Magnetic holder

Abstract

A magnetic holder (10) which attracts and holds a workpiece (12) with a magnetic force of a permanent magnet (56a to 56d), comprising: a housing (20) with a cylinder tube (14) in which a sliding opening (38) is formed through which a piston (58) is moved, and a head cover (18) which is attached to the cylinder tube (14) and closes one end of the sliding opening (38); a retaining element (66) which is connected to the piston (58) and is designed to hold the permanent magnet (56a to 56d); and a partitioning element (42) which is positioned and fixed inside the housing (20) and is designed to form an inner chamber inside the cylinder tube (14) together with the piston (58); wherein the magnetic holder (10) further comprises at least a first damper (84) and a second damper (94), wherein the first damper (84) is arranged on the partitioning element (42) or the piston (58) and is configured to dampen vibrations when the piston (58) strikes the partitioning element (42), and wherein the second damper (94) is provided on the piston (58) or the head cover (18) and is configured to dampen vibrations when the piston (58) strikes the head cover (18), characterized in that a combination of an N-pole and an S-pole is provided as one or more pairs on a magnetic workpiece attraction surface of the permanent magnet (56a to 56d), wherein the magnetic workpiece attraction surface faces the workpiece (12), and that the cylinder tube (14) and the head cover (18) are connected by a connecting element (54a to 54d) made of a ferromagnetic metal, and that the connecting element (54a to 54d) is designed to serve as a rotation-prevention element which prevents rotation of the permanent magnet (56a to 56d).

Description

Background of the invention

[0001] The present invention relates to a magnetic holder which attracts and holds a tool by means of the magnetic force of a permanent magnet.

[0002] A magnetic holder contains either an electromagnet or a permanent magnet. In the case of an electromagnet, a magnetic force is generated when current is applied to the electromagnet (switching it on), and the workpiece is attracted and held by this magnetic force. When the current is switched off, the magnetic force disappears, and the workpiece is released.

[0003] In the case of a permanent magnet, as disclosed, for example, in JP S55-78505A, the arrangement is such that the attraction and holding, as well as the release, of the workpiece can be switched by rotating the permanent magnet. More generally, an arrangement is known in which the permanent magnet is connected to a piston and the permanent magnet is moved together with the piston (see, for example, JP S51-102174U). In the magnetic holder described in JP S51-102174U, a permanent magnet is brought close to a workpiece in accordance with the movement of a piston driven by a pressurized fluid. The workpiece is then attracted and held by the magnet. When the permanent magnet and the piston are moved away from the workpiece, the workpiece is released.

[0004] This type of magnetic holder is, for example, located at the distal end of a robot arm. When the robot performs a defined operation, the attracted and held workpiece is transported to a predetermined position.

[0005] JP S60 - 94 489 U, US 6 086 125 A and US 6 538 544 B1 reveal further magnetic holders from the prior art. Summary of the invention

[0006] For example, if the piston and permanent magnet are moved together, it is assumed that the piston will strike the head cover when it reaches top dead center. In this case, the magnetic holder vibrates, and unpleasant noises can be generated. Furthermore, there is concern that such impact could reduce the piston's lifespan.

[0007] A key objective of the present invention is to propose a magnetic holder in which the occurrence of vibrations can be avoided when the piston arrives at a displacement endpoint.

[0008] Another object of the present invention is the creation of a magnetic holder in which the durability of the piston or the like can be ensured.

[0009] This problem is essentially solved by the invention through the features of claim 1.

[0010] Advantageous embodiments of the invention are set out in the dependent claims.

[0011] According to a preferred embodiment of the present invention, a magnetic holder is provided which attracts and holds a workpiece by the magnetic force of a permanent magnet, wherein the magnetic holder comprises a housing with a cylindrical tube in which a sliding opening is formed through which a piston is moved, and a head cover attached to the cylindrical tube for closing one end of the sliding opening, a retaining element which is connected to the piston and holds the permanent magnet, and a partitioning element which is positioned and fixed inside the housing and together with the piston forms an inner chamber inside the cylindrical tube.The magnetic holder also comprises at least a first damper and a second damper, wherein the first damper is provided on the partitioning element or the piston and is designed to dampen vibrations when the piston strikes the partitioning element, and wherein the second damper is provided on the piston or the head cover and is designed to dampen vibrations when the piston strikes the head cover.

[0012] In a design where a first damper is provided, the first damper is positioned between the piston and the partitioning element when the piston reaches a displacement endpoint (for example, bottom dead center). This mitigates vibrations or shocks that occur when the piston strikes the partitioning element. In a design where a second damper is provided, the second damper is positioned between the piston and the head cover when the piston reaches a different displacement endpoint (for example, top dead center). This mitigates vibrations or shocks that occur when the piston strikes the head cover. For the reasons described above, vibrations or disturbing noises that occur when the piston reaches the displacement endpoints are avoided.Accordingly, it is strongly preferred to provide both the first damper and the second damper.

[0013] Furthermore, the piston, partitioning element, and head cover are protected from damage. Specifically, the durability of these elements is improved. Consequently, the service life of the magnetic holder can be extended.

[0014] The piston and the retaining element can be connected by a shaft with a smaller diameter than the piston. In this case, the partitioning element is positioned and fixed between the piston and the retaining element. The partitioning element also features an insertion opening through which the shaft is inserted. With the design described above, the permanent magnet can be moved to follow the piston, even though the partitioning element is positioned between the piston and the retaining element.

[0015] In this case, the retaining element and the shaft are preferably formed in one piece from the same element. This reduces the number of parts.

[0016] An element encompassing the holding element can be formed by a yoke. The presence of the yoke further increases the attractive force in this case. Consequently, the workpiece can be attracted and held even more effectively.

[0017] Furthermore, a design is provided in which a combination of an N-pole and an S-pole is present as one or more pair(s) on a magnetic workpiece attraction surface of the permanent magnet, wherein the magnetic workpiece attraction surface faces the workpiece.

[0018] In particular, the different magnetic poles can preferably be arranged next to each other.

[0019] In this configuration, a magnetic flux generated by the exposed N-pole on the magnetic workpiece attraction surface is directed towards two adjacent S-poles on the same magnetic workpiece attraction surface. Compared to a situation where the magnetic polarity of the magnetic workpiece attraction surface is either an N-pole or an S-pole—that is, compared to the prior art magnetic holder with only one pole—the magnetic path (magnitude of the magnetic flux) within the workpiece can be increased. This allows a large attractive force to be applied to the workpiece. Even if the workpiece is a thin-walled steel plate, it can therefore be effectively magnetically attracted.

[0020] In other words, with such a configuration, assuming that the materials and properties of the permanent magnet are the same as those of the permanent magnet in the magnetic holder according to the prior art, and if their dimensions are the same, the attractive force on the workpiece can be increased. Since the dimensions of the permanent magnet can be made smaller if the attractive force is the same as that of the permanent magnet according to the prior art, the magnetic holder can also be made smaller (compact design).

[0021] When the permanent magnet is rotated, the magnetic flux density near the autoswitch also changes. As a consequence, it is assumed that this could potentially cause the autoswitch to malfunction. The connecting element that joins the cylinder tube to the head cover acts as an anti-rotation element to prevent the permanent magnets from rotating. This eliminates the concern that the situation described above could occur. In this case, the connecting element is made of a ferromagnetic metal.

[0022] Since the connecting element used to assemble the permanent magnet also serves as the anti-rotation element, it is unnecessary to provide a separate anti-rotation element that differs from the connecting element. Because this avoids increasing the number of parts, the magnetic holder can be built in a more compact form. Such a configuration is also cost-effective.

[0023] If the connecting element is designed as an anti-rotation element, it is preferably positioned at the boundary between the N-pole and the S-pole, which are located next to each other on the magnetic workpiece attraction surface. Instead of placing the anti-rotation element in a different position, this arrangement makes it difficult to rotate the permanent magnet.

[0024] Furthermore, a sealing element is preferably provided on a side wall of the piston, and a point between the piston and the cylinder tube can be sealed via this sealing element. In this case, the piston absorbs a pressure force from the pressure fluid when the permanent magnet is moved forward or backward. The pressure-bearing area of ​​the piston during the forward movement of the permanent magnet and the pressure-bearing area of ​​the piston during the backward movement of the permanent magnet are approximately equal. Therefore, the thrust forces during the forward and backward movements are also essentially the same. Accordingly, the response rates during magnetic attraction and release of the workpiece are also essentially the same.

[0025] Further developments, advantages, and possible applications of the invention will also become apparent from the following description of exemplary embodiments and the drawings. All features described and / or illustrated, individually or in any combination, constitute the subject matter of the invention, irrespective of their compilation in the claims or their cross-reference. Brief description of the drawings Fig. Figure 1 is a perspective view of essential components of a magnetic holder according to an embodiment of the present invention; Fig. 2 is a top view from the direction of arrow A in Fig. 1; Fig. 3 is a section along line III-III in Fig. 2; Fig. Figure 4 is a vertical section showing a state in which a piston, a yoke, and the first to fourth permanent magnets are opposite the one in Fig. The 3 shown states are shifted downwards; Fig. 5A and Fig. Figure 5B shows schematic side views of a magnetic flux at the time when the number of poles on the magnetic workpiece attraction surface is equal to one, or a schematic top view of a magnetic saturation region; Fig. 6A and Fig. Figure 6B is a schematic side view of a magnetic flux at the time when the number of poles is equal to two (the combination of an N pole and an S pole as a pair), or a schematic top view showing a magnetic saturation region; Fig. Figure 7 is a schematic top view showing a magnetic saturation region at a time when the number of poles on the magnetic attraction surface is four (combination of an N pole and an S pole in two pairs); Fig. Figure 8 is a diagram showing a relationship between the number of magnetic poles (number of combinations of an N pole and an S pole) on the magnetic workpiece attraction surface and the generated attractive force; Fig. Figure 9 is a perspective view showing a state in which a magnetic workpiece attraction surface is formed by assembling three U-shaped permanent magnets; Fig. Figure 10 is a view from below showing a state in which a magnetic workpiece attraction surface is formed by assembling two U-shaped permanent magnets; Fig. Figure 11 is a front view showing a state in which a Halbach series is formed with rod-shaped magnets and a combination of a group of N poles and S poles is provided at the magnetic workpiece attraction surface; Fig. Figure 12 is a perspective view of a permanent magnet obtained by magnetizing a cylindrical body, the direction of the magnetic poles therein having a U-shape; and Fig. Figure 13 is a perspective view of a permanent magnet obtained by magnetizing a cylindrical body, wherein the magnetic poles therein are oriented in a direction perpendicular to the magnetic workpiece attraction surface. Description of preferred embodiments

[0026] Preferred embodiments of a magnetic holder according to the present invention are now described in detail with reference to the accompanying drawings. In the following description, the terms "up" and "down" correspond to the upward and downward directions in the Fig. 1, Fig. 3 and Fig. 4. In the present embodiment, an exemplary case is described in which compressed air is used as a working fluid.

[0027] The Fig. Figures 1 to 3 are a perspective view of essential components of a magnetic holder 10 according to an embodiment of the present invention, a top view from the direction of arrow A in Fig. 1 or a cut along line III-III in Fig. 2. The magnetic holder 10 pulls into Fig. The workpiece 12 shown in Figure 3 is attached and held. Naturally, the workpiece 12 is made of a ferromagnetic material. A thin steel plate can serve as a concrete example. The thickness T1 of the workpiece 12 is on the order of 0.5 to 2 mm and is typically about 0.6 mm.

[0028] The magnetic holder 10 comprises a housing 20 formed by attaching a magnetic cover 16 and a head cover 18 to a cylindrical tube 14. With reference especially to Fig. 3. The magnetic cover 16 consists of a hollow body in which a first sliding opening 22 is formed along its longitudinal direction. In the first sliding opening 22, a lower chamber 23 and a first middle chamber 24 are formed by a flange 66 (retaining element) of a yoke 64 described later and a plate element 42 (partitioning element). Specifically, the lower chamber 23 is a space between a bottom wall of the magnetic cover 16 and a lower end face of the flange 66. Furthermore, the first middle chamber 24 is a space between an upper end face of the flange 66 and a lower end face of the plate element 42.

[0029] A hollow cylindrical column 25 is designed to project from the lower end face of the magnet cover 16. A first annular groove 26 is formed in the hollow cylindrical column 25, surrounding the first sliding opening 22 (lower chamber 23). A section of a substantially ring-shaped rubber damping element 28 is pressed into the first annular groove 26, while the remaining section of the rubber damping element 28 projects ring-shaped from the magnet cover 16. Several individual slots 29 (see Figure 2) Fig. 2) are formed in the damping element 28 made of rubber.

[0030] A middle flank section 30 (cf. Fig. 3) The magnetic cover 16 is essentially shaped in the form of a rectangular parallelepiped (cuboid), and an upper end section 32 has an essentially cylindrical shape. Based on these different shapes, a stepped section 34 is formed on the magnetic cover 16 by the middle flank section 30 and the upper end section 32. A first sealing element 36 is provided on a side wall of the upper end section 32.

[0031] Furthermore, a first connection opening 37 is formed on a side surface of the middle flank section 30. The first connection opening 37 is connected to the lower chamber 23.

[0032] A second sliding opening 38, extending along the longitudinal direction of the cylinder tube 14, is formed within it. The cross-section of the second sliding opening 38, perpendicular to the longitudinal direction, is essentially perfectly circular. Furthermore, the second sliding opening 38 opens at an upper end and a lower end of the cylinder tube 14. Specifically, the cylinder tube 14 is a hollow body whose exterior is essentially shaped like a rectangular parallelepiped (cuboid).

[0033] Near the opening at the lower end of the second sliding opening 38, a thin-walled section 40 is formed, the inner wall of which is recessed relative to the side of the outer wall. Thus, the thickness of the thin-walled section 40 is smaller compared to other areas. A lower end surface of the thin-walled section 40 abuts the stepped part 34 of the magnetic cover 16. Furthermore, the upper end section 32 of the magnetic cover 16 is inserted through the second sliding opening 38 and simultaneously into the thin-walled section 40. The area between the thin-walled section 40 and the upper section 32 of the magnetic cover 16 is sealed by the first sealing element 36.

[0034] An outer edge of the plate element 42 is held between an upper end face of the magnetic cover 16 and a roof surface of the thin-walled section 40. In other words, the plate element 42 is clamped by the magnetic cover 16 and the cylindrical tube 14. Details of the plate element 42 will be explained later.

[0035] The opening at the upper end of the cylinder tube 14 is closed by the head cover 18. An inlet element 44, in the form of a substantially cylindrical column, is designed to project from the lower end face of the head cover 18. As the inlet element 44 enters the interior of the cylinder tube 14, the head cover 18 is inserted into the cylinder tube 14. A second sealing element 46 is arranged on the side wall of the inlet element 44 such that the area between the cylinder tube 14 and the head cover 18 is sealed by the second sealing element 46.

[0036] A second connection opening 50 is formed in a side surface of the head cover 18. The second connection 50 is positioned on the same side surface on which the first connection 37 is formed. A feed and drain mechanism (not shown) is connected to the first connection 37 and the second connection 50.

[0037] In the four corners of the housing, rod openings 52 with bases are formed, each extending from the head cover 18 through the cylinder tube 14 and to near the lower end of the central flank section 30 of the magnet cover 16. Threaded sections of the first to fourth tie rods 54a to 54d (connecting elements), which are inserted through the respective rod openings 52, are screwed to threaded sections that are cut near the base sections of the rod openings 52. Furthermore, their heads are held in annularly stepped sections 55 provided in the head cover 18. By screwing the first to fourth tie rods 54a to 54d together, the head cover 18, the cylinder tube 14, and the magnet cover 16 are fastened and connected to one another, thereby forming the housing 20.

[0038] In the assembly described above, the head cover 18, the cylinder tube 14, and the magnet cover 16 are made of a paramagnetic metal, such as an aluminum alloy or the like. On the other hand, the first to fourth tie rods 54a to 54d are made of a ferromagnetic metal, such as cast iron (for example, a material corresponding to SS400 according to the Japanese Industrial Standard JIS). As will be described later, they serve as anti-rotation elements, i.e., so-called rotation stops, which prevent the first to fourth permanent magnets 56a to 56d, which serve as attracting and holding elements, from rotating.

[0039] Inside the housing 20, the first sliding opening 22 and the second sliding opening 38 are separated by the plate element 42. Furthermore, the second sliding opening 38 is divided by a piston 58 and the head cover 18 into a second middle chamber 60 and an upper chamber 62.

[0040] On the other hand, the upper chamber 62 is formed between the piston 58 and the inlet element 44 of the head cover 18. The second connection 50 is connected to the upper chamber 62.

[0041] The magnetic holder 10 comprises the first to fourth permanent magnets 56a to 56d in order to attract and hold the workpiece 12 (cf. Fig. 3) All of the first to fourth permanent magnets 56a to 56d are held in the yoke 64 by their own magnetic force or by a connecting element, such as a retaining bolt or the like.

[0042] As in Fig. As shown in Figure 2, the first to fourth permanent magnets 56a to 56d each have a substantially fan-shaped form, with their central angle in plan view being substantially 90°. By arranging such a column-shaped body in a circle, a permanent magnet with a cylindrical column shape is produced. Specifically, the first permanent magnet 56a is in contact with the second permanent magnet 56b and the fourth permanent magnet 56d, which are located next to the first permanent magnet 56a, and is arranged such that it faces the third permanent magnet 56c.

[0043] The radii of the first to fourth permanent magnets 56a to 56d can, for example, be chosen to have a value on the order of 10–30 mm. A typical example of a radius is approximately 15 mm. In this case, the total diameter of the permanent magnets is approximately 30 mm.

[0044] Furthermore, a typical example of the height (distance from a lower end face to an upper end face) of the first to fourth permanent magnets 56a to 56d is approximately 10 mm.

[0045] For better understanding, in Fig. 2 The bottom wall section of the magnetic cover 16 is not shown. In fact, however, the first to fourth permanent magnets 56a to 56d are covered by the bottom wall section of the magnetic cover 16 (cf. Fig. 3).

[0046] If the first to fourth permanent magnets 56a to 56d are moved so that they, together with the yoke 64 and the piston 58, approach the workpiece 12, the following occurs: Fig. Figure 3 shows workpiece 12 attracted. In detail, for the first to fourth permanent magnets 56a to 56d, a visible surface facing the workpiece 12 serves as a magnetic workpiece attraction surface (attraction and holding surface).

[0047] The magnetic polarity of the workpiece attraction surfaces of both the first permanent magnet 56a and the third permanent magnet 56c is N-polarity (north pole). In contrast, the magnetic polarity of the workpiece attraction surfaces of both the second permanent magnet 56b and the fourth permanent magnet 56d is S-polarity (south pole). Accordingly, the polarities of the workpiece attraction surfaces, proceeding clockwise, form an N pole (first permanent magnet 56a), an S pole (second permanent magnet 56b), an N pole (third permanent magnet 56c), and an S pole (fourth permanent magnet 56d). In this case, combinations of the N pole and the S pole are formed in two pairs on the workpiece attraction surfaces. The magnetic pole surfaces are exposed such that the N pole and the S pole, which have opposite polarities, lie next to each other.

[0048] On the side of the holding surfaces, which are held by the yoke 64, an S-pole (first permanent magnet 56a), an N-pole (second permanent magnet 56b), an S-pole (third permanent magnet 56c) and an N-pole (fourth permanent magnet 56d) are arranged next to each other in this order, in reverse order to the above arrangement.

[0049] The first drawbar 54a is positioned on an outer circumferential side of a transition region between the first permanent magnet 56a and the second permanent magnet 56b, or in other words, on an outer circumferential side of a transition region between the N pole (first permanent magnet 56a) and the S pole (second permanent magnet 56b) on the magnetic workpiece attraction surface. Similarly, the second drawbar 54b, the third drawbar 54c, and the fourth drawbar 54d are each arranged on outer circumferential sides of a transition region between the second permanent magnet 56b and the third permanent magnet 56c, on an outer circumferential side of a transition region between the third permanent magnet 56c and the fourth permanent magnet 56d, and on an outer circumferential side of a transition region between the fourth permanent magnet 56d and the first permanent magnet 56a, respectively.

[0050] Finally, the first to fourth tie rods 54a to 54d are provided at transition areas between magnetic poles on the magnetic workpiece attraction surface.

[0051] Because the first to fourth pull rods 54a to 54d are made of a ferromagnetic material, the magnetic forces from the first to fourth permanent magnets 56a to 56d are also exerted on the first to fourth pull rods 54a to 54d. Specifically, attractive forces are generated between the first to fourth permanent magnets 56a to 56d and the first to fourth pull rods 54a to 54d.

[0052] Since, as described above, mutual attractive forces occur between the first to fourth permanent magnets 56a to 56d and the first to fourth tie rods 54a to 54d, the first to fourth permanent magnets 56a to 56d are prevented from rotating. Ultimately, the first to fourth permanent magnets 56a to 56d act in such a way that they stop the rotation of the piston 58 and the yoke 64. In this way, the rotational torque of the first to fourth permanent magnets 56a to 56d can be reduced to essentially zero by the first to fourth tie rods 54a to 54d, which form the housing 20.

[0053] When the first to fourth tie rods 54a to 54d are positioned as described above, the rotational torque generated in the first to fourth permanent magnets 56a to 56d is reduced to a minimum. In other words, stopping the rotation can be implemented even more efficiently.

[0054] As described above, the first to fourth permanent magnets 56a to 56d are held in the yoke 64 (see figure). Fig. 3) Specifically, the yoke 64 comprises the large-diameter flange 66 and a small-diameter shaft 68. The first to fourth permanent magnets 56a to 56d are held to the flange 66 by their own magnetic force or by connecting elements such as bolts or the like. The flange 66 and the shaft 68 are integrally formed within the yoke 64 (from the same element). Since the yoke 64 is made of a ferromagnetic metal, such as cast iron (a material corresponding to SS400), it is possible for the first to fourth permanent magnets 56a to 56d to be magnetically attracted to the flange 66.

[0055] The thickness of the flange 66 is set, for example, to 10 mm. The flange 66 serves as a safety or backup yoke. A wear ring 70 is also provided on one side wall of the flange 66. The wear ring 70 prevents the center of the flange 66 from shifting or slipping relative to the center of the first sliding opening 22, and the flange 66, and by extension the yoke 64, are guided along the inside of the first sliding opening 22.

[0056] On the other hand, an annular recess or depression 72 is formed on the upper end face of the flange 66, which is set back towards the side of the lower end face. Furthermore, a bolt hole 76, into which a connecting bolt 74 is screwed, is formed at the upper end of the shaft 68.

[0057] The plate element 42 is arranged between the piston 58 and the first to fourth permanent magnets 56a to 56d (the flange 66 of the yoke 64). For this purpose, an insertion hole 78 is formed essentially in the center of the plate element 42 as a through-opening to allow passage of the shaft 68 of the yoke 64. Naturally, the inner diameter of the insertion hole 78 is smaller than the outer diameter of the piston 58.

[0058] Furthermore, a disc-shaped projection 80 is formed on a lower end face of the plate element 42, which projects towards the flange 66. When the piston 58, the yoke 64 and the first to fourth permanent magnets 56a to 56d are positioned at top dead center (cf. Fig. 3), which corresponds to a displacement endpoint, the disk-shaped projection 80 enters the annular recess 72, which is formed in the flange 66 of the yoke 64.

[0059] A wide second annular groove 82 is formed in an upper end face of the plate element 42. An annular first damper 84 is received in the second annular groove 82. A lower end face of the piston 58 abuts the first damper 84 when it reaches bottom dead center, which corresponds to another end point of displacement (see figure). Fig. 4).

[0060] Furthermore, a connecting groove 85 is formed on the plate element 42 near the insertion hole 78, which enables a connection between the first middle chamber 24 and the second middle chamber 60. Through the connecting groove 85, compressed air can move from the first middle chamber 24 into the second middle chamber 60, or vice versa.

[0061] An upper end face of the shaft 68, which was inserted through the insertion hole 78 of the plate element 42, is inserted into an insertion hole 86 formed in a lower end face of the piston 58. A blind bolt hole 88 extends from the upper end face of the piston 58 to the insertion hole 86. The connecting bolt 74, which is stopped in the blind bolt hole, is screwed into the bolt hole 76. This connects the piston 58 and the yoke 64, and the first to fourth permanent magnets 56a to 56d are indirectly held to the piston 58 by the yoke 64.

[0062] A third sealing element 90 is provided on a side wall of the piston 58. This third sealing element 90 seals the area between the piston 58 and the cylinder tube 14. Specifically, it prevents compressed air in the upper chamber 62 from leaking into the second middle chamber 60 via a gap between the side wall of the piston 58 and an inner wall of the second sliding opening 38 of the cylinder tube 14. For the same reason, it also prevents air in the second middle chamber 60 from leaking into the upper chamber 62.

[0063] A wide third annular groove 92 is formed on an upper end face of the piston 58. An annular second damper 94 is accommodated in the third annular groove 92. When the piston 58 reaches top dead center, the second damper 94 abuts the lower end face of the inlet element 44 of the cylinder head cover 18 (see figure). Fig. 3).

[0064] The magnetic holder 10 according to the present embodiment is essentially constructed in the manner described above. Next, the operating mode and advantageous effects of actuating the magnetic holder 10 will be described.

[0065] The magnetic holder 10 is attached, for example, to a distal end of a robot arm (not shown). Furthermore, as the robot performs certain operations, as described in Fig. Figure 3 shows the magnetic workpiece attraction surfaces of the first to fourth permanent magnets 56a to 56d arranged so that they face the workpiece 12. At this time, the piston 58, the yoke 64, and the first to fourth permanent magnets 56a to 56d are positioned at top dead center. Accordingly, at this time, the magnetic forces of the first to fourth permanent magnets 56a to 56d are not applied to the workpiece 12.

[0066] Next, compressed air is supplied to the upper chamber 62 via the second port 50 by the supply and discharge mechanism. The compressed air pushes the piston 58 from its upper end face. Simultaneously, compressed air is discharged from the lower chamber 23 through the first port 37 by the action of the supply and discharge mechanism. The compressed air moves through the connecting groove 85 from the second middle chamber 60 into the first middle chamber 24. Additionally, the compressed air from the first middle chamber 24 passes between the side wall of the flange 66 and the inner wall of the first sliding opening 22 and moves into the lower chamber 23. Subsequently, the aforementioned compressed air is also discharged through the first port 37.

[0067] The piston 58, which has absorbed the pressure from the compressed air in the upper chamber 62, is moved in a direction in which it approaches the plate element 42 (it descends). Since the lower chamber 23, the first middle chamber 24 and the second middle chamber 60 are under negative pressure, the piston 58 can be moved easily.

[0068] Simultaneously with the descent of the piston 58, the yoke 64, which is connected to the piston 58, and the first to fourth permanent magnets 56a to 56d, which are connected to the yoke 64, are also lowered. This brings the first to fourth permanent magnets 56a to 56d closer to the workpiece 12. Finally, the piston 58, the yoke 64, and the first to fourth permanent magnets 56a to 56d reach bottom dead center, so that the Fig. The condition shown in section 4 is produced.

[0069] When the piston 58 reaches bottom dead center, it comes into contact with the first damper 84, which is provided on the plate element 42. Vibrations or collisions occurring at the moment of impact are dampened or buffered by the first damper 84, thus sufficiently preventing vibration of the magnetic holder 10. Since damage to the piston 58 or the plate element 42 is avoided, the durability of the magnetic holder 10 is also improved.

[0070] When the first to fourth permanent magnets 56a to 56d reach bottom dead center, their magnetic forces are exerted on the workpiece 12 because their respective magnetic workpiece attraction surfaces are positioned sufficiently close to the workpiece 12. Specifically, the workpiece 12 is attracted by the magnetic forces of the first to fourth permanent magnets 56a to 56d, and the workpiece 12 is attracted to and held by the bottom wall section of the magnet cover 16. Because the flange 66 of the yoke 64 serves as a backup yoke, the workpiece 12 is attracted and held even more effectively.

[0071] Since the magnetic cover 16 is made of a paramagnetic metal, it cannot function as a yoke. Specifically, the yoke does not extend between the first to fourth permanent magnets 56a to 56d and the workpiece 12. This prevents any influence on the formation of the magnetic path between the first to fourth permanent magnets 56a to 56d and the workpiece 12.

[0072] Since the damping element 28, made of rubber, is provided on the lower end surface of the magnetic cover 16, the loads acting on the magnetic cover 16 and, via the cover, on the magnetic holder 10 are reduced when the workpiece 12 is magnetically attracted to the bottom wall of the magnetic cover 16. Accordingly, vibration of the magnetic holder 10 can be sufficiently prevented, while at the same time preventing damage to the magnetic cover 16 or to the first to fourth permanent magnets 56a to 56d.

[0073] In the Fig. 5A and Fig. Figure 5B schematically represents a magnetic flux occurring in the prior art where the magnetic workpiece attraction surface is merely one pole of an N-pole, and a region where magnetic saturation occurs. In this case, the magnetic flux originating from the N-pole of the magnetic workpiece attraction surface passes through the interior of the workpiece 12 and is directed towards the S-pole on the rear surface. The region where magnetic saturation has occurred has a substantially circular shape.

[0074] On the other hand, the Fig. 6A and Fig. Figure 6B shows schematic views illustrating the magnetic flux that occurs when a combination of an N-pole and an S-pole is formed as a pair on the magnetic workpiece attraction surface, and a region where magnetic saturation occurs. In this configuration, the magnetic flux originating from the N-pole of a magnetic workpiece attraction surface passes through the interior of the workpiece 12 and is directed to an S-pole adjacent to the workpiece attraction surface and to an S-pole on its rear outer surface. Furthermore, the magnetic flux originating from the N-pole located on the rear surface of the magnetic attraction surface passes through the interior of the workpiece 12 and is directed to an S-pole of the workpiece attraction surface, simultaneously passing through the interior of the yoke 64 and being directed to the S-pole on the rear surface of the magnetic workpiece attraction surface.Accordingly, magnetic saturation, apart from being circular, also occurs at a position along the diameter.

[0075] Fig. Figure 7 is a schematic view showing the magnetic flux that occurs when a combination of an N-pole and an S-pole is formed as two pairs on the magnetic workpiece attraction surface, and a region where magnetic saturation occurs. In this case, the magnetic saturation occurs not only in a circular shape but also at positions along two diameters. Compared to the configuration described above, when a combination of N-poles and S-poles is formed, it is understood that the amount of magnetic flux passing through the interior of the workpiece 12 is greater.

[0076] Fig. Figure 8 is a diagram showing a relationship between the outer diameters of the permanent magnets and the attractive forces generated thereby, showing a magnetic holder in which a single permanent magnet is used and the magnetic workpiece attraction surface has a single N-pole formed thereon (▪-line (black square)), a magnetic holder in which two permanent magnets are used and the magnetic workpiece attraction surface has an N-pole and an S-pole, wherein a combination of an N-pole and an S-pole is formed thereon as a pair (♦-line (black diamond)), and a magnetic holder 10 according to the present embodiment in which four permanent magnets of the first to fourth permanent magnets 56a to 56d are used and the magnetic workpiece attraction surface has a combination of N-poles and S-poles formed thereon as two pairs (▲-line (black triangle)).It is understood that the materials and holding forces of the permanent magnets are the same for each of the magnetic holders, and that the overall dimensions of the permanent magnets are the same in each case.

[0077] It also follows from Fig. 8. It is evident that as the number of magnetic poles on the magnetic workpiece attraction surfaces increases, the attractive force also increases. This difference in attractive forces is particularly pronounced when the total outer diameter of the permanent magnets exceeds 20 mm, or when the thickness of the workpiece 12 becomes small. From this, it becomes clear that by forming the combination of N-poles and S-poles on the magnetic workpiece attraction surface as one or more pairs, and especially two or more pairs, a sufficient attractive force is achieved so that even if the workpiece 12 consists of a thin steel plate and is a heavy object, it can be attracted and held.As described above, this is because the combination of N poles and S poles formed on the magnetic workpiece attraction surface increases the magnitude of the magnetic flux passing through the interior of the workpiece 12.

[0078] As noted above, the combination of N-poles and S-poles formed on the magnetic workpiece attraction surface increases the attractive force on the workpiece 12. In particular, according to the present embodiment, the combination of N-poles and S-poles is formed in two pairs on the magnetic workpiece attraction surface. This ensures a sufficient attractive force.

[0079] Assuming that the materials and properties of the permanent magnets are identical, the attractive force on the workpiece 12 can be increased accordingly in the present embodiment and with identical outer diameters. This means that workpieces 12 with a significantly greater weight can be attracted and held.

[0080] Alternatively, if the attractive force is to remain the same, the permanent magnets can be designed with a smaller diameter overall. In other words, the magnetic holder 10 can be designed to be more compact and smaller.

[0081] The distal arm end and the magnetic holder 10 are then moved to suitable positions by the robot performing predetermined operations. The workpiece 12 is also moved during this process.

[0082] Next, the compressed air from the upper chamber 62 is discharged through the second port 50 by the supply and discharge mechanism. Simultaneously, compressed air is supplied from the supply and discharge mechanism through the first port 37 into the lower chamber 23. Some of the compressed air enters the first intermediate chamber 24 between the flange 66 and the side wall of the first sliding opening 22, and also passes through the connecting groove 85 into the second intermediate chamber 60. When the flange 66 of the yoke 64 absorbs the pressure from the compressed air in the lower chamber 23, the piston 58 simultaneously absorbs the pressure from the compressed air in the first intermediate chamber 24. Since the upper chamber 62 is under negative pressure, the piston 58 is moved away from the plate element 42 (it rises).

[0083] According to the present embodiment, the third sealing element 90 is provided on the side wall of the piston 58. Specifically, no sealing element is provided between the yoke 64 and the inner wall of the second middle chamber 60. In the process described above, the element that absorbs the pressure of the compressed air supplied to the upper chamber 62 and the pressure of the gas that has moved into the second middle chamber 60 is, in both cases, the piston 58. Although an area covered by the shaft 68 exists on the lower end face of the piston 58, the flange 66 also absorbs the pressure of the compressed air. Specifically, the pressure-bearing area during the downward movement of the piston 58 and the pressure-bearing area during the upward movement of the piston 58 are essentially the same. Accordingly, a reduction in the thrust required to lift the piston can be avoided.

[0084] Following the raised piston 58, the yoke 64 and the first to fourth permanent magnets 56a to 56d are also raised integrally with it. Specifically, the first to fourth permanent magnets 56a to 56d are physically separated from the workpiece 12, and as a consequence, the magnetic forces of the first to fourth permanent magnets 56a to 56d can no longer be exerted on the workpiece 12. Accordingly, the workpiece 12 is released from the load exerted by the magnetic force of the first to fourth permanent magnets 56a to 56d.

[0085] The piston 58, the yoke 64, and the first to fourth permanent magnets 56a to 56d finally reach top dead center. In other words, the Fig. 3 shown, condition restored.

[0086] When the piston 58 reaches top dead center, the disc-shaped projection 80 of the plate element 42 engages in the annular recess 72 formed in the flange 66 of the yoke 64. Simultaneously, the second damper 94, provided on the piston 58, strikes the inlet element 44 of the head cover 18. Vibrations or impacts occurring during this engagement are dampened and buffered by the second damper 94. Therefore, vibrations of the magnetic holder are sufficiently reduced. Furthermore, since damage to the piston 58 or the head cover 18 is prevented, the durability of the magnetic holder 10 is improved.

[0087] During the process described above, rotation of the first to fourth permanent magnets 56a to 56d is also prevented. As noted above, this is because the first to fourth pull rods 54a to 54d are located near the first to fourth permanent magnets 56a to 56d. Since the rotation of the first to fourth permanent magnets 56a to 56d is restricted in this way, changes in the magnetic flux density near the car switch, for example, can be avoided. Accordingly, malfunctions of the car switch that would be caused by a change in magnetic flux density can also be prevented.

[0088] The first to fourth tie rods 54a to 54d serve as elements that firmly fasten the head cover 18, the cylinder tube 14, and the magnet cover 16 together to form the housing 20. Since the rotation of the first to fourth permanent magnets 56a to 56d is prevented, there is no need to provide other elements for this purpose. Accordingly, an increase in the number of parts is avoided. At the same time, the magnetic holder 10 can be built compactly, which also offers cost advantages.

[0089] The present invention is not particularly limited to the embodiment described above and various modifications can be made to it without departing from the scope of the present invention.

[0090] As in Fig. As shown in Figure 9, for example two or more U-shaped permanent magnets 100 can be combined (in Fig. (9 are three shown), and two or more of the N poles and two or more of the S poles can be provided on the magnetic workpiece attraction surface. Apart from such a combination, the U-shaped permanent magnets 100 (in Fig. (10 are two shown) are combined so that their magnetic pole faces are aligned as shown in Fig. 10 is shown and seen from below.

[0091] Furthermore, as in Fig. Figure 11 shows a combination of three or more rod-shaped magnets 102 (in Fig. 11 are three shown) may be formed in a so-called Halbach array, and a combination of a group of N-poles and S-poles may be provided at the workpiece attraction surface.

[0092] Although several permanent magnets are used in the embodiment described above, a single permanent magnet can also be used, which is produced by magnetizing it so that an arrangement of N poles and S poles in two or more pairs is present on the magnetic workpiece attraction surface.

[0093] As an example of such a permanent magnet, as in Fig. As shown in Figure 12, the magnetization of a specific object, for example a cylindrical body 98, is carried out such that the orientation of the magnetic poles is U-shaped. Such a permanent magnet can be produced by bringing a U-shaped magnet very close to a base surface of the cylindrical body 98. This creates an N pole and an S pole on the base surface. Specifically, one base surface becomes the magnetic workpiece attraction surface, while no magnetic poles are formed on the remainder of the other base surface.

[0094] Apart from arranging a U-shaped permanent magnet very close to a base surface of the cylindrical body 98 or the like, it is also possible to bring another U-shaped permanent magnet very close to the other base surface, as described in Fig.Figure 13 shows a permanent magnet being produced in which an N pole and an S pole are formed on a base surface, which serves as the magnetic workpiece attraction surface, and an S pole and an N pole are formed on the rear surface. Specifically, in this case, the magnetization is carried out such that the magnetic poles are oriented perpendicular to the workpiece attraction surface.

[0095] Furthermore, it is possible to arrange the first damper 84 on the lower end face of the piston 58. Alternatively, the second damper 94 can be arranged on the lower end face of the inlet element 44 of the head cover 18.

[0096] Furthermore, the first damper 84 or the second damper 94 can be omitted.

Claims

[1] A magnetic holder (10) which attracts and holds a workpiece (12) with a magnetic force of a permanent magnet (56a to 56d), comprising: a housing (20) with a cylinder tube (14) in which a sliding opening (38) is formed through which a piston (58) is moved, and a head cover (18) which is attached to the cylinder tube (14) and closes one end of the sliding opening (38); a retaining element (66) which is connected to the piston (58) and is designed to hold the permanent magnet (56a to 56d); and a partitioning element (42) which is positioned and fixed inside the housing (20) and is designed to form an inner chamber inside the cylinder tube (14) together with the piston (58); wherein the magnetic holder (10) further comprises at least a first damper (84) and a second damper (94), wherein the first damper (84) is arranged on the partitioning element (42) or the piston (58) and is configured to dampen vibrations when the piston (58) strikes the partitioning element (42), and wherein the second damper (94) is provided on the piston (58) or the head cover (18) and is configured to dampen vibrations when the piston (58) strikes the head cover (18), characterized by , that a combination of an N-pole and an S-pole is provided as one or more pairs on a magnetic workpiece attraction surface of the permanent magnet (56a to 56d), wherein the magnetic workpiece attraction surface faces the workpiece (12), and that the cylinder tube (14) and the head cover (18) are connected by a connecting element (54a to 54d) made of a ferromagnetic metal, and that the connecting element (54a to 54d) is designed to serve as a rotation-prevention element which prevents rotation of the permanent magnet (56a to 56d). [2] The magnetic holder (10) according to claim 1, characterized by , that the piston (58) and the retaining element (66) are connected via a shaft (68) which has a smaller diameter than the piston (58), wherein the partitioning element (42) is positioned and fixed between the piston (58) and the retaining element (66), and wherein an insertion opening (78) through which the shaft (68) is inserted is formed in the partitioning element (42). [3] The magnetic holder (10) according to claim 2, characterized by , that the retaining element (66) and the shaft (68) are formed in one piece from the same element (64). [4] The magnetic holder (10) according to any of the preceding claims, characterized by , that the element (64) with the retaining element (66) is a yoke (64). [5] The magnetic holder (10) according to any of the preceding claims, characterized by , that the connecting element (54a to 54d) is provided at a transition area between the N pole and the S pole, which are arranged side by side on the magnetic workpiece attraction surface. [6] The magnetic holder (10) according to any of the preceding claims, characterized by , that a sealing element (90) is provided on a side wall of the piston (58) and that an area between the piston (58) and the cylinder tube (14) is sealed by the sealing element (90).

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