EP2843779A1

EP2843779A1 - Crimping press

Info

Publication number: EP2843779A1
Application number: EP13182774.3A
Authority: EP
Inventors: Steven Aerts; Tom Gommé
Original assignee: Exmore Group NV
Current assignee: Exmore Group NV
Priority date: 2013-09-03
Filing date: 2013-09-03
Publication date: 2015-03-04
Also published as: BE1025451B1

Abstract

The present invention relates to a crimp press for fastening a crimped contact to a wire, the wire conductor and wire insulation being fasteneable to the crimped contact by means of crimpers arranged on a press slide and the press slide being drivable by means of a press motor. The invention in particular relates to the ram drive mechanisms with improved control of the vertical movement of press slide. In the ram drive mechanism of the present invention, the rotational movement of the electrical motor is converted into a linear displacement of the ram by means of a first cam mounted on a rotating cam axle, a second cam positioned at one end of the ram, means to maintain the second cam in contact with the first cam during rotation, and wherein one of said cams is eccentric.

Description

FIELD OF THE INVENTION

The present invention relates to a crimp press for fastening a crimped contact to a wire, the wire conductor and wire insulation being fastenable to the crimped contact by means of crimpers arranged on a press slide and the press slide being drivable by means of a press motor. The invention in particular relates to the ram drive mechanisms with improved control of the vertical movement of press slide. In the ram drive mechanism of the present invention, the rotational movement of the electrical motor is converted into a linear displacement of the ram by means of a first cam mounted on a rotating cam axle, a second cam positioned at one end of the ram, means to maintain the second cam in contact with the first cam during rotation, and wherein one of said cams is eccentric.

BACKGROUND TO THE INVENTION

Automatic crimping presses have long been used in the connector industry to effect highspeed mass termination of various cables, such as for example in the field of electronics, telecommunications and automotive electrics. In the crimping process the connection is produced by applied pressure, wherein the force-time curve generated by the press must match with the crimping profile required for generating an optimal crimp for a given wire conductor and crimped contact. If the actual curve differs from the targeted curve, the crimp connection will be defective and should be separated out from the production process.
The ram drive mechanisms of conventional crimping presses, such as for example shown in figures 1 and 2, are of a push link design wherein a crank pin 2, is connected to the ram 20, either by means of a push link 6 and ball joint and socket 11 (Figure 1), or more directly through a drive link 40, that has a pivotal connection with a link pin 50 (Figure 2), with the ram being mounted on either side in a carriage guide 30.
Considering such arrangements wherein all parts are moved relative to one another, and each of said connections and bearings may have play, it is not surprisingly that depending on the type of bearing, the effective forces, the properties of the lubrication in the bearings, the temperature, etc... , the force-time curve of the press will be affected in a largely uncontrolled manner. It is accordingly desirable to provide an improved crimping press, in which the adverse effects, resulting from the bearing play upon the desired force-path curves or force-time curves may be reduced.

SUMMARY OF THE INVENTION

The crimping press of the present invention addresses the aforementioned problem in applying a cam and cam roller in driving the vertical displacement of the ram. Using such configuration one can for example easily adjust the force-time or force-path curves by changing the shape of the cam, allowing for example an increased force concentration at the bottom of the ram drive stroke.
It is thus an object of the present invention to provide a ram drive mechanism for an automated terminal crimping machine, comprising;

a cam axle accommodating an eccentric cam, in particular an eccentric plate cam;
means for rotating the cam axle;
a ram comprising a cam roller;
carriage guides that slidably fit around the ram; and
means to maintain the cam roller in contact with the eccentric cam during rotation thereof.

Various crimping tool heads may be secured to the underside of the ram, and the attached tool-head is driven with the ram into a continues-feed applicator, which tenders the terminal(s) to be crimped. As such, in a further aspect the ram of the ram drive mechanism as disclosed herein further comprises an applicator hook capable of accommodating various crimping tool heads.
As already mentioned hereinbefore and in converting the rotational motion of the eccentric cam into a linear displacement of the ram, the ram drive mechanism comprises means to maintain the cam roller in contact with the eccentric cam during rotation thereof. In principle any system that is capable of pulling or pushing the ram against the eccentric cam with the required force to prevent slipping of the cam roller, can be used. In the exemplified embodiments, further described herein-below, the means to maintain the cam roller in contact with the eccentric cam consists of a spring, hereinafter referred to as the ram compression spring 7. It is accordingly a further object of the present invention to provide a ram drive mechanism for an automated terminal crimping machine, wherein the means to maintain the cam roller in contact with the eccentric cam during rotation consist of a ram compression spring 7.
A benefit of the present ram drive mechanism resides in the ease of adapting the force-time or force-path curves by simply changing the profile of the eccentric cam. To further increase the adaptability of system without having to change the eccentric cam for each given wire conductor and crimped contact, the ram may further comprise an adjusting nut 10. Using such adjusting nut it is possible to adjust the shut height of the crimping machine dependent on the wire conductor and contact/terminal to be crimped. Thus in a further aspect the ram in the ram drive mechanism of the present invention further comprises an adjusting nut, preferably positioned between the ram body and applicator hook.
Evidently the means for rotating the cam axle typically exists of a electric motor, e.g. a AC motor driven by a frequency drive. In a particular embodiment driven by a variable frequency drive (VFD), also known as adjustable-frequency drive, variable-speed drive, AC drive, micro drive or inverter drive. Such drive systems allow to control AC motor speed and torque by varying motor input frequency and voltage. It accordingly enables the incorporation of a start/stop function to control the crimping press without additional electrical components, further simplifying the design of the ram drive mechanism with an accompanying increase in long term reliability. Hence, in one embodiment of the present invention the means to drive the cam axle in the ram drive mechanism consist of an electric motor, in particular an AC electric motor, more in particular an AC electric motor driven by a variable frequency drive (VFD).
In one embodiment the ram drive mechanisms is further characterized in comprising means to determine the die height and/or shut height of the ram body. Given the optional presence of an adjusting nut, this die and shut height may differ from the die and shut height of the crimping press, and correspond to the upper and lower position of the ram body. Consequently, in one embodiment the ram drive mechanism of the present invention comprises means to determine the die height of the ram body. In another embodiment the ram drive mechanism comprises means to determine the die and the shut height of the ram body. In either of said embodiment the means could for example consist of contact switches, but given the high frequencies at which these crimping machines may be operated it is desirable to have contact less means to determine the position of the ram body. Within the exemplified embodiments, said means consist of inductive sensors, also known as electronic proximity sensors, which detect metallic objects without touching them. Using these sensors, it is possible to determine the position of the ram body, and in combination with the VFD allows to stop the ram in its upper and/or lower position.
The skilled artisan is well aware of the cam axle bearings that can be used in the ram drive mechanism of the present invention, such as for example ball-bearings, spherical bearings or needle bearings. In a particular embodiment the cam axle bearing is a needle bearing. Compared to a ball-bearing they have a higher load resistance, contributing to the longevity of the ram drive mechanism of the present invention.
The cam roller, making contact with the eccentric cam, is integrated with/or mounted to one end of the ram. In one embodiment the cam roller is cylindrical and fit around a cam roller bearing with bearing axle. Similar to the bearing axle of the eccentric cam, any art known axle bearing can be used. In one embodiment the bearing axle of the cam roller also consists of a needle bearing. In an alternative embodiment the cam roller is spherical and corresponds to a ball transfer unit integrated with or mounted to one end of the ram.
Any art known carriage guides, such as cast iron sliding blocks or bronze sliding blocks with integrated carbon lubrication, can be used in the ram drive mechanism of the present invention. In a particular embodiment the carriage guides are selected from cast iron sliding blocks or bronze sliding blocks with integrated carbon lubrication. In the exemplified embodiment the carriage guides are bronze sliding blocks with integrated carbon lubrication.
A key difference of the ram drive mechanism of the present invention, when compared to the art known crimping machines resides in the fact that there is no cross-connection (such as a push link or drive link) between the motor driven axle and the ram. The ram is simply kept in contact with a rotating cam. Where in each of the foregoing embodiments the cam axle comprises an eccentric cam and the ram comprises a cam roller, it will be evident to the skilled artisan this order can be inverted wherein the eccentric cam is integrated with/or mounted at one end of the ram and the cam roller is fit around the cam axle. It is thus an object of the present invention to provide a ram drive mechanism for an automated terminal crimping machine, comprising;

a cam axle accommodating an first cam;
means for rotating said cam axle;
a ram comprising a second cam;
carriage guides that slidably fit around the ram; and
means to maintain the second cam in contact with the first cam during rotation thereof, and characterised in that at least one of said first or second cam is an eccentric cam.

In one embodiment the first cam is an eccentric cam as described above, and the second cam a cam roller as provided herein and including the cylindrical and spherical shaped cam rollers described herein before. In another embodiment the first cam is a cam roller and the second cam an eccentric cam as herein provided. In said embodiment the cam roller mounted on the cam axle will be cylindrical and fit around a cam roller bearing.
It is another object of the present invention to provide the use of a ram drive mechanism as described herein before, in a crimping machine. In particular in an automated terminal crimping machine. Thus in a further object the present invention also provides a crimping machine comprising a ram drive mechanism of the present invention..

BRIEF DESCRIPTION OF THE DRAWINGS

With specific reference now to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the different embodiments of the present invention only. They are presented in the cause of providing what is believed to be the most useful and readily description of the principles and conceptual aspects of the invention. In this regard no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

Fig. 1 : Is a front perspective view of a prior art crimping press with a push link 6 and ball joint and socket 11 connection.
Fig. 2 : Is a front view of a prior art crimping press with a drive link 40 and pivotal link pin 50 connection.
Fig. 3 : Shows an exemplary displacement-time curve (b) for an eccentric cam profile (a) used in a ram drive mechanism of the present invention.
Fig. 4 : Is a front view of a ram drive with an eccentric cam 1 and cam roller 4 of the present invention.
Fig. 5 : Perspective cross view of a cam roller used in the ram drive mechanism of the present invention, and showing the a cam roller needle bearing 15 with bearing axle 5.
Fig. 6 : Exemplified embodiment of a ram 20, the ram body 12, comprises at one end an extension with an opening to accommodate bearing axle 5.
Fig. 7 : Assembly view of a crimp press, comprising a ram drive mechanism of the present invention and showing the electric motor 14 with reduction gearbox 24, the press frame with frame plate 16, the cam axle 3 with eccentric cam 1, the ram compression spring 7, the means to determine the die height and shut height of the ram body 13, the carriage guides 30 composed of slide bearings 30a and slide plates 30b, and the ram 20 with at one end a second cam 4 and at the other end the applicator hook 9 with adjusting nut 10.

DETAILED DESCRIPTION OF THE INVENTION

As already mentioned herein before, it has been an object of the present invention to provide a ram drive mechanisms and corresponding crimping press, with as little play as possible to ensure reliability and reproducibility of the force-path curve or force-time curve during the crimp production process.
Different from the prior art crimping presses wherein ram is driven by means of a push link design, the ram drive mechanism of the present invention is based on cam movements comprising one eccentric cam and a cam roller. Other details and advantages of the present invention will become apparent from the following description of such a ram drive mechanism. This description is only given by way of example and does not limit the invention. The reference numbers relate to the attached figures which represent one of the possible embodiments of the present invention.
Figure 4 provides a representative ram drive mechanism of the present invention. In said example an eccentric plate cam 1 is mounted on cam axle 3 driven by en electric motor 14. The eccentric cam converts the rotational movement of the motor into a linear displacement for the crimping press, as shown in the exemplary displacement-time curve of Figure 3. Between positions 1 to 4, the cam profile provides a rapid traverse of the ram to the proximity of the product to be crimped. The actual crimp of the product occurs between positions 4 and 7. As evident from the exemplary displacement-time curve between said position the rotation of the cam is translated in a small vertical displacement of the ram, and even kept at the same height between positions 5 and 6 as further detailed below. In other words, to increase and realise the desired crimp pressure, the ram is further lowered over a short distance between positions 4 and 5, by making the cam profile less eccentric with respect to the cam axle between said positions. In the exemplified embodiment, the cam profile is only 1 mm eccentric between said positions over a length of 90°. The pressure is subsequently maintained by a concentric movement of the cam between positions 5 and 6. The length between positions 5 and 6 accordingly allows to control the retention time of the crimping process. Compared to the prior art push link designs, longer retention times can be achieved using the ram drive mechanism of the present invention. Such longer retention times may be desirable when crimping more resilient materials. In such instances, the material may rebound with undesired and partial reopening of the crimped contact. Through the profile of the eccentric cam, one has full control over the vertical displacement of the ram, allowing amongst others a better optimisation of the pressure retention time for a given wire conductor and crimped contact. The further cam profile between positions 6 and 9 determines the traverse of the ram to its up (die height) position, where it is kept for a given time by a concentric movement of the cam between positions 9 and 10.
Evidently, the cam roller 4, also referred to as the radial follower in Figure 3 a), will only translate the cam profile in the desired displacement when kept in contact with the eccentric cam during the rotation thereof. Further to the means to maintain the cam roller in contact with the cam and the carriage guides of the ram, the cam profile also plays an important role in this respect. The cam profile should have a smooth profile with abrupt changes in eccentricity. Such abrupt changes could result in peak loads of the cam roller and/or in loosening of the contact. A smooth cam profile will not only attribute to a proper transfer, but also reduce wear on the cam and the cam roller.
The cam roller 4 used in the exemplified embodiment of Figure 4, is a standard component sold for these purposes and build around a cam roller needle bearing 15 with bearing axle 5. A perspective cross-view of such cam roller is provided in Figure 5. The outer ring of the bearing is thicker to allow direct contact with the cam, without the need of an additional bearing house. The convex shape of the outer ring further prevents damaging of the bearing in case of a small deviations on the cam axle. The presence of the bearing axle further allows simple integration of the cam roller at one end of the ram. In the exemplified embodiment of Figure 6, the ram body 12, comprises at one end an extension 19 with an opening to accommodate bearing axle 5. In said embodiment the ram body will fit in a recess in the frame plate 16 of the crimping press, and the ram flanges 17 together with the carriage guides 30 will maintain the ram in position and allow a slidable displacement of the ram in said recess. In the exemplified embodiment the carriage guides consist of bronze sliding blocks with integrated carbon lubrication. Such configuration is free of maintenance and has a low friction. Low resistance movement of the ram, is indeed desired as it further contributes to the smoothness of operation and all time contact of the cam roller with the eccentric cam.
A spring 7 localized in a provided cavity 17 of the ram body, pushes the ram against the cam. In the exemplified embodiment a compression spring is being used, and chosen to have sufficient pressure force to maintain the cam roller in contact with the eccentric cam during rotation thereof, and to prevent slippage of the cam roller during said motion. When choosing the spring, it is important that this spring has a given pre-tension and that it never passes its minimal length. The force to be developed by the spring is dependent on the weight of the linear moving parts (the cam roller, the ram, the applicator hook, the adjusting nut, the applicator ...), the profile of the cam and the rotational speed of the cam. In the present instance also the speed with which the ram moved from its lowest (ram shut height) to its highest (ram die height) position has been taken into account, as it determines the inertial force needed to lift the ram from its lowest to its highest position.
In the exemplified crimp press of the present invention the weight of the linear moving parts equaled 4 kg. The vertical displacement of the ram between the lowest and highest position equals 0.04m/s and at operational time it takes the ram 0.1333s to make said displacement.

Under said circumstances the upward acceleration equals; $a = dv / td = 0.04 / 0.133 = 0.3 m / s^{2}$
The Inertial force equals; $F_{i} = m * a = 4 kg * 0.3 m / s^{2} = 1.2 N$
The gravity equals; $F_{g} = m * g = 4 kg * 9.81 m / s^{2} = 39.1 N$
Minimal force to be generated by the spring equals; $F_{i} + F_{g} = 1.2 N + 39.1 N = 40.3 N$

This minimal force is the force needed to maintain the cam roller in contact with the eccentric cam. However, and in order to prevent slippage of the cam roller, the spring is best over-dimensioned. In the exemplified embodiment, a spring has been chosen with a compression force of 236.2N, with a remaining compression force of 135.8N in fully stretched condition.
With reference to Figure 7, all of the foregoing elements are further mounted on a frame plate 16, provided with the necessary elements like, a recess 21 to accommodate the ram body, an aperture 22 to accommodate the cam axle and cam axle bearing, bolt holes 25 for fastening the further elements like the carrier guides 30, electric motor 14 and optional reduction gearbox 24. To assist in proper assembly of the crimp press, the frame plate may further comprises one or more dowel holes 23 to assist in the positioning of the frame plate to the rest of the frame. The skilled artisan is well aware of the size and material dimensions required for the frame. Elements influencing the frame characteristics of a crimping press include the dimensions of the stripunit, the applicator, the guideways of the stripunit, the dimensions of the electric motor, the sizes of the different bearings, the position and dimensions of the recess to accommodate the ram body, etc .... The precision in machining the foregoing elements on the crimping press frame plate is of utmost importance for an accurate performance of the crimping press. The crimping press will be crimping wire conductors and crimped contacts at high speeds, at a high precision (accepted tolerance of 0.02 mm) and a crimping force of at least 2 ton. This requires a frame capable to withstand said forces without bending. The slightest bending or other deformation of the frame will result in a bad crimping process and lost of goods. The skilled artisan is well aware of the material specifications needed to withstand the aforementioned working pressures. In the exemplified crimping press, the frame was accordingly made of sheet steal with a thickness of about 20,0 mm.
Together with the further details on the electric motor, the inductive sensors, the adjusting nut and the applicator hook (supra), this description exemplifies the inventions as defined in the following claims.

Claims

1. A ram drive mechanism for an automated terminal crimping machine, comprising;

- a cam axle accommodating an first cam;

- means for rotating said cam axle;

- a ram comprising a second cam;

- carriage guides that slidably fit around the ram; and

- means to maintain the second cam in contact with the first cam during rotation thereof;
wherein at least on of said first or said second cam is an eccentric cam.

1. The ram drive mechanism according to claim 1, wherein the first cam is an eccentric cam; in particular an eccentric plate cam, and the second cam a cam roller.

2. The ram drive mechanism according to claim 1, wherein the first cam is a cam roller and the second cam an eccentric cam; in particular an eccentric plate cam.

3. The ram drive mechanism according to any one of claims 2 or 3, wherein the cam roller is cylindrical or spherical shaped.

4. The ram drive mechanism according to claim 4, wherein the cam roller is cylindrical and fit around a cam roller bearing with bearing axle.

5. The ram drive mechanism according to claim 4, wherein the cam roller is spherical and corresponds to a ball transfer unit.

6. The ram drive mechanism according to any one of claims 1 to 6, wherein the second cam is integrated with/or mounted to one end of the ram.

7. The ram drive mechanism according to any one of claims 1 to 7, wherein the ram further comprises an applicator hook.

8. The ram drive mechanism according to any one of claims 1 to 8, wherein the ram further comprises an adjusting nut, preferably positioned between the ram body and the applicator hook.

9. The ram drive mechanism according to any one of claims 1 to 9, wherein the means to maintain the second cam in contact with the first cam during rotation thereof, consists of a spring.

10. The ram drive mechanism according to any one of claims 1 to 10, wherein the means for rotating said cam axle consist of an electrical motor; in particular an AC electrical motor driven by a variable frequency drive (VFD).

11. The ram drive mechanism according to any one of claims 1 to 11, further characterised in comprising means to determine the die height and/or shut height of the ram body

12. The ram drive mechanism according to claim 12, wherein said means to determine the die height and/or shut height of the ram body consist of inductive sensors.

13. Use of a ram drive mechanism as defined in any one of claims 1 to 13, in a crimping machine; in particular in an automated terminal crimping machine.

14. A crimping machine comprising a ram drive mechanism as defined in any one of claims 1 to 13.