Abstract:
This disclosure relates to operating table top assemblies and related devices. In some aspects, an operating table top coupling assembly includes a receiver assembly and a hook assembly. The receiver assembly includes first and second spaced walls that define a central recess therebetween. The hook assembly includes an elongate hook member attached to or integrally formed with a housing that is configured to be at least partially disposed within the central recess of the receiver assembly.

Description:
TECHNICAL FIELD 
     This disclosure relates to operating table top assemblies and related devices. 
     BACKGROUND 
     Operating tables are used to support patients during surgical procedures. Some operating tables are modular systems that include multiple different table top components that can be releasably coupled to one another. The components can be coupled together in a manner to provide an operating table top configuration that meets the demands of a particular surgical procedure to be performed. 
     SUMMARY 
     In one aspect of the invention, an operating table top assembly includes a first table top component, a receiver assembly attached to or integrally formed with the first table top component, a second table top component, and a hook assembly attached to or integrally formed with the second table top component. The receiver assembly includes first and second spaced walls that define a central recess therebetween. The first wall has an outer side surface and a projection that extends laterally from the outer side surface. The projection defines an undercut. The hook assembly includes an elongate hook member attached to or integrally formed with a housing. The hook member has a tip portion. The housing is configured to be at least partially disposed within the central recess of the receiver assembly, and the tip portion of the hook member is configured to matingly engage the undercut defined by the projection of the receiver assembly. The housing of the hook assembly is at least partially disposed within the central recess of the receiver assembly when the first table top component is coupled to the second table top component, and the tip portion of the hook member of the hook assembly matingly engages the undercut defined by the projection of the receiver assembly when the first table top component is coupled to the second table top component. 
     In another aspect of the invention, an operating table includes a central column and an operating table top assembly that includes a first table top component mounted on the central column, a receiver assembly attached to or integrally formed with the first table top component, a second table top component that can be coupled to the first table top component, and a hook assembly attached to or integrally formed with the second table top component. The receiver assembly includes first and second spaced walls that define a central recess therebetween. The first wall has an outer side surface and a projection that extends laterally from the outer side surface. The projection defines an undercut. The hook assembly includes an elongate hook member attached to or integrally formed with a housing. The hook member has a tip portion. The housing is configured to be at least partially disposed within the central recess of the receiver assembly, and the tip portion of the hook member is configured to matingly engage the undercut defined by the projection of the receiver assembly. The housing of the hook assembly is at least partially disposed within the central recess of the receiver assembly when the first table top component is coupled to the second table top component, and the tip portion of the hook member of the hook assembly matingly engages the undercut defined by the projection of the receiver assembly when the first table top component is coupled to the second table top component. 
     In an additional aspect of the invention, an operating table top coupling device includes a receiver assembly including first and second spaced walls that define a central recess therebetween. The first wall has an outer side surface and a projection that extends laterally from the outer side surface. The projection defines an undercut. The operating table coupling device also includes a hook assembly including an elongate hook member attached to or integrally formed with a housing. The hook member has a tip portion. The housing is configured to be at least partially disposed within the central recess of the receiver assembly, and the tip portion of the hook member is configured to matingly engage the undercut defined by the projection of the receiver assembly. 
     In a further aspect of the invention, an operating table top coupling device includes a receiver assembly including first and second spaced walls that define a central recess therebetween. The first wall has an outer side surface and a projection that extends laterally from the outer side surface. The projection defines an undercut. The central recess is configured to receive at least a portion of a housing of a hook assembly when the hook assembly is coupled to the receiver assembly, and the undercut is configured to matingly engage a tip portion of a hook member of the hook assembly when the hook assembly is coupled to the receiver assembly. 
     In an additional aspect of the invention, an operating table top coupling device includes a hook assembly including an elongate hook member attached to or integrally formed with a housing. The hook member has a tip portion. The housing is configured to be at least partially disposed within a central recess of a receiver assembly when the hook assembly is coupled to the receiver assembly, and the tip portion of the hook member is configured to matingly engage an undercut defined by a projection of the receiver assembly when the hook assembly is coupled to the receiver assembly. 
     In another aspect of the invention, an operating table top assembly includes a first table top component, a first coupling member attached to or integrally formed with the first table top component, a second table top component, and a second coupling member attached to or integrally formed with the second table top component. The first coupling member includes first and second spaced walls that define a central recess therebetween. One of the first and second walls defines an aperture. The second coupling member is configured to matingly engage the first coupling member in a manner to couple the first table top component to the second table top component. The second coupling member includes a housing configured to be at least partially disposed within the central recess of the first coupling member, a spring-loaded member that can be moved between an extended position in which the spring-loaded member extends from a side surface of the housing and a retracted position in which the spring-loaded member is retracted into the housing, an actuator that is operably connected to the spring loaded member in a manner such that movement of the actuator can move the spring-loaded member from the extended position to the retracted position, and a locking mechanism configured to retain the spring-loaded member in the retracted position when the housing of the second coupling member is matingly engaged with the first coupling member such that the housing of the second coupling member is at least partially disposed within the central recess of the first coupling member. 
     In a further aspect of the invention, an operating table includes a central column and an operating table top assembly including a first table top component mounted on the central column, a first coupling member attached to or integrally formed with the first table top component, a second table top component, and a second coupling member attached to or integrally formed with the second table top component. The first coupling member includes first and second spaced walls that define a central recess therebetween. One of the first and second walls defines an aperture. The second coupling member is configured to matingly engage the first coupling member in a manner to couple the first table top component to the second table top component. The second coupling member includes a housing configured to be at least partially disposed within the central recess of the first coupling member, a spring-loaded member that can be moved between an extended position in which the spring-loaded member extends from a side surface of the housing and a retracted position in which the spring-loaded member is retracted into the housing, an actuator that is operably connected to the spring loaded member in a manner such that movement of the actuator can move the spring-loaded member from the extended position to the retracted position, and a locking mechanism configured to retain the spring-loaded member in the retracted position when the housing of the second coupling member is matingly engaged with the first coupling member such that the housing of the second coupling member is at least partially disposed within the central recess of the first coupling member. 
     In yet another aspect of the invention, an operating table top coupling device includes a housing, an elongate hook member attached to or integrally formed with the housing, a spring-loaded member that can be moved between an extended position in which the spring-loaded member extends from a side surface of the housing and a retracted position in which the spring-loaded member is retracted into the housing, an actuator that is operably connected to the spring loaded member in a manner such that movement of the actuator can move the spring-loaded member from the extended position to the retracted position, and a locking mechanism configured to retain the spring-loaded member in the retracted position when the operating table top coupling member is matingly engaged with an associated operating table top coupling member. 
     Embodiments can include one or more of the following features. 
     In some embodiments, the first wall is positioned outwardly of the second wall relative to the first table top component, and the hook assembly is configured such that the hook member extends along the outer side surface of the first wall of the receiver assembly when the first table top component is coupled to the second table top component. 
     In certain embodiments, the hook member of the hook assembly and the lateral projection of the receiver assembly are visible along a side surface of the operating table top such that a user can visually determine whether the tip portion of the hook member is matingly engaged with the undercut defined by the projection of the receiver assembly. 
     In some embodiments, a width of the central recess of the receiver assembly is no more than about 1.5 mm greater than a width of the housing of the hook assembly. 
     In certain embodiments, a gap is formed between a portion of the housing and the hook member of the hook assembly, and the gap is configured to receive a portion of the second wall of the receiver assembly when the first table top component is coupled to the second table top component. 
     In some embodiments, the hook member is attached to or integrally formed with a side wall extension of the housing, and the gap is adjacent the side wall extension. 
     In certain embodiments, a width of the gap is no more than about 1.0 mm greater than a width of the portion of the second wall of the receiver assembly. 
     In some embodiments, the hook assembly further includes a spring-loaded member that can be moved between an extended position in which the spring-loaded member extends from a side surface of the housing and a retracted position in which the spring-loaded member is retracted into the housing, and one of the first and second walls of the receiver assembly defines an aperture configured to receive a portion of the spring-loaded member when the spring-loaded member is in the extended position. 
     In certain embodiments, the spring-loaded member is completely retracted into the housing when the spring-loaded member is in the retracted position. 
     In some embodiments, the second wall of the receiver assembly defines the aperture. 
     In certain embodiments, the second wall is positioned inwardly of the first wall relative to the first table top component. 
     In some embodiments, the spring loaded-member is a spring-loaded pin. 
     In certain embodiments, the hook assembly further includes an actuator assembly having an actuator that is operably connected to the spring loaded member in a manner such that movement of the actuator can move the spring-loaded member from the extended position to the retracted position. 
     In some embodiments, the hook assembly further includes a locking mechanism that retains the spring-loaded member in the retracted position while the housing of the hook assembly is at least partially disposed within the central recess of the receiver assembly. 
     In certain embodiments, the locking mechanism includes a ball spring that engages a surface of the spring-loaded member while the housing of the hook assembly is at least partially disposed within the central recess of the receiver assembly and the spring-loaded member is retracted. 
     In some embodiments, the ball spring engages a surface of a tab extending from the spring-loaded member. 
     In certain embodiments, the ball spring engages a depression formed in a surface of the spring-loaded member. 
     In some embodiments, the ball spring protrudes from a bottom surface of the housing and contacts an upper surface of a third wall extending between the first and second walls of the receiver assembly while the housing of the hook assembly is at least partially disposed within the central recess of the receiver assembly. 
     In certain embodiments, the one of the first and second walls of the receiver assembly that defines the aperture configured to receive the portion of the spring-loaded member has a ramp portion arranged to depress the spring-loaded member as the housing of the hook assembly is slid into the central recess of the receiver assembly. 
     In some embodiments, the receiver assembly further includes a third wall that extends between the first and second walls and that defines an opening configured to receive a boss extending from the housing. 
     In certain embodiments, the opening is configured to receive only bosses of hook assemblies attached to or integrally formed with second table top components that are intended for use with the first table top component to which the receiver assembly is attached. 
     In some embodiments, the tip portion of the hook member is located at a first end region of the hook member, and the hook member includes a lobe extending from a central region of the hook member. The projection of the receiver assembly further defines a depression configured to receive the lobe when the first table top component is coupled to the second table top component. 
     In certain embodiments, the receiver assembly is attached to or integrally formed with a first side region of the first table top component and the hook assembly is attached to or integrally formed with a first side region of the second table top component. 
     In some embodiments, the operating table top assembly further includes a second receiver assembly attached to or integrally formed with a second side region of the first table top component and a second hook assembly attached a second side region of the second table top component. The second hook assembly is configured to releasably engage the second receiver assembly when the first table top component is coupled to the second table top component. 
     In certain embodiments, the receiver assembly is attached to or integrally formed with a first end region of the first table top component. 
     In some embodiments, the operating table top assembly further includes a second receiver assembly attached to or integrally formed with a second end region of the first table top component. The first end region is opposite the second end region. 
     In certain embodiments, the second receiver assembly is configured to releasably engage a hook assembly attached to or integrally formed with a third table top component when the third table top component is coupled to the first table top component. 
     In some embodiments, the hook assembly is attached to or integrally formed with a first end region of the second table top component, and a receiver assembly is attached to or integrally formed with a second end region of the second table top component. The first end region is opposite the first end region. 
     In certain embodiments, the receiver assembly attached to or integrally formed with the second end region of the second table top component is configured to releasably engage a hook assembly attached to or integrally formed with a third table top component when the third table top component is coupled to the second table top component. 
     In some embodiments, the first table top component is configured to mount on a column of an operating table. 
     In certain embodiments, the second table top component is mounted to a first end region of the first table top component and a third table top component is mounted to a second end region of the first table top component. The first end region is opposite the second end region. 
     In some embodiments, the first table top component is a seat and back component, the second table top component is a head component, and the second table top component is a leg component. 
     In certain embodiments, the locking mechanism includes a ball spring that engages a surface of the spring-loaded member while the housing of the second coupling member is at least partially disposed within the central recess of the first coupling member and the spring-loaded member is retracted. 
     In some embodiments, the ball spring engages a surface of a tab extending from the spring-loaded member. 
     In certain embodiments, the ball spring engages a depression formed in a surface of the spring-loaded member. 
     In some embodiments, the ball spring protrudes from a bottom surface of the housing and is arranged to contact a wall of the associated operating table top coupling member when the operating table top coupling member is matingly engaged with the associated operating table top coupling member. 
     In certain embodiments, the spring-loaded member is completely retracted into the housing when the spring-loaded member is in the retracted position. 
     In some embodiments, the spring loaded-member is a spring-loaded pin. 
     In certain embodiments, the operating table top coupling device further includes a receiver assembly having a side wall forming an aperture configured to receive a portion of the spring-loaded member when the hook assembly is coupled to the receiver assembly and the spring-loaded member is in the extended position. 
     Embodiments can include one or more of the following advantages. 
     In some embodiments, the hook member of the hook assembly is positioned outwardly of the outer side surface of the receiver assembly when the hook assembly and receiver assembly are engaged. This can provide the surgeon and surgical staff with clear visualization of the mated features of the hook and the projection extending from the outer wall of the receiver assembly. As a result, the surgeon and surgical staff can readily determine visually whether the hook assembly and receiver assembly are properly engaged. 
     In certain embodiments, the hook member extends forwardly beyond the front edge of the table top component to which the hook assembly is attached and the receiver assembly extends rearwardly beyond the rear edge of the component to which the receiver assembly is attached. As a result of this arrangement, the surgeon or surgical staff member can clearly see the initial contact between the hook member and the receiver assembly when he or she couples the first and second table top components to one another. This can help the surgeon or surgical staff member to ensure that the hook member is properly aligned with the receiver assembly during the initial phases of the coupling process. 
     In some embodiments, the lateral projection of the receiver assembly forms a ramp along which the hook member slides when the hook assembly is being coupled to the receiver assembly. In this way, the lateral projection of the receiver assembly can carry some of the weight of the table top component to which the hook assembly is attached as that table top component is being coupled to the table top component to which the receiver assembly is attached. This can make it easier for the surgeon or surgical staff member to couple the table top components to one another. 
     In certain embodiments, the hook assembly includes a spring-loaded member that can be configured in an extended position in which it engages an aperture in a wall of the receiver assembly in order to secure the hook assembly to the receiver assembly and can be configured in a retracted position in which it does not engage the aperture of the wall of the receiver assembly. The hook assembly can further include a locking mechanism that automatically holds the spring-loaded member in the retracted position when the hook assembly is coupled with the receiver assembly. Locking the spring-loaded member in this way allows the surgeon or surgical staff to decouple the hook assembly from the receiver assembly without having to apply a constant force to hold the spring-loaded member in the retracted position. 
     In some embodiments, the locking mechanism is configured so that once the hook assembly has been removed from the receiver assembly, the locking mechanism will automatically release the spring-loaded member allowing the spring-loaded member to return to its naturally biased extended position. As a result, the hook assembly will be ready for reattachment to the receiver assembly or to a different receiver assembly without the need for the surgeon or surgical staff member to reset the spring-loaded member to its extended position. 
     In some embodiments, the wall of the receiver assembly that contacts the spring-loaded button of the hook assembly during engagement of those assemblies includes a ramped segment that depresses the spring-loaded button into its retracted position. As a result, there is no need for the surgeon or surgical staff member to manually or otherwise retract the spring-loaded member prior to mating the hook assembly with the receiver assembly. This can reduce the time and effort required to couple the hook assembly to the receiver assembly. 
     In certain embodiments, the wall of the receiver assembly that includes the aperture in which the spring-loaded member is received is spaced inwardly from a side edge of the operating table. For example, the receiver assembly can include an outer wall and an inner wall that is inwardly spaced from the outer wall and the side of the operating table and that defines the aperture. Spacing the aperture inwardly from the side of the operating table in this way results in the aperture and the spring-loaded member protruding therefrom being positioned below the operating table. Due to this positioning, the likelihood of the aperture and spring-loaded member being exposed to body fluids and other surgical byproducts that might obstruct the aperture and negatively affect the operability of the spring-loaded member can be reduced. As a result, the reliability and life spans of the receiver assembly and the hook assembly may be increased. 
     In some embodiments, the spring-loaded member of the hook assembly engages the aperture of the wall of the receiver assembly when the hook assembly is coupled to the receiver assembly. This provides a mechanical connection that helps to secure the hook assembly to the receiver assembly. In addition, the tip portion of the hook member matingly engages the undercut of the projection of the receiver assembly when the hook assembly is coupled to the receiver assembly. This also provides a mechanical connection that helps to secure the hook assembly to the receiver assembly. The engagement between the tip portion of the hook member and the undercut of the projection will advantageously provide a secure connection between the hook assembly and the receiver assembly in the event that the spring-loaded member fails to properly engage the aperture. Further, the mechanical engagement resulting from both the engagement between the spring-loaded member and the aperture and the engagement between the tip portion of the hook member and the undercut of its associated projection can occur automatically as part of the coupling process. There is typically no need for the surgeon or surgical staff member to perform an additional locking step, such as tightening a knob, in order to properly secure the hook assembly to the receiver assembly. 
     In certain embodiments, the operating table top assemblies include various different table top components that can be configured in different ways to provide different table top configurations. In such embodiments, the hook assemblies and receiver assemblies of those table top components can use a mechanical coding system to prevent table top components from being connected to other table top components that are not designed to support the loads that would result from that configuration. The coding system can advantageously be provided by the interaction between a boss extending from the housing of the hook assembly and an opening formed in a transverse wall of the receiver assembly. In such cases, the table top components that are capable of bearing large loads include receiver assemblies with large windows, while the table top components that are capable of bearing only small loads include receiver assembly with smaller windows. Similarly, the table top components that are heavy or will produce large loads during use are equipped with hook assemblies that include large bosses, while the table top components that are light or will produce small loads during use are equipped with hook assemblies that include smaller bosses. In this way, the table top components that are light or that will produce small loads during use can be coupled to table top components that are capable of bearing small loads and table top components that are capable of bearing large loads. In contrast, the heavy table top components cannot be coupled to table top components that are only capable of bearing small loads because the boss of the heavy table top component will be too large to fit within the window of the table top component that can only bear small loads. This type of coding system provides an easy way to alert the user that an improper combination of table top components has been selected for use by preventing the corresponding hook assemblies and receiver assemblies of those components from fully engaging during the coupling process. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an operating table that includes a table top assembly formed of multiple table top components that are coupled together by coupling devices. 
         FIG. 2  is an enlarged view of a region of the operating table of  FIG. 1  in which one of the coupling devices couples a head component of the table top assembly to a seat and back component of the table top assembly. 
         FIG. 3  is an inner perspective view (from above) of a hook assembly of the coupling device shown in  FIG. 2 . 
         FIG. 4  is an outer side view of the hook assembly of the coupling device shown in  FIG. 2 . 
         FIG. 5  is an inner perspective view (from above) of the hook assembly of the coupling device shown in  FIG. 2  with a top cover of the housing removed to show certain actuator assembly components within the housing. 
         FIG. 6  is an inner perspective view (from below) of the hook assembly of the coupling device shown in  FIG. 2 . 
         FIG. 7  is an inner perspective view (from below) of the hook assembly of the coupling device shown in  FIG. 2  with a bottom cover of the housing removed to show a locking mechanism within the housing. 
         FIG. 8  is an outer perspective view (from above) of a receiver assembly of the coupling device shown in  FIG. 2 . 
         FIG. 9  is an outer side view of the receiver assembly of the coupling device shown in  FIG. 2 . 
         FIGS. 10 and 11  are outer and inner perspective views, respectively, of the coupling device shown in  FIG. 2 , in a coupled configuration. 
         FIG. 12  is an outer side view of the coupling device shown in  FIG. 2 , in the coupled configuration. 
         FIGS. 13-16  illustrate a method of coupling the head table top component to the seat and back table top component of the operating table of  FIG. 1 . 
         FIG. 17  illustrates an actuator of the hook assembly of the coupling device of  FIG. 2  being depressed to decouple the hook assembly from the receiver assembly. 
         FIG. 18  is an outer side view of a leg component of the table top assembly of the operating table of  FIG. 1 . The leg component includes right and left hook assemblies secured to sides of a top support board. A top pad member of the leg component has been removed. 
         FIG. 19  is an inner perspective view (from below) of the leg component of  FIG. 18 . The right hook assembly, which is normally secured to the right side of the top support board, has been removed to provide an unobstructed view of the left hook assembly. 
         FIG. 20  is an inner perspective view (from above) of the left hook assembly of the leg component of  FIGS. 18 and 19  with a top cover of a housing of the hook assembly removed to expose various components of an actuator assembly. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 1 , an operating table  100  includes a support column  102  that extends from a base  103 . A table top assembly  104  is mounted on the support column  102 . The table top assembly  104  includes a hinged seat and back component  106  mounted on the support column  102 . A head component  108  extends from the top end of the seat and back component  106 , and a leg component  110  extends from the bottom end of the seat and back component  106 . The table top components  106 ,  108 ,  110  each include a pad positioned atop a support board that is secured to a frame. The head component  108  is releasably coupled to the top end of the seat and back component  106  by right and left coupling devices  112 . Similarly, the leg component  110  is releasably coupled to the bottom end of the seat and back component  106  by right and left coupling devices  113 . Matingly engaging features of the coupling devices  112 ,  113  are visible along the sides of the operating table  100  to allow a surgeon or surgical staff member to determine at a glance whether the various table top components are properly coupled together. 
     The left coupling device  112 , which couples the left side of the head component  108  to the seat and back component  106 , is a mirror image of the associated right coupling device  112 . Similarly, the left coupling device  113 , which couples the left side of the leg component  110  to the seat and back component  106 , is a mirror image of the associated right coupling device  113 . Therefore, the right and left coupling devices  112 ,  113  will not be separately described in detail. 
       FIG. 2  is an enlarged view of the coupling device  112  that couples the right side of the seat and back component  106  to the right side of the head component  108 . The coupling device  112  is made up of a receiver assembly  114  that is attached to the frame of the seat and back component  106  and a hook assembly  116  that is attached to the frame of the head component  108 . The receiver and hook assemblies  114 ,  116  can be attached to the frames of their respective table top components  106 ,  108  using various different types of mechanical fasteners (e.g., screws, bolts, rivots, etc.) and/or bonds (e.g., thermal bonds, such as ultrasonic bonds). The hook assembly  116  and the receiver assembly  114  matingly engage one another to releasably secure the head component  108  to the seat and back component  106 . More specifically, as shown in  FIG. 2 , a tip portion  118  of a crook  120  of a hook member  122  of the hook assembly  116  is secured within a notch or undercut  124  formed by a lateral projection  126  of the receiver assembly  114  to secure the hook assembly  116  to the receiver assembly  114  and thereby secure the head component  108  to the seat and back component  106 . A lobe  128  formed in the bottom region of the hook member  122  also engages a depression  130  formed by the lateral projection  126  to further secure the hook assembly  116  to the receiver assembly  114 . As will be described below, the hook assembly  116  also includes a spring-loaded pin that engages an aperture formed in the receiver assembly  114  to secure those assemblies to one another. 
       FIG. 3  is an inner perspective view (from above) of the hook assembly  116  of the coupling device  112  used to secure the right side of the head component  108  to the right side of the seat and back component  106 . As shown in  FIG. 3 , the elongate hook member  122  of the hook assembly  116  is secured to an outer side wall extension  132  of a box-shaped housing  134 . The hook member  122  is typically secured to the housing  134  using bolts. However, other types of mechanical fasteners, such as screws or rivots, can alternatively be used to secure those components together. As a further alternative, certain types of bonds, including thermal bonds (e.g., laser welds), can be used in some cases to secure the hook member to the housing. 
     Referring to both  FIG. 3  and  FIG. 4 , which is an outer side view of the hook assembly  116 , the hook member  122  includes a J-shaped hook portion that extends from a central area of the hook member  122 . The J-shaped hook portion includes a stem-like member  138  that extends from the central area of the hook member  122  and the crook  120 , which extends from the stem-like member  138 . The tip portion  118  of the crook  120  bends back toward the central area of the hook member to form a notch  140 . The lobe  128  extends downwardly from the central area of the hook member  122 . An end region of the hook member  122  opposite the crook  120  is affixed to the frame of the head component  108 . As a result, the hook member  122  is rigidly fixed to the frame of the head component  108  such that the hook member  122  is substantially prevented from moving relative to the frame. Typically, bolts are used to secure the hook member  122  to the frame of the head component  108 . However, other types of mechanical fasteners, such as screws and rivots, can alternatively be used. As a further alternative, certain types of bonds, including thermal bonds (e.g., laser welds), can be used in some cases to secure the hook member to the frame. 
     The hook member  122  is typically sized so that it does not significantly impact the ability of a use to slide accessories on and off a side rail of the table that is adjacent the hook member  122  when the hook assembly  116  is coupled to the receiver assembly  114 . In some embodiment, the hook member has a thickness of about 11 mm. 
     As shown in  FIG. 3 , due to the side wall extension  132  of the housing  134  to which the hook member  122  is attached, a gap  142  is formed between a length of the housing  134  and the central region of the hook member  122 . The gap  142  is sized to receive a wall of the receiver assembly  114  when the hook assembly  116  and the receiver assembly  114  are matingly engaged with one another. As will be discussed below, this arrangement helps to secure the hook assembly  116  laterally with respect to the receiver assembly  114 . 
     Still referring to  FIG. 3 , a spring-loaded pin  144  is partially disposed within the housing  134  and is biased into an extended position in which the pin  144  protrudes inwardly from an inner side surface of the housing  134 . The pin  144  can be pushed into the housing  134  by applying a force to the exposed portion of the pin  144  in an outward direction (i.e., in a direction toward the hook member  122 ). Upon releasing that force, the pin  144  will be urged back towards its extended position. 
     In addition to being depressed by an outward force applied to the pin  144 , the pin  144  can be moved from the extended position to a retracted position and vice versa through operation of an actuator assembly that includes an actuator  146  located on the outer surface of the hook member  122 . As shown in  FIG. 5 , which shows the hook assembly  116  with the top cover of the housing  134  removed, the actuator  146  is attached to a transverse pivotable lever  148  that extends through vertical slots formed in the hook member  122  and the housing  134 . When the actuator  146  is pushed down, the lever  148  pivots about a pin  150  that is fixed to the end wall of the housing  134 . This movement causes the end of the lever  148  to engage the end of a longitudinal pivotable lever  152  that extends generally along the length of the housing  134 . The movement of the end of the transverse lever  148  causes the end of the longitudinal lever  152  to move toward the inner side wall of the housing  134  (i.e., away from the actuator  146 ). As a result, the longitudinal lever  152  is pivoted about a pin  154  that is fixed to and extends downward from the top cover of the housing  134 . The end of the longitudinal lever  152  opposite the end engaged by the transverse lever  148  is in the form of a cam  156  that sits within a channel  158  formed in a block-shaped portion of the spring-loaded pin  144 . Due to this arrangement, as the longitudinal lever  152  is pivoted about the pin  154  by pressing down on the actuator  146 , the spring-loaded pin  144  is retracted into the housing  134 . From this position, the spring-loaded pin  144  can similarly be extended out of the housing  134  by applying an upward force to the actuator  146 . 
     Referring to  FIG. 6 , which is an inner perspective view (from below) of the hook assembly  116 , a ball spring  160  protrudes slightly from a bottom surface of the housing  134 . The ball spring  160  can be pushed into the housing  134  by applying an upward force to the ball spring  160 . When the spring-loaded pin  144  is in the retracted position and the ball spring  160  is pressed into the housing  134 , the ball spring  160  engages the pin  144  in a manner to retain the pin  144  in the retracted position. 
     As shown in  FIG. 7 , which is an inner perspective view (from below) of the hook assembly  116  with the bottom cover of the housing  134  removed, the spring-loaded pin  144  includes a tab or plate  162  that is attached to the block-shaped portion of the pin  144  and extends rearwardly from the pin  144 . As the pin  144  is caused to retract by either applying a downward force to the actuator  146  or by applying an outward force (i.e., a force in the direction of the hook member  122 ) to the pin  144  itself, the tab  162  is caused to slide along the top of the ball spring  160 . Once the tab  162  has passed outwardly beyond the ball spring  160 , the ball spring  160  extends upward and engages the inner side surface of the tab  162 . This contact between the ball spring  160  and the inner side surface of the tab  162  prevents the pin  144 , which is constantly being urged towards its extended position, from moving from its retracted position to its extended position. 
     Referring again to  FIG. 6 , a boss  164  also protrudes from the bottom surface of the housing  134 . The size of the boss  164  depends on the type of table top component to which the hook assembly  116  is attached. For example, table top components that are heavy or will produce large loads during use are equipped with hook assemblies  116  that include large bosses  164 , while table top components that are light or will produce small loads during use are equipped with hook assemblies  116  that include smaller bosses  164 . As will be described below, each of the receiver assemblies  114  includes an opening or window  166  (shown in  FIG. 8 ) arranged to receive the boss  164  of an associated hook assembly  116  when those assemblies are matingly engaged. Receiver assemblies  114  that are attached to table top components that are capable of bearing large loads include large openings  166 , while receiver assemblies that are attached to table top components that are capable of bearing only small loads include small openings  166 . In this way, the table top components that are light or that will only produce small loads during use can be coupled to table top components that are capable of bearing small loads and to table top components that are capable of bearing large loads. In contrast, heavy table top components or table top components that are intended produce large loads during use cannot be coupled to table top components that are only capable of bearing small loads because the bosses  164  of those heavy table top components will be too large to fit within the openings  166  of the table top component that are designed to only bear small loads. Because the hook assembly  116  that is secured to the head component  108  is intended for use with the receiver assembly  114  that is secured to the seat and back component  106 , the boss  164  of the hook assembly  114  illustrated in  FIG. 6  is able to pass through the opening  166  of the receiver assembly  114  shown in  FIG. 8 . 
       FIG. 8  is a top perspective view of the receiver assembly  114 . The receiver assembly  114  includes an inner vertical wall  168 , an outer vertical wall  170 , and a transverse wall  172  that extends between the inner and outer walls  168 ,  170 . The walls  168 ,  170 ,  172  are typically fastened together using bolts. Similarly, bolts are typically used to fasten the inner wall  160  of the receiver assembly  114  to the frame of the seat and back component  106 . However, other types of mechanical fasteners, such as screws and rivots, can alternatively be used. As a further alternative, certain types of bonds, including thermal bonds (e.g., laser welds), can be used in some cases to secure the walls  168 ,  170 ,  172  to one another and/or to secure the inner wall  168  to the frame of the seat and back component  106 . 
     As shown in  FIG. 8 , an end region of the inner wall  168  includes a through-hole  174  that is sized and shaped to receive the spring-loaded pin  144  of the hook assembly  116 . The edges of the inner wall  168  in the region of the leading upper corner of the inner wall  168  are chamfered to form ramps  176 ,  178  that are angled toward the central space between the inner and outer walls  168 ,  170 . These edges can, for example, extend at about 30 degrees to about 60 degrees (e.g., about 45 degrees) relative to the plane in which the inner wall  168  lies. The ramps or angled edges  176 ,  178  of the inner wall  168  apply a force to the spring-loaded pin  144  as the hook assembly  116  is being coupled to the receiver assembly  114 . Due to the geometry of the ramps  176 ,  178 , the ramps  176 ,  178  can gradually depress the spring-loaded pin  144  from its extended position to its retracted position as the spring-loaded pin  144  slides along the ramps  176 ,  178  toward the through-hole  174 . As described below, this allows the spring-loaded pin  144  to become aligned with and extend into the through-hole  174  when the hook assembly  116  is coupled with the receiver assembly  114 . 
     Referring to both  FIG. 8  and  FIG. 9 , which is an outer side view of the receiver assembly  114 , the lateral projection  126  of the receiver assembly  114  extends outwardly from the outer surface of the outer wall  170 . The end region of the lateral projection  126  opposite the transverse wall  172  forms the notch or undercut  124  in which the tip portion  118  of the hook member  122  is received when the hook assembly  116  and the receiver assembly  114  are coupled. The notch  124  is sized and shaped such that the portion of the lateral projection  126  that forms the notch  124  can matingly engage the tip portion  118  of the hook member  122  and thus limit movement of the hook member  122  relative to the receiver assembly  114 . An upper surface of a central region of the lateral projection  126  is curved and can serve as a ramp along which the crook  120  of the hook member  122  slides when the hook assembly  116  is being coupled to the receiver assembly  114 . The end region of the lateral projection  126  opposite the notch  124  includes the lower rounded depression  130  and an upper rounded depression  180 . The upper and lower rounded depressions  130 ,  180  are generally sized and shaped to receive the lobe  128  of the hook assembly  116  when the hook assembly  116  is coupled to the receiver assembly  114 . As will be described in greater detail below, the lobe  180  of the hook assembly  122  can be disposed within the upper depression  180  during an intermediate phase of coupling the hook assembly  116  to the receiver assembly  114  and can be disposed within the lower depression  130  once the coupling process is complete. 
     Typically, the lateral projection  126  is integrally formed with the outer wall  170 . For example, the outer wall  170  and the lateral projection  126  can be die cast, injection molded, or machined from a single plate of material. However, the lateral projection  126  and the outer wall  170  can alternatively be formed as separate components that are secured to one another using mechanical fasteners, such as bolts or screws, or using thermal bonding techniques, such as laser welding. 
     As noted above, the opening or window  166  that receives the boss  164  that extends from the bottom surface of the housing  134  of the hook assembly  116  when the hook assembly  116  is coupled to the receiver assembly  114  is formed in the transverse wall  172 . The size of the opening  166  depends on the type of table top component to which the receiver assembly  114  is attached. Receiver assemblies  114  used on table top components capable of bearing heavy loads will generally have large openings  166 , while receiver assemblies  114  used on table top components capable of bearing only light loads will generally have small openings  166 . This can ensure that hook assemblies  116  that are coupled to heavy table top components or table top components that will be subjected to heavy loads during use (i.e., hook assemblies that have large bosses  164  extending from their housings) can only be coupled to receiver assemblies  114  attached to table top components that are capable of bearing large loads. The large bosses  164  extending from the housings  134  of hook assemblies  116  attached to such heavy table top components would be too large to fit within the small openings  166  in the transverse walls  172  of receiver assemblies  114  that are used with table top components that are only capable of bearing small loads. As discussed above, because the hook assembly  116  that is secured to the head component  108  is intended for use with the receiver assembly  114  that is secured to the seat and back component  106 , the boss  164  of the hook assembly  114  illustrated in  FIG. 6  is able to pass through the opening  166  of the receiver assembly  114  shown in  FIG. 8 . 
     Still referring to  FIG. 8 , the top surface of the transverse wall  172  is configured to contact the ball spring  160  extending from the bottom surface of the housing  134  of the hook assembly  122  to hold the ball spring  160  in a depressed state when the hook assembly  116  is coupled to the receiver assembly  114 . As discussed above, depressing the ball spring  160  in this manner can serve to hold the spring-loaded pin  144  that extends from the side surface of the housing  134  of the hook assembly  116  in its retracted position. Typically, the top surface of the transverse wall  172  has a width w of about 0.31 inch to about 0.75 inch (e.g., about 0.5 inch) to ensure that the transverse wall  172  remains in contact with the ball spring  160  when the hook assembly  116  is coupled to receiver assembly  114 . The front face of the transverse wall  172  also includes lead ins or chamfers  182  along the top of the wall and around the opening  166 . The chamfers  182  can, for example, extend at an angle of about 30 degrees to about 60 degrees (e.g., about 45 degrees) relative to the vertical plane in which the transverse wall  172  lies. The chamfers  182  facilitate alignment of the boss  164  of the hook assembly  116  as the housing  134  of the hook assembly is slid into the space between the inner and outer walls  168 ,  170  during coupling of the hook assembly  116  to the receiver assembly  114 . The chamfers  182  also facilitate depression of the ball spring  160  that extends from the bottom of the housing  134  as the ball spring  160  slides into engagement with the transverse wall  172 . 
       FIGS. 10 and 11  are perspective views of the coupled hook assembly  116  and receiver assembly  114  from the outer side and inner side, respectively, of the coupling device  112 .  FIG. 12  is a side view of the coupling device  112  in the coupled configuration. As shown in  FIGS. 10 and 12 , in this coupled configuration, the tip portion  118  of the crook  120  of the hook member  122  sits within the notch  124  formed by the lateral projection  126  of the receiver assembly  114 , and the lobe  128  of the hook member  122  sits within the lower depression  130  formed by the lateral projection  126 . The mated engagement of the tip portion  118  of the hook member  122  with the notch  124  helps to prevent inadvertent rearward, upward, and downward forces applied to the hook assembly  116  from disengaging the hook assembly  116  from the receiver assembly  114 . Similarly, the engagement of the lobe  128  with the lower depression  130  helps to prevent inadvertent forward forces applied to the hook assembly  116  from disengaging the hook assembly  116  from the receiver assembly  114 . 
     The actuator  146  of the hook assembly  116 , as shown in  FIGS. 10 and 12 , is in its upper position indicating that the spring-loaded pin  144  of the hook assembly  116  is extended into the through-hole  174  formed in the inner wall  168  of the receiver assembly  114  to lock the hook assembly  116  to the receiver assembly  114 .  FIG. 11  shows the spring-loaded pin  144  protruding into the through-hole  174  of the inner wall  168 . 
     As shown in  FIG. 10 , when the hook assembly  116  and the receiver assembly  114  are coupled together, the housing  134  of the hook assembly  116  sits within the central space between the inner and outer walls  168 ,  170  of the receiver assembly. The width of the space between the inner and outer walls  168 ,  170  is typically no more than about 1.5 mm greater than the width of the housing  134 . The space can, for example, be about 0.5 mm to about 1.5 mm wider than the housing  134 . The width of the gap  142  between the housing  134  and the hook member  122  is typically no more than about 1.0 mm greater than the width of the portion of the outer wall  170  of the receiver assembly  114  that fits therein. The gap  124  can, for example, be about 0.25 mm to about 1.0 mm wider than the outer wall  170 . Due to the similar widths of the space between the inner and outer walls  168 ,  170  and the housing  134  and the similar widths of the gap  142  and the outer wall  170 , lateral movement of the hook assembly  116  relative to the receiver assembly  114 , which can, for example, result from a surgeon or surgical staff member bumping into the side of the operating table  100  during a procedure, can be limited to acceptable levels. 
       FIG. 11  shows the boss of the hook assembly disposed within the opening in the transverse wall of the receiver assembly. It is evident that hook assemblies having wider bosses than the boss shown in  FIG. 11  (e.g., hook assemblies attached to heavier table top components) would not fit within the opening of the transverse wall. As a result, those hook assemblies could not be coupled with the receiver assembly because the housings of those hook assemblies would not be able to slide far enough into the space between the inner and outer walls of the receiver assembly to allow the spring-loaded pins of those hook assemblies to penetrate the through-hole in the inner wall and to allow the tip portions of those hook assemblies to matingly engage the notch of the receiver assembly. 
     The various components of the hook assembly  116  and the receiver assembly  114  are typically formed of lightweight materials that are able to withstand the loads that their coupled table top components experience during use. In certain embodiments, for example, the various components of the hook assembly and the receiver assembly are formed of nickel plated aluminum alloy (e.g., 7075-T6 aluminum alloy having a nickel plating on the order of 0.25 mm thick), which is significantly lighter than certain conventional materials, such as stainless steel. By reducing the weight of these components (as compared to similar components formed of certain conventional materials), the overall weight of the head component  108  and the leg component  110  can be reduced. As a result, the surgeon or surgical staff member can more easily hold and maneuver these table top components during the coupling process. 
       FIGS. 13-16  illustrate a method of securing the head component  108  to the seat and back component  106  by coupling the hook assembly  116  of the head component  108  to the receiver assembly  114  of the seat and back component  106 . As shown in  FIG. 13 , to secure the head component  108  to the seat and back component  106 , the head component  108  is grasped by a surgical staff member and moved toward the seat and back component  106 . Because the hook assembly  116  extends beyond the frame and the pad of the head component  108  (toward the seat and back component  106 ), the hook member  122  can be seen from above by the surgical staff member that is grasping the head component  108 . Additionally, the receiver assembly  114  extends beyond the frame and the pad of the seat and back component  106  (toward the head component  108 ) such that the receiver assembly  114  can also be seen from above by the surgical staff member. The surgical staff member aligns the hook assembly  116  with the receiver assembly  114  as he or she moves the head component  108  toward the seat and back component  106 . The portions of the hook and receiver assemblies  116 ,  114  that extend beyond their respective table top components make it easier for the surgical staff member to align the hook assembly  116  with the receiver assembly  114 . 
     The surgical staff member continues to advance the head component  108  toward the seat and back component  106  until the crook  120  of the hook member  122  of the hook assembly  116  comes into contact with the central region of the lateral projection  126  of the receiver assembly  114 , as shown in  FIG. 14 . Due to this contact between the crook  120  of the hook member  122  and the lateral projection  126 , some of the weight of the head component  108  is distributed to the seat and back component  106 , which decreases the weight that the surgical staff member must carry. At this point, the surgical staff member pushes the head component  108  further toward the seat and back component  106  such that the crook  120  of the hook member  122  slides along the ramp formed by the lateral projection  126 . When the hook member  122  is riding along the lateral projection  126  in this manner, the housing  134  of the hook assembly  116  is aligned with the space formed between the inner and outer walls  168 ,  170  of the receiver assembly  114 . Additionally, the boss  164  extending from the bottom surface of the housing  134  is aligned with the opening  166  formed in the transverse wall  172  that extends between the inner and outer walls  168 ,  170  of the receiver assembly  116  (shown in  FIG. 11 ). Because the head component  108  is compatible with the seat and back component  106  (i.e., because the seat and back component  106  is designed to bear the weight of the head component  108 ), the boss  164  is sized to fit in the opening  166 . Thus, as the surgical staff member continues to push the head component  108  toward the seat and back component  106 , the housing  134  and the boss  164  of the hook assembly  116  slide into the space between the walls  168 ,  170  and the opening  166 , respectively, of the receiver assembly  114 . 
     As the surgical staff member continues to push the head component  108  toward the seat and back component  106 , the crook  120  of the hook member  122  slides beyond the ramp formed by the central region of the lateral projection  126  and drops into a recessed region at the front of the lateral projection  126 , as shown in  FIG. 15 . At this point, the lobe  128  of the hook member  122  is at least partially disposed in the upper depression  180 . 
     Referring to  FIG. 16 , the surgical staff member then pulls back on the head component  108  causing the tip portion  118  of the crook  120  to slide into and matingly engage the notch  124  formed by the lateral projection  126 . As the user pulls back on the head component  108 , the weight of the head component  108  typically causes the lobe  128  to automatically drop down into and matingly engage the lower depression  130 . Alternatively, the surgical staff member may apply a downward force to the head component  108  to force the lobe  128  down into engagement with the lower depression  130 . As the lobe  128  drops down into the lower depression  130 , the spring-loaded pin  144  located along the inner wall of the housing  134  of the hook assembly  116  becomes aligned with the through-hole  174  in the inner wall  168  of the receiver assembly  116  and automatically extends into the through-hole  174  (shown in  FIG. 11 ). This engagement between the spring-loaded pin  144  and the portion of the inner wall  168  that forms the through-hole  174 , locks the hook assembly  116  in place relative to the receiver assembly  114  and thus locks the head component  108  in place relative to the seat and back component  106 . 
     Because the hook member  122  and the lateral projection  126  are the outermost components of the hook and receiver assemblies  116  and  114 , respectively, in the region in which the hook member  122  and the lateral projection  126  engage with one another, it is possible for someone standing at the side of the operating table to easily determine whether the hook assembly  116  has been properly engaged with the receiver assembly  114  and to thus determine whether the head component  108  has been properly secured to the seat and back component  106 . 
     After use of the operating table  100 , it may be desirable to remove the head component  108  from the seat and back component  106 . This can be done, for example, in order to reconfigure the operating table  100  for a different type of surgical procedure. Referring to  FIG. 17 , in order to remove the head component  108  from the seat and back component  106 , the actuator  146  positioned on the outer surface of the hook member  122  is pressed down to retract the spring-loaded pin  144  of the hook assembly  116 . As the spring loaded pin  144  is retracted, the tab  162  extending from the pin  144  slides along the ball spring  160  that is positioned along the bottom surface of the housing  134  (shown generally in  FIG. 7 ). The ball spring is pressed upward by the top surface of the transverse wall  172  of the receiver assembly  114 . After the tab  162  of the spring-loaded pin  144  has slid past the ball spring  160 , the ball spring  160  extends upward. When the actuator  146  is subsequently released by the surgical staff member, the pin  144  is urged back towards its extended position by an internal spring and the side surface of the tab  162  extending from the pin  144  contacts the ball spring  160 . Due to this contact, the pin  144  is locked in its retracted position without the surgical staff member having to hold down the actuator  146 . With the pin  144  held in the retracted position, the surgical staff member pulls upward on the head component  108  to remove the lobe  128  of the hook assembly from the lower depression  130  and then pushes the head component  108  toward the seat and back component  106  to remove the tip portion  118  of the crook  120  from the notch  124 . The surgical staff member then lifts the head component  108  so that the tip portion  118  of the crook  120  is positioned above the lateral projection  126 . The head component  108  is then pulled away from the seat and back component  106  until the hook assembly  116  and the receiver assembly  114  are completely decoupled. 
     As the housing  134  of the hook assembly  116  is removed from the space between the inner and outer walls  168 ,  170  of the receiver assembly  114 , the ball spring  160  is no longer urged upward by the transverse wall  172  of the receiver assembly  114 . As a result, the ball spring  160  drops downward and the spring-loaded pin  144  automatically returns to its extended position. Consequently, there is no need for the surgical staff member to reactivate the pin  144  (e.g., by moving the actuator  146  upward) prior to the next use of the head component  108 . 
     While the methods described with respect to  FIGS. 13-17  above relate to mechanically coupling and decoupling the right side hook assembly  116  of the head component  108  and the right side receiver assembly  114  of the seat and back component  106 , it should be understood that the left side hook and receiver assemblies of those components would be coupled and decoupled in the same manner. 
       FIG. 18  is a left side view of the leg component  110  of the operating table top assembly  104  (shown in  FIG. 1 ). The leg component  110  includes a hook assembly  186  with a rail or spar  188  that is fastened (e.g., via bolts or screws) to a support board  184 . The pad that typically rests on top of the support board  184  has been removed for clarity. The hook assembly  186  and an associated receiver assembly positioned along the left side of the seat and back component  106  form the left coupling device  113  (identified in  FIG. 1 ). The receiver assembly that cooperates with the hook assembly  186  to form the coupling device  113  is similar in structure and function to the receiver  114  described above. 
       FIG. 19  is an inner perspective view (from below) of the leg component  110 . The right hook assembly, which is normally secured to the right side of the top support board  184 , has been removed to provide an unobstructed view of the left hook assembly  186 . Referring to  FIGS. 18 and 19 , the hook assembly  186  includes the hook member  122  and a housing  190  that are secured to an end region of the rail  188 . The housing  190  is similar to the housing  134  described above with respect to the hook assembly  116 . However, the housing  190  is slightly modified to accommodate a different type of actuator assembly. The actuator assembly includes, among other components, a graspable lever  194  that is attached to the rail  188  about midway along the length of the leg component  110 . As will be described below, the graspable lever  194  can be used to retract the spring-loaded pin  144  into the housing  190  in order to unlock the hook assembly  186  from its associated receiver assembly on the seat and back component  106 . In addition, a boss  192  extending from the housing  190  is sized differently than the boss  164  extending from the housing  134  of the hook assembly  116  to indicate that the leg component  110  is heavier than the head component  108 . 
       FIG. 20  is an inner perspective view (from above) of the leg component  110  with the support board  184  removed and the top cover of the housing  190  removed to expose various components of the actuator assembly. As shown, the graspable lever  194  includes a plate  196  having a projection  198  that protrudes through an opening in an elongate bar  200  that extends along the length of the rail  188 . A pin  202  extending from the inner wall of the rail extends through an elongate angled slot formed in the plate  196 . Due to the angle of the elongate slot in the plate  196 , as the user squeezes the lever  194  causing the plate  196  to slide along the pin  202 , the slot causes the projection  198  extending from the top of the plate  196  to move to the right (in the view shown in  FIG. 20 ). This causes the elongate bar  200  to also move to the right. The end region of the bar  200  opposite the projection  198  extends through a slot formed in the end wall of the housing  190 . The end region of the bar  200  is thus disposed within the housing  190  and includes a semi-circular cut out  204  that receives a projection  206  of an L-shaped lever  208  disposed in the housing  190 . As the bar  200  moves to the right, the projection  206  of the L-shaped lever  208  is also pulled to the right. This causes the L-shaped lever  208  to pivot about a pin  210  extending downward from the top cover of the housing  190 . As a result of this movement, a projection or cam  212  within the channel  158  formed by the block-shaped member of the spring-loaded pin  144  causes the spring-loaded pin  144  to retract within the housing  190 . The ball spring  160  (shown in  FIG. 7 ) locks the spring-loaded pin  144  in this retracted position when the hook assembly  186  is matingly engaged with the receiver assembly. Therefore, the user, if desired, can then release his or her grip of the lever  194  and grasp a different portion of the leg component  110  to decouple the hook assembly  186  from the receiver assembly and thus to decouple the leg component  110  from the seat and back component  106 . 
     Apart from squeezing the lever  194  instead of sliding an actuator to retract the spring-loaded pin  144 , the operation of the hook assembly  186  is generally the same as the operation of the hook assembly  116  described in detail above. Therefore, the method of coupling the leg component  110  to the seat and back component  106  will not be described in further detail. 
     While the actuator assembly components disposed within the housing  190  of the hook assembly  186  are slightly different than the actuator assembly components disposed within the housing  134  of the hook assembly  116 , in certain implementations, the actuator assemblies of those respective hook assemblies are designed such that the actuator assembly components disposed within the housings of those respective hook assemblies are identical. This can increase the ease and efficiency of manufacturing the various table top components because the same housing can be used for multiple different types of table top components. 
     While the actuator assemblies used to retract the spring-loaded pins  144  of the hook assemblies  116 ,  186  discussed above have been described as including slidable levers or squeezable levers, other types of actuators can alternatively be used. Examples of other types of actuators that can be used include quarter turn knobs, depressible paddles, triggers, and spring-loaded cuffs. 
     While the assembly used to lock the spring-loaded pin  144  in the retracted position has been described as including the ball spring  160  that engages the tab  162  that extends from the spring-loaded pin  144 , other types of locking mechanisms can alternatively be used. In some embodiments, for example, the ball spring  160  is arranged to slide along the block-shaped member of the spring-loaded pin  144  and to protrude directly into a recess formed in the block-shaped member of the spring-loaded pin  144  in order to retain the spring-loaded pin  144  in its retracted position. Similarly, while the ball spring  160  has been described as being positioned below the spring-loaded pin  144 , in some embodiments, the locking mechanism can alternatively be positioned above the spring-loaded pin  144 . In such embodiments, the locking mechanism can include a pin or other projection that, due to gravity, drops into a recess formed along the top surface of the spring-loaded pin  144  as the spring-loaded pin  144  is retracted in order to retain the spring-loaded pin  144  in its retracted position. 
     While the receiver assembly  114  has been described as being attached to the seat and back component  106  and the hook assemblies  116 ,  186  have been described as being attached to the head component  108  and the leg component  110 , respectively, in certain implementations, hook assemblies are attached to the seat and back component and receiver assemblies are attached to the table top components, such the head and leg components, to be coupled to the seat and back component. 
     While the receiver and hook assemblies  114 ,  116  have been described as being attached to the frames of their respective table top components  106 ,  108 , in some implementations, the receiver assembly is intergrally formed (e.g., die cast or injection molded) with the frame of its respective table top component. Similarly, the hook assembly can be intergrally formed (e.g., die cast or injection molded) with the frame of its respective table top component. 
     While the receiver assembly  114  has been described as being formed of multiple discrete walls  168 ,  170 ,  172  that are secured together, in certain implementations, the receiver assembly is a unitary device. In such embodiments, for example, the receiver assembly can be die cast or injection molded. 
     While the opening  166  of the transverse wall  172  of the receiver assembly  114  has been illustrated as being generally rectangular, the opening  166  can have any of various other shapes. Similarly, while the openings  166  of the transverse walls  172  in the receiver assemblies  114  associated with different table top components (e.g., table top components capable of bearing different weights) have been described as having the same general shape but different sizes, in certain embodiments, the shape of the openings  166  in the transverse walls  172  can differ from one receiver assembly  114  to another to ensure that only intended types of hook assemblies  116  can be coupled to the receiver assemblies  114 . As an example, the transverse walls of receiver assemblies attached to table top components capable of bearing heavy loads can have cross-shaped openings that generally match the cross-shaped openings, while the transverse walls of receiver assemblies attached to table top components capable of bearing heavy loads can have rectangular openings. Similarly, the hook assemblies attached to table top components that are heavy or that are intended to bear heavy loads during use can have cross-shaped bosses that match the cross-shaped openings, while the hook assemblies attached to table top components that are light or that are intended to bear only light loads during use can have rectangular bosses that match the cross-shaped openings. The cross-shaped bosses of the hook assemblies attached to heavy table top components could be disposed within the cross-shaped openings of the receiver assemblies capable of bearing heavy loads but could not be disposed within the rectangular openings of the receiver assemblies capable of bearing only light loads. In contrast, the rectangular bosses of the hook assemblies attached to light table top components could be disposed within the rectangular openings of the receiver assemblies capable of bearing only light loads and within the cross-shaped openings of the receiver assemblies capable of bearing heavy loads. Other combinations of different shapes that provide this type of coding function can also be used. 
     While the various components of the hook assembly and the receiver assembly have been described as being formed of nickel plated aluminum alloy, other materials can be used in some cases. Examples of other suitable materials include titanium and certain beryllium aluminum alloys. 
     While the operating table  100  has been described as including the seat and back component  106 , the head component  108 , and the leg component  110 , various other types of table top components can alternatively or additionally be coupled together to form table tops having different configurations. Examples of other types of table top components that can be equipped with the coupling devices described herein include cantilevered support members, pelvic extensions (e.g., radiolucent pelvic extensions), fracture setting members, boom mounts, therapy delivery mounts, transfer tables, etc. These table top components and various other table top components, like the table top components discussed above, can be equipped with receiver assemblies and hook assemblies. Each receiver assembly can have an opening in its transverse wall that is sized according to a load bearing capacity of the table top component to which it is attached, and each hook assembly can include a boss sized according to the load expected to be applied by the table top component to which it is attached to a coupled table top component during use. Sizing the openings of the receiver assemblies and the bosses of the hook assemblies in this way can provide a coding system that helps to ensure that each of the various table top components can only be coupled to another table top component if that other table top component is capable of bearing the weight of the table top component being coupled to it. 
     Many of the table top components described herein can be equipped with hook assemblies at one end that engage receiver assemblies of another table top component and receiver assemblies at the opposite end that receive hook assemblies of yet another table top component. In this way, it is possible, for example, to secure one table top component directly to the seat and back component  106  and to secure another table top component on the back of the table top component that is secured to the seat and back component  106 . This can allow the surgical staff member to extend the length of the operating table. In many cases, the table top component that is secured directly to the seat and back component  106  will include receiver assemblies that are coded differently (e.g., include differently sized or shaped openings  166 ) than the receiver assemblies of the seat and back component  106 , and the table top component that is secured to the back end of the table top component that is directly secured to the seat and back component  106  will include receiver assemblies that are coded differently than the receivers of both the seat and back component  106  and the table top component that is directly secured to the seat and back component  106  or will include no receiver assemblies at all. 
     Other embodiments are within the scope of the following claims.