Note: Descriptions are shown in the official language in which they were submitted.
~6~2
, ~ -
The present invention is directed to a device which
can be used as a hammer drill or a chipping hammer and includes
a percussion mechanism preferably driven by an electric motor.
The percussion mechanism is composed basically of an actuating
piston supported and reciprocally movable within a working
cylinder. The actuating piston transfers the percussive
energy through the medium of an air cushion to a percussion
piston acting on a tool. The actuating piston is in engagement
with a disk mounted on a driving shaft and the disk rotates with
the shaft.
Percussion mechanisms driven by an electric motor,
as mentioned above, are also called electro-pneumatic systems.
Usually, the actuating piston is reciprocated by a crank drive.
Since in crank drives the axle of the crank shaft always
extends perpendicularly to the axis of the actuating piston,
such an arrangement requires a lot of space. If the percussion
drive is combined with a rotating drive, then a complicated
miter gear unit is needed.
To eliminate these disadvantages, it has been suggested
to use a swash-plate in tead of the crank drive for reciprocating `~
the actuating piston. As compared to a cran~ drive, a swash-
~` plate Xas the advantage that the driving mechanism can be
constructed much more compactly.
Known percussion mechanisms have the common disadvant-
~` age that the percussiv~ ~orce is not continuously variable. This
failing applies to percussion mechanisms with a crank drive as
well as to those using a swash-plate.
Therefore, it is the primary object of the present
invention to provide a pexcussion mechanism where the percussive
force can be regulated.
?6~ `
In accordance with the present invention, the per-
cussive force is regulated by pivotally supporting a driving
disk for the actuating piston on a drive shaft. A control
member secured to the drive shaft so that it rotates with i-t,
is axially movable on -the shaft and regulates the extent to
which the disk is pivoted relative to the axis of the shaft.
With the aid of the control member the dis~ can be
displaced from a neutral position into a working position.
In the neutral position the plane of the disk extends per-
pendicularly to the axis of the driving shaft so that no
reciprocating movement is transmitted to the actuating piston.
In the working position, the disk can be pivoted to a positio~
where it effects the maximum reciprocating movement of the
actuating piston. Intermediate posit:ions of the disk can be
established between the neutral posit:ion and the maximum
pivotally displaced position of the d:isk. In the neutral
position where the actuating piston experiences no reciprocating
movement, the total o~tput of the driving motor of the device
is available for the rotation of the tool mounted in the device.
With the exception of a position parallel to the axis
of the driving shaft, theoretically, the pivot axle of the disk
can be ~n any position. For optimum adjustabili.ty of the disk,
however, it is practical to arrange the pivot axle extending
normally to the axis of the driving shaft. With such an arrange-
ment of the pivot axle depending on the axial movement of the
control member it is possible to achieve an optimum pivotal
deflection of the disk.
In the operation o~ the device capable of use as a
hammer drill or a chipping hammer, it is advantageous to be able
to operate the device in a range from a minimum to a maximum
-- 2 --
percussive force. To afford such variable percussion operation,
it is advantageous if a spring element acts to return the disk
to its neutral position from a pivoted working position. The
restoring force produced by the spring element is supported by
the centrifugal force acting on the disk. The spring element
can be a compression spring arranged around and coaxially to
the driving shaft. A compression spring requires little space
and can be easily replaced~
Various embodiments can be provided for the control
member. In an especially practical embodiment, the control
element is shaped as a drum with its surface facing the disk
extending obliquely of a plane normal to the axis of the
driving shaft. Such an embodiment makes it very simple to
produce the control member. The inclination of the surface of
the control member facing the disk is established relative to
the pivot axle of the disk. Accordingly, for the maximum
deElection of the disk, it is possible that the facing surfaces
of the control mem~er and the disk are in contact.
~Yial movement of the control member can be effected
in different ways from the exterior ~f the device. In a
particularly practical embodiment, however, the movement of the
control~ember is achieved by supporting the working cylinder
so that it is axially movable. The working cylinder is moved by
pressing one end of the cylinder against another surface so that
it is moved in its axial direction against the orce of a
spring. When the force displacing the working cylinder is
removed, the spring effects the return of the working cylinder.
Normally, the displacement is effected by pressing the device
including the working cylinder against a workpiece. When the
device is lifted off the wor~piece, the spring biased displacement
~2~Z
of the working cylinder assures that further percussive action
is prevented. In this arrangement, the working cylinder is in
operative contact with the control member.
Hammer drills are often used for work involving purely
rotational movement. To prevent any percussive force in the
device when only rotational movement is desired, it is
advantageous if an adjustable stop for the working cylinder is
provided. The stop is arranged so tha-t in one position it
prevents any axial movement of the working cylinder while in
another position it permits axial movement of the woxking
cylinder for axial displacement of the control member along the
driving shaft. Therefore, the stop assures the operation of the
device in two operating conditions, "rotation only" and "rotation-
percussion".
The various features of novelty which characterize the
invention are pointed out with particularity in the claims
annexed to and forming a part of this disclosure. For a better
understanding of the invention, its operating advantages and
specific objects attained by its use, reference should be had
to the accompanying drawings and descriptive matter in which
there are illustrated and described preferred embodi~ents of
the invention.
IN THE DRAWING5~
Fig. 1 is a side view of a device useful as a hammer
drill or a chipping hammer, partly in section, with the device
illustrated in the "rotation only" operating condition; and,
Fig. 2 is a side view, partly in section, of the same
device as shown in Fig. 1, however, ilIustrated in the "rotation-
percussion" operating condition.
The device shown in Fig. 1, capable of being used as a
~2~ 1Z
.
hammer drill or a chipping hammer, includes a housing 1 having a
handle 2 at its right-hand end as viewed in the drawing. A
trigger-like switch 3 and an electrical connection line 4 are
provided in the handle 2. As viewed in Fig. 1, the left-hand
end of the device is its front end and its right-hand end is its
. .
rear end. In the rear portion of the housing 1 an electric
motor 5 is located. A shaft 5a extends from the electric motor 5
toward the front end of the housing and the front end of the
shaft i5 constructed as a pinion 6. Pinion 6 is in meshed
engagement with a gear 7 secured on a driving shaft 8, with the
axis of the shaft 8 extending in the rear end-front end direction `~
of the housing parallel to and offset from shaft 5a. Consequently,
the driving shaft 8 is driven via the pinion 6 and the gear 7.
On the shaft 8, forwardly of the gear 7 is an annular disk 9
having an oversize central opening 9a. Disk 9 is pivotally
mounted on the driving shaft 8 about a pin at axle pin 10 extending
perpendicularly of the axis oE rotation of the driving shaft 8.
The size of opening 9a ensures that the disk 9 is pivotally
displaceable about the pivot axle 10 between a neutr~l position
ie perpendicular to shaft 8 and a number of working po~itions
at varying angles to shaft 8. In Fig. 1 the disk 9 is shown in
the neutral position and it is normally biased into this position
by a compression spring 11 coaxial with and laterally surround-
ing the shaft 8 and extending between gear 7 and disc 9. Located
on the opposite side of the disk 9 from the spring 11 is a control
member 12 which is axially movable along the driving shaft 8.
The control member 12 is drivingly connected to the driving
shaft 8 by a wedge drive key 13 so that it rotates with the shaft
8 but can slide axially along it. The front end of the driving
shaft 8 is provided with an elongated tooth or splined arrangement
-- 5 --
~z~
8a extending around the circumference of the shaft, and
ex-tending axially therealong a prede-termined distance. Each
end of shaft 8 is suitably carried in bearings 8b and 8c
located in -the housing.
Control member 12 has a control surface 12 lying in
a plane having a longitudinal axis angled relative to shaft 8,
and a lateral axis para~llel to a~le pin 10. A working cylinder
14 is located wi-thin the housing above the driving shaft 8 and
coaxial with shaft Sa. The axes of the working cylinder 14
and the driving shaft 8 are disposed in parallel relation. The
working cylinder has a front end F (at the lef-t hand of the
drawing) projecting from the front end of the housing 1 and a rear
end R loca-ted within the housing forwardly of the electric motor
5. An actua-ting piston 15 is positioned in the rear part of
the working cylinder and a percussion piston 16 is located
within the working cylinder forwardly oE the actuating piston.
The adjacent facing surfaces of the actuating piston 15 and the
percussion piston 16 are spaced apart forming an air cushion
therebetween. Air cushion 17 transfers the reciprocating motion
of the actuating piston 15 to the percussion piston 16 so that
the percussion piston 16 can transmit percussive force. On
the outside sur~ace of the working cylinder 14 near its rear
end R, an outwardly projecting toothed rim 14a is provided
which forms a pinion and this rim is in meshed engagement with
the elongated toothed surface or spline 8a on the front end
portion of the driving shaft 8. Consequently, the rotation
of the driving shaft 8 causes the working cylinder 14 to be
rotated due to the meshed engagement of the toothed surface 8a
and the toothed rim or pinion 14a. Working cylinder 14 is mounted
in the housing 1 so that it can be moved to and fro for a limited
-- 6 ~
., ~
distance in its axial direction.
For this purpose it is supported in a roller ~earing
21 and a ball bearing 22 spaced apart from one another. Bearing
21 engages an elongated cylindrical raceway 23 on cylinder 14
so that on axial displacement of cylinder 14 the raceway 23
will remain in engagement with bearing 21.
searing 22 is fastened around a forwar~ portion of
cylinder 14 and is secured against shoulder 24 by means of
circlip 25. Bearing 22 is slideably supported in a cylindrical
portion 26 of housing 1, and is axial displaceable therein in
unison with cylinder 14. In the neutral position of the device
illustrated in Figure 1, the working cylinder 14 is kept in a
forward position by means of a compression spring 18 encircling
the working cylinder and pressing on bearing 22, and circlip 25.
An adjustable stop member 19 is rotatably mounted in ~he housing.
Stop 19 has a projection l9a extending into the axial path
of movement of the working cylinder. ~rojection l9a i9 mounted
of~set on disc l9b which is part of stop 19. ~y rotation of
stop 19 it is possible to move projection l9a into and out of
; 20 engagement with the rear end of cylinder 14 and thus to secure
cylinder 14 in the position shown in Figure 1. In this position,
which is called the neutral position, there will be no reciprocation
of the piston 15. The cylinder 14 will simply rotate, thus
causing rotation of a tool bit (not shown) secured in the tool
carrier 14b. In this position, the disc 9, ~eing urged by
spring 11 into its forward position perpendicular to shaft 8,
also urges control member 1~ forwardly on shaft 8, and control
member 1 2 is free to move forwardly until it reaches the rear
end of cylinder 14. In this position therefore disc 9 will
simply rotate in groove I5a of piston 15, without causing any
~7~6~32
reciprocation. `~
In Figure 2, the device illustrated in Figure 1 is
shown in the "rotation-percussion" position. Movement into this
second position is achieved by changing the position of the
stop 19, as well as by pressing the device against a surface,
such as a workpiece. By noting the different positions of
the stop 19 in Figures l-and 2, it can be appreciated that in
Figure,2 it is possible to displace the working cylinder 14
axially rearwardly from the position shown in Figure 1. In
Figure 2, a tool 20 is shown inserted into the tool carrier 14b.
With the stop 19 positioned as in Figure 2 the projection l9a
is swung rearwardly. When the tool 20 extending from the
front end of the working cylinder 14, is pressed against a
surface r the working cylinder moves axially inwardly into the
housing until its rear end contacts the downwardly extending
pro,jection l9a on the stop 19. As the working cylinder moves
inwardly into the housing, the rear end of the working cylinder
in contact with the forwardly facing surface of the control
member 12 moves the control mem~er axially rearwardly relative
: ~ to the drlving sha~t 8. The surface 12a of the control member
facing the disk 9 is i ~lined obliquely to a plane extending
normally of the axis of the driving shaft 8. As the surface
12a contacts~the aisk 9, the disk pivots about its pivot axle
10 , oversize opening 9a permits this pivoting or tilting action,
relative to shaft 8. Since the disk 9 and the control member 12
rotate in this position in unison with the driving shaft 8, the
disk performs a wobbling movement. As it rotates, the disk
9 engages a groove 15a in the lateral surface of the actuating
piston 15. Due to the wobbling movement of the disk 9 as it
rotates, a reciprocating movement is transmitted to the
~2~
actuating piston 15. Accordingly, in the "rotation-percussion"
position shown in Figure 2, the disk 9 is displaced about the
pivot axle 10 to a maximum extent and the reciprocating strokes
of the actuating piston are also at a maximum. Between this
maximum `'rotation-percussion" position and the neutral or "ro-
tation only" position shown in Figure 1, the angular deflection
of the disk 9 and consequently, the percussion stroke, can be
varied by changing the contact pressure or the extent to which
the disk is angularly deflected. When the device is lifted
- 10 off the surface, the working cylinder 14 is displaced axially
outwardly by the compression spring 18 to the position shown in
Figure 1. Further, the centrifugal force acting on the disk 9
and the effect of the compression spring 11 also act on the disk
and through it on the control member, cause the return of the disk
9 to the perpendicular neutral position of Figure 1. Therefore,
this embodiment of the present invention permits a continuous
adjustment of the degree of percussive force acting on the
material being processed by the device.
Having described what is believed to be the best
mode by which the invention may be performed, it will be seen
that the i~vention may be particularly defined as follows:
A device for use as a hammer drill or chipping hammer
including a ~ousing, an axially elongated working cylinder
positioned within said housing and having a front end and a
rear end, a percussion mechanism located within said working
cylinder, means for operating said percussion mechanism,
said percussion mechanism comprising an actuating piston mounted
and reciprocally movable within said working cylinder, a
percussion piston located within said working cylinder between
said actuating piston and the front end of said working cylinder,
~iL?d~3i'2
said percussion piston being s~ ced axially from said actuating
piston forming an air cushion therebe-tween so that the
.reciprocating action of said actuating piston is -transmitted
via the air cushion to said percussion piston, said operating
means comprising a driving shaft spaced laterally from said
working cylinder, and a disk mounted on said driving shaft and
disposed in contact with said actuating piston, wherein the
improvement comprises that said disk extends transversely of
said driving shaft and includes an axle pivotally connecting
said disk to said driving shaft so that the plane of said disk
relative to the axis of said driving shaf-t can be angularly
displaced for effeeting variable axial displacement of said
ae-tuating piston within said working cylinder, and a eon~rol
member positioned on and rotatable with said driving shaEt, and
said eontrol member being displaeeable in the axial direetion of
said drivin~ shaft for movement into contact with said disk for
pivotally displacing said disk .relativ0 to the axis of said
driv.ng shaft.
While speeifie embodiments of the invention have been
shown and described in detail to illustrate the application of
the inventive prineiples, it will be understood that the
inventi~on may be embodied o~herwise without departing from
sueh prine~ples.
