Knob-type closure device
BACKGROUND OF THE INVENTION 
     The present invention relates to a knob closure device for operating and locking glass panes or doors movable in a direction that is substantially axial with respect to the knob. 
     The field of closure systems for cabins of farming machines or earth-movers, of closures for hoods or sliding doors, requires compact devices that can be mounted at any angle and allow a certain angular tolerance in alignment between the normals at the surfaces: EEC standards also prescribe, for vehicle doors, a double snap-engagement action, a first snap-engagement action for ajar retention, and a second snap-engagement action for locking in a closed position. 
     Another desirable characteristic is to be able to release the closure device both by turning and by pulling axially and by acting, on both sides, both on the exposed parts of the knob and on the parts that remain concealed when coupling is performed. 
     Conventional devices do not effectively meet all the above-mentioned requirements. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to obviate the drawbacks of conventional devices, i.e., to provide a knob closure device for operating and locking glass panes or doors which are axially movable with respect to the knob that is compact and easy to install, has an acceptable angular tolerance and a double closing snap-engagement action, and allows actuation by rotation and by pulling, with the possibility of acting from the outside or from the inside of the surface to which the knob is applied. 
     Within the scope of this aim, an object of the present invention is to achieve the above aim with a structure that is simple, relatively easy to manufacture, safe in use, effective in operation, and having relatively low costs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further particularities will become apparent and evident from the detailed description of a preferred but not exclusive knob closure device for operating and locking two surfaces which are axially movable with respect to the knob, according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
     FIG. 1 is a partially sectional front view of the knob closure device, according to the invention; 
     FIG. 2 is a partially sectional side view of the closure device of FIG. 1; 
     FIG. 3 is a sectional side view of the device, taken along axis III--III of FIG. 2; 
     FIG. 4 is a side view, rotated through 90° with respect to FIG. 3, of the device in the engagement condition; 
     FIG. 5 is a view of a detail of FIG. 4, with the device in disengagement condition; 
     FIG. 6 is a sectional side view of a detail of the device, provided with a different type of means for fixing the hollow body. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With particular reference to the above figures, the reference numeral 1 generally designates a knob closure device for operating and locking two surfaces 2 and 3 which are axially movable with respect to each other (arrows A-B); the surfaces 2 and 3 can be of any kind (glass, metal, materials such as plastics, or others) and the only process that must be performed to install the closure device is the formation of respective holes 2a and 3a. 
     The device 1 comprises a pin 4 that is provided with means for fixing to the hole 2a of the first surface 2; said means are constituted by a threaded stem 5, washers 6, a nut 7, and an optional protective cup 8; the pin 4 has a rounded end 9 and is affected by two annular grooves 10a and 10b proximate to its engagement end; the cup 8 is made of a material such as rubber, and while its central region allows a certain clearance to the stem 4 to facilitate its coupling, its cylindrical region acts as protection and cushions impacts during closure. 
     The reference numeral 11 designates a hollow body that is provided with means for fixing in the hole 3a of the second surface 3; said means are constituted by a threaded ring 12 that is screwed on a threaded portion 13 of the body 11 and is adapted to secure the edge of the hole against a peripheral annular raised portion 14 of the body 11. 
     As an alternative, the means for fixing the hollow body can be constituted by a large ring 12a of the type known as an O-Ring, which is inserted in a corresponding annular groove 13a of the hollow body that is formed at the threaded portion 13: it will be noted that the groove 13a is formed advantageously in a position that is slightly shifted toward the raised portion 14, so that the ring 12a is forced slightly during insertion so as to deform slightly and maintain a condition of pressure against the edge of the hole 3a of the surface 3. 
     The hollow body 11 supports, so that they can move axially and rotate, a manual actuation knob 15 on one side and a disengagement cylinder 16 on the other side; said knob and said cylinder are coupled by a diametrical stem 17 that passes through two oppositely arranged holes 18 of the knob and two holes 19 of two elongated lugs 20a and 20b of the cylinder that protrude parallel to the axis of said cylinder and pass through oppositely arranged curved slots 21a and 21b of an intermediate wall 11a of the hollow body 11. 
     The hollow body 11 is centrally provided with a bushing 22 that is rigidly coupled thereto; two oppositely arranged and inclined slots 23a and 23b are formed in said bushing and converge toward each other and toward the free end of said bushing; two transverse shafts 24a and 24b are slidingly mounted in said slots. 
     A washer 25 rests against the shafts 24a and 24b, is centered outside the bushing 22, and is pushed by a compression spring 26 that is arranged between the bottom of the bushing and the washer, so as to push the shafts 24a and 24b into a configuration for tangential engagement in the annular grooves 10a and 10b of the pin 4 to couple it to the bushing. 
     A cam profile 27 is formed on the inlet of the main body, and the stem 17 engages thereto; said stem is adapted to cause, by virtue of the rotation of the knob and the sliding against the cam profile, the axial sliding of the end of the cylinder, in order to move the shafts 24a and 24b into positions that are spaced from the annular grooves of the pin 4 and cause release thereof. 
     The profile of the cam 27 is repeated in two diametrical positions a and b of the main body and has symmetrical crests that are substantially shaped like a wide V to cause disengagement when the knob 15 is turned to the right and to the left. 
     A cap 28 is fitted on the bottom of the hollow body against the biasing action of elastic means that are constituted by a helical compression spring 29: the cap 28 is adapted to push in the direction for expulsion, arrow B, the end of the pin 4 that is inserted in the body. 
     The disengagement of the shafts 24a and 24b from the annular grooves 10 occurs in relation to relative motions of the cylinder 16 with respect to the hollow body 11 in the direction of the arrows C: these relative movements can be provided by rotating the knob 15 to the right or to the left, arrows E and F (by virtue of the V-shaped profiles of the cams 27), and by pulling the knob, again in the direction of the arrows C, with respect to the hollow body, and by acting on the end of the cylinder 16 (in the direction of the arrows C): in practice it is also possible to act for disengagement with elements that are associated with the surface 2; this possibility is particularly advantageous when one wishes to open the door both by means of the knob associated with the surface 3 and by means of an electromagnetic or lever-operated control associated with the surface 2. 
     It is noted that for large-size doors it is possible to install two or more knobs and to act on them for release with a single mechanical control. 
     The double groove 10a and 10b provides the double closure snap-engagement action (10a provides the ajar snap-engagement action, 10b provides it for actual closure); it is noted that once the shafts 24a and 24b have engaged in the grooves 10a or 10b, a force that tends to move the pin away from the body 11 tends to make the shafts enter the grooves and thus tends to increase the force of the coupling between the parts. 
     The closure device according to the invention can be installed in any angular position with respect to the surfaces 2 and 3 and has a considerable angular tolerance; in practice, it is sufficient for the rounded end 9 of the pin 4 to be centered in the inlet of the cylinder 16 to ensure correct subsequent engagement of the pin in the first groove 10a and in the second groove 10b; the coupling is also facilitated by the deformation of the cup 8. 
     It is thus evident that the invention achieves the intended aim and object. 
     The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept. 
     Furthermore, all the details may be replaced with other technically equivalent ones. 
     In practice, the materials employed, as well as the shapes and dimensions, may be any according to the requirements without thereby abandoning the scope of the protection of the appended claims.