A self-latching trailer coupler for use with a ballhead coupling post is disclosed. The coupler includes a housing having a forward portion that forms a receiving socket, and a rear portion. A latching member is disposed within the rear portion of the housing and is adapted for movement between a latched and a released position, the movement of the latch member being controllably guided along a complex path by guide pins and guide slots. The latching member has a socket which engages the ballhead when the coupler is positioned over a ballhead. Downward force on the coupler, as would be due to the load on the tongue of a trailer, automatically translates and rotates the latch member to a fully engaged locked position. A self-actuating locking device is provided for locking the latching member in its latched position. In connection with the locking device, a lever for releasing the locking device is also provided.

BACKGROUND OF THE INVENTION 
1. Field of the Art 
The present invention relates to couplers for hitching trailing vehicles to 
towing vehicles, and more particularly, to latching mechanisms for 
securely latching couplers of trailing vehicles to a spherical ballhead of 
a towing vehicle. 
2. Discussion of the Related Art 
The ballhead coupler is a common type of coupling mechanism used to hitch a 
wide variety of trailers to towing vehicles--e.g., boat trailers, RV 
trailers, flat-bed trailers, cargo trailers, etc. The ballhead coupler is 
characterized by a coupling post having a spherical ballhead securely 
mounted to the rear bumper or frame of a towing vehicle. The mating 
coupler, provided on the nose or tongue of a trailer, has a corresponding 
downwardly opening socket that receives and captures the ballhead to 
achieve a pivotal connection therewith. 
The ballhead coupler just described is popular, in part, because it offers 
tremendous performance advantages over other types of trailer couplers. 
Most notably, the spherical shape of the coupling allows both side-to-side 
and up-down pivotal movement between the trailer and towing vehicle, as 
encountered during turns or travel over bumps, with virtually no torque 
translated through the coupler to the towing vehicle. As a result, a 
smother ride and greater vehicle steering control are achieved. 
In order to facilitate attachment of the trailer to the coupling post, the 
mouth of the downwardly opening receiving socket must be larger than the 
diameter of the ballhead. This allows the coupler to be readily lowered 
onto the ballhead. Without more, however, the trailer would tend to 
uncouple when traveling over bumps or rough roads. Therefore, some type of 
retaining mechanism is needed to lock the coupler with the ballhead 
secured within the socket of the coupler. It is appreciated, however, that 
the retaining mechanism must be designed to allow pivotal movement between 
the receiving socket and the coupling post and, thus, preserve the low 
torque connection between the trailer and towing vehicle. 
Typically, a ball clamp of some type is provided to latch or captively 
engage the ballhead within the receiving socket of the trailer coupler, 
and yet maintain the pivotal connection therebetween. For example, U.S. 
Pat. No. 4,763,917 to Chambers, shows a lever-latch 30 that is manually 
operated to engage a ball clamp against the lower portion of the ballhead 
and, thus, retain the ballhead in the receiving socket. Using a coupler 
such as that illustrated in the Chambers patent requires a conventional 
two-step operation in which a first step seats the ball within the socket, 
and a second subsequent step engages a latching mechanism to latch the 
seated ball in the socket. 
Manual intervention is needed to couple or uncouple the trailer, and the 
Chambers patent is illustrative of the general approach of requiring the 
operator to physically actuate a form of latching or locking mechanism 
after the coupler engages the ball to prevent inadvertent or unwanted 
uncoupling. Applicants are unaware of any reliable coupler design which 
eliminates the need for the operator to physically lock the coupler in the 
latched position. 
Two common problems arise from the use of manually operated latching 
mechanisms which require the operator to lock the mechanism after engaging 
the coupler with the ballhead. First, operators are known to occasionally 
forget to engage the locking mechanism. Unfortunately, this oversight is 
often not noticed until the vehicle and trailer reach a relatively high 
road speed, and the trailer uncouples. The reason for this is that 
trailers are typically designed, by the placement of the axle, for balance 
so that the wheels support the substantial weight of the trailer and the 
coupler or tongue supports a relatively small portion of the trailer 
weight. Nevertheless, this relatively small weight at the coupler is 
usually sufficient to maintain the coupling when traveling at low speeds. 
At higher speeds, however, even small bumps can cause the trailer to 
uncouple, having potentially disastrous consequences. 
A second problem with manually operated latching mechanisms is that they 
are often improperly latched. It is important that the receiving socket of 
the trailer coupler be fully seated over the ballhead before engaging the 
ball clamp. It is known, however, that occasionally 
operators--particularly persons that infrequently use and couple 
trailers--mistakenly engage the manual latch before the receiving socket 
is fully seated over the ballhead. This is sometimes referred to as false 
coupling, and the repercussions are the same as if the latching mechanism 
had not been engaged at all. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary aim of the present invention to provide a 
self-latching trailer coupler. 
Another object of the present invention is to provide a trailer coupling 
mechanism that assures that the ball is fully seated in the jacket, 
thereupon it automatically engages a locking mechanism. 
A further object of the invention is to reduce the possibility of false 
coupling by automatically latching if the coupler is properly placed over 
the ball, or by providing an unstable support for the coupler on the ball 
if not properly seated. 
According to one aspect of the invention, it is an object to provide a 
coupler in which the ballhead cooperates with a latch member in the 
coupler to carry the latch member to the locked position as the ball 
reaches the seated position in the socket, thereby to eliminate the need 
for secondary manually operated latching mechanisms. 
Yet another object of the present invention is to provide a trailer 
coupling mechanism that will signal to the operator that the coupler has 
been properly seated and latched. 
Additional objects, advantages and other novel features of the invention 
will be set forth in part in the description that follows and in part will 
become apparent to those skilled in the art upon examination of the 
following or may be learned with the practice of the invention. The 
objects and advantages of the invention may be realized and obtained by 
means of the instrumentalities and combinations particularly pointed out 
in the appended claims. 
To achieve the foregoing and other objects, the present invention is 
generally directed to a self-latching coupler for hitching a trailing 
vehicle to a ballhead of a towing vehicle. The coupler includes a housing 
having a ball-receiving socket at the forward end. A latching member 
carried in the housing has a forward portion configured to complete the 
socket and a portion to the rear of the forward portion configured to lock 
the latching member. The latching member is mounted in the housing so that 
it has two positions: (1) a released position in which the forward portion 
of the latching member is disposed to open the socket and allow entry of a 
ballhead, and (2) a latched position in which the forward portion of the 
latching member partly underlies an inserted ballhead to capture the 
ballhead within the socket. The forward portion of the latching member is 
disposed in the release position to engage the ballhead and be carried to 
the latched position by the ballhead as it progressively enters the 
socket. Lock means, having a manual release, are provided for locking the 
latching member in the latched position. 
In the preferred embodiment, mounting of the latching member is 
accomplished by guide means which define a complex path for controllably 
directing the transition of the latching member between the released and 
latched positions. Particularly when moving from the released to the 
latched positions, the guide means guides the latching member, while the 
ballhead itself provides the force which moves the latching member from 
the released to the latched position. 
In the preferred form of the invention, the forward portion of the latching 
member is curved. The curve will be cylindrical or spherical. The latching 
member is configured as a latching block having two pinned connections to 
the housing, one of the connections providing for translation of the 
curved surface in the latching member toward or away from the ballhead, 
and the second providing for arcuate movement so that the curved surface 
of the latching member rotates about the ballhead as the ballhead is 
inserted into the socket. Other objects and advantages will become 
apparent from the following detailed description when taken in conjunction 
with the drawings, in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For purposes of illustration, the invention is shown in the drawings as 
embodied in a coupler 10 for hitching the front tongue 31 of a trailing 
vehicle to a spherical ballhead 12 on the rear of a towing vehicle. 
Referring now to FIG. 1, a ballhead-type trailer coupler is shown, and 
generally designated by reference numeral 10. The coupler is associated 
with a ballhead coupling post having a ballhead 12 typically including a 
neck 13 and shoulder portion 14, stationarily mounted as by bolt 15, to a 
mounting base 16. Typically, the base 16 is a flange formed on the rear 
bumper of the towing vehicle. For heavy towing loads, however, the 
mounting base 16 may be attached to the frame of the towing vehicle. 
The coupler 10 is affixed to the tongue 31 of the trailer and includes a 
housing 27 made of heavy sheet metal. The housing has a forward portion 
that defines a socket 17 for receiving the ballhead 12, and a rear portion 
adapted to be secured to the tongue 31 of the trailer. The receiving 
socket 17 has a hemispherically-shaped interior surface 18 that opens 
downwardly to define a mouth 22 that receives the ballhead 12. 
Accordingly, as the trailer coupler 10 is lowered over the coupling post, 
the ballhead 12 is received through the mouth 22 and into the receiving 
socket 17. In this regard, it is appreciated that the 
hemispherically-shaped interior surface 18 closely conforms to the outer 
surface of the ballhead 12. 
In addition to the forward portion of the housing 27 defining the socket 
17, the housing body is of inverted U-shaped cross-section having two 
transversely spaced side walls 19 whose upper margins are integral with an 
inclined top wall 21. The top wall slopes upwardly from the ball socket 
toward a backplate 20. The backplate 20, also of heavy sheet metal, is 
securely fixed within the channel as by welding. A generally horizontal 
section of the channel, to the rear of the backplate, is available to 
receive and secure the tongue 31 of the vehicle to be towed. 
In practicing the invention, a latching member 26 is positioned in the 
housing to the rear of the socket and is adapted to cooperate with a 
ballhead for translation between an unlatched condition shown in FIG. 1 
and a latched condition shown in FIG. 2, wherein the ballhead itself 
carries the latching member between those positions. In the preferred 
embodiment, best illustrated in the exploded view of FIG. 5, the latching 
member 26 is a tapered metal block having a front end 28 configured to 
complete the socket 17. In the illustrated embodiment, the front end 28 is 
contoured to form a socket 30 dimensioned to closely conform to the outer 
contour of the ballhead 12. A horizontally disposed cylindrical surface 
would also function in place of the spherical surface, as will become 
apparent as this description progresses. Guide means, shown herein as 
symmetrically disposed guide pins 32 and 34 project from each side of 
latch 26 and through guide slots 36 and 38 in side-walls 19. As will be 
described in more detail below, latching member 26 is disposed in the rear 
portion of housing 27 and is adapted for movement between a latched 
position (FIG. 2) and an unlatched position (FIG. 1). Movement between the 
unlatched (FIG. 1) and latched (FIG. 2) position requires no manual 
manipulation of the latching member. The operator need only position the 
coupler over the ballhead and allow or assist it to seat. However, 
movement from the latched (FIG. 2) to the unlatched (FIG. 1) position does 
require manual intervention to release the latch. 
In the presently preferred embodiment, and as illustrated in FIGS. 3 and 4, 
guide pin 32 extends completely through latching block 26. Due to the 
placement of a locking means (described below), however, guide pins 34 are 
symmetrically disposed on opposing sides of latching block 26, and extend 
only part way into the block body. Of course, the configuration could be 
readily adapted so both guide pins 32 and 34 would extend completely 
through the body of member 26. As will be appreciated from the discussion 
that follows, guide pins 32 and 34 cooperate with slots in housing 27 to 
define a path of movement for latching member 26 within guide slots formed 
in the housing. Other forms of guide means will also become apparent 
capable of achieving the controlled motion of the latching block described 
herein. 
Guide slot 36 is a substantially horizontally disposed slot, while guide 
slot 38 is a substantially vertically, and arcuately-shaped slot. It is 
important that the arc of the slot 46 not be centered on the ballhead 12 
when the coupler is in the latched position. With the horizontally 
disposed slot 28 allowing translation of the latch member toward or away 
from the ballhead, it is useful to provide a center for the arcuate slot 
38 which is above the ballhead in the latched condition, so that the 
latching member rotates about the ballhead and also translates toward the 
ballhead to achieve the latched condition. 
As illustrated in FIG. 1, when latching member 26 is in the unlatched or 
released position, guide pin 32 is positioned in the rear of guide slot 
36, and guide pin 34 is positioned at the top of guide slot 38. 
Conversely, when member 26 is in the latched position, guide pin 32 is 
positioned in the front of guide slot 36, and guide pin 34 is positioned 
at the bottom of guide slot 38. 
Guide slots 36 and 38, as illustrated, in cooperation with guide pins 32 
and 34 form a guide means that provides a controlled path for movement of 
latching member 26. Indeed, cooperation between the guide pins 32 and 34 
and guide slots 36 and 38, respectively, effectively guide latching member 
26 through its transition between latched and released positions. It is 
understood that arcuately-shaped guide slot 38 provides a rotational 
component to the movement of latching member 26 about the receiving socket 
17, while linearly-shaped guide slot 36 provides a linear component of 
movement. Thus, guide slots 36 and 38 cooperate with guide pins 32 and 34 
to define a complex translational path for latching member 26. Consistent 
with the concepts and teachings of the present invention, however, it 
should be appreciated that the controlled movement of member 26 provided 
by the guide means may be implemented by a wide variety of structural 
variations or adaptations to the guide pin/guide slot combination 
disclosed herein. For example, the particular locations of guide pins 32 
and 34 could be changed, and the shape or location of guide slots 36 and 
38 could be altered, and yet effect a controlled translation of member 26 
between latched and released positions. 
Also forming a part of the present invention is a self-actuating locking 
means that serves to lock the member 26 in its latched position until 
released by manual manipulation of a release lever 40. In the practice of 
the invention, the locking member has two significant functions. First of 
all, when the latch member is carried by a ballhead to the latched 
position, the locking means automatically engages to lock the latching 
member in the secured and closed position, and without the requirement for 
any intervention by an operator. With respect to the second function, the 
locking means cooperates with a manual release mechanism for releasing the 
latching member and allowing the coupler to be withdrawn from the 
ballhead, for the purpose of uncoupling the trailer. As a subsidiary 
feature, a characteristic audible sound created by the locking means 
falling into its locked position can signal the operator that the coupler 
is indeed securely locked. 
In the illustrated embodiment, the locking means is shown as a simple 
spring-loaded plunger secured in the rear end of the latching member 26 
and cooperating with a locking aperture 46 formed in the backplate 20. The 
pin plunger mechanism includes a spring 42 and plunger 44 fit within a 
bore 52 of the latch member 26. The plunger 44 has a reduced diameter 
section 48 for engagement with the aperture 46 in the backplate. 
Preferably, a locking plate (not shown) is affixed to the rear of the 
latch member to prevent the spring 42 from forcing the plunger 44 out of 
the housing beyond the position illustrated in FIG. 2. The plunger 44 is 
preferably an elongate steel rod closely conforming to the bore 52 formed 
in the rear of the latching member 26 so that it will reliably resist any 
torsional unlocking loads imposed on the pin when in the locked condition 
during the use of the coupler. 
When latching member 26 is in its released position (FIG. 1), compression 
spring 42 biases locking plunger 44 outwardly to engage the face of 
backplate 20. When member 26 is motivated into its latched position, 
locking plunger 44 is carried along the backplate 20 and forced into 
socket 52 until the plunger aligns with aperture 46. Compression spring 42 
then urges the end 48 of reduced diameter through anchor hole 46, thereby 
latching member 26 in place. Preferably, the tension of compression spring 
42 is sufficient to briskly snap end 48 through hole 46, and thereby 
produce an audible sound of steel striking steel, loud enough for an 
operator to hear. Advantageously, this audible snap informs the operator 
that the trailer coupler 10 has been fully seated over ballhead 12 and the 
latching mechanism properly engaged. It will also be noted that when in 
the locked condition the rear surface 49 of the latch member has an angle 
which matches the angle of backplate 20. The angle of backplate 20 is 
adapted to carry the latch member forward (so that the pin 32 engages the 
forward end of slots 36). In that position, the angled rear face 49 of the 
latch member lies against the backplate 20 so that any rearward forces 
imposed on the latch member 26 by the ball 12 during operation of the 
vehicle are transmitted directly to the backplate. As a result, the 
backplate and not the latch mechanism or side pins absorbs these forces 
during operation of the vehicle. 
It should be appreciated that, consistent with the broader aspects of the 
present invention, the locking means described above may employ a number 
of structural variations. Indeed, persons skilled in the art will now 
realize that the present invention may be practiced with wide variety of 
modifications or adaptations to the foregoing locking means. For example, 
the rear end of latching member 26 may rest against a hinged backplate 
which is spring loaded toward the latch to automatically lock it in the 
latched position, and allow for manual release for uncoupling. 
In keeping with the description of the preferred embodiment, once member 26 
is latched securely in place, it will remain latched until the locking 
means is manually disengaged. This function is performed by a releasing 
means, which is illustrated as a release lever 40. More particularly, a 
J-shaped release lever 40 is pivotally hinged at 60 so as to provide a 
handle 66 for manual manipulation, and a second end 68 aligned with 
locking aperture 46 of backplate 20. As illustrated, it is preferred to 
provide a release button 62 of reduced diameter on the second end 68 of 
the release lever 40; the diameter of release button 62 is small enough to 
project through anchor hole 46. Advantageously, the shoulder formed 
between release button 62 and the body of release lever 40 provides a stop 
for release lever 40, once release button 62 has projected far enough 
through anchor hole 46 to fully disengage locking plunger 44. In addition, 
the body of release lever 40 is designed to allow a substantial 
load-bearing force to be applied to the handle end 66 of lever 40. As will 
be appreciated by one practicing the invention, the lever 40 may be used, 
not only to disengage the locking plunger 44, but also to lift the trailer 
coupler from the ballhead 12. Accordingly, it is desired to design the 
release lever 40 to withstand such externally applied force. 
Normally, when no external force is applied to release lever 40, a 
compression spring 64 applies a force to lever 40 that biases the lever 
into a normal, rest condition in which release button 62 allows locking 
plunger 44 to protrude through aperture 46. The compression spring 64 is 
preferably held in place by means such as protrusions 65 formed on the 
lever 40 and the backplate 20. As illustrated, the release lever 40 abuts 
the housing of the coupler at 70, which serves as a stop for the lever 40. 
As illustrated in FIG. 6, an upwardly directed external force applied to 
the handle 66 of lever 40 acts to release latching member 26 from its 
locked position, by forcing the reduced end 48 of locking plunger 44 back 
through anchor hole 46. In this regard, the externally applied pressure 
translates, in part, to release button 62, which fully disengages locking 
plunger 44. Continued force applied upwardly at the first end 66 of lever 
40 or otherwise applied to the trailer tongue 31, serves to lift the 
coupler from ballhead 12. 
Having described the structural elements of the preferred embodiment of the 
present invention, a brief description of its operation will now be 
presented. When first applying the coupler 10 to a ballhead coupling post, 
as shown in FIG. 1, the latching member 26 is in its released position. It 
can be appreciated that the second or rear end 56 of member 26, when no 
forces are applied, will tend to rest against the ceiling 21 of housing 
27. This is due to the rearward slope of the backplate 20 which carries 
the rear end 56 of the latch member upwardly as the coupler is withdrawn 
from the ballhead, and the pin plunger 44, biased by the spring 42, which 
engages the sloped surface of backplate 20 to hold the latch member in the 
topmost unlatched condition. 
As the ballhead 12 is received through the mouth 22 of housing 27, it first 
contacts the upper lip of the front end 28 of latching member 26, applying 
an upwardly directed force thereto. Controlled by the guiding means of the 
guide pins 32 and 34 and guide slots 36 and 38, the upward force applied 
by the ballhead 12 to the front end 28 of member 26 results in a downward 
force to the rear end 56 of member 26. The weight of the trailer applies a 
sufficient force to member 26 to overcome the counter-acting force 
resulting from the slope of backplate 20, and as a result the member 26 
begins to translate from the position illustrated in FIG. 1 toward the 
position illustrated in FIG. 2. 
Continued insertion of ballhead 12 into housing 27 carries latching member 
26 through a further translation toward the position of FIG. 2. In effect, 
the curved portion 30 of the latching member 26 rotates about the ballhead 
as the ballhead is inserted into the socket. As the guide pin 34 in the 
arcuate slot causes rotation of the pin 34 about the center of the slot, 
the guide pin 36 in the linear slot translates forwardly, bringing the 
ballhead 12 over a shoulder 18a into the socket 18. The ball 12 is 
ultimately moved forward to conform with the socket 18 at the same time as 
the latch member 26 moves with the pin 34 to the bottom of its arc and the 
pin 36 to the front of its slot, to create a ballhead socket which 
conforms to the size of the spherical ballhead 12, and locks the ballhead 
well below its center so that it cannot be unintentionally released from 
the coupler. 
It is significant to note that the ballhead 12 is the element which engages 
the socket 30 in the latching member to carry the latching member from its 
unlatched to its latched position. If the coupler is not fully engaged 
before the tongue 31 is lifted, the latch member 26 will not translate to 
the locked position, because it is the ballhead 12 which must cause that 
translation. The only way the latching member 26 can reach the locked 
condition is if the ballhead 26 engages the socket and carries the latch 
member 26 through its full range of translation to the locked condition. 
As ballhead 12 becomes fully seated in socket 17, locking plunger 44 aligns 
with aperture 46. At this point, compression spring 42 forces the reduced 
end 48 of locking plunger 44 through aperture 46, thereby locking the 
latching member 26 in place and at the same time generating an audible 
snap which alerts the operator that the coupler is properly installed. In 
this position, it is appreciated that the ballhead 12 is effectively 
captured, by the combination of socket 17 and latch member 26. 
It is also significant to note that the mouth 22 through which the ballhead 
projects upon entry into the coupler provides only a limited area of 
contact for the ballhead with the socket. Thus, as will be appreciated 
from FIG. 1, it is not possible for the ballhead to engage the lowermost 
portion of the latch member 26 and force it to the locked position. The 
ballhead will either slide forwardly into the socket or rearwardly, but in 
either event will not couple. When the ballhead 12 moves forwardly into 
the socket, the forces exerted between the ballhead 12 and the coupler, 
due to the position of the socket and manner in which the travel path of 
the latching member 26 is controlled, causes the ball in the socket to 
carry the latch member to the locked condition. The possibility of a 
partly latched ball is effectively eliminated. The possibility of a 
ballhead 12 being associated with the coupler without latching is also 
substantially reduced due to the fact that the weight of the trailer will 
bring the coupler to the latched condition in almost all instances, and 
the very shallow portion of the socket below the latching shoulder 18a 
makes it abundantly clear if the coupler is loosely riding atop a ballhead 
without reaching the latched condition. Thus, even if tampering, for 
example, results in inadvertent latching of the latch, when an attempt is 
made to couple to a ballhead without unlatching, the ball will underlie 
the latched coupler but in a very unstable condition. False coupling will 
likely be immediately apparent visually, or the coupler will slide off the 
ball if the towing vehicle begins to move. 
Release of the latching member 26 is achieved by applying an upwardly 
directed force to the handle 66 of release lever 40. It is contemplated 
that an operator will grip this portion of the release lever and lift. 
This lift will compress spring 64, allowing release button 62 to unlock 
member 26 by forcing the reduced end 48 of locking plunger 44 back through 
the locking aperture 46 of backplate 20. Continued lift will apply a 
downward force from the ballhead 12 to the lower lip of the socket 30 of 
the latching member front end 28, which, as directed by the guide pins 32 
and 34 and guide slots 36 and 38, causes a corresponding upward force on 
the rear end 56 of member 26. Accordingly, the member translates from its 
latched position illustrated in FIG. 2 to its released position 
illustrated in FIG. 1, allowing the ballhead 12 to exit the mouth 22 of 
the coupler. 
The foregoing description of various preferred embodiments of the invention 
has been presented for purposes of illustration and description. It is not 
intended to be exhaustive or to limit the invention to the precise forms 
disclosed. Obvious modifications or variations are possible in light of 
the above teachings. The embodiments discussed were chosen and described 
to provide the best illustration of the principles of the invention and 
its practical application to thereby enable one of ordinary skill in the 
art to utilize the invention in various embodiments and with various 
modifications as are suited to the particular use contemplated. All such 
modifications and variations are within the scope of the invention as 
determined by the appended claims when interpreted in accordance with the 
breadth to which they are fairly, legally, and equitably entitled.