HYDRAULIC ASSEMBLY FOR DRIVING AND CONTROLLING OF

SMALL HYDRAULIC UNITS, ESPECIALLY OF BRAKE CYLINDERS

AND CLUTCH CYLINDERS OF A FORESTRY WINCH

The invention refers to mechanical engineering, namely to fluid pressure actuators and hydraulics, namely to fluid-pressure actuators. On the other hand the invention may also belong to performing operations, in particular to hydraulic control devices for rope or chain winding mechanisms of winches.

The purpose of the invention is to create a hydraulic assembly, which would enable driving and controlling of small hydraulic units, in particular hydraulic cylinders for controlling of brake and clutch of a forestry winch, which means to establish and also to maintain a pre-determined pressure of a hydraulic media within the hydraulic circuit, wherein at the same time the hydraulic loss should be as low as possible and the quantity of said hydraulic media required for regular operation and maintaining the pressure within the assembly should also be as low as possible.

As known to those skilled in the art, hydraulic assemblies are used also for the purposes of controlling and driving in the field of forestry winches. A winding drum is driven by means of the internal combustion engine of the belonging tractor

via appropriate shaft and a chain reduction gear, and includes a clutch and a brake, which operate alternatively. When the brake is deactivated, the clutch is activated, which then enables turning and driving of a winding drum, upon which by deactivation of said clutch the brake is automatically activated in order to prevent said drum from any further turning. Controlling of said clutch and brake may commonly also be performed by means of electric or any other control units, which is however not always feasible or is much more complicated, when the winch is used in situ, where relevant energy sources are limited or not available at all. Since appropriate hydraulic assembly may no doubt be surmounted to such winch, the pump of which may easily be driven by means of each disposable tractor engine, such appliances for controlling of clutch and brake have already been realized also in the practical use. Appropriate hydraulic circuit comprises a pump, which charges the hydraulic media via appropriately arranged valves and depending on position and adjustment thereof either towards the brake controlling cylinder or a clutch controlling cylinder, by which the residual hydraulic media is then returned back to reservoir i.e. towards said pump. As known to the applicant, a geared pump has exclusively been used for such purposes. Such assembly may no doubt establish a required pressure of the hydraulic media within the hydraulic circuit, but the pump must be able to ensure a sufficient quantity of the media in a required time for the purposes of supplying each cylinder and in order to enable sufficiently short shifting time of control units of the clutch and brake, so that the pumping capacity must be relatively high. Accordingly, the pump must assure sufficiently high capacity all the time, by which the hydraulic loss due to leakage is relatively high, which then in correlation with high pressure results in heating or even overheating of the hydraulic system, which has essential impact to decreasing of quality of hydraulic media and wearing of sealing members, by which the risk of disturbances or damages during operation is then essentially increased. In addition

to that, such assembly is pretty bulky when bearing in mind its overall dimensions, not only due to complex and bulky valves included therein, but also due to huge quantity of the hydraulic media and bulky reservoir for storage thereof. It is also obvious, that a hydraulic assembly containing such quantity of hydraulic fluid is not an environment-friendly one, especially when bearing in mind, that said damages may occur during operation in situ, e.g. in the forest or the like.

Various hydraulic circuits are described also in the patent literature, e.g. in FR 2.116.693, JP 58121306A, JP 60263710, JP63083405A, JP 2004176698 or JP 2004360300A, which belong to various devices and are all very complicated and include numerous components, so that the applicant is of opinion, that none of them solves the previously mentioned technical problem, which is however solved by the proposed invention.

The present invention refers to a hydraulic assembly for driving and controlling of small hydraulic units, especially of brake and clutch cylinders of a forestry winch, wherein such assembly comprises at least a reservoir for hydraulic media, a pump intended for producing a required pressure of hydraulic media, as well as a control unit, which consists of at least one control valve as well as of at least one hydraulic cylinder.

According to the invention, a hydraulic circuit of the hydraulic assembly includes a piston pump, which is at the one hand via a non-return valve, which allows flowing in a direction away from the pump but not also towards said pump, hydraulically connected with a control unit and a reservoir of said hydraulic media, and on the other hand

- either via a switching valve with integrated non-return valve, which allows flowing towards the pump but not also in the opposite direction, in a serial manner into a hydraulic circuit together with a pressure storage tank and the non-return valve,

- or by exceeding a pre-defined pressure by means of automatically shifting of the switching value into a hydraulic circuit, which includes said pump, a switching valve, a control unit and said non-return valve, which are hydraulically interconnected in a serial manner.

Said piston pump consists of a housing, in which a crankshaft is mounted on a belonging eccenter link and is by means of appropriate bolt pivotably connected with a piston, which is equipped with a sealing member and a wiper and inserted within a cylinder, which is integrated within said housing and equipped with appropriate hydraulic connector adapted for charging the hydraulic media into the area adjacent to the front surface of said piston or also for discharging said media there-from. Said eccenter link is preferably mechanically interconnected with a corresponding shaft of a reduction gear of the winch.

The switching valve comprises a non-return valve, which is mounted within a housing of the switching valve and allows flowing towards the pump but not also in the opposite direction, as well as a needle, which is pressed towards said nonreturn valve by means of a spring, which is supported by an adjusting member screwed into the housing, by which said switching valve is also equipped with three hydraulic connectors for charging the hydraulic media into the switching valve or discharging said media there-form. The first hydraulic connector is foreseen adjacent to the non-return valve and allows hydraulic media to flow outwards from the housing of the switching valve. The second hydraulic connector

of the valve is placed within the area of a normal position of the needle, when pressed towards the non-return valve by means of said spring. The third hydraulic connector of the valve is placed in the area corresponding to position of the needle when shifted away from the non-return valve opposite to the reaction force of the spring. Said spring is preferably a compression helical spring. Furthermore, said switching valve is hydraulically connected in the area of its first hydraulic connector with the pump and at the same time via the non-return valve both with the control unit and also with the pressure storage tank, which is at the same time hydraulically interconnected with the third hydraulic connector of the switching valve. Still further, said switching valve is hydraulically interconnected in the area of its second hydraulic connector with a reservoir of the hydraulic media and at the same time also with the control unit, while the interconnection between said second connector and the pump and/or the first connector is disabled by means of the non-return valve.

Such assembly preferably comprises at least one pressure gauge, which is incorporated within the hydraulic circuit between the pressure storage tank and the third hydraulic connector of the switching valve.

The control unit consists of a control valve as well as of at least one control cylinder, which may be via said control valve integrated into the hydraulic circuit, in which the piston pump is integrated either directly or indirectly via the pressure storage tank. In a preferred embodiment and use of the invention such hydraulic assembly includes a control unit, which consists of parallel interconnected cylinder adapted to control a brake of a forestry winch and cylinder adapted to control a clutch, of a forestry winch, which are both via the control valve connected with the

hydraulic circuit, in which the piston pump is included either directly or indirectly via the pressure storage tank.

The control valve as such is either electrically or mechanically controlled 4/3 valve, namely a valve with four hydraulic connectors and three operational positions.

The invention will be described in more detail on the basis of an embodiment, which is shown in the enclosed drawing, wherein

Fig. 1 an embodiment of the assembly for controlling and driving of small hydraulic units according to the invention, which is intended for controlling of brake and clutch of a forestry winch and is shown in its mounted state on the gearbox of the forestry winch during its exploitation;

Fig. 2 a schematically shown hydraulic circuit during the suction operating mode of the pump; and

Fig. 3 a schematically shown hydraulic circuit during the compression operating mode of the pump.

Hydraulic assembly 50 according to the invention, which is shown in Fig. 1, is adapted for being mounted directly to a housing 97 of a forestry winch 99 and is in this particular embodiment attached to a chain transmission i.e. a reduction gear 98 by means of a flange 96 and screws 95, wherein such simple and practical concept results in extremely small overall dimensions of the assembly regardless to the fact, that the pressure achieved therein may be greater than 100 bar by the flow rate 2 1/min and the pump velocity 540 rnin ^'1 .

As evident in Fig. 1 and also in Figs. 2 and 3, such hydraulic assembly 50 according to the invention comprises a piston pump 500, a reservoir 510 for hydraulic media, a pressure storage tank 520, a switching valve 530 together with a non-return valve 535, a non-return valve 540 as well as a control unit 550, and optionally also a pressure measuring unit i.e. a pressure gauge 560. Said parts are interconnected in a manner, which will be explained in more detail in the further description.

The piston pump 500 consists of a casing 501, in which a piston rod 503 is mounted on an eccenter link 502, which is connected with an not-shown shaft of the redμction gear 98 of the winch 99, while said crankshaft 503 is then by means of appropriate bolt 504 in a connected pivotable manner with a piston 505, which is equipped with a sealing member 506 and a washer 507 and inserted into a cylinder 508, which normally forms a part of said casing 501 and includes appropriate hydraulic connector 509, through which the hydraulic media is then charged into said cylinder 508 in the area adjacent to the front surface of said piston 505 or may also be discharged there-from.

The piston pump 500 is by means of said connector 509 hydraulically connected on the one hand via said non-return valve 540, which prevents the flow towards the pump 500 and allows the flow in opposite direction, and also with the reservoir 510 and the control unit 550, and on the other hand with the switching valve 530 via the non-return valve 535 thereof, which allows the hydraulic media to , flow towards the pump 500 but not also in the opposite direction.

The switching valve 530 comprises said non-return valve 535, which is mounted within the housing 531 of said switching valve 535, as well as a needle 532, which

is pressed towards said non-return valve 535 by means of a spring 533, preferably a compression helical spring, wherein said spring 533 is supported by an adjusting member 534, which is e.g. screwed into the housing 531. Said switching valve 530 is equipped with three hydraulic connectors 536, 537, 538 for charging/discharging of hydraulic media into/from the valve 530. The first hydraulic connector 536 is foreseen in the area of said non-return valve 535 and permits exclusively discharging of hydraulic media outwards from the housing 531 of the valve 530. The second hydraulic connection 537 of the switching valve 530 is foreseen in the area of normal position of the needle 532, in which said needle is pressed towards the non-return valve 535 by means of said spring 533. The third hydraulic connector 538 of the switching valve 530 is available in the area, into which the needle 532 is moved from the aforementioned position due to compression of said spring 532, namely apart from the non-return valve 535.

Thanks to its first hydraulic connector 536 the switching valve 530 is hydraulically connected with the pump 500 and at the same time by means of non-return valve 540 with the control unit 550 as well as with the pressure storage tank 520, which is at the same time hydraulically connected with the third hydraulic connector 538 of the switching valve 530. Still further, thanks to its second hydraulic connection 537 the switching valve 530 is hydraulically connected with the reservoir 510 of hydraulic media and at the same time also with the control unit 550, while the connection between said connector 537 and the pump 500 and/or the first connector 536 is disabled by means of a non-return valve 540.

In this particular embodiment the assembly 50 is furthermore equipped with a pressure gauge 560, which is included within the hydraulic circuit between the

pressure storage tank 520 and the switching valve 530, namely the third connector 538 thereof.

Operation of the assembly 50 within the range of previously described pressure and flow capacity of the hydraulic media should normally be feasible, if a standard G 1/4" valve is used as a non-return valve 540, and if the non-return valve 535 within the switch valve 530 is a standard G 3/8" valve.

In this embodiment the control unit 550 consists of a brake control cylinder 551 and a clutch control cylinder 552, which are connected with relevant components of the hydraulic assembly 50 by means of appropriate control valve 555, which is in Figs. 2 and 3 presented like a 4/3 valve i.e. a valve with four connections and three operational options resulting from position thereof.

The piston pump 500 of said hydraulic assembly 50 may either operate in a suction operational mode or in compression operational mode or simply in a mode, in which a pre-determined pressure within a hydraulic circuit is maintained at a desired level.

Operation of said pump 500 is presented in Fig. 2 by means of a dotted line. The pressure in the cylinder 508 is reduced by means of said piston 505, by which the non-return valve 535 in the switching valve 530 is shifted into opened state, which then results in suction of the hydraulic media from the reservoir 510 throughout the second connector 537 of the switching valve 530 towards the pump 500.

Operation in the compression mode is shown in Fig. 3, where the flowing direction of the hydraulic media is presented by means of a dotted line. The hydraulic media

is compressed within said cylinder 508 by means of the piston 508, which is then entering into said tank 520 via the non-return valve 540. As soon as a predetermined value of the pressure, which is preset by means of the adjusting member 534 i.e. by compression of the spring 533 within the switching valve 530 e.g. to approx. 100 bar, is achieved within the system, then the valve 530 is automatically actuated/shifted, by which the needle 532 is moved towards the adjusting member 534 i.e. away from the non-return valve 535 and opposite to compression force resulting from said spring 533.

When a pre-determined pressure is achieved within the hydraulic circuit, the control valve 555 may be shifted to and fro either mechanically or by means of electric or any other means, by which the hydraulic media is then appropriately directed into a desired cylinder 551, 552 or discharged there-from, respectively. If none of cylinders 551, 552 is actuated, the non-return valve 535 of the switching valve 530 is held in its opened position due to the pressure within the systems, by which the hydraulic media is flowing in the same direction as in the aforementioned suction mode according to Fig. 2. In such a mode the pump is still performing its oscillatory movement, so that also the level of the hydraulic media is permanently oscillating, which however has no practical influence with respect to operation of the hydraulic assembly as such. When desired, such oscillating may also be essentially reduced by means of a simple measure, namely by using some thicker hydraulic conduits. On the other hand, there is no leakage within the hydraulic system, and in particular no heating or overheating, which would lead to destruction or decomposition of the hydraulic media and herewith to decreasing of functional characteristics thereof, which would normally result in increasing of risk of damages or disturbances during operation of components of the hydraulic assembly 50.

Exclusively for the purposes of illustration of benefits, which obviously result from such a concept, it should be annotated, that such hydraulic assembly is extremely useful for the purposes of controlling of a clutch cylinder 551 and a brake cylinder 552 of a forestry winch 99, by which the pressure within the hydraulic assembly 50 is normally about 100 bar, and the pump 500 having a capacity of approx. 2 1 of the hydraulic media per minute is driven by means of a shaft, which is turned by 540 min ^"1 , by which the complete quantity of the hydraulic media, which is required for regular operation, should normally not exceed 0,5 1. All these characteristics of the proposed invention consequently result in a solution, which is by taking into account essentially minimized dimensions, number of components and quantity of the hydraulic media, extremely useful not only in the field of forestry winches, but also in the field of controlling any other devices by means of relatively small hydraulic components.