Abstract:
The present invention relates to a rapid-replacing structure of multifunctional saw, including a head housing, a tool rest and an output device, wherein the output device comprises an output shaft. It also includes a quick-change device that consists of a rapid-replacing buckle, an eccentric block, a movable rod, a collet chuck, a tensioning rod and a compression spring. The rapid-replacing buckle and the eccentric block are connected with the top of the head housing through a straight pin. The movable rod is arranged in the output shaft, with its top end closely connected to the eccentric block and its bottom end connected to the tensioning rod by screw thread. The rapid-replacing structure of the multifunctional saw can realize the purpose of blade removal and replacement simply by shifting the rapid-replacing buckle on the upper side of the head housing, without using other auxiliary means, so it is simple and fast to operate.

Description:
TECHNICAL FIELD 
       [0001]    The present invention belongs to the technical field of mechanical equipment and relates to a detachable structure for rapid separation or reassembly of the work head and machine body of a head-replaceable electric tool, in particular to a rapid-replacing structure of a multifunctional saw. The present invention further discloses the rapid-replacing method of the rapid-replacing structure of the multifunctional saw. 
       BACKGROUND TECHNOLOGY 
       [0002]    Multifunctional saws can clamp woodworking saw blades, metal saw blades, triangular sand discs, etc. When clamping woodworking saw blades or metal saw blades, the saws can cut and process wood boards, aluminum alloy materials and other metal materials. When clamping triangular sand discs attached with sandpaper, the saws can conduct sanding and polishing on wood boards, plasterboards or wall surfaces. 
         [0003]    The vast majority of multifunctional saws adopt pressing plates and hexagon socket head cap screws, and such saws need special tools for fastening or unscrewing when replacing saw blades. The structure and change mode of this type of multifunctional saws face troubles in operation, like failure in fastening or demounting. Moreover, such saws need a supporting carry-on hexagon wrench that may be lost easily. Furthermore, without a locking safety structure, the saws have potential safety hazards, which may cause personal injury. 
       SUMMARY OF THE INVENTION 
       [0004]    To overcome the abovementioned defects, expand application scope and improve the product experience, the present invention provides a rapid-replacing structure of multifunctional saw, which not only realizes quick change of blades but also ensures personal safety in the process of replacing. 
         [0005]    To realize the purpose, the technical scheme provided by the present invention is as follows. 
         [0006]    The present invention relates to a rapid-replacing structure of a multifunctional saw, comprising a head housing, a tool rest and an output device, wherein the output device comprises an output shaft. It also comprises a rapid-replacing device, which includes a rapid-replacing buckle, an eccentric block, a movable rod, a spring collet, a tensioning rod and a compression spring. The rapid-replacing buckle and the eccentric block are connected with the top of the head housing through a straight pin. The movable rod is arranged in the output shaft, with its top end closely connected to the eccentric block and its bottom end connected to the tensioning rod by screw thread. The outer side of the tensioning rod is provided with the spring collet, and the outer side of the spring collet is provided with the compression spring. The top end of the compression spring is in close connection with the lower surface of the movable rod, and its bottom end is in close connection with the upper surface of the tool rest. The tool rest is arranged at the bottom of the output shaft; a slope shrinking inwards from top to bottom is arranged on the inner wall of the tool rest, and a bump corresponding to the slope is arranged on the outer surface of the spring collet. There is a certain space between the top end of the spring collet and the lower surface of the movable rod. In addition, the bottom end of the tensioning rod is provided with a tensioning head. 
         [0007]    Preferably, the output device is arranged in the head housing, comprising a shifting fork, an output shaft, a deep groove ball bearing and a needle bearing. The deep groove ball bearing is fixed on the outer side of the top of the output shaft through snap springs, and the shifting fork is arranged on the outer side of the middle portion of output shaft. The needle bearing is arranged on the outer side of the bottom of output shaft. 
         [0008]    Preferably, the output shaft is of a hollow cylinder structure divided into upper, middle and lower sections. The diameter of the upper section of the output shaft is smaller than that of the middle section, and the middle diameter of the output shaft is smaller than that of the lower section. A mounting slot of snap springs is arranged on the outer wall of the upper section of the output shaft. 
         [0009]    Preferably, the snap springs are arranged at the upper and lower end of the deep groove ball bearing respectively. The deep groove ball bearing is connected with the output shaft through the snap spring at the upper end, and with the head housing through the snap spring at the lower end. 
         [0010]    Preferably, a seal ring is arranged in the gap between the head housing on the lower side of the needle bearing and the output shaft. 
         [0011]    Preferably, the rapid-replacing structure of the multifunctional saw also comprises a return limit mechanism that comprises a limit block, a straight pin and a torsion spring. The rapid-replacing buckle is hinged to the top side of the head housing. The upper portion of the head housing is provided with a limit slot, and the whole rapid-replacing buckle is positioned above the limit slot. The limit block is hinged in the limit slot through the straight pin, and the torsion spring is sheathed on the outer ring of the straight pin. One end of the torsion spring acts on the limit slot, and its other end acts on the limit block. A reset handle is arranged at one end of the limit block far away from the straight pin. 
         [0012]    The torsion spring of the present invention is used for rotating the limit block to the designated position of the head housing. 
         [0013]    Preferably, 3-5 pieces of magnetic steel are arranged at the bottom of the tool rest. The magnetic steel is uniformly distributed on the bottom surface of the tool rest in the circumferential direction with the axis of the tool rest as the center. 
         [0014]    Preferably, the limit block and the reset handle are of an integrated structure, and a handle-placing slot corresponding to the reset handle is arranged on the limit slot. 
         [0015]    Preferably, two mounting holes of the straight pin corresponding to each other are arranged in one end where the limit block is connected with the straight pin and on two sides of the limit slot respectively. 
         [0016]    Compared with the prior art, the technical scheme provided by the present invention has the following beneficial effects. 
         [0017]    The rapid-replacing structure of the multifunctional saw can realize the purpose of blade removal and replacement simply by shifting the rapid-replacing buckle on the upper side of the head housing, without using other auxiliary means, so it is simple and fast to operate. When the rapid-replacing buckle returns, the return limit mechanism can prevent the rapid-replacing buckle from returning to the original position instantly, thus protecting personal safety of users. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a schematic diagram of the rapid-replacing structure of multifunctional saw according to embodiment 1; 
           [0019]      FIG. 2  is a schematic diagram of the rapid-replacing structure of multifunctional saw before use according to embodiment 1; 
           [0020]      FIG. 3  is a schematic diagram of the rapid-replacing structure of multifunctional saw in use according to embodiment 1; 
           [0021]      FIG. 4  is a decomposition diagram of the rapid-replacing structure of multifunctional saw according to embodiment 1; 
           [0022]      FIG. 5  is a schematic diagram of the output shaft; 
           [0023]      FIG. 6  is a decomposition diagram of a return limit mechanism according to embodiment 2; 
           [0024]      FIG. 7  is a schematic diagram of the bottom surface of tool rest according to embodiment 2; 
           [0025]      FIG. 8  is a schematic diagram of step 1 of embodiment 2; 
           [0026]      FIG. 9  is a schematic diagram of step 2 of embodiment 2; 
           [0027]      FIG. 10  is a schematic diagram of step 3 of embodiment 2; 
           [0028]      FIG. 11  is a schematic diagram of step 4 of embodiment 2; 
           [0029]      FIG. 12  is a schematic diagram of step 5 of embodiment 2; 
           [0030]      FIG. 13  is a schematic diagram of the rapid-replacing structure of multifunctional saw with assembled blades according to embodiment 2. 
       
    
    
       [0031]    Notes to annotations of the schematic diagrams:  1 -rapid-replacing buckle;  2 -eccentric block;  3 -snap springs;  4 -straight pin;  5 -head housing;  6 -deep groove ball bearing;  7 -compression spring;  8 -shifting fork;  9 -needle bearing;  10 -output shaft;  11 -movable rod;  12 -tool rest;  13 -spring collet;  14 -tensioning rod;  15 -seal ring;  16 -saw blade;  18 -mounting slot of snap springs;  19 -tensioning head;  20 -limit block;  21 -straight pin;  22 -torsion spring;  23 -magnetic steel;  24 -limit slot;  25 -reset handle;  26 -protection zone. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    To further understand the content of the present invention, embodiments of the present invention will be described in reference to the accompanying drawings. The following embodiments described are used merely to illustrate the present invention but not to limit its scope. 
       Embodiment 1 
       [0033]    With reference to  FIG. 1 - FIG. 5 , a rapid-replacing structure of multifunctional saw comprises a head housing  5 , a tool rest  12 , an output device and a rapid-replacing device. The output device comprises a shifting fork  8 , an output shaft  10 , a deep groove ball bearing  6  and a needle bearing  9 . The output shaft  10  is of a hollow cylinder structure divided into upper, middle and lower sections. The diameter of the upper section of the output shaft  10  is smaller than that of the middle section, and the middle diameter of the output shaft  10  is smaller than that of the lower section. A mounting slot  18  of the snap springs is arranged in the outer wall of the upper section of the output shaft  10 . The rapid-replacing device comprises a rapid-replacing buckle  1 , an eccentric block  2 , a movable rod  11 , a spring collet  13 , a tensioning rod  14  and a compression spring  7 . 
         [0034]    The top of the head housing  5  is connected with the rapid-replacing buckle  1  and the eccentric block  2  through the straight pin  4 , and the deep groove ball bearing  6 , the shifting fork  8  and the needle bearing  9  are arranged in a cavity on the inner side of the head housing  5  from top to bottom. The deep groove ball bearing  6  is connected with the inner wall of the head housing  5  through the snap springs  3 , and the upper middle and lower sections of the output shaft  10  are connected with the inner sides of the deep groove ball bearing  6 , the shifting fork  8  and the needle bearing  9  respectively. The mounting slot  18  of the snap springs is arranged on the upper section of the output shaft  10 , and the output shaft  10  is connected with the deep groove ball bearing  6  through the snap springs installed in the mounting slot  18 . The internal diameter of the deep groove ball bearing  6  and the needle bearing  9  is 0.1-0.3 mm bigger than the external diameter of the upper section and the lower section of the output shaft respectively, so the bearings have the effect of positioning. The shifting fork  8  has the function of adjusting the rotating speed of the output shaft  10 . An annular seal ring  15  is arranged in the gap between the head housing on the lower side of the needle bearing  9  and the output shaft  10 . 
         [0035]    The output shaft  10  is of a hollow structure. The movable rod  11  is arranged at the hollow position at the upper end of the output shaft  10 , a round hole is arranged in the lower end of the movable rod  11 , and inner threads are arranged in the hole. Outer threads are arranged at the top end of the tensioning rod  14  and are right matched with the inner threads in the hole arranged in the lower end of the movable rod  11 , so the movable rod is in threaded connection with the tensioning rod  14 . The spring collet  13  and the compression spring  7  sleeve on the outer side of the movable rod in sequence, the tool rest  12  is fixed at the bottom of the output shaft  10 , the top end of the compression spring  7  butts against the lower surface of the movable rod, and the bottom of the compression spring  7  supports on the upper surface of the tool rest  12 . A lump is arranged on the outer side of the spring collet  13 , and a slope shrinking inwards from top to bottom is arranged on the inner side of the tool rest  12  corresponding to the spring collet  13 . When the spring collet  13  touches the slope on the inner side of the tool rest  12  when moving downwards, the spring collet  13  can shrink. A certain space T is reserved between the top end of the spring collet  13  and the lower surface of the movable rod. A tensioning head  19  is arranged at the bottom end of the tensioning rod  14 . 
         [0036]    The working principle of the rapid-replacing structure of the multifunctional saw is as follows. 
         [0037]    Step 1: with reference to  FIG. 1 , the rapid-replacing buckle  1  is driven with the straight pin  21  as the center of rotation, so the rapid-replacing buckle  1  can drive the eccentric block  2  to rotate; 
         [0038]    Step 2: with reference to  FIG. 2 , as the eccentric distance offsets the elastic force of the compression spring  7 , the eccentric block  2  presses the movable rod  11  downwards to drive the tensioning rod  14  to move downwards for the distance T, the top end of the spring collet  13  contacts with the lower surface of the movable rod  11 , then the movable rod  11  continues to move downwards to drive the spring collet  13  to move downwards, the lump at the bottom end of the spring collet  13  touches the slope on the inner wall of the tool rests, and the diameter of the lower end of the spring collet  13  shrinks under the effect of pressing; 
         [0039]    Step 3: with reference to  FIG. 2 , when the diameter of the lower end of the spring collet  13  is smaller than that of the mounting hole of a blade  16 , the blade  16  is arranged at the end of the spring collet; 
         [0040]    Step 4: with reference to  FIG. 3 , the rapid-replacing buckle  1  is driven backwards, the movable rod  11  drives the tensioning rod  14  to move upwards under the effect of the compression spring  7 , the tensioning head  19  of the tensioning rod  14  drives the spring collet  13  to move upwards, the end of the spring collet  13  stretches after losing pressure from the slope on the inner wall of the tool rest  12 , and then the blade is fixed on the tool rest, so a quick change of the blade  16  can be realized. 
       Embodiment 2 
       [0041]    With reference to  FIG. 6 - FIG. 13 , a rapid-replacing structure of a multifunctional saw comprises a head housing  5 , a tool rest  12 , an output device, a rapid-replacing device and a return limit mechanism. The structure of the output device and the rapid-replacing device can be referred to the embodiment 1. 
         [0042]    The return limit mechanism comprises a limit block  20 , a straight pin  21  and a torsion spring  22 . A rapid-replacing buckle  1  is hinged to one side of side of the top of the head housing  5 , a limit slot  24  is formed in the upper portion of the head housing  5 , and the whole rapid-replacing buckle  1  is located above the limit slot  24 . A limit block  20  is hinged in the limit slot  24  through the straight pin  21 , and the torsion spring  22  sleeves on an outer ring of the straight pin  2 . One end of the torsion spring  22  acts on the limit slot  24 , and the other end of the torsion spring  22  acts on the limit block  20 . Two mounting holes of the straight pin for installing the straight pin  21  are formed in two sides of the limit slot  24  at the top of the head housing, and a through mounting hole of the straight pin is also formed in one end of the limit block  20  corresponding to the limit block  24 . During installation of the limit block, the torsion spring  22  sleeves on the outer side of the straight pin  21 , then the straight pin  21  penetrates through the mounting holes of the straight pin on two sides of the limit slot and in the limit block  20  in sequence, the limit block  20  is hinged into the limit slot, and two extension sections of the torsion spring  22  are fixed on the lower surface of the limit block  20  and the bottom surface of the limit slot  24 . The limit block  20  can stretch automatically under the effect of the torsion spring  22  without limitation. As the rapid-replacing buckle  1  cannot return to the original position unless a user initiatively withdraw protection in the return process of the rapid-replacing buckle  1 , a reset handle  25  is arranged at one end of the limit block  20  of the embodiment far away from a rotating shaft, and is integrated with the limit block  20 . A handle placing slot (not marked in the figure) is formed in the limit slot  24 , and the reset handle  25  is located in the handle placing slot when the limit block  20  is in the reset state. When the limit block  20  is in the limit state, one end of the limit block  20  far away from the straight pin is higher than the top surface of the head housing  5 , and the lower surface of the reset handle  25  is clamped on two sides of the limit slot  24 ; when the rapid-replacing buckle  1  returns, the reset handle  25  is matched with the limit block  20 , so a protection zone  26  is formed between the rapid-replacing buckle  1  and the head housing  5 . 
         [0043]    With reference to  FIG. 7 , as the user needs to manually withdraw protection during the protection withdrawal process, three pieces of magnetic steel  23  are additionally arranged on the bottom surface of the tool rest  12  and are distributed on the bottom surface of the tool rest  12  uniformly in the circumferential direction with the axis of the tool rest as the center of a circle. The magnetic steel  23  is used for attracting the blade  16  temporarily so that holding of the blade by hands can be reduced and the user can better operate the rapid-replacing structure with the free hands. 
         [0044]    The working principle of the return limit mechanism is as follows: 
         [0045]    Step 1: with reference to the  FIG. 8 , the rapid-replacing buckle  1  is moved anticlockwise in the arrow direction, the limit block  20  rotates along with the rapid-replacing buckle under the effect of the torsion spring  22 , one end of the limit block  20  far away from the straight pin protrudes upwards until the reset handle  25  is clamped on two sides of the limit slot  24 , and at this moment, one end of the limit block  20  far away from the straight pin  21  is higher than the top of the head housing. The structure is shown in the  FIG. 9 . 
         [0046]    Step 2: at this moment, the limit block  20  stops moving due to limitation from the top of the head housing  5 , and the rapid-replacing buckle  1  is still subject to anticlockwise moving until it rotates to be parallel with the top surface of the head housing overall. Then, the spring collet located at the bottom of the tool rest protrudes, and the diameter of the spring collet is reduced to the extent that the blade  16  can be installed on the spring collet, forming the structure shown in the  FIG. 10 . 
         [0047]    Step 3: at this moment, the blade  16  is arranged on the tool rest  12 , and after the magnetic steel  23  on the tool rest  12  attracts the blade  16 , the user can withdraw his hands holding the blade, and then the blade  16  is attracted to the lower surface of a tool. 
         [0048]    Step 4: with reference to the  FIG. 11 , in the process of fastening the blade, the rapid-replacing buckle  1  is moved clockwise in the arrow direction. When rotating to the position where the limit block  20  is located, the rapid-replacing buckle  1  stops rotating under the limitation effect of the limit block  20 , and a protection zone  26  is formed in the position between the rapid-replacing buckle  1  and the top of the head housing  5 . The position of the protection zone  26  is where the hand holds the multifunctional saw during operation, so the protection zone  26  has the effect of protecting the personal safety. 
         [0049]    Step 5: with reference to the  FIG. 12 , the reset handle  25  is pulled in the arrow direction to compress the torsion spring  22 , so the limit block can return to the original position. At this moment, the rest handle  25  is right located in the handle placing slot; meanwhile the rapid-replacing buckle  1  is pressed downwards so that it can return to the original state, then the rapid-replacing buckle  1  is fastened (generally a snap joint structure is arranged so that the rapid-replacing buckle and the head housing  5  can be fastened tightly), the spring collet returns to the original position, with the diameter enlarging, and the blade  16  will be fastened totally. 
         [0050]    The present invention and its implementation mode are schematically described, but the description is not to limit the present invention. The accompanying figures show only one of embodiments of the present invention, and the real structure is not limited to the embodiments. Thus, those skilled in the art should be enlightened that under the premise of not departing from the spirit of the present invention, similar structures and embodiments of the technical scheme with no creative design belong to the protection scope of the present invention.