FR2552695A1 - PORTABLE PNEUMATIC MACHINE WITH PERCUSSION PROTECTED AGAINST VIBRATIONS - Google Patents

Abstract

THE INVENTION CONCERNS MECHANICAL CONSTRUCTIONS. THE PERCUSSION MACHINE WHICH IS THE OBJECT OF THE INVENTION IS CHARACTERIZED IN THAT ITS BOX 1 IS EQUIPPED WITH A CONNECTING MEANS THROUGH WHICH SUCH BOX AND PISTON 3 ARE KINEMATICALLY LINKED SO AS TO BE ABLE TO MOVE IT. ONE IN RELATION TO THE OTHER, THESE MEANS OF CONNECTION AND PISTON 3 BEING DESIGNED SO AS TO COOPERATE BETWEEN THEM BY FRICTION. THE INVENTION IS APPLIED IN PARTICULARLY AND IN A PARTICULARLY ADVANTAGEOUS MANNER TO LADIES EMPLOYED IN MECHANICAL CONSTRUCTION, IN PARTICULAR IN FOUNDRY FOR TIGHTENING FOUNDRY SANDS USED FOR THE MANUFACTURE OF MOLDS AND CORES.

Description

The present invention relates to percussion machines and in particular

  Purpose A portable pneumatic percussion machine protected against vibrations.

  The invention applies in particular and particularly advantageously to the crushers or tampers employed in mechanical constructions, particularly in the foundry for compacting or clamping foundry sand used for the manufacture of molds and cores of different uses. The invention can be applied also in civil engineering for soil compaction, as well as in other branches of industry where it is necessary to compact or compress pulverulent materials with the aid of

hand machines.

  It is known that portable pneumatic percussion machines are highly effective and are often the only way to mechanize manual work. Their specific disadvantage is also known, which resides in the noticeable vibrations whose action on the operators reduces the productivity of the work and causes occupational diseases. Known solutions to reduce the vibration of portable pneumatic percussion machines, among which the most advanced solution consists of a portable pneumatic percussion machine protected against vibrations (cf United States of America Patent No. 3,223,181, c. 1.173-16 dated March 27, 1962), composed of a housing, a body housed in said housing so as to be able to effect limited axial movement, of a piston disposed in said body in the same manner, an air distributor device for moving said body and said piston back and forth with compressed air,

  and to carry by it the useful blows.

  The vibration of the casing, with which the operator is directly in contact, is significantly reduced here because this casing undergoes only a friction force of variable value and direction resulting from the above-mentioned movements of the body in the casing. vibration, it is advantageous to compensate said force. The peculiarity of this solution, especially when applied to pneumatic snow groomers, is that the housing to which the machine parts are connected must be maintained by the operator manually, which requires great efforts which cause rapid fatigue

  and a lowering of labor productivity.

  In addition, the gravity force of the boxer does not participate

  not at the creation of useful shots, which also lowers the power of the machine for the same mass of it.

  Also known is a portable pneumatic percussion machine, protected against vibrations (cf patent FRG No. 892580, cl 87 b 211 of December 7, 1951), consisting ofa housing provided with control members, a body housed in said in such a manner as to effect a limited axial movement of a piston disposed in said body in the same manner as above, with an air distributor device for putting said body and said compressed air piston in movement back and forth and to carry 25 the latter useful shots, and a device for creating a pushing force or bracing between the housing and the body and to compensate for the force of gravity the housing thus transforming it into a work of useful blows, and embodied as a cavity disposed inside the body or housing and placed in constant communication with a source of compressed air, and a tube of calibrated section, mounted in the housing er or in said body and debouching in

said cavity.

  However, in this case, in addition to the source of vibrations resulting from the friction of the body against the housing, there is still a source of vibrations which results from fluctuations in the value of the bracing force,

  due to the irregular consumption of compressed air supplied by the source of compressed air via the air distributor, and variations in the volume of the cavity mentioned during operation of the machine.

  The dimensions of axial and radial dimensions of this machine are important, which poses great problems

  during its realization pratiquestout especially in the case of the 10 machines of small size.

  A solution is known that makes it possible to reduce the fluctuations in the bracing force resulting from the variations in the volume of the cavity mentioned and to reduce the radial dimensions of dimensions. It is a portable pneumatic percussion machine protected against

  vibration (United States Patent No. 3,892,280, cl.

  173/162 of October 30, 1973), which is constituted by a housing provided with a handle, a body housed in said housing with the possibility of carrying out a limited axial movement, a piston housed in said body in the same manner as the one described above, an air distributor device for putting, with the aid of compressed air, said body and said piston in movement back and forth and to carry by the latter the useful shots, a device creating a bridging force between said housing and said body and executed in the form of a cavity disposed within said body or said housing and in constant communication with a source of compressed air, and a tube of calibrated section, and a device for the compensation of the volume of said cavity, executed in the form of a piston

  auxiliary connected to the piston mentioned first or main piston.

  However, even in this construction, the housing vibrates under the effect of the body friction and residual oscillations of the bracing force due to the irregular consumption of compressed air by the device

air distributor.

  In addition, the dimensions of axial dimensions of this machine are notable. It was therefore proposed to develop a machine

  portable pneumatic percussion machine, wherein the vibration of the housing would be reduced to a minimum by means of compensation of the frictional forces between the housing and the body, and which would furthermore have reduced axial and radial dimensions.

  The problem thus posed is solved with the aid of a portable pneumatic percussion machine comprising a casing, a hollow body mounted in said casing with possibility of axial movement, a piston movable in the cavity of said body, and dispensing means. and supplying the pressurized fluid into the hollow of said body for putting said piston and said body in reciprocating motion, substantially in phase opposition with respect to each other, and for the application useful shots by the piston, these means comprising a calibrated section tube fixed in the housing and adapted to withstand a constant fluid pressure for the compensation of the weight of the housing, characterized, according to the invention, in that the housing is provided with a connecting means through which said housing and said piston are movably connected to one another by means of

  relative to the other, said connecting means and the piston cooperating with each other by friction.

  The connection of the casing and the piston ensuring their friction co-operation makes it possible to apply to the casing still a friction force of variable value and direction. This force is directed substantially in phase opposition with respect to the value and friction force of friction. meaning

  variables previously existing between the case and the body.

  Thus, mutual compensation of these forces is obtained and,

  therefore, a reduction in the vibration of the housing.

  It is advantageous to provide a cavity in the piston and to realize the connecting means in the form of an elongated tube of calibrated section engaged in a sealed manner

in the piston cavity.

  This embodiment solves the problem

  discussed above in the simplest way, that is to say substantially simplify the design of the machine by modifying the existing components already.

  It is advantageous that, in a machine whose piston is provided with a rod passing through the body of the machine and carrying at its end a shoe intended to compact the powdery materials, said rod is made hollow, that the cavity of the piston is connected to the stem cavity and that the calibrated section tube is made to pass through the piston cavity and engage with its

  end into the stem cavity.

  This substantially reduces the axial dimension of the machine.

  Thanks to the invention, it has therefore created a portable pneumatic percussion machine whose vibrations are minimal and which is simpler design, space

minimum and maximum power.

  The invention will be better understood and other purposes, details and advantages thereof will become more apparent in the

  light of the explanatory description which will follow from

  various embodiments given solely by way of non-limiting example with reference to the appended single drawing in which: Figure 1 shows a portable pneumatic percussion machine executed in accordance with the invention (in longitudinal section and partially broken away); Figure 2 is a section on II-II of Figure 1; FIG. 3 is a section along III-III of FIG.

figure 1.

  Hereinafter the invention will be explained by the detailed description of an example of a concrete application, namely

  of a pneumatic portable snow groomer protected against vibrations, it being understood that this example of application should in no way be considered as limiting the field

  of application and the scope of the invention.

  The portable pneumatic percussion machine 10 protected against vibrationjreprésentée in Figure 1, is present, in the case considered in the form of a groomer constituted by the following bodies: a housing 1, a body

2 and a piston 3.

  The housing 1 comprises a handle 4 with an actuating device 15 which can be of any known type and is not shown in the drawings), and a part

  cylindrical 5 screwed into said handle and on which is screwed in turn a cap 6 A resilient element 7, for example rubber, is mounted between the cylindrical portion 20 5 and the cap 6.

  Inside the housing 1 is mounted said body 2 so that it can perform a limited longitudinal movement Said housing and body cooperate with each other by their surfaces 8 and 9, respectively The body 1 is composed of a hollow cylinder 10 in the upper part of which is engaged to the press a sleeve 11, a sleeve 12 provided with a seal being fixed in the

lower part of said cylinder.

  Inside the body 2 is also mounted a piston 3 30 which can perform a limited axial movement The piston 3 comprises a rod 13 having an interior cavity 14 At the end of the rod 13 is fixed a shoe end A sheath 16 is mounted in the upper part of the piston 3 In this same part of the piston 3, is formed a transverse groove 17 opening into the cavity 14 and in which is mounted movable a valve 18 (Figures 1,2) longitudinal grooves formed on the outer surface the upper part of the piston 3 (Figure 1) pass through the groove 17 and form with the sleeve 16 of the channels 19 and 20 The channels 19 are placed in communication with a cavity 21 of travel formed in the body 2 by the piston 3 and delimited inside the cylinder 10 by the sleeve 11 and by the piston 3 The channels 20 communicate with the cavity 22 of return stroke formed inside the cylinder 10 between the piston 3 and the In the position shown in the figures, these channels are closed by the valve 18. The groove 17, the valve 18 and the channels 19, 20 form an air distributor device. evacuation of the spent air cavities 21 and 22, the cylinder 10 has orifices 23 opening into its grooves 24 (Figures 1, 3) which communicate with the atmosphere via

  an annular space 25 (Figure 1) formed between the cylinder 10, the sleeve 12, the cylindrical portion 5, the elastic element 7 and the cap 6.

  Between the handle 4 and the cylindrical portion 5 is fixed with the aid of a cap 26 a tube 27 of calibrated section having an opening longitudinal channel 28 communicating with the channel 29 and, through the starting device, with a compressed air source (not shown in the figures) The tube 27 is sealed with its shoulder and an elastic ring 30 The tube 27 passes to

  through the sleeve 11 and engages the piston 3 and is sealed along its outer surface 31 by the surfaces 32 and 33 of the sleeve 11 and the piston 3, respectively.

  The essence of the invention lies in that the housing 1 is provided with a connecting means by means of which said housing and the piston 3 are connected to each other in a movable manner with respect to each other. connecting means is formed by a tube 27 fixed in the housing 1 and sealingly engaged in the piston 3 The piston 3 and the tube

  27 cooperate with each other by friction.

  The enclosure 34 formed between the housing 1 and the body 2 at their upper part constantly communicates with the atmosphere through holes 35 made in the cap

  26 and through orifices 36 formed in the handle 4.

  The displacement of the body 2 in the housing 1 is limited at the top by the cap 26 and a resilient abutment 37 (for example made of rubber), and at the bottom, by its shoulder 38 and by the elastic abutment 7 of the housing 1. of the piston 3 in the body 2 is limited by the sleeves 11

and 12.

  The portable pneumatic percussion machine shown in FIG. 1 operates in the following manner.

  In the position shown in Figure 1

  and considered for the purposes of the description as the starting position, the return stroke cavity 22 is connected via the exhaust ports 23,

  grooves 24 and the annular space 25 to the atmosphere.

  The channels 20 of the piston 3, intended to put this cavity in communication with the source of compressed air via the groove 17, the cavity 14, the channel 28 25 of the tube 27, the channel 29 of the handle 4 and the starting device, are closed by the valve 18 With respect to the body 2, the piston 3 is in the upper extreme position, which corresponds to the beginning of the forward travel of the machine The cavity 21 of the forward stroke is connected 30 to the source of compressed air through the channels 19, the groove 17, the cavity 14 of the piston 3, the channel 28 of the tube 27, the

  channel 29 of the handle 4 and the starting device.

  With respect to the housing 1, the body 2 occupies a certain intermediate position in which the elastic stop 37 is not in contact with the cap 26, and the shoulder 38

  of the body 2, with the elastic stop 7.

  When the starting device is engaged, the compressed air coming from the source of compressed air 5 passes through the channel 29 of the handle 4 and through the channel 28 of the tube 27 and arrives in the cavity 14 of the piston 3 During operation, the cavity 14 is under a pressure of compressed air approximately equal to the pressure prevailing in said source. Under these conditions, an upwardly and substantially constant force is applied to the boltier 1, the value of this force being equal to the product of the pressure of compressed air in the cavity 14 by the cross-sectional area of the calibrated section tube 27 (including the cross-sectional area of the channel 28 thereof). This value is chosen whatever This value is obtained by a suitable choice of the value of the cross section of the tube 27, because the compressed air pressure is determined by the type The compressed air source used is, and therefore has a substantially constant value. A same force, but in the opposite direction, is applied to the piston 3. The creation of this force makes it possible, first of all, to counterbalance the weight of the casing 1 and the parts 25 which are connected to it, which ensures easy operation, and secondly, to use, thanks to this force, the weight of the case to obtain the useful shots and to raise

  the power of the whole machine.

  From the cavity 14, the compressed air arrives through the groove 17 and the channels 19 into the forward travel cavity 21. Under the action of the compressed air pressure exerted on the side of the forward travel cavity 21, the body 2 and the piston 3 begin to move upwards and downwards, the movement of the latter being favored by the applied force

  to this one on the side of the cavity 14.

  As the body 2 and the piston 3 move together, the sleeve 16 masks the exhaust ports 23 and the air enclosed in the cavity 22 begins to be compressed. The body 2 and the piston 3 continue to move, the Exhaust ports 23 open and bring the cavity 21 in communication with the atmosphere through the grooves 24 and the space 25. The air starts to escape from the cavity 21 to the atmosphere and the pressure of The air therein decreases to a value substantially equal to the atmospheric pressure. The body 2 and the piston 3 continue to move towards each other and the pressure in the cavity 22 increases under the action of pressure. upper acting on it from below, the valve 18 moves to its upper position thus closing the channels 19, and communicates the channels 20 and, therefore, the cavity 22 with the source of compressed air through the groove 17 By overcoming the back pressure ex chained from below, the piston 3 comes to strike by its working end (shoe) 15 the material to be compacted (not shown), thereby performing the desired working work. Next, the piston 3 requested by the

  Pressure in the cavity 22 overcomes the pressure in the cavity 14 and begins to move upward. At approximately this time, the body 2 is braked and begins to descend.

  During the movement of the body 2 downwards and the piston upwards, the exhaust ports 23 are masked and the compression of the air isolated in the cavity 21 of the outbound race begins. The body 2 and the piston 3 conti30 nuant to move, the orifices 23 open and the worn air begins to escape from the cavity 22 back stroke Under the action of the stronger pressure acting from above, the valve 18 moves to its position lower and connects the cavity 21 to the source of compressed air through the channels 1 January 19, the groove 17, the cavity 14, the channels 28, 29 Under the action of the increased pressure in the cavity 21, the body 2 and the piston 3 are braked and begin to move in the opposite direction, ie, the body upwards and the piston downwards Then, the cycle of

  operation of the machine starts again.

  During a cycle of operation of the machine, the casing undergoes the action of the following forces: a) Force of gravity of the box 1 directed downwards 10 and of constant value; b) Force applied to this housing via

  of the tube 27 on the side of the cavity 14 and directed upwards.

  Since the compressed air pressure is substantially constant in the cavity 14, its value is practically constant. These forces are oriented towards each other and almost offset each other.

  Virtually no vibration of the box 1.

  c) friction force whose value and direction are variable and which is caused by the back and forth movement of the surface of the body 2 along the inner surface 8 of the casing 1 and the inner surface 32

  of the body 2 along the outer surface 31 of the tube 27.

  d) friction force whose value and direction are variable and which is caused by the reciprocating movement of the surface 33 of the piston 3 along the surface 31 of the tube 27. As a result of the substantially opposing movement of phase of the body 2 and the piston 3, the directions of these friction forces are practically in phase opposition Their values are practically equal, since the effect resulting from the fact that the contact surface of the body 2 with the casing 1 is much greater than the contact area between the piston 3 and the tube 27 l is compensated by the fact that the speed of movement of the piston 3 relative to the

  casing 1 is substantially greater than the speed of displacement.

  body 2 with respect to the housing 1, given the

  important difference between their masses.

  For these reasons, said friction forces substantially compensate for each other, which also contributes to suppressing vibrations of the housing with which the operator's hands are in contact during work. The absence of vibrations that can be transmitted to the operator increases the productivity of the work and contributes

  the suppression of occupational diseases due to vibration.

  During the operation of the machine, the presence of the cavity 34 has no influence on its parameters, including the vibrations of the housing 1, because this cavity is placed in constant communication with the atmosphere through the orifices 35, 36 , and the pressure in this

  cavity is virtually equal to atmospheric pressure.

  In the established operating mode, the body 2, during its back-and-forth movement, oscillates in the vicinity of a certain midpoint, without coming into contact with the cap 26 by its elastic abutment 37, and with the stop

  elastic 7, by its shoulder 38.

  In the event of occasional collisions of said elements and the appearance of vibrations of the casing 1, these can be

  delete easily by moving it up or down.

  It is advantageous to apply the present invention to groomers used in foundry for clamping foundry sands, in which the piston is permanently connected to the shoe by means of a rod. In this case, the rod is made hollow. and a calibrated section tube, linked to the tierls'engage in said rod Such a design of the machine not only reduces vibration,

  but also to significantly reduce the length of the groomer.

Claims (3)

R E V E N D I C A T I 0 N S CLAIMS   1 Portable pneumatic vibration-proof percussion machine, of the type comprising a casing (1), a hollow body (2) housed in the casing (1) so that it can effect axial movement therein, a piston (3) movably mounted in the cavity of the body (2), and means for distributing the pressure and supplying fluid under pressure into the body cavity (2) for the displacement of the piston (3) and the body (2) in back and forth and substantially in phase opposition with respect to each other and for the appli10 cation of useful shots by the piston (3), said means comprising a tube (27) of calibrated section fixed in the housing (1) and adapted to support a constant fluid pressure for the compensation of the weight of the casing (1), characterized in that the casing (1) is provided with a connecting means 15 through which said casing and the piston (3) are kinematically connected so as to be able to move relative to each other. the other, said connecting means and the piston (3) being designed so as to be able to cooperate with each other by friction.   Portable pneumatic percussion machine according to claim 1, characterized in that the piston (3) comprises a cavity in which said connecting means engages in a sealed manner, the latter being form of an elongate tube (27).   3 Portable pneumatic percussion machine according to   one of claims 1 and 2, wherein the piston (3)   is provided with a rod (13) passing through the body (2) and carrying at its end a shoe (15) for compressing or clamping a powder material, characterized in that the rod (13) is executed hollow, that the cavity of the piston (3) is placed in communication with the cavity (14) of the rod (13) and that the tube (27) of calibrated section is executed so as to pass through the cavity of the piston   (3) and to engage at its end in the cavity (14) of the rod (13).