Holder Device

[0001] The present invention relates to a holder device for holding a cutting tool such as an end mill inserted to a tool insertion portion, the holder device being configured to control a pressure of a pressure medium such as a fluid held therein to deform the tool insertion portion, thereby to apply a pressure to a grasped portion of the cutting tool for grasping thereof.

[0002] In a holder device utilizing a pressure medium, a grasping portion for grasping a cutting tool is formed thin to promote its deformation whereas a support portion is formed thick to minimize its deformation for the sake of pressure loss prevention. In this way, an outer diameter of the support portion of the holder device is increased relative to a shaft diameter of a cylindrical portion of the cutting tool. However, this increased outer diameter of the support portion relative to the small-diameter cutting tool tends to invite interference when a narrow groove shape of an object is to be machined.

[0003] As an example of the holder device utilizing the pressure medium suitable for such a long and thin structure, there is known the holder device including a pressure guide arrangement for transmitting a supplied pressure along an axial distance between a pressure chamber and a pressure generator, the guide arrangement being formed of a sealed gap or passageway which is provided concentrically and annularly relative to a chuck axis line (see Patent Document 1).

[0004] Patent Document 1: Japanese Unexamined Patent Application National Transfer Publication No. 2007-531634

[0005] A tool chuck being elastic by liquid-pressure of Patent Document 1 includes an elastic sleeve disposed on the tool side and surrounded by a pressure chamber, a pressure generator axially spaced apart from the elastic sleeve relative to the axis of the chuck, and a pressure guide arrangement for transmitting a pressure from the pressure generator to the pressure chamber, wherein the elastic sleeve is deformable in a radial direction so as to clamp and fix a tool by an action of a pressure medium held within the pressure chamber. In the above, the pressure chamber is disposed between an end of a clamping sleeve formed integral with the device body and the elastic sleeve disposed on the inner circumference side of the clamping sleeve. The pressure guide arrangement is formed of an annular gap in the inner circumferential face of the clamping sleeve concentric relative to the chuck axis.

[0006] However, with the above-described configuration, due to the long axial distance existent between the pressure chamber and the pressure generator, both the device body and the clamping sleeve need to form a long and thin shaft or hole. And, extreme difficulty arises if an effort is made to enhance the circularity or cylindricality of the chuck portion or deviation precision relative to the chuck axis through a long and thin machining. Further, the pressure chamber is formed between an end of the clamping sleeve formed integral with the device body and the elastic sleeve, so the clamping sleeve should preferably have a high rigidness as a whole. On the other hand, regarding a portion at end of the clamping sleeve where the pressure chamber is to be formed, lower rigidness is sometimes preferred for allowing deformation of the elastic sleeve.

[0007] The object of the present invention is to provide a holder device that uses a pressure medium suitable for grasping a long and thin object to be grasped, the device eliminating need for a diameter-reducing machining for the device body and allowing use of a material suitable for sleeve deformation at a portion where a pressure chamber is formed.

[0008] According to a first characterizing feature of a holder device relating to the present invention, a holder device comprises: a device body; a sleeve disposed at a leading end of the device body and capable of deforming in a radial direction for grasping the grasped object through an action of a pressure medium; a pressure chamber formed circumferentially in the sleeve; and a support portion provided continuously from the device body for forming the pressure chamber together with the sleeve.

[0009] With the above-described configuration, the end of the holder device is comprising the device body, the sleeve and the support portion; and in particular, the leading end portion is comprising the sleeve and the support portion that are provided separately from the device body. Therefore, even with the holder device utilizing a pressure medium suitable for a long and thin construction, by effecting a small-diameter machining on the support portion, a small-diameter machining for the device body becomes unnecessary. Further, by using the sleeve and the support portion provided separately from the device body, a different material can be used for the sleeve and the support from a material used for the device body. With this, through selection from various materials for the sleeve and the support portion, the deformation of the sleeve can be readily controlled through an optimal combination of the sleeve and the support portion. As a result, the compression/expansion function of the sleeve is improved, so that the grasped object can be held rigidly.

[0010] According to a second characterizing feature of the present invention, the device body includes a pressure guide passageway for transmitting a pressure to the pressure chamber, and the pressure chamber is formed between the support portion and the sleeve.

[0011] With the above-described configuration, of the device body, the sleeve and the support portion, the pressure guide passageway is included in the device body, and the pressure chamber is formed by the two members, i.e. the sleeve and the support portion. Hence, the pressure guide passageway is formed in the device body having the rigidity, whereas the pressure chamber is formed with a shape suitable for the deformation of the sleeve by the sleeve and the support portion whose forming materials can be selected. As a result, the machining of the pressure guide passageway becomes easy and the machining precision of the pressure chamber can be improved.

[0012] According to a third characterizing feature of the holder device relating to the present invention, the pressure guide passageway and the pressure chamber are disposed at positions differing in a radial distance from a rotational axis of the device body.

[0013] If the pressure guide passageway and the pressure chamber are disposed at positions differing in a radial distance from a rotational axis of the device body as provided by the above-described arrangement, the position of the pressure guide passageway in the device body can be freely set. The sleeve freely sets the degree of expansion through reduction of thickness at its deforming portion with taking its material characteristics into consideration. For this reason, the pressure chamber is provided normally at a position having a short radial distance from the rotational axis of the device body. On the other hand, the pressure guide passageway can be provided by forming a radially large space at the thickness-wise center of the device body. So, speedy supply of the pressure to the pressure chamber is made possible. Further, when the pressure guide passageway is to be formed, a hole drilling work to the device body can be carried out easily.

[0014] According to a fourth characterizing feature of the holder device relating to the present invention, between the pressure guide passageway and the pressure chamber, there is formed an annular pressure-medium storage space surrounded by an end face of the device body and an end face of the support portion.

[0015] With the above-described arrangement, if an annular pressure-medium storage space surrounded by an end face of the device body and an end face of the support portion is formed between the pressure guide passageway and the pressure chamber, a liquid pressure of the pressure guide passageway will pervade circumferentially of the sleeve via the annular pressure-medium storage space. So that, the liquid pressure of the pressure chamber can easily pervade throughout in the circumferential direction. As a result, the grasped object can be grasped with a uniform pressure throughout in the circumferential direction.

[0019] Next, as an embodiment of the present invention, a screw-operation type holder device will be explained with reference to the accompanying drawings.

[0020] As shown in FIG. 1, a holder device 1 according to this embodiment includes a device body 2, a sleeve 3 provided on a leading end side of a tubular portion 2a of the device body 2, a support portion 9 formed circumferentially of the sleeve 3 on its outer circumference side, and a shank 5 projecting on the rear end side of the device body 2 to be engaged with a spindle of a machining tool. At an intermediate portion of the device body 2, a groove 6 to be grasped by a manipulator is formed.

[0021] The sleeve 3 includes a tubular hole 4 for accommodating and engaging a grasped object 7 such as a cutting tool. Further, in an outer circumference of the sleeve 3, a pressure chamber 8 is provided in such a manner as to surround throughout the inner circumferential face of a tubular hole 4 of the sleeve 3, and around the outer circumference of the pressure chamber 8, there is provided a support portion 9 covering this pressure chamber 8.

[0022] The device body 2 includes a pressure generator P having a female threaded hole 10 extending radially from its outer circumference face and a pressure generation chamber 11 communicating the female threaded hole 10 with the pressure chamber 8. Within the female threaded hole 10 and the pressure generation chamber 11, a threaded bar 12 is attached. This threaded bar 12 includes a head portion 12a and a leading end portion 12b having a smaller diameter than the head portion 12a. At the head portion 12a of the threaded bar 12, a male threaded portion is formed. And, on the outer circumferential face of the leading end portion 12b, a seal member 13 such as an O-ring is provided. The inside diameter of the pressure generation chamber 11 is set smaller than the inside diameter of the female threaded portion 10.

[0023] In operation, as the threaded bar 12 is inserted from its leading end portion 12b into the female threaded portion 10 thereby to threadingly introduce the male threaded portion into the female threaded hole 10 and push the leading end portion 12b of the threaded bar 12 into the pressure generation chamber 11, the seal member 13 at the leading end portion 12b comes into sealing contact with the whole inner circumferential face of the pressure generation chamber 11. As a result, an amount of fluid (pressure medium) such as water, oil, etc., is introduced from the pressure generation chamber 11 into the pressure chamber 8 to be sealed therein.

[0024] As shown in FIG. 1, by engaging a wrench T with the head portion 12a of the threaded bar 12 and then rotatably operating it about the axis of the threaded bar 12, a threading-in engagement amount of the threaded bar 12 relative to the female threaded hole 10 and the pressure generation chamber 11 can be adjusted.

[0025] If the capacity of the pressure generation chamber 11 is reduced by increasing the threading-in amount of the threaded bar 12, there occurs increase in the pressure of the fluid 14 sealed in and between the pressure generation chamber 11 and the pressure chamber 8. With this, the sleeve 3 is expanded toward the tubular hole 4 side, thereby to strongly grip the grasped object 7 engaged in the tubular hole 4 of the sleeve 3.

[0026] On the other hand, if the capacity of the pressure generation chamber 11 is increased by decreasing the threading-in amount of the threaded bar 12, there occurs decrease in the pressure of the fluid 14 sealed in and between the pressure generation chamber 11 and the pressure chamber 8. With this, the sleeve 3 is returned to the pressure chamber 8 side, thereby to allow removal of the grasped object 7 engaged in the tubular hole 4 of the sleeve 3.

[0027] As shown in FIG. 2, the sleeve 3 includes, at an axial center portion thereof, a trapezoidal protruding portion 3a protruding toward the pressure chamber 8 side and includes also thin portions 3c, 3d on axially opposed sides of the trapezoidal protruding portion 3a. Therefore, when the pressure inside the pressure chamber 8 is increased, in the sleeve 3, its thin portions 3c, 3d expand especially largely toward the tubular hole 4 side, so that the grasped object 7 is grasped mainly via the support from the thin portions 3c, 3d.

[0028] When forming the leading end portion of the holder device 1, firstly, the device body 2 and the support portion 9 will be fixedly attached to each other. Then, the sleeve 3 will be inserted from its leading end side for fixedly attaching this sleeve 3 to the device body 2 and the support portion 9.

[0029] The device body 2 includes a pressure guide passageway 15 extending parallel with the axial direction. The pressure guide passageway 15 is formed by a machining e.g. a drilling at a position of the device body 2 different in the radial direction relative to the rotational axis of the device body 2 from the position of the pressure chamber 8. And, this passageway 15 is communicated to an annular pressure-medium storage space 16 formed between the device body 2 and the support portion 9. The pressure-medium storage space 16 is surrounded by an end face of the device body 2 and an end face of the support portion 9 and is communicated to the pressure chamber 8 via a communication passageway 17 formed between an outer circumferential face of the device body 2 and an inner circumferential face of the support portion 9. With the above-described formation of the annular pressure-medium storage space 16 with utilization of an end face of the support portion 9, the liquid pressure of the pressure guide passageway 15 will pervade in the circumferential direction of the sleeve 3 via the annular pressure-medium storage space 16, so that pervading of the liquid pressure of the pressure chamber 8 throughout in the circumferential direction is promoted. As a result, the grasped object 7 can be grasped with uniform pressure from the whole circumferential direction.

[0030] With the above-described arrangement, the end portion of the holder device 1 is formed by the device body 2, the sleeve 3 and the support portion 9, and its leading end portion, in particular, is comprised of the sleeve 3 and the support portion 9 that are provided separately from the device body 2. Therefore, even in the case of a holder device 1 utilizing a pressure medium suitable for a long and thin construction, by effecting a small-diameter machining work to the support portion 9, a small-diameter machining work becomes unneeded for the device body 2. Further, with the use of the sleeve 3 and the support portion 9 that are provided separately from the device body 2, it is possible to employ a different material(s) for the sleeve 3 and the support portion 9 than a material used for the device body 2. With this, through selection from various kinds of material for the sleeve 3, the deformation of the sleeve 3 can be readily controlled by an optimal combination of the sleeve 3 and the support portion 9. As a result, the compression/expansion action of the sleeve 3 is improved, so that the grasped object 7 can be held rigidly.

[0031] Also, the pressure guide passageway 15 is formed in the device body 2 and the pressure chamber 8 is formed along the axial direction between the inner circumferential face of the support portion 9 and the outer circumferential face of the sleeve 3. With this, the pressure guide passageway 15 is formed in the device body 2 having rigidity, whereas the pressure chamber 8 is formed with a shape suitable for the deformation of the sleeve 3 by the sleeve 3 and the support portion 9 whose forming materials can be selected. As a result, the machining of the pressure guide passageway 15 becomes easy and the machining precision of the pressure chamber 8 can be improved.

[0032] Moreover, the pressure guide passageway 15 and the pressure chamber 8 are disposed at positions differing in the radial distance from the rotational axis of the device body 2. So, the position of the pressure guide passageway 15 in the device body 2 can be freely set.

[0033] For the sleeve 3, its expansion degree is set freely by forming its deforming portion thin in view of its material characteristics. For this reason, the pressure chamber 8 is provided at a position having a short radial distance from the rotational axis of the device body 2. On the other hand, the pressure guide passageway 15 is a space having a large diameter formed at the thickness-wise center portion of the device body 2, so speedy supply of pressure to the pressure chamber 8 is made possible.

[0034] (1) In the foregoing embodiment, the communication passageway 17 is provided between the pressure guide passageway 15 and the pressure chamber 8. Instead, as shown in FIG. 3, by increasing the length of the device body 2 and decreasing the length of the support portion 9, a reaction force from the pressure chamber 8 can be caused to be received by the device body 2.

[0035] (2) In the foregoing embodiment, there was shown the example wherein the support portion 9 is disposed on the outer circumferential side of the sleeve 3 and the pressure chamber 8 is formed between the outer circumferential face of the sleeve 3 and the inner circumferential face of the support portion 9. Instead of this, the support portion 9 may be disposed on the inner circumferential side of the sleeve 3 and the pressure chamber 8 may be formed between the inner circumferential face of the sleeve 3 and the outer circumferential face of the support portion 9. Incidentally, in this case, the grasped object is grasped through expansion of the outer diameter of the sleeve 3 with the action of the pressure medium inside the pressure chamber 8.

[0036] (3) In the foregoing embodiment, there was shown the example wherein the pressure chamber 8 is formed by the sleeve 3 and the support portion 9. Instead, the pressure chamber 8 may be formed by the sleeve 3, the device body 2 and the support portion 9.

[0037] (4) At an axial center portion of the sleeve 3, there may be formed a protruding portion which rises gently toward the pressure chamber 8 side. With this, when the pressure inside the pressure chamber 8 is increased, the sleeve 3 as a whole will be expanded toward the tubular hole 4 side. Alternatively, the axial center portion of the sleeve 3 may be formed flat having no protruding portion.

[0038] The present invention is applicable to various holder devices for use in attaching a cutting tool or the like to a spindle of a machining tool.

[0039] 1 holder device

[0040] 2 device body

[0041] 3 sleeve

[0042] 4 tubular hole

[0043] 7 grasped object

[0044] 8 pressure chamber

[0045] 9 support portion

[0046] 14 fluid (pressure medium)

[0047] 15 pressure guide passageway

[0048] 16 pressure-medium storage space

[0049] P pressure generator