Nailing device operation

Pneumatic nailing devices, which are commonly used in the construction industry, emit noise at levels high enough to put workers at risk of hearing loss. A first step towards noise reduction at the source is an accurate identification of noise generation processes.

The objective of the present research is to identify and rank the noise sources in a pneumatic nailing process. In the standardized setup used for the measurement of noise emissions by nailing devices (BSI, 1999), the workpiece is a wooden block placed in a sandbox to minimize its noise contribution and obtain the nailing device noise itself. This raises two questions: (1) Is the sandbox setup efficient in reducing the workpiece radiation? (2) What is a typical workpiece contribution at an actual worksite? To answer these questions, the noise source identification is conducted in two cases, the standardized sandbox setup, and a more realistic arrangement, where the workpiece is placed on a worktable.

Although numerous publications are available covering noise sources in various machines and systems (Akay, 1978; Alonso et al., 2014; Badino et al., 2016; Bi et al., 2015; Campillo-Davo et al., 2013; Hodgson and Li, 2006; Kim et al., 2007; Koruk and Arisoy, 2015; Leclère et al., 2005; Lee et al., 2012; Lefebvre and Laville, 2008; Pallas et al., 2014; Pallas et al., 2011), only three studies (Adelberg et al., 2002; Jayakumar et al., 2015; Tisserand and Triomphe, 2011) have examined the noise problem in pneumatic nailing devices. Adelberg et al. (2002) used a simple experimental setup, in which one microphone captures the sound at the operator position to identify the noise sources. The authors distinguished four noise peaks in the sound pressure time history of the process. They attributed these peaks to the following four sources: (1) air exchange after trigger pulling, (2) piston impact with low piston bumper, (3) air exhaust, and (4) piston return impact.

Tisserand and Triomphe (2011) evaluated the noise reduction obtained during the air exhaust phase when using a silencer device. Recently, Jayakumar et al. (2015) used sound pressure time history and noise maps to determine the possible noise sources and the corresponding transmission paths. In the investigation, the workpiece was supported by a sand bed. The authors identified the impact noise transmitted through the structure and the exhaust-related noise as the first and second contributors, respectively, to the total noise. The study also identified four distinct peaks in the noise time history. The authors associated these peaks with the following sources: (1) compressed air flow through inlet port, (2) piston rod-nail impact, (3) nail-wood impact, and (4) air exhaust. The present study develops a time domain noise source identification strategy similar to the procedure introduced in Jayakumar et al. (2015) and Adelberg et al. (2002) and completes it by a selective wrapping and muffler procedure.

When the trigger valve (20) is in the released position, the compressed air covers the area above the head valve (10). The resultant force of the air pressure on both sides of the head valve and the compression spring (4) downward force keeps the head valve pressed against the cylinder top (5). Depressing the trigger closes the trigger valve, and stops the air flow to the upper area of the head valve. The remaining compressed air in this area flows out to the atmosphere through the air channel (1). As a result, the head valve opens, while simultaneously closing the air exhaust (7). Therefore, the compressed air flows to chamber no.1 (2) above the piston head, pushes the piston downward, and drives out the nail. As the piston moves downward, the air inside the cylinder flows through a series of holes to a return chamber (15). Releasing the trigger valve allows a backward motion of the head valve, which stops the compressed air discharge to the piston head, and opens the air exhaust. The pressurized air inside the return chamber then drives the piston upward, while pushing the air above the piston to the atmosphere (Air exhaust phase) simultaneously.