Horizontal file drawer interlock assembly
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to an improved interlock assembly for preventing more than one horizontally sliding drawer in a file cabinet from being opened at one time. In particular, the present invention relates to an interlock assembly which uses horizontally rotating cam members with opposed cam surfaces and blocks contacting the cam surfaces with mating surfaces each having lobes between valleys which engage when the cam member is rotated in one direction to provide the interlock and which disengage when the cam member is rotated in the opposite direction to release the interlock and provide the lobes in the valleys. 
     (2) Prior Art 
     U.S. Pat. No. 4,480,883 to Young shows an interlock assembly wherein cam elements rotate vertically to raise and lower vertically mounted locking bars provided in a track. The device works well; however, the interlock mechanism is quite expensive to manufacture and assemble. U.S. Pat. No. 4,298,236 to Laroche also describes cam elements which are vertically rotated to move locking bars. This apparatus is more expensive to construct. Other prior art believed to be less pertinent is described in U.S. Pat. No. 4,355,851 to Slusser are U.S. Pat. No. 3,909,090 to Breckner et al. 
     Objects 
     It is therefore an object of the present invention to provide a drawer interlock assembly which provides ease of manufacture and assembly. Further it is an object of the present invention to provide an interlock assembly which provides long and reliable service. Further it is an object of the present invention to provide an inexpensive interlock assembly. These and other objects will become increasingly apparent by reference to the following description and the drawings. 
    
    
     IN THE DRAWINGS 
     FIG. 1 is a perspective view of a cabinet 10 with two horizontally sliding drawers 11 and 12 which can utilize the interlock assembly of the present invention wherein one drawer 11 is open. 
     FIG. 2 is a side cross-sectional view of the cabinet 10 shown in FIG. 1 particularly showing the two horizontally sliding drawers 11 and 12 in the closed position with the interlock assembly 20 in a rest position so that either drawer 11 or 12 can be opened. 
     FIG. 3 is a side cross-sectional view of the cabinet 10 shown in FIG. 1 wherein one of the drawers 12 is pulled out thereby activating the interlock assembly 20 to prevent the other drawer 11 from being opened. 
     FIG. 4 is a plan partial sectional view along line 4--4 of FIG. 2 showing the interlock assembly 20 with the drawer 12 closed. 
     FIG. 5 is a plan partial sectional view along line 5--5 of FIG. 3 showing the activated interlock assembly 20 on drawer 11 which prevents the upper drawer 11 from being opened. 
     FIG. 6 is an exploded view of a portion of the interlock assembly 20 wherein a cam member 23 can be rotated to raise block 26 and thus the upper blocks 24 and 25 and cam member 22 shown in FIG. 2. 
     FIG. 7 is a front view showing a part of the preferred interlock assembly 50, including a rotatable cam member including cam members 51, 52, arms 51c and 51d, pin 53 and tube 59 which engages two spaced apart blocks 54 and 55 in the same manner as in FIG. 6. 
     FIG. 8 is a plan cross-sectional view of the portion of the interlock assembly 50 along line 8--8 of FIG. 7. 
    
    
     GENERAL DESCRIPTION 
     The present invention relates to an improvement in a cabinet apparatus including a housing having a top wall and opposed bottom wall, two opposed side walls, a front wall and a back wall, at least two drawers mounted inside the housing through the front wall so as to slide horizontally away from the front wall to open the drawer and towards the back to close the drawer and an interlock assembly mounted inside and on the housing which engages an extension means from the drawer to prevent both drawers from being opened simultaneously wherein the interlock assembly which comprises: a rod having a longitudinal axis between two ends rigidly mounted in a parallel spaced relationship to a rear portion of each of the drawers; cam means rotatably and slideably mounted around the axis of the rod adjacent the rear portion of each of the drawers, wherein at least one end of the cam means around the axis of the rod has a sinusoidal surface such that there are lobes of the sinusoidal surface and valleys between the lobes on the surface on each cam means; block means slideably mounted on the rod at the one end of each of the cam means having the sinusoidal surface and having mating ends with second sinusoidal surfaces and lobes and valleys offset around the end of the block means when the drawers are closed so that lobes and the valleys of the cam means and block means mate together, wherein the block means extend between cam means for each drawer and between the cam means and the housing; and pivot means mounted on a side between the ends of each cam means which engages the extension means from each drawer; guide means mounted inside the housing supporting the block means for linear movement along the axis of the rod without rotational movement perpendicular to the axis of the rod upon rotation of the cam means by the pivot means and the extension means, wherein when one of the cam means is rotated by the pivot means and extension means of a first of the drawers, the lobes of the cam means and the block means are engaged and the block means between the cam means and housing moves along the axis of the rod to engage the housing, thereby preventing a second cam means from being rotated by the pivot means and extension means of a second of the drawers. 
     In particular the present invention relates to an improvement in a cabinet apparatus including a housing having a top wall and opposed bottom wall, two opposed side walls, a front opening and a back wall, at least two front and second drawers mounted one above the other inside the housing in the front opening so as to slide horizontally away from the front opening to open the drawer and towards the back wall to close the drawer and an interlock mechanism mounted inside and on the housing which engages an extension means from the drawer to prevent the drawers from being opened simultaneously which comprises: 
     a circular cross-sectioned rod having a longitudinal axis between two ends rigidly mounted vertically between the top wall and the bottom wall of the housing parallel to a rear portion of each of the drawers; cam members rotatably and slideably mounted around the axis of the rod adjacent the rear portion of each of the drawers, wherein opposite ends of each cam member have a sinusoidal surface around the axis of the rod such that there are two lobes on the sinusoidal surface opposite each other and two valleys between the lobes, wherein the lobes and valley surfaces are in identical circumferential position around the axis of the rod at each end of the cam members; block members at each of the ends of each cam member slideably mounted on the rod having ends with second sinusoidal surfaces and lobes and valleys offset by about 90° around the end of the block member so that when the drawers are closed the lobes and valleys of the cam members and blocks mate together, wherein the block members extend between each drawer and between the cam members and the housing; pivot members between the ends and on a side of each cam member which engage the extension means from each drawer; and guide brackets mounted on the housing supporting the block members from linear movement along the axis of the rod without rotational movement perpendicular to the axis of the rod upon rotation of the cam member by the pivot member and the extension means, wherein when one of the cam members is rotated on the rod by the pivot means and the extension means of the first of the drawers the lobes of the cam members and the block means are engaged, and a tubular extension mounted on one of the block members moves along the axis of the rod to engage the housing, thereby preventing a second cam member from being rotated by the pivot member and extension means of the second of the drawers. 
     The train of block means and cam means forming the interlock assembly thus are slideably mounted for movement along an axis of the rod so that block means of the assembly engages the housing by means of rotation of one cam member by an extension means engaging a pivot member on the cam member. The result is that a second cam member is prevented from rotation by a second extension means engaging a second pivot means since the train can not move any further on the rod. As will be seen, the interlock assembly is very inexpensive to construct and assemble and provides safe, trouble free service. 
     SPECIFIC DESCRIPTION 
     FIG. 1 shows a file cabinet 10 providing a housing for two drawers 11 and 12 which slide in and out on sliders 13 (one shown) on each side of the drawers 11 and 12. The cabinet 10 includes a top wall 10a, bottom wall 10b, opposed side walls 10c and 10d and a front wall 10e and a back wall 10f which serve as reference points in the following description. 
     A vertically oriented interlock assembly 20 is shown in position in the cabinet 10 in FIGS. 2 and 3. The assembly 20 is preferably positioned about midway on the back wall 10f between side walls 10c and 10d of the cabinet 10. A rod 21 is vertically oriented along axis a--a and securely mounted between the top wall 10a and bottom wall 10b of the cabinet 10 adjacent to and in closely spaced relationship to the drawers 11 and 12. Mounted around the rod 21 are vertically slideable and horizontally rotatable cam members 22 and 23. On either side of and in contact with the cam members 22 and 23 are mounted cam blocks 24, 25, 26 and 27. The cam blocks 24, 25, 26 and 27 are slideable vertically and secured to the back wall 10f of the cabinet 10 by means of brackets 28, 29, 30 and 31 which are joined together as a unit by plate 40. Extending from the back of each drawer 11 and 12 are extensions 32 and 33 which cooperate with the cam members 22 and 23 as hereinafter described in detail. 
     A tubular member 34 extends from block 21 to a point in spaced relationship from the top wall 10a of the cabinet 10 as shown in FIG. 2 with the drawers 11 and 12 closed. A coil spring 35 is mounted on an end of the rod 21 adjacent the inner top wall 10a&#39; of the cabinet 10 in a cup 36 secured to tube 34. The spring 35 urges the cup 36, tubular member 34, blocks 24, 25, 26 and 27 and cam members 22 and 23 downward to urge the interlock assembly 20 into a closed drawer position. The tubular member 34 and/or cup 36 engages the top wall 10a or inner wall 10a&#39; when a drawer 11 or 12 is opened as shown in FIG. 3. A second tubular member 37 spaces the blocks 25 and 26 which can be interconnected in any convenient manner for vertical sliding movement. As shown, drawers 11 and 12 open to the right and are otherwise conventionally constructed as is the cabinet 10. 
     FIG. 3 shows a U-shaped pivot member 38 which is rotated clockwise by extension 33 by pulling drawer 12 (or 11) open. FIGS. 4 to 6 show the rotation of the pivot member 38 when the drawer 12 opens. The pivot member 38 rides on vertical section 38a in an arcuately shaped slot 39 on cam surface 39a. The blocks 26 and 27 have lobes 27a with indentations 27b and valleys 27c between the lobes 27a. The block 26 has corresponding lobes 26a, indentations 26b and valleys 26c. Both ends of cam 23 have lobes 23a and 23b and valleys 23c and 23d. The blocks 24 and 25 and cam 22 are identically constructed to blocks 26 and 27 and cam member 23. The cam members 22 and 23 essentially have a sinusoidal surface or face at each end as do the blocks 24, 25, 26 and 27 which engages the cam members 22 and 23. In the closed drawer position, the lobes 23a and 23b of cam 23 are in valleys 26c and 27c of blocks 26 and 27 and are about 90° around the axis of the rod 21. 
     As can be seen from FIG. 3, when the cam member 23 is rotated by extension 33 engaging pivot member 38, the lobes 23a and 23b engage detents 26b of lobes 26a on block 26 and lobes 23c and 23d engage detents 27b in lobes 27a of block 27. Thus the train of blocks 24, 25 and 26 tubular members 34 and 37 and cam member 22 are moved upward so that the cup 36 engages the inner housing wall 10a&#39; to provide a stop. The spring 35 is compressed by the upward movement of the train. When the drawer 12 is closed, the cam member 23 is rotated by pivot member 38 and the train moves down so that the lobes 23a, 23b, 23c and 23d are in the valleys 26c and 27c of the blocks 26 and 27, thus allowing another drawer 11 or the same drawer 12 to be reopened. Preferably the pivot member 38 moves in an arc perpendicular to the axis of the rod of about 85°. The lobes 23a, 23b, 23c and 23d do not rest completely in the valleys 26c and 27c so that there is some tension between the cam member 23 and the blocks 26 and 27 thereby preventing rebound. The 5° from 90° (i.e. 85°) allows the tension. 
     FIGS. 7 and 8 show an improved moldable interlock assembly 50 wherein cam surfaces are provided by dual spaced apart cams 51 and 52 with lobes 51a and 52a and valleys 51b and 52b. Integral radially extending arms 51c and 52c from the axis b--b of rod 58 along with pin 53 provide a pivot means. Cams 54 and 55 are spaced apart by tube 59 to provide the cam means as in FIG. 6. Tubular members 56 and 57 fit around the rod 58 and provide part of the block means as shown in FIGS. 2 and 3. Brackets 60 and 61 are mounted to the back wall 10f of the cabinet 10 in the manner shown in FIGS. 2 and 3. An extension 62 engages plate 51d on arm 51c to prevent the arm 51c from over rotating in the clockwise direction so that lobes 51a and 52a engage detents 54a and 55a in blocks 54 and 55. In operation, the cams 51 and 52 and blocks 54 and 55 act to provide an interlock in the same manner as the cam member 22 and 23 and blocks 24, 25, 26 and 27 shown in FIGS. 2 and 3. 
     It will be appreciated that the rod member could be positioned at an angle to the vertical between the drawers where the drawers are one above the other. The file drawers can be side by side rather than one above the other with the interlock assembly in a horizontal position. The vertical positioning is preferred for ease of installation and operation of the interlock assembly 20. The coiled spring can also be at the bottom or side wall of the housing. The cam members and blocks are preferably made of a rigid plastic material, preferably nylon or acetyl resin and can be molded in the configurations as shown in FIGS. 7 and 8. A sliding pin on the blocks mounted in slots in the bracket (not shown) can be used to prevent rotation of the blocks perpendicular to the axis of the rod. All such variations will be obvious to those skilled in the art and it is intended that the invention be limited only by the hereinafter appended claims.