DE1207900B - Motor-driven hammer - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

B25d

German KL: 87 b - 3/02

Number: 1207 900.

File number: B 530641 c / 87 b

Filing date: April 30, 1959

Opening day: December 23, 1965

The invention relates to a motor-driven, fast-striking, in particular portable Hammer with a housing in which a hollow cylinder provided with a transverse wall and in the latter a piston are axially displaceably guided, whereby one of the displaceable parts is designed as an impact body, the other, on the other hand, is driven back and forth by the motor via a crank mechanism, and in that between the transverse wall of the hollow cylinder and a transverse wall of the piston an air-filled one Gap of variable due to the relative movement between the hollow cylinder and piston Size exists whose air filling acts as a spring and transmits drive power to the impact body, and which is closed with small distances between the transverse walls, with large distances on the other hand via one channel with the atmosphere controlled by the relative movement between the hollow cylinder and piston connected is.

In the case of hammers, in which a Air filling is used, which is compressed in the space formed between piston and cylinder, the unavoidable air losses during each compression stroke before the next compression stroke can be added. Otherwise the air filling would get smaller and smaller and eventually that Air cushions are no longer present.

In known hammers of this type, the air-filled space is only over due to the relative movement Channels controlled between the piston and the hollow cylinder either with an air reservoir or connected to the atmosphere. The unavoidable when compressing the air filling of the space Air losses can therefore only be supplemented when the space in between is caused by the hasty, piston designed as an impact body has again reached the length at which it during the return stroke of the impactor at the beginning of the previous compression of the air filling has been locked. Before that, the air losses generate a corresponding negative pressure, the brakes the impact body, which is thrown forward towards the tool, so that part of the kinetic energy of the impact body is lost for the impact work.

These disadvantages also occur in those of these known hammers in which the driven Hollow cylinder is closed at both ends and where also in front of the guided in the hollow cylinder Piston an air chamber is arranged, which is temporarily over by the relative movement between KoI-Motorisch powered hammer

Applicant:

Robert Bosch GMBH.,
Stuttgart 1, Breitscheidstr. 4th

Named as inventor:

Dipl.-Ing. Dietrich Schlipf, Esslingen-Weil

ben and hollow cylinder controlled channels connected to the atmosphere.

In another known hammer with a hollow cylinder and closed at both ends a percussion piston guided in it between two air cushions are the air spaces on both sides of the Percussion piston - just as with the hammers of the type mentioned - only through the Relative movement between piston and hollow cylinder controlled channels connected to the atmosphere. In contrast to those hammers, however, in this known hammer the rear air space is in the rear end position and the front air space in the front end position of the impact body with the atmosphere tied together. The air spaces are therefore each at small distances between the transverse walls that delimit them of piston and hollow cylinder connected to the atmosphere and at large distances the Transverse walls completed. The greatest pressure occurring in an air space is therefore the atmospheric, the theoretically smallest possible zero. Therefore, only small forces can act on the impactor are exerted according to the difference in the pressures prevailing in the two air spaces that can at most (theoretically) be equal to atmospheric pressure.

The impact work that can be transferred with this hammer is therefore much smaller than with a hammer, whose air space is connected to the atmosphere during the greatest expansion and whose air filling is compressed to a multiple of atmospheric pressure. The well-known hammer with However, impact body moved by negative pressure has two further disadvantages.

The impactor moves forward from its rearmost end position due to negative pressure in the front air space emotional. The pressure in the front air space increases from the sub-atmospheric to the atmospheric

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spherical, and in the rear air space, the cylinder section lying in front of the impact body sinks from atmospheric to subatmospheric pressure, so that the pressure in the space between them coincides. The compressed air at the end of the stroke escapes into this section.
Impact piston acting resulting compressive forces The air spring can therefore only a very small one

are therefore no longer forwards, but rather backwards after 5% of the kinetic energy of the impact body directed, braking so carry the impact body, and the comab stored in the space, so that part of its kinetic energy for the pressure work is due to the throttling effect in the Impact work is lost. Longitudinal channels converted into heat. This will

The third disadvantage, as with the first, is the bad Wires already mentioned with such hammers known hammers on it, the degree of efficiency is even worse.

supply that between the piston and the hollow cylinder In another known hammer with a

Air space formed by the necessary sliding common guide cylinder for the impact body availability of the piston in the cylinder is not perfect and the driven part is sealed between impact can be. The air space formed during the return stroke of the body and the driven part Impact body due to negative pressure in the front 15, although at small distances from impact body and Air space, undesirably penetrated air volume, operated part closed. If there is a big impact, that the pressure in the front air space would be greater, it is over by the movement of the remains, d. This means that smaller negative pressures arise than the driven part or the impact body in the Zywenn the airspace was completely sealed off, and controlled channels interfered with the atmosphere; this has the consequence that afterwards the flapping 20 bound, namely in the rear end position of the piston forward moving difference of the pressure driven part and · - ■ with soft impacts - Forces behind and in front of the percussion piston are smaller than in the front end position of the percussion body, which with perfect sealing, d. H. theoretically, these channels are therefore not reachable by the relative is. the driven part and impact body, but

There are also hammers with an air cushion, which is affected by the movements of the driven part knows where the impact body and the back and forth or the impact body in the common hollow driven part not interlocked, but controlled by cylinders.

which are in a common cylinder one behind the other - in the air space - parallel to the air filling

are guided so that the hammer mechanism switched relatively - two coil springs are arranged. the becomes long. 30 Air filling should "only" be used for withdrawal

Here, the air space is used in the axial direction by the impactor and only slightly limited by two movable pistons, which are pressed back and forth; it therefore only contributes very little to the impact work of the driven part and the impact body.
so that the air losses during compression are about twice as great as in hammers in which the driven part and its impact body are inserted into one another, for a hammer with a high degree of efficiency, these known hammers can be guided. no information can be found in the construction method.

Furthermore, the paths of the air space are axially off- There are also hammers with a common

sealing two pistons in the common cylinder guide cylinder for the driven part and the • - in a work cycle - about eight times the 40 impact body known, in which the gap The amount of the crank radius is greater than the path of the two different connections to the atmospheric air space sealing parts in such hammers, sphere or to an air storage space. The one in which the driven part and the impact body are connected - similar to hammering that are brought together are and in which the genus is called the path - through movement the only sealing surface only about as large as 45 of the driven part is controlled and then opened, how is the compression stroke. This is when the driven part is in the rear dead position Friction work on the air space sealing is. The other connection is via a valve, Share accordingly larger. its closing member by one in the driven part

Due to the larger air losses and the larger arranged preloaded coil spring against the Friction losses will worsen the efficiency significantly 50 inside the end wall of the driven part than when hammering the aforementioned is pressed and that with his head the front wall Genus in which the impact body and the driven part penetrate and a piece into the air space are led into each other. That is especially true, sticks out.

if excludes to transmit the impact work this valve can not by negative pressure

borrowed or mainly the air filling used 55 in the air space, but it will be opened when will, d. H. when high compression end pressures collide with the impact body against the step. Force of the spring and should be hard blows between

In one of these known hammer with a see impact body and driven part avoid common guide cylinder is in the cylinder. For this, however, at this moment a piston pin holder is also used, the air that is primed in the space is almost completely relaxed on the one hand with the end of the connecting rod and on the other hand stored in the air filling by means of a helical spring with the on-energy can no longer is connected to the impact body overdriven part. The space in between will bear. As a result, the guide cylinder that has in common between this part and the percussion piston, which is in any case bad, is additionally worsened by the relative movement between the driven,
benem part and impact body variable size, otherwise, as indicated, at the moment of

but it is never closed, rather there is a negative pressure in the air space due to the constant blow, so open longitudinal channels in the impact body continuously with the fact that also with these hammers - as well as with the

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Known hammers mentioned at the beginning of the blow big enough that during the rest of the time the

body is slowed down by negative pressure. Piston movement of the air reservoir

In another known hammer, it is filled in order to supplement the air losses again later

air-filled space with the in proportion to being able to.

him large interior space of the crankcase about 5 The first connection to the atmosphere in form pressure-controlled valves connected, which at one by the relative movement between pistons Open the negative pressure in the air space and open the cylinder-controlled channel in the case of positive pressure. maintain the functionality of the hammer

This allows the changing working conditions during compression. When working in any air losses that have arisen are replenished in good time and so- io soft rock, d. H. with more or less plamit can slow down the forward moving stabbing thrust, can be via the pressure-controlled valve Impact body can be avoided by negative pressure. more air from the storage room into the intermediate die pressure-controlled connection of the air space to be sucked in as is necessary to the space the comparatively very large, at least at the time created during the previous compression wise to supplement the crank chamber connected to the atmosphere 15 air losses, because then the impact body but has the disadvantage that in the air space one never goes further forward than with hard bumps. Da-negative pressure can arise, which would be deformed as an impact body by the air filling of the gap Piston can be increased while the cylinder is running backwards. The consequence of such a charge linder sucks backwards. would be that on the next working stroke the compression

To bring the impact body in motion for the first time to ao sion of the air filling with a greater distance of the transverse and to keep moving even if the walls of the piston and cylinder would begin as for example when working in soft rock the one before. In the event of a series of plastic impacts Recoil is small, this process is repeated several times at the open end of the hollow, so that Cylinder a stop ring is required, which will eventually go back and forth during the return stroke The return stroke of the hollow cylinder does not exclude the impact body with the driven part in the gap, Reaching negative pressure could arise more that

Such a stop ring may be useful pulling the impact body backwards, i. h., the for the well-known slow-running hammer, if the impactor would stop hitting, though between the motor and the crank drive, the tool is connected to the (soft) worm drive to be machined as well as a gear reduction 30 stone is pressed.

are inserted; with fast-hitting hammers

but would advance when the stop ring hits the controlled channel. The example of plastic

the impact body generates so strong impacts that the impact via the pressure-controlled valve is too much

Stop ring or gear would soon break; sucked air is during the working stroke of the piston

the stop ring is therefore displaced back to the atmosphere for fast-hitting 35 via this channel,

Hammer unusable. and so long until the further relative

In the case of a hammer, the gate movement mentioned in the introduction is the channel and thus the space

In contrast, device will be pre-closed according to the invention. The channel thus causes

beaten that the interspace a second compression of the air in the interspace - too

the connection to the atmosphere in the form of a more or less plastic one which is more or less plastic

known valve, which in the event of excess pressure in the intermediate joint - always at a certain distance of the

interstitial space closed, but at least with small transverse walls of the piston and cylinder, d. H. with con-

Vacuum is open, and that the valve begins the constant air filling. That is necessary in order to

Gap over an impact body in relation to this - if the tool of the hammer

small air storage space as well as a throttle point with 45 mers is pressed against the rock - also with

the atmosphere connects. changing working conditions, such as those in the company

The pressure controlled valve connects the ones that are customary to keep vibrating.

Air filling receiving space with the embodiments of the subject invention

Atmosphere as soon as - as a result of the above - are described below and in the drawing

outgoing compression unavoidable air 50 shown. It shows

Losses - a small negative pressure F i g in the space. 1 a hammer, partly in section,
adjusts. As a result, the air losses are timely F i g. 2 shows an enlarged detail from FIG. 1 supplemented, and when the impact body with impact body and driven part rushes forward, a partial vacuum braking the latter is avoided in the part of the valve and, in one embodiment, the gap. That gives a high 55 channels,
Efficiency of the hammer. F i g. 3 shows an enlarged detail from FIG. 1

However, only so much can be done from the storage space with a second exemplary embodiment of the channels. Air flow into the space, as initially shown in Fig. 1 shows an electric motor driven Reduction of air losses in all working conditions Hammer, the housing of which consists essentially of a maximum is necessary. The throttle point allows a further 60 a drive motor 1 and a gearbox 2 (both Air only very slowly into the storage space a main part 3 and a covered here) comprehensive flow so that when the piston retreats in the actual percussion mechanism, there is a hollow cylinder air space sets a sufficient negative pressure, the thresh grip part 4 consists. The striking mechanism exists sucks the impact body backwards. As a result, a hollow-cylindrical stroke becomes a special stop ring between piston 65 body 5, which with sliding surfaces 6 in a sleeve 7 and cylinder is dispensable and hard impacts between leads. The sleeve 7 is concentric in the handle cylinder and pistons avoided, d. e., the hammer part 4 of the housing attached so that between them is spared. On the other hand, both parts of the throttle point are a ring through which cooling air flows.

7 8

room 8 exists. In the impact body 5 is a KoI bore 40, from which a longitudinal groove 41 is a piece

ben 9 formed, driven part sliding and far towards the closed side of the impactor

inserted sealingly and running over a piston pin 10. Instead of the longitudinal groove and the narrow one

coupled to one end of a connecting rod 11, the one with bore 40 can also have a plurality of longitudinal grooves

its other end distributed on a pin 12 on the surrounding 5 to the inner surface of the impact body.

A catch can be brought to the transmission 2 via a shaft 13, which is at least as long as the piston

of the hammer connected crank disk 14 and of which one or two to the open

is stored. End of the impact body are pulled through (cf.

The striking body is with a striking face 15 on FIG. 3, reference number 41 '). The hole 39 enables

its closed front wall, with which io light an idle position of the striking mechanism,

he on one, in one resiliently against the sleeve 7 moves the connecting rod 11 forward (in the

supported and the sleeve tightly closing drawing to the left), then the bolt 10

Disc body 16 guided intermediate anvil 17 on the stud holder 23 in the piston 9, and moved over

can hit, which in turn impacts a one of the pretensioned springs 48 and the valve member 26

pluggable, guided in the housing channel 18 and 15 the piston 9 is also pushed forward,

Impact tool 20 held by a bolt 19 when the piston is advanced in the impact body

forwards. The intermediate end cap 17 is at its the air-filled space 28 is reduced,

At the tool-side end with a conical design, part of the compressed air

Deten connection collar 21 is provided, which is at a level initially via the groove 41 and the bore 40

if conical surface 22 of the housing without self-soft 20; however, the end face 24 of the piston has that

inhibition may apply. Exceeded the end of the groove, the remaining

The piston 9 is also a one-sided closed air compressed in the space and finally a hollow cylinder in which the bolt 10 and the impactor 5 are thrown forward.
Bolt holder 23 carrying the end of the connecting rod 11 Once the connecting rod has been guided its forward movement in a displaceable manner. This ends at the end wall 24 25 and the stud holder 23 comes to a standstill, the piston via springs 25 and a valve member so the piston is also stopped. By means of the 26 on a spring 38 towards the open end of the piston it is achieved that this braking of the stop 27 is supported. The valve member 26 is not carried out jerkily so that the piston
create that even with a slight negative pressure in the return stroke of the piston, air can flow into this intermediate space 28 through the one of the impact body 5 and the piston 9 30 bore 40 and the groove 41 in the intermediate space 28. The backward movement of the piston can flow in rule space. however, it is so fast that there is still a negative pressure

A transverse to the housing channel 18 and occurs in the gap, which is sufficient to pull the impact partially into this piece of rubber body into its starting position,
hose 21 'lies behind 35 when the hammer is idling. The path that the impact body 5 travels forwards to the tool 20 while holding the tool depends on the path of the tool 20. Is - even if the hammer is vertically upwards machining material hard, the impact will be held - in its front end position. away from the tool and the impact body short. In contrast, when the hammer is in operation, the piece lies. If it is a soft material, the rubber hose 21 ′ within a recess 19 ′ 40 increases the impact path. In addition, the stroke path of the tool shank is such that it does not hinder the necessary impact body depending on the position of the longitudinal movement of the tool 20. Tool. Is the tool, for example through pressure

When operating the hammer, the crank is pressed against the workpiece as far as possible into its Disc 14 pushed in via the gear 2 and the shaft 13 from the guide track 18, the impact electric motor hits 1 and gives up the rotary moving bodies after a shorter path than if that supply via the connecting rod 11 as a longitudinal movement on the tool 20 is shifted further forward. Of the Piston 9 further. The path of the piston 9, however, is always the same. Of the

By moving the piston forward - in hammer is now set up so that the impact force F i g. 1 to the left - becomes that in the space 28 of the impact body 5 with increasing impact path Trapped air compresses and hurls the 50 becomes weaker. This is achieved with the help of Impact body 5 also forward. This meets the groove 41 and the narrow bore 40. About the the intermediate head 17, which only hits the impact body when the piston is in a position Tool 20 forwards. The guide insert 16 for F i g. 2, then in this position a the intermediate header prevents part of the compressed air from escaping through the groove dust penetrating the guide channel and 55 chen, which results in a drop in energy in the air suspension Moisture can get into the sleeve 7. By means. This energy drop continues to rise resilient support on the sleeve 7 dampens the impact path, since then the length of the the guide insert 16 also bounces off the escaping air to be traversed groove smaller with the back of its conical collar 21 and thus the throttling effect of the groove the insert 16 hitting intermediate anvil 17. 60 decreases. With the tool advanced to the maximum, The impact blows are also used to reduce the force of such bouncing as it occurs when idling the intermediate top is so far forward compared to the body that the Impact body of light weight. Piston - as in FIG. 3 shown - in none

In addition to the valve 26, the space 28 has more of the stroke position that is normally always covered an additional ventilation via recesses 65 covers a relatively large bore 39 in the impact body, in the wall of the impactor. In the coat of the route 42 in FIG. 3 shows the stroke of the Impact body 5 is a through hole 39 on the piston and its position in relation to the impact body is empty (Figs. 2 and 3) and a narrow walk-through position. The bore 39 is large enough to the

Establish air compensation in the space 28 for each piston position. So there remains both a pressure on the impact body as well as a suction effect. The impactor therefore remains in its advanced position Position even with continuous piston drive. A blow does not start again until it is light Pressure of the tool 20 against the rock to be worked, the tool 20 and the intermediate head 17 and the impact body 5 are pushed back.

Details of the valve member 26 are shown in FIG. The piston 9 is at its end face 24 provided with a large round recess 43, over which a pot-like shaped inside of the piston and part 44 connected to the piston face turns inside out. The part encloses an air storage space 45 and runs into a pin 46, which has a narrow concentric throttle bore 47, and over the Disk springs 48 are pushed, with which the stud holder 23 is supported on the part 44. The springs 48 are downstream of the air suspension. Between the piston pin holder, which is ao slidable in the piston 23 and the stop 27 at the open end of the piston, plate springs 38 are also arranged. the Recess 43 is covered by a valve disk 50 provided with bores 49 on its circumference, which has a small free space between the edge of the recess and the part 44. The air storage space 45 is connected to the intermediate space 28 via the bores 49 when the valve disk 50 rests against the end face 24 of the piston. However, the holes are closed when the Valve plate rests on part 44. The springs 48 are so strongly biased that they do not affect the valve.

During the forward stroke, the valve disk is opened by the pressure of the air compressed in the space 28 pressed against the part 44, and the bores 49 are closed. When a negative pressure occurs in the space 28, the valve disk 50 is pulled forward and rests against the end wall 24 of the Piston on. Intermediate space 28 and air storage space 45 are therefore connected to one another. To the space in between a relatively large amount of air can flow away, a negative pressure in the space is compensated for a sufficient period of time and so a braking of the impactor before the Surcharge avoided. - If the impact body 5 hits hard and bounces back, this occurs in the gap 28 an overprint. The very lightly held valve disk quickly lies against the part 44, closes the gap and prevents air loss. However, if the impactor impacts only a little or not at all back, a negative pressure occurs after the impact. During the return stroke, despite the open bores 49 the negative pressure required to retrieve the impactor is reached in the intermediate space 28, since through the throttle bore 47 only slowly more air from the - via channels not shown Continuously connected to the atmosphere - the interior 37 of the piston flows into the storage space 45 can. New air is always required, as part of the air leaks between the Piston and impact body escapes.

The striking mechanism of the hammer can also be designed so that the striking body is designed as a piston and is guided in the hollow cylinder. The valve can then be designed as a driven part Sit hollow cylinder. But it is also possible to arrange valves in the impact body.

Claims (2)

Patent claims: 1. Motor-driven, fast-hitting, especially portable hammer with a housing, in which a hollow cylinder provided with a transverse wall and in the latter a piston axially are displaceably guided, with one of the displaceable parts being designed as an impact body, the other, however, is driven back and forth by the motor via a crank mechanism, and in which between the transverse wall of the hollow cylinder and a transverse wall of the piston an air-filled Gap of variable due to the relative movement between the hollow cylinder and piston Size consists, the air filling acting as a spring drive power on the impactor transmits, and the closed with small distances between the transverse walls, with large distances on the other hand via one controlled by the relative movement between the hollow cylinder and piston Channel is connected to the atmosphere, characterized in that the space (28) a second connection to the atmosphere in the form of a well-known one Valve (26), which is closed when there is overpressure in the space (28), but at least when is open slightly negative pressure, and that the valve (26) the gap (28) via an im Relation to this small air storage space (45) and a throttle point (47) with the atmosphere connects. 2. Hammer according to claim 1, characterized in that the in a known manner in the transverse wall (24) of the driven part (9) attached valve (26) with a cup-shaped, a tight seat for a plate-shaped closing member (50) containing part (section 44) opening (43) located in the end wall (24) on the side facing away from the intermediate space (28) covered and the air storage space (45) delimits, which via a narrow channel (47) with the atmosphere and with the closing member (50) lifted from its seat, in particular above Recesses (49) of the closing member (50), with the intermediate space (28) is connected. Considered publications:
German patents No. 291 218, 285 399, 624; U.S. Patent Nos. 2,067,886, 1,489,312, 207 417. 1 sheet of drawings 509 759/29 12.65 © Bundesdruckerei Berlin