Abstract:
The present invention is directed to a lens barrel that is simplified in structure with the reduced number of components and is facilitated in assembly and associated adjustment. The lens barrel enables an appropriate frictional force against the rotation force caused by manipulating rotary operation rings such as a zooming ring and a focusing ring to effect the optimum operating force on the rotary operation rings. In the lens barrel where a fixed barrel has its inner and outer circumferential surfaces provided with at least two slidable-rotatable members that are rotatably held about the optical axis but unable to move along the optical axis, an annular member is secured to the fixed barrel between the slidable-rotatable members, the annular member being pivotal about the optical axis and being provided with resilient protrusions on the opposite major surfaces toward the subject and the image field; and the resilient protrusions are pressed against a rear end face of one of the slidable-rotatable members closer to the subject and against a fore end face of the other slidable-rotatable member closer to the image field.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a lens barrel and an optical device, and more particularly, it relates to a lens barrel and an optical device that enable an appropriate frictional force against a rotation force caused by manipulating rotary operation rings such as a zooming ring and a focusing ring to effect the optimum operating force on the rotary operation rings. 
   BACKGROUND ART 
   With reference to  FIG. 8 , a prior art lens barrel as disclosed in Document 1 listed below comprises a fixed lens barrel  201  that has a raised portion  201   a  circularly extending along the entire outer circumferential surface and a longitudinal groove  201   b  in parallel with the optical axis. A fore lens frame  205  holds a fore group of component lens pieces (or a fore lens group)  204 , and is provided with a projection  205   a  provided in the outer circumferential surface and passing through the groove  201   b.    
   A zooming ring (or a focusing ring)  202  is fitted on the outer circumferential surface of the fixed lens barrel  201  and the fore lens frame  205 , and is rotatable about the optical axis. The zooming ring  202  includes a projected portion  202   a  radially extended to engage with the raised portion  201   a , and a cam groove  202   b  in which a tip of the projection  205   a  is fitted. The cam groove  202   b  runs helically in an inner circumferential surface of the zooming ring  202 , and rotating the zooming ring  202  in a circumferential direction permits the projection  205   a  to move along the optical axis. Since the projection  205   a  is fitted in and passed through longitudinal groove  201   b , the fore lens frame  205  and the fore lens group  204  are capable of linearly moving along the optical axis relative to the fixed lens barrel  201 . 
   A fixed ring  203  includes threads  210  engaged with a fore end of the fixed lens barrel  201 , and a pusher  214  pressing against a wavy washer  212 . The wavy washer  212  is pressed rearward from the side closer to the subject by the pusher  214 , and this urges the projected portion  202   a  of the zooming (or focusing) ring  202  to move rearward under a predetermined pressing force. The projected portion  202   a  is squeezed between the wavy washer  212  and the raised portion  201   a  of the fixed lens barrel  201 , namely, between two points in a line along the optical axis. 
   Arranged in such a manner, the lens barrel has the zooming ring  202  tightly abutted against the fixed lens barrel  201  without looseness along the optical axis, and the lens barrel enables an appropriate frictional force against the rotation force caused by manipulating rotary operation rings such as the zooming (or focusing) ring so as to rotate the zooming (or focusing) ring over the outer circumferential surface of the fixed lens barrel  201  with a torque imparted thereon in some predetermined perceptible degree. 
   Another prior art embodiment of the lens barrel is disclosed in Document 2 listed below. The lens barrel, as recognized in  FIG. 9 , includes a hollow cylinder-like lens barrel body, one or more movable lens frame(s) disposed inside the lens barrel body and slidable along the optical axis, a guide member guiding the movable lens frame along the optical axis, a cam ring  318  rotatable about an axis along the optical axis inside or outside the lens barrel body and provided with cam grooves  332  that serve to slide the movable lens frame along the optical axis in response to the rotation of the cam ring, and a plurality of pusher means  324  located in a fore or rear end of the cam ring  318  to press the cam ring  318  against the lens barrel body in a single direction along the optical axis. At any location of the fore or rear end of the cam ring  318  pressed by the pusher means  324  other than the point where a trajectory of any of the cam grooves  332  is closest to the fore or rear end, receptacles  344  are formed to drop and rest the pusher means  324  therein. 
   In still another prior art embodiment of the lens barrel, grease may be applied to junctions of the outer circumferential surface of the fixed barrel with the inner circumferential surface of the zooming (or focusing) ring so as to utilize a viscosity of the grease to impart torque in some perceptible degree. 
   Patent Document 1: Japanese Patent Preliminary Publication No. 2001-305409 
   Patent Document 2: Japanese Patent Preliminary Publication No. 2000-180689 
   Since the prior art lens barrel disclosed in Document 1 is provided with a plurality of operation rings, there must be the wavy washers as many as the operation rings to press against the projected portion of the operation rings. Thus, the wavy washers as many as the operation rings desired to impart some appropriate touch of torque must be available in advance. In addition, in order to attain the optimum torque or operation force in manipulating any of the operation rings, namely, in order to impart the torque by an adequate touch, a variety of elastic members, or a variety of wave washers in this case, of various angles and/or various dimensions must be prepared. This brings about an increase in the manufacturing cost as well as the complicatedness of maintaining each component. In fabricating the lens barrel, using such a wider variety of wave washers is prone to lead to troubles during the assembling and the increased number of essential components. 
   In the variation of the exemplary lens barrel disclosed in Document 2, elastic members in  FIGS. 4 and 5  of Document 2, namely, resilient members  46 A,  46 C and a beam 46D are integrally formed. Such an integrated elastic element of the resilient members  46 A,  46 C and the beam  46 D is advantageous in reducing the number of components as well as the steps of assembly, but the issue left unimproved is that the elastic element must be still required for each of the operation rings. Another issue also left unimproved is that a variety of elastic members, or a variety of wave washers in this case, of various angles and/or various dimensions must be prepared in order to attain an appropriate touch of torque on the operation rings. 
   When grease is applied to junctions of the outer circumferential surface of the fixed barrel with the inner circumferential surface of any of the operation rings so as to utilize a viscosity of the grease to impart torque in some perceptible degree, an amount of the applied grease and a variation in temperature vary a reaction force of manipulation. Thus, the touch of the torque imparted on the operation ring is unstable, and the grease adversely infiltrates into surfaces of the component lens pieces as a temperature rises. 
   The present invention is made to overcome the aforementioned disadvantages of the prior art embodiments of the lens barrel, and accordingly, it is an object o the present invention to provide a lens barrel that enables an appropriate frictional force against the rotation force caused by manipulating rotary operation rings such as a zooming ring and a focusing ring to effect the optimum operating force on the rotary operation rings. Thus, since a single resilient element is used to press simultaneously against two of the operation rings, the lens barrel can reduce the number of the components and the steps of assembly and can effectively attain downsizing and cost reduction, compared with a case where two of the operation rings are associated with their respective resilient elements to impart a torque on the operation rings. 
   It is another object of the present invention to provide a lens barrel capable of retaining a constant operation torque, namely, an operation force regardless of a variation in atmospheric temperature. 
   SUMMARY OF THE INVENTION 
   In accordance with a first aspect of the present invention, in a lens barrel where a fixed barrel has its inner and outer circumferential surfaces provided with at least two slidable-rotatable members that are rotatably held about the optical axis but unable to move along the optical axis, an annular member is secured to the fixed barrel between the slidable-rotatable members, the annular member being pivotal about the optical axis and being provided with resilient protrusions on the opposite major surfaces toward the subject and the image field; and the resilient protrusions are pressed against a rear end face of one of the slidable-rotatable members closer to the subject and against a fore end face of the other slidable-rotatable member closer to the image field. 
   In accordance with a second aspect of the present invention, in an optical device where a fixed barrel has its inner and outer circumferential surfaces provided with at least two slidable-rotatable members that are rotatably held about the optical axis but unable to move along the optical axis, an annular member is secured to the fixed barrel between the slidable-rotatable members, the annular member being pivotal about the optical axis and being provided with resilient protrusions on the opposite major surfaces toward the subject and the image field; and the resilient protrusions are pressed against a rear end face of one of the slidable-rotatable members closer to the subject and against a fore end face of the other slidable-rotatable member closer to the image field. 
   The present invention may be exemplified in manners as mentioned below: 
   The protrusions provided in the annular member are fitted in grooves provided in the fixed barrel in order to secure the annular member to the fixed barrel, the grooves being perpendicular to the optical axis and contiguous to grooves extending along the optical axis. 
   Designed in this manner with the reduced number of components and the simplified configuration, the lens barrel and the optical device can adjust a frictional force against a rotary operation force of rotary operation members so as to impart an appropriate touch of torque on the rotary operation members. 
   Each of the groove perpendicular to the optical axis is branched more than one in number and provided in more than one depths along the optical axis of the fixed barrel. 
   Designed in this manner without a replacement of the components but a simple variation in a way of the assembling, the lens barrel and the optical device can adjust a frictional force against a rotary operation force of rotary operation members so as to impart an appropriate touch of torque on the rotary operation members. 
   The fixed barrel is comprised of two barrel members jointed with each other on the edge-to-edge basis in a direction along the optical axis, and both the barrel members, when jointed together, create an abutment at which an object is retained between them. 
   The object retained between the barrel members is the annular member, and the annular member is secured to the fixed barrel when the barrel members jointed together squeeze the protrusions provided in the annular member. 
   Designed in this manner with the reduced components and the simplified configuration, the lens barrel and the optical device can adjust a frictional force against a rotary operation force of rotary operation members so as to impart an appropriate touch of torque on the rotary operation members. 
   The abutment created by the barrel members jointed together is segmented more than one in number and located in more than one depths along the optical axis of the fixed barrel. 
   Designed in this manner without a replacement of the components but with a simple variation in a way of the assembling, the lens barrel and the optical device can adjust a frictional force against a rotary operation force of rotary operation members so as to impart an appropriate touch of torque on the rotary operation members. 
   A lens barrel according to the present invention is simplified in structure with the reduced number of components and is facilitated in assembly and associated adjustment. The lens barrel enables an appropriate frictional force against the rotation force caused by manipulating rotary operation rings such as a zooming ring and a focusing ring to effect the optimum operating force on the rotary operation rings. Specifically, since a single resilient element is enough to press simultaneously against two of the operation rings, the lens barrel is advantageous in that it can reduce the number of the components and the steps of assembly and can effectively attain downsizing and cost reduction, compared with a case where two of the operation rings are associated with their respective resilient elements to impart a torque on the operation rings. 
   Moreover, the lens barrel is capable of retaining a constant operation torque, namely, an operation force regardless of a variation in atmospheric temperature. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial sectional view illustrating a first preferred embodiment of a lens barrel according to the present invention. 
       FIG. 2  is a partial enlarged sectional view of a portion encircled and designated by II in  FIG. 1 . 
       FIG. 3(   a ) is a frontal view of a spring elastic member in the first embodiment of the present invention, and  FIG. 3(   b ) is a side view of the same. 
       FIG. 4  is a perspective view illustrating a first fixed barrel in the first embodiment of the present invention. 
       FIG. 5  is a frontal view illustrating the first fixed barrel in a first variation of the first embodiment according to the present invention. 
       FIG. 6(   a ) is a frontal view illustrating the spring elastic member in a second variation of the first embodiment according to the present invention, and  FIG. 6(   b ) is a side view of the same. 
       FIG. 7  is an exploded perspective view of the first fixed barrel of a second embodiment of the lens barrel according to the present invention. 
       FIG. 8  is a partial sectional view of a prior art embodiment of the lens barrel. 
       FIG. 9  is a perspective view illustrating a cam ring for another prior art embodiment of the lens barrel. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Best Mode of the Invention 
   Preferred embodiments of lens barrels according to the present invention will now be described by way of examples only in conjunction with the accompanying drawings. 
   Embodiment 1 
   A first exemplary lens barrel  10  includes, as partially shown in  FIGS. 1 and 2 , a first group of component lens pieces  11  and a second group of component lens pieces  12 . The lens barrel  10  has a first fixed barrel  14  integrally formed with a mount  16  at which the lens barrel is attached to a camera body (not shown). The first fixed barrel  14  has longitudinal focusing grooves  17  and longitudinal zooming grooves  18  engraved therein. 
   Inside the first fixed barrel  14 , a first lens-holding frame  19  holding the first group of component lens pieces (referred to as the “first lens group” hereinafter)  11  is slidably disposed. The first lens-holding frame  19  includes focusing studs  22  slidably fitted in both the longitudinal focusing grooves  17  and focusing cam grooves  21 , respectively. 
   Over an outer circumferential surface of the first fixed barrel  14 , a focusing drive ring  25  is slidably disposed, having focusing cam grooves  21  engraved inside. Focusing pins  26  are screwed down to attach the focusing drive ring  25  to the first lens holding frame  19 . 
   A second fixed barrel  15  is fixedly disposed behind the first fixed barrel  14 , being closer to the image field. Over an inner circumferential surface of the second fixed barrel  15 , a second lens holding frame  20  holding the second group of component lens pieces (referred to as the “second lens group” hereinafter)  12  is disposed. The second lens holding frame  20  includes zooming studs  24  fitted in the longitudinal zooming grooves  18  and zooming cam grooves  23 , respectively. Over an inner circumferential surface of the second fixed barrel  15 , a zooming drive ring  27  is slidably disposed, having the zooming cam grooves  23  engraved therein. Surrounding the zooming drive ring  27 , a cover  28  is attached thereto by the second fixed barrel  15 . Zooming pins  29  fixed to the zooming drive ring  27  extends through slits  30  that are defined and mutually aligned in the second fixed barrel  15  and the cover  28  to form successive through-holes. 
   A diaphragm unit  34  is located behind the focusing drive ring  25 , closer to the image field. The diaphragm unit  34  includes a holder frame  37  holding upper and lower vanes (not shown) to linearly move them, an aperture drive ring  32  rotatably held relative to the holder frame  37 , and a diaphragm vane retainer (not shown) retaining the upper and lower vanes relative to the holder frame  37 . The diaphragm drive ring  32  has diaphragm operating pins  35  fixed thereto. Manipulating the diaphragm operating pins  35  enables the diaphragm drive ring  32  to rotate so as to adjust a diaphragm aperture. 
   A spring elastic member  31  attached to the first fixed barrel  14  is placed between an end surface of the focusing drive ring  25  closer to the image field and that of the diaphragm drive ring  32  closer to the subject. The spring elastic member  31  has, as shown in  FIG. 3 , a thin, planar substrate member  31   a  shaped like a ring.  FIG. 3  includes a frontal view ( 3   a ) and a side view ( 3   b ) illustrating the spring elastic member  31  incorporated in a body such as the lens barrel. The substrate member  31   a  has detents  31   b  integrally formed in three points therein. There may be four or more of the detents  31   b  in the corresponding number of points equiangularly or non-eqiangularly separated from each other by an identical angle or by different angles. The detents  31   b  are fitted in recesses  33  located in the first fixed barrel  14 , as mentioned later. 
   In a flat major surface of the substrate member  31  closer to the subject, first elastic members  31   c  are integrally formed in three points of the same. There may be four or more of the first elastic members  31   c  in the corresponding number of points equiangularly or non-equiangularly separated from each other by an identical angle or by different angles. The first elastic members  31   c  are elastically transformed when pressed against a flat face  25   a  of the focusing drive ring  25 , and simultaneously rebounds from the flat face  25   a  to force the focusing drive ring  25  toward the subject. An abutment  31   e  of the first elastic members  31   c  against the flat face  25   a  of the focusing drive ring  25  is approximately spherical. 
   Second elastic members  31   d  are integrally formed in three points of a flat major surface of the substrate member  31   a  closer to the image field. There may be four or more of the second elastic members  31   d  equiangularly or non-equiangularly separated from each other by an identical angle or by different angles. The second elastic members  31   d  are elastically transformed when pressed against a flat face  32   a  of the diaphragm drive ring  32 , and simultaneously rebounds from the flat face  32   a  to force the diaphragm drive ring  32  toward the image field. An abutment  31   f  of the second elastic members  31   d  against the flat face  32   a  of the diaphragm drive ring  32  is approximately spherical. 
   Acting force by the first and second elastic members,  31   c  and  31   d , can be calculated, for example, by formulae set force in  Mechanical Engineering Manual , Ver. 8, p. 107 (Sanseido Publishing Co., Ltd.). 
   The first fixed barrel  14  has its outer circumferential surface provided with recesses  33  in three points, as can be seen in  FIG. 4 , in which the detents  31   b  of the spring elastic member  31  are fitted. There may be four or more of the recesses  33 , matching in number with the detents  31   b . Each of the recesses  33  is comprised of a drop  33   a  into which the detent  31   b  of the spring elastic member  31  is preliminarily fitted, a rotary guide  33   b  leading from the drop  33   a  to permit the detent  31   b  to slide and rotate about the optical axis toward the subject, and a retaining socket  33   c  leading from the rotary guide  33   b  to fit the detent  31   b  therein toward the image field and retain the same in that position. 
   In this case, for instance, in order to apply greater force against the flat face  25   a  of the focusing drive ring toward the subject than against the flat face  32   a  of the diaphragm drive ring  32  toward the image field, an interval along the optical axis from the diaphragm drive ring  32  to the spring elastic member  31  may be varied, or the first and/or second elastic members,  31   c  and  31   d , may be reshaped by varying their respective widths, lengths, and the like. In this way, the spring elastic member  31  can be assuredly captured in the retaining socket  33   c  of the first fixed barrel  14 . 
   Although the first and second elastic members,  31   c  and  31   d , are exemplified as in thin and flat portions, they may be shaped in raised or wavy portions somehow or other, allowing for the resiliency as desired. 
   In such a manner, the spring elastic member  31  on the side closer to the subject can be inserted in the recesses  33  of the first fixed barrel  14  and retained by the retaining sockets  33   c  so as not to rotate about the optical axis, and as a result of completing the attachment of the spring elastic member  31  to the first fixed barrel  14 , the first and second elastic members  31   c  and  31   d  of the spring elastic member  31  seemingly frill the first fixed barrel  14  circumferentially outside the same. As has been stated, the torque can be adjustably imparted on each of the two operation rings  25  and  32  on the opposite sides of the spring elastic member  31  in an appropriate perceptible degree as desired by varying the interval along the optical axis between the focusing drive ring  25  and the spring elastic member  31  and/or reshaping the resilient portions of the spring elastic member  31 . 
   With the lens barrel configuration as mentioned above, a frictional force of the focusing drive ring  25  against a rotation force applied thereto through the manipulation can be adjusted to impart a torque on the focusing pins  26  in some appropriate perceptible degree. 
   Similarly, the frictional force of the diaphragm drive ring  32  can be adjusted to impart a torque on the diaphragm operating pins  35  in an appropriate perceptible degree. 
   A first variation of the first embodiment is, as shown in  FIG. 5 , an arrangement where the first fixed barrel  14  is provided with helical grooves  36  in combination with three sets of the rotary guide  33   b  and the retaining socket  33   c  of the spring elastic member  31  as discussed above. The additional helical grooves  36  serve to guide and rotate the spring elastic member  31  about the optical axis. This permits the spring elastic member  31  to move towards the subject while it keeps anchored to the first fixed barrel  14  in any of multi-stages of the retaining sockets  33   c  (three stages are shown herein), which enables a stepwise adjustment of the forward force applied by the spring elastic member  31 . 
   With the lens barrel thus configured, a simple variation in a way of assembling the components without a replacement of them enables an adjustment of the frictional force of the focusing drive ring  25  against the rotation force applied thereto through the manipulation so as to impart a torque on the focusing pins  26  in an appropriate perceptible degree. 
   Similarly, additional simple variation in a way of assembling the components without a replacement of them enables an adjustment of the frictional force of the diaphragm drive ring  32  against the rotation force applied thereto through the manipulation so as to impart a torque on the diaphragm operating pins  35  in some appropriate perceptible degree. 
   In a second variation of the first embodiment, as can be seen in  FIG. 6 , the spring elastic member  31  is further varied to have tabs in more than one points of its inner or outer circumferential surface, and the adjacent two of such tabs,  31   g  and  31   h , for example, are accompanied by bulb-like projections  31   i  and  31   j , respectively, which protrude on opposite sides either closer to the subject or to the image field, respectively, so as to provide elastic members applying resilient force in alternately opposite directions. 
     FIG. 6  includes a frontal view ( 6   a ) and a side view ( 6   b ) illustrating the spring elastic member  31  incorporated in a body such as the lens barrel. 
   Although the tabs represented by  31   g  and  31   h  are exemplified as in thin and flat portions, they may be shaped in raised or wavy portions somehow or other, allowing for the resiliency as desired. 
   Embodiment 2 
   A second embodiment of the lens barrel according to the present invention is, unlike the first fixed barrel  114  in the aforementioned first embodiment, a sawtoothed mating fixed barrel  114  as shown in  FIG. 7 . The remaining components of the second embodiment of the lens barrel are almost the same as those in the first embodiment, and therefore, the descriptions of those components are omitted. 
   The sawtoothed mating fixed barrel  114  is comprised of fore and rear fixed barrel members  112  and  115 , and when the fixed barrel  114  is assembled, the barrel member  112  is located closer to the subject and the fixed barrel member  115  is closer to the image field, with the spring elastic member  31  intervening and retained between them. The fixed barrel member  112  has its end face closer to the image field sawtoothed, with recessed portions  122  and raised portions  124  alternately disposed. The recessed portions  122  include a series of recesses  122   a ,  122   b , and  122   c  of which distances receding towards the subject along the optical axis all vary from one another, and a pattern of these recesses in series is repeated all the way round. All the raised portions  124  have an identical height or distance protruding toward the image field along the optical axis. 
   The fixed barrel member  115  has its end face closer to the subject sawtoothed, with recessed portions  142  and raised portions  144  alternately disposed. The raised portions  144  include a series of protrusions  144   a ,  144   b , and  144   c  of which distances protruding towards the subject along the optical axis all vary from one another, and a pattern of these raised portions in series is repeated all the way round. The series of the recesses  122   a ,  122   b , and  122   c  in the fore fixed barrel member  112  have their respective receding distances complemented with the respective protruding distances of the series of the protrusions  144   a ,  144   b , and  144   c  in the rear fixed barrel member  115 , and therefore, both the fixed barrel members  112  and  115  have their respective sawtoothed edges tightly mated with each other. 
   In assembling the second embodiment of the lens barrel, allowing for the frictional force derived from the sliding motions of the focusing drive ring  25  and the diaphragm drive ring  32  that have their respective flat ends  25   a  and  32   a  pressed respectively by the first and second elastic members  31   c  and  31   d , the detents  31   b  of the spring elastic member  31  are selectively engaged with any of the recesses  122   a ,  122   b , and  122   c . Then, the fore fixed barrel member  112  closer to the subject and the rear fixed barrel member  115  closer to the image field are joined on the edge-to-edge basis so that the recesses  122   a ,  122   b , and  122   c  are mated with the protrusions  144   a ,  144   b , and  144   c . In this way, the spring elastic member  31  is fixed at the detents  31   b  that are squeezed between the fixed barrel members  112  and  115 . 
   Configured in this way, the lens barrel, with a simple variation in a way of assembling the components but without a replacement of them, is capable of adjusting the frictional force of the focusing drive ring  25  against the rotation force applied thereto through the manipulation so as to impart a torque on the focusing pins  26  in an appropriate perceptible degree. 
   Similarly, the lens barrel, with a simple variation in a way of assembling the components but without a replacement of them, is capable of adjusting the frictional force of the diaphragm drive ring  32  against the rotation force applied thereto through the manipulation to impart a torque on the diaphragm operating pins  35  in some appropriate perceptible degree.