem of providing a hydraul c auxiliary valve of the above mentioned type which can be interconnected directly in the hydraulic (or pneumatic) supply conduit for the cylinder or group of cylinders intended to operate with a lower frequence than the other cylinder, and which preferably is formed so as to operate automatically by the actuation of the same hydraulic fluid as the actual cylinder or cylinder group.

According to the invention the auxiliary valve comprises a

valve body having a hydraulic inlet and a hydraulic outlet and between the said two parts a control valve or shutvalve and a servo cylinder which is reciprocatally displaceable in the valve body under the actuation of hydraulic pressure in a branch conduit from the hydraulic inlet, and which performs a reciprocatary function for each working cycle, and between the servo cylinder and the shut valve means for actuating the shut valve on each working cycle towards completely or partly opening or closing and thereby alternating actuation of the two hydraulic cylinders or cylinder groups concurrently or only one hydraulic cylinder or cylinder group alone respectively.

Further characteristics of the invention will be evident from the following detailed description in which reference will be made to the accompanying drawings. It is, however, to be understood that the illustrated and described embodiments of the invention are only illustrating examples and that many alternative and analogous solutions of the inventional idea may be presented within the scope of the appended claims. in the drawings figure 1 diagrammatically shows a cross section through a hydraul c system having two cy nders and including an auxiliary valve according to the invention interconnected in the system. Figure 2 shows a cross section along line II - II of figure 1. Figures 3, 4, 5 and 6 illustrate four different function stages in a system including an auxiliary val e according to the invention having connection and disconnection function means.

The hydraulic system illustrated in figure 1 comprises two hydraulic cylinders 1 and 2 which both are fed with hydraulic fluid under pressure from a hydraulic pump 3. Between the hydraulic pump 3 and the cylinders 1 and 2 is mounted a so called reverse valve 4 of the type which reverses function each time a cyl nder or group of cylinders has performed a complete operation stroke or an operation function. The reverse valve 4 has an inlet 5 for hydraulic fluid and an outlet 6 with a draining tank 7 for

recirculated hydraulic fluid. At the opposite side the reverse valve 4 has two outlets 8a and 8b which alternatingly provide outlet for hydraulic fluid under pressure and drain fluid intake for recirculated fluid. From the outlet 8a a hydraul c conduit 9 leads to one end 10 of one of the hydraulic cylinders 1 which ends are called inlet ends since the cylinders 1 and 2 in the illustrated embodiment operate in the left direction as .shown in the figure. To the outlet 8a also a conduit 11 is connected which leads to the inlet 12 of an auxiliary valve 13 according to the invention. From the outlet 14 of the auxiliary valve 13 a conduit 15 leads to the inlet end 16 of the second cylinder 2 which is the cylinder, the function of which is to be adapted to changes of power demand. The outlets of the cylinders 1 and 2 are connected to a common conduit 17 leading back to the second outlet 8b of the reverse valve 4 through which hydraulic fluid alternatingly is drained and is suppl ed to the outlet ends of the cylinders. The auxiliary valve 13 comprises a valve body 18 having inlet 12 and outlet 14 for the hydraulic fluid and a flow channel

19 between said inlet and outlet. A control valve or shut valve

20 is movably mounted in the flow channel 19 so that the valve can take both a completely opened and a completely closed position, and for some applcations of the invention one or more intermediate positions between closed and opened positions. In the illustrated case the control valve 20 is a rotatable cylindric valve having a through valve bore 21. The cylindrical valve is mounted in a cross cylindrical bore of the valve body 18, and in figure 1 it is shown in its completely closed position which in the following description is referred to as the initial position for the described function. Parallelly to the flow channel 19 there is a servo cylinder channel 22 having a servo cylinder 23 actually movable therein, which cylinder acts as a cylindrical valve which over a pressure spring 24 is biassed in the direction towards the inlet end of the auxiliary valve 13. Over a branch conduit 25 the servo cylinder 23 is subjected to the same pressure as the

pressure in the flow channel 19. For facilitating the function of the servo cylinder 23 there is a little drain opening 26 at the outlet side of the servo cylinder.

For providing the intended function the control or shut valve 22 is formed with teeth 27 round the periphery, and the servo cylinder is on the side thereof facing the control valve 20 formed with an equivalent rack 28. The teeth 27 of the control valve or in the rack 28 or both, are formed as idle running wheel so that the control valve or shut valve is actuated by the servo cylinder only in one moving direction thereof, in the present case in the left direction as shown in figure 1.

The teeth 27 of the control or shut valve and of the rack 28 may be different as concerns number and design. In one embodiment of the invention, which is to be described in connection to figures 3-6 there are four teeth of the shut valve 20 and this means that the valve is closing at every second, operation cycle and is opening at the other every second operation cycle, and this in turn means that the cyl nder 1 executes one operation function for each cycle whereas the cylinder 2 executes one operation function for each second cycle. The number of teeth and rack functions, however, may be lager, and the control valve may be formed differently as obvious to the expert so that the valve 2 executes only one operation fuction for a multiple of operations cycles which is higher than two, for instance every three, every four etc. cycle or so that the control valve from a completely closed position is opened successively to a completely opened position and is thereafter successfully choked and closed. Many different function cases are possible within the scope of the invention. Now a possible example of the invention is to be described in connection to figures 3-6. In this case the shut valve 20 is designed so as to close for every second cycle and to open for every other second cycle. It should be noted, however that this is only one of many possible function cases.

It is presupposed that both valves 1 and 2 in the initial

position are in their inlet position, that is in the right hand position as shown in the figures, that the shut valve 20 is open and that the servo cylinder 23 is in the pressure released position at the right hand side as shown in figure 3. It is also presupposed that the reversed pressure valve 4 is in such position that hydraulic pressure is supplied through the outlet 8a.

Figure 3: From the reverse pressure valve 4 pressure fluid is fed from the outlet 8a both through the conduit 9 to the hydraulic cylinder 1 and through conduit 11 to the auxiliary valve 13. For the operation the hydraulic cylinder 1 needs a relatively large volyme of hydraulic fluid and therefore operates relatively slowly. The same is the case for the hydraulic val e 2 which is opened for pressure in that the shut valve 20 is opened. The servo cylinder 23 which is little and very easy movable in relation to the valves 1 and 2, on the contrary operates very quickly and when subjected to hydraulic pressure through the branch conduit it is very quickly moved from the right hand position marked with full lines in figure 3 to the left position marked with dotted lines. At said displacement of the servo cylinder the rack 28 thereof acts on one or more teeth 27 of the shut valve 20 so that said shut valve is rotated to its completely closed position. This is made so quickly that the hydraulic cylinder 2 has not time enough to execute any noticable movement. All hydraulic pressure thereby will actuate the cylinder 1 which with a large force is moved from the right position marked with full lines in figure 3 to the left position marked with the dotted lines. As long as hydraulic pressure is present in the conduits 9 and 11 this function will last. Figure 4: When the piston of the hydraulic cylinder 1 is coming close to its bottom position the pressure at the outlet side becomes so high that said pressure provides a reverse of the reverse pressure valve 4 and this causes the outlet 8b to become pressurized whereas the outlet 8a is connected to the drain conduit at 6. Hereby the servo cylinder 23 is released from

pressure and is forced back to its initial position by the return spring 24, that is the right hand position of the figure. Since the connection beween the control or shut valve and the servo cylinder is formed as a free wheel coupling the position of the shut valve is not changed during said return movement and the shut valve remains in its closed position. At the same time the previously mentioned "outlet side" of the hydraulic cylinder 1 is put under pressure whereas "the inlet side" is connected through drains over the conduit 9. The piston of the cylinder 1 thereby returns to the illustrated right hand original position. At the same time the reverse pressure valve is subjected to a reversed function depending on a pressure of the hydraulic cylinder 1-, whereby the output 8a once again becomes pressurized and the auxiliary valve is ready for the next operation cycle. Figre 5: The same operation follows as has been described in connection with figure 3 and the servo cylinder 23 is displaced momentarily whereby the shut valve 20 reverses from the closed position to an opened position and in this case thereby both hydraulic cylinders 1 and 2 are force actuated and are moved to the illustrated left positions. Like before the reverse pessure valve reverses so that the outlet 8b becomes pressurized.

Figure 6: "The outlet sides" of the hydraulic cylinders 1 and 2 are pressurized over the conduit 17 and the "inlet sides" are drained over the conduits 9, 11 and 15. The pistons of the hydraul c cylinders are thereby moved in the right hand direction in figure 6 to their initial positions, and the servo cylinder 23 is by the return spring 24 forced back to its initial position. The shut valve 20 remains in its open position depending on the free wheel connection between the servo cylinder and the shut valve.

Thereby a complete series of functions providing a full operation cycle has been ended with the illustrated apparatus in which the shut valve is formed with four teeth. It is obvious to the expert that the number of function stages for a full operation cycle increases when the number of teeth of the control

or shut valve and the servo cylinder rack increases. As previously mentioned ^* any different modifications of functions may be provided by varying the number of teeth, and the teeth distribution of the valve 20 and the servo cylinder 23 respectively. Thus it is possible to provide a successive opening and a successive closing of the valve, or a successive opening and a momentary closing, or a momentary opening and a successive closing etc. as easily appreciated by the expert.

It is also obvious that the auxiliary valve may be connected in a branch conduit 29 having a three way valve 30 so that the system can be operated either with both cylinders at the same time for each cycle and without the assistance of the auxiliary valve, or with the assistance of the auxiliary valve as described above. It is also obvious that both the control or shut valve and the servo cylinder may be designed in other ways. For instance the control or shut valve may be formed as a slide valve rather than as a cylinder valve.