The invention relates to a method for changing fingers in preparatory work conducted externally of a transfer feeder, and a device therefor, and more particularly, to a method for changing fingers, applied to a transfer feeder, in preparatory work conducted externally of the transfer feeder, in which transfer bars adapted to move in a two-dimensional or three-dimensional manner can be individually driven every shaft, and a device therefor.
Generally, installed on a transfer press is a transfer feeder, in which workpieces are successively transferred from one station to the next station by a pair of transfer bars arranged in parallel in a workpiece transfer direction.
Fingers, on which workpieces are placed, are detachably mounted on transfer bars of such transfer feeder, and whenever workpieces transferred are changed, fingers conformed to the fingers are changed in preparatory work conducted externally of the transfer feeder.
Japanese Utility Model Laid-Open Nos. 65432/1990 and 4324/1991 propose devices for changing fingers in preparatory work conducted externally of a transfer feeder.
With the devices described in these publications, transfer bars can be divided into stationary transfer bars and movable transfer bars, and finger holders on the stationary transfer bars to be positioned (positions hidden by uprights) corresponding to the uprights of the transfer press are pulled onto the adjacent movable transfer bars so that the finger holders and the movable transfer bars are transferred out of the transfer press from a workpiece transfer area together with the movable transfer bars.
Such device has an advantage that since the finger holders mounted on the stationary transfer bars disposed in positions hidden by the uprights are transferred outside the transfer press without being disturbed by the uprights, the fingers can be changed in preparatory work conducted externally of the transfer feeder.
Hereupon, since the devices described in the above-mentioned publications are constructed such that the finger holders mounted on the stationary transfer bars are taken out toward the movable transfer bars, air cylinders are necessary for moving the finger holders and besides guide rails or the like must be provided for guiding movements of the holders, by which the transfer bars as a whole are made relatively heavy.
As the transfer bars are increased in weight, they will become liable to flex. Therefore, when the transfer bars are moved at large acceleration, they are subjected to chattering beyond an allowable range, thus causing a problem in generation of a hindrance in transfer of workpieces.
Accordingly, it becomes difficult for the transfer bars to be increased in acceleration, and so it becomes impossible to efficiently actuate the transfer bars in a short cycle time.
Further, with the above-mentioned device, in order to take the finger holders provided on the stationary transfer bars onto the movable transfer bars, it is necessary to avoid interference between the finger holders taken out and the finger holders inherently present on the movable transfer bars.
Hereupon, provided on the stationary transfer bars are air cylinders or the like for turning the finger holders provided on the bars so that the finger holders turned are moved onto the movable transfer bars, whereby interference between the finger holders on the stationary transfer bars and the finger holders on the movable transfer bars is avoided.
Accordingly, air cylinders for turning, in addition to air cylinders for movement and guide rails, increases the transfer bars in weight to further degrade the operating rate of the transfer feeder.
It is an object of the invention to provide a method for changing fingers, for use in a transfer feeder, in preparatory work conducted externally of the transfer feeder, by which method a constitution required for preparatory work conducted externally of the transfer feeder, at the time of finger exchange can be made simple and lightweight and the transfer feeder can be enhanced in operating rate, and a device therefor.
In a first aspect for attaining the above-mentioned object, the invention provides a method for changing fingers in preparatory work conducted externally of a transfer feeder, the fingers being used for the transfer feeder, in which the fingers placing thereon workpieces are detachably mounted on stationary transfer bars and movable transfer bars, respectively, constituting transfer bars, the transfer bars being capable of making at least advancing and returning motions, and connection of the stationary transfer bars and movable transfer bars can be released, the method comprising the steps of: with advancing or returning motion of the transfer bars, moving the transfer bars in a workpiece transfer direction; using a holding means to finger plates for mounting of the fingers, the finger plates being detachably mounted on the stationary transfer bars of the transfer bars, and spacing the holding means and the stationary transfer bars away from each other; with returning or advancing motion of the transfer bars, returning the transfer bars to their original positions in the workpiece transfer direction; using a support means to support the movable transfer bars of the transfer bars; releasing connection of the stationary transfer bars and movable transfer bars; and carrying out the movable transfer bars supported by the support means and the finger plates held by the holding means, together with moving bolsters; the above respective steps being automatically conducted.
In addition, with the method of the invention, it suffices to perform change of fingers in preparatory work conducted externally of a transfer feeder, going through the respective steps, and it is possible to suitably modify the concrete order of the respective steps in practice.
In accordance with the method of the invention, the finger plates mounted on the stationary transfer bars and for mounting of the fingers are moved together with the stationary transfer bars in the workpiece transfer direction.
Since such movement is made in the same advancing or returning motion of the transfer bars as that in normal operation, air cylinders for movement, guide rails and the like are dispensed with unlike a conventional constitution, in which only members holding the fingers can be drawn toward the movable transfer bars.
Also, since the transfer bars can be moved as a whole together with the finger plates, no members interfering with the plates during movement of the finger plates are present, and conventional air cylinders for turning movement or the like are dispensed with.
Accordingly, these conventional parts are dispensed with, by which the transfer bars composed of the stationary transfer bars and the movable transfer bars are made lightweight and it is possible to shorten cycle time of the transfer feeder to enhance the operating rate.
Also, with the above-mentioned method, in order to hold the finger plates with the holding means and to space the finger plates and the stationary transfer bars away from each other, it is desired that the following steps be automatically conducted to include lifting or lowering the transfer bars including the stationary transfer bars with the finger plates mounted thereon by means of lifting or lowering motions, which the transfer bars are designed to enable making; using the holding means to hold the finger plates disposed at a predetermined level, by moving the transfer bars toward the holding means in a horizontal direction perpendicular to the workpiece transfer direction, and/or moving the transfer bars toward the finger plates in the horizontal direction; releasing mounting of the finger plates on the stationary transfer bars; and with the lowering or lifting motion, spacing the transfer bars away from the finger plates disposed at the predetermined level.
With this method, when the finger plates are to be spaced away from the stationary transfer bars and the movable transfer bars, the same lifting or lowering motion of the transfer bars as that in normal operation is made use of, so that it is unnecessary to provide any special parts such as air cylinders or the like, thus preventing an increase of the transfer feeder in weight and maintaining the operating rate favorable.
Further, with the above-mentioned method, in order to space the transfer bars away from the finger plates and to support the movable transfer bars of the transfer bars on the support means, it is desired that the following steps be automatically conducted to include: with the lowering motion, spacing the transfer bars away from the finger plates disposed at the predetermined level, and positioning the same with a minute gap above the support means; with the returning or advancing motion, returning the stationary transfer bars and the movable transfer bars to their original positions in the workpiece transfer direction; and with the lowering motion, lowering again the transfer bars by the minute gap and placing and supporting the movable transfer bars of the transfer bars on the support means.
With this method, the stationary transfer bars and the movable transfer bars are temporarily positioned in a state with a minute gap relative to the support means, so that there is no fear that when returned to the original positions, the transfer bars would contact with the support means and so movement at the time of returning is made smooth.
Also, since the movable transfer bars are placed and supported on the support means, the support construction on the side of the support means is made simple.
In a second aspect for attaining the above-mentioned object, the invention provides a device for changing fingers in preparatory work conducted externally of a transfer feeder, the fingers being used for the transfer feeder, in which the fingers placing thereon workpieces are detachably mounted on stationary transfer bars and movable transfer bars, respectively, constituting transfer bars, the transfer bars being capable of making at least advancing and returning motions, and connection of the stationary transfer bars and movable transfer bars can be released, the device comprising: finger plates detachably mounted on the stationary transfer bars for mounting of the fingers; holding means capable of holding the finger plates, having disengaged from the stationary transfer bars, in a state spaced away from the stationary transfer bars and the movable transfer bars; support means capable of supporting the movable transfer bars; carrying-out means for carrying out the movable transfer bars supported by the support means and the finger plates held by the holding means, together with the moving bolsters; and control means for automatically controlling motions of at least the stationary transfer bars and the movable transfer bars.
With this configuration, the same advancing or returning motions of the transfer feeder itself as that inherently conducted by the transfer feeder during normal operation is made use of to surely draw out the finger plates toward the movable transfer bars, conventionally used parts such as various air cylinders, guide rails or the like are dispensed with to attain making the transfer feeder lightweight, thereby enabling cycle time of the transfer feeder and enhancing the operating rate.
Also, with the above-mentioned configuration, it is desired that the holding means be provided with a clamp means for clamping and holding the finger plates.
With this configuration, the clamp means has the holding means holding the finger plates more firmly, so that falling-off of the finger plates is surely prevented.
Further, with the above-mentioned configuration, it is desired that the support means be designed to be movable horizontally in a direction perpendicular to the workpiece transfer direction, and the holding means be provided integrally with the support means.
With this configuration, the support means is provided to be movable horizontally, whereby at the time of changing the dies on the moving bolsters, the fingers mounted to the movable transfer bars on the support means can be prevented from interfering with the dies.
Also, the holding means is provided integrally with the support means so that the finger plates held by the holding means are also moved concurrently, whereby the fingers mounted on the finger plates can be prevented from interfering with the dies.
Further, the moving mechanism for the support means is made use of to move the holding means toward the finger plates to thereby enable holding the finger plates, whereby there is no need of providing any moving mechanism exclusively used for the holding means, which provides a simplified construction.
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