Impact tools

Abstract

To provide an impact tool which prevents vibration of a striking mechanism from being transmitted to a housing.SOLUTION: An impact tool 100 includes a cylindrical housing 110, a movable part 112 at least partially arranged in the housing 110, and a first spring 114 and a second spring 116 which are arranged between the movable part 112 and the housing 110. The movable part 112 includes a needle holder 126 for holding a needle 102, a cylinder 120 for reciprocating the needle 102 and the needle holder 126, a piston 122 and an anvil 124. The movable part 112 is supported on first and second springs 114 and 116 so as not to bring an outer peripheral surface 112a of the movable part 112 into direct contact with an inner peripheral surface 110a of the housing 110, in a state where at least a striking mechanism is not driven and force in a radial direction does not act on the movable part 112.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an impact tool configured to perform surface processing on a workpiece by impact with vibration caused by a tip tool such as a needle chisel or a chisel.

Background Art

[0002] An impact tool is normally configured such that a piston disposed in a cylinder is reciprocated by compressed air, and the piston strikes a tip tool such as a needle chisel or a chisel or a member holding these tools to apply impact force to the tip tool. During driving, such an impact tool vibrates due to the reciprocation of the piston, the impact from the piston, the impact that the tip tool receives from the workpiece, and the like. If the vibration of the entire impact tool increases, there is a risk that the workability of an operator gripping the impact tool may decrease, or a device holding the impact tool may be damaged. For this reason, impact tools configured to reduce such externally transmitted vibration have been developed. For example, Patent Documents 1 and 2 disclose a configuration in which a cylinder is accommodated in a cylindrical housing so as to be slidable in the front-rear direction, and the cylinder is supported from the front-rear direction by two coil springs. When the cylinder vibrates in the reciprocation direction (front-rear direction) along with the reciprocation of the piston, the vibration is absorbed to a certain extent by the two coil springs, thereby reducing the vibration transmitted to the housing.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the conventional impact tools described above, the cylinder slides in the front-rear direction relative to the housing while the outer surface of the cylinder and the inner surface of the housing are always in contact. Therefore, although the vibration of the impact mechanism, including the cylinder and piston, is reduced to some extent by the spring, some of it is transmitted directly to the housing from the contact point between the outer surface of the cylinder and the inner surface of the housing. In particular, when the impact tool is used mounted on a robot arm, this vibration may interfere with the operation of the robot arm or even damage the robot arm. Therefore, it is desirable to reduce the vibration transmitted to the housing as much as possible.

[0005] Therefore, the present invention aims to provide an impact tool in which vibrations of the striking mechanism are less likely to be transmitted through the housing. [Means for solving the problem]

[0006] In other words, the present invention is A cylindrical housing, A movable part located at least partially within the housing and displaceable relative to the housing in the direction of the housing's longitudinal axis, comprising: a tool holder for holding a tool tip; and a striking mechanism for applying striking force to the tool tip attached to the tool holder in the front-rear direction along the housing's longitudinal axis; A first spring is disposed between the movable part and the housing and biases the movable part forward. A second spring is disposed between the movable part and the housing and biases the movable part toward the rear, Equipped with, The present invention provides an impact tool in which the movable part is supported by the first and second springs such that, at least when the impact mechanism is not driven and no radial force perpendicular to the longitudinal axis is acting on the movable part, the outer surface of the movable part and the inner surface of the housing do not come into direct contact.

[0007] In this impact tool, the movable part is supported by first and second springs such that the outer surface of the movable part and the inner surface of the housing do not come into direct contact, at least when the impact mechanism is not driven and no radial force is acting on the movable part. Therefore, even when the tool is driven, the movable part and the housing do not come into contact, or if they do, the contact pressure is smaller and the contact is temporary compared to conventional designs where they are always in contact and sliding, thus reducing the vibration transmitted from the movable part to the housing.

[0008] Furthermore, the difference between the inner diameter of the housing and the outer diameter of the movable part at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis can be set to 1 mm or more.

[0009] By making the above difference 1 mm or more, it becomes possible to more reliably eliminate contact between the movable part and the housing in the driving state, or at least make contact less likely to occur.

[0010] Furthermore, the difference between the inner diameter of at least one of the first spring and the second spring and the outer diameter of the movable part at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis can be made smaller than the difference between the inner diameter of the housing and the outer diameter of the movable part at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis.

[0011] With the above configuration, when a radial load is applied to the movable part and the movable part is displaced radially, the movable part will contact the first or second spring before the housing. This prevents the movable part from being displaced further radially, suppressing unstable movement of the movable part and, as a result, reducing the vibration of the entire impact tool. Furthermore, even in such cases, since the vibration of the movable part is transmitted to the housing via the spring, it is possible to reduce the vibration transmitted to the housing compared to when the movable part directly contacts the housing and the vibration is directly transmitted to the housing.

[0012] Further, when a load equal to or more than a predetermined value does not act on the tip tool during driving of the striking mechanism, the outer peripheral surface of the movable portion can be prevented from contacting the inner peripheral surface of the housing.

[0013] Furthermore, when a load equal to or more than a predetermined value acts on the tip tool during driving of the striking mechanism, the outer peripheral surface of the movable portion can contact the inner peripheral surface of the housing, so that displacement of the movable portion in the radial direction can be restricted.

[0014] The impact tool can further include a rotation preventing member protruding radially outward from the outer peripheral surface of the movable portion, and the rotation preventing member engages with the housing in the circumferential direction, whereby the movable portion can be prevented from rotating in the circumferential direction relative to the housing.

[0015] Furthermore, the first spring and the second spring can be configured to have the same spring constant.

[0016] Hereinafter, embodiments of the impact tool according to the present invention will be described with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] [Figure 1] It is a sectional view of the impact tool according to the first embodiment of the present invention. [Figure 2] It is a sectional view of the impact tool of Fig. 1 showing a state where a piston has moved forward. [Figure 3] It is a sectional view of the impact tool of Fig. 2 showing a state where an anvil and a needle holder are struck by the piston and have moved forward. [Figure 4] It is an enlarged view of the front annular passage and its periphery in Fig. 3. [Figure 5] It is a sectional view of the impact tool according to the second embodiment of the present invention. DESCRIPTION OF EMBODIMENTS

[0018] The impact tool 100 according to the first embodiment of the present invention shown in Fig. 1 has a plurality of needles 102 (needle chisels) attached as a tip tool, reciprocates the needles 102 by compressed air, and hits a workpiece with the tips of the needles to perform chipping work. The impact tool 100 is assumed to be attached to a robot arm or the like and used in automatic operation.

[0019] The impact tool 100 includes a cylindrical housing 110, a movable part 112 substantially entirely disposed inside the housing 110, a first spring 114 disposed between the movable part 112 and the housing 110 at a front position of the housing 110, and a second spring 116 disposed between the movable part 112 and the housing 110 at a rear position of the housing 110. The movable part 112 is supported by the first spring 114 and the second spring 116 so as to be displaceable in the direction of a longitudinal axis L without contacting the housing 110.

[0020] The movable part 112 includes a cylindrical main body 118 and a cylinder 120 coaxially attached inside the cylindrical main body 118. The movable part 112 further includes, inside the cylinder 120, a piston 122, an anvil 124, and a needle holder (tip tool holding part) 126 sequentially arranged from the rear (upper side as viewed in the drawing) toward the front (lower side as viewed in the drawing). The needle holder 126 holds each needle 102 so as to extend forward from a tip cap 128 attached to the front end of the cylindrical main body 118. The cylindrical main body 118 consists of a main body front part 118a, a main body middle part 118b, and a main body rear part 118c that are connected to each other. An air introduction part 130 for introducing compressed air is provided at the rear end of the main body rear part 118c.

[0021] Compressed air introduced from the air inlet 130 passes through the passage 132 in the rear part 118c of the cylindrical body 118, and through the rear end through hole 134 in the middle part 118b of the body to reach the middle part 118b. The compressed air then passes through the rear annular passage 136 between the middle part 118b of the body and the cylinder 120, and through the rear through hole 138 in the cylinder 120 to reach the inside of the cylinder 120. When the piston 122 is located on the rear side inside the cylinder 120 as shown in Figure 1, the compressed air passes through the passage 140 of the piston 122 to the forward drive chamber 142 formed between the rear end surface 122a of the piston and the inner surface 120a of the rear end of the cylinder. When compressed air is introduced into the forward drive chamber 142 and the pressure inside the forward drive chamber 142 rises, as shown in Figure 2, the pressure drives the piston 122 forward and strikes the anvil 124 from the rear. The anvil 124, struck from the rear, strikes the needle holder 126 located in front of it. As a result, the anvil 124 and needle holder 126 move forward, as shown in Figure 3. In the state shown in Figure 3, the rear through-hole 138 of the cylinder 120 is closed by the outer circumferential surface of the piston 122, and the rear annular passage 136 does not communicate with the passage 140 of the piston 122 and the forward drive chamber 142. Therefore, no forward force acts on the piston 122. On the other hand, as shown in detail in Figure 4, a forward annular passage 144 is formed between the middle part 118b of the cylindrical body 118 and the cylinder 120, extending further forward from the rear annular passage 136. This forward annular passage 144 communicates with the reverse drive chamber 148 through the front through-hole 146 of the cylinder 120 and the passage 147 between the cylinder 120 and the needle holder 126. Therefore, compressed air is introduced into the reverse drive chamber 148. As the pressure in the reverse drive chamber 148 increases, a rearward force acts on the needle holder 126, driving it backward. As the needle holder 126 moves backward, the anvil 124 also moves backward. The anvil 124 collides with the piston 122, causing the piston 122 to move backward. This returns the cylinder to the state shown in Figure 1. When the needle holder 126 has retracted to the position shown in Figure 1, the front through-hole 146 of the cylinder 120 is closed by the outer circumferential surface of the needle holder 126, thus closing the gap between the front annular passage 144 and the reverse drive chamber 148.Compressed air is again introduced into the forward drive chamber 142, driving the piston 122 forward. By repeating the above operation, a striking force is repeatedly applied to the needle 102 in the front-rear direction along the longitudinal axis L of the housing, causing the needle 102 to reciprocate.

[0022] The movable part 112 is supported by a first spring 114 and a second spring 116 such that its outer circumferential surface 112a does not directly contact the inner circumferential surface 110a of the housing 110. The first spring 114 biases the movable part 112 forward, and the second spring 116 biases the movable part 112 backward, so that the movable part 112 is held in a position where the biasing forces of the first spring 114 and the second spring 116 are balanced. The first spring 114 is supported at its end 114a from the radially outer side by the first spring support surface 110b of the housing 110, thereby fixing its radial position. Similarly, the second spring 116 is supported at its end 116a from the radially outer side by the second spring support surface 110c of the housing 110, thereby fixing its radial position. In this embodiment, the first spring 114 and the second spring 116 have the same shape and the same spring constant. When the striking mechanism, which consists of the piston 122, anvil 124, and needle holder 126 of the movable part 112, is driven, the entire movable part 112, including the striking mechanism, vibrates due to their reciprocating motion in the forward and backward directions and collisions between the components. In this impact tool 100, at least when the striking mechanism is not driven and no radial force is acting on the movable part 112, the outer circumferential surface 112a of the movable part 112 is supported by the first spring 114 and the second spring 116 so as not to directly contact the inner circumferential surface 110a of the housing 110. Therefore, even in the driven state, the movable part 112 and the housing 110 do not come into contact, or if they do, the contact pressure is small and temporary compared to conventional designs where they are always in contact and sliding. As a result, all or most of the vibration of the movable part 112 is not directly transmitted to the housing 110 but is damped by the first spring 114 and the second spring 116, making it difficult for vibration to be transmitted to the housing 110.The size of the gap D1 (Figure 4) between the outer circumferential surface 112a of the movable part 112 and the inner circumferential surface 110a of the housing 110 at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis L can be appropriately set considering the size of the impact tool 100, the magnitude of vibration of the movable part 112, the spring constants of the first and second springs 114 and 116, etc. However, it is desirable to set the gap D1 to a size such that the outer circumferential surface 112a of the movable part 112 and the inner circumferential surface 110a of the housing 110 do not come into contact, at least in the unloaded driving state where no load is applied to the needle 102. More preferably, the size of the gap D1 is set so that the outer circumferential surface 112a of the movable part 112 and the inner circumferential surface 110a of the housing 110 do not come into contact when no load above a certain level is applied to the needle 102 in the driving state. Alternatively, the system can be configured so that the outer circumferential surface 112a of the movable part 112 and the inner circumferential surface 110a of the housing 110 do not come into contact with the needle 102, regardless of any load within the range expected under normal use of the impact tool 100.

[0023] The gap D1 described above is caused by the difference between the inner diameter of the housing 110 and the outer diameter of the movable part 112 at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis L. Specifically, this difference between the inner diameter of the housing 110 and the outer diameter of the movable part 112 can be at least 1 mm, more preferably about 2 mm, or 2 mm or more. In this embodiment, the difference between the inner diameter of the housing 110 and the outer diameter of the movable part 112 is set to 2 mm, so when the movable part 112 is located at the center of the housing 110, the gap D1 between the outer circumferential surface 112a of the movable part 112 and the inner circumferential surface 110a of the housing 110 is 1 mm. In this embodiment, the difference between the inner diameter of the first spring 114 and the outer diameter of the movable part 112 at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis L is set to about 0.8 mm. In other words, the gap D2 (Figure 4) between the inner circumference of the first spring 114 and the outer surface 112a of the movable part 112 is set to be approximately 0.4 mm. Therefore, the difference between the inner diameter of the first spring 114 and the outer diameter of the movable part 112 at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis L is smaller than the difference between the inner diameter of the housing 110 and the outer diameter of the movable part 112, and the gap D2 between the first spring 114 and the movable part 112 is smaller than the gap D1 between the housing 110 and the movable part 112.

[0024] When subjected to a radial force, the movable part 112 can also be displaced radially, deforming the first spring 114 and the second spring 116 radially. As described above, because the gap D2 is smaller than the gap D1, when the movable part 112 is displaced radially, for example, when a large load, particularly in the lateral direction, acts on the needle 102, the movable part 112 will contact the first spring 114 rather than the housing 110, at least around the first spring 114. By the movable part 112 contacting the first spring 114 radially, the movable part 112 is guided by the first spring 114 and prevented from vibrating excessively radially, thereby suppressing unstable operation of the movable part 112. This reduces the overall vibration of the impact tool 100. Furthermore, even in such a situation, the vibration of the movable part 112 is transmitted to the housing 110 via the first spring 114, so the vibration transmitted to the housing 110 can be reduced compared to when it is in direct contact with the housing 110. Furthermore, when the movable part 112 comes into contact with the first spring 114, the movable part 112 becomes oblique to the longitudinal axis L, and at positions away from the first spring 114, the movable part 112 may come into direct contact with the housing 110. By the outer circumferential surface 112a of the movable part 112 coming into contact with the inner circumferential surface 110a of the housing 110, the radial displacement of the movable part 112, especially displacement that is oblique to the longitudinal axis L, can be limited.

[0025] A ring member 150 and a nut 152 are screwed onto the rear 118c of the main body of the movable part 112. By tightening the nut 152 against the ring member 150, the ring member 150 is fixed to the rear 118c of the main body. An anti-rotation member 154 is attached to the ring member 150 so as to protrude radially outward from its outer circumferential surface. An anti-rotation hole 156 is formed in the housing 110, extending forward from its rear end, and the anti-rotation member 154 is located within the anti-rotation hole 156. The anti-rotation member 154 engages with the side surface of the anti-rotation hole 156 in the circumferential direction, thereby preventing the movable part 112 from rotating circumferentially relative to the housing 110.

[0026] The magnitude of vibrations transmitted to the housing was measured under various driving conditions for an impact tool according to the present invention (inventive product) and a comparative product (conventional product) designed so that there is virtually no gap between the movable part and the housing and the movable part is always in direct contact with the housing and slides. The results are shown in Table 1. The comparative product has substantially the same configuration as the impact tool 100 according to this embodiment, except for the configuration related to the gap mentioned above. In addition to the impact tool 100 shown in the above embodiment, in which the difference between the inner diameter of the housing 110 and the outer diameter of the movable part 112 at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis L is 2 mm (gap D1 is 1 mm), experiments were also conducted on impact tools with a difference of 1 mm (gap is 0.5 mm) and 4 mm (gap is 2 mm). In terms of driving conditions, "no load" is defined as the state where the workpiece does not come into contact with the reciprocating needle 102, "stroke 0mm" is defined as the state where the tip of the needle 102 comes into contact with the workpiece when the needle 102 is fully retracted and the needle 102 does not substantially displace during driving, and "stroke 5mm" is defined as the state where the tip of the needle 102 comes into contact with the workpiece at a position 5mm forward from the fully retracted position (i.e., the needle 102 can stroke by 5mm). In Table 1, the vibration value of the conventional product under each condition is set to 100%, and the vibration value of the inventive product is shown as a percentage of that. As can be seen from Table 1, in all driving conditions, the vibration value of the inventive product's impact tool is significantly lower than that of the conventional product, which has virtually no gap. Specifically, in the no-load driving state, the vibration value of the inventive product is reduced to 62-45% compared to the conventional product. In the "stroke 5mm" driving state, which is close to actual usage conditions, the vibration value is reduced to 75-62%. In the driving state with a stroke of 0 mm, where the needle 102 is not substantially displaced, the vibration value is reduced to 94-90%. Furthermore, there was no substantial difference in the impact force generated by the needle 102 between the conventional product and each inventive product. [Table 1]

[0027] The impact tool 200 according to the second embodiment of the present invention, shown in Figure 5, is equipped with a chisel 202 as a tip tool. Compressed air drives a piston 222 in the forward and backward direction (up and down direction in the figure), causing the piston 222 to strike and vibrate the chisel 202, and the tip of the chisel 202 strikes the workpiece to perform chipping work, etc. This impact tool 200 is intended to be used by an operator who holds it in their hand and operates it manually.

[0028] The impact tool 200 comprises a cylindrical housing 210, a movable part 212 whose majority is located inside the housing 210, a first spring 214 positioned between the movable part 212 and the housing 210 at a forward position of the housing 210, and a second spring 216 positioned between the movable part 212 and the housing 210 at a rear position of the housing 210. The movable part 212 is supported by the first spring 214 and the second spring 216 such that its outer circumferential surface 212a does not come into contact with the inner circumferential surface 210a of the housing 210. In this embodiment, the difference between the inner diameter of the first spring 214 and the outer diameter of the movable part 212, and the difference between the inner diameter of the second spring 216 and the outer diameter of the movable part 212 are both smaller than the difference between the inner diameter of the housing 210 and the outer diameter of the movable part 212. Therefore, the gap D2 between the first spring 214 and the movable part 212, and the gap D3 between the second spring 216 and the movable part 212, are smaller than the gap D1 between the housing 210 and the movable part 212. In this way, even if a radial force acts on the movable part 212 and the movable part 212 is displaced radially, the movable part 212 will not substantially come into direct contact with the housing 210.

[0029] The movable part 212 comprises a cylindrical body 218 and a cylinder 220 coaxially arranged within the cylindrical body 218. The movable part 212 further comprises a piston 222 located within the cylinder 220 and a chisel holder (tip tool holder) 226 for holding the chisel 202. An air inlet 230 for introducing compressed air is provided at the rear end of the cylindrical body 218. The cylindrical body 218 is also fitted with a ball valve 258 for opening and closing the passage 232, an operating shaft 260 for operating the ball valve 258, and a lever 262 for operating the operating shaft 260. By pivoting the lever 262 toward the housing 210, the operating shaft 260 is pushed, thereby displacing the ball valve 258 from the closed position to the open position shown in the figure. When the ball valve 258 is in the open position, compressed air introduced from the air inlet 230 is introduced into the cylinder 220 through the annular passage 236 between the cylindrical body 218 and the cylinder 220, causing the piston 222 to reciprocate in the front-rear direction along the longitudinal axis L of the housing 210.

[0030] The operating shaft 260, attached to the cylindrical body 218 of the movable part 212, extends to the outside of the housing 210 through an anti-rotation hole 256 formed to extend forward from the rear end of the housing 110. By engaging the side surface of the anti-rotation hole 256 in the circumferential direction with this operating shaft 260, the movable part 212 is prevented from rotating circumferentially relative to the housing 210. In other words, the operating shaft 260 also functions as an anti-rotation member.

[0031] In this embodiment as well, the movable part 212 having the striking mechanism is supported by the first spring 214 and the second spring 216 so as not to come into contact with the housing 210. As a result, vibrations of the movable part 212 are dampened by the first spring 214 and the second spring 216 and are less likely to be transmitted to the housing 210. Furthermore, since the difference between the inner diameter of the first spring 214 and the outer diameter of the movable part 212, and the difference between the inner diameter of the second spring 216 and the outer diameter of the movable part 212 are both smaller than the difference between the inner diameter of the housing 210 and the outer diameter of the movable part 212, even if the movable part 212 is displaced radially, the movable part 212 does not come into direct contact with the housing 210 but is guided by the first spring 214 and the second spring 216. This makes it possible to suppress excessive radial vibrations of the movable part 212 while reducing the vibrations transmitted to the housing 210.

[0032] Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments. The configurations of the first embodiment and the configurations of the second embodiment are mutually applicable. For example, the impact tool of the first embodiment can be modified to be a handheld impact tool by applying the configuration of the ball valve, operating shaft, and lever of the second embodiment. The tip tool can be any tool other than a needle or chisel. Furthermore, in the above embodiments, the impact mechanism is configured by reciprocating a piston with compressed air, but an electrically powered impact mechanism can also be configured using electrical components such as an electric motor. The size, arrangement, and number of springs supporting the movable part can be arbitrarily changed. In addition, the difference between the inner diameter of the second spring on the rear side and the outer diameter of the movable part can be made smaller than the difference between the inner diameter of the housing and the outer diameter of the movable part. Note that it is not necessarily required that either the difference between the inner diameter of the first spring and the outer diameter of the movable part, or the difference between the inner diameter of the second spring and the outer diameter of the movable part, be smaller than the difference between the inner diameter of the housing and the outer diameter of the movable part, and the first and second springs can be configured so that they do not come into contact with the movable part. In this case, when a certain load, particularly radial, is applied to a tip tool such as a needle or chisel, the outer surface of the movable part contacts the inner surface of the housing rather than the spring, thereby limiting the radial displacement of the movable part. Although the above embodiments are all intended for use attached to a robot arm, the housing can also be directly gripped by an operator and used as a handheld impact tool. In that case, it can be a pistol-type handheld impact tool with a radially extending gripping part on the housing. [Explanation of symbols]

[0033] 100 Impact Tools 102 Needle (Tip Tool) 110 Housing 110a Inner surface 110b First spring support surface 110c Second spring support surface 112 Moving parts 112a Outer surface 114 First Spring 114a End 116 2nd Spring 116a End 118 Cylindrical body 118a Front of the main body 118b Main body, middle section 118c Rear of the main unit 120 cylinders 120a Inner surface of the rear end of the cylinder 122 Pistons 122a Piston rear end face 124 Anvil 126 Needle holder (tool tip holder) 128 Tip cap 130 Air intake section 132 Passage 134 Rear end through hole 136 Rear Circular Passage 138 Rear through hole 140 aisles 142 Forward drive chamber 144 Forward Ring Road 146 Front through hole 147 Passage 148 Reverse drive unit 150 Ring component 152 nuts 154 Anti-rotation member 156 Anti-rotation holes 200 Impact Tools 202 Chisel (tip tool) 210 Housing 210a Inner surface 212 Moving parts 212a Outer surface 214 1st Spring 216 2nd Spring 218 Cylindrical body 220 liters 222 Piston 226 Chisel holder (tool holder part) 230 Air intake section 232 aisle 236 Circular Passage 256 anti-rotation holes 258 Ball Valve 260 Operation axis 262 Lever L Longitudinal axis D1 Gap between housing and movable part D2 Gap between the first spring and the movable part D3 Gap between the second spring and the movable part

Claims

1. A cylindrical housing, A movable part located at least partially within the housing and displaceable relative to the housing in the direction of the housing's longitudinal axis, comprising: a tool holder for holding a tool tip; and a striking mechanism for applying striking force to the tool tip attached to the tool holder in the front-rear direction along the housing's longitudinal axis; A first spring is disposed between the movable part and the housing and biases the movable part forward. A second spring is disposed between the movable part and the housing and biases the movable part toward the rear, Equipped with, An impact tool in which the movable part is supported by the first and second springs such that the movable part and the housing do not come into direct contact, at least when the impact mechanism is not driven and no radial force perpendicular to the longitudinal axis is acting on the movable part.

2. The impact tool according to claim 1, wherein the difference between the inner diameter of the housing and the outer diameter of the movable part at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis is 1 mm or more.

3. The impact tool according to claim 1 or 2, wherein at least one end of the first spring and the second spring is supported from the radially outer side by a spring support surface of the housing and its radial position is fixed, and the difference between the inner diameter of the one spring and the outer diameter of the movable part at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis is smaller than the difference between the inner diameter of the housing and the outer diameter of the movable part at mutually adjacent positions in the radial direction perpendicular to the longitudinal axis.

4. The impact tool according to claim 1, wherein when no load above a certain level is applied to the tip tool while the impact mechanism is being driven, the outer circumferential surface of the movable part and the inner circumferential surface of the housing are not in contact.

5. The impact tool according to claim 4, wherein when a load exceeding a certain level is applied to the tip tool while the impact mechanism is being driven, the outer circumferential surface of the movable part contacts the inner circumferential surface of the housing, thereby limiting the radial displacement of the movable part.

6. The impact tool according to claim 1, further comprising a rotation prevention member protruding radially outward from the outer circumferential surface of the movable part, wherein the rotation prevention member engages with the housing in the circumferential direction, thereby preventing the movable part from rotating in the circumferential direction relative to the housing.

7. The impact tool according to claim 1, wherein the spring constants of the first spring and the second spring are the same.

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