Apparatus for feeding crimp terminals on a carrier strip into a crimping press

An apparatus comprising a feeding mechanism for displacing the carrier strip along a feed path; an image capture means adapted to capture an image of a portion of the feed path; and, an image processing means connected to the image capture means and being adapted to (a) determine the position of at least one terminal on the feed path from the image; (b) determine the pitch of the strip either from the image or from a pre-stored value; and, (c) calculate an alignment displacement of the strip along the feed path from the position and pitch such that a further terminal on the strip lies within a crimping zone on the feed path; the image processing means being connected to the feeding mechanism and adapted to provide a control signal thereto such that the feeding mechanism displaces the carrier strip along the feed path by the alignment displacement.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject patent application claims priority to and all the benefits of International Patent Application No. PCT/GB2011/050495 filed on Mar. 14, 2011 with the World Intellectual Property Organization, which claims priority to Great Britain Patent Application No. 1004815.5 filed on Mar. 23, 2010, both of which are incorporated herein by reference.

The present invention relates to an apparatus and method for feeding crimp terminals on a carrier strip into a crimping press. More particularly, but not exclusively, the present invention relates to an apparatus for feeding terminals into a crimping press, the apparatus being adapted to capture an image of at least one terminal and then using the measured position of the terminal and the pitch of the carrier strip, displacing the strip so that a further terminal on the strip lies within a crimping zone.

Apparatus for feeding a carrier strip into a crimping press are known. These are typically mechanical methods whereby guiding fingers or grooves are used to guide the terminals into a crimping press where the terminals are crimped into contact with wires. Such mechanical devices are typically not able to handle strips of different pitch or different types of terminals. Typically different feeding assemblies must be used for each type of strip.

It is known to use a light beam to measure the position of a terminal before it reaches the crimping press. When the light beam is broken the terminal is in the correct position. If the light beam is the correct distance from the crimping press then a terminal further along the carrier strip is correctly arranged within a crimping zone where it can be crimped by the crimping press. If a strip of a different pitch is used however then when the light beam is broken by a terminal the terminal further along the strip will not be correctly aligned in the crimping zone. Each time a strip of a different pitch is used it is necessary to move the position of the beam along the feed path to allow for the difference in pitch. This can be time consuming. Also, since the alignment of the terminal with the press must often be accurate to within a small fraction of a millimeter it can be difficult to achieve.

The apparatus according to the invention seeks to overcome the problems of the prior art.

Accordingly, in a first aspect, the present invention provides an apparatus for feeding crimp terminals on a carrier strip into a crimping press, the separation between the terminals along the strip being the pitch of the strip, the apparatus comprisinga feeding mechanism for displacing the carrier strip along a feed path;an image capture means adapted to capture an image of a portion of the feed path; and,an image processing means connected to the image capture means and being adapted to(a) determine the position of at least one terminal on the feed path from the image;(b) determine the pitch of the strip either from the image or from a pre-stored value; and,(c) calculate an alignment displacement of the strip along the feed path from the position and pitch such that a further terminal on the strip lies within a crimping zone on the feed path;
the image processing means being connected to the feeding mechanism and adapted to provide a control signal thereto such that the feeding mechanism displaces the carrier strip along the feed path by the alignment displacement.

The image processing means may determine the pitch from a pre-stored value.

Alternatively, the image processing means determines the pitch from the image.

The image capture means may comprise a line scan optical sensor.

The line scan optical sensor may capture an image along a line parallel to the feed path.

The line scan optical sensor may capture an image along a line inclined to the feed path.

The image capture means may comprise a camera adapted to capture an image of an area including a portion of the feed path.

The apparatus may include a plurality of image capture means.

In a further aspect of the invention there is provided an assembly comprising an apparatus according to the invention; and, a crimping press arranged to receive terminals from the apparatus and to crimp terminals in the crimping zone.

In a further aspect of the invention there is provided a method of feeding crimp terminals on a carrier strip into a crimping press along a feed path, the separation between the terminals along the strip being the pitch of the strip, the method comprising the steps of(a) providing a carrier strip;(b) capturing an image of the carrier strip along a portion of the feed path;(c) determining the position of at least one terminal on the feed path from the image;(d) determining the pitch of the strip either from the image or from a pre-stored value;(e) calculating an alignment displacement of the strip along a feed path from the position and pitch such that a further terminal along the strip lies within a crimping zone on the feed path;(f) displacing the strip along the feed path by the alignment displacement.

The pitch can be determined from a pre-stored value.

The pitch can be determined from the image.

The method can further comprise the step of crimping the terminal in the crimping zone.

The image can be captured by at least one camera. The image can be captured by at least one optical line scanner.

An important part of the industrial manufacture of electrical wiring assemblies is the automated crimping of electrical connecting terminals onto the ends of wires. The crimping process is usually carried out by a powered crimping press which is often a component of an automatic wire processing machine although sometimes the wire processing is done by a human operator working at a bench mounted press.

The terminals themselves are manufactured in a prior process by passing long strips of sheet metal through a sequence of punching and forming operations to convert them into long strips of terminals. For convenient handling the terminals are coiled onto reels, each reel containing a strip of several hundred or several thousand terminals. The spacing between the terminals on the strip is the pitch of the strip.

A known assembly1comprising a crimping press2and an apparatus3for feeding terminals4on a strip5into the press2is shown inFIG. 1. In use the feeding apparatus3provides a crimp terminal4onto a crimping anvil6in a crimping zone of the crimping press2. The terminal4typically comprises a terminal body7in the plane of the strip5and two upstanding arms8forming a U shaped bucket therebetween. A prepared wire9is positioned in the bucket. A crimping fork10of the crimping press2is then driven down powerfully and precisely to fold the sides of the ‘U’ together around the wire9to press the terminal4and wire9together tightly. A cutting blade (not shown) cuts the terminal4free from the strip5. The fork10is then lifted and the wire9removed along with its newly crimped-on terminal4and passed on for further processing. The carrier strip5is then fed forward along a feed path11by the feeding apparatus3until the next terminal4is arranged on the crimping anvil6.

The most common type of feeding apparatus3for feeding and aligning the terminals4with the anvil6of the press2comprises a ratchet pawl. This is driven through an often complicated arrangement of spring loaded levers and cams by the stroking action of the press.

An alternative type of feeding apparatus (not shown) comprises a pair of motorised wheels which grip the carrier strip5and drive it precisely by an electric motor. The apparatus3further comprises a light beam sensor which detects when a terminal4on the strip5passes beneath it. If the light beam is correctly spaced from the crimping press2along the feed path11then, when one terminal4is beneath the light beam a further terminal4along the strip5is correctly arranged in the crimping zone where it is crimped to the wire9by the crimping press2. Again, such a feeding apparatus3is only suitable for use with a strip5of one pitch. If one wishes to use a strip5of a different pitch then the spacing of the optical beam with respect to the crimping press2along the feed path11needs to be changed. Moving the beam each time one wishes to use a strip5of a different pitch is time consuming. It can also be difficult to achieve the required degree of accuracy in the relative alignment of a beam and crimping press2.

Shown inFIG. 2is an assembly20according to the invention. The assembly20comprises a crimping press21and an apparatus22for feeding crimp terminals23on a carrier strip24into the crimping press21.

The apparatus22comprises a feeding mechanism25for feeding the carrier strip24along a feeding path26into the crimping press21. In this embodiment the feeding mechanism25comprises motorised wheels27which grip the strip24as shown and which rotate to drive the strip24forward. For simplicity the motor which drives the wheels27is not shown.

The apparatus22further comprises an image capture means28which in this embodiment comprises an optical line scanner. The optical line scanner28captures an image along a portion29of the feed path26(in this case a line) as schematically shown. The line includes a plurality of the terminals23on the strip24. The terminals23are back lit and the line scanner28measures the brightness along the line

The image capture means28is connected to an image processing means30. The image processing means30processes the image as will be described in detail below to determine an alignment displacement. The alignment displacement is the distance the strip24must be displaced along the feed path26such that a terminal23on the strip24lies within a crimping zone and so can be crimped by the crimping press21.

The image processing means30is connected to the feeding mechanism25. After having determined the alignment displacement the image processing means30provides a control signal to the feeding mechanism25. In response the feeding mechanism25displaces the strip24by the alignment displacement such that a terminal23on the strip24is arranged in the crimping zone. As before a wire (not shown) is then arranged in the U of the terminal23and the crimping press21crimps the two together. The wire and its crimped terminal23is then removed.

In order to feed the next terminal23into the crimping press21the process is repeated. A further image of the strip24is captured, the alignment displacement is calculated and the strip24moved by the required alignment displacement. Because the line scanner28records the positions of the terminals23each time before the strip24is moved any errors which creep in, for example due to the drive wheels27slipping, are not cumulative.

Shown inFIG. 3is the image captured by the optical line scanner28. The brightness dips around the position of the terminals23. The image processing means30performs a feature recognition algorithm on the image to determine the position of the terminals23. The image processing means30reads a pre-stored value of the pitch of the strip24from memory. By knowing the position of the terminals23measured by the optical line scanner28and knowing the pitch of the strip24, the image processing means28can determine the position of the terminal23closest to the crimping zone and hence its distance from the crimping zone. From this the alignment displacement can be determined.

In this embodiment the pitch is read from memory. Accordingly, as a minimum, the optical line scanner30need only record the position of one terminal23. A more accurate determination of the position of the terminals23may be obtained if the image captured by the optical line scanner28includes the position of a plurality of terminals23.

If the feeding apparatus22is to be used with a strip24of a different pitch then the new pitch can simply be stored in the memory of the image processing means30. The image processing means30will use the new pitch when determining the alignment displacement. Alternatively, the image processing means30can be put into a learning mode. In this mode the image processing means30analyses one or more images recorded by the line scanner28and from these determines the pitch of the strip24. This is then stored in memory for later use. This can be done in a number of different ways. If the image captured by the image capture means28includes a plurality of terminals23then the image processing means30can determine the pitch by determining the distance between two adjacent terminals23. This could be done by determining the distance between two adjacent minima in the captured image. Alternatively it could be done by a more complex curve fitting operation. If only one terminal23is captured by the image capture means30then a different approach is possible. A first image is captured and stored. The strip24is then slowly moved forward and a further image stored. This is repeated until the further image matches the first image to within a predetermined degree of tolerance. Because of the repeating nature of the strip24the distance the strip24has moved is the pitch of the strip24.

In an alternative embodiment of the invention the image processing means30determines the position of the terminals23and the pitch from each image before determining the alignment displacement. In this embodiment there is no need to place the image processing means30in a learning mode when the strip24is changed for one of a different pitch. The image processing means30automatically determines the different pitch and takes this into account when determining the alignment distance. This embodiment works best when the image capture means28captures the position of a plurality of terminals23so there is no need to move the strip24to determine its pitch.

In the above embodiment optical line scanner28measures along a line which is parallel to the feed path26. In an alternative embodiment the optical line scanner28measures along a line which is slightly inclined to the feed path26. The optical line scanner28therefore captures an image slice through each terminal23at a slightly different position along the terminal length depending on its position along the line on which the measurement is made. This provides additional information to the image processing means30to enable it to detect twisted, bent or otherwise misshapen terminals23and prevent them from being fed to the crimping press21.

In an alternative embodiment of the invention (not shown) the image capture means28comprises a camera which captures a two dimensional image of the terminals23on the strip24. The two dimensional nature of the image provides the image processing means30with additional information enabling it to detect malformed terminals23before they are provided to the crimping press21.

In a further embodiment of the invention the feeding apparatus22comprises more than one optical capture means28. With one optical capture means28it can be difficult to determine if one or more of the terminals23is bent out of the plane of the strip24towards the optical capture means28. By use of a plurality of optical capture means28this can be determined. The second optical capture means28is typically inclined to the normal to the strip24.