Abstract:
A torsional vibration damper having guides for tangentially mounted helical springs which extend into the springs far enough to prevent the spring from bending excessively in the radial direction when the device is exposed to centrifugal forces. The guides allow the springs to be mounted in recesses which are open in the outer radial direction.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a torsional vibration damper with at least one tangential spring on a disk, and more particularly concerns such devices wherein the spring is mounted in a window or recess open on the radially outward side, and wherein the device is provided with a guide member which extends internally within the spring to limit or prevent excessive bending in the radial direction when the spring is subjected to high centrifugal force. 
     Conventional torsional vibration dampers usually have several tangential springs at regular intervals that are held in windows of the primary part. These windows have radial sides between which the spring is clamped, and they have tangential sides of which the radially outmost side prevents the spring from bulging too much at high speeds. The spring is tightly held in the window so that it is kept from bending undesirably or slipping out from its mount even when centrifugal force is high. 
     The invention is based on the problem of developing the generic torsional vibration damper so that the spring is held in a different manner. This problem is solved in that the torsional vibration damper has a guide which extends far enough into the spring to prevent the spring from bending in a radial direction. 
     The guide according to the invention allows the spring to be located on the perimeter of a primary part or a secondary part of a torsional vibration damper to increase the torque that acts on the spring. The window does not have to be limited to the outside in a radial direction. With the spring mounted according to the invention, the radially interior parts of the spring press on the inside of the guide at high speeds to prevent excess radial bulging of the spring. 
     The advantage is that either the torsional vibration damper can have a smaller diameter, or its capability is increased by a spring with the same dimensions that may be positioned farther out radially. 
     It is particularly advantageous when the disk is a part of the secondary part. When the springs are on the secondary part, the spring guide according to the invention is particularly useful since, for design reasons, a window limit lying radially to the outside is not necessary. The spring can be affixed in a U-shaped recess to the disk of the secondary part, and the outside of the spring extends up to the radially outermost area of the disk. 
     In order to attach the guide to two opposing points on the disk, it is suggested that the guide extend across the entire length of the spring. Contact surfaces on the faces of the spring are suitable to hold the spring in a set position and allow several springs to be arranged coaxially. 
     The guide can be easily affixed by giving it an interlocking fit with the disk. However, depending on the use, it can be affixed by welding or plastic deformation such as upsetting. It is particularly advantageous when the guide can be clipped to the disk. It is suggested that the guide or a part of the guide be deformable. When the guide is deformable, it is easier to insert the disk and allows a snap-in fit. 
     Since the guide is to resist radially-acting centrifugal force resulting from its own mass and the mass of the spring, it is particularly advantageous when the guide can be deformed perpendicular to the plane of the disk during installation. Such a selective deformability makes it easier to install the guide, and the strength of the guide is not impaired by radially-acting force. 
     In one preferred exemplary embodiment, the guide has recesses in a projection that moves in a plane of the disk on opposing faces to interact with the disk. The guide can be made of a homogenous material, and different thicknesses of the parts of the guides can make it selectively deformable. 
     A preferred material for the guide is plastic since it allows economic manufacture and different elasticity and strengths. 
     Although the guide has been described as being deformable, especially to produce a snap-in fit, it is also possible to make the disk out of plastic or at least make it flexible so that a snap-in fit can be attained by deforming the disk. 
     SUMMARY OF THE INVENTION 
     The invention is an improved torsional vibration damper device comprising a disk member in which are tangentially mounted at least one and preferably plural helical springs. The springs are mounted in generally U-shaped recesses or windows having opposing sides to retain ends of the spring. The windows or recesses are open to the radially outward side, such that no limiting wall or cap is necessary for retention of the spring in the recess. Excessive bending of the spring during exposure to high centrifuigal forces is prevented or limited by providing a guide member which extends from each opposing face into the interior of the spring. The interior surface of the guide abuts the spring to prevent excessive radial bending. The guide preferably extends completely through the entire length of the spring between the opposing sides, and may have a concave interior surface. The guide may be formed of a deformable material, such as metal or plastic, such that a pressure or snap fit may be achieved between the guide and the opposing sides of the spring recess, which preferably has recesses of various configuration to receive the ends of the guide. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view showing half of a disk with an embodiment having two guides that extend into the in different lengths. 
     FIG. 2 is a similar view of a different embodiment, where two guides extend through the entire length of the spring. 
     FIG. 3 is a similar view of still another embodiment, showing an alternate means to affix the spring guide. 
     FIG. 4 a similar view of still another embodiment, showing another alternate means to affix the spring guide. 
     FIG. 5 a similar view of still another embodiment, showing clip attachment for a spring guide. 
     FIG. 6 a partial cross-sectional view of the snapped-in guide, taken along line A—A of FIG.  5 . 
     FIG. 7 is a partial cross-sectional view similar to FIG. 6, showing the guide during insertion into the disk. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawings, the invention will now be described in detail with regard for the best mode and the preferred embodiment. 
     FIGS. 1-5 show the secondary part  1 ,  2 ,  3 ,  4 ,  5 , of a torsional vibration damper. Only one half of the secondary part is shown. The other half of the secondary part mirrors the first. 
     The secondary part  1  in FIG. 1 has a first, essentially U-shaped window or recess  6  with a flat base surface  7  and two side surfaces  8  and  9  in which are located projecting elements  10 ,  11 . These projecting elements  10 ,  11  hold contact surfaces  12 ,  13  that have circular elevation members  14 ,  15  that project to the inside of the U. A small helical spring  16  can be placed on the elevation member. 
     Concentric to the small spring  16  is a large helical spring  17  that abuts the contact surfaces  12 ,  13  and is tangential in the U-shaped window  6  of the disk  1 . like the small spring  16 . 
     In this exemplary embodiment, the circular elevation members  14 ,  15  extend slightly into the small spring  16  and only prevent the spring from bending radially against small radial force. When the radial force is greater, it is necessary for the circular elevation members  14 ,  15  to extend further into the spring to counteract the radial force acting on the springs. 
     Other contact surfaces  19 ,  20  are shown in the other U-shaped recess  18  in FIG. 1 where at least one of the circular elevation members  21 ,  22  extends further into the spring to prevent the spring from bulging radially primarily in the middle as a result of centrifugal force. There is a gap  23  between the elevation members  21 , and  22  to make it easier to insert the spring. This makes it possible to design the elevation members  21  and  22  as one piece with the disk  1 . 
     In FIG. 2 on the left there is a guide  25  that extends the entire length of the spring  24 , while on the right side, there is a corresponding guide  26  for coaxial springs  27 ,  28 . The coaxial springs  27  and  28  extend between two contact surfaces  29 ,  30 , and the individual spring  24  on the left side lies directly on the disk  2  of the secondary part. 
     Both guides  25 ,  26  have a concave surface  31 ,  32  on their radially interior side to allow the springs to bend on a circular arc. In practice, the springs are usually inserted slightly bulging to the outside and hence lie on the concave surface  31 ,  32  of the guide  25 ,  26 . 
     FIG. 3 shows guides  33 ,  34  with faces  35 ,  36 ,  37 ,  38  at a sharp angle to each other that are inserted in the disk  3  so that force radiating outward is captured by the contact surfaces between the guide  33 ,  34  and the disk  3 . 
     FIG. 4 shows another way to attach the guides  39 ,  40  to the disk  4 . Attached to the faces  41 ,  42  of the guide  39  via bars  43 ,  44  are cylinders  45 ,  46  perpendicular to the disk  4  that are attached in corresponding recesses  47 ,  48  on the disk  4 . 
     FIG. 5 shows a particularly useful embodiment in which guides  49 ,  50  are attached to the disk  5  of the secondary part with snap-in locks. The shape of the guides can be seen from comparing FIGS. 5 and 6. There are recesses  53 , in opposing faces  51 ,  52  of the guide  54  to allow interaction with the disk  5 . Lateral cuts  55 ,  56  that extend behind the recesses  53 ,  54  produce projections  57 ,  58  between the recess and cut that move in the plane of the disk  5 . 
     The projections  57 ,  58  are shown moving in the plane of the disk  5  in FIG.  7 . This movement makes it easy to insert the guide  50  with the spring  59  into the U-shaped recesses  60  and  61  at opposing sides  62 ,  63  of the U-shaped recess  64  in the disk  5 . 
     The guides  49 ,  50  are preferably made of plastic so that the projections  57 ,  58  can bend. Beveled surfaces  65 ,  66  on the projections  57 ,  58  make it easier to insert the guide  50  in the recesses  60 ,  61  of the disk  5 . 
     It is contemplated that certain equivalents or substitutions for elements set forth above may be obvious to those skilled in the art, and therefore the true scope and definition of the invention is to be as set forth in the following claims.