Safety Beading

The present invention broadly relates to a new and improved safety beading or ledge which may be disposed along the shock-absorbing edges or closing edges of an automatically movable or driverless contrivance, and more specifically, to a safety beading arranged along the shock-absorbing edges of automatic vehicles or along the closing edges of automatically closing doors, wherein the safety beading comprises an electric switching arrangement which includes contact elements which are carried by elastically deformable insulating bodies.

Such safety beadings or ledge serve the purpose in automatically operating devices, for example in driverless transport vehicles, for factory or warehouse floor transportation or in automatic vehicle doors, to switch-off the drive upon contact with an obstacle, or to initiate a braking action.

Switching beadings or ledges, contact mats and similar arrangements are known which in principle consist of two electric conductors held apart elastically, in the form of metal bands, wires and the like, which upon impact with an obstacle are pressed together, thus to cause a short circuit-like increase in the current of a control circuit.

In such a safety device, as shown in German Published Pat. No. 2,719,438 for the closing edges of automatically operated vehicle doors, there is provided a signal generator which extends over the whole length of the edge, and which comprises two ribbon-like electric conductors, which in the inoperative condition are kept apart at a certain distance in an elastically deformable insulating body. The conductors are provided in the region of one end with a voltage source and with a drive control device, and in the region of the other end they are connected by way of a measuring resistance with one another, whereby a no-load or closed circuit is formed. If the signal generator is pressed together anywhere along its length the two ribbon-like electric conductors come into contact, which results in a change in the resistance of the no-load or closed-current circuit, whereupon, for example, the drive vehicle door is stopped by means of a relay.

In the safety device described above it can happen that because of the presence of corrosion or dirt no contact is made, so that the drive to the vehicle door is not switched-off. Since the switching device which switches-off the drive is activated as a result of an increase in the no-load or closed-circuit current, it is possible that, for example, in the case of a defective relay, switching-off also fails to take place.

Hence, with the foregoing in mind, it is a primary object of the present invention to provide a new and improved kind of safety beading or ledge which does not suffer from the aforementioned drawbacks and limitations of the prior art proposals.

Another and more specific object of the present invention aims at a new and improved safety beading or ledge which eliminates corrosion and dirt.

A further significant object of the present invention is to provide a safety beading which acts as a zero switch so that defects in the electric circuitry, for example a broken winding, can already be detected upon starting-up of the vehicle or door to be actuated.

Yet a further important object of the present invention and for the purposes of eliminating the aforementioned drawbacks and shortcomings is to provide a safety beading which is constructed in such a manner that the switching-off of the drive, upon impact or collision with an obstacle, is accomplished by opening a no-load or closed-current circuit and there is effectively precluded the corrosion and contamination of contact locations.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the new and improved safety beading or ledge according to the present invention is characterized by the features that there are provided a multiplicity of contact elements which are disposed in series or in a line in an elastic pre-stressed tube or tubular member. These contact elements contact one another at contact locations or points thereof in their normal rest or inoperative position. Under the action of an external force, typically for instance upon collision with an obstacle, the contact elements perform a rocking or tilting movement in relation to one another at the corresponding locations of the tube or tubular member, so that the contact at such contact elements is interrupted.

The contact elements are always closed in the normal operating condition and are protected by the tubular member in which they are accommodated. Upon collision with an obstacle the drive circuit is switched-off by breaking the no-load or closed-current circuit, and corrosion and dirtying of the contact points is thus largely eliminated.

A further advantage of the invention resides in the fact that the switching arrangement provided for the emergency cutting-off of the drive functions as a zero or null switch, so that defects, such as for instance rupture of a winding, can be readily and positively ascertained already upon placement into operation of the contrivance which is to be driven.

The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is a longitudinal cross-section of an electric switching arrangement of a safety beading or the like constructed according to the teachings of the present invention in the normal inoperative or rest position;

FIG. 2 is a longitudinal cross-section of the electric switching arrangement of the safety beading in its operative or work position;

FIG. 3 is a cross-section of an entire safety beading according to the invention; and

FIG. 4 is a cross-section of an application, shown by way of example, of a safety beading when disposed in a carrier made of foam material.

Describing now the drawings, in the showing of FIGS. 1 and 2 the numeral 1 generally designates an electric switching arrangement for a safety beading or ledge or the like, as can be used as a collision interruptor device for driverless transport vehicles, for example employed in automatic factory or warehouse floor transportation installations.

The electric switching arrangement 1 is provided with a plurality of similar contact elements 2, which each consist of a substantially cylindrical insulating annular body 3 and of a contact rod or pin 4 having rounded ends 4a embedded therein. The rounded ends 4a of each contact rod 4 constitute contact points 5 and project on each side of the related insulating body 3 by essentially the same amount. The edges 6 of the cylindrical insulating bodies 3 are rounded-off for a purpose which will become apparent as the description proceeds. The contact elements 2 are arranged in a row or series in a tube or hose-like member 7 consisting of an elastically deformable material which is pre-stressed in its longitudinal direction and defining an insulating body.

Referring now to FIG. 3 and FIG. 4, the electric switching arrangement 1 already described is embedded in a structural member 8 consisting of an elastically deformable material and likewise defining an insulating body. For the purpose of reinforcement a leaf or blade spring 9 or equivalent structure is provided running substantially parallel to the electric switching arrangement 1, which is also embedded in the structural member 8. In the application previously mentioned as a safety device in the case of collision, the safety beading or ledge 1, 8, 9 can, for example, be accommodated in a carrier 10 consisting of foam material which is mounted on the collision edge of any suitable and conventional driverless transport vehicle. In this way there is formed a safety bumper for such driverless transport vehicle.

The above-described safety beading or ledge operates as follows:

In its normal inoperative position (FIG. 1) the contact elements 2 are pressed together at the contact points 5 under the action of the pre-stressed tube 7, so that in a suitable control circuit, not shown, the winding of a circuit element is energized, and a contact thereof keeps the drive of the transport vehicle switched-on. Upon collision with an obstacle and with the deformation of the safety beading by an amount S (FIG. 2) the rounded edges 6 of the insulating bodies 3 meet and contact one another, so that the contact elements 2 perform a rocking or tilting movement with respect to one another, the contact points 5 are displaced accordingly, and contact is broken. The voltage in the control circuit falls to zero, so that its own contact opens and the drive is switched-off. Upon removal of the obstacle the elasticity of the tube 7 effects a return of the safety beading into its normal position, whereupon contact between the contact elements 2 is re-established and the drive of the transport vehicle is switched-on again.

Referring to FIG. 2, the amount S of the deformation at which the contact points 5 no longer touch each other can be determined by suitable choice of the dimensions of the contact elements 2. The relationship of length to diameter is the most important. If the safety beading is mounted in the form of an arc, the radius which may be achieved will also depend on this ratio.

Instead of forming the contact elements 2 and the tube 7 as a cylinder, it can also have a different cross-section, such as a quadratic or square one.

While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,