Retracting mechanism and size measuring device provided with same

Abstract

The present invention provides a pneumatic cylinder type retraction mechanism having a cylinder and a piston capable of reciprocating inside the cylinder, the piston being reciprocatingly moved using air pressure, the pneumatic cylinder type retraction mechanism being characterized in that: a seal unit is provided on the inner periphery of the cylinder facing the outer periphery of the piston, and is a stationary seal unit; the sealing unit suppresses pressurized air for operating the piston from leaking from the inside of the cylinder. The retraction mechanism can achieve at least one of effects of reducing starting resistance, improving measurement accuracy of the measurement device, and shortening measurement time.

Description

Technical Field

[0001] The present disclosure relates to a retraction mechanism for bringing a probe into contact with a workpiece during measurement and for retracting the probe from the workpiece during non-measurement, and a dimension measuring device having the retraction mechanism, and in particular to a retraction mechanism suitable for the case where a pneumatic cylinder is used for the contact and retraction of the probe, and a dimension measuring device having the retraction mechanism. Background Art

[0002] In order to electrically measure and inspect the outer diameter of a shaft component, a dimension measuring device equipped with an air cylinder is often used. For example, Patent Documents 1 and 2 describe the use of a measuring jaw or a measuring head to inspect the length dimension of a mechanical component.

[0003] Patent document 1 discloses that the detection head has a housing, a movable arm supporting a probe, a support shaft combined with the housing and the arm so that the arm can move relative to the housing, and a retracting device (retracting mechanism) having a cylinder combined with the housing and a piston sliding in the cylinder. Here, the piston applies force to the arm to a determined non-operating position. In addition, the detection head includes a position sensor that supplies a signal according to the position of the arm relative to the housing. The retracting device includes a bellows seal accommodated in the cylinder and having its ends fixed to the cylinder and the piston.

[0004] Patent document 2 discloses that, in order to ensure a high level of repeatability, the measuring head comprises: a supporting structure having a housing with a groove and a geometric axis in a predetermined length direction; an arm group having an arm and a probe and being movable relative to the supporting structure; a support shaft arranged between the arm and the supporting structure so that the arm can move relative to the supporting structure with the transverse axis as the center; a thrust device arranged between the arm and the supporting structure material and applying force to the probe toward the surface of a mechanical part to be inspected; and a converter connected to the arm and the supporting structure and supplying a signal corresponding to the position of the arm to the supporting structure.

[0005] In addition, in Patent Document 3, in order to retract the arm of the measuring head with a simple structure, the measuring head is provided with a shape memory alloy actuator as a retraction mechanism. The shape memory alloy actuator includes a coil spring and a bias spring made of shape memory alloy, etc. After the coil spring and the bias spring are inserted from the two ends of the rod to the flange fixed to the middle part of the rod, the bias spring is held in a retracted state in the holder. When the coil spring is energized and heated to a temperature above the phase change temperature, the coil spring is deformed, the rod presses down the lower pressing plate, and the contactor retracts.

[0006] Patent Document 4 discloses a structure for preventing condensation from occurring in a pneumatic cylinder. Specifically, the pneumatic cylinder includes a cylinder, a piston that divides the interior of the cylinder into a first chamber and a second chamber, and a sealing unit that is disposed on a piston wall and seals an interface between the piston and the cylinder. Prior art literature Patent Literature

[0007] Patent Document 1: Japanese Patent Application No. 2010-502971 Patent Document 2: Japanese Patent Application Publication No. 2011-64694 Patent Document 3: Japanese Patent Application Publication No. 2001-27503 Patent Document 4: Japanese Patent Application Publication No. 2020-112212 Summary of the invention Problems to be solved by the invention

[0008] In a measuring device having a pneumatic cylinder type retracting mechanism, the arm on which the stylus is mounted is swung by the spring force (restoring force) of the built-in spring to contact the workpiece to be measured, and the displacement of the stylus is measured by a measuring unit, such as a differential transformer, provided on the opposite side of the stylus. After the measurement is completed, the pneumatic cylinder supplies a force that overcomes the spring force of the built-in spring, causing the arm to rotate in the opposite direction, and the stylus is separated from the workpiece, that is, retracted. In the case of multiple measurement objects, this operation is repeated at intervals.

[0009] In the pneumatic cylinder type measuring device, in order to control the swing of the arm, as mentioned above, a built-in spring and a pneumatic cylinder are often used. In addition, in order to be miniaturized, in a single-acting pneumatic cylinder type pneumatic cylinder having only one cylinder, a built-in spring is wound around the piston rod, and pressurized air is guided to the space formed between the piston and the cylinder. A piston ring type seal is arranged between the piston and the cylinder so that the pressurized air effectively presses the piston, in other words, so that the pressurized air does not leak from the space formed by the piston and the cylinder.

[0010] In the measuring jaws or measuring heads for length inspection described in Patent Document 1, a U-shaped sealing gasket is also accommodated in a groove provided in the piston head to prevent pressurized air from leaking from the space formed between the piston and the cylinder. The inventors have found that in such a measuring device with a single-acting cylinder, if the measuring device is used at intervals, the starting characteristics of the piston often deteriorate. One of the reasons for this is considered to be that the sealing gasket installed in the piston and in sliding contact with the cylinder is bonded to the other part (cylinder) at the sliding contact portion. In other words, it is considered that the sealing gasket is bonded (attached) to the other part as time passes. In order to improve the performance of the measuring device, it is hoped to minimize the impact of the bonding of the sealing gasket.

[0011] In Patent Document 2, a bellows is used instead of a pneumatic cylinder to rotate the arm. By introducing pressurized air into the interior of the bellows, the bellows is extended and abuts against the arm, causing the arm to rotate. When the arm rotates in the opposite direction, the inside of the bellows is depressurized and the arm is pulled back by a separately provided spring. The use of air pressure and a spring is the same as Patent Document 1, but since the bellows is formed in a bag shape, no sealing member such as a sealing ring is required, and there will be no sliding problems such as the sticking of the sealing gasket. However, there is a problem in that the bellows is expensive and it takes time to replace it in case of damage.

[0012] Patent document 3 discloses that the spring for applying force to the arm is replaced by a shape memory alloy spring instead of a pneumatic cylinder or bellows for rotating the arm. In this case, the spring contracts below a certain temperature, and extends above a certain temperature. Or vice versa. The extension and retraction of the spring can be switched simply by heating the spring using a piezoelectric element, etc. However, it is very difficult to obtain a stable two-way memory effect using only a shape memory alloy spring monomer, so a method of converting a one-way memory effect into a two-way action with the help of a bias force has to be adopted. It is necessary to be able to maintain a spring force that is twice the force used, and there is still room for improvement in miniaturization.

[0013] In addition, Patent Document 4 solves the problem of condensation generated when the pressurized air is discharged from the space formed between the cylinder and the piston. That is, the technical solution described in this publication is the same as that of the conventional pneumatic cylinder described in Patent Document 1, and there is still room for improvement in the problem of increased starting resistance of the sealing component of the pneumatic cylinder after long-term non-use.

[0014] The pneumatic cylinder type retracting mechanism with a single-acting air cylinder provided in the measuring device has problems in terms of the starting resistance of the retracting mechanism, the measuring accuracy of the measuring device and the measuring time. The purpose of the present disclosure is to solve at least any of the above problems. Means of solving problems

[0015] One embodiment of the retraction mechanism disclosed herein is a pneumatic cylinder type retraction mechanism, which has a cylinder and a piston capable of reciprocating inside the cylinder, and the piston is reciprocated using air pressure. The sealing unit of the pneumatic cylinder type retraction mechanism is arranged on the inner periphery of the cylinder opposite to the outer periphery of the piston, and is a static sealing unit. The sealing unit suppresses the leakage of pressurized air that makes the piston work from the cylinder. Effects of the Invention

[0016] The present disclosure can achieve at least one of the following effects: reducing the starting resistance of the retracting mechanism, improving the measurement accuracy of a measuring device having the retracting mechanism, shortening the measurement time of the measuring device having the retracting mechanism, or miniaturizing the measuring device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a diagram showing a usage example of a sizing device including the retracting mechanism according to the present embodiment. Figure 2 This is a schematic longitudinal sectional view of one embodiment of a sizing device. Figure 3A It is a longitudinal sectional view of the main part of the retracting mechanism. Figure 3B It is a partial cross-sectional view (stereoscopic view) of the sealing unit. Figure 3C It is a cross-sectional view of a part of the retracting mechanism according to the embodiment in which a Y-shaped seal is accommodated in a circumferential groove formed in the cylinder. Figure 3D It is a cross-sectional view of a part of the retraction mechanism of the embodiment in which a Y-type seal is accommodated in a circumferential groove formed in the cylinder (a state in which the piston head is moved upward). Figure 3E It is a cross-sectional view of a part of a conventional retraction mechanism in which a Y-type seal is accommodated in a circumferential groove formed in a piston head. Figure 3F It is a cross-sectional view of a part of a conventional retraction mechanism in which a Y-type seal is accommodated in a circumferential groove formed in a piston head (a state in which the piston head is moved upward). Figure 4A The diagram shows a comparison of the sliding resistance of the retracting mechanism of the embodiment and the retracting mechanism of the prior art. The experimental results of the retracting mechanism of the embodiment are shown by circles, and the experimental results of the retracting mechanism of the prior art (comparative example) are shown by triangles. Figure 4B This is a schematic cross-sectional view of a retracting mechanism of a conventional structure used in experiments. Figure 5A is a transverse (horizontal) cross-sectional view of the retraction mechanism. Figure 5B yes Figure 3A The AA line sectional view is a vertical sectional view at a position displaced from the center line of the piston rod. DETAILED DESCRIPTION

[0018] The first embodiment of the retraction mechanism disclosed in the present invention is a pneumatic cylinder type retraction mechanism, which has a cylinder and a piston capable of reciprocating inside the cylinder, and the piston is reciprocated using air pressure. The sealing unit of the retraction mechanism is arranged on the inner periphery of the cylinder opposite to the outer periphery of the piston, and is a static sealing unit. The sealing unit suppresses the leakage of pressurized air that makes the piston work from the cylinder.

[0019] The retraction mechanism of the first embodiment has a static sealing unit disposed on the inner periphery (surface) of the cylinder. Therefore, when the piston is pushed out by applying pressure, the sealing unit contacts the outer peripheral surface of the piston and seals the outer peripheral surface of the piston and the cylinder. On the other hand, when the piston is pulled back by exhausting the air, the static sealing unit is not likely to become an obstacle to the movement of the piston. Therefore, it is possible to prevent the degradation of the starting characteristics. In addition, the retraction action can be performed smoothly without increasing the diameter of the elastic body (such as a spring, etc.) and the cylinder included in the pneumatic cylinder serving as the retraction mechanism, thereby eliminating the need to enlarge the retraction mechanism in order to enhance the driving force of the retraction mechanism.

[0020] In the second embodiment of the retraction mechanism of the present invention, based on the first embodiment, the sealing unit is a lip-type sealing gasket, which has a lip portion made of elastic material. When pressurized air is introduced into the cylinder in order to push the piston out, the lip portion is pushed against the outer peripheral surface of the piston to inhibit the pressurized air from leaking in the sliding direction of the piston.

[0021] The lip seal is a sealing unit that utilizes the deformation of the lip due to air pressure. Since the lip is made of elastic material, it can actively deform following the changes in the pressurized state and the sliding of the piston. When pressurized air is introduced, the lip deforms due to the air pressure to seal between the cylinder and the piston. On the other hand, when the pressurized air is removed (exhausted), the lip returns to its shape before being pressurized. Since the lip seal is arranged on the inner circumference of the cylinder, when the lip returns to its original shape, the lip seal does not contact the piston, or even if it contacts the piston lightly, it will follow the sliding of the piston and is therefore less likely to hinder the sliding of the piston. Therefore, starting resistance is more easily reduced.

[0022] The third embodiment of the retraction mechanism of the present disclosure is based on the retraction mechanism of the second embodiment, wherein the piston has a piston head capable of sliding on the inner wall of the cylinder and a piston rod extending downward from the center of the piston head in the reciprocating direction of the piston, and the piston head is in sliding contact with the lip.

[0023] In the third embodiment, since the piston head is configured to be able to slide on the inner wall of the cylinder, spaces can be formed on the upper and lower sides of the piston head. In these spaces, pressurized air can be introduced, elastic bodies can be accommodated, and elements for driving the retracting mechanism can be effectively arranged. As described above, the device can be further miniaturized.

[0024] A fourth embodiment of the retracting mechanism of the present disclosure is based on the third embodiment and further includes an elastic body, and the piston is pulled back by the restoring force of the elastic body.

[0025] The fourth embodiment is provided with an elastic body for pulling back. Therefore, the piston can be pushed out using the pressing of the pressurized air, and the elastic body's restoring force (elastic force, acting force) can be used to pull it back. The elastic body can be arranged in one of the spaces divided by the piston head (for example, the piston rod side). According to the fourth embodiment, when the piston is pushed out by the pressurized air, the lip of the lip-shaped seal is deformed by the pressure, thereby sealing between the inner wall of the cylinder and the piston head. On the other hand, when pulling back, the pressurized air is exhausted and the piston is pulled back by the restoring force of the elastic body. When pulling back, the lip made of the elastic material returns to its original shape and does not hinder the sliding of the piston (head). In this way, the starting resistance can be reduced. In addition, usually, even if the pullback is achieved by the restoring force of the elastic body, which sometimes has to rely on a smaller force, it is easier to improve the measurement accuracy of the measuring device because the friction resistance generated in the sliding part is smaller. In addition, it is easier to shorten the time required for pulling back, so as a result, it is easier to shorten the measurement time.

[0026] The fifth embodiment of the retraction mechanism of the present disclosure is based on the fourth embodiment, wherein the elastic body is a coil spring, and the piston head has a space between the side wall opposite to the inner wall of the cylinder with a gap and the piston rod, and the coil spring wound on the piston rod is maintained in the space.

[0027] According to the fifth embodiment, since the coil spring as an elastic body is accommodated in the space below the piston head, the space can be effectively utilized, and the retraction mechanism can be miniaturized. As a result, the measuring device including the retraction mechanism can also be miniaturized.

[0028] A sixth embodiment of the retracting mechanism in the present disclosure is based on the fifth embodiment, and the lip seal is a Y-shaped seal or a U-shaped seal.

[0029] Generally, V-shaped gaskets and the like are often used in overlapping manners, but Y-shaped gaskets or U-shaped gaskets are often designed to be provided with one gasket at an applicable position, and a retraction mechanism having such a gasket can sometimes be more compact.

[0030] The seventh embodiment of the retraction mechanism of the present invention is based on the third embodiment, in which a cylinder seat is arranged at the lower part of the piston head to form an exhaust passage, wherein the exhaust passage has a notch provided on the upper surface of the cylinder seat and extending in the transverse direction, and a connecting passage provided in the shell component that accommodates the retraction mechanism and connected to the notch.

[0031] A first embodiment of the dimension measuring device disclosed in the present invention comprises: a probe that abuts against a workpiece; an arm, one end of which is connected to the probe and the other end of which is connected to the measuring head including a differential transformer; a holding table that holds the arm so that it can swing; and a swing unit that swings the arm, the swing unit comprising a tension spring and a retraction mechanism of any one of the first to seventh embodiments.

[0032] Hereinafter, embodiments of the retracting mechanism will be described using the drawings. Figure 1 1 is a schematic perspective view of an outer diameter measuring device 60 for measuring the outer diameter of a workpiece W. In the outer diameter measuring device 60, a control processing device 20 and a compressed air source 10 are attached to a pair of universal measuring heads. As described later, the outer diameter measuring device 60 includes a retracting mechanism 100 as a pneumatic cylinder for pulling (retracting) the probe 300 away from the workpiece W before or after measurement. During measurement, a spring included in the retracting mechanism 100 causes the probe 300 to contact the workpiece W, and the control processing device 20 processes the output of the working transformer unit.

[0033] Figure 2 1 is a longitudinal sectional view showing details of the outer diameter measuring device 60. The outer diameter measuring device 60 includes a housing member 190 of a substantially rectangular parallelepiped shape, a retracting mechanism 100 as a pneumatic cylinder housed therein, and a differential transformer 180. The lever shaft 132 connected to the probe 300 via an arm 234 extends laterally from the housing member 190. A bellows 220 capable of causing the lever shaft 132 to perform a precession motion is provided between the housing member 190 and the lever shaft 132, and locking portions 222 and 224 are formed at both ends of the bellows 220, respectively. In the housing member 190, the swing shaft 140 is substantially arranged on the lever shaft 132 in a direction perpendicular to the lever shaft 132, and the swing shaft 140 is fitted into a through hole provided in a holding table 142 provided in the middle portion of the lever shaft 132 in the longitudinal direction. Therefore, the lever shaft 132 can swing around the swing shaft 140.

[0034] One side of the housing member 190 is in an open shape, and one end side of the bellows 220 is airtightly held in the opening by a locking portion 222. The other end side of the bellows 220 is airtightly connected to the end 132b of the lever shaft 132 via a locking portion 224. The end 132b of the lever shaft 132 on the side where the bellows 220 is mounted is connected to the arm 234 via a connecting member 232 so that the position can be adjusted.

[0035] A probe holder 236 for holding the probe 300 is mounted on the top end of the arm 234 on the opposite side to the side connected to the lever shaft 132. By adjusting the stop screw 238 fixed to the probe holder 236, the contact part 240 at the top end of the probe 300 is moved in a certain direction. Figure 2 The position can be adjusted in the up and down directions. Figure 1 When measuring the outer diameter as shown, the contact part 240 of this example arranged on the upper side is pressed downward, and the contact part 240 of this example arranged on the lower side is pressed upward, and the workpiece W is clamped for measurement. Hereinafter, the outer diameter measuring device 60 on the upper side will be described. However, the outer diameter measuring device 60 on the lower side has the same structure and function as the outer diameter measuring device 60 on the upper side except that the upper and lower parts are reversed.

[0036] In order to push the contact part 240 downward, a tension spring 146 is provided in the housing member 190 and on the side 132a opposite to the probe side of the holding platform 142 of the lever shaft 132. One end of the tension spring 146 is locked in the support shaft 148 protruding to the inner side of the housing member 190, and the other end of the tension spring 146 is locked in the locking piece 134 provided in the middle part of the longitudinal direction of the lever shaft 132. Therefore, the tension spring 146 acts in a manner of pulling the lever shaft 132 closer at this position, and as a result, the lever shaft 132 swings around the swing shaft 140 as the center, and then pushes the arm 234 downward. Thus, measurement can be performed. The differential transformer 180, the tension spring 146, and the swing shaft 140, which are shown in detail below, constitute a swing unit.

[0037] A displacement shaft 182 is vertically mounted on the lever shaft 132 near the end 132a of the lever shaft 132 on the opposite side of the probe, and a coil 184 is wound around the displacement shaft 182 to form a differential transformer 180. The signal of the differential transformer 180 is input to the terminal processing unit 186 and processed, and then introduced into the control processing device 20 (see Figure 1 ).

[0038] When measurement is completed or when measurement is ready, the contact part 240 is moved away from the workpiece W to protect both the contact part 240 and the workpiece W. Therefore, the retraction mechanism 100 as a pneumatic cylinder is disposed in the longitudinal direction of the lever shaft 132 and between the tension spring 146 and the differential transformer 180 .

[0039] The retracting mechanism 100 mainly comprises: a cap-shaped cylinder 110; a piston 120 which can slide in the cylinder 110 and has a piston head 116 and a piston rod 118; a cylinder seat 112 which is located below the cylinder 110 and is in sliding contact with the lower part of the piston rod 118; and a coil spring 122 which is wound around the piston rod 118 and is arranged between the piston head 116 and the cylinder seat 112. One end side (upper side) of the piston rod 118 is accommodated in the cylinder 110, and the other end side (lower side) extends downward from the cylinder seat 112. The abutment portion 136 which is the lower end portion of the piston rod 118 can abut against the lever shaft 132.

[0040] When the force of the coil spring 122 is applied as in the non-use state or during measurement, the retracting mechanism 100 stops its action. That is, since the air pressure does not act on the space 108 formed between the cylinder 110 and the piston head 116, the space 108 becomes the same atmospheric pressure as the space 106 of the piston head that is connected to the external atmosphere, and the spring force of the coil spring 122 becomes dominant, lifting the piston rod 118 upward. At this time, the lever shaft 132 that contacts the piston rod 118 rotates rightward in the figure around the swing shaft 140 by the tension spring 146, and the probe 300 located at the top of the arm 234 connected to the top of the lever shaft 132 moves downward. In addition, during measurement, the probe 300 contacts the workpiece W and stops moving downward, and the state at this time is measured by the differential transformer 180 provided at the end of the lever shaft 132 on the opposite side of the probe 300. When not measuring, the lever shaft 132 rotates to a position corresponding to the spring force of the tension spring 146 and maintains this position.

[0041] On the other hand, when preparing for measurement or immediately after measurement, the piston rod 118 moves downward against the force of the coil spring 122, and its lower end abuts against the lever shaft 132 to press the lever shaft 132 downward. At this time, the retracting mechanism 100 as a pneumatic cylinder introduces pressurized air into the space 108 formed between the cylinder 110 and the piston head 116. As a result, the contact part 240 is separated from the workpiece W.

[0042] The above is an overview of the outer diameter measuring device 60 using a general single-axis cylinder 110. Figure 3A to Figure 3F The sealing unit (static sealing unit) which is a characteristic structure of the present embodiment will be described in more detail. Figure 3A is a longitudinal sectional view of the main part of the retracting mechanism 100, Figure 3B This is a three-dimensional diagram showing a portion of the sealing unit removed. Figure 3C to Figure 3F It is a diagram for explaining the operation of the sealing unit.

[0043] The sealing unit is also called a lip seal. In this embodiment, a so-called Y-shaped seal 150 is used, but a U-shaped seal or a V-shaped seal of a similar shape can also be used. The Y-shaped gasket 150 is a gasket formed of an elastic material (vulcanized rubber, thermosetting resin, thermoplastic resin, etc.), and is disposed in a circumferential groove 111 formed in the middle portion in the vertical direction of the inner peripheral surface 110 d of the cylinder 110 .

[0044] like Figure 3BAs shown, the Y-type gasket 150 has two lips 162 formed from the base 160 to the upper part in its circumferential section, and the overall cross-sectional shape is a Y. The Y-type gasket 150 is composed of two lips 162 and a groove 164 formed therebetween to form a pressure-bearing surface. The Y-type gasket 150 is configured in such a way that the pressure-bearing surface faces the high-pressure side and the base 160 faces the low-pressure side. When the pressure-bearing surface is subjected to pressure, the lips 162 are pushed open and pressed against the wall surface (here, the outer periphery of the piston head 116 and the inner periphery of the cylinder 110), thereby performing a sealing function.

[0045] The sealing function of the Y-type seal 150 is described in detail. First, the outer peripheral surface 116a of the piston head 116 is in sliding contact with the lip 162 of the Y-type seal 150. When the pressurized air is introduced into the space 108 above the piston head 116, the pressurized air is introduced into the groove 164 formed between the lip 162. With the pressurized air, the inner diameter (inner circumference) side of the lip 162 is pushed in the direction of decreasing diameter (inner circumference direction) and is pushed against the outer peripheral surface of the piston head 116, and the outer diameter (outer circumference) side of the lip 162 is pushed in the direction of increasing diameter (outer circumference direction) and is pushed against the cylinder 110. As a result, the gap between the cylinder 110 and the piston head 116 is closed, preventing the compressed air from leaking from the space 108 to the cylinder base 112 side (see Figure 3C ).

[0046] Next, use Figure 3C to Figure 3F The operation of the retracting mechanism 100 of the present embodiment configured in this manner will be described. Figure 3C and Figure 3D 1 is a cross-sectional view of a portion of the retracting mechanism 100 according to the embodiment in which a Y-shaped seal 150 is accommodated in a circumferential groove 111 formed in a cylinder 110 . on the other hand, Figure 3E and Figure 3F It is a cross-sectional view of a part of the conventional retraction mechanism in which a Y-shaped seal 150 is housed in a circumferential groove 109 formed in a piston head 116 .

[0047] Next, the status of each figure is explained. First, Figure 3C and Figure 3E 1 is a diagram showing a state in which the retracting mechanism 100 is activated and the piston 120 is pressed down to the lowest position. Figure 3D and Figure 3F This is a diagram showing a retraction operation in which the action of the retraction mechanism 100 (exhaustion of pressurized air) is stopped, and the piston 120 is lifted (pulled back) upward by the extension (restoring force) of the coil spring 122 as an elastic body. It should be noted that, in order to facilitate understanding of the operation, the deformation of the Y-shaped gasket 150 is exaggerated in all the drawings.

[0048] exist Figure 3C In the embodiment, the retracting mechanism 100 works, the space 108 is in a state of high pressure, and the lip 162 on the inner peripheral side of the Y-type sealing gasket 150 is pushed open by the pressurized air and is pushed against the outer peripheral surface 116b of the piston head 116. At this time, the pushed surface 116c becomes a circumferential shape. In addition, similarly, the lip 162 on the outer peripheral side of the Y-type sealing gasket 150 is also pushed against the inner peripheral surface of the cylinder 110. Thus, the compressed air is suppressed from leaking in the direction (lower side) where the piston 120 is pushed out.

[0049] On the other hand, Figure 3E In the process, the retracting mechanism 100 (pneumatic cylinder) works, the space 108 is in a high pressure state, and the lip 162 on the outer peripheral side of the Y-type seal 150 is pushed open by the pressurized air and pressed against the inner peripheral surface 110d of the cylinder 110. At this time, the pushed surface 110c becomes a circular shape. In addition, similarly, the lip 162 on the inner peripheral side of the Y-type seal 150 is also pressed against the inner peripheral surface of the piston head. Figure 3C Likewise, leakage of compressed air in the direction (downward) in which the piston 120 is pushed out is suppressed.

[0050] from Figure 3C , Figure 3E The state of retraction mechanism 100 (pneumatic cylinder) stops pressurizing space 108, and pressurized air is discharged from space 108. When the pressure is reduced to approximately atmospheric pressure, the air pressure exerting force on the coil spring 122 wound on the piston rod 118 is lost, so the coil spring 122 stretches due to the restoring force, and the piston 120 is pulled back upward. thus, Figure 3C becomes Figure 3D status, Figure 3E becomes Figure 3F status.

[0051] exist Figure 3D In the embodiment, as the piston head 116 rises, the lip portion 162 on the inner peripheral side in contact with the piston head 116 is deformed so as to be pulled upward. On the other hand, Figure 3F In the embodiment, as the piston head 116 rises, the lip portion 162 on the outer peripheral side in contact with the cylinder 110 is bent downward and deformed in a rolled manner. Although the pressure-bearing surfaces of the Y-type seals 150 are all arranged toward the high-pressure side, the deformation mode of the Y-type seals 150 is different depending on whether the Y-type seals 150 are arranged on the cylinder 110 (fixed) side or the piston 120 (moving) side.

[0052] Comparing the above situation, Figure 3D Such deformation is deformation along the movement of the piston head 116. On the other hand, Figure 3FSuch deformation is deformation against the movement of the cylinder 110, so the friction force μF is more likely to increase. This becomes more significant when the Y-type seal 150 is stuck to the contact portion (piston head 116 or cylinder 110) due to a longer supply time (holding time) of compressed air.

[0053] As described above, the retraction mechanism of the present embodiment is constructed such that the Y-shaped sealing gasket 150 is arranged on the cylinder 110 side (fixed side), and when the pressurized air is introduced, the lip 162 is pushed against the outer periphery of the piston 120 (moving side) to suppress the leakage of the pressurized air in the sliding direction (downward direction) of the piston 120. In other words, the Y-shaped seal 150 is disposed in the cylinder 110 such that the moving direction (downward direction) of the piston 120 during pressurization is opposite to the direction (upward direction) of the pressure receiving surface of the Y-shaped seal 150 .

[0054] Therefore, during decompression, the moving direction (upward direction) of the piston 120 is the same as the direction (upward direction) of the pressure-receiving surface of the Y-type seal 150. Furthermore, if the Y-type seal 150 is disposed on the cylinder 110 side, the deformation of the lip 162 during retraction naturally follows the movement of the piston head 116 (moving side). On the other hand, in the above state, if the Y-type seal 150 is arranged on the moving side (the piston head 116 ), the deformation of the lip portion 162 naturally resists the movement of the piston head 116 .

[0055] In particular, when the retraction action, i.e., the pulling action, is performed by utilizing the restoring force of the elastic body as in this embodiment, the force may have to be designed to be smaller than when the push-out action is performed by utilizing the air pressure. However, with the retraction mechanism of this embodiment, even when the pulling force is reduced, the measurement accuracy of the measuring device is more easily improved due to the characteristic that the friction force μF is easily reduced, and the time required for pulling back is more easily shortened, so as a result, the measurement time is more easily shortened.

[0056] Next, the results of confirming the effects of this embodiment through experiments will be described. Figure 4A This is a diagram showing a comparison of the sliding resistance of the retracting mechanism 100 of the present embodiment and the retracting mechanism of the existing structure. The horizontal axis represents the pressure supply time (recorded as "Time of pressurized air supply (hours)" in the figure. The unit is hour (s)). In addition, the vertical axis represents the sliding resistance (recorded as "sliding friction (N)" in the figure. The unit is N). exist Figure 4A In FIG. 1 , the experimental results of the retracting mechanism 100 of the present embodiment are shown by circular marks. On the other hand, the experimental results of the retracting mechanism of the conventional structure (comparative example) are shown by triangular marks.

[0057] It should be noted that Figure 4B FIG. 1 is a schematic cross-sectional view of a conventional retracting mechanism 100a used in the experiment. Figure 4B In the figure, the cylinder is composed of an upper cylinder 110a and a side cylinder 110b, but there is almost no difference in the internal shape of the cylinder 110. In addition, the state where the piston 120 moves to the lowest position is shown by a dot-dash line.

[0058] Follow the steps below to get Figure 4A The experimental results.

[0059] (Step 1) First, remove the coil spring 122 from the retracting mechanism 100, 100a as the pneumatic cylinder. Figure 4B In the figure, the coil spring is omitted.

[0060] (Step 2) Next, pressurized air is introduced into the space 108 between the cylinder 110 and the piston head 116 of the retracting mechanism 100, 100a. The pressurized state is left or maintained for a predetermined time. This is referred to as "pressure supply time (Hr)".

[0061] (Step 3) The pressurization of the space 108 is stopped, and the pressurized air is exhausted until the space 108 reaches substantially the atmospheric pressure.

[0062] (Step 4) The starting resistance of the piston 120 is measured using a dynamometer, and this resistance is defined as "sliding resistance".

[0063] according to Figure 4A The experimental results made the following clear. (Viewpoint 1) The retraction mechanism of the present embodiment including the Y-shaped seal disposed on the inner wall of the cylinder has a smaller starting resistance regardless of the pressure supply time.

[0064] The above viewpoints show that the retraction mechanism of the present embodiment requires less force for the retraction action than the conventional retraction mechanism. It can be seen that, even when the restoring force of the elastic body is used to pull back the piston, the measurement time can be further shortened and the measurement accuracy can be further improved by using a measuring device having the retraction mechanism of the present embodiment.

[0065] (Viewpoint 2) Regardless of the pressure supply time, the ratio of the starting resistance is more than 2 times, and the difference is at least about 2N. This shows that the effectiveness of the retracting mechanism of this embodiment is more significant than expected.

[0066] (Viewpoint 3) There is a tendency that the longer the pressure supply time is, the larger the difference in sliding resistance is. In the retracting mechanism of this embodiment, even if the pressure supply time increases, the sliding resistance does not increase much. On the other hand, it is known that in the conventional retracting mechanism, when the pressure supply time increases, the sliding resistance increases significantly. This indicates that the effect of the present embodiment is more significant when the pressure supply time is long and the Y-type gasket 150 is adhered to the other material.

[0067] Next, use Figure 5A , Figure 5B An exhaust system and the like for bringing the space 108 to atmospheric pressure will be described. Figure 5A is a cross-sectional view of the retraction mechanism 100 as a pneumatic cylinder, Figure 5B BB line cross-sectional view. Figure 5B yes Figure 3A The AA line cross-sectional view is a cross-sectional view at a position displaced from the center line of the piston rod 118.

[0068] A notch 178 extending in the width direction of the retraction mechanism 100 is formed on the upper surface of the cylinder block 112 on the outer diameter side and facing the bottom surface of the piston head 116 at a position displaced from the center. The notch 178 is connected to an air groove 170 extending to the widthwise end surface of the housing member 194, and a communication passage 172 extending in the vertical direction is connected near the end of the air groove 170. A passage extending to the outside of the retracting mechanism 100 is formed at the upper portion of the communication passage 172, and a joint 174 such as a hose joint is installed in the passage. By configuring the exhaust system as described above, the device can also be housed in the compact housing member 194 . Description of Reference Numerals

[0069] 10: compressed air source; 20: control processing device; 60: measuring device; 100: retracting mechanism; 106, 108: space; 109: circumferential groove; 110: cylinder; 110a: upper cylinder; 110b: side cylinder; 110c: (contact) surface; 110d: inner circumferential surface; 111: circumferential groove; 112: cylinder seat; 116: piston head; 116a: (piston) side wall; 116b: (piston) outer wall surface; 118: piston rod; 120: piston; 122: coil spring; 132: lever shaft; 132a: opposite side of the probe side; 132b: (side) end; 134: locking member; 1 36: abutment portion; 140: swing axis; 142: holding platform; 146: tension spring; 148: support shaft; 150: Y-type sealing pad; 160: base; 162: lip; 164: groove; 170: air groove; 172: connecting path; 178: notch; 180: differential transformer; 182: displacement axis; 184: coil; 186: terminal processing portion; 190: housing component; 194: housing component; 220: bellows; 222, 224: locking portion; 232: connecting member; 234: arm; 236: probe holder; 238: stop screw; 240: contact portion; 300: probe; W: workpiece.

Claims

1. A pneumatic cylinder type retracting mechanism, comprising a cylinder and a piston capable of reciprocating inside the cylinder, wherein the piston is reciprocated using air pressure, characterized in that: The sealing unit is provided at an inner periphery of the cylinder facing an outer periphery of the piston and is a static type sealing unit that suppresses leakage of pressurized air for operating the piston from the cylinder.

2. The retraction mechanism according to claim 1, characterized in that: The sealing unit is a lip-type sealing gasket, The lip seal has a lip portion made of elastic material. When pressurized air is introduced into the cylinder in order to push out the piston, the lip portion is pressed against the outer peripheral surface of the piston to suppress leakage of the pressurized air in the sliding direction of the piston.

3. The retraction mechanism according to claim 2, characterized in that: The piston has a piston head that can slide on the inner wall of the cylinder and a piston rod that extends downward from the center of the piston head in the reciprocating direction of the piston. The piston head is in sliding contact with the lip.

4. The retraction mechanism according to claim 3, characterized in that: An elastic body is also provided, and the piston is pulled back by utilizing the restoring force of the elastic body.

5. The retraction mechanism according to claim 4, characterized in that: The elastic body is a coil spring, The piston head has a space between a side wall facing the cylinder inner wall with a gap therebetween and the piston rod, and the coil spring wound around the piston rod is held in the space.

6. The retraction mechanism according to claim 5, characterized in that: The lip-shaped sealing gasket is a Y-shaped sealing gasket or a U-shaped sealing gasket.

7. The retraction mechanism according to claim 3, characterized in that: A cylinder seat is disposed below the piston head to form an exhaust passage including a notch provided on an upper surface of the cylinder seat and extending in a lateral direction and a communication passage provided in a housing member that accommodates the retracting mechanism and connected to the notch.

8. A size measuring device, characterized in that: have: A probe that abuts a workpiece; an arm, one end of which is connected to the probe and the other end of which is connected to a measuring head including a differential transformer; a holding table that holds the arm so that it can swing; and a swing unit that swings the arm, the swing unit having a tension spring and a retraction mechanism as described in any one of claims 1 to 7.

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