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Патент USA US3037407

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June 5, 1962
A. K. ALLEN ET AL
3,037,397
ADJUSTABLE LIMIT STOP
Filed NOV. 13, 1961
39
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United States Patent 0 "
7
3,037,397
Patented June 5, 196,2.
2
1
housing .11- and carries a spur gear 20. Spur gear 20 has
~
a threaded bore 21 engaging the threaded portion ‘19.
FIG. 4- illustrates in perspective spur gear 20 with its.
3,037,397
ADJUSTABLE-LIMIT STOP
Alton K. Allen, Kings Point, and Norman C. Zatsky,
Huntington, N.Y., assignors to Reeves Instrument Cor
poration, Garden City, N.Y., a eorporationof New
York
Filed Nov. 13, 1961, Ser. No. 151,969
12 Claims. (Cl. 74‘—424.8)
This invention relates tolimit stops and in particular
to miniature adjustable limit stops.
Limit stops are frequenly used in servomechanisms to
threaded bore 21.
The teeth 22 of the spur gear are meshed with the
teeth 23 of a pinion shaft 24. Pinion ‘shaft 24 is pro
vided with cylindricalends 25 and 26 mounted within the
?rst and second end pieces 12 and 13, respectively, for
10
limit the angular travel of shafts, such as the shafts of
A ‘hexagon head cap screw 29 cooperates with a coordi
15 nate clamp mounted within end piece 13 for rigidly lock
ing damage to these devices by stopping the rotation of
the shafts before they reach the end of their travel.
In the design of servomechanisms which are to include
a limit stop,.it has been di?‘icult to readily determine in
advance and to set the angular position at which a ro
tatable shaftshould be brought to a stop. Because of
this di?'iculty, it has been the practice to manually ad
just the. stop positions of the limit stop after the servo
mechanism has been assembled. The conventional limit
stops found in the prior art are not easily adjusted after
installation within a servomechanism. The present inven
tion overcomes this problem by providing an improved
limit stop whose limits may be readily adjusted after in
stallation into a servomechanism assembly.
A principal object of this invention is to provide a limit 30
stop whose limits may be easily, adjusted over a wide
range.
Another object of the invention is to provide a simple
and inexpensive adjustable limit stop whose limits may
be adjusted Without disturbing or removing the limit stop
above an axis parallel with the
The end 26 of the pinion shaft
through hole 27 in end piece
a hexagon shapedv hole 28 for
receiving a standard wrench for rotating the pinion shaft.
motors, potentiometers, angular transducers and related
devices. These limit stops serve the purpose of prevent
rotating the pinion shaft
axis of threaded shaft 18.
24 extends substantially
13 and is provided with
ing the, angular position of the pinion shaft 24. Other
suitable means may be employed for locking the angular
position of pinion shaft 24 without departing from the
invention.
A member 30 having a threaded bore 31 is carried by
the threaded portion 19 of shaft 18. A perspective view
of member 30 with threaded bore 31 is illustrated in
FIG. 3. 0ne end of member 30 is provided with a
U-shaped groove 32 which straddles a cylindrical guiding
rod 33 extending parallel to threaded shaft 18. The
guiding rod 33 is a?‘ixed between end pieces 12 and '13
by machine screws 34 and 34'.
Rod 33 serves the dual
purpose of guiding member 30 as it is driven along the
threaded portion 19 by rotation of shaft 18 and holding
the limit stop together by maintaining the end pieces 12
and 13 ?rmly against the ends of the hollow cylindrical
housing 11. Another identical rod not shown is placed
opposite rod ‘33 for symmetrically holding the end pieces
12 and 13 against the cylindrical housing. The guiding
rod 33 while guiding member 30 also prevents its rota
tion. The invention is not limited to the U-shaped groove
vA further object of the invention is to provide an ad
32 in member 30 straddling rod 33 and other suitable
justable limit stop whose limits may be adjusted by a
means may be employed to guide member 30 and to pre
single adjusting tool.
vent its rotation as shaft 18 is revolved without departing
These and other objects and advantages will become 40 from the invention.
from its servomechanism assembly.
apparent from a study of the following detailed descrip
tion together with the drawing in which the same ref
erence numerals refer to the same or similar parts, and
The threaded portion 19 of shaft 18 is provided with
a ?rst stop pin 35 mounted in-the threaded portion 19 ad
jacent the ?rst ball bearing assembly I14, and a second‘
wherein,
stop pin 36 mounted in the threaded portion 19 adjacent
FIG. 1 is a sectional view of the improved adjustable
the second ball bearing assembly 16.’ Stop pin 35 pro
limit stop of the invention as viewed from the side,
jectsradially from threaded portion 19 by an amountv
FIG. 2 is a sectional view of an alternative embodi
su?icient to engage a third stop pin 37 carried by mem
ment of the invention,
ber 30. Stop pin 37 extends parallel to shaft 18 and pro
FIG. 3 is a perspective view of the threaded and
jects from each side of member Why a distancergreater
grooved member forming an integral part of the limit 50 than the spacing between adjacent threads of the threaded
stops of FIGS. 1 and 2, and
portion 19. Similarly, stop pin 36 projects radially from
‘FIG. 4 is a perspective view of the threaded spur gear
threaded portion 19 by an amount suflicient to engage a
which is an integral part of the limit stops of FIGS. 1
fourth stop pin 38 carried by spur gear 20. Stop pin~<38'
and 2.
extends through and projects from each side of spur gear
Referring to FIG, 1, there isshown a preferred em 55 20 in a similar manner to pin 37. The adjacent ends: of
bodiment of the adjustable limit stop having a hollow
cylindrical housing or case .11 situated between a ?rst
the 'stop‘pins 37 and 38 project toward each other from
the surfaces of member 30 and spur gear 20, respectively,
end piece 112 and a second end piece 13. A ?rst bearing
in order to engage each other and prevent the spur gear
assembly 14 is situated within a central opening 15 in
20 from binding upon threaded portion 19 which would
end piece 112, and a second bearing assembly 16 is situ 60 have resulted if the spacing between spur gear 20'and,
ated within a centrally recessed hole 17 in end piece 13.
member 30, during adjustment, were reduced su?iciently
The ?rst and second bearing assemblies 14 and 16 are
to allow the surface of the spur gear 20'to abut against
coaxially aligned and support shaft 18 for rotation about
theadjacent surface of member 30.
’
Stop pin 35 in threaded portion 19 is located at a?xed
A threaded portion 19 of shaft 18 is situated within 65 distance from the end of shaft 18 and is set at a par
a central axis.
3,037,397
3
ticular angular position in the threaded portion 19 rela
tive to the threads in order to insure that it will overlap
4
fraction of a revolution of shaft 18 to a large number of
revolutions, depending upon the physical length of the
limit stop. The adjustment of the limits is not restricted
to complete turns of shaft 18. Only a single adjusting
tool for insertion in cap screw 29 and hole 28 is required
these two stop pins 35 and 37 are driven into engage
for setting the second limit.
ment by rotation of shaft 18. Similarly, stop pin 36 is
‘It is believed apparent that the limit stop of FIG. 1 may
located at a ?xed distance from stop pin 35 and is set
be modi?ed by interchanging the member 30 with the
at a particular angular position in the threaded portion
spur gear 20 on threaded portion 19 without departing
19 relative to the threads so that it will overlap stop pin
38 by an amount slightly less than the spacing between 10 from the scope of the invention. With this modi?cation,
the stop pin 38 of spur gear 20 would be translated to
adjacent threads of the threaded portion when these two
ward end piece 12 and would engage stop pin 35. The
pins are driven into engagement. While stop pin 35 pro
stop pin 37 by an amount slightly less than the spacing
between adjacent threads of the threaded portion when
?rst limit of shaft 18 would, accordingly, be adjusted by
setting the pinion shaft 24. The second limit would be
pendent upon these particular settings of the angular posi 15 reached when the stop pin 37 of member 30 translated
jects upward and stop pin 36 projects downward in FIG.
1, it should be appreciated that the invention is not de
toward end piece 13 and so as to engage stop pin 36.
The stop pins 35 and 36 may, of course, be resiliently
mounted in threaded shaft 18 to absorb shock and pre
vent damage to the limit stop without departing from the
the threaded member 30 and the spur gear 20 to be driven
together along threaded portion 19 toward end piece 20 invention. Similarly, stop pins 37 and 38 may be resilient
ly mounted in threaded member 30 ‘and spur gear 20, re
12. Member 30 ‘and spur gear 20 do not rotate as they
spectively. If desired, the stop pins 35--38 may be made
travel along threaded portion 19 and the spacing between
of suitable resilient material to absorb shock.
them remains ?xed. Stop pin 35 revolves with shaft 18
The invention is not restricted to the particular angular
and stop pin‘37 travels along with member 30 until the
two are brought into engagement. When this condition 25 disposition of pinion shaft 24 and guiding rod 33 about
the axis of threaded shaft 18 shown in FIG. 1. While
is met, shaft 18 can no longer be revolved relative to the
pinion shaft 24 and guiding rod 33 are diametrically dis
limit stop assembly in a clockwise direction and this angu
posed about threaded shaft 18 in the illustration, it is
lar position of shaft 18 represents the ?rst of the two
apparent that the guiding rod 33 could be disposed closely
limit stops.
tions of the pins 35 and 36.
In the operation of the limit stop of FIG. 1, a clock
wise rotation of shaft 18 will, for example, cause both
However, it is possible to rotate simultaneously the
shaft 18 along with the entire limit stop assembly about
the axis of the shaft. A circular ?ange 39 integral with
end piece 12 is provided for mounting the limit stop in
the conventional servo mount to enable both shaft 18
and the limit stop assembly to be angularly rotated within
its mount before the limit stop assembly is permanently
locked to the mount. This angular positioning may be
done even though shaft 18 carries a gear engaged with
adjacent to the pinion shaft 24 without disturbing the
principle of operation of the limit stop.
FIG. 2 illustrates an alternative embodiment of the
invention in which the necessity for a guiding rod has been
eliminated. In this embodiment, the pinion shaft 24
serves the dual purpose of guiding both member 30 and
spur gear 20. The U-shaped groove 32 of member 30
straddles the pinion shaft 24 which guides the member
30 and prevents its rotation. The operation and adjust~
ment of the limit stop of FIG. 2 is identical with the limit
the shaft of the motor, potentiometer, angular transducer
40 stop of FIG. 1. The cylindrical housing 11 is made an
or other related device whose shaft is to be stopped.
integral part of the end piece 13 and the end piece 12 is
After the ?rst limit has been properly set and the limit
secured to housing 11 by machine screws 40.
stop rigidly locked in its servo mount, the shaft 18 may
Since many changes could be made in the construction
be rotated in a counter-‘clockwise direction. Both the
of the above described limit stops and many widely dif
threaded member 30 and the spur gear 20 will now be
ferent embodiments of the invention could be made with
driven together along the threaded portion 19 toward end
out departing from the scope thereof, it is intended that
piece 13. Stop pin 36 which revolves with shaft 18 will
all matter contained in the above description or shown
be stopped when it engages the stop pin 38 carried by
in the accompanying drawing shall be interpreted as illus»
spur gear 20. The angular position of shaft 18 at which
trative and not in a limiting sense.
stop pins 36 and 38 become engaged to establish the
What is claimed is:
second limit is determined by the position of spur gear 50
1. An adjustable limit stop comprising in combination:
20 relative to the threaded member 30. It is possible,
(a) hollow cylindrical housing means,
therefore, to adjust the second limit for shaft 18, in ac
cordance with the invention, by adjusting the relative po
sition of spur gear 20 with respect to threaded member
30. This is achieved by rotation of spur gear 20 about 55
threaded portion 19 by means of the pinion shaft 24.
A hexagon shaped adjusting tool inserted in the head
of cap screw 29 releases the coordinate clamp upon the
cylindrical end 26 of pinion shaft 24 and permits the
pinion shaft 24 to be rotated. The same hexagon shaped 60
tool is inserted in the hexagon hole 28 and pinion shaft
24 is rotated to rotate spur gear 20 through the teeth 22
and 23 until the spur gear is properly positioned on
threaded portion 19. In the event that the desired sec
ond limit for shaft 18 is required before stop pin 36 has
become engaged with stop pin 38, then the pinion shaft
24 is rotated in a direction to cause spur gear 20 to ap
proach end piece 13 until these two stop pins 36 and'
38 are engaged.
When the second limit has been prop
erly set, the adjusting tool locks end 26 of pinion shaft 70
24 by tightening cap screw 29. It will be observed that
the spacing between spur gear 20 and threaded member
30 remains ?xed when the pinion shaft 24 is locked.
The second limit for shaft 18 with respect to its ?rst
limit may be adjusted over a very wide range, from a
(b) ?rst and second end pieces mounted in the ends of
said hollow cylindrical housing means,
(0) ?rst and second bearing means centrally mounted
in said ?rst and second end pieces, respectively, and
being aligned with the axis of said hollow cylindrical
housing means,
(d) a threaded shaft situated within and coaxially
aligned with said hollow cylindrical housing means
and mounted for rotation within said bearing means.
(2) a spur gear having a centrally threaded bore situ
ated on said threaded shaft.
(f) a longitudinally extending pinion shaft rotatably
mounted within said cylindrical housing means be
tween said ?rst and second end pieces, said pinion
shaft extending parallel with and displaced from the
longitudinal axis of said cylindrical housing means,
said spur gear being in mesh with said pinion shaft
and being adapted for travelling along said threaded
shaft as said threaded shaft is rotated,
(g) a threaded member situated on said threaded shaft.
(h) a longitudinally extending guiding rod situated
within said cylindrical housing means and a?ixed be
tween said ?rst and second end pieces, said guiding
3,037,397"
.
6
rod extending parallel with and displaced. from the
(d) a threaded shaft extending between said ?rst and
longitudinal axis of said cylindrical housingqmeans,
‘ second end pieces and mounted for rotation within
(i) said threaded member situated on said' threaded
shaft havingagroovedportionstraddling said guid
ingrodand being adapted for travelling along said
threaded sh‘art‘as"saia'nrreadea shaft is rotated,
(j) adjusting 'irieans‘a?ixedto saifd'pinion shaft for
rotating ‘said pifiion' shaft and said spur gear to ad
just the spacing between said spur gear and said
threaded member, and
10
(k) means for locking the angular position of said
pinion shaft to hold the relative spacing between said
spur gear and said threaded member ?xed as said
threaded shaft is rotated.
2. The adjustable limit stop as de?ned by claim 1 15
further comprising:
(a) ?rst and second stop pin means affixed to said
threaded shaft adjacent said ?rst and second bearing
means, respectively, said ?rst and second stop pin
means extending radially from the surface of said 20
threaded shaft, and
(b) third and fourth stop pin means af?xed to said
spur gear and said threaded member, respectively,
said third and fourth stop pin means extending par
allel to and displaced from said threaded shaft.
25
3. An adjustable limit stop comprising in combination:
(a) ?rst and second end pieces spaced apart,
(b) ?rst and second bearing means mounted within
said ?rst and second end pieces, respectively,
(0) supporting means coupled to said ?rst and second 30
end pieces for coaxially aligning said bearing means
and maintaining said end pieces in ?xed relation to
each other,
(d) a threaded shaft extending between said ?rst and
second end pieces and mounted for rotation within 35
said bearing means,
(e) a spur gear having a centrally threaded bore situ
ated on said threaded shaft,
(f) a pinion shaft rotatably supported between said
?rst and second end pieces and extending parallel 40
with said threaded shaft, the teeth of said pinion
shaft being in mesh with the teeth of said spur gear,
(g) a threaded member situated on said threaded
shaft, said threaded member having a grooved portion
straddling said pinion shaft, said spur gear and said
threaded member being guided along said pinion
shaft and being driven along said threaded shaft as
said threaded shaft is rotated,
(h) adjusting means provided on said pinion shaft for
rotating said pinion shaft and said spur gear to adjust
the spacing between said spur gear and said threaded
member, and
(i) means for locking the angular position of said
pinion shaft to hold the relative spacing between said
spur gear ‘and said threaded member ?xed as said 55
threaded shaft is rotated.
4. The adjustable limit stop as de?ned by claim 3
further comprising:
(a) ?rst and second stop pin means affixed to said
threaded shaft adjacent said ?rst and second bearing 60
means, respectively, said ?rst and second stop pin
means extending radially from the surface of said
threaded shaft, and
said bearing means,
'
l
(e) a spur gear having a centrally threaded bore situ
ated on said threaded shaft,
(1‘) a threaded member situated on said threaded shaft,
(g) means situated between said ?rst-and secondend
pieces and extending parallel to said threaded shaft
for guiding said spur gear and said threaded member
along said threaded shaft as said threaded shaft is
rotated,
(h) said means including adjusting means for rotating
said spur gear on said threaded shaft to adjust the
spacing between said spur gear and said threaded
member,
(i) means for locking said adjusting means to prevent
rotation of said spur gear and to hold the relative
spacing between said spur gear and said threaded
member ?xed as said threaded shaft is rotated,
(j) ?rst and second stop pin means affixed to said
threaded shaft adjacent said ?rst and second bearing
means, respectively, said ?rst and second stop pin
means extending radially from the surface of said
threaded shaft, and
(k) third and fourth stop pin means a?‘ixed to said
spur gear and said threaded member, respectively,
said third and fourth stop pin means extending par
allel to and ‘displaced from said threaded shaft.
6. An adjustable limit stop comprising in combination:
(a) ?rst and second end pieces spaced apart,
(b) supporting means coupled to said ?rst and second
end pieces for maintaining said end pieces in ?xed
relation to each other,
(0) a threaded shaft extending between and mounted
for rotation within said ?rst and second end pieces,
(d) ?rst and second threaded members situated on said
threaded shaft,
(e) means extending parallel to said threaded shaft
and mechanically intercoupled with said ?rst and
second threaded members for guiding said ?rst and
second threaded members and preventing their rota
tion as said threaded shaft is rotated,
(1‘) said means extending parallel to said threaded
shaft including adjusting means for adjusting the
spacing between said ?rst and second threaded mem
bers, and
(g) locking means coupled to said adjusting means for
locking said adjusting means and maintaining the
spacing between said ?rst and second threaded
members ?xed as said threaded shaft is rotated.
7. The adjustable limit stop as de?ned by claim 6 fur
ther comprising:
'
(a) ?rst and second stop pin means a?’ixed to said
threaded shaft adjacent said ?rst and second end
pieces, respectively, said ?rst and second stop pin
means extending radially from the surface of said
threaded shaft, and
(b) third and fourth stop pin means a?ixed to said
?rst and second threaded members, respectively, said
third and fourth stop pin means extending parallel
to and displaced from said threaded shaft.
8. The adjustable limit stop as de?ned by claim 1
wherein said threaded shaft situated within and coaxially
(b) third and fourth stop pin means a?ixed to said
spur gear and said threaded member, respectively, 65 aligned with said hollow cylindrical housing means in
cludes a non-threaded end portion extending through and
said third and fourth stop pin means extending par
projecting beyond said ?rst end piece.
allel to and displaced from said threaded shaft.
5. An adjustable limit stop comprising in combination:
9. The adjustable limit stop as de?ned by claim 1
wherein said means for locking the angular position of
(a) ?rst and second end pieces spaced apart,
(b) ?rst and second bearing means mounted within 70 said pinion shaft includes clamp means a?ixed to said
said ?rst and second end pieces, respectively,
second end piece.
10. The adjustable limit stop as de?ned by claim 2
(0) supporting means coupled to said ?rst and second
end pieces for coaxially aligning said bearing means
wherein said ?rst and second stop pin means are rigidly
and maintaining said end pieces in ?xed relation to
attached to said threaded shaft at a ?xed spacing there
each other,
75 between.
3,037,397
7
8
11. The adjustable limit stop as de?ned by claim 5
wherein said means situated between said ?rst and sec-
ond end pieces and extending parallel to said threaded
shaft includes a pinion shaft and a longitudinally extending guiding rod.
,
portion straddling said means extending parallel to said
threaded Shaft
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,356,861
L.
12- The adjustable llmlt StOP 21S de?ned by clalrn 6
2,818,744
Nigody _______________ __ Jagn' 7, 1958
wherein one Of said threaded members includes a grooved
2,837,925
Rowley et a] __________ __ June 10, 1958
,
_
_
k ________________ __ Au . 29, 1944
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