Abstract:
An anti-skid device for a vehicle for positioning a traction member beneath a vehicle wheel includes a support member that is attached to the vehicle, a pivoting swing arm with a traction wheel with traction members thereon, and a drive assembly attached to the support member and to the swing arm so as to extend and retract the swing arm. The drive assembly includes a gear-reduced electric motor that is coupled to a worm that meshes with a worm gear that is attached to the swing arm shaft. As the motor moves in a first direction, the gear mesh causes the arm to deploy and, in a reverse direction, the swing arm retracts. Spring-biasing is provided so as to maintain pressure of the traction wheel against the vehicle wheel and limit switches are provided so as to turn the drive motor on and off.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates in general to anti-skid devices for vehicles. More specifically, the present invention relates to a device that provides a rotatable member with links of chain, or other traction or friction increasing means, intended to be thrown sequentially under a wheel of a vehicle for increased traction between the wheel and the road surface. One device of the type generally described above is disclosed in U.S. Pat. No. 4,800,939 issued to Törnebäck. Another device of the type generally described above is disclosed in U.S. Pat. No. 7,118,130, issued Oct. 10, 2006 to Rosenbalm. Both of these U.S. patents are incorporated by reference herein in their entirety. 
   The Törnebäck device utilizes an inflatable bellows to extend the movable arm that includes the pulley. It is important to note that a supply source of air for the bellows is required in order for the Törnebäck device to be operable. A suitable supply of air is likely available with larger vehicles such as semi-tractor trailers. Smaller passenger vehicles such as SUVs and trucks are not likely to have a suitable air supply. Another consideration with smaller passenger vehicles of the type described is the available space within and/or beneath the frame for securing an anti-skid device in position. 
   As described in the &#39;939 patent, devices of this kind typically include a pulley provided with strands or links of chain or some other friction increasing means for sequentially positioning the chain beneath the vehicle wheel between the wheel and the road surface. Devices of this kind are not as simple to construct as would appear from the principle itself. Chains, pulleys, and other supports are, to start with, subject to very substantial forces necessitating heavy duty construction. Furthermore, a relatively large movement is required to displace the chain carrying pulley between its working position in contact with the vehicle wheel and its operative stored or stowed position. To store the pulley is particularly troublesome since different cars and passenger vehicles have different available places for the pulley. Furthermore, the pulley should be sufficiently elevated so that the chains attached to the pulley or chain wheel do not drag on the ground as this causes the links of chain to be worn prematurely. A result of the above requirements and problems that need to be solved with automatic anti-skid devices of the type described is that they are comparatively costly to produce which in turn results in a number of individuals being reluctant to obtain these safety increasing aids. 
   The Rosenbalm device includes an anti-skid device for use in cooperation with a vehicle wheel for positioning a traction member beneath the vehicle wheel includes a frame assembly constructed and arranged to be attached to the vehicle, a swing arm pivotally connected to the frame, and an electric, linear actuator having an extendable shaft. The anti-skid device includes a double pivot link where one end is attached to the frame assembly and the opposite end is attached to the swing arm. The linear actuator is attached to a movable pressure plate and a biasing spring is positioned between the movable pressure plate and a back plate for applying and maintaining contact pressure of the traction wheel against the vehicle wheel. In the preferred embodiment, the traction member is a length of chain that is connected to the traction wheel for positioning between the vehicle wheel and the road surface. 
   While the Törnebäck and Rosenbalm devices represent a couple of design options for these type of tire chain devices, a further option is to use an electric drive motor (but not involving any linear actuator as in Rosenbalm) as part of the deployment structure. The use of a reversible, electric drive motor, properly sized and gear reduced, yields a more compact design without requiring any vehicle or accessory air supply and without requiring any type of linear actuator or solenoid or similar cylinder. The desirable spring-biased aspect of the &#39;130 Rosenbalm patent would preferably still need to be provided, but in a different structural configuration. The presently disclosed structure, as described and illustrated herein, achieves a compact design configuration by the use of an electric drive motor. In addition, a worm and worm gear combination is used for low speed and power amplification in combination with a biasing spring arrangement and appropriate gear reduction. These components and systems are provided and integrated in a novel and unobvious manner. 
   BRIEF SUMMARY 
   An anti-skid device for use in cooperation with a vehicle wheel for positioning a traction member beneath the vehicle wheel according to one embodiment of the present invention comprises a support member constructed and arranged to be attached to a vehicle, a swing arm including a traction wheel with at least one traction member thereon, a drive assembly attached to the support member and to the swing arm and being constructed and arranged to extend and retract wherein extending the swing arm places the traction wheel against the vehicle wheel, and a drive assembly including a worm gear, a worm constructed and arranged to mesh with the worm gear, an electric motor, a shaft for coupling the swing arm to the worm gear, and a second shaft for coupling the electric motor to the worm, wherein operation of the electric motor moves the swing arm by way of the worm and worm gear combination. 
   One object of the present disclosure is to provide an improved anti-skid tire chain device. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a perspective view of an anti-skid tire chain device according to a typical embodiment of the present invention. 
       FIG. 2  is a partial, perspective view of a chain wheel assembly comprising one portion of the  FIG. 1  device. 
       FIG. 3  is a side elevational view of a mounting plate comprising one portion of the  FIG. 1  device. 
       FIG. 4  is a top plan view of the  FIG. 3  mounting plate. 
       FIG. 5  is a perspective view of a swing arm comprising one component of the  FIG. 1  device. 
       FIG. 6  is a perspective view, of the  FIG. 5  swing arm, from a different perspective. 
       FIG. 7  is a perspective view of a chain wheel comprising one portion of the  FIG. 1  device. 
       FIG. 8  is a front elevational view of a chain wheel bolt comprising one portion of the  FIG. 1  device. 
       FIG. 9  is a side elevational view, in full section, of a receiver plate comprising one portion of the  FIG. 1  device. 
       FIG. 10  is a top plan view of the  FIG. 9  receiver plate. 
       FIG. 11  is a front elevational view of an arm shaft comprising one portion of the  FIG. 1  device. 
       FIG. 12  is a perspective view of the  FIG. 11  arm shaft. 
       FIG. 13  is a fragmentary, side elevational view, illustrating the assembly of component parts for the pivoting connection of the  FIG. 5  swing arm with a worm gear that comprises one portion of the  FIG. 1  device. 
       FIG. 14  is a front elevational view, in full section, of a shaft coupling comprising one portion of the  FIG. 1  device. 
       FIG. 15A  is a top plan view of a lower housing section comprising one portion of the  FIG. 1  device. 
       FIG. 15B  is a side elevational view of the  FIG. 15A  lower housing. 
       FIG. 16A  is a top plan view of an upper housing comprising one portion of the  FIG. 1  device. 
       FIG. 16B  is a side elevational view of the  FIG. 16A  upper housing. 
       FIG. 17  is a front elevational view of a drive shaft comprising one portion of the  FIG. 1  device. 
       FIG. 18  is a perspective view of a limit switch, two of which are used for the  FIG. 1  device. 
       FIG. 19  is a perspective view of an electric motor assembly comprising one portion of the  FIG. 1  device. 
       FIG. 20A  is a front elevational view of a tapered bushing comprising one portion of the  FIG. 1  device. 
       FIG. 20B  is a top plan view of the  FIG. 20A  tapered bushing. 
       FIG. 21A  is a front elevational view of an upper bushing comprising one portion of the  FIG. 1  device. 
       FIG. 21B  is a top plan view of the  FIG. 21A  upper bushing. 
       FIG. 22A  is a front elevational view of a lower bushing comprising one portion of the  FIG. 1  device. 
       FIG. 22B  is a top plan view of the  FIG. 22A  lower bushing. 
       FIG. 23A  is a front elevational view of a switch sleeve bushing comprising one portion of the  FIG. 1  device. 
       FIG. 23B  is a top plan view of the  FIG. 23A  switch sleeve bushing. 
       FIG. 24  is a side elevational view, in full section, illustrating the assembly of components parts associated with the drive shaft according to the present invention. 
   

   DETAILED DESCRIPTION 
   For the purposes of promoting an understanding of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated device and its use, and such further applications of the principles of the disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates. 
   Referring to  FIG. 1 , there is illustrated an anti-skid, tire chain device  20  that is constructed and arranged according to the present invention. Device  20  includes a chain wheel  21  with six strands  22  of chain securely attached to the chain wheel  21 , each strand  22  being connected through a corresponding one of six wheel holes  21   a . Also included as part of device  20  is a swing arm  23 , mounting plate  24 , shaft  25 , housing body  26   a , housing cover  26   b , electric motor assembly  27 , drive shaft  28 , worm  29 , worm wheel or gear  30 , springs  31   a  and  31   b , extend limit switch  32 , retract limit switch  33 , switch sleeve bushings  34  and  35 , and sealed ball bearings  36   a  and  36   b . The requisite electric power required to drive the electric motor assembly  27  is provided by vehicle battery power and is activated or controlled by a dashboard-mounted switch (not illustrated). This switch is a toggle switch having an ON position corresponding to a deployed swing arm  23  and an OFF position corresponding to a retracted or stowed position for the swing arm  23 . The electric motor  54  includes a brake  54   a , as further described herein. 
   The mounting plate  24  (see  FIGS. 3 and 4 ) includes two clearance holes  38  for securely connecting the mounting plate  24  to a vehicle axle by the use of a corresponding U-bolt (not illustrated). The swing arm  23  (see  FIGS. 5 and 6 ) is connected to the chain wheel  21  (see  FIG. 7 ) such that the chain wheel  21  is able to turn or rotate freely so as to sequentially fling strands  22  of chain beneath the corresponding vehicle tire (i.e., between the tire and the surface of the road). The inner surface of the vehicle tire is used to contact the outer rubber rim  39  of wheel  21  and thereby drive the chain wheel  21  in a rotary manner. The rotation of the vehicle tire drives the chain wheel  21  in a manner that is similar to a gear set. 
   Referring now to  FIG. 2 , a chain wheel bolt  40  (see  FIG. 8 ) extends through the chain wheel  21  and is secured on one side by a hex nut and is captured on the opposite side by receiver plate  41  (see  FIGS. 9 and 10 ). Plate  41  includes four internally-threaded bolt holes  42  and a center bore  43  that receives the enlarged spherical head  44  of the chain wheel bolt  40 . End  45  of the swing arm  23  includes four clearance holes  46  with a pattern and spacing that corresponds to that of the four bolt holes  42 . The center bore  47  of the swing arm  23  is aligned with the center bore  43 , but center bore  47  is smaller since it is constructed and arranged to provide clearance for only the top portion of the spherical head  44 . This chain wheel-bolt-arm assembly is substantially the same as that illustrated and disclosed in the &#39;130 patent (see FIG. 1 of the &#39;130 patent). 
   End  51  of swing arm  23  is pivotally connected, via tapered hole  51   a , to end  52  of mounting plate  24 , specifically by way of hole  52   a , by the use of shaft  25  (see  FIGS. 11-13 ) and related components such as tapered bushing  48 , see  FIGS. 20A and 20B . Beginning with swing arm  23 , shaft  25  extends upwardly through bushing  48  that is received within hole  51   a . From there, shaft  25  extends through hole  52   a  and through a circular opening  49  in the floor of housing body  26   a . The circular opening  49  is defined by raised boss  74  and this raised boss  74  is positioned within hole  52   a , preferably in a generally concentric relationship, see  FIG. 13 . 
   Tapered bushing  48  is securely attached to end  51  such that, by pinning arm shaft  25  to and within bushing  48 , rotation of shaft  25  results in rotation or pivoting of swing arm  23 . This pinned combination and the secure attachment to end  51  means that the pivoting or rotating action of swing arm  23  occurs in direct response to shaft  25  rotation, without any lag or slippage. As illustrated, the tapered bushing  48  fits into tapered hole  51   a  and is secured around shaft  25  by clamping action. This is facilitated by the two mounting bolts (see  FIG. 13 ). 
   A lower bushing  56  (see  FIGS. 22A and 22B ), is positioned between shaft  25  and opening  49 /boss  74 . The radial flange  56   a  on bushing  56  seats against one end of the worm gear hub  57  (see  FIG. 13 ). The worm gear face  59  seats against the radial lip of shaft  25  identified herein as shaft section  85 . The shaft end, referred to as section  84 , is captured within the blind hole  60  of the upper housing that is defined by inwardly-extending, raised boss  75 . Upper bushing  61  (see  FIGS. 21A and 21B ), is positioned between shaft section  84  and interior boss  75 . This stack up of the components that are cooperatively assembled with shaft  25  is illustrated in  FIG. 13 . 
   End  52  of mounting plate  24  provides a clearance hole  52   a  for arm shaft  25  to extend through for its connection to end  51 . The opposite end  53  of arm shaft  25  is securely pinned to worm gear  30  such that as the worm gear  30  turns, the arm shaft rotates without any lag or slippage. With regard to the manner of “pinning” the arm shaft to end  51  and to worm gear  30 , any conventional approach for pinning a gear to a shaft is acceptable, such as the use of a keyway or key. In the preferred embodiment, a Woodruff key is used. 
   The electric motor assembly  27  includes a reversible, electric drive motor  54 , a brake  54   a , and a gear reduction module  55  that is securely connected to drive shaft  28 . The RPM rating of motor  54  is reduced by gearing to a lower RPM so as to constitute a slow drive for a slow drive speed, something that is compatible with the application of a worm and worm gear combination. This slower RPM becomes the rate of turning or rotation for the drive shaft  28 . The short shaft  55   a  from the gear reduction module  55  is coupled to drive shaft  28  by shaft coupling  58 . Power “on” to the drive motor  54  includes power “on” to the brake  54   a  so as to disengage it. This permits the desired operation and deployment of the swing arm. When the limit switch is tripped, the power is switched “off” and the brake prevents the motor shaft from turning in the reverse direction. 
   Shaft coupling  58  (see  FIG. 14 ) is a hollow, substantially cylindrical component with a pair of spaced-apart, internally-threaded holes  58   a  for receipt of set screws for securing shaft  55   a  and drive shaft  28 . Each shaft includes a “D” flat shape at the shaft end that is inserted into coupling  58 . A snug fit between shafts  55   a  and  28  and the hollow interior of coupling  58  can be used to facilitate a tight and secure connection such that there is no relative motion or slippage. 
   The worm  29  is keyed to the drive shaft  28  such that as the drive shaft  28  turns (i.e., rotates on axis), the worm  29  turns in response without any lag or slippage. However, the worm  29  is keyed to the drive shaft  28  in a manner such that the worm  29  is able to move (i.e., slide) along the axial length of the drive shaft, at least a short distance as will be described hereinafter. 
   The worm gear  30  is meshed with the worm  29  and this particular combination is preferable for low speed applications and where a large amplification of power is desired. As the worm  29  turns, i.e., rotates on axis with shaft  28 , the worm gear  30  is driven and the arm shaft  25  rotates. As this occurs, the worm  29  maintains its “centered” position on the worm gear  30  and its position between the two springs  31   a  and  31   b . Another aspect of a worm and worm gear combination is that the corresponding axes of rotation or drive are at right angles to one another. The turning of arm shaft  25  causes the pivoting of swing arm  23  for both deploying the swing arm as well as for retracting the swing arm. 
   An understanding of worm and worm gear technology and the basic design principles is important to an understanding of what occurs as the motor  54  continues to run. First, as previously noted, the worm  29  includes a keyway and the drive shaft  28  is machined with a matching key that fits into this key way. As the drive shaft  28  turns, the worm  29  turns and the threads of the worm  29  mesh with the gear teeth of the worm gear  30 . The axis of rotation of the gear  30  is perpendicular to the axis of rotation of the worm  29 . The rotation of the gear  30  and its meshing action with the worm  29  creates one force vector tending to turn the worm gear and another force vector tending to move the worm along the axis of the drive shaft  28 . The pair of biasing springs  31   a  and  31   b , one on each side of worm  29 , and each captured by abutment against a corresponding bushing  34  and  35 , respectively, restricts the travel of worm  29 . As the worm remains substantially stationary, the driving forces are focused on rotation of worm gear  30 . As the worm gear  30  rotates about its axis, the swing arm  23  pivots. 
   Device  20  is constructed and arranged and is mounted to the axle of a vehicle such that the pivoting motion of swing arm  23  properly positions the rim  39  of chain wheel  21  against the inside surface of the corresponding vehicle tire. As the tire rotates, it drives the chain wheel  21 , causing the strands  22  of chain to be sequentially thrown between the tire and the road surface. 
   Once the chain wheel  21 , specifically rim  39 , contacts the inner surface of the corresponding tire, more force is required to push the chain wheel  21  against the tire. This force is exerted while the motor assembly  27  continues running and continues to push the chain wheel  21  against the tire. Although the drive motor  54  continues running, at least for a period of time, the swing arm is unable to pivot any farther due to the chain wheel and tire contact. This in turn stops the rotation of the worm gear  30 . With the rotation of worm gear  30  stopped, though with the drive motor continuing to run, the mesh of the worm  29  with worm gear  30  causes the worm  29  to begin to turn and thereby to travel axially along drive shaft  28 . The worm  29  is described as “climbing” the drive shaft  28  in an axial direction. The key portion of the drive shaft  28  and the keyway in the worm  29  allows the worm to move longitudinally along the drive shaft  28 , thereby compressing the extend spring  31   a . As the extend spring  31   a  is compressed, the worm  29  travels in the direction of the extend limit switch  32 . A switch sleeve bushing  34  is mounted between the worm  29  and the extend spring  31   a  and this switch sleeve bushing  34  is used to trip the extend limit switch  32 . The limit switch arm, once tripped by the switch sleeve bushing  34 , shuts off power to the drive motor  54  and the brake  54   a . Once the drive motor  54  is switched off, the worm  29  remains fixed in position and meshed with the worm gear  30 . The brake  54   a  prevents the motor shaft from turning in the reverse direction. The spring  31   a , functioning in a spring-biasing mode, maintains constant pressure of the chain wheel  21  against the tire. With the drive motor  54  shut off and the spring  31   a  compressed, the spring&#39;s function now is to continue pushing the worm  29  against the worm gear  30 , and in turn, maintaining the desired chain wheel  21  contact against the tire. As the rotation has stopped, the worm and worm gear now function as a cog-type gear using the meshed teeth of the worm against the teeth of the worm gear to push the swing arm  23  and keep the chain wheel  21  against the tire. 
   The previously referenced dashboard-mounted switch is a double pull, single throw switch that is wired into device  20  such that when toggled to the retract position, the voltage to the motor assembly  27  is reversed. This causes the motor assembly to turn the drive shaft  28  in the reverse direction. This drives the swing arm  23  back to its retracted position (stowed) and, in the process, the retract limit switch  33  is tripped by a second switch sleeve bushing  35  which is positioned between worm  29  and the retract limit switch  33 . When the retract limit switch  33  is tripped and power to the motor assembly  27  is shut off, the motor  54  stops and the swing arm  23  remains in its stowed position. The retracting action of the swing arm, the overall drive motion and movement, including the timing, and the manner of using the various components are all substantially the same for the retracting cycle as they are for the extending or deploying cycle, albeit in the reverse order or reverse direction. The stack up of components associated with drive shaft  28  are illustrated in  FIG. 24 . 
   With reference to the component part drawings of  FIGS. 3-12  and  14 - 23 B, some of the structural details of the primary parts are illustrated and are further described hereinafter. Referring first to  FIGS. 15 and 16 , the housing  26  is constructed and arranged into two housing sections  26   a  and  26   b , each section being shaped with a hollow interior that is constructed and arranged to provide clearance spaces via cavities  64 - 68  for receipt of various component parts. From a size and tolerance perspective, these cavities  64 - 68  can be used in the “as-cast” condition. The corresponding component parts include, by way of example, the arm shaft  25  (hole  49 ), electric motor assembly  27  (into space  64 ), drive shaft  28  (through hole  68 ), worm  29  (into space  64 ), worm gear  30  (into space  65 ), springs  31   a  and  31   b , limit switch  32 , limit switch  33 , sealed bearings  36   a  and  36   b  (into spaces  66  and  67 ). The two housing sections  26   a  and  26   b  are securely bolted together by hex head bolts  69   a  and  69   b  and cooperating hex nuts  70   a  and  70   b.    
   Hole  49  extends through a raised boss  74  that receives a bushing or bearing. The cover  26   b  includes a matching and aligned interior boss  75  that is constructed and arranged to receive a corresponding bushing or bearing. One end of shaft  25  is received within boss  75  while a portion of the shaft body extends through boss  74  for ultimate assembly to swing arm  23 . 
   Each housing portion  26   a  and  26   b  includes three mounting holes  76   a  and  76   b , respectively, that receive bolts  69   a  and hex nut  70   a . These three holes are arranged in a pattern that matches the three holes  77  in mounting plate  24 . Bolts  69   a  are positioned so that the head is against plate  24 . After the housing cover  26   b  is assembled, the nuts  70   a  are tightened in place. The other two mounting hole locations  78   a  in housing base  26   a  can be either tapped holes into the housing body  26   a  or through holes, similar to holes  77 . If through holes are used, bolts  69   b  and nuts  70   b  are used in a manner similar to bolts  69   a  and nuts  70   a . If tapped holes are used, bolts  69   b  install from the top of the housing cover  26   b  through holes  78   b  and nuts  70   b  are not required. 
   With reference to  FIGS. 11 and 12 , shaft  25  includes five sections  81 - 85  and two recesses  86  and  87 . As illustrated, section  81  has a generally cylindrical shape with a keying recess  86 . Section  82  has a generally cylindrical shape with a keying recess  87 . Section  83  has a beveled shape and is positioned between the smaller diameter of section  81  and the larger diameter of section  82  as a transition portion. Section  84  has a generally cylindrical shape and is inserted into worm gear  30 . Section  85  provides a positioning seat for worm gear  30 . Sections  81 - 85  are all coaxial with each other and the axis of shaft  25  is the axis of rotation for gear  30 . 
   Referring to  FIG. 17 , drive shaft  28  includes three sections  90 ,  91  and  92 . Section  90  includes a D-flat end  93  that inserts into one end of shaft coupling  58 . The opposite end of section  90  is received by bearing  36   b . The flat cooperates with the set screw threaded into one hole  58   a . Section  91  receives worm  29  and uses recess  94  to key the worm  29  onto section  91 . Section  92  is received by bearing  36   a.    
   As for the electronics or electrical control arrangement for the disclosed device, additional details follow. There are two limit switches  32  and  33  and these are each single pole, normally closed momentary switches that are wired in series. When the springs are compressed enough to push the switch trip mechanism, the contacts open and the motor stops. Once the dashboard switch is turned off, the voltage reverses and the motor runs in the opposite direction. However, one of the switches is still open from the activation it just performed. A diode is used to allow the “reversed current” to pass through just long enough to run the motor and worm so that the switch can make contact again and run the motor in the opposite or reverse direction until the retracted switch is opened in the same fashion as the activation switch. The retracted switch also has a diode waiting on the voltage to be reversed again for another activation cycle. At the time the current is reversed, the switch waiting to receive tripping contact by the switch sleeve bushing is always closed, thereby completing the path for the electrical power. The diodes are preferred in order to complete the current path for a very short time until the switch is freed and can make its own contacts. 
   While the preferred embodiment of the invention has been illustrated and described in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that all changes and modifications that come within the spirit of the invention are desired to be protected.