Actuator

Abstract

In a fluid cylinder (1), the piston (2) and the piston rod (3) can be displaced axially by a fluid.

Description

TECHNICAL FIELD

The invention is based on a fluid cylinder as indicated in the preamble of the first claim.

PRIOR ART

Hydraulic and pneumatic cylinders are employed today in a multiplicity of machines and devices as power assist means and/or actuators for displacing, pulling, lifting, rotating, or holding in place.

In a number of applications, additional requirements must be met, such as, for example, precisely positioning a piston, variable piston speeds, or, on the other hand, reliably maintaining the piston in a specific position.

The positional information for the piston is usually implemented by using capacitive or inductive sensors which are located on the cylinder housing, the information sensor being located directly within the piston or the piston rod. Measurement is usually effected linearly, that is, based on the travel of the piston or the piston rod.

The piston speed is controlled—at a given pressure—either through fluid holes or by valves. A servo valve, coupled with piston position measurement, allows for practically any conceivable variation in piston speed over the entire stroke of the piston. For example, to effect end-of-travel dampening, simpler systems get by with a stepped piston in order to dampen the piston and prevent a hard impact at the end stop.

In addition, there are cylinders on the market which must securely hold a piston position even in the event of a failure in the hydraulic or pneumatic lines. Various systems are known which securely retain the piston rod in the event of a pressure drop, for example, check valves which respond to excessive fluid rates, or external locks such as pawl-type locks which directly secure the object to be held, as described, for example, in U.S. Pat. No. 4,529,215, or auxiliary cylinders which perform a simple locking or unlocking function, such as described, for example, in US 2003/0140778 A1.

DESCRIPTION OF THE INVENTION

The goal of the invention is to provide a simple and cost-effective means for a fluid cylinder of the species indicated in the introduction, by which means the various requirements for a fluid cylinder can be met.

This goal is achieved according to the invention by the features of the first claim.

The core principle of the invention is thus that means are located on the fluid cylinder which convert the axial displacement of the piston and the piston rod to a rotary motion.

Among other advantages of the invention is the fact that the fluid cylinder according to the invention can be constructed cost-effectively and compactly. The conversion of the axial motion of the cylinder to a rotary motion enables this rotary motion to be exploited so as to perform a great variety of functions. This radial rotation enables requirements to be met by the fluid cylinder going beyond a simple stroke-like retraction and extension as with conventional fluid cylinders. For example, specifically, a locking can be implemented in at least one travel direction, and/or the passage of fluid into the interior of the fluid cylinder can be controlled, and/or the position of the piston can be measured and/or limited, and/or at least one additional component can be attached.

It is especially advantageous if a spindle is used to convert the axial motion into a rotary motion, the spindle being located in the rod hole of the piston. The axial displacement of the rotationally locked piston rod, or piston, enables the spindle to be rotated, the spindle being axially supported within the cylinder housing.

Additional advantageous embodiments of the invention are described in the subordinate claims.

BRIEF DESCRIPTION OF THE DRAWING

The following discussion explains embodiments of the invention in more detail based on the drawings. Identical elements in the different figures are provided with the same reference numbers.

FIG. 1 is a side view of the fluid cylinder according to the invention with the ability to accept the flanging-on of sensors and piston travel limiters.

FIG. 2 is a rear view of the fluid cylinder of FIG. 1 with sensors and piston travel limiter position.

FIG. 3 is a side view of another fluid cylinder according to the invention having an integrated throttle valve controlled by a camshaft.

FIG. 4 is a side view of another fluid cylinder according to the invention having an integrated throttle valve axially controlled by a screw thread.

FIG. 5 is a side view of another fluid cylinder according to the invention having an integrated secondary drive modification or synchronization means.

FIG. 6 is a side view of another fluid cylinder according to the invention having an integrated locking mechanism and a key interlock.

FIG. 7 is a sectional view through the section AA of the fluid cylinder of FIG. 6 with a view of the mechanical locking by an insert.

Only those elements essential to a direct understanding of the invention are shown.

METHOD OF IMPLEMENTING THE INVENTION

FIG. 1 and FIG. 2 show a fluid cylinder 1 which can be operated hydraulically or pneumatically and in which a piston 2 and a rotationally locked piston rod 3 is located, this rod having a screw thread 4a in the rod hole 4 into which a non-self-locking spindle 5 is inserted.

The cylinder base 6 has a hole 6a through which spindle 5 passes, and at the end of which a rotary disk 7 is attached in a fixed manner to spindle 5. This rotary disk 7 is supported axially (not shown) such that the spindle cannot move axially. When piston 2 moves the maximum travel distance through stroke X-X′ as a result of the introduction of fluid under pressure through openings 20a into one of the two cylinder chambers 8, rotary disk 7 is driven radially. This rotation is effected by the longitudinal motion of piston rod 3 which is prevented from twisting by an antirotation lock. Spindle 5 is now made to rotate by the internal screw thread 4a, and since the spindle is not axially movable, rotary disk 7 connected to the spindle rotates.

This rotation can now be utilized for various purposes in connection with a fluid cylinder.

An angle sensor 9 can be flanged on which performs the same function as a linear position measuring means, although here this sensor is located in compact form at the end of the cylinder, and the measuring cable 12 can be routed out directly at the end of the cylinder. Other elements can also be integrated, such as, for example, one or more switches, such as, for example a proximity switch 10 which invokes a function in response to an information sensor 11, for example, a magnet, whenever magnet and sensor face each other.

Rotary disk 7 can also have a cam 13 which is able to move through a radial recess at the base of the cylinder, where the cam is forced to stop by radial stoppers 14 or appropriate shaping of the recess. As a result, rotary disk 7 with spindle 5 is not able to rotate any further, and piston 2 is stopped. Moving stopper 14 thus enables the travel of piston 2 to be defined. The mechanism and sensors can be protected by a cover 15.

FIG. 3 shows rotary disk 7 which has a cam 13 and is used for the purpose of valve control. In the desired angular position of rotary disk 7, that is, ultimately in the desired piston position, a fluid flow control valve (throttle) 17 is actuated by cam 13 through a valve plunger 16. Valve plunger 16 lifts a valve ball 19, for example, against a valve spring 18, within a flow tube 20, then closes this tube as soon as cam 13 has reached its maximum top point of rotation. As a result, piston 2 is stopped.

In order set piston 2 in motion once again, for example, move it in the opposite direction, a second hole 21 is required to enable the cylinder to be filled. This hole 21 is equipped with a check valve 22 so as to ensure that fluid always flows into the cylinder through this channel component and that no fluid flows out, since the fluid's outflow is controlled by the cam-controlled valve.

Rotary disk 7 can be implemented in the form of a cam disk so that over the entire travel of the piston the partial closing of flow tube 20 in connection with valve spring 18 by valve ball 19 enables operation at repeating variable travel rates.

FIG. 4 shows another possible valve control. Rotary disk 7 can serve to drive a valve shaft 23, via a toothed gearing or belt drive of a second shaft, which valve shaft has a screw thread 24 causing shaft 23 to move axially as provided by a longitudinal toothed gearing or spline 23a. A gear train 26 provides an appropriate speed reduction for the valve control, and at the same time a connection between rotary disk 7 and valve shaft 23. Appropriate valves 25, such as, for example plug valves, are located on valve shaft 23. Axial movement provides the inlet control, or outlet valve control as well, to effect filling of the cylinder 8.

The advantage of this technical design is that both the fluid inlet and the fluid outlet can be simultaneously controlled through the stroke by the axial movement of valve shaft 23. As a result, it is possible to move to a specified stopping point in a precisely metered fashion, as well as to move away gently from this point—all without having a complex servo control.

As was already illustrated in FIG. 3, the valve control described in connection with the figure is also applicable to this variant with valve 25 closed. Thus here as well, second hole 21 is actuated when valve 25 is closed which also has a check valve 22.

In order to additionally provide a highly sensitive measurement, the rotary disk can also be designed with a reduction gearing (not shown), or—as is described below—the disk can also be employed to lock the piston using reduced retention forces.

FIG. 5 shows rotary disk 7 in the form of a means for mechanically synchronizing one or more hydraulic cylinders whereby these can be connected to other components through an additional gear train 26 or shaft 27.

For simple functions, rotary disk 7 can also be employed for implementations of separate actions, that is, in the form of a direct drive. This aspect enables the cylinder to be employed in the conventional manner for a dumping action, that is, emptying a material, for example, in the case of transfer station equipment, while simultaneously exploiting the function of rotary disk 7 of cylinder 1 so as to mechanically actuate a hinged door so as to distribute the material to be emptied over a surface proportional to the emptying process.

FIG. 6 illustrates rotary disk 7 in the form of a locking system. As was already mentioned in the introduction, axially fixed spindle 5 is driven through the piston rod stroke X-X′. Blocking the rotational motion of the spindle blocks piston rod 3 in stroke displacement. If rotary disk 7 connected to spindle 5 is now retained by friction, piston rod 3 is mechanically locked in its position.

With this invention, locking is able to be implemented in various embodiments, but always in a compact and simple manner.

First, a locking piston 29 with an antirotation lock 30 can be supported behind rotary disk 7 which has, for example, a pawl-type locking pattern 28 on one side, the locking piston having a diametrically opposed locking pattern 31. This locking piston 29 is pressed, for example, by a spring 32 against rotary disk 7 and locks pistons rod 3 in at least one direction. If piston 2 is pushed out, pawl-type lock 28, 31—due to its structural shape—will allow rotation of rotary disk 7 in a manner analogous to a ratchet, spindle 5 rotates, and piston rod 3 is able to be moved axially in this specific direction. If a load is now directed against piston 2, and if the fluidic pressure is no longer present to a degree sufficient to bear the load, pawl-type lock 28, 31 locks the rotation of rotary disk 7 in the opposite direction, spindle 5 cannot rotate, and piston 2 cannot move. The cylinder is locked.

To provide two-way locking of piston rod 3, a variant may be chosen in which rotary disk 7 and locking piston 29 engage in a form-locking manner through, for example, a toothed gearing. A clutch can also be conceived whereby the two surfaces prevent any turning of rotary disk 7 frictionally and by appropriately pressing together the surfaces, or where this approach is included through the use of an appropriate speed reduction, as was already mentioned.

Unlocking the locking piston is normally effected by the same fluid as is used to move piston 2. The fluidic pressure feed into one of cylinder chambers 8 to adjust the piston simultaneously achieves the filling of chamber 8a for the locking piston. As a result, locking piston 28 is pressed back against spring 32, thereby unlocking rotary disk 7 or spindle 5. By skillful valve control, piston 2 can first be retained in its position by the fluidic pressure, then unlocked, and only subsequently does the appropriate fluidic pressure and fluidic volume act so as to move the piston.

The control of locking piston can, of course, also be implemented by electrical or manual means.

Retention of spindle 5 can additionally be actively assisted as well whereby means are used to introduce a torque against rotary disk 7 such that spindle 5 braces against piston rod 3. FIG. 5 shows a power take-off or synchronization variant which can be used in the opposing direction to apply force to rotary disk 7 and thus to spindle 5.

FIG. 7 shows a fluid cylinder to be secured which must be protected, for example, when exposed in the open and unattended, or from improper operation, for example, in the case of heavy construction machinery components or lifting platforms. A simple insert 33 between locking piston 29 and cylinder cover 15 prevents the axial motion of locking piston 29, and thus locks the entire cylinder. Insert 33 can be a lug of a component which is able to extend only by means of the safety lock 34.

It is of course understood that the invention is not limited to the embodiments shown and described.

In these embodiments, only axial locking pistons 29 have been mentioned; these may also achieve the same effect by means of suitable radial variants in connection with rotary part 7.

LIST OF REFERENCE NOTATIONS

• 1 fluid cylinder
• 2 piston
• 3 piston rod
• 4 rod hole
• 5 spindle
• 6 cylinder base
• 6 a hole
• 7 rotary disk
• 8 cylinder chambers
• 8 a locking piston cylinder chamber
• 9 angle sensor
• 10 proximity switch
• 11 information sensor
• 12 measurement cable
• 13 cam
• 13 a recess
• 14 stopper
• 15 cover
• 16 valve plunger
• 17 fluid flow control valve
• 18 valve spring
• 19 valve ball
• 20 flow tube
• 20 a openings
• 21 hole
• 22 check valve
• 23 valve shaft
• 23 a spline
• 24 screw thread
• 25 valves
• 26 gear train
• 27 shaft
• 28 pawl-type locking pattern
• 29 locking piston
• 30 antirotation lock
• 31 locking pattern
• 32 spring
• 33 insert
• 34 safety lock
• 28,31 pawl-type lock

Claims

1. A fluid cylinder, comprising: a piston and a piston rod, wherein: the piston and the piston rod interact, and the piston and the piston rod can be displaced axially by fluid, and the fluid cylinder is structured in order to convert an axial motion of the piston and the piston rod to a rotational motion.

2. The fluid cylinder according to claim 1, further comprising: a spindle and a rotatable device connected to the spindle for converting the axial motion of the piston to a rotational motion.

3. The fluid cylinder according to claim 2, wherein the spindle is located within a rod hole of the piston rod, the spindle is axially supported within a housing of the fluid cylinder, and the spindle rotates when the piston moves axially.

4. The fluid cylinder according to claim 1, wherein the fluid cylinder is structured such that at least one of a locking of the piston in at least one travel direction is able to be effected, passage of fluid into an interior of the fluid cylinder is able to be controlled, a position of the piston is able to be measured or limited, and at least one additional component is able to be connected.

5. The fluid cylinder according to claim 4, further comprising: at least one of a pawl-type shape, a form-locking surface, or a frictionally engaging surface that is axially or radially lockable against a spring-loaded or hydraulic piston.

6. The fluid cylinder according to claim 4, further comprising: a cam-disk or a second shaft for controlling the passage of fluid into the interior of the fluid cylinder.

7. The fluid cylinder according to claim 4, further comprising: sensors for measuring the position of the piston.

8. The fluid cylinder according to claim 4, further comprising: a gear train with at least one shaft for connecting an additional component.

9. The fluid cylinder according to claim 1, wherein the piston is able to be blocked by an element actuatable outside the fluid cylinder.