Pens for low torque chart recorders

A disposable marker apparatus for use with low torque recorders includes a bifurcated body with two separate ink reservoirs in the first and second body segments interconnected by a connector segment. The connector segment includes an ink transmitting member. A stylus tube extends from the body. A pivot member is provided to engage an associate pivot support outwardly from said pen body. A substantial portion of the mass of the marker is below the connector segment and the pivot member. The result is a marker having a center of gravity below the pivot so that the swinging marker tends to stabilize after disturbance due to vibration or rapid marker excursion.

FIELD OF THE INVENTION 
This invention relates generally to low torque chart recorders and more 
particularly to markers or pens (the terms "marker" and "pen" are 
generally used interchangeably) for such recorders. The pens and markers 
of this invention include self-contained fibrous ink reservoirs. 
DESCRIPTION OF THE PRIOR ART 
Strip chart and circular chart recorders provide a graphic record of 
voltage, current, watts, frequency, speed, temperature, and numerous other 
variables. 
Pens used with these recorders generally include a self-contained ink 
supply or are connected to a remote ink supply. Such pens are disclosed, 
respectively, in U.S. Pat. No. 2,199,078--Lindemann and U.S. Pat. No. 
2,626,201--Young et al. Remote ink supply pen systems are relatively 
complex (and therefore costly) and are subject to breakdown or failure. 
Self-contained liquid ink supply pens offer some advantages, over remote 
ink supply systems, but must be periodically refilled. 
The Lindemann and Young et al pen systems appear to be intended for use in 
certain types of recording instruments, such as galvanometers, in which 
the recorder driving force or torque is low. In such instruments, referred 
to herein as "low torque recorders," it is important that the marker and 
associated marker holding mechanism have a low moment of inertia about the 
vertical pivot axis of the recorder. 
As is also typical of these low torque recorder marking systems, the 
Lindemann and Young et al pens are delicately balanced on a horizontally 
extending low friction support member to maintain proper writing tip 
pressure and to provide required stabilizing capabilities in response to 
disturbances caused by vibration and rapid marker excursion. That support 
member has a circular cross section in the Lindemann instrument, while 
that shown in the Young et al patent has a knife edge pivotal support with 
a wedge-shaped cross section. Generally, the support member is supported, 
in existing systems, on the upwardly extending arms of a yoke with a 
downwardly extending central pivot member. 
Markers for recording instruments other than low torque recorders have been 
substantially improved over the past several years by the use of capillary 
ink reservoirs comprising ink laden fibrous material. For the most part, 
these markers are considered disposable after a single use. Examples of 
such markers are disclosed in U.S. Pat. Nos. 3,934,255--Taylor, 
4,100,549--Hubbard, and 4,233,609--Hubbard. One such disposable marker is 
disclosed in U.S. Pat. No. 4,367,481--Bunning. The Bunning marker is 
apparently intended for use in an existing low torque recorder. 
The general object of the present invention is to provide a practical, 
functional, easily manufacturable, and easily installable marker for 
certain existing low torque recorders, which marker is well balanced and 
includes optimal weight distribution so as to minimize the moment of 
inertia of the marker-marker mount combination. 
BRIEF DESCRIPTION OF THE INVENTION 
This is accomplished by providing a marker including a bifurcated ink 
reservoir having first and second portions interconnected by at least one 
and preferably two ink transmitting members. Ink retaining reservoir 
material is disposed in two main marker body segments comprising each of 
the first and second portions. The ink transmitting or conveying means 
associated with the bifurcated ink reservoir is housed in a connector 
segment of the marker. 
A stylus tube with an ink delivery means and a writing tip extends from one 
of the main marker body segments (the front segment) in a direction away 
from the other segment. Preferably, a counterbalance means is located on 
the other or rear main marker body segment and consists of a threaded 
support member on which is engaged a threaded counterbalance weight with 
means for resiliently disengaging the threaded engagement therebetween. 
A horizontally disposed support member is located on the underside of the 
connecting members halfway between the two marker body segments. The 
support member extends outward from the connecting members and the outward 
extentions of the support member, which may be wedge or knife edge or 
circular in cross-section to minimize friction, are adapted to be 
received, outboard of the connector segments, in an upwardly extending 
mounting yoke of a low torque recorder. The two marker body segments are 
suspended below the marker support member. As a result, the center of 
gravity of the marker is below the support member and the entire marker is 
located substantially within outer limit lines defined by, and symmetrical 
with a center line defined by the mounting yoke. 
For a more complete description of the present invention reference may be 
made to the following detailed description thereof together with the 
accompanying drawings and the subjoined claims.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings and particularly FIG. 1, recorder 10 includes 
a moving chart 12 enclosed in a housing 14. A marker 16, including a 
stylus tube 20 includes a writing tip 22 resting on chart 12. Marker 16 is 
supported by and balanced on a yoke support (not shown in FIG. 1) so that 
writing tip 22 of tube 20 exerts an acceptable pressure on chart 12. 
Marker 16 is free to pivot on the vertical axis 18 of a yoke support in 
accordance with electronic drive means (not shown) associated with the 
yoke support on which marker 16 is mounted. Chart 12 is electronically 
driven to move relative to tip 22 in a direction indicated by an arrow 
designated M. As a result, a continuous ink residue pattern 24 is 
deposited on chart 12 so that a desired record is accumulated. 
A preferred embodiment of marker 16 is illustrated in FIGS. 2, 3, and 11 
through 15. 
Referring more specifically to FIGS. 2 and 3, marker 16 includes a body 
housing or case 26 enclosing a bifurcated fibrous ink reservoir 60 
consisting of two separate and equal size segments of reservoir disposed 
in body segments 52 and 54. A horizontally extending pivot means 28 is 
centrally disposed on the underside of body connecting segments 56 for 
engaging a yoke support 18, as seen in FIG. 4. Stylus tube 20 extends from 
case 26 in a first direction. A counterbalance 30, including threaded 
receiver 32, extends from case 26 in the opposite direction, and a movable 
balance member 34 is disposed on receiver 32. 
Case 26 is typically formed of a suitable synthetic resin material and 
includes a top 36, a bottom 38, opposed sides 42,44, and opposed ends 
46,48. Case 26 includes first and second body segments 52,54, 
respectively, and relatively smaller connector segments 58. The 
construction of case 26, including first segment 52 and second segment 54 
defines a bifurcated ink reservoir 60 interconnected by connector segments 
58. 
A protrusion 62, FIG. 5, extends from end 46 and includes an aperture in 
the form of a throughbore 64 opening into first body segment. Throughbore 
64 includes an annular chamfer 66 and a cylindrical region 68 in end 46 
interconnected by an intermediate noncylindrical portion 70, see also FIG. 
6, having at least three sides. A vent 72, FIG. 2, is preferably formed in 
the top 36 of second body segment 54 and a suitable resilient vent plug 74 
is provided in vent 72. 
Pivot means 28, FIGS. 2 and 3, extends transversely of sides 42,44 on the 
underside of connectors 58 and includes ends 76 extending outwardly 
therefrom, as seen in FIG. 3. Depending on the type of pivot support 18 to 
be used, pivot means 28 can be of a wedge-shaped or knife edge cross 
section, as seen in FIG. 2, or a circular cross section, as illustrated in 
FIG. 11. Because first and second segments 52,54 of case 26 (as well as 
the reservoir portions housed therein) are disposed substantially below 
pivot means 28, on which marker 16 is supported, the center of gravity of 
marker 16 is also below pivot means 28. 
The yoke support 18 shown in FIG. 4 typically includes a central downwardly 
extending pivot member 18A and a pair of laterally spaced upwardly 
extending yoke arms, each with split ends 18B and 18C forming a crotch 
18D. Support member 28 rests in and extends between the crotches 18D of 
split ends 18B and 18C of the laterally spaced paired yoke arms. 
The lateral spacing between the upwardly extending arms of mounting yokes 
in existing low torque recorders of different manufacturers varies 
somewhat. 
Therefore, in order to adapt marker 26 to the pivot supports of different 
manufacturers (General Electric, Westinghouse, and Esterline Angus all 
make low torque recorders to which the present invention may be adapted) 
it may become necessary to extend sides 42,44 of case 26. For this 
purpose, extensions 78,80, see FIGS. 7, 8, 9, 10, can be formed with sides 
42,44 respectively, or in the alternative, metallic or plastic washers 
82,84 can be attached as extensions to sides 42,44 respectively, in a 
suitable manner such as with an adhesive or the like. In either case pivot 
means 28 will have sufficient length so that ends 76 extend through the 
extensions and the entire marker, in all cases, is located symmetrically 
within mounting yoke 18. 
A commercially available, ink-retaining fibrous reservoir material is used 
to retain ink in case 26, see FIGS. 11 and 12. Preferably, first and 
second equal size segments 86,88 of reservoir material are stored in first 
and second body segments 52,54, respectively. The height, width and length 
(0.29, 0.32, and 0.4 inches, respectively) as well as the overall shape 
(i.e., rectangular) of reservoir segments 86,88 are such that segments 
86,88 can easily be produced from commercially available forms of 
reservoir material. In order to communicate ink between segments 86,88 ink 
conveying wicks 90 extend through connector segments 58 and terminate in 
engagement with sections 86,88. 
Stylus tube 20, FIGS. 2, 3, 5, comprises an elongated cylindrical metal 
tube which may vary in shape and length to accommodate the recorders of 
various manufacturers. Tube 20 has an end 100 which extends into 
protrusion 62 and is press-fit into cylindrical region 68. The resulting 
spaces between noncylindrical portion 70 and cylindrical tube 20 act as a 
reservoir for a suitable adhesive to retain tube 20 attached to case 26. 
Tube 20 has an elongated portion 102, extending from end 100, and a 
perpendicular short portion 22 terminating with a nib 104 of a suitable 
ink transmitting material, which is inserted into the bent short portion 
22 of tube 20. A wick 106 also of suitable ink transmitting capability 
extends from nib 104, substantially along the length of tube portion 22 
and 20 and beyond end 100 so as to protrude into first reservoir segment 
52 in ink transfer communication with reservoir section 86. 
Threaded receiver 32, FIGS. 2 and 3, extends from end 48 of case 26. 
Balance member 34 has a main body 35 formed of a suitable synthetic 
material and can be of any desired size and shape, see FIG. 15. However, 
size and shape will vary according to a necessary increase or decrease in 
volume in order to counterbalance an appropriately sized stylus tube 20. 
Balance member 34 includes an aperture in the form of a smooth throughbore 
108 extending from a first end 110 to a second end 112. A cantilever-type 
resilient member 114 is formed adjacent second end 112. That is, resilient 
member 114 has an end 116, attached to the main body 35 of member 34, and 
extends coaxially along bore 108 to terminate at a free end 118 adjacent 
second end 112. A tooth 120, attached to free end 118, protrudes into bore 
108 so as to engage the threads 31 of threaded receiver 32. More than one 
tooth could be provided but only one tooth 120 is required. Resilient 
member 114 permits balance member 34 to be rapidly guided along threaded 
receiver 32 in a ratchet-like manner for coarse adjustment. Fine 
adjustment is accomplished by rotating balance member 34 axially along 
receiver 32. Movement of balance member 34 axially along receiver 32 is 
limited by sequential engagement of tooth 120 and the threads 31 of 
receiver 32. 
An indicator arrow 122, FIGS. 2, 2A, 3, is mounted on stylus tube 20 
adjacent perpendicular short tube portion 22. Arrow 122 is formed of a 
suitable synthetic resin material and has a first gripper 124 engaged with 
elongated portion 102 and a second gripper 126 engaged with perpendicular 
short tube portion 22. Because of the substantially perpendicular 
relationship between elongated portion 102 and short tube portion 22, 
indicator 122 is maintained in a desired position on tube 20 limited from 
rotation. 
A protective cap 128, FIG. 2, formed of a suitable resilient material, is 
provided with a blind bore 130 suitable for an interference fit with short 
tube portion 22. Cap 128 can therefore be retained on tube 20 to provide 
protection for short tube portion 22 when marker 16 is not in use, such as 
during shipping. 
The foregoing has described a disposable marker apparatus with a variably 
adjustable counterbalance for use with chart recorders. The marker has a 
self contained ink supply and has a counterbalance device which can be 
quickly and easily coarse-fine adjusted to assure acceptable writing tip 
pressure. Also, the marker of this invention is easily adaptable for use 
with a variety of commercially available low torque recorders. This is 
accomplished by changing the length of tube 20, changing the size and 
shape of balance member 34, using case 26 with side extensions 78,80 or 
82,84 using case 26 without any side extensions, or using either a 
wedge-shaped or cylindrical pivot member 28. One such recorder, the 
Esterline Angus, includes a centrally disposed upwardly extending clip 
within the upwardly extending mounting yoke arm. The function of this clip 
is to better retain prior liquid ink pens on the support member. This clip 
is unnecessary with the markers of the present invention and may simply be 
bent downward so as to avoid interference with the marker body. 
Alternatively, the clip may be permitted to extend upwardly and through 
the space between connector segments 58. 
It is anticipated that aspects of the present invention, other than those 
specifically described and illustrated will be apparent from the foregoing 
description and the drawings, and many other variants of the invention may 
be devised. The appended claims are intended to be construed to encompass 
all such variants and aspects which are within the true spirit and scope 
of the invention.