Linear drive with a buffer device

Details Linear drive with a buffer device Linear drive with a buffer device

1994-05-13

1995-11-28

Denion, Thomas E.

Expansible chamber devices

Sealed opening in longitudinal wall of chamber for receiving...

92165R, 277DIG7, F01B 2900

Patent

active

054697751

DESCRIPTION:

BRIEF SUMMARY
SPECIFICATION

The invention relates to a linear drive having a housing with a longitudinal slot, with a drive part which is mounted longitudinally moveable in the housing, with a longitudinal guide being mounted outside of the housing on which a guide element is mounted longitudinally moveable and on which a load to be moved can be mounted and a lug which extends through the longitudinal slot and connecting the drive element with the guide element by forming a moving unit therewith, and a buffer element cooperating in the movement direction of the movement unit and the guide element.
A linear drive of this type is described in the EP-A-0 140 138. It is formed as a so-called slot cylinder, whereby the drive is actuated by means of a pressure medium. The carriage like guide element is guided by a longitudinal guide formed by the cylinder housing and is synchronously moved when displacing the drive element by a coupling with the lug. The guide element forms a power transmission member on which any given loads may be mounted which have to be moved. In light of the external guiding unfavorable loads on the drive element are substantially prevented. The guide element is flanked on both sides by one each runner and connected therewith by means of shock absorbers. Each runner has a brake means which can be selectively actuated for positioning the movement unit, whereby the shock absorber cause a progressive delay of the movement unit.
In such a device the runners with the associated shock absorbers practically form adjustable stroke limiting abutments for the guide element, whereby the effect is principally comparable with the device described in DE-A-39 25 219. However, if the guide element is coupled with a relative heavy load, further high inertia forces occur when the drive element reaches the end positions which stress the lug and may result in the breaking of the same. A given reenforcement of the lug is not possible, since its possible dimensions are limited by the width of the longitudinal slot.
In the case of EP-A-0 294 350 no buffer means is provided. However, due to the particular design of a coupling between the drive element and the guide element it permits certain lateral movements. However, the axial connection is quasi rigid, so that tension and pressure forces are fully transmitted.
It is therefore an object of the invention to provide a linear drive of the aforementioned type wherein the stresses of the lug during the braking action are reduced without expensive adjustments of stroke limiting abutments.
For solving this object it is provided that the buffer element is disposed in the connection between the drive element and the guide element which connects immediately with the lug.
In this manner the guide element and the drive element are decoupled to a certain extent in the movement direction, i.e., in the longitudinal direction of the housing. Beginning with a certain load the buffer element permits an axial relative movement between the guide element and the drive element, whereby the immediate stresses, in particular on the lug are reduced to a degree which exclude any damages. It does not require any external stroke limiting abutments, so that the user of the linear drive does not have to take any adjustment or adjusting operations pertaining to a given use situation. Hence, errors which have to be made in such operations are eliminated and are reliably excluded. A particular advantage of the device is that the buffer effect is fully available independent from the start of the braking action of the drive element. Even when the movement unit brakes at a given location of the stroke, which, by way of example may be performed in the manner described in DE 85 11 577 U1, the effect which reduces the stress remains fully maintained.
Linear drives are described in EP 0 157 892 B1 and the EP 0 113 790 wherein the drive part and the guide element are movable with respect to each other in a limited manner.
This should merely prevent lateral forces from being transmitted to the drive element and its

REFERENCES:
patent: 4856415 (1989-08-01), Noda

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