GB2192824A - Power-driven hammer - Google Patents

Abstract

Power-driven hammer with a pneumatic percussion mechanism having a retention device with holding elements (5, 30, 30', 50, 60, 80, 100, 110, or 120) which retain the striker (3, 3', 3'', 3''', 3'''') during idling. The holding elements (5, 30, 30', 50, 60, 80, 100, 110, or 120) are controlled by the striking pin (4, 4', 4'', 4''', 4''''), the tool shank, a shifting sleeve (69) or another movable component of the percussion mechanism, so that, when the hammer is lifted off from the masonry, they engage with their hook-like extensions (6, 31, 51, 61 or 81) or a groove (7, 7', 7'', 7''') of the striker (3, 3', 3'', 3''', 3'''') and retain the latter. When the hammer drill is restarted, they are automatically disengaged, so that the percussion mechanism is reactivated. By means of the retention device, the idling travel of the striker is reduced considerably; furthermore, it is possible to do away completely with the otherwise customary idling bore provided in the guide tube for the piston. The holding elements may be prestressed outwardly by an inner spring ring 10 and biased radially towards the striker 3 by a spring ring 9. The elements may assume the form of an annular spring, biased rocking levers, elastic blocking sleeve or a sprung rigid sleeve 120. <IMAGE>

Description

SPECIFICATION Power-driven hammer State of the Art The invention starts from a power-driven hammer with a pneumatic percussion mechanism according to the precharacterizing clause of the main claim. Retention devices for the striker during idling are already known. According to German Offenlegungsschrift 2,820,128, there is, for example, an O-ring which is located at the end of the guide tube for the striker and which, during idling, is overrun by an annular shoulder of the striker and prevents the latter from executing the return stroke. In German Offenlegungsschrift 3,335,553, the striker itself has an O-ring held by a sleeve element with an annular shoulder when the striker is in the idling position.However, these retention devices have only a passive effect and therefore require a relatively long idling travel which is sometimes increased even further by damping devices for the striker. But the disadvantage of a long idling travel, besides the higher outlay in terms of material, weight and cost, is that it becomes more difficult to restart the hammer from the idling position, and in work on soft materials, such as, for example, clay, this means that the percussion mechanism is not activated when the critical starting speed is exceeded.

Advantages of the Invention In contrast to this, the advantage of the hammer according to the invention, having the characterizing features of the main claim, is that the idling travel is reduced considerably (for example to a third) by means of the active retention device for the striker. In addition to the saving in terms of weight, overall length and costs achieved thereby, the starting threshold is lowered considerably, that is to say the critical speed is increased, which otherwise would only be possible by reducing the air cushion and incurring the resulting consequences of- either higher pressure peaks in the percussion mechanism or harder impacts on the operator's hand. The lower starting threshold can be used either to increase the efficiency -of the percussion mechanism or to improve comfort by means of a longer air cushion.

In the retention device according to the invention, it is even possible to do away completely with the often customary idling bore provided in the guide tube for the piston, thereby totally eliminating starting difficulties arising from the idling of the percussion mechanism.

Another advantage is that it becomes more difficult for dust and dirt to be transported from the tool into the percussion mechanism, because on account of the shorter idling travel the tool shank is likewise axially displaceable only over a correspondingly short distance.

This also means that the shank length of the tools can be shortened. A further advantage is that there is less wear on the holding elements of the retention device in comparison with the conventional O-rings.

Drawing Several exemplary embodiments are indicated in the drawing and explained in detail in the following description. Figure 1 shows, partially in section, the percussion mechanism and the tool mounting of an exemplary embodiment of a hammer according to the invention, Figure 2 shows, in section, part of another exemplary embodiment of a percussion mechanism, and Figure 3 shows a section along the line A-A in Figure 2. Figure 4 likewise shows part of a percussion mechanism, and Figure 5 shows a section along the line B-B in Figure 4.

A further exemplary embodiment is illustrated in Figures 6 to 9, specifically as a longitudinal section in Figures 6 and 8 in Figure 7 as a cross-section along the line C-C in Figure 6, and in Figure 9 as a cross-section along the line D-D in Figure 8.

Figures 10 to 13 illustrate an example of an elastic holding element, in longitudinal section in figures 10 and 13, in Figure 11 as a view as seen from the direction E in Figure 10, and laid out flat in Figure 12.

Figure 14 shows a further exemplary embodiment in longitudinal section, and Figure 1 5 shows a cross-section along the line F-F in Figure 14.

An example of a blocking sleeve is shown in Figure 16 in longitudinal section and in Figure 1 7 in a cross-section along the line G-G in Figure 16. A further alternative form is shown in Figure 18, again in cross-section. Figure 19 shows a rigid sleeve as a holding element in longitudinal section.

Description of the Exemplary Embodiments Of the pneumatic percussion mechanism 1 of a hammer drill, Figure 1 shows a skirt-type piston 2, a striker 3 movable to and fro in the latter, and a striking pin 4 which is under the effect of the striker 3. The striking pin 4 is surrounded by several holding elements 5, the hook-like extensions 6 of which can engage into a groove 7 of the striker 3. In the middle part, the striker 3 has a cone 28 which, in conjunction with the extensions 6, serves as a vibration damper for the striker 3 during idling.

The holding springs are held by slotted spring rings 9, 10 attached on the periphery and in a recess 8 in the inside diameter. The holding elements 5 each have on the outside a nose 11 which is supported against a damping element 12 consisting of two fixed rings 13, 15 and an elastic ring 14 made, for example, of rubber. The striking pin 4 has a groove 16, a collar 17 and a narrowed portion 18 which serve for controlling the holding elements 5.

The holding elements 5 have control noses 19, 20 projecting inwards and having bevels 21, 22 which, during percussion operation, rest respectively against the collar 17 and the groove 16 of the striking pin 4. The outer spring ring 9 of larger size than the spring ring 10 ensures that, when the hammer is in any operating state, the holding elements 5 are in contact with the striking pin 4. The striking pin 4 can be driven to rotate via the hammer tube 23, the toothed collar 24 of which engages in the toothing 25. At the front end facing the tool holder 26, the striking pin 4 has a bore 27 which is intended for receiving a tool and which is made non-circular or has grooves, so that the rotary movement can be transmitted to the tool shank (not shown).

In Figure 1, the holding elements 5 are in the striking position, that is to say the striker 3 is freely movable. When the hammer drill is lifted off from the rock, since the resistance of the rock ceases the striker knocks the striking pin so far forwards that the control nose 19 rests against the narrowed portion 18 and the control nose 20 rests against the collar 17 of the striking pin 4. As a result, the extensions 6 are tilted inwards and engage into the groove 7 of the striker 3. Consequently, the latter is retained in the idling position and no longer follows the movements of the skirt-type piston 2. The energy still possibly contained in the striker in the form of a return movement of the latter is absorbed in the damping element 12 via the holding elements 5 and their noses 11.As soon as the hammer drill, together with the tool, is pressed against the rock again, the striking pin 4 is shifted to the rear and the Control nose 19 slides-via its bevel 21 onto the collar 17; at the same time, the control nose 20 slides inwards into the groove 16, so that the extensions 6 release the striker 3 and the percussion mechanism is reactivated.

Figure 2 shows, within the hammer tube 23', an exemplary embodiment with three somewhat simpler holding elements 30 in the retention position; that is to say the exten sions 31 engage into the groove 7' of the striker 3'. The inward-projecting control noses 32 with the bevels 33 do not touch the strik ing pin 4' in the retention position. The hold ing elements 30 are pressed inwards by the slotted spring ring 34, as is evident from Fig ure 3. A spring ring 35 resting against the inner face of the holding elements 30 holds these up against the spring ring 34, so that they cannot tilt when they spread open. The striking pin 4', at the end facing the striker 3', has a narrowed portion 36 and can be driven to rotate via the hammer tube 23'.As in the first exemplary embodiment; the extension 31 is supported axially against a damping element consisting of three rings 13, 14 and 15. Figure 4 shows a slightly modified holding element 30' which differs from that shown in Figure 2 in that it has spring rings 37, 38 which are inserted in grooves of the control nose 32' and an extension 31' and which perform the same function as the spring ring 35.

The function of the holding elements 30, 30' corresponds to that of the holding element 5 of the first exemplary embodiment.

Figure 3 shows the idling position, in which the extension 31 engages into the groove 7' of the striker 3' and retains the latter. When the tool (not shown) is pressed against the rock, the control noses 32, 32' slide outwards on the bevel 39 of the striking pin 34', with the result that the holding elements 30, 30' are shifted outwards as a whole parallel to the axis 40 of the percussion mechanism, as shown in Figure 4. At the same time, gaps 41, which can be seen in Figure 5, form between the holding elements 30, 30'. The spring rings 34, 35, 37, 38 are spread open.

Figures 6 to 9 illustrate an example of four holding elements 50 arranged outside the hammer tube 23". These have relatively long extensions 51 and control noses 52 which pass through orifices 53 and 54 in the hammer tube 23". A spring ring 55 presses the holding element 50 inwards. The extensions 51 are supported against a sealing element 12' which is attached outside the hammer tube 23" and which has a design similar to that of the sealing element 12 of the first exemplary embodiment. The striker 3" has a groove 7", into which the extensions 51 can engage. The striking pin 4' has the same design and the same function as in Figures 2 to 5.

The function of this exemplary embodiment corresponds to that of the exemplary embodi ment described above. In Figures 6 and 7, the holding elements 50 are in the retention position; Figures 8 and 9 illustrate the percussion operation.

In Figures 10 to 13, the holding element is designed as an elastic annular holding spring 60 with hook-like extensions 61 and control noses 62 and is inserted between the hammer tube 23 or skirt-type piston 2 and the striker 3"' or striking pin 4". At the front end 63 on the tool side, the holding spring 60 is bent round towards the hammer tube and rests against its collar 24. On the other side, it is held by a disc 65 fixed by a spring ring 64, with two elastic O-rings 66, 67 being inter posed and serving for damping during the re turn stroke of the striker 3"' in the retention position of the holding spring 60 shown in Figure 10. Here, the extensions 61 engage into the groove 7" of the striker 3"' and retain the latter in the idling position. Between the holding spring 60 and the narrowed end 68 of the striking pin 4" is arranged a shifting sleeve 69 axially displaceable on the latter and having two beads 70, 71 on the periphery. The collar 72 of the striking pin 4" and the front end 73 of the striker 3"' have a diameter larger than the inside diameter of the shifting sleeve 69.

The holding spring 60 has intentionally been largely insulated from the shock waves of the percussion mechanism 1, as has the indexing sleeve 69 which is shorter than the length of the narrowed end 68 of the striking pin 4".

Figure 11 shows the holding spring 60 as an individual part with its six tongues 74. There are narrow gaps 75 between these. Figure 12 shows part of the holding spring 60 laid out flat. The control noses 62 are stamped out of the tongues 74 and bent inwards. The basic function of the holding spring 60 is the same as in the exemplary embodiments mentioned above. In the retention position (Figure 10), the control nose 62 is not in contact with the shifting sleeve 69. The latter has been pushed forwards by the striker 3"', since the counterpressure exerted by the rock has ceased. Figure 13 shows the percussion operation in which the striking pin 4" is displaced to the rear together with the shifting sleeve 69, so that the control nose 62 slides on the outer face of the shifting sleeve 69 between the beads 70 and 71.As a result, the tongues 74 are bent outwards, so that the extensions 61 no longer engage into the groove 7" of the striker 3"', and the latter is freely movable.

In the example shown in Figures 14 and 15, four holding elements 80 are designed as rocker levers with extensions 81 and control noses 82. The control nose 82 of the holding element 80 is located at the end of the front control arm 83 which, on the outside, has a groove 84 with an inserted spring ring 85. In the holding arm 86 there is also a groove 87, into which a spring ring 88 weaker than the spring ring 85 is inserted. The striker 3' has a groove 7' for the engagement of the extensions 81. A control cam 89 is located in the rear end region of the striking pin 4"'. The striking pin 4"' can be driven to rotate via the hammer tube 23"'.The holding element 80 can be tilted by means of its U-shaped recess 90 about a pin 91 Ipcated in a bore 92 of a cage 93 (Figure 15); The cage 93 has annular grooves which are iptended for receiving the spring rings 85, 88 and of which only the annular groove 94 on the same side as the control arm can be seen. The cage 93 is held on one side by the hammer tube 23"' and on the other side, with an O-ring 95 interposed for damping, by a disc 96 held by a spring ring 97.

Figure 14 shows a striking pin 4"' in its rearmost position, in which the striker is freely movable. When the hammer drill is relieved of pressure, the striking pin 4"' is- knocked forwards, so that the control noses 82 rest on the control cam 89 and the holding arm 86 is tilted inwards, in order to retain the striker 3' during idling. If the striking pin 4"' is already in front of the striker 3' in the idling position, the holding elements 80 can move aside outwards because of the U-shaped design of the recess 90, allows the striker 3' to pass through and subsequently engage into the groove 7'.Of the exemplary embodiment illustrated in Figure 16, the Figure shows only a striker 3"" with a groove 7"', a holding element designed as an elastic blocking sleeve 100 and a striking pin 4"" with a narrowed portion 104 which, as in the preceding exemplary embodiments, are parts of the percussion mechanism for a power-driven hammer.

The blocking sleeve 100 has lateral rectangular orifices 102, 103 limited by webs, of which only one 101 can be seen. In the state of rest, the blocking sleeve 100 has an oval shape, the smaller diameter being less than the outside diameter of the collar 105 of the striker 3"" (see Figure 17), so that the latter is retained in the retention position. In the retention position, only the narrowed portion 104 of the striking pin 4"" reaches into the blocking sleeve 100 which is thinner than its small diameter (sic).

To activate the percussion mechanism, the striking pin 4"" has to be shifted in the direction of the striker 3"" by the tool (not shown), so that the thicker part 106 of the striking pin 4"" widens the blocking sleeve 100, with a result that the striker 3"" is released. The striker 3"" has a conical tip 107, so that, even when the blocking sleeve 100 is in the retention position, the striker can advance as far as the orifices 102, 103 by widening the blocking sleeve 100, if it was not yet in the region of the blocking sleeve 100 at the moment when the latter closed.

The blocking sleeve 110 shown in Figure 18 is an alternative form to the blocking sleeve 100, again with two rectangular lateral orifices 111, 112. It is open at the top and on the other side has an eyelet-iike extension 113 for increasing the spring excursion. Its function corresponds to that of the blocking sleeve 100.

Figure 19 shows, as a holding element, a tubular rigid sleeve 120 with an inward-directed collar 121, 122 at each end. The sleeve 120 is under the effect of the spring 123 which presses the sleeve 120 against the striking pin 4"". When the collar 121 comes up against the thicker part 106 of the striking pin 4"", the striker 3"" is freely movable for percussion operation, as shown in Figure 19.

As soon as the tool (not shown) is relieved of pressure, the striker knocks the striking pin 4"" to the left. The collar 121 now enters the region of the narrowed portion 104 and is pressed against the latter by the spring 123 in the retention position. Consequently, the collar 122 engages into the groove 7"' of the striker 3"" and retains the striker during idling. Otherwise, the function of this exemplary embodiment corresponds to that described according to Figures 16 to 18.

In all the exemplary embodiments, either skirt-type pistons 2 or cylinder pistons can be used alternatively. Likewise, to control the holding elements 5, 30, 30', 50, 60, 80, 100, 110, 120, an additional shifting sleeve 69 can be provided everywhere or this can be omitted or an appropriately shaped tool shank, intermediate set or the like can perform the control directly.

Claims (11)

1. Power-driven hammer or hammer drill with a pneumatic percussion mechanism and a retention device which during idling retains the striker driven to move to and fro, characterized in that the retention device has one or more movable holding elements (5, 30, 30', 50, 60, 80, 100, 110, 120) which are controlled by a control member, such as, for example, a shifting sleeve (69), a striking pin (4, 4', 4", 4"', 4""), 'an intermediate set or the tool shank and on which are arranged hooklike extensions (6, 31, 51, 61, 81), webs (101) or collars (122) which, when the striker (3, 3', 3"; 3"', 3"") is in the idling or cut-off position, engage into grooves or recesses (7, 7', 7", 7"') arranged in the latter.

2.-Hammer according to Claim 1, characterized in that the holding elements (5, 30, 30', 50, 60, 80, 100, 110, 120) have a soft mounting against a recoil of the striker (3, 3', 3", 3"', 3""), with damping elements (12) or the like interposed.

3. Hammer according to Claim 1 or 2, characterized in that the holding elements (5, 30, 30', 50) are rigid, are pressed inwards by a spring ring (9, 34, 35) and can be shifted radially outwards by the striking pin (4, 4') via control noses (19, 32, 52).

4. Hammer according to Claim 3, characterized in that the holding elements (5, 30, 30') are prestressed outwards by an inner spring ring (10, 35, 37, 38).

5. Hammer according to Claim 3 or 4, characterized in that the -holding elements (50) are arranged outside the hammer tube (23").

6. Hammer according to Claim 1 or 2, characterized in that the holding element is designed as an annular holding spring (60) with tongues (24) and hopk-like extensions (61) directed towards the striker (3"').

7. Hammer according to Claim 6, characterized in that the holding spring (60) has control noses (62) via which the tongues (74) are moved radially away from the striker (3"') or towards it, depending on the operating state of the hammer, by a shifting sleeve (69) axially displaceable by means the striking pin (4") and striker (3"').

8. Hammer accordjng to Claim 1 or 2, characterized in that the holding elements (80) are designed as rocker levers which are mounted rotatably about a pin (91) and which on the two arms have spring rings (85; 88) pressing the rocker levers inwards, the spring ring (85) on the control arm (84) being made stronger than on the holding arm (86) having an extension (81), and the striking pin (4"') serving as a control member has a control cam (89) at its end.

9. Hammer according to Claim 1 or 2, characterized in that the holding element is designed as an elastic blocking sleeve (100, 110) possibly open on one side and oval in the relieved state, with lateral orifices (101, 102 and 111, 112) for retaining the striker (3""), and this blocking sleeve (100, 110) can be widened by the tool or the striking pin (4"") in order to release the striker (3"").

10. Hammer according to Claim 1 or 2, characterized in that the holding elements is (sic) designed as a rigid sleeve (120) pressed on one side against a control member, for example a striking pin (4""), under a spring effect, with collars (121, 122) directed inwards, one (121) serving as a control collar and the other (122) serving as a holding collar for the striker (3"")

11. Any of the embodiments of powerdriven hammer substantially as herein described with reference to the accompanying drawings.