Note: Descriptions are shown in the official language in which they were submitted.
'77~
This invention relates to a tool for rotating a nut,
bolt, screw or like element.
In the case of conventional mechanisms of the type to
which this invention is directed (East German patent No. 62 789)
a head of a wrench is mounted on a ratchet drum which is in turn
mounted for rotation in an eye of a lever. There are a plurality
of pawls on the lever which engage teeth of t:he ratchet drum.
Rotation of the lever drives the ratchet drum in one direction
while free-wheeling of the lever is achieved in an opposite
direction. The lever is driven through a reciprocal rod of a
piston-cylinder unit to which an end of the lever is articulately
connected.
Tools for rotating fastening elements are also known
which utilize a friction belt drive (West German patent No.
583,635). A sleeve which forms the wrench head has passed
around it a tension-applying belt, one end of which is ar-ticulately
connected to a tension-applying lever while an opposite end is
engaged by a projection on the lever such that when the lever is
pivoted the two ends of the belt are pressed toward each other so
that the head of the wrench is frictionally gripped and at the
same time is rotated about its axis. Movement of the lever in
an opposite direction releases the friction belt thus neutralizing
the driving effect.
In the case of the first patent mentioned (mechanisms in
which pawls engage ratchet teeth) there occurs high concentrations
of forces at one or a few of the ratchet teeth engaged by the
pawl or pawls while the other ratchet teeth are not subjected to
any loading whatever. Therefore, the distribution forces are
unfavourable and accordingly such mechanisms are necessarily made
relatively large and heavy.
~77~53
In the case of tools utilizing friction belts a rela-
tively even distribution of forces occurs over the periphery oE
the wrench head but there is a risk of slippage or incomplete
driving particularly where it is necessary to transmit high
torques. Slippage may also occur when dirt, foreign particles,
or the like are present between the friction belt and the sleeve
or wrench head which is driven or rota-ted thereby.
In keeping with the foregoing, the problems oE such
known tools have been eliminated by the tool of the present
invention by avoiding undesired and intense localized concen-
tration of drive forces between pawls and ratchet teeth while
on the other hand there is assured a reliable drive of the wrench
head under all circumstances.
In further accordance with this invention a ring which is
utilized to drive a fastener has ratchet teeth on its periphery
and is at least in part embraced by a curved, flexible tension-
applying belt, one end of which is connected to a lever while an
opposite end engages a support for a pawl whereby upon motion
imparted to the lever in a driving direction there is drive
imparted to the ring through the pawl engaging the teeth of the
latter and also frictional engagement between the flexible
tension-applying belt and the ring.
; In keeping with this invention the tool logically links
pawl drive and freely-running friction belt s~stems with the
lever having two different functions. On one end the lever forms
an end of the flexible tension-applying belt and serves for
tightening the latter while on the other it al~o presses against
the support means for the pawl. By virtue of this dual function
the pawl is on the one end drawn via the friction-applying belt
against the flanks of the ratchet teeth while on the other it is
additionally pressed in the same direction by the lever.
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The friction-applying belt can pass directly over or
upon -the backs of the ratchet teeth of the ring although in
principle it is also possible to allow the fric-tion applying
belt to engage not only on -the ratchet teeth bu-t also on a
cylindrical sleeve associated therewith.
Preferably the pawl constructed in accordance with -this
invention is mounted for sliding movement in a bore of -the lever
and is biased in a direction toward the ratchet teeth with the
pawl preferably having a-t least two catches which each simul-
taneously are received in different gaps between the teethwhich
contributes -to the obtainment of a greater dis-tribution of forces
than would occur through the use of a single catch.
Due -to manufacturing -tolerances the ratche-t teeth of the
ring and bf the -two catches which project from a common block
cannot be rnade sufficien-tly narrow such that both catches are
subject to exactly the same loading and therefore the catch
which is the first to engage in the locking condition is biasingly
mounted so that i-t does not receive the total loading in the drive
direc-tion bu-t is capable of retracting under drive and transmits
a part of -the load to the adjacent catch. With regard -to too-th
pitch, the elastic catch is not exactly in phase to ma-tch the
remaining catch of the pawl but leads slightly to ensure that
this catch is -the first -to be loacled. This means that when -the
ring is rotated in the free running direction the elastic ca-tch
runs over -the vertex of a tooth of the ratchet a trifle later
than the other catch. It may happen tha-t reversal of the direction
of rotation of the ratchet mechanism occurs just a-t the moment
when a catch has already engaged bu-t is still on the flank of
a ra-tchet -tooth and has not yet completely dropped or clicked
into place. Therefore, the pawl cannot fully engage which in the
case of a heavy drive load or force, for example a hydraulically
s~
operated load, can lead -to damage or des-truc-tion o-~ the pawl.
It is thus an object of this invention -to provide a tool
of the type aforesaid having as part of one of -the catches a
re-turn stop or projection which ensures that either the ca-tches
fully engage the ratchet ring -teeth or -the ring -turns back by one
tooth so -that even in borderline cases -there is a guarantee -that
the catches always fully engage the ratche-t. The return stop is
a spring biased projection carried by one of -the catches which is
disposed in front in the free-running direction of -the ratchet
ring. If during retrorotation of the ring the fron-t edge of the
projection is passed by the tip of a ratchet tooth the pawl
carrying the teeth snaps fully into the teeth causing -the projec-
tion to spring back. If the tip of the extended projection is not
reached, the catch slides off the tooth and moves back into its
previous position. In -this twin ca-tch arrangemen-t -the projec-tion
also fulfills the task of compensating for -the phase lead of the
other catch which is spring biased and of ensuring that the rigid
catch does not engage in the ring once the elas-tic catch has
reached a position in which it is also possible for it to engage
the ratchet teeth. Therefore, the projection is preferably carried
by a rigid catch and the spring biasing the same need no-t be
capable of withstanding relatively heavy loads. The loading of
the projection is through a spring -tha-t is therefore naturally
very much softer than the force of a spring which acts on the
rigid catch of the overall pawl.
Furthermore, while the projection is logically employed
in the case of dual ca-tches of a pawl this same measure can be
applied to a single catch of a single pawl to ensure that the tip
of the catch or projection cannot become hooked together wi-th -the
tip of a ratche-t too-th.
~77~S3
Accordingly, the present invention also provides
a tool for rotating an element comprising a ring having a
peripheral surface defining ratchet teeth with gaps therebetween,
pawl means for drivingl~ engaging said teeth upon rotation of
said tool in a first direction and being free running upon rota-
tion of said tool in a second direction opposite said first
direction, said pawl means having at least one catch releasably
engageable with flanks of said teeth to effect said driving
engagement or free running, said catch carrying a projection
movable relative thereto so as to be engageable with the same
tooth flank as the catch, and spring means for biasing said
projection towards the tooth flank engageable by the catch.
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~17~753
An embodiment of the invention will now he described,by way of example, ~ith reference to the accompanying drawings, of
which:
Figure 1 is a longitudinal sectional view through a tool,
and illustrates a lever carrying a pawl and having a friction-
applying belt encircling a toothed ratchet ring.
Figure 2 is a fragmentary end view of the tool of Figure
1, and illustrates details of the ratchet ring including a wrench
socket disposed therein.
Figure 3 is a highly enlarged fragmentary side elevational
view of the lever or drive head of the tool, and illustrates de~
tails of the pawl and dual catches thereof.
Figure 4 is a view slmilar to Figure 3, and more speci-
fically illustrates details of the pawl including a spring bias
projection carried by one of the catches.
- Figure 5 is a view taken from the direction indicated by
the arrow V of Figure 4, and illustrates additional details of
the pawl.
Figure 6 is a top full plan view as viewed from the
direction of the arrow VI of Figure 4, and illustrates further
details of the pawl.
Figure 7 is a longitudinal sectional view through a
piston-cylinder unit associated with the lever 12, and illustrates
components thereof during the working stroke of an associated
piston whose rod is connected to the lever.
Figure 8 is a longitudinal sectional view similar to
Figure 7 and illustrates the components of the piston~cylinder
unit during the return stroke of the piston.
A novel tool for rotating a screw, bolt, nut, or similar
3~ fastening element is clearly shown in Figures 1-6 of the drawings
and includes a generally L-shaped housing 1 (Figure 1) within
which is a ring 10 having teeth (unnumbered) on an exterior
peripheral surface thereof which are engaged by a pawl 14.
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I
77~7~
Rigidly mounted in a long cylindrical arm portion
(unnumbered) of the housing 1 i.s a hydraulic piston-cylinder unit
40. An extensible piston rod 45 is mounted for reciprocal movemen-t
in the unit 40 and an end (unnumbered) thereof is connected to an
arm or lever 12 (Figure 3). The housing 1 has apertures (unnumbered)
through which a wrench soket 4 can be inser-ted into the ring 10 in
the manner clearly apparen-t from ~igures 1 and 2. The ring 10
includes encircling grooves (unnumbered) into which are inserted
spring retaining rings 2 by which the ring 10 is locked in the
housing 1 so that it cannot fall therefrom or be accidentally removed.
The ring 10 has internal teeth 3 into which fi-ts corresponding gaps
on the exterior peripheral surface (unnumbered) of the wrench
socket 4. Thus wrench soke-t 4 is pushed into the opening of the
ring 10 and becomes rotationally rigidly connected thereto. Thus,
when the ring 10 is turned, the socket 4 is entrained -to turn there-
with ~or imparting movement -to a fastener, such as a nut, received
wi-thin the hexagonal opening (unnumbered) of the wrench socke-t 4.
As is illustrated in Figure 1, it is possible -to provide
on the housing 1 a support 4a to dissipate the reac-tion forces
which occur when bolts, nu-ts, or similar elements are -tightened by
the tool. However, in principle, the tool is capable of functioning
without the support 4a by simply bracing the housing 1 against a
suitable abu-tment.
Referring specifically to Figure 3, there is passed
around the ratchet teeth (unnumbered) of the ratche-t ring 10 a
flexible friction belt or friction-applyi.ng bel-t 11 having
opposite ends (unnumbered) which merge with the lever 12 at
~77~53
opposite sides of the pawl 14 (E`igure 3). One end of the ~riction
~elt 11 merges tangentially relative to the ring 1~ with. the
tension-apply.ing l.ever 12 while the leEt-hand end ~Figure 3) is
connected to the tension applying lever a:Lmost at a right-angle.
. The pawl 14 is displaceably or shlftably disposed in a
bore 13 of the tension-applying lever 12. The ex-tension of the
axis of displacement of the pawl 14 extends in the manner of a
secan-t through the ring 10 and is virtually at righ-t angles
to oblique flanks (unnumbered) of the teeth (unnumbered) of the
ratchet ring 10. A spring 30 seated upon a plate (unnu~bered~
at a rear end of the bore 13 normally biases the ball 14 in a
direction toward the ratchet ring 10. The pawl 14 has two catches :
15, 16 w~ich engage synchronously into respective adjacent pairs
of gaps ~unnumbered) between the ratchet or saw teeth (unnumbered)
of the ratchet ring 10.
In the case of the present embodiment of the invention
the orientation of the ratchet teeth is such that a rotation of
the ring 10 in a clockwise direction constitutes the free-running
. direction while rotation of the ring 10 in a counterclockw.ise
direction is blocked by the pawls 15, 16. This blocking action
can be overcome if the pawl 14 is pulled back against the biasing
force of the spring 30 by an appropriate adjusting mechanism.
. The construction of the pawl 14 is set forth in detail
in Figures 4 through 6 to which attention is direc-ted. The catch
: l5 which is in front in the free-running direction consists of a
plate oE springy material which is inserted into a corresponding
slot 17 in the pawl 14 and which protrudes outwardly therefrom
~ to engage a steep flank (unnumbered) of a tooth (unnumbered) of
;. the ratchet ring 10. The steep flank o an adjacent tooth of the
ring 10 is engaged by a rigid catch 16 which is lntegrally formed
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53
as part of the pawl 1~.
The leading ca-tch 15 preferably has a sligh-t springing
effect so that the blocking load of the ring 10 is as ~ar as
possible evenly dis-tributed over the two catches 15 and 16, The
catch 15 mus-t therefore have a cer-tain phase lead over the catch
16, i.e., it must be slightly in advance of -that position which
it would ideally assume. If, therefore7 the -tips of the teeth
o~ the ring 10 run past the catches 15, 16 in the free-running
direction 9 one tooth tip first passes over an edge 19 of the
catch 16 and quite briefly afterwards -the tip of -the preceding
tooth passes over an edge 18 of -the ca-tch 15. To prevent any
blocking action within this brief period in which only the catch
16 but not the catch 15 is engaged the ca-tch 16 is provided with
a spring-loaded s-tud or projection 20 which projec-ts from wi-thin
a bore (unnumbered) of the catch 16 under -the influence of a
spring 21. In the extended or projected position of the projection
20 the latter is an extension of a sliding flank 22 of the catch
16 on which the oblique flanks of the ratchet teeth run as the
ring 10 rotates in the free-running or free-wheeling direction.
Therefore, when rotated in the free-running direction, the projec-
tion 20 extends in effect the flank 22 so tha-t the tip of the
next leading tooth of the ratchet ring 10 has reliably over-
stepped the front edge 18 of the ca-tch 15 when the rear ca-tch 16
engages. When i-t clicks into place -the projection 20 is pushed
back from the steep flank of the relevan-t tooth against the action
of -the spring 21.
S3
The projection 20 is a relatively small s-tud which is
inserted in-to an appropriate bore in the catch 16, as can be
seen particularly in Figures 5 and 6. In order to restrict the
movement of the projection 20 and at the same time to act as a
lateral abutment against total projection outwardly of the bore
a metal pin 23 is located in a bore (unnumbered) of the catch 16
and engages a shoulder (unnumbered) of -the projec-tion 22 (Figure
4).
In order to attach the catch 15 to the pawl 14 the latter
has a bore 25 which is threaded and into which can be threaded a
bolt having first been passed through bores (unnumbered) associated
with the ca-tch 15 and the pawl 14 to the right of the ca-tch 15, as
viewed in Figure 4.
As the piston rod 45 is extended the -tension-applying
lever 12 is at each stroke pressed leftwardly and via -the dual
pawl 14 -the ring 10 rotates clockwise. At each return stroke the
tension-applying lever :L2 is pivoted back rightwardly and the
catches 15, 16 slide on the rear flanks of -the ratchet teeth of
the ratchet ring 10 so that the spring 30 is compressed and the
ring 10 is no longer entrained.
The design and mode o~ operation of the piston-cylinder
uni-t 40 will now be described.
Wi-th a cylinder 39 of the pis-ton-cylinder uni-t 40 is
disposed a working piston 41 which separates the cylinder 39 into
two fluid chambers 42, 43 and for -this purpose the pis-ton 41
carries an annular seal or packing 44. A pis-ton rod 45 of reduced
diameter extends from the piston 41 ou-twardly -through an end face
46 of the cylinder 39 and an aperture (unnumbered) through which
the rod passes is sealed by a packing 47.
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- 1~7~7S3
~ control slide valve 48 is m~unted dis~laceably in a
bore (unnumbered) in a front end wall 49 o the unit 40. In one
of its positions (Figure 7) the valve 48 fluidically links a
pressure line 50 via an annular space 51 with the chamber 43 so
that the hydraulic pressure acts on the entire front surface of
the piston 41. At the same time annular spaces 53, 54 are
connected to each other so that a line 52 which connects ~he
interior of the chamber 42 to the annular space 53 is connec-ted
to a return line 55 which is connected to the annular space 54.
.In the other position of the control slide valve 48 the annular
spaces 51 and 53 are connected to each other while the chamber
43 is connected to the annular space 54 via a longitudinal bore
56 in the interior of the control slide valve 48.
The piston 41 has on an end wall defining the cylinder
chamber 43 a cut-out 57 into whi~h in the retracted position of
the piston 41 a projection 58 protruding from the inside of the
end wall engages. Between the projection 58 and the wall of the
cut-out 57 there is sufficient space not to impede the passage
of pressurized hydraulic fluid, such as oil. The projection 58
is likewise drilled through in the longitudinal direction so:that ,
the control slide valve 48 can slide within .it. The projection
58 has on the inside two annular slots 5~, 60 which serve as
engagement points for a ball catch or latch. The ball catch
consists of two balls 62, 62, a part of the surface of each of
which protrudes from a transverse bore (unnumbered1 in the control
slide valve 48 with the balls 62, 62 being biased apart by a
spring 61. The balls engage in either of the annular slots 59
or 60 and so stabilize or maintain the two possible positions
of the control slide valve 48. The bore 56 of the control slide
valve 48 communicates with the chamber 43 constantly t!hrough the
.
~0~'753
,. ~
bore (unnumbered) of the ball catch and through oblique bores
(not shown), and there is be-tween -the outer wall of -the projection
58 and the inner wall of -the cu-t-out 57 such an in-termediate
space that -the distribu-tion o-f pressure is even over the en-tire
front face of the piston 41.
The piston rod 45 has a longit-udinal bore 62' in-to which
projects a rod 63 which is rigidly connec-ted to -the control slide
valve 48. 'i`he rod 63 serves as a guide for a sleeve 64 and a
disc 65, both of which are freely displaceable on the rod 45.
However, there are in the longitudinal bore 62' abutments 66, 67
which limit the longi-tudinal movement o-f the sleeve 64 and the
disc 65. The abutment 66 consists of an annular shoulder against
which bears the disc 65 and the abutment 67 consists of a lock
washer disposed in an annular groove (unnumbered) against which
the sleeve 64 is supported. Between the sleeve 64 and the disc
65 is a thrust sprlng 68 which presses -the elements 64~ 65 away
from each other so that each of them is applied against its
respective abutment 66, 67.
At an outer end (unnumbered) of the rod 63 is stop
means in the form of a nut 69 against which the disc 66 may abut.
An opposite stop or stop means is formed by an end wall or annular .
shoulder,70 of the control slide valve 48. Against -the annular
shoulder 70 abu-ts a projection 71 of the sleeve 6~ when -the working
piston moves to the righ-t as viewed in Figures 7 and 8.
~ eference is now made -to Figure 7 which illustrates -the
phase of the stroke of the unit 40 in which the pressure line or
duct 50 is placed in fluid communication with the chamber 43
-through the annular space 51 and the oblique ducts or ports
(unnumbered) earlier mentioned adjacent to a narrowed or
- 12 -
~77~
reduced porti~n 72 of the control slide valve 48. The pressure
thus introduced into the chamber 43 from the pressure line 50
is directed against the entire right-handmost face (unnumbered)
of the piston 41 and additionally enters the bore 56 of the contro,
slide valve 48. Due to the position of the control slide valve
48 the chamber 42 is connected through the line 52 to the return
line 55 via the annular spa,ces 53 and 54.
The piston 11 under the influence oE the hydraulic fluid
in the chamber 43 moves to the left, the elements 64, 65 ~eing
entrained therewith, and the spring 68 remaining in its biased
condition. As soon as the element 65 strikes the annular a~ut-
ment shoulder 66 the spring 68 is compressed and after the
elements 64, 65 strike against each other in the final phase o~
' this s-troke, the balls 62, 62 are forced out of the annular
~groove 60 hecause the control slide valve 48 is now entrained
by' the piston 4'1'through the abutment means 67 and the elements
64, 65, 69 and 63. The spring 68 relaxes and drives the control
slide valve 48 to the position shown in Figure 8 in which the
i , balls 62, 62 engage in the annular groove 59. The position
illustrated in Figure 8 corresponds to the return stroke of the
piston 41 in which the chamber 42 is connected to the pressure
line 50. The piston 41 moves to the right and in the final phase
of this movement the projection 71 on the sleeve 64 strikes the
abutment means or face 70 of the control slide valve 48 which
initially does not move. Instead, the spring 68 is first com-
pressed and only when the disc 65 and the sleeve 64 abut each
other do the balls 62, 62 move out of the annular slot 58 so that,
~' during relaxation of the spring 68, control slide valve 48 moves
to the right and the balls 62, 62 are urged into the annular slot
60. Afterwards the first-mentioned stroke is repeated under the
conditions ,illustrated in Figure 7.
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t7S3
Apar-t from -the au-tomatic operation of the control slide
valve 48 a manual switching device 75 is provided in keeping wi-th
this inven-tion by which the con-trol slide valve ~8 can be moved
man-ually into the position shown in Figure 8 so tha-t the piston
~1 can be retracted into the cylinder 39 and retained -therein.
The latter function is desirable in order tha-t the tool can be
manually relieved. Should the piston-cylinder unit be immobilized
during the phase in which the piston rod ~5 is extended then the
entire device would be subject to mechanical tension. The switch-
over to the rearward position of the control slide valve 48
(Figure 8) results in an immobilization of the piston-cylinder
unit in its relieved or unpressurized condition.
The switching device 75 consists of a -tubular sleeve 76
having an interior (unnumbered) which communicates with -the longi-
tudinal bore 56 of the control slide valve ~8. A ring 78 is
clamped rigidly on -the tubular sleeve 76 by means of a set screw
81. The ring 78 moves with the sleeve 76 in a cavity 82 which is
closed on its outer side by a screw cap 83 which is secured in
position by another said screw 84. The screw cap 83 has a blind
bore into which projects the end of the tubular sleeve 76. Also
positioned in the blind bore is a seal 80 which seals the passage
through the sleeve 76. A second seal 79 is disposed at the
opposite end at which the sleeve 76 enters the cavity 82. The
full worlsing pressure which acts on the lef-t-hand end ~ace of
the sleeve 76 is transmitted to -the interior of -the sleeve 76
and also acts on -the right-hand end of the latter. Thus, there
is at the sleeve 76 an equalization of pressure so tha-t in the
event of a movement of the sleeve 76 it is not necessary for the
full hydraulic pressure of the unit to be overcome. The sleeve
76 is adjusted by utilizing a handle 77 which passes through a
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~ ~t7~ ~53
bore in the screw cap 80 and which is threaded into a threaded
bore of the ring 78. Considering the position shown in Figure
7, if the handle 77 is pressed inwardly or -to the left the -tubular
sleeve 76 is displaced in the same direction by the ring 78 and
in turn displaces the control slide valve ~8 to -the lef-t. This
brings the control slide valve ~8 to -the position shown in Figure
8 at which the overall unit is releived of hydraulic pressure.
In order to attach the piston cylinder uni-t to a wall
85 of the housing 1 a spherical bearing consisting of a ball
part 86 is rigidly provided on the housing 1 of -the overall unit.
A ball cup 87 is provided on the ball part 86 and is self-adjusting.
The par-ts 86, 87 are seated on a sleeve 88 in which -the switching
device 75 is located. The sleeve 88 is pushed into a hole in
the wall 85 and is secured from an opposi-te side by a retaining
ring 89 which is held fas-t by a locking washer 90 mounted on the
sleeve 88. ~n elas-tic ring 91 is sea-ted in an annular groove
(unnumbered) of the ring 89 which presses the wall against the
plain side (unnumbered) of the ball cup 87. In this way the
piston-cylinder unit can adjust itself .reely to -the relevant
annular position within -the housing 1.
- 15 -
