GB1569933A - Hydraulic installation comprising a pressure-dependent accumulator-charging valve - Google Patents

Description

(54) A HYDRAULIC INSTALLATION COMPRISING A PRESSURE-DEPENDENT ACCUMULATOR-CHARGING VALVE (71) I, KARL-HEINZ THOMAS, a German citizen, trading as INTEGRAL HYDRAU LIK & Co. of Klosterstrasse 49, 4000 Dusseldorf, Germany, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:: The invention relates to a hydraulic installation having a pressure-dependent accumulator-charging valve especially mobile hydraulic installations, having a first springloaded valve member operable by hydraulic pressure acting on at least one operative surface of the valve member, for the connection of a delivery conduit with an outlet conduit after an upper cut-out pressure is exceeded and for blocking this connection after a lower cut-in pressure is reached, the delivery conduit being connected to a circuit containing a hydraulic accumulator through a non-return valve, and having a second valve member operable by hydraulic pressure acting on an operative surface permanently subjected to the pressure in the hydraulic accumulator for alternately subjecting the operative surface of the first valve member with the pressure in the accumulator and with the pressure of the outlet conduit.

Such an accumulator-charging valve is already known from German patent specification Auslegeschrift 2,103,788. The first valve member is formed as a seating-type valve which is pressed by a spring on to a valve seating and then blocks the throughflow from the delivery conduit to the outlet conduit. The valve member possesses a first operative surface constantly subjected to the pressure in the delivery conduit. The pressure force acting upon this operative surface is directed oppositely to the force of the spring, but does not suffice for the opening of the seating type valve until the cut-out pressure is reached. Only after the cut-out pressure is exceeded does the seating-type valve act in the manner of a pressure-limiting valve.Opening on reaching of the cut-out pressure, which corresponds to the "normal" function, is effected by pressure charging of a second operative surface of the first valve member. For this purpose a spring-loaded second valve member in the form of a double-seating valve is provided which in the zone between cut-in pressure and cut-out pressure relieves the second operative surface and when the cut-out pressure is reached at the same time separates the second operative surface from the return conduit and connects it with the circuit containing the hydraulic accumulator. This accumulatorcharging valve is in fact capable of protecting the pressure generator connected to the delivery conduit effectively against overloading. It is not however capable of protecting the hydraulic accumulator securely against over-loading.This disadvantage, which is contradictory to modern safety provisions and accident prevention regulations, occurs at least when the pressure in the hydraulic accumulator is able to rise due to external influences above the pressure of the pressure generator. A possibility of relief through the first valve member in such a case does not exist on account of the non-return valve arranged between delivery conduit and hydraulic accumulator.

It is therefore the problem of the invention to develop an accumulator-charging valve of the initially mentioned kind so that the hydraulic accumulator and the circuit communicating with it are effectively protected against over-loading, whether an increase of pressure is caused by failure of the first valve member or by external forces influencing the pressure in the hydraulic accumulator. The configura tion is to be simple and cheap and to be realisable substantially within the framework of the construction dimensions as usual hitherto. It is moreover to be usable for a plurality of construction forms of accumulator charging valves.

The solution of this problem is effected according to the invention in that the second valve member is made in the form of a control piston and beside the actuation positions present on reaching of the cut-out pressure and of the cut-in pressure is movable to at least a further third actuation position in response to a pressure in the hydraulic accumulator above the cutout pressure, in which position the control piston connects the circuit containing the hydraulic accumulator with a substantially pressureless return conduit.

So that the first valve member, provided that it has shifted according to function, retains its cut-out position, the control piston may be formed so that the connections produced on reaching of the cut-out pressure are maintained even on reaching of the third actuation position. If the basis is adopted that simultaneous failure of the first valve member and of the non-return valve arranged between pressure generator and hydraulic accumulator is completely improbable, with the embodiment in accordance with the invention the pressure generator is also securely protected against over-loading.

The invention is explained in greater detail with reference to examples of embodiment illustrated in the Figures.

Figure 1 shows, partially with the aid of hydraulic symbols, an arrangement having a first valve member the operative surface of which is loaded with pressure when the cut-out pressure is reached.

Figure 2 shows a corresponding arrangement having a first valve member which possesses two operative surfaces of which one is always loaded with the pressure of the hydraulic accumulator while the other is relieved of the pressure when the cut-out pressure is reached.

A housing 1 has a bore 2 which a first valve member 3 is slidably guided. A second valve member 5 is slidably arranged in a further bore 4. Pressure medium is conveyed from a pressure generator 6 (not shown further) through a pressure conduit 7 and a non-return valve 8 to a user (not defined further). The first valve member 3 is formed as control piston and is hereinafter called the cut-out piston 3. The cut-out piston 3 has three lands 9, 10 and 11 which are separated by reduced shank portions 12 and 13. In the initial position as illustrated the land 9 abuts against the end 14 of the bore 2. In the region of the reduced shank 13 a connection A which is connected through a conduit 15 with the pressure conduit 7 opens into the bore 2. A spring 16 bearing on the housing 1 acts upon the the land 11.The spring space 17 within the bore 2 is connected through a conduit 18 with an outlet T. A channel 19 issuing from the reduced shank 12 within the cut-out piston 3 opens into the spring space 17. The land 10 has a control edge 20 facing the reduced shank 12. The second valve member 5 is likewise formed as a control piston and is also designated as such hereinafter. The control piston 5 has two lands 22 and 23 separated by a reduced shank 21. In the position as illustrated the land 22 abuts against the end 24 of the bore 4. A spring 25 loads the land 23 and bears on an adjustable abutment in the form of a threaded plug 26. The land 22 has a control edge 27 and a cqntrol edge 28 adjacent to the reduced shank 21.In the region of the control edges the bore 4 widens into an annular groove 29 which is connected through a conduit 30 with an annular groove 31 which is formed starting from the end 14 concentrically with the bore 2. The land 23 has a control edge 32 facing the reduced shank 21, in the vicinity of which a channel 33 opens into the bore 4 and leads to the connection T. The part of the bore 4 containing the spring 25 is called spring space 34 and vented through a conduit 35 into the channel 33. The land 23 is surrounded by an annular groove 37 at a certain distance from its end 36 opposite to the control edge 32, which groove is connected through a conduit 38 with the pressure conduit 7 downstream of the nonreturn valve 8. A hydraulic accumulator 39 is connected to the conduit 38.A control conduit 40 branches off from the conduit 38 and opens, through a construction 41, to a connection Z which in turn opens into the end 24. The reduced shanks 12, 13 and 21 are surrounded by annular spaces 42, 43 and 44.

To explain the operation let it be assumed that more pressure medium is delivered by the pressure source 6 than the user requires. The excess quantity is stored in the hydraulic accumulator 39 and there effects a presence rise which inter alia is propagated through the control conduit 40 and the connection Z to the free end face of the land 22. When the force thus exerted upon the control piston 5 exceeds the initial stress of the spring 25 the control piston 5 moves. Then firstly the control edge 28 closes off the annular groove 29 from the annular space 44. After a further movement, when the cut-out pressure is reached, the control edge 27 opens a connection between the annular groove 29 and that part of the bore 4 facing the connection Z.Pressure medium then flows from the connection Z through the bore 4, the annular groove 29 and the conduit 30 to the annular groove 31 and thence to the end 14 of the bore 2. The cut-out piston 3 is thus moved against the force of the spring 16 until the control edge 20 connects the connection A with the annular space 42. Pressure medium can now flow from the pressure conduit 7 through the conduit 15, the connection A, the annular space 42, the channel 19 and the conduit 18 to the connection T which is connected with the outlet. Provided that the pressure downstream of the non-return valve 8 exceeds the cut-out pressure due to external influences, the control piston 5 continues to move until its control edge 32 opens a connection from the annular groove 37 to the annular space 44, which even in this position continues to remain connected with the channel 33.Therefore pressure medium can flow from the conduit 38 communicating with the hydraulic accumulator 39, through the annular groove 37, the annular space 44 and the channel 33 to the connection T. Thus secure relieving of the hydraulic accumulator 39 is guaranteed.

In the case of a prior failure of the cut-out piston 3 even the whole delivery of the pressure source 6 could thus be conducted away without harmful influence. Reverting to the "normal"function of the cut-out piston 3, after its shift into the cut-out position and a certain consumption of pressure medium the pressure in the hydraulic accumulator 39 will drop. The spring 25 then presses the control piston 5 so far that the control edge 27 first closes and then the control edge 28, on reaching of the cut-in pressure, opens the connection between annular groove 29 and conduit 30.

The pressure medium in the end section of the bore 2 is displaced by the force of the spring 16 through the annular groove 31, the conduit 30, the annular groove 29, the annular space 44 and the channel 33 to the connection T. The spring 16 pushes the cut-out piston into the original position again in which the annular space 42 is separated from the connection A by the land 10. The operating cycle as described can commence afresh.

With reference to Figure 2, a housing 45 has a bore 46 in which a cut-out piston 47 serving as first valve member can slide. A control piston 50 serving as second valve member is slidably arranged in a further bore 49. The cut-out piston 47 has two lands 52 and 53 separated by a reduced shank 51. The shank is surrounded by an annular space 54 into which opens a channel 55 leading to an outlet connection T.

The land 53 is loaded by a spring 56 which is arranged in a part of the bore 46 hereinafter called the spring space 57, the spring 56 bearing against the housing 45. In the region of the land 53 the bore 46 widens into an annular groove 58 with a connection A to which a conduit 59 is connected which branches off from a pressure conduit 60. The pressure conduit 60 is fed by a pressure source 61 and leads to a user (not illustrated further). The edge of the land 53 facing the reduced shank 51 is called control edge 62. On the land 52 there is an extension piece 63 which is surrounded by a part of the bore 46 hereinafter called the control space 64. A conduit 65 opens into the control space 64 from a conduit 67 connected with the pressure conduit 60 downstream from a non-return valve 66.

The control piston 50 has three lands 70, 71 and 72 separated by reduced shanks 68 and 69. Within a part of the bore 49 hereinafter called the spring space 73 a spring 74 bearing against an adjustable spring abutment 75 acts upon the land 72. In the vicinity of the land 72 the bore 49 widens into an annular groove 76 which is connected through a conduit 77 with the channel 55. The spring space 73 is vented into the channel 55 through a further conduit 78 opening in the vicinity of the spring abutment 75. The edge of the land 72 remote from the spring 74 is hereinafter called the control edge 79. The reduced shank 69 is surrounded by an annular space 80 into which the conduit 67 opens adjacently to the land 72. The land 71 has two control edges 81 and 82.The annular space 80 widens on both sides of the control edge 82 to form an annular groove 83 from which a conduit 84 leads to the spring space 57. The reduced shank 68 is surrounded by an annular space 85 connected by a conduit 86 to the channel 55. From the conduit 67 a control conduit 87 leads through a constriction 88 to a connection Z which opens into a control space 89 limiting the end of the control piston 50.

A hydraulic accumulator 90 is connected to the pressure conduit 60.

To explain the function let it be assumed here again that the pressure source 61 is just commencing delivery and the hydraulic accumulator 90 is being charged with pressure medium. The pressure rise caused by this is propagated through the conduit 67, the control conduit 87 and the connection Z into the control space 89 and there loads the control piston 50. At the same time the pressure is propagated through the conduit 65 into the control space 64 and passes by way of the annular space 80, the annular groove 83 and the conduit 84 into the spring space 57. Since control space 64 and spring space 57 have the same operative areas, the pressure forces balance one another and the spring 56 holds the cutout piston 47 in its initial position.When the initial stress of the spring 74 is overcome, the control piston 50 moves, the control edge 82 firstly severing the connection between annular space 80 and annular groove 83. Since the pressure medium in the spring space 57 is however locked in, the cut-out piston 47 does not yet move. Only when after a further movement of the control piston 50, on reaching of the cutout pressure, the control edge 81 opens a connection from the annular groove 83 to the annular space 85 is the spring space 57 relieved, namely through the conduit 84, the annular groove 83, the annular space 85, the conduit 86 and the channel 55. The pressure force loading the end of the cutout piston 47 in the control space 64 now shifts this piston against the force-of the spring 56 so that the control edge 62 can open a connection from the annular groove 58 to the annular space 54.This signifies that pressure medium can flow substantially without pressure from the pressure conduit 60 through the conduit 59, the connection A, the annular groove 58, the annular space 54 and the channel 55 to the outlet. If due to incorrect behaviour of the cut-out piston 47 or due to external forces the pressure in the hydraulic accumulator 90 should increase above the cut-out pressure, the control piston 50 is displaced further until the control edge 79 opens a connection between the annular space 80 and the annular groove 76.

Pressure medium can then flow by this route from the conduit 67 into the conduit 77 and thence through the channel 55 to the outlet connection T. The hydraulic accumulator 90 is effectively protected against over-loading. It should be noted that in the actuation position of the control piston 50 as last described the connection between annnular space 85 and annular groove 83 is maintained, so that the actuation condition of the cut-out piston 47 also does not change, provided that correctly functioning actuation has taken place. In "normal" function, the hydraulic accumulator 90 will empty slowly after the cutout operation, which involves a pressure reduction.The cdntrol piston 50 moves under the drive of the spring 74 until the control edge 82 on reaching of the cut-in pressure again restores the connection between annular space 80 and annular groove 83 and the spring space 57 is charged afresh with pressure. The spring 56 then shifts the cut-out piston into the position as illustrated again.

The invention is not limited to the constructions illustrated. Thus for the production of a variable actuation pressure difference it is quite usual in a cut-out piston according to Figure 2 to provide two control pistons to generate a variable actuation pressure difference. The first control piston shuts off the spring space of the cutout piston from the hydraulic accumulator while the second control piston then relieves the spring space. In principle each of these control pistons can possess a further actuation position. It is then left to the designer to decide according to what considerations he selects the one or the other. The Figures are not intended to express anything as to the degree of integration of an accumulator-charging valve according to the invention. Thus it is equally possible to arrange the symbolically illustrated conduits in a housing as bores.On the other hand it is also possible to arrange the control piston in a separate housing and then to produce a pipe or flange connection.

WHAT I CLAIM IS: 1. A hydraulic installation comprising a pressure-dependent accumulator-charging valve having a first spring-loaded valve member operable by hydraulic pressure acting on at least one operative surface of the valve member, for the connection of a delivery conduit with an outlet conduit after an upper cut-out pressure is exceeded and for blocking this connection after a lower cut-in pressure is reached, the delivery conduit being connected to a circuit containing a hydraulic accumulator through a non-return valve, and having a second valve member operable by hydraulic pressure acting on an operative surface permanently subjected to the pressure in the hydraulic accumulator for alternately subjecting the operative surface of the first valve member with the pressure in the accumulator and with the pressure of the outlet conduit, characterised in that the second valve member is made in the form of a control piston and beside the actuation positions present on reaching of the cutout pressure and of the cut-in pressure is movable to at least a further third actuation position in response to a pressure in the hydraulic accumulator above the cutout pressure, in which position the control piston connects the circuit containing the hydraulic accumulator with a substantially pressureless return conduit.

2. A hydraulic installation according to Claim 1, characterised in that the connections effected by the control piston on reaching of the cut-out pressure are also maintained on reaching of the third actuation position.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. the initial stress of the spring 74 is overcome, the control piston 50 moves, the control edge 82 firstly severing the connection between annular space 80 and annular groove 83. Since the pressure medium in the spring space 57 is however locked in, the cut-out piston 47 does not yet move. Only when after a further movement of the control piston 50, on reaching of the cutout pressure, the control edge 81 opens a connection from the annular groove 83 to the annular space 85 is the spring space 57 relieved, namely through the conduit 84, the annular groove 83, the annular space 85, the conduit 86 and the channel 55.The pressure force loading the end of the cutout piston 47 in the control space 64 now shifts this piston against the force-of the spring 56 so that the control edge 62 can open a connection from the annular groove 58 to the annular space 54. This signifies that pressure medium can flow substantially without pressure from the pressure conduit 60 through the conduit 59, the connection A, the annular groove 58, the annular space 54 and the channel 55 to the outlet. If due to incorrect behaviour of the cut-out piston 47 or due to external forces the pressure in the hydraulic accumulator 90 should increase above the cut-out pressure, the control piston 50 is displaced further until the control edge 79 opens a connection between the annular space 80 and the annular groove 76. Pressure medium can then flow by this route from the conduit 67 into the conduit 77 and thence through the channel 55 to the outlet connection T. The hydraulic accumulator 90 is effectively protected against over-loading. It should be noted that in the actuation position of the control piston 50 as last described the connection between annnular space 85 and annular groove 83 is maintained, so that the actuation condition of the cut-out piston 47 also does not change, provided that correctly functioning actuation has taken place. In "normal" function, the hydraulic accumulator 90 will empty slowly after the cutout operation, which involves a pressure reduction.The cdntrol piston 50 moves under the drive of the spring 74 until the control edge 82 on reaching of the cut-in pressure again restores the connection between annular space 80 and annular groove 83 and the spring space 57 is charged afresh with pressure. The spring 56 then shifts the cut-out piston into the position as illustrated again. The invention is not limited to the constructions illustrated. Thus for the production of a variable actuation pressure difference it is quite usual in a cut-out piston according to Figure 2 to provide two control pistons to generate a variable actuation pressure difference. The first control piston shuts off the spring space of the cutout piston from the hydraulic accumulator while the second control piston then relieves the spring space. In principle each of these control pistons can possess a further actuation position. It is then left to the designer to decide according to what considerations he selects the one or the other. The Figures are not intended to express anything as to the degree of integration of an accumulator-charging valve according to the invention. Thus it is equally possible to arrange the symbolically illustrated conduits in a housing as bores.On the other hand it is also possible to arrange the control piston in a separate housing and then to produce a pipe or flange connection. WHAT I CLAIM IS:

1. A hydraulic installation comprising a pressure-dependent accumulator-charging valve having a first spring-loaded valve member operable by hydraulic pressure acting on at least one operative surface of the valve member, for the connection of a delivery conduit with an outlet conduit after an upper cut-out pressure is exceeded and for blocking this connection after a lower cut-in pressure is reached, the delivery conduit being connected to a circuit containing a hydraulic accumulator through a non-return valve, and having a second valve member operable by hydraulic pressure acting on an operative surface permanently subjected to the pressure in the hydraulic accumulator for alternately subjecting the operative surface of the first valve member with the pressure in the accumulator and with the pressure of the outlet conduit, characterised in that the second valve member is made in the form of a control piston and beside the actuation positions present on reaching of the cutout pressure and of the cut-in pressure is movable to at least a further third actuation position in response to a pressure in the hydraulic accumulator above the cutout pressure, in which position the control piston connects the circuit containing the hydraulic accumulator with a substantially pressureless return conduit.

2. A hydraulic installation according to Claim 1, characterised in that the connections effected by the control piston on reaching of the cut-out pressure are also maintained on reaching of the third actuation position.

3. A hydraulic installation having a

pressure-dependent accumulator charging valve substantially as hereinbefore described with reference to Figure 1 or 2 of the accompanying drawings.