Abstract:
A clamping screw for holding a tool to a threaded shaft is provided with a body member having a threaded surface for engagement with the threaded shaft. A flange ring is disposed about the body member and clampingly engages the tool when the body is threaded onto the shaft in engagement with the tool. An operating ring is rotatably disposed about the body member and retained from movement axially away from the flange ring. A torque increasing mechanism is operatively disposed about the body member between the operating ring and the flange ring and is configured to transmit torque from the operating ring to the body member. The torque increasing mechanism includes a first inclined cam surface disposed on the operating ring, a cam ring axially movably disposed but rotationally fixed about the body member, a second inclined cam surface disposed on the cam ring opposite to and corresponding to the first inclined surface, and a bearing supported on a retainer and disposed between the first inclined cam surface and the second inclined cam surface. The operating ring is rotatable with respect to the cam ring so that rotation of the operating ring applies torque and axial force to the cam ring through the bearing. A spring is operatively disposed between the cam ring and the operating ring and biases the cam ring toward an initial position with respect to the operating ring.

Description:
DETAILED DESCRIPTION 
     1. Technical Field of the Invention 
     This invention is a clamping screw such as an attachment nut or an attachment bolt and used to fix to the drive shaft of an electric tool a rotating tool such as the grindstone of a hand grinder or a circular hand saw, and relates to a clamping screw which is able to clamp by increasing the torque of a manually input rotational force. 
     2. Prior Art 
     The above-mentioned attachment nuts or bolts in prior art are clamping screws comprised of a threaded member forming a thread for attachment to the drive shaft of said electric tool, an operating ring to which the rotational force for clamping is input manually, and a differential retardation mechanism provided between these which increases torque by retarding the rotational force of the operating ring (for example, Japanese Patent No.4-257419). 
     Since the above-described differential retardation mechanism increases the torque by retardation, despite the advantage that the rotating tool can be clamped and fixed strongly with a small rotation of the operating ring, the mechanism is complex and has the disadvantage that precision is required in manufacture. 
     Problems To Be Resolved By The Invention 
     This invention has as its purpose the provision of a clamping screw which, unlike a structure such as the above-mentioned differential retardation mechanism, is not complex and does not require precision manufacture, has a power structure (a torque-increasing mechanism) of simple construction, and is able to clamp powerfully with a small rotational input. 
     This invention is characterized in being a clamping screw provided with a threaded member forming an attachment thread which screws together with the thread for attachment of the member to be attached to the shaft part, an operating ring supported on the outer surface of the outer end of said threaded member so as to freely rotate only and to which rotational force is input, a flange ring inserted over the outer surface of the inner end of said threaded member and having a flange surface which abuts the object to be attached on the clamping side from the inner end of said threaded member, and a torque-increasing mechanism on the outer surface of said threaded member between said operating ring and said flange ring and which increases the torque of the rotational force of the operating ring transmitting this to the flange ring, said torque-increasing mechanism being comprised with an inclined cam surface which applies an effective force in the direction of clamping to elements in contact through the rotation in the direction of clamping of said operating ring formed in the circumferential direction of the inner surface of said operating ring, a cam ring which is freely slidable in the axial direction only inserted over the outer surface of said threaded member, a coupled inclined cam surface which corresponds to the sloping cam surface of said operating ring formed on said cam ring, a needle bearing supported on a retainer fitted between the inclined cam surface of said operating ring and the coupled inclined cam surface of said cam ring, and a spring fitted between said cam ring and said operating ring which returns said cam ring to its initial position when the cam ring is not in operation, and moreover is characterized in being a clamping screw fitted with an adjustment ring between said cam ring and flange ring which applies to an adjustment to the rotation relative to the operating ring. 
     According to the invention, up until the point where the flange surface of the flange ring abuts the object to be attached with the attachment thread of the threaded member screwed onto the thread for attachment of member to be attached, since the screw resistance of the attachment thread of the threaded member is small, when the operating ring is rotated the threaded member rotates integrally due to the load resistance of the torque-increasing mechanism, the attachment thread of the threaded member being screwed onto the attachment thread of the member to be attached. When the flange surface of the flange ring comes in contact with the object to be attached, the forward screwing motion of the threaded member ceases and the rotational force on the operating ring thereafter acts on the torque-increasing mechanism and the inclined cam surface on the operating ring side of said mechanism presses against the coupled inclined cam surface of the cam ring via the needle bearing, so that said cam ring presses against the flange ring on the side in the direction of clamping through the increased torque force applied by the cam, the object to be attached being clamped by this increased torque pressure. 
     As a result of the above, since the torque-increasing mechanism is comprised of an inclined cam surface and a coupled inclined cam surface, the structure of the torque-increasing mechanism is simplified, manufacture is simple, and a satisfactory improvement in torque can be obtained without the requirement for precision. 
     Moreover, the use of a needle bearing results in linear contact with the inclined cam surface, so that smooth operation can be achieved over long periods without damage in the form of dents which interfere with smooth rotation being caused by extremely heavy loads acting to the cam surface through point pressure from, for example, ball-bearings. 
     Furthermore, by fitting an adjustment ring, it is possible to sense the degree of increased torque clamping. Moreover, it is possible to prevent both inclined cam surfaces overriding one another by means of two return springs or one return spring and position-restricting balls and restricting grooves, so that an accurate clamping and releasing action can be obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a lateral view of a cross section of the clamping screw; 
     FIG. 2 an exploded view of a cross section of the clamping screw; 
     FIG. 3 is a frontal view of a nut ring; 
     FIG. 4 is a rear view of a nut ring; 
     FIG. 5 is a rear view of an operating ring; 
     FIG. 6 is a frontal view of needle bearings; 
     FIG. 7 is a frontal view of a cam ring; 
     FIG. 8 is a lateral view of the developmental plane of the inclined cam surface; 
     FIG. 9 is a frontal view of one of the return springs; 
     FIG. 10 is a frontal view of the other return spring; 
     FIG. 11 is a frontal view of the adjustment ring; 
     FIG. 12 is a lateral view of a cross section of another clamping screw; 
     FIG. 13 is a frontal view of the cam ring used in FIG. 12; and 
     FIG. 14 is a rear view of the cam ring engaged with the operating ring in FIG.  12 . 
    
    
     PREFERRED EMBODIMENTS 
     An embodiment of the invention will now be described with reference to the drawings below. The drawings show a clamping screw formed in the shape of a nut, and in FIG.  1  and FIG. 2 clamping screw  10  is comprised of retainer  14  which retains nut ring  11 , operating ring  12 , needle bearing  13 , cam ring  15 , return springs  16   a ,  16   b , adjustment ring  17 , and flange ring  18 , the torque-increasing mechanism being comprised of inclined cam surface  27  (to be described later and which is formed on the inside of operating ring  12 ), needle bearing  13 , and cam ring  15 . 
     In the drawings,  19  is, for example, the drive shaft of an electric tool, male attachment thread  20  being formed at its end, rotating tool  22  being fixed to drive shaft  19  by said clamping screw  10  through the agency of fixed flange ring  21 . 
     Said nut ring  11 , as shown in FIG.  3  and FIG. 4, is formed in a ring shape and on its inner surface is formed a female attachment thread  23  for attachment which screws onto male thread  20  of said drive shaft  19 , and on two opposing places on its outer side are formed notches  24 ,  24  so that nut ring  11  may be turned with a wrench. 
     Operating ring  12  is inserted over the outer surface of the outside of nut ring  11 , being held by means of ball-bearings  25  so that rotation only is possible, and retained by retainer ring  26 . 
     As shown in FIG. 5, operating ring  12  has formed on the circumference of its inner surface in three equidistant positions (120° intervals) inclined cam surfaces  27  which apply a force which moves needle bearings  13  in the direction of clamping which are the elements which come into contact when said operating ring  12  rotates in the direction of clamping X, the angle of inclination θ of this inclined cam surface  27  being set at an angle smaller than the angle of inclination of the thread of female thread  23  of said nut ring  11 . 
     Notch hole  28  in one place on said operating ring  12  retains base ends  29   a ,  29   b  of the two above-mentioned return springs  16   a ,  16   b  by inserting them together. Moreover, in the inner surface are formed a number of notch depressions  30 , which retain elastic members  36  of said adjustment ring  17  to be described later. Furthermore, the rotational operation is made easier by forming a suitable knurl in the outer surface (not shown in the diagram). 
     As shown in FIG. 6, in addition to a number of needle bearings  13  being held so as to be able to rotate within retainer  14 , these needle bearing  13  are also held in such a way as to be able to move in the direction of thickness of retainer  14 . 
     Cam ring  15 , as shown in FIG. 7, forms a ring shape, and on the surfaces corresponding with the three inclined cam surfaces  27  of said operating ring  12  are formed three coupled inclined cam surfaces  31  which correspond with the angle of inclination of said inclined cam surfaces  27 , and moreover on part of the inner surface of these (for example over a range of approximately 50°) are formed arc-shaped grooves  33  which respectively retain the free ends  32   a ,  32   b  of said return springs  16   a ,  16   b . Moreover, splines  34  are formed on the inner surface which engage with splines  35  formed on the outer surface of said nut ring  11 , and are held such that they can slide in the axial direction with the small quantity of force required to clamp said cam ring  15 . 
     As will be clear from FIGS. 5 and 7, the three inclined cam surfaces  27  of operating ring  12  and coupled inclined cam surfaces  31  of cam ring  15  are fitted so that there is a spacing of 60° between them in a neutral position, said return springs  16   a ,  16   b  acting to restrain them within the range of ±60° of said neutral position, in other words so that both inclined cam surfaces  27 ,  31  do not override each other. 
     Cam ring  15 , needle bearings  13 , and operating ring  12  come into contact as shown in FIG. 8, and since needle bearings  13  are able to move in the direction of thickness of retainer  14 , it is possible to position cam ring  15  and operating ring  12  in parallel without distorting retainer  14 . 
     This condition is achieved by (diameter of needle bearings  13 )−(stepping of inclined cam surface  27 )&gt;thickness of retainer  14 . 
     Return springs  16   a ,  16   b , as also shown in FIGS. 9 and 10, are formed so that their respective winding directions are opposed to one another, and formed so that an elasticity is generated in their opposing directions of wind, base ends  29   a ,  29   b  being retained together in notch hole  28  of said operating ring  12  and free ends  32   a ,  32   b  engaging with the groove ends of arc-shaped grooves  33  of cam ring  15 . 
     When return springs  16   a ,  16   b  are retained as described above, even if operating ring  12  and cam ring  15  rotate in completely opposite directions with respect to one another, they can move back and forth in a neutral position since the force acting on them is neutralized. 
     Adjustment ring  17  has a ring shape, as shown in FIG. 11, and is cut out to form elastic members  36  to generate an elasticity in three equidistant positions on the outer surface, the heads  37  of elastic members  36  engaging with notch depressions  30  formed in the inner surface of said operating ring  12 , elastic members  36  engaging with notch depressions  30  in the next position through elastic displacement when this adjustment ring  17  and operating ring  12  rotate relative to one another, the rotation of operating ring  12  being adjusted by this engagement. This adjustment ring  17  is held so as to be able to rotate in the step formed in the inner surface of flange ring  18 . 
     Flange ring  18 , as shown in FIG.  1  and FIG. 2, is formed in a ring shape, and flange surface  38  on the clamping side is formed so as to be positioned on the clamping side rather than the inner surface of nut ring  11 , being inserted over the inner side of said nut ring  11  and retained with a slight bracing against operating ring  12  by means of elastic ring (snap ring)  39 . 
     To explain the action of clamping screw  10  of this structure, with reference to FIG. 1, when female thread  23  of nut ring  11  of clamping screw  10  is screwed onto male thread  20  of drive shaft  19 , and since the fixed resistance load of threads  20 ,  23  is initially lighter than the contact resistance load within operating ring  12 , when operating ring  12  is rotated nut ring  11  also rotates with it due to said contact resistance load and screws forward. With this screwing forward, flange surface  38  of flange ring  18  comes into contact with the side surface of rotating tool  22 , and when the forward screwing of nut ring  11  ceases, flange ring  18 , adjustment ring  17  and cam ring  15  cease rotating due to contact resistance, and in this state if operating ring  12  is rotated further in the clamping direction (approximately 30°) inclined cam surface  27  exerts pressure against coupled inclined cam surface  31  of cam ring  15  through the agency of needle bearing  13 , so that this pressure presses against flange ring  18  through the agency of adjustment ring  15 , and rotating tool  22  can be clamped. 
     If the torque of the force acting on inclined cam surface  27  of said operating ring  12  is increased by having the angle of said inclined cam surface  27  less than the angle of inclination of male thread  20  and female thread  23 , by means of the effective transmission of rotational force resulting from the alleviation of rotational loss due to contact resistance acting on needle bearings  13 , flange ring  18  can clamp rotating tool  22  with a force of greatly increased torque in comparison to the clamping force with which nut ring  11  can clamp rotating tool  22  directly, for example. 
     When clamped with a clamping force of increased torque in this way, since a relative rotation is generated between adjustment ring  17  and operating ring  12 , elastic members  36  of adjustment ring  17  are displaced, and the degree of clamping can be sensed through the adjustment of adjustment ring  17 . 
     When the above-described clamping screw  10  is removed, it is sufficient to rotate operating ring  12  in the direction of loosening. In this way contact resistance of flange ring  18  with rotating tool  22  is released so that it becomes free, and cam ring  15  is returned to its initial position by the effect of the force from the side on which the effective force of return springs  16   a ,  16   b  has been stored. 
     According to the above embodiment, the torque-increasing mechanism is comprised of inclined cam surface  27  and coupled inclined cam surface  31 , so that the torque-increasing mechanism has a simplified structure, its manufacture is simple and a satisfactory increase in torque can be obtained without requiring precision. 
     Moreover, since needle bearings  13  are fitted between both cam surfaces  27  and  31 , the loss of rotational force due to contact resistance is alleviated, the rotational force of operating ring  12  is effectively transmitted, and it is possible to clamp powerfully. 
     Furthermore, through the use of needle bearings  13 , there is linear contact with inclined cam surface  27 , so that smooth operation can achieved over long periods without damage in the form of dents which interfere with smooth rotation being caused by extremely heavy loads acting to the cam surface through point pressure from, for example, ball-bearings. 
     In the above embodiment, one or a plurality of inclined cam surfaces  27  may be formed. It is possible to obtain the effect of a satisfactory increase in torque even without needle bearing  13  or even using ball-bearings. Moreover, inclined cam surface  27  and coupled inclined cam surface  31 , may be formed so that one is an inclined surface and the other a projection or convex shape. Still further, in place of nut ring  11 , it is possible to have a threaded member formed with the male thread of a bolt. 
     Furthermore, inclined cam surface  27  is formed integrally in the inside surface of operating ring  12 , but it may be formed as an independent ring member and fixed to the inside surface of operating ring  12 . 
     The above embodiment is arranged with two return springs  16   a ,  16   b  used to act respectively in opposite directions so that both inclined cam surfaces  27 ,  31  do not override each other, but in a further embodiment it is possible to have a structure with a single return spring  16   c  and a rotary restraining means. 
     FIGS. 12,  13  and  14  show an example of a structure comprised of said single return spring  16   c  and rotary restraining means, structural parts having the same function as those in the previously described embodiment being keyed with the same numbers, a detailed description being omitted. 
     In addition to base  29   c  of said return spring  16   c  engaging with retaining aperture  28 , its free end  32   c  engages with retaining aperture  33   c  of cam ring  15 . Furthermore, depressions  41  for retaining balls  40  are formed one position within said notch depressions  30  of operating ring  12  and hold said balls  40 . 
     With the position in which said balls  40  are held as the neutral position for return spring  16   c , restraining groove  42  is formed in the opposing cam ring  15  over a range of approximately  90 °, a little more than 30° in the direction of clamping and within 60° in the direction of release (in a range that does not override inclined cam surfaces  27 ,  31  in the direction of release), restraining the range of relative rotation of operating ring  12  and cam ring  15  so that it does not override both inclined cam surfaces  27 ,  31 . 
     Even where structured in this way, the clamping action can be performed in the same way as for the above-described first embodiment. 
     Of course, since during both clamping and release the relative rotation of operating ring  12  and cam ring  15  is restrained by said balls  40  and restraining groove  42  within a range of just over 30° from the neutral position on the clamping side (since the clamping rotation is set at 30°, a range that makes this possible) and within a range of 60° on the releases side, it is prevented from overriding both inclined cams  27 ,  31 . 
     In respect of the correspondence between the structure of the invention and the above embodiments, even if the threaded member of the invention corresponds to nut ring  11  of the embodiment or to a bolt-shaped threaded member formed with a male thread, and similarly below, the member to be attached corresponds to drive shaft  19 , the thread for attachment corresponds to male screw  20 , the object to be attached corresponds to rotating tool  22 , and the torque-increasing mechanism corresponds to inclined cam  27  of operating ring  12 , coupled inclined cam surface  31  of cam ring  15 , and needle bearings  13 , the invention is not limited merely to the structure of the above embodiments.