Abstract:
An interface apparatus between a tower and platform includes a tower support assembly with opposed angle brackets and a first tower support assembly coupler/decoupler which is repeatably moveable between coupled and decoupled conditions with the tower support assembly. In the coupled condition, the coupler/decoupler is capable of coupling to the tower support assembly at a plurality of predetermined positions along the opposed angle brackets. The interface apparatus includes a second tower support assembly coupler/decoupler which allows the tower to pivot relative to the tower support assembly and rotate relative to the platform.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/098,656, filed on Sep. 19, 2008 by the same inventors, the contents of which are incorporated by reference as though fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to towers for drilling machines, and controlling the tilt thereof. 
     2. Description of the Related Art 
     There are many different types of drilling machines for drilling through a formation. Some of these drilling machines are mobile and others are stationary. Some examples of mobile and stationary drilling machines are disclosed in U.S. Pat. Nos. 820,992, 3,195,695, 3,245,180, 3,561,616, 3,692,123, 3,695,363, 3,708,024, 3,778,940, 3,805,902, 3,815,690, 3,833,072, 3,905,168, 3,968,845, 3,992,831, 4,016,687, 4,020,909, 4,595,065, 4,606,155, 4,616,454, 5,988,299, 6,527,063, 6,672,410, 6,675,915, 7,325,634, 7,347,285 and 7,413,036, as well as in U.S. Patent Application No. 20080210469. Some drilling machines, such as the one disclosed in U.S. Pat. No. 4,295,758, are designed to float and are useful for ocean drilling. The contents of these cited U.S. patents and the patent application are incorporated by reference as though fully set forth herein. 
     A typical mobile drilling machine includes a vehicle and tower, wherein the tower carries a rotary head and drill string. In operation, the drill string is driven into the formation by the rotary head. In this way, the drilling machine drills through the formation. More information about drilling machines, and how they operate, can be found in the above-identified references. 
     In some situations, it is desirable to drill at an angle. Drilling at an angle is useful so that more regions of a formation can be reached with the drill string. For example, in some situations, the drilling machine cannot be positioned directly over a desired region of the formation, so it is not possible to drill straight down and reach this region of the formation. Hence, angled drilling is useful so that the drilling machine can reach a desired region of a formation without being directly over it. In this way, there are many more options available when selecting the location to position the drilling machine. 
     Angled drilling is typically accomplished by tilting the tower relative to an axis of the drilling machine so that the drill string is tilted in response. More information regarding tilting a tower is provided in U.S. Pat. Nos. 3,245,180, 3,561,616, 3,815,690, 3,778,940, 3,905,168, and 3,992,831, and U.S. Patent Application No. 20080210469, as well as some of the other references mentioned above. However, it is desirable to better control the angle that the tower is tilted, and to provide more stability to the tower when it is in a tilted condition. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to a drilling machine for angled drilling, as well as a method of manufacturing and using the drilling machine. The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  is a side view of a drilling machine with a tower rotatably mounted to a tower interface assembly, wherein the tower and tower interface assembly are carried by a platform, and the tower is in a stowed condition. 
         FIGS. 1   b  and  1   c  are opposed side views of the drilling machine of  FIG. 1   a , wherein the tower is in a raised condition. 
         FIGS. 1   d  and  1   e  are close-up front and rear perspective views, respectively, of the drilling machine of  FIG. 1   a , wherein the tower is in the raised condition. 
         FIG. 1   f  is a perspective view of opposed tower brackets of the tower of the drilling machine of  FIG. 1   a.    
         FIG. 2   a  is a rear perspective view of the tower interface assembly being carried by the platform, as shown in  FIGS. 1   a ,  1   b  and  1   c.    
         FIGS. 2   b  and  2   c  are close-up rear and front perspective views, respectively, of the tower interface assembly being carried by the platform, as shown in  FIGS. 1   a ,  1   b  and  1   c.    
         FIG. 2   d  is a front side view of the tower interface assembly being carried by the platform, as shown in  FIGS. 1   a ,  1   b  and  1   c.    
         FIG. 2   e  is a side view of the tower interface assembly being carried by the platform, as shown in  FIGS. 1   a ,  1   b  and  1   c.    
         FIG. 2   f  is a front perspective view of the tower interface assembly of  FIGS. 1   a ,  1   b  and  1   c.    
         FIG. 3   a  is a close-up rear perspective view of the opposed tower brackets of  FIG. 1   f  rotatably mounted to the tower interface assembly of the drilling machine of  FIG. 1   a  with a pivot pin actuator and angle pin actuator, wherein the tower is in the raised condition. 
         FIG. 3   b  is a close-up rear side view of the pivot pin actuator and angle pin actuator of  FIG. 3   a.    
         FIG. 4   a  is a sectional front view, taken along a cut-line  4   a - 4   a  of  FIG. 3   a , of the opposed tower brackets and tower interface assembly. 
         FIG. 4   b  is a perspective view of the pivot pin actuator of  FIGS. 3   a  and  3   b.    
         FIG. 4   c  is an exploded perspective view of a pivot pin of the pivot pin actuator of  FIGS. 3   a  and  3   b , and a pivot pin insert and pivot pin bushing of the tower. 
         FIGS. 4   d  and  4   e  are perspective and side views, respectively, of the pivot pin of the pivot pin actuator of  FIGS. 3   a  and  3   b , and the pivot pin insert and pivot pin bushing of the tower. 
         FIGS. 5   a  and  5   b  are views of the pivot pin actuator of  FIGS. 3   a  and  3   b  in retracted and extended conditions, respectively. 
         FIG. 6   a  is a sectional front view, taken along a cut-line  6   a - 6   a  of  FIG. 3   a , of the opposed tower brackets and tower interface assembly. 
         FIG. 6   b  is a perspective view of the angle pin actuator of  FIGS. 3   a  and  3   b.    
         FIG. 6   c  is an exploded perspective view of an angle pin of the angle pin actuator of  FIGS. 3   a  and  3   b , and an angle pin insert and angle pin bushing of the tower. 
         FIGS. 6   d  and  6   e  are perspective and side views, respectively, of the angle pin of the angle pin actuator of  FIGS. 3   a  and  3   b , and the angle pin insert and angle pin bushing of the tower. 
         FIGS. 7   a  and  7   b  are views of the angle pin actuator of  FIGS. 3   a  and  3   b  in retracted and extended conditions, respectively. 
         FIGS. 8   a ,  8   b ,  8   c  and  8   d  are side views of the opposed angle bracket assemblies of the tower interface assembly. 
         FIG. 8   e  is a perspective view of the tower interface assembly showing planes which extend between opposed angle pin sockets. 
         FIGS. 9   a  and  9   b  are perspective views of the tower of  FIG. 1   a  held at an angle of 0° by the tower interface assembly. 
         FIGS. 9   c  and  9   d  are perspective views of the tower of  FIG. 1   a  held at an angle of 15° by the tower interface assembly. 
         FIGS. 9   e ,  9   f  and  9   g  are perspective views of the tower of  FIG. 1   a  held at an angle of 30° by the tower interface assembly. 
         FIGS. 10   a ,  10   b  and  10   c  are side views of different embodiments of angle bracket arms, which can be included with the tower interface assembly. 
         FIGS. 11   a ,  11   b  and  11   c  are side, side and perspective views of another embodiment of opposed angle bracket assemblies, which each include the angle bracket arm of  FIG. 10   c.    
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1   a  is a side view of a drilling machine  100  with a tower  102  rotatably mounted to a tower interface assembly  118 , wherein tower  102  and tower interface assembly  118  are carried by a platform  103 , and tower  102  is in a stowed condition.  FIGS. 1   b  and  1   c  are opposed side views of drilling machine  100 , wherein tower  102  is in a raised condition.  FIGS. 1   d  and  1   e  are close-up front and rear perspective views, respectively, of drilling machine  100 , wherein tower  102  is in the raised condition. 
     It should be noted that drilling machine  100  can be a stationary or mobile vehicle, but here it is embodied as being a mobile vehicle for illustrative purposes. Some examples of different types of drilling machines are the PV-235, PV-270, PV-271, PV-275 and PV-351 drilling machines, which are manufactured by Atlas Copco Drilling Solutions of Garland, Tex. It should be noted, however, that drilling machines are provided by many other manufacturers. 
     In this embodiment, drilling machine  100  includes an operator&#39;s cab  105 , which is carried by platform  103 . Operator&#39;s cab  105  is positioned proximate to a vehicle front  101   a  of drilling machine  100 . A front  101   c  of platform  103  is positioned proximate to operator&#39;s cab  105 , so that operator&#39;s cab  105  is positioned between front  101   c  of platform  103  and vehicle front  101   a  of drilling machine  100 . In this way, operator&#39;s cab  105  is positioned proximate to a vehicle front  101   a  of drilling machine  100 . 
     In this embodiment, drilling machine  100  includes a power pack  104  which is carried by platform  103 . Power pack  104  typically includes many different components, such as a prime mover. Platform  103  extends to a vehicle back  101   b , and power pack  104  is positioned between platform front  101   c  and vehicle back  101   b . In this way, power pack  104  is positioned proximate to a vehicle back  101   b  of drilling machine  100 . 
     It should be noted that the components of drilling machine  100  are typically operated by an operator in operator&#39;s cab  105 . For example, in this embodiment, drilling machine  100  includes a control system (not shown), which is operatively coupled to power pack  104 . The control system includes one or more control inputs which can be adjusted by the operator in operator&#39;s cab  105 . In this way, power pack  104  is operated by an operator in operator&#39;s cab  105 . Further, the control system includes one or more input controls for controlling the operation of tower  102 , as will be discussed in more detail below. 
     Tower  102  generally carries a feed cable system (not shown) attached to a rotary head  107 , wherein the feed cable system allows rotary head  107  to move between raised and lowered positions along tower  102 . The feed cable system moves rotary head  107  between the raised and lowered positions by moving it towards a tower crown  102   b  and tower base  102   a , respectively. 
     Rotary head  107  is moved between the raised and lowered positions to raise and lower, respectively, a drill string  108  through a borehole. Further, rotary head  107  is used to rotate drill string  108 , wherein drill string  108  extends through tower  102 . Drill string  108  generally includes one or more drill pipes connected together in a well-known manner. The drill pipes of drill string  108  are capable of being attached to an earth bit, such as a tri-cone rotary earth bit. It should be noted that the operation of the rotary head and feed cable system is typically controlled by the operator in operator&#39;s cab  105 . 
     In this embodiment, tower interface assembly  118  rotatably mounts tower  102  to platform  103 . In particular, tower base  102   a  is rotatably mounted to tower interface assembly  118 . In this way, tower  102  is rotatably mounted to platform  103  through tower interface assembly  118 . Tower interface assembly  118  is positioned proximate to platform front  101   c . In particular, tower interface assembly  118  is positioned between platform front  101   c  and power pack  104 . 
     In this embodiment, tower interface assembly  118  operatively couples platform  103  and tower  102  together. Tower  102  and platform  103  are operatively coupled together so that tower  102  can rotate relative to platform  103 . In this way, tower interface assembly  118  provides an interface between tower  102  and platform  103 . 
     Tower interface assembly  118  allows tower  102  to be repeatably moved between raised and lowered positions. In the lowered position, which is shown in  FIG. 1   a , tower crown  102   b  is towards platform  103 , and a back  106   a  of tower  102  is towards platform  103  and prime mover  104 . In the lowered position, tower  102  extends parallel to a reference line  111 , which extends parallel to platform  103 . It should also be noted that tower  102  is in a stowed condition when it is in the lowered position of  FIG. 1   a . Further, tower  102  is in a deployed condition when it is not in the lowered position of  FIG. 1   a.    
     In the raised position, which is shown in  FIGS. 1   b  and  1   c , a tower crown  102   b  of tower  102  is away from platform  103 . In the raised position, a front  106   b  of tower  102  faces operator&#39;s cab  105  and back  106   a  of tower  102  faces prime mover  104 . In the raised position, tower  102  extends parallel to a reference line  110 , which extends perpendicular to platform  103  and reference line  111 . 
     Tower interface assembly  118  allows tower  102  to be held at a desired predetermined angle relative to platform  103 . Tower interface assembly  118  allows tower  102  to be held at the desired predetermined angle relative to platform  103  so that drilling machine  100  can be used for angled drilling. As will be discussed in more detail below, tower interface assembly  118  allows better control of the angle that tower  102  is tilted, and provides more stability to tower  102  when tower  102  is in a tilted condition. 
     It should be noted that tower  102  is in the tilted condition when it is positioned between the raised and lowered positions of  FIGS. 1   a  and  1   b , respectively, as indicated by a reference line  112 . Reference line  112  extends at a non-zero angle θ relative to reference line  110 . Reference line  112  extends parallel to tower  102  when tower  102  is rotatably mounted to tower interface assembly  118 . Hence, reference line  112  is parallel to reference line  110  when tower  102  is in the raised position. 
     In this embodiment, drilling machine  100  includes tower actuators  117   a  and  117   b , as shown in  FIGS. 1   b  and  1   c . Tower actuators  117   a  and  117   b  are operatively coupled between platform  103  and tower brackets  116   a  and  116   b , respectively, of tower  102 . Tower brackets  116   a  and  116   b  are shown in a perspective view in  FIG. 1   f , and can also be seen in  FIGS. 1   a ,  1   b ,  1   c ,  1   d  and  1   e.    
     In this embodiment, tower bracket  116   a  includes tower bracket lower opening  190   a , tower bracket intermediate opening  191   a  and tower bracket upper opening  192   a . Tower actuator  117   a  extends between platform  103  and tower bracket upper opening  192   a . It should be noted that tower bracket intermediate opening  191   a  is positioned between tower bracket lower opening  190   a  and tower bracket upper opening  192   a.    
     In this embodiment, tower bracket  116   b  includes tower bracket lower opening  190   b , tower bracket intermediate opening  191   b  and tower bracket upper opening  192   b . Tower actuator  117   b  extends between platform  103  and tower bracket upper opening  192   b . It should be noted that tower bracket intermediate opening  191   b  is positioned between tower bracket lower opening  190   b  and tower bracket upper opening  192   b.    
     Tower actuators  117   a  and  117   b  can be of many different types of actuators, such as hydraulic cylinders capable of being repeatably moved between extended and retracted positions. When tower actuators  117   a  and  117   b  are in the retracted position, tower  102  is in the lowered position, as shown in  FIG. 1   a . Further, when actuators  117   a  and  117   b  are in extended positions, tower  102  is in the raised position, as shown in  FIGS. 1   b  and  1   c . In this way, tower  102  is repeatably moveable between lowered and raised positions. It should be noted that the operation of tower actuators  117   a  and  117   b  is controlled by the operator in operator&#39;s cab  105 . In this way, the movement of tower  102  between the raised and lowered conditions is controlled by the operator in operator&#39;s cab  105 . 
       FIG. 2   a  is a rear perspective view of tower interface assembly  118  being carried by platform  103 .  FIGS. 2   b  and  2   c  are close-up rear and front perspective views, respectively, of tower interface assembly  118  being carried by platform  103 .  FIG. 2   d  is a front side view of tower interface assembly  118  being carried by platform  103 .  FIG. 2   e  is a side view of the tower interface assembly  118  being carried by the platform  103 , and  FIG. 2   f  is a front perspective view of tower interface assembly  118 . 
     In this embodiment, platform  103  includes longitudinal platform beams  180   a  and  180   b . Longitudinal platform beams  180   a  and  180   b  are longitudinal beams because they extend longitudinally between platform front  103   a  and vehicle back  101   b . Longitudinal platform beams  180   a  and  180   b  provide support for the components of drilling machine  100 , such as power pack  104  and a tower support cradle  109 . Tower support cradle  109  is positioned proximate to vehicle back  101   b , and holds tower  102  when tower  102  is in the stowed condition. Longitudinal platform beams  180   a  and  180   b  can be of many different types of beams, such as I beams. 
     In this embodiment, platform  103  includes forward platform cross beam  181   a  and intermediate platform cross beam  181   b  which extend between opposed longitudinal platform beams  180   a  and  180   b . Forward platform cross beam  181   a  and intermediate platform cross beam  181   b  are cross beams because they extend transversely to longitudinal platform beams  180   a  and  180   b . Forward platform cross beam  181   a  is a forward cross beam because it is positioned proximate to front  101   c  of platform  103 . Intermediate platform cross beam  181   b  is an intermediate cross beam because it is positioned between forward platform cross beam  181   a  and vehicle back  101   b . Further, intermediate platform cross beam  181   b  is an intermediate cross beam because forward platform cross beam  181   a  is positioned between front  101   c  of platform  103  and intermediate platform cross beam  181   b.    
     As mentioned above, tower interface assembly  118  is positioned proximate to platform front  101   c , and between platform front  101   c  and power pack  104 . In this embodiment, tower interface assembly  118  is positioned proximate to forward platform cross beam  181   a  and intermediate platform cross beam  181   b . In particular, tower interface assembly  118  is carried by forward platform cross beam  181   a  and intermediate platform cross beam  181   b , as shown in  FIGS. 2   a ,  2   b ,  2   c ,  2   d  and  2   e.    
     In this embodiment, tower interface assembly  118  includes a tower support assembly  119  ( FIG. 2   f ). Tower support assembly  119  is capable of holding tower  102  at the desired predetermined angle relative to platform  103 , as will be discussed in more detail below. In this embodiment, tower support assembly  119  includes opposed angle bracket assemblies  120   a  and  120   b . Angle bracket assembly  120   a  includes an angle bracket  121   a  coupled to forward platform cross beam  181   a , and an angle bracket arm  135   a . Angle bracket  121   a  extends upwardly towards vehicle front  101   c  and is coupled to angle bracket arm  135   a . As will be discussed in more detail below, angle bracket arm  135   a  includes a plurality of angle pin sockets  125   a  which extend therethrough. The angle pin sockets of angle bracket arm  135   a  are positioned and spaced apart from each other so that tower  102  is held at the desired predetermined angle relative to platform  103 . 
     In this embodiment, angle bracket assembly  120   a  includes an angle bracket support leg  122   a  which includes an angle bracket support leg base  124   a . Angle bracket support leg base  124   a  includes a pivot pin socket  133   a , which allows tower  102  to rotate relative to platform  102 , as will be discussed in more detail below. Angle bracket support leg  122   a  is coupled to angle bracket arm  135   a , and angle bracket support leg base  124   a  is coupled to forward platform cross beam  181   a . Angle bracket  121   a  and angle bracket support leg  122   a  hold angle bracket arm  135   a  above longitudinal platform beam  180   a.    
     In this embodiment, angle bracket assembly  120   b  includes an angle bracket  121   b  coupled to forward platform cross beam  181   b , and an angle bracket arm  135   b . Angle bracket  121   b  extends upwardly towards vehicle front  101   c  and is coupled to an angle bracket arm  135   b . As will be discussed in more detail below, angle bracket arm  135   b  includes a plurality of angle pin sockets  125   b  which extend therethrough. The angle pin sockets of angle bracket arm  135   b  are positioned and spaced apart from each other so that tower  102  is held at the desired predetermined angle relative to platform  103 . 
     In this embodiment, angle bracket assembly  120   b  includes an angle bracket support leg  122   b  which includes an angle bracket support leg base  124   b . Angle bracket support leg base  124   b  includes a pivot pin socket  133   b , which allows tower  102  to rotate relative to platform  102 , as will be discussed in more detail below. Angle bracket support leg  122   b  is coupled to angle bracket arm  135   b , and angle bracket support leg base  124   b  is coupled to forward platform cross beam  181   b . Angle bracket  121   b  and angle bracket support leg  122   b  hold angle bracket arm  135   b  above longitudinal platform beam  180   b.    
     In this embodiment, angle brackets  121   a  and  121   b  are positioned so they oppose each other. In this way, tower support assembly  119  includes opposed angle brackets. Further, angle bracket support legs  122   a  and  122   b  are positioned so they oppose each other. In this way, tower support assembly  119  includes opposed angle bracket support legs. Angle bracket support leg bases  124   a  and  124   b  are positioned so they oppose each other. In this way, tower support assembly  119  includes opposed angle bracket support leg bases. In this embodiment, angle bracket arm  135   a  and angle bracket arm  135   b  oppose each other. In this way, tower support assembly  119  includes opposed angle bracket arms. In this embodiment, angle pin sockets  125   a  and angle pin sockets  125   b  are positioned so they oppose each other. In this way, tower support assembly  119  includes opposed angle pin sockets. 
     It should be noted that, in some embodiments, angle bracket assembly  120   a  is a single integral piece, and angle bracket assembly  120   b  is a single integral piece. However, opposed angle bracket assemblies  120   a  and  120   b  are shown here as each including multiple pieces coupled together for illustrative purposes. 
     In some embodiments, tower interface assembly  118  includes components which provide support to tower support assembly  119 . The components which provide support to tower support assembly  119  provide more stability to tower  102  when tower  102  is in a tilted condition. 
     In this embodiment, tower interface assembly  118  includes an angle bracket support arm  123   a  which provides support to angle bracket assembly  120   a . Angle bracket support arm  123   a  is coupled at one end to longitudinal platform beam  180   a  through a support arm bracket  139   a  ( FIG. 2   f ). Further, angle bracket support arm  123   a  is coupled at an opposed end to angle bracket arm  135   a  through a support arm bracket  138   a . Angle bracket support arm  123   a  restricts the ability of angle bracket arm  135   a  to move towards and away from angle bracket assembly  120   b.    
     In this embodiment, tower interface assembly  118  includes an angle bracket support arm  123   b  which provides support to angle bracket assembly  120   b . Angle bracket support arm  123   b  is coupled at one end to longitudinal platform beam  180   b  through a support arm bracket  139   b  ( FIG. 2   f ). Further, angle bracket support arm  123   b  is coupled at an opposed end to angle bracket arm  135   b  through a support arm bracket  138   b . Angle bracket support arm  123   b  restricts the ability of angle bracket arm  135   b  to move towards and away from angle bracket assembly  120   a.    
     In this embodiment, tower interface assembly  118  includes an angle bracket cross beam  136  which is coupled to angle bracket leg  121   a  and angle bracket leg  121   b . Angle bracket cross beam  136  restricts the ability of angle bracket leg  121   a  and angle bracket leg  121   b  to move towards and away from each other. 
     In this embodiment, tower interface assembly  118  includes a longitudinal angle bracket beam  144   a  which is coupled to angle bracket leg  121   a  and angle bracket support leg  122   a . Longitudinal angle bracket beam  144   a  restricts the ability of angle bracket leg  121   a  and angle bracket support leg  122   a  to move towards and away from each other. 
     In this embodiment, tower interface assembly  118  includes a longitudinal angle bracket beam  144   b  which is coupled to angle bracket leg  121   b  and angle bracket support leg  122   b . Longitudinal angle bracket beam  144   b  restricts the ability of angle bracket leg  121   b  and angle bracket support leg  122   b  to move towards and away from each other. 
     In this embodiment, tower interface assembly  118  includes an angle bracket cross diagonal beam  137   a  which is coupled to angle bracket leg  121   a  and angle bracket support leg base  124   b , as shown in  FIGS. 2   d  and  2   f . Angle bracket cross diagonal beam  137   a  restricts the ability of angle bracket assembly  120   a  and angle bracket assembly  120   b  to move towards and away from each other. 
     In this embodiment, tower interface assembly  118  includes an angle bracket cross diagonal beam  137   b  which is coupled to angle bracket leg  121   b  and angle bracket support leg base  124   a , as shown in  FIGS. 2   d  and  2   f . Angle bracket cross diagonal beam  137   b  restricts the ability of angle bracket assembly  120   a  and angle bracket assembly  120   b  to move towards and away from each other. 
       FIG. 3   a  is a close-up rear perspective view of opposed tower brackets  116   a  and  116   b  rotatably mounted to tower interface assembly  118  with a pivot pin actuator  150  and angle pin actuator  140 , wherein tower  102  is in the raised condition.  FIG. 3   b  is a close-up rear side view of pivot pin actuator  150  and angle pin actuator  140 . 
     Pivot pin actuator  150  is positioned below angle pin actuator  140 , and proximate to forward platform cross beam  181   a , as shown in  FIGS. 3   a  and  3   b . Pivot pin actuator  150  extends between angle bracket assemblies  120   a  and  120   b . In particular, pivot pin actuator  150  is positioned below angle pin actuator  140  so it extends between angle bracket support leg bases  124   a  and  124   b  and pivot pin sockets  133   a  and  133   b  ( FIG. 2   f ). 
     In this embodiment, pivot pin actuator  150  is carried by tower brackets  116   a  and  116   b  ( FIG. 1   f ). In particular, pivot pin actuator  150  is carried by tower brackets  116   a  and  116   b  so it extends between tower bracket lower openings  190   a  and  190   b . As will be discussed in more detail below, pivot pin actuator  150  allows tower  102  to be coupled to tower interface assembly  118  so it can rotate relative to platform  103  and move between the raised and lowered positions. 
     Pivot pin actuator  150  is repeatably moveable between extended and retracted conditions. In the extended condition, and as discussed in more detail below, pivot pin actuator  150  extends through pivot pin sockets  133   a  and  133   b  ( FIG. 2   f ) and tower bracket lower openings  190   a  and  190   b  ( FIG. 1   f ). Pivot pin actuator  150  extends through pivot pin sockets  133   a  and  133   b  in the extended condition so that tower  102  can rotate relative to tower interface assembly  118 . In this embodiment, movement of pivot pin actuator  150  between the extended and retracted conditions is controlled by the operator in operator&#39;s cab  105 . 
     In the retracted condition, and as discussed in more detail below, pivot pin actuator  150  does not extend through pivot pin sockets  133   a  and  133   b  ( FIG. 2   f ). Pivot pin actuator  150  does not extend through pivot pin sockets  133   a  and  133   b  in the retracted condition so that tower  102  can be moved relative to tower interface assembly  118 . 
     In this embodiment, angle pin actuator  140  is positioned above pivot pin actuator  150 , and away from forward platform cross beam  181   a , as shown in  FIGS. 3   a  and  3   b . Angle pin actuator  140  extends between angle bracket assemblies  120   a  and  120   b . In particular, angle pin actuator  140  is positioned above pivot pin actuator  150  so it extends between angle bracket arms  135   a  and  135   b  and angle pin sockets  125   a  and  125   b.    
     In this embodiment, angle pin actuator  140  is carried by tower brackets  116   a  and  116   b  ( FIG. 1   f ). In particular, angle pin actuator  140  is carried by tower brackets  116   a  and  116   b  so it extends between tower bracket intermediate openings  191   a  and  191   b . As will be discussed in more detail below, angle pin actuator  140  allows tower  102  to be coupled to tower interface assembly  118  so tower  102  can be held at the desired predetermined angle relative to platform  103 . Tower interface assembly  118  and angle pin actuator  140  allow tower  102  to be held at the desired predetermined angle relative to platform  103  so that drilling machine  100  can be used for angled drilling. 
     Angle pin actuator  140  is repeatably moveable between extended and retracted conditions. In the extended condition, and as discussed in more detail below, angle pin actuator  140  extends through a selected one of angle pin sockets  125   a  ( FIG. 2   f ) and tower bracket intermediate opening  190   a  ( FIG. 1   f ). Further, in the extended condition, angle pin actuator  140  extends through a selected one of angle pin sockets  125   b  ( FIG. 2   f ) and tower bracket intermediate opening  191   b  ( FIG. 1   f ). It should be noted that, in the extended condition, angle pin actuator  140  extends through opposed sockets of angle pin sockets  125   a  and  125   b . Angle pin actuator  140  extends through angle pin sockets  125   a  and  125   b  in the extended condition so that tower  102  is held at the desired predetermined angle relative to platform  103 . 
     In the retracted condition, and as discussed in more detail below, angle pin actuator  140  does not extend through angle pin socket  125   a  ( FIG. 2   f ). Further, in the retracted condition, angle pin actuator  140  does not extend through angle pin socket  125   b  ( FIG. 2   f ). Angle pin actuator  140  does not extend through angle pin sockets  125   a  and  125   b  in the retracted condition so that tower  102  can be rotated and moved relative to tower interface assembly  118 . In this embodiment, movement of angle pin actuator  140  between the extended and retracted conditions is controlled by the operator in operator&#39;s cab  105 . 
       FIG. 4   a  is a sectional front view, taken along a cut-line  4   a - 4   a  of  FIG. 3   a , of opposed tower brackets  116   a  and  116   b  and tower interface assembly  118  in a region  113  of  FIG. 3   b . In this embodiment, mounting blocks  156   a  and  156   b  are mounted to opposed tower brackets  116   a  and  116   b , respectively. Mounting block  156   a  includes a mounting block opening  157   a  which is aligned with tower bracket lower opening  190   a . Further, mounting block  156   b  includes a mounting block opening  157   b  which is aligned with tower bracket lower opening  190   b . Mounting blocks  156   a  and  156   b  are for holding pivot pin actuator  150  to opposed tower brackets  116   a  and  116   b . As will be discussed in more detail below, pivot pin actuator  150  extends through mounting block openings  157   a  and  157   b . In this way, pivot pin actuator  150  extends between opposed tower brackets  116   a  and  116   b.    
     In this embodiment, a pivot pin insert  172   a  extends through pivot pin socket  133   a  of angle bracket support leg base  124   a , and a pivot pin insert  172   b  extends through pivot pin socket  133   b  of angle bracket support leg base  124   b . A pivot pin bushing  171   a  extends through tower bracket lower opening  190   a  of tower bracket  116   a  and mounting block openings  157   a  of mounting block  156   a . Further, a pivot pin bushing  171   b  extends through tower bracket lower opening  190   b  of tower bracket  116   b  and mounting block openings  157   b  of mounting block  156   b . Pivot pin insert  172   a , pivot pin insert  172   b , pivot pin bushing  171   a  and pivot pin bushing  171   b  each include central openings through which pivot pin actuator  150  moves in response to moving between the extended and retracted positions, as will be discussed below. 
     Mounting block openings  157   a  and  157   b  are repeatably moveable between aligned and unaligned positions with pivot pin sockets  133   a  and  133   b , respectively. Mounting block openings  157   a  and  157   b  are repeatably moveable between aligned and unaligned positions with pivot pin sockets  133   a  and  133   b , respectively, in response to moving tower  102  between the raised and lowered positions. 
     Mounting block openings  157   a  and  157   b  are aligned with pivot pin sockets  133   a  and  133   b , respectively, when tower  102  is rotatably mounted to tower interface assembly  118 . Mounting block openings  157   a  and  157   b  are unaligned with pivot pin sockets  133   a  and  133   b , respectively, when tower  102  is not rotatably mounted to tower interface assembly  118 . In particular, mounting block openings  157   a  and  157   b  are unaligned with pivot pin sockets  133   a  and  133   b , respectively, when tower  102  is in the stowed condition of  FIG. 1   a . It should be noted that mounting block openings  157   a  and  157   b  are aligned with pivot pin sockets  133   a  and  133   b , respectively, in  FIG. 4   a.    
     Tower bracket lower openings  190   a  and  190   b  are repeatably moveable between aligned and unaligned positions with pivot pin sockets  133   a  and  133   b , respectively. Tower bracket lower openings  190   a  and  190   b  are repeatably moveable between aligned and unaligned positions with pivot pin sockets  133   a  and  133   b , respectively, in response to moving tower  102  between the raised and lowered positions. 
     Tower bracket lower openings  190   a  and  190   b  are aligned with pivot pin sockets  133   a  and  133   b , respectively, when tower  102  is rotatably mounted to tower interface assembly  118 . Tower bracket lower openings  190   a  and  190   b  are unaligned with pivot pin sockets  133   a  and  133   b , respectively, when tower  102  is not rotatably mounted to tower interface assembly  118 . In particular, tower bracket lower openings  190   a  and  190   b  are unaligned with pivot pin sockets  133   a  and  133   b , respectively, when tower  102  is in the stowed condition of  FIG. 1   a . It should be noted that tower bracket lower openings  190   a  and  190   b  are aligned with pivot pin sockets  133   a  and  133   b , respectively, in  FIG. 4   a.    
       FIG. 4   b  is a perspective view of one embodiment of pivot pin actuator  150 . In this embodiment, pivot pin actuator  150  includes a pivot pin cylinder  152 , which is repeatably moveable between extended and retracted conditions. The movement of pivot pin cylinder  152  between the extended and retracted conditions is controlled by the operator in operator&#39;s cab  105 . In this embodiment, pivot pin actuator  150  includes pivot pins  151   a  and  151   b . Pivot pins  151   a  and  151   b  move away from and towards each other in response to moving pivot pin cylinder  152  between the extended and retracted conditions, respectively. In this way, pivot pin actuator  150  is repeatably moveable between extended and retracted conditions. 
     In this embodiment, pivot pins  151   a  and  151   b  are tapered pivot pins. More information regarding tapered pivot pins is provided in the above-identified related application. Tapered pivot pins are useful because they increase the likelihood that pivot pin actuator  150  will move from the retracted position to the extended position. For example, tapered pivot pins are useful because they increase the likelihood that pivot pin actuator  150  will move from the retracted position to the extended position in response to misalignment of pivot pin socket  133   a  and tower bracket lower opening  190   a , and misalignment of pivot pin socket  133   b  and tower bracket lower opening  190   b.    
       FIG. 4   c  is an exploded perspective view of pivot pins  151   a  and  151   b , and pivot pin inserts  172   a  and  172   b  and pivot pin bushings  171   a  and  171   b .  FIGS. 4   d  and  4   e  are perspective and side views, respectively, of pivot pins  151   a  and  151   b , and pivot pin inserts  172   a  and  172   b  and pivot pin bushings  171   a  and  171   b.    
     It should be noted that, in the retracted condition, pivot pins  151   a  and  151   b  extend through pivot pin bushings  171   a  and  171   b , respectively. Further, in the retracted condition, pivot pins  151   a  and  151   b  do not extend through pivot pin inserts  172   a  and  172   b , respectively. In the retracted condition, pivot pins  151   a  and  151   b  do not extend through pivot pin inserts  172   a  and  172   b , respectively, so that tower  102  can be moved between the raised and lowered positions. 
     In the extended condition, pivot pin  151   a  extends through pivot pin bushing  171   a  and pivot pin insert  172   a , and pivot pin  151   b  extends through pivot pin bushing  171   b  and pivot pin insert  172   b . In the extended condition, pivot pin  151   a  extends through pivot pin bushing  171   a  and pivot pin insert  172   a , and pivot pin  151   b  extends through pivot pin bushing  171   b  and pivot pin insert  172   b  so that tower  102  is rotatably mounted to tower interface assembly  118 . 
       FIGS. 5   a  and  5   b  are views of pivot pin actuator  150  in retracted and extended conditions, respectively. It should be noted that the view of  FIGS. 5   a  and  5   b  correspond with the view of  FIG. 4   a . In the retracted condition, pivot pin actuator  150  extends between pivot pin mounting blocks  156   a  and  156   b , and extends through pivot pin mounting block openings  157   a  and  157   b . In particular, pivot pins  151   a  and  151   b  extend through pivot pin mounting block openings  157   a  and  157   b , respectively. 
     Further, in the retracted condition, pivot pin actuator  150  extends between tower brackets  116   a  and  116   b , and extends through tower bracket lower openings  190   a  and  190   b . In particular, pivot pins  151   a  and  151   b  extend through tower bracket lower openings  190   a  and  190   b , respectively. 
     In the retracted condition, pivot pin actuator  150  does not extend through angle bracket support leg base  124   a  and  124   b . In particular, pivot pins  151   a  and  151   b  do not extend through pivot pin sockets  133   a  and  133   b , respectively. In the retracted condition, pivot pin actuator  150  does not extend through pivot pin sockets  133   a  and  133   b  so that tower  102  can be moved between the raised and lowered positions. It should be noted that tower  102  is not rotatably mounted to tower interface assembly  118  when pivot pin actuator  150  does not extend through pivot pin sockets  133   a  and  133   b.    
     In the extended condition, pivot pin actuator  150  extends between pivot pin mounting blocks  156   a  and  156   b , and extends through pivot pin mounting block openings  157   a  and  157   b . In particular, pivot pins  151   a  and  151   b  extend through pivot pin mounting block openings  157   a  and  157   b , respectively. 
     Further, in the extended condition, pivot pin actuator  150  extends between tower brackets  116   a  and  116   b , and extends through tower bracket lower openings  190   a  and  190   b . In particular, pivot pins  151   a  and  151   b  extend through tower bracket lower openings  190   a  and  190   b , respectively. 
     In the extended condition, pivot pin actuator  150  extends through angle bracket support leg base  124   a  and  124   b . In particular, pivot pins  151   a  and  151   b  extend through pivot pin sockets  133   a  and  133   b , respectively. In the extended condition, pivot pin actuator  150  extends through pivot pin sockets  133   a  and  133   b  so that tower  102  is restricted from moving between the raised and lowered positions. It should be noted that tower  102  is rotatably mounted to tower interface assembly  118  when pivot pin actuator  150  extends through pivot pin sockets  133   a  and  133   b . It should also be noted that tower  102  is moveable to a tilted condition when pivot pin actuator  150  extends through pivot pin sockets  133   a  and  133   b , as will be discussed in more detail below. 
     As mentioned above, pivot pin actuator  150  is repeatably moveable between the extended and retracted conditions. Pivot pin  151   a  moves away from angle bracket support leg base  124   a  and pivot pin socket  133   a  in response to pivot pin actuator  150  moving to the retracted condition. Further, pivot pin  151   b  moves away from angle bracket support leg base  124   b  and pivot pin socket  133   b  in response to pivot pin actuator  150  moving to the retracted condition. Pivot pin  151   a  moves towards angle bracket support leg base  124   a  and pivot pin socket  133   a  in response to pivot pin actuator  150  moving to the extended condition. Further, pivot pin  151   b  moves towards angle bracket support leg base  124   b  and pivot pin socket  133   b  in response to pivot pin actuator  150  moving to the extended condition. Hence, pivot pins  151   a  and  151   b  are repeatably moveable towards and away from angle bracket support leg bases  124   a  and  124   b  in response to moving pivot pin actuator  150  between extended and retracted conditions, respectively. Further, pivot pins  151   a  and  151   b  are repeatably moveable towards and away from pivot pin sockets  133   b  and  133   b  in response to moving pivot pin actuator  150  between extended and retracted conditions, respectively. 
       FIG. 6   a  is a sectional front view, taken along a cut-line  6   a - 6   a  of  FIG. 3   a , of opposed tower brackets  116   a  and  116   b  and tower interface assembly  118  in a region  114  of  FIG. 3   b . In this embodiment, mounting blocks  146   a  and  146   b  are mounted to opposed tower brackets  116   a  and  116   b , respectively. Mounting block  146   a  includes a mounting block opening  147   a  which is aligned with tower bracket intermediate opening  191   a . Further, mounting block  146   b  includes a mounting block opening  147   b  which is aligned with tower bracket intermediate opening  191   b . Mounting blocks  146   a  and  146   b  are for holding angle pin actuator  140  to opposed tower brackets  116   a  and  116   b . As will be discussed in more detail below, angle pin actuator  140  extends through mounting block openings  147   a  and  147   b . In this way, angle pin actuator  140  extends between opposed tower brackets  116   a  and  116   b.    
     In this embodiment, an angle pin insert  162   a  extends through an angle pin socket  126   a  of angle bracket arm  135   a , and an angle pin insert  162   b  extends through angle pin socket  126   b  of angle bracket arm  135   b . An angle pin bushing  161   a  extends through tower bracket intermediate opening  191   a  of tower bracket  116   a  and mounting block openings  147   a  of mounting block  146   a . Further, an angle pin bushing  161   b  extends through tower bracket intermediate opening  191   b  of tower bracket  116   b  and mounting block openings  147   b  of mounting block  147   b . Angle pin insert  162   a , angle pin insert  162   b , angle pin bushing  161   a  and angle pin bushing  161   b  each include central openings through which angle pin actuator  140  moves in response to moving between the extended and retracted positions, as will be discussed below. 
     Mounting block openings  147   a  and  147   b  are repeatably moveable between aligned and unaligned positions with angle pin sockets  126   a  and  126   b , respectively. Mounting block openings  147   a  and  147   b  are repeatably moveable between aligned and unaligned positions with angle pin sockets  126   a  and  126   b , respectively, in response to moving tower  102  between the raised and tilted positions. More information regarding moving tower  102  between the raised and tilted positions is provided below. 
     Mounting block openings  147   a  and  147   b  are aligned with angle pin sockets  126   a  and  126   b , respectively, when tower  102  is rotatably mounted to tower interface assembly  118  and in the raised position of  FIGS. 1   a  and  1   b . Mounting block openings  147   a  and  147   b  are unaligned with angle pin sockets  126   a  and  126   b , respectively, when tower  102  is rotatably mounted to tower interface assembly  118  and not in the upright position of  FIGS. 1   a  and  1   b . In particular, mounting block openings  147   a  and  147   b  are unaligned with angle pin sockets  126   a  and  126   b , respectively, when tower  102  is in a tilted position. It should be noted that mounting block openings  147   a  and  147   b  are aligned with angle pin sockets  126   a  and  126   b , respectively, in  FIG. 6   a.    
     Tower bracket intermediate openings  191   a  and  191   b  are repeatably moveable between aligned and unaligned positions with angle pin sockets  126   a  and  126   b , respectively. Tower bracket intermediate openings  191   a  and  191   b  are repeatably moveable between aligned and unaligned positions with angle pin sockets  126   a  and  126   b , respectively, in response to moving tower  102  between the raised and tilted positions. 
     Tower bracket intermediate openings  191   a  and  191   b  are aligned with angle pin sockets  126   a  and  126   b , respectively, when tower  102  is rotatably mounted to tower interface assembly  118  and tower  102  is in the raised position. Tower bracket intermediate openings  191   a  and  191   b  are unaligned with angle pin sockets  126   a  and  126   b , respectively, when tower  102  is rotatably mounted to tower interface assembly  118  and not in the raised position. It should be noted that tower bracket intermediate openings  191   a  and  191   b  are aligned with angle pin sockets  126   a  and  126   b , respectively, in  FIG. 6   a.    
       FIG. 6   b  is a perspective view of one embodiment of angle pin actuator  140 . In this embodiment, angle pin actuator  140  includes an angle pin cylinder  142 , which is repeatably moveable between extended and retracted conditions. The movement of angle pin cylinder  142  between the extended and retracted conditions is controlled by the operator in operator&#39;s cab  105 . In this embodiment, angle pin actuator  140  includes angle pins  141   a  and  141   b . Angle pins  141   a  and  141   b  move away from and towards each other in response to moving angle pin cylinder  142  between the extended and retracted conditions, respectively. In this way, angle pin actuator  140  is repeatably moveable between extended and retracted conditions. 
     In this embodiment, angle pins  141   a  and  141   b  are tapered angle pins. More information regarding tapered angle pins is provided in the above-identified related application. Tapered angle pins are useful because they increase the likelihood that angle pin actuator  140  will move from the retracted position to the extended position. For example, tapered angle pins are useful because they increase the likelihood that angle pin actuator  140  will move from the retracted position to the extended position in response to misalignment of angle pin sockets  125   a  and tower bracket intermediate opening  191   a , and misalignment of angle pin sockets  125   b  and tower bracket intermediate opening  191   b.    
       FIG. 6   c  is an exploded perspective view of angle pins  141   a  and  141   b , and angle pin inserts  162   a  and  162   b  and angle pin bushings  161   a  and  161   b .  FIGS. 6   d  and  6   e  are perspective and side views, respectively, of angle pins  141   a  and  141   b , and angle pin inserts  162   a  and  162   b  and angle pin bushings  161   a  and  161   b.    
     It should be noted that, in the retracted condition, angle pins  141   a  and  141   b  extend through angle pin bushings  161   a  and  161   b , respectively. Further, in the retracted condition, angle pins  161   a  and  161   b  do not extend through angle pin inserts  162   a  and  162   b , respectively. In some situations, in the retracted condition, angle pins  161   a  and  161   b  do not extend through angle pin inserts  162   a  and  162   b , respectively, so that tower  102  can be moved between the raised and lowered positions. In other situations, in the retracted condition, angle pins  161   a  and  161   b  do not extend through angle pin inserts  162   a  and  162   b , respectively, so that tower  102  can be moved between tilted positions. 
     In the extended condition, angle pin  141   a  extends through angle pin bushing  161   a  and angle pin insert  162   a , and angle pin  161   b  extends through angle pin bushing  161   b  and angle pin insert  162   b . In the extended condition, angle pin  141   a  extends through angle pin bushing  161   a  and angle pin insert  162   a , and angle pin  141   b  extends through angle pin bushing  161   b  and angle pin insert  162   b  so that tower  102  is held in the upright position. 
       FIGS. 7   a  and  7   b  are views of angle pin actuator  140  in retracted and extended conditions, respectively. It should be noted that the view of  FIGS. 7   a  and  7   b  correspond with the view of  FIG. 6   a . In the retracted condition, angle pin actuator  140  extends between angle pin mounting blocks  146   a  and  146   b , and extends through angle pin mounting block openings  147   a  and  147   b . In particular, angle pins  141   a  and  141   b  extend through angle pin mounting block openings  147   a  and  147   b , respectively. 
     Further, in the retracted condition, angle pin actuator  140  extends between tower brackets  116   a  and  116   b , and extends through tower bracket intermediate openings  191   a  and  191   b . In particular, angle pins  141   a  and  141   b  extend through tower bracket intermediate openings  191   a  and  191   b , respectively. 
     In the retracted condition, angle pin actuator  140  does not extend through angle bracket arms  135   a  and  135   b . In particular, angle pins  141   a  and  141   b  do not extend through angle pin sockets  126   a  and  126   b , respectively. It should be noted that pivot pins  151   a  and  151   b  do not extend through pivot pin sockets  133   a  and  133   b , respectively, in the situations in which it is desirable to move tower  102  between the raised and lowered positions. However, angle pin actuator  140  does extend through angle pin sockets  126   a  and  126   b  so that tower  102  can be moved between the raised and lowered positions. Hence, tower  102  is rotatably mounted to tower interface assembly  118  through angle pin actuator  140  when tower  102  is moved to and from the stowed condition. In particular, tower  102  is rotatably mounted to tower interface assembly  118  through angle pins  141   a  and  141   b  when tower  102  is moved to and from the stowed condition ( FIG. 1   a ). In this embodiment, angle pins  141   a  and  141   b  extend through angle pin sockets  126   a  and  126   b , respectively, when tower  102  is moved to and from the stowed condition. 
     In other situations, in the retracted condition, angle pin actuator  140  does not extend through angle pin sockets  126   a  and  126   b  so that tower  102  can be moved between tilted positions. It should be noted that pivot pins  151   a  and  151   b  extend through pivot pin sockets  133   a  and  133   b , respectively, in the situations in which it is desirable to move tower  102  between tilted positions. 
     In the extended condition, angle pin actuator  140  extends between angle pin mounting blocks  146   a  and  146   b , and extends through angle pin mounting block openings  147   a  and  147   b . In particular, angle pins  141   a  and  141   b  extend through angle pin mounting block openings  147   a  and  147   b , respectively. 
     Further, in the extended condition, angle pin actuator  140  extends between tower brackets  116   a  and  116   b , and extends through tower bracket intermediate openings  191   a  and  191   b . In particular, angle pins  141   a  and  141   b  extend through tower bracket intermediate openings  191   a  and  191   b , respectively. 
     In the extended condition, angle pin actuator  140  extends through angle bracket arms  135   a  and  135   b . In particular, angle pins  141   a  and  141   b  extend through angle pin sockets  126   a  and  126   b , respectively. In the extended condition, angle pin actuator  140  extends through angle pin sockets  126   a  and  126   b  so that tower  102  is held in the upright position. 
     As mentioned above, angle pin actuator  140  is repeatably moveable between the extended and retracted conditions. Angle pin  141   a  moves away from angle bracket arm  135   a  and angle pin socket  126   a  in response to angle pin actuator  140  moving to the retracted condition. Further, angle pin  141   b  moves away from angle bracket arm  135   b  and angle pin socket  126   b  in response to angle pin actuator  140  moving to the retracted condition. Angle pin  141   a  moves towards angle bracket arm  135   a  and angle pin socket  126   a  in response to angle pin actuator  140  moving to the extended condition. Further, angle pin  141   b  moves towards angle bracket arm  135   b  and angle pin socket  126   b  in response to angle pin actuator  140  moving to the extended condition. Hence, angle pins  141   a  and  141   b  are repeatably moveable towards and away from angle bracket arm  135   a  and  135   b  in response to moving angle pin actuator  140  between extended and retracted conditions, respectively. Further, angle pins  141   a  and  141   b  are repeatably moveable towards and away from angle pin sockets  126   b  and  126   b  in response to moving angle pin actuator  140  between extended and retracted conditions, respectively. 
       FIGS. 8   a  and  8   b  are side views of angle bracket assembly  120   a , and  FIGS. 8   c  and  8   d  are side views of angle bracket assembly  120   b . In this embodiment, angle pin sockets  125   a  include seven angle pin sockets, denoted as angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a ,  131   a , and  132   a . Angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a ,  131   a , and  132   a  extend through angle bracket  121   a  and along the length of angle bracket  121   a  and away from support arm socket  134   a . Further, angle pin sockets  125   b  include seven angle pin sockets, denoted as angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b ,  131   b , and  132   b . Angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b ,  131   b , and  132   b  extend through angle bracket  121   b  and along the length of angle bracket  121   b  and away from support arm socket  134   b . In general, the number of angle pin sockets extending through angle brackets  121   a  and  121   b  is the same. 
     In this embodiment, angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a ,  131   a , and  132   a  are spaced apart from each other so that they are at predetermined positions along angle bracket arm  135   a . The predetermined positions of angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a ,  131   a , and  132   a  are chosen so that reference planes extend at predetermined angles through pivot pin socket  133   a  and angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a ,  131   a , and  132   a , wherein, in this embodiment, the predetermined angle is relative to reference line  110 . It should be noted that angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a ,  131   a , and  132   a  are equidistantly spaced apart from each other in this embodiment. However, the spacing between adjacent angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a ,  131   a , and  132   a  can be different, if desired. 
     In this embodiment, angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b ,  131   b , and  132   b  are spaced apart from each other so that they are at predetermined positions along angle bracket arm  135   b . The predetermined positions of angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b ,  131   b , and  132   b  are chosen so that reference planes extend at predetermined angles through pivot pin socket  133   b  and angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b ,  131   b , and  132   b , wherein, in this embodiment, the predetermined angle is relative to reference line  110 . It should be noted that angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b ,  131   b , and  132   b  are equidistantly spaced apart from each other in this embodiment. However, the spacing between adjacent angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b ,  131   b , and  132   b  can be different, if desired. Further, it should be noted that angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b ,  131   b , and  132   b  oppose angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a ,  131   a , and  132   a , respectively. 
       FIG. 8   e  is a perspective view of tower interface assembly  118  and the reference planes mentioned above. As shown in  FIGS. 1   a ,  1   b  and  1   c , reference line  110  extends between angle pin socket  126   a  and pivot pin socket  133   a  along the length of angle bracket support leg  122   a . Further, reference line  110  extends between angle pin socket  126   b  and pivot pin socket  133   b  along the length of angle bracket support leg  122   b.    
     As shown in  FIG. 8   e , a reference plane  200  extends between angle pin sockets  126   a  and  126   b  and pivot pin sockets  133   a  and  133   b  at angle θ 0  relative to reference line  110 , wherein angle θ 0  is about 0° in this example. It should be noted that reference plane  200  extends perpendicular to reference line  111  of  FIGS. 1   a ,  1   b  and  1   c .  FIGS. 9   a  and  9   b  are perspective views of tower  102  held at an angle of about 0° by tower interface assembly  118 . It should be noted that, in  FIGS. 9   a  and  9   b , angle pins  141   a  and  141   b  extend through angle pin sockets  126   a  and  126   b , respectively. 
     A reference plane  201  extends between angle pin sockets  127   a  and  127   b  and pivot pin sockets  133   a  and  133   b  at an angle θ 5  relative to reference line  110 , wherein angle θ 5  is about 5° in this example. A reference plane  202  extends between angle pin sockets  128   a  and  128   b  and pivot pin sockets  133   a  and  133   b  at an angle θ 10  relative to reference line  110 , wherein angle θ 10  is about 10° in this example. 
     A reference plane  203  extends between angle pin sockets  129   a  and  129   b  and pivot pin sockets  133   a  and  133   b  at an angle θ 15  relative to reference line  110 , wherein angle θ 15  is about 15° in this example.  FIGS. 9   c  and  9   d  are perspective views of tower  102  held at an angle of about 15° by tower interface assembly  118 . It should be noted that, in  FIGS. 9   c  and  9   d , angle pins  141   a  and  141   b  extend through angle pin sockets  129   a  and  129   b , respectively. 
     A reference plane  204  extends between angle pin sockets  130   a  and  130   b  and pivot pin sockets  133   a  and  133   b  at an angle θ 20  relative to reference line  110 , wherein angle θ 20  is about 20° in this example. A reference plane  205  extends between angle pin sockets  131   a  and  131   b  and pivot pin sockets  133   a  and  133   b  at an angle θ 25  relative to reference line  110 , wherein angle θ 25  is about 25° in this example. 
     A reference plane  206  extends between angle pin sockets  132   a  and  132   b  and pivot pin sockets  133   a  and  133   b  at an angle θ 30  relative to reference line  110 , wherein angle θ 30  is about 30° in this example.  FIGS. 9   e ,  9   f  and  9   g  are perspective views of tower  102  held at an angle of about 30° by tower interface assembly  118 . It should be noted that, in  FIGS. 9   e ,  9   f  and  9   g , angle pins  141   a  and  141   b  extend through angle pin sockets  132   a  and  132   b , respectively. In this way, the angle pin sockets that extend through angle bracket arms  135   a  and  135   b  are spaced apart from each other at positions which correspond to predetermined angles relative to reference line  110 . 
     It should be noted that angle pin socket  132   a  is rearward of angle pin sockets  126   a ,  127   a ,  128   a ,  129   a ,  130   a  and  131   a  because angle θ 30  is greater than angles θ 0 , θ 5 , θ 10 , θ 15 , θ 20 , and θ 25 . Further, angle pin socket  131   a  is rearward of angle pin sockets  126   a ,  127   a ,  128   a ,  129   a  and  130   a  because angle θ 25  is greater than angles θ 0 , θ 5 , θ 10 , θ 15  and θ 20 . Angle pin socket  130   a  is rearward of angle pin sockets  126   a ,  127   a ,  128   a  and  129   ab  because angle θ 20  is greater than angles θ 0 , θ 5 , θ 10  and θ 15 . Angle pin socket  129   a  is rearward of angle pin sockets  126   a ,  127   a  and  128   a  because angle θ 15  is greater than angles θ 0 , θ 5  and θ 10 . Angle pin socket  128   a  is rearward of angle pin sockets  126   a  and  127   a  because angle θ 10  is greater than angles θ 0  and θ 5 . Angle pin socket  127   a  is rearward of angle pin socket  126   a  because angle θ 5  is greater than angles θ 0 . 
     It should be noted that angle pin socket  132   b  is rearward of angle pin sockets  126   b ,  127   b ,  128   b ,  129   b ,  130   b  and  131   b  because angle θ 30  is greater than angles θ 0 , θ 5 , θ 10 , θ 15 , θ 20 , and θ 25 . Further, angle pin socket  131   b  is rearward of angle pin sockets  126   b ,  127   b ,  128   b ,  129   b  and  130   b  because angle θ 25  is greater than angles θ 0 , θ 5 , θ 10 , θ 15  and θ 20 . Angle pin socket  130   b  is rearward of angle pin sockets  126   b ,  127   b ,  128   b  and  129   b  because angle θ 20  is greater than angles θ 0 , θ 5 , θ 10  and θ 15 . Angle pin socket  129   b  is rearward of angle pin sockets  126   b ,  127   b  and  128   b  because angle θ 15  is greater than angles θ 0 , θ 5  and θ 10 . Angle pin socket  128   b  is rearward of angle pin sockets  126   b  and  127   b  because angle θ 10  is greater than angles θ 0  and θ 5 . Angle pin socket  127   b  is rearward of angle pin socket  126   b  because angle θ 5  is greater than angles θ 0 . 
     As mentioned above, reference line  112  ( FIGS. 1   a ,  1   b  and  1   c  and  FIGS. 9   c  and  9   d ) extends parallel to tower  102 . Hence, tower  102  extends angle θ 0  relative to reference line  110  and reference line  112  extends through reference plane  200  when tower  102  is in the raised position and angle pin actuator  140  extends through angle pin sockets  126   a  and  126   b . In particular, tower  102  extends at angle θ 0  relative to reference line  110  and reference line  112  extends through reference plane  200  when tower  102  is in the raised position and angle pins  141   a  and  141   b  extend through angle pin sockets  126   a  and  126   b , respectively. 
     Tower  102  extends at angle θ 5  relative to reference line  110  and reference line  112  extends through reference plane  201  when tower  102  is in the tilted position and angle pin actuator  140  extends through angle pin sockets  127   a  and  127   b . In particular, tower  102  extends at angle θ 5  relative to reference line  110  and reference line  112  extends through reference plane  201  when tower  102  is in the tilted position and angle pins  141   a  and  141   b  extend through angle pin sockets  127   a  and  127   b , respectively. 
     Tower  102  extends at angle θ 10  relative to reference line  110  and reference line  112  extends through reference plane  202  when tower  102  is in the tilted position and angle pin actuator  140  extends through angle pin sockets  128   a  and  128   b . In particular, tower  102  extends at angle θ 10  relative to reference line  110  and reference line  112  extends through reference plane  202  when tower  102  is in the tilted position and angle pins  141   a  and  141   b  extend through angle pin sockets  128   a  and  128   b , respectively. 
     Tower  102  extends at angle θ 15  ( FIGS. 9   c  and  9   d ) relative to reference line  110  and reference line  112  extends through reference plane  203  when tower  102  is in the tilted position and angle pin actuator  140  extends through angle pin sockets  129   a  and  129   b . In particular, tower  102  extends at angle θ 15  relative to reference line  110  and reference line  112  extends through reference plane  203  when tower  102  is in the tilted position and angle pins  141   a  and  141   b  extend through angle pin sockets  129   a  and  129   b , respectively. 
     Tower  102  extends at angle θ 20  relative to reference line  110  and reference line  112  extends through reference plane  204  when tower  102  is in the tilted position and angle pin actuator  140  extends through angle pin sockets  130   a  and  130   b . In particular, tower  102  extends at angle θ 20  relative to reference line  110  and reference line  112  extends through reference plane  204  when tower  102  is in the tilted position and angle pins  141   a  and  141   b  extend through angle pin sockets  130   a  and  130   b , respectively. 
     Tower  102  extends at angle θ 25  relative to reference line  110  and reference line  112  extends through reference plane  205  when tower  102  is in the tilted position and angle pin actuator  140  extends through angle pin sockets  131   a  and  131   b . In particular, tower  102  extends at angle θ 25  relative to reference line  110  and reference line  112  extends through reference plane  205  when tower  102  is in the tilted position and angle pins  141   a  and  141   b  extend through angle pin sockets  131   a  and  131   b , respectively. 
     Tower  102  extends at angle θ 30  ( FIGS. 9   e ,  9   f  and  9   g ) relative to reference line  110  and reference line  112  extends through reference plane  206  when tower  102  is in the tilted position and angle pin actuator  140  extends through angle pin sockets  132   a  and  132   b . In particular, tower  102  extends at angle θ 30  relative to reference line  110  and reference line  112  extends through reference plane  206  when tower  102  is in the tilted position and angle pins  141   a  and  141   b  extend through angle pin sockets  132   a  and  132   b , respectively. 
     Reference line  112  extends at angle θ 90  relative to reference line  110  and reference line  112  extends parallel to reference line  111  ( FIGS. 1   a ,  1   b  and  1   c ) when tower  102  is in the lowered position. As mentioned above, when tower  102  is in the lowered position, pivot pin actuator  150  is in the retracted condition and does not extend through pivot pin sockets  133   a  and  133   b . In particular, when tower  102  is in the lowered position, pivot pin actuator  150  is in the retracted condition and pivot pins  151   a  and  151   b  do not extend through pivot pin sockets  133   a  and  133   b , respectively. However, angle pin actuator  140  does extend through angle pin sockets  126   a  and  126   b  so that tower  102  can be moved between the raised and lowered positions. Hence, tower  102  is rotatably mounted to tower interface assembly  118  through angle pin actuator  140  when tower  102  is moved to and from the stowed condition. In particular, tower  102  is rotatably mounted to tower interface assembly  118  through angle pins  141   a  and  141   b  when tower  102  is moved to and from the stowed condition ( FIG. 1   a ). In this embodiment, angle pins  141   a  and  141   b  extend through angle pin sockets  126   a  and  126   b , respectively, when tower  102  is moved to and from the stowed condition. 
       FIGS. 10   a ,  10   b  and  10   c  are side views of other embodiments of angle bracket arms which can be included with drilling machine  100 . In  FIG. 10   a , an angle bracket arm  135  includes a number N of angle bracket sockets so that a corresponding number of discrete angles are available. As number N increases, the number of discrete angles available increases and, as number N decreases, the number of discrete angles available decreases. In general, the number of discrete angles available range from 0° to 90°. In this way, the angles available for tower  102  to be tilted correspond to N discrete angular values. It should be noted, however, that the angles can be negative angles wherein tower  102  tilts towards cab  105  and vehicle front  101   a.    
     The number N can have many different values. In one embodiment, the number N has values in a range from two to about ten. In another embodiment, the number N has values in a range from two to about fifteen. In one particular example, N is equal to two. It should be noted, however, that the number N can have values outside of these ranges in other embodiments. 
     In  FIG. 10   b , angle bracket arm  135   a  includes a number of angle bracket sockets which corresponds to seven. More information regarding angle bracket arm  135   a  is provided above with the discussion of tower interface assembly  118 . In the embodiment of  FIG. 10   b , the available angles that tower  102  can be tilted correspond to angle values equal to 0° and 30°, as well as values therebetween that are at 5° increments (i.e. 5°, 10°, 15°, 20°, 25°). In this way, the angles available for tower  102  to be positioned correspond to seven discrete angular values. It should be noted, however, that the angles can have other discrete angular values, and these discrete values can be greater than 30°. 
     In  FIG. 10   c , an angle bracket arm  135   d  includes a number of angle bracket sockets which corresponds to three. In the embodiment of  FIG. 10   c , the available angles that tower  102  can be tilted correspond to angle values equal to 0° and 30°, as well as values therebetween that are at 15° increments. In this way, the angles available for tower  102  to be positioned correspond to three discrete angular values, as will be discussed in more detail presently. 
       FIGS. 11   a  and  11   b  are side views of angle bracket assemblies  120   d  and  120   e , respectively, which include angle bracket arms  135   d  and  135   e , respectively. More information regarding angle bracket arm  125   d  is provided with  FIG. 10   c  above. It should be noted that, in this embodiment, angle bracket arm  135   e  is the same as angle bracket arm  135   d . Hence, for angle brackets  135   d  and  135   e , N is equal to three so that angle bracket arms  135   d  and  135   e  each include three angle pin sockets. The angle pin sockets of angle bracket arms  135   d  and  135   e  are positioned so they oppose each other. 
     In this embodiment, the angle pin sockets of angle bracket arm  135   d  are denoted as angle pin sockets  126   a ,  129   a , and  132   a . Further, the angle pin sockets of angle bracket arm  135   e  are denoted as angle pin sockets  126   b ,  129   b , and  132   b.    
     In this embodiment, angle pin sockets  126   a ,  129   a , and  132   a  are spaced apart from each other so that they are at predetermined positions along angle bracket arm  135   d . The predetermined positions of angle pin sockets  126   a ,  129   a , and  132   a  are chosen so that reference planes extend at predetermined angles through pivot pin socket  133   a  and angle pin sockets  126   a ,  129   a , and  132   a , wherein, in this embodiment, the predetermined angle is relative to reference line  110 . It should be noted that angle pin sockets  126   a ,  129   a , and  132   a  are equidistantly spaced apart from each other in this embodiment. However, the spacing between adjacent angle pin sockets  126   a ,  129   a , and  132   a  can be different, if desired. 
     In this embodiment, angle pin sockets  126   b ,  129   b , and  132   b  are spaced apart from each other so that they are at predetermined positions along angle bracket arm  135   b . The predetermined positions of angle pin sockets  126   b ,  129   b , and  132   b  are chosen so that reference planes extend at predetermined angles through pivot pin socket  133   b  and angle pin sockets  126   b ,  129   b , and  132   b , wherein, in this embodiment, the predetermined angle is relative to reference line  110 . It should be noted that angle pin sockets  126   b ,  129   b , and  132   b  are equidistantly spaced apart from each other in this embodiment. However, the spacing between adjacent angle pin sockets  126   b ,  129   b , and  132   b  can be different, if desired. Further, it should be noted that angle pin sockets angle pin sockets  126   b ,  129   b , and  132   b  oppose angle pin sockets angle pin sockets  126   a ,  129   a , and  132   a , respectively. 
       FIG. 11   c  is a perspective view of tower interface assembly  118   a , which includes angle bracket assemblies  120   d  and  120   e  and the reference planes mentioned above with the discussion of  FIGS. 11   a  and  11   b . As shown in  FIG. 11   c , reference plane  200  extends between angle pin sockets  126   a  and  126   b  and pivot pin sockets  133   a  and  133   b  at angle θ 0  relative to reference line  110 , wherein angle θ 0  is about 0° in this example. 
     Reference plane  203  extends between angle pin sockets  129   a  and  129   b  and pivot pin sockets  133   a  and  133   b  at an angle θ 15  relative to reference line  110 , wherein angle θ 15  is about 15° in this example. Further, reference plane  206  extends between angle pin sockets  132   a  and  132   b  and pivot pin sockets  133   a  and  133   b  at an angle θ 30  relative to reference line  110 , wherein angle θ 30  is about 30° in this example. In this way, the angle pin sockets that extend through angle bracket arms  135   d  and  135   e  are spaced apart from each other at positions which correspond to predetermined angles relative to reference line  110 . 
     As mentioned above, reference line  112  ( FIGS. 1   a ,  1   b  and  1   c ) extends parallel to tower  102 . Hence, tower  102  extends angle θ 0  relative to reference line  110  and reference line  112  extends through reference plane  200  when tower  102  is in the raised position and angle pin actuator  140  extends through angle pin sockets  126   a  and  126   b . In particular, tower  102  extends at angle θ 0  relative to reference line  110  and reference line  112  extends through reference plane  200  when tower  102  is in the raised position and angle pins  141   a  and  141   b  extend through angle pin sockets  126   a  and  126   b , respectively. 
     Tower  102  extends at angle θ 15  relative to reference line  110  and reference line  112  extends through reference plane  203  when tower  102  is in the tilted position and angle pin actuator  140  extends through angle pin sockets  129   a  and  129   b . In particular, tower  102  extends at angle θ 15  relative to reference line  110  and reference line  112  extends through reference plane  203  when tower  102  is in the tilted position and angle pins  141   a  and  141   b  extend through angle pin sockets  129   a  and  129   b , respectively. 
     Tower  102  extends at angle θ 30  relative to reference line  110  and reference line  112  extends through reference plane  206  when tower  102  is in the tilted position and angle pin actuator  140  extends through angle pin sockets  132   a  and  132   b . In particular, tower  102  extends at angle θ 30  relative to reference line  110  and reference line  112  extends through reference plane  206  when tower  102  is in the tilted position and angle pins  141   a  and  141   b  extend through angle pin sockets  132   a  and  132   b , respectively. 
     The embodiments of the invention described herein are exemplary and numerous modifications, variations and rearrangements can be readily envisioned to achieve substantially equivalent results, all of which are intended to be embraced within the spirit and scope of the invention.