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Патент USA US2407235

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Sept’ 10, 1946-
Filéd oct'. 12, 1942 ‘
L..1Zb/Zard//a£5lazd, ‘
Patented Sept. 10, 1946
Laban Richard Halstead, Chicago, Ill., assignor
to Eugene Dietzgen 00., Chicago, 111., a corpo
ration of Delaware’
Application October 12, 1942, Serial No. 461,688
4 Claims. (01. 33-79)
The present invention relates in general to par
allel motion apparatus and has more particular
reference to drafting machines embodying par
allel motion mechanism, the invention relating
more especially to drafting apparatus adapted
for attachment on a drawing board or table for
the support of a ruling guide element, such as
a straight edge, for movement within a drafting
area on the board or table whilemaintaining
the ruling element constantly at a selected an
An important object of the invention is to pro
vide parallel motion drafting apparatus in which
the element supported for parallel movement is
carried on jointed arm means including ?exible
belt means for maintaining the supported device
Another important object is to provide simple
and inexpensive belt covers for apparatus of the
character mentioned, such covers serving not
only to enclose the flexible pulley driving bands
and thus guarding the operator of theapparatus
against the danger of injury through sudden
breakage of the band, but also serving generally
to improve the appearance‘of the apparatusand
to impart additional rigidity in the pulley carry
10 ing arm of the drafting machine without, how
ever, rendering the same absolutely rigid, a de
gree of ?exibility being desirable‘in the arms of
a parallel motion‘drafting machine of the char
acter mentioned.
The foregoing and numerous other important
objects, advantages, and inherent functions of
the invention will be fully understood‘from the
following description, which, taken in connection
with the accompanying drawing, discloses a pre
in a desired angular position regardless of the
movement of the supporting arm within the
drafting area; a further object being to- provide
simpli?ed, inexpensive guard means for enclos 20 ferred embodiment of the invention‘.
ing otherwise exposed portions of the ?exible belt
Referring to the drawing:
Figure 1 is a perspective view of parallel mo
Another important object is to form the guide
support arm of parallel motion drafting appa
ratus by providing a pair of pulley carrying heads
tion mechanism embodying the present inven
Figures 2 and 3 are sectional views, respec
and extensible bar means, preferably a screw rod ‘
tively, taken substantially along-the lines 2-2
for supporting‘ the heads in adjustably spaced
and 3-3 in Figure 1;‘
' relationship, to maintain a flexible endless belt
at a desired tension on the pulleys, and to pro
‘ '
Figure 4 is an enlarged sectional view taken
substantially along the line‘ 4-4 in Figure 2;
vide inexpensive, preferably sheet metal, channel 30 Figure 5 is a perspective view showing a chan-‘
members adapted for demountable assembly on
nel member forming a part of the apparatus il
said heads in position extending therebetween
lustrated in Figures 1-4;
and enclcsing’the endless belt means between the
Figure 6 is a perspective view showing a mod
heads; a further object being to form the spaced
i?ed channel end structure;
walls of the channel members with longitudinally
Figure '7 is a sectiona1 view illustrating the as
extending beads therein for the purpose of
sembly of the structure shown in Figure 6; and
strengthening the same against lateral bending
Figure 8 is a perspective view illustrating an
whereby adequate strength may be had in’chan
other channel end arrangement.
nels comprising lightweight sheet metal of mini
To illustrate the invention, the drawing shows
mum thickness.
40 parallel motion mechanism comprising means
Another important object is to provide sim
forming a pair of arm elements H and IS. The
pli?ed means for mounting the opposed ends of
arms H and I; are preferably of substantially
a belt enclosing guard channel on the spaced
identical construction and may comprise each a
pulley heads of a parallel motion drafting ma
pair of heads, the arm ll comprising spaced
chine; a, further object being to form the heads 45 heads I5 and I1, and the arm l3 comprising
with grooves, notches or slots to interlockingly
spaced heads I9 and 2|.
receive the ends of belt enclosing channels formed
These heads each comprise a rim 22, an em
to lockingly ?t the grooved portions of said slots;
bossment 24 extending radially outwardly of the
a further object being to utilize the inherent re
rim, and a pair of projecting ?ngers 26 extending
silience of the sheet metal channels to hold the 50 tangentially from the rim, the boss 24 and the
same inter-lockingly in the grooved pulley head
projections 26 being parallel and extending in
slots, such construction and arrangement allow
the same direction from the housing. The hous
ing the preformed channel‘members to be snapped
ings'formin‘g the arm I l are maintained in spaced‘
into place and securely held in position on and
relationship by means of a spacing bar 21, the‘
55 opposite ends of which ?t into sockets formed
extending between the spaced pulley heads.
in the embossments 24 of the housings |5 and
members preferably comprise sheet metal chan
nels having spaced side walls 3|, and may be
I1, an end of the bar 21 being in threaded con—
formed from a single strip of sheet metal by
nection with the embossment 24 of at least one
bending the same along a medial line of bend to
of said housings to allow the spaced relationship
of the housings to be adjusted by turning the 5 form a curved channel portion 33 interconnecting
the sides of the channel. In order to strengthen
bar 21 with respect to the housings. The housings
the channel melnber, which is preferably formed
l9 and 2| forming the arm I3 are likewise sup
of thin sheet metal of minimum thickness, the
ported adjustably in spaced apart relationship
side walls are provided with longitudinally ex
by means of a spacing bar which is preferably
10 tending ?utes 35, preferably pressed outwardly
identical to the bar 21‘
The heads l5, I1, I 9 and 2| comprise pulley
housings. The head |5 encloses a pulley ?xed
on a shaft or pin which extends below the hous
in the side walls 3| to form longitudinally ex
tending beads. The projections 26 of the pulley
housings are drilled longitudinally to form a
circular opening 3'! therein extending from the
ing, said pin being rigidly secured in a clamp
bracket 23 by means of which the drafting ma 15 extremity of the projection and opening into the
pulley receiving cavity de?ned by the rim 22.
chine may be anchored on a drafting board or
After the circular opening has been drilled or
table, as at the edge thereof, so that the arms | I
otherwise formed in each of the projections 26
and I3 may be supported for movement over the
of the several heads, said projections may then
drafting surface afforded by the board or table.
Means is provided within the head l5 for sup 20 be sawed or otherwise cut to form a preferably
rectangular slot 39 extending in the projection
porting the same on and for rotary movement
diametrically with respect to the circular open
about the axis of the pin and the pulley carried
ing 31, the slot 39 being open along one side of
by the pin Within the housing l5.
the projection whereby the slot has a closed bot
The housings I‘! and I9 cooperate to form an
enclosure for a duplex pulley or double pulleys 25 tom. The slot is formed preferably so that the
circular opening 31 extends midway between the
drivingly connected, as on a common shaft, one
bottom and open side of the slot 39.
pulley being enclosed in the housing ll, while
The foregoing structure provides an open slot
the other is enclosed in the housing I9, the pulleys
in each projection 26 having longitudinal grooves
being supported for rotation with respect to both
housings whereby the housings Ill and I 3 are 30 38 in the sides of the slot-so that an end of the
channel 29 may be received in the grooved slot
interconnected for relative rotation about the
with the ?utes 35 of the channel interlockingly
axis of the pulleys enclosed thereby.
engaged in the lateral slot grooves 38. A guard
The housing or head 2| also encloses a pulley
member 29, because of the resilience imparted by
supported for rotation therein, said pulley car
the curved portions 33 thereof, may be inserted
rying a ruling guide 25 which preferably extends
through the open sides of the slots in aligned pro
outwardly of the housing 2| at the under side
jections 26 of a pair of pulley heads by com
thereof, the pulley in the housing 2| also carry
pressing the ends of the member 29 to allow the
ing means including the manually operable knob
?uted portions 35 to pass through the open side
39 for adjusting the angularity of the guide 25
of the slot and snap into place in the slot
with respect to the pulley and for latching the
grooves 38. After assembly in such fashion, the
guide in angularly adjusted position.
inherent resilience of the member 29 will insure
The pulleys in the housings I5 and I1 are driv
ingly connected by endless belt means and the
pulleys in the housings l9 and 2| are likewise
drivingly interconnected. The driving belt means
in each arm preferably comprises an endless steel
tape 28 riding in flat grooves formed in the
spaced pulleys drivingly connected thereby, the
belts extending from the pulley housing heads
through channels formed in the projections 26.
By manipulating the spacing bars and thus ad
justing the spacement of the pulley carrying
heads, the driving bands 23 may be placed under
suitable tension in order to drivingly
nect the pulleys whereby to maintain
?xed angular relationship between the
the pulley in the housing 2|, regardless
the same
table and
of swing
ing movement of the arms H and | 3 over the
drafting surface. The belts, in other words, con
nect the pulley in housing 2|, through the pulleys
in housings l1 and I9, to the pulley in housing
l5 which is ?xed to the drafting table. Thus the
pulley in the housing 2| is held against turning
with respect to the drafting surface while sup
ported for swinging movement thereover by the
linked arms II and I3.
In order to enclose and protect the driving
belts 28 between the pulley heads, thereby im
proving the appearance of the drafting machine,
and also bracing and rigidifying the arms I | and
I3 to some extent while guarding the operator
of the machine against injury in the event of
snapping of a belt 23 when under tension in
service or through accidental over-tensioning,
guard members 29 are provided.
These guard
that the same remains latched in mounted posi
It will be seen that the channel member 29 may
be applied in the slots of spaced fingers 26 with
the curved top 33 of the channel uppermost,
whether the slots open upwardly, as in the fingers
26 of the arm l3, or whether the slots open down
wardly, as in the heads of the arm ||. Conse
quently identical channels 29 may be used for
both arms H and I3, and, moreover, the jigs
and ?xtures for slotting the projections 26 may
be identical for all of the heads IE, IT, l9 and 2|.
While the guards 29 formed as shown in Fig
ure 5 are entirely satisfactory for practicing the
present invention in the manner described, it will
be seen that, since the ends of the channels 29
are merely frictionally ?tted in the slots 39, longi
tudial movement of the channel ends in the slotted
projections 26 is allowed freely in either direction,
limited only by engagement of the channel ends
with the peripheral surfaces of the pulleys. The
channels are sized so that neither end of the
channel may be withdrawn axially from the end
of its supporting projection 26. While no harm
will result through engagement of the end of a
channel 29 with the surface of the adjacent
pulley, it is preferable, as a re?nement, to form
the channels with outwardly projecting emboss
ments 4| adjacent the ends thereof, said em
bossments affording shoulders adapted, as shown
in Figure 7, to engage the end of the housing
projection 23 and thereby limit the movement of
75 the channel end into the embossment at a point
such as to prevent the end of the channel from
engaging the periphery of the pulley.
I It will be noted that the embossment 4| li-m
its movement of the channel end in one direc
tion only in the housing projection 26, and it
may be desirable in some instances to anchor at
least one end of the channel in the housing pro
jection in which the same is mounted. To this
end, as shown in Figure 8, the channel, prefer
ably in the grooved portion 35 thereof, may be
formed with an outward embossment 43 of pref
erably hemispheric con?guration, in position to
snap into and engage in an opening 45 formed
in the housing projection 26, such opening 45
preferably being formed by drilling through the
housing projection 26 in a direction at right angles
to the slot 39.
cover extending between and attached at its 015
posite ends on said spaced heads in position en
closing the driving member between said heads,
said cover comprising a shell of resilient mate
rial having an end formed with a longitudinally
extending ?ute and at least one of said heads
having a socket formed with a longitudinal
‘ groove for receiving said ?ute to secure the end
of said cover on said head, said cover having an
embossment forming a, shoulder spaced from and
facing the end of the cover in position to engage
said head at the open end of the socket and limit
longitudinal movement of the end of the cover
inwardly in said socket.
2. In parallel motion apparatus comprising an
arm having a pair of spaced heads, a turnable
member in each head, a driving member inter
It will be seen from the foregoing that the
connecting said turnable members, said driving
?uted channels 29 afford an extremely simple
member including a portion extending between
and inexpensive means for enclosing the steel 20 said heads, the combination of a detachable
tapes 23 between the pulley housings forming the
cover extending between and attached at its op
arms H and i3. These tape guarding channels
posite ends on said spaced heads in position en
29 may be formed of extremely thin, inexpensive
closing the driving member between said heads,
sheet metal and, to minimize manufacturing ex
said cover comprising a resilient shell of sheet
pense, the ?utes 35 and the embossments 4| and
metal having a pair of spaced walls, at least one
43 may be formed in the sheet metal strips, while
of which is formed with an outwardly pressed
the same are in flat condition. After forming
?ute extending substantially throughout the
the ?utes 35 and the embossments M or 43, if
length of the cover for strengthening the same,
desired, .the formed strip may then be bent along
said flute being disposed between the opposite
the line of bend 33 to provide the channel in ?n
sides of the wall in which it is formed, said heads
ished condition ready for assembly in the draft
having each a socket for receiving the opposed
ing machine. When assembled, the channels not
ends of said cover, one of the said sockets com
only serve to enclose the pulley driving tapes-2B,
prising a lateral open slot having opposing walls
but also materially improve the super?cial ap
and a closed bottom, and a longitudinal groove in
pearance of the drafting apparatus, and, fur
a wall of the slot in position between the bottom
thermore, aid to some extent in rigidifying the
and the open side of the slot, whereby the end
arms I! and i3 by minimizing the tendency of
of the cover may be assembled in the slot through
said open side, by compressing the opposed walls
one pulley head to turn, with respect to the
other, about the axis of the spacing rod 21. The
of the cover, the resilience of which, after as
channels 29, however, do not impart absolute 40 sembled, serves to yieldingly press the walls of
the cover apart in said slot and interlock the
rigidity in the arms, for a limited amount of/rel
ative turning of the heads about the axis of the
flute in said groove to retain the cover in the
spacing rod is desirable in order to accommo
date the supported ruling guide 23 to the draft
3. The combination as set forth in claim 2
A :4 wherein said cover is formed with an emboss
ing surface,
It is thought that the invention and its numer
‘ ment forming a shoulder spaced from and fac
ous attendant advantages will be fully under
ing toward an end of the cover in position to en
stood from the foregoing description, and it is
gage the head at the open end of the socket
obvious that numerous changes may be made in
thereof and limit longitudinal movement of the
the form, construction and arrangement of the
end of the cover inwardly of said socket.
several parts without departing from the spirit
4. The combination as set forth in claim 2
or scope of the invention, or sacri?cing any of its
wherein at least one of said heads and the end
attendant advantages, the form herein disclosed
of said cover received therein comprise cooper
being a preferred embodiment for the purpose of
ating latch members including a latching pro
illustrating the invention.
55 jection on one latch member and a cooperative
The invention is hereby claimed as follows:
cavity on the other for receiving said projection,
1. In parallel motion apparatus comprising an
whereby to latch the end of the cover in the sock
arm having a pair of spaced heads, a turnable
et of said head against relative movement of the
cover with respect to the head in the direction of
member in each head, a. driving member inter
the inter?tting ?utes and grooves.
connecting said turnable members, said driving
member including a portion extending between
said heads, the combination of a detachable
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