GB2348464A

GB2348464A - Linear drive

Info

Publication number: GB2348464A
Application number: GB0008135A
Authority: GB
Inventors: Romuald Fries
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-04-03
Filing date: 2000-04-03
Publication date: 2000-10-04
Anticipated expiration: 2020-04-03
Also published as: GB2348464B; DE19915260A1; GB0008135D0; DE19915260B4; FR2792038B1; DE19915260C5; FR2792038A1

Abstract

The starting point of the invention is a linear drive having at least one component 10 which is displaceable in the longitudinal direction between two end positions (14, 16) via an auxiliary energy, and having a damping device (18) which can be set and which brakes the said component in at least one longitudinal direction before it impinges upon a stop (20, 22) in an end position (14, 16). It is proposed that the damping device (18) have at least one sensor (24) via which a characteristic number for a speed of impingement of the component upon the stop (20, 22) can be determined, and thin determination can be used to set the damping device.

Description

Linear d:ive

Prior art

The stariing po-nt of the invention is a linear drive in accordance with the pre-characterising clause of claim 1.

Linear drives are used in order to produce linear movements - Fields of application are, in particular, machine tools, in-plant conveyer systems, railborne vehicles, et-c. Linear drives possess at- least one io component which is displaceable in the longitudinal direction between two end positions via an auxiliary energy. The auxiliary energy may be produced by electrical or electromagnetic energy andlor by gas pressure or liquid pressure, etc.

is Pneumatic and hydraulic linear drives possess a piston which is guided in a cylinder and can be displaced in the longitudinal direction between two end positions. In the said end positions, the piston is, as a rule, braked by stops which may be constituted by the end walls of the cylinder.

In order to permit high speeds between the end positions and minimise wear of the piston and stop, it is known practice to brake the piston with the aid of a damping device on the cylinder before it impinges upon the stop. In the case of pneumatic cylinders, known damping devices possess a throttling point via which it is possible to influence the egress of air from the cylinder, and thereby the speed of impingement of the piston upon the stop. In order to be able to set the linear drive to different marginal conditions, such as, for example, different air temperatures, air pressures and/or wear at the throttling point, use is made of throttling points which can be set.

Advantages of the invention The linear drive according to the invention possesses at least one component which is displaceable in the longitudinal direction between two end positions via an auxiliary energy. The linear drive also possesses a is damping device which can be set and which brakes the said component in at least one longitudinal direction before it impinges upon a stop in an end position.

It is proposed that the damping device have at least one sensor via which a characteristic number for a speed of impingement of the first component upon the stop can be determined. The characteristic number permits simple, rapid, convenient and accurate manual setting and, in particular, completely or at least partially automated setting. The outlay on setting and the wear can be reduced and cost- savings made.

The characteristic number can be ascertained with the aid of various methods of measurement that appear suitable to the person skilled in the art, for example by detecting internal stresses at the stop with the aid of wire strain gauges, pressure sensors which detect a pressure build-up in a cylinder and/or a force at the stop, speed sensors which detect the speed of the first component before the stop, etc.

- %m 1 Ir- is particularly advantageous, however, if the sensor is constituted by an acceleration pick-up. Acceleration pick-ups are produced in large quantities, for example acceleration pick-ups with a piezoelectric element, the so- called "knock sensors", for the internal combustion engines of motor vehicles. Because of this, acceleration pick-ups can be manufactured in a particularly cost-effective manner. Characteristic numbers that can continue to be utilised in a simple manner can also be ascertained with the aid of acceleration pick-ups.

The acceleration pick-up may advantageously be fastened to all points on the linear drive or to ad-joining components to which structure-borne sound can be transmitted by the stop. In order, however, to obtain the largest possible signal and the least and smallest possible disturbance quantities from other devices when ascertaining the characteristic number, it is proposed that the sensor or acceleration pick-up be fastened to a component that constitutes the stop. Under these circumstances, the sensor is preferably fasted to apertures and/or threaded bars that are already present, as a result of which it is possible to save on additional components, expenditure on fitting and costs.

In a refinement of the invention, it is proposed that the damping device have a regulating arrangement which determines the characteristic number and regulates it to an ideal value with the aid-of a positioning unit. Manual setting can be replaced by fully or partially automated setting. A complicated setting operation at points that are difficult to reach can be avoided and the convenience, for example of machine tools, etc., can be increased. Furthermore, a characteristic number which has been ascertained can always be automatically kept within an optimum range by a continuous regulating operation or by a number of regulating intervals, thereby reducing the wear and the intensity of sound around the linear drive.

It- is particularly advantageous if initial setting can be s performed with the aid of the regulating arrangement, as a result of which manual setting can be avoided completely.

In order to avoid the linear drive being destroyed, when it is brought into operation in advance of possible automatic setting, by damping which is set too low, the damping device is advantageously regulated to an optimum range, s-arting from damping which is too high by a safety value.

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The solution according to the invention may be employed particularly advantageously in hydraulic and, in particular, pneumatic linear drives having a piston which is guided in a cylinder. with the aid of an acceleration pick-up, it is possible, on a pneumatic cylinder, to advantageously ascertain a characteristic number for the speed of impingement of a piston upon a stop or upon an end face of the cylinder with little outlay on construction, and to provide a particularly cost-effective linear drive which sets itself. It is also possible, in pneumatic cylinders, to avoid complicated seals towards the outside and to achieve particularly rapid positioning movements.

In a refinement of the invention, it is proposed that the positioning unit of the regulating arrangement have at least one regulable throttling point, via which the egress of a fluid from the cylinder, and thereby the speed of impingement of the piston upon the stop, can be regulated. Damping with a regulable throttling point is particularly cost-effective and low in wear and particularly suggests itself in the case of pneumatic cylinders. However, adjustable impact-dampers are also conceivably possible.

The regulating arrangement may be operated hydraulically, electrically, electromagnetically and/or pneumatically. If 1 it is electrically operated, it is possible to use existing current supplies in most cases, to avoid additional components and to save on costs, particularly in the case of pneumatic linear drives in which no hydraulic pressure 5 medium is available.

Drawing Further advantages emerge from the following description of ' the the drawing, in which an exemplified embodiment o. invention is represented. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will also appropriately consider is the features individually and unite them to form further useful combinations.

Description of the exemplified embodiment

Figure 1 shows a pneumatic linear drive with a piston 10 which is displaceable in a pneumatic cylinder 12 in the longitudinal direction between two end positions 14, 16 with the aid of compressed air via a pressure connection, not represented. With the aid of the piston 10, it is possible to exert a positioning force, via a piston rod 32, on a component, for example part of a machine tool, etc., of which no further details are represented. The linear drive also has a damping device 18 which brakes the piston 10 in both longitudinal directions before it impinges upon a stop 20, 22 in the end positions 14, 16.

The damping device possesses a sensor 24 which is constituted by an acceleration pick-up and via which a characteristic number for a speed of impingement of the piston 10 upon the stops 20, 22 constituted by the cylinder 12 can be determined. The sensor 24 is fastened to the cylinder 12, that is to one of four threaded bars 34 which is mounted on the said cylinder 12 for fastening to a component, of which no further details are represented, but is not being used for fastening purposes. Savings are made 5 on additional components and on costs.

The damping device 18 has a regulating arrangement 26 which determines the characteristic number and automatically regulates it to an ideal value continuously with the aid of a positioning unit. It is also possible to perform initial setting with the aid of the regulating arrangement 26. The positioning unit of the regulating arrangement 26 possesses two regulable throttling points 28, 30, via which the egress of air from the pneumatic cylinder 12, and thereby 1 Jngement of the piston 10 upon the stops L5 the speed of imp 20, 22, can be regulated. The throttling points 28, 30 are adjusted electrically.

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Claims

1. Linear drive having at least one component which is displaceable in the longitudinal direction between two end positions (14, 16) via an auxiliary energy, and having a damping device (18) which can be set and which brakes the said component in at least one longitudinal direction before it impinges upon a stop (20, 22) in an end position (14, 16), characterised in that the damping device (18) has io at least one sensor (24) via which a characteristic number ' impingement of the component upon the stop for a speed o. (20, 22) can be determined.

2. Linear sensor according to claim 1, characterised in is that the sensor (24) is constituted by an acceleration pick-up.

3. Linear drive according to one of the preceding claims, characterised in that the sensor (24) is fastened to a component that constitutes the stop (20, 22).

4. Linear drive according to one of the preceding claims, characterised in that the damping device (18) has a regulating arrangement (26) which determines the characteristic number and regulates it to an ideal value with the aid of a positioning unit.

5. Linear drive according to claim 4, characterised in that.initial setting can be performed with the aid of the regulating arrangement (26).

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6. Linear drive according to claim 4 or 5, characterised in that the regulating arrangement (26) automatically regulates the characteristic number to an ideal value, either continuously or at specific intervals.

7. Linear drive according to one of the preceding claims, characterised in that the first component is a piston (10) which is guided in a cylinder (12).

8. Linear drive according to claim 7, characterised in that the positioning unit of the regulating arrangement (26) has at least one regulable throttling point (2 8, 3 0), via which the egress of a fluid from the cylinder (12), and thereby the speed of impingement of the piston (10) upon the stop (20, 22) can be regulated.

9. Linear drive according to claim 8, characterised in that the cylinder (12) is a pneumatic cylinder and the piston (10) can be adjusted with the aid of compressed air.

10. Linear drive according to one of the preceding claims, characterised in that the regulating arrangement (26) is, at least partially, electrically operated.

Linear drive substantially as hereinbefore described with reference to the accompanying drawing.

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