Patent Application
20060185138
This invention relates to a method and apparatus for deforming metal, specifically modifying barbed tape into concertina.
Coiled barbed tape has long been known as a barrier. It is essentially a coil of steel wire that has razor blades attached every few feet. Each portion of the coil that forms a 360 degree circle is called a “loop” herein. For increased strength and improved ease of handling, the loops of barbed tape can be connected to each other at staggered points. The material having connected loops is referred to herein as concertina, to distinguish it from a coil of barbed tape in which the loops have not been connected, referred to herein as simply a coil.
Historically, concertina is made by loading a coil of barbed steel wire onto a frame that rotates about a central axis. Then a man grabs a first loop of the coil and manually pinches it to the previous loop of the coil while simultaneously using a pneumatic gun to wrap a metal strip around the coils to attach them together. The metal strip is known in the art as a clip. Then, the man rotates the frame a given amount and grabs the first loop of the coil and clips it to the subsequent loop of the coil. The process results in alternate loops being attached to each other. This clipping-and-rotating is repeated until the entire coil is attached at desired points along the entire length of the coil. Loops attached five times are known as “5-clip” concertina in the art; “3-clip,” “7-clip” and “9-clip” configurations are also known in the art.
The conventional manual method of making concertina is dangerous and slow. The barbs are literally as sharp as razor blades and therefore will easily slice through skin. The steel coil is under tension due to the helix configuration (like a Slinky®) and therefore difficult to handle. Further, even a short coil of barbed steel wire is very heavy.
Therefore, it is an object of this invention to provide a faster and easier method and apparatus for clipping coils of barbed tape together to form concertina. It is another object to provide such method and apparatus to automate the connection of the loops of the coil of barbed tape.
The present invention is a method and apparatus for automatically attaching loops of a coil of barbed tape together at desired points. The preferred embodiment of the apparatus comprises a rotatable barrel, wire separators, a clipping assembly further comprising pincers and alignment fingers and a clipping gun. The components cooperate to attach the loops together at desired points. The barrel is driven by a stepper motor to rotate a specific distance about a central axis. The wire separators, fingers, pincers, and clipping gun are driven pneumatically. The motor and pneumatics are controlled with electronic switches.
Each wire separator 16 extends through an aperture in the barrel 14 and can be retracted into the barrel 14. Each wire separator 16 is moveable from one side of the aperture to the other. Preferably the wire separators are operated pneumatically and the pneumatics are controlled electronically. Alternatively, the wire separators may be operated mechanically or electronically.
The loops of the coil are attached at desired points. The preferred embodiment attaches each loop five times, although the loops may be attached as many times as desired, for example to create 3-clip or 7-clip concertina. The attachment has to be robust to withstand the forces tending to pull the loops apart, inherently from the helix structure but also as the concertina is expanded to form a barrier. The loops can be attached together in several ways. The preferred embodiment uses a clip 50, as shown in
To attach the loops together, a coil 10 is loaded onto the barrel 14. See
Each wire separator 16 extends from its aperture at the appropriate side of the aperture to limit the movement of each loop and thus guide each loop in a desired direction along the axis of the barrel. Similarly, each of the alignment fingers extends and retracts through its aperture in the barrel to limit the movement of each loop and thus guide each loop in a desired direction along the lengthwise axis of the barrel. The result is that the appropriate loops can be aligned under the pincers 18 to be attached to each other. The alignment fingers 19 also lift the loops to be attached, as explained below.
In one embodiment, the index loop and loop previous to it are selected and guided with the wire separators to pass under the pincers. Using at least one electronically-controlled alignment finger, the loops are aligned under pincers at the first desired attachment point on the coil. The index loop and previous loop are attached together by first pinching the loops together with the pincers then clipping them together with the clipping gun. This attachment routine for a clipping gun is defined in more detail below. The barrel is then rotated a given distance to align the loops under the pincers at a second desired point. This rotating, aligning and attaching is repeated until all the loops are attached to their neighbors.
In order to use a clipping gun 20 as the attachment device, the loops have to be raised off the barrel so that the jaw of the clipping gun 20 can get under the loops to grasp them. In essence, the attachment routine lift the loops off the barrel, clips them, then lowers the now-clipped loops back to the barrel. This lifting and lowering is accomplished by extending one of the alignment fingers from the barrel to lift the loops off the barrel. Then the pincers are opened, lowered over the loops, and closed on the loops to securely hold them. Then the clipping gun is moved into position so that the jaw of the clipping gun 20 can grasp the raised loops. The clip is attached, clipping gun retracted, pincers opened, and the finger retracted, leaving the now-clipped loops resting on the barrel. Which loops are being attached will determine their position relative to the fingers and therefore which finger needs to be raised to lift the loops of the barrel.
The attachment at the desired points takes place in any order. For example, the previous loop and index loop can be attached at one point, followed by attachment of the index loop and the subsequent loop at a second desired point, followed by attachment of the previous loop and the index loop again at a third desired point. This would require selecting, aligning, and rotating after each attachment. However, once the loops are attached to each other at even one point, it becomes more difficult to separate the loops from each other and select them for attachment. It is easier to separate the loops away from an attachment point that nearer to one. For this reason, wire separators are spaced around the circumference of the barrel to enable the selection and guiding to occur at different distances from an attachment point. It has been found to be most efficient, therefore, to attach all points on a given pair of loops before selecting a second pair of loops. Thus, the preferred embodiment attaches all the desired points on the previous loop and the index loop before moving on to attach all the desired points on the index loop and the subsequent loop. A specific example is illustrative:
While there has been illustrated and described what is at present considered to be a preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the invention. Therefore, it is intended that this invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims.
