Apparatus for inserting and withdrawing subassemblies
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for inserting and withdrawing subassemblies in subassembly holders. A lever which is rotatably mounted on the subassembly and whose arms differ from each other, a locking element arranged on the longer lever arm, that is to say on the arm lying closer to the lever handle, and a shifter element arranged on the shorter lever arm engage with a profile strip which is fixed to the subassembly holder to make up the subassembly. 
     2. Description of the Prior Art 
     Insertion and retraction apparatuses facilitate the insertion and withdrawal of printed circuit boards or of subassemblies for electric and electronic components or inserts. At the same time these apparatuses enable the subassemblies to be locked or immobilized in the inserted or plugged-in condition. 
     Insertion and retraction apparatuses of this kind are commercially available as card extractors. In the case of these known apparatuses, the lever, which is used for extracting and inserting cards with printed circuits, or printed circuit boards, engages, by means of a trapezoidal shifter element provided on the shorter, lower lever arm, in an n-shaped recess of a profiled strip, which is connected to the guide strip of the plate. The torque exerted when the lever is actuated is transmitted to the front or rear wall of the n-shaped recess, resulting in the mutually contacting surfaces or sections, along which the force transmission takes place, sliding on one another. The locking apparatus is disposed below the forwardly-bent handle. For high printed circuit boards, i.e. so-called &#34;double Europe cards&#34;, profiled strips with card extractors of this kind are arranged on the upper and lower frame of the subassembly holder. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is the provision of a lockable insertion and retraction apparatus, which prevents each subassembly which is provided with this apparatus, from accidentally slipping out, and enables the subassembly to be inserted relatively deep into, and withdrawn from, a subassembly holder, this insertion and withdrawal taking place simply and without the use of a tool. 
     The effect of the invention is that the sliding friction, occurring during actuation of the lever, is replaced by a rolling friction between the shifter element in the shorter lever arm and the walls of the profile plate into which this shifter element engages. By shaping these interacting components as toothed wheel segments and a toothed rack section, a longer path of sliding motion becomes possible than is the case with the known card extractor. Manufacture of the interacting components having this profile shape is uncomplicated. Accommodating the locking element in the lever handle makes it possible to give the lever a simple shape, and the locking member may be concealed when the lever is in the locked position, except the actuator which projects under the lever handle. The locking member is guided in a recess of the front plate and is vertically shiftable. 
     By means of the insertion and retraction apparatus according to the invention, not only can individual components, such as printed circuit boards of example, be retracted, inserted and locked in this inserted position, but also larger composite subassemblies when two such levers interconnected by way of an arcuate portion or handle bridge so as to form a double lever are used. This double lever is mounted on the outer side plates of the subassembly. In this case the locking element is preferably arranged on the handle bridge and thus is susceptible to actuation with one hand. 
     A further advantage resides in the fact that, in the case of subassemblies of relatively large height, only one insertion and retraction apparatus is required instead of two such apparatuses, as has hitherto been the case. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several views, and wherein: 
     FIG. 1 is a partial perspective view of the front part of a first embodiment of the subassembly holder, with a subassembly and with an apparatus for inserting and withdrawing this subassembly; 
     FIG. 2 is a side elevational view of a subassembly which is constructed as shown in FIG. 1 and is partially withdrawn; 
     FIG. 3 is a partial, perspective exploded view of the front portion of a subassembly and of the locking member with associated helical spring, and 
     FIG. 4 illustrates a second embodiment of the invention constituted as a double lever with a connecting bridge for compact subassemblies. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Similar components are designated by the same reference symbols in the Figures. 
     The subassembly holder or carrier shown in FIG. 1 comprises a supporting frame 1 with side plates 2 attached to it, and also a cover plate 3, upper and lower locking or inscription-plates 4 and 5, and a front profile plate 6. A subassembly or printed circuit board (panel) 9 is slidably guided in a guide strip 8. A lever 10 is used for withdrawing the printed circuit board 9 and also for inserting this board 9 and locking it in its inserted position; this lever 10 is connected to the printed circuit board 9 by means of a rotary pin 13. Shifter or toothed wheel-segments 11 are provided on the shorter arm of lever 10 and can engage in a substantially horizontally-positioned toothed rack section or profile plate 12. An actuator 18 for securing or locking the position of the lever 10 projects below the lever handle 14 on a faceplate 7 connected to the printed circuit board 9. The locking or inscription-plates 4 and 5, which are illustrated in the disengaged horizontal position, cover the upper and lower parts of the lever 10, and also the profile plate 12, in the locked vertical position, which otherwise would be deleteriously effected. 
     When in its immobilized or locked position, and when the subassembly has been inserted, the lever 10 is in an approximately vertical position. The rotary pin 13 of this lever 10 lies substantially vertically above the toothed wheel segment 11. A screw can be used as the rotary bearing. The (toothed) rack section 12 is secured to the profile plate 6, the guide strip 8, and to the supporting frame 1. 
     In FIG. 2 a locking element or lug 15 is shown, in dotted line, in the lever handle 14. 
     In the partially withdrawn position the lower end of the subassembly or printed circuit board 9 is already out of engagement with respect to a resilient plate 25, which is secured to the rear part of the supporting frame. 
     Details of a locking member 16, which is made of a resilient material, can be best seen in FIG. 3. The locking member 16 has a locking projection 17 which does not extend to the central part, a locking actuator 18 which is connected to this central part or bridge 21, and, in its upper rear part, a guide element 19. On its face the locking projection 17 has an oblique surface against which the locking lug or nose 15 assumes a position of abutment when the lever 10 is pressed in. The locking lug 15 has an interruption in its central area. The width of this interrupted area or opening corresponds to the width of the bridge 21 on the locking member 16. This width is slightly greater than the width of the bridge 21. The guide element 19 has, in the central part of the locking member 16, a vertical non-continuous U-shaped opening, into which a helical spring 22, which is subject to only slight biasing force, is inserted, and, in its vertical position, is prevented from accidentially falling out by a projection 23 in the upper center part of a recess 24 in the front 7 of the subassembly. Two continuous, symmetrical, substantially n-shaped openings 20 are provided along the outside of the arms or shanks of the U-shaped recess; the locking member 16 is guided by these openings 20 at the lateral confines of the opening 24 in the front plate 7. For introducing the locking member 16 into the recess 24 of the front plate 7, the guide element 19 is slightly compressed and is then pushed in from the front. The height of the recess 24 is greater than the height of the guide element 19. The width of this recess 24 substantially equals the outer dimension of the n-shaped openings 20 of the guide element 19. 
     In the locked, vertical position of the lever 10, the actuator 18 projects below the lever handle 14 on the front face of the front plate 7. This actuator 18 preferably has a vertically upwardly-directed arrow-like shape, which is intended to indicate the actuating direction when the subassembly is being secured (i.e. locked) in position. 
     The inserting and retracting apparatus of the kind illustrated in FIGS. 1 to 3, functions in the following way. In the vertical position of the lever 10, shown in FIG. 1, the subassembly or printed circuit board 9 is inserted, and is locked in this inserted position by way of the locking element 15 in the lever handle 14 and by way of the locking projection 17 in the locking member 16. For withdrawing the subassembly or printed circuit board 9, the actuator 18 is pressed upward towards the lever handle 14, and the lever 10 on the handle 14 turned in the clockwise direction. Through pressing the actuator 18 upward, the locking member 16 is shifted upwardly in opposition to the biasing force of the helical spring 22 until the position of mutual engagement between the locking projection 17 and the locking lug 15 is discontinued. While lever 10 is being turned in the clockwise direction, the toothed segment 11 rolls along the (toothed) rack section 12; by way of the rotary bearing 13, lever 10 pulls the subassembly or printed circuit board 9 forward. After it has been withdrawn the subassembly or printed circuit board 9 can be carried by the lever 10. For reinserting the subassembly, the printed circuit board 9 has to be introduced into a groove in the guide strip 8, and the toothed segment 11 into the (toothed) rack section 12. Lever 10 then has to be turned in the counterclockwise direction until the position or locking engagement is restored. 
     Naturally, the invention is not restricted to the subject matter illustrated in FIGS. 1 to 3. Thus, and as illustrated in FIG. 4, the lever may be replaced by a double lever in which two levers 10 are rigidly interconnected by a handle bridge 30 arranged close to the lever handle. The locking member 16 is preferably positioned behind (in respect to the locked position of the double lever) the center of the bridge 30 of the lever handle. Accordingly, the interruption 31, corresponding to the width of the bridge 21 on the locking member 16, in the locking lug 15 is arranged in the middle of the bridge 30 of the lever handle. This insertion and retraction apparatus is particularly suitable for compact subassemblies which are composed of a number of printed circuit boards, and in the case of which appreciable force is required for inserting and withdrawing the subassemblies. 
     The insertion and retraction apparatus according to the invention is particularly suitable for electronic subassemblies but also for other equipment in which a number of subassemblies are combined. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.