192 clutches and power-stop control – Stop mechanism – Safety device
Reexamination Certificate
1999-10-18
2001-05-22
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Stop mechanism
Safety device
C192S133000
Reexamination Certificate
active
06234291
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a safety device for a workshop machine containing a safety screen which is equipped with powering means in order to lower the screen before the machine starts to operate.
DESCRIPTION OF THE RELATED ART
In itself it is known, often inspired by national legislation, to equip workshop machines such as milling devices and eccentric presses with a safety device in the form of a screen which closes automatically before the machine starts to operate. In this manner the machine is screened off during operation and this prevents people coming into contact with the operating machine. The safety screen also protects bystanders from any chips of material thrown off by the machine, which plays a role in particular in milling, sawing, drilling and similar devices.
The known safety screen is operated by means of a pressure cylinder which is powered either pneumatically or hydraulically. This known screen then drops within the order of one or more seconds. The electronics which are present contain a time switch which ensures that the screen is immediately raised if an end point detector at the bottom of the screen has remained untouched at the end of that time. In this manner it is avoided that the machine can start to operate while the screen has not completely closed, for example as a result of the intervention of an arm, hand or any other obstacle.
A disadvantage of this safety device, however, is the relatively long time which is involved in lowering the screen, during which the machine is in principle unnecessarily out of operation. Especially in the case of an obstacle in the path of the screen, one must wait at least three times this time before the machine is operational again.
SUMMARY OF THE INVENTION
The present invention therefore aims at equipping a device of the kind mentioned in the opening paragraph with a safety screen which both closes and reacts considerably faster.
In order to achieve the intended aims a device of the kind described in the opening paragraph is characterised according to the invention in that the powering means contain friction rolls at opposite sides of the screen which are coupled to a drive motor, in that the screen is equipped at the the top side and the bottom side with approach switching means which, when touched, give off an electrical signal to a central processing unit, and in that the central processing unit is able to control the drive motor in accordance with the signals given off by the approach switching means. In practice it turns out that friction rolls, as applied in accordance with the invention, are capable of completely closing or raising the screen in no longer than a fraction of a second. The approach switch at the bottom side furthermore ensures that in the event of an obstacle in the path of the screen a signal can immediately be sent to the central processing unit to raise the screen again, so that one does not have to wait a complete time cycle for that, as in the case of the known device. The device according to the invention can as a result of this, even in the case of an obstacle, nevertheless be operational within a second, which is many times faster than the known device.
In a preferable embodiment the device is characterised according to the invention in that the approach switching means contain a strip at the bottom side of the safety screen which extends over at least virtually the full width of the screen. With such a construction one can achieve the fact that the approach switching means are sensitive across virtually the entire width of the screen, while only a limited number or even just one switching element is required, which can be mounted locally.
A special embodiment of the device is characterised according to the invention in that the friction rolls contain a number of pairs of wheels which are always placed in pairs on opposite sides of the screen at regular distances from one another and which are coupled to the drive motor by means of a common shaft. Such friction rolls, which are more in particular covered with a rubber, whether or not natural, turn out in practice to suffice extremely well and in this manner even form an adequate guide for the screen.
REFERENCES:
patent: 4060160 (1977-11-01), Lieber
patent: 4179987 (1979-12-01), Dohm
patent: 4307798 (1981-12-01), Watanabe
patent: 4527684 (1985-07-01), Eggeman et al.
patent: 2307375 (1974-09-01), None
patent: 88 10 390 (1990-02-01), None
Bonck Rodney H.
Young & Thompson
LandOfFree
Safety device for a workshop machine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Safety device for a workshop machine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Safety device for a workshop machine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2450808