High speed shuttle printer

An improvement to a dot matrix printer of the shuttle variety wherein a printhead is oscillated from side to side within a printer base. The shuttle is disposed within a ballistic energy transfer device mounted for oscillating movement from side to side in the opposite direction to the instantaneous movement of the shuttle. A rebound spring is operably connected to exert a rebounding force against the shuttle to aid it in reversing direction. Also, a centering spring is operably connected for exerting a centering force against the ballistic energy transfer device. A linear motor is connected for driving the shuttle back and forth in an oscillating motion with respect to the ballistic energy transfer device. Optionally, the linear motor is connected for driving the ballistic energy transfer device back and forth in an oscillating motion with respect to the printer base. The turnaround time of the shuttle is adjusted by adjusting the span of the shuttle or the spring constant of the rebound spring. Linear encoders are provided to determine the shuttle position as the shuttle moves back and forth.

BACKGROUND OF THE INVENTION 
The present invention relates to dot matrix printers and, more 
particularly, in a dot matrix printer of the shuttle variety wherein a 
plurality of printheads are disposed across the width of a shuttle which 
is oscillated from side to side within a printer base, to the improvement 
comprising, the shuttle being disposed within a ballistic energy transfer 
device mounted for oscillating movement from side to side in the opposite 
direction to the instantaneous movement of the shuttle; first spring means 
operably connected between the ballistic energy transfer device and the 
shuttle for exerting a rebounding force against the shuttle to aid it in 
reversing direction; and, second spring means operably connected for 
exerting a centering force against the ballistic energy transfer device. 
Dot matrix printers have provided a simple and economical apparatus for 
computer-driven printing. In a dot matrix printer, a printhead such as 
that labelled as 10 in FIGS. 1 and 2 has a magnetic drive unit 12 
connected to a print face 14 such as those shown by way of example in 
FIGS. 3 and 4. One or more print pins 16 are connected between the drive 
unit 12 and the print face 14. For example, FIG. 3 depicts a single print 
pins 16 while FIG. 4 depicts twelve print pins 16 configured in a 
3.times.4 matrix. A print ribbon (not shown) is disposed between the print 
face 14 and the writing paper upon which printing is to take place. When 
the magnetic drive unit 12 pushes the pin(s) 16 out of the print face 14, 
the end(s) push the print ribbon against the paper causing a dot to be 
printed. Dot matrix printers are powerful in capability since they can 
produce both text (i.e. alpha-numeric characters) and graphics as a matrix 
of dots on the page. The process is depicted in FIGS. 5-7. The printhead 
10 is moved back and forth transversely over the paper 18 as the paper is 
moved vertically under the support bar 20 carrying the printhead 10. The 
printhead 10 and paper 18 are moved by apparatus well known in the art 
which is, therefore, not shown for simplicity. Likewise, the magnetic 
drive unit 12 is activated under computer control in a manner well known 
to those skilled in the art which requires no further explanation. The 
printhead 10 is moved across the bar 20 from a starting position at the 
left side of the paper 18 as shown in FIG. 5 to the opposite side of the 
paper 18 where it reverses direction as depicted in FIG. 6. It continues 
across the paper in the opposite direction as depicted in FIG. 7 until it 
reaches its starting point once again. The process then repeats. As the 
printhead 10 moves across the paper 18, the magnetic drive unit 12 is 
activated to create one or more lines of dots (depending on the number of 
print pins 16) which comprise the graphics and/or text 22. The more pins 
16, the fewer passes of the printhead 10 are required. 
As with anything else, dot matrix printers are subject to numerous 
tradeoffs. A printer with only a few pins 16 is simple and inexpensive to 
build. Typically, these are very slow. A printhead 10 with a greater 
number of pins will be faster for a given quality; however, the cost is 
high and the printhead is large. To move the high mass of such a printhead 
across the paper rapidly and then quickly reverse its direction requires a 
large and expensive drive mechanism. Even then, there are limitations as 
to how fast one can make the printhead traverse a wide sheet of paper 
(e.g. fourteen inches) and then reverse direction. 
In commercial printers where cost is not a major factor (as compared to the 
"home" market), shuttle printers such as that depicted in FIGS. 8-10 have 
been introduced as an answer to the above-mentioned problems of single 
printhead dot matrix printers. In a shuttle printer, a plurality of 
printheads 10 are disposed side-by-side on a shuttle 24. The shuttle 24 is 
then oscillated or shuttled from side to side a shuttle distance "d" as 
depicted in the figures. Each head 10 covers only a narrow vertical strip 
on the paper. For example, with eight printheads 10 as shown in FIG. 10, 
the shuttle 24 only has to move one-eighth the distance required to 
traverse the whole width of the paper with one printhead. Typically, the 
side-to-side movement of the shuttle 24 has been created by a rotating 
motor 26 driving a crank 28 which, in turn, reciprocates a link 30 
connected to the shuttle 24. A position wheel 32 attached to the end of 
the motor shaft 34 is sensed by a sensor 36 to provide a signal of the 
position of the shuttle 24 as function of the rotation of the crank 28. 
As can be appreciated, while solving some problems, shuttle printers have 
created problems of their own. Principally, the shuttle 24 with its 
multiple printheads 10 has a high inertial mass. Thus, it is hard to 
reverse to create the desired shuttle motion. Additionally, the sensor 36 
is inexact since it is at the far end of a chain of additive errors from 
the shuttle 24 itself. To keep the mass low, shuttle printers have 
typically employed single pin printheads as depicted in FIG. 3. This, of 
course, means that many more passes or "shuttles" are required to create a 
finished "line" of text or the like. 
Wherefore, it is an object of the present invention to provide a shuttle 
printer which is able to quickly reverse directions. 
It is another object of the present invention to provide a shuttle printer 
which operates with larger, multiple pin printheads so as to require fewer 
shuttle motions to create a line of text or the like. 
It is yet another object of the present invention to provide a shuttle 
printer which can be dynamically adjusted for maximum performance. 
It is still another object of the present invention to provide a shuttle 
printer which does not impart high impact forces from the moving shuttle 
to the printer base. 
It is a further object of the present invention to provide a shuttle 
printer having a position feedback system for the shuttle which accurately 
reflects the position of the shuttle. 
It is still a further object of the present invention to provide a shuttle 
printer having low friction in the components whereby to achieve maximum 
benefit from the driving power. 
Other objects and benefits of the present invention will become apparent 
from the description which follows hereinafter when taken in conjunction 
with the drawing figures which accompany it. 
SUMMARY 
The foregoing objects have been achieved in a dot matrix printer of the 
shuttle variety wherein a plurality of printheads are disposed across the 
width of a shuttle which is oscillated from side to side within a printer 
base by the improvement of the present invention comprising, the shuttle 
being disposed within a ballistic energy transfer device mounted for 
oscillating movement from side to side in the opposite direction to the 
instantaneous movement of the shuttle; first spring means operably 
connected between the ballistic energy transfer device and the shuttle for 
exerting a rebounding force against the shuttle to aid it in reversing 
direction; and, second spring means operably connected for exerting a 
centering force against the ballistic energy transfer device. Preferably, 
the ballistic energy transfer device is of a mass which is at least 
several times the mass of the shuttle. 
In one version, there are a pair of spaced, parallel support rods carried 
by the printer base; means for slidably mounting the shuttle to the 
support rods; and, means for slidably mounting the ballistic energy 
transfer device to the support rods. Additionally, there is a linear motor 
operably connected between the shuttle and the ballistic energy transfer 
device for driving the shuttle back and forth in an oscillating motion 
with respect to the ballistic energy transfer device. According to one 
aspect, the linear motor comprises a linear armature carried by the 
shuttle and a linear coil assembly carried by the ballistic energy 
transfer device. 
In the preferred embodiment, the invention additionally comprises a first 
linear encoder fence carried by the printer base to be parallel to a path 
of movement of the shuttle, the first fence having sensible positional 
indicia thereon and first sensor means carried by the shuttle for sensing 
the positional indicia of the first encoder fence as the shuttle moves 
back and forth and for producing a signal at an output thereof reflecting 
the position of the shuttle with respect to the printer base. Preferably, 
the first encoder fence is of a transparent material and the first sensor 
means includes a light emitting diode disposed on one side of the first 
fence and a phototransistor disposed on the opposite side of the first 
fence so as to develop the signal as a function of light passage through 
the positional indicia on the first fence. 
In the instances where the linear motor is a stepper motor, there is also a 
second linear encoder fence carried by the shuttle having sensible 
positional indicia thereon and second sensor means carried by the 
ballistic energy transfer device for sensing the positional indicia of the 
second encoder fence as the shuttle moves back and forth and for producing 
a signal at an output thereof reflecting the position of the shuttle with 
respect to the ballistic energy transfer device whereby the linear motor 
is more easily controlled. 
Also in the preferred embodiment, speed control circuit means are operably 
connected to the linear motor for adjustably controlling the speed of the 
shuttle. The preferred speed control circuit means includes means for 
adjusting the speed of the shuttle from between 5 inches per second and 
100 inches per second. 
The preferred first spring means comprises a pair of impact pads carried by 
respective ends of the shuttle and a pair of second springs carried by the 
ballistic energy transfer device at the ends of a span of movement of the 
shuttle to be contacted by respective ones of the impact pads whereby the 
second springs are compressed and then rebound to urge the shuttle in the 
opposite direction. For optimum energy conservation, the impact pads are 
disposed on a line running through the center of gravity of the shuttle 
whereby sideward, friction producing forces against the shuttle by the 
second springs are minimized. Also preferably, the second springs are leaf 
springs supported by the ballistic energy transfer device at ends thereof; 
the second springs are positioned transverse the path of travel of the 
shuttle to be impacted and deflected at a center thereof by the impact 
pads; and, the second springs have a spring constant chosen to turnaround 
the movement of the shuttle in less than 3 milli seconds. 
Additionally for the purposes of energy conservation, first balancing means 
are connected to the ballistic energy transfer device for eliminating 
forces therefrom sideward to the path of movement thereof and second 
balancing means are connected to the shuttle for eliminating forces 
therefrom sideward to the path of movement thereof. Also, there are first 
support means for frictionlessly supporting a portion of the weight of the 
shuttle to reduce the frictional drag thereon during movement thereof and 
second support means for frictionlessly supporting a portion of the weight 
of the ballistic energy transfer device to reduce the frictional drag 
thereon during movement thereof. The preferred first support means 
comprises a magnetically attractable plate attached to a top surface of 
the shuttle and a magnet supported above the shuttle close adjacent the 
plate to attract the plate and thereby support a portion of the weight of 
the shuttle. The preferred second support means comprises a coil spring 
disposed vertically between a bottom of the printer base and the ballistic 
energy transfer device. 
An alternate version of the linear motor comprises a vertical member 
carried by the shuttle and a solenoid assembly carried by the ballistic 
energy transfer device and having a moving member operably connected to 
the vertical member. 
In one variation, the ballistic energy transfer device is part of the 
printer base. To accomplish that, there is an embodiment wherein there is 
a support rod carried by the ballistic energy transfer device; means for 
slidably mounting the shuttle to the support rod; and, means for 
supporting the ballistic energy transfer device for the oscillating 
movement wherein the means for supporting the ballistic energy transfer 
device for the oscillating movement comprises a pair of leaf springs 
disposed vertically between a bottom portion of the printer base and the 
ballistic energy transfer device. In another variation, the entire printer 
base is the ballistic energy transfer device with the printer base mounted 
on compliant rubber feet to accomodate the movement of the printer base.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The basic philosophy of the present invention is depicted in simplified 
form in FIGS. 11-13. Rather than slidably connecting the shuttle 24 to the 
printer base 38 as in the prior art, the shuttle printer 40 of the present 
invention employs a ballistic energy transfer device 42 to carry the 
shuttle 24. The ballistic energy transfer device 42 is of a mass which, 
preferably, is (but need not be) at least several times the mass of the 
shuttle 24. Preferably, the ballistic energy transfer device 42 is about 
five times the mass of the shuttle 24. There is a tradeoff which the 
designer must take into consideration when designing a printer employing 
the present invention. The distance and speed of movement of the ballistic 
energy transfer device 42 is in the same ratio as its mass is to the mass 
of the shuttle 24; that is, in the case where the ballistic energy 
transfer device 42 is ten times the mass of the shuttle 24, the ballistic 
energy transfer device 42 will move 1/10 the distance at 1/10th the speed 
of the shuttle 24. Thus, by making the mass of the ballistic energy 
transfer device 42 very large, it can be made to move very slightly from 
side to side at a lower velocity while the shuttle 24 moves quickly 
through its full oscillation cycle to produce the lines of printing. The 
ballistic energy transfer device 42 acts to greatly reduce the energy 
required to drive the shuttle 24. In embodiments tested by the inventors 
herein, a 90% energy transfer (i.e. only 10% of the energy is lost) 
appears to be attainable. 
The shuttle 24 is directly driven longitudinally by a linear motor 44 (or 
other linear drive device) instead of by the crank and link system of the 
prior art as described earlier herein. The coils 46 are carried by the 
ballistic energy transfer device 42 and the armature 48 is carried by the 
shuttle 24 as shown in the figures. Note that the preferred configuration 
is with the ballistic energy transfer device 42 rectangular in shape with 
a rectangular opening 50 in the center thereof into which the rectangular 
shuttle 24 is disposed. As will be seen in one embodiment to be described 
hereinafter, it is possible to employ the printer base 38 as the ballistic 
energy transfer device 42 if desired. The shuttle 24 is positioned between 
a pair of rebound springs 52. In the preferred embodiment, the spring 
constant of the springs 52 is chosen so as to be able to impart a force to 
the shuttle 24 which can affect turnaround cf the shuttle 24 in less than 
3 ms. Turnaround times of less than 1 ms have already been achieved with 
this mechanism in tested embodiments thereof. It should be noted in this 
regard that the turnaround time of the shuttle 24 is independent of the 
speed thereof--within the safe stress limits of the springs 52. In similar 
manner, the ballistic energy transfer device 42 is positioned between a 
pair of centering springs 54 carried by the end walls 56 of the printer 
base 38. The spring constant cf the springs 54 is chosen so as to only 
center the ballistic energy transfer device 42 in the static state. That 
is their only function and their spring constant should not be large 
enough to affect the operation of the mechanism in other ways. As can be 
appreciated, the above-described configuration results in a quick reversal 
of the shuttle 24 at the ends of its oscillation (e.g. under 3 ms) without 
the transfer of forces into the printer base 38. The shuttle 24 and 
ballistic energy transfer device 42 move in opposite directions as 
depicted in the drawing figures. Note that, for simplicity, the drawings 
are not to scale in this regard. The ballistic energy transfer device 42 
and the shuttle 24 are easily reversed without the imparting of large 
forces into the printer base 38. Most of the kinetic energy is transferred 
by the ballistic energy transfer device 42 back to the shuttle 24 and 
never reaches the printer base 38. It should be noted at this point that 
while springs are shown and described herein for various functions, it is 
anticipated that magnet pairs could be substituted for the springs, if 
desired, with like poles adjacent one another so as to create and employ a 
magnetic repulsion force in lieu of a spring force. 
The shuttle printer 40 of the present invention is shown in greater detail 
in FIGS. 14, 15 and 17 with an alternate embodiment, 40,, employing a 
power drive for the ballistic energy transfer device 42 instead of for the 
shuttle 24 shown in FIG. 16. As those skilled in the art will appreciate, 
either device (i.e. the ballistic energy transfer device 42 or the shuttle 
24) can be the driven device in a printer according to the present 
invention. In all other regards, the embodiment of FIG. 16 is virtually 
identical to the embodiment of FIGS. 14, 15 and 17 and, therefore, &.he 
embodiment of FIG. 16 will not be addressed further herein in the interest 
of simplicity and the avoidance of redundancy. 
The shuttle 24 and ballistic energy transfer device 42 are slidably mounted 
on a pair of shafts 58 carried by the printer base 38. To date, acceptable 
performance has been achieved by having narrow points of contact with the 
shafts 58 and the use of phosphor bronze bushings, or the like. If 
desired, other forms of low friction mountings or support could be 
employed in lieu of or in addition to the mountings shown. For example, 
magnetic fields and/or springs could be disposed to support the weight of 
the ballistic energy transfer device 42. This will be shown in other 
embodiments to be described later herein. 
The preferred ballistic energy transfer device 42 is an open rectangle in 
shape and, therefore, already suited for the low contact mounting on the 
shafts 58 described above. The shuttle 24 is generally "H" shaped having a 
rectangular body portion 60 carrying a plurality of pin drivers 62 
disposed in side-by-side relationship. Four legs 64 extend outward from 
the corners of the body portion 60. The shafts 58 pass through respective 
pairs of the legs 64 as shown. The linear motor armature 48 is attached to 
the two bottom legs 64. The coils 46 are linearly attached to the bottom 
66 of the ballistic energy transfer device 42 to position the coils 46 
along the armature 48 in close spaced relationship thereto. The coils 46 
are operably connected to a power source (not shown) through speed control 
circuit 47 which allows the speed of movement of the shuttle 24 to be 
varied for different printing conditions. For example, the inventors 
herein have determined that &:he speed of the shuttle 24 should be 
variable from 5 inches/sec to 100 inches/sec in order to allow for a wide 
range of font selections and graphics resolutions. The preferred centering 
springs 54 are weak coil springs carried between holes 68 in the printer 
base 38 and the ballistic energy transfer device 42 provided therefor. The 
preferred rebound springs 52 are leaf springs which are contacted by 
impact pads 69. The rebound springs 52 are much more critical and will be 
returned to in greater detail shortly. 
As best seen from the cutaway view of FIG. 17, the pin drivers each 
comprise a coil 70 for attracting a spring-loaded armature 72. The end of 
the armature 72 is connected to one end of a print pin 16 which passes 
through a bore 73 in the body portion 60 provided therefor. The other end 
of each print pin 16 emerges close adjacent an adjustable platen 74 
carried by block 76 attached to the printer base 38. A plastic encoder 
"fence" 78 is also carried by the printer base 38 to be parallel to the 
path of movement of the shuttle 24. A sensor 36' is carried by the shuttle 
24 to sense the encoder fence 78 as the shuttle 24 moves back and forth 
and develop a positional signal on its output wires 79 indicating the 
position of the shuttle 24 with respect to the printer base 38. In its 
preferred embodiment, the encoder fence 78 is of transparent plastic and 
the sensor 36' is of the type that has a light emitting diode on one side 
of the fence 78 and a phototransistor on the opposite side so as to 
develop an electrical position signal on wires 79 as a function of light 
passage through positional indicia on the fence 78. 
In initial testing of the present invention, it has been found to be 
beneficial to be able to adjust the length of travel of the shuttle 24. 
While not determined to be as important as of this time, it may also be 
desirable to apply the same provision with respect to the ballistic energy 
transfer device 42 and its centering springs 54. Therefore, it is 
preferred that such provisions be included within a shuttle printer made 
and operating in accordance with the teachings of the present invention. 
Several methods and associated apparatus for this purpose will now be 
discussed. 
In the approach of FIG. 18, a single leaf spring 80 adapted for bilateral 
movement as indicated by the arrows is carried by the moving member 82. 
The bilateral leaf spring 80 is provided with an impact pad 69 on either 
side at the intended points of contact. The stationary member 84 is 
provided with a stop block 86 at each end of the span of travel of the 
spring 80. The stop block 86 is provided with one or more removable stops 
88. If desired, the stops 88 can be added or removed by a solenoid (not 
shown) or the like. Note in this embodiment that the length of the span is 
changeable in a fixed amount while the spring constant, k, of the spring 
80 remains the same. 
A variation of the approach of FIG. 18 is shown in FIG. 19. In this 
embodiment, the length of the span is again changeable while the spring 
constant of the spring 80 remains the same. A pair of unidirectional 
single leaf springs 90 are attached to the stationary member 84 at each 
end of the span of travel. Each leaf spring 90 is provided with an impact 
pad 69 on its inside face at the intended point of contact. Each end of 
the moving member 82 is provided with a stop block 86' which, in turn, is 
once again provided with one or more removable stops 88. As in the 
previous embodiment, if desired, the stops 88 can be added or removed by 
the solenoid 96 or the like. 
A pair of preferred approaches are shown in FIGS. 20 and 21. The approach 
of these figures is similar to the approach of FIG. 19 above. In these 
embodiments, however, the change in span of travel is precipitated by 
changing the spring constant, k, of the associated spring. With reference 
first to FIG. 20, a unidirectional, variable spring constant leaf spring 
90' is once again carried by the stationary member 84 at each end of the 
span of travel (only one being shown in the drawing for simplicity). The 
stop block 86, of this embodiment is a movable block carried on the end of 
a rod 92 carried by the armature 94 of a solenoid 96. By activating the 
solenoid 96, the contact position of the impact pad 69 carried by the stop 
block 86' can be changed so as to contact the spring 90, along its length 
at a low k position or a high k position. As those skilled in the art will 
readily recognize and appreciated, by replacing the two position solenoid 
96 with a variably positionable device, of course, more variations in the 
k of the spring 90, (and, therefore, variations in the span of the moving 
member 82) can be achieved. 
A variation of this general approach is shown in FIG. 21 where the solenoid 
96 is mounted above the spring 90'. A force transfer ball 98 is attached 
to one end of a flexible vane 100 carried on the other end by the armature 
94 of the solenoid 96 (or, optionally, a variable position device as 
mentioned above). The ball 98 can be moved along the spring 90, between 
positions of low k and high k as indicated in the drawing. A force 
transfer spring 90" is positioned on the other side of the ball 98 to be 
contacted along its length by the impact pad 69 carried by the end of the 
moving member 82. As can be appreciated, the spring constant of the 
springs 90' and 90" is additive and should be considered when calculating 
the parameters of each. When the impact pad 69 strikes the spring 90", it 
(at a constant k) transfers the force to the ball 98 at its point of 
contact with the spring 90". The ball 98, in turn, transfers the force to 
the spring 90' at its point of contact. The spring 90' provides a 
variable k of resistive force as a function of the position of the ball 98 
on its length. 
Another important aspect of the present invention determined by testing of 
the inventors herein is the need to balance the system in order to 
minimize energy loss during operation. As shown in FIG. 14, balancing of 
both the ballistic energy transfer device 42 and shuttle 24 is preferably 
accomplished by adding weights 65 at appropriate locations so that the 
rebound force is through the center of gravity. This results in virtually 
no sideward, friction producing components of the energy force within the 
sliding surfaces of the system with resultant rebound energy loss. As a 
consequence, energy conservation is maximized and driving energy 
requirements are minimized. The weights 65 can be of fixed weight or made 
to be adjustable, as desired. Alternatively, of course, instead of adding 
weight at light points to balance the system, weight could be removed from 
heavy points (as by drilling) to accomplish the same result. 
Turning now to FIGS. 23-26, two embodiments of the present invention in its 
best mode as presently contemplated following testing of various 
approaches will now be described. In the embodiment of FIGS. 23 and 24, 
the shuttle 24 is still slidably mounted between the pair of shafts 58. 
The legs 64,, however, have been reduced to a thin web 102 where they 
contact the shafts 58 so as to reduce possible friction. The tops of the 
upper legs 64' have a ferrous plate 104 attached thereto. The printer base 
38 has a pair of horizontal arms 106 extending out over the top of the 
ballistic energy transfer device 42 and parallel thereto. The arms 106 
each carry a magnet 108 which passes through a slot 110 in the ballistic 
energy transfer device 42 into close-spaced proximity to the adjacent 
plate 104 to create an attracting and lifting force therein which tends to 
frictionlessly support a portion of the weight of the shuttle 24 and 
thereby reduce the friction associated with its sliding movement along the 
shafts 58. In like manner, the ballistic energy transfer device 42 is 
supported on a pair of vertically mounted coil springs 112 which 
frictionlessly support a portion of the weight of the ballistic energy 
transfer device 42 while allowing side to side movement thereof and 
thereby reduce the friction associated with its sliding movement along the 
shafts 58. This in combination with the balancing described above 
minimizes the energy loss of the shuttle 24 and the ballistic energy 
transfer device 42 through friction. Note also that the size of the 
armature 48 has been reduced and it is mounted vertically between two 
opposed rows of coils 46 to provide the linear motor 44. In addition to 
reducing the amount of area which is in sliding contact with the shafts 
58, the construction as shown concentrates the majority of the mass of the 
shuttle 24 along the center line thereof passing through the contacting 
impact pads 69. Note that in this embodiment the rebound springs 52, are 
flexure springs supported at both ends so as to provide a stiff, quick 
acting, flicking action in rebounding the shuttle 24 for minimization of 
the turnaround time. Note also that in this embodiment the centering 
springs 54 are disposed along the centerline of the system between the 
shafts 58 so as to impart virtually no sideward forces (even minimal ones) 
against the ballistic energy transfer device 42 which might cause friction 
producing results. 
In the embodiment of FIGS. 25 and 26, there is a substantial change from 
the implementation of the present invention as hereinbefore described. 
Note, however, that the basic manner of operation is still present. The 
first major deviation is that the ballistic energy transfer device 42 is 
no longer mounted for sliding motion on the shafts 58. Rather, it is 
supported at its top (i.e. it hangs) between the tops of a pair of spaced, 
vertical leaf springs 114 extending upward from and carried by the printer 
base 38. As will be recalled, it was mentioned earlier that the printer 
base 38 could be used as the ballistic energy transfer device 42 if 
desired. As those skilled in the art will readily appreciate, it is this 
embodiment that could be so configured in various ways. A large, heavy 
printer base 38 mounted for lateral movement on a support base would 
energy transfer device 42. As in the previous embodiment, the upper legs 
64' have a ferrous plate 104 attached thereto and a pair of magnets 108 
are carried by the upper portion of the ballistic energy transfer device 
42 in close-spaced proximity to respective ones of the adjacent plates 104 
to create an attracting and lifting force therein which tends to 
frictionlessly support a portion of the weight of the shuttle 24 and 
thereby reduce the friction associated with its sliding movement along the 
shaft 58. Note that in this embodiment, as in the previous embodiment, the 
rebound springs 52' are flexure springs supported at both ends so as to 
provide a stiff, quick acting, flicking action in rebounding the shuttle 
24 for minimization of the turnaround time. 
In this embodiment, the linear motor 44 has been replaced by a solenoid 
drive system generally indicated as 116. As those skilled in the art will 
appreciate, the solenoid drive system 116 is a form of linear drive and, 
therefore, the linear motor 44 as described with respect to the previous 
embodiments could be employed with this embodiment. Likewise, the solenoid 
drive system 116 of this embodiment could be substituted for the linear 
motor 44 in any of the previously described embodiments. As shown in the 
drawings, the solenoid drive system 116 includes a U-shaped mounting plate 
118 attached to the bottom of the ballistic energy transfer device 42 
under the shuttle 24. The shuttle 24, in turn, has a mounting plate 120 
attached to the bottom thereof with a vertical member 122 extending 
downward therefrom between the two vertical ends of the mounting plate 
118. The bottom of the mounting plate 118 has a longitudinal slot 124 
therein into which a guide finger 126 extending from the bottom of the 
member 122 fits for sliding motion. If desired, the guide finger 126 can 
have a roller bearing fitted thereon for virtually frictionless movement 
in the slot 124. The finger 126 in the slot 124 replaces the bottom shaft 
58 of the prior embodiments in keeping the shuttle moving back and forth 
in a constant plane and not tending to rotate about the single shaft 58 
from which it is hung. A pair of solenoid coils 128 are mounted to 
respective ones of the two vertical ends of the mounting plate 18. An 
armature core 130 extends from each of the coils 128 to the vertical 
member 122 where it is attached by a pin 132. As those skilled in the art 
will readily recognize and appreciate, the solenoid drive system 116 can 
be of the stored energy type or the moving coil (i.e. voice coil) type, as 
best fits the particular application. As with the linear motor 44, the 
solenoid drive system 116 is operably connected to the speed control 
circuit 47 to be controlled thereby. It should also be noted with respect 
to the choice of drives (i.e. a D.C. stepper motor or a D.C. linear motor 
such as a solenoid or the like) that when a stepper motor is employed, a 
second encoding device such as that described above (e.g. encoder fence 78 
and sensor 36') mounted between the ballistic energy transfer device 42 
and the shuttle 24 is preferred so as to obtain the position of the 
shuttle 24 within the ballistic energy transfer device 42 for optimum 
driving thereof. With a D.C. linear motor (linear actuator, solenoid, or 
the like), the second encoding device is not necessary since the device 
does not move step by step, but rather, once activated moves towards the 
extent of its movement as long as power is applied. 
As those skilled in the art will readily recognize and appreciate, a 
variation of the foregoing approach would be to employ the entire printer 
including cover, electronics, etc. (with the exception of the shuttle 24 
itself) as the ballistic energy transfer device 42. A large, heavy printer 
could be mounted for the necessary lateral movement on compliant rubber 
feet that would allow the printer to move slowly a slight distance from 
side to side during operation thereof. In such an embodiment, the shuttle 
24 could again hang from a pair of thin-webbed legs 64' slidably mounted 
on a single shaft 58 carried by the printer. 
Another aspect of the present invention is also shown with respect to FIG. 
25; however, the various techniques now to be described may be adopted for 
any of the embodiments herein. As can be appreciated, the speed control 
circuit 47 requires positional input information with respect to the 
shuttle 24 in order to effect proper control of the reversal drive forces 
applied thereto. This can be accomplished with an optical fence and sensor 
arrangement as previously described herein. Additionally, however, the 
rebound springs 52 in their various embodiments can also be employed for 
this purpose. For example, by suspending the shuttle 24 from a pair of 
insulating legs 64' slidably mounted on the shaft 58, the rebound springs 
52' and impact pads 69 can be employed as the two contacts of a switch 
providing the signal of interest. In such case, the legs 64' could be 
molded of glass-filled Nylon, or the like, with carbon bearings sliding on 
the shaft 58. Another possibility would be to mount a strain gauge 71 on 
the rebound spring 52' to provide the signal of interest at an output 
thereof as a function of the flexing of the spring 52'. Also, an 
accelerometer 73 could be mounted directly to the shuttle 24 to provide 
the signal of interest at an output thereof as a function of the 
acceleration and deceleration of the shuttle 24. 
Having now discussed the construction and operation of a shuttle printer 
according to the present invention in general according to several 
embodiments thereof, some of the criteria to be considered in actually 
constructing a printer according to the teachings herein will now be 
addressed with particularity. In this regard, reference should also be 
made to the timing and motion chart provided as FIG. 27 herein. 
As described hereinbefore, the shuttle printer of the present invention 
employs uniformly spaced pins across a print line moving at a constant 
speed while printing with a very fast turn around time. It is anticipated 
that turn around times in the order of 1 to 2 MS can be achieved. This is 
accomplished by a novel design that employs a linear shuttle motor and a 
kinetic energy transfer system. The design has the advantage of 
transmitting no inertial forces to the case or platen. The design also 
allows the turn around time to be varied. This feature can be employed, 
for example, to provide time to feed between lines of text without another 
pass of the printheads. In other word, if the shuttle carrying the 
printheads is turned around and begins its return trip before the paper 
can be fed to its next print position, the trip is a lost one and the 
printer will operate in a unidirectional mode. If the turn around time is 
adjusted so that the paper is in position for printing before the shuttle 
begins its return trip, the faster approach of bidirectional printing can 
be applied. 
Another tradeoff that can be employed to good advantage in a shuttle 
printer according to the present invention is that of shuttle speed v. 
number of pins per printhead position. That is, while the prior art 
employs single pin printheads at each print position across the shuttle to 
keep the mass that must be accelerated and reversed to a minimum, the 
present invention allows one to select the best combination for optimum 
printer throughput. In this regard, initial investigation indicates that 
such optimum throughput is probably attained using printheads with 
multiple print pins vertically disposed above one another. For reference 
purposes, the single line of print pins spaced along the shuttle as 
depicted in the drawing figures described earlier herein is referred to as 
an "unfocused" approach while the use of multiple vertical print pins at 
each position, as represented by the shuttle 24' of FIG. 22, is referred 
to as the "focused" approach. Some representative findings are shown in 
the following tables. 
TABLE 1 
______________________________________ 
2800 Hz Printhead Performance 
24 Pins 
33 Pins 48 Pins 66 Pins 
______________________________________ 
10 CPI (48 DPI) 
800 l pm 1052 l pm 1345 l pm 
1800 
l pm 
Shuttle Frequency 
48 Hz 64 Hz 86 Hz 113 Hz 
Printing Efficiency 
90.5% 87.3% 82.7% 77.4% 
10 CPI (60 DPI) 
656 l pm 870 l pm 1176 l pm 
1538 
l pm 
Shuttle Frequency 
39 Hz 52 Hz 71 Hz 95 Hz 
Printing Efficiency 
92% 87.3% 82.7% 77.4% 
Shuttle Motion 
.55" .4" .28" .2" 
Print Line 13.2" 13.2" 13.44" 13.2" 
______________________________________ 
##STR1## 
Time 
______________________________________ 
TABLE 2 
______________________________________ 
Linear Shuttle Throughput (Non Focused) 
28 Pins 
28 Pins 49 Pins 49 Pins 
______________________________________ 
10 CPI (48 DPI) 
888 1pm 804 1pm 1415 1pm 
1214 
1pm 
Shuttle Frequency 
52 Hz 47 Hz 87 Hz 89 Hz 
Printing Efficiency 
86.5% 70.4% 78.3% 61.1% 
10 CPI (60 DPI) 
732 1pm 674 1pm 1188 1pm 
1043 
1pm 
Shuttle Frequency 
43 Hz 39 Hz 69 Hz 71 Hz 
Printing Efficiency 
88.9% 73.3% 81.8% 65.0% 
Shuttle Motion 
.48" .48" .27" .27" 
Print Line 13.44" 13.44" 13.23" 13.23" 
LF/TurnAround 
1 MS 2 MS 1 MS 2 MS 
______________________________________ 
TABLE 3 
______________________________________ 
Linear Hybrid Shuttle Throughput (Focused) 
Pins 2 .times. 7 Pins 
3 .times. 7 Pins 
4 .times. 7 Pins 
7 .times. 7 
______________________________________ 
10 CPI (48 DPI) 
497 1pm 723 1pm 935 1pm 1495 
1pm 
Shuttle 4 Hz 6 Hz 8 Hz 12 Hz 
Frequency 
Printing 94.2% 91.5% 89.1% 82.3% 
Efficiency 
10 CPI (60 DPI) 
402 1pm 588 1pm 765 1pm 1239 
1pm 
Shuttle 3 Hz 5 Hz 6 Hz 10 Hz 
Frequency 
Printing 95.3% 93.0% 91.0% 85.3% 
Efficiency 
Shuttle Motion 
6.6" 4.4" 3.3" 1.9" 
Print Line 13.2" 13.2" 13.2" 13.3" 
LF/TurnAround 
7 MS 7 MS 7 MS 7 MS 
______________________________________ 
Where "2.times.7 pins " two 7-pin heads on the shuttle. 
As those skilled in the art will appreciate, this invention is an 
improvement over the printer of Meloni as disclosed in U.S. Pat. No. 
4,534,287 in that the Meloni apparatus employs a mechanical drive 
incorporating a motor-driven wobble plate or disk (designated as track 74) 
to oscillate a multi-pin print head to effect shuttle printer operation in 
much the same manner as the prior art apparatus shown in FIG. 10. 
Thus, it can be seen from the foregoing that the present invention has 
truly met its stated objectives by providing a shuttle printer that can 
provide high quality output while printing at a much higher speeds than 
prior art dot matrix printers.