Abstract:
A mounting mechanism for releaseably mounting a print head to the carriage of a printer includes a pair of pivotable levers respectively located on opposite sides of the print head. A spring member biases the levers in a predetermined direction. The levers are pivotable between a first position where the print head is secured to the carriage and a second position where the print head is released.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a mounting mechanism for a print head and, in particular, to a mounting mechanism which permits the print head to be easily removed from the printer carriage. 
     In a printing apparatus making use of a print head, the print head needs to be removed and replaced during the assembly of the printing apparatus, when repairs must be made to the printing apparatus, and at the end of the useful life of the print head. Reference is made to FIG. 5 of the drawings which depicts a conventional mounting mechanism for a print head. A print head 31 is secured to a carriage 32 which acts as a mount for the print head by means of screws 33a and 33b. Whenever print head 31 needs to be removed as noted above, print head 31 has to be removed from and remounted on carriage 32 by rotating screws 33a and 33b with a special tool such as a screwdriver. Therefore, prior art mounting mechanisms suffer the disadvantage in that, in order to remove and remount print head 31, an operator requires a special tool such as a screwdriver and is forced not only to perform complicated removal actions but also to spend a considerable period of time doing so. Other examples of prior art mounting mechanisms for print heads are disclosed in U.S. Pat. No. 4,452,542 and U.S. Pat. No. 4,514,100. 
     Accordingly, it is desirable to provide a mounting mechanism for a print head which allows easy and quick removal and replacement of the print head. 
     SUMMARY OF THE INVENTION 
     Generally speaking, in accordance with the present invention, a mounting mechanism for a print head is provided for easy and quick removal and replacement of print heads without the need of any special tools. The mounting mechanism includes a pair of levers respectively located on opposite sides of the print head on a printer carriage which are pivotably supported on the carriage by means of a spring member which biases the levers in a predetermined direction. The first and second levers are pivotable between a first position where the print head is locked to the carriage and a second position where the print head can be removed. 
     Accordingly, it is an object of the present invention to provide an improved mounting mechanism for a print head. 
     Another object of the present invention is to provide a mounting mechanism for a print head which allows the easy removal and replacement of a print head without the use of special tools. 
     A further object of the present invention is to provide an improved mounting mechanism for a print head which allows for the removal and replacement of the print head without many time consuming complicated actions. 
     Still other objects and advantages of the invention will in part be obvious and in part will be apparent from the specification and drawings. 
     The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1(a) is a front elevational view of a mounting mechanism for a print head in which a print head is secured on a printer carriage, constructed in accordance with a first embodiment of the present invention; 
     FIG. 1(b) is a front elevational view of the mounting mechanism for a print head depicted in FIG. 1(a) where the print head is shown unsecured; 
     FIG. 2 is a perspective view of a mounting mechanism for a print head shown with the print head in place, but with the levers and spring of the mounting mechanism omitted for purposes of explanation; 
     FIG. 3 is a perspective view of the mounting mechanism for a print head as depicted in FIG. 2 wherein the print head is shown removed from the printer carriage; 
     FIG. 4 is a front elevational view of a mounting mechanism for a print head constructed in accordance with an alternative embodiment of the present invention; and 
     FIG. 5 is a top plan view depicting a mounting mechansim for a print head constructed in accordance with the prior art. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is first made to FIGS. 1(a) and 1(b), 2 and 3 which depict a print head 1 which prints by utilizing the impact of a set of print wires 9. Print head 1 includes a nose portion 1a with flat regions or legs 1b and 1c extending respectively on each side of nose 1a. Flat regions 1b and 1c each have a convex projection 1d and 1e formed respectively on the top surfaces thereof. 
     A carriage 2 having flat regions or legs 2a and 2b rigidly affixed to carriage 2 by means of a U-shaped support acts as a mount for print head 1. A single upwardly extending pin 8 is provided on each flat region 2a and 2b. Corresponding openings 7 are formed in each flat region 1b and 1c of print head 1. Print head 1 is positioned on carriage 2 such that pins 8 extend through openings 7 thereby allowing print head 1 to lie flush against flat regions 2a and 2b in such a manner that print head 1 is supported and properly positioned on flat regions 2a and 2b of carriage 2. The cooperation between openings 7 and pins 8 determine the relative position of carriage 2 with respect to print head 1. 
     Levers 3 and 4 are rotatably coupled to carriage 2 and are of the same shape. Levers 3 and 4 include grip portions 3c and 4c, respectively, at the upper end thereof for manual operation of levers 3 and 4. Directly below grip portions 3c and 4c are pressing portions 3a and 4a respectively, which engage flat regions 1b and 1c, respectively, of print head 1. Both levers also include a flat surface 3d and 4d, respectively formed at a 45° angle as depicted. Levers 3 and 4 are arranged so that flat portions 3d and 4d come into contact with respective flat surfaces 2c and 2d on carriage 2 after each lever has rotated 45° from the position in which it is engaged with print head 1 to a position in which it comes in contact with surfaces 2c and 2d. 
     Engagement slots 3b and 4b are respectively formed in levers 3 and 4 and are engaged with the two ends of a leaf spring 6. Leaf spring 6 passes through openings 5a and 5b in carriage 2 located in the U-shaped support. Leaf spring 6 is bent in such a manner that its ends are respectively engaged with engagement slots 3b and 4b. Engagement slots 3b and 4b are positioned above openings 5a and 5b  so that when engaged with leaf spring 6, leaf spring 6 is deflected upwards. 
     When print head 1 is secured, leaf spring 6 is deflected upward against upper surfaces 5a-1 and 5b-1 of openings 5a and 5b, respectively. Openings 5a and 5b act as fulcrums which cause leaf spring 6 to apply a downward force to levers 3 and 4. This, in turn, causes pressing portions 3a and 4a of levers 3 and 4 to engage flat regions 1b and 1c of print head 1 and press flat portions 1b and 1c against flat portions 2a and 2b of carriage 2. The resultant force of leaf spring 6 acting on levers 3 and 4 is a force in the direction of arrow A. Convex projections 1d and 1e of print head 1 exert a force with respect to levers 3 and 4 which acts to overcome the force in the direction of arrow A. Therefore, levers 3 and 4 are held securely in position. 
     In order to release print head 1, grip portions 3c and 4c of levers 3 and 4 are pressed manually in the direction of arrow A, with a force sufficient to cause lever 3 and 4 to pass over convex projections 1d and 1e. Engagement portions 3b and 4b remain engaged with leaf spring 6 and act as a second set of fulcrums as levers 3 and 4 rotate. The levers rotate through 45°, after which flat surfaces 3d and 4d come into contact with flat portions 2c and 2d of carriage 2 thereby preventing any further rotation. In this condition, the degree of upward deflection of leaf spring 6 has decreased, but spring 6 is still deflected upward. Therefore, a downward force is still exerted on levers 3 and 4. This secures levers 3 and 4 by pinning them against flat regions 2c and 2d. Levers 3 and 4 are now spread far enough apart to allow clearance for the removal of print head 1. 
     Since print head 1 is held on carriage 2 by its own weight when levers 3 and 4 are rotated, it can easily be removed off of the carriage. To remount and resecure print head 1, levers 3 and 4 are operated in reverse order, that is, a manual force sufficient to cause levers 3 and 4 to pass over the convex projections 1d and 1e in the reverse direction is applied to grip portions 3c and 4c. 
     Referring now to FIG. 4, another embodiment of the present invention is shown for a mounting mechanism for a print head wherein the leaf spring and the levers are integrally formed. A lever 10 is formed of a single integral material having the resiliency of a spring. The upper portions of lever 10 engage print head 1 as described above in connection with the first embodiment. Spring lever 10 is curved upward at its bottom region so that opening edges 5a-1 and 5b-1 still act as a fulcrum enabling spring lever 10 to exert a downward force on print head 1. Print head 1 is removed from carriage 2 with one touch of a finger in the same manner as described above in the first embodiment. 
     It is noted that print head 1 may be an impact print head of the wire dot type, a thermal print head, a matrix type print head or any other type of print head. Also, the rotational angle of each of levers 3 and 4 can be changed by altering the angle at which the flat surfaces 3d and 4d are formed, whereby levers 3 and 4 can be rotated until they stop at the desired angle. 
     Accordingly, by providing a mounting mechanism for a print head as described above, the problems in removing print heads encountered with prior art mounting mechanisms are overcome. The present invention provides a simple and inexpensively constructed mounting mechanism which achieves each of the objects noted above. No special tools are required for print head removal. Quick and easy print head removal can be effected with the present invention. 
     It will thus be seen that the objects set forth above, and those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.