Thermal caulking device

The present invention provides a thermal caulking device which can quickly heat and cool an object to be caulked with low electrical power. Provided is a thermal caulking device which caulks a portion of a plastic part 7 as an object to be caulked, the thermal caulking device including: a metal tip 3 having a pressing part 3a which presses the object to be caulked and a heating rod 3c which is provided upright at a center part of the pressing part 3a; heating means 10c for heating the heating rod 3c; a cooling pipe 9 which cools the heating rod 3c; cooling fluid supply means 4 for supplying a cooling fluid to the cooling pipe 9; a holder 1 which holds the metal tip 3 and the cooling pipe 9 so that the cooling pipe 9 delivers the cooling fluid toward the heating rod 3c; and control means 6 for controlling the heating means 10c and the cooling fluid supply means 4, wherein the control means 6 heats the pressing part 3a from the heating rod 3c by the heating means 10c, and after the object to be caulked is thermally caulked by the pressing part 3a, supplies the cooling fluid from the cooling fluid supply means 4 to the cooling pipe 9 to cool the pressing part 3a from the heating rod 3c.

TECHNICAL FIELD

The present disclosure relates to a thermal caulking device, and more particularly to a thermal caulking device which caulks a plastic part using a metal tip heated by high-frequency induction heating or electrical heating.

BACKGROUND ART

In general, a method of caulking a boss is widely practiced as a method for fixing a metal plate etc. to a plastic part. In this method, a columnar protrusion (hereinafter referred to as a “boss”) of a proper size is provided at a predetermined position in a plastic part, while a hole into which the boss can be inserted is bored in a metal plate or a plastic plate to be fixed to the plastic part. After the two are fitted together, the boss protruding from the hole is subjected to ultrasonic vibration or heat to melt and deform and thereby caulk the boss.

The method using heat is today widely used because of its advantages over the method using ultrasonic vibration: (1) beautiful finish, (2) no influence of vibration on the part, (3) simple principle, hence easy maintenance, and (4) relatively low device cost compared with ultrasonic vibration. A heater used for caulking a boss is molded of a nichrome plate or formed by cutting a metal having a relatively high electrical resistance, and the heater uses Joule heat which is generated as a high current is passed therethrough.

One example of conventional thermal caulking devices is shown inFIG. 22. For the thermal caulking device shown inFIG. 22, a perforated metal plate8′ is fitted with a boss7a′ which is a columnar protrusion of a plastic part7′. This thermal caulking device thermally caulks the boss7a′ by pressing a metal tip30, heated to or above the softening temperature of the plastic part7′, against the leading end of the boss7a′.

As shown inFIG. 22, lead wires31a,31bare electrically connected by welding or screw fixation to flanges30e,30f, respectively, of the metal tip30which serves as a caulking heater. In a cavity30cof the metal tip30, a plastic cooling pipe32, which delivers cooling air cooled to or below normal temperature, is disposed so that the opening end of the cooling pipe32is located near a pressing part30a. The metal tip30, the lead wires31a,31b, and the cooling pipe32are molded, for example, with epoxy resin34, so as to retain their respective desired positions.

FIG. 23is an external perspective view of the metal tip30as a single part. The metal tip30shown inFIG. 23has the pressing part30awhich has an upwardly convex spherical surface, and a cylindrical wall part30brises from around the pressing part30a, forming the cavity30cinside the metal tip30. The wall part30bis divided by slits30sinto left and right portions, and the flanges30e,30fare formed at the upper end of the wall part30b.

InFIG. 22, the pressing part30aof the metal tip30is depicted at a position above and at a distance from the boss7a′. When thermal caulking work is performed, a current flows from the lead wires31a,31bto the metal tip30, and the metal tip30is heated by Joule heat. Upon reaching a predetermined temperature, the metal tip30is lowered as indicated by the arrow Y to bring the pressing part30ainto contact with the leading end of the boss7a′. Then, the leading end of the boss7a′ is softened and melted by the heat of the metal tip30. Thereafter, the application of a current to the lead wires31a,31b, is stopped, and cooling air is sprayed from the cooling pipe32to the pressing part30aof the metal tip. The cooling air flows through the slits30sto the outside. The metal tip30and the leading end of the boss7a′ are cooled to a temperature equal to or lower than the softening point of plastic to solidify the leading end of the boss7a′. Then, the metal tip30is raised again, which completes the caulking work.

FIG. 24AandFIG. 24Bare cross-sectional view showing a state at the start of thermal caulking work and a state at the end of the thermal caulking work.FIG. 24Ashows a stage in which a current is applied from the lead wire31ato the lead wire31bto heat the metal tip30, and the pressing part30ais pressed against the leading end of the boss7a′ to melt and deform the boss7a′. Specifically, inFIG. 24A, electrical power is supplied from a power source (not shown) to the lead wire32a, and a current flows from the lead wire31ato the flange30e, the wall part30b, the pressing part30a, the wall part30b, and the flange30fof the metal tip30, and the lead wire31b. Thus, the flange30e, the wall part30b, the pressing part30a, the wall part30b, and the flange30fare heated in this order according to the flow of the current. When the pressing part30areaches a temperature exceeding the softening point of plastic, deformation of the leading end of the boss7a′, i.e., caulking work starts. By being pressed with the pressing part30a, the leading end of the boss7a′ assumes a predetermined shape.

FIG. 24Bshows a state in which, after the leading end of the boss7a′ has been melted and deformed, the application of a current from the lead wire31ato the lead wire31bis stopped, and coaling air is sprayed from cooling air delivery means (not shown) through the cooling pipe32to the pressing part30ainside the cavity30cto discharge the heat of the metal tip30and the melted boss7a′ through the slits30sand thereby cool the metal tip30and the boss7a′. The flow of the cooling air inside the cavity30cof the metal tip30is indicated by the arrows inFIG. 24B. The cooling air collides with the pressing part30ainside the cavity30c, rises along the wall part30b, and flows through the slits30sto the outside of the metal tip30. That is, the heat of the metal tip30and the melted boss7a′ is discharged through the slits30s. Thus, the boss7a′ of the plastic part7′, which is a molded part, is melted, deformed, cooled, and solidified, so that the perforated metal plate8is fixed to the plastic part7′ (e.g., see Patent Document 1).

FIG. 25is a schematic cross-sectional view of another conventional plastic part thermal caulking device which uses high-frequency induction heating means as metal tip heating means. In the thermal caulking device shown inFIG. 25, a plurality of metal tips40, each having a cavity60through which a cooling fluid is circulated, are respectively attached under cooling pipes70, and an induction heating coil51is wound on the outer periphery of each metal tip40. A high-frequency induction power source50is used to pass a high-frequency current through the coil51and generate an induced current in the metal tip40to thereby heat the metal tip40. Then, a pressing part45of the headed metal tip40is pressed against the leading end of the boss7a′ to melt and deform the leading end of the boss7a′. After the leading end of the boss7a′ has been melted and deformed, the application of a high-frequency current to the coil51is a stopped, and a cooling fluid, such as cooling air, is sprayed from the cooling pipe70inside the cavity60of the metal tip40in the direction toward the pressing part45, to cool the metal tip40and the heated and melted boss7a′. Thus, the boss7a′ of the plastic part7′, which is a molded part, is melted, deformed, cooled, and solidified, so that the perforated metal plate (object to be fixed)8′ is fixed to the plastic part7′. Since high-frequency induction heating can instantly heat the metal tip40, it has an advantage over electrical heating in that the caulking step takes a shorter time (e.g., see Patent Document 2).

Thermal caulking of plastic parts is used not only for caulking bosses and shaft parts of about several millimeters in diameter, such as thermally caulking the rotation shaft of plastic scissors of daily use, but also for thermally caulking smaller plastic parts. For example, in the case of a forceps-type electrical treatment tool shown inFIG. 26, a first forceps piece12band a second forceps piece14bare incorporated into a support67mounted at the leading end of a catheter tube47which can be inserted into the body, and the first forceps piece12band the second forceps piece14bare supported on a plastic support shaft80. The support shaft80is thermally caulked after the support67, the first forceps piece12b, and the second forceps piece14bare passed therethrough, and thus the first forceps piece12band the second forceps piece14bare assembled so as to be able to open and close (e.g., see Patent Document 3).

FIG. 27is a schematic view showing a step in which heated rod-like metal tips110are pressed respectively against both ends of the support shaft80of the support67mounted at the leading end of the catheter tube47to thermally caulk the support shaft80. The catheter tube47is intended to be inserted into the body, such as a blood vessel, and the support67as well as the support shaft80counted at the leading end of the catheter tube47are also small parts. During operation, the first forceps piece12band the second forceps piece14bat the leading end of the catheter tube47inserted into the body are required to open and close as intended by a surgeon (doctor). It is undesirable that, the first forceps piece12band the second forceps piece14bdo not move smoothly due to too tight caulking, or that the first forceps piece12band the second forceps piece14bcome off due to too loose caulking.

Other than the above example, thermal caulking of a stent which is put inside the body by being mounted at the leading end of a balloon catheter, and thermal caulking of a plastic part at the leading end of an endoscope are also known as examples of thermal caulking of catheter-related plastic parts.

FIG. 28Ashows an extended state of a stent17which is put inside the body by being mounted at the leading end of a balloon catheter.FIG. 28Bshows a state in which the stent17shown inFIG. 28Ais formed into a ring shape and a caulking ring18is put thereon.FIG. 28Cis a schematic view showing a step in which the caulking ring18shown inFIG. 28Bis pressed from both sides in the vertical direction with a pair of heated metal tips120to thermally caulk the caulking ring18(e.g., see Parent Document 4),

FIG. 29shows an endoscope attachment of which a fixing member41is fixed by press-fitting and thermal caulking inside a tube37at a leading end part of an endoscope (e.g., see Patent Document 5).

Thus, for thermal caulking of small plastic parts, especially medical plastic parts, it is required that the thermal caulking device itself strictly manages heating and pressing conditions of the metal tip and performs thermal caulking stably and precisely under the required best heating and pressing conditions.

PRIOR ART DOCUMENT

Patent Document

Patent Document 4: International Publication No. WO 2009-050888

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The conventional example shown inFIG. 22which involves electrical heating has the following problems. (1) Since the electrical resistance of the heater (metal tip30) is low (0.5 to 0.1Ω), a thick electrical wire is required for passing a high current of 20 A to 50 A. Moreover, a transformer for high current is required, so that the size of the power source becomes larger. (2) While it is possible to increase the resistance value by thinning the material of the heater, the metal tip should have a plate thickness of at least 0.2 mm to 0.5 mm, for otherwise the mechanical strength would become insufficient. (3) The heater is required to be heated only at the center part with which the boss first comes into contact. However, the structure as shown inFIG. 22causes unnecessary parts to be heated as well, which was wastefully consumes electrical power as well as requires time for heating before caulking work and time for cooling after caulking work. (4) In the case of the conventional example shown inFIG. 22, the metal tip30cannot be replaced alone when the metal tip30, which is the heater, or the lead wires31a,31bare damaged. (5) A current flows from the lead wire31ato the lead wire31b, and the metal tip30generates heat along the direction in which the current flows. Since the metal tip30is provided with the slits30sfor discharging heat, a temperature difference occurs between both sides of the metal tip30across the slits30s. It is unfavorable that a temperature difference in the pressing part30aof the metal tip results in uneven heating and melting of the boss7a′ and thus in an uneven caulking force. If the center of the boss7a′ cools and solidifies before the surrounding area, the caulking force cannot be expected to increase during solidification of the center part of the boss7a′.

The conventional plastic part thermal caulking device shown inFIG. 25which uses high-frequency induction heating has the following disadvantages. (1) The thickness of the metal tip40is large, and the heat capacity of the metal tip40is large. Even if the metal tip40is reduced in thickness to reduce the heat capacity, since the coil51is wound on the outer side of the metal tip40, a high-output power source for high-frequency induction heating is required due to the large diameter of the coil51. In addition, heating takes time. (2) If the diameter of a boss is larger, the outer diameter of the metal tip40needs to be increased. Then, the outer diameter of the coil51is also increased. If the outer diameter of the metal tip40varies according to the outer diameter of the boss, the coil51needs to be replaced with one corresponding to the outer shape of the metal tip40. (3) The space occupied by the coil51interferes with a caulking worker and limits the work space. The coil51interferes with replacement of the metal tip40.

For the caulking devices described withFIG. 26toFIG. 29which are intended for catheter-related plastic parts, small plastic parts at the leading end part of an endoscope, etc., there is a demand for a small and light thermal caulking device of which the metal tip has a small heat capacity and which allows detailed setting of heating and pressing conditions.

The present invention has been devised to solve such problems, and an object of the invention is to provide a thermal caulking device which can quickly heat and cool an object to be caulked with low electrical power. More specifically, objects of the present invention as embodiments thereof are as follows:

(1) To make it possible to sufficiently caulk a thermoplastic resin boss in a short time using a low-output device;

(2) To provide a plastic part thermal caulking device which is highly responsive to heating and cooling;

(3) To increase the caulking force by heating and melting especially the center part of a boss to the maximum temperature so that the boss is cooled and solidified from the periphery toward the center part;

3) To use the same metal tip for thermally caulking bosses of different diameters, even when the outer diameter of the boss is larger or smaller, by heating the boss from the center toward the outer periphery and varying the length of the heating time so as to produce a required amount of heat with the same metal tip;

(5) To allow the metal tip to be easily attached/removed or replaced alone;

(6) To provide a small and light thermal caulking device; and

(7) To provide a plastic part thermal caulking device, especially of a high-frequency induction heating type, which has a high-frequency induction heating coil provided on the inside, not the outside, of the metal tip so as not to interface with a caulking worker.

Means for Solving the Problems

To achieve the above objects, a thermal caulking device according to the present invention is a thermal caulking device which caulks a portion of a plastic part as an object to be caulked, the thermal caulking device including: a metal tip having a pressing part which presses the object to be caulked, a heating rod provided upright in a center part of the pressing part, and a wall part provided upright on the outer periphery of the pressing part; heating means for heating the heating rod; a cooling pipe which cools the heating rod; cooling fluid supply means for supplying a cooling fluid to the cooling pipe; a holder which holds the metal tip and the cooling pipe so that the cooling pipe delivers the cooling fluid toward the heating rod; and control means for controlling the heating means and the cooling fluid supply means, wherein the control means heats the pressing part from the heating rod by the heating means, and after the object to be caulked is thermally caulked by the pressing part, supplies the cooling fluid from the cooling fluid supply means to the cooling pipe to cool the pressing part from the heating rod.

Advantageous Effects of the Invention

According to the present invention adopting the above means, it is possible to quickly heat and cool an object to be caulked with low electrical power. Specifically, the objects listed above are achieved in the embodiments of the present invention. That is, the following objects are achieved: (1) To make it possible to sufficiently caulk a thermoplastic resin boss using a low-output device; (2) To provide a plastic part thermal caulking device which is highly responsive to heating and cooling; (3) To increase the caulking force by heating and melting especially the center part of a boss to the maximum temperature so that the boss is cooled and solidified from the periphery toward the center part; (4) To use the same metal tip for thermally caulking bosses of different diameters, even when the outer diameter of the boss is larger or smaller, by heating the boss from the center toward the outer periphery and varying the length of the heating time so as to produce a required amount of heat with the same metal tip; (5) To allow the metal tip to be easily attached/removed or replaced alone; (6) To provide a small and light thermal caulking device; and (7) To provide a plastic part thermal caulking device, especially of a high-frequency induction heating type, which has a high-frequency induction heating coil provided on the inside, not the outside, of the metal tip so as not to interfere with a caulking worker.

Moreover, the thermal caulking device of the present invention has the following effects: (1) The thermal efficiency is high, since the heat from the heated metal rod is transferred to only near the part in contact with the boss; (2) The cooling time is short, since the wall part of the metal tip is not directly heated; (3) A thin electrical wire having a cross-sectional area of about 1 mm2suffices, since a current passed through the high-frequency induction heating coil is of 2 A to 5 A; (4) The power source is small and light, since only electronic circuits and electronic parts generating high frequency are required and no large transformer is required; and (5) The metal tip is easy to replace when the metal tip gets dirty or damaged.

MODE FOR CARRYING OUT THE INVENTION

First Embodiment

FIG. 1is an overall configurational view showing a plastic part thermal caulking device according to a first embodiment of the present invention. As shown inFIG. 1, the thermal caulking device is provided with a holder cap2at the leading end of a hollow rod-like holder1, the holder1and the holder cap2holding a metal tip3. The holder1and the holder cap2are made of an insulating material, such as plastic, and grasped by a worker or held by a robot or pressing operation means of other production machines. This thermal caulking device can perform thermal caulking operation of integrating a metal plate8etc., which is laid on a plastic part7and penetrated by a boss7a, by pressing a pressing part of the heated metal tip3against the boss7aof the plastic part7.

InFIG. 1, a cooling pipe9, which will be described in detail later, is disposed inside the holder1, and the holder1has a cooling function of forcibly cooling the metal tip3after thermal caulking. For this purpose, the inside of the holder1is left as a cavity1a. A hole1bis formed in the side surface of the holder1, and the hole1bcommunicates with the inside of a hose4aof which one end is connected to the side surface of the holder1. The other end of the hose4ais connected to a cooling fluid supply machine4. Another hole1dis formed in the side surface of the holder1, and a pair of lead wires10a,10b, bundled into one lead wire bundle10, is passed through the hole1d. The lead wires10a,10bare connected to a heating power source5through the hole1din the side surface of the holder1. The cooling fluid supply machine4and the heating power source5are integrally assembled and form a control unit along with a controller6. While this will be described later in detail, to enable thermal caulking work, the controller6is provided with a control circuit which controls thermal caulking work, a memory which stores various control conditions and stores optimal thermal caulking conditions according to predetermined thermal caulking work, and a thermal caulking condition storage/readout part which stores thermal caulking conditions in the memory and reads out the thermal caulking conditions therefrom.

FIG. 2is a cross-sectional view of the major part showing the metal tip3and the holder1and the holder cap2supporting the metal tip3(hereinafter referred to as a “caulking unit of a thermal caulking device”) of the plastic part thermal caulking device according to the first embodiment of the present invention. The metal tip3is shown in the lowermost part orFIG. 2.FIG. 3Ais a cross-sectional view of the metal tip3, andFIG. 3Bis an external perspective view of the metal tip3.

For the understanding of the present invention, the metal tip3will be described first. The metal tip3as a whole has the shape of a closed-end cylinder, and the bottom pert functions as a plate-like pressing part3awhich presses the boss7aof the plastic part. The plate-like pressing part3ahas an upwardly (toward the holder1) convex spherical surface. A heating rod3cis provided upright at the center of the pressing part3aby welding or brazing, for example. A plate-like wall part3brises upward from the outer periphery of the pressing part3a, and the wall part3bis divided by a pair of slits3sinto two regions in the circumferential direction. Plate-like flanges3e,3fare formed at the upper end of the wall part3b. The heating rod3cis desirably made of a ferromagnetic material such as an iron-based alloy or a nickel-based alloy. This is because, as will be described in detail later, the Curie temperature is easy to regulate when the heating rod3cis made of a ferromagnetic material.

FIG. 4is a cross-sectional view along the line B-B ofFIG. 2, and shows the positional relation among the cooling pipe9, the lead wires10a,10b, and a sealant11inside the metal tip3. As shown inFIG. 4, the sealant11is provided on the bottom surface inside the holder1. The clearance between the outer periphery of the cooling pipe9and the lead wires10a,10bis filled with the sealant11, which is silicone rubber or high-density sponge, so that a cooling fluid delivered from the cooling pipe9does not spurts out through the clearance between the outer periphery of the cooling pipe9and the lead wires10a,10b.

Referring toFIG. 2, a thread1gis cut on the outer periphery of a lower end part of the holder1, and a step1fwhich fits with the inner wall of the metal tip3is formed on the lower end surface of the holder1. An odd-shaped hole1cis formed from a center position in the lower end surface of the holder1to the bottom surface on the inside of the holder1, and the cooling pipe9and the lead wires10a,10bare passed through the odd-shaped hole1c. When seen in the cross-section along the line B-B as shown inFIG. 4, the odd-shaped hole1chas a shape in which small-diameter holes for the lead wires10a,10bto pass through are formed on both sides of a large-diameter hole for the cooling pipe9to pass through.

The lead wires10a,10bare originally one lead wire, and obtained by continuously winding the lead wire on the outer periphery of a lower part in the longitudinal direction of the cooling pipe9in advance, and then pulling up both ends of the lead wire through the odd-shaped hole1calong the cooling pipe9to the inside of the holder1. The portion of the lead wire continuously wound on the outer periphery of the lower part of the cooling pipe9serves as a high-frequency induction coil10c, and when a high-frequency current is applied to the lead wires10a,10b, an induced current flows through the high frequency induction coil10c. Then, the heating rod3clocated inside the high-frequency induction coil10cis heated by induction heating and generates high-temperature heat.

The inner surface of the wall part3bof the metal tip fits on the outer peripheral surface of the step1fof the holder1, and the flanges3e,3fbutt against the outer peripheral edge of the step1f. With the metal tip3fitted with the step1fof the holder1, the holder cap2which is also made of plastic and has a female thread cut on the inside is screw-fastened. Since a metal tip holding portion2aprotruding inward is formed at the lower end of the holder cap2, as the holder cap2is fastened to the holder1, the metal tip3is held with the flanges3e,3fof the metal tip3clamped between the outer peripheral edge of the step1fof the holder1and the metal tip holding portion2aof the holder cap. When the metal tip3is thus attached to the holder1, since the heating rod3cis provided upright at the center of the pressing part3aof the metal tip3, the heating rod3cis located inside the high-frequency induction coil10cwound on the outer periphery of the cooling pipe9.

Described below is one example of a thermal caulking method in the case where the boss7apenetrating the metal plate8placed on the plastic part7is the object to be caulked by the thermal caulking device having the above configuration.

First, a high-frequency current is applied from the heating power source5to the lead wires10a,10bunder the control of the controller6of the control unit. Then, an induced current flows from the lead wires10a,10bto the high-frequency induction coil10c, and the heating rod3cof the metal tip is heated by induction heating and generates high-temperature heat. The heat generated in the heating rod3ctransfers to the pressing part3aof the metal tip. The heat having transferred to the pressing part3atransfers to the wall part3band is partially released from the outer surface of the wall part3b. However, since the pressing part3ais supplied with heat from the heating rod3c, the center of the pressing part3aof the metal tip where the heating rod3cis located is kept constantly at a high temperature. As for the heating time or the pressing part3a, since induction heating is used, the temperature of the pressing part3arises instantly to a certain temperature as required for thermally caulking a plastic part.

At a point when an amount of heat as required for thermal caulking has been generated in the metal tip3, or prior thereto, the holder1is lowered to press down the boss7aby the pressing part3a. As the heat of the pressing part3atransfers to the boss7a, the boss7ais melted and softened, so that the head of the boss7aassumes a shape expanded outward following the shape of the pressing part3a, and as a result, the metal plate8is clamped between the head of the boss7aand the plastic part7. Thereafter, the controller6stops the application of a high-frequency current to the lead wire10a, and supplies air at a temperature equal to or lower than normal temperature as cooling air (cooling fluid) from the cooling fluid supply machine4through the hose4ainto the holder1. The cooling air supplied into the holder1is sprayed from the cooling pipe9toward the heating rod3cand the pressing part3a. The cooling air takes away heat from the heating rod3c, the pressing part3a, and the high-frequency induction coil10c, and discharges the heat through the slits3sof the metal tip3, which are heat discharge holes, to the outside of the metal tip3. Thus, the pressing part3aand the heating rod3cof the metal tip are instantly cooled. As a result, the boss7awhich has been temporarily melted and softened is cooled and solidified, which completes thermal caulking.

In the first embodiment of the present invention, the center part which repeatedly generates heat and cools, i.e., the heating rod3c, is located inside the metal tip3protruding from the holder1. The heating rod3cis surrounded by the cooling pipe9which is also protruding from the holder1, and the high-frequency induction coil10cis disposed on the outer peripheral surface of the cooling pipe9. As a high-frequency current is applied to the high-frequency induction coil10cduring heating, the heating rod3cgenerates heat, and the pressing part3aand the wall part3bof the metal tip are heated from the heating rod3c. After thermal caulking, as cooling air is delivered from the cooling pipe9toward the heating rod3cand the pressing part3a, the heating rod3cis cooled, and the pressing part3aand the wall part3bof the metal tip are cooled.

Thus, since the heating rod of the metal tip provided upright at the center of the pressing part is heated and cooled first, the responsiveness to heating and cooling can be enhanced.

Since the thermal caulking device of this embodiment has the high-frequency induction coil10cdisposed inside the metal tip3, the high-frequency induction coil10cdoes not interfere with a worker performing caulking work or with the operation of a robot etc., so that the work efficiency can be enhanced.

Since the heating rod3c, the pressing part3aand the wall part3bof the metal tip, and the high-frequency induction coil10cwhich are repeatedly heated and cooled are located outside the holder1and the holder cap2, the temperature of the holder1does not rise. Moreover, owing to the cooling effect of the cooling air passing through the inside of the holder1and the cooling pipe9, the holder1and the holder cap2can be kept at such a temperature that a worker can grasp them.

In this embodiment, the structure in which the screw of the holder cap2is fastened to thereby attach the metal tip3to the holder1is shown inFIG. 2. That is, the metal tip3fixed on the holder1can be easily replaced with another metal tip by loosening the screw of the holder cap2and removing the holder cap2from the holder1.

As a method for attaching/removing the holder1and the holder cap2to/from each other, methods which allow them to be attached or removed by a single action can also be used other then screw connection using a male thread and a female thread provided in the holder1and the holder cap2. A structure can be used which can attach or remove the holder1and the holder cap2by integrating or disassembling them, for example, a structure in which the holder1has a protruding pin on the outer periphery and the holder cap2is provided with a cam groove to engage with the pin, and the pin and the cam groove are engaged with each other.

With regard to the replacement of the metal tip,FIG. 5shows an exploded cross-sectional view of the caulking unit of the plastic part thermal caulking device according to the first embodiment of the present invention in which the screw of the holder cap2is loosened and the holder cap2is removed from the holder1, along with a cross-sectional view of other replacement metal tips.

As described already, the caulking unit of the thermal caulking device of this embodiment has a structure in which the flanges3e,3fof the metal tip3are clamped and held between the holder1and the holder cap2which are screw-connected to each other. Accordingly, as shown inFIG. 5, loosening the screw of the holder cap2and removing the holder cap2from the holder1can remove the metal tip3. As indicated by the dashed or solid double-headed arrow inFIG. 5, the metal tip3can be replaced with another metal tip. For example, thermal caulking can be performed using such as a metal tip23of which the diameter of the heating rod3cis large and the root of the heating rod3cand the pressing part3aare connected to each other through a curved surface (rounded corner), or a metal tip33of which the length of the heating rod3cis short.

FIG. 6AtoFIG. 6Ceach show a cross-sectional view of yet another replacement metal tip of the plastic part thermal caulking device according to the first embodiment of the present invention. A metal tip43ofFIG. 6Ahas an upwardly curved surface in an area having a diameter D2in a center part of a pressing part43a. The peripheral edge portion other than this area is a flat surface, and the portion continuous with a wall part43bis connected as a curved surface. This metal tip43is convenient when making the head of the boss7aof the plastic part smaller.

A metal tip53ofFIG. 6Bis a two-step metal tip with a wall part53bvaried in diameter. Since the leading end of the wall part53bis small, this metal tip53has an effect that the visibility near the leading end of the metal tip53is good and positioning during thermal caulking work is easy.

A metal tip63ofFIG. 6Chas a pressing part63awhich is downwardly convex at the center of the caulking-side surface and upwardly convex around the center of the caulking-side surface. This metal tip63has an effect that thermal caulking can be performed so as to press down the center of the boss7aby the center of the pressing part53a.

FIG. 7shows changes over time in pressing force, high-frequency current, cooling fluid flow rate, and metal tip temperature during caulking work by the plastic part thermal caulking device according to the first embodiment of the present invention. With the abscissa serving as a time axis,FIG. 7shows changes according to time in pressing force, high-frequency current, cooling fluid flow rate, and metal tip temperature. InFIG. 7, the pressing force (F) between the pressing part3aof the metal tip and the boss7aof the plastic part7starts to increase to a predetermined pressure (F1) at time (t1). At the same time, the high-frequency current (I) starts to be applied until a predetermined current (I1) is reached, so that the metal tip3starts to generate heat and the temperature (T) of the metal tip starts to rise. Thereafter, at time (t2) when the temperature of the metal tip has reached a predetermined temperature (T1), the high-frequency current (I) is stopped, and instead a cooling fluid (Q) is passed in a predetermined amount (Q1) for a predetermined time, until time (t3). Then, the metal tip is cooled and decreases in temperature. When the temperature of the metal tip has returned to normal temperature, thermal caulking is considered as completed, and the metal tip3is raised and separated from the boss7a(time (t4)).

For the temperature regulation of the present invention, Curie temperature automatic regulation is performed under the control of the controller6. Curie temperature automatic control is described as follows. When a current is applied to a high-frequency coil by a high-frequency power source, magnetism is generated around the high-frequency coil. This magnetism causes an eddy current due to the skin effect to flow through the magnetic layer of a heating rod provided in a metal tip, so that the magnetic layer generates heat under Joule heating. This heat transfers through the heating rod, which has high thermal conductivity, to the pressing part. In particular, when the magnetic layer of the heating rod is made of a material having a Curie point, the magnetic properties diminish when the heating rod is heated to or above the Curie point, so that the eddy current due to the skin effect decreases and the Joule heat decreases. When the temperature falls below the Curie point, the magnetic properties are restored and the Joule heat increases again. Curie temperature automatic regulation is about maintaining a predetermined temperature through repetition of this process. InFIG. 7, the metal tip temperature (T) is kept at the predetermined temperature (T1) because Curie temperature automatic regulation is used.

For comparison, the two-dot chain lines inFIG. 7indicate the values of the pressure force etc. in the case where, for example, the conventional thermal caulking device ofFIG. 25is used. Although the same high-frequency induction heating and cooling with a cooling pipe are used, the conventional device takes time to raise the temperature of the metal tip40and to cool the metal tip40due to the large heat capacity of the metal tip40, and as indicated by the two-dot chain line inFIG. 7, it takes a long time to raise the temperature of the metal tip40to a predetermined temperature and to return the temperature back to normal temperature. It is obvious fromFIG. 7that, according to the present invention, the metal tip3has a small heat capacity and therefore the temperature of the metal tip3rises to a predetermined temperature in a short time and returns to normal temperature in a shorter time than the conventional metal tip.

In this embodiment, the heating rod3cis provided at the center of the pressing part3aof the metal tip3, and the heating rod3cis instantly heated and cooled. Therefore, the heat capacity of the heating rod3ccan be set to be just large enough for thermal caulking. Accordingly, the metal tip3can be made thinner and smaller, so that a reduction in size and weight of the device can be achieved. Moreover, as the heat capacity of the heating rod3cis reduced to a minimum heat capacity required for thermal caulking, electrical power required for heating can also be reduced, so that a low-output, energy-saving device can be realized.

When the boss7ais melted and then cooled and solidified, the boss7ais cooled and solidified sequentially from the periphery of the boss7a, which has been melted and crushed to spread around, toward the center. When the center of the boss7ais cooled and solidified last, the boss7ashrinks while the center part thereof is solidifying, resulting in a larger caulking force. If the heating rod3clocated at the center of the pressing part3ahas a larger heat capacity than the other parts, the center part of the boss7acan be cooled last reliably. Thus, an effect that the caulking force increases as the boss7ashrinks while the center part thereof is solidifying can be obtained.

If produced in advance in a larger length, the heating rod3cis easy to process to reduce the length and thereby reduce the heat capacity. If a larger heat capacity is required, the metal tip can be replaced with a metal tip having a thicker heating rod.

In this embodiment, the slits3sof the metal tip function solely as open holes through which the cooling air delivered inside the metal tip is discharged. That is, the slits3sare heat discharge holes through which heat taken away by the cooling air from the heating rod3c, the pressing part3a, and the high-frequency induction coil10cis discharged. In this embodiment, since the pressing part3ais heated from the center through the heating rod, the problem with the conventional device that the temperature of the metal tip becomes uneven due to the slits3sprovided therein is prevented.

A modified example of the first embodiment will be described below.FIG. 8shows the modified example of the first embodiment. The thermal caulking device of the first embodiment of the present invention already shown inFIG. 1is used by a worker grasping the holder1of the caulking unit and pressing the pressing part3aof the metal tip against the leading end of the boss7a. In this case, since the work is performed by a human, the pressing force may vary among workers. In the modified example of the first embodiment, therefore, the holder1is pressed through a compression spring150so that the pressing force does not vary.

That is, in the modified example of the first embodiment of the present invention, as shown inFIG. 8A, a slide holder200which is cylindrical and slidable in the longitudinal direction of the holder1is provided on the outer periphery of the holder1. The compression spring150is provided on the upper end surface of the holder1. A slide holder cap201which regulates the position of the compression spring150is integrally attached to an upper part of the slide holder200. A flange1eis provided at the lower end of the holder1, and a slide holder stopper202, of which the position is regulated by the flange1e, is integrally attached to a lower part of the slide holder200.

FIG. 8Ashows a state before caulking work. In a state where a worker is merely grasping the slide holder200, as shown inFIG. 8A, the compression spring150is pushing up the slide holder cap201to the upper side of the holder1, and the lower end of the slide holder stopper202is in contact with the flange1eof the holder. Thus, in this state, there is a clearance (S) formed between the flange1eof the holder and the lower end of the slide holder200.

It is preferable that screw connection is used to attach the slide holder200and the slide holder cap201to each other and attach the slide holder200and the slide holder stopper202to each other. This is because the amount of compression of the compression spring150and the clearance (S) between the flange1eof the holder and the lower end of the slide holder200can be adjusted by adjusting the amount of screwing of screw connection. Otherwise, these parts may be bonded together with an adhesive or welded together if it is not necessary to adjust the amount of compression of the compression spring150or the clearance (S) between the flange1eof the holder and the lower end of the slide holder200.

Next, as shown inFIG. 8B, when the worker grasps the slide holder200and presses it downward, the pressing part3aof the metal tip hits the leading end of the boss7a. Then, heat of the metal tip3transfers to the boss7aand thermal caulking starts. When the pressing force is continuously applied to the slide holder200, the slide holder cap201compresses the compression spring150, so that the holder1is pressed down by the urging force of the compression spring150. When the slide holder200is lowered, a leading end200aof the slide holder hits the flange1eof the holder1. Unless the worker presses with a larger force at the point when the leading end200aof the slide holder200hits the flange1eat the lower end of the holder1, the pressing force is kept at the pressing force which compresses the compression spring150in a predetermined amount. Then, thermal caulking work can be performed with an almost constant pressing force. Thus, in the modified example of the first embodiment of the present invention, variation in pressing force during thermal caulking work by a worker is eliminated.

In the modified example of the first embodiment of the present invention, the slide holder200, the slide holder cap201, the slide holder stopper202, and the compression spring150correspond to the pressing operation means when a worker grasps and uses the thermal caulking device of the present invention.

Although description about the use of modified examples of the metal tip as shown in the first embodiment will be omitted in the following description of a second embodiment to a seventh embodiment, the modified examples can be similarly applied to any of these embodiments.

Second Embodiment

FIG. 9is an overall configurational view showing a plastic part thermal caulking device according to a second embodiment of the present invention. In the plastic part thermal caulking device according to the second embodiment of the present invention, the holder1with the metal tip3attached thereto is supported by a pressing operation mechanism, such as an air cylinder, so as to be movable in the vertical direction. The second embodiment is characterized in that the pressing part3aof the metal tip3is pressed down to the leading end of the boss7athrough the operation of the pressing operation mechanism such as an air cylinder. Since the pressing work is not manual work performed by a worker but machine work performed by the thermal caulking device, a predetermined pressing force managed to be constant can be applied.

InFIG. 9, a housing100of the thermal caulking device has an L-shape in which a column100aextending in the vertical direction in the sheet plane ofFIG. 9and an anvil100bextending in the left-right direction in the sheet plane ofFIG. 9are integrally coupled to each other. An air cylinder bracket101is attached to the column100a. An air cylinder99is attached to the air cylinder bracket101, with a rod99afacing downward. A slide unit102is attached at the leading end of the rod99a, and the slide unit102can move up and down along the column100a.

A heating power source97which supplies electrical power to the holder1and the high-frequency induction coil, and a cooling fluid supply part98are attached to the slide unit102. Although not shown, lead wires inside the holder1are connected to the heating power source97, and the cooling pipe9is connected to the cooling fluid supply part98. The metal tip3is clamped by the holder1and the holder cap2and is held with the pressing part3afacing downward. InFIG. 9, the controller6is disposed on the right side of the housing100. Although this is not shown either, the controller6is connected to the heating power source97and the cooling fluid supply part98inside the column100a. On the anvil100b, the plastic part7to be thermally caulked and the metal plate8are placed on top of one another. The boss7aof the plastic part7is protruding from the hole of the metal plate8. Alternatively, the heating power source97and the cooling fluid supply part98may be disposed next to the controller6, integrally with the controller6, instead of in the slide unit102.

When a worker selects thermal caulking conditions by operating an input/output part90of the controller6and starts thermal caulking work, under the control of the controller6, the metal tip3, which is heated by a current applied from the heating power source97is pressed down along with the slide unit102by the air cylinder99, which is the pressing operation mechanism, as indicated by the arrow A inFIG. 9. Then, the pressing part3aof the metal tip3hits the leading end of the boss7aand thermally caulks the boss7a. The application of a current by the heating power source97is stopped after a predetermined time, and a cooling fluid is delivered from the cooling fluid supply part98to the cooling pipe9to cool the heating rod3c, the pressing part3a, and the wall part3bof the metal tip3. Thereafter, the metal tip3along with the holder1is moved upward by the air cylinder99to finish the thermal caulking work. The worker can replace the plastic part7and the metal plate8on the anvil100bwith new ones, and perform thermal caulking work by the same procedure.

FIG. 10shows a control block diagram of the plastic part thermal caulking device according to the second embodiment of the present invention. The box of the one-dot chain line inFIG. 10indicates a range corresponding to the controller6ofFIG. 9. Inside the controller6are an overall control part91, a thermal caulking condition storage/readout part92connected to the overall control part91, and a memory93linked to the thermal caulking condition storage/readout part92. Moreover, a heating control part94, a cooling control part95, and a pressing control part96are each linked to the overall control part91, and the thermal caulking device controls thermal caulking through cooperation of the control parts94,95,96.

Specifically, the heating power source97, the cooling fluid supply part98, and the air cylinder99are controlled by the heating control part94, the cooling control part95, and the pressing control part96, respectively. During thermal caulking, information on thermal caulking conditions selected by the worker in the input/output part90is received by the overall control part91, and required information according to the thermal caulking conditions is stored in or read out from the memory93through the thermal caulking condition storage/readout part92, and commands are sent to the heating control part94, the cooling control part95, and the pressing control part96.

FIG. 11shows one example of data configuration for thermal caulking conditions stored in the memory93. For the outer diameter (X) of the boss to be caulked, the caulking amount (Y) of the boss, and the material (Z) of the boss, a plurality of sets of thermal caulking conditions, Condition1, Condition2, Condition3, Condition4, and Condition5, are shown in descending order of the score. For each set of thermal caulking conditions, toe values of the following parameters: pressing part shape (K), wall part outer diameter (D), wall part thickness (N), heating rod diameter (d), heating rod height (H), pressing force (F), high-frequency current (I), cooling fluid flow rate (Q), metal tip temperature (T), pressing/current application start time (t1), current application end/cooling start time (t2), cooling end time (t3), and pressing end time (t4) (the values are represented by the symbols inFIG. 11) are stored along with the scores in the form of a table in the memory93, and the overall control part91controls thermal caulking by reading out the specifications of the items according to the conditions selected by the worker.

For example, when the worker inputs the diameter (X) of the boss to be thermally caulked, the caulking amount (Y), and the material (Z) of the boss in the input/output part90, under the command of the overall control part91, the thermal caulking condition storage/readout part92reads out the conditions to be used from the memory93and presents the conditions to the worker in descending order of the score. When the worker selects the conditions through the input/output part90and starts thermal caulking, the overall control part91commands the heating control part94, the cooling control part95, and the pressing control part96according to the selected thermal caulking conditions to actuate the heating power source97, the cooling fluid supply part98, and the air cylinder99and thereby execute thermal caulking work.

InFIG. 9, the example has been shown in which the holder1with the metal tip3attached thereto is attached to the slide unit102and the slide unit102is supported by the pressing operation mechanism, such as the air cylinder99, so as to be movable in the vertical direction. However, as shown inFIG. 8, the holder1with the slide holder200, the slide holder cap201, the slide holder stopper202, and the compression spring150attached thereto may be attached to the slide unit102. Then, thermal caulking can be performed using a spring force exerted by the compression of the compression spring.

In this embodiment, the metal tip having the metal rod serving as the heating rod welded or brazed at the center of the pressing part is used, and a high-frequency current is applied to the high-frequency induction coil set on the outer periphery of the heating rod to thereby perform thermal caulking through induction heating. Thus, the basic effects of this embodiment are the same as those of the first embodiment.

Third Embodiment

FIG. 12shows a cross-sectional view of the major part of a thermal caulking unit of a plastic part thermal caulking device according to a third embodiment of the present invention.

As shown inFIG. 12, the third embodiment of the present invention is characterized in that portions of lead wires310a,310bwhich are not a winding portion of a high-frequency induction coil310care placed inside a cooling pipe309. Each time a cooling fluid is passed through the cooling pipe309, the portions of the lead wires310a,310bwhich are not the winding portion of the high-frequency induction coil310care cooled inside the cooling pipe309, which has an effect that heat generated in the high-frequency induction coil310cdoes not transfer to where it is not intended.

Instead of a heat discharge slit (opening), such as a slit, provided in a metal tip303, a heat discharge hole301ais bored in a holder301. The heat discharge hole301ais a hole having an L-shaped cross-section formed by a longitudinal hole extending from the leading end of the holder301in the axial direction and a lateral hole extending from the longitudinal hole to the side surface of the holder301.

More specifically, the high-frequency induction coil310cis wound on the outer periphery of the cooling pipe309in a lower part of the cooling pipe309, and a hole is formed at two positions in the side surface on the upper side from the high-frequency induction coil310c. The pair of lead wires310a,310bextending from the high-frequency induction coil310care inserted into the cooling pipe309through the holes bored in the cooling pipe309. Although not shown in detail, it is preferable that the clearance between the lead wires310a,310band the holes of the cooling pipe309is closed with a heat-resistant adhesive etc.

While the holder301has almost the same outer shape as the holder1of the first embodiment, the longitudinal hole portion of the heat discharge hole301acommunicating with the cavity inside the metal tip303is bored in the axial direction of the cooling pipe309. In addition, an O-ring312fills and seals the clearance between the cooling pipe309and the holder301.

In the third embodiment of the present invention, cooling air which is a cooling fluid passed from the cooling pipe309into the cavity of the metal tip303flows along the outer surface of the heating rod303c, and after colliding with the pressing part303a, rises along a wall part303bbefore flowing via the heat discharge hole301ato the outside of the holder301. Thus, heat of the heating rod303cand the pressing part303aof the metal tip as well as of the high-frequency induction coil310cis discharged. In this embodiment, since heat transfers to the holder301and the holder cap302during heat discharge, a longer heat discharge time is provided to return the temperatures of the holder301and the holder cap302to normal temperature.

In the third embodiment, the same effects as those of the first embodiment can be achieved, and since the heat discharge slit is not provided in the wall part303bof the metal tip303, the mechanical strength of the metal tip303can be enhanced. Thus, there is an advantage in that the metal tip303does not deform even when the boss7ais pressed hard with the metal tip303which is further reduced in plate thickness.

Fourth Embodiment

As shown inFIG. 13, a fourth embodiment of the present invention is characterized in that a heating rod403cis provided at the center on the inside of a pressing part403aof a metal tip403, and that the heating rod403cis protruded as a heating rod leading end403gto the outside of the pressing part403a.

FIG. 13is a cross-sectional view showing the major part of a thermal caulking unit of the plastic part thermal caulking device according to the fourth embodiment of the present invention, in juxtaposition with an object to be caulked. On the lower side from the thermal caulking unit ofFIG. 13, a leading end part of a catheter tube is shown which is placed on an anvil460and positioned and fixed by a pressing and fixing member465with a hole. One end480aof a plastic support shaft480at the leading end part of the catheter tube is supported on a convex portion460aof the anvil460, while the other end480bof the support shaft faces the heating rod leading end403gprotruding from the pressing part403aof the metal tip.

The heating rod leading end403gis a portion of the heating rod403cprotruded further in the pressing direction than the pressing part403a, and the heating rod leading end403ghas a pressing surface. When the heating rod403cis induction-heated by a high-frequency induction coil410c, the thermal energy generated in the heating rod403ctransfers to the heating rod leading end403gprotruding from the pressing part403aof the metal tip. When the heating rod leading end403gthermally caulks the other end480bof the support shaft at the leading end part of the catheter tube under the best thermal caulking conditions read out from the plurality of sets of thermal caulking conditions stored in advance in the thermal caulking condition storage means, the other end480bof the small support shaft is thermally caulked into the best state.

Thus, according to the configuration in which the heating rod leading end403gserves as the pressing surface, the same effects as those of the first embodiment can be obtained, as well as the pressing surface can be reduced. This has an effect that it is possible to stably and precisely thermally caulk small plastic parts, like a plastic support shaft at the leading end of a catheter tube to be inserted into the body, under the best thermal caulking conditions stored in advance.

In thermal caulking of precision plastic parts, the diameter of the boss (boss diameter) can be 1 mm or smaller. There are cases where, even when the boss diameter is 0.5 mm, for example, a convex round head needs to be formed on the boss. In such cases, as in the modified example of the metal tip of the fourth embodiment shown inFIG. 14, thermal caulking is performed with a metal tip of which a pressing surface403iof a heating rod leading end403his an upwardly convex curved shape.

Fifth Embodiment

For the first embodiment to the fourth embodiment, the examples in which thermal caulking is performed with one metal tip have been described. As a fifth embodiment, an example in which two metal tips are disposed face to face and an object to be thermally caulked is thermally caulked while being clamped between the two metal tips will be described.

FIG. 15Ashows a state before the metal tips3,3of a thermal caulking device having the same configuration as the first embodiment are moved from the upper side and the lower side as indicated by the outlined arrows to clamp a pipe-like thermal caulking member575which is fitted on a rod-like stent570like the one described withFIGS. 28Ato28C.FIG. 15Bshows a state in which a high-frequency current starts to be applied to the high-frequency induction coil10cwhile the pipe-like thermal caulking member575containing the rod-like stent570is clamped by the metal tips3,3. A groove having a U-shaped curved surface is formed in each of the pressing surfaces of the metal tips3,3.FIG. 16is an external perspective view of a metal tip503as a single part in a modified example of the fifth embodiment. A groove having a U-shaped curved surface is formed in the pressing surface of a pressing part503aof the metal tip503, and a heating rod503is provided upright at the center on the inner side of the U-shaped curved surface. In the case where the rod-like stent570is thin and the thermal caulking member is small, a metal tip having more suitable dimensions and shape can be used instead of the metal tip shown inFIGS. 15A and 15B.

As shown inFIG. 15B, when a high-frequency current is applied to the high-frequency induction coil10c, each of the heating rods3cgenerates heat, and the heat of the heating rods3ctransfers to the pressing part3ahaving a U-shaped curved surface, so that the thermal caulking member575and the stent570clamped by the pair of metal tips3,3generate heat and are thermally caulked.

Such a form of thermal caulking has an effect that it is possible to stably and precisely thermally caulk small plastic parts under the best thermal caulking conditions stored in advance, by applying the thermal caulking device of this embodiment to thermal caulking of the stent shown inFIG. 28or to thermal caulking of the leading end part of the endoscope shown inFIG. 29which have been described as the conventional examples.

Sixth Embodiment

For the first embodiment to the fifth embodiment, the examples in which high-frequency induction heating means is used as metal tip heating means have been described, but the heating means may be electrical heating means. In the sixth embodiment, an example in which electrical heating means is used as the heating means will be described.

In the conventional caulking device described withFIG. 22, the lead wires31a,31bare electrically connected to the flanges30e,30f, respectively, of the metal tip30by welding or screwing fixation, and a current is applied from one lead wire31ato the other lead wire31bto generate heat by Joule heating.

In the sixth embodiment, as shown inFIG. 17,FIG. 18, andFIG. 19which show the outlines of the major part of the caulking unit and the metal tip, lead wires610a,610band a lead wire610care respectively electrically connected by welding or screw fixation to a flange603jof a metal tip603and a heating rod603cprovided upright at the center of a pressing part603aof the metal tip603. In particular, as can be seen fromFIG. 19B, the two lead wires610a,610bare connected at positions facing each other in the flange603jof the metal tip, and the other lead wire610cis connected to the heating rod603c. A current flows from the lead wire610cconnected to the heating rod603cto the lead wires610a,610bconnected to the flange603j.

As shown inFIG. 17, the lead wires610a,610b,610chave predetermined lengths, and have one ends connected to the metal tip603and the other ends screw-fixed on terminal strips613a,613bdisposed inside the cavity of a holder601. Lead wires610d,610econnected to a power source (not shown) are screw-fixed on the terminal strips613a,613bdisposed inside the cavity of the holder601.

When a current is applied from the power source (not shown) through the one lead wire610e, the terminal strip613a, and the lead wire610cto the heating rod603c, the heating rod603cfirst generates heat by being supplied with the current. Then, the current flows from the heating rod603cthrough the pressing part603a, the wall part603b, and the flange603jto the two lead wires610a,610b, and flows through the terminal strip613bto610d. Thus, the center of the pressing part603awhere the heating rod603cis located reaches a high temperature, and the heat diffuses from the center toward the outer periphery of the pressing part603aas shown inFIG. 19C.

As shown inFIG. 17andFIG. 18, in the position of the holder601where the terminal strips613a,613bare provided, the outer periphery of the holder601is cut out, and a lid650is provided so as to close this cutout portion. The lid650is removable so that the lead wires610a,610b,610ccan be attached to or removed from the terminal strips613a,613bdisposed inside the cavity of the holder601.

FIG. 17is a configurational view showing a plastic part thermal caulking device according to the sixth embodiment of the present invention.FIG. 17shows the major part of the thermal caulking unit of the thermal caulking device, the plastic part7with the protruding boss7a, and the metal plate8laid on the plastic part7with the boss7apassing through the hole of the metal plate8.

FIG. 18is an exploded cross-sectional view of the plastic part thermal caulking device according to the sixth embodiment of the present invention in which the screw of a holder cap602is loosened and the holder cap602is removed from the holder601. In the sixth embodiment, the holder601and the holder cap602are screw-connected to each other to hold the metal tip603. Since the metal tip is not molded with a resin materiel as in the conventional example, the device can be used with another metal tip replacing the metal tip.

In the sixth embodiment of the present invention, when replacing the metal tip, it is necessary to remove the lid650of the holder601, loosen the screws fixed on the terminal strips613a,613binside the holder601with a driver, and remove the lead wires610a,610b,610con the metal tip side. Alternatively, the lid650covering the terminal strips613a,613bof the lead wires610a,610b,610cmay be removed from the holder601first, and then the lead wires610a,610b,610con the metal tip side may be removed with a driver, or the lid650may be removed from the holder601first after the screw of the holder cap602is loosened, and then the lead wires610a,610b,610con the metal tip side may be removed with a driver. In either case, the metal tip603can be replaced with another metal tip.FIG. 18is a cross-sectional view of a metal tip shown as another metal tip of which the heating rod has a larger diameter, with the arrow indicating replaceability.

FIG. 19Ais a cross-sectional view showing the metal tip603with the lead wires610a,610b,610cconnected thereto;FIG. 19Bis an external perspective view of the metal tip603; andFIG. 19Cis a plan view of the metal tip603. In the metal tip603, a wall part603brises from around the pressing part603ahaving an upwardly convex spherical surface, and the flange603jis formed at the upper end of the wall part603b. A plurality of open holes603kare formed in the wall part603bthrough which the cavity inside the metal tip603and the outside of the metal tip603communicate with each other. The perspective view ofFIG. 19Bshows that four open holes603kare bored in the well part603b. The lead wires610a,610bare connected to the flange603j, while the other lead wire610cis connected to the heating rod603cprovided upright at the center of the pressing part603a.

The arrows inFIG. 19Cshow an image that the center of the pressing part where the heating rod603cis located reaches a high temperature and heat diffuses from the center toward the outer periphery.

It is the same as with the metal tips shown in the first embodiment to the fifth embodiment that the metal tip603has the cavity inside through which a cooling fluid flows, the open holes through which the cooling fluid is discharged outside, and the heating rod603cprovided at the center of the pressing part603a. However, in the sixth embodiment, electrical power is supplied first to the heating rod603clocated at the center and a current is passed to the periphery of the pressing part603alike an earth.

In the above description, the example in which the one lead wire610cis connected to the heating rod603cand the two lead wires610a,610bare connected to the positions facing each other in the flange603jhas been shown. It is in order to cause a current to flow radially from the one lead wire610cconnected to the heating rod603cthat the two lead wires610a,610bare connected to the positions facing each other in the flange603j. The number of the lead wires connected to positions facing each other in the flange603jshould be at least two, and may be three or four, if the space permits.

Since the metal tip603generates heat by being supplied with a current, the center of the pressing part603awhere the heating rod603c, which is supplied with electrical power first, is located reaches a high temperature, and heat diffuses from the center toward the outer periphery. When pressed with the metal tip603, the boss7ais melted by the heat transferring thereto from the pressing part603a. As cooling air is sprayed from the cooling pipe609toward the heating rod603cand the pressing part603a, the heating rod603cand the pressing part603aare cooled. The heat taken away from the heating rod602cis discharged through the open holes603kto the outside of the metal tip603.

Thus, it is the same as in the first embodiment to the fifth embodiment that pressing part603ais heated from the center, where the heating rod603cof the metal tip603in the sixth embodiment is located, toward the periphery, and that the pressing part603ais cooled from the center toward the periphery. In this way, thermal caulking is performed by rapidly heating and rapidly cooling the boss7aetc. in this embodiment. That current application conditions and pressing conditions are stored in advance and that optimal conditions are read out to perform thermal caulking work are the same as in the first embodiment to the fifth embodiment, and therefore the description thereof will be omitted here.

As in the other embodiments, the metal tip603is structured to be clamped by the holder and the holder cap made of an insulating material such as plastic or wood.

Seventh Embodiment

A plastic part thermal caulking device according to a seventh embodiment of the present invention has sheet metals740,741having spring properties instead of the lead wires610a,610b,610cof the sixth embodiment. That is, while in the sixth embodiment the metal tip603with the lead wires610a,610b,610cjoined thereto in advance is replaceable, in the seventh embodiment, instead of the lead wires610a,610b,610c, the sheet metals740,741having spring properties are incorporated into a holder701so that a metal tip703can be replaced alone.

FIG. 20is a configurational view showing the plastic part thermal caulking device according to the seventh embodiment of the present invention.FIG. 20shows the major part of a thermal caulking unit of the thermal caulking device, the plastic part7with the protruding boss7a, and the metal plate8laid on the plastic part7with the boss7apassing through the hole of the metal plate8.

In the seventh embodiment of the present invention, as in the third embodiment already described, a heat discharge hole701ais formed in the holder701so that heat is discharged along with a cooling fluid through the heat discharge hole701aof the holder701. Thus, the mechanical strength of the metal tip is increased by not providing an opening, such as a slit, in a wall part703bof the metal tip. As a result, it is allowed to press hard the leading end of the boss7awith a pressing part703aof the thin metal tip.

FIG. 21is an exploded cross-sectional view of the plastic part thermal caulking device according to the seventh embodiment of the present invention in which the screw of a holder cap702is loosened and the holder cap702is removed from the holder701. The sheet metals740,741having spring properties are screw-fixed at their upper ends740b,741bto terminal strips713a,713binside the holder701. Therefore, when the screw of the holder cap702is loosened and the holder cap702is removed from the holder701, the metal tip703, which has been pressed against the sheet metals740,741, is separated from the sheet metals740,741and removed along with the holder cap702from the holder701. As necessary, the metal tip703can be replaced with another metal tip in the state ofFIG. 21.

According to the seventh embodiment of the present invention, it is convenient in that lead wires710a,710bneed not be connected in advance to the metal tip703end that only the metal tip needs to be replaced.

Aspects of the Present Invention

A first aspect of the present invention is a thermal caulking device which caulks a portion of a plastic part as an object to be caulked, the thermal caulking device including: a metal tip having a pressing part which presses the object to be caulked, a heating rod which is provided upright at a center part of the pressing part, and a wall part which is provided upright on the outer periphery of the pressing part; heating means for heating the heating rod; a cooling pipe which cools the heating rod; cooling fluid supply means for supplying a cooling fluid to the cooling pipe; a holder which holds the metal tip and the cooling pipe so that the cooling pipe delivers the cooling fluid toward the heating rod; and control means for controlling the heating means and the cooling fluid supply means, wherein the control means heats the pressing part from the heating rod by the heating means, and after the object to be caulked is thermally caulked by the pressing part, supplies the cooling fluid from the cooling fluid supply means to the cooling pipe to cool the pressing part from the heating rod.

A second aspect of the present invention is the thermal caulking device according to the first aspect, wherein the holder holds the metal tip and the cooling pipe so that a leading end portion of the cooling pipe covers the outer peripheral surface of the heating rod of the metal tip with a clearance therebetween; the heating means has a coil which is provided on the inside of the wall part of the metal tip and wound on the outer peripheral surface of the leading end portion of the cooling pipe, and a power source which supplies a high-frequency current to the coil; and the control means applies a high-frequency current from the power source to the coil, and heats the pressing part from the heating rod by high-frequency induction heating through the coil.

A third aspect of the present invention is the thermal caulking device according to the first aspect, wherein the heating means has two or more current-carrying members of which one is connected to the leading end of the heating rod and the other is connected to the leading end of the wall part, and a power source which supplies electrical power to the current-carrying members; and the control means applies a current from the power source through the current-carrying members to the heating rod, and heats the metal tip from the heating rod by electrical heating.

A fourth aspect of the present invention is the thermal caulking device according to any one of the first to third aspects, wherein an opening is formed in the wall part.

A fifth aspect of the present invention is the thermal caulking device according to any one of the first to third aspects, wherein an open hole through which a cavity formed by the wall part of the metal tip and the outside of the holder communicate with each other is formed in a leading end part of the holder.

A sixth aspect of the present invention is the thermal caulking device according to any one of the first to fifth aspects, further including storage means for storing thermal caulking conditions including at least values related to the heating means and values related to the flow rate of the cooling fluid, wherein the control means reads out one or more thermal caulking conditions stored in the storage means, and controls the cooling fluid supply means and the heating means according to the thermal caulking conditions having been read out.

A seventh aspect of the present invention is the thermal caulking device according to any one of the first to third aspects wherein the metal tip has a flange formed at the leading end of the wall part; and the holder is provided with a removable holder cap which, together with a leading end part of the holder, clamps the flange of the metal tip.

An eighth aspect of the present invention is the thermal caulking device according to any one of the first to seventh aspects, wherein the pressing surface of the pressing part has a spherical shape concave in the pressing direction.

A ninth aspect of the present invention is the thermal caulking device according to any one of the first to seventh aspects, wherein the pressing surface of the pressing part has a U-groove shape concave in the pressing direction.

A tenth aspect of the present invention is the thermal caulking device according to any one of the first to seventh aspects, wherein the pressing part uses, as the pressing surface, a heating rod leading end protruding from the heating rod in the pressing direction.

An eleventh aspect of the present invention is the thermal caulking device according to any one of the first to tenth aspects, wherein the cooling fluid is air and the cooling fluid supply means is a blower.

A twelfth aspect of the present invention is the thermal caulking device according to any one of the first to eleventh aspects, further including pressing operation means which can support the holder and move the holder in the pressing direction.

A thirteenth aspect of the present invention is the thermal caulking device according to any one of the first to twelfth aspects, wherein the holder is provided with a spring which urges the holder in the pressing direction, and the object to be caulked is pressed by the urging force of the spring.

A fourteenth aspect of the present invention is the thermal caulking device according to any one of the first to thirteenth aspects, wherein the heating means has a coil which is provided on the inside of the wall part of the metal tip and wound around the heating rod, and a power source which supplies a high-frequency current to the coil, and the high-frequency current is supplied from the power source to the coil to heat the heating rod by high-frequency induction heating through the coil.

INDUSTRIAL APPLICABILITY

The present invention can be widely applied to common plastic part thermal caulking devices, as well as to thermal caulking devices intended, for example, for catheter tubes or other small precision plastic parts.

EXPLANATION OF REFERENCE SIGNS