Abstract:
A retainer for an adjustment device for an over-center fastener for securing and clamping two parts ( 11, 12 ) together by applying a pulling force between the parts by a lever ( 14 ). The adjustment device includes an externally threaded member ( 17   a ) and an internally threaded member ( 19 ) rotatable relative to one another. The internally threaded member has a friction increasing insert ( 24 ) preventing unintentional relative rotation between the externally threaded member and the internally threaded member.

Description:
BACKGROUND OF THE INVENTION  
   1. Field of the Invention 
   The present invention concerns a retainer for an adjustment device of an over-center fastener. 
   2. Description of the Related Art 
   Over-center fasteners (also denominated toggle fasteners or latches) are commonly used for securing—and often clamping—two objects together, such as keeping a lid in a closed position on a box or case. A first part of the fastener, referred to as a striker and often having a hook-like shape, is attached to one of the objects. A base member of the other part of the fastener is attached to the other object. 
   There are two different types of over-center fasteners. 
   In a first type (see e.g.: http://www.ojop.com/700.htm), a first end of a lever is jointed to the base member so as to be swingable about a first axis. The other end of the lever serves as a handle member. At a distance from the first end, an engagement means is linked to the lever so as to be swingable about a second axis parallel to the first axis. In use, the engagement means is brought into engagement with the first part of the fastener and the handle with the second axis is swung about the first axis to move the engagement means closer to the base member. In order to vary the distance between the second axis and the engagement means, and thereby the engagement force, the engagement means has a threaded stem member engaged in the threads of an internally threaded body member rotatably connected to the lever about the second axis. The body member is normally a cylindrical body rotatable about its axis. 
   In a second type of over-center fastener (see e.g.: http://www.ojop.com/900.htm), a first end of a link is jointed to the base member so as to be rotatable about a first axis. A second end of the link is jointed to a first end of a handle member. A second end of the handle member is provided with engagement means for engagement with the first part of the fastener. In use, the engagement means is brought into engagement with the first part of the fastener, and the handle member is operated, involving rotation of the second axis about the first one, thereby moving the engagement means closer to the first part. In order to vary the distance between the first and the second axes, the length of the link is variable in that it comprises a threaded stem member engaged in an internally threaded body member connected to the handle and containing the second axis. In this case, the body member is usually formed from folded sheet metal. 
   In both types of fasteners, there is a desire to prevent undesired relative rotation of the two threaded members. Such rotation often occurs due to vibrations or other exterior influence in the unlocked and unloaded state of an over-center fastener, and may result in that a particular setting of the fastener for a particular clamping case may be lost. This, in turn, may result in that clamping becomes too loose or to tight, or, in case such condition is discovered at all, in a time consuming renewed setting. 
   SUMMARY OF THE INVENTION  
   Thus, the problem to be solved by the present invention, and that must have existed for at least a century, is to provide a means for retaining undesired relative rotation of the externally threaded stem and the internally threaded body of an over-center fastener. 
   According to the present invention this problem is solved by applying what is previously known from various lock nuts, viz., the use of a frictional insert, to an over-center fastener. 
   In practice, this may be accomplished by simply using a conventional lock nut as the internally threaded body, or, by providing the internally threaded body with a friction increasing insert. 
   In the lock nut case, in the first type of fastener, it is sufficient to cut a rectangular aperture through the body member extending at right angle to its rotational axis and at the same time at right angle to its through hole, which is no longer threaded but a smooth hole having an internal diameter slightly larger than the external diameter of the thread of the threaded stem member. The dimensions of the aperture are such that a nut is un-rotationally accommodated within it. 
   In the lock nut case, in the second type of fastener, there is provided a holder for a nut connected to the handle member to be rotatable about the second axis. The holder is formed from sheet metal to receive the nut in an unrotational manner. 
   In the friction increasing insert case, it is proposed still to use the prior art internally threaded body member, but to complete it with a friction increasing insert similarly to what is known from conventional lock nuts. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     Embodiments of the present invention will now be described, reference being made to the accompanying drawings, wherein: 
       FIG. 1  is a side view of a state of art fastener of the first type; 
       FIG. 2  is a plan view of the fastener of  FIG. 1  shown without its associated striker; 
       FIG. 3  is a plan view corresponding to  FIG. 2  of a fastener provided with a lock nut according to the present invention; 
       FIG. 4  is a part cross sectional side view of a fastener of the second type provided with a lock nut according to the present invention and shown in a partially open position; 
       FIG. 5  is a cross sectional side view of the fastener of  FIG. 4  in a locked position; 
       FIG. 6  is a plan sectional view taken along line VI—VI in  FIG. 5 ; 
       FIG. 7  is a plan view of a fastener similar to that according to  FIGS. 1 and 2  provided with a cylindrical, internally threaded body having a friction increasing insert according to the present invention; 
       FIG. 8  is a view corresponding to  FIG. 7  but showing the cylindrical body and portions of the lever sectioned; 
       FIG. 9  is a section through the cylindrical body of  FIG. 8  at an enlarged scale; 
       FIG. 10  is a view towards the side of the cylindrical body according to  FIGS. 7–9  carrying the insert; 
       FIG. 11  is a section taken along line XI—XI in  FIG. 10 ; 
       FIG. 12  is a view corresponding to that of  FIG. 10  of an embodiment of internally threaded body having a square cross section; 
       FIG. 13  is a section taken along line XIII—XIII in  FIG. 12 ; 
       FIG. 14  is a section taken along line XIV—XIV in  FIG. 12 ; 
       FIG. 15  is a view corresponding to that of  FIGS. 10 and 12  of an embodiment of internally threaded body having a hexagonal cross section; 
       FIG. 16  is a section taken along line XVI—XVI in  FIG. 15 ; and 
       FIG. 17  is a section taken along line XVII—XVII in  FIG. 15 . 
   

   DETAILED DESCRIPTION OF THE INVENTION  
   The state of art fastener shown in  FIGS. 1 and 2  is shown to connect and clamp together two separate pieces  11  and  12 . It includes a first part  13 —a striker—fixed to the first piece  11 , and a second part  14  fixed to the second piece  12 . The striker has a hook-like free end  13   a . The second part comprises a base plate  15  fixed to the second piece  12 , a lever  16  and an engagement member  17 . The lever  16  is swingable about rivets  18   a ,  18   b  engaged in spaced brackets  15   a ,  15   b  protruding from the base plate  15 . A first end  17   a  of the engagement member  17  is threaded and engages internal threads of a cylindrical body  19  which is linked to the lever  16  at a distance from the rivets  18   a ,  18   b . More precisely, the cylindrical body  19  is carried between spaced legs  16   a ,  16   b  of the lever  16  so as to be rotational about stub shafts  21  engaged in the spaced legs. A free end of the engagement member  17  is formed with an eye  17   b  engaging the hook-like end  13   a  of the striker  13  in the locked position shown in  FIG. 1 . In the unclamped state of the engagement member, its threaded end is likely to disengage from the threads of the body  19  due to, for instance, vibrations. To overcome this risk, the present invention proposes to use a conventional lock nut, for instance of the kind having a friction increasing inlay at one end of its internal threads. 
     FIG. 3  shows how this may be realized in a fastener of the kind shown in  FIGS. 1 and 2 . A rectangular aperture  22  is machined through the cylindrical body  19 ′ and a lock nut  23 , having a width between two of its opposed sides  23   a ,  23   b  slightly greater than the free width of the aperture  22 , is introduced into the aperture. Thereafter, the threaded end  17   a  of the engagement member is threaded through the nut and a friction increasing inlay  24  provided at one of its ends. The internal threads of the cylindrical block may be maintained, although it is preferred not to have such threads in this case, since they may interfere with the threads of the nut when mounting the threaded end of the engagement member. 
   The inventive idea applied to the second type of fastener is shown in  FIGS. 4–6 , wherein the same reference numerals are used as in  FIGS. 1–3  for corresponding parts. 
   As in the previous embodiment, a first piece  11  is to be clamped to a second piece  12  ( FIGS. 4 and 5 ) by means of a fastener. The fastener is shown in  FIG. 4  to be in a partly open state and in  FIG. 5  to be closed, having clamped the two pieces together. A striker  13 ′ is attached to the first piece  11  and a base plate  15  is attached to the second piece  12 . Again, the base plate has spaced brackets  15   a ,  15   b . A cylindrical body  25  is rotatably carried between the brackets by means of stub shafts  26   a ,  26   b  engaged in a respective bracket. A stem  27  having threads  27   a  at one end has a reduced diameter opposed end  27   b  extending through a diametrically extending hole  28  through the cylindrical body  25 . The stem end  27   b  is jolted at  29  so as to firmly keep the stem in relation to the hole  28  and the cylindrical body. 
   A handle member  30  of inverted U-shaped cross section has spaced flange portions  30   a ,  30   b  and a hooked forward end  30   c  for engagement with the striker  13 ′. 
   A bent sheet metal structure  31  has a generally inverted U-shaped portion including opposed flange portions  31   a ,  31   b  and a web portion  31   c . The flange portions are linked to a respective flange portion  30   a ,  30   b  of the handle member  30  by means of rivets  32   a ,  32   b , respectively. The web portion  31   c  carries an integral extension  33 . A first portion  33   a  of the extension is bent at substantially 90° so as to extend along and abut a respective forwardly directed edge  34  of the flange portions  30   a ,  30   b . A second portion  33   b  of the extension is bent at 90° in relation to the first portion, and a third portion  33   c  thereof is further bent at 90° in relation to the second one. Flap portions  33   f  originally extending in opposite directions from the third portion are bent towards the first portion  33   a  so as to be mutually parallel, thus forming a nut retaining pocket  35 . The distance between the flap portions  33   f  is slightly greater than the width between opposed surfaces  23   a ,  23   b  of a lock nut  23  received within the pocket  35  so as to unrotationally keep the nut therein. Holes  36 ,  37  for the threaded portion  27   a  of the stem  27  are provided in the third and first portions  33   c ,  33   a  of the extension  33 . 
   It will be realized that in operation of the fastener, the extension  33 , and particularly its third portion  33   c  with its flap portions  33   f , will be exposed to only minor stresses keeping the nut unrotational, whereas the clamping forces will be transferred from the stem  27  through the nut and into the first portion  33   a  of the extension, which abuts the edges  34 , thus directing the clamping forces into the opposed flanges of the structure  31 . 
   In the embodiment of the present invention shown in  FIGS. 7 and 8 , the conventional, internally threaded body  19  is completed with a friction increasing insert resembling that of a conventional lock nut. 
   The enlarged section of  FIG. 9  more clearly shows a diametrically extending hole  35  through the body  19  provided with its internal threads  35 ′. The hole has a widened diameter end portion  35 ″ at one end, and a friction increasing insert  36  is received within that end portion so as to rest against a step  37 . The edge of the widened end portion is upset at diametrically opposed locations A, B ( FIG. 10 ) so as to positively keep the insert  36  in place. Like in a conventional lock nut, the internal diameter of the insert is smaller than the external diameter of the threaded end  17   a  of the engagement member  17 . A preferred material of the insert is Nylon®. 
   As one alternative to the cylindrical shape of the internally threaded body  19  it may be advantageous to provide an internally threaded body  38  having a substantially square cross section as shown in  FIGS. 12–14 , or to provide an internally threaded body  39  having a hexagonal cross sections as shown in  FIGS. 15–17 . Such cross sections provide the opportunity to make both ends of the hole  35  in flat opposed surfaces of the respective body. Also, a flat surface enables upsetting the edge of the widened portion of the hole  35  at more than the two diametrically opposed locations A and B shown in  FIG. 12 , viz. also at diametrically opposed locations C and D.