STROKE CONTROL DEVICE FOR USE IN PRESS

Abstract: A device for controlling the length of stroke of a slide (8) in a press has an eccentric member (3) fitting on an eccentric member mounting portion (1) of a drive shaft (2) and having an outer peripheral surface which is at an eccentricity (e) with respect to the drive shaft (2) and sliding surfaces (3c, 3d) which are in vertical sliding engagement with both side surfaces (1c,1d) of the eccentric mounting portion (1). The device also has a connecting rod (5) having an upper end portion rotatably carried by the outer peripheral surface of the eccentric member (3) and a lower end portion swingably connected to the slide (8) of the press. A gear shaft (10) vertically extends through the eccentric member mounting portion (1) and provided with spline-type gear teeth (10a, 10b) on upper and lower end portions thereof, the gear shaft (10) being rotatably supported at its upper and lower ends thereof by the eccentric member (3). A plurality of screw rods (11, 12) are arranged on both sides of the gear shaft (10) such as to extend in parallel with the gear shaft through the eccentric member mounting portion (1), the screw rods (11, 12) being fixed at their upper and lower ends to the eccentric member (3). Gears (13a, 13b,14a, 14b) are screwed to upper and lower end portions of the screw rods (11, 12) and meshing with the spline type gear teeth (10a, 10b) on the upper and lower end portions of the gear shaft (109, the gears contacting upper and lower end surfaces (1a, 1b) of the eccentric member mounting portion (1).

Description: BACKGROUND OF THE INVENTION The present invention relates to a stroke control device comprising: (a) a drive shaft adapted to be rotatingly driven and having an eccentric member mounting portion; (b) an eccentric member fitting on said eccentric member mounting portion, said eccentric member having an outer peripheral surface which is at an eccentricity with respect to said drive shaft and sliding surfaces which are in vertical sliding engagement with both side surfaces of said eccentric member mounting portion; (c) a connecting rod having an upper end portion rotatably carried by the outer peripheral surface of said eccentric member and a lower end portion swingably connected to a slide; (d) a vertically extending first gear provided with gear teeth on upper and lower end portions thereof, said gear being rotatably supported at its upper end by said eccentric member; (e) a plurality of screw rods arranged on both sides of said gear such as to extend in parallel with said gear and through said eccentric member mounting portion; (f) second gears being provided on the upper end portions of said screw rods and meshing with said gear teeth on the upper and lower end portions of said first gear, said second gears contacting upper end surfaces of said eccentric member mounting portion; (g) whereby, when said first gear is rotated, said second gears rotate to cause said screw rods to move up and down relative to said drive shaft together with said first gear and said eccentric member so as to cause a change in the amount of eccentricity of said eccentric member with respect to said drive shaft, thereby allowing a control of the length of stroke of the slide. A stroke control device of this type which is discussed below in detail is disclosed in GB-A-515 585. A stroke control device for a press has been known which incorporates, as disclosed in Japanese Patent Examined Publication No. 51-12150, a pair of eccentric members. More specifically, this stroke control device has an eccentric shaft portion on a drive shaft, and an eccentric sleeve rotatably mounted on the outer surface of the eccentric shaft portion for a rotation relative thereto, the eccentric sleeve having outer peripheral surface centered at a point which is at an eccentricity from the axis of the eccentric shaft portion. The stroke control device further has a connecting rod the upper end of which rotatably fits around the eccentric sleeve, while the lower end of the connecting rod is connected to a slide of a press. In operation, the eccentric shaft portion is rotated relative to the eccentric sleeve so as to vary the amount of eccentricity and, hence, the stroke length of the slide. The stroke control device further incorporates a releasable locking mechanism which, when the press which drives the rotary shaft operates, locks the eccentric shaft portion and the eccentric sleeve against relative rotation, whereas, when the eccentricity is to be varied, unlocks them from each other so as to allow a relative rotation therebetween. This known stroke control device, however, suffers from a disadvantages in that the construction is inevitably complicated due to the use of the releasable locking mechanism. Another problem encountered with this known stroke control device is that, since the transmission of the torque from the eccentric shaft portion to the eccentric sleeve is conducted indirectly through the above-mentioned locking mechanism, the rigidity of the path of torque transmission is undesirably reduced to impair the precision in the torque transmission. Still another problem is that the eccentricity cannot be varied linearly due to the fact that the locking mechanism which locks the eccentric shaft portion and the eccentric sleeve against relative rotation is designed to change the locking position non-linearly, i.e., in a stepped manner. In the stroke control device of the type mentioned in the beginning and described in GB-A-515 585 in order to adjust the amount of eccentricity for changing the length of the stroke, one or more nuts have to be loosened and a bolt with the first gear is rotated to cause longitudinal movement of the screw rods. During this operation, the second gears engaging with the first gear are rotated and hence the screw rods are moved by an identical amount. Consequently, the amount of eccentricity or the stroke is varied. After the eccentricity has been adjusted in the above-mentioned manner, the nut or nuts have to be tightened. It is to be noted that in the structure of GB-A-515 585 the eccentric member mounting portion is formed with screw threads with which the screw rods engage. With such structure, it is difficult to assemble the parts while assuring proper engagement among the parts such as gears and screws. In other words, it is difficult to achieve proper engagement between the second gears and between the screw threads formed in the eccentric member mounting portion and the screw rods. If these parts are designed to be engaged tightly, without substantial clearances thereamong, there is the possibility that the actually worked parts cannot be assembled. For this reason, the parts have to be designed and worked to be assembled or engaged with substantial clearances thereamong. Since substantial clearances must exist among these parts, it is necessary that the nut or nuts are tightened for obviating adverse effects such as rattling which may otherwise be caused by the clearances. It is further to be noted that the nut or nuts need to be tightened each time after the adjustment of eccentricity has been effected. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a stroke control device which is capable of overcoming the above-described problems of the prior art. To this end, according to the present invention, there is provided a stroke control device of the type mentioned in the beginning, which is characterized in that (1) said first gear being a gear shaft extending through a non-threaded through hole in said eccentric member mounting portion; (2) said gear teeth on said gear shaft being spline-type gear teeth; (3) said gear shaft being rotatably supported at its lower end by said eccentric member; (4) said screw rods extending through non-threaded through holes of said eccentric member mounting portion; (5) said screw rods being fixed at their upper and lower ends to said eccentric member; (6) second gears also being screwed to lower end portions of said screw rods; (7) said second gears being screwed to said screw rods; and (8) said second gears contacting permanently upper and lower end surfaces said eccentric member mounting portion. In operation, as the gear shaft is rotated while the drive shaft is fixed, the gear rotates without moving vertically so that the screw rod engaging with the gear is caused to move up and down,with the result that the eccentric member also moves up and down together with the screw rod. In consequence, the amount eccentricity of the eccentric member with respect to the drive shaft is changed to enable the stroke length of the slide to be controlled. The above and other objects, features and advantages of the present invention will become clear from the following description when the same is read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a vertical sectional view of a press incorporating a stroke control device embodying the present invention; and Fig. 2 is a sectional view taken along the line II-II of Fig. 1. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figs. 1 and 2, there is shown a press incorporating a stroke control device in accordance with the present invention. The stroke control device has a drive shaft 2 which is rotatably carried by a housing 4 and provided with an eccentric member mounting portion 1. The stroke control device also has an eccentric member 3 which fits around the eccentric member mounting portion 1 and which has outer peripheral surfaces 3b, 3b, located on a circle centered at an axis 3a which is at an eccentricity e from the axis 2a of the drive shaft 2. The eccentric member mounting portion 1 has flat parallel upper and lower end surfaces 1a and 1b, as well as flat and parallel side surfaces 1c and 1d, thus exhibiting a substantially rectangular cross-section. The side surfaces 1c and 1d of the eccentric member mounting portion 1 slidingly engage with inner surfaces 3c and 3d of the eccentric member 1. The stroke control device further has a connecting rod 5 the upper end of which is held on the eccentric member 3 through a sleeve-type slide bearing 6 such that the upper end of the connecting rod 5 is rotatable relative to the eccentric member 3. The lower end of the connecting rod 5 is rotatably connected to the slide 8 of a press through a pin 7 and a slide bearing 15. The slide 8 is vertically movably carried by the housing 4 through a slide bearing 9. Through holes 1e, 1f and 1g are formed substantially at axially mid portion of the eccentric member mounting portion 1 and on the left and right side of the mid portion as viewed in Fig. 1, in such a manner as to extend vertically through the eccentric member mounting portion 1. These through holes 1e, 1f and 1g receive, respectively, a gear shaft 10,a screw rod 11 and another screw rod 12 which extend in parallel with one another. Spline-type gear teeth 10a and 10bare formed on upper and lower portions of the gear shaft 10. The gear shaft 3 is rotatably supported at its upper and lower ends by the eccentric member 3. A recess 10e of a non-circular cross-section is formed on the end surface of the upper end 10c of the screw shaft 10 so as to be engaged by a suitable tool 16 which can be inserted to reach this recess 10e through continuous holes 4a, 5a and 6a formed in the wall of the housing 4, connecting rod 5 and the slide bearing 6. The screw rods 11 and 12 are fixed to the eccentric member 3 at their upper and lower ends. Gears 13a, 14a and gears 13b, 14b are screwed to upper and lower portions of the screw rods 11 and 12. The upper gears 13a, 14a and lower gears 13b, 14b mesh with the upper and lower gear teeth 10a and 10b. The lower end surfaces 13a,14a of the gear 13a contact the upper end surface 1a of the eccentric member mounting portion 1, while the upper end surfaces of the gears 13b, 14b contact the lower end surface 1bof the eccentric member mounting portion 1b. As will be understood from Fig. 2, the eccentric member 3 is composed of two parts: namely, an upper part presenting the outer peripheral surface 3b and a lower part presenting the outer peripheral surface 3b′. The upper and lower parts are assembled together around the eccentric member mounting portion 1 and fastened to each other by means of bolts 18. In Fig. 1, a reference numeral 17 denotes an oil groove. In operation, as the drive shaft 2 rotates about its axis 2a as indicated by an arrow A,the eccentric member 3 also rotates about the axis 2a as a unit with the drive shaft 2,so that the upper end of the connecting rod 5 moves up and down while being allowed to rotate relative to the eccentric member 3 by virtue of the provision of the slide bearing 6. In consequence, the slide 8 also moves up and down in accordance with the movement of the connecting rod 5. In consequence, a press work is effected on a material which is placed between a lower die disposed under the slide 8 and an upper die which is secured to the underside of the slide 8. The length of stroke of the sliding motion of the slide is twice as large the above-mentioned eccentricity e . When it is desired to change the length of stroke of the slide 8, the operator inserts a tool 16 through the holes 4a, 5a and 6a to bring the end 16a of the tool 16 into engagement with the recess 10e in the end surface of the gear shaft 10 and rotates the gear shaft 10 as indicated by an arrow B while fixing the drive shaft 2 against rotation. The rotation of the gear shaft 10 causes the gears 13a, 13b, 14a and 14bto rotate so that the screw rods 11 and 12 meshing with these gears are moved up and down so that the gear shaft 10 and the eccentric member 3 are moved up and down together with the screw rods. As a result, the amount e of eccentricity of the eccentric member 3 is changed with respect to the drive shaft 2, thus effecting a control of the length of stroke of the slide 8. As will be understood from the foregoing description, in the stroke control device of the present invention, the transmission of the torque from the drive shaft to the eccentric mmeber is made directly through the engagement between both side surfaces of the eccentric mmeber mounting portion of the drive shaft and the sliding surfaces of the eccentric member. In consequence, the construction of the eccentricity control device is simplified and the rigidity of the path of transmission of the torque is increased to enhance the precision of transmission of the torque. In addition, the stroke of the slide can be controlled linearly simply by rotating the gear shaft. Furthermore, the amount of eccentricity, i.e., the stroke of the slide, can be indicated in terms of angle or amount of rotation of the gear shaft with the aid of a suitable gradation, because the eccentricity e varies in proportion to the angle or amount of rotation of the gear shaft.

Claims: A stroke control device comprising: (a) a drive shaft (2) adapted to be rotatingly driven and having an eccentric member mounting portion (1); (b) an eccentric member (3) fitting on said eccentric member mounting portion (1), said eccentric member (3) having an outer peripheral surface (3b) which is at an eccentricity with respect to said drive shaft (2) and sliding surfaces (3c, 3d) which are in vertical sliding engagement with both side surfaces (1c, 1d) of said eccentric member mounting portion (1); (c) a connecting rod (5) having an upper end portion rotatably carried by the outer peripheral surface (3b) of said eccentric member (3) and a lower end portion swingably connected to a slide (8); (d) a vertically extending first gear (10) provided with gear teeth (10a, 10b) on upper and lower end portions thereof, said gear (10) being rotatably supported at its upper end (10c) by said eccentric member (3); (e) a plurality of screw rods (11, 12) arranged on both sides of said gear (10) such as to extend in parallel with said gear (10) and through said eccentric member mounting portion (1); (f) second gears (13a, 14a) provided on the upper end portions of said screw rods (11, 12) and meshing with said gear teeth (10a, 10b) on the upper and lower end portions of said first gear (10), said second gears (13a, 14a) contacting upper end surfaces (1a) of said eccentric member mounting portion (1); (g) whereby, when said first gear (10) is rotated, said second gears (13a, 13b, 14a, 14b) rotate to cause said screw rods (11, 12) to move up and down relative to said drive shaft (2) together with said first gear (10) and said eccentric member (3) so as to cause a change in the amount of eccentricity (e) of said eccentric member (3) with respect to said drive shaft (2), thereby allowing a control of the length of stroke of said slide (8), characterized in that (1) said first gear being a gear shaft (10) extending through a non-threaded through hole (1e) in said eccentric member mounting portion (1); (2) said gear teeth on said gear shaft (10) being spline-type gear teeth (10a, 10b); (3) said gear shaft (10) being rotatably supported at its lower end (10d) by said eccentric member (3); (4) said screw rods (11, 12) extending through non-threaded through holes (1f, 1g) of said eccentric member mounting portion (1); (5) said screw rods (11, 12) being fixed at their upper and lower ends to said eccentric member (3); (6) second gears (13b, 14b) also being provided to lower end portions of said screw rods (11, 12) and contacting lower end surfaces (1b) of said eccentric member mounting portion (1); (7) said second gears (13a, 13b, 14a, 14b) being screwed to said screw rods (11, 12); and (8) said second gears (13a, 13b, 14a, 14b) permanently contacting said upper and lower end surfaces (1a, 1b) of said eccentric member mounting portion (1).

Inventors: KATO, HEIZABURO
Applicants: SANKYO MANUFACTURING COMPANY, LTD.
Application year: 1988
Main classification: B30B1
IPC codes: B30B15, B30B1