WO2015113174A1

WO2015113174A1 - Dual-cylinder servomotor for braking systems

Info

Publication number: WO2015113174A1
Application number: PCT/CL2014/000005
Authority: WO
Inventors: Alberto Antonio SEPULVEDA MUÑOZ
Original assignee: Chesta Ingeniería S.A.
Priority date: 2014-01-31
Filing date: 2014-01-31
Publication date: 2015-08-06

Abstract

The invention relates to a dual-cylinder servomotor to be used in a braking system, in remote-control overhead travelling cranes or other remotely controlled heavy industrial equipment, with two independent actuators that are actuated by means of incompatible hydraulic liquids that should not be mixed. The servomotor has two cylindrical jackets (8, 14), closed at one end and with an anchor therein (15, 22), one jacket having a smaller diameter and moving inside the other; a rod (11) with two pistons at the ends thereof, having grooves (17, 18, 19, 20) such as to include corresponding ring packings (10, 12) and cup packings (9, 13), such that each piston moves inside each jacket. Each piston with each jacket defines corresponding work chambers which are accessed by a different working liquid via the respective connection points, near the aforementioned ends of the jackets.

Description

DOUBLE CYLINDER SERVOMOTOR FOR BRAKE SYSTEMS

The large-scale mining industry tends to use large telecommand machines more and more frequently, as a way to give greater continuity to its operations, improve efficiency, control and registration and safeguard operators from accidents on the spot.

These large machines require for safety a stop, brake system, of greater capacity than traditional hydraulic brakes.

The present invention relates to a mixed cylinder for application in a brake system, in telecommand bridge cranes or other heavy equipment of the telecommanded industry, with two drives, one by a pedal on a brake pump, that works with a brake fluid (for example DOT 3), and the other with an electrohydraulic system, which drives a second hydraulic system. Since there is incompatibility between the liquids used by hydraulic power sources, a single hydraulic cylinder that allows contact between them cannot be used, since when the liquids are mixed they lose their properties (transmit pressure, lubricate and cool, for example) . The invention seeks to solve these problems.

Hydraulic cylinders

1. The hydraulic cylinder in the hydraulic circuit

In addition to the hydraulic motor, in a hydraulic circuit today the hydraulic cylinder is an irreplaceable equipment for the transformation of hydraulic energy into mechanical energy. Is by therefore, the connecting element between the hydraulic circuit and the machine that drives it.

Unlike the hydraulic motor, which performs rotary (rotary) movements, the hydraulic cylinder has the function of carrying out (linear) translation movements and, simultaneously, transmitting forces.

The maximum possible force of the cylinder F depends, disregarding friction, on the maximum permissible operating pressure p and on the effective surface A.

F = p · A (in kN)

For the operation with hydraulic cylinders in linear movements of work machines, the following advantages are obtained:

- Direct drive with hydraulic cylinders is simple in assembly and easily located for the machine builder.

As there is no conversion of rotary motion into linear motion, the cylinder drive has good performance.

A hydraulic cylinder can present its maximum force constantly from the beginning to the end of the race.

A pressure valve offers the possibility of simply limiting the stroke force.

- The piston speed of a hydraulic cylinder depends on the flow rate and the effective piston surface. If the flow rate is kept constant, the piston speed will also be constant from the beginning to the end of the stroke. According to the construction type of a hydraulic cylinder, it can only provide pressure forces or pressure and traction forces.

The directioning of hydraulic cylinders makes it possible to build high-power drives with reduced mounting dimensions,

The most frequent cases of hydraulic cylinders are lifting, lowering, blocking and moving loads.

2. Cylinder types according to their effect

According to their effect the hydraulic cylinders are divided into:

- single acting cylinders and

- double acting cylinders.

2.1 Single acting cylinders

Single acting cylinders can only deliver their strength in one direction. The replacement of the piston can be carried out by means of a spring, by the weight of the piston itself or by the effect of an external force. Basically single acting cylinders have an effective surface.

2.1.1 Immersion piston or piston cylinders without rod

In this cylinder version, according to the technical installation, only compression forces can be transmitted.

According to the case of application, piston cylinders without rod can be made with or without internal stop and guide piston. The magnitude of the pressure force is calculated in all executions by multiplying the surface of the piston rod by the operating pressure. Rodless piston cylinders are used where a clear sense of force allows a safe return to the initial position, such as: in hydraulic presses with inner pistons, lifting devices, etc.

Loading the effective surface through the pipe connection "A" with operating pressure, the piston comes out (<=). The return of the piston must be produced by its own weight or by the effect of an external force.

2.1.2 Cylinder with spring recoil

Cylinders with replacement springs are used where the external replacement force is missing. The replacement springs can be arranged inside or outside the cylinder. Since springs can only run races and generate limited forces, they are especially used in "small cylinders". They are used in the construction of tools such as clamping cylinders or as a mounting tool for repairs.

The output (<=) of the rod is achieved by loading the effective surface of the piston with operating pressure through connection "A". The inlet movement of the rod is carried out by means of the replacement spring.

By loading the effective annular surface with serving pressure through connection "B", the rod inlet is achieved. The output movement (=>) is carried out by means of the reset spring.

2.2 Double acting cylinders

Double acting cylinders have two surfaces of opposite effect, of equal or different size. They have two independent connections to each other. By feeding a pressure medium through the "A" or "B" connections, the piston It can transmit tensile or compressive forces in both directions. This type of cylinder is used in virtually all fields of application.

Double acting cylinders are subdivided into differential cylinders and double rod cylinders.

2.2.1 Differential cylinders

(Cylinders with unilateral rod)

In most application cases the cylinders are made with a single rod. Differential cylinders have a piston: which is fixedly attached to a smaller diameter rod. The name differential cylinder is derived from effective (different) size surfaces. The relationship of surfaces between piston surface and annular surface is called factor e. The maximum transmissible force depends on the output movement of the piston surface and the input movement, the annular surface and the maximum permissible operating pressure. That is, at the same service pressure the output force is greater in the s factor to the input force. The chambers to be filled in each case, given the stroke are equal in length, but different in volume given the differences between piston surface and annular surface. Therefore, the running speeds behave inversely to the surfaces.

That is to say:

- Large surface - »idle

- Small surface - »fast march

2.2.2 Double rod cylinders

(Cylinders with bilateral rod)

Double rod cylinders have a piston, which is fixedly attached to two smaller diameter rods. The maximum transmissible force in both directions depends on the annular surfaces of equal size and maximum permissible operating pressure. That is, at the same service pressure the forces in both directions are equal. Since the surfaces and stroke lengths are identical on both sides, so are the chambers to be filled. It follows that the speeds are also equal.

For special cases of application double rod cylinders can be made with different piston diameters.

In this version the forces and speeds behave (similar to differential cylinders) in the relation of surfaces e of both annular surfaces to each other. 2.3 Special forms of single and double acting hydraulic cylinders

There are cases of application in which single or double acting cylinders can only be used by taking additional measures. Most of these cases are stroke length with extremely low mounting dimensions or large forces at a minimum piston diameter. These and other requirements led a series of special versions, whose manufacture is extremely complicated.

2.3.1 Tandem cylinders

In the double-acting cylinders in tandem version two cylinders are joined in such a way that the rod of one of them presses on the surface of the piston of the other through the base of the latter. Thanks to this arrangement, the surfaces add up and great forces can be transmitted without increasing the service pressure and reduced external diameters. The greatest construction length must be taken into account.

2.3.2 Fast March Cylinders Fast-moving cylinders are especially used in press construction. In this type of cylinder, as long as the full working force is required, only a part of the effective surface of the piston, the so-called fast-moving piston, is loaded. The total effective surface is later connected to the hydraulic pump through the control, by means of the pressure valve reaction and end of course switches.

Advantages:

- Great speed of fast march by small volume

- Great compression force due to large effective piston surface.

2.3.2.1 Fast acting single acting cylinder

- Fast march (<=) via connection "A1"

Reaspiration through line connection "S"

- Compression force (<=) via connection "A2"

- Recoil by own weight or external force, return of "A1" and "A2"

2.3.2.2 Double acting fast-acting cylinder

- Fast march (<=) via connection "A1"

Reaspiration through line connection "S"

- Compression force («=) for working piston through connection" A2 "

- Recoil through connection "B", return of "A1" and "A2"

2.3.3 Telescopic cylinder

Telescopic cylinders differ from "normal" cylinders by their shorter mounting length when they are retracted, compared to "normal" cylinders with a comparable stroke. As a consequence of the shanks that fit together, the mounting dimension is equal to the total divided stroke length by the number of stages plus the zero stroke level (base thickness, guide lengths, stagnation widths, fixing). This means that the mounting length is only slightly larger than a stage. The length of the retracted telescopic cylinder is normally between half and a quarter of its stroke length. Depending on their mounting height, these cylinders are made of two, three, four or five levels. Telescopic cylinders are used in hydraulic elevators, tilting platforms, utility vehicles, lifting platforms, antenna construction, etc.

2.3.3.1 Single acting telescopic cylinders

If the pistons are loaded through connection "A", they exit one after another. The pressure is governed by the magnitude of the load and the effective surface. Consequently, the piston with the effective surface comes out first.

At constant pressure and flow the output movement begins, the greatest force and at low speed and ends with the force; Small and at high speed.

The stroke force to be used must be sized by the smallest effective surface of the piston. In the single-acting telescopic cylinder the order of the input movement is reversed as a result of the external load. This means that the piston with the smallest surface will first be moved to the final position.

2.3.3.2 Double acting telescopic cylinders

In double-acting telescopic cylinders, the output occurs in the same way as in single-acting telescopic cylinders.

The order of the entry movement of the different stages is governed by the size of the annular surface and the load external Here, when loaded with pressure through the "B" connection, the piston with the largest annular surface first moves to the final position.

Double acting telescopic cylinders can also be made as double rod telescopic cylinders. In this version the different stages leave or enter simultaneously. 3. Building principles

The construction of a hydraulic cylinder depends largely on the application case. In machine tools, mobile, hydroelectric, steel and steel industry or in other cases of application. Appropriate construction principles have been developed for each specific case.

Based on the single or double acting differential cylinder that is used most frequently, we will represent the most common construction principles.

Basically, there are two types of construction:

- Strap construction and

- round construction.

3.1 Strap construction

In the rod cylinders the cylinder head, the barrel of the cylinder and the base of the cylinder are firmly connected by traction bars (braces). Strap cylinders are characterized by their especially compact construction.

Given the compact space-saving construction, they are especially used in the machine tool industry and in manufacturing facilities in the automotive industry, such as machining centers.

3.2. Round construction In the round construction hydraulic cylinders the cylinder head, the cylinder tube and the cylinder base are firmly connected by screws, welds or retaining rings.

Due to the robust assembly, the round construction hydraulic cylinders are also suitable for use under extreme operating conditions.

The fields of application of round construction hydraulic cylinders are the general construction of machines, rolling mills, steel mills, hydroelectric factories, shipyards and land and high seas technical.

Regarding the state of the art for mixed cylinders in general, we can cite the patent of invention ES 451 .304, which refers to improvements introduced in a double acting hydraulic cylinder, that is, which can be subjected to load on both sides, for a control system with a piston arranged in the first hollow piston rod and in a second hydraulic cylinder, configured as a recoil cylinder, which through its piston is actively connected to the first hydraulic cylinder, characterized in that The hollow piston rod of the hydraulic cylinder receives the recoil cylinder in which a second piston rod is provided, which has a part of the inner and outer cylinder in whose hollow space a third piston rod, fixedly arranged, movably housed. at the end of the first piston rod in which a second piston connected to the cylinder part is slidably supported or inner, with the first piston rod channel being provided on the first piston rod and the inner cylinder portion that joins a first variable chamber of pressurized agent, disposed between the first and second pistons, to a first connection hole provided in the cylinder housing, while part of the inner cylinder is open in the area of the closed end of the first piston rod and connected to the first connection hole and is closed at the opposite end, forming the third piston rod, with the part of the inner cylinder a second variable pressure agent chamber that is connected to a second connection hole through a second pressurized agent channel provided in the cylinder housing.

Another patent for hydraulic cylinders is found in the invention patent ES 1031589, which refers to an improved double acting rotary hydraulic cylinder; characterized in that an axis comprises a widening that defines a piston, on one axis two annular pieces of different length and of greater diameter are mounted on both sides of the piston than the piston that are joined by screws and that define the cylinder chamber in which and mounted on the shaft appears a bushing that is fixed with screws to one of the faces of the piston and whose bushing incorporates non-return valves in the axial direction arranged in conduits connected with others that appear practiced inside the shaft by which circulates hydraulic fluid than a circuit to which two inlets and outlets of liquid belong; At one end of the shaft, the element that transmits the movement to the machine part is connected, while at the other end a housing with drainage ducts of the remaining hydraulic circuit is mounted.

Another patent of invention is ES 315 803, which refers to a system for converting a double acting hydraulic cylinder into a single direction and vice versa, characterized in that in one of the supply lines of the pressurized fluid to the double hydraulic cylinder effect, a governable distributor is sandwiched at will so that in one position it allows the passage of the pressurized fluid to said hydraulic cylinder so that it acts as a double-acting cylinder, and in another position it closes the passage of pressurized fluid towards the hydraulic cylinder, returning it to a circuit to the tank and make the hydraulic cylinder act as a single acting cylinder, with free return of the piston.

The cylinder for bridging crane braking system or the like of the invention solves the need to have a compatible hydraulic actuator in operation with two sources of hydraulic energy, which work with different hydraulic fluid (synthetic base and mineral base), without the possibility of hydraulic liquids mixing.

The solution of this problem of the technique was formed by creating a single-acting double chamber hydraulic cylinder with no return by diver type spring, called a mixed cylinder. A chamber to work with the synthetic-based liquid (for example DOT 3 or another), and a second chamber to work with the mineral-based liquid (ISO VG 46 was used in the prototype, and it can also be any other similar).

Brief description of the figures

To better understand the essential characteristics of the mixed hydraulic cylinder, for application in brake systems on bridge cranes or the like, it will be described according to the figures that are an integral part of the invention, without this meaning restricting them to obvious modifications that could arise, where:

Figure 1 shows an overview of the brake system for bridge cranes with remote remote control or similar heavy machinery, arranged with the mixed hydraulic cylinder of the invention. Figure 2 shows an exploded perspective view of the mixed hydraulic cylinder for brakes on bridge cranes or similar heavy machinery with remote control of the invention.

Figure 3 shows a perspective view of the mixed hydraulic cylinder for brakes on bridge cranes with remote control or similar heavy machinery of the invention.

Figure 4 shows an internal front view of the operation of one of the chambers of the mixed hydraulic cylinder, for brakes on bridge cranes with remote control or similar heavy machinery.

Figure 5 shows an internal front view of the operation of another chamber of the mixed hydraulic cylinder, for brakes on bridge cranes with remote control or similar heavy machinery.

Description of the Invention

According to figures 1 to 5, the mixed hydraulic cylinder for brakes on bridge cranes with remote telecommand is given in the context of a brake system (according to figure 1) with two drives, one by a pedal (6) on a brake pump (7) that works with brake fluid (in the prototype DOT 3 was used for synthetic ones), and the other one with a pedal (3), but with an electro-hydraulic system for remote control (4) that works with the mineral-based hydraulic fluid. Since there is incompatibility between the liquids used by the hydraulic energy sources (4) and (7), a hydraulic cylinder that allows contact between them cannot be used, since when the liquids are mixed they lose their properties (transmit pressure, lubricate and refrigerate, for example). The mixed cylinder (1), can work with two sources of hydraulic energy that work with different liquids, whether or not they are compatible. Said mixed cylinder (1) is made up of two chambers (16) and (21) that are insulated between them, but that fulfill the objective of generating the linear displacement of a plunger (14), see figure 2.

The liquids with which the mixed cylinder (1) works (synthetic and mineral) will not be mixed in any case in any of the chambers (16) and (21). In the case of the first chamber (16), if a cup seal (13) and an O 'rings (12) are passed due to wear or excess pressure, the fluid will be lost through the area that presents the least resistance , the tolerance between the piston (14) and a cylinder base (8). In addition an O 'rings (10) which also serves to prevent the liquid from entering the second chamber (21). If the second chamber (21) leaks, the fluid will be lost due to the tolerance between the piston (14) and the cylinder base (8), as in the previous case. The means that make up the mixed cylinder (1), allows a visual feedback of the state of cup seals (9) and (13) and the O 'rings (10) and (12), since if they are in bad condition there will be loss of hydraulic fluid, remembering what tends to fail commonly in hydraulic cylinders.

The operation of the first chamber (16) and the second chamber (21) of the mixed cylinder (1), can be separately or together, this means that the first chamber (16) can work even if the second chamber is not activated or present failures and vice versa. In the case that you want to work with both chambers at the same time, you will get the force generated by the mixed cylinder (1) to increase, since the effective area of the piston will increase, see figures 4 and 5. The cup seal (1 3) is suitable for working with DOT 3 brake fluid, as it is made of EPDM. The cup seal (9) is suitable for working with the ISO VG 46 hydraulic fluid, since it is made of polyurethane. It should be noted that chamber one (16) conditioned to work with synthetic-based brake fluid could be used to work with mineral-based hydraulic fluid by changing the cup seal (13) and the O 'rings (12). This change can also be made in the second chamber (21). The cup seal (13) and the O 'rings (12), are installed in grooves (17) and (18) respectively, to prevent them from moving from their working position. For the same purpose, the cup seal (9) and the O 'rings (10), are installed in slots (20) and (19) respectively.

The mixed cylinder (1) has two anchor points (15) and (22) to be installed in the workplace. These points (15) and (22) have the characteristic of being of oscillating fixation, but if it is required to change this condition, it is enough to only modify the conformation of the anchor (15) and (22) of the mixed cylinder (1).

Mixed cylinder operation

The mixed cylinder (1) has the particularity of having the two insulated chambers (16) and (21), in order to be operated, sending pressure through the threaded connection points NPT (2) and (5) separately or together, obtaining in both cases the linear displacement of the piston (14) of the mixed cylinder (1)

When applying hydraulic pressure through the threaded connection point type NPT (5), the hydraulic pressure will be distributed in chamber one (16) generating the linear displacement of the piston (14), given that a piston (1 1) leaves to rest on the base of the cylinder (8) and the only free end will be the piston (14). When applying hydraulic pressure through the threaded connection point type NPT (2), the hydraulic pressure will be distributed in the second chamber (21) generating the linear displacement of the piston (14), since the piston (11) is going to rest on the plunger (14), being the only free end to move.

Given the properties of the means that make up the mixed cylinder of the invention, the pressures of the hydraulic energy sources (4) and (7) are equivalent, greater compression force is generated with the second chamber (21), since its effective area is greater, according to the mathematical expression for force:

F = PA

Where,

F = Strength

P = Pressure

A = Effective area

Claims

one . - Mixed hydraulic cylinder for application in a brake system, in telecommand bridge cranes or other heavy equipment in the telecommanded industry, with two drives, one by a pedal on a brake pump, which works with synthetic-based brake fluid , and the other with an electro-hydraulic system, which drives a second hydraulic system, CHARACTERIZED because a base body (8) and a plunger (14) are formed, which moves linearly through the interior of the base body (8); and both bodies (8) and (9), make up a first chamber (16) and a second chamber (21) being isolated between them, which allows the mixed hydraulic cylinder (1), to work with two sources of hydraulic energy with different types of liquids (synthetic and mineral), whether or not they are compatible; furthermore said mixed cylinder is provided with a piston (1 1), which has at one end, two grooved bodies (17), (18) and the other end also has two grooved bodies (19) and (20); with the difference that these last bodies, are of greater diameter than those of the opposite end of the piston (1 1), since the base body (8) of said mixed hydraulic cylinder (1), has a larger diameter than the piston (14) ; To avoid mixing liquids (synthetic and mineral) between the chambers (16) and (21), the grooved bodies of the piston (1 1) have O 'rings (10) and (12) and cup seals (9 ) and (13), which are located at the ends of the base body and the plunger (14) of the mixed hydraulic cylinder.

2. - Mixed hydraulic cylinder for application in a brake system, in telecommand bridge cranes or other heavy equipment of the telecommanded industry, according to the claim 1, CHARACTERIZED because a mixed hydraulic cylinder has two standard anchor points (15) and (22), which have the characteristic of oscillating fixing and at the same time have threaded connection points (2) and (5), where they can be operated by sending pressure separately or together, obtaining in both cases the linear displacement of the plunger (14).

3.- Mixed hydraulic cylinder for application in a brake system, in telecommand bridge cranes or other heavy equipment of the telecommanded industry, according to claim 1, CHARACTERIZED because the chambers (16) and (21) of the mixed hydraulic cylinder ( 1) are isolated, with the aim of being operated by pressure by the threaded connection points (2) and (5) separately or together, obtaining the linear displacement of the plunger (14).