CYLINDER TYPE HYDRAULIC CLAMP

Abstract: In a cylinder type hydraulic clamp in which a clamping means is adapted to be actuated by means of a hydraulic cylinder, a piston rod 14 is projected through the cylinder body 8 of the hydraulic cylinder 4 and is equipped at its leading end portion with the clamping means 5. The clamping means 5 is arranged concentrically with the piston rod 14 and adapted to be resiliently urged by means of a contraction spring 20 toward its contracted position as well as to be pushed by means of an expansion slant cam 21 toward its expanded position. And at the time of the clamping actuation, when the clamping means 5 is hydraulically actuated toward the cylinder body 8 through the piston 9 and the piston rod 14, firstly the clamping means 5 is expanded diametrally by means of the expansion slant cam 21 against the resilient force of the contraction spring 20 and then a member B to be clamped is fixedly pressed between the cylinder body 8 and the clamping means 5 expanded as mentioned above.

Description: Present invention relates to a cylinder type hydraulic clamp with the features of the first part of claim 1. A hydraulic clamp with the features of the first part of claim 1 is known from US 1 959 081. It is object of the invention to provide a hydraulic clamp in which a good clamping operation is ensured with a great clamping ability and in which the durability of the piston rod is high. The present invention will be described in greater detail in connection with the following drawings wherein: Figures 1 through 14 show embodiments of the present invention; Figure 1 through 5 show a first embodiment thereof; Figure 1 is a vertical sectional view showing a use condition of a hydraulic clamp; Figures 2(a) through 2(c) are operational explanatory views of the hydraulic clamp; Figure 2(a) is a view showing an unclamping condition thereof; Figure 2(b) is a view showing a transitive condition of the change-over thereof; Figure 2(c) is a view showing a clamping condition thereof; Figure 3 is a sectional view on III - III directed line in Fig. 2(a); Figure 4 is a sectional view on IV - IV directed line in Fig. 2(b); Figure 5 is an exploded perspective view showing a clamping means and a contraction spring; Figures 6 through 9 show other embodiments of the present invention; Figures 6(a) through 6(d) show a second embodiment thereof and are operational explanatory views of the hydraulic clamp; Figure 6(a) is a view showing an unclamping condition thereof; Figure 6(b) is a view showing a retracted condition of a clamping means; Figure 6(c) is a view showing a projected condition of the clamping means; Figure 6(d) is a view showing a clamping condition thereof; Figure 7 shows a variant example of the second embodiment and is a view corresponding to Fig. 6(a); Figure 8 shows a third embodiment of the present invention and is a view corresponding to Fig. 2(c); Figure 9 shows a fourth embodiment thereof and is a view corresponding to Fig. 2(c); Figures 10 through 14 show variant examples of the hydraulic clamp respectively; Figure 10 shows a first variant example and is a view corresponding to Fig. 1; Figure 11 shows a second variant example and is a partial view corresponding to Fig. 1; Figure 12 shows a third variant example and is a partial view corresponding to Fig. 11; Embodiments of the present invention will be explained with reference to the drawings. Fig.s 1 through 5 show the first embodiment. In Fig. 1, a workpiece 2 to be clamped is adapted to be fixedly secured onto an upper surface of a fixed table 1 (member A) through a hydraulic clamp 3. The hydraulic clamp 3 is provided with a hydraulic cylinder 4 and a clamping means 5. The hydraulic cylinder 4 is fixedly secured on the underside of the fixed table 1 by means of a plurality of bolts 6, and the clamping means 5 is interlockingly connected to the upper portion of the hydraulic cylinder 4. The clamping means 5 is adapted to be pushed down by a hydraulic pressure in the hydraulic cylinder 4 so that the workpiece 2 can be fixedly pressed to the upper surface of the fixed table 1. The hydraulic cylinder 4 is constructed as a type being returned by a single acting spring 34. That is, a piston 9 is accommodated vertically slidably within the lower portion of the hydraulic cylinder body 8 in an oil-tight manner. A clamping actuation oil chamber 10 is provided above the piston 9 and a spring chamber 11 is provided below the piston 9. The clamping actuation oil chamber 10 is communicated with an unillustrated hydraulic pressure source through an oil supply/discharge port 12. On the other hand, in the spring chamber 11 there is provided a piston returning spring 13 composed of a compression coil spring. A piston rod 14 is projected upwardly from the upper surface of the piston 9 so as to pass through the upper end wall 16 of the cylinder body 8 slidably in an oil-tight manner. Furthermore the piston rod 14 is adapted to be passed vertically slidably through the through-hole 17 of the fixed table 1 as well as the through-hole 18 of the workpiece 2. The piston rod 14 is provided at its upper portion 19 with the clamping means 5, a contraction spring 20 and an expansion slant cam 21. And as shown in Fig. 2, at least the lower portion 23 of the clamping means 5 is adapted to be urged resiliently by the contraction spring 20 toward the unclampable retracted position Y radially close to the periphery of the piston rod 14 and on the contrary to be pushed toward the clampable advanced position X radially remote from the periphery of the piston rod 14. The allowable stroke L of the piston 9 within the cylinder body 8 in the vertical direction is settled in not less than such a dimension obtained by adding a clamping means expansion lift N to a clamp actuation lift M. The clamping means 5 and the contraction spring 20 will be explained with reference to Fig. 1 and Figs 3 through 5. Fig. 3 is a vertical sectional view on III - III directed line in Fig. 2(a), Fig. 4 is a vertical sectional view on IV - IV directed line in Fig. 2(b), and Fig. 5 is an exploded perspective view showing the clamping means 5 and the contraction spring 20. The clamping means 5 comprises three pieces of clamping members 25, 25, 25 arranged in an annular shape, and the respective clamping members 25 are adapted to be shifted radially expansively and contractively with respect to the piston rod 14. That is, the respective clamping members 25 arranged in an annular shape are provided at the middle height of their inner peripheries with expanding and contracting shift guide peripheral grooves 26. A expanding and contracting shift guide ring 27 is fixedly fitted to the upper portion 19 of the piston rod 14 and slidably engaged with the expanding and contracting shift guide peripheral grooves 26. Further, there is provided a guide means for guiding the respective clamping members 25 linearly in the radial direction of the piston rod 14. That is, a rod output portion 28 is formed by diametrally enlarging the rod output portion 19, and three radial guide channels 29, 29, 29 are formed on the underside of the rod output portion 28. Guide pins 30 are projected from the upper surfaces of the respective clamping members 25 so as to be slidably guided and engaged with the guide channels 29. Accordingly, the clamping members 25 are guided slidably only in the radial direction relative to the piston rod 14. Spring receiving grooves 31 are formed on the outer peripheral surfaces of the respective clamping members 25, and the contraction spring 20 is mounted around the spring receiving grooves 31. As shown in Fig. 5, the contraction spring 20 is composed of a spiral plate spring. The spring width at one of the longitudinal opposite end portions of the plate spring is narrowed downwardly and on the contrary the spring width at the other end portion thereof is narrowed upwardly. Therefore, in the spring expanded condition in which the clamping means 5 is changed over to the clampable advanced position X, since the total spring width of the overlapped longitudinal opposite end portions of the contraction spring 20 can be made nearly equal with the spring width of the other portion thereof, the resilient force of the contraction spring 20 to act in the peripheral direction thereof can be equalized. Accordingly, when the clamping means 5 is changed over from the clampable advanced position X to the unclampable retracted position Y, the respective clamping members 25 can be slid smoothly radially inwardly. Next, the expansion slant cam 21 will be explained with reference to Fig. 1. A guide cylinder 33 is projected upwardly from the upper end wall 16 of the cylinder body 8. In an annular space between the guide cylinder 33 and the piston rod 14, there is provided the cylindrical expansion slant cam 21 vertically slidably. The expansion slant cam 21 is resiliently urged upwardly by means of a pushing spring 34 and prevented from shifting up not less than a predetermined lift by an inner stopper flange 35 of the guide cylinder 33. A tapered cam surface 36 which is formed at the upper portion of the expansion slant cam 21 is adapted to be brought in contact with a cam engaging surface 37 formed on the lower inner peripheral surfaces of the respective clamping members 25 by a resilient force of the pushing spring 34. The hydraulic clamp 3 is adapted to be changed over at the time of the clamping and unclamping operations as shown in Fig.s 2(a) through 2(c). Fig. 2(a) shows the unclamping condition, in which the piston 9 is raised to the top dead center by the piston returning spring 13 so that the clamping means 5 is changed over to the unclampable retracted position Y. When the workpiece 2 is exchanged, the workpiece 2 is externally fitted to the piston rod 14 from the upper side thereof so as to be set onto the upper surface of the fixed table 1 under such a condition as to be shown in Fig. 2(a). Then the clamping actuation oil chamber 10 within the cylinder body 8 is supplied with a pressure oil through the oil supply/discharge port 12. Thereupon, the piston 9 is pushed down by the hydraulic pressure against the resilient force of the piston returning spring 13 so that the clamping means 5 can be pushed down by the output portion 28 of the piston rod 14. Under such a condition that the clamping means expanding actuation is performed during the change-over from the state shown in Fig. 2(a) to the state shown in Fig. 2(b), the piston 9 and the piston rod 14 are lowered the distance of the clamping means expansion lift N. Accordingly, the clamping means 5 is advanced radially outwardly along the expanding and contracting shift guide ring 27 against the resilient force of the contraction spring 20 so as to be changed over from the unclampable retracted position Y to the clampable advanced position X. Further, under such a condition that the clamping actuation is performed during the change-over from the state shown in Fig. 2(b) to the state shown in Fig. 2(c), the piston 9 and the piston rod 14 are adapted to be lowered the distance of the clamping actuation lift M provided below the clamping means expansion lift N. Thereupon, the rod output portion 28 formed in the upper portion of the piston rod 14 pushes down the clamping means 5 and fixedly presses the work 2 through the lower portion 23 of the clamping means 5. At the time of the change-over from the clamping condition shown in Fig. 2(c) to the unclamping condition shown in Fig. 2(a), the pressure oil is adapted to be discharged from the clamping actuation oil chamber 10 so that the piston 9 can be returned to the top dead center by the resilient force of the piston returning spring 13. In this case, the expanding and contracting shift guide ring 27 is moved together with the ascent of the piston rod 14. During the transition from the state shown in Fig. 2(b) to the state shown in Fig. 2(a), the ascent of the expansion slant cam 21 is prevented by the stopper inner flange 35. On the contrary, the respective clamping means 25 is raised continuously through the expanding and contracting shift guide ring 27 so that the clamping means 5 can be changed over from the clampable advanced position X to the unclampable retracted position Y by the resilient force of the contraction spring 20. As mentioned above, since the clamping means 5 is changed over interlockingly with the piston 9 of the hydraulic cylinder 4, it becomes unnecessary to manually operate the clamping means 5 and the clamping and unclamping operations for the hydraulic clamp 3 becomes easy. When automating the operations for advancing and retracting the clamping means 5 radially with respect to the periphery of the piston rod 14, since the position of the clamping means 5 is changed over interlockingly with the operation of the hydraulic cylinder 4, the actuation device for attaching and detaching the clamping means 5 is not required differently from the hydraulic clamp having the conventional construction ( refer to Fig.s 15 and 16 or to Fig. 17 ). Furthermore, while the piston 9 is shifted the distances of the respective lifts M, N, since the operational procedure for the positional changing over operation of the clamping means 5 and the clamping and unclamping operations of the hydraulic cylinder 4 is distinguished, the operational procedure control device having the conventional construction is also not required. In this way, since the actuation device for attaching and detaching the clamping means 5 as well as the operational procedure control device can be omitted, the hydraulic clamp 3 can be simplified in construction and made small in size. Further, since the clamping means 5 is expanded substantially uniformly to the position remote from the periphery of the piston rod 14 at the time of the change-over from the unclampable retracted position Y to the clampable advanced position X, the lower portion 23 of the clamping means 5 is arranged around the whole periphery of the rod output portion 28. Therefore, the openings incapable of pressing can be reduced remarkably and the sufficiently large pressing area can be obtained surely. Consequently, the pressing force of the clamping means 5 can be increased and the clamping capability of the hydraulic clamp 3 can be enhanced. Since the pressing area of the clamping means 5 is sufficiently large, the pressure per unit area at the contacting surface of the clamping means 5 with the rod output portion 28 can be decreased. Furthermore, since the clamping means 5 is arranged substantially uniformly around the whole periphery of the rod output portion 28, the stress concentration and the bending stress are hardly generated in the piston rod 14. Accordingly, the durability of the piston rod 14 can be improved. Fig.s 6 through 9 show a second embodiment of the present invention. The hydraulic clamp 38 is so constructed that the upper portion 19 of the piston rod 14 can be retracted below the upper surface of the fixed table 39 ( the fixed member A ). The same component members as those employed in the first embodiment are indicated by the same symbols correspondingly. In Fig. 6(a) showing the unclamping condition, a pneumatic cylinder body 41 of a pneumatic cylinder 40 is fixedly secured onto the the underside of a fixed table 39. The cylinder body 8 of the hydraulic cylinder 4 is accommodated vertically slidably within the upper portion of the pneumatic cylinder body 41 as well as a pneumatic piston 42 is accommodated within the lower portion of the pneumatic cylinder body 41 vertically slidably in an air-tight manner. The upper end of a pneumatic piston rod 43 projected upwardly from the pneumatic piston 42 is connected to the cylinder body 8 of the hydraulic cylinder 4. A pneumatic actuation chamber 44 provided above the pneumatic piston 42 is in communication with a pneumatic source ( not illustrated ) through an air supply/discharge port 45. A ascent spring 47 is mounted within a spring chamber 46 provided below the pneumatic piston 42. The symbol 20 is the contraction spring for the clamping means 5, and the symbol 21 is the expansion slant cam therefor. The hydraulic clamp 38 having the construction as mentioned above is adapted to operate as follows. Under the unclamping condition shown in Fig. 6(a), the oil supply/discharge port 12 of the hydraulic cylinder 4 and the air supply/discharge port 45 of the pneumatic cylinder 40 are not subjected to a pressure, the cylinder body 8 is raised by the resilient force of the ascent spring 47, and the rod upper portion 19 of the hydraulic cylinder 4 projects outside above the upper surface of the fixed table 39. Under the above-mentioned condition shown in Fig. 6(a), a pressurized air is supplied to the pneumatic actuation chamber 44 through the air supply/discharge port 45. Thereupon, as shown in Fig. 6(b), the cylinder body 8 of the hydraulic cylinder 4 is lowered through the pneumatic piston 42 and the pneumatic piston rod 43, and the rod upper portion 19 is retracted below the upper surface of the fixed table 39. Under this condition, a work 48 ( a member B to be fixed ) is adapted to be sent along the upper surface of the fixed table 39. Then, under such a condition that the workpiece 48 is placed on the upper surface of the fixed table 39, the pressurized air within the pneumatic actuation chamber 44 is discharged through the air supply/discharge port 45. Thereupon, as shown in Fig. 6(c), the cylinder body 8 is raised by the resilient force of the ascent spring 47 so that the rod upper portion 19 projects from the upper surface of the work 48. Under this condition shown in Fig. 6(c), oil under a pressure is adapted to be supplied to the clamping actuation oil chamber 10 within the cylinder body 8 of the hydraulic cylinder 4. Thereupon, as shown in Fig. 6(d), the clamping means 5 is pushed down through the piston 9 and the piston rod 14 so that the work 48 is fixedly pressed by the clamping means 5 onto the fixed table 39. Fig. 7 shows a variant example of the embodiment shown in Fig. 6 and is a view corresponding to Fig. 6(a). In this hydraulic clamp 49, a pneumatic piston 53 of a pneumatic cylinder 52 is formed integrally with the upper end portion of a cylinder body 51 of a hydraulic cylinder 50, and a pneumatic actuation chamber 54 is provided above the pneumatic piston 53. The pneumatic actuation chamber 54 is communicated with the air supply/discharge port 56 through a communication groove 55. A ascent spring 59 is mounted between a piston 57 of the hydraulic cylinder 50 and the bottom wall of a spring chamber 58 of the pneumatic cylinder 52. Fig. 8 shows the third embodiment. In this embodiment, a cylindrical forming roll 63 ( a member B to be clamped ) is adapted to be detachably attached to a frame 62 ( a fixed member A ) of a forming machine 61 through a hydraulic clamp 64. The frame 62 is adapted to rotatably support a cylinder body 66 of a hydraulic cylinder 65, and a V belt pulley 67 is fixedly secured to the right end portion of the cylinder body 66. An inner flange 68 formed in the right end portion of the forming roll 63 is adapted to be fixedly pressed onto the left end portion of the cylinder body 66 by a clamping means 69. A pressure oil is adapted to be supplied to a clamping actuation oil chamber 70 within the cylinder body 66 through a rotary joint 71 and a hydraulic hose 72. By the way, the symbol 73 indicates a piston rod, the symbol 74 indicates a contraction spring, and the symbol 75 indicates an expansion slant cam. According to this construction, in case that the external surface of the cylindrical forming roll 63 is damaged by a heavy wear and the like, it is enough to exchange only the forming roll 63 and it is unnecessary to exchange the whole of a roll arrangement differently from a conventional one unit type forming roll. Accordingly, this forming machine 61 is economical because the number of exchanging component members can be decreased at the time of its maintenance. Fig. 9 shows the fourth embodiment. In this embodiment, the right end portion of a cylinder body 77 of a hydraulic cylinder 76 is threadably and fixedly engaged with a fixed pipe 78 ( a fixed member A ), and a pipe 79 to be connected ( a member B to be clamped ) is adapted to be fixedly pressed onto the left end portion of the cylinder body 77 by a clamping means 80. A piston 81 and a piston rod 82 of the hydraulic cylinder 76 are formed in a cylindrical configuration so that both of the pipes 78, 79 can be communicated with each other. Fig.s 10 through 14 indicate variant examples of a hydraulic clamp respectively. Fig. 10 is a view corresponding to Fig. 1, which shows the first variant example. In this variant example, the lower portion of an expansion slant cam 84 is accommodated within an upper end wall 86 of a cylinder body 85 vertically slidably in an oil-tight manner. A stopper outer flange 87 is formed in the lower end of the expansion slant cam 84 so that the expansion slant cam 84 can be prevented thereby 87 from being shifted upwardly not less than a predetermined lift by a hydraulic force exerted in a clamping actuation oil chamber 88 as well as a resilient force of a pushing spring 89. The expansion slant cam 84 may have such a construction as, at least, to be allowed to be lowered with respect to a piston rod 91 at the time of the clamping actuation of a clamping means 90. The push spring 89 may be omitted so that the cam 84 is pushed up only by a hydraulic pressure as a pushing up force. Fig. 11 shows the second variant example and is a partial view corresponding to Fig. 1. An expansion slant cam 95 is formed integrally with the lower portion of a rod upper portion 94 of a piston rod 93, and a rod output portion 96 is arranged above the expansion slant cam 95. A downwardly tapered cam surface 97 of the expansion slant cam 95 is brought in contact with a cam engaging surface 99 of a clamping means 98 by means of a push spring 100. The push spring 100 is mounted between a lower spring retainer 102 fixed to a cylinder body 101 and an upper spring retainer 103 arranged vertically shiftably along a predetermined extent with respect to the lower spring retainer 102. And expanding and contracting shift guide grooves 105 of the clamping means 98 are slidably engaged with an expanding and contracting shift guide ring 104 formed in the upper end of the upper spring retainer 103. A means for guiding the clamping means 98 radially linearly comprises guide pins 106 projected from the upper spring retainer 103 and guide channels 108 formed in respective clamping members 107. Fig. 12 shows the third variant example. This variant example is obtained by further modifying the one shown in Fig. 11. A rod output portion 111 is formed in the lower portion of an expansion slant cam 110.

Claims: A cylinder hydraulic clamp including a hydraulic cylinder (4) and a clamping means (5), comprising: a hydraulic cylinder body (8), and a piston (9) having a piston rod (14) projecting upwardly through an upper end wall of said cylinder body (8) and including at an upper portion (19) thereof the clamping means (5), said clamping means (5) being adapted to be pushed down by a force exerted by the piston (9) and the piston rod (14) under the action of a hydraulic pressure of a pressurized oil supplied to a clamping actuation oil chamber (10) provided within the cylinder body (8), whereby a workpiece (2, B) to be clamped when externally fitted to the piston rod (14) is pressed from an upper side thereof between the cylinder body (8) and the clamping means (5), a lower portion (23) of the clamping means (5) being adapted to be moved between a clamping advanced position radially remote from the periphery of the piston rod (14) and an unclamping retracted position radially close to said periphery of the piston rod (14), an allowable stroke (L) for said piston (9) within the cylinder body (8) being not less than a distance obtained by adding a clamping means expansion lift distance (N) to a clamp actuation lift distance (M), and the clamping means (5) operating in a clamping means expanding actuation condition in which the piston (9) and the piston rod (14) are lowered by a distance equal to the clamping means expansion lift distance (N) from the top dead center position thereof, characterized in that, said clamping means (5) being resiliently urged by a contraction spring (20) toward the unclamping retracted position and, conversely, is pushed by coaction with an expansion slant cam (21) toward the clamping advanced position, said clamping means (5) is adapted to be pushed expansively by the expansion slant cam (21) against the contraction spring (20) from the unclampable retracted position to the clamping advanced position, and in a clamp actuation condition in which the piston (9) and the piston rod (14) are lowered the distance of the clamp actuation lift (M) arranged below the clamping means expansion lift (N), said clamping means (5) is adapted to be pushed down by a rod output portion formed in the upper portion of the piston rod (14), said clamping means (5) comprises a plurality of clamping members (25) arranged in an annular shape; expanding and contracting shift guide peripheral grooves (26) are formed in the respective clamping members (25) arranged in the annular shape, and and an expanding and contracting shift guide ring (27) is engaged with the expanding and contracting shift guide peripheral grooves (26) so as to guide the clamping members radially and slideably, in parallel from the unclamping retracting position (Y) to the clamping advanced position (X) in the clamping means expanding actuation condition in which the piston (9) is actuated to move downwardly the distance of the clamping means expansion lift (N), and conversely so that the expanding and contracting shift guide ring (27) can separate the respective clamping members (25) from the expansion slant cam (28) in the clamping means contracting condition in which the piston (9) is actuated to move upwardly the distance of the clamping means expansion lift (N). A cylinder type hydraulic clamp as recited in claim 1, characterized in that said contraction spring (20) is composed of a spiral plate spring, which is fitted around the plurality of clamping members (25) arranged in an annular shape. A cylinder type hydraulic clamp as recited in claim 1 or 2, characterized in that said cylinder body (8) of the hydraulic cylinder (4) is fixedly secured to a fixed member (A). A cylinder type hydraulic clamp as recited in one of the preceding claims, characterized in that said cylinder body (8, 77) of the hydraulic clamp (38, 49) is adapted to be actuated upwardly and downwardly by a force supplied by a pneumatic cylinder (40, 52). A cylinder type hydraulic clamp as recited in one of the preceding claims, characterized in that said fixed member (A) and said workpiece to be clamped (B) are both pipes (78, 79). A cylinder type hydraulic clamp as recited in one of the preceding claims, characterized in that said cylinder body (8) of the hydraulic cylinder is supported rotatably by the fixed member (A).

Inventors: YONEZAWA, KEITARO
Applicants: KABUSHIKI KAISHA KOSMEK
Application year: 1988
Main classification: B23Q3
IPC codes: B25B5, B21D37