US3750705A

US3750705A - Hydraulic control device

Info

Publication number: US3750705A
Application number: US00195198A
Authority: US
Inventors: A Blumer
Original assignee: Maschinenfabrik und Giesserei Netstal AG
Current assignee: Netstal Maschinen AG
Priority date: 1970-11-19
Filing date: 1971-11-03
Publication date: 1973-08-07
Anticipated expiration: 1990-08-07
Also published as: FR2115229B1; GB1372593A; JPS5372086U; CH524075A; CA932241A; DE2150501A1; FR2115229A1; JPS5841366Y2; IT940596B

Abstract

The control device is designed to control a hydraulically operated piston unit, particularly the melting and injection screw unit of an injection molding machine for plastics. The control device includes a main control valve reciprocable in a cylindrical guide or bore formed in a valve body, and controlling the connections between a source of hydraulic fluid under pressure, a pressure consumer and a return flow collector for the fluid, each of which is connected to a respective passage communicating with the guide. The main control valve is subjected to axial pressures, variable in at least one stage, to control the connections between the passages. A reversing valve is mounted on the housing to form a unit therewith, and one or more anticipatory control-pressure valves are also mounted on the housing. The reversing valve is effective to reverse the position of the main control valve, while the anticipatory controlpressure valves act on the main control valve to determine the magnitude of the flow area between chambers, each connected to a respective passage in the housing.

Description

Blumer [451 Aug.7, 1973 HYDRAULIC CONTROL DEVICE [75] Inventor: Armin Blumer,Schwanden,

Switzerland [73] Assignee: Maschinenfabrik und Giesserel Netstal AG, Nafels, Switzerland [22] Filed: Nov. 3, 1971 [21] Appl. No.: 195,198

[30] Foreign Application Priority Data Nov. 19, 1970 Switzerland 17195/70 [52] U.S. Cl. 137/625.64 [51] Int. Cl. Fl6k 11/00 [58] Field of Search 137/596, 625.65,

Primary Examiner-Henry T. Klinksiek Assistant Examiner-Robert J. Miller Attorney-John J. McGlew et al.

[57] ABSTRACT The control device is designed to control a hydraulically operated piston unit, particularly the melting and injection screw unit of an injection molding machine for plastics. The control device includes a main control valve reciprocable in a cylindrical guide or bore formed in a valve body, and controlling the connections between 2 source of hydraulic fluid under pressure, a pressure consumer and a return flow collector for the fluid, each of which is connected to a respective passage communicating with the guide. The main control valve is subjected to axial pressures, variable in at least one stage, to control the connections between the passages. A reversing valve is mounted on the housing to form a unit therewith, and one or more anticipatory control-pressure valves are also mounted on the housing. The reversing valve is effective to reverse the position of the main control valve, while the anticipatory control-pressure valves act on the main control valve to determine the magnitude of the flow area between chambers, each connected to a respective passage in the housing.

6 Claims, 4 Drawing Figures PAIENIEBAUB mm SHEEI 1 0F 4 iimll I1 Q J. m .5 v l v \Q r If. r! [d II; I; L I JAN Q W s QQA Q M. m 2 1. F F N @lL i Jw HYDRAULIC CONTROL DEVICE FIELD OF THE INVENTION This invention relates to hydraulic control devices for controlling hydraulic pressure consumers and, more particularly, to a novel and improved hydraulic control device in which all necessary adjusting elements and reversing elements act on a single control valve which performs all the necessary functions with respect to supplying pressure to the pressure consumer, terminating the supply of pressure, and return of hydraulic fluid from the consumer to a hydraulic fluid receiver.

BACKGROUND OF THE INVENTION The control of hydraulically operated piston units, particularly the melting unit and injection screw unit of a plastic injection molding machine, requires different control devices corresponding to the different fuctions of the units, for example way valves, pressure regulating valves, flow regulating valves, etc. These different control devices normally are provided individually, or

are assembled to form a block. The expense and time required for attaching or installing these individual control elements in the machine is relatively great. In addition, the pressure medium effecting the hydraulic control in each individual control elements undergoes reversals and throttlings. The resulting pressure losses must be compensated by a relatively high initial pressure.

SUMMARY OF THE INVENTION The main control valve comprises a housing or valve body formed with a longitudinally extending cylindrical bore constituting a cylindrical guide. This bore is radially enlarged at axially spaced area therealong to define respective chambers, and each chamber is connected to a respective passage. The passages are adapted for connection, respectively, to a source of hydraulic medium under pressure, to a pressure consumer and to a return flow collector for the hydraulic medium. The control valve is a cylindrical piston slidable in the bore, and has axially spaced lands thereon cooperating with the bore to control connections between the three chambers, the piston being biased in one axial direction by a spring engaged with the stem of an auxiliary piston in a further chamber.

The auxiliary piston is engageable with a longitudinally adjustable tubular feeler controlling supply of pressure to one side of the auxiliary piston and further limiting the movement of the auxiliary piston, and thus of the main piston or control valve, in one axial direction. A reversing valve is mounted on the valve body or housing and is in communication with the bore, and one or more anticipatory control pressure valves are also mounted on the housing in communication with the bore. The reversing valve is electromagnetically operated.

The anticipatory control pressure valves are adjustable to set the respective control pressures, and in a modification of the invention, only a single anticipatory control pressure valve is provided and is adjustable electromagnetically under the control of a selector switch.

An object of the invention is to provide an improved hydraulic control device for controlling a hydraulically operated piston unit.

Another object of the invention is to provide such a control device in which all necessary adjusting and reversing elements act on a single control valve.

A further object of the invention is to provide such a hydraulic control device in which the single control valve performs all the necessary functions, thereby reducing the mounting expenditure and the transfer losses between the pressure generating point and the pressure consuming point to a minimum.

For a understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accomapnying drawing.

BRIEF DESCRIPTION OF THE DRAWING screw-injection molding machine and illustrating the course of the pressure' medium during the melting phase;

FIG. 2 is a view similar to FIG. 1 but illustrating the course of the pressure medium during the injection phase;

FIG. 3 is an axial sectional view of the main control valve of the control device shown in FIGS. 1 and 2; and

FIG. 4 is a schematic illustration, similar to FIGS. 1 and 2, illustrating a variation of the control device shown in FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the control device illustrated schematically in FIG. 1, a connection A is provided for a pressure line leading to a hydraulically operated piston (not shown) of the plastic melting and injection screw of a plastic injection molding machine. A second connection T is provided for a line leading to a storage tank (not shown) for receiving the return hydraulic pressure medium, and a third connection P is provided for a line leading to a source of hydraulic medium uner pressure.

Respective lines

1, 2 and 3 connect the connection points A, T and P to a main control valve 4. In the embodiment of the invention illustrated in FIG. 1, two anticipatory control pressure valves 5 and 6, for adjusting the back pressure of the screw and of the injection pressure, respectively, are associated with main control valve 4, as is also an electromagnetically actuated reversing valve 7.

Referring to FIG. 3, the control device 4 comprises a housing 10 formed with a longitudinally extending bore or passage 11 in which there is mounted, for reciprocation, a main control valve in the fonn of a slide valve 12 of substantially circular cross section. Valve 12 has three control sections or lands 14a, 14b and 140, spaced axially from each other by two circumferentially extending grooves or recesses 13a and 13b, The lands are guided in four rings or internal annular ribs 15a, 15b, 15c and 15d which define, in passage or bore 11,

chambers

16a, 16b, 16c and 16d.

Reversing valve 7 is mounted on housing 10 and communicates, through bores 17a and 17b, with bores 17c and 17d each communicating with a respective chamber 16b and 16a. Anticipatory control pressure valves 5 and 6 communicate, through a duct 18, with chambers 16a. The

lines

1, 2 and 3 are connected to chambers 16c, 16b and 16d, respectively. A cross bore 19 in control section or land 14b connects chamber 16c with an axial bore in valve 12, and this bore 20 is open in the range of end section or land 14c of valve 12, at the axial end of valve 12.

In a wider end portion of bore 20, there is seated a coil spring 21 which engages the stem of an auxiliary piston 22 movable in chamber I6e. Chamber 16s is in communication with an axial passage 23a of a feeler 23 mounted in coaxial relation with slide valve 12 in housing 10. The parts of chamber 16c on opposite sides of auxiliary piston 22 are in communication with each other through a transverse bore 24a and an axial bore 24b in piston 22. The left and right parts of chamber 16e are connected by respective lines and 26 to electromagnetic reversing valve 7, shown in FIGS. 1 and 2, and valve 7 connects these two lines with either tank connection line 2 or pressure connection line 3. Feeler 23 can be adjusted mechanically so that the minimum size of the space to the right of ausixliary piston 22, when piston 22 has its right face engage feeler 23 extending into chamber 16c, is determined.

The method of operation of the described control device will now be set forth. During the melting process in the injection molding machine, pressure source connection P must be disconnected from pressure consumer connection A, which leads to the pressure side of the screw piston, while connection point A is connected through connection T to the storage tank or reservoir. The position of the various control elements of the device during this melting phase is represented in FIG. 1. Reversing valve 7 is so set that control valve 12 is in its left end position in FIG. 3, as indicated in broken lines. In this position of valve 12, land 14b seals chamber 16b, and thus pressure line 3, from chamber 16c which is, in turn, in communication through angular groove 13b with chamber 16d, so that pressure consumption line 1 is connected with tank line 2.

The pressure acting in line 1, and thus on the hydraulic piston of the screw moving backwardly during the melting phase depends on the passage, in valve 4, between chambers 16c and 16d, and thus on the position of slide valve 12 and its annular groove 13b. The position of slide valve 12 can be adjusted, in the embodiment of the invention shown in FIGS. 1, 2 and 3, by adjusting anticipatory control pressure valve 5. Using valve 5, it is possible to adjust, through line 18, the pressure in chamber 160, and thus the position of slide valve 12 and the flow area of the passage between chambers 16c and 16d through groove 13b. It goes without saying that the desired back pressure can also be regulated in several stages, if necessary, in which case a corresponding number of anticipatory control pressure valves can be provided.

After completion of the melting phase, magnetic reversing valve 7 is energized and switched into the position shown in FIG. 2, with slide valve 12 being displaced into the solid line position shown in FIG. 3, or to the right. Pressure line 3 is thus connected through groove 13a of valve 12 to pressure consumption line 1, while collar 14b seals consumption line 1 from tank or return line 2. The desired injection pressure is adjusted on anticipatory control pressure valve 6, through which the pressure in chamber 160, acting on the end 14a of slide valve 12, is determined. The passage between chamber 16b and 16c, as to its flow area through groove [30, is thus determined by the position of slide valve 12. If the hydraulic pressure of the load, or that acting on the screw, has risen to the value adjusted on valve 6, this valve opens and effects, in chamber 16a, a pressure drop causing valve 12 to move correspondingly to the left as viewed in FIG. 3. Due to the pressure loss between the pressure consumption point and connection A, the pressure on the right hand side of the slide valve 12 varies so that slide valve 12 moves automatically into the correct position.

In the illustrated example, a single-stage back pressure is provided, and is adjusted by means of valve 6. However, the back pressure during injection can also be adjusted in two or more stages by supplying the pressure medium, for example, through a corresponding magnetic reversing valve, through different anticipatory control pressure valves. In this way, different injected pressures can be set. However, in order to be able to vary the injection velocity infinitely, independently of the pressure, the auxiliary piston 22 is moved similtaneously with the start of the injection phase by the magnetic reversing valve 7 into the end position in chamber 162, as shown in FIG. 3 on the right side, so that it closes the opening to feeler passage 23a. The pressure medium supplied to the part of chamber 16:: to the left of piston 22 is applied, through

bores

24a and 24b acting on a diaphragm, in the chamber part to the right of auxiliary piston 22, so that a back pressure is provided on slide valve 12.

This back pressure effects, on the one hand, a variation of the flow cross section of the passage formed by groove 13a between chambers l6dand 160, which is determinant for the injection velocity, and, on the other hand, a disengagement of auxiliary piston 22 from feeler 23. Feeler passage 23 thus communicates with chamber 16c, and pressure medium flows from this chamber through line 26 in valve 27 into line 2, and thus into the tank. Due to the pressure gradient produced between the two sides of auxiliary piston 22, this piston will be disengaged from feeler 23 only so far as to form a relatively small gap, so that the passage between chambers 16b and cannot be closed completely. Depending on the adjustment of feeler 23,

which is axially adjustable mechanically, a pressure equilibrium will be established at the desired size of the flow area of the passage.

As described so far, the anticipatory control pressure valves are adjustable by hand. FIG. 4 illustrated an embodiment in which the anticipatory control pressure valve 6 also can be adjusted by a selector switch 60, and the adjustment of the back pressure can be effected automatically by electric means. In this case,

only one anticipatory control pressure valve is necessary. The electrical contacts can be controlled through end keys in dependence on the distance, or in time dependence, through relays, or electronically, with infinite variation through preselected control cams.

A main advantage of the control device is its compactness. That is, all function controls, for example pressure and velocity of the piston unit to be controlled, are effected by means of a signle control valve, the associated auxiliary elements, such as electromagnetic reversing valves, anticipatory pressure control valves, etc., being assembled with the slide vale to form a unit. In other words, the following functions are possible by a corresponding combination of anticipatory pressure control valves 5 and 6, magnetic reversing valve 7 and auxiliary piston 22 with a single control valve 12 and a valve body 10:

a. Establishment of the connection between pressure source 3 and consumer line 1, which is connected to a cylinder with a piston or to a hydraulic motor, and the chambers 16b and 16c, respectively.

b. Reduction of the hydraulic pressure or of the amount of hydraulic fluid in consumer line 1 to a predetermined infinitely variable value.

c. Interruption of the connection between pressure source 3 and consumer line 1, and between chambers 16b and 16c, respectively.

d. Simultaneous establishment of the connection between consumer line 1 and return line 2, and between chambers 16c and 16d, respectively.

e. Production of an infinitely variable and predeterminable resistance between pressure consumer line 1, or chamber 16c, and return tank 2, or chamber 16d, where the hydraulic fluid is displaced from consumer line 1 by a force acting from the outside.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles,

What is claimed is:

l. A hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages; a reversing valve mounted on said housing and communicating with said guide; at least one anticipatory controlpressure valve mounted on said housing and communicating with said guide; said reversing valve controlling displacement of said main control valve to open and close a first channel connecting the passage for connection of a'so'urce of hydraulic medium under pressure to the passage for connection to a pusher consumer, and controlling opening and closing of a second channel connecting the passage for connection to a pressure consumer to the passage for connection to a return flow collector; each anticipatory control pressure valve being operable to effect a further displacement of said main control valve to determine the effective flow area of each of said channels; an auxiliary piston displaceable in a chamber in said housing which is coaxial with said guide, said auxiliary piston being operatively associated with said main control valve; and an adjustable feeler extending coaxially into said chamber for said auxiliary piston and engageable with said auxiliary piston to limit movement of said auxiliary piston and said main control valve in one axial direction to determine the minimum flow area of said second channel.

2. A hydraulic control device, as claimed in claim 1, in which each anticipatory control valve is manually adjustable.

3. A hydraulic control device, as claimed in claim 1, including electric means operable to adjust automatically each anticipatory control pressure valve.

4. A hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages, said passages including, considered axially of said guide, a first end passage for connection to a source of hydraulic medium under pressure, a second intermediate passage for connection to a pressure consumer, and a third end passage for connection to a return flow collector; said bore being radially enlarged at axially spaced locations therealong to form first, second and third chambers communicating, respectively, with said first end passage, said second intermediate passage and said third end passage; said main control valve being formed with a land, intermediate its length, controlling communication between said first end passage and said second intermediate passage, and controlling communication between said second intermediate passage and said third end passage; said main control valve being formed with two end lands spaced axially in opposite directions from said intermediate land; said main control valve being formed with a first annular groove extending between one end land and said intermediate land and a second annular groove extending between said intermediate land and the other end land; said first annular groove, in a selected position of said valve, defining a flow channel interconnecting said first and second chambers, and said second annular groove, in the opposite position of said main control valve, defining a flow passage interconnecting said second and third chambers; said guide being formed with a fourth chamber adjacent one end of said main control valve and with a fifth radially enlarged chamber adjacent the opposite end of said valve; an auxiliary piston reciprocable axially in said fifth chamber and having a stem extending into said bore; a spring seated in said opposite end of said main control valve and engaged with said stern; and an adjustable tubular feeler projecting into said fifth chamber and engageable with the outer end of said auxiliary piston, to limit displacement of said main control valve toward said fifth chamber.

5. A hydraulic control device, as claimed in claim 4 including an electromagnetically operated reversing valve mounted on said housing; passage means in said housing connecting said reversing valve to said first and fourth chambers for supply thereto and exhaust therefrom of a pressure medium to control displacement of said main control valve; at least one anticipatory control pressure valve mounted on said housing; and further passage means connecting said anticipatory controlpressure valve to said fourth chamber to supply operating fluid under pressure thereto or to exhaust operating fluid therefrom to modulate the axial position of said main control valve as set by said reversing valve to vary the effective cross-sectional area of said channels; said main control valve being formed with an axial passage therethrough extending from said opposite end thereof and communicating, through a cross bore, with said second chamber; said auxiliary piston being formed with passage means therethrough interconnecting the portions of said fifth chamber on opposite sides of said auxiliary piston.

6. A hydraulic control device, as claimed in claim 5, in which said housing comprises a single valve body acting as a slide valve housing; each anticipatory control-pressure valve, said electromagnetically operated reversing valve and said auxiliary piston acting conjointly with said-single main control valve and said single valve body to perform, selectively, the following functions:

a. establishment of a connection between a source of hydraulic medium under pressure and a pressure consumer by establishing a connection between said first and second chambers;

b. reduction of the pressure of the hydraulic medium or the amount of the hydraulic medium in a line connected to said second intermediate passage and to the pressure consumer, to an infinitely variable and predetermined value;

c. interruption of the connection between a source of hydraulic medium under pressure and the pressure consumer by interrupting communication between said first and second chambers;

d. simultaneously with such interruption establishing a connection between the pressure consumer and the flow connector by establishing a connectionbetween said second and third chambers; and

e. production of an infinitely variable and predeterminable resistance between said second chamber, connected to the pressure consumer, and said third chamber, connected to the return flow collector, with the hydraulic medium being displaced from the pressure consumer into said second intermediate passage and said second chamber by an external force acting-on the pressure consumer.

Claims

1. A hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages; a reversing valve mounted on said housing and communicating with said guide; at least one anticipatory control-pressure valve mounted on said housing and communicating with said guide; said reversing valve controlling displacement of said main control valve to open and close a first channel connecting the passage for connection of a source of hydraulic medium under pressure to the passage for connection to a pusher consumer, and controlling opening and closing of a second channel connecting the passage for connection to a pressure consumer to the passage for connection to a return flow collector; each anticipatory control pressure valve being operable to effect a further displacement of said main control valve to determine the effective flow area of each of said channels; an auxiliary piston displaceable in a chamber in said housing which is coaxial with said guide, said auxiliary piston being operatively associated with said main control valve; and an adjustable feeler extending coaxially into said chamber for said auxiliary piston and engageable with said auxiliary piston to limit movement of said auxiliary piston and said main control valve in one axial direction to determine the minimum flow area of said second channel.

4. A hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages, said passages including, considered axially of said guide, a first end passage for connection to a source of hydraulic medium under pressure, a second intermediate passage for connection to a pressure consumer, and a third end passage for connection to a return flow collector; said bore being radially enlarged at axially spaced locations therealong to form first, Second and third chambers communicating, respectively, with said first end passage, said second intermediate passage and said third end passage; said main control valve being formed with a land, intermediate its length, controlling communication between said first end passage and said second intermediate passage, and controlling communication between said second intermediate passage and said third end passage; said main control valve being formed with two end lands spaced axially in opposite directions from said intermediate land; said main control valve being formed with a first annular groove extending between one end land and said intermediate land and a second annular groove extending between said intermediate land and the other end land; said first annular groove, in a selected position of said valve, defining a flow channel interconnecting said first and second chambers, and said second annular groove, in the opposite position of said main control valve, defining a flow passage interconnecting said second and third chambers; said guide being formed with a fourth chamber adjacent one end of said main control valve and with a fifth radially enlarged chamber adjacent the opposite end of said valve; an auxiliary piston reciprocable axially in said fifth chamber and having a stem extending into said bore; a spring seated in said opposite end of said main control valve and engaged with said stem; and an adjustable tubular feeler projecting into said fifth chamber and engageable with the outer end of said auxiliary piston, to limit displacement of said main control valve toward said fifth chamber.

5. A hydraulic control device, as claimed in claim 4 including an electromagnetically operated reversing valve mounted on said housing; passage means in said housing connecting said reversing valve to said first and fourth chambers for supply thereto and exhaust therefrom of a pressure medium to control displacement of said main control valve; at least one anticipatory control pressure valve mounted on said housing; and further passage means connecting said anticipatory control pressure valve to said fourth chamber to supply operating fluid under pressure thereto or to exhaust operating fluid therefrom to modulate the axial position of said main control valve as set by said reversing valve to vary the effective cross-sectional area of said channels; said main control valve being formed with an axial passage therethrough extending from said opposite end thereof and communicating, through a cross bore, with said second chamber; said auxiliary piston being formed with passage means therethrough interconnecting the portions of said fifth chamber on opposite sides of said auxiliary piston.

6. A hydraulic control device, as claimed in claim 5, in which said housing comprises a single valve body acting as a slide valve housing; each anticipatory control-pressure valve, said electromagnetically operated reversing valve and said auxiliary piston acting conjointly with said single main control valve and said single valve body to perform, selectively, the following functions: a. establishment of a connection between a source of hydraulic medium under pressure and a pressure consumer by establishing a connection between said first and second chambers; b. reduction of the pressure of the hydraulic medium or the amount of the hydraulic medium in a line connected to said second intermediate passage and to the pressure consumer, to an infinitely variable and predetermined value; c. interruption of the connection between a source of hydraulic medium under pressure and the pressure consumer by interrupting communication between said first and second chambers; d. simultaneously with such interruption establishing a connection between the pressure consumer and the flow connector by establishing a connection between said second and third chambers; and e. production of an infinitely variable and predeterminable resistance between said second chamber, connected to the pressuRe consumer, and said third chamber, connected to the return flow collector, with the hydraulic medium being displaced from the pressure consumer into said second intermediate passage and said second chamber by an external force acting on the pressure consumer.