Patent Abstract:
A spacer includes a first cam having an inclined cam surface and a second cam having an inclined cam surface. The overall length of the two cams can be changed by contacting the cam surfaces together to move the cams relative to each other.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a spacer and a parts attachment device for attaching a cathode ray tube (CRT) to a TV receiver cabinet while adjusting the spacing between the cabinet and the CRT without warping the cabinet. 
     2. Description of the Prior Art 
     FIG. 20 is a cross-sectional view of the parts of an example of a prior art CRT mounting structure. In FIG. 20, a boss  2  is integrally provided on the inside surface of a cabinet  1 . Reference numeral  3  denotes a CRT, and numeral  4  denotes a CRT mounting flange provided on the side of the CRT  3 . Located on the end of the boss  2  is a recess portion that holds a fixing screw  7  and a matching nut  5 , with the nut  5  being held so that it cannot rotate. Numeral  6  denotes a fitting that is shaped like an inverted U, so it is open at the lower end. The inside of the top portion is indented to allow it to be bent down at each side, forming opposing flaps each having a cutout. The pair of cutouts is used to hold the boss  2  between the flaps. 
     The attachment of the CRT  3  to the cabinet  1  will now be described. First, the cabinet  1  is set level, the nut  5  is inserted into a hexagonal recess formed in the top of the boss  2 , and the fitting  6  is placed over the boss  2 . The CRT  3  is then positioned so that the flange  4  is on the fitting  6 , and the fixing screw  7  is inserted into a hole in the fitting  6  through a hole in the flange  4  and screwed into engagement with the nut  5 . 
     Screwing the fixing screw  7  into the nut  5  draws the nut  5  upward until it is in contact with the fitting  6 , moving the fitting  6  to a position at which the gap between the cabinet  1  and the flange  4  is closed. Further tightening the fixing screw  7  deforms the top of the fitting  6  flat. moving the flaps of the fitting  6  towards each other, clamping the boss  2  between the flaps, to thereby affix the CRT  3  to the cabinet  1 . This type of CRT mounting arrangement is disclosed by, for example, JP-A HEI 11-313276. Tightening the fixing screw  7  moves the fitting  6  into contact with the flange  4 . Since the boss  2  is clamped between the opposing flaps of the fitting  6 , the CRT  3  is attached to the cabinet  1  with an appropriate spacing being maintained between the cabinet  1  and the flange  4  that prevents the cabinet  1  being warped by the operation. However, a drawback of this configuration is that the CRT  3  is attached with a weak attaching force, which is the force by which the boss  2  is clamped by the opposing flaps of the fitting  6 . 
     An object of this invention is to resolve the above-described weak attaching force that is a drawback of the prior art, by providing a spacer and a parts attachment device that enables parts to be securely affixed without warping the member to which the part is affixed. 
     SUMMARY OF THE INVENTION 
     To attain the above object, the present invention provides a spacer comprising a first cam having an inclined cam surface and a second cam having an inclined cam surface, with an overall length of the two cams being changed by contacting the cam surfaces together to move the cams relative to each other. 
     The above object is also attained by a device for attaching parts via a spacer comprising a first cam having an inclined cam surface and a second cam having an inclined cam surface, with an overall length of the two cams being changed by contacting the cam surfaces together to move the cams relative to each other. 
     The spacer can also include a ratchet means for preventing the overall length of the cams from decreasing. A configuration can be used in which the cams are cylindrical and the ratchet means comprises engaging teeth provided on the peripheral wall of one of the cams and a pawl provided on the peripheral wall of the other cam that engages with the engaging teeth of the first cam. Using cams that are cylindrical, the ratchet means can also comprise engaging teeth provided on the cam surface of one cam and a pawl provided on the cam surface of the other cam that engages with the engaging teeth of the first cam. 
     The spacer can also include a torque limiter provided on a threaded engaging portion of one cam that engages with a fixing screw, a torque of the screwing action of the fixing screw relative to the threaded engaging portion being larger than a ratchet torque of the ratchet means, so that when a cam is brought into abutment with a member by rotation of the fixing screw in the threaded engaging portion, the action of the torque limiter screws the fixing screw into the engaging portion. 
     The cams are moved relative to each other in a linear direction to change the overall length of the cams, and it is preferable to provide a means for coupling the two cams together, at least in their initial state. 
     As described in the above, in accordance with this invention, a spacer is constituted of the first and second cams, enabling the overall length of the spacer to be adjusted to match the gap between the CRT fixing flange and the cabinet. Enabling the flange to be directly attached to the cabinet by fixing screws resolves the problem of weak attaching force that is a drawback of the prior art mounting. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and following detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a fixed cam used in a spacer according to a first embodiment of the invention. 
     FIG. 2 is a plan view of the fixed cam of FIG.  1 . 
     FIG. 3 is a bottom view of the fixed cam of FIG.  1 . 
     FIG. 4 is an enlarged, partial cross-sectional view along line IV—IV of FIG.  2 . 
     FIG. 5 is a front view of a rotary cam used in the spacer according to the first embodiment of the invention. 
     FIG. 6 is a plan view of the rotary cam of FIG.  5 . 
     FIG. 7 is a bottom view of the rotary cam of FIG.  5 . 
     FIG. 8 is an enlarged, partial cross-sectional view along line VIII—VIII of FIG.  5 . 
     FIG. 9 is an cross-sectional view along line IX—IX of FIG.  6 . 
     FIG. 10 is a front view showing the spacer with the rotary cam attached to the fixed cam. 
     FIG. 11 is a plan view of the spacer of FIG.  10 . 
     FIG. 12 is a bottom view of the spacer of FIG.  10 . 
     FIG. 13 is a plan view showing part of the back of a cabinet. 
     FIG. 14 is a view of the rib seen in FIG. 13, as seen from the direction indicated by the arrow. 
     FIG. 15 illustrates the attachment of a CRT to the cabinet, using the spacer according to the first embodiment of the invention. 
     FIG. 16 is another illustration of the attachment of the CRT to the cabinet using the spacer according to the first embodiment of the invention. 
     FIG. 17 is a disassembled perspective view of a spacer according to a second embodiment of the invention. 
     FIG. 18 illustrates the attachment of a CRT to a cabinet, using the spacer according to the second embodiment of the invention. 
     FIG. 19 is another illustration of the attachment of the CRT to the cabinet using the spacer according to the second embodiment of the invention. 
     FIG. 20 is a cross-sectional view of parts of an example of a prior art CRT mounting structure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention will now be described with reference to the drawings. FIGS. 1 to  4  show a fixed cam used in a spacer according to a first embodiment of the invention. In the drawings, reference numeral  11  denotes a first cam that is a fixed cam. The fixed cam  11  is formed of synthetic resin, and is cylindrical in shape, comprising a large-diameter portion  12  and a small-diameter portion  15 . The large-diameter portion  12  is provided with a projection  13  that extends radially from the peripheral surface of the large-diameter portion  12 . Two cam surfaces  14  are provided on the upper surface of the large-diameter portion  12 . Each cam surface  14  slopes up at a predetermined angle, extending 180 degrees in a clockwise direction. The peripheral surface of the small-diameter portion  15  has teeth  16  for a ratchet means. A pawl  17  that constitutes a coupling means is provided between predetermined teeth  16 . 
     FIGS. 5 to  9  show a rotary cam used as a second cam in the spacer of the first embodiment. The rotary cam  21  is formed of synthetic resin, and comprises an outer cylinder  22 , a threaded inner cylinder (or threaded engaging portion)  25 , and a ceiling portion  27  that connects the top ends of the outer cylinder  22  and the threaded inner cylinder (or threaded engaging portion)  25 . The lower face of the outer cylinder  22  is provided with two cam surfaces  23 , each of which slopes upwards at the same angle as the cam surface  14  of the fixed cam  11 , extending 180 degrees in a clockwise direction. The peripheral surface is provided with a pawl  24  to form a rachet means. The pawl  24  has teeth  24   a  for engaging with the teeth  16  of the fixed cam  11 . These teeth  24   a  constitute a coupling means. The inside surface of the threaded inner cylinder (or threaded engaging portion)  25  has built-up portions  26  provided at, for example, 120-degree intervals to limit circumferential torque (i.e., the built-up portions  26  on the inside surface of the threaded inner cylinder or threaded engaging portion  25  act as a torque limiter). 
     FIGS. 10 to  12  show the spacer with the rotary cam  21  attached to the fixed cam  11 . As shown by these drawings, the spacer is assembled so the overall length of the cam  11  and cam  21  is at the minimum, which is when the small-diameter portion  15  of the fixed cam  11  is inserted into the outer cylinder  22  of the rotary cam  21  with the teeth  16  engaged with the teeth  24   a  of the pawl  24  and the cam surfaces  14  and  23  pressed into contact. When the resiliency of the pawl  24  enables the teeth  24   a  to ride over the pawl  17 , the top of the teeth  24   a  become positioned at the bottom of the pawl  17 , as shown in FIG. 4, preventing the fixed cam  11  slipping free of the rotary cam  21 . Therefore, the initial assembly state is maintained by the coupling means constituted by the pawl  17  and teeth  24   a . By using the coupling means to prevent the fixed cam  11  disengaging from the rotary cam  21 , the spacer S stays in its initial assembly position, in which it is easier to handle. 
     FIG. 13 is a plan view showing part of the back of a cabinet, and FIG. 14 shows the rib of FIG. 13, as seen from the direction indicated by the arrow. In the drawings, reference numeral  51  denotes a cabinet, and numeral  52  denotes a rib formed integrally with the cabinet  51 , in the shape of a cylinder open at one side when seen in plan view. The rib  52  is used to position the spacer S and control rotation of the fixed cam  11 . Reference numeral  53  denotes a boss located at the center of the rib  52 . The boss  53  is formed as an integral part of the cabinet  51 , with an outside diameter that allows the boss to fit into the fixed cam  11 . 
     FIGS. 15 and 16 show how a CRT is attached to a cabinet, using the spacer of the first embodiment of the invention. In the drawings, reference numeral  61  denotes the part or member to be attached, which is a CRT. On the side of the CRT, there is a fixing flange  62  that has a hole  63  into which a fixing screw  71  is inserted. 
     The attaching of the CRT  61  to the cabinet  51  will now be explained. First, as shown in FIG. 15, the cabinet  51  is placed so it is level, and the boss  53  is inserted into the fixed cam  11  of the assembled spacer S, and the spacer S is positioned inside the rib  52 . Next, the CRT  61  is positioned with the flange  62  on the spacer S. The fixing screw  71  is then inserted into the hole  63  of the flange  62  and screwed into a built-up portion  26  in the inner cylinder  25  of the rotary cam  21 . 
     When the screw  71  is being screwed into the built-up portion  26 , the torque of the screwing action exceeds the ratchet torque of the ratchet means, causing the spacer S to rotate clockwise. The rotation of the fixed cam  11  is prevented by the projection  13  coming into contact with the rib  52 . With the rotation of the fixed cam  11  being thus prevented, only the rotary cam  21  rotates. As the rotary cam  21  rotates, the resiliency of the pawl  24  enables the teeth  24   a  to ride over the teeth  16  one tooth at a time, whereby as the rotary cam  21  rotates clockwise, it is elevated as it is guided along the cam surfaces  14  and  23 , gradually increasing the overall length of the spacer S. In this way, the rotary cam  21  is moved to a position at which the gap between the cabinet  51  and the flange  62  is appropriately closed. 
     When the rotation of the rotary cam  21  moves about two of the teeth  16  past the pawl  17  from the initial position, the pawl  17  and the teeth  24   a  disengage, allowing the rotary cam  21  to move axially. Also, as shown in FIG. 16, when the rotary cam  21  is pressed against the flange  62 , screwing the screw  71  into the built-up portions  26  and the boss  53  clamps the flange  62  between the spacer S and the screw  71 , enabling the CRT  61  to be attached securely to the cabinet  51 . 
     Thus, as described in the above, in accordance with the first embodiment of this invention, the spacer S is comprised of a first cam  11  and a second cam  21 . By pressing the cam surfaces  14  and  23  of the two cams together, the cams  11  and  21  are rotated relative to each other, thereby making it possible to increase the overall length of the spacer S, appropriately closing the gap between the cabinet  51  and the flange  62 . It therefore becomes possible to securely affix the CRT  61  to the cabinet  51  without warping the cabinet  51 . 
     Also, the spacer S is provided with a ratchet mechanism that maintains the spacer in the state in which it is attached, by preventing any shortening of the overall length of the spacer S. Moreover, the cams  11  and  21  are cylindrical, and have a ratchet mechanism provided between the peripheral walls of the cams. This configuration enables a ratchet mechanism to be provided without increasing the overall size of the spacer. The spacer S is also provided with a torque limiter, which enables the overall length of the spacer S to be readily increased to an appropriate length to fill the gap between the cabinet  51  and the flange  62 . A coupling means is also provided between the cams  11  and  21 , which maintains the cams in their initial assembly state, making it easier to handle the spacer and also facilitating the operation of attaching the CRT  61  to the cabinet  51 . 
     FIG. 17 is a disassembled perspective view of a spacer according to a second embodiment of the invention. Parts that are the same as, or correspond to, parts in FIGS. 1 to  16  have been given the same reference numerals or symbols, and further explanation thereof is omitted. In FIG. 17, reference numeral  31  denotes a first cam that is a fixed cam. The first cam  31  is formed of synthetic resin, and comprises a cylindrical portion  32  into which a boss  53  of a cabinet  51  is inserted, and a wedge-shaped cam portion  33 . The upper surface of the cam portion  33  forms a cam surface that slopes upwards at a predetermined angle. Engaging teeth  34  are provided at each side, forming a ratchet mechanism. The cam portion  33  is also provided with a guide groove  35  and a hole  36  (FIG. 18) that communicates with the cylindrical portion  32 . 
     Reference numeral  41  denotes a wedge-shaped second cam, formed of synthetic resin, that is movable. The lower face of the movable cam  41  is formed as a cam surface  42  that slopes upwards at the same angle as the cam engaging teeth  34 . The lower surface also has a ratchet mechanism comprising pawls  43  provided at each side, and a guide member  44 , preventing disengagement from the guide groove  35 . The movable cam  41  has a long hole  45 , which enables the hole  45  to remain in communication with the hole  36  even when the movable cam  41  is moved on the fixed cam  31 . The guide mechanism constituted by the guide groove  35  and guide member  44  also forms a coupling means. 
     FIGS. 18 and 19 illustrate the attachment of a CRT to a cabinet, using the spacer according to the second embodiment of the invention. Parts that are the same as, or correspond to, parts in FIGS. 1 to  17  have been given the same reference numerals or symbols, and further explanation thereof is omitted. FIG. 18 shows the initial assembly state, with the guide member of the movable cam  41  inserted in the guide groove of the fixed cam  31  and the teeth  34  at the lower part in engagement with the pawls  43 . This initial state is maintained by the coupling (i.e. guide) means. In this initial state, the spacer S is easier to handle, since the coupling means keeps the cams together. 
     The attaching of the CRT  61  to the cabinet  51  will now be explained. First, as shown in FIG. 18, with the cabinet  51  (not shown) in a level position, the boss  53  is inserted into the cylindrical portion  32  of the assembled spacer S, and the CRT  61  (not shown) is positioned so that the flange  62  is on the spacer S. The gap between the movable cam  41  and the flange  62  can then be closed, as shown in FIG. 19, by pushing in the movable cam  41 . 
     When the movable cam  41  is thus pushed, the resiliency of the pawl  43  enables it to ride over the engaging teeth  34  one tooth at a time, allowing the movable cam  41  to move up along the guide groove  35  (the cam surface  42 ), thereby increasing the overall length of the spacer S, until the spacer is at a length that fills the gap between the cabinet  51  and the flange  62 . As shown in FIG. 19, the fixing screw  71  is then inserted through the long hole  45  and the hole  36  and screwed into the boss  53 . This clamps the flange  62  between the spacer S and the screw  71 , ensuring that the CRT  61  is attached securely to the cabinet  51 . 
     The same effect that is obtained with the spacer S of the first embodiment can also be obtained with this spacer S of the second embodiment. 
     In the arrangement of the first embodiment described above, a ratchet mechanism is provided between the peripheral surfaces of the first and second cams  11  and  21 . However, the same effect can be obtained by providing the ratchet means on the cam surfaces  14  and  24 . Also, although in the case of the first and second embodiments, the fixed cams  11  and  31  are formed as parts that are separate from the cabinet  51 , the fixed cams  11  and  31  can be formed as integral parts of the cabinet  51 . The coupling means is not limited to the example configuration described with reference to the first and second embodiments. Instead, any configuration may be used that provides the same function. 
     As described in the foregoing, in accordance with this invention, a spacer is provided that is comprised of a first fixed cam and a second movable cam. It is noted that the first cam may be a movable one and the second cam may be a fixed one. The cams are moved relative to each other with the cam surfaces in mutual contact. This enables the overall length of the spacer to be increased, which is used to fill gaps when attaching a part, such as the gap between a CRT and a cabinet in which the CRT is attached. The spacer makes it possible to use screws to effect a strong, direct attachment of parts, without warping the cabinet or other such member to which the part is affixed. 
     A ratchet mechanism is provided that prevents the overall length of the spacer from decreasing, and the assembly state can be maintained. Since the cams can be cylindrically formed and the ratchet mechanism can be provided between the peripheral walls or cam surfaces of the cams, it is possible to provide a configuration that enables a ratchet mechanism to be added without increasing the overall size of the spacer. 
     The spacer can also be provided with a torque limiter that enables the overall length of the spacer to be readily increased to the appropriate length to fill the gap between the part and the member to which the part is attached. 
     A coupling means can be provided between the cams. This maintains the initial assembly state of the spacer, that is, it keeps the cams from separating, making the spacer easier to handle and to use for attaching parts.

Technology Classification (CPC): 8