WELDING GUN WITH A DISPLACEMENT MEASURING SYSTEM

Abstract

Handheld welding gun for welding an element to a component comprising a linear actuator unit with a linear actuator housing and a linear actuator rod adapted to actuate the holding unit in order to move the element between the lift position and the plunge position, the linear actuator rod extending partly inside and partly outside the linear actuator housing. A displacement measuring system communicates with a control card. The linear actuator, the displacement measuring system and the control card are connected together to form a compact actuator unit.

Claims

1. A handheld welding gun for welding an element to a component according to a welding process, the handheld welding gun comprising: a housing with a main portion and a grip with a trigger, the grip extending from the main portion, a holding unit mounted on the main portion and adapted to movably hold one element between a lift position and a plunge position, a linear actuator unit with a linear actuator housing and a linear actuator rod adapted to actuate the holding unit in order to move the element between the lift position and the plunge position, the linear actuator rod extending partly inside and partly outside the linear actuator housing, a nozzle surrounding the holding unit and adapted to contact the component, a welding current contact element arranged in the housing and adapted to direct a welding current to the element, a sensor unit adapted to measure a parameter during the welding process, a processing system with a control card adapted to control the parameter of the welding process, a displacement measuring system communicating with the control card, and wherein the linear actuator, the displacement measuring system and the control card are connected together, and the actuator unit is mounted in the main portion at an opposite side of the holding unit.

2. The handheld welding gun according to claim 1, wherein the displacement measuring system is an optical measuring system and comprises an encoder arranged on the control card and an encoder strip.

3. The handheld welding gun according to claim 2, wherein the encoder strip is fixed to the linear actuator rod through a strip holder and is slidingly movable with regard to the encoder.

4. The handheld welding gun according to claim 2, wherein the encoder is encapsulated.

5. The handheld welding gun according to claim 1, wherein the control card is attached to the linear actuator housing.

6. The handheld welding gun according to claim 1, wherein the linear actuator rod is movable along a longitudinal axis with regard to the linear actuator housing and is secured against rotation around the longitudinal axis.

7. The handheld welding gun according to claim 6, wherein the linear actuator rod is secured against rotation around the longitudinal axis by the linear actuator housing.

8. The handheld welding gun according to claim 1, wherein the linear actuator rod has a non-circular cross-section shape.

9. The handheld welding gun according to claim 8, wherein the linear actuator rod has an oblong cross-section shape.

10. The handheld welding gun according to claim 1, wherein the movable parts of the linear actuator are guided within the linear actuator housing by a bearing.

11. The handheld welding gun according to claim 1, and further comprising: a coil body arranged within the linear actuator housing, and a first bearing and a second bearing each arranged between the coil body and the linear actuator housing, and wherein the first bearing is arranged at a first end of the coil body, and the second bearing is arranged at a second end of the linear actuator housing.

12. The handheld welding gun according to claim 11, wherein the first bearing and the second bearing are in direct contact with the coil body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] A specific embodiment of the present invention will now be described, by way of example only and with reference to the accompanying drawings, of which:

[0041] FIG. 1 shows a perspective view of a handheld welding gun with a housing having a main portion and a grip having a trigger according to the invention.

[0042] FIG. 2 shows a cross-section view of the handheld welding gun of FIG. 1 with a linear actuator, a control card, a holding unit and a nozzle.

[0043] FIG. 3A shows an example of a detection method for detecting an improper use of the welding gun of FIG. 1.

[0044] FIG. 3B shows an example of a welding parameter detection method for automatically detecting welding parameters of the welding gun of FIG. 1.

[0045] FIG. 4 shows the handheld welding gun with the actuator unit mounted within the housing.

[0046] FIG. 5 shows the control card with the displacement measuring system.

[0047] FIG. 6 shows the control card with the gyroscope sensor.

[0048] FIG. 7 shows the actuator unit of FIG. 4.

[0049] FIG. 8 shows the actuator rod and the actuator housing.

[0050] FIG. 9 shows the actuator unit with the bearings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

[0052] FIG. 1 shows a handheld welding gun 10 for welding an element 22 to a component or workpiece. The welding gun 10 comprises a housing 12. The housing 12 is provided with a main portion 14 and a grip 16. The grip 16 is adapted to be held by a user and comprises a trigger 18. The grip 16 extends from the main portion 14, and notably orthogonally extends from the main portion. More particularly, the main portion 14 longitudinally extends along a longitudinal axis X, and the grip portion longitudinally extends along a grip axis Y, the grip axis Y being sensibly perpendicular to the longitudinal axis X.

[0053] As shown in FIG. 1, a holding unit 20 is mounted on the main portion 14. The holding unit 20 is adapted to hold an element 22, for instance a fastener or a stud at a time. The element or fastener is secured to the holding unit 20 and then the holding unit moves the element between a lift position and a plunge position. The holding unit comprises a stud holder adapted to clamp the anchor portion of a stud, the flange portion (destined to be welded to a surface) remaining at a free end of the stud holders. Such stud holders are well known and will not be detailed further.

[0054] A welding current contact element is arranged in the housing 12. The welding contact element is adapted to direct a welding current to the element 22. Welding contact elements are also well known and will not be detailed further.

[0055] A nozzle 24 (or mouthpiece) surrounds the holding unit 20. The nozzle 24 is adapted to contact the component or workpiece. The nozzle may have a cylindrical shape. The nozzle 24 extends from an extremity of the main portion 14. As seen in FIG. 1 or FIG. 2, the nozzle 24 may be provided with indentations 26 arranged at the end of the nozzle destined to contact the component. The nozzle 24 forms position means serving to position the welding gun 10 (and more particularly the element 22 mounted in the welding gun) at a predetermined distance from the component. The nozzle may also be used as a shield. The nozzle 24 may also comprise holes 28 provided in its cylindrical surface (e.g. at a non-zero distance from the surface adapted to contact the workpiece) to prevent wear and pollution, thus reducing the maintenance needs.

[0056] A linear actuator unit 30 is mounted within the main portion 14, as better seen in FIG. 2. The linear actuator unit 30 comprises a linear actuator with a linear actuator housing 32, a linear actuator rod 34 and a motor 36. The motor 36 is for instance a voice coil motor with a coil body and is arranged within the housing 32. The linear actuator rod 34 extends partly inside and outside the housing. The linear actuator rod 34 is movable in translation only and is secured against rotation around the longitudinal axis X. The linear actuator rod 34 is movable along the longitudinal axis X.

[0057] The linear actuator rod 34 is mechanically secured against rotation around the longitudinal axis X, as better seen in FIG. 7 and FIG. 8. As depicted in these figures, the linear actuator rod 34 has a non-circular cross-section and extends outside of the linear actuator housing 32 by an opening 38. The opening 38 has a form-fitting shape which corresponds to the shape of the linear actuator rod's cross section. The linear actuator rod 34 may have an oblong cross-section shape and extends outside from the housing through an opening having a corresponding oblong shape. Other shapes securing the rod against a rotation around the longitudinal axis may be implemented.

[0058] As seen in FIG. 9, the movable parts of the linear actuator are guided within the linear actuator housing 32 by a bearing 40, for example a sintered bronze bearing. However, in other embodiments, other bearings may be implemented. The coil body 42 of the linear actuator is arranged within the linear actuator housing 34. Two bearings 40 are arranged between the coil body 42 and the linear actuator housing. A first bearing 40a is arranged at a first end of the coil body. A second bearing 40b is arranged at a second end, opposite the first end, of the coil body 42. The bearings 40 are in direct contact with the coil body 42. The bearings are glued on the coil body.

[0059] The linear actuator (and more particularly the linear actuator rod 34) interacts with the holding unit 20 in order to move an element between the plunge position and the lift position.

[0060] As depicted in FIG. 2, a gas tube 44 is provided in the grip 16 to provide gas for the welding process. Welding wires 46 and control wires 48 are also represented.

[0061] A sensor unit 50 is arranged within the housing 12 to measure different parameters before and/or during and/or after the welding process. The sensor unit 50 communicates with a processing system 52 comprising a control card 54. The control card 54 is arranged within the housing 12.

[0062] The sensor unit 50 comprises a gyroscope sensor 56. The gyroscope sensor 56 is mounted within the housing 12 and is arranged on the control card 54. The gyroscope sensor 56 allows the monitoring of the welding process. The gyroscope sensor 56 also enable to monitor the correct use of the welding gun and to identify the welding points or positions. Indeed, the gyroscope sensor senses changes twists and angles of the welding gun 10. The gyroscope sensor is adapted to sense the angular velocity of the welding gun and thus the angular position of the welding gun can be detected. The position of the gyroscope sensor on the control card is for instance represented in FIG. 6. For example, the gyroscope sensor is fixed on the control card. More particularly, the gyroscope sensor may be fixed to the side of the control card opposite the side facing the linear actuator housing. In an embodiment, the encoder is fixed on the side of the control card facing the linear actuator housing.

[0063] The sensor unit 50 may also comprise an accelerometer 58 and/or a magnetometer 60. The accelerometer measures the linear acceleration, wherein the magnetometer senses magnetic field. More particularly, these sensors measure parameters, which added to the those measured by the gyroscope sensor allow a full and complete monitoring of the welding gun and the welding process. The sensor unit 50 thus may measure and collect data related to the orientation, the behaviour, the environment, the speed and acceleration of the welding gun 10. The gyroscope sensor and/or the accelerometer and/or the magnetometer are MEMS sensors. These sensors are positioned on the control card 54. The processing system is adapted to process these collected data and establish a corresponding or adapted response. The accelerometer and/or the magnetometer may be arranged on the side of the control card opposite the side facing the linear actuator housing.

[0064] The accelerometer 58 can be integrated with the gyroscope sensor. The accelerometer 58 is for instance a first accelerometer 58 with a first measurement width. A second accelerometer (not illustrated), separate from the first accelerometer, may be provided. The second accelerometer has a second measurement width. The second measurement width is different than the first measurement width. The second accelerometer may be provided in the vicinity of the first accelerometer and arranged on the control card or may be arranged in a different area of the welding gun. The use of a second accelerometer allows a better monitoring of the welding gun, without using expensive sensors.

[0065] The collected data enables for instance to detect an improper use of the welding gun or a fall. Indeed, the acceleration measurement may help to detect a misuse of the welding gun or a fall.

[0066] The measured data enables a monitoring of the welding gun movements during the welding process. Normally during a welding process, the welding gun 10 must be retained securely in place. Two particular mistakes often occurs: the welding gun 10 is removed too early from the component, or there is a lateral shift of the welding gun 10 during the welding process. Both lead to a weak welding joint. Such mistakes can be detected through the sensor unit 50 and the user can be alerted and invited to check the corresponding joint.

[0067] The welding gun 10 may comprise a display and the orientation of the display may be changed depending on the data of the gyroscope sensor.

[0068] FIG. 3A illustrates a broad method P1 for detecting an improper use of the welding gun using the parameters of the sensor unit. At E11, the method P1 collects data from the gyroscope sensor and/or the accelerometer and/or the magnetometer regarding the motion and the position of the welding gun. At E12 the method P1 compares the collected data to target data or to a library comprising different profiles of use. At E13 the method detects a default use based on caparison analysis. In an embodiment, the improper use can be detected based on statistical analysis.

[0069] FIG. 3B shows a method P2 for determining welding parameters which comply with the current welding situation. At E21, the method P2 collects data from the respective sensors (e.g. gyroscope sensor, accelerometer and/or magnetometer). At E22, the method P2 compares the data with pre-recorded data, in order to determine the position and behaviour of the welding gun in its environment. At E23, the method P2 determines the welding parameters (e.g. quantity of gas, energy, time necessary on the lift position, time necessary for the plunge position, . . . ) based on comparison from a library or using a statistical model or both. Once the welding parameters have been determined, they are implemented by the welding gum.

[0070] Different charts of the behaviour of a welding gun provided with the sensor unit can be generated.

[0071] As previously mentioned, the magnetometer detects the movement of the motor. The welding gun first contacts the component. Upon contact, the motor is slightly moved by the nozzle. After the contact, no acceleration and a static magnetic field are recorded. A peak in the magnetic field is recorded when the motor, after initiation of the welding process, is activated. When the welding process is over, no acceleration and no disturbance of the magnetic field are recorded. When the welding gun is removed from the component, a disturbance of the magnetic field and an acceleration peak are recorded.

[0072] Three phases of the welding process can easily be identified through the data provided by the sensor unit, on notably lift on (corresponding to the lift position of the holding unit), hold step and lift off (corresponding to the plunge position).

[0073] When recording the acceleration and the magnetic field, a delay between the end of the welding process and the removal of the welding gun from the component is visible. Such delay, if too short may be synonym of a removal of the welding gun from the component, which is too early.

[0074] A comparison of the data recorded during the welding process with a target state or target situation can be made in order to detect any mistake made by the user during the welding process, as above-mentioned.

[0075] The processing system can automatically set up adapted welding parameters from the data provided by the sensing unit. Indeed, the position of the welding gun enables to determine if the welding joint has to be made downward or upward and welding parameters like gas, intensity, stroke, . . . can be adapted to the welding position of the welding gun.

[0076] It is known in current welding gun to count the number of elements which have been welded to the component. However, through the data measured by the sensor unit, it is also possible to improve the features of the current welding gun by automatic recognition of the welding program used by the welding gun. For instance, the processing system may detect a particular welding program from a library comprising a plurality of predetermined welding program with the recorded orientation of the welding gun. Besides, an element mistakenly positioned could also be detected. Besides, the sensor unit allows counting the number of weld spots by using the data provided. This counting function enables to ensure that the welding cycle is completed, and no spot has been disregarded. Besides, for each weld spot a particular orientation or position of the welding gun may be necessary. The sensor unit can confirm that the element have been welded at the correct spots with correct pre-determined weld parameters.

[0077] The welding gun comprises a displacement measuring system 62 communicating with the control card. The displacement measuring system is more particularly visible on FIG. 2, FIG. 4 and FIG. 5. Actually, the displacement measuring system 62 is mounted on the control card 54. The linear actuator, the displacement measuring system 62 and the control card 54 are connected together to form a compact actuator unit. The actuator unit is mounted in the main portion at the opposite of the holding unit 20. More particularly, the main portion 14 extends along the longitudinal axis X and is provided at one of its ends with the holding unit 20. The linear actuator unit 30 is mounted within the main portion at the opposite end, as previously described.

[0078] The displacement measuring system 62 is for instance an optical measuring system. It comprises an encoder 64 arranged on the control card 54 and an encoder strip 66. The encoder strip 66 is movable (and more particularly slidingly movable along the longitudinal axis X) with regard to the encoder 64. The encoder strip 66 is fixedly connected to the linear actuator rod 34 and moves above the encoder 64, such that the motion of the linear actuator rod 34 can be detected and recorded by the encoder 64. The encoder strip 66 is fixed to the linear actuator rod 34 through a strip holder, as depicted in FIG. 5.

[0079] The encoder 64 is fixed on the control card 54 and is encapsulated in order to avoid any dust or smoulder. The encapsulation is for instance realized with a non-oven material which is arranged around the encoder 64.

[0080] The control card 54 with the sensor unit 50 and the encoder 20 is fixed to the linear actuator housing 32 at one end of the main portion, such that a compact control command unit is realized, and it can directly be integrated within the welding gun 10 and no additional part are needed. More particularly, the control card is fixed on a side of the linear actuator housing which is facing the grip (in other words on the bottom side of the linear actuator housing). Actually, the control card 54 is screwed on the linear actuator housing. In other embodiments, the control card may be snap fitted to the linear actuator housing or glued to it. As illustrated in FIG. 5, the linear actuator housing 34 is sensibly cylindrical.

[0081] The welding gun is thus directly provided with the control command for processing the sensor unit and/or displacement measurement system data, and no additional part to control these data, outside of the welding gun, is necessary. An external controller still controls the welding process per se.

[0082] The welding gun 10 may comprise feeding means by way of which the element 22 can be fed automatically to the holding unit. For example, pneumatic feeding means. The feeding means can feed the element at a posterior end of a tube and then carry them by compressed air as far as an anterior end of the holding means. In another embodiment, the feeding of elements 22 may be manual.

[0083] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

[0084] It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

[0085] welding gun 10

[0086] housing 12

[0087] main portion 14

[0088] a grip 16

[0089] trigger 18

[0090] holding unit 20

[0091] element 22

[0092] nozzle 24

[0093] indentations 26

[0094] holes 28

[0095] linear actuator unit 30

[0096] linear actuator housing 32

[0097] a linear actuator rod 34

[0098] and a motor 36

[0099] opening 38

[0100] bearing 40

[0101] coil body 42

[0102] first bearing 40a

[0103] second bearing 40b

[0104] gas tube 44

[0105] welding wires 46

[0106] control wires 48

[0107] sensor unit 50

[0108] processing system 52

[0109] comprising a control card 54

[0110] gyroscope sensor 56

[0111] accelerometer 58

[0112] and a magnetometer 60

[0113] displacement measuring system 62

[0114] encoder 64

[0115] encoder strip 66