Abstract:
A measuring tape has a check device for automatically preventing a ruler from rewinding. The check device is installed within the casing and positioned between a winding wheel and a ruler body. The check device comprises a rotary wheel formed by an elastic wheel and two ratchets; a guide block having stop blocks; a stop claw; a driven element installed between the press button and the stop claw; and a press. By above components, the ruler body can be installed between the elastic wheel and the guide block. As the ruler body is pulled out, it can be stopped automatically. Only after pressing the press button, the ruler body rewinds. Thereby, the user may operate it by only one hand not to worry about that the hand will be hurt due to the rewinding of the ruler body.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a measuring tape, and particularly to a measuring tape having a check device for automatically preventing a ruler from rewinding. As a ruler body is pulled out, it can be stopped automatically. After pressing a press button, the ruler body rewinds by the elastic force of the reed. Thereby, the user operates it by only one hand not to worry about that the hand will be hurt due to rewinding of the ruler body. 
     2. Description of Related Art 
     The prior measuring tape is installed with a check device. When the ruler body is pulled out, the ruler body will rewind due to the winding spring in the winding wheel. Therefore, a check device is used to fix the ruler body and prevent the ruler body from rewinding. There are two kinds of check devices. One is a positioning switch which is a press button having two operation stages. As the press button is pressed backwards, the ruler body will be positioned and the winding wheel stops to rotate, while as the press button is pressed forwards, the ruler body will be released and the winding wheel rotates to rewind the ruler body. The second kind is an intermittent operation switch. In this switch, a button is pressed by a finger. When the button is pressed continuously, the winding wheel will be stopped so as not to rotate, while if the button is released, the ruler body will rewind. 
     In general, only one hand is used to pull the ruler body. In pulling the ruler body, it is necessary to prevent the ruler body from rewinding, otherwise, the measurement work can not be executed. Therefore, the thumb and first finger must pinch the casing of the ruler body tightly, and another hand serves to pull the ruler body continuously. However, it is often that the hand is hurt since the finger and thumb release the ruler body carelessly. This is dangerous to the users, especially, children. 
     SUMMARY OF THE INVENTION 
     Accordingly, the primary object of the present invention is to provide a measuring tape having a check device for automatically preventing a ruler from rewinding, wherein only after pressing a press button, the ruler body rewinds. Thereby, the user may operate it by only one hand not to worry about that the hand will be hurt due to the rewinding force of the ruler body. 
     Another object of the present invention is to provide a measuring tape having a check device for automatically preventing a ruler from rewinding, wherein when a user presses a press button by a thumb, a block will push the press plate downwards. Then the press plate presses the resisting plate of the stop claw. Thereby, claw pieces will curl upwards and then separates from the ratchets. Therefore, the rotary wheel will separate from the claw pieces to be in a free condition. 
     A further object of the present invention is to provide a measuring tape having a check device for automatically preventing a ruler from rewinding, wherein the rewinding of the ruler body is by pressing a button, and thus the operation is simple and safe. Moreover, in rewinding the ruler body, the button can be pressed properly so that the ruler body rewinds slowly. 
     A further object of the present invention is to provide a measuring tape having a check device for automatically preventing a ruler from rewinding, wherein the user may pull the ruler body rapidly, thereby, the operation time is reduced. 
     To achieve above objects, the present invention provides measuring tape having a check device for automatically preventing a ruler from rewinding. The check device is installed within the casing and positioned between a winding wheel and a ruler body. The check device comprises a rotary wheel formed by an elastic wheel at a center portion and two ratchets at two sides of the elastic wheel; a guide block formed at a lower end of the rotary wheel and having stop blocks; a stop claw; a driven element installed between the press button and the stop claw; and a press. By above components, the ruler body can be installed between the elastic wheel and the guide block. As the ruler body is pulled out, it can be stopped automatically. 
     The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the measuring tape of the present invention. 
     FIG. 2 is an exploded perspective view of the check device in the present invention. 
     FIG. 3 is an exploded perspective view of the check device in the present invention. 
     FIG. 4 is a cross sectional view of the rotary wheel in the present invention. 
     FIG. 5 is a cross sectional view showing the check device and the ruler body of the present invention. 
     FIGS. 6 to  8  show the operation of the check device of the present invention. 
     FIG. 9 shows another embodiment of the present invention. 
     FIG. 10 shows another embodiment of the check device in the present invention. 
     FIG. 11 shows another embodiment of the check device in the present invention. 
     FIG. 12 shows another embodiment of the check device in the present invention. 
     FIG. 13 shows another embodiment of the check device in the present invention. 
     FIG. 14 shows another embodiment of the check device in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiment of the present invention will be described hereinafter. 
     A perspective view of the measuring tape of the present invention is illustrated in the following description. The casing  1  is formed by a left casing and a right casing. A check device  10  is installed in the front side of the casing  10 . The check device  10  is located between an output end of a ruler body  2  and the winding plate for fixing the ruler body. The check device  10  includes (referring to FIG. 2) a press button  11 , a press plate  12 , a stop claw  13 , a reed  14  (a press), a rotary wheel  15  and a slide stop  16 . The center of the rotary wheel  15  has an elastic wheel and two ends thereof have stop means for ratchets. The details are described in FIG.  3 . The rotary wheel  15  is formed by an elastic friction wheel  151 , a left wheel rod  152  and a right wheel rod  153 . The interior of the friction wheel  151  has a hollow tooth groove  152   b . A tooth rod  153  may insert into the tooth groove  153 . Two wheel rods  152  and  153  are installed with single direction ratchets  152   a  and  153   a  at the outer sides thereof. The end walls of the two ratchets have recess  152   c  and  153   c , respectively, and central shafts  152   d  and  153   d , respectively (also referring to FIG.  5 ). 
     Referring to FIGS. 2 and 4, FIG. 4 is a cross sectional view of the ruler of the present invention. The related position after the check device  10  is assembled is illustrated. The press button  11  is protruded from the front upper end of the casing  1 . The bottom of the press button  11  is extended with a block  111 . The block  111  is adhered to the press plate  12 . The press plate  12  is a driven element. By the reed  121  to fix the structure, the press plate  12  is in contact with the resisting plate  133  of the stop claw  13 . The reed  121  is installed on a clamping block  18  installed on the casing. The reed  121  is an elastic restoring element, which may cause that the press plate  12  has a restoring function. 
     The central pivot hole  131  of the stop claw  13  may be pivotally installed with a pivotal shaft  19 . The left and right ends of the front end of the stop claw  13  have claw pieces  132  which are able to be engaged with the unidirectional ratchets  152   a  and  153   a . A notch  134  is formed between the two claw pieces  132  so not to contact the friction wheel  151 . The resisting plate  133  at the rear end is in contact with the press plate  12 . 
     The reed  14  is installed above the stop claw  13 . A clip  141  hangs the reed  14  to the shaft  17 . The pins at the left and right sides of the reed  14  presses the claw pieces  132  so that it is difficult that the claw pieces  132  moves upwards. Therefore, the reed  14  is an elastic press element of the stopper  13 . 
     The guide block  16  is installed at a lower end of the rotary wheel  15 . The guide block  16  is formed by a plurality of rear stop block  161  and a plurality of front stop block  162 . The rear stop blocks  161  are symmetrically disposed at the left and right sides. A gap is formed between two stop blocks  161 , and the top of each stop block  161  is a tilt surface so that a V shape is formed between two stop blocks  161 . Each front stop blocks  162  has the same configuration as the rear stop block  161 . However, the rear stop blocks  161  has a gap with the friction wheel  151  for guiding the ruler body  2  (referring to FIG.  5 ). The ruler body  2  may be in contact with the friction wheel  151  and the rear stop blocks  161  properly and thus a friction force is generated. Since the cross section of the ruler body  2  has a cambered shape which may increase the stress of the ruler body). The V shapes formed by the stop blocks  161  and  162  may generate preferred surface to be in contact with the ruler body  2 . The tilt surfaces  151   a  at two lateral sides of the friction wheel  151  properly contact the ruler body  2 . The front stop blocks  162  serves to guide the movement of the ruler body  2  so that the ruler body  2  does not shift or rub the edge of an outlet. 
     A whole cross sectional view of the check device  10  is illustrated in FIG.  5 . The bottom of the guide block  16  has a tenon  163  which may be embedded into the engaging groove  101  at the bottom of the casing. The two edges  164  of the guide block  16  may be guided into the guide grooves  102  at the bottom of the casing  1  so that the guide block  16  is steadily installed at the lower surface of the casing  1 . Next, two recesses  152   c  and  153   c  at the lateral sides of the ratchets and the central shafts  152   d  and  153   c  are matched to a ring  105  and a protruded shaft  106 . Thereby, the rotary wheel  15  may rotate through 360 degrees. 
     Referring to FIGS. 6 to  8 , the operation of the check device of the ruler in the present invention is illustrated. At first, referring to FIG. 6, when the ruler body  2  is pulled out from the casing  1 , the rotary wheel  15  is driven to rotate clockwise (referring to the figure). Then ratchets  152   a  and  153   a  push the claw pieces  132  so that the claw pieces  132  may adhere to the outer edges of the ratchets  152   a  and  153   a  to rotate with the hatchets. 
     Referring to FIG. 7, when the ruler body  2  stops (no force applies thereon). The ruler body  2  generates a restoring action due to the action of the winding spring. Then, the ruler body  2  will drive the rotary wheel  15  to rotate counterclockwise. The reed  14  presses downwards so that the claw pieces  132  will be engaged with the ratchets  152   a  and  153   a , Thereby, the two ratchets  152   a  and  153   a  will stop to rotate. Thereby, the ruler body  2  is stopped by the friction wheel  151  and thus does not rewind. 
     Referring to FIG. 8, when the user presses the press button  11  by a thumb, the block  111  under the press button  11  will push the press plate  12  downwards. Then the press plate  12  presses the resisting plate  133  of the stop claw  13 . Thereby, the claw piece  132  at another end of the stop claw  13  will curl upwards and then separates from the ratchets  152   a  and  153   a . Therefore, the rotary wheel  15  will separate from the claw pieces to be in a free condition. The ruler body  2  returns to the casing  1  due to the winding spring of the winding wheel  3  until a head  21  is stopped at the outlet end  103 . The rotary wheel  15  rotates counterclockwise due to the rewinding operation of the ruler body  2  until the ruler body  2  stops to rewind. After the ruler body  2  has been rewound, the press button  11  is released. Then the claw pieces  132  are engaged with the ratchets  152   a  and  153   a  due to a pressing-down force of the reed  14  so as to achieve an stop effect. Furthermore, another end of the stop claw  13  will lift upwards, and the press button  11  moves upwards due to the restoring force of the press plate  12  so as to return to the condition illustrated in FIG.  4 . 
     Referring to FIG. 9, another embodiment of the present invention is illustrated. To increase the force for moving the press button  11  upwards and reduce the burdens of the reeds  14  and  121 , the lower end of the press button  11  can be installed with a restoring spring  20  which is fixed to a resisting block  21  installed on the casing  1 . Therefore, the press button  11  has preferred pressing and restoring effects. 
     FIG. 10 shows another embodiment of the check device according to the present invention. In this embodiment, a compressing spring  22  is used to replace the reed  14 . The compressing spring  22  is installed above the stop claw  13 . One end thereof passes through a through hole at the lower end of the press plate  12  to be connected to the resisting plate  133  of the stop claw  13 , and another end thereof is connected to a post  23  installed on the casing  1 . Thereby, the stop claw  13  has a preferred fixing effect. 
     Another embodiment of the check device according to the present invention is illustrated in FIG.  11 . In this embodiment, a restoring spring  24  is used to replace the original reed  14 . The restoring spring  24  is installed at the lower side of the stop claw  13 , and the upper end thereof resists against the resisting plate  133  of the stop claw  13 . The lower end thereof is fixed in the recess  104  of the casing. Thereby, the stop claw  13  has a preferred fixing function. 
     Another embodiment about the check device of the present invention is illustrated in FIG.  14 . In this the present invention, an elastic tape  25  is utilized to replace the original reed  14 . The elastic tape  25  is installed below the stop pieces  132 . The upper end thereof resists against the resisting plate  133  of the stop claw  13 , and the lower end thereof is connected in the recess  104  of the casing. Thereby, the stop claw  13  has a preferred fixing function. Furthermore, FIG. 13 discloses a cambered elastic reed  26  which is utilized to replace the reed  24 . The cambered elastic reed  26  is fixed to the inserting groove  107  which is installed on the casing  1 . 
     Referring to FIG. 14, the front lower end of the press button  11  is connected with a long press plate  112 . The long press plate  112  is utilized to replace the original press plate  12  (i.e., the driven element) so as to contact the resisting plate  133  of the stop claw  13 . An expanding spring  22  is installed below the press button  11  and a stop block  21  for fixing the expanding spring  22 . 
     In summary, in the present invention, the ruler body  2  is pulled to have a check function so as not to rewind. After the press button is pressed, the ruler body  2  may rewind automatically. However, there are many ways for driving the press button  11  and the stop claw  13 , all stopping means connecting the stop claw  13 , rotary wheel  15  and guide block  16  are within the scope of the present invention. 
     The present invention are thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.