Series Spot Welding Gun

Abstract

To provide a series spot welding gun which includes electrodes, and is configured in such a manner that the down-sizing and weight saving of the gun is not disturbed by increase of pitch between electrodes even when the pitch is increased.SOLUTION: A series spot welding gun 100 comprises: a fixed side welding gun 10 and a movable side welding gun 20 which are juxtaposed; a rotating device 50 which rotates two welding guns 10, 20 relatively around an axis C in such a manner that distance between electrode tips 18a, 28a of these two welding guns 10, 20 is variable; single transformer 30 provided together with the fixed side welding gun 10; and a shaft power supply unit 40 having a shaft member 43 provided coaxially with the axis C, a bearing member 41 which rotatably supports the shaft member 43, and a ring-shaped coil spring 44 which comes in contact with each of the shaft member 43 and the bearing member 41.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a series spot welding gun. [Background technology]

[0002] A welding gun of a resistance welding device is configured such that a fixed electrode and a movable electrode are arranged opposite each other and the movable electrode is advanced and retreated relative to the fixed electrode by a pressure drive unit. With this configuration, the movable electrode is advanced toward the fixed electrode, and a workpiece placed between the fixed electrode and the movable electrode is sandwiched and pressurized by both electrodes, and a large current is passed between both electrodes for a short period of time, thereby joining the workpieces.

[0003] There are also series spot welding guns that have two welding guns arranged in parallel on different axes. In a series spot welding gun, each welding gun has only a movable electrode without a fixed electrode, and by passing a current between the electrode tips of the two movable electrodes while they are pressed against different positions on the workpiece, spot welding is performed on the workpiece where the two electrodes come into contact.

[0004] Among series spot welding guns, there is a variable pitch series spot welding gun in which the distance (pitch) between the electrode tips of both welding guns is variable. In a variable pitch series spot welding gun, one is called a fixed welding gun and the other is called a movable welding gun, and the movable welding gun is configured to be linearly movable or rotatable relative to the fixed welding gun, thereby making it possible to change the pitch between the electrode tips of both welding guns (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-319485 Summary of the Invention [Problem to be solved by the invention]

[0006] A series spot welding gun can be configured with only one power supply transformer because it simultaneously supplies current to two electrodes.

[0007] In a variable-pitch series spot welding gun, the movable welding gun moves, so if the transformer is integrated with the fixed welding gun, the distance between the transformer and the movable welding gun changes depending on the pitch. To ensure electrical continuity between the transformer output terminal and the movable welding gun electrode even with this change in distance, the transformer and the movable welding gun are connected by a flexible shunt whose deflection changes depending on the change in distance.

[0008] However, when the amount of pitch variation is increased, the length of the shunt must be increased, which hinders the series spot welding gun from being made smaller and lighter.

[0009] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a series spot welding gun that can increase the amount of variation in the pitch between the electrode tips without hindering miniaturization and weight reduction. [Means for solving the problem]

[0010] The present invention is a series spot welding gun including two welding guns arranged in parallel, a rotation device that rotates the two welding guns relatively around a predetermined axis so as to vary the distance between the electrode tips of the electrodes of the two welding guns, a single transformer provided with one of the two welding guns, and a shank power supply unit having a shank member arranged coaxially with the predetermined axis, a bearing member that rotatably supports the shank member, and a ring-shaped coil spring that contacts the shank member and the bearing member, respectively. [Effects of the Invention]

[0011] According to the series spot welding gun of the present invention, even if the pitch between the electrodes is increased, this does not hinder miniaturization or weight reduction. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing a variable pitch series spot welding gun, illustrating a state in which the distance (pitch) between the electrode tip of the movable electrode of the fixed welding gun and the electrode tip of the movable electrode of the movable welding gun is minimum (pitch P1). [Figure 2] FIG. 1 is a perspective view showing a variable pitch series spot welding gun, showing the state in which the pitch between the electrode tip of the movable electrode of the fixed welding gun and the electrode tip of the movable electrode of the movable welding gun is maximum (pitch P2). [Figure 3] 2 is a bottom view of the series spot welding gun in FIG. 1 taken along an arrow A. FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a cross section of the series spot welding gun taken along line BB in FIG. 3. [Figure 5] 3 is a bottom view of the series spot welding gun in FIG. 2 taken along an arrow A. FIG. [Figure 6] FIG. 6 is a cross-sectional view showing a cross section of the series spot welding gun taken along line DD in FIG. 5. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing details of the axial power supply unit in FIG. 6. [Figure 8] 10 is a plan view showing a ring-shaped coil spring in a state where it is constrained by a groove of a bearing member and a shaft portion of a shaft member. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a series spot welding gun according to the present invention will be described with reference to the drawings.

[0014] <Configuration> 1 and 2 are perspective views showing a variable pitch series spot welding gun 100 (hereinafter simply referred to as welding gun 100), with FIG. 1 showing a state in which the distance (pitch) between electrode tip 18a of movable electrode 18 of fixed side welding gun 10 (an example of one welding gun) and electrode tip 28a of movable electrode 28 of movable side welding gun 20 (an example of the other welding gun) is minimum (pitch P1), and FIG. 2 showing a state in which the pitch between electrode tip 18a of movable electrode 18 of fixed side welding gun 10 and electrode tip 28a of movable electrode 28 of movable side welding gun 20 is maximum (pitch P2 (>P1)).

[0015] 3 is a bottom view of welding gun 100 in FIG. 1 as viewed by arrow A, FIG. 4 is a cross-sectional view showing a cross section of welding gun 100 along line BB in FIG. 3, FIG. 5 is a bottom view of welding gun 100 in FIG. 2 as viewed by arrow A, and FIG. 6 is a cross-sectional view showing a cross section of welding gun 100 along line DD in FIG. 5.

[0016] The illustrated welding gun 100 is one embodiment of a series spot welding gun according to the present invention, and is integrally equipped with two welding guns 10, 20, one power supply transformer 30, an axial power supply unit 40, and a rotation device 50.

[0017] (Rotating device) The rotation device 50 includes a flange member 55, a fixed bracket member 51, a rotating bracket member 52, and a motor 53. A shaft power supply unit 40 (described later) is integrally attached to the rotation device 50. The flange member 55, the fixed bracket member 51, and the rotating bracket member 52 are arranged side by side along the axis C.

[0018] Flange member 55 is a part that is fixed to the tip of a robot arm when welding gun 100 is attached to the robot arm for use. Fixed bracket member 51 is a part that is fixed to flange member 55. Fixed bracket member 51 fixes and supports transformer 30 and one of welding guns 10.

[0019] The rotating bracket member 52 is provided so as to be rotatable about an axis C (a predetermined axis) relative to the flange member 55 and the fixed bracket member 51. The rotating bracket member 52 supports the motor 53 and the other welding gun 20 in a fixed manner.

[0020] Motor 53 is a servo motor that rotates rotating bracket member 52 about axis C relative to flange member 55 and fixed bracket member 51, thereby changing the relative positional relationship between two welding guns 10, 20 between the state shown in Figure 1 and the state shown in Figure 2. Specifically, by rotating rotating bracket member 52, motor 53 varies the distance between electrode tips 18a, 28a of electrodes 18, 28 of two welding guns 10, 20.

[0021] (welding gun) The two welding guns 10, 20 are arranged side by side and parallel to each other. Of the two welding guns 10, 20, the welding gun 10 supported by fixed bracket member 51 will be referred to as the fixed welding gun 10, and the welding gun 20 supported by rotating bracket member 52 will be referred to as the movable welding gun 20.

[0022] The fixed welding gun 10 includes a motor 12, a pressure device 11, a movable electrode 18, and conductive members 13, 14, and 15. The motor 12 is a servo motor and operates the pressure device 11. The pressure device 11 moves a pressure shaft disposed inside it axially forward and backward by the rotation of the motor 12.

[0023] The movable electrode 18 has an electrode tip 18a at its tip that comes into contact with the workpiece to be welded. The movable electrode 18 advances and retreats in the axial direction in accordance with the advance and retreat of the pressure shaft of the pressure device 11, and as the pressure shaft of the pressure device 11 advances in the axial direction, it advances downward in Figures 1 and 2, and the electrode tip 18a is pressed against the workpiece, applying pressure to the workpiece. As the pressure shaft of the pressure device 11 retreats in the axial direction from the state in which it is pressing the workpiece, the movable electrode 18 returns to the upper position shown in Figures 1 and 2, and the electrode tip 18a moves away from the workpiece.

[0024] The conductive members 13, 14, and 15 are conductors that conduct current generated by a transformer 30, which will be described later, to the movable electrode 18. The conductive member 13 is a conductor joined to one output terminal 31 of the transformer 30, as shown in FIG. 3. The conductive member 15 is a conductor joined to the movable electrode 18.

[0025] Conductive member 14 is a flexible shunt formed by stacking multiple thin copper plates and bending them into a roughly U-shape. One end of the U-shape of conductive member 14 is joined to conductive member 13, and the other end of the U-shape is joined to conductive member 15. Conductive member 14 absorbs the movement of movable electrode 18 as it advances and retreats by moving the position of the U-shape.

[0026] Movable welding gun 20 has the same basic configuration as fixed welding gun 10. Welding gun 20 includes motor 22, pressure device 21, movable electrode 28, and conductive members 23, 24, and 25. Motor 22 is a servo motor that operates pressure device 21. Pressure device 21 moves a pressure shaft disposed inside it axially forward and backward as motor 22 rotates.

[0027] The movable electrode 28 has an electrode tip 28a at its tip that comes into contact with the workpiece to be welded. The movable electrode 28 advances and retreats in the axial direction in accordance with the advance and retreat of the pressure shaft of the pressure device 21, and as the pressure shaft of the pressure device 21 advances in the axial direction, it advances downward in Figures 1 and 2, and the electrode tip 28a is pressed against the workpiece, applying pressure to the workpiece. As the pressure shaft of the pressure device 21 retreats in the axial direction from the state in which it is pressing the workpiece, the movable electrode 28 returns to the upper position shown in Figures 1 and 2, and the electrode tip 28a moves away from the workpiece.

[0028] Conductive members 23, 24, and 25 are conductors that conduct the current generated by transformer 30 and introduced from the other output terminal 32 of transformer 30 to axial power supply unit 40 to movable electrode 28. As shown in FIG. 3, conductive member 23 is a conductor joined to extension piece 42 of axial power supply unit 40. Conductive member 25 is a conductor joined to movable electrode 28.

[0029] Conductive member 24 is a flexible shunt similar to conductive member 14. One end of the U-shape of conductive member 24 is joined to conductive member 23, and the other end of the U-shape is joined to conductive member 25. Conductive member 24 absorbs the movement of movable electrode 28 due to the movement of the movable electrode 28 back and forth by moving the position of the U-shape.

[0030] As described above, the two welding guns 10, 20 are each supported by the rotation device 50, and as shown in FIGS. 1 and 2, the rotating bracket member 52 rotates around the axis C, which serves as the center of rotation, relative to the fixed bracket member 51, thereby making it possible to vary the distance between the electrode tip 18a of the fixed welding gun 10 and the electrode tip 28a of the movable welding gun 20 between the minimum pitch P1 shown in FIG. 1 and the maximum pitch P2 shown in FIG. 2.

[0031] (transformer) Transformer 30 supplies welding power to fixed welding gun 10 and movable welding gun 20. Transformer 30 has output terminals 31 and 32. As shown in FIGS. 3 to 6, one output terminal 31 is joined to conductive member 13 of fixed welding gun 10, and the other output terminal 32 is joined to bearing member 41 of shaft power supply unit 40.

[0032] (Axis power supply part) Fig. 7 is an enlarged cross-sectional view showing details of the shaft power supply part 40 in Fig. 6, and Fig. 8 is a plan view showing the ring-shaped coil spring 44 in a state where the outer peripheral part 44b is constrained in the groove 41b of the bearing member 41 and the inner peripheral part 44a is constrained by the shaft part 43a of the shaft member 43. Note that Fig. 8 shows only a part of the ring shape of the coil spring 44 in solid lines, and the other parts are omitted, with the outer peripheral part 44b and the inner peripheral part 44a respectively shown in two-dot chain lines.

[0033] Shaft power supply unit 40 is a conductor that conducts power from transformer 30 to electrode 28 of movable welding gun 20. As shown in Figures 4 and 6, shaft power supply unit 40 is attached to rotation bracket member 52 of rotation device 50. As shown in Figure 7, shaft power supply unit 40 includes a shaft member 43, a bearing member 41, a coil spring 44, and an extension piece 42.

[0034] The shaft member 43 is made of a conductive material, has a shaft portion 43a arranged coaxially with the axis C of the rotation device 50, and is fixed to the rotation bracket member 52. Therefore, the shaft member 43 rotates around the axis C integrally with the rotation bracket member 52. One end of an extension piece 42 made of a conductive material is joined to the shaft member 43. The other end of the extension piece 42 is joined to the conductive member 23.

[0035] The bearing member 41 is made of a conductive material and includes a fixed piece 41d, which is a plate-like body having a substantially L-shaped cross section as shown in Figures 4 and 6, and two bearing caps 41c shown in Figure 7. The fixed piece 41d has a long and short plate portion forming the L shape, and the shorter plate portion is joined to the output terminal 32 of the transformer 30 as shown in Figures 4 and 6. A hole 41a having a diameter larger than the outer diameter of the shaft portion 43a of the shaft member 43 is formed in the longer plate portion of the fixed piece 41d.

[0036] As shown in Fig. 7, a ring-shaped groove 41b with a diameter larger than that of hole 41a is formed in hole 41a, on the inside of the front and back surfaces of fixed piece 41d. A ring-shaped coil spring 44 shown in Fig. 8 is fitted into groove 41b. Coil spring 44 is formed by spirally winding a conductive linear member and connecting the starting end and the ending end of the linear member to form a ring shape as a whole.

[0037] The inner peripheral surface of the fixing piece 41d, which defines the contour of the groove 41b, comes into contact with mainly the outer peripheral portion 44b of the coil spring 44, so that the bearing member 41 and the coil spring 44 are electrically connected.

[0038] In order to stabilize the electrical conduction between the bearing member 41 and the coil spring 44, it is preferable that the outer diameter of the coil spring 44 is equal to or larger than the diameter of the groove 41b.

[0039] 7, bearing caps 41c are fixed to the front and back surfaces of the fixed piece 41d when the coil spring 44 is fitted in the groove 41b. The bearing caps 41c are fixed to the fixed piece 41d by inserting boss-like portions protruding from the front and back surfaces of the fixed piece 41d into the holes 41a.

[0040] 7, with the shaft portion 43a of the shaft member 43 inserted through the bearing cap 41c, the bearing cap 41c supports the shaft portion 43a of the shaft member 43 so as to be rotatable around the axis C. Furthermore, the bearing cap 41c prevents the coil spring 44 fitted in the groove 41b from falling out of the groove 41b before the shaft portion 43a is inserted through the bearing cap 41c.

[0041] In its natural state, when no external force is acting on it, the coil spring 44 has an outer shape that is a nearly perfect circle, and although its outer diameter in its natural state is larger than the diameter of the hole 41a, the ring shape can be easily elastically deformed. Therefore, the coil spring 44 in its elastically deformed state can be easily inserted into the hole 41a, and the coil spring 44 can be easily positioned in the groove 41b.

[0042] The inner diameter of the boss of bearing cap 41c that is fitted into hole 41a is formed to be larger than the inner diameter of coil spring 44. As a result, inner peripheral portion 44a of coil spring 44 protrudes radially inward beyond the inner peripheral surface of the boss of bearing cap 41c.

[0043] Therefore, the shaft portion 43a inserted into the hole 41a and substantially in contact with the inner peripheral surface of the boss of the bearing cap 41c contacts the inner peripheral portion 44a of the coil spring 44 and expands the inner peripheral portion 44a of the coil spring 44 to the outer diameter of the shaft portion 43a, thereby establishing electrical continuity between the shaft member 43 and the coil spring 44.

[0044] With the shaft portion 43a inserted into the hole 41a, the shaft member 43 can rotate freely around the axis C relative to the bearing member 41, but electrical conductivity between the shaft member 43 and the coil spring 44 is maintained at any rotational angle position of the shaft member 43 relative to the hole 41a.

[0045] 8 shows a state in which the coil spring 44 is fitted into the groove 41b of the fixed piece 41d, and the shaft portion 43a, which has an outer diameter larger than the diameter of the inner peripheral portion 44a in its natural state before elastic deformation, is fitted into the inner peripheral portion 44a of the coil spring 44. As a result, the inner peripheral portion 44a is pushed outward in the radial direction about the axis C and elastically deforms, and the inclination of the spiral of the coil spring 44 is at least partially changed compared to the natural state.

[0046] In this way, the outer circumferential portion 44b of the ring of the coil spring 44 is constrained in the groove 41b, and the inner circumferential portion 44a of the ring is constrained to the shaft portion 43a of the shaft member 43, so that the ring-like shape of the coil spring 44 is elastically deformed, and the restoring force due to this elastic deformation acts as a load that urges the bearing member 41 and the outer circumferential portion 44b of the coil spring 44 into contact with each other, and also acts as a load that urges the shaft member 43 and the inner circumferential portion 44a of the coil spring 44 into contact with each other. Therefore, the bearing member 41 and the shaft member 43 maintain electrical continuity via the coil spring 44.

[0047] <effect> In welding gun 100 of this embodiment configured as described above, motor 53 is operated to rotate rotating bracket member 52 relative to fixed bracket member 51 about axis C. This allows welding gun 100 to rotate movable welding gun 20 about axis C relative to fixed welding gun 10.

[0048] As a result, the welding gun 100 can arbitrarily change the pitch between the electrode tip 18a of the fixed welding gun 10 and the electrode tip 28a of the movable welding gun 20 between the minimum pitch P1 shown in Figures 1 and 3 and the maximum pitch P2 shown in Figures 2 and 5.

[0049] Then, welding gun 100 rotates movable welding gun 20 relative to fixed welding gun 10 about axis C using rotation device 50, so that the pitch between electrode tips 18a, 28a is set to any pitch between pitch P1 and pitch P2. In this state, welding gun 100 rotates motor 12 of fixed welding gun 10 and motor 22 of movable welding gun 20.

[0050] As a result, the movable electrode 18 of the fixed side welding gun 10 and the movable electrode 28 of the movable side welding gun 20 move in a direction approaching the workpiece, and with the electrode tips 18a, 28a of both movable electrodes 18, 28 in contact with the fixed workpiece from above, each movable electrode 18, 28 presses the workpiece downward.

[0051] With both electrode tip 18 a and electrode tip 28 a in contact with the workpiece, a predetermined current is input to the input terminal of transformer 30 , and a welding current is output between output terminals 31 and 32 .

[0052] Here, one output terminal 31 is connected to the movable electrode 18 of the fixed welding gun 10 by conductive members 13, 14, and 15, and the other output terminal 32 is connected to the movable electrode 28 of the movable welding gun 20 by a bearing member 41, a coil spring 44, a shaft member 43, an extension piece 42, and conductive members 23, 24, and 25.

[0053] Then, as electrode tip 18a of fixed side welding gun 10 and electrode tip 28a of movable side welding gun 20 are both in contact with the workpiece, a closed circuit is formed between output terminals 31 and 32 of transformer 30 via the workpiece, and a high current flows between output terminals 31 and 32, spot welding the part of the workpiece that is being pressed by electrode tip 18a and the part that is being pressed by electrode tip 28a, respectively.

[0054] In this way, the welding gun 100 of this embodiment can supply power from a single transformer 30 to the electrode tip 18a of the fixed welding gun 10 and the electrode tip 28a of the movable welding gun 20 via the axial power supply unit 40.

[0055] Furthermore, the welding gun 100 can use the rotation device 50 to arbitrarily increase the amount of variation in the pitch between the electrode tips 18a, 28a, and rotate the movable welding gun 20 around the axis C relative to the fixed welding gun 10 so that the pitch can be any value between the minimum pitch P1 and the maximum pitch P2, without preventing the welding gun 100 from being made smaller and lighter.

[0056] In other words, when the movable welding gun 20 of the welding gun 100 rotates around axis C relative to the fixed welding gun 10, the relative positional relationship between the transformer 30 fixed integrally with the fixed welding gun 10 and the movable welding gun 20 changes.

[0057] Here, in welding guns (welding guns to which the present invention does not apply) in which transformer 30 and movable electrode 28 of movable welding gun 20 are electrically connected using a flexible shunt or conductor to absorb changes in the relative positional relationship between transformer 30 and movable welding gun 20, the length of the flexible shunt or conductor must be increased to increase the amount of variation in the variable pitch between electrode tips 18a, 28a. Furthermore, the inclusion of these long flexible shunts or conductors in such welding guns hinders miniaturization and weight reduction.

[0058] In contrast, in the welding gun 100 of this embodiment, the movable electrode 28 and the transformer 30 are electrically connected by the axial power supply unit 40, and no flexible shunt or conductor is used. Therefore, even if the amount of variation in the variable pitch between the electrode tips 18a, 28a is increased, this does not prevent the welding gun 100 from being made smaller and lighter.

[0059] Furthermore, since the axial power supply unit 40 is integral with the rotating device 50 and can rotate freely coaxially with the axis C, which is the rotation center of the rotating device 50, there is no need to increase the size of the axial power supply unit 40 even if the rotation angle of the rotating device 50 is increased in order to increase the pitch difference between the electrode tips 18a and 28a.

[0060] In addition, in the welding gun 100 of this embodiment, a coil spring 44 is fitted into a groove 41b formed in the hole 41a of the bearing member 41, the groove 41b having a diameter larger than the inner diameter of the hole 41a, and a bearing cap 41c having a boss formed therein and having an inner diameter smaller than the diameter of the hole 41a is fitted into the hole 41a from the front and back surfaces of the fixing piece 41d.

[0061] This makes it possible to prevent the coil spring 44 fitted in the groove 41b from falling out of the hole 41a, and also to support the shaft portion 43a of the shaft member 43 so as to be rotatable.

[0062] In the welding gun 100 of this embodiment, the bearing member 41 of the axial power supply unit 40 is connected to the output terminal 32 of the transformer 30, and the axial member 43 is connected to the movable electrode 28 of the movable welding gun 20 through the extension piece 42 and the conductive members 23, 24, and 25, but the opposite configuration may also be applied.

[0063] In other words, the welding gun 100 may be configured such that the bearing member 41 is fixed to the rotating bracket member 52, the bearing member 41 is connected to the movable electrode 28 of the movable welding gun 20 through the extension piece 42 and the conductive members 23, 24, and 25, and the shaft member 43 is connected to the output terminal 32 of the transformer 30. [Explanation of symbols]

[0064] 10 Fixed side welding gun 18,28 Movable electrode 18a, 28a Electrode tip 20 Movable welding gun 30 Transformer 40 Axis power feed section 41 Bearing materials 43 Shaft member 43a Shaft 44 coil spring 50 Rotating Device 100 Series Spot Welding Gun C-axis

Claims

1. Two welding guns arranged in parallel; a rotation device that rotates the two welding guns relatively around a predetermined axis so as to vary the gap between the electrode tips of the electrodes of the two welding guns; a single transformer provided with one of the two welding guns; a shaft power supply unit including a shaft member provided coaxially with the predetermined shaft, a bearing member that rotatably supports the shaft member, and a ring-shaped coil spring that contacts the shaft member and the bearing member, respectively.

2. one of the two output terminals of the transformer is connected to the one welding gun; 2. The series spot welding gun according to claim 1, wherein the other of the two output terminals of the transformer is connected to the other welding gun via the shaft power supply portion.

3. the rotation device includes a fixed bracket member that fixes and supports the one welding gun and the transformer, and a rotating bracket member that fixes and supports the other welding gun, one of the bearing member and the shaft member is connected to the one output terminal of the transformer; 3. The series spot welding gun according to claim 2, wherein the other of the bearing member and the shaft member is fixed to the rotating bracket member and connected to the other welding gun.

4. the bearing member includes a plate-like body having a hole formed therein, and a bearing having a boss inserted into the hole, the bearing rotatably supporting the shaft member, 4. The series spot welding gun according to claim 1, wherein the coil spring contacts the bearing member when inserted into the hole in the plate-shaped body, and an inner peripheral portion of a ring of the coil spring contacts the shaft member.

Images